IRC 78.2014

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(1)IRC:78-2014. STANDARD SPECIFICATIONS AND CODE OF PRACTICE FOR ROAD BRIDGES SECTION. :. VII. FOUNDATIONS AND SUBSTRUCTURE (Revised Edition) (Incorporating. all. Amendments and. INDIAN. Errata Published upto December, 2013). ROADS CONGRESS 2014.

(2) Digitized by the Internet Archiive in. 2014. https://archive.org/details/govlawircy201478.

(3) IRC:78-2014. STANDARD SPECIFICATIONS AND CODE OF PRACTICE FOR ROAD BRIDGES. SECTION. :. VII. FOUNDATIONS AND SUBSTRUCTURE (Revised Edition) (Incorporating. all. Amendments and Errata Published upto December,. 2013). Published by. INDIAN ROADS CONGRESS Kama Koti Marg, R.K. Puram, New Delhi- 10022 1. Price ? 700/-. (Plus packing. &. postage).

(4) IRC:78-2014 1980 (as. First. Published. July,. First. Revision. December, 1983 (Incorporating Part 1,2. and 3. Part-I). September, 1988. Reprinted. October, 1994. Reprinted. September, 1998. Reprinted. September, 2000. Second Revision. December, 2000 April,. :. and Amendment. to Parti). Reprinted. Reprinted. II. 2002. Reprinted. August, 2004 (Incorporates the Amendments). Reprinted. August, 2005. Reprinted. August, 2007 (Incorporates the. Amendments. dated 30.11.2006). Revised Edition. January, 2014 (Incorporating. :. all. Amendments and. Published upto December, 2013). (All. Rights Reserved.. No. Part of this publication shall be reproduced,. translated or transmitted in. any form or by any means without the. permission of the Indian Roads Congress). Printed. at:. Aravali Printers. &. Publishers Pvt.. (1000 Copies). ii. Ltd.,. Errata.

(5) IRC:78-2014. CONTENTS Page No.. Clause No. Personnel of Bridges Specifications and Standards Committee. vii. Background. i. 700. Scope. 3. 701. Terminology. 3. i. o. 701.1. Abutment. o. 701.2. Afflux. o o. 701.3. Balancer. A. 701.4. Bearing Capacity. A. 701.5. Bearing Stress. A. 701.6. Cofferdam. 5. 701.7. Foundation. 5. 701.8. Pier. 5. 701.9. Piles. 5. 701.10. Retaining Wall. 6. 701. Substructure. 7. Well Foundation. 7. 11. 701.12. 702. Notations. 703. Discharge and Depth of Scour. 704. 705. 706. 7 for. Foundation Design. 703.1. Design Discharge of Foundation. 703.2. Mean Depth. 703.3. Maximum Depth. of. Scour of. 9. 9 10. Scour. for. Design of Foundations. Sub-surface Exploration. 11. 12. 704.1. Objectives. 12. 704.2. Zone. 13. 704.3. Methods. of Influence. 13. of Exploration. Depth of Foundation. 13. 705.1. General. 13. 705.2. Open Foundations. 14. 705.3. Well Foundations. 14. 705.4. Pile. 15. Foundations. Loads, Forces, Stability and Stresses 706.1. Loads, Forces and their Combinations. iii. 15 15.

(6) IRC:78-2014. 707. 708. 709. 706.2. Horizontal Forces at Bearing Level. 16. 706.3. Base Pressure. 17. 19. Open Foundations 707.1. General. 19. 707.2. Design. 19. 707.3. Open Foundations. 707.4. Construction. at. Sloped Bed. 21. Profile. 22 23. Well Foundations 708.1. General. 23. 708.2. Well Steining. 23. 708.3. Design Considerations. 25. 708.4. Stability of. 708.5. Tilts. 708.6. Cutting. 708.7. Well Curb. 28. 708.8. Bottom Plug. 29. 708.9. Filling. 708.10. Plug over. 708.11. Well. 708.12. Floating Caissons'. 708.13. Sinking of Wells. 708. 1 4. Pneumatic Sinking of Wells. 30. 708. 1 5. Sinking of Wells by Resorting to Blasting. 31. Pile. and. 26. Well Foundations. 27. Shifts. 28. Edge. 29. the Well. 29. Filling. Cap. 29 30. 30. '. Foundation. 31. 709.1. General. 709.2. Requirement and Steps. 709.3. Geotechnical Capacity of Pile. 36. 709.4. Structural Design of Piles. 40. 709.5. Design of. 709.6. 31. Pile. for. Design and. Installation. Cap. 34. 40. Important Consideration, Inspection/Precautions for Different. Types. 41. of Piles. iv.

(7) IRC:78-2014 44. Substructure 710.1. General. 44. 710.2. Piers. 45. 710.3. Wall Piers. 46. 710.4. Abutments. 46. 710.5. Abutment Pier. 47. 710.6. Dirt Walls,. 710.7. Retaining Walls. 710.8. Pier. 710.9. Cantilever. 710.10. Pedestals below Bearing. Wing Walls and Return Walls. 49. and Abutment Caps. Cap. 48. of Abutment. 49 and Pier. 51. 51. Appendixes Factor for Bed Material Consisting of Clay. 53. 1.. Guidelines for Calculating. 2.. Guidelines for Sub-surface Exploration. 54. 3.. Procedure. 67. 4.. Precautions to be taken during Sinking of Wells. 71. 5.. Capacity of Pile Based on Pile Soil Interaction. 76. 6.. Filling. 7.. Part-1-Pile. Silt. for Stability Calculation. Behind Abutments, Wing and Return Walls. Load Capacity by Dynamic Test Using Wave Equation. Part-2-Standard Test Method for. Low. Strain Pile Integrity Testing. V. 82. 84 93.

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(9) IRC:78-2014. PERSONNEL OF THE BRIDGES SPECIFICATIONS AND STANDARDS COMMITTEE (As on 6.1.2014). 1.. 2.. 3.. Kandasamy,. Director General (RD). C.. &. Spl. Secy, to. Govt, of India, Ministry of Road. New. (Convenor. Transport and Highways, Transport Bhavan,. Patankar, V.L.. Addl. Director General, Ministry of Road Transport and Highways. (Co-Convenor). Transport Bhavan,. Pathak, A.P.. Chief Engineer (B) S&R, (Ministry of RoadTransport. (Member-Secretary ). Transport Bhavan,. New. New. Delhi. Delhi. &. Highways,. Delhi. Members. CPWD. 4.. Agrawal, K.N.. DG(W),. 5.. Alimchandani, C.R.. Chairman. Ghaziabad. (Retd.). & Managing. Director,. STUP Consultants. (P) Ltd.,. Mumbai. MORTH, New. 6.. Arora, H.C.. Chief Engineer (Retd.). 7.. Bagish, Dr. B.P.. C-2/2013, Vasant Kunj,Opp. D.P.S.New Delhi. 8.. Bandyopadhyay,. Dr.. 9.. Bandyopadhyay,. Dr. T.K.. 10.. Banerjee, A.K.. Chief Engineer (Retd.). MORTH, New. Delhi. 11.. Banerjee,T.B.. Chief Engineer (Retd.). MORTH, New. Delhi. 12.. Basa,. 13.. Bhasin,. 14.. Bhowmick, Alok. Ashok P.C.. N.. New. Director, Stup Consultants (P) Ltd.. Joint Director General (Retd.). ADG. (B), (Retd.),. Managing. MOST, New. Director, Bridge. &. Delhi. INSDAG, Kolkata. &. Director (Tech.) B. Engineers. Delhi. Builders Ltd.,. Bhubaneswar. Delhi Structural Engg. Consultants (P) Ltd.,. Noida. Mumbai. 15.. Bongirwar, PL.. Advisor, L&T,. 16.. Dhodapkar, A.N.. Chief Engineer (Retd.). 17.. GhoshalA. Director and Vice President,. 18.. Joglekar,S.G.. Vice President,. 19.. Kand,, C.V.. Chief Engineer (Retd.), MP,. 20.. Koshi,. 21.. Kumar, Ashok. Chief Enginee (Retd.),. 22.. Kumar, Prafulla. DG. 23.. Kumar, Vijay. E-in-Chief (Retd.) UP,. Ninan. DG(RD). (RD). MORTH, New. STUP Consultants. STUP Consultants. & Addl.Secy.,. (Retd). (P) Ltd.. PWD MOST,. New. (Retd.). PWD,. New. (P). Mumbai. ,. Bhopal. MORTH, New. & AS, MORT&H. vii. Delhi. Delhi. Delhi Delhi. Ltd.. Kolkata.

(10) IRC:78-2014 24.. Manjure,. 25.. Mukherjee, M.K.. Chief Engineer (Retd.). 26.. Nagpal, A.K.. Prof.. 27.. Narain, A.D.. DG. 28.. Ninan, R:S.. Chief Engineer (Retd.). 29.. Pandey, R.K.. Chief Engineer (Planning),. 30.. Parameswaran,. Concrete Co.. Director, Freyssinet Prestressed. P.Y.. IIT,. (RD). New. MOST, New. Mumbai. Delhi. Delhi. & AS, MORT&H. New. (Retd.). MORTH New. Delhi Delhi. MORTH, New. New. Dr.. Chief Scientist (BAS), CRRI,. S.. Vice President (Corporate Affairs).. Delhi. Delhi. Lakshmy 31.. Raizada, Pratap. 32.. Rao,. 33.. Roy, Dr. B.C.. Dr.. M.V.B.. Senior Consultant, Ms.. Gammon. SNC LAVALIN. India Ltd.. Mumbai. Infrastructure Pvt. Ltd.. Senior Executive Director, M/s. Consulting Engg. Services India (Pvt.) Ltd.. Gurgaon. Executive Director Construma Consultancy (P) Ltd.. 34.. Saha,. 35.. Sharan, G.. DG(RD) & Spl.Secy. 36.. Sharma,. Chief Engineer (Retd.). 37.. Sinha, N.K.. 38.. Subbarao,. Dr. G.P.. R.S.. DG(RD)&SS, Chairman. Dr.. (Retd.). Mumbai. 39.. Tandon, Mahesh. Managing. 40.. Thandavan,. Chief Engineer (Retd.). 41.. Velayutham,,. V.. DG. 42.. Viswanathan,. T.. 7046, Sector. 43.. The Executive Director. Director,. (RD) SS (Retd.) B,. Dellhi. MORTH New. Delhi. MORT&H New. Delhi. ,. & Managing. Harshavardhan. K.B.. MORTH, New. (Retd.). Director,. Construma Consultancy. Tandon Consultants. MORH, New. MORTH, New. Pocket 10. ,. Mumbai. (P) Ltd.,. New. (P) Ltd. Delhi. Delhi. Delhi. Vasant Kunj ,New Delhi. RDSO, Lucknow. (B&S). The Director and Head,. 44.. (Civil. Bureau of Indian Standards,. New. Delhi. Engg.),. r;. Corresponding Members. 1.. Raina, Dr. V.K.. Consultant (W.B.). 2.. Singh, R.B.. Director, Projects Consulting India (P) Ltd.. Ex-off'icio 1. .. Kandasamy, C.. 2.. Prasad, Vishnu. Delhi. Members. Director General (RD) India,. New. MoRT&H. &. Special Secretary to Govt, of. and President, IRC,. New. Delhi. Secretary General, Indian Roads Congress,. Shankar viii. New. Delhi.

(11) IRC:78-2014. FOUNDATIONS AND SUBSTRUCTURE. BACKGROUND The "Standard. Specifications. and Code. Foundations and Substructure was. first. Features of Design. Later first revision Part. II. of this. the. and Amendments. 1,2. and 3. Road Bridges" Section VII July 1980 as Part - General. of Practice for. published. in. was published. to Part. I. I. in. December, 1983 incorporating. as Unified Code. The second revision. code was undertaken by the Foundation and Structure Committee (B-4) and. initial. draft. was. finalized. Sarma Subsequently, .. by the Committee under the Convenorship of Shri R.H.. the draft. was reconsidered and discussed. in. various meetings. by the reconstituted Foundation, Substructure and Protective Works Committee (B-4). under Convenorship of Shri S.A Reddi. The. as approved by Convenor. final draft. Committee was subsequently approved by the Executive Committee held on 30.8.2000.. It. was. later. approved by the Council. Kolkata on 4.11.2000 for publishing the revised IRC. in its. in. meeting. 160th meeting held at. Code Section. Since then numerous amendments and errata were published to. development. in its. BSS. VII:. this. IRC: 78:2000.. Code based on. design and construction technology.. The current Revised. Edition of IRC:78 includes. all. the. amendments and. errata. published from time to time upto December, 2013.. The Revised. Edition of IRC:78 "Standard Specifications. Bridges" Section VII till. date. all. of Practice for. amendments and. Road. Errata published. was approved by Foundations and Substructure Foundation Substructure. Protective 1. - Foundation incorporating. and Code. Works and Masonry Structures Committee. 6.1 0.201 3.. The Revised. Edition of IRC:78. and Standards Committee. in its. (B-3). in. its. meeting held on. was approved by the Bridges Specifications. meeting held on 06.01 .2014 and Executive Committee. held on 09.01.2014 for publishing.. The composition. of the B-3. Committee. is. given below:. Bongirwar, P.L. Convenor. Joglekar, S.G.. Co-Convenor. Kanhere, D.K.. Member-Secretary. 1.

(12) IRC:78-2014. Members Bagish, BP.. Chonkar, Ravindra. Dhiman, R.K.. Deshmukh,. Elavarson R,. Ganpule,. Dr. V.V.. Dr. V.T.. (expired on 15.03.2013). Gandhi, Prof. S.R. Jaigopal, R.K.. Kothyari, Prof. U.C. (expired on 30.12.2012). Karandikar, D.V.. Kand,. Dr.. C.V. Mhaiskar, Dr.S.Y.. Marwah, M.P.. Nashikkar, Jayant. Nayak,. Ray, S.. Dr. N.V.. Saha, Smt. S.DNigade,.. Subbarao,. Saha,. Singh, M.N.. Dr. G.P.. Singh, Rajeev. Velyutham,. Dr. H.. V.. Corresponding Members Basa, Ashok. Dey, Prof. S.. Heggade, V.N.. Mazumder,Prof. S.K.. Paul, Dipankar. Pitchumani, Dr. N.. Sarma, R.H.. Tarapore, Dr. Z.S.. Viswanathan,. t.. Ex-Officio. Members. C.Kandasamy. (Road Development) & Special Secretary, MoRT&H and President, IRC. Vishnu Shankar Prasad. Secretary General, IRC. Director General. 2.

(13) IRC:78-2014. SCOPE. 700. This code deals with the design and construction of foundations and substructure. road bridges. The provisions of. code are meant to serve as a guide to both the design and construction engineers, but mere compliance with the provisions stipulated herein will not relieve them in any way of their responsibility for the stability and soundness of the structure designed and erected. for. 701 The. this. TERMINOLOGY. following definitions shall be applicable for the purpose of this code.. Abutment. 701.1. The end support. of the. approaches behind. Box. 701.1.1. When. fully. deck (superstructure) of a bridge, which also retains. earth,. fill. of. or partly.. type abutment. and return. wall. the return walls on two sides are integrated with abutment and a back wall parallel to. abutment. is. provided at the end of returns with or without additional internal wall along or. across length,. 701.1.2. this structure is called. box type abutment and return. end. wall, or. block.. Non-load bearing abutment. Abutment, which supports the end span of less than 5 m. 701.1.3. Non-spill through. An abutment 701.1.4. structure. Spill. abutment. where the. soil is. not allowed to. spill. through.. through abutment. An abutment where. soil is. allowed to. spill. through gaps, along the length of abutment, such. column structure where columns are placed below deck beams and gap. as,. free to. spill. earth. (Spilling of earth should not. be permitted above a. level of. in. 500. between. is. mm below. the bottom of bearings).. 701.2. The. Afflux. rise in the flood level of the river. immediately on the upstream of a bridge as a result of. obstruction to natural flow caused by the construction of the bridge and. 3. its. approaches..

(14) IRC:78-2014 Balancer. 701.3. A bridge/culvert like structure of the. embankment. provided on. to other side, for. embankment to. allow flow of water from one side. purpose of avoiding heading up of water on one side. or for avoiding blocking the entry to the other side.. Bearing Capacity. 701.4. The supporting power. expressed as bearing stress. of soil/rock. is. referred to as. it. bearing. capacity.. Allowable bearing pressure. 701.4.1. It. the. is. maximum. gross pressure intensity at which neither the. accounting for appropriate factor of safety) nor there permissible. is. which. is. expected. to. be detrimental. shear, (after. excessive settlement beyond. to the structure.. Net safe bearing capacity. 701 .4.2. it. limits,. is. soil fails in. the net ultimate bearing capacity divided by a factor of safety as per Clause. 706.3.1.1.1.. 701 .4.3. It. is. Net ultimate bearing capacity. minimum. the. 701 .4.4. net pressure intensity causing shear failure of the. Safe bearing capacity. The maximum pressure, which the is. is. the. fails in. can carry safely without. risk of. shear. failure. and. it. Ultimate gross bearing capacity. minimum gross pressure. Bearing Stress. 701 .5. 1. Gross pressure. is. intensity at the. base of the foundation. which the. soil. intensity. the total pressure at the base of the foundation on. of load. at. shear.. 701.5. It. soil. equal to the net safe bearing capacity plus original overburden pressure.. 701 .4.5. It. soil.. and the weight. 701.5.2. of the earth. Net pressure. fill.. intensity. 4. soil. due. to the possible. combinations.

(15) IRC:78-2014 It. is. the difference. intensities of the. gross pressure and the original overburden pressure.. Cofferdam. 701.6. A. in. structure temporary built for the purpose of excluding water or soil sufficiently to permit. construction or proceed without excessive. pumping and. to. support the surrounding. ground.. Foundation. 701.7. The. part of a bridge. 701.8. in. direct contact with. and transmitting load. to the. founding strata.. Pier. Intermediate supports of the deck (superstructure) of a bridge.. Abutment pier. 701 .8.1. Generally use. even. if. in. multiple. span arch bridges. Abutment. one side arch span collapses. it. would be. pier. is. designed. for. These are provided. safe.. a condition that. after three or five. spans.. 701.9. Piles. 701.9.1. Bearing/friction piles. A. pile. driven or cast-in-situ for transmitting the weight of a structure to the founding strata. by the resistance developed at the. pile. base and by. the load mainly by the resistance developed at pile,. and. 701 .9.2. if. mainly by. Bored. A pile formed with it. along. its. base,. it. surface, as a friction. is. along. its. If it. supports. referred to as an end-bearing. pile.. cast-in-situ pile. or without a casing by boring a hole. in. the ground and subsequently. filling. pile. Driven cast-in-situ pile. formed. in. the ground by driving a permanent or temporary casing, and. plain or reinforced concrete.. 701.9.4. A. surface.. with plain or reinforced concrete.. 701 .9.3. A. friction. its. friction. pile. Driven pile. driven into the ground by the blows of a. 5. hammer by. a vibrator.. filling. if. with.

(16) IRC:78-2014 701.9.5. A. Precast pile. reinforced or prestressed concrete pile cast before driving, or installing. in. bore and. grouted.. 701.9.6. A pile. installed at. 701.9.7. One. Raker or batter pile an. inclination to the vertical.. Sheet pile. or a row of piles driven or formed. continuous. wall,. in. the ground adjacent to one another. each generally provided with a connecting. to resist mainly lateral forces. and. to. reduce seepage;. it. joint or interlock,. may be. in. a. designed. vertical or at. an. inclination.. 701 .9.8. A. pile. Tension pile. subjected to tension/uplift. 701.9.9. a load. is. applied to determine and/or confirm the load characteristics (ultimate. load/working load) of the. One. pile. and the surrounding ground.. Working pile. of the piles forming the foundation of the structure.. 701.10. A wall. Retaining Wall. designed. 701.10.1. A. called tension pile.. Test pile. A pile to which. 701 .9.1 0. is. to resist the. pressure of earth. filling. behind.. Return wall. wall adjacent to. abutment generally. parallel to. road or flared up to increased width and. raised upto the top of road.. 701.10.2. A wall. Toe wall. built at. the end of the slope of earthen. or pitching on. embankment to prevent. embankment.. 6. slipping of earth and/.

(17) IRC:78-2014. Wing. 701.10.3. A wall. wall. adjacent to abutment with. upto ground level or a. little. its. above. of road or parallel to the river. top upto road top level near abutment and sloping. at the other end. This is generally at. and follows. The bridge. structure,. superstructure.. earthen banks.. A type. such as, pier and abutment above the foundation and supporting the. shall include returns. It. of foundation. where a. part of the structure. and sunk through ground or water dredge. and wing walls but exclude bearings.. Well Foundation. 701.12. hollow, which. is. to the prescribed. is. generally. built in. parts. depth by removing earth through. hole.. 710.12.1. Tilt. of a well. inclination of the axis of the well. between the axis. 701.12.2. The. 45° to the alignment. Substructure. ;{ t. The. profile or. down. of the well. and the. from the. vertical. expressed as the tangent of the angle. vertical.. Shift of a well. horizontal displacement of the centre of the well at. its. base. in its final. position from. its. designed position.. 702 NOTATIONS For the purpose of. A. this. code, the following notations have been adopted:. Dispersed concentric area 1. A2. Loaded area. B. Width between outer faces of. group. pile. in. plan. parallel. to the. direction. of. movement. C. The allowable bearing pressure. c. Cohesion. Co. The permissible. direct. with near uniform distribution on the founding strata. compressive stress. base. D. Diameter of. pile. 7. in. concrete at the bearing area of the.

(18) IRC:78-2014. Db. Discharge. d. External diameter of circular well. dm. Weighted mean diameter. dsm. Mean depth ~. Fb. Longitudinal force. F. Centrifugal force. in. cubic metre/sec, (cumecs) per metre width. scour. of. in. due. in. in. metre. mm of bed. metre below flood. materiaj level. to braking. .... ,. ,. cf. Fw. Deformation effects. Fh. Horizontal force. Fep. pressure Earth r. Feq. Seismic force. Fer. Erection effects. F. Frictional force at bearings f. Fjm. Impact due to floating bodies. Fs. Secondary. F. Water Current. F. Temperature effects [See Note. effects. (i)]. te. Fwp. Wave. pressure [See Note. G. Dead. load. Gb. Buoyancy. Gs. Snow. h. Minimum thickness. Kg. Co-efficient of active earth pressure. Kp. Co-efficient of passive earth pressure. K. .. sf. L. Silt. (ii)]. load of steining. in. metre. factor. Length between outer faces of. pile. group. in. plan parallel to the direction of. movement l te. Movement. of. deck over bearings, other than due. to applied force. Depth of well. /. /. s. Depth of well. in. metre, up to. MSL.. N. Standard penetration test value. Pa. Total active pressure. Pp. Total passive pressure. Q. Live load. :. 8.

(19) IRC:78-2014. Rg. Dead. Rq. Live load reaction. V. Shear. w. Wind load. CL. Reduction factor. R H. Ratio of lona side to the short side of the footina. su. Undrained shear strenath. a. Undrained III W chohesion \/ w. Li. Co-efficient of friction. 0. Angle of. 8. Settlement of. pile. S. Settlement of. pile. load reaction. r. g. 1. NOTES:. 1. 'w?. 1. rating of elastomeric bearing. (»4. *wfl. \_.. 1. 1. 1. I. 1. V—/. 1. 1. internal friction. group. Temperature effects (FJ in this context is not the frictional force due of bearing but that which is caused by rib shortening, etc.. i). The wave forces. ii). to the. movement. be determined by suitable analysis considering drawing and on single structural members based on rational methods or case of group of piles, piers, etc., proximity effects shall also be. shall. inertia forces, etc.,. model. studies. In. considered.. 703. *. DISCHARGE AND DEPTH OF SCOUR FOR FOUNDATION DESIGN. 703.1. Design Discharge of Foundation. 703.1.1. To provide. be designed. for. for. and adequate margin. of safety, the scour for foundation shall. a larger discharge over the design discharge determined as per IRC:5 as. given below:. Catchment area. in. km. Increase over design. Discharge 0,-3000. NOTES:. i). For. -. percent. 30. 3000- 10000 10000-40000. Above. in. 30-20 20-10. ;. 400Q0. intermediate. 10 values. of. catchment. adopted.. 9. area,. linear. interpolation. may be.

(20) IRC:78-2014 The minimum. ii). vertical. clearance above the. need not be increased due. Mean Depth. 703.2. to larger. HFL. already determined as per IRC:5. discharge calculated above.. of Scour. The mean scour depth below Highest Flood Level (HFL). for natural. channels flowing over. scourable bed can be calculated theoretically from the following equation:. 1 dsm = 1.34/-^) 3. \KsJ. Where. Db. =. The design discharge. for foundation. per metre width of effective. waterway.. K. =. Silt. sf. factor for a representative. sample. of. bed material obtained upto. the level of anticipated deepest scour.. The value. 703.2.1. of. Db may. be determined by dividing the design discharge. foundation by lower of theoretical and actual effective linear waterway as given. 703.2.2. 'K. '. is. sf. in. given by the expression. 1. in. for. IRC:5.. J6jd^ d m being the weighted mean diameter. millimetre.. 703.2.2.1. The value. of. K. sf. for various. grades of sandy bed are given below forready. reference and adoption:. dm. Type of bed material Coarse silt sand Medium sand Coarse sand Fine bajri and sand Heavy sand. Silt/fine. 703.2.2.2. No. scour depth. 703.2.3. bend. is. 0.081 to 0.158. 0.5 to 0.7. 0.223 to 0.505. 0.85 to 1.25. 0.725. 1.5. 0.988. 1.75. 1.29 to 2.00. 2.0 to 2.42. there. of the stream. variation of type of. scour depth for bed material. and boulders (normally having weighted diameter more than 2.00. available. In. may be. If. 0.35. rational formula or data for determining. consisting of gravels. and clayey bed. sf. 0.04. absence. of. any data on scour. calculated following the guidelines given. is. in. any predominant concentration. of flow. immediate upstream or downstream or. bed materia! across the width 10. for. such material, the mean. in. Appendix-1.. in. any. for. part of. waterway due. any other reason,. of channel, then. mm). like,. to. wide. mean scour depth may be.

(21) IRC:78-2014 calculated by dividing the waterway into compartments as per the concentration of flow.. 703.2.4. In. case of bridge mainly adopted as balancer, the mean scour depth. be taken as (Highest Flood Level-Lowest Bed Level) divided by. 'd sm. '. may. 1.27.. Scour depth may be determined by actual observations wherever possible. This is particularly required for clayey and bouldery strata. Soundings, wherever possible, shall be taken in the vicinity of the site for the proposed bridge and for any structures nearby. Such soundings are best during or immediately after a flood before the scour holes have had time to be silted up. The mean scour depth may be fixed based on such observations and theoretical calculation. 703.2.5. Maximum Depth. 703.3. of. Scour for Design of Foundation. The maximum depth of scour below the Highest Flood Level (HFL) for the design and abutments having individual foundations without any floor protection may be. 703.3.1 of piers. considered as follows.. 703 .3.7.7. Flood without seismic combination i). For piers. -. 2.0. dsm. ii). For abutments. -. a). .27. 1. bed b) 2.00 '. 703 3 .. 7. .. .. 2. dsm. with approach retained or lowest. level. dsm. whichever. with scour. is. all. deeper.. around.. Flood with seismic combination. For considering load combination of flood and seismic loads (together with other appropriate. combinations given elsewhere) the. be reduced by multiplying 703.3.1.3. maximum. maximum depth. of scour given. in. Clause 703.3.1 .1 may. factor of 0.9.. For low water level (withoutflood conditions) combined with seismiccombination level of. scour below high flood. level. can be assumed as 0.8 times scour given. in. Clause 703.3.1.. NOTE. :. In. respect of viaduct/ROB having no possibility of scour, resistance of. soil. considered below depth of excavation for services construction, or 2.0. ground 703.3.2. level. whichever. is. maximum. scour depth. i). In. a straight reach. ii). In. a bend. m. below. greater.. For the design of floor protection works for. following values of. may be. may be 1. .27. 1.50 11. raft. or. open foundations, the. adopted:. dsm. dsm. or on the basis of concentration of flow.

(22) IRC:78-2014. The. length of apron on upstream. may be. 0.7 times of the. same on downstream.. Special studies should be undertaken for determining the. 703.4. depth for the design of foundations. in all. situations. where abnormal. maximum. scour. conditions, such as,. the following are encountered:. a bridge being located on a bend of the river involving a curvilinear flow, or. i). excessive shoal formation, or a bridge being located at a site where the deep channel. ii). one. in. the river hugs to. side, or. iii). a bridge having very thick piers inducing heavy local scours, or. iv). where the. v). where a bridge river. obliquity of flow in the river. is. considerable, or. is. required to be constructed across a canal, or across a. downstream. of storage works, with the possibility of the relatively. clear water inducing greater scours, or. a bridge. vi). in. the vicinity of a. where concentration likely to affect. An. vii). weir,. barrage or other. irrigation structures. of flow, aggradations/degradation of bed, etc. are. the behavior of the structures.. when. additional tow-lane bridge. major. NOTE:. dam,. located near to the existing bridge, on. rivers.. These studies. shall. be conducted. for the increase. discharge calculated vide Clause. 703.1.1.. 703.5. If. a river. is. of a flashy nature. and bed does not lend. itself. readily to the. dsm and maximum depth of scour as maximum depth shall be assessed from. scouring effect of floods, the theoretical formula for. recommended. shall not apply. In. such cases, the. actual observations.. 704. SUB-SURFACE EXPLORATION. Objectives. 704.1. The i). objectives of the sub-surface exploration are:. During Preliminary Investigation Stage. As a. part of site selection process to study existing geological. information,. known data and banks,. maps and. other. previously prepared and available site investigation reports, of. nearby structures,. etc.,. which. will. help. in. if. any, surface examination about river. narrowing. 12. down. bed. of sites under consideration.

(23) IRC:78-2014 for further studies for project preparation stage.. Detailed Investigation Stage. ii). To determine the characteristics of the existing geo-materials,. bed material. in. bridge sites. such a way as. in. water courses,. etc. in. like, soil,. rock,. the zone of influence of the proposed. to establish the. design parameters which influence. the choice and design details of the various structural elements, especially the. foundation type.. During Construction Stage. iii). To confirm the characteristics of geo-materials established. in. on which the design choices are made and. same. suit. Zone. (ii). based. or modify to. the conditions met at specific foundation locations.. Zone. 704.2. to re-confirm the. stage. of influence. of Influence. mentioned. Clause 704.1. in. (ii). is. defined as the. full. length of the bridge. and part of approaches covering, (but not restricted to), the full flood zone for water courses, and upto depth below proposed foundation levels where influence of stresses due to foundation is likely to affect the behaviour of the structure, including settlement, subsidence under ground flow of water, etc. The width of the land strip on either side of the proposed structure should include zones in which the hydraulic characteristics of river water are likely to be changed affecting flow patterns, scour, etc. including portion of wing/return wall. Methods of Exploration. 704.3. A. large variety of investigative. methods are. available.. A most. suitable. and appropriate. combination of these shall be chosen. Guidelines for choice of types of investigations,. need be established, the. properties of geo-materials that. laboratory testing are given. in. in-situ. testing,. sampling,. Appendix-2. This may be further supplemented by. specialized techniques depending on the need.. 705 :. General. 705.1. The foundation evaluated. DEPTH OF FOUNDATION. in. shall. be designed. to. withstand the worst combination of loads and forces. accordance with the provisions of Clause 706. The foundations. taken to such depth that they are safe against scour or protected from. it.. shall. Apart from. be. this,. the depth should also be sufficient from consideration of bearing capacity, settlement, liquefaction potential, stability. depth below. It.. In. case. and. of bridges. suitability of strata at the. founding level and sufficient. where the mean scour depth 'dsm' 13. is. calculated with.

(24) IRC:78-2014 Clause 703.2, the depth of foundation in. the. shall not. be less than those of existing structures. vicinity.. 705.2. Open Foundation. 705.2.1. In soil. The embedment. of foundations. shail. in soil. be based on correct assessment of anticipated. scour considering the values given under Clause 703.. may be. Foundation. taken. down. provided good bearing stratum. to a. is. comparatively shallow depth below the bed surface. available,. The minimum depth. of. open foundations. but not less than 2.0. m. below the scour. 705.2.2. In. and the foundation. shall. be upto stratum having safe bearing capacity. is. bed. level or the protected. level.. rocks. For open foundations resting on rock, the depth of rock, which expert. protected against scour.. is. weathered or fissured,. the rock existing below.. shail. be excluded. Where foundations. in. in. the opinion of the geological. deciding the depth of. embedment. into. are to rest on credible rocks, caution shall be. exercised to establish the foundation level at sufficient depth, so as to ensure that they. do not get undermined, keeping for conditions stipulated. below. shall. in. view the continued erosion of the bed. After allowing. above the minimum embedment. be as follows, which. in. case of sloping rock. of the foundations into the rock. profile. can be provided by properly. benching the foundations.. Embedment depth. Type of Rock a). For rocks of moderately strong and above classification of rock (under clause 8.2 of. UCS. of. more than 12.5. core to get the. UCS. MPA or where. it. but extrapolated. is. in. table 2 of. 0.6. m. 1.5. m. appendix 2) having not possible to take. SPT N. value. is. more. than 500 b). For rock of moderately. weak and below. in. table 2 of classifi-. cation of rock (under clause 8.2 of appendix 2) having. UCS. <. 1. 2.5. MPA but. > 2.5. to take core to get the. more than 100 but. MPA or where. UCS. less than. 705.3. Wei! Foundations. 705.3.1. In soil. it. is. but extrapolated. 500. 14. not possible. SPT N. value. is.

(25) IRC:78-2014 Well foundations shall be taken. maximum depth 705.3.2. As. In. of scour. to. a depth which. below the design scour. will. provide a. level specified in. minimum. zone,. all. shall. be taken by. the. all. around the periphery on sound rock. likely. methods. to. in. each case. mentioned above. make. a. (i.e.,. sump. (shear key) of 300. Diameter of sump. minimum. .5m. 1. rock and projected 1.5. mm. in. m. embedment. The extent. may be. above. These. mm. hard rock or 600. Six dowel bars of 25. .. shall. ensure overall and long-term safety of the structure.. to. chiseling/blasting.. size of. and. be decided by the Engineer-in-charge keeping. shall. 1. .5 to. 2. pneumatic. of sinking including. be evenly. devoid of fissures, cavities, weathered. extent of erosion, etc.) by providing adequate. and embedment factors. the. Clause 703.3.. sinking (where considered necessary), dewatering, etc. to foundation level. seated. rd. grip of 1/3. rocks. as possible, the wells. far. down. m. in. It. of seating. in. is. view the. advisable. soft rock inside the well. by. less than inner dredge-hole subject to a. mm dia deformed. may be anchored. in. may be anchored. bars. minimum 65. 1. .5. m. in. mm dia boreholes and. grouted with 1:172 cement mortar.. Foundations. 705.4. Pile. 705.4.1. In soil,. minimum 705.4.2. the. minimum depth. length required for developing. In. of foundations full fixity. below the point of. as calculated by any. rocks, the pile should be taken. down. fixity. should be the. rational formula.. to rock strata. devoid of any. likely. extension of erosion and properly socketed as required by the design.. 706 LOADS, FORCES, STABILITY 706.1. AND STRESSES. Loads, Forces and their Combinations. The loads and forces may be evaluated as per IRC:6 and the purpose of this code will be as follows:. 706.1.1 for. Combination. Combination. G + (Qor GJ + Fwc + F + F. I):. f. II): i). +. b. +. G+ F. cf. +. F, ep. W+ F. wp. or wp. or ii). Combination. iii). +F +Fwp :. G. + Fwc + Gb + Fep +. 15. Fer. + Ff +. their. (WorFe q). combinations.

(26) IRC.78-2014. The permissible increase. 706.1.2. stresses. in. the various. in. members. be 33V 3. will. percent for the combination of wind (W) and 50 percent for the combination with seismic (Fe for. J. The permissible increase. or (FJ.. all. allowable base pressure should be 25 percent. in. combinations except combination. secondary effects (FJ deformation effects. i). (f. d). then permissible increase. combination with. i). bearing pressure. will. However, when temperature effects (FJ, are also to be considered for any members in in. stresses. Horizontal Forces at Bearing Level. 706.2.1. Simply supported spans. 706.2.1.1. For. supported. simply. type). various. members and. on. span with. supports,. stiff. longitudinal direction shall. fixed. be as given below. and. forces. horizontal. Fixed Bearing. at. free. the. bearings bearing. (other level. :. Free Bearing. Non-Seismic Combinations Greater of the two values given below. :. F h -fj(R+RJ. i). Seismic Combinations F,. where. Fh. - Applied horizontal force. R R. - Reaction at the free end due to dead load - Reaction at the free end due to. live. load. q. p. allowable. be 15 percent.. 706.2. Elastomeric. in. - Co-efficient of. assumed. to. friction at. have the allowable values:. ). For steel. i). For concrete. ii). For sliding bearings: a). the movable bearing which shall be. roller. bearings. roller. bearings. Steel on cast iron or steel on steel. 16. 0.03 0.05. 0.4. in. than the.

(27) !RC:78-2014 Grey cast. b). on grey cast. iron. iron. 0.3. :. (Mechanites) c). Concrete over concrete. d). Telflon. on stainless. 0.5. :. steel. 0.03 and 0.05. :. (whichever 706.2.1.2. In. case of simply supported small spans upto 10. provided, horizontal force. -Jj~. 706.2. 1.3. in. orjj(Rg) whichever. resting. =. Shear. =. Movement. r. / te. 706.2.2. and where no bearings are. is. greater sitting. on. identical eiectrometric bearings at. on unyielding supports. +. Force of each end =. V. governing). the longitudinal direction at the bearing level shall be. For a simply supported span. each end and. m. is. K4. rating of the eiectrometric bearings. of. deck above bearing, other than due. Simply supported and continuous span on. flexible. to applied forces. supports. The distribution of applied longitudinal horizontal force (e.g., braking, seismic, wind, etc.) depends solely on shear rating of the supports and may be estimated in proportion to the ratio of individual shear rating of a support to the sum of the shear ratings of all the supports. Shear rating of a support is the horizontal force required to move the top of the 706.2.2.1. support through a unit distance taking into account horizontal deformation of the bridge, flexing of the support. and. rotation of the foundation.. 706.3. Base Pressure. 706.3.1. The allowable bearing pressure and the settlement. different loads. and. testing.. and stresses may be determined on the basis. Though the help. of relevant Indian Standard. taken, the allowable bearing pressure. may be. pressure at the base without deducting the. soil. For open foundations and well foundation resting on taken as 2.5 for. 17. may be. displaced can be computed.. 706.3.. may be. of Practice. calculated as gross so that the gross. Factor of safety. pressure on ultimate bearing capacity. under. of sub-soil exploration. Code. 706. 3.1.1. 1. 1. 1. characteristics. soil,. soil.. the allowable bearing.

(28) IRC:78-2014 706.3.. 1.. 1.2. For open foundations and well foundation resting on rock, the allowable bearing. pressure on rock. may be decided upon. not only on the strength of parent rock but also on. overall characteristics particularly deficiencies, like, joints,. zones,. absence. etc. In. to. shall. in. is. to. be further. restricted to not. Clause 706.1.1. For Factor of safety. of the parent rock. may be. taken. in. over 3. case of. pile. MPa. for load. combination. (i). foundation the clause 709.3.2. be referred. The intermediate geo-materia! as. weathered. 8 unless otherwise indicated on the basis of local experience. The allowable bearing. pressure, thus, obtained. given. faults,. such details or analysis of overall characteristics, the value of. based on unconfined compressive strength. factor of safety. as 6. of. bedding planes,. like. disintegrated weathered or very soft rock. may be treated. soil.. 706.3.2. Allowable settlement/differential settlement. 706.3.2.1. The calculated. settlement between the foundations of simply. differential. supported spans shall not exceed. 1. in. 400. of the distance. between the two foundations from. the consideration of tolerable riding quality unless provision has. been made. for rectification. of this settlement.. 706.3.2.2 to. be fixed. for. to differential settlement, the tolerable limit. has. each case separately.. Permissible tension at the base of foundation. 706.3.3. 706.3.3.. case of structures sensitive. In. 1. 706.3.3.2. No. In. tension shall be permitted under any combination of loads on. case of rock. if. tension. is. found. the base area should be reduced to a size. to. be developed. where no tension. at the. will. soils.. base of foundation,. occur and base pressure. The maximum pressure on such reduced area should not exceed allowable bearing pressure. Such reduced area shall not be less than 67 percent of the total area is. recalculated.. for load. combination including seismic, or impact of barge, and 80 percent for other load. combinations.. 706. 3. 4. Factor of safety for stability. Factors of safety against overturning and sliding are given below. These are mainly relevant. 18.

(29) IRC:78-2014 for. open foundations:. values. With Seismic. Seismic Case. Case. i). Against overturning. 2. 1.5. ii). Against sliding. 1.5. 1.25. iii). Against deep-seated failure. 1.25. 1.15. Frictional co-efficient. Founding. Without. soil. in. may be. between concrete and. soil/rock will. be Tan 0,. 0. being angle of. friction.. foundation of bridge being generally properly consolidated, following. adopted:. and concrete. Friction co-efficient. between. Friction co-efficient. between rock and concrete. soil. 0.5 0.8 for. good rock and 0.7. for fissured rock. 706.3.5. Pile foundations. The allowable. load, the allowable settlement/differential settlement. determine the. same. for pile. foundations are given. 707. in. and the procedures. to. Clause 709.. OPEN FOUNDATIONS. 707.1. Genera!. 707.1.1. Provision of the Clause under 707 shall apply for design of isolated footings. and, where applicable, to combined footings, and. 707.1.2. Open foundations may be. stratum which. is. inerodible or. provided where the foundations can be. where the extent. foundations are to be reliably protected by walls or/and launching aprons as. rafts.. may be. of scour of the. means. bed. is. reliably. laid in. a. known. The. of suitably designed aprons, cut-off. necessary.. 707.2. Design. 707.2.1. The thickness. 707.2.2. Bending moments. 707.2.2.1. For solid wall type substructure with one-way reinforced footing, the bending. of the footings shall not. moments can be determined as one-way. be less than 300 mm.. slab for the unit width subjected to worst. combination of loads and forces.. For two-way. footing,. bending moment at any section of the footing. shall. determined by passing a. vertical. plane through the footing and computing the. moment. 707.2.2.2. of the forces acting over the entire. area of footings one side of the. 19. vertical plane.. be. The.

(30) IRC:78-2014 section of bending shall be at the face of the solid column.. critical. 707.2.2.3. In. circular footings or polygonal footings, the. case of. bending moments. may be determined in accordance with any rational method. Methods Timoshenko and Rowe for Plate Analysis are acceptable.. the footing. For combined footings supporting two or more columns, the. 707.2.2.4. bending moments along the axis of the columns shall be Further, for determination of critical sections for walls,. any. method. The shear. 707.2.3 is. rational. of analysis. 'd' is. 'd'. given by. sections for. at the face of the columns/walls.. bending moments between the column/. be adopted.. strength of the footing. the vertical section at a distance. critical. in. may be checked. at the critical section. which. from the face of the wall for one-way action where. the effective depth of the section at the face of the wall.. For two-way action for slab or footing, the. 707.2.3.1. perpendicular to plan of slab and so located that. approach closer than. half the effective. perimeter. its. section. critical is. should be. minimum, but need not. depth from the perimeter of concentrated load or. reaction area.. To ensure proper load. 707.2.4. width of footing equal to 1:3. is. transfer, a limiting value of ratio of. specified.. effective at the critical section shall. this, for. be the minimum depth. between the extreme edge of the footing all. Based on. at the. depth to length/. sloped footings the depth. end plus. to the critical section for. 1/3. rd. of the distance. design of the footing for. purposes.. The. 707.2.5. critical. section for checking development length of reinforcement bars. should be taken to be the vertical. section as given. planes where abrupt changes. 707.2.6. Tensile. reii. in. in. Clause 707.2.3 and also. all. other. section occur.. iforcei lent i. The tensile reinforcement shall provide a moment of resistance at least equal bending moment on the section calculated in accordance with Clause 707.2.2.. 707.2.6. to the. same. 1. 707.2.6.2. The. resisiting section. a). tensile reinforcement shall. as below:. In. one-way reinforced. calculated for b). be distributed across the corresponding. in. footing,. critical unit. reinforcement shall be. width as mentioned. two-way reinforced square. direction shall. the. in. Clause 707.2.2.1.. footing, the reinforcement extending in. be distributed uniformly across the. 20. same as. full. each. section of the footing..

(31) !RC:78-2014 c). two-way reinforced rectangular. in. footing, the reinforcement in the long. be distributed uniformly across the. direction shall. For reinforcement. full. width of the footing.. the short direction, a central band equal to the short. in. marked along the length. side of the footing shall be. portion of the reinforcement determined. of the footing. and. accordance with the equation. in. given below shall be uniformly distributed across the central band:. Reinforcement Total. Reinforcement. Where. /3. = the. in. ratio of. The remainder. band. centra!. in. 2 '. short direction. the long side to the short side of the footing. of the reinforcement shall be uniformly distributed. in. the. outer portions of the footing. d). In. the case of a circular shaped footing, the reinforcement shall be provided. on the basis of the. moments. in. critical. values of radial and circumferential bending. the form of radial and circumferential steel. Alternatively,. equivalent orthogonal grid can be provided.. The area. 707.2.7. of tension reinforcement should as per IRC: 112,. Clause number. 16.5.1.1. 707.2.8. metre. in. faces of the footing shall be provided with a minimum steel of 250. All. each. direction for. more than 300 mm. This that face,. if. 707.2.9 pier or. all. grades of reinforcement. Spacing of these bars. steel. may be. mm. shall not. 2 /. be. considered to be acting as tensile reinforcement on. required from the design considerations.. In. column. case of shall. piain concrete, brick or stone. masonry. be taken as dispersed through the footing. at. footings, the load from the. an angle not exceeding 45°. to vertical.. 707.3. Open Foundations. 707.3.1. Open. slope. is. foundations. at. may. Sloped Bed rest. Profile. on sloped bed. profile. provided the. stability of. the. ensured. The footings shall be located on a horizontal base.. 707.3.2. For the foundations adjacent to each other, the pressure coming from the. foundations. laid. on the higher. level. should be duly considered on the foundations at the. lower level due to the dispersions of the pressure from the foundation at the higher. The distance between the two foundations to. minimize. this effect taking into. at different levels. account the nature of 21. soil.. may be decided. in. level.. such a way.

(32) IRC:78-2014 707.4. Construction. 707.4. 1. The. protective. works. shall. be completed before the floods so that the foundation. does not get undermined.. Excavation on open foundations shall be done after taking necessary safety. 707.4.2. precautions for which guidance. Where. 707.4.3 to. blasting. is. may be. taken from IS 3764.. required to be. endanger adjoining foundations or other. controlled blasting, providing suitable. done. structures,. mat cover. excavation. for. in. and. rock,. is. likely. necessary precautions, such as,. to prevent flying of debris, etc. shall. be. taken to prevent any damage.. Condition for laying of foundations. 7 07 .4 .4. 707.4.4.. 1. of dewatering by levelling. pumping or depression. course of 100. 707.4.4.2 the situation. method. Normally, the open foundations should be laid dry and every available. If. it. is. of water by well point, etc.. mm thickness in M. may be. resorted. such that the percolation. foundation concrete. may be. laid. A. 10 (1:3:6) shall be provided below foundation.. determined before-hand that the foundations connot be. is. to.. is. laid. dry or. too heavy for keeping the foundation dry, the. under water only by tremie pipe.. In. case of flowing water. or artesian springs, the flow shall be stopped or reduced as far as possible at the time of placing of concrete.. No pumping. of. water shall be permitted from the time of placing of. concrete upto 24 hours after placement.. 707.4.5 All spaces excavated and not occupied by abutments, pier or other permanent works shall be refilled with earth upto the surface of the surrounding ground, with sufficient allowance for settlement. All backfill shall be thoroughly compacted and in general, its top surface shall be neatly graded.. 707.4.6. In. case of excavation. with concrete of. 707.4.6.1. If. M. the depth of. above may be. 707.4.6.2. around the footing. rock, the trenches. be. shall. filled-up. 15 grade upto top of the rock.. above the foundation portion. in. level, filled. fill. required. is. then concrete. more than. 1.5. may be filled. m. in. soft rock or 0.6. upto this level by. M. m. in. hard rock. 15 concrete and. by concrete or by boulders grouted with cement.. For design of foundation on rock. in river. 22. bridges, the design loads. and forces.

(33) IRC:78-2014 shall. be considered upto the bottom of. footing.. The. load of. need not be considered. filling. in. stability calculations. 708. WELL FOUNDATIONS. General. 708.1. deep water cannels shall comprise of properly dimensioned caissons preferably having a single dredge hole. While selecting the shape, size and type of well, the size of abutment and pier to be accommodated, need for effecting streamline flow, the possibility of the use of pneumatic sinking, the anticipated depth of foundation and the nature of data to be penetrated should be kept in view. The minimum dimensions of dredge-hole shall not be less than 3 m. In case there is deep standing water, properly designed floating caissons may be used as per Clause 708.12. Foundations supporting the superstructure located. 708.1.1. However,. in. tidal rivers,. the. number. 708.1.2 in-charge. case of larger bridges across. rivers in. channels with inland waterway. traffic. of intermediate foundations shall be. If. in. wide flood plains prone. and bridges reduced as. coastal/marine locations,. in. far. as practicable.. the external diameter of single circular well exceeds 12. may. to scour, delta/. m. then Engineer-. take recourse to any of the following: Stress. a). in. steining shall be evaluated using 3-Dimensional Finite. Method (3D FEM) or any other Stiffening by. b). suitable analytical method.. compartments may be done. Design of such stiffened wells. Element. for the single circular well.. shall call for. supplemental design and. construction specifications,. Twin D-shaped well. c). The considered when 708.1.3. may be adopted. conditions arising out of sand blow, circular well. is. if. anticipated,. should be duly. analysed using 3D FEM/suitable analytical method or. stiffened circular wells are used.. 708.1.4. Bottom plug of well should be suitably designed. force acting on. it. to resist. maximum upward. during construction following plugging as well as during. life. span of the. structure.. 708.2. Well Steining. 708.2.1. Thickness of the steining should be such so that. well without excessive kentledge. and without. 23. getting. damaged. it. is. possible to sink the. during sinking or during.

(34) IRC:78-2014 excessive. rectifying the. tilts. and. shifts.. The. steining should also. be able. earth pressure developed during sand blow or other conditions,. like,. to resist differential. sudden drop.. Stresses at various levels of the steining should be within permissible conditions for loads that. Use. may be. all. transferred to the well.. of cellular steining with. well steining shall not. under. limits. two or more shells or use of composite material 12. for wells upto. be permitted. m. in. diameter.. Steining thickness 708.2.3.1. The minimum thickness. of the well steining shall not. mm. be less than 500. and. satisfy the following relationship:. h. KdVT. =. minimum thickness. m. h. =. d. = external diameter of circular well of twin. D wells. (for floating. bed. in. smaller dimension. = depth of wells. /. of steining. in. in. dumb. plan. in. bell. shaped. '. in. case of. metres. LWL whichever. metre below top of well cap or. caisson 7. well or. may- be taken as depth. of well. in. is. more. metres below. level).. K - a constant Value of. 708.2.3.2. K shall. follows:. K = 0.03 K = 0.05 K = 0.039. cement concrete brick masonry. i). Well. in. ii). Well. in. iii). Twin. D wells. The minimum. be as. steining thickness. may be. varied from. above. in. following. conditions:. Strata. a). Very. b). Hard clay. c). Boulder strata or well resting on. soft clay strata. strata. Variation from. f. be. Recommended. minimum. variation upto. Reduced. 10%. Increased. 10%. Increased. 10%. rock involving blasting. 24.

(35) SRC:78-2014 However, following aspects may also be considered depending on the. 708.2.3.3. Very soft clay strata: Main. a). criteria for. to prevent the well penetrating. so reduced, the steining. shall. by. its. reduction. own. in. weight.. strata:. steining thickness. When. be adequately reinforced,. the thickness. is is. to get sufficient. strength.. Hard clay. b). in. Depending on the previous experience, the increase steining thickness may be more than 10 percent. strata:. Bouldery strata or well resting on rock involving blasting: higher. c). grade of concrete, higher reinforcement, use of portions, etc., may be adopted.. The recommended values given. 708.2.3.4. based on. local. 708.2.3.5. If. experience and specialised. in. Clause 708.2.3.2 can be further varied. accordance with decision of Engineer-in-charge.. methods. then the steining thickness. in. steel plates in the lower. of sinking,. may be. such. down method,. as, jack. are adopted. adjusted according to design and construction. requirements.. Any. 708.2.3.6. variation from. dimensions as proposed. in. Clause 708.2.3.1 should be. decided before framing the proposal.. When. 708.2.3.7. the depth of well below well cap. is. equal to or more than 30 m, the. thickness of the steining of the well calculated as per Clause 708.2.3. above scour. a slope of. level in. 1. may be reduced. horizontal to 3 vertical such, that the reduced thickness of. the steining should not be less than required as per Clause 708.2.3 for the depth of well. upto scour level with the reduced diameter.. The reduction. in. thickness shall be done. the outer surface of the well. in. The diameter. of. inner dredge hole shall be kept uniform.. The minimum steining. steel. and the concrete grade. below scour. in. the slope portion shall be. for the. level.. Minimum development length of all the vertical steel bars minimum section as shown in the Appendix-3 (Fig. 1). The stress. same as. shall. be provided beyond the. the reduced section of steining shall also be checked.. in. 708.3. Design Considerations. 708.3.1. The. external diameter of the brick. 25. masonry wells. shall not. exceed 6 m. Brick.

(36) IRC:78-2014 masonry wells. for. m. shall not. be permitted.. For brick masonry wells, brick not less than Grade-A having strength not less than. 708.3.2. 7MPa- conforming. to IS. 1077. be used. shall. cement mortar not leaner than. in. 1:3.. For plain concrete wells, vertical reinforcements (whether mild steel or deformed. 708.3.3 bars). depth greater than 20. the steining shall not be less than 0.12 percent of gross sectional area of the actual. in. The. thickness provided. This shall be equally distributed on both faces of the steining.. vertical. reinforcements shall be tied up with hoop steel not less than 0.04 percent of the volume per. as shown. unit length of the steining,. in. the. Appendix-3. (Fig. 2).. case where the well steining is designed as a reinforced concrete element, it shall be considered as a column section subjected to combined axial load and bending. However, the amount of vertical reinforcement provided in the steining shall not be less than 0.2 percent (for either mild steel or deformed bars) of the actual gross sectional area 708.3.4. In. of the steining.. On. minimum. the inner face, a. be provided. The transverse reinforcement. column but. with the provisions for a. in. no case. in. of 0.06 percent (of gross area) steel shall. the steining shall be provided shall. in. accordance. be less than 0.04 percent of the volume. per unit length of the steining.. The. horizontal annular section of well steining shall also. be checked. for ovalisation. moments. by any rational method taking account of side earth pressures evaluated as per Clause 708.4.. The. 708.3.5. vertical. bond rods. of the cross-sectional area 1. 50. mm x. 1. and. 50 mm. These rods. of the steining. and. shall. be. unit length of the steining.. in. brick. be encased. shall. shall. masonry. into. cement concrete. 15 mix of size. The hoop. steel shall. mm wide and. in. be provided. the middle. volume per. in. a concrete band at spacing of 4. is. less.. The. horizontal. RCC. bands. mm high, reinforced with bars of diameter not less 10 mm placed at the corners and tied with 6 mm diameter stirrups at 300 mm centres, as. shall not. shown. in. 708.3.6 tensile in. M. steel not less than 0.04 percent of the. times of the thickness of the steining or 3 metres, whichever. than. of. be equally distributed along the circumference. up with hoop. tied. steining shall not be less than 0.1 percent. be less than 300. the Appendix-3 (Fig.. The stresses. in. 50. 3).. well steining shall. and compressive stresses are. the area of reinforcement or. 708.4. Stability of Well. 708.4.1. The. stability. 1. in. likely to. be checked. at. such. critical. sections where. be maximum and also where there. is. change. the concrete mix.. Foundations. and design. of well foundations shall be. 26. done under the most critical.

(37) IRC:78-2014 combination of loads and forces as per Clause 706. The pressure on foundations shall satisfy the provisions of Clause 706.. Side earth resistance. 708.4.2. The side earth resistance may be calculated as per guidelines given Appendix-3. The use of provisions IRC:45 may be used for pier well foundations 708.4.2.1. cohesionless. on. rock.. If. in. soil.. The. 708.4.2.2. in. side earth resistance shall be ignored. rock strata. is. in. case of well foundations resting. such that the allowable bearing pressure. the side earth resistance. may be. taken. into. 708.4.3. Earth pressure on abutments. 708.4.3.1. If. is. less than. 1. then. IVIPa,. account.. the abutments are designed to retain earth and not spilling. in front,. the. foundations of such abutments shall be designed to withstand the earth pressure and horizontal forces for the condition of scour depth. and 2 d sm with scour. all. around.. case of scour. In. However, where earth. 708.4.3.2 front, relief. due. in. all. front of 1.27 d. around,. live. sm. load. may. from the approaches. spilling. to the spilling earth in front. may be. with approach retained. is. not. be considered.. reliably protected in. considered from bottom of well cap. downwards. 708.4.4 708.4.4. is. Construction stage Stability of the well shall also. 1. no superstructure and the well. current and/or. full. is. be checked. subjected to design scour,. design earth pressure as. in. During the construction of wells. 708.4.4.2 or has not. been plugged, the wells are. current upto. scour. This. full. may. for the construction. when. there. pressure due to water. the case of abutment wells.. when. likely to. result in. full. stage. tilting,. it. has not reached the founding. be subjected sliding. and. to. full. shifting.. level. pressure due to water. As a. part of the safety. during construction, this should be considered and safety of well must be ensured by suitable methods,. 708.5. Tilts. 708.5.1. As. However, a which. will. tilt. where. and. far. of. 1. required.. Shifts. as possible, the wells in. 80 and a. cause most severe. shift of. 1. 50. effect shall. shall. be sunk plumb without any. tilts. and. shifts.. mm due to translation (both additive) in a direction be considered. 27. in. the design of well foundations..

(38) IRC:78-2014 708.5.2. If. the actual. have to be resorted. and. tiits. shifts. exceed the above. to bring the weli within that limit.. If it. is. limits,. then the remedial measures. not possible then. its. effect. on bearing. pressure, steining stress and other structural elements shall be examined, and controlled. if. span length. The Engineer-in-charge may like to specify the maximum tilts and shifts upto which the well may be accepted subject to the bearing pressure and steining stress being within limits, by changing the span length if needed, necessary and feasible, by resorting. and beyond which the Cutting. 708.6. weli will. change. to. in. be rejected irrespective of the. result of. any modification.. Edge. be strong enough and not less than 40 kg/m to facilitate sinking of the well through the types of strata expected to be encountered without suffering any damage. It shall be properly anchored to the well curb. For sinking through 708.6.1. The. rock, cutting. edge should be. 708.6.2. When edge. cutting. of the outer. of the middle. stems. to. more compartments. stems of such wells. prevent rocking, as shown. Well Curb. 708.7.1. The. is. shall. suitably designed.. there are two or. 708 J. well. edge. mild steel cutting. well curb should. be such that. it. shall in. the. in. a well, the lover end of the. be kept about 300. Appendix-3. will offer. the. mm. above. that. (Fig. 2).. minimum. resistance while the. being sunk but should be strong enough to be able to transmit superimposed loads. from the steining to the bottom plug.. The shape and the. 708.7.2 2). may be. (Fig. 2). dimension of the curb as given. outline. taken for guidance. The internal angle of the curb. should be kept at about 30° to 37° and. may be. 'as'. in. Appendix-3. as shown. in. (Fig,. Appendix-3. increased or decreased based on. past experience and geotechnica! data.. The. 708.7.3. well curb shall invariably. than. M. shall. be suitably arranged. and. in. be. in. reinforced concrete of mix not leaner. 25 with minimum reinforcement of 72 kg/cum excluding bond rods. The to. prevent spreading and. splitting of. In. case blasting. is. anticipated, the inner faces of the well curb shall. protected with steel plates of thickness not less than 10 If. it. dia. mild. upto the top of the well. to. 6. mm. for that. increased height.. In. any case,. more than 3 metres unless there. this extra height of the. a specific requirement.. The. such a case should be provided with additional hoop reinforcement of 10. mm. steel should in. mm. be. desired to increase the steel lining above the well curb then the thickness. is. can be reduced. curb. the curb during sinking. service.. 708.7.4. curb.. steel. not be. steel. height of 3. m. or deformed. bars at. into the well steining. 150. mm. above the 28. is. centres which shall also extend curb. Additional reinforcement. upto a. above. this.

(39) iRC:78-2014 height upto two times the thickness of steining should be provided to avoid cracking arising out of. sudden change. 708.8. Bottom Plug. 708.8.1. The bottom plug. lower than 300. bottom plug,. shall. it. be ensured that. 3. fill-up all cavities.. still. wells. and the top. 1. 50. shall. shown. shall. be kept not. the. Appendix-3. in. edge. Before concerting the. inside faces. have been cleaned thoroughly.. bottom plug. shall. its. in. level of the cutting. have a minimum cement content. mm to permit easy flow of concrete through termie to be. laid in. one continuous operation. it. shall. colcrete, e.g., concrete. ail. any dewatering. is. if. is. till. dredge hole. is. used, the grout mix shall not be. be ensured by suitable means, such. that the grout filis-up. 708. 8.4. as, controlling the rate of. interstices upto the top of the plug.. required. it. shall. be carried out. after 7. days have elapsed. bottom plugging.. 708.9 708.9.1 with. in al!. to curtailment of plate.. For under water concreting, the concrete shall be placed by tremie. case grouted. in. leaner than 1:2 and. after. due. water condition and the cement content of mix be increased by 10 percent.. 708.8.3. pumping. of about. Concrete. to required height.. under. be below the. shall. 330 kg/m and a slump. filled. be provided. shall. The concrete mix used. 708.8.2. place. the effective section. the centre above the top of the curb as. in. A suitable sump. (Fig. 2).. of. mm. in. Filling. The. the Well. of the well,. filling. if. considered necessary, above the bottom plug shall be done. sand or excavated material free from organic matter.. 708.10. Plug over. 708.10.1. A 300. 708.11. Weil. 708.11.1 the active. Filling. mm thick plug of M. 15 cement concrete shall be provided over the. filling.. Cap. The bottom of well cap shall be laid as low as possible but above the LWL in channel. Where the bed level is higher than LWL the bottom of well cap may be. suitably raised.. 708.11.2. As many. longitudinal bars. anchored. into the well cap.. 708.11.3. The design. of the well. cap. as possible coming from the well steining. shall. be based on; any accepted. considering the worst combination of loads and forces as per Clause 706.. 29. rational. shall. be. method,.

(40) IRC:78-2014 708.12. Floating Caissons. 708.12.1. Floating caissons. They should have. at least 1.5. considered necessary,. very soft strata,. 708.12.2. of steel, reinforced concrete or. metres free board above the water. any suitable. level. material.. and increased,. if. is. a possibility of caissons sinking suddenly owing to. likely to result. from lowering of caissons, effect of waves, sinking. in. reasons, such as, scour in. may be. case there. etc.. Well caissons should be checked for. stability. against overturning and. capsizing while being towed, and during sinking, due to the action of water current,. wave. pressure, wind, etc.. 708.12.3. The. proper shear transfer at the interface. 708.13. be considered as part of foundation unless. floating caisson shall not is. ensured.. Sinking of Weils. The. be sunk true and vertical. Sinking should not be started till the steining has been cured for at least 48 hours. A complete record of sinking operating including tilt and shifts, kentledge, dewatering, blasting, etc. done during sinking shall be maintained. 708.13.1. well shall as far as possible. may be. For safe sinking of wells, necessary guidance in. taken from the precautions as given. Appendix-4,. 708.14. Pneumatic Sinking of Wells. 708.14.1. Where sub-surface data. necessary. to. indicate the. need. for. pneumatic sinking,. decide the method and location of pneumatic equipment and. its. it. will. be. supporting. adapter.. 708.14.2. In. case. if. concrete steining. restricting the tension in. concrete which. For the circular wells, the tension. in. provided,. is. will. steining. it. shall. be rendered. air tight. by. not exceed 3/8 th of the modulus of rupture.. may be. evaluated by assuming. it. to. be a. thick. walled cylinder.. 708.14.3 against the. 708.14.4. The uplift. steining shall. force and,. Compressed. shall. Air".. It. at different sections for. of the. pneumatic equipment, safety of personnel. comply with the provisions of is. any possible rupture. necessary, shall be adequately strengthened.. The design requirements. and the structure in. if. be checked. IS. 4138 "Safety Code. desirable that the height of the working. chamber. caissons should not be less than 3 metres to provide sufficient head room. 30. in. for. Working. a pneumatic. when. the cutting.

(41) IRC:78-2014. embedded a short distance below the excavated level and in particular to allow blowing down. The limiting depth for pneumatic sinking should be such that the depth. edge for. is. below normal water. of water. sinking. is. proposed should not exceed 30. level upto. which pneumatic. .. Sinking of Wells by Resorting to Blasting. 708.1 5 Blasting for. proposed foundation. level to the. may be employed. with prior approval of competent authority to help sinking of well. breaking obstacles, such as, boulders or for levelling the rock layer for square seating of. wells. Blasting. may be. resorted to only. when. other methods are found ineffective.. FOUNDATION. 709 PILE 709.1. General. 709.1.1. Piles transmit the load of a structure to. competent sub-surface. by the. strata. resistance developed from bearing at the toe or skin friction along the surface or both. piles. may be. 709.1.2. required to carry. The construction. uplift. and. The. loads besides direct vertical load.. lateral. of pile foundation requires a careful choice of piling. system. depending upon subsoil conditions and load characteristics of structures. The permissible limits of total. and. differential settlement,. unsupported length of. pile. under scour and any. other special requirements of project are also equally important criteria for adoption.. 709.1.3. Design and construction. be taken from. IS. 2911 subject. :. For design and construction of piles guidance. to limitations/stipulations given in this code.. may. Appendix-5. gives the design formulae and their applicability.. 709.1.4. For piles. streams,. in. creeks,. rivers,. etc.,. the following criteria. may be. followed:. i). Scour conditions are properly established.. ii). Permanent level. In. strata.. be provided. a). soft soil or soil having. The minimum thickness. in. in. cases given below. The. While constructing the. pile. maximum. be 6. for the. full. depth of. mm. minimum thickness. liner shall. scour. aggressive material,. be used. of liner should. land, steel liners of. which following situations. sandy. at least upto. steel liner of sufficient strength shall. For bridges located. to. be provided. case of marine clay or. permanent such. steel liner should. of 6. be provided up. to. mm. shall. depth up. prevail.. foundation through very soft clay (N < 3) ,very loose. strata (N < 8), bouldery formation. 31. and artesian conditions, wherein the.

(42) IRC:78-2014 wails of boreholes cannot be stabilized by bentoniie circulation.. Where sewage leakage. b). common phenomenon. is. as well as sites with. aggressive soil/water environment. 709.1 .5. Spacing of piles and tolerances. 709.1.5.1. Spacing of piles. Where. a). pier. is. supported on multiple. solid pile cap, the. connected by frame structure or by. piles,. spacing of piles should be considered. of the ground, their behavior. in. relation to the nature. in. groups and the execution convenience. The. spacing should be chosen with regard to the resulting heave or compaction and. should be wide enough to enable the desired number of piles to be installed to the correct penetration without. damage. to. any adjacent construction or. to. the piles themselves.. For land bridges, pier may be supported on single large to. accommodate. to location of piers pile in. as weil as having strength as required by the design. The. such case. Alternatively, to pier. having diameter sufficiently. construction tolerances of pile installation with reference. should be designed to cater for the. connected. pile. pile shaft. cap which. is. maximum. eccentricity of vertical ioad. can be continued. designed. to. to act. accommodate. as a pier and get. the eccentricities due. to construction tolerances.. The. size of a. cap carrying the load from the structure. effective length of a. The spacing. ground beam,. of piles. will. friction piies,. heads, or the size and. influence type, size and spacing of piles.. be determined by many aspects mentioned above. The working. rules which are generally,. For. may. to the pile. though not always, suitable, are as follows:. the spacing centre should not be less than the perimeter of the pile or. for circular pile, three. times the diameter. The spacing of piles deriving their resistance. mainly from end bearing. may be reduced. but the distance between the surfaces of the. shafts of adjacent piies should be not less than the least width of the piles. 709. 1.5.2. Permissible tolerances for piles shall he as under: i). For vertical piles 75. mm. at piling platform level. and. tilt. not exceeding. 150; ii). 709.1.6. For raker piles tolerance of. The maximum rake. to. in. be permitted. bored. i). 1. in. 6 for. ii). 1. in. 6 for driven cast-in-situ. all. 1. 25.. in piie. piles;. piies;. 32. and. shall not. exceed the. following:. 1. in.

(43) IRC:78-2014 1. iii). in. 4. for. The minimum diameter. 709.1.7. beyond the water zone and. 709.1 .8. The. in. estimated from the. superimposed loads,. load,. piles.. for bridges. it. for river/marine bridges.. maximum. and pile capacity. at pile. cap. level,. settlement expected at two foundations for the dead. load and scour effect.. live. For bridges. on land, the diameter may be reduced upto 750 mm.. between two successive foundations taken. clayey soils shall be accounted. of preliminary design,. m. be 1.0. shall. Settlement, differential settlement. Differential settlement. may be. Precast driven. absence. for. In. The increase. in. settlement with time. of detailed calculations, for the. purpose. can be taken as not more than the maximum settlement of any of. the two foundations.. The. differential. settlement shall be limited depending upon the following functional and. structural considerations:. a). Functionally, acceptable differential settlement piers shall not. as specified b). be greater than. in. 1. in. 400. of the. between two neighboring. span. to. ensure. riding comfort,. Clause 706.3.2.1.. The allowable settlement. of a single pile considered for estimating the pile. capacity shall be arrived from correlation of the settlement of pile group to that of single pile, as per c). It. is. Clause 709.3.4.. further provided that the working load capacity of pile. based on the. sub-clause b) shall not exceed 40 percent of the load corresponding to the settlement of 10 percent of pile diameter ultimate load capacity. 709.1. is. water cement. ratio,. slump. shall. safety factor of 2.5 on. ensured).. For both Precast and cast-in-situ. .9. (i.e.. piles,. the values regarding grade of concrete,. be as follows:. Concrete Cast-in-situ by. Precast Concrete. Tremie Grade Min.. of concrete. cement contents. Max. W.C.. ratio. Slump (mm). NOTE. :. i). M. 35. M35. 400 kg/m 3. 400 kg/m 3. 0.4. 0.4. 150-200. 50-75. For improving resistance to penetration of harmful elements from. 33. soil. use of mineral.

(44) IRC78-2014 admixtures (flyash,. fume,. silica. standards) and as per IRC:112 ii). is. GGBS. conforming to respective B!S/lnternational. recommended.. marine conditions and areas exposed. In. to action of harmful chemicals, protection. of pile caps with suitable coating such as bituminous based, coal-tar epoxy based. coating. may be. not be used. in. considered. High alumina cements,. 709.2. Requirement and Steps. 709.2.1. The. initial. for. not. is. and. and load. testing:. final. i). recommended.. Design and. design of an individual. load test or by re-confirmation of actual. required,. quick setting cement) shall. marine conditions. Also when both chlorides and sulphates are present,. use of sulphate-resistant cement. initial. (i.e.. confirmation of. pile,. soil. Installation. capacity by either. its. parameters, modification of design,. adoption should pass through following steps of investigations, design. Comprehensive and detailed sub-surface. investigation. determine the design parameters of end bearing capacity,. and ii). if. lateral. Design of. capacity of pile. and. surrounding the. soil. pile. group based on. for. piles. to. friction. capacity. for specified. bearing. pile.. i). above. strata.. iii). Initial. Initial. load testing: load test on pile of same diameter as design pile for direct confirmation. of design.. The. initial. load test. is. a part of the design process confirming the expected. properties of bearing strata iv). 709.2.2. Steps. The steps. ii). and. for. iii). and the. pile capacity.. should be repeated for different types of strata met at. design and confirmation by tests are given below:. parameters assumed. i). Sub-soil exploration to reconfirm. ii). Provide for the required design capacity of. number and diameter iii). site.. of piles. in. soil. pile. in. the design.. group based on tentative. a group.. The allowable total/differential settlement of single. pile. should be based on. the considerations as per Clauses 709.1 .8 and 709.3.4. Capacity of single pile is to. be based on. static. This step along with step iv). Structural design of piles.. v). Initial. ii). load test as mentioned. formula considering ground characteristics.. may be. in. 34. iterative.. Clause 709.2.1. iii). is. for axial load capacity,.

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