MALVIYA NATIONAL INSTITUTE OF TECHNOLOGY
OF FLYOVER AT
Jaipur Development Authority (JDA) has been committed to
working for the benefit of the citizens of Jaipur with planned
implementation of development schemes and is consistently striving to take Jaipur at higher levels of progress. Jaipur is one of the most well-planned cities of its times and planned development has always been central to its ideology.
Jaipur Development Authority came into existence by the
the growing requirements of a large city in wake of the increasing population and to help give Jaipur a planned look compatible and comparable to any metropolitan city of repute. JDA was authorised powers and a green signal to speed up the development and
progressive growth of the entire city to rapidly change the face of Jaipur. To meet these important needs JDA sprang into action and started to understand the necessary needs of the city.
According to the requisites, JDA has been working towards
time-bound construction, creation and development of the western part of Jaipur based on major scientific and hi-tech strategies. Thus, Jaipur has been beautified intensively to augment the tourist attraction in the city and to raise the living standards to suit convenience of its citizens.
The major undertaking of JDA includes the following:
* Infrastructural development of Jaipur region by construction of flyovers, bridges, parking places.
* Development of commercial projects and residential schemes, etc.
* Development of basic amenities like community centres, parks, ring roads.
* Development and rehabilitation of kacchi bastis etc. * Preparation and implementation of master plan.
* Preparation and implementation of guidelines for colonisation. * Environmental development by planning and implementing roadside plantations and by developing eco-friendly schemes. * Development of rural area around Jaipur.
* Development of transport facilities like Mass Rapid
* Transport System (MRTS), Transport Nagar, and major sector roads.
According to the promises and commitments of the Rajasthan
Government, JDA has been time and again proving itself as a pioneer of development, creating a state-of-the-art city of substance. JDA has been working on widening all main roads, construction of over bridges, under bridges and flyovers to regulate the traffic on roads, minimize pollution, and ensure public convenience and safety. JDA firmly believes in bridging the gap and reaching out to its citizens and to provide them with quick and hassle-free service.
2. Components of flyover
Piers and abutments
iv) Pre-stressed concrete
Backfill and Reinforced earth wall
Construction of Flyover at Transport Nagar Circle(Jaipur)
Transport Nagar Chouraha is one of the gateways to Jaipur on junction of NH-8 (From Delhi) and NH-11 (From Agra). With the view to ease out the traffic congestion at this important junction , after evaluating various options JDA has undertaken construction of three level grade separator at the crossing. The proposal is to construct underpass towards MI Road- Agra side and flyover from Delhi side with one leg flying towards MI Road (Flyover-1) and other towards Jawahar Nagar Bypass road (Flyover-2) along with slip lanes on all the four sides. The other instruments of junction improvement along with improvement of drainage system of the area as well as for new constructed elements are part of the project. Some of the elements like Diaphragm wall, for construction of underpass, will be constructed for the first time in Jaipur and perhaps Rajasthan.
The administrative & financial sanction amounting to Rs. 71.25 Crore has been approved for the project.
M/s Span Consultants have been engaged as the consultants for the Project. The Proof check of the structural design is being done by Structural Department of Malaviya National Institute of Technology, Jaipur.
M/s Petron Supreme (JV) have been awarded work order amounting to Rs. 64.98 Crores for the project with stipulated period of completion as 24 months. The work actually commenced in the month of June.09. Presently , the work of all the three components namely Flyover-1, Flyover-2 and underpass is going on in full swing. All the piers (17 Nos.) of Flyover-1 have been completed and placing of PSC Girders has
commenced. In Flyover-2, 17 out of 19 piers have been completed. The work of retaining wall (Diaphragm wall) is also continuing in satisfactory pace. Presently, works amounting to Rs. 16.00 Crores have been completed.
The Flyover-1 from Delhi Road towards MI Road is scheduled to be completed by Sept. 10. The Flyover-2 from Delhi towards Jawahar Nagar Bypass is scheduled for completion in Dec.10. The project will be concluded with construction of Underpass towards MI Road-Agra direction by June 2011.
Project Cost : Rs 67.67 Crores
Agency : Petron Supreme (JV)
Consultant : Span Consultant Pvt Ltd.,
Date of commencement : 03.10.2008 Stipulated date of completion : 02.10.2010
1. Total Length of the Flyover 565.20 m 2. Total Length of Underpass 365.00 m 3. Vertical Clearance of Underpass 5.50 m 4. Width of Underpass 19.90 m 5. Width of Flyover 20.50 m 6. Nos. of Viaduct 1+10 Nos 7. Length of Viaduct 46.70 / 21.20 m 8. Length of both side approaches of 305.0 m
9. Type of Structure (Flyover) Box Girder in Obligatory Span/Precast PSC Girders with RCC slab on remaining spans 10 Type of Structure (Underpass) Diaphragm wall with Precast
PSC Girders and RCC solid slab
5. SOURCE OF MATERIAL:
S.No. Material Source
1. Stone aggregates Delhi Road 2. Coarse Sand River Banas
3. Cement Any ISI Marked regular brand OPC / PPC 4. Bitumen Mathura Refinery
5. Selected fill for R.E Wall
River Dund bed
6. Reinforcement Steel Any Original Manufacturer confirming to relevant IS Code
SOME IMPORTANT THINGS!!!
1) Always wear a good quality helmet on the
2) Always wear shoes on the site.
3) Wear safety belts if required.
4) Safety nets should be provided wherever it is
MAJOR COMPONENTS OF FLYOVER FOUNDATION
Since the bridge has to carry a big live load and its dead weight is also very large so we cannot go for simple foundation but pile foundation.
Pile foundation is one type of deep foundation. It is used where the good soil is at higher depth (10 or 15m) or soil having low bearing capacity. Pile is also used for tall structures. In pile foundation the load coming from the super structure is taken by pile cap and
equally distributed in no of piles, pile transfers this load into the soil. At Transport Nagar Flyover Pile foundation is proposed for piers and abutment. The piles are 1200 mm dia , 20 m depth M-35 grade cast in situ piles. The pile cap is proposed of M-35 grade.
Detailed arrangement of pile is shown in attached Bottom Plan (Courtsey:Span Consultants)
INSTALLATION PROCEDURE OF PILES
Step 1 --- Excavation of Pile Shaft
The bored pile equipment set including hydraulic oscillator, hydraulic vibrator, hammer grab and rock chisel used in this project is very common and being widely used for shaft excavation.
a. Set out the correct position of the bored pile on site. b. Excavate about 3 - 4m of the pile to remove shallow obstructions and then backfill, wherever necessary.
c. Install the bottom section of temporary casing of required diameter into the ground by oscillating and jacking or by
vibrating motion exerted by the oscillator and the vibrator respectively.
d. Set up hydraulic oscillator or vibrator in conjunction with a crawler crane.
e. Excavate within the casing by hammer grab and redrive the steel casing simultaneously by using the heavy duty casing oscillator / vibrator. Rock chisel in various types will be
employed for removal of obstruction or hard materials during the above process.
f. Extend the steel casing by bolting or welding on additional casing during the excavation.
g. Water will be pumped into the casing during excavation and constant water head will be maintained so as to prevent any ingress of material from the bottom of casing.
h. Verticality of the casing will be monitored by means of spirit level from time to time.
i. Continue the above procedure until the founding level of pile has been reached .
j. Pile base enlargement will be formed by employing a bellout
chisel or a reverse-circulation drill as indicated in the working drawings.
Step 2 --- Cleaning of Pile Shaft
Final cleaning will be carried out by the air-fitting method using high pressure air compressors. The slime and muddy water within the casing will be cleared and delivered into a desilting tank before discharge.
a. The pile shaft will be concreted by "Underwater Tremie
Technique". The tremie pipe sections will be inserted and be jointed until it reaches the bottom of pile shaft. Concrete will be poured into the tremie pipe by using a concrete skip.
Concreting will be carried out in one continuous operation until the required level has been reached.
b. As concreting proceeds, the level of the concrete relative to the ground level will be monitored by measuring with weighted tape after each skip of concrete is placed.
c. The base of the tremie pipe will be kept with a minimum depth of approximate 1 to 2m below the surface of the concrete. d. The temporary casing will be extracted simultaneously by the
oscillator in the course of concreting. A head is always maintained between the top of concrete and the bottom of steel casing.
Step 4 --- Installation of Reinforcement
After the completion of concreting, dowel bars of required length and numbers will be installed into the pile shaft and down to the predetermined level before the extraction of bottom steel casing.
PIERS & ABUTMENTS
The Transport Nagar flyover-1 has 17 piers including two abutments and Flyover-2 has 19 piers including two abutments.
The maximum height of the pier for Flyover-1 is about 9 m and for Flyover-2 is 7m .The piers are M-35 grade rectangular pullers.
Details are shown in Top Plan and Sectional Elevation (Courtsey: Span Consultants).
Piers under construction
The Superstructure is M-40 Grade Deck Slab over precast post tensioned concrete girders in M-40 Grade Concrete. Antiskid
bituminous mastic course 25 mm in thickness is proposed over RC C wearing course.
Approaches: RE wall is proposed in approaches.
Gravitational drainage backed by forced system comprising of suitable pump and appurtenances is proposed for underpass drainage.
The span length is of range of 25 m to 50 m. A typical section of superstructure
pier and pile is shown in figure.
The technique of pre-stressing eliminates cracking of concrete under all stages of loading and enables the entire section to take part in resisting moments. As dead load moments are neutralized and the shear stresses are reduced, the sections required are much smaller than in reinforced concrete.
Prestressing can be accomplished in three ways: pre-tensioned concrete, and bonded or unbonded post-tensioned concrete.
Pre-tensioned concrete is cast around already tensioned tendons. This method produces a good bond between the tendon and
concrete, which both protects the tendon from corrosion and allows for direct transfer of tension. The cured concrete adheres and bonds to the bars and when the tension is released it is transferred to the concrete as compression by static friction. However, it requires stout anchoring points between which the tendon is to be stretched and the tendons are usually in a straight line. Thus, most pretensioned concrete elements are prefabricated in a factory and must be
transported to the construction site, which limits their size. Pre-tensioned elements may be balcony elements, lintels, floor slabs, beams or foundation piles.
Bonded post-tensioned concrete
Bonded post-tensioned concrete is the descriptive term for a method of applying compression after pouring concrete and the curing
process (in situ). The concrete is cast around plastic, steel or
aluminium curved duct, to follow the area where otherwise tension would occur in the concrete element. A set of tendons are fished through the duct and the concrete is poured. Once the concrete has hardened, the tendons are tensioned by hydraulic jacks that react against the concrete member itself. When the tendons have
stretched sufficiently, according to the design specifications (see Hooke's law), they are wedged in position and maintain tension after the jacks are removed, transferring pressure to the concrete. The duct is then grouted to protect the tendons from corrosion. This method is commonly used to create monolithic slabs for house
construction in locations where expansive soils (such as adobe clay) create problems for the typical perimeter foundation. All stresses from seasonal expansion and contraction of the underlying soil are taken into the entire tensioned slab, which supports the building without significant flexure. Post-tensioning is also used in the construction of various bridges; both after concrete is cured after support by falsework and by the assembly of prefabricated sections, as in the segmental bridge.
The advantages of this system over unbonded post-tensioning are: 1. Large reduction in traditional reinforcement requirements as
tendons cannot destress in accidents.
2. Tendons can be easily 'weaved' allowing a more efficient design approach.
3. Higher ultimate strength due to bond generated between the strand and concrete.
4. No long term issues with maintaining the integrity of the anchor/dead end.
Unbonded post-tensioned concrete
Unbonded tensioned concrete differs from bonded
post-tensioning by providing each individual cable permanent freedom of movement relative to the concrete. To achieve this, each individual tendon is coated with grease (generally lithium based) and covered by a plastic sheathing formed in an extrusion process. The transfer of tension to the concrete is achieved by the steel cable acting against steel anchors embedded in the perimeter of the slab. The
main disadvantage over bonded post-tensioning is the fact that a cable can destress itself and burst out of the slab if damaged (such as during repair on the slab).
The advantages of this system over bonded post-tensioning are: 1. The ability to individually adjust cables based on poor field
conditions (For example: shifting a group of 4 cables around an opening by placing 2 to either side).
2. The procedure of post-stress grouting is eliminated.
3. The ability to de-stress the tendons before attempting repair work.
In Transport Nagar flyover the method used for pre-stressing is unbonded post tensioning system. In this system first of all high tensile steel cables/wires (also known as strands or tendons)
encased in sheathing pipes were laid as per design and then
concreting is done. After the hardening of concrete the stretching of wires was done by means of hydraulic jacks. The jacking was done from both ends. The wires were jacked a few percent above their specified initial pre-stress in order to minimize creep in steel and to reduce frictional loss of pre-stress.
The wires are anchored to concrete after stretching by wedge action producing a friction grip on wires.
PROBLEMS LIKELY TO CAUSE DURING OR AFTER CONCRETING
1. Segregation : Segregation of concrete can be defined as
separation of coarse aggregate from mortar, resulting in their non-uniform distribution. Improper mix proportion resulting in large proportion of coarse particles as compared to small proportion of fine particles caused the separation of coarse particles from mortar. Segregation is also caused by incorrect handling of mixed concrete during transportation and
placement, and also by over-compaction.
2. Honeycombing : The separation of coarse aggregate from
mortar leaves voids in coarse aggregate unfilled and this phenomenon is called honeycombing. Honeycombing causes decrease in the density of concrete and hence reduction in the strength of the concrete.
3. Bleeding : Bleeding is a form of segregation in which water in a
concrete mix rises to the surface during placing it. It is because more water is present than is necessary for the cement paste to lubricate the aggregate particles and the solid constituents of the mix are able to hold all the mixing water when they settle down. Thus the water rises up and appears on the
surface of the compacted concrete. Sometimes, finer particles such as cement are also carried with the rising water. The water trapped by the superimposed concrete results in a
porous weak and the non-durable concrete. If the rising water is trapped on the underside of reinforcement, then a zone of poor
bond is created. This water form voids on evaporation and makes the concrete weaker.
PRECAUTION TO BE TAKEN DURING PLACING OF CONCRETE: 1. Under no circumstances, the water should be added to the
concrete during its passage from mixer to the formwork 2. The formwork or the surface which is to receive the fresh
concrete should be properly cleaned prepared and well-watered.
3. As far as possible, the concrete should be placed in single
thickness. In case of deep sections, the concrete should be place in successive horizontal layers and proper care should be taken to develop enough bonds between successive layers. 4. The concrete should be thoroughly worked around the
reinforcement and tapped in such a way that no honeycombed surface appears on removal of the formwork.
5. The concrete should be place on the formwork as soon as possible.
6. During placing, it should be seen that all edges and corners of concrete surface remain unbroken, sharp and straight in line. 7. The placing of concrete should be carried out uninterrupted
between predetermined construction joints.
CONSOLIDATION OF CONCRETE:
The main aim of consolidation of concrete is to eliminate air bubbles and thus to give maximum density to the concrete.
In Transport Nagar flyover the Internal or Immersion vibrators are used for consolidation of concrete. These vibrators consist of a steel
tube which is inserted in fresh concrete. This steel tube is called the poker and it is connected to an electric motor. The poker vibrates while it is being inserted. The internal vibrators should be inserted and withdrawn slowly and they should be operated continuously while they are being withdrawn. Otherwise holes will be formed inside the concrete.
BACKFILL AND REINFORCED EARTH WALL
Reinforced earth is a composite material formed by the friction between the earth and the reinforcement. By means of friction the soil transfers to the reinforcement the forces built up in the earth mass. The reinforcement thus develops tension and the earth
behaves as if it has cohesion. Reinforced members are composed of thin wide strips also called as ties.
For reinforcement the GI strips are used which are 40 mm wide and 5 mm thick and the length varies as according to the tensile stresses at various place and levels.
The facing elements for backfill are precast concrete panels having dimension 1.5m x 1.5m with some aesthetic appearance.
The dry density of the compacted soil was kept 1.85 to 1.9 gm/cc and the moisture content was kept at 8 to 9%.
Place and compact initial lifts of select Granular backfill up to bottom row of panel tie strips. The level of the compacted backfill should be 50mm above the tie strips. In order to avoid pushing the brace
panels out of alignment, initial lifts of backfill are neither placed nor compacted against the back of the panels. Compact each backfill lift using a large smooth-drum vibratory roller except within a 100 cm zone directly behind the panels where a small hand-operated
vibratory compactor must be used to avoid undue panel movement. After compaction has taken place, check wall alignment visually and with a level adjust panels as necessary.
A drainage system is made near panels by laying 20mm coarse
aggregates near panels up to a width of 60 cm throughout the depth and at the bottom a semi perforated pipe is used to drain out the water.
Immediate gradation and moisture testing is required if either excessive panel movement or backfill pumping occurs during construction.
Compaction: Large smooth-drum vibratory rollers are used to accomplish mass compaction of backfill materials, except for fine sands.
Sheep foot rollers are never to be used for compaction of backfill.
Fine uniform sands, which contain more than 60 percent passing a 425 µ sieve used for backfill, must be compacted using a smooth drum static roller.
Vibratory compaction equipment should not be used to compact fine uniform sands.
Moisture content of backfill material during placement should be approximately 1% to 2% more than its optimum moisture content. Reinforcing Strips:-
Place reinforcing strips on the compacted backfill. Position strips perpendicular to the facing panels, unless otherwise shown on the plans. Reinforcing strips are supplied in lengths as shown on plans. Connect each reinforcing strip to the embedded panel tie strip by inserting the end of the reinforcing strip into the gap between the two exposed ends of the tie strip. Match the three holes and push a bolt through the holes from below, threading on a nut and
Dump backfill onto the reinforcing strips so that the toe of the
backfill pile is 3-4 ft from the panels. Spread the backfill by pushing the pile parallel to the panels.
Metal tracks of earthmoving equipment must never come in contact with the reinforcing strips. Rubber-tired vehicles, however, can
operate directly on the exposed strips if backfill conditions permit and care is exercised.
At the joints of panels a special type of semi permeable textile
known as geo-textile is used to stop the backfill from slipping out of the panels.
Spreading of backfill
In the above picture we can see the arrangement of panels. No binding material is used to join the panels they are interlocked with each other.
The underpass is proposed to be constructed with diaphragm wall, 600 mm width in M-35 grade concrete for retaining of earth. The Damp proofing course comprise of two layers of Tapecrete (or approved equivalent) acrylic based polymer
modified cementitious coating. The Superstructure will consist of precast post tensioned concrete girders in 40 Grade Concrete. The Deck will be casted in M-40 Grade mix and is 250 mm in thickness. Antiskid bituminous mastic course 25 mm in thickness is proposed over RC C wearing course.
Construction of Diaphragm Wall
Diaphragm walls are underground structural elements commonly used for retention systems and permanent foundation walls. They can also be used as deep groundwater barriers.
Diaphragm walls are constructed using the slurry trench technique. The technique involves excavating a narrow trench that is kept full of an engineered fluid or slurry. The slurry exerts hydraulic pressure against the trench walls and acts as shoring to prevent collapse. Slurry trench excavations can be constructed in all types of soil, even below the ground water table.
Diaphragm walls are commonly used in congested areas. They can be installed in close proximity to existing structures with
minimal loss of support to existing foundations. In addition,
construction dewatering is not required, so there is no associated subsidence.The cut and cover method is used to construct tunnels. Two parallel diaphragm walls are installed and the area between the walls is excavated. Floor and roof slabs are poured and area above the roof is backfilled.
At transport nagar Flyover Cast-in-place method of construction of diaphragm wall is used.Cast-in-place diaphragm walls are usually excavated under bentonite slurry. Various types of excavation
equipment can be used depending on project conditions, including hydraulic excavators and kelly-mounted or cable-hung clam buckets. Depths in excess 150 feet are possible. (The Hydrofraise, a highly specialized excavation tool, can reach depths of 500 feet.)
Excavation with the help of grab at site.
Diaphragm wall construction begins with the trench being excavated in discontinuous sections or "panels". Stop-end pipes are placed
vertically at each end of the primary panel to form joints for adjacent secondary panels. Panels are usually 8 to 20 feet long, with widths varying from 2 to 5 feet.
Once the excavation of a panel is complete, a steel reinforcement cage is placed in the center of the panel. Concrete is poured in one continuous operation through one or more tremie pipes that extend to the bottom of the trench. The tremie pipes are extracted as the concrete rises; however, the discharge end of the tremie pipe always remains embedded in the fresh concrete.
Diaphragm wall reinforcement & concreteing
Installation of Reinforcement Frame for diaphragm wall
The slurry that is displaced by the concrete is saved and reused for subsequent panel excavations. As the concrete sets, the end pipes are withdrawn. Similarly, secondary panels are constructed between the primary panels to create a continuous wall. The finished wall may be cantilever or require anchors or props for lateral support.