3 Design types and applications for BOMAG compaction technology
1.1 Soil groups under engineering aspects
Classification attributes:
For the description of engineering properties and their suitability according to DIN 18196 all soil types are classified in groups of almost identical material structure and similar characteristics.
The attributes of these groups are purely of mate-rial nature: Particle size fractions according to DIN 4022 (Tab. 2), mass proportions of particle size fractions, plastic characteristics, organic and cal-careous components.
The groups are identified by two identification char-acters each. The first character identifies the main soil types and the second character the properties of highest importance for engineering purposes. In case of fine particle soil types this is the degree of plasticity, for mixed particle soils the type of fine particle additives (silt, clay) and for coarse particle soil types the curve of the particle size distribution determined by the uniformity coefficient U and the curvature coefficient C.
The properties of the soil types within the corre-sponding group change due to various parameters, such as water content level of density.
Soils are classified by application of visual and manual testing methods, identical with those described in DIN 4022. Laboratory tests are sup-plementary used if visual and manual evaluations are not sufficient, and additionally particle size distribution (DIN 18123), consistency limits (DIN 18122), ignition loss and lime content.
Range/ Designation Symbol Particle size range
mm
Blocks Y 200
Stones X > 63 to 200
Gravel particles G > 2 to 63
Coarse gravel gG > 20 to 63
Coarse particle range Medium grav. mG > 6.3 to 20
(sieve particles) Fine gravel fG > 2.0 to 6.3
Sand particles S > 0.6 to 63
Coarse sand gS > 0.6 to 2,0
Medium sand mS > 0,2 to 0,6
Fine sand fS > 0,06 to 0,2
Silt particles U > 0,0002 to 0,06
Coarse silt gU > 0,02 to 0,06
Fine particle range Medium silt mU > 0,006 to 0,02
(Sediment particles) Fine silt fU > 0,002 to 0,006
Clay part. (finest) T < 0,002 Table 2: Particle size ranges acc. to DIN 4022
Part 2
Coarse particle soils:
Coarse particle soils are classified according to their fine particle fraction passing 0.06 mm sieve (less than 5%), the sand or gravel fraction and the particle size distribution (Fig. 41).
The particle size distribution is assessed on the basis of the cumulative proportions of the particle fractions and by means of the uniformity coefficient U and the curvature coefficient C. The prerequisites for a wide graded particle size distribution are met if U > 6 und 1 < Cc < 3
In all other cases the particle size distribution is a close or intermittently graded distribution.
Main group d in mm Group Symbol
< 0,06 > 2,0
coarse particle < 5% > 40% Gravel, gravel-sand mixture GE GI GW
soils < 40% Sand, sand-gravel mixture SE SI SW
Particle <0,06mm:
5-40% > 40% Gravel-silt mixture 5-15% GU
15-40% GU
mixed particle Gravel-clay mixture 5-15% GT
soils 15-40% GT
< 40% Sand-silt mixture 5-15% SU
15-40% SU
Gravel-clay mixture 5-15% ST
15-40% ST
> 40% Silt Ip < 4%1): light plastic WL < 35% UL
medium plastic > 35-50% UM
distinct plastic > 50% UA
fine particle Clay Ip > 7%2): light plastic WL < 35% TL
soils medium plastic > 35-50% TM
distinct plastic > 50% TA
organogenic soils > 40% Silt Ip > 7%3) WL = 35-50% OU
soils with Clay Ip > 7%3) WL = 50% OT
organic < 40% coarse, mixed particle soils with humus, OH OK
admixtures calcarous, siliceous admixtures
Peat, not to slightly decomposed Z = 1-54) HN
organic soils Peat, decomposed Z = 6-10 HZ
Mud F
Filling Soil [...]
Foreign substances A
1) or below A-line 2) and above A-line 3) and below A-line 4) Z Degree of decomposition Table 3: Engineering soil groups acc. to DIN 18196 (main groups)
Part 2
Plasticity diagram (DIN 18196) Fig. 42
Examples of particle size distribution curves Fig. 41
Compaction of soil and rock in earthwork
Fine particle soils:
Fine particle soils are classified by the plastic prop-erties of the fines passing sieve 0.06 mm; the sub-stantial criterion is the plasticity, weighted on the basis of the water content at the liquid limit wL and the plasticity index IP = wL - wPPP. Basis for the clas-sification is the plasticity chart in Fig. 42.
The higher the water content of a fine particle soil, the less dimensionally stable is its mass or the easier it can be deformed. In this respect the soil is differentiated according to various states (of con-sistency):
Consistency Characteristic
solid breaks brittle
semi-solid crumbles when rolled
stiff kneadable
soft easily kneadable
pasty swells out between the fingers liquid not dimensionally stable The states are by standard defined by means of test specific limiting water contents and classified with the help of identification numbers IC and IL (Fig.
43 and table 4).
Mixed particle soils:
Mixed particle soils (mixed soils) contain propor-tions of fine particle material, sand and gravel. The fine particle component is differentiated in silt and
clay with proportions of 5 to 15% passing sieve 0.06 mm and from more than 15 to 40%.
In dependence on the proportional composition and plasticity of the fine particle component the properties of mixed particle soils are classified between a cohe-sive and a non-cohecohe-sive soil mechanical performance.
The limiting value of 15% approximately marks the transition. Below this value the coarse particle frac-tions form a supporting granular skeleton, which has a substantial effect on the properties of the soil.
This is actually a fluid transition within a range of 10 to 40% particles passing sieve 0.06 mm. The 40%-proportion separates the mixed particle from the fine particle soil types.
Organogenic and organic soils:
Organogenic soils and soils with organic admix-tures are classified according to the plasticity chart, as far as they are silts or clays; according to Fig.
42 they are located below the A-curve. In case of coarse and mixed particle soils a differentiation is made on the basis of the type of admixtures (humus, calcareous, siliceous).
Conditions Fig. 43
Conditions in the Liquidity index IL Consistency index IC plastic range w – wP wL – w Table 4: Definition and classification of conditions
wL- wP
IL = IP = 1 - IC IC = IP
wL – w
=
Part 2
Characteristics (solely of fractions > 76.2 mm) Group Typical
symbol designations
Pure gravels Non-uniform particle GW „Well“ graded gravels and
less than structure, „well“ graded gravel-sand mixtures
5% One particle size pre- GP „Poor“ graded gravels
Gravels more <0,074 mm dominant, „poor“ graded and gravel-sand
than 50% of mixtures
coarse fract. Contaminated Silty gravel:
>4.8 mm gravels The fine particle fraction GM „poor“ graded
more than is silty sand-silt mixtures
Coarse soils 12% The fine particle fraction GC Clayey gravel: „poor“
more than <0.074 mm is clayey graded gravel-sand-clay
50% of soil mixtures
>0.074 mm Pure sands Non-uniform particle SW „Well“ graded sands and
less than structure, „well“ graded sand-gravel mixtures
5% One particle size pre- SP „Poor“ graded sands
Sands more <0.074 mm dominant, „poor“ graded and sand-gravel
than 50% of mixtures
coarse fract. Contaminated The fine particle fraction SM Silty sands:
<4.8 mm sands is silty „poor“ graded
more than silt mixtures
12% Clayey sands: „poor“
<0.074 mm The fine particle fraction SC graded sand-clay
is clayey mixtures
Silts and very fine sands,
rock flour, silty or clayey
The fine particle fraction ML fine sands with low
is silt plasticity
Weak plastic silts Clays with low to medium
and clays plasticity
Liquid limit <50% The fine particle fraction CL gravelly or sandy clays,
Fine soils is clay silty clays,
more than light clays
50% of soil Organic silts and
<0.074 mm OL organic silt-clays
with low plasticity
Silts and silty soils
The fine particle fraction MH with medium to high
Plastic and highly plastic is silt plasticity
silts and clays The fine particle fraction CH Clays with very high
Liquid limit >50% is clay plasticity
OH Organic clays with
medium to high
plasticity
Highly organic soils Dark color, odour, Pt Peat and other strongly
spongy feel, fibrous organic soils
texture
Table 5: Soil classification „Unified Soil Classification System“ (USA)
Compaction of soil and rock in earthwork
USC-System:
The engineering soil groups in DIN 18196 comply to a great extent with the internationally used Uni-fied Soil Classification (USC-System) of the US Bureau of Reclamation (Tab. 5) and the AASHO-classification (Tab. 6). See also T 2, para. 1.4.3.3.
Table 6: Soil classification AASHO* (USA)) 1.2 Earth engineering classification
(DIN 18300)
Purpose of classification:
The classification is used for uniform tenders and accounting of quantities as well as for the planning and cost calculation for work and the use of machines. Soil and rock types are classified accord-ing to their level of difficulty duraccord-ing work. The term
„work“ includes the work processes: loosening, loading, conveying, placing and compacting.
Classification characteristics:
The classification is based on soil and rock mechan-ical characteristics, independent from equipment technological performance values. For the level of difficulty for work the following essential criteria are used:
*American Association of State Highway Officials
AASHO A-1-b A-1-a
Classification A-2-7 A-2-6 A-2-5 A-2-4
A3
A4
A5
A6
A-7-6 A-7-5
Unified Soil
Classification GW
OH CH GM-u GM-d
MH OL GC
CL SW
ML SM-d
SC
SM-u GP
SP
Classification Broken
by sight cohesive soils Sand Gravel material
Shrinkage cracks large medium missing
Vegetation rich strong medium light poor to non existent
Condition if saturated with water very soft soft changing solid
Condition dry solid changing rolling
Part 2
a) granulometric sizes: Fines passing sieve 0.06 mm, stones retained on sieve 63 mm, rocks > 0,01 and 0,1 m³
b) plastic properties of the fines
(plasticity index IP, consistency index IC, tenacity)
c) water retaining properties and flow characteristics
d) mineral-chemical coherence (cementation)
e) Strength of rock material acc. to qualitative characteristics
Classification:
Soil and rock are classified into 7 classes with respect to their condition during loosening. Topsoil is listed as an own class with respect to its special treatment, irrespective of its condition during loos-ening.
Class 1: Topsoil
Uppermost layer in the soil profile containing also humus and soil inhabiting life forms, besides e.g.
mixtures of gravel, sand, silt and clay.
Class 2: Flowing soil types
Soil types of liquid or pasty consistency and difficult to drain.
Class 3: Light to loosen soil types
Non-cohesive to slightly cohesive sands, gravel and sand-gravel mixtures containing up to 15% admix-tures of silt and clay (particle sizes passing sieve 0.06 mm) and maximum 30% rocks retained on sieve 63 mm up to a volume of 0,01 m³.
Organic soil types with a low water content. e.g.
solid peat.
Class 4: Moderately difficult to loosen soil types Mixtures of sand, gravel, silt and clay with more than 15% of particles passing sieve 0.06 mm.
Cohesive soils of light to moderate plasticity, which are soft to semi-solid, depending on water content,
and contain maximum 30% rocks retained on sieve 63 mmup to a volume of 0.01 m³.
Class 5: Difficult to loosen soil types
Soil types of classes 3 and 4, however, with more than 30% rocks retained on sieve 63 mm up to a volume of 0.01 m³.
Non-cohesive and cohesive soils with maximum 30% rocks of more than 0,01 m³ to 0,1 m³ in volume.
Distinct plastic clays of soft or semi-solid consist-ency, depending on the water content.
Class 6: Easy to loosen rock and comparable soil types
Rock types with an inherent mineral bonded coher-ence which are, however, excessively jointed, brit-tle, crumbly, slaty, soft or weathered, as well as comparable solid or stabilised cohesive or non-cohesive soils resulting from e.g. desiccation, freez-ing, chemical bonding.
Non-cohesive and cohesive soils with more than 30% of rocks bigger than 0.01 m³ to 0.1 m³ in volume.
Class 7: Difficult to loosen rock
Rock types with an inherent mineral bonded coher-ence and a high structural strength and which are hardly jointed or weathered.
Firmly bedded, non-weathered clay shale, gompho-lite shale, slag piles from steel works and similar.
Rocks with a volume of more than 0,1 m³.
Compaction of soil and rock in earthwork
1.3 Geotechnical suitability of the soil types (Lit. 23)
1.3.1 Material and engineering properties
For soil groups with almost identical soil mechani-cal characteristics DIN 18196 contains information about the assessment of their engineering suitabil-ity.
In connection with the engineering assignment in Tab. 7, Fig. 44 shows the general assignment of the substantial soil mechanical properties.
Compactibility(V) Compaction level DPr
Packing density D Opt. water content
Plastic properties Plasticity, mineral-chemical
composition, water content, consistency Granulometric properties
Particle size range Particle shape Particle roughness
Soil / rock Coarse Fine or mixed particle particle
Compressibility (Z) Deformation modulus EV
Stiffness index ES, swelling index Porosity (D) Shearing resistance (S) friction angle, cohesion
Erosion susceptibility (E) Frost
susceptibility (F) Water
susceptibiloity (W)
Interrelationship between material and engineering properties Fig. 44
Slopes (cut, embankment,
excavation pit) S-V-D-E-W-F
Road subgrade Z-S-V-W-E-F
Road embankment (foundation) Z-S-V-W-F Embankment subgrade (to a depth of 1.0 m)
Z-S-V-W
Foundation for embankments and bridges
Z-S-V-D
Back filling (bridges, constructions, pipelines and
cables) S-V-D
Earthroads and construction roads, base courses
S-V-W-E-F
Table 7: Engineering assignment of soil character-istics
Part 2
In contrast to the purely organic soils of groups HN, HZ and F, the soils of groups OU, OT, OH and OK (organogenic soils and mineral soils with organic admixtures) can only be used to a limited extent as material for earthworks, if their suitability has been exactly verified in an object and purpose related manner.
In general the soil parameters must be determined and applied on the basis of laboratory and field tests. For these investigations the state of the respective soil type and its possible change must be duly considered.
The standard or informative experience values in E DIN 1054 can be applied for the determination of characteristic soil parameters for non-cohesive and cohesive soils, if an exact assignment to the soil types of DIN 18196 is available and the condi-tions or limitacondi-tions for the use of table 8a/8b and 9a/9b according to E DIN 1054 has been taken into account.
Soil type Symbol Packing Unit weight
acc. to soil moist saturated under buoyancy
DIN 18196 γk γk γ‘k
[kN/m3] [kN/m3] [kN/m3]
Gravel, gravel sand, sand GE, SE lose 16.0 18.5 8.5
tightly graded with U<6 med. dense 17.0 19.5 9.5
dense 18.0 20.5 10.5
Gravel, gravel sand, sand GW, GI, SW, SI lose 16.5 19.0 9.0
widely or intermittendly with 6<U<15 med. dense 18.0 20.5 10.5
graded dense 19.5 22.0 12.0
Gravel, gravel sand, sand GW, GI, SW, SI lose 17.0 19.5 9.5
widely or intermittendly with U>15 med. dense 19.0 21.5 11.5
graded dense 21.0 23.5 13.5
Table 8a: Experience values for the unit weight of non-cohesive soils (normative)
Soil type Symbol Packing Friction angle
acc. to φk
DIN 18196 [°]
Gravel, gravel sand, sand GE, SE, GI lose 30.0 - 32.5
tightly, widely or intermittendly SE, SW, SI medium dense 32.5 - 37.5
graded dense 35.0 - 40.0
Table 8b: Experience values for the shearing strength (informative)
Compaction of soil and rock in earthwork
Soil type Symbol Condition Unit weight under
acc. to soil moist saturated buoyancy
DIN 18196 γk γk γ‘k
Silt soils
Anorganic cohesive soils with UL soft 17.5 19.0 9.0
lightly plastic properties stiff 18.5 20.0 10.0
(wL<35%) semi-solid 19.5 21.0 11.0
Anorganic cohesive soils with UM soft 16.5 18.5 8.5
medium-plastic properties stiff 18.0 19.5 9.5
(50%>WL>35%) semi-solid 19.5 20.5 10.5
Clay soils
Anorganic cohesive soils with TL soft 19.0 19.0 9.0
lightly plastic properties stiff 20.0 20.0 10.0
(wL<35%) semi-solid 21.0 21.0 11.0
Anorganic cohesive soils with TM soft 18.5 18.5 8.5
medium-plastic properties stiff 19.5 19.5 9.5
(50%>WL>35%) semi-solid 20.5 20.5 10.5
Anorganic cohesive soils with TA soft 17.5 17.5 7.5
highly plastic properties stiff 18.5 18.5 8.5
(wL>50%) semi-solid 19.5 19.5 9.5
organic soils
Organic silt OU a. OT pasty 14.0 14.0 4.0
Organic clay soft 15.5 15.5 5.5
stiff 17.0 17.0 7.0
Table 9a: Experience values of unit weight for cohesive and organic soils (normative)
Soil type Symbol Condition Shearing strength
acc. to Friction Cohesion
DIN 18196 φk Clk Cluk
[°] [kN/m2] [kN/m2]
Silt soils
Anorganic cohesive soils with soft 0 5 - 60
lightly plastic properties UL stiff 27.5 - 32.5 2 - 5 20 - 150
(wL<35%) semi-solid 5 - 10 50 - 300
Anorganic cohesive soils with soft 0 5 - 60
medium-plastic properties UM stiff 22.5 - 30.0 5 - 10 20 - 150
(50%>WL>35%) semi-solid 10 - 15 50 - 300
Clay soils
Anorganic cohesive soils with soft 0 - 5 5 - 60
lightly plastic properties TL stiff 22.5 - 30.0 5 - 10 20 - 150
(wL<35%) semi-solid 10 - 15 50 - 300
Anorganic cohesive soils with soft 5 - 10 5 - 60
medium-plastic properties TM stiff 17.5 - 27.5 10 - 15 20 - 150
(50%>WL>35%) semi-solid 15 - 20 50 - 300
Anorganic cohesive soils with soft 5 - 10 5 - 60
highly plastic properties TA stiff 18.5 10 - 20 20 - 150
(wL>50%) semi-solid 19.5 50 - 300
Organic soils
Organic silt OU a. OT pasty 0 2 - 20
Organic clay soft 17.5 - 22.5 2 - 5 5 - 40
stiff 5 - 10 20 - 150
Table 9b: Experience values for the shearing strength (informative)
Part 2
1.3.2 Geotechnical suitability for earthwork
1.3.2.1 Clays and silts
The suitability of fine particle soils for embankments depends on the load applied by the earth moving operations, the stability of the embankment slopes and the applied earth loads as well as the magni-tude of the inherent settlement of the embankment.
The permissible placement water content resulting from these various conditions, must ensure opti-mal compaction; otherwise improvement measures including soil exchange or soil redistribution to lower dams and landfills, stabilisation with lime or cement, or a sandwich construction method with coarse par-ticle materials may be necessary (Fig. 45).
Soil stabilising with lime to enhance
the compaction properties Fig. 45
Clays and silts form the main groups of cohesive soils. They differ strongly in particle fineness, min-eral constituents and the plasticity resulting from this. Their soil mechanical suitability for earthwork and embankments is decisively limited sensitivity against water and weather during loosening, load-ing, transport, placement and compaction. The plas-ticity dependent water absorbing capacity of these soils causes solid to pasty-liquid conditions (con-sistencies) This results in a extremely sensitively changing deformation and strength performance.
Silts and clays of low plasticity (wf < 50%, lP < 15%), the consistency of which drops strongly immedi-ately when absorbing stratum water, percolating water, precipitation water or the accumulated water
from frost and thawing periods, show a particularly critical sensibility and may soften and erode down to a considerable depth.
Due to their “toughness” (adhesive strength) the distinct plastic soil types are very difficult to process and compact. On the one hand they are less sen-sitive to water and erosion, but on the other hand they swell when absorbing water or when relieving the load if they contain clay materials with a swell-ing capacity (e.g. opaline and ornoite clays). Durswell-ing this process these materials develop moderate to high swelling pressures when the free deformability is inhibited.
The use of silts and clays with gypsiferous con-stituents shall be avoided because of the extreme swelling properties of the gypsum. If this cannot be avoided because of economical reasons, the place-ment shall be performed under the following condi-tions:
- the gypsiferous constituents in the filling material shall not exceed 10% by volume,
- the gypsiferous material shall be evenly uted in the filling material and compacted under dry weather conditions.
Solid clays may destrengthen similar to mudstone, especially as a result of repetitive dry/wet-cycles or frost/thawing-cycles. The resulting cracky or crum-bly structures increase the depth of water infiltration and softening.
Due to the above mentioned soil mechanical char-acteristics silts and clays are only suitable for earth-work if they are applied in dry weather with the optimum water content for compaction and without subsequent softening. Because of their general deformation sensitive properties and their potential inelastic deformation under permanent load, espe-cially in case of a distinct plasticity, the placement of these materials shall be restricted to such areas in earth or dam constructions which are less stressed by own weight or external forces.
Compaction of soil and rock in earthwork
In subgrade areas under carriageways down to a depth of 0.6 m these materials shall only be used if the demands for optimum placement water con-tent and plasticity characteristics of w<50% and/or l<15% and CBR>10% (after two days of immer-sion at a degree of compaction of at least 95% of the standard density) are met. With these criteria it is intended to permit only such soils in areas jected to traffic loads, the settlement of which sub-sides relatively quickly and which have at least a short-term stability in case of precipitation.
Rules of thumb for the limiting values of the place-ment water content w in dependence on the water content wPp at the plastic limit, e.g.: w ≅ wP + 2 in % or w ≅ 1,2 bis 1,3 · wPp depending on soil type.
As far as permitted by the water contents, silts and
As far as permitted by the water contents, silts and