![Dr.Amit Srivastava, PhD, M.ASCE, LMIGS, LMISRMTT, MITS, MISSMGE,AMIE
[B.E. University of Roorkee (now IIT Roorkee),
M.E. & Ph.D, IISc, Bangalore]
Assistant Professor (Senior Grade), Department of Civil Engineering
Jaypee University of Engineering &Technology,
Agra-Bombay Road, Raghogarh, District: Guna
Madhya Pradesh - 473 226, India
Mob.No. (+91)94797729, Home: 07544267030
Index Properties of Soil](https://image.slidesharecdn.com/3aindexpropertiesofsoil-180419065022/85/3-a-index-properties-of-soil-1-320.jpg)
3 a index properties of soil
- 1. Dr.Amit Srivastava, PhD, M.ASCE, LMIGS, LMISRMTT, MITS, MISSMGE,AMIE [B.E. University of Roorkee (now IIT Roorkee), M.E. & Ph.D, IISc, Bangalore] Assistant Professor (Senior Grade), Department of Civil Engineering Jaypee University of Engineering &Technology, Agra-Bombay Road, Raghogarh, District: Guna Madhya Pradesh - 473 226, India Mob.No. (+91)94797729, Home: 07544267030 Index Properties of Soil
- 2. INDEX PROPERTIES OF SOIL Various classification system in practice place soils in different categories based on certain properties of soil. The tests carried out in order to classify a soil is termed as classification tests. The numerical results obtained from such tests are termed as Index properties of soil. The index properties of soil can be divided into two categories: (1) Soil grain properties, (2) Soil aggregate properties
- 3. INDEX PROPERTIES OF SOIL Soil grain properties are those properties which are dependent on the individual grains of the soil and are independent of the manner of soil formation, such as, mineral composition, specific gravity of soil solids, size and shape of the grains. Soil aggregate properties are those properties which are dependent on the soil mass as a whole and , thus, represent the collective behavior of a soil. Soil aggregate properties are influenced by soil stress history, mode of soil formation and soil structure.
- 4. Soil Texture
- 5. Soil Texture
- 6. Grain Size and Grain Size Distribution
- 7. GRAIN SIZE
- 12. Grain Size Distribution contd.. • Engineering applications − It will help us “feel” the soil texture (what the soil is) and it will also be used for the soil classification (next topic). − It can be used to define the grading specification of a drainage filter (clogging). − It can be a criterion for selecting fill materials of embankments and earth dams, road sub-base materials, and concrete aggregates. − It can be used to estimate the results of grouting and chemical injection, and dynamic compaction. − Effective Size, D10, can be correlated with the hydraulic conductivity (describing the permeability of soils). (Hazen’s Equation).(Note: controlled by small particles) The grain size distribution is more important to coarse-grained soils.
- 13. 13 Some Thoughts about the Sieve Analysis • The representative particle size of residual soils −The particles of residual soils are susceptible to severe breakdown during sieve analysis, so the measured grain size distribution is sensitive to the test procedures (Irfan, 1996). • Wet analysis −For “clean” sands and gravels dry sieve analysis can be used. −If soils contain silts and clays, the wet sieving is usually used to preserve the fine content.
- 14. 14 Some Thoughts about the Hydrometer Analysis Stokes’ law η γ−γ = 18 D)( v 2 ws Assumption Reality Sphere particle Platy particle (clay particle) as D ≤ 0.005mm Single particle (No interference between particles) Many particles in the suspension Known specific gravity of particles Average results of all the minerals in the particles, including the adsorbed water films. Note: the adsorbed water films also can increase the resistance during particle settling. Terminal velocity Brownian motion as D ≤ 0.0002 mm(Compiled from Lambe, 1991)
- 15. Particle Shape
- 17. Atterberg / Consistency Limits Consistency is a term which is used to describe the degree of firmness of a soil in a qualitative manner by using descriptions, such as, soft, medium, firm, stiff or hard. It indicates the relative ease with which a soil can be deformed. It is associated with fine grained soils, especially, clay. The physical properties of a clay are considerable influenced by the amount of water present.
- 19. LIQUID LIMIT It is the water content at which a soil is practically in a liquid state, but has infinitesimal resistance against flow which can be measured by any standardized procedure. PLASTIC LIMIT It is defined as the water content at which a soil would just begin to crumble when rolled into a thread of approximately 3 mm diameter. SHRINKAGE LIMIT It is the maximum water content at which a decrease in moisture content does not cause any decrease in the volume of the soil mass. The soil is just saturated.
- 20. LL Determination Casagrande Method (ASTM D4318-95a) • Professor Casagrande standardized the test and developed the liquid limit device. • Multipoint test • One-point test Cone Penetrometer Method (BS 1377: Part 2: 1990:4.3) • This method is developed by the Transport and Road Research Laboratory, UK. • Multipoint test • One-point test
- 22. LL Determination – Casagrande N w ( ) .log )( /log , 12 21 contNIw valuepositiveachoose NN ww IindexFlow F F +−= − =
- 26. Cone Penetrometer Method •One-point Method (an empirical relation) 44094.1*40,094.1 %,40,15 ≈== == LLFactor wmmdepthnPenetratio
- 27. Plastic Limit Test The plastic limit PL is defined as the water content at which a soil thread with 3.2 mm diameter just crumbles. ASTM D4318-95a, BS1377: Part 2:1990:5.3
- 28. 28 Shrinkage Limit-SL (Das, 1998) Soil volume: Vi Soil mass: M1 Soil volume: Vf Soil mass: M2 )100)(( M VV )100( M MM (%)w(%)wSL w 2 fi 2 21 i ρ − − − = ∆−=
- 29. 29 Shrinkage Limit-SL (Cont.) • “Although the shrinkage limit was a popular classification test during the 1920s, it is subject to considerable uncertainty and thus is no longer commonly conducted.” • “One of the biggest problems with the shrinkage limit test is that the amount of shrinkage depends not only on the grain size but also on the initial fabric of the soil. The standard procedure is to start with the water content near the liquid limit. However, especially with sandy and silty clays, this often results in a shrinkage limit greater than the plastic limit, which is meaningless. Casagrande suggests that the initial water content be slightly greater than the PL, if possible, but admittedly it is difficult to avoid entrapping air bubbles.” (from Holtz and Kovacs, 1981)
- 30. 30 Typical Values of Atterberg Limits (Mitchell, 1993)
- 31. Indices Plasticity index PI For describing the range of water content over which a soil was plastic PI = LL – PL Liquidity index LI For scaling the natural water content of a soil sample to the Limits. contentwatertheisw PLLL PLw PI PLw LI − − = − = LI <0 (A), brittle fracture if sheared 0<LI<1 (B), plastic solid if sheared LI >1 (C), viscous liquid if sheared
- 32. 32 Indices (Cont.) Sensitivity St (for clays) strengthshearUnconfined )disturbed(Strength )dundisturbe(Strength St = (Holtz and Kavocs, 1981) Clay particle Water w > LL
- 33. 33 Indices (Cont.) •Activity A (Skempton, 1953) mm002.0:fractionclay )weight(fractionclay% PI A < = Normal clays: 0.75<A<1.25 Inactive clays: A<0.75 Active clays: A> 1.25 High activity: •large volume change when wetted •Large shrinkage when dried •Very reactive (chemically) Purpose Both the type and amount of clay in soils will affect the Atterberg limits. This index is aimed to separate them. Mitchell, 1993
- 34. 34 • Soil classification (the next topic) • The Atterberg limits are usually correlated with some engineering properties such as the permeability, compressibility, shear strength, and others. − In general, clays with high plasticity have lower permeability, and they are difficult to be compacted. − The values of SL can be used as a criterion to assess and prevent the excessive cracking of clay liners in the reservoir embankment or canal. Engineering Applications −The Atterberg limit enable clay soils to be classified.
- 35. Thank You!
Editor's Notes
- #15: Clay minerals and clay-size particles
- #31: If you have different clay minerals, you will have different Atterberg limit.
- #34: There is fair/good correlation of the activity and the type of clay mineral (chapter 4) However, the Atterberg limits alone are usually sufficient for these purposes, and the activity provides no really new information.
- #35: In general, clays of high plasticity are likely to have a lower permeability, to be more compressible and to consolidate over a longer period of time under load than clays of low plasticity. High-plasticity clays are more difficult to compact when used as fill materials. Relate to the permeability. The values of SL are particular useful to in connection with the placing of puddle clay in reservoir embankments or canal linings. To prevent excessive cracking is some drying out of the clay is likely to occur, the shrinkage range can be limited.