Copyright February 22, Index Properties of Soils Prof. Basuony El-Garhy Geotechnical Engineering and Foundations Civil Engineering Department Faculty of Engineering

2 Introduction  Index properties of soil usually used to classify the soil into groups of similar geotechnical characteristics and to assign symbols.  There are relations between the index properties of soil and the engineering properties such as strength, compressibility, coefficient of permeability.

3 Index properties of soil 1.Water content 2.Specific gravity 3.Grain size distribution 4.Consistency or Atterberg limits 5.In-situ unit weight (density) 6.Relative density

4 Water content  Water content can be measured in the laboratory using a recovered soil samples to obtain the natural water content of the soil. W3 = weight of container + dry soil sample W1 = weight of container W2 = weight of container + wet soil sample Where

5 Specific gravity  The specific gravity of the soil particles is important in computing the void ratio when the unit weight and water content are known.  The test is of moderate difficulty with the major source of error deriving from the presence of entrapped air in the soil sample.

6 Measurement of specific gravity  Specific gravity is determined by determine the volume of displaced water, by known weight of dry soil particles, and the density bottle is used in that purpose according to the following procedure: 1.Weight the empty and dry density bottle (W1) 2.Put a dry soil sample in the density bottle, and weight the density bottle + dry soil sample (W2)  Preparation of sample: The soil sample (50g) should, if necessary, be ground to pass through a 2mm (Sieve # 10). A 5 to 10g sub-sample should be obtained by riffling and oven-dried at a temperature of 105 to 110oC.

7 Measurement of specific gravity 5.Calculate the specific gravity from the following equations: 3.Added distilled water to the density bottle to fill it and make sure that all the voids of soil sample filled by water, then weight the density bottle + soil sample + distilled water (W3) 4.Empty the density bottle and refill it by the distilled water only, and weight the density bottle + the distilled water (W4)

8 Measurement of specific gravity

9 Grain size distribution  The grain size distribution curve is used for soil classification, for designing filters and for estimating the coefficient of permeability.  The grain size distribution curve for coarse grained soils (i.e., particle sizes larger than mm-U.S. No. 200 sieve) can be obtained by sieve analysis test.  The grain size distribution curve for fine grained soil (i.e., particle sizes smaller than mm) is obtained by Hydrometer test.

10 Sieve analysis test  For purely coarse grained soil, dry sieve analysis test is performed.  For coarse grained soil containing fines, wet sieve analysis test is performed  Sieve analysis test is used to determine the grain size distribution curve for coarse grained soil.

11 Procedure of sieve analysis test ASTM Standard Sieve Sieve No.2 in.1.5 in¾ in.3/8 in Opening (mm) The test sample is dried to a constant weight at a temperature of o C and weighed. ASTM Standard Sieve 3.The sample is sieved by using a set of IS Sieves. 2.Weight the soil sample (W)

12 Sieve Analysis stack of sieves sieve shaker 4.On completion of sieving, the retained on each sieve is weighted (Weight of retained). 5.Cumulative weight passing through each sieve is calculated as a percentage of the total sample weight as shown in the following table Procedure of sieve analysis test

13 Sieve No Sieve Opening (mm) Weight of retained (gm) Weight of total retained (gm) % Total retained % Passing 44.76R1 R1/TR1-(R1/TR) R2R1+R2(R1+R2)/TR R3R1+R2+R RnR1+R2+..+Rn PanRpSum = TR Check (Weight of soil sample, W = TR) Results of sieve analysis test

14 Photos show the procedures of sieve analysis test

15 Photos show the procedures of sieve analysis test

16 Procedure of Hydrometer analysis  Analysis based on Stoke’s Law, velocity proportional to diameter 1.Soil passed through Sieve No. 200 (0.075 mm) along with distilled water are collected and put into a 1000ml jar for hydrometer analysis. More water, if required, is added to make the soil water suspension just 1000ml. The jar is put on the table. 2.A graduated hydrometer is carefully inserted into the suspension with minimum disturbance. 3.At different time intervals, the density of the suspension at the centre of gravity of the hydrometer is noted by seeing the depth of sinking of the stem. The temperature of the suspension is noted for each recording of the hydrometer reading.

17 Procedure of Hydrometer analysis 4.Hydrometer readings are taken at a time intervals of: 0.5, 1, 2, 4, 8, 15, 30 min, 1, 2, 4, 8, 24, 48 hrs 5.Correct the Hydrometer readings through its graphs 6.the percentage smaller than the specified diameter is determined using the chart given or calculated as follows:

18 Hydrometer Analysis hydrometer soil/water suspension r = Corrected Hydrometer reading*1000 r w = Hydrometer reading in water*1000 W d = Weight of soil sample N = the percentage smaller than the specified diameter

19 Photos show the procedures of Hydrometer analysis test

20 Photos show the procedures of Hydrometer analysis test

21 Grain Size Distribution Curve (GSDC) You can find % of gravels, sands, fines D 10, D 30, D 60.. defined as above

22 Parameters obtained from GSDC 3.Coefficient of Permeability 1.Uniformity Coefficient Cu 2.Coefficient of Curvature Cc

23 WWell graded UUniform graded PPoorly graded CWell graded with some clay FWell graded with an excess of fines Different shapes of GSDC

24 Consistency limits Solid state  Based on the water content, the behavior of fine grained soils can be divided into four basic states: Liquid stateSemi solid statePlastic state Water content Shrinkage limit SL Plastic limit PL Liquid limit LL Strain Stress Stress-strain curves at different states

25 Liquid limit (LL)  The liquid limit is defined as the water content corresponding to a limit between the liquid and plastic states of consistency. It is also the minimum water content at which the soil is still in the liquid state but, has a small shearing resistance against flowing.  The liquid limit is routinely determined for cohesive soils.

26 Measurement of LL  The LL is measured in the laboratory by using standard apparatus (Liquid limit device) based on the following procedures: 1.The soil sample mixed with distilled water to form a uniform paste. 2.A portion of the paste is placed in the cup and cut with a grooving tool. 3.The apparatus handle is rotated and the number of blows is counted until the two parts of the soil come into contact on a distance of 13mm

27 Measurement of LL 7.The liquid limit is obtained from the graph as the water content corresponding to 25 blows. 4.A small sample is taken near the closed groove to determine its water content. 5.The test is repeated at least three times with the water content changed and the corresponding number of blows is recorded. 6.A graph is ploted between the number of blows and the water content on a semi log scale as shown below.

28 Photos show liquid limit device and test procedures

29 Photos show liquid limit device and test procedures صور توضح جهاز حد السيولة وخطوات الاختبار

30 Liquid limit chart From the chart above LL = 26%

31 Plastic limit  The plastic limit is defined as the water content separate between the plastic state and the semi solid state.  Or the water content at which the soil crumbles when rolled into threads of 3.2 mm in diameter.

32 Photos show plastic limit device and test procedures

33 Photos show plastic limit device and test procedures

34 Plasticity index (PI)  The plasticity index indicates the range of consistency within which a soil exhibits plastic properties and it is defined as: PI = LL - PL  The plasticity index is important in classifying fine grained soils using plasticity chart.

35 Shrinkage limit (SL)  The shrinkage limit is defined as the maximum water content at which a reduction in water content will not cause a decrease in the volume of the soil or the water content that separate between solid and semisolid states of the soil water Content (%) Volume LL SL PL

36 Liquidity index (LI) Where w = in situ water content  The relative consistency of a cohesive soil in the natural state can be defined by a ratio called the Liquidity index, which is given by Liquidity the following equation:  The in situ water content for a sensitive clay may be greater than the liquid limit. In this case LI > 1.  The in situ water content for heavily over consolidated may have in situ water content less than the plastic limit. In this case LI < 0.

37 Consistency index (CI)  The consistency index is useful is studying the field behavior of saturated fine grained soil and calculated from the following equation: Where w = natural water content  If w = LL, the CI = 0  if w = PL, the CI = 1

38 Relative density  The relative density is an index property used to describe the compactness of coarse grained soils and calculated as follows: 0 Loosest 1 Densest  The relative density can be calculated from the following equation: e = natural void ratio e max = maximum void ratio e min = minimum void ratio

39 Relative density e = natural void ratio نسبة الفراغات الطبيعية e max = maximum void ratio نسبة  الفراغات  القصوى e min = minimum void ratio نسبة  الفراغات  الصغرى  The relative density can be calculated from the following equation:

40 Compactness of coarse grained soil Relative Density (%)Compactness Very loose Loose Medium dense Dense Very dense