List of Tables
Chapter 4 Experimental Investigations and Methodology
4.4 Physical characterizations of soil .1 Specific gravity
The specific gravity (G) of the soils was determined by following the guidelines provided in IS: 2720 (Part III); ASTM D 854 with the help of specific gravity bottles. For the sake of accuracy, the average specific gravity was obtained from the results of minimum 5 tests. The results are presented in table 4.3.
4.4.2 Gradational characterization
The particle size characteristics of the soils are determined based on ASTM D 422- 63. The results of percentage size fractions of the soils obtained from grain size curve are listed in table 4.4.
4.4.3 Atterberg limits
The consistency limits of the soil samples were determined as per guidelines provided by ASTM D 4318 and IS: 2720 (Part V) for liquid limit (LL) and plastic limit (PL).
4.4.4 Soil classification
Based on the physical characteristics, the classification of the soils was done by following unified soil classification system (USCS) (ASTM D 422). The details of the classification are listed in table 4.4.
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4.4.5.1 Desiccator method
In this method, specific surface area is calculated by considering the formation of unimolecular layer of water formed on the soil surface (Sridharan and Rao., 1972). The procedure adopted is as follows:
1. About 5gm of oven dried soil sample and was kept in a desiccator at a constant relative humidity of 20% with partial pressure of 0.20.
2. An aqueous solution of sulphuric acid as per ASTM E 104-85 was used to maintain the required relative humidity about 20% at 25ºC, with a density of 1.4789gm/cm3. 3. The solution is placed at the bottom of the desiccator. The soil is placed in this
desiccator for 24hr to 48hr depending up on type of soil.
4. The equilibrium moisture content was determined using a balance with a sensitivity of 0.0001gm; and the specific surface area can be obtained from the Eq. 4.2
SSA= ×104×) ×A×10-16 M
× N
(w (4.2) where S is the specific surface area in m2/gm, w is the equilibrium moisture content in gm adsorbed per gm of soil, N is Avogadro’s number(6.025x1023), M is the molecular weight of water (18.016 gm), and A is the area in square Angstroms per water molecule (10.8 Ǻ2).
4.4.5.2 EGME method
By conducting Ethylene Glycol Monoethyl Ether ( EGME), adsorption on soil surface the total specific-surface area was determined (Carter et al., 1986; Cerato and Lutenegger., 2002).
1. 2 g of air-dried material was spread uniformly on the bottom of a glass dish (40 mm internal diameter and 20 mm in height) and covered with a perforated watch-glass.Six such dishes, with sample in them, were placed in a vacuum desiccator containing 250 g of P2O5. This helps in maintaining a constant vapour pressure inside the desiccator.
2. The sample was evacuated by applying vacuum for 2 h and was weighed. This process was repeated several times, until sample attains almost a constant weight.
3. 6 ml of analytical grade EGME solution was added to the sample and the mixture was swirled, gently, until it becomes slurry.
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4. The slurry was then placed in the desiccator over a desiccant (mixture of 100 g CaCl2
and 20 ml EGME) for 12 h.
5. This helps in maintaining a constant vapour pressure which is just sufficient to form monolayer on the sample.
6. Initial weight of the slurry along with the glass dish was measured using the precision balance and the dish was replaced in the desiccator for evacuation under vacuum.
7. The glass dish was taken out of the desiccator, weighed and replaced in it several times, till it attains a constant weight.
8. Calculation of SSA for soil is given below, (Cerato and Luteneggerl 2002)
s a
0.000286W
= W
SSA (4.3)
Where SSA = Specific Surface Area in m2/g.
Wa = weight of ethylene glycol monoethyl ether (EGME) retained by the sample in grams (final slurry weight – Ws)
0.000286 = weight of EGME required to form a monomolecular layer on a square meter of surface (g/m2)
Ws = oven dry weight of soil (g) 4.5 Geotechnical Characteristics
4.5.1 Proctor compaction characteristics
The compaction characteristics of the soil samples used in the study have been established by using standard Proctor compaction procedure (IS: 2720: part 7; ASTM D 698).
The compaction characteristics of the soils are presented in the form of relationship between dry unit weight, γd and moisture content, w, as depicted in Fig.4.27. The salient characteristics such as maximum dry unit weight, γdmax, the optimum moisture content (OMC), of the soil are listed in table 4.5.
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6 12 18 24 30 36
15 20
d(kN/m3 )
W (%)
IBent FBent Kao RS FC LS FAsh
Fig.4.21 Compaction characteristics for all soils
Table 4.5 Physical properties and classification of the soils
Property Soil
IBent FBent Kao RS FC LS FAsh
Specific gravity (G) 2.61 2.65 2.6 2.62 2.71 2.74 2.12 Particle size characteristics (%):
Sand (4.75-0.075 mm) 5 1.17 3 26 46 11 34
Coarse sand (4.75-2 mm) 0 0 0 0 0 0 0
Medium sand (2-0.425) mm)
0 0 0 5 22 0 0
Fine sand (0.425-0.075) mm)
5 4.18 10 21 24 11 34
Silt (0.075-0.002 mm) 31 30.09 80.85 67 38 59 66
Clay (<0.002 mm) 64 64.45 50.97 7 16 30 0
Atterbergs Limit
Liquid limit 272 345 52 46 28 42 -
Plastic limit 51 56 35 27 16 20 -
Plasticity index 221 289 17 19 12 22 -
USCS(Classification) CH CH CL CL CL CL SM /class SSA (m2/g) (Dessicator) 136.50 112.45 12.56 50.62 11.23 9.34 1.21 F SSA (m2/g) (EGME) 244 219.12 36.62 94.12 26.12 20.12 2.66
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Table 4.6 Compaction characteristics
Soil IBent FBent Kao RS FC LS FAsh
γdmax
(kN/m3) 28.66 29.8 23.5 18.68 19.23 18.6 20.32 OMC (%) 15.70 16.05 15.552 14.56 14.98 14.88 13.76 4.6 Determination of retention characteristics
Retention characteristics of the soils with selected contaminants has been obtained.
The different methods employed are discussed as follows:
4.6.1 Batch method (ASTM D 4646-03)
The aim of this method is to determine the retention affinity of contaminants by geomaterials in aqueous solution, which is expressed in terms of distribution coefficient (K).
This test method is applicable to both organic and inorganic constituents, but fully prohibitive for volatile chemical constituents.
Apparatus: a) A rotary solid waste extractor equipment for agitation b) 0.45 micrometer pore size membrane filter equipment for phase separation, for organic matter glass or stainless steel used. c) Generally round, wide mouth bottles are used. But high density, linear polyethylene bottles are used for nonvolatile inorganic constitute with 125ml, 250ml, 2lit bottles for sample sizes of 5, 10, 70gm respectively. d) A balance having a minimum capacity of 70g and sensitivity of ±0.005g shall be used. e) Reagents: chemicals of high purity, and water having a lower conductivity i.e deionised or pure water. The brief procedure of the test is given below
1. Air dried soil sample is sieved through 2-mm sieve and the required amount is weighed.
2. The weighed soil sample is then transferred into polyethylene bottle and mixed with contaminant solution in the ratio of 1:10 (solid:liquid).
3. Place the closed container with soil solution on a shaker and agitate continuously for 24 hrs 25 ± 2°C.
4. Open the container and note any change in solution such as color, odor, temperature pH etc.
5. The solution is filtered through 0.45-μm pore size membrane and stored in a refrigerator at 4±2°C until analyzed.
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6. The results of the analysis are then used to develop retention isotherm.
4.6.2 Preparation of single and multiple contaminant solution
Single and multiple contaminant stock solution were prepared by dissolving appropriate amounts of salt/ salts of analytical reagent grade in ultrapure water. For example, a single stock solution of monovalent Na+ was prepared by mixing 2.54 gms of NaCl salts in 1000ml of ultrapure water. A multiple stock solution comprising of binary common ions of Na+K for 1000mg/L was prepared by mixing 2.54 gms and 1.91 gm of NaCl and KCl in 1000 ml of ultrapure water. The different ranges of desired concentration were achieved by diluting the solution again in ultra pure water.