IIT Bombay Slide 1 22.10.2014 Lecture No. 10 Lecture Name: Geomaterial Characterization Sub-topics • Specific Surface Area determination • Chemical characterization Pore-solution sampling Corrosion potential Sorption-Desorption • Thermal Characterization • Electrical Characterization Environmental Geomechanics Lecture No. 10 D N Singh
IIT Bombay Slide 2 Specific-surface Area (SSA) Soil-water-contaminant interaction is strongly dependent on SSA SSA is indicative of activity (reactivity) of fine-grained soils A classification scheme based on SSA would help to establish: • Swelling and shrinkage characteristics • Frost heave • Collapse and compressibility • Cation-exchange capacity • Water retention characteristics • Sorption and desorption characteristics These characteristics mainly depend on the grain-size distribution of the soil (i.e., the clay-size fraction) and its mineralogical composition. SSA can capture the combined effect of these factors and hence, can be used for predicting engineering behavior of fine-grained soils. Environmental Geomechanics Lecture No. 10 D N Singh
IIT Bombay Slide 3 Determination of SSA o f fine-grained soils A. gas or vapor adsorption techniques BET nitrogen adsorption water-vapor adsorption B. absorption of the polar liquids and dyes on the soil surface Ethylene glycol (EG) method Ethylene Glycol Monoethyle Ether (EGME) method p-Nitrophenol method Methylene blue (MB) dye method C. application of the state-of-the-art instruments Mercury intrusion porosimetry (MIP) Internal reflectance spectroscopy X-ray diffraction Gas pycnometer Environmental Geomechanics Lecture No. 10 D N Singh
IIT Bombay Some Relationships Slide 4 Arnepalli, D.N., Shanthakumar, S., Rao, H.B. and Singh, D.N., “Comparison of Methods for Determining Specific Surface Area of Fine-grained Soils", Geotechnical and Geological Engineering , 2008, 26(2), 121-137. 600 Shah and Singh (2005), and CS & WC 160 Shah and Singh (2005), and CS & WC Cerato and Lutenegger (2004) Low (1980) Dolinar and Trauner (2004) Cerato and Lutenegger (2004) 450 Farrar and Coleman (1967) 120 - - - 95% confidence limit CEC (meq./100g) LL (%) 300 80 150 40 0 0 1 10 100 1000 0 200 400 600 800 1000 SSA (m2/g) 2 /g) SSA (m 4 300 Shah and Singh (2005) and CS & WC Shah and Singh (2005), and CS & WC Erdal (2002) Cerato and Lutenegger (2004) 3 225 Activity FSI (%) 2 150 1 75 0 0 10 100 1000 0 150 300 450 600 750 SSA (m2/g) SSA (m 2 /g) Environmental Geomechanics Lecture No. 10
IIT Bombay Slide 5 Hedley et al.(2000) Banin and Amiel (1969) Dirksen and Dasberg (1993) Combine data (CD) SSA = 0.0012·( σ h/ σ dry )+16.6 600 SSA=1.88 k diff +9.4 2 /g) SSA (in m2/g) 400 SSA (m 200 σ h, σ dry : Hygroscopic and dry soil electrical conductivity, 0 respectively 80 k diff (= k h- k dry) 60 CEC (meq/100 g) Shah, Paresh H. and Singh, D. N., 40 " Methodology for Determination of Hygroscopic Moisture Content of Soils ”, 20 Journal of ASTM International. 3(2), (2006), 14 Pages. 0 0 2 4 6 8 10 12 w hygroscopic (%) Environmental Geomechanics Lecture No. 10 D N Singh
IIT Bombay pH determination Slide 6 Glass calomel electrode is used Soil solutions with different Liquid to solid ratios ● pH ● Temperature ● Total Dissolved Solids ● Electrical Conductivity ● Chemical Oxygen demand Environmental Geomechanics Lecture No. 10 ● Biological Oxygen D N Singh
IIT Bombay Slide 7 Chloride and Sulphite contents determination The chloride and sulphite contents of the soils can be obtained on an extract of 2:1 Liquid to solid ratio. Indion Easy test kit (Ion Exchange, India Ltd.), an ion exchange resin, is employed A sort of a titration Change in color of the solution due to addition of chemicals Environmental Geomechanics Lecture No. 10 D N Singh
Determination of Cation exchange capacity (CEC) IIT Bombay Slide 8 Is the amount of cations a soil can hold. Summation of exchangeable cations (Na+, K+, Ca+2 and Fe+3) Factors affecting CEC are: charge carrying capacity of the soil, pH, ionic strength of the pore-solution and presence of salts. Guidelines presented by IS 2720 (part XXIV, 1976) and (EPA SW-846) are followed for the determination of CEC of the soil sample. IS 2720 (Part XXIV 1976) : The sample is first treated with hydrogen peroxide (H2O2), and boiled thoroughly for 1 h to remove organic contents. The treated sample is oven-dried and its 5 g is mixed with 50 ml 1N Sodium acetate (CH3COONa) solution with pH=5. This mixture is digested in a boiling water bath for 30 min., with intermittent stirring, and later centrifuged at a speed of 5000 to 6000 rpm, for 15 min. The supernatant liquid is discarded and the sample, settled at the bottom of the centrifuge tube is again treated with 50 ml of 1N CH3COONa solution (pH=5) and centrifuged. Repeat this process thrice, so as to ensure exchange of Ca2+ in the soil by Na+, completely. Environmental Geomechanics Lecture No. 10 D N Singh
IIT Bombay Slide 9 This sample is treated with 1N Calcium chloride (CaCl2) solution and is again digested and centrifuged. This process is repeated thrice, so as to ensure exchange of Na+ by Ca2+. The sample is treated again with 50 ml 1N CH3COONa solution (pH=7) and again digested and centrifuged. This operation is performed thrice. The resulting supernatant from the last three steps is collected in a 250 ml volumetric flask, and the concentration of Ca2+ present in the solution is determined using the Atomic Absorption Spectrometer, AAS. + + µ × × × 2 Concentrat ion of Ca orNa ( g/ml) 100 Vol. of extract (ml) dilution = CEC (meq./100g ) × × Equivalent weight of the cation 1000 wt. of soil (g) Minerals Present in soils(XRD) CEC (meq./100g) Montmorillonite 18.6 Kaolinite, Illite 4.989 Environmental Geomechanics Lecture No. 10 D N Singh
IIT Bombay Pore-solution Sampling Slide 10 The pore-solution sampling is identical to blood sampling A Prerequisite to Soil-Water-Contaminant Interaction Studies To predict transport/fate of contaminants in the soil mass Design of suitable containment/Barrier system Assessment of safe waste disposal limits: Quantity & Concentration Leaching/Attenuation characteristics of soils Intrusion of pollutants in ground water resources Prediction of the loss of nutrients from the root zone Detection of the microbial activity in soils Validation of solute transport models Environmental Geomechanics Lecture No. 10 D N Singh
IIT Bombay Slide 11 Sampling Techniques In-situ (Field) • Lysimeter ● Zero-tension Lysimeter ● Tension Lysimeter • Soil Salinity Sensors • Absorption Techniques Laboratory • Centrifugation • Pressure-membrane extractor (PME) Environmental Geomechanics Lecture No. 10 D N Singh
IIT Bombay Slide 12 In-situ studies Objective: To simulate disposal facility in a Control Volume based on moisture movement concentration of contaminant(s) Using a Lysimeter A device which collects and senses percolating water through soil mass and helps in determining the Concentration of water soluble contaminant(s) As a function of time and space Environmental Geomechanics Lecture No. 10 D N Singh
IIT Bombay Slide 13 Lysimeter Studies Simulate the effect of percolating rainfall on the release of contaminants from waste froms Provide insight in understanding the site as well as validating water balance studies and radionuclide migration in the unsaturated zone Data obtained from the study provide a link between the laboratory and field conditions and thus aid in predicting radionuclide migration from shallow land disposal facility Environmental Geomechanics Lecture No. 10 D N Singh
IIT Bombay Slide 14 Lysimeter ( Pore Solution Collection Device) Zero Tension Lysimeter Collects Pore Solution From Saturated Soils Percolating water Control volume Soil Pervious fill Collection device to Collection bottle Environmental Geomechanics Lecture No. 10 D N Singh
IIT Bombay Slide 15 Basic Philosophy Rain water Upper compartment with fill material, sensors and moisture extraction cups Lower compartment for leachate collection Leachate Performance assessment of solidified radioactive waste Attenuation properties of soils Validation of theoretical model by fitting Mathematical model to Lysimeter data Environmental Geomechanics Lecture No. 10 D N Singh
IIT Bombay Tension Lysimeter Slide 16 Collects pore-solution from “Unsaturated Soils” To sample bottle To Vacuum pump Ground PVC pipe I – Inflow of pore solution Porous ceramic cup under vacuum applied I I Environmental Geomechanics Lecture No. 10 D N Singh
Recommend
More recommend
