ENVIRONMENTAL GEOMECHANICS CE-641 Lecture No. 13 Prof. D N Singh - - PowerPoint PPT Presentation

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ENVIRONMENTAL GEOMECHANICS CE-641 Lecture No. 13 Prof. D N Singh Department of Civil Engineering 23.09.2019 Lecture No. 13 Lecture Name: Geomaterial Characterization Sub-topics Chemical

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ENVIRONMENTAL GEOMECHANICS

CE-641 Lecture No. 13

Prof. D N Singh

Department of Civil Engineering

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Sub-topics

Chemical characterization

Pore-solution sampling Corrosion potential Sorption-Desorption

Thermal Characterization
Electrical Characterization
Magnetic Characterization

23.09.2019 Lecture No. 13 Lecture Name: Geomaterial Characterization

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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

Pore-solution Sampling

The pore-solution sampling is identical to blood sampling

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In-situ (Field)

Lysimeter
Zero-tension Lysimeter
Tension Lysimeter
Soil Salinity Sensors
Absorption Techniques

Laboratory

Centrifugation
Pressure-membrane extractor (PME)

Sampling Techniques

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Lysimeter (Pore Solution Collection Device)

Collection device to Collection bottle Pervious fill Percolating water Soil Control volume Zero Tension Lysimeter Collects Pore Solution From Saturated Soils

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Field Lysimeter

Waste rock material 485 mm 40 mm thick creek sand 50 mm thick Gravel (5-7 mm) 300 mm thick Gravel (14mm) Gravel (5-7 mm) To collect leachate Percolating water Occurrence of preferential flow Influence of mobile colloids on contaminant mobility Extra organic matter in soil reduced colloid release

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Undisturbed soil core Sand Loose fill Sloping bottom A O A : Air inlet O : Pore solution extraction

Zero-tension Lysimeter

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Clay liner Granular Backfill Flexible membrane liner P P : Perforated pipe

To detect leakage from the clay liner
To determine in situ hydraulic conductivity of the liners
To demonstrate proper functioning of the clay liner

Collection Basin Lysimeter

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Performance assessment of solidified radioactive waste
Attenuation properties of soils

Upper compartment with fill material, sensors and moisture extraction cups Lower compartment for leachate collection Validation of theoretical model by fitting Mathematical model to Lysimeter data

Basic Philosophy

Rain water Leachate

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Tension Lysimeter

Collects pore-solution from “Unsaturated Soils” To Vacuum pump To sample bottle Ground Porous ceramic cup

PVC pipe

I I I – Inflow of pore solution under vacuum applied

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Importance of Lysimetric studies

Field studies

No control of boundary conditions, cost and time intensive

Laboratory studies

Cannot simulate field conditions, Spatial variability cannot be taken into account

Lysimetric study Intermittent approach

Simulates In-situ conditions with better control on boundary conditions

Lysimeter Device which creates a control volume of soil for studying various contaminant transport mechanisms under in-situ conditions Lysimeter identified as a potential tool for studying radioactive contaminant Interaction and migration in Geoenvironment

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R is the soil spiked (with Cs, Co & Tritium)

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Slurry of native soil

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Vial for pore-solution collection

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Details of the suction sampler

Stopper Sample Collector Flexible rubber tube To the vacuum Pump Ceramic thimble Perspex tube Soil slurry

Screw cap

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Activities at a Glance

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TDR studies

200 180 160 140 120 100 80 60 40 20 0.0 0.1 0.2 0.3 0.4 0.5

 Depth(cm)

15/06/05 20/06/05 05/07/05 14/07/05 18/07/05 26/7 flash floods 26/08/05 27/09/05

GSL

Hanumantha Rao, B, Sridhar, V., Rakesh, R.R., Singh, D.N., Narayan, P.K. and Wattal, P.K., “Application of In-situ Lysimetric Studies for Determining Soil Hydraulic Conductivity”, Geotechnical and Geological Engineering, 2009, DOI 10.1007/ s10706-009-9260-5. Published Online: 13 May 2009.

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Variation of 137Cs and 60Co activity concentration with depth in dry soils after a period of 500 days

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Pressure Membrane Extractor

S PG PME A P PG C R RU B Air inlet Pressure gauge Drain Expelled water to the sampling bottle Air pressure