The concept of the suction stress characteristic curve (SSCC) for unsaturated soil is presented. Particle-scale equilibrium analyses are employed to distinguish three types interparticle forces: (1) active forces transmitted through grains; (2) at or near contacts; and (3) passive, counterbalancing, contacts. It proposed that second type force, which includes physicochemical forces, cementation surface tension force arising from negative pore-water pressure, may be conceptually combined into...

Accurate estimates of soil hydraulic parameters representing wetting and drying paths are required for predicting mechanical responses in a large number applications. A comprehensive suite laboratory experiments was conducted to measure hysteretic soil-water characteristic curves (SWCCs) wide range types. Results were used quantitatively assess differences uncertainty three simplifications frequently adopted estimate wetting-path SWCC from more easily measured curves. They the following: (1)...

A theory that accurately describes tensile strength of wet sand is presented. closed form expression for unifies characteristics in all three water retention regimes: pendular, funicular, and capillary. Tensile characteristically increases as soil content the pendular regime, reaches a peak funicular reduces with continuing increase capillary regime. Three parameters are employed theory: internal friction angle (at low normal stress) ϕt , inverse value air-entry pressure α pore size spectrum...

Hydraulic conductivity was evaluated for eight commercially available geosynthetic clay liners (GCLs) permeated with leachate characteristic of low-level radioactive waste (LLW) disposal facilities operated by the U.S. Department Energy (DOE). Two GCLs (CS and GS) contained conventional sodium bentonite (Na-B). The others a bentonite–polymer mixture (CPL, CPH, GPL1, GPL2, GPH) or composite (BPC). All (except GPL2 were directly two synthetic LLW leachates that are essentially identical,...

Hydraulic conductivity tests were conducted on two commercially available bentonite–polymer composite (BPC) geosynthetic clay liners (GCLs) containing the same dry blend of sodium bentonite (NaB) and polymer sandwiched between nonwoven geotextiles (GTs) bound by needlepunching: a GCL (BP GCL) with silt film (BPS GCL). The GCLs essentially identical except that BPS contained woven slit-film GT to constrain elution. was located inside adjacent downstream GT. test liquids deionized (DI) water...

Abstract Soil water potential is a cornerstone in defining the thermodynamic state of soil required to quantify phenomena such as phase change, movement, heat transfer, electric current, chemical transport, and mechanical stress deformation earth's shallow subsurface environment. This has historically been conceptualized free energy stored until volume water. Though concept evolving over past 120 yr, consensual definition still lacking, answers some fundamental questions remain controversial...

Constitutive relationships among water content, matric suction, and capillary stress in unsaturated granular soils are modeled using a theoretical approach based on the changing geometry of interparticle pore menisci. A series equations is developed to describe net force particles attributable combined effects negative pressure surface tension for spherical grains arranged simple-cubic or tetrahedral packing order. The contact angle at liquid–solid interface considered as variable evaluate...

Abstract A comprehensive series of three-dimensional x-ray computed tomography (XCT) imaging experiments was conducted to quantitatively assess the multiphase particle- and pore-scale properties fine Ottawa (F-75) sand. The specimens were prepared saturations ranging from approximately 5 % 80 %. Specimens doped with 10 CsCl pore fluid solution imaged using a monochromatic synchrotron source at energies below above Cs absorption k-edge allow for high contrast between solid, liquid, air...

A model for the water retention behavior of unsaturated granular soil is developed by extending classic bundled cylindrical capillary representation pore space to a geometry more closely approximating that porous media. Expressions pore-scale saturation are derived as functions matric suction three-dimensional unit comprising angular bounded spheres in simple cubic packing order. Water curves modeled assigning statistical distribution sizes optimized best match experimentally determined...

Specific surface area (SSA) is a fundamental property of soil. A new methodology for SSA determination both expansive and nonexpansive soil based on interpretation the water retention curve (SWRC) proposed evaluated. The SWRC-based relies Khorshidi-Lu sorption model, where hydration soils interpreted to occur three distinct surfaces in sequential order: exchangeable cations, intercrystalline surfaces, external particle surfaces. Hydration at these different sites responsible commonly...

Specific surface area (SSA) is a valuable intrinsic property of clayey soils that can be directly related to more general properties and engineering behavior, including plasticity, cation exchange capacity, swelling among many others. Laboratory methods available for estimating SSA, however, remain somewhat complicated are not routinely used in geotechnical practice. This paper evaluates compares determining SSA using the conventional ethylene glycol monoethyl ether (EGME) method various...

The sensitivity of sodium bentonite (Na-B) to adverse chemical interactions has spurred development enhanced bentonites (EBs) for geosynthetic clay liners (GCLs) that provide superior properties containment systems. EB-GCLs are engineered control contaminant transport by maintaining low hydraulic conductivity (k) when exposed solutions with high ionic strength, a preponderance divalent cations, and/or extreme pH (<2 and >12). An overview current EB-GCL technologies is provided....

Experiments were conducted to evaluate the hydraulic conductivity of geosynthetic clay liners (GCLs) containing bentonite–polymer composites (BPCs) permeated with coal combustion product (CCP) leachates. Eight synthetic CCP leachates used: five characteristic from a leachate database and three based on actual chemistries. Hydraulic tests non-prehydrated prehydrated BPC GCL specimens at an effective stress 20 kPa. Prehydration was achieved by contact subgrade for 60 days or permeation...

A rigorous closed-form analytical solution is developed for analyzing the rate of capillary rise in soils. The new can be reduced to Terzaghi's classical if nonlinearity hydraulic conductivity with changing soil suction ignored. Results obtained using are compared and a series previously documented experimental data from open-tube tests. significant improvement over previous solution, thus providing more realistic practical predictions unsaturated

Laboratory tests were conducted to examine the applicability of Brazilian tensile strength (BTS) method (ASTM D3967-16) for measuring compacted clay. A correction function obtained from using disk-shaped kaolinite specimens over wide range void ratio was developed account variability in among replicate specimens. Tests prehydrated with water vapor humidity-controlled chambers and then oven-dried revealed that increased increasing prehydration, an observation attributed cementation during...

Abstract Modifications to a conventional laboratory testing system are described for direct shear of unsaturated soils at relatively low matric suction and net normal stress. Matric ranging from zero (saturated) about 10 kPa is controlled using hanging column assembly (ASTM D6836). Net stress 0.3 by directly applying dead loads the specimen via series aluminum top caps machined varying thicknesses. Precise control within these ranges makes apparatus ideal examining strength behavior sands,...

Abstract Laboratory tests were conducted to assess the performance of a dynamic equilibrium method for rapidly measuring water vapor sorption isotherms clays and clayey soils. Emphasis was placed on quantifying temperature stability, measurement reproducibility, establishing recommended testing protocol, comparing dynamically generated with those obtained using conventional method. Adsorption-desorption loops activity (aw) or relative humidity ranging from 0.03 0.95 containing as many 140...

A new approach is proposed for modeling thermal conductivity dryout curves (TCDCs) using measurements of soil-water characteristic (SWCCs) coarse-grained unsaturated soils. The based on observation similitude between a bimodal formulation the SWCC in form S(ψ) and TCDC λ(ψ). model may be used either an empirical curve-fitting capacity to best-fit measured data or predictive estimate from SWCC. Applying facilitates numerical heat transfer problems by providing continuous function TCDC....

We summarize and numerically compare two approaches for modeling simulating the dynamics of dry granular matter. The first one, discrete-element method via penalty (DEM-P), is commonly used in soft matter physics geomechanics communities; it can be traced back to work Cundall Strack [P. Cundall, Proc. Symp. ISRM, Nancy, France 1, 129 (1971); P. O. Strack, Geotechnique 29, 47 (1979)GTNQA80016-850510.1680/geot.1979.29.1.47]. second approach, complementarity (DEM-C), considers grains perfectly...