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Several widely used field methods for estimating postliquefaction ground deformation are based on the laboratory data from one series of cyclic simple shear tests performed on one uniform clean sand reconstituted to three relative densities. It is not clear if the trends of this one data set are applicable to other clean sands, nonplastic silty sands, and nonplastic silts. A database of 579 test results on postliquefaction volumetric strain, including 299 test results that relate maximum shear strain to the factor of safety against liquefaction triggering, was compiled and used to examine trends for these soils. The database includes postcyclic test data on 10 clean sands, 2 gravels, 3 silty sands, 5 silts, and 3 clayey soils. The enlarged cyclic testing database was used to develop models that estimate postliquefaction volumetric strain and maximum shear strain as a function of soil type, state, and seismic demand. The models are applicable to uniform nonplastic soil. The state parameter was used in addition to relative density and void ratio to characterize the state of the soil. Correlations between these parameters enable the full data set to inform the models. [ABSTRACT FROM AUTHOR]

Soil suction–based analyses are paramount to proper design of foundations in expansive soils, yet availability of field soil suction profiles from direct measurement is limited. A method was developed, using directly measured suction profiles obtained from sites across the US, by which routine geotechnical tests can be used to estimate soil suction to expand the database for estimation of field suction profiles. Herein, the expanded database is used to develop best-estimate clay soil suction envelopes for boundary conditions associated with covered or uncovered ground surface subjected to natural climatic surface flux. Where appropriate for site conditions, the proposed soil suction profile envelopes can be used with any suction-based heave/shrinkage analysis. Key features of the field suction envelopes, consistent with current popular approaches, include climate-dependent estimates for equilibrium suction at depth, depth to equilibrium (stable) suction, and variation in soil suction at the ground surface. Comparisons to existing soil suction envelope recommendations are made. Finally, a limited number of cases of developed/irrigated sites are presented for comparison to soil suction profiles obtained for natural climatic surface flux conditions. [ABSTRACT FROM AUTHOR]

In most geotechnical construction works, compacted soils of cohesive-frictional nature are expected to remain mostly under partially saturated conditions and hence experience continuous changes in the suction state (negative pore-water pressure) stemming from seasonal weather and temperature variations throughout any given year. Over the last decade, a few studies have demonstrated that the suction stress characteristic curve (SSCC) can be used to describe the state of stress in partially saturated soils and therefore assess, with reasonable accuracy, the additional shear strength contribution resulting from matric or total suction. However, limited experimental data are available to conclusively verify the magnitude of suction stress at rather high values of suction, especially well beyond the residual suction. In the present work, the SSCC for compacted silty sand has been thoroughly assessed in light of recent experimental data obtained from suction-controlled triaxial testing over a wide range of matric and total suction values (0.05–300 MPa). The suction stress in the test soil was observed to increase with increasing suction even beyond the residual suction state, in contrast with findings from previous works reported in the literature for predominantly sandy or clayey soils. In addition, experimental data from suction-controlled true triaxial, ring shear, and plane strain (biaxial) tests, recently conducted on six different types of cohesive-frictional soils in the low-to-medium matric suction range, were also analyzed to obtain the corresponding SSCCs. Finally, suitable model equations are presented in order to best fit the multiple experimental data sets and hence predict the SSCC for each of the test soils under the different suction-controlled testing techniques. [ABSTRACT FROM AUTHOR]