Results of laboratory oedometer tests on reconstituted specimens of four clays prepared at different initial water contents, ranging from the liquid limit to 1.75 times the liquid limit, show that ...

Determining intrinsic compressibility of fine-grained soils

It is known that the mechanical properties of low-plasticity silt are similar to those of sand, and yet silts are frequently used as coastal reclamation materials in many cities and industrial areas and will thus be susceptible to liquefaction. Samples of a low-plasticity silt have been tested under monotonic and cyclic loading under isotropic and anisotropic stress conditions to characterize liquefaction, cyclic failure, and to develop an empirical model describing its cyclic strength. A sedimentation technique produced samples that had the highest susceptibility to liquefaction. Contractive behavior of monotonically loaded samples was triggered when the stress path reached an initial phase transformation (IPT) in both compression and extension tests. The samples became dilative after reaching a phase transformation (PT) point. The cyclic shear behavior of the silt samples prepared using the sedimentation method and consolidated at various initial sustained deviator stress ratios was examined in terms of...

Liquefaction, Cyclic Mobility, and Failure of Silt

Effect of anisotropic consolidation stress paths on the undrained shear behavior of reconstituted Wenzhou clay

In the early days of Soil Mechanics and Foundation Engineering, two important assumptions were made as a part of the limiting equilibrium stability analysis of undrained failure of soft clay and silt deposits. It was assumed that undrained shear strength is independent of the laboratory or in situ testing methods used to determine it, and that the shear strength mobilized in a full-scale undrained failure in the field is equal to the undrained shear strength measured by a laboratory or in situ test. However, during the latter part of Geotechnical Engineering, it was realized that these two assumptions, in general, are not correct because undrained shear strength is influenced by mode of shear, shearing time to failure, progressive failure, and soil disturbance. As these controlling factors are rarely the same for any two testing methods or for any test and a full-scale field failure situation, undrained shear strengths determined by various tests are expected to be different; and the laboratory and in situ test measurements must be corrected before they are used for stability analysis of full-scale field undrained failures. Using undrained shear strength data back-calculated from failures of embankments, footings, and excavations, and data from in situ and laboratory tests, the relationship of suo(mob) is reviewed to suo(FV), suo(UC), suo(TC), suo(TE), suo(DSS), and also to Nk from push cone penetration test.

Shear strength mobilized in undrained failure of soft clay and silt deposits

Torsional ring shear tests were performed to evaluate the effect of shear displacement rate on the internal shear strength of a needle-punched geosynthetic clay liner (GCL) under different normal stresses The test results suggest that the internal shear strength of the needle-punched GCL depends on the following three factors: (i) resistance against reinforcement fibers pulling out and/or tearing; (ii) amount of positive pore-water pressure induced during shear; and (iii) bentonite water content at the time of shearing The laboratory tests indicate that the net effect of these three factors result in the peak internal shear strength being less sensitive to shear displacement rate at normal stresses between 200 and 400 kPa than at normal stresses less than 200 kPa Shear displacement rate appears to have little influence on the residual internal shear strength regardless of normal stress The amount of shear displacement required to reach the peak and residual internal shear strengths is dependent on the

Effect of Shear Displacement Rate on Internal Shear Strength of a Reinforced Geosynthetic Clay Liner

Block samples of a Boston Blue clay crust were used in a detailed study of the relationship between undrained shear strength and consolidation pressure in the compression and extension shear modes. The glacial silty clay sample that was mainly composed of quartz, feldspar, illite and chlorite has developed an overconsolidation ratio near to 3·0 by desiccation. The in situ coefficient of earth pressure at rest was near to 0·9 as compared to K0p = 0·56 of the normally consolidated young clay in the compression range beyond the preconsolidation pressure. In the compression range, for each consolidation-shear mode, undrained shear strength to vertical consolidation pressure ratio as well as shearing-induced pore water pressure to vertical consolidation pressure ratio, friction angle mobilized at yield, and the coefficient of earth pressure at rest, were constant and independent of consolidation pressure. The mobilized undrained shear strength of the normally consolidated young clay obtained by consolidating s...

S B Ali

Papers

Undrained shear strength of a glacial clay overconsolidated by desiccation

Hydraulic fracturing in embankment dams