Shuying Wang

A Slurry Consolidation Approach to Reconstitute Low-Plasticity Silt Specimens for Laboratory Triaxial Testing

Silt specimen reconstitution using a slurry consolidation approach is commonly used for laboratory testing. This paper presents a new slurry consolidation approach to reconstitute silt specimens for use in triaxial testing. Silt specimens were reconstituted in a split vacuum mold mounted on a special experimental setup. The uniformity of the reconstituted specimens was verified by measuring the water content and grain size distribution throughout the specimens. The testing program was expedited using a special sample handling technique to move the specimen from the special experimental setup to the triaxial chamber base platen. The handling process did not disturb the specimens to a measurable degree. Further, the replicas of the reconstituted specimens were verified by submitting them to basic volumetric measurements followed by static and cyclic triaxial tests. The triaxial test results reported very small differences.

Monotonic Behavior of Mississippi River Valley Silt in Triaxial Compression

The static behavior of Mississippi River Valley silt was characterized using triaxial compression testing. Silt specimens, especially overconsolidated ones, showed dilation behavior. There was no unique critical state among specimens with different overconsolidation ratios (OCRs). With OCRs of 1, 2, and 8, the specimens exhibited normal behavior and dilated more as effective consolidation pressure dropped. However, for an OCR of 4, the specimens showed opposite behavior and dilated more as effective consolidation pressure rose. The friction angle of the silt was computed on the basis of several failure criteria, and the limiting strain was found to be the best one owing to better consistency and rational results of the friction angle. The silt showed a unique behavior compared with sand and clay: The critical state line was not parallel to the normal consolidation curve in the e-lnp 0 space; the stress-strain behavior can be normalized by effective consolidation pressure. The normalized shear strength of overconsolidated specimens was correlated to that of a normally consolidated specimen using Ladd et al.s equation with an mvalue of 0.58 for low-plasticity silts. However, the normalized shear strength of overconsolidated silts cannot be related to OCR directly. It was indicated that at least the normalized shear strength of a normally consolidated specimen needs to be tested for low-plasticity silts to obtain the normalized shear strength of overconsolidated specimen using Ladd et al.s equation. DOI: 10.1061/ (ASCE)GT.1943-5606.0000603.

Compressibility Characteristics of Low-Plasticity Silt before and after Liquefaction

AbstractLow-plasticity silt is known to have a potential to liquefy during earthquakes. The compressibility characteristics could change before and after a dynamic event that produces liquefaction. This research investigates the liquefaction resistance and postliquefaction reconsolidation characteristics of Mississippi River Valley (MRV) silt using laboratory cyclic triaxial compression testing. The MRV silt experienced initial liquefaction under cyclic loading, and the results are presented as cyclic stress ratio versus loading cycle curve. After cyclic loading, the liquefied specimens were reconsolidated. Permeability did not change significantly as a result of liquefaction. The reconsolidation curves are more parallel to the compression line than the recompression line in e-logσ3′ space, suggesting reconsolidation behaved more like preliquefaction compression. The postliquefaction compression and recompression indexes show less compressibility when compared with preliquefaction conditions. These charac...

Effect of Plasticity on Shear Behavior of Low-Plasticity Fine-Grained Soil

AbstractTo study effect of plasticity on shear behavior of low-plasticity fine-grained soil, a Mississippi River Valley (MRV) silt with a plasticity index (PI) of 5.8 was treated with different dosages of sodium bentonite to modify its plasticity up to a PI of 13.5. The naturally occurring material originated from the MRV exhibited dilative behavior under normally consolidated conditions. The silt-bentonite mixtures tend to lose quasi-steady-state strength and dilative characteristics as the plasticity increased. At a PI of 13.5, the silt-bentonite mixture had plastic stress-strain clay-like behavior. Overconsolidation did not influence the friction angle of the natural silt, but for silt-bentonite mixtures with PIs of 6.2 and 9.4 the influence of prestress was evident. The normalized shear strength was significantly reduced with an increase in PI from 5.8 (natural MRV silt) to 6.0 (natural MRV silt with 2.5% bentonite added). Compared to the predictive relationships proposed by other researchers, the nor...