Mitigation of liquefaction and associated ground deformations by stone columns

A new desiccation theory is developed that provides a rational framework for the consolidation and desiccation analysis of soft fine-grained waste soils. The theory includes four consecutive segments that correspond chronologically to the phases that a soft soil layer undergoes in the field after deposition: consolidation under one-dimensional compression; desiccation under one-dimensional shrinkage; propagation of vertical cracks and tensile stress release; and desiccation under three-dimensional shrinkage. A general form of the finite strain governing equation of the overall consolidation and desiccation process is formulated. It includes the cracking function and the nonlinear constitutive relations. The experimentally obtained consolidation and desiccation characteristics for soft china clay, which are needed for the overall analysis of a given field problem, are presented. The predictions of this theory for the response of a hypothetical soft china clay layer undergoing self-weight consolidation, see...

Desiccation theory for soft cohesive soils

Cyclic undrained behavior of silty sand

Centrifuge modeling of pore pressure buildup in a sand deposit as a result of shaking is evaluated by comparison with a large-scale experiment. In large-scale Test SG-1, a 5.6-m-thick, mildly sloping deposit of hydraulic fill clean Ottawa sand of Dr=40%, was subjected to 5 s of low-intensity base shaking (<0.02g) that induced excess pore pressures short of liquefaction. Three centrifuge experiments using various soil deposits and saturation fluids were conducted and compared with the large-scale test. One of these centrifuge simulations used the same Ottawa sand and Dr=40% of the prototype, a viscous pore fluid, and dry pluviation deposition, which created a soil fabric stiffer than the prototype. The other two centrifuge simulations used silty sand saturated with water. The pore pressure buildup in one of the silty sand tests was in good agreement with the prototype, while the other two centrifuge deposits did not develop any excess pore pressure. The various responses in the four tests are expla...

Centrifuge and Large-Scale Modeling of Seismic Pore Pressures in Sands: Cyclic Strain Interpretation

This paper examines in detail the mechanics of lateral spreading observed in a full-scale test of a sloping saturated fine sand deposit, representative of liquefiable, young alluvial and hydraulic fill sands in the field. The test was conducted using a 6-m tall inclined laminar box shaken at the base. At the end of shaking, nearly the whole deposit was liquefied, and the ground surface displacement had reached 32 cm. The presented analysis of lateral spreading mechanics utilizes a unique set of lateral displacement results, DH, from three independent techniques. One of these techniques—motion tracking analysis of the experiment video recording—is especially useful as it produced DH time histories for all laminar box rings and a complete picture of the lateral spreading initiation with an unprecedented degree of resolution in time and space. A systematic study of the data identifies the progressive stages of initiation and accumulation of lateral spreading, lateral spread contribution of various depth ranges and sliding zones, their relation to the simultaneous pore pressure buildup, and the soil shear strength response during sliding. DOI: 10.1061/ASCEGT.1943-5606.0000409 CE Database subject headings: Soil liquefaction; Residual strength; Hydraulic fill; Full-scale tests; Lateral displacement. Author keywords: Liquefaction; Residual strength; Hydraulic fill; Full-scale tests; Lateral displacement.

James K. Mitchell

Papers

Densification and Improvement of Hydraulic Fills