No abstract

The potential of a novel, bio-mediated soil improvement to increase resistance to liquefaction triggering and to reduce the consequences of liquefaction if it occurs was evaluated. Microbial induced calcite precipitation (MICP) binds sand particles together through calcite crystal formation at particle-particle contacts. This results in an increase in the small-strain stiffness and strength of treated loose sand. Geotechnical centrifuge tests were used to evaluate the increased resistance of MICP treated sand relative to untreated loose sand when subjected to seismic shaking. Results of one model with a structure founded on sand treated to a moderate level of cementation and another model with the structure founded on loose untreated sand are compared. The centrifuge models were subjected to ground motions consisting of sine waves with increasing amplitudes. The accelerations, pore pressures, and shear wave velocities measured in the soil during shaking are presented. The resistance to liquefaction and deformation in the MICP treated model showed significant increases, as evidenced by substantial decreases in excess pore pressure ratios and vertical strains beneath the structure.

No abstract

This paper presents a field monitoring study with emphasis on the design and construction of a subsurface drainage system and evaluation of its stabilization efficiency on the slope of You-Ye-Lin landslide using a three-dimensional finite element method program (Plaxis 3D) for the groundwater flow and slope stability analyses. The subsurface drainage system consists of two 4-m diameter drainage wells with multi-level horizontal drains and was installed to draw down the groundwater level and stabilize the unstable slope of the landslide. Results demonstrate that the subsurface drainage system is functional and capable of accelerating the drainage of the infiltrated rainwater during torrential rainfalls during the typhoon season. The large groundwater drawdown by the subsurface drainage system protects the slopes from further deterioration and maintains the slope stability at an acceptable and satisfactory level.