Wei F. Lee

This paper aims to introduce research progress on liquefaction resistance and internal erosion features of non-plastic silty sand. Contents of this paper include the field application of a new sampling technique that would allow sensitive and high-fines content silty sand material to be retrieved in sounding condition; laboratory test results on liquefaction resistance of non-plastic silty sand emphasized on the influence of fines content; and finally, results of utilizing a specially designed test device, Flexible Wall Pin Hole Test Device, to investigate the internal erosion characteristics of non-plastic silty sand. It concludes that higher non-plastic fines content of silty sand would result in lower cyclic liquefaction resistance as well as higher internal erodibility. Moreover, the indicated trends would become more obvious when such non-plastic silty sand was subjected to disturbance. Results of this study will to improve engineers' understanding on engineering behavior of non-plastic silty sand.

This paper presents numerical modeling work as part of a forensic investigation on a catastrophic roadside slope failure in Taiwan. It includes three stages of numerical modeling analysis of the failure slope. Two-dimensional (2D) limited equilibrium analysis numerical modeling is first carried out to check the original design. A series of parametric studies are then introduced to investigate the influences of controlling design factors on slope stability. Finally, three-dimensional (3D) finite-element difference analysis is conducted to further examine possible failure scenarios and the failure states. As a result of this study, the failure mechanism and triggering factors were possibly verified via the numerical analyses. The purpose of the presented study hopefully introduces the applications of numerical modeling in similar forensic investigations, as well as appropriate means of adapting numerical modeling in a forensic investigation.

The exposure of bridge foundations due to scouring has been recognized as the most critical cause for highway bridge failures in Taiwan, yet difficulties have been found to identify its risk level. In an effort to develop an efficient measure for the detection and estimation of the scour of bridge foundations, a series of field vibration measurements were conducted on selected highway bridges of which the foundations had been suffered different levels of scouring. In this paper, theoretical background of utilizing vibration measurement to estimate the exposure of bridge foundation is introduced. The setup of vibration measurement on bridges and schemes of data processing are described. Results of the mentioned field tests on bridges are presented, and the feasibility of using vibration measurement to evaluate the scour of bridge foundations is thus verified. The findings of this study are helpful in developing the inspection and monitoring technology for bridge scouring.