Journal of Natural Disaster Science

Relationship Between Grain Crushing and Excess Pore Pressure Generation by Sandy Soils in Ring-Shear Tests

Fawu WANG
Department of Civil Engineering, Kanazawa University, Kanazawa 920-8667, Japan.
and
Kyoji SASSA
Disaster Prevention Research Institute, Kyoto University, Uji, Kyoto 611-0011, Japan.

(Received for 2 February, 2001 )

Abstract

The grain crushing character of sandy soil greatly affects its excess pore pressure generation behavior during rapid landslide motion. Ring-shear apparatuses were used in an experimental study of the relationship between grain crushing and excess pore pressure generation by sandy soils. Three samples with different grain crushing susceptibilities were used. Drained tests were conducted to investigate these samples' grain crushing susceptibilities. Undrained tests (speed-controlled and cyclic-loading ones) were conducted to investigate excess pore pressure generation behavior. Based on the findings for sample-height change in the drained tests and for the excess pore pressure ratio in the undrained tests together with shear displacement, dilatancy characteristics of sandy soils could be divided into three phases: "initial negative dilatancy", "initial positive dilatancy", and "negative dilatancy due to grain crushing". The first two phases were mainly affected by the initial structure, whereas the last one was affected by the grain crushing susceptibility. Once the steady state was reached, excess pore pressure apparently was determined by grain crushing susceptibility, whereas the initial density did not have this effect. In the undrained cyclic-loading tests, the effect of the frequency of cyclic-loading on excess pore pressure also was found negligible.

Key words

grain crushing, exess pore pressure, dilatancy, sample-height change, cyclic-loading