Abstract: Understanding rainfall infiltration process and rain-induced failure mechanism in unsaturated soils depends on experimental study with joint monitoring of multi-physical parameters. Based on the monitoring technology of soil response under a high-gravity environment, centrifuge modelling of rainfall infiltration in a unsaturated loess is carried out. Effects of high-gravity on micro-probe of time domain reflectometers (TDR) and tensiometer were evaluated. TDR probes, tensiometers, bender elements were jointly used to monitor the multi-physical response in the soil model. The experimental results showed that consistent waveforms were measured by the TDR probes for a given soil subjected to at different g levels. It indicated that the measurement by TDR was not influence by the high gravity, and the measurement error of gravimetric moisture content was within 2%. The value of matric suction measured by the tensiometer appeared to decline during centrifugal acceleration process. After the acceleration reached the stable value of 40g, the recorded suction was recovered to the initial suction measured under normal gravity within 10 minutes. During the process of rainfall infiltration, the TDR, tensiometer and bender element, which were buried at same depth, showed a concurrent response to the arrival of wetting front. Rainfall infiltration resulted in an increase in moisture content, a decline in matric suction, and a decrease in shear-wave velocity. The joint monitoring of muti-physical parameters will provide useful data for establishing the relationships among moisture content, matric suction and shear modulus.

Key words: unsaturated soil, rainfall infiltration, centrifuge modelling, TDR probe, tensiometer, bender element