Volume 33, Issue 4 (July 2010)
Real-Time Diagnosis Method of Compaction State of Subgrade during Dynamic Compaction
Dynamic compaction (DC) has become a popular method for deep improvement of subgrade. Dynamic settlement is often used as the termination index of DC. However, the index is external and experiential and cannot directly reflect the compaction state of a soil mass. In this regard, this paper presents a method for a real-time diagnosis of compaction state of subgrade, which is based on the analysis of dynamic pore pressure and dynamic soil stress induced by the impact of tamper weight. A field test was conducted to measure the dynamic pore water pressure and soil stress in a road subgrade under DC for expressway widening. After a certain number of compactions, the amplitudes of dynamic stress and pore pressure were stabilized and correlated well with both the compaction degree of soil and the dynamic settlement of ground. The dynamic response of the subgrade under different impact number reflects the variation of stiffness and strength of soil. With the findings the method for determining the optimum compaction number and the optimum single impact energy was presented.