Monitoring of Pore Pressure Response during Cavern Excavation in Soft Rock and Numerical Discussion on Its Mechanism

The aim of this paper is to study the mechanism of pore pressure response in soft rock excavation. During a cavern excavation for investigating the Excavation Disturbed Zone (EDZ) of the radioactive waste disposal cavern, pore pressure responses near side-wall of cavern were shown as follows : i) at the 1st bench excavation, pore pressures went up temporarily and then went back to ordinary state. ii) at the 2nd bench excavation, they went down temporarily and then went back to ordinary state. It is supposed that these pore pressure responses would be problems proper to soft rock. The mechanism of the pore pressure response is numerically proved by applying the three dimensional hydro-mechanical coupled finite element analysis.