Abstract:Combined with water gushing in pit,the laboratory model test research is carried out. By comparison between the parameters before and after the test,the development regulation of physico-mechanical parameters of the substratum of pit is found. The cohesion and modulus of compression of the substratum are deeply reduced after water gushing in pit,but the internal friction angle of the substratum doesn¢t change. According to the results of the test,when the head pressure of confined aquifer is equal to the earth pressure of the super stratum,the gushing in pit doesn¢t occur. So this paper points out the disadvantages of pressure balance method,traditional judgment method of water gushing in pit. Based on the theoretical analysis of the test results,considering the cohesion force component of the shear strength,the judgment method of gushing in pit is quantified for the first time and is compared with engineering practice. The results show that the traditional judgment method of water gushing in pit is overestimated when it is used to design the pit in soft soil.