Abstract: For deep excavation using the top-down method,the soil heave may produce significant effect on the underground structure.In the calculation of soil heave,the deformation modulus is obtained by taking the unloading path as the basic stress path and the effect of dewatering is not taken into account.However,for deep excavations in soft soil deposits,especially for excavation depth more than 20³0 m,large depth of water table lowering within the excavation has to be faced.The strength and deformation properties of the soil within the diaphragm walls under the alternate effect of excavation and dewatering are studied using triaxial tests.The test results show that compared with the test results obtained by only considering the effect of excavation,the dewatering in pit excavation can improve the strength properties of the soil.Large depth dewatering can also remarkably reduce the total soil heave due to excavation.Due to the remarkable influence of large depth dewatering on the strength and deformation properties of the soil in the passive region,the effect of dewatering on the soil heave must be taken into account.