Experimental studies on influence of pit dewatering on soil deformation at different locations below excavation base

Based on the analyses of soil stress changes in passive region under the alternate effect of excavation and dewatering, the deformation properties of the soil with different horizontal locations are studied using triaxial tests. Compared with those just considering the effect of excavation, the following conclusions can be drawn. First, the deformation properties of the soil in the excavation base with different horizontal locations under the alternate effect of dewatering and excavation are all significantly improved and the initial unloading modulus is remarkably increased compared with that just considering the effect of excavation. The total heave of the soil in all the horizontal locations is also decreased. However, the dewatering will increase the soil heave in each excavation step compared with that just considering the effect of excavation, as the soil stress relief in each excavation step is significantly increased due to the effect of dewatering. The test results also show that the heave of soil elements close to diaphragm wall under the alternate effect of excavation and dewatering is remarkably larger than that in the center of excavation. The total heave of the soil elements close to diaphragm walls under the alternate effect of excavation and dewatering is even larger than that just considering the effect of excavation. The influences of dewatering inside the pit on the deformation properties and soil heave are closely related to the dewatering time, dewatering depth, the coefficient of permeability of pore water and so on and should be considered in deep pit excavation under the groundwater level.