Studies Of The Effect Of Deep Excavation Dewatering On Support And Surroundings In Soft Clay

Deep excavation is a complex temporary engineering and strong regional. Different hydrological and engineering geological conditions of deep excavation are very different. Dewatering is necessary in the evcavation under water level in soft clay, which provide a dry environment for the excavation and enhancing the strength of the soil.But the surroundings ground settlement caused by excessive dewatering tends to affect the environment.Changing of soil and water pressure and even influenced the stability of the foundation pit. In this paper we take deep excavation of the Youth Olympic axis engineering as an Example, But practical designs often use investigation data to design of dewatering and supporting before the dewatering. And practical construction after dewatering, there is deviation with real situation. This paper is approximate to the actual construction state, using moisture content to evaluate dewatering, and analyzed effect of the surrounding environment and supporting in soft clay.In this paper, the following research work:(1) Summarizing the engineering properties of soft soil and the current studies of deep excavation in soft soil area effecting on the surroundings. Studying about Nanjing youth Olympic axis of deep excavation dewatering effect on support and surroundings in soft clay. Considering the soft soil layer soil parameter are different after investigation and dewatering, on the basis of the state of soft clay and measured data. Simulating different depth of soft soil dewatering effect respectively divided into different moisture content and taking water content as effect of dewatering(2) Under the condition of different moisture content, compaction degree reshape Nanjing Hexi muddy silty clay samples, the deformation, strength and permeability, creep characteristics were analyzed and separately experimented with consolidation test, shear test, penetration test, uniaxial compression creeptest, direct shear creep test. The test results were analyzed and obtaining physical mechanical properties index of soil clay.(3) Simulation results of deep excavation engineering of youth Olympic axis partition dewatering show the armed police force in the ground settlement around the biggest J3 area,32 mm, and beyond the depth of ground subsidence control. Requiring the pit ground injection processing, take single well injection quantity for 1/3 of the dewatering for numerical simulation, it is concluded that the area around J3 armed forces in groundwater to rise 2 m, ground subsidence back to 16 mm for settlement under control.(4) Supports structure of the biggest land subsidence area about J3 are analyzed on the west side of drilling pouring pile as an example, it is concluded that under different conditions supporting pile deformation and internal force, and bending moment by horizontal displacement, shear force increases with the excavation depth. The biggest displacement, bending moment, shear force occurred were all in the last condition, were 19.98 mm, 845.24 kN/m,1265.63 kNm/m.The horizontal maximum displacement occurs near the bottom of the foundation pit two-thirds, about 10 m below the ground; Compared with monitoring data analysis, calculation results and the measured has good consistency. Comparing simulation results of later and former supporting structure showed that the horizontal displacement and bending moment are increased; the largest is 22.32 mm,1543.26 kNm/m respectively. Recirculation while control ground subsidence to expand but for supporting structure deformation and bending moment are increased, so the internal force of support structure and horizontal displacement monitoring become more important.