Numerical Simulation Analysis Of Dewatering Project Of Strip Pit In Zhengzhou Eastern

In recent years, with the development and utilization of urban underground space, deep excavation works more and more attention. To ensure the smooth progress of excavation for the Eastern District of Zhengzhou, the quality of stratified (silt and silty clay alternating), the successful excavation dewatering is a critical success factor. Dewatering is a typical three-dimensional seepage problem. ABAQUS,a finite element analysis software,is employed to simulate dewatering progress and is proved feasible in simulating engineering foundation pit by comparing those simulation results with the theoretical calculation.Based on plenty of previous relevant theories, A finite element model is builted to simulate foundation pit considering the peculiar layered soil engineering geological conditions of Zhengzhou Eastern. The reasons of land displacement problem and the distribution characteristics of displacements occurring in each soil layer are analysed. Otherwise, the problem concerning waterproof curtain's high efficiency to protect the surrounding soil environment is also performed.Results of numerical simulations indicate that the combination of tube wells and light wells is an effective way to solve excavation dewatering problem in the Eastern District of Zhengzhou.The main results are showed as follows:(1) Dynamic water level is introduced to the simulation for the sake of more accurate results by inserting the observation data obtained during dewatering to the model.The simulation results are approaching the practical displacement, and It provided an easy acess to calculation parameters and convenient calculation process. The possible deviation of given dynamic water level from practical position have an impact on the drawdown,but the results of displacement will be scarcely influenced.(2) In layered soils of the Zhengzhou region, the subsidence(i.e.vertical displacement) occuring in fine sand layer takes large part of the ground settlement,with the maximum approching to half of the total value.The distribution of each soil layer'horizontal displacement is approximately parabolic and the maximum horizontal displacement of each soil layer occurs in a certain distance away from the edge of excavation. The horizontal displacement of fine sand layer takes large of the total horizontal displacements, about half of the total land surface horizontal displacements.(3) The subsidence occuring in fine sand layer presents a characteristic called " released water settlement ", but subsidences of the silt and silty clay layers are the combined result of "released water settlement" and "vacuum deposition".(4) The waterproof curtain will play active role in cut-off sealing only when it goes through silt set layer of dewatering areas. Taking economic efficiency into consideration,the waterproof curtain should be carefully used.(5) The results demonstrated that combining tube wells with light wells is an effective Technique to pump groudwater during lager and deep foundation pit. The only light well system cannot reach enough deepth.The only tube well system performs an inefficient dewatering,which may lead to slope instability and other defects because of the detained water in soil. The combining tube wells with light wells could overcome both weakness.This system brings about a quick dewatering progress and prevents the detained water permeating into excavation, achieving lower construction costs and high economic efficiency.