| The economy of our major city had a great growing along with the in-depth development and the underground engineering space exploiting during this century,the environment around the foundation pit has become more and more complex,the scale and the depth of it have also continued to increase.During the procedure of excavation,the deep and large foundation pit will inevitably bring additional deformation and internal force to the surrounding buildings and underground pipelines.If the design and construction are improper,the damage will be caused,and the normal use will be seriously affected and even cause safety accidents.Therefore,it is very important to improve the deformation control ability of foundation pit during construction.There are many kinds of foundation pit support systems,and the inner support structure plays an important role in it.Many experts and scholars have done a lot of researches on the influencing factors of the deformation of the inner support structure.Taking the foundation pit of the east square of the underground space utilization project of Hefei University City as an example,the major work of this paper is analyzing the displacement pattern of the foundation pit and exploring the optimization of the foundation pit support program.The main work of this paper is to monitor the stress in the deep soil on the east side of the construction site during the excavation,and obtain the first-hand monitoring data.Build a model of the foundation pit by Midas GTS/NX,simulated the displacement during the whole construction procedure,and compared its results with the on-site monitoring data to verify the model’s reliability and credibility.Based on the calculation results of the model,this paper summarized the variation pattern of the displacement in various aspects of the foundation pit during the excavation process,gave the reasons of the certain pattern,and optimized the support system according to the problems founded in the deformation analysis,which can provide a reference to similar foundation pit engineering design.The main conclusions are as follows:（1）The excavation area of the foundation pit is relatively large,and the elastic uplift caused by the unloading of the soil at the excavation surface of the foundation pit is relatively serious.The uplift of the pit floor causes the same upward tendency of the retaining piles to which it is attached.（2）The maximum lateral displacement of the retaining structure is generally in the middle and upper parts of the it,and the inclined displacement of each section of the retaining structure in the area with only tilted bracing is generally larger than that in the fan-shaped area of the foundation pit with concrete horizontal supports.So the concrete horizontal supports have better control effect of pile lateral movement.（3）In the area with only tilted bracing support,the surrounding surface settlement is basically "grooved".After the final excavation,the surface settlement around the soil surface becomes "inverted triangle" due to the loss of support.Because the fan-shaped area of the foundation pit have two concrete horizontal supports and one tilted support,the settlement of the surrounding surface is relatively small,and the settlement section is "grooved".The inner support system of the fan-shaped area has a better control effect of the displacement.（4）Through the optimization analysis,it is concluded that the support setting in section E is insufficient,and the optimization effect of adding diagonal bracing is better in terms of deformation control of the foundation pit;Adjusting the horizontal bracing can reduce the total displacement of the enclosure pile by 5.2%,while the diagonal bracing is only 1.79%.For the deformation control effect of the enclosure structure,the cross-sectional size of the internal bracing has a greater influence than the elastic modulus.The best optimization scheme is obtained by comparing the simulation results.Figure [78] Table [7] Reference [63]... |
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