| With the development of city construction and the city underground space,more and more deep foundation pit engineering break out.Because of the increase of area and depth of excavation of deep foundation pit and the complex of surrounding environment,there are lots of geological disasters such as foundation pit instability occur which seriously affect the safety of excavation and the excavation.Currently,the slope safety evaluation method focus on foundation pit slope deformation monitoring,which takes the deformation control value as the evaluation criteria.But the type of foundation pit excavation engineering,level of security,working conditions,surrounding environment,engineering geological conditions of each foundation pit engineering are not the same,so it is not reasonable that take the same deformation control value to monitors all of engineering.At the same time,the design of foundation pit hypothesis is not entirely consistent with the actual situation of the project,so the design and construction of the whole project basically rely on experience design.Therefore,based on the of the previous research,the author puts forward an evaluation model of pit slope stability,carry out simulation using the analysis of the finite element simulation software ABAQUS,verify the validity and accuracy of evaluation parameters in evaluating the stability of foundation pit slope,and gives evaluation and guidance for the stability of original supporting structure using the parameters and the value of the stability criterion,provides an effective evaluation theory method for foundation pit supporting structure design,the original slope support structure optimization treatment and the slope stability evaluation after support.The main research contents of this paper are as follows:(1)Propose the stability evaluation parameters of the foundation pit slope based on the data of dynamic displacement monitoring of foundation pit slope,a comprehensive evaluation parameter that can reflect the characteristic of displacement deformation and the characteristic of slope failure mechanics--Displacement Vector Ratio Parameters Of Foundation Pit Slope(DVRPFPS),in order to evaluate thestability of foundation pit slope during the whole foundation pit excavation;(2)Take a deep foundation project in Ji’nan as an example,to simulate the excavation process for the example project under the condition of no support using finite element simulation software ABAQUS,to look for the quantitative relationship between DVRPFPS and the stability coefficient of the foundation pit slope,and then to evaluate the effectiveness and applicability of the proposed evaluation parameters,and according to the quantitative relationship and the principle of mathematical statistics,propose abnormal evaluation criterion,and take this criterion as the stability criterion for foundation pit excavation for the slope;(3)Using the ABAQUSfinite element simulation software to simulate the process of excavation engineering under the condition of soil nailing,to analyze the change rule of DVRPFPS of foundation pit excavation slope under the condition of different soil nail length,find the optimal length of soil nailing;(4)Establish the foundation pit excavation dynamic monitoring and evaluation methods through the establishment of the foundation pit slope displacement vector than the critical criterion for stability evaluation parameters,and to determine whether support in each layer of the foundation pit excavation is needed or to adjust the original support and carry out the foundation pit support information dynamic optimization design;(5)Through comparison between the simulation results and the monitoring data,analyze the displacement variation law of the two factors,verify the accuracy of the simulation work and whether the results and rules are valid and reliable which are obtained from the theoretical evaluation method presented in this paper. |
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