Optimization Of Foundation Pit Monitoring Scheme Based On Three-Dimensional Geological Model And Construction Of Foundation Pit Monitoring Information Platform

At present,foundation pit projects are developing in a deeper,larger and more complex direction,and the degree of safety risk is getting higher and higher.As a correct guide for the construction of foundation pit engineering,effective monitoring is a necessary measure to avoid accidents.It has now become an essential and important link in underground engineering construction.The practice shows that the foundation pit monitoring scheme based on the traditional theoretical model is unreasonable in the aspects of monitoring range,monitoring point,monitoring control value and monitoring frequency.In this regard,based on the No.1 Foundation Pit Project of Nanjing Qingliangshan subway station,through the monitoring data and numerical simulation analysis,this paper studies and discusses the irrationality of the monitoring scheme based on the traditional theoretical model in terms of monitoring scope,monitoring points and monitoring control values,as well as the shortcomings of numerical simulation analysis.Based on the construction of three-dimensional geological model,the detailed numerical simulation analysis of foundation pit excavation is carried out,and the monitoring scheme is optimized and adjusted according to the results of numerical simulation analysis.Finally,the foundation pit monitoring information platform is built to improve the collection,processing,analysis and display of monitoring data.The main research contents are as follows:(1)Based on the monitoring data,through the comparative analysis of symmetrical points and the selection and analysis of the maximum deformation value,this paper studies and discusses the irrationality of the monitoring scheme of the project in terms of monitoring scope,monitoring points and monitoring control value.(2)Based on the traditional theoretical model,a complex three-dimensional finite element model considering the interaction of soil,support structure and horizontal support system is established,and the whole process of foundation pit excavation is numerically simulated and analyzed.By comparing the monitoring data with the numerical simulation results,the deficiency of numerical simulation analysis which layers geological bodies horizontally and assigns the same attribute value to each layer is studied.(3)According to the geological exploration data,on the basis of constructing the standard stratigraphic sequence of Qingliangshan Metro Station No.1 foundation pit project area,the three-dimensional geological structure model of the area is constructed by using the borehole modeling method.Based on the structural model,combined with the geological attribute information in the borehole database,the Kriging interpolation method is used to construct a three-dimensional geological attribute model of the area regarding elastic modulus,Poisson’s ratio,internal friction angle,and cohesion.(4)Based on the three-dimensional geological attribute model,detailed numerical simulation analysis of foundation pit excavation is carried out.Comparing and analyzing the numerical simulation analysis results and monitoring data,the applicability and accuracy of the detailed numerical model are verified.Based on the detailed numerical simulation results,the stress and deformation characteristics of the enclosure structure and surrounding geological bodies of the project are analyzed,and the monitoring range,monitoring points and monitoring control values in the monitoring scheme of the project are optimized and adjusted accordingly.(5)The optimization process of foundation pit monitoring scheme based on detailed numerical simulation is systematically summarized.Firstly,the electronic borehole database is standardized and the three-dimensional geological model of attribute structure matching is established.Secondly,the whole process of foundation pit excavation is simulated by nondestructive coupling numerical calculation element model and three-dimensional geological model.Then,the stress and deformation of foundation pit are analyzed regularly to form the pre-judgment list of Engineering dangerous areas.Finally,the foundation pit monitoring scheme is optimized according to the pre-judgment list of dangerous areas.(6)The whole cycle safety management platform of foundation pit is constructed through real-time perception technology of monitoring object state,data middle stage construction,data analysis technology based on entropy weight AHP fuzzy comprehensive evaluation,twin construction simulation analysis technology and foundation pit whole domain digital twin electronic sand table,so as to realize three-dimensional visual presentation and operation and digitize all monitoring behaviors.Automatic data collection,analysis and judgment,early warning and alarm through computer means,so as to make the monitoring more detailed.