Safety Risk Assessment And Countermeasures For Deep Foundation Pit Excavation In Lanzhou Metro Station

In recent years,with the rapid development of our country's economy and the people's need for a high quality of life,the urban population has grown rapidly and the radius of the city has continued to expand.It was born to ease the pressure on urban traffic and meet the travel needs of citizens.Due to the complex surrounding environment along the subway,the uncertainties involved in the construction of subways are increasing,and the safety risks are also increasing.It is necessary to use scientific and reasonable methods to effectively manage the safety risks in subway construction and prevent security accidents.The thesis takes the research on the safety risk evaluation of the deep foundation pit excavation of Lanzhou subway as the starting point,and further improves the safety risk management system of deep foundation pit construction in Lanzhou,which has importantly theoretical and practical significance.The thesis takes the deep foundation pit project of Dongfanghong Square Station of Lanzhou Metro as a carrier to carry out a case study of safety risk management,combines domestic and foreign engineering risk research theories and methods,and analyzes horizontal process and vertical basic risk sources based on WBS-RBS technology.A safety risk identification coupling matrix is established to identify safety risk factors in the deep foundation pit excavation of Lanzhou Metro.Based on the identification of safety risk factors for deep foundation pit excavation,the hierarchical structure among risk factors is straightened out and standardized,and a safety risk evaluation system for deep foundation pit excavations in Lanzhou subway stations is established.How to establish a safety risk evaluation model for the deep foundation pit excavation of Lanzhou subway station? Firstly,establish the safety risk evaluation index set for the deep foundation pit excavation of Lanzhou subway station,and construct a hierarchical judgment matrix.Then,use the judgment matrix to calculate the weighting of each risk factor and sort it to select the a high contribution to the safety risk of deep foundation pit excavation.Based on the BP neural network model,calculate the higher safety risk level of deep foundation pit excavation,make a choice that weigh the risk consequences and the probability of occurrence.Finally,compared with the monitoring of risk factors in case engineering,the monitoring of deep foundation pits can only play a simple feedback role,while the evaluation model enables the system to dynamically and comprehensively evaluate the safety level of deep foundation pit excavations,indicating that the safety risk assessment model has Certain applicability and guiding significance.In view of the evaluation results,the thesis focuses on the research of four safety risk countermeasures,including deformation of cast-in-situ piles and supporting structures,gushing water from foundation pits,uplift at the bottom of foundation pits,and settlement andcracking of shallow municipal pipelines.In order to avoid and prevent the possible occurrence of unexpected risk accidents,effectively reduce the safety risk level of the deep foundation pit excavation at Lanzhou subway station,and ensure the safety of subway station construction operations.