Numerical Simulation On Supporting Schemes Of LongShan Civil Air Defense Reconstruction Project

The civil air defense projects are for protecting people’s lives,important materials and equipment,preventing air raids and nuclear radiation during wartime.All the time,China has not completely stopped the special construction of civil air defense.In the early days of new China,civil air defense construction is mainly used for military defense.However,with the rapid and healthy development of contemporary China’s economy,the important role of civil air defense engineering is also expanding.At present,civil air defense engineering has gradually developed into a part of urban civil air defense infrastructure.Support is an important construction link in the process of construction management of civil air defense engineering.By reading a large number of relevant academic literature and referring to some successful construction technical cases at home and abroad,this paper analyzes and summarizes the performance advantages and disadvantages of several common support construction methods.Considering Qingdao Longshan civil air defense reconstruction project,several support schemes are put forward,and the numerical simulation analysis is carried out,and the optimal support scheme is obtained by comparison.All the results provide practical data reference for the actual support construction work.The constitutive model of the civil air defense supporting structure is established by using ABAQUS finite element analysis software,and the safety factor,vertical stress and displacement under different types of supporting structure schemes are numerically simulated and analyzed.The research work of this paper is as follows:(1)The basic theories and equations such as strength criterion are studied,and the type and mechanism of supporting structure are analyzed and summarized.Then relying on the geological structure and stratigraphic parameters of the Longshan civil air defense reconstruction project in Qingdao,the original ground stress of the existing chamber is calculated and balanced by using ABAQUS finite element software,so that the numerical model can obtain an initial stress without initial strain.(2)The stress,displacement and plastic zone of the existing chamber are analyzed.Through the analysis of the stress and displacement field of the existing chamber,the weak part of the structure is identified and the support scheme is designed.According to the simulation results of the existing chamber stress and displacement field,several chamber expansion support schemes are analyzed and put forward.Based on the selected expanded excavation support scheme,the numerical simulation software is used to simulate different support schemes.(3)Comprehensive analysis of the chamber stress,displacement and structural changes of the plastic zone after secondary excavation and support under different working conditions is executed.The strength reduction method is used to calculate the safety factor of chamber excavation support under different working conditions.According to the maximum tensile stress and displacement variation of some key points for different excavation conditions,the optimal support scheme is obtained and can be used to reconstruct the Longshan civil air defense engineering.