Study On The Influence Of Underground Tubular Structure On Earthquake Subsidence Of Soft Soil Field

Under the action of earthquake,the earthquake subsidence of engineering foundation is one of the main damage of soft soil site.Soft soil foundation usually has the characteristics of easy compression,low strength and low permeability.Its mechanism of earthquake subsidence is complex and there is no unified understanding at present,and the engineering method of earthquake subsidence analysis is also inadequate.There are a lot of soft soil engineering sites in Beijing-Tianjin-Hebei region,Yangtze River Delta region,Guangdong-Hong Kong-Macao Greater Bay Area and major river basins areas.In order to meet the needs of three-dimensional expansion of urban space in the region,more and more underground structures have been or will be built in these soft soil sites,and there are few reports on the influence of underground structures on the seismic subsidence of soft soil engineering sites.The supplement and development of this research will help meet the needs of urban pipe corridor projects,underground rail transit projects,civil air defense projects and other infrastructure construction and renovation projects,at the same time,it is conducive to the the foundation earthquake subsidence risk assessment work for the development and utilization of the above-ground sites in the area where the underground structure exists.In this paper,based on the commonly used tools of dynamic response analysis of engineering site,the model and method of earthquake subsidence analysis of soft soil site engineering are established,and the basic influence law of the tubular underground structure on the upper engineering foundation is explored.The main related research work and results are as follows:1.Based on the FLAC 3D and the vibration softening model,which are commonly used in the field analysis of engineering,the method of soft soil earthquake subsidence analysis of raft shallow foundation is established,and the feasibility of analyzing the complex engineering problem of soft soil earthquake subsidence based on the conventional simulation method is explored.2.In this paper,the damage caused by soft soil subsidence of typical building foundation in Tanggu new port area of Tianjin during 1976 Tangshan earthquake is simulated,and the rationality of the simulation method in this paper is verified by comparing the measured seismic damage data with the calculation examples of the two-dimensional dynamic finite element program of the previous code method.3.Taking raft shallow foundation and square section underground tubularstructure as examples,the paper analyzes the earthquake subsidence of different layers of superstructure under the working condition of vertical underground structure,and points out the general influence law of the existence of vertical underground tubular structure on the earthquake subsidence of soft soil ground foundation.4.Based on the model,the paper analyzes the earthquake subsidence of raft foundation in soft soil field under different buried conditions and cross-section sizes of tubular underground structure,and establishes the preliminary understanding of the influence of factors such as buried depth,buried distance and cross-section size of tubular underground structure with square cross-section on the earthquake subsidence of single foundation.