Research On Influence Of Excavation Of Foundation Pit And Cement-soil Reinforcement On Deformation Of Adjacent Tunnel

In recent years,urban rail projects have continued to develop,and urban subway construction is changing with each passing day.At the same time,urban buildings are dense,and large buildings are often accompanied by subway stations and subway lines.Excavation of building foundation pits brings unloading of earthwork,which will cause redistribution of stress in surrounding soil,and deformation of nearby tunnels within this range And internal force changes,leading to cracking of tunnel segments,bringing potential danger and economic loss.Especially in soft soil areas such as Shanghai and Hangzhou,large and deep foundation pits will cause different degrees of damage to adjacent subway tunnels.At present,the foundation pit project near the tunnel adopts block excavation,passive zone reinforcement and other protective measures.These measures can protect the adjacent tunnel,but the study of the reinforcement parameters of the passive zone of the foundation pit and the internal force and deformation of the tunnel itself-The situation analysis is less,based on this,the research content of this article is as follows:(1)Combined with the soft soil quality characteristics of Hangzhou,26 cases of foundation pit projects near the operating subway tunnel in Hangzhou were counted to study the influencing factors of tunnel deformation,the distance between the foundation pit and the tunnel,and the relative height of the foundation pit and the tunnel were analyzed The influence of poor and excavation area of the foundation pit on the deformation of the adjacent tunnel,and analyze the protection effect of the reinforcement method of the foundation pit on the adj acent tunnel;(2)Choose one of the cases,use Plaxis 3D to establish a finite element model,compare the displacement of the tunnel in the model with the measured displacement,study the protection of the passive area of the foundation pit in the project on the protection of the adjacent tunnel,and compare the HS and CTS models Accuracy of reinforcement in the passive area of simulated foundation pits;(3)Select the most unfavorable cross-section in the above case,establish a two-dimensional finite element simplified calculation model,and use the orthogonal analysis method as the basis to use the adjacent tunnel displacement as the control index to strengthen the mechanical and interval parameters of the foundation pit bottom Perform a sensitivity analysis.Using the parameter analysis method,analyze the influence of the interval parameters of the passive zone of the foundation pit on the adjacent tunnel,study the optimal reinforcement interval of the foundation pit for protecting the adjacent tunnel,and analyze the protection effect of the reinforced soil on the adjacent tunnel under different cement and soil contents;(4)Using the ABAQUS finite element software and the load structure method,the surrounding stress field changes caused by the excavation of the foundation pit act on the tunnel through the soil spring,changing the depth of the tunnel and the excavation depth of the adjacent foundation pit.The stress and deformation of the adjacent tunnel under the reinforcement of the circle.