Study On Ground Settlement And Construction Optimization Of Multiple Tunnels Under Repeated Disturbances In Short Distance

With the rapid economic development and large-scale urban construction in China,urban land resources are increasingly scarce,and urban ground traffic is also increasingly congested.In order to solve this problem,large-scale underground space development and utilization have been undertaken.Since China has entered the era of large-scale development and utilization of underground space,underground rail transportation is gradually emerging and constructed on a large scale,especially in the case of large cities.As a result,subway lines and the transition lines of subway arises spontaneously and double hole or even multiple tunnel appears.Tunnel surrounding rock and Overburden soil are not only affected by the construction of single line tunnel but also be affected by the construction of tunnels in close proximity to other lines,resulting in repeated disturbance of surrounding rock,overburden soil and ground surface,which makes these problems more complex.To address the above problems,the surrounding rock,the overlying rock and soil,and the surface of the tunnel were regarded as related bodies,and the strata displacement(deformation of surrounding rock,the subsidence of overlying rock and soil and the surface subsidence)under the condition of repeated disturbance of the construction of the multiple tunnel was studied,which is collectively referred to as the stratum subsidence,that is,the root cause of the ground subsidence is revealed from the root research,and the settlement law of the ground displacement caused by the tunnel construction is finally passed to the ground,so that the ground settlement of similar projects can be accurately predicted,and multiple reasonable construction optimization design and settlement risk control of the tunnel.The main research contents and research results obtained in this paper are as follows:(1)On the basis of literature review,Peck formula,and the characteristics,laws and mechanism of ground settlement caused by the excavation of single-hole tunnel,the variations of stress field and displacement field of the surrounding rock mass in double-hole tunnel and three-hole tunnel are described qualitatively.The new characteristic points and parameters of the ground subsidence curve were invstigated,and the repeated disturbance system under the construction condition of multiple tunnel was developed;(2)Based on the study of the mechanical mechanism of strata displacement(surrounding rock deformation,overburden soil subsidence and surface subsidence)under the condition of repeated disturbance during the construction of multiple tunnel,the influence angle of excavation and the coefficient of repeated disturbance were introduced into the calculation formula of overburden subsidence and surface subsidence to study the new prediction model of peck formula for the surface subsidence and overburden subsidence of multiple tunnel.The research outputs provide much insights into the prediction model of peck formula,leading to applications in the prediction of ground and overburden subsidence caused by subway tunnel construction.(3)The two-dimensional numerical model of single hole tunnel,double hole tunnel and three hole tunnel is established based on the prototype of the main line of double hole tunnel of Qingdao Metro Line 1,the leading line of wawuzhuang station and the main line of the tunnel.The simulation results are compared with the monitoring data,and the characteristics and laws of surface subsidence and overburden subsidence are quantitatively analyzed;(4)The finite element software,ABAQUS,was used to establish a threedimensional model and perform numerical verification,analyze the ground settlement caused by the construction of a small clear-space three-hole tunnel under different working conditions,and to focus on the study of repeated repeated disturbances in subway tunnel construction,and further to optimize the construction design of the parallel three-hole small-clearance tunnel to determine the best tunnel construction process,the longitudinal spacing of the tunnel and the tunnel construction steps,which provides a reference for the design and construction of the tunnel project.The impact on surface settlement was completed by the development and verification of a series of numerical simulations.The complexity of formation displacement and surface settlement caused by repeated disturbances in the construction of multiple tunnels was systematically investigated by means of qualitative theoretical analysis,numerical simulation verification,theoretical expansion research,and on-site monitoring.The corresponding results are obtained,which provides basis for the follow-up optimization design of short-range construction of shallow multiple tunnel,and also promote the direction of stratum settlement caused by tunnel construction progress.