Study On Grouting Active Control Of Deformation Of Adjacent Metro Tunnel Caused By Excavation Of Foundation Pit

With the continuous development of the urban economy,the city began to develop from two-dimensional planarization to three-dimensional three-dimensional,and inevitably there will be a phenomenon of foundation pit excavation beside the tunnel.At the same time,along with the improvement of tunnel deformation control requirements,the tunnel deformation control has reached the millimeter-level control precision,but the current research depth and breadth of the pit tunnel deformation control technology is still far from sufficient.Based on this,this paper mainly studies the grouting active control technology caused by the foundation pit causing the deformation of the adjacent subway tunnel.Firstly,the standard model under the convex deformation mode of the retaining structure is established in this paper.After that,the influence of foundation pit excavation on the deformation of adjacent tunnel,the influence of grouting on the deformation control of the tunnel,the influence of grouting on the deformation of retaining structure and surface deformation are studied.The research shows that the excavation of the foundation pit mainly causes the movement of the adjacent tunnel to the maximum deformation of the foundation pit retaining structure.The maximum horizontal displacement of the tunnel exhibits a semi-convex deformation mode near the foundation pit along the depth direction,and exhibits a cantilever-type deformation mode away from the foundation pit.At the same time,due to the influence of the displacement field of the soil outside the pit caused by the excavation of the foundation pit,the soil outside the pit can be divided into the settlement zone,the deformation transition zone and the uplift zone.Secondly,parametric analysis of different grouting directions,different grouting distances and different grouting pressures is carried out.The research and analysis of tunnel deformation response in different settlement affected areas are carried out.Deformation of the tunnel,deformation of the retaining structure and surface settlement are a joint deformation system.Grouting will cause settlement on the surface of the pit.When the deformation of the tunnel is caused by grouting,the deformation of the retaining structure will be larger,and the surface will also have greater settlement deformation;The effect of grouting on the deformation control effect of the tunnel has a relatively large relationship with the area where the tunnel is located.In general,grouting along the main vector direction of the tunnel deformation has the best effect on the deformation control of the tunnel,and the bottom grouting will have a relatively large lifting effect on the tunnel;At the same time,single point grouting will cause the change of the maximum position of the tunnel deformation.It is likely that the deformation at a certain position of the tunnel meets the control requirements,while the other position of the tunnel is unreasonably deformed due to grouting.Therefore,it is recommended to use the "multi-point grouting" control method when grouting;There is an optimal grouting pressure when the grouting control tunnel is deformed.When the grouting pressure is too small,the grouting will only have a micro-disturbing effect on the tunnel deformation,and when the grouting pressure is greater than the optimal grouting pressure The tunnel deformation will increase dramatically.Last but not least,the paper analyzes the active control of grouting in combination with the foundation pit support project of Zhuhai Hengqin Financial Leasing Headquarters Building.The deformation effect on the tunnel of vector grouting,grouting within the tunnel height range and grouting while excavating are analyzed.The research shows that deformation control effect of vector grouting is the best,effect of grouting in the height of the tunnel is second,and effect of grouting while excavating is the worst.