Model Test And Numerical Analysis Of Excavation Behavior Of Deep Foundation Pit In Complex Surrounding Environment

The local support failure reduces the overall stiffness of the support structure and increases the displacement,which increases the support load of the adjacent internal support,often leads to the continuous failure of the support,resulting in the instability and collapse of the foundation pit;the local foundation soil leakage behind the pile causes the rapid collapse of the soil outside the pit;on the one hand,the soil pressure behind the pile decreases due to the loss of sand,resulting in the unloading effect;on the other hand,the local foundation soil seepage Leakage failure causes redistribution of soil stress and forms horizontal soil arch,which results in loading effect.A large number of studies show that the instability of foundation pit is often caused by local failure,but at present,there are few studies on the influence of local failure on foundation pit support structure,and few studies on the influence of complex surrounding environmental factors are reported.In this paper,through model test and numerical simulation,the local damage of foundation pit and the excavation of deep foundation pit in Loess field supported by pile anchor are studied.In this paper,the influence of local support failure and local soil leakage outside the pit on the foundation pit support structure is studied by indoor model test.The test results show that: when the local support fails,part of the load is transferred to the adjacent support through the purlin,which can lead to the failure of the adjacent support;when the support fails continuously,the increase of the support load of the non failure support increases significantly,which can lead to the further failure of the support;when there are buildings around the foundation pit,the increase of the support load of the non failure support is significantly greater than that of the foundation pit There is no building condition around,which is more likely to cause continuous failure of support.After the leakage of local soil behind the pile,the soil is damaged by a conical sliding surface from near to far,and causes the redistribution of soil stress to form a horizontal soil arch,resulting in the loading effect,increasing the positive displacement of adjacent support piles to the pit,and the bending moment of pile body;the leakage of local soil behind the pile causes the redistribution of ground stress,and the soil near the building is slightly uplifted upward.Then,a three-dimensional finite element model of pile and anchor support in a loess foundation pit is established.Considering the interaction between the retaining structure and the soil,the whole process of excavation is studied.The deformation of the retaining structure,the settlement of the soil at different depths behind the wall,the rebound of the soil at different depths below the pit bottom and the void of deep excavation are analyzed Inter effect.The results show that: the surface settlement presents a groove shape,the maximum settlement is located on the surface,the maximum settlement curve is located on the symmetrical plane of the center of the foundation pit,and the settlement amount and influence range of the pit corner are far smaller than the middle of the foundation pit,and the pit corner effect makes the foundation pit form a "settlement groove" in the longitudinal direction.Finally,the numerical method is used to further analyze the influence of the length of adjacent buildings around the foundation pit,the distance between the buildings and the edge of the foundation pit,and the road load on the excavation behavior of the foundation pit.The results show that: the existence of adjacent buildings reduces the spatial effect coefficient of rectangular foundation pit,the distance between the foundation pit and adjacent buildings has a greater impact on the surrounding environment,and the maximum settlement increases with the increase of the load of adjacent roads;under the action of adjacent buildings,the influence range of pit angle effect increases,but with the increase of the length of buildings,the influence range changes less;with the increase of adjacent loads and With the increase of the distance between pits,the influence range of pit angle effect decreases;with the increase of road load,the influence range of pit angle effect increases.