| In recent years,the rapid development of rail transportation projects in the city,and the large depth of the subway station pit,the surrounding environment is complex,the deep pit support projects put forward higher requirements.Therefore,this paper investigates the deformation characteristics of the rock-soil combination pit and the ultimate bearing capacity of the embedded rock section through statistical analysis and numerical simulation of the on-site monitoring data,and then optimizes the design of the supporting structure based on this.The main contents and conclusions of this paper are as follows.By statistical analysis of the measured data,the deformation characteristics such as ground settlement and horizontal displacement of the support pile were studied for three types of support pits.The results show that.(1)The ground deformation of the rock-soil combination pit is still dominated by settlement,and most of the final surface deformation values are small,the maximum settlement is about 0.046%H,the average value is 0.024%H,less than the design requirements of 0.2%H.(2)Most of the ground settlement and horizontal displacement of the pile body outside the rock-soil combination pits supported by the end-suspended piles are produced in the excavation stage,while most of the ground settlement has been completed in the first stage of the slope excavation of the slope nail wall pit,and the ground settlement is larger when the lower part of the slope embedded pile combination support is excavated.Through the comparison and expansion of the measured analysis by the numerical model method,and the stress deformation characteristics of the three support pits were analyzed by three sets of 38 two-dimensional finite element models,and the influence of factors such as rock depth,shoulder width,pile diameter,pile spacing,and anchor prestress were analyzed.The results of the calculations show that.(1)The range of influence on the settlement and horizontal displacement of the soil outside the hammock pit is about 0.7H;the sloping part of the sloping soil nail wall and the sloping embedded rock pile combination support pit will produce a large deformation of the bulge;the bottom of the rock-soil combination pit is a rock formation,so the bottom of the pit will have less deformation of the bulge.(2)The anchor prestressing of the end-suspended pile pit increases,the ground settlement outside the pit and the horizontal displacement of the pile body is significantly reduced,and the shear force and bending moment of the pile body is also reduced;the shear force and bending moment of the pile body increases with the width of the rock shoulder and the bending rigidity of the pile body.(3)In the sloping rock pile combination support pit,the greater the anchor prestress and bending stiffness,the smaller the horizontal displacement of the pile body;the greater the anchor prestress,the smaller the shear moment of the pile body,the greater the bending stiffness of the pile body,the greater the shear moment of the pile body;the influence of various factors on the deformation of the pit and the pile body stress is small.Three-dimensional numerical simulation analysis was carried out for the embedded part of the end-suspended pile and the embedded rock pile,and the force deformation characteristics,ultimate bearing capacity and deformation resistance of the embedded rock part were studied,and the influence of factors such as depth of the embedded rock,shoulder width,pile diameter and pile spacing were analyzed.The results of the calculations show that.(1)The P-Y curve of the hammock and inlay piles can be divided into three distinct zones:the initial linear zone,the transition zone,and the terminal linear zone;most of the rock around the pile body in the terminal linear zone enters the plastic zone;the ultimate bearing capacity and deformation resistance of the inlay portion of the hammock pile are much smaller than that of the inlay pile.(2)With the increase of the depth of the embedded rock,the load-bearing capacity of both the end-suspended piles and the rock socketed pile increased,but the depth of the embedded rock is greater than 3 m,the impact on the modulus of the foundation is less.The greater the pile spacing,the greater the bearing capacity of the pile body,and the pile diameter has less influence on the bearing capacity.As the shoulder width increases,the bearing capacity and foundation modulus of the end-suspended piles increases;when the reserved shoulder width is 3m,there is still a large difference between the bearing capacity of the end-suspended piles and the rock socketed pile. |
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