Numerical Analysis Of Buckling Stability Of Laterally Supported Piles In Soil Excavationunder

The addition of a basement in an existing building can not only solve the problems of parking difficulty and ease the traffic pressure,but also can be used as a civil air defense project to rationally use the city’s underground space resources and improve the city’s ability to prevent and reduce disasters.When adding underground space to an existing building,it is necessary to replace the pile to support the superstructure,and then excavate the surrounding soil,but with the excavation of the earthwork,the stability of the pile will decrease,and the pile body is used to add lateral support the method can effectively improve the stability of the pile.Therefore,it is of great significance to study the buckling stability of piles with lateral supports under the excavation conditions around the piles.In this paper,the ANSYS finite element software is used.First,a two-dimensional numerical analysis model of the compressive stability of the foundation with lateral support piles is established to study the pile buckling ultimate load and support axial force at different positions,support line stiffness ratio and number of supports the changing law.Second,establish a three-dimensional numerical analysis model of the compressive stability of the reinforced concrete pile foundation with lateral support,change the excavation depth of the soil around the pile,geotechnical parameters and the reinforcement ratio of the pile body,and study the ultimate load of the pile buckling and the support shaft under axial compression Change law of force;change soil excavation depth,geotechnical parameters and load eccentricity around pile,and study the change law of pile buckling ultimate load and supporting axial force under the action of bias pressure.The formula for calculating the ultimate bearing capacity of reinforced concrete piles with lateral bracing under axial compression and bias compression is also proposed.The results of two-dimensional numerical analysis of the compressive piles show that:(1)A support is added at the ratio of the soil excavation value around the pile to 0.5 times,and the pile buckling ultimate load and the support axial force reach the maximum.(2)As the supporting stiffness increases,the pile buckling ultimate load and supporting axial force increase,but the stiffness increases to a certain value,and the increase in pile buckling ultimate load and supporting axial force is not obvious.(3)The ultimate load of pile buckling increases with the increase of the number of supports,but the increase rate gradually decreases.The results of three-dimensional numerical analysis of the pile under axial compression show that:(1)The buckling ultimate load and supporting axial force of the pile increase with the increase of the reinforcement ratio of the pile body.(2)As the excavation ratio increases,the pile buckling ultimate load gradually decreases,but the supporting axial force gradually increases,and the stress state of longitudinal reinforcement in the pile gradually changes from compressive yield on both sides to compressive yield on one side.Lateral compression does not yield.(3)When the excavation ratio is greater than 0.667,the difference in the pile buckling ultimate load between different excavation ratios suddenly increases.The results of the three-dimensional numerical analysis of the pile under bias pressure show that:(1)The pile buckling ultimate load and supporting axial force decrease as the load eccentricity increases.(2)When the reinforcement ratio of the pile body is 0.883% and the ratio of the load eccentricity to the pile section side length is greater than 0.78,the pile is damaged by large eccentric compression;when the ratio is less than 0.78,the pile is damaged by small eccentric compression.(3)The supporting axial force increases with the increase of the pile buckling ultimate load.(4)Select the typical working condition to compare the numerical simulation value and the formula calculation value,and find that the deviation between the results obtained by the two methods is small,which verifies the rationality of the proposed calculation formula.Finally,a numerical simulation is carried out in conjunction with the engineering example of the compressive stability of the foundation with lateral support piles,and it is concluded that the underpinning scheme of this project is safe,indicating that numerical simulation can be used directly to guide engineering practice.