Study On Soil Squeezing Effect And The Influence On Slope Stability Of Pile Driving Adjacent To Slope

With the constant development of the city,the jacked pile is widely used in the practical engineering.However,soil effect during the process of pile sinking will adversely affect the surrounding environment.Yet,as a lot of research findings have been derived regarding the adverse effect on surrounding environment attached by cavity expansion and compaction piles with symmetric boundary,plenty of research needs to be done on the effect of cavity expansion and compaction piles with non-symmetric boundary and much of knowledge needs to be explored regarding lateral movement rules and stress mechanism of soil mass.Therefore,a full understanding of mechanism and squeezing displacement law in the process of pile sinking has become an important problem that needs to be solved urgently.The mechanism and squeezing displacement law during the process of pile sinking is studied by theoretical analysis and numerical simulation,and a detailed analysis of the change of slope stability coefficient in the whole process of the pile driving is carried out.At the same time,the theoretical results are verified by the numerical simulation method and the main conclusions are drawn as follows:(1)The horizontal surface and inclined slope displacement boundaries of squeezing effect have been revised based on the analytical solution under semi-infinite soil,and the current analyzing method has been improved via the methods of coordinate transformation and superposition.Hereby a relatively simple solution to the soil compaction displacement field caused by spherical cavity expansion under non-axisymmetric displacement boundary has been deviated,together with an analysis of the impact upon slope angle and the distance between the spherical cavity and the free boundary.And the inclination boundary condition has an obvious influence on squeezing displacement of both sides of the Spherical cavity.With the increase of inclination the influence of boundary inclination angle to the soil compaction displacement would be gradually deeper;and the larger the distance from spherical cavity position to the free boundary is,the smaller effect on the soil squeezing displacement will be.(2)The dynamic process of jacked pile penetration of soil was simulated based on the analytical solution under non-axisymmetric displacement boundary via the elastic superposition method with the principle that sphere volume was equal to the column volume.Hereby a relatively simple solution to the soil compaction displacement field caused by single pile jacked under non-axisymmetric displacement boundary has been deviated,together with an analysis of the impact upon the slope angle and the distance between the spherical cavity and the free boundary.With the increase of inclination the influence of boundary inclination angle to the soil compaction displacement would be gradually deeper;and the larger the distance from jacked pile position to the free boundary is,the smaller effect on the soil squeezing displacement will be.(3)Investigations have been carried out on the effect of the pile driving force,the plastic zone around the pile tip and the anti-sliding effect of the pile body on slope stability coefficient,respectively.The cavity expansion theory with the consideration of elasto-plasticity of soil has been employed.A detailed analysis of the change of slope stability coefficient in the whole process of the pile driving is carried out.And the influence of pile diameter,slope angle and the distance between the pile and slope top on slope stability coefficient change is discussed.The results show that the pile driving force and the plastic zone at pile top have an adverse effect on slope stability which leads to a decrease in safety coefficient,while the anti-sliding effect of the pile has a positive contribution to the stability of the slope,especially when the end of pile is below the sliding surface.The stability coefficient decreases significantly with the increase of the pile diameter.The greater the slope angle is,the stability coefficient after pile driving is smaller;the stability coefficient drops more slowly with the increase of the distance of the pile away from the top of slope;and the influence of plastic zone on the stability coefficient is also gradually reduced.The pile driving will not affect the stability of the sliding surface when the pile is far from the top of the slope.(4)Prebored hole can reduce the compaction displacement effectively,the reducing effect close to the slope side is more obvious than the other side and the top part is more obvious than the deep part close to the slope side and vice.The diameter of prebored hole has a significant influence on the compaction displacement of soil,the larger the diameter,the more obvious the reducing effect of soil displacement.Prebored hole also has a certain influence on slope stability.Prebored hole is equivalent to reduce the pile diameter according to equivalent principle of soil compaction when the prebored hole reaches the sliding surface.Finally,a method for evaluating the stability of slope in the process of pile sinking is proposed.