| In recent years,with the continuous construction of high-rise buildings and underground structure projects,the engineering community has become more and more demanding for foundation pit support technology.The double-row pile retaining structure is widely used due to its large lateral stiffness and reasonable force of the pile body.However,its force deformation mechanism and design calculation are complicated.The current theoretical research still lags far behind engineering practice.Therefore,this paper carries out the following research work on the mechanism of the deformation of the double-row pile retaining structure in the layered foundation:Firstly,the calculation method commonly used in double-row pile retaining structure is briefly introduced.In view of the fact that the current calculation theory can not fully consider the problem of pile-soil interaction,considering the stressdeformation characteristics of the double-row pile retaining structure and the interaction between pile and soil The front and rear piles are regarded as the elastic foundation beams placed vertically,and based on the Eulernuni double-layer beam theory,the deflection control of the front and rear piles is established by the force balance conditions of the piles.The differential equation,and then the analytical solution of the equation is obtained according to the constraint of the pile end and the continuous condition at the bottom plane of the foundation pit.Secondly,considering the existence of layering in the soil layer of double-row piles in actual engineering,the layered soil is regarded as a horizontal homogeneous elastic medium and simulated with springs of different stiffness.According to the stress balance conditions,the pile structure of each section is obtained.The flexural deformation equation is combined with the continuous condition of the joints of the piles and the boundary conditions of the pile bottom to obtain the power series solution of the double-row pile retaining structure in the layered foundation,and then the double row piles can be obtained.Deformation and internal force values at various points of the retaining structure.Then,the effects of soil layer properties,pile diameter,pile length,pile spacing and pile spacing on the internal force displacement of the double-row pile retaining structure are analyzed with the example,and the following conclusions are obtained:(1)The lateral displacement of the pile and the maximum positive and negative bending moment of the pile are increased with the increase of the pile spacing.The reasonable range of the recommended pile spacing is 2d~4d.(2)When the row spacing and pile diameter of the double-row piles are taken to the appropriate value,the double-row piles can play a good supporting role.The reasonable value range of the recommended pile spacing is 4d~5d.The reasonable range of the pile diameter is 800mm~1000mm.(3)The influence of the length of the rear pile on the internal force and displacement of the double-row pile retaining structure is less than that of the front pile.It is recommended that the pile length of the front and rear piles be the same.Finally,relying on engineering examples,the monitoring data and the calculation data of this method are compared and verified.The results show that:(1)The maximum bending moment of the front and back piles is located at the top of the pile,and the maximum negative bending moment is 3m below the bottom of the pit.Up to 4m,and the entire pile bending moment is basically "S"-like distribution.(2)There is a significant inflection point in the bending moment of the pile body,and the position of the inverted bending point is generally located on the bottom surface of the foundation pit.(3)The lateral displacement of the top and bottom piles is the largest,with the bottom of the foundation pit as the boundary line.The lateral displacement of the pile above the bottom of the foundation pit is smaller than that of the pile below the bottom of the foundation pit. |
PDF Full Text Request