Research On The Bearing Characteristics Of Squeezed Uplift Piles Based On Load Transfer Method

The squeezed branch pile is a new type of energy-saving variable cross-section pile with high efficiency.Due to the existence of its bearing plate,the bearing capacity and displacement control capacity of the pile are improved.Especially when the squeezed branch pile is used as the uplift pile,the bearing effect is better,so it is widely used in engineering.However,the existence of the bearing plate makes it difficult to study the bearing mechanism of the expanded pile.Therefore,this paper studies the calculation method of the bearing capacity of the expanded pile based on the load transfer method,and verifies its reliability.At the same time,it analyzes and plateusses the value of the empirical parameters in the calculation method,so as to carry out a series of analysis on the bearing mechanism of the expanded pile.(1)Based on the load transfer method,the calculation formula is established,and the hyperbolic function is used to describe the load displacement relationship between the pile side and the plate end of the squeezed branch pile.According to the pile end resistance transfer parameters,the bearing plate end resistance transfer parameters are derived.(2)According to the load displacement curve,it can be seen that the curve is slowly changing.With the increase of plate diameter ratio,the bearing capacity and displacement control capacity increase;Through the analysis of plate end resistance and pile side resistance,the plate resistance accounts for 51% of the maximum.At the same time,according to the test of six single plate piles with different plate diameter ratio,the plate resistance displacement relationship is measured,and the modified function of plate end load is fitted by the least square method ζ(β).(3)The theoretical calculation and test results of the bearing capacity of the single plate compaction pile in homogeneous soil are verified and analyzed.The error of the ultimate bearing capacity of the pile is less than-7%.In the three groups of test analysis of double plate pile,it is found that changing the diameter of the lower bearing plate has a more significant effect on improving the bearing capacity and controlling the displacement capacity,and when the large diameter bearing plate is arranged at the lower part,the bearing capacity and controlling the displacement capacity are better.The theoretical calculation of the bearing capacity of the double plate pile and the verification and analysis of the test results show that the error of the ultimate bearing capacity is less than-10%.Through theoretical calculation,analysis and verification of layered soil engineering piles,it is concluded that the error of ultimate bearing capacity is within-9%.Therefore,the calculation formula based on the load transfer method is reliable for the prediction of pile bearing capacity under the conditions of homogeneous soil and layered soil.(4)According to the established theoretical calculation method,the values of three groups of empirical parameters,including the angle of soil failure surface,horizontal earth pressure coefficient and lateral resistance failure ratio,are analyzed.Increasing the included angle of soil failure surface and horizontal earth pressure coefficient can improve the predicted uplift bearing capacity of squeezed piles;Increasing the ultimate failure ratio of pile side resistance can restrain the predicted uplift bearing capacity of squeezed piles.Moreover,changing the horizontal earth pressure coefficient has the greatest impact on the calculation method of the bearing capacity of the expanded pile,and the error may exceed 20%.Changing the ultimate failure ratio of the pile side has the second impact,and changing the included angle of the pile-soil failure surface has the least impact.Figure 32 Table 17 Reference 81...