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极限分析法是常用的计算桩后推力的方法,但计算中无法考虑桩的变形因素,这种方法假定桩后岩土体变形不受限制,抗滑力充分发挥,计算出的推力是主动土压力。当桩变形受限制而使抗滑力不能充分发挥时,计算结果与实际有偏差。有限元用于计算桩后推力时,遵循桩–土共同作用的原则,它不是极限分析法,算出的推力依据桩的变形,可能是主动土压力,也可能不是主动土压力,此外还可以得到相应的推力分布。当滑坡设计安全系数较小时,岩土体抗滑强度未得到充分发挥,有限元与极限分析法有一定差距;随着设计安全系数的增大,岩土体逐渐达到极限情况,有限元与极限分析法算出的推力趋于一致。依据经验,在一般桩设计安全系数下,两者计算得出推力一致,表明有限元用于计算桩后推力是可行的。本文对影响有限元计算推力的几种因素进行了分析,并与极限分析法(不平衡推力法、Spencer法)进行了比较,说明了两种方法何种情况下计算结果一致,何种情况下不一致。
Limit analysis method is commonly used to calculate the post-thrust method, but the calculation of the pile deformation can not be considered, this method assumes that post-pile deformation of rock and soil is unlimited, full play of anti-sliding force, the calculated thrust is active soil pressure. When the pile deformation is limited so that the anti-skid force can not fully exert, the calculation result deviates from the actual. When the finite element method is used to calculate the pile thrust, it follows the principle of pile-soil interaction. It is not the limit analysis method. The calculated thrust force may be the active earth pressure or not the active earth pressure according to the deformation of the pile. In addition, The corresponding thrust distribution. When the safety factor of landslide design is small, the anti-skid strength of rock and soil is not fully exerted, and there is a certain gap between the finite element method and the limit analysis method. With the increase of design safety factor, the rock and soil body gradually reach the limit condition, and the finite element and limit Thrust calculated by the analysis tends to be consistent. Based on experience, under the general design safety factor of pile design, the two calculated the same thrust, indicating that finite element method is feasible to calculate the pile thrust. In this paper, several factors that affect the thrust of finite element calculation are analyzed and compared with the limit analysis method (imbalance thrust method, Spencer method), which shows that the two methods are consistent in the calculation results, under what circumstances Inconsistent.