排桩支护明挖隧道基坑桩侧极限抗力系数研究

Study on Pile Side Resistance Limit Coefficient of Row Pile Supported Ming Dig Tunnel Excavation Foundation Pit

为了研究单排桩支护明挖隧道基坑桩侧土抗力系数特性,首先,建立了考虑桩侧土体受力状态的基坑桩侧土压力力学模型和位移模式;其次,根据虚功原理和位移场模式,建立排桩支护明挖隧道基坑桩侧土体功和速度场计算公式,引入极限上限方法,提出了考虑桩-土界面粗糙度系数的排桩支护明挖隧道基坑排桩的水平承载力系数计算方法,将该方法应用于计算实例,通过与已有理论计算方法对比分析,计算结果验证了本文方法的合理性与可行性;最后,利用本文建立的方法,分析了桩间距、桩-土接触面系数以及埋置深度对基坑排桩水平抗力系数的规律.结果表明:排桩的水平承载力随着桩距的减小而减小,直到达到一个最小值.排桩的水平承载力系数Np随着桩-土界面粗糙度系数α的增大而增大;当桩-土界面粗糙度系数α一定时,水平承载力系数Np随着埋置深度的增加而增加,当埋置深度率Z/D>7时,水平承载力系数Np随着埋置深度的增加趋于定值.

In order to study the resistance characteristics of pile supported Ming dig tunnel excavation pile lateral soil, mechanical model and displacement modelare set up considering pile foundation pile lateral soil pressure insoil mass stress state. Secondly, according to the principle of function and displacement mode, the function and formula of velocity fieldfor pile supported Ming dig tunnel excavation pile lateral soil is established.Then, through the introduction of extreme limit method, the coefficient calculation methodis put forward considering the interface roughness coefficient of pile-soil pile horizontal bearing capacity of pile foundation pit supported Ming dig tunnel. At the same time, this method was applied to calculate examples. A comparative analysis between the theoretical calculation method and calculated results demonstrates the rationality and feasibility of this method. Finally, by using the method established in this paper, the influence of pile spacing,pile and soil contact surface coefficient and pile embedment depth of foundation pit on horizontal resistance coefficient is also analyzed. The results show that the horizontal bearing capacity of pile decreases with the decrease of the pile spacing and reaches to a minimum value. The level of the pile bearing capacity coefficient of Nppile soil increases with the increasing interface roughness coefficient alpha. When the pile-soil interface roughness coefficient alpha is unchanged,the horizontal bearing capacity coefficient of Npincreases with the increase of buried depth. When the embedment depth ratio Z/D is larger than 7, the horizontal bearing capacity coefficient of Npincreases with the increase of embedment depth and reaches a constant value.