桩基荷载作用下隧洞破坏模式研究与安全分析

 以重庆市朝天门隧道为工程实例，采用有限元强度折减法进行桩基荷载作用下隧洞的稳定性分析。桩与隧洞相互作用是一个桩–岩土–结构共同作用的复杂过程，主要有3种破坏模式：隧洞破坏、桩基破坏、衬砌破坏。隧洞破坏与桩基破坏属于土体剪切破坏，可以采用有限元强度折减法求其稳定安全系数。针对桩基荷载作用下隧洞稳定性的各种影响因素：岩体强度、桩基荷载、桩与隧洞距离及桩的埋深等，建立6种计算方案、16种计算桩位，求出相应的安全系数，并分析其内在规律。桩与隧洞之间存在临界距离与临界埋深，当桩位于临界距离或临界埋深范围之内时，桩对隧洞稳定性有较大影响，隧洞先发生破坏，反之则桩对隧洞影响较小，桩基先发生破坏。

FAILURE PATTERN STUDY AND SECURITY ANALYSIS OF TUNNEL AFFECTED BY PILE LOAD

The stability analysis of Chaotianmen Tunnel affected by pile load is carried out by strength reduction finite element method. Interaction between pile and tunnel is a complex procedure of pile-soil-structure interaction. It contains three kinds of failure patterns：tunnel failure，pile foundation failure and lining failure. Tunnel failure and pile foundation failure are shear breakage of soil. The safety factor can be calculated by strength reduction finite element method. Six kinds of calculation schemes and sixteen kinds of pile positions are established，in order to study the influence factors of stability of tunnel by pile loading such as strength of rock mass，pile load，distance between pile and tunnel，depth of pile，etc.. Through analyzing the calculation result of safety factor，it is found there are critical distance and critical depth between tunnel and pile. Pile has greatly influence on tunnel，if it is located within critical distance or critical depth，and tunnel will fail firstly. Conversely，pile has little influence on tunnel，and pile foundation will fail firstly.