基于开挖卸荷效应的地铁隧道施工过程数值分析

 在地铁隧道实际施工过程中，围岩处于加、卸载的复杂变化过程中。隧道的开挖与支护过程是一个多步骤的、且上一步开挖都会对随后的各次开挖产生影响的复杂过程。依据地下工程问题的特点，即“先受力，后开挖，再支护”，描述并模拟地铁隧道开挖卸荷效应下的真实施工过程。对地铁隧道施工中开挖卸荷效应进行详细分析，提出模拟地铁隧道开挖卸荷效应的四阶段模拟方法。以北京地铁8号线二期01标段西清区间隧道为工程背景，对地铁隧道盾构施工真实过程和开挖卸荷效应进行数值模拟与计算。分析开挖面支护力、支护时机、填充注浆以及考虑与不考虑开挖卸荷效应等因素对地铁隧道开挖与支护的影响，获得基于开挖卸荷效应的地铁隧道盾构施工的围岩–支护作用机制。

NUMERICAL ANALYSIS OF SUBWAY TUNNEL CONSTRUCTION PROCESS BASED ON EXCAVATION UNLOADING EFFECT

During the actual construction process of subway tunnel，the surrounding rock is in a complex process of loading and unloading. Meanwhile，the excavation and support are completed in multiple steps. During this process，the previous excavation step will influence the subsequent excavation. Based on the characteristics of underground engineering，that is，loads are applied first，then excavation is conducted，and supports are provided at last，the actual construction process of subway tunnel under excavation unloading effect was described and simulated. The excavation unloading effect during the process of subway tunnel construction was analyzed in detail；and the 4-stage simulation method was put forward，which can simulate the excavation unloading effect during the construction process of subway tunnel. Taking the tunnel in Xisanqi—Qinghe section of Beijing metro line No.8 as engineering background，the actual process of shield construction of subway tunnel and the excavation unloading effect were simulated. The effects of excavation face supporting pressure，supporting time and filled grouting on excavation and support of metro tunnel were studied，with and without consideration of the excavation unloading effect. The surrounding rock-support working mechanism of metro shield tunnel was obtained based on the excavation unloading effect.