为探明深埋隧洞开挖过程中孔压演化规律、确定三维渗流计算模型的纵向范围取值，以监测断面为中心建立深埋长隧洞整体三维有限元模型。首先，采用隧洞一次性挖穿计算方案，研究施工开挖期孔压消散的时间历程；
然后，基于隧洞掌子面推进历程，分析隧洞开挖地下水位线的降低特征与掌子面推进过程中孔压的演化规律； 最后，以构建监测断面上完整的孔压演变曲线为目标，研究开挖推进过程中掌子面的前后扰动范围，并最终给出三维渗流计算模型纵向范围取值以及监测断面设置的建议。研究结果表明： 1）分步开挖法比一次挖穿法更能反映出掌子面推进过程中渗透孔压的时空演化规律。2）当掌子面推进距离为22.5D（D为洞径）时，掌子面向前扰动范围基本稳定在80D；当掌子面越过监测断面推进到155D时，掌子面向后扰动范围基本稳定在72D。可以看出，构建数值分析模型时需要较大的纵向模型范围，需要将监测断面选择在掌子面的前后影响范围之外，即要求模型纵向范围不小于174.5D。
To explore the evolution patterns of pore pressure
during the excavation of a deep tunnel and determine the longitudinal value of
a threedimensional seepage calculation model, a threedimensional finite element model of a deepburied
long tunnel is established with the monitoring section as the center. First, a
scheme, in which the tunnel is excavated through one time, is adopted and the
timehistory of pore pressure dissipation during
excavation is studied. Then, the drawdown of the water table and the evolution
of pore water pressure are investigated with excavation process. To construct
an entire curve of pore water pressure evolution on the monitoring section, the
influence scope of the tunnel face in the process of excavation is explored.
Finally, the suggestions for the longitudinal value in threedimensional seepage numerical model and the setting of monitoring
section are given. The results show the following: (1) The stepped excavation
method can better reflect the mechanism of pore water pressure evolution than
the onetime excavation method. (2) When the excavation
distance is 22.5〖WT〗D, where refers
to the tunnel diameter, the forward influence scope of the tunnel face
gradually reaches 〖WT〗80D. 〖WT5《TNR》〗(3) When the tunnel face goes across
the monitoring section and the excavation distance reaches 〖WT〗155D, 〖WT5《TNR》〗the backward influence scope of the tunnel face gradually reaches 〖WT〗72D. Therefore, a large longitudinal model range is required, and the
monitoring section should be outside the forward and backward influence scope
of tunnel face, which should be more than 〖WT〗174.5D.
