为探究王家寨隧道第三系富水半成岩物理力学性质，于现场取样开展颗粒筛分、XRD以及扫描电镜试验，并以现场试样的干密度为基准，制备重塑试样进行三轴压缩试验，研究其矿物组成、微观结构及力学特性，结合Mod-Flow模拟地下水位对隧道进行施工灾害分析。研究表明： 1）王家寨隧道第三系半成岩级配不均，具备明显的弱胶结特征，在低含水率下具有明显的水敏性与遇水软化特性。随着含水率增长，试样的抗剪强度呈先增后减趋势，当含水率为11%时达到最大值459.03 kPa；当含水率低于12%时，黏土矿物形成胶结物填充颗粒间隙，使试样黏聚力增大；随着含水率持续增大，大量的自由水赋存于颗粒间隙，造成胶结结构破坏，试样抗剪强度明显下降。2）王家寨隧道涌水模拟结果显示，2段典型的富水段掌子面涌水量分别为2 805 m3/d和5 025 m3/d，表明在隧道富水段开挖极易发生涌水灾害，且灾害涌水量偏高。3）第三系半成岩水敏性强、遇水易软化的物理力学性质，高压富水环境以及工程扰动是王家寨隧道开挖诱发地质灾害的主要因素。
Tertiary semi-diagenetic rocks were sampled from the water-rich section of the Wangjiazhai tunnel for particle screening, X-ray diffraction, and scanning electron microscopy tests. Based on
the dry density of the field samples, remolded samples were prepared for
triaxial compression tests to examine their mineral composition,
microstructure, and mechanical properties. Finally, a construction disaster
analysis of the tunnel was conducted using Mod-Flow
simulation of groundwater levels. The research findings reveal the following:
(1) The grading of tertiary semi-diagenetic rocks from
the Wangjiazhai tunnel is uneven, with weak cementation characteristics leading
to notable water sensitivity and water softening under low moisture content. As
moisture content increases, the shear strength of the samples first rises and
then declines, peaking at 459.03 kPa when the moisture content is 11%. When the
moisture content is below 12%, clay minerals form cements that fill particle
gaps, enhancing sample cohesion. However, with further moisture increase, a
large volume of free water accumulates in the particle gaps, disrupting the
cementation structure and significantly reducing shear strength. (2) The water
inflow simulation results for the Wangjiazhai tunnel indicate that water
inflows in two typical water-rich sections are 2 805
and 5 025 m3/d, respectively, suggesting a high
likelihood of water inflow disasters during tunnel excavation, with substantial
water volumes involved. (3) The physico-mechanical
properties of tertiary semi-diagenetic rocks show
strong water sensitivity and a tendency to soften in water. The high-pressure, water-rich environment, coupled
with engineering disturbances, are the primary factors inducing geological
disasters during the Wangjiazhai tunnel excavation.
