【摘要】 为探求适合弱膨胀土浅埋隧道的施工工法,基于在建三淅高速公路李家坪隧道工程,借助三维有限元软件分别模拟了弱膨胀土地区隧道环形开挖预留核心土法及CD法开挖过程中的围岩稳定性,对比研究了围岩的受力与变形情况。有限元计算结果表明:环形开挖预留核心土法施工对软弱围岩掌子面的变形能起到有效控制,但对于控制浅埋段隧道整体沉降效果不大;相对于环形开挖预留法,CD法开挖工作面小,且各工作面封闭成环时间短,各工作面支护有效限制了塑性区发展,尤其是在隧道拱顶处,CD法开挖比环形开挖预留法开挖扰动引起的塑性区范围小很多,CD法更适用于弱膨胀土地区隧道施工。此外,根据收敛约束法的理念,推导了膨胀土隧道围岩特征曲线,结果表明:膨胀性围岩对含水率变化非常敏感,尤其是围岩变形较小时,膨胀压力可以达到塑性形变压力的数倍。综合理论推导、数值模拟和现场监测数据,分析了李家坪隧道施工时产生塌方冒顶的原因。由于雨季施工使隧址区的弱膨胀土围岩含水量增大,吸水膨胀后释放应力,隧道自稳能力下降,加上薄弱的支护体系,是造成隧道塌方的主要原因。研究成果可为弱膨胀土地区隧道施工提供一定的参考依据和实践经验。更多还原

【Abstract】 In order to explore the suitable construction scheme for shallow buried tunnel in weak expansive soil area,based on Lijiaping tunnel project on Sanmenxia-Xichuan expressway under construction,the stabilities of tunnel surrounding rock in weak-expansive soil area by the reserving core soil with ring excavation method and the CD method are simulated using 3 D FE software,and the stresses and deformations of surrounding rock are compared. The FE analysis result shows that( 1) It effectively controls the deformation in tunnel face with weak surrounding rock by the reserving core soil with ring excavation method,but has little effect in controlling the shallow buried tunnel subsidence.( 2) Compared to the reserving core soil with ring excavation method,the excavation face is much smaller using the CD method,the closing time of each working face is shorter,the development of the plastic zone is effectively restricted by the support of each working face,the plastic zone caused by the excavation disturbance is much smaller,especially in thetunnel vault. Thus,the CD method is more suitable for tunnel excavation in weak-expansive soil area. In addition,according to the idea of convergence constraint method,the tunnel surrounding rock characteristic curve is derived. The result shows that expansive surrounding rock is very sensitive to the change of water content,especially when the surrounding rock deformation is small,the expansion pressure can reach several times of plastic deformation pressure. The cause of collapse of the tunnel under construction is analyzed based on theoretical derivation,numerical simulation and field monitoring data. The construction during the rainy season increased the water content of expansive soil and surrounding rock at tunnel site,when the water is swellable,the stress is released,and the self stability of the tunnel is reduced coupled with poor supporting system,all of which are the major causes of tunnel collapse. The research result can provide some references and practical experience for tunnel construction in weak expansive soil area.更多还原