隧道衬砌结构崩落特征及主要诱发因素

为了科学地预测、控制、避免衬砌崩落灾害的发生,研究隧道衬砌结构崩落特征及主要诱发因素,找出衬砌崩落的潜在规律和关键性诱因,对35座衬砌崩落隧道案例信息进行归纳整理,统计分析了衬砌崩落时间、空间位置、地层岩性、二次衬砌材料的特征及规律。根据诱因数量,诱因类别以及每种诱因类别中各个诱因的占比情况,归纳总结了隧道衬砌崩落的主要诱发因素,分析了隧道衬砌崩落诱发因素的特征。结果表明:50%的衬砌崩落发生在隧道建成后10 a内,90%的衬砌崩落发生在隧道建成后40 a内;衬砌崩落主要发生在雨季和低温期,拱顶是预防衬砌崩落发生的主要位置;衬砌崩落多发生在围岩较为软岩的地层中,以及地下水丰富的硬岩地层;二次衬砌材料为素混凝土的隧道更容易发生衬砌崩落灾害;衬砌崩落诱发因素分为结构因素类和外部环境类2类,结构因素类诱因包括混凝土材料耐久性、质量缺陷和结构病害,外部环境类诱因包括围岩冻胀、围岩膨胀、高地应力、衬砌背后水压、滑塌、溶洞落石、地震和列车振动;衬砌崩落灾害主要是单一诱发因素引起,单一诱发因素中外部环境是主要诱因类别;结构因素中质量缺陷占比最大,其次是结构病害;外部环境因素中衬砌背后水压、围岩膨胀和高地应力是关键性因素。

Effect of induction unloading on weakening of rock mechanics properties

The effects of induction unloading such as drilling, blasting, lancing and water-infusion softening on weakening of rock mechanics properties were investigated. Three stress paths were chosen as test schemes corresponding to the triaxial compressive test, pre-peak and post-peak unloading the confining pressure tests. The results show that compression deformation is the main cause of rock failure under loading condition. However, the strong dilatation leads to the rock failure along unloading direction. Rock failure happens even under little axial stress with confining pressure unloading. Poisson ratio increases with the decrease of confining pressure during the process of unloading. Elastic modulus increases slowly along with the decline of confining pressure, but decreases rapidly when unloaded to yielding strength. It shows that the weakening rate of rock intensity tends to be faster with easily failure under the unloading condition.