高地应力软岩隧道大变形已经成为制约工程进度以及增加工程成本的关键问题。依托某高原高地应力碳质板岩软岩隧道,对其大变形作用机理、岩体力学参数以及大变形处治技术进行了研究,结果表明:(1)软岩隧道围岩大变形主要跟弹性模量、泊松比、开挖半径以及地应力水平有关,除上述因素外,塑性区半径还跟岩体的黏聚力、内摩擦角以及支护阻力相关;(2)开展室内单轴以及三轴试验,确定了依托工程岩体弹性模量平均值为9.003 GPa,泊松比为0.246,内摩擦角为36.09°,黏聚力为4.79 MPa;(3)根据工程类比给出了依托工程隧道大变形采用“初支早封闭,预应力长锚索+双层初支放抗结合的主被动控制”的处治方法;(4)原设计施工最大累积水平收敛值达到 72 cm,拱顶下沉累积量达到38 cm,采用变更处治方法后试验段测试数据表明其变形量控制在水平收敛为11 cm,拱顶下沉值仅3.5 cm,达到了控制大变形且使隧道进尺稳步推进的目的。研究成果可为类似岩性隧道大变形控制提供借鉴。

The problem of large deformation in high-stress soft rock tunnels has become the key to constraining the project's progress and increasing the cost. Based on a plateau high-stress carbonaceous slate soft rock tunnel, the mechanism of large deformation, rock mechanical parameters, and large deformation treatment technology were studied in this paper. The results show that: (1) The large deformation of soft rock tunnel peripheral rock is mainly related to the modulus of elasticity, Poisson's ratio, excavation radius, and the level of ground stress; the radius of the plastic zone in addition to the above factors is also related to the cohesion of the rock body, the angle of internal friction, and the resistance of support. (2) Through indoor uniaxial and triaxial tests, the average value of elastic modulus of the rock body of the dependent project was determined to be 9.003 GPa, Poisson's ratio to be 0.246, the angle of internal friction to be 36.09°, and the cohesion to be 4.79 MPa and the above values were taken as the input parameter values for numerical calculations. (3) According to the engineering analogy, the design change treatment method of “early closure of the initial support, prestressed long anchor cable + double-layer initial support release resistance combination of active and passive control” is given for the large tunnel deformation of the dependent project. (4) According to the original design, the maximum cumulative horizontal convergence value reached 72 cm, and the cumulative amount of vault subsidence reached 38 cm. The test data of the test section after adopting the change of treatment method showed that the deformation was controlled at the level of convergence of 11 cm, and the value of vault subsidence was only 3.5 cm, which achieved the purpose of controlling the large deformation and making the tunnel progress steadily. The research results can provide a reference for the control of large deformation in tunnels with similar lithology.