Abstract
A carbonaceous mudstone tunnel is a type of soft rock tunnel. There is little research on the prevention and control measures for the deformation and failure of carbonaceous mudstone tunnels. In this article, we investigated the construction of the Qiguding carbonaceous mudstone tunnel in Meizhou City, Guangdong Province, China. We monitored and analyzed the deformation and stress characteristics of a section under the original support scheme. The monitoring data showed that this section had large peripheral convergence, vault subsidence, steel arch strain, and concrete strain. The deformations exhibited significant differences in the horizontal and vertical directions, eventually resulting in concrete cracking, steel arch bulging, and distortion in the section. The analysis showed that the primary mechanisms for the failure were the softening characteristics of the carbonaceous mudstone, the plastic rheology, and the shear slip of the rock stratum. Based on a comparative analysis and numerical simulation, we proposed a new support measure called the longitudinal rigid enlarged foundation that consists of a steel arch longitudinal connection system and a locking foot anchor pipe system. Several comparative tests were performed at the tunnel site. The results demonstrated the excellent performance and reliability of the proposed support scheme for the deformation control of the carbonaceous mudstone, providing a reference for similar projects.
Highlights
Tunnels have the advantages of shortening the mileage and reducing the slope of highways and are widely used in engineering
The research on large deformation support methods of soft rock tunnels can be divided into two categories. e first category is research on support theory, including strong-soft combined support theory, a joint support theory, energy support theory, block sliding support theory, bolt-shotcrete-arc plate support theory, loose circle theory, and uniform support theory of deep surrounding rock [7,8,9,10,11,12]
Significant progress has been made in the research on the large deformation mechanism of soft rock and the deformation control measures, and the theories and techniques have solved many problems related to the support of tunnels in weak surrounding rocks
Summary
Tunnels have the advantages of shortening the mileage and reducing the slope of highways and are widely used in engineering. Scholars have conducted extensive research on the deformation and failure mechanism of rock tunnels in soft rock [1,2,3,4,5,6] and have proposed and developed support methods for these types of rock tunnels. Wang et al [17], Chen et al [18], and Wu et al [19] developed high compression and low plastic foam concrete and used it as a filling material for the deformation layer between the first and second linings of large-span soft rock tunnels. Significant progress has been made in the research on the large deformation mechanism of soft rock and the deformation control measures, and the theories and techniques have solved many problems related to the support of tunnels in weak surrounding rocks. On-site monitoring data show that the LREF provides excellent performance for controlling the deformation of carbonaceous mudstone tunnels
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