Analysis of Stress and Deformation Characteristics of Deep‐Buried Phyllite Tunnel Structure under Different Cross‐Section Forms and Initial Support Parameters

Abstract

Deep-buried soft rock tunnels exhibit low strength and easy deformation under the influence of high ground stress. The surrounding rock of the soft rock tunnel may undergo large deformation during the construction process, thereby causing engineering problems such as the collapse of the vault, bottom heave, and damage to the supporting structure. The Chengwu Expressway Tunnel II, considered in this study, is a phyllite tunnel, with weak surrounding rock and poor water stability. Under the original design conditions, the supporting structure exhibits stress concentration and large deformation. To address these issues, three schemes involving the use of the double-layer steel arch to support, weakening of the steel arch close to the excavation surface, and weakening of the steel arch away from the excavation surface to support were proposed. Using these schemes, the inverted radius was varied to explore its influence on different support schemes. For simulation, the values of the inverted radius selected were as follows: 1300 cm, 1000 cm, and 700 cm. The proposed support plan was simulated using FLAC3D, and the changes in the pressure between the initial support and surrounding rock, the settling of the vault, and the surrounding convergence were investigated. The numerical simulation results of monitoring the surrounding rock deformation show that the double-layer steel arch can effectively reduce the large deformation of the soft rock well. When the stiffness of one of the steel arches was weakened, the support’s ability to control the deformation was weakened; however, it still showed reliable performance in controlling deformation. However, changing the radius of the invert had an insignificant effect on the deformation and force of the supporting structure.

Study on Instability Mechanism and Support Scheme of the Tunnel Face in Carbonaceous Phyllite Stratum under High Geo‐Stress

“…Internal friction angle φ 26.97 °and cohesion c 7.69 kPa can be calculated from equation (2). ere is little di erence between the experimental results and the macroscopic mechanical parameters of the actual model listed in Table 1, which indicates that the calibration result is reasonable.…”

“…In order to accommodate the huge tra c volume, an increasing number of deepburied, large cross section and long-distance highway tunnels in complex geological conditions are being constructed. However, tunnel construction in weak surrounding rock under high geo-stress often faces the risk of large deformation of the soft rock and collapse of the tunnel face, which seriously a ects construction safety and hinders construction progress [1][2][3].…”

Study on Large Deformation Prediction and Control Technology of Carbonaceous Slate Tunnel in Lixiang Railway

“…Zhang et al, Takeda et al,Chen et al, collected the tunnel deformation characteristics under different excavation methods and studied the influence of excavation methods on the large deformation of soft rock tunnel. Weidong et al, Guo et al, Wu et al, and Ren et al [5,[13][14][15] studied different tunnels with the same excavation method and pointed out that the deformation characteristics of high stress soft rock tunnel are diverse, with remarkable characteristics such as fast deformation rate, long deformation time, and large total deformation. On this basis, Yuan, Fang et al, and Pan and Cheng [16][17][18] gave reasonable construction control measures based on the characteristics and genetic mechanism of large deformation and failure of tunnels in different soft slate strata in different regions, so as to provide reference for the construction of similar slate tunnels.…”

Analysis for bearing performance and construction mechanical behavior of supporting structure for the large cross-section tunnel by half bench CD method

“…At present, the research on the construction mechanical behavior of the support structure for large cross-section tunnels using the partial excavation method mainly focuses on the traditional construction methods such as CD, CRD and the two-side pilot hole method, and there is little research on the half bench CD method which can improve the construction efficiency and save the cost of project. At the same time, the previous researches mainly focus on the comparative analysis and applicability analysis between different construction methods [27][28][29], and seldom collaboratively consider the mechanical characteristics and deformation laws of the supporting structure, which is very important for the safety and stability and dynamic control of the tunnel construction. In the past, numerical simulation is often used in the complicated excavation process [30][31][32][33][34].…”