• Geomechanics and Engineering
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• v.25 no.2
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• pp.123-134
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• 2021

In this paper, the carbon fiber reinforced plastic (CFRP) grids embedded in polymer cement mortar (PCM) shotcrete (CFRP-PCM method) was conducted to repair the degraded tunnel linings with a cavity. Subsequently, the reinforcing effect of the CFRP-PCM method under different degrees of lining deterioration was quantitatively evaluated. Finally, the limit state design method of the M-N interaction curve was conducted to determine whether the structure reinforced by the CFRP-PCM method is in a safe state. The main results indicated that when the cavity is at the shoulder, the lining damage rate is more serious. In addition, the remarkably reinforcing effect on the degraded tunnel linings could be achieved by applying a higher grade of CFRP grids, whereas the optimization effect is no longer obvious when the grade of CFRP grids is too high (CR8); Furthermore, it is found that the M-N numerical values of the ten reinforcing designs of the CFRP-PCM method are distributed outside the corresponding M-N theoretical interaction curves, and these designs should be avoided in the corresponding reinforcing engineering.

• Geomechanics and Engineering
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• v.21 no.1
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• pp.63-71
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• 2020

Strength anisotropy is a typical feature of thin-bedded rock masses and their strength will be degraded subjected to water immersion effect. Such effect is crucial for the operation of hydropower plant because the impoundment lifts the water level of upstream reservoir and causes the rock mass of nearby slopes saturated. So far, researches regarding mechanical property of natural thin-bedded rock masses and their strength variation under water immersion based on field test method are rarely reported. This paper focuses on a thin-bedded stratified rock mass and carries out field test to investigate the mechanical property and strength variation characteristics. The field test is highlighted by samples which have a large shear dimension of 0.5 m*0.5 m, representing a more realistic in-situ situation than small size specimen. The test results confirm the anisotropic nature of the concerned rock mass, whose shear strength of host rocks is significantly larger than that of bedding planes. Further, the comparison of shear strength parameters of the thin-bedded rock mass under natural and saturated conditions show that for both host rocks and bedding planes, the decreasing extent of cohesion values are larger than friction values. The quantitative results are then adopted to analyze the influence of reservoir impoundment of a hydropower plant on the surrounding rock mass stability of diversion tunnels which are located in the nearby slope bank. It is evaluated that after reservoir impoundment, the strength degradation induced incremental deformations of surrounding rock mass of diversion tunnels are small and the stresses in lining structure are acceptable. It is therefore concluded that the influences of impoundment are small and the stability of diversion tunnels can be still achieved. The finings regarding field test method and its results, as well as the numerical evaluation conclusions are hoped to provide references for rock projects with similar concerns.