Due to the thick soil layer, short backfill time, and low degree of consolidation of the soil-rock mixture backfill in Chongqing city, metro train tunnels passing through this type of strata are prone to large settlements during operation, which greatly affects the stability of the tunnel and the safety of metro train operations. In response to this problem, the dynamic triaxial test of the soil-rock mixture backfill under cyclic loading was carried out to study the dynamic characteristics of the soil-rock mixture backfill under cyclic loading. The effect of initial consolidation degree, effective consolidation confining pressure, and rock content on the stiffness softening of soil-rock mixture backfill was analyzed. The results show that the initial consolidation degree, effective consolidation confining pressure, and rock content are all important factors affecting the stiffness of soil-rock mixture backfill under cyclic loading. As the number of cycles increases, the lower the initial consolidation degree and effective consolidation confining pressure, the faster the attenuation of the softening index, and the larger the amplitude. As the rock content increases, the softening index increases and the stiffness of the backfill changes from softening to hardening. Based on the test data, the softening-hardening model of the soil-rock mixture is established, which is in good agreement with the field test results. This study can provide a reference for predicting and controlling the postconstruction settlement of the metro tunnel in the soil-rock mixture backfill.

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An indoor dynamic triaxial test was performed on the soil–rock mixture (SRM) backfill in Chongqing to study the cumulative strain characteristics of the SRM under the cyclic dynamic loading of the metro train. The effects of different consolidation degrees U, rock block contents P, and effective consolidation confining pressures σ 3 ′ were then analyzed. Results showed that when σ 3 ′ and P are the same, the lower the U, the faster will be the increase in cumulative strain. When U and P were the same, the lower the σ 3 ′ , the greater will be the increase in cumulative strain and the higher will be the cumulative strain stable value of the stability curve. When U and σ 3 ′ were the same, the lower the P, the faster will be the increase in cumulative strain. An empirical model of the cumulative strain of the SRM considering the influence of U, P, and σ 3 ′ was established on the basis of the results of the dynamic triaxial tests. The accuracy of the prediction model was verified against the actual test results. This study provides a theoretical basis for the settlement and deformation evaluation of SRM backfill subgrades under metro train cyclic loading.

Anti-sliding piles are commonly implemented to reinforce landslides. Considering the complex nature of this medium, there is substantial spatial variability in the mechanical parameters of rock and soil masses. However, the influence of spatial variability on the anti-sliding pile remains unclear. In this study, the Erdaogou landslide is taken as a case study in terms of the random response of anti-sliding piles considering spatial variability. Based on comprehensive on-site investigations, various numerical calculations were conducted for the comparative analysis, involving stability analysis and the reliability evaluation of the Erdaogou landslide. The results show that treating mechanical parameters of sliding masses as random variables could result in the probability of overestimating landslide failure, leading to the squandering of supporting materials. Specifically, the coefficient of variation has the greatest influence on failure probability, and the vertical scale of fluctuation showed a larger impact on reliability than that of the horizontal scale of fluctuation. As for the rotation anisotropy, the failure probability fluctuated with the increase in the rotation angle. Taking spatial variability into account, pile top displacements and maximum bending moments tower above those obtained via stability analysis. The related studying methods could provide guidance for the optimal design of anti-sliding piles and the threat control of landslides.