In this paper, the material point strength reduction method is used to investigate the stability of soil–rock mixture (SRM) slopes and the whole process of large deformation occurring after destabilization. A comparative study with homogeneous soil slopes is conducted. First, a material point slope model with typical shapes, a homogeneous soil slope, and an SRM slope with stones of different sizes distributed inside is established. Next, gravity is linearly added to establish the initial state of the slopes. Then the material strength of the slope is discounted according to the criterion of strength discounting. The material point method (MPM) simulations of the two slopes are carried out separately until the slope’s displacement changes abruptly to determine the slope’s safety factor. The final accumulation form of the slope after the damage is studied. Finally, the deformation characteristics of the two slopes under extreme conditions are explored. The research shows that the stones are beneficial to the slope in maintaining slope stability, and due to the presence of stones, the slope presents different characteristics from the pure soil slope when damage occurs.

The interaction mechanism between a two-lane shield tunnel and an existing tunnel during oblique underpass is a matter of widespread concern in the engineering community, and knowledge in this area remains crude. In the construction of subway tunnels in mountainous cities with huge topographical fluctuations, internal forces and deformations are inevitable in existing tunnels. To verify the applicability of existing shield construction technology and empirical parameters to the Guiyang area, a systematic and refined numerical analysis was conducted on the shield passing under the existing tunnel section of the Tao-Hua interval of Guiyang Metro Line 3. In this paper, the accuracy of the numerical simulation is verified by comparing the calculated results with the data measured in the field; the settlement pattern that appeared above the existing tunnel during the construction of the shield with slurry hardening is analyzed; the internal forces, lateral deformation, and torsional deformation of the existing tunnel caused during the excavation of the new tunnel are obtained based on the numerical simulation results; finally, the effect of the old and new tunnels on the torsional deformation and settlement of the existing tunnel under different spatial intersection angles is studied. The results show that the internal forces, lateral deformation, and surface settlement of the existing tunnel due to the diagonal underpass show obvious asymmetric characteristics. Additionally, the existing tunnel experiences local irrecoverable torsional deformation, with the maximum torsional deformation occurring at the intersection of the old and new tunnels, and the spatial intersection angle of the old and new tunnels has a great influence on the maximum settlement of the tunnel vault and arch bottom, which shows a negative correlation.