In southwest mountainous area of China, there are a large number of composite strata with thin covering layer, good engineering properties of overlying bedrock but difficult excavation, and the mountainous terrain is steep and complicated, which is not conducive to transmission tower infrastructure construction. To solve this problem, a short-pile foundation with inclined anchor is taken as transmission tower foundation, whose can make full use of the bearing capacity of the bedrock while reducing the excavation depth and construction difficulty. In order to explore the mechanical characteristics and main control factors of short pile foundation with inclined anchor, a numerical model was established by FLAC^3D, and the effects of anchor bar diameter and bolt angle on the tensile bearing characteristics of short pile foundation with inclined anchor were discussed. The results show that when the load is large, the bearing ratio of the anchor rod structure increases obviously with the increase of the diameter of the anchor bar, but if the diameter of the anchor bar is too large, the bearing ratio of the anchor rod has less room for lifting. As the bolt Angle decreases, the uplift bearing capacity of short pile foundation with inclined anchor increases under pure uplift load, but its resistance to horizontal load weakens. Considering comprehensively, In the siltstone stratum, anchor bar diameter 40mm and bolt Angle 25° are the optimal design parameters of short pile foundation with inclined anchor.

Taking the transfer hall project of a subway station as an example, FLAC^3D numerical simulation software was used to analyze and summarize the influence law of the excavation of the deep excavation of the upper span on the deformation of the underpass three-dimensional cross tunnel with different spatial distances and distribution forms. Combined with the field monitoring data and the mutual verification of the numerical simulation results, the results showed that: (1) The effect of excavation unloading on the structural deformation of the tunnel is mainly manifested as vertical displacement, and its deformation is closely related to the spatial position of the foundation pit and the unloading amount of the rock-soil mass of the foundation pit; (2) The monitoring data of the whole construction cycle of the left and right tunnels of Line 1 are in good agreement with the numerical simulation results, which verifies the accuracy of the judgment of the influence of the numerical calculation method on construction activities; (3) The vertical displacement of the cascade tunnel coupled with multiple stress states is significantly affected by superposition effect, and the maximum vertical displacement is located in the area with many influencing factors, and the maximum vertical displacement is 34. 84 mm; (4) Tunnels with shallow burial depth are more sensitive to construction disturbance than those with deep burial depth. The deformation dispersion at different locations is stronger, and the deformation has certain integrity and coordination.

The landslide is affected by the topography and sliding surface morphology. In the process of movement, it often shows complex behaviors such as steering, bifurcation and aggregation. It is of great significance to study the mechanism of landslide steering deformation under complex moving paths for prevention and mitigation of landslide disaster. Based on the three-dimensional geological modeling technology, the three-dimensional particle flow model of Pangjiawan landslide is constructed. Through PFC simulation of landslide movement process, following conclusions are conducted: Steering and aggregation occurred in the Pangjiawan landslide, and the sliding direction of the soil in the middle and back of the landslide deflected and the soil aggregates with that from the northeast region at slope toe; The particles with turning movement in the middle of the landslide begin to slide first with fast speed, and the speed decreases radially from the middle of the landslide to the surrounding area. The leading edge of the landslide keeps a high speed during the whole movement, while the trailing edge of the landslide moves slowly. In addition, the surface velocity of the landslide is larger than that of the interior and bottom of the landslide, and the different velocity of each part of the landslide is an important reason for the steering deformation of the landslide. It reveals the movement law and steering deformation mechanism of complex moving landslides, and provides a theoretical basis for evaluating landslide risks and adopting more reasonable prevention schemes.

To address the challenges faced by transmission line tower foundation projects in complex mountainous environments, a root pile foundation composed of a short pile and three inclined anchor rods evenly distributed around the pile is proposed, aiming to enhance the uplift resistance of the pile foundation. Through field prototype testing, the vertical displacement of the pile top, anchor rod axial force, failure modes, and load distribution coefficient of the root pile foundation under uplift load were investigated. The results show that: The uplift load-displacement curve of the root pile foundation can be divided into three stages, including initial elastic straight line stage, elastoplastic curve transition stage, and the linear failure stage. In the early loading stage, the load-bearing capacity of the anchor rods is not significantly demonstrated, but as the load increases, the axial force of the anchor rods continues to grow. The ultimate uplift bearing capacity of the root pile foundation increased by 29.41% compared to that of the short pile foundation, indicating that the inclined anchor rods significantly improved the load-bearing capacity of the root pile foundation. Additionally, radial and circumferential cracks formed around the root pile foundation, with the main cracks concentrated in the area where the inclined anchor rods were arranged, presenting a radial distribution. This is because the anchor rods compress the soil and rock mass upwards, causing tensile failure in the upper soil and rock mass, and ultimately leading to the failure of the anchor rod structure due to tensile damage. Analyzing the bearing mechanism of the root pile foundation, the load distribution coefficient between short piles and inclined anchor rods can be used to characterize the bearing characteristics of the root pile foundation, and both components working together to bear the load. During the test, the load distribution coefficient of the inclined anchor rods gradually increased from a low level in the early loading stage to 48%, effectively dispersing and transferring the load. The research findings can provide a theoretical basis for the design and optimization of transmission line tower foundations in complex mountainous environments.