Application analysis of soil nail and cable support in deep excavations of loess regions under complex environmental conditions

To evaluate the effectiveness of a prestressed anchor cable combined with soil nailing technology in supporting deep foundation pits in loess regions, comprehensive field monitoring was conducted to measure horizontal and vertical displacements at the pit crest, as well as deep-seated horizontal deformations of the support system. A two-dimensional numerical model was developed using MIDAS GTS NX to facilitate comparative analysis. The results demonstrate that the integrated support system effectively controls deformation during excavation. The maximum displacement at the top of the support structure was recorded as 3.91 mm, while the maximum horizontal displacement below a depth of 0.5 m did not exceed 1.6 mm-both values are substantially below the predefined alarm thresholds. The vertical profile of horizontal displacement exhibits a fluctuating pattern, with relatively smaller displacements observed at the elevations corresponding to soil nails and anchor cables, indicating localized reinforcement effects. Finite element analysis reveals that horizontal displacement within the excavation zone and surface settlement at the pit edge increase progressively with excavation depth, exhibiting an approximately linear trend. In the unsupported scenario, numerical instability occurred at an excavation depth of 3.6 m, beyond which shear failure propagated through the soil mass. Although the simulated displacements prior to failure were higher than those measured in the field, this discrepancy is attributed to the minimal external loading under actual site conditions and the simplified representation of full-length grouting effects in the simulation model, which may underestimate the confinement provided by reinforced soil. In conclusion, the integration of prestressed anchor cables with soil nailing walls demonstrates high performance in deep foundation pit engineering in loess regions, offering effective deformation control and enhanced structural stability.