Fabrication of rock foundation materials and uplift test of model foundation based on similarity theory

[Objective] he excavation-anchored composite foundation is widely applied in transmission line towers for layered foundations consisting of overlying fully/strongly weathered rock and underlying weak/medium weathered rock. To further investigate its load-bearing performance and load-sharing evolution patterns under uplift-horizontal composite loads, this study conducted experimental investigations to reveal its mechanical behavior and failure modes.[Methods] Using rock-like materials with varying proportions, an indoor stratified foundation model was constructed featuring "overlying strongly weathered rock and underlying moderately weathered rock." Bearing tests were conducted on excavation-anchor composite foundations under vertical uplift loads and combined vertical uplift-horizontal loads to analyze load-sharing evolution patterns and foundation failure mechanisms.[Results] Experimental results demonstrate: (1) The composite foundation system combining excavation and anchor reinforcement exhibits approximately 32% higher bearing capacity compared to excavation-only foundations. The deep anchoring effect of anchor rods promotes horizontal expansion of failure surfaces, thereby expanding the soil's load-bearing capacity range. (2) Under combined horizontal and uplift loads, the system demonstrates about 11% greater load-bearing capacity than pure uplift scenarios. The horizontal load alters stress paths, effectively mobilizing anchor rod forces to enhance structural integrity. Anchor load ratios initially range from 65%-70%, subsequently decreasing to 20%-30% due to stiffness differential-induced load transfer dynamics: initial high anchor stiffness leads to preferential load distribution, followed by lateral friction resistance from excavation foundations, with anchor rods ultimately maintaining stability through ductile deformation. [Conclusions] The excavation-anchor composite foundation effectively enhances bearing capacity and adapts to composite loads. The load-sharing evolution reveals the synergistic mechanism between anchor rods and foundation, providing theoretical support and engineering application references for layered foundation design.