As urban underground space development extends to ever greater depths, geohazards and stability problems induced by the combined effects of high geostress and high water pressure are becoming increasingly critical. Existing physical model tests, however, struggle to reproduce such extreme stress and hydraulic conditions in a controlled and repeatable manner. To address this limitation, a novel experimental apparatus has been developed for simulating geotechnical failure in deep underground environments. The system incorporates a segmented trapdoor that allows independent control of multiple subsidence zones and enables progressive unloading and failure simulations. It can apply earth pressures equivalent to an overburden depth of up to 120 m and water pressures corresponding to a hydraulic head of 153 m, while precisely regulating seepage. Drawer-type, high-seal earth-pressure sensors provide continuous and accurate monitoring and can be replaced rapidly when required. Using this platform, a series of model tests are carried out under coupled high geostress, high water pressure, and seepage. The results show that downward trapdoor movement induces pronounced stress redistribution and the formation of a distinct soil arching structure: vertical pressure above the unloading zone decreases by up to 30%, whereas lateral undisturbed zones experience increases of up to 1.3 times the initial value. At the stabilised stage, the zones influenced by vertical and horizontal displacements extend to approximately four and two times the trapdoor width ( B ), respectively. The apparatus therefore provides a robust basis for investigating geohazard mechanisms in deep underground construction and for improving stability assessment and disaster prevention strategies in high risk projects such as tunnelling and deep excavations.
Lin et al. (Sun,) studied this question.