Model test to investigate waterproof-resistant slab minimum safety thickness for water inrush geohazards

The study of waterproof-resistant slab minimum safety thickness for water inrush geohazards is of great significance during the design and construction phase of tunnel engineering. Firstly, to obtain minimum safety thickness of rock wall of tunnel face, a simplified model for simulating the whole process of water inrush disasters is established. Then a three-dimensional (3D) model test system which can be applied to simulate water inrush geohazards, is researched and manufactured. Based on Yuelongmen tunnel of Chengdu to Lanzhou railway line in China as the engineering background, a series of large-scale geomechanical model test have been carried out. The effect of strata pressure, hydraulic pressure and waterproof-resistant slab thickness of surrounding rock on water inrush disaster is studied. Model test results show that minimum safety thickness increases with the increase of strata pressure and decreases with the increase of hydraulic pressure. Besides, there are two main destruction characteristics on tunnel face for water inrush disaster. One is the shear failure occurred at the center of tunnel face which accounts for most of the destruction form. The other is osmotic instability occurred at the edge of tunnel face.