Test of mechanical properties of limestone under hydraulic pressure-stress coupling

To study the mechanical properties of limestone with water-rich saturated circumstance under water pressure-stress coupling, compression failure tests of limestone samples with different water pressure were carried out by using a self-developed permeability test device, the device can realize uniaxial compression test. Then, the stress-strain characteristics of limestone, the effect of hydraulic pressure on uniaxial compressive strength, the elastic modulus and the deformation modulus, and the correlation between breaking characteristics and hydraulic pressure were tested. The results show that the increased hydraulic pressure has a significant influence on the stress-strain curve and strength characteristics. With the increase of hydraulic strength, the compaction stage of stress-strain curve is relatively prolonged and elasticity stage is relatively shortened, the peak strength decreases exponentially while the elastic modulus and the deformation modulus decrease linearly, indicating that the brittleness of limestone is significantly reduced by water-rock interaction. Besides, the elastic modulus and the deformation modulus of limestone are linearly related to the peak strength. The increased hydraulic pressure has a significant effect on the macroscopic fracture of limestone but not on its failure type. With the increase of hydraulic pressure, both the homogenization coefficient and the pore volume per unit mass of limestone increase by exponential function. The experimental results could provide reference for the excavation stability analysis of water-rich rock mass in tunnel construction.