Study on Strength of Rock Salt with Mudstone Based on the Hoek-Brown Criterion

Abstract

ABSTRACT: According to the short-term strength of rock salt with mudstone, the applicability of Hoek-Brown criterion to the strength of rock salt with mudstone is studied. Uniaxial and triaxial compression tests have been carried out on rock salt with mudstone samples of Jintan gas storage to analyze the short-term strength and deformation characteristics of rock salt. The rock salt shows obvious strain hardening under the confining pressure of over 5 MPa. In order to study the volumetric strain characteristics of rock salt with mudstone, the stress corresponding to the strain of 4% is selected as the strength to discussed. Different strength criteria are compared to analyze the strength of rock salt, the result shows that the Hoek-Brown criterion has a good fit effect. The Hoek-Brown model is used in FLAC3D to simulate the triaxial strain hardening of rock salt with mudstone. By modifying the plastic deformation proportionality coefficient γ in the model, a new calculation equation of γ is proposed, and the deviatoric stress and volumetric strain curve obtained by the modified model are in good agreement with the experimental curve, which verifies its rationality. 1. INTRODUCTION As a national strategic issue, energy reserves can prevent energy crises caused by war and can adjust the imbalance of production and use, so they are highly valued. Rock salt is considered to be an ideal medium for oil and natural gas storage and for radioactive waste disposal because of its excellent characteristics such as damage self-recovery, low porosity, low permeability, and large plastic deformation ability (Yin et al., 2019). Therefore, gas storage caverns in rock salt are widely used and studied in the world. Since the gas storage cavern in rock salt has a strategic reserve application background, in order to make them better used in engineering practice, many scholars have done a lot of research on rock salt. The strength of rock salt is an important characteristic. However, there are more studies on the long-term strength of rock salt, but fewer on its short-term strength. The short-term strength of rock salt mainly refers to the experimental characteristics and theoretical analysis of rock salt under uniaxial and triaxial stress without considering the time effect, and the establishment of the strength and deformation theory of rock salt. Liang et al. (2006) performed a linear regression on the rock salt strength curve and obtained the regression equation. Ma et al. (2015) assumed that the relationship between the maximum and minimum principal stress was linear. Sriapai et al. (2013) conducted true triaxial tests on the rock salts of Mahasarakham, and determined the cohesion and internal friction angle of rock salt based on the Coulomb criterion.