Experimental investigation on the evolution of damage and seepage characteristics for red sandstone under thermal–mechanical coupling conditions

Abstract

Rock masses in underground space usually experience the coupling of high-temperature field, stress field and seepage field, which gives them complex mechanical behavior and permeability characteristics. In order to study the mechanical properties and permeability characteristics of red sandstone under different temperature environments, a seepage test under high temperature and triaxial compression is carried out based on the RLW-2000 multi-field coupling tester. The results show that the plastic flow of red sandstone at the stress peak under the same temperature is more obvious with the increase of confining pressure. In addition, as the confining pressure gradient increases, the permeability decreases and the trend becomes slower. And the higher the operating temperature, the easier to produce seepage channels inside the rock sample. The development of fissures is rapidly developed under the effect of temperature, so the seepage channels are widened and increased, and the permeability is greatly increased. The constitutive model of rock statistical damage considering the interaction of high temperature and osmotic pressure was constructed based on the experimental data and combining theoretical methods to reveal the characteristics of permeability evolution induced by thermal damage of rocks. The research results can be used as a reference for monitoring rock stability during geological engineering projects involving thermal-seepage-stress coupling conditions.

Real-time permeability evolution of limestone under high temperature and triaxial stresses

“…( 1) for the calculation of high temperature and high pressure online permeability. In the actual measurement process, one measurement can be completed when the differential pressure ∆P decays to about 50% of its initial value (Jiang et al 2021), and the nitrogen dynamic viscosity and…”

“…The permeability is a macroscopic reflection of the microstructural changes in the rock, and the value and number of microcrack openings in the high-temperature triaxial stress state during the warming process are gradually enhanced by the limitation of triaxial stress, so the value and number of microcrack openings caused by thermal stress in the free state are greater than those in the high-temperature triaxial stress state (Zhao et al 2017a, b). The physical properties of the rock in the high temperature real time state decreases significantly relative to the room temperature state, the cementation strength between particles decreases, the softening and ductility of the rock is enhanced (Jiang et al 2021), and the long-term high temperature and triaxial stress loading occur creep (Brace 1980;Liu et al 2015), and a significant decrease in permeability.…”

Evaluation of Thermophysical and Mechanical Properties of Sandstone Due to High-Temperature

“…The combined effect of the structural stress associated with the gasification chamber formation and the thermal stress induced by high temperature will damage the rock. When the damage reaches a certain level, the rock will experience the expansion of original fractures and the generation of new fractures, eventually leading to rock fracturing [ 12 , 13 , 14 , 15 , 16 ]. Furthermore, it may cause roof caving, excessive movement, fracturing damage, and surface subsidence of rock strata above the gasification chamber at worst.…”