Experimental study on the dynamic evolution of rock pore structure in real-time monitoring based on nuclear magnetic resonance

The rock structure determines the stability and reliability of underground engineering. Great achievements have been made in the study of rock structural damage, but there are few studies on real-time monitoring of rock structural changes under different increasing and unloading decreasing pressures. In this paper, the dynamic evolution rule of pore structure in rock under the combined action of water pressure and different confining pressure of increasing and decreasing is monitored by NMR technique. The porosity and permeability of rock under different confining pressures are consistent. The increase of confining pressure leads to the closure of pores, which leads to the decrease of porosity and permeability, but the amplitude and time of change are different. During the process of decreasing confining pressure, the T₂ spectral curve, porosity and permeability of the rock did not fully recover due to the reduction of confining pressure, indicating that plastic deformation occurs inside the rock at this time. The mathematical relationship between porosity and permeability is established, and the permeability of rock is not only related to the size of porosity, but also closely related to the pore structure of rock.