Mechanical properties and energy evolution of drilling shaft lining concrete under hydro-mechanical coupling

Abstract

As the drilling shafts in the western mines of China are going to cross the deep water-rich and weakly cemented rock layer, investigating the mechanical properties and energy evolution of shaft lining concrete within the context of hydro-mechanical coupling is crucial. In this study, concrete compression tests were conducted using the TAW-2000 rock testing machine. The concrete damage and rupture mechanisms were analyzed using a combination of mercury intrusion porosimetry and scanning electron microscopy. Moreover, a thorough investigation of the energy evolution throughout the concrete stress-strain process was conducted. The key results include the following: (1) The formulation of the normalized decay equation for the characteristic strength of concrete under hydraulic coupling was derived by computing the ratio of pore water pressure to confining pressure as the characteristic parameter. (2) The effective shear strength reduction factor characterizing the impact of water pressure on the effective shear stress with a correlation coefficient greater than 0.999. (3) The pore water pressure adversely affected the pore size distribution within the concrete, enhancing the connectivity between pores. (4) The total input energy, elastic energy, and dissipated energy were positively related to the confining pressure and negatively related to the pore water pressure. The energy consumption ratio served as a tentative criterion for assessing the strength failure of the shaft lining concrete, which is considered to be in a critically stable state when the energy consumption ratio is 1. These results provided valuable insights into the damage laws and energy-driven mechanisms of shaft-lining concrete under hydraulic coupling conditions.