Experimental study on the acoustic emission response and permeability evolution of tunnel lining concrete during deformation and failure

Abstract

Due to long-term coupling of ground stress and water pressure during operation processes, lining concrete will experience different degrees of cracking and spalling, which seriously affect the safety of tunnels during service. In this paper, lining concrete seepage tests under different confining pressures are performed; the mechanical properties and acoustic emission (AE) responses during the loading process and the relationship between load-induced plastic deformation and lining concrete specimen permeability are studied. The plastic internal variable definition is introduced to characterize concrete specimen plastic deformation and is calculated after unloading. Different initial stress states and stress levels during loading and unloading processes affect pore and fissure development in lining concrete. The peak intensity increases with increasing confining pressures, and deformation parameter variation has elastoplastic coupling characteristics. AE parameters and axial stress show good agreement. The AE signal of the samples shows a transition from the Kaiser effect to the Felicity effect before the peak, indicating that AE can be an effective means of monitoring internal sample damage. A power function relationship can represent the relationship between the initial permeability and confining pressure, and the permeability evolution model of concrete samples in the plastic phase is established after the initial yielding.