Influence of seasonal melt layer depth on the stability of surrounding rock in permafrost regions based on the measurement

Abstract

During tunnel construction in permafrost regions, control of the temperature field and depth of the seasonal melt layer of surrounding rock are the key factors that determine the stability of surrounding rock and the security of a structure. Based on the monitoring data on the temperature of the surrounding rock at two sections of Jiangluling Tunnel, the distribution regularities of the temperature field of the surrounding rock in different depths from the tunnel wall are obtained. These findings are used to determine the changing rules of the depth as well as the increasing speed of the depth of seasonal melt layer with time. At the same time, the influence of the surface of the accumulated temperature of surrounding rock to seasonal melt layer is analyzed, and the influence of the rule of the depth of seasonal melt layer on the stability of surrounding rock and arch crown settlement is determined. Results show that the temperature of the surrounding rock and the depth of the seasonal melt layer are controlled by engineering geological conditions of the surrounding rock and the temperature inside the tunnel. The temperature of the surrounding rock decreases with the increase in depth from the tunnel wall. Correspondingly, the depth of seasonal melt layer increases along with the temperature inside the tunnel. It is a positive correlation between seasonal melt layer and the surface of the accumulated temperature of surrounding rock, and with the increase in the depth of seasonal melt layer, the arch crown settlement increases, whereas the stability of the surrounding rock decreases.