Coupling Effect of High Temperature and Fatigue Loading on Ballastless Track Concrete in Geothermal Tunnel

Abstract

To elucidate the fatigue evolution mechanisms of ballastless track concrete under high geothermal conditions, the mechanisms of fatigue performance under the coupling effect of high temperatures and fatigue loading were investigated. The results showed that static mechanical and fatigue performance of concrete started to decline when temperatures surpassed 60 ℃. When the temperature raised to 80 ℃, the static mechanical performance of the ballastless track concrete decreases by 6.6% to 10.9%, and the fatigue life decreases by 32.1%. The principal reason for the accelerated degradation of concrete fatigue performance is the damage caused by high temperature. When the temperature is over 60 ℃, the porosity and pore diameter of concrete increased, the internal pore structure began to deteriorate, and the ettringite within cement hydration products decomposes. Due to the coupled effect of high geothermal condition and fatigue loading, the energy absorption and plastic deformation of concrete decrease, which diminishes the fatigue performance ballastless track concrete in tunnel.

Keywords: High geothermal environment, high-speed railway tunnel, ballastless track concrete, high-frequency fatigue load, coupling effect