The pressure field inside water-rich cracks of tunnel linings during high-speed train passing through tunnels using air–water two-phase flow simulation

Abstract

Water-rich cracks are a common type of damage in high-speed railway tunnels. When high-speed trains passing through tunnels, the dramatic changing in aerodynamic pressure repeatedly acts on water-rich cracks, potentially causing further crack expansion or even more severe structural damages. This study employs the dynamic overlapping grid method and the volume of fluid (VOF) model to establish a multiphase flow coupling model of air-train-tunnel-water-rich cracks, analyzing the spatiotemporal variation characteristics, influencing factors, and mechanisms within water-rich cracks when a high-speed train passes through a tunnel. The main conclusions are as follows: (1) The pressure changes inside the water-rich cracks exhibit a significant pressure amplification phenomenon. Compared to the tunnel wall, the increase in positive peak value (C_p,max) and negative peak value (C_p,min) of the aerodynamic pressure near the crack tip is as high as 22.91 % and 51.71 %. (2) The pressure variation trend along the length direction inside the water-rich crack has a distinct one-dimensional feature, while along the depth direction is significantly different. The pressure waves do not change with depth of the crack in water-free section, but the pressure fluctuation amplitude in the water-rich section increases with the depth. (3) The positive and negative pressure waves exert thrust and suction forces on the water body inside the water-rich crack, leading to fluctuation in air density near the crack tip, thus causing oscillation and amplification in the pressure. The water in the water-rich cracks exhibits increased motion amplitude and peak acceleration with greater depth, causing the pressure in water also intensifies. (4) Compared to those outside the crack at 300 km/h, the C_p,max near the water-rich crack tip increased by 6.69 %, 77.98 %, and 62.03 % when the train speed is 300 km/h, 350 km/h, and 400 km/h, and the C_p,min increased by 57.71 %, 111.25 %, and 161.73 %, respectively. The maximum pressure fluctuation amplitude occurring at a water content of 80 %. The results can provide theoretical basis for the healthy and high-quality operation of high-speed railway tunnels.