突发高压渗流作用下黄土地铁隧道水压阶跃效应分析

Step effects of hydraulic pressure of metro tunnels in loess under sudden high-pressure seepage

高压水源外泄具有突发性、快速性和释能效应,诱发的黄土围岩灾变性态及隧道结构劣化影响要比静力入渗作用更严重。为揭示高压渗流作用下黄土围岩水压阶跃效应的传递特征、诱因及其对隧道结构受力的影响规律,通过开展相似模型试验,对黄土围岩渗流性态的时空演化及隧道力学响应进行研究。研究表明:突发高压渗流过程依次经历了黄土局部湿陷侵蚀→产生隐伏空腔→形成优势通道→围岩水压及结构内力阶跃波动→渗流趋于稳定;局部湿陷势释放和优势运移通道的孕育发展是围岩水压及结构受力阶跃波动的主要原因;在不同水源位置下,起拱线以下衬砌内力变化均显著大于上部结构,且拱底位置受力影响最大,其中在上部水源时轴力的最大阶跃增幅为324kN,在下部水源时弯矩的最大阶跃增幅为84 kN·m;优势运移通道下侧围岩区域所受影响最大,在不同水源位置下衬砌内力影响程度表现为上部水源>下部水源>侧部水源。

The leakage of a high-pressure water source has sudden,rapid and energy-release effects.Its destructive behavior of surrounding rock of loess and deterioration of tunnel structures is more severe than static infiltration.To reveal the transmission characteristics and inducement of the step effects of surrounding rock of loess under high-pressure seepage as well as the influences on the tunnel structures,the temporal and spatial evolution of seepage behavior of surrounding rock of loess and the mechanical response of tunnels are studied through the similar model tests.The research shows that the seepage process has successively experienced local collapsible erosion of loess→generation of the hidden cavity→formation of the preferential channels→step fluctuation of water pressure of surrounding rock,and structural internal force→seepage stability.The release of the local collapsible potential and the development of the preferential seepage channels are the main reasons for the step fluctuation of the water pressure of surrounding rock and structural stress.Under different water source locations,the changes of internal force of linings below the arch springing line are significantly greater than those of the upper structures,and the arch bottom location is most affected by the force.The maximum step increase of its axial force is 324 kN under the upper water source,and that of its bending moment is 84 kN·m under the lower water source.The surrounding rock area at the lower side of the dominant preferential channel is most affected.The influence degree of the internal force of linings under different water source positions is shown as upper water source>lower water source>side water source.