振动荷载下安家庄隧道红黏土工程力学特性研究

Study on Engineering Mechanical Properties of Red Clay in Anjiazhuang Tunnel under Vibratory Load

安家庄隧道紧邻既有铁路线路,该隧道红黏土洞段为转辙机扩挖段,临线列车振动荷载对扩挖洞段的安全施工和运营构成了严重挑战。通过开展安家庄隧道振动前后红黏土的标准固结、直剪和电镜扫描等试验,从宏观和细观的角度研究了安家庄隧道红黏土力学特性和细观结构在振动荷载下的演化规律,并基于数值方法计算评估了振动荷载对安家庄隧道围岩安全性的影响程度。研究表明,振动荷载作用后安家庄隧道红黏土压缩模量减小了约42.8%,抗剪强度最大降低了约23.48%,围岩变形最大增加了约293.31%,土体微观结构也出现了一定程度劣化。因此,振动荷载对红黏土的工程特性具有显著影响,隧道设计施工时应充分考虑振动荷载的作用。同时,建议在安家庄隧道施工时对开挖土体应尽早支护,为临空面土体提供及时的支撑力。

The Anjiazhuang tunnel is close to the existing railway,and the red clay section is the expanding section of the switch machine.The vibratory load of train from the existing railway brings serious challenges to the construction safety and management in the expanding excavation section.Based on the tests such as standard consolidation,direct shear test,and scanning electron microscope(SEM),the evolution law of mechanical properties and microstructure of red clay in Anjiazhuang tunnel under vibratory load were studied from macroscopic and microscopic view.On the basis of numerical simulation,the influence degree of vibratory load on the safety of surrounding rocks in Anjiazhuang tunnel was evaluated.The results indicated that,after the effect of vibratory load,the compressive modulus and shear strength of the red clay in Anjiazhuang tunnel were respectively decreased by 42.8% and 23.48%,and the deformation of the surrounding rock was increased by about 293.31% in the maximum.Moreover,the microstructure of soil also had some deterioration.Therefore,the vibratory load had a significant effect on the engineering properties of red clay,so that the influence of vibratory load should be fully considered in the design and construction of tunnels.Meanwhile,it was suggested that the excavated soil should be supported as soon as possible during the construction,so as to provide timely support for the soil with free-face.