盾构下穿既有隧道诱发沉降后注浆抬升试验研究

    Experimental study on grouting uplift after settlement induced by shield tunneling under existing tunnels

    • 摘要: 为探明囊袋注浆法整治盾构下穿既有隧道诱发沉降的效果,在完成的盾构下穿模型试验基础之上,自主设计出囊袋注浆法的注浆工艺,进行了盾构下穿既有隧道诱发沉降注浆抬升试验研究,对盾构下穿既有隧道诱发沉降注浆试验过程中既有隧道的挠曲变形、隧道沉降、附加土压力变化进行研究。试验结果表明:在距离隧道北端部120~250 cm处,既有隧道发生了明显的横椭圆变形;同样在此位置处既有隧道抬升高度明显,抬升最大值在隧道中部约为15 mm。并且附加土压力变化显著,且均为上升趋势,在隧道中部时,附加土压力增长值最大;在注浆过程中,囊袋注浆法对于浆液有着良好的束缚作用,浆液压力主要集中在囊袋注浆口附近,使周围土体产生了土拱效应;在实际工程当中,建议采用多点位同时注浆,让隧道整体抬升,使整治后的隧道结构内力以及结构形态恢复至下穿前的状态。同时加强在注浆过程中对隧道抬升的监测,以防隧道抬升超出。

       

      Abstract: To investigate the efficacy of the bag grouting technique in mitigating settlement induced by shield tunneling, a distinct grouting process is formulated subsequent to the completion of a model test simulating the said scenario. Subsequently, an uplift test is conducted to evaluate the technique's impact on the tunnel's flexural deformation, settlement, and changes in additional earth pressure exerted on the superstructure during the grouting-induced settlement test of an existing tunnel beneath a shield tunnel. The experimental findings reveal transverse elliptical deformations occurring within a zone of 120 cm to 250 cm from the northern terminus of the tunnel. Notably, a significant uplift in the superstructure is observed at this location, with the peak uplift reaching approximately 15 mm at the tunnel's midpoint. The greatest increment in additional earth pressure is recorded at the tunnel's midpoint as well. During the grouting operation, the bag grouting method exerts a robust binding effect on the grouting slurry and concentrates the slurry pressure predominantly around the injection point, thereby inducing a soil arching effect in the adjacent soil mass. In practical engineering, it is recommended to employ concurrent multi-point grouting to elevate the tunnel as a integral unit, thereby restoring the tunnel's internal forces and structural configuration to their pre-underpass conditions. Moreover, enhanced monitoring of the tunnel's uplift should be implemented throughout the grouting phase to avert excessive uplift.

       

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