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随着地铁网络不断完善,越来越多的新建盾构隧道近距离穿越既有隧道,然而对于盾构隧道近距离穿越既有隧道影响的研究尚不够完善。以上海典型软弱地层为背景,通过离心模型试验,研究了不同注浆率下的盾构上穿越施工对既有隧道以及周围地层的影响。选用排液法在离心场中模拟盾构施工,在不停机状态下成功模拟隧道开挖卸载、地层损失和注浆效应。分析了在不同的注浆率条件下,既有隧道在上穿越施工期和工后长期的位移、周围孔压和纵向应力的变化规律。试验结果表明,新建隧道近距离上穿越既有隧道时,隧道开挖的卸载效应等会导致既有隧道的隆起,但随着注浆率增大,既有隧道的隆起量减小。但过高注浆率对周围土体扰动较大,从而导致工后既有隧道的沉降也越大。
As the subway network continues to improve, more and more new shield tunnels cross the existing tunnels at close range. However, the research on the effect of shield tunnels passing through the existing tunnels at short distances is not yet perfect. Taking the typical weak strata in Shanghai as the background, the influence of tunnel construction on existing tunnels and surrounding strata under different grouting rates was studied by means of centrifugal model test. Drainage method is adopted to simulate the construction of shield in centrifugal field and successfully simulate the tunnel excavation unloading, formation loss and grouting effect without stopping the machine. The variation of displacement, surrounding pore pressure and longitudinal stress of existing tunnels during the construction period and post-construction period under different grouting rates were analyzed. The experimental results show that when the new tunnel passes through the existing tunnel at close range, the unloading effect of tunnel excavation will lead to the uplift of the existing tunnel. However, as the rate of grouting increases, the uplift of the existing tunnel decreases. However, the high grouting rate perturbed the surrounding soil more, resulting in the settlement of existing post-existing tunnels also greater.