不同加固方案下富水黄土隧道地层变形规律分析

以西安地铁5号线暗挖隧道为工程背景,采用降水加固与注浆加固2种地层加固措施,建立渗流-应力耦合数值计算模型,对富水黄土隧道地表沉降、洞周土体变形及力学效应进行了研究,并结合现场监测资料进行了验证。结果表明:降水加固隧道施工最大地表沉降是注浆加固的13.7倍,2种加固方案洞周土体变形规律一致,开挖10 d内变形值均达到稳定值的70%~80%左右;注浆加固下洞周土体均为压应力,降水加固开挖过程中在中隔壁及中隔板处土层出现拉应力;注浆加固下衬砌各部位受力均大于降水加固;降水加固塑性区极值是注浆加固的11.3倍,主要分布在两侧拱肩、拱腰及拱脚处;2种加固方案下地表沉降以及洞周土体变形的模拟值与监测值相近且变化规律基本一致。

Strata Deformation Law of Water-rich Loess Tunnel in Different Reinforcement Schemes

With the tunnel segment of Xi'an Metro Line 5 as engineering background, we examined and compared the ground settlement, soil deformation around the tunnel, and mechanics effect of water-rich loess tunnel reinforced by different methods (dewatering reinforcement and grouting reinforcement) via a seepage-stress coupling numerical model. We further validated the numerical result according to site monitoring data. Results demonstrated that the maximum ground settlement of the tunnel strengthened by dewatering reinforcement was 13.7 times that by grouting reinforcement. The laws of soil deformation around the tunnel under these two reinforcement schemes were consistent, and the deformation value of surrounding rock in ten days of excavation reached about 70%-80% of the stable value. Soil around the tunnel suffered from compressive stress under grouting reinforcement, while tensile stress appeared in the soil layer of the middle wall and the middle plate during the excavation under dewatering reinforcement. The stress of the lining under grouting reinforcement was larger than that under dewatering reinforcement. The extreme value of plastic zone under dewatering reinforcement was 11.3 times that of grouting reinforcement, mainly distributing at the shoulders, waists and feet of the arch on both sides. The simulated values of ground settlement and soil deformation around the tunnel under the two reinforcement schemes were similar and basically consistent with the change law of the monitored value.