隧道穿越段长江大堤渗流稳定性分析

Seepage Stability Analysis of Yangtze River Levee as Tunnel Traversing

某长江隧道盾构机穿越江北大堤后,堤身出现裂纹且累计沉降较大,工程采用深层搅拌桩对堤身进行加固。为了检验深层搅拌桩对长江大堤堤身加固后的渗流稳定性,采用三维饱和-非饱和渗流有限元法,根据具体的工况建立了大堤的有限元渗流分析模型,并运用该模型分析了历史最高水位条件下加固后大堤的渗流性态。计算结果表明:深层搅拌桩消减水头的作用明显,土体渗透系数越大,深层搅拌桩的阻水作用越明显;堤身与堤基的渗透坡降均小于相应土体的允许渗透坡降,加固后长江大堤的渗流性态是正常的、安全的。

After the tunnel-shield-driving machine excavating through the north levee of Yangtze River, some cracks ap- peared in the levee, and the accumulative settlement of the levee was very large, so the levee was enhanced by deep mix- ing pile in the project. A three-dimensional saturated and non-saturated seepage finite element method is adopted here to check up the seepage stability of the enhanced Yangtze River Levee. Then, the finite-element seepage analysis model is established based on the actual project condition, and by using this model, the seepage behaviors of the enhanced levee under the condition of historical highest water level are analyzed. The calculation results show that the function of deep mixing piles for reducing water head is evident, and the larger the permeability coefficient of soil, the more evident is the water-tight action of deep mixing piles. The seepage gradients in levee body and foundation are less than the permissive permeability gradients in corresponsive soils, and the seepage behavior of the enhanced Yangtze River Levee is normal and safe.