含施工裂缝隧道穿越段堤防渗流和稳定分析

某长江隧道穿越江北大堤,堤身出现施工贯穿式裂缝,且累计沉降较大。考虑长江大堤堤身不同深度施工裂缝对堤身渗透稳定及堤坡抗滑稳定的影响,建立隧道穿越段大堤渗流有限元模型和边坡稳定分析模型,采用饱和-非饱和渗流有限元法和瑞典圆弧法,计算分析历史最高水位条件下不同深度裂缝堤防的渗流性态和堤坡稳定性。计算结果表明:深层搅拌桩对堤防渗流和稳定均有利;贯穿式裂缝对裂缝周围地层的渗流场影响较大,但当裂缝深度小于8.5 m时,堤身与堤基的最大渗透坡降分别为0.206和0.181,均小于相应材料的允许渗透坡降值,堤防渗透稳定能满足要求;贯穿式裂缝位置和深度对堤坡稳定影响显著,当裂缝深度为8.5 m时,两个不同裂缝位置的堤防抗滑稳定安全系数分别为2.419和1.844,当裂缝深度小于8.5 m时,经过深层搅拌桩加固处理后,堤坡稳定能满足要求。

Seepage and stability analysis of embankment with construction cracks in tunnel crossing section

After the tunnel-shield-driving machine excavated through the north levee of Yangtze River, several transverse construction cracks appeared in the river embankment, and the accumulative settlement of the embankment was large. This paper considered the influence of the cracks in the embankment construction of different depths on the seepage and slope stability of the Yangtze River embankment. Based on the saturated-unsaturated seepage finite element method and the Sweden slice method, the seepage and slope stability analysis models of the embankment in the tunnel crossing section were established to calculate the seepage behavior and slope stability of the embankment under different crack depths, when the river level was the highest in history. The results show that the deep mixing pile has significantly reduced the water head and reinforced the slope of the embankment. The through cracks have great influence on the seepage field of the stratum around cracks. When the crack depth is less than 8. 5 m, the maximum seepage gradient of dam foundation and body is 0. 181 and 0. 206 respectively, which is less than the allowable seepage gradient of the corresponding soil layer. Therefore, the seepage stability of the embankment satisfies the requirement. Moreover, the influence of location and depth of through cracks on the slope stability of the embankment is obvious. When the crack depth is 8. 5 m, the safety factors of slope under two different positions of through cracks are 2. 419 and 1. 844 respectively after the reinforcement of deep mixing piles. The slope stability of the reinforced embankment with deep mixing piles can meet the standard requirements when the crack depth is less than 8. 5 m.