土钉支挡结构在地铁基坑边坡稳定性分析中的应用

Application of Soil Nail Retaining Structure in Stability Analysis of Subway Foundation Pit Slope

武汉地铁12号线某基坑采用放坡开挖施工方法,针对基坑开挖后边坡土体自稳能力降低、存在滑坡与垮塌风险的安全问题,依据力学平衡和数值模拟理论,采用平面滑动法和瑞典圆弧法,分别计算天然工况和土钉支挡工况下的边坡安全系数,以midas GTS NX数值模拟分析天然工况和土钉支挡工况下的边坡位移变化,并对杆体直径和喷射混凝土厚度等支护参数进行优化。结果表明:采用杆体直径为22 mm、坡面混凝土喷射厚度为150 mm的土钉支挡结构,边坡安全系数提高至1.39,大于天然工况下的0.495;边坡的竖向位移控制在1.8 mm,小于天然工况下的5.7 mm,表明土钉支挡结构提高了边坡稳定性,增加土体滑裂面的抗滑力。

A foundation pit of Wuhan Metro Line 12 adopts the construction method of slope excavation.In view of the safety problems of slope soil mass self-stability reduction and landslide and collapse risk after foundation pit excavation,according to the mechanical balance and numerical simulation theory,the plane sliding method and Swedish arc method are used to calculate the safety factor of slope under natural conditions and soil nail retaining conditions respectively.The midas GTS NX numerical simulation was used to analyze the slope displacement changes under natural and soil nailing conditions,and the supporting parameters such as rod diameter and shotcrete thickness were optimized.The results show that the safety factor of the slope is increased to 1.39 by using the soil nail retaining structure with the diameter of the rod body is 22 mm and the thickness of the slope concrete injection is 150 mm,the safety factor of the slope is increased to 1.39,which is greater than 0.495 under the natural condition.The vertical displacement of the slope is controlled at 1.8 mm,which is less than the natural condition of 5.7 mm,indicating that the soil nail retaining structure improves the stability of the slope and increases the anti-sliding force of the soil sliding surface.