摘要
目前抗隆起稳定计算方法多是基于均质土推导得出安全系数计算公式,将其应用于分层土地基时,通常将各土层的抗剪强度指标按土层厚度加权平均,这种方法既没有考虑滑动面实际经过各土层的弧长也没有考虑滑动面上法向应力大小。分析了分层土地基中土层分布影响抗隆起稳定性的因素,针对均质土中的抗隆起稳定验算公式提出了两种修正方法,按弧长加权平均法和按弧长与滑动面法向应力加权平均法。通过工程实例计算分析表明,传统层厚加权平均法得到的安全系数与精确解法得到的安全系数相差较大,不能合理反映各土层的抗隆起贡献;而两种修正方法,尤其是第二种,所得到的安全系数接近精确解法得到的结果,可以合理地反映不同深度土层对抗隆起稳定的贡献及基坑抗隆起稳定安全系数随土层分布变化的变化规律,并且计算简便,易于工程技术人员使用。此外,针对土层分布变化对抗隆起稳定的影响研究得出,滑动面下部土层对基坑稳定性影响最显著,因此在工程实践中,应尽可能将全部或部分支护结构的底端嵌入较好的土层中。
When the traditional basal stability analysis methods based on homogeneous ground are used in layered soils,usually the shear strength is weighted average considering soil layer thickness,but they don＇t consider either the actual arc length that the sliding surface goes through in every layer or the normal stress on the sliding surface.The factors that how distribution of soil layers influences the basal stability in layered soils are investigated.Two correction methods for the traditional basal stability analysis methods based on homogeneous ground assumption in layered soils are proposed,i.e.weighted average method considering arc length and weighted average method considering arc length and normal stress.Through the calculations of engineering examples,it is found that the results of the weighted average method considering soil layer thickness are far from the actual condition,but the two correction methods,especially the latter,can obtain a result that is close to that predicted by the layered integration method,and can better reflect the effect of soil layers beneath formation of excavation on the basal stability,and what＇s more,the calculation process is simple and convenient.The calculated results indicate that the lower layer of sliding surface is extremely important for basal stability,so it＇s better to embed the supporting structure fully or partially to the comparatively hard soil layer.
出处
《岩土工程学报》
EI
CAS
CSCD
北大核心
2012年第5期781-789,共9页
Chinese Journal of Geotechnical Engineering
基金
国家重点基础研究发展计划(973计划)项目(2010CB732106)
天津市科技支撑计划项目(11ZCGYSF00800)
关键词
基坑
坑底抗隆起稳定
圆弧滑动法
弧长
法向应力
excavation
basal stability
circular sliding method
arc length
normal stress
作者简介
郑刚（1967-），男，贵州贵阳人，博士，教授，博士生导师，从事土力学及岩土工程的教学与科研工作。E-mail：zhenggang1967@163．com。
