高速公路软土地基硬壳层作用效应研究

Study on Excitation Effects of Hard Shell Course on Soft Clay Foundation in Highway

天然双层软土地基上的硬壳层具有应力扩散、反压护道、沉降滞后和封闭作用等特征。对于在硬壳层软土地基上修建的路堤,经硬壳层应力扩散后,施加到软土层顶面的附加应力可望小于软土的强度,从而可直接在硬壳层上修建路堤,而不必对软土地基进行处理。基于有限元数值分析,研究了硬壳层刚度、路堤高度以及软基厚度对硬壳层软土地基变形特征和硬壳层应力扩散效果的影响。结果表明硬壳层的应力扩散性能随路基荷载的增加而减小,随其下软土地基厚度的增加而提高,并且硬壳层的刚度越大,其应力扩散性能越明显。基于考虑硬壳层的应力扩散、反压护道等作用,在不破坏硬壳层基础上,当路基高度与硬壳层的比值不大于1.5时,可不作处理或采用冲击压实、砂垫层+土工格栅等浅层处理措施。结合工程实际,验证了该结论的有效性,为类似工程的设计与施工提供参考。

The hard shell course on soft clay foundation has such characters as stress distribution, back berm, lagging behind of settlement and closed action. So based on the stress distribution character of the hard shell course, we can build the subgrade on the hard shell course directly and need not tread the soft clay basement. According to the result of FEM, the effect of the stiffness of the hard shell course, the height of subgrade and the thickness of soft clay on the foundation settlement and the stress distribution are studied. The ability of stress distribution decreases with the increasing subgrade height and improves with increasing the thickness of soft clay and stiffness of the. Taking into account the effect of stress distribution and the back berm, when the ratio of subgrade height and the thickness of the hard shell course is less than 1.5, the foundation can not be treated or impact pressed, or treated with sand blanket and geogrids measures. At last, the correct conclusion is validated with the engineering practice.