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进行了一系列压实膨胀土的大型静力模型试验,对边坡土体吸湿后的含水率、膨胀变形等进行了实时监测。试验成果显示,膨胀土边坡浅层土体吸湿后其含水率场分布不均匀,干湿分界面处土体易由于不均匀膨胀变形而导致局部剪切错动,并随水分在坡体内的迁移,局部滑动面逐渐向边坡纵深扩展,在不同深度、不同部位形成多重剪切滑动面,最终导致边坡整体塌滑。针对静力模型试验进行了考虑膨胀性的非线性有限元计算,比较了边坡自重条件下和吸湿后应力场的变化,可知吸湿引起顺坡向正应力在干湿分界面处变化剧烈,剪应力明显增大,强度折减法得到的模型试验边坡安全系数仅0.92。研究成果表明:影响膨胀土边坡浅层稳定性的最根本原因并非膨胀土的超固结性或裂隙性,而是土的胀缩特性。
A series of large-scale static model tests of compacted expansive soil were carried out to monitor the moisture content, expansion and deformation of the slope soil after moisture absorption in real time. The experimental results show that the moisture content of the shallow soil in the expansive soil slope is not uniform after moisture absorption. The soil at the interface of the wet and dry soil is easy to move due to the uneven deformation and lead to partial shear displacement. With the increase of water content in the slope Migration, partial sliding surface gradually extended to the depth of the slope, in different depths, different parts of the formation of multiple shear sliding surface, eventually leading to the entire slope collapse. For the static model test, a non-linear finite element calculation considering the expansibility is carried out. The changes of the stress field under self-weight of the slope and after moisture absorption are compared. It can be seen that the normal stress of the cis-slope changes sharply at the wet- The stress increases obviously, the slope safety coefficient of the model test obtained by the strength reduction method is only 0.92. The research results show that the most fundamental reason that influences the shallow stability of expansive soils is not the over consolidation or fissure of expansive soils but the expansibility and shrinkage of soils.