弱膨胀土工程特性及其路基处治对策

针对湖北襄—荆高速公路膨胀土，在室内开展了弱膨胀土的压实特性、胀缩性状、力学特性试验研究，发现压实膨胀土的工程性状受含水率与压实度的影响，胀缩特性是膨胀土的固有特性，其大小取决于起始湿度和密度；击实膨胀土的最佳含水量和最大干密度随击实功变化而变化，压实功愈大，土的最大干密度也愈大，而对应的最佳含水量愈小；膨胀土的CBR值随其含水率的变化规律类似于击实曲线，但CBR峰值含水率大于最佳含水率，为深入认识膨胀土的工程特性提供了帮助。因此，利用弱膨胀土填筑路堤时，不仅要考虑经过击实后的土的性质，而且还要考虑在填方建成、条件改变后土的性能；膨胀土路堤填筑除考虑压实度与CBR值要求外，尚需考虑胀缩总率的影响。最后，推荐了弱膨胀土路堤结构型式，并提出了弱膨胀土用于路堤填筑的控制标准。

Engineering behaviors of weak expansive soil and its treatment measures for roadbed filling

Compacting properties,swelling-shrinkage behavior and mechanical behavior of compacted sample for weak expansive soils in Xiang-Jing Expressway of Hubei Province are investigated.It is discovered that the engineering behavior of weak expansive soils is controlled by the coupled action of water content and degree of compaction,while the swelling-shrinkage behavior is inherent property of weak expansive soils and its value depends on the initial water content and dry density;the optimum moisture content and maximum dry density of expansive soils depends on tamping effort,bigger tamping effort;bigger the maximum dry density,and smaller the optimum moisture content correspondingly;the variation of California bearing ratio(CBR)of the expansive soils with water content is similar to the compaction curve.However,the water content of soil corresponding the maximum CBR is higher than the optimum water content.In the construction of expansive soil embankment,the influence of total swell-shrink ratio should be considered besides the degree of compaction and CBR value;and it is helpful to understand the engineering properties of expansive soils.At last,the structural shape of weak expansive soil embankment and the standard of controlling compaction of weak expansive soil for constructing embankment are suggested.