砂石粒径对改良膨胀土的影响研究

为研究砂石改良膨胀土工程特性随砂石粒径的变化规律,通过直剪试验、收缩试验、膨胀力试验、无荷膨胀率试验,分析了膨胀土抗剪强度、胀缩特性与砂石掺量、砂石粒径的关系。试验结果表明:随着砂石掺量增加,膨胀土的抗剪强度有所提高,内摩擦角增大,黏聚力先增大后减小,膨胀土的胀缩特性逐渐改善,相同掺量下,掺砂石的粒径越大,膨胀土的黏聚力和内摩擦角越大,胀缩特性改善效果越明显,掺入砂石粒径越大,胀缩特性得到改善并趋于稳定的砂石掺量越小,最优砂石掺量逐渐减小。建议不同粒径砂石改良膨胀土的最优掺量分别为:风化细砂40%,风化中砂30%,碎石25%。掺大粒径的砂石改良膨胀土更加经济有效。

Study on the Effect of Sandstone Size on the Improvement of Expansive Soil

In order to study the variation of engineering properties of expansive soils with the particle size of sand and gravel, a series of laboratory tests including direct shear test, shrinkage test, swelling force test and unloaded expansion ratio test are conducted, while relationships between the shear strength, expansion-shrinkage characteristics, the content of sand and gravel and the particle size of sand and gravel are analyzed. The results show that, with increasing of sand and gravel content, the shear strength of improved expansive soil increases, which the internal friction angle also increases, but the cohesion of improved expansive soil firstly increases and then decreases, and that expansion and shrinkage characteristics of expansive soils are gradually improved. When a certain amount of sand and stone is mixed, the bigger particle size of sand and gravel is, the greater the cohesion and internal friction angle of the improved expansive soil is, the more obvious improvement effect of swelling and shrinkage characteristics is. The larger particle size of sand and gravel is, the smaller amount of sand and gravel to achieve the improvement effect is, while the optimum content of sand and gravel decreases gradually. It is suggested that the optimum content of sand and gravel is that: weathered fine sand is 40%, weathered medium sand is 30% and gravel is 25%. It is more economical and effective to improve expansive soil with large size sand and gravel.