粗颗粒含量对川西地区混合土压缩特性的影响

为解决川西地区混合土路基压缩变形问题，为该地区高速公路、铁路建设提供理论分析基础，针对该地区路基常用混合土，考虑粗颗粒含量影响，进行天然混合土大型压缩试验研究。选取川西地区3组典型天然混合土土样，对其分别采用筛分法剔除20，10，5 mm粒径颗粒，制备粗颗粒含量不同的天然混合土土样，进行粗粒土压缩试验研究。通过对比不同粗颗粒含量的土样在相同试验条件下的孔隙比及压缩模量的不同变化情况，分析川西地区混合土压缩特性受粗颗粒含量的影响规律及其影响机理，确定粗颗粒含量对川西地区混合土压缩特性的影响过渡区间。结果表明：大于5 mm粗颗粒含量对川西地区混合土压缩特性有显著影响，同种混合土中大于5 mm的粗颗粒含量越高，在相同竖向荷载下的单位沉降量越小，孔隙比变化越小，压缩模量越大；大于5 mm粗颗粒含量对川西地区混合土压缩特性的影响过渡区间为30%~45%，土体压缩时，混合土中大于5 mm粗颗粒含量小于30%时，细颗粒起主要承担作用，土体可压缩性高，此时粗颗粒含量的增加，对于混合土的压缩特性影响不大；当粗颗粒含量超过30%时，粗、细颗粒共同作用，粗颗粒骨架逐渐形成，粗颗粒对混合土压缩特性的影响开始逐渐起作用；当大于5 mm粗颗粒含量大于45%时，粗颗粒的骨架作用起主要作用，土体可压缩性显著降低；土体中的矿物成分对压缩特性也产生影响，高岭石含量高的土样，强度较高，但压缩性较低。

Effect of Coarse Particle Content on the Compression Characteristics for Chuanxi Mixed Soil

There is a need to solve the problem of the mixed soil subgrade compression and deformation and to provide a theoretical basis for the construction of the expressway and railway in the Western Sichuan area. Hence, large-scale compression tests were carried out on natural mixed soils considering the influence of the coarse particle content. Three groups of typical natural mixed soil samples were selected from Western Sichuan and processed using the sieve method to separate the 20 mm, 10 mm, and 5 mm particles each. These soil samples with different coarse particle contents were prepared for use in a large-scale compression test. The influence of coarse particle content on the compression characteristics of mixed soil, its influence mechanism, and its influence interval were analyzed by comparing the void ratio and compression modulus of the soil samples with different coarse particle content under the same test conditions. The results demonstrate that the content of coarse particles greater than 5 mm (>5 mm) had a significant influence on the compression characteristics of mixed soil. The compression modulus is greater when the content of coarse particles (>5 mm) is higher in the same mixed soil. The appropriate coarse particle content affecting the compression characteristic transition interval is observed to be 30%-45%. When the coarse particle content is less than 30%, the fine particles played a major role in the compression process, thus leading to high soil compressibility, whereas the increase in coarse particle content demonstrated little effect on the compression characteristics. When the coarse particle content is over 30%, a coarse particle skeleton is gradually formed, which played a gradual role on the compression characteristics of the mixed soil. When the coarse particles content is higher than 45%, the skeleton function of the coarse particles played a significant role in decreasing soil compressibility. The mineral composition in the soil also had an effect on the compression characteristics wherein soil samples with high kaolinite content demonstrated higher strength but lower compressibility.