Testing Research On Engineering Properties Of Expansive Soil Modified With Fibers

Expansive soil is a kind of high plastic clay. It has obvious swell and water shrinkage properties, montmorillonite and illite-montmorillonite are the main mineral elements. Its swell-shrink properties brought great harm for the engineering construction. So it is necessary to modified expansive soil’s engineering properties through some methods. In this paper, we mainly focus on the research of expansive soil which from a construction site in Hefei through adding polypropylene fiber in the expansive soil to improved expansive soil. To investigate the engineering properties of expansive soil after adding fiber, we conduct the direct shear test, consolidation test, swelling ratio test and shrinkage test as well as the determination of soil water characteristic curve test. To investigate the fiber content, soil water content and dry density’s influences on the fibers modified expansive soil’s engineering properties, we conduct test at different initial fiber content (0.1%,0.2%and0.3%), different initial dry density (1.34g/cm3,1.66g/cm3) and different water content (17%、20%and23%) on the fiber-modified expansive soil samples. Through experiments, we can obtain the following conclusions:1) Under the same fiber content, cohesion decreases with the increase of moisture content; Under the same moisture content, cohesion increases with the increase of fiber content. The cohesion has the largest growth when the fiber content is0.2%. With the increase of fiber content, angle of internal friction decreases slightly.2) Under the same moisture content, with the increase of fiber content, the compression coefficient increases slightly; with the increase of dry density, the compression coefficient decreases obviously. This shows that fiber mixed with no obvious effect on compression properties of expansive soil.3) With the increase of fiber content, the expansive ratio of fiber-modified expansive soil decreases. This shows the incorporation of the fiber can effectively restrain the expansion of expansive soil.4) Under the same dry density and moisture content, expansion force decreases with the increase of fiber content. It shows adding fiber in the expansion soil can restrain the expansion of the expansion soil.5) By osmotic method and filter paper method, we obtain the soil water characteristics of fiber modified expansive soil, and analyze the multiple solution problem when we fit SWCC.