Study On Filling Performance And Soil Characteristics Of Guangxi Red Clay

In this paper,an experimental research on Wuming and Guilin red clays have been carried out systematically. Through basic physical and mechanical test, compaction test and CBR test, properties such as filling performance and changing patterns of engineering properties on condition that soil is improved by different materials are studied. And this paper preliminarily reveals the microscopic mechanism on engineering properties of Guangxi red clay from mineral constituent, cements, and microscopic structure and so on. The main conclusions are as follows:(1) The Guilin red clay is superior to Wumin red clay on the filling performance because the maxima value of CBR of Guilin red clay is about two times as the value of Wuming red clay, and its swelling amount is obviously less than the value of Wuming red clay. According to the related standard, both clays belong to the high liquid limit soil and have to be improved to filling. Through synthetically analysis water stability, value of CBR and liquid plastic limit of red clay when it is improved by different materials, the mixed sand ratio of Guilin red clay should be controlled in20%～30%and its mixed lime ratio should be controlled in3%; the optimal sand ratio of Wuming red clay is30%and its mixed lime ratio should be controlled in3%. (2) Through further analysis, we can find that the CBR and water stability of Guangxi red clay is mainly affected by the content of effective cementation. Although both clays have similar content of gibbsite, the content and existing form of goethite is quite different. For Guilin red clay the content of goethite is15.61%which is5%higher than that of Wuming red clay. Furthermore,80%goethite of Wuming red clay is accretion with particle size greater than2mm by which effective cement can not form. So effective cement in red clay is one of the most important factors affecting fill performance and the better fill performance of Guilin red clay. In the red clay, the content and existing form of cement depends on laterization. Mother rocks of the two red clays are limestone and the main mineral of Wuming limestone is calcite while Guilin limestone is dolomite. Weathering in Guilin red clay is stronger than that in Wuming red clay, judged by the changes of SiO2, Al2O3and Fe2O3between red clays and mother rock.(3) Through SEM test, the microscopic structure types of Wuming red clay mainly are the aggregate stack structure and overhead structure; and the microstructure types of Guilin red clay mainiy are enclosed flocculation structure, and a small amount of turbulent structure. Compared with flocculation structure and turbulent structure, overhead structure is not a stable structure, which has great displacement space. The difference on microscopic structure types is one of reasons, which cause mechanical properties of Guilin red clay are superior to Wuming red clay’s, when red clay is in the original state Through analysis original cohesion and curing cohesion of them by ξ, potential and cements, the original cohesion and curing cohesion of Guilin red clay is superior to Wuming red clay’s.