Study On The Engineering Characteristics And The Construction Techniques Of High Liquid Limit Soil

A large amount of high liquid limit clay exists in the region of Yongzhou, HunanProvince, which the Heng-Shao Highway passes through, taking account60%of thetotal earth volume. This sort of soil contains several undesirable engineeringproperties, such as poor compatibility, tendency of crack, long time of consolidationand deformation, high natural water content, wide range of CBR Value, and weekwater stability, etc. Thus it is difficult for this kind of soil to construct the subgrade ofhigh way. In addition, if we chose to replace it, the corresponding project would behuge, the ecological environment destroyed and the project schedule prolonged. So itis of great necessity to find the suitable improved treatment technology which can beapplied to construct and design the high liquid limit clay subgrade of this region.Firstly, a large number of field and laboratory tests were carried out to study themineral composition, the causes and the engineering properties of the high liquid limitclay along the Heng-Zao Highway, clarify the high liquid limit clay on site with threecategories: one was directly filled, one was filled after improvement treatme nt andabandoned and give the engineering technical requirements of the soil filled directly.Secondly, several treatment measures were carried out, such as the Core Method, theImproved Method of lime, the Modified Method of cement as well as the SandyGravel Improved Method, etc. for the soil cannot be directly built on site. In addition,the corresponding construction technology, quality control method and matters neededattention were proposed. What is more, combined with the actual situation of theHeng-Zao Highway, research for the strength of the high liquid limit clay was carriedout based upon several control indexes: CBR Value, shear strength index, resilientmodulus; the stability analysis and the settlement calculation method were putforward as well. In the final analysis,3test sections from K114+600~K117+290ofthe Heng-Shao Highway were selected to use respective method of building thesubgrade, to verify the rationality and feasibility of the construction program andimproved Treatment Measures in this paper. The settlement of the subgrade of the3sections was observed through the buried settlement plate and the stratifiedsedimentation instrument.The observation and measurement of the water content, compactness, CBR Value,resilient modulus and settlement indicate that these indicators can satisfy the requirement of design and code, without showing subgrade cracking, differentialsettlement and stability problems. This thesis shows that most of the high liquid limitclay along the highway can be used directly for subgrade construction, only part ofwhich was needed the necessary improvements Treatment. Not only can this save a lotof investment to the construction of the entire project, but also shor ten theconstruction duration. Meanwhile, a protective effect was played on the localecological environment. In a nutshell, the results of this study have importantpractical value and good economic benefits for the highway construction for the southregion and the country.