The Mechanical And Environmental Properties Of Clay Improved By Tung Oil And Stick Rice Juice

Clay has played an important role in waste containment system of MSW landfills. Xiaoshan clay is a kind of marine deposits, which has low hydraulic conductivity and high adsorption capacity against chemicals. After compaction, its hydraulic conductivity is approximately 10~-7 cm/s, which already meets the clay liner requirement. Sticky rice juice is a material of high stickiness and adsorption, and low expansibility and conglomeration, so that it can cement clay grains; Tung oil has many beneficial properties, such as high solidity and adsorption, low stickiness, good resistance to acid, alkali, water, sunlight and atmosphere. In many historical literatures, Tung oil and sticky rice juice were mentioned as construction materials for ramparts and walls of the palace because of their high stickiness and durability. Tung oil was also used in the shipbuilding to improve the caking property and impermeability of the watercraft. The basic problems of clay liners, hydraulic conductivity, strength, adsorption capacity and diffusion capacity are considered, and the feasibility of the mixed soil (Xiaoshan clay, stick rice juice and Tung oil) as the barrier material of landfill liners are discussed. Geotechnical and geoenvironmental characteristics of the mixed soil are investigated in the following aspects:1) In order to examine whether the mixed soil has lower permeability and higher strength, compaction tests, permeability tests, direct shear tests have been done. The permeability and the strength of the mixed soils with different mix ratio, where stick rice juice and Tung oil are regarded as additives, are investigated and compared with those of original soil. It demonstrates that friction angle increases greatly and the strength heightens as the molecular film of Tung oil enwraps soil grains plentifully; meanwhile, with the increase of sticky rice juice, it bonds soil grains and decreases pore space so that the permeability coefficient of the mixedsoil is lower than that of the original clay by 2 orders of magnitude. The best ratio for the mixed soil is 90:5:5.2) Tung oil and sticky rice juice are considered as additives in the research, but in fact, sticky rice juice contains water. For instance, when calculating the moisture content in sticky rice juice, the actual optimum water content increases to 29.6% from 24%, and if containing Tung oil, the liquid content will reach 35.1%. Considering the influence of water content to permeability coefficient and strength, coherent complemental experimentations were done to examine whether is proper to regard Tung oil and sticky rice juice as additives. In the additional research, permeability tests and shear tests in which water content of sticky rice juice was calculated have been done, and it is shown that the permeability coefficient is higher than that when regarding sticky rice juice as an additive, while the strength is lower. Therefore, it is reasonable to treat sticky rice juice as an additive.3) In order to study the lasting properties of the mixed soil, wetting-drying tests of the mixed soil and the original soil have been done. It is shown that, through comparison, the durability of the mixed soil is much better than that of the original soil, as the associated operation of Tung oil and sticky rice juice greatly counteracts the influence of wetting and drying cycle.4) Because of the contaminants in the filtrate, like heavy metal ion, the ability to adsorb metal cations and block ion diffusion of the mixed soil as a clay liner should be investigated. Through Batch tests and vertical diffusion tests, it is shown that organic materials, like Tung oil and sticky rice juice, in the mixed soil, can adsorb metal cations to a large extent so that diffusion coefficient of cations through mixed soils is reduced.It is shown in this dissertation that the geoenvironmental characteristics of the mixed soils are better than that of original soils and they are suitable for clay liners of landfills.