【摘要】：膨脹土富含2μm的黏粒和強親水性粘土礦物,密實時滲透性極低,水分難以入滲。而工程實際中,在大氣濕干循環(huán)作用下,膨脹土中會產(chǎn)生大量裂縫,縱橫交錯的裂隙使得其滲透性大增,雨水入滲常引起路塹邊坡成群坍滑破壞。為弄清膨脹土這一特殊工程性質(zhì),本文取南寧外環(huán)膨脹土為主要對象,室內(nèi)模擬大氣影響開展試驗,探究濕干循環(huán)下不同密度的膨脹土開裂規(guī)律及其滲透性能。首先,比較了已有的裂隙定量化描述指標以及采集方法,確定用面裂隙率作為定量化描述裂隙的指標;利用數(shù)碼相機拍攝采集試樣表面裂隙,而試樣內(nèi)部斷面裂隙則用ICT采集。盡可能模擬實際大氣狀況而設(shè)計了整個試驗研究方案。嚴格按設(shè)定方案完成系列試驗,獲得濕干循環(huán)下試樣表面、內(nèi)部裂隙的開展及其滲透性變化的規(guī)律,表明ICT獲得的SD值能較好的表征裂隙開展狀況;濕干循環(huán)下裂隙開展及其滲透性變化與試樣初始密度密切相關(guān),試樣密度增大,其裂隙開展及飽和滲透系數(shù)均變小;表面裂隙率與飽和滲透系數(shù)間呈良好對數(shù)關(guān)系;飽和滲透系數(shù)的絕對增長率隨試樣干密度而變化的曲線存在一峰值,當試樣密度較峰值所對應干密度越大時,其絕對增長率越小,從而驗證了膨脹土填筑施工時控制其干密度的必要性。為檢驗本文設(shè)計的試驗方案和測試結(jié)果是否有代表意義,還選取廣西百色和北京豐臺兩種膨脹土開展了對比分析試驗,結(jié)果證明本研究的結(jié)論具有普遍性。最后,運用灰色關(guān)聯(lián)理論分析了膨脹土密度、土性參數(shù)對裂隙開展及飽和滲透系數(shù)絕對增長率的影響程度,并探討了濕干循環(huán)下膨脹土開裂及飽和滲透系數(shù)變化的原因。
[Abstract]:Expansive soil is rich in 2 渭 m clay and strongly hydrophilic clay minerals. The permeability of expansive soil is very low and water content is difficult to infiltrate. In engineering practice, a large number of cracks will occur in expansive soil under the action of atmospheric wet-dry circulation, and the permeability of expansive soil will be greatly increased by the crisscross cracks. Rain Water infiltration often results in the collapse failure of cutting slopes in groups. In order to make clear this special engineering property of expansive soil, this paper takes Nanning outer ring expansive soil as the main object, carries on the laboratory simulation atmosphere influence experiment, explores the expansive soil cracking law of different density under wet-dry cycle and the permeability of expansive soil. Firstly, the existing quantitative index of fracture description and collection method are compared, and the surface crack rate is determined as the quantitative index to describe the crack, and the sample surface crack is captured by digital camera, while the fracture of the inner section of the specimen is collected by ICT. The whole experimental research scheme is designed by simulating the actual atmospheric conditions as much as possible. A series of tests were carried out strictly according to the set scheme, and the rules of surface, internal crack development and permeability change under wet-dry cycle were obtained, which indicated that the SD value obtained by ICT could better characterize the crack development status. The fracture development and permeability change under wet-dry cycle are closely related to the initial density of the specimen, increase the sample density, decrease the crack development and saturation permeability coefficient, and the surface fracture porosity has a good logarithmic relationship with the saturated permeability coefficient. There is a peak value of absolute growth rate of saturated permeability coefficient with the dry density of the sample. When the density of the sample is larger than the corresponding dry density of the sample, the absolute growth rate of the sample is smaller. Therefore, it is necessary to control the dry density of expansive soil during filling construction. In order to test whether the test scheme and test results are representative, two expansive soils, Baise in Guangxi and Fengtai in Beijing, are selected to carry out comparative analysis tests. The results show that the conclusions of this study are universal. Finally, the influence degree of expansive soil density and soil parameters on crack development and absolute growth rate of saturated permeability coefficient is analyzed by using grey relational theory, and the causes of cracking and saturated permeability coefficient change of expansive soil under wet-dry cycle are also discussed.
【學位授予單位】：長沙理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TU443

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