【摘要】：膨脹土是一種遇水膨脹,失水收縮的特殊土體,對(duì)工程結(jié)構(gòu)安全有非常重要的影響。近年來(lái),國(guó)內(nèi)外關(guān)注比較多的是膨脹土在遇水或濕化時(shí)的膨脹變形特征,而對(duì)膨脹土在失水或干燥時(shí)的收縮變形特征沒(méi)有給予足夠的關(guān)注。但在實(shí)際工程中,由膨脹土收縮導(dǎo)致的工程地質(zhì)問(wèn)題和災(zāi)害時(shí)有報(bào)道,并產(chǎn)生巨大經(jīng)濟(jì)損失。因此,系統(tǒng)掌握膨脹土在干燥失水過(guò)程中的體積變化規(guī)律,對(duì)于指導(dǎo)膨脹土地區(qū)的防災(zāi)減災(zāi)具有重要的理論意義和工程意義。 本文以優(yōu)秀青年科學(xué)基金(41322019)和江蘇省自然科學(xué)基金(BK2011339)項(xiàng)目為依托,以膨脹土為研究對(duì)象,對(duì)比分析了不同收縮體積測(cè)量方法的優(yōu)缺點(diǎn),通過(guò)開(kāi)展大量室內(nèi)試驗(yàn),系統(tǒng)研究了膨脹土失水干燥過(guò)程中的體積收縮特性及其影響因素和抑制技術(shù),探索了膨脹土干燥收縮過(guò)程中主要力學(xué)性質(zhì)的演變規(guī)律,在對(duì)試驗(yàn)結(jié)果進(jìn)行理論分析的基礎(chǔ)上提出了膨脹土收縮模型。論文主要取得以下成果： 1.分析對(duì)比了當(dāng)前四大主要土體收縮體積測(cè)量方法,即直接測(cè)量法、間接測(cè)量法、數(shù)字圖像處理技術(shù)和激光掃描成像法,指出了各個(gè)方法的優(yōu)缺點(diǎn)和適用條件； 2.基于收縮特征曲線,研究了土質(zhì)成分、含砂量和初始?jí)簩?shí)狀態(tài)(含水率和干密度)三個(gè)因素對(duì)膨脹土在干燥過(guò)程中收縮特性的影響,采用控制變量法,掌握了各個(gè)影響因素對(duì)膨脹土收縮特征的影響規(guī)律,明確了其影響機(jī)理； 3.提出了膨脹土收縮抑制技術(shù),包括石灰改性技術(shù)、水泥改性技術(shù)和高分子固化劑改性技術(shù)；通過(guò)開(kāi)展大量的室內(nèi)試驗(yàn),并結(jié)合理論分析,掌握了各技術(shù)對(duì)膨脹土收縮變形的抑制效果和機(jī)理； 4.發(fā)現(xiàn)了膨脹土收縮存在顯著的各向異性現(xiàn)象,通過(guò)引入收縮幾何因子r,對(duì)膨脹土收縮各向異性進(jìn)行了定量描述,明確了土質(zhì)成分、含砂量和含水率等因素對(duì)膨脹土收縮各向異性的影響規(guī)律； 5.基于大量的室內(nèi)收縮試驗(yàn)數(shù)據(jù),提出一個(gè)二次多項(xiàng)式模型來(lái)描述膨脹土收縮過(guò)程中孔隙比和含水率的變化關(guān)系,發(fā)現(xiàn)該模型對(duì)浦口膨脹土的擬合效果最好,其次為高廟子膨潤(rùn)土和Romainville膨脹土； 6.通過(guò)開(kāi)展無(wú)側(cè)限抗壓和單軸抗拉試驗(yàn),研究了膨脹土干燥收縮過(guò)程中無(wú)側(cè)限抗壓強(qiáng)度和抗拉強(qiáng)度隨含水率的變化規(guī)律,發(fā)現(xiàn)：在膨脹土干燥過(guò)程中,隨著含水率的減少,土體的無(wú)側(cè)限抗壓強(qiáng)度和抗拉強(qiáng)度都不斷增大,且增加速率也不斷變大；無(wú)側(cè)限抗壓強(qiáng)度和抗拉強(qiáng)度隨含水率的減小都呈指數(shù)增加,且兩者具有線性關(guān)系；不同初始含水率的膨脹土在干燥到相同含水率時(shí)對(duì)應(yīng)的抗拉強(qiáng)度隨著初始含水率的增加而增加。
[Abstract]:Expansive soil is a special soil with water expansion and loss of water, which has a very important effect on the safety of engineering structure. In recent years, much attention has been paid to the characteristics of swelling deformation of expansive soil in water or wetting, but insufficient attention has been paid to the shrinkage and deformation of expansive soil during water loss or drying. However, the engineering geological problems and disasters caused by the shrinkage of expansive soil have been reported in the actual engineering, resulting in huge economic losses. Therefore, it is of great theoretical and engineering significance to systematically grasp the law of volume change of expansive soil in the process of drying and losing water, which is of great theoretical and engineering significance for guiding disaster prevention and mitigation in expansive soil area. Based on the excellent Youth Science Foundation (41322019) and the Natural Science Foundation of Jiangsu Province (BK2011339), and taking expansive soil as the research object, this paper compares and analyzes the advantages and disadvantages of different shrinkage volume measurement methods, and carries out a large number of indoor tests. The volume shrinkage characteristics of expansive soil during dehydration and its influencing factors and inhibition techniques are studied systematically. The evolution law of main mechanical properties in the drying process of expansive soil is explored. Based on the theoretical analysis of the experimental results, a shrinkage model of expansive soil is proposed. The main achievements are as follows: 1. This paper analyzes and compares the four main measuring methods of soil shrinkage volume, that is, direct measurement, indirect measurement, digital image processing and laser scanning imaging, and points out the advantages and disadvantages and applicable conditions of each method. 2. Based on the shrinkage characteristic curve, the effects of soil composition, sand content and initial compaction state (moisture content and dry density) on the shrinkage characteristics of expansive soil during drying were studied. The effects of various factors on the shrinkage characteristics of expansive soils are studied, and the mechanism is clarified. 3. The shrinkage inhibition technology of expansive soil was put forward, including lime modification, cement modification and polymer curing agent modification. Through a large number of laboratory tests and theoretical analysis, the inhibition effect and mechanism of various techniques on shrinkage and deformation of expansive soil are grasped. 4. It is found that the shrinkage of expansive soil has obvious anisotropy phenomenon. The shrinkage anisotropy of expansive soil is quantitatively described by introducing the shrinkage geometry factor r, and the soil composition is clarified. The effect of sand content and moisture content on shrinkage anisotropy of expansive soil; 5. Based on a large number of indoor shrinkage test data, a quadratic polynomial model is proposed to describe the relationship between porosity and water content in the shrinkage process of expansive soil. It is found that the model has the best fitting effect on Pukou expansive soil. Secondly, Gaomiaozi bentonite and Romainville expansive soil; 6. By carrying out unconfined compression and uniaxial tensile tests, the variation of unconfined compressive strength and tensile strength with moisture content during drying shrinkage of expansive soil is studied. It is found that the moisture content decreases with the decrease of moisture content in the drying process of expansive soil. The unconfined compressive strength and tensile strength of soil are increasing, and the increasing rate is also increasing. The unconfined compressive strength and tensile strength increase exponentially with the decrease of moisture content, and they have a linear relationship. The tensile strength of expansive soil with different initial moisture content increases with the increase of initial moisture content when drying to the same moisture content.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類(lèi)號(hào)】：TU443;TU411

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本文編號(hào)：2402856