本文關(guān)鍵詞： 膨脹土 恒體積法 膨脹力 土-水特征曲線 相對(duì)濕度　出處：《桂林理工大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：膨脹土遇水膨脹軟化、失水收縮干裂,工程性質(zhì)復(fù)雜,常常引發(fā)膨脹土所在地區(qū)的巖土工程災(zāi)害。膨脹土無(wú)論是在飽和環(huán)境下還是在非飽和環(huán)境下,都會(huì)發(fā)生不同程度的膨脹,表現(xiàn)出不同的膨脹力,給膨脹土所在地區(qū)造成工程災(zāi)害。盡管目前人們對(duì)飽和土的膨脹特性有了較為深入的了解,但是在非飽和環(huán)境下有關(guān)膨脹土的力學(xué)特性的研究仍較為缺乏,尤其是膨脹力的測(cè)試及其機(jī)理解釋方面仍然存在諸多爭(zhēng)議。本文針對(duì)廣西寧明膨脹土在純水飽和環(huán)境與控制濕度的非飽和環(huán)境下,分別測(cè)量各自的極限膨脹力與自然膨脹力,并分析其膨脹機(jī)理。本文的研究?jī)?nèi)容包括飽和環(huán)境下膨脹土極限膨脹力的測(cè)試與非飽和環(huán)境下膨脹土自然膨脹力的測(cè)試,主要成果如下:(1)目前測(cè)量土體膨脹力的主要方法有膨脹反壓法、加壓膨脹法、平衡加壓法和恒體積法四種。基于測(cè)量膨脹力的恒體積法,利用TST-55型滲透儀、高精度壓力傳感器和數(shù)采系統(tǒng)改進(jìn)了測(cè)量土體膨脹力的裝置,并測(cè)定了寧明膨脹土的極限膨脹力。試驗(yàn)結(jié)果表明,土樣初始含水量和干密度對(duì)土體的極限膨脹力都存在顯著的影響,并建立了極限膨脹力與干密度之間的定量關(guān)系式;較低初始含水量時(shí),不同干密度的土樣在膨脹力達(dá)到峰值之后,均有不同幅度的降低,且隨著干密度的增大而降低的越多,并且發(fā)現(xiàn)極限膨脹力降低值與干密度之間在雙對(duì)數(shù)坐標(biāo)軸上存在線性關(guān)系;而在較高初始含水量時(shí),不同干密度的土樣在膨脹力達(dá)到峰值之后,會(huì)保持平穩(wěn)趨勢(shì)。極限膨脹力的對(duì)數(shù)值與初始含水量之間具有很好的線性關(guān)系,土樣吸水量的對(duì)數(shù)值與初始含水量以及干密度均有著很好的線性關(guān)系。(2)為了研究膨脹土在非飽和環(huán)境下的膨脹力,結(jié)合測(cè)量膨脹力的恒體積法與控制吸力的蒸汽平衡法(控制相對(duì)濕度),本試驗(yàn)設(shè)計(jì)了一種能夠測(cè)量膨脹土在非飽和環(huán)境下膨脹力的儀器。本文試驗(yàn)結(jié)果表明,膨脹土的自然膨脹力隨著相對(duì)濕度的增大而增大;通過(guò)軸平移法與蒸汽平衡法聯(lián)合測(cè)定全吸力范圍內(nèi)寧明膨脹土的土水特征關(guān)系曲線,發(fā)現(xiàn)寧明膨脹土的吸濕曲線與脫濕曲線兩者不重合,存在滯回現(xiàn)象,構(gòu)成一個(gè)滯回圈。自然膨脹力在到達(dá)峰值后會(huì)稍微降低,最終達(dá)到穩(wěn)定值,即殘余膨脹力;自然膨脹力與殘余膨脹力的平衡時(shí)間均與相對(duì)濕度相關(guān);膨脹力與吸力之間的關(guān)系可以采用Fredlund-Xing模型類似的公式進(jìn)行很好地描述,并獲得某一初始狀態(tài)膨脹土在飽和度任意改變條件下的的膨脹力公式。
[Abstract]:The expansive soil often causes geotechnical engineering disasters in the region where the expansive soil is located due to water swelling and softening, shrinkage and dry cracking of water loss, and complex engineering properties. The expansive soil will expand in varying degrees in both saturated and unsaturated environments. Showing different expansive forces, causing engineering disasters to the region where the expansive soils are located, although people now have a deeper understanding of the expansion characteristics of saturated soils. However, the study on the mechanical properties of expansive soil in unsaturated environment is still lacking. In particular, there are still many controversies in the measurement of expansive force and the explanation of its mechanism. In this paper, the limit expansion force and natural expansion force of Ningming expansive soil in pure water saturated environment and unsaturated environment with controlled humidity are measured respectively. The research contents of this paper include the measurement of the limit expansive force of expansive soil in saturated environment and the test of natural expansive force of expansive soil in unsaturated environment. The main results are as follows: (1) at present, the main methods for measuring the swelling force of soil are four kinds: the method of back pressure, the method of expansion under pressure, the method of balance pressure and the method of constant volume. Based on the constant volume method of measuring expansion force, the TST-55 type osmometer is used. The high precision pressure sensor and the data mining system have improved the device of measuring the soil swelling force and measured the limit expansion force of Ningming expansive soil. The test results show that, The initial water content and dry density of soil samples have a significant effect on the limit expansion force of soil, and the quantitative relationship between the limit expansion force and dry density is established, and when the initial water content is low, the quantitative relationship between the limit expansion force and the dry density is established. Soil samples with different dry densities decreased in different amplitude after the peak expansion force, and with the increase of dry density, the more decreased, It is also found that there is a linear relationship between the decreasing value of limit expansion force and the dry density on the double logarithmic coordinate axis, and when the initial water content is higher, the soil samples with different dry densities reach the peak value after the expansion force reaches the peak. The logarithmic value of the limit expansion force has a good linear relationship with the initial water content, The logarithmic values of water absorption of soil samples have a good linear relationship with the initial water content and dry density. Combining the constant volume method of measuring expansion force with the steam equilibrium method of controlling suction (controlling relative humidity), an instrument is designed to measure the expansion force of expansive soil in unsaturated environment. The natural expansive force of expansive soil increases with the increase of relative humidity, and the soil-water characteristic curves of Ningming expansive soil in the range of full suction are determined by axial translation method and steam equilibrium method. It is found that the hygroscopic curve and dehumidification curve of Ningming expansive soil do not coincide with each other, and there exists hysteresis, which forms a hysteresis loop. The natural expansion force will decrease slightly after reaching the peak value, and finally reach the stable value, that is, residual expansion force. The equilibrium time of natural expansion force and residual expansion force is related to relative humidity, the relationship between expansion force and suction force can be well described by the similar formula of Fredlund-Xing model. At the same time, the expansion force formula of an initial expansive soil is obtained under the condition of arbitrary change of saturation.
【學(xué)位授予單位】：桂林理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TU443

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