本文關(guān)鍵詞： 膨脹土 基質(zhì)吸力 土水特征曲線 濾紙法 數(shù)值模擬　出處：《南昌航空大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：膨脹土主要以非飽和土的形式存在,基質(zhì)吸力是影響非飽和土的重要參數(shù)之一,因此,研究基質(zhì)吸力對非飽和土的影響十分必要。本文以宜春地區(qū)膨脹土為研究對象,采用濾紙法量測了不同干密度、干濕循環(huán)條件下非飽和膨脹土的基質(zhì)吸力與總吸力,并基于試驗(yàn)結(jié)果,進(jìn)行了干濕循環(huán)條件下基坑滲流與穩(wěn)定性分析。取得了如下主要成果:(1)采用濾紙法開展了不同初始條件下土體總吸力與基質(zhì)吸力試驗(yàn)研究,結(jié)果表明:相同初始條件下,濾紙與土樣表面距離對總吸力影響較大,3cm時(shí)所測得的總吸力離散程度較小,可考慮將3cm作為濾紙法測定總吸力時(shí)的標(biāo)準(zhǔn)測試距離;通過引入偽基質(zhì)吸力的概念,根據(jù)總吸力-距離擬合公式求得了不同初始條件下土體偽基質(zhì)吸力值,并與由試驗(yàn)得到的真基質(zhì)吸力進(jìn)行比較,認(rèn)為土體偽基質(zhì)吸力與真基質(zhì)吸力之間表現(xiàn)較好的線性關(guān)系;并據(jù)此提出了測量土體基質(zhì)吸力的預(yù)測方法。(2)采用Fredlund和Xing三參數(shù)模型對干濕循環(huán)條件下膨脹土土水特征曲線進(jìn)行擬合,獲得了擬合參數(shù)與循環(huán)次數(shù)n之間的變化規(guī)律,建立了一個(gè)與干濕循環(huán)次數(shù)n有關(guān)的經(jīng)驗(yàn)?zāi)Ｐ?并對其合理性進(jìn)行了初步驗(yàn)證。(3)基于干濕循環(huán)條件下膨脹土土水特征曲線經(jīng)驗(yàn)?zāi)Ｐ?采用有限元分析軟件Geo-Studio對干濕循環(huán)條件下基坑的滲流與穩(wěn)定性進(jìn)行數(shù)值模擬。結(jié)果表明:相同含水率條件下,隨著循環(huán)次數(shù)的增加,土體基質(zhì)吸力逐漸下降,基坑安全系數(shù)總體呈下降趨勢,且降低的幅度越來越小。因此,在基坑滲流與穩(wěn)定分析時(shí)宜考慮干濕循環(huán)對其影響。
[Abstract]:Expansive soil mainly exists in the form of unsaturated soil, and matrix suction is one of the important parameters affecting unsaturated soil. Therefore, it is necessary to study the effect of matrix suction on unsaturated soil. The matrix suction and total suction of unsaturated expansive soils with different dry densities and dry and wet cycles were measured by filter paper method, and the results were based on the experimental results. The seepage and stability analysis of foundation pit under dry and wet circulation conditions is carried out. The main results are as follows: 1) the experimental study of soil total suction and matrix suction under different initial conditions is carried out by filter paper method. The results show that under the same initial conditions, the soil total suction and matrix suction are tested under the same initial conditions. When the distance between the surface of filter paper and the soil sample has a greater influence on the total suction, the dispersion of the total suction measured is relatively small, so we can consider using 3cm as the standard test distance when the total suction is measured by the filter paper method, and by introducing the concept of pseudo matrix suction, According to the formula of total suction and distance fitting, the pseudo matrix suction values of soil under different initial conditions are obtained, and compared with the true matrix suction obtained from the test, it is concluded that the relationship between pseudo matrix suction and true matrix suction is better. Based on this, a prediction method for measuring the suction of soil matrix is proposed. The Fredlund and Xing three-parameter models are used to fit the characteristic curves of expansive soil and soil under dry and wet cycles, and the law of variation between the fitting parameters and the number of cycles n is obtained. An empirical model related to the number of dry and wet cycles n is established, and its rationality is preliminarily verified. The seepage and stability of foundation pit under dry and wet circulation were simulated by finite element analysis software Geo-Studio. The results show that the suction of soil matrix decreases with the increase of circulation times under the same moisture content. The safety factor of foundation pit is decreasing, and the extent of decrease is becoming smaller and smaller. Therefore, the influence of wet and dry circulation on the seepage and stability of foundation pit should be taken into account in the analysis of foundation pit seepage and stability.
【學(xué)位授予單位】：南昌航空大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU443

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本文編號：1512487