本文選題：砂土液化　切入點：低有效應力　出處：《中國礦業(yè)大學》2014年碩士論文　論文類型：學位論文

【摘要】：我國是一個地震多發(fā)國家，震后引起的飽和砂土液化問題是巖土工程界研究的熱點與難點之一。目前針對砂土液化的影響因素、液化產生機理、液化勢的判別等方面已有很多研究成果，并得到廣泛認可。而對于飽和砂土液化后在低有效應力狀態(tài)下土體的應力應變行為認識尚不充分，而且現(xiàn)有的研究中很少或沒有考慮伴有超孔隙水壓力的消散過程中，孔隙水滲流對液化后砂土受力變形特性的關聯(lián)影響�；诖耍疚牟捎昧耸覂葘嶒灱皵�(shù)值模擬的技術深入研究了飽和砂土在低有效應力狀態(tài)下滲透和變形特性。 （1）以土體重固結理論為基礎，結合砂沸機理，對常規(guī)常水頭滲透試驗裝置做了改進，獲得了一套可測定飽和砂土處于低有效應力狀態(tài)下的滲透系數(shù)的滲透試驗裝置，并對該裝置的使用方法及試驗步驟做了詳細介紹。 （2）利用新的滲透試驗裝置進行滲透試驗研究，對顆粒級配不同的三種砂土在低有效應力狀態(tài)下的滲透特性做了研究。試驗發(fā)現(xiàn)，在有效應力為零時，他們的滲透系數(shù)都有不同程度的增大。其中XZ砂變化最大，其滲透系數(shù)為液化前的4倍左右；1#砂增幅次之，為液化前的2.5倍左右；2#砂增幅最小，為液化前1.5倍左右。隨著有效應力的增大，砂土的滲透系數(shù)也在慢慢減小，其中1#砂和2#砂最終都恢復到初始值左右，而XZ砂最終保持在初始滲透系數(shù)的2.2倍左右。 （3）利用全自動三軸儀模擬飽和砂土在低有效應力狀態(tài)下的靜力加載過程。試驗結果表明，在本試驗條件下的飽和砂土在不同有效應力狀態(tài)下的靜力再加載應力應變曲線可分為三個階段：低強度階段、強度恢復階段和應變軟化階段。文章中還從砂土的初始相對密實度、砂土液化程度的不同、土層的埋置深度等三個方面研究了它們對應力~應變曲線發(fā)展趨勢的影響。 （4）結合三軸試驗結果以及滲透試驗結果，，本文將有效應力與初始有效應力之比'0'50%的飽和砂土所處的應力狀態(tài)定義為低有效應力狀態(tài)。 （5）將低有效應力狀態(tài)下土體的滲透和變形特性研究成果整合到數(shù)值模擬分析中，研究了砂性土邊坡在孔隙水壓力作用下伴隨著孔隙水自下而上的滲流的邊坡安全穩(wěn)定性。
[Abstract]:China is an earthquake-prone country. The problem of saturated sand liquefaction caused by earthquake is one of the hot and difficult problems in geotechnical engineering. Many research achievements have been made on the determination of liquefaction potential, which has been widely accepted. However, there is still insufficient understanding of the stress-strain behavior of saturated sandy soil under low effective stress state after liquefaction. Moreover, in the present research, the influence of pore water seepage on the deformation characteristics of sand soil after liquefaction is seldom or not taken into account in the process of dissipation with excess pore water pressure. In this paper, the permeability and deformation characteristics of saturated sand under low effective stress are studied by laboratory experiments and numerical simulation. 1) based on the consolidation theory of soil weight and combined with the mechanism of sand boiling, a set of permeation test equipment for measuring the permeability coefficient of saturated sand under low effective stress is obtained by improving the conventional constant head permeation test device. The application method and test procedure of the device are introduced in detail. 2) the permeability characteristics of three kinds of sand with different particle gradation under low effective stress state are studied by using a new permeation test device. The experimental results show that the effective stress is 00:00, Among them, XZ sand has the biggest change, and its permeability coefficient is about 4 times of that before liquefaction, followed by the increase of sand about 2.5 times before liquefaction and the smallest increase of sand before liquefaction. With the increase of effective stress, the permeability coefficient of sand is gradually decreasing, in which both 1# sand and 2# sand finally return to the initial value, while XZ sand is kept at 2.2 times of initial permeability coefficient. 3) the static loading process of saturated sand under low effective stress is simulated by fully automatic triaxial apparatus. The experimental results show that, The static reloading stress-strain curves of saturated sand under different effective stress states can be divided into three stages: low strength stage. In this paper, the influence of the initial relative compactness of sand, the different liquefaction of sand and the buried depth of soil layer on the development trend of stress-strain curve is also studied in terms of strength recovery stage and strain softening stage. 4) combined with the results of triaxial test and permeation test, the stress state of saturated sand with the ratio of effective stress to initial effective stress is defined as low effective stress state. 5) the research results of seepage and deformation characteristics of soil under low effective stress are integrated into the numerical simulation analysis, and the safety and stability of sandy soil slope under the action of pore water pressure accompanied by percolation of pore water from bottom to top are studied.
【學位授予單位】：中國礦業(yè)大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TU441

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