【摘要】：隨著社會經(jīng)濟的發(fā)展,建筑業(yè)也隨之飛速發(fā)展。高大建筑如雨后春筍不斷地拔地而起,深基坑、高邊坡工程層出不窮,這就對地基基礎(chǔ)工程的設(shè)計與施工提出了更高的要求。同時,隨著科技的進步和發(fā)展,人們對工程的經(jīng)濟性、合理性有了更深刻的認(rèn)識和更高的要求,尤其是工程的安全性和經(jīng)濟性成為工程中的熱點話題。在很多工程中地基基礎(chǔ)所占的投資比例都很高。大量的理論研究和工程實踐表明運用飽和土力學(xué)處理非飽和土力學(xué)的工程問題是不準(zhǔn)確的,甚至可能會造成工程事故。這對工程的造價和安全等方面來說是不利的。因此,研究非飽和土的力學(xué)性質(zhì),在保證工程安全的前提下最大限度的利用非飽和土自身的強度和工程特性,成為了節(jié)約成本提高工程經(jīng)濟性的有效途徑之一。由于對非飽和土的研究起步較晚,研究成果較少,所以,目前對非飽和土的認(rèn)識無論是國外還是國內(nèi)都還遠(yuǎn)遠(yuǎn)達不到工程需要的程度。對于河北省石家莊地區(qū)非飽和土的研究更是如此。因此,對非飽和土的力學(xué)性質(zhì)尤其是抗剪強度特性的研究,無論對于土力學(xué)理論發(fā)展,還是對工程實踐都是十分必要和有意義的。本文利用TFB-1型非飽和土三軸儀,通過三軸試驗對石家莊地區(qū)某基坑工程的非飽和粉質(zhì)粘土進行了研究。通過試驗得出了不同初始含水量下的土—水特征曲線。并對其進行了比較分析,證明其不僅與基質(zhì)吸力有關(guān)還與初始含水量有關(guān)。三軸固結(jié)排水剪切試驗固結(jié)過程中排水量隨著基質(zhì)吸力的增加而增加,固結(jié)所用時間與進氣值與圍壓的比值有關(guān)。在圍壓保持不變的情況下,主應(yīng)力差隨著基質(zhì)吸力的增加有減小趨勢,減小幅度不大,而有效大主應(yīng)力σ1'卻有增大趨勢,并且增大幅度較大。土體剪切過程應(yīng)力應(yīng)變曲線呈非線性應(yīng)變硬化趨勢,破壞形態(tài)為鼓狀破壞。圍壓不變的情況下,進氣值在一定范圍內(nèi)變化,非飽和土破壞時有效主應(yīng)力比σ1'/σ3'趨近一個常數(shù)。三軸剪切試驗表明該非飽和粉質(zhì)粘土的粘聚力c隨著進氣值的增大而增大,而進氣值(基質(zhì)吸力)對有效內(nèi)摩擦角的影響卻很小。將這一規(guī)律運用到邊坡穩(wěn)定性計算、地基承載力計算和擋土墻設(shè)計的算例當(dāng)中,可以看出充分利用非飽和土的性質(zhì)對工程的經(jīng)濟性有很大提高。同時可以得知,水對于非飽和土的抗剪強度影響是非常大的,在巖土工程中要十分注意水對邊坡穩(wěn)定、地基承載力以及擋土墻受力等方面的影響。
[Abstract]:With the development of social economy, the construction industry also develops rapidly. Tall buildings are springing up continuously, deep foundation pit and high slope engineering emerge one after another, which puts forward higher requirements for the design and construction of foundation engineering. At the same time, with the progress and development of science and technology, people have a deeper understanding of the economy and rationality of the project, especially the safety and economy of the project has become a hot topic in the engineering. Foundations account for a high proportion of investment in many projects. A large number of theoretical studies and engineering practices show that the application of saturated soil mechanics to the engineering problems of unsaturated soil mechanics is inaccurate and may even cause engineering accidents. This is detrimental to the cost and safety of the project. Therefore, to study the mechanical properties of unsaturated soil and make maximum use of the strength and engineering characteristics of unsaturated soil under the premise of ensuring engineering safety has become one of the effective ways to save costs and improve the engineering economy. Because the research on unsaturated soil started late and the research results are less, the current understanding of unsaturated soil is far from the engineering need, both at home and abroad. This is especially true for the study of unsaturated soils in Shijiazhuang area of Hebei Province. Therefore, it is necessary and meaningful to study the mechanical properties, especially the shear strength properties of unsaturated soils, both for the development of soil mechanics theory and engineering practice. In this paper, the unsaturated silty clay of a foundation pit project in Shijiazhuang area was studied by using TFB-1 type unsaturated soil triaxial apparatus and triaxial test. The soil-water characteristic curves under different initial water content were obtained by experiments. It is proved that it is not only related to the matrix suction but also to the initial water content. During the consolidation process of triaxial consolidation drainage shear test, the water displacement increases with the increase of the matrix suction, and the ratio of the consolidation time to the intake air value to the confining pressure is related to the consolidation time. Under the condition that the confining pressure remains constant, the principal stress difference decreases with the increase of the matrix suction, but the magnitude of the decrease is small, while the effective large principal stress 蟽 1 'increases and increases greatly. The stress-strain curve of soil is nonlinear strain hardening, and the failure form is drum. Under the condition of constant confining pressure, the inlet air value varies within a certain range, and the effective principal stress ratio 蟽 _ (1) / 蟽 _ (3') of unsaturated soil under failure is approaching to a constant. The results of triaxial shear test show that the cohesive force c of the unsaturated silty clay increases with the increase of the intake value, but the influence of the intake value (matrix suction) on the effective internal friction angle is very small. By applying this law to the calculation of slope stability, the calculation of foundation bearing capacity and the design of retaining wall, it can be seen that making full use of the properties of unsaturated soil can greatly improve the economy of the project. At the same time, the influence of water on the shear strength of unsaturated soil is very great. In geotechnical engineering, we should pay great attention to the influence of water on slope stability, bearing capacity of foundation and force of retaining wall.
【學(xué)位授予單位】：河北工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TU411.7
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本文編號：2372305