本文選題：黃土　切入點：節(jié)理　出處：《西安建筑科技大學》2014年博士論文　論文類型：學位論文

【摘要】：節(jié)理是黃土地區(qū)普遍存在的一種地質(zhì)現(xiàn)象。節(jié)理的存在破壞了土體的整體性和連續(xù)性。節(jié)理面是剪切弱面，會使水分運動加快，，對黃土地區(qū)洞室和邊坡的穩(wěn)定構(gòu)成安全隱患。目前對節(jié)理的研究多集中在其地質(zhì)屬性上，而工程性質(zhì)的研究尚不足，尚缺乏黃土節(jié)理剪切和滲流特性的研究文獻。基于此本文對黃土節(jié)理的剪切性質(zhì)和滲流性質(zhì)展開研究工作。 通過對不同含水率、干密度以及表面形態(tài)的黃土節(jié)理進行直剪試驗，研究了黃土節(jié)理強度參數(shù)變化規(guī)律。結(jié)果表明：黃土節(jié)理內(nèi)摩擦角隨含水率呈開口向下的拋物線形態(tài)變化。存在一個界限含水率，使土樣的含水率為該界限值時，節(jié)理面的摩擦角最大。在低含水率時節(jié)理表面形態(tài)對粘聚力的影響較大。粗糙節(jié)理面的粘聚力明顯大于平整節(jié)理面。隨著含水率的逐漸升高，表面形態(tài)對節(jié)理面粘聚力的影響逐漸減小。 通過室內(nèi)節(jié)理變水頭試驗、表面飽和入滲試驗以及現(xiàn)場節(jié)理滲水試驗研究了黃土節(jié)理的滲流性質(zhì)。結(jié)果表明：黃土中有節(jié)理存在時，其流動仍然可以用達西定理來描述，但隨著水頭的增大，試驗結(jié)果逐漸偏離達西定律；在表層飽和入滲的情況下，節(jié)理對水分入滲有促進作用，其滲透性隨著節(jié)理開度的增大而增大；現(xiàn)場節(jié)理入滲試驗表明黃土中的垂直節(jié)理在入滲初期具有高滲透性。黃土沿節(jié)理方向的入滲速度遠大于水平方向的入滲速度。 對黃土節(jié)理滲流問題進行了理論分析。黃土節(jié)理滲流屬于沿節(jié)理方向入滲和垂直于節(jié)理方向往黃土體入滲的二維滲流問題�？紤]節(jié)理內(nèi)流體向土體的入滲及土體自身流速的影響，建立了黃土節(jié)理二維滲流模型，采用歐拉變數(shù)法推導了流體元運動微分方程，得到了以流速為函數(shù)的滲流微分方程。進而基于黃土節(jié)理滲流特征及邊界條件，推導得到黃土節(jié)理二維穩(wěn)態(tài)流的流量方程，表明巖體節(jié)理立方定律可歸結(jié)為此方程在特定條件下的簡化形式。進一步結(jié)合達西定律推導得到黃土節(jié)理滲透系數(shù)的表達式�？紤]水分沿黃土節(jié)理的二維運動時，因為有水平向流動的影響，流體的廣義阻力增大。 建立了黃土節(jié)理滲流問題的數(shù)值分析方法。首先給出了黃土節(jié)理二維滲透系數(shù)矩陣，并建立了當考慮黃土中節(jié)理的存在時，水分場數(shù)值計算的模型。隨后針對現(xiàn)有的在非飽和土體水分場數(shù)值計算中普遍存在的不考慮主滲透系數(shù)與坐標軸不重合的情況，采用四邊形一次等參元研究建立了非飽和土體瞬態(tài)滲流的有限元算法。最后運用該數(shù)值模型和算法對多種邊界條件下的黃土節(jié)理二維水分入滲問題進行了數(shù)值計算。驗證了模型的適用性，并得到了節(jié)理入滲過程中濕潤峰運動規(guī)律。
[Abstract]:Joint is a common geological phenomenon in loess area. The existence of joint destroys the integrity and continuity of soil. The stability of caverns and slopes in loess area is a safety hazard. At present, the study of joints is mostly focused on its geological properties, but the study of engineering properties is still insufficient. There is a lack of literature on the shear and seepage characteristics of loess joints, based on which the shear and seepage properties of loess joints are studied. Through the direct shear test of loess joints with different moisture content, dry density and surface morphology, The variation law of the strength parameters of loess joints is studied. The results show that the internal friction angle of loess joints varies with the moisture content in the parabola. There is a limit moisture content, when the moisture content of the soil sample is the limit value, The friction angle of joint surface is the largest. The influence of surface morphology on cohesion is greater at low moisture content. The cohesion of rough joint surface is obviously greater than that of flat joint surface. The effect of surface morphology on the cohesion of joint surface decreases gradually. The seepage properties of loess joints are studied by laboratory tests of joint head change, surface saturation infiltration test and field joint seepage test. The results show that the flow of loess joints can still be described by Darcy's theorem when joints exist in loess. However, with the increase of water head, the experimental results deviate from Darcy's law gradually, in the case of surface saturated infiltration, joints promote water infiltration, and its permeability increases with the increase of joint opening. The in-situ joint infiltration tests show that the vertical joints in loess have high permeability in the early stage of infiltration, and the infiltration velocity along the joint direction of loess is much higher than that in horizontal direction. The seepage problem of loess joint is analyzed theoretically. The seepage of loess joint belongs to the two dimensional seepage problem, which is perpendicular to the joint direction and to the loess body perpendicular to the joint direction. The infiltration of fluid into soil and soil in the joint are considered. The effect of body velocity, The two-dimensional seepage model of loess joints is established, and the differential equation of fluid element motion is derived by using Eulerian variable method, and the differential equation of seepage flow with velocity as function is obtained, which is based on the seepage characteristics and boundary conditions of loess joints. The flow equation of two-dimensional steady flow in loess joints is derived. It is shown that the cubic law of rock mass joints can be reduced to the simplified form of the equation under certain conditions. Furthermore, the expression of permeability coefficient of loess joints is derived by combining Darcy's law. When considering the two-dimensional movement of water along loess joints, Because of the influence of horizontal flow, the generalized resistance of the fluid increases. The numerical analysis method for the seepage problem of loess joints is established. Firstly, the two-dimensional permeability coefficient matrix of loess joints is given, and when the existence of joints in loess is considered, The model of numerical calculation of water field. Then, the existing numerical calculation of unsaturated soil water field does not consider that the principal permeability coefficient does not coincide with the coordinate axis. The finite element method for transient seepage of unsaturated soil is established by using quadrilateral isoparametric element method. Finally, the numerical model and algorithm are used to calculate the two-dimensional water infiltration problem of loess joints under various boundary conditions. The applicability of the model is verified. The movement law of wetting peak in the process of joint infiltration is obtained.
【學位授予單位】：西安建筑科技大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：TU444

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