【作者】 荣冠；

【导师】 周创兵；

【作者基本信息】 武汉大学 ， 岩土工程， 2005， 博士

【摘要】 饱和非饱和渗流现象是岩土介质中普遍客观存在的地下水运动规律,由于其对岩土体稳定性、地下水资源利用、污染控制、石油天然气开采等工程问题均具有重要影响,同时近十来年由于国内外在上述领域工程需求增加,使饱和非饱和渗流研究正成为岩土工程的热点问题。本文首先对岩土体饱和非饱和渗流、渗流场与应力耦合作用和降雨入渗条件下边坡稳定性方面研究情况进行了介绍,在总结前人研究成果的基础上对岩土介质饱和非饱和渗流理论及非饱和渗透试验、饱和非饱和渗流有限元模拟、降雨入渗及其对边坡岩体稳定性影响、渗流与变形耦合等几个方面进行了分析,主要研究和探讨的内容有: 1.对多孔介质饱和渗流基本理论进行了简要论述,给出了多孔介质饱和渗流基本微分方程。阐述了非饱和土水势、多孔介质土水特征曲线和各种经验公式及非饱和渗透系数的影响因素等。研究了不同特征裂隙的渗透特性,并在此基础上分析了裂隙岩体的渗透特性,介绍了裂隙岩体REV的概念。基于已有的裂隙非饱和渗流试验资料,研究了岩石裂隙开度分布规律,进行了裂隙非饱和水力参数拟合及理论分析,同时对岩石裂隙非饱和渗流机理作了初步探讨。 2.根据渗流基本理论分析推导了连续介质三维饱和非饱和渗流问题微分方程以及渗流基本边界条件,在此基础上给出了饱和非饱和渗流方程Galerkin有限元格式。推导的饱和非饱和渗流有限元求解中以压力水头为基本未知量,将稳定与非稳定、饱和与非饱和渗流场统一起来进行研究,整个渗流场采用一个支配方程,自由面只是正压区与负压区的分界面,计算中不须进行自由面迭代。饱和非饱和渗流有限元求解相应的缺点有:非饱和参数不易确定、计算精度不易控制、由于负区与正区方程类型不同导致求解和收敛困难。针对上述问题讨论了求解中材料非饱和参数选取及逸出面的处理、非线性迭代技术及收敛标准和初始压力水头边界的确定等问题。 在三维饱和非饱和渗流有限元程序进行验证的基础上,对某库区边坡岩体库水位升降条件下的渗流场进行了模拟计算,计算结果反映:随着水位的上升,渗流场总体变化规律为,负压区范围逐渐变小,正压区压力水头变大,部分岩体由非饱和状态变为饱和状态,零压线上升明显滞后于库水位的上升。由于边坡初始压力水头(对应含水量)和岩土材料非饱和渗透参数的差异性,使负压区水头和零压面的变化较复杂。水位下降时,零压面随库水位下降而迅速下降,负压区也随之增大,正、负压区压力水头均逐渐变小。地下水流速矢量方向总体为斜坡倾斜方向,且零压面附近流速最大。更多还原

【Abstract】 Saturation-unsaturated seepage is the widespread and objective regularity of groundwater movement. Because its significant influence on rock and soil slope stability, the use of groundwater resources, pollution control, the exploitation of petroleum and hydrocarbon gases, as well as last ten years domestic and international engineering demands increase greatly in the above realms, the saturation-unsaturated seepage research becomes a hot-spot problem of geotechnical engineering. At first the saturation-unsaturated seepage, coupling problem between stress field and seepage field, the stability analysis of slope under the condition of rain infiltration etc are introduced in the paper. Base on the former research, the theory of saturation-unsaturated seepage about porous media and rock, the test of single fracture unsaturated penetration, FEM simulation of saturation-unsaturated seepage, rain infiltration and its influence on the stability of slope and coupling interaction of seepage field and stress field are analyzed. Its major contents are as follows:1. The theory of saturated seepage of porous media and its differential equation are introduced. The unsaturated soil-water potential theory, the soil-water characteristic curve of porous media, various empirical equations and the influencing factor of unsaturated permeability coefficient are formulated. The permeability characteristic of various fractures are analyzed and jointed rock mass also are presented. The conception of REV about fractured rock is also introduced and expression of REV is deduced. Based on the laboratory measurement data of capillary pressure-saturation relationships in rock fracture, the distribution function of fracture apertures is studied. The imitation of fracture unsaturated permeability parameters and theoretics analysis are carried out; the mechanism of unsaturated flow in fracture is discussed.2. Basing on basic seepage theory, the differential equation of the 3D saturated-unsaturated seepage of continuous medium and the basic boundary conditions are deduced. The Galerkin FEM formation regarding pressure water head as basic unknown quantity is presented. Unifying the saturated-unsaturated, stable-unstable seepage problems and saturated-unsaturated seepage field, a uniform governing equations is applied in the whole seepage field. The free surface is only the interface of positive water pressure andnegative water pressure, so it is unnecessary to adjust seepage free surface in computation. But there are some disadvantages in saturated-unsaturated Galerkin FEM. For example, the unsaturated permeability parameters are not easy to confirm, it is not easy to control calculating precision and hard to gain the solution and convergence because the type of different control equations is not unified in the plane between positive water pressure and negative water pressure. The selection of the unsaturated permeability parameters, the disposal of the overflow surface, the nonlinear iteration technology and the convergence standard and to confirm the initial pressure waterhead conditions are discussed.Based on the verification by the 3D saturated-unsaturated seepage FEM program, simulation computation on seepage field is done as the water level lowering and rising. The results show that negative pressure zone become reduced and pressure head in positive pressure zone become raised and partial rock become saturated from unsaturated. The rising of the zone-pressure line lags behind the rising of the reservoir level can also be seen. Owing to the differences of initial pressure head in slope and the unsaturated permeability coefficient of rock, the negative head pressure and the zone-pressure plane vary complicated. As the water level lowering, the zone-pressure plane fall rapidly and the negative zone become lager and the pressure head in positive and negative zone fall gradually. The vector of groundwater velocity directs the dip direction of the slope as a whole. The velocity adjacent to the zone-pressure is greatest. The rapider the water level fall, the greater the hydraulic slope become, the greater the flowing pressure along slope becomes. So the stability of the slope becomes worse. The computing results show the regularity of the pressure head and velocity during the variation of the water level are reasonable.3. According to the principle of soil hydro-dynamics, the general mechanism of rain infiltration is presented. It includes that the flow regulation of groundwater at the condition of rain infiltration, the boundary condition of ground surface infiltration and one dimension infiltration model such as experience formation, Green-Ampt model and Richards equation.The simulating method is presented base on saturated-unsaturated FEM calculation and the methods of handling boundary of rain infiltration and calculating seepage flux are analysed. At the same time, some examples about rain infiltration are calculated, including the regulation of infiltration, redistribution and drainage of groundwater at rain infiltration condition in one dimension sand column. The affect of the intensities, duration of rainfall, the change of initial pressure waterhead and the permeability coefficient on the saturated-unsaturated seepage field is analyzed. The variation process of thesaturated-unsaturated seepage field of one slope is simulated at the conditions of rain infiltration.The seepage field considering the atomizing rainfall is simulated aiming at Jinping first hydropower project high slope on the side of left bank. The results show that the pressure head is raised at superficial place in the high slope by atomizing rainfall and temporary saturated zone can exist at gentle base of slope. Without regard to drainage facility, the pressure head raise about 140m at the base of the slope because of the atomizing rainfall, the other way round, about 60m. The moisture content and the increase of pressure head in the slope surface are affected by the strength of rainfall. Without regard to drainage facility, the cumulative infiltration rate in the atomizing region is 27.62%, the other way round, 5.00%. The waterproof and drainage work can suppress effectively the increase of pressure head and the appearance of temporary saturated zone because of the surface infiltration. So slope protection and the effective drainage for the surface flow and the rational layout of drainage outlet in superficial layer can enhance markedly the stability of the slope.Base on unsaturated material strength theory and the limited balance analysis method, the slope stability analysis method considering the material strength variance in the unsaturated region is studied according to the variance of saturated-unsaturated seepage field during rainfall, taking the Jinping first hydropower project high slope on the side of left bank as the example. The computation results of VI-VI section show the stability factor decrease as the infiltration of the surface water reduce and when rain is over, after a period of time the stability factor recover. The atomizing rainfalls have a great effect on superficial layer slide (the stability factor decrease at most 14%) and a slight effect on deep layer slide (the stability factor decrease at most 14%). The waterproof measure in the slope surface and the drainage measure in the slope body play an important role on the control of infiltration and improvement of slope stability.4.The FEM equation of unstable seepage considering the variety of porosity ratio is deduced base on the differential equation of saturated unstable seepage field and the stress-strain FEM method is discussed. The coupling mathematical model and FEM calculating formation are presented considering the interaction between seepage field and stress field. And the coupling mechanism of the interaction between seepage field and stress field is studied and computation method to calculate seepage force in FEM is analyzed. The influence of the stress field of the two kinds of material on permeability character is discussed.Taking Maopingxi earth dam project in TGP as an example, utilizing the mathematical model of seepage field coupling with stress field and its FEM equation, the deformation field during construction period and the coupling of steady seepage field and stress field at 135.0m and 175.0m water level are calculated. The result shows that the deformation of dam body by computation can be uniform with the measured deformation and the whole regularity of stress field is rational. At 135.00m water level, the deformation field considering the seepage have some obvious characteristic. For example, both the horizontal displacement and vertical displacement of dam increase, but the vertical displacement increase more, the vertical displacement increases along gravity direction. The deformation and seepage regularity of earth dam gained by computation accord with the factual regularity, so the selection of computation model and parameters are reasonable. At 175.00m water level, the computation result considering the coupling shows the water head of the rock mass of upstream core wall at base of dam lower slightly, and that the water head of bottom and downstream core wall rise slightly, the total leakage increase slightly, both the horizontal displacement and vertical displacement increase respectively, the influence of coupling is limited.5. At last, conclusions and prospects are drawn from the studies of saturated-unsaturated seepage and the tentative ideas about this domain are presented.更多还原