充填砂裂隙在剪切位移作用下渗流规律的实验研究

对充填砂裂隙进行控制位移的剪切渗流实验，结合充填砂的物性，揭示了岩体裂隙发生剪切位移时的渗流规律，并对剪切位移与隙宽、剪切位移与流量、隙宽与流量的关系进行了探讨，提出了砂粒的微小扰动与孔隙比（隙宽）的增加是影响裂隙流量的主要因素。     

砂岩隙宽变化与CT数变化的相关关系

利用最新研制的中低压多功能CT机配套专用渗流试验装置，分别对干燥砂岩试样和渗流砂岩试样进行了三维应力状态下的实时CT观测，根据试验结果初步讨论了砂岩裂隙隙宽变化与CT数变化的相关关系，并提出了裂隙隙宽的计算公式。     

岩石粗糙裂隙宽配曲线和糙配曲线

 受河流动力学中泥沙粒配曲线的启发, 提出表征岩石粗糙裂隙开度和粗糙度大小及其分布的新方法——宽配曲线和糙配曲线。特别是它们反映出来的中值隙宽、中值凸度和水力隙宽、凸度的代表特征值以及非均匀系数等,对该领域的研究有重要的意义。     

新型对拉GFRP螺栓止水性能试验分析

概述对拉螺栓应用发展现状,提出将GFRP材料用作对拉螺栓杆体。对48个传统及新型对拉螺栓圆台柱体抗渗试件的界面渗透性能进行了试验研究,对比分析不同对拉螺栓形式对粘结界面渗透性能的影响;对粘结界面的渗流特性和层面力学参数,如等效水力隙宽、渗透系数等进行了分析。结果表明,对拉螺栓与混凝土粘结界面是渗水的主要通道,止水片可以提高粘结界面的抗渗性能,新型对拉GFRP止水螺栓具有较好的止水性能。在粘结界面渗水高度和渗透时间测试的基础上,根据渗透压力和渗透时间,推导了粘结界面的等效水力隙宽及渗透系数的计算公式,粘结界面的渗流基本上符合层流渗流。不同的对拉螺栓与混凝土之间的粘结界面渗透系数和等效水力隙宽存在较大差异。     

基于区间有限元的渗流分析

对于渗流问题,特别是地下岩体中的渗流,由于条件复杂随机性,具有不确定性。结合区间分析基本理论,给出了裂隙网络渗流区间控制方程。并结合算例利用Monte-Carlo区间分析方法对层状裂隙隙宽为区间变量的流场进行了渗流分析。     

裂隙岩体核素迁移模型及其在高放废物地质处置库安全性能评价中的应用

通过一维迁移模型的线性叠加，提出了基于裂隙参数随机分布的多途径裂隙核素迁移模型。模型可计算任意给定点处核素的弥散通量(Bq／a)。模型从随机分布的裂隙导水系数出发，将随机分布的裂隙导水系数平均分成有限个单元，每1单元即代表1条运移途径，并具有其相应的裂隙参数(如导水系数、隙宽)和分布频率。裂隙中任意给定点处核素的弥散通量则由各运移途径的计算结果按导水系数的分布频率进行叠加得出。     

裂隙岩体渗流-弹塑性应力耦合分析

引入能反映裂隙剪胀特性的非线性弹塑性本构模型 ,从而考虑了裂隙非线性法向变形和剪胀对裂隙隙宽的影响 ,更实际地反映了裂隙变形对岩体渗透性的影响。给出的算例表明所提出的方法是可信的     

多级加载下岩石裂隙渗流分段特性试验研究

利用自行研制的岩石裂隙辐射型渗流系统,试验研究室温下粗晶大理岩、中砂岩、灰岩和细晶大理岩4个岩石张裂隙在法向闭合过程中的渗流分段特性及加载历史的影响。根据闭合裂隙的接触状态及流域分布特征,裂隙渗流可分为群岛流、过渡流、沟槽流3个阶段;单位水头流量与法向应力呈指数函数关系,随法向应力增加而降低,后次加载中相同法向应力下单位水头流量明显较低;单位水头流量与力学隙宽呈幂函数关系,幂指数范围为1.93～2.60,可认为接触型粗糙岩石裂隙渗流量与力学隙宽呈次立方关系;后次加载时,相同力学隙宽下单位水头流量也明显较低;水力等效隙宽与力学隙宽呈分段的线性关系,修正的立方定律在相应分段内成立。研究结果对岩体裂隙渗流计算有一定的理论意义。     

基于Barton剪胀模型的粗糙节理渗流分析

 为研究粗糙节理在剪切过程中的渗流规律,首先,采用Barton剪胀模型分析节理在剪切过程中的剪胀效应,计算节理在不同剪切位移下的剪胀位移,采用Brown-Scholz(B-S)理论模型分析法向应力作用下的节理闭合变形;通过初始隙宽、法向闭合变形和剪胀位移建立剪切过程中的节理隙宽与法向应力和剪切位移之间的关系,在此基础上得到剪切过程中的节理渗流计算公式;然后,在对节理试件进行渗流试验的基础上,分别采用基于Barton剪胀模型的节理渗流计算公式和Barton经验公式计算通过节理试件的理论渗流流量,并将预测结果与实测值进行比较,比较结果表明,基于Barton剪胀模型的节理渗流计算公式的预测结果与实测值较为一致,而Barton经验公式预测值与实测值偏差较大,从而验证了该公式在计算节理剪切过程中的渗流情况的正确性。     

岩体楔形裂隙水压力分布探讨

岩体所具有的节理、裂隙等缺陷是岩体渗流的主要通道,当岩体由于开挖或加载导致岩体的原始地应力状态发生变化时,岩体裂隙的隙宽将会发生变化,而岩体裂隙宽度的变化将引起裂隙中的水压力分布发生变化.假定岩体应力发生变化时,裂隙由平行板裂隙变为楔形板裂隙,由此推导了楔形板裂隙中的水压力分布公式,并与前人的研究结果进行了对比.     

Uncertainty analysis of groundwater inflow into underground excavations by stochastic discontinuum method: Case study of Siah Bisheh pumped storage project,Iran

This paper presents a framework for the near-field stochastic discontinuum modeling and uncertainty analysis of groundwater inflow into underground excavations by direct utilization of discrete fracture network (DFN) concept. The sources of uncertainty in the groundwater inflow into underground excavations in fractured rocks were classified into two different groups including the geometrical and hydraulic properties of fractures. The main input data for stochastic discontinuum modeling of groundwater inflow were captured from site investigations in Siah Bisheh pumped storage project in Iran. Detailed measurements of groundwater inflow into powerhouse and transformer caverns provided the possibility to determine the hydraulic aperture through back calibration. The validity of calibrated hydraulic aperture was explored by simulation results of the groundwater inflow into transformer cavern, and shows high accuracy when compared with data obtained from field measurements. The statistical results of these groundwater flow simulations with constant calibrated hydraulic aperture reflected the uncertainty associated with geometrical properties of fractures. Finally, the role of hydraulic properties of fractures on the uncertainty of groundwater inflow was investigated by the variation of standard deviation of hydraulic aperture through the sensitivity analysis. The results of this study demonstrated that the geometrical properties of fractures did much greater uncertainty in the groundwater inflow into underground excavations than hydraulic properties. Moreover, it was found that both the mean and standard deviation of simulated groundwater inflow into underground excavations decrease non-linearly by increasing the standard deviation of hydraulic aperture even though it is generally anticipated that the uncertainty of hydrogeological systems increases by increasing the variance of hydraulic parameters.     

光滑裂隙高流速非达西渗流运动规律的试验研究

 采用光滑平行板模拟岩体裂隙,研制可变裂隙开度、高水力梯度、自循环水流的单裂隙室内渗流模型试验装置。试验研究宽裂隙高水力梯度下的非达西渗流运动规律,建立流速与水力梯度的非线性关系曲线。将试验结果与Lomize紊流公式、速宝玉紊流半经验公式进行对比分析,发现三者在低水力梯度情况下结果较为一致,对于高水力梯度情况会出现较大的差异。最后探讨单裂隙高流速非达西渗流运动特点及判别准则等问题,建立非达西渗流流速与裂隙开度的关系曲线,以便于工程应用。     

应力对裂隙岩体渗流影响的研究

研究了应力变化对裂隙岩体渗流特征的影响。假设裂隙网络由等效隙宽相等的相互平行的一组裂隙组成，由于应力变化而导致的隙宽变化控制了裂隙岩体渗流的变化，据此得出了裂隙岩体渗透系数及渗流量与应力的关系式。通过裂隙岩体渗流试验，证实了关系式的正确性。利用此关系式及有限元方法计算，得出了裂隙岩体渗透系数随应力的变化值。     

Estimation of closure of a fracture under normal stress based on aperture data

The closure of 41-mm hydraulic fractures under normal stress in both loading and elastic closure (unloading) was estimated according to the formula proposed by Brown and Scholz and based on data measured for the initial aperture. By introducing the concept of an effective/ineffective initial aperture and by assuming Gaussian and χ² probability density functions (PDFs) of the initial aperture, the normal stress versus closure curve was determined from the standard deviation (SD) and the spectral moments of the initial aperture and the ratio of the mean effective initial aperture to the SD of the initial aperture. The results showed that the non-linearity in the normal stress versus closure curve at large normal stresses was reproduced better by the χ² PDF of the initial aperture than the Gaussian PDF for both loading and elastic closure. Furthermore, based on the ratio of the mean effective initial aperture to the SD of the initial aperture determined for the hydraulic fractures, the effect of size on the normal stress versus closure curve was estimated for fracture areas in a tensile fracture of 1 m. The results showed that closure increases with the size of the fracture area, and that the effect of size on the closure of the fracture is governed by the SD of the initial aperture.     

Effects of external temperature and dead volume on laboratory measurements of pore pressure and injected volume in a rock fracture

The accurate evaluation of pore pressure and injected volume is crucial for the laboratory characterization of hydromechanical responses of rock fractures. This study reports a series of laboratory experiments to systematically demonstrate the effects of external temperature and dead volume on laboratory measurements of pore pressure and injected volume in a rock fracture. We characterize the hydraulic aperture of the fracture as a function of effective normal stress using the exponential aperture model. This model is then employed to predict the pore pressure change and injected volume in the fracture without the influences of external temperature and dead volume. The external temperature changes in the cyclic loading test due to the Joule-Thompson effect for fluids. The effect of external temperature on pore pressure change in the fracture can be well explained by thermal pressurization of fluids. Our results also show that the external dead volume can significantly lower the pore pressure change in the fracture during the cyclic loading test under undrained conditions. The injected volume can also be substantially enlarged due to the external dead volume in a typical pore pressure system. Internal measurement of the pore pressure in the fracture using a fiber optic sensor cannot exclude the influences of external temperature and dead volume, primarily because of the good hydraulic communication between the fracture and pore pressure system. This study suggests that the effects of external temperature and dead volume on pore pressure response and injected volume should be evaluated for accurate laboratory characterization and inter-laboratory comparison.     

Size effect on aperture and permeability of a fracture as estimated in large synthetic fractures

Synthetic fractures of from 0.2 to 12.8 m in size were created on a computer by a new spectral method to reproduce the ratio of the power spectral density of the initial aperture (the aperture when the surfaces are in contact at a single point) to that of the surface height determined for a tensile fracture of 1 m. First, the size effect on the standard deviation of the initial aperture was analyzed for fractures with and without shearing. Next, by taking aperture data at constant intervals to establish a flow area, water flow was simulated for fractures during both normal closure and closure after shearing, by solving Reynolds equation to determine the hydraulic aperture. When the fracture is closed without shearing and has the same mean aperture, the effect of the fracture size on the hydraulic aperture disappears if the fracture is larger than about 0.2 m, since beyond this size the standard deviation of the initial aperture is almost independent of the fracture size. When the fracture is closed after shearing, the hydraulic conductivity shows remarkable anisotropy, which becomes more significant with both shear displacement and closure. However, the relation between the hydraulic aperture normalized by the mean aperture and the mean aperture normalized by the standard deviation of the initial aperture is almost independent of both the fracture size and shear displacement when the shear displacement is less than about 3.1% of the fracture size, at which point the standard deviation of the initial aperture of the sheared fracture is almost independent of the fracture size.     

钻孔岩体裂隙几何参数确定方法研究及其应用

 裂隙岩体渗透性是高放废物处置库场址选择和评价的重要考虑因素。钻孔岩体渗透性特征主要依靠钻孔电视获得的裂隙几何参数来确定。针对传统统计法确定裂隙几何参数存在的不足和误差,提出了新的统计方法和计算公式。研究认为：(1) 由于岩体裂隙空间分布多变性,提出了以裂隙密度和产状为基础的岩体均质区划分方法;(2) 钻孔岩体裂隙发育优势产状采用聚类分析方法来统计;(3) 裂隙间距的确定考虑了测量误差的影响并提出了修正公式;(4) 裂隙有效水力隙宽提出按照力学成因来确定。将获得的裂隙几何参数代入渗透张量计算程序中,得到钻孔岩体的渗透张量以及渗透主值和主渗透方向,从而为钻孔岩体渗透性分析提供依据。     

三轴压应力–化学溶液渗透作用下单裂隙花岗岩裂隙开度演化

 为研究单裂隙花岗岩在应力–化学溶液渗透条件下的开度演化规律,开展单裂隙花岗岩在恒定三轴压应力及化学溶液渗透作用下的试验。对试验过程中渗透溶液离子浓度进行分析,结果表明,压应力作用下,裂隙接触面矿物溶解、自由面矿物溶解以及矿物沉淀3个过程影响裂隙开度的演化规律。通过裂隙面三维扫描数据获取裂隙开度变化与接触面积率的关系,并基于此在已有研究基础上分别建立酸性溶液和碱性溶液渗透作用下花岗岩裂隙开度演化模型。模拟结果表明,模型计算结果与试验结果符合较好,能够很好地描述裂隙在化学溶液渗透和应力作用下的演化规律;酸性溶液渗透作用下,接触面矿物溶解过程的强弱控制着裂隙开度的演化,而碱性溶液渗透作用下,矿物的沉淀过程也发挥着重要作用。     

Experimental and numerical study of the geometrical and hydraulic characteristics of a single rock fracture during shear

Coupled shear-flow tests were conducted on two artificial rock fractures with natural rock fracture characteristics under constant normal loading boundary conditions. Numerical simulations using the 3-D Navier–Stokes equations taking account of the inertial effects of fluid were conducted using the void space geometry models obtained from the coupled shear-flow tests. The test and numerical simulation results show that the evolutions of geometrical and hydraulic characteristics of rock fracture exhibit a three-stage behavior. Transmissivity of a certain void space geometry within a fracture is related to the Reynolds number of fluid flow due to the inertial effects of fluid, which can be represented by the Navier–Stokes equations, but cannot be represented by some simplified equations, such as the cubic law, the Reynolds equation or the Stokes equations. The mechanical aperture is usually larger than the hydraulic aperture back-calculated from measured flow rate, and the difference between them is found strongly related to the geometrical characteristics of the fractures. A mathematical equation is proposed to describe the relation between hydraulic aperture and mechanical aperture by means of the ratio of the standard deviation of local mechanical aperture to its mean value, the standard deviation of local slope of fracture surface and Reynolds number.