Study on long-term permeability of fracture in rock mass

岩体裂隙长期渗透率研究

• 批准号: 12450411
• 负责人: MATSUKI Koji
• 金额: $ 6.4万
• 依托单位: Tohoku University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12450411/
• 关键词: Permeability of fracture; Shear deformation; Time-dependent closure; Theory of viscoelasticity; Confining pressure test; Control of confining pressure; rock; き裂の閉鎖; き裂のせん断変形; 一般的応力条件; 時間依存性

For prediction and control of the long-term permeability of a fracture in rock mass, it is indispensable to clarify permeable change of an underground fracture with time. The purpose of this study is to establish a method for prediction of long-term permeability of a fracture. For this purpose, firstly, it was carried out that theoretical study of time-dependent closure of a fracture with rough surfaces under constant normal stress. Secondary, the relaxation modulus of rock was measured by using proposed indentation-test system. Finally, the permeable change of a fracture in the rock under both of shear stress and normal stress with time was clarified experimentally and theoretically.Main results obtained in this study are summarized as follows:1) A formula for the relationship between constant normal stress and time-dependent closure as a function of time was derived, based upon the distributions of aperture local minima and their radii. It was shown that the ultimate closure of a fra … More cture under constant normal stress can be estimated from the normal stress-elastic closure curve and the relaxation modulus of rock. The ultimate time-dependent closure was shown to be independent of the normal stress if the elastic closure is linear with the logarithm of the normal stress (Goodman's fracture).2) Indentation-test system for estimating the relaxation modulus and the elastic constant of rock was developed. A Monte Carlo simulation on time- dependent closure of a fracture under constant normal stress was performed by using the fracture model and the measured relaxation modulus.The results qualitatively showed that the time-dependent closure for granite is not dependent on normal stress and that for sandstone is dependent on normal stress. However, simulated time-dependent closure was fairly smaller than that of experimental results. It was thought that this difference was the main causes with the size effect by the difference of contact area.3) Permeability test of a fracture applying shear deformation with constant/uniform normal stress under confining pressure was carried out. Less

为了预测和控制岩体裂隙的长期渗透率，必须明确地下裂隙渗透率随时间的变化。本研究的目的是建立一种预测岩体裂隙长期渗透率的方法。为此，首先，对恒定法向应力下粗糙表面裂缝的时间依赖性闭合进行了理论研究，最后，使用所提出的压痕测试系统测量了岩石的松弛模量。这从实验和理论上阐明了岩石裂隙在剪应力和正应力作用下渗透率随时间的变化。本研究取得的主要结果概括如下：1）恒定正应力与时间相关关系的公式根据孔径局部最小值及其半径的分布，导出了作为时间函数的闭合结果。结果表明，恒定法向应力下裂缝的最终闭合可以通过法向应力-弹性闭合曲线来估计。如果弹性闭合与法向应力的对数呈线性关系（古德曼断裂），则最终的时间相关闭合被证明与法向应力无关。2) 用于估计松弛模量的压痕测试系统。利用裂缝模型和测量的松弛模量，对恒定正应力下裂缝的时间相关闭合进行了蒙特卡罗模拟。结果定性地表明，裂缝的时间相关闭合。花岗岩不依赖于法向应力，而砂岩则依赖于法向应力。然而，模拟的时间相关闭合比实验结果小得多，人们认为这种差异是由差异引起的尺寸效应的主要原因。 3) 进行围压下恒定/均匀正应力剪切变形裂缝渗透率试验。