岩石裂隙渗透性尺寸效应的试验及机理研究

Scale effects for permeability of rock fracture is common in the study of rock hydraulics, however, the evolution rules and the corresponding control mechanism of scale effects of rock fracture permeability are still unclear. The experiment acts as a main mean in investigating the rules even though facing several practical insufficiencies, such as, the sample is not representative enough, and the sizes of the sample are relatively small and simple. To address those problems, firstly, the distribution regularities for surface morphology of natural rock joint will be analyzed, and then the representative sampling method for rock fractures of different scales will be established by applying probability sampling theory. Subsequently, modeling materials will be determined according to the similarity principle, then serial-scale rock fracture models will be fabricated through inverse controlling technology by using the materials. The flow-through experiments for rock fracture in serial scales are conducted on the designed large-scale permeameter, scale effects for permeability of rock fractures having various roughness coefficients and under various hydraulic gradients are revealed. The dominant factors affecting scale effects for permeability of rock fracture are further analyzed based on the experimental results, and the mechanism model of scale effects of rock fracture permeability will be built after exploring the dominant mechanization. Scale effects and corresponding mechanism for permeability of rock fracture are thoroughly studied by the project, aiming to provide reliable fracture permeability and an objective mechanism model for the research of rock hydraulics.

岩石裂隙渗透性尺寸效应是岩体水力学研究中一种常见的现象，但其演变规律和控制机理还不甚明了。试验是探索尺寸效应规律最主要的手段，然而试验研究中尚存在模型试样取样代表性不足、尺寸较小且较单一的问题。本项目针对上述问题，根据概率取样原理，分析原岩结构面表面形态分布规律，建立系列尺寸岩石裂隙面模型试样的代表性取样方法。随后依据相似性原理选择模型材料，基于逆向工程技术在原岩结构面上制作系列尺寸的岩石裂隙面模型试样。接着采用设计的大尺寸岩石裂隙渗透试验仪，开展系列尺寸岩石裂隙的渗透试验，研究不同粗糙度、不同水力梯度条件下的岩石裂隙渗透性尺寸效应规律。最后基于渗透试验研究，分析尺寸效应的主要影响因素，阐明其中的控制机制，建立适用于不同条件的岩石裂隙渗透性尺寸效应机理模型。本研究系统地对岩石裂隙渗透性尺寸效应规律及其控制机理进行探索，旨在为岩体水力学研究和工程实践提供客观、可靠的裂隙渗透参数和机理模型。

岩石裂隙渗透性尺寸效应是岩体水力学研究中一种常见的现象，但其演变规律和控制机理还不甚明了。试验是探索尺寸效应规律最主要的手段，然而试验研究中尚存在模型试样尺寸较小，且尺寸较单一的问题。本项目针对上述问题，首先采用有机玻璃制作了大尺寸透明单裂隙试样，并在试样不同位置处设置水压测孔，实现在同一大尺寸试样上开展系列尺寸岩石裂隙渗透试验研究。随后采用自主研发的大尺寸岩石裂隙渗透试验系统，开展了系列尺寸岩石裂隙的渗透试验研究。试验结果表明：单裂隙渗透性存在尺寸效应，且渗透系数随试样尺寸的增加而增大；通过改变水力梯度、裂隙粗糙度，开展了变条件下的渗透试验，无论从测得的渗透系数还是高速相机拍摄的渗透进程图均揭示：裂隙渗透性明显受到粗糙度的影响，随着粗糙度的增加，裂隙的渗透性逐渐降低。最后，为探明岩石裂隙渗透性尺寸效应的主要影响因素，基于COMSOL构建系列尺寸的粗糙岩石单裂隙，通过求解Reynolds方程开展了变裂隙开度、粗糙度和法向应力下的渗透数值试验。模拟结果同样表明：岩石裂隙渗透性存在尺寸效应，其渗透系数随试样尺寸的增加而增大，随后趋于稳定，模拟获得的临界尺寸介于12-15m之间。通过进一步的参数敏感性分析揭示：临界尺寸与裂隙开度呈负相关关系，裂隙开度越大，渗透性临界尺寸越小，与粗糙度和法向应力则呈正相关关系；且相较于粗糙度和法向应力，裂隙开度对岩石裂隙渗透性尺寸效应的影响更显著。