The structure of fractures in nature rock appears irregular and induces complicated seepage flow behavior.The mechanism and quantitative description of fluid flow through rock fractures is a difficult subject that has been greatly concerned in the fields of geotechnical,mining,geological,and petroleum engineering.In order to probe the mechanism of fluid flow and the effects of rough structures,we conducted a few laboratory tests of fluid flow through single rough fractures,in which the Weierstrass-Mandelbrot fractal function and PMMA material were employed to produce the fracture models with various fractal roughnesses.A high-speed video camera was employed to record the fluid flow through the entire single rough fracture with a constant hydraulic pressure.The properties of fluid flow varying with the fracture roughness and the influences of the rough structure were analyzed.The components of flow resistance of a single rough fracture were discussed.A fractal model was proposed to relate the fluid resistance to the fracture roughness.A fractal equivalent permeability coefficient of a single rough fracture was formulated.This study aims to provide an experimental basis and reference for better understanding and quantitatively relating the fluid flow properties to the structures of rock fractures.
JU YangZHANG QinGangYANG YongMingXIE HePingGAO FengWANG HuiJie
Reactive powder concrete(RPC) is vulnerable to explosive spalling when exposed to high temperature.The characteristics of micro pore structure and vapor pressure of RPC are closely related to the thermal spalling.Applying mercury intrusion porosimetry(MIP) and scanning electron microscopy(SEM) techniques,the authors probed the characteristics of micro pore structures of plain RPC200 when heated from 20-350℃.The pore characteristics such as specific pore volume,threshold pore size and most probable pore size varying with temperatures were investigated.A vapor pressure kit was developed to measure the vapor pressure and its variation inside RPC200 at various temperatures.A thin-wall spherical pore model was proposed to analyze the thermo-mechanical mechanism of spalling,by which the stresses varying with the vapor pressure q(T) and the characteristic size of wall(K) at any point of interest were determined.It is shown that the pore characteristics including specific pore volume,average pore size,threshold pore size and most probable pore size rise significantly with the increasing temperature.200℃ appears to be the threshold temperature above which the threshold pore size and the most probable pore size climb up dramatically.The increase in the specific pore volume results from the growth both in quantity and in volume of the transition pores and the capillary pores.The appearance of the explosive spalling in RPC200 is mainly attributed to being unable to form pathways in favor of releasing water steam in RPC and to the rapid accumulation of high vapor pressures as well.The thin-wall sphere domain where the vapor pressure governs the spalling is bounded through the pore model.
JU YangLIU HongBinTIAN KaiPeiLIU JinHuiWANG LiGE ZhiShun
