Experiment On Hydro-Mechanical Coupling Mechanism Of Rock Based On CT Real-time Observation

The coupling system of stress field and seepage flow field is a common problem occurred in practical engineering. For this reason, it is necessary to study mechanical mechanism of water-rock interaction and evolution process of inside rock micro-damage as well as broken patterns, whereby the damage expansion mechanism of water-rock interaction, the process of rock micro-damage process and the broken patterns, as well as internal mechanical mechanism of water-rock inter-reactions are indicated from the micro- and macro-aspects. This is the research project in basic science for the solving of the key problems in priority engineering works and prevention and control of geological disasters, and is of the important scientific significance and practical application values.SIEMENS SOMATOM plus Type X-Ray screw CT machine and multi-purpose geo-tech seepage flow testing device with medium and low pressure are adopted in the tests. The sandstone with medium cementation and better permeated properties from Tongchuan area in Shaanxi can be served as research specimens. In the state of tri-axial stress, the 3-D real time CT dynamic observation and measurement of the stress of sandstone samples and the whole damaging process of seepage flow inter-actions are made.In sections of chapter 2, the tests of macro-stress and strain properties of sandstone samples in the state of dry sandstone as well as the macro-stress and strain properties of sandstone samples under the action of permeable water pressures are carried out, whereby the basic concept and mathematical equations for the confining pressure upon the strength of testing sample and depreciation-reduction rate of deformation as well as permeable water pressureupon sample strength and depreciation-reduction rate of deformation are suggested.In sections of chapter 3, the 3 -D real time CT observation and measurement of water-rock interactions are made of sandstone samples. Also, the mathematical analysis of density variation in sandstone sample is made in the testing process, whereby the mathematical equation is derived in the state of seepage flow and based on the micro-analysis of the increments of sandstone sample density damages. And at the same time, the correlative relations among sandstone stress and strain state and CT number variations as well as the correlative relations between the effect of confining pressure upon CT number variations and permeable water pressure and CT number variations are analyzed.In sections of chapter 4, the mathematical analysis of the width variations in sandstone porosity widths is made based on micro-analysis. Accordingly, the correlative relations between variations in crack width of sandstone cracks and CT number variations are advanced; the formula for calculating the crack width of sandstone sample cracks is suggested on the basis of CT number variations; the formula for calculating the crack width of sandstone sample cracks is presented on the basis of CT number images; and the correlative relations between the permeable water pressure and the width variations of sandstone cracks and the mathematical equation are given in this thesis. The research findings indicate that apart from that fact that stress can cause deformation damages to rocks, permeable water pressure can also can cause deformation damages to rocks; and that also, the inter-reactions between seepage flow and stress state may have great effect upon rocks. Accordingly, permeable water pressure force can have a remarkable and sensitive effect upon the strength and deformation of sandstone samples.