Research On The Damage Mechanism Of Siltstone From Xiangxi River Bank In Drying And Wetting Cycle

Within the scope of the reservoir area, intense water-rock interaction will be inspired after reservoir being built. Human factors caused strong impacts on the geological environment. Around the reservoir, between the geotechnical environment and groundwater system are constantly being broken and reply for water-rock interaction. In order to learn the geological environment changing, we should focus on research about water-rock interaction.Dry-wet circulation effect is an important aspect of water-rock interaction for the soil and rock reservoir slope. Degradation of rock and soil mechanics properties under the condition of dry-wet circulation has been a threat to the stability of the slope. The research on damage mechanism about dying and Wetting Cycle of rock and soil should be to strengthen. In order to well understanding the impact of stability and risk to reservoir slope, as well as the formulation of the long-term planning of disaster prevention and reduction.At present, scholars at home and abroad have gotten great achievement on water-rock interaction, but much research is on regular pattern and mechanism of disruption about Easy disintegrating rock under the condition of drying and wetting cycle effect. As well as, the research about Weak disintegrating rock Stay under the condition of drying and Wetting Cycle effect just stay on the changing law of mechanical parameters. Also, this kind of rock under the condition of drying and Wetting Cycle effect is lack of a comprehensive research on features and mechanism of damage.This research is based on the analysis of the geological environment of bank slope of Xiangxi river brook in the three gorges reservoir. Combined with the project requirement, two different kinds of siltstone samples, that different content of clay powder, were chosen clay content of two kinds of powder sandstone. Firstly the basic properties of the both samples, such as basic physical index, cementation material composition and structural characteristics, have been gotten. Then, the evolvement rule of both samples under the condition of drying and wetting cycle effect has been studied on physical and mechanical property, as well as Macro and micro structure. Deteriorating law of physical and mechanical properties has been analyzed. At last, Comprehensive analysis on the damage mechanism under the condition of drying and wetting cycle effect has been given. Main research contents and conclusions are as follows:First of all, the basic properties of the both samples, such as basic physical index, cementation material composition and structural characteristics, have been gotten, that is to lay a foundation for the analysis of damage mechanism.Particle analysis tests showed that1th sample is Containing clay Siitstone with poor Particle size distribution, and2th is Clayey Siltstone with good Particle size distribution. Material components test results indicates that:two samples contained trace amounts of soluble salts; Two samples are contains quartz long stone clay mineral and so on. Quartz and long stone are skeleton components. Clay mineral is the key role of mineral under the condition of dry-wet circulation effect. Contain clay siltstone, specimen clay mineral total for10%, which Chlorite and illite stone are accounted for clay mineral total of50%. Clayey siltstone, specimen clay mineral total for26%, which Chlorite, illite and the fudge stone are respectively accounted for clay mineral total of15%,25%and60%. Cement testing results indicated that:Contain clay siltstone cements are mainly calcareous cementation of the sample, containing a small amount of clay cement; Contain clay siltstone cements are mainly shale cements of the sample, containing small amounts of calcareous cementation. Analysis of the structural characteristics of the sample showed that:Contain clay siltstone is contact cement type and clastic support type; Clayey siltstone is basement cement type and clastic support type hybrid base support type.Second, rule of deterioration of physical and mechanical properties of the samples should be focused, under the condition of drying and wetting cycle effect. Physical properties include two indicators such as saturated water absorption rate and specific surface area and so on. Mechanical properties include contents such as strength, deformation and failure characteristics and so on.Saturated water absorption rate and specific surface have the same variation. Growth rate of two physical indicators of Contain clay siltstone sample gradually decay as the number of cycles increased, but Growth rate of two physical indicators of Contain clay siltstone sample remain constant. Mechanics such as uniaxial compressive strength, tensile strength, modulus of elasticity have the same variation, Attenuation rate of Contain clay siltstone specimen mechanics gradually reduced, but Attenuation rate of Clayey siltstone specimen mechanics remain constant.The contents of deformation and failure characteristics mainly includes:curves in uniaxial compression, instability fracture when the sample distribution features and split test section morphology. Uniaxial compression tests of "stress-strain" curve shows:an increase of Contain clay siltstone specimen in plastic property affected by drying-wetting cycles, a reduce of Contain clay siltstone specimen in plastic property affected by drying-wetting cycles. Test specimen under uniaxial compression buckling fracture distribution of indicates that:two specimens from the effects of wet and dry cycles under single fissure control of unstable mode gradually evolve into cracks control of unstable mode,1th specimens are mainly managed in the primary fissure, Clayey siltstone sample splitting prominence under the influence of wet-dry cycle is strongly. Split testing split surface characteristics:0split surface for dry and wet specimens are more flat, surface of splitting the sample of Contain clay siltstone affected by drying-wetting cycles slight increase in prominence, the sample splitting prominence of Clayey siltstone under the influence of wet-dry cycle is strongly.Once again, structure characteristics evolution, including macro-and micro-levels have been studied under the condition of dry-wet circulation. Macro-areas:macro-structure deterioration of the specimen of Contain clay siltstone does not so clear, Macro-fissure of Clayey siltstone gradually increased and longer, wider, connectivity enhancements under the condition of dry-wet circulation. Micro-structure:Micro-morphological characteristics of morphology and micro-pore, pore size and pore size distribution evolution have been studied under the condition of dry-wet circulation.the deterioration of physical and mechanical properties of the sample principle have been try to reveal,from macro-and micro-levelsFinally, the damage mechanism was been under summarized the condition of dry-wet circulation. Comprehensive analysis of the damage mechanism has been given.Under the condition of dry-wet circulation, injury mechanism of the sample consists of three areas:Clay cement expansion and contraction mechanism, mechanism of corrosion damage, fatigue damage mechanism. View content of clay mineral species are determining factors in specimen damage, under summarized the condition of dry-wet circulation. Shrinkage and expansion mechanism of clay cement is the main specimen wet-dry cycling injury dynamics, and fatigue damage mechanisms are damage accumulation process. Wet-dry cycling injury, internal power of Contain clay siltstone is less than the Clayey siltstone sample. Following dry-wet circulation, Contain clay siltstone specimens of wet-dry cycling injury Dynamics gradually decreased, Clayey siltstone specimens remain constant. This great point explains evolution of the internal mechanism, which include specimen of physical and mechanical properties, as well as structure of the samples.