Experimental And Theoretical Analysis On Mechanical Properties Of Fractured Rock Under Water-Rock Interaction

Research on rock mechanical behavior under Water-Rock coupling is one of the most basic forefront issues for geotechnical engineering. Actually engineering rock mass have many cracks, and the safety of fractured rock are affected by Water-Rock coupling. However, at present it's little research on the mechanical damage evolution and deformation and fracture mechanism of fractured rock under Water-Rock coupling. The corresponding damage and fracture mechanical constitutive model has not yet been established. In order to focus on the research on the effect mechanism of strength and deformation fracture process for fractured rock under Water-Rock coupling, a series of physical and mechanical tests which contained uniaxial compression test and corrosion test and joint strength characteristics test and in situ shear testing have been carried out. The micro-crack initiation, propagation and through and the process of internal evolution and mechanical damage evolution mechanism are analyzed. The damage fracture criterion and the constitutive model have been established. Main research contents and results are as follows:Firstly, for the first time processing arrangement of three pre-cut crack in the length of 100mm,50mm diameter cylindrical standards of the real specimen. All the angle of pre-cut crack are 45°, and the bridge angle of pre-cut two cracks are 75°and 105°. The length of single pre-cut crack is 10mm, and the maximum radial penetration thickness is 50mm. The success of pre-cut crack product and test provide new method and mean for study on rock deformation and fracture mechanism. The first time study on mechanical experiment with the pre-cut crack under Water-Rock Chemical coupling provides the basis for the research on Hydraulic-Mechanics and Hydraulic-Mechanics-Chemical coupling process.Secondly, based on the results of uniaxial compression tests, the characteristics of complete stress-strain curves of cracked rocks under different chemical environment are analyzed, and the behavior of deformation and strength of cracked rocks under different Water-Rock chemical environment(immersion flow rate, pH value) are obtained. Thirdly, failure process and failure modes of uniaxial compression are analyzed, and the modes of crack coalescence and crack interaction mechanism are analyzed. Based on the results of uniaxial compression test, revealed the fractured process and mechanical properties of deformation and fracture mechanism of damage evolution from microstructure, chemical corrosion and damage fracture. Based on the above analysis, damage constitutive model considered Water-Rock chemical coupling is established.Fourthly, the time-dependent characteristics of cracked rocks under different chemical environment are obtained based on the analysis of test data at different time of specimens soaked in different chemical solutions. The results show that Water-Rock Interaction is that meso-structure and construction of chemical corrosion and lead to deterioration and variation of macro physical and mechanical properties.Fifthly, based on the shear test of different joints under Water-Rock coupling, analyzed the joints shear mechanical properties and damage fracture mechanism, explained the nonlinear and macro features of shear constitutive model. With energy principle, joint shear stress-strain relationship based on damage mechanics and shear mechanical model under Water-Rock Interaction are established.Lastly, based on in situ shear test of fractured rock mass under different water contents and normal stress, obtained shear stress-shear deformation curves and shear strength parameters, analyzed the shear stress-shear deformation curves characteristics and variation and effects of shear strength and deformation of fractured rock mass in Hydraulic-Mechanics coupling. It's revealed that the effect law of fractured rock mass strength and deformation. Fractured rock mass cohesion has a good negative exponential relationship with moisture content, and the angle of internal friction has the approximate logarithmic relationship with moisture content. We concluded from the results that shear strength criteria of fractured rock mass which moisture content was taken into account have been established. Finally, shear strength parameters index variability have been analyzed by using probability and statistics.