Study On Sandstone Degradation Effect Under Alternation Of Wet And Wet

The interaction between water and rock is important in the field of study of engineering rock and soil stability, in recent years, it has always been the frontier of research of relative geotechnical engineering subject. The proper comes from the project named "The study of strength deteriorating mechanism and damage constitutive relation of shaly sandstone in the effect of alternation of drying and wetting" supported by National Nature and Science Fund(No.41202229),with the research of slope shaly sandstone of an open-pit mine in Yunnan, the study purpose is the effect of alternation of drying and wetting and developing and evolving process of microstructure of shaly sandstone under natural conditions, binding with relative in-situ observational data, through in-door strength and deformation experiment and macroscopic test. Revealing the strength and deformation change law of shaly sandstones under the condition of drying and wetting cycle, analyzing the micromechanism of effect of drying and wetting cycle, the main results of this research are as follows:(1) Measuring the mineral ingredient and amount of sandstones through powder X-ray diffraction, energy spectrum analysis and other testing approaches; Carrying out water absorption experiment of sandstones under alternation of drying and wetting, the results show that along with the increase of range of drying and wetting cycle, the absorption rate increase. Establishing a function of moisture content with times of drying and wetting cycle.(2) Carrying out uniaxial compression deformation experiment on different condition sandstone samples, getting stress-strain curve, strength parameters and deformation index of sandstones under different state, on this base, the paper quantitatively and qualitatively explored the drying and wetting cycle effect of sandstones.(3) Carrying out acoustic emission characteristic experiment of sandstone samples uniaxial compression deformation for key test points, the results show that the accumulative number of ring of AE and accumulative energy of AE in the dry state is much greater than corresponding acoustic emission parameters after the process of drying and wetting cycle, and with the increase of number of drying and wetting cycle, the acoustic emission parameters of sandstones reduced gradually, that is, the acoustic emission activity weaken gradually, meanwhile, it had a obvious time lag of acoustic emission.(4) Based on the uniaxial compression deformation experiment result, establishing statistical damage constitutive model of sandstone with the considering of effect of drying and wetting cycle, through the verification of the model, it shows that the statistical damage constitutive model is rational.(5) Carrying out direct shear test of sandstone samples which are under the effect of different drying and wetting cycle, the results show that the shear strength of sandstones is positively correlated with the normal force and negatively correlated with the number of drying and wetting cycle, the shear strength parameters of sandstones reduced along with the range of drying and wetting effect, and the cohesion c had a greater response to drying and wetting cycle than internal friction angle φ.(6) From the microscopic angle, observing the changing situation of interior pore"s texture and particle cementing way of different state sandstone samples through polarized light microscope. The analysis shows that the interior texture had obvious change with the increase of number of drying and wetting cycle, then, it can fundamentally reveal the mechanism of action of alternation of drying and wetting on the weakening of properties of rock.