Study On The Effect Of Dry-Wet Cycle On The Mechanical Properties Of Fractured Rock Under Acidic Environment

In the natural environment,the repeated process of frequent rainfall and rainwater evaporation,the rise and fall of groundwater level,the flood storage and discharge of rivers,the fluctuation of dam water level and mine water level make the rock mass in the complex environment of dry-wet cycle for a long time.This occurrence environment will inevitably cause a certain degree of damage to the physical and mechanical characteristics of the rock mass,and then endanger the stability and safety of the rock mass.In this paper,red sandstone is taken as the research object.Through the combination of laboratory test and theoretical analysis,uniaxial compression test is carried out on rock samples under natural conditions and after different times of dry-wet cycles in different p H solutions.The physical and mechanical properties,failure modes,acoustic emission characteristics and energy evolution law of rock samples are explored.The main contents are as follows :(1)The red sandstone was made into complete,single-crack,double-crack and three-crack standard rock specimens,and 1,3 and 5 dry-wet cycle tests were carried out in p H = 7.0,4.5 and 2.0 solutions.The effects of acidic environment and dry-wet cycle times on the quality,water absorption and longitudinal wave velocity of rock specimens were analyzed.The test results show that under given conditions,with the increase of the number of dry-wet cycles,the acidity of the soaking solution and the number of cracks,the cumulative mass loss rate,the change rate of water absorption and the change rate of longitudinal wave velocity of the rock samples gradually increase.(2)Uniaxial compression tests were carried out on rock samples in natural state and after wetting-drying cycles in different p H solutions.The stress-strain relationship curves,peak strength,elastic modulus and failure modes of intact and fractured rock samples were obtained.The test results show that the peak strength and elastic modulus of intact and fractured rocks decrease with the increase of dry-wet cycle times and solution acidity.Under given conditions,the peak strength and elastic modulus of rock samples decrease with the increase of the number of cracks.(3)With the increase of the number of dry-wet cycles and the acidity of the soaking solution,there is no effect on the failure mode of intact,double-fractured and three-fractured rock samples,and the failure mode of single-fractured rock samples changes from shear failure to tensile-shear failure.With the increase of the number of cracks,the failure mode of rock samples is changed from shear failure to tensile shear failure.(4)Based on the acoustic emission and energy characteristics of rock during uniaxial compression : with the increase of solution acidity and the number of dry-wet cycles,the maximum ringing count and cumulative ringing technology of rock samples gradually decrease;the total energy absorbed by the rock sample at the peak strength and the stored elastic strain energy show a gradual decrease trend,and the dissipation energy shows an irregular fluctuation downward trend.