Influence Of Different Mixing Water On Mechanical Properties And Acoustic Emission Characteristics Of Backfill

The backfill is an important core bearing unit in backfill mining,and its mechanical properties and stability are the key issues that mines pay attention to.As the country vigorously promotes the construction of green mines,backfill mining has gradually become a widely used mining method in mines.At the same time,mine water pollution is also an important problem that needs to be solved urgently in the construction and development of green mines.For mines with beneficiation plants,if the beneficiation wastewater can be fully utilized for underground filling,it will be a win-win solution to the goaf and water pollution.The premise of realizing this measure is to clarify the influence of beneficiation wastewater on the mechanical properties of the backfill.Therefore,in this paper,three kinds of beneficiation wastewater and ordinary tap water with different p H values were used as mixing water to prepare filling bodies with curing ages of 7d,14 d,21d,and 28 d respectively,and uniaxial compression and three-point bending acoustic emission tests were carried out on them.,to study the influence of different types of mixing water on the mechanical properties of the backfill,and combined with SEM scanning electron microscope tests to study the change characteristics of the microstructure of the backfill under the action of different types of mixing water,and obtained the following main conclusions:(1)Compared with ordinary tap water,the use of beneficiation wastewater as mixing water will reduce the consistency,slump and bleeding rate of the filling slurry,which shows that the use of mineral processing wastewater as mixing water will reduce the flow of the filling slurry.It can improve the stability of the filling slurry during transportation,but the effect is low.(2)The changing law of the strength of the four different mixing water backfills affected by the curing age is basically the same.The trend of "increase first and then decrease" changes.Under the condition of the same curing age,the mineral processing wastewater has a certain deterioration effect on the strength of the backfill.The greater the p H value of the mineral processing wastewater,the more obvious the deterioration effect.(3)Regardless of uniaxial compression or three-point bending conditions,the cumulative number of acoustic emission events when the filling body using tap water as the mixing water reaches the peak load is generally higher than that of the filling body using mineral processing wastewater as the mixing water.The change of p H value of beneficiation wastewater has a certain influence on the acoustic emission of the backfill,that is,with the increase of p H value of the beneficiation wastewater,the cumulative number of acoustic emission events when the backfill reaches the peak load gradually decreases.(4)Under the condition of uniaxial compression,the overall variation law of the acoustic emission ringing count during the failure process of the backfill with different mixing water is relatively similar.With the increase of the curing age,the acoustic emission ringing count rate appears "surge" phenomenon The corresponding relative stress level is higher.(5)During the failure process of the four different mixing water fillings,the correlation dimension D value of acoustic emission ringing counts changes with the relative load level is basically the same,and the correlation dimension D value of acoustic emission ringing counts appears under the condition of uniaxial compression The relative stress level corresponding to the "minimum value" phenomenon continues to increase with the increase of the curing age.Under the three-point bending condition,the relative stress level corresponding to the "minimum value" phenomenon of the dimension D value associated with the acoustic emission ringing count appears "minimum value" phenomenon.The load level showed an "increasing-decreasing" trend with the increase of the curing age.(6)The change law of the microstructure of the filling body under the influence of different mixing water was studied by SEM scanning electron microscope.The research shows that the number of hydration products in the same mixing water filling increases gradually with the increase of curing time,the fractal dimension of SEM image increases,the internal pores gradually decrease,and the internal structure gradually becomes denser.The number of hydration reaction products in the filling body using tap water as mixing water is generally more than that using mineral processing wastewater as mixing water.The change of p H value of beneficiation wastewater has a certain influence on the microstructure of the filling body,that is,as the p H value of the beneficiation wastewater increases,the number of hydration reaction products in the filling body is less,and the fractal dimension value of the SEM image is smaller,and the filling body is smaller.The more pores inside.