| The mechanical properties of the backfill have a direct impact on the movement of the overlying strata and the surface subsidence in the mining area.As the mining depth continues to extend downward,the cemented backfill is affected by high geotemperature and high crustal stress.A full understanding of the mechanical properties of the cemented backfill under the influence of geotemperature and crustal stress is of great significance.This paper is based on the National Natural Science Foundation project"Research on the unified theory and control technology of rheology,creep and solid-flow transformation of deep soft rock mass"(51674149).Prepared cemented tailings backfill samples by cement and the full tailings of a gold mine in Shandong and explored the effects of temperature and confining pressure on the strength and creep characteristics of the cemented tailings backfill.This paper carried out uniaxial compressive strength tests of cemented tailings backfill with different curing temperature and age,triaxial compressive strength tests under the combined effects of temperature and confining pressure,uniaxial creep tests under different curing temperature and different confining pressure,which studied the influence of confining pressure and curing temperature on the strength and creep characteristics of the cemented tailings backfill.On this basis,the structure and composition differences of the cemented tailings backfill were analyzed by scanning electron microscopy.The main research contents and conclusions of this article are as follows:(1)Orthogonal experiments on the influence of cement type,mortar-to-sand ratio,mass concentration and age on the strength of the cemented tailings backfill were carried out.In this paper,a sample of cemented tailings backfill with P·O 42.5,a lime-sand ratio of 1:6 and a mass concentration of 75%was prepared.Conventional uniaxial compression tests were carried out on the cemented tailings backfill cured at 0?,20?,40?,60?and 80?for 3 days,5 days,7 days,14 days,21 days and 28 days.The strength characteristics and deformation of the cemented tailings backfill under different curing temperature and age were studied,which can provide a certain reference for the strength design and mining of the cemented tailings backfill.(2)The triaxial compression tests of the cemented tailings backfill with different curing temperature and confining pressure were carried out,and the strength and deformation characteristics of the cemented tailings backfill under the effects of curing temperature and confining pressure were explored.According to the test results,the Mohr stress circle of the cemented tailings backfill was drawn,and the cohesion c and the friction angle ? were obtained.Based on the Lemaitre strain equivalence principle and the Weibull statistical damage theory,the damage constitutive model and the damage evolution equation of the cemented tailings backfill under confining pressure and temperature were established.The established damage constitutive equation can better describe the stress-strain law of cemented tailings backfill under different temperature and confining pressure.Besides,the relationship between the critical damage value Dcr and the curing temperature and confining pressure was also analyzed.(3)Creep tests under different curing temperature(0°C,20°C,60°C and 80°C)and confining pressure(0.3MPa,0.6MPa,0.9MPa and 1.2MPa)were carried out on the samples of the cemented tailings backfill.The steady-state creep rate under the same level of stress had an overall tendency to increase with temperature.The instantaneous elastic deformation of the cemented packing increased with the increase of the stress level and the confining pressure.The creep stage was manifested as an obvious decelerating creep stage and stability.In the creep stage,with the higher confining pressure,the more obvious the deceleration creep stage and the greater the creep deformation became.Burgers model and Poyting-Thomson model to simulate the creep characteristics of backfills can describe the decelerated creep phase and stable creep phase of the full tailings cemented backfill well.The results of the simulation test by ABAQUS and FLAC 3D were basically consistent with the results of the indoor model test,which proved the rationality of the test and the results obtained the accuracy of the conclusion. |
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