Research On The Mechanical Characteristics And Its Response Mechanism Of Cemented Paste Backfill Under The Effect Of Stress And Temperature

In the traditional design of strength for cemented paste backfill(CPB),the mix proportion of the CPB was determined by the standard laboratory experiment with constant temperature and humidity.However,the on-site curing environment of the CPB was quite different from the traditional laboratory experiment.The study showed that the strength of CPB obtained by the field sampling is significantly higher than the strength obtained by the laboratory experiment samples.In order to solve this problem,it was supported by the national natural science foundation of China(51674012),the curing experiment device considering the effect of stress and curing temperature was developed.The CPB under the effect of stress and temperature was selected as the research object,the aim is to design a more economic and safe CPB,the main research works were carried out as follows:(1)The source of stress and temperature for CPB in deep mines was clarified,the ranges of stress and temperature were determined,the characteristics of traditional curing stress and curing temperature devices were analyzed,and an experimental device considering the effect of stress and temperature for curing CPB was developed.(2)The mechanics performance test experiment was done for the CPB under the effect of stress and temperature,the effect law of stress,temperature and time for the strength,peak strain and elastic modulus were discovered.Also the strength prediction model of CPB considering the stress and temperature was established,based on the experiment data,the accuracy of the strength prediction model was verified.(3)The deformation characteristics of CPB under the effect of stress and temperature were analyzed,and the damage constitutive model of CPB considering the effect of stress and temperature was established.Also the simulation model of CPB was established,the influence of stress and temperature on particle contact characteristics,force chain distribution and crack distribution characteristics for CPB was studied.(4)The multi-physical performance monitoring experiment of the CPB under the effect of stress and temperature was done,so the internal temperature,moisture content,matrix suction and conductivity changing with curing time for the CPB were obtained.The effect law of stress and temperature for the internal temperature,moisture content,matrix suction and the conductivity were discovered,which reveals associated mechanism of the thermo-hydro-mechanical-chemical performance for CPB.(5)The experiment of X-ray diffraction phase analysis,electron microscopy scanning method,mercury injection pore structure test,thermogravimetric and differential thermal analysis of CPB under the effect of stress and temperature were carried out,the influence law of stress and temperature on phase composition,hydration products,microscopic structure and pore structure of CPB.The relevance between the strength of CPB and the curing stress,curing temperature was studied,and the response mechanism for the effect of the stress and temperature on the mechanical properties of CPB was revealed.(6)The new method to optimize the mix proportion of CPB was developed considering the effect of stress and temperature.And the research results were applied to the mix proportion optimization design of CPB in a copper mine,the engineering proposals for mix proportion design of CPB were put forward considering the effect of stress and temperature.