Initial Temperature-dependence Of Multi-field Property Correlation And Mechanical Behaviors For Cemented Paste Backfill

Cemented paste backfill (CPB) is a multiphase composite material featured with a specific initial temperature once delivered to stope. The following CPB curing is a coupled thermo-hydro-mechanical-chemical (T-H-M-C) process. The object of this thesis is to investigate the T-H-M-C property of CPB at various initial temperature for a more economic and safe CPB structure design, via the following projects.1. The evolution of physical (eg. porosity, saturation and volumetric water content) and mechanical property in CPB with different initial temperature and curing age were tested. A phenomenon of strength inversion at the initial temperature of 50 ? was found. The effect mechanism of initial temperature on the strength of CPB was revealed by implementing macro analysis using XRD.DTA and SEM.2. An innovative experimental set-up was developed for T-H-M-C property monitoring. Temperature (T), volumetric water content (H), suction (M) and electric conductivity (C) of CPB were simultaneously monitored at each initial temperature for curing age of 28 days. Suction monitoring result shows a curved intersection phenomenon, which verified the phenomenon of strength inversion aforementioned.3. Correlative mechanism for T-H-M-C property in CPB was firstly established. Correlation of strength and self-desiccation, hydraulic-chemical reaction and mechanical behavior, as well as thermo-chemical coupling effect on the strength development were detailed analyzed and discussed. Ultimately, the evolution of temperature, electric conductivity, volumetric water content, suction and UCS were simultaneously illustrated for each initial temperature. A theoretical prototype was formed for interaction of multi-field property in CPB.4. Mechanical behavior of CPB at various initial temperature was detailed investigated. The stress-strain shape of CPB is obviously affected by its initial temperature. Ascent stage of stress-strain curve is more steep at a higher initial temperature, followed by more suddenly decreasing after the peak stress. Elasticity modulus and square root of UCS in CPB are linearly related independent of initial temperature. A prediction model of elasticity modulus of CPB was proposed on the basis of hydration degree.5. The stress-strain constitutive equations of CPB at various initial temperature are deduced and constructed. According to these constitutive equations, a general elastic damage constitutive model was proposed as temperature-time coupling model. This model was implanted into solid mechanics module of COMSOL Multiphysics software for the CPB stress-strain simulation at different initial temperature and curing time. Results of stress-strain simulation are in accordance with experimental data, which validates reliability of the temperature-time coupling model.6. Since too high or too low initial temperature negatively impacts on the early strength development of CPB, controlling technology for the CPB with initial increasing and decreasing temperature strategies are given. Also, effect of initial temperature on the strength and project suggestions are studied for a copper mine. On the basis of interaction and correlation of multi-field property in CPB, a monitoring appliance and method for field stope was designed, which provides a possible investigation of multi-field property in actual stope.