| Cemented paste backfill (CPB) is an engineered mixture of dewatered tailings, hydraulic binders and water, with up to 60% solid tailings. CPB is used as backfill material for underground mine voids. CPB contributes to the stability and safety of mine workplaces as well as extractions of more minerals in a safer way. Furthermore, CPB greatly benefits the environment by reducing surface tailings disposal. In the last 15 to 20 years, CPB has been commonly used in mine backfilling around the world. The strength is one of the crucial parameters in the design of CPB structures. From an engineering performance point of view, it is important to know when the CPB reaches its reasonable strength. This information is required not only to reduce the mining cycle but also to ensure the safety of mine workers. However, most of the design data are based on laboratory prepared, cured and tested CPB specimens. Field conditions, especially the curing temperature, temperature history and pore water pressure development, vary from one site to another and also from one CPB structure to another, leading to different strength characteristics. Moreover, field investigations show that CPB field properties differ from laboratory results. This is mainly due to the fact that CPB in the field is subjected to various coupled loadings. These coupled processes include several factors, such as temperature (thermal factors), binder hydration (chemical factors), hydraulic factors (e.g water flow, pore water pressure) and mechanical factors (e.g. stress, deformation). The modeling of these coupled processes is necessary towards reliable prediction of the performance of CPB structures, i.e. for a cost-effective and safe design of CPB structures. In this thesis, FLAC based numerical models were developed to model the coupled thermo-chemical, thermal-mechanical and thermo-chemo-hydraulic processes in hydrating CPB structures. |
