Research On Mechanism And Online Early-Warning Method For Tailings Dam Failure

Methods to identify and acquire precursor information of tailings dam failure are viewed as a key technology to ensure safe operation of tailings, and also a current hot issue. By means of engineering test and laboratory tests, this thesis is mainly about mechanism and online early-warning method of dam failure based on the theory of rheology, and also with early-warning system and its practical engineering application. Meanwhile, paths and causes of tailings dam failure were investigated applying cause and effect diagram based on statistical analysis of domestic and foreign160tailings pond accidents.Physical and mechanical properties experiments of tailings were conducted. The results show that tailings compactness changes from big to small and grain-size changes from coarse to fine since the dam to the direction of the water. Although the intermittent character of the tailings grain-size can be discovered, tailings compactness and grain-size with depth vary similarly with the rule of the horizontal direction. The stiffness and strength of tailings increase with increasing of its confining pressures presenting obvious compressive hardening and shows shear dilatation characteristics. Tailings have notable rheological behavior and shear failure is the only crack.The behavior of rheological characteristic of tailings is studied through analysis and tests. It turned out to be that deformation of tailings dam increases with the increase of time, and cohesion and internal friction angle of tailings decrease with time gradually. Accordingly, this thesis puts forward the rheology-mutation mechanism of tailings dam failure. Experimental process to dam-break consists of three stages, including attenuation deformation, steady deformation as well as accelerating deformation.The results show that typical tailings dam failure modes are seepage failure, dam overtopping, over rising phreatic line of dam, steep slope of the dam, too fast rise of subsequent dikes and seismic liquefaction. Paths and causes of tailings dam failure were investigated applying cause and effect diagram. By means of the principle of correlation analysis method, this thesis establishes the index system for evaluating the risk of tailings dam failure. Combined with the technological development level of monitoring instrument, this thesis analyzes index system one by one and establishes the online monitoring index. Early-warning system and method for preventing tailings dam failure have been analyzed. From expounding warning meaning, finding warning sources, analyses of warning sign, predicating warning degree and releasing warning alarm, the running mechanism of early warning system are discussed by logical detail. The situation index, the warning factor index, the source index and warring sign index have been established. The early-warning method for tailings dam failure, including indicators early-warning method, statistical early-warning method, model of early-warning method and comprehensive early warning method, has been put forward.A new on-line monitoring and warning system for preventing tailings dam failure has been developed by using C#. This system can act the part of information management, early warning analysis, and danger promulgating. Once this system is constructed and put into service, the monitoring and forecasting system of dam failure will be automatized. Practical engineering application in Fujian Longyan Tailings Pond indicates that this system is an effective system and has favorable application foreground.