Tailing Flow Routing Simulation And Risk Assessment Of Tailing Dam Break Due To Overtopping

Tailing facilities is not only an important component of mining production factors, but also potential hazard meanwhile. With the continuous development of mining engineering, tailing dams accidents have occurred quite frequently. Tailing dam break will not only cause tailing spill out and destroy the ecological environment of the downstream area, but also result in enormous loss of human lives and property. There are many factors for dam safety influence, such as design, management, dam construction material and dam construction way, etc, and in general main factors causing dam break include flood overtopping, liquefaction by earthquake, slope instability and seepage destruction, etc. Major fatal tailing accidents both at home and abroad are mostly caused by flood overtopping, and therefore it has an important significance to carry out tailing dam break due to overtopping on many aspects, such as improving tailing reservoir safety and safety management, reducing and controlling dangerous and harmful factors of tailing reservoir, reducing the risk of tailing production safety and prevention of accidents and guiding flood prevention of tailing dam in flood periods, etc.The dissertation from the hydraulics, soil mechanics, hydrology, sediment dynamics and tailing engineering, etc, thoroughly and systematically studies the mechanism and process of tailing dam break due to overtopping, establishes controlling equation of tailing flow routing in the downstream, and carries out risk assessment of tailing dam break due to overtopping. Main research works of the dissertation are as follows:(l)That tailing reservoirs flood calculation and flood regulating calculation which are related to overtopping is studied. The calculation methods including flood peak flow and total amount of flood, as well as the drawing of flood process line are studied in the flood calculation section. The purpose of the flood regulating calculation is to determine regulating storage capacity needed and discharged flow according to established drainage system. This paper takes a IV class tailing reservoir of copper mine for example, and carries on flood regulating calculation to check drainage system respectively according to different frequency(P=l%and P=l‰).(2)Two basic thories:shear stress(or traction stress) and "headcut" erosion are discussed. The dam-surface erosion after overtopping and mechanism of dam break due to overtopping are studied. Based on the research and analysis of the destruction process of earth-rock dam break due to overtopping and combined with tailing dam its own charateristics and related theories, The destruction process of tailing dam break due to overtopping is proposed.(3) Two calculation methods of discharged tailing flow process are studied. On one hand, tailing dam belongs to granular dam and tailing dam break is considered to be gradual break, based on DAMBRK model and combined with water balance equation, the water process line of dam-break is firstly proposed, and considering discharged tailing and changing the time-varying process, the discharged tailing flow process line of gradual break of tailing dam is proposed. On the other hand, because of tailing dam break often accompanied by heavy rain and tailing being saturated, for safety, the most adverse circumstance that dam break occurs instantaneously is often considered, and four-time parabola is used to generalize the discharged tailing flow process line of tailing dam break.(4)The tailing flow discharged after tailing dam break essentially belongs to landslide or debris flow, the movement of the tailing flow is similar to that of fluid flow, and continuity equation and motion equation of tailing flow can be established according to the law of mass conservation and momentum conservation in the case of considering tailing flow movement affected by its gravity, hydrodynamic pressure and bed shear resistance. Equations consisting of continuity equation and motion equation is controlling equation that can be used to describe the routing process of tailing flow, both the operator splitting and the method of characteristics are used to solve the controlling equation of tailing flow routing and the discrete format of the controlling equation is constructed. The calculated results of a failuring tailing dam coincide reasonably with the measured ones, which proves that the controlling equation is correct.(5)Take Beijing Heshangyu tailing reservoir for example and the controlling equation of tailing flow routing is used to simulate the routing and movement of tailing flow in the downstream after tailing dam break.(6)The quantitative risk assessment menthod of tailing dam break due to overtopping is proposed based on Bayesian Networks(BN). Ground on the fault tree of tailing dam break due to overtopping accident, it uses GeNIe to model and analysis, calculates the probability of overtopping dam-break accident, posterior probability of each basic events, importance degree, and the average order of importance degree. Combined with the possibility of tailing dam break due to overtopping and severity results of dam break, risk classification assesement model of tailing dam break due to overtopping is proposed.