Research On The Characteristics Of Seismic Dynamic Responses Of Tailings Pond Based On Numerical Simulation And Model Test

The continuous aggravation of mining exploration activities in recent years leads to the amount of tailings pond increasing rapidly. Because of the negligence of management and maintenance, some of tailings ponds exist in security risk. Disasters of tailings pond at home and abroad not only caused great loss of life and property but also brought serious environmental problems. Earthquake is one of the main reasons that caused tailings pond disasters, so it has significance to research the stability of tailings pond under earthquakes. Existing research achievements mainly focused on using different analysis methods to calculate the safety factor of static and dynamic stability of tailings dam under the different conditions. Therefore the present paper selects Xiangchong tailings pond in Gejiu as the research object, adopts the combining methods of numerical simulation and model test to research the characteristics of seismic dynamic responses of tailings pond systematacially. The main accomplished works and the achievements as follows:1. The construction suitability is evaluated by analyzing the characteristics of strata attitude, spring location and overland flow based on hydrogeologic and engineering geologic data of tailings pond surface. The engineering geology analytical method of ground evaluation based on the data of geological survey is presented. The results show that:(1) gullies developed in equally spaced indicate that the strata anti-erosion ability has the characteristics of homogeneity and isotropy; there is less possibility that the strata in the tailings pond area have dominant faulted structures. (2) The distribution rule of lithology indicates that the strata have a complete sedimentary succession; almost strata dip to the north and have stable occurrence. (3) Springs have the obvious features of large amount, high density, low flow and random distribution; the size of gullies flow shows positive correlation with the catchment area above the measuring point and the thickness of loose deposits; above features show that the main type of groundwater is pore water. (4) The integrality and water resisting property of strata is conducive to tailings pond construction and operation safety.2. The numerical simulation of dynamic calculation of large complex ground is simplified because of generalization of the stratum using the relationship between the kinetic parameters of stratum and its depth. The characteristics of displacement field and stress field are studied, the effects of tailings parameters and damming technology on static stability of tailings pond are discussed based on numerical simulation. Some conclusions obtained from above research as following:(1) the main deformation of tailings pond under the gravity is sedimentation, dam crest has the most obvious deformation of embankment; tailings dam tends to slide to downstream along certain circular sliding surface. (2) Stress distribution of the foundation strata show approximate horizontally bedded form, the dam crest of embankment exists in tensile stress. (3) There is not obvious effect of tailings parameters variation on the distribution characteristics of displacement field and stress field of tailings pond, but the change of tailings parameters can give rise to variation of displacement and stress values. (4) There is a negative correlation between static displacement and tailings elasticity modulus; it is more stable of embankment built with classified tailings than unclassified tailings.3. The characteristics of displacement, stress and acceleration of tailings pond under earthquake are studied systematacially, the effects of the dynamic responses of tailings pond on different tailings parameters are discussed based on numerical simulation. The results show that:(1) Dynamic displacement changes with time stepping and has not obvious rules; tailings dam has an obvious tendency of deformation towards to free face. (2) There is a negative correlation between dynamic displacement and tailings elasticity modulus; the vertical seismic dynamic responses are more sensitive. (3) Embankment that built with classified tailings is more stable according to the orientation and the value of maximal displacement and the value of Y-axis permanent displacement. (4) Dynamic stress is mostly compressed stress, tensile stress is mainly present at the edge of tailings pond and the ridge of watershed in the tailings which have lower thickness of tailings accumulation; there is not obvious correlation between tailings parameters, damming technology and the distribution features of principal stress and shear stress. (5) Dynamic responses are affected by medium catastrophe, which means the dynamic magnification level in the centre areas is lower than the side and the tail of tailings pond; the effect will be more obvious if the different of parameters between tailings and foundation strata become lager. (6) Dynamic responses are affected by surface amplification of tailings dam; it has high dynamic magnification level at the 1/2 height of tailings dam, means tailings dam has the similar dynamic responses features with slope. (7) Dynamic responses are affected by medium stiffness, which means the level of acceleration amplification will be increased with the increase of tailings elasticity modulus. (8) Dynamic responses are affected by attitude, which means the dynamic responses level will be increased by the increase of attitude; there is not strict correlation between acceleration amplification coefficient and attitude because of the superposition of above effects.4. A large physical model of tailings pond which include its ground and surrounding massif is built, the model test of the dynamic responses research is completed by large-scale shaking table, the conclusions of the test as following:(1) the dynamic responses of tailing pond are dull to the input seismic waveform but sensitive to the peak of input seismic acceleration, so the dynamic responses are affected by peak seismic acceleration, which means the level of acceleration magnification will be higher with lower peak seismic acceleration. (2) Dynamic responses are affected by medium stiffness, which means the displacement of monitoring points and their average values will be increased, whereas the acceleration amplification coefficient will be decreased with the increase of moisture content of tailings, in other words, the more soft of tailings, the higher of the magnification level. (3) Dynamic responses are affected by medium catastrophe, which means the contact regions of tailings pond and mountain or model boundary have high level of acceleration magnification when the tailings has low stiffness; the effect will be amplified with the decrease of tailings stiffness. (4) Dynamic responses are affected by attitude, which means dynamic magnification shows positive correlation with attitude, but the top of embankment is not the highest region of acceleration magnification because of the superposition of above effects.5. The general characteristics of tailings pond dynamic responses are summarized by comparing the results of numerical and model test. The mechanical mechanism of the characteristics of tailings pond dynamic responses is discussed by using the shear vibration model and the conservation of energy principle. The results of numerical simulation and model test are almost consistent. The research achievements of this paper have important significance for the research of earthquake resistant design and seismic measures of tailings pond and revealing the dynamic responses rules of large scale structures under earthquake.