| Vietnam is located in the tropical monsoon region,and the climate is divided into two separate seasons: dry and rainy season.Rainfall in the rainy season is large,maximum reaches 3076 mm/yr.Vietnam’s open-pit mines are characterized by seasonally depthed mining,and most of them use trucks to transport rocks and uphill loading.In this case,the cost of transportation and dumping depend on dumping bench height.In addition,the influence of seapage during the rainy season also reduces the slope stability.The paper uses models and experiences to study reasonable dumping bench heights.The results show that the lower the bench,the lower the transportation energy consumption and cost.But the longer the truck hour works,the greater the amount of bulldozing.A reasonable dumping bench height is a condition that satisfies the minimum dumping cost and slope stability.According to the model research and the result of the dump test,the formula for determining the reasonable dumping bench height of Vietnamese open-pit mine is obtained.According to the conditions of different stability coefficients,this paper reveals the relationship between the function of the final slope angle and the function of dump site height,and put forward the dump site final slope angle determining formula.The area of the dump site depend on many different factors.Among them,increasing the height,the final slope angle of the dump site,and reducing the waste rock loosening coefficient are three feasible ways to reduce the area of dump site.These three fators can be adjusted independently in the process of dumping without being affected by the stope and terrain conditions.The increase and decrease rule of waste rock cohesion,internal friction angle and slope stability factors are similar.When waste rock cohesion,internal friction angle decrease they have a greater impact on the stability than when they increase.The lower the height of dumping bench,the more uniform the distribution of rock particles,the smaller the looseness coefficient and the greater the compression effect of the dumper.The dump site slope stability depend on the dump site parameters and the distribution law of waste rock particles in dump site.The pore water pressure increases along the rainfall hours increase,after the rainfall,the pore water pressure continues to increase to the peak value,and then gradually decreases.The law of change of pore water pressure and stability coefficient is similar.When the slope is affected by the blasting vibration,the blasting wave disturbs the rock,broke the conection between rock mass,redistribute rock mass stress and reduce the effective stress,resulting in a decrease in the stability coefficient of the slope.According to the model analysis result,the mainly influence of the dumping site closed to pit on the pit slope stability is that it increases the weight of the sliding body,thereby increasing the sliding force.The distribution of the force components on the slip surface was analyzed in the bedding slope which contains aquifers and weak interlayers.According to the strength of bond and the aquifers distribution in slope,the numerical model is introduced to analyze the stability of the slope.The most dangerous slip surface will occur in the bond between rock layers or in the weak interlayer.According to the seepage theory,the aquifer in the floor slope is modeled,and the vertical drilling system combined with pumps is used to dewater.The finite element method is used to analyze the process of dewatering,and the position of the phreatic surface is predicted.Combined with the clearing method to improve the stability of the floor slope,the stability factors increased after the treatment,ensuring the stability of the slope. |
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