Dynamic Stability Analysis and Forecast of Surface Mine Dump

Malugou Dump is close to Jinduicheng Molybdenum surfaces mine and affected by blasting vibration all its lifetime, it is meaningful to monitor the blasting vibration and analyze the stability of dump under blasting vibration so as to ensure the safety of the dump. Firstly, dynamic test was done about Malugou Dump. Then dynamic stability analysis of the dump is simulated with Geo-studio software. The results show that the present blasting vibration has little effect on the dump and the safety factor of dump under blasting vibration is about 1.158, which indicates that Malugou Dump is safe. At last, the relationship between safety factor and maximum single explosion charge, the horizontal distance between monitoring points and blast source and elevation difference is obtained by simulating and regressing, which can be used as a guidance of production blasting in Jinduicheng Molybdenum mine.


Introduction
Dump is one of the main facilities in mines, and dump stability will be affected by production activities and economic benefits of mines.The factors that affect the stability of dumps are underground water, dumping process, production blasting, rainstorm etc. [1,2].
Malugou Dump is located at 400 meters away from the southeast corner of Jinduicheng opencast, and the total dumping area is 455,517.3m 2 .The dump slope height now is 150 m, and the final designed dump slope height is 205 m.The main geomorphic types in this range are alluvial valleys and erosion slopes with bedrock.Malugou is converged from 4 upriver finger valleys and the largest width of that is 180 m.The valley is overall calabash type with large inside and small outfall.The bedrock slope is widely protruded at both sides of valleys, and the slope ratio is more than 1:2.Most area of slope is lush with plants except few with bedrock exposed.And there is a small range of artificial crushed stones in the dumping area of dump.
The water bodies in the valleys are surface water and groundwater.The surface water is from the natural rainfall, and the maximum daily precipitation at rainstorm of Malugou is 114.11mm.The groundwater is from the Quaternary pore water and the erosion bedrock crevice water.The pore water is located at the region of colluvium gravel soil and alluvial gravel layer, and the maximum buried depth of which is 15 m.The crevice water is small, located at the cracks of bedrock.

Dynamic Stability Analysis of Malugou Dump
A typical section (Figure 1) is selected to analyze the stability of Malugou dump under blasting vibration loading.A 2-dimension model of dump is built with the Geostudio software, X is the horizontal direction, and Y is the vertical direction.There are four testing points, 1#, 2#, 3# and 4# (Figure 2), used to test the dynamic response of dump during production blasting.

Parameters of Dumping Materials
Malugou dump is stacked with four kinds of materials, permeable dam, slag, gravel soil and bedrock.The physical and mechanical parameters (Table 1) [3] of saturated dumping materials are acquired from the related data of Malugou dump.

Dynamic Stability Analysis of Dump
The dynamic stability of Malugou dump is analyzed with Geo-studio software.Firstly the dynamic response of blasting vibration is firstly analyzed in QUAKE/W module, and then the dump slope stability is analyzed in SLOPE/W module [4].The testing data from testing point 4 used to analyze the dynamic stability of dump are listed in Table 2 and       The displacement time history curve (Figure 9) can be obtained by taking a fist-order integral to the measured velocity data with blasting vibration analysis software.
Comparing Figure 8 with Figure 9, a conclusion can be drawn that the values at corresponding moments are almost the same but with contrary symbols.The reason for that is the forward direction defined in monitoring and simulation is opposite.The maximum displacement simulated is 0.000132 m, and the maximum displacement integrated is 0.000134 m.
The safety factor time history curve (Figure 10) and the critical slip surface (Figure 11) of dump under blast-ing vibration can be simulated by Geo-studio.
The stability analysis of fully saturated du asting vibration shows that the minimum safety factor is 1.15772, and the maximum is 1.15792.
Repeating the operation mentioned abov d data 3, the safety coefficient can be obtained, shown in Table 3.The static safety factor of fully saturated dump is about 1.158, which meets the request of Chinese regulation of mine dump.And a conclusion can be drawn that the blasting vibration has little effect on the stability of dump, and the dump is safe.under blasting vibration linearly decreases with the in ctor can be drawn as follows.

According to the physical and mechanical parame fully saturated materials of Malugou dump in Table 1, if
crease of blasting vibration acceleration.And a linear equation between acceleration and the minimum safety fa 1.1573 0.0002 According to the regression treatment of tested data, the relationship between safety factor (Fs) and maximum single explosion charge (Q), the horizontal distance between testing points and blast source (R) and elevation difference (H) can be obtained as follows.
From the equation above, the safety factor of the dump under the production blasting can be calculated as long as the maximum single explosion charge, the horizontal distance between testing points and blast source, and elevation difference are known, which is an effective method to guide the production blasting of Jinduicheng molybdenum mine.

Conclusions
the peak acceleration curves of data 1 are shown in Figures 3 and 4.

Figure 1 .
Figure 1.Typical section of present dump.

Figure 3 .
Figure 3. Measured acceleration time history curve of X Figure 4. Measured acceleration time history curve of Y direction.direction.

Figure 10 .
Figure 10.Safety factor time history curve.

Figure
Figure 11.Critical slip surface.

Figure 12 .
Figure 12.Initial acceleration time history curve of horizontal direction.

Figure 13 .y
Figure 13.Initial acceleration time history curve of vertical direction.

Figure 18 .
Figure 18.Safety factor time history curve with magnification of 500 times.

Figure 19 .
Figure 19.Safety factor time history curve with magnification of 1000 times.

Figure 21 .
Figure 21.Critical slip surface of dump under blasting vibration.

FigureFigure 23 .
Figure 22.Relationship between minimum safety factor.horizontal acceleration and The dynamic stability of fully saturated Malugou dump under blasting vibration from Jinduicheng Mo bdenum h Geo-studio software.And different safety factor time history curves with the change om the simulation.maximum single explosion charge, the horizontal distance between monitoring points and blast sou elevation difference is obtained based on numeric lation and regression analysis, which is helpful to the H. Yang, "Slope Stability Controlling Typical Dumps," Metallurgical Industry ly open pit mine is analyzed wit of accelerations are obtained fr Th basically maintains a constant value of 1.158.And the minimum safety factor of dump under blasting vibration linearly decreases with the increase of blasting vibration acceleration.An equation between the safety factor rce, and al simuproduction blasting in Jinduicheng Molybdenum mine.