Investigation and disposal of hidden danger of open-pit mine slope and dump

I. Factors affecting slope stability

(1) Influence of rock strength and rock mass structure on slope

1. The effect of rock strength

Most landslides are shear failure, so the shear strength of rock is a necessary condition to measure the stability of slope.

2. Influence of rock mass structural plane

The instability of rock mass usually occurs along the structural plane. The influence of rock mass structure on slope stability is that the cracks in the rock mass structure plane are often filled with secondary minerals that are easy to weather. The developed rock mass provides a good channel for the infiltration of surface water and the activity of groundwater.

(2) Influence of hydrogeological conditions on slope stability

The influence of water on the stability of slope rock mass is great. A large number of facts have proved that landslides usually occur in rainy season or thawing period.

1. Hydrostatic pressure and buoyancy

The direction of hydrostatic pressure is perpendicular to the fracture wall, forming a triangular stress distribution, which is a driving force to promote slope failure.

2. Hydrodynamic pressure

The direction of water is consistent with the direction of infiltration, especially when the groundwater is connected with the structural plane, the threat to the stability of the slope is greater.

3. Physical and chemical damage of rock mass on slope caused by water

The physical effect of water on rock mass is to fracture it. When water freezes, it may have a great expansion force on rock mass, and the evaporation of water often leads to shrinkage cracking, which leads to different degrees of damage.

The chemical action of water on rock mass is manifested in that, under certain conditions, minerals in rock mass absorb or lose water molecules, resulting in hydration or dehydration, which can cause the expansion or contraction of mineral volume in the process of water absorption or dehydration, especially in the presence of CO2, resulting in the destruction of rock mass.

(3) The influence of blasting vibration on slope stability

Open pit blasting is an important factor affecting slope stability. The rock mass of slope is deformed and destroyed under the instantaneous impact of blasting power.

The crack zone produced by blasting vibration is often one of the important reasons that lead to the collapse or sliding of slope rock mass.

(4) The influence of other factors on slope stability

1. Slope geometry

From the point of view of rock stability, conical stope is the most ideal. Convex slope is suitable for open pit slope with soil or weathered rock mass in the upper part and high strength in the deep part.

2. Surface mining depth

3. weathering

4. Human factor

For example, the accumulation of stones and equipment in the upper part of the slope and the establishment of various buildings, some mines dig the foot of the slope and so on.

Second, slope stability monitoring and evaluation

(1) Slope stability monitoring

(1) Parameters of the slope. Such as the structure of the slope, the thickness of the topsoil, the length of the slope, the height of the slope, the width of various platforms, and the angles of various slopes.

(2) Observation of slope rock mass structure and slope movement. The structure of rock mass mainly refers to structural planes such as faults and large joints. It is required to draw the position of the structural plane on the slope and record the relevant parameters. The observation of slope movement refers to the use of instruments or simple equipment to detect the displacement and deformation law of slope rock mass.

(3) Overall observation and inspection of the slope. The main inspection is whether there is illegal mining on the production slope, such as the location, scope and severity of illegal mining such as umbrella eaves, Yinshan canes, voids, etc. should be sketched.

(4) Groundwater monitoring. Groundwater monitoring includes monitoring of water pressure and water level. The pore water or fracture water pressure can be measured by pipe pressure gauges or "zero flow" pressure gauges, and should be installed and measured at different depths in boreholes with confined water. Groundwater level observation is also a common observation method for monitoring slope stability and evaluating the reliability of drainage measures.

(5) Monitoring of earthquake and blasting vibration.

(2) Slope stability analysis and evaluation

According to the monitoring data of slope stability, it is concluded that the monitored slope belongs to stable slope or unstable slope through analysis. An unstable slope can be determined if the following problems exist:

(1) Most of the parameters of the slope do not meet the specified requirements.

(2) In the slope parameters of a certain test section, the slope Angle exceeds the specified requirements, which may cause the collapse and failure of the rock mass of the slope.

(3) The topsoil layer in the upper part of the stope is not stripped in advance according to the requirements, resulting in the upper slope Angle exceeding the requirements may cause the topsoil collapse phenomenon.

(4) According to the monitoring analysis, there are advantageous structural planes in the rock mass of the slope in the stope, which may cause local damage to the rock mass of the slope.