Metal and nonmetal mine production is the industrial production of high-risk industries, their chances of accidents and deaths account for a large proportion of industrial production in the field of security. Slope stability management is an important part of the safe production of open pit mining. Most of the accidents occurred in open pit mining enterprises are caused by slope instability. The causes of open pit slope damage (mainly collapse and landslide) are often caused by many factors. It can be roughly divided into two categories, natural factors and human factors. The main natural factors are: 1 geological structure (layering, joints, faults, folds, etc.) in the range of the slope; 2 lithology (strength, permeability, porosity, expansion, etc.); 3 groundwater and surface topography, climate Features, earthquakes, etc. The human factors mainly include: 1 the shape of the slope; 2 the blasting vibration around the surface; 3 the vegetation damage on the surface and the artificial structures such as the reservoir and the drainage field. Generally, it is superimposed by several factors, which together cause the slope to be destroyed, but there is also a single factor that causes the slope to be destroyed. When many factors work together, they tend to be dominated by one or two. Other factors only promote this and two factors.
The slope of an open pit mine is an entity that is forcibly controlled in order to meet the needs of producing ore in production activities. In order to achieve safety, speed and economy, the structure and characteristics of the slope are mastered, and the type of damage of the slope is summarized. Related
The technology is especially important in preventing problems before they happen.
Second, the structure and characteristics of hillside open-pit mining slope
In hillside open-pit mining, the ore is usually divided into horizontal layers of a certain thickness and is mined from top to bottom. As a result of this mining, open-pit mining forms stepped steps, often referred to as step mining. A slope consisting of multiple steps is called an open pit mine side, that is, the final slope of an open pit mine. This method is mostly used for large-scale exposed mining mountains, and multiple working faces can be operated at the same time without affecting each other. There is also a special case for small open pit mining. That is, according to the Interim Provisions on the Safety Production of Small Open-pit Quarry, promulgated and implemented by the State Administration of Work Safety, "If step-type mining is not possible, it shall be mined from top to bottom." The method is to divide the open-pit mining ore into a plurality of parallel strips from top to bottom, and then divide the first block (the outermost strip) from top to bottom into several stages, first mining the uppermost nugget, Mining down in turn. At each stage, the ore is thrown to the bottom platform of the stope, also called the bottom working flat plate, and the rear shovel is shipped out. {The first block is mined, and the second, third, and nth blocks are successively mined. . Until mining to the bottom platform of the stope, start a new round of mining from the second block. In this way, the side of the open pit mine has been two steps, that is, the highest point on the slope of the soil and the step being produced. When the mining is over, two conditions are also formed: the former slope of the former is an imaginary slope composed of a plurality of steps; the latter is a perfect slope. For the latter, it is also considered to add some steps according to the geological structure when the final slope is formed, such as a safety platform and a cleaning platform to enhance its stability.
For hillside open-pit mining, the final slope angle is limited by the engineering geological conditions and height of the rock mass. The general structure of the final slope consists of a safety platform, a sweeping platform and a transport platform. The final slope angle, steps, mining height and various technical parameters are generally determined by design before mining.
The characteristics of the slope basically have five aspects: 1 the upper slope has a long service life and the lower slope has a short service life, so the stability of the upper and lower slopes should be treated separately. 2Slope-type open-pit mining slopes are generally high, ranging from tens of meters to several hundred meters. The length of strikes ranges from tens of meters to several kilometers. Therefore, there are many strata exposed by slopes, and the geological strips of different parts are large and complex. . 3 Mining frequently perforates, blasts and transports every day. Slope rock mass is often affected by external force vibration. 4 Open pit slopes are formed by means of perforation, blasting, mechanical (or manpower) excavation. The slope rock mass is relatively broken, and it is easily affected by weathering and other secondary cracks, which damage the complete stability of the rock mass and reduce the strength of the surrounding rock. 5 The stability of the slope changes with the operation of the mining operation, especially in some small mining mines. The management of the slope is not strict enough and the change is greater.
Third, the type of damage of the slope
Open-pit mining itself is a kind of damage to the original rock. The mining operation breaks the original stress balance state inside the rock mass of the slope, and the secondary stress field appears. The slope is often caused by the secondary stress field and other factors. The rock mass is deformed and destroyed, that is, the rock mass is unstable. The type of rock failure of slope can be divided into plane failure, wedge failure, circular arc damage and dumping damage according to the type of failure.
(1) Plane slope failure: This type of failure means that the slope slides along a major structural plane such as a layer, joint or fault plane, and its sliding line exhibits linearity. Such a sliding failure is likely to occur if there is a structural weak surface in the slope that is similar or consistent with the slope tendency, and the inclination angle is smaller than the slope angle and smaller than the internal friction angle between the weak surfaces. When the lower end of the structural plane is exposed on the slope, the shear strength of the rock layer cannot resist the sliding force of the sliding rock mass, that is, the damage occurs along the plane.
(2) Wedge failure: In the slope rock mass, two or more sets of structural planes intersect with the slope, and the rock masses are mutually intersected into a wedge shape to cause damage. When the tendency of the combined intersection of two or more sets of structural planes is similar to the slope, the inclination is smaller than the slope angle and larger than the internal friction angle of the structural plane, such sliding is likely to occur, which sometimes occurs in a single On the steps, it may also occur on several steps or even on the entire slope.
(3) Arc-shaped damage: When the rock mass of the slope is damaged, its sliding surface is broken by arc. This type of damage generally occurs in earthy ore bodies or in rocks with moderate toughness. The fractured rock mass of a loose-body structure or the slope of a weak sedimentary rock is often destroyed in this form, and the damaged side is destroyed before the damage. Slopes often exhibit significant static cracks and deformation.
(4) Dumping damage: When the structural plane or level in the rock mass is steep, each single-layer weak surface is deformed by the moment formed by gravity and deformed to the free surface. When the structural plane of the layered rock mass is parallel to the slope, the tendency of the structural plane is opposite to that of the slope, and the inclination angle is between 70° and 80°, due to the compression of the rock mass at the foot of the slope, or due to the overburden Extrusion, the layered rock mass is bent, broken and dumped. This type of damage is different from the damage of the first three types. It is mainly not shear failure but lateral collapse of the rock under the action of gravity. This phenomenon often occurs at the bottom of the slope and is also the most dangerous.
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