The side of the open pit mine

the profile of the sides of the open pit mine

SIDE OF THE OPEN PIT MINE (EN: pit edge, flank of an open cast; DE: Tagebaugrenze, Tagebaurand; FR: parement de carriere; ES: borde talud de una cantera o mina a cielo abierto; RU: борт карьера) is the lateral bounding surface of the open pit mine, which is formed by the set of the slopes and horizontal places of the benches. The lines of intersection between the side of the open pit mine with the Earth's surface and with the bottom of the open pit mine create, respectively, the upper and lower contours of the open pit mine (see the Figure); the angle between the conventional surface, which is passing through them, and horizontal plane, is named the angle of inclination of the side of the open pit mine. They distinguish between the working and non-working sides of the open pit mine: at the working side of the open pit mine, there are conducted the excavation and loading of the rock masses (it moves itself during the process of the mining works), while there is called the non-working the side of the open pit mine, at which mining works are not performed during the given instance of time. During the development of the inclined and steep depositions of useful minerals, there are placed at the non-working side of the open pit mine the protective and transport berms. The parameters for the side of the open pit mine are: the height (the distance along the vertical direction between the upper and lower contours of the open pit mine), and the angles of inclination.

The angle of inclination of the side of the open pit mine at the instance of time during the termination of maintenance works is named the general angle, or the angle of extinguishment, while during the period of operation, it is named the operating angle; this angle depends on the height and angles of inclination of individual benches, on their quantity, on the width of the transport and protective berms. The increase for the angles of inclination for the side of the open pit mine leads to the decrease for the volumes of the mining works (for example, within the open pit mine with the depth of 500 metres, the decrease for the angle of inclination from 45 degrees to 40 degrees leads to the increase for the volume of overburden, namely, for 24 million cubic metres per each 1000 metres along the length of the side of the open pit mine).

(Table) The angles of inclination for the sides of the open pit mine, degrees
Rocks Working side Non-working side
Hard 18-25 35-45
Semi-hard and bound under the usual conditions 18-20 28-35
Clayish, difficult to dry 10-15 18-25

During the establishment of the angles of inclination for the benches and side of the open pit mine, they take into account the physical-mechanical properties of the rocks, which are forming the benches, natural angles of the dip of the layers of the rock stratum. The guidance values for the angles of inclination for the side of the open pit mine for various rocks are given within the table. The stability of the side of the open pit mine is estimated by the analytical methods, which are based on the determination of the shearing and restraining forces, which are acting along the most probable surface of the slip. During the increase of the depth of the open pit mine, and of the intensity of development, there emerges the necessity for the control of the stability for the side of the open pit mine, and for the slopes of the benches. This problem is solved by the special measures: the artificial fixation of the unstable places for the side of open pit mine, and the strengthening of the rocks, which are forming this side of the open pit mine. The principles for the fixation of the slopes are based on the redistribution of the stresses within the massif of the rocks. The means for the fixation of the slopes of the benches, which are used in this case, are: piles, rods, rope cords, retaining and protective walls, buttresses, and others. The artificial fixation for unstable places of the side of the open pit mine provides significant economic effect, permits to increase the economically acceptable depth of the open pit mines for 35-40 metres on average. The strengthening of the rocks within the open pit mines is limited; there has been mastered the method for cementation of the cracked hard rocks in combination with mechanical means of fixation, namely, with piles and rods.