INTRODUCTION
Challenges of maintaining adequately high performance and sustainable rate of mining operations, length reduction of the material handling lines, assurance of required economy of the work in deep quarries before the quarry machinery and handling equipment there appear. As a rule, the given conditions are achieved only by sequential use of several types of transport within a uniform transport system, i.e. by means of a combination of transport [1].
THE THEME ACTUALITY
This question has attracted attention of both our and foreign scientists, such as: S.G.Molotilov; E.I.Vasiljev; O.B.Kortelev; Sheshko Å.Å.; Astafjev J.P.; Polishchuk G.K.; Butkevich G.R., etc.
Mining conditions of mineral deposits development in the years to come will be marked by further deepening of the quarry and extension of transportation distances, growth of the hard rock's and ores' share in the total amount of mined rock which is bound to lead to an increase of the mining cost and reduction of its competitiveness. In the view of the above there is a necessity to make essential amendments into the approaches to the solution of quarry operation problems .
The introduction of the combined transport ensures reduction of fuel costs, reduction in personnel numbers, and in some cases - growth of productivity, improvement of quarrymen operating conditions and preservation of the environment while maintaining flexibility of the system which is based upon the use of tippers. With the combined usage each type of transport operates in the most convenient and favourable conditions.
The most complete usage of all the advantages of the combined transport can be achieved if the sphere of its application is correctly substantiated (fig. 1), efficient conditions for trucking operations are created, the latter dependent on number, its location in the quarry and shift interval of the transfer points.
Fig. 1 - Spheres of application of different types of transport depending on quarry's output and transportation distances: 1 - railway transport; 2 - trucking; 3 - conveyors; 4 - rope lines
PRACTICAL VALUE
The practical value of the present work comes down to an increase in quarry's transport system activity that lies in:
THEME DEVELOPMENTS
One of the progressive directions in the field of upgrading the continuous flow machines as well as expansion of their application sphere is deemed to be development and introduction of new designs of high-angle conveyors into different industries [2].
The key problem resulting out of increase of the slope angle is the method of keeping the cargo on the carrying body of the conveyor, the reason being when the angle is increased over the "critical" value the frictional force of a cargo against the carrying body becomes less than the cargo weight longitudinal component at which point the cargo starts sliding downwards [3] .
While scrutinizing the operation of a high-angle conveyor with pusher-bars it has been found that:
Fig. 2 Conveyor's output dependence on its inclination at different trough angles (the given image is animated, 4 staff; 5 recurrences)
LITERATURE USED