Drilling and blasting operations in the cyclic-flow technology of earth-dam construction

Abstract

The cyclic-flow technology in the construction of high earth dams is the most effective, providing an increase in the rate of construction, reduction of construction time, and decrease of labor consumption. One of the labor-consuming processes in earth-dam construction is the transport of materials from borrow pits to the dam. With the existing cyclic technology it is accomplished mainly by dump trucks. In the cyclic-flow technology of earthworks the material is transported from the borrow pit or quarry by continuous mechanisms, particularly conveyors. This type of transport in comparison with vehicular is less labor-consuming and cheaper [I]. However, on the existing belt conveyors it is possible to transport material with a panicle size to 400 mm [2], and in the case of a flexible suspension of the conveyor rollers up to 600 ram. The quarry rock obtained by blasting has a size to 1600 mm and more [3].Conveyors that can transport ran-of-pit rock larger than 600 mm are presently being developed. Presently, large rock before delivery to the conveyor belt is crushed to transportable pieces. In this connection, loosening of the rock in the quarry by drilling and blasting is arranged so that the rock has a minimum quantity of oversize pieces larger than 400 ram. The existing traditional drilling and blasting technology in quarries does not always meet these requirements. Blasting is usually done in vertical boreholes on a selected face.The physical and mechanical properties of rocks, their tensile strength, block character of the rock mass and especially fracturing are not taken into account completely in a number of cases when calculating the parameters of drilling and blasting operations. The classification of rock masses [4] according to the degree of fracturing and content of large pieces is given in Table 1.