The dragline is not flexible enough for loading, the accuracy is not enough, and the efficiency is relatively low. This has limited its application, and construction draglines are mainly used for underwater excavation.
The larger drag shovel found its place in the open-pit mine. Its ultra-long boom enables a large working range and a large excavation depth, which is very suitable for the stripping of the coal mine cover. In pursuit of efficiency. People make draglines bigger and bigger, the working weight increases sharply, so that the crawler-type walking mechanism is difficult to bear. For this reason, a walking type walking mechanism is applied to the dragline to reduce weight.
Longitudinal joints should use hot joints as much as possible. Since the temperature of the admixture of the two adjacent panels is not much different during the echelon operation, the materials at the ply joints can still be squeezed and have good adhesion, as long as a suitable overlap is selected. The amount (usually the smaller the better, the maximum 3 cm), you can get good overlap quality. If a cold seam is used, it should be cut flat with a screed or cut with a cutting machine after cooling to form a flat seam to make subsequent laps easier to control.
Overlapping assembly has two negative impacts on the entire ply and joints: First, it will cause settlement due to roller compaction. Although the amount of settlement is smaller than the pellets of the asphalt mixture, excessive lapping will cause the pellets to break and may cause cold. The organizational structure at the edge of the layer is damaged; the second is that the floating of the screed will be disturbed. The screed is not supported by the asphalt mixture on this side but raised by the height of the overlap area. Obviously, even after compaction, the compactness of the area will inevitably decrease or indent.