Determining the productivity of excavating rocks with water jets

Abstract

1. Local caving of a rock or soil when acted on by a water jet begins at the moment when the ratio of the head to the jet diameter at its zone of impact on the face reaches a certain value which depends on the characteristics of the material being worked, i.e., its porosity (permeability), particle diameter, and tensile strength (Formula (2)). 2. The productivity of local washing excavation depends on the hydraulic characteristics of the water jet (power and diameter) and the water-strength characteristics of the rock being worked (the permeability in the direction of the jet and the tensile strength). 3. The productivity of local caving by various water jets (m3/h) is proportional to the jet power, to the square root of the permeability, and to the size of the particles broken away by the jet, and inversely proportional to the jet diameter at its zone of incidence and the tensile strength of the rock (formula (14)). 4. The rate of undercutting of the face (the undercut area per unit time) is independent of the jet diameter. It is proportional to the dynamic jet head (at the point of impact) raised to the power 3/2, to the square root of the permeability of the rock (in the direction of action of the jet), and to the diameter of the particles broken off, and is inversely proportional to the tensile strength of the worked material (formula (15)). In addition, it depends on correct management of the jet.