NEW METHODOLOGY FOR CALCULATING PARAMETERS OF DRILLING AND BLASTING DURING THE CONSTRUCTION OF SUBWAY TUNNELS

Purpose. The aim of this work is to develop a new method for calculating the parameters of drilling and blasting (D&B) for the construction of subway tunnels, taking into account the hole size, the pressure of the blast products, the compressive strength of the rocks, their structural composition, fracturing and compaction under the action of rock pressure. Methodology. To develop a method for calculating the parameters of D&B during the construction of metro tunnels, we used the well-known laws of elasticity theory and the basic provisions of the quasi-static-wave hypothesis of the mechanism of destruction of a solid medium under the action of an explosion, which is based on the principle of placing groups of boreholes according to the areas they occupy in the tunnel face and their location along the blast contours. Findings. A new method for calculating the parameters of D&B in the construction of subway tunnels has been developed. It is based on the principle of arranging groups of blast-holes by the areas they occupy in the tunnel face and arranging them along the blast contours. The first stage of the method includes calculating and designing straight cuts, the distance between the blast-holes in which is determined by the radius of the crushing zone. The second stage of the method includes calculating: specific and total explosive (Е) consumption per face, the value of the line of least resistance (LLR) for a blast-hole by the radius of the intensive crushing zone, areas of blast-holes groups, the number of boreholes, the estimated and actual distance between blast-holes, the actual charge per blast-hole, and the actual specific and total Е consumption per face. Originality. The parameters of the blast-hole arrangement in the face of the interstation tunnel are implemented according to the power dependence of the change in the LLR on the hole size, the pressure of the explosion products, the compressive strength of the rocks, their structural structure, fracturing and compaction under the action of rock pressure. Practical value. The developed method for determining the parameters of D&B for the construction of subway tunnels allows for rationalizing the arrangement of blast-hole in the face and saving resources during tunneling operations by up to 14 %.