PROCEDURE AND SYSTEM FOR THE PASSIVE GENERATION OF FREE FACES USING THE UNDERGROUND MINING METHOD OF LONG HOLE DRILLING THROUGH THE USE OF SACRIFICIBLE POLYMERIC DUCTS IN CEMENTED FILL

Abstract

The invention consists of a system and procedure for the passive generation of free faces in underground mining (longhole drilling or sublevel stoping), using sacrificial polymer ducts that act as permanent formwork within the cemented backfill. The main objective is to replace the drilling and blasting of free faces with a pre-installed relief cavity, eliminating the operational uncertainty of conventional slots. The system comprises a modular network of ducts (preferably PVC or HDPE) with mechanical strength configured to withstand the hydrostatic pressure of the backfill and low acoustic impedance that facilitates rock expansion during detonation. The technical innovation lies in utilizing the cemented backfill phase of the previous stope to create the necessary void for the next section, guaranteeing an expansion volume free of obstructions, debris, or lithostatic collapses.The system fulfills three fundamental technical functions: 1. Operational shielding, preventing external elements from filling the cavity; 2. Structural support, maintaining the cross-section intact against the pressures of the cemented backfill; and 3. Low-impedance interface, allowing the detonation energy to fragment the polymer without resistance, facilitating the immediate expansion of the rock. The procedure is carried out in the following stages: 1. Installation and Anchoring: After the extraction of the first section of ore, the ducts are positioned using flexible traction elements anchored to the working levels. Safety accessories such as a mobile protection platform and a stop cradle are used to preserve the integrity of the ducts against backfill and hauling equipment. 2.Passive Confinement: A cemented backfill is poured (partially for stabilization and then completely), preserving the void inside the ducts while the material sets. 3. Equivalent Configuration: A modular arrangement is used, the density and geometry of which are determined according to the relief requirements of the working. In a preferred embodiment, the system uses 8 units (configured in 4 columns of coupled ducts), a configuration that proved to optimize the relief area and structural stability in field validations. 4. Successive Exploitation: Once the backfill has set, the production holes are drilled and detonated directly into the preserved void, eliminating the drilling and blasting of free faces from the second section of the bench onward.The implementation of this invention reduced the mining cycle considerably (e.g., from 52 to 35 days) in the mining operation that was tested, optimized the consumption of drilling steels and reduced the consumption of explosives, minimized the dilution of the ore and increased safety by reducing the exposure of personnel in critical opening areas.