Cost effective photogrammetric measurements as possible solution for convergence and lining deformations monitoring in KGHM SW-4 mineshaft

This article investigates the feasibility of using cost-effective photogrammetry for monitoring convergence and lining deformation in the SW-4 mineshaft operated by KGHM. The study begins with a detailed description of the geological and operational environment of the mineshaft, with particular emphasis on the challenges posed by the rheological behavior of rock salt, which can lead to time-dependent deformations impacting shaft stability and safety. The methodology includes an overview of conventional convergence measurement techniques currently in use, followed by the design and implementation of a custom stereo-photogrammetric research platform. This platform was subjected to comprehensive validation, both in surface conditions and within the underground environment of the shaft. Surface trials incorporated comparative analysis with data acquired using a professional terrestrial laser scanner to assess the accuracy and reliability of the photogrammetric approach. Despite certain limitations in data acquisition due to the harsh underground conditions, two successful photogrammetric surveys were conducted within a shaft interval previously measured using high-precision laser tachymetry. These trials produced two dense point clouds that enabled precise measurement of displacement in both the shaft lining and the mining face over a four-month period. The results demonstrate the potential of this approach for detecting small-scale deformations and suggest that, with minor refinements to data capture and processing workflows, the proposed method can become a valuable tool for long-term monitoring and geomechanical analysis in the SW-4 rock salt section.