Vegetation Filtering of a Steep Rugged Terrain: The Performance of Standard Algorithms and a Newly Proposed Workflow on an Example of a Railway Ledge

Point clouds derived using structure from motion (SfM) algorithms from unmanned aerial vehicles (UAVs) are increasingly used in civil engineering practice. This includes areas such as (vegetated) rock outcrops or faces above linear constructions (e.g., railways) where accurate terrain identification, i.e., ground filtering, is highly difficult but, at the same time, important for safety management. In this paper, we evaluated the performance of standard geometrical ground filtering algorithms (a progressive morphological filter (PMF), a simple morphological filter (SMRF) or a cloth simulation filter (CSF)) and a structural filter, CANUPO (CAractérisation de NUages de POints), for ground identification in a point cloud derived by SfM from UAV imagery in such an area (a railway ledge and the adjacent rock face). The performance was evaluated both in the original position and after levelling the point cloud (its transformation into the horizontal plane). The poor results of geometrical filters (total errors of approximately 6–60% with PMF performing the worst) and a mediocre result of CANUPO (approximately 4%) led us to combine these complementary approaches, yielding total errors of 1.2% (CANUPO+SMRF) and 0.9% (CANUPO+CSF). This new technique could represent an excellent solution for ground filtering of high-density point clouds of such steep vegetated areas that can be well-used, for example, in civil engineering practice.

Hydrodynamical and Hydrochemical Assessment of Pumped-Storage Hydropower (PSH) Using an Open Pit: The Case of Obourg Chalk Quarry in Belgium

Pumped storage hydropower (PSH) enables the temporary storage of energy, including from intermittent renewable sources, and provides answers to the difficulties related to the mismatch between supply and demand of electrical energy over time. Implementing a PSH station requires two reservoirs at different elevations and with large volumes of water. The idea of using old, flooded open-pit quarries as a lower reservoir has recently emerged. However, quarries cannot be considered as impervious reservoirs, and they are connected to the surrounding aquifers. As a result, PSH activities may entail environmental impacts. The alternation of the pumping–discharge cycles generates rapid and periodic hydraulic head fluctuations in the quarry, which propagate into the surrounding rock media forcing the exchange of water and inducing the aeration of groundwater. This aeration can destabilize the chemical balances between groundwater and minerals in the underground rock media. In this study, two numerical groundwater models based on the chalk quarry of Obourg (Belgium) were developed considering realistic pumping–discharge scenarios. The aim of these models was to investigate the hydrodynamic and hydrochemical impact of PSH activities on water inside the quarry and in the surrounding rock media. Results showed that (1) water exchanges between the quarry and the adjacent rock media have a significant influence on the hydraulic head, (2) the frequency of the pump–discharge scenarios influence the potential environmental impacts, and (3), in the case of chalk formations, the expected impact of PSH on the water chemical composition is relatively limited around the quarry. Results highlight that those hydrogeological and hydrochemical concerns should be assessed when developing a project of a PSH installation using a quarry as a lower reservoir, considering all particularities of the proposed sites.

MODERN METHODS OF GROUND-BASED INTERFEROMETRY IN MONITORING ADJACENT ROCK MASSES IN OPEN PIT MINING

This article analyzes modern monitoring methods using ground-based interferometric radars. Currently, there are only a few companies on the world market that offer interferometric scanning solutions. These are IDS (Italy), part of the Hexagon group, Groundprobe (Australia), Reutech (South Africa) and the very rare LISA (JRC-Lisalab) and GPRI (Gamma Remote Sensing). Such radars can be used in the open pit mine development of mineral resources for monitoring the safety of adjacent rock masses, dumps and dams. The article considers the general principle of interferometric radars’ operation and differences between them. It also describes different types of aerials, which are being used nowadays in ground-based interferometric scanning. The analysis results enabled to formulate the recommendations for using different type radars depending on the strategy of geotechnical monitoring.

Moderate blasting technologies: Experience and prospects for introduction in Polyus mines

It is commonly known that rock fragmentation by blasting is the most economically efficient method to prepare large volumes of rock mass to excavation and handling. The drilling and blasting technology accepted by a mine governs both rock fragmentation quality and mining safety connected with slope stability. Therefore, optimization of drilling and blasting is an objective calling for the effective blast design and control. This article presents the main principles and methods of moderate blasting implemented at Polyus company towards minimization of impact on pit walls and benches. The main point is stagewise reduction of the dynamic effect exerted by blasting on rock mass when approaching the ultimate pit limits. Polyus company initiated the far and wide review and introduction of the best international practices for improvement of blasting operations near the ultimate pit limits. The article describes the activities undertaken within implementation of projects on drilling and blasting technology justification and improvement to enhance stability of pit walls and, as a consequence, to reduce geotechnical hazards. As a complimentary measure to abate seismic effect of explosions on adjacent rock mass, the nonelectric blasting is replaced by electronic blast initiation systems with more accurate delay intervals, which almost nullifies probability of simultaneous ignition of two or more charges and ensures, thereby, the acceptable and seismically safe modes of blasting of large rock blocks. Furthermore, the introduction of the electronic blasting cardinally changes the approach to blasting order and sequence per intervals in blast holes depending on the current task within a block to be blasted.

APPLICATION OF THE GROUND LASER SCANNING RESULTS IN MONITORING OF ADJACENT ROCK MASSES OF DEEP CAREERS

The method of laser scanning, used in combination with the traditional mine surveying, is one of the most effective and safest ways to carry out mine surveying and instrumental observations on deforming areas of open mining objects. The article presents the results of ground-based laser scanning of the Kharanutsky coal pit and a comparative analysis to determine the deformations and displacements of the sides for different periods, which was performed in the RISCAN PRO environment. Digital elevation models (DEM) were built, distinguishing observation cycles by color. As a result of comparison, the places of manifestation of deformations and displacements were revealed. Based on the results of geomonitoring, it was concluded that critical displacements and deformations were not detected, despite the places where small rockslides were manifested, and further systematic observations were recommended. The results of laser scanning are confirmed by the data of satellite observations on the control points and the survey of the section sides

NUMERICAL SIMULATION OF THE STABILITY OF THE SIDES OF COAL MINES UNDER THE INFLUENCE OF DISTRIBUTED LOADS

The open method of solid minerals winning occupies a significant place in the total opening of the mining complex deposits of the Republic of Kazakhstan. In the energy band, a prominent role belongs to the Ekibastuz coal basin, where a number of large coal strip mine operates. The level of subsurface, equal parts of spoil bank of the external and internal stripping after a while lead to complex problems of ensuring the stability and safety of mining operations. The location of large external rock dumps on the bead surface has a negative effect on the stability of the latter. The purpose of the work was to establish the degree of the external rock dump influence located on the bead surface on the stability of adjacent rock mass of the coalmine depending on the distance of the dump to the upper edge of the side. There was numerical simulation of stress-strain state of adjacent rock mass under action of distributed load from rock dump carried out. It has been shown that studies of any point stability of the array from this type of load should be carried out on the basis of elasticity and the use of the finite element method theory implemented in packages of programs oriented specifically to scientific and engineering applications. There are the methodology and results of numerical modeling of quantitative assessments of various sections stability of the side loaded with an external rock dump with a height of 160m presented on the example of «Ekibastuz» coal mine. Based on a certain theory of rock strength and the criteria for their discontinuity, limit estimates of the critical distance of the external rock dump from the upper edge of the side were obtained, at which the latter may lose stability.