Improvement of Workflow for Topographic Surveys in Long Highwalls of Open Pit Mines with an Unmanned Aerial Vehicle and Structure from Motion

Conducting topographic surveys in active mines is challenging due ongoing operations and hazards, particularly in highwalls subject to constant and active mass movements (rock and earth falls, slides and flows). These vertical and long surfaces are the core of most mines, as the mineral feeding mining production originates there. They often lack easy and safe access paths. This framework highlights the importance of accomplishing non-contact high-accuracy and detailed topographies to detect instabilities prior to their occurrence. We have conducted drone flights in search of the best settings in terms of altitude mode and camera angle, to produce digital representation of topographies using Structure from Motion. Identification of discontinuities was evaluated, as they are a reliable indicator of potential failure areas. Natural shapes were used as control/check points and were surveyed using a robotic total station with a coaxial camera. The study was conducted in an active kaolin mine near the Alto Tajo Natural Park of East-Central Spain. Here the 140 m highwall is formed by layers of limestone, marls and sands. We demonstrate that for this vertical landscape, a facade drone flight mode combined with a nadir camera angle, and automatically programmed with a computer-based mission planning software, provides the most accurate and detailed topographies, in the shortest time and with increased flight safety. Contrary to previous reports, adding oblique images does not improve accuracy for this configuration. Moreover, neither extra sets of images nor an expert pilot are required. These topographies allowed the detection of 93.5% more discontinuities than the Above Mean Sea Level surveys, the common approach used in mining areas. Our findings improve the present SfM-UAV survey workflows in long highwalls. The versatile topographies are useful for the management and stabilization of highwalls during phases of operation, as well closure-reclamation.

Glacifluviálně-glacilakustrinní sekvence u Vidnavy na severním okraji Žulovské pahorkatiny

Glaciofluvial and glaciolacustrine sediments were discovered in a small sandpit situated 800 m SE from Vindava (the Polský kopec Site). Sediments fill two channels located in superposition. Three facies associations (FA) were distinguished in this sedimentary section. The base of the lower channel is formed by gravel lag overlain by gravel-sandy sediments of 3-D dunes and a side bar (FA1). The upper channel infill begins also by basal lag and grades to a fining-upwards sequence from sand to silt (FA2). The sequence is formed from the base up by sediments of small 3-D dunes, A-type ripples, B-type ripples, C-type ripples, and horizontally laminated sediments. The sequence reveals a vertical transition from glaciofluvial (sand) to glaciolacustrine (silt) sedimentation. The sedimentary section is terminated by flat glaciofluvial bedforms (FA3) deposited under upper plane bed conditions. These bedforms arose after the restoration of glaciofluvial conditions. The base of the glaciolacustrine sequence is located at an altitude of ~ 275 m as well as the Old Kaolin Mine Site (850 m SW from the Polský kopec Site) where very similar sediments have been already described. The sediments of both localities represent a proglacial outwash plain in front of the retreating ice sheet (FA1 consists of ~ 23% of erratic rocks), where a relatively large lake, or a system of smaller lakes evolved at the same time.

The long post-closure period of a kaolin mine

Aiming at deriving good practice recommendations for mine closure, this paper reviews the case of a kaolin mine whose production ceased more than ten years ago, but as yet didn't meet its completion criteria. Document review, interviews and site visits showed that: (i) rework was needed to satisfactorily implement land rehabilitation measures such as contouring, slope stabilization, erosion and sediment control and revegetation; (ii) underground water quality was affected during mine operation, causing the mine to be included in the State contaminated sites register. Despite being a small operation, the closure of this mine illustrates a number of problems faced by mining companies in planning and implementing mine closure measures: (1) lack of clear land rehabilitation objectives; (2) the need to manage liabilities related to contaminated sites; (3) loss of organizational memory. The research found that good practices, generally recommended in guidebooks, were not adopted by the company. The main lesson from this relatively simple case - a small mine situated near a dynamic and expanding urban area - are that decommissioning and closure cannot be a makeshift add-on to mine management; these are not trivial activities and require careful planning and integration with mine planning itself.

A study of cordierite ceramics synthesis from serpentine tailing and kaolin tailing

Cordierite ceramics was synthesized using a composition prepared by the mixture of three different materials: waste serpentine mine tailing (WST), waste kaolin mine tailing (WKT) and alumina. The formation of cordierite was achieved with the solid-state sintering reactions at 1350?C for 3 h. The synthesized cordierite ceramics was characterized by X-ray diffractometer (XRD), thermal analysis (TG-DTA), and SEM-EDS (Scanning Electron Microscopy-Energy Dispersive Spectrometer). The XRD analysis results showed the cordierite with typical rhombic system as a major phase, and its compositions consisted of O, Al, Si and Mg by means of SEM-EDS.