25 / 2020-03-01 04:50:44

Comprehensive inventory surveys of the shaft hoist assembly using laser technologies

headframe, shaft, dynamic, laser scanning, GNSS

The shaft hoist assembly, understood as the hoisting machine, the headframe and the shaft, is the basis for the manufacturing of the underground mine. The measuring service periodically or continuously monitors the state of the geometry of the hoist assembly, indicating the rectification process. The purpose of those surveys is a comprehensive inventory of the hoisting machine, including determining the rope friction angles on the pulleys and machine drum, the inclination of the hoisting machine shafts and the pulleys and determining the verticality of the headframe. Exceeding of those factors may lead to critical failures. The classical methods of geodetic inventory surveys used so far were usually based on plumbing, angle-linear indentation or projection.
Currently, replacing optical plumbing and angle-linear measurements or tachoemetry by laser plumbing and scanning, it is possible to obtain significantly much more information in the shortest time. Additionally, the use of laser technologies can be crucial from not only an economic point of view, but also for the safety of employees performing measurements. Laser scanners provide a huge amount of data about spatial objects in non-invasive way. The final product of scanning process is a point cloud which contains from several hundred to several hundred million points with known Cartesian coordinates. Intensity of the reflected laser beam is the fourth coordinate. Moreover, adding oriented photos provides R, G, B data, therefore the point cloud can be represent in real colours. In comparison to classic geodetic surveys such as tacheometry, point clouds consist not only of characteristic (chosen by the surveyor) points on the object, but it is also the representation of the entire surroundings, the shape, orientation, location and size of objects in a very high resolution. Furthermore, scanning takes place automatically and allow to perform other geodetic works during the measurement. What can be also important underground – laser scanners do not require lighting.
This article presents the results of the headframes stability measurements carried out with a FARO FOCUS 3D laser scanner. The device enables the acquisition of the data with a resolution of 5 mm per 10 m distance with an accuracy not worse than ± 2 mm for a single measuring station. Additionally, elements crucial for the performed analysis (inclination of hoisting machine shafts and pulleys) have been determined by the precision levelling. Precise measurements of the geodetic network ensured the internal consistency of the point cloud. Another important aspects of the research was dynamic test of headframe’s inclination during its’ operation. The research was carried out using laser scanning technology, compared to GNSS reference surveys, at the movement of the shaft cage at a speed of 2 m/s.
The point clouds from laser scanning measurements allowed to make digital models of inventoried headframes, allowing for subsequent analyses. Post-processing of the data was based on determining the characteristic points located on the axles of hoisting machines and rope wheels and establishing transverse profiles on headframes and on the ropes. The characteristic points database obtained in this way was used to make a spatial arrangement of the machine drum axis, rope wheels, headframe structure and ropes. Sketches of azimuths of rope axes, wheels and drum shaft, real angles of friction, shaft inclination and verticality of ropes descent into the shaft from the level of rope wheels were presented for the machine-rope wheel assembly. The all collected information allows to determine whether the inventoried object can be still use safely, obtain data necessary for rectification and BIM purposes, and also is a great source needed to complete the documentation required by the law regulations.