Application of the terrestrial laser scanner technology to measure strata displacements in underground excavations is becoming increasingly popular due to broad spectrum of measured data, its ease of use and data quality it produces. Mine environment presents many challenging problems that limit application of the laser scanner technology in unfavorable conditions including the explosion risk atmosphere, dust, humidity and instability of mine excavations. This technology has been currently used to monitor the coal mine roadway and pillar stability in the firstly developed room and pillar panel trial in the Czech part of Upper Silesian Coal Basin (Czech Republic). The purpose is to monitor the long term coal pillar deformations that develop over time. A comprehensive picture of the ongoing strata deformation has been obtained from the repetitive laser scanning results. The strong roof strata subject to minimum deformation has provided the stable reference for scanning purpose which is very important in evaluation process. The difference between each scan was then used to detect changes in strata displacements.
The room and pillar method has been trialled in the shaft protective pillar at the CSM Mine within the Upper Silesian Coal Basin. A comprehensive coal pillar monitoring was essential as this was the first application of the room and pillar mining method in the Czech Republic at great depth. Two selected coal pillars (V1 and V2) within the panel V located in the seam No. 30 were intensively monitored to ensure stability of the panel and safe mining procedures (see Figure 1). Several monitoring instruments were used to measure stresses, displacements and load of bolting in this trial (Waclawik et al. 2015). By coal pillar V2, one of these instruments was the 3D laser scanner to measure strata surface displacements during and after mining took place.
Laser scanning has started to be a widely applied technology in a variety of industries. These scanning systems excel in the ability to provide contactless determination of spatial coordinates of any object such as buildings, interior space, terrain and other structures. To survey the entire area of interest it is usually essential to take scans from several positions that are automatically stitched together. The method can be used with exceptional speed, accuracy, comprehensiveness and safety. The scanned objects are visualised in the form of a point cloud, which can be subsequently used for a wide variety of analytical tasks, and also to generate 3-dimensional models of these objects (Kuda et al. 2014).