MONITORING OF THE UNDERMINED TERRITORIES OF KARAGANDA COAL BASIN ON THE BASIS OF SATELLITE RADAR INTERFEROMETRY

In the Karaganda coal basin, mines are located in close proximity to each other and to the city of Karaganda and ongoing mining operations are accompanied by a dangerous process of settling the earth's surface and monitoring are essential for the region 's economy. Underground mining leads to the formation of voids in the rock mass, which cause displacement of the earth surface. This paper demonstrates an innovative use of the integrated approach for monitoring on the example of Karaganda coal basin, which includes estimation of the rock mass displacement using leveling profile lines and satellite radar interferometry. It is proved that satellite radar interferometry provides reliable results of surface subsidence measurements in mining areas and can be used for considered sort of monitoring.


INTRODUCTION
The foundations of the satellite radar interferometry were developed at Italian Applied Sciences School in Milano at the beginning of 2000 under supervision of Dr. A. Ferreti (Ferretti, A., Perissin, D., Prati C., Rocca, F., 2004) and Dr. R.F.Hanssen of Delft University of Technology (Hanssen, R., 2001).Many European Universities and research organizations are working on satellite interferometry monitoring problems.Among them are Clausthal University of Technology represented by Dr.W.Bush (Hebel, H., Busch, W., Schäfer, M., Walter, D., 2008) and Dr.S.Knospe (Knospe, S., Busch, W., 2009) Underground mining leads to the formation of voids in the rock mass, which cause displacement of the earth surface.Share voids to prevent collapse caused by displacement of the rock mass, for economic reasons in Kazakhstan are rarely used (Ozhigin S., Nizametdinov F., Ozhigina S., Ozhigin D., 2014).
In the Karaganda coal basin, mines are located in close proximity to each other and to the city of Karaganda and ongoing mining operations are accompanied by a dangerous process of settling the earth's surface and monitoring are essential for the region's economy (Ozhigina S., Urdubayev R., Ozhigin D., Ozhigin S., 2015).
To control these processes in the Karaganda State Technological University in collaboration with Michigan Technological University we are working on a comprehensive approach including calculating the displacement of the earth's surface, leveling profile lines over the undermined mountain range and technology of satellite radar interferometry.In real-time monitoring of large areas of mine workings which undermined the earth's surface, it is necessary to define a method which allows implementing it in real time with high accuracy and clarity.Described in this paper is a comparison of calculation results of displacement of the earth surface, leveling profile lines and received by satellite radar interferometry.Sedimentation showed good reproducibility in the measurement of the earth's surface subsidence underworked mine workings.

DEFINITION OF UNDERMINED EARTH'S SURFACE DISPLACEMENT NEAR KUZEMBAEVA MINE BY METHOD OF GEOMETRICAL LEVELLING
The boundaries of the danger zone were applied to mining plans T. Kuzembaev mine and presented as a circle in Figure 1.They were obtained by superimposing the mining plans of the mine on the image taken from Google maps.In the center of this area is the intersection of the railway track and the A17 freeway (Mozer D., Fofanov O., Yavorskiy V., 2014 ).Work within the limits of the dangerous section was conducted from April to September, which is about 6 months.During this period, coal was mined in the area.Comparing our results with the results of theoretical calculations, it can be noted that the magnitude of subsidence, measured over a period of 6 months differs by 20%.The maximum value of subsidence during this period amounted to 0.16m (leveling) and 0.2 m on theoretical calculations.

DEFINITION OF UNDERMINED EARTH'S SURFACE DISPLACEMENT NEAR KUZEMBAEVA MINE BY METHOD OF THE SATELLITE RADAR INTERFEROMETRY
Currently there are 2 archival chains of radar space pictures from the ENVISAT and ALOS satellite for the territory of Karaganda city.Processed space pictures from ENVISAT satellite showed not absolutely good results.It is connected with lack of a full-fledged chain of pictures of one and the same track of the big temporary and basic line.It is possible to distinguish COSMO_SkyMed, Italy and TerraSAR-X, Germany from the existing satellite systems.Basing on the territory of interest and shooting time the Italian satellite was chosen for implementation of the project.Pairs of space pictures for further processing were chosen in the "Connection Graph tool" of ENVI program in the automated mode.As a result two graphs, which display pairs of space pictures as connections in the network connecting each image with another, were created (figure 5).

Figure 5. Definition base lines of pictures
According to the results of image processing, it was determined that the best pairs of images, with normal baseline to 1000 meters and a small time base to 10 days, and for each of them interferograms (Figure 5) were built (Mansurov, V., Satov, M., Jantuev, R., Kantemirov ,Y., 2012).
Results of processing of radar pictures showed that from April to November there was an intensive formation of subsidence area around a railway crossing and the A17 road.These subsidence troughs are located in areas of coal mining of T. Kuzembayev mine (Figure 6).As a result of space pictures processing subsidence isolines and earth surface subsidence graph for the specific point with the maximum subsidence were made.From the schedule it is notable that the maximum subsidence during supervision period made more than 145mm (Figure 7).This allows make a conclusion about the possibility of using satellite radar interferometry in practical problems of displacement monitoring the earth's surface on undermined areas.

CONCLUSIONS
Values of the ground surface subsidence, obtained by different methods showed good correlation.In this case, the satellite radar interferometry for displacement monitoring of undermined earth surface area has a number of advantages over trad itional methods subsidence surveying and calculation.It should also be noted that it allows us to observe large territory and get visible results and timing of observations depending on the demands.This allows us to recommend satellite radar interferometry as a reliable method for monitoring of subsidence and deformations of the rock mass.

Figure 1 .
Figure 1.Determination of the undermined territory and overlapping on the territory plan in Google Maps

Figure 2 .
Figure 2. Carrying out of a ground monitoringAccording to(Monserrat, O., Crosetto, M., Luzi, G., 2014), the time interval between the re-leveling set, based on the expected velocity of recent vertical crustal movements.Detailed information about the process of displacement, in addition to the initial and final observations, carried out at least 5 sets of observations over the interval:

Figure 3 .
Figure 3. Graphical representation of the earth surface subsidence profile lines as a result of levelling

Figure 6 .
Figure 6.Samples of differential interferogram of the area of T. Kuzembaev mine based on different image pairs

Figure 7 .
Figure 7. Isolines and subsidence graph based on 22 space pictures of the territory of T. Kuzembayev mineFrom the graphs in Figure7it shows that the maximum subsidence during the observation period was 0.145 m.The graph shows that at the point of maximum surface subsidence for the period from April to October, 2014 there is a good correlation between the results of ground measurements and satellite radar monitoring.According to monitoring results , the coal department of Mittal Steel Temirtau.The recommend to add additional sections to the base construction of electric transmission lines, which are on the territory of undermined.In the spring of 2015 electric transmission lines have been reconstructed, thus avoiding breaking high-voltage wires and to prevent disturbance situations.(Figure8)