Natural Hazards

, Volume 65, Issue 3, pp 2311–2330

Monitoring deformations on engineering structures in Kozlu Hard Coal Basin

Authors

    • Department of Geodesy and Photogrammetry Engineering, Engineering FacultyBulent Ecevit University
  • Çetin Mekik
    • Department of Geodesy and Photogrammetry Engineering, Engineering FacultyBulent Ecevit University
  • Şenol Kuşcu
    • Department of Geodesy and Photogrammetry Engineering, Engineering FacultyBulent Ecevit University
  • Hakan Akçın
    • Department of Geodesy and Photogrammetry Engineering, Engineering FacultyBulent Ecevit University
Original Paper

DOI: 10.1007/s11069-012-0477-x

Cite this article as:
Can, E., Mekik, Ç., Kuşcu, Ş. et al. Nat Hazards (2013) 65: 2311. doi:10.1007/s11069-012-0477-x

Abstract

Underground coal mining activities in Kozlu Hard Coal Basin have reached a level affecting ground layers inside the mining seams and the surface just above the mining operations, causing movements in vicinity of the basin. The movements emerge as collapsing in vertical direction and as sliding, curling and bending in horizontal direction and are termed mining subsidence since they exhibit themselves in ground layers and on earth surfaces in mining environments. These mining-induced movements cause damages and destructions on structures inside and on the surface of mining grounds, and the dimensions of these damages depend upon quality of structures and magnitude of movements. In order to contribute toward a solution to these problems and to mitigate the effects arising during and after mining activities, one should identify and investigate damage prone movements and determine the movement–time relationship. Therefore, it is immensely important to observe, investigate, and measure these movements in regions where mining activities take place. This study focuses on the surface movement-related deformations on the engineering structures in the basin such as Kozlu Seaport and some part of the Zonguldak-Kozlu Road. For this reason, subsidence monitoring points were established on the engineering structures in the basin in a geodetic network concept, and three periods of precise leveling and static GPS observations were conducted. Analyzing these two types of geodetic observations, active and residual subsidence effects were determined for both Kozlu Seaport and the Road nearby.

Keywords

Horizontal and vertical displacementsZonguldak Hard Coal BasinKozlu coal production regionEngineering structuresDeformation

1 Introduction

It is a well-known fact that mining production tasks cause to create gaps inside the ground. The ceilings of the gaps withstand the load over it by arching inside the ground and prevent caving-in as long as they are opened deeper into ground and remain in smaller proportions as is the case in mining galleries depending upon the production length. With the production gaps reaching larger dimensions, however, the ground just above the gaps starts to collapse by layers breaking away and fills up the production gaps. The movements of ground on the surface triggered by the collapse of cascading internal ground layers are termed as mining subsidence (Kratzsch 1983; Kusçu 1991; Perski and Jura 2003; Deck et al. 2003; Duzgun 2005; Akçin et al. 2006; Saeidi et al. 2009; Can et al. 2011, 2012a, b; Song et al. 2012; Wang et al. 2008). These movements cause deformations on the earth surface and in the affected ground layers and disruptions on the natural balance of ground (Kwinta 2010). As a consequence of this, engineering structures inside the affected ground and on the earth surface above the subsidence region either accommodate to these deformations or sustain damages. These damages whether they occur on natural or man-made structures by means of mining subsidence are called mining damages. A geometry resembling a tub or a boat emerges on the earth surface under the influence of subsidence occurring during or post-mining activities. This surface which tub-shaping forms on due to mining operations is described as the surface subsidence influence area in which all the structural damages occur (Akçın et al. 2006). Mining subsidence as a result of mine productions underneath the settlement areas, especially in Western European countries where underground coal mining is of great value, has been long a crucial mining issue with economic, social, technical, and environmental aspects. Various scientists recently have conducted studies on adverse mining subsidence effects, especially with regard to urbanization and mining subsidence monitoring on the earth’s surface and the structures. For instance, Mancini et al. (2009) examined salt mining-induced ground subsidence effects on buildings, Wu et al. (2009) submitted a study of the influences of mining subsidence on the ecological environment, and Gayarre et al. (2010) presented a forensic analysis of ground subsidence triggered by the collapse of abandoned underground mining operations. The researchers using synthetic aperture radar (SAR) images deduce that underground mining galleries cause surface subsidence (Wang et al. 2004). There are also a few researchers determining subsidence effects caused by mining operations using interferometric synthetic aperture radar (InSAR) techniques in our test field Zonguldak-Kozlu Hard Coal Basin, where the ground deformations are determined by SAR images (Akçin 2010). Also, Akçin et al. (2006) compare the deformations obtained from the InSAR technique with the ones based on GPS observations and found out the coherence as 0.789 between InSAR and GPS methods interval of 132 days in 1996. Recent publications by Can et al. (2011, 2012a, b) indicate the similar subsidence findings in the same study area. In Zonguldak-Kozlu Hard Coal Region, coal seams dip mostly at high angle and their thicknesses are not uniform; therefore, mining subsidence problems are most likely to occur causing very serious problems with regard to urbanization. This study details the precise leveling and Global Positioning System (GPS) monitoring results for the basin to determine the mining-induced horizontal and vertical displacements.

2 Mining subsidence measurements

It is necessary to gather information on general and regional properties of subsidence formation and effective constituents which eventually cause damages on structures in order to mitigate mining subsidence-induced issues and to provide solutions. Therefore, it is of great importance that subsidence measurements and observation should be conducted on the earth surface and, if necessary, in the underground. Even though the mining activities have been going on for 160 years in Zonguldak Hard Coal Basin, there exists little or no knowledge on this, which is needed dearly today especially with the densification of settlement areas just above the old coal production galleries and mining activities continuing under new settlement areas. The coal seams in Kozlu production region have steep inclinations as is generally the case in Zonguldak Hard Coal Basin (see next section for details of the basin), and the subsidence occurring in this region has adverse effects on social, economic, and legal aspects of life (Turer et al. 2008). Figure 1 depicts the subsidence formation and its influence areas after mining activities in inclined coal seams in the region.
https://static-content.springer.com/image/art%3A10.1007%2Fs11069-012-0477-x/MediaObjects/11069_2012_477_Fig1_HTML.gif
Fig. 1

Subsidence tub forming after production in inclined coal seams and the other related definitions (Kratzsch 1983)

In times when the main source of energy was coal in a region, much of the effort was spent on obtaining coal reserves under the settlement areas with less production losses and subsidence damages as much as possible. This naturally gave way to important work and research for maintaining this purpose and then to the birth of a discipline called subsidence engineering which is specialized in five topics as follows (Kusçu 1991)
  • Subsidence measurements

  • Subsidence estimations

  • Subsidence damages

  • Subsidence control

  • Subsidence-related laws and regulations.

In order to determine the subsidence occurring due to mining activities in an underground mine production region, subsidence measurements are utilized to ascertain:
  • Subsidence parameters (critical and limit angles, displacement values, etc.),

  • Relationship between subsidence and geology, tectonics and topography,

  • Relationship between subsidence and production speed and time,

  • Relationship between subsidence and production method,

  • Damaging effects of subsidence on engineering structures and amenities,

  • Relationship between subsidence and dimensional (geometric) properties such as width, length, and depth of a production gap and thickness of a seam.

  • Legal issues pertaining subsidence induced problems.

A subsidence measurement campaign consisting of geodetic methods to determine the aforementioned aspects should have the stages stated below:
  • Selection of measurement method and equipment, and installing ground markers and monumentation,

  • Establishing a geodetic network and its grid sheet,

  • Conducting geodetic measurements at certain periods,

  • Evaluating and analyzing the measurements, and then interpretation and assessment of findings.

3 Geographical and geological features of Kozlu coal production region

Kozlu-Zonguldak Hard Coal Basin is a formation of the Late Plaeozoic–Mesozoic Age, consisting of various faults and topographic irregularities along the North Anatolian Mountain Range. The town of Kozlu within the Zonguldak Hard Coal Basin was established in 1941 and has a coal production rate of 780,000 ton per year along with 3.3 million ton per year in the whole basin (URL1 2011; URL 2 2011). Kozlu is located in the Western Black Sea Region of Turkey at latitudes 41°–27′N and longitudes 31°–49′E (Citiroglu and Baysal 2011). It borders the city of Zonguldak to the northeast, Eregli to the southwest, Caycuma to the east, and Devrek to the southeast. The coastline forms the north–northwest boundary of the study area (Fig. 2). Kozlu is divided into 7 districts, namely Merkez, Tasbaca, Ihsaniye, Kilic, 19 Mayis, Güney, and Fatih. The settlement of Kozlu is completely surrounded by mountainous areas. The streams within the study area include Kozlu Stream and its branch Kilic Stream (Ekinci 2005). Zonguldak-Kozlu-Kandilli (West Hard Coal Basin) is situated to the west of the Filyos River. The Carboniferous clastic sequence of Zonguldak basin contains several coal seams that have been mined since 1848 by underground methods.
https://static-content.springer.com/image/art%3A10.1007%2Fs11069-012-0477-x/MediaObjects/11069_2012_477_Fig2_HTML.gif
Fig. 2

Kozlu Seaport in Kozlu coal production region (left), Zonguldak-Kozlu Dual Carriageway (right), and the mining galleries in the region (above)

Coal seams are located in a Namurian to Westfalian D progradational delta and fluid plain sequence that is approximately 3,500 m thick (Karacan and Okandan 2000). These units are affected by Hercynian orogenic movements. Related tectonism and uplift led to a widespread erosion. Consequently, younger units, mainly Cretaceous shallow-marine carbonates, rest nonconformably on different sections of the Carboniferous strata. There exist up to 8 coal seams in Namurian, 20–26 in Westfalian A, and up to 8 coal seams in Westfalian B, C, and D. The average combined thickness values are 8, 34, and 7 m, respectively. However, due to the lateral changes in seam thickness and due to the erosion, both the number and combined thickness of coal seams may change remarkably (Duzgun 2005). The process of rapid burial with some occasional interruptions led to an almost continuous increase of coalification. Westfalian strata in this region contain thin coal seams with shales (Karacan and Okandan 2000).

4 Geometrical properties of old and new production panels affecting Kozlu Seaport and Road

The coal seams under the engineering structures focused on in this study have steep inclination angles, and house production panels working on longwall method. Figure 3a and b demonstrates Ikonos satellite images containing old and new production panels just under Kozlu Seaport and the Zonguldak-Kozlu Road with active and residual subsidence effects.
https://static-content.springer.com/image/art%3A10.1007%2Fs11069-012-0477-x/MediaObjects/11069_2012_477_Fig3_HTML.gif
Fig. 3

a Influence areas of old and new production panels in Kozlu Seaport under active and residual subsidence influences. b Influence areas of old and new production panels in Kozlu Road under active and residual subsidence influences

Table 1 lists the geometrical properties of panels in Kozlu Seaport region such as opening year, inclination, thickness, and width, and Table 2 lists the maximum possible subsidence magnitudes and parameters computed in accordance with the Subsidence Engineering Handbook of National Coal Board (NCB) (NCB 1975). Table 3 presents the geometrical properties of production panels under the Zonguldak-Kozlu Road, while Table 4 lists the maximum possible subsidence magnitudes and parameters computed in accordance with the NCB in the same region.
Table 1

Geometrical properties of production panels under Kozlu Seaport

Panel name

Years

Inclination

Thickness (m)

Width (m)

Hmean (m)

E.U.2 (old)

1988

40°

3

60

−456

E.U.3 (old)

1990

40°

3

60

−434

E.U.4 (old)

2004

58°

3

50

−510

E.U.5 (old)

2006

32°

2

110

−508

E.U.6 (old)

1989

26°

1.5

190

−400

E.U. 10 (old)

1987

28°

3

120

−283

E.U.12 (old)

1990

27°

3

80

−256

E.U.13 (old)

1990

17°

3

60

−321

Y.U.2 (new)

2009

29°

2.5

130

−510

Y.U.3 (new)

2009

20°

2

30

−445

Y.U.4 (new)

2009

44°

2

20

−450

Table 2

The maximum possible subsidence magnitudes and parameters computed in accordance with the NCB in Kozlu Seaport region (NCB 1975)

Panel name

Smax (vertical) (cm)

Subsidence type

γlower

γmedium

γupper

E.U.2 (old)

0.4

Residual

28°

55°

85°

E.U.3 (old)

0.2

Residual

28°

55°

85°

E.U.4 (old)

1.1

Residual

29°

55°

84°

E.U.5 (old)

1.3

Residual

29°

55°

83°

E.U.6 (old)

9.5

Residual

32°

55°

81°

E.U. 10 (old)

1.9

Residual

30°

55°

83°

E.U.12 (old)

5.9

Residual

30°

55°

82°

E.U.13 (old)

0.6

Residual

38°

55°

75°

Y.U.2 (new)

3

Active

30°

55°

82°

Y.U.3 (new)

1

Active

37°

55°

76°

Y.U.4 (new)

0.3

Active

27°

55°

85°

Table 3

Geometrical properties of production panels under Kozlu Road

Panel name

Year (m)

Inclination

Thickness (m)

Width (m)

Hmean (m)

E.U.1 (old)

2006

40°

3

60

−417

E.U.2 (old)

1988

40°

3

60

−456

E.U.3 (old)

1990

40°

3

60

−434

E.U.4 (old)

2004

58°

3

50

−510

E.U.5 (old)

2006

32°

2

110

−508

E.U.8 (old)

1986

57°

1.5

60

−441

E.U. 10 (old)

1987

28°

3

120

−283

E.U. 11 (old)

1990

15°

2

80

−96

E.U.12 (old)

1990

27°

3

80

−256

E.U.13 (old)

1990

17°

3

60

−321

E.U.14 (old)

1988

28°

3

110

−339

Y.U.5 (new)

2009

55°

2

10

−462

Y.U.6 (new)

2009

60°

2

10

−492

Y.U.7 (new)

2009

17°

2

10

−447

Y.U.8 (new)

2009

61°

2

20

−494

Y.U.9 (new)

2009

52°

2.5

10

−599

Table 4

The maximum possible subsidence magnitudes and parameters computed in accordance with the NCB in Kozlu Road region (NCB 1975)

Panel name

Smax (vertical) (cm)

Subsidence type

γlower

γmed

γupper

E.U.1 (old)

2.7

Residual

28°

55°

85°

E.U.2 (old)

0.4

Residual

28°

55°

85°

E.U.3 (old)

0.2

Residual

28°

55°

85°

E.U.4 (old)

1.1

Residual

29°

55°

84°

E.U.5 (old)

1.3

Residual

29°

55°

83°

E.U.8 (old)

0.5

Residual

28°

55°

84°

E.U. 10 (old)

1.9

Residual

30°

55°

83°

E.U. 11 (old)

13.5

Residual

38°

55°

74°

E.U.12 (old)

5.9

Residual

30°

55°

82°

E.U.13 (old)

0.6

Residual

38°

55°

75°

E.U.14 (old)

2.2

Residual

30°

55°

82°

Y.U.5 (new)

0.9

Active

28°

55°

85°

Y.U.6 (new)

0.9

Active

30°

55°

84°

Y.U.7 (new)

0.3

Active

39°

55°

74°

Y.U.8 (new)

0.2

Active

30°

55°

83°

Y.U.9 (new)

0.8

Active

28°

55°

86°

Table 5 lists the computed semi-major and semi-minor axes values of an ellipse enveloping possible subsidence affected areas of old and new production panels in Kozlu Seaport under residual and active subsidence effects for plotting purposes, while Table 6 presents the values for the old and new production panels under the Zonguldak-Kozlu Road.
Table 5

Elliptic parameters for possible subsidence influence areas of old and new production panels in Kozlu Seaport region

Panel name

https://static-content.springer.com/image/art%3A10.1007%2Fs11069-012-0477-x/MediaObjects/11069_2012_477_Figa_HTML.gif Semi-major and -minor axes of subsidenceinfluence areas

a (m)

b (m)

Area (km2)

E.U.2 (old)

1,002

748

0.59

E.U.3 (old)

961

668

0.50

E.U.4 (old)

1,091

994

0.85

E.U.5 (old)

1,147

870

0.78

E.U.6 (old)

1,052

750

0.62

E.U. 10 (old)

693

476

0.26

E.U.12 (old)

591

588

0.27

E.U.13 (old)

565

558

0.24

Y.U.2 (new)

1,142

784

0.70

Y.U.3 (new)

736

652

0.38

Y.U.4 (new)

959

720

0.54

Table 6

Elliptic parameters for possible subsidence influence areas of old and new production panels under Kozlu Road

Panel name

https://static-content.springer.com/image/art%3A10.1007%2Fs11069-012-0477-x/MediaObjects/11069_2012_477_Figb_HTML.gif Semi-major and –minor axes of subsidence influence areas

a (m)

b (m)

Area (km2)

E.U.1 (old)

925

994

0.72

E.U.2 (old)

1,002

748

0.59

E.U.3 (old)

961

668

0.50

E.U.4 (old)

1,091

994

0.85

E.U.5 (old)

1,147

870

0.78

E.U.8 (old)

1,018

836

0.67

E.U. 10 (old)

693

476

0.26

E.U. 11 (old)

243

194

0.04

E.U.12 (old)

591

588

0.27

E.U.13 (old)

565

558

0.24

E.U.14 (old)

791

584

0.36

Y.U.5 (new)

932

646

0.62

Y.U.6 (new)

926

918

0.67

Y.U.7 (new)

690

704

0.38

Y.U.8 (new)

964

760

0.58

Y.U.9 (new)

1,188

1,058

0.99

5 Precise leveling and GPS measurements in Kozlu Seaport and Kozlu Road

In order to determine subsidence magnitudes in the aforementioned region just under the engineering structures, three periods of precise leveling and GPS measurements were conducted in August 2009, May 2010, and November 2010. The 1-h static GPS data were collected at the subsidence monitoring points with an observation epoch of 2009.58 in the first period, 2010.40 in the second period, and 2010.90 in the third period avoiding any multipath creating surroundings (Mekik and Can 2010). The GPS observations were conducted using 7 double frequency GPS receivers with 10° cutoff angle and 5 s intervals so as to determine the horizontal movement component of the subsidence occurred in the region. Each observation set from the periods was first processed in each observation epoch and then all the observation sets from the periods were shifted to the reference epoch of 2009.58 with an intention to ascertain the overall movements in the region. In all processes and assessments, zonal central meridian is chosen to be 33° and GRS-80 ellipsoid is utilized, and also the coordinates and velocities of the three TUSAGA-Aktif (Turkish Continuously Operating Reference Stations Network-CORS-TR) reference stations nearby the study area, namely Karabük, Bartin, and Bolu stations, were used (see Mekik et al. 2011 for the TUSAGA-Aktif network in detail). For the precise leveling works, a digital level and bar code rods were made use and a great attention is paid to employ base plates for leveling rods for extra precision in height determination.

This study focuses on the subsidence monitoring measurements carried out only in Kozlu Seaport and the Zonguldak-Kozlu Road sections of an extensive research enveloping the whole region (Can et al. 2012a). The precise leveling measurements carried out in a geodetic network in the whole region were put on the F-test to determine whether the findings are of subsidence or measurement errors. The F-test values were found to be 42.04 for 1st and 3rd periods, while the F table value remained 2.45. As for the GPS observations, the F-test values were computed to be 3.46 when the F table was 1.23 for the same periods of observations. It is statistically possible to deduce that the results from both types of measurements indicate the deformations or subsidence in the general study area and engineering structures since the computed F values are greater than the table values. Table 7 lists horizontal displacement vectors of subsidence monitoring points T34, T35, T36, T37, T38, T39, and T40 in Kozlu Seaport, while Table 8 lists the points from T1 to T18 in the Zonguldak-Kozlu Road along with their root mean square error (RMSE) values computed using the period pairs, namely the periods of I and II (August 2009 and May 2010), the periods of II and III (May 2009 and November 2010) and the periods of I and III (August 2009 and November 2010). Table 8 lists the horizontal displacement vectors of subsidence monitoring points in the Zonguldak-Kozlu Road with their RMSE values for the period pairs.
Table 7

Horizontal displacement vectors of subsidence monitoring points in Kozlu Seaport with their RMSE values for the period pairs

Point #

Point #

Y (Easting) (m)

X (Northing) (m)

Horizontal disp. vector (m)

RMSE (±) (m)

Differences between periods I and II (August 2009–May 2010)

T.34

T.34

−0.063

0.014

0.065

0.0042

T.35

T.35

−0.069

0.008

0.070

0.0045

T.36

T.36

−0.056

−0.013

0.058

0.0058

T.37

T.37

−0.051

0.005

0.051

0.0063

T.38

T.38

−0.070

0.027

0.075

0.0037

T.39

T.39

−0.068

0.037

0.077

0.0036

T.40

T.40

−0.073

0.051

0.089

0.0054

Differences between periods II and III (May 2010–November 2010)

T.34

T.34

−0.021

0.012

0.024

0.0040

T.35

T.35

−0.016

0.025

0.029

0.0031

T.36

T.36

−0.022

−0.004

0.022

0.0037

T.37

T.37

−0.028

0.004

0.029

0.0028

T.38

T.38

−0.017

0.002

0.017

0.0036

T.39

T.39

−0.017

0.028

0.033

0.0035

T.40

T.40

−0.051

0.039

0.064

0.0034

Differences between periods I and III (August 2009–November 2010)

T.34

T.34

−0.085

0.026

0.089

0.0043

T.35

T.35

−0.085

0.033

0.091

0.0050

T.36

T.36

−0.078

−0.017

0.080

0.0054

T.37

T.37

−0.080

0.009

0.080

0.0063

T.38

T.38

−0.087

0.029

0.092

0.0043

T.39

T.39

−0.085

0.065

0.107

0.0039

T.40

T.40

−0.124

0.089

0.153

0.0052

Influencing production panels: old panels: E.U.2, 3, 4, 5, 6, 10, 12, 13; new panels: Y.U.2, 3, 4

Table 8

Horizontal displacement vectors of subsidence monitoring points in Kozlu Road with their RMSE values for the period pairs

Point #

Point #

Y (Easting) (m)

X (Northing) (m)

Horizontal disp. vector (m)

RMSE (±) (m)

Differences between periods I and II (August 2009–May 2010)

T1

T1

−0.079

0.053

0.095

0.0036

T2

T2

−0.071

0.063

0.095

0.0035

T3

T3

−0.035

0.082

0.089

0.0052

T4

T4

−0.053

0.027

0.059

0.0058

T5

T5

−0.094

0.017

0.096

0.0059

T6

T6

−0.054

0.028

0.061

0.0059

T7

T7

−0.077

0.021

0.080

0.0036

T8

T8

−0.027

0.036

0.045

0.0066

T9

T9

−0.038

0.007

0.039

0.0062

T10

T10

−0.060

0.024

0.065

0.0044

T11

T11

−0.033

0.003

0.033

0.0045

T12

T12

−0.043

0.009

0.044

0.0072

T13

T13

−0.021

0.008

0.022

0.0063

T14

T14

−0.026

0.003

0.026

0.0067

T15

T15

−0.010

0.014

0.017

0.0047

T16

T16

−0.011

0.010

0.015

0.0061

T17

T17

0.020

−0.009

0.022

0.0058

T18

T18

0.018

−0.007

0.019

0.0045

Differences between periods II and III (May 2010–November 2010)

T1

T1

−0.019

−0.001

0.019

0.0036

T2

T2

−0.034

0.015

0.037

0.0030

T3

T3

−0.016

0.007

0.017

0.0044

T4

T4

−0.013

0.013

0.018

0.0031

T5

T5

−0.015

0.047

0.049

0.0037

T6

T6

−0.024

0.015

0.028

0.0041

T7

T7

−0.015

0.019

0.024

0.0033

T8

T8

−0.028

0.011

0.030

0.0038

T9

T9

−0.026

0.002

0.026

0.0037

T10

T10

−0.022

0.002

0.022

0.0043

T11

T11

−0.027

−0.012

0.030

0.0030

T12

T12

−0.026

−0.011

0.028

0.0028

T13

T13

−0.007

−0.004

0.008

0.0045

T14

T14

−0.005

0.013

0.014

0.0042

T15

T15

−0.002

−0.009

0.009

0.0037

T16

T16

−0.001

−0.011

0.011

0.0028

T17

T17

0.002

−0.009

0.009

0.0070

T18

T18

0.006

−0.024

0.025

0.0036

Differences between periods I and III (August 2009–November 2010)

T1

T1

−0.098

0.052

0.111

0.0041

T2

T2

−0.105

0.078

0.131

0.0031

T3

T3

−0.051

0.089

0.103

0.0056

T4

T4

−0.066

0.040

0.077

0.0053

T5

T5

−0.109

0.064

0.126

0.0064

T6

T6

−0.078

0.043

0.089

0.0064

T7

T7

−0.092

0.040

0.100

0.0037

T8

T8

−0.055

0.047

0.072

0.0078

T9

T9

−0.064

0.009

0.065

0.0067

T10

T10

−0.082

0.026

0.086

0.0044

T11

T11

−0.060

−0.009

0.061

0.0045

T12

T12

−0.069

−0.002

0.069

0.0073

T13

T13

−0.028

0.004

0.028

0.0070

T14

T14

−0.031

0.016

0.035

0.0062

T15

T15

−0.012

0.005

0.013

0.0052

T16

T16

−0.012

−0.001

0.012

0.0075

T17

T17

0.022

−0.018

0.028

0.0080

T18

T18

0.024

−0.031

0.039

0.0050

Influencing production panels: old panels: E.U.1, 2, 3, 4, 5, 8, 10, 11, 12, 13, 14; new panels: Y.U.5, 6, 7, 8, 9

Figure 4a and b depicts Ikonos satellite images containing horizontal displacement vectors obtained using the three periods of GPS measurements on the subsidence monitoring points in Kozlu Seaport and the Zonguldak-Kozlu Road.
https://static-content.springer.com/image/art%3A10.1007%2Fs11069-012-0477-x/MediaObjects/11069_2012_477_Fig4_HTML.gif
Fig. 4

aHorizontal displacement vectors obtained from GPS measurements in Kozlu Seaport. bHorizontal displacement vectors obtained from GPS measurements in Kozlu Road

Kozlu Seaport and Road are under the influence of both old and new production panels; thus, it is reasonable to consider that residual subsidence is in effect for the horizontal displacement vectors and their directions computed in this study as well as active subsidence. It is hard to imply that horizontal displacements have caused any visual deformations or functional defects in the seaport and road during the three periods of GPS and precise leveling measurements in the region. The maximum subsidence velocity in the Kozlu Seaport, computed by maximum horizontal displacement over 15 months, has been determined 10.2 mm/month on the base of the period pair of I and III. Similarly, the maximum subsidence velocity in the Zonguldak-Kozlu Road has been found as 8.7 mm/month.

As for the vertical displacements, Tables 9 and 10 list the findings obtained from the three period pairs of precise leveling measurements for Kozlu Seaport and the Zonguldak-Kozlu Road, respectively.
Table 9

Vertical displacement vectors of subsidence monitoring points in Kozlu Seaport with their RMSE values for the period pairs

Point #

Vertical displacements (m)

 

Period pair I–II (Aug 2009–May 2010) (m)

RMSE (m)

Period pair II–III (May 2010–Nov 2010) (m)

RMSE (m)

Period pair I–III (Aug 2009–Nov 2010) (m)

RMSE (m)

Period pair III–IV (Nov 2010–Jun 2012) (m)

RMSE (m)

T34

−0.067

0.003

−0.027

0.003

−0.094

0.004

−0.165

0.002

T35

−0.065

0.003

−0.026

0.003

−0.091

0.004

−0.162

0.002

T36

−0.045

0.003

−0.020

0.003

−0.065

0.004

−0.092

0.002

T37

−0.042

0.003

−0.019

0.003

−0.061

0.004

−0.078

0.002

T38

−0.045

0.003

−0.015

0.003

−0.060

0.004

−0.055

0.002

T39

−0.045

0.003

−0.019

0.003

−0.064

0.004

−0.072

0.002

T40

−0.066

0.003

−0.031

0.003

−0.097

0.004

−0.104

0.002

Table 10

Vertical displacement vectors of subsidence monitoring points in Kozlu Road with their RMSE values for the period pairs

Point #

Vertical displacements (m)

Period pair I–II (Aug 2009–May 2010)

RMSE (m)

Period pair II–III (May 2010–Nov 2010)

RMSE (m)

Period pair I–III (Aug 2009–Nov 2010)

RMSE (m)

T1

−0.037

0.003

−0.017

0.003

−0.054

0.004

T2

−0.042

0.003

−0.015

0.003

−0.057

0.004

T3

−0.037

0.003

−0.016

0.003

−0.053

0.004

T4

−0.038

0.003

−0.013

0.003

−0.051

0.004

T5

−0.034

0.003

−0.014

0.003

−0.048

0.004

T6

−0.032

0.003

−0.012

0.003

−0.044

0.004

T7

−0.036

0.003

−0.011

0.003

−0.047

0.004

T8

−0.030

0.003

−0.012

0.003

−0.042

0.004

T9

−0.027

0.003

−0.010

0.003

−0.037

0.004

T10

−0.031

0.003

−0.007

0.003

−0.038

0.004

T11

−0.030

0.003

−0.010

0.003

−0.040

0.004

T12

−0.024

0.003

−0.010

0.003

−0.034

0.004

T13

−0.024

0.003

−0.008

0.003

−0.032

0.004

T14

−0.028

0.003

−0.011

0.003

−0.039

0.003

T15

−0.027

0.002

−0.016

0.003

−0.043

0.003

T16

−0.024

0.002

−0.009

0.003

−0.034

0.003

T17

−0.027

0.002

−0.013

0.002

−0.040

0.002

T18

−0.028

0.002

−0.019

0.002

−0.047

0.002

Figure 5a and b depicts Ikonos satellite images containing vertical displacement vectors obtained using the three periods of precise leveling measurements on the subsidence monitoring points in Kozlu Seaport and the Zonguldak-Kozlu Road.
https://static-content.springer.com/image/art%3A10.1007%2Fs11069-012-0477-x/MediaObjects/11069_2012_477_Fig5a_HTML.gifhttps://static-content.springer.com/image/art%3A10.1007%2Fs11069-012-0477-x/MediaObjects/11069_2012_477_Fig5b_HTML.gif
Fig. 5

aVertical displacement vectors obtained from the precise leveling measurements in Kozlu Seaport. bVertical displacement vectors obtained from the precise leveling measurements in Kozlu Road

In Kozlu Seaport, the maximum subsidence velocity, computed by vertical horizontal displacement over 15 months, has been determined 6.5 mm/month on the base of the period pair of I and III, while the maximum subsidence velocity in the Kozlu Road has been found as 3.8 mm/month. Similar to horizontal displacements, it has not been observed that the vertical displacements resulted from residual and active subsidence effects have caused any visual deformations or functional defects in the seaport and road during the three periods of precise leveling measurements in the region.

Subsidence contours for the entire study area were determined and given in Fig. 6 in order to graphically analyze the study area in detail with respect to subsidence and the precise leveling results conducted in the study area. In the determination of subsidence contours, the height differences were computed by the heights obtained from the first and the third periods of precise leveling measurements conducted in August 2009 and November 2010, respectively. In perusing the subsidence contours depicted in Fig. 6, one can deduce that the contours around Kozlu Seaport region which houses new coal productions fall in between −5 and −9 cm while they are between −7 and −4 cm along the Zonguldak-Kozlu Road where the old production panels are.
https://static-content.springer.com/image/art%3A10.1007%2Fs11069-012-0477-x/MediaObjects/11069_2012_477_Fig6_HTML.gif
Fig. 6

Subsidence contours for the entire study area

In addition to the analysis above, the subsidence graph is given in Fig. 7a for the subsidence monitoring points along the Zonguldak-Kozlu Road in A1–A2 Route after analyzing the height differences obtained from the first and third measurement periods. This route intercepts the coal seams in east–west direction.
https://static-content.springer.com/image/art%3A10.1007%2Fs11069-012-0477-x/MediaObjects/11069_2012_477_Fig7_HTML.gif
Fig. 7

a A1–A2 Route for mine subsidence analyses along the Kozlu-Zonguldak Road. b Graphical representation of vertical displacements in the Kozlu-Zonguldak Road

Figure 7b illustrates the cross-section of A1–A2 Route and vertical displacements along the route in which the red line represents the first period measurements, while the yellow the third period measurements. Moreover, Fig. 7b depicts both heights and inter-point distances for the periods obtained for the subsidence points of T1, T3, T5, T6, T8, T9, T12, T13, T16, and T17 along the A1–A2 Route. It has been found that the residual subsidence has occurred on the points from T1 to T16 assumed to be resulting from the old production lines and that the subsidence effects of both residual and active nature have occurred on T16 and T17 where both the old and new production panels coincide.

Furthermore, one recent period of precise leveling measurements was conducted in June 2012 in Kozlu Seaport which may constitutes the fourth period of measurements. However, this period of precise leveling measurements does not cover the subsidence points along the Zonguldak-Kozlu Road since they were destroyed during road renewal works in 2011. The heights of the subsidence points obtained in the fourth period were determined with an accuracy of 0.002 m. Table 9 lists the vertical displacements observed in the points which occurred in 19 months since the third period of measurements (November 2010). The following vertical displacements can be given: −0.165 m on T34, −0.162 m on T35, 0.092 m on T36, −0.078 m on T37, −0.055 m on T38, −0.072 m on T39, and −0.104 m on T40.

The vertical and horizontal displacements resulting from the mining-induced subsidence throughout the measurement periods, it has been observed no adverse effects on the engineering structures in the study region in terms of their proposed functions. Nevertheless, it should be noted that the subsidence occurrence in the region has to be monitored by further and more comprehensive geodetic and geological measurement campaigns and be prepared for suspected damages on the structures that may eventuate in future.

6 Conclusions

It has been estimated that the Zonguldak Hard Coal Basin (ZHCB) including Kozlu Basin has approximately 1.3 billion tons of coal reserve which can be unearthed. Nevertheless, a majority part of this reserve lies under the dwelled areas and possible settlement areas. Owing to the diminishing residential areas available in the region with the hardship of introducing effective zoning plans for the already occupied land parcels, this coal reserve is planned to be excavated in years to come, albeit the existence of arguments toward its being not economical.

This region with extensive mining activities houses many crucial engineering structures such as Kozlu Seaport and Kozlu Road which are the cores of this study and there are plans for new constructions on even daily basis in the region. In order to maintain the mining operations along with urban developments in a healthy way, the subsidence monitoring measurements and observations play important role in mitigating or even preventing the damages that possibly will occur in future and in giving way to desired urban development in the region.

In this study, it has been determined that the horizontal displacements in Kozlu Seaport vary from 8.0 to 15.3 cm with their rmse values of 3.9 to 6.3 mm, respectively, obtained from the GPS measurements between the periods of I (Aug 2009) and III (Nov 2010), while in Kozlu Road, they are 1.2 to 12.6 cm with 3.1 and 8.0 mm rmse values. On the other hand, the vertical displacements obtained from the three periods of precise leveling measurements have been found to deviate from 6.0 to 9.7 cm in the seaport region with 3.0 and 4.0 mm rmse values while they vary 3.2 to 5.7 cm in Kozlu Road with 2.0 and 4.0 mm rmse values.

Since the mining operations under Kozlu Seaport and Road will also be active in future, in the lights of findings obtained from this study, it is suggested that an extensive subsidence monitoring measurements with longer periods should be carried out to mitigate and even prevent functional problems that may arise in these engineering structures in future.

Acknowledgments

This study was funded by Bulent Ecevit University, Scientific Research Projects Unit (2009-45-05-02). The authors would like to express their gratitude to Bülent Ecevit University for their financial support. The authors are grateful to Turkish Hard Coal Enterprise for its assistance.

Copyright information

© Springer Science+Business Media Dordrecht 2012