Research on the correlation between crustal deformation characteristics and impact geopressure in the Hegang mining area based on GNSS monitoring

doi:10.21203/rs.3.rs-3639486/v1

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Research on the correlation between crustal deformation characteristics and impact geopressure in the Hegang mining area based on GNSS monitoring

https://doi.org/10.21203/rs.3.rs-3639486/v1

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The crustal deformation characteristics of the mining area are a reflection of the evolution of the overburden rock structure force and deformation of coal seam mining, Impact geopressure is a result of the overburden rock movement, which disrupts the stress balance of the coal rock body surrounding the quarry, leading to a dynamic disaster, and the crustal deformation characteristics are closely related to Impact geopressure.To gain a deeper understanding of the relationship between crustal deformation and impact ground pressure in the Hegang mining region. Using the available GNSS observation data from the study area, six new GNSS observation stations in the key areas of the mining region have been encrypted, a thorough analysis is conducted on both the regional microseismic events catalog and the mine earthquake events catalog, which are under the surveillance of seismic stations, and the regional crustal deformation overtime during the occurrence of larger energy events is studied quantitatively. The findings indicate a direct relationship between the frequency of energy occurrences in the mining region and the vertically aligned time series of the GNSS stations, as the vertical direction experiences a rapid decline, the magnitude increases and the greater the cumulative energy emitted by the subsequent energy occurrences. The findings of this research can serve as a point of reference for proactively alerting and averting microseismic energy incidents in the southern mining region of Hegang

crustal deformation

GNSS

impact geopressure

mine energy event

microquake events

Impact geopressure is a process of evolution of damage and catastrophe induced by gradual rupture in complex engineering geological media with strong inhomogeneity, strong discontinuity, and strong non-linearity ^[1–3].Its essence is the initiation, development, penetration, and instability of microfracture induced by stress perturbation or increase in strain in the coal mining process ^[5–7]. The characteristics of crustal deformation in mining areas are the comprehensive reflection of the stress and deformation evolution of overlying rock mass structures in coal seam mining. Impact geopressure is a kind of dynamic disaster induced by breaking the stress equilibrium state of the coal and rock mass around the stope caused by the strata movement. Therefore, there is a close relationship between the characteristics of crustal deformation and impact geopressure.

Relevant scholars at home and abroad have done a lot of research and applications on GNSS monitoring surface deformation characteristics. Jun W monitored the Beijing plain by acquiring GNSS data and studied the three-dimensional crustal deformation in Beijing ^[8]. The Journal of Surveying Engineering reported that the ground was monitored by GNSS technology ^[9]. Hanbin G. et al. used GNSS technology to analyze wave measurement and directional spectrum ^[10]. Cejing monitors landslide deformation through GNSS technology ^[11]. DeSanto B J et al.conducted GNSS observations of the limited slip of the Simonov earthquake in Alaska ^[12].

The above GNSS technology research focuses mainly on civil engineering, surveying and mapping, etc., for the application of GNSS technology in the field of coal mine impact geopressure prevention and control, further research and discussion are still needed.Therefore, this paper uses the GNSS observation data covering the southern mining area of Hegang and the data of the mining area microseismic energy monitoring system to analyze the correlation between regional crustal deformation and microseismic energy events and provide a reference for the monitoring, early warning, and prevention of microseismic energy events.

The Hegang coalfield is mainly composed of nine coal mines: Xingshan Mine, Yixin Mine, Zhenxing Mine, Niaoshan Mine, Nanshan Mine, Xinlu Mine, Fuli Mine, Xing 'an Mine, and Junde Mine. This study area mainly involves three mining areas in the south of Hegang, Fuli Mine, Xing an Mine, and Junde Mine.

A total of 26 impact geopressure occurred in the Junde Coal Mine, including 6 typical impact geopressure. The last one was on 25 September 2016, and there has been no impact geopressure disaster since 2017. In view of the impact risk level of the working face in the Junde Coal Mine, the SOS microseismic monitoring system is currently used.The KJ550 stress online monitoring system and the KBD5 electromagnetic radiation monitoring system are used to monitor impact geopressure events in the mining area, and the relevant impact geopressure prevention measures are used to ensure normal production.

In 2011 and 2012, there were 8 and 4 Impact geopressure in Xing 'an Coal Mine, respectively, and there were no major Impact geopressure events after that. Xing an coal mine in terms of impact geopressure monitoring. There are mainly regional monitoring SOS microseismic monitoring systems and local monitoring KJ743 stress online monitoring system or KBD5 electromagnetic radiation monitoring system and cooperate with regional de-danger measures and local control measures to ensure the normal production of the minefield.

There were 8 times of impact geopressure in the Fuli Coal Mine from 1998 to 2014, and it has not occurred since 2014. Among them, the typical impact geopressure occurred three times, respectively, on June 15, 1998, October 20, 2003, and May 28, 2014. In the monitoring of impact geopressure in Fuli Coal Mine, there are mainly SOS microseismic monitoring systems for regional monitoring and the KJ550 / KJ743 stress online monitoring system, and the KBD5 electromagnetic radiation monitoring system for local monitoring, and cooperate with regional crisis relief measures and local control measures to ensure normal production of the minefield.

Considering that the background of Impact geopressure in the Junde mining area in the southern mining area of Hegang is the strongest, and its monitoring system for energy events in the mining area is relatively the most perfect, the correlation between Impact geopressure and crustal deformation characteristics is analyzed by using the catalog of energy events in the mining area recorded daily by the anti-scour office of Junde mining area, combined with GNSS monitoring data.

2.1 Global Navigation Satellite System ( GNSS ) measurement technology

GNSS measurement technology mainly uses more than 4 navigation satellite signals received by the monitoring station to carry out rear intersection measurement, to calculate the three-dimensional position of the monitoring station. According to the state of the monitoring station in the measurement, it can be divided into static measurement and dynamic measurement. In monitoring regional crustal deformation, static measurement is used mostly. Based on the positioning results, it can be divided into absolute positioning and relative positioning.Absolute positioning refers to the calculation of the exact position of the receiving station on Earth through the received satellite signal.This positioning method can be completed independently without other auxiliary information. Relative positioning is to calculate the position of the target station by processing the satellite signals received by the reference station and the target station when the position of a reference station is known. With the continuous refinement of GNSS data processing technology and various geophysical models, absolute positioning and relative positioning technology in regional crustal deformation monitoring have good results.

2.2 Layout of an intensive crustal deformation monitoring network in the southern Hegang mining area

At present, although the existing terrestrial network GNSS reference station ( HLHG Heilongjiang Hegang GNSS reference station ) can monitor crustal deformation in the Hegang area, it is still insufficient in a small range of regional accuracy. To further study the relationship between impact geopressure and crustal deformation, six new GNSS observation stations were established in cooperation with the Institute of Engineering Mechanics of China Earthquake Administration and the China Seismological Network Center.To meet the monitoring needs of the mine's small area level. When selecting the target point, it should be selected to meet the large deformation, strong impact geopressure response, and poor geological conditions, conducive to observation of the location. The specific location of the selection of the observation station is shown in Table 1.

Table 1

Location of new GNSS observation points
order number	Site name	New GNSS observation point position
1	HGKW	Stairway platform angle on the northeast side of observation room of seismic station of mining bureau
2	HGNS	Inside the courtyard wall of Niaoshan Coal Mine
3	HGJY	Inside the courtyard of the ambulance brigade
4	HGXL	Xinlu Coal Mine Parking Lot
5	HGJD	Xing 'an mine mechanical and electrical department courtyard
6	HGHY	Inside the Huahe Coal Chemical Industrial Park of China Offshore Oil

The Hekuang Group strongly supported the construction of new GNSS stations and dispatched relevant staff to complete the construction of six GNSS observation stations from 28 May to 8 June 2021. After 21 days of spontaneous coagulation and sedimentation, the six newly built GNSS observation piers went to Hegang from July 2 to 6, 2021 to carry out the installation and commissioning of the equipment. Its physical map is shown in Fig. 1 ( The sites in Fig. 1 are HGKW, HGNS, HGJY, HGXL, HGJD, and HGHY in order from left to right ). The distribution map of the GNSS site used in this paper is shown in Fig. 2.

3.1 GNSS single station original position time series

The time series of the original position of a single GNSS station refers to the time-varying sequence of the position data of a single station recorded by the GNSS receiver. The time series of the original position of the single station can reflect the crustal deformation change of the station position. The time series of the original location of each station is shown in Fig. 3

3.2 Baseline time of the GNSS station

The baseline time series of the GNSS station refers to the time-varying sequence of the relative position between two receivers calculated by the Global Navigation Satellite System ( GNSS ) observation data. The baseline time series can reflect the relative motion between the two GNSS stations of the group baseline, that is, the baseline is elongated, indicating that there is an extensional motion in the area represented by the two GNSS stations, and vice versa, that is, there is a squeezing motion. According to the scope of the mining area and the positional relationship with other sites, two baselines of HGHY-HGJD and HLHG-HGJY were selected to investigate the tectonic activities of the Junde mine, Xing the an mine, and the Fuli mine. The two baseline time series covering the southern mining area of Hegang are shown in Fig. 4

It can be seen from Fig. 4 that both baselines show that long-term compression to rapid extension began to appear at the end of April 2022, indicating that regional tectonic activities have been adjusted.

3.3 GNSS regional strain time series

Similarly to the baseline time series of the site, the regional strain time series can describe the deformation characteristics of the study area as a whole and reflect the evolution of the deformation information of the study area with time. It is independent of the reference datum, and the strain time series can also reflect the deformation characteristics in different directions. Three areas covering the mining area were selected, namely HLHG-HGXL-HGNS-HGKW,HGXL-HGJD-GHY, and HGJD-HGJY-HGHY. The results are shown in Fig. 5

It can be seen from Fig. 5 that the above three regions are in different degrees of extrusion state, and the extrusion direction is different. Maximum shear strain also began to decrease around April 2022, and overall extrusion and shear movement slowed, indicating that the regional tectonic stress state in the southern mining area of Hegang is slowly adjusting.

4.1 Correlation analysis between vertical component timing and energy event timing of GNSS observation station

Since the six new GNSS observation stations began recording data in July 2021, the data since July 2021 are emphatically analyzed.The number of daily energy events in the energy event catalog recorded by the anti-scour office of the Junde mining area is counted to characterize the background value of energy events in the mining area. ( For example, a total of 84 energy events were recorded on September 19, 2021, and a total of 123 energy events were recorded on September 20, 2021), as shown in Fig. 6. It was found that the number of energy events decreased rapidly from mid-August to late October. The possible reason is the weakening of mining activities or the decreasein regional crustal tectonic stress levels. The Pearson correlation coefficient method is used to analyze the correlation between the vertical position time series and the energy event series of the six new stations (the Pearson coefficient method is a statistical method used to measure the linear correlation between the two variables. It ranges from 1 to 1, where 1 means completely negative correlation, 0 means no correlation, and 1 means completely positive correlation ). The results are shown in Fig. 7.

It can be seen from Fig. 7 that the two stations of HGJD and HGXL show negative relativity with energy events and the correlation coefficients are 0.41 and 0.22, respectively. The other four stations show positive relativity, of which the highest is HGHY station 0.59, followed by HGKW station 0.38, HGNS station 0.28, and HGJY station 0.19. In view of the fewer observation data of the HGKW station, the calculated correlation is not representative, so it is not considered in the later analysis

By comparing the vertical timing of the HGHY station with the timing of energy events, it is found that the changing trend of the two is relatively consistent, that is, the phenomenon of rising and falling at the same time in most periods is shown in Fig. 8. For the four major energy events ( black histogram in the figure ) that occurred during the period, it is found that .

( 1 ) Before each large energy event, the HGHY station showed rapid or continuous subsidence, and the corresponding vertical subsidence amplitudes of the HGHY station before the four energy events were about 45mm, 27mm, 27mm, and 8mm, respectively.

( 2 ) When the background value of the energy event is greater than 100, the corresponding second and third large energy events occur. The vertical subsidence trend of the HGHY site is consistent with the trend of energy event reduction. That is, when the energy background value is high ( greater than 100 times/day), the vertical rapid subsidence of the site reaches about 30 mm, which may be accompanied by the occurrence of large energy events

( 3 ) When the first large energy event occurred, the HGHY station was built in less than half a month. During this period, the vertical movement was manifested mainly as the self-settlement of the observation pier, so it could not be used to characterize the vertical movement of the surface in this area.The fourth large energy event occurred at a low energy background value ( about 40 times/day). Although the downward trend of the two was consistent, the vertical downward amplitude of the corresponding HGHY site was only about 8 mm. Compared with the 27 mm when the energy background value was higher, the difference between the two was nearly 3 times, and the microseismic energy was 3.5 times

It can be inferred that when the energy background value of the mining area is high ( more than 100 times/day), if the GNSS continuous observation station above the mining field or in a small area near the mining area has a rapid subsidence movement in the vertical direction and the decline range is about 30 mm or higher, the mining area corresponding to the GNSS observation station is more likely to have a large energy event. When the energy background value of the mining area is low ( less than 40 times/day),the vertical rapid subsidence range of the corresponding GNSS station and the energy released by the subsequent energy events are reduced accordingly.

In order to eliminate the uncertainty caused by the short observation time and verify the above inference, the vertical position timing of the Hegang GNSS reference station HLHG of the land state network since January 1, 2020, and the energy event time series of the mining area are compared and analyzed as shown in Fig. 9, and the correlation coefficient between vertical change and energy event is calculated as shown in Fig. 10. The results show that from the perspective of long time scale, the HLHG station shows relatively regular annual andsemiannual fluctuations in the vertical direction, and the correlation coefficient calculated from the time series of energy events is only 0.08, showing no correlation.The reason may be related to the fact that the HLHG station is far from the Junde mining area, which also shows that the influence range of energy events in the mining area is limited. At the same time, it shows that the magnitude of vertical change of the GNSS station is related to the size and distance of reflected energy events.

4.2 Analysis of the influence of epicentral distances on the characteristics of crustal deformation

In order to analyze the influence of epicentral distances on vertical time series and energy event time series, the seismic station monitored three large energy events with magnitudes of M1.8, M1.9, and M2.2 at 07: 42: 49.06 on January 18, 2022, 13: 20: 19.91 on April 24, 2022 and 01: 14: 51.11 on May 27, 2011 in the Xinlu mine and Xing 'an mine of the Hegang mining area.The vertical time series and energy events of the GNSS stations HGXL and HGJD closest to the above three large energy events were analyzed.The results are shown in Fig. 11:

From Fig. 11, it can be concluded that before the three large energy events, the nearby GNSS stations showed continuous and rapid sinking movements in the vertical direction, with sinking amplitudes of about 23 mm, 12 mmand 52 mm, respectively. The nearest stations of the epicenters of the three large energy events were HGXL stations, but the epicenter distances were different

From Fig. 11, it can be concluded that before the three large energy events, the nearby GNSS stations showed continuous and rapid sinking movements in the vertical direction, with sinking amplitudes of about 23 mm, 12 mm and 52 mm, respectively. The nearest stations of the epicenters of the three large energy events were HGXL stations, but the epicenter distances were different。

The HGXL is farther away from the epicenter of the large-energy event on January 18 than the large-energy event on April 24.Although the magnitude of the two large energy events is similar, the rapid decline in the vertical direction before the event is different. This also reflects that the rapid decline in the vertical direction of the GNSS site is related to the epicenter distances. The farther the epicenter distance, the greater the rapid decline in the vertical direction of the GNSS site before the large energy event of the same magnitude。

Comparing the two large energy events on April 24 and May 27, the difference between the vertical rapid decline of the HGJD station and the HGXL station is about 40 mm.Considering that the magnitude of the earthquake differs by one level, the energy released by the two is 32 times. According to this calculation, the energy released by the 2.2-level large energy event on May 27 is nearly 5 times that released by the 1.9-level vibration event on April 24, which also reflects that the GNSS station has the same epicentral distance before the large energy event occurs. The greater the rapid decline in the vertical direction, the greater the total energy released by the corresponding subsequent energy events.

A. There is a positiveassociation between the crustal deformation characteristics of the southern Hegang mining area and themicroseismic energy event of Impact geopressure, but the influence of the microseismic energy event of Impact geopressure on crustal deformation is limited and only affects the surface deformation above or near it.

B.For regions with a high frequency of microseismic energy events, if a large vertical deformation suddenly occurs on the surface, large energy events are more likely to occur in this area.

C.The vertical deformation amplitude of the surface is positively correlated with the epicenter distances of the microseismic energy event. The farther the source location is, the greater the rapid decline of the surface deformation characteristics.

D. Vertical deformation of the surface is positively associated with the energy of the microseismic energy event of the Impact geopressure, and the greater the rapid decline of the vertical deformation of the surface, the greater the total energy released by the corresponding subsequent energy event.

Therefore, the crustal deformation velocity in the mining area is closely related to the large energy mine earthquake, and the occurrence of a large energy mine earthquake can directly induce impact geopressure.Therefore, the risk of impact geopressure can be predicted by closely observing the characteristics of crustal deformation.

Data availability

The datasets used and/or analysed during the current study available from the corresponding author on reasonable request.

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No competing interests reported.

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Research on the correlation between crustal deformation characteristics and impact geopressure in the Hegang mining area based on GNSS monitoring

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Abstract

Figures

Introduction

Engineering situations

Crustal deformation monitoring in the Hegang mining area

2.1 Global Navigation Satellite System ( GNSS ) measurement technology

2.2 Layout of an intensive crustal deformation monitoring network in the southern Hegang mining area

Characteristics of the Crustal Movement of the Hegang Mining Area

3.1 GNSS single station original position time series

3.2 Baseline time of the GNSS station

3.3 GNSS regional strain time series

Correlation analysis between crustal deformation characteristics and microseismic energy events in the southern mining area of Hegang

4.1 Correlation analysis between vertical component timing and energy event timing of GNSS observation station

4.2 Analysis of the influence of epicentral distances on the characteristics of crustal deformation

Conclusions

Declarations

References

Additional Declarations

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