Estimation of in-situ stress in the Latrobe Valley Coal mines with special reference to Loy Yang Mine, Australia

2020 ◽  
pp. 601-606
Author(s):  
D.K. Nag
Keyword(s):  
Special Reference ◽  
Coal Mines ◽  
In Situ Stress

scholarly journals In-Situ Stress Measurements and Stress Accumulation Level Analysis of Coal Mines in Northern Ordos Basin

2020 ◽  
Author(s):  
Donghui Yang ◽  
Zhangxuan Ning ◽  
Yongming Li ◽  
Zhaoheng Lv ◽  
Yuandong Qiao
Keyword(s):  
Stress Measurement ◽  
Ordos Basin ◽  
Coal Mines ◽  
In Situ Stress ◽  
Test Method ◽  
Principal Stresses ◽  
Stress Regime ◽  
In Situ Stress Measurement ◽  
Stress Accumulation

Abstract For non-directional drilling cores, the sample selection and test method for Kaiser effect (KE) in-situ stress measurement were proposed, and the magnitude and direction of its principal stresses were theoretically derived. Based on this method, the KE of 423 samples in Burtai and Baode coal mines in northern Ordos Basin (NOB) were tested. The results show that σH, σh and σv vary with depth and location, and their values increase with increasing of depths. Generally, horizontal stresses play a leading role. There are main stress regimes in NOB: σH > σh > σv (Burtai, <172m; Baode, <170m) and σH > σv > σh (Burtai, 170-800 m; Baode, 170-400 m), and the σv > σH > σh stress regime is mainly distributed in moderately deep to deep coal mines. For rock masses with a depth of 350m, k ((σH + σh) / 2σv) tends to 1, indicating that deep critical state will gradually emerge. The test results were compared with those of overcoring method (OC), elastic strain recovery (ASR) and micro-hydraulic fracturing (HF). The relative errors of σH, σh and σv are 14.90%, 19.67%, 15.47% (Burtai) and 10.74%, 22.76%, 19.97% (Baode), and they are all within a reasonable range required by the project, which verifies the reliability of KE method. The dominant orientation of σH (Burtai, NE-NNE; Baode, NEE) was obtained by using paleomagnetic technology, which is consistent with that (NE-NEE) of earthquake focal mechanisms in this area. Based on Byerlee-Anderson theory, the stress accumulation level of mine rock mass was discussed. Under dry rocks or hydrostatic pressure rocks, the friction coefficient of faults is both low, which is less than the lower limit (0.6) of strike-slip faults slip, indicating that the fracture stress with a low level around the study area is lower than the friction limit stress. The stress accumulation level in Baode mine is slightly larger than that in Burtai mine.

scholarly journals A Novel in Situ Stress Monitoring Technique for Fracture Rock Mass and Its Application in Deep Coal Mines

2019 ◽  
Vol 9 (18) ◽  
pp. 3742 ◽  
Author(s):  
Bin Liu ◽  
Yuanguang Zhu ◽  
Quansheng Liu ◽  
Xuewei Liu
Keyword(s):  
Rock Mass ◽  
Coal Mines ◽  
Three Dimensional ◽  
In Situ Stress ◽  
Hole Drilling ◽  
Stress Monitoring ◽  
Underground Engineering ◽  
In Situ Tests ◽  
Monitoring Method

A novel in situ stress monitoring method, based on rheological stress recovery (RSR) theory, was proposed to monitor the stress of rock mass in deep underground engineering. The RSR theory indicates that the tiny hole in the rock can close gradually after it was drilled due to the rheology characteristic, during which process the stress that existed in the rock can be monitored in real-time. Then, a three-dimensional stress monitoring sensor, based on the vibrating wire technique, was developed for in field measurement. Furthermore, the in-field monitoring procedures for the proposed technique are introduced, including hole drilling, sensor installation, grouting, and data acquisition. Finally, two in situ tests were carried out on deep roadways at the Pingdingshan (PDS) No. 1 and No. 11 coal mines to verify the feasibility and reliability of the proposed technique. The relationship between the recovery stress and the time for the six sensor faces are discussed and the final stable values are calculated. The in situ stress components of rock masses under geodetic coordinates were calculated via the coordinate transformation equation and the results are consistent with the in situ stress data by different methods, which verified the effectiveness of the proposed method.

scholarly journals In situ stress measurement and analysis of the stress accumulation levels in coal mines in the northern Ordos Basin, China

2021 ◽  
Author(s):  
Donghui Yang ◽  
Zhangxuan Ning ◽  
Yongming Li ◽  
Zhaoheng Lv ◽  
Yuandong Qiao
Keyword(s):  
Principal Stress ◽  
Stress Measurement ◽  
Ordos Basin ◽  
Coal Mines ◽  
In Situ Stress ◽  
Principal Stresses ◽  
Earthquake Focal Mechanism ◽  
In Situ Stress Measurement ◽  
Stress Accumulation

AbstractFor non-directional drilling cores, selection of samples and the test methods for in situ stress measurements to evaluate the Kaiser effect (KE) were proposed, and the magnitude and direction of the principal stresses were derived from first principles. Based on this approach, the KE for 423 samples in the Burtai and Baode coal mines in the northern Ordos Basin (NOB), China, have been investigated. The results show that the maximum horizontal principal stress (σH), the minimum horizontal principal stress (σh) and the vertical stress (σv) varied with depth and location, and the values increase with increasing depth. Generally, the horizontal stresses play a leading role. For the main stress regimes in the NOB, σH > σh > σv (Burtai Mine, < 172 m; Baode Mine, < 170 m) and σH > σv > σh (Burtai Mine, 170–800 m; Baode Mine, 170–400 m), and the σv > σH > σh stress regimes are mainly distributed in moderately deep to deep coal mines. For rock masses with a depth of 350 m, k ((σH + σh)/2σv) tends to 1, indicating that a deep critical state will gradually emerge. The test results are compared with those for the overcoring (OC) method, the anelastic strain recovery (ASR) method and micro-hydraulic fracturing (HF). The relative errors for σH, σh and σv were 14.90%, 19.67%, 15.47% (Burtai Mine) and 10.74%, 22.76%, 19.97% (Baode Mine), respectively, and the errors are all within an acceptable range, thus verifying the reliability of the KE method. The dominant orientation for the σH (Burtai mine, NE-NNE; Baode Mine, NEE) is obtained via paleomagnetic technology, and the data are consistent with those (NE-NEE) of the earthquake focal mechanism solutions for the area. Based on the Byerlee–Anderson theory, a discussion is given on the levels of stress accumulation in the rock mass of the mines. For dry rocks or hydrostatic pressure rocks, the friction coefficients of the faults are low for both locations, and the values are less than the lower limit (0.6) of the strike-slip faults slip, indicating that the stress fractures at a low level around the study areas are lower than the friction limit stress. The stress accumulation levels in the Baode Mine are slightly larger than those in the Burtai Mine.

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