scholarly journals Analytical Investigation for In Situ Stress Measurement with Rheological Stress Recovery Method and Its Application

2016 ◽  
Vol 2016 ◽  
pp. 1-12
Author(s):  
Quansheng Liu ◽  
Jingdong Jiang ◽  
Chengyuan Zhang ◽  
Yuanguang Zhu
Keyword(s):  
Rock Mass ◽  
Initial Stress ◽  
Stress Measurement ◽  
In Situ Stress ◽  
Stress Recovery ◽  
Recovery Stress ◽  
Principal Stresses ◽  
Recovery Method ◽  
In Situ Stress Measurement

In situ stress is one of the most important parameters in underground engineering. Due to the difficulty and weakness of current stress measurement methods in deep soft rock, a new one, rheological stress recovery (RSR) method, to determine three-dimensional stress tensor is developed. It is supposed that rock stresses will recover gradually with time and can be measured by embedding transducers into the borehole. In order to explore the relationship between the measured recovery stress and the initial stress, analytical solutions are developed for the stress measurement process with RSR method in a viscoelastic surrounding rock. The results showed that the measured recovery stress would be more close to the initial stress if the rock mass has a better rheological property, and the property of grouting material should be close to that of rock mass. Then, the RSR method, as well as overcoring technique, was carried out to measure the in situ stresses in Pingdingshan Number 1 coal mines in Henan Province, China. The stress measurement results are basically in the same order, and the major principal stresses are approximately in the direction of NW-SE, which correlates well with the stress regime of Pingdingshan zone known from the tectonic movement history.

Measurement and the Distribution Law of In Situ Stresses at Deep Depth of Xingcun Coal Mine

2012 ◽  
Vol 450-451 ◽  
pp. 1601-1607 ◽  
Author(s):  
Jiong Wang ◽  
Zhi Biao Guo ◽  
Feng Zhou ◽  
Feng Bin Su ◽  
Bao Liang Li
Keyword(s):  
Stress Field ◽  
Principal Stress ◽  
Coal Mine ◽  
Stress Measurement ◽  
In Situ Stress ◽  
Distribution Law ◽  
Principal Stresses ◽  
In Situ Stress Measurement ◽  
In Situ Stress Field

Many kinds of in situ stress measurement methods are used nowadays, two most common of which are the overcoring and the hydraulic fracturing methods. In order to study the distribution law of in situ stress field in the deep position of Xingcun coal mine, 4 points of in situ stress measurement were carried out in underground roadways at the -1200 m level adopting the overcoring method. The hollow included technique was used to measure the 4 points of in-situ stress. According to the analysis of the measurement data, the results indicated that: (1) Among the three principal stresses on all measurement points, two principal stresses were nearly horizontal and one was nearly vertical. Furthermore, the maximum horizontal principal stress was more than the vertical principal stress, and the magnitude of vertical stress was equal to the weight of overburden rock mass;(2)The value of the maximum horizontal principal stress reached 52.3 MPa , the directions mainly concentrated on the extension of N42°W – N85°W, and the obliquity mainly concentrated on the extension of -29° – 10°;(3)The ratio of maximum horizontal principal stress to vertical principal stress was 1.42 - 1.64 with an average value of 1.55. The result presented that the in situ stress field in Xingcun coalmine at the depth of -1200m was dominated by tectonic horizontal stress. According to the results above, we gained the in situ stress states and the distribution law in the measured region. At the same time, it can offer reasonable basic parameters for underground roadway layout and support design of Xingcun coalmine.

scholarly journals Numerical Simulation of the Stress Field in Repeated Mining of Coal Seams Based on In Situ Stress Measurement

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Donghui Yang ◽  
Bohu Yang ◽  
Zhaoheng Lv ◽  
Yongming Li ◽  
Hongming Cheng ◽  
...  
Keyword(s):  
Rock Mass ◽  
Stress Field ◽  
Stress Measurement ◽  
Initial Conditions ◽  
Main Roof ◽  
Strength Criterion ◽  
Maximum Principal Stress ◽  
In Situ Stress ◽  
In Situ Stress Measurement

We established an evaluation index of the rock mass stress state for underground coal mines using the strength-stress ratio based on the measured in situ stress and the generalized Hoek–Brown strength criterion. Three in situ stress states, σcm/σ1m < 1.4 (high), 1.4 < σcm/σ1m < 3.6 (medium), and σcm/σ1m > 3.6 (low), were established based on the value of the unconfined compressive strength (σcm) and the maximum principal stress of the rock mass (σ1m). This index classifies the Burtai mine as a medium-high in situ stress field, which is in agreement with the on-site situation, establishing the reliability of the index. The working face was a three-dimensional geological model based on the log sheets. The initial conditions for the model were determined using the combined measurements of the in situ stress regression model. We performed numerical simulations of the roof stress field distribution under repeated mining. Mining the overlying coal seam leads to significant variation in the value and direction of the main roof, σ1, within the range of the front abutment pressure under the pillar and gob. Along the main roof strike direction, σ1 under the pillar is 1.5 times that under the gob, and the σ1 direction under the pillar is deflected by 5°, which is 30° smaller than that under the gob. This provides a reference for optimized underground coal mining.

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.

In Situ Stress Measurements in Siliceous Mudstones at Horonobe Underground Research Laboratory, Japan

2010 ◽  
Author(s):  
Hiroyuki Sanada ◽  
Takahiro Nakamura ◽  
Yutaka Sugita
Keyword(s):  
Initial Stress ◽  
Stress Measurement ◽  
In Situ Stress ◽  
Movement Direction ◽  
Tectonic Movement ◽  
Principal Stresses ◽  
Initial Stress State ◽  
Overburden Pressure ◽  
Stress Measurements

The stress measurement methods implemented during the surface-based investigations and during construction of the underground facilities in the Horonobe mudstones, as well as information on the initial stress state around the Horonobe URL, are described in this paper. During the surface-based investigations, determination of deep in situ stress was conducted using HF, BB information in deep boreholes and core-based methods such as AE and DSCA. During construction of the underground facilities, subsurface investigations utilizing CCBO, HTPF and the monitoring of spalling around the shafts were conducted in order to verify results from initial stress measurements in the surface-based investigations. HF results indicate that magnitude of the horizontal maximum and minimum principal stresses increases linearly with depth. The maximum principal stress estimated from the HF and borehole breakout data is almost E-W. This is similar to the tectonic movement direction in the vicinity of the Horonobe URL. Due to tectonic movement, horizontal maximum stress is almost 1.5 times larger than the horizontal minimum stress. The minimum horizontal principle stress is almost equivalent to overburden pressure. Stress condition determined from HTPF in the investigations during construction of the underground facilities is almost equal to the results during surface-based investigations.

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.

In Situ Stress Measurement and Inversion in Deep Roadway

2013 ◽  
Vol 734-737 ◽  
pp. 759-763 ◽  
Author(s):  
Yong Li ◽  
Yun Yi Zhang ◽  
Ren Jie Gao ◽  
Shuai Tao Xie
Keyword(s):  
Field Measurement ◽  
Stress Measurement ◽  
Measurement Data ◽  
Back Analysis ◽  
In Situ Stress ◽  
Deep Mine ◽  
Accuracy Requirement ◽  
Initial Stress Field ◽  
In Situ Stress Measurement

Jixi mine area is one of the early mined areas in China and it's a typical deep mine. Because of large deformation of underground roadway and dynamic disasters occurred frequently in this mine, five measurement points of in-situ stress in this mine was measured and then analyzed with inversion. Based on these in-situ stress measurement data, numerical model of 3D in-situ stress back analysis was established. According to different stress fields, related analytical samples of neural network were given with FLAC program. Through the determination of hidden layers, hidden nodes and the setting of parameters, the network was optimized and trained. Then according to field measurement of in-situ stress, back analysis of initial stress field was conducted. Compared with field measurement, with accuracy requirement satisfied, it shows that the in-situ stress of rock mass obtained is basically reasonable. Meanwhile, it proves that the measurement of in-situ stress can provide deep mines with effective and rapid means, and also provide reliable data to optimization of deep roadway layout and supporting design.

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