scholarly journals In situ stress characteristics of the NE Sichuan basin based on acoustic emission test and imaging logging

2021 ◽  
Vol 3 (12) ◽  
Author(s):  
Xinxin Fang ◽  
Hong Feng
Keyword(s):  
Principal Stress ◽  
Sichuan Basin ◽  
Tectonic Stress ◽  
In Situ Stress ◽  
Vertical Stress ◽  
Clastic Rock ◽  
Rock Formation ◽  
Marine Carbonate ◽  
Northeast Sichuan Basin

AbstractThis study presents the distribution rule of in situ stress in the northeast Sichuan basin and its relationship with fracture. Sixty-seven sets of core samples of 21 Wells from the terrigenous clastic rock formation (Shaximiao, Qianfoya, Xujiahe) and marine carbonate formation (Jialingjiang, Leikoupo, Feixianguan) in the northeast Sichuan basin were tested by acoustic emission experiment. The in situ stress variation with the depth was established and the corresponding regression analysis was done. The horizontal principal stress direction of terrigenous clastic rock formation and marine carbonate rock formation was obtained by combining the dual diameter data of 6 wells and the imaging logging data of 3 wells. The results show that the vertical stress in the northeast of Sichuan basin has a linear relationship with the depth, and there is little difference between the vertical stress and the overburden weight of rocks. The maximum and minimum horizontal principal stress and horizontal shear stress increase with the burial depth. The divergence degree of horizontal shear stress with depth greater than 3000 m is greater than that of the stratum smaller than 3000 m. The horizontal stress plays a dominant role in the northeast Sichuan basin. With the increase in depth, the influence of tectonic stress field decreases and the vertical stress increases. Impacted by Dabashan and Qinling plate tectonic movement, the direction of in situ stress in marine carbonate strata is nearly east–west. The direction of maximum horizontal principal stress in terrigenous clastic rock formation is basically northwest–southeast. The imaging logging data show that the fracture direction is consistent with the horizontal principal stress direction, and the present in situ stress direction is favorable to the secondary reconstruction of natural fractures, and the fractures keep good opening. The distribution law of in situ stress in northeast Sichuan basin shows σH > σV > σh, indicating that the fault activity in this area is dominated by strike-slip type, the tectonic stress field is dominated by horizontal tectonic stress, in addition that the stress state is conducive to reverse fault activity.

scholarly journals Study on in-Situ Stress Distribution in the East and West of Sichuan Basin

2021 ◽  
Author(s):  
Xinxin Fang ◽  
Hong Feng
Keyword(s):  
Acoustic Emission ◽  
Elastic Modulus ◽  
Principal Stress ◽  
Carbonate Rock ◽  
Sichuan Basin ◽  
In Situ Stress ◽  
Vertical Stress ◽  
Western Sichuan ◽  
Northeastern Sichuan

Abstract This paper statistically analyzed 112 acoustic emission experimental data of cores from 38 wells in the Upper Permian Changxing Formation, Triassic Xujiahe Formation, Leikoupo Formation, Jialingjiang Formation, and Feixianguan Formation in the northeastern Sichuan Basin, and 106 acoustic emission test data of cores from 32 wells of the Jurassic Shaximiao Formation and Penglai Formation in western Sichuan, eliminated data with large errors, established scatter plots of in-situ stress changing with depth in northeastern and western Sichuan, and carried out corresponding regression analysis. Studies show that the in-situ stress distribution rules in northeastern Sichuan and western Sichuan are quite different, which are mainly related to the evolution and tectonic movement of basin. The vertical stress of two blocks is generally linear with the depth, and the vertical stress value is related to the rock. The difference between overburden weight and vertical stress is small. The maximum and minimum horizontal principal stresses gradually increase with buried depth, and the degree that horizontal principal stress increase with buried depth in northeastern Sichuan is generally greater than that in western Sichuan. The horizontal shear stress is also linear with buried depth. The corresponding linear relationship is stronger in the western part of Sichuan, while the dispersion in the eastern part of Sichuan has an increasing trend as the buried depth increases. The elastic modulus of rock directly affects stress value of rock. Generally, the higher the elastic modulus of rock, the better it is to maintain higher stress. The elastic modulus of rocks of different genesis is obviously different, and the relationship between the stress value of rock and the elastic modulus is quite different. Because strength of carbonate rock is greater than that of sandstone, the change of elastic modulus is the maximum level of carbonate rock. The influence of principal stress is greater than that of sandstone, and the influence of minimum principal stress of sandstone is greater than that of carbonate rock. In carbonate rock, the effect of elastic modulus on the minimum horizontal principal stress is greater than the maximum horizontal principal stress, while in sandstone it is the opposite.

scholarly journals Geological Core Ground Reorientation Technology Application on In Situ Stress Measurement of an Over-Kilometer-Deep Shaft

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Chunde Ma ◽  
Xibing Li ◽  
Jiangzhan Chen ◽  
Yanan Zhou ◽  
Sen Gao
Keyword(s):  
Principal Stress ◽  
Stress Measurement ◽  
Stress Relief ◽  
Maximum Principal Stress ◽  
In Situ Stress ◽  
Vertical Stress ◽  
Geometry Model ◽  
In Situ Stress Measurement ◽  
Stress Changes

As mining progresses to depth, engineering activities face the extreme challenge of high in situ stress. To efficiently measure the deep in situ stress before engineering excavation, an innovative deep in situ stress measurement method capable of the geological core ground reorientation technology and acoustic emission (AE) technology was proposed. With this method, nonorientation geological cores collected from the thousand-meter-deep borehole were reoriented based on the spatial spherical geometry model and borehole bending measurement principle. The distribution of deep in situ stress of an over-kilometer-deep shaft in the Xiangxi gold mine was investigated with real-time synchronized MTS 815 material testing machine and PCI-II AE instrument. The results show that the in situ stress changes from being dominated by horizontal stress to being dominated by vertical stress with depth. The horizontal maximum principal stress and vertical stress gradually increase with depth and reach a high-stress level (greater than 25 MPa) at a depth of 1000 m. The direction of the maximum principal stress is near the north. Meanwhile, to analyze the accuracy of the measured in situ stress comparatively, the stress relief measurements were performed at a depth of 655–958 m in the mine, using the Swedish LUT rock triaxial in situ stress measurement system. The distribution of deep in situ stress obtained by the stress relief method agrees well with that by the AE method, which proves the reliability of the AE in situ stress testing method based on the geological core ground reorientation technology.

scholarly journals Research on In Situ Stress Distribution of the Railway Tunnels in Southwest China Based on the Complete Temperature Compensation Technology

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Weibin Ma ◽  
Jinfei Chai ◽  
Degou Cai ◽  
Xiaoyan Du ◽  
Jie Dong ◽  
...  
Keyword(s):  
Principal Stress ◽  
Temperature Compensation ◽  
Southwest China ◽  
Confining Pressure ◽  
Tectonic Stress ◽  
Maximum Principal Stress ◽  
In Situ Stress ◽  
Surrounding Rock ◽  
Regional Tectonic

In situ stress is the natural stress existing in the stratum without engineering disturbance, also known as initial stress, absolute stress, or original rock stress. In order to master the in situ stress of the Manmushu Tunnel and Mamo Tunnel in Southwest China, the casing stress solution method is adopted in this paper. Through the combination of field measurement and laboratory test, the basic data such as initial strain during stress relief are collected, and the in situ stress values are analyzed in combination with indoor temperature compensation test, confining pressure calibration, and relevant rock mechanics tests. The measured results show the following: (1) the maximum horizontal principal stress σh.max ranges from 6.44 MPa to 19.74 MPa; the vertical principal stress σ v ranges from 4.11 MPa to 13.48 MPa; and the minimum horizontal principal stress ranges from 4.32 MPa to 11.22 MPa. (2) The maximum horizontal principal stress directions of the five measuring points are all located in the NW direction, which is basically consistent with the maximum principal stress direction of the regional tectonic stress field. The maximum horizontal principal stress (σh.max), the minimum horizontal principal stress (σh.min), and the vertical principal stress ( σ v ) all increase with the increase of buried depth, and the relationship is approximately linear. It is suggested that, in the actual construction process, the construction method and construction parameters should be optimized scientifically and reasonably to reduce the disturbance of blasting on the tunnel surrounding rock. After tunnel excavation, support measures should be taken quickly, timely, and scientifically to reduce and control the deformation of the surrounding rock.

scholarly journals A Simple and Accurate Interpretation Method of In Situ Stress Measurement Based on Rock Kaiser Effect and Its Application

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Kang Zhao ◽  
Shuijie Gu ◽  
Yajing Yan ◽  
Keping Zhou ◽  
Qiang Li ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Fractal Dimension ◽  
Principal Stress ◽  
In Situ Stress ◽  
Time Range ◽  
Kaiser Effect ◽  
Time Stress ◽  
Stress Curve ◽  
Interpretation Method

Many deep underground excavation practices show that the size and distribution of in situ stress are the main factors resulting in the deformation and instability of the surrounding rock structure. The in situ stress measured by the Kaiser effect of rock is used by engineers because of its economy and convenience. However, due to the lack of quantitative judgment basis in determining the Kaiser point position, there is a large artificial error in the practical application. In response to the problem, this study systematically investigates the characteristics of rock acoustic emission curve on the basis of the fractal theory and establishes an accurate and simple interpretation method for determining the Kaiser point position. The indoor rock acoustic emission test was carried out by drilling a rock sample at a mine site. By using the conventional tangent method, the cumulative ringing count rate-time-stress curve of rock acoustic emission is analyzed to preliminarily determine the time range of Kaiser point appearance. Considering that the fractal dimension of the rock Kaiser point is lower than the adjacent point, the minimum point of the fractal dimension of this time range can be determined from the fractal dimension-time-stress curve. Such determined point is the Kaiser point. The size of the in situ stress is calculated using an analytical method. Based on the value of the in situ stress, the distribution of the in situ stress in the mining area is further analyzed using the geological structure of the mine. The maximum principal stress is 19.38 MPa, with a direction of N (30°-40°) E, and the minimum principal stress is 8.02 MPa with a direction of N (50°-60°) W. The maximum and minimum principal stresses are approximately in the horizontal plane. The intermediate principal stress is 11.73 MPa in vertically downward. These results are basically consistent with the distribution statistical law of the measured in situ stress fields in the world. The results presented in the study could provide a reference for the later mining, stability evaluation, and support of the surrounding rock.

In Situ Stress Measurement and Surrounding Rock Stability Analysis of the Gaoligong Mountain Tunnel

2014 ◽  
Vol 501-504 ◽  
pp. 1766-1773
Author(s):  
Lin Hai Bao
Keyword(s):  
Large Deformation ◽  
Principal Stress ◽  
Stress Measurement ◽  
Pressure Coefficient ◽  
Horizontal Stress ◽  
Wall Rock ◽  
In Situ Stress ◽  
Rock Stability ◽  
Mountain Tunnel

Gaoligong Mountain tunnel is the key project in the Dali-Ruili Railway. In order to optimize the design and guide construction, In-situ stress has been conducted in five boreholes using hydraulic fracturing method, the current shallow crustal in-situ stress state at the project area are obtained according to the measurements results, and deep in-situ stress is predicted using lateral pressure coefficient. The test results show that at depths ranging from 299-979m, the maximum horizontal principal stress is 5.33-30.12Mpa, the minimum horizontal principal stress is 4.94-23.11Mpa, the horizontal principal stress reach 30Mpa at maximum the depth of burial, indicating that the engineering stress filed is dominated by horizontal stress. Based on the In-situ stress data and different distinguish methods, rockburst and large deformation are predicted. The results show that In-situ stress magnitude in this area is classified as high level, and the direction of the maximum horizontal stress is NEE, In-situ stress orientation is conductive to stable of the tunnel. When the tunnel passes through the deep-burial and hard rock, the wall rock may happen rockburst; and the large deformation may happen when the tunnel pass through the weak rock. In order to avoid the disadvantage conditions, reasonable excavation method and safety support method should be adopted during tunnel excavating.

scholarly journals Study on In Situ Stress Measurement and Surrounding Rock Control Technology in Deep Mine

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Zhongcheng Qin ◽  
Bin Cao ◽  
Yongle Liu ◽  
Tan Li
Keyword(s):  
Stress Field ◽  
Principal Stress ◽  
Coal Mine ◽  
Maximum Principal Stress ◽  
In Situ Stress ◽  
Measured Data ◽  
Surrounding Rock ◽  
In Situ Stress Measurement ◽  
Surrounding Rock Control

In situ stress is the direct cause of roadway deformation and failure in the process of deep mining activities. The measured data of in situ stress in the Shuanghe coal mine show that the maximum principal stress is 44.94~50.61 MPa, and the maximum principal stress direction is near horizontal direction, which belongs to tectonic stress field. The maximum horizontal principal stress is 1.66~1.86 of the vertical stress. The horizontal principal stress controls the deep stress field. According to the measured data of in situ stress, the high-strength prestress bolt and cable collaborative support form is designed in the Shuanghe coal mine. Based on the stress field research of bolt and cable, the optimal prestress ratio of bolt and cable is proposed as 3. When the prestress ratio of bolt and cable is constant, the smaller the length ratio of bolt and cable is, the better the effect of prestressed field formed by cooperative support is. The results are applied to the support design of the mining roadway in the Shuanghe coal mine. Through the field monitoring test results, it is found that the maximum roof subsidence is 86 mm, the maximum floor deformation is 52 mm, and the maximum deformation of two sides is 125 mm. The surrounding rock control effect of the roadway is good, and the surrounding rock deformation conforms to the engineering technology standard requirements. The research results of this paper can provide some reference for the surrounding rock support of high ground stress mining roadway under similar conditions.

scholarly journals Numerical Investigation of a Hydrosplitting Fracture and Weak Plane Interaction Using Discrete Element Modeling

Water ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 535
Author(s):  
Shuaiqi Liu ◽  
Fengshan Ma ◽  
Haijun Zhao ◽  
Jie Guo ◽  
Xueliang Duan ◽  
...  
Keyword(s):  
Shear Stress ◽  
Principal Stress ◽  
Stress Ratio ◽  
Water Pressure ◽  
Maximum Shear Stress ◽  
Water Inrush ◽  
Discrete Element ◽  
Maximum Principal Stress ◽  
In Situ Stress

Water inrush caused by hydrosplitting is an extremely common disaster in the engineering of underground tunnels. In this study, the propagation of fluid-driven fractures based on an improved discrete element fluid-solid coupling method was modeled. First, the interactions between hydrosplitting fractures (HFs) and preexisting weak planes (WPs) with different angles were simulated considering water pressure in the initial fracture. Second, the influence of the in situ stress ratio and the property of WPs were analyzed, and corresponding critical pressure values of different interactions were calculated. Lastly, the maximum principal stress and maximum shear stress variation inside the pieces were reproduced. The following conclusions can be drawn: (1) Five different types of interaction modes between HFs and natural WPs were obtained, prone to crossing the WPs under inclination of 90°. (2) The initiation pressure value decreased with an increased in situ stress ratio, and the confining stress status had an effect on the internal principal stress. (3) During HFs stretching in WPs with a high elastic modulus, the value of the maximum principal stress was low and rose slowly, and the maximum shear stress value was smaller. Through comprehensive analysis, the diversity of the principal stress curves is fundamentally determined by the interaction mode between HFs and WPs, which are influenced by the variants mentioned in the paper. The analysis provides a better guideline for understanding the failure mechanism of water gushing out of deep buried tunnel construction and cracking seepage of high head tunnels.

Quantitative analysis of the shallow crustal tectonic stress field in China mainland based on in situ stress data

2014 ◽  
Vol 85 ◽  
pp. 154-162 ◽  
Author(s):  
Shuxin Yang ◽  
Luyuan Huang ◽  
Furen Xie ◽  
Xiaofeng Cui ◽  
Rui Yao
Keyword(s):  
Quantitative Analysis ◽  
Stress Field ◽  
Tectonic Stress ◽  
In Situ Stress ◽  
Tectonic Stress Field ◽  
China Mainland

scholarly journals Large Deformation Mechanics of Gob-Side Roadway and Its Controlling Methods in Deep Coal Mining: A Case Study

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Jianwei Zheng ◽  
Wenjun Ju ◽  
Xiaodong Sun ◽  
Zhongwei Li ◽  
Shuai Wang ◽  
...  
Keyword(s):  
Stress Field ◽  
Large Deformation ◽  
Coal Mining ◽  
Tectonic Stress ◽  
In Situ Stress ◽  
Field Analysis ◽  
Underground Mines ◽  
Roof Structure ◽  
Deformation Mechanics

Maintaining surrounding rock mass stability of roadways is essential to the safety of deep coal mining. In this study, the No. 2-2092 roadway of the No. 2-209 mining face in Ganhe coal was taken as the target roadway for field analysis. The selected region can be considered a typical area with dominating geological tectonic stress, based on the geological survey and in situ stress results. A mechanical model of roadway overburdens was developed to analyse the large deformation and stress field distribution. It is found that the large deformation is caused by the combined superposed stress field including laterally transferred stress formed in structures at overlying strata, mining-induced advanced abutment pressure, and the regional in situ stress. Thus, a Two-Direction Hydrofracturing Technique (TDHT) was proposed to reduce the pressure of the No. 2-2092 roadway by altering the roof structure in the influenced zones. Compared with the original roadway without fracturing, it is found that the roof to floor convergence has dropped by nearly 47% after fracturing; the displacement of sidewalls has reduced by almost 31%, demonstrating the effectiveness of the proposed method in pressure relief. Results from this study can provide guidance on controlling the large deformation of roadways in deep underground mines.

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