IN-SITU STRESS MEASUREMENT BY OVERCORING AND HYDRAULIC FRACTURING OF PAHANG-SELANGOR RAW WATER TRANSFER PROJECT

Estimation of in-situ stress orientation and magnitude is necessary for assessing the excavation risks for Pahang-Selangor Raw Water Transfer (PSRWT) tunnel project. However, the in-situ stress state of the rock generally differs according to area and depth. Therefore, the in-situ stress measurements test in the tunnel are determined in three (3) locations, which are at Adit 2, TBM 2, and Adit 3, in which the overburdens are 227, 1130, and 570 m, respectively. The stress relief method of overcoring technique and hydraulic fracturing by high stiffness system were applied for this project. The results demonstrate that the existence of high vertical stress was estimated in particular in the TBM 2. The maximum principal stress is determined nearly along the vertical direction. Meanwhile, the stress in the horizontal plane is relatively small, and the horizontal to vertical stress ratio is less than one (1). The direction of the horizontal stress obtained is N8E, N14W, and N41E. Results indicate that this method is suitable for estimating in-situ stresses in deep tunnels. The above data and their interpretations enhance the stress database for Peninsular Malaysia

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Rock Overstressing in Deep Tunnel Excavation of Pahang-Selangor Raw Water Transfer Project

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.802.16 ◽

2015 ◽

Vol 802 ◽

pp. 16-21 ◽

Cited By ~ 2

Author(s):

Romziah Azit ◽

Mohd Ashraf Mohamad Ismail ◽

Sharifah Farah Fariza Syed Zainal ◽

Norzani Mahmood

Keyword(s):

Rock Strength ◽

Stress Measurement ◽

In Situ Stress ◽

Water Transfer ◽

Stress Factors ◽

Raw Water ◽

Tunnel Excavation ◽

In Situ Stress Measurement ◽

Assessment Approach

Tunneling under high overburden and in-situ stress may cause tunnel instability because of rock overstressing. Evaluating overstressing in deep hard rocks is crucial to minimize excavation risks. The excavation of the Pahang-Selangor Raw Water Transfer Tunnel is evaluated in this study. A potential overstressing problem is expected at a tunnel depth more than 500 m. Therefore, the possibility of rock overstressing is assessed based on the evaluations of in-situ stress measurement, rock strength, and actual observations during the tunnel excavation. An analytical method is used to analyze the behavior of the tunnel under high overburden stress based on rock strength and tangential stress factors. The empirical assessment approach to the observation of actual overstressing appeared to be valid for the prediction of overstressing. These approaches facilitate the reasonable prediction of tunnel behavior under different rock conditions, support systems, and overburden stresses, which serve as useful tools in the observational design and construction method of long and deep tunnels.

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Development of hydraulic fracturing in-situ stress measurement technology and its application

In-Situ Rock Stress ◽

10.1201/9781439833650.ch16 ◽

2006 ◽

pp. 121-126

Author(s):

Q Guo ◽

Q Chen ◽

C Wang

Keyword(s):

Hydraulic Fracturing ◽

Stress Measurement ◽

In Situ Stress ◽

Measurement Technology ◽

In Situ Stress Measurement

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Integrated Application of Three In Situ Stress Measurement Techniques

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.301-303.949 ◽

2011 ◽

Vol 301-303 ◽

pp. 949-953

Author(s):

Yuan Li ◽

Lan Qiao ◽

Zhi Li Sui

Keyword(s):

Acoustic Emission ◽

Hydraulic Fracturing ◽

Stress Measurement ◽

Stress Relief ◽

In Situ Stress ◽

In Situ Stresses ◽

In Situ Stress Measurement ◽

Iron Mine ◽

Acoustic Emission Test

The CSIRO overcoring stress relief and hydraulic fracturing methods are the most popular methods used for the measurement of in-situ stress at depth. One major advantage of the CSIRO overcoring stress relief method is that the three dimensional state of stress can be obtained, but the measurement must be done in an excavated tunnel[1]. Hydraulic fracturing method can be carried out on the ground surface, but it assumed that one of the principal stresses direction is vertical[2,3]. In terms of the disadvantages of the two methods, the techniques based on core orientation and acoustic emission behavior of rocks are incorporated in the in-situ stress measurement in order to obtain the in-situ stress conditions at depth in Shuichang Iron Mine. According to the comparison of the measurement data obtained from the acoustic emission test in the laboratory and CSIRO overcoring stress relief measurement in the field, effectiveness of the acoustic emission test is confirmed. In addition, the relationships between in-situ stresses and tectonic settings are analyzed. Finally, the distribution of in-situ stresses in Shuichang Iron Mine is given, which provides a meaningful guideline for the following mining and design.

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

Advances in Civil Engineering ◽

10.1155/2020/8830593 ◽

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.

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