Microseismic Monitoring of Strainburst Activities in Deep Tunnels at the Jinping II Hydropower Station, China

Xu, Nuwen; Li, T. B.; Dai, Feng; Zhang, R.; Tang, Chun’an; Tang, Liexian

doi:10.1007/s00603-015-0784-0

Cited by 119 publications

(28 citation statements)

References 27 publications

(40 reference statements)

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“…ese two significant geohazards could affect the safety of personnel and infrastructure in excavations and deep underground mines. For example, severe strain burst occurred along a considerable length of tunnel section during tunnel excavation of the China Jinping II hydropower station project [5].…”

Section: Introductionmentioning

confidence: 99%

Microscopic Characteristics of Fractured Sandstone after Cyclic Freezing‐Thawing and Triaxial Unloading Tests

Shen

Zhu

2019

Advances in Civil Engineering

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e understanding of tunneling rock failure characteristics under unloading conditions in the cold region is critical for the proper design of rock tunneling support and mining safety operation. Given this understanding is currently limited, this study aimed to investigate the characteristics of fractured sandstone samples in the microscale after cyclic freezing-thawing and triaxial unloading tests. e samples were first subjected to different cycles of freezing and thawing, followed by the triaxial unloading test and scanning electron microscopy imaging. e peak strength and damage dilatancy stress were measured from the stress-strain curves. e microcrack characteristics (number, length, and width) were obtained through the image analysis. e results show that the decrease in peak strength and damage dilatancy stress was more significant by the first 20 freezing-thawing cycles when the pore pressure gradient is maximum compared to the later freezing-thawing cycles. e mechanical properties also significantly deteriorated when the severe freezing-thawing treatments were performed. e fracture section mainly had the morphology of honeycomb-like microstructure, stripped microstructure, and flocculent microstructure. e cracking extent was mainly influenced by the freezing-thawing rather than the triaxial unloading test, but the azimuthal angle of microcracks was significantly altered by the triaxial unloading. To properly design rock tunneling support and safe operation of mining in the cold region, both impact of cyclic freezing-thawing and the excavation operation direction should be considered.

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Section: Introductionmentioning

confidence: 99%

Microscopic Characteristics of Fractured Sandstone after Cyclic Freezing‐Thawing and Triaxial Unloading Tests

Shen

Zhu

2019

Advances in Civil Engineering

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“…e propagation directions of MS waves generated by microcracking are almost the same leading to a tangent orientation mode which was discussed by Xu et al [49]. It is clearly found that the source location errors perpendicular to the tunnel Advances in Civil Engineering 7 axis are relatively large.…”

Section: Sensor Array and Source Locationmentioning

confidence: 60%

Microseismic Monitoring of Energy Changes in Deep Tunnels during the TBM Tunneling of the Jinping II Hydropower Station

Zhuang

Tang

et al. 2018

Advances in Civil Engineering

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e TBM tunneling at the Jinping II hydropower station in Southwest China has received extensive concerns around the world because of its large engineering scale and the high rockburst risks faced in the tunnel advancement. e associated energy changes of rockbursts and control method for safe TBM tunneling are to be further investigated. A movable microseismic (MS) monitoring system was established to capture the MS events and rockbursts when the TBM excavated the headrace tunnel #1 at the Jinping II hydropower station. e spatial and temporal patterns of the energy changes in the tunnel rock masses were studied. Meanwhile, the evolution of a rockburst encountered in front of the TBM excavation face was revealed, and the performance of the top pilot tunnel method on the reduction of the rockburst risks in the headrace tunnel #1 was evaluated based on the energy changes of the surrounding rock masses. It can be concluded that energy accumulation and energy release firstly occurred in the surrounding rock masses at the southern end of the top pilot tunnel section of the headrace tunnel #1. en, energy transference of the rock masses took place from the southern end to northwest of the top pilot tunnel giving rise to the occurrence of a moderate rockburst about 30 m in front of the tunnel. However, no rockbursts appeared when the TBM excavated through the top pilot tunnel section of the headrace tunnel #1. erefore, the top pilot tunnel method really works in reducing the risks of rockbursts during the TBM tunneling in deep tunnels.

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“…Drilling and blasting are some of the most commonly used methods for rock breaking. Due to their advantages of good applicability to various geotechnical conditions, low cost, and easy operation, they have been widely applied to mine chamber excavation and water conservancy and hydropower engineering [1][2][3]. The conventional blasting technique has certain limitations and normally leads to undesirable effects.…”

Section: Introductionmentioning

confidence: 99%

Damage Evolution Mechanisms of Rock Induced by Blasting with the Aid of Empty-Hole Effect

et al. 2020

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Blasting has been widely used in coal mining as a method of reducing the integrity of rock mass. Its low controllability often leads to the unsatisfactory fragmentation effect of rock mass. The empty borehole effect has great significance in avoiding the excessive breakage of rock mass and guiding the directional propagation of blasting-induced fractures. Nevertheless, the rock mass damage type evolution induced by the empty borehole has been rarely studied. A tension-compression constitutive model of rock mass damage is established in this paper. The model is incorporated into the numerical modeling code LS-DYNA as a user-defined material model. Then, LS-DYNA is used to investigate the evolution mechanism of rock mass damage under the empty borehole effect. The damage types of rock mass caused by the empty borehole effect are also studied. The Fortran language is utilized to monitor the number variation of the tensile damaged elements and the compressive damaged elements in the rock mass around the empty borehole. The results indicate that existence of the empty borehole significantly enhances the tensile stress and the stress concentration factor in the rock mass nearby the empty borehole. Meanwhile, the rock mass nearby the empty borehole mainly damages in tension. Both the number of the tensile damaged elements and the tensile stresses in the elements increases as the empty borehole diameter increases. The number of the compressive damaged elements decreases with increasing empty borehole diameter.Energies 2020, 13, 756 2 of 21 mass. Yue et al. [4] found that the empty borehole is able to change the stress distribution in the rock mass and induce the initiation and directional propagation of the blasting-induced fractures.The existence of the empty borehole in the rock can change the stress distribution and the damage zone in the rock mass [5]. The empty borehole concept has been successfully applied to rock fracturing, tunnel excavation, and coal seam gas extraction [6,7]. The dynamic evolution of the blasting-induced stress and the directional propagation of the blasting-induced fractures have been widely studied by many researchers based on theoretical analysis and laboratory experiments. Cho et al. [8] investigated the influence of the empty borehole on fracture propagation, using polymethyl methacrylate (PMMA) and revealed the law of fracture propagation from the aspect of stress concentration. Based on the evolution characteristics of the fractures between blasting boreholes, He and Yang [9] studied the law of fracture propagation between adjacent boreholes, using a high-speed camera and digital image processing. Ma and An [10] simulated the stress evolution and fracture propagation around an empty borehole in the blasting process by numerical modeling and provided a theoretical basis for the formation of blasting-induced fractures. Chen et al. [11] used LS-DYNA (a numerical modeling code) to simulate the effective stress distribution in the rock under the superimposition effect of stress waves and refl...

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Microseismic Monitoring of Strainburst Activities in Deep Tunnels at the Jinping II Hydropower Station, China

Cited by 119 publications

References 27 publications

Microscopic Characteristics of Fractured Sandstone after Cyclic Freezing‐Thawing and Triaxial Unloading Tests

Microscopic Characteristics of Fractured Sandstone after Cyclic Freezing‐Thawing and Triaxial Unloading Tests

Microseismic Monitoring of Energy Changes in Deep Tunnels during the TBM Tunneling of the Jinping II Hydropower Station

Damage Evolution Mechanisms of Rock Induced by Blasting with the Aid of Empty-Hole Effect

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