Mechanical response of surrounding rock of tunnels constructed with the TBM and drill-blasting method

Fault is one of the most important factors affecting tunnel instability. As a significant and casual construction of Jinping II hydropower station, when the drain tunnel is excavated at depth of 1600 m, rockbursts and water inrush induced by several huge faults and zone of fracture have restricted the development of the whole construction. In this paper, a progressive failure progress numerical analysis code-RFPA (abbreviated from Rock Failure Process Analysis) is applied to investigate the influence of faults on tunnel instability and damaged zones. Numerical simulation is performed to analyze the stress distribution and wreck regions of the tunnel, and the results are consistent with the phenomena obtained from field observation. Moreover, the effects of fault characteristics and positions on the construction mechanical response are studied in details. Some distribution rules of surrounding rock stress of deep-buried tunnel are summarized to provide the reasonable references to TBM excavation and post-support of the drain tunnel, as well as the design and construction of similar engineering in future.

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Comparative Study of the Excavation Damage and Rockburst of the Deeply Buried Jinping II Diversion Tunnels Using a TBM and the Drilling-Blasting Method

Advances in Civil Engineering ◽

10.1155/2020/8876214 ◽

2020 ◽

Vol 2020 ◽

pp. 1-14

Author(s):

Jing Yang ◽

Xing-Guo Yang ◽

Jia-Wen Zhou ◽

Yong Liu ◽

Bao-Shun Dong ◽

...

Keyword(s):

Rock Mass ◽

Stress Concentration ◽

High Stress ◽

Tunnel Boring Machine ◽

In Situ Stress ◽

Surrounding Rock ◽

High In Situ Stress ◽

Damaged Zone ◽

Blasting Method

The rock mass failure induced by high in-situ stresses during the excavation of deep diversion tunnels is one of the key problems in the construction of the Jinping II Hydropower Station. Based on the results of acoustic wave tests and rockburst statistical analysis conducted, this study focuses on the excavation damaged zone (EDZ) and rockburst events in the Jinping II diversion tunnels excavated using the tunnel boring machine (TBM) method and the drilling-blasting method. The unloading failure mechanism and the rockburst induced by the two different excavation methods were compared and analyzed. The results indicate that, due to the different stress adjustment processes, the degree of damage to the surrounding rock mass excavated using the drilling-blasting method was more serious than that using the TBM method. The EDZ induced by the TBM was usually distributed evenly along the edge of the excavation surface. While, the drilling-blasting method was more likely to cause stress concentration, resulting in a deeper EDZ in local areas. However, the TBM excavation method can cause other problems in high in-situ stress areas, such as strong rockbursts. The drilling-blasting method is more prone to structural controlled failure of the surrounding rock mass, while the TBM method would induce high stress concentration near the edge of excavation and more widely distributed of stress adjustment induced failure. As a result, the scale and frequency of the rockburst events generated by the TBM were significantly greater than those caused by the drilling-blasting method during the excavation of Jinping II diversion tunnels. The TBM method should be used carefully for tunnel excavation in high in-situ stress areas with burial depths of greater than 2000 m. If it is necessary to use the TBM method after a comprehensive selection, it is suggested that equipment adaptability improvement, advanced prediction, and prediction technology be used.

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Research on the Mechanical Response of Tunnel Structure under Water Softening Surrounding Rock

IOP Conference Series Materials Science and Engineering ◽

10.1088/1757-899x/741/1/012083 ◽

2020 ◽

Vol 741 ◽

pp. 012083

Author(s):

Kun Qian ◽

Xiaoming Wang ◽

Rongqing Zhu ◽

Wenqi Ding

Keyword(s):

Mechanical Response ◽

Surrounding Rock ◽

Tunnel Structure ◽

Water Softening

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Mechanical response features and failure process of soft surrounding rock around deeply buried three-centered arch tunnel

Journal of Central South University ◽

10.1007/s11771-015-2951-6 ◽

2015 ◽

Vol 22 (10) ◽

pp. 4064-4073 ◽

Cited By ~ 4

Author(s):

Yu Zhao ◽

Zhi-gang Zhang

Keyword(s):

Mechanical Response ◽

Failure Process ◽

Surrounding Rock

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Analysis of Soft Rock Tunnel Mechanics Effects Based on Strain Softening Model of Surrounding Rock

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.424-425.520 ◽

2012 ◽

Vol 424-425 ◽

pp. 520-525

Author(s):

Jie Hong Zhang

Keyword(s):

Numerical Analysis ◽

Strain Softening ◽

Mechanical Response ◽

High Stress ◽

Soft Rock ◽

Mechanical Effect ◽

Surrounding Rock ◽

Plastic Range ◽

Construction Design ◽

Rock Tunnel

Aiming at mechanical response of soft surrounding tunnel affected by high stress, the mechanical effect in the process of excavation and supporting of surrounding rockmass was analyzed by softening model. First of all, mechanics properties of soft surrounding rock and strain softening model have been discussed. Then, based on strain softening model, numerical analysis was carried out, and stress and displacement field, plastic range in the in the process of excavation and supporting was obtained. The result was very useful for the optimization of construction design and perfection for supporting program.

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Analysis on the Characteristics of Displacement Field Distribution around the Deep Buried and Great Complex Section Tunnel

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.446-449.2251 ◽

2012 ◽

Vol 446-449 ◽

pp. 2251-2255 ◽

Cited By ~ 1

Author(s):

Sheng Xiang Lei ◽

Bo Gao ◽

Qing Hua Xiao

Keyword(s):

Retaining Wall ◽

Maximum Principal Stress ◽

Surrounding Rock ◽

Rock Deformation ◽

Hydropower Station ◽

Spring Back ◽

Rock Stress ◽

Large Section ◽

Blasting Method ◽

Underground Chamber

Taken the excavation of TBM assembly underground chamber with deeply buried super large and complex section in Jinping Ⅱ Hydropower Station as the background, apply theoretical analysis and experimental method to study the rock deformation and displacement analysis. The result shows that, drilling and blasting method is used for construction which is divided into four layers from top to bottom according to the excavation, they are 8.5m, 5.5m, 6.0m,7.0m from top to bottom, respectively. the displacement of surrounding rock generally moves toward the direction of the free surface. The rock possesses spring back deformation pointing to internal underground chamber. The displacements of arch crown and floor are mainly vertical, and displacement of retaining wall is mainly horizontal. This is significantly different from the rock deformation of underground chamber under general stress after excavation. The chamber displacement distribution under high crustal stress is closely related to stress direction. Location axis of underground chamber should parallel the direction of maximum principal stress. Under the complex and great deeply buried condition, excavation of large section tunnel by digging from the top layer can better release the rock stress, and the rock displacement changes gently, which is conducive to rock mass stability and structure security.

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“Wireline + Wireless” Networking Remote Monitoring Technology for Analysing the Unloading Deformation Characteristics of the Fractured Surrounding Rock Mass Induced by Underground Excavation

Advances in Civil Engineering ◽

10.1155/2019/4242936 ◽

2019 ◽

Vol 2019 ◽

pp. 1-10

Author(s):

Bin Hu ◽

Jianlong Sheng ◽

Jing Li ◽

Peng-Zhi Pan ◽

Guangquan Zhang ◽

...

Keyword(s):

Rock Mass ◽

Mechanical Response ◽

Wireless Networking ◽

Surrounding Rock ◽

Subway Tunnel ◽

Mechanical Responses ◽

Support Measure ◽

Signal Collection ◽

Excavation Process ◽

Extensive Property

Collapse or large deformation of fractured surrounding rock mass occurs frequently in underground tunnelling and results in many casualties and extensive property damage. This paper proposed a new type of remote telemetry system for monitoring the mechanical responses of underground tunnels during unloading. This system adopted both wired and wireless networking schemes, including a signal collection and transmission subsystem, a management analysis subsystem, and a remote receiving subsystem, in the tunnels. The application of this new approach in a subway tunnel indicated that the complete unloading performance of a surrounding rock mass can be captured in real time and high frequency using this method, recording the deformation of the surrounding rock, the stress in the bolts, and the stress in the shotcrete between the surrounding rock and steel arch. The in situ experimental study also found that deformation of the fractured surrounding rock mass in the Dashizi Tunnel showed a step-like fluctuating growth pattern. Additionally, the mechanical response of the surrounding rock mass during unloading tended to stabilize when the opening face was approximately 35 m away from the monitoring section, providing new ways to optimize the excavation process and support measure.

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Elastic Analysis of Nonhomogeneous Frozen Wall under Nonaxisymmetric Ground Stress Field and in State of Unloading

Advances in Materials Science and Engineering ◽

10.1155/2018/2391431 ◽

2018 ◽

Vol 2018 ◽

pp. 1-13 ◽

Cited By ~ 1

Author(s):

Wen Zhang ◽

Baosheng Wang ◽

Yong Wang

Keyword(s):

Stress Field ◽

Mechanical Response ◽

Tangential Force ◽

Circumferential Stress ◽

Radial Force ◽

Surrounding Rock ◽

Soil Freezing ◽

Frozen Ground ◽

Ground Stress ◽

Frozen Wall

The mechanical analysis of frozen walls is a cornerstone technology of artificially frozen ground. The mechanical response of frozen walls is affected by heterogeneity, excavation unloading, uneven ground pressure, and the characteristics of surrounding rock. However, these factors are rarely taken into full consideration in existing analysis models. To address this shortfall, this study presents a plane-strain model that considers the inhomogeneity of frozen walls, the unloaded state of the frozen-wall inner edge, and the nonuniform ground stress field (abbreviated as “IF model”). The solution of the IF model is based on the superposition of thin concentric cylinders under two types of contact conditions: complete contact and smooth contact, and its validity is tested by a finite-element calculation. The calculation indicates that the excavation reduces the radial force and increases the tangential force between the frozen wall and the surrounding earth mass; the ground principal stress is rotated after the excavation. If the radial unloading equals the tangential unloading at the inner edge of the frozen wall, the response of the radial stress differs from that of the tangential stress at the outer edge of the frozen wall. The circumferential stress and the radial displacement at the inner edge correlate linearly with the nonuniform coefficient of the ground press and the unloading ratio. If the nonuniform coefficient is relatively small, the inner edge of the frozen wall may incur tensile damage. Compared with the model of a homogeneous frozen wall (abbreviated as “HF model”), which has a uniform temperature distribution, the absolute value of the circumferential stress is lower (higher) for the IF model where the temperature is above (below) average. When the frozen wall is relatively thick, the circumferential stress of the inner edge of the frozen wall is lower for the IF model than for the HF model. The percent reduction is 8.12%∼9.32% for rock freezing and 13.41%∼18.03% for soil freezing. The IF model proposed herein thus reflects the characteristics of frozen walls and surrounding rock more clearly and accurately than the HF model and obtains stress states closer to the reality. Therefore, the IF model is recommended for the design and construction of frozen walls.

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Failure Analysis and Control Measures of Deep Roadway with Composite Roof: A Case Study

10.21203/rs.3.rs-548508/v1 ◽

2021 ◽

Author(s):

Yongliang LI ◽

Renshu Yang ◽

Shizheng Fang ◽

Hai Lin ◽

Shaojie Lu ◽

...

Keyword(s):

Rock Mass ◽

Mechanical Response ◽

Surrounding Rock ◽

Control Measures ◽

Shanxi Province ◽

Efficient Production ◽

Stable Layer ◽

Failure Characteristics ◽

Geological Conditions ◽

Unstable Layer

Abstract There is great variation in the lithology and lamination thickness of composite roof in coal-measure strata; thus, the roof is prone to delamination and falling, and it is difficult to control the surrounding rock when developing roadway in such rock strata. In deep mining, the stress environment of surrounding rock is complex, and the mechanical response of the rock mass is different from that of the shallow rock mass. For composite-roof roadway excavated in deep rock mass, the key to safe and efficient production of the mine is ensuring the stability of the roadway. The present paper obtains typical failure characteristics and deformation and failure mechanisms of composite-roof roadway with a buried depth of 650 m at Zhaozhuang Coal Mine (Shanxi Province, China). On the basis of determining a reasonable cross-section shape of the roadway and according to the failure characteristics of the composite roof in different regions, the roof is divided into an unstable layer, metastable layer, and stable layer. The controlled unstable layer and metastable layer are regarded as a small structure while the stable layer is regarded as a large structure. A superimposed coupling support technology of large and small structures with a multi-level prestressed bearing arch formed by strong rock bolts and highly prestressed cable bolts is put forward. The support technology provides good application results in the field. The study thus provides theoretical support and technical guidance for ground control under similar geological conditions.

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