scholarly journals Application of Constant Resistance and Large Deformation Anchor Cable in Soft Rock Highway Tunnel

2019 ◽  
Vol 2019 ◽  
pp. 1-19 ◽  
Author(s):  
Xiaoming Sun ◽  
Bo Zhang ◽  
Li Gan ◽  
Zhigang Tao ◽  
Chengwei Zhao
Keyword(s):  
Large Deformation ◽  
Support System ◽  
Field Tests ◽  
Soft Rock ◽  
Internal Force ◽  
Surrounding Rock ◽  
Gansu Province ◽  
Tunnel Engineering ◽  
Anchor Cable ◽  
Constant Resistance

Muzhailing Highway Extra-long Tunnel in Lanzhou, Gansu Province, China, belongs to the soft rock tunnel in the extremely high geostress area. During the construction process, large deformation of the soft rock occurred frequently. Taking the no. 2 inclined shaft of Muzhailing tunnel as the research object, an NPR (negative Poisson’s ratio) constant resistance and large deformation anchor cable support system based on high prestress force, constant resistance, and releasing surrounding rock pressure was proposed. The characteristics of the surrounding rock under the steel arch support and NPR anchor cable support were compared and analyzed by using 3DEC software. A series of field tests were conducted in the no. 2 inclined shaft, and the rock strength, displacement of the surrounding rock, deep displacement of the surrounding rock, internal force of steel arch, and axial force of anchor cable were measured to study the application effect of the NPR anchor cable support system in tunnel engineering. Moreover, the 3DEC numerical simulation results were compared with the field test results. The research results show that the application of NPR constant resistance and large deformation anchor cable support system in tunnel engineering has achieved good results, and it plays a significant role in controlling the large deformation of the tunnel surrounding rock.

scholarly journals Constant-Resistance, Rigid, and Flexible Coupling Support Technology for Soft Rock Entrances in Deep Coal Mines:A Case Study in China

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Yong Zhang ◽  
Chengwei Zhao ◽  
Ming Jiang ◽  
Jiaxuan Zhang ◽  
Chen Chen ◽  
...  
Keyword(s):  
Large Deformation ◽  
Support System ◽  
Soft Rock ◽  
High Strength ◽  
Surrounding Rock ◽  
Constant Resistance ◽  
The Stability ◽  
Control Principle ◽  
Soft Rock Roadway ◽  
Rock Roadway

The stability control of a soft rock roadway is a crucial problem for sustainable utilization of limited coal resources in deep mining practices. To solve it, the soft rock types and failure mechanism of −890 entrance surrounding rock have been analyzed, taking Daqiang Coal Mine of China as an engineering example. The analysis shows that the damage to the surrounding rock was characterized by asymmetry, large deformation, severe damage, and extended durations. The surrounding rock can be divided into high-stress-jointed-strong expansion soft rock based on S-M scanning and mineral analysis. Numerical simulation is used to reproduce the failure process of the original supporting system and analyze the deformation of the surrounding rock, range of plastic zone, and distribution of the stress field. The failure mechanism is thus defined for a deep soft rock roadway. Combined with the above studies, the deformation mechanics of the surrounding rock is summarized as type IABIIABIIIABC. The stability transformation mechanism of the surrounding rock is proposed, based on which the control principle of deformation stability of a surrounding rock is formed. According to the control principle, “high strength support controls the surrounding rock deformation. The large deformation of the flexible support system releases the accumulated energy to the surrounding rock, and long-term deformation of the surrounding rock is controlled by high strength truss support.” Meanwhile, the constant-resistance, rigid, and flexible coupling (CRRFC) support system is proposed. The numerical analysis demonstrated that the CRRFC support system can effectively reinforce the shallow surrounding rock and improve the bearing capacity. Simultaneously, the development of the surrounding rock malignant plastic zone is effectively controlled. The application results show that the large deformation of the roadway can be effectively controlled by the CRRFC support system, which provides applications for similar engineering.

scholarly journals Analysis on Loose Circle of Surrounding Rock of Large Deformation Soft-Rock Tunnel

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Rui Wang ◽  
Yiyuan Liu ◽  
Xianghui Deng ◽  
Yu Zhang ◽  
Xiaodong Huang ◽  
...  
Keyword(s):  
Large Deformation ◽  
Theoretical Calculations ◽  
Rapid Development ◽  
Field Tests ◽  
Soft Rock ◽  
Strength Criterion ◽  
Surrounding Rock ◽  
Distribution Law ◽  
Geological Conditions ◽  
Rock Tunnel

With the rapid development of tunnel construction in China, deep buried and long tunnel projects are emerging in areas with complex engineering geological conditions and harsh environment, and thus large deformation of tunnels under conditions of high in situ stress and soft rock becomes increasingly prominent and endangers engineering safety. Therefore, it is of great significance to control the deformation and improve the stability of surrounding rock by analyzing the thickness and distribution law of loose circle according to the unique mechanical properties and failure mechanism of surrounding rock of large deformation soft-rock tunnel. Based on unified strength theory, this paper deduces the radius calculation formula of the loose circle by considering the influence of intermediate principal stress. Furthermore, the theoretical calculations and field tests of the loose circle in the typical sections of grade II and III deformation of Yuntunbao tunnel are carried out, and the thickness and distribution law of loose circle of surrounding rock of large deformation soft-rock tunnel is revealed. The results show that the formula based on the unified strength criterion is applicable for a large deformation tunnel in soft rock.

scholarly journals Presplitting Blasting the Roof Strata to Control Large Deformation in the Deep Mine Roadway

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Chaowen Hu ◽  
Xiaojie Yang ◽  
Ruifeng Huang ◽  
Xingen Ma
Keyword(s):  
Large Deformation ◽  
Field Tests ◽  
Soft Rock ◽  
Surrounding Rock ◽  
Deep Mine ◽  
Mining Depth ◽  
Working Face ◽  
Support Conditions ◽  
Mine Roadways ◽  
Roof Strata

As the mining depth increases, under the influence of high ground stress, the surrounding rock of deep mine roadways shows soft rock characteristics. Under the influence of mining disturbance at the working face, large deformation of the roadway has occurred. To control the large deformation of the roadway, many mines have adopted the form of combined support, which has continuously increased the support strength and achieved a certain effect. However, since the stress environment of the surrounding rock of the roadway has not been changed, large deformation of the roadway still occurs in many cases. Based on the theoretical basis of academician Manchao He’s “short cantilever beam by roof cutting,” this paper puts forward the plan of “presplitting blasting + combined support” to control the large deformation of the deep mine roadways. Without changing the original support conditions of the roadway, presplitting blasting the roof strata of the roadway, by cutting off the mechanical connection of the roof strata between the roadway and gob, improves the stress distribution of the roadway to control the large deformation. Through field tests, the results show that after presplitting blasting the roadway roof, the roadway roof subsidence is reduced by 47.9%, the ribs displacement is reduced by 45.7%, and the floor heave volume is reduced by 50.8%. The effect is significant.

scholarly journals Constant Resistance and Yielding Support Technology for Large Deformations of Surrounding Rocks in the Minxian Tunnel

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Jinyan Fan ◽  
Zhibiao Guo ◽  
Xiaobing Qiao ◽  
Zhigang Tao ◽  
Fengnian Wang ◽  
...  
Keyword(s):  
Large Deformation ◽  
Large Deformations ◽  
Field Tests ◽  
Field Application ◽  
Deformation Monitoring ◽  
Surrounding Rock ◽  
Maximum Deformation ◽  
Constant Resistance ◽  
Structural Deformations ◽  
Yielding Support

During the excavation of the Minxian tunnel, problems of large deformations of surrounding rocks and failure of support structures appeared frequently, which caused serious influences on construction safety and costs of the tunnel. Based on laboratory analysis of mineral composition and field investigations on deformation characteristics of the surrounding rocks, the large deformation mechanism of surrounding rocks of the tunnel was considered as water-absorbing swelling molecules of carbonaceous slate and stress-induced asymmetric structural deformations of the surrounding rocks. The structural deformations of surrounding rocks mainly include bending deformation, interlayer sliding, and crushing failure of local rock blocks. Then, a new constant resistance and yielding support technology based on the constant resistance and large deformation (CRLD) anchor cable was proposed to control large deformations of surrounding rocks. The field tests and deformation monitoring were carried out. The monitoring results showed that compared with original support measure, the surrounding rock deformations, stresses of primary supports, and permanent lining using new support technology decreased greatly. Among them, the maximum deformation of surrounding rock was only 73 mm. The effects of field application and results of deformation monitoring showed that the new support technology can effectively control large deformations of the surrounding rocks in the Minxian tunnel.

scholarly journals Frame Structure and Engineering Applications of the Multisource System Cloud Service Platform of Monitoring of the Soft Rock Tunnel

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Fengnian Wang ◽  
Songyang Yin ◽  
Aipeng Guo ◽  
Zhicai Wang ◽  
Meng Mi ◽  
...  
Keyword(s):  
Real Time ◽  
Large Deformation ◽  
Monitoring System ◽  
Early Warning ◽  
Soft Rock ◽  
Cloud Service ◽  
Surrounding Rock ◽  
Anchor Cable ◽  
Time Operation ◽  
Rock Tunnels

Throughout engineering construction, large deformation disasters in soft rock tunnels are encountered increasingly frequently. Therefore, structural health monitoring not only ensures accurate construction management but also provides a basis for dynamic adjustment of the support structure. The existing monitoring technology has certain shortcomings, such as poor anti-interference ability, non-real-time operation, and great security risks. Consequently, high-precision real-time monitoring has become a key scientific issue in tunnel engineering. For this work, multisource information fusion technology was adopted, while data security reserve systems, such as cloud server (ECS) based on the fiber Bragg grating multisource sensing system, cloud database (RDS), and cloud website, were embedded into the No. 2 inclined shaft of the Muzhailing tunnel. Based on the negative Poisson’s ratio (NPR) anchor cable control technology for large deformation of the soft rock in the No. 2 inclined shaft of the Muzhailing tunnel, reasonable and effective intelligent monitoring was carried out for tunnel construction. Monitoring and early warning cloud service platforms, based on the Internet of Things and cloud technology, could quickly produce query and statistic tunnel monitoring information. The monitoring system provided the collection, transmission, storage, processing, and early warning information sending of data, such as NPR anchor cable axial force, steel arch stress, deep surrounding rock displacement, surrounding rock deformation, and contact pressure between primary support with secondary lining. This monitoring system ensured construction safety and provided monitoring application case support for the related problems of similar projects.

scholarly journals Research on Supporting Measure at Intersection of Inclined Shaft and Major Tunnel in Highway

2020 ◽  
Vol 2020 ◽  
pp. 1-15 ◽  
Author(s):  
Xiaoming Sun ◽  
Bo Zhang ◽  
Zhigang Tao ◽  
Chengwei Zhao ◽  
Jian Wang
Keyword(s):  
Large Deformation ◽  
Three Dimensional ◽  
Surrounding Rock ◽  
Local Pressure ◽  
Tunnel Support ◽  
Maximum Deformation ◽  
Anchor Cable ◽  
Constant Resistance ◽  
Before And After ◽  
High Geostress

The deformation characteristics of the rock mass in the intersection between the Muzhailing highway tunnel and the inclined shaft is a complicated three-dimensional problem. Under the influence of high geostress, large deformation hazards may occur in the surrounding rock. Taking this as the research background, this paper analyzes the deformation mechanism of surrounding rock before and after prestressed anchor cable support through numerical simulation. Then, through theoretical analysis, a new tunnel support method using high prestressed constant resistance and large deformation anchor cable was proposed. The field monitoring results show that the constant resistance and large deformation anchor cable support can well control the deformation of surrounding rock, and the maximum deformation is within 300 mm. At the same time, the constant resistance anchor cable can always maintain a high prestress, which makes the stress of the surrounding rock uniform, and reduces the risk of damage to the steel arch due to local pressure. Moreover, the support method limits the expansion of the plastic zone and improves the overall stability of the surrounding rock.

scholarly journals Nonlinear Large Deformation Mechanism and Stability Control of Deep Soft Rock Roadway: A Case Study in China

2019 ◽  
Vol 11 (22) ◽  
pp. 6243 ◽  
Author(s):  
Dong Wang ◽  
Yujing Jiang ◽  
Xiaoming Sun ◽  
Hengjie Luan ◽  
Hui Zhang
Keyword(s):  
Large Deformation ◽  
Coal Mine ◽  
Deformation Mechanism ◽  
Soft Rock ◽  
Stability Control ◽  
Surrounding Rock ◽  
Gansu Province ◽  
Soft Rock Roadway ◽  
Coupling Support ◽  
Rock Roadway

Improving the safety and stability of soft surrounding rock with nonlinear large deformation gives a strong guarantee for the safe mining and sustainable development of deep coal mines. In order to control the nonlinear large deformation of the surrounding rock in a deep soft rock roadway, this paper discusses the nonlinear large deformation mechanism and coupling support countermeasures of a typical engineering application at Xin’an coal mine in Gansu province, China. The series of experiments and theoretical analysis described in this paper reveal the phenomena, properties, and reasons for the nonlinear large deformation of soft surrounding rock in detail. Then, the type of nonlinear large deformation mechanism is determined and transformed from a composite one to a simple one. Based on experimental results and mechanism transformation, a suitable coupling support countermeasure, which contains the Constant Resistance Large Deformation (CRLD) bolt, steel mesh, floor hollow grouting cable, and steel fiber concrete, is proposed to reduce the nonlinear large deformation and the potential risk during mining. The application shows that the coupling support countermeasure can effectively reduce the nonlinear large deformation of the surrounding rock and help to maintain the stability of the deep soft rock roadway at Xin’an coal mine.

scholarly journals Research on Full-Section Anchor Cable and C-Shaped Tube Support System of Deep Layer Roadway

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Renliang Shan ◽  
Shupeng Zhang ◽  
Pengcheng Huang ◽  
Weijun Liu
Keyword(s):  
Support System ◽  
Surface Displacement ◽  
Field Tests ◽  
Soft Rock ◽  
Shear Resistance ◽  
Tectonic Stress ◽  
Anchor Cable ◽  
Shaped Tube ◽  
Roadway Deformation ◽  
Prestressed Anchor

Deep roadway deformation due to soft rock, rock dip, and horizontal tectonic stress is uneven and asymmetrical primarily in large loose zones. Traditional anchor support is influenced by the yield strength and shear strength of the anchors and has a limited prestress capacity or shear resistance. When the roadway roof is laminated rock or when the roadway passes through layered rock or rock interfaces, interlayer sliding commonly occurs, which can easily lead to anchor cables being sheared off. The tape tunnel in the Zhengling Mine passes through several rock strata and requires anchors to achieve a high shear resistance and prestress. To solve these problems, an anchor cable and C-shaped tube that can bear lateral shear forces were developed, and a full-section anchor cable and C-shaped tube support system were created based on extruded arch theory. Numerical results from FLAC3D show that the new scheme effectively controls surface convergence and plastic zone extension. Field tests have demonstrated that the amount of surface displacement was at least 42% smaller in the new support scheme. The extruded arch formed by the highly prestressed anchor cable and concrete spray layer can effectively control the bulking load within the loose zone, and the ACC effectively resists interlayer shear.

scholarly journals Study on Deformation Mechanism and Support Measures of Soft Surrounding Rock in Muzhailing Deep Tunnel

2020 ◽  
Vol 2020 ◽  
pp. 1-14 ◽  
Author(s):  
Zhigang Tao ◽  
Jindong Cao ◽  
Liu Yang ◽  
Aipeng Guo ◽  
Ruifeng Huang ◽  
...  
Keyword(s):  
Large Deformation ◽  
Support System ◽  
Deformation Mechanism ◽  
High Stress ◽  
Soft Rock ◽  
Maximum Principal Stress ◽  
Surrounding Rock ◽  
Single Type ◽  
Deep Tunnel ◽  
Support Measures

The deformation of Muzhailing deep tunnel is about 2.3 m in the process of construction, which is difficult to be controlled by the traditional “anchor-grouting integration” support system. This paper deeply analyzes the geological characteristics, rock mechanics characteristics, and surrounding rock failure characteristics of Muzhailing tunnel. The deformation mechanism and the failure of the support system are analyzed through the numerical simulation, theoretical analysis, and field test. The authors propose support measures suitable for Muzhailing tunnel based on the analysis results. The maximum buried depth is 600 m, and the engineering rock mass at the depth has nonlinear physical and mechanical phenomenon. The maximum principal stress of Muzhailing tunnel is 25.7 MPa, which belongs to high-stress joint swelling soft rock tunnel. The NPR cable can achieve large deformation under the condition of constant support resistance. The authors put forward the coupling support mode of “NPR cable + steel arch frame + concrete,” which is based on the idea of transforming the composite deformation mechanism to a single type. The stress concentration appears in the range of 12 m in the surrounding rock circle, and the lateral and vertical stress distributions are relatively symmetrical after the improved support. The circumferential strain of the surrounding rock is greatly reduced, and the range of strain is reduced by 10%. The field monitoring results show that the new support system can well control the large soft rock deformation of Muzhailing tunnel (0.5 m). The support strategy proposed can effectively control the large deformation and promote the formation of new support concept for deep tunnel.

scholarly journals Effects of High-Pretension Support System on Soft Rock Large Deformation of Perpendicularly Crossing Tunnels

2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Li Gan ◽  
Ma Weibin ◽  
Tian Siming ◽  
Zhou Wenhao
Keyword(s):  
Theoretical Analysis ◽  
Large Deformation ◽  
Support System ◽  
Control Mechanism ◽  
Three Dimensional ◽  
Soft Rock ◽  
Surrounding Rock ◽  
Control Effect ◽  
Support Design ◽  
The Stability

The control mechanism of prestressed support system is studied by means of three-dimensional discrete element numerical simulation, theoretical analysis, and field measurement. The actual project is selected to analyze, and the control effect is demonstrated. The theoretical analysis results show that the prestressed support can improve the self-bearing capacity of surrounding rock, which is conducive to the stability of the surrounding rock. The numerical calculation shows that, under the control of the long and short cables, the prestress can spread effectively and form two bearing arches. The deformation is difficult to control, which is in the arch crown and the arch shoulder of the tunnel intersection. However, the deformation of the surrounding rock decreases with the increase of prestress. Through the analysis of the measured results, it shows that the pretension support design scheme can effectively control the large deformation of the surrounding rock.

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