scholarly journals Study on the Treatment Timing of Large Deformation of the Tunnel in Swelling Rock

2018 ◽  
Vol 206 ◽  
pp. 01005
Author(s):  
Zhongmin Yang ◽  
Yongtao Gao ◽  
Ziqiao Cheng ◽  
Zijie Cong
Keyword(s):  
Large Deformation ◽  
Surrounding Rock ◽  
Stress Release ◽  
Construction Time ◽  
Treatment Timing ◽  
Final Stress ◽  
Initial Support ◽  
Swelling Rock ◽  
Rock Tunnel ◽  
Deformation Treatment

When large deformation of the tunnel occurred in the swelling rock, the large deformation treatment will not only greatly delay the construction time, but also lead to instability or even collapse of the tunnel. Selecting the reasonable timing for large deformation initial support replacement can solve this problem effectively. Based on the LiRang tunnel, the deformation and stress of the tunnel in anhydrite were analysed by FLAC software after excavation. Then replace the deformed first liner at different vault settlement value. The displacement and stress of surrounding rock were analysed when the model reaches equilibrium state again. The results showed that stress concentration at the arch wall and arch foot of the tunnel, and the stress release at the vault and invert is very large after excavation. If the large deformation was treatment when the crown settlement of the tunnel reaches 90% ~95% of the final predicted settlement value, the tunnel deformation and the final stress state could be in a small value. This study can provide a reference for the treatment of large deformation in the swelling rock tunnel.

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.

Research on Spacial Displacement Regulations in Soft Surrounding Rock Tunnel

2013 ◽  
Vol 690-693 ◽  
pp. 886-889
Author(s):  
Bao Long Lin
Keyword(s):  
High Speed ◽  
Surrounding Rock ◽  
Construction Process ◽  
High Speed Rail ◽  
Tunnel Stability ◽  
Construction Methods ◽  
Minimum Principal Stress ◽  
Initial Support ◽  
Rock Tunnel ◽  
Weak Surrounding Rock

Based on the engineering background of Dongkeling tunnel of Guizhou-Guangzhou high-speed rail, construction process in soft surrounding rock is simulated by using finite difference software——FLAC according to large-deformation characteristics in water-rich and weathering altered granite weak surrounding rock. Several aspects, such as vault settlement, invert uplift, clearance convergence, surface settlement, the maximum and minimum principal stress of the initial support and plastic zone of surrounding rock, are analyzed to determine the tunnel stability with different construction methods.

scholarly journals Analysis of Stress and Deformation Characteristics of Deep-Buried Phyllite Tunnel Structure under Different Cross-Section Forms and Initial Support Parameters

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Hao Wu ◽  
Xiaohua Yang ◽  
Shichun Cai ◽  
Binjing Zhao ◽  
Kunlong Zheng
Keyword(s):  
Large Deformation ◽  
Double Layer ◽  
Soft Rock ◽  
Surrounding Rock ◽  
Original Design ◽  
Supporting Structure ◽  
Initial Support ◽  
Stress And Deformation ◽  
Rock Tunnels ◽  
Layer Steel

Deep-buried soft rock tunnels exhibit low strength and easy deformation under the influence of high ground stress. The surrounding rock of the soft rock tunnel may undergo large deformation during the construction process, thereby causing engineering problems such as the collapse of the vault, bottom heave, and damage to the supporting structure. The Chengwu Expressway Tunnel II, considered in this study, is a phyllite tunnel, with weak surrounding rock and poor water stability. Under the original design conditions, the supporting structure exhibits stress concentration and large deformation. To address these issues, three schemes involving the use of the double-layer steel arch to support, weakening of the steel arch close to the excavation surface, and weakening of the steel arch away from the excavation surface to support were proposed. Using these schemes, the inverted radius was varied to explore its influence on different support schemes. For simulation, the values of the inverted radius selected were as follows: 1300 cm, 1000 cm, and 700 cm. The proposed support plan was simulated using FLAC3D, and the changes in the pressure between the initial support and surrounding rock, the settling of the vault, and the surrounding convergence were investigated. The numerical simulation results of monitoring the surrounding rock deformation show that the double-layer steel arch can effectively reduce the large deformation of the soft rock well. When the stiffness of one of the steel arches was weakened, the support’s ability to control the deformation was weakened; however, it still showed reliable performance in controlling deformation. However, changing the radius of the invert had an insignificant effect on the deformation and force of the supporting structure.

scholarly journals In Situ Needle Penetration Test and Its Application in a Sericite Schist Railway Tunnel, Southwest of China

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 4) ◽  
Author(s):  
Jiaxing Dong ◽  
Runxue Yang ◽  
Chenggang Guo ◽  
Meiqian Wang ◽  
Yonghong Wu ◽  
...  
Keyword(s):  
Large Deformation ◽  
Soft Rock ◽  
Reference Value ◽  
Surrounding Rock ◽  
Mechanical Parameters ◽  
Penetration Index ◽  
Needle Penetration ◽  
Joint Direction ◽  
Rock Tunnel

Abstract The sericite schist is a typical metamorphic soft rock. Large deformation of surrounding rock often occurs in the construction of a tunnel in this stratum. Due to the broken rock mass structure and poor mechanical strength in Baishitou tunnel project of Dalin line of Southwest railway, it is impossible to prepare standard samples for a traditional rock mechanical test. Therefore, we chose penetrometer (SH-70) for an in situ test. Firstly, we monitored the deformation of typical sections and analyzed the characteristics of large deformation of soft rock in the tunnel. Secondly, we tested the needle penetration index of fresh excavation face and side wall. Then, we estimated some mechanical parameters of sericite schist by a needle penetrometer and Hoek-brown criterion and discussed the acquisition of mechanical parameters of soft rock. The results show the following: (1) the characteristics of extrusion rock tunnel are summarized as large deformation, fast deformation rate, and obvious construction disturbance. (2) The reference value of penetration index of sericite schist (the vertical joint direction) is 3.90~7.77 N/mm, and the parallel joint direction is 1.27~2.99 N/mm. (3) The uniaxial compressive strength estimated by a penetrometer is 0.78~8.53 MPa, and the strength of the surrounding rock is negatively correlated with the amount of deformation. Therefore, it can be considered that the insufficient strength of surrounding rock is the fundamental reason for large deformation. (4) The reference value of cohesion of sericite schist estimated by a penetrometer is 0.203 MPa, and the reference value of internal friction angle is 18.224°. Compared with the common estimation methods, the penetrometer is more convenient and economical, which can provide a new idea for obtaining the mechanical parameters of sericite schist soft rock tunnel.

The Simulation Analysis of Large Cross-Section Soft Rock Tunnel Excavation under the Bias Terrain

2011 ◽  
Vol 90-93 ◽  
pp. 1853-1858
Author(s):  
Gang Zhang ◽  
Hong Bing Liu
Keyword(s):  
Soft Rock ◽  
Internal Force ◽  
Structure Design ◽  
Surrounding Rock ◽  
Tunnel Excavation ◽  
Advantages And Disadvantages ◽  
Area Distribution ◽  
Tunnel Design ◽  
Initial Support ◽  
Rock Tunnel

Abstract: Taking a High-speed railway tunnel as the background, This paper analyses not only the stress and displacement of surrounding rock , the plastic area distribution and size, but also the size and distribution of initial support internal force in two excavation schemes, based on the criterion of underground engineering structure design theory and rock elastic-plastic succumb Drucker-Prager, Under the guidance of New Austria Tunneling Method, this paper makes numerical simulation of soft rock tunnel excavation in large sections and initial support with the finite software ANSYS11.0. The stress and displacement of surrounding rock and the plastic area distribution and size under two excavation schemes are analyzed, the size and distribution of initial support internal force under two excavation schemes are also investigated .By comprehensive comparing advantages and disadvantages of two schemes, this paper makes some significant conclusions and gives reference for the similar tunnel design and construction.

scholarly journals Research on the Large Deformation Prediction Model and Supporting Measures of Soft Rock Tunnel

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Junying Rao ◽  
Yonghu Tao ◽  
Peng Xiong ◽  
Chongxin Nie ◽  
Hao Peng ◽  
...  
Keyword(s):  
Large Deformation ◽  
Soft Rock ◽  
Surrounding Rock ◽  
Rock Deformation ◽  
Maximum Displacement ◽  
Deformation Prediction ◽  
Significant Difference ◽  
Rock Tunnel ◽  
Surrounding Rock Deformation ◽  
Bolt Support

The weak surrounding rock has the characteristics of easy softening, poor integrity, low mechanical strength, etc., which makes it easy to induce different degrees of deformation and damage under excavation disturbance and then seriously affects the stability of the tunnel. Carrying out soft rock tunnel deformation prediction research and designing the supporting structure according to the predicted value is of great significance to engineering construction and design. Based on the grey theory, the large deformation of the vault, shoulder, and waist of the soft rock tunnel are predicted, and then the specific bolt support is designed in the maximum predicted value (Smax·R) area. The control effects of different bolts, spacing (d), length (L) on the maximum displacement (Smax·M), and maximum stress (σmax·M) the surrounding rock are analyzed by numerical simulation. Results show that the gray model has high prediction accuracy, the best prediction time is one week, and the maximum error is only 2.99%; with the decrease in d, resin bolt support has a significant supporting effect compared with mortar bolt support, with Smax.M and σmax·M reduced by 64.38% and 10.35%, respectively; as the L of bolt increases, compared with the mortar bolt support, the resin bolt support has a more obvious restraining effect on the surrounding rock deformation, and Smax·M and σmax·M are reduced by 28.20% and 10.00%, respectively; when 4.5 m < L < 6.0 m and 0.6 m < d < 0.7 m, resin bolt support should be adopted; in other ranges, mortar bolt support or resin bolt support has a less significant difference in controlling surrounding rock deformation.

Significant Analysis of Soft Rock Tunnel Disaster-Causing Factors Based on Orthogonal Test

2012 ◽  
Vol 594-597 ◽  
pp. 1331-1337
Author(s):  
Jian Ping Chen ◽  
Ying Xu ◽  
Chang Qun Zuo ◽  
Yi Yi
Keyword(s):  
Large Deformation ◽  
Pressure Coefficient ◽  
Soft Rock ◽  
Tectonic Stress ◽  
Surrounding Rock ◽  
Joint Spacing ◽  
Dependent Relationship ◽  
Side Pressure ◽  
Dependence Relationship ◽  
Rock Tunnel

The impacting effect of lithological features, tectonic stress, the mechanical parameters, structure surface contrasts were comparative analysis, to explore the effect from mentioned factors to surrounding rock-lining in schist tunnel. In order to make sure the dependence relationship of large deformation with these factors, the significant and interaction on large deformation in rock-mess and lining mechanical mechanism were studied according to the experiment data and statistics theory. The result shows that elastic modulus E, side pressure coefficient λ, and joint spacing S have obvious influence on the mechanical properties of surrounding rock-lining, and there is interaction among them. Furthermore, the influence of the interaction between S and λ to rock-lining is found to be significant, and there is an obviously dependent relationship between anchor failure and joints spacing. Therefore, when discussing the reduction measures to avoid the large deformation, the most appropriate method is to study it in overall factors and with the interaction.

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