Displacement ratio dichotomy back analysis of surrounding rock-initial support system of weathered rock tunnel

2019 ◽  
Vol 12 (6) ◽  
Author(s):  
Jiancong Xu ◽  
Yedi Ni
Keyword(s):  
Support System ◽  
Back Analysis ◽  
Surrounding Rock ◽  
Weathered Rock ◽  
Displacement Ratio ◽  
Initial Support ◽  
Rock Tunnel

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.

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 Installation Time of an Initial Support for Tunnel Excavation upon the Safety Factors of Surrounding Rock

2020 ◽  
Vol 10 (16) ◽  
pp. 5653
Author(s):  
Yan-Jun Zhang ◽  
Kai Su ◽  
Hong-Ze Zhu ◽  
Zhong-Dong Qian ◽  
He-Gao Wu
Keyword(s):  
Safety Factor ◽  
Support System ◽  
Surrounding Rock ◽  
Engineering Practice ◽  
Tunnel Face ◽  
Tunnel Section ◽  
Initial Support ◽  
Global Safety Factor ◽  
The Stability ◽  
Installation Time

In engineering practice, the initial support system is commonly installed in the vicinity of the tunnel face after excavation, whereas the self-capacity of rock mass will fail to be utilized and the cost of the initial support system will be expensive. In this study, a methodology is proposed to determine the appropriate timing of initial support installation to find out the balance of tunnel safety and construction cost. Firstly, the global safety factor is introduced as the critical indicator to evaluate tunnel stability. Then, the comprehensive graphic relationship between the global safety factor and the distance to the tunnel face is established. Once the global safety factor decreases to an admissible value, the stability of the surrounding rock is in a critical state and the corresponding distance is the recommended location for installing the initial support. In these procedures, the installation time of the initial support at the typical tunnel section can be quickly designed and fed back by a direct indicator during construction. Meanwhile, several cases with different conditions have been carried out to discuss the regularity of the method.

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 Multiparameter Inversion Early Warning System of Tunnel Stress-Seepage Coupling Based on IA-BP Algorithm

2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Junxiang Wang ◽  
Jie Sun ◽  
Haijun Kou ◽  
Yaxian Lin
Keyword(s):  
Neural Network ◽  
Rock Mass ◽  
Bp Neural Network ◽  
Back Analysis ◽  
Soft Rock ◽  
Surrounding Rock ◽  
Bp Algorithm ◽  
Analysis Method ◽  
Rock Tunnel ◽  
Design And Construction

Under construction disturbance, the surrounding rock of a soft rock tunnel shows obvious aging characteristics. The creep characteristics of a rock mass under stress-seepage coupling greatly influence the long-term stability of a project. How to simply, quickly, and accurately determine the creep parameters of a rock mass under coupling conditions is significant to engineering structure design and construction. The optimal weights and thresholds of the BP neural network are sought through the immune algorithm to avoid the problem of slow convergence speed of the BP neural network and easy to fall into local optimum. Therefore, an intelligent back analysis method based on the IA-BP algorithm is established, which leads to the development of the corresponding intelligent back analysis program. The creep effect of the rock mass was simulated herein using the Drucker–Prager yield criterion and the time hardening creep law as the forward optimization method constitutive model. In addition, a sensitivity analysis of the parameters was performed to determine the optimal number of inversion parameters. By comparing and analyzing the residual between the inversion results of the IA-BP algorithm, PSO-BP algorithm, and the test values, the high precision of the IA-BP algorithm is proved. Taking the Lan Zhou-Hai Kou national expressway tunnel as an engineering example, a multiparameter creep inversion of the tunnel surrounding rock under the stress-seepage coupling condition was conducted using the inverse analysis method of the IA-BP algorithm. The results showed that the proposed IA-BP algorithm can effectively prevent the BP neural network from falling into a local minimum. Also, the algorithm is fast and accurate. The intelligent back analysis method based on the IA-BP algorithm is applied to the multifield coupling parameter back analysis, provides the basis and help for the structural design and construction of soft rock tunnel in water-rich stratum.

Rheology-Based Stability Analysis of Soft Rock Tunnel in Construction Suspension

2014 ◽  
Vol 934 ◽  
pp. 129-135
Author(s):  
Su Min Zhang ◽  
Yong Quan Zhu
Keyword(s):  
Stability Analysis ◽  
Cross Section ◽  
Back Analysis ◽  
Soft Rock ◽  
Calculation Model ◽  
Surrounding Rock ◽  
Tunnel Construction ◽  
Rock Tunnel ◽  
Primary Support ◽  
Water Contents

Suspension in tunnel construction usually cause tunnel callapse in weak ground if the suspension time is long. Dongkeling tunnel on Guizhou-Guangxi line being as the engineering background, the indoor rheological experiment and back analysis were performed to obtain the rheological model and parameters of the surrounding rock, and the 3D viscoelasto-plastic calculation model was established to find the evolving rules of deformation at critical locations under two different water contents. It was found that the primary support has little effect on rheology of tunnel work face but on the cross section, and decreasing the water content of the surrounding rock to medium or low saturation level favors the tunnel stabillity greatly for water abundent tunnels.

scholarly journals Experimental Study of Mechanical Characteristics of Tunnel Support System in Hard Cataclastic Rock with High Geostress

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Minglei Sun ◽  
Yongquan Zhu ◽  
Xinzhi Li ◽  
Zhengguo Zhu ◽  
Benguo He
Keyword(s):  
Support System ◽  
Side Wall ◽  
High Strength ◽  
Tectonic Stress ◽  
Surrounding Rock ◽  
Steel Frame ◽  
Frame Structure ◽  
Tunnel Support ◽  
High Geostress ◽  
Initial Support

In hard cataclastic surrounding rock with high geostress, the rock monomer strength is high and the rock is broken, and tunnel excavation in it is apt to cause large deformation, collapsing, and breaking, causing initial support crack and even intruding of the initial support deformation. The characteristics of the support system under different support parameters and shapes are analyzed, and the reasonable support section shape and support parameters are determined. The results showed that (1) under the condition of high geostress and hard cataclastic surrounding rock, the initial support deformation is large, the horizontal convergence is much larger than the settlement of arch, and the deformation duration is relatively short; (2) the distribution of pressure and stress in initial support are very uneven on the cross-section and greatly affected by the construction process; (3) in the case of large horizontal tectonic stress, the use of large curvature side wall support is beneficial to improve the quality of support and control the deformation of the structure, especially to improve the stress of concrete; (4) the closure time of the supporting system greatly influences the stress state and deformation, so it is necessary to shorten the length of the lower bench and the distance of the invert as possible so as to close the support as early as possible; (5) different location of the tunnel surrounding rock stress distribution is very uneven, the measured value is much larger than calculated value in level III based on the specification of surrounding rock; (6) under high strength and ground stress, the initial supporting stress of steel frame increases rapidly, and the measured stress is larger. This indicates that the steel frame structure bears heavy early load. Therefore, the stiffness of the steel frame should be as large as possible to meet the loading requirements.

Judgement Method for Surrounding Rock Stability of Guanjiao Tunnel Based on Catastrophe Theory

2011 ◽  
Vol 90-93 ◽  
pp. 2307-2312 ◽  
Author(s):  
Wen Jiang Li ◽  
Su Min Zhang ◽  
Xian Min Han
Keyword(s):  
Plastic Strain ◽  
Catastrophe Theory ◽  
Soft Rock ◽  
Surrounding Rock ◽  
In Situ Monitoring ◽  
Engineering Practice ◽  
Stability Of Surrounding Rock ◽  
The Stability ◽  
Rock Tunnel

The stability judgement of surrounding rock is one of the key jobs in tunnel engineering. Taking the Erlongdong fault bundle section of Guanjiao Tunnel as the background, the stability of surrounding rock during construction of soft rock tunnel was discussed preliminarily. Based on plastic strain catastrophe theory, and combining numerical results and in-situ data, the limit displacements for stability of surrounding rock were analyzed and obtained corresponding to the in-situ monitoring technology. It shows that the limit displacements obtained corresponds to engineering practice primarily. The plastic strain catastrophe theory under unloading condition provides new thought for ground stability of deep soft rock tunnel and can be good guidance and valuable reference to construction decision making and deformation managing of similar tunnels.

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