Experimental Study on Creep of Surrounding Rock Mass in Argillaceous Soft Rock Tunnel

2012 ◽  
Vol 193-194 ◽  
pp. 826-830 ◽  
Author(s):  
Qiu Yan Fan ◽  
Jia Yan Lu ◽  
Zhen Zhu
Keyword(s):  
Rock Mass ◽  
Rock Fracture ◽  
Soft Rock ◽  
Creep Damage ◽  
Surrounding Rock ◽  
Laboratory Simulation ◽  
Creep Process ◽  
Laboratory Model ◽  
Accelerated Creep ◽  
Rock Tunnel

Due to the complexity of underground engineering, study on creep characteristics of surrounding rock mainly adopts laboratory simulation experiment. Recently, the similar materials are used to do the experiment both at home and abroad, yet it can't reflect the original nature and others of rock fissure in original rock mass. Through the field collection of undisturbed sample of Tertiary mudstone, the conclusions are made by laboratory model test on surrounding rock of underground tunnel and creep process regularity and failure mechanism in the surrounding rock in this paper as follows: there are three obvious stages of creep under certain stress levels, which is measured on the surface of surrounding rock mass in argillaceous soft rock tunnel--decay creep ,steady creep and accelerated creep. The surrounding rock will produce the accelerated creep damage when the stress level is over a threshold value. Creep damage of surrounding rock mainly includes the forms of roof sinking, floor working up, and forming a macro- fracture surfaces etc. Test results showed that the undisturbed surrounding rock fracture would be dissimilar to the homogeneous surrounding rock without fracture in damage model, and original fissure have a larger effect on creep damage of surrounding rock.

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.

Influence exerted by underground excavation shape and by effective stresses on the formation of a tensile strain zone at a depth greater than 1 km

2020 ◽  
pp. 67-75
Author(s):  
Van Min Nguyen ◽  
V. A. Eremenko ◽  
M. A. Sukhorukova ◽  
S. S. Shermatova
Keyword(s):  
Rock Mass ◽  
Cross Sections ◽  
Tensile Strain ◽  
Rock Fracture ◽  
Strain Analysis ◽  
Surrounding Rock ◽  
Underground Excavation ◽  
Secondary Stress ◽  
Principal Stresses ◽  
Mining Depth

The article presents the studies into the secondary stress field formed in surrounding rock mass around underground excavations of different cross-sections and the variants of principal stresses at a mining depth greater than 1 km. The stress-strain analysis of surrounding rock mass around development headings was performed in Map3D environment. The obtained results of the quantitative analysis are currently used in adjustment of the model over the whole period of heading and support of operating mine openings. The estimates of the assumed parameters of excavations, as well as the calculations of micro-strains in surrounding rock mass by three scenarios are given. During heading in the test area in granite, dense fracturing and formation of tensile strain zone proceeds from the boundary of e ≥ 350me and is used to determine rough distances from the roof ( H roof) and sidewalls ( H side) of an underground excavation to the 3 boundary e = 350me (probable rock fracture zone). The modeling has determined the structure of secondary stress and strain fields in the conditions of heading operations at great depths.

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.

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.

The Bench Method Numerical Simulation of Soft Rock Tunnel

2013 ◽  
Vol 438-439 ◽  
pp. 949-953
Author(s):  
Hao Bo Fan ◽  
Jin Xing Lai ◽  
Dan Dan Hou
Keyword(s):  
Numerical Simulation ◽  
Measurement Data ◽  
Soft Rock ◽  
Simulation Method ◽  
Internal Force ◽  
Surrounding Rock ◽  
Supporting Structure ◽  
Highway Tunnel ◽  
Tunnel Design ◽  
Rock Tunnel

This paper based on Chaoyang tunnel by bench method excavation, using the finite element numerical simulation method, simulates the surrounding rock displacement of soft rock tunnel and the stress characteristics of supporting structure to get the various stages of tunnel surrounding rock stress, strain and the internal force changes of tunnel supporting structure. After the analyses of the numerical simulation results and field monitoring measurement data, the safety and rationality of the method are determined. The research provides certain reference for highway tunnel design and construction.

Discussion for Displacement Control Criteria of Soft Rock Tunnel in the Seismic Area

2013 ◽  
Vol 353-356 ◽  
pp. 1440-1445
Author(s):  
Jin Hua Xu ◽  
Chuan He ◽  
Yi Zhou ◽  
Hai Bin Wu
Keyword(s):  
Cross Section ◽  
Soft Rock ◽  
Surrounding Rock ◽  
Great Earthquake ◽  
Displacement Control ◽  
Deformation Control ◽  
The One ◽  
Rock Tunnel ◽  
Control Criteria ◽  
Seismic Area

This paper studies on a certain highway project which passes through Longmen Shan fault zone, the one triggers 5.12 Wenchuan earthquakes directly. The region where the project resides is characterized by high percentage of soft rock mass, in particular the phyllite. Series of landslide have hitherto happened due to the instability of mountains along the highway which was caused by the great earthquake. Besides, since the phyllite-dominated rock was low-strength and easily soften by water, engineering disasters such as cave-in and large deformation of surrounding rock occurred frequently during the construction of tunnels located along the highway. The existing deformation control criteria fail gradually to fill the requirements of safe tunnelling. The author analyzed monitoring data from different tunnels with different cross-section types and different surrounding rock conditions, referred to relevant norms and eventually proposes new deformation control criteria based on allowable deformation and deformation rate.

scholarly journals Structure Strengthening Method for Enhancing Seismic Behavior of Soft Tunnel Portal Section

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Guangyao Cui ◽  
Jianfei Ma
Keyword(s):  
Seismic Response ◽  
Seismic Performance ◽  
Shaking Table Test ◽  
Soft Rock ◽  
Surrounding Rock ◽  
Shaking Table ◽  
Key Factor ◽  
Rock Tunnel ◽  
Tunnel Portal ◽  
Strengthening Method

Tunnel portal sections always suffer serious damage under strong earthquakes. This paper aims to study the seismic performance of lining strengthening method in soft rock portal section by employing the model test. Firstly, the shaking table test considering the test cases, the modified input motions, the boundary condition, and monitoring equipment are conducted to simulate the seismic response of the soft tunnel portal section. Then, the lining strengthening method of increasing concrete grade is applied to the tunnel structure to study the aseismic performance of the soft rock tunnel portal section, and the seismic effects of the tunnel linings with different concrete grades are compared and analyzed. The result shows that the proportion of soft rock to total surrounding rock is the key factor affecting the seismic response of soft rock tunnel portal section; the larger the proportion of soft rock in surrounding rock, the more vulnerable the structure to earthquake damage; the seismic performance of the lining strengthening in hard rock portal is remarkable while limited in soft rock portal section. The stiffness and strength of the lining are larger than those of surrounding rock; the seismic performance of the soft portal section could hardly be improved only by the lining strengthening method. It is suggested to adopt both the structure strengthening and isolation method in the seismic design of soft portal section.

scholarly journals Analysis of Surrounding Rock Creep Effect on the Long-Term Stability of Tunnel Secondary Lining

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Xiaoqian Zhang ◽  
Chengmin Wei ◽  
Heng Zhang
Keyword(s):  
Stress Measurement ◽  
Soft Rock ◽  
In Situ Stress ◽  
Calculation Model ◽  
Surrounding Rock ◽  
In Situ Stress Measurement ◽  
Rock Creep ◽  
Secondary Lining ◽  
Rock Tunnel

The secondary lining failure of deep buried soft rock tunnel often occurs, which is obviously related to the time factor. The formation mechanism of this phenomenon is studied in this paper. Therefore, the combination of in situ stress measurement and neural network inversion is used to analyze the distribution characteristics of in situ stress. At the same time, the creep characteristics of surrounding rock are tested in laboratory, and the key parameters are obtained. Combined with the characteristics of surrounding rock, the calculation model is established by using discrete element simulation technology and considering the joints of surrounding rock. According to the above multiple information, the stress characteristics of the secondary lining in different time periods are analyzed creatively. Finally, the method of setting arch and adding anchor bolt in key parts is proposed, and significant effect results are obtained.

Research on the Surrounding Rock Damage of Deep Hard Rock Tunnels Caused by Bottom Excavation

2012 ◽  
Vol 170-173 ◽  
pp. 1700-1703
Author(s):  
Zhen Wang ◽  
Chu Nan Tang ◽  
Tian Hui Ma ◽  
Lian Chong Li ◽  
Yue Feng Yang
Keyword(s):  
Numerical Simulation ◽  
Rock Mass ◽  
Hard Rock ◽  
Surrounding Rock ◽  
Rock Damage ◽  
Simulation Approach ◽  
High Geostress ◽  
Intact Rock Mass ◽  
Rock Tunnels ◽  
Rock Tunnel

The damage features of surrounding rock in the process of bottom excavation in deep hard rock tunnel were investigated, combining with the actual tunnel data of JinpingⅡHydropower Station and using numerical simulation approach. The evolution mechanism of microfractures initiation, growth and expansion in deep intact rock mass was performed. It’s shown that the fractures caused by bottom excavation develop to deeper surrounding rock due to stress adjustment, and the zone that have been supported also has some damage. The research results provide important references to understand the damage features of surrounding rock in deep hard rock under high geostress.

Sign in / Sign up

Export Citation Format

Share Document