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Rockburst process and strength-weakening effect of the high-stress circular tunnel under internal unloading

Journal of Rock Mechanics and Geotechnical Engineering 2023年第4期15卷 864-885页

作者： Fengqiang Gong Wuxing Wu Li Ren Engineering Research Center of Safety and Protection of Explosion&Impact of Ministry of Education(ERCSPEIME) Southeast UniversityNanjing211189China School of Civil Engineering Southeast UniversityNanjing211189China Key Laboratory of Deep Earth Science and Engineering Ministry of EducationSichuan UniversityChengdu610065China

To investigate the influence of unloading effect of a circular tunnel face on rockburst process,by innovatively combining rock drilling unloading devices and triaxial systems,the strain rockburst simulation under the entire stress path of“high initial stressþinternal unloadingþstress adjustment”(HUS test)was realized for the intact cubic red sandstone samples(100 mm×100 mm×100 mm).Comparative tests were conducted on cubic red sandstone samples with prefabricated circular holes(425 mm)under the stress path of“prefabricated circular hole+þhigh initial stress+stress adjustment”(PHS test),thereby highlighting the influence of internal unloading on rockburst failure.The test results revealed that with an increase in vertical stress,the sidewalls in both the HUS and PHS tests suffered strain rockburst failure.Compared with the PHS test,the initial failure stress in the HUS test is lower,and it is easier to induce sidewall rockbursts.This indicates that the internal unloading influences the sidewall failure,causing an obvious strength-weakening effect,which becomes more significant with an increase in buried depth.The strain rockburst failure was more severe in the HUS test owing to the influence of internal unloading.V-shaped rockburst pits were formed in the HUS tests,whereas in the PHS test,arcshaped rockburst pits were produced.It was also found that strain rockburst failure may occur only when the rock has a certain degree of rockburst proneness.

关键词： Rockburst Unloading Strength-weakening effect Deep rock V-shaped notch circular tunnel

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Shaking table tests on the liquefaction-induced uplift displacement of circular tunnel structure

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Underground Space 2023年第3期10卷 182-198页

作者： Saber Nokande Yaser Jafarian Abdolhosein Haddad Department of Civil Engineering Semnan UniversitySemnan 35131-19111Iran International Institute of Earthquake Engineering and Seismology(IIEES) Tehran 19537-14453Iran Deltares Boussinesqweg 1DelftSouth Hollands 2629 HVNetherlands

Underground structures are susceptible to float and move upward during earthquakes when located in a liquefiable soil deposit.There are examples of this phenomenon in past major earthquake events.In this study,the uplift of circular tunnels in a liquefiable sand layer was investigated with a series of shaking table tests.The research has focused on the buried depth of the tunnel,tunnel diameter,tunnel weight,liquefaction extent,uplift mechanism,and factor of safety against liquefaction-induced uplift.According to the test results,the shallow buried depth,larger diameter,and lower weight can intensify the tunnel uplift,so the displacement in post-liquefaction time continues at the same rate as during the shaking time.Due to the shear-induced dilation,pore water pressure generation around the tunnel was reduced compared with that of the free field.The excess pore water pressure dissipation in the soil overlying the uplifted tun-nel was significant,which leads to suction in the soil deposit.Furthermore,the acceleration response of overlying soil with the uplifted tunnel was similar to that of the free field.However,the soil acceleration response around the tunnel without uplift was similar to the base motion.

关键词： Liquefaction tunnel uplift Underground structures Shaking table test circular tunnel

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Design equation for stability of a circular tunnel in anisotropic and heterogeneous clay

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Underground Space 2022年第1期7卷 76-93页

作者： Suraparb Keawsawasvong Boonchai Ukritchon Department of Civil Engineering Thammasat Engineering SchoolThammasat UniversityPathumthani 12120Thailand Centre of Excellence in Geotechnical and Geoenvironmental Engineering Department of Civil EngineeringFaculty of EngineeringChulalongkorn UniversityBangkok 10330Thailand Center of Excellence on Earthquake Engineering and Vibration Department of Civil EngineeringFaculty of EngineeringChulalongkorn UniversityBangkok 10330Thailand

The safety assessment of tunnel stability is critical to tunnel construction and requires accurate analysis to obtain a reliable prediction.Strength anisotropy is an important aspect of clay behavior,but it is mostly neglected in practical stability analyses.In this study,the effects of undrained strength anisotropy and strength nonhomogeneity on the stability of unlined circular tunnels in clays are investi-gated.The static approach of lower-bound(LB)analysis using finite-element and second-order cone programming is employed to exam-ine the aforementioned effects.The anisotropic shear strength of clay is modeled by employing an elliptical yield function under plane strain conditions.A complete set of dimensionless parameters covering the cover depth ratios of tunnels,normalized overburden pressure ratios,normalized strength gradient ratios of clays,and anisotropic strength ratios,are systematically investigated.The new LB solutions indicate that the stability load factor of the problem has a nonlinear relationship with the cover depth ratio and the anisotropic strength ratio,and there exists a linear relationship with the normalized overburden pressure and the normalized strength gradient.Their influ-ence on the predicted failure mechanism is parametrically evaluated.A statistically approximate stability equation of unlined circular tunnels in anisotropic and non-homogeneous clay is proposed for the first time,which contains four new stability factors,namely,con-stant undrained strength,linearly increasing strength gradient,undrained strength anisotropy,and soil unit weight,and it can serve as a fast and accurate tool for predicting the undrained stability of this problem in practice.

关键词： circular tunnel Anisotropy Nonhomogeneity Lower bound Second-order cone programming

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MECHANISM AND CATASTROPHE THEORY ANALYSIS OF circular tunnel ROCKBURST

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Applied Mathematics and Mechanics(English Edition) 2006年第6期27卷 841-852页

作者：潘岳张勇于广明 College of Civil Engineering Qingdao Technological University Qingdao 266520P. R. China

Mechanism of circular tunnel rockburst is that, when the carrying capacity of the centralized zone of plastic deformation in limiting state reduces, the comparatively intact part in rock mass unloads by way of elasticity; rockburst occurs immediately when the elastic energy released by the comparatively intact part exceeds the energy dissipated by plastic deformation. The equivalent strain was taken as a state variable to establish a catastrophe model of tunnel rockburst, and the computation expression of the earthquake energy released by tunnel rockburst was given. The analysis shows that, the conditions of rockburst occurrence are relative to rock＇s ratio of elastic modulus to descendent modulus and crack growth degree of rocks; to rock mass with specific rockburst tendency, there exists a corresponding critical depth of softened zone, and rockburst occurs when the depth of softened zone reaches.

关键词： circular tunnel plastic deformation localization rockburst fold catastrophe model critical depth of softened zone

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Elasto-plastic analysis of the surrounding rock mass in circular tunnel based on the generalized nonlinear unified strength theory

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International Journal of Mining Science and Technology 2016年第5期26卷 819-823页

作者： Huang Xiujie Zhang Jixun Yang Ling Yang Shikou Wang Xingli College of Water Conservancy and Hydropower Hohai University Nanjing 210098 China College of Hydrology and Water Resources Hohai University Nanjing 210098 China

The present paper aims to establish a versatile strength theory suitable for elasto-plastic analysis of underground tunnel surrounding rock. In order to analyze the effects of intermediate principal stress and the rock properties on its deformation and failure of rock mass, the generalized nonlinear unified strength theory and elasto-plastic mechanics are used to deduce analytic solution of the radius and stress of tunnel plastic zone and the periphery displacement of tunnel under uniform ground stress field. The results show that: intermediate principal stress coefficient b has significant effect on the plastic range,the magnitude of stress and surrounding rock pressure. Then, the results are compared with the unified strength criterion solution and Mohr–Coulomb criterion solution, and concluded that the generalized nonlinear unified strength criterion is more applicable to elasto-plastic analysis of underground tunnel surrounding rock.

关键词： circular tunnel Generalized Hoek–Brown strength criterion Generalized nonlinear unified strength criterion Intermediate principal stress Elasto-plastic stress and displacement

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Study on Ground Motion Intensity Measures for Seismic Response Evaluation of circular tunnel

Study on Ground Motion Intensity Measures for Seismic Respon...

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作者： Chengming Zhang Zilan Zhong Mi Zhao Key Laboratory of Urban Security and Disaster Engineering of Ministry of Education Beijing University of Technology

Ground motion intensity measure（IM） is a key link between the seismic hazard analysis and structural seismic response analysis,which play an important role in the performance-based earthquake engineering framework.In order to find suitable IM for seismic response evaluation of circular tunnel,nonlinear dynamic time-history analyses are conducted on a two-dimensional finite element model of tunnel-surrounding rock interaction in this study.The near field ground motions without velocity pulse and far field ground motions as recommended by FEMA-P695 are used as the input ground motions for the numerical model.Besides,the overall lining damage indices in compression and in tension are used as engineering damage measures（DMs） to estimate the lining damage state.The applicability of 20 existing ground motion IMs commonly used in engineering practice are investigated in this study.Statistically regression analysis is carried out for results obtained from nonlinear time-history analyses.Based on the criteria of efficiency and sufficiency,Arias intensity is identified as the optimal IM for seismic response prediction of circular tunnel structure.

关键词： intensity measure circular tunnel efficiency sufficiency nonlinear dynamic analysis

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NUMERICAL-AIDED ELASTO-PLASTIC MODEL FOR circular tunnel IN HOEK-BROWN ROCK MASSES Paper No.261

NUMERICAL-AIDED ELASTO-PLASTIC MODEL FOR CIRCULAR TUNNEL IN ...

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ISRM-Sponsored International Symposium on Rock Mechanics:"Rock Characterisation,Modelling and Engineering Design Methods"(SINOROCK2009)

作者： Reza.R.Osgoui GEODATAS.p.A.Corso Duca degli Abruzzi 48/E.10129

This paper presents an elasto-plastic analytical solution for an axi-symmetrical circular tunnel.On account of the mathematical complexity,numerical treatments have been used to assist the elasto-p

ISBN: (纸本)9789628014170

This paper presents an elasto-plastic analytical solution for an axi-symmetrical circular tunnel.On account of the mathematical complexity,numerical treatments have been used to assist the elasto-p

关键词： Residual strength rock masses Stress analysis strength parameter circular tunnel Elastoplasticity

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Transient response of a concrete tunnel in an elastic rock with imperfect contact

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International Journal of Mining Science and Technology 2020年第5期30卷 605-612页

作者： R.Shakeri A.Mesgouez G.Lefeuve-Mesgouez UMR 1114 EMMAH Avignon UniversityF-84916 AvignonFrance Department of Civil Environmental&Architectural EngineeringUniversity of Colorado BoulderCO 80309USA

The two-dimensional transient response of an imperfect bonded circular lined pipeline lying in an elastic infinite medium is investigated.Imperfect boundary conditions between the surrounding elastic rock and the tunnel are modelled with a two-linear-spring design.The novelty of the manuscript consists in studying at the same time transient regimes and imperfect bonded interfaces for simulating the dynamic response of a tunnel embedded in an elastic infinite rock.Wave propagation fields in tunnel and rock are expressed in terms of infinite Bessel and Hankel series.To solve the transient problem,the Laplace transform and the associated Durbin’s algorithm are performed.To exhibit the dynamic responses,influences of various parameters such as the quality of the interface conditions and the thickness of the lining are presented.The dynamic hoop stresses and the solid displacements of both the tunnel and the rock are also proposed.

关键词： Dynamic response Imperfect interface circular tunnel Semi-analytical approach Transient wave propagation

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Investigating Effect of tunnel Gate Shapes with Similar Cross Section on Inserted Forces on Its Coverage and Soil Surface Settlement

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Open Journal of Civil Engineering 2016年第3期6卷 358-369页

作者： Arash Rostami Nima Asghari Morteza Askari Ziarati Saman Jahani Bahman Shahi Department of Civil Engineering Central Tehran Branch Islamic Azad University Tehran Iran Department of Civil Engineering Noshiravani University of Technology Babol Iran Department of Civil Engineering UAE Branch Islamic Azad University Dubai UAE Railway Engineering Department Faculty of Civil Engineering Isfihan University Isfihan Iran

According to technology development and relative facilitation in digging and underground structures, ways, highways, all types of tunnels, underground train network, and other underground settle, storage are number of structure built and developed in advanced countries. In most situation, tunnel digging operations are done years after its construction or are not recorded in new structures regulations;therefore, this research investigates soil settlement and inserting force to tunnel coverage by limiting studies about effects of tunnel shapes on soil settlement using Plaxis, Seismo Signal, and Seismo Aspect. This study shows that rectangular tunnel has the most settlement in soil surface and circular tunnel has the least settlement but horseshoe tunnel has similar behavior to circular tunnel;however, earth subsidence level by digging this tunnel is more than circular tunnel. In addition, sectional shape has direct effect on inserting forces on tunnel coverage.

关键词： Soil Settlement Rectangular tunnel circular tunnel Horseshoe tunnel Concrete Coverage

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Elasto-plastic Analysis of circular tunnels in Jointed Rock Masses Satisfy the Hoek-Brown Failure Criterion

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International Journal of Mining Science and Technology 2007年第3期17卷 393-398页

作者： SUN Jin-shan,LU Wen-bo,ZHU Qi-hu,CHEN Ming State Key Laboratory of Water Resource and Hydropower Engineering Science,Wuhan University,Wuhan,Hubei 430072,China State Key Laboratory of Water Resource and Hydropower Engineering Science Wuhan University Wuhan Hubei 430072 China

The relationship between the Hoek-Brown parameters and the mechanical response of circular tunnels is il-lustrated. Closed-form and approximate solutions are given for the extent of the plastic zone and the stress and dis-placement fields under axisymmetrical and asymmetric stress conditions. For the same rock masses and under axisym-metrical stress conditions,the radius of the plastic zone in terms of Hoek-Brown criterion is generally an approximation of the radius in terms of the Mohr-Coulomb criterion. The radius in terms of the Hoek-Brown criterion is larger under low stress conditions. For poor quality rock masses (GSItunnels. It is not advisable to improve the sta-bility of the tunnels by providing a small support resistance p through shotcrete,except for very poor quality jointed rock masses. Without reference to the quality of the rock mass,the disturbance factor D should not less than 0.5. Meas-ures which disturb rock masses during tunnel construction should be taken carefully when the tunnel depth increases.

关键词： jointed rock masses circular tunnel general Hoek-Brown failure criterion elasto-plastic analysis con-struction measures

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