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Long-term mechanical analysis of tunnel structures in rheological rock considering the degradation of primary lining

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Underground Space 2023年第3期10卷 217-232页

作者： Chang Liu dingli zhang Sulei zhang Qian Fang Zhenyu Sun Key Laboratory of Urban Underground Engineering of Ministry of Education Beijing Jiaotong UniversityBeijing 100044China School of Civil Engineering Qingdao University of TechnologyQingdao 266033China

Rock load on lining structures increases over time for tunnels buried in rheological rock,and in addition deterioration of primary lining is common due to its structural characteristics and service environment attack,where these delayed features affect the mechanical response of ***,accounting for these delayed features in long-term stability assessment of tunnel structures is complex and has not attracted enough *** this paper,an analytical approach is proposed for investigating long-term mechanical response of tunnel structures in rheological rock influenced by degradation of primary *** this purpose,degradation of primary lining,char-acterized by decreasing concrete stiffness over time,is quantitatively described by an exponential *** rheological characteristic of surrounding rock is simulated by the Burgers *** time-varying solutions for rock deformation and support pressure are obtained by considering the coordinated interaction between surrounding rock and linings,and their correctness is verified by comparing them with numerical *** results revealed that the pressure imposed on linings due to the rheological behavior of surrounding rock increases over *** the primary lining degrades,the rheological load is transferred from primary lining to secondary lining,leading to increasing pressure on secondary lining;and a faster degradation rate of primary lining leads to greater pressure on secondary ***,the primary lining should not be overlooked in long-term safety assessment of operation tunnels because of its role in bearing and transmitting ***,the tunnel’s design and operational maintenance strategy are discussed when the delay effects of surround-ing rock and lining are taken into account.

关键词： Tunnel structure Rheological rock Primary lining degradation Secondary lining Analytical model Mechanical response

Scientific problems and research proposals for Sichuan–Tibet railway tunnel construction

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Underground Space 2022年第3期7卷 419-439页

作者： dingli zhang Zhenyu Sun Qian Fang Sichuan–Tibet Railway Research Institute Beijing Jiaotong UniversityBeijing 100044China Key Laboratory for Urban Underground Engineering of Ministry of Education Beijing Jiaotong UniversityBeijing 100044China

The Sichuan–Tibet railway construction has received significant attention from both China and *** new section from Ya’an to Nyingchi is about 1018.6 km long,including 69 tunnels with a total length of 841.7 *** longest tunnel(Yigong tunnel)is 42.4 km *** successful construction of the Sichuan–Tibet railway depends largely on tunnel *** to the complex conditions,tunnel construction for the Sichuan–Tibet railway poses great challenges to the research *** paper aims to illustrate the necessity of interdisciplinary and joint research to solve problems associated with tunnel construction that will be encountered in the immediate future and facilitate the communication and exchange of ideas between *** this end,based on a systematic analysis of the available data related to Sichuan–Tibet railway tunnels,six major aspects of the geology,environment,and engineering conditions are ***,based on the engineering responses from the Sichuan–Tibet railway tunnels,potential technical problems and risk characteristics are predicted and ***,six key scientific issues are identified and discussed based on a coupled multi-layer analysis of essential tunnel engineering ***,research directions,technical ideas,and research methods that should be carried out for this project are proposed.

关键词： Sichuan–Tibet railway tunnels Key scientific problems Complex stress environment Deformation mechanism of surrounding rock Dynamic response

Formation estimation and evolution mechanism of the pressure arch for non-circular tunnels under asymmetrical stress field

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Science China(Technological Sciences) 2024年第9期67卷 2919-2938页

作者： SUN ZhenYu zhang dingli XU Tong CHEN Xu Key Laboratory for Urban Underground Engineering of Ministry of Education Beijing Jiaotong UniversityBeijing 100044China

The tunneling-induced stress redistribution is dependent on the tunnel shape and the in-situ stress field, and the previous arch characterization method based on the circumferential or maximum principal stresses is only suitable for the circular tunnels under the hydrostatic stress field. In this study, a unified characterization method of the pressure arch for non-circular tunnels under the arbitrary stress field is proposed. By comparing the variations of compressive stress in different directions due to excavation, the ratio of the most significant increase in compressive stress is presented to characterize the arch effect, and the corresponding numerical algorithm is given. Since the proposed method takes the stress element as the basic analytical model, it can be easily applied to various complex excavation situations. Thereafter, combined with the established folding catastrophic model, an objective and unified quantitative method of the pressure arch boundaries is given. Using the proposed method, the longitudinal evolution of the pressure arch is analyzed. According to the expansion rate of the arch boundaries, three evolution stages including the initial formation, rapid expansion and stabilization are categorized. Parametric studies are conducted to illustrate the effect of ground properties and support stiffness on the pressure arch formation. It is found that the ground strength parameters and burial depth affect the arch range at a decreasing rate, while they have little effect on the arch shape. The lateral pressure coefficient has a significant effect on both the shape and range of the pressure arch. Increasing the support stiffness helps reduce the pressure arch range with a decreasing rate, while the synchronous variation of the elastic moduli of the surrounding rock and support does not affect the arch range under a certain relative elastic modulus. Finally, field monitoring is conducted to validate the proposed method in actual support design.

关键词： pressure arch stress redistribution numerical simulation quantitative characterization longitudinal evolution parametric study

Discontinuous mechanical behaviors of existing shield tunnel with stiffness reduction at longitudinal joints

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Frontiers of Structural and Civil Engineering 2023年第1期17卷 37-52页

作者： Xiang LIU Qian FANG Annan JIANG dingli zhang Jianye LI Liaoning Key Laboratory of Marine Environmental Bridge and Tunnel Engineering Dalian Maritime UniversityDalian 116026China Key Laboratory for Urban Underground Engineering of Ministry of Education Beijing Jiaotong UniversityBeijing 100044China

An analytical model is proposed to estimate the discontinuous mechanical behavior of an existing shield tunnel above a new tunnel. The existing shield tunnel is regarded as a Timoshenko beam with longitudinal joints. The opening and relative dislocation of the longitudinal joints can be calculated using Dirac delta functions. Compared with other approaches, our method yields results that are consistent with centrifugation test data. The effects of the stiffness reduction at the longitudinal joints (α and β), the shearing stiffness of the Timoshenko beam GA, and different additional pressure profiles on the responses of the shield tunnel are investigated. The results indicate that our proposed method is suitable for simulating the discontinuous mechanical behaviors of existing shield tunnels with longitudinal joints. The deformation and internal forces decrease as α, β, and GA increase. The bending moment and shear force are discontinuous despite slight discontinuities in the deflection, opening, and dislocation. The deflection curve is consistent with the additional pressure profile. Extensive opening, dislocation, and internal forces are induced at the location of mutation pressures. In addition, the joints allow rigid structures to behave flexibly in general, as well as allow flexible structures to exhibit locally rigid characteristics. Owing to the discontinuous characteristics, the internal forces and their abrupt changes at vulnerable sections must be monitored to ensure the structural safety of existing shield tunnels.

关键词： tunnel–soil interaction discontinuous analysis longitudinal joints existing shield tunnel Timoshenko beam Dirac delta function

Face stability of shield tunnels considering a kinematically admissible velocity field of soil arching

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第2期14卷 505-526页

作者： Wei Li Chengping zhang dingli zhang Zijian Ye Zhibiao Tan Key Laboratory for Urban Underground Engineering of the Ministry of Education Beijing Jiaotong UniversityBeijing100044China School of Civil Engineering Beijing Jiaotong UniversityBeijing100044China

Existing mechanism of simulating soil movement at tunnel face is generally based on the translational or rotational velocity field,which is,to some extent,different from the real soil movement in the arching *** simulations are carried out first to investigate the characteristics of the velocity distribution at tunnel face and above tunnel *** a new kinematically admissible velocity field is proposed to improve the description of the soil movement according to the results of the numerical *** on the proposed velocity field,an improved failure mechanism is constructed adopting the spatial discretization technique,which takes into account soil arching effect and plastic deformation within soil ***,the critical face pressure and the proposed mechanism are compared with the results of the numerical simulation,existing analytical studies and experimental tests to verify the accuracy and improvement of the presented *** proposed mechanism can serve as an alternative approach for the face stability analysis.

关键词： Tunnel face stability Velocity field Failure pattern Improved failure mechanism Critical face pressure

Analytical solutions for deep tunnels in strain-softening rocks modeled by different elastic strain definitions with the unified strength theory

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Science China(Technological Sciences) 2022年第10期65卷 2503-2519页

作者： SUN ZhenYu zhang dingli FANG Qian DUI GuanSuo CHU ZhaoFei Key Laboratory for Urban Underground Engineering of Ministry of Education Beijing Jiaotong UniversityBeijing 100044China School of Civil Engineering Wuhan UniversityWuhan 430072China

This paper presents the analytical solutions for the responses of tunnels excavated in rock masses exhibiting strain-softening behavior. Since previous analyses give little consideration to the effect of the intermediate principal stress on the strain-softening rock behavior, the unified strength theory was introduced to analyze the tunnel response. Four cases of different definitions of the elastic strain in the softening and residual regions, used in the existing solutions, were considered. The tunnel displacements,stresses, radii of the softening and residual zones and critical stresses were deduced. The proposed solutions were verified by comparing with numerical simulations, model tests and existing solutions. Furthermore, the solutions of the four cases were compared with each other to investigate the influence of the elastic strain expressions on the tunnel responses. The results showed that the intermediate principal stress coefficient b has a significant effect on the tunnel displacements, stress fields, and plastic radii. Parametric studies were performed to analyze the influences of the softening and residual dilatancy coefficients,softening modulus and residual strength on the tunnel responses. The parametric analysis indicated that the existing models should be carefully evaluated in the analysis of tunnels constructed through average-quality rocks;the proposed solutions outperformed the existing models in solving the mentioned problem.

关键词： analytical solution elastic strain definition unified strength theory strain-softening intermediate principal stress model test

Theoretical prediction of ground settlements due to shield tunneling in multi-layered soils considering process parameters

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Underground Space 2024年第3期16卷 29-43页

作者： Liqiang Cao Xiangsheng Chen Dechun Lu dingli zhang Dong Su Institute of Geotechnical and Underground Engineering Beijing University of TechnologyBeijing 100124China Underground Polis Academy Shenzhen UniversityShenzhen 518060China Key Laboratory of Urban Underground Engineering of Ministry of Education Beijing Jiaotong UniversityBeijing 100044China Key Laboratory for Resilient Infrastructures of Coastal Cities(MOE) Shenzhen UniversityShenzhen 518060China

This paper conducts a theoretical analysis of ground settlements due to shield tunneling in multi-layered soils which are usually encountered in urban *** proposed theoretical solution which is based on the general form of the Mindlin’s solution and Loganathan-Poulos formula can comprehensively consider the in-process tunneling parameters including:unbalanced face pressure,shield-soil friction,unbalanced tail grouting pressure,unbalanced secondary grouting pressure,overloading during tunneling and the ground volume *** method is verified by comparing with the field data from the Qinghuayuan Tunnel Project in terms of the ground surface settlements along the longitudinal and transverse *** to the local settlement or heave caused by the certain tunneling parameters,the ground surface settlements calculated using current solution along the longitudinal direction presents an irregular S-shaped curve instead of the traditional S-shaped *** also find that the effect of the unbalanced secondary grouting pressure and the overloading during tunneling cannot be ignored.

关键词： Tunneling Shield Ground settlements Theoretical analysis Urban areas Multi-layered soils Qinghuayuan Tunnel

Grouting techniques for the unfavorable geological conditions of Xiang'an subsea tunnel in China

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Journal of Rock Mechanics and Geotechnical Engineering 2014年第5期6卷 438-446页

作者： dingli zhang Qian Fang Haicheng Lou Key Laboratory for Urban Underground Engineering of the Education Ministry Beijing Jiaotong University

One of the major challenges during subsea tunnel construction is to seal the potential water inflow. Thepaper presents a case study of Xiang＇an subsea tunnel in Xiamen, the first subsea tunnel in China. Duringits construction, different grades of weathered geomaterials were encountered, which was the challengingissue for this project. To deal with these unfavorable geological conditions, grouting was adoptedas an important measure for ground treatment. The grouting mechanism is first illustrated by introducinga typical grouting process. Then the site-specific grouting techniques employed in the Xiang＇ansubsea tunnel are elaborated. By using this ground reinforcement technique, the tunneling safety of theXiang＇an subsea tunnel was guaranteed. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

关键词： Subsea tunnel Weathered rocks Grouting Water inflow

Analytical study on pretensioned bolt-cable combined support of large cross-section tunnel

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Science China(Technological Sciences) 2020年第9期63卷 1808-1823页

作者： LUO JiWei zhang dingli FANG Qian LI Ao SUN ZhenYu CAO LiQiang Key Laboratory for Urban Underground Engineering of the Ministry of Education Beijing Jiaotong UniversityBeijing 100044China

To study the mechanical responses of large cross-section tunnel reinforced by pretensioned rock bolts and anchor cables, an analytical model is proposed. Considering the interaction between rock mass and bolt-cable support, the strain softening characteristic of rock mass, the elastic-plastic characteristic of bolt-cable support, and the delay effect of installation are considered in the model. To solve the different mechanical cases of tunneling reinforced by bolt-cable support, an analytical approach has been put forward to get the solutions of stress and displacement associated with tunneling. The proposed analytical model is verified by numerical simulation. Moreover, parametric analysis is performed to study the effects of pretension force,cross-section area, length, and supporting density of bolt-cable support on tunnel reinforcement, which can provide references for determining these parameters in tunnel design. Based on the analytical model, a new Ground Response Curve(GRC)considering the reinforcement of bolt-cable support is obtained, which shows the pretension forces and the timely installation are important in bolt-cable support. In addition, the proposed model is applied to the analysis of the Great Wall Station Tunnel, a high-speed railway tunnel with a super large cross-section, which shows that the analytical model of bolt-cable support was a useful tool for preliminary design of large cross-section tunnel.

关键词： bolt-cable combined support analytical model pretension force large cross-section tunnel reinforcement