Theoretical solutions for displacement and stress of a circular opening reinforced by grouted rock bolt

Zou, Jin-Feng,Xia, Zhang-Qi,Dan, Han-Cheng Techno-Press 2016 Geomechanics & engineering Vol.11 No.3

This paper presented solutions of displacement and stress for a circular opening which is reinforced with grouted rock bolt. It satisfies the Mohr-Coulomb (M-C) or generalized Hoek-Brown (H-B) failure criterion, and exhibits elastic-brittle-plastic or strain-softening behavior. The numerical stepwise produce for strain-softening rock mass reinforced with grouted rock bolt was developed with non-associative flow rules and two segments piecewise linear functions related to a principle strain-dependent plastic parameter, to model the transition from peak to residual strength. Three models of the interaction mechanism between grouted rock bolt and surrounding rock proposed by Fahimifar and Soroush (2005) were adopted. Based on the axial symmetrical plane strain assumption, the theoretical solution of the displacement and stress were proposed for a circular tunnel excavated in elastic-brittle-plastic and strain-softening rock mass compatible with M-C or generalized H-B failure criterion, which is reinforced with grouted rock bolt. It showed that Fahimifar and Soroush's (2005) solution is a special case of the proposed solution for n = 0.5. Further, the proposed method is validated through example comparison calculated by MATLAB programming. Meanwhile, some particular examples for M-C or generalized H-B failure criterion have been conducted, and parametric studies were carried out to highlight the influence of different parameters (e.g., the very good, average and very poor rock mass). The results showed that, stress field in plastic region of surrounding rock with considering the supporting effectiveness of the grouted rock bolt is more than that without considering the effectiveness of the grouted rock bolt, and the convergence and plastic radius are reduced.

Influences of seepage force and out-of-plane stress on cavity contracting and tunnel opening

Zou, Jin-Feng,Chen, Kai-Fu,Pan, Qiu-Jing Techno-Press 2017 Geomechanics & engineering Vol.13 No.6

The effects of seepage force and out-of-plane stress on cavity contracting and tunnel opening was investigated in this study. The generalized Hoek-Brown (H-B) failure criterion and non-associated flow rule were adopted. Because of the complex solution of pore pressure in an arbitrary direction, only the pore pressure through the radial direction was assumed in this paper. In order to investigate the effect of out-of-plane stress and seepage force on the cavity contraction and circular tunnel opening, three cases of the out-of-plane stress being the minor, intermediate, or major principal stress are assumed separately. A method of plane strain problem is adopted to obtain the stress and strain for cavity contracting and circular tunnel opening for three cases, respectively, that incorporated the effects of seepage force. The proposed solutions were validated by the published results and the correction is verified. Several cases were analyzed, and parameter studies were conducted to highlight the effects of seepage force, H-B constants, and out-of-plane stress on stress, displacement, and plastic radius with the numerical method. The proposed method may be used to address the complex problems of cavity contraction and tunnel opening in rock mass.

Theoretical Solutions for a Circular Opening in an Elastic–brittle–plastic Rock Mass Incorporating the Out-of-plane Stress and Seepage Force

Zou Jin-feng,Li Shuai-shuai,Xu Yuan,Dan Han-cheng,Zhao Lian-heng 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.2

Seepage force is simplified as seepage volumetric force in the stress field along the radial direction. Out-of-plane stress and seepage force are incorporated, and the theoretical solutions for stress, displacement, and plastic radius of a circular opening for the elastic-brittle-plastic and elastic-plastic rock mass are proposed based on the Mohr–Coulomb (MC) and generalized Hoek-Brown (HB) failure criteria. The presented solution and Wang’s solution (2012) are compared, and the corrected version of the proposed method is validated. Numerical examples of the proposed method based on the MC and generalized HB failure criteria reveal that the distributions of stress and displacement in the surrounding rock of the tunnel are significantly influenced by seepage force and out-ofplane stress. Displacement and plastic radius when seepage force and out-of-plane stress are considered are larger than those when the seepage force is not considered; the regulations of stress, however, run opposite. The results of displacement and plastic radius based on the generalized HB failure criterion are larger than those based on the MC failure criterion.

Three-Dimensional Face Stability Assessments of Seismic Tunnels in Weak Rock Masses

Jin-feng Zou,Shiwei Li,Guang-hui Chen 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.6

The face stability assessments of seismic tunnels have been complicated and crucial problems. To solve this issue, an advanced three-dimensional (3D) rotational failure mechanism with considering seismic effects is developed to assess the seismic face stability of shield tunnels in weak rock masses. The Hoek-Brown (HB) failure criteria is employed to characterize rock masses with weak strength. The corresponding Mohr-Coulomb (MC) parameters are determined using the tangential line method. The modified pseudo-dynamic (MPD) approach is utilized to accurately involve damping property of geomaterials, realistic surface boundary conditions and dynamic properties of seismic waves in face stability assessments. The upper limit analysis approach is utilized for the determination of critical face pressures of seismic tunnels. Comparisons against numerical and analytical solutions demonstrate the efficacy of proposed approach for evaluating the seismic face stability. Subsequently, the impacts of seismic actions and weak rock parameters on face stability are analyzed and a design table is provided for practical use. Finally, the proposed approach is tested by conducting seismic face stability assessments of the JinXiu tunnel with actual seismic response.

An improved radius-incremental-approach of stress and displacement for strain-softening surrounding rock considering hydraulic-mechanical coupling

Zou, Jin-Feng,Wei, Xing-Xing Techno-Press 2018 Geomechanics & engineering Vol.16 No.1

This study focused on the mechanical and hydraulic characteristics of underwater tunnels based on Mohr-Coulomb (M-C), Hoek-Brown (H-B) and generalized H-B failure criteria. An improved approach for calculating stress, displacement and plastic radius of the circular tunnel considering hydraulic-mechanical coupling was developed. The innovation of this study was that the radius-incremental-approach was reconstructed (i.e., the whole plastic zone is divided into a finite number of concentric annuli by radius), stress and displacement of each annulus were determined in terms of numerical method and Terzaghi's effective stress principle. The validation of the proposed approach was conducted by comparing with the results in Brown and Bray (1982) and Park and Kim (2006). In addition, the Rp-pin curve (plastic radius-internal supporting pressure curve) was obtained using the numerical iterative method, and the plastic radius of the deep-buried tunnel could be obtained by interpolation method in terms of the known value of internal supporting pressure pin. Combining with the theories in Carranza and Fairhurst (2000), the improved technique for assessing the reliability of the tunnel support was proposed.

A new approach for the cylindrical cavity expansion problem incorporating deformation dependent of intermediate principal stress

Zou, Jin-Feng,Xia, Ming-yao Techno-Press 2017 Geomechanics & engineering Vol.12 No.3

The problem of cylindrical cavity expansion incorporating deformation dependent of intermediate principal stress in rock or soil mass is investigated in the paper. Assumptions that the initial axial total strain is a non-zero constant and the axial plastic strain is not zero are defined to obtain the numerical solution of strain which incorporates deformation-dependent intermediate principal stress. The numerical solution of plastic strains are achieved by the 3-D plastic potential functions based on the M-C and generalized H-B failure criteria, respectively. The intermediate principal stress is derived with the Hook's law and plastic strains. Solution of limited expansion pressure, stress and strain during cylindrical cavity expanding are given and the corresponding calculation approaches are also presented, which the axial stress and strain are incorporated. Validation of the proposed approach is conducted by the published results.

A new approach for the quasi-plane strain-softening problem of cylindrical cavity expansion based on Cam-Clay model

Zou Jin-feng,Du Jia-min 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.3

This paper focuses on the quasi-plane strain-softening problem of cylindrical cavity expanding in Cam-Clay soil mass. The quasi-plane strain-softening problem is defined based on the assumptions that the initial axial total strain is a non-zero constant and the axial plastic strain is not zero. A new approach for the major, intermediate, and minor principal strains are proposed based on the associated flow rule, 3-D plastic potential function, Hooke’s law, stress equilibrium equation and Cam-Clay model. The correctness of the proposed approach is validated by the results in Cao and Teh. Parametric studies were performed to investigate the influences of the intermediate principal stress on the radial and circumferential stresses and the radial displacement, respectively.

Traditional medicine for post-viral olfactory dysfunction: A systematic review

Zou, Xiang-yun,Liu, Xue-han,Lu, Chun-li,Jin, Xin-yan,He, Bai-xiang,Liao, Yi-lei,Liu, Ting,Dai, Yi-dan,Qi, Shi-hao,Sheng, Zhu-jun,Yan, Zhan-feng,Yang, Guo-Yan,Stub, Trine,Liu Jian-Ping 한국한의학연구원 2024 Integrative Medicine Research Vol.13 No.2

Background: Post-viral olfactory dysfunction (PVOD) is the common symptoms of long COVID, lacking of effective treatments. Traditional Chinese medicine (TCM) is claimed to be effective in treating olfactory dysfunction, but the evidence has not yet been critically appraised. We conducted a systematic review to evaluate the effectiveness and safety of TCM for PVOD. Methods: We searched eight databases to identified clinical controlled studies about TCM for PVOD. The Cochrane risk of bias tools and GRADE were used to evaluate the quality of evidence. Risk ratio (RR), mean differences (MD), and 95 % confidence interval (CI), were used for effect estimation and RevMan 5.4.1 was used for data analysis. Results: Six randomized controlled trials (RCTs) (545 participants), two non-randomized controlled trials (non-RCTs) (112 participants), and one retrospective cohort study (30 participants) were included. The overall quality of included studies was low. Acupuncture (n = 8) and acupoint injection (n = 3) were the mainly used TCM therapies. Five RCTs showed a better effect in TCM group. Four trials used acupuncture, and three trials used acupoint injection. The results of two non-RCTs and one cohort study were not statistically significant. Two trials reported mild to moderate adverse events (pain and brief syncope caused by acupuncture or acupoint injection). Conclusions: Limited evidence focus on acupuncture and acupoint injection for PVOD and suggests that acupuncture and acupoint injection may be effective in improving PVOD. More well-designed trials should focus on acupuncture to confirm the benefit. Protocol registration: The protocol of this review was registered at PROSPERO: CRD42022366776.

A Facile and Efficient Synthesis of Dronedarone Hydrochloride

Feng Li,Chunhua Jin,Jianwei Zou,Jun Wu 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.7

A facile and efficient synthesis of dronedarone hydrochloride starting from commercially available 4- nitrophenol is described. This approach features a tandem-type synthesis of 3-carbonylated benzofuran involving cyclization of 2-ethynylphenol followed by CO2 fixation at the 3-position of the benzofuran ring mediated by potassium carbonate without the addition of any transition metal catalyst.

Expression profiles of glutathione S-transferase genes in larval midgut of Bombyx mori exposed to insect hormones

Zou, Feng-Ming,Lou, De-Shuai,Zhu, Ya-Hong,Wang, Sheng-Peng,Jin, Byung-Rae,Gui, Zhong-Zheng Springer-Verlag 2011 Molecular biology reports Vol.38 No.1