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.

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.

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.

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.

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

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.

Baicalin attenuates TNBS-induced colitis in rats by modulating the Th17/Treg paradigm

Ying Zou,Shi-Xue Dai,Hong-Gang Chi,Tao Li,Zhi-Wei He,Jian Wang,Cai-Guo Ye,Guo-Liang Huang,Bing Zhao,Wen-Yang Li,Zheng Wan,Jin-Shan Feng,Xue-Bao Zheng 대한약학회 2015 Archives of Pharmacal Research Vol.38 No.10

Baicalin, a flavonoid, has a wide range ofpharmacological properties, including immunomodulation. The objective of this study was to investigate the effect ofbaicalin on the balance of T helper 17 (Th17) and regulatoryT (Treg) cells in a colitis model. The rat colitis modelwas induced by 2,4,6-trinitrobenzene sulfonic acid(TNBS). Baicalin (10 ml/kg, each) or mesalazine (positivecontrol) was then administered orally for 7 days. Inflammatoryand immunological responses were evaluated bypathology, enzyme-linked immunosorbent assay, real-timepolymerase chain reaction, western blot analysis, and flowcytometry. Our study showed that baicalin not only significantlyattenuated TNBS-induced colitis by reducing thedisease activity index as well as macroscopic and microscopicscores, but it also improved the weight loss andshortening of the colon. Baicalin treatment also induced asignificant decrease in the levels of inflammatory mediators,including the myeloperoxidase activity, the levels oftumor necrosis factor a, IL-1b, and Th1-related cytokinesIL-12 and IFN-c. Furthermore, the beneficial effects ofbaicalin seem to be associated with regulation of the Th17and Treg paradigm. We found that administration ofbaicalin significantly downregulated the number of Th17cells and the levels of Th17-related cytokines (IL-17 andIL-6) and retinoic acid receptor-related orphan receptor ct. In contrast, there was an increase in Treg cells numbers,Treg-related cytokines transforming growth factor-b andIL-10, and forkhead box P3. Our results suggest that theanti-inflammatory effect of baicalin may be linked tomodulation of the balance between Th17 and Treg cells inTNBS-induced ulcerative colitis.

A Facile and Efficient Synthesis of Dronedarone Hydrochloride

Li, Feng,Jin, Chunhua,Zou, Jianwei,Wu, Jun Korean Chemical Society 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 $CO_2$ fixation at the 3-position of the benzofuran ring mediated by potassium carbonate without the addition of any transition metal catalyst.