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 on Distribution of Solute Atoms in Cu‑8Fe Alloy Solidification Process Under Rotating Magnetic Field

Jin Zou,Qi‑Jie Zhai,Fang‑Yu Liu,Ke‑Ming Liu,De‑Ping Lu 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.6

A rotating magnetic field (RMF) was applied in the solidification process of Cu-8Fe alloy. Focus on the mechanism of RMFon the solid solution Fe(Cu) atoms in Cu-8Fe alloy, the influences of RMF on solidification structure, solute distribution, andmaterial properties were discussed. Results show that the solidification behavior of Cu–Fe alloy have influenced through thechange of temperature and solute fields in the presence of an applied RMF. The Fe dendrites were refined and transformed torosettes or spherical grains under forced convection. The solute distribution in Cu-rich phase and Fe-rich phase were changedbecause of the variation of the supercooling degree and the solidification rate. Further, the variation in solute distributionwas impacted the strengthening mechanism and conductive mechanism of the material.

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.

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.

A sandwich‑like CMC‑based/graphene/CMC‑based conductive agent prepared from needle coke for high‑performance LiFePO4 batteries

Jin Zou,Xi‑Xi Long,Jia‑Le He,Shi‑Peng Yu,Sheng‑Wen Zhong 한국탄소학회 2023 Carbon Letters Vol.33 No.7

Liquid phase exfoliation of natural graphite is an industrially effective solution for graphene preparation. However, many countries have identified natural graphite as a strategic resource and restricted its mining. In this report, we used abundant and readily available needle coke (NC) as a graphene exfoliation precursor and sodium carboxymethyl cellulose (CMC) as a dispersant to prepare a sandwich structured conductive graphitized NC nanosheets (GNCNs) by liquid phase exfoliation, freeze-drying and high-temperature graphitization, in which a graphene layer is sandwiched between two thin CMC layers. CMC could increase the liquid absorption and retention ability of the conductive agent and improve the migration rate of lithium ions. The highly ordered graphene layer could accelerate the transmission of electrons. The GNCNs with 0.4 wt% CMC addition showed good rate performance (144.6 mAh g? 1 at 5 C) and high cycle stability (96.2% after 200 cycles at 1 C) for LiFePO4 (LFP) battery. The traditional Super-P (SP) conductive agent exhibited low-rate performance (113.9 mAh g? 1 at 5 C) and cycle performance (89.9% after 200 cycles at 1 C). This study offers a novel approach to selecting graphene precursors and has promising applications for conductive additives in high-performance LFP batteries.

Correction: A sandwich-like CMC-based/graphene/CMC-based conductive agent prepared from needle coke for high-performance LiFePO4 batteries

Zou Jin,Long Xi-Xi,He Jia-Le,Yu Shi-Peng,Zhong Sheng-Wen 한국탄소학회 2024 Carbon Letters Vol.34 No.3

Liquid phase exfoliation of natural graphite is an industrially effective solution for graphene preparation. However, many countries have identified natural graphite as a strategic resource and restricted its mining. In this report, we used abundant and readily available needle coke (NC) as a graphene exfoliation precursor and sodium carboxymethyl cellulose (CMC) as a dispersant to prepare a sandwich structured conductive graphitized NC nanosheets (GNCNs) by liquid phase exfoliation, freeze-drying and high-temperature graphitization, in which a graphene layer is sandwiched between two thin CMC layers. CMC could increase the liquid absorption and retention ability of the conductive agent and improve the migration rate of lithium ions. The highly ordered graphene layer could accelerate the transmission of electrons. The GNCNs with 0.4 wt% CMC addition showed good rate performance (144.6 mAh g−1 at 5 C) and high cycle stability (96.2% after 200 cycles at 1 C) for LiFePO4 (LFP) battery. The traditional Super-P (SP) conductive agent exhibited low-rate performance (113.9 mAh g−1 at 5 C) and cycle performance (89.9% after 200 cycles at 1 C). This study offers a novel approach to selecting graphene precursors and has

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.

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.

Albumin-to-Fibrinogen Ratio as an Independent Prognostic Parameter in Untreated Chronic Lymphocytic Leukemia: A Retrospective Study of 191 Cases

Yi-Xin Zou,Jia Qiao,Hua-Yuan Zhu,Rui-Nan Lu,Yi Xia,Lei Cao,Wei Wu,Hui Jin,Wen-Jie Liu,Jin-Hua Liang,Jia-Zhu Wu,Li Wang,Lei Fan,Wei Xu,Jian-Yong Li 대한암학회 2019 Cancer Research and Treatment Vol.51 No.2

Purpose Chronic lymphocytic leukemia (CLL) is one of the most frequent type of B-cell chronic lymphoproliferative disorders and chronic inflammation takes part in the development of CLL. However, there has been no valid immune biomarker to predict the prognosis of untreated CLL patients. Materials and Methods In this retrospective study, we analyzed the clinical correlations and prognostic value of albumin-to-fibrinogen ratio (AFR) detected at diagnosis in 191 CLL patients. Results The cut-off value of AFR was 9.7 calculated by X-tile. Patients who were more than 65 years old were often accompanied by low level of AFR (p < 0.001). Survival analysis showed that patients with low level of AFR had shorter overall survival (OS) than patients with high level of AFR (p < 0.001). Multivariate analysis illustrated that AFR had a negative impact on OS (p=0.003) and was independent of parameters involved in CLL international prognostic index and other prognostic markers such as CD38 and ZAP-70. Conclusion These data provide a comprehensive view of AFR and shows that AFR at diagnosis is an adverse prognostic factor in untreated CLL patients.