Upper-bound Finite Element Analysis of Stability of Tunnel Face Subjected to Surcharge Loading in Cohesive-frictional Soil

Feng Yang,Jian Zhang,Lianheng Zhao,Junsheng Yang 대한토목학회 2016 KSCE Journal of Civil Engineering Vol.20 No.6

The stability of a plane strain tunnel face in a cohesive-frictional soil (idealized as a homogeneously Mohr-Coulomb material) subjected to ground surface surcharge loading was investigated. Continuous loading is applied to the ground surface, and both smooth and rough interface conditions are modeled. The upper-bound solutions with critical load parameters for a practical range of tunnel depth-to-height values, as well as the soil properties, are obtained by using the Upper-bound Finite Element Method with Rigid Translatory Moving Elements (UBFEM-RTME). For practical use, the results are presented in the form of dimensionless stability charts. Failure mechanisms consisting of two groups of slip lines, which explicitly reflect the relative movement of blocks, are also presented. To verify the solutions, the Upper-bound Finite Element Method with Plastic Deformation Elements (UMFEMPDE) has been developed and the collapsed loads are compared with those from UBFEM-RTME. The solutions obtained with these two upper-bound finite element methods are found to be in good agreement with each other.

Performances of Concrete Columns with Modular UHPC Permanent Formworks Under Axial Load

Yibo Yang,Baixi Chen,Yong Chen,Huanyang Zhou,Fucai Liu,Xiangming Xie,Junsheng Chen,Wenying Guo,Hengchang Wang 한국콘크리트학회 2023 International Journal of Concrete Structures and M Vol.17 No.5

This research proposed the modular prefabricated permanent formwork system made of ultra-high-performance concrete (UHPC). Two kinds of modular formwork shapes were designed: the flat formwork and the ribbed. The experimental investigation on the axial compression performance of the composite columns that consist of the normal strength concrete (NSC) core and the modular UHPC permanent formwork was demonstrated. Compared with the flat formwork, the ribbed formwork exhibited better bonding with the NSC core. As observed from the test results, the composite column with the ribbed formwork presented a similar axial behavior as the NSC column with a slight improvement in ultimate loads. Therefore, the modular UHPC ribbed permanent formwork could be regarded as the additional cover to the conventional NSC column. In addition, the finite element analysis (FEA) model was also developed to simulate the composite columns numerically. The predicted capacities agreed with the experimental results, which validated the numerical models. The crack pattern estimated by the FEA model revealed that the interaction between the permanent formwork and the inner concrete introduced many tiny cracks to the concrete core. However, as protected by the UHPC permanent formwork, the overall durability of the composite columns can still be enhanced.

Spectrum allocation strategy for heterogeneous wireless service based on bidding game

( Jing Cao ),( Junsheng Wu ),( Wenchao Yang ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.3

The spectrum scarcity crisis has resulted in a shortage of resources for many emerging wireless services, and research on dynamic spectrum management has been used to solve this problem. Game theory can allocate resources to users in an economic way through market competition. In this paper, we propose a bidding game-based spectrum allocation mechanism in cognitive radio network. In our framework, primary networks provide heterogeneous wireless service and different numbers of channels, while secondary users have diverse bandwidth demands for transmission. Considering the features of traffic and QoS demands, we design a weighted interference graph-based grouping algorithm to divide users into several groups and construct the non-interference user-set in the first step. In the second step, we propose the dynamic bidding game-based spectrum allocation strategy; we analyze both buyer`s and seller`s revenue and determine the best allocation strategy. We also prove that our mechanism can achieve balanced pricing schema in competition. Theoretical and simulation results show that our strategy provides a feasible solution to improve spectrum utilization, can maximize overall utility and guarantee users` individual rationality.

Cenozoic tectonic evolution in the western Qaidam Basin inferred from subsurface data

Yadong Wang,Junsheng Nie,Tao Zhang,Guoqiang Sun,Xin Yang,Yuhu Liu,Xingwang Liu 한국지질과학협의회 2010 Geosciences Journal Vol.14 No.4

It is an agreement that collision of Indian and Asian plates causes uplift of the Tibet Plateau. However, great controversy exists about uplifting history and mechanisms of the Tibetan Plateau. Uplift history of the Tibetan Plateau has been well recorded in the Qaidam Basin, located in the northern margin of the Tibet Plateau. In this paper, we recognize and classify faults recorded by subsurface seismic data in the western Qaidam Basin. In addition, we reconstruct the Cenozoic deformation history of the Qaidam Basin based on balanced section of 5 seismic profiles. The results indicates that 1) Faults in the western Qaidam Basin can be classified as growth faults and non-growth faults, and the growth faults could be divided into three subcategories. 2) According to timing and manner of fault activities, faults and strata in the western Qaidam Basin could be divided into two structural layers: the lower (Lulehe Fm-Xia Youshashan Fm) and the upper (Shang Youshashan Fm-Qigequan Fm) layer. 3) The western Qaidam Basin has experienced two intensive tectonic deformations: the first phase occurs at 43.8−22 Ma (Middle Eocene−Early Miocene), which reached peak at 31.5 Ma (Early Oligocene); the second phase occurred between 14.9 and 0 Ma (Middle Miocene−Present), and the second phase is stronger than the first phase. Recognizing early fault activities confirm previous results that northern Tibet has sensed collision between the India and the Asia shortly after the collision. However, our results here emphasize that the northern Tibet has experienced another phase of shortening and uplift in the late Neogene. It was the two-stage tectonic activities that work together to produce the current Tibetan Plateau.

Structural monitoring and analyses on the stability and health of a damaged railway tunnel

Zhao, Yiding,Yang, Junsheng,Zhang, Yongxing,Yi, Zhou Techno-Press 2021 Advances in concrete construction Vol.11 No.5

In this paper, a study of stability and health of a newly-built railway tunnel is presented. The field test was implemented to monitor the secondary lining due to the significant cracking behaviors influenced the stability and health of the tunnel structure. Surface strain gauges were installed for monitoring the status of crack openings, and the monitoring outputs demonstrated that the cracks were still in the developing stage. Additionally, adjacent tunnel and poor condition of surrounding rock were identified as the causes of the lining cracking by systematically characterizing the crack spatial distribution, tunnel site and surrounding rock conditions. Reconstruction of partial lining and reconstruction of the whole secondary lining were designed as the maintenance projects for different cracking regions based on the construction feasibility. For assessing the health conditions of the reinforced lining, embedded strain gauges were set up to continuously measure the strain and the internal force of the reconstructed structures. For the partially reconstructed lining, the outputs show the maximum tensile elongation is 0.018 mm during 227 days, which means the structure has no obvious deformation after maintenance. The one-year monitoring of full-section was implemented in the other two completely reconstructed cross-sections by embedded strain gauge. The outputs show the reconstructed secondary lining has undertaken the pressure of surrounding rock with the time passing. According to the calculated compressive and tensile safety factors, the completely reconstructed lining has been in reliable and safe condition during the past year after reinforcement. It can conclude that the aforementioned maintenance projects can effectively ensure the stability and health of this tunnel.

Numerical Simulation of Temperature Effects on Mechanical Behavior of the Railway Tunnel in Tibet

Shouhua Liu,Jinyang Fu,Junsheng Yang,Han Feng 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.12

Under the influence of plate collision, the high geothermal is a widespread phenomenon within the region of Tibet. Due to the aforementioned high geothermal, lining cracking is a common disaster in Sangzhuling tunnel during construction period. This paper presented the mechanical behaviour of tunnel lining under high geothermal temperature, which is studied by thermo-mechanical numerical method. The results both from field investigation and numerical analysis demonstrate that high geothermal temperature can cause the tunnel lining cracking and the variation of the stress of the tunnel lining. Thus, a novelty sandwich composite lining supporting scheme is proposed to overcome such geothermal temperature effects, in which a thermal insulation layer between primary supporting and secondary supporting is designed. The numerical analysis results indicate that the insulation layer can significantly improve the mechanical characteristics of the lining structure. In addition, the effect of the insulation layer is not linear with its thickness. For this reason, the optimuminsulation thickness of the insulation layer is chosen as 0.06 m, which was optimized by a numerical parametric analysis. The research can provide a reliable reference for tunnelling works in high geothermal regions.

Preparation and Photoelectrocatalytic Performance Study of Au-RGO/TiO2 NTs Photoelectrode

Zuo Jin Long,ShaoDong Yang,YiWen Li,Chong Tan,Zhi Xia,SiYing Yuan,ShiYou Yu,JunSheng Li 한국고분자학회 2022 Macromolecular Research Vol.30 No.11

In our research, The Au-reduced graphene oxide (RGO)/TiO2 nanotubes (NTs) photoelectrode was prepared by electrodeposition, and was characterized and analyzed by scanning electron microscope, X-ray energy scattering spectroscopy, X-ray diffraction, photoluminescence spectroscopy, and photoelectrochemical methods. The results show that the best preparation conditions is setting deposition voltage as 0.2 V and deposition time as 30 s. At the same time, the nano-gold is well supported on RGO/TiO2 NTs without changing the original nanotube array structure. After a 35 W mercury lamp and a 15 V bias are applied, the photoelectric degradation efficiency of methylene blue is 72%, slightly higher thanthose of the other two electrodes. which show demonstrate that the photocatalytic activity of Au-RGO/TiO2 NTs photoelectrodes under visible light is improved effectively.

The Shear Behavior of Double-superposed Panels Reinforced with Different Shear Connectors

Wenying Zhang,Lianping Yang,Shaole Yu,Junsheng Yan 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.10

The shear behavior of a new type of sandwich structure, double-superposed panels, is investigated by conducting push-out test and finite element analysis in this paper. Experiments have been carried out to characterize the effect on the shear behavior of two different shear connector configurations: truss connector and tic-tac-toe connector. Based on finite element analysis, a parameter study is conducted, with the major parameters considered being the diameter, height and pitch of shear connector. Test results indicate that the delamination between the precast layers and core layer is the main failure mode for all specimens, and the crack formation and crack development between the two interfaces is not in synch. It’s also revealed that the specimens with tic-tac-toe connections present higher ultimate shear strength, as well as better ductility during the process of failure, compared to those with truss connections. The results of the numerical simulations show that the ultimate shear strength and the ductility of both connector configurations increases as the diameter of the shear connector increases; increasement in height of shear connector has a negligible effect on the shear behavior; when the pitch length is increased, the ultimate shear strength of the truss connector specimen increases, which is the inverse behavior of the specimen with tic-tac-toe connector.

Fracture behaviors of tunnel lining caused by multi-factors: A case study

Zhao, Yiding,Zhang, Yongxing,Yang, Junsheng Techno-Press 2019 Advances in concrete construction Vol.8 No.4

The cracking and spalling caused by fracture of concrete lining have adverse impacts on serviceability and durability of the tunnel, and the subsequent maintenance work for damaged structure needs to be specific to the damaging causes. In this paper, a particular case study of an operational tunnel structure is presented for the serious cracking and spalling behaviours of concrete lining, focusing on the multi-factors inducing lining failure. An integrated field investigation is implemented to characterize the spatial distribution of damages and detailed site situations. According to results of nondestructive inspection, insufficient lining thickness and cavity behind lining are the coupled-inducement of lining failure bahaviors. To further understanding of the lining structure performance influenced by these multiple construction deficiencies, a reliable numerical simulation based on extended finite element method (XFEM) is performed by using the finite element software. The numerical model with 112 m longitudinal calculation, 100 m vertical calculation and 43 m vertical depth, and the concrete lining with 1450 solid elements are set enrichment shape function for the aim of simulating cracking behavior. The numerical simulation responses are essentially in accordance with the actual lining damaging forms, especially including a complete evolutionary process of lining spalling. This work demonstrates that the serious lining damaging behaviors are directly caused by a combination of insufficient thickness lining and cavity around the surrounding rocks. Ultimately, specific maintenance work is design based on the construction deficiencies, and that is confirmed as an efficient, time-saving and safe maintenance method in the operational railway tunnel.

Study on Color Analyzer based on the Multiplexing of TCS3200 Color Sensor and Microcontroller

Li Qiaoyi,Xiong Yanling,Yang Wenlong,Han Junsheng,Liang Huan 보안공학연구지원센터 2014 International Journal of Hybrid Information Techno Vol.7 No.5