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RISS 인기검색어
- 검색키워드
- 저자 : Yongfang Jia (검색결과 5 건)
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Surface Settlement Prediction for EPB Shield Tunneling in Sandy Ground
Yongfang Jia,Chuan He,Ali Nazem,Zhigang Yao,Jacob Grasmick 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.7
Ground volume loss induced by shield tunnel construction is the major factor leading to ground settlement and deformation. The general equations predicting surface settlement based on ground volume loss involve a settlement trough width coefficient (parameter i) which in previous models was set as a constant in both the transverse and longitudinal directions. In this work, the equations predicting surface settlement during the construction were modified by introducing the parameter j – the width coefficient in the longitudinal direction, assumed to be different from that in the transverse direction. A model shield machine was adopted to carry a laboratory test under 1 g to investigate surface settlement induced by earth-pressure-balance shield tunnel construction in unsaturated sandy soil. The surface settlement during the excavating observed in the test was compared with that predicted by general equations from previous studies and the modified. The results showed that surface settlement above shield machine obtained by the modified equation proposed here fits the test data better than those obtained by the general equations because of the introduced longitudinal width coefficient.
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Liner Behavior of a Tunnel Constructed Below a Caved Zone
Yongfang Jia,Zhigang Yao,Gabriel Walton,Yapeng Fu 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.10
Underground mining leads to deformation of the surrounding rock strata. Over time, this deformation tends to stabilize after mining has completed. However, ground movement can easily reactivated if another adjacent underground project is excavated nearby. When tunnelling underneath caved mining areas, the associated effects on load distribution and liner behavior of this caved zone can be significant. This paper presents a series of scale model tests to understand these effects. In these tests, various testing material compositions were used to simulate intact rocks, a caved zone, primary support and secondary liner based on similarity theory. Various caved zone-tunnel distances (d) and different buried depths were considered in the tests. Results such as deformation, thrust force and bending moment of the liner were recorded and compared. The results show that the caved zone has an obvious impact on the liner when it is located above and nearby the tunnel, but this influence decreases rapidly as a function of d. If the caved zone-tunnel distance is between 50% and 100% of the tunnel span, the bearing capability of the rock immediately surrounding the excavation is significantly reduced, which leads to more vertical load on the support of the tunnel compared to a tunnel without a caved zone. Furthermore, as the shape of broken rock is irregular and the arrangement is random, the caved zone creates an asymmetrical distribution of displacements if the tunnel is near the caved zone. Additionally, this may result in large moments and damage at the tunnel crown.
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Photoelectrochemical and Charge Transfer Properties of SnS/TiO2 Heterostructure Nanotube Arrays
Yongfang Jia,Feng Yang,Fanggong Cai,Cuihua Cheng,Yong Zhao 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.3
SnS/TiO2 heterostructure nanotube arrays (NTAs) were synthesized through a successive ionic layer adsorption and reaction process. The photoelectrochemical (PEC) property of SnS/TiO2 heterostructure NTAs was evaluated in liquid junction PEC solar cells. The results revealed that SnS/TiO2 heterostructure NTAs exhibited PEC property with an open-circuit voltage of 1.08 V, a short-circuit current density of 1.55 mA/cm2, and a conversion efficiency of 0.75% under 1 sun illumination. These values are higher than those of pristine SnS nanoparticles and TiO2 NTAs. Surface photovoltage spectroscopy and phase spectroscopy measurements were conducted to verify the formation of heterojunction and probe charge transfer between SnS and TiO2NTAs. The PEC property and surface photovoltaic response enhancement of SnS/TiO2 heterostructure NTAs can be attributed to the enhanced electron-hole separation due to the effect of interfacial electric field in SnS/TiO2 heterostructure NTAs.
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Performance of Slurry TBM Tunnelling in Sandy Cobble Ground – A Case Study in Lanzhou
Shunze Cao,Jian Cui,Yongfang Jia,Ruyong Deng 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.7
The slurry tunnelling boring machine (TBM) was used to construct the tunnel of the Lanzhou Metro Line 1 undercrossing the Yellow River, China. The ground is characterized by sandy cobble with high cobble content. There are many challenges for slurry TBM tunnelling in sandy cobble ground because the cobble is hard to break and transport. This paper focuses on the performance of slurry TBM tunnelling, summarizes the lessons of shield driving and suggests countermeasures for the cobble breaking and disposal including cutterhead improvement, double pebble crusher and clasts collection tank. The chamber pressure and grouting pressure during the driving process were recorded and compared with the theoretical ground stress. The key parameters including the thrust force of cylinders, advance rate, torque and rotation speed of the cutterhead were recorded and analysed. Field test results show that the surface settlement induced by slurry TBM tunnelling in sandy cobble ground can be well controlled and the longitudinal surface settlement can be predicted by the Attewell formula and modified Attewell formula. This paper provides a good reference for slurry TBM tunnelling in sandy cobble ground.
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Yang, Yankang,Qiu, Beibei,Chen, Shanshan,Zhou, Qiuju,Peng, Ying,Zhang, Zhi-Guo,Yao, Jia,Luo, Zhenghui,Chen, Xiaofeng,Xue, Lingwei,Feng, Liuliu,Yang, Changduk,Li, Yongfang The Royal Society of Chemistry 2018 Journal of materials chemistry. A, Materials for e Vol.6 No.20
<P>Solution-processed organic solar cells (OSCs) have been attracting more and more attention for a series of well-known advantages, and power conversion efficiencies (PCEs) of over 11% have been reported. However, the highest PCE of the OSCs based on small molecule donor/polymer acceptor blends is only 4.82%, which was much lower than those of other types of OSCs due to weak absorption of the polymer acceptor and the unbalanced charge carrier mobility of the small molecule donor and the polymer acceptor. Here, we fabricated small molecule donor/polymer acceptor-based OSCs using the wide bandgap SM1 and DR3TBDTT as the small molecular donor and the low-bandgap n-type conjugated polymer PZ1 as the polymer acceptor. With the treatment of a solvent additive, which can promote the absorption intensity, enhance the carrier mobility and suppress the charge carrier recombination, the SM1-based devices and the DR3TBDTT-based devices show PCEs of 3.97% and 5.86%, respectively. It is worth mentioning that the PCE of 5.86% is the state-of-the-art efficiency for OSCs based on the small molecular donor/polymer acceptor system.</P>
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