Coefficient of Restitution and Kinetic Energy Loss of Rockfall Impacts

Li-Ping Li,Shang-qu Sun,Shucai Li,Qian-qing Zhang,Cong Hu,Shao-shuai Shi 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.6

This paper presents the results of the coefficient of restitution and the kinetic energy loss rate obtained by lab experiment, two parameters that are crucial for rockfall impact. However, various definitions of coefficient of restitution exist and the most appropriate one is still not formed and obtained. In addition, the energy variation during the rockfall impacts has important significance in practical design. In this research, two kind shapes of blocks including plate and strip were adopted in the laboratory testing and the block material was tested before, indicating that the material has sufficient strength to prevent shattering during the impact. Furthermore, an apparatus specifically built for this study was established including a base, a slope and a releasing device. The falling testing was performed using plate and strip block while the falling height as well as the slope angle and releasing height were altered during the tests in order to estimate the effect of each parameter on the coefficients of restitution and energy loss rate. It was observed that collision reflection angle is less than impact angle for all, suggesting energy loss in collision. Impact angle decreases with increasing slope angle while there was no obvious effect of releasing height and releasing angle on impact angle. The relevant coefficient of restitution was found to decrease with impact angle, and the kinetic energy loss rate increased. Finally, the kinetic energy before and after the impact was found to significantly affect the COR and energy loss rate and the results can provide basis for mitigation measures.

Numerical analysis and fluid-solid coupling model test of filling-type fracture water inrush and mud gush

Li, Li-Ping,Chen, Di-Yang,Li, Shu-Cai,Shi, Shao-Shuai,Zhang, Ming-Guang,Liu, Hong-Liang Techno-Press 2017 Geomechanics & engineering Vol.13 No.6

The geological conditions surrounding the Jijiapo Tunnel of the Three Gorges Fanba Highway project in Hubei Province are very complex. In this paper, a 3-D physical model was carried out to study the evolution process of filling-type fracture water inrush and mud gush based on the conditions of the section located between 16.040 km and 16.042 km of the Jijiapo Tunnel. The 3-D physical model was conducted to clarify the effect of the self-weight of the groundwater level and tunnel excavation during water inrush and mud gush. The results of the displacement, stress and seepage pressure of fracture and surrounding rock in the physical model were analyzed. In the physical model the results of the model test show that the rock displacement suddenly jumped after sustainable growth, rock stress and rock seepage suddenly decreased after continuous growth before water inrushing. Once water inrush occured, internal displacement of filler increased successively from bottom up, stress and seepage pressure of filler droped successively from bottom up, which presented as water inrush and mud gush of filling-type fracture was a evolving process from bottom up. The numerical study was compared with the model test to demonstrate the effectiveness and accuracy of the results of the model test.

Dynamic Unloading Instability Mechanism of Underground Cavern Based on Seepage-Damage Coupling

Li-Ping Li,Wenfeng Tu,Zongqing Zhou,Shao-shuai Shi,Mingguang Zhang,Yuxue Chen 대한토목학회 2020 KSCE Journal of Civil Engineering Vol.24 No.5

The seepage-damage coupling effect will aggravate the instability of the surrounding rock during the unloading process of underground cavern excavation. Considering this coupling effect and excavation disturbance, the theoretical solution of the stress state of surrounding rock is derived by using the elastic-brittle damage model. The dynamic criterion of the instability and water inrush is presented. Based on the theoretical derivation, the calculation program for the seepage-damage analysis of the surrounding rock under dynamic unloading is programmed, and the seepage flow and the radius of the damage zone of the surrounding rock are calculated. By analysing the variation of radius of the damaged zone with pore water pressure and excavation radius under different calculation conditions, the influence of dynamic unloading disturbance on the damaged zone of the surrounding rock is discussed. The radius of the damaged zone increases with the pore water pressure and excavation radius. Considering the effect of dynamic unloading, the calculation result of the damaged zone radius and seepage discharge of underground cavern are much larger than the theoretical calculation and coupling calculation of seepage-damage without dynamic unloading. Research methods and results can provide guidance and reference for similar engineering research.

Highly active bifunctional oxygen electrocatalysts derived from nickel- or cobalt-phytic acid xerogel for zinc-air batteries

Wang, Shuai,Nam, Gyutae,Li, Ping,Jang, Haeseong,Wang, Jia,Kim, Min Gyu,Wu, Zexing,Liu, Xien,Cho, Jaephil The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.33

<P>Developing highly efficient non-noble metal electrocatalysts for oxygen electrode reactions is highly desirable for industrial scale application in energy related devices. Herein, two new kinds of Ni (POxN3−x)2/NPC and Co (POxN3−x)2/NPC (NPC: N, P-co-doped carbon) are synthesized through a facile post-treatment of nickel- or cobalt-phytic acid xerogel, followed by an annealing procedure under an argon and ammonia atmosphere at 800 °C. The as-prepared catalysts exhibit outstanding catalytic activities for both the oxygen reduction and evolution reactions, which are comparable to those of Pt/C and IrO2. Furthermore, the primary zinc-air batteries assembled with Ni (POxN3−x)2/NPC and Co (POxN3−x)2/NPC as the cathodes show gravimetric energy densities of 894 and 836 W h kgZn<SUP>−1</SUP>, which are superior to that of Pt/C (793 W h kgZn<SUP>−1</SUP>). In addition, the rechargeable zinc-air battery assembled with Ni (POxN3−x)2/NPC exhibits an excellent round-trip efficiency, which is shown by a slight increase in the sum of the overpotentials for discharge-charge cycling at a current density of 20 mA cm<SUP>−2</SUP>, even after experiencing 33 h of testing. To the best of our knowledge, there are few reports on metaphosphate salts where oxygen is partially replaced by nitrogen as bifunctional oxygen electrode catalysts for zinc-air batteries. This work provides an easy, low-cost and scalable avenue to develop new kinds of catalyst for application in energy devices.</P>

Superluminescent diode integrated with monitor photodiode

Zhou Shuai,Liu Kun,Li Peng,Pang Fu-Bin,Zhang Jing,Kong Xiang-Ping,Duan Li-Hua,Zhang Chang-Chun 한국물리학회 2023 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.82 No.2

Ridge-waveguide superluminescent diodes with integrated rear-side monitoring photodiode have been fabricated. When electrical isolation trench is not etched to active layer, the leakage current of monitoring photodiode is determined by the resistance between active region electrode and monitoring photodiode electrode, i.e. the resistance multiplied by the leakage current approximately equals to 0.8 V. In order to reduce the leakage current of monitoring photodiode, the electrical isolation trench must be etched into substrate layer. In addition, the electrical isolation trench has to be far enough away from the active region so that the superluminescent diode could achieve small spectral ripple.

Methodology effects on determining the energy concentration and the apparent total tract digestibility of components in diets fed to growing pigs

Huang, Chengfei,Li, Ping,Ma, Xiaokang,Jaworski, Neil William,Stein, Hans-Henrik,Lai, Changhua,Zhao, Jinbiao,Zhang, Shuai Asian Australasian Association of Animal Productio 2018 Animal Bioscience Vol.31 No.8

Objective: An experiment was conducted to investigate the effects of different diet formulations: F1 (Two complicated basal diets containing different crude protein levels plus tested feedstuff) vs F2 (A simple corn soybean meal [SBM] basal diet plus tested feedstuff) combined with total collection (TC) or chromic oxide ($Cr_2O_3$) marker or acid-insoluble ash (AIA) marker method, and freeze-dry or oven-dry (OD) technique on estimation of nutrient digestibility in diets fed to growing pigs. Methods: In F1, twelve barrows were allocated to two $6{\times}4$ Youden Squares. The treatment diets included a high protein basal (HPB) diet, a low protein basal (LPB) diet, a corn diet and a wheat bran (WB) diet formulated based on the HPB diet, and a SBM diet and a rapeseed meal (RSM) diet formulated based on the LPB diet. In F2, eight barrows were allocated to two $4{\times}4$ Latin Squares. The treatment diets included a corn basal diet, a SBM basal diet formulated based on the corn diet, and a WB diet and a RSM diet formulated based on the SBM diet. Results: Concentration of digestible (DE) and metabolizable energy (ME), and the apparent total tract digestibility of gross energy, ash, neutral detergent fibre, and acid detergent fibre determined by $Cr_2O_3$ marker method were greater than those determined by TC and AIA marker methods in HPB, LPB, and RSM diets formulated by F1 and in corn diet formulated by F2 (p<0.05). The DE values in WB and both DE and ME values in SBM and RSM estimated using F1 were greater than those estimated using F2 (p<0.05). Conclusion: From the accuracy aspect, the AIA marker or TC method combined with OD technique is recommended for determining the energy concentration and nutrient digestibility of components in diets fed to growing pigs.

The establishment of IB-SEM numerical method and verification of fluid-solid interaction

Wang, Jing,Li, Shu-cai,Mao, Xuerui,Li, Li-ping,Shi, Shao-shuai,Zhou, Zong-qing Techno-Press 2018 Geomechanics & engineering Vol.15 No.6

The interaction between particles and fluid was investigated by IB-SEM numerical method which is a combination of combing the spectral/hp element method and the rigid immersed boundary method. The accuracy of this numerical method was verified based on the computed results with the traditional body-fitted mesh in numerical simulation of the flow through the cylinder. Then the governing equations of particles motion and contact in fluid are constructed. The movement of the particles and the interaction between the fluid and the particles are investigated. This method avoided the problem of low computational efficiency and error caused by the re-division of the grid when the solids moved. Finally, the movement simulation of multi particles in the fluid was carried out, which can provide a completely new numerical simulation method.

Applicability Analysis of Microseismic Technology in Tunnel Water Inrush Monitoring

Yan-hao Chen,Shuai Cheng,Li-Ping Li,Jun-yan Yang,Hong-liang Liu,Wen-feng Tu 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.7

Water inrush disaster is one of the most serious geological disasters in tunnel construction. There are still some problems in the existing researches, such as the activity information of surrounding rock is difficult to obtain, the mechanism of water inrush disaster is unclear, the correlation between water inrush disaster and microseismic (MS) information is missing, which have caused the water inrush disaster to be passively controlled. Combining with the practical experience of tunnel engineering, the application problems of MS technology in tunnel engineering is summarized, which provides ideas for monitoring of surrounding rock activity. The formation mechanism of water inrush disaster caused by rock mass fracturing and filling medium instability has been revealed. The MS characteristics of the water inrush channel in different water inrush disasters have also been revealed. The MS response characteristics of water inrush and rockburst disasters are compared, which provides guidance for the improvement of MS monitoring technology and the analysis of effective MS information. The compression failure test of limestone under saturated and natural conditions is carried out. The results show that the presence of water weakens the ability of rock to store energy. The acoustic emission (AE) phenomenon is weaker in the process of saturated limestone failure, which increases the difficulty of AE monitoring. The number of AE events of natural limestone and saturated limestone shows a slow increase to a sudden increase in the process stress loading, which can be regarded as an important precursor of rock failure.

Risk assessment of water inrush in karst tunnels based on a modified grey evaluation model: Sample as Shangjiawan Tunnel

Yuan, Yong-cai,Li, Shu-cai,Zhang, Qian-qing,Li, Li-ping,Shi, Shao-shuai,Zhou, Zong-qing Techno-Press 2016 Geomechanics & engineering Vol.11 No.4

A modified grey clustering method is presented to systematically evaluate the risk of water inrush in karst tunnels. Based on the center triangle whitenization weight function and upper and lower limit measure whitenization weight function, the modified grey evaluation model doesn't have the crossing properties of grey cluster and meets the standard well. By adsorbing and integrating the previous research results, seven influence factors are selected as evaluation indexes. A couple of evaluation indexes are modified and quantitatively graded according to four risk grades through expert evaluation method. The weights of evaluation indexes are rationally distributed by the comprehensive assignment method. It is integrated by the subjective factors and the objective factors. Subjective weight is given based on analytical hierarchy process, and objective weight obtained from simple dependent function. The modified grey evaluation model is validated by Jigongling Tunnel. Finally, the water inrush risk of Shangjiawan Tunnel is evaluated by using the established model, and the evaluation result obtained from the proposed method is agrees well with practical situation. This risk assessment methodology provides a powerful tool with which planners and engineers can systematically assess the risk of water inrush in karst tunnels.

Multicomponent assessment and ginsenoside conversions of Panax quinquefolium L. roots before and after steaming by HPLC-MS<SUP>n</SUP>

Xin Huang,Yan Liu,Yong Zhang,Shuai-Ping Li,Hao Yue,Chang-Bao Chen,Shu-Ying Liu 고려인삼학회 2019 Journal of Ginseng Research Vol.43 No.1

Background: The structural conversions in ginsenosides induced by steaming or heating or acidic condition could improve red ginseng bioactivities significantly. In this paper, the chemical transformations of red American ginseng from fresh Panax quinquefolium L. under steaming were investigated, and the possible mechanisms were discussed. Methods: A method with reversed-phase high-performance liquid chromatography coupled with linear ion trap mass spectrometry (HPLC-MS<SUP>n</SUP>)-equipped electrospray ionization ion source was developed for structural analysis and quantitation of ginsenosides in dried and red American ginseng. Results: In total, 59 ginsenosides of protopanaxadiol, protopanaxatriol, oleanane, and ocotillol types were identified in American ginseng before and after steaming process by matching the molecular weight and/or comparing MS<SUP>n</SUP> fragmentation with that of standards and/or known published compounds, and some of them were determined to be disappeared or newly generated under different steaming time and temperature. The specific fragments of each aglycone-type ginsenosides were determined as well as aglycone hydrated and dehydrated ones. The mechanisms were deduced as hydrolysis, hydration, dehydration, and isomerization of neutral and acidic ginsenosides. Furthermore, the relative peak areas of detected compounds were calculated based on peak areas ratio. Conclusion: The multicomponent assessment of American ginseng was conducted by HPLC-MS<SUP>n</SUP>. The result is expected to provide possibility for holistic evaluation of the processing procedures of red American ginseng and a scientific basis for the usage of American ginseng in prescription.