Numerical Analysis on Failure Modes and Mechanisms of Mine Pillars under Shear Loading

Severe damage occurs frequently in mine pillars subjected to shear stresses. The empirical design charts or formulas for mine pillars are not applicable to orebodies under shear. In this paper, the failure process of pillars under shear stresses was investigated by numerical simulations using the rock failure process analysis (RFPA) 2D software. The numerical simulation results indicate that the strength of mine pillars and the corresponding failure mode vary with different width-to-height ratios and dip angles. With increasing dip angle, stress concentration first occurs at the intersection between the pillar and the roof, leading to formation of microcracks. Damage gradually develops from the surface to the core of the pillar. The damage process is tracked with acoustic emission monitoring. The study in this paper can provide an effective means for understanding the failure mechanism, planning, and design of mine pillars

Microseismic Monitoring of Energy Changes in Deep Tunnels during the TBM Tunneling of the Jinping II Hydropower Station

The TBM tunneling at the Jinping II hydropower station in Southwest China has received extensive concerns around the world because of its large engineering scale and the high rockburst risks faced in the tunnel advancement. The associated energy changes of rockbursts and control method for safe TBM tunneling are to be further investigated. A movable microseismic (MS) monitoring system was established to capture the MS events and rockbursts when the TBM excavated the headrace tunnel #1 at the Jinping II hydropower station. The spatial and temporal patterns of the energy changes in the tunnel rock masses were studied. Meanwhile, the evolution of a rockburst encountered in front of the TBM excavation face was revealed, and the performance of the top pilot tunnel method on the reduction of the rockburst risks in the headrace tunnel #1 was evaluated based on the energy changes of the surrounding rock masses. It can be concluded that energy accumulation and energy release firstly occurred in the surrounding rock masses at the southern end of the top pilot tunnel section of the headrace tunnel #1. Then, energy transference of the rock masses took place from the southern end to northwest of the top pilot tunnel giving rise to the occurrence of a moderate rockburst about 30 m in front of the tunnel. However, no rockbursts appeared when the TBM excavated through the top pilot tunnel section of the headrace tunnel #1. Therefore, the top pilot tunnel method really works in reducing the risks of rockbursts during the TBM tunneling in deep tunnels

Review on Early Warning Methods for Rockbursts in Tunnel Engineering Based on Microseismic Monitoring

Due to the different geological conditions and construction methods associated with different projects, rockbursts in deep-buried tunnels often present different precursor characteristics, bringing major challenges to the early warning of rockbursts. To adapt to the complexity of engineering, it is necessary to review the latest advancements in rockburst early warning and to discuss general early warning methods. In this article, first, microseismic monitoring and localization methods applicable under tunneling construction are reviewed. Based on the latest engineering examples and research progress, the microseismic evolution characteristics of the rockburst formation process are summarized, and the formation process and mechanism of structure-type and delayed rockbursts are analyzed. The different methods for predicting the risk and level of rockbursts using microseismic indices are reviewed, and the implementation methods and application cases for predicting potential rockburst areas and rockburst probability based on a mechanical model are expounded. Finally, combined with the new practice in early warning methods, development directions for the early warning of rockbursts are put forward

The Activity of Alloy CuNi Electrode in Electroreduction of Aromatic NitroCompounds

本文采用共沉积法制备了以铜为基体的不同Ｃｕ／Ｎｉ比的Ｃｕ－Ｎｉ合金镀层，并用稳态极化法研究了这些镀层在使用硝基苯（ＮＢ）和１，５－二硝基蒽醌（１．５－ＤＮＡ）制备对氨基苯酚（ＰＡＰ）及１，５－二氨基－４，８－二羟基蒽醌（１，５－ＤＡ－４，８－ＤＨＡ）等电化学还原过程中的阴极活性．研究表明，在ＰＡＰ和１，５－ＤＡ－４，８－ＤＨＡ电合成体系中，不同Ｃｕ／Ｎｉ比的合金阴极具有不同的交换电流密度（ｉｏ）和表观活化能（ＥＡ），其中以０．０５ｍｏｌ／ＬＣｕＳＯ４·５Ｈ２Ｏ＋０．６ｍｏｌ／ＬＮｉＳＯ４·６Ｈ２Ｏ＋０．２５ｍｏｌ／ＬＮａ３Ｃｉｔ·２Ｈ２Ｏ组成的镀液，并在控制电流密度为０．６Ａ·ｄｍ－２、ｐＨ值为６、体系温度为５０℃等工艺条件下镀制的Ｃｕ－Ｎｉ合金试片（ＣＮ－３０），具有最大的ｉｏ和最小的ＥＡ值，与常规所用的Ｃｕ、Ｃｕ／Ｈｇ、蒙乃尔合金等阴极相比，ＣＮ－３０试片的电极性能最佳CuNi alloy on the basis of copper at different ratio Cu/Ni are prepared by codepostion. The cathode activtiy of film are studied by steadystate polarization for electroreduction nitrobenzene (NB) and 1,5dinitroanthraquinone (1,5DNA) to paminophenol and 1,5diamino4,8dihydroanthraquinone respectly. The results show that the alloy cathodes at different ratio Cu/Ni have different exchange current density (io) and apparent activition energy (EA). The alloy (CN30) has maximal io and minimal EA by codeposition at the following conditions: electrolyte: 0.05 mol/L CuSO4·5H2O+0.6 mol/L NiSO4·6H2O+0.25 mol/L Na3Cit·2H2O; current density: 0.6 A/dm2 , pH=6, temperature at 50 ℃. Compared with the common cathodes such as Cu, Cu/Hg, Monel alloy, CN30 alloy is more suitable in these system.作者联系地址：浙江工业大学化学工程学院应用化学系Author's Address: Chem. Engin. Coll., Zhejiang Univ. of Tech., Hangzhou 31001

Study on Electrochemical Reduction Properties of Nitrobenzene

采用准稳态极化、循环伏安、线性扫描和恒电位阶跃等测试方法，对Ｈ２ＳＯ４ 溶液中硝基苯的电还原特性进行研究，评价了硝基苯在Ｃｕ 、Ｃｕ＿Ｈｇ 和Ｃｕ＿Ｎｉ 电极的电还原反应活性，研究了硝基苯电还原为ＰＡＰ的中间步骤，并对反应机理进行了探讨．结果表明，硝基苯在酸性介质中的电还原反应存在中间步骤，并伴有反应物吸附现象，硝基苯电还原反应受硝基苯及其还原产物在溶液中的液相传质步骤控制The electrochemical reduction characteristics of nitrobenzene was extensively investigated by using the techniques such as quasi_steady_state polarization,cyclic voltammetry,fast linear potential sweep method and chronoamperometry in this paper.The electroanalytic properties of Cu,Cu_Hg and Cu_Ni electrodes were evaluated.Based on the study of the transient steping behaviour of nitrobenzene to PAP,the reduction mechanism was discussed.The results showed that the transition steps existed on the electrochemical reduction of nitrobenzene in acidic solution,the reactant is also absorbed on electrodes surface. The control step in the reduction of nitrobenzene was ascribed to the diffusion of nitrobenzene and its electrochemical reductive products in the acid solution.作者联系地址：浙江工业大学化工学院!杭州310027,浙江工业大学化工学院!杭州310027,浙江工业大学化工学院!杭州310027,浙江工业大学化工学院!杭州310027,浙江大学生物学系!杭州310027,浙江大学生物学系!杭州310027Author's Address: Dept.of Applied Chemistry,Zhejinag Univ. of Tech.,Hangzhou 310014 Liu Meixing Tong Shaoping Dept. of Biol.,Zhejiang Univ.,Hangzhou 3120