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Aiming at the problem that many high-strength rock bolts fail at the thread part without obvious decrease in diameter, analytical analysis on the stress status of the thread was performed. The results show that stress concentration due to the change in diameter and self-locking of the domed washer due to inappropriate rotation center of the washer worsen the mechanical status of rock bolts. Laboratory tests on fractured threads was carried out, chemical analyses were performed on the fractured threads, the effect of the varied installation angles on the bending fracturing of rock bolts was tested. The mechanical status and the stress distribution in the thread was carried out using finite element method,and the most unfavorable position of the rock bolts was identified. Field tests were performed in the roadways suffering severe dynamic mining-induced stresses in the Zhangcun Coal Mine, many optimization plans were proposed to solve the rock bolt fracturing issue and to relieve the effects of the unfavorable forces on the rod of rock bolts. [ABSTRACT FROM AUTHOR]

Pre-coagulation enhanced by KMnO4 before ultrafiltration (KCUF) was compared with normal pre-coagulation by alum (CUF) in the ultrafiltration of water from the Songhua River, China. The transmembrane pressure (TMP) with KCUF was much lower than that when alum alone was used. With KCUF a slower increment of TMP occurred, even under conditions of high river water turbidity. The results also showed that the removal of COD, UV254 and TOC was appreciably higher after adding 0.5mg/L KMnO4 compared with CUF. Although assimilable organic carbon (AOC) was increased by permanganate treatment, the AOC of the permeate from KCUF was nearly the same as that from CUE, showing that the cake layer on the surface of KCUF membrane could adsorb small molecules more effectively than that of CUE. This result was confirmed by the apparent molecular weight (MW) distribution measured by size exclusion chromatography (SEC). It was shown that flocs formed by KMnO4 and alum were larger than those formed only by alum, causing higher removal of flocs and higher permeation flux. Lower NOM was found in the permeate from the KCUF systems because oxidation and adsorption of organic matter on the flocs occurred. The membrane was partly clogged by organic matter or other materials including some small flocs. [ABSTRACT FROM AUTHOR]

The breakage of overhead covered conductors on distribution lines resulting from the short-circuit arcs caused by lightning flash becomes a challenge as the application of covered conductors increases on distribution lines. Based on various methodologies and devices developed to avoid the covered conductor breakage in the world, novel arc-guided devices, including arcing protection hardware with barbs, clamping post composite insulator, and barb electrode clamping post porcelain/composite insulator are presented in this paper. Experimental results are also presented to validate these new developed devices. Devices based on the developed technologies have been widely applied on the power grids in China successfully. [ABSTRACT FROM AUTHOR]

Red-bed soft rock covers a large area in China and is often used as filling materials for highway roadbed and embankment, while the disintegration of red-bed soft rock often causes serious settlement of the roadbed and decreased stability. To thoroughly study the disintegration properties of red-bed soft rock, a series of slake durability tests were performed using different test methods. First, the gradation of disintegrated red-bed soft rock was investigated, and the shape of the gradation curve mainly presented as reverse sigmoidal and hyperbolic. Moreover, the evolution model of the disintegration breakage of red-bed soft rock using the Morgan-Mercer-Florin (MMF) model was derived, and the model parameters were analysed. Based on the test results, the disintegration behaviours of red-bed soft rock were measured by the disintegration ratio; then, the new formula to calculate the disintegration ratio based on the concept of the traditional disintegration ratio was derived using the established model. Finally, the effect of different test methods, i.e., different test devices, drying temperatures and sizes, on disintegration breakage under cyclic wetting and drying was analysed, and the test results showed that the rate of disintegration was accelerated by the slake durability apparatus, a higher drying temperature and a larger size. • The evolution model of disintegration breakage based on the Morgan-Mercer-Florin (MMF) model was derived and verified. • The effect of different test methods, i.e., different test devices, drying temperatures and sizes, on the disintegration breakage under cyclic wetting and drying was analysed. [ABSTRACT FROM AUTHOR]