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Types of tunnel supports
Published in Benjamín Celada Tamames, Z.T. Bieniawski von Preinl, Mario Fernández Pérez, Juan Manuel Hurtado Sola, Isidoro Tardáguila Vicente, Pedro Varona Eraso, Eduardo Ramón Velasco Triviño, Ground Characterization and Structural Analyses for Tunnel Design, 2020
Mario Fernández Pérez, Benjamín Celada Tamames, Isidoro Tardáguila Vicente
At the end of the 20th century, micronized silica, obtained as a sub-product of the semiconductor industry, began to be commercially produced to fill the existing gaps between the cement particles in the concrete and to increase its compactness. In this way the following advantages are achieved: A greater cohesion of the mixture, as well as an increase of the bonding with the ground and an improvement in the shotcrete projection performances in vault zones Reduction of the rebound, to levels lower than 10% Increased workability and reduction of the dust in the working site Increase of the initial and final compressive strength, thus reducing the accelerant dosage Decrease of the shotcrete's permeability, with water ingresses smaller than 30 mm, thereby increasing its resistance to carbonation and its durability
Proportion optimization and strength prediction of CGS backfill materials based on GA-ELM mode
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Yonglu Suo, Caixin Zhang, Lang Liu, Huisheng Qu, Pan Yang, Geng Xie
The CGS base backfill material is composed of aggregate, cementitious material, and an activator. Coal gangue is used as aggregate, cement and CGS as composite cementitious material, and Na2SO4 as an activator. According to the performance index of national standard GB175–2007 “general silicate cement,” P.O 42.5 cement of a cement plant in Yulin is selected. The coal gangue is selected from a mine in Yulin, with a density of 67 g/cm3 and a uniformity coefficient of 7.1. The raw slag of CGS is provided by China Coal Group. The treatment process of the CGS is as follows: (1) under the condition of a blast dryer, the coal gasification furnace slag is dried at 60°C for 24 hours; (2) the sorted crude CGS is crushed with a crusher, and Screening with 0.5 mm sieve; (3) The sieved CGS is ground with a planetary ball mill for 75 min. The specific grinding method is to grind in the forward direction for 35 min, stop for 5 min, let the ball mill fully dissipate heat, and then continue grinding in the reverse direction for 35 min, to get the CGS micronized powder.
Preparation, characterization and catalytic behavior of copper oxide nanoparticles on thermal decomposition of ammonium perchlorate particles
Published in Particulate Science and Technology, 2018
Seyed Ghorban Hosseini, Esmaeil Ayoman, Abolfazl Kashi
The CuO NPs were prepared using planetary milling in argon atmosphere (99.99% purity). Commercial micronized CuO (99.9%, 20–30 µm) powder was used as the raw material. The starting powders were loaded into a tungsten carbide jar. In addition, 50 mL of isopropyl alcohol as a wetting agent was introduced into the jar. Then, the micronized CuO was milled using a Pulverisette-5-type planetary high-energy ball-milling apparatus. Tungsten carbide balls of 10 mm diameter were used for milling. The micronized CuO was milled with a ball charge ratio of 10:1 at a rotation speed of 150 rpm and the other parameters remained constant during the experiments. The process of the starting powders was carried out inside a glove box to protect from pollution. Grinding of CuO micro powders was taken at intervals of 20 and 30 h and named as CW20 and CW30, respectively.
Thermodynamic and kinetic studies of heavy metal adsorption by modified nano-zeolite
Published in Geosystem Engineering, 2021
Hossein Kamran Haghighi, Mehdi Irannajad, Alireza MohammadJafari
Natural clinoptilolite was obtained from a mine located in Iran near the city of Semnan. The samples were ground and sieved. As a result, the size distribution was in the range of 0.3–1 mm. 500 g sample was ground by a ball mill mixed with 5 g of sodium hexametaphosphate for 6 hours. The detailed synthesis procedure of this nano-zeolite has been published elsewhere (Irannajad, Kamran Haghighi, Mohammadjafari et al., 2016). Ground samples were micronized and then were ground for 6 hours using a dry planetary ball mill. The planetary ball mill contained a 100 mL stainless steel jar with 5 mm tungsten carbide balls. The dry milling speed was 150 rpm.