scholarly journals Utilisation of Water-Washing Pre-Treated Phosphogypsum for Cemented Paste Backfill

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 175 ◽  
Author(s):  
Yikai Liu ◽  
Qinli Zhang ◽  
Qiusong Chen ◽  
Chongchong Qi ◽  
Zhu Su ◽  
...  
Keyword(s):  
Setting Time ◽  
Microstructural Analysis ◽  
Engineering Application ◽  
Cemented Paste Backfill ◽  
Water Washing ◽  
Paste Backfill ◽  
Pre Treatment ◽  
Chinese Standard ◽  
Better Than

Recycling phosphogypsum (PG) for cemented paste backfill (CPB) has been widely used at phosphate mines in China. However, the impurities in PG prolong the setting time and reduce the uniaxial compressive strength (UCS), limiting the engineering application of PG. This paper aims to investigate the feasibility of treated PG (TPG) washed repeatedly using deionised water (DW) for CPB. A water-washing pre-experiment was first conducted to find the proportion with the least DW demand and the effects of water-washing on ordinary PG (OPG). Then, based on the PG:DW ratio obtained from the pre-experiment, the properties of the OPG-based CPB (OCPB) and TPG-based CPB (TCPB) were tested using slump tests, UCS tests, and microstructural analysis. The results show that (1) after 11 water-washings at the PG:DW ratio of 1:1.75, the pH of the supernatant (pH = 6.328) meets the requirements of Chinese standard GB 8978-1996. (2) Water-washing improves the particle gradation quality of PG and removes the soluble impurities adsorbed at the surface of PG crystals. (3) The initial slump values of TCPB are 0.19–1.15 cm higher than that of OCPB, furthermore, the diffusivity values of TCPB are better than the performance of OCPB, with 0.61–1.68 cm of superiority. (4) The UCS values of TCPB are up to 0.838 MPa, 1.953 MPa, and 2.531 MPa, after curing for 7, 14, and 28 days. These are 0.283 MPa, 0.823 MPa, and 0.881 MPa higher than that of OCPB, respectively. It can be concluded that water-washing pre-treatment greatly improves the workability and mechanical property of PG-based CPB. These results are of great value for creating a reliable and environmentally superior alternative for the recycling of PG and for safer mining production.

scholarly journals In Situ Remediation of Phosphogypsum with Water-Washing Pre-Treatment Using Cemented Paste Backfill: Rheology Behavior and Damage Evolution

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6993
Author(s):  
Yikai Liu ◽  
Qiusong Chen ◽  
Yunmin Wang ◽  
Qinli Zhang ◽  
Hongpeng Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fractal Dimensions ◽  
Principal Component ◽  
High Amplitude ◽  
Cemented Paste Backfill ◽  
Maximum Increase ◽  
Residual Structure ◽  
Water Washing ◽  
Paste Backfill ◽  
Pre Treatment

The accumulation of original phosphogypsum (OPG) has occupied considerable land resources, which have induced significant environmental problems worldwide. The OPG-based cemented paste backfill (OCPB) has been introduced as a promising solution. In this study, a water-washing pre-treatment was used to purify OPG, aiming to optimize the transport performance and mechanical properties of backfills. The overall results proved that in treated phosphogypsum-based cemented paste backfill (TCPB), the altered particle size distribution can alleviate the shear-thinning characteristic. The mechanical properties were significantly optimized, of which a maximum increase of 183% of stress value was observed. With more pronounced AE signals, the TCPB samples demonstrated better residual structures after the ultimate strength values but with more unstable cracks with high amplitude generated during loading. Principal component analysis confirmed the adverse effects of fluorine and phosphorus on the damage fractal dimensions. The most voluminous hydration products observed were amorphous CSH and ettringite. The interlocked stellate clusters may be associated with the residual structure and the after-peak AE events evident in TCPB, indicate that more significant stress should be applied to break the closely interlocked stitches. Ultimately, the essential findings in this experimental work can provide a scientific reference for efficient OPG recycling.

scholarly journals Mechanism of Rockburst Prevention in Deep Thick Coal Seams with Cemented Paste Backfill: A Case Study

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 4) ◽  
Author(s):  
Qingliang Chang ◽  
Qiang Leng ◽  
Xikui Sun ◽  
Guichen Li ◽  
Biao Zhang
Keyword(s):  
Engineering Application ◽  
Bending Moment ◽  
Cemented Paste Backfill ◽  
Coal Seams ◽  
Overburden Pressure ◽  
Mining Condition ◽  
Geological Conditions ◽  
Paste Backfill ◽  
Roof Strata

Abstract The aim of this study is to explore a safe mining method to effectively excavate the deep thick coal seams in rockburst-prone mines. Based on the theory of elastic foundation and geological conditions of the Xinhe Coal Mine, the cemented paste backfill (CPB) is proposed to prevent rockburst. In this study, the roof fracture mechanism of block caving mining (BCM) and CPB methods are established. Then, the stress evolution of the surrounding rock and the subsidence of roof strata with these two methods are compared. The results show that the maximum bending moment appears in the middle of the roof, and the value is far below the critical bending moment of the roof by using the CBP. While using the BCM, this value exceeds the critical bending moment of the roof, which may trigger rockburst-related problems. In addition, there is no first weighting and periodic weighting phenomena by using the CPB method as the overburden pressure is gradually transferred to the backfill body, resulting in a safer mining condition. Furthermore, the engineering application indicates that the frequency of daily microseismic events and the burst energy are significantly reduced by using the CPB.

scholarly journals Recycling Lead–Zinc Tailings for Cemented Paste Backfill and Stabilisation of Excessive Metal

Minerals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 710 ◽  
Author(s):  
Zhu Su ◽  
Qiusong Chen ◽  
Qinli Zhang ◽  
Deming Zhang
Keyword(s):  
Mechanical Properties ◽  
Environmental Stability ◽  
Cemented Paste Backfill ◽  
Class Iii ◽  
Pollution Potential ◽  
Environmental Friendliness ◽  
Paste Backfill ◽  
Lead Zinc ◽  
Chinese Standard ◽  
Safe Mining

This study demonstrates the feasibility of recycling lead–zinc tailing (LZT) as a cemented paste backfill (CPB) by considering the mechanical properties and environmental effects, thus providing an approach for safe and environmentally friendly treatment of LZT. First, the mechanical properties of CPB samples were tested. When the cement/tailing ratio was 1:6 and the slurry concentration was 70%, the maximum unconfined compressive strength (UCS) of the CPB cured for 28 days reaching 2.05 MPa, which could ensure safe mining. Then, the metals with pollution potential in the backfill slurry were investigated through static leaching. Finally, after adding immobilisation materials to stabilise excessive metals, the environmental stability of the CPB was demonstrated through dynamic leaching and a toxicity characteristic leaching procedure. The results show that the lead leached from the backfill slurry still exceeds the Chinese standard for groundwater quality (GB/T14848-2017 Class III). The addition of 2 mg/L polyaluminium sulfate (PAS) can further improve the strength of the CPB and maintain the environmental friendliness of the CPB. Therefore, the technology of recovering LZT as a CPB proposed in this study is an effective alternative to deal with LZT, which can help lead–zinc mines meet the requirements of cleaner production.

scholarly journals Analysis of damage failure in uniaxial compressive of cemented paste backfill by ultrasonic pulse velocity test

2021 ◽  
Vol 37 (2) ◽  
Author(s):  
B. Wang ◽  
L. Li ◽  
Y. Yu ◽  
B. Huo ◽  
J. Liu
Keyword(s):  
Mass Fraction ◽  
Damage Mechanics ◽  
Microstructural Analysis ◽  
Ultrasonic Pulse Velocity ◽  
Cementitious Materials ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Experimental Results ◽  
Cemented Paste Backfill ◽  
Paste Backfill

Cemented paste backfill (CPB) is prepared by mixing cementitious materials, tailings and water. Uniaxial compressive strength (UCS) is one of the most commonly used indicators for evaluating the mechanical performance of CPB. Ultrasonic pulse velocity (UPV) testing which is a non-destructive measurement, can also be applied to determine the mechanical properties of cement-based materials such as CPB. In order to study the failure mechanism of CPB,144 CPB samples prepared at different mass fraction and cement-tailing ratios were subjected to the UCS and UPV tests at 7,14 and 28 days of curing age. The effect of cement-tailing ratio and mass fraction on the UCS and UPV of CPB samples were obtained, the UCS values were correlated with the corresponding UPV data. Microstructural analysis was also performed on CPB samples to understand the effect of microstructure on the UCS data. The results show that the UCS and UPV values of CPB increased with cement-tailing ratio, mass fraction and curing time. Based on the experimental results, the damage constitutive equations and the damage evolution equations of different backfills were proposed on the basis of damage mechanics. Moreover, comparative analysis of constitutive model and experimental results were made to verify the reliability of the damage model. The results acquired by this paper provide a scientific basis for the rational strength design of backfill mine.

A Study on Copper Surface Pre-Treatment and Welding With Lasers

2016 ◽  
Author(s):  
Junke Jiao ◽  
Qiang Wang ◽  
Feiya Wang ◽  
Wenwu Zhang
Keyword(s):  
Copper Surface ◽  
Welding Parameter ◽  
Laser Machine ◽  
Welding Quality ◽  
Micro Hardness ◽  
Welding Seam ◽  
Graphite Coating ◽  
Pre Treatment ◽  
Better Than

To improve the copper absorption coefficient to lasers, and to realize a high welding quality with a low power laser machine, a black-treating method was proposed in this study. With this method, the reflection coefficient of the copper to lasers with 1064nm wavelength could be reduced from 95% to 15.5%. The experimental study of copper welding with a 500 W fiber laser machine was carried out. The shape, the strength and the micro-hardness of the welding seam with different welding velocity and defocus amount were compared. And, the best welding parameter was obtained. Moreover, the laser welding quality of copper with black-treating and that with graphite coating was compared, and the result showed that the micro-hardness and the strength of the welding seam of copper with black-treating was better than that with graphite coating.

Experimental Investigation on the Process of Jet Electrochemical Machining and Guided Laser Beam Machining

2010 ◽  
Vol 458 ◽  
pp. 325-330
Author(s):  
Li Xin Yuan ◽  
Jia Wen Xu ◽  
Jian She Zhao
Keyword(s):  
Laser Beam ◽  
Electrochemical Machining ◽  
Engineering Application ◽  
Recast Layer ◽  
Experimental Results ◽  
Laser Beam Machining ◽  
Metallurgical Defects ◽  
Jet Electrochemical Machining ◽  
Better Than

Laser beam machining is often associated with the metallurgical defects related with spatter, recast layer and heat-affected zone. In order to overcome the defects, this paper presents a process of jet electrochemical machining and guided laser beam machining (JECM-GLBM). On the explain of experimental principle and apparatus, jet electrochemical machining and laser beam machining(JECM-LBM) and JECM-GLBM experiments have been performed on 0.5mm thick 321S20 stainless steel under the same experimental condition respectively. The experimental results show that the entry circularity, repeatability and the surface quality of JECM-GLBM are significantly better than JECM-LBM, and the spatter and the recast layer of hole-wall has been mostly removed in JECM-GLBM. In addition, increasing the IEG leads that the taper and overcut are decreased in JECM-GLBM. By analyzing the experimental results, the best IEG is 10mm, which is unusually beneficial for the design of equipment in engineering application.

Kepuasan Masyarakat Terhadap Pelayanan Kelurahan Setelah Pemekaran Di Tangerang Selatan

Liquidity ◽  
2018 ◽  
Vol 2 (2) ◽  
pp. 151-159
Author(s):  
Pitri Yandri
Keyword(s):  
Public Perception ◽  
Service Personnel ◽  
Urban Services ◽  
Hospitality Workers ◽  
Care Workers ◽  
Before And After ◽  
Cartesian Diagram ◽  
Better Than

The purpose of this study is (1) to analyze public perception on urban services before and after the expansion of the region, (2) analyze the level of people's satisfaction with urban services, and (3) analyze the determinants of the variables that determine what level of people's satisfaction urban services. This study concluded that first, after the expansion, the quality of urban services in South Tangerang City is better than before. Secondly, however, public satisfaction with the services only reached 48.53% (poor scale). Third, by using a Cartesian Diagram, the second priority that must be addressed are: (1) clarity of service personnel, (2) the discipline of service personnel, (3) responsibility for care workers; (4) the speed of service, (5) the ability of officers services, (6) obtain justice services, and (7) the courtesy and hospitality workers.

Implementasi Voip Server Berbasis IPV6 Dengan Raspberry PI

2019 ◽  
Vol 9 (01) ◽  
pp. 47-54
Author(s):  
Rabbai San Arif ◽  
Yuli Fitrisia ◽  
Agus Urip Ari Wibowo
Keyword(s):  
Internet Protocol ◽  
Wireless Transmission ◽  
Raspberry Pi ◽  
Test Results ◽  
Average Delay ◽  
Ipv6 Network ◽  
Ip Network ◽  
Selection Of ◽  
Better Than

Voice over Internet Protocol (VoIP) is a telecommunications technology that is able to pass the communication service in Internet Protocol networks so as to allow communicating between users in an IP network. However VoIP technology still has weakness in the Quality of Service (QoS). VOPI weaknesses is affected by the selection of the physical servers used. In this research, VoIP is configured on Linux operating system with Asterisk as VoIP application server and integrated on a Raspberry Pi by using wired and wireless network as the transmission medium. Because of depletion of IPv4 capacity that can be used on the network, it needs to be applied to VoIP system using the IPv6 network protocol with supports devices. The test results by using a wired transmission medium that has obtained are the average delay is 117.851 ms, jitter is 5.796 ms, packet loss is 0.38%, throughput is 962.861 kbps, 8.33% of CPU usage and 59.33% of memory usage. The analysis shows that the wired transmission media is better than the wireless transmission media and wireless-wired.

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