scholarly journals Application of High-Strength Lightweight Concrete in Gob-Side Entry Retaining in Inclined Coal Seam

2020 ◽  
Vol 2020 ◽  
pp. 1-20 ◽  
Author(s):  
Daoyong Zhu ◽  
Weili Gong ◽  
Yi Su ◽  
Aipeng Guo
Keyword(s):  
Performance Test ◽  
Lightweight Concrete ◽  
High Strength ◽  
Small Range ◽  
Optimal Arrangement ◽  
Working Face ◽  
Binder Ratio ◽  
Concrete Blocks ◽  
Support Resistance ◽  
Pillar Mining

Gob-side entry retaining (GSER) is a popular no-pillar mining technology that can increase coal recovery rate. We propose the application of high-strength lightweight (HSLW) concrete to construct the gob-side support body (GSSB) in NO. 411 inclined working face of Jingang Coal Mine. Firstly, the mechanical model of retained roadway was established, and the calculation for limit angle of GSSB stability and support resistance was mathematically derived. Using the performance test, the optimal proportion of LC50 concrete was determined as follows: the water-binder ratio was 0.3; the silica fume dosage was not more than 10%; the fly ash dosage was 10–20%; and the sand ratio was 0.45–0.50. Based on theoretical deduction and laboratory analysis, the width of GSSB was obtained to be 0.75 m, and the optimal arrangement of concrete blocks with “two longitudinal and one horizontal, crisscross, and staggered joints” was determined. FLAC3D software was used to study the influence of different widths and material strengths on the surrounding rock deformation and verify the reasonable width and strength of the designed GSSB. Finally, field monitoring of retained roadway shows that the deformation is controlled in a small range, and the retained roadway effect is better, thus proving the feasibility of HSLW for constructing the support body for GSER. Our findings can serve as a theoretical guide for safety and effective implementation of HSLW as GSSB.

scholarly journals Gob-Side Entry Retaining Involving Bag Filling Material for Support Wall Construction

2020 ◽  
Vol 12 (16) ◽  
pp. 6353
Author(s):  
Zhaowen Du ◽  
Shaojie Chen ◽  
Junbiao Ma ◽  
Zhongping Guo ◽  
Dawei Yin
Keyword(s):  
Field Tests ◽  
Filling Material ◽  
Construction Technology ◽  
Working Face ◽  
Support Resistance ◽  
Pillar Mining ◽  
High Production ◽  
Wall Construction ◽  
Thin Seam ◽  
Seam Mining

Gob-side entry retaining, also termed as non-pillar mining, plays an important role in saving coal resources, high production and efficiency, extending the service life of mine and improving the investment benefit. Herein, a gob-side entry retaining method involving the use of bag filling material for wall construction is proposed based on the thin seam mining characteristics. First, a gob-side entry retaining mechanical model is established, and the side support resistance of the 8101 working face is calculated. The mechanical properties of the bag material are investigated through experiments, and the construction technology of the gob-side entry retaining approach involving the use of bag filling material for wall construction is introduced. The deformation on the two sides, the roof and floor of the roadway, are simulated via numerical methods and monitored during field tests. The results show a small control range for the deformations and a good roadway retention effect, thereby proving the feasibility of the bag filling material for wall construction. This study provides a reference for the development of gob-side entry retaining mining for thin coal seams.

scholarly journals Study on Surrounding Rock Structure Evolution Characteristics and Roof Control Techniques of the Retained Roadway Formed by Roof Cutting in Inclined Coal Seams

2021 ◽  
Vol 2021 ◽  
pp. 1-20
Author(s):  
Guangyuan Yu ◽  
Jiong Wang ◽  
Jianjun Ren ◽  
Jinzhu Hu ◽  
Zhifu Pan ◽  
...  
Keyword(s):  
Structure Evolution ◽  
Coal Seams ◽  
Supporting System ◽  
Working Face ◽  
Evolution Characteristics ◽  
Rock Structure ◽  
Support Resistance ◽  
Pillar Mining ◽  
Three Stages ◽  
Constant Support

To control the roof during gob-side entry retaining by roof cutting in inclined coal seams, the retained gob-side roadway is zoned based on the mechanical principle and technological process of no-pillar mining with gob-entry retention. A simplified mechanical model for surrounding rocks in different subzones was established by using theoretical analysis and numerical simulation to attain the demand for the support resistance and deformation of the roof in different subzones. According to load and deformation characteristics of the roof and mechanical characteristics of NPR cables, single props, and a sliding-type gangue-retaining structure formed by U-shaped steel inserts, the supporting systems for roadways in different subzones and the constitutive model thereof were established. On this basis, the action of the supporting system was analysed and a field test was performed. The results show that the supporting system undergoes three stages of behaviour, i.e., pressure growth, yielding under constant pressure, and stabilisation during whole entry retention. It can guarantee the collaborative deformation of the supporting systems with the roof on the premise of constant support resistance, thus satisfying the requirement for roadway protection. The roadway 150 m back from the working face is stable, and the final convergence between the roof and floor of the retained entry is 257 mm, showing a favourable entry-retention effect.

Technology Research on Waterworks Sludge for Ceramsite

2011 ◽  
Vol 383-390 ◽  
pp. 3352-3355
Author(s):  
Jun He ◽  
Qi Shan Wang
Keyword(s):  
Bulk Density ◽  
Performance Test ◽  
High Strength ◽  
Raw Material ◽  
Technology Research ◽  
Technological Parameters ◽  
Factors Affecting ◽  
Concrete Blocks ◽  
Waterworks Sludge ◽  
Bearing Structure

On the basis of analysis of the component of the sludge from Lingzhuang waterworks and the technological process was studied which use the sludge for raw material to produce the sludge ceramsite. Through a lot of experiments, the several factors affecting the nature of ceramsite were developed and the technological parameters were confirmed. A performance test of the ceramsite shows that when the optimized temperature is 1130°C~1170 °C, the optimized baking time is 5 min, strength of tube pressure of the ceramsite is 8 MPa, bulk density of it is 1200 kg/m3compressive strength of concrete blocks is 40 MPa. So the products could meet the demand on high strength ceremsite. It is gained that the way of waterworks sludge for ceramsite is feasible and can bring certain economical profits, social profits and environmental profits. The products can be used widely to load bearing structure in construction profession.

Patent Analysis of Concrete Testing Technology

2017 ◽  
Vol 726 ◽  
pp. 120-124
Author(s):  
Peng Fei Huang
Keyword(s):  
Research And Development ◽  
Performance Test ◽  
Lightweight Concrete ◽  
High Strength ◽  
Patent Analysis ◽  
High Durability ◽  
Test Technology ◽  
Testing Technology ◽  
Concrete Testing ◽  
Technical Features

Discover Patent existing concrete performance test technology at home and abroad in the field of analysis of the existing concrete performance test technical features, difficulties and trends, noted that the current domestic patent technology in concrete performance test encountered utilization, protection and disputes, high durability and lightweight concrete and avoid patent risk recommendations for the structure to adapt to the development of the next building needs and provide research and development of high strength.

scholarly journals The Rapid Chloride Migration Test in Assessing the Chloride Penetration Resistance of Normal and Lightweight Concrete

2021 ◽  
Vol 11 (16) ◽  
pp. 7251
Author(s):  
Jorge Pontes ◽  
José Alexandre Bogas ◽  
Sofia Real ◽  
André Silva
Keyword(s):  
Lightweight Concrete ◽  
Chloride Transport ◽  
Penetration Resistance ◽  
Chloride Penetration ◽  
Migration Test ◽  
Simple Method ◽  
Chloride Migration ◽  
Binder Ratio ◽  
Chloride Penetration Resistance ◽  
Water Binder Ratio

Chloride-induced corrosion has been one of the main causes of reinforced concrete deterioration. One of the most used methods in assessing the chloride penetration resistance of concrete is the rapid chloride migration test (RCMT). This is an expeditious and simple method but may not be representative of the chloride transport behaviour of concrete in real environment. Other methods, like immersion (IT) and wetting–drying tests (WDT), allow for a more accurate approach to reality, but are laborious and very time-consuming. This paper aims to analyse the capacity of RCMT in assessing the chloride penetration resistance of common concrete produced with different types of aggregate (normal and lightweight) and paste composition (variable type of binder and water/binder ratio). To this end, the RCMT results were compared with those obtained from the same concretes under long-term IT and WDT. A reasonable correlation between the RCMT and diffusion tests was found, when slow-reactive supplementary materials or porous lightweight aggregates surrounded by weak pastes were not considered. A poorer correlation was found when concrete was exposed under wetting–drying conditions. Nevertheless, the RCMT was able to sort concretes in different classes of chloride penetration resistance under distinct exposure conditions, regardless of the type of aggregate and water/binder ratio.

scholarly journals Thermal Inertia Characterization of Multilayer Lightweight Walls: Numerical Analysis and Experimental Validation

2021 ◽  
Vol 11 (11) ◽  
pp. 5008
Author(s):  
Juan José del Coz-Díaz ◽  
Felipe Pedro Álvarez-Rabanal ◽  
Mar Alonso-Martínez ◽  
Juan Enrique Martínez-Martínez
Keyword(s):  
Lightweight Concrete ◽  
Thermal Flux ◽  
Experimental Studies ◽  
Thermal Inertia ◽  
Transient State ◽  
Experimental Tests ◽  
Building Design ◽  
Experimental Methodology ◽  
Improve Energy Efficiency ◽  
Concrete Blocks

The thermal inertia properties of construction elements have gained a great deal of importance in building design over the last few years. Many investigations have shown that this is the key factor to improve energy efficiency and obtain optimal comfort conditions in buildings. However, experimental tests are expensive and time consuming and the development of new products requires shorter analysis times. In this sense, the goal of this research is to analyze the thermal behavior of a wall made up of lightweight concrete blocks covered with layers of insulating materials in steady- and transient-state conditions. For this, numerical and experimental studies were done, taking outdoor temperature and relative humidity as a function of time into account. Furthermore, multi-criteria optimization based on the design of the experimental methodology is used to minimize errors in thermal material properties and to understand the main parameters that influence the numerical simulation of thermal inertia. Numerical Finite Element Models (FEM) will take conduction, convection and radiation phenomena in the recesses of lightweight concrete blocks into account, as well as the film conditions established in the UNE-EN ISO 6946 standard. Finally, the numerical ISO-13786 standard and the experimental results are compared in terms of wall thermal transmittance, thermal flux, and temperature evolution, as well as the dynamic thermal inertia parameters, showing a good agreement in some cases, allowing builders, architects, and engineers to develop new construction elements in a short time with the new proposed methodology.

High strength flowable lightweight concrete incorporating low C3A cement, silica fume, stalite and macro-polyfelin polymer fibres

2021 ◽  
Vol 281 ◽  
pp. 122410
Author(s):  
Huiyuan Liu ◽  
Mohamed Elchalakani ◽  
Ali Karrech ◽  
Sherif Yehia ◽  
Bo Yang
Keyword(s):  
Silica Fume ◽  
Lightweight Concrete ◽  
High Strength

Effects of Two Polypropylene Fibers on the Properties of High Strength Concrete

2013 ◽  
Vol 357-360 ◽  
pp. 1328-1331
Author(s):  
Bai Rui Zhou ◽  
Dong Dong Han ◽  
Jian Hua Yang ◽  
Yi Liang Peng ◽  
Guo Xin Li
Keyword(s):  
Portland Cement ◽  
Modulus Of Elasticity ◽  
High Strength Concrete ◽  
Polypropylene Fiber ◽  
High Strength ◽  
Polypropylene Fibers ◽  
Strength Concrete ◽  
Reticular Fiber ◽  
Binder Ratio ◽  
Water To Binder Ratio

Portland cement, crushed stone, sand and superplasticizer were used to obtain a high strength concrete with a low water to binder ratio. A reticular polypropylene fiber and a single polypropylene fiber were used to improve the strength of the high strength concrete, but the effects of the two fibers on the slump and strengths were quite different. The reasons of the differences were the surface area and the modulus of elasticity of the fibers. The results show the reticular fiber was better to used in high strength concretes.

The Optimization Research of Wide Strip and Full-Pillar Mining under Villages

2012 ◽  
Vol 616-618 ◽  
pp. 406-410
Author(s):  
Gui Liu ◽  
Hua Xing Zhang ◽  
Jin Hui Chen ◽  
Chao Gao
Keyword(s):  
Surface Structures ◽  
Strip Mining ◽  
Mining Method ◽  
Sequence Optimization ◽  
Wide Strip ◽  
Deformation Limit ◽  
Working Face ◽  
Specific Analysis ◽  
Pillar Mining ◽  
Coal Pillars

By making full use of the advantages of strip mining method and full-pillar mining method, the wide strip and full-pillar mining method can achieve the aim of mining under villages. However, at the full-pillar mining stage, the difficulty in managing several workfaces which are at work at the same time still exists. To improve the wide strip and full-pillar mining method’s applicability, an optimization of extraction sequence for coal pillars instead of the multi-working-face is put forward at the stage of full-pillar mining, and in the case of the deformation limit of surface structures is satisfied, to extract all the coal pillars which are under villages. By specific analysis of the extraction sequence optimization of the coal pillars in No.1 mine under Qian Xudapo village which belongs to Chang Chun coal Co., LTD., a better result is got which also acts a technological reference for the extraction under villages.

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