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Hydraulic ECC materials are characterized by large deformation ability, strong crack resistance and good self-healing capacity. In this paper, two strength grades of hydraulic ECC materials with water-binder ratio of 0.35 and 0.25 are prepared, and the influence of artificial sand grading on compressive strength and splitting tensile strength of hydraulic ECC materials is studied. Moreover, key factors affecting the self-healing capacity of hydraulic ECC materials are analyzed by using compressive strength ratio as evaluation index. Experimental results reveal that artificial sand grading has a significant effect on the workability of hydraulic ECC materials, while there is no notable correlation between artificial sand grading and compressive strength, and self-healing capacity and while splitting tensile strength increases slightly with the decrease in artificial grading. Hydraulic ECC material has good strength growth characteristics and self-healing capacity, and the compressive strength at 90 d age can be 30%~40% more than that of 28 d age. It is worth noting that hydraulic ECC materials strength after healing is possibly more than that of undamaged sample in early stage. [ABSTRACT FROM AUTHOR]

As the core unit of backfill mining method, the strength of backfill is an important indicator to ensure safe mining. Na-based bentonite features a high methylene blue adsorption capacity and green compressive strength, making it a high-quality additive for preparing filling materials. However, there are few studies probing into the relationship between the dosage and the strength of the filling materials. This paper analyzes the changes in shear wave velocity, dominant frequency amplitude, amplitude attenuation coefficient, and waveform fractal dimension of filling materials with different Na-based bentonite dosages at different ages through ultrasonic testing technology and uniaxial compression tests. Combined with sensitivity analysis, we selected the most sensitive acoustic parameters to changes in compressive strength. Furthermore, this study establishes a strength prediction model for backfill with different Na-bentonite contents and combining significance testing and comparative analysis. The research findings can serve as a valuable reference for theoretical research and engineering applications related to predicting the uniaxial compressive strength of backfill materials. [ABSTRACT FROM AUTHOR]

Copyright of Multipurpose Utilization of Mineral Resources / Kuangchan Zonghe Liyong is the property of Multipurpose Utilization of Mineral Resources Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Multipurpose Utilization of Mineral Resources / Kuangchan Zonghe Liyong is the property of Multipurpose Utilization of Mineral Resources Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To reveal the mesoscopic failure mechanism of plastic concrete, this paper establishes a triaxial test model with flexible membrane boundary to investigate the meso-deformation and failure mechanism of plastic concrete based on PFC-FLAC3D simulation. The empirical function is derived to describe the relationship of the macroscopic uniaxial mechanical strength and triaxial mechanical strength in plastic concrete under different confining pressure by multivariate nonlinear method. The results show that the higher confining pressure restricts the internal particle motion and the shear band shape is more obvious under lower confining pressure. High confining pressure helps to improve the structural integrity and weaken the size effect of compressive strength. As the size of sample increases, the lateral bulging deformation of sample decreases and the particles connect within the oblique section decrease, resulting in the reduction of the X-shaped shear surface. Finally, the multivariate nonlinear fitting method is used to describe the relationship of uniaxial mechanical strength and triaxial mechanical strength under different confining pressure in terms of quantitative, which provides a theoretical basis for subsequent research. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Hydrogeology & Engineering Geology / Shuiwendizhi Gongchengdizhi is the property of Hydrogeology & Engineering Geology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Mine Automation is the property of Industry & Mine Automation Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Atomic Energy Science & Technology is the property of Editorial Board of Atomic Energy Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to solve the problem of hydraulic fracturing presure relief and permeability improvement technology applied in underground field due to the substandard sealing and control quality, in this paper, on the basis of summarizing the existing hole sealing materials and sealing methods at home and abroad, through a large number of basic experiments, the influence of auxiliary materials such as ordinary cement added with special composite cement, swelling agent and water reducing agent on the basic properties of anti-high pressure sealing materials such as setting time, fluidity, compressive strength and swelling multiplication rate was studied. The best water-cement ratio of 0.5, 20%-25% of special composite cement, 4% of compound expander and 1.6% of naphthalene water reducer were determined to ensure the early strength and high strength of the anti-high-pressure sealing material with the premise of flowability and expansion rate. It also conducted on-site industrial experiments in Pinggang Coal Mine of Longmei Coal Group, and its parameters such as solidification time and compressive strength met the performance requirements.

Copyright of Journal of Hebei University of Science & Technology is the property of Hebei University of Science & Technology, Journal of Hebei University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Hebei University of Science & Technology is the property of Hebei University of Science & Technology, Journal of Hebei University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The low-velocity impact and compressive failure processes of composite laminate were investigated by the acoustic emission (AE) technique in this paper. The test procedure was monitored by the acoustic emission (AE) technique. Combined with load-displacement curve during testing, the AE energy amplitude and the peak frequency of a dominant frequency band after treated with the fast Fourier transform (FFT) were analyzed. The frequency spectrums of the waveforms for the type signals were discussed. Results reveal that the behavior of AE parameters described well the damage process on the low-velocity impact and residual compressive behaviors of the composite laminates. [ABSTRACT FROM AUTHOR]

The stability of sandwiched water-resisting strata plays a significant role in the closed multiple-seam mining. The upper accumulated water in the upper gobs can seeped and flow into the lower mining space once the stability of sandwiched water-resisting strata is destroyed. In some situations, a sudden release of upper accumulated water is occurred, which brings serious threats for the safe mining of lower coal seam. The basic concept of water-resisting control strata under the influence of multiple mining was proposed in this paper. The damage parameter（D）calculation model of interbuRDen was established based on theories of damage mechanics. The relationships between the damage parameters（D）and the compressive strength/the damage range of interbuRDen were analyzed, respectively. Then, the influence of multiple mining damage on the stability of water-resisting control strata was investigated. The results showed that（1）The water-resisting control strata referred to the strata which did not broken under the multiple mining influences and played a significant role in preventing the downwaRD seepage and expansion of accumulated water in the upper gobs. （2）The damage parameter（D）could be used to measure the damage range of interbuRDen under multiple mining influences. （3）The relationship between the compressive strength （RD） of the interbuRDen and the damage parameter（D）was:RDof the interbuRDen showed a linear decreasing trend with the increasing of D. The reduction factor was 1-D. （4）The maximum failure depth/height(Hmax)and the maximum distance to the working face (Lmax) increased with the increase of damage parameter（D）. The larger the damage parameter（D）, the greater the increase of Hmax and Lmax. （5）The stability of water-resisting control strata was closely related with the superimposed damage induced by the multiple mining. It was necessary to comprehensively evaluate the damage range of interbuRDen under the multiple mining of upper and lower coal seams. The stability of water-resisting control strata under six different conditions were determined and the reasonable control measures were then complemented to ensure the safety of lower coal seam mining. The study on the influence of multiple mining damage on the stability of water-resisting control strata can provide a theoretical guidance for the safe mining of lower coal seam under the water accumulation area. [ABSTRACT FROM AUTHOR]

This is a paper in the field of metallurgical engineering. Pellets were prepared from vanadium and titanium magnetite concentrates from Liaoxi, and the preheating characteristics and roasting characteristics of the pellets were studied. Results show that the strength of preheating ball can reach 819 N when preheating for 15 min at 900℃, and the strength of the ball reached 3020 N at 1100℃ for 15 min under the optimum preheating system. The oxidation degree of the pellet is 97% at 900℃ for 15 min, and the temperature has a stronger influence on the oxidation degree than time.With the increase of oxidation temperature, with the increase of preoxidation temperature, magnetite in the pellets changes into hematite and ilmenite into ferrobrookite. With the increase of calcination temperature, the crystal in pellet grows up, the porosity decreases and the structure becomes denser.

The fire in mine goaf directly threatens the safe and efficient production of mining. Filling the air leakage channel in goaf is the most effective way to prevent spontaneous combustion of coal in goaf. In this paper, the effects of accelerators and foaming agents on the strength of inorganic foaming paste filling materials were discussed, and the mechanism of the reinforcing agents was analyzed. The results show that the inorganic solidified foam material has faster solidification with the increase of the amount of quick-setting admixture; the compressive strength of the filling material with a foaming ratio of 10 is above 1.7 MPa after curing for 7 days; the large number of bubbles existing in the material form numerous uniform defects, and the reinforcing agent causes the aluminum-oxygen component in the paste slurry to react with the cement component on a large scale and quickly to form an excellent hydrated mineral ettringite, so that the overall structure of the material does not change when the material is stressed, and no crack occurs in the middle portion, and the material effectively blocks the cracks in the fire zone and isolate oxygen to prevent fires in the goaf.

In order to provide a high-quality, low-price paste filling material ratio for filling and mining in Shagoucha Coal Mine in northern Shaanxi Province. In this paper, aeolian sand is used as the filling aggregate, and four factors of different (fly ash, cement, aeolian sand) and slurry mass concentration are used as the objects, three levels were taken from each object, and the effect of these levels on the slump, bleeding rate, and compressive strength of the filling material at 7 days and 28 days was studied by means of a repetitive orthogonal experiment. The results showed that: the slurry concentration had the most significant influence on the slump and the bleeding rate, and the other factors had less influence; when the slurry mass concentration of 74% and 76% was selected, the requirements of slump and bleeding rate were met. Through the analysis of range and variance, it is found that the most obvious and most important factor for the compressive strength of the filling body at 7 days and 28 days is the cement content, followed by the amount of fly ash, and then the amount of aeolian sand, but, when the amount of aeolian sand is more than 45%, the compressive strength at different ages is gradually reduced. Finally, the slurry mass concentration has the least influence on the compressive strength. Through comprehensive analysis, the optimal ratio was obtained: the fly ash was 440 kg/m3, the cement was 220 kg/m3, the eoluvial sand was 45%, and the mass concentration was 76%.

In view of the coal spontaneous combustion accident caused by air leakage in the mine, this paper studied the foaming cement solidified filling material used for mine filling and plugging with cement as the base material, foaming agent, gypsum and polypropylene fiber as additives. Through the single factor test method, the optimized ratio of the main components affecting the compressive strength and expansion ratio of the foamed cement solidified filling material was determined as the water-cement ratio 0.5, the foaming agent content 1%, and the gypsum content 6%, polypropylene fiber 0.4%. Taking Cuimu Mine as the experimental background, through the design of reasonable and effective filling technology scheme, the 21303 wind tunnel in the lower part of 22306 working face of Cuimu Mine was filled. The test results show that the foamed cement solidified material effectively enhances the airtightness of the wind tunnel and the roadway.

In order to achieve the expected reinforcement effect and ensure safety of the project, this paper aims to analyze the requirements of geological conditions on the performance of grouting materials based on the characteristics of coal mine underground engineering. The effects of polyether polyols and isocyanate index on the strength and toughness of grouting materials are explored. Through the modification, the compressive strength of the material is as high as 85 MPa, the bond strength is as high as 6.2 MPa, and it has suitable toughness. The results indicate that the strength and toughness of polyurethane reinforced materials can be controlled by changing the parameters of polyether polyol and isocyanate index. The appropriate material properties and reasonable support methods can effectively prevent the deformation of the roadway and to significantly improve the stability of the roadway.

Large amount of circulating fluidized bed combustion fly ash (CFA) were generated in power plants.In this paper, foam geopolymer material was prepared using CFA, water glass (WG) and sodium hydroxide (NaOH) as raw material and hydrogen peroxide as foaming agent.By adopting (wt) 3%-8% hydrogen peroxide, the properties of foaming multiple, pore size distribution, apparent density, macro porosity and compressive strength were tested.The balance of foaming driving force and paste resistance and the influence of macro pore structure on compressive strength were studied.The results showed that the balance of the foaming driving force and paste resistance was content of H2O2 (wt) of 5%; and the foaming multiple, apparent density, macro porosity and compressive strength were 4.2, 255 kg/m3, 81.7% and 0.65 MPa respectively when the H2O2 foaming agent(wt) was 5%.The different pore size distribution had different degree of the decrease on compressive strength, the gray correlation degree between compressive strength of samples and pore diameter range of 10-20 μm was the greatest, that was, the range of pore size was 10-20 μm as the key factor, and the effect on compressive strength of samples was the largest.