scholarly journals Numerical Calculation Analysis of the Structural Stability of Cemented Fill under Different Cement-Sand Ratios and Concentration Conditions

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Kang Zhao ◽  
Qiang Li ◽  
Yajing Yan ◽  
Keping Zhou ◽  
Shuijie Gu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Efficiency ◽  
Structural Characteristics ◽  
Key Factors ◽  
Principal Stresses ◽  
Filling Materials ◽  
Cemented Backfill ◽  
The Stability ◽  
Pillar Structure ◽  
Safety And Stability

The effect of lime-sand ratio and slurry concentration on the mechanical properties of backfills is important. To achieve green and high-efficiency mining, accurately determining the optimum ratio of cemented tailings for certain tungsten tailings and ensuring the safety and stability of the mine stope structure are important. The cement-sand ratios used in this research were 1 : 6 and 1 : 8. The mechanical properties were evaluated by using 68%, 72%, and 78% of tailing cemented filling materials. The corresponding physical and mechanical parameters were obtained through uniaxial compression, splitting, and shearing mechanical experiments on the backfill specimens. FLAC3D was used to investigate the mechanical properties of cement-filled pillars and the stability of supporting surrounding rocks on the basis of the mine’s current room pillar structure size parameters and mining sequence. The key factors that affect the stability of the goaf were analyzed by evaluating the plastic zone area of the stope, maximum and minimum principal stresses, and displacement change. The structural characteristics of stope structures and changes of rock mass damage were obtained under different cement-tailing ratios and concentrations. A cemented backfill with a cement-tailing ratio of 1 : 8 and a concentration of 68% was selected as the best solution for the mine in terms of safety and economic considerations.

scholarly journals Experimental Study on Mechanical Properties and Structural Characteristics of Modified Sludge in Foundation Pit

CONVERTER ◽  
2021 ◽  
pp. 11-21
Author(s):  
Shuren Wang, Et al.
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Portland Cement ◽  
High Efficiency ◽  
Cement Content ◽  
Structural Characteristics ◽  
Curing Time ◽  
Hydration Products ◽  
Foundation Pit ◽  
Early Strength

To explore the efficient method of sludge modification, Ultra-fine Portland cement (UPC) was introduced as a sludge modifier regarding Ordinary Portland Cement (OPC) modified sludge as a reference. The mechanical properties and microstructural changes of UPC-modified sludge with different curing time and cement content were carried out by unconfined compressive strength (UCS), X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM) tests. Results show that the UCS of UPC-modified sludge varies with curing time and cement content in the same way as that of OPC-modified sludge. However, compared with OPC-modified sludge, UPC has a higher sludge modification efficiency, and the UPC-modified sludge has greater compressive strength, significantly early-strength, and stronger resistance to deformation. The stress-strain curves of UPC-modified sludge present significant peak stresses, and which show a brittle failure mode. The combination of the hydration products calcium silicate hydrate (C-S-H) gels and ettringite (Aft) crystals are the essential reason for the improvement of the macroscopic strength of the modified sludge. In contrast to OPC, the UPC hydrates faster and more fully. The UPC-modified sludge can generate more hydration products under the same conditions, this is why that has high efficiency and early-strength. The conclusions obtained in this study can provide a reference for the similar engineering application of ultra-fine cement in modified sludge.

scholarly journals Applicability of Yielding–Resisting Sand Column and Three-Dimensional Coordination Support in Stopes

Materials ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 2635 ◽  
Author(s):  
Fanbao Meng ◽  
Zhijie Wen ◽  
Baotang Shen ◽  
Yujing Jiang ◽  
Shaoshuai Shi ◽  
...  
Keyword(s):  
Structural Characteristics ◽  
Three Dimensional ◽  
Sand Column ◽  
Existing Problems ◽  
Filling Materials ◽  
Working Face ◽  
Initial Stage ◽  
Supporting Effect ◽  
Stress And Deformation ◽  
The Stability

In view of the existing problems of stope roadways, which are difficult to maintain under the influence of high ground and mining-induced stresses, the structural characteristics and movement regularities of stopes surrounding rocks were analysed. Through the construction of a three-dimensional mechanical model of the coordination support of a stope, the adaptability index of the support in stope is presented, and its mechanism of operation is expounded. Yielding–resisting sand column (YRSC) sidewall-support technology with satisfactory compressibility and supporting strength was developed. The structure and actual mechanical properties of the YRSC were investigated through laboratory experiments, and the optimum ratio of filling materials was obtained. The good applicability of the load and deformation adaptability index of the three-dimensional coordination support in the stope and YRSC sidewall-support technology were demonstrated in practice at the No. 12306 working face of the Dongda coal mine. It was shown that the designed carrying capacity and compression of the sand columns satisfied the site requirements. The actual stress and deformation of the YRSC exhibited three stages: Slow growth at the initial stage, a large increase in the medium term, and a stable trend at the end. The adaptability index of the three-dimensional coordination support in the stope considers all bearing structure units of the stope as an interconnected whole, and the stability conditions of the stope roadway can be quantitatively described. The supporting effect of the YRSC is remarkable and can be applied to the construction of tunnels, bridge systems and other engineering fields.

Investigation of mechanical properties of gold nanocoating using nanoindentation experiments

2015 ◽  
Vol 230 (2) ◽  
pp. 240-247 ◽  
Author(s):  
Xuesong Han ◽  
Qian Jane Wang
Keyword(s):  
Mechanical Properties ◽  
Contact Area ◽  
Coupling Effect ◽  
Dynamics Simulation ◽  
Surface Generation ◽  
Generation Process ◽  
Key Factors ◽  
Principal Stresses ◽  
Plastic Deformation Process ◽  
Original Crystal

Molecular dynamics simulation is used to determine the mechanical properties of gold coating from indentation. The results show that the depressed surface generation process should be attributed to three key factors: first, the atom inclined to go to its original crystal position under the molecular interactions; second, the attractive force exerted by the indenter at the unloading stage; third, the self-organization effect induced by surface/subsurface atoms, and the final depressed surface is generated through the strong nonlinear coupling effect of these three basic factors. There are little anisotropy phenomenon in the elastic deformation stage while obvious anisotropy phenomenon is observed in the plastic deformation process. The maximum value of contact pressure is located at the edge of contact area and vanished outward from the contact circle. The magnitudes of the maximum principal stresses appear to shift outward, away from the center of contact area.

An analysis of the transport properties and mechanical stability of rapidly solidified Al-Sb alloy

2015 ◽  
Vol 10 (2) ◽  
pp. 2663-2681
Author(s):  
Rizk El- Sayed ◽  
Mustafa Kamal ◽  
Abu-Bakr El-Bediwi ◽  
Qutaiba Rasheed Solaiman
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Melt Spinning ◽  
Elastic Moduli ◽  
Mechanical Stability ◽  
Microstructural Analysis ◽  
Alloy System ◽  
Antimony Content ◽  
The Stability ◽  
Rapidly Solidified

The structure of a series of AlSb alloys prepared by melt spinning have been studied in the as melt–spun ribbons  as a function of antimony content .The stability  of these structures has  been  related to that of the transport and mechanical properties of the alloy ribbons. Microstructural analysis was performed and it was found that only Al and AlSb phases formed for different composition.  The electrical, thermal and the stability of the mechanical properties are related indirectly through the influence of the antimony content. The results are interpreted in terms of the phase change occurring to alloy system. Electrical resistivity, thermal conductivity, elastic moduli and the values of microhardness are found to be more sensitive than the internal friction to the phase changes. 

REMOVAL OF HEAVY METAL Cr (II), Ni (II), Cu (II), Zn (II), Cd (II), Pb (II) IONS FROM AQUEOUS SOLUTION BY MENTHA PIPERITA EXTRACT

2020 ◽  
pp. 15-20
Author(s):  
Ersin Yucel ◽  
Mine Yucel
Keyword(s):  
Aqueous Solution ◽  
Metal Ions ◽  
High Efficiency ◽  
Correlation Coefficients ◽  
Langmuir Model ◽  
Mentha Piperita ◽  
Freundlich Model ◽  
Biosorption Capacity ◽  
Peppermint Extract ◽  
The Stability

In this study, the usage of the peppermint (Mentha piperita) for extracting the metal ions [Mg (II), Cr (II), Ni (II), Cu (II), Zn (II), Cd (II), Pb (II)] that exist at water was investigated. In order to analyze the stability properties, Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms were used at removing the metal ions and the highest correlation coefficients (R2) were obtained at Langmuir isotherm. Therefore, it is seen that the Langmuir model is more proper than the Freundlich model. However, it was found that the correlation coefficients of removing Ni and Cd is higher at Freundlich model than Langmuir and low at Dubinin-Radushkevich isotherm. It is established that the biosorption amount increase depends on the increase of biosorbent and it can be achieved high efficiency (95%) even with small amount (0.6 mg, peppermint extract) at lead ions. It is also determined that the peppermint extracted that is used at this study shows high biosorption capacity for metal ions and can be used for immobilization of metals from polluted areas.

Effect of the surface chemistry on the stability and mechanical properties of the Zirconia-Hydroxyapatite bioceramic

2021 ◽  
Vol 23 ◽  
pp. 100980
Author(s):  
M. Es-saddik ◽  
S. Laasri ◽  
M. Taha ◽  
A. Laghzizil ◽  
A. Guidara ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Surface Chemistry ◽  
The Stability

scholarly journals Studies on the Volumetric Stability and Mechanical Properties of Cement-Fly-Ash-Stabilized Steel Slag

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 495
Author(s):  
Mingkai Zhou ◽  
Xu Cheng ◽  
Xiao Chen
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Steel Slag ◽  
Critical Issue ◽  
Expansion Behavior ◽  
Strength Tests ◽  
Road Materials ◽  
Base Course ◽  
The Stability ◽  
Aggregate Base

The stability of steel-slag road materials remains a critical issue in their utilization as an aggregate base course. In this pursuit, the present study was envisaged to investigate the effects of fly ash on the mechanical properties and expansion behavior of cement-fly-ash-stabilized steel slag. Strength tests and expansion tests of the cement-fly-ash-stabilized steel slag with varying additions of fly ash were carried out. The results indicate that the cement-fly-ash-stabilized steel slag exhibited good mechanical properties. The expansion rate and the number of bulges of the stabilized material reduced with an increase in the addition. When the addition of fly ash was 30–60%, the stabilized material was not damaged due to expansion. Furthermore, the results of X-CT, XRD and SEM-EDS show that fly ash reacted with the expansive component of the steel slag. In addition, the macro structure of the stabilized material was found to be changed by an increase in the concentration of the fly ash, in order to improve the volumetric stability. Our study shows that the cement-fly-ash-stabilized steel slag exhibits good mechanical properties and volumetric stability with reasonable additions of fly ash.

scholarly journals Effect of Photoinitiator on Precursory Stability and Curing Depth of Thiol-Ene Clickable Gelatin

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1877
Author(s):  
Kai-Hung Yang ◽  
Gabriella Lindberg ◽  
Bram Soliman ◽  
Khoon Lim ◽  
Tim Woodfield ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Visible Light ◽  
Rheological Properties ◽  
Swelling Ratio ◽  
Sodium Persulfate ◽  
Photo Polymerization ◽  
Gelation Kinetics ◽  
The Stability ◽  
Over Time

Recent advances highlight the potential of photopolymerizable allylated gelatin (GelAGE) as a versatile hydrogel with highly tailorable properties. It is, however, unknown how different photoinitiating system affects the stability, gelation kinetics and curing depth of GelAGE. In this study, sol fraction, mass swelling ratio, mechanical properties, rheological properties, and curing depth were evaluated as a function of time with three photo-initiating systems: Irgacure 2959 (Ig2959; 320–500 nm), lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP; 320–500 nm), and ruthenium/sodium persulfate (Ru/SPS; 400–500 nm). Results demonstrated that GelAGE precursory solutions mixed with either Ig2959 or LAP remained stable over time while the Ru/SPS system enabled the onset of controllable redox polymerization without irradiation during pre-incubation. Photo-polymerization using the Ru/SPS system was significantly faster (<5 s) compared to both Ig2959 (70 s) and LAP (50 s). Plus, The Ru/SPS system was capable of polymerizing a thick construct (8.88 ± 0.94 mm), while Ig2959 (1.62 ± 0.49 mm) initiated hydrogels displayed poor penetration depth with LAP (7.38 ± 2.13 mm) in between. These results thus support the use of the visible light based Ru/SPS photo-initiator for constructs requiring rapid gelation and a good curing depth while Ig2959 or LAP can be applied for photo-polymerization of GelAGE materials requiring long-term incubation prior to application if UV is not a concern.

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