High Water Content Materials Research Articles

Spatial evolution characteristics of the mechanical properties of gangue-cemented paste backfill with high-water-content materials: an experimental investigation

ABSTRACT The mechanical properties of cemented paste backfill (CPB) directly determine the effect of backfilling in coal mining. However, the current studies on the mechanical properties of CPB are all based on standard cylinder or cube specimens, which cannot accurately characterise the distribution of mechanical properties in different spatial positions of CPB in situ. In addition, high-water-content material (HWM) has developed rapidly as a new binder in recent years. Therefore, in this paper, the uniaxial compressive strength (UCS) and elastic modulus of CPB with gangue as the aggregate and HWM as the binder (GHW-CPB) were investigated under different gangue particle sizes. The following conclusions were drawn: (1) The spatial evolution and distribution characteristics of mechanical properties of GHW-CPB are analysed. (2) The spatial evolution regression models of mechanical properties of GHW-CPB are established. (3) We improved the GHW-CPB spatial evolution regression models for mechanical properties due to their limitations and confirmed its validity and rationality. Through the research results of this paper, the failure position of the CPB in the goaf can be accurately predicted, so that manual interventions can be carried out in the vulnerable areas in advance to reduce the risk of coal mining production.

Intraocular Lens Opacification After Descemet's Membrane Endothelial Keratoplasty-Risk Factors and Outcomes After Intraocular Lens Exchange.

To determine risk factors for intraocular lens opacification (IOLop) after Descemet membrane endothelial keratoplasty (DMEK) and to analyze clinical outcomes after IOL exchange. Cross-Sectional Study: Analysis of all cases of IOL exchange because of post-DMEK IOLop with a minimum of 6-month postoperative follow-up observed in clinic between November 2021 and April 2022. Main outcomes analyzed at the study visit were change in logarithm of the minimum angle of resolution (logMAR) best-corrected visual acuity after IOL exchange, endothelial cell loss (ECL), and graft survival. An historical cohort of 232 pseudophakic DMEK eyes was retrospectively analyzed to determine risk factors for post-DMEK IOLop. Cross-Sectional Study: Four eyes were observed (median follow-up = 45 (35.5-86.8) months). IOL materials were hydrophilic acrylic IOLs in 2 eyes and hydrophobic-hydrophilic in the other 2. At the study visit, improvement in median best-corrected visual acuity after IOL exchange was statistically significant (0.25 (0.19-0.41) logMAR to 0.00 (0-0.10) logMAR; P = 0.041). ECL ranged between 57.7% and 85.3%, without cases of graft failure. In the historical cohort, 21 eyes (9.05%) had some IOLop. In multivariate logistic regression model (105 eyes where IOL material data was available), IOLs with high water content material (odds ratio = 65.5, P = 0.0005) and rebubbling (odds ratio = 9.51, P = 0.0138) were independent risk factors for post-DMEK IOLop. Post-DMEK IOLop is infrequent, but a non-neglectable proportion of cases may require IOL explantation. IOL exchange is safe and effective in these eyes but may pose a risk for increased ECL. This study confirms that IOL material and number of rebubblings are major risk factors for post-DMEK IOLop.

A homochiral tartrate-bridged dinuclear chromium(III) complex anion with a resonance-assisted hydrogen bond for proton conduction.

The synthesis of a homochiral building block based on L-tartrate-chromium(III) complex anions is reported. The dinuclear complex anion, which contains two bridging L-tartrate ligands and one aromatic N-donor ligand coordinated to chromium(III) ions, exhibits a boat conformation in which intramolecular resonance-assisted hydrogen bonding is present. The sodium L-tartrate-chromium(III) compound with the formula Na[Cr2(bpy)2(L-tart)2H]·9H2O (1) crystallizes from a methanol-water solution as a high water content material in the monoclinic space group P2. The as-synthesized compound is only stable at high relative humidity and undergoes structural transformations during drying, which are accompanied by water loss. However, these transformations are reversible and upon wetting, the material returns to its high water content structure. Based on a combination of experimental techniques (PXRD, in situ ATR-FTIR and EPR spectroscopy), the structure of the complex anions appears to be insensitive to the humidity variable processes (wetting and drying). Due to the presence of several hydrogen acceptor and donor groups in the L-tartrate-chromium(III) complex anion, we investigated the proton transport properties of a sodium L-tartrate-chromium(III) compound by impedance spectroscopy under dry and wet conditions at different temperatures. Since the relative humidity affects the structural transformations in this system, it also has a large influence on the proton conductivity, which varies by up to four orders of magnitude depending on the degree of hydration. These results confirm that the proton conductivity can be tuned in flexible structures in which non-covalent interactions determine the crystal packing.

Fluidity and Strength of Loess-Based Quick Consolidated Backfill Material with One High-Water Content.

To study the flow and strength characteristics of loess-based backfill materials, orthogonal tests were used to design a cemented backfill material combining loess, high-water content materials, cement, and fly ash. By using the range, analysis of variance, and multi-variate regression analysis, influences of four key factors on the initial setting time, diffusivity, compressive strength, and shear strength of the backfill material were investigated. These four factors included the mass concentration of loess water (A), the content of high-water content materials (B), cement content (C), and content of fly ash (D). The results showed that the initial setting time, diffusivity, compressive strength, and shear strength of the backfill material were 13~33 min, 400~580 mm, 0.917-3.605 MPa, and 0.360-0.722 MPa, respectively, all distributed in wide ranges. For the initial setting time, the four factors were listed in descending order as A > D > B > C according to their influences; for diffusivity, the four factors were listed as A > B > C > D; for the compressive strength, the four factors were ranked as A > C > D > B; for the shear strength, the four factors were ranked such that A > C > D > B. With regard to the comprehensive index, the four factors were such that A > B > D > C. That is, the factors were listed in descending order as the mass concentration of loess water, cement content, the content of fly ash, and content of high-water content materials according to their significance in influencing characteristics of the loess-based backfill material. Comprehensive analysis indicated that the fluidity of the material was mainly influenced by the mass concentration of loess water, and the two were negatively correlated. The hydro-consolidation effect of materials with high-water contents accelerated material solidification. The strength of the backfill material was mainly influenced by the cement content while only slightly affected by contents of other materials. In this way, a prediction model for characteristic parameters, namely, fluidity and strength, of the loess-based backfill material under the action of various factors was established.

Extreme Extensibility in Physically Cross-Linked Nanocomposite Hydrogels Leveraging Dynamic Polymer-Nanoparticle Interactions.

Designing yield stress fluids to exhibit desired functional properties is an integral challenge in many applications such as 3D printing, drilling, food formulation, fiber spinning, adhesives, and injectable biomaterials. Extensibility in particular has been found to be a highly beneficial characteristic for materials in these applications; however, few highly extensible, high water content materials have been reported to date. Herein we engineer a class of high water content nanocomposite hydrogel materials leveraging multivalent, noncovalent, polymer–nanoparticle (PNP) interactions between modified cellulose polymers and biodegradable nanoparticles. We show that modulation of the chemical composition of the PNP hydrogels controls the dynamic cross-linking interactions within the polymer network and directly impacts yielding and viscoelastic responses. These materials can be engineered to stretch up to 2000% strain and occupy an unprecedented property regime for extensible yield stress fluids. Moreover, a dimensional analysis of the relationships between extensibility and the relaxation and recovery time scales of these nanocomposite hydrogels uncovers generalizable design criteria that will be critical for future development of extensible materials.

Investigation of the Optimal Layout of the Roadway in Closely Spaced Ultra-Thick Coal Seams Mining with Remaining Coal Pillars

The reasonable layout of the roadway in closely spaced, ultra-thick coal seam mining is of great significance to mining safety. Based on the research background of repeated roof leaks in the process of repairing the return air roadway in working face No. 30503 in the Tashan Coal Mine, theoretical analysis, in situ engineering testing, and numerical simulation were jointly adopted to evaluate the stability of the return air roadway under two schemes of repairing the original return air roadway and excavating a new return air roadway. The results show that the vertical mining-induced fissure above the roadway will cause severe damage to the roadway due to the influence of working-face mining when restoration of the roadway excavation is adopted. When choosing to excavate a new return air roadway, the new return air roadway just staggers the vertical cracks located in the top slab of the original return air roadway, putting the roadway in a state of stress reduction, making the roadway itself more stable and conducive to support. Therefore, the new air return tunnel was selected to establish the working face. To ensure safety of the working face during the mining of the original return air roadway, the original return air roadway was filled with high water content materials. Site investigation data show that this material plays a cushioning role in the filling section of the original return air roadway during the mining of the 30503 working face, and the deformation of the new return air roadway during the filling section crossing the original return roadway is stable and well controlled.

Fate and transport of particle matter during GEOTextile tube dewatering of a dioxin and furan (PCDD/F) contaminated sediment

Geotextile tube dewatering is a pre-treatment method utilized in the remediation of high-water content materials (i.e. sediments and slurries). However, given the association some contaminants (e.g. dioxins and furans, (i.e. PCDD/F)) have with particulate matter in these contaminated sediments, understanding the fate and transport of this particle matter in the dewatered effluent is essential. In this paper, pressure filtration tests (PFTs) were conducted to investigate the effect of pressure and filter cake formation on both geotextile filtration efficiency and effluent quality. Transport tests were then performed to evaluate the particle transport through the developed filter cake, as well as the hydraulic characteristics of the medium during dewatering. HYDRUS, a one-dimensional model contaminant transport model was then employed to simulate the experimental particle transport test results. Three different mechanisms of particle transport (i.e. attachment only, detachment only, both attachment and detachment) through saturated porous media were examined to identify the possible mechanisms of observed effluent particle concentration. HYDRUS modeling outputs suggest that both attachment and detachment mechanisms are involved in a given particle's fate and transport during geotextile dewatering. In addition, parameters such as confining pressure and filter cake properties affect the particle concentration in the effluent.

Test and research on red mud used in bauxite washing mud solidification

Bauxite washing mud is the high water content and strong fluidity material. After being dehydrated to water content of less than 40% with dehydrating agent, it is still in a flow-plastic state. In order to eliminate the potential safety hazards of washing mud pond, it can be solidified. In order to solidify Pingguo bauxite washing mud, Preparated of curing agent with red mud, cement, fly ash and desulfurization gypsum, then added into the washing mud at a weight ratio of 10% of the dry amount of the washing mud. This study shown that after adding curing agents, the water content of the washing mud is further reduced, the liquid limit and plastic limit are further increased, the particle size is increased, and the plastic state is changed to a hard state, which greatly reduces the safety hazards of the washing mud pond. Through the screening test of curing agent, this study found that the reasonable and effective curing agent formula is: 15% fly ash, 25% cement, 15% gypsum, 45% red mud, the liquid limit index of the cured material is reduced to -0.27, which is in a hard state, the clay washing mud was changed to clay loam, which is suitable for dry tailings storage.

Grouting of bed separation spaces to control sliding of the high-located main key stratum during longwall mining

The gob-side entry 150 – 180 m behind the 14201 working face at Majialiang coal mine is severely deformed. We developed a new technique to control the behaviour of the high-located main key stratum (HMKS) to improve mine safety. The failure type and breaking span of the HMKS were determined based on key stratum theory and the voussoir beam model. By monitoring the deformation of the entry and surface subsidence, we found that the main cause of the large deformation of the gob-side entry was sliding of the HMKS. A new technique is proposed to add grout between the separated beds during mining. Physical simulations indicated that this technique is efficient in controlling sliding of the HMKS and avoiding strong dynamic loading, with the peak abutment stress reduced by 59%. Grouting stations were set up at a spacing of 150 m behind the advancing work face based on the principles and key parameters of the technique and the geological conditions at Majialiang coal mine. Before the HMKS began to slide, we injected high-water content materials with a water to cement ratio of 1.5:1 into the bed separation space to prevent breaking of the key strata.

Microwave-Induced Thermoacoustic Imaging for Embedded Explosives Detection in High-Water Content Medium

Improvised explosive devices (IEDs) have always been a major threat to personnel safety with continuous evolutions and new variants. Traditional methods for detecting IEDs, such as X-ray, have some drawbacks, so safe and efficient new detection techniques are highly desired. Microwave-induced thermoacoustic imaging (MITAI), being widely investigated for biomedical applications, is a promising candidate for detecting explosives embedded in high-water content materials due to its intrinsic advantages of nonionizing radiation, high contrast, and easy imaging procedure. Proof-of-concept demonstration is theoretically and experimentally carried out by successful detection of an explosive surrogate sample immersed in water. Good accordance between the experimental and simulation results validates the effectiveness of this approach. A parametric study of some key parameters is then performed to investigate their impact on detection efficiency and to evaluate the performance of a practical MITAI system for explosive detection.

Experimental study on excavating strip coal pillars using caving zone backfill technology

Strip mining was the major method to control surface subsidence when mining under buildings in China; however, its coal recovery ratio was only 30 to 50%, resulting in a large amount of coal resource waste due to the retained strip coal pillars. As such, it is of important significance to recover the retained pillars while guarantee the safety of the buildings at surface. In order to address this issue, excavating strip coal pillars using caving zone backfill technology was proposed in this study. The process of this technology was to grouting backfill the original strip caving zones using high-water content material at first, creating a combined backfill body of caved gangue and high-water content material, the backfill body acted as the temporary support. Then the retained pillars were excavated and the newly produced caving zones were backfilled with one interval, which effectively prevented the movement and deformation of the strata. The backfilling system and technology were designed and trailed to excavate the retained pillars at mining area 911 in Bucun colliery. It was found that the backfilling rate reached 96.8 to 98.7% in the original caving zones, the backfilling body in caving zones was highly compacted, and the maximum surface subsidence was only increased to 67 mm with no growth in the failure depth of floor. The retained coal pillars in three of the mining areas were safely excavated and the safety of buildings on the ground was preserved.

Characterization of Hydrogen in Basaltic Materials With Laser‐Induced Breakdown Spectroscopy (LIBS) for Application to MSL ChemCam Data

AbstractThe Mars Science Laboratory rover, Curiosity, is equipped with ChemCam, a laser‐induced breakdown spectroscopy (LIBS) instrument, to determine the elemental composition of nearby targets quickly and remotely. We use a laboratory sample set including prepared mixtures of basalt with systematic variation in hydrated mineral content and compositionally well‐characterized, altered basaltic volcanic rocks to measure hydrogen by characterizing the H‐alpha emission line in LIBS spectra under Martian environmental conditions. The H contents of all samples were independently measured using thermogravimetric analysis. We found that H peak area increases with weight percent H for our laboratory mixtures with basaltic matrices. The increase is linear with weight percent H in the mixtures with structurally bound H up to about 1.25 wt.% H and then steepens for higher H‐content samples, a nonlinear trend not previously reported but potentially important for characterizing high water content materials. To compensate for instrument, environmental, and target matrix‐related effects on quantification of H content from the LIBS signal, we examined multiple normalization methods. The best performing methods utilize O 778‐ and C 248‐nm emission lines. The methods return comparable results when applied to ChemCam data of H‐bearing materials on Mars. The calibration and normalization methods tested here will aid in investigations of H by LIBS on Mars with ChemCam and SuperCam. Further laboratory work will aid quantification across different physical matrices and heterogeneous textures because of differences we observed in H in pelletized and natural rock samples of the same composition.

Study on combined heat pump drying with freeze‐drying of Antarctic krill and its effects on the lipids

AbstractTo better preserve quality of Antarctic krill for wide food application, a drying method by the combining both the heat pump drying (HPD) and freeze‐drying (FD) was investigated. The effect on its dehydration efficiency, and effects on lipid extraction rate and lipid qualities and cost of the process were compared. The Antarctic krill was first treated by HPD, followed by the FD method. The lipids extracted from the various dehydrated samples were compared. In addition, the time and energy consumption during the process of dehydration and the physical properties such as color and microstructure of the Antarctic krill samples dehydrated by various drying methods were also compared. The results indicated that Antarctic krill drying by combined dehydration had good color and microstructure, which were both close to the FD sample, and better than the heat pump and hot air drying samples alone. The procedure was performed with an optimal dehydration temperature of HPD at 60 °C and a transition point of 40% moisture content, followed by freezing‐drying up to moisture content of 10%. Lipids extracted from Antarctic krill dried through procedure would have high lipid extraction rate (21.02%), low acid value (10.4 mg KOH/g), high astaxanthin content (200 mg/kg). Importantly it would save about 62 and 50%, respectively, of time and energy consumption in comparison of freezing‐drying method. Therefore, this study was for the first time to show that the combined dehydration of HPD and FD could be viable applicable dehydration method for Antarctic krill treatment.Practical applicationsHPD can provide efficient dehydration with a low temperature and energy consumption for high water content materials. The combined dehydration procedure of HPD and FD for Antarctic krill treatment could supply excellent quality of Antarctic krill as foodstuffs and for its further processes such as lipid extraction. This procedure would be more feasible for the food industrial processes.

Surface subsidence control during bag filling mining of super high-water content material in the Handan mining area

This paper focuses on the analysis of the overburden strata control mechanisms in stopes utilising bag filling mining super high-water content material. The factors affecting the mining-induced surface subsidence were determined, and control methods were applied to improve the filling rates of the working faces. The effects of filling rate changes on overburden failure and surface subsidence were investigated quantitatively using the field data. The results indicate that high filling rates and small changes could improve surface subsidence control. When the filling rate exceeded 86%, a 1% increase in the filling rate could decrease the average surface subsidence speed and distance by 5% and 7%, respectively. According to the current geological conditions of the Handan mining area, surface subsidence was observed as 260 mm at a 92% filling rate. Thus, these surface movements and damage indicators could be used to meet the requirements of I-level building codes and adequately control surface subsidence. [Received: July 28, 2015; Accepted: January 14, 2016]

Thermal–mechanical behaviour of chitosan–cellulose derivative thermoreversible hydrogel films

Hydrogels are high water content materials prepared by polymer crosslinking that are able to release active species, such as therapeutic, antibacterial, antiperspirant and moisturising agents, and fragrances. In recent years, several hydrogel systems have been reported based on both natural and synthetic polymers. Among the natural polymers, chitosan and cellulose-derivatives have been extensively studied, due to their stimuli responsive properties (pH and temperature sensitivity, respectively). In this work, we have developed physically crosslinked hydrogel films based on chitosan (CH) and (hydroxypropyl)methyl cellulose (HPMC). These films were prepared by two methodologies: solvent casting and freeze–thaw techniques. The resulting membranes, were assessed in terms of thermal (DSC and TGA), mechanical (stress–strain mechanical assays and DMA) and structural (X-ray) properties. The obtained results indicate that the developed CH:HPMC membranes show a good compatibility between the two component biopolymers. Additionally, these materials display an excellent thermal stability (having a TDecomposition > 270 °C), good mechanical properties (especially for the compositions with similar contents of both polymers), a glass transition temperature (Tg) higher than 194 °C and predominate amorphous character. The described characteristics turn the designed CH:HPMC membranes suitable candidates as active species carriers, for the envisaged textile application.

Comparison of Tear Film Surface Quality Measured In Vivo on Water Gradient Silicone Hydrogel and Hydrogel Contact Lenses

Recently, a new water gradient silicone hydrogel material has been introduced for a daily disposable lens. The aim of this study was to assess, in vivo, the prelens tear film surface quality (TFSQ) of this new lens in comparison with that of another daily disposable lens from the same manufacturer. Eleven subjects wore two pairs of hydrogel nelfilcon A and silicone hydrogel delefilcon A lenses in two nonconsecutive days. The noninvasive lateral shearing interferometry was used to analyze the prelens tear film and distinguish between different contact lens materials. Measurements were taken in natural blinking conditions after 6 hours of wear. Additionally, the subjective comfort was evaluated. The presence of both lenses resulted in a TFSQ reduction as compared with the bare eye condition. Statistically significant (Wilcoxon rank sum test, P<0.012) smaller change in TFSQ was introduced by the water gradient material than the high water content material. A statistically significant correlation between the TFSQ results of the two lenses was found (Pearson correlation coefficient R=0.8, P<0.003), indicating high linearity of the measurement methodology with respect to the tested lens material. The correlation of subjective comfort in lenses was lower and found to be insignificant (R=0.6, P>0.05). Although the prelens TFSQ is not always directly proportional to the lens water content, the results of the in vivo study showed that the new water gradient silicone hydrogel material impact less TFSQ as compared with its predecessor.

Existence and uniqueness of a classical solution for the coupled heat and mass transfer during the freezing of high-water content materials

A recent model for the coupled problem of heat and mass transfer during the solidification of high-water content materials like soils, foods, tissues and phase-change materials was developed. This model takes into account the role played by material properties and process variables on the advance of freezing and sublimation fronts, temperature and water vapour profiles and weight loss. The goal of this paper is to determine the existence of a unique local classical solution for the corresponding two-phase coupled free boundary problem in an adequate functional space. Copyright © 2011 John Wiley & Sons, Ltd.

Consolidation Behaviour of The Neutralisation Spent Pickle Liquor (NSPL) Sludge from Steel Works

The disposal of industrial waste sludge at a landfill has become a global problem especially when dealing with high moisture content material. Neutralisation Spent Pickle Liquor (NSPL) sludge waste generated in steel industry has been categorized as one of the slurry wastes in geotechnical engineering and poses serious handling problem due to its high water content. The NSPL sludge waste is categorized as a high water content material with a low solid concentration.The main objective in this paper is present a study related to compressive behaviour of the NSPL sludge material under external load. A series of consolidation tests of different NSPL initial water content and load pressure using Rowe cell equipment were performed. The consolidation behaviour of the NSPL sludge was shown to be complex, especially during the initial stages of the loading process. For any given load increment, an instantaneous compression was observed but no pore water dissipation were detected. The coefficient of permeability was found to be very high during the first few minutes, i.e. in the range of 10-4 – 10-5 m/s, and reduces significantly to 10-10 m/s after the first 17 hours of the test. The compression behaviour of the sludge materials are directly related to their coefficient of permeability

Asymptotic solution for coupled heat and mass transfer during the solidification of high water content materials

This paper focuses on obtaining an asymptotic solution for coupled heat and mass transfer problem during the solidification of high water content materials. It is found that a complicated function involved in governing equations can be approached by Taylor polynomials unlimitedly, which leads to the simplification of governing equations. The unknown functions involved in governing equations can then be approximated by Chebyshev polynomials. The coefficients of Chebyshev polynomials are determined and an asymptotic solution is obtained. With the asymptotic solution, the dehydration and freezing fronts of materials are evaluated easily, and are consistent with numerical results obtained by using an explicit finite difference method.

Contact lens material characteristics associated with hydrogel lens dehydration

To determine the association between material dehydration and hydrogel contact lens material characteristics, including water content and ionicity. Water content and refractive index data were derived from automated refractometry measurements of worn hydrogel contact lenses of 318 participants in the Contact Lens and Dry Eye Study (CLADES). Dehydration was determined in two ways; as the difference between nominal and measured (1) water content and (2) refractive index. Multiple regression models were used to examine the relation between dehydration and material characteristics, controlling for tear osmolality. The overall measured and nominal water content values were 52.58 +/- 7.49% and 56.88 +/- 7.81% respectively, while the measured and nominal refractive indices were 1.429 +/- 0.015 and 1.410 +/- 0.017. High water content and ionic hydrogel lens materials were associated with greater dehydration (p < 0.0001 for both) than low water content and non-ionic materials. When dehydration was assessed as the difference in refractive index, only high water content was associated with dehydration (p < 0.0001). High water content and ionic characteristics of hydrogel lens materials are associated with hydrogel lens dehydration, with the former being more strongly associated. Such dehydration changes could in turn lead to important clinical ramifications such as reduced oxygen transmissibility, greater lens adherence and reduced tear exchange.