The Yucca Mountain Drift Scale Test (DST) is a multiyear, large-scale underground heater test designed to study coupled thermal-hydrological-mechanical-chemical behavior in unsaturated fractured and welded tuff. As part of the international cooperative code-comparison project DECOVALEX, four research teams used four different numerical models to simulate and predict coupled thermal-hydrological-mechanical (THM) processes at the DST. The simulated processes included above-boiling temperature changes, liquid and vapor water movements, rock-mass stress and displacement, and THM-induced changes in fracture permeability. Model predictions were evaluated by comparison to measurements of temperature, water saturation, displacement, and air permeability. The generally good agreement between simulated and measured THM data shows that adopted continuum model approaches are adequate for simulating relevant coupled THM processes at the DST. Moreover, TM-induced rock-mass deformations were reasonably well predicted using elastic models, although some individual displacements appeared to be better captured using an elasto-plastic model. It is concluded that fracture closure/opening caused by change in normal stress across fractures is the dominant mechanism for TM-induced changes in intrinsic fracture permeability at the DST, whereas fracture shear dilation appears to be less significant. This indicates that TM-induced changes in intrinsic permeability at the DST, which are within one order of magnitude, tend to be reversible.

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Coupled thermal-hydrological-mechanical analyses of the Yucca Mountain Drift Scale Test - Comparison of field measurements to predictions of four different numerical models

New insights into the interactions between Pb(II) and fruit waste biosorbent.

Modeling, optimization and understanding of adsorption process for pollutant removal via machine learning: Recent progress and future perspectives.

Modeling and optimization of the adsorptive removal of crystal violet dye by durian (Durio zibethinus) seeds powder: insight into kinetic, isotherm, thermodynamic, and adsorption mechanism

In the present work, an effort has been made to utilize Phyllanthus emblica (PE) fruit stone as a potential biomaterial for the sustainable remediation of noxious heavy metals viz. Pb(II) and Cd(II) from the aqueous solution using adsorption methodology. Further, to elucidate the adsorption potential of Phyllanthus emblica fruit stone (PEFS), effective parameters, such as contact time, initial metal concentration, temperature, etc., were investigated and optimized using a simple batch adsorption method. It was observed that 80% removal for both the heavy metal ions was carried out within 60 min of contact time at an optimized pH 6. Moreover, the thermodynamic parameters results indicated that the adsorption process in the present study was endothermic, spontaneous, and feasible in nature. The positive value of entropy further reflects the high adsorbent–adsorbate interaction. Thus, based on the findings obtained, it can be concluded that the biosorbent may be considered a potential material for the remediation of these noxious impurities and can further be applied or extrapolated to other impurities.

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Utilization of Phyllanthus emblica fruit stone as a Potential Biomaterial for Sustainable Remediation of Lead and Cadmium Ions from Aqueous Solutions

Abundant fruit waste materials can be utilized as sustainable biosorbents for heavy metal removal from aqueous solutions. In this study, mango seed (MS) comprising seed kernel and shell showed the maximum adsorption capacities of 263.4 mg-Pb/g at pH 5.0 and 93.7 mg-Cd/g at pH 7.5. The best fitting of the adsorption isotherms to the Redlich-Peterson model indicated multilayer adsorption of Pb(II) and Cd(II) on the heterogeneous surface of MS. The adsorption was rapid with 93% of Pb(II) and 78% of Cd(II) adsorption accomplished within 10 min. More than 99% of the sequestered Pb(II) and 88% of the sequestered Cd(II) were recovered by desorption using 0.2 M HNO3, and the regenerated MS maintained 96–97% of the adsorption capacities. A combination of physicochemical and spectroscopic approaches showed that carboxyl, hydroxyl, amine, and ether groups were the binding sites; electrostatic attraction, microprecipitation, complexation, and ion exchange (with Ca2+ and Mg2+) jointly contributed to the adsorption. The seed kernel which has a more amorphous structure and a higher ion exchange capability favored higher Pb(II) and Cd(II) adsorption compared with the seed shell which contains a higher content of crystalline cellulose. These findings imply the application potential of MS for heavy metal removal and provide important information for the (bio)sorbent development. 

Efficient removal of Pb(II) and Cd(II) from aqueous solutions by mango seed biosorbent

• WR biosorbent exhibited high and rapid uptake of Cd(II) from aqueous solutions. • 86–99% of the Cd(II) adsorption capacity of WR was remained after desorption. • Cd(II) was bound to hydroxyl, carboxyl, ether, and amine groups on WR. • Ion exchange with Mg 2+ and Ca 2+ contributed to 83% of Cd(II) adsorption. • Microprecipitation, electrostatic interaction, and complexation co-occurred. Recycling of agricultural waste as adsorbents for pollutant removal realizes “Waste to Resource”. This study utilized an abundant fruit waste material, watermelon rind (WR), to remove Cd(II) from aqueous solutions (Cd(II) solution in distilled deionized water) in a batch mode, and the underlying adsorption mechanism was deciphered by complementary methods. The Cd(II) adsorption process rapidly reached equilibrium in 60 min, with 90% of adsorption finished in 10 min (50 mg/L Cd(II), 0.5 g/L WR). The maximum Cd(II) adsorption capacity of WR was 102.0 ± 0.1 mg/g at pH 7.0 (25–500 mg/L Cd(II), 1.0 g/L WR), and the Dubinin-Radushkevich isotherm and pseudo-second-order kinetic models provided the best description to the adsorption process. Spectroscopic analysis using Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) showed hydroxyl, carboxyl, ether, and amine groups as the binding sites, probably via complexation. Physicochemical analysis such as zeta potential measurement and scanning electron microscopy coupled with electron dispersive X-ray spectroscopy (SEM-EDS) revealed the occurrence of electrostatic interaction and microprecipitation. Moreover, ion exchange of Cd(II) with Mg 2+ and Ca 2+ bound to WR contributed to 83% of the Cd(II) adsorption. The findings indicate the great potential of WR for Cd(II) removal from wastewater. The mechanism elucidation uncovered the interactions between Cd(II) and the WR surface, providing insights to the development and optimization of biosorbents derived from agricultural waste. 

Utilization of low-cost watermelon rind for efficient removal of Cd(II) from aqueous solutions: Adsorption performance and mechanism elucidation

With the further development of deep rock mechanics engineering, such as the exploitation and utilization of geothermal resources, the exploitation of deep mineral resources, and the safe disposal of nuclear waste, the study of mechanical properties of deep high-temperature rock is gaining the attention of the researchers. However, not only the high temperature but also the cooling condition/method that will be used in the construction such as drilling cooling will also greatly affect the mechanical properties of the rock. In this paper, the mechanical behaviour and the evolution of the mechanical properties of the high-temperature (600°C–1,000°C) granite under different cooling methods are studied. The following conclusions can be obtained: (1) The peak stress of the granite decreases with the heating temperature. Compared with natural cooling, water cooling has a more significant effect on strength degradation. (2) The increase of the heating temperature increases the maximum axial strain of the granite. The water cooling method more greatly induces the maximum axial strain of granite than the natural cooling. The maximum axial strain of the specimen under the water cooling reaches 117.3% of that under natural cooling (800°C). (3) The elastic modulus of the granite decreases with the heating temperature. Water cooling will have a stronger effect on the reduction of the elastic modulus than natural cooling. The maximum difference value (2.02 GPa) of the elastic modulus under the different cooling methods occurs at the temperature of 800°C. (4) Poisson’s ratio of the granite increases with heating temperature, and the cooling method does not have an evident effect on it. The relationship between Poisson’s ratio and the heating temperature under different cooling methods can be described using the linear model. (5) According to the influence of the temperature on the peak stress, the elastic modulus, and Poisson’s ratio, the heating temperature domain can be divided into the unapparent zone, the significant zone, and the mitigation zone. (6) The thermal stress due to the nonuniform temperature field and the different thermal expansion coefficients is incompatible. Such incompatibility stresses the essences of the degradation of the mechanical properties of the granite.

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An Experimental Study on the Mechanical Properties of High-Temperature Granite under Natural Cooling and Water Cooling

The rapid and accurate identification of the physical characteristics of coal by means of ultrasonic detection is of great significance to ensure safe mining of coal and efficient development of coal seam methane. In this paper, the ultrasonic velocity testing experiments of coal during gas adsorption and desorption were carried out, utilizing a low frequency petrophysical measurement device with primary and fractured coal as the research objects. The variations in the elastic mechanical parameters and ultrasonic velocity of coal samples were analyzed to elucidate the influence mechanism that gas adsorption and desorption have on them. During gas adsorption and desorption, the longitudinal wave velocity of the primary structure coal varies from 1990 m/s to 2200 m/s, and the transverse wave velocity varies from 1075 m/s to 1160 m/s, while the longitudinal wave velocity of the fractured structure coal varies from 1540 m/s to 1950 m/s, and the transverse wave velocity varies from 800 m/s to 1000 m/s. The elastic modulus and wave velocities, in both directions of the primary structural coal, were higher than those of the fractured structural coal. In comparison to the fractured structural coal, the main structural coal had a lower Poisson’s ratio. In addition, the spread of the elastic mechanical parameters and wave velocities, in both the longitudinal and transverse directions, was more pronounced in the fracture−structured coal than in the primary−structured coal. During gas adsorption and desorption, the speed of the coal’s longitudinal waves increased, and then decreased, due to the combined effect of gas adsorption expansion and pore gas pressure compression matrix effect. For this experiment, the maximum longitudinal wave velocity of the coal occurred at a gas pressure of 1.5 MPa. Primary structural coal has a longitudinal wave speed of 2103 m/s, whereas fragmented structural coal has a speed of 1925 m/s. The variation in the shear wave velocity of the coal is controlled only by the gas adsorption expansion effects. The shear wave velocity increases during gas adsorption and decreases during gas desorption. With the change of gas pressure, the longitudinal wave velocity can increase by 23.34%, and the shear wave velocity can increase by 17.97%. Coal undergoes changes to both its Poisson’s ratio and elastic modulus as a result of gas adsorption and desorption; these modifications are analogous to the velocity of longitudinal and shear waves, respectively.

Experimental Study on the Effect of Gas Adsorption and Desorption on Ultrasonic Velocity and Elastic Mechanical Parameters of Coal


 The rock fragmentation and crack propagation of anisotropic rock induced by tunnel boring machine (TBM) tunneling is studied in this paper. First, a numerical model based on the 2D particle flow code (PFC2D) is established and calibrated to reveal the four stages of rock fragmentation. In Stage I (indentation depth 0–0.4 mm), the indentation force beneath the cutterhead increases and decreases dramatically with the accumulation and release of mechanical energy. Such a phenomenon indicates that a hydrostatic core (crushed zone) can be observed. In Stage II (indentation depth 0.4–1.1 mm), many median cracks propagate dramatically with the indentation force. Meanwhile, the hydrostatic core is pushed because the mechanical energy of the cutterhead is reaccumulated in the specimen. In Stage III (indentation depth 1.1–2.6 mm), lateral cracks begin to develop due to the further increase in indentation depth. In Stage IV (indentation depth 2.6–5 mm), the lateral cracks and median cracks continue to propagate, and rock chips can be found on the sides of the cutterhead. Then, with increasing confining pressure, lateral cracks begin to gradually develop and the maximum angle of lateral cracks is 70.5°. Furthermore, the magnitude of the intrusion velocity can seriously influence the evolution of the indentation force during Stages III and IV because of the accumulation and release of mechanical energy. The accumulation and release of mechanical energy are more obvious with a higher intrusion velocity of the cutterhead.

https://academic.oup.com/jge/article-pdf/19/6/1355/47763149/gxac088.pdf

Yunlong Wang

Papers

Efficient removal of Pb(II) and Cd(II) from aqueous solutions by mango seed biosorbent

Utilization of low-cost watermelon rind for efficient removal of Cd(II) from aqueous solutions: Adsorption performance and mechanism elucidation

An Experimental Study on the Mechanical Properties of High-Temperature Granite under Natural Cooling and Water Cooling

Experimental Study on the Effect of Gas Adsorption and Desorption on Ultrasonic Velocity and Elastic Mechanical Parameters of Coal

The rock fragmentation and crack propagation under TBM tunneling based on particle flow code