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Based on the basic principle of rock mechanics, a virtual simulation software for rock and rock mass mechanics parameter estimation is developed. Through this software, students can conduct virtual simulation experiments of rock mechanics, physical and mechanical parameter analysis of rock specimen, rock mass structural plane identification, and rock mass mechanical parameter analysis to master the estimation methods of rock and rock mass mechanics parameters. The virtual simulation experiment is not only a useful supplement to the traditional indoor rock mechanics experiment, but also an attempt to broaden the testing of rock mechanics parameters, which is beneficial for improving the students' learning effect. [ABSTRACT FROM AUTHOR]

Ordered mesoporous silica, SBA-15 and MCM-41, and three-dimensionally ordered macroporous SiO2 were used as the supports of H4PMo11VO40 heteropolyacid for methacrolein oxidation. The dispersion and structural evolutions of the heteropolyacid along with thermal treatment were investigated. It was found that the heteropolyacid entered the one-dimensional mesoporous channels of SBA-15 and MCM-41, and the crystallization and growth were limited, leading to high dispersion of the heteropolyacid. However, the thermal stability was decreased under high dispersion. The migration of the heteropolyacid was observed to the end of the one-dimensional channels of SBA-15 and the outer surface of MCM-41 with calcination, accompanied by the decomposition of the heteropolyacid and the formation of MoO3. In comparison, the crystallization and growth of heteropolyacid were not limited in the open macropores of three-dimensionally ordered macroporous SiO2. Dispersed particles on the surface of the macropores with size of about 5 nm exhibited a higher thermal stability. The decomposition of the heteropolyacid in the SBA-15 and MCM-41 supported catalysts resulted in the loss of strong acid sites, causing low selectivity to methacrylic acid in methacrolein oxidation. High thermal stability with high exposure of the active sites in the three-dimensionally ordered macroporous SiO2 supported catalyst contributed to the enhancement in the catalytic performance. [ABSTRACT FROM AUTHOR]

Heavy metal ions have attracted considerable concern for their high toxicity and potential malign effects on the water environment, and adsorption has been regarded as one of the most versatile and effective techniques towards water treatment. In view of this, hierarchical porous carnation-like Ca4B10O19·7H2O microspheres self-assembled by two-dimensional (2D) quasi-hexagonal nanoplates are successfully synthesized for the first time as far as we know, by a facile and surfactant ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) assisted hydrothermal approach using CaCl2·2H2O, NaOH and H3BO3 as the raw materials. The as-obtained carnation-like Ca4B10O19·7H2O microspheres exhibit a uniform morphology, ca. 89% of which have a diameter within the range of 8.0–11.0 μm. A probable EDTA-2Na assisted self-assembly formation mechanism has also been proposed based on systematic control experiments. Meanwhile, the carnation-like Ca4B10O19·7H2O microspheres demonstrate a transparent characteristic from the ultraviolet to the visible region, a hierarchical porous structure (specific surface area: 32.79 m2 g−1, pore volume: 0.151 cm3 g−1, average pore diameter: 3.704 nm) and satisfactory thermal stability. In addition, the carnation-like microspheres are confirmed as great satisfactory adsorbents for heavy metal ion (Pb2+) removal with an adsorption capacity qm of 256.4 mg g−1, which may also be employed as excellent adsorbent candidates for other heavy metal or organic dye removal in water treatment as well as catalyst carriers in heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

Fractures in coal seams are channels for gas migration, and their geometric characteristics can affect permeability, thereby affecting the effectiveness of coalbed methane (CBM) extraction and carbon dioxide sequestration. The surface of natural fractures is rough and composed of minerals with complex shapes. At present, research on rough fracture is mainly focused on surface characteristics, with less attention given to the dynamic effects of rough structure in fractures on coal permeability considering effective stress and matrix adsorption expansion during different stages of methane extraction. In this work, we construct the complex geometric structure in the fracture surface into simplified rough elements. First, a physical model of fracture rough elements was constructed by using the analytical geometry method; meanwhile, the roughness applicable to this model was proposed, and the characterization of roughness degree of different-shaped rough elements was unified. Subsequently, a definition and an approach for selecting and computing effective fracture aperture were proposed. By taking into account the competition between effective stress and matrix adsorption expansion, the change of effective fracture aperture related to pore pressure was determined. Additionally, a novel permeability evolution model was formulated according to the cubic law and compared with the numerical simulation of other researchers for verification. The variation patterns of permeability, gas pressure and fracture aperture under diverse characteristic fracture roughness elements during CBM extraction were obtained by utilizing the proposed model. The findings indicate that the fractures with smaller roughness, higher stagger degree and gentler inclination angle of rough elements are more favorable for CBM extraction. This has inspired a new understanding of the mechanism of CO 2 -enhanced coal bed methane recovery (CO 2 -ECBM) technology in deep coal seams with regard to fracture rough element characteristics, which offers valuable theoretical support for the practical implementation of this technology. • A new physical model of rough-walled fractures is proposed that simplifies each bump on the surface into a regular rough element. • The effective fracture aperture that varies nonlinearly with the extraction process is defined. • Dynamic effect of roughness, stagger degree and shape of rough elements on methane migration is analyzed. • The mechanism of injecting CO 2 into deep coal seams to promote methane production is discussed. [ABSTRACT FROM AUTHOR]

One-dimensional (1D) nanostructured metal borates have drawn considerable attention owing to their versatile applications in a multitude of fields, but it is still a great challenge to achieve a high aspect ratio in these materials via a facile and feasible route. Herein, ultralong Ca2B2O5·H2O nanowires with a length of 110–230 μm and ultrahigh aspect ratio of 240–750 are successfully synthesized for the first time via a facile water-bath pretreated eco-friendly hydrothermal technique in the absence of any additives, using low cost CaCl2, H3BO3 and NaOH as the raw materials. The formation mechanism of the ultralong nanowires is studied in detail by varying the process parameters (water-bath and hydrothermal temperature, duration time, etc.). The water-bath treatment plays a key role in the formation of thin hexagonal Ca(OH)2 nanoplates, favoring subsequent conversion to ultralong nanowires with a high aspect ratio. The as-obtained Ca2B2O5·H2O:5.0%RE3+ (rare earth, RE = Eu, Tb) nanophosphors exhibit strong photoluminescence emission and excitation performance, with corresponding Commission Internationale de l'Eclairage (CIE) values determined as (0.635, 0.364) and (0.320, 0.597) within the red and green regions, respectively. This not only suggests that the ultralong Ca2B2O5·H2O nanowires are promising structure- and function-integrated photoluminescent host candidates, but also provides a novel and facile route for the formation of high aspect ratio 1D nanostructures of other metal borates. [ABSTRACT FROM AUTHOR]

Dynamic disturbance such as blasting may significantly affect the creep of rock. Quantification of the influence of dynamic disturbance on the creep behavior of rock is a prerequisite to the understanding of the long-term behavior of rock around excavations. In this study, a new creep-impact test machine that is capable of testing the rock failure behavior under combined creep loading and dynamic disturbance was introduced. We performed creep experiments on sandstone while a dynamic disturbance was applied. Axial strain, volumetric strain and acoustic emission (AE) events were measured. The results from the creep-impact experiment show that the rock creep was greatly affected by the dynamic disturbance. Dynamic disturbance may introduce further damage on rock and shorten the time-to-failure of creeping rock specimens. Combination of creep stress and dynamic disturbance resulted in two failure conditions: failure along with accelerating creep and failure during dynamic disturbance. If the dynamic disturbance was not followed by failure, the axial strain consisted of an instantaneous response as the dynamic disturbance was applied, followed by a primary phase of decelerating creep and a steady-state creep phase. This pattern was repeated after the next dynamic disturbance until the last dynamic disturbance that led to the failure. The creep resulted from micro-fracturing in the rock, which can be characterized by the cumulative AE energy if the AE events were monitored during the creep-impact test of rock. The creep behavior was more sensitive to dynamic disturbance under higher creep stress. Under the same creep stress, a dynamic disturbance with higher impact energy resulted in a higher axial strain rate, absolute volumetric strain rate and AE energy rate. Dynamic disturbance not only increased the axial strain rate but also promoted the dilatancy of the rock specimens. The failure of the rock specimens was mostly in the shear mode, and this failure pattern was merely affected by the dynamic disturbance, even though the specimens became more fragmented under the higher creep stress and higher impact energy. [ABSTRACT FROM AUTHOR]

Abstract As a simple supporting structure, rockbolts are responsible for maintaining the integrity and stability as well as controlling the deformation, displacement, and crack development in the surrounding rock mass. Knowledge of rockbolt load-transfer behaviors constitutes valuable information, as the rockbolt functionality is affected by load-transfer processes. A series of pullout tests was conducted on a rockbolt with a long embedment length (1500 mm). The critical rockbolt embedment length at which yielding or necking occurs together with the friction coefficient at the residual axial stress was analyzed numerically. Additionally, the failure modes of rockbolt-grouted systems and the effects of several parameters, including the rockbolt diameter (18, 20, and 25 mm) and cement mortar strength, were assessed. The rockbolt strain and energy absorption during the pullout process were also investigated. The identified rockbolt failure modes, which are dependent on the cement mortar strength and rockbolt diameter, include pullout accompanied by partial concrete splitting failure parallel to the rockbolt. Under the same cement mortar strength, the maximum load increases and the rockbolt displacement at the maximum load decreases as the rockbolt diameter increases. When diameter is held constant, the maximum load and corresponding displacement increase as the cement mortar strength increases, but the residual load is irregular. The energy absorbed by the rockbolt in the pullout test is related to the cement mortar strength and failure mode. With an increasing embedment length, the failure process is converted from a completely damaged interface with little simultaneous damage to the cement mortar at the free end to the expansion of the cracks at the loaded and free ends toward each other. The interface is completely damaged when the cracks at both ends become connected. [ABSTRACT FROM AUTHOR]

Abstract The reliable prediction of excavation responses for squeezing rock remains a challenging issue in rock engineering. This paper presents a numerical procedure for a strain-softening rock mass around highly deformed circular opening based on the finite strain theory, so the overall elasto-plastic analysis is a Lagrangian method which focuses on the motion of each material point and is well suited for the problems involving large deformation. The influence of axial in-situ stress is considered by introducing the initial axial stress into the elastic constitutive equations, and the axial plastic flow is realized by redefining the plastic internal variable and considering different stress distributions in the plastic zone. Thus, the numerical procedure enables prediction of the rock deformation and squeezing potential in a more rational and rigorous manner. The capability of the method for estimating the small strain and squeezing deformation is verified by being compared with the existing analytical results and the field measuring data. Negligence of the axial in-situ stress or the axial plastic flow underestimates the rock deformation, and the induced deviation essentially depends on the post-peak constitutive relation and the rock heterogeneity after rock yields. The higher level of the material homogeneity in the plastic zone, the lower effects of the axial in-situ stress on the rock responses. The stress distribution and strain-softening behavior of surrounding rock can be significantly affected by the axial in-situ stress and the critical plastic internal variable η *. Tunnel instability is independent of large deformation for the high η * but is closely associated with the squeezing problem when η * is small. As η * decreases, both of the plastic radius and wall convergence increase initially and remain constant afterwards. Lastly, the paper investigates the rock responses and ground-support interaction when the small strain theory is applied on the squeezing rock. [ABSTRACT FROM AUTHOR]

Highlights • The FBGs were used to measure CTB temperature and internal strain evolution. • In the liquid stage, the binder content had no effect on settlement behavior. • CTB internal strain was influenced by combined chemical and thermal effects. • No significant change occurred in settlement and strain in the hardened stage. Abstract The philosophy of the use of backfill is to return much of tailings waste to underground voids and increase working place stability to safely extract more minerals. The key issue for the safe and efficient design of cemented tailings backfill (CTB) structure is its mechanical properties and interaction with the surrounding rock. As a cemented material, CTB's strength is a function of hydration degree. As hydration is an exothermic reaction and results in net volume reduction, thermal expansion and chemical shrinkage occur simultaneously in the mixture. Each CTB component plays a significant role during this process and the most important factor is the binder content, because it influences the amount of cement hydration products that provide binding phases between tailing particles. In this paper, a number of fiber Bragg gratings (FBGs) were directly embedded into the 7-day cured CTB specimens to measure their temperature and internal strain evolution, with settlement development measured by Linear Variable Differential Transformer (LVDT). The experimental results showed that binder content had a significant effect on CTB temperature and internal strain evolution. Furthermore, the evolution of internal strain and settlement was an indicator of the transformation in different stages (such as fluid, skeleton formation and hardening) during the hydration process. [ABSTRACT FROM AUTHOR]

Relative to water-based fluids, non-aqueous fracturing fluids have the potential to increase production, reduce water requirements, and to minimize environmental impacts. Since the viscosity of supercritical CO 2 is one-tenth that of water, its density is close to that of water, and is capable of promoting sorptive rejection of methane, it is an attractive substitute for water in the extraction of shale gas and coalbed methane. The following defines a geomechanical model accommodating the interaction of fluid flow, adsorption-induced swelling stress, solid deformation and damage to quantify rock-gas interactions during supercritical CO 2 fracturing for shale gas production. The architecture of the shale is accommodated that includes both pore- and micro-crack-based porosity. According to the microcrack model representing shales with low porosity, both analytical and numerical results show that the effective stress coefficient is much smaller than unity. We analyze the potential advantages of fracturing using supercritical CO 2 including enhanced fracturing and fracture propagation, increased desorption of methane adsorbed in organic-rich portions of the shale and the potential for partial carbon sequestration. Rock-gas interactions include both the linear poroelastic response and the chemo-mechanical interaction due to sorption. Simulation results demonstrate that supercritical CO 2 fracturing indeed has a lower fracture initiation pressure and a significantly lower breakdown pressure, as observed in experiments, and that fractures with greater complexity than those developed with liquid CO 2 and water fracturing result. With increasing dynamic viscosity of the fracturing fluids, the predicted breakdown pressure also increases, consistent with experimental observations. [ABSTRACT FROM AUTHOR]