Experimental Investigation of Water-Rich Fully Weathered Granite on Water Bursting and Mud Bursting

In order to investigate the mechanism of water-rich and fully weathered granite on the water bursting and mud bursting, the single-factor variable method is adopted in this study. The particle size gradation, initial porosity, water pressure, confining pressure, and anti-outburst thickness are chosen to determine each factor on the evolution of sand gushing, porosity, permeability, fine particle concentration, and water gushing velocity. Results indicate that a particle loss is the most critical reason for the water bursting and mud bursting of water-rich and fully weathered granite. The transition of water bursting from the linear to the nonlinear stage is the most significant feature. Soil particles with a larger Talbol power index are more likely to lead to water bursting. In addition, there is a critical water pressure to control the occurrence of water bursting and mud bursting. It is found that when the confining pressure reached the soil yield strength, the evolution of water bursting and mud bursting is independent of the increase in confining pressure. The increase in anti-outburst thickness can also effectively limit the risk of water bursting and mud bursting.

Effect of Particle-Size Gradation on Coarse Sand-Geotextile Interface Response in Cyclic and Postcyclic Direct Shear Test

In order to investigate the influence of sand particle-size gradation on cyclic and postcyclic shear strength behaviour on sand-geotextile interfaces, a series of monotonic direct shear (MDS), cyclic direct shear (CDS), and postcyclic direct shear (PCDS) tests were performed using a large-scale direct shear apparatus. The influence of cyclic shear history on the direct shear behaviour of the interface was studied. The results indicated that cyclic shear stress degradation occurred at the sand-geotextile interface. Shear volumetric contraction induced by the cyclic direct shear increased with the increase in cycle number. The lowest final contraction value was observed in discontinuously graded sand. In the MDS tests, there were great differences in interface shear strength due to the different particle-size gradations, whereas the differences between shear volumes were negligible. In the PCDS tests, the shear stress-displacement curves exhibited postpeak stress hardening behaviour for different particle-size gradations, and differences in shear volumes were detected. The well-graded sand-geotextile interface had a higher value of shear stiffness and a higher damping ratio relative to the other interfaces. Postcyclic shear stress degradation was observed for the discontinuously graded sand-geotextile interface.

Experimental Study on Nonlinear Seepage Characteristics and Particle Size Gradation Effect of Fractured Sandstones

Seepage mutation of fractured rock mass is one of the main inducements of dump slide and other disasters. Pore structure is a significant factor affecting the seepage characteristics of fractured rock mass, while particle size gradation has an important effect on the distribution of pore structure. Through the self-developed experimental system, the nonlinear seepage test on the fractured sandstones of the coalseam roof was conducted to investigate the influence of seepage pressure, porosity, and fractal dimension. Besides, the nonlinear seepage model was established by Barree–Conway theory. The results showed that, during the seepage process of fractured sandstone, there were significant nonlinear characteristics, which increased with the increase of the seepage pressure. With the increasing porosity, there was greater average pore size of fractured sandstone, stronger permeability, and weaker nonlinear seepage. The seepage characteristics approximated to that of Darcy model. However, with increasing grading fractal dimension, there were smaller average pore size of fractured sandstone, weaker permeability, and stronger nonlinear seepage. The seepage characteristics approximated to that of Forchheimer model.

Effect of AlF3 Addition on Electric Conductivity of NiFe2O4-Based Cermet Inert Anode

In this study, a combination of a two-step sintering and a particle size gradation technique was used to prepare cermet samples. We focused on the impact of the AlF3 additive on the performance of the cermet. We found that the addition of AlF3 doesnt significantly improve the density and porosity of Ag-NiFe2O4, since the addition of the AlF3 did not reduce the particle size, nor did it promote the tight packing of NiFe2O4 in a spinel-based cermet. However, we did observe a significant enhancement in its conductivity. The sample with 3% additive has the highest conductivity at 22.53S·cm-1 at 900°C, nearly 3.8 times better than the pure sample. An Analysis of the cermet microstructure showed that adding AlF3 can improve wetting between the ceramic phase and the silver metallic phase. It also facilitates the distribution of silver along the contour of the ceramic particles, which contributes to the improved conductivity of the nickel-based cermet.

Deformation Characteristics Research on Gravel Bed for Deep Buried Immerse Tunnel

Taking some deep buried immerse tunnel as background, deformation characteristics of foundation gravel bed is discussed by physical model test. The results show that small particle size gradation is not suitable for the foundation gravel bed, and compared with the non-groove gravel, compression modulus is greatly reduced in case of gravel with groove, and in case of pile foundation, gravel crushing phenomenon is obvious at the end of loading, and the ultimate bearing capacity of gravel bed is about 480kPa. If pile and gravel bed are used as the immerse tunnel foundation plan, it needs to take measure to control the stress level under the ultimate bearing capacity of gravel bed.

Effects of Compound Additives on Properties of Cermet Inert Anodes

In this paper, a combination of a two-step sintering and a particle size gradation technique was used to prepare cermet samples. The effects of compound additives with various combination of SnO2 and BaO on the performance of cermet were investigated. The results showed that, the performance of cermet could be improved by doping compound additives. The density of cermet sample reached to 5.61g•cm-3, and the porosity fell to 2.01%. Furthermore, we did observe a significant enhancement in its conductivity. The sample with 1% BaO additive has the highest conductivity at 8.02S/cm at 960°C, is increased by about 36% compared with the BaO undoped cermets.