Frost heave in rocks is caused by the frost heave pressure (pore ice pressure) generated by the freezing of pore water, which then cracks the rock. The present work attempts to clarify the frost heave pressure of rocks by experiments at four temperature conditions. Ohya tuff and Kimachi sandstone, in which the occurrence of frost heave has previously been confirmed, were used as specimens. Measurements of these experiments were the internal temperature of the rocks during the freezing process and the location where the ice lens formed. These two parameters made it possible to determine the temperature of the location where the ice lens formed. A generalized Clausius-Clapeyron equation was used to calculate the pore ice pressure. The results indicated that the temperature at the location of ice lens formation depends on the types of rock, but not on the temperature gradient during freezing. It was also confirmed that frost heave in rocks with a higher tensile strength appears at locations with a lower temperature, while that in rocks with a lower tensile strength appears at location of temperatures close to 0°C. These findings suggest that the location and temperature of the ice lens formation are dependent on the strength of the rock.
In this study, drained triaxial compression tests were conducted on artificial methane-hydrate-bearing sediments containing fine fraction. Toyoura sand (average particle size: D50 = 0.230 mm, fine fraction content: Fc = 0%) , No.7 silica sand (D50 = 0.205 mm, Fc = 1.1%) and No.8 silica sand (D50 = 0.130 mm, Fc = 11.5%) were used as the skeleton of each specimens. Axial loading was conducted at an axial strain rate of 0.1 %/min at a constant temperature of 278 K. The cell pressure and pore pressure were kept constant during axial loading. We found that the strength of the hydrate-sand specimens is almost independent of the type of sand forming the skeleton of the specimen. On the other hand, the stiffness of the specimens containing finer sand particles is lower, probably because fine sand particles can more easily penetrate between the sand and hydrate particles, resulting in larger axial deformation. During the dilatant behavior, the lateral expansive displacement of specimens containing finer sand particles is smaller because the compaction process may continue to occur even when the dilatant behavior becomes the dominant mechanism. The formula expressing the secant Young's modulus obtained from the triaxial compression tests was constructed as a function of methane hydrate saturation and effective confining pressure and was introduced to a numerical simulator. The compressive displacement observed in the earlier work concerning the laboratory-scale experiments of methane hydrate dissociation was simulated by the numerical simulator.
Prewash treatment, a leaching test, and a particle-size fractionation test were conducted as preliminary investigations for the establishment of an assessment procedure for harmful elements leaching from cathode-ray tube (CRT) glass. The glass sample used in this study was recycled funnel glass that was initially fractured and then divided into two parts (<0.125 mm and 1-2 mm) by sieving. In a 5 min ultrasonic wash treatment, glass content elements were dissolved in wash solution. Si, As, and Sb showed a greater dissolution tendency than other glass content elements. A leaching test with a washed glass sample confirmed that the prewash treatment with alcohol wash solution was slightly more effective in the removal of fine particles, which were generated during the fracture of the glass sample, than the treatment with water. However, differences in elute behavior caused by glass surface alteration, which could be due to the difference in the employed wash solutions, were not observed. The fractionation test, in which glass-derived particles in the elute were fractionated by using filters of different pore sizes, confirmed that in acid solution, most Pb was included in particles having diameters smaller than 0.45 μm, whereas in neutral and alkali solutions, most Pb was included in particles having diameters of 0.45-10 μm. Results of zeta potential measurement showed that the glass particles in alkali solution were more dispersive than those in neutral solution. Therefore, the mobility evaluation of the particles was found to be important in the assessment of harmful elements leaching from CRT glass, particularly in an alkaline environment. Finally, based on the information obtained through this study, the methods of prewash treatment and leaching test can be considered the most appropriate at this time are suggested.
In an attempt to recover nickel and remove unnecessary elements during the copper smelting, crushed waste Printed Circuit Board (PCB) was treated by means of heat treatment and magnetic separation. Many multi-layered ceramic capacitors (MLCCs) including nickel have been mounted on PCB. Some MLCCs would be concentrated among the relatively small particles of crushed PCB, whereas others wouldn't be stripped from main board because MLCC has been downsized. In the first experiment, PCB without mounted parts excluding MLCC was treated in a nitrogen atmosphere at temperature, ranging from 773 to 973K, while the residue was magnetically separated. Nickel was concentrated in magnetics, whereas copper was mainly collected in non-magnetics. Nickel grade in magnetics was higher at relative high temperature. When the magnetic separation (magnetic field strength of 0.1T) was carried out after the sample was heated at 873K and screened with a 4mm screen, the nickel grade was enhanced from 0.16% to 6.7%, recovering 74% of feed. Copper loss, on the other hand, in magnetics was less than 1%. 82% of lead and 92% of tin were separated from non-magnetics of over 4mm in size. In the second experiment, crushed PCB with the size under 4mm was magnetically separated. Most nickel was collected into magnetics, which contains also a small amount of gold. In addition, some lead parts made of copper, nickel, tin and zinc plated with gold were also collected as magnetics. Heat treatment and magnetic separation were conducted for magnetics to separate gold from magnetics after separating lead parts. The magnetic fraction of 2 to 4mm in size, which was collected by magnetic separation (magnetic field strength of 0.1T) , after the sample was heated in the air atmosphere at 873K, had a nickel grade of 6.9%, whereas the gold loss was less than 1%. 82% of iron and nickel was separated as magnetics.
We have been investigating the development of the hybrid-separation system for mutual separation rare-earth element in a number of rare-earth elements. The hybrid-separation systems use electrolytic oxidation and liquid membrane supported TBP techniques. In the present work, electrolytic oxidation behaviors of Ce (III) and Nd (III) as simple condition were investigated with the flow type electrolytic cell. In this work, it was found that Ce (III) can be effectively oxidized to Ce (IV) using the flow type electrolytic cell. Furthermore, separation behavior of Ce from Nd in medium nitric acid solutions after the electrolytic oxidation were investigated using the liquid membrane supported TBP. In this study, it was obtained that Ce (IV) can be separated from Nd (III) by this separation system in nitric acid medium.