Theory of an elastic anomaly in the heavy fermion system CeTe

The elastic anomaly observed in the coherent Kondo state of Ce heavy fermion compounds is analyzed by using the Anderson lattice model simulating the energy level scheme of CeTe. The $\Gamma_7$ doublets and $\Gamma_8$ quartets of the 4f states are considered in the model. We solve the mean field equations to derive the temperature dependences of elastic constants, using the random phase approximation like expression for the interaction between the elastic strain and the crystalline field splitting. We compare the calculation with the $(c_{11} - c_{12})/2$ and $c_{44}$ constants of CeTe. The presence of the downward dip and the observed overall temperature variations of the two constants are well described by the present theory. The origin of the dip is the coupling between the elastic strain and the splitting of the $\Gamma_8$ quartets.Comment: submission to Phys. Rev. B, 16 pages, 3 figures (sent by the snail mail

Evaluation of Mode I Fracture Toughness Assisted by the Numerical Determination of K-Resistance

The fracture toughness of a rock often varies depending on the specimen shape and the loading type used to measure it. To investigate the mode I fracture toughness using semi-circular bend (SCB) specimens, we experimentally studied the fracture toughness using SCB and chevron bend (CB) specimens, the latter being one of the specimens used extensively as an International Society for Rock Mechanics (ISRM) suggested method, for comparison. The mode I fracture toughness measured using SCB specimens is lower than both the level I and level II fracture toughness values measured using CB specimens. A numerical study based on discontinuum mechanics was conducted using a two-dimensional distinct element method (DEM) for evaluating crack propagation in the SCB specimen during loading. The numerical results indicate subcritical crack growth as well as sudden crack propagation when the load reaches the maximum. A K-resistance curve is drawn using the crack extension and the load at the point of evaluation. The fracture toughness evaluated by the K-resistance curve is in agreement with the level II fracture toughness measured using CB specimens. Therefore, the SCB specimen yields an improved value for fracture toughness when the increase of K-resistance with stable crack propagation is considered

Surface subsidence due to underground mining operation under weak geological condition in Indonesia

Subsidence analysis and prediction with measured data have been conducted and applied to local strata and mining conditions worldwide. Underground coal mines chose the most suitable analysis and prediction method for them. However, there was no study based on the measured data of subsidence induced by underground mining operation in Indonesia. This paper describes the condition of underground coal mine in Indonesia and then discusses the subsidence behavior due to longwall mining operation based on measured data in Balikpapan coal-bearing formation in Indonesia

Application of injection material for rehabilitation of underground pipeline using fly ash surfactant mixtures

A large amount of waste is produced at coal preparation plants. The properties of the waste vary depending on the mineralogical content of the mother rock in which the coal is embedded. The quality of the waste depends on the method of mining and cleaning, but it consists mostly of clays, quartz, carbonaceous materials, mica, pyrites and so on. About 80% of coal-ash is now utilised in Japan, and the remaining is disposed of at disposal sites. However, the life span of each disposal site is limited and it is difficult to find new disposal sites. It is therefore desirable that the percentage of utilisation of fly ash be increased in every possible way in Japan. One way of achieving this goal is to incorporate more fly ash in cement mixes that can be applied as the injection material for natural/artificial openings. In this study, different combinations of fly ash, surfactants and water were investigated to determine the influence of surfactants on the properties of fly ash mixtures used in slurry pipe jacking.Web of Science24117

Application of Flash Setting Material for Temporary Earthquake Disaster Restoration of Gas Pipelines Using Fly Ash Cement Mixtures

There are many earthquakes in Japan. If a large earthquake were to occur, it is necessary to consider how pipelines such as: gas, sewage, telecommunications, and so on are restored quickly. At that time, damaged gas pipelines are very dangerous because fire in large areas could be caused by the leakage of gas from the damaged pipeline. Accordingly, it is necessary for gas companies to stop the supply of gas to houses over a large area. Once the gas supply is stopped, there is a considerable amount of time to repair the pipelines over the area. For this reason, a quick method for restoring damaged gas pipelines would be useful after an earthquake. Recently, we have been developing new flash setting material for the damaged gas pipeline by an injection into the house connection of gas when the gas supply is stopped quickly in an emergency. From there points of view, in order to clarify to what degree the contents of flash setting material affect the properties of the injected fly ash mixture causing heavy damage to the gas pipeline in an earthquake, different combinations to fly ash, chemical agents and water were considered in several experiments