A coupling scheme for boundary and finite elements using a joint element     

Y. Mitsui  Y. Ichikawa  Y. Obara  T. Kawamoto 《国际地质力学数值与分析法杂志》1985,9(2):161-172

A coupling scheme for boundary and finite elements using a joint element is proposed. The scheme is based on the finite element discretization (i.e. the equivalent FE procedure). Footing problems founded on multiple layers are solved. Furthermore, the scheme is extended to a non-linear analysis.  相似文献   

A non-linear rheological analysis of deeply located tunnels     

Tomoyuki Akagi  Yasuaki Ichikawa  Hidetaka Kuroda  Toshikazu Kawamoto 《国际地质力学数值与分析法杂志》1984,8(5):457-471

A rheological model which is able to explain the delayed failure phenomenon has been proposed and applied to the analysis of the time dependent behaviour of deep tunnels. The model is the three element Voigt type before yielding and becomes the five element Voigt type after yielding. This means that the stiffness of the model is decreased by yielding. It is assumed that the yielding takes place when the stored elastic energy density of distortion reaches a certain maximum value. Some experiments to determine material constants are proposed. The numerical results clearly exhibited a delayed failure state of the rock masses around the tunnel surface. It was found that the extension of the yielding zone due to tunnel excavation depends on the opening method.  相似文献   

Quartz dissolution experiments at various pH, temperature and stress conditions: CLSM and ICP-AES investigations     

Jung Hae Choi  Kazushi Kimoto  Yasuaki Ichikawa 《Environmental Earth Sciences》2012,66(8):2431-2440

To understand the effects of temperature, pH and mechanical stress on the pressure dissolution of quartz, two experiments using monocrystalline quartz samples were conducted. The first was a closed-fluid experiment to investigate the effect of pH, and the second was a flow-through experiment to investigate stress and temperature effects. To initiate the pressure dissolution, a pair of samples was immersed in a solution with a prescribed pH. The samples were stressed mechanically by pressing one sample against the other. In the closed-fluid experiments, the pH of the solution was fixed to 7, 9, 11 and 13, the applied stress was approximately 200 MPa and temperature 25°C. The flow-through experiments were conducted at three different temperatures (35, 50 and 75°C) at the same pH 11.7. The value of the applied stress was 7.32, 13.72, 21.42 or 25.27 MPa. During each of these dissolution tests, the solution was regularly sampled and analyzed by an Inductively Coupled Plasma-Atomic Emission Spectrometry technique to measure Si-concentration. With the measured Si-concentration, a dissolution rate constant was computed the different pH, stress and temperature conditions. The rate constant is proportional to pH, stress and temperature, as indicated in the literature. It should be noted that the rate constant for the highest stress (200 MPa) was considerably greater than for the other cases. In addition, island-channel patterns characterized by micro-cracks a few nanometers in length were seen on the dissolved parts of the samples. The findings and the measured data in this paper may be useful for the future development of theoretical models for pressure dissolution and its validation.  相似文献   

Effects of the copepod community structure on fecal pellet flux in Kagoshima bay,a deep,semi-enclosed embayment     

Toru Kobari  Hiroyasu Akamatsu  Masato Minowa  Toshihiro Ichikawa  Kazuo Iseki  Ryuji Fukuda  Masataka Higashi 《Journal of Oceanography》2010,66(5):673-684

Seasonal changes in the shape and size composition of fecal pellets were investigated with sediment trap samples from 50 and 150 m in Kagoshima Bay to evaluate how the mesozooplankton community affects fecal pellet flux. Deep vertical mixing was evident in March, and thermal stratification was developed above 50 m in June, August and November. Chlorophyll a, suspended particulate organic carbon (POC) and copepod abundance were uniform throughout the water column during the seasonal mixing and concentrated above 50 m in the stratified seasons. Calanoids were the most predominant copepods in March and poecilostomatoids composed more than 45% of the copepod community in June, August and November. Fecal pellet fluxes at 50 and 150 m were the highest in March, nearly half of POC flux. The relative contribution declined considerably in the other months, especially for less than 4% of POC flux in August. The decline was corresponded to the predominance of cyclopoids and poecilostomatoids. Cylindrical pellets dominated the fecal matters at both depths throughout the study period, while larger cylindrical pellets nearly disappeared at 150 m in June, August and November. Copepod incubation revealed that cylindrical and oval pellets were egested by calanoids and the other copepods, respectively. We suggest that cylindrical fecal pellets produced by calanoid copepods contribute to feces flux but the predominance of poecilostomatoids and/or cyclopoids decreases feces flux via the increase of oval pellets and fragmentation of larger cylindrical pellets.  相似文献