Estimation of physical properties of rock is essential to design rock structures and to evaluate the stability of rock slopes. It is well known that rock properties often vary from site to site, and even from specimen to specimen. So, in many cases, it requires many rock samples, much effort and cost to obtain the reliable data. In this study, an efficient testing method with small rock specimens was proposed and examined. At first, the preparation process for a cylindrical specimen, 10mm in diameter and 20mm in length, was developed. In the experimental work, the transparent triaxial vessel, developed by Okubo et al., was modified and used for the small specimen. Triaxial compression tests with constant loading rate were conducted with small specimens of Tage tuff, and it was found that cohesion, C, and angle of internal friction, φ, can be precisely obtained. By this test, the loading rate dependency of a stress-strain curve can be also obtained by just one small specimen with the loading rate alternately switching during a test. Small specimens are easy to carry and it is effective especially for geophysical researches in foreign countries. So, in this study, triaxial compression tests, noted above, were also conducted with rocks obtained around the Three Gorges Reservoir in China.
Discontinuities in rock masses have an important influence on the deformational behavior and stability of deep underground spaces, and the surface roughness of discontinuities in rock masses is an important factor to analyze the mechanical and hydraulic characteristics of rock joints. In this study, we carried out direct shear tests on rock joints under both constant normal load (CNL) and constant normal stiffness (CNS) conditions, and measured the surfaces of rock joints before and after shear by using a 3-D laser scanning profilometer system. By using the projective covering method (PCM) and the measured data, we evaluated the relation of surface characteristics of rock joints to their shear behaviors. Moreover, a new hydro-mechanical test apparatus for rock joint was developed, based which a number of coupled shear-flow tests were conducted to estimate the hydraulic behavior of rock joints during a shear process.
The propagation of microcracks in granite was studied experimentally, focusing on the effects of the temperature and relative humidity on the properties of P-wave propagation. Since it is difficult to observe the propagation of a microcrack directly, P-wave propagation was investigated while controlling the temperature and relative humidity. The results showed that changes in the temperature and relative humidity of the surrounding environment affected the P-wave velocity and amplitude. An increase in the relative humidity affected the P-wave velocity if the temperature was high. On increasing the humidity at high temperature, the P-wave velocity decreased due to subcritical growth of microcracks arising from stress corrosion. We concluded that subcritical growth of microcracks arises from thermal stress and increased humidity.
To investigate the effect of the degradation on the mechanical behavior, the degraded rock samples were prepared to the uniaxial compression test. The degradation methods are divided into two types. One type is submerged in the 10% saline water (10%NaCl) for 90 days, and another one is freezing and thawing for 240 cycles. The degraded Småland-granites were preserved in saline water. Kurihashi-granodiorite, Tage-tuff and Funyu-tuff were imposed on freezing and thawing test to make degraded state. The damage parameters were identified from the stress-strain relation obtained from the uniaxial compression tests. The damage parameters are Kv, nv, Kd, nd and B0. Kv and nv are related to expansive strain. Kd, nd and B0 are subject to behavior of Young's modulus. By investigating the change in the damage parameters of the degraded rock, the effect of the degradation was tried to infer. As the results, it was inferred using the damage parameters that the Småland-granite becomes more expansive material and the damage occurs earlier due to saline water degradation. Moreover, it was considered that the Kurihashi-granodiorite and Tage-tuff become more expansive and the axial strain at the failure decreases by freezing and thawing degradation, however the axial strain of the Funyu-tuff at the failure becomes large. It was found the proposed damage parameters can be good index for volumetric strain behavior after degradation.
The aim of this paper is to study the mechanism of pore pressure response in soft rock excavation. During a cavern excavation for investigating the Excavation Disturbed Zone (EDZ) of the radioactive waste disposal cavern, pore pressure responses near side-wall of cavern were shown as follows : i) at the 1st bench excavation, pore pressures went up temporarily and then went back to ordinary state. ii) at the 2nd bench excavation, they went down temporarily and then went back to ordinary state. It is supposed that these pore pressure responses would be problems proper to soft rock. The mechanism of the pore pressure response is numerically proved by applying the three dimensional hydro-mechanical coupled finite element analysis.
In mountain tunnel construction projects, geological surveys as typified by borehole exploration and seismic exploration are conducted prior to design works by project owners. In this investigation phase, the limitation of budget allocated to survey makes it impossible to construct a lot of boreholes, which figure out the correct geological condition but lead to substantial cost. Seismic exploration result therefore has a large share of estimation of geological condition. However, in the estimation with seismic exploration, there are some accuracy problems caused by assumptions for seismic velocity analysis. In fact, some cases that ground condition in construction phase differs substantially from that in design phase. From such a view point, this study aims at developing a reasonable methodology estimating the ground condition by integration of seismic exploration result and borehole exploration result. In details, seismic velocity in the project site is estimated by them with ‘external drift kriging method’, which is one of the geostatistics methodologies. And, ground condition is estimated by the seismic velocity with the core point evaluation method calculated by tunnel face point evaluation. Furthermore, this methodology has been applied in the actual mountain tunnel construction project. Finally, the result made it clear that methodology proposed in this paper was very effective to estimate the rock classification for a mountain tunnel design.
Generally, the groundwater flow in rock slope depends on the direction for the development of rock joints sets, those are very complicated. It is a very important problem on civil and disaster prevention engineering to grasp the groundwater behavior included to the flow conditions in rock slope. In particular, the groundwater flow in a rock slope which has random joint sets is very complicated, and the specific methods which to monitor this flow don't have been developed. The electric resistivity methods have been mainly used to make a survey of the aquifer. However, the investigations in associate with the continuous monitoring of the groundwater flow in rock slope are very few. In this paper, the continuous change of electric resistivity are measured in order to monitor the movement of groundwater flow in rock slope site by dipole-dipole electric resistivity technique on the period of rainfall, and the proposed analysis of groundwater flow in this slope based on the measured resistivity data are tried out. As the results, it is shown the possibility that proposed technique is very useful for the monitoring of groundwater flow in rock slope, and the groundwater conditions through the fracture zone and the rock joints in this site are monitored by this technique.
In this research, the applicability of the satellite multispectral data to the predictions of slope failures has been attempted by using the data characterized by its broadness, synchronism, and periodicity, and by analyzing the causalities of various elements considered to be involved in the slope failures through the use of the qualification theory II. Moreover, the risk assessment chart for slope failure will be made based on the result of it, which ultimately will make it possible to specify the slopes with failure risks on the basis of the development of risk assessment system for slope failure.
High-resolution tilt meters have been applied to measure subtle underground tilt variations. As one of the application of high-resolution tilt meters system, the tilt variations recorded by the tilt meter can be used to monitor the distribution of underground volumetric deformation for CO2 injection. The signal recorded by the tilt meter is frequently affected by noises. In order to monitor the flow zone of injected CO2 using the tilt meters, it is important to consider eliminating the tilt variations due to noises such as earth tide, ground vibration, temperature variation, atmospherical pressure change, rainfall, and snowfall. In this paper, using the tilt data obtained from the observation field in Yubari, Hokkaido where high-resolution tilt meters are installed during CO2 injection test, we tried to estimate the tilt variations influenced by rainfall and snowfall. The tilt variations are theoretically determined by the elastic modulus of the surface soil in the field. First, we estimated the elastic modulus of the surface soil in the observation field using the load test and evaluated the tilt variations when removing snow using the estimated elastic modulus. Second, applying the tank model to precipitation data in the observation field, we estimated the tilt variations influenced by rainfall. The estimated tilt variations influenced by rainfall and removing snow are fit to tilt values observed in the field. Estimating tilt variations by rainfall and snow fall using the load test and the tank model is effective to evaluate the tilt variations influenced by the external factors.
As is known, there are many fractures in rock slope, and these fractures are often the cause of failure. Especially, the mechanism of toppling failure depends on fractures in rock slope. In this paper, two-dimensional simulation analysis and visualization for toppling failure of rock slope by distinct element method are carried out. In related with this simulation, the tensile stress of rock mass can be tried to be expressed by bonding theory. The rock slope model with this analysis can be freely setting the slope shape and the location of joints. Using this analytical model, it is tried to be simulated an actual toppling failure of rock slope. As the results of this analysis, it is recognized that this simulation can be expressed on this toppling failure phenomena. Moreover, the process of toppling failure can be visualized.
Based on mass conservation law a coupled scheme of diffusion and seepage is given for porous media saturated with a multi-component solution. Note that both phenomena have independently treated in the classical theory of porous materials. In the seepage problem we shed light on a physical implication of seepage velocity. In the diffusion problem we show sorption can be introduced on concepts of a source term, a distribution factor or an equation of adsorption isotherm. A practical procedure to evaluate diffusion coefficient is also shown.
At the construction site of underground facilities, such as tunnel and cavern, geological investigations using borings and elastic waves are conducted to grasp geological conditions. It is practically impossible, however, to clarify uncertainties in geological conditions (hereinafter referred as geotechnical risks) of the whole construction site in the phase of feasibility study, F/S. Therefore, the construction cost, which is estimated based on geological data obtained in the phase of F/S, will overrun if the actual condition is worse than expected. This cost variation risk is interested by sponsors and lenders of the construction project, for it is closely connected with cash flow, which represents the project profitability. From such a viewpoint, this study aims to propose a project investment evaluation method considering variations of construction cost caused by geotechnical risks. In details, a geostatistical approach, such as indicator kriging, is utilized to calculate the variations of construction cost. The cost variation risk is represented by the risk curve, which is widely used theory in the field of financial engineering. Moreover, project financial analysis is carried out by using investment evaluation indices, such as Project IRR, Equity IRR, and DSCR, which are useful for sponsors and lenders. These values are calculated in the model of dynamic cash flow with construction cost variations caused by geotechnical risks.
Heterogeneous vapor phase reaction of cellulose powder and wood meal with maleic anhydride (MA) was carried out at 140 to 180°C under the existence of excessive amount of MA to the sample without catalyst. The reaction product was fractionated depending on the stability of the formed linkages by additional heating and water leaching. The weight percent gain (WPG) after heating was regarded as a measure of net amount of the product, and analyzed by means of reaction kinetics. Concerning the cellulose powder, it was found that only a part of amorphous region of cellulose participates in the reaction, and that the ratio of stable linkages to unstable ones increases at elevated temperature because of low ultimate WPG compared to the theoretical one and its remarkable dependency on temperature, respectively. Meanwhile, another rate equation was applied to the data for wood meal, in which the contributions of cellulose and substances except for cellulose (lignin and hemicellulose) were separately taken into consideration. The results showed that the dependence of ultimate WPG on reaction temperature was not significant for the substances except for cellulose. The apparent activation energy estimated from the rate constant for the substances except for cellulose was about 40 kJ/mol, which suggests the diffusion-controlled reaction. The rate constant and ultimate WPG suggested the relatively lower reactivity for cellulose than that for the substances except for cellulose.
The effect of a duplex surface modification on the fatigue properties of Ti-6Al-4V alloy was examined. This method was composed of plasma carburizing and fine particle bombarding (FPB) treatment. Plasma carburizing at the first stage was conducted to form a hardened layer due to the diffusion of carbon. FPB treatment at the next stage was aimed for eliminating the brittle compound layer which was formed at the outermost surface and introducing compressive residual stress. In the case of the material plasma-carburized for 14.4ks at 1123K, cracks were initiated from the compound layer at relatively low stress amplitude level, so that the fatigue strength was greatly reduced. When the plasma-carburized material was further FPB-treated using SiC particles and high hardness steel particles, the compound layer was completely eliminated and compressive residual stress was introduced. As a result, the initiation sites of fatigue cracks were moved to the inside of the material just under the hardened layer and the fatigue strength was recovered to about the fatigue strength level of the untreated alloy. The above results showed that the duplex surface modification method examined in this study was effective to form the hardened layer which can improve the wear resistance without the great reduction in the fatigue strength of Ti-6Al-4V alloy.
GaAs epitaxial layers were grown by organometallic vapor phase epitaxy (OMVPE) using TEGa and TBAs over a wide range of growth temperature (350°C-700°C) and V/III ratio (2-9). GaAs with excellent surface morphology was obtained when the growth temperature was higher than 600°C. The GaAs surface tended to be rough with decreasing growth temperature below 550°C. When the growth temperature was decreased to 400°C, p-type GaAs was obtained with specular surface. The hole concentration increased with decreasing V/III ratio. The hole concentration was as high as 5.5×1017 cm–3 for the sample grown at 400°C with V/III ratio = 2.