Diffusion in clay and mudstone is a peculiar phenomenon because of involved clay minerals. Clay and mudstone are a microinhomogeneous material. In order to understand the true behavior, first we specify the microstructure by a conforcal laser scanning microscope (CLSM) together with SEM, second the material properties of each constituent component are identified by a molecular dynamics simulation (MD), and third the macroscale characteristics are related to the macroscale behavior by a multiscale homogenization analysis method (HA). Note that the bentonite generally consists of montmorillonite with the size of about 100nm and chalcedony with the size of about 10-50μm, so we introduce the multiscale HA with mesoscale and microscale systems. We show diffusion characteristics of tritium water (HTO) in bentonite. The numerical results of this MD/HA procedure are consistent experimental ones.
Investigation of a 3D flow behavior in a single fracture is important to evaluate productivities of fractured oil or geothermal reservoirs. The Reynolds equation is conventionally adopted for a simulation of fluid flow in a single fracture, but the vertical component of the flow cannot be estimated in this method. To overcome this problem, the Lattice Boltzmann Method (LBM), which is a new numerical simulation method for the fluid flow, is applied in this paper. Consequently, the 3D flow in a single fracture is exactly evaluated by using the LBM.
The technologies of the numerical analysis made remarkable progress to understand the geoscience phenomena. In these approaches, however, the subsurface has been modeled by a continuum medium and the finite difference method, finite element method or boundary element method is adopted to solve the governing equations. Therefore, it is hard to treat the discontinuous phenomena. We applied a granular model to represent the bedrock medium to handle this problem. In this paper, we introduced the normal and shear springs to connect particles in granular model and this leads the Poisson's ratio of the medium changeable. We simulated the elastic wave propagation phenomena and also the Hopkinson bar phenomena in the granular model. The simulation results show this approach is quite useful for analyzing the fracturing and/or discontinuity phenomena in the subsurface.
Before the underground structures such as tunnels will be constructed, because of the sensitivity for the water included for the rock mass, electrical prospecting for geological surveys is often executed. However, the relationship between resistivity and the physical property of the rock mass has not quantitatively been clarified. Especially, in the jointed rock mass, it is important to grasp the influence of the joint for the resistivity. In this paper, 2 kinds of jointed rock mass model are made. One is the discontinuity model, which is made to change the open width of discontinuity by intervening the various number of filter paper for discontinuity. The other is the heated model, which is generated the micro opening crack inside of the rock by heating by the electricity muffle furnace. And then, using these models, the characteristics of resistivity for the jointed rock mass are examined.
In this paper, using natural rock joint specimens and direct shear-testing machine, the influences of joint aperture and roughness on shear behavior of rock joint are experimentally investigated. The index of joint roughens is applied on JRC, and in case of joint aperture, new index “γ” can be suggested. It is recognized that index “γ” is independent of JRC. As the results of this experiments, “γ” is very useful index to make indication of joint aperture condition, and the shear strength formula including joint roughness and aperture can be proposed.
In this paper, both the theory of Three-Dimensional Discontinuous Deformation Analysis (3D DDA), and its application to simulate rock slope failure problems are discussed. DDA belongs to one of the discontinuous numerical analysis methods, and the contact judgment and contact force computation should be concerned to produce contact forces when blocks contact to each other. It is shown that a normal contact spring is employed to calculate the normal contact forces to prevent blocks from penetrating to each other during contacts. However, the normal contact spring is deleted when blocks are leaving. In addition, the failure along discontinuous surfaces can be simulated easily by applying the Mohr-Coulomb failure criterion. The appropriate contact spring arrangement in 3D DDA follows the criterion of “No-penetration and No-Tension” to obtain correct contact forces during contacts. The new approach has been successfully applied to simulate a rock slope toppling at Amatoribashi-nishi site in Japan. The simulation results are quite in agreement with the video pictures obtained from the field. We believe that the simulation is very helpful on investigation of the failure mechanism and process, which can provide useful knowledge for study such events in future.
In tunnel constructions, heterogeneity of rock bodies such as faults and related fracture zones can be serious problem for safety management, construction planning and excavation costs. Thus, the estimate of geological conditions and rock properties ahead of the tunnel faces is strongly required and several methods of such fore survey have been proposed by many researchers. For this purpose, we have developed “DRISS”, the Drilling Survey System, for fore surveys at tunnel faces with higher accuracy, and report here the application of this system to tunnel construction sites. In this paper, we outline our fore survey system, and show the successful fore survey results including the improvement in drilling techniques at the tunnel construction site with soft rocks.
The present paper describes an improved Conical-End Borehole Method (ImCEBM) and its field application to initial rock stress measurement. The ImCEBM is an improved version of the Conical-End Borehole Method (CEBM). The improvements are made such ways as 1) an inspection borehole is bored ahead of the conical-end borehole, 2) the samediameter overcoring as that of the borehole is done. By use of the Fast Multipole Boundary Element Method (FMBEM), simulation of the overcoring was made and strains induced by overcoring are obtained. Using the strains, the conversion matrix from measured strains to initial rock stresses was determined. Field measurements were successfully carried out at a site of sandy shale and of fine-grained sandstone, respectively. Initial compressive principal stresses are, for example, 36, 12 and 7MPa, respectively directed in N100°E and horizontal, N10°E and 60° declined from the vertical, and N160°W and 30° declined from the vertical.
Core disking and tunnel deformation like rockburst have occurred at soft tuffaceous rock masses at a point 220 meters deep from the surface in Iwate Tunnel. The physical properties suggest that these rock masses have the possibility of swelling. The estimated earth pressure affecting a drilling hole is larger than five times the tensile strength of the rocks, which is considered to be a condition to cause core disking. Plate-shaped rock fragments continuously exfoliated like rockburst from the face of this tunnel, and deformation at the wall exhibited plasticity. The magnitude of this tunnel deformation is not influenced by either overburden or physical properties of rock masses, but mainly by geological structure.
Active mobilization of bearing capacity of rock mass surrounding an underground opening characterizes the NATM (New Austrian Tunneling Method) concept of supporting. There have been many attempts to give quantitative expressions for this capacity but no one has ever completely solved the question. In the first part of this paper the theoretical relations between support pressure and tunnel wall displacements are briefly discussed. We derive a simplified solution of a circular lined-tunnel in an elastic ground under the plain strain for full-slip and no-slip conditions. These two conditions at the ground-lining interface make it possible to explain the effects of shear stress transmission and relative shear displacement. The lateral free-field ground stresses for this solution are restricted to a fixed value of the vertical stresses (σV*=-p, σH*=-kp). An actual tunnel opening is excavated and supported after the load corresponding to the free-field stresses. We introduce an assumption of the actual “excavation unloading” conditions that occur during tunneling. By advancing this derivation, the strict solution is utilized successfully to construct a theoretical characteristic curve of tunneling. The characteristic curve shows clearly the bearing capacities of a tunnel lining, the surrounding ground and the total by using an index, “relative-support-stiffness”. The elastic theory of the stress distribution around tunnels demonstrates that the deviatoric stresses are maximum at the periphery of the excavation. Therefore, the rock mass may yield in the overstressed zone surrounding the excavation. Discussion here should include the dependence of the characteristic curve on the zone of yielded ground and the discontinuity in the ground. We have carried out numerical simulations for a discontinuous ground with Distinct Element Modeling. The realistic ground reaction curves by the analyses are examined with the theoretical solution derived above. We will learn that while the ground may work, more or less, as a load bearing structural component to the load corresponding to the free-field stresses, overestimation must be avoided.
Excavation of tunnel in Japan recently faces a lot of difficult conditions such that very complex geology, interaction with adjacent structures and groundwater problems in relation to environmental impact. This paper describes a new observational method executed in Inariyama Tunnel (Kyoto) intended to carry out construction with higher reliability, including groundwater control. Since Inariyama tunnel (10m diameter) crosses under an existing aqueduct tunnel at a distance of 27m, control of the mechanical and groundwater impact on the active aqueduct tunnel was considered to be a crucial issue. Very careful excavation was done with accurate measurements of deformation to eliminate instability of both tunnels. The observational method for groundwater is performed not only by a preliminary survey and numerical analysis for prediction, but also by flow rate into the tunnel and water pressure distribution measurement with 3 dimensional groundwater finite element analysis at each stage of excavation. Measured and calculated results are compared to grasp the subsequent work. Construction was successful with this proposed method.
Mogao Grottos are located at the eastern foot of the Mingsha Dunes, 25km southeast of Dunhuang town. It faces east toward Sanwei Mountain, one range of Qilian Mountains, and in front of it Daquan River runs. The caves were excavated into the cliff on the west bank of the Daquan River. The stratum in which the caves were excavated is the alluvial and pluvial Jiuquan conglomerate in which there is argillaceous and calcareous cementation. The wall paintings in the caves are subject to the severe deterioration generated by recrystallization of salt. It relates with the movement of water/moisture in rock formation. The basement of Mogao Area consists of granite and gneiss formed in the Pre-Cambrian Age. Through the satellite image analysis and geological survey, it has been clarified that the movement of ground water is governed by the fault system and the geographical nature is specified by the aggressive tectonic movement from the south.
Investigation of Ionic Migration (IM) in printed wiring board with narrow spacing between Cu conductors (<50μm) has been described, and an effect of epoxy resin coating on IM also has been investigated. An endurance test was carried out in a chamber controlled at 85°C, 85%RH and 20V. As the result, the insulating resistance remained 107Ω over the test period of 1000hr, however, deposits between the conductors were observed on the surface of all specimens by an optical microscope. From the results of observation of the deposit and element analysis by EPMA, it is clear that epoxy coating is not effective and the growth of deposits accelerates under narrow spacing condition (20μm). Furthermore, we have to be careful to interface treatment between conductors and substrates because Ni, which is one of elements composed of bonding layer, was detected in the deposits. It is revealed that the obtained results are very useful for the insulation reliability of the fine and high-density wiring.
The thermal fatigue strength of BGA solder joints is one of important properties for design. However, the traditional approach to estimate the fatigue life consumes much time and cost. As a method of evaluating the thermal fatigue lives more efficiently, the evaluation of S-N diagram by the combination of thermal fatigue tests and finite element analysis was described. To estimate the design margin, each fatigue data is transformed into normalized fatigue strength, because the distribution of normalized fatigue strength can be estimated by the small number of samples. As a result, it becomes possible to estimate the design margin with a given probability of failure and confidence level considering an effect of number of samples. Based on the obtained S-N curve with a design margin, distribution of fatigue lives for other types of BGA specimens can be also estimated without additional experiments. It is revealed that the proposed method is very useful for the reliability estimation of solder joints.
An adsorption of proteins on the needle-like hydroxyapatite (N-HAp) after heat treatment at 100-700°C was investigated. Adsorbed amount of Bovine Serum Arubumine (BSA) as an acidic protein decreased with increasing heat treatment temperature except 700°C, whereas that for Lysozyme chloride (LYZ) as a basic protein increased with treatment temperature. Colloidal vibration potentials (CVP) of all N-HAps showed negative potentials in a phosphate buffer solution at pH6.8, and shifted to more negative regions with increasing treatment temperature. Based on the XRD patterns, the N-HAps treated at 100-400°C were HAp phase only, but β-TCP (Ca3(PO4)2) phase appeared in the N-HAp treated at 700°C.