Bottom clay layer at the coastal landfill site is required to maintain its hydraulic barrier performance even if steel piles are installed through the clay layer to ensure the bearing capacity of structures constructed over the landfill sites. The transmissivity of the interface between the clay and the steel was measured with a newly-developed rigid-wall permeameter, which has been designed to measure the side-wall friction. Kaolinite clay specimen was pre-consolidated at 90 or 180 kPa, and trimmed with its diameter of 2 mm smaller than that of the permeameter cell to intentionally create a gap between the clay and the steel side-wall. A hydraulic gradient across the specimen was applied under the vertical pressure ranging from 11.3 to 360 kPa. As the vertical stress increased, the friction between the clay and the side-wall grew larger, and the interface transmissivity decreased. The measured transmissivity was very low, when the clay was under a normal state of consolidation or the OCR (over-consolidation ratio) was smaller than 1.5, and ranged from 0 to 2×10-7 cm2/s. Two different indices of equivalent hydraulic conductivity were proposed, namely, one gives the equivalent leakage rate and another gives the equivalent seepage velocity, to verify the adverse effect of the steel pile installation on the barrier performance of the clay layer. Although the experimental work presented in this paper represents the preliminary investigation and the simplicity of the test program limits the application, it is considered that the installation of piles through the bottom clay layer at coastal landfill sites may not induce the leakage flow under the certain conditions in which the clay is deformable enough against the overburden pressure to close the gap between the clay and the pile.
This paper shows application potential of H-jointed steel pipe sheet piles (SPSPs) and H-H joints on vertical cuttoff barriers used in coastal landfills. The authors have developed a number of technologies such as developing the H-jointed SPSPs and H-H joints for SPSP joint sections aimed at improving performance and widening application areas of SPSPs. Hydraulic conductivity of the H-jointed SPSPs with H-H joints was evaluated by experimental studies. In addition, a new construction technique is proposed for vertical cuttoff barriers in which H-jointed SPSPs with H-H joint is applied. The technique uses soil-cement columns to make pile driving easy and simultaneously improves the soil around and underneath the foundation of the structure.
The applicability of a granulated coal ash to construction material (geomaterial) was investigated to promote the recycling. Especially, the characteristics of the individual particle such as shape, physical properties and strength were measured. The features of the granulated coal ash were clarified in comparing with the result of the natural sands. The following conclusions were obtained. (1) The aspect ratio Ar of the granulated coal ash is lower and roundness coefficient Rc is higher than those of natural sands. (2) The void ratio of the granulated coal ash become high because of larger roundness coefficient Rc and containing intragranular voids. (3) It become clear that single particle crushing strength of granulated coal ash is lower than that of natural sands, however, its strength increase as the curing days, in the observation for 900 days. (4) It is found that single particle crushing strength of granulated coal ash doesn't depend on the particle size. (5) It is confirmed that the Weibull modulus mf of granulated coal ash is larger than that of natural sands, and the variability of maximum crushing strength is small. (6) It is found that the Weibull modulus mf doesn't depend on the particle size and curing days.
Excavating the ground which consists of the marine deposits formed during Neogen and/or Quaternary period, the acid sulfate soil occasionally appears on the execution basis. As this soil includes sulfuric acid produced with the oxidation of sulfide, the growth of plants is disturbed and it becomes difficult to improve the soil by adding a stabilizer. In general, the calcic materials such as stone powder and zeolite have been employed to neutralize the acid sulfate soil from the past. Therefore, the shells which are composed mainly of a calcium carbonate can also be considered to be useful as a material for the neutralization process. We have ascertained the stabilization effect due to the using of crushed oyster shell by comparing the amount of swelling and CBR value for soil-stabilizer-shell mixture with those for soil-stabilizer mixture. Mixing crushed oyster shell into the soil, pH value of the mixture gradually shifted to neutral with elapsed time and its water content decreased immediately. Furthermore, the amount of swelling which occurred during submergence curing was extremely small for soil-stabilizer-shell mixture and CBR value of this mixture was 1.5 to 4 times larger than that of soil-stabilizer mixture. These results indicate that both surplus soil and non-industrial waste will be utilized effectively as embankment and subgrade materials at a time.
There are many abandoned lignite mines in the Tokai region of Japan. They are now being filled with materials because of the possibility of caving and collapsing or subsidence in urbanized areas above these abandoned mines. The filling material is initially in a slurry state and it solidifies with time after filling the cavities. The main material of slurry is by-products produced at a neighboring macadam factory. The utilization of by-products as filling materials could not be done until now due to the restrictions of some regulations. There are two purposes of this research. The first purpose is to examine the suitability of various recycling materials as filling materials all over Japan. The second purpose is to develop new cavity filling materials from recycling materials. It is experimentally confirmed that some of by-products can be successfully utilized as cavity filling materials.
Soil improvement method of Liquefied Stabilized Soil Method (LSS) could not be applied for building foundation, since LSS has been mainly used as a temporary backfilling works and filling works to place the space with recycled excavated surplus soil or light-weight cement mixed soil. However, Japanese building standard law was revised, and LSS has been recognized that it has high-quality and sufficient performance to support the building structure. In this report, the design of strength and quality control method of LSS used as building foundation is proposed, and future perspective is discussed.
This paper presents experimental investigations on particular failure patterns of foundation piles found in Hyogo-ken Nambu earthquake that were probably induced by seismic up-down vibrations. Impact tests on cylindrical mortar specimens were conducted in different loading modes. Vertical splitting failure was observed in static compression tests whereas horizontal tensional fracture occurred in static tension tests and impact tension tests. Depending on the level of impact energy, failure patterns in impact compression tests were found varying from cone splitting failure to X-shape shearing failure to cone shearing failure to 45-degree shearing failure, and to horizontal tensional fracture due to reflection stress wave.
Sand compaction pile, SCP, is widely adapted to reclaimed ground as a counter-measure against liquefaction of ground during earthquake. However, many case studies imply that the current design with evaluation of improvement effects by N-value is, considerably conservative. In this paper, we propose a new evaluation method for the over-all dynamic properties of the improved ground in terms of a finite difference analysis and a non-linear seismic response analysis with homogenization theory. The finite difference simulation of seismic waves shows that both share wave and surface wave propagate with constant velocity, which can be estimated by homogenization method, even if in heterogeneous improved ground. The overall evaluation including the lateral earth pressure increase around SCP showed that the improvement effects were controlled not only by an increase in liquefaction resistance, but also by an decrease in dynamic amplitude and the natural period; these results are valid for the seismic resistant design for reclaimed grounds.
This paper describes the restoration project done on Angkor complex in Cambodia by JSA (Japanese Government Team for Safeguarding Angkor), which is started 1994. Especially it focuses on laterite block tower's original geotechnical structure and the current earth mound of foundation using slaked lime stabilized soil as a test result of the reconstruction project. Angkor ruins have been damaged to go to deteriorate by the geographical natural cycle of dry season and rainy season. Such environmental factor have been causing deformation and making foundation harder. Hence, the seasonal change of soil characteristics had to be taken account, and accommodated for improving mound stability even with slaked lime stabilized soil which is arranged for filing. This paper shows the soil properties of the original foundation, N-value distribution in soil layers, and the relation between additive content of slaked lime and the change in the foundation property, whose strength was our goal for the laterite block tower foundation.
Conventional design method for soil nailing is based on the effects of tensile force developed in reinforcement installed in cut slope. As the tensile force is affected by the deformation of reinforced slope, the approach of the design method should be on the basis of the allowable deformation. On the other hand, it is said that the restraint effect in reinforced zone is more effective for reinforced slope stability under conditions of small allowable deformation. However, even the definition of the restraint effect for bar of reinforcement is still not clear. In this study, the reinforcement mechanism of restraint effect is investigated by distinct element method firstly, and secondly the effect of the interval of reinforcements on the development of restraint effect is examined by finite element method. Finally, it concludes that the design method of considering the restraint effect is effective to the reinforcement of high priority structure as a cut slope in important road system.
Fractography is the most popular method for failure analysis. This method, however, has been mainly applied to structural steels, and has not been always effective to cast irons. Since many factors like graphite, matrix, cast defects, and so on affect fracture of cast iron, they made it difficult to estimate failure causes from the fracture surfaces. In this study, therefore, quantitative fracture surface analysis was carried out on spheloidal graphite cast iron to improve accuracy of the estimation. When fracture surface analysis is conducted on images obtained with scanning electron microscopes (SEM) that are commonly used in the failure analysis fields, the characteristic values extracted from the images can possibly depend upon the contrast of the images. To minimize the contrast influence, we proposed the fracture surface analysis method that edges are extracted from the SEM images by differentiating them and fracture surface analysis is conducted on the texture images. The proposed method was applied to the fracture surfaces formed by a fracture toughness test. By computing run length statistics which are parameters widely used in texture analysis, we could divide the fatigue fracture surface produced in introducing a pre-fatigue crack from the rapid fracture surface produced during the fracture toughness test.
A new composite fabric has been developed for a balloon envelope possessing both excellent strength and gas barrier as well as low density, and perforation behavior under impact load is presently focused. The perforation test was experimentally conducted to clarify the effect of loading rate on the fracture behavior, together with the tensile test to evaluate the strain rate effect on the strength of the present material. Rate dependence of the stress strain relation of the material was clearly identified; the strength is significantly increased while the strain at fracture is decreased with a rise of strain rate. This fact well explains the experimental results where perforation strength is almost independent of loading rate, but the behavior is much more brittle due to localized deformation around perforated region at impact loading. It is also found that delamination of inter-laminar fibers in the composite fabric is able to relieve stress concentration and will be served to prevent a brittle fracturing independent of loading rate.
In order to improve the strength, fracture toughness and thermal stability of 12Ce-ZrO2 ceramics, Zirconia composites consisting of 12Ce-ZrO2 and 3Y-ZrO2 were fabricated by normal sintering at 1450°C and post HIP treatment at 1350°C. Some mechanical properties were evaluated for these composites. The bending strength and fracture toughness were measured by three-point bending test and indentation fracture (IF) method, respectively. The microstructures of the composites were characterized by SEM observations and TEM-EDS analysis. The phase stability in these composites were also evaluated by hydrothermal aging test at 150°C and 0.48 MPa. The addition of Y-ZrO2 into Ce-ZrO2 suppressed grain growth of 12Ce-ZrO2 matrix and improve the mechanical properties of 12Ce-ZrO2. Ce-ZrO2/Y-ZrO2 composites exhibited higher bending strength above 1000 MPa and higher fracture toughness above 8 MPa · m1/2 in the composition region of 80∼90 wt% 12Ce-ZrO2. The tetragonal→monoclinic phase transformation under hydrothermal conditions was inhibited in this composition region. It was found that the distribution of CeO2/Y2O3 in the ZrO2 matrix has a great influence on the mechanical properties and phase stability.
To clarify the corrosion resistance of ELID ground stainless steel, electrochemical corrosion tests were carried out using a three electrode electrochemical cell connected to a computer driven potentiostat. Before the tests, morphologies of the finished surfaces were analyzed by a Scanning Electron Microscope (SEM) equipped with an Energy Dispersive X-ray analyzer (EDX) and X-ray Photoelectron Spectroscopy (XPS). A very smooth surface was achieved by the ELID grinding process with the use of extremely fine abrasives. The value of the surface roughness (Ra) for the ELID ground sample was similar to that of the sample polished with an alumina powder. The corrosion properties of the ELID ground samples with a smooth surface were superior to those of alumina polished specimens. This was attributed to the ELID grinding, producing a very thick and stable oxide layer which showed a superior corrosion resistance compared to that of the alumina polished samples. Consequently, the ELID process seems to be a promised technology in this forthcoming future for bio-implants and other engineering components used under a corrosive environment.
High power spallation targets for neutron sources are being developed in the world. Mercury target will be installed at the material science and life facility in J-PARC, which will promoted innovative science. The mercury target is subject to the pressure wave caused by the proton bombarding in the mercury. The pressure wave propagation induces the cavitation in mercury that imposes localized impact damage on the target vessel. The impact erosion is a critical issue to decide the lifetime of the target. The electro Magnetic IMpact Testing Machine, MIMTM, was developed to reproduce the localized impact erosion damage and evaluate the damage formation. Additionally, droplet impact analysis was carried out to investigate the correlation between isolate pit profile and micro-jet velocity. We confirmed that value of depth/radius was able to estimate micro-jet velocity. And the velocity at 560 W in MIMTM was estimated to be 225∼325 m/s. Furthermore, surface-hardening treatments inhibited pit formation in plastic deformation.
This paper describes an experimental study of ultrasonic welding of thin ceramics and metals using inserts. Ultrasonic welding has made it possible to join various thick ceramics, such as Al2O3 and ZrO2, to aluminum at room temperature, quickly and easily compared to other welding methods. However, for thin ceramics, which are brittle, it is expected that welding is difficult to perform without causing damage. In this experiment, anodizing aluminum oxide film was used as thin alumina ceramics. Actually, aluminum was not able to be directly welded to an anodic oxide film without breakage. Vapor deposition of aluminum alloys (target material : A2017, A6061, A7075) on the film was contributed as an effective insert layer for welding at low pressure and a short duration without causing damage to the anodic oxide film. For example, the ultrasonic welding of thin Al2O3/Al was accomplished under the conditions of ultrasonic horn top amplitude of 32 μm, welding pressure of 5 MPa and required duration of 0.1s.