In order to investigate the efficiency of the in-situ electrokinetic method for the remediation of the soil contaminated with heavy metals, a mathematical model based on the physico-chemical transport phenomena has been constructed and the remediation process is simulated numerically with use of the model. The elecrokinetic remediation is realized by applying a fixed low voltage direct current between the anode and the cathode which are set into the contaminated zone and saturating the zone with purge water. The numerical simulations show that the electrokinetic method is effective for the remediation of the polluted soil especially with heavy metals. The electric current and the electric potential between the anode and the cathode are the important operational variables for the elecrokinetic remediation. It has been proved that the removal process can be divided into the two stages, i.e., the first stage and the second stage, according to the manner of the time variation of the electric current (i.e., the time variation of the spatial characteristics of the removal). The remediation process progresses from the anode to the cathode.
Recently, a great deal attention is being has attached the problem of durability of strength and impermeability of grouted sand. However, the durability has yet to be fully clarified. This paper examines the prediction methods of the long-term strength of grouted sand concerning the durability. As a result, we were able to obtain two estimation methds. One is the xtrapolation method, other is the Arrehenius Plot method of the same shape. It is possible to estimate the long-term strength of grouted sand by these methods.
Kanto loam mainly consists of allophane clay mineral. Geologically, Kanto loam is distributed in the order of Tachikawa loam and Musashino loam from earth surface. Tachikawa loam is the newest stratum and its allophane content exceeds 50%. Whereas, the allophane content of Musashino loam is less than 40%. Kanto loam has very high water content and high sensitivity caused by containing allophane clay mineral. Therefore, the most effective stabilization of Kanto loam is chemical one such as quick lime stabilization. The equation of dehydration of quick lime cannot apply to Kanto loam, because allophane in Kanto loam must have influence on it. Lime stabilized soil is high alkaline, and then the leached water through the soil becomes high alkaline. As the buffer ability for acid and alkaline solution increases with increasing allophane content, Tachikawa loam has higher buffer ability. On the other hand, Musashino loam can be expected to increase the strength by adding quick lime. Thus, the embankment considering the environment can be designed by using geological formation of Kanto loam, such that Musashino loam is used for the embankment material and Tachikawa loam is used for the buffer material. The result of this study shows that the thickness of the buffer material is related to the thickness of the embankment material and the rate of allophane content of both materials.
In the Law for the Utilization of Recyclable Resources, the reasonable disposal, restraint of generation and decrease of cons-truction by-products are demanded. Recently, processing and disposal of construction surplus soils are common subjects of metro-polises, and the development of recycling technology of soil generated from various kinds of sites is very important. The purpose of this study is utilization of the surplus soil that does not reach the material sta-ndard. In this paper, the authors report about the new soil improvement machine that mixes unreusable soils such as soft soils, gravelly soils, concrete lumps and so on. The machine is able to change the unreusable soils into embankment materials in the short term. That techno-logy has been developed with the aid of the Kinki Technology Office of the Ministry of Construction. As a result, the surplus soils that are mixed with concrete lumps achieve the material standard of High Standard Levee. The utilization of the surplus soils is possible because the grain size distribution and the strength of the mixed soils has been improved. It has been made clear that the mixture performance of the new soil improvement machine is good.
As an effective reuse method of surplus soil and sludge, the authors proposed the crushed cement-stabilized sludge which is made of cement, polymer, surplus soil and dewatered sludge. Its geotechnical properties and applicability to the drainage material in sand drain and sand compaction pile methods were investigated. The geotechnical properties were almost similar to those of general granular materials except high alkaline. The crushed cement-stabilized sludge was applicable to the dranage material judging from its acceleration effect of soil consolidation.
The containment ability of Pb++ and Cd++ by cement-bentonite slurry wall and its application to minimize the spread of groundwater contamination has been evaluated. Column specimens of cement-bentonite were permeated with 10ppm Pb(NO3)2 and 7.13ppm Cd(NO3)2 solutions, and the pH as well as heavy metal concentrations of the effluents were measured. The pH showed high alkali values at the early stages, and then gradually reached 10-10.5. Pb concentration showed values between 0.1-0.2ppm in the early stage and then decreased to 0-0.1ppm, whereas Cd concentration varies between 0-0.01ppm. The mechanism of containment of the above heavy metals in cement-bentonite has been discussed with regard to formation of complex ions, pH and hydraulic conductivity. The decrease in pH comprises the deterioration of containment ability of cement-bentonite. Since the cumulative mass of Cd leaked out from cement-bentonite is linearly related to the hydraulic conductivity, lowering the hydraulic conductivity due to larger quantity of cement additions resulted in the higher containment capacity of heavy metal. Applicable duration of cement-bentonite wall in the field (which can be parametrically calculated) showed that the thickness of cement-bentonite wall and hydraulic gradient across the wall might have a significant effect on the durability of cement-bentonite wall.
For shallow soil improvement, most of the hardening materials used are powders, and a lot of the powder is air/windborne and flies everywhere, which is called “dust”. Recently, the flying dust has become a serious problem at sites near residential areas and for workers' health. The purpose of this study is to further the development of “dustless hardening materials” that contain small amounts of oil. As a result of study up to now, it has been found that the dustless hardening material is successful for the reduction of the amount of dust produced, and for the strength of the treated soil. In this paper, the amount of oil eluted from treated soil is investigated with the three types of tests in order to confirm no influence of the oil on circumferential environment. As a result, in the case of sandy soil treated, a thin loose layer is observed near the surface of specimens with small compaction energy. Then, the amount of oil eluted from treated soil is about 3.5mg/l. In the case of sandy soil treated for high strength and clayey soil treated, the amount of oil eluted is very little because there is no loose layer even with small compaction energy. It has been found that the amount of oil eluted from treated soil is extremely little in comparison with the specification limit (15mg/l) of the environmental standard. Therefore, the new dustless hardening material can be applied increasingly to a lot of construction sites in order to secure the environmental conditions.
In order to study the effect of dwarf bamboo for the stability of a slope surface, a series of laboratory tests were conducted with an intensive field investigation on the slope slid by the earthquake. As a result of shear tests, it was considered that the effect by the rhizome of dwarf bamboo is quite similar to that of geotextile. Using the parameters obtained from the tension test of rhizome, the field investigation and the earthquake record, the slope stability was evaluated by the safety factor which was given as a function of tensile force of the rhizome per unit slope length. In this analysis, it was shown that the factors were less than 1.0 during the earthquake while they exceeded 1.2 under the static condition, so that the results supported the sliding slope.
In the metro area, cheap and high quality ground improving material for backfilling is in shortage and development of its alternative is required. On the other hand, volume reduction, harmlessness and recycling of municipal solid waste (MSW) becomes necessary due to present MSW dumping sites are almost beyond their capacity. In these situations, we studied, through chemical, physical and mechanical testing, the applicability of MSW direct melting slag as ground improving material which is produced from “direct melting, recycling system” developed by us. As a result, we confirmed that the MSW direct melting slag cleared the standard of ground improving material with excellent applicability. The ground improving method stands for Sand Compaction Pile Method and Sand Drain Method in this report.
This paper describes the effect of improvement against liquefaction by using electrohoresis of Fixative materials in model ground. As a result of being electrohoresis at some Fixative materials, it was found that the case of using solution before mixing Sodium silicate No.3 and Calcium chloride is the most effective of soil improvement. And the effective voltage radient is 1.0V/cm, but the distance between electrodes is 100cm, the strength of improved ground is decreased at the center part. There is a possibility that temperature variation in ground under electric loading has an influence on strength of improved ground.
Dynamic consolidation method was used to improve loose reclaimed silty sand ground against liquefaction at Mailiao in Taiwan. Cone penetration tests (CPT) were conducted to confirm the effect of the improvement. The cone tests are very economical and speedy to evaluate the improvement. Where qc-values were below a required value set out as the improvement criterion, boreholes were sunk with standard penetration tests (SPT) and disturbed soil samples were obtained for laboratory soil tests. A correlation between qc, fs and N-value proposed by Robertson was used to estimate N-values from the cone test results of qc and fs. Liquefaction potential was then calculated from the N-values so established. This procedure allowed the authors to made quick and economical evaluation of the liquefaction potential using the cone test results.
Now, the construction sludge that is produced from sites of soil-cement diaphragm walls (SMW sludge)is disposed as industrial wastes. Therefore, recycling the construction sludge brings the effective use of resource from the viewpoint of the environment preservation and also brings the reduction of the building expenses. Two ways of recycling are thought of “Recycling A; for the material of subsequent SMW it utilizes the particle muddy water that is sifted from the SMW sludge with addition of water”, and “Recycling B; it utilizes the sludge with addition of water and soil stabilizer for backfill material.” Recycling A could get unconfined compressive strength that was higher than the original SMW by the use of the particle muddy water. Recycling B could attain reach the target value by the SMW sludge that was adopted in the “liquefied soil stabilization.”
The thermal spraying process is widely used to the metalizing of electronic ceramic for forming the electric conductor and/or the underlayer for bonding. However, mechanical properties of thermal sprayed coatings, which have an important effect on the adherent strength, have not always been clarified. Two kinds of free-standing aluminum specimens, which were formed by an atmospheric plasma spraying (APS) process and an electric arc spraying (EAS) process, were machined from the thick coatings and were used for experiments. The Young's modulus, Poisson's ratio, four-point bending strength and bending angle were measured at room temperature in comparison with a rolled aluminum plate. The experimental results suggested that the crack length and crack density in aluminum coatings, which were composed of pores and aluminum oxide, had an important effect on the mechanical properties. Namely, low strength, high ductility, high thermal conductivity and low electric resistivity could be obtained from the aluminum coatings sprayed by APS process, because of low pore volume and low oxide content.
The thermal spraying process is widely used to the metalizing of electronic ceramic for forming the electric conductor and/or the under layer for bonding. However, residual stress characteristics of thermal sprayed coatings, which have an important effect on the adherent strength, have not always been clarified. Thermal and mechanical properties were measured for two kinds of thermal sprayed aluminum coatings, which were formed by an atmospheric plasma spraying (APS) process and an electric arc spraying (EAS) process for investigating the characteristics of residual stress. It was confirmed by the X-ray diffraction technique that the residual stress of sprayed aluminum coatings over zinc-oxide substrate was always compressive in no relation to the spraying process and coating thickness. It was found that the compressive residual stress of sprayed aluminum coatings was induced by the low thermal conduction effect of zinc-oxide substrate.
The effect of shot peening on the fatigue strength of Ti-6Al-4V alloy was investigated in the temperature range of 20°C to 450°C. Specimens with a semicircular and a 60° V-shaped notches were used. The increase in fatigue strength of semicircular specimens was 34.3%, 27.6%, -7.4% and -37.5%, and that of V-shaped specimens was 26.5%, 20.9%, 0% and 0% at 20°C, 250°C, 350°C and 450°C, respectively. The shot effect decreased with increasing temperature and became null or negative at 450°C. The behavior of the semicircular notched specimens was similar to that of unnotched specimens. The fatigue strength of semicircular specimens as well as unnotched specimens was decreased drastically by shot-peening at 450°C. The decrease in the shot effect with increasing temperature could be explained as a consequence of the relief of compressive residual stress originating in cyclic loading at elevated temperatures. The fatigue strength of both the semicircular and the unnotched specimens was mainly controlled by the development of microcracks in the surface layer of specimens, and therefore the strength was sensitive to the surface roughness. At 450°C, the surface roughness remained and compressive residual stress became null during cyclic loading, so a severe drop in strength resulted in. At 450°C, the shot peened, and then electropolished specimens showed fatigue strength comparable to that of the unpeened and surface polished specimens. The fatigue strength of V-shaped notched specimens is controlled by the nonpropagating behavior of a crack developed from a sharp notch root. The fatigue behavior of this specimens is insensitive to surface roughness. Therefore, even at 450°C, where the compressive residual stress could become null, there is no negative effect as found in semicircular nocthed specimens.
The effect of residual stress on matrix cracking in unidirectional continuous fiber-reinforced ceramic matrix composites was investigated for both longitudinal and transverse directions with respect to the fiber direction. In particular, the effect of thermal expansion coefficient on the residual stress distribution have been considered. The matrix cracking strength was estimated in case of chemical vapor infiltrated (CVI), hot pressed (HP) and reaction sintered (RS) SiC matrix composite. It was confirmed that the matrix cracking strength was extremely affected by the residual stress distribution. Also, it was shown that in matrices with low Young's modulus and low thermal expansion coefficient in comparison with the fibers, matrix cracking can be prevented.
This paper presents an experimental study on the dynamic ultimate limit states of prestressed concrete (PC) and prestressed reinforced concrete (PRC) beams under high speed loading. First, the static and high speed loading tests were performed for the PC and PRC beams with different bond conditions, respectively. It was found from the tests that the ultimate deformations of unbonded PC and PRC beams become about 1.6-2.6 times larger than those of the bonded PC and PRC beams under high speed loading. Second, it was also noted that the ultimate deformations of bond PRC beams are in general about 30% larger than those of PC beams with the same flexural strength. Finally, it was found from the PC tendon strain distributions that the unbond condition of PC tendon influences remarkably on the ultimate deformations of unbond PC and PRC beams.
VAMAS project which aims to establish the standard test method of creep crack growth for creep brittle advanced materials is being conducted. The round robin tests on TiAl intermetallic compound with fully lamellar structure were carried out. Based on the results of round robin, the recommended test method was proposed. Fatigue pre-cracking was not applicable to this material as a standard method because fatigue crack deviated along the lamellar structure. In the present study, the machined V-notch specimen was recommended based on the experimental results and stress distribution analysis ahead of the V-notch. Creep crack growth properties and creep fracture mechanism of the present TiAl were clarified. Creep crack growth properties depending on test temperatures were also investigated in terms of the creep fracture mechanism for this material.
With a view to developing the high-strength Al-Zn-Mg alloy for weld structure, the mechanical properties and stress-corrosion cracking sensitivities have been investigated using the samples containing 1-2%Mg and 4-7%Zn, and under the different conditions of heat treatment. At the same time, the sample with 1.75%Mg and 6.0%Zn was selected as an alloy excelling in the aforesaid both properties. Next, 0.1-0.6%Cu and 0.2-0.6%Ag were added to improve the stress corrosion cracking sensitivity, then the stress corrosion cracking sensitivity was investigated. The authous have confirmed that the addition of Cu and Ag remarkably improves the stress corrosion cracking life, which can be explained by anodic dissolution of the grain boundary precipitates to be restrained, due to the reduction of the potential difference with the matrix.
With a view to developing the high-strength Al-Zn-Mg alloy for weld structure, the weld cracking sensitivity and the stress corrosion susceptibility has been investigated using the samples containing 1-2%Mg, 4-7%Zn, 0.1-0.6%Cu and 0.2-0.6%Ag. The additional elements of Mn, Cr and Zr were slightly added, and the weld cracking sensitivity was investigated to study the improvement of weldability. The results revealed that each element improved the weld cracking sensitivity, and particularly the improved effect proved to be remarkable with the addition of Zr. The reason is considered to be the grain size at the weld metal becoming finer due to the addition of Zr, causing the tensile stress exerted on the grain boundary at the time of solidification shrinkage to be dispersed and reduced. Various welded joints were produced by using the samples containing the chemical composition of final selection, and were subjected to the investigation of mechanical properties. The results have revealed that compared with the conventional weld metal of JIS7NO1, the proof stress of the newly developed alloy was found to be approximately 40% higher in the base metal, and approximately 30% higher in the weld metal.
In this paper, the stress functions for a half-infinite anisotropic plate with a crack parallel to the free edge are obtained. These functions, which must be satisfied the boundary conditions on the free edge, are constructed by superposition of a series of stress functions for infinite anisotropic plates with a crack. It is learned that the obtained stress functions provide finite stress concentration in the assumed fracture process zones and generate normal stresses along the edge of the crack, which is corresponding to internal pressure. Two numerical examples using the obtained functions are shown. The first is for the analysis of a rock material with a crack subjected to internal pressure. The second is for the analysis of the ground protuberance problem by grouting. The results suggest that the proposed functions be applicable to the practical engineering field.
The hole drilling method is a well-established technique for measuring residual stresses in a wide range of materials. In this paper, in order to improve the measurement accuracies of hole drilling method, several numerical results are shown in two cases such that radial strains and tangential strains around the circular hole are detected, by consideration of strain variation in the finite region of each gage area. The results obtained are summarized as follows. (1) The measurement accuracies become higher by detection of tangential strains than radial one. (2) It is necessary to calculate the strain average in each gage area for residual stress measurement. (3) The analytical theory which considers the strain variation are proved to be valid by the experiment using steel specimens.
The material recyclability of cut waste of biodegradable fabrics generated during the manufacture of non-woven fabric as a matrix material for fiber reinforced biodegradable composite was investigated. Waste product of cotton fiber was selected as representative reinforcement and the composites were molded using a simple injection molding method. In this system, the cut waste of biodegradable fabrics with lower melting point was fed into the injection machine directly together with the waste of cotton fiber. The tensile modulus and strength of molded composites increased with increasing content of cotton fiber and were discussed based on SEM observation results of fracture surface. The results suggest that the injection molding method described herein shows promise in contributing toward the material recycle of cut waste of biodegradable non-woven fabrics and waste of cotton fiber as molding materials of fiber reinforced biodegradable composite.
Thermal barrier coating (TBC) of 8wt% Y2O3-ZrO2 was made by low-pressure plasma spraying. The coated film with 0.3mm in thickness was removed from the substrate of Nimonic-263 by electropolishing. Tension and compression tests of removed films were conducted by using a specially designed gap jig. TBC films showed stress relaxation while keeping the displacement constant both tensile and compressive deformation. The X-ray method was used to measure the stress in the TBC film under bending. The stress measured by the X-ray method changed proportionally to the bending stress up to the magnitude of about 10MPa both in tension and compression. When the bending stress of about 20MPa was applied to the films, the X-ray stress did not increase because of sliding of the lamella structure. The sliding stress between lamellae was determined from the residual curvature of films after bending. It was about 10MPa, which agreed with limit stress measured by the X-ray method.