The undisturbed samples are obtained from the Higashi-Osaka sensitive clay area in the eastern part of Osaka. By the examination of physical, chemical and engineering properties of the clay, it is clear that the sedimentary environment, leaching and consolidation stress history have effects upon the clay properties, as follows. The clay accumulates under two different types of environment, i.e. the upper is non-marine clay and the lower is marine one. The both clay are influenced considerably by leaching and become high sensitive clay. As the properties of bottom clay of the lower is close to those of non-marine clay because of the leaching and the over-consolidation state, the depth distributions of water content, void ratio and so on are bowed. The strength is mainly depended on the overburden pressure. The consolidation properties of the sensitive clay are affected by the methods of loading, i.e. incremental loading and constant rate of strain loading. And the degree of soil structure appears in the overshoot of e-log p curve of constant rate of strain loading.
In this study, the static and impact splitting tensile tests were carried out by loading the cylindrical mortar/granite specimens horizontally, and the crack propagation velocities were obtained by the image analysis using the ultra high-speed video camera, which is the fastest in the world, developed by Etoh et al.(2003). The correlations between the impulse and the crack propagation velocity indicate that there appears to be a critical state in which the crack propagation velocity does not exceed a certain value even though the increased impulse is applied. The critical value obtained was 2.6km/s for both mortar and granite specimens. Furthermore, crack propagation velocity determined by the image analysis was verified by the dynamic strain analysis.
Centrifuge model tests were conducted to investigate the failure behavior of the composite ground improved by Sand Compaction Pile method, which consisted of sand piles and clay layer. In the model tests, the improved ground under a caisson block was leaded to failure by backfill loading. Results of model tests showed that the improved portion deformed toward the sea side with bending deformation mode. Circular slip analyses which simulated the model tests estimated large ground stability. Limit equilibrium analyses considering bending and sliding modes were carried out to be compared with the centrifuge model test on the failure behaviors. The results demonstrated that the limit equilibrium method on the bending mode closely approximated the model test of the improved ground under backfill loading.
The Deep Mixing Method, an in-situ soil stabilization technique using cement and/or lime, is often applied to improve soft soils. The group column type improvement is extensively applied to stabilize foundations of embankment or lightweight structures. The improved ground design procedure in Japan assumes two failure patterns related to external and internal stabilities. External stability is evaluated for the possibility of sliding failure, in which DM columns and clay between show horizontal displacement on a stiff layer without any rearrangement of columns. For internal stability, the possibility of rupture breaking failure is evaluated by slip circle analysis, assuming the shear failure mode of DM columns. In this study, a series of centrifuge model tests was carried out to investigate the internal stability of improved ground under embankment loading. This paper describes the failure modes of DM columns and a proposed simple calculation that takes into account the bending failure mode.
Authors have developed a technique, called the cement-mixing and mechanical dehydration (CMD), as one of waste recycling and pollutant stabilization techniques. In order to investigate the strength improvement of the CMD in terms of physical properties of sample and cement mixing condition, unconfined compression test was performed for dredged clay at Kumamoto port, Kaolin clay, Masado (decomposed granite), Toyoura sand and blast-furnace slag treated by the CMD. Based on the result of unconfined compressive strength, principal component analysis was performed for the purpose of investigating the main factor to obtain high-strength cement-treated soil. Finally, the multiple linear regression function consisted of plastic limit, degree of saturation and water-cement ratio was proposed to estimate the unconfined compressive strength of soils treated by the CMD.
This paper describes the field experiment of permeation grouting for soil improvement using horizontal directional drilling and chemical grouting. The rapid permeation grouting method was newly developed and subjected to the field test. Five improvement bodies were made applying different grouting processes and performance of the present method was found to be feasible. Investigations were conducted after grouting, which included the removal of overburden, direct observations of the improved bodies and laboratory tests performed on undisturbed samples. Effectiveness of improvement was found through unconfined compressive strengths and cyclic loading performance compared with the original soil.
Static design for soil nailing is based on both of the effects of tensile force developed in reinforcement (internal stability) and overall stability of reinforced zone (external stability). Authors have already obtained the result that external stability due to restraint effect is more important for the actual design of reinforced cut slope in the ordinary condition. On the other hand, usual design method takes no consideration of the stability under seismic load condition, so it is necessary to identify the behavior of the reinforced structure under seismic loading. Present study employed New-Mark method and distinct element method to investigate behavior of the reinforced slope due to seismic loading. Finally, following conclusions were obtained. If the reinforcement installed at the interval that the restraint effect sufficiently works in the ordinary condition, the deformation of the reinforced slope under the seismic loading is controllable to small value, and the stability may be guaranteed.
In recent years, various reinforced earth methods of natural slope are proposed. The authors also proposed a new reinforced natural slope method which consists of five main parts such as rock bolts, tie rods, steel wing plates, cap plates and pressure plates and has a holding effect of slope surface by combining with five parts. We have investigated and confirmed the surface holding effect on stabilizing mechanism of natural slope through direct and zone shear tests. In this paper, we investigated the surface holding effect through direct and zone shear tests and compared the proposed method with concrete frame method with reinforcements about the surface holding effect. And we also performed the same tests in a different ground condition. As the results, the surface holding effect on stabilizing mechanism of dense sand was clear in the zone shear test. It was confirmed that the proposed method and concrete frame method have similar shear strength and surface holding effect in the dense sand.
This paper shows an effect of steel chain on reinforcement of fill based on pull out test results of large scale. The pull out resistance of steel chain is taken account apparently by dividing into the two components, role of inner frictional angle and dilatancy effect. Tests were conducted by combining different kinds of chain shapes and fill soils, and comparing with pull out resistance of different reinforcement materials in the markets. A basic concept in this study is a frictional correction factor modified by the reference pressure of 100kN/m2. This factor is clearly described to have the dilatancy effect similar with the behavior of compacted soils. And the governing equations are proposed individually for the each role of inner frictional angle and dilatancy after the phenomena in the test results is reviewed.
This paper shows impermeable properties of H-jointed steel pipe sheet piles (SPSPs) and H-H joints on impermeable walls 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 and it was clarified experimentally that H-jointed SPSPs with H-H joints can demonstrate the hydraulic conductivity of the 1×10-8cm/s order. The features in maintenance and management repair of the H-jointed SPSPs with H-H joints for the conventional steel pipe sheet pile are also shown.
Recently, light weight soil made of dredged slurry with cement and air foam is applied to waterfront construction. The characteristics of this material can be influenced by the seawater when it is used to coastal area. And it can be weathered if the water is absorbed into it. These phenomena are affected by absorption properties of the material. The objective of this study is to evaluate absorption properties of light weight soil with air foam under wet sand condition using micro focus X-ray CT scanner. In this paper, a series of absorption tests was conducted for specimens under both water and wet sand condition, and absorption mechanism was investigated by CT scanning the specimens during absorption tests. And then, the light weight soil with air foam for backfilling a quay wall was sampled at Kobe Port Island in 2005. This field was the first application of light weight soil with air foam and reconstructed due to Kobe earthquake in 1995. And the absorption properties of these samples surrounding wet sand were investigated with X-ray CT scanner. Based on these results, the absorption property of light weight soil with air foam under wet sand condition was different from that under water condition.
It is often being used for construction works such as backfill, void packing and widening of embankment because the foamed cement milk (FCM) consisting of cement, water and air bubble is a lighter and more fluid material. On one hand, the geotextile which has function to strengthen earth structure with a tensile resisting force of fiber has been employed in the reinforcing construction of banking and reinforced soil wall method from the past. In the present study, we have devised a material combining these advantages namely the geotextile-made bag (hereinafter referred to as “FCM bag”) which was filled with FCM, and have ascertained its efficiency as pavement materials by examining the bending strength of square column specimen and the elastic modulus of slab sized to actual execution. According to result obtained from the laboratory test, both bending strength and deformation before reaching a failure of FCM bag tended to become larger than those of specimen without bag. This is considered to be the effect of adhesion between solidified FCM and an inner side of bag on increase of a tensile stress due to bending occurring in specimen. Secondly, we carried out the non-destructive bearing capacity test by dropping a weight as to the slablike FCM bags (a length of 5m, a width of 2m and thickness of 0.15 to 0.2m) which were laid on improved ground and conventional ground. Having executed the inverse analysis with measurement records following the site investigation, it was found that the elastic moduli of FCM bags were equal to or greater than those of about 0.5m thick stabilized layers. Moreover, the output consequences of the structural calculations of asphalt pavement using multi-layer elasticity theory indicated that the appropriating of FCM bag to subbase course brought a reduction in thickness of pavement, providing elastic modulus of subgrade exceeded 40MPa. Based on such results, it can be concluded that the FCM bag is particularly suitable for material of the subbase course built on soft subgrade, because of its superior lightness and its prominent attendantness against flexural tension.
Physical and chemical properties of cement based secondary materials, such as waste concrete aggregates and cement stabilized wastes, may change significantly under environmental conditions due to the loss of soluble salts and/or the surface wearing. Thus, it is necessary to develop the testing method to simply evaluate their long-term leaching behavior. In this study, three different acceleration tests, intermittent wetting-drying test, freezing-thawing test and abrasion test which are considered to actually occur in field conditions, are conducted respectively for waste concrete aggregate (WCA) to evaluate the effect of the exposure to these conditions on the leaching characteristics of hexavalent chromium (Cr(VI)) contained in the mortar of WCA. Leaching amounts obtained are compared with those in the conventional batch leaching test. Testing results indicate that the exposure to these accelerated conditions increases the leaching amount of Cr(VI). Particularly, effect of the intermittent drying-wetting is most significant. Leaching amounts of granular WCA exposed to these conditions are no more than that in the conventional batch leaching test, which is conducted for crushed WCA with < 2mm in grain size. This finding suggests that the Cr(VI) leaching amount of WCA exposed under environmental conditions, such as intermittent wetting-drying, freezing-thawing and abrasion, can be conservatively estimated by the conventional batch leaching test.
With the aim of using granulated coal ash mixed with natural sand as geo-material, laboratory experiments were performed on the composite material to understand its cyclic shear characteristics. A series of undrained cyclic shear tests was performed on loose samples of the composite material to assess the effect of the mixed proportion on the cyclic shear characteristics. The tests revealed that (1) the composite material in which the proportion of granulated coal ash mixed was about 50% or more has cyclic shear strength almost equal to that of pure granulated coal ash, irrespective of the type of natural sand used ; (2) The cyclic shear strength of the composite material increased when the particle strength of the natural sand was low ; (3) When the composite material consisted of about 30% natural sand, the initial shear modulus G0 of the mixture was almost equal to that of granulated coal ash. Based on these test results, it was shown that when the mixed proportion of granulated coal ash was about 50%, the cyclic shear characteristics and dynamic deformation characteristics of the composite material were almost similar to those of pure granulated coal ash.
The purpose of this study is to develop a new geo-material using recycled scrap tire. In this study, triaxial compression test with X-ray CT scanning was conducted for the material of treated soil mixing with tire chips and cement. The material of tire chips can be realized as an elastic property and in order to evaluate the effect of the property of tire chips in the soil, treated soils with different mixing materials such as sand particles as a rigid materials and EPS beads as an elasto-plastic materials were also examined. Based on a series of triaxial compression test with CT scanning for all the treated materials, the engineering properties of these treated soils were discussed. Finally, the deformable characteristic of the treated soil with tire chips was confirmed using X-ray CT scanning, which are visual CT images and the results after image processing analysis.
An effective strain measurement system for small region in electronic packages using digital image correlation method (DICM) was developed. The accuracy of measurement using the DICM was affected by the distortion of captured images. An error correction method using a piezo-stage was proposed to improve the accuracy of the DICM. The measured distribution of thermal strain in a print circuit board accurately correlated to the macroscopic warpage measured by a laser displacement meter. It proved the accuracy of the measured strain. The distributions of thermal strain in chip embedded print circuit boards were measured using the DICM. The measured distributions of strain qualitatively corresponded with those calculated by the finite element method.
The purpose of this study is to determine the tension softening diagram and post-crack tensile strength of polypropylene fiber-reinforced lightweight concrete from bending tests and pull-out tests. Lightweight concrete has been actively applied in civil engineering applications, because the lightweight concrete is effective to reduce the dead load of structures and to improve the earthquake response of substructures. The addition of discontinuous fibers to cementitious materials drastically extends the toughness and strength of concrete. The tension softening diagram and fracture energy are important factors to analyze the mechanical behavior of concrete structures. And also, the post-crack tensile strength has been applied to predict the shear strength of fiber-reinforced concrete beams. In this study, the tension softening diagram and post-crack tensile strength of polypropylene fiber-reinforced lightweight concrete was determined by the bending test and the method based on the poly-linear approximation analysis. Furthermore, the post-crack tensile strength was clarified by the fiber-matrix interfacial bond strength obtained from the pull-out test.