Small diameter caisson type piles have been used for the foundations of the structures built in mountainous areas, such as bridges, power lines and so on. Therefore, those piles will continue to be important foundations of the structures built in mountainous area. The small diameter caisson type piles, however, have been constructed by manpower mostly under dangerous and terrible situations. For example, digging, assembling retaining wall, spraying shotcrete, assembling rebar, and compaction of placed concrete are all carried out by manpower at the bottom of the small diameter pile hole. Furthermore, the dug soil is conveyed from the pile hole to outside, retaining wall and rebar are carried into the pile hole, in the situation that the workers are working at the bottom of the pile hole. Due to the poor construction situation, decreasing the number of young workers who take care of the future construction of piles has been accelerating. Therefore, improving the construction situation of the small diameter caisson type pile is an urgent issue, which has to be solved rapidly. The authors have proposed an unmanned construction system for the small diameter caisson type pile, in which workers do not need to go into the pile hole during the pile construction. The applicability of the system has already confirmed from test constructions of three real piles, which were performed at the two construction sites of expressway. The applicability confirmed from the test constructions as well as the details of the proposed system are summarized in this paper.

Tumuli were constructed more than 1300 years ago and have been conserved as historical cultural heritages but many of them are seriously damaged by rainfall infiltration. In the present paper, a capillary barrier formed at the coarser-finer soil interface under unsaturated condition is studied as a feasible means for protecting tumuli from rainfall induced damages. The mechanism of water shielding by a capillary barrier and the diversion capacity are quantitatively discussed by conducting model chamber tests and numerical analyses. A series of the model chamber tests indicates that a capillary barrier is formed when the coarser grained soil has lower hydraulic conductivity than that of the finer grained layer and the diversion capacity is controlled by the inclination of the soil interface, the thickness of the finer grained layer and the intensity of precipitation because these factors are related to the degree of the difference in hydraulic conductivity of the finer and coarser grained soils.

A large earthquake such as Nankai Trough Earthquake is concerned to occur in the near future and there is fear that coastal levees will sink by liquefaction. Authors proposed installing double sheet-piles into the levee and additionally combining another sheet-pile as a partition wall perpendicular to the extension direction to the levee. It has been confirmed by model tests that this countermeasure is very effective for the deformation/settlement reduction of levees during an earthquake. However, since the partition wall was modelled by the steel plate in the model tests, the effect of the joints between sheet-piles could not be taken into consideration. Authors also reproduced the model test results by using a two-dimensional effective stress analyses (code:LIQCA2D12) with high accuracy. In the numerical study, the slippage effect of joints between sheet-piles for the partition wall was taken into account. As a result, it was confirmed that the shear distortion generated between the joints weakens the constraint of the ground inside double sheet-piles, but in spite of this negative effect, the settlement of levee was reduced down to 15% compared to the case without countermeasure.

Oceanic methane hydrates are now viewed as energy resource because they contain rich methane. However, they generally exist in relatively shallow and uncemented seabed ground layer, thus large deformation and degradation of seabed sediments may occur during gas production from methane hydrate bearing sediments. Moreover, because they are often found in seismically active regions, including the Nankai Trough area of Japan, there is a risk of large earthquakes during gas production. Seabed sediments damaged by gas production may become trigger of disasteres like seabed slides. Furthermore, effects of pore pressure change induced by earthquake on methane hydrate dissociation behavior are also curious problem. In the present study, we have shown a numerical method which can simulate the seismic and chemo-thermo-mechanical coupled behaviors of seabed grounds during gas production, such as phase changes from hydrates to water and gas, temperature changes, ground deformation and the flow of pore fluids. Numerical analyses are performed for the hydrate-bearing sediments at the Daini-Atsumi knoll, Eastern Nankai Trough, Japan, where the world’s first offshore production test of methane hydrates was conducted using a predicted Nankai Trough Earthquake for investigating the earthquake-induced dynamic behavior during gas production. From the results, effects of gas production on mechanical behavior of seabed grounds during earthquake is small for this ground conditions. Small increase of the pore pressure due to methane hydrate dissociation during earthquake results in temporal stability of methane hydrates.

Partially saturated soils are composed of three phases: soil particle, pore water and pore air. The pore water forms menisci among soil particles at which suction works. Suction is higher at the upper part of partially saturated soils due to the higher negative pressure head. It is therefore likely that degree of saturation in partially saturated soils distributes in a vertical direction with different suction levels. Additionally, partially saturated soils show more brittle mode of failure compared with fully saturated soils for which investigation of distribution changes in degree of saturation and void ratio is important. In this present study, triaxial compression tests for partially saturated Toyoura sand specimens are conducted and x-ray computed tomography scans are performed at initial state and after tests. Trinarisation technique by taking into account partial volume effect is applied to evaluate the volume of each three phase, through which the distribution of void ratio and degree of saturation in a vertical direction of partially saturated trixial sand specimens are discussed. It is found that degree of saturation is lower in larger voids while degree of saturation was higher in smaller voids. At the middle of specimen where large deformation is observed, void ratio and degree of saturation significantly changes while those at the other position where less deformation is observed slightly changes.

Bearing capacity of open-ended piles installed in sandy grounds depends heavily on the degree of soil plugging. A fully-plugged pile generally produces a bearing capacity similar to a closed-ended pile. In this paper, soil plugging behavior of inner-sleeved open-ended piles driven in sandy soils is discussed. The piles were penetrated in dense and loose sands. The degree of soil plugging is discussed using a modified version of incremental filling ratio. The results suggest that loose sand produces a relatively higher degree of soil plugging. The results also indicate that the open-ended piles penetrated in dense sand produce larger penetration resistance than loose sand. The results further suggest that a pile of a taller sleeve produces a larger resistance than shorter counterparts in both loose and dense sands. The results also indicate that a pile of a very short sleeve (e.g., 10mm) produces very small or no inner frictional resistance. The results also indicate that the inner frictional resistance develops rapidly with the sleeve length in dense sand than loose sand. Therefore, we recommend a use of a tall sleeve in loose sand while relatively a short sleeve in dense sand for effective use of the inner sleeve in mobilising inner frictional resistance.

Damages to detached houses, including settlement and tilting, were reported as a result of the 2011 off the Pacific coast of Tohoku Earthquake. Because liquefaction countermeasures usually employed for public works were expensive, common liquefaction countermeasures were difficult to apply to detached houses and a clear design method for the ground improvement against liquefaction has not seen in the Building Standards Law, the effective ground treatment has not been carried out to detached houses. In this study, for detached houses, in order to propose a simplified design method capable of predicting the settlement and tilting of the houses, model shaking table tests and numerical simulation are carried out. As the result, in this paper, the following conclusions are obtained.1. Terzaghi’s ultimate bearing capacity can be calculated using circular slip method.2. The numerical analyses are found to be able to reproduce the experimental results very well.3. In the simple design method, regardless of the friction angle, the excess pore water pressure ratio is lower, the higher the safety factor is. Furthermore the water lever is deeper, the higher the safety factor is.

The two-hinge precast arch culvert has a hinge function in its main body. Thus, it harnesses subgrade reactions positively, by permitting deflection, and becomes a mechanically stable structure. Compared with a box culvert, which supports external forces by the rigidity of the member, the thickness of the members of this two-hinge precast arch culvert is small. However, because the design of the two-hinge precast arch culvert is entirely different from that of a conventional culvert, the mechanical behavior of the culvert has become an important issue. The authors conducted 1/5 scale model tests to investigate the deformation behavior in the construction stage and the seismic performance of a two-hinge precast arch culvert. In this study, the relationship between the deformation of the culvert and the earth pressure acting on the culvert during the construction process is discussed.

There are many historic masonry structures collapsed due to deformation and/or failure of their foundation ground, and then, it is demanded to investigate the deterioration mechanisms and the rational restoration methods based on the geotechnical engineering. In case of the Angkor ruin in Cambodia, buildings were constructed on the foundations consist of the man-made soil embankment and the masonry stones, so-called ‘ platform’. Therefore, to achieve the restoration ensuring structural stability, the bearing capacity characteristics of the masonry platform in various structural conditions should be investigated. In this paper, the bearing capacity analyses of the masonry foundation with different number of layers were carried out using NMM-DDA (coupled Numerical Manifold Method and Discontinuous Deformation Analysis) enhanced with the node-based uniform strain element, and the influence of the structural features on the ultimate load was discussed.

The additional pile method is a technique used to reinforce existing foundations by piles and footings. The main problem with this method is that it takes a lot of time and effort to combine the existing foundation and the additional foundation. Another problem is that the design of this method cannot be sufficiently rationalized because the load share mechanism is unclear due to the generation of the pile group effect. The objectives of this study are to develop a new high-workability combining method and to investigate the load share mechanism of the reinforced foundation. In this paper, 1G seismic loading tests are conducted on group piles, namely, 4 existing piles and 6 additional piles. Then, a simulation analysis of the loading tests is performed. Finally, a parametric analysis that simulates the superstructure and the steel outer shell is conducted.

The maintenance work of pavement is often planned based on MCI and FWD data. However, the repeated damages of pavement are observed at many places. This surface damage of pavement is partly originated by the weakness of subgrade, damage of the filled up ground and ground water. In order to avoid repeated maintenance works of pavement, the condition of earthfill structure should be evaluated by an easy logging technique from pavement surface. In this paper, the automation technique for check and diagnosis of pavement as well as earthfill structure is proposed by using surface wave logging and electric resistivity. The efficiency of the proposed system is discussed based on some case studies.

An adaptive substepping explicit integration scheme is proposed for a subloading surface plasticity (SSP) model for unsaturated soils. The constitutive laws of the SSP model are established in the space of Bishop’s effective stress and effective degree of saturation (Θ). The model includes a convex subloading surface in the p-q plane and a nonconvex subloading surface in the p-Θ plane. The convex/nonconvex subloading surface in the model may cause problems of incorrect loading-unloading decisions during the stress update. A Double Cosine loading-unloading decision method (DC method) is revised and embedded into the explicit integration. The local error of the effective degree of saturation is introduced in the error control for each substep. The performance of the DC method is discussed. The importance of involving the effective saturation in the error control is also demonstrated via numerical examples.

Bangladesh is almost a complete delta area located at the apex of the Bay of Bengal in the Indian sub-continent of South Asia. The land is composed of around 80% clay soil, such that rural soil roads are impassable in the rainy season. For this reason, the locally available geotextile technology, called Do-nou technology in Japanese and consisting of the piling up of soil-filled sacks, was applied to build a base course by members of the community. Do-nou technology has been adopted to reinforce the bearing capacity of the base course, which normally consists of sandy gravel materials, to improve trafficability. However, in rural areas of Bangladesh, it is difficult to obtain reasonable base course materials. In this study, crushed bricks have been identified as one of the alternatives for base course materials. It is anticipated that reinforcing the shear strength of the inner materials through Do-nou technology will make crushed bricks applicable to the base course of roads. Crushed bricks are available and cheap, and they can be utilized as coarse aggregates of concrete as a substitute for traditionally applied crushed stones. In this paper, the construction costs and the productivity are examined in advance of further research.

An extensive experimental study on mechanical properties of a sandstone subjected to cyclic loadings are presented and discussed in this study. Cyclic loading test were performed in triaxial condition at confining pressure of 4 MPa. The mechanical properties of the rock were altered by cyclic loading; dependent upon the applied stress level during cyclic loading the rock may experience damage or hardening as a result of cyclic loading. It was identified that a critical maximum normalized deviator stress (i.e. deviator stress at the beginning of unloading normalized by rock peak strength) exists between 92-95% which defines the limit between hardening and damage behavior during cyclic loading. If the cyclic loading deviator stress is lower than this critical boundary, the peak strength my increase in post-cyclic monotonic loading. This increase in peak strength is directly proportional to the normalized deviator stress in unloading; the amount of increase in peak strength decreases with a decrease in cyclic loading deviator stress. In cyclic damage tests, in general, the increase of Poisson’s ratio, v, and the degradation of tangent Young’s modulus, Etan, indicate the progressive accumulation of damage in the rock sample over the loading cycles. In cyclic hardening tests, however, v values for the cyclic hardening test remained fairly constant and Etan values slightly increased. Moreover, it was found that in cyclic damage tests the amount of axial and lateral strains cumulated during cyclic testing in much greater than those values for cyclic hardening tests.

Unsaturated soil behaviour, such as volume change, shear strength and yield stress, is usually interpreted and modelled in terms of stress and suction. This approach is consistent with laboratory tests where suction is a controllable variable. However, it also suffers some limitations. This paper presents an alternative approach for interpreting unsaturated soil behaviour, which is built in the space of stress versus degree of saturation. A new volume change equation is proposed in terms of stress and degree of saturation, to give a better explanation to the non-linear change of soil compressibility under constant suctions. The soil compression index is assumed to be a function of the effective degree of saturation and is interpolated from the known compressibility at the fully saturated state and that at a dry state. An alternative approach to simulate hydraulic hysteresis and hydro-mechanical interaction is then introduced, which enables the calculation of the effective degree of saturation under complex stress and suction paths. The loading-collapse yield surface is derived based on the proposed volume change equation in the plane of the effective degree of saturation and the Bishop effective stress. The proposed volume change equation and the corresponding yield surface are generalised to three-dimensional stress states by incorporating with the Modified Cam-clay model, following the same procedure introduced in the Sheng-Fredlund-Gens (SFG) framework. Finally, the proposed model is validated against a variety of experimental data including drained and undrained tests, isotropic and triaxial tests.

The seismic performance of precast arch culverts in the culvert longitudinal direction has not been clarified even though the principal cause of embankment disasters is earthquakes in this direction. On the other hand, precast arch culverts are constructed by continuously arraying and connecting each segment. That is why the dynamic behavior of precast arch culverts in the culvert longitudinal direction is believed to depend heavily on the method with which the culverts are connected. Accordingly, the aim of this study is to evaluate the influence of the connecting condition of precast arch culverts on the dynamic behavior in the culvert longitudinal direction by conducting dynamic centrifuge tests. It is found that connected culverts, compared with separated culverts, are relatively advantageous in decreasing the enlargement of the bending moment on the bottom slab of the arch culverts which leads to cracks in the culverts.

Natural sedimentary soils often exhibit marked anisotropy from early stages of deformation, in some cases manifesting even a few times greater stiffness in one direction than in another. Capturing this characteristic will lead to more accurate prediction and rational interpretation of ground movements in 2D and 3D problems. However, rigorous assessment of the 'effective-stress-based' stiffness anisotropy in laboratory tests requires considerable skill and expertise, particularly for fine-grained soils, which require slow, stable loading and measuring capabilities allowing full drainage. This study set out to catalogue and demonstrate general typologies of small-strain anisotropy found in naturally sedimented fine-grained soils to offer geotechnical designers a rough guide to stiffness estimation. A mechanical framework and experimental/interpretative innovations to facilitate the above are summarised.

In the 2011 Great East Japan Earthquake the rail yard embankment constructed by use of coal ash was damaged by severe liquefaction, resulting in the differential settlement of railway track. In the railway the settlement is limited to ensure safety, however the evaluation method for differential settlement is not established. It is thus necessary to establish the evaluation method for the differential settlement of railway track induced by liquefaction. In this study, cyclic undrained triaxial tests were performed to validate whether the fill material contained coal ash is liquefied in Mito. It was found that the fill material was possibility to be liquefied sufficiently. In addition, field level survey and surface wave exploration method were conducted to examine the effect of the thickness of liquefiable layer and S-wave velocity distribution on differential settlement caused by liquefaction. The results revealed that the differential settlement is concerned with distribution of the S-wave velocity and the thickness of the liquefiable layer.

We evaluate the long-term geomechanical behavior in the near-field of a deep geological disposal repository by the centrifugal model test. The model consisted of a sedimentary rock mass, bentonite buffer, and model overpack, and was enclosed within a pressure vessel. Tests were conducted with a centrifugal force field of 30 G under isotropic stress-constraint conditions with confining pressures and injection of pore water. The temperature conditions of the overpack are constantly 25 °C and 95 °C (normal temperature- and heating-test, respectively). As the result, the values of heating-tests showed similar behaviors to that of the normal temperature tests partially. However, the density of the buffer was lower than that of the normal temperature-tests by X-ray CT imaging in the post-tests.

Kakamigahara plateau is located in the central southwest of the Japanese Islands. It is close to the Pacific Ocean and is located in the northern edge of Nobi Plain. There are plural dales on Kakamigahara plateau and the outskirts. These topography is ducts of the water which an old river produced. It is considered that it was formed by the Atsuta transgression (Shimosueyoshi transgression) approximately 130,000 years ago and later regression. By the main subject, we copy a dale from the map of modern era as possible exactly and consider the plateau formation and the relations with the old river duct while inspecting various opinions conventionally. In addition to?, with the example of the municipal road construction site of the plateau blood relation part, We inspect it about the bench formation by the old duct and a residual duct.

Soft soil reinforcement methods by using the granular piles are very popular by improving the strength and deformation characteristics of the soft soils. There were many analytical methods such as Aboshi, Priebe, Vesic, Barksdale and Bachus’s method… to estimate the settlement and the load-bearing capacity of soft grounds reinforced by the stone columns. This paper analyzes the applicability of these methods, as well as the finite element method, via software PLAXIS 3D Foundation, with a real construction in Long An, Mekong delta, Viet Nam. The back analysis of measured settlements by applying Asaoka method showed a remarkable difference between the calculated and the observed settlements. The load-bearing capacity tests of the stone columns were carried out to confirm the real bearing capacity and failure mechanism of the stone columns. Finally, the recommendations to determine the settlement and the load-bearing capacity of soft grounds reinforced by the stone columns are proposed.

Soil arching effect is a common phenomenon within geogrid-reinforced and pile-supported (GRPS) embankments. It is in nature a three-dimensional (3-D) problem and a series of soil arching would form within the embankment fill. In this study, the group effect of soil arching is investigated using a 3-D finite element model. The numerical results show a good agreement with the measured data from a full scale experiment. By controlling the settlements of subsoil at different locations, the variations of soil arching are analyzed. It is found that the soil arching becomes more obvious when lowering the settlement of the underlying subsoil. The settlement of subsoil mainly influences the above soil arching, but hardly influence the adjacent soil arching. The height of soil arching at the middle and shoulder regions of the embankment fill is close to each other and it reaches a limit value when the subsoil settlement continues to increase.

In seasonal cold regions like Hokkaido, the soil surface up to a shallow depth is frozen during the winter. An earthquake during the freezing period and thawing period may cause severe disasters i.e. slope failures induced by the combined effects of seismicity and snow melt water. The influences of freezing conditions on the seismic behaviour of soil need to be studied elaborately. In this study, a series of shaking table tests were performed with frozen surface layer and numerical analysis has been performed to simulate the seismic behaviour of soil under the frozen surface state. The numerical analysis has been done based on the series of shaking table tests performed under two different conditions i.e. without a frozen soil surface layer and with 10 cm frozen soil at the surface. Loose density (Dr=30~35 %) and high density (Dr=75~80 %) Toyoura sand have been used to study the liquefaction behaviour. Different liquefaction behaviour is observed when considering surface frozen conditions under both loose and high relative densities of soil. Through the shaking table tests and numerical simulations performed, it is clear that the frozen surface layer severely affects the seismic response of the soil and if these conditions prevail on a soil slope during an earthquake, a sliding slope failure causing the movement of frozen soil layer may occur conceivably.

Since we concern about physical damage of levees due to liquefaction by a large earthquake such as the anticipated Tokyo Metropolitan earthquake and the Nankai trough earthquake, we are strongly involved in examining seismic countermeasures for special levees in urban areas as well as for natural levees. However, the detailed research on nonlinear seismic behaviors for special levees induced by a strong ground motion and liquefaction has not been promoted enough until now. Hence, by dynamic centrifuge experiments we clarified nonlinear dynamic behavior of a special levee and verified the effectiveness of seismic countermeasures for existing special levees. In addition, we improved the models of horizontal load acting onto a seismic countermeasure by comparing the values by current design procedure and the experimental values.

The authors have proposed a new testing method for obtaining appropriate parameters of deformation characteristics of soils necessary for time-domain nonlinear seismic ground response analysis, in which Level 2 earthquake is considered. The proposed method is composed of two types of testing method: a strain-controlled 1 cycle stage shear test and a strain-controlled constant strain cyclic shear test. The latter test can also provide information of soil liquefaction, which can be used for an assessment of soil liquefaction potential based on the theory of the accumulated dissipation energy. Trial tests by the proposed method using Toyoura sand were conducted and applicability of the method was examined.

This study reports a fundamental experimental program that aims to propose an approach towards developing a descriptive framework that extends the concept of effective stress and viscoplasticity to frozen states. A series of triaxial compression tests was conducted on reconstituted Kasaoka Clay at different temperatures (three temperatures below the freezing temperature and one above it) and strain rates. The specimens were isotropically normally consolidated to 100, 200 or 400kPa before freezing and sheared at constant strain rates of 10-3, 10-4 and 10-5 min-1 after the test temperature got stabilized. The observed behavior was interpreted through comparisons with that of unfrozen specimens, which were subjected to a same strain path as that for the frozen specimens through consolidation and swelling corresponding to the volumetric changes due to pore water phase changes. The strength of frozen specimens, as well as being far larger than that of unfrozen specimens, showed much more significant dependence on the strain rate, which is probably due to the presence of the ice. In light of Ladanyi and Morel’s (1990) hypothesis on the uniquely related strain path and effective stress path of both frozen and unfrozen states of the same soils, the “effective stress paths” followed by the soil skeleton of the frozen soil were probed by the carefully controlled parallel tests on the frozen and unfrozen states. The Critical state lines (CSLs) at different temperatures were thus plotted based on the envisaged effective stress paths. The above characterization of frozen and unfrozen soils is expected to lead to construction of a unified framework for describing the behaviors of both states.

Bamboo is a kind of natural resource that has ability to grow in varying conditions. Besides its high water absorbability as the main advantage of bamboo, effect of bamboo material structure can be utilized to improve characteristic of loose and poorly graded sand soil under saturated condition. This type of soil is very susceptible to liquefaction. An understanding of production process influence to the performance of bamboo materials type, influence of cement addition in the mixture and curing time to the mechanical behaviour were observed by static triaxial CU test. In addition, SEM (Scanning Electron Microscopic) analysis was also conducted to understand the particle interaction in mixture. This study can be developed as one of the proposed ideas in the utilization of environmental friendly materials in geotechnical field.

The symbol of the exhibition EXPO-2017 will be the Kazakhstan platform itself made in the sphere form several floors high with 24000 m2 in total. The symbol of the exhibition is located in the center of the exhibition village. It is surrounded by international, thematic and enterprise platforms. The results and comparing of soil tests of the piles for following methods: Vertical static test Static Load Test (hereinafter SLT) and the Bi-Directional Static Load Test (hereinafter BDSLT). Experienced bored piles with a length of 31.5 m, diameter 1000 mm. Bi-directional static load tests and Static load tests carried out in accordance with ASTMD1143. The method proposed by George Osterberg, allows to simultaneously determining the estimated soil resistance under the lower end of piles and on its lateral surface. Feature of O-cell test is that the load is applied not on the pile head, and the body of the pile, where is a jack (power cell), which works in two directions. Power cell (O-Cell) shares the experimental pile into two parts: upper (upper test item) and the bottom (lower test item). The target of this tests was obtaining of bearing capacity of piles on problematical soils ground of Expo 2017 (Astana, Kazakhstan).