Pile foundation has been designed against the lateral load acting on the superstructure which is induced by the seismic coefficient method. After the Great Hanshin Earthquake, the response displacement method has been employed to assess the reaction force acting on pile. However, this method overestimates the interaction force from the viewpoint of practical design. Various specifications recommend to use the bilinear model on reaction force by considering that the ground goes through the pile. This paper evaluates the ultimate resistance of ground against lateral movement of pile by both model test and rigid plastic finite element analysis. The validity of obtained results is examined through the comparison of both results. The followings are obtained in this study. (1) Ultimate lateral resistance of pile was obtained as 12~13c for clayey ground where c is an undrained shear strength of clay. It was examined by model tests and numerical analyses. The failure area of ground reached to 2.5~3D from the pile center, where D denotes the diameter of pile foundation. (2) Effect of friction cut between pile and ground was investigated. Ultimate lateral resistance of pile was obtained as 9c which is almost same with Brom's formula. Besides, the effect of strength reduction in surrounding ground due to pile installation was parametrically investigated. (3) Ultimate lateral resistance of group piles was obtained as 11c in case of the pile center spacing of 3D. It matched with that of single pile in case of 5D. (4) The current specifications were shown to provide the smaller estimation on ultimate lateral resistance of pile in case of depth that is deeper than effective length on pile (1/β), where the ground deforms through the pile by earthquake vibration. It reveals the specifications may prescribe the dangerous side evaluation in design.
Seismic stability has not been considered in the design of traditional culverts in Japan. In recent years, however, the construction of precast arch culverts, which include hinges in the main body and are outside of the range of conventional culverts, has been increasing. In this study, large-scale shaking table tests, using a strong earthquake response simulator, were conducted to clarify the seismic behavior of a three-hinge precast arch culvert. Furthermore, the inner space displacement and the earth pressure of the culvert were measured at each construction stage. From the results, it was found that the modification mode of the component changed according to the banking height and that the culvert behaved as expected in the construction stage. Moreover, it was confirmed that the hinge part did not break prior to the ultimate behavior of the arch element during a large earthquake.
A granular material can be obtained by crushing a solidified dredged marine deposit mixed with cement. It is convenient if this can be used as an alternative fill material for such as reclamation behind seawall, however, it has not been well known with sufficient back data if the material can be used for such purpose. This paper introduces the results of the strength test for the crushed cement-mixed soil. A dredged marine deposit having water contents of 110% was mixed with the cement with dosage of 100-400 kg/m3, cured for 28 days and then crushed. Two kinds of test were performed. One is a compression test on single particles of 4.75-9.5mm and the other is a triaxial compression test (CD) on crushed soils with particle size distribution of 0.85-2mm and 2-4.75mm. The test results revealed that though quantity of volume compression by particle destruction is larger than that of sand/gravel, internal friction angle is over 30°.
This study reports the field survey on ground and foundation structure of the Ohkouzu old movable weir. The geological map around the old movable weir was drawn by boring survey with data in the past references. It indicated the timber piles were point bearing piles which were supported by sandy layers, and the edge of steel sheet piles were driven into clayey layer. They proved the construction work of that time was properly conducted by taking account of geological stratum. Timber piles were shown to be sound and satisfy the required performance in design by both the site loading test and the robust test of piles, although they were constructed about eighty years ago. The cavity was shown to be successively distributed between foundation and ground around the old movable weir and the groundsill. The field survey indicated that the cavity developed in the area where bearing piles or sheet piles were employed in construction. Since the old movable weir experienced 1964 Niigata earthquake and liquefaction damages were widely observed around the old movable weir, the undisturbed soil was sampled from the surface ground below the old movable weir and the liquefaction resistance was investigated by dynamic triaxial test. By the conventional liquefaction analysis, the loose sandy soils was shown to be liquefied or almost liquefied during the Niigata earthquake. Through the case studies in shaking table tests, it was concluded that the cavity below the weir foundation was generated mostly by the ground settlement of loose sandy layers due to earthquake.
Many damages of historical tumulus mounds are caused by precipitation associated with slope failure of tumulus mounds and deterioration of the stone chambers. Rainwater infiltration control is hence indispensable for conservation of tumuli. A capillary barrier is one of feasible options. A barrier is formed at the contact between a finer soil layer and an underlying coarser one. The infiltrating rainwater in the upper layer is diverted at the contact without flowing down to the underlying layer. In this paper, the mechanism of a capillary barrier and the factors that affect on the diversion capacity are studied by model chamber tests. Then, a series of numerical analysis is conducted to simulate the chamber tests. The calculated performance reveals that a barrier functions with the difference in hydraulic conductivity in the two layers. Degree of the diversion is controlled by the intensity of precipitation, the inclination of contact plane and the thickness of the upper layer because the hydraulic conductivity of the soil layers in the steady state changes to keep the total volume of seepage water when the three factors change.
Microscopic observation using scanning electron microscope (SEM) and compound identification using X-ray diffraction (XRD) are performed in order to discuss latent hydraulicity of granulated blast furnace slag and its effect on the increase in stiffness and strength of the slag. It is confirmed that curing of granulated slag in artificial seawater under relatively high temperature is rather effective to excite latent hydraulicity of the slag and to accelerate generation process of deposits. Addition of fine powder of granulated slag as stimulating agent is also effective in accelerating elution process of granulated slag into curing liquid and generation process of deposits. It is revealed that several kinds of deposits having structure of aggregates, film or pillar are generated by latent hydraulicity of granulated slag and they work to solidify contact points of granulated slag particles or to fill void space between slag particles.
Two kinds of slaking tests, ordinary accelerated slaking tests and newly-developed 1d compression-slaking tests, are conducted on three kinds of mudstone in order to investigate slaking phenomena, namely, weathering due to cyclic process of wetting and drying. Variation in grading occurred by slaking and resulting, irreversible changes in mechanical characteristics are discussed based on the results of accelerated slaking tests. The experimental results of one-dimensional compression slaking test show that: particle crushing during compression process causes increase in compressibility; the wetting and drying cycles causes slaking-induced change of grading and this change causes significant volumetric compression. Finally, it is mentioned that constitutive modeling considering slaking is possible by describing evolution of grading due to slaking through the grading index IG and linking maximum and minimum void ratio or critical state void ratio with IG.
A floating underground dam has been proposed as one of the promising means to increase the volume of water in freshwater lens. One of the most concerning things is residual salinity of groundwater while fresh water is infiltrating into underground. We conducted laboratory tracer tests for Ryukyu limestone as an example of Quaternary carbonate, using a microfocus X-ray CT to reveal its characteristics of mass transport. The results showed that large pores in this act as main flow paths of fluid flowing. In matrix part some flow paths were observed too. These results suggest that taking flow in matrix part into account is important to make a numerical model of Ryukyu limestone as distinguishing large pore and matrix.
A reproduction analysis from a view point of practical design was conducted on a case history where a high railway cut slope consisting of clayey soils failed during the 2011 Off the Pacific Coast of Tohoku Earthquake. The extent of the damage was so large that its restoration works required significant time. Therefore, a series of in-situ geotechnical survey and laboratory soil testing on undisturbed samples were conducted, and a two-dimensional earthquake response analysis was executed while considering the strong motion record that was observed nearby. Based on the laboratory test results, the properties of strength reduction to be mobilized along a failure plane were also formulated, and earthquake-induced sliding displacement was evaluated using modified Newmark method. As a result, the damage extent of the failed slope could be reasonably simulated.
The aim of this study was to elucidate that how granulated blast-furnace slag can suppress cadmium release and neutralize acid pH in excavated soil in which pyrite is being oxidizing. In the soil without granulated blast-furnace slag, soil pH decreased with the increase in incubation time, while the amount of cadmium release increased. The addition of granulated blast-furnace slag at rates of 7.5wt% and 25wt% led the amounts of cadmium release less than 0.05 mg/kg during 90 days incubation, and kept soil pH at neutral and alkaline ranges, respectively. The addition of granulated blast-furnace slag did not cause the change of pyrite oxidation reaction. The unconfined compressive strength of soil with granulated blast-furnace slag was not significantly different from that of soil without granulated blast-furnace slag. Over 90% of cadmium removed in solution by granulated blast-furnace slag under neutral pH range was not dissolved at neutral to alkali pH ranges. These results suggest that the granulated blast-furnace slag is useful material to reuse excavated soil containing pyrite.
As for the low permeable layer, important functions are expected as an engineered barrier of radioactive waste disposal for low-level waste with comparatively high radiation levels. On examining the construction methods of this low permeable layer, it is important to confirm the possibility of the construction in the conditions similar to the actual constructed conditions with a true scale size. Therefore, the construction examination for the side part of the low permeable layer by bentonite and the performance check test of the low permeable layer were carried out. The result of the construction examination showed that the possibility of the construction were confirmed, and the result of performance check test showed that it was possible to ensure the required performance of the low permeable layer, such as hydraulic conductivity.
A series of undrained triaxial tests was conducted in order to evaluate liquefaction properties, strength and deformation characteristics after liquefied, and small strain stiffness of fine sands containing nonplastic silt. Tested materials were prepared by mixing silica sand No. 6, in which particles with a diameter larger than 0.25 mm were removed from the original material, and nonplastic silt called ‘‘DL clay’’. Cylindrical specimens having a dimension of 5 cm in diameter and 10 cm in height were produced by wet tamping method. The test results showed that: 1) the liquefaction resistance decreased with increasing fines content ranging from 0 to 50%; 2) the postliquefaction undrained strength increased with decreasing fines content under otherwise the same condition; 3) no clear tendency was observed in the relationship between the liquefaction resistance and small strain stiffness; and 4) the liquefaction resistance correlated with secant Young's modulus at a vertical strain of 0.1% and undrained shear strength without undrained cyclic loading history.
The purpose of this paper is to examine the soil structure and flow path in order to standardize an upflow column test using an X-ray CT based numerical analysis. The soil structure and flow path are visualized of a porosity distribution by the X-ray CT. Methods of filling sample to the inside column were used ‘Free fall method’ and ‘Water tightening method’. Porosity of the Water tightening method, sample was maintained 35%-40% before and after in wet condition. And the porosity distribution is confirmed that uniforms and not to change removable with water flow. It is suggested that fluid flux in porosity distributions is stabile in the column. On the other hand, Porosity of the Free fall method, sample was observed that is increased 5% before and after water flow and the chap is occurred before water flow between layers. The porosity distribution is confirmed unevenness forms which have layers and part of large and small pores in the column. These unequal porosity distribution are thought that fluid flux has become spiro-flow and changed flow variation with time. It is revealed that the porosity distribution is significantly different due to differences in the soil filling method even same soil sample. It is considered that most important for standardization and generalization of column test methods and results is understood phenomenon (fluid flux, transport and response) resulting due to porosity distribution and consolidated reproducible test method for radical soil porosity distribute in the column.