This paper examines in-situ cyclic loading test method using a horizontally vibratory cone probe for the purpose of further improving the accuracy of liquefaction assessment. First, the outline of the device developed in this research was introduced, and an interpretation of the dynamic behaviour of a probe vibrating in the ground was attempted with a simplified model. Furthermore, among various test methods that combine vibrating operation with a vibratory cone and push-in/pull-out operation with a press-in device, three methods were selected for comparison: vibration push-in test method, vibration pull-out test method, and fixed-depth vibration test method. The applicability of these three methods as a test method for liquefaction characteristics was confirmed by field experiments and model experiments, and the merits and demerits of each method were summarized. Based on the results of a series of studies, it was concluded that the fixed-depth vibration test method is the most promising for future development in terms of the clarity of the test principle and work efficiency.

The authors have proposed a pile-slab type embankment in which geotextile reinforced embankment is constructed to directly support a concrete roadbed, and materials that are considered unsuitable for slab track embankments can also be used. The seismic performance of the pile-slab embankment has been investigated mainly by shaking table experiments. In this paper, the dynamic behavior of the pile-slab embankment is simulated by 2-dimensional dynamic FEM analysis and trial design, and it is confirmed that the pile-slab embankment is applicable to high embankments and embankments on soft ground. In addition, it was confirmed that the pile-slab embankment is more economical than the conventional embankment.

The chemical injection method is one of the ground improvement methods used to stop water and increase strength. It is essential for soft ground improvement. Although the chemical injection method is a proven technique, it still faces technical challenges. The improved area and strength are generally non-uniform because the area to be improved cannot be controlled artificially due to the nature of the method. This study aims to identify and evaluate three causes of infiltration behavior. Firstly, the effects of different viscosities of various types of chemicals and different ground permeability on chemical infiltration behavior were evaluated through infiltration flow analysis. Secondly, the effects of ground uncertainty on infiltration behavior were assessed through infiltration flow analysis and Monte Carlo simulation. Lastly, the influence of rheological properties of the chemical solution on infiltration behavior was evaluated using a coupled MPS-DEM analysis. By presenting these three evaluation procedures, this study proposes a new method to evaluate the performance of chemical injection methods.

The D_F—K_d model considering both adsorption—desorption and intra-particle diffusion in the solid phase has been developed to evaluate solute transport more realistic. Since the applicability of the D_F—K_d model has yet to be investigated based on experimental results, the differences between experiments and numerical analysis were discussed. Firstly, a method for obtaining parameters used in the model was established. Herein, partition or diffusion coefficients were obtained against arsenic contamination. Partition coefficients assuming instantaneous equilibrium were obtained at 0.25—0.60 L/kg, while diffusion coefficients in the solid phase on the order of 10^-15 to 10^-14 m²/s were obtained from serial batch sorption tests. Secondly, the results of batch tests and simulations were compared. When the obtained parameters were applied to the D_F—K_d model to simulate the experimental results of batch tests, a relative error of less than 77% was obtained. These results support that the D_F—K_d model can reasonably simulate the solute transport on soils more realistic.

In order to examine the shear strength characteristics of direct shear tests on coarse-grained soil, the effects of the sedimentation angle α formed during specimen preparation and the specimen preparation method are investigated. For specimens prepared by the free-fall method, the shear resistance angle increases with the sedimentation angle regardless of the density of the specimen, and the rate of increase increases with the flattening of the particles. In addition, compared to the free-fall method, the specimens prepared by the ramming method have a larger particle inclination angle β, which is the angle between the shear plane and the particle long axis direction. This effect increases the number of particles that exhibit rotational resistance, which is a factor that increases strength, but it also causes the skeletal structure to become lower, regardless of the flatness ratio, which is a factor that decreases shear strength.

Warning and evacuation based on early detection are important to mitigate the damage caused by debris flows. The authors consider that measuring ground vibrations caused by the movement of soil material is an effective way to detect debris flows, and have been studying it experimentally. In this study, debris flow experiments were conducted under artificial rainfall conditions to examine the effects of rainfall and material movement on ground vibration. The results show that when rainfall intensity is high, ground vibrations caused by debris flows are sometimes difficult to detect because they are buried by rainfall-induced vibrations. In this case, since the frequency characteristics of the two are different, the frequency domain detection proved to be effective. Furthermore, a vexing problem in debris flow sensing is securing the installation place of the measuring instrument and the electric power supply. Therefore, as a method to solve both problems at the same time, the idea of using the electric pole as the installation place of the measuring instrument was investigated. Then, the effectiveness of the vibration measurement at the upper part of the electric pole was confirmed.

This study explores the fluidity and strength characteristics of cement stabilized soil utilizing three different sand content ratios. The research scrutinizes the relationship between the water content ratio, flow value, and 28-day unconfined compression strength (q_u28), while maintaining a constant water cement ratio. It was determined thatq_u28 of the cement stabilized soil is influenced by both the water cement ratio and the mass of soil particles, given that the original soil remains constant. Additionally, an examination of the mix proportions of cement stabilized soil with a field strength of 500 kN/m² was conducted under four conditions of flow values: 90, 120, 150, and 210 mm. A comparison between the mix proportion of 100% clay and a 50% sand mixture in cement stabilized soil revealed that the latter reduced the cement mass by 33 to 42 kg/m³ (a ratio of 22 to 20%).

The compaction characteristics of embankment sand as construction materials for the Tokyo Bay Fortresses built in the Meiji and Taisho periods, and the strength and deformation characteristics of concrete, bricks, and rocks were examined. The average spreading depth of the sand used for reclamation of the First fortress was 18 cm, and although specifications were specified according to the standards of the time, it was sand subject to liquefaction. The strength and deformation characteristics of stone, brick, and concrete, such as secant Young’s modulus, Poisson's ratio, and fragility coefficient, were related to dry density and unconfined compressive strength, and regression equations useful for the soundness and future maintenance of civil engineering historic sites were obtained.

In this study, to obtain the basic data for developing “slow and economical carbon treatment technology” that is as low cost as possible, by using different three methods in contact fresh steelmaking slag discharged from steelworks with atmosphere, we confirmed the change of the basic properties of steelmaking slag with elapsed days. From the results obtained, it was found that pH(H₂O) , electric conductivity and calcium ion concentration decreased, calcium carbonate content increased with elapsed aging day and the watering operation or the contact operation with atmosphere influenced on the tendency. Moreover, it was found that the electric conductivity decreasing showed the centralized tendency regardless of the contact process with steelmaking slag and atmosphere.

While total renovation of embankments are being carried out on Japanese expressways for the purpose of disaster prevention and mitigation, there is a problem in easily grasping and evaluating the water levels of the enormous number of embankments. So, we propose a new idea of water level assessment called “water level condition” and analyze water level observation data collected at expressway embankments nationwide using this method. As a result, we perceive some tendency in the conditions of embankments where the water level tends to be high. Moreover, we suggest an evaluation division of embankment water levels to systematically advance total renovations by organizing the levels, applying the water level condition method.