In order to evaluate the applicability of soil nailing method on embankment ground, pulling tests, digging observation of the fixing body, and comparative evaluation with the geotechnical strength were performed. As a result, the diameter of the fixing body tended to be expand 1.1 times for the cohesive soil, 1.2 times for the sandy soil ground, and 1.3 to 1.4 times for gravel and cobble stone mixture soil compared to the diameter of the drilled hole. In addition, it can be said that appropriate spacer specification for each embankment type, or securing the soundness of the fixing body by outbreak of the tip is necessary. Furthermore, it was found that the surface roughness of the fixing body affects the pulling capacity, and especially the expanded tip shape had a high reinforcement effect. On the other hand, as for the shaft frictional strength (τ value) of the ground which affects the pulling capacity, the evaluation formulas of the N and Nd values were proposed, and it was confirmed that this could be applied to the actual installation work. Furthermore, it was found that the estimated value of the peripheral surface frictional resistance indicated in the cut soil guideline can be applied to the embankment.
Basic data on geological environment are collected and organized in relation to the geological disposal of the high-level radioactive waste. While the importance of the collecting microbial information has recognized in the recent international trends, microbiological knowledge for deep subsurface environments is currently limited. In order to make a database of basic microbial information, it is essential to systematize a series of analytical methods. In this paper, we reported the results of microbial analyses of deep subsurface groundwater. Groundwater sample was collected from deep well located in the coastal area of Horonobe, Hokkaido, Japan. Then, we proposed an analysis flow to obtain the density of microbes, community structure, activity, and community constituents in the subsurface environment as basic data on microbes in a single sampling opportunity.
This paper introduces polymeric material (synthetic polymer grouting material) developed for the purpose of liquefaction countermeasures by chemical grouting. The safety, improved strength, durability, and applicability of the chemicals to actual ground are reported. Regarding safety, as a result of carrying out elution tests using sand gels, they met the standards of the Soil Contamination Countermeasures Law. The following were also carried out: Acute toxicity test of fish, abrupt swimming inhibition test of crustacean and zooplankton, growth inhibition test of algae and seagrass, and it was proven that the effect of this chemicals on aquatic organisms was very small. With regard to the improved strength, it was found that the sand gel produced by this chemical solution obtained unconfined compressive strength of 100 to 500 kN/m2 and liquefaction strength specific RL20 of about 1.0, both when neutral sand was used and when alkaline (pH 9 to 12) sand was used. Regarding long-term durability, a decomposition acceleration test in which a sand gel was placed under a high temperature of 80℃ was carried out, and unconfined compressive strength did not decrease even after 180 days (equivalent to 30 years) passed. Similar studies were also conducted using pH 11 adjusted sands, and the unconfined compressive strength did not decrease after 160 days (equivalent to 28 years). The permeability coefficient of the sand gel was 1×10-6 to 1×10-9 cm/s (1×10-8 to 1×10-11 m/s) in the range of chemical concentration used (6 to 18%). After confirming these basic physical properties, a field test using this chemical was carried out at a reclaimed ground in the coastal area. As a result, the radius of the improved body secured the design value, and the improved strength satisfied the design standard strength.
In this study, behaviors of the volumetric water content and the soil suction due to rainfall infiltration and drainage characteristics under relatively high suction state were discussed through the macro-pores part and the matrix part separately based on the results of in-situ measurement made at the fill slope where macro-pores developed. As a result, despite the volume water content drops below the field capacity at the start of in-situ rainfall and the pore pressure is less than the corresponding values, the process of rainfall infiltration and drainage characteristics exhibited along the boundary drainage of the matrix flow at maximum field capacity corresponds to the scanning curve. In addition, even if the installation position of the measurement interval was about 0.4m in this slope, the extremely heterogeneous distributions in volumetric water content and pore pressure lead to a lack of synchronicity observed between the volumetric water content and the pore pressure when the macro-pore flow occurred. Therefore, the effect of the measurement interval should be considered when interpreting the measurement results.
As for the landslide that occurred during the excavation construction of the road in Mine-shi, Yamaguchi Prefecture, based on the results of the countermeasure method examined by the committee of experts, it was proposed to excavate the gradient of the cut slope to about “i=1:2.0” and to discharge the unnecessary earth. Due to the shape of the cut slope, it remained stable for a long time after the road was completed. However, the landslide occurred again 40 years after opening. Since the landslide had occurred in the past and from the sings of past behavior, sliding and resting had repeatedly occurred in this block of landslide, and it was determined that the sliding surface strength is in a residual state. Therefore, it was necessary to adequately consider the residual strength when examining the stability of the slope. This paper reports a case where the landslide surface was determined for two sliding surfaces adjacent to the cut slope based on the soil survey and dynamic observation results from existing documents, and the residual strength constant obtained by the ring shear test and the strength constant obtained by the inverse analysis method was roughly the same.
Tracer test is useful for understanding mass transport in groundwater. However, there is a limited number of research reported on this topic because it is difficult to conduct a tracer test and to evaluate its data. Therefore, a laboratory test is conducted to investigate the basic procedure and evaluation method for tracer tests. In this study, simple pulse input method was developed. It is found that it is important to reduce the volume of the test section in the well. The measurement setup and size of a well should be carefully considered to evaluate the effective porosity resulted from a tracer and the dispersion coefficients calculated from theoretical solutions. The measurement technique developed in this study can be expected to be applied to in-site test.
Since the conventional compaction management is a method based on point measurement after construction on site, it is difficult to guarantee the quality of the entire construction area plane, and it is likely to cause rework of construction. Therefore, with the aim of realizing quick and area compaction management, we propose a compaction management method that utilizes a compaction management device (CCV system) based on the acceleration response method, which is one of the soil stiffness indexes. In this study, we conducted a compaction test using a full-scale compaction machine in a large soil concrete pit, and compared the CCV value, which is the soil stiffness index by the CCV system, with the soil stiffness index that has been used conventionally. We also derived a relational expression between the CCV value, the dry density ρd, and the saturation degree Sr, and proposed a method to be applied to compaction management.
This study proposes a method to assess the risk of landslide and valley-filling embankment slopes at the time of earthquake. The method is applicable to landslide and sliding and falling of embankment triggered by earthquake. To assess the risk triggered by earthquake, the study proposes a method to calculate slope stability using shear resistance coefficient (φp). Also. the study proposes a calculation method, which user peak ground acceleration (PGA) featuring space domain interpolation, to calculate the seismic coefficient (ke) used in the calculation of slope stability. Both values are computed through the calculation of slope stability at the time of earthquake. The risk at the time of earthquake shall be assessed from the acceleration limit, where the collapse occurs, and the safety rete. Through the verification and analysis of earthquake-triggered landslide and sliding and falling of embankment, the study obtained useful information beneficial for the establishment of the method to assess risk at the time of earthquake. The authors have established a system to assess risk of landslide and valley-filling embankment slopes during earthquake.