In soil investigation of small buildings, Screw Weight Sounding test (SWS) has spread. There are each feature and subject in soil investigations. Authors focused on three subjects of SWS test in a soft residential land. They are the checks of self-settlement layers quality, load bearing layer of a pile, and potentiality of liquefaction. To solve these subjects, for the purpose of complementing SWS test by additional information, authors proposed the Hammer Drill Sounding (HDS) test. The index obtained by HDS test approximates satisfactorily with N value of Standard Penetration Test, and N value converted from SWS test. And it is the feature that this examination does not almost have self-settlements. In addition, hard layers were investigated as compared with SWS test. Therefore, the index was estimated by the same measure from soft layers to hard layers. Moreover, by repeated vibration, the potentiality of liquefaction was checked. About the above contents, authors report the verification result of 33 examination sites.

A theoretical model for soil-water characteristic curves (SWCCs) with the regular packing structure was developed based on the pore-scale water retention mechanism. In this model, the rhombohedron structure, whose structure and density vary with angle 𝜃, was employed as the unit cell of the regular packing structure. Assuming that 𝜃 follows k-gamma distribution derived from the density distribution of random sphere packing, a density distribution was introduced into this SWCC model, and the applicability was examined. The proposed SWCC model was compared to the conventional SWCC model without density distribution using uniform unit cells. The SWCC estimated by the proposed model provided a more moderate decrease in the degree of saturation than that estimated by the conventional model. This indicates that the density distribution increases the diameter variance of the pore throat, which is the air path into the water-saturated pore. Since the variation in the throat diameter is affected by both the particle size distribution and the density distribution, the effect of density distribution on SWCC is more significant for poorly graded soil with relatively small variation in particle size distribution.

The objective of this study was to develop a better understanding of the mechanisms of arsenic adsorption by iron particles in the remediation of arsenic leaching soil. During the study, the following observations were made: 1) in-crease in the addition ratio of iron particles in soil slurry resulted in decrease of arsenic leaching, 2) removal of all iron particles from the slurry by magnetic force resulted in the return to original arsenic leaching value level, and 3) arsenic leaching from the soil appeared to be pH-dependent. From these results, the following conclusions were de-duced: (a) soluble arsenic in soil slurry is adsorbed by amorphous iron oxy-hydroxide produced from the reaction of iron ions eluted from the iron particles, (b) arsenic leaching increased due to lack of available iron oxy-hydroxide, reduced by the removal of iron particles, and (c) arsenic leaching ability of cleaned soil varies in accordance with re-sidual quantity of iron oxy-hydroxide. Furthermore, the following rationale behind the conventional method of add-ing acid together with iron particles was inferred: (a) lowers the slurry pH values resulting in reduced arsenic leach-ing values, and (b) promotes elution of iron ions from iron particles resulting in increased production of iron oxy-hydroxide (adsorbent).

It is reasonable to expect that sensing ground vibration caused by mass wasting and issuing warning information promptly will lead to a reduction in the risk of disaster. By monitoring ground vibration induced by debris flow moving through mountain streams or towns, stakeholders can assess the severity of the hazard and issue an alarm if needed. In this study, ground vibrations were observed in debris flow experiments, and the characteristics of the ground vibration during the debris flow were investigated. Based on the findings of the analysis, the effectiveness of the detection method of debris flow was shown by focusing on high frequency pulses. Furthermore, the practicality of the detection method was improved by introducing a method for avoiding false detection of seismic waves by utilizing the difference in the frequency characteristics of ground vibration.

This paper presents a new method for estimation of shear strength of cohesive soil for design use su(mob) using CPTU results only. The su(mob) is estimated through a cone factor which is calculated by linear relational expression between net cone resistance and strength increment ratio on normally consolidated state which is determined by excess porewater pressure during cone penetration. The method is established based on the data obtained from 31 locations of 25 sites on Japanese, East Asian and South East Asian cohesive grounds. Reliability and applicability of the su(mob) obtained from the proposed method are verified by comparing with the su(mob) from various laboratory tests using undisturbed samples and in situ tests. The method can evaluate the su(mob) without a process associated with human error among boring, undisturbed sampling and laboratory testing.

The applicability of the strength obtained by consolidated constant-volume box shear test, was examined using the data of geotechnical investigation carried out for D-runway construction project of Tokyo International Airport. It was confirmed that the design shear strength obtained by 0.85_su(DST0) of undisturbed specimens, which is sheared at 0.25mm/min after the consolidation with the in-situ effective overburden pressure. Regarding the strength development by the consolidation, the comparison was made on the shear strength normalized to the consolidation pressure (strength increase rate) obtained by the constant-volume box shear and the consolidated-undrained triaxial test. It was found that 70% of the strength obtained by the consolidated-undrained triaxial test should be used to estimate the strength increase after consolidation.

The Percentage of Vegetational Cover (PVC), an indicator of the evaluation of slope revegetation with herbaceous plants by seeding works used in the industry, is usually measured manually through visual inspection. Hence, the measurement results of the same subject might not be constant. To overcome this situation, RGB image analysis has been introduced. In this study, the camera settings to minimize variation of the PVC measurement results and the impacts of natural sunlight were investigated. In conclusion, the cameras set as minimum ISO with fixed white balance were preferable to measure PVC when the equipment have program automatic exposure. The variation of the PVC measurement results under the conditions of this study was approximately ±2.5~7.3% (95% prediction intervals) under the natural sunlight condition with different solar altitude and/or weather. In addition, the standard deviation of the PVC measurement results calculated with photographs taken on a day in the condition of constant weather was approximately ±1.8%.