This paper discusses an experimental study and existing site condition of rainfall induced landslide sensitive mountainous site. Soil behavior of the site was understood by using slope angle, soil gradation test. Disturbed and undisturbed soil samples were taken from the site for testing purpose. Shear deformation with the change of volumetric water content was checked by using 1.3(g/m³) and 1.4(g/m³) bulk density sample. The modified shear test apparatus was used to determine the shear failure at different slope angle such as 25, 30 and 35 degrees. Shear box sample size was 30cm x20cm x 7cm and overburden pressure on the sample was applied by using steel plates. Constant water flow was uniformly applied on top and bottom surface of the soil sample which is enclosed by the shear box. Numbers of three moisture sensors were used in shear plane to measure the volumetric water content (VWC) and displacement transducer was used to measure the shear displacement of the shear box. The results suggest that ground with high bulk density is more resist to shear failure. The results also shown that the required moisture content for the shear failure is decreasing when increasing the sample slope angle of the similar bulk density condition.

A procedure to evaluate directly the local deformation properties of sand specimens was developed by using a transparent membrane and adding colored sand particles to the original ones. By combining it with indirect observation based on the image analysis of the membrane deformation, their comparison was made. The local deformation properties of a dense Toyoura sand specimen that was evaluated by the indirect observation during the liquefaction process in cyclic triaxial test up to a double amplitude axial strain of 5% were consistent with those evaluated by the direct observation, except for the regions near the top and bottom ends of the specimen.

Implement or performance to unsaturated soil mechanism including concept of cyclic phenomena is necessary to prevent, decrease earthquake-induced great damages. Also, human soil structures such as road-embankment, railway-embankment and river dike have received strong rain fall, and the permeation induce increment of soil moisture and some deformation or settlement regard to safety factor. The experimental works and establish mathematical modelling for unsaturated soil is significant to realize the practice problems. This study aims to interpret unsaturated soil properties subjected saturation-unsaturation. The difference three experimental tests as hydraulic conductivity test, monotonic compression triaxial test and cyclic triaxial test were performed for a silt material, and low matric suction was controlled. The accurate measurement of volume shrinkage was accomplished, that change of void ratio was important factor to interpret the properties of apparent saturation silt. The repetition of saturation-unsaturation induced considerable influence to hydration conductivity and shear strength.

In recent years, the phenomenon of ground subsidence in major cities has caused social problems such as damage to roads and structures, inhibition of people’s safety, and property damage. A survey released by the City of Seoul has showed that more than 80% of the phenomenon of ground subsidence occurred mainly around sewer pipes. Since sewer pipes tend to rapidly deteriorate, a technical standard is needed in order to effectively carry out replacements and repair reinforcement by evaluating the soundness of the existing sewer pipe and identifying any common occurrences of danger. In this study, the effective seismic survey technology for detecting a cavity near to sewer pipe was chosen as GPR, density logging, and impulse response method for the deteriorated sewer pipe. The pilot plant test was carried out so as to verify the performance of the cavity detection of the corresponding technique. Each method could detect the cavity proximity to the sewage pipe, but there was a difference in the applicable limit and detection performance according to each method.

The measurement systems based on digital image analysis have been widely attempted in geotechnical testings (e.g., physical model tests) for observing the deformation of soils. The accuracy of digital image analysis is influenced by various factors such as image pattern of test materials, performance of digital camera, target area, and analysis conditions. Therefore, optimal analysis conditions should be determined and applied to obtain high quality results on soil deformations. In this study, various influence factors of the accuracy of digital image analysis and the optimizing procedure were described. Finally, the digital image analysis was adopted to evaluate the deformation during lateral drainage consolidation under the given optimal condition.

In order to increase the maximum width to which the slope can be undercut, slope stabilization shear pins is required. In this study, two layout patterns of pencil leads, 2 mm in diameter, were placed into physical models of undercut slope made of a confined block of humid silica sand No.6 resting a Teflon plate. The soil pressure and slope movement during which the slope was undercut from the center line until reaching the failure were monitored by a set of pressure gauges, digital camera and high-speed VDO camera. The experimental results revealed that for a given similar number of pencil leads, the layout in vertical row has a higher influence on the stability than that in horizontal row.