Koji Ichii

Scale ratio ICP for 3D point clouds with different scales

In this paper we propose a method for matching the scales of 3D point clouds. 3D point sets of the same scene obtained by 3D reconstruction techniques usually differ in scale. To match scales, we estimate the ratio of scales of two given 3D point clouds. By performing PCA of spin images over different scales of two point clouds, two sets of cumulative contribution rate curves are generated. Such sets of curves can be considered to characterize the scale of the given 3D point clouds. To find the scale ratio of two point clouds, we register the two sets of curves by using a variant of ICP that estimates the ratio of scales. Simulations with the Stanford bunny and experimental results with 3D reconstructions of artificial and real scenes demonstrate that the ratio of any 3D point clouds can be effectively used for scale matching.

Scale alignment of 3D point clouds with different scales

In this paper, we propose two methods for estimating the scales of point clouds to align them. The first method estimates the scale of each point cloud separately: each point cloud has its own scale that is something like the size of a scene. We call it a keyscale, which is a representative scale and is defined for a given 3D point cloud as the minimum of the cumulative contribution rates of PCA of descriptors over different scales. Our second method directly estimates the ratio of scales (scale ratio) of two point clouds. Instead of finding the minimum, this approach registers the two sets of curves of the cumulative contribution rate of PCA by assuming that those differ only in scale. Experimental results with simulated and real scene point clouds demonstrate that the scale alignment of 3D point clouds can be effectively accomplished by our scale ratio estimation.

A probabilistic evaluation of the size of earthquake induced slope failure for an embankment

The seismic design method for earth structures considers only the safety factor, subsidence and sliding displacement. However, the estimation of the size of slope failures is necessary to judge the remaining function of an embankment after an earthquake event. The size of slope failures due to an earthquake is investigated by considering the heterogeneity of the ground strength and was based on slope stability analysis of two case histories: the 2001 Geiyo Earthquake (Mj6.7) and 2009 Suruga Bay Earthquake (Mj6.5). As a result, we propose a method for slope failure size estimation based on the maximum slip surface. The proposed method enables a rational assessment of the functional loss of an embankment in terms of the slope failure size.

A practical method for identifying parameters in the seismic design of embankments

The effect of heterogeneity of soils on a seismic design procedure based on residual displacement according to safety factors is examined. Although soils are heterogeneous in nature, at present the seismic designs of embankments implement the assumption that soils are homogeneous. In this study, a seismic reliability analysis using a Monte Carlo simulation and considering the heterogeneity of soil strength was applied to the Newmark sliding block method. The data of the analysis in this study were based on in-situ soil test results of actual airport embankments. This paper indicates a rational and practical approach to modifying the actual heterogeneous soil conditions into homogeneous design parameters for the Newmark sliding block method in homogeneous ground conditions.

Extraction and visualization of numerical and named entity information from a large number of documents

We have developed a system that can semi automatically extract numerical and named entity sets from a large number of Japanese documents and can create various kinds of tables and graphs. In our experiments, our system has semiautomatically created approximately 300 kinds of graphs and tables at precisions of 0.2-0.8 with only two hours of manual preparation from a two-year stack of newspapers articles. Note that these newspaper articles contained a large quantity of data, and all of them could not be read or checked manually in such a short amount of time. From this perspective, we concluded that our system is useful and convenient for extracting information from a large number of documents.

Surface Wave-Based Health Monitoring Method for a Sheet Pile Quay Wall

Port structures such as pile supported piers and quay walls generally face severe conditions, and deterioration of port structures is often observed. For an example, at a sheet pile quay wall, sheet pile is a structural component which is easily deteriorated by corrosion. As a result of deterioration of sheet pile, the backfilled soil would be washed out due to the tidal action. Suffusion, the phenomena of the washed out of fine particles and loosening of soil layer, is a problem to be considered in the maintenance of a quay wall. Therefore, a health monitoring method for the backfill of a sheet pile quay wall is necessary. In this study, the applicability of a surface-wave method for health monitoring of a sheet pile quay wall was examined. First, the variation of shear wave velocity in the ground due to suffusion and variation in water content is measured from bender element tests. Then, 2D finite element method (FEM) dynamic analysis was conducted to simulate a surface-wave measurement on a sheet pile quay wall. From the result of the analysis, the estimated shear wave velocity profile based on surface-wave method agrees fairly well with the assumed soil profile. Finally, surface-waves were measured at a sheet pile quay wall, and the measured results were compared with the result of Swedish weight sounding test at the site. Furthermore, the difference between the shear wave velocity profiles at ebb tide and that at high tide was successfully measured by the surface-wave method. Thus, the applicability of the surface-wave method for a sheet pile quay wall is demonstrated in this study.

EVALUATION OF SEISMIC INDUCED RELATIVE DISPLACEMENT FOR CONTAINER CRANES ON CAISSON WALLS

The seismic design for quay walls and cargo handling facilities is important since the functional loss of ports may cause severe economic loss in a region. It is necessary to conduct a seismic design in terms of functionality so that cargo handling facilities may continue to function even after severe earthquakes. Relative displacement is an important index when the functionality of crane rails on caisson-type quay walls is discussed. There is a strong correlation on the level of displacement when the distance of the caissons is short, and estimation of the horizontal displacement of each caisson considering such correlation is possible by giving the correlation coefficient corresponding to the distance between the caissons. With this model, the relative displacement between caissons can be generated stochastically. As a result, evaluation of the post-earthquake functionality of a crane rail based on the allowable relative displacements becomes possible.

Analysis of Liquefaction During 2011 East Japan Earthquake – Part 2: Effective Stress Analysis Considering the Permeability of the Ground ~ Liquefaction at Reclaimed Land in the Main and After Shocks of the 2011 Great East Japan Earthquake

A series of effective stress dynamic analyses considering permeability was performed in areas with and without liquefaction damage at reclaimed land in Urayasu city in the Tokyo Bay area due to the 2011 Tohoku Earthquake off the Pacific coast. Liquefaction damage was significant because the ground shook with earthquake motions for an extremely long duration (more than 2 min for the main shock) followed by an aftershock about 30 min later. In particular, the delayed sand boil, which occurred much later than the main shock, was monitored by a security camera at the site. In typical earthquake motions with a shorter duration, the permeability of the ground is ignored in the seismic response analyses. However, whether the effect of permeability can be ignored becomes questionable when the duration of earthquake motion is extremely long and additional effects occur due to an aftershock such as the case with the 2011 earthquake. The results of the effective stress analyses incorporating the effect of permeability are consistent with the behavior of the ground with and without liquefaction damage. In particular, the delayed sand boiling at the liquefied site is well simulated by the effective stress analysis for a specific combination of permeability assigned above and below the groundwater table, indicating that it is important to carefully evaluate the permeability in the analysis of liquefaction.

Tsunami Damage: What Is Unexpected?

The 2011 Great East Japan Earthquake brought severe damage to Japanese society. The scale of the earthquake and tsunami was so large that no one could expect it in advance. This chapter is written to start the discussion about the “unexpected” issues related to tsunamis and geotechnical structures. First, brief outlines of our conventional effort for tsunami hazard mitigation and real phenomena in the 2011 Great East Japan Earthquake are introduced. Then the “unexpected” issues are discussed. Finally, a proposal for the safety and relief of the society is presented.

DEFORMATION CHARACTERISTICS OF IMPROVED GROUND BY SAND COMPACTION PILE METHOD USING IRON AND STEEL SLAG

The Sand Compaction Pile Method (SCP) is a major method to improve soft clay ground. Natural sand is generally used as a filling material of SCP. However, iron and steel slag has been recently applied as a new material because natural sand is difficult to be obtained in Japan. When the slag piles are installed into the soft clay ground, the expected ground deformations are lesser than the case of natural sand piles. In this study, loading tests using hollow cylindrical torsional test apparatus were conducted to investigate the deformation behavior of composite ground consisting of slag and clay. The deformation behavior of these materials is examined by numerical analyses. The shear strength parameters and the resistance of the treated ground under earthquake excitation were examined through the current series of tests.