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SE9-001
16:10
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16:30
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CURRENT STATUS OF, AND PROBLEMS WITH, HAZARD MAPS FOR SOIL LIQUEFACTION
This paper introduces the development history, current situation and problems concerning hazard maps for soil liquefaction. A zonation manual entitled "Manual for Zonation on Seismic Geotechnical Hazards", produced by the TC 4 of ISSMFE in 1993, is introduced first. Then, the development of hazard maps for liquefaction in Japan is reviewed. A hazard map for liquefaction was first created by Ishihara and Ogawa in 1978. By 1991, hazard maps had been created for 13 administrative divisions and major cities. Currently, hazard maps exist for all administrative divisions of 47 administrative zones. However, they are not being fully used. In order to be fully used, i) accurate and reliable hazard maps must be made, especially by considering local soil characteristics, ii) it is necessary to create hazard maps that can quantitatively predict the damage to each structure, such as a wooden house, and iii) hazard maps should show not only the probability of liquefaction, but also time lines of temporary risks after an earthquake. Examples in which the first two issues were resolved are introduced, and comments on the difficulty of resolving the third issue are given.
Susumu Yasuda
earthquake geotechnical engineering, hazard map, soil liquefaction,
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F4-013
16:30
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16:50
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EFFECT OF GROUND IMPROVEMENT THROUGH DYNAMIC COMPACTION ON LIQUEFACTION OF RECLAIMED LAND
This paper presents findings of a study on the effect of ground improvement through dynamic compaction on liquefaction potential of sands. The effect of ground improvement is observed in the increase in soil strength and the reduction in the variation of soil strength. The above concept is illustrated through a case study of a site where CPTs were conducted before and after dynamic compaction and where liquefaction manifestation was observed in the 1999 Chi-Chi earthquake. The results of the analysis of these CPTs for liquefaction potential at the study site before and after dynamic compaction are reported.
Chih-Sheng Ku, Mengfen Shen, Charng Hsein Juang
coefficient of variation, dynamic compaction, liquefaction, reclaimed ground
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F5-012
16:50
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17:05
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A FEW EXAMPLES OF LIQUEFACTION ASSESSMENT OF GROUND DURING EARTHQUAKE USING PIEZO DRIVE CONE IN TAIWAN
Cone penetration test is one of the most important and convenient tools for subsoil investigation and many efforts have been made in the recent decades in Japan to extend its application to a variety of field of geotechnical engineering. The present paper addresses a new development of dynamic cone penetration with pore water pressure measurement during dynamic penetration. A few Examples of the validation test results in Taiwan indicate that this newly developed equipment is highly useful for mitigation of liquefaction-induced problems due to earthquakes. This article addresses the new development of cone penetration device that is equipped with pore pressure transducers. It is shown herein that the new device, which is called the Piezo Drive Cone, is a time-efficient tool that can evaluate the liquefaction risks such as the factor of safety and ground subsidence. The time efficiency makes it possible to study a large area in a relatively short period. Through the examples in Taiwan, the problem and solution of using the Piezo Drive Cone is extracted.
Shun-ichi SAWADA, Chao-Wen Wang, Nobukyuki HIRUMA
cone penetration, dynamic penetration, liquefaction, pore water pressure, Taiwan
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SE9-013
17:05
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17:20
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A NEW SIMPLIFIED METHOD FOR ASSESSING LIQUEFACTION POTENTIAL OF SOILS: TWENTY YEARS DEVELOPMENT OF HBF METHOD
This paper presents the twenty years development of a new localized simplified method for assessing soil liquefaction potential in Taiwan after Chi-Chi earthquake. The framework of the method is summarized with a flowchart. Its main features and merits are illustrated. The comparison of its performance with other well-known methods is made by a great number of earthquake cases and the micro-zonation maps of Taipei basin produced by them. The results show that the prediction accuracy of the new method is as good as NCEER method (Youd et al., 2001).
Chih-Chieh Lu, Jin-Hung Hwang, Cheng-hsing Chen, Charng-Hsein Juang
Chi-Chi earthquake, liquefaction, localized, simplified method
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SE9-011
17:20
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17:35
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VS BASED APPROACH TO REFINE LIQUEFACTION HAZARD MAP
After the 2016 Meinong Earthquake, the issue of soil liquefaction was brought great attention to the public in Taiwan. The Central Geological Survey of Taiwan declared the liquefaction potential maps of various counties and cities. The development of maps is based on the calculated liquefaction potential index using the existing borings, and then the liquefaction potential of the area is interpolated spatially. The procedure is limited by the amount of drilling work and the distribution of borings. In order to improve the accuracy of the liquefaction potential map and reduce the cost during its development, this study proposes to utilize shear wave velocity (Vs) as complementary information to refine the low-precision liquefaction potential maps. First, the relationship between the liquefaction potential index and the average shear wave velocity of 10m, 20m and 30m under the surface (Vs,10, Vs,20, Vs,30) is established by the boring data and shear wave velocity profile in the Engineering Geological Database. Based on that, the spatial Vs can be converted into liquefaction potential index, and thus to refine the liquefaction potential map. The proposed procedure is illustrated by refining the currently declared liquefaction hazard map of Changhua County.
Chi-Chin Tsai, Shu-Hui Lin
Liquefaction Potential Index, liquefaction potential maps, shear wave velocity, surface wave technique
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SE9-012
17:35
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17:50
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FACTORS CONSIDERED IN PRODUCING A REFINED SOIL LIQUEFACTION POTENTIAL MAP: A CASE STUDY OF TAIPEI BASIN
The purpose of this study is to address several factors considered in producing a refined soil liquefaction potential map taking the case of Taipei Basin as an example. In this example, over 4 thousands boreholes widely distributed in the Taipei Basin were first collected from different databases. With the geological boreholes, the soils were first classified by the unified soil classification system (USCS) and a brief introduction of geological characteristics for the area was given accordingly to the statistical analysis for different soils. After that, the consideration of the external forces for the soil liquefaction evaluation including the PGA of the earthquake and the ground water table is introduced, and the soil liquefaction evaluation was then conducted to determine the factor of safety against soil liquefaction for each soil layer of the boreholes, and the concept of liquefaction potential index (PL) was adopted to evaluate the soil liquefaction effect of a liquefiable soil column. To better consider the surface manifestation of liquefaction, the evaluation frameworks with further considering the thickness of the surface un-liquefiable crust proposed by the Japanese researchers were used to analyze the collected boreholes. Finally, the results by different surface manifestation of liquefaction evaluation frameworks will be compared and a brief summary can be given.
Chih-Chieh Lu, Hsien-Li Huang, Jin-Hung Hwang
Liquefaction Potential Index, Soil Liquefaction, Surface Manifestation
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