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F2-001
13:30
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13:50
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LIQUEFACTION ANALYSIS ADOPTING EFFECTIVE STRESS METHOD FOR PETOBO SITE POST MW 7.4 PALU EARTHQUAKE
An earthquake with moment magnitude 7.4 occurred in Central Sulawesi on September 28, 2018. The epicenter was 26 km North of Donggala city and 72 km Northwest of Palu city with depth of 10 km. This earthquake is associated with Palu-Koro faults that the earthquake rupture extends to Palu city. Post earthquake site survey was carried out and showed severe damages due to flow liquefaction in several regions, such as Petobo, Jono Oge, and Balaroa. To assess the subsurface conditions and better understand the behavior of the site, subsurface exploration was carried out in several liquefied sites. Moreover, some soil samples were collected and tested in laboratory. Results of the tests showed that the samples were susceptible to liquefaction. Additionally, numerical analyses, adopting an effective stress approach were performed to verify the liquefaction and its seismic vulnerability of the site due to Palu earthquake. The effective stress dynamic analyses were carried out using FLAC2D Version 7.0 (Itasca, 2011) utilizing UBCSAND constitutive model. In this study, acceleration time histories were obtained from record of PCI-PALU (BMKG – JICA) station with PGA of 0.33g. Results of this study has verified the liquefaction occurrence and provide the liquefied sand behavior in the form of deformations, settlements, and pore-water pressures development due to the earthquake.
Wayan Sengara, Ahmad Sulaiman
Dynamic analysis, effective stress, Finite difference method, liquefaction, Palu earthquake
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F2-012
13:50
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14:05
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ONE MAPPING MODEL FOR LPI BY CPTU AND SPT METHODS
This paper gathers high- qualified CPTu (Piezocone Penetration Test) records with respected to the adjacent SPT (Standard Penetration Test) ones from some representative sites in Taiwan, and exploits them to testify whether the differences between Liquefaction Potential Index (LPI) assessed by CPTu and SPT methods results from different data resolution of the two types of tests. If the impact of data resolution is not significant, the calibration on LPI assessed by CPTu and SPT methods based on the collected data records could be conducted in the paper for consistency of liquefaction assessment based on CPTu and SPT methods.
Jiun- Shiang Wang, Chih-Chieh Lu, Jin-Hung Hwang
CPTu-qc methods, Soil Liquefaction, SPT-N methods.
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F2-015
14:05
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14:20
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LIQUEFACTION RESISTANCE OF PENGHU CALCAREOUS SAND
Calcareous sand is formed by biodegradation, composed of calcium carbonate, and weak structurally compared to quartz/silica sand. Calcareous sand has high void ratio and angular particle shape. They can be found in tropical and subtropical shallow waters. It is highly likely that calcareous sand would be encountered in the construction of coastal and offshore structures, such as port facilities, sea base, and offshore wind turbines. In this study, a series of cyclic triaxial tests were performed on reconstituted calcareous sand specimens obtained from Penghu. Liquefaction resistance of Penghu calcareous sand with different relative densities were determined and compared to that of silica sand.
ON LEI ANNIE KWOK, Jia-Ren Liu, Chia-Ying Lien
Liquefaction, Calcareous Sand, Penghu, Cyclic Triaxial Test
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F2-013
14:20
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14:35
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PARAMETRIC STUDY OF FACTORS AFFECTING TUNNEL UPLIFT INDUCED BY SOIL LIQUEFACTION
The Bay Area Rapid Transit (BART) Offshore Transbay Tube (TBT) was constructed in the 1960’s. Because of the low relative density (< 50%) of the gravelly backfill materials around the tunnel, the occurrence of the soil liquefaction of the backfill materials is expected during major earthquakes. Two centrifuge model tests were performed to study the stability and the seismic behavior of the BART TBT (Chou, 2010; Chou et al., 2011). In addition, numerical simulations using a finite difference program, FLAC 2D, were also performed to verify the ability of FLAC 2D program to simulate the uplift mechanisms observed in the centrifuge tests and to calibrate the input parameters of UBCSAND model (a constitutive model used to model the liquefiable materials) (Chou et al., 2010). In this article, a parametric study using the verified numerical tool is performed to understand effects of geometry characteristics and soil properties on the seismic behavior of the tunnel. Parametric study results and observations can be used as guidelines for the retrofit design of tunnels and other underground structures to minimize the uplift induced by soil liquefaction.
Jui-Ching Chou, Bruce Kutter
FLAC 2D, liquefaction, Numerical Simulation, Tunnel Uplift, UBCSAND
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F2-011
14:35
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14:50
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A DISCUSSION ON THE DAMAGE MECHANISMS OF HUALIEN HARBOR IN 20180206 HUALIEN EARTHQUAKE
After Hualien earthquake on February 6th, 2018, sand volcanoes of soil liquefaction and serious settlement were observed at gravel backfill backlands of wharf no. 19~25 and western breakwater, which seriously obstructed shipping work in Hualien Harbor. In order to better realize the liquefaction and settlement mechanisms of gravel backfill ground, this research first chose a site with obvious liquefaction evidence and settlement at the backland of wharf no. 25 to execute a series tests including a field test pit, standard penetration tests, shear wave velocity measurements, and laboratory tests. For comparison, the other site without obvious damage evidence and close to the wharf no. 25 was selected to perform similar tests. The distance between the two sites is about 35 m. Afterward, the testing results and seismic records of Hualien Harbor station have been collected to evaluate the liquefaction potential of the studied sites by using SPT- and VS-based simplified methods. Based on the field reconnaissance, testing results, analysis results, and existed completion drawings, the causes of the serious settlement of the wharf no. 25 are preliminarily deduced from the liquefaction at shallow loose gravel and the densification effect of deeper reclaimed ripraps due to the strong ground vibration. In addition, the seismic densification of gravel soil may cause higher shear wave velocity and SPT-N values after the Hualien earthquake.
Chih-Chieh Lu, Yuan-Chang Deng, Jin-Hung Hwang
20180206 Hualien Earthquake, gravel soil, Hualien Harbor, liquefaction
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F2-014
14:50
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15:05
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A PRELIMINARY STUDY OF THE LIQUEFACTION POTENTIAL OF GRAVELLY SOILS USING SHAKING TABLE TESTS
In recent years, the damages of ports filled with gravelly sandy soils due to earthquake-induced liquefaction have been observed and drawn lots of attention in geotechnical engineering. In order to study the liquefaction behavior and dynamic characteristics of sand-gravel composites, it is performed that a series of 1g shaking table tests with the large-scale biaxial laminar shear box filled with the gravelly sandy soils sampling from Hualien Port, as a case study of the failures of Hualien Port in Taiwan due to 0206 Hualien Earthquake in 2018. For specimen preparation, the wet pluviation technique with a pluviator is adopted to simulate the in-situ condition of the sand-gravel composites in the wharf area. For input motions, not only the records of 0206 Hualien Earthquake with varying amplitude are select in this study, but white noises and sinusoid sweep are also applied for further comparison. For measurements, the instrument sensors including accelerometers, piezometers, and linear displacement transducers (LDT) are exploited to record the accelerations, pore water pressure responses, and displacements of the soil specimen during the dynamic test. Finally, the test results are demonstrated and would be discussed.
Kuan-Yu Chen, Hsuan-Chih Yang, Chia-Han Chen, Jin-Hung Hwang
gravelly soils, gravel-sand composites, Shaking table test, Soil Liquefaction
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F2-019
15:05
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15:20
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LIQUEFACTION POTENTIAL EVALUATION BASED ON SPT, CPT AND PDC IN-SITU TESTS AND THEIR CORRELATIONS FOR KAOHSIUNG SOILS
The Meinong earthquake with a magnitude of 6.4 on the Richter scale struck southern Taiwan on 6 February 2016, in which soil liquefaction occurred at the base of many buildings caused the buildings to damage. The soil liquefaction issues had many public concerns and therefore a national project was conducted, of which thousands of SPT in-situ tests as well as tens of CPT tests, for the evaluation of liquefaction potential to establish the liquefaction map. Aside from the traditional methods which are based on SPT and CPT tests, the Piezo Drive Cone (PDC) equipment developed by a Japanese company is also carried out in this Kaohsiung soil liquefaction hazard map development project of which was the first oversea site for the PDC test.A correlation for estimating equivalent SPT N-values from CPT data although has been presented accounting for variations in soil grain size and SPT energy input in previous research worldwide. This paper focused on comparing the evaluation results and develop the correlations among the above mentioned in-situ tests for Kaohsiung soils in the area of high residential density.
Min-Chang Wu, Chen-En Chiang, Chih-Wei Lu, Pao-Sheng Kuo, Wen-Chih Liu
Kaohsiung soils, PDC, Soil Liquefaction, SPT-N and CPT correlation
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