Experimental study of relationships between various void parameters and liquefaction behavior for gravelly sand using cyclic simple shear

• Main Authors: Ming-ChungＷei, 魏銘忠
• Other Authors: 林炳森
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/32657019087846948808

碩士 === 國立中興大學 === 土木工程學系所 === 94 === The distributed range of the gravel layer is wide in Taiwan. On the topography, the gravel layers often appear in the low and flat place, such as the river valley , plain , tableland and hills areas. These areas are mostly densely populated and the industry is developed. The huge buildings and public constructions are numerous in the area. Taiwan lies between the Eurasia plate and Philippine''s sea plate, plates movement cause the seismic activity to be frequent. Chichi earthquake occurs on September 21 of A.D. 1999, Richter Magnitude of Earthquake (ML )is large to 7.3, and it causes the extensive and serious calamity . The rare gravel soil liquefaction phenomenon were found in Nantou County and Wufeng town from many liquefaction cases. Two kinds of admixture were selected in experiment, including gravel of single size (1”) and Ottawa sand respectively. Besides, a cyclic simple shear of large size instrument were used to the test of the liquefaction resistance for remolded samples . At the same time of the test, Bender Element were placed in the top of the sample to measure shear wave velocity . The critical liquefaction resistance curve for Andrus & Stokoe’s about shear wave velocity assessment method were drawed repeatedly. The measured results of shear wave velocity about this research, Pei-Cong Wu and Yuan-Wei Shi (2004) were integrated with Andrus and Stokoe’s（2000）data of gravel. Finally, the paper used regress analysis of Minimum of Misclassified Points to get the critical liquefaction resistance strength curve of the gravel layer where , a is equal to 0.033on the best-fitting curve,b is equal to 2.4 on the best-fitting curve,calculate the normalized shear modulus (Vsl) after correcting for the overburden pressure, is 270 m/s. The results of the test show that the minimum liquefaction resistance was observed for specimens with 40 % fines. The liquefaction resistence strength of gravel soil drop with increase of the content of fines. It is attributed to variations of microstructures of gravel sands and can be explained with variations in gravel skeleton and interfine void ratios according to the fines contents of gravel. For gravel soils with more than 40 % of fines contents, the gravel soils behave like clean sands and the liquefaction resistance increas with decreasing of gravel skeleton void ratio.