Mapping spherically weathered "Boulders" using 2D microtremor profiling method: A case study along subway line 7 in Shenzhen

doi:10.6038/j.issn.0001-5733.2012.06.034

	Mapping spherically weathered "Boulders" using 2D microtremor profiling method: A case study along subway line 7 in Shenzhen
	Xu Pei-Fen 1; Shi Wen 1,2; Ling Su-Qun 3; Guo Hui-Li 1,2; Li Zhi-Hua 4,5
刊名	CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION
	2012-06-01
卷号	55 期号:6 页码:2120-2128
关键词	2D Microtremor profiles Microtremor survey Apparent S-wave velocities "Boulder" Subway engineering investigation
ISSN号	0001-5733
DOI	10.6038/j.issn.0001-5733.2012.06.034
文献子类	Article
英文摘要	A "boulder stone" is referred to the remnant of a granite body which has been unevenly weathered. These "boulders" become a common geological feature in areas close to the shoreline in south of China. They are typically randomly distributed and buried in soil or weathered rocks with varying shapes and sizes. Their existence poses a serious operational risk to the subway tunnel construction. Boulder detection has been a difficult problem in geotechnical investigation and surveying for subway building. This paper documents the first application of a 2D microtremor profiling method to map spherically weathered "boulders". Principles of the method will be described followed by real application examples. Two microtremor profiles were obtained between Chegongmiao and Shangsha along subway line 7 in Shenzhen. The microtremor data, combined with limited drilling data, were used for lithostratigraphic classification and boulder interpretation. On the 2D profiles, we observed different apparent S-wave velocity values for different lithologic sediment layers, such as plain fill, silty clay, rudaceous sediments. In particular, there appeared a strong correlation between apparent S-wave velocity and the degree of weathering of the granitic layers (namely completely, strongly, moderately, slightly, and non-weathered). With the help of limited drilling data, it is possible to quantify, at least qualitatively, the degree of the granite weathering from the apparent S-wave velocity characteristics. Local high apparent S-wave velocity anomalies in otherwise moderately to strongly weathered granitic layers interpreted as unweathered "boulders". Our results demonstrate that the 2D rnicrotremor profiling is a very effective technique for "boulder" detection and mapping. The lithological variation and weathering in both vertical and horizontal directions, the depth of the bedrock and its undulating configuration can be shown clearly in 2D microtremor apparent S-wave velocity profile. Therefore, the method can also provide geophysical basis for designing the pile foundations for the high-rise buildings. As a new method for "boulder" detection and mapping, the 2D microtremor profiling method is particularly useful in densely-populated urban areas with crowded high-rise buildings and heavy traffic.
WOS关键词	VELOCITY STRUCTURE ; PHASE-VELOCITY
WOS研究方向	Geochemistry & Geophysics
语种	英语
出版者	SCIENCE PRESS
WOS记录号	WOS:000306159400034
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/84690]
专题	中国科学院地质与地球物理研究所
通讯作者	Xu Pei-Fen
作者单位	1.Chinese Acad Sci, Inst Geol & Geophys, Beijing 100029, Peoples R China 2.Grad Univ, Chinese Acad Sci, Beijing 100049, Peoples R China 3.Geoanal Inst Co Ltd, Tokyo 1840012, Japan 4.Third Railway Survey, Tianjin 300251, Peoples R China 5.Design Inst Grp Corp, Tianjin 300251, Peoples R China
推荐引用方式 GB/T 7714	Xu Pei-Fen,Shi Wen,Ling Su-Qun,et al. Mapping spherically weathered "Boulders" using 2D microtremor profiling method: A case study along subway line 7 in Shenzhen[J]. CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION,2012,55(6):2120-2128.
APA	Xu Pei-Fen,Shi Wen,Ling Su-Qun,Guo Hui-Li,&Li Zhi-Hua.(2012).Mapping spherically weathered "Boulders" using 2D microtremor profiling method: A case study along subway line 7 in Shenzhen.CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION,55(6),2120-2128.
MLA	Xu Pei-Fen,et al."Mapping spherically weathered "Boulders" using 2D microtremor profiling method: A case study along subway line 7 in Shenzhen".CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION 55.6(2012):2120-2128.