Engineering and geological characteristics of granite weathering pro®les in South China H.X. Lan a, * , R.L. Hu b , Z.Q. Yue c , C.F. Lee c , S.J. Wang b a LREIS, Institute of Geographical Sciences and Natural Resource Research, Chinese Academy of Sciences, No. 3, Datunlu, Chaoyang District, Beijing 1000101, People's Republic of China b Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing 100029, People's Republic of China c Civil Engineering Department, University of Hong Kong, Hong Kong, People's Republic of China Received 30 March 2001; revised 19 November 2001; accepted 26 February 2002 Abstract Granite weathering pro®les are widely distributed in South China. Their engineering and geological characteristics are major geotechnical subjects that are important in the design and construction of civil engineering projects. This paper presents a summary of the weathering characteristics and zoning of granite weathering pro®les in South China and discusses their engineering and geological properties. A ®ve- grade scheme has been adopted in the zoning of a granite weathering pro®le. Studies have shown that the completely weathered granites (CWG) in South China have the following characteristics: low moisture content, low to medium plasticity (W L 22:5±39:0%; I p 6:5±11:8%), medium void ratio (0.36±1.29), weak shrinkage and medium compressibility a 1±2 0:24±0:8 MPa 21 and high shear strength f 20±308; c 20±40 KPa: The CWGs are usually at a low or high plastic state and most of them are over-consolidated soils. A majority of the physical and mechanical properties have good statistical correlations with the degree of weathering. The data presented in the paper are important in geotechnical engineering projects such as slope stability evaluation in China. q 2002 Elsevier Science Ltd. All rights reserved. Keywords: Granite weathering pro®le; Weathering zoning; Engineering geological characteristics; Slope stability 1. Introduction Granite weathering pro®les (or weathered granitic crust) with thicknesses in the range of 20±60 m are widely distrib- uted in South China. These pro®les include geological struc- tures with mixed soils and rocks originating from weathered parent rocks and remaining in situ. These pro®les have more complex engineering properties than other sedimentary soils. For example, they possess noticeable structural strength, but are also sensitive to moisture alternation. Since the conventional methods for testing and analyzing common transported soils are usually not appropriate for GWPs, it is dif®cult to determine the mechanical parameters for the slope stability assessment or foundation design in granite weathering pro®les in the mainland of China, Hong Kong, South Africa, and Brazil. (Onodera, 1976; Blight and Brummer, 1980; Wang and Tang, 1991; Hill, 1998). Some research has been done on the geological evolution of gran- ite weathering pro®les in some areas (Liu 1985; Cheng and Zhang, 1990; Cheng and Liu, 1990; Wei, 1991; Huang and Fu, 1998), but few papers provide an overall understanding of the comprehensive engineering and geological character- istics observed in South China. By reviewing the relevant literature collected during the past 10 years, this paper tries to gain an understanding of the state of the art research, engineering approaches and char- acteristics of granite weathering pro®les in South China. Most research in the preceding references focus on the East China, especially the coastal areas to the southeast within the tropic and sub-tropic areas, where large-scale granite intrusions are widespread (Fig. 1). The granite weathering pro®les in China are mostly developed in the Guangdong, Fujian and Hainan provinces. Therefore, the compiled papers basically represent the current level of research on weathered granites in South China. 2. Development of granite weathering pro®les in South China 2.1. Geochemical types The formation and evolution of weathering pro®les in Journal of Asian Earth Sciences 21 (2003) 353±364 1367-9120/03/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved. PII: S1367-9120(02)00020-2 www.elsevier.com/locate/jseaes * Corresponding author. Tel.: 186-10-64-88-9764. E-mail address: [email protected] (H.X. Lan).
