Abstract
To investigate the bond yield characteristics of undisturbed completely decomposed granite (CDG) which is widely distributed in Southern China, a series of conventional drained tests were conducted. From the test data, some insights are obtained as follows: for undisturbed CDG soils, the bond yield point during shearing could be identified on the curve of the normalized tangential stiffnessEtan/p′versus axial strain on log-log scale. The consolidation pressureP0′has a significant influence on the bond yield characteristics of undisturbed CDG during shearing, the bonds inside undisturbed CDG tend to be damaged relatively more seriously asP0′is higher, accordingly the initial normalized stiffnessEitan/p′will be smaller at the beginning of the shearing process, and the axial strain at the bond yield point will also be smaller. Once consolidation pressureP0′excesses a critical value such as 475 kPa for this studied CDG, the bonds inside soil will be damaged totally at the consolidation compression stage. In this case, there will be no bond yield occurring during shearing and theEtan/p′-εacurves will coincide with the ones of reconstituted CDG soil. For reconstituted soils, no bond yielding was observed during shearing; theEtan/p′-εacurves are tightly consistent with no dependence of the value ofP0′.
Highlights
In Hong Kong district and Guangdong province of China, about 63% of the urban areas are developed on granite [1]
The completely decomposed granite soil used in this study was taken from the #D1 construction site located at the Zhonghang Mall of Futian District, Shenzhen city, China
In order to obtain the physical properties of the soil, the free-fall method proposed by the Japanese Society of Soil Mechanics and Foundation Engineering (JSSMFE, 1982) [14] was adopted to ensure that small lumps of soil specimens were broken up consistently
Summary
In Hong Kong district and Guangdong province of China, about 63% of the urban areas are developed on granite [1]. To investigate the influence of stress ratio and stress path on the behaviors of loose composed granite, laboratory tests including undrained tests, drained tests with constant deviator stress, and a decreasing mean effective stress path were conducted by Ng et al [4] As these studies revealed, the isotropic compression lines (ICL) and critical state lines (CSL) are rather steady with no dependence of stress paths for CDG soils in their reconstituted states. It has been well known through engineering practices that the mechanical behaviors of undisturbed CDG are significantly different from its reconstituted state Such differences may be aroused by the existent of the initial soil structure (fabric and bonds) inside undisturbed soil [9, 10].
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