Abstract
Mechanical properties of intact completely decomposed granite (CDG) soil, widely distributed in South China, decrease drastically as encountering external load-related disturbance or soaked by water. In this study, staged triaxial consolidated drained (CD) test and microscopic scanning were conducted using intact CDG specimens extracted from a construction site to investigate the mechanical behavior and microscopic pore distribution. The results show that the stress-strain relationship reveals a shrinking behavior in the first-stage loading and a brittle behavior in the second-stage loading. The development of cracks is affected by the principal stress, which causes the pores and cracks to shrink or partially close. In addition, Esec-1 increases linearly with the increase of confining pressure, but Esec-2 decreases exponentially.
Highlights
With the rapid economic development of Shenzhen in recent years, a large number of modern infrastructures have been constructed extensively. Engineering problems, such as failures of cutting slopes and excessive uplifting of tunnels, occur frequently in this area that is mainly covered with completely decomposed granite (CDG) soils
Decomposed granite soil is widely distributed in many parts of the world
Wang et al [18] investigated the effects of fines contents on the mechanical behavior of CDG during dynamic compaction grouting. e shear strength parameters of the CDG can be used for the stability calculation of the excavation slope [19, 20]
Summary
With the rapid economic development of Shenzhen in recent years, a large number of modern infrastructures (metros) have been constructed extensively. Engineering problems, such as failures of cutting slopes and excessive uplifting of tunnels, occur frequently in this area that is mainly covered with completely decomposed granite (CDG) soils. Decomposed granite soil is widely distributed in many parts of the world It approximately covers 40% of the surface land area with thickness in the range of 0–60 m in Shenzhen, China [1,2,3]. Understanding the relationship between secant modulus and unloading modulus and confining pressure is crucial to evaluate the deformation of infrastructures such as filled subgrade settlement or tunnel uplift problem involving the weathered granite profile [21,22,23,24,25]
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