Study on crack propagation and shear behavior of weak muddy intercalations submitted to wetting-drying cycles
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ORIGINAL PAPER
Study on crack propagation and shear behavior of weak muddy intercalations submitted to wetting-drying cycles L. P. He 1 & J. Y. Yu 1 & Q. J. Hu 1
&
Q. J. Cai 2 & M. F. Qu 1 & T. J. He 1
Received: 9 August 2018 / Accepted: 2 May 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract This study addresses the crack evolution law and shear behavior of weak muddy intercalations (WMIs) during wetting-drying cycles. The original crack images of WMI were processed; adjustments were made to overcome the reflective differences of crack on the surface of the WMI samples caused by the uneven surface and impurities, effectively distinguishing the crack and noncrack areas in the images of the WMI sample surface. In addition, the total length, average width, area ratio, and number of cracks were extracted as the index represents the crack condition of the WMI sample surface. Shear testing on surface of the WMI sample was used to analyze the shear properties for different wetting-drying cycles, and the relationships between crack propagation and shear properties in the wetting-drying cycles were considered. The results show that the wetting-drying cycles elongate crack on the surface of the WMI sample. The average widths of the cracks also increase, and a large number of new tensile cracks are generated. As a result, the crack degree increases with the wetting-drying cycles. Crack propagation could also weaken the WMI structure as the development of the crack may reduce the tight contact points between WMI particles, leading to decreased cohesion in the WMI. As for the shear behavior of the WMI, the shear strength may decline with the wetting-drying cycles but tends to stabilize after a certain number of cycles. Keywords Weak muddy intercalations . Wetting-drying cycles . Crack evolution laws . Shear behavior
Introduction Weak muddy intercalations (WMIs) are a common type of weak interlayers in slopes with very weak mechanical properties, causing it to be a main factor for slope instability (Huang et al. 2013; Quesada et al. 2009; Xiao et al. 2000; Zhou and Burbey 2014; Liu et al. 2017a, 2017b; Yuan et al. 2017; Zhang et al. 2011). In nature, WMI is often subject to wetting-drying cycles when, for example, rainwater seeps into interlayers from natural cracks, or the sloped banks of a reservoir fall with rising water level. Meanwhile, increased excavation activities have led to a growing exposure of WMI to nature. Numerous studies have demonstrated that the increase
* Q. J. Hu [email protected] 1
School of Civil Engineering and Geomatics, Southwest Petroleum University, Chengdu 610500, People’s Republic of China
2
School of Transportation and Logistics, Southwest Jiaotong University, Chengdu 611756, People’s Republic of China
in wetting-drying cycles means that rock or soil mass are generally characterized by enlarged original cracks with the formation of a large number of new cracks and everweakening shear properties over repeated cycles. Crack development and shear properties are i
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