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ORIGINAL PAPER

Study of the effects of clay content on loess slope failure mode and loess strength Jianqi Zhuang 1

&

Jianbing Peng 1 & Yi Zhu 2

Received: 15 July 2020 / Accepted: 22 November 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020

Abstract The particle size of loess in the Loess Plateau varies from northwest to southeast due to wind direction which is predominantly from the northwest. The clay content of loess is significantly different in the loess area of China resulting in different physical characteristics of loess and loess failure process. To determine the failure process triggered by rainfall, a series of studies were conducted via flume and triaxial tests using loess samples with different clay contents. The effects of clay on water content (WC) change, pore-water pressure (PWP) generation, and the failure process of loess slope were analyzed. The changes in WC and PWP response to the failure process of the slope at different positions were different, and the changes in the shallow layer were found to be more prominent than those at other positions. The changes in WC and PWP gradually decreased with increasing clay content. The clay in loess also plays an important role in the failure process of the loess mass, and the failure process changed from regressive overall failure to erosion-shallow sliding failure and then to erosion failure with increasing clay content. Finally, loess strength with different clay contents was tested and discussed. The strength increased and the M value decreased gradually with increasing clay content. Based on the experimental results, it was concluded that clay in loess has a significant impact on the failure process and strength of the loess mass, and the results of the current study would provide support for loess slope mitigation. Keywords Mechanism . Failure process . Fine particle . Clay content . Loess

Introduction Loess is widely deposited all over the world and formed via accumulation of mainly wind-blown dust (Li et al. 2020). The wind-formed loess areas in China cover a total area of approximately 631,000 km2 of the country’s land (Liu 1985). Loess has certain special characteristics, such as macro-pores, structural, and vertical joints, which makes it water-sensitive and prone to failure when subjected to external perturbation (Derbyshire et al. 2000; Dijkstra et al. 1995; Zhuang et al. 2017, 2018). Field investigations revealed that nearly 10,000 landslides occurred in the Loess Plateau of the Shaanxi

* Jianqi Zhuang [email protected] 1

College of Geological Engineering and Geomatics, Chang’an University, Xi’an 710054, China

2

College of Land Engineering, Chang’an University, Xi’an 710054, China

province, and 85% of those landslides were triggered by water, including precipitation and irrigation (Zhuang et al. 2018). Some examples of catastrophic loess landslides in the Loess Plateau are those that occurred on March 10, 2010, in Zizhou county, September 17, 2011, in Xi’an, and March 7, 1983, of Sale landslide, which resulted in