A prediction model for rock planar slides with large displacement triggered by heavy rainfall in the Red bed area, South
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Bin Yu I Erlong Ma I Jiajun Cai I Qiang Xu I Weile Li I Guang Zheng
A prediction model for rock planar slides with large displacement triggered by heavy rainfall in the Red bed area, Southwest, China
Abstract Landslides with large displacements are more dangerous than landslides with small displacements, because the first category causes more serious damages. In this paper, a new prediction method is introduced for rock planar slides with large displacements. The prediction model is not limited to a certain region but limited to a certain failure mechanism of a landslide. This case study was carried out in the red bed area, Nanjiang County, Sichuan Province, China, and validated in the red bed area of Yunyang and Fengjie Counties, Chongqing, China. The topographic factor T was proposed as a topographical indicator. The influence of the normalized rainfall R which is a combination of the duration of rainfall (D) and the average intensity (I) of rainfall was analyzed. A threshold value for rock planar sliding with large displacement was obtained by establishing a relationship between the T factor and the R factor. The primary probability factor P gives a final indication of the probability of rock planar sliding with large displacement. The prediction model is applied to the existing rock planar slides or the slopes with the presence of a number of preconditions for sliding. The prediction model obtained from Nanjiang County was validated successfully in the red bed area of the Yunyang and Fengjie Counties. It is assumed that the prediction model is suitable for other regions with a red bed structure as well. Keywords Prediction model . Rock planar slide . Displacement . Red bed area Introduction Rainfall-induced landslides may cause considerable damage to lives and infrastructures, and demand greater attention in recent years. The landslides with large displacements are more dangerous than the small-displacement landslides, because the landslides with large displacements cause more serious damage. The extreme rainstorm in September 2011 induced many landslides in the “red bed” area in Nanjiang County, Sichuan Province, China (Fig. 1). Because of the particular properties of strata, the red beds are prone to sliding (Wu et al. 2018). Red beds are sedimentary strata with a red color and are widely developed in the Sichuan Basin in the southwest of China (Fig. 2). The red beds are composed of an alternation of thick sandstone and thin mudstone layers, and are formed in the Jurassic and Cretaceous ages (Huang et al. 2005). Differential deformation between these two rock types generated a number of vertical tension cracks (Xu et al. 2016). Landforms in the red bed area represent middle and low mountain landscapes, and the rock structure is dominated by a gentle dip of the rock strata. Landslides typically develop in these gentle dipping or nearly horizontal layers with dipping angles commonly between 3 and 22° (Fan et al. 2009; Wu et al. 2018).
Compared with soil slips, rock planar slides occurred less frequently but w
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