Experimental Study on Mechanism of Heavy Rainfall-induced Loess-mudstone Landslides in Tianshui Area,Gansu

doi:10.19657/j.geoscience.1000-8527.2020.024

Abstract

Abstract:

Rainfall-induced loess-mudstone landslide disasters are common every year in the Tianshui area (Gansu Province), causing significant loss of life and property. Based on field geological survey, engineering geological drilling, and rock and soil mechanics analyses, and through laboratory large-scale physical modelling experiment, we explore the dynamic deformation process of heavy rainfall-induced landslides (which are characterized by loess-mudstone bimodal structure), and reveal the failure mode and mechanism for this type of landslide. The results show that the slope deformation is mainly manifested as sliding damage under heavy rainfall. The role of water is mainly on increasing the soil weight and pore water pressure, and decreasing the soil strength, effective stress, and sliding resistance of the structural surface. Meanwhile, the failure mode of landslide is mainly manifested by slope shoulder erosion→microcrack growth and interconnection→local failure→overall sliding failure. Our findings are important for early-stage landslide recognition and provide scientific basis for landslide-related disaster prevention in the region.

Key words: rainfall-induced landslide, slope, landslide mechanism, model experiment

CLC Number:

HAN Shuai, SUN Ping, LI Rongjian, ZHANG Jin, LI Xiaobin, ZHU Enzhen. Experimental Study on Mechanism of Heavy Rainfall-induced Loess-mudstone Landslides in Tianshui Area,Gansu[J]. Geoscience, 2021, 35(03): 720-731.

Figures/Tables 17

Fig.1 Examples of major landslides in the study area

Fig.2 Schematic diagram of the modelling experiment setup

Fig.3 Sampling location and characteristics of loess and mudstone

Table 1 Physical parameters of experimental materials

岩土类型	干重度/(kN/m³)	初始体积含水率/%	饱和体积含水率/%	渗透系数/(m/s)	黏聚力/kPa	内摩擦角/(°)
重塑黄土	12.5	13.75	43	2.8×10^-7	11.28	21.1
重塑泥岩	14.0	19.60	48	3.1×10^-4	55.15	22.0

Table 2 Rainfall parameters for the experiment

降雨类型	人工降雨强度 /(mm/h)	降雨时间	降雨类型
人工模拟降雨	89.71	间歇性降雨,降2 min,稳定28 min,直至斜坡破坏	大雨

Table 3 Slope design scheme of the experiment

实验类型	坡度/ (°)	地层结构	结构面	水分仪 /个	土压力盒/个
工况1	60	黄土、泥岩	预制垂直裂隙,预制滑动面位于黄土内部	19	5
工况2	60	黄土、泥岩	预制垂直裂隙,预制滑动面深入泥岩内部	18	5

Fig.4 Model slope design and sensor layout for the experiment

Fig.5 Slope deformation and failure process under working condition 1

Fig.6 Volumetric water content variation under working condition 1

Fig.7 Soil pressure variation under working condition 1

Fig.8 Slope deformation and failure process under working condition 2

Fig.9 Volumetric water content variation under working condition 2

Fig.10 Soil pressure variation under working condition 2

Fig.11 Failure mode of rainfall-induced loess-mudstone contact surface landslide(working condition 1)

Fig.12 Failure mode of rainfall-induced loess-mudstone composite landslide(working condition 2)

Fig.13 Strength decay curve of loess under different volumetric water contents

Table 4 Strength parameters of loess under different water contents

体积含水率/%	内摩擦角/(°)	黏聚力/kPa
5	21.5	20.5
10	21.8	15.2
15	21.4	11.5
20	21.5	8.6
25	21.7	6.5

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