Abstract
The surficial failure of most expansive soil cutting slopes, subjected to the repeated wet‐dry cycles, often occurs during or after rainfall following a long drought. The reason for this, however, is still unclear. Therefore, the laboratory tests were conducted to gain the saturated drained shear strength of the natural Nanning expansive soil considering the combined effects of swelling with loading and wet‐dry cycles. The findings indicate that the envelope of shear strength, which significantly drops close or equal to zero, can be well fitted by the generalized power function. At the same time, the effect of shear strength parameters on the stability of the expansive soil cutting slope was investigated. The reasons for the shear strength attenuation of the natural expansive soil and the surficial failure of the expansive soil cutting slopes were analyzed. It is evident that the effective cohesion being small is a vital factor influencing the occurrence of surficial failure of an expansion soil slope. Moreover, an effective flexible support treatment measure was provided.
Highlights
Expansive soils, which are regarded as a problem soil, are typically encountered around the world. e total distribution areas of expansive soil are more than one hundred thousand square kilometers in China [1]. ese soils have three typical properties due to hydrophilic minerals such as montmorillonite. eir strengths are sensitive to changes in the surrounding environment.e failure of expansive soil slopes, especially surficial failure, is one of the most serious geological disasters that frequently occurs during the construction of highways, railways, and hydraulic engineering projects in expansive soil areas in China [1]
Wang et al [3] reported that the sliding depth generally ranged from 1.0 to 2.5 m, and the reason for the surficial failure of expansive soil slopes may be a drastic reduction in the strength of slope surface soil
Overburden pressures signi cantly in uence the amount of water absorbed by the soils, and smaller overburden pressures lead to higher soil water absorption capacities. erefore, it is evident that the water lm between the clay particles subjected to lower overburden pressures will be thicker and the dry densities will be lower
Summary
Expansive soils, which are regarded as a problem soil, are typically encountered around the world. e total distribution areas of expansive soil are more than one hundred thousand square kilometers in China [1]. ese soils have three typical properties (i.e., significant swelling and shrinkage, fissures, and overconsolidation) due to hydrophilic minerals such as montmorillonite. eir strengths are sensitive to changes in the surrounding environment.e failure of expansive soil slopes, especially surficial failure, is one of the most serious geological disasters that frequently occurs during the construction of highways, railways, and hydraulic engineering projects in expansive soil areas in China [1]. Numerous researchers have studied the depth of the surficial failure of expansive soil slopes by field investigations. Wang et al [3] reported that the sliding depth generally ranged from 1.0 to 2.5 m, and the reason for the surficial failure of expansive soil slopes may be a drastic reduction in the strength of slope surface soil. It results from the occurrence of swellingshrinkage cracking and fissures due to the repeated wetdry cycles.
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