Abstract
Soil-rock mixtures (S-RMs) composed of rock slope colluvium and landslide deposits are common in superficial hazards of bank slopes. The physical and mechanical properties of S-RMs are closely related to environmental conditions, especially reservoir water level fluctuation. Therefore, immersion-air dry (I-AD) circulations tests were carried out to simulate the phenomenon in this study. The macroscopic, mesoscopic, and microcosmic studies of S-RMs are carried out after experiencing cycles (N) of 0, 1, 5, and 10, respectively. Conventional triaxial tests, particle analysis tests, and scanning electron microscopy were performed to study the physical and mechanical properties of S-RMs. According to test results, the maximum deviator stress of S-RMs samples with confining pressures of 100, 200, 300, and 400 kPa after ten cycles is reduced by 41.13, 37.11, 32.17, and 30.20%. With the increase in N there is a significant trend towards reducing the strength of S-RMs, and the strength deterioration after the first I-AD circulation reached 15.73%. After I-AD circulations, the content of fine particles in S-RMs decreases, the grain-size characteristic and non-uniformity coefficient increase significantly, and the gradation of S-RMs shows discontinuity. Moreover, the repeated changes of water pressure have an irreversible impact on the microstructure of S-RMs, which will cause an increase in pore size and a higher pore disorder. In addition, it is found from the established strength parameter evolution equation that when N approaches infinity, S-RMs decomposes the weathering into cohesionless silt with an angle of repose of 0.90322φ0. The study results in this paper clarify the deterioration characteristics of wading S-RMs, and might be used in the bank slopes stability analysis.
Highlights
Soil-rock mixtures (S-RMs) are widely distributed in the mountainous areas of southwestern China, which formed in Quaternary are a type of uneven, loose accumulation geotechnical medium (Xu et al, 2008; Xu et al, 2011)
The shear strength (Goh et al, 2014; Wang Jun-Jie et al, 2019), permeability (Ng and Leung 2012; Gallage and Uchimura 2016), deformation characteristics (Wang et al, 2018; Al-Dakheeli and Bulut 2019), and physical properties (Yang et al, 2018; Yang et al, 2019) of geomaterials will be affected by immersion-air dry (I-AD) circulations
The shear strength of coal-bearing soil after I-AD circulations is measured by the shear strength test, and it is pointed out that the total cohesion and the total internal friction angle are greatly affected by the moisture content (Fan et al, 2021)
Summary
Soil-rock mixtures (S-RMs) are widely distributed in the mountainous areas of southwestern China, which formed in Quaternary are a type of uneven, loose accumulation geotechnical medium (Xu et al, 2008; Xu et al, 2011). The shear strength (Goh et al, 2014; Wang Jun-Jie et al, 2019), permeability (Ng and Leung 2012; Gallage and Uchimura 2016), deformation characteristics (Wang et al, 2018; Al-Dakheeli and Bulut 2019), and physical properties (Yang et al, 2018; Yang et al, 2019) of geomaterials will be affected by immersion-air dry (I-AD) circulations. A water-rock interaction test with the layered sandstone as the study object was carried out, and the deformation and strength characteristics of the layered sandstone showed a significant deterioration trend (Jiang et al, 2019). To gain further insight into the shear strength characteristics of unsaturated soils after many I-AD circulations, the drying and wetting shear strength of sand-kaolin mixtures were studied through unsaturated consolidated drained (CD) triaxial tests (Goh et al, 2014). The deterioration process of geomaterials caused by I-AD circulations is inseparable from the microstructure change
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