Study On Water Characteristics And Slope Stability Of Industrial Bagasse-low Alkali Eco-cement Improved Expansive Soils Under Dry And Wet Cycles

Expansive soil is a special type of clay soil characterized by fissures,superconsolidation,and expansion and contraction.Its engineering properties are highly sensitive to changes in moisture and temperature.Expansive soil is widely found in Guangxi,where the subtropical monsoon climate brings frequent cycles of wet and hot conditions,leading to frequent regional disasters caused by expansive soil.One common method for improving expansive soil is through the combination of fiber and inorganic binder.Guangxi is a major producer of industrial sugar in China,resulting in large quantities of industrial bagasse being accumulated.Therefore,there is an urgent need to explore alternative ways of utilizing industrial bagasse.This study aims to address the limitations of the traditional approach,which relies on silicate cement for improving expansive soil.Additionally,it considers the issues of limited utilization of industrial bagasse and environmental pollution.As an innovative solution,the study proposes the use of industrial bagasse(IB)and low alkali eco-cement(LAEC)for improving expansive soil.The research aligns with the development concept of promoting sustainability,with the idea that "green water and green mountain are as valuable as gold." To investigate the soil-water characteristics and slope stability of industrial bagasse and low alkali ecocement improved expansive soil under dry and wet cycles,a series of indoor experiments and finite element numerical simulation analyses were conducted.Furthermore,the study examined the slope stability under rainfall conditions.The main conclusions drawn from these experiments and numerical simulations are as follows::(1)The experiment conducted to measure the soil-water characteristic curve demonstrated that the combination of industrial bagasse and low alkali eco-cement had a positive impact on maintaining stable soil-water conditions for expansive soil.The improved expansive soil exhibited a more stable soilwater characteristic curve,providing a relatively consistent environment for plant growth in later stages.As the wet and dry cycles increased,gradual development of soil fissures was observed.In the unimproved expansive soil,after five wet and dry cycles,two main fissures were formed.However,when low alkali eco-cement alone was used,the development of fissures was more pronounced compared to the unimproved expansive soil.Interestingly,the addition of industrial bagasse helped suppress the formation of fissures.(2)The shear strength of the expansive soil amended with industrial bagasse and low alkali eco-cement exhibited significant improvement.Among the test groups,the 1.2% IB-7% LAEC combination showed the greatest enhancement in shear strength.The cohesion of this group was approximately seven times higher than that of the unamended expansive soil,and the internal friction angle was approximately twice as large.The wet and dry cycles had a notable weakening effect on the shear resistance of the swelling soil.The majority of the shear resistance reduction occurred during the initial three wet and dry cycles.However,even after undergoing five wet and dry cycles,the shear resistance of the expansive soil improved with industrial bagasse and low alkali eco-cement remained stronger compared to the unimproved expansive soil.(3)The electron microscopy scans revealed distinct effects of different admixtures on the microstructure of expansive soils.In the unimproved expansive soil,the distribution of mineral particles became uneven after undergoing wet and dry cycles.The linkage between mineral particles was weak,and noticeable pores were present.The addition of industrial bagasse improved the distribution of microscopic fractures in the expansive soil.Furthermore,the amendment of low alkali eco-cement enhanced the connection between mineral particles,reduced the internal pore space,and mitigated water erosion.However,it was observed that the low alkali eco-cement-amended expansive soil exhibited a higher number of microscopic fissures,with most of them being fine in nature.(4)Under identical rainfall conditions,the modified expansive soil slope exhibits smaller plastic strain and displacement compared to the unmodified expansive soil slope.In the unimproved expansive soil slope,the displacement and plastic strain caused by rainfall are primarily concentrated at the foot of the slope.Conversely,in the modified soil slope,these effects are predominantly concentrated at the top of the slope.Taking into account the reduction in slope strength,an inward U-shaped slip zone becomes apparent within the slope.The displacement and plastic strain of the unimproved expansive soil slope are three times and four times greater than those of the improved soil slope,respectively.In an overall comparison,the soil slopes modified with a combination of 1.2%IB and 7% LAEC demonstrate improved safety.(5)The study combined ecological and environmental protection strategies with engineering applications,and explored the feasibility of applying industrial bagasse and low alkali eco-cement to expansive soil slope projects from the indoor test results and numerical simulation results.