Performance evaluation of laterite soil embankment stabilized with bottom ash,coir fiber,and lime

In tropical regions,heavy rainfall induces erosion and shallow landslides on road embankments.Cement-based stabilization methods,common in these regions,contribute to climate change due to their high carbon footprint.This study explored the potential application of coir fiber-reinforced laterite soil-bottom ash mixtures as embankment materials in the tropics.The objective is to enhance engineered embankment slopes'erosion resistance and stability while offering reuse options for industrial byproducts.This study examined various mix designs for unconfined compressive strength(UCS)and permeability,utilizing 30%bottom ash(BA)and 1%coir fiber(CF)with varying sizes ranging from 10 to 40 mm,6%lime,and laterite soil(LS),followed by microstructural analyses.The results demonstrate that the compressive strength increases as the CF length increases to 25 mm.In contrast,permeability increases continuously with increasing CF length.Lime-treated mixtures exhibit superior short-and long-term strength and reduce permeability owing to the formation of cementitious materials,as confirmed by microstructural analyses.A lab-scale slope box was constructed to evaluate the surface erosion of the stabilized laterite soil embankment.Based on the rainfall simulation results,the LS-BA-CF mixtures show better resistance to erosion and deformation compared to untreated LS,especially when lime is added to the top layer.This study provides insights into a sustainable and cost-effective approach for slope stabilization using BA and CF,offering a promising solution for tropical regions susceptible to surface erosion and landslides.

Experimental analysis for the dynamic initiation mechanism of debris flows

Debris flow is one of the major secondary mountain hazards following the earthquake. This study explores the dynamic initiation mechanism of debris flows based on the strength reduction of soils through static and dynamic triaxial tests. A series of static and dynamic triaxial tests were conducted on samples in the lab. The samples were prepared according to different grain size distribution, degree of saturation and earthquake magnitudes. The relations of dynamic shear strength, degree of saturation, and number of cycles are summarized through analyzing experimental results. The findings show that the gravelly soil with a wide and continuous gradation has a critical degree of saturation of approximately 87%, above which debris flows will be triggered by rainfall, while the debris flow will be triggered at a critical degree of saturation of about 73% under the effect of rainfall and earthquake(M>6.5). Debris flow initiation is developed in the humidification process, and the earthquake provides energy for triggering debris flows. Debris flows are more likely to be triggered at the relatively low saturation under dynamic loading than under static loading. The resistance of debris flow triggering relies more on internal frication angle than soil cohesion under the effect of rainfall and earthquake. The conclusions provide an experimental analysis method for dynamic initiation mechanism of debris flows.

Effects of nano carbon on soil erosion and nutrient loss in a semi-arid loess region of Northwestern China

Since 2005,the application of nano carbon(NC)in agriculture and environmental remediation has received considerable attention with most of the research focusing on plant growth and heavy metal absorption.However,little is known about the potential effects of NC on soil erosion and nutrient loss.In this study,rainfall simulation tests were conducted on a soil plot(1 m×1 m,located in a semi-arid loess region of northwestern China),in which a mixture(5-cm below the soil surface)of NC(0,0.1%,0.5%,0.7% and 1.0% on a mass base)and sandy soil(same as the one in the plot)was embedded as three bands(5 cm wide,1 m long and 5 cm thick)at the three positions(top,middle and bottom of the plot),respectively.Before the rainfall simulation test,a mixed solution of potassium bromide(1.0 mol/L KBr),potassium nitrate(1.0 mol/L KNO_(3)),monopotassium phosphate(1.0 mol/L KH_(2)PQ_(4))was sprayed on the soil surface.Results showed that the sandy soil on the Loess Plateau with 0.7%NC addition(36.47 kg/hm^(2) on a mass basis)could improve soil water runoff,sediment yield,and nutrient loss in the semi-arid loess region of northwestern China,in addition to preventing soil water from deep percolation.Therefore,NC may have a great potential in soil erosion control on the Loess Plateau of China.