Study On Soil Consolidation Effect Of Basalt Residual Soil Improved By Guar Gum Combined Fiber

Basaltic residual soils are widely distributed in the southwest of China.Due to Yunnan’s subtropical location,abundant rainfall and distinct wet and dry seasons,the local basaltic residual soils generally have undesirable characteristics such as high liquid limit,large pore ratio,dry hard and wet soft.For a long time,the wet and dry cycle has caused geological disasters such as landslides and cave-ins in basaltic residual soils.In addition to the high cost of traditional consolidation methods,the sudden increase in CO₂ emissions and hazardous waste,there is an urgent need to find a green consolidation method to reinforce the residual soil.Using Kunming basaltic residual soil as the research object,this study investigates the effect of guar gum and basalt fiber soil hardeners on the mechanical properties of basalt residual soils and analyses the disintegration characteristics of the residual soils and the protective effect of guar gum and basalt fiber hardeners on the scour resistance of the slope with the aim of treating basalt residual soils in an environmentally friendly way,improving the engineering properties of the slope surface and increasing the stability of the slope scour.The stability of the residual soil slopes was also tested using Geo-studio software.At the same time,slope vegetation technology was introduced into the slope scour resistance test to investigate the positive effect of residual soil consolidation technology and vegetation slope protection technology on the overall improvement of residual soil slope stability and slope scour resistance.The following conclusions were obtained:（1）Direct shear tests were conducted to investigate the shear strength indices and their influencing factors of basalt residual soils improved by four doses of guar gum（0.5%,1.0%,1.5%,2.0%）and four doses of basalt fiber（0.1%,0.3%,0.5%,0.7%）at four maintenance ages（7d,14d,28d,60d）.The results show that the shear strength of the guar-amended soil tends to increase and then decrease with the increase of guar-amending amount and curing age,and the cohesion of the cured soil increases with the increase of hardener amount and age within a certain range,and the improvement effect is best when the maintenance age is14d and the amount of guar gum is 1.0%;the shear strength of the basalt fiber-improved soil shows a tendency to decrease and then increase with the increase of the fiber amount,the internal friction angle of the cured soil increases with the increase of the hardener,and the improvement effect is best when the fiber amount is 0.5%;guar gum combined with fiber reinforcement to improve basalt residual soil can improve the shear properties of basalt residual soil to a certain extent,but it did not achieve the expected improvement effect.Combining the three improvement methods,guar gum is the most preferred,followed by composite,and basalt fiber is the worst.（2）Disintegration tests were conducted to investigate the disintegration pattern of residual soils.The disintegration tests of basalt residual soils were carried out with four amounts of guar gum（0.5%,1.0%,1.5%,2.0%）and four amounts of basalt fiber（0.1%,0.3%,0.5%,0.7%）alone,as well as the disintegration tests of basalt fiber-guar gum composite on basalt residual soils using a homemade disintegration apparatus.The results show that the disintegration process of the original basalt residual soil is rapid and takes a short time due to its characteristics;the disintegration coefficient and the average disintegration rate of the specimens show a tendency to increase and then decrease with the increase of guar gum content of the improved basalt residual soil.When the guar gum content is 1.0%,the residual soil has the best disintegration resistance.When the guar gum content is certain,the disintegration coefficient and the average disintegration rate of the specimens show the growth state with the increase of the number of wet and dry cycles,and the disintegration coefficient increases by 8 times.The basalt fiber improved soil disintegrated rapidly and disintegrated significantly during the disintegration process of the first wet and dry cycle,and had no significant disintegration resistance advantage over the unimproved basalt residual soil under the same conditions.（3）The slope scour resistance test and slope stability analysis were carried out.By simulating rainfall scour tests on cured soil slopes and cured grassed slopes,to explore the effect of each hardener on the scour performance of slopes,and to explore the effect of comprehensive measures of cured grassing on improving the scour resistance of slopes.Then,the slope stability of the residual soil improved soil slope was analyzed based on the dry conditions.The results show that the hardener can significantly enhance the scour resistance of the residual soil slope.The slope of pure residual soil showed a large landslide within 15minutes,basalt fiber cured soil showed a gully after scouring,guar gum cured soil showed a complete slope structure with fine puddles after scouring,while the slope structure was complete after scouring with composite with no significant changes;The size of the scour resistance of each cured soil slope in the order of 1.0%GG+0.5%fiber composite>1.0%GG>0.5%fiber>basalt residual soil vegetation;The addition of hardener promotes the growth of vegetation to a certain extent,while the basalt residual soil slope surface after the hardener and plants are reinforced together has better scouring resistance and better ecological slope protection effect;Using Geo-studio software to simulate the stability of each improved soil slope under dry conditions,it is found that the safety coefficient of residual soil slope shows a tendency of increasing and then decreasing with the increase of guar gum amount,and increasing with the increase of basalt fiber amount,and the safety coefficient is highest when the guar gum amount is 1.0%.（4）Considering the effects of the two green improvement materials on residual soil shear strength,disintegration characteristics,slope scour resistance,and vegetation growth,combined with the results of the slope safety factor analysis,it is recommended that guar gum hardener be used at a rate of 1.0%in residual soil reinforcement and slope protection projects.At the same time,the combined reinforcement of guar gum improved soil and grass planting can significantly improve the ability of residual soil slope to resist scouring.The interaction between guar gum and vegetation root system prevents slope instability caused by slope erosion damage to a certain extent,and achieves the dual purpose of green planting stabilization slope protection and ecological slope protection.