喀斯特区2种护坡灌木单根拉拔摩擦试验

Experimental study on the pull-out friction of two kinds of slope protection shrubs in karst area

为探讨喀斯特地区边坡绿化灌木的力学特性,以4年生双荚决明和多花木蓝为研究对象,采用单根垂直拉拔的方式进行根系与土体间的摩擦试验。结果表明:试验力与位移关系特征曲线有3个明显的阶段:黏性摩擦阶段、脱黏摩擦阶段以及键合摩擦阶段;双荚决明和多花木蓝根径和埋深均与摩擦力呈现极显著正相关关系,而单位面积上的摩擦力无显著差异;双荚决明根土间摩擦系数大于多花木蓝,且双荚决明根皮表面有密集的裂纹并形成槽口,其表面结构的复杂程度强于多花木蓝,即双荚决明单根在拉拔摩擦试验中所释放的力要大于多花木蓝,增强土体强度及抵抗变形破坏能力更优。研究结果可为该研究区边坡绿化树种的筛选、固土机制以及防治浅层滑坡提供基础的理论依据。

[Background]The root system is the organ that directly contacts with the soil and has the function of supporting the plant and fixing the soil.In karst area,the soil layer is shallow,the soil erosion is serious,and the ecological environment is poor.With the development of economy,climate change,debris flow,landslides and other natural disasters occur frequently,the stability of slope soil has aroused widespread concern.[Methods]In order to study the mechanical characteristics of slope greening shrubs in karst area,taking 4-year-old Cassia bicapsularis and Indigofera amblyantha as the research objects,the root diameters were divided into four grades.Under the loading rate of 100 mm/min,the friction test between the root and soil was carried out by using a single root vertical pull-out method.The effects of root length,root surface interaction and root length on the soil were investigated.The soil bulk density and water content were 1.43 g/cm^(3) and 17.15%.[Results]1)The root bark surface of C.bicapsularis had dense longitudinal cracks and formed notches,while the root bark surface of I.amblyantha was scaly.The root-soil friction coefficient of C.bicapsularis was higher than that of I.amblyantha,the root system of C.bicapsularis had better ability of strengthening soil strength and resisting deformation and failure than that of I.amblyantha.2)In the process of friction between single drawing and soil interface,the characteristic curve of force displacement relationship experienced three stages:viscous friction stage,debonding friction stage and bonding friction stage.3)The friction force between the roots and soil of C.bicapsularis and I.amblyantha increased with the increase of burial depth.The longer the extension of vegetation roots in soil,the greater the role of force.4)The root diameter of C.bicapsularis and I.amblyantha showed a significant positive correlation with their maximum friction,while with the change of diameter,there was no significant difference in the friction per unit area.[Conculsions]That is to say,the force released by a single root of C.bicapsularis in the pull-out friction test was greater than that of the latter,and it was better to enhance the soil strength and resist the deformation and failure.Therefore,it is suggested that C.bicapsularis should be used as vegetation slope protection.The results provide a theoretical basis for the selection of greening tree species,soil consolidation mechanism and prevention of shallow landslide in the study area.