青藏高原东北部黄土区护坡灌木柠条锦鸡儿根系拉拔摩擦试验研究

 为研究灌木植物根系与土体间摩擦阻力的特性，对种植在西宁盆地及其周边黄土边坡试验区生长16个月的灌木植物柠条锦鸡儿的根系，分别在1.22，24.39，36.59，51.22 kN四个等级垂直压力下，以2.67 mm/min的速率对其施加水平拉力进行拉拔摩擦试验，试验结果表明，柠条锦鸡儿根–土之间的摩擦力随根系在土体中位移的增加而逐渐增大，根–土间摩擦力与位移关系曲线在试验开始阶段均呈线性关系，随后表现出显著的非线性关系；试验过程中，随着根系在土体中相对位移的增大，根–土之间的摩擦力增幅显著，且增大到一定程度时，趋于峰值并保持恒定，说明此时根–土之间的摩擦力发挥到最大且与拉拔力平衡；随着根系在土体中相对位移的逐渐增大，根–土之间的摩擦力趋于逐渐减小，当减小到某一程度时就不再减小，并保持稳定状态，进而处于新的平衡状态。试验结果还表明，根–土之间的摩擦力随垂直压力的增大而显著增加，并且这种增加呈线性关系。同时，随着土体含水量的增加，根–土间的摩擦力呈逐渐降低的趋势，且在试验研究范围内近似呈线性关系。上述研究对进一步探讨灌木植物根系对土体加筋与锚固作用机制，增强试验区边坡土体稳定性、防治坡面浅层地质灾害具有理论指导意义和实际应用价值。

RESEARCH ON PULL-OUT FRICTION TEST OF SHRUB CARAGANA KORSHINSKII ROOTS FOR SLOPE PROTECTION IN LOESS AREA OF NORTHEAST QINGHAI—TIBETAN PLATEAU

To study the relationship between shrub roots and soil friction，the shrub Caragana korshinskii is planted on the slopes of the test area in Xining basin and the test is carried out on the roots when Caragana korshinskii grew for sixteen months. The pull-out friction test for Caragana korshinskii roots are carried out by speed rate 2.67 mm/min in the vertical pressures 1.22，24.39，36.59，51.22 kN. The test results show that the root-soil friction grew with displacement of roots increasing in the soil；relationship curve between root-soil friction and displacement represents a linear relation in the initial stage of test，then represents an obvious non-linear relation with the development of the experiment；with the displacement of roots increasing in the soil，root-soil friction obviously increases，and a given degree increases；when the friction increases to a certain degree，it arrives at its peak and keeps constant，showing that at this time root-soil friction reaches to the largest and keeps balance with pull-out，with displacement of roots increasing in the soil，root-soil friction gradually decreases to a given degree，then to a steady state and a new balance. The test results also show that the root-soil friction obviously increases with the increasing vertical pressure，representing a linear relation，at the same time，the root-soil friction gradually decreases with soil moisture content increasing，representing an approximate linear relation in this experimental investigation. It is useful to further discuss the mechanism of roots reinforcement and anchorage that increase soil strength of slopes，and meanwhile，it is of theoretical significance and practice value in preventing the geological hazards that happen in shallow soil of the slopes.