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Abstract 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.
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Received: 17 December 2010
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2011, Vol. 30 
