筋土间相互作用是加筋土强度提高的根本原因，是土工合成材料加筋加固应用中的核心问题。通过室内拉拔试验，分析了法向应力、砂垫层厚度、土工格栅横肋间距3个因素对加筋体极限拉拔力的影响，从宏观角度揭示了筋土界面间的力学特性。结果表明:增设5 cm厚的砂垫层后，格栅的极限拉拔力得到显著提高;高法向应力下，砂垫层厚度对拉拔试验结果影响更显著;在土工格栅加筋软土体中，增大横肋间距会减小筋土界面摩擦角，但是对黏聚力影响不大;格栅网格形态是筋土界面特性的重要影响因素。

The interaction between soil and reinforcement is the fundamental cause of the strengthening of reinforced soil. It is also a key issue in the application of geosynthetic reinforced soils. In this article, the effects of normal stress, sand cushion thickness and spacing between transverse ribs on ultimate pullout resistance of reinforced body were analyzed through pullout test. The mechanical properties of reinforcement-soil interface were also revealed in a macro-sense. Results suggest that sand cushion of 5 cm thickness could remarkably enhance the ultimate pullout resistance of geogrid. The influence of sand cushion thickness on test result is more obvious under large normal stress. Moreover, the frictional angle of geogrid-soil interface decreases with the increasing of the spacing between transverse ribs; but the cohesion stays stable. The shape of geogrid is also an important factor affecting the properties of interface between reinforcement and soils.