土工格栅与土界面作用特性试验研究

土工格栅与土的界面摩擦特性指标是加筋土工程设计的关键。通过分析土工格栅与土的界面摩擦作用和进行了直剪摩擦试验和拉拔摩擦试验，测试了两种试验条件的界面摩擦特性。在两种试验条件下，土工格栅加筋土复合体的抗剪强度均有界面摩擦角φsq和界面凝聚力csq，且土工格栅与土相对位移量的不同，其复合体的强度机理有区别。在拉拔摩擦试验中，剪应力峰值强度对应的剪切变形值高于直剪摩擦试验中剪应力峰值强度的剪切变形值5～10倍以上。两种试验均有其适用性，而土与土工格栅的相对位移较小时直剪摩擦试验较能反映实际；土与土工格栅相对位移较大时土与格栅双面均发生相对位移，拉拔摩擦试验更为合适。随法向应力的增大，直剪摩擦和拉拔摩擦试验的剪应力峰值以及剪应力峰值对应的位移均提高。直剪摩擦的剪切速度小，剪应力峰值强度高，且达到峰值强度的剪切位移大；增加剪切速度，剪应力峰值强度降低，且对应的位移也减少，其原因是界面上的孔隙水压力消散和筋材的应力松弛。应根据具体工程的需要选择直剪摩擦试验和拉拔摩擦试验确定设计参数。

Experimental research on interface friction of geogrids and soil

Indexes of interface friction between geogrids and soil are key of design of geosynthetic reinforced soil. The analysis of soil-geogrids interface friction and the direct shear friction tests and pullout friction tests have been carries out for interface friction characteristic of two tests. In the direct shear friction tests and pullout friction tests, shear strength tested interface angle of friction φsq and interface cohesion csq on composite soil of geogrids reinforced soil; the relative displacements of geogrids and soil are not same, their strength mechanism are distinguishable. Direct shear friction test and pullout friction test are to be each applications; shear displacements of shear stress peak value on pullout friction tests are about five to ten times greater than the shear displacements of shear stress peak value on direct friction tests. The relative displacements of geogrids and soil are little, direct shear friction test can be applied; and the relative displacements are large, pullout friction test can be applied. Normal stress is increase, shear stress pear strength and its shear displacements of direct shear friction tests and pullout friction tests are increase. Shear strain rate is little, shear stress peak value is large, and its shear displacement is large too; shear strain rate is increase, shear stress peak value and its shear displacement is lower, the reasons are dissipation of pore water pressure of soil-geogrids interface and stress relaxation of geogrids. To each projection, there are correct choose direct shear friction test and pullout friction test to determine design parameters.