格栅加筋土工作机理的试验研究

加筋土的设计理论落后于工程实践，为了改变这种现状，必需弄清加筋机理。采用大型叠环式剪力仪进行了土工格栅的拉拔试验，分析了格栅与填土之间界面的特性，它是了解加筋作用的关键。研究表明，界面产生了2方面的影响：界面本身的摩阻力对土体侧向变形的约束作用增强了土体抗变形的能力；界面对筋材两侧一定范围内土体的应力状态进行了改变。前者可称为直接加筋作用，后者可视为对土体的间接加固作用。这种间接加固是由于界面受剪时扰动了界面两侧一定范围土体内的颗粒，促使加筋土体强度的增大。试验测得了这种影响范围的大小，它有助于确定筋材布置的合理间距。同时进行了仿真的数值分析，加强了对上述加筋机理的认识。通过三轴试验，对由筋材、填土和界面组成的加筋土体的整体性状也进行了研究。上述成果将为建立合理的设计方法提供理论依据。

Mechanism of Soil Reinforced with Geogrid

Understanding the reinforcement mechanism is necessary to establishing a reasonable design method for reinforced-soil structure. In this purpose, pullout test was carried out on HDPE(High Density Polyethylene) geogrid using large scale multi-ring shear apparatus. Firstly, characteristics of the interface between soil and geogrid was analyzed, which is the key to understanding the reinforcement mechanism. The frictional resistance in the interface restricts the soil deformation at the contact zone along the interface, thus enhances the anti-deformation capability of soil, which can be regarded as a direct reinforcement. The frictional resistance also  alters the stress distribution in both sides of the reinforced soil, which can be named as  indirect reinforcement action. The latter occurs in a certain area at both sides of the interface due to soil particles in this area disturbed by the shearing, hence the strength of the reinforced soil is increased. The scope influenced by the above actions is obtained by tests, which can help determine the reasonable interval between the geo-grids. Numerical analysis was also conducted to verify the above understanding. Besides, a number of triaxial tests on the reinforced soil were carried out to investigate the overall properties of reinforced soil  and its failure pattern. All these research results are helpful to establish a reasonable design method for reinforced soil structures.