土工格栅–土体界面特性大型直剪试验研究

土工格栅与土体的界面特性直接影响了加筋土工程的安全和稳定性,土工格栅两侧为不同材料的界面特性研究还较少。采用双向土工格栅为加筋材料,对其两侧分别为不同含水率粉质黏土及不同粒径石英砂的界面特性开展一系列的大型室内直剪试验,分析法向应力、粉质黏土含水率、剪切速率、石英砂粒径及粉质黏土压实系数等因素对土工格栅–土体界面抗剪强度的影响。结果表明:土工格栅–土体界面抗剪强度与法向应力呈线性相关,符合莫尔–库仑理论;粉质黏土含水率的变化对土工格栅–土体界面抗剪强度有较大的影响,在最优含水率时其界面抗剪强度指标最高;剪切速率的大小和石英砂的粒径变化对土工格栅–土体界面的抗剪强度有一定的影响,其影响范围分别在±10%和±7%内;粉质黏土压实度的增加能有效增加界面抗剪强度,压实系数越高,其提高幅度越大。这些影响应在工程应用中适当考虑。

Large-scale direct shear tests on properties of geogrid-soil interfaces

The properties of geogrid-soil interface directly influences the safety and stability of reinforced earth projects. However, there are few researches on the interface properties of geogrid with different soil materials at the two sides of geogrid. A series of large-scale direct shear tests are conducted by using two-way geogrid as reinforced materials, silty clay with different water contents and quartz sand with different grain sizes. The effects on shear strength of geogrid-soil interface are analyzed under different influence factors, such as normal stress, water content of silty clay, shear velocity, grain size of quartz sand, and compaction degree of silty clay. The results show that the relationship between shear strength of geogrid-soil interface and normal stress is a linear correlation and in accordance with Mohr-Coloumb theory. The shear strength of geogrid-soil interface is influenced by the water content of silty clay. The shear strength index of interface is the highest at the optimum water content of silty clay. The shear strength of geogrid-soil interface is influenced little by the shear velocity and grain size, and their influence range is within ±10% and ±7%, respectively. The compaction degree of silty clay can improve the shear strength of geogrid-soil interface. The higher the degree of compaction is, the greater the shear strength-improving amplitude is. These factors must be considered properly in the engineering applications.