通过4组湖北力特生产的BOP系列小尺寸单向格栅不同加筋方式的膨胀土三轴固结排水试验，研究了土工格栅的导水作用，并在现场试验中得到验证。研究结果表明：低围压下土工格栅的导水作用显著，且随着围压的增大，导水作用减小；加筋膨胀土中土工格栅不仅提高了土体强度，还增添了导水通道。因此，在加筋土坡设计中，要充分考虑格栅加筋后加筋土层渗流状态的变化，合理地发挥加筋土层的优势。

Weak expansive soil reinforced by geogrid, as a protective layer on the slope, is one of the side slope treatments in South-to-North Water Transfer. We performed triaxial consolidated drain tests on expansive soils reinforced by 4 groups of small size unidirectional grids to research their water conductivity. Results show that the water conductivity of geogrid increases under low confining pressure, while reduces with the rise of confining pressure. Geogrid improves the soil strength and works as a water route which accelerates drainage, particularly by vertical reinforcement in the whole section. The results are verified by field tests. It's concluded that the variation of seepage  in expansive soil reinforced with geogrid should be taken into consideration.