Abstract: The geocells are widely used in the reinforcement and diseases treatment of subgrade bed of road or railway. And the reinforcement effect of geocells is significantly affected by different geometric dimensions. Nine different types of geotextiles, combination of weld distance of 340, 400, 680 mm and height of 0.10, 0.15, 0.20 m, and traditional method of sand replacement are applied to treat subgrade subsidence. Then dynamic stress attenuation law in different treatment experiments is analyzed. The test results show that with height increased 0.01 m, dynamic stress decreased more about 0.6%-1%; and the attenuation decreased by about 5% for augmenting 100 mm of weld distance. On the whole, geocell is better than traditional treatment method; as dynamic stress attenuation is faster, stress distribution is more balance and subgrade strength is higher. Finally, design theory of replacement thickness called allowable stress design method is proposed on the basis of field test results, which considering subgrade stress level, dynamic stress attenuation law of different treatment and the allowable bearing capacity of subgrade. A theoretical design method for replacement thickness design is provided.

Key words: geocell, subgrade bed, dynamic stress, replacement thickness, field test