Abstract: In the South-to-North Water Diversion Project, a large number of expansive soil slopes slid due to the long and gently inclined fissures. The micropiles had achieved good application in the rescue and reinforcement project of the expansive soil slopes. The study on the reinforcement mechanism and the influence of parameters of micropiles in reinforcing the soil slope with long and gently inclined fissures is of great significance for the design of such projects. Based on the actual project of reinforcing expansive soil slope with micropiles, the thrust was applied on the sliding body along the direction of the fissure surface, and the failure tests of the non-piled slope with different angles of the gently inclined fissure were carried out. After taking the pile length, row spacing and pile position as influence parameters, the model tests of micropile-reinforced soil slope with long and gently inclined fissures were carried out, the displacement characteristics of the slope and the stress characteristics and the reinforcement effect of the micropile were analyzed. The test results showed that the micropile had a good anti-slide reinforcement effect for the slope with gently inclined fissures, and could maintain the anti-slide resistance at a high level. The anti-slide resistance provided by micropiles increased with the increase of pile length (anchorage ratio), while the increase efficiency decreased with the increase of pile length. It was suggested that the anchorage ratio of micropiles should be 0.5 when the pile is arranged at upper 1/3 position of the slope, and less than 0.65 when it is arranged at lower 1/3 position of the slope. The distribution of bending moment and shear force of the piles was reversed S-shape, and the maximum values were located near the fissure surface. The double-row piles can enhance the toughness of the slope to resist damage. When the row spacing was 200 mm (10 times the pile diameter), the front and rear rows of piles can well coordinate, which could give full play to the anti-slide effect and greatly increased the anti-slide thrust of the slope.

Key words: micropile, gently inclined fissure, soil slope, similarity model test, mechanical behaviors