Abstract: The widely application of precast concrete micro piles in the emergency reinforcement of expansive soil slope with long cracks in the South-to-North Water Diversion Project highlights their significance in ensuring slope safety. Studying the reinforcement mechanism is essential. Based on similar model test, a model was established to examine the interaction between the sliding mass and the micro single row pile in the slope with fracture surface. A thrust force was applied parallel to the fracture surface, and both similar model test and numerical simulation were conducted. The results demonstrated the effectiveness of preventing sliding by micro single row pile reinforcement. It maintained a high level of anti-sliding force in the slope system, increased slope toughness against failure, and significantly improved slope stability. The slope’s resistance to sliding decreased as the pile spacing increased. The influence of a single micro pile only extended over a limited range. As the pile spacing increased, the soil arching effect gradually weakened. Ignoring the interaction between piles became feasible when the pile spacing exceeded 12 times the pile diameter. It is recommended to maintain a pile spacing 8 times of the pile diameter. Moreover, the strengthening effect of micro piles arranged in the middle of the slope surpassed that of those arranged in the upper 1/3 of the slope.

Key words: micro pile, gently inclined long fissure, expansive soil slope, similarity model test, numerical simulation