兰州地区开展平山造地工程产生了大量黄土堆填场，因其压实度低，缺乏必要防护，导致黄土洞穴、滑坡等地质灾害广泛发育，具有较大安全隐患。通过扫描电镜和Image J软件对不同含水率原状堆填黄土的孔隙微观结构进行定量研究，结合分形理论，获取了不同含水率下堆填黄土的孔隙类型、数量、面积、分维数变化规律，并初步分析了孔隙结构与黄土湿陷、洞穴发育的动态关系。结果表明：堆填黄土随含水率增大，大、中架空孔隙数量、面积占比逐渐减小，而小架空孔隙数量占比虽有所下降，但面积占比呈增大趋势，大、中架空孔隙坍塌是其产生湿陷变形的主要原因；堆填黄土的孔隙分维数与含水率呈线性负相关关系，与湿陷性呈正相关关系，原状堆填黄土平均孔隙分维数为1.251；基于黄土堆填场洞穴发育特点，提出应从修建排水沟渠、加固洞穴、边坡防护等3方面进行防护处理。研究成果可为兰州堆填黄土区工程建设及地质灾害防治研究提供理论支撑。

A large number of loess landfills have been generated by the Pingshan land formation project carried out in Lanzhou area, which has a large safety hazard due to its low compaction and lack of necessary protection, resulting in the extensive development of geologic hazards such as loess caves, landslides, and so on. The pore microstructure of in-situ loess landfill with different water content was quantitatively studied through scanning electron microscope and Image J software, combined with fractal theory, the pore type, number, area, and change rule of the number of dimensions of the pore of the landfill loess with different water content was obtained, and the dynamic relationship between the pore structure and the wetting of loess and development of the caves were preliminarily analyzed. The results show that: with the increase of water content, the number and area of large and medium-sized hollow pores gradually decrease, while the number and area of small hollow pores decrease, but the area of small hollow pores increase, and the collapse of large and medium-sized hollow pores is the main reason for wet subsidence and deformation of loess; the pore dimension number of landfill topsoil has a linear negative correlation with water content, and a positive correlation with wet subsidence; the average pore dimension number of in-situ topsoil is 1.251, and the average pore structure is 1.251. The average pore dimension is 1.251; based on the characteristics of cave development in loess landfill, it is proposed that the protection treatment should be carried out in three aspects, such as the construction of drainage ditches, the reinforcement of caves, and the protection of slopes. The research results can provide theoretical support for the engineering construction and geologic disaster prevention and control research in Lanzhou landfill loess area.