Abstract: Since the early 2 000 s, numerous new airport construction and expansion projects have been initiated across Southwest China, with the red-bed strata of the Sichuan-Chongqing region becoming a focal area for such developments. These projects inevitably encounter engineering challenges associated with red-bed mudstone, particularly in zones requiring deep embankment fills to form runway and taxiway subgrades. Because airport pavement foundations must provide adequate bearing capacity, the mechanical properties of subgrade fill—such as strength, California bearing ratio (CBR), resilient modulus, and degree of compaction—must satisfy stringent design specifications. Consequently, the selection of fill materials is highly restrictive, typically requiring Class A fill. However, in many projects, on-site materials fail to meet these criteria. For example, at Leshan Airport, high-quality granular fill is scarce, and importing suitable material would significantly increase construction costs. Meanwhile, large quantities of mudstone are excavated on site, presenting an opportunity for in-situ utilization. Whether this mudstone can be improved for use as subgrade fill is therefore a question of practical significance. To address this issue, a full-scale trial embankment was constructed at Leshan Airport. Tests were conducted to determine the optimal cement content, CBR, subgrade reaction modulus, organic matter content, and other relevant parameters. The results show that mixing mudstone with an appropriate proportion of cement markedly improves its engineering properties. Considering both technical performance and economic feasibility, technical specifications are proposed for using cement-stabilized mudstone as fill for non-airfield pavement subgrade cushion layers. The recommended criteria include: cement content ≥2%, well-graded particle size distribution, maximum particle size ≤6 cm, uniform mixing, eight passes of compaction, degree of compaction ≥98%, CBR≥8%, and subgrade reaction modulus ≥60 MN/m³.

Key words: Mudstone, Cement Improvement, Road Base Technical Specifications, CBR Test, Airport Bedding