English：

The soil of the Third Phase Reconstruction and Expansion Site of Tianjin Binhai InternationalAirport is weak, the water content is high, and the soil quality in different regions is significantlydifferent. To find out the influencing factors of the subgrade reaction modulus of the double⁃layercomposite roadbed, taking the replacement of mucky soil with hill⁃skill stones as an example, thetheoretical formula of the subgrade reaction modulus was established, and the solution formula of thereplacement thickness of hill⁃skill stones was analyzed. Based on the field test of replacement hill⁃skillstones, combined with the calculation results of the three⁃dimensional numerical model, the rationality,and accuracy of the theoretical formula of the subgrade reaction modulus were verified, and the predictionmodel of the replacement thickness of the hill⁃skill stones in the airport runway area and the non⁃runwayarea was obtained to adjust the replacement thickness of the hilly stones in time and realize the optimalutilization of the replacement materials.