Abstract: The intelligent bidirectional deep mixed cement spray pile has been widely applied in the marine soft soil foundation of the Lianyungang-Suqian expressway project. In-situ tests were conducted on piles at different ages, and unconsolidated and undrained triaxial shear and uniaxial compressive tests were performed on soil-cement samples taken from different depths of the pile to verify the reinforcement effect of the intelligent construction technology. Based on the in-situ and laboratory mechanical tests, the strength index of the mixed cement piles was studied, and the bearing capacity of the single pile and composite foundation was deduced. The research results show that the intelligently mixed pile has high strength, a uniform pile body, and good pile quality. There is a linear positive relationship between the shear strength and the confining pressure of the soil-cement pile. Based on the Mohr-Coulomb strength criterion, the cohesive forces of soil-cement core samples at 7, 14, and 28 days were 402.9 kPa, 557.3 kPa, and 593.1 kPa, respectively, while the internal friction angles were 35.8°, 36.8°, and 39.9°, respectively. The uniaxial compressive strength of the sample is linearly related to the standard penetration number, and both meet a logarithmic function relationship with age. According to the composite foundation calculation method proposed in this paper, the foundation bearing capacities with pile spacings of 1.4 m and 1.2 m for the expressway project are 137 kPa and 177 kPa, respectively. The calculated results are close to the field load test results, which verifies the accuracy and applicability of the formula proposed in this study. At the same time, the foundation reinforcement effect of the intelligent bidirectional mixing powder spray pile is also verified.