Research progress of intelligent testing technology and evaluation methods for subgrade engineering

Subgrade engineering is a fundamental aspect of infrastructure construction in China. As the primary structural element responsible for bearing and distributing traffic loads, the subgrade must not only withstand the substantial pressures exerted by vehicles, trains, and other forms of transportation, but also efficiently transfer these loads to the underlying foundation, ensuring the stability and longevity of the roadway. In recent years, advancements in subgrade engineering technology have propelled the industry towards smarter, greener, and more sustainable practices, particularly in the areas of intelligent monitoring, disaster management, and innovative construction methods. This paper reviews the application and methodologies of intelligent testing equipment, including cone penetration testing (CPT) devices, soil resistivity testers, and intelligent rebound testers, in subgrade engineering. It examines the operating principles, advantages, limitations, and application ranges of these tools in subgrade testing. Additionally, the paper evaluates the practical use of advanced equipment from both domestic and international perspectives, addressing the challenges encountered by various instruments in real-world applications. These devices enable precise, comprehensive testing and evaluation of subgrade conditions at different stages, providing real-time data analysis and intelligent early warnings. This supports effective subgrade health management and maintenance. As intelligent technologies continue to evolve and integrate, these tools will increasingly enhance the accuracy, efficiency, and sustainability of subgrade monitoring. • The roadbed supports traffic but can be damaged by settlement and frost heaving. • Intelligent sensors are key for subgrade testing. • IoT, big data, and AI improve subgrade monitoring efficiency and accuracy.