The flourishing subgrade widening and reconstruction is one of the important challenges facing the highway industry at present. In this paper, focusing on the research progress of highway subgrade widening and reconstruction, the existing classification methods of subgrade widening and reconstruction projects are comprehensively summarized to propose a new classification corresponding to the comprehensive design of subgrade and pavement. The design indexes and standards under different types of subgrade widening are systematically reviewed, and the corresponding main control measures are classified. Then the next research focus of the subgrade widening and reconstruction is proposed from the improvement of the design index system, the composition and calculation analysis of differential settlement, and the active adaptation of the pavement structure. This study is of great reference significance in guiding the scientific decision-making on design indexes, standards, and treatment measures for different types of subgrade widening and reconstruction.
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