Abstract: To satisfy the requirements of the existing transportation and economic transformation needs, some parts of China are gradually upgrading and widening existing expressways. Guangdong Province is in the Pearl River Delta, the soft soil is extensive and poor in nature, so it is very important to perform the targeted investigation in the soft soils in the reconstruction and widening projects. By collecting and analyzing the practical experience data of the existing reconstruction and widening projects in Guangdong Province, this paper discusses the properties of soft soils, the main contents of soft soil engineering investigation, the related requirements of laboratory test and in situ test, etc. Before the investigation begins, it is necessary to comprehensively collect the monitoring deformation, reinforcement treatment and other data of the existing project for comprehensive analysis, to make a reasonable exploration plan and select the appropriate laboratory test and insitu test method. This paper summarizes and proposes the key points of investigation methods for the highway reconstruction and widening in soft soils in Guangdong Province, and provides guidance and reference for the investigation of highway reconstruction and widening projects in other soft soils.

Key words: Expressway, Reconstruction and Widening Projects, Soft Soils Investigation, Geotechnical Tests