A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, School of Engineering and Technology

Thesis (M.Sc.) - Asian Institute of Technology, 2005

The Red River Delta (RRD), considered as the largest center of economics, culture and agriculture of Viet Nam, has been developing rapidly. Annually, the amounts of goods, agricultural and industrial products are being produced more and more, which need to be distributed to the other parts of the country and inside the RRD. The not-up-to-date site investigation technique and poor characterization of subsoil along the highways route contribute to poor quality of many of them, resulting in their improvement and upgrading become important work to be done in the RRD. One example is the Road Network Improvement Project funded by World Bank to maintain and improve 600km of highways (National Highway 10,21,388,39 and so on) in the RRD. This study deals with a geotechnical-geophysical study of the clay of the RRD in the North of Viet Nam, especially characterization of the subsoil profiles along a number of national highways in above mentioned project. A very big amount of data were collected in this study. To manage these data, the database was developed to manage the geotechnical data from borehole to sample levels by using Microsoft Access. The borehole worksheet database consists of a full set of borehole information (x, y location, total depth, data of drilling, groundwater tables, borelog and so on), which can be input in to the database to link to other programs (Rockwork2002, Mapinfo7.5) to display borehole data on a map or to visualize the subsoil profiles. From the geotechnical database, the characterization of the shallow subsoil profiles along NH21, 38B and 18 were made based on laboratory and field test results. One of significant outputs of this study is to perform successfully a 1-km long survey line of electric imaging with three kinds of electrode configurations (Wenner, Wenner-Schlumberger and Haft-Wenner) from Km 165.5 to Km 166.5 along the National Highway 21. This geophysical study has certainly value-added the investigation of the highway by giving a continuous imaging of the subsoil between two boreholes and indicating the pocket of weak soil in it. The integrated approach using geotechnical and geophysical techniques to investigate the subsoil along the highway as employed in this study is strongly recommended for site investigation practice in the projects of highway upgrading that are taking place in the RRD.