Abstract: The flat dilatometer test is an advanced in-situ test method, which can obtain a variety of important geotechnical parameters. This paper presents the application of flat dilatometer tests in deep soft soil layers in Whenzhou Suburban Railway Project to provide design and construction support of the underground engineering. The results indicate that: the horizontal consolidation coefficient obtained from the flat dilatometer test is about 0.74 times that of from the pore pressure dissipation test, and the undrained shear strength obtained from the flat dilatometer test is about 1.04 times that of the field vane shear test, and the static lateral earth pressure coefficient and the subgrade horizontal coefficient obtained from the flat dilatometer test are close to that obtained from laboratory test and the empirical value recommended in the design code. Therefore, the flat dilatometer test can provide accurate geotechnical parameters for the design and construction of underground engineering. The results of flat dilatometer test show that the soft soil layer in the Wenzhou Suburban Railway Project has the characteristics of weak consolidation and permeability, low undrained shear strength, large coefficient of static lateral earth pressure and small coefficient of horizontal subgrade bed. During underground engineering construction, the safety risk is high of underground engineering construction.

Key words: Wenzhou Suburban Railway, Underground Engineering, Flat Dilatometer test (DMT), Horizontal Consolidation Coefficient, Undrained Shear Strength, Static Lateral Earth Pressure Coefficient, Subgrade Horizontal Coefficient