Abstract: High-quality undisturbed samples for the silty fine sand soils are usually difficult to obtain, and the laboratory tests results are often unreliable due to the sample disturbance. A series of in-situ tests of the silty fine sand soils in Xiamen area were performed. These test included standard penetration tests, cone penetration test, seismic flat dilatometer test and cross-hole shear wave velocity test. The in-situ engineering properties such as horizontal stress, strength characteristics, over-consolidation ratio, stiffness characteristics, and degree of compaction in soil were systematically investigated using these in-situ testing methods. In addition, the soil stratigraphy and soil classification were independently estimated by using these methods. The results showed that the Xiamen silty fine sand is an over-consolidated soil with a static earth pressure coefficient between 0.52 and 0.70. With the increase of depth, the strength and stiffness of the soil gradually increase, but the density does not increase significantly. In contrast to the flat dilatometer test results, the seismic flat dilatometer test can obtain the maximum shear modulus and stiffness attenuation curve of the soils, the test strain range is wider, and the result is more reliable. This study can provide theoretical support for the foundation construction in the silty fine sand formations in Xiamen area.

Key words: Silty Fine Sand, In-Situ Properties, Seismic Flat Dilatometer, Cone Penetration Test, Shear Wave Velocity, Stiffness Characteristics