Abstract: Drilling for the geotechnical borehole or for the piled foundation in thick cobble soils will frequently encounter difficulties, such as, severe drill bit wearing, low drilling rate, borehole instability, difficult in drill waste or rock core removal. Properly and accurately characterizing the grain size distribution and geotechnical properties are critical to the success of piled foundations in the cobble soils. This paper presents a case history of geotechnical investigations and castinplace pile installation in thick cobble soils for the Jili Yellow River Crossing Bridge. The effectiveness of drilling technique and borehole stability in the thick cobble soils layers are evaluated. Suggestions for the end bearing, side frictions of pile and pile installations in cobble soils are also provided in the paper.

Key words: bridge foundations, cobble soils, geotechnical investigations, piled foundation constructions