Abstract: Due to the hidden and heterogeneous characteristics of rock cavities in well developed karst terrain, the geotechnical investigation work in these areas is complicated and critically important. To ensure the investigation quality, accumulated geotechnical drilling in soil and rock experience and skills are necessary. This paper presents a geotechnical investigation case history of test boring drilling in New World 3F Contract Block Project in Guiyang. The frequently encountered issues in the testing boring drilling, such as, fluid leak and loss, drill bit jam, borehole caving, drill bit loss, ground subsidence surround borehole and low rock core recovery, are discussed int eh paper. Improvement methods are also proposed.

Key words: well developed karst terrain, geotechnical engineering investigations, drilling methods, treatment methods