Abstract:Since the hydrofracturing field testing method was first introduced to Korean geotechnical engineers in 1994,there have been lots of progresses in a hardware system as well as an interpretation tool. The hydrofracturing system of first generation was the pipe-line type,so it was not easy to handle with. It had been modified to a wire-line system at its second generation. It is more compact one but it also needs an additional air-compressor. The currently developed system is much more compact and operated by all-in-one system,so it doesn¢t need an additional air-compressor. With a progress in a hardware system,the software for analyzing the in-situ stress regime has also been programmed. For example,the shut-in pressure,which is the most ambiguous parameter to be obtained from hydrofracturing pressure curves,can now be automatically acquired from the various methods. While the hardware and software for hydrofracturing tests are being developed during the last decade,the paper could accumulate the field test results which can cover the almost whole area of South Korea. Currently these field data are used widely in a feasibility study or a preliminary design step for tunnel construction in Korea. Regarding the difficulties in a site selection and a test performance for the in-situ stress measurement at an off-shore area,the in-situ stress regime obtained from the field experiences in the land area can be used indirectly for the design of a subsea tunnel. From the hydrofracturing stress measurements,the trends of magnitude and direction of in-situ stress field are shown identically with the geological information in Korea.