十年来韩国隧道施工的地应力水压致裂法测试经验

自1994年以来,韩国的土木工程师们首次接触到水压致裂法,在仪器开发、解释技法领域均有长足进展。在仪器开发方面:第一代水力致裂试验装备为管道形状,操作较为困难,之后简化到管线状,至今已研制出更加小型化、便于操作的设备。在解释技法领域也取得很多成就:水力致裂应力曲线中最难判读的龟裂闭锁压力曲线,也可以利用各种分析方法自动锁定。通过过去10a年来的探测经验,韩国已积累了国内大部分地区地应力的检测结果,而且这些参数资料一直在隧道工程的各种设计中得到应用。因此,考虑到沿岸地区的地应力测试固有的局限性,路域地区的测试资料可作为较好的参考资料,将其应用于海底隧道工程的设计当中。

A DECADE'S HYDROFRACTURING EXPERIENCES OF IN-SITU STRESS MEASUREMENT FOR TUNNEL CONSTRUCTION IN KOREA

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.