Abstract
Though many researches on the hydraulic fracture initiation pressure have been done for cohesive soil specimens, the hydraulic fracture phenomena in actual grounds are different from those in the laboratory. The main reason is that the extension of hydraulic fracture in actual ground may become very large. Therefore, we investigate hydraulic fracture initiation pressure and the fracture extending pressure in a field test by well bores. The extending speed of the hydraulic fracture was calculated from the injection rate of slurry into the hydraulic fracture space. The main objective was to investigate hydraulic fracture problems when the slurry type shield is used to excavate through cohesive soil ground. Therefore, in addition to the well bore test, hydraulic fracture experiments using a model slurry type shield were done. From both experimental results, the hydraulic fracture situation for an actual slurry type shield could be predicted.
