Development of undisturbed sampling method using thick water-soluble polymer

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A new sampling method using thick water-soluble polymer was invented to obtain undisturbed samples from even difficult ground. The objectives of this study were to understand the characteristics of this method, to evaluate the polymer immersion effect, to allow this method for deep ground and to apply this method for down-hole triaxial test. The following conclusions were drawn.1)Measurement of normal and shear stresses on the drill-core surface was made by the core barrel rotation experiments. The results revealed that, the shear stress was minimal while normal stress of several kilo Pascal's was recorded due to Wisenberg effect of the thick polymer. In addition, seepage tests were conducted to elucidate seepage characteristics of polymer into sand.2)A series triaxial compression tests were conducted on sand specimen with polymer. The test results demonstrated that, there was practically no influence on the angle of internal friction whereas increase of the cohesion value was limited as no more than several kilo Pascal's.3)A core barrel was developed for this polymer sampling from deep ground, and an attempt was made to obtain undisturbed samples from unconsolidated sand layers. Continuous drill cores of 100 millimeter diameter apparently with no sign of disturbance were obtained from 10 to 22 meters deep ground. Moreover, a larger diameter core barrel of 200 millimeter diameter was also successfully developed for the polymer sampling from non-uniform ground including large gravels or large pieces of sea shells.4)A technique to prepare the test specimens for down-hole triaxial tests was developed utilizing this polymer sampling method. Trial attempts on mortar ground demonstrated that cylindrical specimens can be accurately drilled in the ground by this technique.