Development of the Multiple-Purpose Borehole Testing Device in Soft Rocks
|Keywords:||軟弱岩石;鑽孔千斤頂試驗;鑽孔剪力試驗;平板載重試驗;soft rock;borehole jack test;borehole shear test;plate loading test|
The outcrops in the central and northern regions of Western Taiwan often contain weak, poorly cemented and young rock formations. The typical rock coring process has a tendency to damage the structure that originally existed in situ. Soft rocks are likely to contain defects, such as fissures, bedding and joints. An ideal in situ test method should be able to reflect the effects of these defects on the behavior of the rock mass that is tested. The existing field testing methods for soft rocks often involve large pieces of equipment and are costly to perform. The main objective of this research is to develop a medium sized, versatile in situ testing device specifically for soft rock. The new device, referred to as the multiple-purpose Borehole Testing Device (BTD), is capable of performing lateral jacking test, direct shear test and plate bearing test at the bottom of a borehole. The radial and longitudinal stress-strain relationships can be determined simultaneously using the new device. The design of this new device follows the concept of a "retrievable rig" plus the capability equivalent to a Goodman jack. The new equipment consists of four radial filler plates at the top and a circular bearing plate that moves in the longitudinal direction at the bottom. The design and fabrication of the new BTD have been completed. Preliminary instrument calibration tests have indicated that the device had a low compliance and the possibilities of error in volumetric strain measurement under high stress were low. This thesis gives a brief background of the soft rock in Taiwan and existing technologies in characterizing soft rock in situ. Details of the design concept, functions and calibration performance of the various components of the new BTD are described.
|Appears in Collections:||Thesis|