The author have developed a new testing machine "Borehole Hammer" which can easily evaluate deformation characteristics of in situ rock mass. In-situ, it has been investigated that the newly developed equipment has excellent operability and simplicity in use and permits evaluation and estimation of Young's modulus of rocks at a comparatively higher accuracy. From the above, it is considered that the practicability of the Borehole Hammer has been proven.
Les auteurs one developpe unt machine d'essais, "Marteau de trou de forage" qui peut facilement evaluer les caracteristiques de deformation concernant les materiaxu de roche sur le terrain. On a constate quele nouvel equipement venant d'etre Mis au point possede une excellente capacite de fonctionnement et simplicite d'emploi. En outre, il permit d'evaluer et d'estimer Ie module de Young des roches avec une exactitude relativement plus grande. d'apres ce qui a ete observe plus haut, on considere que la practicabilite du marteau de forage de trou a ete prouvee.
Die Autoren entwickelten ein neues Testgerat, "Bohrhammer", mit dem die Deformations charakteristik von Gestein in der ursprunglichen lage einfach bewetet werden kann. Bei Versuhen an Ort und Stelle konnte festgestellt werden, daE das neue Gerat uber ausgezeichnete Eisetzbarkeit und Einfachheit in der Bedienung verfugt und die Bewertung und Einschatzung von Elastizitatsmodulen aus Gestein mit einer relativ hohen Genauigkei ermogricht. Aus obigen Sachverhalten wird geschlossen, daE die Einsetzbarkeit des Bohrlochhammers bewisesn ist.
In the case that we examine the foundation of civil engineering construction, it is necessary to grasp the engineering properties. These values are obtained by several kinds of in situ rock tests such as plate bearing test and in situ shearing test, but these tests are so expensive that we cannot make enough tests to estimate the rock mass properties of the objective region for design. Because of these situations, we have desired the establishment of easier and cheaper in situ rock test system. A test system using "Rock Schmidt Hammer" is often used to evaluate the rock mass properties, simply. The Strike Response Value is measured by using this machine, and the modulus of elasticity can be expected. In order to apply this principle to the borehole investigation, the authors have developed a new tool "Borehole Hammer" (Figure 1) ¹. In situ Borehole Hammer tests has been carried out at the several fields and the borehole expansion test is also carried out at that fields in order to compare the elastic moduli (moduluos of deforaability and moduluos of elasticity) with the Strike Response Value.
Borehole Hammer is broadly divided the insertion part into the borehole (sonde) and the data gathering part. The velosity of the hammer is measured as the function of time and the acceleration change can be calculated immediately. Figure 2 shows the typical velosity and acceleration waveforms obtained from Borehole Hammer test. Using the velosity and acceleration data, Strike Response Value (unit:m 5 -¹) can be obtained as the index for the deformability of rock masses; The theoretical study was carried out by supposing the spring model as the rock mass model. As the results, we obtained that the Strike Response Value is dependent on the elasticity of rock mass. The laboratory testing using rock specimen was also carried out and we obtained that the Strike Response Value is proportional to the modulous of elasticity and uni-axial strength of rock specimen. 2) However, in situ testing has never been made.