The dynamic behaviour of rocks during the failure process is not being investigated so far, although it has very important implications on the failure response of rock engineering structures as well as ground motions induced by earthquakes. The authors performed some experiments under different loading environment on various types geo-materials in order to enhance our knowledge and understanding on the dynamic behaviour of rocks during fracturing. Following some brief information on the testing machines and testing procedures, the experimental results are presented according to each experimental configuration and their implications are discussed. The results clearly indicate that the accelerations of the mobile part of the loading system are always greater than those of the stationary part.
The dynamic responses of geo-materials during fracturing have not received any attention in the fields of geo-engineering and geo-science. However, these responses may be very important in the failure phenomenon of geo-engineering structures (i.e. rockburst, squeezing, sliding) and the ground motions induced by earthquakes. For example, the estimation of the travel distance and path of rock fragments during rockbursts in underground excavations is very important for assessing the safety of workmen and equipments. It is also known that the ground motions induced by earthquakes could be higher in the hanging-wall block or mobile side of the causative fault as observed in the 1999 Kocaeli earthquake (Aydan et al. 2000) and the 1999 Chi-chi earthquake (Tsai & Huang, 2000). The recent advances in measurement, monitoring and logging technologies enable us to measure and to monitor the dynamic responses of geo-materials during fracturing. Therefore, the studies concerning the dynamic responses of geomaterials during fracturing can now be easily undertaken as compared with that in the past.The authors have been carrying out such a study in recent years. The experiments have been performed on geo-materials ranging from very soft materials such as clay to hard rocks such as siliceous sandstone by using different loading schemes and loading frames.
The experiments have been carried out at the rock mechanics laboratories of three institutes, namely, Tokai University (TU) and Ryukyu University (RU) in Japan and Middle East Technical University (METU) in Turkey. The loading machines of the TU and the RU are low-stiffness machines with a loading capacity of 2000 kN while the loading machine of the METU is a servo-control high stiffness machine with a 2000 kN loading capacity. Fig. 1 shows the experimental set-ups at three institutes. In all experiments, the loads imposed on and displacements of the samples are simultaneously measured through the utilization of load cells and contact type displacement transducers during experiments. The acceleration responses of the samples during fracturing were measured by Yokogawa WE7000 measurement station using the AR-10TF type accelerometers of TOKYO SOKKI, which can measure three components of accelerations up to 10G with a frequency range of 0–160 Hz (Aydan 2003).
