Fragmentation and Deposition of Rock Mass with Joint Strength Due to Rock Fall
Date Issued
2010
Date
2010
Author(s)
Lien, Tsun-Kai
Abstract
The pre-research mainly discuss the single rock fall movement or cluster of rockfall movement, the research of fragmentation of rock mass was less. This research starts from the small scale rock fall tests to discuss the relationship of joint strength of rock mass and fragmentation. Then use the distinct element method PFC3D to analyze and to discuss the energy disappearance and the movement of the fragmentation. Then use the adopted numerical analysis to analyze the full scale model, the Tzau An Cliff rock fall area. And this research would use aerial-photo interpretation to estimate the volume of rockfall of the source area and combines the field investigation to calibrate.
Through the aerial-photo interpretation, we found that there is a rockfall above the rock-shed 140m whose volume is about 35000m3 has fallen after year 2001, and the rock-shed has not been totally destroyed. Also the talus is composed of small rocks. So we figure out that the rockfall must have crush through its movement.
The field investigation shows that there are Malaishan Synclinorium and a lot of small shear zones through the slope. It results that the geological structure here is very broken and it may result rockfall. Observaing the talus, there are not founded that the rock is as big as possible to destroy the rock-shed. It is supposed that it is controled by the joint (at least 3 sets), and the results is the same with the aerial-photo interpretation’s.
Through the small scale rock fall tests and PFC3D simulation, we found that the joint strength has the negative trend with the run out distance, in addition, with the volume increasing, the run out distance of the fragmentation will run farther and the fragmentation which is near the toe will be more . This result has the same trend with Okura et al. (2000). In addition, it is found that the run out distance of the fragmentation which impact on 45 degrees slope is farther than the one which impact on 90 degrees, and it also founded that the rockfall which impact on 45 degrees slope, its fragmentation is more broken.
Through the sensitive of joint strength analysis of the full scale simulation, the rockfall which fragmentize gradually along its movement has the maxium kinetic energy. It is because that the fragmentation was big enough, so that the interaction between fragmentations was not much fierce. It is observed that the results have the same trend with the rockfall which fragmentizes partly on 45 degrees slope in the small scale rockfall test simulation.
Subjects
rockfall
rock mass with joint strength
impact
rockfall test
distinct element method
Type
thesis
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