Erosion of Soft Bedrock by River and Jet Flows: Small - Scale Experiment, and Field Exploration
Date Issued
2011
Date
2011
Author(s)
Chou, Ching-Lan
Abstract
In Taiwan, the issue of soft bedrock erosion has become of increasing concern following the uplifting of the 921 Earthquake. Following this event, bedrock has become exposed downstream of many hydraulic structures like dams and weirs. This thesis is going to introduce lots of bedrock erosion examples at different places in Taiwan. We use these examples as motivation to design small scale laboratory experiments simulating soft bedrock erosion.
For the bedrock material of our experiments, we mix plaster, fine sand and water. By carefully choosing the mixing ratio, the physical model can approximate the characteristic of bedrock, and can be eroded in a short time. We set the experiment environment as the reach downstream of a dam, and add abrasive to accelerate erosion. Other surface design for experimental channel including: stairs, interaction of different material and river curvature.
We recorded the evolution of river topography using laser scanning, measured surface flow velocity using particle tracking, and developed a water-jet strength test to determine the material strength of soft bedrock from the experiment and from the field. We also developed a mesh generator using polar coordinate system to address the difficulties of complex topography.
In the end, we compare our experimental results with field observations, especially of Chichi Weir, and found a lot of similarities. As for the water-jet strength test, we need more data and more testing to improve the accuracy and construct a relation between bedrock strength and water-jet eroded depth.
Subjects
bedrock erosion
physical experimental model
image analysis
Chichi Weir
water jet
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-100-R98521303-1.pdf
Size
23.32 KB
Format
Adobe PDF
Checksum
(MD5):a603175e178becfc4ae6af136922fbea