Determination of the shape and the depth of scour hole on rocks using fluctuating dynamic pressure distribution

• Main Authors: Cheng, Meng-Hsiung, 鄭孟雄
• Other Authors: Liao, Jyh-Jong
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/58543747063778714880

博士 === 國立交通大學 === 土木工程系所 === 104 === Scour would occur when the erosive capacity of water exceeds the erodability resistance of geo-materials. The scour on the doundation of a hydraulic structure could cause foundation damage and endanger the structural stability. To determine the local scour holes downstream of a hydraulic structure plays an important role in the planning and design stages. In general, geo-materials include granular soil, cohesive soil and rock. Most of current researches deal with granular materials using laboratory or field data to develop their empirical or semi-empirical formulae. In those researches, the grain size is the sole material parameter characterizing the erodibility property of geo-materials. The erosion behavior of rock materials is much more complex than that of granular materials. Therefore, it deserves more study to understand and to determine the local scour holes on rocks. Several approaches were developed for the plucking mechanism in order to estimate the ultimate depth of scour holes in rocks. However, not many approaches have dealed with the range and shape of scour holes. This study proposes an approach for estimating the shape and the depth of the scour hole on weak rocks. This approach integrates the concepts for the stream power of water jet (Annandale, 2006), the dissipation energy and the longitude pressures distribution (Castillo et al, 2014). A new method with applicable procedures for estimating the shape and depth of the scour hole was developed. This study compared the simulated data and in-situ data surveyed at the stilling basin downstream the spillway of several dams to examine the applicability of the proposed approach. The comparison reveals that the proposed approach models reasonablly well for the freefall condition, but may underestimate the extent and shape of sour holes for the ski-jump condition. Nevertheless, it appears the new method is able to improve the estimation of scourhole depth, shpae and extention, comparatively to other existing methods.