Year

1994

Degree Name

Doctor of Philosophy

Department

Department of Civil and Mining Engineering

Abstract

The main objectives of the present research can be summarised as:

i-Critical investigation and computer programming of the existing sediment discharge computation methods, and

ii-Fundamental development of more accurate and simpler sediment discharge and concentration distribution equations.

The thesis can be divided into three parts. In the first part, technical comments and computational procedures are provided for a number of sediment transport estimation models. The models included the most popular theories of Meyer-Peter and Muller, Einstein, Bagnold, Engelund-Hansen, Toffaleti, Ackers-White, and Yang, and the recently developed methods of van Rijn, Wiuff, Samaga et aI, and Celik-Rodi. Deficiency and drawbacks of the selected theories are analysed and modified equations are suggested for a number of theories.

Since the computation of the transport rate of sediment loads in open channel flows is usually a complicated and laborious task, new computer programs have been developed for all of the 11 selected methods as well as for the proposed transport equations. The developed computer package (SEDLOAD) can be regarded as an efficient and powerful tool for practicing alluvial hydraulic engineers. Using the advantages of regression analysis and numerical integration techniques, analytical procedures are presented for all graphs and tables given in the selected theories.

The selected sediment load predictors are tested against 333 sets of sediment transport data from both laboratory flumes and natural rivers. Limitations in the applicability of the theories are highlighted through this analysis. The test results generally show large discrepancies between the predicted transport rates and the actual measurements from one theory to another. None of the methods were found to be adequate for all conditions.

In the second part of the thesis which is more significant, based on the fundamental concepts of hydraulics, turbulence energy and particle motion, a new theory is developed for the estimation of concentration as well as bed and suspended load transport rates of non-uniform bed material in river systems. The proposed equations are applicable to uniform steady sediment-laden flows. The relations are derived for bed material load and do not include wash load. The sediment transport capacity of the flow is computed through the proposed equations, assuming that the bed material supply is more than the transport capacity. The proposed equations are non-dimensional and fully analytical.

The parameters involved are well-known and easily measurable. A number of other formulae, such as depth-averaged concentration, transport concentration, and reference concentration have been determined using the developed theory.

In comparison with the well-established Rouse concentration equation, the proposed concentration formula produced better concentration profiles when applied to a number of published laboratory flume measurements. Applying the developed suspended load equation to 175 sets of suspended load data resulted in a score of 91 % which is regarded as an exce1lent accuracy in the field of sediment transport. When applied to abou t 100 sets of bed load transport data and compared with the other existing bed load predictors, the developed bed load formula always gave better predictions. In general, testing against 333 sets of sediment transport data confirmed the better predicability of the proposed transport equations compared to the other selected theories.

The recent contributions and difficulties of sediment transport research in Australian rivers are discussed in the third part. Fine grain sizes, a high proportion of wash load, and low values of energy slope are the main characteristics of major inland rivers in Australia. An attempt was made to introduce the most appropriate sediment load predictor for the computation of bed material transport rate in a particular Australian rivulet. However, due to the unavailability of measured sediment transport data, no conclusive decision could be made. It is, therefore, recommended that no particular equation be selected unless its accuracy is tested against actual measured data from sediment loads. Review of the Australian literature indicates that the major difficulty with sediment transport research all around Australia is the lack of published data.

Share

COinS