Civil Mining and Environmental Engineering

ABSTRACT This paper presents the result of laboratory model tests using water hyacinth limited life geotextiles (LLGs) as well as using Vetiver and Ruzi grasses for erosion control. The mass per unit area and tensile strength of water hyacinth LLGs were obtained. The tensile properties of Ruzi and Vetiver grass roots were obtained after growing periods of 2, 3, 4, 5 and 6 months. Moreover, the rainfall effects were conducted in the laboratory model tests for the erosion control tests. Lateritic soil and sandy soil were investigated separately with LLGs and vegetation covers. Water hyacinth LLGs with opening size 8 mm by 8 mm and 12 mm by 12 mm was used to cover the bare soil. Ruzi and Vetiver grasses were planted in the container and tested at the age of 4, 6, 8 weeks, respectively. The model slope angle of 1H:1V, 2H:1V and 3H:1V were used for the tests. The maximum rainfall intensity used in this study was 120 mm/h which normally occurs in Thailand. The runoff rate and soil loss were used to measure the soil erosion. The results shows that the soil loss and runoff rate of lateritic soil were higher than sandy soil. Furthermore, the steeper slopes of 1H:1V yielded highest runoff rate and soil loss than flatter slopes of 2H:1V and 3H:1V. Slope 3H:1V with vegetation cover had the highest resistance to erosion. Generally, bare soil with woven LLGs 12 mm by 12 mm opening size resulted in less amount of runoff rate than 8 mm by 8 mm opening size for both soil types. In contrast, bare soil with LLGs 12 mm by 12 mm indicated higher soil loss than 8 mm by 8 mm opening size for both soil types. Additionally, the bare soil with Ruzi grass reduced the amount of runoff rate and soil loss than Vetiver grass. The combination of Ruzi and Vetiver grasses with lateritic soil can produce the best runoff rate and soil loss yield with slope 3H:1V. As slopes become steeper the surface runoff increased. The increasing growing periods at 4, 6, 8 weeks of Vetiver and Ruzi grasses reduced the amount of soil loss and surface runoff because of increasing coverage of vegetation. The observed data indicated the important role of vegetation in soil erosion prevention at different slope inclinations. The combination of Vetiver and Ruzi grass was highly effective against soil erosion and reducing the runoff rate.

A full scale test embankment (6 m height) was constructed by Department of Highways, the Bureau of Road Research and Development in Phitsanulok, Thailand. A surcharge fill of 1.2 m thick without reinforcements was added at the top of the embankment equivalent to 2 tsm of load. One side of this embankment was reinforced with polymeric reinforcements consisting polyester (PET), polypropylene (PP) and high density polyethylene (HDPE) and referred as reinforced steep slope (RSS), which is at an angle of 70 degrees from horizontal. The other side of the embankment was reinforced with metallic reinforcements consisting of metallic strips (MS) and steel wire grids (SWG) combined with precast concrete panel and termed as mechanically stabilized earth wall (MSEW). The comparisons of these reinforcing materials in terms of stiffness from highest to lowest are metallic strip (MS), steel wire grids (SWG), polypropylene (PP), high density polyethylene (HDPE) and polyester (PET). The behavior of ...

Free body diagrams (FBD) present a conceptual challenge for Engineering students. These diagrams are the simplest abstraction of the external forces and moments acting on a physical object. Some people "get" FBD's the first time they are shown them while many struggle and continue to produce incorrect diagrams well into their university studies. Having received feedback from lecturers of 3 rd year subjects that FBD skills were still below expectations an intervention was implemented in a University of Wollongong first year subject to (a) test students' understanding of FBD's (b) diagnose common misconceptions and errors and (c) reinforce the importance of constructing FBDs that are accurate and complete. This intervention has taken the form of a staged mastery skills test early in the first session of the first year of the engineering degree courses. The quiz is used as a stage gate for the subject and everyone must achieve the mastery skill to pass the subject...

Mechanics is a key foundation topic for many engineering disciplines, the study of which usually constitutes a significant proportion of first and second year engineering undergraduate studies. Many engineering students experience substantial difficulties with introductory mechanics, and it is widely noted in the literature that pass rates in mechanics courses tend to be unacceptably low. This paper details the interim

In an ongoing research project focusing on improving learning in first year engineering mechanics, a framework for engineering mechanics knowledge has been identified. The framework has been applied to break down and categorise common mistakes made by students at four separate institutions to find out where students are struggling in their efforts to learn statics and dynamics. The framework separates knowledge into factual, procedural, conceptual, and principle areas in a semi hierarchical manner. In using this framework, it has become clearly evident that the marks students are awarded for their work tend to be biased towards procedural knowledge, rather than conceptual knowledge as one might expect for an introductory course. The implication here is that students make most of their mistakes in the problem solving procedures for which most marks are awarded. We propose in our efforts to encourage a deep conceptual understanding needed for further study in engineering mechanics, we...

This paper relates to the optimisation of structural design using Genetic Algorithms (GAs) and presents an improved method for determining the fitness of genetic codes that represent possible design solutions. Two significant problems that often hinder design optimisation using genetic algorithms are expensive fitness evaluation and high epistasis. Expensive fitness evaluation results in slow evolution and occurs when it is computationally expensive to test the effectiveness of possible design solutions using an objective function. High epistasis occurs when certain genes lose their significance or value when other genes change. Consequently, when a fit genetic code has an important gene changed this can have a dramatic effect on the fitness of that genetic code. Often the reduction in fitness results in failure of the genetic code being selected for reproduction and inclusion in the next generation. This loss of evolved genetic information can result in the solution taking consider...

This paper describes a process used for, and interim findings of a comparison of final mechanics exam papers for first year engineering mechanics courses at the University of Wollongong, the University of Tasmania, the University of Technology, Sydney, and the Australian Maritime College. The process developed for the purpose emphasized a transparent and sequenced approach to comparing the concepts included in each exam paper, as well as the perceived level of difficulty of exam questions. The exercise was carried out remotely, using readily available communications technology, including telephone, email, and Skype teleconferencing. This process is an example of a simple, easy to implement, and readily transportable approach to cross-institutional peer review of assessments, and an effective way of enhancing collaborative links between engineering educators.