Civil Engineering May 2021 | Vol 29 No 4

Civil Engineering May 2021 21 the small-scale model produced high variability in the measurements, the general trend indicated that the outer layers contain the highest energy region, with limited energy penetrating the core (34% on average). The armour layer has the highest measured energy when the median rock mass of the filter layer is small, since the flow is concentrated in the armour layer. When the median rock mass of the filter layer is larger, the water is dissipated into the filter layer and becomes less violent in the armour layer, resulting in the highest energy region being in the filter layer. Equations were developed using dimensional analysis to predict the energy in the rubble-mound berm layers based on identified factors affecting the flow through porous media. The results indicate that a well-designed berm can effectively dissipate the approaching wave energy and accordingly limit the energy penetrating the core and so reduce scouring.  REFERENCE Streuderst, A. 2021. Design of rubble-mound structure as scour protection for vertical seawalls: layer thickness, median rock mass and energy distribution through the layers. M. Eng. Thesis, Stellenbosch University, Stellenbosch. Figure 2 Wave breaking against the Seawall (Credit: A Buys) Peak wave period varies Our range of heavy on-track tamping machines is a reflection of the extensive research and technical development invested into creating the world’s highest standards of reliability, quality and features. The result of this is evident in the durability of the tamped track. Different tamping machine designs are available to meet every possible tamping requirement. Plasser South Africa provides specialist advice to select the right machine with regards to production, its position in the existing fleet, whether it should be plain or universal track, and if universal is selected; many different features must be considered such as 3rd rail lifting, split units, wheel base, etc. Selecting the Right Tamping Machine is Essential for Productivity and Durability Plasser South Africa (Pty) Ltd | PO Box 103, Maraisburg, 1700 | Tel: 011-761-2400 | info@plasser.co.za HIGH CAPACITY I PRECISION I RELIABILITY 3 sleeper continuous action tamping for high production plain track tamping with integrated stabilisation Universal split units for high production plain track and turnout tamping with 3rd rail lifting and integrated stabilisation