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Evaluation of Ex-Situ Soil Washing as a Remedial Strategy for Heavy Metal Removal From Railyard Ballast
Published in Gregory D. Boardman, Hazardous and Industrial Wastes, 2022
Ballast, the ubiquitous railyard surface material, generally consists of gravel, broken stone, ash/cinder, and slag. It is placed under and between railroad ties to give stability, provide drainage, and distribute loads. Ballast thickness varies between two and eight feet depending on site-specific conditions, but generally varies from two to four feet below grade. Based on actual data collected from a typical mid-Atlantic railyard for a ballast sampled collected from two — four feet below grade, grain size distribution test results revealed a silt/clay (or fines) fraction is 10%, with the sand and gravel fraction accounting for 70% and 20%, respectively. The percentage distribution was based on the fraction the #4 sieve for sand/gravel and the #200 sieve for sand/fines [1].
Economic analysis of rail facility preservation
Published in Zongzhi Li, Transportation Asset Management, 2018
Ballast: Ballast is the crushed stone layer under sleepers. The main purpose of using ballast is to carry load from sleepers to subgrade so as to keep the track strong against vertical, longitudinal, and lateral movements. These movements are absorbed by the irregular shape of ballast materials. In addition, basalt helps with water drainage under rails and sleepers.
Parameters for track design
Published in Buddhima Indraratna, Trung Ngo, Ballast Railroad Design: SMART-UOW Approach, 2018
Buddhima Indraratna, Trung Ngo
Ballast is a free draining granular material that helps transmit and distribute an induced cyclic load to the underlying sub-ballast and subgrade at a reduced and acceptable level of stress (Indraratna et al. 1998; McDowell et al. 2008). It is a natural or crushed granular material with a typical thickness of 250–450 mm that is placed beneath the track superstructure and above the sub-ballast (capping) or subgrade (Ionescu 2004; Sun et al. 2016). Conventionally, coarse-sized, angular, crushed, hard stones and rocks that are uniformly graded, free of dust and not prone to cementing action have been considered as good ballast materials (Lackenby et al. 2007; Ngo et al. 2014; Selig and Waters 1994; Sun et al. 2014a; Tutumluer et al. 2007). Owing to limited universal agreement on the engineering characteristics of ballast, the selection of ballast sources generally depends on availability and economic considerations. Ballast gradation conforms to the gradation limit specified in Australia (AS-22758.7 1996). Table 2.1 shows the grain size characteristics of ballast materials used by the author in the laboratory tests. The typical particle size distribution curves (PSD) of ballast used in this study are plotted in Figure 2.5, together with the PSD of sub-ballast and coal fines.
Elastic inclusions in ballasted tracks – a review and recommendations
Published in International Journal of Rail Transportation, 2023
H. G. S. Mayuranga, S. K. Navaratnarajah, C. S. Bandara, J. A. S. C. Jayasinghe
The ballasted track is a prominent track system used in many railway networks, and it offers several advantages, primarily in terms of energy dissipation, initial construction cost, and routine maintenance cost [1–3]. Ballast is the prime load-bearing element in a ballasted track and maintains the stability of the track under high dynamic loads by effectively distributing the stresses to the underlying layers. With rapid population growth, the global demand for faster and heavier trains to transport passengers and goods under efficient mobility has accelerated. However, due to high speed and heavy engines, ballast particles are subjected to severe degradation, fouling, lateral spreading, and settlement, which compromises the shear strength and the permeability characteristics of ballast while also damaging track elements [4–7]. Conversely, extreme ballast fouling caused by wind sand pollution in desert areas and coal accumulation due to the spilling of coal materials from coal freights partially or completely fills the void space of ballast, increases ballast layer density, changes ballast particle contact, and consequently has a great influence on the mechanical behaviour of track structure [8–10]. The higher ballast degradation and fouling under these conditions lead to frequent and costly track maintenance [11–13] and that highlights the necessity for improvements of ballasted tracks [8,14].
A case study of the deep-sea tailings outfall in the tropical south Pacific
Published in Journal of Applied Water Engineering and Research, 2020
Albert Tsz Yeung Leung, Aurelien Hospital, Chris Young, Daniel Potts, James Stronach, Allister Thompson
Ballast is required on the outfall pipe to prevent sideways motion of the pipe due to wave and current forces and to prevent flotation of the pipe. The forces acting on the pipe can be categorized into two groups: static forces (weight and buoyancy) and hydrodynamic forces (drag force, inertial Force and lift force) from water motion: where is the density of water in kg/m3; CD, CM and CL are drag, inertia and lift coefficients, respectively; D is representative diameter in m; U is the undisturbed water velocity in m/s, and dU/Dt is the acceleration of the undisturbed flow field. Typically, the inertial forces are evaluated using Morison’s equation (Sarpkaya and Issacson 1981), and the other two are based on standard hydrodynamic theory.
Membrane desalination of ballast water using thermoelectric energy from waste heat
Published in Journal of Marine Engineering & Technology, 2022
While ballast water presents environmental concerns, it can also be considered a valuable resource from which freshwater can be produced through desalination processes. Large quantities of energy are required for freshwater production through desalination processes. These energy requirements can be provided by on-board waste heat sources as discussed before (Gude 2019). Therefore, specific objectives of this research are to: (1) evaluate the electrical energy recovery from the waste heat generated by a bulk carrier ship; (2) evaluate the specific energy consumption of a RO unit; and (3) quantify the freshwater output rates from the RO unit considering variations in the feed water temperature.