Agricultural machinery traffic is one of the main causes of soil compaction in modern agriculture. Soils with weak inherent soil structural stability already have low bearing capacity and, when subjected to intensive tillage with a high frequency of traffic, are susceptible to severe soil compaction. In this study, repeated wheeling experiments were carried out on an Iranian clay soil prepared at two water contents (corresponding to 0.9 and 1.35 × water content at the lower plastic limit), two wheel loads (light and heavy rear wheel loads of a two-wheel-drive tractor) and two vehicle travel speeds (0.5 and 1 m s–1). The experiments tested whether the stress variations due to repeated wheeling are mainly due to variations in rut depth with repeated tyre passes and whether traffic at a higher travel speed has a smaller compaction effect. Mean normal stress was measured at three depths (0.15, 0.25 and 0.35 m) beneath the centre of tyres using cylindrical Bolling probes. Rut depth and cone index were measured after each pass. The results showed a linear increase in rut depth with consecutive tractor passes, with a greater increase on wet soil. However, bulk density increased more in dry soil than in wet soil at 0.15 and 0.25 m depth, most likely due to soil water content being close to the optimum Proctor water content. At 0.35 m depth, the bulk density increase was larger for wet soil, with obvious impacts of wheel load and travel speed (greater increase for slower speed and heavier wheel). Cone index generally increased with repeated tractor passes, with the greatest increase at 0.35 m depth in wet soil under heavy rear wheel traffic. Stress generally increased with increasing rut depth due to repeated wheeling. Reduced distance between the soil–tyre interface and the Bolling probes with increasing rut depth was investigated as a potential reason using analytical stress simulations, but could not fully explain the increase in stress with rut depth. Therefore, additional factors (e.g. soil strength) must have contributed to the stress increase with increasing number of tractor passes.
In recent decades, population growth and progress of technology have shaped large and compact urban settlements.Existence of huge transportation systems and developed urban infrastructures are among the most important properties of modern cities. In spite of prompt transit and facilitated daily activities, development of transportation systems causes many problems, including traffic, air and noise pollutionand so on. Noise pollution as one of the most important human health threats can cause annoyance, sleep disturbance, decreased learning ability and even cardiovascular problems and blood pressure in long time. Sound is caused by a wide range of activities and processes. Road traffic, railways, airplanes landing, workrooms, industries and communicate places are the most important noise sources. Awareness of the noise emission status in urban environments and the identification of people at risk are primary steps that should be taken in planning as a basic information to reduce vulnerability. Currently, trains running along railways, after traffic jams, are ecoming the crucial source of noise pollution. This is especially important in a large city such as Tehran, which crosses the rails a long way in residential areas. In this study, a spatial approach was used to model the noise pollution caused by railway transport in Tehran. To this end, the RMR standard was used to calculate the noise level generated in the source of sound (rail path).The noise emission and its attenuation in the environment was also modeled based on the method presented in ISO 9613-2.According to the results, the railway noise range in the studied area varies from 43 to 88 dB. The comparison of the estimated noise level with the measured values indicates a 3.5 dB RMSE. The overlapping of the noise map with the demographic data indicates that around 200,000 people are exposed to noise pollution of more than 70 dB and about 730,000 are exposed to noise pollution greater than 60 dB. Obviously, in the absence of proper residential insulation, the health of a large population of residents adjacent to the railway is at serious risk
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.