What are advantages and disadvantages of wooden sleepers?
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Advantages include: They do not rot like timber sleepers, extra weight makes track more stable (particularly with changes in temperature), they can withstand fire hazards better than wooden sleepers, they give more retentivity to the track, they have a longer life than wooden sleepers, and they need less maintenance, resulting in lower ongoing costs and fewer track closures. Additionally, concrete sleepers are not soaked in creosote like most wooden sleepers (used mainly in Europe), therefore they are environmentally friendlier.
Disadvantages include: When trains derail and the wheels hit the sleepers, timber sleepers tend to absorb the blow and remain intact, while concrete sleepers tend to shatter and have to be replaced. Initial costs are greater, and they are unsuitable for change of gauge, unless this is already taken into account. Concrete sleepers are up to 300 lbs heavier than their wooden counterparts. As a result, larger sized ballast is required to both support and hold in place the sleepers on the roadbed. Additionally, they do not absorb as much vibration from passing trains as wooden sleepers do. This can cause degradation of the sleepers themselves ranging from small cracks to complete failure over time. This problem is most prevalent when the sleepers are located next to joints in the rails. For this reason, railroads which used concrete sleepers for plain line avoided them on turnouts and interlockings; however, modern designs allow use of concrete bearers for turnouts and they have become standard for switch renewals on many railways. Another potential fault is lateral rigidity which may cause cumulative metal fatigue, particularly on reverse curves where the stresses are accentuated by the abrupt change of lateral forces. This in turn may be the cause of gauge corner cracking in the rails themselves as well as the steel sleeper reinforcement. German railways have experienced cracking of their sleepers on high speed lines and have had to replace many thousands of them after only a short life; however, this was found to be due to use of inappropriate aggregate in the concrete mix.[7] Damaged concrete sleepers cannot be repaired. Old concrete sleepers can be used for things like retaining walls, else they might be crushed to recycle gravel and the steel reinforcing.[8]
Disadvantages include: When trains derail and the wheels hit the sleepers, timber sleepers tend to absorb the blow and remain intact, while concrete sleepers tend to shatter and have to be replaced. Initial costs are greater, and they are unsuitable for change of gauge, unless this is already taken into account. Concrete sleepers are up to 300 lbs heavier than their wooden counterparts. As a result, larger sized ballast is required to both support and hold in place the sleepers on the roadbed. Additionally, they do not absorb as much vibration from passing trains as wooden sleepers do. This can cause degradation of the sleepers themselves ranging from small cracks to complete failure over time. This problem is most prevalent when the sleepers are located next to joints in the rails. For this reason, railroads which used concrete sleepers for plain line avoided them on turnouts and interlockings; however, modern designs allow use of concrete bearers for turnouts and they have become standard for switch renewals on many railways. Another potential fault is lateral rigidity which may cause cumulative metal fatigue, particularly on reverse curves where the stresses are accentuated by the abrupt change of lateral forces. This in turn may be the cause of gauge corner cracking in the rails themselves as well as the steel sleeper reinforcement. German railways have experienced cracking of their sleepers on high speed lines and have had to replace many thousands of them after only a short life; however, this was found to be due to use of inappropriate aggregate in the concrete mix.[7] Damaged concrete sleepers cannot be repaired. Old concrete sleepers can be used for things like retaining walls, else they might be crushed to recycle gravel and the steel reinforcing.[8]
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adventage is there it protect us from electric shpck
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