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A pothole is a type of failure in an asphalt pavement,〔 〕 caused by the presence of water in the underlying soil structure and the presence of traffic passing over the affected area. Introduction of water to the underlying soil structure first weakens the supporting soil. Traffic then fatigues and breaks the poorly supported asphalt surface in the affected area. Continued traffic action ejects both asphalt and the underlying soil material to create a hole in the pavement. == Formation == According to a U.S. Army Corps of Engineers publication, ''Pothole primer—A public administrator's guide to understanding and managing the pothole problem'', (Eaton, et al.), pothole formation requires two factors to be present at the same time: water and traffic. Water weakens the soil beneath the pavement; traffic applies the loads that stress the pavement past the breaking point. Potholes form progressively, first from fatigue of the road surface, which can lead to a precursor failure pattern known as crocodile cracking. Finally, chunks of pavement between the fatigue cracks gradually work loose, and may eventually be plucked or forced out of the surface by continued wheel loads to create a pothole.〔 In areas subject to freezing and thawing, frost heaving can damage a pavement and create openings for water to enter. Spring thaw of pavements accelerates this process when thawing of upper portions of the soil structure in a pavement cannot drain past still-frozen lower layers, thus saturating the supporting soil and weakening it.〔 Potholes can grow to several feet in width, though they usually only develop to depths of a few inches. If they become large enough, damage to tires, wheels, and vehicle suspensions is liable to occur. Serious road accidents can occur as a direct result, especially on those roads where vehicle speeds are greater.〔 〕 According to Eaton, et al., potholes may result from four main causes:〔 :1. Insufficient pavement thickness to support traffic during freeze/thaw periods without localized failures. :2. Insufficient drainage. :3. Failures at utility trenches and castings (manhole and drain casings). :4. Miscellaneous pavement defects and cracks left unmaintained and unsealed so as to admit moisture and compromise the structural integrity of the pavement. File:Asphalt deterioration.jpg|Crocodile cracking showing moisture seepage, a sign of a weakened soil structure beneath the failed asphalt. File:Pothole.jpg|Detail of pothole, showing presence of water in soil structure, on a road in Montréal, Québec. File:Newport Whitepit Lane pot hole.JPG|Example of a pothole reappearing on a newly patched roadway, also showing the transition between crocodile cracking and the pothole, with water dried up, in a road on the Isle of Man. Image:Banbury's Bretch Hill Pothole, 2010..png|Small potholes, showing isolated failures of the pavement and its subsurface structure, in a road in Banbury, UK. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「pothole」の詳細全文を読む スポンサード リンク
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