【正文】 long time. Archaeologists have found ancient Egyptian roadsthat carried blocks to the pyramids in 4600 BCE. Later,the Romans built an extensive road system, using the same principles we use today. Some of these roads are still in service. If you follow the basic concepts of road building, you will create a road that will last. The ten mandments of a good road are: （ 1） Get water away from the road （ 2） Build on a firm foundation （ 3） Use the best materials （ 4） Compact all layers properly （ 5） Design for traffic loads and volumes （ 6） Design for maintenance （ 7） Pave only when ready （ 8） Build from the bottom up （ 9） Protect your investment （ 10） Keep good records 1． Get water away from the road We can’t overemphasize the importance of good estimate that at least 90% of a road’s problems can be related to excess water or to poor waterdrainage. Too much water in any layer of a road’sstructure can weaken that layer, leading to failure. In the surface layer, water can cause cracks and potholes. In lower layers it undermines support, causing cracks and potholes. A mon sign of water in an asphalt road surface is alligator cracking — an interconnected pattern of cracks forming small irregular shaped pieces that look like alligator skin. Edge cracking, frost heaves, and spring breakup of pavements also point to moisture problems. To prevent these problems remember that water: ? flows downhill ? needs to flow someplace ? is a problem if it is not flowing Effective drainage systems divert, drain and dispose of water. To do this they use interceptor ditches and slopes,road crowns, and ditch and culvert systems. Divert — Interceptor ditches, located between the road and higher ground along the road, keep the water from reaching the roadway. These ditches must slope so they carry water away from the road. Drain — Creating a crown in the road so it is higher along the centerline than at the edges encourages water to flow off the road. Typically a paved crown should be 1?4 higher than the shoulder for each foot of width from the centerline to the edge. For gravel surfaces the crown should be 1?2 higher per foot of width. For this flow path to work, the road surface must be relatively water tight. Road shoulders also must be sloped away from the road to continue carrying the flow away. Superelevations (banking) at the outside of curves will also help drain 河南理工大學(xué) 09 級交通工程專業(yè)外文翻譯 2020 3 the road surface. Dispose — A ditch and culvert system carries water away from the road structure. Ditches should be at least one foot lower than the bottom of the gravel road layer that drains the roadway. They must be kept clean and must be sloped to move water into natural drainage. If water stays in the ditches it can seep back into the road structure and undermine its strength. Ditches should also be protected from erosion by planting grass, or installing rock and other erosion control measures. Erosion can damage shoulders and ditches, clog culverts, undermine roadbeds, and contaminate nearby streams and lakes. Evaluate your ditch and culvert system twice a year to ensure that it works. In the fall, clean out leaves and