Economics Of Road Construction PDF Download

Excerpt from Economics of Road Construction The roads of the Romans were built at enormous cost, probably not less than $50,000 a mile. They were constructed of stone laid in mortar, the courses aggregating about 36 ins. in thickness. No regard was paid to topography. Hills were climbed or excavated, even where by a slight deflection they could have been avoided, and drainage ditches seem to have been entirely omitted. It was not until 1764 that Tresaguet, a French engineer, began to construct roads upon scientific principles by using small broken stone placed upon a well-shaped bed of larger fragments set on edge. The same type of road was later introduced into England by Telford about 1824, and roads so constructed are generally known by his name. About the same time, or possibly a little earlier, a genius appeared in the person of Macadam, who discovered that the foundation course of large stone set on edge was unnecessary; and that, provided the soil was well drained, a bed of loose broken stone some 6 to 12 ins. in thickness would become sufficiently bound together under traffic to uphold the heaviest of wagon loads. No further advance in the science of road construction occurred until the invention of the stone-crusher and the introduction of the steam road roller, both within recent years. It may be safely said that half the controversies between engineers over the subject of road construction are due to the fact that one class of engineers still adheres to the rules of Macadam without recognizing the changes wrought by the steam roller and the crusher. The broken stone road of to-day is quite a different structure from the type of road built by Macadam, who used hand broken stone that was practically uniform in size, laid in the road without the addition of a binder of stone dust or sand and left to be compacted by passing wheels. What was the result? About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.