Arizona republican., 1921-05-03
The Subqrade

The Subgrade
 One of the problems and fundamental one in road construction is the subgrade with which the county highway commission is working. All other problems simpler for the reason that ex- perence has already furnished solution of them. The best section the best mix and the best of anything relating to road building has been deter mined and standards have been set subject per haps to modification to slightly varying cond tons various localities. But there can be no standard sub grade. What do for part of the country not do for another; what may do in one place may not do mile away
 This is important subject than it formerly and it will be still more important. few years ago the most advanced road builders gave little attention, but the constant increase of traffic units have made it most important matter.
 When the famous Roman roads were built there were units of exceptionally heavy traffic, and that respect the traffic highways not mater ially changed until the advent the truck
 H. G. Shirley, secretary of the Federal Highway Council has interesting article the sub grade in the current number of The American City. He says When reads of the adoption of a standard specification calling for uniform thickness (of the highway crust) all classes of soil he feel that there is something radically wrong in the adoption of such standard and that if persisted there will be written the blackest pages recorded in engineering history.
 "The crying need at the present time is to build a road that will have uniform strength so carry specific load over it's entire length without danger to it's structure On gravel and other stable soils with high bearing power, thick surfacing not re- quired. whereas soils consisting of clay and adobe very much thicker surfacing needed to carry the same load at certain the year. Millions are being wasted annually in using in some places greater thickness material than is needed and in not putting down in a sufficient depth in other places"
 Investigation has shown that failures that occur on roads built on soil of high bearing power run about IT per cent, on clay and adobe about 70 per cent On stable gravel and sandy failures run down as low as or per cent. But a certain per- centage of these failures may be attributed to bad workmanship.
 The article of MT. Shirley contains illustrations of broken down roads due faulty subgrade but in all but the cause of the break downs illus trated due to frost action, something that we may disregard in study of the problem.
 The subject Shirley is now receiving the attention of the Bureau of Public Roads whose problem committee outlined it as follows: Problem l. Securing of samples of the subgrade materials at points where the failures have occurred and samples where failures have not occurred the same vicinity under similar conditions. Problem g. Developing field tests for bearing power of soils.
 experimental sections of roads Problem 4. study of chemical methods of sub grade treatment for increasing bearing or pre- venting absorption
 Problem B. A study of mechanical methods of subgrade treatment.
 | Problem 6. study of the effect of freezing and thawing on the volume and on the supporting prop critics of soils
 | Problem T. study of the effect of moisture on the volume changes in soils.
 l Problem S. A study of the transmission of pressure transmitted to the subgrade through diff ferent thicknesses and different types surfacing
 Problem g. A study to ascertain the practical classifcations of subgrade materials. l Problem 10. Special problems. | It will be interestins and at the same time gratifying, to that the engineering department of the county highway commission has for month: been engaged all of the problems outlined above except Problem 6. Laboratory tests made of the various soils to ascertain their probable bearing power One of the foremost highway engineers O California said week, after inspection of th' highway work now going on. that he believed tha nowhere else in the whole country was there such comprehensive study of the subject of the subgrad under way.
 n conclusion MT. Shirley writes;
 sIt is hoped that the time will whel some simple test will determine the bearing power o the soil. inspector look on his blueprint and tell the type and character of surfacing tha should be used that particular kind of soil; o that he will be able to turn to specifications see the treatment necessary bring the soil to certain bearing power. He will then know immediate lv how to proceed with the construction of the roa in order that it may have uniform strengt throughout entire length at all seasons of tn year and be capable of carrying specified loa without danger destruction"
 Gasoline fumes a garage kill well know mining man." a headline screamed yesterda morning. Gasoline fumes outside garage have a equally destructive effect private bank roll