قراءة كتاب American Rural Highways
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AGRICULTURAL ENGINEERING SERIES
E. B. McCORMICK, Consulting Editor
FORMERLY DEAN OF ENGINEERING DIVISION
KANSAS STATE AGRICULTURAL COLLEGE
AMERICAN
RURAL HIGHWAYS
McGraw-Hill Book Co. Inc.
PUBLISHERS OF BOOKS FOR
Coal Age — Electric Railway Journal
Electrical World — Engineering News-Record
American Machinist — Ingenieria Internacional
Engineering & Mining Journal — Power
Chemical & Metallurgical Engineering
Electrical Merchandising
FrontispieceAMERICAN
RURAL HIGHWAYS
BY
T. R. AGG, C.E.
PROFESSOR OF HIGHWAY ENGINEERING
IOWA STATE COLLEGE
First Edition
McGRAW-HILL BOOK COMPANY, Inc.
NEW YORK: 239 WEST 39TH STREET
LONDON: 6 & 8 BOUVERIE ST., E. C. 4
1920
COPYRIGHT, 1920, BY THE
McGRAW-HILL BOOK COMPANY, INC.
PREFACE
American Rural Highways was written for use as a text or reference in courses dealing with rural highways and intended for agricultural engineers, students in agriculture and for short courses and extension courses. The reader is assumed to have familiarity with drawing and surveying, but the text is adapted primarily for students who do not receive training along the lines of the usual course in Highway or Civil Engineering.
The text is intended to familiarize the student with the relation of highway improvement to national progress, to indicate the various problems of highway administration and to set forth the usual methods of design and construction for rural highways in sufficient detail to establish a clear understanding of the distinguishing characteristics and relative serviceability of each of the common types of roadway surface.
Experience with classes made up of students in agriculture or agricultural engineering and with trade school students in road making served as a guide in the selection and arrangement of the material. Detailed discussion of tests of materials and of the theory of design has to a considerable extent been eliminated as being outside of the scope of the course for which the text is intended.
In the preparation of American Rural Highways reference was had to many books on highway subjects and to current periodical literature. Wherever direct extracts were made from such source, appropriate acknowledgment appears in the text.
Ames, Iowa
August 18, 1920.
CONTENTS
vii
THE PURPOSE AND UTILITY OF HIGHWAYS
Transportation Problem—National in Scope—Development in Traffic—Location or Farm to Market Traffic—Farm to Farm Traffic—Inter-City Traffic—Inter-County and Inter-State Traffic—Rural Education—Rural Social Life—Good Roads and Commerce
1-12
HIGHWAY ADMINISTRATION
Township Administration—County Administration—State Administration—Federal Administration—Special Assessments—Zone Method of Assessing—General Taxation—Vehicle Taxes—Sinking Fund Bonds—Annuity Bonds—Serial Bonds—Comparison of Methods of Issuing Bonds—Desirability of Road Bonds
13-28
DRAINAGE OF ROADS
The Necessity for Drainage—Importance of Design—Surface Drainage—Run-off—Ordinary Design of Ditches—Underground Water—Tile Drains—Lying Tile—Culverts—Length of Culvert—Farm Entrance Culverts—Metal Pipe—Clay and Cement Concrete Pipe—Concrete Pipe—Endwalls for Culverts—Reinforced Concrete Box Culverts—Drop Inlet Culverts
29-41
ROAD DESIGN
Necessity for Planning—Road Plans—Problems of Design—Preliminary Investigations—Road Surveys—Alignment—Intersections—Superelevation—Tractive Resistance—Rolling Resistance—Internal Resistance—Air Resistance—Effect of Trades—Energy Loss on Account of Grades—Undulating Roads—Guard Railing—Width of Roadway—Cross Section—Control of Erosion—Private Entrances—Æsthetics
42-62
EARTH ROADS
Variations in Soils—Variation in Rainfall—Cross Sections Elevating Grader—Maney Grader—Slip Scraper—Fresno Scraper—Elevating Grader Work—Use of Blade Grader—Costs—Maintenance—Value of Earth Roads
63-73
SAND-CLAY AND GRAVEL ROADS
The Binder—Top-soil or Natural Mixtures—Sand-clay on Sandy Roads—Sand-clay on Clay or Loam—Characteristics—Natural Gravel—The Ideal Road Gravel—Permissible Size of Pebbles—Wearing Properties—Utilizing Natural Gravels—Thickness of Layer—Preparation of the Road—Trench Method—Surface Method—Maintenance
74-88
BROKEN STONE ROAD SURFACES
Design—Properties of the Stone—Kinds of Rocks used