This book is included in the Self Reliance Water & Wells section.
ACKNOWLEDGEMENTS
The writer wishes to acknowledge his appreciation of the assistance
given him by Mr. Jas. D. Schuyler, M. Am. Soc. C. E., Consulting
Hydraulic Engineer, in reviewing this paper, and in making
suggestions of value. Appendix II. contains a list of authors
whose writings have been freely consulted, and to whom the
writer is indebted ; the numerous citations in the body of the paper
further indicate the obligations of the writer.
CONTENTS CHAPTER I. - Introductory CHAPTER II. - Preliminary Studies and Investigations CHAPTER III. - Outline Study of Soils. Puddle CHAPTER IV. - The Tabeaud Dam, California CHAPTER V. - Different Types of Earth Dams CHAPTER VI. - Conclusions APPENDIX I. - Statistical Descriptions of High Earth Dams APPENDIX II. Works of Reference
CHAPTER I.
Introductory.
The earth dam is probably the oldest type of dam in existence,
antedating the Christian Era many hundreds of years. The literature
upon this subject is voluminous, but much of it is inaccessible
and far from satisfactory. No attempt will here be made to collate
this literature or to give a history of the construction of earth dams,
however interesting such an account might be. The object will
rather be to present such a study as will make clear the application
of the principles underlying the proper design and erection of this
class of structures. In no way, therefore, will it assume the
character or dignity of a technical treatise.
Dams forming storage reservoirs, which are intended to impound
large volumes of water, must necessarily be built of considerable
height, except in a very few instances where favorable sites may
exist. Recent discussions would indicate that a new interest has
been awakened in the construction of high earth dams. As related
to the general subject of storage, it is with the high structure rather
than the low that this study has to do. To the extent that "the
greater includes the less," the principles here presented are applicable
to works of minor importance.
Many persons who should know better place little importance
upon the skill required for the construction of earthwork embankments,
considering the work to involve no scientific problems. It
is far too common belief that any ordinary laborer, who may be able
to use skillfully a scraper on a country road, is fitted to superintend
the construction of an earth dam. It has been said that the art of
constructing earth dams is purely empirical, that exact science furnishes
no approved method of determining their internal stresses,
and that in regard to their design experience is much more valuable
than theory. When the question of stability is fully taken into
consideration, it certainly requires a large amount of skill successfully
to carry out works of this character.
Extreme care in the selection of the site, sound judgment in the
choice of materials and assiduity in superintending the work while
in progress, are all vitally essential.
Classification of Dams.
Dams may be classified according to their purpose as diverting
dams or weirs and as storage dams. The former may be located
upon any portion of a stream where the conditions are favorable,
and the water used for manifold purposes, being conveyed by means
of canals, flumes, tunnels and pipe lines to places of intended use.
These dams are generally low and may be either of a temporary
01 permanent character, depending upon the uses to which the water
is put. Temporary dams are made of brush, logs, sand bags,
gravel and loose rock. The more permanent structures are built of
stone and concrete masonry.
Storage dams may be classified according to the kind of material
entering into their structure, as follows: (1) Earth; (2) Earth and
Timber; (3) Earth and Rock-fill; (4) Rock-fill; (5) Masonry; (6)
Composite Structures.
Low dams forming service reservoirs for domestic water supplies
and for irrigation comprise by far the most numerous class.
They are not designed to impound a large volume of water and
therefore may be built across a small ravine or depression, or even
upon the summit of a hill, by excavating the reservoir-basin and
using the material excavated to form the embankment. These reservoirs
may be used in connection with surface or gravity systems,
artesian wells, or underground supplies obtained by pumping. The
dams forming these reservoirs being of moderate size and height
may vary greatly in shape and dimensions. The form may be made
to suit the configuration of the dam site. When the earthwork requires
it, they may be lined with various materials to secure watertightness.
Often such dams are made composite in character,
partly of earth and partly of masonry or some other material. They
are also frequently accompanied by numerous accessories, such as
settling-basins, aerating devices and covers, which present a diversity
in form and appearance. A presentation of the different types
of dams thus employed, with a discussion of the questions pertaining
to utility in design and economy in construction, would be exceedingly
valuable and of general interest. Service-reservoirs will
receive only a passing notice, with the hope expressed that some
competent authority will discuss them in the future.
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