Transcriber’s Notes:
Underscores “_” before and after a word or phrase indicate _italics_
in the original text.
Small capitals have been converted to SOLID capitals.
Illustrations have been moved so they do not break up paragraphs.
Typographical and punctuation errors have been silently corrected.
EARTH DAMS
_A STUDY_
BY
BURR BASSELL, M. Am. Soc. C. E.
_Consulting Engineer_
NEW YORK
THE ENGINEERING NEWS PUBLISHING COMPANY
1904
COPYRIGHT, 1904
BY
THE ENGINEERING NEWS PUBLISHING CO.
ACKNOWLEDGMENTS.
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.
PAGE
CHAPTER I.
Introductory 1
CHAPTER II.
Preliminary Studies and Investigations 3
CHAPTER III.
Outline Study of Soils. Puddle 12
CHAPTER IV.
The Tabeaud Dam, California 17
CHAPTER V.
Different Types of Earth Dams 33
CHAPTER VI.
Conclusions 63
APPENDIX I.
Statistical Descriptions of High Earth Dams 67
APPENDIX II.
Works of Reference 68
ILLUSTRATIONS.
PAGE
Fig. 1. Longitudinal Section of Yarrow Dam Site 10
2. Cross-Section of the Yarrow Dam 10
3. Plan of the Tabeaud Reservoir 17
4. Tabeaud Dam: Plan Showing Bed Rock Drains 18
5. Details of Drains 18
6. View of Drains 19
7. North Trench 20
8. South Trench 21
9. Main Central Drain 21
10. Embankment Work 23
11. Dimension Section 26
12. Cross and Longitudinal Sections 27
13. View of Dam Immediately After Completion 29
14. Cross-Section of Pilarcitos Dam 34
15. San Andres Dam 34
16. Ashti Tank Embankment 35
17. Typical New England Dam 40
18. Two Croton Valley Dams Showing Saturation 41
19. Studies of Board of Experts on the Original Earth
Portion of the New Croton Dam 43
20. Studies of Jerome Park Reservoir Embankment 46
21 to 24. Experimental Dikes and Cylinder Employed
in Studies for the North Dike of the Wachusett
Reservoir 49
25. Cross-Section of Dike of Wachusett Reservoir 49
26. Working Cross-Section of Druid Lake Dam 53
27 to 29. Designs for the Bohio Dam, Panama Canal 55
30. Cross-Section of the Upper Pecos River Rock-Fill Dam 59
31. Developed Section of the San Leandro Dam 59
EARTH DAMS
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 or 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 water-tightness. 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.