Knowledge Core Collection:
https://hdl.handle.net/11681/27263
2024-03-28T13:08:17ZExperiments with dry ice for cooling fresh concrete
https://hdl.handle.net/11681/27321
Title: Experiments with dry ice for cooling fresh concrete
Authors: Porter, Leland C.
Abstract: In the Summer of 1952 tests were made to determine the efficiency of dry ice (solid CO₂) for cooling fresh concrete. Observations were also made to determine whether the concrete is adversely affected by its contact with the carbon dioxide gas liberated by the dry ice. Two mixes were made (one with and one without the addition of dry ice) and cylinders were cast for compressive strength tests at 1, 3, 7, and 28 days' age. The dry ice was crushed to about minus 3/8 inch in size and introduced into the mixer immediately, following the mix water. Calculations for quantities of dry ice were based theoretically on producing a temperature drop of about 10° F in the concrete. Only the heat of sublimation (heat required to change from a solid to a gas at the same temperature) was considered as it was assumed the gas would escape from the mixer as soon as formed and would not be effective in further cooling the concrete. Based on these calculations, 2.3 pounds of dry ice were added to 1-1/2 cubic feet of concrete, which amounts to 40.8 pounds of dry ice per cubic yard of concrete. An additional 0.9 pound of dry ice was included to cool the mixer drum.
Description: Technical Report1952-12-01T00:00:00ZStable channel profiles
https://hdl.handle.net/11681/27316
Title: Stable channel profiles
Authors: Glover, Robert E. (Robert Ellsworth), 1896-; Florey, Q. L.
Abstract: In order to deal intelligently with certain problems of maintenance of channels in erodible materials, it is important to know what shape and dimensions a channel should have in order to avoid changes of cross section due to scour or sediment deposition. A knowledge of stable shapes finds application to the problem of designing canals in earth and to the problems of river regimen. The computations of stable shape patterns described herein have been made at the request of Mr. E. W. Lane who has also laid down the basis for the computations.
Description: Technical Report1951-09-01T00:00:00ZInfluence of soil properties and construction methods on the performance of homogeneous earth dams
https://hdl.handle.net/11681/27264
Title: Influence of soil properties and construction methods on the performance of homogeneous earth dams
Authors: Sherard, James L.
Abstract: The purpose of the investigation is to study the consequences of important departures from those practices accepted at the present time for construction of homogeneous earth dams. At the present time, essentially identical construction methods are usually employed for all soil types. The consequences of deviating from these methods, and particularly the influence of the embankment soil properties on these consequences, are not yet understood except in a very general way. Up to 1900, relatively few large earth dams had been built and little experience was available. In the period between 1900 and 1920, due largely to the expansion of irrigation in the western United States, a great number of earth dams were built. Because of lack of experience, there were no generally accepted methods available for the design and construction of these dams. It was a period of experimentation. In different places, widely varying designs and construction methods were used. Many of the dams constructed in this period failed in some degree. By 1920, engineering literature was filled with descriptions of earth dam failures and the profession had become thoroughly alarmed by their high frequency. In the early 1920's, the experience of the previous two decades already was strongly influencing earth dam construction practice. Failures were studied and dams were patterned after the successful structures. Because there were no means available for defining quantitatively the properties of fine grained soils, none of the descriptions of dam failures in the literature included the soil type. As a consequence, the methods of construction which evolved were not influenced by soil properties and were adequate for the worst soil type. By the early 1930's, slopes were made, in general, flat enough to eliminate danger from slides. About the same time, wide acceptance of Proctor's control procedures assured well-constructed embankments. As a result, the percentage of failures has been reduced practically to zero in the past 15 years. Yet, some of the dams which were constructed before 1920 with little or no compaction equipment and no moisture control have given adequate performance. This fact indicates that for some types of soils, and perhaps under other special conditions, present methods of construction are unnecessarily conservative . It was believed that a study of a group of these old dams might lead to a valuable correlation between soil type, construction method, and performance. Particularly for small dams, this correlation would justify relaxation of present construction practices for some soil types.
Description: Technical Memorandum1953-01-01T00:00:00Z