mulated. Specific needs for field observations, implying the use of commercial instruments, are:

(1) Pressure and strain measurements adjacent to tunnels, shafts, and other large cavities in earth and soft rock.

(2) Pressure measurements in compacted backfills.

(3) Measurement of pore pressure and total stresses in large earth dams during and following construction.

(4) Measurement of strains and horizontal and vertical movements in earth- and rock-fill dams.

(5) Studies of soil motion induced by earthquakes.

Commercial porous ceramic stones to determine pore pressure. The characteristics of cohesive soils are of current interest. Factors needing clarification are time required for pore pressure distribution to stabilize and drainage to develop, and pore pressure as an influence on basic shear strength. Commercial porous ceramic stones have been adapted to laboratory pressure measuring equipment to determine pore pressures. More refined equipment with greater accuracy is desired.

Pressure cells to determine contact pressures and deformation.— Relationships between contact pressures and deformation characteristics should be established for soils and structures. A laboratory pressure cell has been developed to yield these data. Inexpensive commercial cells of several pressure ranges are needed to enable field testing on a variety of structures.

Testing of expansive soils.-The expansion and compression of soils can lead to undesirable volume changes and loss in strength. Techniques for the identification of expansive soils and an understanding of the causes of volume changes have shown much success and progress in Bureau of Reclamation research, but methods are needed for the overall control of expansion. Treatments to minimize shrinkage and expansion and to increase stability should be investigated and equipment developed to accomplish treatment.

Chemicals needed to stabilize soil.-Cement, lime, and several chemicals have proved to be suitable soil additives to stabilize soils. The cost of these additives and/or processing with soils is often prohibitive, however, and cheaper materials easier to process are needed. Irrigation projects have urgent need for inexpensive chemicals to reduce permeability on canal slopes, and to increase permeability in drainage areas.

Chemicals for grouted cutoff curtains for dams.-Chemical grouting offers a means of sealing very narrow joints and fine cracks in foundations. Chemicals may also be applicable to the design of grouted cutoff curtains for dams after development of adequate installation techniques. Industry can render invaluable assistance in the identification of suitable chemicals and the design of equipment to apply them.

Split-spoon penetration test.-The Bureau established procedures for the use of the split-spoon penetration test for evaluating foundation sands in which the effects of overburden pressure were considered. The method permits more accurate evaluation of the quality of a foundation at various depths below the surface. The Bureau also developed recently empirical methods for closely estimating the lengths of timber piles required for given load-bearing values, through the use of this field penetration test.

Vane shear test of soils.-Major improvements in a vane shear test procedure for investigating soft clay foundations have increased accuracy and eliminated from measurements of soil strength all effects of friction. The vane shear test apparatus includes a four-blade vane inserted into undisturbed soil and rotated. The torque required to shear a cylindrical surface is measured.

Earth dams in loess.-Bureau studies have resulted in several pioneering procedures for construction of structures and major earth dams in loess. These include: (a) Pretreatment of foundation areas by ponding to cause settlement before and during construction instead of after construction, and (b) establishing minimum requirement for pretreatment and limitations of predrilling for pile placement.

Low-density soils identification. Identification of low-density soils which subside upon wetting is made possible by new procedures involving simplified laboratory tests. The procedures are being used for San Luis Canal (Calif.) construction to identify areas where preconstruction treatment is necessary to control subsidence.

Apparatus to determine shear properties of gravelly soil.-Through laboratory studies in the Bureau of Reclamation, apparatus has been developed to more accurately determine the compaction and shear properties of gravelly soil, particularly where fine fractions of the soil are cohesive. This knowledge has been applied to the design of numerous dam and canal embankments to provide economical and safe structures.

Heavy drilling mud and chemical additives to support drill holes.— Good undisturbed samples must be obtained for investigation of foundation settlement and stability. One of the important developments from sampling research was the use of heavy drilling mud and chemical additives to support the sides of the drill holes, thus eliminating the requirement of casing. A considerable saving in time and expense was effected.

Electric power

High voltage transmission and larger generators. Electric power production in large blocks and transmission at extra high voltages offer unlimited opportunities for the utilization of new materials and equipment. With the increased interconnection of transmission systems, larger individual generating units appear feasible. At present, 500-megawatt turbines and generators are being studied for future plants and appear entirely feasible. Units of this size will be used as soon as they become available.

High voltage transmission of a.c. and d.c. current

Extra high voltage transmission of both a.c. and d.c. offers advantages which cannot be disregarded. Foreign countries lead at the present time in development work and completed installations for both high voltage a.c. and d.c. Some experimental work in the a.c. field has been in progress recently, but a Swedish firm is still the only producer of large technical equipment in the high voltage d.c. category. A task group is studying interconnection of transmission systems by high voltage lines. New materials and equipment are not only being used as they become available, but industry is being encouraged to accelerate development work.

Plastics, rubber and epoxy resins for arc resistance

Use of new plastics in electrical equipment for insulation and bearings is responsible for increased output, greater efficiency, and less maintenance. Series switch sectors cast in a rubber mold with an epoxy resin compound of high arc resistance considerably reduce maintenance of transformer tap changers. The new sectors have an arc resistance of 250 seconds compared to 5 seconds for the replaced phenolic parts.

Silicone grease to protect ceramic line insulators

A special silicone grease is used to protect ceramic line insulators from dirt pickup, thereby reducing shorts and total failure and increasing the useful life of insulators.

Testing equipment for generating units

Field testing of excitation equipment for generating units, to encourage improvements and obtain basic data on actual operation, is being undertaken. Improved performance is constantly sought and becomes more essential as the complexity of large transmission networks increases. Galloping, or low-frequency vibration, of transmission-line conductors presents operational difficulties due to faulting of the conductors and subsequent outages. Experimental test sections of lines are being installed in areas which experience this phenomenon. In such sections, new vibration devices and duplex conductor are being incorporated as suggested by representatives of industry.

Closed TV circuit, and new design of transmission-line towers

Integration of individual powerplant operations with system requirements by closed-circuit TV is being investigated. Remote control by this method may reduce requirements for operating personnel. This program illustrates present concern for new and improved methods, as well as equipment. Another program pertains to development of new designs for transmission-line towers. One experimental section of a new line utilizes towers of aluminum, steel, and reinforced concrete with several different configurations. Appreciable cost reductions may be realized as a result of this study.