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PILE HAMMER SELECTION A FUNCTION OF SOIL AND TYPE
The variables to be considered in the selection process relate to the type of pile, the general terrain condition, the equipment available and local problems such as noise restrictions. Core samples that reveal underlying soil and its density in varying strata, are an aid in making the choice. Two classes of soil, cohesive (clayey) and non-cohesive (sandy) are briefly reviewed. The consistency of cohesive or the relative density of non-cohesive soil can be measured by a penetrometer test. Such values generated in various types of soils are tabulated. A half-dozen principal hammer categories of varying sizes (hammer size is related to its rated energy in ft-lb. Speed, expressed in blows per min is an adjunct to energy) is described. Drop hammers are heavyweight rams hoisted and dropped on the pile top. Simple-acting units use either air or steam to elevate the ram and generally carry energy ratings of 7,260 to 60,000 ft-lb. Speeds range between 50 and 70 blows per min. This hammer type is ideal in true cohesive soils and mixtures that are dominantly cohesive. Double-acting hammers are described which give best results in non-cohesive or soft clay soils. The single-acting diesel units get ram-raising force from the one-cylinder hammer's action. These light hammers are especially suited to heavy piling such as H-beams, pipes and timers. This design provides a cushioning effect that reduces damage to the pile head, and works best in medium to hard driving soil. The double-acting diesel displays greatest effectiveness in non-cohesive and soft clay soils. The vibratory drivers which transmit motion to the pile by means of a hydraulic clamp, perform best with light to heavy sheet steel piling, H-beams, wood sheet, and open-end pipe in non-cohesive soils.
330 West 42nd Street
Construction Methods and Equipment
Old TRIS Terms:
Construction; Geotechnology; Highways; Materials
Nov 12 1974 12:00AM