Laterally Loaded Piles and Shafts
3.6.1 Introduction of Laterally Loaded Piles and Shafts
In the 1950s and 1960s laterally loaded piles were analyzed primarily by three methods. The first method specified the allowable lateral loading on vertical piles or poles. These allowable lateral loadings were based on local load test experience. For example, a 12-inch diameter timber pile driven into sand or medium clay had an allowable lateral loading of 1500 pounds per pile; if soft clay was present the allowable lateral force was often limited to 1000 pounds per pile or less. To resist a 15 000 pound lateral loading by vertical piles driven into medium stiff clay, you needed 10 piles.
The second method was based on the assumption that lateral loading on piles was similar to vertical loading on spread footings. The upper 5 to 10 feet of the pile was assumed to resist lateral forces (some codes allowed up to 15 feet of pile), and so the area resisting lateral forces was assumed to be equal to the width of the pile times 5 or 10 feet, see Figure 3.6.1. Building codes gave values of allowable lateral bearing pressure or allowable lateral loading per foot of pile for soils described as loose, dense, soft, or hard. The 2000 International Building Code gave allowable lateral bearing pressures for isolated poles supporting buildings as 400 pounds per square foot for sandy gravel, 300 pounds per square foot for silty sand, and 200 pounds per square foot for silty clay. All you had to do to ...