Horizontal Subgrade Reaction Estimated from Lateral Loading Tests on Timber Piles

Lateral loading tests on timber piles in a variety of soil conditions are reported. Measured horizontal deflections and slopes of the piles are compared with predicted movements based on elastic theories and published values of horizontal subgrade reaction. It was found that the actual deflections and slopes of the piles were consistently less than the computed values, particularly for cohesionless soils. Based on the test results presented in this paper, suggested relationships between horizontal subgrade reaction and soil consistency are given.

The horizontal subgrade reaction is a function of the magnitude and position of load application (it decreases with increasing soil stress). For cohesionless soils, increases in soil density caused by driving displacement piles apparently increase the horizontal subgrade reaction.