COMPREHENSIVE INVESTIGATIONS OF HORIZONTALLY LOADED PILES IN COHESIONLESS SOILS

down to 10% at near-critical loads, i.e., friction forces along the side surfaces come into full operation before the limiting state is reached, and in the early stages of loading greatly affect the total reactive resistance. However, these conclusions require refinement because in the tests, the intensity of contact pressures was measured only at the middle of the pile width, and the distribution of the soil reaction over its width was assumed to be uniform; furthermore, no investigations at all were made of the intensities of the friction forces. Meanwhile, Baguelin and Jezequel [5] had established on the basis of thorough tests that, at large displacements, the soil-reaction pressure at the center of a plane surface of a pile is 30% greater than at its edges. From this it is obvious that account must be taken of the characteristic features of the reactive-pressure distribution along the contact surface, in order to reliably determine the average reactive pressure of the soil where large displacements are involved. Where cylindrical piles are under investigation, the problem becomes even more complex; and in order to determine the average soil-reaction pressure over the pile perimeter, one has to install 3-5, or even a greater number, of soil dynamometers. As has already been remarked above, the p vs u relationship is nonlinear; therefore, the variable modulus of subgrade reaction or, as it is more aptly named-modulus of horizontal soil resistance K is a function of depth z and displacement u. If the function K = f(u, z) is known, then the problem of the bending of a pile subjected to external force factors can be solved by an electronic computer. The quantitative description of modulus K is best realized by a family of p--u graphs plotted to give the soil reaction pressure p as a function of pile displacement u for each of the design sections along the pile depth [6]. The results of tests during which measurements are taken of all the soil-reaction components and pile displacements at various depths, enable K(u, z) to be determined in the most definite and reliable manner.