Calculation of the effective length of hanging under-ream bored piles under compressive load in a homogeneous ground of the base

The article considers the calculation of the effective length of an under-ream bored pile and a pile without broadening. The pile is located under axial compression conditions in a homogeneous ground of the base. Reducing the cost of piles is an important problem, since the manufacture of piles with broadening is characterized by increased cost. This can be achieved by identifying the value of the effective pile length. The length of the pile is considered effective if a stress in the ground is reached under its widened part equal to the calculated value R of the resistance of the ground of the base. The values of soil resistance are given in SP 24.13330.2011 (2021) for different soils at different depths of immersion of the Hc pile. In the paper, the tabular values of H and R are presented as a dependence of R on Hc (functions). The type of these functions is determined by the least squares method. In contrast to the instructions for the calculations of piles according to JV 24.13330.2011 (2021), a different design scheme for the operation of the pile in the ground of the base is proposed without bringing it to a “breakdown”. As a result, a calculation equation is presented to determine the effective length of the under-ream bored pile. Similar calculations are applicable for piles without broadening.