SHAFT is a computer program used to evaluate the axial capacity and the short-term, load-settlement curves of drilled shafts (bored piles) and continuous flight auger (CFA) piles or auger-cast piles (ACIP) in various types of soils. In general, the majority of axial capacity methods used by SHAFT are based on the latest FHWA manuals. In addition, several other axial capacity methods are provided for clay shales, gravels, and gravelly sands.

SHAFT can analyze the axial capacity and settlement behavior of drilled-shafts and ACIP piles in several types of soil and rock models. SHAFT can accommodate any combination of soil and rock layers in a layered profile. The soils and rock models in SHAFT are the following:


  • LRFD principles for axial response of deep foundations enabling users to specify separate reduction factors for side resistance and end bearing on each soil layer.
  • Three new soil models were added in SHAFT v2017. These are the models for gravel and gravelly sand developed by Rollins, et al. (2005) and for decomposed rock/gravel/granular glacial till developed by Mayne & Harris (1993) with modifications by O'Neill (1996).
  • For models in soils, SHAFT produces a single graph showing the upper-bound, lower-bound, and trend (averaged) load vs. settlement curves.
  • Axial load-transfer curves for side resistance (t-z curves) are automatically provided by SHAFT on a text file and plots for top, middle and bottom of each soil layer.
  • A chart option shows the soil profile along with the predicted shaft capacity as a function of depth.
  • An option has been provided to allow analyses that include both axial side resistance and end bearing in rock sockets.
  • SHAFT computes the side, end-bearing and total resistance for every foot of penetration and also predicts the load-vs-settlement curve of the top and bottom (in output text file) of the drilled shaft.
  • Users can investigate capacities of drilled shafts of multiple diameters in one run and comparative output graphs thus helping on the selection of most economical sizing.
  • Profiles of the modeled shafts may be either straight-sided or with underreams (bell).
  • Users may specify separate factors of safety for side resistance and for end bearing.
  • The user can also control the lengths of exclusion zones for side resistance at the top and/or bottom of the shaft to account for possible surface cracking in the soil due to moisture change or for other factors.
  • SHAFT allows the computation of axial shaft resistance to uplift forces. The program can use any reduction factor specified by the user for friction transfer in uplift of straight shafts.
  • The program produces output tables of load capacity values or bearing graphs, as a function of depth. These tables show axial capacity in side resistance and in end bearing, along with the sum of the two. The volume of concrete is also shown for each depth.
  • SHAFT produces graphs for side resistance, end-bearing (tip) resistance, and total axial capacity as a function of shaft length (ultimate or with load factors).
  • It also produces graphs of the short-term, load-settlement curve for any user-specified penetration.
  • SHAFT generates output reports as plain text. A sample output file normally contains the following data:
    • Printing of all input-data parameters (used for checking inputted values).
    • Summary results of skin friction, tip resistance, and ultimate capacity as a function of depth.
    • Tabulation of the approximate volume of concrete that would be required per depth.
    • Summary results of total allowable loads as a function of depth (using inputted factors of safety).