SHAFT is a computer program used to evaluate the axial
capacity and the short-term, load-settlement curves of drilled
shafts or bored piles in various types of soils. In general,
the majority of axial capacity methods used by SHAFT are based
on the latest FHWA manual. In addition, several other axial
capacity methods are provided for clay shales, gravels, and
SHAFT can analyze the axial capacity and settlement behavior
of drilled-shafts in eight 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:
clay - cohesive geomaterial (FHWA)
sand - cohesionless geomaterial
clay - shale (Reese &
strong rock - using either side
resistance or end bearing (FHWA)
strong rock - using both side
resistance plus end bearing (for comparison)
weak rock - cohesive
intermediate geomaterial (FHWA)
gravel - cohesionless
intermediate geomaterial (Rollins et al)
gravelly sand (Rollins et
LRFD principles for axial response of deep
foundations enabling users to specify separate reduction
factors for side resistance and end bearing on each soil
Three new soil models have been added in SHAFT.
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 provided by SHAFT on a text file 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
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
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
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).