Strain influence factor charts for settlement evaluation of spread foundations based on the stress-strain method
Journal
Applied Sciences
Date Issued
June 1, 2020
Author(s)
DOI
10.3390/app10113822
Abstract
In this paper, the stress–strain method for the elastic settlement analysis of shallow
foundations is revisited, o ering a great number of strain influence factor charts covering the most
common cases met in civil engineering practice. The calculation of settlement based on strain influence
factors has the advantage of considering soil elastic moduli values rapidly varying with depth, such as
those often obtained in practice using continuous probing tests, e.g., the Cone Penetration Test (CPT)
and Standard Penetration Test (SPT). It also o ers the advantage of the convenient calculation of
the correction factor for future water table rise into the influence depth of footing. As is known,
when the water table rises into the influence zone of footing, it reduces the soil sti ness and thus
additional settlement is induced. The proposed strain influence factors refer to flexible circular
footings (at distances 0, R/3, 2R/3 and R from the center; R is the radius of footing), rigid circular
footings, flexible rectangular footings (at the center and corner), triangular embankment loading
of width B and length L (L/B = 1, 2, 3, 4, 5 and 10) and trapezoidal embankment loading of infinite
length and various widths. The strain influence factor values are given for Poisson’s ratio value of
soil, ranging from 0 to 0.5 with 0.1 interval. The compatibility of the so-called “characteristic point”
of flexible footings with the stress–strain method is also investigated; the settlement under this point
is considered to be the same as the uniform settlement of the respective rigid footing. The analysis
showed that, despite the e ectiveness of the “characteristic point” concept in homogenous soils,
the method in question is not suitable for non-homogenous soils, as it largely overestimates settlement
at shallow depths (for z/B < 0.35) and underestimates it at greater depths (for z/B > 0.35; z is the depth
below the footing and B is the footing width).
foundations is revisited, o ering a great number of strain influence factor charts covering the most
common cases met in civil engineering practice. The calculation of settlement based on strain influence
factors has the advantage of considering soil elastic moduli values rapidly varying with depth, such as
those often obtained in practice using continuous probing tests, e.g., the Cone Penetration Test (CPT)
and Standard Penetration Test (SPT). It also o ers the advantage of the convenient calculation of
the correction factor for future water table rise into the influence depth of footing. As is known,
when the water table rises into the influence zone of footing, it reduces the soil sti ness and thus
additional settlement is induced. The proposed strain influence factors refer to flexible circular
footings (at distances 0, R/3, 2R/3 and R from the center; R is the radius of footing), rigid circular
footings, flexible rectangular footings (at the center and corner), triangular embankment loading
of width B and length L (L/B = 1, 2, 3, 4, 5 and 10) and trapezoidal embankment loading of infinite
length and various widths. The strain influence factor values are given for Poisson’s ratio value of
soil, ranging from 0 to 0.5 with 0.1 interval. The compatibility of the so-called “characteristic point”
of flexible footings with the stress–strain method is also investigated; the settlement under this point
is considered to be the same as the uniform settlement of the respective rigid footing. The analysis
showed that, despite the e ectiveness of the “characteristic point” concept in homogenous soils,
the method in question is not suitable for non-homogenous soils, as it largely overestimates settlement
at shallow depths (for z/B < 0.35) and underestimates it at greater depths (for z/B > 0.35; z is the depth
below the footing and B is the footing width).
File(s)![Thumbnail Image]()
Name
applsci-10-03822-v3.pdf
Size
12.59 MB
Format
Adobe PDF
Checksum (MD5)
ad101b9f7e5e8510142b113e5a51286f