United States Department of Transportation
i
Assessment of site variability from analysis of cone penetration test data.
-
2015-01-01
[PDF-5.51 MB]
Details:
-
Creators:
-
Corporate Creators:
-
Corporate Contributors:
-
Subject/TRT Terms:
-
Publication/ Report Number:
-
DOI:
-
Resource Type:
-
Geographical Coverage:
-
Corporate Publisher:
-
Abstract:Soil property values for use in geotechnical design are often estimated from a limited number of in situ or laboratory tests. The
uncertainty involved in estimating soil properties from a limited number of tests can be addressed by quantifying the variability within
individual soundings and of the collection of soundings at a site. It has been proposed that factors of safety or resistance factors used in
design be linked to site variability. Site variability can be assessed by studying the correlation structure of in situ test data. The cone
penetration test (CPT), which is a reliable and widely‐accepted in situ test, can be used for this purpose. Soil behavior type (SBT) charts
are often used to obtain the subsurface soil profile from CPT parameters such as the cone resistance and the sleeve friction. A soil
profile generation algorithm was developed in this research to generate a soil profile from an individual CPT sounding using two
modified SBT charts. Soils are variable in both the vertical and horizontal directions. A vertical variability index (VVI) was defined to
quantify variability in a CPT sounding. The average of the VVIs for all CPT soundings performed at a site is the site VVI. A site horizontal
variability index (site HVI) was also developed, based on cross‐correlation between cone resistances, the cone resistance trend
differences and the spacing between every pair of CPTs considered, to quantify the soil variability of a site in the horizontal direction. A
site variability rating (SVR) system, integrating the vertical and horizontal site variability, was developed to assess the overall site
variability. Depending on the SBT chart selected, the soil profile generated using the soil profile generation algorithm may be slightly
different; however, the SBT chart effect on the variability indices that compose the SVR index is small. Close agreement was found
between the SVRs obtained using the two SBT charts selected for this research. In order to illustrate the use of the algorithms
for VVI and HVI calculations and SVR of sites, CPTs from across the state of Indiana were analyzed. CPT data were obtained from
Purdue's own database, INDOT’s data repository and the U.S. Geological Survey (USGS) website. Site variability is calculated for specific
depths of interest. For example, that depth of interest will be shallower for shallow foundations than for deep foundations. Site
variability rating maps (SVR maps) for various depths of interest were constructed for the state of Indiana, illustrating the potential use
of the site variability assessment methodology. An optimal sounding spacing calculation methodology was also developed to make the
site investigation process more efficient, cost‐effective and reliable.
-
Format:
-
Funding:
-
Collection(s):
-
Main Document Checksum:
-
Download URL:
-
File Type:
