Details:

Creators:
Salgado, Rodrigo ; Prezzi, Monica ; Ganju, Eshan
Salgado, Rodrigo ; Prezzi, Monica ; Ganju, Eshan Less -
Corporate Creators:
Purdue University. Joint Transportation Research Program
Corporate Contributors:
Indiana Department of Transportation ; United States. Federal Highway Administration
Indiana Department of Transportation ; United States. Federal Highway Administration Less -
Subject/TRT Terms:
[+]
Algorithms Cone Penetrometers COV CPT Sounding Spacing Cross-correlation LRFD Methodology Scale Of Fluctuation Site Investigation Site Variability Soil Penetration Test Sounding
Publication/ Report Number:
FHWA/IN/JTRP-2015/04
DOI:
http://dx.doi.org/10.5703/1288284315523
Resource Type:
Tech Report
Geographical Coverage:
United States
Corporate Publisher:
Purdue University. Joint Transportation Research Program
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:
PDF
Funding:
SPR-3408
Collection(s):
US Transportation Collection
Main Document Checksum:
[+]
urn:sha256:e153b677225cf98a75cd84c52b7655b04660ae49cb8827d8c2becfc4128cfec2
Download URL:
https://rosap.ntl.bts.gov/view/dot/30940/dot_30940_DS1.pdf
File Type:

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