Field Borings and Cone
Richard P. Ray, Ph.D., P.E.
Civil and Environmental Engineering
University of South Carolina
The purpose of the Drilling Program is to determine the:
Lateral Extent, and
Physical Properties of Each Layer of Soil
Presence, Depth and Pressure of Water in the Soil
Coupled with the Topographic Survey, This provides a 3D view
of the site and the soil underneath.
If the Upper Soils are Weak, a Deep Foundation system must be
This investigation may also determine where to find suitable fill
material from Borrow pits.
To Properly Characterize a Site requires:
Literature Investigation to Determine
What Has Happened at the Site Before (Prior History)
What Investigations have been Made Near the Site
Geology, USDA Soil Profiles, Utility Crossings, etc.
On Site Surveying, Borings and Drilling, Bag Samples, etc.
Laboratory Testing for Soil Properties and Classification
Produce a Report about the site for the Owner
Maybe develop a Foundation Design, Retaining Structures,
Embankments, Cuts and Fills
Stem Augers With
Removable Drill Rod
And Center Head
Split Spoon Sampler
– Disturbed Samples
• When pore pressure is collected, referred to as piezocone
or CPTu . Three basic measurements qc, fs, u2.
• qc is typically corrected for pore pressure effects (qt).
• qt = qc + u2(1-a), where a is net area ratio of tip, ranges
from 0.6 to 0.8 depending on probe design.
• Normalization for overburden stress.
Qt = (qt-σvo)/σ′vo
Fr = 100%[fs/(qt-σvo)]
Bq = (u2-u0)/(qt-σvo) = pore pressure parameter
Estimated parameters from standard CPTu
• Undrained shear strength, Su
• Drained friction angle, phi
• Stress History, OCR
• Equivalent N60
• Coefficient of lateral earth stress, Ko
• Total density, relative density and void ratio, ρ , DR, eo
• Constrained modulus, M
• Sensitivity, St
• Fines Content
• Additional parameters