Improvement of the Geotechnical Axial Design Methodology for Colorado's Drilled Shafts Socketed in Weak Rocks

Abstract

The contents of this report reflect the views of the author(s), who is(are) responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views of the Colorado Department of Transportation or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. The preliminary design recommendations should be considered for only conditions very close to those encountered at the load test sites and per the qualifications described in Chapter 6. Use of the information contained in the report is at the sole discretion of the designer.

A Synthetic Material to Simulate Soft Rocks and Its Applications for Model Studies of Socketed Piles

“…As seen in Figure 4, the relationship between uniaxial compressive strength and the deformation modulus of simulated soft rock falls into the range seen in natural soft rocks. Meanwhile, in uniaxial compressive tests, the failure strain of the simulated rock is in the range of 0.8%∼1.3%, which is almost consistent with the observations of natural rocks by Abu-Hejleh et al [6], that is, 0.9%∼3.7%. For most of the natural rocks, the strain in the compaction stage varies in a relatively large range and accounts much for the failure strain.…”

“…of 0.34 MPa were in the range of 13 ∘ ∼53 ∘ and 0.1∼2.5 MPa which were collected and sorted from the natural soft rocks in the literature published previously [5][6][7][8][9][10][11][12][13][14][15].…”

Load and resistance factor design of drilled shafts in shale using SPT and TCP measurements

“…Equations 2.3 and 2.4 produce "allowable" values for unit tip and side resistance and include an unknown factor of safety inherent in the equations (Abu-Hejleh, et al 2003).…”

“…This factor of safety is frequently presumed to be equal to 3, due to the lack of information (Abu-Hejleh, et al 2003). If the factor of safety is taken as being equal to 3, the ultimate unit tip and side resistance can respectively be predicted as where is the predicted ultimate unit tip resistance (ksf), is the predicted ultimate unit side resistance (ksf), and is the corrected SPT -value (blows/ft).…”

“…While the "original" Colorado SPT based method (CSB) described above has reportedly been used for many years without notable problems, there is also little direct evidence available to demonstrate its accuracy (Abu-Hejleh, et al 2003 where is the predicted allowable unit tip resistance (ksf), is the predicted allowable unit side resistance (ksf), and is the corrected SPT -value (blows/ft).…”