Evaluating Properties of Weak Shales in Western Missouri


Evaluation of the geomechanical properties of shales, especially weak ones is always problematic. The Missouri Department of Transportation (MODOT) recently undertook a major research initiative to achieve significant and recurring cost savings for MODOT by developing improved, technically sound design specifications. Test drilling in shale was conducted; Boreholes were typically drilled in pairs, side-by-side, with one boring being used for core sampling, and the other being used for in situ penetration testing. Coring methods were modified to provide better quality samples. Testing was conducted on or as near the site immediately after recovery. On site point load testing was introduced and used along with slake durability testing to rank the shale in the Franklin Shale Rating System. Samples of shale too weak for point load testing were tested for plasticity index, which is also part of the Franklin Shale rating system. In the penetration boreholes, alternating split-barrel sampler penetration and Texas cone penetration tests were conducted at 2.5 foot intervals using a standard automatic safety hammer. Between tests, the borehole was cleaned and drilled to the next testing level using a tri-cone roller bit.

Meeting Name

44th US Rock Mechanics Symposium and the 5th US/Canada Rock Mechanics Symposium (2010: Jun. 27-30, Salt Lake City, UT)


Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

Cone Penetration Tests; Core Sampling; Geomechanical Properties; In-Situ; Missouri Department Of Transportations; Missouris; Penetration Testing; Plasticity Indices; Rating System; Recurring Costs; Research Initiatives; Slake Durability; Sound Designs; Boreholes; Load Testing; Rock Mechanics; Sampling; Shale; Plasticity Testing

Geographic Coverage

Western Missouri

Document Type

Article - Conference proceedings

Document Version


File Type





© 2010 American Rock Mechanics Association (ARMA) (ARMA), All rights reserved.

Publication Date

01 Jun 2010

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