The Application of the Cerchar Abrasivity Index (CAI) to ... · PDF filePIANC-USA / COPRI-ASCE...
Transcript of The Application of the Cerchar Abrasivity Index (CAI) to ... · PDF filePIANC-USA / COPRI-ASCE...
PIANC-USA / COPRI-ASCE / Dredging12
The Application of the Cerchar Abrasivity Index’s
to Dredging Hard Rockby
Luis A. Prieto-Portar PhD, PE, SE
The mining and tunneling industry define the rate of wear as the velocity of metal removal from the tool, or “drill tooth lifetime” expressed in excavated
cubic meters per tooth (m3 excavated per bit). The table shows the rate of wear used calculate the tool consumption.
The Unconfined Compressive Strength Test (UCS) on rock core specimens is performed following ASTM D 2983 or AASHTO T 226. The test yields the
unconfined compressive strength of an intact piece of rock core sample, which may be used to estimate allowable bearing capacity values for bedrock. A rock
specimen must be intact, and at least measure 2”f by 4” long.
The Cerchar index is obtained from a sharpened steel needle’s “sharp point” (shown at left). The test produces a conic blunt surface (shown at right) where its new diameter is measured in integers of 0.1 mm with a scale going from 0
for minimum wear to 6 for maximum wear.
Table 2 provides a classification of the Cerchar, and compares it with a newly proposed abrasivity index: the Schimazek F-value.
Freshwater limestone of the Fort Thompson in Miami, may have strength that exceeds 5,000 psi. Notice the lack of joints and large voids that would permit easy
excavation using a toothed bucket.