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GeoConSol
Geotechnical & Tunnel Consultants

A consultant is a universal observer who can look at a problem outside the environment in which the problem came to be, thereby creating a solution that was never possible before.  Fernando Flores

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EXPERT / FORENSIC SERVICES
DIFFERING SITE CONDITIONS
-->DSC Technical Principles
-->DSC Standards for Entitlement
-->DSC Independent Review
-->DSC Case Histories
-->Case History of a Bogus Expert
GEOTECHNICAL / CONSTRUCTION
-->Rock Testing/Boreability
-->Impact Hammer Feasibility
ARTICLES / PUBLICATIONS
TUNNELS / TUNNELING
-->Tunnel Boring
-->Excavation Improvement
-->Microtunneling/Pipe-Jacking
-->Selection of TBMs & MTBMs
-->Forensic Investigations
-->Safety
-->Detection of Covert Tunnels
CLIENTS
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Peter J. Tarkoy

Rock Testing for TBM Boreability

Total Hardness
(The only laboratory with consistent personnel of 40 years experience)

 

Rebound Hardness (HR)

Schmidt Hammer by ASTM D 5873 

Taber Abrasion Hardness (HA )

 

Click for Test Specifications

 



Download Rock Testing Specifications for Total Hardness

 

Total Hardness

HT = HR x (HA )1/2

 

The Total Hardness rock testing series has been in use for about 45 years in the United States and internationally.  It was first used to provide an indication of rock comminution, then directly applied to predicting tunnel boring machine penetration rates and cutter rolling path life

The test values and their applicability to construction behavior of rock are well known throughout the construction industry.  The test series have been applied to assessing  roadheader excavation, drill & blast excavation, and various rock breaking applications in construction, including dredging.

The tests are simple yet very useful in assessing rock comminution.  Unlike more elaborate and complex methods that require detailed calculations to arrive at precise values, the Total Hardness gives an indication of feasibility and general rock excavation performance.  It avoids providing a precise calculation for performance which depend on some identifiable parameters such as equipment and operational variables.  However, it will also influenced by unquantifiable variables such as operator idiosyncrasies and tool maintenance.  In this way, minor variations in rock properties will not be a source of spurious claims. 

The vast databank of Total Hardness is applicable to local conditions and may be applied using the chart for the Range of Total Hardness provided below:

 

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