A Failure Criterion of Weak and Crushable Limestone Rock in Mining Field containing Karstic Cavities

Abstract

This study aims to correlate the mechanical properties measured in the laboratory and the field for weak and crushable limestone in a mining site containing random karstic cavities. Compressive tests were performed in the laboratory to obtain Unconfined Compressive Strength (UCS) and rock mass modulus (Erm). Field tests were: i) boring and drilling cores that allowed obtaining Rock Quantification Distribution (RQD) and recovery rock parameter (REC), and ii) Ground Penetration Radar (GPR) to detect and locate random cavities in the underground limestone deposit. The correlation between the Em/UCS rate and the RQD was determined and analyzed. Based on the role of the new interpretation of the Geological Strength Index (GSI) and its relationship with the Erm/UCS rate, a mathematical relationship was determined to link GSI and RQD. This relationship was a basis for modifying the generalized Hoek-Brown criterion, involving the amplitude of reflected electromagnetic waves (EM) provided by GPR field tests.

Keywords

• weak limestone rock
• Unconfined Compressive Strength (UCS)
• rock mass modulus (Em)
• Rock Quality Designation (RQD)
• weak Limestone rock; unconfined compressive strength (UCS), rock mass modulus (Erm) Rock Quality Designation (RQD), Karstic cavities, Ground Penetration Radar (GPR), Failure Creterion
• Ground Penetration Radar (GPR)