Detection of thin weak zone in weathered rocks from automatic monitoring of pneumatic rotary-percussive drilling

Abstract

Weathered rock mass can have thin weak zones or cavities. These weak zones or cavities may not be detected during conventional ground investigation because the drillhole investigation is limited and the weak zones are thin. This paper uses the recently developed DPM methodology to divide the DPM data into sub-processes such as pushing, pulling and drilling and builds criteria so that thin weak zones can be detected from the sorted DPM data. The method establishes the relationship between the drilling rate and its downward thrust pressure and the relationship between the pushing-in rate and its downward thrust pressure. Case studies are given to illustrate the detection method. The case studies demonstrate that the proposed method has good potential for accurately detecting thin weak zones in weathered granitic or volcanic rocks. © 2008 Taylor & Francis Group.