AN IMPACT PENETROMETER FOR ASSESSING THE CUTTABILITY OF SOFT ROCKS

During the TRRL tunnelling trials at Chinnor it was necessary to characterize the tunnel face in terms of cuttability. No existing technique was suitable for indexing the chalk and an impact penetrometer was developed. A 76 mm hardened steel cone was fired into the chalk and the depth of penetration recorded. The resulting values of penetration strength were closely related to the cutting forces; the penetration strength profile and cutting force profile around a pick cutting circle were very similar. The correlation coefficient between peak penetration strengths and peak cutting forces was 0.85 when the cutting forces were similar before and after penetrometer indexing. It is likely that the impact penetrometer can be used for assessing cuttability or general quality of any soft rock with a compressive strength between 1 and 15 mn/sq.m. With the existing penetrometer, a single measurement takes 1 minute; this will be significantly reduced with the use of the integrated penetrometer described in this report. (A) /TRRL/

• Corporate Authors:

  Transport and Road Research Laboratory (TRRL)

  Wokingham, Berkshire  United Kingdom 
• Authors:
  • HUDSON, J A
  • Drew, S D
• Publication Date: 1976

Language

• English

Media Info

• Features: Figures; Photos; References; Tables;
• Pagination: 32 p.

Subject/Index Terms

• TRT Terms: Chalks; Coefficients; Compressibility; Compressive strength; Correlation analysis; Cutting; Dynamic penetration test; Force; Fracture mechanics; Measuring instruments; Pendulum tests; Penetrometers; Rocks; Soft rock; Strength of materials
• Uncontrolled Terms: Breaking up
• ITRD Terms: 6155: Apparatus (measuring); 3604: Breaking up; 4120: Chalk; 6410: Coefficient; 5905: Compressibility; 6296: Dynamic penetration test; 5421: Force; 6285: Penetration; 4154: Rock; 5544: Strength (mater)
• Subject Areas: Bridges and other structures; Construction; Data and Information Technology; Geotechnology; Highways; I43: Rock Mechanics; I54: Construction of Tunnels;

Filing Info

• Accession Number: 00138925
• Record Type: Publication
• Source Agency: Transport and Road Research Laboratory (TRRL)
• Report/Paper Numbers: TRRL LR 685
• Files: ITRD, TRIS, ATRI
• Created Date: Oct 26 1976 12:00AM