Study on Combined Energy Absorption Support for Rockburst Disaster Control in Tunnelling
Table 2
Summary of test results.
Condition
Failure characteristics
State of specimen
Ultimate strength (MPa)
1
Static, shear failure
The fragments were large and uneven, leaving obvious conical residues at the top and bottom of the specimen.
12.5
2
Static, shear failure
15
3
Static to burst
The concrete was broken and flew out, the farthest distance was 1.7 m.
12
4
Static to burst
The concrete was broken and flew out, the farthest distance was 1.9 m.
13.8
5
Static to burst
The specimen burst violently, the fragment flew out 3 m, and the concrete had broken to the gravel degree.
20
6
Static to micro-motion expansion to burst
When the loading pressure reached 25 MPa, the concrete on the top of the specimen was slowly crushed, spring bounced back, which led to the axial compression deformation and radial dilation on the top of the specimen. The specimen came back to a stable state after the loading decreased to 12 MPa. When the loading continually pressed on the specimen, the iron wire ring broke and loosed, and the specimen burst violently without a significant increase in loading.
25
7
Static to micro-motion expansion to large deformation
The burst was finally been prevented under the confinement of rubber, the specimen recovered stable after large expansion deformation, and the pressure decreased to 2 MPa. A continued loading was performed, but the specimen did not present any signs of destruction even the loading reached the jacking range.
