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Field test and finite element analysis of vermiculite expansive rock cracking

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Document pages: 11 pages

Abstract: In previous studies, laboratory tests were carried out to measure the expansion of vermiculite during heating and convert it into expansion pressure. Based on these test results, this study mainly focuses on the field tests to verify that the expansion pressure obtained by heating vermiculite material is sufficient to break large and hard granite for tunnel excavation. In order to carry out the test, a hexahedral granite sample with a circular hole in the center was made. The round hole is filled with vermiculite and thermal conductive material, and then heated with a barrel heater. As a result, cracks appeared on the surface of all hexahedral granite samples after 700 seconds of thermal heating, and finally divided into two Peces completely. The specimen of larger size only requires more heating time and expansion pressure. The material properties of granite rocks, which were obtained from the experimental tests, were utilized to produce finite element models used for numerical analyses. The analysis results show good agreement with the experimental results in terms of initial cracking, propagation direction, and expansion pressure.

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