New Fracture Toughness Tests for Rock and Concrete with Particular Reference to Rock
This thesis applies the concepts of Fracture Mechanics to some of the problems of Rock Mechanics. A review of the literature shows that Fracture Mechanics is applicable to ceramic materials, such as rocks and concrete, but no test has been available which can quickly and easily measure the fracture toughness of these materials. Three new fracture toughness tests are proposed which are relatively easy to apply to in situ materials. The stress intensity factor for each test specimen is derived. The tests are developed, to varying degrees, using concrete as a test material. The relative merits of the three tests are discussed, and their advantages emphasised. The tests are shown to give reproducible results for two rock types. Fracture failure criteria are derived for three simple rock structures, and use the results obtained from the new fracture toughness tests. The criteria are compared with conventional tensile strength ones. The final chapter draws conclusions from the project, and makes suggestions for a future program of work.
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