Point load test

Eigure 7.8 Flexural third-point load test in progress. 

Figure 7.11 shows a uniform load test (actually, quarter-point loading test) of a railing system. 

Figure 5 Three point load test setup.

With the three point loading test, the stresses were concentrated essentially at the corners, and the panel had a tendency to move downwards in a rigid manner. Failure occurred at the corners. Cracks appeared little by little at each corner and suddenly grew more rapidly at one of the corners then an unstable state took place, and the panel collapsed. 

It is also interesting to see that during the three point loading test, the deflection remained symmetrical with respect to the transverse axis of symmetry of the panel till fracture occurred. In the case of the single point loading, the deflection became non-symmetrical before fracture and this accelerated the process of crack growth. 

Franklin. J.L. and Broch. E. 1972. The point load test. International Journal Rock Mechanics and Mining Science, 9. 669-697. 

Point load test This is a quick lab test to measure strength. It should be conducted with the uniaxial compression test as described by Broch and Franklin (1972). 

Strength Unconfmed compressive strength Triaxial test Indirect tensile strength test (such as Brazilian splitting test) Point load test (Zs50) Most widely used measure of strength Unusual, weak rock only Must be supported by compressive strengths 1... 

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