EFFECTS OF CYCLIC LOADING ON MECHANICAL PROPERTIES OF MAHA SARAKHAM SALT
Keywords:
Fatigue, creep, elasticity, strength, viscosity, saltAbstract
Series of laboratory testing have been performed to assess the effects of cyclic loading on compressivestrength, elasticity and time-dependency of the Maha Sarakham rock salt. Results from the cyclic loadingtests indicate that the salt compressive strength decreases with increasing number of loading cycles,which can be best represented by a power equation. The salt elastic modulus decreases slightly duringthe first few cycles, and tends to remain constant until failure. It seems to be independent of the maximumloads within the range used here. Axial strain-time curves compiled from loci of the maximum load ofeach cycle apparently show a time-dependent behavior similar to that of creep tests under static loading.In the steady-state creep phase, the visco-plastic coefficients calculated from the cyclic loading test areabout an order of magnitude lower than those under static loading. The salt visco-plasticity also decreaseswith increasing loading frequency. Surface subsidence and cavern closure simulated using parameterscalibrated from cyclic loading test results are about 40% greater than those from the static loadingresults. This suggests that application of the property parameters obtained from the conventional staticloading creep test to assess the long-term stability of storage caverns in salt with internal pressurefluctuation may not be conservative.
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