Study of concrete porosity effect on in-situ stress measurements by Acoustic Emission method

摘要

When rock samples are loaded, Acoustic Emission (AE) occurs when stress reaches a level greater than that which the rock has previously experienced. This phenomenon, known as Kaiser Effect, which has been used as an indirect method of in-situ stress measurement in rock mass that can be one of the most important parameters in designing of underground structures. Several physical parameters have effect on Kaiser Effect such as porosity, sample size, moisture content and so on. In this research, effect of porosity as a physical property of rock on in-situ stress measurement using AE method is studied. Porosity, creating a heterogeneous environment in the rock sample and causes effects on propagation of acoustic signals. In order to omit interfering with other parameters artificial rock samples (Ferro Cement Mortar), with fixed grading concrete and no memory of previous stress are used so the only variable factor is air cavities in the samples (porosity). Several samples with different porosity percentages ranging %14 to %20 were compressed uniaxialy. The results shown that porosity have effect on Kaiser Effect and in-situ stress amount perdition. Ultimately, amongst various AE parameters, energy and count parameters are better for determination of pre stress.