In-Situ Stress Determination in Soil and Rock Using the Acoustic Emission Method.

摘要

A project was undertaken to determine how well acoustic emission (AE) techniques could be used to determine the existing stress state in rock and soil masses. It was found in rock that the Kaiser Effect (No AE until previous stress level EXCEEDED) was obeyed for short times (delay times) after stress application, but was not obeyed for delay times longer than about 100-1000 hours. In soil, the Kaiser effect was obeyed, but the effect of delay times was not investigated. These results apply to a very wide variety of rock and soil types. A Goodman rock jack was retrofitted with an AE transducer assembly and field tested in large discrete rock masses at a rock quarry and in bore holes in six different sites with varying rock types. This acoustic-rock jack functioned very well above and below the water table. The existing horizontal stresses, predicted from breaks in the AE versus applied stress curves, were of the same order (on the higher end) as those determined by more conventional mthods of determining the existing stress state. A Menard pressuremeter was retrofitted with an AE transducer assembly, and used in bore holes in the field in various soil types. Preliminary field work has shown this acoustic pressuremeter to work well to depths of 10 feet (only used above the water table so far). The existing horizontal (lateral) stresses predicted from the AE pressuremeter results were in the higher portion of the expected values.