ABSTRACT
Two different types of in-situ stress measurements, hydro-fracturing and overcoring method, have been carried out to analyze the stability of an oil storage facility in underground before and during excavation. Two measurements for each method have been executed in different boreholes. The results of measurements show that, even though the test area is not so large, the states of stress are different according to the location. The magnitudes of K value vary from 3.1 to 0.85 for four tests. Such a change of stresses seems to have been affected by a series of faults crossing between the measured sites. Two horizontal stresses measured by both methods in the same region are nearly identical in the magnitude of the stress ratio, K, as well as their direction. The K values tend in general to decrease according to an increase of the topographic depth. The results of this research point out that stress measurements should be necessarily performed to know the real state of stresses when constructing an important and large facility in underground.
