Abstract: To address the issue of the prediction of rock lateral pressure coefficient in oil and gas engineering, we studied the formation mechanisms of horizontal stress in a medium, and methods for calculating lateral pressure coefficients. We analyzed differences in the horizontal stresses of three different media (water, soil, and rocks) and the engineering significance of the lateral pressure coefficient. Further, we investigated methods for predicting lateral pressure coefficients of rocks. We found that the mechanisms of horizontal stress formation in rocks are completely different from those in water and soil, due to differences in the structure and fluidity of these media. Horizontal stresses in soil and water are produced by their intrinsic weights, whereas horizontal stresses in rocks are primarily generated by tectonic actions. As these tectonic actions vary greatly in strength, the horizontal stresses of rocks also vary over a large range, and the rock lateral pressure coefficient varies between -∞ and +∞. Therefore, methods for calculating the lateral pressure coefficient in soil media cannot be used to calculate the lateral pressure coefficient of rocks. In addition, since methods for predicting the lateral pressure coefficient are based on measurements of crustal stress, the predictions yielded from these methods are meaningless in practice.

Key words: rocks, fluids, soil, pressure, stress, vertical stress, horizontal stress, lateral pressure coefficient