Modeling of the in situ state of stress in elastic layered rock subject to stress and strain-driven tectonic forces

Abstract

Abstract. In this study we describe and compare eight different strategies to predict the depth variation of stress within a layered rock formation. This reveals the inherent uncertainties in stress prediction from elastic properties and stress measurements, as well as the geologic implications of the different models. The predictive strategies are based on well log data and in some cases on in situ stress measurements, combined with the weight of the overburden rock, the pore pressure, the depth variation in rock properties, and tectonic effects. We contrast and compare stresses predicted purely using theoretical models with those constrained by in situ measurements. We also explore the role of the applied boundary conditions that mimic two fundamental models of tectonic effects, namely the stress-or strain-driven models. In both models, layer-to-layer tectonic stress variations are added to initial predictions due to vertical variation in rock elasticity, consistent with natural observations, yet describe very different controlling mechanisms. Layer-to-layer stress variations are caused by either local elastic strain accommodation for the strain-driven model, or stress transfers for the stressdriven model. As a consequence, stress predictions can depend strongly on the implemented prediction philosophy and the underlying implicit and explicit assumptions, even for media with identical elastic parameters and stress measurements. This implies that stress predictions have large uncertainties, even if local measurements and boundary conditions are honored.

Insights From Micromechanical Modeling of Intact Rock Failure: Event Characteristics, Stress Drops, and Force Networks

“…Since the latter have often negative magnitudes (Cipolla et al, ; Van der Baan et al, ), indicating fracture lengths on the order of meters to tens of meters, the existence of strong stress heterogeneities is very likely even at several kilometers depth. Indeed, numerical modeling of stresses in elastic media shows that stress and material heterogeneity are coupled (Roche & Van der Baan, , ).…”

Brittle Shear Tectonics in a Narrow Continental Rift: Asymmetric Nonvolcanic Barmer Basin (Rajasthan, India)

“…This is because the acute angle between the two conjugate faults exceeds considerably the Andersonian 607. The Barmer rift being filled up by layer sedimentary rocks, the applied tectonic stress varied, presumably through those layers (e.g., Roche and van der Baan 2017). This possibly produced non-Andersonian faulting within the basin.…”

Use of Rock Mass Rating (Rmr) Values for Support Designs of Tunnels Excavated in Soft Rocks Without Squeezing Problem

“…), terrestrial stresses like seasonal variations, moon pull, diurnal stresses and other geological features [45][46][47][48][49][50][51]. Because in-situ stress distribution and k ratio can immediately change underground, safe yielding zone estimation is preferable for the rock support design in engineering applications [52][53][54][55]. The k ratio of 2 is not extraordinary high to see in the rock engineering applications.…”