Stress field

About: Stress field is a research topic. Over the lifetime, 11926 publications have been published within this topic receiving 226417 citations.

Nonuniform prestress from prior earthquakes and the effect on dynamics of branched fault systems

Abstract: [1] To examine the effects of branched fault geometry on the dynamics of fault systems in the long term, we perform multicycle simulations on generic faulting models. An explicit finite element algorithm is used to simulate spontaneous dynamic rupture of earthquakes. The fault stress during the interseismic period is evaluated by an analytical viscoelastic model. We find that the fault prestress field becomes highly nonuniform near the branch point and on the two branch segments over multiple earthquake cycles, owing to the branched fault geometry and stress interaction between the two segments. The principal prestress on faults rotates over multiple earthquake cycles and departs from the regional stress field significantly near the branch point. After a number of earthquake cycles, the branched fault systems evolve to a steady state in which several patterns of the fault prestress and earthquake rupture repeat. The nonuniform prestress developed from previous earthquakes has large effects on the rupture and slip patterns. Several different rupture scenarios can occur on a given branched fault system. In addition, backward branching can occur in the nonuniform prestress field, either driven by slip on the ‘‘stem’’ of the fault system or through a triggering mechanism. These modeling results may have important implications for understanding fault-branching behavior observed in the 1992 Landers, the 1999 Hector Mine, and the 2002 Denali fault earthquakes and for seismic hazard analysis in the areas where branched fault systems exist.

A theoretical model for thrust-induced deep groundwater expulsion with application to the Canadian Rocky Mountains

Abstract: This paper presents a numerical model for simulating deformation and induced fluid flow in fold-and-thrust belts. Unfractured rock strata are modeled as poroelastic media while fault zones are treated as plastic-elastic media. We introduce the slip element technique into a finite element code to accommodate large deformations along faults. Thrust displacements, stress field changes, and the effects of thrust faulting on groundwater flow are investigated by solving the coupled stress and flow equations numerically. The calculation shows that when a thrust sheet is displaced along its fault surface, the displacement-induced stress generates high pore pressure zones near the tectonic stress boundary and beneath low permeability ramps. These overpressures cause transient fluid flow across the thrust belt. Sensitivity studies on the hydrologic properties of the fault zone suggest that hydraulic conductivities within a fault play important roles in initiating slip deformation and in determining the extent of transient disturbances to the flow field. Low permeability can result in rapid pore pressure buildup in the fault, thereby reducing the effective strength of the fault which leads to earlier failures. A low-permeability fault can also impede the movement of flow into the footwall, thereby limiting the tectonic impact on the flow system within the hanging-wall. Application of the model to the McConnell Thrust in the Canadian Rockies indicates that the total volume of fluid flow induced by tectonic compression could have been of the order of 105 to 106 m3 over a time period of tens to hundreds of years accompanied by an average 100 m of thrust movement.

Thermo-mechanical XFEM crack propagation analysis of functionally graded materials

Abstract: A computational method based on the extended finite element method (XFEM) is implemented for fracture analysis of isotropic and orthotropic functionally graded materials (FGMs) under mechanical and steady state thermal loadings. The aim is set to include the thermal effects in loading, governing equations, and the interaction integral for inhomogeneous materials with a complementary study on available crack propagation criteria in orthotropic FGMs under thermal loading conditions. The isotropic and orthotropic crack tip enrichments are applied to reproduce the singular stress field near crack tips. Mixed-mode stress intensity factors are evaluated in isotropic and orthotropic FGMs by means of the interaction integral. In addition, the mesh dependency and number of elements around the crack tip are substantially reduced in comparison with the standard finite element method with the same level of accuracy. Both mode-I and mixed-mode fracture problems with various types of mechanical and thermo-mechanical functionally graded material properties are simulated and discussed to assess the accuracy and efficiency of the proposed numerical method. Good agreements are observed between the predicted results and the reference results available in the literature with far lower degrees of freedom.

Micropolar theory for two–dimensional stresses in elastic honeycomb

Abstract: A micropolar theory has been used to calculate the stress field generated by a fundamental boundaryvalue problem in planar elasticity; namely, a normal line force acting on the surface of a honeyco...