Abstract
AbstractIn this study, we present a new granular rock-analogue material (GRAM) with a dynamic scaling suitable for the simulation of fault and fracture processes in analogue experiments. Dynamically scaled experiments allow the direct comparison of geometrical, kinematical and mechanical processes between model and nature. The geometrical scaling factor defines the model resolution, which depends on the density and cohesive strength ratios of model material and natural rocks. Granular materials such as quartz sands are ideal for the simulation of upper crustal deformation processes as a result of similar nonlinear deformation behaviour of granular flow and brittle rock deformation. We compared the geometrical scaling factor of common analogue materials applied in tectonic models, and identified a gap in model resolution corresponding to the outcrop and structural scale (1–100 m). The proposed GRAM is composed of quartz sand and hemihydrate powder and is suitable to form cohesive aggregates capable of deforming by tensile and shear failure under variable stress conditions. Based on dynamical shear tests, GRAM is characterized by a similar stress–strain curve as dry quartz sand, has a cohesive strength of 7.88 kPa and an average density of 1.36 g cm−3. The derived geometrical scaling factor is 1 cm in model = 10.65 m in nature. For a large-scale test, GRAM material was applied in strike-slip analogue experiments. Early results demonstrate the potential of GRAM to simulate fault and fracture processes, and their interaction in fault zones and damage zones during different stages of fault evolution in dynamically scaled analogue experiments.
Highlights
Natural faults and fractures form the most common geological structures and control the mechanical strength and fluid flow in the Earth’s crust
The dynamic scaling provided by granular rock-analogue material (GRAM) material enables the simulation of fault damage zones at the structural scale, with 1 cm in the model corresponding to 10.65 m in nature
The experiment GRAM test-7 described in Section 5.c above demonstrated the characteristic geometries, kinematics and dynamics of fracture nucleation and damage zone evolution leading to an interconnected shear zone, that is, a primary deformation zone (PDZ)
Summary
Natural faults and fractures form the most common geological structures and control the mechanical strength and fluid flow in the Earth’s crust. For the simulation of upper crustal deformation processes, cohesion-less granular materials, such as dry quartz sand, are widely used (Reber et al 2020) These materials show nonlinear frictional properties similar to natural rocks and are ideal to simulate the 3D architecture of complex regional-scale fault systems. Cohesion-less granular materials are not able to form extension fractures and cannot provide suitable dynamic scaling and spatial resolution for the simulation of fault–fracture networks in fault damage zones. The simulation of coupled fault–fracture processes in scaled analogue experiments can help to develop predictive tools for the understanding of such complex structures, analysing the dynamical interaction of faults and fractures during the different stages of deformation
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