[Paper Review] Interdependent evolution of robustness, force transmission and damage in a heterogeneous quasi-brittle granular material: from suppressed to cascading failure

Antoinette Tordesillas, Sanath Kahagalage+3 more|arXiv (Cornell University)|Aug 30, 2018

Rock Mechanics and Modeling40 references3 citations

TL;DR

This study develops a data-driven, multiscale framework to model the interdependent evolution of robustness, force transmission, and damage in heterogeneous quasi-brittle granular materials. By analyzing discrete element simulation data, it identifies two key transmission patterns—optimized flow routes and force bottlenecks—that predict damage propagation and macrocrack formation, revealing a cooperative mechanism among bottlenecks that delays failure but ultimately enables cascading collapse.

ABSTRACT

A heterogeneous quasi-brittle granular material can withstand certain levels of internal damage before global failure. This robustness depends not just on the bond strengths but also on the topology and redundancy of the bonded contact network, through which forces and damage propagate. Despite extensive studies on quasi-brittle failure, there still lacks a unified framework that can quantify the interdependent evolution of robustness, damage and force transmission. Here we develop a framework to do so. It is data-driven, multiscale and relies solely on the contact strengths and topology of the contact network for material properties. Using data derived from discrete element simulations of concrete specimens under uniaxial tension, we uncover evidence of an optimized force transmission, characterized by two novel transmission patterns that predict and explain damage propagation from the microstructural to the macroscopic level. The first comprises the optimized flow routes: shortest possible paths that can transmit the global transmission capacity. These paths reliably predict tensile force chains. The second are the force bottlenecks. These provide an early and accurate prediction of the ultimate pattern, location and interaction of macrocracks. A two-pronged cooperative mechanism among bottlenecks, enabled by redundancies in transmission pathways, underlies robustness in the pre-failure regime. Bottlenecks take turns in accommodating damage, while member contacts spread the forces to confine damage to low capacity contacts which leave behind a web of strong contacts to support and curtail the failure of tensile force chains in the region. This cooperative behavior, while serving to minimize the inevitable reduction in global transmission capacity, progressively heightens the interdependency among these contacts and elicits the opposite effect.

Motivation & Objective

• To address the lack of a unified framework for quantifying the interdependent evolution of robustness, force transmission, and damage in heterogeneous quasi-brittle granular materials.
• To understand how microstructural topology and contact strength redundancies contribute to pre-failure robustness and eventual cascading failure.
• To identify predictive patterns in force transmission that explain the transition from suppressed to cascading failure.
• To develop a network-based approach that maps microscale contact properties to macroscale mechanical behavior.
• To enable rational design of mechanically robust particulate materials through microstructural optimization.

Proposed method

• The framework uses discrete element method (DEM) simulations of concrete specimens under uniaxial tension to generate microscale data on contact strengths and network topology.
• It constructs a complex flow network from contact strengths and connectivity, treating each contact as a link with a defined transmission capacity.
• Optimized flow routes are identified as the shortest paths that transmit the global transmission capacity, predicting tensile force chain formation.
• Force bottlenecks are detected as critical contacts that dominate force transmission and whose failure triggers macrocrack initiation.
• The model tracks the cooperative redistribution of forces among bottleneck contacts via redundant pathways, confining damage to low-capacity links.
• Robustness is quantified through the system's ability to maintain load-bearing capacity despite progressive damage, mediated by network redundancy.

Experimental results

Research questions

• RQ1 How do force transmission pathways evolve during progressive damage in a heterogeneous quasi-brittle granular material?
• RQ2 What role do network topology and contact strength redundancy play in enabling robustness before global failure?
• RQ3 Can force bottlenecks serve as early predictors of macrocrack location, pattern, and interaction?
• RQ4 How does the cooperative behavior among bottleneck contacts delay failure while simultaneously increasing interdependency?
• RQ5 What mechanisms lead to the transition from suppressed to cascading failure in the pre-failure regime?

Key findings

• Two novel transmission patterns—optimized flow routes and force bottlenecks—were identified that reliably predict tensile force chain formation and macrocrack initiation.
• The optimized flow routes correspond to the shortest possible paths that transmit the global transmission capacity, explaining the emergence of force chains.
• Force bottlenecks provide an early and accurate prediction of the ultimate failure pattern, location, and interaction of macrocracks.
• A two-pronged cooperative mechanism among bottlenecks, enabled by redundant transmission pathways, delays failure by spreading damage across low-capacity member contacts.
• This cooperation confines damage to weak links and preserves a web of strong contacts that support force chains, thereby enhancing pre-failure robustness.
• Despite this, the progressive interdependency among dominant bottleneck contacts eventually leads to a critical point where minor force increases trigger a cascading failure sequence.