[
    {
        "id": "thesis:18555",
        "collection": "thesis",
        "collection_id": "18555",
        "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05122026-171140300",
        "type": "thesis",
        "title": "Multiscale Response of Granular Materials under Cyclic Shear: Packing State, Force Chains, and Stress Transmission",
        "author": [
            {
                "family_name": "Toledo Barrios",
                "given_name": "Patricia Amanda",
                "orcid": "0009-0000-2018-7616",
                "clpid": "Toledo-Barrios-Patricia-Amanda"
            }
        ],
        "thesis_advisor": [
            {
                "family_name": "Ravichandran",
                "given_name": "Guruswami",
                "orcid": "0000-0002-2912-0001",
                "clpid": "Ravichandran-G"
            }
        ],
        "thesis_committee": [
            {
                "family_name": "Shaikeea",
                "given_name": "Angkur",
                "orcid": "0000-0002-6706-0492",
                "clpid": "Shaikeea-Angkur-J"
            },
            {
                "family_name": "Andrade",
                "given_name": "Jose E.",
                "orcid": "0000-0003-3741-0364",
                "clpid": "Andrade-J-E"
            },
            {
                "family_name": "Bhattacharya",
                "given_name": "Kaushik",
                "orcid": "0000-0003-2908-5469",
                "clpid": "Bhattacharya-K"
            },
            {
                "family_name": "Ravichandran",
                "given_name": "Guruswami",
                "orcid": "0000-0002-2912-0001",
                "clpid": "Ravichandran-G"
            }
        ],
        "local_group": [
            {
                "literal": "div_eng"
            }
        ],
        "abstract": "<p>Granular materials are widely encountered in natural and engineered systems, yet their behavior under cyclic loading remains difficult to predict because bulk response emerges from complex grain-scale interactions. Repeated loading can produce irreversible deformation, history dependence, and evolving internal load-transfer mechanisms that are not fully captured by macroscopic measurements alone. Although cyclic behavior has been studied extensively at the continuum scale, direct experimental characterization of the grain-scale processes governing cyclic response remains limited.</p>\r\n\r\n<p>This thesis investigates the multiscale behavior of dry, cohesionless granular materials subjected to quasi-static cyclic simple shear loading through laboratory experiments coupled with the Granular Element Method (GEM), a mechanics-based force-inference framework for estimating interparticle contact forces from experimentally measurable grain-scale data. An experimental framework was developed by upgrading an existing simple shear apparatus to enable controlled cyclic loading and by integrating imaging, tracking, and post-processing methods for multiscale measurements.</p>\r\n\r\n<p>At the macroscale, the experiments show that cyclic simple shear produces direction-dependent and history-dependent behavior. Repeated loading generates asymmetric stress and deformation responses, incomplete recovery of the initial state, and progressive changes that depend on packing condition and confinement level. Densely packed and loosely packed assemblies exhibit qualitatively different cyclic responses, while normal confinement primarily influences the strength and persistence of those responses.</p>\r\n\r\n<p>At the grain-scale, the results show that cyclic behavior is governed largely by the reorganization of the internal force network rather than by large changes in overall contact connectivity. Force chains evolve continuously with loading direction and cycle history, while anisotropy plays a central role in linking internal structure to bulk shear resistance. Dense systems initially develop stronger, more coherent load-bearing structures that weaken with repeated cycling, whereas loose systems deform via more distributed force transmission and progressive compaction.</p>\r\n\r\n<p>Overall, this work provides a mechanistic framework for understanding how granular materials accumulate history, weaken, and reorganize under repeated shear. The combined experimental and GEM results also provide benchmark data to calibrate and validate physics-based particle models for broader granular systems and relevant engineering applications.</p>",
        "doi": "10.7907/eydy-1z48",
        "publication_date": "2026",
        "thesis_type": "phd",
        "thesis_year": "2026"
    }
]