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Influences of Mechanical Contrast on Failure Characteristics of Layered Composite Rocks Under True-Triaxial Stresses
Abstract Layered composite rocks (LCRs) are often encountered in underground excavation in which extensive deformation, buckling and local collapse near the layer interface frequently occur. However, there is limited advance knowledge of the failure mechanisms of LCRs to interpret the field observations due to the relative scarcity of polyaxial compression testing. To that end, this study conducts the true-triaxial experiments with the acoustic emission (AE) monitoring on the LCR specimens, with the emphases being on the effects of mechanical contrast (MC) between the layers on the fracture behaviors under true-triaxial stresses. First, the strength of LCRs is controlled by the weaker layer. Second, at the unstable fracturing phase, high AE event rate is faithfully recorded but intermittently interrupted by macrofracturing in granite but not in sandstone. Third, main failure planes of LCRs appear sub-orthogonally to σ3 (minimum principal stress), taken the form of delamination fracture and exhibited the mode of σ3-transverse-symmetric fracturing. As the distance from the unloaded surface increases, the fracturing transitions from σ3-transverse-symmetric spalling to σ3-transverse-symmetric shearing. Depending on the MC, both the fracture propagation through the interface and the fracture containment within sandstone are registered. Moreover, the interface effect is numerically revealed through a 3D finite-element modeling. This study gets insights into the failure mechanisms of LCRs with a changing mechanical property in individual layers under true-triaxial stresses.
Highlights True-triaxial experiment investigations of layered composite rocks in a brittle-brittle sequence.Quantitative interpretations of acousto-mechanical properties and fracturing behaviors in layered composite rocks.The fracture propagation through the interface is registered, as well as the fracture containment within the sandstone.The delamination fracture along $ σ_{3} $-unloading direction dominates the feature of $ σ_{3} $-transverse-symmetric fracturing.The interface effect is revealed by a 3D finite-element modelling.
Influences of Mechanical Contrast on Failure Characteristics of Layered Composite Rocks Under True-Triaxial Stresses
Abstract Layered composite rocks (LCRs) are often encountered in underground excavation in which extensive deformation, buckling and local collapse near the layer interface frequently occur. However, there is limited advance knowledge of the failure mechanisms of LCRs to interpret the field observations due to the relative scarcity of polyaxial compression testing. To that end, this study conducts the true-triaxial experiments with the acoustic emission (AE) monitoring on the LCR specimens, with the emphases being on the effects of mechanical contrast (MC) between the layers on the fracture behaviors under true-triaxial stresses. First, the strength of LCRs is controlled by the weaker layer. Second, at the unstable fracturing phase, high AE event rate is faithfully recorded but intermittently interrupted by macrofracturing in granite but not in sandstone. Third, main failure planes of LCRs appear sub-orthogonally to σ3 (minimum principal stress), taken the form of delamination fracture and exhibited the mode of σ3-transverse-symmetric fracturing. As the distance from the unloaded surface increases, the fracturing transitions from σ3-transverse-symmetric spalling to σ3-transverse-symmetric shearing. Depending on the MC, both the fracture propagation through the interface and the fracture containment within sandstone are registered. Moreover, the interface effect is numerically revealed through a 3D finite-element modeling. This study gets insights into the failure mechanisms of LCRs with a changing mechanical property in individual layers under true-triaxial stresses.
Highlights True-triaxial experiment investigations of layered composite rocks in a brittle-brittle sequence.Quantitative interpretations of acousto-mechanical properties and fracturing behaviors in layered composite rocks.The fracture propagation through the interface is registered, as well as the fracture containment within the sandstone.The delamination fracture along $ σ_{3} $-unloading direction dominates the feature of $ σ_{3} $-transverse-symmetric fracturing.The interface effect is revealed by a 3D finite-element modelling.
Influences of Mechanical Contrast on Failure Characteristics of Layered Composite Rocks Under True-Triaxial Stresses
Zhang, Ting (author) / Chen, Quan-Zhen (author) / Zhang, Jian-Zhi (author) / Zhou, Xiao-Ping (author)
2023
Article (Journal)
Electronic Resource
English
BKL:
38.58
Geomechanik
/
56.20
Ingenieurgeologie, Bodenmechanik
/
38.58$jGeomechanik
/
56.20$jIngenieurgeologie$jBodenmechanik
RVK:
ELIB41
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