A New Approach to Characterise the Impact of Rock Bridges in Stability Analysis

Locked segment-dominated landslides initiate when locked segments are sufficiently damaged to be unlocked. The evolution of such slopes toward instability displays either an exponentially or stepwise accelerated displacement pattern, but the underlying mechanisms of these patterns are elusive. We show that the displacement pattern is governed by mechanical synergy (resistance homogenization) between the ruptured locked segment and the transfixion segment. Using a mechanical model, we demonstrate that rapid and slow resistance homogenizations, which depend mainly on the brittleness of locked segments, cause two unlocking-induced startup mechanisms that lead to loss of slope stability: one occurring at the peak-stress points and the other at the residual-strength points of the locked segments. Accordingly, the evolution toward instability exhibits one of the two abovementioned patterns. External factors, such as rainwater, can deteriorate the strength of geomaterials but hardly alter the inherent mechanical rules that a locked segment adheres to. These findings provide insights into the mechanism of locked segment-dominated landslides and pave the way for reliably predicting their occurrence.

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“…In (b), points Q and S denote the suspension and resumption of displacement acceleration, respectively. 4 Geofluids…”

Section: Analysis and Resultsmentioning

confidence: 99%

“…Such a slope becomes unstable only when a locked segment becomes unlocked (fails). Rock bridges [3] are the most common locked segments in rock slopes [4][5][6]. An example is the Yanchihe slope in Hubei, China (E117.298 °, N31.208 °, Figure 1(a), [7]).…”

Section: Introductionmentioning

confidence: 99%

Rapid and Slow Unlocking-Induced Startup Mechanisms of Locked Segment-Dominated Landslides

Chen

Cui

et al. 2023

Geofluids

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“…The coalescence of cracks means the failure of rock bridge between them (Lee et al 2017;Aliha et al 2008), and thus the failure process of rock bridge reveals the coalescence mechanism of rock cracks. In the literature (Elmo et al 2021), rock bridges are generally defined as a portion of intact rock separating discontinuity surfaces. However, whether a portion of intact rock resists failure depends on the failure mechanisms of the rock mass, the discontinuity persistence and intact rock bridges are critical factors that influence the stability of rock engineering (Zack et al 2016;Fereshtenejad and Song, 2021), and the intact rock bridges can increase the cohesion and tensile strength of the incipient failure surface.…”

Section: Introductionmentioning

confidence: 99%

“…By using a 3D numerical model, Paronuzzi et al (2015) studied the contribution of shear strength of rock bridge in rock wedge failure and the range of cohesion when rock bridge was destroyed, and found that it depended on different friction angles of rock bridge. Based on digital image techniques, Elmo et al (2021) introduced a new rock mass quality indicator, the NCI-network connectivity index, which can characterize the influence of rock bridges in stability analysis. Romer and Ferentinou (2019) studied the effect of rock bridges on rock slope stability by incorporating nonpersistent joint networks in numerical models.…”

Section: Introductionmentioning

confidence: 99%

Theoretical study on fracture mechanism of rock bridge considering crack plastic propagation

Zhou¹,

Gao

Chen

2023

Preprint

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The research on the fracture mechanism of rock bridge is helpful to better understanding the failure process of rocks. In this paper, in order to study the influence of wing crack propagation on the stability of rock bridges, a new maximum plastic zone size fracture criterion is established according to the extension of plastic zone accompanied by crack propagation. Based on the new crack fracture criterion, a corresponding critical judgment condition is proposed considering the influence of multi-crack interaction on the wing crack propagation. Then, the fracture mechanism of rock bridges from the perspective of plastic zone extension was explored based on three different crack distribution models (cracks of equal length in parallel). It was found that the fracture mode of the rock bridge is deeply influenced by the dip angle of the rock bridge in the case where the rock bridge is of equal length to the pre-existing crack. The contact speed and contact mode of plastic zone varies for different dip angles of the rock bridge, but all the contact of plastic zone will eventually cause plastic yielding in the rock bridge zone. And then, the secondary cracks always start to propagate in the range of the plastic zone formed by the wing cracks, and eventually the rock bridge forms a macroscopic fracture damage due to the propagation of the secondary cracks.

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“…It is outstanding that, despite different techniques being introduced in the literature, a procedure for complete rock mass characterization has not yet been achieved [24,[42][43][44][45][46][47].…”

Section: Introductionmentioning

confidence: 99%

QDC-2D: A Semi-Automatic Tool for 2D Analysis of Discontinuities for Rock Mass Characterization

et al. 2021

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Quantitative characterization of discontinuities is fundamental to define the mechanical behavior of discontinuous rock masses. Several techniques for the semi-automatic and automatic extraction of discontinuities and their properties from raw or processed point clouds have been introduced in the literature to overcome the limits of conventional field surveys and improve data accuracy. However, most of these techniques do not allow characterizing flat or subvertical outcrops because planar surfaces are difficult to detect within point clouds in these circumstances, with the drawback of undersampling the data and providing inappropriate results. In this case, 2D analysis on the fracture traces are more appropriate. Nevertheless, to our knowledge, few methods to perform quantitative analyses on discontinuities from orthorectified photos are publicly available and do not provide a complete characterization. We implemented scanline and window sampling methods in a digital environment to characterize rock masses affected by discontinuities perpendicular to the bedding from trace maps, thus exploiting the potentiality of remote sensing techniques for subvertical and low-relief outcrops. The routine, named QDC-2D (Quantitative Discontinuity Characterization, 2D) was compiled in MATLAB by testing a synthetic dataset and a real case study, from which a high-resolution orthophoto was obtained by means of Structure from Motion technique. Starting from a trace map, the routine semi-automatically classifies the discontinuity sets and calculates their mean spacing, frequency, trace length, and persistence. The fracture network is characterized by means of trace length, intensity, and density estimators. The block volume and shape are also estimated by adding information on the third dimension. The results of the 2D analysis agree with the input used to produce the synthetic dataset and with the data collected in the field by means of conventional geostructural and geomechanical techniques, ensuring the procedure’s reliability. The outcomes of the analysis were implemented in a Discrete Fracture Network model to evaluate their applicability for geomechanical modeling.

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A New Approach to Characterise the Impact of Rock Bridges in Stability Analysis

Cited by 20 publications

References 21 publications

Rapid and Slow Unlocking-Induced Startup Mechanisms of Locked Segment-Dominated Landslides

Rapid and Slow Unlocking-Induced Startup Mechanisms of Locked Segment-Dominated Landslides

Theoretical study on fracture mechanism of rock bridge considering crack plastic propagation

QDC-2D: A Semi-Automatic Tool for 2D Analysis of Discontinuities for Rock Mass Characterization

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