Fracturing behaviour of sandstone specimens with a cavity formed by intersecting excavations under compression: Experimental study and numerical modelling

Wu, Hao; Zhao, Guoyan; Kulatilake, Pinnaduwa H.S.W.; Liang, Weizhang; Wang, Enjie

doi:10.1111/str.12316

Cited by 14 publications

(11 citation statements)

References 36 publications

(24 reference statements)

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“…The excavation damaged zone (EDZ) is affected by multiple factors, such as unloading rate, rock lithology, tunnel shape, and in situ stresses . It is widely confirmed that tunnel shape plays an important role in affecting the failure intensity and destruction area of tunnels at great depth . This is primarily because the stress concentration, displacement, and deformation distribution are strongly related to the tunnel structure (straight line or curve) and cross‐sectional area.…”

Section: Introductionmentioning

confidence: 99%

Analysis of fractures of a hard rock specimen via unloading of central hole with different sectional shapes

Fan

Chen

et al. 2019

Energy Science & Engineering

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Hard rock failure and rockburst hazards under high in situ stresses have been the subject of deep rock mechanics and engineering. Previous investigations employed cubic rock specimens with a central hole for simulation of rock fracturing around deep tunnels at a laboratory scale, while the failure characteristics and crack evolution behavior around different shapes of holes induced by excavation unloading response have been barely considered. A commercially combined finite‐discrete element method (combined FEM/DEM) was used to investigate the failure characteristics and crack propagation process of typical hard rock specimens (marble) via the unloading of central hole with different shapes. Rock heterogeneity was also considered in the model in combination with the engineering reality. The combined FEM/DEM approach was first validated by simulating uniaxial compression and Brazilian tests. Then, the parametrical analysis was conducted in detail on the basis of five different sectional shapes of central holes, including a circle, ellipse, U‐shape, trapezoid, and cube, and two lateral pressure coefficients. Analysis of crack propagation paths, released strain energy, displacement, and average velocity distribution of the monitoring points around the central hole suggests that the failure degree and destruction intensity are strongly related to the sectional shape and lateral pressure coefficients. Hard and brittle rock failure induced by the excavation unloading effect can be classified as stable failure (slabbing failure) and unstable failure (strain rockburst). The cubic, trapezoidal, and U‐shaped holes within the specimen are the most likely to induce unstable failure, while stable failure is the dominant failure pattern around circular and elliptical holes. The lateral pressure coefficient λ was also found to affect failure position and intensity (only for the axisymmetric section) around the central hole. The influence of rock heterogeneity on failure intensity and range around the central hole within the specimen was also discussed. This study emphasizes the importance and necessity of the excavation unloading effect when evaluating surrounding rock failure around deep tunnels.

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Section: Introductionmentioning

confidence: 99%

Analysis of fractures of a hard rock specimen via unloading of central hole with different sectional shapes

Fan

Chen

et al. 2019

Energy Science & Engineering

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“…e excavation depth for metal mines worldwide has reached −1000 m to −2000 m, and the maximum mining depth is over −4000 m [1]. e in-situ stress for deep mines is normally high, which results in more and more mining/ excavation-induced hazards, including rockburst, roof collapses, and shaft failure.…”

Section: Introductionmentioning

confidence: 99%

Improving the Stability of Subsurface Structures in Deep Metal Mines by Stress and Energy Adjustment: A Case Study

Liu

Tan

et al. 2021

Advances in Civil Engineering

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In deep hard-rock mines, the failure of subsurface structures (e.g., tunnels, stopes, and shafts) has been a significant problem affecting mining safety due to the high-stress environment. In this paper, the mechanism of structural failure and instability is discussed, and optimized excavation methods are proposed for stress control in deep gold mines. Based on the field observation and investigation of the joints distribution and rock failure modes at 800–1200 m depth of several large gold mines and a typical ultradeep borehole (2017 m depth) in northwest Jiaodong Peninsula, three engineering methods for reducing stress, including the stress transferring by mining optimizations, pressure relief by boreholes, and energy release in advance by optimizations of excavation and support, are analyzed by numerical simulation and field monitoring. Results show that stress reduction by excavation alone is limited and the backfill mining method is more conducive to stress transfer than the opening stope method. Roof contacted backfill can produce an unloading zone around the stope and reduce the stress of the surrounding stope. Relief boreholes can reduce the stress concentration of stopes, but the effect of cutting seams generated by presplitting blasting on pressure relief is not significant. The technology “short excavation and short support” releases less energy. By increasing the bench height and the reasonable timing of support by calculating, the elastic strain energy of rock in the shaft is prereleased, which benefits the long-term stability of the shaft.

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“…Basic modes of crack extension are sketched in Figure 1. In the rock mechanics and the fracture mechanics literature, a large number of studies have been devoted to the study of initiation, propagation and coalescence of cracks in rocks and brittle materials under different loading conditions (Gehle and Kutter 2003;Kulatilake et al 2001;Le et al 2018;Lee and Jeon 2011;Lee and Ravichandran 2003;Manouchehrian et al 2014;Park and Bobet 2010;Wang et al 2011;Wong and Einstein 2009;Wong and Chau 1998;Wu et al 2019c;Yang et al 2013;Zhang et al 2009;Zhuang et al 2014). These studies revealed many fracturing characteristics of rocks and led to the improvement of safety in rock structures.…”

Section: Introductionmentioning

confidence: 99%

Failure Mechanism of Rock Specimens with a Notched Hole Under Compression - A Numerical Study

Manouchehrian

Kulatilake

2021

Preprint

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Discontinuities are natural structures that exist in rocks and can affect the stability of rock structures. In this article, the influence of notch presence on the failure evolution around a hole in compressed rock specimens is investigated numerically. Firstly, the uniaxial compressive test on a rock specimen with a circular hole is modeled and the failure evolution in the specimen is simulated. In a separate model, notches are created at the surface of the hole. Results show that when the notches are created in the model, failure zone around the hole is transferred to a distance away from the surface of the hole. In addition, a parametric study is carried out to investigate the influence of the notch length and the confining pressure on the fracturing behavior of the specimen. Numerical results presented in this article indicate that the presence of notches at the surface of the hole and their dimensions can affect the fracturing mechanism of the specimen. In some cases, the failure at the boundary of the hole is prevented when the notches of certain dimensions are added to the hole. The insights gained from this numerical study may be helpful to control the failure around underground excavations.

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Fracturing behaviour of sandstone specimens with a cavity formed by intersecting excavations under compression: Experimental study and numerical modelling

Cited by 14 publications

References 36 publications

Analysis of fractures of a hard rock specimen via unloading of central hole with different sectional shapes

Analysis of fractures of a hard rock specimen via unloading of central hole with different sectional shapes

Improving the Stability of Subsurface Structures in Deep Metal Mines by Stress and Energy Adjustment: A Case Study

Failure Mechanism of Rock Specimens with a Notched Hole Under Compression - A Numerical Study

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