Effects of the Loading and Unloading Conditions on Crack Propagation in High Composite Slope of Deep Open‐Pit Mine

Chang, Zhiguo; Cai, Qingxiang; Zhou, Wei; Jiskani, Izhar Mithal; Wang, Rui

doi:10.1155/2019/3168481

Cited by 11 publications

(5 citation statements)

References 32 publications

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“…The uplift at the bottom of the foundation pit of the auxiliary tunnel was also controlled within 3 cm. This is consistent with the results of previous studies [28][29][30].…”

Section: Resultssupporting

confidence: 94%

Design, construction and analysis for super-wide, deep and large foundation pit

Shi

Tian

Zheng³

et al. 2021

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Both developing and developed countries are facing a series of difficulties and challenges in the process of urbanization. In recent years, in order to alleviate the problem of urban congestion, underground space has developed rapidly, and the excavation of foundation pit is the most important step in the development of underground space. This paper takes the foundation pit of the tunnel under construction in Suzhou as a research object. The design width of the foundation pit reaches 61.5 m and the depth reaches 18 m, so it belongs to the super wide and deep foundation pit. Numerical analysis is performed by finite element software to calculate the deformation of the foundation pit. The research shows that the main problem to be solved is the deformation of the foundation pit, and the deformation of side wall of foundation pit tunnel is the most obvious. The maximum deformation of the side wall of the main tunnel and the auxiliary tunnel reached the maximum at 15 m. The maximum deformation of the main tunnel is about 1.3 cm, and that of the auxiliary tunnel is about 0.9 cm. Through targeted design and construction, the mechanical performance of the foundation pit retaining structure is optimized, and the stability of the foundation pit is strengthened. The reasonable retaining structure can ensure the good construction quality. The design and construction of the project can provide reference for related engineering construction.

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“…The uplift at the bottom of the foundation pit of the auxiliary tunnel was also controlled within 3 cm. This is consistent with the results of previous studies [28][29][30].…”

Section: Resultssupporting

confidence: 94%

Design, construction and analysis for super-wide, deep and large foundation pit

Shi

Tian

Zheng³

et al. 2021

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show abstract

“…An abundance of experimental and theoretical research results has laid a solid foundation for the study of the unloading mechanical behavior of deep hard rock, providing a wealth of research data and experience (Chang et al, 2019;Yang et al, 2017;Li et al, 2014;Chen et al, 2020). However, most of the existing results indirectly study the degradation characteristics of rock mass strength through the weakening of macro-mechanical parameters.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Numerical simulation of true triaxial unilateral unloading effect of fractured rock

Zhang,

Fu,

Wang

2023

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PurposeThe interaction between rock mass structural planes and dynamic stress levels is important to determine the stability of rock mass structures in underground geotechnical engineering. In this work, the authors aim to focus on the degradation effects of fracture geometric parameters and unloading stress paths on rock mechanical properties.Design/methodology/approachA three-dimensional Particle Flow Code (PFC3D) was used for a systematic numerical simulation of the strength failure and cracking behavior of granite specimens containing prefabricated cracks under conventional triaxial compression and triaxial unilateral unloading. The authors demonstrated the unique mechanical response of prefabricated fractured rock under two conditions. The crack initiation, propagation, and coalescence process of pre-fissured specimens were analyzed in detail.FindingsThe authors show that the prefabricated cracks and unilateral unloading conditions not only deteriorate the mechanical strength but also have significant differences in failure modes. The degrading effect of cracks on model strength increases linearly with the decrease of the dip angle. Under the condition of true triaxial unilateral unloading, the deterioration effect of peak strength of rock is very significant, and unloading plays a role in promoting the instability failure of rock after peak, making the rock earlier instability failure. Associating with the particle vector diagram and crack coalescence process, the authors find that model failure mode under unilateral loading conditions is obviously distinct from that in triaxial loading. The peak strain in the unloading direction increases sharply, resulting in a new shear slip.Originality/valueThis study is expected to improve the understanding of the strength failure and cracking behavior of fractured rock under unilateral unloading.

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“…Chang et al (Wang et al, 2020b) studied the fracture behavior of slope rock under the unloading effect. Wang et al (Chang et al, 2019) analyzed the instability mechanism of slopes containing trailing edge cracks and provided a slope stability calculation method. Although the aforementioned studies focused on relatively homogeneous materials such as rock or concrete, they all lacked the analysis (theoretical, for example) of specific macrostructural characteristics of slope rock, which made it difficult to analyze the mechanism of crack initiation and propagation and coalescence of slope rock under unloading conditions.…”

Section: Introductionmentioning

confidence: 99%

Failure mechanism and stability analysis of an open-pit slope under excavation unloading conditions

et al. 2023

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Excavation unloading significantly contributes to rock slope failure in an open-pit mine. At present, there is no relevant theoretical study on the failure mechanism of the rock slope under excavation unloading. Therefore, in this study, based on the theory of fracture mechanics, the expression of the stress intensity factor at the crack tip on the rock mass at the vertical distance, h, from the slope top under excavation unloading is derived, the calculation method of the crack initiation angle is given, the expression of the ultimate safe height of the slope under unloading is obtained, and the ratio of the fracture toughness of the slope rock mass to the composite stress intensity factor at the crack tip on the rock mass is defined as the slope stability factor, which is verified by an engineering example. The results show that the crack initiation angle decreased when crack inclination was increased, and the crack initiation angle increased when the side-pressure coefficient, slope angle, and friction coefficient were increased. The ultimate safety height of the slope decreased first and then increased with the increase in the crack angle, and it was approximately linear with the crack length and inversely proportional with the slope angle. The stability coefficient calculated by this method is the same as that calculated by the limit equilibrium method and is small, which indicates the accuracy and rationality of this method. Results in this study can provide a theoretical basis for understanding and controlling the slope collapse disaster induced by excavation unloading.

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Effects of the Loading and Unloading Conditions on Crack Propagation in High Composite Slope of Deep Open‐Pit Mine

Cited by 11 publications

References 32 publications

Design, construction and analysis for super-wide, deep and large foundation pit

Design, construction and analysis for super-wide, deep and large foundation pit

Numerical simulation of true triaxial unilateral unloading effect of fractured rock

Failure mechanism and stability analysis of an open-pit slope under excavation unloading conditions

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