Conversion Timing of Tunnel Excavation Methods in Upper-Soft and Lower-Hard Stratum Based on Displacement Direction Angle Theory: Case Study

Wang, Wei; Hu, Maorong; Zhang, Hengwen; Zhang, Xuemin

doi:10.1061/(asce)gm.1943-5622.0001380

Cited by 7 publications

(7 citation statements)

References 7 publications

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“…When underground engineering is conducted in composite strata, improper construction may cause engineering disasters, such as uneven stress causing the surrounding rocks to collapse, along with other potential risks (Wu et al, 2019). Studies on composite strata have primarily focused on tunnel construction (Rad and AYassaghi, 2004;Tang and Xu, 2016;Yang et al, 2018;Wang et al, 2019) and coal mining (Liu et al, 2015;Zhang et al, 2018). In addition, rock masses with different physical characteristics in composite rock strata have different strengths, permeabilities, and other mechanical properties.…”

Section: Introductionmentioning

confidence: 99%

Mechanical properties and failure law of composite rock containing two coplanar fractures

Yuan

Xiao²,

She³

et al. 2023

Front. Earth Sci.

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Composite rocks comprise the rock structures that are commonly used in geotechnical engineering. The fracture configuration has a substantial influence on the mechanical behavior, failure mode, and crack propagation of composite rocks. In this study, we considered a composite rock with two prefabricated coplanar fractures. Through laboratory uniaxial compression tests and using a digital image acquisition system, we systematically studied the effects of different fracture lengths and inclination angles on the mechanical properties and failure characteristics of the rocks. We obtained the following results: 1) during the loading deformation of the rock sample, the peak stress and elastic modulus increased with an increase in the fracture inclination angle and decreased with an increase in the fracture length. The deterioration coefficient k (the ratio of the difference between the peak strength of intact and fractured rock sample to that of intact rock sample) decreased with an increase in the fracture inclination angle and increased with an increase in the fracture length. 2) The failure type of the rock samples was primarily controlled by the fracture inclination angle and material of the two rock types, and the fragmentation degree was primarily controlled by the fracture length. With an increase in the fracture inclination angle, the failure mode of rock sample exhibited the following order of changes leading to failure: a double-Y type (trwo wing and one antiwing cracks appeared on each prefabricated fracture) → double-Z type (two wing cracks appeared on each prefabricated fracture) → Z type (one wing crack appeared on each prefabricated fracture). 3) The type of coalescence of the rock bridge was controlled by the fracture inclination angle and structural plane. The crack positions were primarily affected by the fracture length. 4) At a low fracture inclination angle (α ≤ 30°), the propagation of the microcracks showed aggregated band formation. Above moderate fracture inclination angles (α > 30°), the microcrack aggregation band gradually weakened and expanded in the direction of dispersion.

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Section: Introductionmentioning

confidence: 99%

Mechanical properties and failure law of composite rock containing two coplanar fractures

Yuan

Xiao²,

She³

et al. 2023

Front. Earth Sci.

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“…The construction progress is fast, and it can be adopted for large-scale mechanized operation. The central diaphragm (CD) method, cross diaphragm (CRD) method, and other methods can be adopted in the case of weak surrounding rock mass (Wang et al, 2019;Chen et al, 2020). When introducing the CD or CRD method, one side of a tunnel is excavated first, then a diaphragm is constructed, and finally, the other side is excavated.…”

Section: Introductionmentioning

confidence: 99%

Research on the Stability of Shallow-Buried Large Cross-Section Tunnel by Construction Method Conversion

Zhang¹,

Zhao

Peng³

et al. 2022

Front. Earth Sci.

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The blind and random use of the combined construction method may have a great impact on tunnel stability. To determine the influence of construction method conversion on tunnel deformation and the reasonable conversion condition, a numerical model is established to simulate the construction method transforms from central diaphragm method to the benching tunneling method based on Jiaoweiqin Tunnel. The conversion condition is determined based on the results of tunnel geological prediction and in-site monitoring, and the temporary two-bench tunneling method is adopted to ensure the success of construction method conversion. Besides, the parameter analysis is done to analyze the influence of mechanical properties of surrounding rock mass and bench length on tunnel stability. Research results indicate that the construction safety should be evaluated before construction method conversion is carried out by analyzing the design blueprint, tunnel geological prediction results, geological survey reports, rock mass conditions in front of tunnel face, in-site monitoring data, and numerical simulation results. Meanwhile, the construction method conversion can be carried out in the order of central diaphragm method, two-bench tunneling method, and bench tunneling method. Parameter analysis results reveal that the deformation of primary support decreases in a negative exponential form with the increase in elasticity modulus and increases approximately linearly with the increase in bench length. For shallow buried and large cross-section tunnels, the tunnel deformation is in a small state when the elastic modulus of rock mass reaches a certain value. The construction method conversion can be carried out when the rock mass has a certain stability, and the length of construction method conversion should be small to ensure construction safety.

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“…Zhang et al [10] discussed and expounded upon the issues of the surrounding rock self-stability of the metro tunnel in the soil-rock dualistic stratum from the three aspects of the stress, the displacement, and the safety factor. Wang et al [11] studied the conversion timing of tunnel excavation method in upper soft and lower hard strata based on displacement direction angle theory under different working conditions. e catastrophe theory was put forward by om, a French scholar, in the 1970s [12] and was then expanded into a perfect system by Trotman and Zeeman [13], Zeeman et al [14], and Poston and Stewart [15].…”

Section: Introductionmentioning

confidence: 99%

Distribution Features of the Minimum Rock Cover Thickness of the Surrounding Rock Self‐Stability of the Metro Tunnel in the Soil‐Rock Dualistic Stratum

Zhang

Cao

et al. 2020

Advances in Civil Engineering

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Based on the maximum value of the self-stability of surrounding rock, the key issues affecting the distribution of the minimum mock cover thickness of the surrounding rock self-stability (MRCT-SRS) of the metro tunnel in the soil-rock dualistic stratum are discussed. The MRCT-SRS was studied for different soft stratum thicknesses Hs and excavation spans D based on cusp catastrophe theory. Moreover, the 3D spatial distribution was determined, and the fitted curves were constructed according to the MRCT-SRS, Hs, and D. This facilitated the assessment of the stability of the surrounding rock in the excavation of a metro tunnel. Combined with the construction practices used for the Qingdao metro project, the validity of the obtained MRCT-SRS has been verified by the inverse analysis of the monitored data from the metro tunnel. Furthermore, the application of the MRCT-SRS in determining the reasonable buried depth of a metro line has been explored. The research results have provided theoretical support and scientific basis for the preparation, revision, and improvement of the relevant codes, standards, and guidelines for metro tunnel planning and design.

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Conversion Timing of Tunnel Excavation Methods in Upper-Soft and Lower-Hard Stratum Based on Displacement Direction Angle Theory: Case Study

Cited by 7 publications

References 7 publications

Mechanical properties and failure law of composite rock containing two coplanar fractures

Mechanical properties and failure law of composite rock containing two coplanar fractures

Research on the Stability of Shallow-Buried Large Cross-Section Tunnel by Construction Method Conversion

Distribution Features of the Minimum Rock Cover Thickness of the Surrounding Rock Self‐Stability of the Metro Tunnel in the Soil‐Rock Dualistic Stratum

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