Experimental Investigation of Spalling Failure of D-Shaped Tunnel Under Three-Dimensional High-Stress Conditions in Hard
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ORIGINAL PAPER
Experimental Investigation of Spalling Failure of D‑Shaped Tunnel Under Three‑Dimensional High‑Stress Conditions in Hard Rock Xuefeng Si1 · Linqi Huang1 · Xibing Li1 · Chunde Ma1 · Fengqiang Gong1,2 Received: 9 January 2020 / Accepted: 14 October 2020 © Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract The D-shaped cross section is a commonly used tunnel cross section in underground engineering. To simulate the failure process of a D-shaped hole under deep three-dimensional (3D) high-stress conditions, true-triaxial tests were conducted on cubic granite specimens with a through D-shaped hole, and the failure process of the hole sidewall was recorded in real time. Results show that the spalling failure process of the D-shaped hole sidewall can be divided into four periods: calm, fine particle ejection, crack generation and propagation, and rock slab gradually buckling and spalling. Afterwards, symmetrical V-shaped notches were formed on both sidewalls between the corner and arch springing. The spalling failure shows tensile failure characteristics. Under high vertical stress and constant horizontal axial stress, increasing the lateral stress reduces the severity of the spalling failure and the depth of the V-shaped notch. The initial failure vertical stress of the D-shaped hole sidewall is higher than that of circular hole sidewall, and the failure of D-shaped hole sidewall is mainly characterized by static failure. The failure of the circular hole sidewall is a more severe dynamic failure. When the vertical applied stress is the maximum principal stress, the position of the V-shaped notch tip is 0.20–0.25 h (h is the height of the D-shaped tunnel) from the tunnel floor, whereas that in the circular tunnel is 0.5 d (d is the diameter of the circular tunnel) from the tunnel floor. Specific support schemes should therefore be designed for tunnels with different cross sections according to the damage location, depth of failure zone, and severity of failure. Keywords Deep D-shaped tunnel · Spalling failure · True-triaxial test · Three-dimensional high-stress · V-shaped notch List of Symbols d Diameter of the circular tunnel h Height of the D-shaped tunnel Greek Symbols 𝜎h max , 𝜎h min Maximum horizontal geostress and minimum horizontal geostress 𝜎v Vertical geostress 𝜎X , 𝜎Y , 𝜎Z Horizontal axial stress, lateral stress, and vertical stress Abbreviations 3D Three-dimensional CT Computed tomography ISRM International Society for Rock Mechanics * Linqi Huang [email protected] 1
School of Resources and Safety Engineering, Central South University, Changsha 410083, Hunan, China
School of Civil Engineering, Southeast University, Nanjing 211189, China
2
1 Introduction Many types of tunnel cross section shapes are used in underground engineering. The D-shaped cross section is one of the commonly used tunnel cross sections. Under the action of deep high-stress, spalling failure often occurs in tunnel surrounding rock (Dowding and Andersson 1986; Ortlepp and Stacey 1994;
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