Shear Characteristics and Failure Mode of Hard Brittle Marl with Parallel Discontinuous Structural Plane

  • PDF / 2,454,508 Bytes
  • 11 Pages / 595.276 x 790.866 pts Page_size
  • 11 Downloads / 245 Views

DOWNLOAD

REPORT


RESEARCH ARTICLE-CIVIL ENGINEERING

Shear Characteristics and Failure Mode of Hard Brittle Marl with Parallel Discontinuous Structural Plane Zhiming Yin1,2,3 · Xinrong Liu1,2,3 · Zhongping Yang1,2,3 · Yuanwen Jiang1,2,3 · Yalong Zhao1,2,3 · Shiqi Li1,2,3 Received: 12 February 2020 / Accepted: 25 May 2020 © King Fahd University of Petroleum & Minerals 2020

Abstract Engineering practice shows that the failure of rock bridges between structural planes which makes the discontinuous structural plane evolve into a continuous sliding fracture plane leads the instability of many slopes. In order to further understand the shear failure mechanism of rock mass with discontinuous structural plane, the direct shear tests under different normal pressures were carried out on the hard brittle limestone samples with different structural plane dip angles. The test results show that the fracture surface of rock bridge is mainly tensile failure, while both sides of the fracture surface are mainly shear failure. Both two flanks and the middle fracture surface show that both ends of the fracture surface are mainly shear failure, while the middle of the fracture surface is mainly tensile failure. When σ is large and α is small, the rock is mainly shear failure. When σ is large and α is large, or σ is small and α is small, the rock is mainly tension-shear mixed failure. When σ is small and α is large, the rock is mainly tensile failure. The failure mode of the sample may vary with the change of the structural plane inclination and normal stress. But overall speaking, it can be summarized as five typical failure modes that are STS–STS–STS, STS–T–STS, S–STS–S, S–S–S and T–T–T. The peak shear stress of the sample increases with the increase in normal stress, and decreases first and then increases with the increase in the dip angle of the structural plane. When α = 0°, the peak shear stress is the largest; when α = 45°, the peak shear stress is the smallest. When α is small, the shear strength of the sample is mainly affected by the inclination angle θ of the rock bridge. When α is large, the shear strength of the sample is mainly affected by the length L of the rock bridge. Keywords  Parallel discontinuous structural plane · Dip angle · Normal stress · Shear properties · Failure modes

1 Introduction A large number of discontinuous interface, such as fractures, faults and joints, exist in the rock mass of slope, which play an important role in the stability of slope [1–5]. In natural rocks, preexisting flaws usually appear in sets or groups

with similar orientations and characteristics [6, 7]. Engineering practice shows that the failure of rock bridges between structural planes, which makes the discontinuous structural plane evolve into a continuous sliding fracture plane, leads the instability of many slopes [8–13], such as the fracture of Aishihik river bank slope in Canada [10] (Fig. 1a), the

* Xinrong Liu [email protected]

1



School of Civil Engineering, Chongqing University, Chongqing 400045, China

* Zhongping Yang yang‑[email protected]