Quantitative anisotropies of palaeopermeability in a strike-slip fault damage zone: Insights from micro-CT analysis and numerical simulations

Knowledge from historical earthquake events indicates that a submarine tunnel crossing active strike-slip faults is prone to be damaged in an earthquake. Previous studies have demonstrated that the flexible joints are an effective measure for a submarine tunnel crossing a strike-slip fault. The background project of this paper is the second submarine tunnel of Jiaozhou bay. In this work, model tests and numerical simulations are conducted to investigate the deformation and failure mechanism of a submarine tunnel with flexible joints under a strike-slip fault dislocation. The influence of strike-slip faults on a tunnel with flexible joints has been investigated by examining the deformation of rock mass surface, analyzing lining stains, and crack propagation from model tests. Numerical simulations are conducted to study the effects of the design parameters of a tunnel with flexible joints on the mechanical response of the lining. The results showed that the ‘articulated design’ measure can improve the ability of the tunnel to resist the strike-slip faults. In terms of the mechanism of design parameters of a tunnel with flexible joints, this paper finds that increasing the lining thickness, decreasing the lining segment length, and decreasing the tunnel diameter to a reasonable extent could effectively improve the performance of this faulting resistance measure for a tunnel under the strike-slip fault zone dislocation. Compared with the horseshoe tunnel cross-section, the circular tunnel cross-section can improve the ability of the faulting resistance of a tunnel with flexible joints, while the optimal angle of the tunnel crossing the fault zone is 90º. It is concluded that the wider fault zone, smaller flexible joint width, and less stiffness of the flexible joint could make lining safer under a strike-slip fault dislocation. The above research results can serve as a necessary theoretical reference and technical support for the design of reinforcement measures for a submarine tunnel with flexible joints under strike-slip fault dislocation.

Download Full-text

Fault zone architecture of a large plate-bounding strike-slip fault: a case study from the Alpine Fault, New Zealand

10.5194/se-2019-109 ◽

2019 ◽

Author(s):

Bernhard Schuck ◽

Anja M. Schleicher ◽

Christoph Janssen ◽

Virginia G. Toy ◽

Georg Dresen

Keyword(s):

Fault Zone ◽

Complex Geometry ◽

Damage Zone ◽

Strike Slip ◽

Strike Slip Fault ◽

Unconsolidated Sediments ◽

Multiple Slip ◽

Large Plate ◽

Alpine Fault ◽

Fault Zone Architecture

Abstract. New Zealand's Alpine Fault is a large, plate-bounding strike-slip fault, that ruptures in large (MW > 8) earthquakes. Its hazard potential is linked to its geometrical properties. We conducted field and laboratory analyses of fault rocks to elucidate their influence on its fault zone architecture. Results reveal that the Alpine Fault zone has a complex geometry, comprising an anastomosing network of multiple slip planes that have accommodated different amounts of displacement. Within it, slip zone width is demonstrably not related to lithological differences of quartzofeldspathic lithologies, which vary slightly along- strike. The young, largely unconsolidated sediments that constitute the footwall in some outcrops have a much more significant influence on fault gouge rheological properties and structure. Additionally, seismic investigations indicate that the exposed complex fault zone architecture extends into the basement. This study reveals the Alpine Fault contains multiple slip zones surrounded by a broader damage zone; properties elsewhere associated with carbonate or phyllosilicate-rich faults.

Download Full-text