Abstract
In practical geotechnical engineering, most of rock masses with multiple cracks exist in water environment. Under such circumstance, these adjacent cracks could interact with each other. Moreover, the seepage pressure, produced by the high water pressure, can change cracks’ status and have an impact on the stress state of fragile rocks. According to the theory of fracture mechanics, this paper discusses the law of crack initiation and the evolution law of stress intensity factor at the tip of a wing crack caused by compression-shear stress and seepage pressure. Subsequently, considering the interaction of the wing cracks and the additional stress caused by rock bridge damage, this paper proposes the intensity factor evolution equation under the combined action of compression-shear stress and seepage pressure. In addition, this paper analyzes the propagation of cracks under different seepage pressure which reveals that the existence of seepage pressure facilitates the wing crack’s growth. The result indicates that the high seepage pressure converts wing crack growth from stable form to unstable form. Meanwhile, based on the criterion and mechanism for crack initiation and propagation, this paper puts forward the mechanical model for different fracture transfixion failure modes of the crag bridge under the combined action of seepage pressure and compression-shear stress. At the last part, this paper, through investigating the flexibility tensor of the rock mass’s initial damage and its damage evolution in terms of jointed rock mass's damage mechanics, deduces the damage evolution equation for the rock mass with multiple cracks under the combined action of compression-shear stress and seepage pressure. The achievement of this investigation provides a reliable theoretical principle for quantitative research of the fractured rock mass failure under seepage pressure.
Highlights
In recent years, rock mechanics is supposed to consider the most striking feature of rock masses that their blocky structures are caused by the discontinuity surfaces such as joints, cracks, and faults
Based on previous studies and the rock fracture mechanics criterion, this paper proposes the mechanical model of the multicrack rock mass under the action of seepage pressure and investigates traits of gradual fracture and damage evolution of the multicrack rock under seepage pressure on the basis of exploring the law of the compression-shear crack initiation, branch crack growth, and rock bridge connection
The wing crack initiation from microcracks to the completely damage of the rock mass is a process of evolution and accumulation of the rock mass damage, as well as a process of the fracture of the connection between cracks [24]
Summary
Rock mechanics is supposed to consider the most striking feature of rock masses that their blocky structures are caused by the discontinuity surfaces such as joints, cracks, and faults. A vast number of scholars have made great effort in developing crack propagation theories [6,7,8] or developing techniques to calculate the stress intensity factors of crack tips [9,10,11,12], or studying the relationship between microdamage development and macrodeformation of rock under uniaxial compression [13,14,15]. The former studies mainly focus on mechanical mechanism of special single crack rather than the effect of seepage pressure. This paper applies the self-consistent theory to setting up the constitutive and damage evolution equation for the multicrack rock mass under seepage pressure
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