Antikrak og lavineudløsning

Abstrakt

antikrack er en form for skråningsfejl karakteriseret ved kernedannelse og udbredelse af forskydningsbelastede, mixed-mode frakturer, der delaminerer det svage lag over et bredt område. Den resulterende ikke-lineære kollapsbølge kan føre til lavinefare og udløsning. I denne artikel beregner vi tilstanden af ​​stressforstyrrelse genereret af en simpel, model antikrack. Vi viser, at den genererer en forskydningsbølge med en amplitude, der afhænger af styrken af ​​det svage lag og kan fortolkes i form af en Griffith-spændingskoncentrator. Denne stresskoncentration producerer en-echelon-brud, svarende til dem, der er observeret i marken. Vi viser, at disse en-echelon-frakturer bidrager til den store deformation af kollapsbølgen og den deraf følgende stigning i lavinekinetisk energi.

In models in which brittle fracture is assumed, a crack is characterised by a single size parameter, the radius or half-length of the crack, and a unique characteristic mechanical energy, called the crack energy V(r). In addition to the stress applied to the crack, this energy is also dependent on cohesion, geometry, applied strain and any material defects (f.eks. pores).

In a continuum description of the stress field in the weak layer the mechanical energy of an antikrack can be divided into a contribution proportional to t2 and a portion that is proportional to s2. We use a two-dimensional BEM code to calculate the state of stress induced by a model antikrack CB, and compare it with the normal stresses obtained with the Eshelby approach. Near the antikrack tip the antikrack solution is very close to the Eshelby solution, but for any distance beyond this point the mismatch drops to less than 1%.