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Appendix CEffect of slip on bending experimentIn this appendix we analyze the effect of slip on the measured load W in a three-pointbeam bending experiment. The effect of slip is modeled in the form of a time-dependentdeflection term, i.e. ∆ = ∆(t). The strain ε z is directly proportional to the deflection,therefore ε z = ε z (t). In the following we consider a rectangular elastic plate (as wasdescribed in the Section 7.2). The plate is saturated with a Newtonian fluid. The constitutiveequations are [131]ε x = 1 E p[σ x − ν p (σ y + σ z )] −ε y = 1 E p[σ y − ν p (σ x + σ z )] −ˆb3K pP,ˆb3K pP,(C.1)(C.2)ε z = 1 E p[σ z − ν p (σ x + σ y )] −ˆb3K pP,(C.3)where σ is the pore stress, P is the stress in the fluid, which is equal to the pressure butopposite in sign, and ˆb is the Biot coefficient defined byˆb = 1 −K pK S.(C.4)After the beam is bent the pressure in the pore fluid is dissipated due to flow of the fluidwithin the pores. The continuity equation is given by [131]∂P∂θ = ∂2 P∂v 2 + κ∂2 P∂w + E pˆb2 3µ∂ε z∂θ ,(C.5)where µ readsµ = (1 − ρ)K pK L+ (ρ − K p/K S )K p+ 2(1 + ν (p)1 − K ) 2p.K S 3 K S(C.6)The solution of Eq. C.5 with the usual boundary conditions (P = 0 at the boundary) isgiven by [131]P (v, w, θ) = 8E ∫θpˆbazµL 30Ω A (θ − θ ′ )Ω B [κ(θ − θ ′ )] d∆dθ ′ dθ′ ,(C.7)149