Evidence That Strain-Rate Softening Is Not Necessary for Material Instability Patterns

Tracking time with ricequakes in partially soaked brittle porous media

“…3 . Following our previous work ( 10 ), we found that the stiffness of puffed rice is linearly pressure-dependent with K 0 = κ p *, and thus …”

“…Under the pressure level p* at the start of the wetting part of the experiments, we find the initial position of the center of the carriages z i 0 ¼ ð1 À p*=K 0 Þl m  i. According to Valdes et al (10), for the order of the p* ≈ 50 kPa in our experiments, K 0 ≈ 15 MPa from shear wave measurements. This gives p* K 0 ≈3  10 À3 ¼ 1, and thus, the initial positions of the carriages can be calculated as z ðiÞ 0 ¼ l m  i.…”

“…According to Valdes et al . ( 10 ), for the order of the p * ≈ 50 kPa in our experiments, K 0 ≈ 15 MPa from shear wave measurements. This gives , and thus, the initial positions of the carriages can be calculated as .…”

“…3 (D and E), our model also successfully predicts the overall deformation over time, while revealing the two consolidation mechanisms of ricequake and creep compaction described above. To establish this comparison, we used the puffed rice constrained modulus K 0 = κ p * with κ = 470 previously established using P -wave propagation velocity measurements ( 10 ) with piezoelectric sensors. The remaining property was the critical fluid activity a cr = 0.96 that we determined as a free fitting parameter.…”

“…The substitution of subject materials by surrogate materials has been widely effective in science. Specifically, dry cornstarch, carbomer, and silicone have been used to demonstrate transient deformations in correspondingly brittle, semibrittle, and ductile crustal rocks ( 7 ), while cereal (puffed rice) has been used to reveal previously hidden propagating compaction patterns in dry porous media ( 8 – 10 ). Following these first observations with puffed rice, the compaction of dry snow also disclosed similar patterns ( 11 )—this is likely because rocks, dry snow, and cereals all share the properties of brittle porous media.…”