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Table 2 List of friction experiments with ash. \(\phi _{\mathrm{b (Ramdom)}}\) and \(\phi _{\mathrm{b (Compacted)}}\) are the gas fractions in the ash before and after imposing a normal stress, respectively

From: Physical characteristics of scoriae and ash from 2014–2015 eruption of Aso Volcano, Japan

Temperature (\({^{\circ }}\hbox {C}\)) Sieve (\(\upmu \hbox {m}\)) Thickness (mm) \({\upphi }_{\mathrm{b(Random)}}\) \({\upphi }_{\mathrm{b(Compacted)}}\) \(\upsigma _{\mathrm{N}}\) (kPa) Results
950 <53 2.0 0.65 0.46 26 Sintered
950 53–1000 3.2 0.46 0.43 26 Partially sintered
950 <53 2.3 0.65 0.54 5.1 Sintered
700 \(<53\) 2.0 0.65 0.47 26 Powder
700 53–1000 3.0 0.46 0.40 26 Powder
500 <53 2.1 0.65 0.48 26 Powder
500 53–1000 2.8 0.46 0.37 26 Powder
500 <53 2.3 0.65 0.52 5.1 Powder
  1. The thickness is the final value of the measurement, and \(\sigma _{\mathrm{N}}\) is the desired normal stress to be imposed