Dilatancy plots under HSR. The plots are arranged according to initial confinement pressure $σ′3$ and initial void ratio $e0$⁠: (a) $σ′3$ = 98 kPa; e = 1·03; (b) $σ′3$ = 98 kPa; e = 0·93; (c) $σ′3$ = 350 kPa; $e$ = 1·03; (d) $σ′3$ = 350 kPa; $e$ = 0·93