Failure condition of the soil threads. (a) Specimen A at PL (d = 3 mm; F = 0·5; w = 578%); (b) specimen B at ‘PL’ (d = 6 mm; F = 0·5; w = 85%); (c) specimen C at ‘PL’ (d = 10 mm; F = 0·5; w = 597%); (d) specimen D (d = 16 mm; F = 0·2; w = 628%); (e) specimen E at ‘PL’ (d = 18 mm; F = 0·1; w = 616%). Note: d, thread diameter at crumbling condition; F, reduction in diameter achieved at failure of the thread, expressed as a fraction of its starting diameter; w, water content