Compression stage of CIUC and CIDC triaxial tests on saturated compacted As-Samra WWTP biosolid material: (a) deviatoric stress against axial strain; (b) excess pore water pressure against axial strain; (c) pore pressure coefficient A and volumetric strain against axial strain; (d) pore pressure coefficient A at failure; (e) p′–q′ traces; (f) inferred failure envelope