Thrust line criterion in embankment stability analysis

Abstract

A METHOD OF ANALYSING THE STABILITY OF EMBANKMENTS IS DESCRIBED WHICH ACCOUNTS FOR THE INTER-SLICE FORCES AND SATISFIES FORCE AND MOMENT EQUILIBRIUM CONDITIONS. THE METHOD IS APPLICABLE TO ANY SHAPE OF SLIP SURFACE WITH OR WITHOUT A TENSION CRACK. EXPRESSIONS ARE GIVEN FROM WHICH THE POSITIONS OF THE LINES OF THRUST FOR TOTAL AND EFFECTIVE STRESS CAN BE OBTAINED. SOLUTIONS ARE GIVEN TO TWO SERIES OF PROBLEMS. IN THE FIRST SERIES THERE IS NO TENSION CRACK BUT VARIOUS SHAPES ARE ASSUMED FOR THE SHAPE OF THE SLIP SURFACE AND DIFFERENT ASSUMPTIONS MADE REGARDING THE SLOPES OF THE INTER-SLICE FORCES. HOWEVER, NONE OF THESE SOLUTIONS LEADS TO A SATISFACTORY POSITION FOR THE LINE OF THRUST FOR EFFECTIVE STRESS. IN THE SECOND SERIES A TENSION CRACK WITH WATER PRESSURE ACTING IN IT IS ASSUMED PRESENT. IT IS SHOWN THAT A SATISFACTORY THRUST LINE IS OBTAINED WHEN THE DEPTH OF THE TENSION CRACK IS TAKEN TO BE THE DEPTH OF ZERO ACTIVE EFFECTIVE STRESS AND THE SLOPE OF THE INTER-SLICE FORCES IS CONSTANT, EXCEPT FOR A REDUCTION AT THE UPPER END OF THE SLIP SURFACE. THE INCLUSION OF THE TENSION CRACK WITH WATER PRESSURE ACTING IN IT DOES NOT AFFECT THE VALUE OF THE FACTOR OF SAFETY IN THIS PROBLEM. /TRRL/