What checks does the programme perform on the tie-rods?

The programme provides the factor of safety as the ratio between the resistance of the tendon (minimum of the three failure mechanisms: yielding of the reinforcement, bulb-soil displacement, reinforcement-mortar displacement) and its reaction, calculated according to the type chosen: active tendon, passive tendon.
A minimum length of the free section must also be defined, so that the tendons fulfil their static function of supporting the wall, the bulb should be completely outside the active thrust wedge. Assuming that the thrust wedge is bounded by a line inclined to the horizontal by 45+φ/2, this line should be shifted upwards by h/3 where h represents the excavation height. The minimum value of the free length is thus defined.