Anchor position is specified by head point, free length l, root length lk and by the slope α. The anchor force is input as the pre-stressing force acting in the anchor. The head point is always located on the ground surface; the anchor force always acts in the direction of a soil body. The anchor force when computing equilibrium on a given block (slice) is added to the weightless surcharge of the slope.
Two options are available to account for anchors:
- Compute anchor lengths - analysis assumes infinite lengths of anchors (anchors are always included in the analysis) and computes the required free lengths of anchors (distance between the anchor head and intersection of the anchor with the slip surface) subsequently. The anchor root is then placed behind the slip surface. This approach is used whenever we wish the anchor to be always active and thus contribute to the increase of the slope stability and we need to know its minimum distance.
- Analysis with specified lengths of anchors - the analysis takes into account only those anchors that have their endpoints of roots behind the slip surface. If the slip surface intersects the free length of the anchor, a calculation is carried out with full anchor force. When the slip surface intersects the anchor root, anchor force is reduced linearly, with full force at the root begin and zero value at the end of the root. This approach is used always whenever we wish to evaluate the current state of the slope with already existing anchors, since it may happen that some of the anchors may prove to be short to intersect the critical slip surface so that they do not contribute to the increase of slope stability.