MSE Wall design - Matlab

Description:
    > The script was written to primarily for design of MSE walls.
    > The script calculates minimum length of geogrid required to resist loads from the pressure from 
    > (1) earth and (2) surcharge with groundwater (GW) level is low to not effect the MSE wall.

Assumption and Considerations:
    (1) groundwater (GW) level is very low - does not effect the MSE wall stability.
    (2) global stability is adequate.
    (3) the surcharge load is uniform surcharge; no point load or line load
    (4) geogrid is assumed to be extandable; hence, follows failure wedge defined by Rankine theory
        for internal stability check. 
    (5) all the geogrid length and vertical spacing is kept constant for simplicity.
    (6) pull-out resistance factor of geogrid is assumed to be 0.7*tan(effective friction angle of MSE fill)
    (7) inclination of wall and backfill is vertical and horizontal, respectively.
    (8) minimum width-to-height ratio (B/H) for MSE wall is 0.7