3.3.4 Effect of excavation width（B）

Varying excavation widths appear to have no significant effect on the strut force as long as the excavation width is about 3 times the excavation depth.A constant B／T ratio of 1 is maintained for these studies for the purpose of eliminating possible interference from the clay thickness effect.However，for a narrower excavation，more passive resistance below the excavation level is mobilized due to the interaction from both sides of the wall，which results in reduced strut forces，especially as the lower strut levels.It appears that，when the B／H ratio is below 1，the reference APD is able to compute strut forces satisfactorily.