3.3.5 Effect of thickness to hard stratum（T）

The thickness of soft clay below the excavation level is seen to impose strong effect on the strut force.When the T／B ratio drops below 1，the restraining effect from the presence of hard stratum at shallow depth reduces the strut force.A maximum of 80% reduction is noted at the lowest strut level as the T／B ratio scales down from 1 to 0.25.Conversely，as the T／B ratio increases above 1，the effect of clay thickness becomes negligible.It is，therefore，postulated that，for a braced excavation with a T／B ratio more than 1，the layer of soil below a depth of 1B from the excavation level could be neglected from the strut force analysis.