CONSOLIDATION SETTLEMENT UNDER A PILE GROUP
Sometimes, a pile group may be embedded above a soft clay layer and transfer suffi cient load to it (soft clay) to cause consolidation settlement. To estimate the consolidation settlement, the full design load is assumed to act at a depth of 2/ 3 L and is then distributed in the ratio of 2:1 (vertical:horizontal). The increase in vertical stress at a depth z in the soft clay layer .
Assumed distribution of load for calculating settlement of a pile group.
where Qag is the allowable group load, Bg is the width of the group, Lg is the length of the group, and z is the depth from the load transfer point on the pile group to the location in the clay layer at which the increase in vertical stress is desired. The primary consolidation settlement is then calculated using the procedure.
PROCEDURE TO ESTIMATE SETTLEMENT OF SINGLE PILES AND GROUP PILES:
The procedure to estimate the settlement of single piles and group piles is:
1. Obtain the required parameters Qaf or Qag, Eso, and Ep.
2. Calculate the elastic settlement, res, for a single pile using.
3. Calculate the elastic shortening (rp) using Equation .
4. Calculate the total elastic settlement, ret 5 res 1 rp.
For group piles, skip procedure 4 and continue as follows:
5. Calculate Rs using an estimated value of F.
6. Calculate the group settlement from (re)g 5 Rsres 1 rp.
7. Calculate the consolidation settlement, rpc, if necessary.
8. Add the elastic and the consolidation settlement to obtain the total group settlement.
THE ESSENTIAL POINTS ARE:
1. Settlement of piles is determined using numerical analyses assuming the soil is an elastic material or empirical correlations.
2. The equations for pile settlement will give only an estimated settlement.