CSETTLEMENTYULVI ZAIKA

OUTCOMES OF STUDY• Introduce consolidation settlement

• Understand 3 conditions primary consolidation based on pre consolidation stress

• Calculation primary consolidation settlement

• Calculation secondary consolidation settlement

COMPRESION OF SOIL• If the clay layer of thickness H when subjected to an increase in average

effective overburden pressure from ´0 to ´1 ( ´0+´) there will be consolidation settlement of H.

• in field in laboratory Equating: then H

H: settlement

CALCULATION SETTLEMENT• There are two different methods to calculate settlement:

1. Using mv :

2. Using e – log diagram

SETTLEMENT COMPUTATIONcomputing e using e log v’ plot

• If the clay is normally consolidation, the entire loading path along virgin consolidated line (VCL) e0

e

e1

0’ 0’+

VCL

SETTLEMENT COMPUTATIONcomputing e using e log v’ plot

• If the clay is over consolidation and remain so by the end of consolidation

e0

ee1

0’ 0’+

VCL

SETTLEMENT COMPUTATIONcomputing e using e log v’ plot

• If the over consolidated clay become normal consolidation by the end of consolidation e0

e

e1

0’ 0’+

VCL

c

SECONDARY CONSOLIDATION SETTLEMENT

This is also called Secondary compression (Creep). “It is the change in volume of a fine grained soil due to rearrangement of soil particles (fabric) at constant effective stress”. The rate of secondary consolidation is very slow when compared with primary consolidation.

The secondary compression index:

Where e : change in void ratio

ep : void ratio at the end of primary consolidation

Ssc : Settlement of secondary consolidation

Flow chart for calculation primary consolidation settlement

Data: soil characteristic(,Cc,Cs,c,e0) soil layers load of upper structure

If clay layer is more than 2 m Divide layer in to some thick layers.Define the reference point for every layer

Calculate overburden pressure from soil surface to the reference points

Calculate applied load from foundation base ()To reference points

Calculte

If normal consolidation (NC)

If over consolidation (OC) If over consolidation (OC)

Summation settlement of every layers

𝑆𝑐=𝐶𝑐𝐻1+𝑒0

log𝜎 0′ +∆𝜎𝜎 0′