Terzaghi assumption

1. 1. Why did Barden think that Terzaghi theory was over simplified?
=> Barden thought that Terzaghi theory was over simplified as Terzaghi’s assumption of soil
was it behaves as a linear elastic material but in nature soil doesnot behave elastically all the
time.So the main rheological model of soil skeleton proposed by Terzaghi was for very ideal
soil having elastic nature only. Furthermore Terzaghi couldnot explain about secondary
deformation caused by dissipation of pore water pressure , And thus Barden claimed his theory
was over simplified.
2. What parameters described by Terzaghi are in discrepancies with Barden Major
consideration?
=>The main parameters described by Terzaghi are in discrepancies with Barden major
consideration are as follows;
a) The value of c:
The value of c, deduced by one of the accepted methods from a compression time plot is used to
predict the rate of dissipation of the mid-plane pore pressure, the measured dissipation rate is
often found to be greater, particularly in the early stages of the test, Taylor (1942).
b)Not consideration of Secondary deformation or creep:
When the pore pressure has dissipated to zero the settlement does not cease, but is generally
followed by a secondary or creep deformation under constant effective stress, which has
presumably been developing since the start of the test.
c)Not consideration of Thickness and Pressure increment ratio:
The relative amount of secondary is greatly increased as the pressure increment ratio is
decreased, and also as the thickness of the sample is decreased.
Briefly the main discrepancies are (i) the validity of Darcy’s law, (ii) constant permeability and
compressibility over a given pressure increment, and (iii) a void ratio effective stress relationship
independent of time (no creep).
3. What are the similarities between Terzaghi and Taylor hypothesis and what is the main
difference?
=>The similarities and difference are
Both considered secondary compression to be caused by the remoulding or disturbance of the
structure induced by primary compression
Terzaghi considered soil as linear elastic model whereas Taylor considered to be viscoelastic
model.

2. In Taylor’s hypothesis the film bond of Terzaghi is replaced by a “plastic structural resistance to
compression” which is a function of the rate of shear strain.
Terzaghi in his general hypothesis describes qualitatively the complete continuous process of
primary and secondary consolidation whereas By Taylor in his Theory B, treats only primary
consolidation
Jyoti Khatiwada
Roll no. 10