Soil mechanics question answers
- 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