VARIATION OF DAMPING RATIO AND SHEAR MODULUS WITH PLASICITY INDEX CONFINING PRESSURE
Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
project report tiger
Active In SP
**

Posts: 1,062
Joined: Feb 2010
#1
08-02-2010, 08:29 AM



.ppt   VARIATION OF DAMPING RATIO AND SHEAR MODULUS WITH PLASICITY INDEX AND CONFINING PRESSURE.ppt (Size: 508 KB / Downloads: 157)
VARIATION OF DAMPING RATIO AND SHEAR MODULUS WITH PLASICITY INDEX AND CONFINING PRESSURE

INTRODUCTION

Behaviour of soil under cyclic loading is non-linear

Non-linear behaviour commonly characterised by:

Damping coefficient, D

Shear modulus, G


DEFINITION

Damping coefficient
Is defined as the measure of energy dissipation
Shear modulus
Is the ratio of shear stress to shear strain
Plasticity index
Is the difference between liquid limit and plastic
limit
Confining pressure
Is the pressure applied around the surface of a body


EFFECT OF CYCLIC STRAIN ON DYNAMIC PROPERTIES

Shear modulus decreases with increase in shear strain.

Damping increases with increase in shear strain.


HISTORY OF STUDIES

1974 “ Hardin
Studied the effect of confining pressure on dynamic
properties. Found out relations relating shear modulus
reduction to confining pressure and plasticity index.
1993 “Laird
Carried out resonant column tests. Found that increase in confining pressure decreases the shear modulus. Also found that confining pressure affects damping ratio.
2008-Cabalar & Cevik
Found out variation of dynamic properties with
plasticity index and confining pressure.



EXPERIMENTAL STUDY

THEORY
Soil samples with different PI values are collected.
Specimens of required dimensions are prepared and
placed in the apparatus.
Specimens are initially subjected to isotropic
consolidation.
Samples are then loaded harmonically by applying
sinusoidal excitation at one end of specimen.
Test is repeated under different effective stresses and confining pressures.


TESTING APPARATUS PARTS AND THEIR FUNCTIONS

1)rigid pedestal at the fixed base to hold one end of the
specimen with zero vibration.

2)resonant column driver to apply confining pressure

3)electric motor with eight coils and four magnets at the
vibration end to induce sinusoidal excitation.

4)power amplifier and function generator to run the
motor

5)Accelerometer to determine resonance frequency
during the test

6)Bath of silicon oil to prevent migration or air into the specimen

7)Cylindrical membrane to hold the specimen in shape

8)Gas pressurized outer cell which encloses the apparatus


WORKING PROCEDURE

SAMPLE PREPARATION
Soil samples with different values of plasticity index- 47,52,65,71 were taken.
Samples were placed in a split mould with 70mm diameter and 140mm height.
Specimen along with the mould was placed on the pedestal.
Cylindrical membrane was stretched around the specimen.
Vacuum was applied on top to allow the specimen to hold the shape.

Mould was carefully split without disturbing sample.




PROCEDURE

Two stages:
consolidation stage

excitation stage

consolidation stage


confining pressure of 350kPa was applied using
resonant column driver
effective pressure 50kPa was applied
consolidation test was conducted under undrained
conditions

Excitation stage

Sinusoidal excitation was applied on vibration end of
the specimen.
Vibration amplitude of the specimen was noted.
Longitudinal displacement and accelerometer
readings were recorded.
Excitation frequency was increased and the test was
repeated.
On completion of 2 stages:

consolidation of same sample with PI =65 at:
effective pressure = 100,150kPa
confining pressure = 350kPa

excitation under same range of frequencies

Above cycle was repeated for confining pressure of 400 & 450kPa. Then other samples with PI=52,65,71were taken and tested similarly .Results were plotted.

RESULTS

Response of soil to oscillation becomes stiffer as PI increases.
As effective stress increases, G increases and D decreases.
As PI increases, G increases and D decreases regardless of confining pressure
For a given PI, G increases and D decreases as the confining pressure increases.


CONCLUSION

As PI increases, G increases and D decreases.

As confining pressure increases, G increases and D decreases.
Reply

Important Note..!

If you are not satisfied with above reply ,..Please

ASK HERE

So that we will collect data for you and will made reply to the request....OR try below "QUICK REPLY" box to add a reply to this page

Quick Reply
Message
Type your reply to this message here.


Image Verification
Please enter the text contained within the image into the text box below it. This process is used to prevent automated spam bots.
Image Verification
(case insensitive)

Possibly Related Threads...
Thread Author Replies Views Last Post
  Effect of Waste Polymer Materials on Shear Strength of Unsaturated Clays Report study tips 0 610 17-07-2013, 03:24 PM
Last Post: study tips
  PUSHOVER ANALYSIS OF A 19 STORY CONCRETE SHEAR WALL BUILDING pdf project girl 0 615 28-01-2013, 03:54 PM
Last Post: project girl
  Shear walls full report. seminar surveyer 2 12,717 27-11-2012, 01:07 PM
Last Post: owen23
  SIEVE ANALYSIS AND FINENESS MODULUS uploader 0 680 28-05-2012, 10:50 AM
Last Post: uploader
  Soil Sub-Grade Modulus seminar flower 0 885 19-05-2012, 05:28 PM
Last Post: seminar flower
  Quantification of Damage Index for High Rise Building smart paper boy 0 1,563 27-07-2011, 09:27 AM
Last Post: smart paper boy
  Shear strength increment of soft soils using Prefabricated Vertical Drains summer project pal 0 1,346 05-02-2011, 08:25 AM
Last Post: summer project pal
  SHEAR STRENGTH IN PREEXISTING LANDSLIDES summer project pal 0 1,449 05-02-2011, 08:15 AM
Last Post: summer project pal
  SEMINAR REPORT ON EVALUATION OF FLOW LIQUEFACTION AND LIQUEFIED SHEAR STRENGTH summer project pal 0 2,430 05-02-2011, 07:43 AM
Last Post: summer project pal
  BLOCK SHEAR FAILURE IN TENSION MEMBERS full report computer science technology 4 7,614 01-01-2011, 06:55 PM
Last Post: science projects buddy