powerpoint presentation presentations/2020/dey, msit, 20… · meghnad saha institute of technology...

8/20/2020

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Live Webinar Series

Spectrum: Civil Engineering Today

Department of Civil EngineeringMeghnad Saha Institute of Technology

Dr. Arindam DeyAssociate Professor

Geotechnical Engineering Division

Department of Civil Engineering

IIT Guwahati

18-Aug-20 Spectrum, MSIT, 2020 2

A brawl where no one

wants to budgeAngry couple facing

away from each other

Signpost at the crossroads

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Blending Theory and Practice

A Typical Geotechnical Project


construction site

Geo-Laboratory

for testing

Design Office

~ for design & analysisSoil properties

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Geotechnics to Infrastructures

Infrastructures are the physical components of interrelated systems providing commodities and

services essential to enable, sustain, or enhance societal and economic living conditions


Geotechnics to Marvels

Helps to create marvels of infrastructure


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Geotechnics to Failures


Vistas of Geotechnical Engineering

Geotechnical and Geophysical Investigations

Shallow, Deep and Hybrid foundations on horizontal grounds and slopes

Ground Improvement for constructions in difficult subsoil conditions

Soil Dynamics, Earthquake Geotechnics, Ground Response and Liquefaction Analysis

Soil-Structure Interaction

Rainfall Induced Landslides, Landslide Hazard and Slope Stabilization

Geosynthetic Engineering and Reinforced Soil Structures

Rigid and Flexible Earth Retention Systems

Pavement and Railway Geotchnics

Dam and Embankment Engineering


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Investigations for Subsurface Characterization

Intrinsic or Extrinsic geotechnical properties

Specific Gravity and Water content

Particle Size Gradation

Relative Density and Consistency Indices

Hydraulic Conductivity and Soil-Water Characteristic Curve (SWCC)

Shear Strength and Shear Strength Parameters

Stress-strain-time Behavior

Stiffness Characteristics of Soils

Compaction and Consolidation Characteristics

Dynamic Characteristics of Soils

Shear modulus, its degradation and Damping characteristics

Response of soils to waves

Shear wave velocity of soil and the corresponding stratification

Electrical, Thermal and Magnetic Characteristics


Index Characteristics

Hydraulic Characteristics

Strength Characteristics

Deformation Characteristics

Special Characteristics

Dynamic Characteristics

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Experimental Investigations for Soil Properties

Experimental investigations

Laboratory tests

Sieve and Hydrometer test

Density index and Atterberg limit tests

Saturated and Unsaturated Permeability tests

Direct Shear, Triaxial Shear, Torsional Shear, Simple Shear tests

Proctor Compaction and Oedometer tests

Cyclic shear tests (triaxial, direct or simple), Bender Element Tests, Resonant Column Tests and Ultrasonic

Pulse tests

In-situ tests

Exploratory borings or Borehole Stratigraphy

SPT, SCPT, DCPT, DMT, PMT

All the above tests are conducted on DISTURBED

or QUASI-DISTURBED soil samples


Representative Exploratory Borings

Most common method to identify representative subsurface stratigraphy

Most common method to collect representative soil samples


Geological or

Morphological Profiles

Subsurface

Stratigraphy

Discontinuous stratum

Undulated trail

WHY REPRESENTATIVE ???

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Exploratory Borings vs Geophysical Surveys

Exploratory borings

Drilling and boring technique is excessively costly

Spacing between boreholes have every possibility of

missing the subsurface profile variation

NDT surveys

Application of waves and propagation geophysics

Continuous subsurface profiling


Not Replacement Surveys

but Complementary surveys

Help in demarcating appropriate

locations of borehole drilling

Various Types of NDT Geophysical Surveys


Electrical Resistivity

Tomography (ERT)

Nuclear/Proton Magnetic

Resonance (NMR/PMR)

Ground Penetrating

Radar (GPR) Seismic Refraction and

Reflection Surveys

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Multichannel Analysis of Surface Waves (MASW)

Identify variation of ground stiffness

1D, 2D or 3D formats


2

max sG V

Roll-Along Mode

Types of MASW Survey


Active seismic source e. g. a sledge hammer

Linear receiver array

Lesser depth of investigation

Uses surface waves generated from

ambient sources

Uses 2-D receiver array and gives deeper

investigation depth

- Laborious field operation

Passive Roadside

Uses surface wave generated from local

traffic sources

5-20 Hz frequency conforming to 30-100m

wavelengths

Uses 1D receiver array

-Easier field operation

Passive Remote

Passive MASW

Active MASW

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MASW Survey Components


Hammer

Plate

The energy mediumGeophones placed

in a linear array

Offset and

spacing – 2m

Data Acquisition system

Data Recording

Geophones

Basic Procedure of MASW

Three-step investigation: Data collection, Dispersion analysis, Inversion analysis


Principle of Dispersion

Waves of different frequency

travel with different velocity

through the heterogeneous media

Phase Velocity

Frequency

Dispersion Curve

Vs

Depth

Soil

Layers

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Dispersion Analysis


Fourier Transformation

01

sinn n nn

x t c c t

Inversion Analysis


Real problems

have Non-

Unique Solution

Inverse Optimization Problem

Vs Model

Updation

Error

Backpropagation

Initial Vs model can

be from SPT-N profile

0.31497sV N

Result Cause

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MASW Survey at a Jia-Bharali River Bridge Site

A new 4-lane (1.2 km) carriageway bridge over

Jiya-Bharali River bed

National Highway and Infrastructure Development

Corporation Limited (NHIDCL)

Located in Tezpur District, Assam state

Connects NH-52A and NH-37

Project completed with Simplex Infrastructures Ltd


MASW Survey at a Bridge Site

Superstructure span 1.2 km - 24 Piers

- 2 Abutments

Pier spacing 48 m

MASW test - Active mode

10 kg sledge hammer impact as seismic

source

4.5 Hz Geophones

Piers 1- 4

Submerged under river water

Roll Along method of Active MASW

test

Shifting equipment from pier to pier with

a 12 m overlap


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Bandpass filtering with mild temporal muting

Dispersion image stacking to enhance resolution


Raw DataFiltered and

Muted Data

Dispersion image from single record

Dispersion

image after

stacking 4-

records


Automated extraction of dispersion curve and Inversion

Profiles obtained as a roll-along method

Test at each pier location

Tests at intermediate locations between piers


Extracted multimodal

dispersion curve

1D Shear wave velocity profile

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Jumrik

Madhulatha

Rana

Chiranjib

The longest single stretch of MASW survey done in India until date

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Ground Response Analysis

Response of soil substrata subjected to vertically

propagating horizontal shear waves

Inherent Assumption: Horizontally layered soil deposit

Fundamental principles required

Wave propagation and wave mechanics

Strong motion characterization

Dynamic characterization of soils

Dynamic properties and liquefaction parameters


Types of Ground Response Analysis

Several variants of GRA

Linear / Equivalent Linear / Nonlinear analysis

Dependency on the induced strain and solution

approach

Time-domain / Frequency domain analysis

Mode of analysis

Total stress / Effective stress analysis

Dependency on the consideration of pore-pressure

Masing / Non-Masing analysis

Type of loading-unloading-reloading rules applied

for the cyclic hysteresis generation

1D / 2D / 3D GRA

Problem and rigor depedent


Nonlinear Time-domain Effective-stress based analysis using Non-Masing rules

http://deepsoil.cee.illinois.edu/Default.html#

1D GRA

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Requirement of Ground Response Analysis

Shear wave velocity profile of the substrata


1D MASW

Roll-along 2D MASW

0.31497sV N

Cross-hole test SPT-N


Strong motion input characteristics (Amplitude, Frequency, Duration)


SEISMOSIGNAL

Software

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Requirement of Ground Response Analysis Dynamic soil properties

Strain and Stress-controlled Cyclic Triaxial or

Cyclic Simple Shear tests

Shear modulus degradation curve

Strain-dependent damping ratio

Liquefaction potential parameters


Cyclic Triaxial ApparatusOn-sample Transducers


Dynamic soil properties

Strain and Stress controlled Cyclic Triaxial tests

Shear modulus degradation




-0.12

-0.09

-0.06

-0.03

0

0.03

0.06

0.09

0.12

0 10 20 30 40

Ax

ial

Str

ain

(%

)

Number of cycles

(a)

-30

-20

-10

0

10

20

30

40

50

0 10 20 30 40

Dev

iato

r st

ress

(k

Pa)

Number of cycles

(b)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 10 20 30 40

Exce

ss p

ore

pre

ssu

re r

ati

o (Δ

u/σ

ʹ c)

Number of cycles

(c)

-50

-40

-30

-20

-10

0

10

20

30

40

50

-0.15 -0.1 -0.05 0 0.05 0.1 0.15

Dev

iato

r S

tres

s (k

Pa)

Axial Strain (%)

(d)

1E-4 1E-3 0.01 0.1 1 100.0

0.2

0.4

0.6

0.8

1.0

G/Gmax_BS

G/Gmax_RS

D_BS

D_RS

Shear strain (%)

G/G

ma

x

0

5

10

15

20

25

30

Da

mp

ing

ra

tio

, D

(%

) Str

ain

-co

ntr

oll

ed t

ests

Str

ess-

con

tro

lled

Dynamic

parameters

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Dynamic soil properties

Strain and Stress controlled Cyclic Triaxial tests

Shear modulus degradation




Brahmaputra Sand

GRA of Guwahati City and IIT Guwahati, Assam, India


Guwahati City

IIT Guwahati

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GRA of Guwahati City and IIT Guwahati, Assam, India


Typical Borehole Profile

0.31491sV N

Vs Profile

Input Strong Motions

1E-4 1E-3 0.01 0.1 1 100.0

0.2

0.4

0.6

0.8

1.0

G/Gmax_BS

G/Gmax_RS

D_BS

D_RS

Shear strain (%)

G/G

max

0

5

10

15

20

25

30

Da

mp

ing

ra

tio

, D

(%

)

Dynamic

parameters

Typical GRA Results and Representations


Hysteresis

Loops

PGA

Spectral

Acceleration

Liquefaction

Susceptibility

Maximum

Strain Profile

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Typical PGA and AF Contour Map of Guwahati City

Manifestation of Local Site Effects due to varying geology

Local Amplification and Attenuation of bedrock motion


Nepal Eq: Peak Bedrock Acceleration (PBRA) = 0.18g

PGA AF

Typical PGA and AF Contour Maps of IIT Guwahati

Manifestation of Local Site Effects due to varying geology (How much local?)

Local Amplification and Attenuation of bedrock motion


Sikkim Eq: PBRA = 0.36g

PGA AF

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Liquefaction Susceptibility FoS Maps of IIT Guwahati

Influence of peak bedrock acceleration

No liquefaction susceptibility for lower

bedrock motions

FoS > 1 at all places in the campus



Substantial liquefaction susceptibility at higher

bedrock motions

FoS < 1 at many places in the campus at both shallow

and deeper strata


1 m 10 m

Liquefaction Potential Index (LPI) Maps of IIT Guwahati

Indicates severity of liquefaction

LPI < 5 No liquefaction

5 < LPI < 15 Moderate liquefaction

LPI > 15 Severe liquefaction


Sikkim Strong Motion

0.02 g

0.06 g0.18g

0.36 g

Why LPI is better than FoS ?

Madhulatha Pankaj

Shiv Devdeep

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Landslides

Landslide is the movement of a mass

of rock, debris or earth down a slope


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Landslides: Causes and Triggers


Landslide trigger

The single event that finally

initiates the landslide

Landslide causes

Factors that make the slope

vulnerable to failure

Factors that predisposes the

slope to become unstable

Landslide Analyses


Local-Scale Landslide Analyses

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Rainfall Induced Landslide Hazard of Guwahati City

Study area and characterization of hillslope soils


0

50

100

150

200

250

0 150 300 450 600

τ

σ'


Local-scale deterministic slope stability analysis


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Local-scale probabilistic slope stability analysis

Application of Random Field for soil parameters for catering uncertainty in soil parameters


Regional Landslide Susceptibility and LHZ of Guwahati City

Regional Scale Stability Analysis

Landslide Hazard Zonation and Landslide Susceptibility Studies

SHALSTAB, TRIGGRS, SINMAP, Physically-based Models

GIS platform for Digital Elevation Models (DEM)


DEM

Stability Index Map

8/20/2020

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0

5

10

15

20

25

0 10 20 30 40 50 60

Dep

th o

f S

oil

Form

ati

on

Slope Angle in Degrees

Estimated Soil Depth (H)

Soil Depth from Bore-hole data

H = 25.0e-0.075β

Rainfall Induced Landslide in Guwahati Region

Regional Scale Landslide Hazard Analysis

Incorporation of variability in rainfall and soil depth


Monthly mean rainfall based on 100 years

data (1901-2002) at Kamrup metropolitan

I-D-F curves for Guwahati region

Variation of weathered soil

thickness and slope angle

Rainfall-Induced Landslide Hazard Map of Guwahati City


Ha

za

rd

Ma

p i

s a

co

mb

ina

tio

n o

f

ind

ivid

ua

l re

turn

perio

d m

ap

s

Influence of

Return Periods

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Probabilistic Landslide Hazard Analysis of Guwahati City

Incorporating uncertainty of soil parameters


Probability of Failure (PoF) Map of Guwahati City


Chiranjib

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Soft Ground Improvement using Preloading with PVDs


Vertical Drain Installation

Accelerated consolidation through vertical and radial drainage and excess PWP dissipation

Solo Preload

Preload with PVD

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Finite Element Modeling and Analysis

2D Plane-strain

Full 3D

Plan of

Preload

Deformation

Shear StressesPWP before consolidation

PWP after consolidation

PWPmax = 90 kPa

PWPmax = 76 kPa

OUTCOMES



Influence of PVDs

Reduction in PWP zone

Preloading

Preloading + PVD

Excess PWP vs Time

Settlement vs Time

Smear: Reduction of permeability

around the drain due to driving (ks<kh)

Sai Kiran Rajesh

8/20/2020

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Influence of PVD

spacing and depth

Uniform fine spacing

Uniform sparse spacing

Unequal spacing

Flo

ati

ng

PV

D f

or

thic

k s

oft

str

atu

m Choose per design

requirement

Heritage Railway Station, Udaipur, Agartala

Application of preloading and PVD for developing of railway

yard in a ditch marshland


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Incorporation of strength gain in the analysis

Saves unnecessary preloading requirement


Strength gain during consolidation


Application of preloading and

PVD for developing of railway

yard in a ditch marshland


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Final Remarks


Theory V/S Practice Theory + Practice

Acknowledgement

Organizers of the Conference

A platform to discuss interesting issues

All my students

The workforce to bring out the intricate findings

All my academic and industry partners

The brains and The funds

Those researchers who laid the foundation

of present day discussions


Rankine Taylor PeckCassagrande BjerrumSkempton Janbu

Zeevaert

Seed

Terzaghi

Coulomb

8/20/2020

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Thank You for Patient Hearing

http://www.iitg.ac.in/arindam.dey/homepage/index.html#

https://www.researchgate.net/profile/Arindam_Dey11

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