8/20/2020 1 Live Webinar Series Spectrum: Civil Engineering Today Department of Civil Engineering Meghnad Saha Institute of Technology Dr. Arindam Dey Associate Professor Geotechnical Engineering Division Department of Civil Engineering IIT Guwahati 18-Aug-20 Spectrum, MSIT, 2020 2 A brawl where no one wants to budge Angry couple facing away from each other Signpost at the crossroads
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8/20/2020
1
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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2
18-Aug-20 Spectrum, MSIT, 2020 3
Blending Theory and Practice
A Typical Geotechnical Project
18-Aug-20 Spectrum, MSIT, 2020 4
construction site
Geo-Laboratory
for testing
Design Office
~ for design & analysisSoil properties
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3
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
18-Aug-20 Spectrum, MSIT, 2020 5
Geotechnics to Marvels
Helps to create marvels of infrastructure
18-Aug-20 Spectrum, MSIT, 2020 6
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Geotechnics to Failures
18-Aug-20 Spectrum, MSIT, 2020 7
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
18-Aug-20 Spectrum, MSIT, 2020 8
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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
18-Aug-20 Spectrum, MSIT, 2020 10
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
18-Aug-20 Spectrum, MSIT, 2020 11
Representative Exploratory Borings
Most common method to identify representative subsurface stratigraphy
Most common method to collect representative soil samples
18-Aug-20 Spectrum, MSIT, 2020 12
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
18-Aug-20 Spectrum, MSIT, 2020 13
Not Replacement Surveys
but Complementary surveys
Help in demarcating appropriate
locations of borehole drilling
Various Types of NDT Geophysical Surveys
18-Aug-20 Spectrum, MSIT, 2020 14
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
18-Aug-20 Spectrum, MSIT, 2020 15
2
max sG V
Roll-Along Mode
Types of MASW Survey
18-Aug-20 Spectrum, MSIT, 2020 16
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
18-Aug-20 Spectrum, MSIT, 2020 17
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
18-Aug-20 Spectrum, MSIT, 2020 18
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
18-Aug-20 Spectrum, MSIT, 2020 19
Fourier Transformation
01
sinn n nn
x t c c t
Inversion Analysis
18-Aug-20 Spectrum, MSIT, 2020 20
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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11
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
18-Aug-20 Spectrum, MSIT, 2020 21
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
18-Aug-20 Spectrum, MSIT, 2020 22
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12
MASW Survey at a Bridge Site
Bandpass filtering with mild temporal muting
Dispersion image stacking to enhance resolution
18-Aug-20 Spectrum, MSIT, 2020 23
Raw DataFiltered and
Muted Data
Dispersion image from single record
Dispersion
image after
stacking 4-
records
MASW Survey at a Bridge Site
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
18-Aug-20 Spectrum, MSIT, 2020 24
Extracted multimodal
dispersion curve
1D Shear wave velocity profile
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13
18-Aug-20 Spectrum, MSIT, 2020 25
Jumrik
Madhulatha
Rana
Chiranjib
The longest single stretch of MASW survey done in India until date
8/20/2020
14
Ground Response Analysis
Response of soil substrata subjected to vertically