istvs research grants program 1st award progress presentation

Sep, 2016 - 1

Advanced Vehicle

Dynamics Laboratory

A Technical Survey on Equipment

and Techniques for Testing and

Parametrization of Soft Soil for

Vehicular Applications

Virginia Tech: Mr. Rui He, Prof. Corina Sandu

University of Pretoria: Mr. Glenn Guthrie, Prof. Schalk Els

8th American Regional conference of ISTVS, Troy, MI, USA

Sep, 2016 - 2

Advanced Vehicle

Dynamics Laboratory

Context

Work funded by the first ISTVS research grant “Systematic

Testing and Parameterization of Soft Soil for Vehicular

Applications”, co-PIs Corina Sandu, Virginia Tech and

Schalk Els, University of Pretoria

Work Goals

• Task 1: Perform literature survey for equipment and techniques used

to characterize soft soil (year 1: 2015-2016)

• Task 2: Compile a list of resources (equipment, facilities, capabilities,

and expertise available within the community (year 2: 2016-2017)

• Task 3: Build a soil properties database from literature and any other

source available to serve the ISTVS community (year 3: 2017-2018)

• Task 4: Propose additions and changes for the ISTVS standards for

testing and parameterization of soft soil (2018)

Sep, 2016 - 3

Advanced Vehicle

Dynamics Laboratory

Context

Work on-going for Task 1. Currently performing

comprehensive literature survey to find research and soil

data that is already available in the literature.

Data is being systematically collected, analyzed, and the

relevant information fed into tables and databases.

Longer document with research work will be made available

to the ISTVS community; illustrative examples of on-going

work are presented today

Sep, 2016 - 4

Advanced Vehicle

Dynamics Laboratory

Approach and Content for Task 1

Soil properties and testing

• Determine common physical soil properties and corresponding

measurement techniques

• Summarize empirical models to assess vehicle mobility, parameters

required and corresponding measurement techniques

• Theoretical model parameters and corresponding measurement

techniques

Compressive stress and deformation

Shear stress and deformation

For each item:

• Brief description (if available from current ISTVS standards)

• Table containing information gathered from the literature

• References

Sep, 2016 - 5

Advanced Vehicle

Dynamics Laboratory

Definition

• ISTVS 1977 standard [1]

Typical Measuring Instruments

• Bulk density soil sampling kit

• High accuracy scale

Physical Properties Bulk Density

Bulk density soil sampling kit,

AMS

/

: the mass of the sample after

it has been dried to constant weight

: volume of the sample

d s

s

W V

W

V

Unit volume of soil divided

into its components

Sep, 2016 - 6

Advanced Vehicle

Dynamics Laboratory

Physical PropertiesBulk Density Table

Bulk density (Dry density)

If defined in 1977

ISTVS standard Yes/No Yes /d sW V

Experimental

Methodology

Measuring

Instruments Soil Type References

Gamma attenuation

method

Two-probe

density gauge Sandy loam [3]

Gamma attenuation

method

Two-probe

density gauge Sand, loamy sand, sandy loam [4]

Direct measurement Core sampler Sandy loam, sand, Loamy sand [4]

Direct measurement Core sampler Clay loam [6]

Sand replacement

method

Sand pouring

cylinder Sand [5]

Sep, 2016 - 7

Advanced Vehicle

Dynamics Laboratory

Water Content

Definition

• ISTVS 1977 standards [1]

Typical Measurement Methods

• Thermogravimetric measurement (reference method)

Measure the weight of a wet sample before and after oven drying at

105℃ for 24 h.

Provide calibration of other soil water content sensors.


• High accuracy scale

100

: mass of water present in the sample

: mass of sample after it has been dried to constant weight

w

s

w

s

Ww

W

W

W

Sep, 2016 - 8

Advanced Vehicle

Dynamics Laboratory

Water Content

Water Content (Moisture Content)

If defined in 1977 ISTVS

standard Yes/No Yes 100w

s

Ww

W

Experimental

Methodology Measuring Instruments Soil Type References

Thermogravimetric

measurement High accuracy scale All types [7]

Dielectric measurement Dielectric sensor All types [8]

Resistivity measurement Electrode N/A [9]

Neutron scattering

technique Soil moisture neutron probe

Sand, silt loam, silty

clay loam, sandy loam,

clay loam, clay

[10]

Measurement of soil

thermal

properties

Temperature sensors,

heated needle, heat-pulse

sensors

Sandy loam, sand [11]

Acoustic wave methods Transmitter

Sandy clay loam, loam,

silt loam, silt, silty clay,

sandy clay, clay loam,

silty clay loam, clay

[12]

Sep, 2016 - 9

Advanced Vehicle

Dynamics Laboratory

Definition [13]:


• Pycnometer

• Digital weighing scale


• Pycnometer method (ASTM, 1958, p.

80; u.S. Dep. Agric., 1954, p. 122)

Specific Gravity

Specific gravity sample and pycnometer

[( ) ( )]

: weight of pycnometer plus soil sample corrected to oven-dry water content

: weight of pycnometer filled with air

: weight of pycnometer filled with soil and water

: weig

s as

s a sw w

s

a

sw

w

W WG

W W W W

W

W

W

W

ht of pycnometer filled with water at temperature observed

Sep, 2016 - 10

Advanced Vehicle

Dynamics Laboratory

Specific Gravity

Specific Gravity

If defined in 1977

ISTVS standard Yes/No No

[( ) ( )]

: weight of pycnometer plus

soil sample corrected to oven-dry

water content

: weight of pycnometer

filled with air

: weight of pycnometer

filled with soil and water

: weig

s as

s a sw w

s

a

sw

w

W WG

W W W W

W

W

W

W

ht of pycnometer

filled with water

at temperature observed

[13]

Experimental

Methodology

Measuring


Pycnometer method Pycnometer Clay [5], [14], [15]

Pycnometer method Pycnometer

Pycnometer method Ultra-Pycnometer Loam, clay loam, clay, silty clay,

clay, [16]

Sep, 2016 - 11

Advanced Vehicle

Dynamics Laboratory

Definition [17]

• Based on particle size distribution curve


• Sieving

• Pipette

• Hydrometer


• Drying trays, wooden rolling pin, etc.

• Beakers, centrifuges, etc.

• Standard hydrometer, electric stirrer, etc.

Average Grain Size

Schematic diagram of ASTM 152 H-type hydrometer [18]

50 : Diameters of the soil particles that have a percentage finer by weight of 50%D

Sep, 2016 - 12

Advanced Vehicle

Dynamics Laboratory

Average Grain Size

Average Grain Size

If defined in 1977 ISTVS

standard Yes/No No

50 : Diameters of the soil particles that have

a percentage finer by weight of 50% [17]

D

Experimental

Methodology

Measuring


Pipette method Beakers, centrifuges,

etc. Clay, sand [18], [19]

Hydrometer method Standard hydrometer,

electric stirrer, etc.

Silty clay, silt clay

loam, sandy clay [18], [20], [21]

Laser-diffraction

techniques

Laser diffraction

particle-size analyzer

Clay, silty clay, silty

clay loam, clay loam,

sandy clay loam, silt

loam

[18], [22]

X-ray attenuation SediGraph Silt loam [18], [23]

Particle counting Electrical sensing zone

(ESZ) instrument

Silt loam, silt clay

loam, clay loam [18], [24]

Sep, 2016 - 13

Advanced Vehicle

Dynamics Laboratory

Definition [1]

• Based on particle size distribution

curve


• The same as that for average grain size


• The same as that for average grain size

Coefficient of Uniformity

60

10

60

10

: Diameters of the soil particles that have a percentage finer by weight of 60%

: Diameters of the soil particles that have a percentage finer by weight of 10%

c

DU

D

D

D

A sample particle size distribution curve [17]

Sep, 2016 - 14

Advanced Vehicle

Dynamics Laboratory



If defined in 1977

ISTVS standard

Yes/No

Yes

60

10

60

10

: Diameters of the soil particles that have

a percentage finer by weight of 60%

: Diameters of the soil particles that have

a percentage finer by weight of 10%

c

DU

D

D

D

Experimental

Methodology

Measuring


The same as that for

Average Grain Size


Average Grain Size


Average Grain Size


Average Grain Size

Sep, 2016 - 15

Advanced Vehicle

Dynamics Laboratory

Empirical Models

Model

Name

If defined in

1977 ISTVS

standard

Yes/No

Expression/Definition References

Mobility

Index for

tracked

vehicle

No contact pressure factor weight factor

Mobility Index = bogie factor -clearance factortrack factor grouser factor

engine factor transmission factor

[2]

Vehicle

Cone

index of

tracked

vehicle for

one pass

Yes 1

39.2VCI 7.0 0.2MI ( )

MI 5.6

[2]

Vehicle

Cone

index of

tracked

vehicle for

50 pass

Yes 50

125.79VCI 19.27 0.43MI ( )

MI 7.08

[2]

Soil-tire

Numeric No

1/2

3/2

CI 1

1 ( / 2 )

( )

CI

c

s

cs

bdN

W h b d

G bdN

W h

bdN

W

[2]

Sep, 2016 - 16

Advanced Vehicle

Dynamics Laboratory

Empirical Models

Parameter

Name

If defined in 1977

ISTVS standard

Yes/No


Cone index (CI) Yes

Penetration resistance force per

unit base area for static

penetrometer

[1], [2], [26]

Remolding index

(RI): Yes

The ratio of the cone index of

a soil after remolding to that

before remolding

[1]

Rating cone index

(RCI): Yes RCI RI CI [1]

Penetration

resistance

(pressure)

No Penetration resistance force per

unit base area [28]

Penetration

resistance (force) No

The force applied to the

penetrometer by the soil

causing the penetrometer to

decelerate from its initial

velocity to zero velocity for

hammer type dynamic

penetrometer

[26]

Ramm pressure No ( ) /Ramm

Whnp W Q A

z [25]

Typical Testing Methods

• Penetration test

Cone penetrometer

Empirical Parameters

Determined

• Cone Index (CI)

• Remolding Index (RI)

• Rating Cone Index (RCI)

US Army Corps of Engineers Cone

Penetrometer

Sep, 2016 - 17

Advanced Vehicle

Dynamics Laboratory

Empirical Models

Experimental

Methodology

Measuring

Instruments

Parameter

Determined Soil Type References

Penetration

test

Rammsonde

cone

penetrometer

Ramm pressure Snow [25]

Penetration

test

Dynamic

cone

penetrometer

Penetration

resistance (force) Clay loam [26]

Penetration

test

Cone

penetrometer

Penetration

resistance

(pressure)

All types [27]

Penetration

test

Penetrometer

–shearometer

Penetration

resistance

(epressure)

Sandy clay loam [28]

Penetration

test

Cone

penetrometer CI Sandy loam [29]

Penetration

test

Vane-cone

penetrometer CI Snow [30]

Sep, 2016 - 18

Advanced Vehicle

Dynamics Laboratory

Theoretical Models - Compressive Stress

Model

Name

If defined in 1977

ISTVS standard

Yes/No


Reece’s

model No ,

n

r r c

zp k k ck k b

b

[31]

Bernstein’s

model No np kz [31]

Bekker’s

model Yes ,n ck

p kz k kb

[1]

N2M model No 0

1 11 expm m

m m m

m

C s s zp z

B B C B

[34]

Wong’s

model for

muskeg

No 24 /m hp kz m z D [35]

Repetitive

loading

model

No ( ), +u u u u o u up p k z z k k A z [35]

Sep, 2016 - 19

Advanced Vehicle

Dynamics Laboratory


Sinkage plate of three shapes and sizes [38]

Tractor-mounted

Bevameter [38]


• Bevameter test

Selection of plate size or plate shape

is based on the tire and track to be

simulated.

Theoretical Parameters Determined

• Bekker’s pressure-sinkage parameters,

𝑛, 𝑘𝑐 and 𝑘∅

• Reece’s pressure-sinkage parameters,

𝑛, 𝑘′𝑐 and 𝑘′∅

• Unloading or reloading function

parameters, 𝑘𝑜 and 𝐴𝑢

Sep, 2016 - 20

Advanced Vehicle

Dynamics Laboratory


Experimental

Methodology

Measuring

Instruments

Parameter


Sinkage test

Penetration-shear

device, combined

[1], sinkage plates

Parameters of

Reece’s model, n ,

rk ; parameters of

Bernstein’s model,

n , k

Loam [31]

Penetration

test

Rammsonde cone,

bevameter, Rammsonde cone

on bevameter

Parameters of

Bekker’s model,

n , k , k , ck

Snow [25]

Sinkage test PNFI Bcvameter N/A N/A [32]

Sinkage test Portable soil plate

penetrometer N/A Loam [33]

Sinkage test

Grenoble Sinkage

equipment with

circular plate

powered by

hydraulic ram

Parameters of

N2M model, m ,

mC , ms , and 0s

Silty sand, sand, silt [34]

Sep, 2016 - 21

Advanced Vehicle

Dynamics Laboratory


Experimental

Methodology

Measuring

Instruments

Parameter


Sinkage test

Vehicle-mounted

bevameter,

portable automatic

data-processing

system

Parameters of Wong’s model for

muskeg, k and

mm ; Parameters

of repetitive

loading model,

uk , ok and uA

Muskeg [35]

Sinkage test Bevameter

Parameters of

Bekker’s model,

n , k , ck

Sand, silt [36]

Sinkage test Tractor-mounted

bevameter

Parameters of

Bekker’s model,

n , k , ck

Loam [38]

Sep, 2016 - 22

Advanced Vehicle

Dynamics Laboratory

Theoretical Models - Shear Stress

Shear Stress and Deformation Models

• Mohr-coulomb criterion

• Shear stress-shear displacement relationship


• Direct shear test

• Tri-axial compression test

• Unconfined compression test

• Vane shear test

• Bevameter test

Sep, 2016 - 23

Advanced Vehicle

Dynamics Laboratory


Shear Model

Name

If defined

in 1977

ISTVS

standard

Yes/No

Expression/Definition Soil type References

Mohr-Coulomb

Criterion Yes tanc

All types

assuming soil

as plastic

medium

[1]

Janosi-Hanomoto

model for shear

stress-shear

displacement

profile without a

hump

No /( tan )(1 e )j Kc

Loose sand,

saturated clay,

dry fresh snow,

and most of

the disturbed

soils.

[2]

Wong’s model for

shear stress-shear

displacement

profile with a

hump

No

(1 / )( tan )( / )e wj K

wc j K

Organic terrain

(muskeg) with

a mat of living

vegetation on

the surface and

saturated peat

beneath

[2]

Wong’s model for

shear stress-shear

displacement

profile with a

hump

No

(1 / ) ( / )

( tan ) [1 1/ ( (1 1/ )) 1

e ] 1 ew w

r r

j K j K

c K K e

Compact sand,

silt and loam,

and frozen

snow

[2]

Sep, 2016 - 24

Advanced Vehicle

Dynamics Laboratory


Direct Shear Test

• In-situ & laboratory test

• Shearing speed between

0.05~2mm/min

• Small shearing speed and shear

displacement in comparison to

that with vehicles

Parameters Determined

• Cohesion, 𝑐

• Angle of friction, 𝜑

• Shear deformation modulus, 𝐾

Schematic of a direct shear box apparatus [56]

Sep, 2016 - 25

Advanced Vehicle

Dynamics Laboratory


Tri-axial Compression Test

• Laboratory test

• Three test regimes: consolidated

undrained (CU), consolidated

drained (CD), and unconsolidated

undrained (UU)

• Not applicable to soft cohesive soil

that will fail under its own weight


• Cohesion, 𝑐

• Angle of soil friction, 𝜑

Schematic of triaxial compression test

apparatus. [57]


Sep, 2016 - 26

Advanced Vehicle

Dynamics Laboratory


Unconfined Compression Test

• Laboratory test

• Undrained test

• A special case of the tri-axial compression test,

with later or confining pressure being zero

• Aimed at fully saturated soil with zero angle of

soil friction, e.g. Clay soil


• Cohesion, 𝑐

Unconfined compression load frame /

test system, Geocomp

Sep, 2016 - 27

Advanced Vehicle

Dynamics Laboratory


Vane Shear Test

• In-situ & laboratory test

• Aimed at undrained, saturated

clay.

• Not suitable for the cases where

the shear strengths in the

horizontal and vertical directions

are hugely different.


• Cohesion, 𝑐 Schematic of a shear vane. [17]

Sep, 2016 - 28

Advanced Vehicle

Dynamics Laboratory

Test and Parameters Determined

Bevameter Test

• In-situ test

• Torsional/translational shear

test

• Selection of the size of shear

annulus, grouser number and

grouser height depends on

the size and grouser feature

of the track to be simulated

Parameters Determined Schematic of a bevameter [37]

𝑐 𝜑 𝐾 𝐾𝑤 𝐾𝑟

Cohesion Angle of soil

friction

Shear

deformation

modulus

The shear

displacement where

the peak shear stress

occurs

The ratio of the

residual stress

to the peak

shear stress

Sep, 2016 - 29

Advanced Vehicle

Dynamics Laboratory


Experimental

Methodology

Measuring

Instruments

Parameter


Direct shear test Modified direct shear

box Friction angle, Sand [39], [40]

Direct shear test Modified direct shear

apparatus

Cohesion, c , and

friction angle, Clay loam [6], [41], [44]

Direct shear test Direct shear testing

machine

Shear deformation

modulus, K Loam [42]

Direct shear test Direct shear box

Cohesion, c ,

friction angle, ,

and shear

deformation

modulus, K

Mojave Martian

Simulant

(MMS)

[43]

Triaxial test Triaxial test

apparatus. Friction angle, Sand [45], [47]

Triaxial test Triaxial test

apparatus.

Cohesion, c , and

friction angle, Clay [45], [46], [47]

Unconfined

compression

test

Unconfined

compression test

apparatus.

Cohesion, c Clay [49], [50], [51]

Sep, 2016 - 30

Advanced Vehicle

Dynamics Laboratory


Experimental

Methodology

Measuring

Instruments

Parameter


Vane shear test Miniature vane shear Cohesion, c Clay [52]

Vane shear test Shear vane Cohesion, c

Sandy clay,

loam, clay,

sandy loam

[53]

Vane shear test Shear vane Cohesion, c Clay loam, clay,

silt clay loam [54]

Torsional shear

test Bevameter

Cohesion, c ,

friction angle, ,

and shear

deformation

modulus, K

Loam [55]

Torsional

shear test Bevameter, grouser

Cohesion, c , and

friction angle, Sand, silt [36]

Translational

shear test

Penetration-shear

device, combined [1],

grouser plates

Cohesion, c ,

friction angle, ,

and shear

deformation

modulus, K

Loam [31]

Sep, 2016 - 31

Advanced Vehicle

Dynamics Laboratory

Closing Remarks

Thanks to ISTVS for providing the opportunity to conduct this joint

research

The study is still in the early stages and the process of gathering

information is ongoing

We are soliciting input from the community regarding test equipment

and soil data

Future Work Task 2. Compile a list of resources (equipment, facilities,

capabilities, and expertise available within the community)

Prepare a full report/conference/journal review paper with findings

Sep, 2016 - 32

Advanced Vehicle

Dynamics Laboratory

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Sep, 2016 - 33

Advanced Vehicle

Dynamics Laboratory

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Sep, 2016 - 34

Advanced Vehicle

Dynamics Laboratory

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Advanced Vehicle

Dynamics Laboratory

References

40. Guo, Peijun. "Modified direct shear test for anisotropic strength of sand." Journal of geotechnical and

geoenvironmental engineering 134.9 (2008): 1311-1318.

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