Comparison of permeability test methods

to characterize on-site rainwater infiltration

July. 4. 2017

Jooho Chung, Miyajawa Hiroshi, Mooyoung Han

Seoul National University

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Contents

1. Introduction

2. Materials & Methods

3. Results & Discussion

4. Conclusion

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1. Introduction

(1) Background

(2) Low Impact Development (LID) Facilities

(3) Infiltration Facility Installation Procedure

(5) Objectives

3

(4) Necessity of proper Hydraulic conductivity

Drought

1) Introduction

(1) Background

Heat island phenomena Urban flooding

4

Low Impact Development

Heavy Rain

Heavy Rain

Retention

Runoff reduction

River runoff Reduction

Rain-Harvesting facility

Infiltration facility

Reservoir

Retention

Retention

Infiltration Retention

[LID- Sponge city]

• A project to solve the country's flooding problems.

• To overcome urban floods and droughts and

encourage the securing of water resources.

(2) Low Impact Development (LID) Facilities

5

吸

排

滞

用

蓄

Sponge city concept

infiltration

净

cleaning harvesting

using discharging

saving

1. Soil characteristic measurement 2. Infiltration facility design 3. Infiltration facility construction

Hydraulic conductivity, K

1) Introduction

(3) Infiltration Facility Installation Procedure

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(4) Necessity of proper Hydraulic conductivity

Efficiency & Affordability

Hydraulic conductivity, K

Overestimated A lack of facility installation

Underestimated Excessive installation of facilities

Possibility of Flood

Economic waste

1) Introduction

(4) Objectives

Determination of

applicable permeability test

for infiltration of rainwater

Identification of rainwater

infiltration characteristics

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2. Materials and methods

(1) On-site Infiltration characteristics of rainwater

(2) Hydraulic Conductivity methods

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PERCOLATION

INFILTRATION from saturated pond

RUN OFF

Soil zone UNSATURATED

Ground water zone SATURATED

Capillary fringe

0

50

100

150

Monthly Precification(mm)

2. Vertical Infiltration

Rainwater infiltration during

rainfall is due to gravity and

infiltrates vertically.

3. Different flow velocity

and direction

Evaporation

Run off, Percolation,

Infiltration, Storage.

4. Three phase

①Air

②Soil Particle

③Water

1. Unsaturated Soil

Surface zone of soil is

unsaturated zone and remain as

unsaturated soil even in the event

of rainfall.

5. Influence of Previous rainfall

2) Materials and methods

(1) On-site Infiltration characteristics of rainwater

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2) Materials and methods

(2) Hydraulic Conductivity methods

[ Typical methods used to measure the permeability of soil ]

TSB

Ring Infiltrometer

ETC

(based on Darcy’s law)

K

Disc Permeameter

Comparison of permeability tests with rainwater characteristics.

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1.TSB Method

scale standpipe

seal casing

Borehole extension L

Smear zone

H H

TBM step1 TBM step2

2. Ring infiltrometer 3. ETC (Darcy’s Law)

surface

Diameter 20cm

Auger hole

Filter(gravel) Filter (sand)

• Fully saturated soil

• Kv, Kh

• Measure the water level

based on falling head

method.

• Fully saturated soil

• Kv, Kh

• Measure the constant

water level changing

in Inner ring

• Fully saturated soil,

horizontal flow

• Kh

(2) Hydraulic Conductivity methods

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4. Disk Permeameter

z2

• Unsaturated permeability

• Measures decreasing water level in mariotte bottle

occurred by small negative pressure at ponding on soil

surface.

Disk with membrane

Tube A

Tube B

Bubble

tower

Mariotte

bottle

Relatively low-permeability soil

Relatively high-permeability soil

Z1

Z2

(2) Hydraulic Conductivity methods

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3. Results and discussion

(1) Hydraulic Conductivity comparison

(2) Hydraulic Conductivity Test Methods Comparison

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3) Results and Discussion

(1) Hydraulic Conductivity comparison

Site Soil

Condition Type Depth

In-situ Clay (USCS) 40m • Steady water flow

• Same water ponding

1. Two Stage Borehole test / Double-ring Infiltrometer

Hydraulic Conductivity (K) [×E-10 cm/s]

TSB test Double-ring Infiltrometer

2.1 < 33

In TSB method, Hydraulic conductivity is underestimated

by excavation surface disturbance.

Comparison of four methods to assess Hydraulic conductivity

C.Benson et al. (1997) 16

1571%

2. Double-ring Infiltrometer / Disk Permeameter

Double-ring and tension infiltrometer measurements Of hydraulic conductivity and mobile soil regions

John M. Köhne et al.(2011)

Hydraulic Conductivity (K) [×E-4 cm/s]

Double ring Infiltrometer Disk Permeameter

2.3 > 0.17

Pressure losses across thin sand layer is the reason.

Site Soil Condition

Type Depth

Dummerstorf.

Germany Sandy loam

( WRB classifications) 50mm

• Annual precipitation: 65mm

• Annual temperature: 8.2 C

• Steady water flow

• Same water ponding

(1) Hydraulic Conductivity comparison

17

1352%

3. Two stage borehole method/ Disk Permeameter

Report of on-site infiltration methods in Chiba ken

Miyajaki takeshi.(2005)

Hydraulic Conductivity (K) [×E-3 cm/s]

Two Stage Borehole Disk Permeameter

1.17 < 8.36

In TSB method, Hydraulic conductivity is underestimated

by excavation surface disturbance.

Site Soil Condition

Type Depth

Chiba.Japan Sandy soil mixed

with clay( USCS) 30mm

• Annual precipitation: 139mm

• Annual temperature: 17.5 C

• Same water ponding

(1) Hydraulic Conductivity comparison

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714%

[Hydraulic conductivity Comparison]

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Hydraulic conductivity(cm/s)

Methods Clay

(a) Benson, et al (1997)

Sandy loam

(b) Rostock (2005)

Sandy soil mixed with

clay

(c) 宮澤 博 (2012)

Ring

infiltrometer 3.3E-09 2.3E-02 -

Difference 1571% 1352% 714%

TSB 2.1E-10 - 1.17E-03

Disk

permeameter - 1.7E-03 8.36E-03

Remarks

• TSB

Risk of soil disturbance

Underestimated hydraulic

conductivity

• Ring Infiltrometer

Difficulty to apply a wide

range of soil characteristics

Overestimated hydraulic

conductivity

• TSB

Risk of soil disturbance

Underestimated hydraulic

conductivity

PERCOLATION

INFILTRATION from saturated pond

RUN OFF

Soil zone UNSATURATED

Ground water zone SATURATED

Capillary fringe 2. Vertical Infiltration

3. Different flow velocity and direction

4. Three phase

1. Unsaturated Soil

5. Influence of Previous rainfall

2) Materials and methods

(1) On-site Infiltration characteristics of rainwater

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6. on-site infiltration

Vertical

infiltration

Unsaturated

soil

Different flow

velocity and

direction

Three

phase

Influence of

Precious

rainfall

Remarks

ETC

(Darcy’s law) X X X X X

• Cam measure only horizontal

flow

• In-situ experiments fail to

detect site characteristics

TSB ○ X X X X • Assuming saturated soil

• Possible disturbance during

construction.

Ring

infiltrometer ○ X X ○ X • Assuming saturated soil

Disk

permeameter ○ ○ ○ ○ ○

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The most reliable measurement method in the on-site hydraulic conductivity evaluation is

the disk permeameter

(2) Hydraulic Conductivity Test Methods Comparison

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Infiltration rate Runoff rate

Infiltration velocity measurement using Disk Permeameter gives

approximately similar result compare to the modeling data

(P.Nyman,2014)

[ Disk Permeameter’s reliable data ]

Comparison of rainfall infiltration to Creek in eastern. P.Nyman, et al. (2014)

4. Conclusion

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4) Conclusion

• Rainwater infiltration is gaining much attention to improve the water

circulation status in LID or Spongy city projects around the world.

• However, Rainwater infiltration into the soil is unique area, unlike general

infiltration.

1. vertical infiltration 2. Unsaturated soil 3. characteristic of on-site soil

• The proper determination of rainwater permeability in soil is essential in

the design.

• Until now, the permeability test was either an in-site test or did not take

into account the infiltration characteristics of rainwater during the on-site

test.

Among several existing permeability test methods,

the most accurate method is found to be Disk permeameter method.

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What about your country?

what do you think?

Thank you

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[ Future study ]

1. Determination of proper hydraulic conductivity with soil characteristics of the

Korea and China

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2. Suggestion of the standards of infiltration facility design

3. Prediction of infiltration facility performance

• Maximize the facility performance & Reduction of Flood effect

Storage

StorageInfiltarion

Infiltarion