THESIS

1
THESIS
EFFECTIVENESS OF BACK- FLUSHING FOR CLEANING
POROUS PAVEMENTS
By- Nilesh Shirke
Fall 2006
2
Outline

• Introduction
• Problem Statement
• Research Question
• Methodology
• Construction of a Model
• Detailed Procedure of Experiments
• Experiments and Results
• Analysis of Data
• Result and Conclusion
• Future Research

3
Committee Members

• Dr. Scott Shuler (Adviser/Chair)
• Dr. Angela Guggemos
• Dr. Charles Smith
• Dr. Ramchand Oad (Outside Committee member)

4
Introduction

• Increased runoff
• Drainage
• Alternative pavement
• Void content
• Direct infiltration of rain water
• Replenish ground water
• Sustainable construction

Bean, Hunt, Bidelspach, Smith, 2004 Leopold,
Wolman, Miller, 1964 James, W., Langsdorff,
H., 2003 Bachtle, 1974 Caltrans, 2004 Georgia
concrete and products association, 2005, p. 2
Surface System Drainage Design, 2005
5
Layers of Porous pavement

• Porous Concrete Layer
• Top Filter Layer
• Reservoir Layer
• Bottom Filter Layer

Georgia Stormwater Management Manual, 2002
6
Typical Cross-section of Porous Pavements
The Urban Land Institute, 1992, p 6.
7
Advantages of porous pavements

• Percolation of rainwater into the soil
• Aquifer recharge
• Ambient air temperature
• Snow and ice
• Soil erosion
• Decreases need of storm drains

Adams, 2003 Bachtle, 1974 Field, 1982 Ferguson
1994 Magnus, 2000 Pratt 1997 The Pervious
Company, 2005 Georgia Concrete and Products
Association, 2005 Miller, 2005
8
Disadvantage of Porous Pavements

• Susceptibility to clogging
• Reduces infiltration levels
• Groundwater contamination
• High failure rate

Field, 1982 UNI-Group U.S.A., 1998 United
States Environmental Protection Agency, 1999.
9
Problem Statement

• Maintaining infiltration capacity
• Clogging at the bottom
• Periodic maintenance
• Traffic levels and type of usage
• Severe clogging

James Langsdorff, 2003 The Urban Land
Institute, 1981 United States Environmental
Protection Agency, 1999 Siew-Ann et al., 2003
Georgia Stormwater Management Manual, 2002
10
Periodic Maintenance
Georgia Stormwater Management Manual, 2002, p 37
11
Research Hypothesis

• When water is flushed through the pavement from
  bottom to the top with enough pressure, it
  removes the debris particles trapped in the pores
  of porous concrete layer.

12
Research Question

• When water is pumped into the stone reservoir of
  the pavement, it will try to come out through the
  clogged porous concrete layer. While coming out
  from bottom to the top of the pavement, water
  should remove the particles and debris trapped in
  the pores of the pavement. The result of this
  flushing should make the pavement permeable
  again.

13
Concept of Back Flush Method
14
Diagram of a Model Constructed for the Analysis
of Back-Flush
15
Methodology

• Fabrication of steel frame
• Construction of a porous concrete layer
• Installation of model on a steel frame
• Construction of various layers
• Sieve analysis for clogging materials
• Calculation of initial permeability
• Clogging
• Back-flushing

16
Methodology

• Measurement of permeability cleaned concrete
  layer
• Back flush it for the second time.
• Measurement permeability after 2nd back-flush
• Repetition of the procedure
• Data collection
• Analysis of the results
• Conclusion

17
Photograph Showing Various Sections a Model
18
A Photograph Showing Full View of a Model
19
Section 1

• A two feet long and 8 diameter pipe for the
  construction of porous concrete layer
• Material Weight Proportions
• - Cement-600 lbs, Aggregates 3/8-2900 lbs,
  Water-242 lbs
• Sampling - ASTM C 702-98 splitting method
• Sieve Analysis - for 3/8 aggregates as per ASTM
  C 136-01
• Curing of concrete - ASTM 192 C511 Storage tank
  in hydrated lime

20
Analysis of 3/8 aggregates as per ASTM C 136-01
21
Section 2

• A three feet long and 8 diameter pipe for
  construction of filter layers, stone layer of the
  pavement in it.

22
Section 3, 4 5

• Section 3 A ten feet long and 8 diameter pipe
  to store water to create head difference
• Section 4 A 1½ diameter pipe connected to tap
  water with water flow control valve in between.
• Section 5 A 1½ diameter pipe connected to
  section 1 and which is used to drain the water
  out after back-flushing.

23
Procedure of experiment

• Calculation of permeability
• k QL / Ath
• Where,
• k permeability, in/s
• Q quantity of flow, cu. inch
• L length of specimen, inch
• A cross-sectional area of specimen, sq. inch
• t interval of time over which flow Q occurs, s
• h difference in hydraulic head across the
  specimen, in

24
Procedure of experiment

• Unclamp Section 1
• Check permeability
• Clogging
• Measurement of permeability
• Placement of section 1 over section 2
• Attach section 5 to the section 1
• Choose the head and fill section 3
• Back-flush
• Close the valve after back-flush
• Detach section 5 from section 1

25
Procedure of experiment

• Unclamp section 1
• Check permeability after back-flush
• Attach Section 1 for 2nd back-flush
• Attach section 5 to section 1
• Back-flush for the 2nd time
• Check permeability
• Repeat the procedure
• Efficiency of back-flush
• k (back-flush)- k (clogged) / k (Initial) k
  (clogged)

26
Experiments and Results

• Average Strength of porous concrete
• High Porous Concrete - 895.59 psi
• Low Porous Concrete - 1164 psi

27
Classification of clogging materials

• Classification and gradation of soils by ASTM D
  2487-00
• Cu D60/D10
• Cc (D30D30) / (D60D10)
• Where,
• Cu Coefficient of Uniformity
• Cc Coefficient of Curvature
• D10, D60 and D30 Particle size diameters
  corresponding to 10, 60 and 30 respectively,
  passing on cumulative particle-size distribution

28
Classification of Sand 1 Sand 2

• Sand 1
• A Graph gives the value for D10 0.15, D60
  1.15 and D30 0.4
• Hence,
• Cu 8.33, Cc 1.05
• Cugt6 and 3gtCcgt1
• Hence, it is a Well Graded Sand (SW).
• Sand 2
• A Graph gives the value for D10 0.45, D60 1.8
  and
• D30 0.8
• Hence,
• Cu 4, Cc 0.79
• Cult6 and 1gtCc.
• Hence, it is a Poorly Graded Sand (SP).

29
Percentage Removal of Clogged Particles After
Back-Flush
30
Average Permeability Recorded on High Porous
Concrete Sample
31
A Chart for Average Permeability Recorded on
High Porous Concrete Sample
32
Average Permeability Recorded on Less Porous
Concrete Sample
33
A Chart for Average Permeability Recorded on
Less Porous Concrete Sample
34
Analysis of Data

• ANOVA
• Four variables
• Class Levels Values
• Pressure 4 H L M VL
• Porosity 2 High Low
• Clogging 2 Sand 1 Sand 2
• Flush 2 Q1 Q2

35
SAS Output

• Source
  DF Type III SS Mean Square F
  Value Pr gt F
• Pressure 3
  3325.215458 1108.405153 5.58 0.0018
• Porosity 1
  6.211837 6.211837 0.03
  0.8602
• Clogging 1
  79.570417 79.570417 0.40
  0.5291
• Flush 1
  93.102204 93.102204 0.47
  0.4962
• PressurePorosity 3
  652.060537 217.353512 1.09 0.3583
• PressureClogging 3
  668.936625 222.978875 1.12 0.3468
• PressureFlush 3
  71.115388 23.705129 0.12
  0.9485
• PorosityClogging 1
  265.268504 265.268504 1.33 0.2523
• PorosityFlush 1
  121.770150 121.770150 0.61 0.4366
• CloggingFlush 1
  674.690104 674.690104 3.39 0.0700
• PressuPorosiCloggi 3
  71.967954 23.989318 0.12
  0.9476

36
Student-Newman-Keuls Test

• Alpha 0.05
• Error Degrees of Freedom 64
• Error Mean Square 198.7347
• Number of Means 2
  3 4
• Critical Range 8.1301265
  9.7646019 10.734814
• Means with the same letter are not
  significantly different.
• SNK Grouping
  Mean N Pressure
• A
  79.953 24 H
• A
• B A 72.753
  24 M
• B
• B
  66.196 24 VL
• B
• B
  65.321 24 L

37
Analysis

• No fixed pattern in particle removal
• Pressure- significant variable
• No significance of number of flushes
• Less water requirement
• Low pressure efficiency

38
Results and Conclusion

• Simplified Maintenance
• Monthly or quarterly back-flushing
• Increased use of porous pavements
• Low pressure works good
• Possible to create in the field

39
FUTURE RESEARCH

• More research work
• Laboratory study and Field study
• A very low pressure of water (0.5 psi)
• Drainage pipes in the porous pavement
• Division of porous pavement
• Storage of drained water

40
Thank You !!!