Pavement

Subsoil Drains v Round Pipe

Presentation

• Products

• Specifications

• Design

• Performance

• Installation

• QA / Testing

• Case studies

Megaflo

• Flat panel geocomposite drainage panel

• Rigid corrugated core

• High compressive resistance

• Internal post support

• Ribs support geotextile

• Water proof invert

• A14 Geotextile Filter (Strength Class A)

Round Pipe - Class 1000

1.PVC ribbed core

2.Low Compressive Modulus

3.Moderate stiffness

4.Low longitudinal rigidity

5.Knitted sock filter

Drainage Core

Properties Megaflo 170mm 100 dia. CL 1000 pipe Core size 40 x 170mm 100mm dia. Core Size Slot Size 2 x 25mm 1.2 x 7.4mm

Compressive Strength (5% defl) >1000 kN/m/m (mod) >1000kN/m/m Compressive Strength (horz) 200 kPa N.A.

Clear Water Opening (mm) >12000 7668

Megaflo • A14 geotextile filter wrap • Washed sand backfill • High compressive modulus

Minimum cover = 100mm • Structural Rigidity for

installation stability

• No bedding required • Exceeds class 1000 spec

Round pipe – Class 1000 • Knitted sock filter wrap • Aggregate backfill • Minimum cover = 500mm • Higher deflection under load • Requires bedding layer • Exceeds class 1000 spec

Inflow Design (research based) • Water needs to drain completely from structural

pavements

• Effective drainage can extend pavement life by over 7 years

• Geocomp Panel drains higher profile provides faster response - prevents seepage

• Panel configuration maintains velocity to prevent silting

• Washed sand backfill provides important stage 1 filter to geotextile

• Round pipe invert should be 100mm below subgrade.

Inflow Response • Research by; Dempsey - Uni of Illinois 1991

Straub - Ohio Dept Transport 1991

• Comparison of Megaflo v 100 dia. round pipe

• Asphalt pavement surface

• 1.7M 8t axle loads per year

• Megaflo drainage response 30% faster

• Joint faulting 60% less after 4 years

• Round pipe flow - lag of 1 hour

Same Road, Same Storm, Same Slope

Illinois Department of Transportation Testing

MEGAFLO® Removed 36% More Water, in Only 56% of the TimeMEGAFLO® Removed 36% More Water, in Only 56% of the Time

MEGAFLO®2380 litres

4650 litres

4” Corrugated PE1115 litres

2910 litres

After 2 hrs

After 4 hrs

OfResponse

Time

Importance

Edge Drain Moisture Profile At Time T1

Megaflo

Sresidual

% Saturation 100

De

pth

A

Edge Drain Moisture Profile At Time T1

Round Pipe

Sresidual

% Saturation 100

De

pth

Variation of Modulus with

Moisture

Mo

du

lu

s E

(M

Pa

)

Moisture Content Relative to

Optimum Moisture Content

(MC/OMC)

Basecourse &

Sub-base Soils

Soils Probably Soaked

Subgrade Soils

3.0

500

400

300

200

0.5 1.0 1.5 2.0 2.5

100

[Adapted from: Fig 17 CSIR (South Africa)

Research Report 644]

Equivalent Traffic for

Varying Subgrade Modulus

A = 5 x 106 passes

B = 1.5 x 106 passes

C = 2 x 105 passes

Eq

uiv

ale

nt

Tra

ffic

Subgrade Modulus E (MPa)

107

105

106

200 100 250

C

A

B

150

Granular Base/Subbase

Megaflo

Inflow Design

Materials - Rates of flow;

• Road Pavement; ~0.6l/min

• Road Verge; ~1.0l/min

• Washed Sand; ~40l/min

• 10mm Screenings; ~850l/min

Design pavement FOS;

Multiplier for drainage medium; 10x

Inflow Design Bernoulli’s Equation

Catchment Area – Class 1000 • Six inflow slots per two corrugations

• Two only accept vertical flow

• Catchment area 1/12 of pipe dia.

[30mm x 17mm]

Horiz. flow path is slowest flow

• Wide trench = higher catchment

• Wide trench = slower response

• Assumed bottom two slots clog with silt

Flow

30mm

Inflow Design (Bernoulli’s Equation) Catchment Area – Megaflo • Four inflow slots per corrugation

• Catchment area - 80mm long x 17mm wide [3x

that of 100 dia.]

• Narrow trench backfill = faster flow = lower hydraulic head

• Designed for 100 - 200mm wide trench

• Vertical inflow capacity > 2x round pipe

• Inflow less dependant on trench width

Inflow rates; Inflow Design using Bernoulli’s Equation

Estimated slot flows for 10mm Aggregate backfill–

Class 1000 round pipe Megaflo 170

(300 trench) (200 trench)

Vert inflow; (10/7 agg.) 0.9 l/m 2.3 l/m

Horiz inflow; (10/7 agg.) 8.0 l/m 6.8 l/m

Total 8.9 l/min 9.1 l/min

Inflow Performance per metre

• Round pipe inflow / metre;

- 300 wide trench

- 3 slots per corrugation

=16 l/min/m

• Megaflo inflow per metre;

- 200mm wide trench

- 4 slots per corrugation

=23.4 l/min/m

0

50

100

150

200

250

0 0.5 1 1.5 2

Lit

res/m

in

Grade %

Megaflo Flow Rates (Vert.)

Meg450

Meg300

Meg150

Design Exercise

Filtration

Retained backfill - exhumed sample analysis;

(US Research – Mlynarek, Bonnell, Broughton and Rollin - 1994)

- 200g Non Woven geotextile;

90% of fines retained above 90um

- 120g knitted sock;

32% of fines retained above 90um

Deflection;

AS2439 test allows for 5% deflection limit for classification Round pipe deflection classified; - Class 400 = 400kN/m/metre of pipe for 4.8mm (deflection 5%) - Class 1000 = 1000kN/m/metre pipe for 4.8mm (deflection 5%)

Geofabrics Lab Analysis;

• Round pipe deflection;

- Class 1000 (1350N to create 5mm deflection)

• Megaflo 170 deflection;

- Exceeds Class 1000 (2000N to create 8mm deflection)

Load Capacity - Megaflo

Simulated trench Loading; Kentucky test – ASTM 6244 - Loading 156kPa - Cover 100mm Megaflo = no deflection due to shape and structure Slight increase in internal area

Megaflo Installation benefits;

• Rigid stable panel

• Fast efficient installation

• Narrow width of excavation

• No requirement for bedding

• Low cost of washed sand backfill

• Low excess spoil material

• 100mm min cover

• Alternatives • Megaflo – 100 – 200mm wide trench

• Round pipe – 300mm wide trench standard

D1 D2

Granular

Fill

Geotextile

Round

Pipe

Replaced

Fill

D1

Granular

Fill

Geotextile

Sock

Megaflo

Replaced

Fill

Megaflo Cost Comparison • Trench width variables;

- 100 - 200mm wide excavation v 300mm wide

- Spoil disposal for narrower trench

- Cost of laying (savings in no trench bedding

(saving compaction time with washed sand

- Cost of backfill - Washed sand v screenings

• Megaflo cost balance;

- Megaflo cost similar to class 1000 pipe

• Overall Megaflo system savings range from 20 – 50%

• Cost comparison

Cover – Road Edge

Drainage

Specified installation cover;

(for Hwy installation)

- Megaflo 170 300mm

- Strip Drain 200 500mm

- Class 1000 500mm

Megaflo - Outlet Fittings

• Roads - Std coupling, end cap,

side and end outlets

• Connect to 100 HDPE and 110

O.D. uPVC pipe

• Upright herringbone fittings

• Flush-out and inspection point

assemblies

QA

• Manufactured to ISO 9001:2000

• NATA compliant laboratory

• Megaflo Specifications

- published Typical values

• QA certification from production QC results

Megaflo

Megaflo

Research

Roads;

• UniSA flow rates report 2009

• UniSA infiltration testing report 2011

Mining;

• Megaflo Ultra FEA report – P.B.

Thank you

Rod Fyfe

Business Development Manager

Geotextiles and Drainage

www.geofabrics.com.au