Flexible linings in Reno mattress and gabions for canals and canalized water courses

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Flexible linings

in Reno mattress and gabions

for canals and

canalized water courses

Pre face

Flexible

structures have been usedfor

some time

and with

great success in river and irrigation works,for retaining

walls,

and for the

con trol

ofunstable

areas in mountain

regions. In thefollowing

pages, af ter a briefexamination

ofthe

various

me-thods and materials generally adopted for revetting canals and canalized water courses, a study of liningsformed

with

Reno

mattress and Maccaferri gabions i

s

made.

Other brochures

dealing with the

numerous

otheruses

of the

two products

includ-ing

road

construction, river training, marine

works,

retaining

structures

and thefacing

of

earth-fill dams are

available.

In

this series ofpublications,

we propose

to illustrate

the salient

characteristics of theflexible structure

composed ofthe

Reno

mattress and

gabions

which constitute

the

basis

of our production.

At the same

time, we

wish to provide

information relating

to the behaviour of these structures

in their various fields

of application,

and thereby,

to

suggest criteriafor the selection of

material

andfor structural design.

We

hope that this

brochure

wil/ be

of help to

engineers and technicians

who are

interested

in the study

and in the design of these

works.

We also hope that it may

serve to increase

the

use

ofsuchjlexible

structures

which, we

have

no doubt, offer technical and

economie advantages

over other methods

in many situations.

We

wish

to

express

our

grateful thanks

to Prof

Dolt.

Ing. Alberto

Bizzarri,

Professor of Soil Conservation in

the

Faculty

of

Engineering,

University

of

Bologna,

for his invaluable

assistance

in the

preparation and

editing

of

this edition of the

bro-chure

published in 19

76,

and

in

the study

of

the

test

programme carried

on in Fort Collins (Colorado U.s.A.).

Bologna, January 1985

dolt.

ing. Andrea Papetti

GENERAL MANAGER

Index

Foreword _{page 9}

CHAPTER I General characteristics

1.1

Introdu

e

tion

1.2 General criteria for the design and construction of canals 1.3 Functions and characteristics of canal linings

1.4 Types of revetment page 11

»

11 » 12 »

13

CHAPTER 1I

Characteristics of f1exible Iinings of Reno mattress and gabions 2.1 Permeable, ungrouted linings

2.2 Semi permeable and impermeable linings with sand asphalt mastic

page 15

» 23

CHAPTER III

Design and calculation criteria for revetments using Reno mattress and gabions in open channels 3.1 Hydraulic calculation for open channels

3.l.l Flow equations

3.1.2 Values and selection of coefficients of rougbness for Reno mattress and gabions 3.1.3 Types of sections and their hydraulic characteristics

3.2 Dimensioning of revetments using Reno mattress and gabions 3.2.1 Experiments carried out at Fort Collins (Colorado -U.S.A.) 3.2.2 Research method

3.2.3 Revetment stability - Design criteria considering shear stresses 3.2.4 Revetment stability -Design criteria considering water velocity 3.2.5 Deformation evaluation

3.2.6 Velocity at the mattress - base soil interface - Use of filters

3.2.7 Performance of Reno mattress and gabion revetments grouted with sand asphalt mastic 3.2.8 Comparison between Reno mattress revetments and loose stone rip-rap revetments 3.2.9 Design criteria for Reno mattress and gabion revetments

3.2.10 Rapid design methods 3.3 Analysis of the safety factor

3.4 Proteetion of banks against wave action

3.4.1 Designing Reno mattress and gabion bank proteetion revetments against wave action

3.4.2 Programme of tests conducted in Grenoble, France 3.4.2.1 Research methods

3.4.2.2 Analysis of results

3.4.2.3 Comparison between Reno mattress revetments and concrete or loose stone rip-rap linings

3.4.3 Linings for navigation canals

3.5 Examples of calculations for the design of Reno mattress and gabion revetments

page 30 » 30 » 32 » 34 » 37 » 37 » 39 » 40 » 41 » 42 » 43 » 43 » 44 » 45 » 46 » 47 » 47 » 47 » 48 » 48 » 48 » 49 » 50 » 52 CHAPTERIV

Examples of completed works 4.1

Introdu

e

tion

4.2 Works carried out in dry conditions 4.3 Works carried out under water

4.4 Linings grouted with sand asphalt mastic in dry conditions 4.5 Linings grouted with sand asphalt mastic under water

page 58 » 58 » 86 » 96 » 101

6

List of tables

page 12 » 16 » 23 » 25 » 26 » 33 » 34 » 36

»

38 » 39 » 39 » 45 Table 1 - Limiting veloeities at bed level for various soils [1,2,3]

Table 2 - Standard dimensions of Reno mattress and gabions

Table 3 - lndieative thieknesses of Reno mattress and gabion revetments, as a funetion of water veloeity

[11]

Table 4 -Applieation rates of sand asphalt mast ie for eonsolidating and for sealing Reno mattress

and gabions

Table 5-lndieative thieknesses of Reno mattress and gabions treated with sand asphalt mastie, as a funetion of water veloeity [11]

Table 6 - Coeffieients of roughness

Table 7- Side slopes of unlined ehannels [30]

Table 8- Typical eanal seetions and their geometrie hydraulie properties [22]

Table 9 - Dimensions of model-scale and full-seale Reno mattress tested at Fort Collins (Colorado U .S.A.) Table 10 - Measurement taken from test n. 2on a prototype Reno mattress of 0.23 m

Table 11 - Measurement taken from test n. 4 on a model seale Reno mattress of 0.15 m

Table 12- Comparison of the thieknesses of aReno mattress revetment and an alternative loose stone revetment for eertain hydraulie eonditions occurring during the tests at Fort Collins (Colorado U.s.A.)

Foreword

The intention ofthis man uaI istogive basic information and to study some new criteria which has been evolved for the de-sign ofgabion and Reno mattress linings for open channels and canalized waterways.

Recently, tests to full and model scales have been made bythe undermentioned bodies:

- Hydraulic Laboratory Engineering Research Center, Colo-rado State University (Fort Collins - USA)

- Sogreah Ingenieurs Conseils (Grenoble -France) - Delft Hydraulics Laboratory (Netherlands)

The results of the tests and the interpretation ofthem to for-mulate anew approach todesign are discussed in the following pages. Officine Maccaferri S.p.A. consider that the information

given will simplify the work ofengineers involved in the design of gabion linings and their confidence inthe material which, as is weil known, isbeing increasingly used throughout the world.

The major problems encountered in channel design and their solutions are outlined in anumber of actual examples of completed schemes. Construction techniques which will be of interest to contractors are also described.

For a fuller and detailed study of the subject, the reader should refer to the publications and papers listed in the biblio-graphy, At the same time, Officine Maccaferri S.p.A. will be pleased to give assistance in fïnding a solution to any specific problem bymaking available the experience ithas acquired over the last century.

CHAPTERI

General characteristics

1.1 Introduetion

The term "canal" is usually understood to mean an open arti-ficial channel that permits the free flow ofwater. Common uses are for irrigation, drainage, navigation, hydro-electric power and water supply.

This manual deals only with the types of revetment used in canals and canalized water courses.

It does not cover any form of construction concerned with tun-nels or closed conduits.

1.2 General criteria for the design

and construction of canals

In the planning of a canal the numerous elements of design which have to be considered vary in nature according to its pur-pose. The basic and most important ones are the alignment,

longitudinal gradients and, inter-dependent on these, the shape and dimensions of the cross sections.

The course of a canal consists of straight stretches connected by curves.

The choice of route between given upstream and down-stream points must necessarily take into account intervening features such as built-up areas, railways and roads, natural and artificial water courses, ground liable to subsidence, broken terrain or unsuitable soil.

If such obstacles cannot be avoided or if a detour is too long, special works (e.g., inverted syphons, bridges, pumping sta-tions) will be needed, at extra cost, to overcome them.

Canals are either excavated or built above ground with their beds contained between embankments. The cross section is usually trapezoidal, with or without berms, the side slopes de-pending primarily on the type of soil. With unlined banks, the slope can range from a minimum of 1:3 (vertical to horizontal),

for very fine non-cohesive soils to a maximum of 1:

l.5

for com-pact clay.

Canals excavated in rock can of course have vertical banks (See Table 7). Other sections which are commonly used, are circular,

triangular and rectangular. Less common ones are polygonal,

parabolic and polycentric.

Having decided on the type and dimensions of the section, and the gradient, the next step is to ensure that the mean velocity of the water remains within predetermined limits, to prevent too rapid silting from material carried in sus pension or erosion of the canal bed and banks. The lower limit, between 0.1and 0.5

mis,

is determined by the type of material carried in suspension, re-ducing with the partiele size ofthe material which may be clay,

chalk, silt or fine to coarse sand. The higher limit depends on the type of soil in the canal bed and banks. It ranges from a mi-nimum of 0.3

mis

for muddy soils to 3

mis

or more for sections excavated in rock.

Chapter 111 sets out the formulae usually employed in de-signing canals, and contains tables from which the most econo-mical dimensions can be extracted. The reader should refer to that chapter and to the references it cites, for further informa-tion on the design criteria.

1.3 Functions and characteristics

of canal linings

A

linin

g o

n th

e

b

e

d

a

nd/or

o

n th

e s

id

es o

f

a ca

n

a

l

has a

num-b

e

l' o

f e

ffe

c

t

s

,

a

m

o

n

g

th

e

m

t

h

e

f

o

llowin

g:

a)

Reduction of seepage from

or into the canal.

Th

e

probl

e

m

s

of limitin

g

w

a

t

e

r lo

ss ass

um

es g

r

ea

t

irnpor

-t

a

nce wh

e

n w

a

t

e

r i

s s

hort or wh

e

n it is

e

xp

e

n

s

iv

e

to bring it t

o

th

e

c

a

n

a

l

.

Th

e ex

tr

a

co

s

t of

a

r

e

v

e

tm

e

nt

to mi nimi

se

th

e

lo

sses

i

s

th

e

n

c

omp

e

n

sa

t

e

d

.

Simil

a

rl

y,

infilt

ra

tion

into

a

dr

a

in

a

ge or

irri

ga

ti

o

n

ca

n

a

l

ca

n b

e a se

riou

s

probl

e

m;

but

,

a

g

a

in

,

th

e

addi

-tional co

s

t of rev

e

tm

e

nt can b

e

balanc

e

d b

y sa

vings in

e

xcava-tion

, as

th

e ca

n

a

l

,

b

e

ing dim

e

nsion

e

d

to

ca

rr

y a s

m

a

ll

e

r flow

,

h

as a s

m

a

ll

e

r

c

r

oss sec

tion

.

Ho

weve

r

, i

n mo

s

t

cases

it i

s

di

f

fi

c

ult to

es

tim

a

t

e

th

e

d

eg

r

ee

of

see

p

age

thr

o

u

g

h th

e

b

e

d

a

nd b

a

nk

s,

wh

e

th

e

r th

ey a

r

e

r

eve

tt

e

d

o

r not.

A co

m

pa

ri

s

on

of

th

e c

o

s

t

s

ofth

e

v

a

riou

s

po

ssi

bl

e

r

e

m

e-di

es

i

s a

l

so f

r

a

u

g

ht with un

ce

rt

a

in

ty.

S

om

et

im

es

,

a ca

n

a

l i

s ex

c

ava

t

e

d without pro

v

i

si

on

fo

r

i

t

s

r

e-ve

tm

e

nt but

a

linin

g

i

s a

dded

s

ub

se

qu

e

ntl

y

when m

eas

urabl

e

l

oss

of w

a

t

er

h

as

b

ec

om

e a

pp

a

r

e

nt. Su

c

h

a

proc

e

dur

e

h

a

s it

s

d

raw

b

ac

k

s

.

Initi

a

ll

y,

th

e c

an

a

l f

a

il

s

to op

e

r

a

t

e a

t full c

a

p

a

cit

y:

late

r th

e c

r

oss sec

ti

o

n m

ay

h

a

v

e

to b

e c

h

a

n

ge

d t

o o

n

e

whi

c

h

wh

e

n r

e

v

e

tt

e

d will

ca

rr

y

th

e

d

es

i

g

n

e

d flow

.

Thi

s a

dd

s g

r

ea

tl

y

t

o

th

e

fin

a

l

cos

t

a

nd d

e

l

ay

s th

e e

ffici

e

nt op

e

r

a

tion of th

e c

an

a

l.

It

is th

e

r

efo

r

e a

dvi

sa

bl

e

to m

a

k

e a

thorou

g

h

s

oil

s

ur

vey

ofth

e

gro

und tr

ave

r

se

d b

y

th

e ca

n

a

l

b

e

for

e

h

a

nd

a

nd pl

a

n for

a

n

y

r

e

-v

e

t

t

in

g

th

a

t m

ay

b

e

r

e

quir

e

d in th

e

d

es

i

g

n

s

t

age.

b) Stabili

s

ation of the

banks.

A

r

eve

trn

e

nt

,

or linin

g,

is u

s

u

a

ll

y

onl

y s

uppo

r

t

e

d b

y

th

e

b

a

nk

,

bu

t

m

ay o

n o

cca

sion

s

function

as a

ret

a

inin

g s

tru

c

tur

e

.lts

us

e

e

n

a

bl

es

th

e s

lop

e

o

f

th

e

b

a

nk to b

e

incr

ease

d. Th

e a

d

va

nt

age

i

s

p

ar

ti

c

ul

ar

l

y

m

a

r

ke

d in th

e case o

f

ca

n

a

l

s

in wh

ic

h th

e water

l

e

-Table

1

-

Limiting veloeities at bed level for various soils [1

, 2, 3

]

.

ve

l v

a

r

ies, excava

t

e

d in soil

s

with

a

pr

eva

iling

c

l

ay co

nt

e

nt.

C

h

a

n

ges

in th

e

w

a

t

e

r

c

ont

e

nt

o

fth

e so

il

s a

lt

e

rn

a

tin

g

b

e

tw

ee

n

v

e

r

y

dr

y a

nd s

a

tur

a

tion

,

l

ea

d to fi

s

surin

g

ofth

e s

lop

es a

nd th

e-r

e

b

y

d

ec

r

ease

d

s

t

a

bilit

y a

nd imp

e

rm

ea

bilit

y.

T

o co

unt

e

r

t

hi

s

te

nd

e

n

cy,

th

e s

id

e s

l

o

p

es

mu

s

t b

e ve

r

y ge

ntI

e.

Th

e a

ddition

ofa

r

eve

tm

e

nt

e

n

a

bl

es

th

e

di

sa

d

va

nt

ages

to b

e

ov

e

r

c

om

e

,

a

nd

a

ll

o

w

s

th

e

slop

e

to b

e

in

c

r

ease

d.

H

e

r

e a

gain

,

th

e

c

o

s

t of th

e

r

e

v

e

tm

e

nt

must b

e

b

a

lan

ce

d

aga

inst th

e

re

s

ultin

g

b

e

n

e

fit

s s

u

c

h

as

r

e

du

ce

d

excava

tion

a

nd th

e s

m

a

ll

e

r t

o

p width

r

e

quir

e

d b

y

th

e ca

n

a

l owin

g

to th

e stee

p

e

r

s

id

e s

l

o

p

es

.

c)

Proteetion of the canal bed and banks

from

erosion.

Ar

eve

tm

e

nt

h

as

th

e

fun

c

ti

o

n

o

f pr

ov

idin

g

th

e

n

a

tur

a

l

s

oil

w

i

th m

ec

h

a

ni

ca

l

prot

e

etion

aga

in

st

e

r

os

i

o

n.

Th

e

pr

i

n

c

ip

a

l

c

a

u

ses ofe

ro

s

ion

a

r

e

:

a

tmo

s

ph

e

r

ic

age

nt

s: ra

in

,

w

ind

a

nd fro

s

t

;

w

a

v

es, a

nd th

e

h

y

dr

o

-d

y

n

a

mi

cs

o

f th

e c

ur

re

nt,

p

a

rti

c

ul

a

rl

y i

n

fas

t-fl

ow

in

g

c

h

a

nn

e

l

s

a

nd in

a

r

eas o

f

a

bn

o

rm

a

l

tu

r

bulen

ce

ca

u

se

d b

y

obst

a

cl

es

or th

e

un

e

v

e

nn

ess

o

n th

e

b

e

d

o

r b

a

nk

s.

In

a

rtifi

c

i

a

l ch

a

nn

e

l

s

th

e c

r

oss sec

ti

o

n i

s ca

l

c

ul

a

t

e

d

s

o th

a

t

th

e ve

lo

c

it

y

ofth

e

flow on th

e

inv

e

rt

, (

u

s

u

a

ll

y 7

0-

8

0

%

o

fm

ea

n

ve

lo

c

it

y)

do

es

not

e

x

ce

ed th

e

limit

i

n

g va

lu

e c

h

a

r

ac

t

e

ri

s

ti

c

o

f

th

e

b

e

d m

a

t

e

ri

a

l

a

t whi

c

h ero

s

ion would

occ

ur. Th

e

limitin

g

v

e

-loeiti

es

for th

e

mor

e

common t

y

p

es

of b

e

d m

a

t

e

ri

a

l

a

r

e

list

e

d in

T

a

bl

e

l. Pl

a

cing

a

r

eve

tm

e

nt on th

e

b

e

d

a

nd b

a

nk

s a

llows th

e

a

dopti

o

n of

g

r

ea

t

e

r v

e

loeiti

es a

nd r

e

du

c

tion

o

f th

e

cro

ss sec

-tion

.

N

ea

rl

y a

ll c

a

n

a

l

s a

r

e

prot

ec

t

e

d

on

s

h

a

rp

c

urv

es a

nd

a

lso on

wid

e

r

eac

h

es

whi

c

h

a

r

e s

ubj

ec

t t

o wave ac

ti

o

n

.

Pr

otec

ti

ve

r

eve

t-m

e

nt

s a

r

e a

l

s

o u

se

d

e

xt

e

n

s

iv

e

l

y

to pr

o

t

eet

th

e

b

a

nk

s a

nd b

e

d

s

of n

a

tur

a

l

w

a

t

e

r

c

our

ses s

ubj

ec

t to

e

r

os

i

o

n.

a

nd

occas

ion

a

ll

y

whol

e

f

as

t flowin

g

str

e

tch

e

s

a

r

e

c

a

n

a

li

ze

d to off

e

r

a

con

ve

ni

e

nt

a

ltern

a

tiv

e

to th

e

u

se

of d

r

op

s

tru

ct

ur

es

o

r

s

ill

s.

V

e

lo

c

it

y

in m

e

tr

es

p

e

r

sec

ond

B

e

d M

a

t

e

ri

a

l

No m

a

t

e

ri

a

l

Colloidal m

a

t

e

ri

a

l

ca

r

r

i

e

d in

s

u

s

p

e

nsion

ca

rri

e

d in

s

u

s

p

ens

ion

Fin

e sa

nd

. (

N on

-co

ll

o

id

a

l

) .

0.4

5

0

.7

5

S

a

nd

y

cl

ay

.

(

N

o

n-

co

lloid

a

l

)

0

.55

0

.7

5

Soft

c

l

ays

0.

60

0

.

90

Mud

s.

0

.75

l.05

Co

a

r

se sa

nd

0

.75

l.50

M

e

dium cl

ay

.

1.15

l.50

Gr

ave

l

1.20

l.85

Shin

g

l

e

1.

5

0

1.70

H

a

rd cl

ay

_l.8

₅

_1.85

12

d)Rough faced Iinings.

With certain materials arevetment can be expected toreduce the roughness to below that of unlined sections. Less rough-ness allows smaller sections to beused and thus brings econo-mies in excavation and in the superficial area ofthe ground oe-cupied.

In other cases, the objective isto achieve the opposite effect-i.e.to produce surfaces ofconsiderable roughness. An example isacanal which is to be constructed in steeply sloping ground. As an alternative to inserting drop structures or sills to dissip -ate the energy combined with lower gradients to reduce the ve-locity, the canal is excavated with its bed sloping parallel to the

.ground. The energy isdissipated byfriction around the wetted perimeter formed by a revetment of sufficient roughness and which is robust enough to withstand the incidental velocities.

A lined canal will also tend to maintain its designed capacity throughout its lifetime without reduction of flow capacity, whereas the growth of vegetation in an unlined canal will re-duce its capacity at a rate which increases with time.

The presence of arevetment discourages the growth of grass and anyvariations in roughness are usually due toageing ofthe revetment and not to growth of vegetation.

e)Reduction in maintenance costs.

A common maintenance operation, weed clearance, has to be carried out from time to time to prevent loss of capacity. A revetment, since it reduces or inhibits growth, permits this ope -ration to becarried out less frequently, or not at all. Moreover, mechanical weed clearance is usually simpier on revetted than on unrevetted canals.

The adoption of a lining and its selection from the many types available, is dictated by technical andeconomie considerations and by practical experience.

The problems met during design are numerous and ofa va-ried nature - problems of seepage, slope stability, erosion, maintenance and of operation, among others.

Their cornplexity, the inter-action of the various factors and the impossibility ofevaluating them econornically, make plan -ning a painstaking exercise. In seeking the optimum solution, the designer's ability and experience can be usefully supple-mented by analysis of similar existing projects.

For this reason, in the pages that follow, the most widely used types of lining are discussed, and examples of existing works illustrated.

1.4

T

y

p

es of

r

evet

m

e

n

ts

The si rnplest type of revetment is turfwhich is formed either

by sodding, or soiling and seeding. Because of its great disad-vantage of impeding the flowas it grows, it isusually only used for tlood banks or side slope proteetion above normal water le-vel. Puddled clay is still an effective method of lining and sea-ling channels flowing through permeable soils and brushwood orshingle, held in position bywire netting anchored to the bed and side slopes, are equally effective in preventing the fissuring of cohesive soils in dry conditions.

Random tipped stone iscommonly used on rivers and occa -sionally on canals. Although simpier to place, particularly un-der water by tipping, than any other systern, it is not easy to control the thickness, and wastage occurs in attempting to ob -tain the minimum requirement. As it is not bonded in any way, additional allowance has to bemade for losses caused byerosion.

Pitched stone, which is economical in material, was apopular method until the 1960's but has since become very expensive in labour. Masonry and brickwork which are also expensive be -cause of their skilled labour content are now generally only used in short lengths of proteetion adjacent to bridges and

other structures.

They, unlike tipped and pitched stone, are rigid in character and likely to rupture ifaffected by settlement.

Concrete is used inagreat many forms: in situ, mass or rein -forced; pre-cast in slabs or in interlocking blocks; in mattress form by injecting it into man-made fibre quiltings. Concrete provides a smooth surface when placed in situ or as pre-cast slabs and gives a very economical channel cross section. How-ever, this form of construction is impermeable and inflexible and should be used with caution in ground conditions which give rise to settlement or uplift. Pre-cast blocks which may be keyed so that they interlock, or joined with steel pins or ties, provide amore flexible and semi permeable lining but a roug-her surface. The injected mattress type will conform to any pro-filewhen initially placed, but is rigid thereafter. Some of these latter are semi permeable, all are usually rough faced.

Asphalt, asphaltic concrete, sand asphalt mastic grouted stone, and sand asphalt mastic are all impervious but flexible, and linings of them may be rough or smooth faced [5], [6]. Membrane linings of butyl rubber, poly-vinyl or polythene are 13

completely impermeable and flexible but onlyhave alimited life due to their lack of resistance to puncturing and to weathering.

From the variety ofmaterials mentioned above, the designer must choose one which has the qualities ofirnperrneability, ro-bustness, flexibility, roughness, durability andeconomy tosuit his requirements. With regard to the choice offlexible or rigid linings, the former have a decided advantage in that they can conform to ground movement due to settlement or heave in the invert or side slopes with no change in their effectiveness [4]. The stone filled wire mesh Reno mattress and gabion have these characteristics, and although rough faced and permeable

14

in their normal form, they can be made impervious by laying waterproof sheeting under them or impervious and smooth faced by grouting with sand asphalt mastic.

Their other advantages are that they are structurally mono-lithic, their construction does not require skilled labour and they can be placed under water in pre-fabricated sections with comparative ease.

The following chapters contain descriptions of the Reno mattress and gabions, design data for their use as channel li-nings, and a study ofthe methods employed in their construc -tion.

CHAPTER

11

Characteristics

of flexible linings

of Reno mattress

and gabions

2

.

1

P

ermeable, ungrouted

l

ini

n

gs

The stee! wire mesh box gabions and their applications are

weil known. They have been adequately described in other publications [7]; and further treatment here is superfluous. Box gabions are used for heavy retaining structures in slip contro! in mountainous areas [8] and in road construction generally [9]. They are also used for revetments of considerable thickness on rivers and canals [10].

The Reno mattress, on the other hand is specifically intended to provide a comparatively thin but highly flexible channel lin-ing which is described in detail be!ow.

a) The Reno mattress

The Reno mattress can be described as a gabion ofwhich the depth is small in proportion to its length and width. It is divided into several cells by transverse diaphragms and is fabricated from woven hexagonal steel wire netting (Figs. 1,2). The base, sides and ends are formed from one single panel of netting on which the diaphragms are fixed at 1 m centres. The lid is supplied as a separate panel of mesh. A typical assembied unit would be 6 m long by 2 m wide (Fig. 1),and divided into 6 cells. The external

edges of all the mesh panels are selvedged with wirewhose dia

-meter is about 30%greater than that used in the mesh fabric.

This selvedge wire adds structural strength to the cage and faci

-litates installation during which the units are wired together

and the lids laced down tothe sides and diaphragms (Figs. 3,4).

The steel wire used in the manufacture of the mesh is zin

c-Table 2 -

Standard

dimensions of Reno mattress and gabions.

coated to an internationally recognised standard. When the

mattress is tobe installed inconditions which are agressive t

o-wards the zinc coating the wire is additionally protected by

PVc. Technical data on the standard Reno mattress units is gi -ven in Table 2.

Zinc-coated Reno mattress Zinc-coated Reno mattress with PVC sleeve

Mesh Type Wire D_mmiameter Thickness Mesh Type Wire Thickness

m elCore mrn elExternaJ rnrn m 2.00 0.17 2.00 3.00 0.17 6 x 8 0.23 6x8 0.23 2.20 _0.30 2.20 3.20 0.30 0.15 5 x 7 2.00 0.20 0.25 Width: 2.00- 3.00 m-Length: 3.00-4.00- 5.00 -6.00 m

Zinc-coated gabions Zinc-coated gabions with PVC sleeve

Mesh Type Wire D_miameter_rn Thickness_m Mesh Type Wire Thickness

elCore mm elExternaJ mm m 10 x 12 2.70 10 x 12 2.40 3.40 3.00 2.70 3.70 0.50 2.70 _0.50 8 x 10 2.40 3.40 1.00 8 x 10 3.00 2.70 3.70 6x8 2.20 2.70 1.00 5x7 2.00 2.40 Width: 1.00- 2.00 m-Length: 2.00 -3.00 - 4.00 m far 1.00 mwide gabions; 3.00-4.00 -5.00 m for 2.00 mwide gabions

Reno rnauress and gabions aremanufactured with double-twisted hexagonal mesh made with annealed mild steel wire, zinccoaiedaccording to Circ, Cons. Sup. LL. PP. No. 2078 dd. 27.8.1962. 10BS443-1982 and tou.s.Federal Specificatien QQ-W-461 H finish S-class 3.

PVC-coated mauress are made withwire coated by extrusion with a special, highly corrosion resistant PVC. The types indicated in the table are srandards: for more detailed information, see general caralogue [7J.

b) Assembly.

The individual units are supplied folded flat to facilitate both their erection and transportation.

Before placing in position the mattress is easily assembled by

lacing the vertical edges ofthe end and diaphragm panels tothe

longitudinal sides which, asmentioned above, are integral with the base. The line on which the sides hinge upwards isclearly

indicated by a wire of larger diameter woven into the mesh

(Fig. 1).

c) Placing in position.

The units should be assembied onflat ground a short distance from their final position, firstlyfor convenience ofworking and se-condly toavoid impairing the prepared side slope orbase (Fig. 5).

16

A number of assembied units are placed in position and joined by lacing together all tbe adjoining edges. The lacing sbould be carried out by passing the binding wire continuously through each mesh in turn and making a double turn at every second mesh. It is important that this operation is effected wben tbe units are ernpty. It is difficult after they have been filled.

The joining together of the units, 'which is normal gabion construction practice, ensures that a continuous monolithic structure, and therefore one which is the most effective, is ob-tained (Figs. 6, 7).

d) Filling.

The Reno mattress is simple to fill using any mechanical plant which is suitable for the particular site conditions. As the stone size is smal!, a minimum ofmanual works is required (Figs. 8,9,10).

The filling material can be any hard, durable stone which re-sists weathering and should have aspecific gravity of not less than 2000 kg/m' (bulk density 1300 kg/m').

e)Fitting the lids.

Immediately after the mattresses have been filled the lid

pa-nels (Fig. 1) or wire rolls (Fig. 11)are wired down to the tops of

all the sides and the diaphragms

.

It

is recommended that lacing to the two long sides should be

completed first

,

followed by the two ends and the diaphragms.

The sequence of operations in the assembly and fitting of the

Reno mattress can therefore be briefly summarised as follows:

1) assembly of the mattress units;

2) placing in position and lacing together;

3) fil!ing with stone;

4) fitting the lids.

f) Reno mattress placed in situ.

It

has already been said that the advantages offered by the

Reno mattress as a channellining are that it is both flexible and

permeable.

It

is also a relatively thin lining which has no ability

to support

,

or retain, earth bebind it. Hence it is essential, when

it is placed on an earth slope, that the slope is basically stable,

and not steep enough to induce the mattress to slide down it.

Notwithstanding this restrietion it should be added that the

mattress is capable of resisting or conforming to smalllocal

fai-lures occurring underneath it.

The mattress unit should be placed with its diaphragrns lying

perpendicular to the direction in which the stone fil!ing wil!

tend to move, either under the influence of flowing water

,

or

down a slope. The purpose is to restriet as far as possible the

mi-gration ofthe stones inside the wire netting and thus to prevent

the formation ofvoids through which fine material could leach

from under the mattress. On steep slopes therefore, units

should be positioned with the diaphragms running

horizontal-ly, and on the beds offast flowing channels with them at right

angles to the current.

It

is not always expedient to follow this

rule meticulously during construction and a compromise may

have to be made

,

for example in a very small channel or in one

with steep sides and an invert less than 1 m wide all the units

would be laid with diaphragms parallel to the flow. Conversely

if the cross section has gentle side slopes

,

and the water

velo-city is high, the diaphragms would all be perpendicular to the

flow (See Figs

.

12

,

13).

One of the most vulnerable parts of a channel lining is the

upstream edge.

It

should not cause undue turbulence and it

must be sufficiently weil anchored to resist uplift and

move-ment.

One method of anchoring

,

is to lay the upstream end of the

mattress in a trench excavated in the bed and side slopes. The

downstream side ofthe trench is sloped so that the mattress lies

on a smooth vertical radius and emerges with its top flush with

the surface of the channel. The trench is backfil!ed and

com-pacted after the mattress has been laid and filled

.

Another

me-thod is to form a cut-off wall with a lx l m course of gabions

sunk in below the surfaceacrossthe sectionwith the Reno mattress

2.00-3.00m

I·

·1

18

wired down secure1y to it (Figs, 14, 15).

The growth ofvegetation has a beneficial effect in cana1s lined with Reno mattress in that the roots will bind the stone filling and further re duce any tendency in soilleaching (Figs. 16,17,

18, 19).At some stage however, it must be cleared to prevent too great a reduction in capacity, using a herbicide, (one which will

not corrode the wire netting) or mechanica1 equipment.

The soil condition

s

along the cours

e

of a canal will

v

ar

y

and

there will

a

lways be small loc

a

lised pockets of unstable

mate-rial such as soft clays

,

running sand

,

fine silts etc. The Reno

mattress alone may not be adequate as a revetment at these points

and ma

y

have to be replaced or reinforeed with 0.5 or 1.0m

t

hick

gabions on the lower part ofthe side slope and at the toe to

pro-vide sufficient support.

In the case of superficial landslides

,

it may be sufficient to

use

,

just in the areas of the bank involved

,

a 1arger heavier

ga-Fig. 14 -Stepped cut-offwall 1.00 - 2.00 m wide formed with gabions shaped on site.

Fig. 15 - Continuous gabion cut-off wall 2.00 mwide.

r---~

15

Fig. 16-17 -Reno mattress lining on the Tagliamento River, (Latisana) atthe completion of construction (1969) and 15 years after (1984).

16

Fig. 18-19 - Reno mattress lining on the Brenta River, (Padua), during construction (1971) and 13 years af ter (1984).

18 ₁₉

21

1.00m

H

1

H

.00 m

1:Gabion revetment,0.50 m thick

22,---, 23

26

bion revetment of 0.50 or 1.00 m thick

(

Figs

.

20

,

21

,

22

,

23)

.

In mountainous areas, canals constructed as part of

hydro-electric power schemes

,

or training works

,

will probabl

y

be very

fast flowing because of the steep gradients and may transport

heav

y

stones and boulders. Any lining must necessarily be of

a robust nature and the Reno mattre

s

s

,

if used

,

should b

e

reinfore

e

d and combin

e

d with g

a

bions or other suitabl

e

m

a

t

e

-rials

.

If more serious problems ha

v

e to be fac

e

d in the tr

a

ining

and proteetion works of natural wat

e

r courses with rapid current

s

c

a

rrying a l

a

rge amount of solid material

,

he

a

vi

e

r lon

g

itudin

a

l

protections and groynes are used

.

In comparison with rigid or semi-rigid structures or loos

e

stone linings

,

R

e

no m

a

ttress rev

e

tm

e

nts h

a

v

e

th

e

ad

va

nt

ag

e o

f

flexibilit

y

in situ

a

tion

s

wh

e

r

e

s

e

ttling

a

nd ero

s

ion

o

f th

e

b

a

s

e

material are expected

(

Figs

.

24

,

25

,

26

,

27

,

28

).

g) Placing under water.

The more traditional methods of carrying out protective

works under water are: sheet piling, random tipping of stone

'and by

sinking fascine mattresses. The first can o

n

ly be

u

sed for

bank protection

,

the second is difficult to control and is

waste-f

u

l in materia

l

and t

h

e thir

d

requires a

p

lentif

ul

s

u

pp

l

y ofwattle

a

nd

of

l

a

b

o

u

r to c

u

t it a

n

d to fa

br

icate it into a mattress.

Using simp

l

e pontoons, or pontoon rafts fttted with tilting

platforms or lifting gear

,

pre-fi

ll

e

d R

eno mattress units ofup to

10 m x 10 m in size can

b

e place

d

accurately

u

nder wa

t

er on to

the

b

eds and side slopes of canals or rivers (Fig

.

29) [14,15, 16,

17]

.

As the

u

nits are assem

b

Ied and then fiUe

d

mechanica

ll

y on

a level surface on the pontoons, the pre-fabricat

i

on is fast and

simple

.

The operation of positioning the units requires no

more specialised equipment no

r

skill than that nee

d

ed for

nor-mal underwater work. The method has proved to be effective

and economical, and has been a

d

opted for a variety of

u

n

d

er-water proteetion schemes.

D

etai

l

s of typical

operations and of

the equipment can be fo

un

d in Chapter

I

V section 4.3 where

examples of comp

l

eted works are treated.

h

)

Acc

e

ptabl

e

h

y

draulic condition

s

for R

e

no mattre

ss

and gabion

r

ev

etment

s

.

Th

e

stability of

R

eno mattress linings depends on the thick

-ness of the structure

,

the s

i

ze of the stone fill and the robust

-ness of the wire netting.

Assuming the

"

average velocity

"

of the flow as being

repre-sentative ofthe stresses acting on the

l

ining, the c

h

oice ofthose

three design parameters is easi

l

y obtained from the figures va

-lid for Froude number

:s

1.5 in Tab

l

e No. 3 and from the

graphs in Fig. 61 in Chapter lIl.

In Table No

.

3

, "

critical velocity

"

can be defined as the

maxi-mum velocity at which no movement ofthe filling material will

occur. The term ''Limit Velocity" is used to

d

enote the velocity

at which modest deformation of the mattress has occurred due

to movement ofthe fill material and which does not materially

affect the discharge capacity.

An analytical procedure for the design of Reno mattress

li-nings is described in Chapter IIl.

The guide and values given in Ta

b

le No

.

3 for design pur

-poses are compile

d

f

r

om the resu

l

ts of tests conducted in 1982

-83

b

y the Hydra

ul

ics La

b

oratory of the Engineering

R

esearch

Centre of Colora

d

o State University

i

n Fort Collins, U.S.A

.

This researc

h

has also quantified the advantages that derive

fro

m

containment ofthe fi

ll

material by mesh when compared

with

l

oose rip rap protection.

It

has been shown that Reno mattress linings have double the

stability of rip rap of the stone grading against bed tractions.

Furthermore, it was verified that, for a given

velocity of flow

,

the Reno mattress needs only be 1/3 to 1/4 as thick as a rip rap

lining.

Table 3 - Indicative thicknesses of Reno mattress and gabion revetments [11].

Rock Fill _{Critical Limit}

Type Thickness velocity velocity

m Size dso

_mis

_mis

mm

m

7

0 - 100

0.085

3

.5

4

.

2

0.1

5

- 0

.

17

7

0 - 150

0

.

110

4

.

2

4.5

7

0 - 100

0

.

085

3

.6

5

.

5

R

e

no m

a

tt

ress

0.23 - 0.2

5

7

0 - 150

0.120

4.5

6.1

7

0 - 120

0

.

100

4

.

2

5

.

5

0.30

100 - 150

0

.

125

5

.

0

6.4

100 - 200

0

.

150

5

.

8

7.

6

G

a

bion

s

0

.

50

120

-

250

0

.

190

6.4

8.0

Where th

e r

e

v

etment

has

to b

e

pl

a

c

e

d unde

r

w

a

t

e

r the

thick-n

es

s of th

e

R

e

no m

a

ttr

ess

remain

s

the

s

am

e

since it

ca

n be

launch

e

d from

a

pontoo

n whe

r

e

as rip

r

ap h

a

s to b

e

incre

a

sed b

y

50

%

[12

,

13

,

4

9,

50

,

51]

.

The b

ig

reduction in the revetment thickn

ess,

which is

achieved usin

g

Reno mattress instead of r

i

p

r

ap

,

i

s of economie

significane

e

in prote

e

tion project

s

in l

a

r

g

e ri

ve

rs

,

g

iv

en th

e

s

a

me

a

rea

of

w

ork

, a

nd

,

th

e

r

e

fore

,

th

e

qu

a

nt

i

t

y

of mat

e

ri

a

l used

.

2.2

S

emi permea

bl

e and impermea

b

le linings

with sand aspha

l

t mastic

.

a) Gene

r

a

l

characteristics of san

d

asp

ha

lt m

a

stic g

r

oute

d R

e

n

o

mattress.

The combin

a

t

i

on ofthe

s

ton

e

filled R

e

no m

a

ttr

es

s

a

nd s

a

nd

as

phalt masti

c

h

as

th

e c

har

a

ct

er

istics of both gab

i

on work and

a

sph

a

lt concret

e

. Th

e a

ddit

i

on o

f

bituminous m

as

ti

c

to th

e

R

e

no m

a

ttr

ess

produ

ce

s

a s

tru

c

tur

e w

hich

c

ombin

e

s the pro

-perti

es a

nd p

e

rfo

r

man

ce

o

f

both m

a

t

e

ri

a

I

s.

Th

e

m

a

ttr

ess

r

e

-t

a

in

s

it

s

fl

e

xib

i

lit

y,

while th

e

d

e

n

si

ty o

f

th

e

filling i

s

in

crea

sed

a

nd th

e

r

ef

or

e

th

e

efficienc

y

of th

e

prot

e

ction

.

If

a

ll th

e

voids

b

e

twe

e

n th

e s

ton

e

s in the la

ye

r

a

r

e

fill

e

d and th

e

surface of th

e

m

a

ttres

s co

v

e

red

,

th

e

linin

g

will b

e

compl

e

tel

y

imp

e

rviou

s.

The masti

c a

lso p

r

ot

e

ct

s

the w

i

r

e

m

es

h

agai

nst

c

orrosion

a

nd

from

a

bra

s

ion b

y

tr

a

nsported m

a

t

e

rial.

Th

e

wi

re

mesh r

e

info

r

e

e

s the

g

rout

e

d ston

e

l

a

y

e

r

a

nd

g

i

ves

i

t

str

e

ngth in t

e

n

s

ion

.

H

e

nce

,

th

e

thi

c

kn

e

ss of th

e

combin

e

d

s

tructure

c

an b

e

con

s

id

e

r

a

bl

y

less th

a

n th

a

t of ordinar

y

m

as

t

i

c

grout

e

d

s

ton

e

to withstand the

sa

m

e s

tre

sses

. Th

e

r

es

ulting

s

a

ving in bitum

e

n

a

nd ag

g

r

e

gate

,

and th

e

in

c

r

ea

s

e

d tlexibilit

y

du

e

to the

re

duced thicknes

s,

hav

e

gi

v

en ri

s

e to

e

xten

s

i

ve

u

se

of this t

y

pe of linin

g

for proteetion in

a va

ri

e

t

y

of w

a

t

e

rwa

y

s.

b

) Mix

d

esign of s

and

as

ph

alt mastic.

To

av

oid excessive det

a

il

,

onl

y

th

e

fund

a

m

e

nt

a

l d

ata

on mi

x

design i

s g

i

ve

n h

e

r

e.

For full

e

r inform

a

tion

,

r

ef

er

e

n

c

e

s

hould

be made to th

e

specific publi

ca

tion

s

li

s

t

e

d in th

e

bibl

i

ograph

y

[

5,

6]

.

Sand asphalt mastic is cornposed of sand, a filter and bitu-men, the proportions of which will vary according to the parti-cular purpose and conditions for which

th

e

mattress

i

s

int

e

n-d

e

d.

Generally,

proportion

s

ar

e

within th

e

lirnits

s

hown in th

e

T

a

ble b

e

l ow.

C

on

st

i tu

e

nt

s

In the dry

_{Under water}

-

Sand 0 to

3

mm

_{66 to 73}

_%

_{by mass}

_{65 to 75}

_%

_{by mass}

10 to 15

%

by rnass

-

Fill

e

r

_{12 to 16}

_%

_by

mass

15 to 20

%

by ma ss

-

Bitum

e

n

_{15 to}

₁

₈

_%

_b

_y

_rnass

Th

e

sa

nd

s

h

o

uld b

e a

n

g

ul

a

r

,

it mu

s

t b

e

cl

e

an

a

nd fr

ee

of

a

n

y

ex

t

ra

n

eo

u

s

m

ate

riaI

s.

Th

e

fill

e

r

ca

n b

e

h

y

dr

a

t

e

d lim

e,

portland

ce

m

e

nt

o

r

as

ph

a

lti

c

fill

e

r

;

it mus

t

b

e

fin

e e

nou

g

h to p

a

ss

com-p

l

e

t

e

l

y

th

ro

u

g

h

a

n A

.

S.T

.

M

.*

n.

80

se

iv

e

a

nd to pass

a

t le

a

st 80

%

of

i

ts

bul

k

through

a

n A

.

S.T

.

M

.

n

.

200 seiv

e.

T

h

e s

p

ec

i

fica

ti

o

ns

for th

e

bitum

e

n

a

r

e as

follows:

-

F

or a

p

p

licati

o

n

in th

e

dr

y

B

40/50

,

B 60170

or B 801100 [as per C.N

.

R

**

-

A.S.T

.

M

.

specificat

i

ons

]

-

Fo

r

a

p

p

li

ca

ti

o

n

und

e

r w

a

t

e

r to

a

d

e

pth

g

r

ea

t

e

r than 2

.

00 m

-

For

ap

pli

ca

t

io

n

under w

a

t

e

r to

a

d

e

pth of 2.00 m

B 80/100 or B

1201200

[as per C.N

.

R. - A.S.T

.

M

.

specifications]

B 1801200

[as per C.N.R

.

- A

.

S.T.M

.

spec

i

fications]

T

h

e

mastic

i

s

mi

xe

d

a

nd pl

ace

d hot. Application

tempera

-t

u

res

are

g

i

ve

n b

e

l ow

.

*A.S.T.M. -American Society Ior Testing Matcrials.

** C.N.R. - National Council lorResearch.

- F

or

a

p

p

li

ca

ti

o

n

in th

e

dr

y

with

-

For

a

ppl

ic

ation

und

e

r w

a

t

e

r to

a

depth of 2

.

00 m

,

with

-

For

a

ppli

ca

tion und

e

r w

a

ter to a depth

g

r

e

ater th

a

n 2

.

00 m

,

with

B 40/50 pen bitum

e

n

160 to 180

°

C

B

60170

pen bitum

e

n

155 to 175

°

C

B 80/100 pen bitumen

150 to 170

°

C

B 80/100 p

e

n bitum

e

n

140 to 160

°

C

B

180/200 pen bitumen

130 to 150

°

C

B

1801200

pen bitumen

110 to 140

°

C

c) Reno mattress revetments grouted and sealed with sandasphalt mastic.

Th

e

n

ecessa

r

y a

pplic

a

tion r

a

t

e o

f

sa

nd

a

sph

a

lt m

a

stic will d

e-p

e

nd upon

the

d

es

i

re

d r

es

ult

s.

Th

e

rnastic

ca

n b

e

applied

to th

e

stone filled mattr

e

ss to

eli-min

a

r

e

th

e

p

e

rm

e

abilit

y

cornpl

e

t

e

l

y

or m

e

r

e

ly r

e

duc

e

it.ln the

l

a

tt

e

r c

a

se

,

th

e a

rnount of rn

a

sti

c

should onl

y

bind the ston

e

to-g

e

th

e

r and allow th

e

mattr

e

s

s

to

deforrn

a

nd to r

e

tain

sorne

of

it

s

perrneability

(

Fig

.

30

).

Althou

g

h

this proc

e

dur

e

r

e

duces th

e

perrneability,

it

in-cre

a

s

es

th

e s

t

a

bilit

y

of th

e s

ton

e

fill and th

e

proteetion of the

24

soil b

a

se

.

High

e

r resistance to shear stresses and wave action,

plus

a

reduction in the thickness of the mattress also result.

To obtain compl

e

t

e

imp

e

rrneability

,

the mastic must entirely

penetrate and fill

the

int

e

rstices betw

e

en the stones for the fu

ll

depth ofthe mattress and cover the wire mesh lid by 20 to 30

mrn

(Fig. 31).

Irnperrneable Reno mattress provides one ofthe most effective

linings

a

vailable

,

and

i

ts characteristics offlexibility, impermeabil

-ity and structural strength provided by the wire mesh are superior

to any cornparable product.

I

nstallation and maintenance costs are

also compar

a

tively lower.