Proprietary Trench Support Systems

Licensed copy:SHARON SMITH, 20/01/2014, Uncontrolled Copy, © CIRIA

TECHNICAL NOTE 95 (Third edition, fully revised)

PROPRIETARY TRENCH SUPPORT SYSTEMS

E B Mackay DIC CEng MICE

Price £10 (£3 to CIRIA members)

ISBN 0 86017 264 3 ISSN 0305 1781

€) CIRIA 1986

CONSTRUCTION INDUSTRY RESEARCH AND INFORMATION ASSOCIATION

6 Storey's Gate Westminster London SW1P 3AU Telephone 01-222 8891


The research project leading to this Technical Note was carried out under contract to CIRLA by Tarmac Construction Limited, where Mr Mackay is Senior Geotechnical Engineer in the Central Engineering Department.

The Technical Note was prepared with the help and guidance of the project Steering Group. In addition to Mr Mackay, the Group comprised:

H H Potter MA CEng MICE MIHT (Chairman)

D J Irvine BSc(Eng) CEng FICE

F Lane

D S Large BScTech CEng MICE

DEPhillips

P B Rumsey BSc(Eng) MSc(Eng) DIC CEng MICE

Construction Industry Training Board

Tarmac Construction Limited

Sir Robert McAlpine & Sons Limited

North West Water Authority

Shorco Trench Systems Limited

WRc Engineering

A R McAvoy BSc CEng MICE was CIRIA's Research Manager for the project.

The project was financed by the Department of Environment and CIRIA.

This Technical Note replaces the second edition of CIRIA Technical Note 95 published in 1982.

2


CONTENTS

List of Tables Summary

1. Introduction

2. General considerations 2.1 Battered trenches 2.2 Vertically cut trenches 2.3 Groundwater control 2.4 Restrictions on use of proprietary 2.5 Design criteria and testing

3. Types and choice of proprietary support

4. Hydraulic frames

5. Shores

6. Boxes

7. Slide rail systems

8. Shields

9. Piling frames

LIST OF TABLES

Table 1 Details of waling frames

Table 2 Details of manhole braces

Table 3 Details of shores

Table 4 Details of boxes

Table 5 Details of slide rail systems

Table 6 Details of shields

Table 7 Details of piling frames

Table 8 Suppliers and agents - addresses systems available

3

Page

3 4

5

6 6 6 7

systems 7 7

9

10

14

16

18

20

22

12

13

15

17

19

21

24

and 25


SUMMARY

Proprietary trench support systems available and in use in UK have been surveyed and assessed for this new edition of CIRIA Technical Note 95. There is now more familiarity with and use of proprietary systems. This has encouraged continued development and preferences are now easier to discern. Where ground support is essential, trench sheeting or piling is still the most flexible and widely used support but it is now often combined with proprietary piling frames and/or a hydraulic strut and waling systems. In open ground, where ground movement may be permitted, proprietary systems are primarily used to protect personnel rather than to give positive support to the ground.

4


1. INTRODUCTION

An increasing amount of trench support is being provided by proprietary trench support systems. In 1984, for example, 50% of respondents to a CIRIA questionnaire had used proprietary systems compared with 20% in 1978.

The reasons for this trend include the following:

• The spacings of struts and walings in traditional timbering limit the use of excavators and the pipe lengths which can be installed.

• The lack of operatives skilled in traditional timbering.

• The higher productivity possible with the reduced number of support components coupled with machine handling.

• The lower risk to operatives because the support is simpler and, usually, safer to install.

Traditional timbering is now seldom used, having been superseded by the combination of steel trench sheets or sheet piles, timber or metal walings and proprietary trench struts. Now, these are being displaced to an increasing extent by the proprietary systems described in this Technical Note.

5


2. GENERAL CONSIDERATIONS

2.1 Battered trenches

Battered trenches are usually cheap and quick to excavate in open ground. Guidance on temporary safe slopes is given in CIRIA Report 97(1). Appropriate proprietary equipment can be used in battered trenches primarily to protect personnel. Such protection would be particularly useful where:

• the safe temporary slope of the ground is difficult to determine or is unusually shallow.

• the ground may become unsafe if any delay occurs (eg. in clay soils).

• the slope employed is generally stable but there are odd pockets of less stable ground.

If the safe temporary slope is difficult to determine or unusually shallow, it may be economic to:

• find, by trial excavation, an angle of slope that is generally stable for the time required to complete the permanent works.

• provide proprietary trench support equipment to protect personnel against the worst possible failure of the side slopes (bear in mind that this is likely to be a failure of one side only) •

2.2 Vertically cut trenches

Where the overall working space is restricted, particularly in urban areas, the trench faces will usually have to be vertical. The effect of the Construction Regulations(2) is to require trenches over 1.2 m in depth to be supported unless the trench is in stable ground.

1. IRVINE, D.J. and SMITH, R.J.H. Trenching practice CIRIA Report 97, LONDON, 1983

2. Construction (General Provisions) Regulations 1961 Part IV Excavations Shafts and tunnels HMSO London

6


A survey of trench collapses(3) emphasised the dangers of omitting or providing inadequate trench support. In ground that will stand vertically for a reasonable time trenches less than 1.2 m deep need not be supported provided the conditions of working are otherwise safe.

General guidance on trenching is given in CIRIA Report 97, Trenching Practice. Guidance on the use of timber in excavations not exceeding 6 m deep is given in a TRADA publication(4), although the use of timber is now generally confined to small works, especially short trenches and shafts for repairs to services. Support for trenches over 6 m deep requires careful evaluation of the characteristics of the ground, calculation of the ground pressures(5) and design of the support by an experienced temporary works designer. Deep trenches, particularly those over 6 m, are costly to construct and it may prove more economic to consider alternatives to trenching such as tunnelling, pipe-jacking or other trenchless methods.

2.3 Groundwater control

Many excavations, including both open cut and vertical cut trenches, go below groundwater level and require some form of groundwater control to keep the excavation stable and/or permit installation of the permanent works in the dry.

3. THOMPSON, L.J. and TANENBAUM, R.J. Survey of construction related trench cave-ins American Society of Civil Engineers, Journal of the Construction Division September 1977, Vol. 193, No C03, pp 501-512.

4. TIMBER RESEARCH AND DEVELOPMENT ASSOCIATION Timber in excavations TRADA, High Wycombe, 2nd Edition 1984.

5. TERZAGHI, K and PECK, R.B. Soil mechanics in engineering practice John Wiley and Sons, New York, 1967.

7

I

I t I I 1\·· t I \ \ .lj .J:~I\ / / " \ ""\ '-.. ~ / 1\ \ '-.-' / I Flrw \. ,, ___ ~" J. \ ' ..... __ / /. !il1lS

'- ,/ , ,/

' ......... _-----" ' .... _-.-,,,""'"


CIRIA Report 113, London, 1986. Brief guidance on groundwater control is given in CIRIA Report 97 (see p.6) and more detailed advice is provided in CIRIA Report 113 (6).

2.4 Restrictions on use of proprietary systems

There are restrictions on the use of some proprietary systems. These include the presence of crossing services and the insistence of some engineers that trench sheets or sheet piles be used. These engineers are concerned about excessive ground movement that can damage roads, nearby buildings and services crossing or adjacent to the trench. Some proprietary trench support systems aim to take account of these restrictions.

2.5 Design criteria and testing

Manufacturers and suppliers now supply more data on the load capacities of their products than was the case in 1978. Such data is based on theoretical analyses often checked by test loading of components or even whole systems, or else proven by field use. However, there are no international standards and frequently no national standards defining such tests, therefore the results are not strictly comparable.

Theoretical analyses can vary, for instance, from elastic analyses using permissible stresses or characteristic strengths, to computer stress analyses using yield stresses. The results of such theoretical analyses can indicate widely differing 'Factors of Safety' for the same support structure. Confusion arises where some manufacturers and suppliers allow for soil/structure interaction in assessing the capacity of their systems; this introduces the many variables of ground conditions and earth pressure theories.

The potential user,of any proprietary support system should therefore not accept stated load capacities uncritically.

6. SOMERVILLE, S.H. Control of groundwater for temporary works CIRIA Report 113, London, 1986.

8

5f,wi~iliRj of pilHt fouu4diur.1 ""'!9 hie ~ "!I_~"UM' _.~fflt".


3. TYPES AND CHOICE OF PROPRIETARY SUPPORT

The systems included in this review have been limited to those that:

• are available in the UK for sale or hire; and

• can provide trench support before any person enters the trench.

This Technical Note describes each generic type of proprietary trench support system, summarises the advantages and disadvantages and lists details of specific products. The generic types of system are:

1. Hydraulic frames (primarily waling frames and manhole braces)

2. Shores 3. Boxes 4. Slide rail systems s. Shields 6. Piling frames. (Illustrated on p.22)

When selecting a proprietary system, the range of choice may be narrowed and thereby made easier by considering the following questions:

• Can the trench sides be cut to steep slopes? (Protection rather than support is needed)

• Is there a high density of crossing services? (An easily adjusted system will be necessary)

• Will the system be required to restrict ground movement as well as provide a safe working environment?

• Is the ground such that support must be installed ahead of excavation?

• For pipe laying operations, what are the pipe lengths and diameters to be used and the testing requirements?

• Do the circumstances and extent of the job in hand justify obtaining purposemade rather than standard equipment?

Before a product is finally selected for the particular job, reference to the suppliers is advisable, because the range and availability of systems continues to expand.

9

1

2

3

4

5


4. HYDRAULIC FRAMES

Hydraulic frames are constructed of structural sections attached to hydraulic struts and include:

• waling frames • manhole braces

The systems can be installed without anyone entering the excavation. Light weight frames employ aluminium alloy.

Waling frames

Proprietary waling frames are used in conjunction with trench sheets as a substitute for traditional timbering. Gaps may be left between trench sheets to accommodate crossing services. If pipes are to be machine-handled the clear distance between the hydraulic struts should be not less than the pipe length.

The sequence of installation in ground with an adequate 'stand up' time is:

• Excavate trench to full depth over short length

• Place leading and trailing trench sheets and toe them in (1).

• Connect pump to hydraulic struts. • Lower complete frame into trench. • Pressurise struts and remove hydraulic

hoses (2). • Install further frames as required (3). • Install in-fill trench sheets. • Support frames by hangers/puncheons. • Insert timber wedges between frames and

sheets as necessary.

Alternatively, in ground that will not 'stand up' (or where support must be installed ahead of excavation):

• Excavate to sufficient depth for top frame and install (struts closed)

• Place trench sheets and push well in • Pressurise struts of top frame • Excavate to next frame level, position

frame and pressurise struts • Push sheets down and install further

frames as depth requires • Install hangers or puncheons and wedges

Note: A CIRIA Video 'Trenching - good practice' illustrates a method of 'leap-frogging' the lower frame(s) from a completed section of trench to a section being excavated.

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Manhole braces

Hydraulic manhole braces are telescopic box sections arranged in a frame with two-way jacking and provide waling frames for small coffer dams, particularly for manhole shafts.

Sequence of construction: Even in ground with adequate 'stand-up' time, it may not be possible to excavate to full depth and keep all four faces trim and vertical. Therefore it may be better always to adopt the method used for hydraulic walings in ground that will not 'stand up'. (see above). When setting out the excavation, check that the clear inside plan dimensions of installed braces will be sufficient for closed-up braces to pass through.

Advantages • Majority of support installed from

ground level, minimising risk to operatives.

• Can be used in soils which require support before excavation.

• Lightweight (aluminium alloy) struts and walings allow manhandling.

• Speed of operation • Can be used with a wide range of

sheets. • Can be adapted to service crossings. • Wide range of trench depths and widths

catered for. • All frames, lightweight or otherwise,

are suited to machine handling. • Hydraulic struts, being less stiff than

solid timber or metal struts, can relieve any build-up of ground pressure.

• Positive connection of struts to walings.

• High load-capacity walings allow greater distances between struts and hence longer pipe lengths.

Disadvantages • Cost compared with traditional separate

walings and struts. • Ensuring loading is within

manufacturer's recommendations. • Skilled maintenance and servicing

required.

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'lBble 1: Deta1ls of ~ u-

FraDe FraDe ~m1t M9x1nun Strut

~ length breadth handling wt pipe length S\oL (m) (m) (kg) (m) (kN)

GCN Kwikfonn 2.4 0.53 to 2.06 62 to 781< 1.9 105 3.6 85 to 117 1.4 to 3.1* 105 4.8 100 to 140" 2.0 to 4.3* 105

(LF 1.5)

~ 3.0 0.60 to 4.50 90 to 180 Governed ~ 86 (~ ooly) 4.0 frame and 86

5.0 strut 86 arrangeuent (LF=2)

Mabey Hire: Ahmlniun 3.4 0.66 to 4.9 94 to 150 3.0 1SO

5.0 130 to 210 2.3 to 3.5 150

Steel 3.4 0.66 to 4.90 270 to 360 3.0 150 5.0 400 to 530 2.3 to 3.5 1SO

Mechplant: A Series 2.44 0.56 to 4.50 51 to 260 1.8 57 to 74

3.66 3.0 (LF 2) 4.88 2.0

E Series 4.2 0.56 to 4.SO 95 to 360 3.2 74 6.1 2.0 to 5.5 57 to 74

(LF 2)

M:;F 3.5 0.60 to 4.6 90 to 180 Go'lerned ~ 86 (Kri~ type) 5.0 frane and strut 86

arrangenent (LF=2)

&;B 2.0 0.60 to 2.40 66 to 87 1.5 86 3.0 (up to 5 m 90 to 111 2.5 86 3.S usi~ standard 102 to 124 3.0 86 5.0 cylinder and 144 to 179 2.2 to 2.85 86

M<2 soldiers) (LF=3)

ihorco: AluniniUD 3.0 0.55 to 5.20 80 to 240 2.45 60 to 150

4.0 100 to 260 3.3 (LF=1.7) 5.0 135 to 370 2.10 (3 struts)

4.26 (2 struts)

Steel 5.0 0.75 to 5.4 468 to 628 4.7 to 3.1* 60 to 1SO

SpeEd Shore: Standard 2.44 0.56 to 4.26 53 to 141 1.98 89 to 111

3.66 74 to 161 3.20 (LF=1.25) 4.88 100 to 231 2.20

lfavy D.1ty 3.66 1.30 to 9.00 170 to 1000 3.2 190 4.88 2.2 (3 struts) 190

4.4 (2 struts) 190 (LF=1.25)

Vibroplant 3.0 0.55 to 5.20 80 to 240 2.45 60 to ISO (ihorpak) 4.0 100 to 260 3.3 (LF=1.7)

5.0 135 to 370 2.10 (3 struts) 4.26 (2 struts)

• This table is based on information provided ~ the suppliers.

• All equil"lEnt is for sale or hire unless otherwise indicated.

• Maxinun pipe dianl!ter depends on height of l~st Wiling fraIlE above trench fornation.

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Wal1~ 10ld Critical capacity CODpll1ent

(kN/m)

23.9 Wa.li~ 10.2 to 40.6* def~ction

5.6 to 22.3*

15 to 2()1< ~ def~tion

13.0 to 23.6 Wa~ deflection

32.0 Wa~ 23.6 to 57.5

24.4* Wali~ 9.4* deflection

19.6*

13.5* Waling 4.5 to 35* deflection

15.0 to 20.0 Waling deflection

20 Wali~ 15 def~tion

12 20

23.2* Gererally 13.1* waling 35.3* deflection 15.6* Struts at

large span

16 to 57* Struts at large spans

281< Wali~ 1 ()I< deflection 21*

35* Waling 74* deflection 181<

23.2 Gererally 13.1 Wiling 35.3* deflection 15.6* Struts at

large span

~:

LF = Load factor = Test load SWL

*Varies with nunber, le~th and spacing of struts.


'DIble 2: Details of IIIIIIbDle tnces

Brace Brace Mix mit Mix pipe

~ Mldel/type lsIgt:h breadth haOOllng wt length (m) (m) (kg) (m)

Mabey Hire Type A 3.0 to 4.0 3.0 to 4.0 668 4.0

Type B 4.0 to 5.0 4.0 to 5.0 800 5.0

Type 0 1.4 to 2.18 1.4 to 2.18 265 2.1

Type 1 2.1 to 3.0 2.1 to 3.0 520 3.9

'l}>pe 2 2.9 to 3.9 2.9 to 3.9 520 3.9

Tadt 7.16 2.2 to 3.2 1100 7.0 Brace 1

Tadt 9.2 2.2 to 3.2 2300 9.0 Brace 2

'!,'ad< 10.2 2.2 to 3.2 2550 10.0 Brace 3

9:!aft 2.0 to 8.80 2.0 to 8.80 2100 8.8 Brace

9:!aft 7.0 to 20 7.0 to 20 (be leg 10.0 Brace* 1200

~plant 400/500 1.2 to 3.3 1.2 to 3.3 200 to 436 0.9 to 3.0 Series

600/700 2.3 to 10.5 2.3 to 10.5 600 to 2004 1.9 to 7.2 Series

5GB 1 2.0 to 2.9 2.0 to 2.9 291 1.4 to 2.5 2 2.9 to 3.8 2.9 to 3.8 353 2.5 to 3.4 3 3.8 to 4.7 3.8 to 4.7 418 3.4 to 4.2

Slorco A 1.9 to 2.8 1.9 to 2.8 370 1.6 to 2.5 B 2.4 to 3.3 2.4 to 3.3 450 2.1 to 3.0 C 3.1 to 4.5 3.1 to 4.5 1120 2.7 to 4.1 D 4.6 to 6.0 4.6 to 6.0 2500 4.1 to 5.5

SpeedslYJre Stan:lard 1.54 to 4.26 1.52 to 4.26 190 to 278 1.2 to 4.0 (4 no) ora~

canbination

ieavy JlJty 2.13 to 7.16 2.13 to 7.16 454 to 1165 1.9 to 6.8 ora rec~r

canbination

Vibroplant A 1.9 to 2.8 1.9 to 2.8 370 1.6 to 2.5 (SOOrpak) B 2.4 to 3.3 2.4 to 3.3 450 2.1 to 3.0

C 3.1 to 4.5 3.1 to 4.5 1120 2.7 to 4.1 D 4.6 to 6.0 4.6 to 6.0 2500 4.1 to 5.5

• This table is based on infor1IBtion provided by the suppliers.

• All equiprent is for sale or hire tnless otherwise indicated.

• Max1nun pipe dianeter depends on heigl1t of lowest waling frame above trench fortll9.tion.

• IobIking load capacity may vary widely, depending on span.

13

Strut Waling load Critical Sl<l. capacity ~nt

(kN) (kN/m)

150 3z+" Waling

150 2J+ Waling

150 20+- Wiling

150 10+- Wiling

150 15 to 32 Waling

150 25 Waling

150 36 Waling

150 25 Waling

200 1z+" Waling

200 1z+" Waling

57 10+- Waling (IF 2) (Can be cross deflection

braced)

57 1z+" Waling (IF 2) deflection

86 18 Wali1l?; 86 11 deflection 86 7

(LF-=3)

120 36+ 120 3d" Generally 120 26.7+ Waling 120 16.]+ deflection

(LF-=1.25)

III 10+- Wali1l?; (LF-=1.25) deflection

190 7.S-+- Waling (LF-=1.25) deflection

120 36+ Generally 120 3d" Wali1l?; 120 26.7+ deflection 120 16.]+

IF = Load factor = Test load SWL

+ Value quoted is for omdm..m span. * Inchrled intermediate bracir~

struts.


5. ~OUS

Hydraulic shores are frames comprised of two vertical rails connected to two or more hydraulic struts. They are the proprietary equivalent of 'pinchers' , pairs of trench sheets supported independently by struts without walings. They may be appropriate where:

• full sheeting is not required • crossing services are so congested that

walings cannot be used. • the ground will stand up for some time • only a short length of trench can be

open at a time.

Sequence of construction:

• Excavate trench to full depth • 'Fold' first shore and insert from one

side of trench • 'Unfold' shore against far side of

trench • Pressurise hydraulic struts within

indicated safe pressure range • Install remaining shores at appropriate

centres

Advantages • Support installed from ground level,

minimising risk to operatives. • Ease of manhandling. • Speed of operation • Particularly convenient where crossing

services are congested. • Fair range of trench depths and widths

catered for.

Disadvantages • Cannot be used in soils which require

support to be installed ahead of excavation or fully sheeted support.

• May be difficult to lower pipe lengths between shores where ground requires shores at close centres.

• Given shore is suitable only for limited range of trench depths.

• Progressive withdrawal of support as backfilling proceeds is inconvenient.

• Operatives may be at risk if compaction of backfill in layers is specified.

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Table 3: Details of stmes

Rail Trench Imt mit Strut Rail loa! Critical Coopany height width handling wt 51{. capacity coqxment

(m) (m) (kg) (kN) (kN/m)

G<N Kwikfonn 1.5 0.53 to 2.06 31 to 47 105 ~ Rail (LF 1.5) deflection

2.1 0.53 to 2.06 37 to 53 105 15 (12 1.5)

l'echplant 0.3 to 3.60 0.56 to 4.50 10 to 80 74 to 57 9.2 Rail (LF 2) deflection

g;s 1.5 0.60 to 2.40 38 to 50 86 12 Rail 2.0 0.60 to 2.40 44 to 56 86 12 deflection 2.5 0.60 to 2.40 57 to 70 86 12

(LF=3)

Shorco 1.5 0.55 to 1.90 25 to 33 80 20 Rail 2.1 0.55 to 1.90 32 to 40 80 35 cantilever

(LF=2) beta. bottom stl\Jt

Speed Shore 0.3 to 3.66 0.56 to 4.26 9 to 126 89 to 111 6 to 34 Rail (LF=1.25) deflection

Vibroplant (Shorpak) 1.5 0.55 to 1.90 25 to 33 80 20 Rail

2.1 0.55 to 1.90 32 to 40 80 20 cantilever (12=2) bela.!

bottom stlUCt

~:

• This table is based on infornation provided by the suppliers. • All equipnent is for sale or hire wless othetwise indicatES!.

• Maxim.m pipe length depends on horizontal spacing of shores.

• Maxim.m pipe d.i.aDeter depends on height of lower stl\Jt above trench formation.

lS

12 - Load factor = 'lest loa! 51{.


6. BOXES

Boxes are modular strutted support walls which are installed by lowering them into a pre-dug trench (in this case acting as a safety box to protect workmen) or by digging them in progressively (thereby providing more positive support to the trench face).

Boxes of this type can generally be extended in width by changing the modular struts and in height by stacking the boxes (see illustration).

Problems have arisen in the past when trying to pull boxes out of the trench; these difficulties tend to increase the longer the box has been in position, or when trench depths exceed 4 m. It is important to consider the possible loss of ground at the gap between adjacent boxes, particularly where a larger than usual gap is left to accommodate a crossing service.

Advantages • Ready made, modular support for any

ground condition. • Installed complete by excavator before

personnel enter trench. • Support can be provided as excation

proceeds. • Can be used for trenches up to 6 m

deep • Very simple to use and understand.

Disadvantages • Boxes can get out of line. • Ground can move into gap between box

and trench side. • Possible loss of ground at gaps between

boxes. • Crossing services interrupt system. • Space taken up by boxes when not in use • Double struts at module junctions. • Ensuring the system is used within the

manufacturer's recommendations. • Can be damaged by mishandling by

machines. • Can be difficult to remove. • No stopend provision.

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Table 4 (opposite)

Notes:

1. This table Is based on Information provided by the suppliers.

2. All equipment Is for sale or hire except as otherwise Indicated.

3. Unit handling weights are given for the base unit and "extra" unlt(s) that may be

added to suit the trench depth. The stacked weight Is that of the maximum number of units that can be stacked.

Key:

LF = L~d Factor Test Load SWL


Table 4: Details of bmaes

Box Box Box Unit Max pipe Max pipe Strut Panel Critical C'.on.,any M:ldel/type length breadth depth handling wt length dianeter ~" capacity e~nt

(m) (m) (m) (kg) (m) (m) (kN) (kN!nf )

G<N Kw.I.kfo[1D Jayvil1e 3.5 0.75 to 2.5 to Base: 1450 3.1 1.5 165 30 None System 30 3.15 4.0 Extras: 850 (LF=2) quoted

Stacked: 2300

Jayville 3.5 0.75 to 2.5 Base: 1700 3.1 1.5 230 40 System 40 4.35 6.0 Extras: 925 (speeial (LF=2)

Stacked: 4500 to 2.16)

Krings (as Krings publieity data-typical range indicated) (Sale only)

I<S Boxes 3.5 0.96 to 2.6 to Stacked: 4500 3.1 1.5 150 to 38.4 None 5.0 6.0 760 quoted

Mahey Hire Stronghox 3.0 1.0 to 1.0 to 740 per m depth 2.6 1.1 to 147 34 Tie bolt 4.0 5.0 6.0 900 per m depth 3.6 2.5 147 34

(speeia1)

~hp1ant Jayville 3.5 0.9 to 2.5 to Base: 3.1 1.5 230 40 Ibte System 40 3.0 6.0 1700 to 2000 (LF=2) quoted

Extras: 990 to 1150

Stacked: 3700 to 4300

Eoergency 2.0 to 0.6 to 0.3 to 40 to 85 1.8 to Go"",rned 74 to 57 7 Units 2.3 2.0 2.0 2.1 by strut (LF 2) to Panel

dearanee 10

ICF Standard 3.5 0.9 to 2.6 to Base: 1600 3.1 1.5 4.5 6.0 Extras: 975

Total: 4525

Krings 3.5 0.96 to 2.4 to Base: 1600 type 5.0 6.0 Extra: 975 3.1 1.5 150 to 32 None KS 2000 total 4525 760 quoted

5GB Krings I<S82 3.5 0.96 to 2.5 to Base: 1600 3.1 1.5 150 to 32 Generally

5.0 3.9 Extra: 975 760 plate Total: 2600 defleetion,

Strut at breadth) 4.4m

Shoreo Mini 3.0 0.8 to 2.0 to Base: 2.7 1.1 375 25 Cantilever 4.5 3.0 1000 to 1480 be1CM

Extra: battau 500 to 740 strut

Stacked: 1500 to 2220

Standard 3.4 0.95 to 2.6 to Base: 3.0 1.4 375 34 Cantilever 4.5 6.0 1827 to 2307 belCM

Extra: bottOOl 1050 to 1290 strut Stacked: 4977 to 6177

3.4 1.04 to 4.0 to Base: 3.0 2.4 375 34 Canti1e"",r 4.5 6.0 2900 to 3380 belCM

Extra: bottan 1050 to 1290 strut Stacked 3950 to 5960

MignLm 4.0 0.95 to 4.0 Base: 3.6 2.4 375 Cantilever Extra 4.5 3150 to 3630 be1CM

bottcm strut

Trendmm rm"co 3.4 0.65 to 2.4 to 1lase: 1530 3.0 1.5 31 Plate 4.5 3.9 Extra: 874 def1eetion

Total: 2404

Unipas Jayvi11e 3.5 0.8 to 2.5 to Base: 1595 3.0 1.5 165 None System 30 3.5 3.9 Extra: 975 quoted

Total: 2570

Krin!llS 3.5 0.9 to 2.5 to Base: 1700 3.1 1.5 150 to 38 None KS 2000 4.0 3.9 Extra: 1000

Thta1: 2700 760 <p:>ted

Vibroplant Kritl!llS 3.5 0.96 2.6 to Staeked 3.1 1.5 150 to 38.4 lb!e I<S 2000 5.0 6.0 4500 760 <p:>ted

17


7. SLIDE RAIL SYSTEMS

These generally consist of vertical slide rails strutted apart, with panels spanning between them to support the trench face, forming the equivalent of a fully sheeted excavation.

Sequence of installation:

• Set up two pairs of slide rails and one pair of panels at ground level, ensuring slide rails are vertical.

• Push slide rails partially into ground with excavator bucket.

• Excavate between panels and push down panels and slide rails. Repeat operation until tops of panels and slide rails are at ground level.

• Install extra panels if trench depth requires.

• Set up next pair of panels and slide rails at ground level. Repeat sequence.

Special care is needed when setting out the line for a slide rail system and when dealing with crossing services and manhole positions. Slide rail systems can be dismantled into smaller components and are often easier to remove from 'tight' ground than boxes.

Advantages • Suitable for any ground condition. • Installed complete by excavator before

personnel enter trench. • Support can be installed as excavation

proceeds • Small, light units for handling and

storage. • Continuous (joined) support. • Single struts at module junctions. • Many module sizes (maximum depth 8 m). • Reasonably simple to use.

Disadvantages • Careful alignment necessary. • Ground can move into gap between panel

and trench side. • Crossing services interrupt system. • Ensuring loading is within

manufacturer's recommendations. • Ensuring assembly, method and use

follow manufacturer's recommendations. • Ensuring system is adequate for the

ground and water conditions. • No stopend provision. • Deviation from line can make

installation and extraction difficult. • Deflection of plates can make

extraction difficult.

18


Table 5: Details of slide rail systas

Panel Trench Slide rail Max unit Max pipe Max pipe Strut Panel Critical Cootpany Model/type length width height haMUng wt length dimeter ~ capacity canponent

(m) (m) (m) (kg) (m) (m) (kN) (kNtnt)

!{rings I<R single and 1.0 to 1.28 to to 8.0 1110 4.6 1.8 to ISO to 24 to N:me qu>ted (sale only) dooble slide 5.5 5.5 2.8 760 83

rail

8GB !{ring/! single 3.0 1.28 to 3.7 Panel: 660 2.9 1.8 ISO to 19.1 Plate slide rail 3.5 5.0 Parel: 8SO 3.4 1.8 760 16.4 deflection,

Frame: 700 !J!III!ra1ly. Strut at ;. 4.4 m

Kring/! double 3.0 1.6 to 6.0 Panel: 970 2.9 2.8 ISOto 38 lime slide rail 3.5 5.9 Parel: 1344 3.4 2.8 760 qu>ted

Frame: 940 to 1465

Shoi:co Slide rail 3.95 0.5 to 4.0 to 6.0 Pairs base 3.75 1.45 375 40 l.oier strut 4.5 rails: (Special at II!IXiJ1un

1460 to 1712 3.0) width

Trenclmm Imeco slide 3.4 0.85 to 2.4 to 3.4 Plate: 860 3.0 1.5 400 34 to Plate rail 5.0 Frame: 540 (Specials 60 deflection

for extra clearance)

lTnipas Krings single 3.0 0.9 to 2.4 to 6.0 Frame: 1100 2.9 1.8 230 38 Plate and double 3.5 4.0 3.4 1.8 at 4m deflection rail width

Notes:

• This Thb1e is based on infoI'llBtion provided by the suppliers.

• All equiJlIent is for sale or hire unless otherwise indicated.

• A frame ~rises tIolO slide rails and the associated struts.

19


8. SHIELDS

These are also known as drag boxes or saddles. The basic form of shield is two vertical plates permanently braced apart to provide a safe working place between them. They are mostly of welded steel construction. The length of the shield must be sufficient for the work to be carried out, e.g. handling and jointing pipes. In battered trenches, shields are used for protection of those working in the trench against instability of the cut slope.

In trenches with vertical sides, shields do not provide significant support to the trench sides. They are used mainly for protecting operatives while working in the trench where the ground is generally self-supporting but occasional collapse of the trench face is possible. The trench is excavated ahead of the shield allowing clearance to the sides of the shield. The shield is pulled along the trench using the trench excavator standing at ground level. Shields should be robust enough to withstand the maximum pulling force of the excavator and a certain amount of mishandling.

Shields are inconvenient to use where water tables are high or where services cross the line of the trench.

Advantages • Simple to manufacture, use and repair. • Positive protection of operatives. • Rapidly moved from one section of the

trench to next. • Specials can be made to order.

Disadvantages • Robust shields are heavy and require

heavy-duty excavator/crane to handle. • Lighter shields may suffer frequent

damage. • May be difficult to establish degree of

protection against ground failure. • Limited working length. • Ground movement unrestrained. • Cannot use where crossing services are

frequent. • Cannot backfill to full depth within

shield. • May be difficult to provide safe access

to shield if battered slopes are unstable.

20


Table 6: Iletails of shields

Shield Shield Shield ~unit ~ pipe ~ pipe Panel Critical Coapmy r,txIel/ type length breadth depth handling wt length d:i.anEter capacity component

(m) (m) (m) (kg) (m) (m) (kNlnf)

G<N KwikfoIlD Jayville 4.7 0.64 to 1.5 2.5 2800 3.4 1.5 40 Panel General (inside) deflection

JayviUe Jayvil1e 4.7 to 0.64 to 3.0 2.5 to 2750 to 3.4 1.5 40 Panel (sale only) GeDaral 7.25 (inside) 4.0 4500 (2.0 for deflection

specials)

MIni 3.25 0.65 to 0.95 1.5 700 3.0 0.7 15 Panel deflection

Also: Specials 0Bde to order

~ Olnstruction Saddles: Specials DBde to order (sale only)

Mabey Jayvil1e 4.7 0.64 to 1.5 2.5 2800 3.4 1.2 40 Panel General (inside) deflection

M;F I'GF - 1 4.5 0.9 to 2.10 2.6 3200 3.5 1.8 N:>t N:>t given given

Shorco MIF 5 0.75 to 2.5 2.5 3600 to 3.5 1.4 24 Panel 4000 deflection

MIF+ Ext 5 0.75 to 2.5 4.0 5400 to 3.5 1.4 24 Panel 6000 deflection

B 6 1.3 to 3.0 3.0 6200 to 4.0 1.8 34 Panel 6800 deflection

C 6 1.5 to 6.0 4.0 6300 to 4.0 2.5 34 Panel 11000 deflection

Also: Specials DBde to order

lbipas Jayville 4.7 0.65 to 1.55 2.5 2BOO 3.5 1.5 40 Panel deflection

Standard 7.5 0.65 to 1.55 2.5 N/s 3.5 1.5 40 Panel deflection

Mini 3.0 0.65 to 0.95 1.5 700 2.9 0.7 15 Panel deflection

Also: Specials 0Bde to order

N:>tes:

• This table is based on inforoution provided by the suppliers •

• All equipomt is for sale or hire unless othetwise indicated.

21


9. PILING FRAMES

Non-powered systems

Many proprietary piling frames are adaptations of box systems. They use 0.75 m to 1.3 m deep box frames with the addition of guides for trench sheets or sheet piles. The frame is lowered into a shallow trench (0.5 m to 1.5 m deep) and the box sides jacked against the trench sides by hydraulic struts. As excavation is continued, the trench sheets or sheet piles are pushed down by the excavator bucket through the guide frame and additional waling frames are installed as required by the depth, ground loading and strength of sheeting used. Some frames are specially built to allow adjustment in length and width and to accommodate a range of sheet pile sections.

Powered systems

There are only two systems on the market at present, both marketed by the same manufacturer.

The Rollshor is a rail mounted piling frame which uses hydraulic power to drive purpose-made sheet piles. In addition to a waling frame at ground level, additional waling frames can be carried by the machine and lowered into position as required by the depth of excavation and ground loading. On completion of a section of trench, the machine is pulled forward by the excavator.

The Ramshor is a waling frame which, rather like the non-powered types, sits in the upper part of the intended excavation. As the lower portion of the trench is excavated, single sheet piles or group of piles are driven down by hydraulic rams. When the lower part of the excavation is backfilled and the piles withdrawn, the upper part of the next section of trench is excavated and the machine pushed forward by the reaction of a hydraulically-operated stopend at the rear of the machine. The sequence of operation is: extend stopend to give required increment of foreward movement, retract stopend, fill gap between existing backfill and stopend with excavated material, extend stopend again to compact the new backfill.

22


This sequence is repeated until the machine has been moved to the next section of trench. The second stage of excavation can then start.

Advantages • Upper 0.5 to 1.0 m supported by box or

rapidly installed piles. • Adaptable to any ground conditions. • Crossing services can be accommodated. • Can insert or extract both trench

sheets and piles • Suitable for wide range of trench

depths. • Hydraulic installation of piles

(powered systems). • Units moved 'en bloc' (powered systems)

Disadvantages • Weight and size (particularly of

powered systems). • Extra width shallow trench to

accommodate frame and walings (except Rollshor system).

• Setting up and dismantling takes time and space.

• Requires skilled use and maintenance. • Ensuring the system is used in

accordance with the manufacturer's recommendations.

• Most trenching plant operations from one end of support system.

• Waling installation essential, depending on sheeting size and penetration, but often neglected.

• Gaps between sheets where pairs of guide sections are tied together (non-powered systems)

• No provision for stopend (non-powered systems).

23


Table 7: Details of pi1.iDg fmIes

ImdnuD width of !oW<

():)npiny and Pile pile Trench trench !oW< pipe !oW< pipe Strut I6ling Panel Critical nxxlel/ type type panels width depth !oW< wts length diaueter S\olL capacity capacity canponent

(m) (m) (m) (tormes) (m) (m) (kN) (kN/m) (kNtnf)

Noo r nwred syate.

Kri~ 3.0 1.0 to * Unit: 1.8 2.25 Depems Not Not Not None qwted (Sale only) 2.7 on pile given given given

4.0 1.0 to * Unit: 2.5 3.25 size, 2.7 toe-in,

etc.

Mabey: !{7 and 4.3 1.5 to * Unit: 1.63 3.6 Depends 147 Not 35 Struts Strongfran.:. Mll 5.0 on pile given

size, toe-in, etc.

!GF: Various 4.12 1.0 to 1.0 to 1.7 3.4 Depends Pile Frame 3.7 * on pile Infonmticn not available

size, Krings type 4.85 1.0 to * 3.2 4.0 toe-in

5.0 etc.

5GB: BSC 4.0 1.0 to * Unit: 1.5 3.25 Depends 250 Not 60 Plate Kri~ Sheets 2.62 on pile to given

size, 760 toe-in, etc.

Sh:>rco: Depends 375 20 Not loSlings on pile

1Ype B 5.0 0.82 to * \bit: 1.4 4.7 size, 4.5 to 1.7 toe-in,

etc. given at max span

~ syab!ia.l.

M:>rrice: Various 9.03 2.45 to 6.0 to Unit: 7.0 4.0 2.1 Not Not 35 Piles if Ranllhor 4O':X) 4.45 8.0 Total: 33.0 given given based on toe-in or

to 39.0 Larsen 1oBl~ DJ sheet inadequate

Raoshor 5000 11.06 2.88 to 6.0 to Unit: 9.0 6.0 2.1 Not rbt 35 Piles if 4.45 8.0 Total: 44.0 given given toe-in or

to 51.0 loBli~ inadequate

Rollshor I 6.0 1.5 to 2.0 to Unit: 9.0 5.40 3.5 1450 350 126 \oIalings at 5.0 9.0 Total: 22.0 max span

Rollshor II 6.0 1.0 to 1.5 to \bit: 6.0 5.50 3.0 1130 335 114 waJ.ings at 4.0 6.0 Total 14.0 (based en max span

standard equipt.)

Notes:

• This table is based on infonmtion provided by the suppliers. * Maxi.nun trench depth is dependent on size and type of sheet pile, ground ccnditicns and plant used for pile-

• All equ1p1leDt is for sale or hire unless otherwise indicated. driving.

24


Table 8: Suppliers and agents - addresses and systems available (all equipment is for sale or hire unless otherwise indicated).

Supplier or agent

GKN Kwikform Ltd

Jayville Engineering Ltd

Krings International (UK) Ltd

Mabey Hire Co. Ltd.

Mechplant Limited

MGF (Trench Construction Systems Limited)

Address and tel. no.

Winchester House 53/55 Uxbridge Road Ealing London W5 5SE

01-567 3083 (also local depots)

Heslop llalesfield 24 Telford Shropshire

0952 583041

5 Elton Road Clevedon

TF7 4NS

Avon BS2l 7RA

0272 876174

Floral Mile Twyford Reading BERKS RGlO 9SQ

073 522 3921 (also local depots)

Fulford Road Industrial Estate

Hospital Fields Road York YOI 4EW

0904 36621 (also local depots)

Greenham Yard Astley Industrial Estate Wallwork Road Astley Greater Manchester M29 4TQ

0942 096282 25

Systems available

Waling frames Shores Boxes Shields

(Sales only) Shields

(Sales only) Waling frames Boxes Slide rail systems Shields Piling frames

Waling frames Manhole Braces Boxes Shields Piling frames

Waling frames Manhole braces Shores Boxes

Waling frames Boxes Shields Piling frames


A.R. Morrice, Ltd 80 Station Parade Harrogate North Yorkshire HG1 1HG

0423 68136

Scaffolding (Great Britain) Ltd 23 Willow Lane

Shorco Trench Systems Limited

Speed Shore (UK) Ltd

Trenchman Lining Systems Ltd

Unipas Services Limited

Vibroplant PLC

Mitcham Surrey CR4 4TQ

01-648 3400 (also local depots)

Cross Green Way LEEDS W. Yorks LS9 OSE

0532 497497

5B15 Thorp Arch Trading Estate Wetherby West Yorkshire LS23 7BJ

0937 844841

Parks ide House Edge Lane Street Roy ton Greater Manchester OL2 6DS

061 6260541

Harborough Road Brixworth Northampton NN6 9BX

0604 881134

POBox 12 Prospect Road Starbeck Harrogate N. Yorks HG2 7PW

0423 885911 (also local depots)

26

Piling frames

Waling frames Manhole braces Shores Boxes Slide rail Piling frames

Waling frames Manhole braces Shores Boxes Slide rail Shields Piling frames

Waling frames Manhole braces Shores

Boxes Slide rail

Boxes Slide rail Shields

Waling frames Manhole braces Shores Boxes


HeaHh and safety Effective Depths of trenches Ground movement Information needed Identifying the ground Temporary safe slopes Coping with the ground Groundwater control Selection of support method Sheeting, wallngs and struts Use of sheeting Design of wallngs and struts -

calculation method Quick reference table of wallngs

and strut arrangements Installing open sheeting support Installing full sheeting support

In 'poor' ground Installing sheet piling ahead

of excavation Proprietary support systems Soldier pile support Trench support at manholes Installing two-stage sheeting Working clearances Final design checks Planning checks Checks during construction Safety: selected legal

requirements

Trenching Practice Price £20.00 (£6 CIRIA members)

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CIRIA is the Construction Industry Research and Infonnation Association. It is a non-profit-distributing organisation carrying out research on behalf of its members.

Membership includes all types of finns and organisations which have an involvement with construction, including clients, designers, consultants, contractors and suppliers.

The members collaborate in research aimed at improving the efficiency of design, construction and management, and the perfonnance and serviceability of buildings and civil engineering works. They initiate and take part in the research programme, and have preferential access to the results of research projects.

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For further details and subscription rates apply to The Secretary, CIRIA, 6 Storey's Gate, Westminster, London SWIP 3AU. TelephoneOl-222 8891.

Documents

Proprietary Trench Support Systems