box excavation

8/12/2019 box excavation

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User Guide

Backhoe Boxes - Issue 2 - Apr 2012

Backhoe Boxes

Important Notes

All excavation work must be thoroughly planned before work commences onsite to identify hazards and assess risk.

These instructions form guidance for backhoe manhole and trench boxes.Non-standard applications should be approved by a suitably qualified

engineer.

Ensure all personnel engaged in installation operations are properly briefedand adequately supervised by a competent person.

All hires for this equipment will usually be accompanied by a generalarrangement or scheme specific drawing. This must be read in conjunction

with these instructions

IF IN ANY DOUBT SEEK FURTHER ADVICE:

ON FREEPHONE - 0800 000 345


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User Guide


Introduction

Equipment Identification

Type Length(m)

Height(m)

InternalWidth (m)

PanelThickness

(mm)

Clearancebetween

struts (m)

Clearanceunder

struts (m)

PanelWeight

(kg)

ApproxWeight ofbox (kg)

Trench Base 2.85 2.0 0.3 - 2.35 63 2.65 1.3 310 740*

Trench Top 2.85 1.0 0.3 - 2.35 63 2.65 1.3 175 394*

2.5m ManholeBase

2.5 2.0 2.38 60 2.35 1.2 427 1116**

2.5m ManholeTop

2.5 1.0 2.38 60 2.35 N/A 225 526**

3.0m ManholeBase

3.0 2.0 2.88 60 2.87 1.2 487 1305**

3.0m ManholeTop

3.0 1.0 2.88 60 2.87 N/A 280 605**

* Typical value, the weight will vary with strut configuration supplied** Weights for Square set up. Other widths are possible if trench box struts are used.

2.0m Manhole

Base

2.0 2.0 1.88 60 1.85 1.2 420 912**

2.0m ManholeTop

2.0 1.0 1.88 60 1.85 N/A 220 456**

The Backhoe Box range has been developed to meet the needs of the contractor when using smaller 180 O

backhoe or rubber tyred excavator. With minimum weights of 645kg for the trench version, and 960kg forthe 2.5m manhole version, most small excavators can handle these boxes. The load capacity of 20 kN/m2allows the box to be used to depths of 4 metres in most soil types.

Lifting Chains: The end-user has a responsibility under LOLER to ensure that all lifting equipment is fit for use

Never snatch at the chain during removal of the box whilst using the four-legchain. If the box becomes stuck, seek further advice from Groundforce

Note:Handrail unitsare available for most

box types. ContactFreephone

0800 000 345 fordetails


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User Guide


Assembly Instructions

MAIN BOX ASSEMBLY (applies to both types)

Using a certified sling connected to the four corners lifting points, place both box plates on firm level groundone facing up, and one facing down.

Place all four struts onto the bosses protruding from the panel facing upwards, and secure them using the20mm pin and retaining clip supplied.

Reconnect the sling to the lifting points of the panel facing downwards, and lift it into position above thestruts.

Lower the plate carefully, guiding the bosses into the ends of the upstanding struts.

Secure the struts to the panel with the remaining 4 pins and retaining clips.

Disconnect the lifting sling legs from the two lower lifting points, and lift the box to the upright working po-sition. Note: when not in use, it is essential that the boxes are stored on flat stable ground. If indoubt, they should be dug into the ground by at least 0.5m or stored flat on their side.

Connect the two free legs of the lifting sling to the upper lifting points of the other panel before lifting thebox into the trench.

Top extension boxes can be assembled in the same way, but only 2 struts are installed.

Always adopt safe working practices during assembly and use.

Connection Details and Width Arrangements

Strut LengthL (mm)

Strut Weight(kg)

InternalClearance

I (mm)

ExternalWidth

W (mm)250 5 300 430

375 8 425 555

425 9 475 605

550 12 600 730

700 15 750 880

850 18 900 1030

1150 * 24 1200 1330

1280 27 1330 1460

1780 ** 38 1830 1960

* denoted strut extension required forsquare set up on 2.5m manhole box

** denoted strut extension requiredfor square set up on 3m manhole box


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User Guide


Connection Details and Width Ranges (cont)Connection Details and Width Ranges (cont)

The range of widths available can be increased by the use of the Strut Connector shown below. This allowsthe standard struts to be used in pairs in three combinations as shown below right. The assembledarrangement for the minimum configuration is shown below left, and the table shows the box dimensions for

all combinations in ascending width order.

Strut 1 Strut 2

Internal Dimension I (mm) External Dimension W (mm)

Configuration

Minimum Intermediate Maximum Minimum Intermediate Maximum

250 250 600 750 900 730 880 1030

250 375 725 875 1025 855 1005 1155

250 425 775 925 1075 905 1055 1205

250 550 850 1000 1150 980 1130 1280

375 425 900 1050 1200 1030 1180 1330

425 425 900 1050 1200 1030 1180 1330

375 550 950 1100 1250 1080 1230 1380

250 700 1025 1175 1325 1155 1305 1455

425 550 1050 1200 1350 1180 1330 1480375 700 1075 1225 1375 1205 1355 1505

550 550 1175 1325 1475 1305 1455 1605

250 850 1200 1350 1500 1330 1480 1630

425 700 1200 1350 1500 1330 1480 1630

375 850 1225 1375 1525 1355 1505 1655

550 700 1325 1475 1625 1455 1605 1755

425 850 1350 1500 1650 1480 1630 1780

700 700 1375 1525 1675 1505 1655 1805

550 850 1500 1650 1800 1630 1780 1930

700 850 1650 1800 1950 1780 1930 2080

850 850 1800 1950 2100 1930 2080 2230

NOTE: Struts above 850mm should NOT be used with the connector

Configuration


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Installation Procedures

After the ground has been excavated to about 1m or deeper as ground conditions permits, the box is lowered intothe trench using a 4-leg chain sling of the correct capacity. (Do notenter an unsupported excavation)

The excavator driver then progressively excavates between the two faces of the box plates and pushes down oneach of the four corners of the box in turn using the back of the machine bucket. The difference in heightbetween panel corners must not exceed 100mm during this operation otherwise damage to the boxmay occur This method continues until the desired depth is reached. Where top extensions are used, theseshould be attached to the base using the connectors supplied at each corner. This should be done when the topof the base is approximately 200mm above ground level. Each connector is secured using a pair of pins andretaining clips.

Extraction of the units is simply a reverse of the process, back filling the trench and then progressively pulling thebox upwards using the chain sling. If top extensions have been used, these should be disconnected as the jointbecomes clear of the ground, and then lifted clear before reconnecting the sling and continuing the extraction.

Note on flying the box above formationIt is recommended hat the box panels extend over the full height of the dig and not be flown

above the base of the excavation unless both the following conditions are met. a) The box isadequately supported and b) has been approved as a safe method of work by a risk assessmentundertaken by a competent person. In any case, the maximum height of unsupported ground

should always be minimised and never exceed 1m.

NOTE: ALWAYS USE A SECURED LADDERTO ENTER OR EXIT THE BOX.

NEVER ENTER AN UNSUPPORTED TRENCH


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Dos and Donts

Do Do Not

Inspect all components at start of every shift Assess weights correctly and use

appropriately certified lifting equipment. Toe-out base boxes by 50mm Provide support over the full height of the

dig Ensure all pins & clips are correctly fitted Use four panel connectors for upper box

attachment

Use only lifting points for chain attachment Provide edge protection or handrail panels Push the plates at the corner positions only Keep personnel clear of excavator slewing

zone Always use a banksman Locate underground services before

excavating Lay box flat before dismantling. Store assembled boxes on firm, level ground

only or lay flat on their sides

Exit the box into an unsupported area

Push plates down by more that 150mm at a

time Snatch the chain during removal

Climb on the struts always use a secured

ladder

Hang/store materials on the struts

Excessively force the box into the ground

Permit personnel in the box during installation

Accidentally strike the struts

Drag the box by any means

Use more than four extension bars per strut

Use more than two top extension boxes

unless specified by Groundforce

Load the struts laterally or vertically

Fly the boxes above the base of the

excavation unless approved by a competentperson

box excavation

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