GB1572082A

GB1572082A - Support of trenches

Info

Publication number: GB1572082A
Application number: GB481176A
Authority: GB
Original assignee: Galliford & Sons Ltd
Current assignee: Galliford & Sons Ltd
Priority date: 1977-02-04
Filing date: 1977-02-04
Publication date: 1980-07-23

Description

(54) IMPROVEMENTS RELATING TO THE SUPPORT OF TRENCHES (71) We, GALLIFORD & SONS LIMITED, a British Company, of Wolvey, Hinckley, Leicestershire, LE10 3HL, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to the construction of trenches and, in particular, it concerns means for, and a method of, forming a reinforced trench by supporting the side walls thereof.

It has for long been recognised that in constructing ground-excavated trenches having any substantial depth, great care must be exercised in ensuring that the side walls are adequately supported, and this is of especial importance where the trench is such that workers have to operate within the trench.

Up to several decades ago, the generally accepted method of supporting the side walls of trench excavations involved the use wholly of timber planks and struts which were fixed in position to construct a supporting framework by skilled labourers, known in the trade as 'timbermen'.

Within about the last thirty years, however, the use of all-timber reinforcing or supporting methods has progressively been discarded within the industry in favour of the use of steel trench support plates or sheets in conjunction with adjustable metal struts which are expanded to brace apart the plates or sheets against the trench side walls. This trend away from the original traditional method has been promoted by a shortage of skilled 'timbermen' and by the general availability of suitable rolled steel trench sheets and strut compoents which can be fitted by unskilled labour and which have a good safety factor, if fixed correctly, together with a fair life span relative to their capital cost.

The conventional methods using such steel trench support plates or sheets and adjustable metal struts have, nevertheless, had disadvantages. In particular, it has usually been necessary for the reinforcing or supporting structure to be assembled in an excavated trench by two operatives standing in the bottom of the trench. During this period, until the struts are positioned and expanded, the two operatives are at risk from the sides of the trench caving in. Similarly, during removal, an operative has to release the pressure on the struts to enable the support plates or sheets to be extracted, and whilst doing so he is again at risk as this operation has again usually had to be carried out from within the trench.

As a result, there has been a need for improvements in the safety aspect and two further developments have sometimes been used. In one, the struts provided have been in the form of adjustable hydraulic jacks rigidly connected between opposite support plates or sheets to form a structure which can be lowered into the trench from the top, it being arranged so that the jacks can then be expanded by an operator activating a pump situated remotely at a safe distance away.

Although this system can function satisfactorily, it is relatively costly and is subject to mechanical failures of the jacks after use in the field under service conditions.

In the second development referred to, a supporting structure has been provided made up of a pair of opposite support plates or sheets interconnected in spaced-apart parallel relationship by a scissor-action system of bracing levers activated by a screw jack operable manually by an operative from above. This arrangement, however, is also somewhat complex and costly, and can also be liable to damage, especially to the jack screw threads, and to mechanical failure under service conditions.

It is accordingly an object of the present invention to provide an effective and simplified arrangement, usable with a high safety factor, for supporting the side walls of trench excavations.

More specifically, the present invention provides a trench support device, for supporting the side walls of an excavated trench of substantial size, in the form of a frame structure comprising a pair of elongate side members in parallel relationship which are arranged in use to engage against respective opposite side walls of the trench and which are interconnected by at least two spacedapart parallel struts forming a parallel motion Iinkage, the ends of the struts each being pivotally jointed ta the respective side members inwardly of the ends of the latter for angular movement in the plane incIuding the IongitudinaI axes of said side members and each strut being composed of at least two relatively adjustable parts interconnected by adjustable mechanical coupling means by which each said strut can be adjusted to a particular preselected length in apreliminary pre-setting operation prior to use of the device, thereby to enable the spacing between the side members, when the frame structure is opened out fully from a folded condition in which the struts extend obliquely to a condition in which the struts extend perpendicularly to the side members, to be set commensurate with the width of the trench, said device being such that in use, after carrying out said preliminary pre-setting operation to adjust the length of the struts, it can first be lowered in a folded or partly folded condition into the trench with the side members extending vertically in confronting relationship with the trench side walls and disposed one higher than the other, and the frame structure can then be fully opened out by applying a downwards force ta the top end of the uppermost side member thereby ta force the side members laterally against the trench side walls and to thus impart a compression loading to the struts.

The invention thus also provides a method of forming a reinforced excavated trench consisting in utilising a trench support device, in the form of a frame structure as defined above, in the manner hereinabove set forth.

The term 'excavated trench of substantial size' is used herein to denote a ground excavated parallel sided trench having a depth greater than one and a half metres and a width greater than halfametre. In practice, trenches in connection with which the present invention may be used, may be as deep as five metres. As the lengths of the side members should be approximately equal to or somewhat greater than the depth of the trench, they will generally be within the range of two to six metres. The side members themseIves are preferably in the form of elongate rolled steel plates or sheets.The distance between the said two struts will preferably be within the range of one-third to two-thirds of the length of the side members, and each of said two struts will preferably be spaced from the nearest adjacent end of each of the side members to which it is connected by a distance which is at least one sixth of the length of the side pressure members.

To provide for the necessary length adjust ment, the struts conveniently include a twopart telescopic construction, the two parts being locked together in adjusted positions by a disengageabIe locking pin. The side members are also conveniently provided with eyelets or hook like formations or fittings for hooking engagement with a hoist lifting chain, and they may further be adapted to carry and support waling timbers.

By way of exampIe, the construction and use of one form of trench support device in accordance with the invention is illustrated somewhat diagrammatically, in the accompanying drawings. In said drawings, Figure I shows the support device, in a partly folded condition, being placed in position in an excavated trench; Figure 2 is a similar view showing the support device opened out into its final operative position; Figure 3 is a view of the support device in a fully folded out-of-use condition, as when being lifted or hoisted for example; Figure 4 is an elevational view of one of the side members of the support device; Figure 5 is a sectional view on line V-V of Figure 4;Figure 6 is a sectional view on line VI-VI of Figure 4; Figure 7 is a sectional view on line VII-VII of Figure 4; Figure 8 shows the assembly of a strut component of the device; and Figure 8a shows an optional additional extension piece for use with the strut assembly of Figure 8.

The trench support device illustrated consists basicaIIy of a jointed frame structure made up of a pair of elongate rolled steel sheets 12, 1Z, commonly known as 'trench sheets', forming side members interconnected in parallel relationship along their length by a pair of spaced apart parallel struts 14, 14, forming a parallel motion linkage, the ends of these struts being pivotally jointed as shown to the respective trench sheets for angular movement in the plane including the longitudinal axes of the trench sheets.

Each strut 14 has a similar construction and is adjustable in respect of length when unloaded prior to use of the device.

For use of the device in supporting and shoring up the sides of an excavated trench, the length of the struts 14, 14, is set in a preliminary pre-setting operation so that the trench sheets, when separated to their maximum extent, are spaced apart by a distance very slightly greater than the width of the trench.

The device is then lowered into the trench from the top with the frame structure in a folded condition, the trench sheets 12, 12 depending vertically and the struts 14, 14 extending at an oblique angle so that one of the side trench sheets is lower than the other.

The lowermost trench sheet is then positioned against the floor and one side wall of the trench 15, as shown in Figure 1, following which the frame structure is opened out by forcing down the other trench sheet to bear against the opposite side wall of the trench, as shown in Figure 2. This may be carried out by applying a downwards force, indicated by arrow F in Figure 1, to the upper end of the second trench sheet using, for example, the weight of the bucket of an excavator machine.

As a result, the struts 14, 14 turn into a position substantially perpendicular to the trench sheets 12, 12, and become loaded under an axial compression force which braces the two trench sheets apart forcing them against the opposite walls of the trench which are thereby supported and stabilised.

To subsequently remove the device, it is necessary only to exert an upwards fore on one of the trench sheets, as for example by using a hoist of which the lifting chain is hooked on to the trench sheet to which the upwards force is tobe applied. As soon as this trench sheet commences to move up, the compression loading of the struts is relieved and the structure again folds permitting easy removal of the device.

It will thus be appreciated that the entire operation of fitting and of removing the device in a trench, can be performed safely by a single operative working entirely from the top of the trench, thereby not exposing himself to any risk whatsoever associated with the ground excavated. It will further be appreciated that the struts 14, 14, are adJusted only in a preliminary operation for positioning the trench sheets 12, 12, at the correct distance apart to suit the particular trench, and no adjustment is carried out or is practicable after lowering the device into the trench.

Further details of the construction of the particular form of trench support device illustrated in Figures 1 to 3 are shown in Figures 4 to 8. Each trench sheet 12 compnses a length of channel profile rolled steel sheet conveniently of 4 mm. gauge having, in this example, a width of 0.330 metres and a length of 3.5 or 4.5 metres. A mild steel reinforcing plate 20 is welded transversely to the upper end to provide a reinforced driving cap, and the lower section, extending for say 2 metres, of each sheet 12 is strengthened by an angle section reinforcing bar 21 welded to the body of the sheet. And on at least one of the pair of trench sheets 12, slightly below the upper end, a pair of projecting bracket plates or lugs 23 are rigidly secured to the face of each sheet to carry a cross-pin 24 to form a lifting eye engageable with a hook of a hoist lifting chain.

At staggered spaced positions, in this particular embodiment, each sheet is also provided with plates 25 welded in place which are slotted for detachably securing stirrupform metal straps or hoops, 26, termed 'waling straps', for carrying and supporting waling timbers which can be fitted to extend transversely, along the walls of the trench, between adjacent spaced-apart support devices positioned therein. As indicated, the free ends of each waling strap 26 has a short cross piece 27 which seats within the channel formation of the respective sheet 12 behind the plate 25 which retains said strap. The slot arrangement in the plate 25 enables the waling strap to be removed by lifting and then turning through 90 , and fitting in place is carried out by a reverse sequence of operations.It will be understood, however, that in an alternative simplified construction, the plates 25 may be omitted and the waling straps, with plain free ends, may each be welded directly to the respective sheets 12.

For pivotally connecting the struts 14, 14, each sheet 12 has welded thereto a pair of spaced mounting brackets 28,28, for carrying transverse pivot pins which engage with the ends of the respective struts.

The construction of each strut 14 is best seen from Figure 8 in conjunction with Figure 1. It comprises apair of tubular members, an outer member 2 and an inner member 30, fitted together telescopically, the inner member 30 being provided with a series of spaced holes 31 to engage selectively with a locking pin32 inserted through a longitudinal slot 34 in the inner end portion of the outer member 29. This inner end portion of the outer member 29 is also formed with an external screw thread 35 engaging with a threaded collar 36 which can be screwed along, using a handle portion 37, to vary the effective length of the slot 34.Since the locking pin 32, when the strut is in compression, will always engage the effective inner end of slot 34, a wide range of adjustment for the effective strut length is thereby obtained, first by selecting any one of the holes 31 in which to engage the locking pin, and then by adjusting the position of the collar 36. It may be emphasized, however, that the collar 36 is not intended to be adjusted whilst the strut is under load so that the struts do not function as screw jacks.

As shown, the outer end of each strut part 29 and 30 has a bearing aperture 44 or 45 provided by a transversely drilled hole and a cross-tube 41,41', welded inside, for the pivot pins carried by the respective mounting brackets 28 of the trench sheets 12, 12.

The two parts 29, 30, of each strut are prevented from separating completely, when the locking pin 32 is removed, by an internal retaining strap 40 consisting of an elongate metal loop which embraces firstly a transverse retaining pin 42 welded to the inner part after assembly and secondly the internal cross-tube 41 of the outer part.

In a modification for providing a greater range of adjustment, an additional extension piece as shown at 50 in Figure 8a may be supplied for each strut. This extension piece 50 comprises a length of tube which is adapted to fit telescopically over the outer tube 29 and has a series of spaced holes 51 of which any one can be selected to receive a locking pin (not shown) which is passed through the bearing aperture 44 to fix the extension piece 50 is adjusted position on the outer part 29.The one end of the extension piece 50 is fitted with a short sleeve, welded m place, which is drilled and provided with a short cross-tube 52 to form a bearing aperture 54, this then being engaged with the pivot pin carried by the respective mounting bracket of one of the trench sheets in the same way as the bearing aperture 44 when the extension piece is not used.

It will of course, be appreciated that many other modifications may be made, within the scope of the invention, in the physical details of the trench support device hereinabove described, without altering the general principles of construction, operation and use of the device.

WHAT WE CLAIM IS: 1. A trench support device, for supporting the side walls of an excavated trench of substantial size, in the form of a frame structure comprising a pair of elongate side members in parallel relationship which are arranged in use to engage against respective opposite side walls of the trench and which are interconnected by at least two spacedapart parallel struts forming a parallel motion linkage, the ends of the struts each being pivotally jointed to the respective side members, inwardly of the ends of the latter, for angular movement in the plane including the longitudinal axes of said side members and eac strut being composed of at least two relatively adjustable parts interconnected by adjustable mechanical coupling means by which each said strut can be adjusted to a particular preselected length in a preliminary pre-setting operation prior to use of the device thereby to enable the spacing between the side members, when the frame structure is opened out fully from a folded condition in which the struts extend obliquely to a condition in which the struts extend perpendicularly to the side members, to be set commensurate with the width of the trench, after carrying out said preliminary pre-setting operation to adjust the length of the struts, said device being such that in use, it can first be lowered in a folded or partly folded condition into the trench with the side members extending vertically in confronting relationship with the trench side walls and disposed one higher than the other, and the frame structure can then be fully opened out by applying a downwards force to the top end of the uppermost side member thereby to force the side members laterally against the trench side walls and to thus impart a compression loading to the struts.

2. A trench support device as claimed in claim 1, wherein the side members comprise elongate sheets of rolled steel plate having a length within the range of two to six metres.

3. A trench support device as claimed in claim 2, wherein the sheets each have a channelled cross-section and are provided with a reinforcing cap member at the upper end.

4. A trench support device as claimed in claim 2 or 3, wherein a lowermost portion of each trench sheet is reinforced by reinforcing members fixed thereto.

5. A trench support device as claimed in any of the preceding claims, wherein at least one of the side members is fitted with an eye or hook formation towards its upper end for engagement with a hoist lifting hook or chain.

6. A trench support device as claimed in any of the preceding claims, wherein the side members are each provided with a plurality of waling strap members for carrying and supporting waling timbers which, in use, can be fitted to extend transversely, along the walls of the trench, between adjacent pairs of a plurality of said support devices positioned therein.

7. A trench support device as claimed in claim 7, wherein the waling strap members are detachably fitted to the side members.

8. A trench support device as claimed in any of the preceding claims, wherein said two struts are spaced apart by a distance which lies within a range of between one-third and twothirds of the length of the side members.

9. A trench support device as claimed in any of the preceding claims, wherein each of said two struts is spaced from the nearest adjacent end of the side members to which it is connected by a distance which is equal to at least one sixth of the length of said side members.

10. A trench support device as claimed in any of the preceding claims, wherein each struthas a telescopic construction in which said two interconnected parts fit together in adjustable telescopic relationship, and locking means are provided for locking together said two parts in adjusted positions.

11. A trench support device as claimed in claim 10, in which the locking means comprises a disengage able locking pin arranged to be engaged with selected registering pairs of holes and/or slots in the two parts.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. The two parts 29, 30, of each strut are prevented from separating completely, when the locking pin 32 is removed, by an internal retaining strap 40 consisting of an elongate metal loop which embraces firstly a transverse retaining pin 42 welded to the inner part after assembly and secondly the internal cross-tube 41 of the outer part. In a modification for providing a greater range of adjustment, an additional extension piece as shown at 50 in Figure 8a may be supplied for each strut. This extension piece 50 comprises a length of tube which is adapted to fit telescopically over the outer tube 29 and has a series of spaced holes 51 of which any one can be selected to receive a locking pin (not shown) which is passed through the bearing aperture 44 to fix the extension piece 50 is adjusted position on the outer part 29.The one end of the extension piece 50 is fitted with a short sleeve, welded m place, which is drilled and provided with a short cross-tube 52 to form a bearing aperture 54, this then being engaged with the pivot pin carried by the respective mounting bracket of one of the trench sheets in the same way as the bearing aperture 44 when the extension piece is not used. It will of course, be appreciated that many other modifications may be made, within the scope of the invention, in the physical details of the trench support device hereinabove described, without altering the general principles of construction, operation and use of the device. WHAT WE CLAIM IS:

1. A trench support device, for supporting the side walls of an excavated trench of substantial size, in the form of a frame structure comprising a pair of elongate side members in parallel relationship which are arranged in use to engage against respective opposite side walls of the trench and which are interconnected by at least two spacedapart parallel struts forming a parallel motion linkage, the ends of the struts each being pivotally jointed to the respective side members, inwardly of the ends of the latter, for angular movement in the plane including the longitudinal axes of said side members and eac strut being composed of at least two relatively adjustable parts interconnected by adjustable mechanical coupling means by which each said strut can be adjusted to a particular preselected length in a preliminary pre-setting operation prior to use of the device thereby to enable the spacing between the side members, when the frame structure is opened out fully from a folded condition in which the struts extend obliquely to a condition in which the struts extend perpendicularly to the side members, to be set commensurate with the width of the trench, after carrying out said preliminary pre-setting operation to adjust the length of the struts, said device being such that in use, it can first be lowered in a folded or partly folded condition into the trench with the side members extending vertically in confronting relationship with the trench side walls and disposed one higher than the other, and the frame structure can then be fully opened out by applying a downwards force to the top end of the uppermost side member thereby to force the side members laterally against the trench side walls and to thus impart a compression loading to the struts.

12. A trench support device as claimed in

claim 11, wherein the locking pin engages with holes arranged to provide a relatively coarse length adjustment for each strut, and screw-threaded means are incorporated for providing a relatively fine length adjustment.

13. A trench support device as claimed in any of claims 10 to 12, wherein each strut has a removable additional extension piece which fits telescopically thereon and which is arranged to be locked in position to extend further the range of length adjustment.

14. A trench support device constructed and arranged substantially as herein described with reference to the accompanying drawings.

15. A trench fitted with a plurality of reinforcing trench support devices in accordance with any of the preceding claims.

16. A method of forming a reinforced excavated trench consisting in utilising a trench support device, constructed in accordance with any of claims 1 to 14, in the manner herein set forth.