GB2099478A - Trench shoring assembly - Google Patents

Abstract

The trench shoring assembly is a development of that described in U.K. Patent Specification No. 1597833. A pair of shoring sheets (1) engage with opposite sides of a trench and are each supported by a respective pair of wheeled jacks (9). Each jack (9) cooperates with a respective rack for raising and lowering the shoring sheets. A ground engaging platform consists of parallel skids 12, one on each side of the trench, each skid carrying a rail on which runs the pair of jacks on that side of the trench. In order to prevent serious trench wall collapse in front of or behind the shoring sheets, a pair of front guard sheets (18) or a pair of rear guard sheets are provided and are arranged to overlap with the shoring sheets (1). A respective stabilizer beam may connect the pair of jacks on each side of the trench to restrict pivotal movement of the jacks. <IMAGE>

Description

SPECIFICATION Trench shoring assembly This application relates to a trench shoring assembly.

In U.K. Patent Application No. 9380/77 of T. P.

Treacy (U.S. Patent No. 4 1 93 717) is described a trench shoring assembly which comprises two vertical shoring sheets with braces to hold the sheets apart, a pair of ground engaging base plates laid on the surface of the ground adjacent to the respective sheets on opposite sides of the trench, and jacks supported on wheels running on rails mounted on the base plates and engaging with respective vertical racks and guides provided on the sheets.

Operation of the jacks raises, lowers or tilts the shoring sheets as necessary. As the trench is progressively advanced and back-filled, the base plates are first pulled forwards over the ground by an excavator, whilst the shoring sheets remain stationary, and then the jacks with the shoring sheets are pulled forwards along the rails.

Whilst the previously disclosed shoring assembly has been found to be generally satisfactory in operation, it has been found on occasions, particularly in unstable ground, that the sides of the trench just in front of the shield and behind the shield can collapse. This could be dangerous to workers in the trench and the first aspect of the present invention is concerned with reducing the danger of such a collapse.

According to one aspect of the invention a trench shoring assembly comprises two vertical shoring sheets for holding apart the opposite sides of a trench, a platform comprising a pair of parallel ground engaging members for supporting by the surface of the ground on opposite sides of the trench, respective sheet conveying means on opposite sides of the trench adapted to run along the respective ground engaging members whilst substantially supporting the weight of the shoring sheets, and a pair of guard sheets for engagement with opposite sides of the trench in front of, or behind, the shoring sheets, the guard sheets being arranged to overlap with the respective shoring sheets and being movable independently of the shoring sheets.

Thus, the guard sheets can be arranged to prevent serious trench wall collapse in front of or behind the shoring sheets depending upon where the guard sheets are chosen to be located.

Preferably the guard sheets are carried by the platform, and they may then be arranged to be carried forwards with the platform, or to be movable independently of the platform.

Since the guard sheets overlap with the shorting sheets there is no possibility of the trench walls collapsing in the space which might otherwise have appeared between the guard plates and the shoring sheets during movement of the platform or shoring sheets.

The conveying means may comprise wheels running on rails, or it might comprise skids which slide on the ground engaging members.

Preferably the assembly comprises a forward pair of such guard sheets at the front of the shoring sheets, and a rearward pair of guard sheets at the rear of the shoring sheets, in order to support the trench sides both in front of and behind the shoring sheets.

Usually it will not be necessary for the guard plates to extend down as far as the shoring sheets, since it is generally the upper parts of the trench walls that are susceptible to collapse.

The guard plates preferably project along the trench beyond the ground which is supporting the platform.

Braces may be employed to extend between the opposed guard plates to hold them apart, but often such braces will not be necessary.

The shoring sheets may be provided with rigid arms which project along the trench and engage with the exposed surfaces of the guard plates to hold the guard plates against the trench sides.

Rollers are preferably then provided between the arms and the guard plates to facilitate relative forward and rearwards movement of the arms and guard plates.

A connection between the guard plates and the platform is preferably arranged to enable the guard plates to be raised substantially clear of the trench.

Preferably a pivoted connection is provided between the guard plates and the platform. This is particularly advantageous for guard plates at the rear of the shoring sheets where back-filling operations are performed.

A second aspect of the invention is concerned with a mechanism for stabilising the movement of jacks in a trenching shield of the kind claimed in claim 1 of U.K. Patent Application No. 9380/77, in the form in which that application was in order for acceptance.

That claim specifies a shoring assembly for supporting the sides of a trench or hole in the ground comprising two vertical shoring sheets engaging with opposite sides of the trench or hole, means extending between the sheets of hold them apart, a respective substantially vertically extending rack provided on, or connected to, each of the sheets, a respective jack for raising and lowering each sheet, each jack comprising a base supported on the surface of the ground adjacent to the trench or hole and a jacking head supported by the base and engaged with the respective rack, a respective guide means provided on, or connected to, each sheet and extending parallel to the respective rack, and a respective guide member secured to the respective jacking head and cooperating with the respective guide means to restrain each jack from moving horizontally relative to the respective sheet.Such an assembly will hereinafter be referred to as a "shoring assembly of the stated kind".

When the base of the jacks of a shoring assembly of the stated kind are mounted on wheels running on rails on a ground engaging platform it has been found that some slewing of the jacks occurs in certain circumstances, that is, a jack tends to pivot about a vertical axis. This is undesirable because it can increase the wear on the various moving parts.

It is not, however, desirable rigidly to connect together the jacks associated with one shoring sheet, since during tilting of the shoring sheet by differential operation of jacks at the front and rear of the shield, for example in order to manoeuvre over services, the relative spacing apart of the jacks on each side will alter.

According to a second aspect of the invention in a shoring assembly of the stated kind in which a respective pair of jacks is provided for engagement with each shoring sheet, and the bases of the jacks are mounted on wheels running on rails supported on the surface of the ground, each pair of jacks is connected by a stabilizer beam which is so arranged as to hold each jack of the pair against pivotal movement relative to the beam about a vertical axis but to permit pivotal movement of each jack relative to the beam about a respective horizontal axis extending transversely of the trench, and also to permit relative movement apart of the connected jacks.

The beam preferably incorporates a telescopic section to provide for said relative movement apart of the jacks.

In order to keep the weight of the beam to a minimum yet provide maximum rigidity against bending about vertical axes of the beam, the beam is preferably constructed as a flat latticework extending in a horizontal plane.

A trenching assembly in accordance with the invention will now be described, by way of example oniy, with reference to the accompanying drawings in which: Figure 1 is a half front elevation of the trenching assembly shown in its position of use, but omitting the bracing in the rear half of the assembly; Figure 2 is a half rear elevation of the assembly, but omitting the bracing in the front half of the assembly; Figure 3 is an inside elevation of the assembly looking from the direction of the arrow A in Figure 1, but with the braces omitted; Figure 4 is a half plan view of the assembly, the front of the assembly being at the left; Figure 5 is an outside elevation of the assembly, the front of the assembly being at the left;; Figure 6 is an enlarged section on the line 6-6 of Figure 4 showing the pivotal connection between a rear guard plate and the platform; and Figure 7 is a section on the line 7-7 of Figure 6.

Figures 1 and 2 will be seen to be on a larger scale than Figures 3 to 5.

With reference to Figures 1 to 5 the shoring assembly comprises a pair of shoring sheets 1 which are held apart by a series of adjustable braces 2. Each shoring sheet 1 is made up of three shoring panels 3, 4, 5 bolted together on top of one another. Each panel comprises a lattice-work of horizontal and vertical channel section girders welded to the back face of sheeting which engages with the trench walls. There are also two principal vertical channel sections 6, 7 of each panel, shown best in Figure 3, to which the braces 2 are connected by releasable pin and socket joints. The interior of the channel sections 6, 7 face outwardly of the panels 3, 4, 5 towards the trench walls, and the panel sheeting is arranged not to cover the channel sections 6, 7 so that the interior of the channel sections 6, 7 is accessible on the outside of the panels.Within the channel sections 6, 7 is welded an I-beam 8 provided with respective vertical rack 8', seen best in Figure 5.

The details of this are shown in our earlier patent application.

The two racks 8 of each panel connect with the racks of the panels above and below to provide two continuous racks on each shoring sheet 1 extending for the full height of the shoring sheets 1.

A pair of jacks 9 is arranged alongside each shoring sheet 1 to engage with the respective racks 8 of that sheet 1 for raising and lowering the sheets 1 along with their interconnecting braces 2. The jacks 9 each comprise a jack base 10 carrying a wheel 11, shown in Figure 5, which run on rails 1 fixed tithe upper surface of a skid 12 which lies on the surface of the ground alongside the trench. The two skids 1 2 together with brace 14' connecting the rear ends 1 6' of the skids 1 2 constitute a ground engaging platform which substantially supports the weight of the shoring sheets 1 during raising and lowering of sheets 1.

The brace 14' is adjustable in length to control the width of the rear end of the platform.

Each jack 9 comprises a jacking head 14 provided with vertically spaced guide yokes 15, indicated generally in Figure 2 which engage around the flanges of the respective I-beam 8 slidably to guide the jacking head 14 relative to the shoring sheet 1. Each jacking head 14 carries an hydraulic ram 16, indicated in dotted outline in Figure 2 for raising and lowering a respective pawl assembly 1 7 engageable with the respective rack 8' for raising and lowering the sheets 1.

The assembly so far described is substantially the same as that described in the complete Specification of the previously mentioned U.K.

Application No. 9380/77 and further reference should be had to that Specification for details of its operation.

The assembly differs from that of the earlier application in the following important respects.

A pair of front guard sheets 18 and a pair of rear guard sheets 1 9 are carried by the front and rear of the ground engaging platform and extend downwardly into the trench in contact with the trench sides in front of and behind respectively the shoring sheets 1. Rear guard sheets 1 9 move with the platform, but front guard sheets 1 8 are independently slidable relative to the platform in the forward and reverse directions of the platform.

Front guard sheets 18 are supported by the platform by respective forwardly directed slide bars 20' carrying suspension brackets 20 at their front ends and slidably supported at their rear ends by respective box section stubs 21, Figure 1, received in a corresponding box section socket 22 extending across and welded to the front end 1 5 of each skid 12.

An optional brace 23 is connectable between hooked lugs 24 provided adjacent to the front edge of plates 1 8 to provide additional bracing of plates 1 8 in particularly unstable ground. The principal sideways support for the front guard sheets 1 8 is provided by a respective pair of arms 25 carried by the front end of the respective shoring sheet 1.The arms 25 each comprise a channel section member 26 with the open side of the channel facing the associated guard sheet 18, and the arms socket over any chosen one of a series of vertically spaced cutting teeth 27 provided on the front edge of panels 3, 4, 5. A strap, indicated at 26' in Figure 4, bridges the channel of member 26 to fit behind the tooth 27 to provide the socket action, and the rear end 28 of the member 26 is secured to the panel buy a removable pin, not shown. Thus, the arms 25 may be arranged at any desired heights.

The members 26 each carry a pair of rollers 29, 30 rotatable about vertical axes and engaging with the inner surface of the respective guard sheet 18 to maintain the sheet 1 8 pressed firmly against the trench walls, through the action of braces 2.

Guard plates 18 at their rear ends 31 overlap with the front end of shoring sheets 1 as shown in Figure 3, in that the rear ends 31 are sandwiched between the smooth face of sheets 1 and the trench wall. This overlap ensures that no material can fall into the trench from the upper part of the trench wall between the plates 18 and the sheets 1, and furthermore it helps to retain the plates 1 8 against the trench wall.

For working in deeper trenches further guard plates 1 8 may be provided below the existing plates 18, additional arms 25 being provided, and the tops of the additional plates being connected to the bottoms of the corresponding existing plates by suitable means.

The front guard plates 1 8 are pulled forwards by attaching a chain to the hooks of lugs 24, the plates 1 8 being pulled forwards before the platform and then the shoring sheets are moved forwards, the plates 18 remaining stationary during movement of the platform and sheets.

The rear guard plates 19 are mounted in a different manner from that of front guard plates 18. Shoring sheets 1 are each extended rearwardly by respective extension plates 32 which are slidably guided at their front edges on I-beams 8 for vertical movement relative to the panels 3, 4, 5. In order to maintain the plates 32 in the vertical position shown in Figure 3 during raising and lowering of the panels 3,4, 5, the upper front corner of each plate 32 is connected by a bracket 33, Figures 3 and 5, to a lug 34 provided on the respective rear jack 9.

Alternatively, one of a series of vertically spaced holes 33' in plate 32 may be used to connect plate 32 to lug 34, to give a different height of plate 32.

Rear guard sheets 19 each overlap at their front ends 35 with the rear ends 36 of the respective extension plate 32, the plate 32 being sandwiched between the respective guard sheet 1 9 and the trench wall. Thus, again no earth can fall from the upper part of the trench walls between the shoring sheets 1 and the guard sheets 19.

Guard sheets 1 9 extend rearwardly substantially beyond the rear end of skid 1 2 to provide support for the trench walls in the region in which the trench is back-filled.

The manner in which the rear guard sheets 19 are supported and held against the trench walls will now be described with reference in particular to Figures 6 and 7. A respective box section sleeve 37 is arranged with its axis vertical and is open at the top and bottom. Sleeve 37 is supported in a fixed vertical position by a box-section stub 38 welded thereto and extending horizontally into a respective box-section socket 39 welded to the rear end of the respective skid 12, the stub 38 being slidable in socket 39. An L-shaped support arm 40 is welded at one end 41 to the upper end of the respective guard plate 19, extends around brace 14, as showngin Figure 3, and is pivotally secured at its other end 42 to the sleeve 37 by a horizontal pivot pin 43 welded to sleeve 37.

Arm 30 is suitably strengthened by three elongate vertical webs 44 and by a flat reinforcing plate 45.

Thus, the rear guard sheets 19 are capable of being pivoted about the pivot pins 43 to be lifted out of the trench when necessary.

Guard sheets 1 9 are each held apart by a brace 51 acting against respective reinforcing frameworks comprising a vertical box-section stanchion 46 which extends slidably at its upper end through the respective sleeve 37, and a respective rearwardly extending channel-section arm 47 adjustably connected thereto by a boxsection sleeve 48 welded to the front end of arm 47. Stanchion 46 is provided with a series of vertically spaced holes engageable by a peg, not shown, carried by sleeve 48. The stanchions 46 with the arms 47 can each be raised when necessary by engaging a hook with an eye 49 secured to a flat plate 50 welded to the top of the respective stanchion 46 and which normally rests, as shown, in engagement with the top of sleeve 37.

The rear guard sheets 19 can be secured in the position shown by locking pins 47' carried by the respective arms 47.

The brace 51 extends between the arms 47, and the position of attachment of the ends of the brace 51 to the arm 47 is arranged to be adjustable along the arms. Brace 51 controls the spacing of guard plates 19, lateral transverse movement of the sheets 1 9 relative to the skids 12 being accommodated by sliding of stubs 1 8 in sockets 39.

It will therefore be appreciated that providing the front guard plates 18, the platform, and the shoring sheets 1 are moved successively a short distance at a time along the trench the overlap between the sheets 1 and both the front and rear guard sheets 18 and 1 9 can be maintained.

The front ends 15 of the skids 12 are provided with respective hooks 53 which are engageable by a transversely extending tow bar 54, as shown in Figures 1, 3 and 4, which can be engaged by the digger of an excavator to advance the platform along the trench. The tow bar 54 is connected at opposite sides of the trench by respective chains 55 to the shoring sheets 1, so that when the tow bar 54 is disengaged from hooks 53 it can be used for drawing forwards the sheets 1.

A further important feature of the illustrated assembly is the provision of a stabiliser beam 56, Figures 4 and 5, for connecting together the bases 10 of the jacks 9 in order to prevent slewing of the jacks as the jacks are rolled along the platform.

Beam 56 comprises an elongate, lattice frame 57 of relatively small vertical width but of substantial horizontal width in order to provide maximum resistance to bending of the beam about vertical axes commensurate with keeping the weight of the frame 57 within reasonable iimits. One end of the frame 57 is connected to the base 20 of the respective jack by a horizontal pivot 58 and its other end is provided with a longitudinally projecting rod 59 which is slidably received within a tubular socket 60 connected by a further horizontal pivot 61 to the base 10 of the corresponding jack 9. Thus the rod 59 and socket 60 provide a telescopic connection which permits relative movement apart of the jacks, which takes place when the jacks at one end are raised to tilt the sheet 1 , when negotiating a service for example. The pivots 58 and 61 accommodate the pivoting of the jacks relative to the platform during such a tilting operation, but the beam 56 is effectively rigid in opposing any tendency of the jacks to pivot about vertical axes.

The stabilizer beam 56 may conveniently be used for mounting hydraulic pumps for the jack cylinders 1 6.

A further feature of the assembly is the provision on each jack base 10 of a downwardly extending rectangular guide plate 62, Figure 5, which supports a pair of rollers, not shown, which engage under the head of rail 11' to prevent any substantial lifting of the jack base relative to the platform. The jacks may then be used in some circumstances to lift the platform clear of the ground, using these rollers, when it is desired to pack up the platform.

Claims (10)

1. A trench shoring assembly comprising two vertical shoring sheets for holding apart the opposite sides of a trench, a platform comprising a pair of parallel ground engaging members for supporting by the surface of the ground on opposite sides of the trench, respective sheet conveying means on opposite sides of the trench adapted to run along the respective ground engaging members whilst substantially supporting the weight of the shoring sheets, and a pair of guard sheets for engagement with opposite sides of the trench in front of, or behind, the shoring sheets, the guard sheets being arranged to overlap with the respective shoring sheets and being movable independently of the shoring sheets.

2. A trench shoring assembly as claimed in claim 1 in which the guard sheets are carried by the platform.

3. A trench shoring assembly as claimed in claim 1 or claim 2 in which the guard plates project along the trench beyond the ground which is supporting the platform.

4. A trench shoring assembly as claimed in any of the preceding claims in which the shoring sheets are provided with rigid arms which project along the trench and act upon the exposed surfaces of the guard plates to hold the guard plates against the trench sides.

5. A trench shoring assembly as claimed in claim 4 comprising rollers arranged between the arms and the guard plates to facilitate relative forward and rearwards movement of the arms and guard plates.

6. A trench shoring assembly as claimed in claim 2 or any of claims 3 to 5 as appended to claim 2 comprising a connection between the guard plates and the platform so arranged as to enable the guard plates to be raised substantially clear of the trench.

7. A trench shoring assembly as claimed in claim 6 in which the connection is a pivotal connection.

8. A trench shoring assembly as claimed in any of the preceding claims comprising both a forward pair of guard sheets at the front of the shoring sheets, and a rearward pair of guard sheets at the rear of the shoring sheets, in order to support the trench sides both in front of and behind the shoring sheets.

9. A shoring assembly of the stated kind in which a respective pair of jacks is provided for engagement with each shoring sheet, and the bases of the jacks are mounted on wheels running on rails supported on the surface of the ground, each pair of jacks is connected by a stabilizer beam which is so arranged as to hold each jack of the pair against pivotal movement relative to the beam about a vertical axis but to permit pivotal movement of each jack relative to the beam about a respective horizontal axis extending transversely of the trench, and also to permit relative movement apart of the connected jacks.

10. A shoring assembly substantially as described with reference to the accompanying drawings.