GB2272921A

GB2272921A - Supporting an excavation

Info

Publication number: GB2272921A
Application number: GB9224793A
Authority: GB
Inventors: Anthony Philip Gould
Original assignee: MECHPLANT Ltd
Current assignee: MECHPLANT Ltd
Priority date: 1992-11-26
Filing date: 1992-11-26
Publication date: 1994-06-01
Anticipated expiration: 2012-11-26
Also published as: GB2272921B; GB9224793D0

Abstract

A method of supporting an excavation comprising the steps of installing lining material 14 for opposed side walls of an excavation, disposing a pair of stanch ions 30 in load transmitting relationship with the lining material with an upper part of each stanchion projecting above the top of the excavation, and installing an upper cross strut 31 between said upper parts of the stanchions at a position spaced above the top of the excavation. <IMAGE>

Description

Title: "Supporting an Excavation" Description of Invention This invention relates to a method of and an apparatus for, supporting an excavation and more particularly, but not exclusively, for enabling an article such as a vessel to be introduced in an excavation.

Hitherto a vessel has been installed in an excavation, for example, by first digging an excavation, supporting opposed side walls of the excavation with lining material, the upper ends of which are maintained spaced apart by a bracing means comprising a plurality of cross-struts disposed at or adjacent the top of the excavation.

To permit the vessel to be installed, cross-struts were temporarily removed to allow entry of the vessel into the excavation with a consequent risk of the excavation collapsing whilst the cross braces are removed.

An object of the invention is to overcome or reduce the above described problem and a further object is to provide a new and improved apparatus for use in such an improved method.

According to one aspect of the invention, we provide a method of supporting an excavation comprising the steps of installing lining material for opposed side walls of an excavation, disposing a pair of stanchions in load transmitting relationship with the lining material with an upper part of each stanchion projecting above the top of the excavation, and installing an upper cross-strut between said upper parts of the stanchions at a position spaced above the top of the excavation.

The method may include the further step of introducing an article such as a vessel into the excavation between the stanch ions and beneath the upper cross strut.

Lower cross struts may be installed between the lining material at or adjacent the top of the excavation prior to introduction of the article into the excavation and removed to permit of introduction of the article into the excavation.

The lining material may comprise pile sections or trench sheeting.

The lining material may be provided with waling beams.

The lower cross struts may be installed to act between the waling beams.

The stanchions may be disposed in load transmitting relationship with the waling beams.

The stanchions may be disposed outside the waling beams and lining material.

Alternatively, the stanchions may be disposed inside the waling beams and lining material.

The excavation may be provided with a concrete base at least in way of the stanchions and the lower end of the stanchions may engage the concrete base to maintain the lower ends spaced apart.

The stanchions and the associated waling beams may be interconnected by a bracket having a first part to receive a stanchion and a second part to receive the waling beams.

The first and second parts may be of tubular configuration.

The second part may have a portion releasably secured in position to permit of entry of a waling beam into the second part.

After installing the lower cross struts between the lining material, the article may be disposed between the stanchions above the lower cross struts; the upper cross strut may be installed and the lower cross struts removed and the article then introduced into the excavation, lower cross struts re-installed and the upper cross struts may be removed.

The article may initially be disposed between the stanchions at a first, lower, level and then raised to a second, higher level, which may be adjacent the underside of the upper cross strut whilst the lower cross struts are removed.

Alternatively, after installing the lower cross struts between the lining material, the upper cross strut may be installed and lower cross struts removed followed by introducing the article into the excavation between the stanchions and beneath the upper cross strut and then re-installing the lower cross struts and the upper cross strut may then be removed.

Where the stanchions are disposed inside the waling beams, the lower ends of the stanchions may be engaged with a socket provided in or on the concrete base.

Guide cross struts may be provided to afford lateral stability to the stanchions in the longitudinal direction of the excavation.

Where the stanchions are disposed outside the waling beams, the method may comprise the further steps of effecting a local excavation and, if necessary, removing or relieving the lining material to permit of access to the waling beams, mounting a bracket on each waling beam, inserting a stanchion into the bracket and causing relative movement of the stanchion through the bracket until the lower end of the stanchion extends below the level of the top of the concrete base.

If desired, more than one upper cross strut may be provided between the stanchions adjacent the upper end thereof.

If desired, more than one pair of stanchions and associated upper cross strut or struts may be provided at desired positions along the length of the excavation.

According to another aspect of the invention, we provide an apparatus for supporting an excavation comprising a pair of stanchions, an upper cross strut and a connecting means to connect the upper cross strut to the stanchions at or adjacent the upper ends of the stanchions.

Each stanchion may be provided with a bracket having a first part to receive a stanchion and permit of sliding movement between the stanchion and the bracket in the longitudinal direction of the stanchion and a second part to receive a waling member.

The first and second parts may be of tubular configuration.

Each stanchion may be provided with a second connecting means spaced below the first connecting means to connect a second upper cross strut to the stanchions.

Examples of the invention will now be described with reference to the accompanying drawings, wherein: FIGURE 1 is a diagrammatic plan view showing a stage in a method embodying the invention; FIGURE 2 is a diagrammatic perspective view showing a stage of the method subsequent to the stage shown in Figure 1; and FIGURE 3 is an enlarged perspective view of part of Figure 2 showing a stanchion to waling beam connection.

Referring now to the drawings.

An excavation 10 is dug in the ground 11 in conventional manner. In this example the excavation has spaced parallel side walls 12 which are typically 12 metres to 20 metres long and transversely extending opposed end walls 13 which are typically 4 metres to 10 metres long. The excavation is typically 4 metres to 6 metres deep.

In the illustrated example, the tank is 20 metres long 5 metres wide and the excavation is 6 metres deep.

The side and end walls 12, 13 of the excavation 10 are supported in conventional manner by lining material which, in the present example, comprise conventional pile sections 14. At a position spaced below the top of the excavation the pile sections are provided with a waling frame 15 comprising longitudinally extending waling beams 16 of conventional kind and, at their ends the waling beams 16 are connected together by end braces 17 which provide end waling members of the waling frame to support the pile sections 14 for the end walls 13 of the excavation.

The waling beams 16 are made in conventional manner from a plurality of sections and an end section is provided with a hydraulic ram operable so as to force the end waling members against the end wall 13 of the excavation. The end braces 17 are likewise provided with a hydraulic ram operable to force end parts 18 thereof out of a central part 19 to force the waling beams 16 against the side walls 14 of the excavation.

A desired plurality of lower cross struts 20, of similar construction to the end braces 17, are provided between the waling beams 16 to ensure that the side walls are properly supported.

Thus far the method described is conventional and further description is unnecessary as it will be familiar to those of skill in the art. It may be observed however that the waling beams 16 are supported on the pile sections 14 by means of chains 21 in conventional manner until the waling frame is stressed by operating the hereinbefore mentioned hydraulic rams.

At a position adjacent the mid-point of the side walls 12 but displaced approximately 1 metre towards one end of the excavation, an upper part of a pile section 14 on each side of the excavation at that position is cut off and removed and the ground excavated locally in the region of the removed pile part. A bracket 25 is then bolted to the waling beams 16.

The bracket 25 comprises first and second parts 26, 27 both of tubular configuration having a rectangular cross-section.

The longitudinal axis of the tube of the first part 26 is disposed vertically whilst that of the second part 27 which receives the waling beam, is disposed horizontally. The part 27 comprises a first portion 28 welded to the first part 26 and a releasable portion 29 which is bolted to the first portion 28 and which together with the first portion 28 provides the tubular configuration with the longitudinal axis of the tube extending horizontally.

A stanchion 30 is then lowered into each bracket part 26 and forced downwardly, for example by a hammer push driving or vibrating to depth until the bottom of the stanchion 30 is at a level with the underside of a concrete base provided at the bottom of the excavation 10 in conventional manner. Suitable wedges are then driven between the stanchion 30 and its associated part 26 to provide torsional restraint.

Thereafter the method of this present invention can be performed in two alternative ways. The first, and preferred, alternative will now be described.

An upper cross strut 31 of similar construction to the cross struts 20 described hereinbefore is installed between the stanchions 30 adjacent their upper ends 32.

The stanchions are provided with a pair of horizontally spaced lugs which receive an end part of the cross strut therebetween and are pinned thereto.

The hydraulic ram of the upper cross strut 31 is then actuated to force the upper ends of the stanchion 30 apart. If desired, more than one cross strut 31 may be installed between further pairs of lugs or other attachment means adjacent the upper end of the stanch ions 30 to provide an adequately strong biasing force.

When the or each upper cross strut 31 has been installed the lower cross struts 20 are removed.

The vessel to be installed in the excavation, in the present example a sewage holding tank 33, is then lifted with a suitable crane and moved between the stanchions 30 beneath the or each upper cross strut 31 as illustrated in Figure 2.

Because of the off-set of the stanchions 30 towards one end of the excavation 10 in general it will be possible to manoeuvre the tank into position but if in a particular case this is not possible, it may be necessary temporarily to support the tank on cross beams extending across the top of the excavation to enable a sling 34 by which the tank is connected to a crane hook 35 to be reset either side of the or each upper strut 31.

When the tank has been moved into position, it is lowered into the excavation. The lower cross struts 20 are then re-installed and their rams actuated to force the waling beams against the pile sections 14. The or each upper strut 31 is then removed and back-filling operations performed in conventional manner together with removal of the stanchions 30, pile sections 11 and the waling frame.

The above described method requires only the use of a single crane since the lower cross struts 20 are removed by the crane before the crane is required to move the tank into position and the crane has lowered the tank into the installation before it is required to be used to re-install the lower cross struts.

In the second alternative, after installing the stanch ions 30 and before installing the or each upper cross strut 31, a crane is utilised to move the tank 33 between the stanchions 30 and it is temporarily supported on cross beams at or near the level of the top of the excavation, or, if desired, it may be held by a crane at this time.

The or each cross strut 31 is then installed between the stanchions 30 using a second crane if necessary.

A crane then lifts the tank 33 until the top of the tank is adjacent the or the lower or lowest cross strut 31 and once the tank is suspended at this height a second crane is used to remove the lower cross struts 20. Thereafter the tank 33 is lowered into the excavation, at least one of the cranes is then used to reinstall the cross struts 20 and to remove the or each upper cross strut 31.

The above described method requires the use of two cranes and so is less preferable than the first alternative.

Although in the above described examples the stanchions have been described as being disposed outside the waling beams 16, if desired the stanchions 30 may be disposed inside the waling beams 16. This is not preferred since for a given size of tank it requires the side walls 12 of the excavation to be spaced further apart than does the previously described embodiment.

In this modification, a bracket 25 is not used but instead, at a longitudinal position where it is desired to install the stanchions 30, a pair of suitably spaced apart cross struts 20 are provided to provide guide struts between which the stanchions 20 are inserted. The guide struts having been spaced apart so as to provide a snug sliding fit for the stanchions 20.

The stanchions 20 are chained to the waling frame 16 before they are disconnected from the crane so as to ensure that they remain vertical until the or each upper cross strut 31 is installed. Either of the two alternatives previously described may be performed with this modification or where the stanchions are disposed inside the waling beams 16.

In this modification it is necessary to provide a locating means for the bottom of each stanchion which is preferably provided by a socket cast in the concrete base slab.

In the examples described hereinbefore, each stanchion is 10 metres long and weighs approximately 3 tons. If desired however, the stanchions may be of other height but typically have a minimum height of about 3 metres above ground level but they are more typically at least 4 metres high.

In all cases, when the stanchion 30 and the upper cross struts 31 are removed, they may be removed as individual components or simply lifted out as a single interconnected assembly.

Although a single pair of stanchions 30 has been described hereinbefore, if desired more than one pair of stanchions may be provided at suitable positions along the length of the excavation depending upon the size of the vessel to be introduced. If desired the vessel may comprise a pipe section or a continuous pipe instead of a tank or, instead any other suitable article.

Although it is preferred to cross brace the waling beams with lower cross struts 20 as described hereinbefore, if desired, depending upon the size of the excavation and the waling beams and the number, disposition and strength of the stanchions and the or each upper cross strut, the excavation may be initially made and supported without the use of lower cross struts and solely by the use of stanchions and upper cross strut or struts arranged as desired together with, if appropriate, waling beams and end braces.

Although the method has been described in connection with installing a vessel, in the excavation in the broadest aspect the invention may be used simply to make an excavation without the introduction of any article.

For example, to permit of access of equipment to the excavation, for example, when the excavation has revealed an already present article which needs servicing or repair with bulky equipment or to construct a structure within an excavation whose upper surface extends above ground level.

The features disclosed in the foregoing description, or the accompanying drawings, expressed in their specific forms or in the terms or means for performing the desired function, or a method or process for attaining the disclosed result, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

CLAIMS:

1. A method of supporting an excavation comprising the steps of installing lining material for opposed side walls of an excavation, disposing a pair of stanchions in load transmitting relationship with the lining material with an upper part of each stanchion projecting above the top of the excavation, and installing an upper cross strut between said upper parts of the stanchions at a position spaced above the top of the excavation.

2. A method according to Claim 1 wherein the lining material comprises pile sections or trench sheeting.

3. A method according to Claim 1 or Claim 2 comprising the further step of introducing an article into the excavation between the stanchions and beneath the upper cross strut.

4. A method according to Claim 3 wherein lower cross struts are installed between the lining material at or adjacent the top of the excavation prior to introduction of the article into the excavation and removed to permit of introduction of the article into the excavation.

5. A method according to any one of the preceding Claims wherein the lining material is provided with waling beams.

6. A method according to Claim 5 when dependant on Claim 4 wherein the lower cross struts are installed to act as waling beams.

7. A method according to Claim 5 or Claim 6 wherein the stanchions are disposed in load transmitting relationship with the waling beams.

8. A method according to any one of Claims 5 to 7 wherein the stanchions are disposed outside the waling beams and lining material.

9. A method according to any one of Claims 5 to 7 wherein the stanchions are disposed inside the waling beams and lining material.

10. A method according to any one of Claims 5 to 8 wherein the stanchions and the associated waling beams are interconnected by a bracket having a first part to receive a stanchion and a second part to receive the waling beams.

11. A method according to Claim 10 wherein the first and second parts are of tubular configuration.

12. A method according to Claim 10 wherein the second part has a portion releasably secured in position to permit of entry of a waling beam into the second part.

13. A method according to Claim 4 or any one of Claims 5 to 12 when dependant directly or indirectly on Claim 4 wherein after installing the lower cross struts between the lining material, the article is disposed between the stanchions above the lower cross struts, the upper cross strut is installed and the lower cross struts removed and the article then introduced into the excavation, the lower cross strut re-installed and the upper cross struts are removed.

14. A method according to Claim 13 wherein the article is initially disposed between the stanchions at a first, lower, level and then raised to a second, higher level.

15. A method according to Claim 14 wherein the second level is adjacent the underside of the upper cross strut whilst the lower cross struts are removed.

16. A method according to Claim 4 or any one of Claims 5 to 12 when directly or indirectly dependant on Claim 4 wherein after installing the lower cross struts between the lining material, the upper cross strut is installed and the lower cross struts are then removed, followed by introducing the article into the excavation between the stanchions and beneath the upper cross strut and then re-installing the lower cross struts and the upper cross struts are then removed.

17. A method according to any one of the preceding Claims wherein guide cross struts are provided to afford lateral stability to the stanchions in the longitudinal direction of the excavation.

18. A method according to any one of the preceding Claims wherein the excavation is provided with a concrete base at least in the way of the stanchions and the lower end of the stanchions engage the concrete base to maintain the lower ends thereof spaced apart.

19. A method according to Claim 10 or any one of Claims 11 to 18 when dependent directly or indirectly on claim 10 wherein the method comprises the further steps of effecting a local excavation and mounting a said bracket on each waling beam, inserting a stanchion into the bracket and causing relative movement of the stanchion through the bracket to lower the stanchion.

20. A method according to Claim 19 when dependent on claim 18 wherein the stanchion is lowered until the lower end of the stanchion extends below the level of the top of the concrete base.

21. A method according to Claim 18 when dependent directly or indirectly on claim 9 wherein the lower ends of the stanchions are engaged with a socket provided in or on the concrete base.

22. A method according to any one of the preceding Claims wherein more than one upper cross strut is provided between the stanchions adjacent the upper end thereof.

23. A method according to any one of the preceding Claims wherein more than one pair of stanchions and associated upper cross strut or struts are provided at desired positions along the length of the excavation.

24. A method substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

25. An apparatus for supporting an excavation comprising a pair of stanchions, an upper cross strut and a connecting means to connect the upper cross strut to the stanchions at or adjacent the upper ends of the stanchions.

26. An apparatus according to Claim 25 wherein each stanchion is provided with a bracket having a first part to receive a stanchion and permit of sliding movement between the stanchion and the bracket in the longitudinal direction of the stanchion and a second part to receive a waling member.

27. An apparatus according to Claim 26 wherein the first and second parts are of tubular configuration.

28. An apparatus according to Claim 26 or Claim 27 wherein the second part has a portion releasably secured in position to permit of entry of a waling beam into the second part.

29. An apparatus according to any one of the preceding Claims wherein each stanchion is provided with a second connecting means spaced below said connecting means to connect a second upper cross strut to the stanchions.

30. An apparatus substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

31. Any novel feature or novel combination of features disclosed herein and/or illustrated in the accompanying drawings.