GB2579441A - Improvements in or relating to demolition - Google Patents

Abstract

A cutting pattern for collapsing a box section column comprises a generally parallel pair of cuts designed to create a gap in the column, the gap allowing top and bottom sections of the column to slide off one another without front and back edges jamming. A method of collapsing the column includes the steps of making a generally parallel pair of cuts. A further method of cutting a column comprises the steps of explosively pre-weakening the column and collapsing the column. Collapse may be triggered by a kicking step and pre-weakening may comprise cross cuts. A pre-collapse pattern for a column comprising a pair of generally parallel, mutually spaced cuts is also claimed, as is a demolition system using the methods or patterns. A further cutting pattern for collapsing a column comprises a first cut angled in a first direction and two cuts angled in a second direction. A further method for collapsing a structural member includes the steps of: non-explosively pre-cutting the member in order to remove structural redundancy without weakening the structure; explosively pre-weakening the member beyond its design strength; and, a final explosive destabilising cutting step causing the member to lose its structural integrity.

Description

IMPROVEMENTS IN OR RELATING TO DEMOLITION

The present invention relates generally to demolition and particularly, although not exclusively, to the cutting of structural columns, beams, piers legs and the like as part of a demolition process.

The present invention may, for example, relate to box sectioned columns but also where there is any risk of a horizontal cut forming a parallel interface between two cut sections (on bigger H sectioned columns) which are big enough for the structure to sit and not be easy to move laterally to trigger a collapse.

Conventionally angled cuts are made to allow a slide and remove, by burning out enough material where there might have been a potential sit or a sit is deliberately formed, even adding greased shims into the sit cut before then fully cutting the flanges.

The structure will then sit/settle onto the shims and is in a stable, static state. The collapse is then triggered by either putting chains around the structure and pulling or, in bigger structures, by applying an explosive charge to push laterally so that the cut section of column moves laterally until it is free from the shims and is then able to collapse.

Traditionally, box columns are fully pre-weakened and cut with horizontal cuts packed with shims. The collapse of the column is triggered by using explosives to kick a column section out of line. However, all the cuts are done manually and this is potentially very dangerous.

A traditional sit cut is shown in Figures I and 2. The only way for the two parts of the column to move relative to each other is by a horizontal movement caused by a massive kick. The bearing horizontal surfaces slide on the shims.

Sometimes shims are not used and explosives are used to make the final cuts, but because the structure essentially goes into freefall, once the slanting sides make contact the forces required to kick the structure increase almost exponentially and very powerful kicking charges are needed, such as the charge described in GB2553502.

An aspect of the present invention provides a cutting pattern for collapsing a column, comprising a generally parallel pair of cuts designed to create a gap in the column, the gap designed to allow top and bottom sections of the column to slide off one another without front and back edges jamming.

A further aspect provides a method of collapsing a column, using explosively pre-weakening in conjunction with final explosive destabilising cuts comprising the steps of making a generally parallel pair of cuts designed to create a gap in the column, the gap designed to allow top and bottom sections of the column to slide off one another without front and back edges jamming.

A further aspect of the present invention provides a method for cutting a column comprising the steps of: i) explosively pre-weakening the column; and ii) collapsing the column.

Some aspects and embodiments of the present invention employ a multi-stage process comprising of "pre-cutting" the member (non-explosively) in order to remove structural redundancy without weakening the structure, ("structural redundancy removal") an "explosive pre-weakening" step after which the structure would still be able to stand but in which it has been weakened beyond its design strength followed by a "final explosive destabilising" cutting step which would cause the column or structural member to lose its structural integrity and finally an optional "explosive kicking" step to displace the cut components such that the cut member is no longer capable of supporting the main structure triggering the collapse of the main structure or preventing the element from receiving transferred loads from other cut members.

All the steps after the initial pre-cutting in the sequence would normally be timed to occur automatically, typically within a few milliseconds of each other.

Some aspects and embodiments of the present invention provide a way of pre-cutting to remove redundancy in columns and the like so that they remain inherently stable.

The pre-cutting could be part of the collapse mechanism or it could happen in advance.

The pre-weakening step may comprise a cutting step. In some embodiments the step is configured so as not substantially to weaken the column.

The explosive collapse step may comprise a cutting or kicking step.

The method of some aspects and embodiments of the present invention allows the structure to slide without needing shims or sliding surfaces or, potentially, kicking charges (although they made be used in addition).

The explosive collapse step may comprise a kicking step. For example an explosive kicking charge may be used to cause part of the column to move.

The pre-weakening step may comprise one or more cuts comprising two cooperating, generally parallel, mutually spaced cuts.

The pre-weakening step may comprise cross cuts. In some aspects and embodiments this is the key part of the invention.

In some embodiments, in a first step two "letterboxes" are formed, one low down on the side to which the column needs to move and another higher up on the opposite side approximately 45 degrees apart when viewed from the side. Two horizontal cuts, either both explosively, or by partial burning and explosively cutting, in which case the force of the explosive will naturally kick the "letterbox" out, or potentially fully burning and using explosives to kick the letterbox out. The letterbox cut can be configured to remove the material that would otherwise jam.

A second step is to make diagonal cuts (approximately 45 degrees) perpendicular to the letterbox cut that intersect with each of the letterboxes. The weight of the structure will cause the column section, which must also be cut higher up, to slide and rotate.

The second configuration described is an evolution of this in which we also make additional intersecting cuts with the 45-degree cut and a single additional horizontal cut above the lower letterbox. That would form a separate wedge which would further destabilise the system. This may be instead of a X-Cut.

What we are trying to avoid is fully cutting the structure so that it is just balanced on cut edges or shims, but we do not want to use excessive amounts of explosive, so we will pre-cut as much steel as we can without weakening it beyond its design strength. All final cuts may be done using explosives.

For example a first cut angled in a first direction, and two cuts angled in a second direction, each of the two cuts intersecting the first cut and being non-intersecting with each other.

The pre-weakening step may utilise one or more linear cutting charges.

The pre-weakening step may comprise a plurality of cuts, all the cuts being made on angles and all angles being different in order to make it impossible for the structure to find a stable position during collapse.

The step of collapsing the column may be performed explosively.

The present invention also provides a pre-collapse cutting pattern for a column, comprising a pair of cooperating, generally parallel, mutually spaced cuts.

The present invention also provides a cutting pattern for collapsing a column, comprising a first cut angled in a first direction, and two cuts angled in a second direction, each of the two cuts intersecting the first cut and being non-intersecting with each other.

The present invention also provides a cutting pattern for collapsing a column, comprising a generally parallel pair of cuts designed to create a gap in the column, the gap designed to allow top and bottom sections of the column to slide off one another without front and back edges jamming.

The present invention also provides a demolition system using a method or pattern as described herein.

A further aspect provides a method for collapsing a structural member comprising the steps of: non-explosively pre-cutting the member non-explosively in order to remove structural redundancy substantially without weakening the structure; explosively pre-weakening the member after which it can still stand but in which it has been weakened beyond its design strength; and a final explosive destabilising cutting step which causes the member to lose its structural integrity.

The method may further comprise an explosive kicking step to displace the cut components such that the cut member is no longer capable of supporting a main structure, triggering the collapse of the main structure and/or preventing the element from receiving transferred loads from other cut members.

Examples of the utility of the present invention include large industrial buildings and structures such as powerplants and chemical refineries.

Different aspects and embodiments of the invention may be used separately or together.

Further particular and preferred aspects of the present invention are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with the features of the independent claims as appropriate, and in combinations other than those explicitly set out in the claims.

The present invention is more particularly shown and described, by way of example, in the accompanying drawings.

The example embodiments are described in sufficient detail to enable those of ordinary skill in the art to embody and implement the systems and processes herein described. It is important to understand that embodiments can be provided in many alternative forms and should not be construed as limited to the examples set forth herein.

Accordingly, while embodiments can be modified in various ways and take on various alternative forms, specific embodiments thereof are shown in the drawings and described in detail below as examples. There is no intent to limit to the particular forms disclosed. On the contrary, all modifications, equivalents, and alternatives falling within the scope of the appended claims should be included. Elements of the example embodiments are consistently denoted by the same reference numerals throughout the drawings and detailed description where appropriate.

Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art. It will be further understood that terms in common usage should also be interpreted as is customary in the relevant art and not in an idealised or overly formal sense unless expressly so defined herein.

In the description, all orientational terms, such as upper, lower, radially and axially, are used in relation to the drawings and should not be interpreted as limiting on the invention.

Figures 3 to 12 illustrate a column cutting technique formed in accordance with the teachings of the present invention.

A double cut is used to produce a "letterbox gap" that allows the column sections to move without snagging. Without this, large kicking charges are required to move the column before the gap closes and the friction becomes too great to overcome. The letterbox cut allows the two sections to slide over each other without the two horizontal surfaces meeting and preventing movement. This is a unique way of cutting.

The drawings illustrate where the columns are pre-cut to reduce the amount of explosive cutting subsequently required, but the key is to not weaken the structure by making the cuts. Furthermore, by using appropriate angled cuts explosively, the structure is able to move without the need for kicking charges.

Using cutting charges allows all the final weakening to be done remotely.

In a further embodiment (not shown) all the cuts are made on angles and all angles are different in order to make it absolutely impossible for the structure to find a stable position.

Figure 13 is an annotated explanation of a letterbox cut formed in accordance with the present invention.

Figures 14 and 15 illustrate a horizontal letterbox prior to detonation. Figures 16 to 18 show the movement of upper and lower column sections following detonation.

This embodiment employ a multi-stage process comprising of "pre-cutting" the member (non-explosively) in order to remove structural redundancy without weakening the structure, ("structural redundancy removal") an "explosive pre-weakening" step after which the structure would still be able to stand but in which it has been weakened beyond its design strength followed by a "final explosive destabilising" cutting step which would cause the column or structural member to lose its structural integrity and finally an optional "explosive kicking" step to displace the cut components such that the cut member is no longer capable of supporting the main structure triggering the collapse of the main structure or preventing the element from receiving transferred loads from other cut members. All the steps after the initial precutting in the sequence would normally be timed to occur automatically, typically within a few milliseconds of each other.

Figures 19 to 21 illustrate, for purposes of comparison, the same type of detonation, but without a letterbox cut, and shows the collision of the column sections avoided by the present invention.

Figure 22 shows a pre-cutting pattern formed in accordance with an embodiment of the present invention. Placement of charges for an associated explosive pre-weakening step is shown in Figure 23.

Figure 24 shows an alternative pre-cutting pattern; and Figure 25 shows a corresponding pre-weakening explosive charge placement pattern.

Figures 26 to 30 show alternative cutting geometries.

Figure 26 shows two angled, parallel cutting lines. Pre-cuts are made at the ends of the lines before destabilising cuts are made along the line.

Figure 27 shows a pair of cuts, with the cuts being opposingly angled.

Figure 28 shows a single cut line embodiment, with two axially spaced edge cuts joined by an angled cut.

Figure 29 uses the cut of Figure 28, with an additional cut higher up the column and a kicking charge is used between the cuts.

Figure 30 shows a cross cut geometry. A first cut is angled in a first direction, and two cuts are angled in a second direction (generally opposite to the first direction). Each of the two cuts intersects the first cut and they non-intersecting with each other. In this embodiment the two second direction cuts are generally parallel. This cutting arrangement defines three different parts of the column. When these cuts are made part 3 tends to move outwards as illustrated. Section I is then likely to roll clockwise and section 2 may also move. This creates a collapsing column with three moving parts.

Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiments shown and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.

Claims (18)

1. CLAIMSI. A cutting pattern for collapsing a box section column, comprising a generally parallel pair of cuts designed to create a gap in the column, the gap designed to allow top and bottom sections of the column to slide off one another without front and back edges jamming.
2. 2. A method of collapsing a column, comprising the steps of making a generally parallel pair of cuts designed to create a gap in the column, the gap designed to allow top and bottom sections of the column to slide off one another without front and back edges jamming.
3. 3. A method for cutting a column comprising the steps of: i) explosively pre-weakening the column; and ii) collapsing the column.
4. 4. A method as claimed in claim 3, in which the pre-weakening step comprises a cutting step.
5. 5. A method as claimed in claim 3 or claim 4, in which the explosive collapse step comprises a cutting step.
6. 6. A method as claimed in any of claims 3 to 5, in which the explosive collapse is triggered by a step that comprises a kicking step.
7. 7. A method as claimed in any of claims 3 to 6, in which the pre-weakening step comprises one or more cuts comprising two cooperating, generally parallel, mutually spaced cuts.
8. 8. A method as claimed in any of claims 3 to 7, in which the pre-weakening step comprises a generally parallel pair of cuts designed to create a gap in the column, the gap designed to allow top and bottom sections of the column to slide off one another without front and back edges jamming
9. 9. A method as claimed in any of claims 3 to 8, in which the pre-weakening step comprises cross cuts.
10. 10. A method as claimed in any of claims 3 to 9, in which the pre-weakening step utilises one or more linear cutting charges.
11. A method as claimed in any of claims 3 to 10, in which the pre-weakening step comprises a plurality of cuts, all the cuts being made on angles and all angles being different in order to make it impossible for the structure to find a stable position during collapse.
12. 12. A method as claimed in any of claims 3 to II, in which the step of collapsing the column is performed explosively.
13. 13. A pre-collapse cutting pattern for a column, comprising a pair of cooperating, generally parallel, mutually spaced cuts.
14. 14. A cutting pattern for collapsing a column, comprising a first cut angled in a first direction, and two cuts angled in a second direction, each of the two cuts intersecting the first cut and being non-intersecting with each other.
15. 15. A demolition system using a method or pattern as claimed in any preceding claim.
16. 16. A method for collapsing a structural member comprising the steps of: non-explosively pre-cutting the member non-explosively in order to remove structural redundancy substantially without weakening the structure; explosively pre-weakening the member after which it can still stand but in which it has been weakened beyond its design strength; and a final explosive destabilising cutting step which causes the member to lose its structural integrity.
17. 17. A method as claimed in claim 16, further comprising an explosive kicking step to displace the cut components such that the cut member is no longer capable of supporting a main structure, triggering the collapse of the main structure and/or preventing the element from receiving transferred loads from other cut members.
18. 18. A cutting sequence and pattern for collapsing a box section column, comprising a generally parallel pair of cuts designed to create a gap in the column, the gap designed to allow top and bottom sections of the column to slide off one another without front and back edges jamming.