GB2613187A

GB2613187A - An excavator for use in underpinning operations

Info

Publication number: GB2613187A
Application number: GB2117080.8A
Authority: GB
Inventors: John Ranford Robert
Original assignee: Charlton Piling & Foundations Ltd
Current assignee: Charlton Piling & Foundations Ltd
Priority date: 2021-11-26
Filing date: 2021-11-26
Publication date: 2023-05-31
Also published as: GB202117080D0

Abstract

An excavator for use in underpinning operations comprises a rotary excavation member 2, a screw conveyor 3 and an actuation unit 4 that drives both the member 2 and conveyor 3. The conveyor 3 comprises a screw 5 arranged to rotate in a conveyor housing to convey material excavated by the excavation member to an outlet 7 of the conveyor 3. A method of using the excavator is further provided, whereby excavation is performed below a structure to from a cavity below the structure, using the conveyor 3 to convey material out of the outlet 7, and reinforcing the structure by introducing a reinforcement into the cavity. The outlet may be an aperture in a wall of the housing, and the member 2 and conveyor 3 may be mounted on and driven by a common drive shaft 8. The excavator may comprise a cutter which cuts a generally square shaped cavity in the earth, wherein the rotary excavation member 2 rotates within the footprint of the cutter. An excavator assembly with the excavator mounted on a support structure may be further provided, whereby a support structure actuator actuates the support structure to actuate axial movement.

Description

AN EXCAVATOR FOR USE IN UNDERPINNING OPERATIONS

Field of the Invention

The present invention relates to an excavator for use in underpinning operations. The present invention also relates to a method of underpinning a structure.

Background of the Invention

In the construction or renovation of a building or other structure, underpinning is the process of strengthening the foundation of the structure. This may be necessary, for example, because the original foundation isn't strong or stable enough, the usage of the structure has changed, the properties of the supporting the structure may have changed, possibly through subsidence, etc. In underpinning, the depth and/or breadth of the existing building foundation may be extended so that the foundation either rests on a more supportive soil stratum and/or so that the load is distributed across a greater area.

There are various different types of underpinning, including mass concrete underpinning, beam and base underpinning, etc. In general terms, underpinning requires excavating below a structure, using an excavator, to form a cavity below the structure and reinforcing the structure by introducing a reinforcement into the cavity.

In some instances the excavation is performed either by hand digging or by using an excavator with digger bucket. However, this can present a number of problems. Hand digging is slow and time-consuming, thereby increasing costs. Also, there is increased danger associated with such manual work, for example the danger of collapse of the earth above onto the worker.

Using an excavator with digger bucket can cause damage to the existing brickwork or foundations if the digger bucket inadvertently collides with it.

Furthermore, with both hand digging and an excavator with digger bucket, it can be time consuming and labour intensive to remove the excavated material from the cavity and dispose of it.

The present invention seeks to address or mitigate at least some of the above-mentioned problems. Alternatively, or additionally, the present invention seeks to provide an improved excavator for use in underpinning operations. Alternatively, or additionally, the present invention seeks to provide an improved method of underpinning a structure.

Summary of the Invention

According to a first aspect of the invention there is provided an excavator for use in underpinning operations, comprising: a rotary excavation member; a screw conveyor; and an actuation unit configured to drive the excavation member and screw conveyor; wherein the screw conveyor comprises a screw arranged to rotate in a conveyor housing to convey material excavated by the excavation member to an outlet of the screw conveyor.

The excavator may provide for a relatively fast and efficient means of excavation during underpinning operations. In this respect, the rotary excavation member may be driven at a relatively high rotational speed to rapidly excavate a cavity, with the screw conveyor able to convey the excavated material from the excavation member, to the outlet, at a rate that is fast enough to match the rate of excavation. This can significantly reduce the overall time of the underpinning operation, compared to the above known methods, thereby saving substantial cost.

Due to the use of an actuator powered rotary excavation member and screw conveyor, the excavator may be used by a worker positioned outside of the cavity being excavated, thereby removing the danger of the cavity collapsing on the worker.

The conveyor housing may prevent excavated material from coming off the rotating screw, for example by propelled under centripetal force, due to the rotation of the screw, and/or under gravity, and out of the housing. Accordingly, the excavated material may only exit the housing at the outlet, thereby allowing for efficient and controlled collection of the excavated material at the outlet.

The conveyor housing may prevent the rotating screw from contacting and damaging a structure that is being underpinned.

In embodiments of the invention the conveyor housing is arranged to retain excavated material on the rotating screw, as it is conveyed along the screw. This may provide for a particularly effective and complete conveyance of the excavated material, to the outlet of the screw conveyor.

In this respect, the conveyor housing may have an inner surface that is proximal to the circumferentially outer periphery of the screw. The inner surface may extend substantially around the circumferentially outer periphery of the screw. The inner surface may extend substantially along the axial extent of the screw. The inner surface may have the general shape of the inner surface of a hollow cylinder. An outer surface of the conveyor housing may have the general shape of an outer surface of a cylinder. In this respect, the conveyor housing may have the general shape of a hollow cylinder. This may provide a conveyor housing that is relatively compact and that has relatively high structural strength.

Optionally the outlet is an aperture in a wall of the conveyor housing. This may provide for a compact overall arrangement, whereby the outlet is integrated into a wall of the housing. The outlet may be arranged such that the excavated material can pass out of the outlet under gravity. This may provide for relatively consistent and straightforward output of the excavated material. In this respect, the outlet may be in a lower side of the housing.

Optionally the excavation member and screw conveyor are driven by a common drive shaft. In this case, the excavation member and screw may be mounted on the common drive shaft, so as to rotate with the drive shaft. The use of a common drive shaft may provide for a relatively compact overall arrangement, which may be particularly advantageous in underpinning operations, due to the space constraints Involved.

The rotary excavation member may be any excavation member that is configured to be rotatably driven to cut into the earth to excavate a cavity that is suitable to have a reinforcement introduced into to underpin a structure of a building. The rotary excavation member may be a rotary cutting blade configured to excavate such a cavity, for example. The rotary cutting blade may, for example, comprise one or more teeth, for example, earth teeth, rock teeth and/or tungsten teeth.

Optionally the excavator is configured to excavate a cavity that has a generally square cross-sectional shape. This may advantageously allow the cavity to have a shape that matches that of a structural reinforcement, for example a beam, inserted into the cavity during underpinning operations.

Optionally the excavator comprises a cutter configured to cut a generally square shape into the earth as the excavator is driven into the earth. The rotary excavation member may be configured to rotate within the footprint of the cutter. Optionally the screw is helical. The screw may be a screw blade mounted on a central shaft. This may provide for support of the screw blade during underpinning operations. The shaft may be said common driveshaft.

Optionally the excavation member is provided at a front end of the screw. In this respect, the screw may extend rearwardly from the excavation member to the outlet of the screw conveyor.

In embodiments of the invention the actuation unit is coupled to the excavation member and screw conveyor to drive the rotation of the excavation member and screw conveyor (i.e. to drive the rotation of the screw of the screw conveyor).

In embodiments of the invention the actuation unit comprises a rotary actuator that is so coupled to the excavation member and screw conveyor. Optionally the actuator is a hydraulic actuator. The actuator may be any suitable type of actuator, for example a pneumatic actuator, hydraulic actuator, electric actuator, etc. Optionally the actuation unit is a single actuator configured to drive both the excavation member and screw conveyor. This may advantageously provide for a relatively compact and light weight excavator.

Optionally the excavator comprises a mount, for mounting the excavator to a support structure.

Optionally the mount is adjustable such that the excavator may be mounted to the support structure in a plurality of orientations. The mount may comprise a mounting bracket that is attachable to a mounting part of the mount, in first and second orientations, such that the excavator may be mounted to the support structure in first and second orientations respectively. It will be appreciated that any suilable means of releasable attachment may be used, to allow the orientation to be adjusted.

According to a second aspect of the invention there is provided an excavator assembly comprising an excavator according to the first aspect of the invention and a support structure on which the excavator is mounted.

The support structure may be any structure for providing support to the excavator in use.

Optionally the excavator assembly comprises a support structure actuator configured to actuate the support structure so as to actuate anal movement of the excavator.

It will be appreciated that, unless otherwise stated, a reference to axial movement refers to movement that has at least a directional component in the axial direction (i.e, in the direction of the rotational axis of the rotary excavation member) and does not necessarily require that it is parallel to the axial direction. Optionally said axial movement is substantially parallel to the axial direction.

For example, the excavator may be mounted to an arm that is connected to an actuator to drive movement of the arm. The arm may be an arm of an excavation machine, for example an arm of an excavator with digger bucket, forklift truck, wheel loader, etc. Alternatively, or additionally, the support structure may be part of a wheeled vehicle that is driven in the axial direction by an engine of the vehicle.

According to a third aspect of the inventicn there is provided a method of underpinning a structure, comprising: providing an excavator for use in underpinning operations, the excavator comprising: a rotary excavation member; a screw conveyor; and an actuation unit configured to drive the excavation member and screw conveyor; wherein the screw conveyor comprises a screw arranged to rotate in a conveyor housing to convey material excavated by the excavation member to an outlet of the screw conveyor; excavating below a structure to be underpinned, using the excavator, to form a cavity below the structure; conveying material excavated by the excavation member to the outlet, using the screw conveyor, and reinforcing the structure by introducing a reinforcement into the cavity.

The excavator may be an excavator according to the first aspect of the invention.

The excavator may be the excavator of the excavator assembly of the second aspect of the invention. In this respect, the excavator may be mounted to a support structure, to form the excavator assembly of the second aspect of the invention. The method may comprise providing said excavator assembly.

The support structure actuator may actuate the support structure so as to actuate axial movement of the excavation member.

The excavator may be used in a non-vertical orientation.

In this respect, the excavator may be used in a substantially horizontal orientation.

Optionally the excavator is used to excavate the cavity from a lateral side of the cavity.

The cavity may be directly underneath the structure (i.e. within the footprint of the structure) and/or at least partially laterally offset from the structure (i.e. at least partially outside the footprint of the structure).

The features of any of the above aspects of the invention may be combined with one or more features of any of the other aspects of the invention, in any combination. In this respect, the excavator referred to in the excavator assembly of the second aspect of the invention may have any of the features of the excavator of the first aspect of the invention, in any combination, and vice-versa. Similarly, the method of the third aspect of the invention may have any of the features of the excavator or excavator assembly of the first and second aspects of the invention and vice-versa.

Other preferred and advantageous features of the invention will be apparent from the following description.

Description of the Drawings

A specific embodiment of the invention will now be described

with reference to the description and drawings.

Figure 1 shows a perspective view of an excavator according to an embodiment of the invention, where a mount of the excavator is in a first orientation; Figure 2 shows a plan view of the excavator shown in Figure 1; Figure 3 shows a side view of the excavator shown in Figures 1 and 2; Figure 4 shows a rear view of the excavator shown in Figures 1 to 3; Figure 5 shows a front view of the excavator shown in Figures 1 to 4 (with a rear portion of the excavator omitted for illustrative purposes); Figure 6 shows a side view of an excavator assembly comprising the excavator show in Figures 1 to 5, but where a conveyor housing of the excavator is shown as transparent for illustrative purposes; Figure 7 to 9 shows schematic illustration of the method of underpinning a structure, with Figure 8 showing a cross-sectional view of the excavated cavity (and building 31), and Figure 10 shows a view corresponding to that of Figure 1 but where the mount of the excavator is in a second orientation (and where the base 17 and mounting bracket 16 are shown exploded from the platform 14 and the cylindrical motor housing 9 is shown in an exploded view for illustrative purposes).

Detailed Description

Referring to Figures 1 to 6 there is shown an excavator 1, for use in underpinning operations, according to an embodiment of the invention.

In summary, the excavator 1 comprises a rotary excavation member 2, a screw conveyor 3 and an actuation unit 4 (see Figure 6) configured to drive the excavation member 2 and screw conveyor 3. The screw conveyor 3 is configured to convey material excavated by the excavation member 2 to an outlet 7 of the screw conveyor 3.

In more detail, the excavator 1 comprises a drive shaft 8 (see Figure 6) configured to rotate in a conveyor housing 6 about a rotational axis A that is co-axial with a central longitudinal axis of the conveyor housing 6. It will be appreciated that, unless otherwise stated, references to the axial direction' are in relation to the rotational axis A. A rotary excavation member 2, in the form of a cutting blade 2, is fixedly mounted to a first end of the drive shaft 8, so as to rotate with the drive shaft 8 about the rotational axis A. The opposite, second, end of the drive shaft 3 is mechanically connected to an actuation unit 4 in the form of a hydraulic rotary motor 4 configured to drive rotation of the drive shaft 3 about its rotational axis A. The hydraulic motor 4 is connected to a hydraulic fluid supply (shown schematically as 15 in Figure 3). The hydraulic motor 4 is mounted in a cylindrical motor housing 9 that is itself mounted to a rear end of the conveyor housing 6.

The cutting blade 2 is located in front of the front end of the conveyor housing 6. In this respect, the cutting blade 2 is external to the conveyor housing 6. The cutting blade is configured to rotate with the drive shaft 8, about the rotational axis A. The conveyor housing 6 has a main body 20 (see Figure 2) that has the general shape of a hollow cylinder with a longitudinal axis that is co-axial with the rotational axis A of the drive shaft 8. The main body 20 comprises a cylindrical wall 25 that defines a cylindrical inner volume with a circular front opening 24 (see Figure 6), at the front of the main body 20.

The conveyor housing 6 also has a front section 21, mounted to a front end of the main body 20. The front section 21 has the general cross-sectional shape of a hollow square that circumscribes the front end of the cylindrical main body and is centred on the rotational axis A. The front section 21 defines a generally square front opening 22 (see Figure S) that is in communication with the circular front opening 24 of the main body 20 such that material excavated by the cutting blade 2 can pass from the cutting blade 2 and into the main body of the housing 6 (as described further below).

The square front section 21 acts as a cutter, that cuts a square shape, as it is pushed through the earth, with the cutting blade 2 rotating within the square footprint of the front section 21, so as to excavate a cavity with a substantially square cross-sectional shape.

In the currently described embodiment, the rotary cutting blade 2 comprises a plurality of earth teeth 60, in the form of clay spades, which are made of tungsten. It will be appreciated that any suitable type and configuration of teeth may be used, including rock teeth, for example, which may be of any suitable material.

The excavator 1 also comprises a screw conveyor 3 that comprises the conveyor housing 6 and a helical screw 5 fixedly mounted on the drive shaft 8, so as to rotate with the drive shaft 8. In this respect, both the cutting blade 2 and screw are rotatably driven by the motor 4, via rotation of the common drive shaft 8. The use of a common drive shaft 8, to drive both the cutting blade 2 and screw 5, may provide for a relatively compact overall arrangement, which may be particularly advantageous in underpinning operations, due to the space constraints involved.

The screw 5 extends rearwardly along the drive shaft R, along a helical path around the drive shaft 8, from a rear side of the cutting blade 2 to the axial location of the rear side of an outlet window 7 (described in more detail below) in the conveyor housing 6.

The outlet window 7 is an arcuate window provided in a lower side of the housing 7 and extends through the thickness of the wall 25 of the housing 6. The window 7 extends along a lower portion of the circumference of the housing wall 25 such that it has an arcuate shape and extends through the thickness of the wall 25 to provide an outlet that connects the inner volume defined by the conveyor housing 6 with the exterior of the conveyor housing 6.

The outlet window 7 extends along a rear axial section of the screw 5. In this respect, excavated material being conveyed by the screw 5 passes out of the outlet window 7 under gravity. Providing the outlet window 7 in the wall 25 of the conveyor housing 6 may provide for relatively consistent and straightforward output of the excavated material, as well as a relatively compact overall arrangement.

The screw 5 rotates substantially within the housing 6 (with only a small front part of the screw 5 extending out of the front of the housing 6).

The conveyor housing 6 is arranged to retain excavated material on the rotating screw 5, as it is conveyed along the screw 5. In this respect, the cylindrical inner surface of the conveyor housing wall 25 is proximal to, and extends around, the circumferentially outer periphery of the rotating screw 5 and extends along substantially the axial extent of the screw 5 (with only a small front part of the screw 5 extending out of the front of the housing 6). This retention of the excavated material on the screw 5, by the housing 6, may provide for a particularly effective and complete conveyance of the excavated material, to the outlet window 7.

The excavator 1 also comprises a mount 11, which mounts the excavator 1 to a support structure 12 to form an excavator assembly 27 (see Figure 6). The mount 11 comprises a cylindrical stem 13 and a disc shaped platform 14 mounted on an end of the stem 13, such that the platform 14 extends in a plane that is generally perpendicular to a central longitudinal axis of the stem 13.

The mount 11 further comprises a mounting bracket 16 mounted on a generally disc shaped base 17. The mounting bracket 16 comprises a pair of substantially parallel, spaced apart, mounting plates 16 that are each extend in a plane that is substantially perpendicular to the plane of the base 17.

Each plate 18 is provided with a pair of apertures 19, that pass through the thickness of the plate 18, for attachment to the support structure 12 via nuts and bolts (not shown). It will be appreciated that any type of attachment may be used.

The base 17 is attachable to the platform 14 in a first orientation, shown in Figure 1, and a second orientation, shown in Figure 10, that is rotated 90° relative to the first orientation, in a plane that is generally perpendicular to the central longitudinal axis of the stem 13. In the first orientation, the mounting plates 18 each extend in a plane that is substantially parallel to the axial direction A. In the second orientation, the mounting plates 18 each extend in a plane that is substantially perpendicular to the axial direction A. The platform 14 and base 17 each have four circumferentially distributed apertures 51, 51' that are aligned when the base 17 is in the first and second orientations, so that the base 17 can be attached to the platform 14, in each of said orientations, by passing bolts 52 through the aligned apertures and fixing the base and platform 14 together by screwing nuts 52 onto the bolts 52. It will, of course, be appreciated that any suitable means of attachment may be used, including any number of apertures 51, 51'. The base 17 is releasably attachable to the platform 14 in each configuration, to allow the orientation of the base 17 to be adjusted. In this respect, the nuts 53 may be unscrewed from the bolts 52 and the bolts removed from the apertures 51, 51'. The orientation of the base 17 can then be adjusted from one of said orientations to the other and the bolts 52 inserted into the newly aligned apertures 51, 51' in the base 17 and platform 14 and the nuts 53 screwed onto the bolts 52 to reattach the base 17 to the platform 14 in the new orientation. The adjustable mount 11 allows the excavator 1 to be attached to the support structure 12 in a first orientation, (shown in Figures 1 and 6) and a second orientation (shown in Figure 10) that is rotated 90° relative to the first orientation, in a plane that is generally perpendicular to the central longitudinal axis of the stem 13.

This flexibility in the mounting orientation of the excavator 1 to the support structure 12 allows the excavator 1 to be mounted to a variety of support structures 12 and therefore driven by machines of different configurations. In particular, it may facilitate driving axial movement of the excavator 1 into a cavity being excavated, from a position laterally adjacent to the cavity, i.e. from a lateral side of the cavity 32.

In the described embodiment, the support structure 12 is an articulated arm 12 of a digging machine (shown schematically as 40 in Figure 6). The articulated arm 12 is connected to an actuator (shown schematically as 41 in Figure 6) of the digging machine 40 to drive movement of the arm 12, so as to drive forward movement of the excavator 1 into the cavity, in a direction substantially parallel to the axial direction A, as it excavates a cavity. It will be appreciated that, in alternative embodiments, said axial movement by not be parallel to the axial direction A but may have at least a component in the axial direction A. This also drives rearward axial movement to remove the excavator 1 from the cavity, once the excavation has been completed.

A method of underpinning a structure, according an embodiment of the invention, using the excavator 1 of the above described embodiment, will now be described with reference to Figures 7 to 9. In the described embodiment the structure 31 being underpinned is a building 31.

The rotating cutting blade 2, of the excavator 1, is driven into the earth 30 beneath the building structure 31 from a position horizontally adjacent to a cavity 32 to be excavated. The cavity 32 is located directly below the foundations of the building structure 31. As shown in Figure 7, the excavator 1 is driven forward in the axial direction A, into the earth 30, via the actuator driven articulated arm 12, on which the excavator 1 is mounted.

The earth excavated by the rotating cutting blade 2 passes from the blade 2 to the screw conveyor 3, through the front opening 22 of the conveyor housing 6, and is conveyed by the screw conveyor 3 to the outlet window 7, where it passes out of the housing 6, under gravity, to a collecting device (shown schematically as 10 in Figure 6). In the currently described embodiment the collecting device 10 is a bucket. However, it will be appreciated that any suitable collecting device may be used. The movement of the excavated earth is illustrated by the arrows in Figure 6.

The excavated cavity 32 has a generally square cross-sectional shape, as shown by Figure 8. In the described embodiment, the cavity 32 is directly underneath the building 31 (i.e. within the footprint of the building 31). Alternatively, or additionally, the cavity 32 may be at least partially laterally offset from the building 31 (i.e. at least partially outside the footprint of the building 31).

Once the cavity 32 has been excavated, the excavator 1 is withdrawn from the cavity 32 and a reinforcement is introduced 33 into the cavity 32 so as to reinforce the structure 31. In the currently described embodiment the reinforcement is a concrete beam 33, with a generally square cross-sectional shape that substantially matches that of the cavity 32. However, it will be appreciated that any suitable reinforcement may be used. As the cutting blade 2 cuts a generally square shape, this advantageously allows the cavity 32 to have a cross-sectional shape that matches that of the square beam 33.

The excavator 1 may provide for a relatively fast and efficient means of excavation during underpinning operations.

In this respect, the cutting blade 2 may be driven at a relatively high rotational speed to rapidly excavate a cavity 32, with the screw conveyor 3 able to convey the excavated material from the cutting blade 2, to the outlet window 7, at a rate that is fast enough to match the rate of excavation.

This can significantly reduce the overall time of the underpinning operation, compared to the known methods, thereby saving substantial cost.

In addition, due to the use of an actuator unit powered cutting blade 2 and screw conveyor 3, the excavator I may be used by a worker positioned outside of the cavity 32 being excavated, thereby removing the danger of the cavity 32 collapsing on the worker.

The conveyor housing 6 may prevent excavated material from coming off the rotating screw 5, for example by propelled under centripetal force, due to the rotation of the screw-5, and/or under gravity. Accordingly, the excavated material may only exit the housing 6 at the outlet window 7, thereby allowing for efficient and controlled collection of the excavated material at the outlet window 7.

Furthermore, the conveyor housing 6 may prevent the rotating screw 5 from contacting and damaging a structure that is being underpinned.

It will be appreciated that numerous modifications to the above described design may be made without departing from the scope of the invention as defined in the appended claims. For example, in the described embodiment, the rotary excavation member is a rotary cutting blade. However, it will be appreciated that rotary excavation member may be any excavation member that is configured to be rotatably driven to cut into the earth to excavate a cavity that is suitable to have a reinforcement introduced into to underpin a structure of a building. For example, the rotary excavation member may be a body with a fluted cutting surface, that extends helically along the body. In this respect, the excavation member may be a drill bit, in one alternative example.

In the described embodiment, the screw conveyor comprises a helical screw blade mounted on a central shaft, to rotate with the shaft. However, it will be appreciated that any type of screw conveyor may be used. For example, the helical screw blade may shaftless, with the helical screw blade driven at one end, by the actuation assembly, and free at its other end, i.e. at its front end.

In the described embodiment a hydraulic motor 4 drives rotation of both the cutting blade 2 and the screw 5, with the cutting blade 2 and drive shaft 3 mounted on a common drive shaft 8. Alternatively, the cutting blade 2 and the screw 5 may be driven by respective first and second motors, via respective first and second drive shafts. It will be appreciated that, in this case, the actuation unit comprises the first and second motors.

It will also be appreciated that any suitable type of actuator may be used, for example, a pneumatic motor, hydraulic motor, electric motor, etc. Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims.

Claims

Claims 1. An excavator for use in underpinning operations, comprising: a rotary excavation member; a screw conveyor; and an actuation unit configured to drive the excavation member and screw conveyor; wherein the screw conveyor comprises a screw arranged to rotate in a conveyor housing to convey material excavated by the excavation member to an outlet of the screw conveyor.
2. An excavator according to claim I wherein the outlet is an aperture in a wall of the conveyor housing.
3. An excavator according to either of claims 1 or 2 wherein the excavation member and screw conveyor are driven by a common drive shaft.
4. An excavator according to claim 3 wherein the excavation member and screw are mounted on the common drive shaft.
5. An excavator according to any preceding claim wherein the excavator is configured to excavate a cavity that has a generally square cross-sectional shape.
6. An excavator according to claim 5, wherein the excavator comprises a cutter configured to cut a generally square shape into the earth as the excavator is driven into the earth, wherein the rotary excavation member is configured to rotate within the footprint of the cutter.
7. An excavator according to any preceding claim wherein the excavator comprises a mount, for mounting the excavator to a support structure.
8. An excavator according to claim 7 wherein the mount is adjustable such that the excavator may be mounted to the support structure in a plurality of orientations.
9. An excavator assembly comprising an excavator according to any preceding claim and a support structure on which the excavator is mounted.
10. An excavator assembly according to claim 9 wherein the excavator assembly comprises a support structure actuator configured to actuate the support structure so as to actuate axial movement of the excavation member.
11. A method of underpinning a structure, comprising: providing an excavator for use in underpinning operations, the excavator comprising: a rotary excavation member; a screw conveyor; and an actuation unit configured to drive the excavation member and screw conveyor; wherein the screw conveyor comprises a screw arranged to rotate in a conveyor housing to convey material excavated by the excavation member to an outlet of the screw conveyor; excavating below a structure to be underpinned, using the excavator, to form a cavity below the structure; conveying material excavated by the excavation member to the outlet, using the screw conveyor, and reinforcing the structure by introducing a reinforcement into the cavity.
12. A method according to claim 11 wherein the excavator is an excavator according to any of claims 1 to 8.
13. A method according to either of claims 11 or 12 wherein the excavator is the excavator of the excavator assembly of either of claims 9 or 10 and the method comprises providing said excavator assembly.
14. A method according to claim 13 wherein the excavator assembly is the excavator assembly of claim 10 and wherein the support structure actuator actuates the support structure so as to actuate axial movement of the excavation member.
15. A method according to any of claims 11 to 14 wherein the excavator is used in a non-vertical orientation.
16. A method according to claim 15 wherein the excavator is used in a substantially horizontal orientation.
17. A method according to either of claims 11 to 16 wherein the excavator is used to excavate the cavity from a lateral side of the cavity.