GB2420574A

GB2420574A - A system for medium diameter long distance boring

Info

Publication number: GB2420574A
Application number: GB0425994A
Authority: GB
Inventors: John Stephen Orchard
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-11-26
Filing date: 2004-11-26
Publication date: 2006-05-31
Also published as: GB0425994D0

Abstract

A system comprising an excavation machine (1 Fig. 1) which is able to propel itself through the ground. The excavation machine (1 Fig. 1) is remotely operated and employs several pneumatic boring devices (6 Fig. 1) to be able to excavate through any type of ground. The excavated ground is removed by the use of a multiplicity of pipes (9 Fig. 1) which are connected to a multiplicity of vacuum interface valves (10 Fig. 1). The process employs two-phase vacuum flow to remove the excavated ground. The hole bored through the ground is lined with either a cylindrical preformed bore liner (19 Fig. 2) or by a rapidly setting fluid that is extruded or sprayed so as to form the liner to the bore. Within the bore liner (19 Fig. 2) is installed an inner liner (22 Fig. 2) made of a tube with outer ribs (23 Fig. 2). Between the bore liner (19 Fig. 2) and the inner liner (22 Fig. 2) is injected a lubricant (28 Fig. 2) so that the inner liner (22 Fig. 2) can be pushed into the lined bore over long distances. The entire system enables medium diameter bores to be remotely installed over long distances.

Description

1 2420574 A System for Medium Diameter Long Distance Boring The invention

relates to a means of installing a medium diameter bore over long distances through the ground. The bore could be carried out through ground that is under water such as through the seabed or through land based ground. The existence of water in the ground through which the bore is being made is immaterial.

In general for this invention medium diameter means above one metre internal diameter and less than two meters diameter. In general for this invention, long distances means in excess of five hundred metres and up to ten kilometres. However, in particular circumstances the invention or any part of it might be applied for any diameter of bore or for any length of installation.

The invention addresses the means of excavating the ground over the length of the bore, the means of removing the excavated ground, the means of lining the bore so as to provide a stable structure and the means of servicing the installation processes.

The installation of long distance bores is important for the provision of many modern services.

For instance, the provision of utility services to remote locations such as offshore islands might require the installation of a long distance underground bore. Another example is the requirement to comiect to offshore alternative energy supply schemes such as wind farms and wave generation power stations.

Furthermore, greater constraints are being applied to traditional methods for the provision of such services. For instance, the use of overhead power lines has been resisted in certain locations due to environmental, health and aesthetic concerns.

Traditionally such long distance service connections have been provided either by stringing cables or ducts above ground using posts or pylons or installing such services in trenches.

There has also been the option to install a much larger bore than is needed using conventional tunnelling technology and then installing the service required within the tunnel bore.

The reluctance to use alternatives to these methods is generally driven by either additional cost concerns or due to lack of a suitable technology.

However, there has been a move towards a non-disruptive method of installing ducts of all types and sizes underground without using traditional excavation methods. This more recent technology is often termed Trenchless Technology'.

Trenchiess Technology offers solutions with regard to the long distance installation of small diameter bores or short distance installation of medium diameter bores. Between the two there exists a technology void.

Long distance installation of smaller diameter bores is carried out using methods such as horizontal directional drilling (FIDD). However, this method relies upon the sequential reaming or opening of the bore. Over long distances when slowly reaming increasing bore diameters the ground around the bore perimeter may not be supported by the normal HDD method of filling the void with a dense fluid. Therefore, for the diameters contemplated by this invention HDD does not offer a solution.

Remote controlled tunnelling often called microtunnelling' offers a solution for the installation of medium diameter bores. This technique relies upon the principle of pushing a rigid duct into the excavated bore at the same time pushing forward the machine that is carrying out the excavation of the bore.

There are several limits that apply to this system. The first is that the load being applied to the pipe rises in an approximate proportion to the length of pipe being installed. This is because of the friction acting on the circumference of the pipe. This friction comes from the pipe-ground interface. Thus the pipe needs to be either forever stronger or there needs to be a distribution of the pushing forces down the length of the pipeline. The distribution of pushing forces down the length of the pipe is possible but the procedure slows the installation rate until it generally becomes unfeasible.

Another difficulty is the means by which the excavated ground is removed. Generally this is carried out by either the use of slurry or the use of augers. Due to the need to provide power along the length of the slurry or auger system, there exist concerns as to the distance over which these systems can be employed.

Another difficulty is the requirement to service the excavation machine. The installed microtunnelled pipe will generally have a thick wall in order to accommodate the pushing loads. The remotely operated excavation machine is therefore inhibited from being withdrawn down the installed line for the purposes of repair, servicing and replacement of wear parts.

The contemplation of this invention is to offer solutions to the limitations mentioned above to enable the remote installation of a medium diameter bore.

The invention contemplates how to excavate the ground using a method that will excavate almost any type of ground. The excavation method permits the replacement and refurbishment of the excavation tools. It enables the tools to be replaced when operating under water and in flowing unstable ground conditions. It also accepts the inevitability of humid and damp conditions and is not adversely affected by this issue.

Further the invention explains how the excavation machine is able if required to propel itself through the ground, thereby eliminating the need for propulsion from behind. The invention describes how the excavation machine can be remotely guided over the distances contemplated.

Further the invention explains how the excavated ground can be removed from within the bore.

This employs a method that has a proven ability to operate over the distances targeted. It is also a method, which can accommodate the damp and humid conditions and is not adversely affected by this issue.

The invention then addresses the lining of the bore so that it has both structural integrity and excludes the water, which will in many cases be present outside the bore.

A preferred embodiment of the invention will now be described with reference to the accompanying drawings in which: Figure 1 shows a central longitudinal section of the front of the excavation machine demonstrating the means of excavation and the way that excavated ground is removed.

Figure 2 shows a central longitudinal section of the rear of the excavation machine demonstrating the means of lining the excavated bore.

Figure 3 shows a cross section of the front of the excavation machine identifying a typical layout of the boring devices.

Figure 4 shows a cross section of the mid section of the excavation machine identifying the way that the boring devices may be replaced and the ground is removed.

Figure 5 shows a cross section of the rear section of the excavation machine identifying how the bore liners are installed.

Figure 6 shows a detail of the bore liner joint

Description

As shown in Figure 1 the excavation machine I comprises two steel cylinders, which are joined at a sliding joint 2. The front and rear sections of the excavation machine 1 can be moved one against the other by the use of one or more double-acting rams 4.

Both sections of the machine may be equipped with grippers 3 that are pushed out into the surrounding ground. By an alternating process of extending the grippers 3 first the front and then the rear section of the excavation machine 1 can be secured in the outer ground. The hydraulic rams 4 within the excavation machine I can open or close the sliding joint 2 between the two steel cylinder in coordination with the use of the grippers 3 so as to enable the excavation machine I to move forward under its own power.

The excavation machine I may be used as a self-propulsion machine or may be propelled by other means if so preferred.

The centre of the front face of the excavation machine 1 might be connected to a rod like device such as a drill rod that has been preinstalled along the chosen path of the bore. Such a system could offer the guidance necessary to ensure that the excavation machine 1 installs the bore along the correct chosen path. Such a rod like device 5 could also serve to transmit services to the excavation machine I. it could also potentially be used as a means of removing excavated ground.

As shown in Figure 1 the excavation machine I is equipped with a number of pneumatic boring devices 6. The location of these boring devices 6 within the face of the excavation machine 1 enables the excavation head to excavate a complete cross-section of the required bore. The air supply to these boring devices 6 is supplied by a multi armed air inlet manifold 13. Each arm of this air inlet manifold 13 is connected to the boring device 6 by an automatic gripper valve 14. The air inlet manifold 13 is serviced by an air feed duct 27.

Each of these boring devices 6 can be removed by remote means and replaced with another boring device 7. When a substitution of a boring device 6 is required the air inlet manifold 13 is retracted and rotated using the sliding frame 16. The boring device 6 is then retracted by a hydraulic operated device attached to a centrally located carriage system 15. In order to prevent the ground from entering the excavation machine through the void created when the boring device 6 is removed, the front of the excavation machine 1 would be retracted and a fluid such as a bentonite cement grout that consolidates to form a weak but rigid material would be pumped into the void to form a temporary restraining plug.

Afler the boring device 6 is replaced the air inlet manifold 13 is reinserted and the excavation machine 1 will excavate the retaining plug before entering the new ground.

As the excavation machine I is operated, each boring device 6 will rotate. In addition the face of the excavation machine 1 will be rotated by an external ring drive 17. In this way the entire front of the face of the bore can be excavated.

There might be a sealing hatch 26 installed so as to enable the face of the excavation machine 1 to be sealed from the rest of the bore if it is so required. This might be done if it is necessary to increase the air pressure in the front of the excavation machine 1 during the process to replace the boring device 6. Such an increase in air pressure could assist in preventing any ingress of fluid through the face of the excavation machine 1. Such an increase in air pressure might also be used to increase the efficiency of the vacuum extraction system.

The ground excavated by the boring devices 6 will be a fine material comprised of crushed ground. It is very likely that it will be mixed with water thereby forming a paste or slurry. This material will fall to the bottom of the excavation machine I and gather in a sump 8 located in the base of the excavation machine 1. There are one or more pipes 9 projecting into the sump 8. These pipes 9 are connected to one or more vacuum interface valves (VIV) 10, which are located in the rear part of the excavation machine 1. The VIV 10 are in turn connected to pipes 11 that lead the length of the bore and are connected at the commencement of the bore to a combined vacuum reservoir and excavated ground reception sump. A sliding section 12 permits the pipes 11 to accommodate the movement of the two sections of the excavation machine 1.

At periodic intervals down the length of the bore the pipes 11 incorporate a step of approximately 300mm height. This system operates in accordance with the principle of the saw tooth profile that is generally used for two-phase flow vacuum fluid and slurry transfer. The use of a simple single-phase vacuum extraction will not function effectively over the contemplated distances. Two-phase flow is a unique process that requires the use of the VIV and the steps at regular intervals.

As shown in Figures 2 and 5 at the rear of the excavation machine I are installed a device 18 for receiving a bore liner 19. The bore liner 19 comprises of a cylindrical section of a flexible material that has a joint in its wall 20. The joint permits that one side of the joint 20 might be compressed inside the other so as to make a cylinder of smaller diameter that can be transported down the length of the bore. The bore liner 19 is retained in this position by an external restraining strap. When in its correct position the strap is burst by the use of the installation arms 21 so that the bore liner 19 can expand to fill the circumference at the rear of the excavation machine 1. In this position it will butt against the previously installed bore liner 19 so as to provide a full circumferential lining to the bore.

In Figure 6 it is shown that the formed joint 20 will make the bore liner 19 into a cylindrical hoop capable of resisting the initial loads from outside of the bore until the inner liner 22 is installed within it. The inner liner 22 is designed to carry the principle external loadings as well as any installation loadings from the pushing process.

In another embodiment of the invention the bore liner 19 is made in two sections. The two sections can be transported down the bore together one inside the other so as to minimise the overall size of the unit. The two sections of the bore liner 19 would then be assembled in situ by the reception device 18 to form a complete circumferential bore liner 19.

In yet another embodiment of the invention a material is extruded circumferentially out of the external rear of the excavation machine 1. The material would solidify rapidly around the outer circumference of the bore so as to provide a lining to the bore. The excavation machine I would slide out of the lining so formed.

In yet another embodiment of the invention a material would be sprayed circumferentially against the internal surface of the steel cylinder that comprises the rear of the excavation machine 1. The material would solidify rapidly to form a lining inside the rear of the excavation machine 1. The steel sleeve that comprises the rear of the excavation machine 1 would be continuously lubricated to prevent the sprayed material from adhering to the rear of the excavation machine 1. As the excavation machine I advanced it would slip away from the sprayed material that would adhere to the previously sprayed material.

In yet another embodiment of the invention a rotary device is employed to install a flexible strip that has a profile that permits it to connect to a previously laid flexible strip already installed around the circumference of the bore. The strips would be laid so as to form a continuous lining to the bore. The principle of installing an interconnecting strip using a rotary device is well established for the purposes of lining existing pipelines. However, it is an inventive contemplation to consider using the method to line the interior of a newly excavated bore.

An inner liner 22 would be pushed within the bore liner 19. The inner liner 22 could be made of one or more different types of material provided that it has sufficient strength to act as the permanent bore lining and is able to resist all applied forces including both the installation forces and the final external forces. The choice of lining material might also be made to accommodate the chosen purpose for the bore.

The inner liner 22 would have a smooth interior but on the outer side of the inner liner 22 would be installed circumferential ridges 23 at regular intervals. Injected into the void created by the ridges between the bore liner 19 and the inner liner 22 would be a lubricating fluid 28.

The lubricating fluid 28 would be injected at the commencement of the bore and might be topped up through valves in the inner liner 22 at intervals down the length of the bore. A wider specially designed circumferential ridge 24 might be installed at the front of the inner liner 22 in order to secure that the lubricating fluid 28 is retained at the front of the inner liner 22.

in another embodiment of the invention the bore liner 19 would have raised strips on the inner surface and the inner liner 22 would be smooth on the inside surface.

The purpose of the lubricating fluid 28 is to permit the inner liner 22 to be pushed into place within the bore liner 19 using the minimum pushing force.

A specially designed seal 25 would be employed at the rear of the excavation machine I. This would permit the excavation machine to move forward whilst preventing fluids or other material from outside the bore to penetrate into the excavation machine 1.

The innovative steps in the patent include the following inventions: Firstly the use of a number of remotely replaceable pneumatic bore devices in the face of an excavation machine to remotely bore through the ground; Next the use of two-phase vacuum flow to transport excavated ground from within the excavation machine and move it out of the bore; Next the use of a pre-bored duct to provide resources to the excavation machine or to remove excavated material from the front of the bore; Next the use of a bore liner within which is installed an inner liner by sliding is innovative when used with horizontal boring or tunnelling; Next the use of compressed cylindrical liner units to form a bore liner to line the inside of a bore; Next the use of interconnecting strip material wound around the inside of the bore so as to form a cylindrical lining to the bore; Next the use of an externally extruded liner to form the bore liner; Next the use of a rapid setting fluid extruded outside the excavation machine or sprayed against the lubricated inside of the excavation machine in order to provide a liner to the bore when the excavation machine advances; Next the use of either a bore liner or an inner liner with circumferential ribs to assist in the lubrication of the inner liner pushing process. g

Claims

1 claim: An arrangement of excavating machine that can install a duct over a long distance using pneumatic boring heads and which uses vacuum extraction to remove the excavated ground and which uses an inner liner installed within an outer liner with an arrangement to ensure lubrication is retained between the two liners

2. A method according to claim whereby the boring heads can he remotely removed and replaced when required.

3. A method according to claim I whereby the excavated material is removed using two-phase flow vacuum extraction.

4. A method according to claim I whereby an initial bore is made which permits a tube to be connected to the front of the excavation machine in order to permit the transfer of resources to the excavation machine.

5. A method according to claim I and 4 whereby the preinstalled tube assists the guidance of the excavation machine.

6. A method according to claim I and 4 whereby the excavated material may be removed through the tube connected to the front of the excavation machine.

7. A method according to claim I whereby the bore may be lined using a compressed cylindrical tube.

8. A method according to claim I whereby the bore may be lined by the installation of two part sections of tube which when assembled form a bore liner.

9. A method according to claim I whereby the bore may be lined by winding circumferentially a strip that interlocks with itself

10. A method according to claim 1 whereby the bore may be lined by the installation by extrusion of a fast setting fluid outside of the excavation machine.

11. A method according to claim I whereby the bore may be lined by the installation by extrusion of a fast setting fluid inside of the excavation machine.

12. A method according to claim 1 whereby an inner liner is pushed into an outer bore liner with a lubricating fluid separating the two liners.

13. A method according to claim I and I I whereby an inner liner is equipped with circumferential raised ridges that assist in entrapping, carrying and using more effectively the lubricating fluid.

14. A method according to claim I and Ii whereby an Outer bore liner is equipped with circumferential raised ridges that assist in entrapping and using more effectively the lubricating fluid.