The hollow members can be any member which is usually buried in ground, to conceal it and thus to provide a hidden, yet useful and environmentally friendly member, as it is non-intrusive in the environment. Such members are often hollow members, for example, sewers, conduits, water mains, and pipelines, and they may carry fluid such as water, oil or gas, or may house other elements such as cabling. Ground can have differing characteristics, and can move, thus causing subsidence and this in turn can disrupt a buried hollow member, it being understood that the term"buried"includes partially buried.

Timber headings, or shuttering, is therefore often used, in which the members are laid. Backfill material is then laid between the headings and the member. Sometimes, perhaps owing to poor workmanship, incorrect backfilling of material or lack of it, voids are formed between the external surface of the member and the headings, usually in the form of timber boards. This can lead to damage, perhaps rupture of the member as it is not supported over its entire external surface.

It is an object of the invention to seek to mitigate this disadvantage.

According to a first aspect of the invention there is provided a method for stabilising ground round a buried hollow member, the interior of which is too small for human entry, comprising providing means to monitor condition of ground at the member, positioning the means within the member and establishing condition of the ground by determining position of void (s) in the ground exteriorly of the member means from interiorly of the member, providing means to provide an orifice through a boundary wall of the member, positioning the means within the member adjacent a void, forming an orifice through the wall of the member, providing a means to provide a grout, positioning the grout means adjacent the orifice and in fluid communication therewith and passing grout from the means through the orifice into the void (s) whereby to fill same and provide stabilisation of the ground.

There may be an initial step of providing means to establish the condition of the element before deployment of the ground condition monitoring means.

There may be a step of monitoring the grout passing step using the initial condition establishing means.

The ground condition monitoring means may comprise a ground probing radar means.

The step of determining the position of the void (s) may comprise establishing any areas of voiding at intervals of 90° round the member.

The step of forming the orifice may comprise cutting the orifice through the wall of the member.

The member may be a tubular member, the step of determining void (s) in the ground exteriorly of the member may comprise determining the position of such void (s) aiong the length of the member, and the step of cutting the orifice may comprise cutting an orifice through the wall of the tubular member adjacent the further downstream void, and then progressively cutting holes adjacent voids upstream of the most downstream void.

There may be the step of checking for leaks around the orifice providing means prior to passing the grout through the orifice.

The step of checking for leaks may comprise pumping water through the orifice forming means and grout means.

The orifice forming means and the grout means may comprise separate means.

The step of establishing the condition of the ground may comprise using ground probing radar means as the means to monitor the condition of the ground.

The initial step may comprise deployment of a close circuit television means to establish the condition of the element.

According to a second aspect of the invention there is provided apparatus for stabilising ground round a buried hollow member the interior of which is too small for human entry, comprising means to form an orifice through the wall of the member from the interior thereof.

There may be means to pass a void filling material from the interior of the member into any void, exteriorly thereof.

The means may comprise a piston and cylinder arrangement and a device to seal against an interior surface of the member adjacent the orifice.

The device may be a resilient head of the piston at an end thereof remote from the cylinder.

The resilient head may comprise a rubber head.

The cylinder, piston and head may have a passage therethrough for passing grout through the orifice.

The means to form the orifice and means to pass a void filling material may comprise separate means.

According to a third aspect of the invention there is provided a system for stabilising ground round a buried hollow member the interior of which is too small for human entry, comprising means to monitor condition of ground at the member, means to provide an orifice through a boundary wall of the member and means to pass grout through the orifice in use whereby to fill a void and provide stabilisation of the ground.

The means to monitor the condition of the ground may comprise radar means.

There may be means to check the condition of the member, preferably the said means comprising a close circuit television means.

According to a fourth aspect of the invention there is provided ground, whenever stabilisation by a method as hereinbefore defined, apparatus as hereinbefore defined or a system as hereinbefore defined.

A method, apparatus and system for stabilising ground at or round a buried hollow member the interior of which is too smalt-for human entry are hereinafter described, by way of example, with reference to the accompanying drawings.

Fig. 1 is a schematic flow diagram showing an operation to stabilise ground round a buried hollow member the interior of which is too small for human entry including a method according to the invention.

Fig. 2 is a schematic transverse sectional view of a member in the form of a pipe with part of apparatus in one condition, for carrying out the method embodying the invention.

Fig. 3 is a view similar to Fig. 2, with the apparatus in a second operating condition.

Referring to the drawings, particularly Fig. 1, an operational scheme for a method of stabilising ground round a hollow member in the form of a pipe 2 (Fig. 2,3) is shown, the interior 3 of the member essentially defining non-human entry confined space.

The first step 4 in the operational scheme which includes the method of the invention involves gaining access to the interior 3 of the pipe 2 cleaning it, and removing silt, where the pipe carries say water.

This is effected remotely, by a robot means which can be guided along the pipe 2 from a remote location.

Then means (not shown) to establish the condition of the pipe, otherwise known as establishing condition grade, is inserted as shown at 5 in the pipe 2, this means in the embodiment being a close circuit television means (CCTV). Testing such as air testing to establish seal on joints is carried out in this step or stage, as is lining of the pipe 2 with a soft liner or structural liner if necessary or desirable.

Flow in the pipe 2 is then controlled to about 20% of the pipe fill flow, in the next operational stage 6.

Next, 7, means to establish the condition of the ground is deployed in the pipe. This means in the embodiment is a ground probing radar which in operation establishes areas of voiding'V'around the buried pipe 2. In the embodiment, the radar means is passed along the pipe from a furthest downstream position to an upstream position, void (s) being assessed at 3,6,9,12 and"0"clock positions, i. e. at radially orthogonal positions relative to the longitudinal axis of the pipe 2.

The radar results are interpreted remotely, that is generally above ground away from the pipe 2, and the areas where voids'V'exist are established.

Apparatus carrying means for providing orifice (s) through the boundary wall of the pipe adjacent any void (s) is then deployed, 8.

This means is in the embodiment a cutting means and the apparatus is a robot having a chassis carrying the means.

The apparatus is deployed so that it is interiorly of the pipe 2 adjacent the farthest downstream void. An orifice 12, suitably in the embodiment a 50mm diameter hole, is then formed through the wall 2'of the pipe 2 so that communication is established between the interior 3 of the pipe 2 and the furthermost downstream void'V'. The means inclues a cutting or drilling rig with a 50mm water cooled diamond tipped drilling or cutting head. Once this hole 12 is drille, the apparatus is moved to cut or drill the vent hole to the next upstream void, and so on progressively so that there is a series of holes along the pipe 2 leading to adjacent voids, along the pipe from the downstream to the upstream end. All the cutting or drilling operations are monitored using CCTV, which may be part of the apparatus, or a separate CCTV monitor deployed in the pipe.

Once the orifices are completed, means for passing grout to the voids is deployed 9. This is part of a separate apparatus which is a grout injection apparatus 13 and in the embodiment comprises a steel tubular chassis with a piston 14 and cylinder 15 arrangement and a seal 16. The seal 16 is a spherical, resilient, in the embodiment rubber, seat mounted on the free end of the piston 14 of the piston and cylinder arrangement, which is pneumatic. The means can move in all three axis with sufficient control to position the seal 16 over a hole 12 and provide an efficient seal, as shown in Fig. 3. There is a passage 17 through the cylinder 15, piston 14 and seal 16 which provides a conduit for grout. When the means is in the Fig. 3 operational condition at the furthest downstream orifice, the efficacy of the seal 16 is checked by pumping water through the means to see if there are any leaks. If there are, the pressure round the rubber seal or head is increased by extending the piston to seal the leaks.

Any leaks to joints and at cracks or fractures are cured by initial pumping of a bentonite mix through the means, more persistent leaks being sealed using a polymer grout. Then, the leaks having been cured, cementitious grout'G'is pumped through the passage 17 into the void'V'. to fill it, 10. Injection of grout is ceased on refusal of acceptance of more, when the maximum delivery pressure is reached, the estimated volume is reached, and/or grout flows through an upstream hole, the grouting operation being monitored on CCTV. Once the furthest downstream void has been filled, the apparatus is moved remotely along the pipe to the next upstream orifice, the void adjacent thereto is filled, and so on until all voids are filled.

There is then a final pass of the ground probing radar, 11 to check the efficacy of the void filling. The system comprising the apparatus, CCTV and radar means are then removed,'R', from the pipe. Thus the ground round the pipe 2 is stabilised.

For the cementitious grout typically a batch was mixed in a high Shear Colloidal mixer and then transferred to a hopper of a rotary screw, positive displacement pump. The mixer and pump were mounted on a mobile chassis and both driven by a 20 BHP diesel engine.

The grout in the embodiment is ordinary Portland Cement and Bentonite Clay with a water/cement ratio of 2 parts water to 1 part cement, with 5% Bentonite WW.

After 28 days the grout will attain a compressive strength > = 2 N/mm2 which becomes thixotropic when at rest. It is a-high fluid, penetrative grout.

To assist in sealing open joints the polymer grout referred to is used, supplied by CMS Pozament Ltd. This material has a working life of 60 minutes, and can only be used when the pumping distance is < = 30 metres as pumping pressure rises significantly.

Sand can be added to the Bentonite grout to provide increased'body' and this assists in closing smaller defective joints.

Thus the method, apparatus and system described with reference to the drawings provides for total remote working in non-man entry confined spaces and involves accurately pin-pointing the voided areas and injecting cementitious grout (or other similar approved fill) from within the pipe, thus filling the voids and stabilising the ground and pipeline.

It will be understood that the term"grout"used herein refers to any suitable flowable, injectable material that can be used to shore up ground.