GB2389296A

GB2389296A - Improving the drainage of ground

Info

Publication number: GB2389296A
Application number: GB0313084A
Authority: GB
Inventors: Robert David Essler
Original assignee: Keller Ltd
Current assignee: Keller Ltd
Priority date: 2002-06-06
Filing date: 2003-06-06
Publication date: 2003-12-10
Anticipated expiration: 2023-06-06
Also published as: GB0313084D0; GB0212981D0; GB2389296B

Abstract

In order to treat ground to improve its drainage, in particular ground underneath transport structures such as roads and railways, a flowable medium comprising a biodegradable material, sand and water is injected into a drainage zone 6 in the ground. As a result, fractures 11 are created in the zone 6. The fractures fill up with the flowable material. Once the biodegradable material has been degraded, passages are left in the fractures 11 through which water can flow into a pipe 7 through perforations in the perforated section 10 of the pipe 7, thereby improving the drainage of the ground 6. The pipe 7 leads to a collection zone (7a figure 2).

Description

M&C Folio: GBP84552 2389296 IMPROVING TIlE DINAGE OF GROUND The present

invention relates to a method of improving the drainage of ground, particularly ground beneath transport structures such as roads and railways.

It is often necessary to treat ground material if the ground material is unsuitable in its untreated fond for a particular purpose. It is frequently necessary to treat the ground in order to improve drainage of water from it. This is particularly important for ground which lies beneath transport structures such as railway tracks and road surfaces.

If there is poor drainage of water beneath such structures, there can be problems due to softening of the ground material, caused by pending of water such as rain water. This is particularly a problem where the ground comprises cohesive or clay material. The passage of trains or other vehicles sets up cyclic pressures and vibrations in the ground which can increase the problem by increasing water pressure in the ground. It can also cause movement of fine material into the ground which can effect the stability of th ground. This phenomenon is known as pumping.

The problem of pending of water in the ground beneath transport structures has been dealt with in the past by providing drainage ditches along the side of the transport structure. However, the drainage provided by such ditches is often found to be insufficient because the permeability of the ground itself is not sufficient to allow the water to drain away into the ditches.

The present inventors have sought to deal with the problem of improving ground to improve drainage, particularly in ground beneath transport structures. The present inventors have particularly sought a method of improving ground which can be carried out in ground underneath an existing transport structure without disruption to the transport structure itself.

The present inventors have discovered that the drainage of the ground can be improved by increasing the porosity of the ground by injecting into the ground a

medium comprising degradable material. When the degradable material degrades' pores are left behind through which water can drain, thereby improving the drainage of the ground into which medium has been injected.

Accordingly, the present invention provides a method of treating ground, comprising the steps of delivering a nowable medium under pressure into a drainage zone in the ground' whereby passages comprising the medium are fonned in the ground, and constructing a drainage passage from the drainage zone to a collection zone, wherein the medium comprises degradable material, so that when the degradable material in the passages is degraded, pores are formed, whereby water can be drained from the drainage zone to the collection zone via the drainage passage.

The method of the invention is particularly suitable for treating subgrade beneath transport structures such as railway tracks and road surfaces. As noted above, such ground is subjected to cyclic pressures and vibrations which can lead to long-term degradation of the ground. The present invention allows the porosity of the ground to be improved, whereby drainage of the water which leads to the degradation can be improved, thereby protecting the ground from degradation.

The method of the invention can be carried out without disruption to the transport structure itself. It is not necessary to excavate the ground. As discussed further below, simple apparatus can be used which is driven into the ground without major disruption.

In the method of the invention, a flowable medium is delivered under pressure into the drainage zone in the ground. The medium under pressure forms fractures in the ground into which the medium flows, so that passages are formed in the ground. The flowable medium may be selectively delivered (o the drainage zone. This can be achieved using known apparatus for injecting flowable material under pressure into ground, for example pressure grouting apparatus.

The medium itself preferably comprises a degradable material and particulate material suspended in water. The medium may comprise a degradable mud. The

particulate material may comprise any suitable material allowing good drainage, such as sand, small grravel, vermiculite or other fine material. The weight ratio of water to particulate material to degradable material may be selected to obtain good flowablity through pump and pipes. The weight ratio of water to solids is in the range 0.1:] to 1:1, preferably 0.2:1 to 0.5:1, most preferably around 0.3:1.

The degradable material suitably comprises biodegradable material.

Alternatively, material which becomes soluble under the conditions in the ground may be used, for example acid or alkali soluble material.

Suitably' the degradable material is a biodegradable fluid or a solution of a biodegradable material, preferably an aqueous solution.

Suitably, the flowablc medium comprises a suspending material for improving the suspension of the particulate material. Suitably, this suspension medium comprises biodegradable material It is preferred that the biodegradable material is guar gum. This material is water soluble, biodegradable and acts a as a suspending medium. The weight ratio of degradable material to water is suitably in the range 1-12%, preferably 510%.

The rate at which the degradable material degrades can be set to any suitable rate.. The drainage pipe may be of any suitable diameter, being suitably in the range I Omm to 200mm, more preferably 25mm to 1 50mm, more preferably around 50-75mm.

The drainage pipe may be placed in the ground by any suitable method, for example by driving it into the ground. The pipe may be constructed of any suitable material, for example metal or plastic. Suitably, the collection zone is located at a lower level than the drainage zone so that water will drain under gravity to the collection zone. In the alternative, the collection zone may comprise pumping means for withdrawing water along the passage from the drainage zone.

For example, where ground beneath a transport structure mounted on an embankment is to be improved, the collection zone can be located further down the embankment than the drainage zone. If however the transport structure is located on level ground or in a cutting, it is preferred to excavate a collection zone so that it is located below the level of the drainage zone.

The pipe of the drainage passage may be perforated at selected positions in order to allow water to drain into the pipe.

The pipe may comprise a single pipe or plurality of pipe sections which are inserted one after the other into the ground so that, when assembled, they form a single drainage passage. The sections of the pipe may be identical to one another or they may be different. The sections of the pipe may comprise perforated sections, plain sections or a mixture of perforated and plain sections The collection zone may simply comprise an area to the side of the ground to be treated where collection of water is not a problem. In a preferred embodiment, the collection zone comprises a contained collection area, such as a sump, tank, pipe or other formation.

In all cases, the collection zone may be located to the side of the ground being treated, so that the ground being treated is not substantially disturbed. Where the drainage passage comprises a pipe, it can be driven into the ground being treated from the side, so that the ground itself does not have to be excavated. A transport structure placed on the ground need not be disturbed in order to carry out the method of the invention. A filter medium can be provided in the pipe to prevent the pipe becoming clogged. For example, the filter medium may be located around the circumference of the pipe. The filter medium may be located inside or outside the pipe.

In a preferred embodiment, in a first step, a pipe is constructed in drainage zone to act as a drainage passage and in a second step, means for delivering llowable medium under pressure is passed through the pipe to the drainage zone, flowable medium being delivered under pressure into the ground in the drainage zone. In this way, the pipe can

be used to provide a channel for the injection device The Plowable material may be injected into the ground through perforations in the pipe.

A drainage system may be provided for collecting water from the collection zone. Where a large volume of ground is to be treated, the Plowable medium may be delivered under pressure into the ground at a plurality of points. These points are suitably spaced by distance in the range 0.5-5.0 metros, preferably 1.0 -.3.0 metros, depending upon the quantity of water which is to be drained and the natural porosity of the untreated ground. For example, a grid of points maybe defined, Plowable medium being delivered under pressure into the ground at each point. For example, a linear, square or rectangular grid may be defined in the ground. The points may be located at different levels in the ground.

The present invention will be further described by way of example only with reference to the accompanying drawings, in which: Figure I is a schematic view of ground beneath a railway structure for treatment.

Figure 2 is a schematic view of a first step in the method of the present invention. Figure 3 is a schematic view, at a larger scale, of the injection of flowable medium into the ground.

Figure 4 is a schematic view of ground in an embankment underneath the railway track after treatment by the invention.

Figure 5 is a schematic view of level ground underneath the railway track after treatment by the invention.

Figure 6 is a schematic view of ground underneath the railway track in a cutting aver treatment by the method of the invention.

Figure 1 is a schematic view of ground to be treated by the present invention. In the embodiment shown, a railway comprising two railway tracks 2 resting on a layer of ballast 3 is shown. The layer of ballast 3 is constructed on an embankment 4 which is raised above the normal ground level 5. In figure 1, there is particular danger of settlement or movement of the ground in zone 6 shown in the drawings. In particular, in zone 6, pending of water may occur which will be particularly a problem if the ground of the embankment 4 contains clay or similar cohesive impermeable material.

In order to treat the zone 6 (the drainage zone) in the method of the invention, in the first step shown in figure 2, a pipe 7 is driven into the ground from the side of the embankment 4 using equipment (not shown) which is known in the art. The pipe 7 extends from a collection zone 7a.

In the second step, a Plowable medium comprising sand, water and a bio-

degradable material is prepared and injected along the pipe 7 into the ground in the zone A. The biodegradable material comprises guar gum.

The pipe 7 is perforated at a number of positions along its length. Figure 3 shows, at a larger scale, the injection of Plowable medium into the ground 6. Pipe 7 is constructed out of longitudinal sections which are joined together. The sections of the pipe 7 are of diameter in the range 50-75mm. The sections 8 and 9 are plain unperforated sections. They are joined by a perforated section 10. Flowable medium is injected in the direction of the arrow and passes out of the perforations in the section 10 into the ground 6. As a result of the injection of Plowable medium under pressure into the ground' fractures 11 are formed, along which the Plowable medium flows. The flowab}e material is suitably injected at injection pressures around 10 bar gauge.

As a result of the injection process, the fractures I 1 are filled with the medium comprising water, sand and de-biogradable material. The biodegradable material comprises guar gum which is dissolved in the waterat a level of 5-10% by weight. The weight ratio of the solution of guar gum to sand is 0 3:1 Over a period of months, the biodegradable material will

biodegrade, leaving channels in the fractures 11, through which water can pass from the ground 6 through the perforations in the pipe 10 and along the pipe 7. As can be seen in figure 2, the pipe 7 is installed at an angle so that water will flow out of the left-hand end away from the zone 6. In this way, the drainage of zone 6 can be improved.

Other zones of the embankment 4 can be treated in similar way, resulting in a structure as shown in figure 4. A drainage system (not shown) can be provided to collect the water drained by the pipes 7 from the zone 6 and the zone 12.

Figure 5 shows level ground treated by the method of the invention. In this case, a collection channel 13 has ct collection zone for collecting water drained from the drainage zone 6 and 12.

Figure 6 shows ground treated by a method according the invention at the bottom of a cutting 14. In this case, a similar ditch I S has been excavated into which the pipes 7 from the drainage zones 6 and 12 lead.

Claims

CLAIMS:

I. A method of treating ground comprising the steps of: delivering a flowable medium under pressure into a drainage zone in the ground, whereby passages comprising the medium are formed in the drainage zone, and constructing a drainage passage from the drainage zone to a collection zone; wherein the medium comprises degradable material, so that when the degradable material in the passages is degraded, pores are formed in the ground, whereby water can be drained from the drainage zone to the collection zone via the drainage passage.
2. A method according to Claim 1, wherein the medium comprises particles

suspended in water and a degradable material.
3. A method according to claim I or 2 wherein the degradable material is biodegradable.
4. A method according to Claim 4, wherein the biodegradable material is guar gum.
5. Ground treated by the method of any of claims 1 to 4.
6. A method of treating ground, substantially as herein described with reference to figures 2-6 of the accompanying drawings. I
7. Ground treated by the method, substantially as herein described with reference to figures 2-6 of the accompanying drawings.