GB2064931A - Improvements relating to land drainage - Google Patents

Abstract

A method of draining land comprising the steps of removing a strip of top soil so as to expose subsoil, fragmenting the subsoil in situ to the desired depth, adding a backfill stabilizer so as to be admixed with the subsoil during fragmentation, and replacing the top soil. The invention includes an implement adapted to be moved over the ground for forming a drain comprising: a first earth-working means 3, 5, 6 arranged for removing a strip of top soil so as to expose subsoil, coupled together with a second earth-working means 11 for fragmenting the exposed subsoil to a desired depth, a third earth-working means 15 for replacing the top soil over the fragmented subsoil, and an applicator 8 for applying a subsoil stabilizer in a position to be admixed with subsoil during fragmentation. <IMAGE>

Description

SPECIFICATION Improvements relating to land drainage The present invention relates to a method of drain ing land and also to an implement for use in draining land. Traditional techniques of land drainage involve a system of clay or plastic pipes placed in the subsoil, commonly to a depth of 1 to 2 m, with a permeable backfill of gravel, stones or clinker.

Secondary cultivation is normally necessary, involv ing subsoiling or mole-drainage to improve the pXermeability of the soil, in order to enable move ment of water through the soil into the pipeworkvia the backfill. This secondary cultivation is normally at a shallower depth, e.g. down to a 1/2 or 3/4 m. On heavy clay soils in particular this secondary cultiva- tion may be inadequate to allow sufficient water movement into the pipework. Furthermore, mole drainage tends to be a temporary expedient since the soil closes up. It is known to fill in the mole slits with gravel but this is a difficult and unsatisfactory operation due to the narrow dimensions of the slit.

Trenches for pipes are cut by continuous chains or rotary implements which mix top soil and subsoil, which is a disadvantage to subsequent cultivation.

Other disadvantages are the need to carry pipework for continuous laying and means for feeding permeable backfill above the pipe. The qunatities of backfill required are a major cost item in any drainage scheme.

The invention is aimed at providing a simple and efficient method of drainage and an implement suitable for use with the method.

According to one aspect of the invention there is provided a method of draining land comprising the steps of removing a strip of top soil so as to expose subsoil, fragmenting the subsoil in situ to the desired depth, adding a backfill stabilizer so as to be admixed with the subsoil during fragmentation, and replacing the top soil.

Conveniently the steps are carried out continuously, in a single pass.

It has been proposed to mix various additives as stabilizers to heavy soils to maintain improved permeability resulting from fragmentation. Ingredients which have been proposed as stabilizers include lime in the form of cement, burnt lime or slaked lime, ground limestone and phosphoric acid.

Any of these materials can be used in accordance with the method of the present invention, but the preferred material is burnt, or slaked lime or Portland cement or other building cement containing calcium. It may be added at a rate from 5 to 100 kg per tonne of dry soil, preferably 20 to 40 kg per tonne. When it is mixed with clay subsoil material there results a more granular and friable structure which is permeable to water.

The incorporation of such stabilizers has been proposed as an additive to soil for the provision of backfill over pipes. This involves trench digging and laying the pipes and thereafter mixing the stabilizer in large quantities with the excavated clay on the field surface prior to re-incorporating it in the trench.

This is an expensive and time consuming operation.

The method of the invention can therefore be seen to demonstrate the following advantages: 1. There is no mixing of the top soil and subsoil; 2. Backfill and pipes are eliminated, reducing cost, simplifying the operation and increasing the work rate; 3. Because of reduced cost the stabilized drains can be less deep and more closely spaced thereby eliminating the need for mole-drainage, or subsoiling; 4. Because the facilities for carrying pipes and feeding backfill are not required, the resulting imple ment can be made lighter; 5. The implement can therefore be made cheaperto buy and to operate; and 6. The method requires less critical control over depth than traditional techniques of land drainage which simplifies the operation and reduces the cost.

According to another aspect of the invention there is provided an implement adapted to be moved over the ground for forming a drain comprising: a first earth-working means arranged for removing a strip of top soil so as to expose subsoil, coupled together with a second earth-working means for fragmenting the exposed subsoil to a desired depth, a third earth-working means for replacing the the top soil over the fragmented subsoil, and an applicator for applying a subsoil stabilizer in a position to be admixed with subsoil during fragmentation.

The first earth-working means may comprise a vertical blade aligned in the direction of motion to divide the top soil and means behind the blade arranged to displace top soil to both sides of the implement.

The fragmentation means may comprise a rotor mounted for rotation about a horizontal axis and fitted with earth engaging elements.

Preferably the second earth working means is so mounted relative to the first earth working means that in operation the axis of the said rotor is positioned below the normal ground level of the earth being worked.

The third earth working means may comprise a pair of rotatable dished covers obliquely angled to the direction of motion so as to approach each other towards the rear of the implement.

Other preferred features will appear from the claims accompanying this specification.

Preferred forms of the invention are hereafter described with reference to the accompanyings, in which Figure 1 is a schematic side elevational view of an implement in accordance with the invention; Figure 2 is a schematic plan view of the implement of Figure 1; Figures 3a to d illustrate the use of the implement in carrying out the method of the invention.

The implement of Figures 1 and 2 comprises a main beam or frame 1 fitted with a standard 3 point hitch 2 for attachment and support from a tractor.

Suspended from the frame lisa vertical blade in the form of a rotatable disc 3 which is arranged to make a vertical cut into the top soil in the vertical medial for-and-aft plane of the implement. The disc 3 is supported from the frame by a leg 4 which is adjustable in height as indicated.

Following the disc 3 in the direction of motion is a share 6 which is adapted to make a horizontal cut below the top soil e.g. at a depth of 20 to 25 cms.

Integral with the shares is a pair of mouldboards arranged for right-hand and left-hand operations respectively. The disc and the share and mouldboards are arranged so as to split the top soil and displace it on both sides of the implement so as to expose the subsoil. A leg 7 is provided for enabling adjustment of the depth of the mouldboard and share.

Immediately behind the share and between the rear portions of the mouldboard is a delivery tube or pipe 10 through which the soil stabilizer is fed. The pipe 10 is attached to a hopper 8 which is shown diagrammatically. In practice the hopper may extend over the full length of the implement and to either side of the implement and side wheels may be required to stabilize the implement and to help support the weight of the hopper and to assist in manoeuverability. These are not shown. At the junction of the hopper and the pipe 10 there is preferably provided a metering means indicated at 9 which may be of standard form used for delivering powdered material from storage e.g. a rotor or vibrator or fan which may be electrically driven or connected to the power take-off or hydraulic motor to be described.

The stabilizer may be stored in bulk in a secondary vehicle driven alongside or behind the implement. In this case part of the metering equipment may be carried by the vehicle. The applicator on the imple mentmaytaketheform of a coupling device, but a separate small hopper and metering device on the implement is normally desirable.

The second earth-working means is constituted by a rotor 11 which is preferably mounted to the frame 1 in such a way that its height is adjustable relative to the frame so that it can operate at different operating depths. The rotor is shown driven by an enclosed chain drive or gear transmission 12 from a hydraulic motor 13. The chain or gears could alternatively be driven directly from the tractor power take-off.

The rotor may be generally similar two that described in British Patent No. 1,512,480 but is of narrower dimensions. Preferably there are two hubs fitted with pick tines. The overall diameter of the rotor will be much greater than that of Patent 1,512,480.

The implement is designed to provide a trench which is preferably from 50 to 200 mm wide, e.g. 100 mm and to work the soil down to a depth from 1 to 1.5 m. Thus the top soil may be lifted to a depth of for exampie 20 to 25 cm., and the rotor may have a radius of 75 to 130 cm. It will normally (but not necessarily) be positioned with its axis generally on the level of the top of the exposed subsoil.

Behind the second earth-working means, in the direction of motion, will be found the third earthworking means which in the embodiment consists of a pair of rotatable dished coverers 15 which are mounted as shown so as to be adjustable in height over the ground and in angle of pivot. They extend obliquely to the central medial vertical plane so as to approach one another behind the implement and are concave in the direction of motion. When being pulled over the ground they are caused to rotate and lift the top soil and turf two close the excavation.

Angled scraper blades may be used instead. If desired a roller may be drawn behind the third earth-working means.

Figures 3a to d illustrate the operation of the implement and the steps of the method of the invention. Figure 3a shows the action of the cutting disc 3, the level of the division 20 between top soil and subsoil and the line of cut 21 of the first earth-working means and of the cut 22 of the second earth-working means. Figure 3b shows the action of the first earth-working means in lifting the cut top soil to each side to expose the surface of the subsoil at 23.

Figure 3c shows the fragmentation of the subsoil at 24 to provide the subsoil trench and the admixture of the fragmented subsoil similtaneously with the soil stabilizer. Finally, Figure 3d shows the action of the third earth-working means in lifting and turning the top soil to close the trench.

It will be apparent that the invention provides for a simple and economic system for land drainage which can operate to a depth of up to 1.5 m and which will not interfere with subsequent cultivation.

Other materials than those listed are useful as stabilizers, notably synthetic resins and other polymers such as polyvinyl alcohol.

Claims (21)

1. A method of draining land comprising the steps of removing a strip of top soil so as to expose subsoil, fragmenting the subsoil in situ to the desired depth, adding a backfill stabilizer so as to be admixed with the subsoil during fragmentation, and replacing the top soil.

2. A method according to claim 1 wherein the steps are carried out continuously in a single pass.

3. A method according to claim 1 or claim 2 wherein the stabilizer comprises slaked lime.

4. A method according to claim 1 or claim 2 wherein the stabilizer comprises a material selected from cement ground limestone, slaked lime, burnt lime and phosphoric acid.

5. A method according to any preceding claim wherein the stabilizer is added in an amount from 0.5 to 10% by weight based on the dry weight of soil.

6. A method according to any preceding claim wherein the stabilizer is applied to the exposed subsoil before or during fragmentation.

7. A method according to any preceding claim wherein the exposed subsoil is from 50 to 200 mm wide.

8. A method according to claim 7 wherein the exposed subsoil is substantially 100 mm wide.

9. A method according to any preceding claim wherein the fragmentation extends to a depth from 1 to 1.5 m.

10. An implement adapted to be moved over the ground for forming a drain comprising: a first earth-working means arranged for removing a strip of top soil so as to expose subsoil, coupled together with a second earth-working means for fragmenting the exposed subsoil to a desired depth, a third earth-working means for replacing the top soil over the fragmented subsoil, and an applicator for applying a subsoil stabilizer in a position to be admixed with subsoil during fragmentation.

11. An implement according to claim 10 wherein the applicator is positioned for delivering stabilizer to the exposed subsoil prior to or during fragmentation.

12. An implement according to claim 10 or claim 11 wherein the first earth-working means comprises a vertical blade aligned in the direction of motion to divide the top soil and, means behind the blade arranged to displace top soil to both sides of the implement.

13. An implement according to claim 12 wherein the top soil displacing means comprises a share and left-hand and right-hand mouldboards.

14. An implement according to any of claims 10 to 13 wherein the fragmentation means comprises a rotor mounted for rotation about a horizontal axis and fitted with earth engaging elements.

15. An implement according to claim 14wherein the earth engaging elements comprise pick tines.

16. An implement according to any of claims 10 to 15 wherein the first and second earth-working means are arranged to work a strip of earth from 50 to 200 mm wide.

17. An implement according to any of claims 10 to 16 wherein the first and second earth-working means are arranged to fragment subsoil to a depth from 1 to 1.5 m.

18. An implement according to any of claims 10 to 17 wherein the third earth-working means comprises a pair of rotatable dished coverers obliquely angled to the direction of motion so as to approach each other towards the rear of the implement.

19. An implement according to any of claims 10 to 18 wherein the applicator comprises a hopper fitted with a delivery tube and metering means, the hopper extending over the earth-working means.

20. An implement according to claim 20 including side wheels.

21. An implement according to claim 10 substantially as described herein with reference to the accompanying drawings.