GB2202885A

GB2202885A - Piling

Info

Publication number: GB2202885A
Application number: GB08707907A
Authority: GB
Inventors: Philip Hayes Derbyshire; Michael John Turner; David Edward Wain
Original assignee: WESTPILE INT UK Ltd
Current assignee: WESTPILE INT UK Ltd
Priority date: 1987-04-02
Filing date: 1987-04-02
Publication date: 1988-10-05
Anticipated expiration: 2007-04-02
Also published as: EP0289147A3; GB2202885B; GB8707907D0; EP0289147A2

Description

1 2202885 Piling Backcround of The Invention.

The present invention relates generally to a method of piling comprising inserting or screwing an auger into the ground until the required depth is reached. to form a bore, and extracting the auger and passing a settable pile-forming material into the ground as the auger is extracted using a duct associated with the auger and which is extracted as the auger is extracted, in order to form a pile. As the auger is extracted, it lifts spoil out of the bore. Normally, the settable material will be concrete or grout and normally the duct will be a hollow stem of the auger itself. Normally the auger will have a substantially continuous flight.

One cannot rely upon the volume of concrete required corresponding to the volume of the flow. If the soil is poor. concrete flows out laterally into the soil and considerably more concrete is required. The amount of concrete required per unit time depends primarily upon the rate of extraction of the auger which determins the rate of formation of the void to be occupied by the 2 concrete. The rate of extraction must not be so fast that a larger void is being formed than can be filled by the inflowing concrete. However too slow a rate is uneconomic. wastes concrete and can cause practical difficulties in extracting the auger. The correct extraction rate is therefore important for the satisfactory formation of the pile. and it is desirable to find a method in which there is reasonable certainty of the correct withdrawal rate being used.

The Invention The present invention provides methods as set forth in Claims 1, 2, 5 or 9 and augers as set forth in Claims 6 or 8. The remaining Claims set forth preferred features of the invention.

By sensing the conductivity (or other property) of the contents of the duct or stem. one can determine the level of the concrete (or other settable material) during extraction. If the level is above the conductivity sensor or probe, a higher conductivity will be sensed. Provided the level is kept above a certain critical level at all times. the pile will be satisfactorily formed. Although essentially very simple. this invention can lead to improved formation of piles and reduced wastage of concrete.

1 3 Although more sophisticated methods of sensing may in theory be possible. it is found that simple conductivity sensing provides an arrangement which can resist the very aggressive environment in which the auger will be working - the ground can contain bricks or gravel or pieces of rock, etc., and the inside of the stem is subject to abrasion from the pumped settable material.

Preferred Embodiment The invention will be further described. by way of example, in which:

Figure 1 is a schematic view, showing a continous flight auger of the invention. being screwed into the ground; Figure 2 is a detail looking in the direction of the arrow II in Figure 1; Figure 3 is a section along the line III-III in Figure 2 Figure 4 is an axial section. on an enlarged scale compared to Figure 1. of the head of the auger; and Figure 5 is a section along the line W-W in Figure 4.

4 The auger has a hollow stem 1, a continous flight 2. a rotary drive head 3. and a steel swivel assembly 4 for connection to a concrete pump (not shown).

The auger has a number of conductivity monitors or sensors 5. There are typically two diametricallyopposed monitors 5 adjacent the bottom of the auger, i.e. adjacent to the point of injection, and there are other monitors higher up. The positioning of the monitors 5 depends upon the length of the auger and ground conditions (for instance wet sand and gravel well below the water table may require a much higher head of concrete than stiff clay); in general, it is desireable to have concrete about half way up the auger. There should be monitors 5 located at this level; additional monitors 5 near the top and bottom of the auger have been found useful.

Figures 2 and 3 show one monitor 5. The monitor 5 is operative on the inside of the stem 1 and is in the form of a screwed insert 6 carrying a steel probe 7 with a suitable insulating sleeve 8. There is a protective housing 9 with a screw cap 10.

A pipe 11 (such as a gas barrel) is strongly welded to the auger stem 1 and has suitable Tee-pieces 12 having short branch pipes 13 which penetrate the respective housings 9. enabling leads 14 to be taken to the probes 7. The housings 9 can be protected by welded-on strapping 15.

The leads 14 have to be taken out in a suitable manner since the auger stem is continuously rotating during drilling and construction of the pile. Figure 4 shows that slip rings 16 can be used with sliding contacts carried on a stationary annular housing 17 suspended below the drive head 3 with a suitable gland packing or water-proofing 18. Further pairs of slip rings can be added for each pair of monitors 5.

Figure 1 shows a single auger of for instance 6 m or 8 m length. but a string of augers can be made up for piling to greater depths. Joints can be formed between lengths of auger by providing suitable joints for the pipes 11 and connectors for the leads 14.

In the present assembly, an electric current is passed between the head of one probe 7 and the diametrically-opposed probe 7 and the electrical conductivity is monitored between the probes 7. If the concrete becomes depleted, air (normally under reduced pressure) will be present and the conductivity will fall sharply. The current flowing can be indicated on ammeters 19 for the various pairs of probes 7.

6 Monitoring the conductivity at different levels enables information to be provided to the operator, so that he can control the extraction more precisely. As shown in Figures 1 and 4, monitors 5 can be provided on the swivel assembly 4. or they can even be provided closer to the concrete pump. Particularly if the concrete pump is the conventional piston pump the monitors 5 above the drive head 3 can detect surges or pulses in the concrete; as it is known what volume of concrete is pumped by each stroke or cycle of the pump, this detection can give a good indication of the rate of flow. This mechanism appears to be a change in conductivity when there is a pressure stroke from the pump which is clearly distinguishable from both the 'pause' stroke of the pump and the case when there is air only between the monitors 5.

It is not essential that the conductivity should be measured between opposed. localised monitors. For instance. one probe 7 could be used with the auger stem 1 itself acting as the other pole (at earth potential).

The present invention has been described above purely by way of example. and modifications can be made within the spirit of the invention. The invention also consists in any individual features described herein or any combination of such features or any generalisation 1 7 of such features or combination. Furthermore, pressure sensors. or other means of measuring physical properties that indicates the presence or absence of concrete or grout. could be used in place of the electrical conductivity sensors.

8

Claims

CLAIMS.

1. A method of piling, comprising inserting an auger into the ground to form a bore, extracting the auger and passing a settable pile-forming material into the ground as the auger is extracted using a duct associated with the auger and which is extracted as the auger is extracted, in order to form a pile, the electrical conductivity or another property of the contents of the duct being sensed and the rate of extraction of the duct being reduced or extraction being stopped if the conductivity drops substantially or the other property alters substantially.

2. A method of piling. comprising forming a bore with an auger which has a hollow stem, passing settable pile-forming material down the interior of the stem into the bottom of the bore and extracting the auger whilst monitoring the level of concrete inside the stem of the auger using an electrical conductivity sensor or means for sensing a property of the concrete other than electrical conductivity, and reducing the rate of extraction or ceasing to extract if no settable material is sensed. until settable material is again sensed.

3. The method of Claim 1 or 2, wherein the electrical conductivity is sensed between sensors at the same level V 9 in the duct or barrel.

4. The meth.od of Claim 1 or 2, wherein the electrical conductivity is sensed between sensors at different levels in the duct or barrel.

5. A method of piling. substantially as herein described with reference to the accompanying drawings.

6. An auger for piling. by inserting the auger into the ground and extracting the auger while passing settable pile-forming material down the auger stem into the ground to form a pile, the auger having a hollow stem and at least one sensor inside the stem for sensing the electrical conductivity or another property of the contents of the stem, to thereby enable the level of settable pile-forming material inside the stem to be monitored and the rate of extraction of the auger to be controlled.

7. The auger of Claim 6. wherein each sensor is in the form of an electrically-conductive element on the inside of the stem wall carried on an insect fixed to the stem wall and insulated from the element. the exterior of the element projecting radially outwards of the stem wall and being protected by a housing.

1-2-

8. An auger for piling. substantially as herein described with reference to. and as shown in. the accompanying drawings.

X

9. A method of piling, comprising inserting an auger into the ground to form a bore. extracting the auger and passing a settable pile-forming material through a duct into the ground as the auger is extracted. in order to form a pile. the electrical conductivity or another property of the contents of the duct being sensed in order to determine the rate of flow of the settable material along the duct.

Published 1988 at The Patent Office, State House, 66171 High Holborn, London WC1R 4TP. Further copies may be obtained froM The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent. Con. 1187.

7. The auger of Claim 6, wherein each sensor is in the form of an electrically-conductive element on the inside of the stem wall carried on an insert fixed to the stem wall and insulated from the stem wall. the exterior of the element projecting radially outwards of the stem wall and being protected by a housing.

8. An auger for piling. substantially as herein described with reference to, and as shown in, the accompanying drawings.

R 9. A method of piling. comprising inserting an auger into the ground to form a bore, extracting the auger and passing a settable pile-forming material into the ground as the auger is extracted, in order to form a pile, the electrical conductivity or another property of the contents of the duct being sensed in order to determine the rate of flow of the settable material along the duct.

1 Amendments to the claims have been filed as follows 2202m in the duct.

4. The method of Claim 1 or 2. wherein the electrical conductivity is sensed between sensors at different levels in the duct.

6. An auger for piling by inserting the auger into the ground and extracting the auger while passing settable pile-forming material down the auger stem into the ground to form a pile. the auger having a hollow stem and at least one sensor inside the stem for sensing the electrical conductivity or another property of the contents of the stem. to thereby enable the level of settable pile-forming material inside the stem to be monitored and the rate of extraction of the auger to be controlled.