GB2246590A

GB2246590A - Forming piles in situ

Info

Publication number: GB2246590A
Application number: GB9015817A
Authority: GB
Inventors: Hsi-Huan Lu
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-07-25
Filing date: 1990-07-18
Publication date: 1992-02-05
Also published as: DE4023627A1; GB9015817D0

Abstract

An air compression grout tank 16 is connected to an assembled anchoring steel key 1, 2, 5 and 11 after the latter is driven down to the stratum. Then premixed and batched concrete contained in the grout tank is pressed into the ground bore drilled by the anchoring steel key. Such an air compression type anchoring steel key and construction method are particularly effective when used on strata of broken rocks, jointing-abundant rock layers, gravel stones and may effectively prevent the grout poured from being thinned or flushed away by underground flows at the anchor end during construction. <IMAGE>

Description

-, - c- -j --3 G) -e - -- ---2 A- AN AIR COMPRESSION TYPE ANCHOR

CONSTRUCTION METHOD AND APPARATUS THEREOF The present invention relates to an air compression type anchor construction method and apparatus thereof, particularly to an air compression construction method and apparatus used to press concrete into anchoring steel keys.

For side slope earth work, tie back anchorage or against uplife anchorage usually used in civil engineering, there are times we meet strata of pyroclastic rocks, jointing-abundant rock, and volcanic aggregate rocks and gravel stones that have high water permeability. In these cases, grout leaked and lost during grouting up is frequently tremendous, and cement grout pouted may be as many as tens, hundreds, or even thousands of sacks (as we had seen in the Southern Round Island Highway Project). However, even so big amount of cement grout can not necessarily produce anchorage force which meets required tension force specified in design. What is more troublesome is the underground flow found at the anchor end during grouting up; cement grout at the anchor end actually might have been thinned or flushed away while grout at the opening of anchor bore is overflowing. It is therefore tried by the applicant with his years experiences in earth rock anchors to develop an air compression type anchor construction 1 i -2 method and apparatus thereof which are convenient and fast in construction, cement saving, high tension, easy in operation, time saving, labour saving and economical.

The construction method and apparatus thereof disclosed in the present invention may be fully understood by referring to the following detailed description and the accompanying drawings in which

Fig. 1 shows an assembled air compression type 10 anchoring steel key of the present invention; Fig. 2 shows the structure of the air compression apparatus used in the present invention; Fig. 3 shows the steel key collar and the PE pipe compression head being compressed by an oil compressor; Fig. 4A illustrates a grouted bore completed by conventional anchor construction method; and Fig. 4B illustrates a grouted bore completed by the construction method of the present invention.

Please refer to Fig. 1, in which an assembled steel key is shown which includes in sequence a tipped leading head 1, an anchorage-variation head 2, a percussion stem head 5, and a percussion stem 11. In the anchorage-variation head 2, a set of clamping plates 4 for clamping steel wire ropes 9 as well as an air and concrete outlets 3 are provided. An air and concrete inlet 7 also passes across the center of the anchoragevariation head 2. A plurality of steel key collars 8 j i with a thickness of 10mm are provided on each steel wire rope 9 at an interval about 60cm and are compressively collared on the steel wire ropes 9 by an oil compressor 18 (as shown in Fig. 3). Each of the free ends of the steel wire ropes 9 is spread with tallow or anticorrosive and then inserted into a PE pipe 12. Through a PE pipe compression head 10, each PE pipe is fixedly attached to the steel wire rope 9. The percussion stem 11 is formed by connecting a plurality of 2-to 3-meter long stems.

After the above-mentioned steel key is assembled, an air compression grout tank 16 is connected to the rear end of the percussion stem 11 (i.e. the end extends out of ground surface through a concrete and air-venting elbow 13, a convenient adapter 14, and a high pressure out-pipe 15 connected to the bottom of the grout tank 16). An O-ring 23 is provided at the connection of grout tank 16 and the high pressure out- pipe 15 to prevent the high pressure air in the high pressure pipe from- leaking. Please refer to Fig. 2 for the structure of the air compression apparatus. The air compression grout tank 16 is provided with a seal cover 21 which is tightly screwed to the top of the grout tank 16 with removable screws 20. A cement compressing platform 19 and the O-ring 23 are provided inside the grout tank 16 to facilitate the compression of grout inside the grout tank 16. On top of the grout tank 16, a high pressure in-pipe 17 is connected, through there a height pressure air source is guided into the grout tank 16.

As shown in Fig. 3, the PE Pipe compression head 10 at the free end of a steel wire rope 9 may be compressed by the oil compressor 18 to fitly connect the steel key collar 8 and the PE pipe compression heads 10 so compressed do not easily loosen or slip off, the steel wire ropes 9 are allowed to extend freely during,prestressing.

The steps during construction are as following:

1. Use Aluminum Belt Percussion Drill to drill a bore with a diameter more that 1 Ocm and to a predetermined depth; 2. To assemble the anchoring steel key; 3. To drive the anchoring steel key. Use the percussion drill to percuss while expels airin the bore. In the event the bore wall collapses and causes difficulty in driving the steel key, then the steel key shall be downwardly driven while air is expelled via the air and concrete inlet 7 so that the steel key may be pushed to a predetermined depth.

4. To flush with water. Pour water through the air and concrete inlet 7 to f lush of f mud from the air i and concrete outlet 3. Flush for 5 minutes or so; 5. The same as step 4 but to f lush with high pressure injection air instead of water; 6. Premix with mixer the batched concrete 5 (including water, gravel, sands, and cement). Consistency of concrete depends upon the stratum breakage and jointing conditions, and a common watercement-fine gravel- sand ratio is 0.35:1:1:4. Mixed concrete is then transported into the grout tank 16.

When being pressed by the air from air compressor 18 through the high pressure in-pipe 17, the cement compressing platform 19 presses the mixed concrete in the grout tank 16 to pass the high pressure out-pipe 15, the convenient adapter 14, the concrete and air venting elbow 13, the air and concrete inlet 7, and the air and concrete outlet 3 and finally enters the bore drilled to form a concrete wall 22. The cement compressing platform 19 moves downward until it reaches the O-ring at bottom of the grout tank 16. An usual volume for the air compression grout tank 16 is from 100 1 to 200 1; 7. Pull back, the percussion stem 11. After the percussion stem 11 is pulled back, the steel key collars 8 on the steel wire ropes 9 may prevent the steel wire ropes 9 from attaching the bore wall 22 and being corroded by the bore wall 22. Further, the steel key collars 8 can also enhance the grip force of the steel wire ropes 9 to the concrete wall 22; 8. Await 14 days allowing the concrete to harden; and 9. To apply prestress. Since the PE pipe compression heads provided at the free ends of steel wire ropes 9 do not easily loosen after they are compressed by the oil compressor 18, the steel wire ropes 9 are allowed to freely extend during applying prestress.

From Fig. 4A, we can see an anchoring steel key driven by conventional construction method; grout has overflowed from the bore opening while the grout at the anchor end has already been thinned or flushed away by underground flow 201. And, the water-cement ratio used is 0.45:1 and the grout is poured into the bore by a water pump. In Fig. 4B, an anchoring steel key driven by the construction method of the present invention is shown. The water-cement- sand-fine rubble ratio used in the air compression type anchor construction method is 0.35:1:4:1, and the grout is pressed into the bore drilled by an air compressor.

i

Claims

I CLAIM:

An air compression type anchor construction method comprising:

a. percussing and drilling by a percussion drill a ground bore with a diameter about 10cm to a predetermined depth; b. Assembling anchoring steel key; C. driving the assembled anchor steel key down the ground and expelling air in the bore drilled from an air and concrete inlet in the steel key at the same time; d. flushing the bore drilled by pouring water from the air and concrete inlet so that unnecessary mud and air are flushed and expelled from an air and concrete outlet; and e. transporting premixed and batched concrete into an air compression grout tank and allowing a high pressure air source from an air compressor to enter the grout tank via a high pressure in-pipe and to downwardly press a cement compressing platform, so that the concrete in the grout tank passes a high pressure outpipe, a convenient adapter, a concrete and air-venting elbow, the air and concrete inlet, and the air and concrete outlet and finally enters the bore drilled; and f. Upwardly pulling back a percussion stem while pouring or pressing the concrete into the bore drilled so that the anchor end of the steel key may be f illed with concrete.
2. An air compression type anchor construction method as claimed in claim 1 wherein the following step may be further included between the steps d. and e.: pressing high pressure air into the air and concrete inlet as well as the air and concrete outlet to flush the bore drilled; at the same time, upwardly pulling back the percussion stem while grouting up concrete so 10 that concrete may fill up the anchor end.
3. An air compression type anchor construction method as claimed in claim 1 wherein the premixed and.batched concrete mentioned in step e. has a cement15 water-sand-fine rubble ratio of 1:0.35:4:1.
4.

An air compression type anchor construction apparatus comprising:

a. a tipped leading head which has a sealed front 20 and a rear end provided with air and concrete outlets; b. an anchorage variation head having an air and concrete inlet passes its center and a set of clamping plates for clamping steel wire ropes; C. a percussion stem head connected behind said anchorage variation head; d. - a percussion stem formed by a plurality of connected 2-to 3-meter long percussion stems; e. steel wire ropes being clamped i i i 1 in said 41' anchorage variation head; f. steel key collars provided on said steel wire ropes at a proper interval and being compressed by an oil compressor to tightly collar on said steel wire ropes; g. PE pipe compression heads f or receiving tallowor anticorrosive-spread free ends of said steel wire ropes before the same are inserted into PE pipes; and h. an air compression grout tank f or containing premixed and batched concrete being connected to the rear end of said percussion stem of said assembled steel key via a convenient adapter, a high pressure out-pipe, and a concrete and air venting elbow; grout contained in said air compression grout tank being pressed into a ground bore drilled by said anchoring steel key via the above-mentioned path by a high pressure air source from an air compressor into said grout tank through a high pressure in-pipe.
5. An air compression type anchor construction method substantially as hereinbefore described with reference to the accompanying drawings.
6. An air compression type anchor construction apparatus substantially as hereinbefore described with reference to the accompanying drawings.

Published 1992 at The Patent Office. Concept House, Cardiff Road, Newport. Gwent NP9 111H. Further copies may be obtained from Sales Branch. Unit 6. Nine Mile Point. Cwmfelinfach, Cross Keys, Newport, NPI. 7HZ. Printed by Multiplex techniques lid. St Mary Cray, Kent.