AU603257B2 - A precast diaphragm wall method - Google Patents

Description

COMMONWEALTH OF AUSTRALIA Patent Act 1952 60 3 C O M P L E T E S P E C I F I CAT I O N

(ORIGINAL)

Class Int. Class Application Number PI 4297 Lodged 11 September 1937 Complete Specification Lodged Accepted Published Priority: Related Art q 4 imTT-- Name of Applicant FRANKIPILE AUSTRALIA PTY. -t Address of Applicant 5th Floor, 69 Phillip Street, j Parramatta, New South Wales, Commonwealth of Australia Actual Inventor Malcolm Wood Address for Service F.B. RICE CO., Patent Attorneys, 28A Montague Street, BALMAIN. 2041.

Complete Specification for the invention entitled: "A Precast Diaphragm Wall Method" The following statement is a full description of this invention including the best method of performing it known to Us:- Alt i r I r. V 2 The present invention relates to a method of forming a precast prestressed diaphragm wall.

The present invention is of particular use in the construction of underground car parks, multi-level basements, road tunnels, railway tunnels, underground stations, and earth-retaining walls in general.

When constructing an underground car park, or the like, in sandy soil it is necessary to provide a retaining 1 wall. In the prior art, this retaining wall has generally consisted of a number of bored piles in close *t array, or a concrete wall formed in-situ. Both of these *Ott means for providing a retaining wall are not entirely ,o satisfactory either from a cost point of view, or due to inadequacies in the integrity of the wall, in that soil or water leak through the wall. In addition, such walls generally have a poor architectural finish.

The present invention seeks to overcome these o LLdifficulties by providing a novel method of forming a precast prestressed diaphragm wall.

S 20 The present invention conoists in a method for the formation of a precast, prestressed diaphragm wall comprising the following steps:- 1 i. Providing a plurality of precast prestressed extruded panels, each panel having a top and a base and a plurality of hollow cores extending from the top of the panel to the base thereof; 2. Cutting each panel so as to form at least one slot, said slot extending from an 'uter surface of the panel to a hollow core therein, thereby forming at least one female joint member; 3. Aligning one panel relative to at least one other panel such that the female joint member of the one panel is in juxtaposition to the female joint member of at least ono other panel; 4. Inserting a male joint member into the juxtaposed I i ii II c_ 3 female joint members thereby linking each of the panels to at least one other panel; Fixing the base of the linked panels in concrete; and 6. Grouting the male-female joints.

In a further aspect the present invention consists in a precast, prestressed diaphragm wall comprising a plurality of precast, prestressed extruded panels, each panel having a top and a base and a plurality of hollow o cores extending from the top of panel to the base thereof, characterized in that each panel is linked to at least one other panel by means of a male-female joint, the a« male-female joint comprising a male joint member inserted into at least two juxtaposed female joint members, and o wherein each female joint member consists of a slot cut in the panel extending from an outer surface thereof through to a hollow core therein and the male joint member consists of at least two rod-like members connected together by means of a web(s).

In a preferred embodiment of the present invention the open slots cut in each panel extend from the top of the panel to the base of the panel. The male joint member preferably consists of two open cylindrical members connected by a web. Preferably, the male joint member is j| of such a length that when inserted into the juxtaposed female joint members it extends from the top of the panels at least 80% of the way to the base of the panels.

i Preferably, the male-female joints are grouted by pouring grout down the hollow cylindrical members of the male joint member. The grout flows from the cylindrical member of the male joint member into the female joint member. Gcout is supplied until the male-female joint is completely filled with grout. The ends of the cylindrical members of the male joint member to be inserted into the female joint member are preferably s.it, to assist in the flow of grout from the male joint member into the female joint member.

It is preferable that the male joint member extends a into the concrete into which the base of the linked panels are fixed.

While it is preferable that the web connecting the rod-like members of the male joint is straight, it will be appreciated by persons skilled in the art, that in instances where it is desired that the wall deviates from a straight line, this can be achieved using a male joint member in which the web is angled or cranked.

S As stated above, it is preferable that the male joint i0 member consists of two rod-like members connected by a web, however, where it is required to form a second wall Idea at right angles to the first wall, the male joint member .o s will comprise three rod-like members connected by two o o webs. Other variations on this principle would be readily apparent to the person skilled in the art, and are included within the scope of the present invention.

oTypically, the present invention will be used in the construction of underground car parks and the like. This will generally involve the excavation of a trench under a bentonite slurry and the positioning of the precast, prestressed panels within the trench. It is preferred that once the linked panels are set in concrete that a coulis is provided between the outer surface of the wall and the wall of the trench. Generally a cement/bentonite coulis will be used. The use of such a coulis assists in waterproofing and maintaining the integrity of the diaphragm wall.

Tn addition to the ease of construction and the production of a diaphragm wall of high integrity, a number of other advantages stem from the method of the present invention. The method of the present invention enables the provision of cut-outs to the hol -w cores of the precast panels, to enable starter bar6 to be grouted in, to form a positive connection and shear key for floors, ramps or other structures to be connected to the diaphragm wall. This is achieved by cutting out the face of the panel through to the hollow cores therein. A grout plug is then inserted into the cut-out and suspended a distance down the hollow core. Reinforcement is then placed in position and grouted in.

Another advantage obtained using the present invention is the possible provision of a water stop between the diaphragm wall and the basement floor. This is of particular advantage where seepage may occur between 1 i0 the wall and the basement floor. This is achieved by gluing a plastic water seal to the bottom face of the *ooo panel before the panel is built into the wall (the seal 0: may be further reinfo'ced if required). The top of the water seal is fixed to the panel with tape. After the wall has been completed and excavated, the top of the water seal is detached from the panel and incorporated into the floor slab water sandwich, the lower half of the water seal being cast into the concrete footing.

In order that the nature of the present invention may be more clearly understood, preferred embodiments thereof will now be described with reference to the following figures in which:- Fig. 1 shows the guidewall positions; Fig. 2 shows typical wall details; Fig. 3 shows a single panel to which other panels will be linked; Fig. 4 shows a single panel with cut-outs for inclusion of starter bars to form a positive connection and sheer key; Fig. 5 shows a single panel with cut-outs including starter bars; Fig. 6 shows the provision of starter bars in the cut-outs; Figs. 7-12 show a number of different forms of joints included within the present invention; and i-Li I~ iri-i i ii- cu Fig. 13 shows the provision of a water stop at the foot of the wall.

Fig. 1 shows the setup for positioning of the panel 12 within the trench 10. The panel 12 is suspended by a support pipe 14 and the position of the panel 12 is adjusted using wedges 16. The soil 20 on either side of the trench is compacted beneath the support beams 18 provided. The support pipe 14 stretches across the trench resting on wedges 22 provided on the support beams 18.

Adjustment of wedges 22 enables movement of the panel 12 vertically, whilst adjustment of wedges 16 enables movement of the panel 12 horizontally.

As shown in Fig. 2 the panel 12 is set in concrete 28 and coulis 26 is provided between the panel 12 and the soil 20. If required a temporary anchor 24 may be provided to maintain the panel 12 in position. In addition, as shown in Fig. 2 floors 30 may be connected to the panel 12.

As shown in Fig. 3 the panel 12 includes a nunibur of hollow cores 32. A slot is cut to extend from an outear surface of the panel 12 to a hollow core 32 forming a female joint member 34. One panel is aligned with another so as to bring the female members 34 into juxtaposition A male joint member 36 is inserted into the juxtaposed female joint members As shown in Fig. 4 cuts can be made through the outer surface of the panel 12 to the hollow cores 32 to provide cut-outs 38. As shown in Fig. 5 starter bars 40 can be inserted into the cut-outs 38 to aid in the connection of floors to the panels 12.

The starter bar 40 is mounted in the cut-out 38 as shown in Fig. 6. A grout plug 44 is inserted through the cut-out 38 into the hollow core of the panel 12. The grout plug is suspended within the hollow core by means of a wire 42. The starter bar 40 is then fixed within the 7 cut-out by filling the hollow core of the panel 12 with sand/cement grout 46.

As shown in Figs. 7 through 12 the male joint member 36 typically consists of two open cylindrical members connected by a web 52. As shown in Fig. 10 this web 52 may be cranked. Once the male joint member 36 is inserted in the juxtaposed female joint members 35 the juxtaposed female joint members 35 and the open cylindrical members of the male joint are filled with grout 54. In the situation where the web 52 is cranked it may be necessary to provide an insert 56 to partition off the juxtaposed female joint members As shown in Fig. 9, where it is required that a panel 12 is provided perpendicular to other panels 12 the male joint member 36 may consist of three hollow cylindrical members 50 joined by a T-%haped web 52.

As is shown in Figs. 11 and 12, by adjusting the alignment of the panels 12 corners within the wall may be provided.

As shown in Fig. 13, a water seal 58 may be attached by means of pin 62 to the panel 12. Once the panel 12 is fixed in concrete 28 one end of the water seal 58 may be detached from the panel 12 and included into the floor slab In order that the nature of the present invention may be more clearly understood a detailed example of a preferred form of the method will now be discussed. While this example includes specific measurements, and other details, it will be appreciated that these are provided merely for the sake of clarity and are in no way intended to be construed as limitations on the method of the present invention.

EXAMPLE 1 In use, it will be necessary to supply guide beams and associated other equipment 0 ensure the correct I -8alignment of the individual panels. The general location of the guide beams and associated equipment, related to the wall position, is shown in Fig. i.

Under worst circumstances, the outside of the wall is the most critical and this should be established first and all other setting out should be related to it.

If there is adequate room available, and it is permitted by adjacent property owners, the outer guide beam can be located outside the site and in this case the 1 0 back of the wall will be only 100mm from the site boundary. (The 100mm filled with coulis).

If the guide beam is to be on site, the back of the oi wall will be at least 400mm from the site boundary unless special provisions are made. Such provisions can include the use of deep narrow guide beams (for example 150mm wide by 1 metre deep), support of panels on existing slabs, foundations or other structures, etc. Deep narrow guide beams would normally be cast in place in concrete.

It should be noted that guide beams should be placed so as not to load adjacent footings, unless these have been specifically checked to ensure that such loading is permitted.

Having established the location of the back of the i wall, this should be set out to line and level, with adequate off-sets to re-establish the line when necessary.

The excavation for the guide beams should be made as close to exact width and depth as possible. In particular P care should be exercised that the depth of excavation is Lsomewhat less than the final depth to allow for compaction of the ground below the beams.

After compaction of the ground below the beams, it should be finally cut to level and the beams seated. The gap between the beams should be 50mm greater than the maximum width of the excavator bucket. This width must be measured, as all buckets seem to be different and a -9nominal width is not accurate enough.

When the guide beams have been placed to line and level, they should be secured by guide beam braces, tack welded at suitable intervals along the beams. It may also be worthwhile to use pickets, driven into the ground outside the guide beams, to further fix them.

At each stage, the beams should be repeatedly checked to ensure they have not been moved. The location of these beams is critical to the easy installation of the panels.

The beams must then be backfilled with compacted backrill on the outside, back to ground level.

Compaction will depend on the soil type, but in sands, a vibrating plate should be used and the soil must be suitable for compaction, both in type and water content. If the natural soil is inadequate, an imported soil should be used and, if necessary, gravel or other material may be added to the soil below the beams before compaction.

Excavation of the trench is conducted under bentonite. Excavation at the commencement or end of a line must be carried out with the cut as near vertical as possible. The shape of the cut should be established by feeling the slope with a probe and controlled in this manner. In addition it is necessary to ensure that the depth of the trench is not overdug, and this should also be checked with a probe.

As excavation proceeds, the probe should be used to check the trench is to the correct depth and clean and that there are no obstructions or protrusions into the trench which would interfere with the placing of the panels. Once the trench is dug it should be interfered with as little as possible to reduce the risk of inducing local collapse.

Any over-dig or side overbreak will be taken up by concrete below the lower floor level. Any overbreak on 10 the outside of the wall will be taken up with coulis and any overbreak on the inside wall will be filled with bentonite. Over-dig in the bottom of the trench must not be filled with sand or other material which could result in a soft spot below the footings. Overbreaks should be identified only so that the overbreak material can be removed and so that allowance can be made in quantities of concrete, coulis or bentonite to replace these areas.

At all times, excavation should proceed slowly and steadily, with greater care to ensure as accurate a cut as possible, with the trench full of bentonite at all times.

On completion of a section of trench, ready for panel installation, the excavation should be carefully checked with the probe to ensure that the trench is clean and of adequate depth and width to permit installation of all panels in the length of wall to be constructed.

On completion of excavation and checking of the excavation with the probe, the survey for the final line and level of the panels must be re-established. This will 20 include the provision of wire lines or string lines, to exactly define, in line and level, the top of the panels.

The guide beams should also be checked to see that they have not significantly moved during excavation and are still adequately located to support and position the panels, if necessary with increased wedging. It is particularly important to see that the guide beams h,.ve not risen to a level where they are higher than the panel support height. If this does occur, the beams will need L- to be repositioned.

The panel should be lowered into position slowly, ensuring that it does not touch the guide beams or the walls of the excavation. The panel should be lowered to its correct level and wedged with four sets of spacer plates and wedges, so that it is exactly in position and vertical, both at right angles to the line of the wall and 11 along the line of the wall.

When hanging subsequent panels, they can be suspended at about the final level, at 1 or 2cm from the already hung panel and then moved sideways to the existing panel.

When panels are part of a corner or angular change system, the support tubes may be differently positioned, or may be shorter to prevent fouling of other tubes or panels.

As the panels are placed, they will displace bentonite, which will f!.ow along the excavation and must eitleo be allowed to flow into new excavation work in progress, or be pumped back to storage if no excavation can be undertaken at that time. The open excavation should be maintained full of bentonite at all times.

When the panels are hung in the trench, they should be straight, vertical and exactly aligned, joint to joint. If this is not the case, the joint will not fit.

The joint will be manufactured with slots back and front of each pipe, at a level just above the top of the concrete footing to the panel. The joint may have a hole in the web about 20mm from the top, to allow reinforcing wire to be used to support the joint in position.

The joints should slide into place by its own weight. A little vibration may be required if the concrete in the cores is rough. The joint should not be driven in. If difficulty is experienced in entering a joint, check the straightness of the joint and the alignment of the panels. Slight movement of the panels on Sthe wedges without significant change in position is usually sufficient to enter the joint.

The joint should be hung with the top of the joint below the top of the panel to ensure a minimum cover of grout for the steel, When all the panels in a particular construction line have been jointed, check the alignment and level of the i i _1 12 panels to ensure that they have not been moved from true line aiA. level.

When the joints have all been entered and the panels have been checked for line and level, using the probe, check that the excavation, both back and front of the wall, is clear of obstruction for the full excavated depth, 300mm below the bottom of the panel.

If small volumes of collapsed sol are found, these should be removed by air lifting and this process continued until the excavation is clear throughout its entire length and full depth. No concrete should be S placed until the excavation below the wall is satisfactory.

Sr" Attached stop ends will have been positioned on the appropriate panels and will be in place. The pneumatic stop ends have now to be placed outside the fixed stop ends and inflated. The stop ends should be positioned slightly closer to the soil wall than to the panel, so that expansion can be concentrated at the edge of the fixed stop end rather than close to the panel. The spikes at the bottom of the pneumatic packers should be pushed firmly into the bottom of the trench and the top lashed firmly to the guide beam to prevent the pressure of the concrete pushing the packer out of position. Care should be taken in placing the stop ends, to ensure that a collapse of the excavation wall is not produced. When inflating the stop ends, inflate each side in increments so as to avoid a significant differential pressure on the panel, which could tend to move it off-centre.

After the packers have been placed and inflated, again check line and level of the panels and the bottom of the excavation to ensure that no collapse has occurred.

The tremie will be 75mm to 150mm, long enough to reach the bottom of the excavation, and with a funnel at th') top.

The tremie should be carefully inserted into the

I

-r-II -LUI 13 trench, in front of the panel, taking care not to cause collapse of the soil. The tremie should be pla i ,.ose to the stop end at the beginning of the wall or close to the section previously concreted. Initially, the tremie should sit on the bottom of the excavation so that it can be filled with concrete. When full, the tremie should be raised slightly to allow the concrete to flow out, additional concrete being added from the agitator truck to keep the funnel topped up. As the concrete is tremmied S 10 in, the level should be checked continuously at both sides of the wall using the probe. When the concrete has achieved the desired level adjacent to the tremie, the tremie should be lifted to empty at that point and then be moved further along the trench, lowered into the already poured concrete, or to the bottom of the excavation and again filled with concrete before lifting to permit flow, Concrete may be allowed to flow from the tremie only when the end of the tremie is on the bottom of the excavation, or well below the surface of already poured 20 concrete.

Concrete should be poured continuously until the correct level is achieved, both in front of and behind the wall. It may be necessary to use the tremie behind the wall for finally topping up there, if a difference in level between the front and rear of the wall is observed, The tremie should always be placed in the excavation tight up to the panel and should be lowered slowly and carefully to avoid disturbance and collapse of the sides of the excavation.

As soon as the initial set of concrete has occurred, replacement of the bentonite behind the wall with coulis can commence.

A quantity of old bentonite (previously used in the trench), with a reasonable sand content, should be pumped into the mixing tank, The quantity will depend on the 14 length of wall to be treated, but will normally be less than about 6m 3 This bentonite will be mixed with cement and when thoroughly mixed will be pumped to the wall.

The coulis should be injected close to the first stop end, or the previously replaced coulis, and should be pumped through a 60mm diameter steel pipe to the top of the newly placed concrete. Pumping should be quite slow, allowing the coulis to flow out of the injection tube, rather than pumping under pressure.

When the concrete and coulis are adequately set, it is necessary to grout the male-female joint. A grout station is connected by a flexible hose to the top of each joint pipe in turn and grout is pumped until it reappears at the top of the joint channels in the panels. The progress of the grouting w4ll be evident by the flow of bentonite to the top of the joint.

When a joint is full of grout, the pipe is disconnected and the next joint grouted. During the curing process, there may be some settlement of the grout and topping up may be necessary.

A connection for the grout pipe to a 30mm steel pipe Should be provided so that if grout fails to circulate to all areas of the joint, the small pipe can be used to grout areas not filled.

As stated above, the use of the method of the present invention results in a number of other advantages, including the ability to provide starter bars to form a positive connection for floors, ramps or other structures, and the ability to provide a water stop between the wall and basement floor. These additional features will now be described.

4. Cut into precast panel wall for intermediate floor or ramp connection.

The cut in for floor or ramp construction is wherever -4 15 possible, commenced during the panel casting. It can be done after the wall is exposed, but this is expensive and laboureous (see below).

The 'cut-ins' are to be into the four central cores of the panel, as shown in Fig. 5. The cut is the core width, 100mm, and extends from the proposed floor level down for 200mm. The cut is made about 2 hours after the panel has been cast, when initial set is commencing and is made using a trowel. Much of the cut concrete falls into the core, but is easily loosened when the panel has set Sand is lifted from the bed.

When the construction of the wall is complete and the wall exposed, the bentonite is flushed from the cores and the grout plug a piece of sponge plastic supported by a wire, is inserted into the cores, about 400mm down from the bottom of the 'cut-in'.

The reinforcement is then placed in position and grouted in as shown in Fig. 6.

The reinforcement shown in the sketch is nominal, in that bending moments at the joint are very small.

More steel can be incorporated and vertical bars inserted in the cavity from the top and grouted in for an extended length and can be used to improve the moment carrying capacity of the joint and the wall.

During the concreting of the floor, concrete is vibrated into the 'key-in' apertures and grout can be placed from the top of the panel above this concrete, to give more rigidity if required.

b. Provision of water stop between wall and basement floor.

Where some seepage may occur between the wall and the basement floor, a water seal can be provided as illustrated in Fig. 12.

A plastic water seal is glued to the bottom face of ,_i 16 00 0 0 00 0000 0 S000 0 0 0o00 000 0 0 0 00 0 0 the panel before the panel is built into the wall and the seal is further reinforced by a wooden batten ramset fixed to the panel. The top of the water stop sheet is fixed to the panel with tape. After the wall has been completed and excavated, the top of the water stop will be detached from the panel and incorporated in the floor slab water sandwich. The lower half of the water seal will be cast into the concrete footing.

Note, this is not intended to be a water stop to restrain a significant head of water outside the wall, it is intended to assist in reducing occasional seepage.

0 0 0 0 o 0 0 o 00 0 00 00 0 0004 0 o 60 4 4

Claims (11)

1. 2. Cutting each panel so as to form at least one slot, said slot extending from an outer surface of the panel to a hollow core therein, thereby forming at least one female joint member; Aligning one panel relative to at least one other o .i panel such that the female joint member of the one panel is in juxtaposition to the female joint member of at least one other panel;
2. 4. Inserting a male joint member into the juxtaposed female joint members thereby linking each of the panels to at least one other panel; Fixing the base of the linked panels in concrete; and
3. 6. Grouting the male-female joints. 2. A method as claimed in claim 1 in which the male joint member consists of at least two open cylindrical members connected by a web(s). 3. A method as claimed in claim 2 in which the male joint member consists of two open cylindrical members connected by a web. 4. A method as claimed in any one of claims 1 to 3 in which the male joint member is of such a length that when inserted into the juxtaposed female joint members it extends from the top of the panels at least 80% of the way to the base of the panels. A method as claimed in any one of claims 2 to 4 in which the male-female joints are grouted by pouring grout down the hollow cylindrical members of the male joint member. i i -C- 18 6. A method as claimed in any one of claims 2 to 5 in which the ends of the open cylindrical members of the male joint member to be inserted into the female joint member are slit.
4. 7. A method as claimed in any one of claims 1 to 6 in which the male joint member extends into the concrete into which the base of the linked panels are fixed.
5. 8. A precast, prestressed diaphragm wall comprising a plurality of precast, prestressed extruded panels, each panel having a top and a base and a plurality of hollow cores extending from the top of panel to the base thereof, characterized in that each panel is linked to at least one other panel by means of a male-female joint, the male-female joint comprising a male joint member inserted into at least two juxtaposed female joint members, and wherein each female joint member consists of a slot cut in the panel extending from an outer surface thereof through to a hollow core therein and the male joint member consists of at least two rod-like members connected together by means of a web(s).
6. 9. A precast, prestressed diaphragm wall as claimed in claim 8 in which the slot cut in each panel extends from the top of the panel to the base of the panel. A precast, prestressed diaphragm wall as claimed in i claim 8 or 9 in which the male joint member is of such a length that when inserted into the female joint member it extends from the top of the panel at least 80% of the way to the base of the panel.
7. 11. A precast, prestressed diaphragm wall as claimed in any one of claims 8 to 10 in which the rod-like members of the male joint are hollow.
8. 12. A precast, prestressed diaphragm wall as claimed in any one of claims 8 to 11 in which the male-female joint is grouted.
9. 13. A precast, prestressed diaphragm wall as claimed in 44 i I -I -C- 19 claim 11 in which the male-female joint is grouted by pouring grout down the hollow rod-like members of the male joint member.
10. 14. A precast, prestressed diaphragm wall as claimed in claim 11 or 13 in which the ends of the hollow rod-like members of the male joint member inserted into the juxtaposed female joint members are slit. A method of forming a precast, prestressed diaphragm wall substantially as hereinbefore described with reference to any of the figures or Example 1.
11. 16. A precast, prestressed diaphragm wall substantially as hereinbefore described with reference to any of the figures or Example 1. D. 'FD this 9th day of September 1988 FRANKIPILE AUSTRALIA CA Patent Attorneys for the Applicant: F.B. RICE CO. p