NL2007685C2

NL2007685C2 - Method for installing a reinforcement into a ground.

Info

Publication number: NL2007685C2
Application number: NL2007685A
Authority: NL
Inventors: Dirk Liesbeth Guido Smet
Original assignee: Smet F & C N V S A
Priority date: 2011-10-31
Filing date: 2011-10-31
Publication date: 2013-05-06

Description

Method for installing a reinforcement into a ground

The present invention relates to a method for installing a reinforcement into a ground with the purpose of reinforcing said ground or a ground and/or structure in the vicinity 5 of said ground. The present invention in particular relates to a method for installing a reinforcement into a profiled ground, such as a dike for instance.

Due to climate changes the safety of civil and/or marine structures such as dikes has to be reconsidered. An increasing supply of river water and a rising sea level will 10 substantially increase the mean water level of rivers. Existing dikes and the ground on which they have been build also frequently settle which may give rise to a substantial lowering of the height of the crest of the dike. There is therefore an increasing need to reinforce dikes and the like.

15 Traditional dike reinforcement methods involve heightening of the dike by adding more dike material on the crest. However, such dike heightening also gives rise to a broadening of the dike. Such broadening requires additional space that is less and less available, due to the presence of houses or other buildings, or of recreation and nature areas around the dike. To avoid undesired broadening, the dike is sometimes reinforced 20 by applying sheet piling to the side of the dike that may not be broadened.

The known method involves applying reinforcement such as sheet piling to the dike by using equipment which is operated from the crest of the dike. Although this method allows houses and vegetation on and near the slope of the dike to be preserved and 25 minimizes nuisance thereto, the dike itself will have to be closed for traffic of all kind during the reinforcement works. Another disadvantage is the damage caused to nearby constructions, such as houses, due to vibrations during installation of the sheet piles.

One of the aims of the invention is to provide a method for installing a reinforcement 30 into a ground, and in particular into a profiled ground, without substantially interrupting, disrupting or hampering the normal activities on or in the vicinity of a dike, such as car or train traffic for instance. Another aim is to avoid damage to nearby constructions such as houses by providing a low vibration method.

2

In accordance with the invention, a method for installing a reinforcement into a ground is provided, the method comprising the steps of: A) providing at least two piles into the ground; B) positioning a structural platform onto the piles such that the piles support the 5 structural platform to form a support surface; C) positioning onto the support surface of the structural platform a device for constructing reinforcement piles; and D) providing the ground with reinforcement piles using the device supported by the structural platform.

10

The distinguishing feature of the present ground reinforcement method is that a ground may be reinforced without damage or disturbance to the surroundings and nuisance to the area above said ground by installing a reinforcement from a platform supported by piles.

15

In an embodiment of the invention, a method is proposed wherein providing the at least two piles into the ground comprises forming structural elements onto or into the ground, positioning onto the structural elements a device for constructing the at least two piles, and providing the ground with the at least two piles using the device. This embodiment 20 provides a ground reinforcement by installing a reinforcement from a platform supported by piles and the structural elements.

A further embodiment of the method according to the invention is characterized in that the at least two piles are adapted to support the structural elements.

25

Another embodiment of the method in accordance with the invention provides the structural elements in the form of a sheeted or supported trench.

Once the structural elements have been formed into or onto the ground and supported 30 by forming the at least two piles underneath the structural elements, an embodiment of the method according to the invention comprises positioning the structural platform onto the structural elements.

3 A particularly useful embodiment of the method according to the invention comprises structural elements in the form of elongated beams and positioning the structural platform onto the structural elements such that it is can be moved along the structural elements in the direction of elongation. In this embodiment, the structural beams are 5 typically formed onto or into the ground such that the beams extend in a substantially horizontal direction.

In another embodiment of the method according to the invention, the structural platform comprises a support surface, supported by preferably four upstanding poles or posts at 10 the comers of the support surface, whereby the upstanding poles extend above ground level. A space below the support surface and between the plurality of poles is thus created that may give room to housing and the like, and/or provide room for additional operations.

15 In still another embodiment, providing the at least two piles into the ground is carried out such that the stmctural platform provides a substantially horizontal support surface, onto which a device for constructing reinforcement piles can easily be positioned, or any other device for similar purposes, such as a device for constmcting soil nailing or bank-dowels.

20 A further embodiment of the invention provides a method wherein the stmctural platform is removed after the ground has been reinforced at least partly by providing it at least partly with the reinforcement piles. Although it is possible according to the invention to also remove the at least two piles after the ground has been reinforced at 25 least partly with the reinforcement piles, a preferred embodiment is characterized in that the at least two piles remain in the ground at least partly and/or wherein at least some of the at least two piles remain in the ground, such embodiments providing additional reinforcement to the ground.

30 Although the method in accordance with the invention may be applied for reinforcing any ground, it is particularly suitable in situations wherein the ground to be rienforced, and preferably a soft soil, is profiled to form a slope. A useful embodiment of the method then installs the at least two piles in the slope of the ground. A preferred embodiment places one pile or row of piles along an upper edge of the slope, and 4 another pile or row of piles at some distance from the upper edge in a lower part of the slope.

Another embodiment of the invention provides a method wherein the installation of the 5 at least two piles into the ground is carried out by driving the at least two piles into the ground.

In still another embodiment of the method in accordance with the invention, the installation of the at least two piles into the ground is carried out by forming bores into 10 the ground, introducing, preferably injecting, a grout mixture in the bores under high pressure and hardening of the grout/ground mixture. The grout mixture is injected into the ground at high pressure through a drill shaft with ejection nozzles in order for the grout to cut and loosen the ground in an area surrounding the drill shaft. Simultaneous rotation and slow retraction of the drill shaft leads to a mixing of the ground with the 15 injected grout mixture surrounding the drill shaft, whereby the excess ground/grout mixture is forced upwards along the space between the drill shaft and the cut ground.

It may be advantageous to install a reinforcement such as for instance steel bars in said bores. According to a possible embodiment, said reinforcement is applied in the still 20 liquid grout material, or, alternatively, said reinforcement is applied in the already hardened grout material, wherefore destructive borings are carried out in the hardened grout material into which additional grout material may be added.

An even more preferred method for constructing the underground piles (as well as the 25 reinforcement piles, see below) comprises driving a drill head to which one or a plurality of interconnected pipes is coupled into the ground by rotating the drill head and the at least one pipe and simultaneously supplying, preferably injecting, a grout mixture through the pipe to the drill head, whereby the grout mixture is ejected from the drill head at a high pressure of at least 50 bar to cut an area of ground and form a bore, 30 evacuating the excess ground, and filling the bore with the grout mixture and hardening the grout mixture to form the reinforced underground pile. It may be desirable to make the pile with a changing diameter, which may be achieved by changing the ejection pressure at certain depths, whereby a bore with a larger diameter is obtained by 5 increasing the ejection pressure, for instance to at least 200 bar, more preferably at least 250, and most preferably around 400 bar.

A device for carrying out such method of executing the at least two piles and/or the 5 reinforcement piles comprises a drive unit for rotating the drill head and holding the assembly of drill head and at least one pipe. The drill head comprises one or more high pressure ejection nozzles for ejecting the grout mixture into the ground surrounding the drill head, typically at a pressure of at least 50 bar, for cutting ground in the vicinity of the drill head over a diameter which is approximately equal to or larger than the 10 diameter of the drill head. The speed at which the drill head is advanced downward into the ground can be controlled by the drive unit.

Especially in the context of the present invention, the drive unit for rotating the drill head and the high pressure device, with which the drill head is forced into the ground 15 are preferably separated. This allows to locate the high pressure device at a distance from the driving of the shaft part, so that these units do not need to be supported both by the support surface or the structural elements. The drill unit for installing the at least two piles from the support elements is preferably compact such that its weight can be supported by the structural elements.

20

An embodiment of the method according to the invention wherein the bores are formed from the ground level to a lower (underground) level comprising sand provides an improved reinforcement. This reinforcement is further improved in an embodiment of the method wherein the bores are broader at their underside and at their top side, than in 25 a middle section of the bores. This may be achieved by increasing the injection pressure at the top and at higher depths.

A further embodiment of the method according to the invention is characterized in that the piles are installed in an overlapping way such that they form a network of piles.

In still another embodiment of the invention, a method is provided wherein the installation of the reinforcement piles in the ground is carried out by driving the reinforcement piles into the ground.

30 6 A further embodiment of the method according to the invention proposes that the installation of the reinforcement piles in the ground is carried out by forming bores into the ground, introducing and preferably injecting a grout mixture in the bores under high pressure and hardening of the grout mixture.

5

Still in accordance with the invention, a method is provided wherein the reinforcement piles are installed in an overlapping way such that they form a network of piles.

The embodiments of the method of the invention offer several advantages compared to 10 the known ground reinforcement methods. The structural platform that is supported by the piles, and by the structural elements in one embodiment, not only allows to avoid nuisance to an area above or in the near vicinity of the ground but also allows to execute and install reinforcement piles (or soil nailing or bank-dowels) virtually at any position in the ground. This is particularly advantageous in less accessible areas, such as in 15 sloped grounds. An embodiment wherein the reinforcement piles are created by forming bores into the ground, introducing a grout mixture in the bores under high pressure and hardening the grout mixture is particularly useful because the support platform can in this case be constructed relatively lightly. For some embodiments, the at least two piles offer additional reinforcement to the ground, apart from the reinforcement offered by 20 the reinforcement piles themselves.

To sustain horizontal forces on the structural platform during installation of the piles and/or the reinforcement piles, elongated members are in the present embodiment provided into the ground under a nonzero angle with the horizontal, such as slanted 25 piles or nails, using the same methods as for the installation of the piles and/or reinforcement piles. Such elongated members preferably extend under a nonzero angle from an upper part of the structural platform to a position under the ground.

The invention will now be described in more detail with reference to the following 30 figures without however being limited thereto. Other details and advantages of the invention will appear from the following description of an embodiment of the method.

Figures 1-7 schematically illustrate the subsequent steps of an embodiment of the method according to the invention. In the figures: 7 - figure 1 shows a side view of a dike and a first step of an embodiment of the method according to the invention; - figure 2 shows a second step of the embodiment of the method according to the invention as shown in figure 1; 5 - figure 3 shows a third step of the embodiment of the method according to the invention as shown in figure 1; - figure 4 shows a fourth step of the embodiment of the method according to the invention as shown in figure 1; - figure 5 shows a fifth step of the embodiment of the method according to the invention 10 as shown in figure 1; - figure 6A shows a top view of a sixth step of the embodiment of the method according to the invention as shown in figure 1; - figure 6B shows a side view of the sixth step of the embodiment of the method according to the invention as shown in figure 1; 15 - figure 6C shows another side view of the sixth step of the embodiment of the method according to the invention as shown in figure 1; - figure 7A shows a top view of a seventh step of the embodiment of the method according to the invention as shown in figure 1; and finally - figure 7B shows a side view of the seventh step of the embodiment of the method 20 according to the invention as shown in figure 1.

With reference to figure 1, a cross-section of a ground in the form of a dike 1 is shown. The dike 1 is profiled to form a slope 2 that extends from the crest 3 of the dike 1 to a lower part 4 thereof The crest 3 of the dike is provide with a road surface 6 for traffic. 25 Although not shown in detail in figure 1, the slope 2 of the dike 1 may comprise buildings or other obstacles. This is however not necessary in the context of the invented method. The existing body 5 of the dike 1 is positioned onto several subsoil layers (5a-5h), which may for instance comprise layers of clay, peat, stone, loose or consolidated sand, and/or other materials. In the example given layer 5h comprises a 30 layer of consolidated sand.

In a first step of the embodiment shown in the figures, two structural elements in the form of sheeted or supported trenches (20a, 20b) are formed first to a depth of for instance 1 m, and a length 21 (see figure 6A) that may vary in accordance with the 8 desired length of the reinforcement 10. The length dimension is defined in the direction parallel to the extension of the dike 1. Referring to figure 1 (inset), construction of the supported trenches (20a, 20b) involves excavation of a trench 201 by hand or using small excavating equipment to the desired depth, and support of the sidewalls of the 5 trench with relatively small prefabricated concrete panels 202. These panels 202 are kept in position by placing struts 203 or buttresses between the panels 202 facing both sidewalls. The struts 203 therefore span the space between the sidewalls of the trench 201. The trench 201 is then further deepened and new panels 202 are placed against the sidewalls underneath the already placed panels until the desired depth of the trench 201 10 has been reached. Steel reinforcement bars 204 may then be placed against the concrete panels 202 covering the sidewalls and concrete 205 cast into the trench 201. As shown some (central) openings are left in order to be able to fabricate the piles (11a, 1 lb, 11c, 1 Id) as elucidated below. The prefabricated concrete panels 202 then act as a lost formwork to the concrete. The dimension of the steel bars 204 to be installed into the 15 trench 201 may be increased to give more bearing capacity to the formed structural elements (20a, 20b). The bearing capacity of the structural elements (20a, 20b) may be adopted in function of the drill rig that will be needed to install the reinforcement piles, piles, soil nailing and/or bank-dowels.

20 In a second step of the embodiment of the method shown in the figures, a reinforcement 10 is formed into the dike 1 by installing four piles (11a, lib, 11c, lid) into the slope 2 of the dike 1. Two piles (11a, 1 lb) are provided along an upper edge 7 of the slope 2, while two other piles (11c, 1 Id) are provided at some distance 8 from the upper edge 7 in a lower part 9 of the slope 2. With reference to figures 2 and 3, the piles (11a, lib, 25 1 lc, 1 Id) are now made in situ by positioning a drive unit 30 equipped with a drive head (not shown) on the dike 1 at position 7 and connected to a high pressure unit (not shown) onto one of the supported trenches (20a, 20b) and driving the drill head to which one or a plurality of interconnected pipes is coupled into the body 5 of the dike 1 at the position of the upper edge 7 by rotating the drill head and the pipe(s) and 30 simultaneously supplying, preferably injecting, a grout mixture through the pipe to the drill head, ejecting the grout mixture from the drill head at a high pressure of at least 50 bar to cut out a bore hole, evacuating excess ground, filling the bore with the grout mixture, and hardening the grout mixture to form one of the piles (11a, lib, 11c, lid). By increasing the ejection pressure to 400 bar at a certain depth, a larger bore diameter 9 is obtained. In the example shown in figures 2 and 3, this depth corresponds to a depth where the compact sand layer 5h of the subsoil, or a similar load bearing layer, is located. The whole operation is then repeated for each pile location to obtain four piles that form a square when viewed from above (see figure 6A). The dimensions of the 5 drive unit 30 are relatively compact due to the relatively low bearing capacity of the structural elements (20a, 20b). Once formed, the piles (11a, lib, 11c, lid) actually support the beamlike structural elements (20a, 20b). The preferred way of supporting comprises a seating or bearing support, whereby the elements (20a, 20b) simply rest on top of the piles (11a, 1 lb, 11c, lid). Other ways of connection such as anchoring the 10 elements (20a, 20b) into the piles (11a, 1 lb, 1 lc, 1 Id) or vice versa are also possible.

Optionally, elongated members in the form of sub-horizontal anchors or nails 50 are installed into the ground under a nonzero angle 51 with the horizontal 52 to cope with horizontal forces onto the structural elements (20a, 20b), see figures 4, 5 and 6, using 15 the same methods as for the installation of the piles (1 la, 1 lb, 1 lc, 1 Id) and/or the reinforcement piles 12. Vertical forces acting on the structural elements (20a, 20b) are transferred to the grout piles (11a, 1 lb, 11c, 1 Id) through the local thickened sections at the top of the piles (1 la, lib, 11c, lid) on which the elements (20a, 20b) rest, or via normal friction between concrete and steel.

20

Once the piles (11a, 1 lb, 11c, lid), and optionally the anchors 50, have been installed in the dike 1, a structural platform 23 having four legs 21 of different height (to accommodate the slope 2 of the dike 1) and provided with wheels 24 is positioned onto the structural elements (20a, 20b), as shown in figure 4. The wheels 24 allow the 25 structural platform 23 to translate along the dike 1 by riding on the structural elements (20a, 20b) in the form of elongated beams, such that the platform 23 can be moved along the structural elements in the direction of elongation of the beams. Structural platform 23 provides a substantially horizontal support surface 22 for equipment such as a device for the execution of constructing a foundation, reinforcement piles 12, soil 30 nailing or bank-dowel. In order to accommodate the slope 2 of the dike 1, the legs 21 are preferably extendable or can be shortened, as the case may be.

In a further step, a device 40 for constructing foundation or reinforcement piles 12 or soil nailing and/or bank-dowel is positioned onto the structural platform 23, as shown in 10 figure 5, and the dike 1 provided with reinforcement piles 12 using the device 40 supported by the platform 23. In the embodiment shown, device 40 comprises a crane 41 that is equipped with a drill head and drill pipe assembly 42 to form a plurality of bores 43 into the ground, injecting a grout mixture in the bores 43 thus formed under 5 high pressure and hardening out the grout mixture to form the foundation piles 12, that extend from a depth lower than the ground level to a lower level which more or less corresponds to the compressed sand layer 5h, or a similar load bearing layer.

Typical pressures for injecting the grout mixture into the bores range from about 50 bar 10 to about 400 bar, but lower or higher pressures may be used, depending on the circumstances. The angle at which the bores extend into the subsoil may be varied at will and may range from 0 degrees (the vertical direction) to 80 degrees or more. Preferred bore angles range between 0 and 60 degrees, more preferred between 4 and 40 degrees, and most preferred between 5 and 20 degrees. It is also possible to combine 15 angles. The bores 43 preferably have a rather limited diameter of between 5 and 160 cm, more preferred between 40 and 70 cm. A grout mixture is injected through the drill pipe and ejected at high pressure to fill the bores 43 with the grout mixture and to form the piles 12 after hardening of the grout mixture.

20 By repeating the above method steps, a screen 13 of piles 12 may be installed into the body 5 of the dike 1 and below, and shown in figures 6A, 6B, 7A and 7B. The reinforcement piles 12 may be installed in an overlapping way such that they form a relatively closed network of piles, for instance against groundwater.

25 Although the layout of the screen 13 seen from above is that of a square (see the top views of figures 6A and 7A), other layouts may be applicable. The formed screen may be reinforced further by applying tensioning anchors into the ground.

In a last step the structural platform 23 is removed from the piles (11a, 1 lb, lie, 1 Id) as 30 shown in figure 7B, which also shows an embodiment in which the piles (1 la, 1 lb, 11c, lid) have all been removed as well to leave into the dike 1 the plurality of reinforcement piles 12 only.

11

In another embodiment, shown in figure 6B, the piles (11a, lib, lie, lid) remain in the ground to offer additional reinforcement.

By applying the method according to the invention, and by using the high pressure 5 techniques for making the support piles (11a, lib, lie, lid) and the reinforcement or foundation piles 12, widely varying underground structures may be realised to reinforce grounds, such a dikes by installing into the ground a network of piles that yield a massive structure, the characteristics of which may be adapted to the local circumstances at will.

10

Claims

A method for installing a reinforcement in a soil, the method comprising the steps of:

2. Method as claimed in claim 1, wherein providing the at least two piles in the bottom comprises forming supporting elements on or in the bottom, positioning a device for manufacturing the at least two piles on the supporting elements, and arranging the at least two posts in the soil using the device.

3. Method as claimed in claim 2, wherein the at least two posts are adapted to support the bearing elements.

4. Method as claimed in claim 2 or 3, wherein the bearing elements comprise a trenched or supported slot.

5. Method as claimed in any of the foregoing claims, wherein arranging the at least two piles in the bottom is carried out by driving the at least two piles into the bottom.

A) providing at least two posts in the bottom; B) positioning a support platform on the posts such that the posts support the support platform and form a support surface; C) positioning a device for manufacturing reinforcement posts on the support surface of the support platform; and

6. Method as claimed in any of the foregoing claims, wherein arranging the at least two piles in the soil is carried out by forming boreholes in the soil, applying a high-pressure mortar mixture in the boreholes and curing the mortar mixture .

7. Method as claimed in any of the foregoing claims, wherein the support platform is positioned on the support elements.

8. Method as claimed in claim 7, wherein the support elements comprise elongated beams 5 and the support platform is positioned on the support elements such that it can be moved along the support elements in the longitudinal direction of the beams.

9. Method as claimed in any of the foregoing claims, wherein arranging of the at least two posts in the bottom is carried out such that the supporting platform forms a substantially horizontal supporting surface.

A method according to any one of the preceding claims, wherein the support platform is removed after the bottom has been provided with at least partially the reinforcement posts. 15

D) arranging reinforcement piles in the ground using the device supported by the support platform.

A method according to any one of the preceding claims, wherein at least some of the at least two posts remain at least partially in the bottom.

12. Method as claimed in any of the foregoing claims, wherein the bottom is profiled to form a slope, and wherein the at least two posts are arranged in the slope.

13. Method as claimed in any of the foregoing claims, wherein arranging the at least two piles in the soil is carried out by forming boreholes in the soil, arranging a mortar mixture in the boreholes under a preferably high pressure and curing of the mortar mixture.

14. Method as claimed in claim 6 or 13, wherein the boreholes are formed from the ground level up to a lower level that substantially corresponds to a compressed sand layer or similar load-bearing bottom layer.

The method of claim 6, 13 or 14, wherein the boreholes are wider at their bottom and at their top than at the center.

The method of any one of claims 13-15, wherein the reinforcement posts are arranged in an overlapping manner such that they form a network of posts.