Method for manufacturing a tubular foundation in the ground

The invention relates to a method for manufacturing a tubular foundation in the ground, comprising the following steps, in appropriate sequence, of:

• (1) providing a tool for making holes in the ground comprising a ram tip and coupling means for connecting to a drive device, for instance a hydraulically or pneumatically operating tool driving machine or a vibrator operating for instance with eccentrically placed rotatably drivable masses for successively exciting the ram tip in the direction of the free end with vibration or percussion;
• (2) providing a drive device as specified in step (1);
• (3) coupling the tool to the drive device;
• (4) selecting a location for making a hole in the ground;
• (5) placing the tool thereat;
• (6) setting the drive device into operation such that the tool is excited with vibration or percussion at a chosen frequency in the direction of the free end of the ram tip; and
• (7) pulling the ram tip out of the hole.

The method steps (1) through (7) are derivable from US-A-4 193 459. The method according to the known art does not allow that a hollow foundation of the type obtained with this method makes it possible to later remove supporting means arranged therein, should this be necessary.

It is a purpose of the present invention to provide a method for manufacturing a tubular foundation in the ground, which method allows later removal of supporting means arranged in said tubular foundation, in cases wherein these supporting means are wholy incorporated into cured concrete.

In order to achieve this purpose, the invention provides a method which is characterized by the steps of:

• (8) making a hole with the method as specified in the steps (1) - (7), the depth of which is smaller than the depth of a tubular foundation to be manufactured;
• (9) partially filling the hole with pourable concrete;
• (10) re-inserting the ram tip in the hole before the concrete has cured and setting the drive device into operation again such that the hole is extended to the desired depth and the concrete present therein forms a concrete tube round the ram tip and is compacted;
• (11) pulling the ram tip out of the thus obtained tubular foundation.

It will be apparant that a hollow foundation of the type herewith obtained makes it possible to later remove supporting means arranged therein, should this be necessary.

In a particular practical embodiment the method can be characterized by

   (12) performing step (8) such that the depth of the hole amounts to roughly half the depth of the finished foundation.

Easy exchangeability of supporting means is ensured with an embodiment characterized by

   (13) anchoring in the tubular foundation supporting means whereof the active cross section is smaller than the cross section of the tubular foundation.

If desired the anchoring can take place by pouring in sand, gravel or other suitable filler material.

Optimum use is made of the total available height in an embodiment characterized by

   (14) performing the method such that the concrete extends to the top edge of the hole.

The above described method for manufacturing a tubular foundation in the ground brings about a greater compacting of the ground material in the immediate area of the hole, and therefore the later foundation, whereby the bearing capacity thereof is improved. The concrete is also pressed into the ground material whereby the cohesion between foundation and ground material is improved.

The invention will now be elucidated with reference to the annexed drawing.

In the drawing:

• figure 1 shows a tool according to the invention carried by a tool driving machine;
• figures 2-6 show schematic sections through the ground and a tool according to the invention in successive stages of manufacturing a foundation in the ground;
• figure 7 is a schematic cross section through a foundation in which is arranged a frofile supporting pile.

Figure 1 shows a lifting device 1 carrying a hydraulic tool driving machine 2. This tool driving machine 2 carries a chisel 3 which in a manner to be further described bears a ram tip 4. This is suitable for making holes in the ground 5. The device 1 comprises a hydraulic pressure source for driving the device 2 by means of flexible hydraulic lines 6, 7 such that the chisel is excited with vibration or percussion.

To make a hole in the ground the ram tip 4 is placed at the desired position, the tool driving machine 2 is set into operation by appropriate energizing of the hydraulic source and the ram tip is moved downward while vibrating through control of the hydraulic lifting cylinders generally designated with 8. The ground material is hereby displaced, thus creating a hole, the immediate area of which has undergone a considerable compacting.

Figures 2-6 show schematic vertical sections through a hole 42 made in the ground 5 by a ram tip 43.

The depth of the hole 42 is designated with 1/2T. This 5 will be discussed further with reference to figures 4 and 5.

After the hole 42 has been formed in the manner shown schematically in figure 2, the ram tip 43 is removed from the hole 42. A concrete mass 44 is then poured into the hole 42. The filling with concrete takes place in this embodiment such that the hole is approximately half filled with concrete.

Before the concrete mass 44 has cured the ram tip 43 is replaced in the hole 42 in the manner shown in figure 4 and the hole is made longer by appropriate driving of the tool driving machine (not drawn here). During this phase the concrete is distributed along the ram tip 4 so that a tubular concrete casing 45 is created. In this embodiment the total length to be reached equals T. The concrete has also partially penetrated into the ground material, whereby the casing 45 is firmly anchored in its immediate surrounding area.

After retracting the ram tip 43 the tubular foundation is completed, as indicated with 46 in figure 6.

After the concrete casing has cured the supporting pile 47 for the crash barrier 48 is mounted in the obtained foundation 46. As shown in figure 6, the supporting pile 47 does not entirely fill the space inside the foundation 46. The remaining space can be filled up for instance with sand or gravel.