Patent Description:
Such soil penetrating tools often rely on crawler cranes which suspend the tool. In projects with large penetration depths, the cost of such crawler cranes can be a substantial part of total cost. If such soil penetrating tools could be built in sections that enter the soil in steps as is, for example, the case for deep drilling techniques where multiple drill rods are connected sequentially to reach the required depth, the cranes could be lighter in weight.

While this is feasible for drill rods, it is highly unpractical for other techniques, for example the production of bottom feed stone columns, since the supply to the vibroflot with electricity, flushing air and water, and the air tight transport of stones etc. are not easy achievable with extendable length segments like they are used with drill rods.

Substantially, the working process includes one or more penetration phases during which the soil penetrating tool is (completely or partially) driven down into the soil and one or more pulling phases during which the soil penetrating tool is (completely or partially) pulled out of the soil (e.g. retracted). During the penetration phase(s), the soil penetrating tool normally has to overcome a considerable soil resistance. The deeper the soil layers to be reached, the higher soil resistance. This is because the surface friction, in addition to the tip resistance, substantially contributes to the soil resistance the soil penetrating tool needs to overcome, and such surface friction rises with increased depth as it is a function of the soil overburden stress. Therefore, a high weight of the soil penetrating tool during the penetration phase(s) is advantageous.

However, during the pulling phase(s), a high weight of the soil penetrating tool is detrimental since it adds to the total weight the crane has to lift. The high weight reduces the stability of the crane, especially if it is strongly inclined. In addition, the ground under the crane is heavily loaded, which can trigger landslides if the crane is located close to a raised edge of the terrain as is, for example, often the case in coal mine reclamation fill compaction projects. In such projects, the center of the crane conventionally needs to be at a certain safe distance from the location where the soil penetrating tool enters the soil so that the crane is required to stay at a safe distance from locations of potential landslides. Hence, there is a need for an improved solution.

<CIT> discloses a method for driving and pulling rod-like elements like sheet piles using a vibrator that includes eccentric weights each rotating about a shaft. The rotational positions of the eccentric weights are adjustable relative to one another so that an imbalance which causes a driving or pulling force acting on the rod-like element can be adjusted.

<CIT> relates to a vibrator assembly for creating stone columns and to a method for operating such a vibrator assembly. The stone columns are produced by a material like rubble, sand, gravel etc. which is stored in a supply unit. The vibrator assembly further includes a silo pipe which is designed to penetrate at least to some extent into the ground and to move up and down when the vibrator assembly is in operation. Thereby, the material stored in the supply unit is supplied to the silo pipe and released from the silo pipe into the ground, where it is compacted by the vibrator.

<CIT> describes a vibratory pile driver for driving a pile into the ground. The driving is assisted by tensioning a cable, which is guided upwards to a driving machine via a return sheave, so that a tractive force acting downward is applied to the pile. During operation, however, it may happen that leads of the pile driver are lifted due to the cable being guided over the sheave. To avoid this, tubes of the leads can be filled with water to increase the weight.

According to the present invention, a variable weight load device is used to add extra weight to the soil penetrating tool during its penetration phase(s) but to reduce or remove (e.g. disengage) the extra weight such that it does not contribute to the total weight suspended by the crane during the pulling phase subsequent to a previous penetration phase.

One aspect of the present invention relates to a method for introducing a soil penetrating tool into a soil using a variable weight load device which is coupled to the soil penetration tool. The method includes a penetration phase and a pulling phase. During the penetration phase, the soil penetrating tool is at least partially driven into the soil with the variable weight load device providing a penetration phase weight which acts on the soil penetrating tool. During the pulling phase, the penetrating tool is at least partially pulled out of the soil with the variable weight load device providing a pulling phase weight which acts on the soil penetrating tool and which is lower than the penetration phase weight. The variable weight load device includes at least one liquid storage reservoir which is filled with a liquid in order to provide the penetration phase weight. In order to provide the pulling phase weight, the liquid is at least partially removed from the at least one liquid storage reservoir.

A further aspect of the present invention relates to an underground construction device comprising a soil penetrating tool, a variable weight load device coupled to the soil penetration tool, and a ground-based tank. The variable weight load device comprises at least one liquid storage reservoir. The underground construction device is configured to perform a penetration phase during which the soil penetrating tool is at least partially driven into the soil with the variable weight load device providing a penetration phase weight which acts on the soil penetrating tool. The underground construction device is further configured to perform a pulling phase during which the soil penetrating tool is at least partially pulled out of the soil with the variable weight load device providing a pulling phase weight which acts on the soil penetrating tool and which is lower than the penetration phase weight. The underground construction device is further configured to fill the at least one liquid storage reservoir with a liquid in order to provide the penetration phase weight; take the liquid for filling the at least one liquid storage reservoir from the ground-based tank in order to provide the penetration phase weight; and at least partially remove the liquid from the at least one liquid storage reservoir in order to provide the pulling phase weight and to fill back the at least partly removed liquid in the ground-based tank.

For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which.

<FIG> shows an underground construction device <NUM> with a crawler crane <NUM> and a bottom feed rig <NUM> suspended from the crawler crane <NUM>. An enlarged section of the rig <NUM> is illustrated in <FIG>. The underground construction device <NUM> serves to produce gravel columns in a soil <NUM>. By help of a guide fork <NUM>, a bucket <NUM> filled with gravel fills the gravel into a hopper <NUM> from where it drops into a silo tube <NUM>. A vibroflot <NUM> is attached to the bottom end of the silo tube <NUM>. For operation, the lower part of the silo tube <NUM> and the vibroflot <NUM> attached thereto are introduced (i.e. moved down) into the soil <NUM> to a pre-defined depth. From the silo tube <NUM>, the gravel gets to a tremie pipe (not shown) along the vibroflot <NUM> to the bottom tip of vibroflot <NUM> where it is released into the soil <NUM>.

Simultaneously or subsequently, the released gravel is compacted by the vibrating vibroflot <NUM>. During compaction, the silo tube <NUM> with the attached vibroflot <NUM> may be pulled up and moved down alternately. Thereby, the bottom part of the silo tube <NUM> and the vibroflot <NUM> may remain below the surface <NUM> of the soil <NUM>. The result is a section of a gravel column to be produced. In this manner, the gravel column can be completed by sequentially forming such sections one above the other at different depths. When the gravel column is completed, the silo tube <NUM> with the attached vibroflot <NUM> may be completely pulled out of the soil <NUM>. In the following, the part of the rig <NUM> penetrating the soil <NUM> is also referred to as soil penetrating tool.

The described process includes two kinds of phases: penetration phases and pulling phases. A penetration phase is a phase in which the bottom end of the rig <NUM> (in this embodiment the bottom part of the silo tube <NUM> and the vibroflot <NUM>) is in contact with the soil <NUM> and moves downward into the soil <NUM>. A pulling phase is a phase in which the rig <NUM> is moved upward, i.e. in a direction in which it can be pulled out of the soil.

As initially described, a heavy weight load acting on the rig <NUM> can advantageously support the penetration in the penetration phases. In contrast, in the pulling phases the weight load acting on the rig <NUM> is reduced. In order to temporarily provide such a heavy weight load acting on the rig <NUM> during the penetration phases but not during the pulling phases, the rig <NUM> is equipped with a variable weight load device which in the present embodiment is at least one ballast tank <NUM>. In the following, the ballast tank <NUM> is also referred to as liquid storage reservoir.

In the illustrated embodiment there are six ballast tanks <NUM>. However any other number of ballast tanks <NUM> may also be used. For example, there may be just one ballast tank <NUM>, or at least two ballast tanks <NUM>. These ballast tank(s) <NUM> can be filled with a liquid (partially or completely), for example water, and (partially or completely) emptied via either only one hose <NUM>, or they can be filled via one hose <NUM> and emptied via another hose <NUM>. The liquid can be operated in a closed cycle via a ground-based tank <NUM> from which it is pumped back and forth between ground-based tank <NUM> and the ballast tank(s) <NUM>. If such a ground-based tank <NUM> is used, the hose(s) <NUM> (and <NUM>, if provided) each connect the ground-based tank <NUM> and the at least one ballast tank <NUM>. It is to be noted that the liquid is not restricted to water. In principle, any other liquid may be used as well. In particular, a mixture of water and antifreeze agent may be used.

In preparation for the penetration phases, the ballast tank(s) <NUM> can be partially or completely filled with the liquid in order to provide a heavy weight load (in the following also referred to as penetration weight) on the rig <NUM>, and in preparation for the pulling phases, the ballast tank(s) <NUM> can be partially or completely emptied in order to provide a reduced weight load (in the following also referred to as pulling weight) on the rig <NUM>. That is, the pulling weight is significantly lower than the penetration weight. For example, the difference between the penetration weight and the pulling weight may be at least <NUM>,kilograms, at least <NUM> kilograms or even at least <NUM> kilograms.

Some more details of a possible variant of such temporary liquid ballasting system are shown in <FIG>. The rig <NUM> is suspended from the crawler crane <NUM> via a lifting head <NUM>. The bucket <NUM> in this variant is not impeded in its motion by the ballast tanks <NUM> which are installed on a support frame <NUM>. In the present example, the capacity of each of six ballast tanks <NUM> is, at least <NUM><NUM>. That is, the total capacity amounts to at least <NUM><NUM>. If a liquid having at least the density of water is used, the maximum possible difference between the penetration phase weight and the pulling phase weight may be <NUM>. Of course, any other difference of more than <NUM> and less than <NUM> may be used as well.

If there are two or more ballast tanks <NUM>, all ballast tanks <NUM> may be interconnected via hoses <NUM>, <NUM> in fluid connection so that they can commonly be filled and emptied via either a common hose <NUM> or, as illustrated in <FIG>, a pair of hoses <NUM> and <NUM>.

As illustrated in <FIG>, the gravel is transported by a bucket <NUM> that is guided by a fork <NUM> to drop the gravel into the hopper <NUM> and from there into a first tank <NUM>. This first tank <NUM> is separated from the hopper <NUM> by an air tight gate. Further, the first tank <NUM> is separated from a second tank <NUM> by another gate. The two gates together form the so called "double lock".

According to a further embodiment illustrated in <FIG>, a variable weight load device (not shown) may be installed in a space between a lower end of a bucket frame <NUM> holding at least one gravel bucket <NUM>, <NUM> and the at least one gravel bucket <NUM>, <NUM>. In the embodiment of <FIG>, the variable weight load device may also include at least one ballast tank <NUM> which is/are installed in the space between the lower end of the bucket frame <NUM> and the at least one gravel bucket <NUM>, <NUM> and which is/are operated using a ground-based tank <NUM>, one or two hoses <NUM>, <NUM> and a liquid as described above with reference to <FIG> and <FIG>. The ground based tank <NUM> is optional if the liquid is water, in which case the water can also come from a water mains or a surface water body (pond, lake, river) directly.

According to <FIG>, a variable weight load device may include an additional ballast weight <NUM> which is suspended by wire ropes <NUM>. The wire ropes <NUM> run through two winches <NUM> which are coupled to the silo pipe <NUM> and the vibroflot <NUM> coupled to the silo pipe <NUM>. As illustrated example, the winches <NUM> are mounted to the hopper <NUM>. Instead, the winches could be mounted to any other suitable part of the rig <NUM>.

When the ballast weight <NUM> shall act to support penetration, i.e. during the penetration phases, it is lifted by the winches <NUM> from the soil surface <NUM> (<FIG>), while when it shall not act as additional weight, i.e. during the pulling phases, it can rest on the soil surface <NUM> (<FIG>). If in a penetration phase the ballast weight <NUM> is hovered above the soil surface <NUM>, the ballast weight <NUM> is active and acts on the rig <NUM> thereby supporting the penetration process. If in a pulling phase the ballast weight <NUM> rests on the soil surface <NUM>, the ballast weight <NUM> is inactive and does not act on the rig <NUM> so that the crawler crane <NUM> is not required to hold the weight of the ballast weight <NUM>.

Using this principle allows for quickly switching from a penetration phase to a pulling phase and vice versa since the ballast weight <NUM> only has to be raised or lowered by a small distance. That is, in order to make a transition from the penetration phase to the pulling phase, the ballast weight <NUM> may be moved along the soil penetrating tool so that it is moved from a suspended state into a state in which it rests on the surface <NUM> of the soil <NUM>. As compared to the embodiments described with reference to <FIG>, such a switching between the penetration phase and the pulling phase and vice versa is much faster than the time needed to fill or empty a ballast tank <NUM>.

The ballast weight <NUM> may be a solid weight, e.g. made of stone or metal like iron, steel, etc, or a liquid-filled container. In case of a liquid-filled container, the same kinds of liquids described with reference to <FIG> may be used. According to one example, the ballast weight <NUM> may have a ring shape (e.g. a "donut shape") and surround the soil penetrating tool.

In the following, some example embodiments of the present invention are summarized here. Other embodiments can also be understood from the entirety of the specification and the claims filed herein.

Example <NUM>: An underground construction device for vibro compaction and stone column installation, or vibrated sheet pipe or pile segment, is temporarily ballasted by an extra weight during penetration phase.

Example <NUM>: The underground construction device of example <NUM> using liquid storage reservoirs as shown for example in <FIG> and <FIG> that are filled and emptied via hoses and thereby allow to raise the total weight of the rig during its penetration to depth, when higher weight is favorable to reach the necessary depth, and reduce its weight during retrieval of the rig from the ground, so that the necessary pulling capacity of the carrier crane, which is pulling on lifting head, is minimized.

Example <NUM>: The underground construction device of example <NUM> or <NUM>, where the ballast weight is part of a secondary tool (for example the gravel bucket as per <FIG>) that is at least temporarily suspended not from a carrier rig but by the primary soil penetrating tool itself, thus adding extra weight to such tool during penetration without needing extra lifting capacity from the crawler crane.

Example <NUM>: The underground construction device of one of examples <NUM> to <NUM>, where the ballast weight, favorably in a ring-shape (e.g. "donut shape"), with the soil penetrating tool (e.g. vibroflot rig) running through the middle of such donut, is lifted by a winch attached to the soil penetrating tool but not connected to any secondary device such as gravel bucket.

Example <NUM>: The underground construction device of one of examples <NUM> to <NUM> having the advantage that the acting ballast weight can be rapidly changed by the ballast weight hovering close to the soil surface so it can be either fully suspended and hence act with its full weight or be deactivated by setting it on the ground surface.

Example <NUM>: The underground construction device of one of examples <NUM> and <NUM> with the ballast weight resting on the soil surface and the at least one winch allowing for a computer-controlled force activation that can mobilize any desired force between zero and the full weight of the ballast weight.

Example <NUM>: The underground construction device of any one of the preceding claims, wherein the device comprises a vibroflot.

In all embodiments of the present invention, the underground construction device may be operated such that during none of the pulling phases the respective variable weight load device imposes weight on the soil penetrating tool. This helps to avoid that the initially described problems occur at any time.

Claim 1:
A method for introducing a soil penetrating tool into a soil (<NUM>) using a variable weight load device coupled to the soil penetration tool, the method comprising:
a penetration phase during which the soil penetrating tool is at least partially driven into the soil (<NUM>) with the variable weight load device providing a penetration phase weight which acts on the soil penetrating tool, and
a pulling phase during which the soil penetrating tool is at least partially pulled out of the soil (<NUM>) with the variable weight load device providing a pulling phase weight which acts on the soil penetrating tool and which is lower than the penetration phase weight;
wherein the variable weight load device includes at least one liquid storage reservoir (<NUM>) and wherein:
the at least one liquid storage reservoir (<NUM>) is filled with a liquid in order to provide the penetration phase weight;
the liquid is at least partially removed from the at least one liquid storage reservoir (<NUM>) in order to provide the pulling phase weight.