Patent Publication Number: US-10774494-B2

Title: Methods and devices for improving the subsoil

Description:
This application is the U.S. National Stage of International Application No. PCT/EP2015/079428, filed Dec. 11, 2015, which claims foreign priority benefit under 35 U.S.C. § 119 of German application no. 102014225726.3 filed Dec. 12, 2014. 
     The invention relates to a method for producing bored piles and a boring tool. Objects of the present invention are also a depth vibrator for displacement and consolidation of a construction subsoil material. 
     In the erection of building structures, the quality of the construction soil is of major significance. In particular with large buildings and those of substantial mass, high demands are imposed on the stability, or load-bearing capacity of the soil. Under usual circumstances, an expert opinion describes the properties of the soil. Dead loads, live loads, and climatically-induced loads must be transferred permanently, reliably, and with little settlement onto the subsoil. If the subsoil is not suitable for resisting the planned loads imposed, a technical adjustment of the properties of the subsoil to meet these demands must be considered. 
     The depth vibrator for the displacement and compaction of the subsoil, as well as the production of bored piles as additional stability-enhancing structural elements represent established methods in this respect. 
     One possibility of improving the properties of the subsoil during construction projects consists of establishing pile-like foundation elements in the subsoil, by means of which relatively high loads can be transferred. One possibility for producing pile foundations is provided by the establishment of bored piles. Generally, with this method a boring tool is introduced into the subsoil with the application of a vertical force and a drilling torque or moment. An additional material is introduced into the borehole which is created, which then forms the bored pile. The additional material can be introduced through a hollow core of the boring tool, in this case also referred to as a core driller, or can be filled separately into the borehole. 
     By way of example, the part-displacement and full-displacement boring method will be considered. Other embodiments of the method are known to the person skilled in the art, and will therefore not be considered separately. 
     With the part-displacement boring method, a continuous hollow auger is used. This consists of a bore tube which is provided on the outside with a helical worm and is closed at a lower end by a footplate. Conventional hollow augers for such operational purposes are some 3 to 50 meters long and have a diameter of some 300 to 1100 mm. Under the application of a vertical force and a torque moment, the auger is introduced into the subsoil. The surrounding subsoil is displaced and simultaneously compacted. Due to the helical worm, also referred to as a hollow core worm, fitted on the outside of the boring tube, construction material is additionally conveyed. Once the auger has penetrated as far as an area of the subsoil capable of bearing loads, material referred to as reinforcement is, in part, introduced into the hollow core. Next, concrete or an alternative filling material such as mortar for the displacement bored pile is pumped in or filled in, with the simultaneous withdrawal of the hollow auger. In this situation, the footplate usually remains in the subsoil, if it is intended that the reinforcement should be introduced before the withdrawal. 
     With the full-displacement boring method, a bore tube, at the end of which is located a leader tip, usually with screw threads, is introduced into the soil under the imposition of a vertical force and a torque moment. In this situation, a number of variants have become established, which differ mainly in the shape of the drill tip and of the part of the tip which remains in the soil. Conventional full-displacement boring tools for such operational purposes as this are some 3 to 50 m long and have a diameter of some 200 to 1000 mm. In this situation, the tip displaces the soil almost entirely in the lateral direction, and thereby compacts the area of the earth which surrounds what will later be the pile. In this case, there is no vertical conveying of soil to the surface worth mentioning. Once the bore tube has penetrated as far as the subsoil with load-bearing capacity, reinforcement is introduced in part into the bore tube. Next, the concrete is pumped or poured in, with the simultaneous withdrawal of the bore tube. 
     The diameter of full-displacement bored piles is usually in the range from 200 to 1000 mm. 
     When reference is made in connection with the invention described here to full-displacement bored piled, hollow boring tools, or general boring tools, this always includes all known configuration variants of methods and corresponding tools. 
     In addition to the variants of boring tools described here, all other known variants of boring tools also form the technological background for the invention described in this application. There are, for example, boring tools with which the tip can remain in the subsoil, or with which the tip can be extracted from the subsoil again along with the boring tool. There are also boring tools with which the auger is provided optionally at the tip, the bore tube, or at the tip and at the bore tube. Boring tools without augers are also possible, with which the boring torque moment can be transferred to the subsoil, for example via an outer surface with corresponding friction properties. Any combinations of these and other known variants are also conceivable. 
     A further possibility for improving the properties of the subsoil during construction projects consists of what are known as the deep vibration methods. These consist in general of methods for compacting and consolidating construction substrates, wherein the subsoil is displaced by a tool, referred to as a depth vibrator, and in the process is compacted. This method, and the associated tools, the depth vibrators, are generally known to the person skilled in the art. In this situation, the depth vibrator is introduced into the subsoil under the application of a vertical force, and during the sinking incurs horizontal vibration. Conventional depth vibrators for such operational purposes are some 2 to 5 m long, have a diameter of some 300 to 900 mm, and weigh about 1 to 6 tonnes. Their length is adjusted to the anticipated working depth by means of extension tubes. In this situation, the depth vibrators are guided by cranes, mechanical diggers, or specially developed carrying devices. A frequency of the vibrations generated by conventional depth vibrators lies in the range of the natural frequency of the subsoil, typically between 25 and 60 Hz. The vibrations are therefore present both as dynamic horizontal deflection of the depth vibrator as well as in the form of a dynamic horizontal force, which is exerted by the depth vibrator onto the surrounding soil area. Since such mechanical relationships are adequately known to the person skilled in the art, hereinafter no further distinction will be made between a force vibration and deflection vibration, since a force which takes effect on a body also always exerts an acceleration effect on this body, which has the consequence of a certain deflection of the body. The horizontal vibrations are therefore transferred onto the surrounding subsoil. If the material of the subsoil is compressible, the horizontal vibrations inherently lead to a displacement and therefore compaction of the subsoil. The compaction results in a consolidation of the subsoil. 
     By way of example, what is referred to as the vibroflotation method will be considered in detail, a particular form of the deep vibration method, in which the depth vibrator is sunk into the subsoil and then withdrawn repeatedly and at specific distance intervals. Due to the vibrations of the depth vibrator, the friction force between the subsoil grains in relation to one another is briefly reduced. As a consequence of gravity, the grains of the subsoil material then transform into a denser deposit state as soon as the depth vibrator is withdrawn from the area of the subsoil which it has displaced. In this way, existing cavities in the subsoil are made smaller or closed entirely. Subsoils which are particularly coarse-grained, such as those consisting of coarse sand, gravel, or small stones, are well-suited for such compaction. Since the compaction results in a decrease in volume, this must, as a rule, be compensated by surface deposition of material. A consolidated subsoil with the same height level is produced, which is well-suited for carrying substantial loadings. 
     By way of further example, another particular form of the deep vibrator method is described, referred to as vibro displacement densification. This is well-suited for subsoil materials with small grain sizes, such as silt or clay, as well as organic materials. With such materials, a compaction of the subsoil in itself is no longer possible to an adequate degree. With the vibro displacement densification method, a depth vibrator is operated in alternating steps. With the depth vibrator sunk in the subsoil, an additional material, such as gravel or crushed rock, or even concrete, is introduced into the subsoil, which, after completion, exhibits a higher degree of rigidity than the surrounding soil. The additional material emerges at the tip of the depth vibrator when this carries out a lifting movement. As a rule, the additional material is introduced into the depth vibrator on the ground surface through a lock arrangement, and is conveyed through an external hollow core down to the operating depth of the depth vibrator. The emerging additional material is compacted at the sinking movement of the depth vibrator which follows the lifting movement, as well as being displaced sideways into the subsoil. In this way, what are referred to as plug piles are created successively, which in conjunction with the subsoil are well-suited for bearing the loads. 
     When reference is made hereinafter to deep vibration methods or depth vibrators, all known configuration embodiments are always included. 
     By way of example, a conventional depth vibrator is described. Depth vibrators are generally and adequately known to the person skilled in the art. They comprise a bar or rod section, which consists of one or more extension tubes. By means of this, the depth vibrator can be sunk to the desired depth. With depth vibrators for the vibro flotation method, a hollow core can additionally be provided for the conveying of the additional material. The head of the depth vibrator is connected to the bar by means of an elastic coupling. As a rule, the head consists of an elongated housing, arranged in the interior of which are a mechanical elements module and a drive energy source for producing horizontal vibrations. The mechanical elements module consists of a mass with eccentric mass centre of gravity, in other words an unbalance element, as well as a bearing mounting and a drive shaft. The bearing mounting restricts the degrees of freedom of the drive shaft and unbalance element to a rotational degree of freedom. 
     With conventional depth vibrators, an electric or hydraulic motor is provided as the drive energy source, which in most cases is operationally connected to the drive shaft by means of a positive-fit gear element. The motor with the gear element and the mechanical module together form a drive train. When the motor begins to deliver drive energy to the drive shaft with the unbalance element, the shaft begins to rotate. Dynamic centrifugal forces take effect on the mass with eccentric center of gravity, which result in a transverse acceleration of the entire mechanical module. The mechanical module is therefore set into horizontal vibration. By means of the bearing mounting, the vibrations are transferred onto the housing of the depth vibrator. 
     The known drive concepts do however exhibit a number of disadvantages. For example, electric drives develop a high degree of waste heat. The system costs and the maintenance expenditure are likewise negatively influenced. With hydraulic drives, the disadvantage lies in the necessary storage and permanent provision of the hydraulic fluid. Leakage losses and pressure losses in the pipelines and hose lines represent further negative aspects. 
     One object of the present invention consists of providing a method for producing bored piles and a corresponding boring tool of the generic type referred to in the preamble, for producing boreholes and bored piles, wherein, additionally, the boring tool is intended to be of simple configuration and flexibly adjustable to the particular subsoil in each case. 
     A further object of the invention is to provide a method for displacing and compacting subsoil material, as well as a depth vibrator of the generic types referred to in the preamble, which is of simple configuration and is flexibly adjustable to the subsoil in each case. The objects are solved by the items with the features as set forth hereinafter. 
     The object of the present invention is a method for producing bored piles. 
     A boring tool is in this situation sunk into the subsoil under the application of a torque moment and a vertical force, then withdrawn, and an additional material is introduced into the borehole created. According to the invention, it is provided that the boring tool, while being sunk into the subsoil and/or during the withdrawing of the boring tool, is set into vibration by one or more actuating elements, wherein a resulting vibration amplitude comprises a horizontal portion. 
     This offers the advantage that the friction between the subsoil and the boring tool is reduced, and therefore the forces required for a displacement and/or movement of the subsoil by the boring tool are also reduced, and a horizontal force, taking effect outwards, is exerted onto the subsoil. The wear on the boring tool is thereby reduced, and a compaction of the subsoil material is favored. 
     Preferably, actuating elements are used which create a vibration with an amplitude in the range from 0.01 mm to 5 mm, for further preference from 0.02 mm to 3 mm, and for special preference 0.03 mm to 2 mm in respect of a horizontal or radial deflection respectively of the boring tool. An amplitude in respect of a horizontal or radial force respectively amounts preferably to 0.5 kN to 1000 kN, for further preference 1 kN to 700 kN, and for particular preference 25 kN to 400 kN. This offers the advantage that a lateral displacement of subsoil only takes place to the extent that is required for the reduction of the friction between the subsoil and the boring tool, and, as applicable, a vertical conveying of subsoil material is not impeded. The energy requirement for the actuator elements is also advantageously kept low. 
     Preferably, the actuating elements are configured as one or more mutually independent fluid flow machines, particularly preferred as one or more pneumatic turbines, into which, in each case, one or more unbalance elements are integrated. 
     This provides the advantages that a large band width of operational frequencies and centrifugal forces which can be produced are available, and therefore comparatively flexible and economical forms of actuating elements are used. 
     The pneumatic turbines are preferably operated at revolution speeds from 1 rev/min to 100,000 rev/min, particularly preferred from 1 rev/min to 50,000 rev/min, and especially preferred from 1 rev/min to 30,000 rev/min. 
     If it is intended that the pneumatic turbines should be operated at different revolution speeds, then use may be made for example of turbines with adjustable turbine blades. Means for influencing the air flow can also be used, such as valves, flap valves, or suitably designed housing elements of the boring tool. In principle, methods for the mutually independent operation of a plurality of turbines are known to the person skilled in the art. 
     Further advantageous embodiments of the invention are represented in the subclaims. 
     In a further preferred embodiment of the method according to the invention, it is provided that, as the boring tool, a hollow boring tool is used, which comprises at least one hollow core, and that additional material is filled through the hollow core of the hollow boring tool into the borehole, before the beginning and/or during and/or after the withdrawal of the hollow boring tool. 
     This provides the advantage that both the bore hole as well as the bored pile can be produced in one working cycle. 
     In a further preferred embodiment, it is provided that a reinforcement element is introduced into the hollow core of the hollow boring tools before the filling material is filled into the hollow core of the hollow boring tool. 
     This provides the advantage that the bored pile can be produced together with the reinforcement element in one working cycle. 
     A further aspect of the present invention relates to a boring tool for producing bore holes or bored piles in a subsoil. The bore holes produced are suitable in particular for bored piles. According to the invention, it is provided that the boring tool comprises at least one fluid flow machine, wherein at least one unbalance element is integrated into at least one rotor of the at least one fluid flow machine, and the rotor is mounted in the boring tool such as to rotate about a longitudinal axis of the boring tool, such that a resulting vibration can be produced, the vibration amplitude of which comprises at least one horizontal portion. 
     Boring tool in the meaning of the invention is any device with which a bore torque moment, i.e. a circumferential force, is transferred by way of an outer surface of the device onto the surrounding subsoil. 
     This provides the advantage that by a corresponding arrangement of the at least one unbalance element, a dynamic operational behavior of the boring tools can be adjusted. 
     The fluid flow machine can preferably be operated at revolution speeds from 1 rev/min to 100,000 rev/min, particularly preferred from 1 rev/min to 50,000 rev/min, and especially preferred from 1 rev/min to 30,000 rev/min. The unbalance element is preferably configured in such a way, and integrated into the rotor of the fluid flow machine, that the boring tool is configured such that in operation it produces a vibration with an amplitude in the range from 0.01 mm to 5 mm, further preferred from 0.02 mm to 3 mm, and especially preferred from 0.03 mm to 2 mm in respect of a horizontal or radial deflection respectively of the boring tool, or, respectively, a vibration with an amplitude in respect of a horizontal or, respectively, a radial force of preferably 0.5 kN to 1000 kN, further preferred 1 kN to 700 kN, and especially preferred 25 kN to 400 kN. This provides the advantage that the fluid flow machine can be operated at a high revolution speed, which exerts a positive effect on a degree of efficiency of the fluid flow machine. 
     Further preferred embodiments of the present invention derive from the features referred to in the subclaims. 
     It is particularly preferred, for example, that the boring tool is provided at least in sections with an auger and/or a tip with screw threads. 
     This provides the advantage that the boring tool can be flexibly adjusted in respect of its suitability for conveying and/or displacing subsoil material. 
     In a further preferred embodiment, provision is made for the boring tool being a hollow boring tool, comprising at least one hollow core. 
     This provides the advantage that, with the hollow boring tool, bored piles can be produced with the method according to the invention for producing bored piles. 
     It is further preferred that the at least one fluid flow machine is configured as at least one pneumatic turbine. 
     This provides the advantage that very high revolution speeds can be attained, and the turbine can be driven with an economically advantageous and low-risk operating fluid. 
     If it is intended that the pneumatic turbines should be capable of being driven at different revolution speeds, then they can, for example, comprise adjustable turbine blades. Means can also be provided for influencing the air flow in the boring tool, such as valves, flap valves, or suitably configured housing elements. In principle, it is known to the person skilled in the art how turbines, and, respectively, the system which provides the operating fluid, are to be configured in order that they can be operated at different revolution speeds. 
     In a further preferred embodiment it is provided that at least one rotor with turbine blades is mounted on a hollow axle, which is configured as a hollow core. 
     This provides the advantage that the complexity of the structural design is reduced. 
     A further aspect of the present invention relates to a depth vibrator for displacing and compacting a subsoil material, comprising at least one rotationally movable unbalance element, wherein the depth vibrator comprises at least one fluid flow machine as the drive for the unbalance element, and wherein the at least one fluid flow machine comprises at least one pneumatically driven turbine. According to the invention, it is provided that the at least one pneumatically driven turbine is operationally connected to the at least one unbalance element by means of at least one induction coupling. 
     A pneumatic turbine can advantageously be configured such as to be permanently driven at a maximum torque moment. Revolution speed differences between the turbine and the unbalance element can advantageously be compensated for by the induction coupling, such that no mechanical gear arrangement based on a positive fit connection is required. Friction losses can thereby be advantageously avoided. This leads to reduced maintenance effort and expenditure. The configuration with air as the operating fluid for the turbine further provides the advantage that storage and permanent provision of the operating fluid can be done without. 
     The induction coupling is of the class of externally-actuated switchable couplings with a non-positive working principle. The transfer of force and torque respectively is based in this situation on the principle of a changing magnetic field, which takes effect on a passive electrical conductor. The drive side of the coupling, for example, can create the magnetic field, and is designated hereinafter as the active side. Both permanent magnets as well as electromagnets can be used in order to produce the magnetic field. If an electromagnet is used, it can consist of one or more electrical conductors, through which a regulatable current can flow. With induction couplings, no physical contact takes place between the drive side (active side) and the output side (passive side), referred to hereinafter as the passive side. The passive side can preferably comprise an inherently short-circuited electrical conductor, which is not actively supplied with an electric voltage. If a revolution speed difference pertains between the active and passive side, this results in a relative movement between the active and passive sides. The magnetic field produced by the active side is therefore moved relative to the short-circuited conductor on the passive side. As a result, the Lorenz force takes effect on the short-circuited conductor, as a result of which a torque moment can be transferred from the drive side (active side) onto the output side (passive side) of the induction coupling. The torque moment can preferably take place by the regulating of the electric current which flows through the electrical conductor of the active drive side. A changeover of the active and passive sides is likewise possible. Also possible is the use of two active sides. These structural design alterations can if necessary be undertaken independently by the person skilled in the art. The induction coupling allows for an operation with a sustained revolution speed difference between the drive side and the output side. 
     Preferably, an induction coupling is used which is configured such as to transfer torque moments of more than 1 Nm on the drive side. Preferably, the drive-side transferrable torque moment values lie in the range from 5 Nm to 100 Nm, and particularly preferably from 10 Nm to 40 Nm. Also preferably, the induction coupling can be operated in the revolution speed ranges on the drive side between 500 rev/min (revolutions per minute) and 50,000 rev/min, preferably between 10,000 rev/min and 40,000 rev/min, and particularly preferably between 10,000 rev/min and 30,000 rev/min. A mechanical force which can be transferred by the induction coupling lies preferably in the range 5 kW to 200 kW, particularly preferably from 10 kW to 60 kW, and especially preferably from 20 kW to 50 kW. 
     This provides the advantage that substantial revolution speed differences between the pneumatic turbine and the rotating unbalance element can be compensated for, and, at the same time, a high torque moment is available for driving the unbalance element. The spatial requirement of the induction coupling in this situation remains advantageously in the range of a diameter of conventional depth vibrators. 
     Preferably, an induction coupling with permanent magnets is used. 
     This provides the advantage that an active supply of the induction coupling with electrical energy can be done without. 
     For further preference, an induction coupling with an electromagnet is used. 
     This provides the advantage that the mechanical and thermal behavior of the induction coupling can be controlled by means of the current flow. 
     It is further preferred that the drive side of the induction coupling, in other words the side of the induction coupling facing the pneumatic turbine, is configured as the passive side, and that the output side, i.e. the side facing the unbalance element, is configured as the active side. 
     This provides the advantage that resistance losses on the passive side (drive side) incurred by the electrical current flow in the form of heat can be conducted away and conveyed to the pneumatic turbine. 
     Further preferred is an arrangement of a plurality of induction couplings connected in series. 
     This provides the advantage that the relative revolution speeds necessary for an effective torque moment transfer between the drive side and output can be reduced. 
     Preferably, a mass of the rotationally movable unbalance element amounts to between 1 kg and 200 kg, particularly preferably between 5 kg and 60 kg. A mass center of gravity of the rotationally movable unbalance element, related to an axis of rotation, preferably lies at a maximum radial distance interval from the axis of rotation. The structural space available has the effect of a delimiting peripheral condition. 
     This provides the advantage that, due to the rotation of the unbalance element at revolution speeds which correspond to the range of the natural frequency of the subsoil, adequately large centrifugal forces or vibration amplitudes can be produced. 
     The pneumatic turbine can preferably be driven at revolution speeds of 500 rev/min and 50,000 rev/min, preferably between 10,000 rev/min and 40,000 rev/min, and especially preferably between 10,000 rev/min and 30,000 rev/min. 
     A torque moment which can be produced by the pneumatic turbine lies preferably in the range from 1 Nm to 100 Nm, particularly preferably from 10 Nm to 40 Nm, especially preferably at 15 Nm to 25 Nm. A pressure difference of an air quantity which can be used for the operation of the pneumatic turbine, from a turbine inlet to a turbine outlet, preferably amounts to between 1 bar and 30 bar, for further preference between 2 bar and 20 bar, and particularly preferably between 3 bar and 15 bar. This provides the advantage that the pneumatic turbine can provide a high torque moment with a high degree of efficiency. 
     Further preferred embodiments of the present invention derive from the features presented in the subclaims. 
     For example, it is provided in a preferred embodiment that the induction coupling is configured such as to convert rotation frequencies on the drive side (drive shaft) into rotation frequencies of preferably between 5 Hz and 120 Hz, particularly preferably between 15 Hz and 90 Hz, and especially preferably between 25 Hz and 60 Hz at the shaft on the output side (output shaft) of the induction coupling. 
     This provides the advantage that the pneumatic turbine can be permanently operated in a revolution speed range which is optimum for it, while the revolution speed of the rotationally movable unbalance element can be settled in the natural frequency range of the subsoil. 
     According to a further aspect of the present invention, a method is disclosed for the displacement and compaction of a subsoil material, wherein a depth vibrator is sunk into the subsoil under the application of a vertical force, and the depth vibrator is set into vibration during the sinking, wherein a resulting vibration amplitude comprises at least one horizontal portion. According to the invention, it is provided that the vibrations are produced by at least two kinematically independent rotationally moved unbalance elements, wherein the resulting vibration can be adjusted by the superimposition of the individual vibrations of the independent unbalance elements. 
     This provides the advantage that adjustment can be made to the frequency of the resulting vibration independently of the rotation frequency of the rotationally moved unbalance elements, and that it is possible to make flexible adjustment to the natural frequency of the subsoil. 
     Preferably, the rotation frequencies of the respective rotationally moved unbalance elements lie between 20 Hz and 600 Hz, particularly preferably between 30 Hz and 500 Hz, and especially preferably between 50 Hz and 450 Hz. The frequency of the resulting superimposed vibration lies preferably between 5 Hz and 120 Hz, particularly preferably between 15 Hz and 90 Hz, and especially preferably between 25 Hz and 60 Hz. 
     This provides the advantage that, due to the large individual rotation frequencies, high centrifugal forces can be produced, and, at the same time, the frequency of the resulting vibration can be adjusted to the lower natural frequency of the subsoil. 
     For further preference, with the method a dynamically resultant centrifugal force is produced by the rotating unbalance elements. A maximum amount of the resultant centrifugal force is preferably 25 kN to 700 kN, for preference 50 kN to 600 kN, and particularly preferably 100 kN to 500 kN. For further preference, with the method a dynamically resulting radial or, respectively, horizontal deflection (amplitude) of the depth vibrator is produced, related to a state outside the subsoil, in which a free vibration is possible which amounts to a maximum amount of preferably 2 mm to 40 mm, for further preference 5 mm to 30 mm, and particularly preferably 7 mm to 20 mm. 
     It has been found that these process parameters allow for a particularly advantageous compaction of subsoil materials which are processed with the method according to the invention. 
     Further preferred embodiments of the present invention are derived from the features referred to in the subclaims. 
     In a further advantageous embodiment it is provided that the rotational movement of the unbalance elements is effected by at least one fluid flow machine. 
     Fluid flow machines, due to the high revolution speeds which they can achieve, provide particular advantages in the production of high centrifugal forces. 
     In a further advantageous embodiment, it is provided that at least one pneumatic turbine is used as the at least one fluid flow machine. The pneumatic turbine is preferably operated at revolution speeds from 500 rev/min to 50,000 rev/min, particularly preferably from 10,000 rev/min to 40,000 rev/min, and especially preferably from 10,000 rev/min to 30,000 rev/min. A torque moment produced by the pneumatic turbine lies preferably in the range from 1 Nm to 100 Nm, particularly preferably from 10 Nm to 40 Nm, and especially preferably from 15 Nm to 25 Nm. A pressure difference of an air quantity used for the operation of the pneumatic turbine, from a turbine inlet to a turbine outlet, amounts preferably to between 1 bar and 30 bar, for particular preference between 2 bar and 20 bar, and especially preferably between 3 bar and 15 bar. 
     This provides the advantage that very high revolution speeds are achieved, and the turbine is operated at a working point at which the degree of efficiency is high. Further advantages are derived from an economic and low-risk working fluid in the form of compressed air. 
     If it is intended that the pneumatic turbines should be operated at different revolution speeds, then use can be made, for example, of turbines with adjustable turbine blades. It is also possible to use means for influencing the air flow such as valves, flap valves, or suitably designed housing elements of the depth vibrator. In principle, methods are known to the person skilled in the art for the mutually independent operation of a plurality of turbines. 
     According to a further aspect of the present invention, a depth vibrator for the displacement and compaction of a subsoil material is disclosed, which comprises one or more rotationally movable unbalance elements. According to the invention, it is provided that the unbalance elements are integrated in each case in an assigned pneumatic turbine. 
     This provides the advantage that the depth vibrator comprises a lower number of moved components, in particular relative to one another. The complexity of the system is advantageously reduced. 
     In an advantageous embodiment, the unbalance elements are arranged in one or more rotors of the pneumatic turbine. Also possible is an arrangement of the unbalance elements in each case in a shaft, in the event of all the turbine stages being mounted on a separate shaft. 
     Both variants provide the advantage that a mass distribution of the unbalance elements can be arranged in a specific and precise manner. Moreover, a decentralized arrangement of the unbalance elements in the turbine allows for a partial rearrangement, in order for the mass characteristics of the turbine or of the unbalance elements to be changed in a specific manner. 
     If it is intended that the pneumatic turbines should be capable of being driven at different revolution speeds, they can, for example, comprise adjustable turbine blades. Means can also be provided for influencing the air flow in the depth vibrator, such as valves, flap valves, or suitably configured housing elements. In principle, it is known to the person skilled in the art how turbines, or, respectively, the system which provides the operating fluid, are to be configured such that they can be operated at different rotational speeds. 
     Preferably, masses of the rotationally movable unbalance elements amount in each case to between 0.1 kg and 3 kg, particularly preferably between 0.2 kg and 2 kg. A mass center of gravity of the rotationally movable unbalance element, related to an axis of rotation, preferably lies at a maximum radial distance interval from the axis of rotation. A restrictive peripheral condition is the structural space which is available. 
     This provides the advantage that, due to the rotation of the unbalance elements at revolution speeds which, due to the vibration superimposition, correspond to the range of the natural frequency of the subsoil, adequately high centrifugal forces and vibration amplitudes respectively can be created. 
     The pneumatic turbines with the unbalance elements can preferably be driven at revolution speeds from 1 rev/min to 100,000 rev/min, particularly preferably from 1 rev/min to 50,000 rev/min and especially preferably from 1 rev/min to 30,000 rev/min. 
     Further embodiment variants are derived from advantageous combination of the features referred to and contained in the exemplary embodiments. Moreover, a transfer of the disclosed technical teaching to further methods and associated devices for improving the mechanical subsoil properties are possible, with which a creation of horizontal vibrations provides a specific advantage. 
    
    
     
       The invention is described in greater detail hereinafter on the basis of an exemplary embodiment and the associated drawings. The figures show: 
         FIG. 1  a preferred embodiment of a method according to the invention for producing displacement bored piles; 
         FIG. 2  a preferred embodiment of a hollow boring tool according to the invention; 
         FIG. 3  a preferred embodiment of a depth vibrator according to the invention, with pneumatic turbine and induction coupling; 
         FIG. 4  a preferred embodiment of a method according to the invention for displacing and compacting a subsoil material, and 
         FIG. 5  a preferred embodiment of a depth vibrator according to the invention with two independent pneumatic turbines with integrated unbalance elements; 
     
    
    
       FIG. 1  shows a preferred embodiment of a method according to the invention for producing displacement bored piles in a schematic representation. The temporal sequence of the method steps derived from the following description. A hollow boring tool  47  is in this situation sunk into the subsoil  28  with the application of a drilling torque or moment  48  about a rotation axis R and a vertical force  50  along a rotation axis R. 
     By means of actuating elements  56  in the form of two mutually independent pneumatic turbines  42  with integrated unbalance elements  76 , the hollow boring tool  47 , while sunk into the subsoil  28 , is set into vibration  58 . In this situation, initially multiple vibrations  36  are incurred by the two unbalance elements  76  moved rotationally by the turbines  42 . The resulting vibration  58  can be adjusted by the superimposition of the individual vibrations  36  of the independently rotationally moved unbalance elements  76 . A resulting vibration amplitude comprises a horizontal portion  62 , which accounts for more than 95% of the total vibration amplitude. The rotation frequencies of the two rotationally moved unbalance elements  76  are 200 Hz and 300 Hz, wherein the allocation in a design arrangement is freely selectable. In the process, a vibration  58  is produced which corresponds to a dynamic resulting centrifugal force F which exhibits a maximum amount of 175 kN. Moreover, the vibration  58  corresponds to a dynamic radial or horizontal deflection W respectively of the hollow boring tool  47  with a maximum amount of 0.2 mm. When the hollow boring tool  47  is sunk into the subsoil  28 , a vertical subsoil conveyance  110  takes place by means of an auger  66 , which is arranged on the outside of the hollow boring tool  47 . When a predetermined operating depth in the subsoil  28  has been reached, concrete is filled as additional material  52  through a hollow core  54  of the hollow boring tool  47 , and the hollow boring tool  47  is then withdrawn. 
       FIG. 2  shows a schematic representation of a preferred embodiment of a hollow boring tools  47  according to the invention. The hollow boring tool is particularly well-suited for the method described in  FIG. 1 . The hollow boring tool  47  is provided with an outer surface with an auger  66 , and comprises a hollow core  54 . The hollow boring tool  47  further comprises two mutually independent pneumatic turbines  80 , of which the rotors  82  are fitted with turbine blades on a common longitudinal axis  78 , which forms the hollow core  54 . Integrated into the rotors  82  of the turbines  80  is in each case an unbalance element  76 . The turbines  80  are designed for a rated revolution speed of 25,000 rev/min. The unbalance elements  76  are configured in such a way, and integrated into the rotors  82  of the turbines  80  in such a way that the hollow boring tool  47  is arranged such that, in operation, it creates a vibration with a maximum amplitude of 0.4 mm in respect of a horizontal or radial deflection respectively of the hollow boring tool  47 , or a vibration with a maximum amplitude in respect of a horizontal or radial force of 150 kN. 
       FIG. 3  shows a schematic representation of a preferred embodiment of a depth vibrator  10  according to the invention, with a pneumatic turbine  16  and induction coupling  18 . The depth vibrator  10  comprises a rotationally movable unbalance element  12 . The unbalance element  12  can be driven by a fluid flow machine, which is configured as a two-stage pneumatically-driven turbine  16 . Two rotors  84  of the turbine  16  are arranged on a common shaft  86  with a rotation axis R. One end of the shaft  86  is a drive shaft  20  for the induction coupling  18 . A drive side  90  of the induction coupling  18 , i.e. a side of the induction coupling  18  facing towards the pneumatic turbine  16 , is configured as the passive side  94 , and an output side  92 , i.e. a side facing towards the unbalance element  12 , is configured as the active side  88 . The induction coupling  18  is configured such as to transfer a rated torque moment of 25 Nm, at a rated revolution speed of 20,000 rev/min, onto the drive shaft  20  and 50 Hz onto an output shaft  22 . A mechanical force transferrable by the induction coupling  18  lies in the range of 60 kW. The induction coupling  18  is provided on the active side  88  with permanent magnets, which are configured such as to produce an induction magnetic field. A mass of the rotationally movable unbalance element  12  amounts to 20 kg. The pneumatic turbine  16  is designed for a nominal revolution speed of 20,000 rev/min and a rated torque moment of 25 Nm. A rated output which can be provided by the pneumatic turbine  16  is 60 kW. A pressure difference of an air volume flow  100 , which can be used for the operation of the pneumatic turbine  16 , from a turbine inlet  104  to a turbine outlet  102 , amounts to 7 bar at a rated operating point. 
       FIG. 4  shows a schematic representation of a preferred embodiment of a method according to the invention for the displacement and compaction of a subsoil material. The temporal sequence of the method steps is derived from the following description. A depth vibrator  24  is in this situation sunk into the subsoil  28  under the application of a vertical force  26 . The depth vibrator  24  is set in vibration  30  during the sinking. Multiple vibrations  36  are produced in this situation by two kinematically independent rotationally moved unbalance elements  38 , The rotational movement of the unbalance elements  38  is generated by two pneumatic turbines  42 . The resulting vibration  30  can be adjusted by superimposition of the individual vibrations  36  of the independent unbalance elements  38 . A resulting vibration amplitude comprises a horizontal portion  34 , which makes up more than 95% of the total vibration amplitude. In the process, a resulting vibration  30  is produced, which corresponds to a dynamic resulting centrifugal force F of the rotating unbalance elements  38  with a value of 150 kN. Moreover, the resulting vibration  30  corresponds to a dynamic radial or horizontal deflection W respectively of the depth vibrator  24 . A maximum amount of the resulting radial or horizontal deflection W respectively of the depth vibrator  24  is 8 mm. 
       FIG. 5  shows a schematic representation of a preferred embodiment of a depth vibrator  44  according to the invention, with two independent pneumatic turbines  42  with integrated unbalance elements  38 . The unbalance elements  38  are in each case integrated in an associated pneumatic turbine  42 , or, respectively, are in each case integrated in a rotor  118  of the associated turbine  42 . The rotors  118  are mounted on a common rotation axle R. Masses of the rotationally movable unbalance elements  38  are 0.25 kg and 0.5 kg, wherein the allocation of the masses to the unbalance elements  38  in a structural design arrangement is freely selectable. A resulting mass centre of gravity S of the rotationally movable unbalance elements  38 , related to the rotation axle R lies at a maximum radial distance interval d, which is limited by the structural space available. 
     REFERENCE FIGURE LIST 
     
         
         
           
               10  Depth vibrator 
               12  Unbalance element 
               16  Pneumatically driven turbine 
               18  Induction coupling 
               20  Drive shaft 
               22  Output shaft 
               24  Depth vibrator 
               26  Vertical force 
               28  Subsoil 
               30  Vibration 
               34  Horizontal portion 
               36  Vibrations 
               38  Unbalance elements 
               42  Pneumatic turbine 
               44  Depth vibrator 
               47  Hollow boring tool 
               48  Drilling torque moment 
               50  Vertical force 
               52  Additional material 
               54  Hollow core 
               56  Actuating elements 
               58  Vibration 
               62  Horizontal portion 
               66  Auger 
               76  Unbalance element 
               78  Longitudinal axis 
               80  Pneumatic turbine 
               82  Rotors 
               84  Rotors 
               86  Shaft 
               88  Active side 
               90  Drive side 
               92  Output side 
               94  Passive side 
               96  Coupling disks 
               100  Air volume flow 
               102  Turbine outlet 
               104  Turbine inlet 
               110  Vertical subsoil conveyance 
               118  Rotor 
             d Radial distance interval 
             F Resulting centrifugal force 
             R Rotation axis 
             S Mass centre of gravity 
             W Deflection