METHOD FOR ASSESSING THE AXIAL BEARING CAPACITY OF AN INSTALLATED PILE

Description

[0001] The application relates to a method for assessing the axial load-bearing capacity of an installed pile. Furthermore, the application relates to a measuring system, a computer program product, a measuring set, and a vibrator device.

[0002] Wind farms are increasingly being built in offshore areas to generate electrical energy. The advantages of offshore locations are the higher wind probability and the higher average wind speeds. This results in a higher electrical energy yield from a wind farm built in an offshore area, especially compared to onshore locations.

[0003] An offshore wind farm typically comprises a number of offshore structures, such as a number of offshore wind turbines, at least one offshore substation and / or at least one offshore measurement mast.

[0004] Such offshore structures, as well as other onshore and offshore structures (e.g., oil drilling platforms or the like), are typically founded with at least one pile on or in the underwater bed. During the installation of an offshore structure, at least one pile is first driven into the underwater bed at the desired installation location.

[0005] In the current technology, pile installation is carried out using a percussion hammer and / or a vibrator device. A percussion hammer, also called a driving hammer, applies shock pulses to the pile head to drive the pile to the desired embedment depth. A vibrator device transmits pulse sequences or vibrations to the pile. The pulse sequences transmitted to the pile lead to liquefaction of the subsurface soil, thus driving the pile into the subsurface.

[0006] After a pile has been driven into the soil, it may generally be necessary to determine the axial load-bearing capacity of the installed pile. In particular, it may be necessary to provide evidence of sufficient axial load-bearing capacity of the installed pile.

[0007] For this purpose, the current state of the art, particularly for offshore piles, involves performing a so-called dynamic loading test using a pile hammer. During dynamic loading, a pile is subjected to a (short) shock pulse by briefly impacting the pile head with the impact of the hammer. The generated impact pulse subsequently propagates as an impulse wave or strain wave from the pile head to the pile toe of the installed pile. The generated impulse wave is reflected at the pile toe and travels back to the pile head (damped).

[0008] The reflected impulse or strain wave can be recorded by at least one motion data sensor attached to the pile. The recorded motion data can be evaluated using a predefined method (e.g., CAPWAP method) to determine a load-bearing capacity criterion. This can then be evaluated, for example, using a predefined verification criterion (e.g., a minimum hardening factor) to determine whether or not the installed pile has sufficient axial load-bearing capacity.

[0009] A disadvantage of the described state of the art is that a pile driver is always required after the pile has been driven to apply the driving impulse to the pile during dynamic loading tests. This is particularly disadvantageous when using a vibrator device, as in this case, a pile driver is also required after the pile has been driven. This increases the effort required for installing piles and, in particular, for providing proof of sufficient (axial) load-bearing capacity.

[0010] Furthermore, DE 10 2006 060643 A1 relates to a method for inserting elongated profiles, wherein the dynamic stress on the profile is measured during the insertion process.

[0011] Therefore, the application is based on the task of creating a possibility that enables a reduction in the effort involved in installing piles and, in particular, in providing evidence of sufficient (axial) load-bearing capacity.

[0012] The object is achieved according to a first aspect of the application by a method according to claim 1. The method serves to determine, in particular to assess, the (axial) load-bearing capacity of an installed pile. The method comprises: Applying a measuring pulse sequence to the inserted pile by a vibrator device arranged on the inserted pile during at least one vibration period, detecting, by at least one detection module, movement data of the inserted pile caused by the measuring pulse sequence during a measurement period, determining at least one downward movement data set from the detected movement data, and evaluating the downward movement data set in such a way that a load-bearing capacity criterion is determined.

[0013] By using a vibrator device instead of a pile driver in the method according to the application, in contrast to the prior art, a reduction in the effort required for installing piles and, in particular, for providing evidence of sufficient (axial) load-bearing capacity is achieved. In particular, according to the application, instead of a driving impact with a pile driver, the pile is subjected to a measuring pulse sequence, generating a corresponding plurality of pulse or strain waves. The resulting movement data is evaluated in such a way that the load-bearing capacity of the installed pile can be assessed.

[0014] The method according to the application serves to assess whether a pile driven into a soil to a certain embedment depth has sufficient load-bearing capacity or not, in particular whether it has sufficient axial load-bearing capacity.

[0015] In particular, a pile is at least one part of a building's foundation. A building can be formed, in particular, by the foundation and at least one structure to be supported by the foundation.

[0016] In the present case, the structure is preferably an offshore structure. Particularly preferably, the offshore structure can be an offshore structure of an offshore wind farm, such as an offshore wind turbine, an offshore substation, and / or an offshore met mast. Furthermore, an offshore structure can be a drilling or production platform (e.g., an oil or gas platform) or another offshore platform, preferably configured for the extraction, conversion, and / or storage of energy, such as, for example, an offshore facility for the production of hydrogen. The offshore structure can comprise the installed pile.

[0017] The foundation of an offshore structure is preferably a monopile, tripod, triple pile, or jacket foundation. This type of foundation allows an offshore structure to be directly anchored to or in the underwater subsoil, particularly the seabed.

[0018] A pile according to the application refers in particular to a tower-shaped, particularly cylindrical, foundation structure, preferably in the form of a hollow structural element. Such a pile generally has a circumferential pile wall extending in the longitudinal or axial direction, with the pile wall being defined on the underside by a lower end face and on the upper side by an upper end face. In this context, the terms "upper," "lower," etc., refer to the installed state of the pile. The upper end of the pile can also be referred to as the pile head, and the lower end of the pile as the pile base.

[0019] A pile according to the application can be made of a metallic material. Steel is particularly well suited for such a foundation structure due to its strength and rigidity properties. Alternatively or additionally, a pile can be made of a mineral building material. The mineral building material is preferably concrete, which is a mixture of cement, gravel, sand, and water and is hardened, especially after pouring.

[0020] Furthermore, a pile according to the application preferably has a circular cross-sectional area. In other variants of the application, a different cross-sectional area can also be provided, such as an oval, rectangular, or similar shape. Preferably, the cross-sectional area remains constant in the longitudinal direction. In other variants, the cross-sectional area can also change, for example, by tapering towards the pile base.

[0021] According to the application, an installed pile is subjected to a measuring pulse sequence (also referred to as measuring vibrations or measuring oscillations). According to the application, an installed pile is, in particular, a pile that is installed in the soil at a specific or desired embedment depth. Preferably, the pile can be vibrated into place using a vibrator device. However, the use of another device is also conceivable.

[0022] According to the application, a vibrator device is used to apply a measuring pulse sequence to the pile. The vibrator device can, in particular, be force-locked to the pile (preferably the pile head). The vibrator device can be configured to generate measuring vibrations or a measuring pulse sequence in the vertical direction (i.e., in the longitudinal direction of the installed pile). For example, the vibrator device can have an eccentric device that can be driven via a drive of the vibrator device. The eccentrics of the eccentric device, which are arranged in particular in pairs, can preferably rotate at the same angular velocity, but in opposite directions. The at least two eccentrics can generate centrifugal forces. The horizontal forces can cancel each other out, while the vertical components can add up to form a total centrifugal force. The pulses or forces generated therebyDue to the force-locking connection between the vibrator device and the pile, vibrations can be transmitted to the pile. This generates a multitude of impulse or strain waves.

[0023] The pile is subjected to a measuring pulse sequence during a vibration period.

[0024] During a measurement period, the method according to the application records movement data from the pile. The movement data is generated by the measuring pulse sequence or the measuring vibrations. In particular, the movement data of the generated pulse or strain waves are recorded.

[0025] The detectable movement data include, in particular, force parameter values ​​and / or velocity parameter values. Preferably, the compression (force) and / or acceleration (velocity and displacement) can be measured on the pile (particularly at the pile head).

[0026] Preferably, a measuring device comprising the detection module can comprise at least one motion data sensor and / or be connected to at least one motion data sensor. In a preferred embodiment, the measuring device can comprise at least one (preferably exactly two) strain sensor(s) and / or at least one (preferably exactly two) acceleration sensor(s) and / or be connected to at least one (preferably exactly two) strain sensor(s) and / or at least one (preferably exactly two) acceleration sensor(s). The at least one motion data sensor can be attached to the pile head.

[0027] The vibration period preferably comprises the measurement period, wherein the measurement period is preferably shorter than the vibration period. This means in particular that the measurement period lies within the vibration period. The vibration period can preferably be composed of a start-up period, a (immediately) subsequent measurement period and in particular a (immediately) subsequent decay period. The start-up period or lead-in phase is in particular the period during which the vibrator device is ramped up from a frequency of 0 to a (specific) minimum measurement frequency from which the aforementioned detection can take place. The decay period or lag-in phase is in particular the period during which the vibrator device is ramped down again to frequency 0 after the measurement period.

[0028] Furthermore, according to the application, at least one downward movement data set is determined from the recorded movement data. According to the application, it has been recognized that in order to assess the load-bearing capacity of the installed pile, it is necessary to identify the impulse wave or expansion wave generated by the vibrator device through a downward movement (i.e., a movement of the vibrator device toward the pile base) (and in particular, reflected at the pile base), and thus, in particular, to determine the associated movement data of this impulse wave.

[0029] According to the application, the movement data associated with a pulse wave are referred to in particular as downward movement data. A downward movement data set can be assigned to a downward movement or a corresponding pulse wave, thus, in particular, containing only the data of one pulse wave.

[0030] In variants of the registration, data from two or more pulse waves may also be included.

[0031] According to a preferred embodiment, determining the downward movement data set or the corresponding movement parameter values ​​may comprise applying a filter function to the acquired movement data or movement parameter values.

[0032] The filter function is, in particular, synchronized or coordinated with the vibrator device or the generated measurement pulse sequence and / or takes into account the pile dimensions (e.g., pile length, pile diameter, pile wall diameter, pile cross-sectional shape, etc.). Filtering by the filter function is performed, in particular, in such a way that, from all the recorded movement data, the downward movement data is determined that was caused by a reflection of the at least one pulse wave generated by a downward movement at the pile toe, i.e., the movement data of the reflected pulse wave. In other words, the wave data generated by a downward movement of the vibrator device and reflected at the pile toe, i.e., the corresponding downward movement data set, containing, in particular, the compression and acceleration parameter values, is identified by the filter function.

[0033] The at least one specific, in particular identified, downward movement data set (in a preferred embodiment, a plurality of downward movement data sets can be determined from a corresponding plurality of downward movements) is subsequently evaluated, in particular with regard to the (axial) load-bearing capacity of the installed pile.

[0034] According to a preferred embodiment, the evaluation of the at least one downward movement data set can be carried out by means of modeling based on wave theory, e.g. based on the CAPWAP method, TNOWAVE method or CASE method (these methods are known to the person skilled in the art).

[0035] For example, a pile-soil model (CAPWAP) can be developed by inverse system identification based on the at least one down-movement data set, from which the static pile resistances (preferably skin friction and / or tip pressure) can then be derived to determine whether there is sufficient (axial) bearing capacity of the installed pile (or not).

[0036] According to the application, a bearing capacity criterion can be determined, such as a skin friction and / or tip pressure criterion. In particular, a resistance-settlement curve and / or a distribution of pile skin and pile toe resistance can be determined as a bearing capacity criterion by evaluating the determined movement data.

[0037] A verification criterion for sufficient load-bearing capacity of the pile can, for example, be a specified limit load-bearing capacity (e.g. limit skin friction and / or limit peak pressure), which must be observed so that an installed pile is assessed as a pile with sufficient (axial) load-bearing capacity.

[0038] If this criterion is not met, the axial load-bearing capacity is insufficient. Further measures can then be taken (e.g., the pile can be embedded deeper) and, if necessary, the current procedure can be repeated.

[0039] According to a further embodiment of the method according to the application, the (predescribed) steps of applying, detecting and determining can be carried out again after a decay time (and optionally a further (specifiable) waiting time). The further waiting time can also be referred to as a second solidification time, which can in particular be shorter than a first solidification time (described in more detail below).

[0040] In particular, this test procedure—i.e., applying, detecting, and determining—can be performed multiple times, each time interrupted by at least the specified decay time (and, if applicable, the specified waiting time). Subsequently, a (joint) evaluation of the downward movement data sets determined in each case can be performed. Appropriate testing can provide a more precise evaluation. It goes without saying that an evaluation can also be performed after each test procedure.

[0041] According to a further embodiment of the method according to the application, the acquisition of the movement data (or parameter values) (by the measuring device) can be carried out at a sampling rate of at least 10,000 values ​​per second, in particular at a sampling rate of at least 40,000 values ​​per second (and, for example, at most 200,000 values ​​per second). This enables a determination, in particular identification, of individual downward movements of the vibrator device and a subsequent determination, in particular identification (e.g., by the described filter function), of the pulse wave caused by an identified downward movement and reflected at the pile base. In particular, the measuring sensors and the acquisition module, comprising at least one A / D converter of a data logger, can record movement data at a sampling rate between 10,000 values ​​per second and 40,000 values ​​per second (e.g., PDI measuring system).

[0042] It has also been recognized that, in order to reliably assess the load-bearing capacity of the pile, it should not be inserted (significantly) deeper into the ground during the measurement period. According to a preferred embodiment of the method according to the application, it is proposed in particular that a maximum measuring frequency of the measuring pulse sequence (during the measuring period) is at least below a (specified) cut-off frequency. The maximum measuring frequency can in particular be selected such that it is ensured that the soil at the installation site does not liquefy. The cut-off frequency can therefore be a frequency at which the soil is not yet liquefied. The cut-off frequency can be specified depending on the local soil conditions (e.g. sandy soil or cohesive soil (e.g. clay soil)) at the installation site.

[0043] According to the method according to the invention, a maximum measuring frequency of the measuring pulse sequence (during the measuring period) is a maximum of 80% of the (maximum) installation frequency, preferably a maximum of 60% of the (maximum) installation frequency, particularly preferably a maximum of 40% of the (maximum) installation frequency. The (maximum) installation frequency means in particular the (maximum) frequency with which the pile is installed to the specific installation depth. In other words, the (maximum) installation frequency is in particular the maximum installation frequency used during the previous installation of the pile to the specific installation depth. It should be noted that the installation frequency can depend in particular on the soil type or the soil conditions at the installation site of the pile. Accordingly, the maximum measuring frequency can then depend on the soil type.

[0044] Furthermore, according to a further embodiment of the method according to the application, a maximum measuring frequency of the measuring pulse sequence can be at most 10 Hz (during the measuring period), preferably at most 8 Hz, particularly preferably at most 6 Hz. The measuring frequency can be between 1 Hz and 10 Hz during the measuring period, preferably between 2 Hz and 8 Hz, particularly preferably between 3 Hz and 7 Hz.

[0045] For a particularly precise and simultaneously effective evaluation, according to a further embodiment of the method according to the application, the measurement time can be between 0.5 minutes and 20 minutes, preferably between 1.5 minutes and 15 minutes, particularly preferably between 2.5 minutes and 7.5 minutes. The measurement time can depend at least on the soil type (as can the application time).

[0046] According to a particularly preferred embodiment of the method according to the application, prior to applying the measuring pulse sequence to the installed pile, the installed pile may not be subjected to pulses or vibrations by the vibrator device for a (predeterminable) (first) hardening period. Thus, during the first hardening period, the pile is particularly vibration-free.

[0047] For a particularly accurate assessment, preferably after the pile has been installed to a specific embedment depth, the application of the vibration should be delayed until it is certain that the soil has (sufficiently) settled or stabilized. The first settling time therefore represents, in particular, the period during which no impulses are transmitted to the pile by the vibrator device. The first settling time is selected in such a way that the accumulated excess pore water pressure in the soil has at least largely stabilized at the original value (i.e., before the pile was installed).

[0048] Particularly preferably, the hardening time can be determined depending on the soil type (in particular underwater soil type) at the pile installation site, wherein the (first) hardening time can be, in particular, between 10 minutes and one week, preferably between one hour and one day. The said second hardening time can, in particular, be shorter than the first hardening time and, for example, be between 1 minute and 10 minutes.

[0049] According to a further embodiment of the method according to the application, the method may further comprise: After driving the pile to a specific embedment depth, releasing a force-locking connection between the vibrator device and the pile, maintaining the released force-locking connection between the vibrator device and the pile during a settling time period, wherein the application of a measuring pulse sequence to the driven pile during at least one vibration time period comprises re-establishing the force-locking connection between the vibrator device and the pile during the vibration time period.

[0050] When the force-locking connection is released, no more impulses are transmitted from the vibrator device to the pile (even if the vibrator device continues to generate vibrations). Shutting down and restarting the vibrator device is no longer necessary.

[0051] In addition, the above-described detection can preferably be carried out immediately after the frictional connection has been released.

[0052] Furthermore, it is assumed that, for the evaluation of the recorded movement data, performing cavitational vibration ramming is advantageous for the determination module to clearly identify the downward movement data. Therefore, according to a preferred embodiment, cavitational vibration ramming is performed.

[0053] A further aspect of the application is a measuring system, in particular configured for assessing the (axial) load-bearing capacity of an installed pile. The measuring system comprises at least one control module configured for controlling a vibrator device arranged on an installed pile such that the vibrator device applies a measuring pulse sequence to the installed pile during at least one vibration period. The measuring system comprises at least one acquisition module configured for acquiring movement data of the installed pile caused by the measuring pulse sequence during a measurement period. The measuring system comprises at least one determination module configured for determining at least one downward movement data set from the acquired movement data.The measuring system comprises at least one evaluation module configured to evaluate the downward movement data set in such a way that a load-bearing capacity criterion is determined (in particular based on at least one verification criterion).

[0054] The measuring system can be implemented in particular by the method described above.

[0055] The control module, the acquisition module, the determination module, and the evaluation module can preferably be integrated into a measuring device comprising at least one processor. For example, a computer can form the measuring device.

[0056] The control module is configured to control the vibrator device. The detection module can be connected, in particular, to at least one motion data sensor. The at least one motion data sensor provides, in particular, a (continuous) sensor signal, which can be sampled and recorded by the detection module, in particular in the manner described above.

[0057] The movement data thus acquired can then be further processed by the determination module in the manner described above. In particular, the determination module can include a filter function (as described above) and apply it to the acquired movement data. This processed movement data can be evaluated by the evaluation module in the manner described above.

[0058] According to a further embodiment of the measuring system according to the application, the measuring system can comprise at least one vibrator device that can be force-fitted to a pile. In particular, a local control of the vibrator device can be connected to the control module of the measuring system via a (wired and / or wireless) communications network. The control module can control the local control via the communications network. The control module can, in particular, transmit a command data set containing control commands such as maximum measurement frequency, vibration duration, start time, end time, and / or the like.

[0059] Furthermore, according to a further embodiment, the measuring system can comprise at least one motion data sensor. For example, the measuring device can comprise at least one motion data sensor and / or be connected to at least one motion data sensor. In a preferred embodiment, the measuring system can comprise at least one (preferably exactly two) strain sensor(s) and / or at least one (preferably exactly two) acceleration sensor(s). According to one embodiment of the measuring system, the at least one motion data sensor can be attached to the pile head.

[0060] Alternatively or additionally, according to a further embodiment of the measuring system, at least one motion data sensor can be arranged on the vibrator device. According to the application, it has been recognized that, due to the force-locking connection or coupling between the vibrator device and the pile, the motion data can also be measured on the vibrator device. Furthermore, the vibrator device is always force-locked to the pile head during the vibration period. By (fixedly) arranging the at least one motion data sensor, preferably all motion data sensors, on the vibrator device, the effort required to assess the load-bearing capacity can be significantly reduced. In particular, the complex attachment (and subsequent removal) of the at least one motion data sensor on the pile head can be eliminated.

[0061] A further aspect of the application is a vibrator device for driving a pile into the ground. The vibrator device comprises at least one fastening module configured for force-fitting the vibrator device to the pile (head). The vibrator device comprises at least one motion data sensor arranged on the vibrator device (as described above in particular).

[0062] The vibrator device ice a part of the measuring system described above and / or is used by the measuring system described above to carry out the assessment of the load-bearing capacity.

[0063] Yet another aspect of the application is a computer program product with instructions (or software code) executable on a processor (in particular a previously described measuring device), wherein the instructions are adapted so that the processor carries out the following steps: Controlling a vibrator device arranged on an installed pile such that the vibrator device applies a measuring pulse sequence to the installed pile during at least one vibration period, detecting movement data of the installed pile caused by the measuring pulse sequence during a measuring period, determining at least one downward movement data set from the detected movement data, and evaluating the downward movement data set such that a load-bearing capacity criterion is determined (in particular based on at least one verification criterion).

[0064] The computer program product, in particular the instructions or

[0065] Program instructions can be stored in a computer program memory, particularly a program memory. For example, a program memory is a non-volatile memory such as flash memory, magnetic memory, EEPROM (electrically erasable programmable read-only memory), and / or optical memory.

[0066] Additionally, a measuring device may have a main memory, for example, a volatile or non-volatile memory, in particular a random access memory (RAM), such as static random access memory (SRAM), dynamic random access memory (DRAM), ferroelectric random access memory (FeRAM), and / or magnetic random access memory (MRAM). The processor of the measuring device may, for example, store intermediate results or the like in the main memory.

[0067] In particular, the computer program product may comprise a plurality of software modules, in particular at least one previously described control module, one previously described detection module, one previously described determination module and one previously described evaluation module.

[0068] Yet another aspect of the application is a measuring set comprising at least one vibrator device (e.g. comprising at least one motion data sensor attached to the vibrator device) and at least one measuring device with at least one processor configured to execute the computer program product described above.

[0069] A device, module, or apparatus may be formed at least partially from software and / or at least partially from hardware. In particular, a device / element may comprise suitable computing elements (e.g., processor, memory, etc.). Furthermore, it should be noted that terms such as "first" and "second" do not indicate an order, but merely serve to distinguish elements, such as the solidification period.

[0070] The features of the methods, measuring systems, vibrator devices, computer program products, and measuring sets can be freely combined with one another. In particular, features of the description and / or the dependent claims may be independently inventive, even if they completely or partially circumvent features of the independent claims, either alone or in freely combined form.

[0071] There are now numerous possibilities for designing and further developing the method according to the application, the measuring system according to the application, the vibrator device according to the application, the computer program product according to the application, and the measuring set according to the application. Reference is made, on the one hand, to the claims subordinate to the independent claims and, on the other hand, to the description of exemplary embodiments in conjunction with the drawing. The drawing shows: Fig. 1 is a schematic view of an example of an offshore structure with an installed pile, Fig. 2 is a schematic view of an embodiment of a measuring system according to the present application, Fig. 3 is a diagram of an embodiment of a method according to the present application, Fig. 4 is a diagram of another embodiment of a method according to the present application, Fig. 5 is a schematic view of an embodiment of a vibrator device according to the present application, and Fig. 6 is a schematic view illustrating the difference between so-called cavitation vibration piling and non-cavitation vibration piling.

[0072] Similar reference numerals are used below for identical elements. Furthermore, z denotes the vertical axis or direction, and x denotes a horizontal axis or direction.

[0073] The Figure 1shows a schematic view of an example of an offshore structure 180 with an installed pile 102. In the example shown, the installed pile 102 forms the foundation 103 of the offshore structure 180.

[0074] The offshore structure 180 is formed in particular from the foundation 103 and an offshore facility 182. As can be seen from the Figure 1 As can be seen, the offshore structure 180 in this case is an offshore wind turbine 180.

[0075] The offshore wind turbine 180 is, in particular, a conventional wind turbine 180. As an offshore facility 182, the wind turbine 180 has a tower and a nacelle mounted on the tower. With the help of a converter, the wind energy is converted into electrical energy. This is fed into an internal wind farm grid via a transformer and an electrical connection. For example, the generated electrical energy can be fed into an onshore distribution grid via an offshore substation of a wind farm.

[0076] The pile 102 can be made of steel and / or concrete. Preferably, the pile 102 can have a circumferential pile wall. The pile 102 has an upper pile end 104 (in the illustrated installed or inserted state), also called the pile head 104, and a lower pile end 106, also called the pile base 106.

[0077] Reference numeral 114 denotes the water surface, reference numeral 112 denotes the ground surface (in this case, a seabed surface), and reference numeral 110 denotes the soil (in this case, a seabed). As can be seen, an "installed pile 102" means that the pile 102 is installed in the soil 110 at a specific embedment depth 116 (from the ground surface 112 to the pile base 106).

[0078] The method according to the application, described in more detail below, serves to determine whether the installed pile has sufficient (axial) load-bearing capacity. The method according to the application can be carried out, in particular, after the pile has been driven into the ground and before the offshore facility is installed.

[0079] The Figure 2shows a schematic view of an embodiment of a measuring system 200 according to the present application. In one embodiment, the measuring system 200 can be formed by only one measuring device 240. The measuring device 240 can be formed, in particular, by a computer device 240 having at least one processor for executing a computer program product. The computer program product can be formed, in particular, by modules 242, 244, 246, and 248.

[0080] The measuring device 240 comprises at least one control module 242, configured to control a vibrator device 220 arranged on an installed pile 202, such that the vibrator device 220 applies a measuring pulse sequence to the installed pile 202 during at least one vibration period, a detection module 244, configured to detect movement data of the installed pile 202 caused by the measuring pulse sequence during a measurement period, a determination module 246, configured to determine at least one downward movement data set from the detected movement data, and an evaluation module 248, configured to evaluate the downward movement data set such that a load-bearing capacity criterion is determined (in particular based on at least one verification criterion).

[0081] The modules 242, 244, 246 and 248 mentioned may preferably be formed as software modules which can be executed by the processor of the measuring device 240.

[0082] Furthermore, a measuring device 240 may comprise an output module 250 configured to output the evaluation result, such as an assessment of whether the installed pile has sufficient load-bearing capacity or not.

[0083] As can be seen, at least one (wireless and / or wired) communication network 254 can be provided for communication of the measuring device 240 with other components, for example of the vibrator device 220.

[0084] In the present exemplary embodiment, the measuring system 200 (additionally) comprises a vibrator device 220. The vibrator device 220 is configured to generate oscillations / vibrations in the form of a measuring pulse sequence with a specific (maximum) measuring frequency at least during a vibration period. Preferably, the vibrator device 220 can also be used to drive the pile 202 into the ground at an insertion frequency that is, in particular, greater than the measuring frequency.

[0085] The vibrator device 220 shown here as an example is arranged on the pile 202, in particular the pile head 204, via a fastening module 222. In particular, a (temporary) force-locking connection between the vibrator device 220 and the pile 202 can be established by means of the fastening module 222.

[0086] Furthermore, the vibrator device 220 has a first base body 221 (also called an excitor block) and a second base body 232 (also called a suppressor housing) connected to the first base body 221 via elastic damping elements 234. While the first base body 221 also experiences the vibrations, the second base body 232 is essentially decoupled from them by the damping elements 234. A suspension 236, for example, for a crane device, is provided on the second base body 232.

[0087] An eccentric device 226, comprising a plurality of eccentric masses, is arranged in the first base body 221. The eccentric device 226 includes a motor 224 for driving the eccentric masses. The motor 224 is powered by a power supply 228 or a generator 228, which is connected to the second base body 232 via a power line 230. The motor can be powered via a further line (not shown).

[0088] The eccentric masses, which are arranged in pairs, preferably rotate at the same angular velocity but in opposite directions. The at least two eccentrics or eccentric masses can generate centrifugal forces. The horizontal forces can cancel each other out, while the vertical components can add up to a total centrifugal force, thus generating vibrations in a vertical direction, i.e., in the direction of the longitudinal axis of pile 202 (indicated by arrow 225). The resulting impulses or vibrations can be transmitted to the pile due to the force-locking effect, thus generating a multitude of strain or impulse waves.

[0089] To control the motor 224, the vibrator device 220 may include a local controller 238. This controller may, in particular, control the motor 224 of the vibrator device 220 according to the control commands received from the control module 242.

[0090] As can also be seen, at least one motion data sensor 252 can be provided. In particular, the measuring system 200 can comprise the at least one motion data sensor 252. The motion data sensor 252 is configured, in particular, for (continuously) measuring motion data of the pile 202. For this purpose, the motion data sensor 252 (in particular a strain sensor and / or an acceleration sensor) can be (force-lockingly) attached to the pile head. Preferably, two strain sensors and two acceleration sensors can be provided.

[0091] The functionality of the measuring system 200 is explained in more detail below with the help of the Figure 3 described. The Figure 3 shows a diagram of an embodiment of a method according to the present application for assessing the load-bearing capacity of an installed pile 202.

[0092] In a first step 301, a vibrator device 220 arranged (in a force-locking manner) on the inserted pile 202 applies a measuring pulse sequence to the inserted pile 202 for at least one vibration period.

[0093] In particular, a control module 242 can transmit a command data set (containing, for example, the starting time, vibration duration, measurement duration, end time, and / or maximum measurement frequency) to the local controller 238. This particularly controls the vibrator device 220 arranged on the installed pile 202 such that the vibrator device 220 applies a measurement pulse sequence to the installed pile 202 during at least one vibration duration.

[0094] In a further step 302 (which is performed in particular in parallel with step 301), at least one acquisition module 244 acquires movement data of the inserted pile caused by the measurement pulse sequence during a measurement period. Preferably, the acceleration and compression of pulse waves on the pile 202 can be measured as movement data by preferably a plurality of corresponding movement data sensors 252. The measurement signals are provided to the acquisition module 244, which records the movement data in particular at a sampling rate of, for example, at least 10,000 values ​​per second.

[0095] The measurement time is particularly within the vibration time.

[0096] In step 303, at least one downward movement data set is determined from the recorded movement data. In particular, the determination module 246 applies a previously described filter function to the recorded movement data. This allows the movement data or pulse wave data associated with a downward movement of the vibrator device 220 to be determined. This movement data, in particular, forms the at least one downward movement data set.

[0097] Then, in step 304, an evaluation module 348 evaluates the at least downward movement data set in such a way that a load-bearing capacity criterion is determined, in particular based on at least one verification criterion.

[0098] According to a preferred embodiment, the evaluation of the at least one downward movement data set can be carried out by means of modeling based on wave theory, e.g. based on the CAPWAP method, TNOWAVE method or CASE method (these methods are known to the person skilled in the art).

[0099] For example, a pile-soil model (CAPWAP) can be developed by inverse system identification based on the at least one down-movement data set (or signals), from which the static pile resistances (preferably skin friction and / or tip pressure) can then be derived to determine whether there is sufficient (axial) bearing capacity of the installed pile (or not).

[0100] The verification criterion can be a specified ultimate bearing capacity, which must be met in order for an installed pile to be classified as a pile 202 with sufficient (axial) bearing capacity. If this criterion is not met, the axial bearing capacity is insufficient. For example, further measures can then be taken (e.g., pile 202 can be embedded deeper) and, if necessary, the present procedure can be repeated.

[0101] The analysis / evaluation is described in more detail using the CAPWAP method (model analysis), which is generally known to those skilled in the art. CAPWAP (Case Pile Wave Analysis Program) is a so-called signal matching program. This method assumes that the force introduced by the vibrator device during a downward movement and its response are known (from the wave up and wave down curves). This movement data is determined, as described, in step 303.

[0102] However, the static and dynamic soil model is not initially known in this procedure. This is determined during the evaluation. In particular, the following steps are performed during the evaluation in step 304: 1. Create a pile model and make initial assumptions for the skin friction and the toe friction. 2. Use the determined and previously measured compression and / or acceleration data as the basis for calculating the corresponding force. 3. Then, the calculated force is compared with the measured force. 4. Based on the comparison result, the skin friction and the toe friction are adjusted.

[0103] In particular, steps 2 to 4 are repeated until sufficient agreement is achieved in step 3.

[0104] Then, as described, it can be determined on the basis of a verification criterion whether the installed pile 202 has sufficient axial load-bearing capacity or not.

[0105] The Figure 4shows a diagram of another embodiment of a method according to the present application. To avoid repetition, only the differences from the previous embodiment are described below. The method according to Figure 4 includes in particular an installation procedure.

[0106] In a first step 401, a pile is installed at a specific installation location. In particular, the pile is driven into the ground by a vibrator device that is force-fitted to the pile head, in particular to a specific embedment depth.

[0107] After the pile has been driven and before the measuring pulse sequence is applied to the driven pile (step 403), the driven pile may not be subjected to pulses or vibrations by the vibrator device for a (specifiable) first settling time period in step 402. For a particularly accurate assessment, it is preferable to wait until after the pile has been driven to the determined embedment depth before applying vibrations for the measurement until it is ensured that the soil around the pile has (sufficiently) settled. The first settling time period therefore represents, in particular, the period during which no pulses are transmitted to the pile by the vibrator device.

[0108] Particularly preferably, the duration of the hardening time can be determined depending on the type of soil (in particular underwater soil type) at the installation site of the pile, wherein the first hardening time can in particular be between 10 minutes and one week, preferably between one hour and one day.

[0109] After the first hardening period has elapsed, in step 403 the pile is subjected to vibrations in the form of the measuring pulse sequence, as described in step 301.

[0110] In step 404, movement data of the inserted pile caused by the measuring pulse sequence are recorded during a measuring period, as described in particular in step 302.

[0111] The maximum measuring frequency of the measuring pulse sequence during the measuring period can preferably be at least below a specified cutoff frequency. The cutoff frequency can, in particular, be selected to ensure that the soil at the installation site does not (re)liquefy, thus causing the pile to sink deeper.

[0112] According to the invention, a maximum measurement frequency of the measurement pulse sequence (during the measurement period) is a maximum of 80% of the insertion frequency, preferably a maximum of 60% of the insertion frequency, particularly preferably a maximum of 40% of the insertion frequency. The insertion frequency refers in particular to the frequency (maximum during insertion) with which the pile was inserted to the determined insertion depth in step 401. It should be noted that the insertion frequency depends in particular on the soil type at the pile's installation location. Accordingly, the maximum measurement frequency depends on the soil type.

[0113] In addition, a maximum measuring frequency of the measuring pulse sequence can be at most 10 Hz during the measuring period, preferably at most 8 Hz, particularly preferably at most 6 Hz. The measuring frequency can be between 1 Hz and 10 Hz during the measuring period, preferably between 2 Hz and 8 Hz, particularly preferably between 3 Hz and 7 Hz.

[0114] For a particularly precise and effective evaluation, the measurement duration can be between 0.5 minutes and 20 minutes, preferably between 2.5 minutes and 15 minutes, and particularly preferably between 2.5 minutes and 7.5 minutes. The measurement duration can depend at least on the soil type (as can the application time).

[0115] In step 405, at least one downward movement data record is determined from the acquired movement data, as described in step 303.

[0116] In the present exemplary embodiment, after the detection (and the determination, which can take place in parallel with the detection), that is to say in particular after the measuring time period and after a decay time period, a step 406 takes place in which the pile is not subjected to vibrations.

[0117] After this second solid growth period, which may in particular be shorter than the first solid growth period, the (previously described) steps of applying (403), detecting (404), and determining (405) can be performed again. In particular, this test procedure, i.e. applying (403), detecting (404), and determining (405), can be performed several times, each interrupted at least by the specified decay time and the second solid growth period.

[0118] The said second waxing time period may in particular be shorter than the first waxing time period and may, for example, be between 1 minute and 10 minutes.

[0119] Subsequently, a (joint) evaluation of the respective downward movement data sets can be performed in step 407 (cf. step 304). Appropriate testing can provide a more precise evaluation.

[0120] The assessment result can then be output in step 408 and, for example, presented to a user via a display.

[0121] In another embodiment (not shown), the following steps may be provided after step 401: After driving the pile to a specific embedment depth, releasing a force-locking connection between the vibrator device and the pile, maintaining the released force-locking connection between the vibrator device and the pile during a settling time period, wherein the application of a measuring pulse sequence to the driven pile during at least one vibration time period comprises re-establishing the force-locking connection between the vibrator device and the pile during the vibration time period.

[0122] The Figure 5 shows a schematic view of an embodiment of a vibrator device 520 according to the present application. To avoid repetition, only the differences from the embodiment of a vibrator device 220 according to the Figure 2 described.

[0123] The key difference is that the motion data sensors 560, 562 (in particular, two strain gauges 560 and two acceleration sensors 562) are permanently and in particular non-removably attached to the vibrator device 520. For example, the at least one motion data sensor 560, 562 can be attached to the outside of the vibrator device 520.

[0124] As from the Figure 5 As can be seen, the at least one motion data sensor 560, 562 is attached to a part 521 of the vibrator device 520, which also experiences the vibrations (almost undamped). For example, the at least one motion data sensor 560, 562 is attached to the first base body 521, which includes the eccentric device 526. The generated oscillations or vibrations, particularly in the form of the measuring pulse sequence, are transmitted to the pile via the at least one fastening module 522, which can be connected to a pile in a force-locking manner. In Accordingly, the pulse waves reflected by the pile base can be transmitted to the vibrator device 520, in particular the fastening module 522 and the first base body 521, and measured by the at least one motion data sensor 560, 562.

[0125] In other variants of the application, the at least one motion data sensor can alternatively or additionally be attached to a different position, for example to the attachment module.

[0126] A measuring device 540 can be communicatively connected to the at least one motion data sensor 560, 562. In variants of the application, the measuring device can also be arranged on the vibrator device and / or encompassed by it and, for example, transmit the at least one evaluation result to at least one user terminal.

[0127] According to the application, a pile can be driven into the ground to a specific final / target depth using a vibrator / vibration device, which may involve switching off the vibration system.

[0128] During the last few centimeters of the penetration process, motion data from the motion data sensors (preferably strain and / or acceleration) attached to the pile can be recorded using a data logger. This process is known as "end of driving" and particularly characterizes the EoD value. Subsequently, the method according to the application, which can also be referred to as a dynamic vibro-restrike test, is carried out. In particular, the following procedure can be used (as already described): Wait until the soil has "settled" or become firmly established, i.e., the built-up pore water excess pressure has at least largely settled back to its original level (i.e., prior to pile installation). Depending on the soil conditions, the duration / firmness-setting period can range from a few minutes to several hours, or even days. However, premature conduct of the Vibro-Restrike test is always possible; however, the results must then be evaluated accordingly. Following this, the vibrator / vibration device is briefly moved onto the pile for a few seconds to a few minutes, while simultaneously the motion data sensors attached to the pile record the motion data using a logger / acquisition module. Significant (further) subsidence of the pile is not expected here and can, if necessary, be prevented by switching off the vibrator in good time.

[0129] The process described above can be repeated after several days or even several weeks in order to determine and, in particular, to demonstrate a possible growth effect of the pile.

[0130] The vibration frequency during the installation of offshore piles can typically range between approximately 10 and 25 Hz. This installation frequency can depend, in particular, on the penetration depth and the condition and / or type of soil. When the vibrator is restarted, i.e., when the pile is subjected to a measuring pulse sequence (for the vibro-restrike test), this can be done in such a way that the maximum measuring frequency is (significantly) lower than in the continuous process. Reduced system frequency values, preferably above 40%, are conceivable in this case.

[0131] Furthermore, it is assumed that, for the evaluation of the recorded movement data, performing cavitational vibration ramming is advantageous for the determination module to clearly identify the downward movement data. Therefore, according to a preferred embodiment, cavitational vibration ramming is performed.

[0132] Again Figure 6 can be removed, in contrast to non-cavitation vibration ramming ( Fig. 6b) a loss of contact during cavitational vibration ramming ( Fig. 6 a) between the ground and the pile during the upward movement. This knowledge can be used in the filter function so that the desired movement data of a downward impulse can be determined / identified with greater accuracy.

[0133] Using a vibrator / vibrator device, piles can be driven into the ground quickly and quietly. The vibrator, in particular, uses at least two rotating imbalances to generate a rapid sequence of up and down movements (oscillations or pulse sequences), which partially liquefies the soil.

[0134] This method allows the force and velocity of the penetration process at the pile head to be recorded on the vibrated pile at a high sampling rate. This high sampling rate allows individual downward movements to be clearly identified with sufficient measured values. The evaluation of this specific movement data is carried out primarily using comprehensive modeling based on wave theory (e.g., CAPWAP or TNOWAVE methods).

[0135] As a result, the resistance-settlement curve and / or the distribution of pile shell and pile toe resistance can be determined. Disturbing influences from upward movement can be eliminated mathematically (e.g., using the filter function) if necessary. To ensure that the pile resistance can also be recorded after the installation process, the vibrator can be restarted at least once after a specified period of time, and the resistance to the pile's downward movement can be measured in the "settled" soil. The actual load-bearing capacity of the pile can thus be determined at the selected time.

Claims

1. A method for assessing the load bearing capacity of an inserted pile (102, 202), , comprising: - inserting the pile (102, 202) by a vibrator device (220, 520) with a maximum inserting frequency, - applying, by the vibrator device (220, 520) arranged at the inserted pile (102, 202), after the insertion of the inserted pile (102, 202) with a measuring pulse string during at least one vibration time period, wherein a maximum measuring frequency of the measuring pulse string is at most 80 % of the maximum inserting frequency, - detecting, by at least one detection module (244), motion data of the inserted pile (102, 202) caused by the measuring pulse string during a measuring time period, - determining at least one downward motion data set from the detected motion data; and - evaluating the downward motion data set such that a load bearing capacity criterion is determined.

2. The method according to claim 1, characterized in that - the motion data is detected at a sampling rate of at least 10,000 values per second, in particular at a sampling rate of at least 40,000 values per second.

3. The method according to claim 1 or 2, characterized in that - the maximum measuring frequency of the measuring pulse string is at least below a limit frequency.

4. The method according to any one of the preceding claims, characterized in that - the maximum measuring frequency of the measuring pulse string is at most 60 % of the inserting frequency, particularly preferably at most 40 % of the inserting frequency.

5. The method according to any one of the preceding claims, characterized in that - the maximum measuring frequency of the measuring pulse string is at most 10 Hz, preferably at most 8 Hz, particularly preferably at most 6 Hz.

6. The method according to any one of the preceding claims, characterized in that - the measuring time period is between 0.5 minutes and 20 minutes, preferably between 1.5 minutes and 15 minutes, particularly preferably between 2.5 minutes and 7.5 minutes.

7. The method according to any one of the preceding claims, characterized in that - before applying the measuring pulse string to the inserted pile (102, 202) for a fixed growth time period, the inserted pile is not applied with pulses by the vibrator device (220, 520).

8. The method according to claim 7, characterized in that - the fixed growth time period is determined depending on the underwater soil type at the installation site of the pile (102, 202), - wherein the fixed growth time period is in particular between 10 minutes and one week, preferably between one hour and one day.

9. The method according to any one of the preceding claims, characterized in that the method further comprises: - releasing, after inserting of the pile (102, 202) to a specified anchoring depth, a force-fit connection between the vibrator device (220, 520) and the pile (102, 202), - maintaining the released force-fit connection between the vibrator device (220, 520) and the pile (102, 202) during a fixed growth time period, - wherein applying a measuring pulse string to the inserted pile (102, 202) during at least one vibration time period comprises re-establishing the force-fit connection between the vibrator device (220, 520) and the pile (102, 202) during the vibration time period.

10. A measuring system (200), comprising: - a vibrator device (220, 520) configured to insert a pile (102, 202) with a maximum inserting frequency, - at least one control module (242) configured to control the vibrator device (220, 520) arranged at the inserted pile (102, 202) in such a way that the inserted pile (102, 202) is applied with a measuring pulse string by the vibrator device (220, 520) during at least one vibration time period, wherein a maximum measurement frequency of the measuring pulse string is at most 80% of the maximum inserting frequency, - at least one detection module (244) configured to detect motion data of the inserted pile (102, 202) caused by the measuring pulse string during a measuring time period, - at least one determination module (246) configured to determine at least one downward motion data set from the detected motion data, and - at least one evaluation module (248) configured to evaluate the downward motion data set such that a load bearing capacity criterion is determined.

11. The measuring system (200) according to claim 10, characterized in that - the measuring system (200) comprises at least one vibrator device (220, 520) that is connectable to a pile (102, 202) in a force-fit manner, - wherein at least one motion data sensor is arranged at the vibrator device (220, 520).

12. A computer program product having instructions executable on a processor, wherein the instructions are adapted to cause the processor to perform the following steps: - controlling a vibrator device (220, 520) for inserting a pile (102, 202) with a maximum inserting frequency - controlling the vibrator device (220, 520) arranged at the inserted pile (102, 202) in such a way that the vibrator device (220, 520) applies a measuring pulse string to the inserted pile (102, 202) during at least one vibration time period, wherein a maximum measurement frequency of the measuring pulse string is at most 80% of the maximum inserting frequency, - detecting motion data of the inserted pile (102, 202) caused by the measuring pulse string during a measuring time period, - determining at least one downward motion data set from the detected motion data; and - evaluating the downward motion data set such that a load bearing capacity criterion is determined.