Apparatus and method for cone penetration testing of soils

Abstract

The invention relates to a cone penetration test device comprising a probing cone (1), and in particular a peripheral friction sleeve (2), a probe with an inclinometer and a pore pressure gauge, a transmission linkage (4, 5, 6) connected to the probe at one of its ends (7) and configured to push the probe into the soil area to be probed by applying pressure, and a seismic measurement device (9, 10, 11, 12) for acquiring seismic signals. The aim of acquiring seismic measurement data through several channels is achieved by a seismic measurement device comprising several seismic sensors (e.g. pressure sensors, accelerometers, geophones) (9, 10, 11, 12) integrated in one or several elements (4, 5, 6) of the transmission linkage and spaced apart from one another along the longitudinal direction of the transmission linkage. The various seismic pressure sensors may feed their measurement data to a shared signal conductor (15).

Description

[Technical field]

[0001] The invention belongs to the field of measuring instruments and is used with particular advantage during soil probing.

[0002] For example, in geotechnical investigations of soils in onshore and offshore areas, a test known as the Cone Penetration Test (CPT) is often employed in which a probe is driven into the ground. The probe usually has a cone shape with an apex angle of 60° at its tip, and as the probe is driven in, a measurement of the penetration force at the tip of the probe is taken to obtain information about the properties of the soil.

[0003] The measured data is usually transmitted by means of a data cable to a measuring station located at the surface, for example in a test vehicle or on a ship. If provision is made to use a transmission linkage for introducing the probe to deeper soil depths, which is successively assembled as the penetration depth progresses, such a data cable is run through the cavity of a tubular linkage or is already threaded through the transmission linkage at the beginning of the probing process. There are also alternatives to the transmission linkage, for example the coiled rod method and the downhole CPT method.

[0004] If seismic pressure sensors or geophones, also introduced into the soil, are added to the probe instrumentation, it becomes possible to carry out continuous seismic surveys at various depths (seismic CPT), in each case while the probe remains in situ. In this process, pulses are introduced into the soil from the surface, or from the seabed in the case of offshore applications, and the signal reaching the seismic sensor is measured.

[0005] An apparatus and method for performing geotechnical investigations is known from publication DE 10 2020 001 184 A1, in which other methods are employed for transmitting measurement data from a probing device to a data processing device. The document mentions, for example, the option of establishing wireless data transmission by means of a battery-powered transmitter integrated in the probe, or, in another variant, the option of storing the measurement data in the probe and subsequently reading said data out after the probing process is completed and the probe is removed.

[0006] SUMMARY OF THE DISCLOSURE OF THE DISCLOSURE Against the background of the prior art, it is an object of the present invention to improve and extend the capture of measurement data, particularly seismic data, and its provision to a data processing device of a cone penetration test apparatus.

[0007] This object is achieved according to the invention by a cone penetration test device having the features of claim 1. The dependent claims present advantageous embodiments of such a cone penetration test device. The invention also relates to a method for cone penetration testing.

[0008] The invention therefore relates to a cone penetration testing device comprising a probe having a probing cone, and in particular a circumferential friction sleeve, and more particularly an inclinometer, a transmission linkage connected to said probe at one of said ends and configured to push said probe into the soil area to be probed while applying pressure, and a seismic measuring device for capturing seismic signals. According to the invention, this object is achieved by said seismic measuring device comprising a number of seismic sensors integrated in several elements of said transmission linkage and spaced apart from one another along the longitudinal direction of said transmission linkage.

[0009] The transmission linkage may comprise a number of rods or tubes arranged axially side by side and connected to one another, which form the elements of the transmission linkage.

[0010] A number of seismic sensors, e.g. geophones, multi-component sensors, accelerometers, are provided along the transmission linkage and are simultaneously available for measurements after being introduced into the soil, so that seismic measurements can be made by sensors located at various soil depths at a position of the transmission linkage, for example while the advancement of the probe is interrupted. These measurements can be made simultaneously or successively at short intervals at various, several or all of the seismic sensors. In this way, a number of measurements can be obtained that are individually or collectively meaningful for the various soil depths. This significantly improves the measurement data acquisition of seismic data compared to known methods, since it is not necessary to repeatedly interrupt the advancement of the probe or the transmission linkage to make seismic measurements. Also, the relative positions of the seismic sensors with respect to each other along the transmission linkage are known. Since the seismic sensors are distributed among several elements of the transmission linkage, a sufficient distance between the sensors can be created, which ensures that the measurements are of sufficiently high quality. According to the method of the invention, one depth measurement is sufficient to obtain this information, which allows to measure the depth of one of the subsurface seismic sensors, the depths of the remaining sensors can be derived from their known relative positions. An inclinometer integrated in the probing device can be used to monitor and measure the forward heading angle, thus ascertaining more accurate data regarding the sensor depths.

[0011] The seismic sensors may be distributed among several, in particular at least two or three, elements of the transmission linkage, so that the sensors can be at a greater distance from each other, making it possible to perform initial measurements already before all the elements of the transmission linkage are introduced into the soil.

[0012] A probing cone is placed at the tip of the cone penetration test device, which greatly facilitates the penetration of the probe and the transmission linkage into the soil. The probing cone is usually provided with a force measuring unit, which allows the thrust force to be measured continuously. In a manner also known, a peripheral friction sleeve may also be provided behind the probing cone, which allows the peripheral friction to be measured during the forward movement of the probe. In addition to the inclinometer, it is also possible to provide a measuring device for the pore water pressure in the vicinity of the probing cone, usually between the probing cone and the peripheral friction sleeve, in order to be able to measure the pore pressure. The seismic sensor is suitable for recording the various modes of seismic waves. It is possible to provide two or three, four or more such seismic sensors, each capturing both P and S seismic waves.

[0013] The cone penetration test device may advantageously be configured in that at least some of the seismic sensors are arranged on the sides of one or more elements of the transmission linkage arranged side by side in the longitudinal direction. For this purpose, the elements of the transmission linkage may be designed as tubes having a borehole through their wall, into each of which a seismic sensor is inserted so as not to protrude beyond the tube wall in the radial direction.

[0014] The sensor may advantageously be placed slightly recessed in the exterior side of the element of the transmission linkage, and it may advantageously be provided that the surface of the seismic sensor at the exterior side of one or more elements of the transmission linkage is covered with a protective layer, in particular made of a plastic material, more particularly of an epoxy resin. Such a coating may also be provided when the surface of the seismic sensor terminates at the side of the element of the transmission linkage. In this case, the layer should be designed so that it does not create, or only creates a minimal amount of additional friction resistance during the advancement of the transmission linkage.

[0015] The cone penetration test apparatus may be further advantageously configured in that each of the seismic sensors is connected to a signal conductor for transferring a measurement signal to a second end of the transmission linkage positioned opposite the first probe end or probing tip, and / or each seismic sensor includes a unit for digitizing and / or modulating a signal for said transmission via the signal conductor.

[0016] The measurement signals of the seismic sensors are to be conducted to a second end of the transmission linkage, located opposite the probing tip, to which a data processing device is made available. For this purpose, individual signal conductors may be provided for each seismic sensor; however, it is also possible to collectively utilize the signal conductors of several seismic sensors to transfer the signals of several seismic sensors. For example, a line comprising several individual conductors, each of which conducts one of the signals of the seismic sensors, may be provided as signal conductor. It is also possible to provide a conductor for supplying a supply voltage to the seismic sensors.

[0017] For this purpose, it can be provided, for example, that the signal conductors are in each case integrated into the elements of the transmission linkage, in particular arranged in a central cavity or in a wall of the elements. The individual signal conductors can, for example, be threaded through the not yet assembled transmission linkage and / or already connected to the individual elements of the transmission linkage before the cone penetration test is carried out. For this purpose, the signal conductors can, for example, be located in the inner cavity of a tubular element of the transmission linkage or can be attached to the inner wall of the element or to the outside of the element.

[0018] Particularly advantageously, it may be provided that the signal conductors are composed of signal conductor sections which are removably connected to one another at the ends of the elements of the transmission linkage, the signal conductor sections being terminated in each case in particular in plug connection elements connected to each end of the elements of the transmission linkage. The plug connection elements may have a multi-pole design to establish a connection for each seismic sensor and the signal conductors assigned thereto. In general, the signal conductor sections may be connected to one another, for example, by means of plug or screw connections or by bayonet catches. This obviates the need to introduce long signal conductors into the elements of the transmission linkage to be used before introducing the transmission linkage, the signal conductor or conductors being respectively connected to a part of the signal conductor / several signal conductors already introduced in the soil, the individual elements of the transmission linkage being added successively. As a result, for example, it is not necessary to predefine a maximum measurement depth for the selection of signal conductors, and the overall length of the signal conductors can be adapted based on the development of the measurement project. In this way, the use of excessively long data cables is avoided and individual sections can be easily replaced in the event of a malfunction.

[0019] Instead of several parallel signal conductor sections, it is also possible to use a single longitudinally split signal conductor, in which case one or several seismic sensors are connected to it. However, it is also possible to assign a dedicated signal conductor to each of the seismic sensors. In this case, several signal conductors may run parallel to one another through the transmission linkage.

[0020] Advantageously, it may be provided that the signal conductor sections are formed by one or more electrically insulated electrical conductors and / or light guides. The individual signal conductor sections may accordingly be assembled, for example, in the context of a plug connection, or they may be soldered to one another, adhesively joined in a conductive manner or welded to one another. Advantageously, screw connections are also conceivable. If the signal conductor is a light guide, connections are also known which can be readily established to the light guide.

[0021] The seismic sensors may already be installed and connected to the signal conductors during production of the elements of the transmission linkage. In case of multi-pole signal conductors, the seismic sensors may be identified by the conductor poles assigned thereto. In case of a bus solution, an identification code may be assigned to the respective sensor for transmission.

[0022] The measurement signal may be transmitted, for example, in the form of a voltage signal via one or more signal conductors, and the data may be transmitted, for example, by voltage level, but also by AC voltage signal, in encoded form, by frequency or in digitalized form. For this purpose, each of the seismic sensors as well as the probe or probing cone and the peripheral friction sleeve, as well as the pore pressure measuring device, may be equipped with an analog / digital converter for digitalizing the measurement data. If the data of the individual seismic sensors are transmitted in encoded digital form or transmitted continuously in a time division multiplexed manner, it is also possible to provide only a few signal conductors, in the extreme case only a single signal conductor, along the transmission linkage for data transmission. Encoding the signal ensures that each sensor, and therefore also the measuring point, can be assigned to an individual signal.

[0023] In a particular embodiment of the invention, it may for example be provided that the signal conductor section is formed by the element of the transmission linkage, in which case an electrical signal, for example in the form of a digital voltage signal, may be transmitted by the element of the transmission linkage.

[0024] In addition to the cone penetration test apparatus described above, the present invention also relates to a method for probing using such a cone penetration test apparatus, wherein the signal conductor is made up of signal conductor sections, and the elements of the transmission linkage are assembled successively as the penetration depth of the probe increases, the signal conductor sections also being connected to each other in the process.

[0025] The present invention further relates to a method for using the cone penetration test apparatus described above, wherein after at least a portion of the transmission linkage has been introduced, the penetrating movement of the probe is interrupted and one or more seismic measurements are taken using a number of pressure sensors spaced from one another in the longitudinal direction of the transmission linkage. [Brief description of the drawings]

[0026] The invention is illustrated and explained hereinafter on the basis of exemplary embodiments in the figures, in which: FIG.

[0027] [Figure 1] FIG. 2 is a schematic longitudinal section of a probe comprising elements of a transfer linkage; [Diagram 2] FIG. 2 shows a schematic diagram of a probe with several elements of a transfer linkage prior to assembly; [Diagram 3] FIG. 1 shows a longitudinal section of an element of a transfer linkage mechanism comprising two seismic sensors. [Figure 4] FIG. 2 shows the two elements of the transfer linkage before they are joined together. [Diagram 5] FIG. 13 shows elements of a transmission linkage including a seismic sensor. [Figure 6] FIG. 13 is a diagram showing an application to offshore as an example of application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] FIG. 1 shows a partially longitudinally cut view of a probe with a probing cone 1, a peripheral friction sleeve 2 and a filter element 3 for pore pressure measurement, which together form a probe that is pushed into the soil to be investigated. The probe is connected to a first element 4 of a transmission linkage designed as a tube. The seismic sensors / geophones 9, 10, 11 are arranged in the wall of the tube and are attached in openings that penetrate the tube wall. The reference number 13 designates an insulating layer that covers and embeds the seismic sensors. A signal conductor 15 is arranged inside a cavity 19 of the element 4 of the transmission linkage. The signal conductor 15 is divided in the longitudinal direction corresponding to the length of the element 4 of the transmission linkage, the individual signal conductor sections being connected to each other by means of removable connections, as will be explained in more detail below. In FIG. 1 a screw thread 22 is shown that is used to connect the signal conductor sections designed as coaxial conductors.

[0029] 2 shows a schematic representation of the probe 1, 2 and the transmission linkage, which consists of two elements 4, 5 and has a first end 7 connected to the probe 1, 2 and a second end 8 opposite the probing tip, which is close to the ground or soil surface during the measurement process and in particular at its top protrudes from the soil. A signal conductor 15 runs longitudinally inside the elements 4, 5 of the transmission linkage, in each case being connected by means of a plug connection element 20, 21 at the transition between the two elements 4, 5 of the transmission linkage. The signal conductor 15 may be designed, for example, as a single insulated conductor, as a conductor bundle or as a light guide. A design as a waveguide, for example in the form of a coaxial cable, is also conceivable.

[0030] Various seismic sensors 9, 10, 11 distributed along the length of the transmission linkage between the various elements 4, 5 of the transmission linkage are connected to a signal conductor 15. One or more seismic sensors 9, 10, 11 may be provided on a single element 4, 5.

[0031] The signal conductors may be formed by a signal bus which may have a single-pole or multi-pole design and may include voltage supply units used for operating the communication modules of the individual seismic sensors, for example in the form of an analog / digital converter, an encoder or a frequency converter.

[0032] FIG. 3 shows two examples of integrating a seismic sensor into the wall of the element 6 of the transmission linkage. The seismic sensor 10 is arranged in a continuous opening in the wall of the tubular element 6 in such a way that it forms a recess so that its surface is positioned behind the side of the tube. The resulting cavity is filled with a covering layer 13, for example made of epoxy resin, so that the sensor 10 is protected from environmental conditions. A second seismic sensor 11 is arranged in the opening of the element 6 so that it terminates on the peripheral surface of the element 6. Also provided is a covering layer 14, for example made of epoxy resin, which covers both the seismic sensor 11 and the adjacent part of the tubular element 6. The layer 14 should be dimensioned so that it does not prevent the transmission linkage from penetrating the soil, but has a sufficient thickness and stability to protect the seismic pressure sensor. Each of the two sensors 10, 11 is connected to a signal conductor 15 in a cavity 19 of the element 6.

[0033] 4 shows an exemplary embodiment in which the signal conductor is made up of two or more signal conductor sections 16, 17 which are fixedly connected to the walls of the elements 4, 5 of the transmission linkage, for example being located in grooves on the inside of the tube walls of the elements 4, 5 or attached to the inside of the walls of the elements 4, 5 by gluing. Each of the signal conductor sections 16, 17 terminates in a plug connection element 20, 21 which is likewise fixedly connected at its other end to the elements 4, 5 of the transmission linkage, so that the plug connection elements 20, 21 can likewise be securely coupled when the elements 4, 5 of the transmission linkage are connected.

[0034] The signal conductor may be held in the center of the cavity of the element of the transmission linkage, for example by a spacer against the cylindrical inner wall, thus preventing damage to the signal conductor when two adjacent elements of the transmission linkage are connected.

[0035] 5 shows an embodiment of the present invention in which a seismic pressure sensor 12 is arranged in an electrically isolated manner on the wall of the transmission linkage element 5. An electrical insulation layer 23 is provided which provides both electrical insulation of the sensor 12 against the metal tube of the element 5 and mechanical protection at the sides of the transmission linkage element.

[0036] The sensor 12 further comprises a transducer 18 which converts the measurement signals into digital signals and feeds the electric signal thus formed to the element 5 of the transmission linkage, or more precisely to the wall of the element 5, by means of a feed line 24. The elements 4, 5, 6 of the transmission linkage can thus function as a signal conductor as a whole after being combined. If, for example, the measurement signals are converted into high-frequency digital signals, these can thus be transmitted without interruption via the transmission linkage. It is therefore also possible to transmit the signals of the various seismic sensors separately from one another using a time-division multiplexing solution.

[0037] Figure 6 shows an offshore application of a probe with a multi-part transmission linkage, where transmitters 28, 29 for seismic pulses may be provided on the vessel 26 and / or on the seabed foundation 27. The transmission linkage 30 is shown in an enlarged form in the right part of the figure. The transmission linkage comprises a probing cone and transmission linkage elements 30, 31, 32, where one or more sensors 9a, 10a, 11a may be provided on each of the transmission linkage elements 31, 32.

[0038] In this exemplary embodiment, the sensor is located inside the element of the transmission linkage and, as is evident from the cross-sectional view of the sensor 11a, may be located and attached inwardly, but also radially inwardly, with respect to the side of the element, for example centrally on the central axis of the transmission linkage, in which case the sensor may be attached, for example, via a retaining element on the inner side of the element of the transmission linkage, in particular a web or lug 25. The attachment may be configured in such a way that a suitable acoustic coupling occurs.

Claims

1. A cone penetration test apparatus comprising a probe having a probing cone and in particular a circumferential friction sleeve and more in particular an inclinometer, a transmission linkage connected to the probe at one of its ends and configured to push the probe into the soil area to be probed by applying pressure, and a seismic measurement device for capturing seismic signals, the seismic measurement device having a plurality of seismic sensors integrated into a plurality of elements of the transmission linkage and spaced apart from one another along the longitudinal direction of the transmission linkage.

2. 2. The cone penetration test apparatus of claim 1, wherein at least some of the plurality of seismic sensors are disposed on sides of one or more elements of the transfer linkage that are arranged side by side in the longitudinal direction.

3. 3. The cone penetration test device of claim 2, wherein the surfaces of the seismic sensors on the outer sides of the one or more elements of the transmission linkage are covered with a protective layer, in particular made of a plastic material, more particularly an epoxy resin.

4. 4. A cone penetration test apparatus as claimed in any one of claims 1 to 3, wherein each of the plurality of seismic sensors is connected to a signal conductor for transferring a measurement signal to a second end of the transmission linkage positioned opposite the probe-side first end, and / or each seismic sensor includes a unit for digitizing and / or modulating a signal for transmission via the signal conductor.

5. 5. A cone penetration test device according to claim 4, in which the signal conductors are in each case integrated into an element of the transmission linkage, in particular arranged in a central cavity or in a wall of said element.

6. 5. A cone penetration test device as claimed in claim 4, wherein the signal conductor is made up of signal conductor sections which are removably connected to each other at the ends of the elements of the transmission linkage, the signal conductor sections terminating in each case specifically in plug connection elements connected to each end of an element of the transmission linkage.

7. 7. The cone penetration test device of claim 6, wherein the signal conductor section is formed by one or more electrically insulated electrical conductors and / or light guides.

8. The cone penetration test apparatus of claim 6 , wherein the signal conductor section is formed by the plurality of elements of the transfer linkage.

9. 4. A method for probing using a cone penetration test apparatus as claimed in any one of claims 1 to 3, wherein the signal conductor is made up of signal conductor sections, in which the elements of the transfer linkage are successively coupled as the penetration depth of the probe increases, the signal conductor sections also being connected to each other in the process.

10. 4. A method for probing using a cone penetration test apparatus as claimed in any one of claims 1 to 3, wherein after at least a portion of the transmission linkage has been introduced, motion of the probe is interrupted and one or more seismic measurements are taken using a number of pressure sensors spaced from each other along the length of the transmission linkage.

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