Technical Field

[1 ] The present invention relates to a device for performing a soil investigation test on a seafloor, more particularly a seafloor device for facilitating soil testing from the seabed.

Background of the Invention

[2] Geotechnical surveys are commonly performed to obtain information on soil properties. This information is used in myriad applications, ranging from site investigation for building structures to offshore drilling. It is often required to obtain soil samples or data on soil properties from different depths and in areas with limited accessibility.

[3] Obtaining soil data from the seafloor (i.e. the seabed) presents further challenges. At great water depths, it becomes necessary to build up a larger string in order to reach and penetrate the seafloor. Additionally, it is important to transmit the information obtained at the seafloor, such as soil resistance, to a terminal above sea level. It is preferred to transmit the data during the test to monitor if the equipment is working correctly, the test is performed as planned and no irregularities occur. It is observed that, in the present document, the terms“sea” and “seafloor” are to be understood in a broad sense. It is intended to cover all larger amounts of water including lakes, seas and oceans.

[4] In known systems developed for sampling the seafloor, a plurality of rods are connected on a vessel, and an umbilical wire is fed through the centers of the rods. One end of the wire is communicatively coupled to sensors at the soil testing equipment, whilst the other is communicatively coupled to a terminal in a vessel or on land.

[5] Soil testing equipment can include a variety of testing methods, e.g. cone penetration testing (CPT) and vane testing. In this document, soil testing such as CPT is described. CPT is a testing procedure in geotechnical research for measuring soil properties. A cone is pushed into the soil at a constant speed. During this operation the resistance of the cone, soil friction along the sleeve and potentially other parameters are measured and recorded. To this end, a test string is constructed with a cone on a ground penetrating end. The cone is fitted with sensors used to measure soil resistance and other soil properties. Rod sections are attached to the cone in order to extend the test string.

[6] NL 2002608 discloses a CPT string comprising a plurality of rod sections which communicate with each other. Each rod section comprises communication means for communicating with the adjacent rods. The uppermost rod section is configured to communicate with a control cabin. The power sources in each rod section require batteries and/or charging capabilities, which may additionally introduce environmental concerns. The need for each rod section to communicate in this way with its neighboring rod sections may further lead to problems in reliability. [7] The increased weight can impose further restrictions on vessels deploying the CPT string, and complicates recovery of the CPT string. Additionally, the system is susceptible to technical failure, as it is essential for each communication unit (i.e. in each rod section) to be working properly. Otherwise, the data from the seafloor may not reach the control cabin.

[8] There is therefore a need for a device with a more reliable communication system.

[9] Additionally, known systems require wired communication means for obtaining data during the CPT testing process. It is difficult to assemble CPT rods with a pre-rigged wire from an unmanned subsea system. Additional length of wire is needed to allow for handling and storage of the rods. New rods need to be handled and inserted with the wire already inserted. This has practical problems in the additional length that needs to be handled, and the loose wire can get tangled, caught or damaged during the assembly phase.

[10] There is therefore a need to enable automated assembly of the device on the seafloor.

Summary of the Invention

[11] The present invention seeks to address the problems and disadvantages described above.

[12] The above advantages are provided by enabling the transmission of a light signal from the soil penetrating end of a test string to a control unit at an opposite end of the test string. In this way, the communication system is not reliant on wires and the disadvantages found with wire- based systems are avoided.

[13] In a first aspect of the invention, there is therefore provided a device for performing a test to determine soil properties from a seafloor. The device comprises a cone rod unit comprising a cone rod interface unit, the cone rod interface unit comprising at least one first light source configured to generate a first light signal containing first data. The device further comprises a control unit, comprising a first sensor configured to detect the first light signal containing said first data, and a communication unit configured to transmit and receive data to and from a data acquisition unit. The device further comprises one or more intermediate rod units arranged between the cone rod unit and the control unit, configured to guide said first light signal from the cone rod interface unit to the first sensor of the control unit.

[14] The device is thus configured to guide a light signal from a cone rod unit to a control unit, via one or more intermediate rod units. The use of a light signal removes the need for wires, which may introduce problems with reliability.

[15] In an embodiment, the first light signal may comprise a modulated signal where the

modulation is at least one of time modulation, frequency modulation, phase modulation and amplitude modulation. These are only examples of a modulation that can be used. Digital modulation is preferred as this does not suffer from degradation of the information when the signal-to-noise ratio of the channel decreases. The choice of modulation is based on:

efficiency (power needed for a minimum acceptable bit error rate), ease of implementation, and the communication channel characteristics. [16] Advantageously, the device can be further configured such that the cone rod unit further comprises a first light guiding element, and/or each intermediate rod unit comprises a respective intermediate light guiding element. The presence of at least one such light guiding element improves the transmission of the light signal. For example, if the test string deviates from a strictly vertical alignment, the light guiding element(s) may enable the light signal to be curved, bent or otherwise adjusted accordingly.

[17] Advantageously, at least one of the first light guiding elements and each intermediate light guiding element may be made of at least one of a glass and a polymer.. Light guiding elements made of any of these materials (or combinations thereof) are particularly suited to transmitting a light signal.

[18] Advantageously, at least one of the first light guiding element and each intermediate light guiding element may be coated with a light reflecting layer. The use of a light reflecting layer may further improve the transmission of a light signal, by reducing or preventing light from leaking out of the light guiding element(s).

[19] Advantageously, the at least one first light source may comprise at least one of a light emitting diode (LED) and a laser. The use of LEDs may consume a low amount of energy, and simplify maintenance and construction as LEDs are physically robust and operate predictably at a range of environmental conditions. LEDs are also small, enabling them to be fitted into a small space, and have high switching rates, which facilitates reliable signal modulation.

[20] Advantageously, the at least one LED may emit at least one of blue, violet and green light.

These colors, which are associated with wavelengths between 400-600nm, are particularly suited to propagate through water and through any light guiding elements present.

[21 ] Advantageously, the cone rod unit may further comprise a lens arranged in a light path of the at least one first light source. The use of a lens may improve the propagation of the first light signal through the device by producing parallel rays, by aligning the rays with the longitudinal axis of the device.

[22] Advantageously, the control unit may comprise a second light source configured to generate a second light signal containing second data, and the cone rod interface unit further comprises a second sensor configured to detect said second light signal emitted by the second light source. The use of a light source at either end of the device enables bidirectional communication between the cone rod unit and the control unit, which may enable the test to be adjusted based on received signals and therefore be reactive.

[23] Advantageously, the first light guiding element and a first intermediate light guiding element of a first intermediate rod unit of the at least one rod unit may be arranged to be separated by a light coupling gap. The presence of a light coupling gap may reduce or prevent damage to the ends of the light guiding elements.

[24] Advantageously, the intermediate light guiding elements of adjacent intermediate rod units of the at least one intermediate rod unit may be arranged to be separated by a light coupling gap. The presence of a light coupling gap may reduce or prevent damage to the ends of the light guiding elements. [25] Advantageously, the device may further comprise at least one repeater intermediate rod unit, which comprises a first intermediate light source disposed in a first end of the at least one repeater intermediate rod unit, an intermediate power source disposed in the at least one repeater intermediate rod unit, and a first intermediate light sensor disposed in a second end of the at least one repeater intermediate rod unit, opposite to the first end of the at least one repeater intermediate unit. The use of at least one repeater intermediate rod unit in the test string may boost or improve the transmission of the signal, especially if the signal has attenuated too much.

[26] In a second aspect of the invention, there is provided a system for automatically performing a test to determine soil properties. The system comprises a cone rod unit comprising at least one sensor and at least one light source, the at least one light source configured to generate a first light signal containing first data. The system further comprises a control unit configured to be arranged at a position above a test position on a seafloor at which the test is to be performed, the position and the test position defining a firing line therebetween. The system further comprises a frame configured to collect a first intermediate rod unit from one or more intermediate rod units from a rod storage region, position the first intermediate rod unit in the firing line, directly above the cone rod unit, such that the first intermediate rod unit is axially aligned with the cone rod unit, attach the first intermediate rod unit to the cone rod unit to assemble a test string, push the assembled test string into soil of the seafloor, and hold the test string during assembly. The cone rod unit is configured to transmit said first light signal to the control unit when the frame pushes the assembled test string into said soil, and the control unit is configured to sense the transmitted first light signal and communication with a remote data acquisition unit.

[27] The above described construction is advantageous because it enables the test to be

performed whilst the test string is being assembled, in an automatic fashion. In this way, the test string may be assembled at the seafloor in a simple and reliable manner.

[28] Advantageously, the frame may be further configured to collect a second intermediate rod unit from the plurality of intermediate rod units from the rod storage region, position the second intermediate rod unit in the firing line, directly above the first intermediate rod unit, such that the second intermediate rod unit is axially aligned with the first intermediate rod unit, and attach the second intermediate rod unit to the first intermediate rod unit to extend the test string. The addition of the second intermediate rod unit (and subsequent intermediate rod units) may enable the assembly and ongoing testing of soil until a desired depth is reached, and particularly advantageously, the desired depth may be determined during the testing procedure in real time or near-real time.

[29] Advantageously, the frame may be configured to push the assembled test string into the soil at a constant speed of between 1 -5 cm/s, for instance, approximately 2 cm/s.

[30] In a third aspect of the invention, there is provided a method of performing a test to determine soil properties using the system described above. The method comprises holding the cone rod unit in the firing line, attaching the first intermediate rod unit of the one or more intermediate rod units to the cone rod unit to assemble a test string, the first intermediate rod unit and the cone rod unit being axially aligned, pushing the assembled test string into the soil of the seafloor, transmitting a light signal from the at least one light source of the cone rod unit to the light sensor of the control unit, and transmitting a signal from the control unit to the data acquisition unit, holding the assembled test string in the firing line, and extending the test string by attaching at least a second intermediate rod unit of the plurality of intermediate rod units to the assembled test string.

[31 ] This method has the advantage that it may be employed automatically and remotely, enabling the test to be performed at the seafloor whilst being monitored and/or controlled remotely.

[32] Advantageously, the operation of extending the test string may be repeated until the test string is between 20 m and 100 m in length, and preferably between 50 m and 80 m in length.

These lengths provide a suitable depth for many soil investigation tests.

[33] Advantageously, the operation of pushing the assembled test string into the soil of the seafloor may comprise pushing the assembled test string into the soil of the seafloor at a constant speed of between 1 - 5 cm/s, for instance, approximately 2 cm/s. A constant speed in this range may provide reliable testing and facilitate the collection of reliable data.

Brief Description of the Drawings

[34] Embodiments of the present invention will be described hereinafter, by way of example only, with reference to the accompanying drawings which are schematic in nature and therefore not necessarily drawn to scale. Furthermore, like reference signs in the drawings relate to like elements.

[35] Fig. 1 a shows a test string during assembly according to an embodiment of the present

disclosure;

[36] Fig. 1 b shows a device for performing a CPT test on a seafloor according to an embodiment of the present disclosure;

[37] Fig. 2 depicts an exploded view of elements of a device for performing CPT on a seafloor according to an embodiment of the present disclosure;

[38] Fig. 3 shows a control unit according to an embodiment of the present disclosure;

[39] Fig. 4a shows a top-down view of an interface unit according to an embodiment of the present disclosure;

[40] Fig. 4b shows a side-view of an arrangement of light sources in an interface unit according to an embodiment of the present disclosure;

[41 ] Fig. 4c shows a side-view of an alternative arrangement of light sources in an interface unit according to an embodiment of the present disclosure;

[42] Fig. 4d shows a side-view of a further alternative arrangement of light sources in an interface unit according to an embodiment of the present disclosure;

[43] Fig. 5 shows a cone rod unit according to an embodiment of the present disclosure; [44] Fig. 6a shows a construction of a device for performing CPT on a seafloor according to an embodiment of the present disclosure;

[45] Fig. 6b shows an optional repeater intermediate rod unit according to an embodiment of the present disclosure;

[46] Fig. 6c shows an arrangement for connecting adjacent rod units according to an embodiment of the present disclosure;

[47] Figs. 7a to 7d show a system for performing CPT on a seafloor according to an embodiment of the present disclosure; and

[48] Fig. 8 shows a flowchart of a method for performing CPT on a seafloor according to an

embodiment of the present disclosure;

[49] Fig. 9 shows an example of a processor unit as can be used at several locations in the system of the present disclosure.

Detailed Description of the Drawings

[50] Figure 1 a schematically shows a string, such as a CPT string, during assembly according to an embodiment of the present disclosure. The test string 100 of Figure 1 a comprises a cone rod unit 1 10 coupled to a cone 140, and at least one intermediate rod unit 120-n (n = 1 , 2, ...). Figure 1 a further shows a data acquisition unit (DAC) 130.

[51 ] The cone 140 is driven into the seafloor 50 in order to measure soil properties. The test string 100 is lengthened by adding further intermediate rod units 120-1 , 120-2 and 120-3, sequentially, until a desired depth is reached, or until further pushing is not possible, e.g. due to required force or too much deflection from the vertical. As the test string is lengthened, the cone 140 is driven deeper below the seafloor. In an example, the test string 100 is extended to reach a length between 20 m and 100 m, for instance, between 50 and 80 m. A possible target length may be 60 m +/- 10%.

[52] The intermediate rod units 120-1 , 120-2, 120-3 are added automatically to the test string.

Each intermediate rod unit is added to the end of the test string opposite to the end on which the cone 140 is provided. Equipment to automatically add a new intermediate rod unit 120-n on top of another intermediate rod unit 120-n-1 is, in one embodiment, installed on the seafloor and is provided with suitable position measurement devices to measure position and mechanical tools to perform all required mechanical actions. Such mechanical tools include tools to grasp the rod units 120-n and connect adjacent rod units 120-n and 120-n-1 . Then, the test string is pushed deeper into the ground.

[53] Figure 1 b shows a device for performing a test on a seafloor according to an embodiment of the present disclosure. The device comprises the assembled test string 100 as well as a control unit 150, arranged on top of the test string 100. In other words, whilst the cone 140 is arranged at a first end of the test string 100 to penetrate the seafloor, the control unit 150 is arranged at a second end of the test string 100, opposite to the first end. The control unit 150 comprises a communication unit 152 which is configured to communicate with the DAC 130. In an embodiment, the communication between the DAC 130 and the communication unit 152 is wired. However, this communication may be via a wireless connection instead, such as an optical or acoustic communication system. The control unit 150 will be further described with reference to Figures 2 and 3. The test string 100 is extended by adding intermediate rod units 120-n, such that the test string 100 comprises n intermediate rod units 120, n being an integer, until the desired length is achieved. As shown in an exaggerated way in Figure 1 B, the cone 140 can deviate from the vertical when it is pushed into the ground. In practice, this deviation from the vertical position may be up to 15-20°. This can lead to a situation where a direct line of sight between the cone rod 1 10 and control unit 150 is no longer available.

[54] The control unit 150 is provided with a suitable processor unit schematically indicated with reference number 154, which is configured to control all actions to be performed by the control unit 150 as explained hereinafter. An example of such a processor unit is explained with reference to Figure 9.

[55] Figure 2 depicts an exploded view of elements of a device for performing a test to determine soil properties on a seafloor according to an embodiment of the present disclosure. The device comprises a cone rod unit 1 10, at least one intermediate rod unit 120 and a control unit 150. The cone rod unit 1 10 may be coupled to a cone 140. The cone 140, the cone rod unit 1 10 and the at least one intermediate rod unit 120 form the test string 100 of Figures 1 a and 1 b. The cone 140 is fitted with at least one sensor 142 used to measure soil resistance and other soil properties, like soil friction, pore pressure and/or temperature.

[56] The cone rod unit 1 10 comprises a cone rod interface unit 210 which comprises a power source and processor unit 216 and at least one light source 212. Preferably, the at least one light source 212 is at least one light-emitting diode (LED), but other light sources, such as laser diodes and the like, may be used. The at least one light source 212 preferably may emit visible light. Preferably, the light emitted by the light source is in the blue/green part of the spectrum, i.e, has a wavelength in a vacuum between 400 and 600 nm. A wavelength of 470nm is especially suitable in sea water.

[57] The light as emitted by at least one light source 212 is produced such that it contains data as collected by means of the at least one sensor 142 and can be transmitted to control unit 150. To that end, the light may comprise a modulated signal where the modulation may be done in any form known in the art, e.g. in at least one of time modulation, frequency modulation and amplitude modulation, or any other modulation form known in the art. For example, the signal may show an on-off pattern on a carrier, such as binary phase shift keying or differential binary phase shift keying, where the time periods of the on stages and off stages contain the data to be transmitted. Digital modulation is preferred as this does not suffer from degradation of the information when the signal to noise ratio of the channel decreases, although analogue modulation may also be used.

[58] At least one light sensor 214 may be provided to receive light transmitted by control unit 150, as will be explained in more detail hereinafter. [59] The cone rod unit 1 10 is provided with a suitable processor unit schematically indicated with reference number 218, which is configured to control all actions to be performed by the cone rod unit 1 10, using standard electronics, as explained hereinafter. To that end, the processor unit 218 is connected to the at least one sensor 142, the at least one light source 212, the at least one light sensor 212, and the power source and processor unit 216. An example of such a processor unit is explained with reference to Figure 9.

[60] The cone rod interface unit 210 will be described in more detail with reference to Figures 4 and 5.

[61 ] The cone rod unit 1 10 is arranged at a first end of the test string 100, which is the end that first penetrates the seabed. The control unit 150 is arranged at a second end, opposite of the first end, of the test string 100. The second end of the test string 100 is the end most near the surface of the water when the test string 100 is in use. In some embodiments, the control unit 150 is attached to the second end, whilst in other embodiments, the control unit 150 is held at a position above the second end. Measures should be taken to prevent light from an external source to distort the communication between the cone rod interface unit and the control unit

150. For example, a narrow bandpass filter between the light sensor and the environment may suppress light outside the narrow passband (both natural and artificial light). As another example, a mechanical cap or collar configured to fit over the rod may be used to prevent light from entering the inside of the rods. As a further example, a control unit housing design that fits on top of the cone rods may also prevent external light from entering the cone rods.

[62] Between the cone rod unit 1 10 and the control unit 150 is at least one intermediate rod unit 120. The test string is extended by adding further intermediate rod units 120 until a desired length (or depth) is achieved.

[63] The control unit 150 comprises a light sensor 250 arranged to detect light signals received from cone rod unit 1 10 and derive data from them.

[64] The light sensor 250 of the control unit 150 is configured to detect light emitted by the at least one light source 212 of the cone rod interface unit 210. In other words, light emitted by the at least one light source 212 in the cone rod unit 1 10 passes through each intermediate rod unit 120 of the assembled test string 100 and is detected by light sensor 250. In this way, wireless transmission of data from the cone rod unit 1 10 to the control unit 150 can be achieved. Each intermediate rod unit 120 may be hollow. Preferably, however, each intermediate rod unit 120 comprises a light guiding element (shown as 620 in figure 6a) arranged to guide the light emitted by the at least one light source 212, through the intermediate rod units 120-n and to the light sensor 250 of the control unit 150. By using light guiding elements, light can be transmitted over a larger distance, and also without a direct line of sight between the at least one light source 212 and the light sensor 250. The light guiding element will be discussed in more detail with reference to Figure 6a.

[65] The cone rod unit 1 10 need not but may comprise a light guiding element (not shown). In some embodiments, the cone rod unit 1 10 and each intermediate rod unit 120 comprises a respective light guiding element. In other embodiments, the cone rod unit 1 10 is provided with a light guiding element and an intermediate rod unit 120 is not provided with a light guiding element. In some embodiments, at least some rod units (i.e. cone rod unit 1 10, intermediate rod units 120-1 to 120-n, and control unit 150) are provided with a light guiding element.

[66] The control unit 150 is configured to communicate with the DAC 130. In some embodiments, the control unit 150 communicates with the DAC 130 by a wired connection means, and in other embodiments, a wireless connection, such as an optical or acoustic signal, is used. In this way, information from the light sensor 250 is relayed to the DAC 130.

[67] Figure 3 shows a control unit 150 according to an embodiment of the present disclosure.

[68] The control unit 150 may further comprise at least one light source 312, arranged to transmit light to the cone rod interface unit 210. In this embodiment, the cone rod interface unit 210 is further provided with the light sensor 214, arranged to detect the light emitted by the at least one light source 312. In this way, information can be transferred from the cone rod unit 1 10 to the control unit 150, and from the control unit 150 to the cone rod unit 1 10. In other words, the communication may be bi-directional.

[69] The light as emitted by at least one light source 312 is produced such that it contains data to be transmitted to cone rod unit 1 10, e.g., to send commands to the cone rod unit 1 10. To that end, the light may comprise a modulated signal where the modulation may be done in any form known in the art, e.g. in at least one of time modulation, frequency modulation, phase modulation and amplitude modulation, or any other modulation form known in the art. For example, the signal may show an on-off pattern on a carrier, such as binary phase shift keying or differential binary phase shift keying, where the time periods of the on stages and off stages contain the data to be transmitted. Digital modulation is preferred as this does not suffer from degradation of the information when the signal to noise ratio of the channel decreases, although analogue modulation may also be used.

[70] The at least one light source 312 of the control unit 150 preferably comprises an LED, but may additionally or alternatively comprise a laser diode or the like. The at least one light source 312 may be provided in a control interface unit 350. The control interface unit 350 comprises the at least one light source 312 and the light sensor 250. The control interface unit 350 is thereby configured to communicate with the cone rod unit 1 10 and with the DAC 130, via processor unit 154 and communication unit 152.

[71 ] Figure 4a shows a top-down view of a control interface unit 350 according to an embodiment of the present disclosure.

[72] Although the control interface unit 350 of the control unit 150 is described below, the

description applies equally to the cone rod interface unit 210 of the cone rod unit 1 10 unless otherwise stated. The control interface unit 350 and the cone rod interface unit 210 may be identical or may differ in their configuration.

[73] The control interface unit 350 comprises at least a light sensor 250 and a power source and processor unit 216. The cone rod interface unit 210 comprises at least one light source 212. Preferably, however, both the cone rod interface unit 210 and the control interface unit 350 comprise at least one light source 212 or 312 and a light sensor 250, in order to facilitate bidirectional communication.

[74] Figure 4a shows the control interface unit 350 with six LEDs 312 arranged around the light sensor 250. However, any number of light sources may be used. Using multiple LEDs, for example, increases the light output and may improve the propagation distance of the light.

The light sources 312 may be arranged in a circular distribution. A circular distribution of light sources 312 ensures that the light sources are positioned substantially centrally whilst allowing space for a light sensor 250 to be positioned in the center.

[75] In some embodiments, it is preferable for the cone rod interface unit 210 to be provided

without a light sensor, and to position the at least one light source 212 centrally. The central positioning of the at least one light source 212 improves the distance through which the light propagates along the device. As an alternative, it is possible to have a configuration in which a light source is positioned centrally and a light sensor is arranged around it, or a configuration in which a light source and a light sensor are adjacent. It may be beneficial to give each light source or photo sensor its own lens to ensure emitted light is parallel to the light guide, and parallel light from the light guide is focused at the light sensor. An alternative is to create a special lens which both contains a toroidal section (for the ring of LEDs), and a spherical section in the middle (for the photo sensor), or a special lens which has multiple focal points. LEDs here are drawn as wired components. It may be beneficial to use SMD LEDs as these are smaller, where a lens can be optimized and be fitted closer to the component.

[76] As a further example, each light source or photo sensor may be provided its own lens to

ensure emitted light is parallel to the light guiding element, and parallel light from the light guiding element is focused at the light sensor. Alternatively, a special lens may be used which contains both a toroidal section for a ring of LEDs and a spherical section in the middle, which houses a photo sensor. A special lens having multiple focal points may also be used.

[77] Figure 4b shows a side-view of an arrangement of light sources 212 in a communication unit 350 according to an embodiment of the present disclosure. In particular, three LEDs 212 are shown on an interface unit such as cone rod interface unit 210 or control interface unit 350. However, the light sources may comprise laser diodes or the like. Additionally, the number of light sources is not limited to three. For example, a single light source may be used.

Preferably, between one and six light sources are used.

[78] Figure 4c shows a side-view of an alternative arrangement of light sources 212 in a control interface unit 350 according to an embodiment of the present disclosure. The arrangement of Figure 4c differs from that of Figure 4b in that the light sources 212 are angled towards the center of the cone rod interface unit 210 such that light produced by them in use is directed towards a common point in space, e.g., located on a lens 510 (cf. Figure 5) or other input of a light guiding element like light guiding element 514 (cf. Figure 5), or located on an end surface of a light guiding element 620 (cf. Figure 6a). This is referred to as a clustered arrangement, as the light sources 212 are clustered in the center of the cone rod interface unit 210. As described above, a central distribution of light sources improves the light propagation through the test string 100.

[79] According to an embodiment of the present disclosure, an interface unit such as control

interface unit 350 or cone rod interface unit 210 may comprise a plurality of LEDs as light sources.

[80] Figure 4d shows a side-view of a further alternative arrangement of light sources in an

interface unit, such as cone rod interface unit 210 and control interface unit 350, according to an embodiment of the present disclosure.

[81 ] The arrangement of Figure 4d differs from that of Figures 4b and 4c in that each light source 312 (or equivalent, 212) is provided with a respective lens, arranged to guide the light into parallel beams. Additionally, each light sensor is also provided with a respective lens arranged to guide light emitted from the opposing interface unit to the light sensor. For example, light is emitted from the cone rod interface unit 210 and is guided through a first lens such that the beam is parallel to the longitudinal axis of the cone rod unit, and is detected by a light sensor in the control interface unit 350 by passing through a second lens corresponding to the light sensor in the control interface unit 350.

[82] Figure 5 shows a cone rod unit according to an embodiment of the present disclosure.

[83] The cone rod unit 1 10 as shown in Figure 5 comprises the cone rod interface unit 210,

including at least one light source 212, as previously described. The cone rod unit 1 10 further comprises an optional lens 510. The lens 510 is arranged between the cone rod interface unit 210 and a connection to an intermediate rod unit 120 (such as those shown in Figure 1A and 1 B) in order to guide the light emitted by the at least one light source 212 into the intermediate rod unit 120, and preferably into light guiding element 620 within the intermediate rod unit 120. The lens 510 should be separated from the light source 212 by a window of air.

[84] Additionally, an optional light guiding element 514 may be provided within the cone rod unit 1 10. The light guiding element 514 is arranged on the side of the lens 510 opposite that on which the cone rod interface unit 210 is positioned. In other words, the lens 510 is arranged between the light guiding element 514 and the cone rod interface unit 210, such that light emitted by the at least one light source 212 passes through the lens 510 and into the light guiding element 514, before continuing through the at least one intermediate rod unit 120 to the light sensor 250 of the control unit 150.

[85] Additionally or alternatively, each intermediate rod unit 120 is coated with a light reflecting layer, such as a silver tape or reflective paint, in order to improve the internal reflection of light within each intermediate rod unit 120.

[86] Figure 6a shows a construction of a device for performing soil testing on a seafloor according to an embodiment of the present disclosure.

[87] A simplified test string 100 (also referred to as a CPT string) is shown in Figure 6a, comprising the cone 140, the cone rod unit 1 10, an intermediate rod unit 120 and the control unit 150. In this diagram, a single intermediate rod unit 120 is shown, although it is preferable to include a plurality of intermediate rod units 120-1 to 120-n, as shown in Figure 1 b. [88] According to an embodiment of the present disclosure, at least one of the cone rod unit 1 10 and the at least one intermediate rod unit 120 comprise a light guiding element, such as light guiding element 514 or light guiding element 620.

[89] The light guiding elements 514 and/or 620 may comprise a bundle of light guiding fibers. The light guiding elements 514 and/or 620 may be made of polymer, such as Perspex ® (i.e. , poly(methyl methacrylate) (PMMA)), and/or glass. The light guiding elements 514 and/or 620 preferably have a low overall attenuation. Light guiding element 514 has one end surface directed towards light sources 212 which end surface is configured to receive light from light sources 212 as much as possible. These end surfaces are, preferably, optimized for that purpose in any way known in the art. Additional light receiving elements, like lenses, may be applied.

[90] Optionally, the light guiding element 514 and/or 620 is coated with a light reflecting layer, such that light directed axially through the light guiding element 514 and/or 620 is reflected within the light guiding element 514 and/or 620. The end surfaces of the light guiding element 514 and/or 620 are not coated. A light reflecting layer may prevent light from leaking from the light guiding elements 514 and/or 620, and thus improve light propagation from the cone rod interface unit 210 to the light sensor 250 of the control unit 150.

[91 ] In some embodiments, the light guiding element 514 is arranged to stay in physical contact with the light guiding element 620 in order to prevent light from leaking at connection points between adjacent rod units. Alternatively, the light guiding elements 514 and 620 may be kept separated by a coupling gap (not shown) in order to prevent or reduce damage to the ends of the light guiding elements 514 and 620. The coupling gap should be large enough to avoid the ends of the light guiding elements touching when adjacent rods units are connected, but as small as possible to limit the losses of light. The effect of length variations due to temperature differences should be taken into account. In practice, a coupling gap may have a width of 2-5 mm but the invention is not limited to this example. The light coupling gap may be filled with water. Preferably, the ends of the light guiding elements are polished to a flat and smooth surface, in order to minimize losses due to diffusion.

[92] In some embodiments, only the intermediate rod units 120 are provided with respective light guiding elements 620. Then, in the assembled state, light guiding element 620 has one end surface directed towards light sources 212 which is configured to receive as much light from light sources 212 as possible. These end surfaces are, preferably, optimized for that purpose in any way known in the art. Additional light receiving and/or optical elements, such as lenses, may be applied. Optionally, the cone rod unit 1 10 may be internally coated with a light reflecting layer in order to improve light propagation. Moreover, preferably, the at least one light source 212 is placed towards the uppermost end of the cone rod unit 1 10.

[93] Figure 6b shows an optional repeater intermediate rod unit according to an embodiment of the present disclosure. In an embodiment, at least one repeater intermediate rod unit 120’ may be used in the test string 100. Repeater intermediate rod unit 120’ comprises a light sensor 650 at a first end and a power unit 616 and a light sensor 612 at a second end opposite the first end. The use of at least one repeater intermediate rod unit 120’ may boost and/or improve the transmission of the signal, especially if it has attenuated too much. Optionally, repeater intermediate rod unit 120’ may further comprise a power source, although a power source is not required.

[94] In some embodiments, a plurality of repeater intermediate rod units 120’ may be used

sporadically or periodically along the test string 100. For example, a repeater intermediate rod unit 120’ may be used every 5 or 10 rod units in order to improve transmission of the signal from one end of the test string to the other. Preferably, a repeater intermediate rod unit 120’ is arranged to boost a signal transmitted from the cone rod unit 1 10 to the control unit 150. In some embodiments, however, the repeater intermediate rod unit 120’ may additionally or alternatively be arranged to boost a signal transmitted from the control unit 150 to the cone rod unit 140. However, the repeater intermediate rod units 120’ may alternatively be sporadically arranged (and not evenly distributed along the test string) or may be differently arranged.

[95] In some embodiments, repeater intermediate rod unit 120’ may comprise a further light sensor 614 at the second end and a further light source 613 at the first end, in order to boost signals bi-directionally.

[96] Figure 6c shows an arrangement for connecting adjacent rod units according to an

embodiment of the present disclosure. Intermediate rod units 120, repeater intermediate rod units 120’ and the cone rod unit 1 10 are examples of rod units. The arrangement for connecting adjacent rod units shown in Figure 6c may be applied to any two adjacent rod units, such as between the cone rod unit 1 10 and an intermediate rod unit 120-1 , and/or between the intermediate rod unit 120-1 and the intermediate rod unit 120-2. For the sake of conciseness, Figure 6c is described in reference to a connection between two intermediate rod units 120-1 and 120-2.

[97] A first end of the intermediate rod unit 120-1 is tapered such that it can be inserted into a second end of adjacent intermediate rod unit 120-2. The second end of adjacent intermediate rod unit 120-2 is shaped to receive the tapered first end of the intermediate rod unit 120-1 .

[98] Optionally, the intermediate rod unit 120-1 comprises a first intermediate light guiding element 620-1 arranged in axial alignment with the intermediate rod unit 120-1 . Optionally, the adjacent intermediate rod unit 120-2 comprises a second intermediate light guiding element 620-2, arranged in axial alignment with intermediate rod unit 120-2.

[99] Adjacent (i.e. successive) rod units may be removably attached by a screw and thread

system, a click-lock system, a bayonet fitting system or any other known mechanical coupling system.

[100] By removably attaching adjacent rod units, upon completion of a soil investigation test such as a CPT test, a test string (e.g. a CPT string) may be disassembled and the component rod units reused in future tests.

[101 ] Figures 7a to 7d show a system and a method for performing CPT on a seafloor according to an embodiment of the present disclosure. Although the system and method are described in relation to performing CPT, it is to be understood that this is merely an exemplary application and that the same system and method may be used in other soil investigation tests.

[102] In addition to the CPT string described in relation to Figures 1 through 6b, the system shown in Figures 7a to 7d comprises a fixed clamp 701 , a movable clamp 703 and a manipulator arm 705, all arranged as part of a frame 707. The frame 707 is provided with suitable devices to control movement of movable clamp 703 and manipulator arm 705 in a way as explained hereinafter. These devices may also be configured to control location and orientation of fixed clamp 701 and then keep fixed clamp 701 in a predetermined location and orientation. These devices may include mechanical steering mechanisms, a communication unit to communicate with a processor unit onboard of the vessel and a processor unit controlling these mechanical steering mechanisms and the communication unit. The processor unit is shown with reference number 721 . An example of a suitable processor unit is shown in Figure 9.

[103] The control unit 150 is arranged above a position on the seafloor at which the CPT test will be performed. The vertical line between the CPT test position on the seafloor and the control unit 150 defines a firing line 709, which defines a line in which the CPT string will be assembled during the CPT test.

[104] The cone rod unit 1 10 is placed in the firing line 709, e.g. by means of movable clamp 703, on a seabed frame at the CPT test position, and is held in place by the fixed clamp 701 .

[105] As shown on the right hand side of an arrow 715, the control unit 150 is moved towards, cf. arrow 713, and connected to the top of cone rod unit 1 10 by any suitable means known in the art. In an embodiment, the control unit 150 is connected to the frame 707. The frame 707 may be a drill mast positioned around the firing line 709. The frame 707 may move over rails, via a mechanical connection and/or by means of a further manipulator arm. Proximity sensors may be used to detect a rod unit, and an automatic locking device may be used to position the control unit 150 on top of the rod unit.

[106] Then, the fixed clamp 701 releases cone rod unit 1 10, and cone rod unit 1 10 and control unit 150 are pushed together into the soil by the movable clamp 703. Data is transmitted during the pushing operation. This data is collected by the at least one sensor 142 of cone unit 140 and may include, for example, cone resistance, sleeve friction, or angular deflection.

[107] Next, as indicated at the right hand side of an arrow 717, the fixed clamp 701 will hold the cone rod unit 1 10. The control unit 150 and the movable clamp 703 are moved to their upwards position. This creates room for the first intermediate rod 120-1 to be placed on top of the cone rod unit 1 10.

[108] An external rod unit storage area 71 1 may be provided to store a plurality of intermediate rod units 120. The rod storage area 71 1 may be a rack or carrousel or the like. Intermediate rod units 120 can be stored vertically or horizontally. In some embodiments, a rack or carrousel is a component in the system. The manipulator arm 705 is arranged to collect a first intermediate rod unit 120-1 from the rod unit storage area 71 1 , as shown in Figure 7a, and position the first intermediate rod unit 120-1 in the firing line 709, above the cone rod unit 1 10, and below the control unit 150, as illustrated in Figure 7b. The intermediate rod unit 120-1 is then taken over by the movable clamp 703. The movable clamp 703 is used to attach the first intermediate rod unit 120-1 to the cone rod unit 1 10, for example by a screwing motion, a click-lock motion or similar. The control unit 150 is connected to the upward facing end of the first intermediate cone rod 120-1 . The attached first intermediate rod unit 120-1 and the cone rod unit 1 10 forms the initial CPT string, which may be extended by attaching further intermediate rod units 120- 2, as shown in Figure 7b.

[109] The movable clamp 703 is configured to grip the first intermediate rod unit 120-1 positioned in the firing line 709 and push the CPT string deeper into the soil, as illustrated in Figures 7c and 7d. Then, the assembled CPT string is then held in place by the fixed clamp 701 . During the pushing operation, again data is collected by means of at least one sensor 142 and transmitted to the control unit 150. The control unit 150 and the movable clamp 703 are moved to their upwards position. This creates room for a further intermediate rod 120-2 to be inserted.

[1 10] The manipulator arm 705 then collects further intermediate rod unit 120-2 from the rod unit storage area 71 1 , as shown in Figure 7b, positions said further intermediate rod unit 120-2 in the firing line 709 above the assembled CPT string and below the control unit 150. The further intermediate rod unit 120-2 is connected to the first intermediate rod unit 120-1 by the movable clamp 703, extending the assembled CPT string. At this point, the assembled CPT string comprises the cone rod unit 1 10, the first intermediate rod unit 120-1 and the second intermediate rod unit 120-2. The control unit 150 is connected to the upward facing end of the second intermediate cone rod 120-2. Then, the movable clamp 703 pushes the assembled CPT string down, deeper into the soil. The system is configured to repeat this process until the CPT string reaches a desired length. The desired length is preferably between 20 m and 100 m, for instance, between 50 and 80 m. A possible target length may be 60 m +/- 10%. In an embodiment, intermediate rod units 120 may have a length of about 3 m but the invention is not restricted to this example.

[1 1 1 ] During each pushing operation, as further intermediate rod units 120-n are added, the system is configured to take a measurement of soil properties. In particular, once the movable clamp 703 pushes the assembled CPT string into the soil, the cone rod interface unit 210 is configured to transmit a signal using the at least one light source 212. The control unit 150 detects presence of light and demodulates its content, e.g. it is either on or off. By high frequency switching the light on and off, data can be transmitted. This is also known in the art as visible light communication (VLC). This may be done in so-called bursts, where packages of data are transmitted. In a two-way system, bursts of data from the cone to the surface may be alternating with instruction data packages from the surface to the cone.

[1 12] That is, after each extension of the CPT string, or after a predetermined number of extensions, the at least one light source 212 is configured to emit light. The light sensor 250 of the control unit 150, positioned above the firing line 709, is arranged to detect the light emitted by the at least one light source of the cone rod unit 1 10. Upon detecting light, the control unit 150 is configured to transmit a signal to a data acquisition unit located remotely, for example on land or on the vessel floating at the sea surface.

[1 13] Preferably, the movable clamp 703 is configured to push the assembled CPT string into the soil at a constant speed of, e.g., between 1 -5 cm/s, e.g. approximately 2 cm/s. In case of a threaded connection between the rod units 1 10, 120, the movable clamp 703 is further configured to rotate the intermediate rod units 120 while attaching them to an adjacent intermediate rod unit 120 or the cone rod unit 1 10.

[1 14] In some embodiments, the cone rod unit 1 10 is provided with the cone unit 140 pre-attached.

In other embodiments, the cone unit 140 is initially positioned at the CPT test position on the seafloor, held in place by the fixed clamp 701 , and the cone rod unit 1 10 is attached to the cone unit 140 in the same manner as that described for attaching the intermediate rod unit

120-1 to the cone rod unit 1 10.

[1 15] Figure 8 shows a flowchart of a method for performing CPT on a seafloor according to an embodiment of the present disclosure. Control of these operations is e.g. performed by the processor on board the vessel or located elsewhere. Control may be semi-automatic, i.e. some actions may be controlled by the processor as instructed by an operator, or fully automatic, as controlled by suitable software stored in a suitable memory.

[1 16] In operation 810, the cone rod unit 1 10 is placed at a CPT test position of the CPT test on the seafloor. The control unit 150 is positioned above the CPT test position and defines the firing line 709 as shown in Figures 7a to 7d. The position of the control unit 150 may be below, at or above sea water surface. The cone unit 140 is held in place by the fixed clamp 701 .

[1 17] In operation 815, the movable clamp 703 engages the cone rod unit 1 10.

[1 18] In operation 820, control unit 150 is moved to cone rod unit 1 10 and attached on top of cone rod unit 1 10.

[1 19] In operation 825, the movable clamp 703 engages the cone rod unit 1 10 and pushes the

assembled CPT string into the soil. Preferably, the movable clamp 703 pushes the assembled CPT string into the soil at a constant speed, for example a constant speed between 1 and 5 cm/s, e.g., approximately 2 cm/s. Preferably, during this operation, the at least one light source 212 of the cone rod unit 1 10 transmits a light signal containing data to control unit 150. Alternatively, it is possible to postpone sending this data until after the pushing operation. However, this is not preferred. The light signal is received by the light sensor 250 of the control unit 150, which communicates this data, e.g. wirelessly, with remote data acquisition unit 130. Control unit 150 may be configured to process the received data before forwarding the data. The data acquisition unit 130 may be located on land or on a vessel.

[120] In operation 830, after lowering (i.e. pushing) the assembled CPT string into the soil, the

assembled CPT string is held in place by the fixed clamp 701 and the movable clamp 703 is released and raised. The control unit 150 is also released and raised.

[121 ] In operation 840, the manipulator arm 705 collects intermediate rod unit 120-1 from the rod storage area 71 1 and positions the intermediate rod unit 120-1 in the firing line 709, directly above the cone rod unit 1 10. [122] In operation 845, the movable clamp 703 engages the intermediate rod unit 120-1 . The manipulator arm is then released.

[123] In operation 850, the movable clamp 703 attaches the intermediate rod unit 120-1 to the cone rod unit 1 10 to extend the CPT string. At this point, the assembled CPT string comprises the cone rod unit 1 10 and the intermediate rod unit 120-1 .

[124] In operation 855, the control unit 150 is moved to intermediate rod unit 120-1 and attached to the top end of the intermediate rod unit 120-1 . In other words, one end of the intermediate rod unit 120-1 is attached to the cone rod unit 1 10, and the opposite end of the intermediate rod unit 120-1 is connected to the control unit 150.

[125] In operation 860, the fixed clamp 701 is released from the assembled CPT string.

[126] In operation 865, movable clamp 703 pushes the assembled CPT string into the soil, for example at a constant speed, such as approximately 2 cm/s. Similarly to operation 825, at the same time a light signal containing data as collected by at least one sensor 142 may be transmitted from the at least one light source 212 of the cone rod unit 1 10 to the light sensor 250 of the control unit 150.

[127] In operation 870, the assembled CPT string is held in place by the fixed clamp 701 and the movable clamp 703 is raised. The control unit 150 is released and raised.

[128] In operation 875, it is determined whether the CPT string has reached a desired length. This decision may be made by determining the current length of the CPT string and comparing the current length to a predetermined length, in other words the desired length of the CPT string has been predetermined. The decision may be taken automatically by the processor on board the vessel by keeping track of the number of intermediate rod units 120 used in the CPT string. It may also be manually controlled by an operator controlling that processor.

Alternatively, the decision may be based on the data transmitted to the data acquisition unit 130 remotely. In other words, the decision may be reactive based on the data acquired by the device.

[129] In order to extend the CPT string, the operations 840 to 860 are repeated by attaching further intermediate rod units 120 to the previously attached intermediate rod units. Each time an intermediate rod unit is added, a light signal is transmitted from the at least one light source 212 of the cone rod unit 1 10 to the light sensor 250 of the control unit 150, and the control unit 150 communicates with a remote data acquisition unit 130, as described in operations 825 and 865.

[130] Figure 9 shows an example of a processor unit as can be used at several locations in the system of the present disclosure where devices have to perform one or more functions as explained above. Claims of the invention, therefore, may relate to such processor units with such functionalities, methods of such functionalities, computer program products with data and instructions which, once loaded by the processor unit, provide such a processing unit with such functionalities. Processor unit 900 comprises a processor 910, a memory 920, at least one sensor module 930, an output unit 940, at least one communication module 950 and at least one electronic networking module 960. [131 ] The memory 920, sensor module(s) 930, output unit 940, communication module(s) 950 and electronic networking module(s) 960 are each connected to processor 910. The connections need not be physical connections, but may also include wireless connections and/or indirect connections. Not all functional elements shown in Figure 9 need to be present, as is apparent from the foregoing description and following claims.

[132] All connections intended for transmission of data may be physical connections, such as wires, however, they may alternatively be wireless and based on transmission of electromagnetic / light radiation.

[133] The processor 910 may be any suitable processing unit known from the art. The processor 910 may include at least one central processing unit (CPU) and/or at least one application processor (AP).

[134] Memory 920 may comprise different types of sub-memories, like read-only memory (ROM), suitable for storing program instructions and data to run the processor 910. Memory 920 may comprise random access memory (RAM) for storing temporary data. Some or all of the submemories may be physically located remotely from the other components. A local memory may be included in the memory 920 and may be physically located within the processor unit 900. Memory 920 may also store a processor unit ID identifying processor 910 for use in external communications with other devices.

[135] Sensor module(s) 930 may include one or more location and/or positioning sensors, such as accelerometers, gyrometers/gyroscopes, GPS units, and the like. Such location and/or positioning sensors measure the processing unit’s own motion, location and orientation. This may be used, for example, to position the device during assembly of a test string.

[136] Output unit 940 may comprise one or more sub-output units, such as a display or a speaker.

[137] Communication unit(s) 950 may comprise means to receive and/or transmit data to and from external devices or other internal components.

[138] Electronic networking module(s) 960 may comprise one or more of LTE (Long Term

Evolution), Ethernet, WiFi, Bluetooth, powerline communication, Wide Area Network (WAN), Internet of Things (loT) and near field communication (NFC) modules.

[139] In the foregoing description of the figures, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the scope of the invention as summarized in the attached claims.

[140] In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

[141 ] In particular, combinations of specific features of various aspects of the invention may be made. An aspect of the invention may be further advantageously enhanced by adding a feature that was described in relation to another aspect of the invention. [142] It is to be understood that the invention is limited by the annexed claims and its technical equivalents only. In this document and in its claims, the verb "to comprise" and its

conjugations are used in their non-limiting sense to mean that items following the word are included, without excluding items not specifically mentioned. In addition, reference to an element by the indefinite article "a" or "an" does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements. The indefinite article "a" or "an" thus usually means "at least one".

[143] It will be appreciated that the present invention has been described with reference to a

number of non-limiting exemplary embodiments and modifications can be made to the above described embodiments without departing from the scope of the invention. Moreover, features from the above-described embodiments can be combined with other embodiments described herein.