FIELD OF THE INVENTION

[0001] The present disclosure generally relates to a heat flow penetrometer test system for measuring subsurface thermal conductivity, and more particularly to a heat flow module for use in a heat flow penetrometer system, to a method of producing a heat flow penetrometer system, to a method of determining a subsurface thermal conductivity, and to a kit of parts for producing and using a heat flow penetrometer system. Unlocking insights from Geo-Data, the present invention further relates to improvements in sustainability and environmental developments: together we create a safe and liveable world.

BACKGROUND OF THE INVENTION

[0002] There is a general and ongoing need to improve the quality of data acquisition of subsurface surveying. The determination of the subsurface characteristics is used to identify objects below the surface of the ground, as well as determining the soil characteristics, such as soil type, density, moisture content, shear modulus, and the like, which may be used in foundation planning and/or management. Subsurface information may be used for e.g., site characterisation for infrastructure projects, foundation calculations, and the like. For such applications, it is important to generate a comprehensive understanding of the subsurface with a high degree of accuracy in an efficient manner.

[0003] One of the methods of performing such tests is known as a cone penetration test (CPT). The cone penetration is a geotechnical investigation method for determining soil and groundwater characteristics, wherein a cone penetrometer is pushed into the soil for measuring. Typical parameters measured by a probe are cone tip resistance, sleeve friction and pore-water pressure. Usually, the test method comprises pushing an instrumented cone penetrometer, with the tip facing down, into the ground at a controlled rate.

[0004] There is a need to determine thermal characteristics of the soil. One such characteristic is thermal conductivity of the soil, which provides a measure of energy dissipation through soil. The thermal conductivity of a material is a measure of its ability to conduct heat and is defined as the transport of energy due to random molecular motion across a temperature gradient. This is an important characteristic to determine since it influences e.g., foundation design, cable routing and cable design, insulation properties of subsurface structures, and the like. The measure of heat conduction influences for example how fast heat produced in power and/or data cables can dissipate so as to stop such cables from overheating. Optimal cable routing may also be influenced by a measure of heat dissipation such that a route is chosen in which the thermal conductivity of the soil does not negatively influence the operating characteristics of the cable.

[0005] Known methods of performing such a CPT utilise a cone penetrometer assembly being built from a plurality of rod segments, forming a string of rods with a cone penetrometer positioned at the tip which is able to measure at the required depth. Other known methods utilize coiled CPT systems in which an elongated pushrod is used, in which the pushrod bent into a coiled shape such that the pushrod may be straightened prior to being advanced into the soil. Conventional CPT systems do not provide the possibility of measuring thermal conductivity.

[0006] Attempts have been made to produce CPT systems that allow for the determination of thermal conductivity. A known CPT system comprises a cone penetrometer having a friction sleeve being positioned between a cone and the pushrod, which is arranged to be heated through friction heating as the CPT system is advanced into the soil. As the CPT system is advanced into the soil, the cone penetrometer heats up storing an amount of energy. Once the cone penetrometer has achieved a certain temperature, the propagation of the CPT system is halted, so that no further friction-induced energy is provided to the system. The cone penetrometer then starts to give off heat to the surrounding soil as the temperature of the cone penetrometer is higher than the temperature of the surrounding soil. The speed with which the temperature of the cone penetrometer reduces is indicative of the thermal conductivity of the soil surrounding the CPT system. If the soil has a higher thermal conductivity, the heat dissipates at a higher rate, leading to a higher average temperature differential and as a result a higher reduction of temperature of the cone penetrometer. A thermometer is generally positioned in the cone of the cone penetrometer, which measures the decrease of the temperature after the cone and friction sleeve have heated through friction with the soil.

[0007] In particular, the dissipation of thermal energy through the soil, i.e., thermal conductivity, determines the speed with which the temperature gradient between the cone penetrometer and the soil is reduced. If the soil heats up but cannot dissipate the energy quickly, the temperature of the soil directly surrounding the cone penetrometer will rise, such that the temperature differential between the cone penetrometer and the soil is reduced and the rate of the temperature reduction of the cone penetrometer flattens. As a result, the temperature decline of the cone penetrometer is less steep, providing information on a low thermal conductivity of the soil. Similarly, if the rate at which the energy dissipates is very high, i.e., the rate of temperature reduction of the cone penetrometer is high, the thermal conductivity of the surrounding soil is high. [0008] A problem associated with the known cone penetrometers is that soil-friction-induced heating generally requires a temperature change of at least 3 °C, which corresponds approximately to at least 3 MPa cone resistance as being advanced at least about 1 m through the soil. If a lower cone resistance is provided by the soil, the required temperatures to perform an accurate measurement are not achieved. As a result, such passive CPT systems cannot be used in softer soils as these do not provide sufficient cone resistance. Further, even if sufficient heat is generated over a longer depth, this reduces the measurement resolution of the CPT system, as it requires a longer travel path into the soil to generate sufficient heat to perform the test. In addition, as the CPT system only comprises a single thermometer in the cone of the CPT system, having sufficient the time needed to perform testing over a relevant section of soil is long.

[0009] To mitigate the problem of measuring thermal conductivity in softer soils, a known approach is to utilize a heat flow needle. This is a thin, elongated needle provided at the tip an in- situ probe. Such a heat flow needle is provided on an in-situ probe and does not measure cone resistance and sleeve friction, requiring extra testing and more expensive additional soil testing procedures. This needle is actively heated and is thus not dependent on friction-induced heating. A needle is used since it defines an aspect ratio of length with respect to its diameter which allows the thermal conductivity to be modelled under the assumption that the needle is defined as an infinite line model, which has an analytical solution to energy dissipation. The needle must have a small diameter-length ratio since it otherwise does not adhere to an infinite line model. Solving for the thermal conductivity for a short cylinder based on an analytical solution would require a much longer measurement time than would be reasonably feasible. However, due to its small diameter, the heat flow needle is fragile and cannot be used in harder soils. Also, similar as with the friction- induced thermal CPT system, the single heat flow needle takes a long time to measure soil characteristics over a depth range.

[0010] Since the heat flow needle cannot be utilized in harder soils, a hard layer overlaying a soft layer cannot be measured. That is, the soft layer underneath may be reached by the robust friction sleeve system, but this system cannot measure in the soft soil because the friction-induced heat is too low. The heat flow needle system cannot penetrate the hard soil to begin with and can thus not reach the soft soil underneath. An option is to create a borehole to advance the needle into the soft soil through the drilled hole. However, this is very expensive and inefficient.

[0011] The known state of the art for cone penetration testing thus does not provide a solution for acquisition of high-quality data which includes thermal conductivity in different types of soils. [0012] As a result, there is a need for improved cone penetrometer systems and methods of performing cone penetrometer testing providing information on thermal properties of the target soil that address the issues explained above.

BRIEF SUMMARY OF THE INVENTION

[0013] In one aspect of the invention there is provided a heat flow penetrometer test system for measuring subsurface thermal conductivity. The heat flow penetrometer system comprises a penetrometer extending between a tip and a proximal end. The heat flow penetrometer further comprises a pushrod arranged to translate a compressive force to the penetrometer and having a connection section. The heat flow penetrometer further comprises at least one heat flow module, the heat flow module being provided between the proximal end of the penetrometer and the connection section of the pushrod. According to the present disclosure, the at least one heat flow module comprises at least one heating element and at least one temperature sensor.

[0014] In an advantageous embodiment, the penetrometer is a cone penetrometer. The penetrometer may be a dummy penetrometer, having any shape. The penetrometer may be a dummy penetrometer having no measurement capabilities. Advantageously, the penetrometer may contain measurement equipment such as is generally understood as being standard in CPT measurements. In an advantageous embodiment, the penetrometer has a shape allowing for penetration in the soil with a reduced pushrod pressure and/or soil resistance. In an embodiment, the penetrometer may have a substantially flat tip surface. The penetrometer may have a substantially demi-spherical tip surface. In an advantageous embodiment, the penetrometer comprises a cone-shaped tip. Hereinafter, reference may be made to a CPT system, referring to a cone penetration test system. All embodiments described in the context of this disclosure may be used in combination with any penetrometer tip shape and are not limited to conventional cone shapes.

[0015] By using at least one heat flow module having a heating element and a temperature sensor, the system can be used in many different types of soils. The heating element may be a heating wire, a chemical heating element, or the like. The heating element may be formed as a flat sheet having a resistance such that electrical energy is transformed into heat. The heating element may be integrally formed with the heat flow module or be detachably coupled to the heat flow module. In an advantageous embodiment, the heating element comprises an elongated wire. The heat flow module may also be provided around the pushrod, or partially around the pushrod. The heat flow modules should comprise a section which is able to translate a compressive force required to drive the CPT system into a target soil. To this end, either the pushrod extends through the heat flow modules, or the heat flow modules comprise a strengthened section arranged to translate a compressive force to the cone. The heat flow module may advantageously be disconnected from the CPT system. Alternatively, the heat flow module may be integrally formed with the cone penetrometer.

[0016] Subsurface in the context of this disclosure is understood comprising as any region under the surface of the ground, either shallow or deep. It shall not be limited to a particular region of the soil under the surface of the ground. It may refer to soil under the surface of the ground on land or in sea, i.e., below the seafloor or below ground level.

[0017] Cone penetration tests in the context of the present disclosure may be performed onshore and offshore, as applicable. In the context of the present disclosure, soil can originate from any type of onshore and offshore grounds. In the context of the present invention, the term ground is to be understood as any terrain on land or underwater. The apparatus according to the present invention can be used to test soil from onshore and offshore grounds. The terms sea, seafloor or seabed can be understood in a broad sense and refer in the context of the present disclosure as any underwater ground including, but not limited to, lakes, ponds, rivers, seas, and oceans. [0018] Advantageously, the heat flow cone penetrometer may provide information that allows for the determination of heat capacity values through estimations with empirical relations from literature.

[0019] In an advantageous embodiment, the heat flow module has a diameter substantially equal to a diameter of the cone penetrometer. In an embodiment, the diameter of the heat flow module is substantially equal to about the average diameter of the whole CPT system comprising the penetrometer and the pushrod.

[0020] The diameter of the heat flow module being substantially equal to the cone penetrometer advantageously results in a larger volume of soil being measured. When compared to a heat flow needle system, the present invention provides a heat flow module having a larger contact surface with the soil. This increased soil volume leads to a larger heat dissipation and a higher measurement accuracy as a result.

[0021] In an embodiment, the heat flow cone penetrometer system comprises at least two heat flow modules, advantageously comprising at least 3 heat flow modules.

[0022] In an embodiment, the heat flow cone penetrometer system may comprise at least 4 heat flow modules, advantageously at least 5 heat flow modules, more advantageously at least 6 heat flow modules. The use of multiple heat flow modules advantageously allows to measure the thermal conductivity of the soil at multiple locations simultaneously. The heat flow cone penetrometer system is advanced into the soil and is halted at an appropriate depth to attain measurements. The two or more heat flow modules provided in the heat flow cone penetrometer system then can take thermal conductivity measurements simultaneously and provide a larger amount of soil information in a shorter period of time. As such, the process of data acquisition is made more efficient through the use of multiple heat flow modules in the heat flow cone penetrometer system.

[0023] In an embodiment, the heat flow module comprises a dissipation sleeve and an inner sleeve, the dissipation sleeve being provided around the inner sleeve, and wherein the inner sleeve comprises the heating element.

[0024] In an embodiment, the heat flow cone penetrometer system comprises at least two heat flow modules. In an embodiment, the one or more heat flow modules each comprise a dissipation sleeve and an inner sleeve, the dissipation sleeve being provided around the inner sleeve, and wherein the inner sleeve comprises the heating element. The inner sleeves are advantageously spaced in an axial direction extending along the pushrod and the cone penetrometer. In an advantageous embodiment, a first inner sleeve is distanced from a second inner sleeve by between about 1 cm to 50 cm, advantageously by between about 2 cm and 40 cm, more advantageously by between about 5 cm and 30 cm, still more advantageously by about 10 cm.

[0025] Advantageously, the spacing of the inner sleeves in the heat flow modules is chosen such that the required resolution of the measurements is attained, without having the heat sources of different heat flow modules interfere.

[0026] In an embodiment, the at least one inner sleeve defines a length of between about 3 and 30 cm, advantageously of between about 5 and 25 cm, more advantageously of about 10 and 20, still more advantageously of about 15 cm.

[0027] Having a shorter maximum length of the inner sleeves in the heat flow modules allows for an improved resolution of the thermal conductivity measurements. If, contrarily, a single elongated heat flow module with a single inner sleeve were used, one large temperature front would be created. As such, the dissipation sleeve of the heat flow module would be influenced by several small layers in the soil of e.g., about 20 cm in layer thickness. The use of several thermally insulated heat flow modules makes it possible to measure the thermal conductivity of single smaller layers. With shorter modules the change is larger to measure properties in a single thin layer, leading to improved resolution. In homogeneous soil units, multiple measurements could help to quantify reliability and repeatability of measurements and/or local variations in one soil unit.

[0028] In an embodiment, the at least one heat flow module defines a distance to the cone penetrometer tip of at between about 10 cm and 1 m, advantageously of at between about 20 cm and 80 cm, more advantageously of at between about 25 cm and 60 cm, still more advantageously of at between about 30 cm and 50 cm.

[0029] Advantageously, positioning the at least one heat flow module close to the cone penetrometer tip, heat produced by soil friction may aid in heating the heat flow modules, requiring less time for the temperature of the heat flow module to increase. Further, by providing the heat flow module at a distance from the cone penetrometer tip, a standard cone penetrometer may be used, which does not require further modifications. In addition, the spacing between the heat flow module and cone penetrometer tip may allow fur additional space for the electronics of the heat flow module and the cone penetrometer to be housed, and for any connection units which may be advantageously provided between the heat flow modules and the cone penetrometer.

[0030] By providing an inner sleeve and a dissipation sleeve as separate components of the heat flow module, the heating element may be embedded in the inner sleeve, positioned within the dissipation sleeve. As a result, the inner sleeve and its components are protected from the soil through which the CPT system is advanced. As a result, the material choice may be optimally chosen to adhere to the thermal requirements. For example, a highly conductive material which is less resistant to mechanical wear may be chosen for the inner sleeve, while the dissipation sleeve comprises a material which has a higher abrasive resistance. In an embodiment, the inner sleeve comprises at least one of aluminium, copper, gold, silver, graphite, and technical ceramics. In an advantageous embodiment, the inner sleeve comprises aluminium. In an embodiment, the dissipation sleeve comprises steel, advantageously hardened steel. In an embodiment, the dissipation sleeve comprises nitrated steel and/or ceramics. In addition, the protection of the inner sleeve further allows the incorporation of the heating element in the inner sleeve in a thermally optimal manner, without having to take the abrasive forces on the CPT system into account.

[0031] In an embodiment, the inner sleeve comprises aluminium. The use of aluminium for the inner sleeve is advantageous since it conducts heat well. Other types of metal and/or other heat conducting materials, such as graphite, may also be used. In an embodiment, the dissipation sleeve comprises hardened stainless steel. The use of hardened stainless steel advantageously limits wear by soil friction.

[0032] In an embodiment, the dissipation sleeve comprises an abrasive-resistant material, advantageously a metal. In an embodiment, the dissipation sleeve comprises stainless steel, advantageously hardened stainless steel. The use of an abrasive-resistant material helps reduce the mechanical wear on the dissipation sleeve, leading to improved structural integrity. The use of steel, advantageously stainless steel, helps prevent the formation of an insulating oxidated layer between the dissipation sleeve and inner sleeve. The prevention of such oxidation maintains optimized heat transfer.

[0033] In an embodiment, the heating element comprises a heating wire, the heating wire being provided over an outer surface of the inner sleeve. In an advantageous embodiment, the inner sleeve comprises a spiral groove to accommodate the heating wire. In an embodiment, the groove is provided on an outer surface of the inner sleeve. Alternatively, or additionally, a groove for accommodating a heating wire may be provided on an inner surface of the inner sleeve.

[0034] The use of a spiral groove ensures that a single wire may be used, while covering substantially the whole surface of the inner sleeve. In an alternative embodiment, two or more heating wires may be utilized, in the same or separate grooves over the inner sleeve. Advantageously, a thermal paste is provided between the inner sleeve and the dissipation sleeve. Such a thermal paste may aid in the homogenous heating of the inner sleeve and the dissipation sleeve. The number of spirals around the inner sleeve may further influence the heating homogeneity of the heat flow module. For example, if a thermal paste is used, the grooves defining the spiral around the inner sleeve may be spaced further apart to attain a similar level of heating homogeneity. In an embodiment, the dissipation sleeve and the inner sleeve may be pressed together such that no spacing is defined therebetween. This limits the risk of an insulating air layer being present between the inner sleeve and the dissipation sleeve. In an alternative embodiment, the inner sleeve and the dissipation sleeve are integrally formed.

[0035] To achieve a uniform heating of the inner sleeve and the heat flow module, advantageously, a spiral heating wire with several windings may be utilized as the heating element. In combination with a highly conductive material, such as aluminium, of the inner sleeve, heat dissipation through the dissipation sleeve and inner sleeve heat flow module is increased, leading to a more homogeneous temperature profile throughout the dissipation sleeve and inner sleeve. In an advantageous embodiment, a thermal paste may be utilized between the inner sleeve and the dissipation sleeve, which further aids in the thermal dissipation of energy between the dissipation sleeve and the inner sleeve.

[0036] In an embodiment, the inner sleeve comprises at least one slot to accommodate the temperature sensor. In an embodiment, the inner sleeve comprises at least one hole, the at least one hole being arranged such that the heating wire and/or a data wire of the temperature sensor can protrude through the hole. In an embodiment, the heating wire is led through a first hole, and a data wire of the temperature sensor is led through another hole. It may be advantageous to separate the heating wire and the data wire due to the heat produced by the heating wire. In an alternative embodiment, the heating wire and the data wire protrude through the same hole. An additional access hole may be provided in the inner sleeve such that an inner region of the inner sleeve may be reached, even if the data wire and the heating wire are already installed and protrude through the at least one hole.

[0037] In an embodiment, the heat flow cone penetrometer system further comprises an electronic control unit, arranged to control the temperature sensor and/or the heating element. In an embodiment, the electronic control unit only controls the heating element, such that the temperature sensor is automated to measure and store and/or transmit the measurement results. The electronic control unit may further be arranged to provide communication between all sensors and the control software. Further, the electronic control unit may measure output changes of the sensors and advantageously translate these measured electric values to, e.g., a temperature value. In an advantageous embodiment, the electronic control unit measures temperature, current, and/or voltage. The electronic control unit may be provided in a middle region of a heat flow module, such that it is provided within an inner sleeve of the heat flow module. In an embodiment, each heat flow module comprises an electronic control unit. In an alternative embodiment, the heat flow cone penetrometer system comprises a single electronic control unit which is arranged to control a plurality of heat flow modules.

[0038] In an embodiment, the heat flow module comprises at least one insulation ring, provided at a distal end of the heat flow module. In an embodiment, the insulation ring comprises a plastic, advantageously polyether ether ketone (PEEK). In an embodiment, the insulation ring comprises at least one of rubber, thermally non-conductive and/or insulating plastics, such as Teflon, insulating glass filled plastics. In an embodiment, the insulation ring comprises ceramics. Advantageously, the insulation ring is used to help prevent heat loss into the rod above and below the inner sleeve, in an axial direction of the heat flow cone penetrometer system. In addition, the insulation ring may be arranged such that the inner sleeve and the dissipation sleeve are supported by the insulation ring.

[0039] In such an embodiment, the insulation ring may be arranged such that a thermal barrier is defined between the inner sleeve and an inner core of the heat flow cone penetrometer to prevent heat loss the core of the CPT system in radial direction. This helps shield any components of the CPT system in the rods against excess heat produced by the inner sleeve and retains the energy so that a larger proportion of the energy dissipates into the target soil. In an advantageous embodiment, each heat flow modules comprises two insulation rings, one positioned below, and one positioned above each of the heat flow modules. In an embodiment, the heat flow modules may share insulation rings, such that a lower insulation ring of one heat flow module is the upper insulation ring of another heat flow module. As a result, all heat flow modules are thermally insulation from the rest of the CPT system.

[0040] According to an aspect of the invention, there is provided a heat flow module for use in a heat flow cone penetrometer system. Any of the embodiments of the heat flow module described in relation to the heat flow cone penetrometer system may be applied to this aspect of the invention. The heat flow module advantageously comprises a dissipation sleeve and an inner sleeve. In an embodiment, the dissipation sleeve is provided around the inner sleeve. Advantageously, the inner sleeve comprises a temperature sensor. The temperature sensor measures the decrease or increase in temperature of the heat flow module, such that the heat dissipation through the soil may be determined. Advantageously, the heat flow module is arranged for use in a heat flow cone penetrometer system according to any of the embodiments disclosed herein.

[0041] According to an aspect of the invention, there is provided a method of producing a heat flow cone penetrometer system comprising the steps of providing a cone penetrometer, providing a pushrod, providing at least one heat flow module, attaching the at least one heat flow module between the cone penetrometer and the pushrod to form a thermal cone penetration system according to any of the embodiments disclosed herein.

[0042] According to an aspect of the invention, there is provided a method of determining a subsurface thermal conductivity, comprising the steps of providing a heat flow cone penetrometer system according to any of the embodiments disclosed herein, advancing the heat flow cone penetrometer into a target soil, heating the heat flow module by providing power to the heating element of the heat flow module, measuring the temperature of the heat flow module using the temperature sensor of the heat flow module to determine a temperature gradient as a function of time as the heat flow module is cooled by the surrounding target soil.

[0043] In an embodiment, the step of heating the heat flow module comprises providing a variable voltage input, such that a constant power output is provided. The use of a variable voltage input allows the provision of a constant power output by the heating element. With increasing temperature, the resistivity of the heating element, such as the heating wire, will decrease. As a result, the input voltage must be changed to allow for a constant (heating) power output over time. This allows for a more accurate determination of the thermal conductivity of the surrounding soil. In an advantageous embodiment, the power output is controlled by the electronic control unit. [0044] The heat flow from the heat flow module into the surrounding soil is dependent on the temperature gradient between the two. As the surrounding soil dissipates the energy from the heat flow module, the temperature of the heat flow module decreases and so does the temperature gradient. The speed at which the temperature gradient is reduced is dependent on the energy dissipation through the soil and the total amount of energy in the heat flow module. Knowing the amount of energy in the heat flow module thus allows for a more accurate determination of the dissipation through the soil. In an alternative, or additional, embodiment, the temperature is monitored during the heating of the inner sleeve, such that the heating of the soil is measured.

[0045] According to an aspect of the invention, there is provided a kit of parts for producing and using a heat flow cone penetrometer system, comprising, a cone penetrometer, a pushrod, and at least one heat flow module according to any of the embodiments disclosed herein.

[0046] Advantageously, the kit of parts is arranged for producing and using a heat flow cone penetrometer system according to any of the embodiments disclosed herein. Additional features and advantages of the disclosure will be set forth throughout this disclosure, and in part will be obvious from the description, or can be learned by practice of the herein disclosed principles. The features and advantages of the disclosure can be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to describe the manner in which the above-recited and other advantages and features of the disclosure can be obtained, a more particular description of the principles briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only exemplary embodiments of the disclosure and are therefore not to be considered to be limiting of its scope, the principles herein are described and explained with additional specificity and detail through the use of the accompanying drawings in which:

[0048] FIG. 1 is a side view of the heat flow cone penetrometer system according to an embodiment of the invention;

[0049] FIG. 2 is a cut-out view of the heat flow cone penetrometer system according to an embodiment of the invention;

[0050] FIG. 3 is a three-dimensional view of the inner sleeve of a heat flow module in the heat flow cone penetrometer system according to an embodiment of the invention; and

[0051] FIG. 4 is a three-dimensional cross-sectional view of a section of the heat flow cone penetrometer system according to an embodiment of the invention showing a heat flow module.

DESCIPTION OF ILLUSTRATIVE EMBODIMENTS

[0052] The following is a description of certain embodiments of the invention, given by way of example only and with reference to the drawings.

[0053] Various embodiments of the disclosure are discussed in detail below. While specific implementations are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations may be used without parting from the spirit and scope of the disclosure. Thus, the following description and drawings are illustrative and are not to be construed as limiting. Numerous specific details are described to provide a thorough understanding of the disclosure. However, in certain instances, well-known or conventional details are not described in order to avoid obscuring the description. A reference to an embodiment in the present disclosure can be a reference to the same embodiment or any other embodiment. Such references thus relate to at least one of the embodiments herein.

[0054] Reference to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by some embodiments and not by others.

[0055] The terms used in this specification generally have their ordinary meanings in the art, within the context of the disclosure, and in the specific context where each term is used. Alternative language and synonyms may be used for any one or more of the terms discussed herein, and no special significance should be placed upon whether or not a term is elaborated or discussed herein. In some cases, synonyms for certain terms are provided. A recital of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification including examples of any terms discussed herein is illustrative only and is not intended to further limit the scope and meaning of the disclosure or of any example term. Likewise, the disclosure is not limited to various embodiments given in this specification.

[0056] Without intent to limit the scope of the disclosure, examples of instruments, apparatus, methods, and their related results according to the embodiments of the present disclosure are given below. Note that titles or subtitles may be used in the examples for convenience of a reader, which in no way should limit the scope of the disclosure. Unless otherwise defined, technical and scientific terms used herein have the meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. In the case of conflict, the present document, including definitions will control.

[0057] Additional features and advantages of the disclosure will be set forth in the description which follows, and in part will be obvious from the description, or can be learned by practice of the herein disclosed principles. The features and advantages of the disclosure can be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features of the disclosure will become more fully apparent from the following description and appended claims or can be learned by the practice of the principles set forth herein. [0058] Referring to FIG. 1, a side view of the heat flow cone penetrometer system 1 according to an embodiment of the invention is shown. The heat flow cone penetrometer system 1 is arranged to measure subsurface thermal conductivity. The heat flow cone penetrometer system 1 comprises a cone penetrometer 2. The cone penetrometer may be a standard cone penetrometer commonly used in industry. The cone penetrometer 2 extends between a tip 21 and a proximal end 22. The heat flow cone penetrometer system 1 further comprises a pushrod 3, which is arranged to translate a compressive force to the cone penetrometer 2 as it is being driven into a target soil. The pushrod 3 comprises a connection section 31. The connection section 31 of the pushrod 3 is arranged to couple pushrod 3 to components of the heat flow cone penetrometer system 1.

[0059] The heat flow cone penetrometer system 1 in the shown embodiment comprises three heat flow modules 4, separated by intermediate sections 7. The heat flow modules 4 are provided between the proximal end 22 of the cone penetrometer 2 and the connection section 31 of the pushrod 3. Each of the heat flow modules 4 of the illustrated embodiment comprises at least one heating element 41 and at least one temperature sensor 42.

[0060] Between the heat flow modules 4 in the shown embodiment, a plurality of insulation rings 6 are provided. These insulation rings 6 are arranged to insulate the heat flow modules from one another, such that the produced heat of a first heat flow module 4 does not affect the temperature measurements of the temperature sensor 42 of a second heat flow module 4.

[0061] The heat flow modules 4 are axially stacked between the cone penetrometer 2 and the connection section 31 of the pushrod 3. The heat flow cone penetrometer system 1 may comprise more or fewer heat flow modules 4, as may be appropriate to achieve sufficient resolution of thermal dissipation in the target soil, and/or to increase the total range of measurement depth in one measurement cycle.

[0062] Now referring to FIG. 2, a cut-out view of the heat flow cone penetrometer system 1 according to an embodiment of the invention is shown. For illustrative purposes, FIG. 2 shows only a single heat flow module 4 between the connection section 31 of the pushrod 3 and the proximal end 22 of the cone penetrometer 2. The heat flow module 4 comprises a dissipation sleeve 43 and an inner sleeve 44. The dissipation sleeve 43 is provided around the inner sleeve 44. The inner sleeve 44 comprises the heating element 41. In this case, the heating element 41 is a heating wire, which is spooled around the inner sleeve 44 through grooves provided on an outer surface of the inner sleeve 44. [0063] The heat flow module 4 further comprises a temperature sensor 42, which is contained in a slot on the outer surface of the inner sleeve 44. The heat generated by the heating element 41 in the form of a heating wire 41 provided in the grooves on the outer surface of the inner sleeve is distributed through the inner sleeve 44 and the dissipation sleeve 43, which is provided around the inner sleeve 44. Once the measurement is started, the heat production through the heating wire 41 is halted, after which the temperature sensor 42 measures the decline in temperature as heat dissipates from the inner sleeve into the soil. In an alternative embodiment, the measurement is performed during the heating of the heating wire 41, such that the measurements through the temperature sensor 42 are taken simultaneously as the heat production through the heating wire 41 is started.

[0064] The heat flow module 4 further comprises an electronic control unit 5, which is provided in the middle of the heat flow module 4 such that it extends through the inner sleeve 44. The electronic control unit 5 is arranged to control the heat provided by the heating wire 41 and retrieve the measurement results from the temperature sensor 42 as the heat dissipation through the soil is measured.

[0065] An insulation ring 6 is provided at both ends of the heat flow module 4. The insulation ring 6 is used to help prevent heat loss into the rod above and below the inner sleeve 44, in an axial direction of the heat flow cone penetrometer system 1. In addition, the insulation ring 6 is arranged such that the inner sleeve 44 and the dissipation sleeve 43 are supported by the insulation ring 6. As a result, an insulating air gap is defined between the inner sleeve 44 and an inner core of the heat flow cone penetrometer system 1 to prevent heat loss the core of the CPT system in radial direction.

[0066] Now referring to FIG. 3, a three-dimensional view of the inner sleeve 44 of a heat flow module 4 in the heat flow cone penetrometer system 1 according to an embodiment of the invention is shown. The inner sleeve 44 of the shown embodiment comprises a set of two offset spiral grooves 47, which are arranged to receive a heating wire 41. The inner sleeve further comprises a plurality of slots 45, arranged to receive temperature sensors 42. These temperature sensors 42 are arranged to measure the change in temperature of the heat flow module 4 to determine the heat dissipation through a target soil.

[0067] The inner sleeve 44 of the shown embodiment further comprises a hole 46, which extends through the inner sleeve 44 from an outer surface of the inner sleeve 44 to an inner surface of the inner sleeve 44. The hole 46 is arranged to receive the heating wire 41, which may protrude through the hole 46 and extend through the inner sleeve 44 such that the heating wire 41 may be controlled and provided with power from within the inner sleeve 44 where the electronic control unit 5 is provided.

[0068] The inner sleeve 44 further comprises a temperature sensor cable hole 47, which is provided separately from the through-hole 46 for the heating wire 41. The temperature sensor cable hole 47 is provided such that a cable extending from the temperature sensor 42 may extend through the inner sleeve 44 in a similar manner as the heating wire 41, but without being provided in the same hole.

[0069] Now referring to FIG. 4, a three-dimensional cross-sectional view of a section of the heat flow cone penetrometer system 1 according to an embodiment of the invention is shown. The section illustrates a heat flow module 4 of the heat flow cone penetrometer system 1. The heat flow module 4 of the shown embodiment comprises an inner sleeve 44 and a dissipation sleeve 43 provided around the inner sleeve 44. The inner sleeve 44 comprises grooves, in which a heating wire 41 is contained, such that the heating wire 41 turns around the inner sleeve 44. A plurality of temperature sensors 42 are provided in slots provided on an outer surface of the inner sleeve.

[0070] The heat flow cone penetrometer system 1 comprises an electronic control unit 5 provided in the heat flow module 4. In the shown embodiment, a single electronic control unit 5 is provided in a single heat flow module 4. Similar heat flow modules 4 may also comprise an electronic control unit 5. Alternatively, one electronic control unit 5 may be utilized to control a plurality of heat flow modules 4.

[0071] Two insulating rings 6 are provided on either side of the heat flow module 4, such that the insulation rings 6 support the dissipation sleeve 43 and the inner sleeve 44. The insulation rings 6 are provided such that they reduce the internal heat flow in an axial and radial direction of the heat flow cone penetrometer system 1, improving the data acquisition quality.

[0072] The invention has been described by reference to certain embodiments discussed above. It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those of skill in the art.

[0073] Further modifications in addition to those described above may be made to the structures and techniques described herein without departing from the spirit and scope of the invention. Accordingly, although specific embodiments have been described, these are examples only and are not limiting upon the scope of the invention.