Patent Publication Number: US-2017356832-A1

Title: Devices and method for evaluating the integrity of soil behind an infrastructure

Description:
FIELD 
     The improvements generally relate to methods and systems for inspecting a buried infrastructure such as a pipe and more particularly to methods and systems for evaluating the presence or absence of soil behind a wall of the buried infrastructure. 
     BACKGROUND 
     Inspecting infrastructure such as culverts, levees and storm sewers is of relevance in order to manage maintenance thereof. For instance, such infrastructures can be provided in the form of underground channels allowing passage of water under roadways and are generally obtained by burying a large diameter pipe under soil (e.g., sand gravel and/or aggregates). 
     Culverts, levees and/or storm sewers can deteriorate over time due to, for instance, erosion of the soil surrounding the pipes. As the soil surrounding a pipe gradually erodes, voids can be created between the surrounding soil and the pipe, thus increasing risks of failure (e.g., washout due to flooding). As deterioration of such infrastructure depends on external physical factors, inspecting each infrastructure is key in providing a satisfactory maintenance plan. 
     Inspection of such infrastructures is typically provided in the form of visual inspection and/or acoustic inspection. There thus remains room for improvement. 
     SUMMARY 
     In accordance with an aspect, there is provided a device for use in evaluating the integrity of soil behind a wall of an infrastructure, the device comprising: a frame having a plurality of rests adapted to be received onto the wall during use; a hammer assembly having an actuator fixedly mounted to the frame and a hammer element having a head movably mounted to the frame, the actuator being actuatable to move the head to strike the wall while the plurality of rests hold the frame in a fixed position relative to the wall; and a sensor configured and adapted to sense vibrations of a portion of the wall resulting from the strike and to generate a vibration signal indicative thereof. 
     In accordance with another aspect, there is provided a computer-implemented method of evaluating an integrity level of soil behind a wall of an infrastructure, the method comprising: activating an actuator to cause a hammer strike onto the wall; receiving a vibration signal representing vibrations of a portion of the wall after the hammer strike; determining at least one of a signal strength and a decay rate of the vibration signal; and assigning the at least one of the signal strength and the decay rate as the soil integrity level. 
     In accordance with another aspect, there is provided a computer-implemented method of evaluating an integrity level of soil behind a wall of an infrastructure, the method comprising: activating an actuator to cause a hammer strike onto the wall; receiving a vibration signal representing vibrations of a portion of the wall after the hammer strike; determining a decay rate of the vibration signal; and assigning the decay rate as the soil integrity level. 
     In accordance with another aspect, there is provided a computer-implemented method of evaluating an integrity level of soil behind a wall of an infrastructure, the method comprising: activating an actuator to cause a hammer strike onto the wall; receiving a vibration signal representing vibrations of a portion of the wall after the hammer strike; determining a signal strength of the vibration signal; and assigning the signal strength as the soil integrity level. 
     In accordance with another aspect, there is provided a device for evaluating an integrity level of soil behind a wall of an infrastructure, the device comprising: a computer-readable memory having stored thereon program code executable by a processor; and a processor configured for executing the program code, the processor being configured for: activating an actuator to cause a hammer strike onto the wall; receiving a vibration signal representing vibrations of a portion of the wall after the hammer strike; determining at least one of a signal strength and a decay rate of the vibration signal; and assigning the at least one of the signal strength and the decay rate as the soil integrity level. 
     In accordance with another aspect, there is provided a device for evaluating an integrity level of soil behind a wall of an infrastructure, the device comprising: a computer-readable memory having stored thereon program code executable by a processor; and a processor configured for executing the program code, the processor being configured for: activating an actuator to cause a hammer strike onto the wall; receiving a vibration signal representing vibrations of a portion of the wall after the hammer strike; determining a signal strength of the vibration signal; and assigning the signal strength as the soil integrity level. 
     In accordance with another aspect, there is provided a device for evaluating an integrity level of soil behind a wall of an infrastructure, the device comprising: a computer-readable memory having stored thereon program code executable by a processor; and a processor configured for executing the program code, the processor being configured for: activating an actuator to cause a hammer strike onto the wall; receiving a vibration signal representing vibrations of a portion of the wall after the hammer strike; determining a decay rate of the vibration signal; and assigning the decay rate as the soil integrity level. 
     Many further features and combinations thereof concerning the present improvements will appear to those skilled in the art following a reading of the instant disclosure. 
    
    
     
       DESCRIPTION OF THE FIGURES 
       In the figures, 
         FIG. 1  is a schematic view of an exemplary device for evaluating the integrity of soil behind a wall of an infrastructure; 
         FIG. 2  is an axial view of a buried infrastructure having a cylindrical wall receiving, at a first portion thereof, the device of  FIG. 1 ; 
         FIG. 2A  is a graph of an exemplary vibration signal representing vibrations of the first portion after a hammer strike by the device of  FIG. 1 ; 
         FIG. 3  is an axial view of a buried infrastructure having a cylindrical wall receiving, at a second portion thereof, the device of  FIG. 1 ; 
         FIG. 3A  is a graph of an exemplary vibration signal representing vibrations of the second portion after a hammer strike by the device of  FIG. 1 ; 
         FIG. 4  is a flow chart of an example method for evaluating the integrity of soil behind a wall of an infrastructure using the device of  FIG. 1 ; 
         FIG. 5  is a block diagram of an example of the device of  FIG. 1 ; 
         FIGS. 6A-C  are sectional views of an exemplary hammer assembly during a hammer strike on a wall of an infrastructure; 
         FIG. 7  is an image showing an embodiment of the device of  FIG. 1 ; 
         FIG. 8  is an image showing another embodiment of a device for evaluating the integrity of soil behind a wall of an infrastructure; 
         FIG. 9  is a top view of an example of a sensor of the device of  FIG. 8 ; and 
         FIG. 10  is a block diagram of another embodiment of a device for evaluating the integrity of soil behind a wall of an infrastructure portion. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an example of a device  100  that can be used for evaluating the integrity of soil behind a wall  20  of an infrastructure  12 . Such an infrastructure can be a pipe typically having a cylindrical wall with an accessible inner face. The device  100  can be used also with pipes being corrugated along their lengths, i.e. corrugated pipes. In some embodiments, the device  100  can be used with other types of buried infrastructure. 
     Broadly described, the device  100  includes a hammer assembly  110  and a sensor  120  mounted directly or indirectly to a frame  140 . The frame  140  can be provided in the form of a housing that may be water-resistant. As it will be described, the device  100  can have a processor  130  in communication with the sensor  120 , with a computer-readable memory  160  and/or with the hammer assembly  110 . 
     As shown in  FIG. 1 , the frame  140  has rests  142  adapted to be received onto the wall  20  of the infrastructure  12  during use. The hammer assembly  110  has an actuator fixedly mounted to the frame  140  and a hammer element  114 . The hammer element  114  has a head  114   a  movably mounted to the frame  140 . The actuator is actuatable to move the head  114   a  to strike against the wall  20  while the rests  142  hold the frame  140  in a fixed position relative to the wall  20 . The strike can cause a portion of the wall  20  to vibrate for a given period of time. Any suitable type of actuator can be used to perform such a function. For instance, the actuator can be hydraulic, pneumatic, electric, thermal, magnetic, mechanical and/or any combination thereof. 
     The sensor  120  is configured and adapted to generate a vibration signal representing vibrations of the portion of the wall  20  after the strike from the head  114   a  of the hammer element  114 . 
     For instance, in the embodiment shown, the sensor  120  can be made integral to a sensing one of the rests  142 , and the sensing one of the rests  142  has a pointed tip. As depicted, the hammer assembly  110  can be surrounded by the rests  142  such that the hammer element  114  strikes a point proximate that of the sensor  120 . In some embodiments, the rests are provided in a narrow linear arrangement such as to be positioned along a corrugation of a corrugated pipe. In some other embodiments, the rests  142  are provided with pressure-sensitive sensors allowing to maintain the rests  142  received onto the wall  20  at a given pressure. This can allow uniformity and repeatability between successive measurements. 
     The mechanical strike can be initiated by a user input received at a user interface  150  of the device  100 . In an embodiment, the user interface  150  is embodied by a trigger switch mounted to the frame  140 . The user interface  150  can be provided in any other suitable forms. For instance, in alternate embodiments, the user interface is embodied by a touch-sensitive liquid crystal display or a remote external device (e.g., a smart phone or an electronic tablet). 
     After the mechanical strike, the sensor  120  can pick up the vibrations of the portion of the wall  20  and generate a vibration signal representing the vibrations of the wall  20 . The vibration signal can be analyzed by the processor  130  to evaluate the integrity of soil behind the wall  20  such as evaluating if there is a presence or an absence of soil behind the wall  20 . The evaluation of the integrity of soil behind the wall  20  can be performed by instructions  170  stored on the memory  160  and executable by the processor  130  to measure a value indicative of soil integrity behind the wall based on the vibration signal. The value (or soil integrity level) can include a decay rate, a signal strength, a mean amplitude, a frequency and/or a combination thereof. In some embodiments, the processor  130  and the memory  160  are part of a computer. 
     Once generated, the soil integrity level can be displayed on the user interface  150 . 
     It is appreciated that the hammer assembly  110  is designed such that it can mechanically strike the wall  20  with a substantially repeatable force. Knowing the force at which the wall  20  is stroke by the hammer assembly  110  with a satisfactory accuracy can reduce several variables that can cause artifacts in the vibration signal. Such variables can include an initial amplitude of the vibrations in the portion of the wall  20 , an angle of impact and multiple strikes. 
     It is noted that the processor  130  is in a wired communication and/or in a wireless communication with the hammer assembly  110 , the sensor  120  and the user interface  150 . It is further noted that the processor  130  can be provided in the form of a microcomputer having a non-volatile memory and firmware and/or a processor in communication with a computer-readably memory. The instructions  170  can include signal processing algorithms, reference and/or threshold values for use in generating the value, which can be stored on a memory of the processor  130  once determined. The processor  130  can include a power source such as a battery (e.g., a rechargeable battery). 
     For instance,  FIGS. 2 and 3  show axial views of an example of an infrastructure  12  provided in the form of a pipe fully buried into soil  16 . In this case, the wall  20  is cylindrical. 
     As shown, the device  100  is sized and shaped to be handheld. For instance, the frame  140  is adapted to be received onto the wall  20  such as to remain in a fixed position at least during the inspection with aid of a support structure  22  and/or of a user. For instance, in the embodiment shown, the rests  142  of the frame  140  are maintained against the wall  20  where an inspection is to be performed. As it will be understood, the type of frame and its construction can vary from an embodiment to another. 
     The design of the device  100  is based on the fact that the wall  20  can resonate differently when soil is pushed-up against an outer face  24  of the infrastructure  12  in comparison to when there is no soil contacting the outer face  24 . When a presence of soil  16  is present behind the wall  20  of the infrastructure  12 , the vibratory energy generated by the mechanical strike is likely to be absorbed quickly by the soil in intimate contact with the outer face  24  of the infrastructure  12 , translating into a relatively short-lived damped oscillation in the wall  20 . In other words, the decay rate of that damped oscillation will be smaller than a decay rate threshold. 
     Conversely, when an absence of soil  16  is present behind the wall  20 , meaning no soil is in contact with the outer face  24  of the infrastructure  12 , the decay rate of the damped oscillation in the wall  20  will be longer (than the decay rate threshold) because the vibratory energy imparted to the wall  20  by the mechanical strike is not absorbed quickly by the soil (because there is less of it or none). 
     For instance,  FIG. 2  shows the device  100  during an inspection of a first portion  20   a  of the wall  20  of the infrastructure  12 , from the interior of the infrastructure  12 . When the rests  142  of the device  100  are received on the wall  20 , the user interface can receive a user input to cause the hammer assembly to mechanically strike the wall  20 . This mechanical strike generally causes the first portion  20   a  to vibrate during a given period of time. The sensor  120 , in contact with the wall  20 , can sense vibrations associated with the vibrating first portion  20   a  and can generate a first vibration signal  104   a  indicative of an amplitude of the vibrations of the portion over a period of time following the mechanical strike. 
     An example of the first vibration signal  104   a  is shown in  FIG. 2A . As mentioned above, the first vibration signal  104   a  can be used to evaluate the integrity of soil behind the first portion  20   a . As it can be seen in this example, the first vibration signal  104   a  has a few cycles of different amplitudes and is characterized by a first decay rate  106   a  that can be determined by the processor  130 . 
     In this embodiment, the processor  130  can be operated to compare the first decay rate  106   a  with a decay rate threshold that is stored on the memory. For instance, in the case of the first portion  20   a , as expected from  FIG. 2 , the first decay rate  106   a  is smaller than a given decay rate threshold so the device  100  can evaluate that there is a presence of soil  16  behind the first portion  20   a  of the wall  20 . 
       FIG. 3  shows the device  100  during an inspection of a second portion  20   b  of the wall  20  of the infrastructure  12 , from the interior of the infrastructure  12 . An inspection similar to the one above is performed with the device  100  which, in this case, generates a second vibration signal  104   b.    
     An example of the second vibration signal  104   b  is shown in  FIG. 3A . As mentioned above, the second vibration signal  104   b  can be used to evaluate the integrity of soil behind the second portion  20   b . More specifically, as it can be seen, the second vibration signal  104   b  is characterized by a second decay rate  106   b.    
     In this case, the processor  130  is operable to compare the second decay rate  106   b  with the decay rate threshold to determine the integrity of soil behind the wall  20 . For instance, the second decay rate  106   b  is longer than the decay rate threshold so the device  100  can evaluate that there is an absence of soil  16  behind the second portion  20   b  of the wall  20 . 
       FIG. 4  shows a flow chart of an exemplary computer-implemented method  400  for evaluating an integrity level of soil behind a wall of an infrastructure. The method  400  can be performed using the device  100  and will be described with reference to  FIG. 1 . 
     At step  402 , the device  100  activates an actuator of the hammer assembly  110  to cause a hammer strike onto the wall  20 . The activation of the actuator of the hammer assembly  110  can include powering the actuator with an electrical signal. Depending on the type of actuator used, the electrical signal can vary. In some embodiments, this step can be initiated upon receiving a user input at the user interface  150 . 
     At step  404 , the device  100  receives a vibration signal representing vibrations of the portion of the wall  20  after the hammer strike. The vibration signal is measured using the sensor  120 . 
     At step  406 , the device  100  determines a signal strength and/or a decay rate of the vibration signal using the processor  130 . In some embodiments, the vibration signal is analyzed by the processor  130  to find an equation which can fit the vibration signal. This equation can be of the form y=Ae kx  where y is the amplitude of the vibration signal, x is the sample&#39;s time stamp, A is a constant indicative of the signal strength and k is a constant indicative of the decay rate. In some other embodiments, the vibration signal is converted to a log scale using w=log e (y). Wth the data points for each test converted to a log scale, constants m and b can be determined such that the line w=mx+b is best fitted to the data. In this case, e b  is indicative of the signal strength and m is indicative of the decay rate. 
     At step  408 , the device  100  assigns the signal strength and/or the decay rate as the soil integrity level. In some embodiments, the device  100  displays the soil integrity level on the user interface  150 . The soil integrity level can be a value corresponding to the determined signal strength and/or decay rate in some embodiments. 
     In some embodiments, as per steps  410  and  412 , the device  100  compares the signal strength and/or the decay rate to a threshold and signals an absence of soil behind the wall  20  when the signal strength and/or the decay rate is below the threshold. In some embodiments, the threshold is stored on the computer-readable memory  160 . In some embodiments, the device  100  receives an input indicating which type of infrastructure (e.g., culverts, levees, storm sewers, foundations) or material (e.g., steel, concrete, wood, metal, plastics) is being inspected. In this way, the threshold can be selected among a plurality of thresholds each associated with a respective type of infrastructure or material. 
     The processor  130  may comprise more than one processor and/or any suitable devices configured to cause a series of steps to be performed so as to implement the computer-implemented method  400  such that software instructions  170  (see  FIG. 1 ), when executed by a processor  130  or other programmable apparatus, may cause the execution of functions/acts/steps specified in the methods described herein. The processor  130  may comprise, for example, any type of general-purpose microprocessor or microcontroller, a digital signal processing (DSP) processor, a central processing unit (CPU), an integrated circuit, a field programmable gate array (FPGA), a reconfigurable processor, other suitably programmed or programmable logic circuits, or any combination thereof. 
     The memory  160  may comprise any suitable known or other machine-readable storage medium. The memory  160  may comprise non-transitory computer readable storage medium such as, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. The memory  160  may include a suitable combination of any type of computer memory that is located either internally or externally to device such as, for example, random-access memory (RAM), read-only memory (ROM), compact disc read-only memory (CDROM), electro-optical memory, magneto-optical memory, erasable programmable read-only memory (EPROM), and electrically-erasable programmable read-only memory (EEPROM), Ferroelectric RAM (FRAM) or the like. Memory may comprise any storage means (e.g., devices) suitable for retrievably storing machine-readable instructions executable by processor. 
       FIG. 5  is a block diagram of an exemplary embodiment of the device  100 , which can be implemented by the processor  130 . As depicted, a signal strength and decay rate module  500  and a soil integrity level module  502  embody the software instructions  170  shown in  FIG. 1 . 
     The signal strength and decay rate module  500  is configured to activate the actuator of the hammer assembly  110 , as per step  402 , to receive a vibration signal, as per step  404 , and to determine a decay rate of the vibration signal, as per step  406 . Once determined, the decay rate is provided to the soil integrity level module  502 . 
     The soil integrity level module  502  receives the decay rate from the signal strength and decay rate module  500  and assigns the decay rate as the soil integrity level, as per step  408 . Once determined, the soil integrity level can be displayed on a user interface and/or stored on a database  504  coupled to the soil integrity level module  502 . Previously stored soil integrity levels can form history data accessible by the soil integrity level module  502 . 
     The soil integrity level module  502  can also be configured to obtain a decay rate threshold, to compare the decay rate to the decay rate threshold, as per step  410 , and to signal an absence of soil behind the wall  20  when the decay rate is below the decay rate threshold, as per step  412 . The decay rate threshold can be stored in the database  504  or in any other storage medium. 
     As it will be understood, different embodiments of the hammer assembly  110  can be used. For instance,  FIGS. 6A-C  show an embodiment of the hammer assembly  110  which includes an actuator  112  and a hammer element  114 . 
     The actuator  112  is fixedly mounted to the frame  140 , and the hammer element  114  is actuatable by the actuator  112 . During use, the actuator  112  can be used to actuate the hammer element  114  to move from a rest position to a second position protruding from the frame and towards the wall  20  to strike it. The mechanical strike between the hammer element  114  and the wall  20  is of sufficient importance to cause the portion to vibrate for a satisfactory period of time and at satisfactory amplitudes. 
     As shown in  FIGS. 6A-C , the hammer element  114  has a biasing element  116  so that the hammer element  114  can be biased to a retracted position after the mechanical strike. This can prevent subsequent strikes of the hammer element  114  on the given portion from happening, which may add undesirable artefacts to the vibration signal. In this embodiment, the biasing element  116  is provided in the form of a compression spring. The biasing element  116  is optional as, in this embodiment, retracting the hammer element  114  can be performed by the actuator  112 . 
     As shown, the hammer element  114  is provided in the form of an electromechanical hammer. More specifically, the hammer assembly  110  has the actuator  112  which is provided in the form of a solenoid actuator. In this example, the actuator  112  includes a guiding sleeve  118  around which is provided a number of turns N of a conductive wire  120  of a given diameter D. In this example, the hammer element  114  is made of a ferromagnetic material such that when the actuator  112  is powered, an electromotive force forces the hammer element  114  to be outwardly projected. As it can be seen, the hammer element  114  is slidably received into the guiding sleeve  118  of the actuator  112 . 
     At  FIG. 6A , the actuator  112  is provided as part of an electrical circuit  122  having a capacitive element  124  (e.g., a large value capacitor), a charge pump  126  and an electrical switch  128 . Prior to actuating the hammer element  114 , the charge pump  126  charges the capacitive element  124  so that a given amount of charges is stored therein. When a user input is received via the user interface, the processor is operable to close the electrical switch  128  of the electrical circuit  122  which causes the charges stored in the capacitive element  124  to be dumped in the conductive wire  120 , thus creating the electromotive force and the desired mechanical strike. By repetitively dumping the same amount of charges into the conductive wire  120  at each mechanical strike, the electromotive force can be known and calibrated. 
     It is noted that the processor  130  monitors the voltage level on the capacitive element  124  and when it reaches a satisfactory level, the charge pump  126  is stopped and the charge in the capacitive element  124  is maintained at a given level. 
     Following the projection of the hammer element  114 , the head  114   a  strikes the wall  20  which causes extension of the biasing element  116  as shown in  FIG. 6B . The extension of the biasing element  116  stores energy that is used to retract the head  114   a  of the hammer element  114  inwardly back towards the frame as shown in  FIG. 6C . More specifically, the head  114   a  of the hammer element  114  projects just far enough to strike against the wall  20  of the infrastructure  12 , then is quickly retracted by the biasing element  116 , preventing multiple contacts with the wall  20 . 
       FIG. 7  shows an image representative of the device  100 . As shown, the frame  140  of the device  100  is open to show its interior. In this case, the frame  140  has a cover to close the frame  140  in order to protect its internal components. In this example, the sensor  120  is made integral to one of the three rests  142 . As it can be seen, the support structure  22  is pivotably mounted to the support structure  22  via a joint  26 . As depicted, a handle  26  is provided to pivot the frame  140  relative to the support structure  22  during use. 
     Providing the sensor  120  with a pointy tip has been found satisfactory to pick up vibrations. As shown, the hammer element  114  is in its rest position. The hammer element  114  is surrounded by the rests  142  such that when the hammer element  114  is projected outwardly, the head  114   a  protrudes from a plane formed by extremities of each rest  142 . In this embodiment, it is noted that the sensor  120  is isolated vibration-wise from the hammer assembly  110  such that vibration generated by the hammer assembly  110  does not affect the vibration signal picked up by the sensor  120 . 
     In this embodiment, the processor  130  and the memory  160  are provided in the form of an integrated-circuit. The user interface  150  includes a series of LEDs to display the soil integrity level. A red one of the LEDs can be lighted when an absence of soil behind the wall  20  is to be signaled whereas a green one of the LEDs can be lighted when a presence of soil behind the wall  20  is to be signaled. A yellow one of the LEDs can be lighted when it is determined that the decay rate is below the threshold but only by an acceptable amount. 
       FIG. 8  shows an image representative of another example of a device  800  for evaluating the integrity of soil behind a wall of an infrastructure. As depicted, the device  800  has a frame  840 , a hammer assembly  810 , a sensor  820  and a processor  830 . 
     As it will be understood, the processor  830  typically includes a power source port  832  connectable to a power source to power the hammer assembly  810 , the sensor  820  and the user interface during use. In an embodiment, the power source port  832  is connected to a rechargeable battery mounted to the frame  840 . In this embodiment, however, the power source port  832  is connected to an external power supply cord  834  supplying electricity from an external power source  836 . 
     In an embodiment, it is contemplated that the user interface includes a display and that the processor is operable to display the soil integrity level on the display. 
       FIG. 9  shows a schematic view of another example of the sensor  820 . In this embodiment, the sensor  820  and the processor are in communication via an electrical cord  822  allowing the sensor  820  to have a reduced impact on the way the vibratory energy is absorbed in the wall  20 . 
     As shown in this embodiment, the sensor  820  includes an accelerometer  824  and an attachment head  826  secured to one another via a thin sheet  828  of hard rubber to improve mechanical wave propagation of the vibrations to the accelerometer  824 . The attachment head  826  is used to attach the sensor  820  to any given portion of the wall  20 . Any suitable type of attachment can be provided. 
     The accelerometer  824  can generate a vibration signal that is proportional to the acceleration in its axis of detection. When attached to the wall of the infrastructure with its axis normal to the direction of the vibrations, the vibration signal can be representative of an amplitude and of a frequency of the vibrations caused by the mechanical strike. Indeed, the vibrations of the portion of the wall can create a pushing and pulling force on the accelerometer which then gets converted into the vibration signal. An example of such an accelerometer is a commercially available piezoelectric accelerometer. 
     For instance, in this embodiment, the attachment head  826  includes a permanent magnet so as to be magnetically attached to the wall of the infrastructure when the latter is made of a ferromagnetic material. 
       FIG. 10  shows a block diagram of another example of a device  1000  for evaluating the integrity of soil behind a wall of an infrastructure. As shown, the device  1000  has a hammer assembly  1010 , a sensor  1020 , a processor  1030 , a user interface  1050  and a power source  1060 . 
     More specifically, the hammer assembly  1010  has a solenoid hammer  1012  and a hammer driver  1014 . The sensor  1020  includes an accelerometer. The processor  1030  includes a memory  1032 , an arithmetic logic unit  1034 , an analog-to-digital converter  1036  and ports  1038 . The user interface  1050  includes a liquid crystal display  1052  and user input switches  1054 . The liquid crystal display  1052  and the user input switches  1054  are connected to the processor  1030  via the ports  1038 . The processor  1030  includes an input port  1039  connectable to a USB port  1037 . The sensor  1020  is connected to the processor  1030  via a bandpass filter  1022  which includes two integrating amplifiers  1024  (with gains of 10 and 15, respectively) and a signal rectifier  1026 . The power source  1060  is connected to the sensor  1020  via an accelerometer power supply  1062  and further includes an analog chain power supply  1064  and a digital process power supply  1066 . 
     It is noted that the vibration signal is generally AC in nature (i.e. it swings positive and negative) and has a large direct current offset so it is coupled to a buffer circuit by way of a direct current blocking capacitor. The capacitor can be required to block the direct current power supply bias voltage of the sensor. An attenuator can be provided to allow matching of the voltage output level of the vibration signal to an input range of an analog-to-digital converter. The buffer circuits provide a low impedance source to a precision rectifier circuit placed ahead of the analog-to-digital converter. The precision rectifier can be required ahead of the analog-to-digital converter to ensure the signal fed to the converter is positive. The precision rectifier can invert the negative-going swings of the AC vibration signal, making them positive such that it can ensure that no portions of the vibration signal is lost due to polarity blocking. Another following buffer is provided between the precision rectifier and the analog-to-digital converter to again provide a low impedance source to the input circuitry of the converter. A low impedance source can ensure a relatively fast signal response by the sample-and-hold circuit that is part of the converter. 
     Moreover, it is noted that the analog-to-digital converter can be built into the processor. This analog-to-digital converter can have a 10-bit resolution. The analog-to-digital converter can be able to quantize the vibration signal voltage changes as 1 mV and at a rate of 9 600 conversions per second. The conversion results can be stored on a dynamic memory of the processor for further processing. 
     In some embodiments, the evaluation devices  100 ,  800  and/or  1000  may be accessible remotely from any one of a plurality of external devices over connections. The external devices may be any one of a desktop, a laptop, a tablet, a smartphone, and the like. The external devices may have a device application provided thereon as a downloaded software application, a firmware application, or a combination thereof, for accessing the devices  100 ,  800  and/or  1000 . Alternatively, the external devices may access the device  100  via a web application, accessible through any type of Web browser. The external devices may be configured to receive the vibration signal, to determine the value indicative of soil integrity (e.g., a decay rate, an amplitude, a frequency) based on the vibration signal and to display the value. 
     The connections may comprise wire-based technology, such as electrical wires or cables, and/or optical fibers. The connections may also be wireless, such as RF, infrared, W-Fi, Bluetooth, and others. The connections may therefore comprise a network, such as the Internet, the Public Switch Telephone Network (PSTN), a cellular network, or others known to those skilled in the art. Communication over the network may occur using any known communication protocols that enable external devices within a computer network to exchange information. The Examples of protocols are as follows: IP (Internet Protocol), UDP (User Datagram Protocol), TCP (Transmission Control Protocol), DHCP (Dynamic Host Configuration Protocol), HTTP (Hypertext Transfer Protocol), FTP (File Transfer Protocol), Telnet (Telnet Remote Protocol), SSH (Secure Shell Remote Protocol). 
     In some embodiments, each device  100 ,  800  and  1000  is provided at least in part on any one of external devices. For example, each device  100 ,  800  and  1000  may be configured as a first portion provided in the frame  140  to obtain and transmit the vibration signal and/or the decay rate to a second portion, provided on one of the external devices. The second portion may be configured to receive the vibration signal and/or the decay rate, as per steps  404  and  406  of the method  400 , and perform any one of steps  408  to  412  on one of the external devices. Alternatively, each device  100 ,  800  and  1000  is provided entirely on any one of the external devices and is configured to receive from the vibration signal and/or the decay rate. Also alternatively, each device  100 ,  800  and  1000  is configured to transmit, the connections, one or more of the vibration signal and/or the decay rate. Other embodiments may also apply. 
     One or more databases, such as database  504  may be provided locally on any one of the devices  100 ,  800 ,  1000  and the external devices, or may be provided separately therefrom. In the case of a remote access to the database  504 , access may occur via the connections taking the form of any type of network, as indicated above. The various database  504  or other described herein may be provided as collections of data or information organized for rapid search and retrieval by a computer. The database  504  may be structured to facilitate storage, retrieval, modification, and deletion of data in conjunction with various data-processing operations. The database  504  may be any organization of data on a data storage medium, such as one or more servers. The database  504  illustratively has stored therein raw data representing a plurality of features of the inspection, the features being, for example, a relation between the decay rate and the type of material or infrastructure. 
     Each computer program described herein may be implemented in a high level procedural or object oriented programming or scripting language, or a combination thereof, to communicate with a computer system. Alternatively, the programs may be implemented in assembly or machine language. The language may be a compiled or interpreted language. Computer-executable instructions may be in many forms, including program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform particular tasks or implement particular abstract data types. Typically the functionality of the program modules may be combined or distributed as desired in various embodiments. 
     Various aspects of the present device  100 ,  800  and/or  1000  may be used alone, in combination, or in a variety of arrangements not specifically discussed in the embodiments described in the foregoing and is therefore not limited in its application to the details and arrangement of components set forth in the foregoing description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments. Although particular embodiments have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects. The appended claims are to encompass within their scope all such changes and modifications. 
     It is contemplated that the processor can amplify, rectify and/or filter the vibration signal prior to processing it. Further, the processor can also convert the vibration signal from an analog signal to a discrete digital signal. 
     As can be understood, the examples described above and illustrated are intended to be exemplary only. The scope is indicated by the appended claims.