Dual array resistivity pore pressure static cone penetrometer

Abstract

The application discloses a double-array resistivity hole pressure static sounding device, which comprises a conical probe, a hole pressure filter ring, a sidewall upper friction cylinder, a resistivity testing module, a digital circuit board and an analog-digital converter; the conical probe is connected with the sidewall upper friction cylinder through the hole pressure filter ring; the sidewall upper friction cylinder is connected with the resistivity testing module; the sidewall upper friction cylinder is internally provided with a hole pressure sensor, a cone tip resistance sensor, a side friction resistance sensor, a temperature compensator and an inclinometer which are connected with the digital circuit board; the digital circuit board is connected with the resistivity testing module; the digital circuit board is connected with the analog-digital converter through a coaxial cable; the coaxial cable is connected with the analog-digital converter and a data acquisition instrument outside the device; the soil body horizontal resistivity measured by the application has the characteristics of in-situ, rapid, continuous and reliable, and provides a powerful detection tool for geotechnical engineering practice.

Description

A dual-array resistivity pore pressure static cone penetration device Technical Field

[0001] This invention relates to the field of geotechnical engineering, and specifically to a dual-array resistivity pore pressure static cone penetration test device. Background Technology

[0002] Pore ​​pressure static cone penetration testing (PPP), as a lightweight, rapid, and efficient in-situ testing technique, has been widely used in soil engineering investigation and geotechnical engineering monitoring and testing. Adding a resistivity testing module to a conventional PPP device allows for the measurement of in-situ soil resistivity. Current resistivity static cone penetration probes generally employ the four-electrode method. This involves placing a resistivity testing module at the tail of a conventional PPP probe, vertically arranging four annular electrodes on an insulating sleeve, and internally housing the testing circuitry. The measured soil resistivity is primarily vertical. However, how to determine the horizontal resistivity of soil in situ using PPP to further obtain detailed information such as horizontal contaminant migration and shallow gas distribution within the soil layer has become a pressing problem in geotechnical engineering in-situ testing. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing static cone penetration testing (CPPT) techniques in China by proposing a static cone penetration testing device that can directly measure the in-situ horizontal resistivity of soil.

[0004] To achieve the above functions, this invention designs a dual-array resistivity pore pressure static cone penetration device, including a conical probe 1, a pore pressure filter ring 2, a friction cylinder on the side wall 3, a resistivity testing module 9, a digital circuit board 10, and an analog-to-digital converter 11; wherein, the conical probe 1 is located in the front half of the device, the conical probe 1 is connected to the friction cylinder on the side wall 3 through the pore pressure filter ring 2, and the friction cylinder on the side wall 3 is connected to the resistivity testing module 9;

[0005] The friction cylinder 3 on the side wall is equipped with a pore pressure sensor 4, a cone tip resistance sensor 5, a side friction resistance sensor 6, a temperature compensator 7, and an inclinometer 8. The rear half of the device is equipped with a resistivity testing module 9. At the tail of the device, there is a digital circuit board 10 and an analog-to-digital converter 11. The digital circuit board 10 is connected to the resistivity testing module 9, and a coaxial cable 12 is used to connect the digital circuit board 10 to the analog-to-digital converter 11. The coaxial cable 12 connects the analog-to-digital converter 11 to the data acquisition instrument 13 outside the device. The digital circuit board 10 is connected to the pore pressure sensor 4, the cone tip resistance sensor 5, the side friction resistance sensor 6, the temperature compensator 7, and the inclinometer 8 inside the friction cylinder 3 on the side wall.

[0006] As a preferred technical solution of the present invention: the outer layer of the resistivity testing module 9 is an insulating sleeve 9.1, the middle layer is a PVC inner cylinder 9.2, the PVC inner cylinder 9.2 is provided with a cable 9.3 inside, which is connected to the digital circuit board 10; the remaining space is filled with insulating mineral oil 9.4, and the resistivity testing module 9 is provided with two sets of circular electrode arrays horizontally distributed along the circumference of the resistivity testing module 9.

[0007] As a preferred embodiment of the present invention: the resistivity testing module 9 comprises two circular electrode arrays, including a lower electrode array 9.5 and an upper electrode array 9.6. Each electrode array consists of two opposite current electrodes C1 and C2 and two sets of potential electrodes. Each set of potential electrodes includes potential electrodes P1 and P2. The electrodes are equidistantly distributed along the inner wall of the insulating sleeve 9.1. The straight line connecting the current electrodes C1 and C2 is the diameter along the insulating sleeve 9.1. The two sets of potential electrodes are respectively distributed on both sides of the straight line connecting the current electrodes C1 and C2. Each electrode is connected to a cable 9.3, which is connected to the digital circuit board 10.

[0008] As a preferred embodiment of the present invention, the lower electrode array 9.5 and the upper electrode array 9.6 operate independently, reversing at a preset frequency to provide alternating rectangular waveform current.

[0009] As a preferred embodiment of the present invention, the digital circuit board 10 includes a MOS-EFT switch, a constant current source, a high-pass filter, an instrumentation amplifier, an anti-aliasing filter, and a multiplexing processor;

[0010] The output terminals of the current electrodes C1 and C2 of the lower electrode array 9.5 and the upper electrode array 9.6 are connected to the input terminals of the MOS-EFT switch, respectively. The constant current source is connected to the MOS-EFT switch. The output signals of the lower electrode array 9.5 and the upper electrode array 9.6 are divided into two paths. The potential electrodes P1 and P2 of each electrode array are connected to the two input terminals of the high-pass filter, respectively. The two output terminals of the high-pass filter are connected to the two input terminals of the instrumentation amplifier. The output terminal of the instrumentation amplifier is connected to the input terminal of the anti-aliasing filter. The output terminal of the anti-aliasing filter is connected to the input terminal of the multiplexing processor. The pore pressure sensor 4, cone tip resistance sensor 5, side friction resistance sensor 6, temperature compensator 7, and inclinometer 8 inside the friction cylinder 3 on the side wall are connected to the input terminal of the multiplexing processor.

[0011] Beneficial effects: Compared with the prior art, the advantages of the present invention include:

[0012] In geotechnical engineering practice, determining soil resistivity is crucial. Resistivity is an indirect indicator describing soil characteristics such as porosity, density, contaminant distribution, and gas-bearing layer distribution. Currently, in field tests using static cone penetration testing, soil resistivity is mostly measured vertically. High-density electrical resistivity methods (EDS) are generally used for large-scale soil profiles at project sites, but their accuracy is relatively low.

[0013] This invention overcomes the limitation of existing domestic static cone penetration testing techniques, which cannot directly measure the horizontal resistivity of soil. It enables convenient and rapid measurement of in-situ horizontal resistivity of soil layers, and is particularly effective in detecting the horizontal migration of pollutants and the horizontal distribution patterns of aerated soil layers. This allows static cone penetration testing technology to be applied more accurately and comprehensively in the field of geotechnical engineering. This technology is characterized by high stability, reliability, and repeatability. Attached Figure Description

[0014] Figure 1 is a schematic diagram of a dual-array resistivity orifice pressure static cone penetration device according to an embodiment of the present invention.

[0015] Figure 2 is a schematic diagram of the resistivity testing module provided according to an embodiment of the present invention;

[0016] Figure 3 is a schematic diagram of the structure of a digital circuit board according to an embodiment of the present invention;

[0017] Figure 4 is a horizontal arrangement diagram of the electrode array in the resistivity testing module provided according to an embodiment of the present invention;

[0018] In the diagram: 1. Conical probe; 2. Pore pressure filter ring; 3. Friction cylinder on the side wall; 4. Pore pressure sensor; 5. Cone tip resistance sensor; 6. Side friction resistance sensor; 7. Temperature compensator; 8. Inclinometer; 9. Resistivity testing module; 9.1. Insulating sleeve; 9.2. PVC inner cylinder; 9.3. Cable; 9.4. Insulating mineral oil; 9.5. Upper electrode array; 9.6. Lower electrode array; 10. Digital circuit board; 11. Analog-to-digital converter; 12. Coaxial cable; 13. Data acquisition instrument. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0020] The present invention provides a dual-array resistivity pore pressure static cone penetration device, referring to Figure 1, including a conical probe 1, a pore pressure filter ring 2, a friction cylinder on the side wall 3, a resistivity testing module 9, a digital circuit board 10, and an analog-to-digital converter 11; wherein, the conical probe 1 is located in the front half of the device, the conical probe 1 is connected to the friction cylinder on the side wall 3 through the pore pressure filter ring 2, and the friction cylinder on the side wall 3 is connected to the resistivity testing module 9;

[0021] The friction cylinder 3 on the side wall is equipped with a pore pressure sensor 4, a cone tip resistance sensor 5, a side friction resistance sensor 6, a temperature compensator 7, and an inclinometer 8. The rear half of the device is equipped with a resistivity testing module 9. At the tail of the device, there is a digital circuit board 10 and an analog-to-digital converter 11. The digital circuit board 10 is connected to the resistivity testing module 9, and a coaxial cable 12 is used to connect the digital circuit board 10 to the analog-to-digital converter 11 to transmit signals and data. The coaxial cable 12 connects the analog-to-digital converter 11 to the data acquisition instrument 13 outside the device. The digital circuit board 10 is connected to the pore pressure sensor 4, cone tip resistance sensor 5, side friction resistance sensor 6, temperature compensator 7, and inclinometer 8 inside the friction cylinder 3 on the side wall, thereby measuring various parameters of the in-situ soil.

[0022] Referring to Figure 2, the outer layer of the resistivity testing module 9 is an insulating sleeve 9.1, the middle layer is a PVC inner cylinder 9.2, and the PVC inner cylinder 9.2 is equipped with a cable 9.3 connected to the digital circuit board 10; the remaining space is filled with insulating mineral oil 9.4. The resistivity testing module 9 is provided with two sets of circular electrode arrays that are horizontally distributed along the circumference of the resistivity testing module 9.

[0023] The resistivity testing module 9 has two sets of circular electrode arrays, including a lower electrode array 9.5 and an upper electrode array 9.6. Each electrode array consists of two opposite current electrodes C1 and C2 and two sets of potential electrodes. Each set of potential electrodes includes potential electrodes P1 and P2. The electrodes are equidistantly distributed along the inner wall of the insulating sleeve 9.1. The straight line connecting the current electrodes C1 and C2 is the diameter along the insulating sleeve 9.1. The two sets of potential electrodes are distributed on both sides of the straight line connecting the current electrodes C1 and C2. Each electrode is connected to a cable 9.3, which is connected to the digital circuit board 10.

[0024] The lower electrode array 9.5 and the upper electrode array 9.6 operate independently, reversing at a preset frequency to provide alternating rectangular waveform current.

[0025] Referring to Figure 3, the digital circuit board 10 includes a MOS-EFT switch, a constant current source, a high-pass filter, an instrumentation amplifier, an anti-aliasing filter, and a multiplexing processor;

[0026] The output terminals of the current electrodes C1 and C2 of the lower electrode array 9.5 and the upper electrode array 9.6 are connected to the input terminals of the MOS-EFT switch, respectively. The constant current source is connected to the MOS-EFT switch. The output signals of the lower electrode array 9.5 and the upper electrode array 9.6 are divided into two paths. The potential electrodes P1 and P2 of each electrode array are connected to the two input terminals of the high-pass filter, respectively. The two output terminals of the high-pass filter are connected to the two input terminals of the instrumentation amplifier. The output terminal of the instrumentation amplifier is connected to the input terminal of the anti-aliasing filter. The output terminal of the anti-aliasing filter is connected to the input terminal of the multiplexing processor. The pore pressure sensor 4, cone tip resistance sensor 5, side friction resistance sensor 6, temperature compensator 7, and inclinometer 8 inside the friction cylinder 3 on the side wall are connected to the input terminal of the multiplexing processor.

[0027] The dual-array resistivity pore pressure static cone penetration test device designed in this invention measures the horizontal resistivity of soil in situ, which is fast, continuous, and reliable, providing a powerful testing tool for geotechnical engineering practice.

[0028] The principle by which the device of the present invention measures horizontal resistivity is as follows:

[0029] Existing research has shown that, based on the relationship between resistivity and resistance in the tested soil, the resistivity ρ can be obtained as follows:

[0030]

[0031] In the formula, V W Where I is voltage, I is current, and k is a calibration coefficient related to electrode geometry.

[0032] The upper and lower electrode arrays operate independently. Referring to Figure 3, a DC constant current source provides 10mA (with a maximum potential difference of 30V), inverted at a frequency of 1200Hz to provide an alternating rectangular waveform current of 600Hz. A complete cycle is fed back to the current electrode of the first electrode array, and 10 resulting potential data samples are synchronously acquired from the corresponding potential electrodes arranged in parallel within each electrode array. The first array is then disconnected, and the next cycle is fed to the second array, repeating the sampling process. Finally, the 10 samples from each individual electrode array are combined into a single RMS value. Therefore, both electrode arrays measure in a time-multiplexed manner, with a final sampling frequency of 300Hz. These samples are acquired whenever the arrays switch to sample the orifice pressure, tip resistance, side friction, and depth at a frequency of 300Hz.

[0033] Figure 4 shows the horizontal arrangement of the upper and lower electrode arrays. Based on existing theoretical research, the voltage V... W It is obtained from the voltage between the four circular electrodes:

[0034] V W =V(r) A ∣r M )-V(r A ∣r N )-V(r B ∣r M )+V(r B ∣r N )

[0035] In the formula, V(r) A ∣r M ) represents the voltage between electrodes AM, V(r) A ∣r N ) represents the voltage between electrodes AN, V(r) B ∣r M ) represents the voltage between electrodes BM, V(r) B ∣r N ) represents the voltage between electrodes B and N.

[0036] Assuming the resistivity testing module is an infinitely long cylinder with radius a, the following relationship exists between a and k:

[0037]

[0038] In the formula, x is the integral variable related to the Bessel function, f(x) is the Bessel function, and m is an integer in the series, used to represent the number of terms in the series.

[0039] As a function of x, the integrand is monotonically decreasing, causing the upper limit of integration to reach a six-digit precision at x = 12. Numerical calculations on the right-hand side of the above equation yield 0.099968, thus establishing the following relationship between k and a:

[0040] k = 10.00319·a

[0041] By combining the above formula, the horizontal resistivity ρ of the soil can be determined.

[0042] In engineering practice, computer-programmed methods can be used to obtain in-situ horizontal resistivity profiles of soil layers, which is more intuitive and faster. The method of this invention is characterized by stability, reliability, and repeatability.

[0043] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A dual-array resistivity orifice pressure static cone penetration test device, characterized in that, The device includes a conical probe (1), a pore pressure filter ring (2), a sidewall friction cylinder (3), a resistivity testing module (9), a digital circuit board (10), and an analog-to-digital converter (11). The conical probe (1) is located in the front half of the device. The conical probe (1) is connected to the sidewall friction cylinder (3) via the pore pressure filter ring (2). The sidewall friction cylinder (3) is connected to the resistivity testing module (9). The sidewall friction cylinder (3) contains a pore pressure sensor (4), a cone tip resistance sensor (5), a side friction resistance sensor (6), and a temperature compensator. 7) and inclinometer (8); the rear half of the device is equipped with a resistivity testing module (9); at the tail of the device, there is a digital circuit board (10) and an analog-to-digital converter (11). The digital circuit board (10) is connected to the resistivity testing module (9), and a coaxial cable (12) is used to connect the digital circuit board (10) to the analog-to-digital converter (11). The coaxial cable (12) connects the analog-to-digital converter (11) and the data acquisition instrument (13) outside the device; the digital circuit board (10) is connected to the pore pressure sensor (4) and the cone tip resistance sensor inside the friction cylinder (3) on the side wall. The resistivity test module (9) is connected to the device (5), the side friction resistance sensor (6), the temperature compensator (7), and the inclinometer (8); the outer layer of the resistivity test module (9) is an insulating sleeve (9.1), the middle layer is a PVC inner cylinder (9.2), and the PVC inner cylinder (9.2) is equipped with a cable (9.3) which is connected to the digital circuit board (10); the remaining space is filled with insulating mineral oil (9.4), and the resistivity test module (9) is provided with two sets of circular electrode arrays that are horizontally distributed along the circumference of the resistivity test module (9); the two sets of circular electrode arrays of the resistivity test module (9) It includes a lower electrode array (9.5) and an upper electrode array (9.6). Each electrode array consists of two opposite current electrodes C1 and C2 and two sets of potential electrodes. Each set of potential electrodes includes potential electrodes P1 and P2. The electrodes are equidistantly distributed along the inner wall of the insulating sleeve (9.1). The straight line connecting the current electrodes C1 and C2 is the diameter along the insulating sleeve (9.1). The two sets of potential electrodes are distributed on both sides of the straight line connecting the current electrodes C1 and C2. Each electrode is connected to a cable (9.3) and connected to the digital circuit board (10) through the cable (9.3).

2. The dual-array resistivity orifice pressure static cone penetration test device according to claim 1, characterized in that, The lower electrode array (9.5) and the upper electrode array (9.6) operate independently, reversing at a preset frequency to provide alternating rectangular waveform current.

3. The dual-array resistivity orifice pressure static cone penetration test device according to claim 1, characterized in that, The digital circuit board (10) includes a MOS-EFT switch, a constant current source, a high-pass filter, an instrumentation amplifier, an anti-aliasing filter, and a multiplexing processor. The output terminals of the current electrodes C1 and C2 of the lower electrode array (9.5) and the upper electrode array (9.6) are connected to the input terminals of the MOS-EFT switch, and the constant current source is connected to the MOS-EFT switch. The output signals of the lower electrode array (9.5) and the upper electrode array (9.6) are divided into two paths. The potential electrodes P1 and P2 of each electrode array are connected to the two input terminals of the high-pass filter, the two output terminals of the high-pass filter are connected to the two input terminals of the instrumentation amplifier, the output terminal of the instrumentation amplifier is connected to the input terminal of the anti-aliasing filter, and the output terminal of the anti-aliasing filter is connected to the input terminal of the multiplexing processor. The pore pressure sensor (4), cone tip resistance sensor (5), side friction resistance sensor (6), temperature compensator (7), and inclinometer (8) inside the friction cylinder (3) on the side wall are connected to the input terminal of the multiplexing processor.

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