Light soil dynamic and static probing detection device and method combined with time domain reflection technology

Abstract

The invention relates to a light soil dynamic and static probing detection device and method combined with a time domain reflection technology. The device comprises a probing rod; the penetration mechanism is configured to drive the probe rod to penetrate into the detected light soil body; the dynamic sounding module is detachably mounted at the upper part of the probe rod and is used for realizing dynamic sounding; the time domain reflection test module and the static sounding test module are sequentially connected with the lower end of the probe rod. Compared with the prior art, by combining the static sounding technology, the time domain detection technology and the dynamic sounding technology, the problem of light soil field detection is solved, and the light soil which is poured in layers and has different ages and different strengths can be detected to obtain the mechanical property, the integrity, the crack distribution condition, the strength forming rule and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of in-situ testing of lightweight soil in geotechnical engineering, and relates to a lightweight soil dynamic and static detection device and method combined with time domain reflection technology. Background Art

[0002] Foam lightweight soil, as a lightweight, high-strength filling material, has been widely used in the transportation civil engineering industry, meeting the filling needs of road engineering and bridge and culvert foundations. Due to its low density, it can effectively reduce the burden on the foundation and is suitable for projects with soft soil foundations or high fill. For example, in the roadbed filling of highways, the use of lightweight soil can reduce settlement and stability problems; in high fill areas, the use of lightweight soil can improve the anti-slip and anti-overturning performance of the structure by setting settlement joints and other measures; because lightweight soil is easy to construct and the construction process is relatively simple, it can be constructed quickly and the construction period can be greatly shortened. At the same time, its high fluidity and adjustable mix ratio allow the material to be optimized according to specific engineering needs, which can alleviate the problem of material shortage.

[0003] However, due to various factors such as the proportion of lightweight soil materials and the process control of the pouring process, it is difficult to detect the quality of lightweight soil, which is mainly reflected in the following two aspects: 1. During the solidification process of lightweight soil materials, due to heat release, material expansion and contraction, cracks are prone to appear on its surface, and it is difficult to measure the depth and width of crack development with existing technology; 2. The strength formation law and overall uniformity of lightweight soil materials are difficult to judge, and there is a lack of relevant in-situ testing technology. Therefore, it is necessary to develop an instrument that can detect lightweight soil at different ages and strengths under layered pouring conditions, so as to quickly, comprehensively and accurately evaluate the performance and integrity of the poured lightweight soil on site. Summary of the invention

[0004] The purpose of the present invention is to provide a static and dynamic detection device for lightweight soil combined with time domain reflection technology. By combining static sounding technology, temperature detection technology, time domain detection technology and dynamic sounding technology, the problem of on-site detection of lightweight soil is solved, and lightweight soil of different ages and strengths cast in layers can be detected to obtain static mechanical properties, temperature, dielectric information and the number of penetration blows of dynamic sounding, etc., so as to analyze and evaluate the strength and integrity of lightweight soil.

[0005] In order to solve the problem of mechanical property testing, the present invention proposes to adopt static probing combined with dynamic probing technology. Due to its own characteristics, lightweight soil is in a fluid state when it is first poured, which is suitable for static probing to test its initial strength; but with the increase of age, the lightweight soil gradually hardens, and the lightweight soil roadbed is often poured in layers. On-site testing shows that the poured soil is still in a fluid state but the bottom has hardened and has a certain strength, and the static probing may be difficult to penetrate. At this time, dynamic probing is used to continue to test the strength of the deep lightweight soil.

[0006] At the same time, the hardening process of lightweight soil is related to the reaction of its cementitious materials, and its temperature change law can effectively determine the strength formation process of lightweight soil. Therefore, the embedded temperature sensor of the penetration system is used to test the temperature at different positions of lightweight soil.

[0007] In addition, the TDR system and radar have similar signal transmission principles. A voltage signal is emitted by the signal transmitter, and the electromagnetic wave propagates along the coaxial cable and the probe. When encountering other media, the signal is reflected. After the reflected signal is captured and analyzed, the dielectric information of the medium can be obtained. Dielectric information such as conductivity can be used to evaluate the overall integrity of lightweight soil and whether abnormal structural density and other characteristics occur.

[0008] The purpose of the present invention can be achieved by the following technical solutions:

[0009] In one aspect, the present invention provides a lightweight soil dynamic and static detection device combined with time domain reflection technology, comprising:

[0010] Probe;

[0011] A penetration mechanism, which is configured to drive the probe rod to penetrate into the light soil to be tested;

[0012] A dynamic sounding module detachably mounted on the upper part of the probe rod and used to realize dynamic sounding;

[0013] And a time domain reflection test module and a static penetration test module which are sequentially connected to the lower end of the probe rod.

[0014] Furthermore, the penetration mechanism includes a support seat for fixedly mounting on the surface of the lightweight soil to be measured, and a penetration drive assembly arranged on the support seat and fixedly connected to the probe rod, and the penetration drive assembly is configured to drive the probe rod to move up and down in the height direction.

[0015] Furthermore, the dynamic probing module includes a guide rod detachably connected to the probe rod, an anvil installed at the bottom of the guide rod, and a core hammer sleeved on the guide rod and movable up and down.

[0016] Furthermore, the side surface of the core-piercing hammer is also provided with a handle for easy lifting;

[0017] The guide rod is threadedly connected to the probe rod.

[0018] Furthermore, the moving stroke of the core piercing hammer on the guide rod is 0.4-0.6 m, and the mass of the core piercing hammer is 8-12 kg.

[0019] Furthermore, the time domain reflection test module includes a first joint connected to the lower part of the probe rod, a three-pin TDR probe fixed on the surface of the first joint, and a host and a first computer connected to the three-pin TDR probe through a first coaxial cable signal. The host contains a signal generator and a first data acquisition unit, and the first computer is configured to process the signal data transmitted by the host and obtain the dielectric information of the lightweight soil being tested. Due to its advantages such as simple structure, easy on-site use, and strong signal stability, the present invention adopts a three-pin TDR probe for post-penetration detection. Based on the Maxwell equations, the distribution of the electric potential field around the lightweight soil can be solved, and then the uniformity of the lightweight soil casting within the elliptical test range near the probe at different depths can be analyzed, and the crack position and width can be tested and evaluated. The main innovation of the present invention here is to integrate the time domain reflection test module into the probe part of the device to achieve penetration into the underground for testing. Specifically, the process of the three-pin TDR probe specifically detecting and obtaining the dielectric constant and other information of the lightweight soil through subsequent processing is based on conventional technical means. The surface reflection method can be used to calculate the material density variation law, crack width and location information based on the cracking characteristics of lightweight soil and foam density characteristics by combining the dielectric constant and electromagnetic wave two-way travel time.

[0020] The formula for calculating the propagation speed of electromagnetic waves is:

[0021]

[0022] In the formula, V is the propagation speed of electromagnetic waves in the medium, c is the propagation speed of electromagnetic waves in vacuum, ε r is the dielectric constant of the medium;

[0023] Distance between crack and probe ε r,crack The calculation formula is:

[0024]

[0025] In the formula, A p , A o is the amplitude position of the crack and surface reflection wave.

[0026] Furthermore, the three-needle TDR probe has a length of 8 to 12 cm and a diameter of 2 to 4 mm.

[0027] Furthermore, the first joint is a threaded joint.

[0028] Furthermore, the static penetration test module includes a second connector connected to the time domain reflection test module and a conical probe fixedly arranged below the second connector. The conical probe is also connected to a second data acquisition unit and a second computer via a second coaxial cable signal. The second computer is configured to process the signal data transmitted by the second data acquisition unit.

[0029] Here, the cone probe mainly collects the cone tip resistance as the basis for judging the mechanical properties. The collection and implementation process is a conventional technology in this field and will not be repeated here. The static penetration test module uses titanium alloy to strengthen the probe cone tip and high-rigidity, low-deformation stainless steel as the main part of the probe, so as to realize the characteristics of light soil that changes from soft to hard, and proposes static penetration testing suitable for light soil when it is relatively soft (strength ≤ 300kPa); at the same time, it meets the needs of cone dynamic penetration testing after light soil hardening (strength> 300kPa).

[0030] At the same time, a temperature sensor is arranged on the back side of the cone probe to collect the temperature of the light soil. In order to achieve the purpose of timely response to the internal temperature of the light soil, this part uses a titanium metal package temperature sensor with a thickness of <1mm and fills it with liquid metal (thermal conductivity>40W / m·K) to improve the temperature test efficiency and ensure the timeliness of the test. Furthermore, the second joint is a threaded joint.

[0031] In a second aspect, the present invention provides a method for dynamic and static detection of lightweight soil combined with time domain reflection technology, which comprises the following steps:

[0032] At the test point of the light soil to be tested, the probe is connected to the time domain reflection test module and the static penetration test module from top to bottom, and is uniformly penetrated into the light soil to be tested through the penetration mechanism, and the static properties of the light soil to be tested are detected by the static penetration test module;

[0033] When the time domain reflection test is needed, the penetration operation is stopped and the dielectric information of the light soil being tested is obtained by the time domain reflection test module;

[0034] When dynamic probing is required, a dynamic probing module is installed on the upper part of the probe rod to detect the strength characteristics of the lightweight soil being tested.

[0035] Compared with the prior art, the present invention realizes the in-situ testing function of lightweight soil roadbed. Through this equipment, the performance of lightweight soil of different ages and strengths can be comprehensively measured. From static properties, dynamic penetration number to dielectric information of time domain reflection test, the performance of lightweight soil is comprehensively evaluated from multiple aspects, which improves the speed, comprehensiveness and accuracy of field testing. In the field test of lightweight soil roadbed in geotechnical engineering, the performance of cast lightweight soil can be evaluated efficiently, conveniently and accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of a lightweight soil dynamic and static detection device combined with time domain reflectometry technology;

[0037] Figure 2 This is a schematic diagram of the structure of the dynamic penetration test module;

[0038] Figure 3 It is a schematic diagram of the structure of the time domain reflection test module;

[0039] Figure 4 This is a schematic diagram of the static penetration test module structure.

[0040] Description of the markings in the figure:

[0041] 1-dynamic probing module; 101-guide rod; 102-penetration hammer; 103-anvil; 2-probe rod; 3-penetration mechanism; 4-time domain reflection test module; 401-first computer; 402-host; 403-first coaxial cable; 404-first connector; 405-fixed structure; 406-three-needle TDR probe; 5-static probing test module; 501-second computer; 502-collector; 503-second coaxial cable; 504-conical probe. DETAILED DESCRIPTION

[0042] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0043] In the following implementation manners or examples, unless otherwise specified, functional components or structures are conventional components or structures used in the art to achieve corresponding functions.

[0044] In order to comprehensively evaluate the performance of lightweight soil from multiple aspects, from static properties, dynamic penetration blows to dielectric information of time domain reflection test, and improve the convenience, comprehensiveness and accuracy of field testing, the present invention provides a lightweight soil dynamic and static detection device combined with time domain reflection technology, including:

[0045] Probe 2;

[0046] A penetration mechanism 3, which is configured to drive the probe rod 2 to penetrate into the light soil to be measured;

[0047] A dynamic sounding module 1 detachably mounted on the upper portion of the probe rod 2 and used to implement dynamic sounding;

[0048] And a time domain reflection test module 4 and a static penetration test module 5 which are connected to the lower end of the probe rod 2 in sequence.

[0049] In some specific embodiments, the penetration mechanism 3 includes a support base for fixedly mounting on the surface of the lightweight soil to be measured, and a penetration drive assembly arranged on the support base and fixedly connected to the probe rod 2, and the penetration drive assembly is configured to drive the probe rod 2 to move up and down in the height direction.

[0050] In some specific embodiments, the dynamic probing module 1 includes a guide rod 101 detachably connected to the probe rod 2, an anvil 103 installed at the bottom of the guide rod 101, and a core hammer 102 mounted on the guide rod 101 and movable up and down.

[0051] In a more specific embodiment, the side surface of the core hammer 102 is also provided with a handle for easy lifting;

[0052] The guide rod 101 is threadedly connected to the probe rod 2 .

[0053] In a more specific implementation, the moving stroke of the core piercing hammer 102 on the guide rod 101 is 0.4-0.6 m, and the mass of the core piercing hammer 102 is 8-12 kg.

[0054] In some specific embodiments, the time domain reflection test module 4 includes a first connector 404 connected to the lower part of the probe rod 2, a three-pin TDR probe 406 fixed on the surface of the first connector 404, and a host 402 and a first computer 401 connected to the three-pin TDR probe 406 through a first coaxial cable 403 signal, wherein the host 402 contains a signal source and a first data acquisition unit, and the first computer 401 is configured to process the signal data transmitted by the host 402 and obtain information such as the dielectric constant of the measured lightweight soil. Due to its simple structure, easy on-site use, and strong signal stability, the present invention adopts a three-pin TDR probe for post-penetration detection. Based on the Maxwell equations, the electric potential field distribution around the lightweight soil can be solved, and then the uniformity of lightweight soil pouring within the elliptical test range near the probe at different depths can be analyzed, and the crack position and width can be tested and evaluated. The main innovation of the present invention is to integrate the time domain reflection test module into the probe part of the device to achieve underground penetration testing. Specifically, the three-pin TDR probe specifically detects and obtains information such as the dielectric constant of lightweight soil through subsequent processing based on conventional technical means. The surface reflection method can be used to combine the dielectric constant and the two-way travel time of electromagnetic waves to calculate the material density change law and the crack width and location information for the cracking characteristics and foam density characteristics of lightweight soil.

[0055] The formula for calculating the electromagnetic wave propagation speed is:

[0056]

[0057] In the formula, V is the propagation speed of electromagnetic waves in the medium, c is the propagation speed of electromagnetic waves in vacuum, ε r is the dielectric constant of the medium;

[0058] Distance between crack and probe ε r,crack The calculation formula is:

[0059]

[0060] In the formula, A p , A o is the amplitude position of the crack and surface reflection wave.

[0061] In a more specific embodiment, the three-needle TDR probe 406 has a length of 8 to 12 cm and a diameter of 2 to 4 mm.

[0062] In a more specific embodiment, the first joint 404 is a threaded joint.

[0063] In some specific embodiments, the static penetration test module 5 includes a second connector connected to the time domain reflection test module 4, a cone probe 504 fixedly arranged below the second connector, and the cone probe 504 is also connected to the second data acquisition unit and the second computer 501 through the second coaxial cable 502 signal, and the second computer 501 is configured to process the signal data transmitted by the second data acquisition unit. Here, the cone probe mainly collects the cone tip resistance as the basis for judging the mechanical properties, and its collection implementation process is a conventional technology in this field, which will not be repeated here. The static penetration test module adopts titanium alloy to strengthen the probe cone tip, and high rigidity and low deformation stainless steel as the main body of the probe, so as to realize the characteristic that light soil will change from soft to hard, and proposes a static penetration test suitable for light soil when it is soft (strength ≤ 300kPa); at the same time, it meets the needs of cone dynamic penetration test after light soil hardening (strength> 300kPa).

[0064] At the same time, a temperature sensor is also arranged on the back side of the cone probe 504 to collect the temperature of the light soil. In order to achieve the purpose of timely response to the temperature inside the light soil, this part uses a titanium metal package temperature sensor with a thickness of less than 1mm and is filled with liquid metal (thermal conductivity> 40W / m·K) to improve the temperature test efficiency and ensure the timeliness of the test.

[0065] In a more specific embodiment, the second joint is a threaded joint.

[0066] The above embodiments may be implemented individually or in any combination of two or more.

[0067] The above implementation is described in more detail below with reference to specific examples.

[0068] Embodiment 1:

[0069] like Figures 1 to 4 As shown, this embodiment provides a light soil dynamic and static detection device combined with time domain reflection technology. In the detection device, the penetration mechanism 3 is responsible for penetrating the time domain reflection test module 4 and the static penetration test module 5 connected to the probe rod 2 from top to bottom into the light soil. The dynamic penetration module 1 is connected to the top of the probe rod 2 to realize the test function of dynamic penetration. In the dynamic penetration module 1, the guide rod 101 is connected to the anvil 103, and the guide rod 101 passes through the core hammer 102. In the time domain reflection test module 4, the three-pin TDR probe 406 is constrained on the first joint 404 by the fixed structure 405, and its first coaxial cable 403 passes through the first joint 404 and is connected to the host. The host 402 transmits the signal to the first computer 401 and processes it using the corresponding software in the computer system. In the static penetration test module 5, the conical probe 504 transmits the signal to the acquisition instrument (i.e., the second data acquisition unit) 502 through the second coaxial cable 503, and the acquisition instrument 502 transmits the data to the connected computer system. In this embodiment, the fixing structure 405 may adopt an existing conventional structure for mounting a probe, such as welding, threaded connection, etc.

[0070] After reaching the test point, the probe rod 2 is connected from top to bottom to the time domain reflection test module 4 and the static penetration test module 5, and the penetration rate is controlled to be a constant 2cm / s through the penetration mechanism 3 to ensure uniform penetration into the light soil. At this time, the dynamic penetration module 1 can be disconnected. During the test, the cone probe 504 in the static penetration module 5 transmits the test signal to the collector 502 through the second coaxial cable 503, and the collector 502 transmits the signal to the connected computer 501 and processes the data through the software in the computer system. When the time domain reflection test is to be carried out, the penetration operation is stopped, and the signal source in the host 402 emits a voltage signal, and the electromagnetic wave propagates along the first coaxial cable 403 and the three-pin TDR probe 406. When the signal encounters a light soil medium, the signal is reflected, and the data acquisition instrument in the host 402 captures the reflected signal and is displayed by the oscilloscope in the host 402. The signal is transmitted from the host 402 to the first computer 401 for processing using the corresponding software in the computer system. The dielectric information of the medium such as light soil can be obtained by analyzing the reflected signal, which is used to further evaluate the performance of the light soil. When it is necessary to perform dynamic penetration on light soil with a long age and high strength, a dynamic penetration module 1 is installed on the top of the device, and the function of dynamic penetration is realized by lifting the core hammer 102 to the top of the guide rod 101 and then releasing the core hammer 102 to let it fall freely to hit the anvil 103. The strength characteristics of the light soil can be evaluated by the number of hammer strikes required for dynamic penetration of a fixed distance. After the test is completed, the normal penetration operation is resumed and the aforementioned static penetration test, time domain reflection test and dynamic penetration test steps are repeated at the next predetermined detection point.

[0071] Specifically, in this embodiment, the drop distance of the guide rod 101 is 0.5m; the mass of the core hammer 102 is 10kg; the diameter of the upper end of the anvil 103 is 45mm, and the diameter of the lower end is consistent with that of a conventional probe rod; the length of the time domain reflection test module 4 is 10-20cm; the host 402 includes a signal generator, a data acquisition processor and an oscilloscope; the frequency range of the electromagnetic pulse emitted by the signal generator of the host 402 is 1MHz-1GHz; the three-needle TDR probe 406 is 10cm long and the probe diameter is 3mm; the cone angle of the conical probe 504 is 60-80°, and the cross-sectional area of ​​the cone bottom is 12.6cm 2 .

[0072] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A lightweight soil dynamic and static detection device combined with time domain reflection technology, characterized in that: include: Probe; A penetration mechanism, which is configured to drive the probe rod to penetrate into the light soil to be tested; A dynamic sounding module detachably mounted on the upper part of the probe rod and used to realize dynamic sounding; And a time domain reflection test module and a static penetration test module which are sequentially connected to the lower end of the probe rod.

2. According to claim 1, a lightweight soil dynamic and static detection device combined with time domain reflection technology is characterized in that: The penetration mechanism includes a support seat for fixedly mounting on the surface of the light soil to be measured, and a penetration drive assembly disposed on the support seat and fixedly connected to the probe rod, wherein the penetration drive assembly is configured to drive the probe rod to move up and down in the height direction.

3. The light soil dynamic and static detection device combined with time domain reflection technology according to claim 1 is characterized in that: The dynamic probing module comprises a guide rod detachably connected to the probe rod, an anvil seat installed at the bottom of the guide rod, and a core hammer sleeved on the guide rod and movable up and down.

4. The light soil dynamic and static detection device combined with time domain reflection technology according to claim 3 is characterized in that: The side surface of the core-piercing hammer is also provided with a handle for easy lifting; The guide rod is threadedly connected to the probe rod.

5. The light soil dynamic and static detection device combined with time domain reflection technology according to claim 3 is characterized in that: The moving stroke of the core piercing hammer on the guide rod is 0.4-0.6m, and the mass of the core piercing hammer is 8-12kg.

6. The light soil dynamic and static detection device combined with time domain reflection technology according to claim 1 is characterized in that: The time domain reflection test module includes a first joint connected to the lower part of the probe rod, a three-pin TDR probe fixed on the surface of the first joint, and a host and a first computer connected to the three-pin TDR probe through a first coaxial cable signal. The host contains a signal source and a first data acquisition unit. The first computer is configured to process the signal data transmitted by the host and obtain dielectric information of the lightweight soil being tested.

7. The light soil dynamic and static detection device combined with time domain reflection technology according to claim 6 is characterized in that: The three-needle TDR probe has a length of 8 to 12 cm and a diameter of 2 to 4 mm.

8. The light soil dynamic and static detection device combined with time domain reflection technology according to claim 6 is characterized in that: The first joint is a threaded joint.

9. The light soil dynamic and static detection device combined with time domain reflection technology according to claim 1 is characterized in that: The static penetration test module includes a second connector connected to the time domain reflection test module and a conical probe fixedly arranged below the second connector. The conical probe is also connected to a second data acquisition unit and a second computer via a second coaxial cable signal. The second computer is configured to process the signal data transmitted by the second data acquisition unit.

10. A method for dynamic and static detection of lightweight soil combined with time domain reflection technology, based on the lightweight soil dynamic and static detection device according to any one of claims 1 to 9, characterized in that: The lightweight soil dynamic and static detection method comprises the following steps: At the test point of the light soil to be tested, the probe is connected to the time domain reflection test module and the static penetration test module from top to bottom, and is uniformly penetrated into the light soil to be tested through the penetration mechanism, and the static properties of the light soil to be tested are detected by the static penetration test module; When the time domain reflection test is needed, the penetration operation is stopped and the dielectric information of the light soil being tested is obtained by the time domain reflection test module; When dynamic probing is required, a dynamic probing module is installed on the upper part of the probe rod to detect the strength characteristics of the lightweight soil being tested.

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