Soil high-fidelity acquisition method based on pore water electrolysis resistance reduction

Abstract

The application provides a soil high-fidelity collection method based on pore water electrolysis resistance reduction, comprising the following steps: step 10, drilling at a sampling point to a groundwater level position to form a pre-hole; step 20, inserting a plurality of electrode plates around the sampling point; inserting a sampling drill rod into the pre-hole, connecting the sampling drill rod with a negative electrode of an adjustable power supply, and connecting the electrode plates with a positive electrode of the adjustable power supply; in the process of driving the sampling drill rod to penetrate below the groundwater level by a traction unit, the electrode plates and the sampling drill rod are electrified, the interstitial water in the soil near the sampling drill rod is electrolyzed, and bubbles are generated; at the same time, a vertical vibration unit drives the sampling drill rod to reciprocate in the vertical direction, inducing liquefaction of the soil near the sampling drill rod until the soil sample in a preset sampling depth range is taken out. The soil high-fidelity collection method based on pore water electrolysis resistance reduction provided by the application reduces disturbance, prevents obvious change of soil structure, and improves the fidelity effect of the soil sample.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of soil drilling sampling, and particularly relates to a soil high-fidelity collection method based on pore water electrolysis resistance reduction. BACKGROUND

[0002] Contaminated site fidelity sampling is the basis of green low-carbon remediation and risk management of contaminated sites. The existing static pressure penetration type soil sampling drill, the acoustic vibration type soil sampling drill and the method for collecting soil samples often have a large deformation, and the soil structure is significantly changed. Although the vibration function of the sampling drill can induce slight liquefaction of the soil layer in the saturated zone below the groundwater level, the sampling efficiency and the undisturbed structure of the soil are improved to a certain extent. However, due to the small particle size and large inter-particle cohesion of the clay soil such as silt and silty clay, it is difficult to achieve good liquefaction state under the action of vibration, and the collected sample is still not ideal. Therefore, it is urgent to improve the existing static pressure penetration type soil sampling drill, the acoustic vibration type soil sampling drill and the soil sampling method, reasonably control the structure state of the soil at the interface between the drill rod and the soil layer, and effectively improve the sampling quality of the contaminated soil sample in the clay layer. SUMMARY

[0003] The technical problem to be solved by the present application is to provide a soil high-fidelity collection method based on pore water electrolysis resistance reduction, which reduces disturbance when collecting soil samples below the groundwater level, prevents the shape of the soil sample from changing significantly, and improves the fidelity effect of the soil sample.

[0004] To solve the above technical problems, the present application adopts the following technical solutions:

[0005] The present application provides a soil high-fidelity collection method based on pore water electrolysis resistance reduction, comprising the following steps:

[0006] Step 10: drilling at the sampling point to the position of the groundwater level to form a pre-hole;

[0007] Step 20: inserting a plurality of electrode plates around the sampling point, the insertion depth of the electrode plates being consistent with the preset sampling depth; penetrating the sampling drill rod from the pre-hole, connecting the sampling drill rod with the negative electrode of the adjustable power supply, and connecting the electrode plates with the positive electrode of the adjustable power supply; during the process of penetrating the sampling drill rod below the groundwater level to collect the soil sample driven by the traction unit, the electrode plates and the sampling drill rod are electrified to electrolyze the pore water in the soil near the sampling drill rod to generate bubbles; at the same time, the vertical vibration unit drives the sampling drill rod to reciprocate in the vertical direction to induce liquefaction of the soil near the sampling drill rod until the soil sample in the preset sampling depth range is taken out.

[0008] As a further improvement of the present application, the amplitude of the vertical vibration unit is determined by formula (1):

[0009] Formula (1)

[0010] In the formula, represents the amplitude of the vertical vibration unit, with the unit of mm; represents the median particle size of the soil, with the unit of mm; represents the shape adjustment coefficient, with the value range of -1.50~ -0.70, and dimensionless; I p represents the plasticity index of the soil, and dimensionless; I p0 represents the reference plasticity index of the soil, with the value range of 4~7, and dimensionless; β represents the activity adjustment coefficient, with the value range of 0.15~0.45, and the unit of mm.

[0011] As a further improvement of the present application, in the step 20, drilling parameters are collected in real time, and the drilling parameters are transmitted to the adjustable power supply, and the adjustable power supply adjusts the output voltage in real time according to the drilling parameters; the drilling parameters include formation conductivity, formation temperature, the length of the sampling drill rod below the groundwater depth, and the penetration rate value of the sampling drill rod.

[0012] As a further improvement of the present application, in the step 20, the output voltage is determined by using formula (2):

[0013] Formula (2)

[0014] In the formula, represents the output voltage, with the unit of v; represents the electrode plate and sampling point plane distance adjustment coefficient, with the value range of 2.5~4.3, and the unit of m 3 ⋅mol⋅min⋅Ω⋅kg -1 ; represents the diameter of the sampling drill rod, with the unit of cm; represents the median particle size of the soil, with the unit of mm; represents the penetration rate value of the sampling drill rod, with the unit of m / min; represents the length of the sampling drill rod below the groundwater depth, with the unit of m; represents the formation conductivity, with the unit of mS / cm; represents the ideal gas constant, with the value of 8.31, and the unit of J·mol -1 ·K -1 ; represents the formation temperature, with the unit of K.

[0015] As a further improvement of the present application, the formation conductivity and the formation temperature are both collected by the temperature and resistivity in-situ collection device installed at the bottom end of the sampling drill rod.

[0016] As a further improvement of the present invention, the length of the sampling drill rod below the groundwater depth is obtained by a depth sensor placed on the ground and whose movable end is connected to a clamp.

[0017] As a further improvement of the present invention, several electrode plates are connected in sequence by wires, and one of the electrode plates is connected to the positive terminal of the adjustable power supply.

[0018] As a further improvement of the present invention, several electrode plates are evenly arranged around the sampling point.

[0019] As a further improvement of the present invention, the number of electrode plates is 4 to 8.

[0020] As a further improvement of the present invention, step 20 specifically includes:

[0021] Step 201: Insert several electrode plates around the sampling point. The insertion depth of the electrode plates is consistent with the preset sampling depth. Connect the electrode plates to the positive terminal of the adjustable power supply.

[0022] Step 202: Install the first rod at the top of the drill bit, insert the drill bit into the pre-drilled hole, and then install the second, ..., ... rods sequentially at the top of the first rod. m +1 rod body, until the bottom of the drill bit reaches the groundwater depth, and the first m +1 The bottom of the pole is located near the ground; m It is an integer greater than or equal to 0; p =1; will the first p The sampling tube is inserted into the sampling drill rod, at the first... m +1 A top cap is installed at the top of the rod; the top cap, rod and drill bit connected in sequence form a sampling drill rod, and the sampling drill rod is connected to the negative terminal of an adjustable power supply;

[0023] Step 203: Based on the collected layer conductivity, formation temperature, the length of the sampling drill rod below the groundwater depth, and the penetration velocity of the sampling drill rod, adjust the output voltage of the adjustable power supply; connect the adjustable power supply to the electrode plate and the sampling drill rod to electrolyze the pore water in the soil surrounding the sampling drill rod, generating bubbles; simultaneously, the vertical vibration unit drives the sampling drill rod to reciprocate vertically, promoting soil liquefaction near the sampling drill rod, thereby reducing disturbance; the traction unit drives the vertical vibration unit and the sampling drill rod to penetrate deeper into the formation for sampling; when the first... m + p When the entire rod is pressed into the ground, the adjustable power supply is turned off, and the vertical vibration unit and traction unit stop working; remove the first... p The sampling tube obtained the first sample below the groundwater level. p Section soil sample;

[0024] Step 204, the first m + p The top end of the root rod body is provided with the first m + p + 1 root rod body, p The value of the number is increased by 1; the first p The sampling pipe is installed in the sampling drill rod, and the first m + p The top cap is installed at the top end of the root rod body; the top cap, the rod body and the drill bit connected in sequence constitute the sampling drill rod, and the sampling drill rod is connected with the negative electrode of the adjustable power supply; the top cap is connected with the vertical vibration unit; step 203 is repeated until the soil sample in the preset sampling depth range is taken out.

[0025] Compared with the prior art, the technical scheme of the present application has the following beneficial effects:

[0026] The soil high-fidelity collection method based on pore water electrolysis resistance reduction provided by the present application inserts a plurality of electrode plates around the sampling point during the process of collecting the soil sample below the underground water level, the electrode plates are electrified as anodes, the sampling drill rod is electrified as a cathode, the interstitial water in the soil body near the sampling drill rod is electrolyzed, and bubbles are generated. On the one hand, under the vibration load, the bubbles significantly prolong the drainage path through the cyclic compression-expansion effect, enhance the accumulation of the excess pore water pressure, and thus promote the liquefaction of the soil body; on the other hand, under the vibration effect, the bubbles can occupy a certain volume of soil pores, interfere with the effective stress transmission between the particles, hinder the extension of the force chain, and promote the rearrangement of the soil particles in a smaller range. In addition, the bubbles can form a gas-liquid mixed lubricating layer between the sampling drill rod and the soil contact surface, reduce the direct frictional contact between the surface of the sampling drill rod and the soil particles, and due to the compressibility of the bubbles, a proper volume of bubbles can dynamically adjust the interface state and reduce the friction coefficient in the vibration, so as to reduce the disturbance of the soil sample during the sampling process. Moreover, the electrolysis voltage is adjusted in real time according to the sampling depth, the soil layer resistivity and the temperature, the bubble content of the contact interface between the sampling drill rod and the soil layer is ensured, the soil pore saturation is adjusted in real time, the conditions for the disordered movement and liquefaction suspension of the soil particles are provided, and the sampling fidelity effect is enhanced. The soil high-fidelity collection method based on pore water electrolysis resistance reduction provided by the present application reduces the disturbance when collecting the soil sample below the underground water level, prevents the soil sample from changing significantly in shape, and improves the fidelity effect of the soil sample. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a flowchart of the method of the embodiment of the present application;

[0028] Figure 2 is a construction schematic diagram of the method of the embodiment of the present application;

[0029] Figure 3 is Figure 2 a distribution schematic diagram of the electrode plates.

[0030] In the diagram: 1. Sampling drill rod, 11. Top cap, 12. Drilling rig, 2. Adjustable power supply, 3. Electrode plate, 4. Traction unit, 5. Vertical vibration unit, 6. Clamp, 7. Groundwater level, 8. Ground surface, 9. Detailed Implementation

[0031] The technical solution of the present invention will be described in detail below.

[0032] This invention provides a high-fidelity soil sampling method based on drag reduction through pore water electrolysis, such as... Figure 1 As shown, it includes the following steps:

[0033] Step 10: Drill to groundwater level 8 at the sampling point to form a pre-drilled hole.

[0034] Step 20: Insert several electrode plates 4 around the sampling point, with the insertion depth of the electrode plates 4 consistent with the preset sampling depth. Insert the sampling drill rod 1 through the pre-drilled hole, connecting the sampling drill rod 1 to the negative terminal of the adjustable power supply 3, and the electrode plates 4 to the positive terminal of the adjustable power supply 3. During the process of the traction unit 5 driving the sampling drill rod to penetrate below the groundwater level to collect soil samples, the electrode plates and the sampling drill rod are energized, electrolyzing the interstitial water in the soil near the sampling drill rod to generate bubbles. Simultaneously, the vertical vibration unit 6 drives the sampling drill rod 1 to reciprocate vertically, promoting soil liquefaction near the sampling drill rod, reducing resistance during drilling, until soil samples within the preset sampling depth range are extracted.

[0035] The method described in this invention uses a low-disturbance drilling tool to collect soil samples below the groundwater level. For example... Figure 2 As shown, the low-disturbance drilling tool includes a drilling rig 2, a traction unit 5, a vertical vibration unit 6, a clamp 7, and a sampling drill rod. The traction unit 5 is slidably mounted on the guide beam of the drilling rig 2, the vertical vibration unit 6 is mounted on the traction unit 5, and the clamp 7 is mounted on the vertical vibration unit 6. The clamp 7 is used to hold the sampling drill rod. The traction unit 5 is used to drive the sampling drill rod to move along the guide beam of the drilling rig, driving the sampling drill rod downward into the formation and pulling it out of the formation. The vertical vibration unit 6 is used to drive the sampling drill rod to reciprocate in the vertical direction. Both the traction unit 5 and the vertical vibration unit 6 adopt existing structures.

[0036] The sampling drill rod includes a drill bit, a hollow rod body 11, and a top cap 12. The top end of the rod body 11 is fitted with the top cap 12, and the bottom end is fitted with the drill bit. In use, the top cap, multiple rod bodies, and the drill bit are connected sequentially from top to bottom to form the sampling drill rod. The number of rod bodies is determined based on the preset sampling depth at the site. A clamp 7 holds the top cap 12, and a traction unit 5, via a vertical vibration unit and the clamp, drives the sampling drill rod downwards into the formation. Simultaneously, the vertical vibration unit 6, via the clamp, drives the sampling drill rod to reciprocate vertically.

[0037] Preferably, the drill bit bottom end is provided with a temperature and resistivity in-situ acquisition device, which is an existing device, used to collect and obtain formation conductivity and formation temperature at different depths while the drill bit is drilling down.

[0038] Preferably, in step 20, the frequency of the exciting force generated by the vertical vibration unit is 30-150 Hz.

[0039] Preferably, the amplitude of the vertical vibration unit is determined by formula (1):

[0040] Formula (1)

[0041] In formula (1), represents the amplitude of the vertical vibration unit, with the unit of mm. represents the median particle size of the soil, with the unit of mm; the particle size of 50% of all soil particles is greater than and the particle size of 50% of all soil particles is less than . represents the shape adjustment coefficient, with the value range of -1.50 to -0.70, and is dimensionless. I p represents the plasticity index of the soil, which is dimensionless. I p0 represents the reference plasticity index of the soil, with the value range of 4-7, which is dimensionless. β represents the activity adjustment coefficient, with the value range of 0.15-0.45, with the unit of mm.

[0042] In this embodiment, the amplitude of the vertical vibration unit is determined according to the particle size of the soil particles and the plasticity index of the soil, and the soil body near the contact surface of the sampling drill pipe and the soil is liquefied, so that a liquefied zone with a suitable thickness range can be obtained, and the degree of disturbance damage is reduced.

[0043] Preferably, in step 20, drilling parameters are collected in real time, and the drilling parameters are transmitted to the adjustable power supply 3, and the adjustable power supply 3 adjusts the output voltage thereof in real time according to the drilling parameters. The drilling parameters include formation conductivity, formation temperature, the length of the sampling drill pipe below the groundwater depth, and the penetration speed value of the sampling drill pipe.

[0044] Specifically, the output voltage is determined by formula (2):

[0045] Formula (2)

[0046] In formula (2), represents the output voltage, with the unit of v; represents the distance adjustment coefficient between the electrode plate and the sampling point plane, the value range is 2.5-4.3, and the unit is m 3 ⋅mol⋅min⋅Ω⋅kg -1 ; represents the diameter of the sampling drill rod, and the unit is cm; represents the median particle size of the soil, and the unit is mm; represents the penetration speed value of the sampling drill rod, and the unit is m / min; represents the length of the sampling drill rod below the groundwater depth, and the unit is m; represents the formation conductivity, and the unit is mS / cm; represents the ideal gas constant, the value is 8.31, and the unit is J·mol -1 ·K -1 ; represents the formation temperature, and the unit is K.

[0047] Preferably, step 20 specifically comprises:

[0048] Step 201, insert several electrode plates 4 around the sampling point, as shown in the figure, the insertion depth of the electrode plate 4 is consistent with the preset sampling depth, and the electrode plate 4 is connected with the positive electrode of the adjustable power supply 3. Figure 2

[0049] Preferably, as shown in the figure, several electrode plates 4 are connected in turn through wires, and one of the electrode plates is connected with the positive electrode of the adjustable power supply 3. The several electrode plates are uniformly arranged around the sampling point. Figure 3

[0050] The number of electrode plates 4 is 4-8. If the electrode plates 4 are too few, the electron transmission efficiency between the electrode plates 4 and the sampling drill rod will be reduced, the bubbles will be unevenly distributed on the surface of the sampling drill rod, the surrounding soil will be deformed unevenly, and the integrity of the soil sample will be reduced. If the electrode plates 4 are too many, it will take a long time to install and recover the electrode plates 4, increase the sampling time cost, and too many electrode plates 4 will also occupy more construction operation surface, which will significantly reduce the sampling work efficiency.

[0051] Step 202, install the first rod body at the top end of the drill bit, extend the drill bit into the preformed hole, and install the second, …, and the m +1th rod bodies in turn at the top end of the first rod body, until the bottom end of the drill bit reaches the groundwater level position, and the bottom end of the m +1th rod body is located near the ground 9. Among them, m is an integer greater than or equal to 0. p =1. Install the p th sampling pipe into the sampling drill rod, and install the m ​​+1 rod body top end installation top hat. The top hat 12, rod body 11 and drill bit connected in turn constitute a sampling drill rod, the sampling drill rod and the negative electrode of the adjustable power supply are connected. The top hat 12 is connected with the vertical vibration unit 6.

[0052] Step 203, according to the collected layer conductivity, formation temperature, the length of the sampling drill rod below the groundwater depth and the penetration speed value of the sampling drill rod, the output voltage of the adjustable power supply is adjusted; the adjustable power supply is connected with the electrode plate and the sampling drill rod, and the interstitial water in the soil around the sampling drill rod is electrolyzed to generate bubbles. At the same time, the vertical vibration unit 6 drives the sampling drill rod to reciprocate in the vertical direction, promoting the liquefaction of the soil near the sampling drill rod 1, so as to reduce the disturbance. The traction unit 5 drives the vertical vibration unit 6 and the sampling drill rod to penetrate into the formation for sampling. When the first m + p The adjustable power supply stops outputting voltage when the rod body is fully pressed into the formation, and the vertical vibration unit and the traction unit stop working. The vertical vibration unit and the top hat are separated, the top hat and the first m + p The rod body is separated, and the first p The sampling tube is taken out, and the first p The soil sample below the groundwater level is obtained.

[0053] Step 204, the top end of the first m + p The rod body is installed with the first m + p +1 rod body, p The value of the number increases by 1. The first p The sampling tube is installed in the sampling drill rod, and the first m + p The top end of the first The top hat, the rod body and the drill bit connected in turn constitute a sampling drill rod, the sampling drill rod and the negative electrode of the adjustable power supply are connected. The top hat 12 is connected with the vertical vibration unit 6. Repeat step 203 until the soil sample in the preset sampling depth range is taken out.

[0054] In the above embodiment, during the downward penetration sampling, the electrolysis voltage is adjusted in real time according to the sampling depth, the soil layer resistivity and the soil layer temperature at the depth, which can ensure the bubble content of the interface between the sampling drill rod and the soil layer, provide conditions for the disorderly movement and liquefaction suspension of soil particles through the immediate adjustment of soil pore saturation, and enhance the sampling fidelity effect.

[0055] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above specific embodiments, and the above specific embodiments and the description in the specification are only for further illustration of the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. A soil high fidelity acquisition method based on pore water electrolysis drag reduction, characterized in that, The method comprises the following steps: Step 10, drilling to the position of the underground water level (8) at the sampling point to form a pre-hole; Step 20, inserting a plurality of electrode plates (4) around the sampling point, the insertion depth of the electrode plates (4) being consistent with the preset sampling depth; inserting the sampling drill rod (1) from the pre-hole, connecting the sampling drill rod (1) with the negative pole of the adjustable power supply (3), and connecting the electrode plates (4) with the positive pole of the adjustable power supply (3); during the process of driving the sampling drill rod by the traction unit (5) to penetrate into the underground water level to collect the soil sample, the electrode plates and the sampling drill rod are electrified to electrolyze the pore water in the soil body near the sampling drill rod to generate bubbles; at the same time, the vertical vibration unit (6) drives the sampling drill rod (1) to reciprocate in the vertical direction to induce the liquefaction of the soil body near the sampling drill rod until the soil sample in the preset sampling depth range is taken out.

2. The soil high fidelity acquisition method based on pore water electrolysis drag reduction of claim 1, wherein, The amplitude of the vertical vibration unit (6) is determined by formula (1): Formula (1) In the formula, represents the amplitude of the vertical vibration unit, in mm; represents the median particle size of the soil, in mm; represents the shape adjustment coefficient, with a value range of -1.50 to -0.70, dimensionless; I p indicates the plasticity index of the soil, dimensionless; I p0 represents the reference plasticity index of soil, the value range is 4-7, dimensionless; β represents the activity adjustment coefficient, the value range is 0.15-0.45, unit: mm.

3. The soil high fidelity acquisition method based on pore water electrolysis drag reduction of claim 1, wherein, The plurality of electrode plates are connected in sequence by wires, and one of the electrode plates is connected with the positive pole of the adjustable power supply.

4. The soil high fidelity acquisition method based on pore water electrolysis drag reduction of claim 1, wherein, The plurality of electrode plates are uniformly arranged around the sampling point.

5. The soil high fidelity acquisition method based on pore water electrolysis drag reduction of claim 1, wherein, The number of the electrode plates is 4-8.

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