Construction device and pile uniformity control method for cement mixing piles based on real-time magnetic field monitoring

Abstract

This invention relates to the field of pile foundation testing technology, specifically to a cement mixing pile construction device and a pile uniformity control method based on real-time magnetic field monitoring. The device includes a drilling rig with a drill rod, which is driven by the drilling rig to rotate around its axis and drill into the soil to a target depth along its axis. A mixing component is located at the bottom of the drill rod, forming a mixing zone of a predetermined diameter in the soil. A grouting port is also located at the bottom of the drill rod, and a grouting channel is located inside the drill rod, with the outlet of the grouting channel connected to the grouting port. This application uses a magnetoresistive sensor at the bottom of the drill rod to collect magnetic field parameters in real time. Combined with the distribution of ferromagnetic powder in the precast grout, the uniformity of the cement slurry mixing with the soil can be directly assessed during construction. In particular, through magnetic field parameter feedback, dynamic control of the construction process can be achieved, forming a closed-loop control of detection-feedback-adjustment, significantly improving the consistency of pile quality.

Description

Technical Field

[0001] This invention relates to the field of foundation pile testing technology, and more specifically to a cement mixing pile construction device and a method for controlling pile uniformity based on real-time magnetic field monitoring. Background Technology

[0002] Cement mixing piles, as a foundation treatment technology, have been widely used in the reinforcement of soft soil foundations in highways, railways, and buildings since the 1970s. Their core principle is to mechanically mix cement slurry or dry powder with the original foundation soil to form a continuous and uniform cement-soil composite pile, thereby improving the bearing capacity and deformation resistance of the foundation.

[0003] The method of forming cement mixing piles usually involves high-pressure injection of cement slurry through the grouting nozzle at the bottom of the drill rod, while simultaneously rotating and mixing the soil to form a homogeneous pile. This process is highly adaptable, but it requires high coordination and control of slurry fluidity, drill rod lifting speed and mixing torque. Therefore, the quality of the mixed piles after pile formation may have defects such as uneven cement distribution, and quality testing of the pile body is usually required after pile formation.

[0004] Traditional pile quality testing relies on destructive methods (such as core drilling and static load tests) and indirect evaluation methods (such as standard penetration tests), which have limitations such as low efficiency, high cost, and inability to cover the entire area. Therefore, non-destructive testing (NDT) technology has gradually become a research hotspot.

[0005] Acoustic wave transmission method: It inverts the uniformity of sound wave propagation speed in the pile, but it is significantly affected by the heterogeneity of the pile material and is difficult to identify minute defects.

[0006] Ground-penetrating radar (GPR) method: It uses the electromagnetic wave reflection characteristics to detect cavities or segregation, but its resolution is limited by the attenuation of high-frequency signals and it is not sensitive enough to non-conductive materials.

[0007] Resistivity imaging method: assesses quality by measuring the resistivity distribution of the pile body, but is easily affected by groundwater level and ion concentration.

[0008] While the methods described above can partially replace traditional testing, they still face challenges such as strong signal interference, complex interpretation models, and limited applicability. Therefore, developing a nondestructive testing method suitable for complex working conditions has become an urgent need in the industry. Summary of the Invention

[0009] To address the technical problems existing in existing cement mixing piles, the first aspect of this invention proposes a technical solution: a cement mixing pile construction device based on real-time magnetic field monitoring, comprising:

[0010] The drilling rig is equipped with a drill rod, which can be driven by the drilling rig to rotate around its axis and drill into the soil to a target depth along its axis. The bottom of the drill rod is equipped with a stirring component, which is used to form a stirring zone of a predetermined diameter in the soil. The bottom of the drill rod is also equipped with a grouting port, and the inside of the drill rod is equipped with a grouting channel, the outlet of which is connected to the grouting port.

[0011] A slurry mixing plant is used to prepare pre-made slurry and deliver the pre-made slurry to the inlet of the grouting channel at a predetermined pressure, so that the grouting channel is filled with pre-made slurry and injected into the mixing area through the grouting port;

[0012] The pre-mixed slurry in the slurry mixing plant contains a predetermined proportion of ferromagnetic powder. A magnetoresistive sensor is provided at the bottom of the drill rod. The magnetoresistive sensor is configured to collect magnetic field parameters of a predetermined depth layer in the mixing area. The drilling rig is configured to control the mixing state of the mixing components at the predetermined depth layer according to the magnetic field parameters of the target depth.

[0013] Preferably, the magnetoresistive sensor is offset from the axis of the drill rod, so that the magnetoresistive sensor forms a spiral motion trajectory during the transmission of the drill rod.

[0014] Preferably, the drilling rig is configured to control the drill rod to complete at least four mixing processes. In the first mixing process, the drill rod drills from the soil surface to the target depth and breaks up the soil layer to form a mixing zone by rotating the mixing component. In the second mixing process, the drill rod is raised from the target depth to the soil surface and pre-prepared grout is injected into the mixing zone through the grouting port. In the third mixing process, the drill rod drills from the soil surface to the target depth for the second time and the mixing zone is mixed a second time by the mixing component. In the fourth mixing process, the drill rod is raised from the target depth to the soil surface and pre-prepared grout is injected into the target depth of the mixing zone a second time through the grouting port.

[0015] Preferably, the pre-mixed slurry configured in the slurry mixing plant includes a first pre-mixed slurry and a second pre-mixed slurry. The first pre-mixed slurry includes a mixed slurry formed by cement mortar and iron powder in a first proportion, and the second pre-mixed slurry includes a mixed slurry formed by cement mortar and iron powder in a second proportion. During the second mixing process, the first pre-mixed slurry is injected into the mixing area through the grouting port. During the fourth mixing process, the second pre-mixed slurry is injected into the mixing area to the target depth through the grouting port.

[0016] Preferably, the magnetoresistive sensor samples at a predetermined frequency during the second and fourth stirring processes, and the sampling frequency of the magnetoresistive sensor is matched with the lifting speed of the drill pipe;

[0017] The stirring area is divided into several depth layers along the axial direction, and the number of sampling points of the magnetoresistive sensor is the same in each depth layer.

[0018] Preferably, the magnetic field parameters include the mean axial magnetic field strength, the range of radial magnetic field strength, and the abrupt change rate of the axial magnetic field gradient.

[0019] The mean axial strength of the magnetic field is the average magnetic field strength of multiple sampling points in the target depth layer;

[0020] The radial strength range of the magnetic field is the difference between the maximum and minimum values ​​of the radial sampling points within the target depth layer;

[0021] The abrupt change rate of the magnetic field axial gradient is the degree of gradient change in the axial direction of the magnetic field per unit time and within a height range.

[0022] Preferably, when the average axial strength of the magnetic field is less than a preset value, the current height layer is marked as the first defect area with insufficient cement content, and cement is added for the fourth time; when the average axial strength of the magnetic field is greater than a preset value or the abrupt change rate of the magnetic field gradient is greater than a preset value, the current height layer is marked as the second defect area with iron powder accumulation, grouting hole blockage or abnormal rotation speed, uneven mixing, and mixing is stopped for the third time, and cement is added.

[0023] When the radial strength difference of the magnetic field is greater than the preset value, the current height layer is marked as the third defect region with uneven stirring, and stirring is stopped for the third time.

[0024] Preferably, the first proportion of iron powder is a first iron powder with a volume ratio of 0.8% to 1.2%, and the second proportion of iron powder is a second iron powder with a volume ratio of 2.8% to 3.2%. The first iron powder includes red iron oxide powder, and the second iron powder includes black magnetic powder. The particle size of both the first iron powder and the second iron powder is 45μm to 80μm.

[0025] The second aspect of this invention proposes a technical solution: a method for controlling the uniformity of cement mixing piles, using the aforementioned cement mixing pile construction device based on real-time magnetic field monitoring, comprising the following steps:

[0026] Step 1: Prepare a pre-mixed slurry containing a predetermined proportion of ferromagnetic powder;

[0027] Step 2: Control the drill rod with the drilling rig to drill from the soil surface and mix to the target depth, forming a mixing zone of the predetermined depth;

[0028] The steps involve controlling the drill rod to be raised from the target depth to the soil surface by the drilling rig. During this process, the magnetic field parameters of the predetermined depth layer in the mixing area are collected by the magnetoresistive sensor, and the pile quality at the current depth layer is evaluated by the magnetic field parameters.

[0029] The ferromagnetic powder accounts for less than 5% of the total volume of the precast slurry. During the process of raising the magnetoresistive sensor from the target depth to the surface of the soil layer, the mean value of the axial magnetic field strength, the range of the radial magnetic field strength, and the abrupt change rate of the axial magnetic field gradient of the current depth layer are obtained by sampling at multiple points layer by layer.

[0030] Preferably, when the average axial strength of the magnetic field is less than a preset value, the current height layer is marked as a first defect region; when the average axial strength of the magnetic field is greater than a preset value or the abrupt change rate of the magnetic field axial gradient is greater than a preset value, the current height layer is marked as a second defect region.

[0031] When the radial strength difference of the magnetic field is greater than a preset value, the current height layer is marked as the third defect region.

[0032] Compared with the prior art, the advantages of the present invention are as follows:

[0033] This application uses a magnetoresistive sensor at the bottom of the drill rod to collect magnetic field parameters in real time. Combined with the distribution of ferromagnetic powder in the precast grout, it can directly assess the uniformity of the mixing of cement grout and soil during construction. In particular, through the feedback of magnetic field parameters, dynamic control of the construction process can be achieved, forming a closed-loop control of detection-feedback-adjustment, which significantly improves the consistency of pile quality.

[0034] Replacing traditional post-piling detection with real-time magnetic field parameter detection using sound waves, electromagnetic waves, or resistivity avoids problems such as signal attenuation and material heterogeneity interference, achieving higher detection accuracy. Furthermore, by marking defect areas in real time, targeted repair actions can be triggered, which helps improve repair efficiency. Attached Figure Description

[0035] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in the various figures may be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the invention will now be described by way of example and with reference to the accompanying drawings, wherein:

[0036] Figure 1 This is a schematic diagram of the cement mixing pile construction device based on real-time magnetic field monitoring as shown in this invention.

[0037] Figure 2 This is a schematic diagram of the initial stirring of the drill pipe according to the present invention;

[0038] Figure 3 This is a schematic diagram of the drill pipe re-stirring process shown in this invention. Detailed Implementation

[0039] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0040] {Example 1}

[0041] Combination Figure 1 As shown, the first aspect of the present invention proposes a technical solution: a cement mixing pile construction device based on real-time magnetic field monitoring, including a drilling rig 100 and a slurry mixing station.

[0042] The drilling rig 100 is equipped with a drill rod 110, which can be driven by the drilling rig 100 to rotate around its axis and drill into the soil to the target depth along its axis.

[0043] Furthermore, the bottom of the drill rod 110 is provided with a mixing component 120, which is used to form a mixing zone of a predetermined diameter in the soil layer. The bottom of the drill rod is also provided with a grouting port, and the inside of the drill rod is provided with a grouting channel, the outlet of which is connected to the grouting port.

[0044] Understandably, the mixing component 120 breaks up and mixes the soil layer by rotating, forming a loose area of ​​a predetermined diameter. By injecting grout into the loose soil layer, cement and broken soil are mixed together to form the pile body. In this process, the uniformity of the mixing of cement and soil reflects the strength of the pile body.

[0045] In order to effectively control the uniformity of the mixing of cement slurry and soil, it is necessary to monitor and intervene during the mixing process.

[0046] Furthermore, the slurry mixing plant is used to prepare pre-made slurry and deliver the pre-made slurry to the inlet of the grouting channel at a predetermined pressure, so that the grouting channel is filled with pre-made slurry and injected into the mixing area through the grouting port.

[0047] The pre-mixed slurry in the slurry mixing plant contains a predetermined proportion of ferromagnetic powder. A magnetoresistive sensor 150 is provided at the bottom of the drill rod 110. The magnetoresistive sensor 150 is set to collect the magnetic field parameters of a predetermined depth layer in the mixing area. The drilling rig 100 is set to control the mixing state of the mixing component 120 in the predetermined depth layer according to the magnetic field parameters of the target depth.

[0048] It should be understood that the drill pipe 110 includes a drilling cycle and a lifting cycle, and includes initial stirring and re-stirring. The initial stirring cycle is the first drilling and lifting of the drill pipe 110, and the re-stirring cycle is the second drilling and lifting of the drill pipe 110. The grouting process occurs during the lifting cycle. At the same time, the magnetoresistive sensor 150 also detects the magnetic field parameters after grouting during the lifting process. During the lifting process, the magnetoresistive sensor 150 can detect the magnetic field intensity at different depths. By measuring the rate of change of magnetic field intensity in the axial direction and the rate of change of magnetic field intensity in the radial direction, it can be determined whether the distribution of the injected grout in the stirring area is uniform.

[0049] In an optional embodiment, the magnetoresistive sensor 150 is positioned off-axis from the drill rod 110, so that the magnetoresistive sensor 150 forms a spiral motion trajectory during the transmission of the drill rod 110.

[0050] Thus, the magnetoresistive sensor 150 has high accuracy in recognizing the radial magnetic field gradient.

[0051] In an optional embodiment, the magnetoresistive sensor 150 is embedded in the bottom of the drill pipe 110 and covered by a wear-resistant alloy cover, maintaining consistency with the original bottom contour of the drill pipe 110.

[0052] In an optional embodiment, the drilling rig is configured to control the drill rod to complete at least four mixing processes, including two initial mixing processes and two secondary mixing processes.

[0053] During the initial stirring process: [combination] Figure 2 As shown in S1 to S2, during the first mixing process, the drill rod 110 drills from the soil surface to the target depth, and the soil layer is broken up by the rotation of the mixing component 120 to form a mixing zone. Figure 2 As shown in S3 to S4, during the second mixing process, the drill rod 110 is raised from the target depth to the surface of the soil layer and precast grout is injected into the mixing area through the grouting port.

[0054] During the re-stirring process: [combination] Figure 3 As shown in S5 to S6, during the third mixing process, the soil layer is drilled a second time from the surface to the target depth, and the mixing area is mixed a second time by the mixing components. Figure 3 As shown in S7 to S8, during the fourth mixing process, the drill rod is raised from the target depth to the soil surface, and precast grout is injected a second time into the target depth of the mixing area through the grouting port.

[0055] Furthermore, the precast slurry configured in the slurry mixing plant includes a first precast slurry and a second precast slurry. The first precast slurry includes a mixed slurry formed by cement mortar and iron powder in a first proportion, and the second precast slurry includes a mixed slurry formed by cement mortar and iron powder in a second proportion.

[0056] Specifically, the slurry mixing plant includes a mixing chamber 210, a valve 220, and a mud pump 230. The mixing chamber 210 is divided into a first mixing chamber 210 and a second mixing chamber 212. The first mixing chamber 210 stores the first pre-prepared slurry, and the second mixing chamber 212 stores the second pre-prepared slurry. The pre-prepared slurry is injected into the drill pipe 110 through two independent mud pumps 230.

[0057] Furthermore, the drill pipe 110 is provided with a first grouting channel 141 and a second grouting channel 142 inside. The end of the first grouting channel 141 is connected to the first grouting port 131, and the end of the second grouting channel 142 is connected to the second grouting port 132. The first pre-prepared grout can be injected into the soil layer through the first grouting port 131, and the second pre-prepared grout can be injected into the soil layer through the second grouting port 132.

[0058] Specifically, especially during the second mixing process, the first pre-mixed slurry is injected into the mixing area through the first grouting port 131, and during the fourth mixing process, the second pre-mixed slurry is injected into the target depth of the mixing area through the second grouting port 132.

[0059] Preferably, the first proportion of iron powder is a first iron powder with a volume ratio of 0.8% to 1.2%, and the second proportion of iron powder is a second iron powder with a volume ratio of 2.8% to 3.2%. The first iron powder includes red iron oxide powder, and the second iron powder includes black magnetic powder. The particle size of both the first iron powder and the second iron powder is 45μm to 80μm.

[0060] Thus, the proportion of iron powder in the two injected slurries is different, and the magnetoresistive sensor 150 can evaluate the uniformity of slurry injection in each stirring process during the second or fourth stirring process.

[0061] Furthermore, since the iron powder in the two injections of grout is of different colors, if core sampling is required later, the distribution of the different colored powders can be used to verify the contribution of the two groutings to the uniformity of the pile body.

[0062] In an optional embodiment, the magnetoresistive sensor 150 samples at a predetermined frequency during the second and fourth stirring processes, and the sampling frequency of the magnetoresistive sensor 150 is matched with the lifting speed of the drill rod 110.

[0063] The stirring area is divided into several depth layers along the axial direction, and the number of sampling points of the magnetoresistive sensor 150 is the same in each depth layer.

[0064] In a specific embodiment, taking a depth layer of 5 as an example, the stirring area is divided into a first depth layer h1, a second depth layer h2, a third depth layer h3, a fourth depth layer h4, and a fifth depth layer h5, from bottom to top. In each depth layer, the magnetoresistive sensor 150 performs several samplings, for example, 200 samplings per depth layer. Therefore, for any given depth layer, the magnetic field strength collected by the magnetoresistive sensor 150 includes 200 data points, i.e., B. i 1. B i 2. B i 3、…、B i 200, where i represents the label of the current depth layer (i = 1, 2, 3, 4, 5).

[0065] Furthermore, each collected magnetic field strength data is matched with the current depth and radial position, and then the mean axial magnetic field strength, the range of radial magnetic field strength, and the abrupt change rate of the axial magnetic field gradient are calculated using each magnetic field strength data.

[0066] The mean axial magnetic field strength is the average magnetic field strength of multiple sampling points in the target depth layer.

[0067] Specifically, for the mean axial magnetic field strength Bz at a certain depth layer i = (B i 1+B i 2+B i 3+…+B i 200) / 200, where i represents the label of the current depth layer (i = 1, 2, 3, ..., n).

[0068] Among them, the radial intensity range of the magnetic field is the difference between the maximum and minimum values ​​of the radial sampling points within the target depth layer.

[0069] Specifically, for the radial strength range ΔBr of the magnetic field in the depth layer i =Br i max-Br i min;

[0070] Among them, B i `max` represents the maximum radial magnetic field strength within the current depth layer, Br i min represents the minimum radial magnetic field strength within the current depth layer, ΔBr i Reflecting the radial distribution difference of iron powder in the current depth layer, when ΔBr i If the value exceeds the preset value, it indicates that the current target depth layer is not stirred evenly.

[0071] Optionally, if ΔBr i If ≤0.25mT, then the iron powder is uniformly distributed radially, corresponding to a cement dosage deviation of <10%. If ΔBr i If the concentration is greater than 0.4 mT, the mixing will be severely uneven, and the cement content deviation may be greater than 30%.

[0072] Among them, the magnetic field axial gradient abrupt change rate represents the degree of change of the magnetic field along the axis of the pile.

[0073] Specifically, in, This represents the axial magnetic field gradient.

[0074] In a specific embodiment, the detection time interval is 15s, and the axial movement distance within this time interval is 20cm. That is, axial magnetic field gradient data is acquired every 15s. If the mutation rate is within ±5% / min, it indicates that the magnetic field axial gradient mutation rate is normal. If the mutation rate is >15% / min, it indicates that the material supply is abnormal, the lifting is paused, and the pump flow rate is checked.

[0075] In the above embodiments, the mean axial strength of the magnetic field, the range of radial strength of the magnetic field, and the abrupt change rate of the axial gradient of the magnetic field are continuously detected. When the mean axial strength of the magnetic field is less than the preset value, the current height layer is marked as the first defect area, indicating that the cement content is insufficient and cement can be added during the fourth mixing process.

[0076] When the average axial strength of the magnetic field is greater than the preset value or the abrupt change rate of the axial gradient of the magnetic field is greater than the preset value, the current height layer is marked as the second defect area, which is characterized by iron powder accumulation. This may be caused by blockage of the grouting orifice, abnormal rotation speed, or uneven mixing. By checking whether the above defects continue to exist in adjacent height layers, it is verified whether they are caused by blockage of the grouting orifice. If so, the mud pump pressure is adjusted. Furthermore, after marking the above height layer, it can be stopped at this height layer during the third mixing process and repeatedly mixed to ensure that the cement and mud are fully mixed, or cement slurry can be added to this height layer during the fourth mixing process and mixed again to optimize the defective height layer.

[0077] When the radial strength difference of the magnetic field is greater than the preset value, the current height layer is marked as the third defect region, which may be caused by uneven stirring. During the third stirring process, the stirring is carried out at this height layer.

[0078] {Example 2}

[0079] The second aspect of this invention proposes a technical solution: a method for controlling the uniformity of cement mixing piles, using the aforementioned cement mixing pile construction device based on real-time magnetic field monitoring, comprising the following steps:

[0080] Step 1: Prepare a pre-mixed slurry containing a predetermined proportion of ferromagnetic powder;

[0081] Step 2: Control the drill rod 110 through the drilling rig 100 to drill from the soil surface and mix to the target depth, forming a mixing zone of predetermined depth;

[0082] Step 3: The drill rod 110 is raised from the target depth to the soil surface by the drill rig 100. During this process, the magnetic field parameters of the predetermined depth layer in the mixing area are collected by the magnetoresistive sensor 150, and the pile quality of the current depth layer is evaluated by the magnetic field parameters.

[0083] Among them, the proportion of ferromagnetic powder to the total volume of precast slurry is less than 5%. During the process of the magnetoresistive sensor 150 being raised from the target depth to the surface of the soil layer, the mean value of the axial strength of the magnetic field, the range of the radial strength of the magnetic field, and the abrupt change rate of the axial gradient of the magnetic field in the current depth layer are obtained by sampling at multiple points layer by layer.

[0084] The mean axial magnetic field strength is the average magnetic field strength of multiple sampling points in the target depth layer.

[0085] Specifically, for the mean axial magnetic field strength Bz at a certain depth layer i = (B i 1+B i 2+B i 3+…+B i 200) / 200, where i represents the label of the current depth layer (i = 1, 2, 3, ..., n).

[0086] Among them, the radial intensity range of the magnetic field is the difference between the maximum and minimum values ​​of the radial sampling points within the target depth layer.

[0087] Specifically, for the radial strength range ΔBr of the magnetic field in the depth layer i =Br i max-Br i min;

[0088] Among them, B i `max` represents the maximum radial magnetic field strength within the current depth layer, Br i min represents the minimum radial magnetic field strength within the current depth layer, ΔBr i Reflecting the radial distribution difference of iron powder in the current depth layer, when ΔBr i If the value exceeds the preset value, it indicates that the current target depth layer is not stirred evenly.

[0089] Optionally, if ΔBr i If ≤0.25mT, then the iron powder is uniformly distributed radially, corresponding to a cement dosage deviation of <10%. If ΔBr i If the concentration is greater than 0.4 mT, the mixing will be severely uneven, and the cement content deviation may be greater than 30%.

[0090] Among them, the magnetic field axial gradient abrupt change rate represents the degree of change of the magnetic field along the axis of the pile.

[0091] Specifically, in, This represents the axial magnetic field gradient.

[0092] In a specific embodiment, the detection time interval is 15s, and the axial movement distance within this time interval is 20cm. That is, axial magnetic field gradient data is acquired every 15s. If the mutation rate is within ±5% / min, it indicates that the magnetic field axial gradient mutation rate is normal. If the mutation rate is >15% / min, it indicates that the material supply is abnormal, the lifting is paused, and the pump flow rate is checked.

[0093] In the above embodiments, the mean axial strength of the magnetic field, the range of radial strength of the magnetic field, and the abrupt change rate of the axial gradient of the magnetic field are continuously detected. When the mean axial strength of the magnetic field is less than the preset value, the current height layer is marked as the first defect area, indicating that the cement content is insufficient and cement can be added during the fourth mixing process.

[0094] When the average axial strength of the magnetic field is greater than the preset value or the abrupt change rate of the axial gradient of the magnetic field is greater than the preset value, the current height layer is marked as the second defect area, which is characterized by iron powder accumulation. This may be caused by blockage of the grouting orifice, abnormal rotation speed, or uneven mixing. By checking whether the above defects continue to exist in adjacent height layers, it is verified whether they are caused by blockage of the grouting orifice. If so, the mud pump pressure is adjusted. Furthermore, after marking the above height layer, it can be stopped at this height layer during the third mixing process and repeatedly mixed to ensure that the cement and mud are fully mixed, or cement slurry can be added to this height layer during the fourth mixing process and mixed again to optimize the defective height layer.

[0095] When the radial strength difference of the magnetic field is greater than the preset value, the current height layer is marked as the third defect region, which may be caused by uneven stirring. During the third stirring process, the stirring is carried out at this height layer.

[0096] As mentioned above, by real-time monitoring of the magnetic field parameters during the second mixing process, the mixing effect of mud and cement slurry at the current height layer is evaluated. For those with poor mixing effect, the cement and mud in the cement mixing pile are made more uniform by stopping the mixing during the third mixing process to fully mix and by injecting cement slurry again during the fourth mixing process.

[0097] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A cement mixing pile construction device based on real-time magnetic field monitoring, characterized in that, include: A drilling rig (100) is provided with a drill rod (110), which can be driven by the drilling rig (100) to rotate around its axis and drill into the soil layer to a target depth along its axis. The bottom of the drill rod (110) is provided with a stirring component (120), which is used to form a stirring area of ​​a predetermined diameter in the soil layer. The bottom of the drill rod (110) is also provided with a grouting port. The drill rod (110) is provided with a grouting channel inside, and the outlet of the grouting channel is connected to the grouting port. A slurry mixing plant is used to prepare pre-made slurry and deliver the pre-made slurry to the inlet of the grouting channel at a predetermined pressure, so that the grouting channel is filled with pre-made slurry and injected into the mixing area through the grouting port; The pre-mixed slurry in the slurry mixing station contains a predetermined proportion of ferromagnetic powder. The bottom of the drill rod (110) is provided with a magnetoresistive sensor (150). The magnetoresistive sensor (150) is set to collect the magnetic field parameters of a predetermined depth layer in the mixing area. The drilling rig (100) is set to control the mixing state of the mixing component (120) in the predetermined depth layer according to the magnetic field parameters of the target depth.

2. The cement mixing pile construction device based on real-time magnetic field monitoring according to claim 1, characterized in that, The magnetoresistive sensor (150) is positioned off-axis from the drill rod (110), so that the magnetoresistive sensor (150) forms a spiral motion trajectory during the transmission of the drill rod (110).

3. The cement mixing pile construction device based on real-time magnetic field monitoring according to claim 1, characterized in that, The drilling rig (100) is configured to control the drill rod (110) to complete at least four mixing processes. In the first mixing process, the drill rod (110) drills from the soil surface to the target depth and breaks up the soil layer to form a mixing area by rotating the mixing component (120). In the second mixing process, the drill rod (110) is raised from the target depth to the soil surface and pre-made slurry is injected into the mixing area through the grouting port. In the third mixing process, the drill rod (110) drills from the soil surface to the target depth for the second time and the mixing area is mixed a second time by the mixing component (120). In the fourth mixing process, the drill rod (110) is raised from the target depth to the soil surface and pre-made slurry is injected into the target depth of the mixing area a second time through the grouting port.

4. The cement mixing pile construction device based on real-time magnetic field monitoring according to claim 3, characterized in that, The pre-mixed slurry configured in the slurry mixing plant includes a first pre-mixed slurry and a second pre-mixed slurry. The first pre-mixed slurry includes a mixture of cement mortar and iron powder in a first proportion. The second pre-mixed slurry includes a mixture of cement mortar and iron powder in a second proportion. During the second mixing process, the first pre-mixed slurry is injected into the mixing area through the grouting port. During the fourth mixing process, the second pre-mixed slurry is injected into the target depth of the mixing area through the grouting port.

5. The cement mixing pile construction device based on real-time magnetic field monitoring according to claim 3, characterized in that, The magnetoresistive sensor (150) samples at a predetermined frequency during the second and fourth stirring processes, and the sampling frequency of the magnetoresistive sensor (150) is matched with the lifting speed of the drill rod (110). The stirring area is divided into several depth layers along the axial direction, and the number of sampling points of the magnetoresistive sensor (150) is the same in each depth layer.

6. The cement mixing pile construction device based on real-time magnetic field monitoring according to claim 5, characterized in that, The magnetic field parameters include the mean axial strength of the magnetic field, the range of radial strength of the magnetic field, and the abrupt change rate of the axial gradient of the magnetic field. The mean axial strength of the magnetic field is the average magnetic field strength of multiple sampling points in the target depth layer; The radial strength range of the magnetic field is the difference between the maximum and minimum values ​​of the radial sampling points within the target depth layer; The abrupt change rate of the magnetic field axial gradient is the degree of gradient change in the axial direction of the magnetic field per unit time and within a height range.

7. The cement mixing pile construction device based on real-time magnetic field monitoring according to claim 6, characterized in that, When the average axial strength of the magnetic field is less than a preset value, the current height layer is marked as a first defect region; when the average axial strength of the magnetic field is greater than a preset value or the abrupt change rate of the magnetic field gradient is greater than a preset value, the current height layer is marked as a second defect region. When the radial strength difference of the magnetic field is greater than a preset value, the current height layer is marked as the third defect region.

8. The cement mixing pile construction device based on real-time magnetic field monitoring according to claim 4, characterized in that, The first proportion of iron powder is a first iron powder with a volume ratio of 0.8% to 1.2%, and the second proportion of iron powder is a second iron powder with a volume ratio of 2.8% to 3.2%. The first iron powder includes red iron oxide powder, and the second iron powder includes black magnetic powder. The particle size of both the first iron powder and the second iron powder is 45μm to 80μm.

9. A method for controlling the uniformity of the pile body in cement mixing piles, characterized in that, The cement mixing pile construction device based on real-time magnetic field monitoring according to any one of claims 1-8 includes the following steps: Step 1: Prepare a pre-mixed slurry containing a predetermined proportion of ferromagnetic powder; Step 2: Control the drill rod (110) to drill from the soil surface and mix to the target depth using the drilling rig (100) to form a mixing zone of predetermined depth; Step 3: Control the drill rod (110) to be raised from the target depth to the soil surface by the drilling rig (100). During this process, the magnetic field parameters of the predetermined depth layer in the mixing area are collected by the magnetoresistive sensor (150), and the pile quality of the current depth layer is evaluated by the magnetic field parameters. The ferromagnetic powder accounts for less than 5% of the total volume of the precast slurry. During the process of the magnetoresistive sensor (150) being raised from the target depth to the surface of the soil layer, the mean value of the axial magnetic field strength, the range of the radial magnetic field strength, and the abrupt change rate of the axial magnetic field gradient of the current depth layer are obtained by sampling at multiple points layer by layer.

10. The method for controlling the uniformity of the cement mixing pile body according to claim 9, characterized in that, When the average axial strength of the magnetic field is less than a preset value, the current height layer is marked as a first defect region; when the average axial strength of the magnetic field is greater than a preset value or the abrupt change rate of the magnetic field gradient is greater than a preset value, the current height layer is marked as a second defect region. When the radial strength difference of the magnetic field is greater than a preset value, the current height layer is marked as the third defect region.

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