A high-pressure jet grouting pile forming diameter quantitative monitoring method based on a double lateral resistivity principle

Abstract

The application discloses a high-pressure rotary jet pile forming diameter quantitative monitoring method based on a double lateral resistivity principle, and comprises the following steps: acquiring background resistivity data of an original land layer, wherein the background resistivity data is obtained by scanning the original land layer by using a detection probe in a downhole hole guiding process; acquiring deep detection resistivity and shallow detection resistivity, wherein the deep detection resistivity is used for reflecting the electrical characteristics of a deep soil layer in a radial direction of a pile body, and the shallow detection resistivity is used for reflecting the electrical characteristics of a shallow soil layer in the radial direction of the pile body; calculating a real resistivity value of a mixture of a downhole cement slurry and a soil body according to the shallow detection resistivity; and monitoring the pile forming diameter at each depth according to the real resistivity value, the background resistivity data and the deep detection resistivity. The application can overcome the defects in the existing rotary jet pile forming diameter detection technology, such as limited detection depth, serious lag of results, inability to real-time remedy, and great interference caused by cement slurry fluctuation and penetration and so on.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering monitoring and foundation treatment quality testing technology, and particularly relates to a quantitative monitoring method for the diameter of high-pressure jet grouting piles based on the principle of dual lateral resistivity. Background Technology

[0002] High-pressure jet grouting, the most commonly used form of high-pressure jet grouting technology, involves injecting a high-pressure grout stream (typically 20-40 MPa) through a nozzle at the end of the drill rod. This grout impacts and cuts the soil, forcibly mixing with soil particles to form a cylindrical reinforced pile within the soil. Due to its lightweight equipment, rapid construction speed, and significant reinforcement effect, high-pressure jet grouting is widely used in key projects such as improving foundation bearing capacity, foundation pit cutoff walls, subway tunnel boring machine (TBM) reinforcement, and water conservancy dam seepage prevention. Under certain specific engineering requirements, by controlling the nozzle rotation angle, methods such as fixed-jet (forming a panel-like structure) and swivel-jet (forming a fan-shaped structure) have been developed to create continuous reinforced surfaces. Regardless of the method, the dimensions of the reinforced body (such as the pile diameter of the jet grouting pile and the thickness of the fixed-jet wall) are the most crucial indicators for evaluating construction quality, directly determining the load-bearing capacity and seepage prevention effect of the reinforced body. However, due to factors such as uneven distribution of underground soil layers, fluctuations in construction pressure, and unstable construction speed, jet grouting piles are prone to quality defects such as necking, pile breakage, or insufficient diameter. Since jet grouting piles are underground concealed works, how to achieve real-time, quantitative monitoring of the deep pile diameter has always been a challenge for the geotechnical engineering community.

[0003] Currently, the commonly used methods for measuring the diameter of jet grouting piles in engineering mainly include excavation inspection and core drilling. Excavation inspection is the most direct method, involving manual or mechanical excavation of the soil around the pile head to directly measure the pile diameter. However, due to site conditions and safety costs, the excavation depth is usually limited to within 2 meters below ground level, failing to reflect the formation of the deeper pile body. For long piles reaching depths of ten or even tens of meters, there is a significant quality blind spot. Core drilling is the currently recognized standard method, determining the pile diameter and strength by drilling core samples from the pile body. However, core drilling can usually only be performed 28 days after construction is completed, when the pile strength meets the standards. The test results have a significant lag; once quality problems are discovered, the best remedial opportunity is often missed, resulting in high rework costs. Furthermore, jet grouting piles have small diameters and a certain degree of verticality deviation in the strata, making it easy for the core drilling hole to deviate from the pile body, leading to false judgments of "false pile breakage," thus limiting the reliability of the test.

[0004] To compensate for the shortcomings of the aforementioned physical testing methods, geophysical exploration techniques such as low-strain reflection wave analysis and ultrasonic testing have also been attempted for pile diameter detection. Low-strain reflection wave analysis infers pile integrity by analyzing waveform reflection; however, jet grouting piles are made of cement-soil material with high dynamic damping, low wave velocity, and complex wavefield characteristics, making them extremely insensitive to gradually narrowing defects and difficult to quantitatively calculate the diameter. Ultrasonic testing is widely used in the detection of bored piles, but during jet grouting pile construction, the borehole is filled with high-concentration, high-viscosity cement slurry, causing ultrasonic signals to attenuate extremely rapidly, resulting in a detection distance often less than 10 centimeters, which is completely insufficient for detecting piles with conventional diameters (0.6 meters to 1.2 meters).

[0005] In summary, existing methods for detecting the quality of jet grouting piles have significant shortcomings in terms of real-time performance, depth coverage, and quantitative accuracy. There is an urgent need in engineering for a method that can quickly and objectively measure the diameter of deep piles on the construction site. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a quantitative monitoring method for the diameter of high-pressure jet grouting piles based on the principle of dual lateral resistivity. This method overcomes the shortcomings of existing jet grouting pile diameter detection technologies, such as limited detection depth, severely delayed results, inability to provide real-time corrections, and significant interference from cement slurry fluctuations and infiltration.

[0007] To achieve the above objectives, this invention provides a method for quantitatively monitoring the diameter of high-pressure jet grouting piles based on the principle of dual-lateral resistivity, comprising: Background resistivity data of the undisturbed soil layer is obtained by scanning the undisturbed soil layer with a detection probe during the drilling process. The deep resistivity and shallow resistivity are obtained. The deep resistivity is used to reflect the radial deep electrical characteristics of the pile body containing the original soil layer, and the shallow resistivity is used to reflect the radial shallow electrical characteristics of the pile body. The actual resistivity value of the cement slurry mixed with the soil after shallow resistivity detection is calculated. Based on the actual resistivity value, background resistivity data, and deep-probe resistivity, the pile diameter at each depth is monitored.

[0008] Optionally, obtaining background resistivity data of the undisturbed soil layer includes: During the drilling process of the jet grouting rig, the detection probe is placed in the deep detection focusing mode, so that the shielding electrode and the main electrode are kept at the same potential, and the main electrode current is injected into the deep part of the original soil perpendicular to the hole diameter direction. Based on the data recorded in real time by the depth encoder installed on the drilling rig guide rail, the real undisturbed soil background resistivity curves at each depth are generated. Based on the background resistivity curve, obtain the background resistivity data of the undisturbed soil layer.

[0009] Optionally, obtaining deep-penetrating resistivity and shallow-penetrating resistivity includes: During the window period after the shotcrete construction is completed and before the grout initially sets, the detection probe is statically lowered to the bottom of the pile using the drilling rig's power head; During the process of uniformly raising the detection probe, the current loop is switched in a time-division multiplexing manner through the ground control system: in deep detection mode, the shielding electrode and the main electrode are connected to the same potential and the current flows to the ground loop electrode to obtain the deep detection resistivity; in shallow detection mode, the shielding electrode is switched to the return loop and the main electrode current flows to the adjacent shielding electrode to obtain the shallow detection resistivity.

[0010] Optionally, the detection depth in shallow detection mode is controlled at 100mm-150mm from the probe surface.

[0011] Optionally, the actual resistivity value of the mixture of downhole cement slurry and soil can be calculated based on the shallow resistivity detection. include: ; Where K is the electrode system constant; V0 and I0 are the voltage and current applied to the main electrode, respectively.

[0012] Optionally, monitoring the pile diameter at each depth based on the actual resistivity value, background resistivity data, and deep-penetration resistivity includes: Substituting the actual resistivity value, the background resistivity at the corresponding depth, and the deep-detection resistivity into the analytical formula of the coaxial cylinder series conductive model, the pile radius at each depth is solved, and thus the pile diameter is obtained.

[0013] Optionally, the actual resistivity value, the background resistivity at the corresponding depth, and the deep-probe resistivity are substituted into the analytical formula of the coaxial cylinder series conduction model to solve for the pile radius at each depth, thereby obtaining the pile diameter D, including: ; In the formula, r0 is the radius of the detection probe, L is the effective length of the main electrode, and r ∞ Let be the effective radius of influence constant of the current field in the undisturbed soil. ρ mix This is the actual resistivity value. ρ soi Background resistivity, R LLD To deeply probe resistivity.

[0014] Optionally, monitoring the pile diameter at various depths includes: The built-in multi-dimensional physical criteria are invoked to verify the validity of the pile diameter. The multi-dimensional physical criteria include electrical integrity criteria, depth-to-shallow resistance ratio criteria, and signal variance criteria. If the verification passes, a depth-pile diameter quantitative curve will be generated and displayed; if the verification fails, an early warning will be issued and a prompt will be made to check the equipment or perform targeted spraying.

[0015] Compared with the prior art, the present invention has the following advantages and technical effects: (1) Real-time quality inspection: By utilizing the "golden window period" after the construction of jet grouting piles, defects such as necking and broken piles can be quantitatively identified before the initial setting of the grout and real-time re-grouting can be guided, thus fundamentally avoiding the quality risks and high remedial costs caused by post-construction inspection. (2) Environmental and process interference is eliminated: the influence of complex formation background is automatically offset by differential logic of background scanning during drilling and lateral measurement during lifting; the real resistivity of the mixed slurry in the well is locked in real time by using the extremely shallow detection mode, eliminating slurry ratio fluctuation and bubble interference, and ensuring the physical accuracy of diameter inversion. (3) High engineering reliability. The static pressure retesting process and external cable technology are adopted to avoid the mechanical problems of internal wiring in the drill pipe and high-pressure rotary sealing. The low-voltage high-current design takes into account both signal strength and the construction safety of on-site personnel. This invention is applicable not only to jet grouting piles with circular cross-sections, but also to plate-wall or fan-shaped reinforced bodies formed by fixed or oscillating jet grouting. When used for monitoring fixed or oscillating jet grouting, by introducing a shape correction coefficient related to the jetting angle into the inversion model, the calculated electrical equivalent diameter is converted into the measured thickness or diameter of the reinforced body. Attached Figure Description

[0016] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is an overall implementation architecture diagram of the quantitative monitoring of characteristic dimensions of high-pressure jet grouting piles and reinforced bodies according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the electrode distribution structure of the detection probe according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the current flow direction and focusing principle in the deep detection mode (LLD) of this invention. Figure 4 This is a schematic diagram of the current flow and local loop in the shallow detection mode (LLS) of this invention. Figure 5 This is a schematic diagram of a coaxial cylindrical series conductive physical model of a high-pressure jet grouting pile according to an embodiment of the present invention; Figure 6 This is a schematic diagram showing a comprehensive comparison of the background resistivity curve, the measured resistance curve of the shallow and deep detection, and the inverted pile diameter curve obtained during the monitoring process of this embodiment of the invention. Figure 7 This is a flowchart of a method for quantitative monitoring of the diameter of high-pressure jet grouting piles based on the principle of dual-lateral resistivity, according to an embodiment of the present invention. Among them, 1-Jet jet grouting drill; 2-Power head (with static pressure lowering function); 3-Drill rod; 4-External armored cable; 5-Depth encoder; 6-Ground control system (including power supply and acquisition module); 7-Ground loop electrode B; 8-Detection probe substrate; 9-Main electrode A0; 10-Shielding electrode A1; 11-Shielding electrode A'1; 12-Insulating short section; 13-Teflon anti-adhesion coating; 14-Mixed grout reinforced body (pile body); 15-Original soil; 16-Permeability intrusion zone (transition zone); 17-Deep detection current beam (focused current); 18-Shallow detection current beam (local current). Detailed Implementation

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0018] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0019] This embodiment proposes a quantitative monitoring method for the diameter of high-pressure jet grouting piles based on the principle of dual lateral resistivity. Figure 7 As shown, the specific steps include: Background resistivity data of the undisturbed soil layer is obtained by scanning the undisturbed soil layer with a detection probe during the drilling process. The deep resistivity and shallow resistivity are obtained. The deep resistivity is used to reflect the radial deep electrical characteristics of the pile body containing the original soil layer, and the shallow resistivity is used to reflect the radial shallow electrical characteristics of the pile body. The actual resistivity value of the cement slurry mixed with the soil after shallow resistivity detection is calculated. Based on the actual resistivity value, background resistivity data, and deep-probe resistivity, the pile diameter at each depth is monitored.

[0020] Specifically, this embodiment combines the dual-stroke (drilling and grouting) process characteristics of high-pressure jet grouting pile construction. It acquires undisturbed soil background data through scanning during the drilling stage and, within the initial setting window after grouting, utilizes deep and shallow dual-lateral current focusing measurement technology to obtain real-time electrical feedback between the mixed grout inside the pile and the deep strata. By establishing a physical inversion model, it achieves quantitative back-calculation of the pile diameter across the entire depth range of the jet grouting pile. This method not only solves the problem of the "invisible" deep pile diameter but also enables the detection of defects before grout solidification and guides real-time re-grouting, greatly improving the quality control level of jet grouting pile projects.

[0021] Furthermore, obtaining background resistivity data of the undisturbed soil strata includes: During the drilling process of the jet grouting rig, the detection probe is placed in the deep detection focusing mode, so that the shielding electrode and the main electrode are kept at the same potential, and the main electrode current is injected into the deep part of the original soil perpendicular to the hole diameter direction. Based on the data recorded in real time by the depth encoder installed on the drilling rig guide rail, the real undisturbed soil background resistivity curves at each depth are generated. Based on the background resistivity curve, obtain the background resistivity data of the undisturbed soil layer.

[0022] Specifically, S1: Parameter precalibration and benchmark establishment.

[0023] Before construction, the initial resistivity value of the cement grout was measured using a ground-based measuring device. ρ slurry Simultaneously, a loop electrode B is set on the ground, and the detection probe is connected to the ground control system. The system operating voltage is set to a safe DC pulse voltage of 12V to 36V. S2: Formation background scan during the pilot hole stage.

[0024] During the drilling process of the jet grouting rig, the detection probe is activated and placed in deep detection focusing mode: the shielding electrode A1 and the main electrode A0 are kept at the same potential, so that the main electrode current is injected into the deep part of the undisturbed soil perpendicular to the borehole diameter, thereby eliminating the interference of the borehole medium (water or thin mud) and adjacent strata on the resistivity of the tested strata; in conjunction with the depth encoder installed on the drilling rig guide rail, the depth is recorded and generated in real time. H The actual undisturbed soil background resistivity curve ρ soil ( H ).

[0025] Furthermore, obtaining deep-penetrating resistivity and shallow-penetrating resistivity includes: During the window period after the shotcrete construction is completed and before the grout initially sets, the detection probe is statically lowered to the bottom of the pile using the drilling rig's power head; During the process of uniformly raising the detection probe, the current loop is switched in a time-division multiplexing manner through the ground control system: in deep detection mode, the shielding electrode and the main electrode are connected to the same potential and the current flows to the ground loop electrode to obtain the deep detection resistivity; in shallow detection mode, the shielding electrode is switched to the return loop and the main electrode current flows to the adjacent shielding electrode to obtain the shallow detection resistivity.

[0026] Specifically, S3: dynamic measurement of both sides during the pile formation stage.

[0027] During the window period after jet grouting and before the grout initially sets, the drilling rig's power head is used to statically lower the detection probe to the bottom of the pile. While the probe is being raised at a constant speed, the ground control system uses a relay array to switch the current loop in a time-division multiplexing manner, alternately acquiring the deep resistivity at various depths. R LLD and shallow resistivity detection R LLS : (1) Deep detection mode (LLD): The shielding electrode and the main electrode are connected to the same potential, and the current flows to the ground circuit electrode B to obtain the deep electrical characteristics affected by the pile diameter and the stratum. (2) Shallow Probe Mode (LLS): The shielded electrode is switched to a return loop, and the main electrode current flows directly to the adjacent shielded electrode to obtain shallow electrical characteristics that are only affected by the mixed slurry around the probe.

[0028] Furthermore, the detection depth in shallow detection mode is controlled at 100mm-150mm from the probe surface.

[0029] Furthermore, the actual resistivity value of the mixture of downhole cement slurry and soil is calculated based on the shallow resistivity detection. include: ; Where K is the electrode system constant; V0 and I0 are the voltage and current applied to the main electrode, respectively.

[0030] Furthermore, based on the actual resistivity value, background resistivity data, and deep-penetration resistivity, the pile diameter at each depth is monitored, including: Substituting the actual resistivity value, the background resistivity at the corresponding depth, and the deep detection resistivity into the analytical formula of the coaxial cylinder series conductive model, the pile radius at each depth is solved, and thus the pile diameter is obtained. When the construction process is fixed spraying or swing spraying, a shape correction coefficient is introduced into the coaxial cylindrical series conductive model.

[0031] Specifically, S4: Quantitative inversion calculation of pile diameter.

[0032] shallow probe resistivity obtained in step S3 R LLS Based on the probe's geometric constants, the true resistivity of the cement slurry mixed with the soil in the well is calculated. ρ mix ; then ρ mix The background resistivity obtained in step S2 ρ soil ( H and measured depth detection resistance R LLD Substituting the analytical formula of the coaxial cylinder series conduction model, the pile radius at each depth can be solved. r x Thus, the pile diameter D is obtained.

[0033] Among them, the H Piling diameter at depth D The calculation formula is: ; In the formula, r0 is the radius of the detection probe, L is the effective length of the main electrode, and r ∞ Let be the effective radius of influence constant of the current field in the undisturbed soil. ρ mix This is the actual resistivity value. ρ soi Background resistivity, R LLD For deep resistivity detection; ; Among them, R mix R is the radial resistance of the pile. soil The original radial resistance of the soil.

[0034] When the construction process is fixed spraying or swivel spraying, the coaxial cylindrical series conductive model introduces a shape correction coefficient. η Transform it into an asymmetric reinforced body model to calculate the wall thickness or the radius of the sector reinforcement; where the coefficients η Preset based on spray angle and nozzle configuration parameters. For 360-degree rotary spray... η =1.

[0035] Furthermore, monitoring the pile diameter at various depths includes: The built-in multi-dimensional physical criteria are invoked to verify the validity of the pile diameter. The multi-dimensional physical criteria include electrical integrity criteria, depth-to-shallow resistance ratio criteria, and signal variance criteria. If the verification passes, a depth-pile diameter quantitative curve will be generated and displayed; if the verification fails, an early warning will be issued and a prompt will be made to check the equipment or perform targeted spraying.

[0036] Specifically, S5: Multi-criteria data verification and real-time evaluation.

[0037] The system calls the built-in multi-dimensional physical criteria in real time to verify the validity of the calculation results in step S4. The criteria matrix includes: electrical integrity criteria for excluding hardware short circuits or open circuits, deep-shallow resistance ratio criteria for determining the logical relationship between deep and shallow detection, and signal variance criteria for distinguishing between necking and segregation phenomena. If the verification passes, a depth-pile diameter quantitative curve is generated and displayed. If the verification fails, an early warning is issued and manual equipment inspection is prompted based on the abnormal characteristics, or the construction site is guided to perform targeted spraying.

[0038] Preferably, the detection probe in step S3 is lowered using a static pressure implantation process. During the lowering process, the drilling rig rotation drive is not turned on, and the measurement signal is transmitted in real time through an armored cable attached to the outer wall of the drill rod.

[0039] Preferably, insulating short sections 12 are symmetrically arranged between the main electrode A09 and the shielding electrode A110 and shielding electrode A'111 of the detection probe to physically insulate the main electrode and the shielding electrode.

[0040] Preferably, the outer surface of the electrode of the detection probe adopts a flat-head streamlined design and is coated with a polytetrafluoroethylene anti-adhesion coating to prevent high-viscosity cement slurry from adhering and scaling on the electrode surface.

[0041] Preferably, the detection probe has a solid metal counterweight inside, ensuring that the overall density of the probe is not less than 7.8 g / cm³. 3 This ensures that it can smoothly sink to the bottom of the high-viscosity slurry by relying on the static pressure of the drilling rig when it is not rotating.

[0042] Preferably, in steps S3 and S4, the shallow detection mode is used to obtain... ρ mix The detection depth is controlled within the range of 100mm to 150mm from the probe surface to ensure that the electrical parameters of the grout can still be accurately extracted even when the pile diameter is reduced to its limit.

[0043] Preferably, all electrical data collected in steps S2 and S3 are time-depth synchronized and correlated using a depth encoder installed on the drilling rig guide rail.

[0044] The following is a detailed description of this embodiment: S1: Parameter pre-calibration and benchmark establishment. The initial resistivity value of pure cement slurry is measured on the construction surface using a measuring device. ρ slurryThis serves as the physical lower limit benchmark for system logic judgment. A ground loop electrode B7 is installed at a distance from the pile location (typically greater than 20 meters). The detection probe base 8, integrating the main electrode A09 and shielding electrodes A1 and A'1, is connected to the ground control system 6 via a conductive device at the top of the drill rod 3. The operating voltage of the measurement system is set to a safe DC pulse voltage of 12V to 36V to ensure safe operation in muddy and wet environments.

[0045] S2: Focused scanning of the formation background during the pilot hole stage. For example... Figure 1 and Figure 7 As shown, during the drilling process of the jet grouting rig 1, the detection probe base 8 is activated and placed in deep detection focusing mode (LLD). At this time, the shielding electrodes A1 and A'1 are connected to the same potential as the main electrode A0, generating a focusing electric field that forces the main electrode current to be injected into the formation perpendicular to the borehole diameter. Using the ground control system 6 in conjunction with the depth encoder 5 installed on the drilling rig guide rail, the true background resistivity curve of the undisturbed soil at each depth H is scanned and recorded in real time. ρ soil (H). This step eliminates the short-circuit diversion effect of the in-hole pilot medium (water or thin mud) to obtain an accurate calculation reference.

[0046] S3: Bilateral dynamic measurement during the pile lifting stage. After high-pressure jet grouting is completed and before the grout initially sets (usually within 30 minutes after construction), the probe base 8 is statically lowered to the pile bottom using the drill rig's power head 2. During the lowering process, the rotary drive and high-pressure system are not activated; the external armored cable 4 descends with the probe through the annular space between the drill rod 3 and the borehole wall. During the uniform lifting of the probe base 8, the ground control system 6 alternately acquires the measured resistance at various depths using a relay array in a time-division multiplexing manner (e.g., switching cycles once per second). R LLD Shallow detection measured resistance R LLS : 1) Deep Detection Mode (LLD): The ground control system keeps the shielded electrodes A1 and A'1 at the same potential as the main electrode A0. The focused current emitted by the shielded electrodes spatially forces the current emitted by the main electrode to be compressed into a thin disc shape and horizontally projected into the deep part of the undisturbed soil, forming a deep detection current beam (focused current) 17, which eventually flows back to the ground loop electrode B. The measured resistance at this time reflects the comprehensive information of the pile's characteristic radius and the surrounding strata, such as... Figure 3 As shown.

[0047] 2) Shallow Probing Mode (LLS): The ground control system switches shielded electrodes A1 and A'1 via relays, converting them into loop electrodes (i.e., connected to the negative terminal of the power supply), while simultaneously disconnecting the ground loop electrode B. At this time, the current emitted by the main electrode A0 is attracted by nearby opposite charges and immediately flows back to the adjacent shielded electrode after leaving the probe surface, forming a shallow probing current beam (local current) 18. In this mode, the electric field is confined within the mixed grout solidified body 14 inside the pile body, without energy exchange with the undisturbed soil 15. The probing depth is limited to 100mm to 150mm from the probe surface, thereby obtaining the true resistance of the near-well mixed grout, such as... Figure 4 As shown.

[0048] S4: Quantitative Inversion Calculation of Feature Size. Using the shallow probe measured resistance RLLS obtained in step S3, combined with the probe geometric coefficients, the true resistivity value of the cement slurry mixed with the soil in the well is calculated in real time. ρ mix Then the ρ mix The background resistivity at the corresponding depth obtained in step S2 and ρ soil (H) and the measured resistance of the deep probe in step S3 R LLD Substituting the inversion formula based on the coaxial cylinder series conduction model, the characteristic radius at each depth is solved. r x .

[0049] For full-circumferential spraying, the pile diameter D =2 r x The calculation formula is as follows: ; In the formula, r 0 represents the probe radius. L Main electrode length, r ∞ To effectively influence the radius, a shape correction coefficient is introduced into the formula for both stationary and swivel spraying conditions. η The thickness or sector radius of the reinforced wall is obtained through geometric conversion.

[0050] The specific testing principles and device details of this invention in practical engineering applications are described below with reference to the accompanying drawings.

[0051] 1) Design of testing equipment and environmental adaptability: like Figure 1 and Figure 2 As shown, the detection probe substrate 8 is designed as a streamlined stainless steel column, filled with a high-density metal weight to ensure an overall density of not less than 7.8 g / cm³. 3This ensures the probe can penetrate viscous cement slurry. The probe surface and electrode ring surface are coated with a Teflon anti-adhesion coating 13 to prevent cement scale from affecting electrode contact. The measurement system employs a low-voltage, high-current design (12V-36V) to ensure a strong signal (ampere-level current) in the low-resistivity medium of cement slurry while also ensuring the safety of personnel on site.

[0052] 2) Test analysis principles and inversion methods: like Figure 5 As shown, the physical model established in this invention is based on the assumption that the current diffuses radially. The total resistance encountered by the measuring current emitted from the main electrode as it flows into the deep formation... R LLD It consists of two parts connected in series: a. Near-well pile resistance section: Current flows from the probe surface (radius) r 0) Passing through the area where cement grout and soil are mixed (reaching radius) r x The resistance generated during this process is affected by the resistivity of the mixed slurry in this section. ρ mix control; b. Far-field layer resistance segment: Current leaves the boundary of the reinforced body (radius) r x Continue deeper into the strata (to reach the effective radius of influence) r ∞ The resistance generated during diffusion. This section is affected by the background resistivity of the undisturbed soil. ρ soil control.

[0053] Due to the total resistance R LLD It is the algebraic sum of the radial series resistances of these two regions, and ρ mix It has been accurately measured by the shallow detection mode (LLS). ρ soil This has already been obtained from the background scan during drilling, and therefore becomes the only unknown in the equation. Calculations using the above analytical formula can eliminate the diameter enlargement interference caused by the seepage intrusion zone 16 in the sand layer, and the measured... r x It accurately reflects the characteristic dimensions of the stress-bearing region of the reinforced core.

[0054] like Figure 6 As shown, based on the results of a typical resistivity test, the possible expansion and contraction points during the high-pressure jet grouting pile construction can also be directly determined. Theoretically, the background resistivity at any depth... ρ soil Maximum, shallow probe mode (LLS) measured resistivity of mixed slurry ρ mixAt its minimum, the Deep Loop (LLD) mode includes resistivity information from both the mixed slurry and the original background soil layer; the measured resistivity (red line) should lie between the two. When the measured resistivity in LLD mode is significantly closer to [a certain value] than at other locations... ρ mix This means that the area traversed by the focused current 17 is almost entirely composed of mixed grout, and the pile diameter at this location is significantly larger than at other locations, indicating diameter expansion. When the measured resistivity under deep detection mode (LLD) is significantly closer to that at other locations... ρ soil If this is the case, it means that the area through which the focusing current 17 passes is almost entirely the original soil layer. At this time, the grout range is significantly smaller than other locations, i.e., necking occurs.

[0055] This invention, through the aforementioned testing methods and inversion algorithms, achieves real-time quantitative monitoring after construction in the field of high-pressure jet grouting for the first time. It eliminates the need for 28 days of curing and does not damage the pile body. It can not only accurately measure the diameter of jet grouting piles, but also accommodate fixed jetting and swing jetting methods, which can greatly make up for the deficiencies of existing hidden engineering detection methods in geotechnical engineering.

[0056] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for quantitatively monitoring the diameter of high-pressure jet grouting piles based on the principle of dual-lateral resistivity, characterized in that, include: Background resistivity data of the undisturbed soil layer is obtained by scanning the undisturbed soil layer with a detection probe during the drilling process. The deep resistivity and shallow resistivity are obtained. The deep resistivity is used to reflect the radial deep electrical characteristics of the pile body containing the original soil layer, and the shallow resistivity is used to reflect the radial shallow electrical characteristics of the pile body. The actual resistivity value of the cement slurry mixed with the soil after shallow resistivity detection is calculated. Based on the actual resistivity value, background resistivity data, and deep-probe resistivity, the pile diameter at each depth is monitored.

2. The method for quantitative monitoring of high-pressure jet grouting pile diameter based on the principle of dual-lateral resistivity, as described in claim 1, is characterized in that... The background resistivity data of the undisturbed soil layer were obtained, including: During the drilling process of the jet grouting rig, the detection probe is placed in the deep detection focusing mode, so that the shielding electrode and the main electrode are kept at the same potential, and the main electrode current is injected into the deep part of the original soil perpendicular to the hole diameter direction. Based on the data recorded in real time by the depth encoder installed on the drilling rig guide rail, the real undisturbed soil background resistivity curves at each depth are generated. Based on the background resistivity curve, obtain the background resistivity data of the undisturbed soil layer.

3. The method for quantitative monitoring of high-pressure jet grouting pile diameter based on the principle of dual-lateral resistivity, as described in claim 1, is characterized in that... Obtaining deep-penetrating resistivity and shallow-penetrating resistivity includes: During the window period after the shotcrete construction is completed and before the grout initially sets, the detection probe is statically lowered to the bottom of the pile using the drilling rig's power head; During the process of uniformly raising the detection probe, the current loop is switched in a time-division multiplexing manner through the ground control system: in deep detection mode, the shielding electrode and the main electrode are connected to the same potential and the current flows to the ground loop electrode to obtain the deep detection resistivity; in shallow detection mode, the shielding electrode is switched to the return loop and the main electrode current flows to the adjacent shielding electrode to obtain the shallow detection resistivity.

4. The method for quantitative monitoring of high-pressure jet grouting pile diameter based on the principle of dual-lateral resistivity, as described in claim 3, is characterized in that... In shallow detection mode, the detection depth is controlled at 100mm-150mm from the probe surface.

5. The method for quantitative monitoring of high-pressure jet grouting pile diameter based on the principle of dual-lateral resistivity, as described in claim 1, is characterized in that... The actual resistivity value of the mixture of downhole cement slurry and soil was calculated based on the shallow resistivity detection. include: ； Where K is the electrode system constant; V0 and I0 are the voltage and current applied to the main electrode, respectively.

6. The method for quantitative monitoring of high-pressure jet grouting pile diameter based on the principle of dual-lateral resistivity, as described in claim 1, is characterized in that... Based on the actual resistivity value, background resistivity data, and deep-penetration resistivity, the pile diameter at each depth is monitored, including: Substituting the actual resistivity value, the background resistivity at the corresponding depth, and the deep-detection resistivity into the analytical formula of the coaxial cylinder series conductive model, the pile radius at each depth is solved, and thus the pile diameter is obtained.

7. The method for quantitative monitoring of high-pressure jet grouting pile diameter based on the principle of dual-lateral resistivity, as described in claim 6, is characterized in that... Substituting the actual resistivity value, the background resistivity at the corresponding depth, and the deep-probe resistivity into the analytical formula of the coaxial cylinder series conduction model, the pile radius at each depth is solved, and thus the pile diameter D is obtained, including: ； In the formula, r0 is the radius of the detection probe, L is the effective length of the main electrode, and r ∞ Let be the effective radius of influence constant of the current field in the undisturbed soil. ρ mix This is the actual resistivity value. ρ soi Background resistivity, R LLD To deeply probe resistivity.

8. The method for quantitative monitoring of high-pressure jet grouting pile diameter based on the principle of dual-lateral resistivity, as described in claim 1, is characterized in that... Monitoring the pile diameter at various depths includes: The built-in multi-dimensional physical criteria are invoked to verify the validity of the pile diameter. The multi-dimensional physical criteria include electrical integrity criteria, depth-to-shallow resistance ratio criteria, and signal variance criteria. If the verification passes, a depth-pile diameter quantitative curve will be generated and displayed; if the verification fails, an early warning will be issued and a prompt will be made to check the equipment or perform targeted spraying.

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