A method for detecting and evaluating the effect of external grouting of a deep buried underground water tunnel in a water-rich soft foundation

Abstract

The application discloses a kind of water-rich soft ground deep-buried underground water conveyance tunnel exterior grouting effect detection evaluation method, and relates to the technical field of tunnel engineering.The core is "laboratory verification-site detection-numerical evaluation", first through field soil sampling, dynamic triaxial test and grouting model construction, combined with nondestructive testing to establish "detection result-solid information-dynamic elastic modulus" mapping relationship;Then in situ test, impact image method and high-density surface wave method are used in engineering site, at grouting key node detection and quantization detection result and elastic modulus correlation, obtain static elastic modulus;Finally, according to design data, simulation model is built, bolt stress, transverse joint opening amount and shock subsidence displacement are calculated to determine grouting effect.The application organically integrates the three, forms a complete technical system, realizes water-rich soft ground deep-buried underground water conveyance tunnel grouting effect nondestructive accurate evaluation, and provides guarantee for engineering quality and operation safety.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering technology, and more specifically to a method for detecting and evaluating the external grouting effect of a deep-buried underground water conveyance tunnel in a water-rich soft soil foundation. Background Technology

[0002] Water-rich soft soil foundations are characterized by high water content, low permeability, high compressibility, and high sensitivity, resulting in poor self-stability. After excavation, they are prone to uneven settlement and deformation of tunnels, seismic liquefaction, and other problems. High pore water pressure exacerbates the rheological properties of the soil, leading to long-term settlement during construction and operation. Furthermore, water-rich soft soil foundations are often accompanied by sand layers or lenses, making them susceptible to geological disasters such as sudden water inrush and sand gushing. Grouting technology, through the splitting, squeezing, pile, and water-blocking effects of the grout, can effectively improve the mechanical properties of the soil, increase its elastic modulus, and enhance the bearing capacity of the foundation, thereby strengthening the stability of the tunnel structure and preventing collapse or excessive deformation.

[0003] Grouting is a type of underground concealed engineering. Due to the complexity of geological conditions, despite significant advancements in grouting technology in recent years, it is still impossible to guarantee that all grout will accurately enter the predetermined injection area, resulting in missed areas. Under these circumstances, the detection of missed areas and the determination of engineering parameters of the composite soil after grouting become urgent issues.

[0004] In deep underground water conveyance tunnel projects on water-rich soft soil foundations, existing methods for detecting grouting effectiveness still have significant shortcomings: sampling tests and drilling methods are highly destructive and inefficient; among geophysical methods, the standard penetration test (SPT) can only provide point data, the resistivity method is severely affected by reinforcement interference, the acoustic method has large errors under water-rich conditions, and the surface wave method has insufficient shallow resolution, making it difficult to accurately identify grouting omissions or thin-layer defects. Especially under conditions of high water pressure, soft soil rheology, and complex strata, existing technologies cannot simultaneously meet the requirements of non-destructive, efficient, and high-precision detection, resulting in blind spots in grouting quality assessment and seriously affecting the long-term stability of water conveyance tunnels.

[0005] Therefore, how to propose a method for detecting and evaluating the external grouting effect of deeply buried underground water conveyance tunnels in water-rich soft soil foundations, and achieve reliable evaluation of the grouting effect, is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention provides a method for detecting and evaluating the external grouting effect of a deep underground water conveyance tunnel with water-rich soft soil foundation, which obtains a reliable evaluation of the grouting effect without damage.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for evaluating the external grouting effect of a deep-buried underground water conveyance tunnel in a water-rich soft soil foundation includes the following steps:

[0009] In-situ tests were conducted to determine the engineering properties of soil and rock masses, and soil samples were collected and prepared from the site.

[0010] Dynamic triaxial tests were conducted on the sampled soil to determine the dynamic parameters and obtain the dynamic elastic modulus; a laboratory grouting model was constructed, and non-destructive testing methods were used to test it before and after grouting to obtain the test results; the grouting model was demolded and verified to obtain the structural information; the test results, structural information and dynamic elastic modulus were correlated to establish a mapping relationship between test results, structural condition and dynamic elastic modulus;

[0011] Select test areas at the engineering site and arrange measuring points and lines; before and after grouting, use non-destructive testing methods to process the on-site test data and quantify the mapping relationship between the test results and the elastic modulus;

[0012] Based on the design data, a typical cross-section is selected, and the results of laboratory simulation tests and on-site in-situ tests are combined to set material parameters and boundary conditions for simulation. The grouting effect is then comprehensively evaluated based on the simulation results.

[0013] Preferably, the non-destructive testing method includes ground penetrating radar, high-density electrical resistivity tomography, ultrasonic penetration testing, and impact imaging.

[0014] Preferably, the laboratory grouting model includes a sand-filled model and a mud-filled model;

[0015] The sand-filled model was tested using the impact imaging method before grouting and 36 hours after grouting.

[0016] The test data of the mud-filled model before grouting, 12 hours after grouting, and 36 hours after grouting were tested on different models using the ultrasonic through-hole method.

[0017] The test results of the impact imaging method were plotted into standardized impact response intensity cloud maps before and after grouting. By comparing the impact signal intensity at different locations and times of the sand model through the standardized impact response intensity.

[0018] The results of the ultrasonic through-hole test were plotted as wave velocity change cloud maps before and after grouting, and the changes in ultrasonic wave velocity at different locations and times of the silty soil model were compared.

[0019] Preferably, the model after grouting is disassembled, and the disassembled solid is subjected to three-dimensional scanning. The position of the solid is compared with the test results, and the dynamic elastic modulus measured by the dynamic triaxial test is linked with the comparison results to establish a joint relationship between the test results, the solid condition, and the dynamic elastic modulus.

[0020] Preferably, before and after grouting, non-destructive testing methods are used to process the on-site test data, quantifying the mapping relationship between the test results and the elastic modulus, including:

[0021] Impact imaging and high-density surface wave method were selected as the core methods for on-site non-destructive testing. Impact imaging method was used to detect anomalies in the tunnel lining segments at a depth of 0-0.5m close to the foundation, while high-density surface wave method was used to detect changes in grouting density and bearing capacity within 5m of the lower part of the tunnel lining segments.

[0022] The data acquired by the shock imaging method are preprocessed, normalized, waveform processed, and wavefield separated to calculate the standardized shock response intensity. The data acquired by the high-density surface wave method are segmented and denoised. The phase velocity is calculated by dispersion analysis, and the formation shear wave velocity is obtained by combining genetic algorithm and least squares method.

[0023] Based on the shear wave velocity, the dynamic shear modulus and dynamic elastic modulus are calculated. Combined with the soil layer characteristics, the dynamic elastic modulus is converted into the static elastic modulus. The mapping relationship between the standardized impact response intensity, wave velocity and elastic modulus is established and quantified.

[0024] Preferably, by combining the results of laboratory simulation tests and in-situ field tests, material parameters and boundary conditions are set for simulation, and the grouting effect is comprehensively evaluated based on the simulation results, including:

[0025] A simulation model including the tunnel cross-section, grouting reinforcement zone, and soil domain was established using Abaqus or OpenSees software.

[0026] The parameters for the water-rich soft soil zone were determined based on field surveys and indoor simulation tests, including permeability coefficient, compression index, and undrained shear strength. The parameters for the grouting reinforcement zone were determined based on field non-destructive testing, including elastic modulus, Poisson's ratio, and compressive strength. The lining structure parameters were set according to the design data.

[0027] The boundary conditions are set as follows: the bottom of the model is fixed, in-situ stress is applied laterally, and pore water pressure is set below the water level.

[0028] Simulation calculations were performed on different combinations of burial depth, grouting angle, grouting intensity, and grouting depth to obtain data on bolt stress, transverse joint opening, and seismic subsidence displacement. The distribution patterns of maximum bolt stress and opening, as well as the trend of maximum seismic subsidence displacement, were analyzed for different cross-sections under different geological conditions before and after reinforcement. This determined whether the tunnel structure after grouting met the bearing capacity requirements under uneven settlement deformation and seismic liquefaction conditions. If it did, the grouting effect was deemed qualified; otherwise, it was deemed unqualified.

[0029] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a method for detecting and evaluating the external grouting effect of a deep-buried underground water conveyance tunnel with water-rich soft soil. The core process is "laboratory model detection and verification - on-site multi-detection non-destructive testing - numerical evaluation". First, through on-site soil sampling, dynamic triaxial tests and grouting model construction, the mapping relationship between test results, structural information and dynamic elastic modulus is established by combining non-destructive testing such as impact imaging method and ultrasonic penetration method. Then, on the engineering site, in-situ tests, impact imaging method and high-density surface wave method are used to detect and quantify the correlation between test results and elastic modulus at key grouting nodes, and obtain static elastic modulus to match the calculation requirements of seismic subsidence liquefaction. Finally, a simulation model is constructed based on design data, material parameters and boundary conditions are set, bolt stress, transverse joint opening and seismic subsidence displacement are calculated, and the grouting effect is comprehensively judged. This invention organically integrates laboratory verification, field testing, and numerical simulation to form a complete technical system covering parameter calibration, field application, and effect verification. It can achieve non-destructive and accurate evaluation of the grouting reinforcement effect of deep-buried underground water conveyance tunnels in water-rich soft soil, providing comprehensive technical support for engineering quality testing and operational safety. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0031] Figure 1 The method flowchart provided by the present invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] This invention discloses a method for detecting and evaluating the external grouting effect of a deep-buried underground water conveyance tunnel in a water-rich soft soil foundation, with reference to... Figure 1 It includes the following steps:

[0034] S1. Determine the engineering properties of soil and rock mass through in-situ tests, and sample and prepare soil from the site.

[0035] In-situ tests were conducted to determine the engineering properties of the soil and rock mass at the engineering site, including deformation modulus, and to measure its basic physical properties such as specific gravity, water content, and apparent density. Sand and silty soil samples were taken from the engineering site. The silty soil was then soaked in water in the laboratory to restore its water content to the level required for the engineering site, thus completing the soil preparation.

[0036] S2. Construct a model in the laboratory and perform grouting. Use non-destructive testing technology to test the grouting effect before and after grouting, and perform demolding verification to establish the relationship between test results, solidification, and dynamic elastic modulus.

[0037] S21. Perform dynamic triaxial tests on the sampled soil to determine the dynamic parameters and obtain the dynamic elastic modulus.

[0038] Dynamic triaxial tests were conducted on the prepared soil to simulate the stress state and dynamic conditions of the soil under engineering conditions. Dynamic parameters such as dynamic elastic modulus were tested and calibrated. The shear stress-shear strain hysteresis curves, shear stress-confining pressure relationships and excess pore water pressure time history curves of different soil layers were determined. The nonlinear deformation and energy dissipation of soil layers under cyclic loading were obtained, showing the accumulation process of pore pressure in saturated soil.

[0039] S22. Construct a laboratory grouting model and conduct tests using non-destructive testing methods before and after grouting to obtain the test results.

[0040] Multiple grouting box non-destructive testing models were constructed. Due to laboratory limitations, wooden box models without concrete cladding were used. Sand and silt were filled into the models respectively, creating sand-filled and silt-filled models for grouting tests. Grouting pipes were pre-inserted into the sand and silt boxes before filling. The filling process was carried out in three stages, with each layer of soil manually compacted. The bottom and middle layers were 30cm thick, and the top layer was 40cm thick. After filling, the moisture content and density of the soil were measured. Single-pipe grouting was used. Through holes with a diameter of 8mm were drilled from the top of the grouting pipe to 50cm, with a spacing of 10cm between the holes in a staggered pattern. After preparation, grouting was performed, and the grouting volume and pressure were recorded.

[0041] According to the formula Calculate the weighted average elastic modulus after grouting.

[0042] Meanwhile, the bearing capacity of ungrouted sand and sand grouted with different mix proportions of self-compacting grout were tested to estimate the bearing capacity of different soil layers in the box, so as to compare the changes in bearing capacity of each layer before and after grouting and the differences in effect between different grouting materials.

[0043] Commonly used non-destructive testing methods, such as ground-penetrating radar, high-density electrical resistivity tomography (EDT), acoustic emission (AE), and impact imaging, are employed. The appropriate method is selected based on both laboratory and actual engineering conditions. For example, given the water-rich soft soil foundation conditions at the project site in this embodiment, and the fact that the tunnel is a deeply buried underground water conveyance tunnel with reinforced outer lining segments, the impact imaging method and ultrasonic penetration testing were comprehensively selected.

[0044] For the grouting box, measuring tapes and markers were used to mark the test points according to the designed grid layout. For the sand-filled model, 100 test points were arranged on the top surface of the model at a 0.10m × 0.10m interval, with a test point spacing of 0.10m and a test area distance of 0.05m from the edge of the model. For the mud-filled model, 16 receiving points were arranged on the front and right sides of the model, and 16 excitation points were arranged on the rear and left sides of the model. The test point spacing was 0.2m, the test area distance from the edge of the model was 0.2m, and the excitation point positions corresponded one-to-one with the test point positions, with an excitation point spacing of 0.2m as well.

[0045] For the sand-filled model, the impact imaging method was used for testing. The detector was fixed to a specially designed metal disc, which was placed flat on the testing surface with its center aligned with the testing point. The disc was pressed down firmly by hand to ensure good coupling with the model. Similarly, a metal disc was placed flat at the excitation point, and a hammer handle was used to strike the disc to ensure good coupling with the model. The distance between the strike point and the receiver point was 0.20m (the distance between two measuring points). The center of the metal disc was struck vertically with an impact hammer, and the detector automatically collected data upon signal triggering. After data recording, keeping the distance between the excitation and receiver points constant, the entire system was moved forward 0.10m to the next testing point, and the above process was repeated until all measuring points were measured. Tests were conducted before grouting and 36 hours after grouting, resulting in a total of 200 data points. The data acquisition parameters for the impact imaging method are as follows:

[0046] Number of channels: 1

[0047] Sampling interval: 0.00001 Sec.

[0048] Record length: 0.5 Sec.

[0049] Recording delay time: 0.001 sec.

[0050] Excitation offset distance: 0.20m

[0051] Measurement point spacing: 0.10m

[0052] Distance from the survey area to the model edge: 0.05m

[0053] The theoretical basis of the impact imaging method is the theory of elastic waves. The distribution of the elastic wave field on the surface of a medium is a mapping of the internal structure of the medium onto its surface. The structure of the object being tested is simplified as a layered semi-infinite medium model, containing local defects. The surfaces of these internal defects form strong reflection interfaces, and the medium surface is also a strong reflection interface. The elastic wave will undergo multiple reflections between these two strong reflection interfaces. After multiple reflections and superposition, the elastic wave waveform received at the medium surface can be expressed as:

[0054]

[0055]

[0056] In the formula: r(t) — reflection coefficient sequence;

[0057] R—Reflection coefficient of the internal defect interface;

[0058] T0—the two-way reflection time of the elastic wave between the two interfaces.

[0059] In engineering testing, a detection line is set up on the surface of the medium, and detection points are arranged along the line at intervals of X0. Excitation is performed at each point on the medium surface, and the response waveform is received by a sensor at an offset distance D. Finally, the waveforms are compiled together, and by observing the changes in the waveform train, a preliminary judgment can be made regarding significant anomalies in the response waveform received near a highly reflective interface with defects within the medium. Further analysis of waveform characteristics such as average amplitude and dominant frequency allows for the inference of the defects within the medium.

[0060] For data detected by the impact imaging method, the processing mainly includes data preprocessing, data normalization, waveform processing, and wave field separation.

[0061] 1. First, data preprocessing is required to convert the raw data in the instrument-specific format into a universal format and match the coordinate data to establish a correlation between the data and the physical location;

[0062] 2. Due to differences in operators or variations in excitation voltage, the excitation force of the vibration source can be affected. Therefore, during data processing, it is necessary to use the impact acceleration data recorded by the sensors on the impact hammer to normalize the data and ensure that the excitation intensity is the same.

[0063] 3. Examine the raw data one by one. For data containing time-varying interference, design a special time window function to remove noise. For single-channel data containing special noise, delete it and complete it by interpolation between adjacent channels.

[0064] 4. Conduct spectral analysis on the full dataset to clarify the spectral characteristics of different wavefields, design filters for filtering, suppress noise, and improve the signal-to-noise ratio;

[0065] 5. Based on the known geometric shape and material properties of the structure under inspection, analyze the characteristics of various wave fields theoretically, compare them with actual data, and extract the wave field components that reflect the internal defects of the structure based on its time domain and frequency domain characteristics, that is, extract the response waveform of the structure to the excitation source.

[0066] 6. Divide the measured amplitude (or energy) of the impact signal by a reference value (such as the maximum impact signal amplitude, the signal strength at a specific reference location, or the theoretically calculated reference value) to obtain a dimensionless ratio, which is defined as the standardized impact response intensity.

[0067] Due to limitations in experimental conditions, test data for the mud-filled models before grouting, 12 hours after grouting, and 36 hours after grouting were collected using the ultrasonic through-beam method on different models. First, the measuring point and excitation point locations were marked on two sides of each of the three models. Then, the geophone was held perpendicular to the side of the model and pressed firmly, and the corresponding excitation point locations were struck with an impact hammer. To improve the quality of the collected data, each excitation point was excited 5 times and 5 valid data points were collected before grouting and 12 hours after grouting, resulting in 5 × 16 = 80 data points collected from each side, for a total of 160 data points. Due to limitations in data collection conditions, only 80 valid data points were collected from one side during the test 36 hours after grouting. The ultrasonic through-beam method data acquisition parameters are as follows:

[0068] Number of channels: 2

[0069] Sampling interval: 0.00001 Sec.

[0070] Record length: 0.5 Sec.

[0071] Recording delay time: 0.001 sec.

[0072] Measurement point spacing: 0.2m

[0073] Distance from the survey area to the model edge: 0.2m

[0074] The theoretical basis of the ultrasonic penetration method is that when ultrasonic waves propagate through different materials, parameters such as sound velocity, attenuation coefficient, and waveform change due to factors such as material density, elastic modulus, internal defects (e.g., pores, cracks), and microstructure. By emitting ultrasonic waves through one side of the material and receiving them through another, the physical and mechanical properties of the material can be inferred by analyzing the changes in the signal. The propagation speed of ultrasonic waves can be calculated using the following formula:

[0075] V=ΔX / ΔT

[0076] Where: ΔX—the straight-line distance between the sensor and the excitation point;

[0077] ΔT—The propagation time of ultrasound waves from the excitation point to the receiving point.

[0078] In engineering testing, an impact hammer strikes the test surface at the excitation point. The impact force generates elastic waves within the specimen, which propagate in a straight line to the velocity sensor on the opposite side, where they are detected. At the instant the impact hammer contacts the test surface, the force sensor on the impact hammer outputs a signal to the data acquisition module. The data acquisition module then synchronously acquires the signals from the impact hammer and the velocity sensor, recording the time difference between the start-up time of the force sensor signal and the start-up time of the velocity sensor signal. This time difference is used as the propagation time of the ultrasonic wave from the excitation point to the receiving point.

[0079] For ultrasonic through-hole monitoring data, the processing mainly includes data preprocessing, data channel balancing, and bandpass filtering.

[0080] 1. First, data preprocessing is required to convert the raw data in the instrument-specific format into a universal format and match the coordinate data to establish a correlation between the data and the physical location;

[0081] 2. Then, data channel balancing processing is performed to accurately acquire the initial arrival times of the signals from the impact hammer force sensor (charge-type acceleration type) and the wave velocity test sensor (moving coil velocity type), and the wave propagation speed is calculated through the time difference;

[0082] 3. A specific algorithm is used to adjust the amplitude so that the waveforms acquired by the two sensors can be displayed in a coordinated manner in the same window;

[0083] 4. For data containing low-frequency interference below 100Hz and high-frequency interference above 2000Hz, a bandpass filter is used for filtering.

[0084] The results of the impact imaging method were plotted as standardized impact response intensity cloud maps before and after grouting. The impact signal intensity at different locations and times was compared using this standardized impact response intensity parameter. Similarly, the results of the ultrasonic penetration method were plotted as wave velocity variation cloud maps before and after grouting, allowing for comparison of ultrasonic wave velocity changes at different locations and times in the silty soil model.

[0085] S23. Demold and verify the model after grouting to obtain structural information; associate the test results, structural information and dynamic elastic modulus to establish a mapping relationship between test results, structural condition and dynamic elastic modulus.

[0086] After the results are recorded by S22, the box is demolded, and the demolded solid body is three-dimensionally scanned. The location of the solid body is compared with the test results. Then, the dynamic elastic modulus measured by the dynamic triaxial test is linked with the comparison results to establish a joint relationship between the test results, the solid condition, and the dynamic elastic modulus. This allows for a more accurate reflection of the characteristic changes of the underground medium and provides a quantifiable and standardized analytical basis for the evaluation of grouting effect.

[0087] S3. Before and after grouting at the engineering site, non-destructive testing was conducted using multiple detection technologies. The test results were correlated with laboratory tests to quantify the relationship between the test result parameters and the elastic modulus. Reference indicators for evaluating the effect of grouting reinforcement were determined, in accordance with the requirements of the comprehensive elastic modulus limit in earthquake liquefaction vibration analysis.

[0088] Based on the tunnel structure, preliminary model tests, and non-destructive testing results, the following technology is adopted as a non-destructive testing and evaluation method for grouting effect:

[0089] 1. Impact imaging method. Mainly used to detect the area of ​​tunnel lining segments close to the foundation, with a detection depth of 0~0.5m, reflecting abnormalities such as non-compactment or voids in the foundation of the tunnel lining.

[0090] 2. High-density surface wave method. Primarily used to detect changes in grout density and bearing capacity within a 5m range below the outer lining segments of tunnels.

[0091] S31. Select a test area at the engineering site and arrange measuring points and lines.

[0092] Based on the geological conditions at the engineering site, the scope and mileage interval of the grouting test section were determined. Four survey lines were laid out in each mileage interval, resulting in a total of 16 survey lines for high-density surface wave method and impact imaging method. The survey lines were parallel to the tunnel axis and 15m long. The test section was laid out according to the on-site grouting conditions. Since the on-site grouting range was divided into 180° grouting and 360° grouting, with the tunnel top as 0° and increasing clockwise, the 180° grouting range was 90°~270°, and the 360° grouting range was 0°~360°. The four test survey lines in each mileage interval were arranged at 135°, 160°, 200°, and 225° in the circumferential direction. Impact imaging method survey points were laid out along the survey line direction, with a spacing of 0.25m between adjacent survey points. Each survey point required two excitations, with the excitation source (hammer excitation) offset distances of 0.25m and 0.5m respectively. The detectors used for high-density surface wave excitation are spaced 0.5m apart and arranged in a length of 5.5m. An excitation point is set at the end of the arrangement at a distance of 2.0m, 4.0m and 6.0m from the detectors, and each measuring point is excited three times.

[0093] S32. Before and after grouting, non-destructive testing methods are used to process the on-site test data and quantify the mapping relationship between the test results and the elastic modulus.

[0094] S321. When using the impact imaging method for testing, two velocity sensors are used for data acquisition, connected via a PVE tube. The test is conducted strictly according to the pre-set measurement points. During the test, one person holds the sensor steady while another person is responsible for exciting the wave with an impact hammer. To protect the tube segment from damage, a rubber pad is placed under the hammer head when exciting the elastic wave. The data acquisition parameters for the impact imaging method are as follows:

[0095] Number of channels: 2

[0096] Sampling interval: 0.00001 Sec.

[0097] Record length: 0.5 Sec.

[0098] Recording delay time: 0.001 sec.

[0099] Excitation offset distance: 0.25m, 0.5m

[0100] Measurement point spacing: 0.25m

[0101] The theoretical basis and data processing procedures of the impact imaging method can be found in the relevant content in S22.

[0102] S322. When using the high-density surface wave method for detection, two different probes were used depending on the location of the survey line. For survey lines near the tunnel's waistline, a handheld high-density surface wave array was used. Four sensors were fixed together using connectors, with a sensor spacing of 0.25m. During data acquisition, three people were responsible for fixing the sensors, while a fourth person used an impact hammer to excite the elastic wave at the designed excitation point. The instrument operator was responsible for recording the data and taking notes. For survey lines near the bottom of the pipeline, a towed high-density surface wave array was used. The high-density surface wave sensor array consisted of 24 sensors, sensor coupling bases, and a traction belt. The sensor spacing was 0.25m. During data acquisition, the array's sensors were aligned with the detection point, and the excitation operator excited the elastic wave at the designed position according to the excitation offset. The high-density surface wave method data acquisition parameters are as follows:

[0103] Number of channels: 24

[0104] Lane spacing: 0.25m

[0105] Excitation offset distances: 2.0m, 4.0m, 6.0m

[0106] Sampling interval: 0.00002 Sec (0.02 ms)

[0107] Record length: 1.0 Sec.

[0108] The theoretical basis of the high-density surface wave method is that the penetration depth of a surface wave propagating along the surface of a medium is related to its wavelength. The amplitude of a Rayleigh surface wave decays rapidly from the surface along the depth direction, concentrating over 80% of its total energy within approximately half a wavelength and over 95% within one wavelength. Therefore, the propagation speed of a Rayleigh surface wave is primarily determined by the medium from the surface to a depth of half a wavelength, and is almost independent of the medium at depths of one wavelength or more. High-frequency surface waves have shorter wavelengths and can only penetrate very shallow strata near the surface; their propagation speed reflects only shallow subsurface structures. Low-frequency surface waves, with much longer wavelengths, can penetrate from the surface to deep strata, and their propagation speed reflects the comprehensive influence of subsurface structures from the surface to deep layers. Therefore, obtaining the propagation speeds of Rayleigh surface waves from high to low frequencies provides information reflecting the entire subsurface structure. By mathematically separating this information by depth, the entire subsurface structure can be understood.

[0109] For high-density surface wave (SSW) data, the processing mainly includes data acquisition, waveform processing, dispersion analysis, and subsurface structure analysis. However, since high-density SSW is an extension of traditional SSW into 2D and 3D, its data acquisition and analysis methods differ significantly from those of traditional SSW.

[0110] 1. In terms of data acquisition methods, high-density surface wave exploration uses a segmented arrangement to acquire data. There is some overlap between each segment (arrangement). Then, during data processing, the data is synthesized by superposition processing to form a set of co-excitation point data that can cover the entire survey line.

[0111] 2. Add coordinate information to the data and remove noise, then use the repeated seismic traces between each segment (arrangement) to connect the independently acquired data of each segment (arrangement) to form a "large arrangement" that can cover the entire survey line;

[0112] 3. Starting from one end of the survey line, the data covering the entire survey line is re-segmented, with some overlap between segments. Then, dispersion analysis is performed on each segment to obtain the dispersion curve corresponding to that segment. Let the surface wave measurement data be u(x,t), and its Fourier transform be U(x,f), where x=n x, x represents the detector spacing. The phase difference Δ between detector n and detector 1 is... =ψ(c,x) is caused solely by the distance difference x between the two detectors and the phase velocity c=C(f). If the data is corrected using the phase velocity, the corrected data will be completely in phase, and their superposition will yield the maximum amplitude. Therefore, by testing with a series of C(f), the velocity value corresponding to the maximum superimposed amplitude can be obtained, that is, the phase velocity value corresponding to that frequency can be obtained. This process can be described by the following formula:

[0113]

[0114]

[0115] 4. A series of 1D structures are used to approximate the 2D or 3D underground structures for structural analysis. Then, the dispersion curves at each point are inverted through coupling analysis, thus achieving quasi-2D or quasi-3D inversion. Initially, a genetic algorithm is used for inversion. Once the error converges to a certain level, this output model is used as the initial model for least squares inversion to accelerate error convergence. According to the theory of wave propagation in layered media, the phase velocity of Rayleigh surface waves in layered media can be expressed as:

[0116] C(f)=R(Vs1,Vp1,D1,H1,Vs2,Vp2,D2,H2,…,Vsi,Vpi,Di,Hi),i=1,2,…,N

[0117] Where Vsi, Vpi, Di, and Hi represent the shear wave velocity, longitudinal wave velocity, density, and layer thickness of the i-th layer, respectively. The thickness and elastic parameters of the concrete lining are used as constraints.

[0118]

[0119] Among them, C cal =R(Vs1,Vp1,D1,H1,Vs2,Vp2,D2,H2,…,Vsi,Vpi,Di,Hi,f) is the theoretical phase velocity, C obs The measured phase velocity is obtained from field data analysis. The inversion analysis is to obtain (Vs1,Vp1,D1,H1,Vs2,Vp2,D2,H2,Vsi,Vpi,Di,Hi) (i=1,2,…,n).

[0120] S323. Calculate the dynamic shear modulus and dynamic elastic modulus based on the shear wave velocity, convert the dynamic elastic modulus to the static elastic modulus based on the soil characteristics, and establish and quantify the mapping relationship between the standardized impact response intensity, wave velocity and elastic modulus.

[0121] Plot the standardized impact response intensity changes before and after grouting along the survey line, analyze the magnitude of the standardized impact response intensity at different locations before and after grouting (impact response intensity has no fixed unit and needs to be calibrated according to the specific material), and then correlate the changes in standardized response intensity before and after grouting with the changes in wave velocity measured by the high-density surface wave method. Calculate the dynamic elastic modulus using the following formula:

[0122] The formula for calculating the shear wave velocity of a formation is:

[0123]

[0124]

[0125] In the formula: v s —Shear wave velocity of the formation (m / s).

[0126] v R denoted as the surface wave velocity of the stratum (m / s).

[0127] η s —The conversion factor between surface wave and shear wave velocities is related to Poisson's ratio and can be approximately taken as 0.92, corresponding to a Poisson's ratio of 0.25;

[0128] μ d —Poisson's ratio;

[0129] The wave velocity measured by elastic waves reflects the dynamic shear modulus of the formation, and the calculation formula is as follows:

[0130]

[0131] Among them G d —Dynamic shear modulus (Pa);

[0132] ρ—mass density (kg / m3);

[0133] The formula for calculating the dynamic elastic modulus of a formation is:

[0134]

[0135] Where E d The dynamic elastic modulus (Pa);

[0136] The formula for calculating the Poisson's ratio of a formation is:

[0137]

[0138] Based on soil characteristics, the dynamic elastic modulus is converted into the static elastic modulus, which serves as the equivalent elastic modulus in the calculation of seismic liquefaction limits. This becomes an important reference indicator for determining whether grouting reinforcement or the original soil layer can meet the requirements for seismic liquefaction, echoing the requirement of comprehensive elastic modulus limits in seismic liquefaction vibration analysis. The relationship between the test result parameters and the elastic modulus is quantified, and combined with the results of laboratory tests, the relationship between non-destructive testing result parameters and changes in geological conditions is obtained, thereby evaluating the grouting effect.

[0139] S4. Based on the design data, select a typical section, and combine the results of laboratory simulation tests and on-site in-situ tests to set material parameters and boundary conditions for simulation. Based on the simulation results, comprehensively evaluate whether the grouting effect is qualified.

[0140] Based on the design data, the typical cross-sections of two tunnel sections lying in sandy soil, one typical cross-section of a vertical shaft connection section, and one typical cross-section of a tunnel section crossing rock were identified for analysis. The tunnel cross-sections, grouting reinforcement zones, and soil domains were established using Abaqus or OpenSees.

[0141] Based on the results of laboratory simulation tests and in-situ field tests, material parameters were set. Based on field surveys and indoor simulation tests, the permeability coefficient k, compression index Cc, and undrained shear strength Su of the water-rich soft soil zone were determined. Based on field non-destructive testing, the elastic modulus E, Poisson's ratio v, and compressive strength fc of the grouting reinforcement zone were determined. The material type of the lining structure was determined based on the design data.

[0142] Set boundary conditions, fix the bottom, apply in-situ in-situ stress laterally, and set pore water pressure below the water level. Then, divide the grid, setting corresponding grids for different areas such as the lining and grouting zone, and the soil, and refine the grid at the boundaries, while paying attention to controlling the global grid transition ratio.

[0143] By combining typical cross-sections at different burial depths with grouting angles, strengths, and depths to create various working conditions, bolt stress, transverse joint opening, and seismic subsidence displacement are calculated. The distribution patterns of maximum bolt stress and opening, as well as the trend of maximum seismic subsidence displacement, are analyzed for different cross-sections under different geological conditions before and after reinforcement. This allows for the determination of whether the tunnel structure meets the bearing capacity requirements under uneven settlement deformation and seismic liquefaction conditions after grouting, thereby verifying the effectiveness of the grouting reinforcement measures.

[0144] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0145] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for detecting and evaluating the external grouting effect of a deep-buried underground water conveyance tunnel in a water-rich soft soil foundation, characterized in that, Includes the following steps: In-situ tests were conducted to determine the engineering properties of soil and rock masses, and soil samples were collected and prepared from the site. Dynamic triaxial tests were conducted on the sampled soil to determine dynamic parameters and obtain the dynamic elastic modulus. A laboratory grouting model was constructed, and non-destructive testing methods were used before and after grouting to obtain test results. The grouting model was then disassembled for verification to obtain structural information. The test results, structural information, and dynamic elastic modulus were correlated to establish a mapping relationship between test results, structural condition, and dynamic elastic modulus. The non-destructive testing methods included ground-penetrating radar, high-density surface wave method, ultrasonic through-hole method, and impact imaging method. Select test areas at the engineering site and arrange measuring points and lines; before and after grouting, use non-destructive testing methods to process the on-site test data, quantify the mapping relationship between the test results and the elastic modulus, including: Impact imaging and high-density surface wave method were selected as the core methods for on-site non-destructive testing. Impact imaging method was used to detect anomalies in the tunnel lining segments at a depth of 0-0.5m close to the foundation, while high-density surface wave method was used to detect changes in grouting density and bearing capacity within 5m of the lower part of the tunnel lining segments. The data acquired by the shock imaging method are preprocessed, normalized, waveform processed, and wavefield separated to calculate the standardized shock response intensity. The data acquired by the high-density surface wave method are segmented and denoised. The phase velocity is calculated by dispersion analysis, and the formation shear wave velocity is obtained by combining genetic algorithm and least squares method. Based on the shear wave velocity, the dynamic shear modulus and dynamic elastic modulus are calculated. Combined with the soil layer characteristics, the dynamic elastic modulus is converted into the static elastic modulus. The mapping relationship between the standardized impact response intensity, wave velocity and elastic modulus is established and quantified. Based on the design data, a typical cross-section is selected, and the results of laboratory simulation tests and on-site in-situ tests are combined to set material parameters and boundary conditions for simulation. The grouting effect is then comprehensively evaluated based on the simulation results.

2. The method for detecting and evaluating the external grouting effect of a deep-buried underground water conveyance tunnel in a water-rich soft soil foundation as described in claim 1, is characterized in that... The laboratory grouting model includes a sand-filled model and a mud-filled model; The sand-filled model was tested using the impact imaging method before grouting and 36 hours after grouting. The mud-filled model was tested using ultrasonic penetration method on different models before grouting, 12 hours after grouting, and 36 hours after grouting. The test results of the impact imaging method were plotted into standardized impact response intensity cloud maps before and after grouting. By comparing the impact signal intensity at different locations and times of the sand model through the standardized impact response intensity. The results of the ultrasonic through-hole test were plotted as wave velocity change cloud maps before and after grouting, and the changes in ultrasonic wave velocity at different locations and times of the silty soil model were compared.

3. The method for detecting and evaluating the external grouting effect of a deep-buried underground water conveyance tunnel in a water-rich soft soil foundation as described in claim 1, characterized in that, The grouting model was disassembled, and the disassembled solid was subjected to three-dimensional scanning. The location of the solid was compared with the test results. The dynamic elastic modulus measured by the dynamic triaxial test was then linked with the comparison results to establish a joint relationship between the test results, the solid condition, and the dynamic elastic modulus.

4. The method for detecting and evaluating the external grouting effect of a deep-buried underground water conveyance tunnel in a water-rich soft soil foundation as described in claim 1, characterized in that, Combining the results of laboratory simulation tests and in-situ field tests, material parameters and boundary conditions are set for simulation. The grouting effect is then comprehensively evaluated based on the simulation results, including: A simulation model including the tunnel cross-section, grouting reinforcement zone, and soil domain was established using Abaqus or OpenSees software. The parameters for the water-rich soft soil zone were determined based on field surveys and indoor simulation tests, including permeability coefficient, compression index, and undrained shear strength. The parameters for the grouting reinforcement zone were determined based on field non-destructive testing, including elastic modulus, Poisson's ratio, and compressive strength. The lining structure parameters were set according to the design data. The boundary conditions are set as follows: the bottom of the model is fixed, in-situ stress is applied laterally, and pore water pressure is set below the water level. Simulation calculations were performed on different combinations of burial depth, grouting angle, grouting intensity, and grouting depth to obtain data on bolt stress, transverse joint opening, and seismic subsidence displacement. The distribution patterns of maximum bolt stress and opening, as well as the trend of maximum seismic subsidence displacement, were analyzed for different cross-sections under different geological conditions before and after reinforcement. This determined whether the tunnel structure after grouting met the bearing capacity requirements under uneven settlement deformation and seismic liquefaction conditions. If it did, the grouting effect was deemed qualified; otherwise, it was deemed unqualified.

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