A method for rapid evaluation of building foundation performance based on drop hammer deflection response

Abstract

The application discloses a kind of based on drop hammer type deflection response building ground performance rapid evaluation method, belong to geotechnical engineering ground detection technical field, method includes: obtaining ground foundation information and dividing test partition;Determine drop hammer type deflection meter test parameter;Develop drop hammer type deflection test and obtain dynamic deflection basin curve;Extract four characteristic parameters of maximum deflection index, deflection basin influence area index, deflection basin curvature index, deflection basin attenuation index;Based on Boussinesq theory solution and introduce deflection basin form three-dimensional correction function to calculate dynamic deformation modulus;For natural ground, replacement ground, composite ground and reinforcement treatment ground respectively establish bearing capacity conversion model;According to bearing capacity ratio value division grade and output evaluation report.The application effectively solves the technical problem of large-area building ground bearing performance rapid detection, and provides reliable basis for the partition management and differentiation of construction area ground performance.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering foundation testing technology, specifically relating to a rapid evaluation method for building foundation performance based on falling weight deflection response. Background Technology

[0002] The testing and evaluation of the bearing capacity of building foundations is a crucial step in ensuring structural safety and construction quality. Currently, engineering practice primarily employs methods such as plate load tests, static cone penetration tests, and light dynamic cone penetration tests to assess foundation bearing capacity. While plate load tests can directly reflect the load-settlement relationship of the foundation, they have inherent limitations, including cumbersome equipment, the need for large reaction devices, and long testing cycles (from hours to days) at single points, making them unsuitable for rapid, batch testing in large-area sites or during construction. Although static and dynamic cone penetration tests are relatively convenient, their results are mostly empirical indicators, and their conversion relationship with foundation bearing capacity is significantly affected by factors such as soil type and water content, resulting in limited accuracy and reliability. With the expansion of urban construction, the number of engineering scenarios involving large-area backfilled foundations, composite foundations, reinforced foundations, and large temporary construction platforms is increasing, making the need for rapid, non-destructive, and large-scale evaluation of foundation bearing capacity increasingly urgent.

[0003] Falling weight deflectometers (FWD) collect dynamic deflection responses at multiple points on a structural surface under transient impact loads, completing single-point tests within minutes. They are widely used in road engineering for evaluating the structural stiffness of subgrades and pavements. However, the FWD evaluation system in road engineering is developed for layered pavement structures. Its core indicators (such as subgrade resilient modulus) and mechanical models lack direct theoretical connections and conversion methods with the bearing capacity characteristics of natural or artificial foundations in building engineering. More importantly, building foundations involve diverse soil types (cohesive soil, sandy soil, gravelly soil, etc.) and complex working conditions (different construction techniques, water content, and reinforcement forms). Existing FWD methods lack correction mechanisms for these complex factors, making it difficult for test results to accurately reflect the actual bearing capacity of the foundation.

[0004] Therefore, how to leverage the rapid testing advantages of falling weight deflection response to establish a rapid evaluation method specifically tailored to the characteristics of building foundations, capable of comprehensively considering soil property differences and state influences, and directly outputting bearing capacity characteristic values ​​has become a pressing technical challenge in the field of geotechnical engineering testing. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a rapid evaluation method for building foundation performance based on falling weight deflection response. This method collects the dynamic deformation response of the building foundation at multiple points under falling weight impact load, constructs a deflection basin characteristic parameter system tailored to the characteristics of the building foundation, and combines a dynamic deformation modulus conversion model based on elastic half-space theory and a dimensionless bearing capacity conversion model considering foundation type and state factors to achieve rapid, non-destructive, and comprehensive evaluation of the bearing capacity of the building foundation. This solves the problems of low detection efficiency, limited testing range, and the inability to use dynamic response parameters for building foundation bearing capacity evaluation in existing technologies.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention discloses a rapid evaluation method for building foundation performance based on falling weight deflection response, comprising: S1. Obtain the basic information of the foundation of the building to be tested and divide it into test zones. Based on the basic information, the foundation of the building to be tested is divided into several test zones. The foundation type, soil structure and construction technology are consistent within the same test zone. S2. Based on the soil structure and physical parameters of the test zones, determine the test parameters for the falling weight deflectometer in each test zone. The test parameters include: the impact load of the falling weight deflectometer. Load application time Radial spacing of measuring points And the displacement sensor arrangement scheme; S3. A falling weight deflectometer is used to apply transient impact loads to each test zone according to the test parameters. Deflection values ​​at each measuring point are collected by displacement sensors placed at different radial positions from the loading center to form dynamic deflection basin curves for each test zone. ,in The radial distance from the measuring point to the loading center; S4. Based on the dynamic deflection basin curve Calculation center maximum deflection index Indicators of the influence of the deflection basin area Deflection basin curvature index Deflection Basin Attenuation Index This forms the deflection response characteristic vector for each test zone. : S5. Based on the theoretical solution of the surface displacement of an elastic half-space under a circular uniformly distributed impact load, and combined with the characteristic parameters of the deflection basin, a dynamic elastic modulus calculation model is established. : in, ; In the formula, Poisson's ratio of soil Let the radius of the drop hammer bearing plate be . This is a function to correct the shape of the deflection basin. , , This is the morphological correction factor. and These are the theoretical curvature and theoretical decay index values ​​of a standard uniform half-space, respectively. S6. Establish dynamic deformation modulus and characteristic values ​​of foundation bearing capacity for different foundation types. The conversion model; S7. Based on the calculated characteristic value of the foundation bearing capacity The characteristic value of bearing capacity required by the design ratio According to the preset grading standards, the foundation performance is divided into four levels: Level 1, Level 2, Level 3, and Level 4. S8. Output the test evaluation report, summarizing the test parameters, deflection basin characteristic parameters, dynamic deformation modulus, bearing capacity characteristic values ​​and performance levels of each test zone, and generating a rapid test evaluation report on the bearing capacity of the building foundation.

[0007] Furthermore, in step S6, the dynamic deformation modulus and characteristic values ​​of foundation bearing capacity for different foundation types are... The conversion models include: For natural foundations and replaced foundations: For composite foundations: For foundation reinforcement: In the formula, The characteristic value of foundation bearing capacity, For dynamic deformation modulus, The unit base modulus, The natural density of the soil. For reference density, This refers to the natural moisture content of the soil. For reference moisture content, The area replacement ratio of the composite foundation. For the unconfined compressive strength of the solidified body, For reference strength; , , These are the modulus coefficients for different foundation types. Modulus index , , , This is the state correction index.

[0008] Furthermore, in step S4, each indicator is calculated using the following formula: Maximum deflection index at center ;in, The maximum deflection value at the loading center location; Influence of deflection basin on area index ,in The effective radius of influence of the deflection basin; Deflection Basin Curvature Index ,in and These are the first and second derivatives of the deflection basin curve at the loading center, respectively; Deflection Basin Attenuation Index ,in For reference radial distance.

[0009] Furthermore, in step S2, Impact load of falling weight deflectometer The method for determining it is as follows: ,in As the benchmark impact load, For reference compression modulus, The compression modulus of the soil to be tested. The load adjustment index is between 0.3 and 0.5. radial spacing of measuring points The method for determining it is as follows: , The distance between the reference measuring points, The diameter of the drop hammer bearing plate is... For reference bearing plate diameter, The spacing adjustment index is between 0.8 and 1.2.

[0010] Furthermore, in step S3, the displacement sensor is positioned radially below the loading center: , , , , , , , ,in The radius of the bearing plate; the placement of the displacement sensors is based on the compression wave velocity of the foundation soil. and impact load duration Optimization and adjustments were made based on the compressed wave velocity. and the half-peak duration of impact load Estimate the propagation distance of the stress wave at the peak of the impact load. ,when Less than 3 At that time, to The arrangement of the elements tapers inward radially, with a shrinkage coefficient of [value missing]. All displacement sensors are installed on the same radial straight line and arranged symmetrically on both sides with the loading center as the center of symmetry. The arithmetic mean of the deflection values ​​at the corresponding positions on both sides is taken as the final deflection value at that radial distance.

[0011] Furthermore, in step S4, the deflection basin curve The interpolation fitting methods include: using cubic spline interpolation to interpolate discrete measurement point data to obtain continuously differentiable deflection basin curves. The continuous curve obtained by interpolation is located at the loading center. Taylor expansion is performed at =0, and the result is determined by fitting measurement data near the loading center. and The numerical value; automatically optimize the interpolation nodes based on the local curvature changes of the deflection basin curve; the effective influence radius of the deflection basin. The deflection value is calculated point by point from the loading center outwards, and the value is determined when the deflection value first decays to a level less than the maximum deflection value at the center, which is a preset ratio.

[0012] Furthermore, the morphological correction coefficient , , The calibration method includes: establishing an axisymmetric finite element numerical model of the foundation type to be tested; using viscous absorbing boundaries for the radial boundaries of the finite element model and fixed constraints for the bottom boundaries; adopting an elastoplastic model considering strain rate effects for the soil constitutive model; and applying the impact load of the falling weight deflectometer determined in step S2 to the finite element model. Equivalent dynamic load; calculate theoretical deflection basin curves under different combinations of soil parameters; extract from theoretical deflection basin curves , , , and calculate the corresponding Theoretical value; obtained by finite element method. The theoretical value is the target value, with In the function , , For the parameters to be determined, a nonlinear least squares method is used for parameter fitting; where the theoretical curvature value of the standard uniform half-space is... and theoretical decay index value The displacement was obtained by calculating the Boussinesq displacement of an elastic half-space under a circular uniformly distributed load.

[0013] Furthermore, the modulus coefficient , , and modulus index and State Correction Index , , , The value of is determined by the following method: For each type of foundation, comparative test data are collected separately. Each set of comparative test data includes the characteristic value of foundation bearing capacity obtained from plate load tests conducted at the same test point. Dynamic deformation modulus obtained from drop weight deflection test ;by and state correction variables are independent variables. The least squares method is used to fit the parameters of the transformation model, with the dependent variable being the least squares method; the area replacement rate m is calculated based on the pile diameter and pile spacing.

[0014] Furthermore, the pre-defined grading standard for foundation performance is as follows: when A value ≥ 1.2 is considered Grade 1, indicating good load-bearing capacity; When 1.0 ≤ A value less than 1.2 indicates a Class II load-bearing capacity that meets design requirements. When 0.8 ≤ A value less than 1.0 indicates a Level 3 load-bearing capacity that is close to the design limit; verification is recommended. when A value less than 0.8 indicates a level four load-bearing capacity deficiency, and intervention is recommended.

[0015] Furthermore, in step S7, after the foundation performance grading evaluation, the following follow-up processing steps are performed: For test zones rated as Level 1, the test report is marked as having good bearing capacity; for test zones rated as Level 2, the test report is marked as meeting design requirements; for test zones rated as Level 3, a verification process is triggered, which includes densely deploying falling weight deflection test points within the test zone and conducting plate load tests at representative points for verification; for test zones rated as Level 4, a processing process is triggered, which includes expanding the test range to determine the boundaries of areas that do not meet the requirements and proposing foundation reinforcement treatment suggestions; the rating results and test data of all test zones are entered into the building foundation performance database; based on the spatial coordinates and rating results of each test point, a contour map of the foundation performance level distribution of the entire test area is generated using a spatial interpolation method, and the boundary coordinates of abnormal areas rated as Level 3 and Level 4 are automatically identified and marked.

[0016] The beneficial effects of this invention are as follows: 1. The transient impact loading method eliminates the need for a large reaction system, shortening the single-point testing time and improving testing efficiency. 2. This invention establishes differentiated bearing capacity conversion models for natural foundations, replacement foundations, composite foundations, and reinforced foundations, and introduces state correction parameters such as density, moisture content, replacement rate, and reinforcement strength, overcoming the limitation of existing FWD technology being only applicable to road structures. 3. This invention introduces a three-dimensional correction function that includes area ratio, curvature, and attenuation index into the calculation of dynamic deformation modulus. It can effectively distinguish the differences in foundation stiffness corresponding to the same maximum deflection value but different deflection basin shapes. 4. This invention uses the Drucker-Prager model considering strain rate effects and the finite element method for viscous absorbing boundaries to calibrate correction coefficients. The calibration process has clear physical meaning and reproducibility. The invention also uses the Kriging space interpolation method to generate contour maps of foundation performance level distribution, which can automatically identify the boundaries of abnormal areas and provide a visual decision-making basis for construction zoning management. Attached Figure Description

[0017] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided for illustration: Figure 1 This is a flowchart of an embodiment of the present invention. Detailed Implementation

[0018] like Figure 1 As shown, this invention discloses a rapid evaluation method for building foundation performance based on falling weight deflection response, comprising the following steps: S1: Obtain the basic information of the foundation of the building to be tested and divide it into test zones. The basic information includes foundation type, soil structure, and natural soil density. Natural moisture content Porosity Liquid limit Plastic Limit Compression modulus The information includes construction technology information and groundwater depth information; based on the aforementioned basic information, the foundation of the building to be tested is divided into several test zones, with the foundation type, soil structure and construction technology being consistent within the same test zone; The foundation types include natural foundations, replacement foundations, composite foundations, and reinforced foundations; the construction process information includes: for natural foundations, recording their formation history and disturbance conditions; for replacement foundations, recording the type of replacement material and the coefficient of uniformity of the gradation curve. and curvature coefficient The compaction degree and replacement thickness are recorded. For composite foundations, the pile type (including flexible piles, semi-rigid piles, and rigid piles), pile length, pile diameter, pile spacing, and area replacement ratio are recorded. For reinforced foundations, the reinforcement method (including dynamic compaction, vibro-compaction, preloading, and chemical reinforcement), reinforcement depth, and bearing capacity design requirements after treatment are recorded. This step makes the evaluation model no longer solely based on soil properties, but incorporates the quantitative contribution of the degree of human intervention (such as replacement ratio and compaction degree) to the bearing capacity. This provides a refined feature dimension for the multi-factor nonlinear regression in step S6, significantly improving the accuracy of bearing capacity conversion for composite and reinforced foundations, and avoiding underfitting of the model caused by relying solely on natural density and moisture content correction. S2: Determine the test parameters of the falling weight deflectometer for each test zone, and determine the impact load of the falling weight deflectometer based on the soil structure and physical parameters of the test zone. Load application time Radial spacing of measuring points and the displacement sensor arrangement scheme; wherein, the impact load The method for determining it is as follows: , As the benchmark impact load, For reference compression modulus, The compression modulus of the soil to be tested. The load adjustment index is between 0.3 and 0.5; the radial spacing of the measuring points The method for determining it is as follows: , The distance between the reference measuring points, The diameter of the drop hammer bearing plate is... For reference bearing plate diameter, The spacing adjustment index is between 0.8 and 1.2; Among them, the impact load of the falling weight deflectometer In the method for determining the reference impact load, The value range is 30kN to 50kN, and the reference compressive modulus The value range is from 8MPa to 12MPa, and the load adjustment index The value of is determined by the following method: when the soil to be tested is cohesive soil, Take 0.35; when the soil to be tested is sandy soil, Take 0.45; when the soil to be tested is gravelly soil, Take 0.40; the radial spacing of the measuring points In the method for determining the distance between the reference measuring points The value range is from 150mm to 300mm, and the diameter of the reference bearing plate is... The spacing adjustment index is 300mm. The value of is determined by the following method: when the estimated radius of influence of the deflection basin is less than 600 mm, Take 1.0; when the estimated radius of influence of the deflection basin is greater than or equal to 600 mm and less than 1000 mm, Take 1.1; when the estimated radius of influence of the deflection basin is greater than or equal to 1000 mm, Take 1.2; This step endows the testing equipment with the ability of "soil hardness sensing", realizes the automatic matching of testing parameters, avoids the inefficient operation of repeatedly adjusting the drop height by relying on manual experience; ensures that no plastic failure occurs in soft foundation (obtaining pure elastic response), and obtains deflection data with a sufficiently large signal-to-noise ratio in hard foundation, which greatly improves the success rate and data validity of field testing. S3: Conduct falling weight deflection tests and collect dynamic deflection data. Using a falling weight deflectometer, apply transient impact loads to each test zone according to the test parameters determined in step S2. Collect deflection values ​​at each measuring point using displacement sensors positioned at different radial distances from the loading center to generate dynamic deflection basin curves for each test zone. ,in The radial distance from the measuring point to the center of loading. This represents the deflection value at that radial distance; S4: Extract the characteristic parameters of the deflection basin for each test zone, based on the dynamic deflection basin curve obtained in S3. Calculate the following characteristic parameters of the deflection basin: (1) Maximum deflection index at the center: That is, the maximum deflection value at the loading center location; (2) Indicators of the area affected by the deflection basin: ,in The effective radius of influence of the deflection basin is defined as the radial distance corresponding to when the deflection value decays to 5% of the maximum deflection value at the center. (3) Curvature index of the deflection basin: ,in and These are the first and second derivatives of the deflection basin curve at the loading center, respectively; (4) Deflection basin attenuation index: That is, at the reference radial distance The double logarithmic slope of the deflection value with respect to the radial distance, where the reference radial distance is... Take it as 2 to 3 times the radius of the bearing plate; Form the deflection response characteristic vector of each test zone ; S5: Calculate the dynamic deformation modulus of each test zone. Based on the theoretical solution of the surface displacement of an elastic half-space under a circular uniformly distributed impact load, and combined with the characteristic parameters of the deflection basin extracted in S4, establish the dynamic deformation modulus. Computational model: in The impact load determined by S2, Poisson's ratio of soil Let the radius of the drop hammer bearing plate be . The maximum deflection value at the center, The function for correcting the shape of the deflection basin is expressed as follows: in , , These are the shape correction coefficients calibrated through finite element numerical simulation. and These are the theoretical curvature value and theoretical decay index value of a standard uniform half-space, respectively. All correction terms in the function are dimensionless. S6: Establish a conversion model between dynamic deformation modulus and characteristic values ​​of foundation bearing capacity, and establish conversion models for different foundation types: For natural foundations and replaced foundations: For composite foundations: For foundation reinforcement: in The characteristic value of foundation bearing capacity, The dynamic deformation modulus calculated for S5. The unit reference modulus (taken as 1 MPa). The natural density of the soil. For reference density (the density of water is taken as 1000 kg / m³). This refers to the natural moisture content of the soil. The reference moisture content is 0.6 times the soil liquid limit. The area replacement ratio of the composite foundation. For the unconfined compressive strength of the solidified body, For reference strength (taken as 1 MPa); , , These are the modulus coefficients for different foundation types. It is the modulus exponent (ranging from 0.5 to 0.9). , , , The modulus coefficient, modulus index, and state correction index are determined by the following method: collecting no less than 30 sets of comparative data from plate load tests and falling weight deflection tests of different foundation types, calibrating the model parameters using nonlinear regression analysis, and verifying the generalization ability of the model using ten-fold cross-validation. S7: Foundation performance classification evaluation, based on the characteristic value of foundation bearing capacity calculated from S6. The characteristic value of bearing capacity required by the design ratio The foundation performance is classified into the following levels: when A value ≥ 1.2 indicates Level 1, signifying good load-bearing capacity; a value ≤ 1.0 indicates... A value less than 1.2 indicates a Class II load-bearing capacity, meaning the load-bearing capacity meets design requirements; when 0.8 ≤ A value less than 1.0 indicates Level 3, meaning the load-bearing capacity is close to the design limit; verification is recommended. A value less than 0.8 indicates a level four load-bearing capacity deficiency, and treatment is recommended. S8: Output test and evaluation report - Summarize the test parameters, deflection basin characteristic parameters, dynamic deformation modulus, bearing capacity characteristic values ​​and performance levels of each test zone to generate a rapid test and evaluation report on the bearing capacity of building foundations.

[0019] In one embodiment of the present invention, the displacement sensor in S3 is disposed at a radial position below the loading center: , , , , , , , ,in The radius of the bearing plate; the radius of the bearing plate The displacement sensor's position is determined based on the soil structure of the foundation under test and the estimated depth of influence, with a range of 150mm to 450mm. The placement of the displacement sensor is further determined based on the compression wave velocity of the foundation soil. and impact load duration Optimize and adjust as follows: Based on the compressed wave velocity and the half-peak duration of impact load Estimate the propagation distance of the stress wave at the peak of the impact load. ,when Less than 3 At that time, to The arrangement of the elements tapers inward radially, with a shrinkage coefficient of [value missing]. To ensure that the far-field sensor can capture the main area affected by stress wave propagation, all displacement sensors are installed on the same radial straight line and arranged symmetrically on both sides with the loading center as the center of symmetry. The arithmetic mean of the deflection values ​​at the corresponding positions on both sides is taken as the final deflection value at that radial distance.

[0020] This scheme overcomes the drawbacks of traditional rigid fixed positioning, which results in "measurements being too close in hard soil (waves not propagating) or too far in soft soil (waves having attenuated)," ensuring the integrity of the deflection basin curve in the far field. This prevents truncation errors in the calculation of the integral area and attenuation index due to the lack of effective measurement points, thus improving the robustness of characteristic parameter extraction.

[0021] In one embodiment of the present invention, the deflection basin curve in S4 The interpolation fitting method employs the following steps: First, using radial distance... For independent variables, deflection value As the dependent variable, cubic spline interpolation was used to interpolate the discrete measurement point data to obtain a continuously differentiable deflection basin curve. Secondly, the continuous curve obtained by interpolation is located at the loading center. Perform a Taylor expansion at the point =0. The data was determined by fitting data from 3 to 5 measurement points near the loading center. and The numerical values ​​are then used; specifically, the interpolation nodes are automatically optimized based on the local curvature changes of the deflection basin curve, namely: calculating the curvature of the deflection basin curve at each measuring point. When the absolute value of curvature is greater than a preset threshold Interpolation densification points are automatically added within the defined section, with the number of densification points proportional to the curvature integral value of that section, to ensure higher fitting accuracy of the deflection basin curve in areas of drastic deflection changes; finally, the effective influence radius of the deflection basin... The following method was used to determine the deflection value: Deflection values ​​were calculated point by point from the loading center outwards. The value was determined when the deflection first decreased to less than 0.05 × 10⁻⁶. When, the radial distance corresponding to that point is If the measured deflection value at the farthest measuring point is still greater than 0.05× Then, the exponential decay model is used to extrapolate and determine... .

[0022] This adaptive encryption strategy significantly improves the calculation accuracy of the deflection basin curvature index (involving second-order derivatives) while maintaining overall computational efficiency, overcoming the problem of severe oscillations in the second derivative caused by insufficient spatial resolution under equidistant sampling. It standardizes... The judgment process prevents the integral area from fluctuating due to the artificial truncation of the tail end of the bend basin, thus improving the consistency of the evaluation indicators.

[0023] In one embodiment of the present invention, the morphological correction coefficient in S5 , , The calibration method includes the following steps: establishing an axisymmetric finite element numerical model of the foundation type to be tested, wherein the radial boundary of the finite element model adopts a viscous absorbing boundary to simulate the energy radiation effect of an infinite half-space, and the bottom boundary adopts a fixed constraint; the soil constitutive model adopts the Drucker-Prager elastoplastic model considering the strain rate effect, wherein the strain rate effect is described by the Cowper-Symonds overstress model. in For dynamic yield stress, It is the static yield stress. For strain rate, and The material rate sensitive parameter; an impact load determined by S2 is applied in the finite element model. The equivalent half-sine wave dynamic load is analyzed using an implicit integral algorithm, with the time step not exceeding the load application time. 1 / 100; calculate different combinations of soil parameters (including compression modulus) ,density Poisson's ratio Cohesion internal friction angle The theoretical deflection basin curve is obtained from the theoretical deflection basin curve. , , , and calculate the corresponding Theoretical value; obtained by finite element method. The theoretical value is the target value, with In the function , , For the parameters to be determined, the Levenberg-Marquardt nonlinear least squares method is used for parameter fitting, such that... The root mean square error between the calculated and theoretical values ​​is minimized; the theoretical curvature value of the standard uniform half-space body is minimized. and theoretical decay index value The displacement was obtained by calculating the Boussinesq displacement of an elastic half-space under a uniformly distributed circular load.

[0024] This approach addresses the drawbacks of high costs and difficulty in covering extreme conditions (such as extremely soft soil or extremely hard rock) in pure field testing calibration by supplementing the data dimensions through numerical experiments. By incorporating the strain rate effect and energy radiation effect under impact loading into the calibration source, the calibrated shape correction function... It has a clear physical explicit background, rather than a "black box" fitting parameter.

[0025] In one embodiment of the present invention, the modulus coefficient in S6 , , The value of is determined by the following method: For each type of foundation, no less than 30 sets of comparative test data are collected. Each set of comparative test data includes the characteristic value of foundation bearing capacity obtained from plate load tests conducted at the same test point. Dynamic deformation modulus obtained from drop weight deflection test ;by For independent variable, As the dependent variable, the least squares method is used to fit the parameters of the dimensionless transformation model. The model form is as follows: in For the first One state correction variable (including natural soil density) Natural moisture content Replacement ratio m, reinforcement strength wait), Its corresponding reference value, The corresponding state correction index; for natural foundations and replaced foundations, the state correction index is... and The value of is determined by the following method: under different density states ( = 0.85 to 1.15) and different moisture content states ( At least five comparative experiments were conducted at values ​​ranging from 0.7 to 1.3, and the multivariate nonlinear regression method was used to determine the... and For composite foundations, the area replacement ratio m is calculated as follows: when circular cross-section piles are arranged in a square pattern, ,in The diameter of the pile body. The spacing between piles; for triangular pile arrangement, The modulus index The value ranges from 0.5 to 0.9. This index is determined through a total regression analysis of all comparative experimental data. The values ​​apply to all foundation types to maintain model consistency.

[0026] This solution achieves a clean decoupling of the factors affecting bearing capacity, enabling engineers to clearly quantify the independent increments in bearing capacity caused by "a 1% increase in moisture content" or "a 0.1% increase in replacement rate".

[0027] In one embodiment of the present invention, after the foundation performance grading evaluation described in S7, the following follow-up processing steps are performed: For test zones rated as Level 1, the test report is marked as "Good bearing capacity, design can be optimized" and it is recommended to appropriately reduce the test density in this area; for test zones rated as Level 2, the test report is marked as "Meets design requirements" and monitoring continues at the conventional test density; for test zones rated as Level 3, the test report is marked as "Review recommended" and a review verification process is triggered. The review verification process includes densely deploying falling weight deflection test points in the test zone and selecting no less than 3 representative points to conduct plate load tests for verification; for test zones rated as Level 4... Test zones are marked as "recommended treatment" in the inspection report and trigger a processing flow. The processing flow includes expanding the inspection range to determine the boundaries of areas that do not meet the requirements, and proposing targeted foundation reinforcement treatment suggestions based on foundation treatment design specifications. The rating results and inspection data of all test zones are entered into the building foundation performance database for continuous optimization of the subsequent model and dynamic updates of correction coefficients. At the same time, based on the spatial coordinates and rating results of each inspection point, a contour map of the foundation performance level distribution of the entire inspection area is generated using the Kriging spatial interpolation method, and the boundary coordinates of abnormal areas rated as level three and four are automatically identified and marked, providing a visual decision-making basis for construction zone management and differentiated pile driving.

[0028] This solution elevates the detection results from "a bunch of data tables" to "a management map with spatial decision-making attributes," enabling differentiated and dynamic control of construction zones. Automatic identification of abnormal area boundaries eliminates the arbitrariness of manual demarcation, providing precise target area coordinates for grouting reinforcement or pile reinforcement processes, effectively avoiding economic losses caused by "over-reinforcement" or "reinforcement omissions."

[0029] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A rapid evaluation method for building foundation performance based on falling weight deflection response, characterized in that, Includes the following steps: S1. Obtain the basic information of the foundation of the building to be tested and divide it into test zones. Based on the basic information, the foundation of the building to be tested is divided into several test zones. The foundation type, soil structure and construction technology are consistent within the same test zone. S2. Based on the soil structure and physical parameters of the test zones, determine the test parameters for the falling weight deflectometer in each test zone. The test parameters include: the impact load of the falling weight deflectometer. Load application time Radial spacing of measuring points And the displacement sensor arrangement scheme; S3. A falling weight deflectometer is used to apply transient impact loads to each test zone according to the test parameters. Deflection values ​​at each measuring point are collected by displacement sensors placed at different radial positions from the loading center to form dynamic deflection basin curves for each test zone. ,in The radial distance from the measuring point to the loading center; S4. Based on the dynamic deflection basin curve Calculation center maximum deflection index Indicators of the influence of the deflection basin area Deflection basin curvature index Deflection Basin Attenuation Index This forms the deflection response characteristic vector for each test zone. : S5. Based on the theoretical solution of the surface displacement of an elastic half-space under a circular uniformly distributed impact load, and combined with the characteristic parameters of the deflection basin, a dynamic elastic modulus calculation model is established. : in, ; In the formula, Poisson's ratio of soil Let the radius of the drop hammer bearing plate be . This is a function to correct the shape of the deflection basin. , , This is the morphological correction factor. and These are the theoretical curvature and theoretical decay index values ​​of a standard uniform half-space, respectively. S6. Establish dynamic deformation modulus and characteristic values ​​of foundation bearing capacity for different foundation types. The conversion model; S7. Based on the calculated characteristic value of foundation bearing capacity The characteristic value of bearing capacity required by the design ratio According to the preset grading standards, the foundation performance is divided into four levels: Level 1, Level 2, Level 3, and Level 4. S8. Output the test and evaluation report, summarizing the test parameters, deflection basin characteristic parameters, dynamic deformation modulus, bearing capacity characteristic values ​​and performance levels of each test zone, and generating a rapid test and evaluation report on the bearing capacity of the building foundation.

2. The rapid evaluation method for building foundation performance based on falling weight deflection response according to claim 1, characterized in that: In step S6, the dynamic deformation modulus and characteristic values ​​of foundation bearing capacity for different foundation types are... The conversion models include: For natural foundations and replaced foundations: For composite foundations: For foundation reinforcement: In the formula, The characteristic value of foundation bearing capacity, For dynamic deformation modulus, The unit base modulus, The natural density of the soil. For reference density, This refers to the natural moisture content of the soil. For reference moisture content, The area replacement ratio of the composite foundation. For the unconfined compressive strength of the solidified body, For reference strength; , , These are the modulus coefficients for different foundation types. Modulus index , , , This is the state correction index.

3. The rapid evaluation method for building foundation performance based on falling weight deflection response according to claim 1, characterized in that: In step S4, each indicator is calculated using the following formula: Maximum deflection index at center ;in, The maximum deflection value at the loading center location; Influence of deflection basin on area index ,in The effective radius of influence of the deflection basin; Deflection Basin Curvature Index ,in and These are the first and second derivatives of the deflection basin curve at the loading center, respectively; Deflection Basin Attenuation Index ,in For reference radial distance.

4. The rapid evaluation method for building foundation performance based on falling weight deflection response according to claim 1, characterized in that: In step S2, Impact load of falling weight deflectometer The method for determining it is as follows: ,in As the benchmark impact load, For reference compression modulus, The compression modulus of the soil to be tested. The load adjustment index is between 0.3 and 0.

5. radial spacing of measuring points The method for determining it is as follows: , The distance between the reference measuring points, The diameter of the drop hammer bearing plate is... For reference bearing plate diameter, The spacing adjustment index is between 0.8 and 1.

2.

5. The rapid evaluation method for building foundation performance based on falling weight deflection response according to claim 1, characterized in that: In step S3, the displacement sensor is positioned radially below the loading center: , , , , , , , ,in The radius of the bearing plate; the placement of the displacement sensors is based on the compression wave velocity of the foundation soil. and impact load duration Optimization and adjustments were made based on the compressed wave velocity. and the half-peak duration of impact load Estimate the propagation distance of the stress wave at the peak of the impact load. ,when Less than 3 At that time, to The arrangement of the elements tapers inward radially, with a shrinkage coefficient of [value missing]. All displacement sensors are installed on the same radial straight line and arranged symmetrically on both sides with the loading center as the center of symmetry. The arithmetic mean of the deflection values ​​at the corresponding positions on both sides is taken as the final deflection value at that radial distance.

6. The rapid evaluation method for building foundation performance based on falling weight deflection response according to claim 3, characterized in that: In step S4, the deflection basin curve The interpolation fitting methods include: using cubic spline interpolation to interpolate discrete measurement point data to obtain continuously differentiable deflection basin curves. The continuous curve obtained by interpolation is located at the loading center. Taylor expansion is performed at =0, and the result is determined by fitting measurement data near the loading center. and The numerical value; automatically optimize the interpolation nodes based on the local curvature changes of the deflection basin curve; the effective influence radius of the deflection basin. The deflection value is calculated point by point from the loading center outwards, and the value is determined when the deflection value first decays to a level less than the maximum deflection value at the center, which is a preset ratio.

7. The rapid evaluation method for building foundation performance based on falling weight deflection response according to claim 1, characterized in that: Morphological correction factor , , The calibration method includes: establishing an axisymmetric finite element numerical model of the foundation type to be tested; using viscous absorbing boundaries for the radial boundaries of the finite element model and fixed constraints for the bottom boundaries; adopting an elastoplastic model considering strain rate effects for the soil constitutive model; and applying the impact load of the falling weight deflectometer determined in step S2 to the finite element model. Equivalent dynamic load; calculate theoretical deflection basin curves under different combinations of soil parameters; extract from theoretical deflection basin curves , , , and calculate the corresponding Theoretical value; obtained by finite element method. The theoretical value is the target value, with In the function , , For the parameters to be determined, a nonlinear least squares method is used for parameter fitting; where the theoretical curvature value of the standard uniform half-space is... and theoretical decay index value The displacement was obtained by calculating the Boussinesq displacement of an elastic half-space under a circular uniformly distributed load.

8. The rapid evaluation method for building foundation performance based on falling weight deflection response according to claim 2, characterized in that: Modulus , , and modulus index and State Correction Index , , , The value of is determined by the following method: For each type of foundation, comparative test data are collected separately. Each set of comparative test data includes the characteristic value of foundation bearing capacity obtained from plate load tests conducted at the same test point. Dynamic deformation modulus obtained from drop weight deflection test ;by and state correction variables are independent variables. The least squares method is used to fit the parameters of the transformation model, with the dependent variable being the least squares method; the area replacement rate m is calculated based on the pile diameter and pile spacing.

9. The method for rapid evaluation of building foundation performance based on falling weight deflection response according to claim 1, characterized in that, The pre-defined grading standard for foundation performance is as follows: when A value ≥ 1.2 is considered Grade 1, indicating good load-bearing capacity; When 1.0 ≤ A value less than 1.2 indicates a Class II load-bearing capacity that meets design requirements. When 0.8 ≤ A value less than 1.0 indicates a Level 3 load-bearing capacity that is close to the design limit; verification is recommended. when A value less than 0.8 indicates a level four load-bearing capacity deficiency, and intervention is recommended.

10. The method for rapid evaluation of building foundation performance based on falling weight deflection response according to claim 1, characterized in that: In step S7, after the foundation performance is graded and evaluated, the following follow-up processing steps are performed: for test zones rated as Level 1, the test report is marked as having good bearing capacity; for test zones rated as Level 2, the test report is marked as meeting design requirements; for test zones rated as Level 3, a verification process is triggered, which includes densely deploying falling weight deflection test points within the test zone and selecting representative points to conduct plate load tests for verification. For test zones rated as Level 4, a processing procedure is triggered, which includes expanding the detection range to determine the boundaries of areas that do not meet the requirements and proposing foundation reinforcement treatment recommendations. The rating results and test data of all test zones are entered into the building foundation performance database. Based on the spatial coordinates and rating results of each test point, a contour map of the foundation performance level distribution of the entire test area is generated using spatial interpolation method, and the boundary coordinates of abnormal areas rated as level three and level four are automatically identified and marked.

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