Quasi-3D detection and interpretation method of karst body at highway bridge pile foundation location

Abstract

The present invention discloses a pseudo-three-dimensional detection and interpretation method for karst bodies at highway bridge pile foundation locations. This detection and interpretation method has strong site applicability and can completely cover the area where the highway bridge pile foundation is located within the detection range. Parallel survey lines are arranged to cover the area where the pile foundation is located, and the survey line spacing is controlled to be greater than 1 / 2 of the pile foundation diameter to ensure detection resolution. The two-dimensional interpretation profile is gridded, and the weighted center point position of the abnormal area in the profile is calculated. The correlation of anomalies in different profiles is determined using a weighted center point projection distance algorithm. Spatial interpolation behavior is used to form a pseudo-three-dimensional interpretation result of the bridge pile foundation in the karst area that includes the bridge pile foundation range. This method can solve the problem of two-dimensional planarization of geological radar survey line interpretation results in the field of pile foundation karst detection in the past.

Description

Technical Field

[0001] The present invention relates to the field of non-destructive detection of karst in highway bridges, namely, a pseudo-three-dimensional detection and interpretation method of karst bodies at the pile foundation positions of highway bridges. Background Art

[0002] To ensure safety, highway bridges crossing karst areas require investigation of the extent and size of hidden karst beneath the bridge pile foundations, as required by regulations. Limited by the difficulty of drilling rig access in some areas, the high cost of drilling, and the limited insight afforded by a single borehole, geophysical exploration combined with drilling can effectively determine the pseudo-three-dimensional spatial distribution of karst. Among the geophysical exploration methods used in highway engineering projects, high-density electrical methods, electromagnetic wave CT, and geological radar can all be used to detect karst development. However, high-density electrical methods require numerous on-site acquisition devices, are difficult to deploy, and require long acquisition times. Electromagnetic wave CT data acquisition relies on boreholes and has limited penetration distances. Geological radar data acquisition is convenient, cost-effective, and less restricted by site conditions. Currently, the "geological radar 2D profile + borehole 1D verification" model is widely used for karst exploration. However, interpretation of karst anomalies still relies on planar delineation on the profile. Existing 3D radar antenna arrays are large, making access difficult in the original terrain of some bridge locations during the survey phase. Currently, there is no established, convenient method for interpreting 3D karst development in highway engineering surveys. Summary of the Invention

[0003] The purpose of the present invention is to provide a pseudo-three-dimensional detection and interpretation method for karst bodies at the position of highway bridge pile foundations.

[0004] The technical solution adopted by the present invention to solve the above technical problems is:

[0005] The pseudo-three-dimensional detection and interpretation method for karst bodies at highway bridge pile foundation locations specifically includes the following steps:

[0006] Step 1: Based on the coordinate position of the design axis of the highway bridge pile foundation and the design pile diameter L, design three parallel geological radar acquisition lines, which are recorded as lines I, II, and III, with a line spacing of D. Line I is located at the design axis of the pile foundation, and lines II and III are located at the small and large piles of the design axis of the pile foundation, respectively.

[0007] Step 2: Measure and place points under the original topographic conditions during the highway bridge pile foundation survey phase, and remove the surface vegetation within the designed survey line to provide favorable conditions for the coupling of the geological radar antenna;

[0008] Step 3: For sites with a target depth of less than 20m, select an antenna with a frequency of 25-50Hz, set the measurement point spacing d to 0.25m, and the sampling window range to 500-800ns to ensure that the wavelet morphology is normal and free of interference during data collection;

[0009] Step 4: Process the collected pulse signal through trace header editing, signal delay time adjustment, gain adjustment, background denoising, filtering, and adding elevation information processing flow to form a two-dimensional inversion profile of the survey line;

[0010] Step 5: Based on the known drill core data of the survey line profile and the changes in the inversion profile waveform, the electromagnetic wave propagation velocity is set to circle the abnormal development location and bedrock surface development depth to form the radar survey line interpretation profile;

[0011] Step 6: Grid the radar line interpretation profile. The grid size should be no larger than d. The interpretation profile is divided into m×n discrete grids. The profile is regarded as the XOZ plane. The coordinates of each grid center point can be approximately regarded as (i, j), where i = 0, 1, ..., n, j = 0, 1, ..., m. The horizontal direction of the vertical survey line is determined as the Y direction. Let the Y direction coordinate be k. The three XOZ planes corresponding to the three survey lines II, I, and III have k = -D, 0, D respectively. The coordinates of each grid point in the three survey lines are (i, k, j), where i = 0, 1, ..., n, k = -D, 0, D, and j = 0, 1, ..., m.

[0012] Step 7: According to the position of the grid in the interpretation section, set the weight factor p(i, k, j) respectively. The weight factor of all grids within the anomaly range is 1, the weight factor of the edge grid is 0.5, and the weight factor of the grid outside the anomaly range is 0. At this time, each interpreted anomaly has a corresponding coordinate set {x yc ,y yc ,z yc}, and determine the maximum major axis dimension D of the abnormality yc ;

[0013] Step 8: Calculate and determine the weighted center coordinates of each anomaly in the XOZ plane of the profile.

[0014]

[0015] The value ranges of i and j are the horizontal and vertical boundary ranges of the anomaly respectively;

[0016] Step 9: Project the weighted center points of the anomalies in the two side sections to the XOZ plane of Y=0, select the original anomaly on the plane and the weighted center point of the anomaly projected to the plane for distance r matching, and the coordinates of the weighted center points of the two anomalies on the plane are (x yc0 ,z yc0 ) and (x yc1 ,z yc1 ), the major axis dimensions of the two anomalies are D yc0 ,D yc1 ,

[0017]

[0018] When r≤max(D,D yc0 ,D yc1 ), determine that there is a correlation between the two anomalies, and repeat the operation to all anomalies in this plane; select another section and repeat the above operation;

[0019] Step 10: When displaying the interrelated anomalies in quasi-3D, use interpolation software to perform spatial grid interpolation. It should be ensured that the areas with the same weight factors are connected, that is, the edge positions of the original interpreted anomalies are connected to ensure the control of the anomaly body shape. At this time, there is a special judgment. When there are related anomalies in the two sections k=-D and k=D, and there is no anomaly in the position range of the k=0 section, the above-mentioned anomaly association situation does not hold.

[0020] Preferably, the survey line length is determined based on the design range of the bridge pile foundation, ensuring that all pile positions within the cross section are covered and extending to both ends by a length of twice the pile diameter L. If L is not an integer, it is rounded up. The selection criteria for the survey line spacing D on both sides parallel to the design axis of the pile foundation are: And D = 0.5 × N, N = 1, 2, 3, ..., which is convenient for the subsequent explanation of the display of the results diagram.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] This detection and interpretation method has strong site applicability and can completely cover the area where highway bridge pile foundations are located within the detection range. The interpretation results of the radar survey network for pile foundation locations are gridded, and the weighted center point location of the anomaly area is calculated. A weighted center point projection distance algorithm is used to determine the correlation between the interpreted anomaly areas in different sections. Spatial interpolation is used to generate a pseudo-three-dimensional interpretation of bridge pile foundations in karst areas that includes the bridge pile foundations. This method solves the problem of the two-dimensional planarization of geological radar survey line interpretation results in the field of pile foundation karst detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the geological radar survey line layout for the pile foundation position of the highway bridge design in the present invention;

[0024] Figure 2 This is a schematic diagram of the gridding of the geological radar interpretation profile;

[0025] Figure 3 It is a schematic diagram of the three-dimensional spatial relationship of the pile foundation karst measurement network;

[0026] Figure 4 It is a schematic diagram of the pseudo-three-dimensional interpretation results of the karst anomaly body. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to the accompanying drawings and examples, but they are not intended to limit the present invention.

[0028] The pseudo-three-dimensional detection and interpretation method of karst body at the location of highway bridge pile foundation includes the following steps:

[0029] Step 1: Based on the coordinate position of the design axis of the highway bridge pile foundation and the design pile diameter L, design three parallel geological radar acquisition lines, which are recorded as lines I, II, and III, with a line spacing of D. Line I is located at the design axis of the pile foundation, and lines II and III are located at the small and large piles of the design axis of the pile foundation, respectively. Figure 1 This corresponds to the design process of geological radar survey line for highway bridge pile foundations described in step 1;

[0030] The length of the survey line is determined based on the design scope of the bridge pile foundation, ensuring that all pile positions within the cross section are covered and extending to both ends by a length of twice the pile diameter L (rounded up if L is not an integer). The spacing D between the survey lines parallel to the design axis of the pile foundation is selected as follows: And D = 0.5 × N, N = 1, 2, 3, ..., which is convenient for the subsequent explanation of the display of the results diagram.

[0031] Step 2: Measure and place points under the original topographic conditions during the highway bridge pile foundation survey phase, and remove the surface vegetation within the designed survey line to provide favorable conditions for the coupling of the geological radar antenna.

[0032] Step 3: For sites with a target depth of less than 20m, select an antenna with a frequency of 25-50Hz, set the measurement point spacing d to 0.25m, and the sampling window range to 500-800ns to ensure that the wavelet morphology is normal and free of interference during data collection;

[0033] Step 4: Process the collected pulse signal through trace header editing, signal delay time adjustment, gain adjustment, background denoising, filtering, adding elevation information and other processing procedures to form a two-dimensional inversion profile of the survey line;

[0034] Step 5: Based on the known drill core data of the survey line profile and the changes in the inversion profile waveform, the electromagnetic wave propagation velocity is set to circle the abnormal development location and bedrock surface development depth to form the radar survey line interpretation profile;

[0035] Step 6: Gridding the radar line interpretation profile. The grid size should not be larger than d, preferably 1 / 8d to 1 / 4d. The interpretation profile can be divided into m×n discrete grids. Considering the profile as the XOZ plane, the coordinates of each grid center point can be approximately regarded as (i, j), where i = 0, 1, ..., n, j = 0, 1, ..., m. Determine the horizontal direction of the vertical survey line as the Y direction. Let the Y direction coordinate be k. Then the three XOZ planes corresponding to the three survey lines II, I, and III have k = -D, 0, D respectively. The coordinates of each grid point in the three survey lines are (i, k, j), where i = 0, 1, ..., n, k = -D, 0, D, j = 0, 1, ..., m. Figure 2 Corresponding to the gridding process of the interpretation profile in step 6, the magenta circles represent the anomaly development locations circled in the radar line interpretation profile obtained in step 5, and the dark black and light gray correspond to the process of assigning weight factors in step 7;

[0036] Figure 3 Corresponding to the construction of three-dimensional spatial relationship in step 6, the three XOZ planes can be regarded as Figure 1 The three red lines in the middle are three-dimensional;

[0037] Step 7: According to the position of the grid in the interpretation section, set the weight factor p(i, k, j) respectively. The weight factor of all grids within the anomaly range is 1, the weight factor of the edge grid is 0.5, and the weight factor of the grid outside the anomaly range is 0. At this time, each interpreted anomaly has a corresponding coordinate set {x yc ,y yc ,z yc}, and determine the maximum major axis dimension D of the abnormality yc ;

[0038] Step 8: Calculate and determine the weighted center coordinates of each anomaly in the XOZ plane of the profile.

[0039]

[0040] The value ranges of i and j are the horizontal and vertical boundary ranges of the anomaly respectively;

[0041] Step 9: Project the weighted center points of the anomalies in the two side sections to the XOZ plane of Y=0, select the original anomaly on the plane and the weighted center point of the anomaly projected to the plane for distance r matching, and the coordinates of the weighted center points of the two anomalies on the plane are (x yc0 ,z yc0 ) and (x yc1 ,z yc1 ), the major axis dimensions of the two anomalies are D yc0 ,D yc1 ,

[0042]

[0043] When r≤max(D,D yc0 ,D yc1 ), determine that there is a correlation between the two anomalies, and repeat the operation to all anomalies in this plane; select another section and repeat the above operation;

[0044] Step 10: When displaying the interrelated anomalies in quasi-3D, use interpolation software to perform spatial grid interpolation. It should be ensured that the areas with the same weight factors are connected, that is, the edge positions of the original interpreted anomalies are connected to ensure the control of the anomaly body shape. At this time, there is a special judgment. When there are related anomalies in the two sections k=-D and k=D, and there is no anomaly in the position range of the k=0 section, the above-mentioned anomaly association situation does not hold.

[0045] Figure 4 Corresponding to the pseudo-three-dimensional interpretation results formed after the judgment in steps nine and ten, the anomaly in the lower left corner means that there are anomalies in the area in the three planes and they are interconnected, and it is determined that the anomalies are connected. The anomaly in the upper right corner means that there are anomalies in sections II and III, but there is no anomaly at this position in section I, so the anomalies in sections II and III must not be connected.

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A quasi-3D detection and interpretation method for karst bodies at highway bridge pile foundation locations, characterized by: Specifically include the following steps: Step 1: Based on the coordinate position of the design axis of the highway bridge pile foundation and the design pile diameter L, design three parallel geological radar acquisition lines, which are recorded as lines I, II, and III, with a line spacing of D. Line I is located at the design axis of the pile foundation, and lines II and III are located at the small and large piles of the design axis of the pile foundation, respectively. Step 2: Measure and place points under the original topographic conditions during the highway bridge pile foundation survey phase, and remove the surface vegetation within the designed survey line to provide favorable conditions for the coupling of the geological radar antenna; Step 3: For sites with a target depth of less than 20m, select an antenna with a frequency of 25-50Hz, set the measurement point spacing d to 0.25m, and the sampling window range to 500-800ns to ensure that the wavelet morphology is normal and free of interference during data collection; Step 4: Process the collected pulse signal through trace header editing, signal delay time adjustment, gain adjustment, background denoising, filtering, and adding elevation information processing flow to form a two-dimensional inversion profile of the survey line; Step 5: Based on the known drill core data of the survey line profile and the changes in the inversion profile waveform, the electromagnetic wave propagation velocity is set to circle the abnormal development location and bedrock surface development depth to form the radar survey line interpretation profile; Step 6: Grid the radar line interpretation profile. The grid size should be no larger than d. The interpretation profile is divided into m×n discrete grids. The profile is regarded as the XOZ plane. The coordinates of each grid center point can be approximately regarded as (i, j), where i = 0, 1, ..., n, and j = 0, 1, ..., m. Determine the horizontal direction of the vertical survey line as the Y direction, and let the Y direction coordinate be k. Then the three XOZ planes corresponding to the three survey lines II, I, and III have k = -D, 0, D respectively. The coordinates of each grid point in the three survey lines are (i, k, j), i = 0, 1, ..., n, k = -D, 0, D, j = 0, 1, ..., m; Step 7: According to the position of the grid in the interpretation section, set the weight factor p(i, k, j) respectively. The weight factor of all grids within the anomaly range is 1, the weight factor of the edge grid is 0.5, and the weight factor of the grid outside the anomaly range is 0. At this time, each interpreted anomaly has a corresponding coordinate set {x yc ,y yc ,z yc }, and determine the maximum major axis dimension D of the abnormality yc ; Step 8: Calculate and determine the weighted center coordinates of each anomaly in the XOZ plane of the profile. The value ranges of i and j are the horizontal and vertical boundary ranges of the anomaly respectively; Step 9: Project the weighted center points of the anomalies in the two side sections to the XOZ plane of Y=0, select the original anomaly on the plane and the weighted center point of the anomaly projected to the plane for distance r matching, and the coordinates of the weighted center points of the two anomalies on the plane are (x yc0 ,z yc0 ) and (x yc1 ,z yc1 ), the major axis dimensions of the two anomalies are D yc0 ,D yc1 , When r≤max(D,D yc0 ,D yc1 ), determine that there is a correlation between the two anomalies, and repeat the operation to all anomalies in this plane; select another section and repeat the above operation; Step 10: When displaying the interrelated anomalies in quasi-3D, use interpolation software to perform spatial grid interpolation. It should be ensured that the areas with the same weight factors are connected, that is, the edge positions of the original interpreted anomalies are connected to ensure the control of the anomaly body shape. At this time, there is a special judgment. When there are related anomalies in the two sections k=-D and k=D, and there is no anomaly in the position range of the k=0 section, the above-mentioned anomaly association situation does not hold.

2. The method for pseudo-three-dimensional detection and interpretation of karst bodies at highway bridge pile foundation locations according to claim 1, characterized in that: The length of the survey line is determined based on the design scope of the bridge pile foundation, ensuring that it covers all pile positions within the section where the design axis of the highway bridge pile foundation and the pile diameter L of the bridge pile foundation are located, and extends to both ends by a length of twice the pile diameter L. If L is not an integer, it is rounded up. The selection criteria for the spacing D of the survey lines parallel to the two sides of the design axis of the pile foundation are: And D = 0.5 × N, N = 1, 2, 3, ..., which is convenient for the subsequent explanation of the display of the results diagram.

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