A method for advanced and accurate diagnosis and treatment of leakage in foundation pit retaining structure

Abstract

The present invention relates to a method for advanced and precise diagnosis and treatment of leakage in foundation pit retaining structures, and belongs to the technical field of foundation pit construction. It includes hole measurement layout, data collection, data inversion, formation resistivity background value calibration, leakage diagnosis, targeted treatment, re-inspection, foundation pit excavation and slight water seepage treatment. The diagnosis of leakage in foundation pit retaining structures is divided into four levels: severe leakage, general leakage, slight water seepage, and no obvious signs of leakage. In case of severe leakage, measures such as interlocking piles or plain ground-connected walls are taken in the leakage area outside the foundation pit; in case of general water seepage, measures such as vertical positioning of drilling holes and local precise grouting are taken in the leakage area outside the foundation pit; in case of slight water seepage, measures are taken to monitor the foundation pit excavation process and quickly fill it with polyurethane materials; in case of no obvious signs, no treatment is done. The present invention can be widely used in any working condition during the foundation pit excavation process, which can reduce costs and speed up construction period.

Description

Technical Field

[0001] The invention relates to a method for advanced and precise diagnosis and treatment of leakage of a foundation pit retaining structure, belonging to the technical field of foundation pit construction. Background Art

[0002] Leakage from foundation pit retaining structures is a major cause of construction accidents, potentially causing settlement of surrounding buildings, ground subsidence, pipeline rupture, and even pit collapse. Due to the rapid progression of soil seepage damage, monitoring data during excavation often lacks clear signs. Leakage often escalates quickly, even leading to sand inrush risks. This makes leakage incidents difficult and costly to manage. Therefore, the focus of controlling leakage risks from foundation pit retaining structures should shift from addressing them during excavation to pre-excavation measures.

[0003] Pre-treatment of leakage risks in foundation pit retaining structures involves leak diagnosis and remediation measures. Currently, technologies for diagnosing leakage in foundation pit retaining structures primarily include ultrasonic methods, tracer methods, sonar permeability testing, fiber optic permeability testing, and micro-well electrical logging. However, each diagnostic method presents varying degrees of high cost, poor accuracy, complex construction, and environmental pollution. Remediation measures primarily focus on leaks occurring after excavation, including backfilling, grouting outside the pit, and decompression drainage. However, addressing severe leakage often presents high costs, time-consuming tasks, and significant risks. The above-mentioned existing technologies are mainly concentrated on a leakage position detection method for ultra-deep foundation pit retaining structure disclosed in CN117385945A, a leakage hidden danger detection method for foundation pit retaining structure based on current field method disclosed in CN110888171A, a deep foundation pit retaining structure interlocking pile anti-leakage construction method based on sonar detection technology disclosed in CN116289969A, and a leakage detection method for deep foundation pit retaining structure in saturated soft soil disclosed in CN114993569A. Summary of the Invention

[0004] The purpose of the present invention is to address the defects of the above-mentioned existing technologies and provide a method for advanced and accurate diagnosis and treatment of leakage of foundation pit retaining structure. The method accurately diagnoses the leakage of the retaining structure before foundation pit excavation or during construction, and then carries out targeted treatment of different levels of leakage according to the diagnosis results, thereby ensuring the safety of the subsequent construction process.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A method for advanced and accurate diagnosis and treatment of leakage of a foundation pit retaining structure comprises the following steps:

[0007] S1. Measuring hole layout: Based on the foundation pit retaining structure design, engineering survey report, and groundwater level monitoring data, measuring holes are laid out at appropriate locations outside the foundation pit.

[0008] S2. Data Acquisition: Place the same number of electrodes in adjacent wells and connect them to an electrical analyzer for automated data acquisition.

[0009] S3. Data inversion: Perform inversion calculations on the automatically collected data and create formation resistivity cloud maps based on the inversion results.

[0010] S4. Calibration of formation resistivity background value: Measure the water resistivity and soil porosity in observation wells outside the foundation pit to initially explore the distribution of formation resistivity background values. Calibrate the actual formation resistivity background value based on the distribution in the formation resistivity cloud map.

[0011] S5. Leakage diagnosis: Compare and analyze the formation resistivity cloud map with the formation resistivity background value to identify areas with sudden resistivity drops. Classify the leakage of the foundation pit retaining structure based on the percentage of the sudden resistivity drop. Also, determine the extent of the leakage based on the size of the sudden resistivity drop area.

[0012] S6. Targeted treatment: Based on the leakage classification of the foundation pit retaining structure in S5, targeted treatment is carried out;

[0013] S7. Re-inspection: For severe and general leakage in the foundation pit retaining structure, after taking targeted measures in step S6 before excavation, repeat steps S2, S3, and S5 to re-inspect the leakage; if the re-inspection result is severe or general leakage, repeat step S6;

[0014] S8. Excavation of foundation pit and treatment of minor water seepage: If the re-inspection result of step S7 is minor water seepage or no obvious signs, the foundation pit excavation can be carried out; during the foundation pit excavation process, focus on monitoring the minor water seepage points and promptly use polyurethane materials for rapid filling.

[0015] Furthermore, in step S1, the appropriate position outside the foundation pit generally refers to 1.5 to 2.0 m outside the foundation pit, with a measurement hole spacing of 6 to 20 m, crossing the potential leakage point.

[0016] Furthermore, in step S3, the inversion calculation includes data preprocessing, initial model construction, forward calculation and inversion iteration, and the inversion calculation uses the least squares method to optimize model parameters.

[0017] Furthermore, in step S4, the distribution of the background value interval of the initial formation resistivity is calculated according to the following formula (1):

[0018] ρ=ρ ω n -2 (1)

[0019] in, is the background value of formation resistivity, ρ ω is the resistivity value of water in the observation well outside the foundation pit, The porosity of the soil is outside the foundation pit.

[0020] Furthermore, in step S5, the leakage situation of the foundation pit retaining structure is classified into four levels; the minimum resistivity value of the sudden drop area / the actual formation resistivity background value = β is defined, when β≤20%, it is serious leakage; when 20%<β≤60%, it is general leakage; when 60%<β≤80%, it is slight leakage; when β>80%, there is no obvious sign.

[0021] Furthermore, in step S6, the specific method of targeted treatment is: for serious water leakage, take measures such as implementing interlocking piles or ground-connected walls in the leakage area outside the foundation pit; for general water seepage, take measures such as implementing vertical drilling and local precise grouting in the leakage area outside the foundation pit; for minor water seepage, monitor the foundation pit excavation process and use polyurethane materials for rapid filling; for situations without obvious signs, no treatment is done.

[0022] Furthermore, the foundation pit retaining structure is an underground continuous wall structure, a three-axis mixing pile structure or a high-pressure rotary jet pile structure.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) Through the calibration of formation resistivity and leakage analysis, it can be widely used in any working condition before or during foundation pit excavation.

[0025] (2) Targeted treatment based on the leakage situation of the foundation pit retaining structure can reduce costs, speed up construction period, and reduce carbon emissions and pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the process of the method for advanced and accurate diagnosis and treatment of leakage of foundation pit retaining structure of the present invention;

[0027] Figure 2 This is a schematic diagram of the arrangement of measuring points in measuring area No. 1 according to an embodiment of the present invention;

[0028] Figure 3 This is a schematic diagram of the arrangement of measuring points in measuring area No. 2 according to an embodiment of the present invention;

[0029] Figure 4 This is a graph showing the detection results of measurement area No. 1 according to an embodiment of the present invention;

[0030] Figure 5 This is a diagram of the detection results of measurement area No. 2 in Example 2 of the present invention. DETAILED DESCRIPTION

[0031] The following is combined with Figure 1-5 The present invention will be further described in detail with specific implementations to facilitate a clear understanding of the present invention, but they do not constitute a limitation to the present invention.

[0032] Example 1

[0033] The foundation pit in this embodiment is 500 meters long and 28 meters deep, and the retaining structure is an underground continuous wall structure with a thickness of 1.5 meters. During the initial excavation of the foundation pit to the basement level, significant leakage occurred. Therefore, before the subsequent excavation of the foundation pit, the method for preemptive and precise diagnosis and treatment of leakage in the foundation pit retaining structure proposed in this invention was adopted to ensure subsequent construction safety.

[0034] S1. Layout of measuring holes. According to the foundation pit retaining structure design drawings, engineering survey reports, and groundwater level monitoring data, the foundation pit retaining structure is an underground continuous wall structure 1. Due to its construction process characteristics, the joints of the underground continuous wall often become potential leakage points for various reasons. When arranging measuring holes, it is necessary to cross the underground continuous wall joints 2. Taking all factors into consideration, in this embodiment, if Figure 2-3 As shown, the two measuring holes 3 in measuring area 1 are arranged 1.5m outside the foundation pit, spanning three ground-connected wall joints 2, with one hole each at 2.0m on both sides of the outermost ground-connected wall joint 2, and the hole depth is 40m; the two measuring holes in measuring area 2 are arranged 1.5m outside the foundation pit, spanning three ground-connected wall joints 2, with one hole each at 1.0m outside the leftmost ground-connected wall joint 2 and 2.0m outside the rightmost ground-connected wall joint 2, and the hole depth is 39m.

[0035] S2. Data Collection. Place the same number of electrodes in adjacent measurement holes 3 and connect them to an electrical analyzer for automated data collection.

[0036] In this embodiment, 32 electrodes are arranged in each measuring hole 3 in measuring area 1. However, due to the early excavation of the foundation pit, the groundwater level outside the pit has dropped to a depth of about 15 meters, and the number of effective electrodes in each measuring hole is 26; 32 electrodes are arranged in each measuring hole 3 in measuring area 2. However, due to the early excavation of the foundation pit, the groundwater level outside the pit has dropped to a depth of about 15 meters, and the number of effective electrodes in each measuring hole is 25.

[0037] S3. Data Inversion. The automatically collected data undergoes data preprocessing, initial model construction, forward calculation, and inversion iteration. The model parameters are optimized using the least squares method, and formation resistivity cloud maps are drawn based on the inversion results.

[0038] S4. Calibration of formation resistivity background value. Detect the water resistivity value, soil porosity and other data in the observation well outside the foundation pit, and use the formula ρ=ρ ω n -2 , a preliminary exploration of the distribution of formation resistivity background values. is the background value of formation resistivity, ρ ω is the resistivity value of water in the observation well outside the foundation pit, The porosity of the soil is outside the foundation pit.

[0039] Specifically, in this embodiment, the water resistivity in the observation well outside the foundation pit in survey area 1 is 22-24 Ω·m, and the soil porosity is 0.39-0.42. Therefore, the preliminary estimate of the background formation resistivity is 124-158 Ω·m. Based on the initial exploration of the background formation resistivity value interval distribution, combined with the distribution in the formation resistivity detection cloud map, the actual background formation resistivity value is calibrated to 130 Ω·m. The water resistivity in the observation well outside the foundation pit in survey area 2 is 24-25 Ω·m, and the soil porosity is 0.34-0.37. Therefore, the preliminary estimate of the background formation resistivity value is 175-216 Ω·m. Based on the initial exploration of the background formation resistivity value interval distribution, combined with the distribution in the formation resistivity detection cloud map, the actual background formation resistivity value is calibrated to 200 Ω·m.

[0040] S5. Leakage diagnosis. Compare and analyze the formation resistivity cloud map with the formation resistivity background value information to identify areas with sudden resistivity drops. Leakage in the foundation pit retaining structure is graded based on the percentage of resistivity reduction in these areas. The extent of the leakage is also determined based on the size of the area with the sudden resistivity drop.

[0041] Specifically, the leakage of foundation pit retaining structures is classified into four levels; the minimum resistivity value of the sudden drop area / the actual formation resistivity background value = β is defined. When β≤20%, it is serious leakage; when 20%<β≤60%, it is general leakage; when 60%<β≤80%, it is slight leakage; when β>80%, there is no obvious sign.

[0042] In this embodiment, Figure 4-5 As shown, the formation resistivity background value in measurement area 1 is 130 Ω·m. The sudden drop occurs at a depth of 33 m between the middle diaphragm wall joint and near the center of the second diaphragm wall on the left at a depth of 39 m. The minimum resistivity is 10 Ω·m, so β ​​= 7.7%, indicating severe leakage in the foundation pit retaining structure at this location. The formation resistivity background value in measurement area 2 is 200 Ω·m. The sudden drop occurs at a depth of 37 m between the leftmost diaphragm wall joint and the minimum resistivity is 60 Ω·m, so β ​​= 30%, indicating moderate leakage in the foundation pit retaining structure at this location.

[0043] S6. Targeted treatment. Targeted treatment will be implemented based on the level of leakage within the foundation pit retaining structure. Specific methods for targeted treatment include: For severe leakage, interlocking piles or ground-connected walls will be installed in the leakage area outside the foundation pit; for moderate leakage, localized precision grouting will be implemented through vertical drilling and positioning in the leakage area outside the foundation pit; for minor leakage, monitoring will be conducted during the excavation process, and rapid filling with polyurethane materials will be implemented; for leakage without obvious signs, no treatment will be taken.

[0044] Specifically, in response to the serious water leakage in measurement area No. 1 in this embodiment, measures are taken to install plain concrete interlocking piles in the leakage area outside the foundation pit. The pile diameter is 600mm, the pile center spacing is 600mm, the pile length is 40m, the distance from the edge of the ground-connected wall is 0.5m, and the horizontal range is 2~12m from the left measurement hole.

[0045] To address the general water leakage in measurement area No. 2 in this example, localized precise grouting measures were implemented by drilling vertically positioned holes in the leaking area outside the foundation pit. Using the sleeve valve pipe grouting method, localized grouting reinforcement and sealing was carried out at a depth of 35 to 39 meters, 0.3 meters outside the leftmost ground-connected wall joint.

[0046] S7. Re-inspect. For severe or moderate leakage in the foundation pit retaining structure, after taking targeted measures in step S6 before excavation, repeat steps S2, S3, and S5 to re-inspect the leakage. If the re-inspection result indicates severe or moderate leakage, repeat step S6.

[0047] S8. Excavation of the foundation pit and treatment of minor water seepage. If the re-inspection result of step S7 indicates minor water seepage or no obvious signs, excavation of the foundation pit can proceed. During the excavation process, focus on monitoring minor water seepage points and promptly fill them with polyurethane materials.

[0048] Example 2

[0049] In this embodiment, the foundation pit retaining structure is a three-axis mixing pile structure, and its diagnosis and treatment method is the same as that in Example 1.

[0050] Example 3

[0051] In this embodiment, the foundation pit retaining structure is a high-pressure rotary jet grouting pile structure, and its diagnosis and treatment method is the same as that in Example 1.

[0052] The above is merely a preferred embodiment of the present invention and does not constitute any formal limitation on the structure of the present invention. The layout and number of the present invention are not limited to this example and can be optimized according to actual engineering practices. Any modifications, equivalent changes, and decorations to the above embodiment based on the technical principles of the present invention that do not depart from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for advanced and accurate diagnosis and treatment of leakage in foundation pit retaining structure, characterized in that: The steps include: S1. Measuring hole layout: Based on the foundation pit retaining structure design, engineering survey report, and groundwater level monitoring data, measuring holes are laid out at appropriate locations outside the foundation pit. In step S1, the appropriate location outside the foundation pit refers to 1.5 to 2.0 meters outside the foundation pit, with a spacing of 6 to 20 meters between measuring holes, spanning potential leakage points. S2. Data Acquisition: Place the same number of electrodes in adjacent wells and connect them to an electrical analyzer for automated data acquisition. S3 data inversion; the automated data collection is inverted and calculated, and the formation resistivity cloud is drawn based on the inversion results; in the step S3, the inversion calculation includes data preprocessing, initial model construction, forward calculation and inversion iteration, the inversion calculation uses the least squares method to optimize model parameters; S4. Calibration of formation resistivity background value: Detect the water resistivity and soil porosity in the observation well outside the foundation pit, and preliminarily explore the interval distribution of the formation resistivity background value; calibrate the actual formation resistivity background value based on the distribution in the formation resistivity cloud map; in step S4, the preliminarily explored interval distribution of the formation resistivity background value is calculated according to the following formula (1): ρ=ρ ω n -2 （1） in, is the background value of formation resistivity, ρ ω is the resistivity value of water in the observation well outside the foundation pit, Outside the foundation pit is the soil porosity; S5. Leakage Diagnosis: Compare and analyze the formation resistivity cloud map with the formation resistivity background value to identify areas of sudden resistivity drop. Leakage levels are classified based on the ratio of the resistivity drop in these areas. The scope of the leakage is also determined based on the size of the sudden resistivity drop area. In step S5, leakage levels are classified into four levels. The minimum resistivity value in the sudden resistivity drop area / the actual formation resistivity background value = β. When β ≤ 20%, it indicates severe leakage; when 20% < β ≤ 60%, it indicates moderate leakage; when 60% < β ≤ 80%, it indicates minor leakage; and when β > 80%, it indicates no obvious leakage. S6. Targeted treatment: Based on the leakage classification of the foundation pit retaining structure in S5, targeted treatment is carried out; S7. Re-inspection: For severe and general leakage in the foundation pit retaining structure, after taking targeted measures in step S6 before excavation, repeat steps S2, S3, and S5 to re-inspect the leakage; if the re-inspection result is severe or general leakage, repeat step S6; S8 excavation and minor water seepage treatment: When the re-inspection result of step S7 is minor water seepage or no obvious signs, the excavation can be carried out; during the excavation process, focus on monitoring the minor water seepage points and promptly use polyurethane materials for rapid filling; The foundation pit retaining structure is an underground continuous wall structure, a three-axis mixing pile structure or a high-pressure rotary jet pile structure.

2. The method for advanced and accurate diagnosis and treatment of leakage of foundation pit retaining structure according to claim 1 is characterized in that: In step S6, the specific method of targeted treatment is: for serious water leakage, take measures such as implementing interlocking piles or ground-connected walls in the leakage area outside the foundation pit; for general water seepage, take measures such as implementing vertical drilling and local precise grouting in the leakage area outside the foundation pit; for minor water seepage, monitor the foundation pit excavation process and quickly fill it with polyurethane materials; for situations without obvious signs, no treatment is taken.

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