Backwater side seepage drainage and pressure reduction anti-seepage method based on built sandy soil embankment foundation

Abstract

The invention discloses a backwater side seepage drainage and pressure reduction anti-seepage method based on a built sandy soil embankment foundation, and relates to the field of hydraulic engineering embankment seepage control. The technical problems that in existing sandy soil embankment foundation seepage drainage design, due to dynamic change of soil layer permeability, the drainage effect is poor, and slope stability is difficult to guarantee are solved. The method comprises the following steps: establishing a seepage field model through a three-stage hydraulic fracture test, and measuring a permeability coefficient, critical pressure and a failure criterion; the groove is dynamically excavated in three stages, the excavation depth and the slope gradient are corrected in real time according to actually measured data, and the shape of the groove is verified through a model; and finally, laying an inverted filter layer, a drainage body and an anti-scouring layer, wherein the permeability coefficient of the inverted filter layer and the aperture ratio of the drainage body are dynamically adjusted according to actually measured data. According to the method, accurate control over seepage drainage and pressure reduction of the sandy soil embankment foundation is achieved through dynamic coupling of testing, construction and a numerical model, and the method is mainly used for seepage treatment of the backwater side of a built embankment and slope stabilization and reinforcement.

Description

Technical Field

[0001] The present invention belongs to the technical field of seepage control of water conservancy project embankments, and particularly relates to a backwater side seepage drainage, pressure reduction and anti-seepage method based on an existing sandy soil embankment foundation. Background Art

[0002] In the field of water conservancy, drainage and pressure reduction on the backwater side of sandy soil embankments has always faced numerous technical challenges. Due to its high permeability, sandy soil is prone to seepage damage under long-term seepage, threatening the stability of the embankment structure. Traditional drainage methods mainly rely on static measures such as pre-set drainage ditches or pressure relief wells, but these methods have significant limitations in practical application.

[0003] First, existing technologies lack effective responses to the dynamic changes in the permeability characteristics of sandy soils. The permeability coefficient of sandy soils can vary significantly due to factors such as changes in soil structure and the development of cracks. Traditional methods employ fixed design parameters that are difficult to adapt to these dynamic characteristics. This can lead to insufficient drainage capacity or excessive drainage in actual operation, impacting drainage effectiveness. The main reasons for this problem are the lack of real-time monitoring of soil permeability characteristics and the failure to establish a dynamic response mechanism between permeability parameters and construction measures.

[0004] Secondly, there are deficiencies in slope stability control. Traditional methods typically employ fixed-slope designs, which fail to adapt to actual soil deformation during construction. Sandy soil slopes are prone to progressive failure due to seepage, and static designs struggle to detect and address these changes in a timely manner. This is primarily due to a lack of effective real-time monitoring technology and dynamic analysis methods, which results in a disconnect between design parameters and actual conditions.

[0005] Furthermore, existing technologies fail to adequately consider the coupling between seepage and stress fields. Sandy soil embankment foundations produce complex stress-strain responses under seepage, and traditional methods often separate seepage analysis from stability assessment, resulting in unreliable design solutions. This limitation stems from a lack of understanding of soil failure mechanisms and a lack of effective multi-field coupling analysis tools.

[0006] Furthermore, there is room for optimization in the design of the filter layer and drainage structure. Traditional methods typically use fixed-size filter materials and drainage structures, which are difficult to adapt to the actual seepage conditions in different sections. This can lead to localized blockage or scouring, affecting long-term performance. This problem stems from the failure to establish a quantitative relationship between seepage characteristics and drainage facility parameters.

[0007] In actual engineering applications, these technical deficiencies have led to a series of construction difficulties. For example, in sandy soils with highly variable permeability, construction plans often need to be repeatedly adjusted, resulting in project delays and increased costs. Furthermore, the lack of a reliable early warning system makes it difficult to promptly detect and address safety hazards such as slope instability.

[0008] These issues make it difficult to ensure effective drainage and pressure reduction treatment for sandy soil embankments, and also increase the difficulty of project maintenance. This is primarily due to the inability of existing technologies to effectively address key issues such as the dynamic changes in soil parameters, multi-field coupling, and real-time response mechanisms. These technical bottlenecks have hindered the development and application of drainage treatment technologies for sandy soil embankments. Summary of the Invention

[0009] This invention provides a method for draining and reducing pressure on the backside of an existing sandy soil embankment. Through the dynamic coupling of testing, construction, and numerical modeling, this method achieves precise control of draining and reducing pressure on the sandy soil embankment. The method is primarily used for managing seepage on the backside of existing embankments and for strengthening slope stability. This method addresses issues such as dynamic permeability changes and difficulty in real-time slope stability control associated with draining and reducing pressure on the backside of sandy soil embankments.

[0010] In order to achieve these objects and other advantages of the present invention, a backwater side drainage, pressure reduction and anti-seepage method based on an existing sandy soil embankment foundation is provided, comprising: S1. Establish the initial seepage field numerical model through three-stage hydraulic fracturing test. The three stages are: S101, low-pressure permeability test stage, to determine the permeability coefficient K0 of the soil foundation; S102, medium-pressure crack detection stage, to calibrate the critical seepage pressure P of crack development. c ; S103, high pressure parameter calibration stage, determine the soil failure criterion σ f ; S2. Trench excavation is carried out in three stages, with each stage dynamically combining hydraulic fracturing testing with construction: S201, first stage excavation: use K0 to determine the initial excavation depth D init =K0×t, where t is the time coefficient; after the excavation is left to stand for 24 hours, the actual seepage volume Q1 is collected; the corrected permeability coefficient K1 is calculated as: K1=K0×(Q1 / Q0) 0.3 , where Q0 is the model-predicted seepage rate, and the reference depth D0 is recalculated based on the modified permeability coefficient K1, D0=H+0.5+0.1×((K1-K0) / K0), where H is the elevation of the top of the aquitard after updating based on K1; S202, second stage excavation: dynamically adjust the excavation depth D = D0 + ΔD, ΔD = 0.05 × (P act -P c) / 10, where ΔD is the dynamic adjustment amount, P act is the real-time seepage pressure, the depth unit is meter, and the seepage pressure unit is kPa; According to the critical seepage pressure P of fracture development c , obtain the initial clay slope S1 init =0.5ln(P c / P0), initial sandy soil slope S2 init =ln(P c / P0), where P0 is the initial pore seepage pressure; after excavation, the excavation was left to stand for 24 hours, and the real-time strain ε was monitored. The average strain in the last 2 hours was taken for the subsequent third-stage slope adjustment; S203, the third stage of excavation: adjust the slope of clay soil to S1 = 1: (0.5-0.1 × ε / 0.1%), the slope of sandy soil to S2 = 1: (1.0-0.2 × ε / 0.1%); according to σ f Verify the final groove morphology, if |Δ m -Δ a | / Δ a >15%, using the latest P act and ε recalibrate the model until |Δ m -Δ a | / Δ a ≤10%, where Δ m is the model predicted displacement, Δ a is the measured displacement; S3. Lay the filter layer, drainage body and anti-scour layer in the trench from bottom to top. The permeability coefficient of the filter layer is the final corrected value of K1, and the opening ratio of the drainage body is adjusted according to the ratio of Q1 / Q0.

[0011] Preferably, the filter layer, the drainage body and the anti-scour layer are laid in the trench from bottom to top, specifically: S301, paving the filter layer: a, the lower layer is paved with non-woven fabric, the equivalent pore size is 0 95 The value range is 0.07-0.20mm, the gradient ratio GR≤3; the middle layer is paved with medium-coarse sand with a thickness of 15-20cm, D 15 The value range is 0.5-0.8mm, and the mud content is ≤5%; the upper layer is paved with graded crushed stone with a thickness of 10-15cm and a maximum particle size of ≤30mm; b. Overall permeability coefficient K f Take the final correction value of K1, and the allowable deviation is ±10%; when K1>5×10 -1 cm / s, increase the number of non-woven fabric layers to 2; S302. Construction of drainage body: a. Dynamic adjustment of opening ratio: basic opening ratio φ0=20%, actual opening ratio φ=φ0× , limited to 15-25%; b. Use modular plastic drainage box, single size 50×50×30cm, drainage box side wall opening diameter d=8-12mm, according to the φ value to adjust the hole distance L= ; S303. Anti-scour layer setting: a. Constructed in two layers, the lower layer is dry masonry block stone with a thickness of 20-30 cm and a block stone particle size of 20-40 cm; the upper layer is a crushed stone cushion layer with a thickness of 10 cm and a particle size of 5-10 mm; b. When φ>22%, the total thickness of the anti-scour layer is increased by 10%. When Q1 / Q0>1.5, an anti-scour tooth wall is added.

[0012] Preferably, the initial seepage field numerical model is established through a three-stage hydraulic fracturing test, specifically: S101, low-pressure permeability test stage: drill a hole or set a pressure measuring tube on the backwater side and apply a low-pressure head; record the stable seepage volume Q0 and the corresponding water pressure P0; calculate the foundation permeability coefficient K0 of the soil layer, specifically: , , where A is the cross-sectional area of ​​the water flow, i is the hydraulic gradient, is the head difference, L is the seepage path length; S102, medium pressure crack detection stage: gradually increase the water pressure to the critical seepage pressure P for crack development c , monitoring the sudden change of seepage volume or strain rate, and locating the fracture area by combining acoustic wave or resistivity imaging; S103, high pressure parameter calibration stage: continue to pressurize to 1.2~1.5 times of the design water head, and record the ultimate strain when the soil fails and breaking pressure , fitting the Mohr-Coulomb criterion; The construction of the initial seepage field numerical model includes: based on K0, P c 、 Establish a finite element model, set the upstream side as the constant head boundary and the downstream side as the free seepage boundary; dynamically modify the model parameters based on the measured data to ensure that the model predicts the displacement Δ m Compared with the measured displacement Δ a The deviation is ≤10%.

[0013] Preferably, the elevation H of the top plate of the aquitard is updated according to the modified permeability coefficient K1, specifically: Obtain the original top elevation H0 of the aquitard based on the initial geological exploration data; The elevation adjustment ΔH is calculated by the ratio of the corrected permeability coefficient K1 to the initial permeability coefficient K0, specifically: , where ΔH is in meters and the adjusted aquitard top elevation H = H0 + ΔH; When |ΔH / H0|>5%, geological radar or drilling verification is required to ensure the accuracy of H.

[0014] Preferably, the specific implementation of monitoring the real-time strain ε includes: Deploy the strain monitoring system: Arrange fiber optic strain sensors in a grid pattern on the slopes and bottom of the excavated trench, with a vertical spacing of ≤2m and a horizontal spacing of ≤3m; add vibrating wire strain gauges at key locations on the potential sliding surface, with an installation depth of 0.5m below the expected sliding surface; Data acquisition and processing: Use a strain monitoring system to collect strain data in real time, with a sampling frequency of ≥1Hz; upload vibrating wire strain gauge data using a wireless transmission module, with a transmission interval of ≤5 minutes; calculate the comprehensive strain value ε: , where ε i is the real-time strain value of the i-th measuring point, ε0 is the initial strain value, and n is the number of valid measuring points; Warning: When ε exceeds the warning value ε a , ε a Take 0.1% or σ f Corresponding strain ε f When the working temperature reaches 60%, the sound and light alarm will be triggered automatically and the construction will be suspended.

[0015] Preferably, in step 203, the method for dynamic slope adjustment and model verification includes: S2031. Dynamic slope adjustment: a. Calculate the slope based on the real-time strain ε: the slope of the clay soil is S1 = 1: (0.5-0.1×ε / 0.1%), and the slope of the sandy soil is S2 = 1: (1.0-0.2×ε / 0.1%); b. Slope adjustment is performed through a hydraulically adjustable support device, with the adjustment command taking strain data as the only input parameter; S2032. Model verification and recalibration: a. Compare the model-predicted displacement Δm with the measured displacement Δa. When the deviation rate |Δm-Δa| / Δa>15%, the following operations are automatically triggered: suspend excavation; use the real-time seepage pressure P act , recalibrate the seepage field model with real-time strain ε; continue construction after iterative update until the deviation rate is ≤10%; S2033. When ε / 0.1%>8, start the following steps simultaneously: calculate the anti-slip pile spacing D=2.5-3.0×(1-S1) according to the slope S1, and make the piling equipment construct according to the calculated anti-slip pile spacing D; after the slope adjustment is completed, immediately implement pile reinforcement.

[0016] Preferably, the time coefficient t is in the range of 0.8-1.2 and is dynamically adjusted according to the density of the soil layer: when the soil porosity e≥0.7, t=1.2 is taken; when 0.5≤e<0.7, t=1.0 is taken; when e<0.5, t=0.8 is taken.

[0017] Preferably, the setting of the anti-collision tooth wall meets the following conditions: the tooth wall height h = 0.3 × (Q1 / Q0-1.0) × H0, where H0 is the designed depth of the groove, and the minimum value of h is not less than 0.5m; the tooth wall spacing L = 2.0 × h, in a staggered arrangement.

[0018] Preferably, the fitting of the Mohr-Coulomb criterion adopts a three-parameter method: ,in, tanφ represents friction resistance, c is cohesion, E is deformation modulus, m is strain hardening exponent, and ε through high pressure stage f and σ f Inversion confirmed.

[0019] The present invention has at least the following beneficial effects: First, by combining three-stage hydraulic fracturing tests with dynamic construction, precise control of the permeability characteristics of sandy soils was achieved, effectively addressing the difficulty of traditional static designs in adapting to dynamic soil changes. Excavation depth and slope gradient were adjusted based on real-time seepage and strain data, significantly improving drainage effectiveness and slope stability. A model validation mechanism ensured that construction parameters closely matched actual conditions, reducing project risks. The three-stage hydraulic fracturing tests comprehensively calibrated the soil permeability coefficient, critical fracture pressure, and failure criterion, providing precise input parameters for the numerical model. The dynamic correction mechanism of the finite element model ensured prediction accuracy and provided a reliable basis for construction decision-making. The dynamic correction mechanism for the aquitard top elevation scientifically adjusted design parameters based on changes in permeability coefficient, addressing the disconnect between geological conditions and design issues encountered in traditional methods. Verification mechanisms (geological radar or drilling) further ensured the accuracy of elevation data. Dynamically coupling slope gradient with real-time strain to achieve precise slope adjustment through mathematical relationships ensured safety while avoiding resource waste caused by overdesign. A model recalibration mechanism further optimized slope parameters. The quantitative relationship between the time coefficient and the soil porosity ratio makes excavation depth calculation more scientific and reasonable. Dynamic adjustment of the coefficient based on different densities balances construction efficiency and safety.

[0020] Second, the dynamic design of the filtration layer and drainage body effectively avoids localized clogging or scouring by adjusting the permeability coefficient correction value and the seepage rate ratio. The modular drainage box and layered filtration structure improve the adaptability and durability of the drainage system, extending the service life of the project.

[0021] Third, the integrated strain monitoring system, through a high-density sensor layout and real-time data transmission, enables comprehensive monitoring of slope deformation. An early warning mechanism automatically triggers based on strain thresholds, significantly improving construction safety and mitigating potential landslide risks.

[0022] Fourth, the dynamic correlation between the height and spacing of the anti-scour tooth walls and changes in seepage volume enables precise configuration of protective measures. Minimum height restrictions and staggered layout further enhance anti-scour effects.

[0023] Fifth, the improved Mohr-Coulomb criterion significantly improves the prediction accuracy of failure pressure in sandy soils by introducing a strain hardening term. The three-parameter inversion method ensures the reliability of the criterion parameters, providing a more accurate theoretical basis for slope stability assessment.

[0024] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a flow chart of the backwater side drainage, pressure reduction and anti-seepage method based on an existing sandy soil embankment foundation. DETAILED DESCRIPTION

[0026] The present invention is described in further detail below so that those skilled in the art can implement the invention with reference to the description.

[0027] It should be understood that terms such as “having”, “including” and “comprising” used herein do not preclude the existence or addition of one or more other elements or combinations thereof.

[0028] like Figure 1 As shown, the present invention provides a backwater side drainage, pressure reduction and anti-seepage method based on an existing sandy soil embankment foundation, comprising: S1. Establish the initial seepage field numerical model through three-stage hydraulic fracturing test. The three stages are: S101, low-pressure permeability test stage, to determine the permeability coefficient K0 of the soil foundation; S102, medium-pressure crack detection stage, to calibrate the critical seepage pressure P of crack development. c ; S103, high pressure parameter calibration stage, determine the soil failure criterion σ f ; S2. Trench excavation is carried out in three stages, with each stage dynamically combining hydraulic fracturing testing with construction: S201, first stage excavation: use K0 to determine the initial excavation depth D init =K0×t, where t is the time coefficient; after the excavation is left to stand for 24 hours, the actual seepage volume Q1 is collected; the corrected permeability coefficient K1 is calculated as: K1=K0×(Q1 / Q0)0.3 , where Q0 is the model-predicted seepage rate, and the reference depth D0 is recalculated based on the modified permeability coefficient K1, D0=H+0.5+0.1×((K1-K0) / K0), where H is the elevation of the top of the aquitard after updating based on K1; S202, second stage excavation: dynamically adjust the excavation depth D = D0 + ΔD, ΔD = 0.05 × (P act -P c ) / 10, where ΔD is the dynamic adjustment amount, P act is the real-time seepage pressure, the depth unit is meter, and the seepage pressure unit is kPa; According to the critical seepage pressure P of fracture development c , obtain the initial clay slope S1 init =0.5ln(P c / P0), initial sandy soil slope S2 init =ln(P c / P0), where P0 is the initial pore seepage pressure; after excavation, the excavation was left to stand for 24 hours, and the real-time strain ε was monitored. The average strain in the last 2 hours was taken for the subsequent third-stage slope adjustment; S203, the third stage of excavation: adjust the slope of clay soil to S1 = 1: (0.5-0.1 × ε / 0.1%), the slope of sandy soil to S2 = 1: (1.0-0.2 × ε / 0.1%); according to σ f Verify the final groove morphology, if |Δ m -Δ a | / Δ a >15%, using the latest P act and ε recalibrate the model until |Δ m -Δ a | / Δ a ≤10%, where Δ m is the model predicted displacement, Δ a is the measured displacement; S3. Lay the filter layer, drainage body and anti-scour layer in the trench from bottom to top. The permeability coefficient of the filter layer is the final corrected value of K1, and the opening ratio of the drainage body is adjusted according to the ratio of Q1 / Q0.

[0029] In the above embodiment, in the three-stage hydraulic fracturing test, the head difference in the low-pressure permeability test stage can be set to 0.5-1.0m, and the hydraulic gradient i ranges from 0.1 to 0.3. The critical seepage pressure P in the medium-pressure fracture detection stage is c It can be measured by acoustic wave detection equipment or resistivity imaging instrument, and its value is usually between 50-200kPa. f The ultimate strain can be measured by a triaxial tester. The range is 0.5%-2.0%.

[0030] The test equipment can be selected from existing permeameters, pressure sensors and strain gauges. In terms of materials, standard sandy soil samples can be selected, and their porosity e can be controlled within the range of 0.5-0.9. During the test, the pressure tubes can be installed on the backwater side with a spacing of 2-3m to ensure the accuracy of data collection. After the test is completed, based on K0, P c and σ f The established finite element model can be configured with the upstream side as a constant head boundary and the downstream side as a free seepage boundary. Model parameters are dynamically modified using measured data to ensure that the deviation between the predicted and measured displacements does not exceed 10%.

[0031] Initial depth D of the first stage excavation init =K0×t can be adjusted by the time coefficient t. The value range of t is 0.8-1.2, which is determined by the soil porosity e. When the soil porosity e≥0.7, t=1.2 is taken. When 0.5≤e<0.7, t=1.0 is taken. When e<0.5, t=0.8 is taken. After the excavation is left to stand for 24 hours, the seepage rate Q1 can be measured by a flow meter. The calculation formula of the corrected permeability coefficient K1 is K1=K0×(Q1 / Q0) 0.3 , where K0 is in cm / s, and Q0 and Q1 are in cm 3 / s. It should be noted that after excavation, the water was allowed to stand for 24 hours, during which the seepage rate was continuously monitored. The average value of the last 2 hours was taken as the actual seepage rate Q1. If the fluctuation range was greater than 10%, the standing time was extended until the seepage rate stabilized.

[0032] The dynamic adjustment amount ΔD of the second stage excavation can be calculated by the real-time seepage pressure P act Calculation, ΔD = 0.05 × (P act -P c ) / 10. Slope S1 init and S2 init Through the critical pressure P c and the initial pore pressure P0. A small excavator can be used as excavation equipment, and slope adjustment can be achieved using hydraulic support devices in existing technologies. It should be noted that strain monitoring is initiated immediately after excavation is completed, and data is continuously recorded during a 24-hour standstill period and processed according to the following rules: Initial value ε0: The average strain within 30 minutes of excavation completion is taken; Real-time strain ε: Recorded every 5 minutes during the standstill period. If the strain rate is greater than 0.01% / h, the standstill period is extended; Final value: The average strain of the last 2 hours is taken as ε, which is used for the third stage of slope adjustment.

[0033] During the third phase of excavation, the slope gradient was adjusted based on the strain ε. For clayey soils, the slope gradient S1 was set to 1: (0.5-0.1 × ε / 0.1%), and for sandy soils, the slope gradient S2 was set to 1: (1.0-0.2 × ε / 0.1%). The strain ε was monitored using fiber-optic strain sensors, with spacing ≤2m vertically and ≤3m horizontally.

[0034] The paving of the filter layer can be made of non-woven fabric, the equivalent pore size of which is O 95 The thickness of the coarse sand in the middle layer is 15-20cm, D 15 The porosity of the drainage body can be calculated by the formula φ = φ0× Calculation shows that the foundation opening rate φ0 is 20%.

[0035] The anti-scour layer is composed of dry masonry stone with a thickness of 20-30 cm and a particle size of 20-40 cm. The upper crushed stone cushion is 10 cm thick with a particle size of 5-10 mm. When φ > 22%, the total thickness of the anti-scour layer is increased by 10%. The height of the anti-scour tooth wall is h = 0.3 × (Q1 / Q0 - 1.0) × H0, with a minimum height of no less than 0.5 m. The spacing is L = 2.0 × h, and the teeth are arranged in a staggered pattern.

[0036] It should be noted that the coupling logic of the three-stage excavation and hydraulic fracturing test is as follows: a. Parameter transfer: Each excavation stage calls the output parameters of the corresponding test stage, that is, S201 calls the output parameters of S101, S202 calls the output parameters of S102, and S203 calls the parameters of S103; dynamic feedback: monitoring data after excavation, such as Q1 and ε, are used to correct model parameters to form a closed-loop control; final verification: the failure criterion σ of the high-pressure test f Stability acceptance criteria for direct constraints on groove morphology.

[0037] Technical Results: Through three-stage hydraulic fracturing tests and dynamic excavation, the drainage and pressure reduction process can be precisely controlled to adapt to the dynamic changes in sandy soil permeability. The dynamic design of the filter layer and drainage body prevents localized clogging and scouring, improving the durability of the drainage system. Real-time slope adjustment and strain monitoring ensure construction safety and reduce engineering risks.

[0038] In one specific embodiment, the filter layer, the drainage body and the anti-scour layer are laid in sequence from bottom to top in the trench, specifically: S301, paving the filter layer: a, the lower layer is paved with non-woven fabric, the equivalent pore size is 0 95The value range is 0.07-0.20mm, the gradient ratio GR≤3; the middle layer is paved with medium-coarse sand with a thickness of 15-20cm, D 15 The value range is 0.5-0.8mm, and the mud content is ≤5%; the upper layer is paved with graded crushed stone with a thickness of 10-15cm and a maximum particle size of ≤30mm; b. Overall permeability coefficient K f Take the final correction value of K1, and the allowable deviation is ±10%; when K1>5×10 -1 cm / s, increase the number of non-woven fabric layers to 2; S302. Construction of drainage body: a. Dynamic adjustment of opening ratio: basic opening ratio φ0 = 20%, actual opening ratio φ = φ0× , limited to 15-25%; b. Use modular plastic drainage box, single size 50×50×30cm, drainage box side wall opening diameter d=8-12mm, according to the φ value to adjust the hole distance L= ; S303. Anti-scour layer setting: a. Constructed in two layers, the lower layer is dry masonry block stone with a thickness of 20-30 cm and a block stone particle size of 20-40 cm; the upper layer is a crushed stone cushion layer with a thickness of 10 cm and a particle size of 5-10 mm; b. When φ>22%, the total thickness of the anti-scour layer is increased by 10%. When Q1 / Q0>1.5, an anti-scour tooth wall is added.

[0039] In the above embodiment, the filter layer adopts a three-layer structure: the lower layer can be made of non-woven fabric with an equivalent pore size of O 95 The thickness of the sand is 0.07-0.20mm, and the gradient ratio GR≤3; the middle layer can be paved with medium-coarse sand with a thickness of 15-20cm, D 15 The permeability coefficient of the filter layer is 0.5-0.8mm, and the mud content is ≤5%. The upper layer can be paved with graded gravel with a thickness of 10-15cm and a maximum particle size of ≤30mm. f Take the final correction value of K1, and the allowable deviation is ±10%. -1 cm / s, the number of non-woven fabric layers can be increased to 2.

[0040] For non-woven fabrics, needle-punched geotextiles made of polyester or polypropylene can be used. For medium-coarse sand, natural river sand or machine-made sand can be used. For graded gravel, crushed granite or limestone can be used. When laying the non-woven fabric, it must adhere closely to the bottom and sidewalls of the trench. The medium-coarse sand and gravel layers must be compacted layer by layer, with each layer achieving a compaction level of ≥95%. The filter layer is laid from bottom to top, first with the non-woven fabric, then the medium-coarse sand, and finally the graded gravel. The overlap width of the non-woven fabric can be set to 30-50cm. The medium-coarse sand and gravel can be laid using a small forklift or manual labor.

[0041] The basic opening ratio φ0 of the drainage body can be set to 20%, and the actual opening ratio φ is calculated by the formula φ=φ0× Dynamic adjustment is limited to 15-25%. The drainage body can be a modular plastic drainage box with a single size of 50×50×30cm, a side wall opening diameter d of 8-12mm, and a hole spacing L calculated by the formula L= Calculated and determined. It should be noted that φ=φ0× Based on the principle of seepage-drainage coupled balance, the square root relationship is derived from the square root relationship between flow rate and opening area in the orifice outflow formula, as well as the nonlinear response of soil seepage pressure and drainage velocity. The porosity ratio is limited to 15% to 25% to ensure a balance between structural safety and drainage efficiency.

[0042] Plastic drainage boxes can be made of high-density polyethylene (HDPE) or polypropylene (PP), and the openings on the side walls can be arranged in a plum blossom pattern or rectangular array. The drainage box must be installed in close contact with the filter layer, and the connection between the boxes can be fixed with clips or bolts.

[0043] The porosity can be adjusted by replacing box modules with different hole spacings, or by drilling holes on site. During construction, the porosity should be dynamically selected based on the ratio of the real-time seepage volume Q1 to the model-predicted value Q0 to ensure that drainage capacity matches seepage pressure. The anti-scour layer is constructed in two layers: the lower layer can be paved with 20-30cm thick dry masonry blocks with a particle size of 20-40cm; the upper layer can be paved with a 10cm thick crushed stone cushion with a particle size of 5-10mm. When φ>22%, the total thickness of the anti-scour layer can be increased by 10%. When Q1 / Q0>1.5, anti-scour tooth walls can be added. The tooth wall height is h = 0.3 × (Q1 / Q0 - 1.0) × H0, with a minimum height of no less than 0.5m. The tooth wall spacing is L = 2.0 × h, and the teeth are staggered.

[0044] Basalt or granite can be used for dry masonry, and limestone or quartz sand can be used for the crushed stone base. Stone blocks should be laid with staggered joints, and gaps filled with crushed stone. The crushed stone base should be leveled and compacted, maintaining a 5-10 cm gap from the top of the drainage body. Precast concrete blocks or cast-in-place concrete can be used for the anti-scouring tooth wall, and the tooth wall foundation should be embedded at least 0.5 m into the bottom of the trench. The construction sequence for the anti-scour course is: first lay the dry block stone layer, then lay the crushed stone cushion layer, and finally install the tooth walls as needed. The tooth walls should be arranged perpendicular to the direction of water flow and staggered to disperse the scour force.

[0045] Technical Results: The layered filtration structure and dynamic permeability control effectively prevent fine particle loss and filter layer clogging. The modular drainage box and dynamic adjustment of the aperture ratio enhance the adaptability and maintenance ease of the drainage system. The layered design of the anti-scour layer and the addition of tooth walls enhance scour resistance and extend the project's service life. The overall solution achieves a balance between seepage control and structural stability.

[0046] In one specific embodiment, the initial seepage field numerical model is established through a three-stage hydraulic fracturing test, specifically: S101, low-pressure permeability test stage: drill a hole or set a pressure measuring tube on the backwater side and apply a low-pressure head; record the stable seepage volume Q0 and the corresponding water pressure P0; calculate the foundation permeability coefficient K0 of the soil layer, specifically: , , where A is the cross-sectional area of ​​the water flow, in cm 2 ; i is the hydraulic gradient, dimensionless; is the head difference, in cm, L is the seepage path length, in cm; S102, medium pressure crack detection stage: gradually increase the water pressure to the critical seepage pressure P for crack development c , monitoring the sudden change of seepage volume or strain rate, and locating the fracture area by combining acoustic wave or resistivity imaging; S103, high pressure parameter calibration stage: continue to pressurize to 1.2~1.5 times of the design water head, and record the ultimate strain when the soil fails and breaking pressure , fitting the Mohr-Coulomb criterion; The construction of the initial seepage field numerical model includes: based on K0, P c 、 Establish a finite element model, set the upstream side as the constant head boundary and the downstream side as the free seepage boundary; dynamically modify the model parameters based on the measured data to ensure that the model predicts the displacement Δ m Compared with the measured displacement Δ a The deviation is ≤10%.

[0047] In the above embodiment, the hydraulic head difference during the low-pressure permeability test can be set to 0.5-1.0 m, and the hydraulic gradient i can range from 0.1-0.3. A standard permeameter can be used as the testing equipment, with a graduated cylinder with a precision of 0.1 ml to measure the permeability Q0. The pressure measuring tubes can be 50 mm diameter PVC pipes, installed at intervals of 2-3 m.

[0048] During the test, drill a hole or install a pressure gauge on the backwater side and apply a low-pressure head of 0.5-1.0 m. Once the seepage stabilizes, record the seepage volume Q0 and the corresponding water pressure P0. The permeability coefficient K0 is calculated using the formula K0 = Q0 / (A × i), where A is the cross-sectional area of ​​the water flow and i is the hydraulic gradient. Repeat the test three times and take the average value to ensure data reliability.

[0049] The piezometer should be installed vertically in the soil layer to be tested, with the bottom of the tube at least 0.5 m from the top of the aquitard. The test area should avoid obvious cracks or holes, and at least three measuring points should be arranged for each test section. The hydraulic head must be kept stable during the test, with fluctuations not exceeding ±5%.

[0050] The water pressure in the medium pressure stage can be increased by 10kPa / step until the seepage rate suddenly changes. c The criteria for determining if a seepage rate suddenly increases by more than 50%, or if the strain rate exceeds 0.01% / min. Testing equipment can include a resistivity imager or an acoustic wave detector in conjunction with a vibrating wire strain gauge.

[0051] During the test, gradually increase the water pressure to 50-70% of the design value, and monitor the seepage and strain changes. When a sudden change in seepage or an abnormal strain rate occurs, immediately record the pressure value at that time as P c The fracture area can be located by resistivity imaging or acoustic wave velocity changes, and the imaging resolution should reach 0.1m.

[0052] Strain gauges can be arranged in a 2m x 2m grid across the test area, with a closer grid of 1m x 1m at key locations. The resistivity imager's electrode spacing can be set to 0.5m, with a test frequency of 1-10Hz. Data collection intervals should not exceed 5 minutes, and abnormal data must be reviewed immediately.

[0053] The upper limit of the pressure increase in the high pressure stage can be set to 1.2-1.5 times the design water head. The warning value can be set to 0.5%, breaking pressure The test accuracy should reach ±5kPa. The test equipment can use a triaxial test system with displacement sensors and pressure sensors. It should be noted that the test pressure is 1.2~1.5 times the design water head, which is intended to calibrate the soil failure parameters and is only implemented in a small test area; graded loading (each level ≤20kPa) and real-time monitoring (strain, seepage) are used, and once the failure standard (ε≥0.5% or seepage mutation) is reached, it is stopped immediately; after the test, the damaged area is grouting and reinforced to ensure that it does not affect the overall stability of the embankment foundation; in actual construction, the design water head is taken as 80% of the test value to ensure sufficient safety.

[0054] The pressure is increased by 20kPa / level, and each level is kept stable for 30 minutes. When the strain reaches 0.5% or the pressure reaches a peak, the ultimate strain at this time is recorded. and breaking pressure The Mohr-Coulomb criterion parameters were determined by fitting the three-parameter method, where the test error of the cohesion c did not exceed ±2 kPa, and the error of the internal friction angle φ did not exceed ±1°.

[0055] Specimens can be taken from undisturbed soil drilled on-site, with a diameter of 50 mm and a height of 100 mm. During the test, the strain rate must be controlled at 0.1% / min, and the data sampling frequency must be no less than 1 Hz. Each test group should include three replicate specimens, and the data should be averaged.

[0056] Technical Results: Through a three-stage hydraulic fracturing test, the permeability characteristics, critical fracture development value, and failure parameters of the soil layer can be accurately determined. The basic permeability coefficient obtained during the low-pressure stage provides a basis for subsequent design. The critical pressure determined during the medium-pressure stage can be used to control construction parameters. The failure criterion calibrated during the high-pressure stage provides a theoretical basis for stability assessment. The entire testing method provides reliable data and standardized operation, meeting engineering design requirements.

[0057] In one specific embodiment, the updating of the elevation H of the top plate of the aquitard according to the modified permeability coefficient K1 is specifically as follows: Obtain the original top elevation H0 of the aquitard based on the initial geological exploration data; The elevation adjustment ΔH is calculated by the ratio of the corrected permeability coefficient K1 to the initial permeability coefficient K0, specifically: , where ΔH is in meters and the adjusted aquitard top elevation H = H0 + ΔH; When |ΔH / H0|>5%, geological radar or drilling verification is required to ensure the accuracy of H.

[0058] In the above embodiment, the original roof elevation H0 can be obtained through geological exploration drilling. The drilling holes can be spaced 20-30 meters apart, and the drilling depth should penetrate the aquitard by at least 2 meters. Exploration equipment can be a rotary drill or percussion drill, used in conjunction with a standard soil sampler. Exploration holes should be arranged along the embankment base axis, with spacing increased to 10-15 meters in key areas.

[0059] During exploration, detailed records of the interface elevations of each soil layer are required, particularly the location of the aquitard top. Sampling intervals can be set at 1 meter, increasing to 0.5 meter intervals at locations where soil layers change. Core samples can be sealed in PVC tubes for storage and subjected to indoor permeability tests. Immediately after drilling, the water level in the hole should be observed and the stable water level recorded.

[0060] The original elevation data should include the results of at least three verification drill holes. The average elevation of each hole should be taken as H0, provided the elevation difference between the holes does not exceed 0.3 m. The exploration report must include a drill hole histogram, sampling locations, and field test data to serve as the basis for subsequent design.

[0061] The elevation adjustment ΔH can be calculated using the formula ΔH=0.2×ln(K1 / K0), where K1 is the corrected permeability coefficient and K0 is the initial permeability coefficient. When calculating, the units of K1 and K0 must be unified as cm / s, and the unit of ΔH is meter. When the K1 / K0 ratio is within the range of 0.8-1.2, the absolute value of ΔH generally does not exceed 0.15m. The calculation of the elevation adjustment ΔH is based on the impact of changes in the permeability coefficient on the impermeable performance of the weak permeable layer, and is calculated using the empirical formula ΔH=0.2×ln(K1 / K0). The permeability coefficient ratio K1 / K0 reflects the change in the seepage capacity of the soil layer, and the logarithmic relationship reflects the nonlinear effect; the coefficient 0.2 integrates the soil compressibility, seepage field distribution and engineering safety margin, and comes from the fitting of actual engineering data.

[0062] The permeability coefficient data required for calculation should be derived from field measurements. The average of at least three sets of data should be taken for each section. If the calculated ΔH exceeds 0.5 m, the input parameters must be rechecked. The adjusted elevation H = H0 + ΔH. The calculated result should be rounded to two decimal places; negative values ​​indicate a decrease in elevation.

[0063] For critical engineering locations, ΔH calculations should be reviewed and verified. This can be done using test data from different sections or time periods. If the results differ by more than 0.1 m, the cause should be investigated. The calculation process should include documentation of the source of each parameter and the calculation steps to create a complete technical archive.

[0064] When |ΔH / H0| > 5%, on-site verification is required. Verification equipment can include geological radar or supplemental exploratory drilling. Geological radar can use a 100MHz antenna, and the survey line spacing can be set to 5m, with an increased spacing of 2m in key areas. Supplemental drilling can be located in areas with the largest calculated adjustments, with a minimum number of 20% of the total number of holes.

[0065] Geological radar should survey to a depth of 1 meter below the aquitard, with a data acquisition density of no less than 20 channels / m. Any abnormal areas discovered should be immediately verified by drilling. Sampling and testing requirements for supplementary drilling should be consistent with those for the initial survey, and newly acquired elevation data should be used to correct the H value.

[0066] After verification is complete, the geological model must be updated and the design parameters for each section recalculated. The final elevation value adopted should be a weighted average of the verification results, with weights determined based on data reliability and regional importance. All verification data must be included in the project archive as a basis for construction and acceptance.

[0067] Technical Results: Through a systematic elevation determination and verification method, the spatial distribution characteristics of the aquitard can be accurately determined. The dynamic adjustment mechanism reflects the impact of changes in permeability coefficient on geological conditions, ensuring the reliability of design parameters. A rigorous verification process avoids engineering risks caused by data errors and provides accurate basic data for subsequent construction. This method, with standardized operation and reliable results, is suitable for geological condition assessment of various embankment foundation projects.

[0068] In one specific embodiment, the specific implementation of monitoring the real-time strain ε includes: Deploy the strain monitoring system: Arrange fiber optic strain sensors in a grid pattern on the slopes and bottom of the excavated trench, with a vertical spacing of ≤2m and a horizontal spacing of ≤3m; add vibrating wire strain gauges at key locations on the potential sliding surface, with an installation depth of 0.5m below the expected sliding surface; Data acquisition and processing: Use a strain monitoring system to collect strain data in real time, with a sampling frequency of ≥1Hz; upload vibrating wire strain gauge data using a wireless transmission module, with a transmission interval of ≤5 minutes; calculate the comprehensive strain value ε: , where ε i is the real-time strain value of the i-th measuring point, ε0 is the initial strain value, and n is the number of effective measuring points; Warning: When ε exceeds the warning value ε a , ε a Take 0.1% or σ f Corresponding strain ε f When the working temperature reaches 60%, the sound and light alarm will be triggered automatically and the construction will be suspended.

[0069] In the above embodiment, the strain monitoring system can deploy fiber optic strain sensors in a grid pattern, with vertical spacing no greater than 2 meters and horizontal spacing no greater than 3 meters. Vibrating-wire strain gauges can be installed at key locations along the potential sliding surface, at a depth of 0.5 meters below the anticipated sliding surface. These sensors can be fiber Bragg grating (FBG) or resistance strain gauges, with a measurement range of 0-5000 με.

[0070] Sensors must be calibrated before installation, with an error controlled within ±1%. Fiber optic sensors can be laid out in an S-shaped pattern along the trench slope and secured with a dedicated clamp. Vibrating wire strain gauges can be installed in the borehole, backfilled with a material similar in properties to the original ground. All sensor cables must be waterproofed and protected with protective casing.

[0071] The monitoring section should cover the entire excavation area, with key monitoring areas including slope turning points, soil interface, and areas of concentrated seepage. Each monitoring section should have at least three measuring points, forming a three-dimensional monitoring network. Initial sensor values ​​should be collected after sensor installation to serve as a baseline for subsequent data processing.

[0072] The data acquisition system can utilize a distributed fiber optic demodulator or a multi-channel vibrating wire data acquisition instrument, with a sampling frequency of at least 1 Hz. Vibrating wire strain gauge data can be uploaded via a wireless transmission module, with a transmission interval of no more than 5 minutes. The acquisition equipment should have local storage capabilities with sufficient storage capacity for 30 days of continuous monitoring.

[0073] The real-time strain value ε is calculated by the formula, where ε i is the real-time strain value at the i-th measuring point, ε0 is the initial strain value, and n is the number of valid measuring points. Data with obvious abnormalities must be excluded during calculation, and data with fluctuations exceeding ±10% must be manually reviewed. The comprehensive strain value is updated every 5 minutes, and historical data is fully preserved.

[0074] Data processing software can include automatic filtering capabilities, using a sliding average method to eliminate short-term fluctuations. Strain curves and cumulative deformation reports are generated daily, with key data displayed in real time on the monitoring terminal. All raw data must be backed up and stored for at least the project warranty period.

[0075] Warning threshold ε a Can be set to 0.1% or σ f Corresponding strain ε f 60% of the above, whichever is smaller. a When the alarm is triggered, the system will automatically trigger the sound and light alarm and display the warning location on the monitoring terminal. The alarm signal will be sent to the mobile terminal of relevant personnel at the same time, and the response time will not exceed 1 minute. a Take σ f Corresponding strain ε f 60% of the total soil pressure, because the soil enters the stage of accelerated plastic deformation after exceeding this value, and timely intervention is required.

[0076] When an alert is triggered, construction should be suspended immediately and the emergency plan activated. Technical personnel should arrive on-site within 30 minutes to verify and confirm the cause of the alert. The alert can be lifted only if the strain level remains stable and below 90% of the threshold for two consecutive hours. Each alert event must be recorded in detail, including the trigger time, location, strain level, and response measures.

[0077] The early warning system can set up a multi-level response mechanism and take different measures according to the degree of strain exceeding the limit. a ) Only need to strengthen monitoring, level 2 warning (ε≥ε a ) Construction must be suspended. The system must be tested and drilled monthly to ensure that all links respond normally.

[0078] Technical Results: A high-density strain monitoring network provides comprehensive visibility into soil deformation during construction. A real-time data processing system promptly detects abnormal changes, providing a basis for engineering decision-making. A tiered early warning mechanism ensures project safety while avoiding unnecessary downtime. The entire system operates stably, provides reliable data, and effectively mitigates construction risks.

[0079] In one specific embodiment, in step 203, the method for dynamic slope adjustment and model verification includes: S2031. Dynamic slope adjustment: a. Calculate the slope based on the real-time strain ε: the slope of the clay soil is S1 = 1: (0.5-0.1×ε / 0.1%), and the slope of the sandy soil is S2 = 1: (1.0-0.2×ε / 0.1%); b. Slope adjustment is performed through a hydraulically adjustable support device, with the adjustment command taking strain data as the only input parameter; S2032. Model verification and recalibration: a. Compare the model-predicted displacement Δm with the measured displacement Δa. When the deviation rate |Δm-Δa| / Δa>15%, the following operations are automatically triggered: suspend excavation; use the real-time seepage pressure P act , recalibrate the seepage field model with real-time strain ε; continue construction after iterative update until the deviation rate is ≤10%; S2033. When ε / 0.1%>8, start the following steps simultaneously: calculate the anti-slip pile spacing D=2.5-3.0×(1-S1) according to the slope S1, and make the piling equipment construct according to the calculated anti-slip pile spacing D; after the slope adjustment is completed, immediately implement pile reinforcement.

[0080] In the above implementation, slope adjustment is based on real-time strain ε calculation. For clayey soils, the slope S1 can be adjusted according to a ratio of 1:(0.5-0.1 × ε / 0.1%), while for sandy soils, the slope S2 can be adjusted according to a ratio of 1:(1.0-0.2 × ε / 0.1%). Adjustment can be performed using a hydraulically adjustable support device with a stroke accuracy of ±1 cm and a maximum thrust of no less than 50 kN. Slope adjustment instructions are derived directly from strain monitoring data, without manual intervention.

[0081] Hydraulic support devices are deployed every 3 meters along the slope, operating synchronously via a central control system. Adjustment is performed using a graded loading method, with each adjustment not exceeding 5% of the design value, and adjustment intervals of at least 30 minutes. Each adjustment requires a two-hour wait for strain to stabilize before the next round of data collection and calculation. The hydraulic support devices utilize existing technology.

[0082] The slope adjustment range should be controlled within ±20% of the initial design value. If the calculated adjustment exceeds this range, an expert evaluation process should be initiated. Adjusted slope surfaces should be promptly covered with an impermeable membrane to prevent rainwater infiltration and affect the accuracy of monitoring data.

[0083] The model validation standard is set to |Δm-Δa| / Δa≤10%. When the deviation exceeds 15%, the recalibration procedure is automatically triggered. Finite element analysis software can be used for recalibration. The input parameters include the real-time seepage pressure P act The computing server configuration should meet the requirements of 8-core CPU, 32GB memory, and a single computing time should be controlled within 30 minutes.

[0084] The recalibration process begins by freezing the current construction state and collecting the latest monitoring data. Model parameters such as the permeability coefficient and elastic modulus are then updated, and the predicted displacement Δm is recalculated. The calculation is iterated until the deviation requirements are met, with a maximum of three iterations. The results of each iteration are graphically compared with the on-site monitoring data.

[0085] After the model is updated, a detailed parameter adjustment report must be generated, documenting the parameter changes and the computational convergence process. All excavation operations are suspended during the recalibration period, but the monitoring system remains operational. Once verified, the new parameters are immediately applied to subsequent construction guidance.

[0086] When ε / 0.1%>8, the anti-slip pile reinforcement program is automatically started. The anti-slip pile spacing D can be calculated as D=2.5-3.0×(1-S1), the pile diameter can be selected as 300-500mm, and the pile length should be at least 2m deep into the stable soil layer. The piling equipment can be a static pressure pile driver or a rotary drilling rig, and the construction accuracy is controlled within ±5cm. It should be noted that in the formula for the anti-slip pile spacing D, the essence of S1 is the m value in the slope ratio, that is, m=0.5-0.1×ε / 0.1%. Therefore, the S1 value in the formula should take this m value, ε / 0.1% is a dimensionless ratio, and the m value range must be constrained to m≥0.3 to avoid slopes steeper than 1:0.3. The unit of the anti-slip pile spacing D is meter.

[0087] Anti-slip piles can be precast concrete or steel pipe piles, with a pile strength grade of at least C30. Piles should be positioned away from monitoring sensors, with a minimum clearance of at least 1 meter. Piling should be carried out from the toe of the slope to the top, with daily construction progress not exceeding 20% ​​of the designed total.

[0088] After the pile is installed, the pile top coupling beam should be constructed within 24 hours. This coupling beam can be cast-in-place reinforced concrete, with a cross-section no less than 300mm x 400mm. Three additional monitoring sections should be established in the reinforced area, with the monitoring frequency increased to every 15 minutes for seven consecutive days.

[0089] Technical Results: The dynamic slope adjustment mechanism optimizes slope morphology based on actual deformation conditions, enhancing stability. The automated model validation process ensures the accuracy of the numerical model, providing a reliable basis for construction decision-making. The tiered, triggered anti-slide pile reinforcement measures effectively mitigate significant landslide risks. The entire system achieves a closed-loop management system for monitoring, analysis, and action, enhancing project safety control.

[0090] In one specific embodiment, the setting of the anti-collision tooth wall meets the following conditions: the tooth wall height h=0.3×(Q1 / Q0-1.0)×H0, where H0 is the designed depth of the groove, and the minimum value of h is not less than 0.5m; the tooth wall spacing L=2.0×h, in a staggered arrangement.

[0091] In the above embodiment, the height h of the impact wall can be calculated using the formula h = 0.3 × (Q1 / Q0 - 1.0) × H0, where H0 is the designed trench depth and the minimum height limit is 0.5m. The calculation parameters Q1 are the actual seepage rate, and Q0 are the model-predicted seepage rate. Both must be expressed in m³ / s. The calculated height is rounded to the nearest 0.1m. If the calculated value is less than 0.5m, the value of 0.5m is mandatory.

[0092] The tooth wall can be constructed using C25 cast-in-place concrete or precast concrete blocks with a strength grade of at least MU20. The concrete mix should contain at least 300 kg / m³ of cement, and the maximum aggregate size should not exceed 40 mm. Steel formwork can be used for cast-in-place construction, and the formwork rigidity must ensure deformation does not exceed 1 / 500 of the span.

[0093] The height measurement reference point is the bottom of the trench, and the construction layout error is controlled within ±2cm. The elevation of the tooth wall top surface must take into account the thickness of the subsequent anti-scour layer, and reserve sufficient elevation difference. A height inspection section is set every 10 meters, and the elevation is verified using a level.

[0094] The spacing between tooth walls (L) is calculated as L = 2.0 × h, rounded to the nearest 0.5m. The minimum spacing must not be less than 1.0m, and the maximum spacing should not exceed 3.0m. Spacing adjustment should take into account the direction and velocity of the water flow, and may be increased appropriately in special locations such as bends.

[0095] Spacing can be determined using a total station or theodolite, with a positioning error of no more than ±3cm. The spacing between adjacent tooth walls should be within ±5%. During construction, the axis position should be marked first, and then the centerline of each tooth wall should be calibrated based on the calculated results. Control stakes should be installed at key locations to facilitate verification during construction.

[0096] In sections with significant seepage rate fluctuations, different spacing values ​​can be used in sections. The transition zone should be at least three times the spacing variation to avoid sudden changes in flow. Spacing adjustment records should clearly indicate the reason for the adjustment and the specific parameters.

[0097] The tooth walls are staggered, with adjacent rows spaced 0.5L apart. They can be rectangular or trapezoidal in cross-section, with a top width of at least 0.3m and a base width 0.6-0.8 times the height. The tooth walls must be embedded at least 0.3m deep into the trench bottom, and the backfill material must have the same compaction as the surrounding soil.

[0098] Construction should proceed against the flow of water, starting downstream and then upstream. Concrete pouring should be continuous, and construction joints should be provided with mortise and tenon joints or dowels. Curing should last no less than seven days, and the surface should be kept moist during curing. A rubber waterstop with a width of at least 30 cm should be installed at the joint between the tooth wall and the drainage body.

[0099] After completion, a water flushing test is required to verify the tooth wall's scour resistance. The test water flow rate should be controlled within 80%-120% of the design value, and the duration should be no less than 2 hours. Check the tooth wall for obvious signs of scour, and the displacement monitoring value should not exceed 3mm.

[0100] Technical Results: The tooth wall height calculated using a formula can adapt to varying seepage conditions, and the minimum height limit ensures basic protection effectiveness. A scientific spacing determination method ensures the continuity of the protection system and avoids gaps in protection. The staggered layout effectively disperses the impact of water flow and improves overall anti-impact stability. The flexible choice of cast-in-place or prefabricated construction methods can meet the needs of different project conditions. The entire protection system has controllable construction quality and reliable protection effectiveness.

[0101] In one embodiment, the fitting of the Mohr-Coulomb criterion adopts a three-parameter method: ,in, tanφ represents friction resistance, is normal stress, c is cohesion, E is deformation modulus, m is strain hardening exponent, and ε through high pressure stage f and σ f Inversion confirmed.

[0102] In the above embodiment, the Mohr-Coulomb criterion is expressed using a three-parameter method, including friction resistance tanφ, cohesion c, and deformation modulus E. The friction angle φ can be set in the range of 25°-35°, and the cohesion c can be set in the range of 5-20 kPa. The deformation modulus E can be set in the range of 50-200 MPa depending on the soil type, and the strain hardening exponent m can be set in the range of 0.3-0.7.

[0103] The test equipment can be a triaxial apparatus or a direct shear apparatus. The pressure sensor has a range of 0-500kPa and an accuracy of ±0.5%FS. The displacement sensor can have a resolution of up to 0.01mm, meeting the requirements for measuring small strains. The test system can be equipped with an automatic data acquisition device with a sampling frequency of at least 10Hz.

[0104] Samples should be prepared from undisturbed or remolded soil, with diameters of 50 mm or 100 mm, maintaining a 2:1 height-to-diameter ratio. Sample saturation can be achieved using either the vacuum saturation method or the backpressure saturation method, with a saturation level of at least 95%. At least three replicate samples should be prepared for each test to ensure data reliability.

[0105] Parameter inversion is based on ε in the high pressure stage f and σ f The data is fitted using the least squares method. Geotechnical engineering analysis software can be used for inverse calculations, with the number of iterations set to 50-100 and the convergence criterion set to a residual sum of squares less than 0.01. Initial parameter values ​​can be selected based on empirical data from geotechnical tests.

[0106] During the inversion process, first, fix φ and optimize c and E. Then, fix c and optimize φ and E. Finally, adjust all three parameters comprehensively. After each iteration, calculate the correlation coefficient between the predicted curve and the measured data, with an R² ≥ 0.9. Parameter sensitivity analysis can determine the influence of each parameter on the fitting results.

[0107] Inversion results must be validated using independent samples tested under identical conditions, with prediction errors kept within ±5%. The coefficient of variation for the key parameters c and φ should not exceed 15%, otherwise resampling and testing are required. The final parameter value should be the average of the three inversion results.

[0108] The pressure applied in the high pressure test is 1.2-1.5 times the design water head, and the loading rate can be controlled at 5kPa / min. f The threshold is set at 0.5%, and the test is terminated when this value is reached or the stress drops significantly. Data collection should include the stress-strain curve and pore water pressure changes throughout the entire process.

[0109] During the test, the strain values ​​corresponding to the initial yield point, peak strength, and residual strength should be recorded. Each strain stage should be maintained for at least 10 minutes to observe the deformation trend. Immediately after the test, samples should be taken to measure moisture content and density and analyze changes in soil structure.

[0110] When applying high-pressure data to modify the finite element model, it must be converted into equivalent nodal force and displacement boundary conditions. Eight-node hexahedral elements can be used as the element type in the model, and integration points should be set to account for strain localization. After updating parameters, the safety factor must be recalculated to verify slope stability.

[0111] Technical Results: The three-parameter criterion better reflects the strain hardening characteristics of sandy soils than traditional methods, improving the accuracy of failure pressure prediction. A systematic inversion method ensures scientific parameter determination and avoids bias due to human experience. The full utilization of high-pressure test data provides a reliable basis for numerical simulation. The entire method is standardized and produces reproducible results, making it suitable for stability analysis of various sandy soil embankment foundations.

[0112] The number of devices and processing scales described herein are intended to simplify the description of the present invention. Applications, modifications, and variations of the present invention will be readily apparent to those skilled in the art.

[0113] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to specific details.

Claims

1. A backwater side drainage, pressure reduction and anti-seepage method based on an existing sandy soil embankment foundation, characterized in that: include: S1. Establish the initial seepage field numerical model through three-stage hydraulic fracturing test. The three stages are: S101, low-pressure permeability test stage, to determine the permeability coefficient K0 of the soil foundation; S102, medium-pressure crack detection stage, to calibrate the critical seepage pressure P of crack development. c ; S103, high pressure parameter calibration stage, determine the soil failure criterion σ f ; S2. Trench excavation is carried out in three stages, with each stage dynamically combining hydraulic fracturing testing with construction: S201, first stage excavation: use K0 to determine the initial excavation depth D init =K0×t, where t is the time coefficient; after the excavation is left to stand for 24 hours, the actual seepage volume Q1 is collected; the corrected permeability coefficient K1 is calculated as: K1=K0×(Q1 / Q0) 0.3 , where Q0 is the model-predicted seepage rate, and the reference depth D0 is recalculated based on the modified permeability coefficient K1, D0=H+0.5+0.1×((K1-K0) / K0), where H is the elevation of the top of the aquitard after updating based on K1; S202, second stage excavation: dynamically adjust the excavation depth D = D0 + ΔD, ΔD = 0.05 × (P act -P c ) / 10, where ΔD is the dynamic adjustment amount, P act is the real-time seepage pressure, the depth unit is meter, and the seepage pressure unit is kPa; According to the critical seepage pressure P of fracture development c , obtain the initial clay slope S1 init =0.5ln(P c / P0), initial sandy soil slope S2 init =ln(P c / P0), where P0 is the initial pore seepage pressure; after excavation, the excavation was left to stand for 24 hours, and the real-time strain ε was monitored. The average strain in the last 2 hours was taken for the subsequent third-stage slope adjustment; S203, the third stage of excavation: adjust the slope of clay soil to S1 = 1: (0.5-0.1 × ε / 0.1%), the slope of sandy soil to S2 = 1: (1.0-0.2 × ε / 0.1%); according to σ f Verify the final groove morphology, if |Δ m -Δ a | / Δ a >15%, using the latest P act and ε recalibrate the model until |Δ m -Δ a | / Δ a ≤10%, where Δ m is the model predicted displacement, Δ a is the measured displacement; S3. Lay the filter layer, drainage body and anti-scour layer in the trench from bottom to top. The permeability coefficient of the filter layer is the final corrected value of K1, and the opening ratio of the drainage body is adjusted according to the ratio of Q1 / Q0.

2. The backwater side drainage, pressure reduction and anti-seepage method based on an existing sandy soil embankment foundation according to claim 1, characterized in that: The filter layer, drainage body and anti-scour layer are laid in the trench from bottom to top, specifically: S301, paving the filter layer: a, the lower layer is paved with non-woven fabric, the equivalent pore size is 0 95 The value range is 0.07-0.20mm, the gradient ratio GR≤3; the middle layer is paved with medium-coarse sand with a thickness of 15-20cm, D 15 The value range is 0.5-0.8mm, and the mud content is ≤5%; the upper layer is paved with graded crushed stone with a thickness of 10-15cm and a maximum particle size of ≤30mm; b. Overall permeability coefficient K f Take the final correction value of K1, and the allowable deviation is ±10%; when K1>5×10 -1 cm / s, increase the number of non-woven fabric layers to 2; S302. Construction of drainage body: a. Dynamic adjustment of opening ratio: basic opening ratio φ0 = 20%, actual opening ratio φ = φ0× , limited to 15-25%; b. Use modular plastic drainage box, single size 50×50×30cm, drainage box side wall opening diameter d=8-12mm, according to the φ value to adjust the hole distance L= ; S303. Anti-scour layer setting: a. Constructed in two layers, the lower layer is dry masonry block stone with a thickness of 20-30 cm and a block stone particle size of 20-40 cm; the upper layer is a crushed stone cushion layer with a thickness of 10 cm and a particle size of 5-10 mm; b. When φ>22%, the total thickness of the anti-scour layer is increased by 10%. When Q1 / Q0>1.5, an anti-scour tooth wall is added.

3. The backwater side drainage, pressure reduction and anti-seepage method based on an existing sandy soil embankment foundation according to claim 1, characterized in that: The initial seepage field numerical model is established through the three-stage hydraulic fracturing test, specifically: S101, low-pressure permeability test stage: drill a hole or set a pressure measuring tube on the backwater side and apply a low-pressure head; record the stable seepage volume Q0 and the corresponding water pressure P0; calculate the foundation permeability coefficient K0 of the soil layer, specifically: , , where A is the cross-sectional area of ​​the water flow, i is the hydraulic gradient, is the head difference, L is the seepage path length; S102, medium pressure crack detection stage: gradually increase the water pressure to the critical seepage pressure P for crack development c , monitoring the sudden change of seepage volume or strain rate, and locating the fracture area by combining acoustic wave or resistivity imaging; S103, high pressure parameter calibration stage: continue to pressurize to 1.2~1.5 times of the design water head, and record the ultimate strain when the soil fails and breaking pressure , fitting the Mohr-Coulomb criterion; The construction of the initial seepage field numerical model includes: based on K0, P c 、 Establish a finite element model, set the upstream side as the constant head boundary and the downstream side as the free seepage boundary; dynamically modify the model parameters based on the measured data to ensure that the model predicts the displacement Δ m Compared with the measured displacement Δ a The deviation is ≤10%.

4. The backwater side drainage, pressure reduction and anti-seepage method based on an existing sandy soil embankment foundation according to claim 1, characterized in that: The above method of updating the elevation H of the aquitard top according to the modified permeability coefficient K1 is as follows: Obtain the original top elevation H0 of the aquitard based on the initial geological exploration data; The elevation adjustment ΔH is calculated by the ratio of the corrected permeability coefficient K1 to the initial permeability coefficient K0, specifically: , where ΔH is in meters and the adjusted aquitard top elevation H = H0 + ΔH; When |ΔH / H0| > 5%, verification by geological radar or drilling is required to ensure the accuracy of H.

5. The backwater side drainage, pressure reduction and anti-seepage method based on an existing sandy soil embankment foundation according to claim 1, characterized in that: The specific implementation of monitoring the real-time strain ε includes: Deploy the strain monitoring system: Arrange fiber optic strain sensors in a grid pattern on the slopes and bottom of the excavated trench, with a vertical spacing of ≤2m and a horizontal spacing of ≤3m; add vibrating wire strain gauges at key locations on the potential sliding surface, with an installation depth of 0.5m below the expected sliding surface; Data acquisition and processing: Use a strain monitoring system to collect strain data in real time, with a sampling frequency of ≥1Hz; upload vibrating wire strain gauge data using a wireless transmission module, with a transmission interval of ≤5 minutes; calculate the comprehensive strain value ε: , where ε i is the real-time strain value of the i-th measuring point, ε0 is the initial strain value, and n is the number of effective measuring points; Warning: When ε exceeds the warning value ε a , ε a Take 0.1% or σ f Corresponding strain ε f When the working temperature reaches 60%, the sound and light alarm will be triggered automatically and the construction will be suspended.

6. The backwater side drainage, pressure reduction and anti-seepage method based on an existing sandy soil embankment foundation according to claim 3, characterized in that: In step 203, the slope gradient dynamic adjustment and model verification method includes: S2031. Dynamic slope adjustment: a. Calculate the slope based on the real-time strain ε: the slope of the clay soil is S1 = 1: (0.5-0.1×ε / 0.1%), and the slope of the sandy soil is S2 = 1: (1.0-0.2×ε / 0.1%); b. Slope adjustment is performed through a hydraulically adjustable support device, with the adjustment command taking strain data as the only input parameter; S2032. Model verification and recalibration: a. Compare the model-predicted displacement Δm with the measured displacement Δa. When the deviation rate |Δm-Δa| / Δa>15%, the following operations are automatically triggered: suspend excavation; use the real-time seepage pressure P act , recalibrate the seepage field model with real-time strain ε; continue construction after iterative update until the deviation rate is ≤10%; S2033. When ε / 0.1%>8, start the following steps simultaneously: calculate the anti-slip pile spacing D=2.5-3.0×(1-S1) according to the slope of the clay slope S1, and make the piling equipment construct according to the calculated anti-slip pile spacing D; after the slope adjustment is completed, immediately implement pile reinforcement.

7. The backwater side drainage, pressure reduction and anti-seepage method based on an existing sandy soil embankment foundation according to claim 1, characterized in that: The time coefficient t has a value range of 0.8-1.2 and is dynamically adjusted according to the density of the soil layer: when the soil porosity e≥0.7, t=1.2 is taken; when 0.5≤e<0.7, t=1.0 is taken; when e<0.5, t=0.8 is taken.

8. The backwater side drainage, pressure reduction and anti-seepage method based on an existing sandy soil embankment foundation according to claim 2, characterized in that: The setting of the anti-collision tooth wall meets the following conditions: the tooth wall height h=0.3×(Q1 / Q0-1.0)×H0, where H0 is the designed depth of the groove, and the minimum value of h is not less than 0.5m; the tooth wall spacing L=2.0×h, and is staggered.

9. The backwater side drainage, pressure reduction and anti-seepage method based on an existing sandy soil embankment foundation according to claim 3, characterized in that: The fitting of the Mohr-Coulomb criterion adopts the three-parameter method: ,in, tanφ represents friction resistance, c is cohesion, E is deformation modulus, m is strain hardening exponent, and ε through high pressure stage f and σ f Inversion confirmed.

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