Preparation method of composite geotextile

Abstract

The invention discloses a preparation method of composite geotechnical cloth, belongs to the technical field of geotechnical material processing, and solves the problems of insufficient interlayer bonding strength, poor permeation stability and incapability of adapting to regional differentiation mechanical requirements in the traditional process. According to the method, two layers of synthetic fiber geotextile and a layer of polymer geomembrane are selected, and a gradient needling machine is adopted to implement a double-station gradient needling process, specifically, thick needle needling pre-reinforcement is synchronously conducted on the upper side and the lower side till the membrane thickness is 50-60% of the depth, then fine needle needling finishing is conducted till the membrane thickness is 70-80% of the depth, the needling density is preset to be 20-70 needles / cm according to different stress areas of a membrane material, and the needling density is 20-70 needles / cm according to different stress areas of the membrane material; in the process, data of needling depth, needling density and membrane material tension are collected in real time through a dynamic monitoring system, parameters are automatically adjusted, and finally a stable structure is formed through heat setting treatment at 120-140 DEG C for 8-12 minutes. The composite geotextile prepared by the method has a high-strength bonding interface and excellent anti-seepage performance, and is suitable for the engineering fields of water conservancy project anti-seepage, road base reinforcement, refuse landfill isolation and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of geotechnical material processing. More specifically, the present invention relates to a preparation method of a composite geotextile. Background Art

[0002] In the field of civil engineering, composite geotextiles are widely used in engineering scenarios such as anti-seepage, isolation, and reinforcement. Traditional composite geotextiles mostly adopt single-layer needling or hot pressing composite processes, but there are problems such as insufficient interfacial bonding strength and poor seepage stability. Especially in water conservancy projects, due to the long-term action of water pressure and soil stress, the existing products often show the phenomenon of delamination between the polymer film and the fabric, resulting in a sharp decline in the anti-seepage performance. Analysis shows that the traditional needling process uses single-direction and single-time needling, which cannot form an effective three-dimensional bonding structure. The single setting of the needling depth and density is difficult to adapt to the stress distribution differences in different regions, leading to premature failure in weak areas. In addition, the parameter control of the heat setting process is rough, and the uneven temperature field distribution is likely to cause material shrinkage and deformation, affecting the dimensional stability of the final product. The existing technology attempts to improve the performance by increasing the needling density or adopting a multi-layer composite structure, but excessive needling will damage the continuity of the polymer film, instead reducing the anti-seepage effect. How to achieve high-strength bonding while ensuring the integrity of the polymer film and taking into account the mechanical property requirements of different regions has become an urgent technical problem to be solved. During the production process, due to the complex non-linear relationship between the needling process parameters and the product performance, the traditional empirical parameter setting method is difficult to achieve precise control, resulting in a product qualification rate of less than 70%. The existing dynamic monitoring systems mostly use a single sensor for off-line detection and cannot provide real-time feedback to adjust the process parameters, seriously affecting the production efficiency and product consistency. Summary of the Invention

[0003] An object of the present invention is to provide a preparation method of a composite geotextile, which solves the problems of single needling process in the preparation process of traditional composite geotextiles, resulting in insufficient interfacial bonding strength, poor seepage stability, and inability to meet the differentiated mechanical property requirements of different engineering regions.

[0004] To achieve these objects and other advantages of the present invention, according to one aspect of the present invention, there is provided a preparation method of a composite geotextile, comprising the following steps: Step 1: Select two layers of synthetic fiber geotextiles with a unit area mass of 100 - 300 g / m² and a breaking strength greater than 15 kN / m, and a polymer geotextile membrane with a thickness of 0.5 - 3.0 mm and a permeability coefficient less than 1×10⁻¹ 3 cm / s; Step 2: Stack two layers of synthetic fiber geotextiles on the upper and lower surfaces of the high molecular geomembrane respectively, and then send them to a gradient needle punching machine. Adopt a double-station gradient needle punching process to simultaneously perform rough needle punching pre-reinforcement from both the upper and lower sides. The needle punching depth is 50 - 60% of the thickness of the high molecular geomembrane. Then, simultaneously perform fine needle punching finishing from both the upper and lower sides. The needle punching depth is 70 - 80% of the thickness of the high molecular geomembrane. The needle punching density is preset according to the force requirements of different regions of the high molecular geomembrane. And during the needle punching composite process, adjust the needle punching parameters in real time through a dynamic monitoring system; Step 3: Perform heat setting treatment on the needle punched composite geotextile. The heat setting temperature is controlled at 120 - 140 °C and the time is 8 - 12 min. Then perform surface treatment on the heat set geotextile to finally obtain the composite geotextile.

[0005] Preferably, the material of the synthetic fiber geotextile is polyester fiber, and the material of the high molecular geomembrane is high density polyethylene.

[0006] Preferably, in the Step 2, the preset values of the needle punching density are as follows: Divide the high molecular geomembrane into a core stress area, an edge strengthening area, a weak and sensitive area, and a conventional area; among them, The preset value of the needle punching density in the core stress area is 35 - 45 needles / cm², and an orthogonal cross needle punching path is adopted; The preset value of the needle punching density in the edge strengthening area is 50 - 60 needles / cm², and a spiral progressive needle punching path is adopted; The preset value of the needle punching density in the weak and sensitive area is 60 - 70 needles / cm², and an annular encryption needle punching path is adopted; The conventional area is the main part except for the above special areas, accounting for 60 - 70% of the total area of the high molecular geomembrane. The preset value of the needle punching density is 20 - 30 needles / cm², and a uniform parallel needle punching path is adopted.

[0007] Preferably, the stitch pitch of the orthogonal cross needle punching path is 5 - 8 mm and the angle is 90°; the stitch pitch of the spiral progressive needle punching path is 3 - 5 mm and the spiral radius increases; the annular radius of the annular encryption needle punching path is 1 - 2 mm; the stitch pitch of the uniform parallel needle punching path is 10 - 15 mm.

[0008] Preferably, the dynamic monitoring system includes a displacement sensor installed on the side of the needle punching needle base of the needle punching machine for real-time monitoring of the needle punching depth, an industrial camera installed directly above the needle punching machine for detecting the distribution density of the needle punching points through an image recognition algorithm, and a tension sensor installed at both ends of the conveying roller shaft of the high molecular geomembrane for real-time monitoring of the film tension.

[0009] Preferably, the dynamic monitoring system collects the acupuncture depth, acupuncture density, and the tension of the high molecular geotextile in real time, and regularly samples and tests the composite geotextile to obtain its breaking strength, permeability coefficient, and peel strength. These data and the collected acupuncture depth, acupuncture density, and the tension of the high molecular geotextile are processed by data normalization through an industrial Internet platform to establish a prediction model based on the BP neural network. The training sample size of the prediction model is ≥1000 groups, and R²≥0.95. The quality of the composite geotextile is predicted by analyzing the output results of the model in real time. When the prediction result exceeds the preset control range, the system automatically adjusts the acupuncture parameters.

[0010] Preferably, the adjustment method of the acupuncture parameters is specifically as follows: Adjustment of acupuncture depth: According to the deviation between the prediction result and the control range, it is adjusted in steps of 0.02 mm, and the maximum adjustment range is set to ±0.2 mm, and the adjustment period is 3 min. If the predicted breaking strength is lower than the control lower limit, the acupuncture depth is increased by 0.02 mm. If the predicted permeability coefficient is lower than the control lower limit, the acupuncture depth is decreased by 0.02 mm. Adjustment of acupuncture density: The acupuncture density is changed by adjusting the motor speed of the acupuncture machine through a frequency converter. The adjustment range based on the reference speed is ±15%. If the predicted breaking strength or peel strength is lower than the control lower limit, the running speed of the acupuncture machine is increased, and the speed increase ratio is 10%. If the predicted permeability coefficient is lower than the control lower limit, the running speed of the acupuncture machine is decreased, and the speed reduction ratio is 10%. Adjustment of the tension of the high molecular geotextile: It is adjusted according to the deviation between the prediction result and the control range. If the predicted peel strength is lower than the control lower limit, the tension of the high molecular geotextile is increased by 5 N. If the predicted permeability coefficient is lower than the control lower limit, the tension of the high molecular geotextile is decreased by 3 N.

[0011] Preferably, the adjustment method of the acupuncture parameters has a priority mechanism, specifically: setting the control lower limit and upper limit of the permeability coefficient, the control lower limit of the breaking strength, and the control lower limit of the peel strength; when the predicted permeability coefficient is less than the control lower limit or greater than the control upper limit, the predicted breaking strength is less than the control lower limit, and the predicted peel strength is less than the control lower limit, the corresponding indicators are respectively determined to be abnormal; When multiple abnormalities occur simultaneously, the parameter adjustment is performed in the priority order of permeability coefficient abnormality > breaking strength abnormality > peel strength abnormality; If the permeability coefficient is abnormal, the acupuncture parameters are adjusted in the order of the tension of the high molecular geotextile, acupuncture depth, and acupuncture density; if the permeability coefficient is normal and the breaking strength is abnormal, the acupuncture parameters are adjusted in the order of acupuncture depth, acupuncture density, and the tension of the high molecular geotextile; if the permeability coefficient and breaking strength are also normal and the peel strength is abnormal, the acupuncture parameters are adjusted in the order of the tension of the high molecular geotextile, acupuncture density, and acupuncture depth.

[0012] Preferably, the method for adjusting the needling parameters has an anti-conflict mechanism, specifically: Pre-define the conflicts between the increase in needling depth and the decrease in needling density, the increase in needling density and the decrease in the tension of the high molecular geotextile membrane, and the increase in needling depth and the increase in the tension of the high molecular geotextile membrane; When there is a conflict between the increase in needling depth and the decrease in needling density, the needling depth adjustment is preferentially executed; When there is a conflict between the increase in needling density and the decrease in the tension of the high molecular geotextile membrane, the tension adjustment of the high molecular geotextile membrane is preferentially executed; When there is a conflict between the increase in needling depth and the increase in the tension of the high molecular geotextile membrane, if the permeability coefficient is abnormal, the needling depth is preferentially adjusted; if the permeability coefficient is normal, the tension of the high molecular geotextile membrane is preferentially adjusted.

[0013] The present invention has at least the following beneficial effects: The present invention controls the needling depth in stages through a gradient needling process. The thick needles are pre-reinforced to form a basic bonding structure, and the thin needles are used for finishing to strengthen the interface bonding. The bonding depth reaches 80% of the film thickness to ensure a three-dimensional interlocking effect. The needling density is preset in different zones to achieve differential strengthening. The medium density is adopted in the core zone to maintain the integrity of the film, and the high density is adopted in the edge zone to enhance the tear resistance. The heat setting temperature and time are precisely controlled to make the polymer chain segments arranged orderly, eliminate internal stress, and effectively improve the dimensional stability of the product. The dynamic monitoring system adjusts the process parameters in real time, effectively improving the product qualification rate.

[0014] Other advantages, objectives, and features of the present invention will be partially reflected by the following description, and partially will be understood by those skilled in the art through the research and practice of the present invention. Detailed Embodiments

[0015] The following further detailed description of the present invention is made in conjunction with the detailed embodiments, so that those skilled in the art can implement it according to the description in the specification.

[0016] It should be understood that the terms such as "having", "comprising", and "including" used herein do not exclude the presence or addition of one or more other elements or their combinations.

[0017] It should be noted that the experimental methods described in the following embodiments are all conventional methods unless otherwise specified, and the reagents and materials can be obtained from commercial channels unless otherwise specified.

[0018] The present invention provides a method for preparing a composite geotextile, including the following steps: Step 1: Select two layers of synthetic fiber geotextiles with a unit area mass of 100 - 300 g / m² and a breaking strength greater than 15 kN / m, and a polymer geomembrane with a thickness of 0.5 - 3.0 mm and a permeability coefficient less than 1×10⁻¹ 3 cm / s; Step 2: Stack the two layers of synthetic fiber geotextiles on the upper and lower surfaces of the polymer geomembrane respectively, and then send them to a gradient needle punching machine. Adopt a double-station gradient needle punching process to perform rough needle punching pre-reinforcement simultaneously from the upper and lower sides. The needle punching depth is 50 - 60% of the thickness of the polymer geomembrane. Then, perform fine needle punching finishing simultaneously from the upper and lower sides. The needle punching depth is 70 - 80% of the thickness of the polymer geomembrane. The needle punching density is preset according to the force requirements of different regions of the polymer geomembrane. And during the needle punching composite process, adjust the needle punching parameters in real time through a dynamic monitoring system; Step 3: Perform heat setting treatment on the needle punched composite geotextile. Control the heat setting temperature at 120 - 140°C and the time at 8 - 12 min. Then perform surface treatment on the heat set geotextile to finally obtain a composite geotextile.

[0019] In the lamination process of this technical solution, the lamination of the geotextile and the geomembrane can be completed by an automatic laminating machine. Using the vacuum adsorption platform equipped with this equipment can ensure the flatness of the interlayer bonding. The adsorption pressure is controlled at -0.05 - -0.08 MPa. The laminating speed is set at 2 m / min. The laminated material is conveyed to the needle punching process through a conveying roller. The gradient needle punching machine in Step 2 can select a double-sided needle punching machine, equipped with two specifications of needle punches: 9×25 mm and 15×40 mm. Select the 15×40 mm needle punch group during rough needle punching; switch to the 9×25 mm needle punch group during fine needle punching. The needle punching frequency in the pre-reinforcement stage is set at 600 times / min, and it is increased to 800 times / min in the finishing stage. Adopt a conical needle tip (apex angle 60°) to reduce the piercing resistance and avoid tearing of the membrane material. The adjustment cycle of the needle punching machine parameters can be extended to 10 seconds, synchronized with the mechanical response time (such as the servo motor acceleration time of 5 seconds).

[0020] In another technical solution, the material of the synthetic fiber geotextile is polyester fiber, and the material of the polymer geomembrane is high-density polyethylene.

[0021] In another technical solution, in Step 2, the preset value of the needle punching density is: Divide the polymer geomembrane into a core stress area, an edge strengthening area, a weak and sensitive area, and a conventional area; among them, The preset value of the needle punching density in the core stress area is 35 - 45 needles / cm², and an orthogonal cross needle punching path is adopted; The preset value of the needle punching density in the edge strengthening area is 50 - 60 needles / cm², and a spiral progressive needle punching path is adopted; The preset needle punching density of the weak and sensitive area is 60 - 70 needles / cm², and an annular encryption needle punching path is adopted. The conventional area is the main part except the above - mentioned special areas, accounting for 60 - 70% of the total area of the geosynthetic clay liner. The preset needle punching density is 20 - 30 needles / cm², and a uniform parallel needle punching path is adopted.

[0022] In this technical solution, a zoning - differentiated needle punching process is adopted, and the geosynthetic clay liner is divided into four functional areas for targeted treatment. The area division can use a Shanghai Hugong HG - MK30 type laser marking machine to pre - mark the zoning lines on the surface of the geosynthetic clay liner. The core stress - bearing area is located in the middle of the membrane material, accounting for 20% of the total area. An orthogonal cross - needle punching path is adopted, and the needles alternately puncture in two mutually perpendicular directions to form a grid - like structure. The needle punching density is controlled within the range of 35 - 45 needles / cm², significantly improving the warp - weft strength balance of this area. The edge strengthening area is located within 5 cm of the outer edge of the membrane material. A spiral progressive needle punching path is adopted, and the needles gradually puncture from the outside to the inside along the Archimedes spiral trajectory. The needle punching density is increased to 50 - 60 needles / cm², effectively enhancing the edge anti - peeling performance. An infrared thermal imager is used to automatically detect weld defects and preset defect points. The weak and sensitive area is set as an annular area with a radius of 15 mm around the preset defect point. An annular encryption needle punching path is adopted, and concentric circles are punctured multiple times with the defect point as the center. The needle punching density reaches 60 - 70 needles / cm², specifically improving the performance of weak links such as weld joints. The remaining 60 - 70% of the area is the conventional area, and a uniform parallel needle punching path is adopted. The needle punching density is controlled within 20 - 30 needles / cm² to ensure the overall structural stability. The area division is realized through a laser projection positioning system, which projects different - colored light spots on the surface of the membrane material to mark the boundaries of each area, and the positioning accuracy is controlled within ±0.5 mm. The needle punching path is driven by a servo - motor to move the crossbeam of the needle punching machine according to the preset trajectory, and the motion repeat positioning accuracy reaches ±0.1 mm, ensuring the accurate execution of complex paths. The identification of the weak and sensitive area uses an infrared thermal imager to detect abnormal temperature points on the surface of the membrane material and automatically delimit the area range that needs to be strengthened. The needle punching parameters for different areas are switched in real - time through a PLC control system to ensure the coordinated operation of multiple process parameters. After the zoning treatment, the warp - weft breaking strength ratio of the core stress - bearing area is significantly improved, and the structural symmetry is significantly enhanced. The anti - peeling strength of the edge strengthening area is higher than that of the homogeneous area, effectively preventing edge delamination. Through the annular encryption punching in the weak and sensitive area, the fluctuation range of the permeability coefficient around the defect point is greatly reduced, and the leakage risk is significantly reduced.

[0023] In another technical solution, the stitch density of the orthogonal cross needle-punching path is 5 - 8 mm, and the angle is 90°; the stitch density of the spiral progressive needle-punching path is 3 - 5 mm, and the spiral radius increases; the circular radius of the circular encryption needle-punching path is 1 - 2 mm; the stitch density of the uniform parallel needle-punching path is 10 - 15 mm.

[0024] In another technical solution, the dynamic monitoring system includes a displacement sensor installed on the side of the needle-punching needle base of the needle-punching machine for real-time monitoring of the needle-punching depth, an industrial camera installed directly above the needle-punching machine for detecting the distribution density of the needle-punching points through an image recognition algorithm, and a tension sensor installed at both ends of the polymer geomembrane conveying roller shaft for real-time monitoring of the film tension.

[0025] In this technical solution, the dynamic monitoring system includes a laser displacement sensor installed on the side of the needle-punching needle base of the needle-punching machine, with a measurement accuracy of ±0.01 mm and a sampling frequency of 1000 Hz, to real-time monitor the deviation between the actual displacement of the needle and the set value. The industrial camera uses a 5-megapixel CMOS sensor, equipped with a ring-shaped LED light source, and takes needle-punching point images at a speed of 30 frames per second, and calculates the needle-punching density distribution through an image processing algorithm. The tension sensor is a strain gauge type, installed at both ends of the film conveying roller shaft, with a measuring range of 0 - 200 N and a resolution of 0.1 N, to real-time monitor the change in the film conveying tension. The laser displacement sensor is installed on the side of the needle-punching needle base, arranged at a 45° angle to avoid oil pollution interference, and realizes real-time monitoring of the needle displacement with an accuracy of ±0.01 mm. The industrial camera accurately calculates the needle-punching density distribution through morphological opening operation and Hough transform algorithm. The data acquisition module transmits the sensor signals to the PLC controller, and the built-in fuzzy PID algorithm realizes multi-parameter coordinated control. By driving the servo motor to adjust the needle-punching stroke, and then adjusting the needle-punching depth; by adjusting the frequency converter of the main shaft of the needle-punching machine to change the running speed, thereby changing the needle-punching density; by controlling the output torque of the unwind magnetic powder brake, changing the film tension.

[0026] In another technical solution, the dynamic monitoring system real-time collects the needle-punching depth, needle-punching density, and the tension of the polymer geomembrane, and regularly samples and tests the composite geomembrane to obtain its breaking strength, permeability coefficient, and peel strength. These data and the collected needle-punching depth, needle-punching density, and the tension of the polymer geomembrane are subjected to data normalization processing through an industrial Internet platform, and a prediction model based on a BP neural network is established. The training sample size of the prediction model is ≥1000 groups, and R²≥0.95. By real-time analyzing the output results of the model, the quality of the composite geomembrane is predicted. When the prediction result exceeds the preset control range, the system automatically adjusts the needle-punching parameters.

[0027] In this technical solution, an intelligent control and quality prediction of the production process of composite geotextiles are realized through a dynamic monitoring system based on the industrial Internet. The system uploads the real-time data of displacement sensors, industrial cameras, and tension sensors to the industrial Internet platform through the Modbus protocol to form a digital twin model of the production process. The data normalization process includes: scaling the original voltage signal of the needling depth proportionally to a range of 0.1 - 1.0 mm to ensure the comparability of data with different dimensions; counting the number of needle holes per unit area after graying and binarizing the needling density image; and using a moving average filter with a window width of 50 sampling points for the film tension data to effectively eliminate high-frequency noise interference. The BP neural network prediction model adopts a three-layer architecture. When constructing the prediction model, the training data includes 1200 sets of production samples. The input layer contains three parameters: needling depth, needling density, and film tension. After normalization, the value range is [0, 1]. The hidden layer is set with 8 neurons, and the activation function uses ReLU. The output layer corresponds to three quality indicators: breaking strength, permeability coefficient, and peel strength. The model is trained based on 1200 sets of historical production data. The Levenberg-Marquardt algorithm is used to optimize the weight parameters, the learning rate is set to 0.01, and the training is stopped when the mean square error is less than 0.005. During online prediction, the model outputs the quality prediction value every 5 seconds. When the permeability coefficient or breaking strength is outside the preset control range, the system automatically triggers a parameter adjustment instruction. The system maps the original data to the standard interval through the data normalization formula to ensure the stability of the model input. The neural network adopts a dynamic update mechanism. The model is retrained every time 200 sets of production data are added to maintain the prediction accuracy R² greater than 0.93. This prediction system enables short quality detection response time, high efficiency, and small error, reducing the frequency of quality spot checks and saving detection costs in practical applications.

[0028] In another technical solution, the method for adjusting the needling parameters is specifically as follows: Adjustment of needling depth: Based on the deviation between the prediction result and the control range, adjust it in steps of 0.02 mm, and set the maximum adjustment range to ±0.2 mm. The adjustment period is 3 minutes. If the predicted breaking strength is lower than the control lower limit, increase the needling depth by 0.02 mm. If the predicted permeability coefficient is lower than the control lower limit, decrease the needling depth by 0.02 mm. Adjustment of needling density: Adjust the motor speed of the needling machine through a frequency converter to change the needling density. Based on the reference speed, the adjustment range is ±15%. If the predicted breaking strength or peel strength is lower than the control lower limit, increase the operating speed of the needling machine by a ratio of 10%. If the predicted permeability coefficient is lower than the control lower limit, decrease the operating speed of the needling machine by a ratio of 10%. Tension adjustment of the polymer geomembrane: Adjust according to the deviation between the prediction result and the control range. If the predicted peel strength is lower than the lower control limit, the tension of the polymer geomembrane is increased by 5 N. If the predicted permeability coefficient is lower than the lower control limit, the tension of the polymer geomembrane is decreased by 3 N.

[0029] In this technical solution, the adjustment of the needle punching depth adopts a closed-loop control strategy. When the predicted breaking strength is lower than 15 kN / m, the servo motor drives the needle guide rail to move down by a step size of 0.02 mm / time, and the maximum cumulative adjustment amount is +0.2 mm. If the predicted permeability coefficient is lower than 5×10⁻¹ 4 cm / s, then it is adjusted in the reverse direction and moved up by 0.02 mm / time, with a lower limit of -0.2 mm. The adjustment of the needle punching density is achieved by changing the speed of the main shaft motor through a frequency converter. The reference speed of 1500 rpm corresponds to a density of 30 needles / cm², and for every increase or decrease of 100 rpm in the speed, the density changes by ±2 needles / cm². The tension adjustment of the membrane material uses a PID controller to adjust the current of the magnetic powder brake, and the current-tension conversion coefficient is 0.5 N / mA. When it is necessary to increase the tension by 5 N, the current is increased by 10 mA. The system is set with an adjustment period of 180 seconds, and after each adjustment, a 30-second stabilization period is waited before collecting new data. The needle punching depth is calibrated by using a standard gauge to calibrate the zero point of the displacement sensor daily to compensate for the mechanical wear error. The acceleration / deceleration time of the frequency converter is set to 10 seconds to avoid broken needles caused by sudden changes in speed. The parameters of the tension closed-loop control are proportional coefficient Kp = 2.5, integral time Ti = 5 s, and derivative time Td = 0.5 s to ensure the balance between the response speed and stability. The adjustment of the needle punching depth reduces the fluctuation range of the breaking strength from ±1.8 kN / m to ±0.5 kN / m. The frequency conversion speed regulation accuracy reaches ±1 rpm, and the control error of the needle punching density is <±1 needle / cm². The response time of the tension adjustment is <2 seconds, and the overshoot is <3%. This control strategy can significantly improve the consistency of product performance.

[0030] In another technical solution, there is a priority mechanism for the adjustment method of the needle punching parameters, specifically: setting the lower and upper control limits of the permeability coefficient, the lower control limit of the breaking strength, and the lower control limit of the peel strength; when the predicted permeability coefficient is less than the lower control limit or greater than the upper control limit, the predicted breaking strength is less than the lower control limit, and the predicted peel strength is less than the lower control limit, the corresponding indicators are respectively determined to be abnormal; When multiple abnormalities occur simultaneously, the parameter adjustment is performed in the priority order of permeability coefficient abnormality > breaking strength abnormality > peel strength abnormality; If the permeability coefficient is abnormal, adjust the needling parameters in the order of the tension of the geosynthetic clay liner, the needling depth, and the needling density; if the permeability coefficient is normal but the breaking strength is abnormal, adjust the needling parameters in the order of the needling depth, the needling density, and the tension of the geosynthetic clay liner; if both the permeability coefficient and the breaking strength are normal but the peel strength is abnormal, adjust the needling parameters in the order of the tension of the geosynthetic clay liner, the needling density, and the needling depth.

[0031] In this technical solution, during the implementation of the priority mechanism, when both the abnormal permeability coefficient (<1×10⁻¹³ cm / s) and the abnormal breaking strength (<14.8 kN / m) are detected simultaneously, the adjustment related to the permeability coefficient is preferentially executed, and the tension is adjusted by +5 N, the needling depth is adjusted by -0.02 mm, and the needling density is adjusted by -10% in sequence. If both the abnormal peel strength (<0.6 kN / m) and the abnormal breaking strength occur simultaneously, on the premise that the permeability coefficient is normal, the needling depth is preferentially adjusted, and it is adjusted by +0.02 mm, the needling density is adjusted by +10%, and the tension is adjusted by +3 N in sequence. The parameter adjustment instructions are securely transmitted to each actuator through the OPC UA protocol, and log information such as time, parameter type, and adjustment amount is recorded. The abnormal determination thresholds are set as follows: the lower control limit of the permeability coefficient is 1×10⁻¹³ cm / s, and the upper limit is 5×10⁻¹ 4 cm / s; the lower limit of the breaking strength is 15 kN / m; the lower limit of the peel strength is 0.7 kN / m. The conflict handling monitors the abnormal flag bits in real time through the state machine program and triggers the adjustment instructions according to the preset priority matrix. The instruction interlock mechanism ensures that when the needling depth increases, the tension adjustment is automatically paused for at least 60 seconds to avoid mechanical overload. The priority mechanism reduces the incidence of serious quality defects (permeation failure) and shortens the adjustment decision-making time in the multi-parameter conflict scenario.

[0032] In another technical solution, there is an anti-conflict mechanism in the adjustment method of the needling parameters, specifically: Pre-define the conflicts between the increase in the needling depth and the decrease in the needling density, the increase in the needling density and the decrease in the tension of the geosynthetic clay liner, and the increase in the needling depth and the increase in the tension of the geosynthetic clay liner; When the conflict between the increase in the needling depth and the decrease in the needling density occurs, the needling depth adjustment is preferentially executed; When the conflict between the increase in the needling density and the decrease in the tension of the geosynthetic clay liner occurs, the tension adjustment of the geosynthetic clay liner is preferentially executed; When the conflict between the increase in the needling depth and the increase in the tension of the geosynthetic clay liner occurs, if the permeability coefficient is abnormal, the needling depth is preferentially adjusted; if the permeability coefficient is normal, the tension of the geosynthetic clay liner is preferentially adjusted.

[0033] In this technical solution, the anti-collision mechanism presets three types of collisions: ① The conflict between the increase in needle penetration depth and the decrease in needle density; ② The conflict between the increase in needle density and the decrease in tension; ③ The conflict between the simultaneous increase in needle penetration depth and tension. When type ① occurs, the needle penetration depth adjustment is preferentially executed and the density parameter is frozen for 1 adjustment cycle; for type ②, the tension adjustment is preferentially executed and the density increase amplitude is limited to ≤5%; for type ③, it is selected according to the permeability coefficient status: if the penetration is abnormal, the depth is preferentially adjusted (allowing the tension to overshoot by ±2N), otherwise the tension is preferentially adjusted. The conflict signal is processed by the arbitration module, and the conflict instructions are prohibited from being output simultaneously through the hardware interlock circuit. The conflict detection algorithm compares the adjustment instruction queue in real time and triggers the conflict flag when a reverse operation instruction is detected. The suspended adjustment instruction is re-evaluated for execution conditions after a delay of 1 cycle (180 seconds). The overshoot tolerance is set to allow the tension to temporarily exceed the limit by ±3N during conflict handling, but it needs to be restored within the next cycle. The historical conflict data is stored in the SQL database, and an optimization suggestion report is generated weekly. The anti-collision mechanism reduces the number of mechanical system overload alarms and improves the success rate of parameter adjustment in conflict scenarios.

[0034] <Example> The composite geotextile is prepared by using the method of the present invention as follows: I. Raw material selection and pretreatment Synthetic fiber geotextile Material: Polyester fiber (PET) non-woven fabric, unit area mass 150 - 250 g / m², breaking strength ≥18 kN / m, warp density 12 - 14 roots / cm, weft density 10 - 12 roots / cm.

[0035] High molecular geotextile membrane Material: High density polyethylene (HDPE), thickness 1.0 - 2.0 mm, permeability coefficient ≤8×10⁻¹ 4 cm / s.

[0036] II. Gradient needle punching composite process Laying and preheating Two layers of geotextiles are symmetrically laid on the upper and lower surfaces of the HDPE membrane, and then sent to the gradient needle punching machine. The double-station gradient needle punching process is adopted to simultaneously carry out rough needle punching pre-reinforcement from the upper and lower sides, and then simultaneously carry out fine needle punching finishing from the upper and lower sides. The needle density is preset according to the force requirements of different regions of the high molecular geotextile membrane.

[0037] Differential needle punching in different zones Core stress area (accounting for 20%): Orthogonal cross path (needle pitch 5 - 8 mm, angle 90°), density 35 - 45 needles / cm², improving the balance of warp and weft strength.

[0038] Edge strengthening area (outer edge 5 cm): Spiral progressive path (needle pitch 3 - 5 mm, initial radius 10 - 12 mm, increasing 1.5 - 2.5 mm per turn), density 50 - 60 needles / cm², enhancing anti-peeling performance.

[0039] Weak and sensitive area (around the defect point 15 mm): Circular encryption path (radius 1 - 2 mm), density 60 - 70 needles / cm², specifically improving the risk of weld leakage.

[0040] Conventional area (60 - 70%): Parallel path (needle pitch 10 - 15 mm), density 20 - 30 needles / cm², ensuring the overall structural stability.

[0041] Dynamic monitoring and control Sensor configuration: Laser displacement sensor (accuracy ±0.01 mm) monitors the needle penetration depth in real time. When the deviation > ±0.05 mm, the servo motor adjusts the stroke.

[0042] 5 - megapixel industrial camera (30 frames per second) detects the needle density. When the deviation > 5 needles / cm², the frequency converter adjusts the rotation speed.

[0043] Tension sensor (range 0 - 200 N) controls the film tension within the fluctuation range of ±2 N, and the response time of the magnetic powder brake < 150 ms.

[0044] Quality prediction model: The input layer of the BP neural network has 3 nodes (depth, density, tension), the hidden layer has 8 nodes (ReLU activation), and the output layer has 3 quality indicators (R² ≥ 0.95).

[0045] The predicted value is output every 5 seconds. When the permeability coefficient > 1×10⁻¹³ cm / s or the breaking strength < 14.5 kN / m, and the peeling strength < 0.7 kN / m, parameter adjustment is triggered.

[0046] III. Intelligent regulation Parameter adjustment strategy Depth adjustment: Insufficient breaking strength → +0.02 mm / time (maximum +0.2 mm); Insufficient permeability → -0.02 mm / time (maximum -0.2 mm).

[0047] Density adjustment: Insufficient strength / peeling → Increase speed by 10%; Insufficient permeability → Decrease speed by 10% (base rotation speed 1500 rpm ± 15%).

[0048] Tension adjustment: Insufficient peeling → +5 N (current +10 mA); Insufficient permeability → -3 N (current -6 mA).

[0049] Priority and anti - conflict Priority: Penetration anomaly > fracture anomaly > peeling anomaly. Adjust the order according to tension → depth → density or depth → density → tension.

[0050] Anti - conflict: When the depth increase conflicts with the density decrease, the depth is adjusted first; when the tension and density conflict in the opposite direction, the tension is adjusted first; when the depth and tension conflict in the same direction, the decision is made according to the penetration state.

[0051] IV. Post - treatment Heat setting and surface treatment Heat setting: Hot air circulation treatment at 125 - 135°C for 9 - 11 min, cooling rate ≤ 4°C / min, to eliminate internal stress and stabilize dimensions.

[0052] Corona treatment: Power 4 - 6 kW, treatment speed 6 - 8 m / min, surface tension ≥ 40 mN / m, and finally obtain the composite geotextile.

[0053] Control example > The composite geotextile is prepared by traditional process as follows: I. Material selection Synthetic fiber geotextile Material: Polyester fiber (PET) non - woven fabric, unit area mass 200 g / m², breaking strength 18 kN / m.

[0054] High - molecular geotextile membrane Material: High - density polyethylene (HDPE), thickness 1.2 mm, permeability coefficient 5×10⁻¹ 4 cm / s.

[0055] II. Traditional process steps Laying and needling Lay two layers of geotextiles on the upper and lower surfaces of the HDPE membrane and directly carry out needling.

[0056] Single - layer needling: Only needling from one side, without staged treatment of thick needles and thin needles.

[0057] Uniform needling: The same parameters are used for the whole membrane, without zonal differential design: Type of needle: Single conical needle (diameter 0.6 mm).

[0058] Needling depth: 0.6 mm (50% of the membrane thickness).

[0059] Needling density: 25 needles / cm² (parallel path, needle pitch 15 mm).

[0060] III. Post - treatment Heat setting and surface treatment Heat setting: Treat with hot air circulation at 125 - 135 °C for 9 - 11 min, and the cooling rate ≤ 4 °C / min to eliminate internal stress and stabilize dimensions.

[0061] Corona treatment: Power 4 - 6 kW, treatment speed 6 - 8 m / min, surface tension ≥ 40 mN / m, and finally obtain the composite geotextile.

[0062] The performance of the composite geotextiles prepared in the examples and comparative examples was detected and compared, and the results are shown in Table 1 below.

[0063] Among them, the detection standards for the longitudinal and transverse breaking strengths refer to GB / T 15788 - 2017 "Geosynthetics - Wide strip tensile test". During the test, specimens are cut along the longitudinal (warp) and transverse (weft) directions of the geotextile, and the samples are made into wide strips with a width of 200 mm × a length of 100 mm. The two ends of the wide strip are clamped by the pneumatic fixture of the tensile testing machine for stretching. The clamping pressure is 0.5 MPa to prevent the specimen from slipping. The stretching speed is 50 mm / min. Record the tensile force - displacement curve, take the maximum tensile force value (kN), and calculate the strength per unit width (kN / m), which is the longitudinal and transverse breaking strengths.

[0064] The detection standard for the interlayer peel strength refers to GB / T 2791 - 1995 "Test method for peel strength of adhesives". During the test, the samples are made into wide strips with a width of 25 mm × a length of 150 mm. The upper and lower layers of fibers of the composite geotextile and the intermediate membrane are pre - peeled by 50 mm, the peeling end is clamped, and the testing machine is started. The peeling angle is 180° (T - type peeling), and the stretching speed is 100 mm / min. Record the average force value (N) during the peeling process, and calculate the peel strength per unit width (kN / m), which is the interlayer peel strength.

[0065] The detection standard for the permeability coefficient refers to GB / T 19979.1 - 2005 "Geosynthetics - Anti - seepage performance - Part 1: Determination of hydrostatic pressure resistance". During the test, the samples are made into circular specimens with a diameter of 200 mm, and the specimens are clamped in a permeameter (such as a flexible wall permeameter) to ensure airtightness. Gradient pressure is applied (initial pressure 0.1 MPa, increasing by 0.05 MPa for each level, and maintaining for 30 min), and record the water seepage volume per unit time (mL / min) at each pressure level. When the water seepage volume suddenly increases or the specimen ruptures, the test is terminated, and the hydrostatic pressure value before rupture is taken. The calculation formula for the permeability coefficient (k) is: ; where Q is the water seepage volume (mL), d is the specimen thickness (cm), A is the permeation area (cm²), ΔP is the pressure difference (kPa), and t is the time (s).

[0066] The test method for the film material breakage rate is as follows: Randomly select 10 samples of 1 m². A visible pinhole, crack or delamination area (area ≥ 1 mm²) on the surface of the film material can be defined as breakage. Locate the breakage points through visual inspection combined with light transmission detection (illuminated by a backlight table). Use a digital microscope (such as Keyence VHX-6000) to confirm the breakage size. Calculate the proportion of the breakage area, which is the film material breakage rate.

[0067] The test method for the edge peel strength is as follows: Cut the sample along the edge of the composite geotextile to ensure that the peeling interface is at the edge joint. Make the sample into a width of 25 mm × a length of 150 mm, and the edge area (within 5 mm from the edge) is the test area. Clamp the sample, with a peeling angle of 90° and a tensile speed of 50 mm / min, and record the peel force curve. Calculate the peel strength per unit width (kN / m), which is the edge peel strength.

[0068] Table 1 Comparison of the properties of composite geotextiles Note: The film material breakage rate refers to the proportion of the breakage area to the total area, %.

[0069] As can be seen from Table 1, in the comparative example, the traditional process uses single-layer uniform needling and lacks gradient strengthening design, resulting in insufficient entanglement between fibers and the film material, and the mechanical properties are significantly lower than those of the preparation process of the present invention in the examples. In terms of mechanical properties, the present invention adopts double-station gradient needling and zoned differential design, enabling sufficient entanglement between fibers and the film material to form a good three-dimensional structure. This makes the longitudinal breaking strength reach 28 - 32 kN / m, the transverse breaking strength is 25 - 28 kN / m, and the transverse strength reaches 96% of the longitudinal strength, with good structural symmetry and better adaptability to the stress requirements in different directions. In terms of anti-seepage performance, the present invention effectively reduces the permeability coefficient, and the average value is stably within 2×10⁻¹ 4 ~4×10⁻¹ 4 cm / s, with a very small fluctuation range of only ±10%, much lower than the fluctuation level of the traditional process in the comparative example. The permeability coefficient at the weld can also be strictly controlled within the engineering allowable value (1×10⁻¹³ cm / s), greatly reducing the leakage risk. In terms of process stability, the present invention introduces a dynamic monitoring system, which can accurately adjust parameters in real time. The film material breakage rate is as low as 2 - 3%, greatly reducing material waste. The parameter adjustment response is rapid, avoiding the lag of manual adjustment, ensuring the construction quality and efficiency, and fully meeting the requirements of high-standard projects.

[0070] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those skilled in the art, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and the examples shown and described herein.

Claims

1. A method for preparing a composite geotextile, characterized in that: The following steps are involved: Step 1: Select two layers of synthetic fiber geotextile with a unit area mass of 100~300 g / m² and a breaking strength greater than 15 kN / m, and a thickness of 0.5~3.0 mm and a permeability coefficient less than 1×10⁻¹ 3 cm / s polymer geomembrane; Step 2: overlap two layers of synthetic fiber geotextiles on the upper and lower surfaces of the polymer geomembrane respectively, and then send them to the gradient needling machine, adopt a double-station gradient needling process, and perform coarse needle needling pre-reinforcement from both sides at the same time, and the needling depth is 50-60% of the thickness of the polymer geomembrane, and then perform fine needle needling finishing from both sides at the same time, and the needling depth is 70-80% of the thickness of the polymer geomembrane. The needling density is preset according to the force requirements of different areas of the polymer geomembrane, and during the needling composite process, the needling parameters are adjusted in real time through the dynamic monitoring system; Step 3: heat-set the geotextile after needle punching and compounding, the heat-setting temperature is controlled at 120-140°C, the time is 8-12 min, and then the heat-set geotextile is surface treated to finally obtain the composite geotextile.

2. The method for preparing a composite geotextile according to claim 1, characterized in that: The material of the synthetic fiber geotextile is polyester fiber, and the material of the polymer geomembrane is high-density polyethylene.

3. The method for preparing the composite geotextile according to claim 1, characterized in that: In step 2, the preset value of acupuncture density is: The polymer geomembrane is divided into the core stress area, edge reinforcement area, weak sensitive area and conventional area; among them, The acupuncture density of the core stress-bearing area is preset to 35-45 needles / cm², using an orthogonal cross acupuncture path; The acupuncture density of the edge reinforcement zone is preset to 50-60 needles / cm², and a spiral progressive acupuncture path is adopted; The preset value of the acupuncture density of the weak sensitive area is 60-70 needles / cm², and a circular encrypted acupuncture path is adopted; The conventional area is the main part except the above-mentioned special area, accounting for 60-70% of the total area of ​​the polymer geomembrane. The preset value of the needle density is 20-30 needles / cm², and a uniform parallel needle path is adopted.

4. The method for preparing a composite geotextile according to claim 3, characterized in that: The needle spacing of the orthogonal cross acupuncture path is 5-8 mm, and the angle is 90°; the needle spacing of the spiral progressive acupuncture path is 3-5 mm, and the spiral radius increases; the annular radius of the annular encrypted acupuncture path is 1-2 mm; the needle spacing of the uniform parallel acupuncture path is 10-15 mm.

5. The method for preparing a composite geotextile according to claim 1, characterized in that: The dynamic monitoring system includes a displacement sensor installed on the side of the needling needle seat of the needling machine for real-time monitoring of the needling depth, an industrial camera installed directly above the needling machine for detecting the distribution density of the needling points through an image recognition algorithm, and a tension sensor installed at both ends of the polymer geomembrane conveying roller for real-time monitoring of the tension of the membrane material.

6. The method for preparing the composite geotextile according to claim 5, characterized in that: The dynamic monitoring system collects the needling depth, needling density and polymer geomembrane tension in real time, and regularly samples and tests the composite geotextile to obtain its breaking strength, permeability coefficient and peel strength. These data are normalized with the collected needling depth, needling density and polymer geomembrane tension through the industrial Internet platform, and a prediction model based on the BP neural network is established. The training sample size of the prediction model is ≥1000 groups, R²≥0.95, and the quality of the composite geotextile is predicted by real-time analysis of the model output results. When the prediction result exceeds the preset control range, the system automatically adjusts the needling parameters.

7. The method for preparing a composite geotextile according to claim 6, characterized in that: The method for adjusting the acupuncture parameters is specifically as follows: Needle puncture depth adjustment: according to the deviation between the predicted result and the control range, the adjustment is made in 0.02 mm steps, and the maximum adjustment range is set to ±0.2 mm, and the adjustment cycle is 3 min. If the predicted fracture strength is lower than the control lower limit, the needling depth is increased by 0.02 mm; if the predicted permeability coefficient is lower than the control lower limit, the needling depth is reduced by 0.02 mm. Needle density adjustment: The needle density can be changed by adjusting the motor speed of the needle machine through the frequency converter. The adjustment range is ±15% based on the reference speed. If the predicted breaking strength or peeling strength is lower than the lower control limit, the speed of the needle machine is increased by 10%. If the predicted permeability coefficient is lower than the lower control limit, the speed of the needle machine is reduced by 10%. Adjustment of polymer geomembrane tension: Adjust according to the deviation between the predicted result and the control range. If the predicted peel strength is lower than the lower control limit, the tension of the polymer geomembrane will be increased by 5 N. If the predicted permeability coefficient is lower than the lower control limit, the tension of the polymer geomembrane will be reduced by 3 N.

8. The method for preparing a composite geotextile according to claim 7, characterized in that: The method for adjusting the acupuncture parameters has a priority mechanism, specifically: setting the lower and upper control limits of the permeability coefficient, the lower control limit of the fracture strength, and the lower control limit of the peel strength; when the predicted permeability coefficient is less than the lower control limit or greater than the upper control limit, the predicted fracture strength is less than the lower control limit, and the predicted peel strength is less than the lower control limit, the corresponding indicators are judged to be abnormal. When multiple abnormalities occur at the same time, parameter adjustment is performed in the order of priority: permeability abnormality > fracture strength abnormality > peel strength abnormality; If the permeability coefficient is abnormal, adjust the needling parameters in the order of polymer geomembrane tension, needling depth and needling density; if the permeability coefficient is normal but the breaking strength is abnormal, adjust the needling parameters in the order of needling depth, needling density and polymer geomembrane tension; if the permeability coefficient and breaking strength are normal but the peeling strength is abnormal, adjust the needling parameters in the order of polymer geomembrane tension, needling density and needling depth.

9. The method for preparing a composite geotextile according to claim 7, characterized in that: The method for adjusting acupuncture parameters has an anti-collision mechanism, specifically: Predefine the conflict between increased needling depth and decreased needling density, the conflict between increased needling density and decreased tension of polymer geomembrane, and the conflict between increased needling depth and increased tension of polymer geomembrane; When there is a conflict between increasing the acupuncture depth and reducing the acupuncture density, the acupuncture depth adjustment is performed first; When there is a conflict between the increase in needle density and the reduction in the tension of the polymer geomembrane, the tension adjustment of the polymer geomembrane shall be performed first; When there is a conflict between the increase in puncture depth and the increase in polymer geomembrane tension, if the permeability coefficient is abnormal, the puncture depth should be adjusted first; if the permeability coefficient is normal, the polymer geomembrane tension should be adjusted first.

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