Degradable drain board core board based on degradation control thickness and preparation method

Abstract

The invention relates to the technical field of foundation treatment engineering, in particular to a degradable drain board core board based on degradation control thickness and a preparation method thereof.The degradable drain board core board comprises a core board body extending in the length direction of a drain board, and the core board body is made of a degradable high polymer material through integral extrusion molding; the core plate body consists of skeleton units and sacrifice units; the framework unit is used for maintaining the bearing stability and the continuity of the water passing channel for a long time in the full service cycle of the drainage plate; the sacrifice unit is used for participating in bearing in a construction period and a main consolidation period of a foundation and assisting in guaranteeing smoothness of a drainage channel, and is preferentially degraded in a long-term service period after construction so as to weaken the drainage capacity; the degradation control thickness of a degradable high polymer material is measured through an accelerated degradation test for simulating an engineering service environment, and the drainage capacity of the drainage plate is controllable in time and space by introducing a partition structure of a framework unit and a sacrifice unit into the cross section of a core plate, so that rapid consolidation in a construction period and additional settlement control in an operation period are both considered.

Description

Technical Field

[0001] This invention relates to the field of foundation treatment engineering technology, and in particular to a biodegradable drainage board core based on degradation-controlled thickness and its preparation method. Background Technology

[0002] Prefabricated vertical drainage boards (PVD) are widely used in soft soil foundation treatment for port terminals, site backfilling, high-speed railways, and municipal roads due to their high construction efficiency and low material cost. Existing projects commonly use non-degradable plastics such as polypropylene (PP) and polyethylene (PE) as the core material of the drainage boards, wrapped with non-woven geotextile to form drainage channels, thus accelerating the consolidation of soft soil.

[0003] However, in projects with high surcharge and long design life, while maintaining a large drainage capacity in the long term is beneficial for shortening the primary consolidation time, it may lead to the continuous development of post-construction additional settlement, causing problems such as uneven settlement of the roadbed or stockpile, ballast heave, and cracking of structures during the operation period. In engineering, it is often desirable for drainage boards to have high rigidity and water permeability during the construction and primary consolidation stages, while their drainage capacity can be appropriately reduced in the later stages of operation to mitigate subsequent consolidation and additional settlement. This is difficult to achieve with existing rigid core board products, creating a technical contradiction: "high drainage and high rigidity are required during construction, while a moderate reduction in drainage capacity is desired during operation."

[0004] In recent years, both domestic and international researchers have begun to explore the use of biodegradable polymers such as polylactic acid (PLA) and aliphatic-aromatic copolyester (PBAT) for drainage board cores, aiming to achieve automatic degradation, reduced drainage capacity, or complete decommissioning after a period of service. However, existing biodegradable drainage boards mostly utilize the traditional PP / PE core board structure with equal-thickness ribs, adjusting drainage function solely through the decay of overall material strength and stiffness over time. On the one hand, the decay process of stiffness and water flow capacity is difficult to pre-design and quantitatively control; on the other hand, different environmental temperatures, media (soft soil or groundwater), and stress levels significantly affect the degradation rate of biodegradable materials, making engineering design highly dependent on experience.

[0005] Furthermore, existing technologies for the structural design of biodegradable drainage board cores mainly focus on geometric parameters such as rib height, rib spacing, and fabric wrapping area. They have not established a quantitative relationship between "material degradation behavior, cross-sectional geometric parameters, and the evolution of drainage function," and lack a systematic design method for "preferential degradation in local areas of the core board and control of drainage capacity according to time sequence." Summary of the Invention

[0006] In view of the above-mentioned problems of not establishing a quantitative relationship between "material degradation behavior - cross-sectional geometric parameters - drainage function evolution", and lacking a system design method for "preferential degradation of local areas of core board and control of drainage capacity according to time sequence", this invention is proposed.

[0007] Therefore, the purpose of this invention is to provide a biodegradable drainage board core board with controlled thickness based on degradation and a method for its preparation.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a biodegradable drainage board core board with controlled thickness based on degradation, comprising: The system includes a core board body extending along the length of the drainage board, the core board body being integrally extruded from a biodegradable polymer material, and the core board body being composed of a skeleton unit and a sacrificial unit. The skeleton unit is used to maintain load-bearing stability and water passage continuity throughout the entire service life of the drainage board, and its minimum wall thickness in the drainage direction is t1. The sacrificial unit is used to participate in bearing and assist in ensuring the smooth flow of drainage channels during the construction period and the main consolidation period of the foundation. During the long-term service period after construction, it will preferentially degrade to weaken the drainage capacity. Its minimum wall thickness in the drainage direction is t2, and it satisfies t1>t2. For the aforementioned biodegradable polymer material, its degradation control thickness h was determined through accelerated degradation tests simulating engineering service environments. c The wall thicknesses of the skeleton unit and the sacrificial unit need to satisfy t1≥k1·h respectively. c t2≤k2·h c , where k1 is a dimensionless coefficient of 1.3 to 2.0 and k2 is a dimensionless coefficient of 0.4 to 0.8.

[0009] As a preferred embodiment of the biodegradable drainage board core based on degradation-controlled thickness of the present invention, the ratio t1 / t2 of the minimum wall thickness t1 of the skeleton unit to the minimum wall thickness t2 of the sacrificial unit is 1.8 to 2.2. This ratio can ensure that when the sacrificial unit degrades to the point of functional failure, the skeleton unit still maintains a certain compressive strength to take into account the stability of load bearing and water flow.

[0010] As a preferred embodiment of the biodegradable drainage board core based on degradation-controlled thickness of the present invention, the core board body has a cross-section provided with a plurality of ribs extending along the length direction, and vertical drainage channels are formed between adjacent ribs. The rib height is 2.8 to 3.8 mm, and the net distance between adjacent ribs is 2.0 to 3.0 mm. Among them, the skeleton ribs account for 40% to 70% of the total number of ribs, and the sacrificial ribs account for 30% to 60% of the total number of ribs.

[0011] As a preferred embodiment of the biodegradable drainage board core based on degradation-controlled thickness of the present invention, the thick toothed area of ​​the skeleton rib plate and the thin toothed area of ​​the sacrificial rib plate are arranged alternately along the cross section, with one thin toothed area between every two thick toothed areas, and the center-line distance between the thick toothed area and the thin toothed area is 2.5 to 4.5 mm, so that the water passage cross section of the drainage channel is uniformly weakened and local water accumulation is avoided.

[0012] As a preferred embodiment of the biodegradable drainage board core based on degradation-controlled thickness of the present invention, the thick toothed area of ​​the skeleton rib plate and the thin toothed area of ​​the sacrificial rib plate are arranged in a "thick-thin-thick" combination along the cross section to form a repeating arrangement unit. The width of each unit is 5.5 to 7.5 mm, which is suitable for soft soil foundations with a depth of more than 10 m, and realizes gradient control of drainage capacity at different depths.

[0013] As a preferred embodiment of the biodegradable drainage board core based on degradation-controlled thickness of the present invention, wherein: the chain extender in the biodegradable polymer material is an epoxy chain extender, and the toughening agent is an ethylene-vinyl acetate copolymer or polycaprolactone; the melt flow rate (190℃ / 2.16kg) of the biodegradable polymer material is 5~15g / 10min, and the elongation at break is ≥30%, which meets the requirements of extrusion molding process and construction rigidity.

[0014] As a preferred embodiment of the method for preparing a biodegradable drainage board core based on degradation-controlled thickness according to the present invention, the method includes the following steps: Preparation of the biodegradable polymer material: Polylactic acid (PLA), aliphatic-aromatic copolyester (PBAT) and functional additives are weighed according to the mass ratio; the raw materials are fed into a twin-screw extruder and extruded and granulated to obtain biodegradable polymer masterbatch; Degradation control thickness h of core board c Determination: The obtained biodegradable polymer masterbatch was prepared into samples with an initial thickness of 1.0–2.0 mm according to the standard for flat sample preparation. Using soil or solution similar to the environment of the foundation to be treated as a medium, the flat sample made of the biodegradable polymer material was placed in an accelerated degradation environment of 45–55°C. The sample thickness was periodically measured, and the compressive strength or water flow rate was tested simultaneously. When the sample thickness was reduced to h… c When the thickness is ±0.02 mm, the compressive strength or water flow rate decreases to 70%–85% of the initial value, and subsequent samples are easily broken or difficult to measure completely under the clamp. The corresponding average residual thickness at this time is h. c ; The values ​​of each structure of the core board body are determined by: determining h c After the value is obtained, t1≥k1·h c t2≤k2·h cFurthermore, t1 / t2 is 1.8 to 2.2, preferably 2.0, to determine the minimum wall thickness t1 of the skeleton unit and the minimum wall thickness t2 of the sacrificial unit; at the same time, the arrangement of the core board body ribs is satisfied, so that the skeleton ribs and the sacrificial ribs are staggered. Integrated extrusion molding: The obtained biodegradable polymer masterbatch is fed into a single-screw extruder, with the barrel temperature set to 170–195℃, the die temperature to 180–200℃, the traction speed to 1–3 m / min, and the degradation control thickness h. c The minimum wall thickness t1 of the skeleton unit and the minimum wall thickness t2 of the sacrificial unit are extruded using a mold, cooled and shaped, and then cut to obtain the biodegradable drainage board core.

[0015] As a preferred embodiment of the method for preparing a biodegradable drainage board core based on degradation-controlled thickness according to the present invention, the mass ratio of polylactic acid to aliphatic-aromatic copolyester is 60-80:40-20, and the functional additive is 0.1-3.0 parts by mass of chain extender or toughening agent; the above raw materials are fed into a twin-screw extruder, melt-blended at a processing temperature of 160-190℃ and a screw speed of 20-40 r / min, and extruded and granulated to obtain biodegradable polymer masterbatch.

[0016] As a preferred embodiment of the method for preparing a biodegradable drainage board core based on degradation-controlled thickness according to the present invention, the temperature segments of the twin-screw extruder are set as follows: feeding section 160-170℃, compression section 175-185℃, homogenization section 180-190℃; the temperature segments of the single-screw extruder are set as follows: feeding section 170-180℃, compression section 180-190℃, homogenization section 185-195℃; the die temperature is adjusted according to the core board thickness, and the temperature of the die area corresponding to the thick tooth area is 5-10℃ higher than that of the thin tooth area to ensure uniform melt filling.

[0017] As a preferred embodiment of the method for preparing a biodegradable drainage board core based on degradation-controlled thickness according to the present invention, the cooling and shaping adopts water bath cooling, the water temperature is controlled at 20-30℃, the cooling length is 1-2m, the traction speed is matched with the extrusion speed, and the core board cross-sectional dimension deviation is ≤±0.05mm, and the wall thickness uniformity error is ≤5%.

[0018] The benefits of this invention are: (1) The behavior of rapid decay of mechanical properties and water permeability of biodegradable polymer materials near a specific thickness is transformed into core plate geometric design parameters, thereby realizing the quantitative correlation between material degradation behavior and structural design.

[0019] (2) By designing the thickness ratio between the skeleton unit and the sacrificial unit, the core plate maintains sufficient rigidity and drainage capacity during the construction and main consolidation stages. In the later stages of construction, the sacrificial unit degrades preferentially and weakens the water passage section locally, thereby controlling the rate of long-term additional settlement and resolving the technical contradiction between maintaining high drainage capacity in the long term and controlling settlement during operation.

[0020] (3) By spatially arranging the thick toothed area and the thin toothed area on the cross section, the drainage capacity can be spatially configured according to the reinforcement requirements of different depths or different areas of the foundation, providing a more flexible drainage consolidation scheme for complex soft soil foundations.

[0021] (4) By introducing a partitioned structure of “skeleton unit + sacrificial unit” in the core board section and taking advantage of the law that the mechanical and water flow performance of degradable materials decays rapidly near the characteristic thickness, the drainage capacity of the drainage board can be precisely controlled in time and space, thus taking into account both rapid consolidation during construction and additional settlement control during operation. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the split structure of a biodegradable drainage board core based on degradation-controlled thickness.

[0024] Figure 2 This is a schematic diagram of a biodegradable drainage board core structure based on degradation-controlled thickness.

[0025] Figure 3 This is a schematic diagram of the cross-sectional structure of a biodegradable drainage board core based on degradation-controlled thickness.

[0026] Figure 4 This is a flowchart of a method for preparing a biodegradable drainage board core based on degradation-controlled thickness. Detailed Implementation

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0028] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0029] Secondly, the term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it a single embodiment or an embodiment selectively excluded from other embodiments.

[0030] Secondly, the present invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not according to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In addition, actual fabrication should include the three-dimensional spatial dimensions of length, width, and depth.

[0031] Example Reference Figure 1 - Figure 4 As an embodiment of the present invention, a biodegradable drainage board core board based on degradation-controlled thickness is provided, including a core board body 1 extending along the length direction of the drainage board. The core board body 1 is made of biodegradable polymer material by integral extrusion molding, and the core board body 1 is composed of skeleton unit 2 and sacrificial unit 3. The skeleton unit 2 is used to maintain the load-bearing stability and water passage continuity throughout the entire service life of the drainage board, and its minimum wall thickness in the drainage direction is t1. The sacrificial unit 3 is used to participate in bearing and assist in ensuring the smooth flow of drainage channels during the construction period and the main consolidation period of the foundation. During the long-term service period after construction, it is preferentially degraded to weaken the drainage capacity. Its minimum wall thickness in the drainage direction is t2, and it satisfies t1>t2. For biodegradable polymer materials, the degradation control thickness h is determined through accelerated degradation tests simulating engineering service environments. c The wall thicknesses of skeleton element 2 and sacrificial element 3 need to satisfy t1≥k1·h respectively. c t2≤k2·h c , where k1 is a dimensionless coefficient of 1.3 to 2.0 and k2 is a dimensionless coefficient of 0.4 to 0.8.

[0032] Specifically, the ratio t1 / t2 of the minimum wall thickness t1 of the skeleton unit 2 to the minimum wall thickness t2 of the sacrificial unit 3 is 1.8 to 2.2. This ratio ensures that when the sacrificial unit 3 degrades to the point of functional failure, the skeleton unit 2 still maintains a certain compressive strength to balance the stability of load bearing and water flow.

[0033] Furthermore, the cross-section of the core board body 1 is provided with several ribs extending along the length direction, and vertical drainage channels are formed between adjacent ribs. The rib height of the ribs is 2.8 to 3.8 mm, and the net distance between adjacent ribs is 2.0 to 3.0 mm. Among them, the skeleton ribs 21 account for 40% to 70% of the total number of ribs, and the sacrificial ribs 31 account for 30% to 60% of the total number of ribs.

[0034] Furthermore, the thick toothed area 22 of the skeleton rib plate 21 and the thin toothed area 32 of the sacrificial rib plate 31 are arranged alternately along the cross section, with one thin toothed area 32 between every two thick toothed areas 22, and the center line distance between the thick toothed area 22 and the thin toothed area 32 is 2.5 to 4.5 mm, so that the water passage cross section of the drainage channel is uniformly weakened and local water accumulation is avoided.

[0035] Furthermore, the thick toothed area 22 of the skeleton rib plate 21 and the thin toothed area 32 of the sacrificial rib plate 31 are arranged in a "thick-thin-thick" combination along the cross section to form a repeating arrangement unit. Each unit has a width of 5.5 to 7.5 mm, which is suitable for soft soil foundations with a depth of more than 10 m and realizes gradient control of drainage capacity at different depths.

[0036] Furthermore, the chain extender in the biodegradable polymer material is an epoxy chain extender, and the toughening agent is an ethylene-vinyl acetate copolymer or polycaprolactone; the melt flow rate (190℃ / 2.16kg) of the biodegradable polymer material is 5~15g / 10min, and the elongation at break is ≥30%, which meets the stiffness requirements of extrusion molding process and construction period.

[0037] A method for preparing a biodegradable drainage board core based on degradation-controlled thickness includes the following steps: S1. Preparation of biodegradable polymer materials: Weigh polylactic acid (PLA), aliphatic-aromatic copolyester (PBAT) and functional additives according to the mass ratio; put the raw materials into a twin-screw extruder and extrude and granulate to obtain biodegradable polymer masterbatch; The mass ratio of polylactic acid to aliphatic-aromatic copolyester is 60-80:40-20, and the functional additive is 0.1-3.0 parts by mass of chain extender or toughening agent. The above raw materials are fed into a twin-screw extruder and melt-blended at a processing temperature of 160-190℃ and a screw speed of 20-40 r / min. The resulting material is then extruded and granulated to obtain biodegradable polymer masterbatch. The temperature segments of the twin-screw extruder are set as follows: feeding section 160-170℃, compression section 175-185℃, and homogenization section 180-190℃; the temperature segments of the single-screw extruder are set as follows: feeding section 170-180℃, compression section 180-190℃, and homogenization section 185-195℃. The die head temperature is adjusted according to the core plate thickness. The temperature of the die head area corresponding to the thick tooth zone 22 is 5-10℃ higher than that of the thin tooth zone 32 to ensure uniform melt filling.

[0038] S2, Degradation control thickness h of the core board c Determination: The obtained biodegradable polymer masterbatch was prepared into samples with an initial thickness of 1.0–2.0 mm according to the standard for flat sample preparation. Using soil or solution similar to the environment of the foundation to be treated as a medium, the flat samples made of biodegradable polymer material were placed in an accelerated degradation environment of 45–55℃. The sample thickness was periodically measured, and the compressive strength or water flow rate was tested simultaneously. When the sample thickness was reduced to h… c When the thickness is ±0.02mm, the compressive strength or water flow rate decreases to 70% to 85% relative to the initial value, and subsequent samples are easily broken or difficult to measure completely under the clamping fixture. The corresponding average residual thickness at this time is hc. S3, Determination of numerical values ​​for each structure of the core board body 1: By determining h c After the value is obtained, t1≥k1·h c t2≤k2·h c And t1 / t2 is 1.8 to 2.2, preferably 2.0, to determine the minimum wall thickness t1 of the skeleton unit 2 and the minimum wall thickness t2 of the sacrificial unit 3; at the same time, the arrangement of the ribs of the core plate body 1 is satisfied, so that the skeleton ribs 21 and the sacrificial ribs 31 are staggered. S4. Integrated Extrusion Molding: The obtained biodegradable polymer masterbatch is fed into a single-screw extruder, with the barrel temperature set to 170–195℃, the die temperature to 180–200℃, the traction speed to 1–3 m / min, and the degradation control thickness h. c The minimum wall thickness t1 of skeleton unit 2 and the minimum wall thickness t2 of sacrificial unit 3 are extruded using a mold, cooled and shaped, and cut to obtain the biodegradable drainage board core board; The cooling and shaping process uses water bath cooling, with the water temperature controlled at 20-30℃ and the cooling length at 1-2m. The traction speed is matched with the extrusion speed to ensure that the core board cross-sectional dimension deviation is ≤±0.05mm and the wall thickness uniformity error is ≤5%.

[0039] Based on the above content, the following evidence is provided: Among these, the degradation control thickness h of a specific degradable material system was determined through accelerated degradation experiments. cA blend of polylactic acid (PLA), aliphatic-aromatic copolyester (PBAT), and chain extender ADR-4468 was prepared at a mass ratio of 70 / 30 / 0.4. Flat samples with a thickness of approximately 0.48 mm were prepared by extrusion molding. The samples were subjected to accelerated degradation under four conditions: "45℃ soil-water saturated soft soil environment," "45℃ controlled solution environment," "50℃ controlled solution environment," and "55℃ controlled solution environment." Samples were taken every 15 or 30 days, and the average thickness was measured using a micrometer, and the standard deviation was calculated.

[0040] Table 1 shows the thickness and standard deviation of the samples at different ages under soil conditions at 45℃. It can be seen that the average thickness of the samples gradually decreased from about 0.480 mm at 30 days to about 0.426 mm at 90 days, and then stabilized in the range of 0.412–0.418 mm from 105 to 165 days. The variation was small, indicating that the main body of the material had completed most of the structural degradation within this thickness range, leaving only a relatively stable skeletal phase.

[0041] As shown in the table below:

[0042] Table 1 shows the variation of plate sample thickness over time under soil environmental conditions at 45℃. The sample thickness and standard deviation under 45℃ solution environment conditions are listed in Table 2. The thickness decreased from about 0.482 mm at 30 days to about 0.428 mm at 90 days and about 0.416 mm at 105 days. The results are basically consistent with the trend under soil environment.

[0043] Table 2 shows the variation of plate sample thickness over time under 45℃ solution environment conditions. Under 50°C solution conditions (Table 3), the thickness rapidly decreased from approximately 0.471 mm at 30 days to approximately 0.414 mm at 60 days, and then remained in the range of 0.410–0.416 mm for 75–105 days.

[0044] Table 3 shows the variation of plate sample thickness over time under 50℃ solution environment conditions. In a solution environment at 55℃ (Table 4), the sample thickness remained basically between 0.410 and 0.412 mm during the period of 30 to 75 days. During sampling at 90 days and beyond, the samples broke under the grip of the micrometer clamp, making it difficult to obtain an effective thickness reading. At the same time, their mechanical and water permeability properties deteriorated to the point that they could not meet the requirements for use as drainage boards.

[0045] Table 4 shows the variation of plate sample thickness over time under 55℃ solution environment conditions. Based on the thickness-time evolution under four operating conditions, it can be seen that for this PLA / PBAT / ADR-4468 material system, when the residual thickness drops to approximately 0.41 mm, the material is close to the critical state between structural integrity failure and service performance. Therefore, this embodiment approximates 0.41 mm as the degradation control thickness h of this material system in a soft soil-pore water environment. c This provides a basis for the thickness design of the subsequent core board skeleton unit 2 and sacrificial unit 3.

[0046] In practical engineering design, the thickness h can be controlled based on degradation as follows: c Core plate cross-section design was completed: First, candidate biodegradable materials were selected based on the soft soil type, pore water environment, and design life of the target project. Accelerated degradation tests were then conducted according to the method shown in Example 1 to obtain thickness-time curves and determine h. c Then, based on the expected consolidation rate during construction and the target for additional settlement control during the later stages of construction, the required safe thickness range for skeleton unit 2 and sacrificial unit 3 is determined, and accordingly, units satisfying t1≥k1·h are selected. c t2≤k2·h c The specific thickness value of t1 / t2 falling within the preset range is determined; then, the cross-sectional shape and arrangement of the core board are designed according to the selected thickness value and the conventional geometric parameters of the drainage board; finally, the core board is prepared by extrusion molding process and combined with non-woven geotextile to form a biodegradable prefabricated vertical drainage board for soft soil foundation treatment.

[0047] The degradation control thickness h determined above c With a thickness of approximately 0.41 mm, a biodegradable drainage board core section design was completed for foundation treatment of typical coastal soft clay sites.

[0048] like Figure 1 As shown, the core board cross-section has 31 ribs extending along its length, of which 16 are skeleton ribs 21 and 15 are sacrificial ribs 31. The skeleton ribs 21 are arranged in the middle of the cross-section and near the sides of the core board to provide the main load-bearing capacity and overall stiffness; the sacrificial ribs 31 are arranged between the skeleton ribs 21 and near the boundary of the drainage channel to preferentially degrade in the later stage.

[0049] According to h c ≈0.41mm. In this embodiment, the minimum wall thickness t1 of the thick toothed region 22 of the skeleton rib 21 in the drainage direction is designed to be 0.60mm, and the minimum wall thickness t2 of the thin toothed region 32 of the sacrificial rib 31 is designed to be 0.30mm. The ratio of the two is t1 / t2=2.0, which satisfies the thickness ratio relationship proposed in this invention: t1≥1.3·h c t2≤0.8·hc Furthermore, t1 / t2 falls within the preferred range of 1.8 to 2.2. The rib height is 2.8 to 3.8 mm according to conventional PVD design, and the net distance between adjacent ribs is 2.0 to 3.0 mm to ensure sufficient drainage channel cross-sectional area during construction.

[0050] During the construction and main consolidation phases, since the thicknesses of both the skeleton rib 21 and the sacrificial rib 31 are greater than h... c or close to h c At the upper limit, the sacrificial rib 31 still possesses good mechanical strength and creep resistance, providing high rigidity and continuous vertical drainage channels together with the skeleton rib 21; as service time increases, the thin toothed area 32 of the sacrificial rib 31 preferentially undergoes surface erosion and volume erosion, locally thinning until it is below h. c Ultimately, under the combined effects of water erosion and earth pressure, the cross-section of the water passage at the corresponding location is partially or completely severed, while the frame rib 21 still maintains a thickness greater than h. c It continues to bear the main load and water flow functions, thereby achieving the goal of actively weakening some drainage channels in the later stage.

[0051] In this embodiment, the core board is hot-pressed together with double-sided wrapped polypropylene nonwoven geotextile to form a biodegradable prefabricated vertical drainage board. These boards are installed at 1.0m intervals in the soft soil foundation of the port storage yard and reinforced using a combination of surcharge preloading and vacuum preloading. Field monitoring results show that the water head within the drainage board decreases rapidly during the preloading maintenance phase, and the settlement rate decreases significantly after the main consolidation period. Within 3–5 years after operation, the additional settlement of the foundation develops slowly and tends to stabilize, indicating that the core board cross-section design in this embodiment can effectively coordinate rapid drainage during construction with additional settlement control during operation.

[0052] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A biodegradable drainage board core board with controlled thickness based on degradation, characterized in that: The system includes a core board body (1) extending along the length of the drainage board. The core board body (1) is made of biodegradable polymer material by integral extrusion molding, and the core board body (1) is composed of a skeleton unit (2) and a sacrificial unit (3). The skeleton unit (2) is used to maintain load-bearing stability and water passage continuity throughout the entire service life of the drainage board, and its minimum wall thickness in the drainage direction is t1. The sacrificial unit (3) is used to participate in bearing and assist in ensuring the smooth flow of drainage channels during the construction period and the main consolidation period of the foundation. It is preferentially degraded during the long-term service period after construction to weaken the drainage capacity. Its minimum wall thickness in the drainage direction is t2, and it satisfies t1>t2. For the aforementioned biodegradable polymer material, its degradation control thickness h was determined through accelerated degradation tests simulating engineering service environments. c The wall thicknesses of the skeleton unit (2) and the sacrificial unit (3) need to satisfy t1≥k1·h respectively. c t2≤k2·h c , where k1 is a dimensionless coefficient of 1.3 to 2.0 and k2 is a dimensionless coefficient of 0.4 to 0.

8.

2. The biodegradable drainage board core board based on degradation-controlled thickness according to claim 1, characterized in that: The ratio t1 / t2 of the minimum wall thickness t1 of the skeleton unit (2) to the minimum wall thickness t2 of the sacrificial unit (3) is 1.8 to 2.

2. This ratio can ensure that when the sacrificial unit (3) degrades to the point of functional failure, the skeleton unit (2) still maintains a certain compressive strength to take into account the stability of load bearing and water flow.

3. The biodegradable drainage board core based on degradation-controlled thickness according to claim 1 or 2, characterized in that: The core board body (1) has a cross section with several ribs extending along the length direction, and vertical drainage channels are formed between adjacent ribs. The rib height is 2.8 to 3.8 mm, and the net distance between adjacent ribs is 2.0 to 3.0 mm. Among them, the skeleton ribs (21) account for 40% to 70% of the total number of ribs, and the sacrificial ribs (31) account for 30% to 60% of the total number of ribs.

4. The biodegradable drainage board core board based on degradation-controlled thickness according to claim 3, characterized in that: The thick toothed area (22) of the skeleton rib (21) and the thin toothed area (32) of the sacrificial rib (31) are arranged alternately along the cross section. One thin toothed area is set between every two thick toothed areas (22), and the center line distance between the thick toothed area (22) and the thin toothed area (32) is 2.5 to 4.5 mm, so that the water flow section of the drainage channel is uniformly weakened and local water accumulation is avoided.

5. The biodegradable drainage board core board based on degradation-controlled thickness according to claim 4, characterized in that: The thick toothed area (22) of the skeleton rib (21) and the thin toothed area (32) of the sacrificial rib (31) are arranged in a "thick-thin-thick" combination along the cross section to form a repeating arrangement unit. Each unit has a width of 5.5 to 7.5 mm, which is suitable for soft soil foundations with a depth of more than 10 m, and realizes gradient control of drainage capacity at different depths.

6. The biodegradable drainage board core board based on degradation-controlled thickness according to claim 5, characterized in that: The chain extender in the biodegradable polymer material is an epoxy chain extender, and the toughening agent is an ethylene-vinyl acetate copolymer or polycaprolactone; the melt flow rate (190℃ / 2.16kg) of the biodegradable polymer material is 5~15g / 10min, and the elongation at break is ≥30%, which meets the requirements of extrusion molding process and construction rigidity.

7. A method for preparing a biodegradable drainage board core based on degradation-controlled thickness, comprising the biodegradable drainage board core based on degradation-controlled thickness as described in any one of claims 1 to 6, characterized in that: Includes the following steps: Preparation of the biodegradable polymer material: Polylactic acid (PLA), aliphatic-aromatic copolyester (PBAT) and functional additives are weighed according to the mass ratio; the raw materials are fed into a twin-screw extruder and extruded and granulated to obtain biodegradable polymer masterbatch; Degradation control thickness h of core board c Determination: The obtained biodegradable polymer masterbatch was prepared into samples with an initial thickness of 1.0–2.0 mm according to the standard for flat sample preparation. Using soil or solution similar to the environment of the foundation to be treated as a medium, the flat sample made of the biodegradable polymer material was placed in an accelerated degradation environment of 45–55°C. The sample thickness was periodically measured, and the compressive strength or water flow rate was tested simultaneously. When the sample thickness was reduced to h… c When the thickness is ±0.02 mm, the compressive strength or water flow rate decreases to 70%–85% of the initial value, and subsequent samples are easily broken or difficult to measure completely under the clamp. The corresponding average residual thickness at this time is h. c ; The values ​​of each structure of the core plate body (1) are determined by: determining h c After the value is obtained, t1≥k1·h c t2≤k2·h c And t1 / t2 is 1.8 to 2.2, preferably 2.0, to determine the minimum wall thickness t1 of the skeleton unit (2) and the minimum wall thickness t2 of the sacrificial unit (3); at the same time, the rib arrangement of the core plate body (1) is satisfied, so that the skeleton rib (21) and the sacrificial rib (31) are staggered; Integrated extrusion molding: The obtained biodegradable polymer masterbatch is fed into a single-screw extruder, with the barrel temperature set to 170–195℃, the die temperature to 180–200℃, the traction speed to 1–3 m / min, and the degradation control thickness h. c The minimum wall thickness t1 of the skeleton unit (2) and the minimum wall thickness t2 of the sacrificial unit (3) are extruded using a mold, cooled and shaped, and cut to obtain the biodegradable drainage board core.

8. The method for preparing a biodegradable drainage board core based on degradation-controlled thickness according to claim 7, characterized in that: The mass ratio of polylactic acid to aliphatic-aromatic copolyester is 60-80:40-20, and the functional additive is 0.1-3.0 parts by mass of chain extender or toughening agent. The above raw materials are fed into a twin-screw extruder and melt-blended at a processing temperature of 160-190℃ and a screw speed of 20-40 r / min. The mixture is then extruded and granulated to obtain biodegradable polymer masterbatch.

9. The preparation method according to claim 8, characterized in that: The temperature segments of the twin-screw extruder are set as follows: feeding section 160~170℃, compression section 175~185℃, homogenization section 180~190℃; the temperature segments of the single-screw extruder are set as follows: feeding section 170~180℃, compression section 180~190℃, homogenization section 185~195℃. The die head temperature is adjusted according to the core plate thickness. The temperature of the die head area corresponding to the thick tooth area (22) is 5~10℃ higher than that of the thin tooth area (32) to ensure uniform melt filling.

10. The method for preparing a biodegradable drainage board core based on degradation-controlled thickness as described in claim 8, characterized in that: Cooling and shaping are achieved using water bath cooling, with the water temperature controlled at 20–30℃ and the cooling length at 1–2m. The traction speed is matched with the extrusion speed to ensure that the core board cross-sectional dimension deviation is ≤±0.05mm and the wall thickness uniformity error is ≤5%.

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