Construction method of arched channel flexible revetment system

Abstract

This invention relates to a construction method for an arched flexible revetment system for waterways, belonging to the field of ecological revetment technology. The method includes: stacking mulberry straw within an inverted U-shaped thin steel reinforcement frame and compressing it; after reaching a predetermined height, bending the protruding vertical steel reinforcement to the opposite side to form straw bundles; sawing both ends to form limiting mating surfaces; driving wooden piles, forming two planar overlapping surfaces on their soil-facing side; driving trapezoidal cross-section wooden piles with narrow faces facing the soil between adjacent wooden piles; and filling the straw bundles between the wooden piles to form an arched structural unit protruding towards the soil-facing side. Preferably, geotextile is laid on the overlapping surfaces, limiting nails are driven in, and anti-slip wooden strips are driven on the water-facing side of the straw bundles. This invention utilizes the "compression instead of bending" advantage of the arched structure, significantly improving load-bearing capacity and reducing structural deformation; the multiple node constraint mechanism effectively solves the problem of brittle instability caused by easy slippage and detachment of straw-based flexible revetments, enhancing structural ductility and safety reserves.

Description

Technical Field

[0001] This invention relates to a construction method for an arched waterway flexible revetment system, belonging to the field of ecological revetment technology. Background Technology

[0002] To prevent soil erosion, bank collapse, and waterway slope instability, current waterway revetment projects generally employ rigid structures such as gravity concrete, dry-laid rubble masonry, gabions, and sheet piles. While these structures offer good erosion and sliding resistance, they generally suffer from poor permeability, low ecological connectivity, poor aesthetic appeal, and high construction costs, making them unsuitable for meeting the current demands of green waterway and ecological revetment construction.

[0003] In recent years, flexible ecological revetments have received widespread attention due to their excellent permeability and ecological compatibility. Typical forms include structures such as wooden piles, bamboo piles, bamboo fences, and vegetated concrete. Among them, common wooden pile revetments include densely arranged wooden pile structures and sparsely arranged "wooden pile + bamboo fence" structures. While densely arranged wooden pile revetments have good soil retention and erosion control performance, they require a large number of wooden piles, resulting in high costs and significant resource consumption. On the other hand, while sparsely arranged wooden pile revetments save materials, their soil retention capacity and durability are insufficient, and the bamboo fence portion is prone to damage over long-term use, leading to serious soil erosion behind the piles.

[0004] To overcome the shortcomings of traditional structures, existing technologies attempt to incorporate the arched stress characteristics into revetment systems. The applicant's search revealed that Chinese patent CN108532540A discloses a cotton stalk arch-pile channel revetment system and its construction method, such as... Figure 1 As shown, this scheme utilizes cotton stalks soaked in tung oil, arranged vertically and bundled to form an arched cotton stalk arch, supported by wooden piles. The arch structure's bearing capacity counteracts the active earth pressure on the back side. To prevent soil leakage, the system also requires the placement of geotextile bags filled with soil behind the stalk arch.

[0005] However, existing straw-based flexible revetments still have limitations in practical engineering applications: 1) The existing method involves excavating a trench behind the wooden piles, which usually requires the installation of geotextile bags. On-site, the geotextile is cut, lifted, and vertically fixed, followed by layered backfilling, compaction, and final sewing. The complex on-site organization and manual operations place high demands on construction organization, which limits construction efficiency and makes it difficult to ensure consistent construction quality. The construction process is cumbersome and inefficient.

[0006] 2) The system relies heavily on geotextile bags for soil retention. In areas with fluctuating water levels, geotextile bags are subject to long-term wave disturbances, impacts from floating objects, and alternating wet and dry conditions, making them highly susceptible to damage or joint failure. Once damage or joint failure occurs, it will lead to the loss of fine particles in some areas, affecting the overall stability of the revetment.

[0007] 3) When the straw arch is vertically tied, the arch shape is prone to deformation under uneven soil pressure or continuous water flow disturbance, which leads to the reduction of the arch height and weakens the continuous stress performance of the arch structure. Under extreme working conditions, there is a risk of component slippage or insufficient overall overturning resistance. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a construction method for a flexible ecological revetment system for waterways that has a good effect in preventing soil erosion, is easy to construct and assemble, has low material costs, and has high long-term stability.

[0009] To address the aforementioned technical problems, this invention proposes a construction method for an arched waterway flexible revetment system, comprising the following steps: Step 1: Stack the mulberry stalks along the height direction inside the inverted U-shaped thin steel frame and press them tightly. After reaching the predetermined height, bend the vertical steel bars that are higher to the opposite side to form a closed rectangular constraint frame, thereby making a horizontal bundle of mulberry stalks. Cut both ends of the horizontal bundle of mulberry stalks at a predetermined angle to form a limiting mating surface. Step 2: Drive wooden piles in rows along the waterway shoreline. The wooden piles are equipped with overlapping surfaces that match the limiting mating surfaces. Step 3: Drive at least one trapezoidal cross-section wooden pile between two adjacent wooden piles. The narrow side of the trapezoidal cross-section wooden pile faces the soil-facing side and the wide side faces the water-facing side. The two sides of the trapezoidal cross-section wooden pile form an overlapping surface that matches the limiting mating surface. Step 4: Place the horizontal mulberry stalk bundles prepared in Step 1 between adjacent wooden posts, trapezoidal cross-section wooden posts, and between two adjacent trapezoidal cross-section wooden posts, so that the limiting mating surfaces at both ends of the horizontal mulberry stalk bundles fit into the overlapping surfaces of the wooden posts or trapezoidal cross-section wooden posts; the two adjacent wooden posts, together with the trapezoidal cross-section wooden posts and the horizontal mulberry stalk bundles located between them, form an arched structural unit protruding towards the soil side.

[0010] In the revetment system constructed using the method of this invention, the wooden piles, trapezoidal cross-section wooden piles, and transverse bundles of mulberry straw form an overlapping and limiting fit, thereby constructing a composite arch-type load-bearing system. Compared with traditional planar or vertically arranged flexible revetment structures, this system can fully utilize the load-bearing advantage of the arch structure by "replacing bending with compression," converting the soil pressure on the uphill side into compressive force along the arch axis and transmitting it to the wooden pile support system on both sides, thereby reducing the bending deformation and local instability risk of transverse components. Simultaneously, this composite arch structure forms a stable load-bearing path through geometric constraints, making it less prone to overall forward movement or bulging deformation of the transverse bundles of mulberry straw during the load-bearing process. This helps maintain the span-to-span relationship of the arch structure, slows down the attenuation of the arch effect, improves the long-term load-bearing stability of the structure, increases the efficiency of soil pressure transmission, and reduces structural deformation. Moreover, by using renewable materials such as straw and wood, construction is simple, cost-effective, and ecologically compatible.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) This invention constructs a revetment system with an arched load-bearing structure protruding towards the soil side by using overlapping and limiting connections between wooden piles, trapezoidal cross-section wooden piles, and transverse bundles of mulberry stalks. This system fully utilizes the mechanical advantage of the arch shape—"compression instead of bending"—converting the soil pressure on the soil side along the arch axis into compressive force, which is then transmitted to the wooden pile support system on both sides, effectively reducing the bending deformation and local instability risk of the transverse components. Comparative tests show that the cumulative displacement level of the arched structural unit under graded loading conditions is significantly lower than that of the traditional vertical straight-line structure. In the transverse compression loading test, the peak bearing capacity of the optimized composite structure is significantly higher than that of the traditional vertical structure, exhibiting excellent mechanical performance.

[0012] 2) By setting a planar overlapping surface on the wooden stake, the present invention increases the contact stability between the wooden stake and the straw bundle. The rectangular constraint frame formed by the inverted U-shaped thin steel frame after being compressed and bent to the opposite side by the vertical steel bars forms a closed enveloping constraint on the straw bundle, thereby improving the geometric stability of the straw bundle during the compression process.

[0013] 3) Traditional straw-based revetments often experience rapid instability due to node failure after reaching the ultimate load, exhibiting typical brittle failure characteristics. This invention uses multiple constraint measures to transform the structural failure mode from sudden brittle failure to a relatively gradual evolution process. Experimental verification shows that the optimized revetment system has a relatively smooth load evolution curve in the post-peak stage, without obvious rapid node detachment, significantly improving the safety reserve of the revetment system.

[0014] 4) The revetment system prepared by the method of this invention mainly uses renewable plant materials such as mulberry straw and wood, which has good ecological compatibility and meets the requirements of green waterway construction. Compared with traditional densely packed wooden pile revetments, this invention reduces the amount of wood used and lowers material costs while ensuring soil retention performance. Moreover, the construction method is simple. By combining factory-prefabricated straw bundles with on-site modular assembly, it replaces the cumbersome on-site sewing and layered backfilling process of geotextile bags in traditional solutions, greatly improving construction efficiency and quality consistency. Attached Figure Description

[0015] The invention will now be further described with reference to the accompanying drawings.

[0016] Figure 1 This is a schematic diagram of the stress and deformation of the straw arch sparse pile waterway revetment structure in the existing technology.

[0017] Figure 2 This is a top view of the bank protection system obtained in an embodiment of the present invention (showing a structure with multiple units arranged side by side).

[0018] Figure 3 yes Figure 2 Axonometric view of one unit.

[0019] Figure 4 This is a schematic diagram of the overlapping surface and limiting structure of the wooden piles.

[0020] Figure 5 This is a schematic diagram of the overlapping surface and limiting structure of a trapezoidal cross-section wooden pile.

[0021] Figure 6 This is a schematic diagram of a vertical, straight-line revetment.

[0022] Figure 7 This is a schematic diagram of a vertical arched revetment.

[0023] Figure 8 This is a schematic diagram of a horizontally arched revetment.

[0024] Figure 9 This is a schematic diagram of the structure of a horizontal and vertical integrated arched revetment.

[0025] Figure 10 yes Figures 6-9 The load-displacement curve of the bank protection system under lateral compressive loading is shown.

[0026] Figure 11 yes Figure 2 The load-displacement curve of the bank protection system under lateral compressive loading is shown.

[0027] Reference numerals in the attached diagram: 1. Wooden stake; 2. Trapezoidal cross-section wooden stake; 3. Horizontal bundle of mulberry stalks; 4. Rectangular constraint frame; 5. Geotextile; 6. Nail; 7. Anti-slip wooden strip; 8. Limiting nail. Detailed Implementation

[0028] This embodiment illustrates a construction method for an arched waterway flexible revetment system, such as... Figures 2 to 5 As shown, it includes the following steps: First, step one is performed to create the transverse mulberry stalk bundle 3. Specifically, the mulberry stalks are stacked along the height direction within an inverted U-shaped thin steel reinforcement frame and compressed. After reaching the predetermined height, the protruding vertical steel reinforcement is bent to the opposite side, forming a closed rectangular constraint frame 4, thus obtaining the transverse mulberry stalk bundle 3 of predetermined thickness and height. This enveloping structure can effectively constrain the straw bundle, significantly improving the integrity and deformation resistance of the straw bundle under pressure. During this process, according to the requirements of the arch structure, the two ends of the transverse mulberry stalk bundle 3 need to be sawn at a predetermined angle to form a limiting mating surface that matches the support system, ensuring effective load transfer. The final shape of the transverse mulberry stalk bundle 3 is a rectangle in the cross-section perpendicular to the length direction and a trapezoid in the longitudinal section parallel to the length direction.

[0029] As a preferred option, before performing step one, in order to enhance the durability of the material, the mulberry stalks can be treated with anti-corrosion measures after being sorted. Specifically, they can be soaked in a quaternary ammonium copper (ACQ) solution or tung oil to give the originally easily perishable stalks strong corrosion resistance and extend the service life of the bank protection system.

[0030] Next, proceed to step two, driving rows of wooden stakes 1 along the waterway revetment. When the wooden stakes 1 are round wooden stakes, two vertically extending planar overlapping surfaces that match the limiting mating surfaces are sawn on their soil-facing side. When the wooden stakes 1 are square wooden stakes, their side surfaces are used as overlapping surfaces to provide a stable force transmission reference surface for the subsequent assembly of the arch structure. To prevent the straw bundles from slipping under stress or water level fluctuations, limiting nails 8 are driven into the vertical edges on both sides of the overlapping surfaces of the wooden stakes 1. The limiting nails 8 physically restrict the detachment of the transverse mulberry straw bundles.

[0031] The wooden stakes can be made of round timber, etc. When round timber is used, it is sawn along the axial direction to form two overlapping surfaces. The height of the overlapping surfaces matches the height of the horizontal bundle of mulberry stalks. When square timber is used, the side of the square timber can be used directly as the overlapping surface.

[0032] Then, in step three, at least one trapezoidal cross-section wooden pile 2 is driven between two adjacent wooden piles 1, with the narrow face of the trapezoidal cross-section wooden pile 2 facing the soil-facing side and the wide face facing the water-facing side. The two sides of the trapezoidal cross-section wooden pile 2 form an overlapping surface, thereby guiding the arch-shaped force path using geometric shapes. In this embodiment, two trapezoidal cross-section wooden piles 2 are set between two adjacent round wooden piles; wherein, the middle of the arch uses isosceles trapezoidal transverse bundles of mulberry stalks 3, and the two sides of the arch use right-angled trapezoidal transverse bundles of mulberry stalks 3. In this step, to further improve the shear strength of the node and increase contact friction, geotextile 5 is cut to a suitable size and fixed to the overlapping surface of the wooden pile 1 and the trapezoidal cross-section wooden pile 2 with multiple nails 6 in an alternating manner. The interface reinforcement structure of the geotextile 5 is used to suppress the relative slippage of the contact surface; at the same time, limiting nails 8 are also driven into the vertical edges of the two sides of the trapezoidal cross-section wooden pile 2, which, together with the limiting nails at the wooden pile 1, form a slip constraint system for the entire system.

[0033] Finally, in step four, the transverse mulberry stalk bundles 3 prepared in step one are placed between adjacent wooden posts 1 and trapezoidal cross-section wooden posts 2, as well as between two adjacent trapezoidal cross-section wooden posts 2, ensuring that the limiting mating surfaces at both ends of the transverse mulberry stalk bundles 3 are tightly fitted with the overlapping surfaces of the wooden posts 1 or trapezoidal cross-section wooden posts 2. Through this assembly method, two adjacent wooden posts 1, the trapezoidal cross-section wooden posts 2 located between them, and the transverse mulberry stalk bundles 3 cooperate to form an arched structural unit protruding towards the soil-facing side. This arched structure can leverage the mechanical advantage of "compression instead of bending," converting the soil pressure on the soil-facing side into compressive force along the arch axis, effectively reducing the risk of bending deformation of the components.

[0034] To enhance the overall stability of the bank protection system, preferably, anti-slip wooden strips 7 are installed on the water-facing side of the transverse mulberry straw bundles 3, so that they pass through the edge of the transverse mulberry straw bundles 3 and are inserted into the soil to form an anti-slip limiting structure. In this way, the anti-slip wooden strips 7 can offset part of the active earth pressure and suppress the bank protection system from moving backward, falling out or overturning under extreme working conditions.

[0035] To further verify the stress performance and stability of the bank protection system prepared by the method of this invention, the applicant conducted targeted comparative experimental studies. The relevant experimental results can serve as strong support for the technical advantages of the method of this invention: The experiment compared and analyzed the performance of vertical I-shaped revetments through model box graded loading tests and lateral compression loading tests (see [reference]). Figure 6 Vertical arched revetment (see) Figure 7 ), transverse arched revetment (see Figure 8 ) and horizontal and vertical integrated arched revetments (see Figure 9The mechanical response under earth pressure. The transverse arched revetment structure consists of short and long transverse straw bundles. During fabrication, the ends of the straw bundles are sawn at a certain angle to form flat ends, allowing the long and short straw bundles to overlap and form an arched structure. Several transverse straw bundles are stacked sequentially along the height direction and overlapped with wooden piles to form an overall arched structure. The combined transverse and vertical arched revetment structure is composed of transverse and vertical straw bundles. The ends of the transverse straw bundles are processed into arc-shaped end faces that can fit against wooden piles or vertical straw bundles. Through multi-layer stacking and overlapping with components, a composite arched structure is formed.

[0036] Regarding deformation control capabilities, the results of the graded loading test in the model box showed that the traditional vertical straight revetment structure exhibited a significant indentation in the middle under load, with the cumulative displacement at each measuring point reaching 3.1cm to 6.5cm during the final loading stage; the cumulative displacement of the vertical arched structure was also at a relatively high level, ranging from 4.6cm to 5.9cm. In contrast, the revetment with a transverse arched configuration showed a significantly lower cumulative displacement level than the aforementioned vertical structures, with relatively smaller changes in overall shape, exhibiting only a slight forward tilt at the bottom, demonstrating the superiority of the arched load-bearing system in suppressing overall deformation.

[0037] Regarding load-bearing capacity and failure modes, lateral compression loading tests show that, Figure 10 As shown, the load-bearing capacity of each revetment system, from highest to lowest, is as follows: Integrated horizontal and vertical arched revetment system (approximately 7kN) > Horizontal arched revetment system (approximately 4.75kN) > Straight revetment system > Vertical arched revetment system. It is evident that the arched revetment system has significant advantages. However, in the early stages of implementing an unoptimized arched revetment system, after reaching peak load, the load-displacement curve exhibits a significant drop due to slippage or detachment of the horizontal straw bundles at the overlaps, demonstrating a typical brittle failure mode and posing a potential engineering hazard of rapid instability.

[0038] The method of the present invention is aimed at Figure 8 and Figure 9 The problems with the shown transverse arched revetment system are addressed by constructing a composite revetment system combining timber piles, trapezoidal cross-section timber piles, and transverse bundles of mulberry straw (e.g.). Figure 2 As shown in the figure, the revetment system structure was systematically optimized by combining multiple constraint measures such as geotextile 5 for interface reinforcement, limiting nails 8 for mechanical restraint, and anti-slip wooden strips 7. The results of the compression test on the optimized structure show a significant improvement in its load-displacement response. During loading, the bearing capacity continuously and steadily increased due to the effective suppression of early slippage by the nodal constraints (e.g., ...). Figure 11 (As shown in the figure). More importantly, the failure mode of the optimized structure changed from sudden instability in the early stage to a gradual evolution process. The post-peak evolution curve was relatively flat, and there was no obvious phenomenon of rapid node detachment.

[0039] The above experimental data show that the wood pile-straw bundle composite arch revetment system prepared by the method of the present invention maintains the advantages of high load-bearing capacity and low deformation, while effectively solving the brittle instability problem that is prone to occur in straw-based flexible revetments through a multi-node constraint mechanism, and significantly improving the engineering ductility and safety reserve of the structure.

Claims

1. A construction method for an arched flexible revetment system for waterways, characterized in that, Includes the following steps: Step 1: Stack the mulberry stalks along the height direction inside the inverted U-shaped thin steel frame and press them tightly. After reaching the predetermined height, bend the vertical steel bars that are higher to the opposite side to form a closed rectangular constraint frame, thereby making a horizontal bundle of mulberry stalks. Cut both ends of the horizontal bundle of mulberry stalks at a predetermined angle to form a limiting mating surface. Step 2: Drive wooden piles in rows along the waterway shoreline. The wooden piles are equipped with overlapping surfaces that match the limiting mating surfaces. Step 3: Drive at least one trapezoidal cross-section wooden pile between two adjacent wooden piles. The narrow side of the trapezoidal cross-section wooden pile faces the soil-facing side and the wide side faces the water-facing side. The two sides of the trapezoidal cross-section wooden pile form an overlapping surface that matches the limiting mating surface. Step 4: Place the horizontal mulberry stalk bundles prepared in Step 1 between adjacent wooden posts, trapezoidal cross-section wooden posts, and between two adjacent trapezoidal cross-section wooden posts, so that the limiting mating surfaces at both ends of the horizontal mulberry stalk bundles fit into the overlapping surfaces of the wooden posts or trapezoidal cross-section wooden posts; the two adjacent wooden posts, together with the trapezoidal cross-section wooden posts and the horizontal mulberry stalk bundles located between them, form an arched structural unit protruding towards the soil side.

2. The construction method of the arched waterway flexible revetment system according to claim 1, characterized in that: Before performing step one, the mulberry stalks are sorted and then treated with preservatives.

3. The construction method of the arched waterway flexible revetment system according to claim 1, characterized in that: In step three, the geotextile is cut to a size that matches the overlapping surface of the wooden piles and trapezoidal cross-section wooden piles, and then fixed to the overlapping surface of the wooden piles and trapezoidal cross-section wooden piles with nails.

4. The construction method of the arch-type flexible revetment system for waterways according to claim 1, characterized in that: In step four, anti-slip wooden strips are driven into the soil on the water-facing side of the horizontal bundle of mulberry stalks to form an anti-slip limiting structure, which is used to supplement or strengthen the overall anti-overturning capacity of the structure.

5. The construction method of the arched flexible revetment system for waterways according to claim 1, characterized in that: In step two, limit nails are driven into the vertical edges on both sides of the overlapping surface of the wooden stakes.

6. The construction method of the arch-type flexible revetment system for waterways according to claim 1, characterized in that: In step three, limiting nails are driven into the vertical edges of the two sides of the trapezoidal cross-section wooden pile.

7. The construction method of the arch-type flexible revetment system for waterways according to claim 2, characterized in that: When the mulberry stalks are sorted and then subjected to anti-corrosion treatment, the anti-corrosion treatment involves soaking the mulberry stalks in a quaternary ammonium copper solution or tung oil.

8. The construction method of the arch-type flexible revetment system for waterways according to claim 3, characterized in that: The geotextile is fixed to the overlapping surfaces of the wooden piles and trapezoidal cross-section wooden piles by multiple nails in an alternating pattern.

9. The construction method of the arch-type flexible revetment system for waterways according to claim 1, characterized in that: The wooden stakes are either round or square. When the wooden stakes are round, the overlapping surfaces are formed by sawing two vertically extending planes on the soil-facing side; when the wooden stakes are square, the overlapping surfaces are the sides of the square stakes.

10. The construction method of the arch-type flexible revetment system for waterways according to claim 1, characterized in that: The rectangular constraint frame is formed by an inverted U-shaped thin steel bar frame, which is made by bending thin steel bars. The length of the vertical steel bars on both sides is higher than the height of the horizontal straw bundle. The straw bundles are stacked in the frame and pressed tightly. After reaching the predetermined height, the vertical steel bars that are higher are bent to the opposite side. Each straw bundle is fixed by at least two rectangular constraint frames.

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