Bionic bamboo joint connector of bamboo winding pressure pipeline and processing technology of bionic bamboo joint connector

Abstract

The invention relates to the technical field of bamboo winding composite material pipelines, and discloses a bionic bamboo joint connector of a bamboo winding pressure pipeline and a processing technology of the bionic bamboo joint connector, the bionic bamboo joint connector is arranged at the connecting part of two sections of axially aligned bamboo winding pipelines, and the bionic bamboo joint connector sequentially comprises an inner lining layer and an outer lining layer from inside to outside, the embedded steel bar reinforcing layer consists of a reinforcing material and embedded steel bar glue; the film covering restraint layer is composed of fiber reinforced cloth and impregnating resin; the socket fastening layer is composed of a metal fastening piece which is connected with the two pipes in a bridging mode. A protective layer is poured, and the whole connector is wrapped with polymer modified cement mortar; the invention further provides a processing technology of the bionic bamboo joint connector. The processing technology comprises the following six steps of pretreatment, lining welding, embedded steel bar reinforcement, film covering constraint, socket fastening and pouring protection. Through the composite structure of crossed truss type embedded steel bars, polymer modified mortar pouring and socket fastening, the connector obtains high connection strength, excellent anti-drawing performance and long-term durability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bamboo winding composite pipe, in particular to a bionic knotty interface of bamboo winding pressure pipe and a processing technology thereof. BACKGROUND

[0002] As a new type of bio-based composite pipe, bamboo winding pipe is made of natural bamboo as the base body and resin as the adhesive through winding process. It has a wide application prospect in the fields of water transportation, municipal engineering, farmland irrigation, etc. due to its green environmental protection, high specific strength, corrosion resistance and other advantages. However, as a linear engineering material, the connection technology of the pipe is the key link and technical bottleneck for safe, stable and long-term operation of the whole pipe network system.

[0003] At present, many technical solutions have been explored and applied for the connection of bamboo winding pipe. The more common ones include the socket type flexible connection by referring to the traditional plastic pipe, that is, a groove for accommodating a rubber sealing ring is arranged at one end of the pipe, and the other end of the pipe is inserted as a plug, and the sealing is realized by the elastic compression of the rubber ring. In addition, there is also a flange connection method, that is, metal flanges are respectively fixed at the ends of two pipe sections, and the connection is realized by fastening bolts and cooperating with sealing gaskets. In some cases, a hot melt butt welding of the inner lining layer is also used to enhance the water tightness of the interface, or an external metal sleeve is used for simple reinforcement.

[0004] Although the existing technology has solved the connection problem of bamboo winding pipe to some extent, there are still some deficiencies in dealing with complex engineering environment and long-term service requirements.

[0005] The existing connection method often couples the two core functions of "sealing" and "force bearing" in a single and fragile mechanism, lacking systematic structural design. For example, the socket type connection mainly relies on the compression and rebound of the rubber ring to realize sealing, but the rubber ring as a flexible non-structural material is essentially waterproof rather than load-bearing, and therefore cannot provide effective axial pull-out resistance. When the pipe is subjected to axial force due to water hammer effect, temperature change or uneven settlement of foundation, the interface is prone to be pulled off.

[0006] In addition, the existing connection method generally lacks long-term and three-dimensional protection of the interface area, resulting in insufficient durability. Both the rubber sealing ring and the flange gasket have inherent problems of material aging, and will lose elasticity due to environmental erosion when buried in the ground for a long time, thus leading to sealing failure. More importantly, these connection methods expose the end surface of the pipe structure layer (i.e. the cutting surface of bamboo) directly or indirectly to the external environment, and moisture will invade from these weak links, causing swelling and decay of bamboo, and thus leading to the collapse of the structural strength of the whole interface from the inside. SUMMARY

[0007] In view of the defects of the prior art, the present application provides a kind of bionic bamboo joint of bamboo winding pressure pipeline and its processing technology, solve the interface of existing bamboo winding pipeline because of single structure, force and sealing mechanism exist defects, caused by low connection strength, poor pullout performance and long-term sealing reliability and durability problem.

[0008] To achieve the above object, the present application is implemented by the following technical solutions: a kind of bionic bamboo joint of bamboo winding pressure pipeline, the interface is set to the connecting part of two axial alignment bamboo winding pipes, the connecting part is sequentially included from inside to outside:

[0009] Inner lining welding layer, the inner lining layer of two bamboo winding pipes is connected by welding process;

[0010] Rebar reinforcement layer, by embedding reinforcing material in the structure layer of two bamboo winding pipes and curing rebar glue;

[0011] Film constraint layer, by winding fiber reinforced cloth outside the interface and impregnated resin after curing;

[0012] Bundling fastening layer, by multiple metal fasteners across the two bamboo winding pipes;

[0013] Pouring protective layer, by pouring and covering polymer modified cement mortar of rebar reinforcement layer, film constraint layer and bundling fastening layer, the polymer modified cement mortar includes the following components by weight fraction:

[0014] Silicate cement: 90-110 parts;

[0015] Quartz sand: 150-250 parts;

[0016] Polypropylene chopped fiber: 0.5-1.5 parts;

[0017] Styrene-acrylic emulsion: 15-25 parts.

[0018] Preferably, the reinforcing material in the rebar reinforcement layer forms a cross truss locking structure between the structure layers of the two bamboo winding pipes.

[0019] Preferably, the metal fastener in the bundling fastening layer has a threaded, grooved or knurled shaped surface in the part embedded in the pouring protective layer, and the metal fastener is connected to the two bamboo winding pipes at both ends.

[0020] Preferably, the reinforcing material in the rebar reinforcement layer is carbon fiber bar or glass fiber bar;The rebar glue is modified epoxy rebar glue.

[0021] Preferably, the fiber reinforced cloth in the film constraint layer is a glass fiber cloth or a carbon fiber cloth; and the resin is an epoxy resin.

[0022] The application also provides a processing technology of the bionic bamboo joint of the bamboo winding pressure pipeline, which is used for preparing the bionic bamboo joint and comprises the following steps:

[0023] S1, pretreatment: aligning two sections of the bamboo winding pipeline and polishing and cleaning the pipe wall outside the joint;

[0024] S2, inner lining welding: welding the inner lining layer of the two sections of the bamboo winding pipeline from the inside of the pipeline to form an inner lining welding layer; when the inner lining layer is high-density polyethylene, a hot melt welding process is adopted; and when the inner lining layer is stainless steel, a tungsten electrode argon arc welding process is adopted;

[0025] By directly welding the inner lining layer of the inner wall of the pipeline, a continuous and seamless waterproof and corrosion-resistant inner container is formed, the welding layer is responsible for preventing the leakage of fluid medium, and a dry and stable operation foundation is provided for the construction of all subsequent external force-bearing structures, so that the long-term water tightness of the entire joint is ensured.

[0026] S3, reinforcing by planting roots: planting reinforcing materials in the structural layer of the two sections of the bamboo winding pipeline to form a reinforcing layer by planting roots;

[0027] The high-strength reinforcing materials are anchored in the deep structure layer of the two sections of the pipeline through the planting root glue. Through this design, when the joint bears tension, the force is no longer only applied to the surface of the joint, but is transmitted to the deep structure of the pipe wall through these “root systems”, so that the pull-out resistance and shear resistance of the joint are improved, and the separation of the pipeline is fundamentally prevented.

[0028] S4, film constraint: winding a fiber reinforced cloth outside the joint and coating a resin to form a film constraint layer;

[0029] S5, fastening of the joint: installing a plurality of metal fasteners outside the film constraint layer to form a joint fastening layer, the two ends of the metal fasteners are connected to the two sections of the bamboo winding pipeline respectively, and the surface of the metal fasteners has a special-shaped surface for forming mechanical engagement with the cast protective layer material;

[0030] By means of the metal fasteners across the two sections of the pipeline, a mechanical interlocking independent of any bonding strength is formed. The design introduces the concepts of “redundant design” and “ultimate locking”, that is, even if the bonding interface fails under extreme working conditions, these “nail-like” fasteners can still provide a final and reliable physical connection, ensuring the ultimate safety performance of the joint.

[0031] S6, casting protection: casting polymer modified cement mortar to completely cover the joint structure, and forming a cast protective layer after solidification.

[0032] Preferably, in the step S3, the step of implanting the reinforcing material comprises:

[0033] A plurality of inclined holes are drilled in opposite directions at the ends of the two-section bamboo winding pipe, and the reinforcing material is implanted in the inclined holes by using the modified epoxy resin anchoring glue to form a cross-shaped truss locking structure.

[0034] Preferably, the preparation method of the modified epoxy resin anchoring glue comprises the following steps:

[0035] Preheating and dissolving: in a reaction kettle with a heating jacket and a mechanical stirrer, 90-110 parts of epoxy resin are added; stirring is carried out at a stirring speed of 100-200 rpm and a temperature of 60-70℃;

[0036] Toughening and dilution: under continuous stirring, 10-20 parts of DBP active diluent and 5-15 parts of CTBN toughening agent are slowly added dropwise, and stirring is continued at a temperature of 60-70℃ for 60-90 minutes to ensure that all components are completely dissolved and a uniform transparent mixture is obtained;

[0037] Thickening and homogenization: the temperature of the reaction kettle is reduced to 40-50℃, and 2-4 parts of fumed silica are slowly added in 3-4 times; after each addition, the stirring speed is increased to 800-1200 rpm for high-speed shearing dispersion for 5-10 minutes; after all the thixotropic agents are added, high-speed stirring is continued for 20-30 minutes until no particles are formed, and an anti-sagging modified epoxy resin anchoring glue is obtained.

[0038] Preferably, in the step S6, the preparation method of the polymer modified cement mortar comprises the following steps:

[0039] The portland cement, quartz sand and polypropylene chopped fibers are placed in a forced mixer and dry mixed for 2-3 minutes to fully disperse and uniformly distribute the polypropylene chopped fibers in the dry powder;

[0040] The liquid formed by pre-mixing the styrene-acrylic emulsion and water is slowly and uniformly added to the dry powder being stirred while the mixer is kept running;

[0041] After all the liquid is added, wet mixing is continued for 5-8 minutes until the slurry color is uniform and there are no dry powder clumps, and a polymer modified cement mortar is obtained.

[0042] The pouring protective layer firmly encapsulates and bonds all the discrete reinforcing structures in the interior into a high-strength composite whole, so that the layers work in cooperation; secondly, the external profile like bamboo joints can smoothly transition the stress at the interface to the pipe body, avoiding stress concentration; finally, the external pouring protective layer uses polymer cement mortar modified by benzene-polymer emulsion and polypropylene fiber, instead of traditional brittle cement mortar, which endows the interface with excellent toughness, crack resistance and bonding performance with the internal structure.

[0043] Preferably, in the step S4, the step of film covering includes:

[0044] On the outer surface of the cured reinforcing layer and the adjacent pipe polishing area, evenly apply a layer of low-viscosity epoxy resin with a thickness of 0.5-1.0mm as a primer;

[0045] Using a tension control device, tightly wrap the glass fiber cloth or carbon fiber cloth as the fiber reinforced cloth along the pipe in the circumferential direction with a constant tension of 10-50N;

[0046] During the wrapping process, after each layer is wrapped, use a roller brush or a brush to apply a layer of low-viscosity epoxy impregnated resin, and wrap 5-20 layers;

[0047] After completing the wrapping of all layers, immediately tightly wrap the outer surface with 2-3 layers of polyethylene stretch wrapping film with sufficient tension, so that the shrinkage force of the film exerts pressure on the internal uncured resin and fiber to squeeze out excess resin and bubbles.

[0048] Through the multi-layer wrapping of high-strength fiber cloth, a strong radial restraint force is provided for the interface area, which restrains the stress concentration that may occur at the end of the reinforcing bar and prevents the pipe wall from being torn by the reinforcing bar under extreme tension; on the other hand, it integrates the dispersed multiple reinforcing bar anchoring points into a continuous force-bearing whole and provides a regular and tough base surface for subsequent processes.

[0049] The present application provides a kind of bamboo winding pressure pipe's bionic bamboo joint and its processing technology.There are the following beneficial effects:

[0050] 1、The present application improves the structural strength and tensile resistance of the bamboo winding pipe interface by constructing a multi-level composite structure that works in cooperation, and by setting a reinforcing bar reinforcing layer that penetrates into the pipe wall and uniquely forming a cross-shaped truss locking structure, the axial tension borne by the interface is efficiently converted into compressive stress and shear stress on the pipe wall, achieving a "deep rooting" type of firm anchoring.Combined with the physical locking of the external beam joint fastening layer, a three-dimensional load-bearing system coexists with chemical bonding and mechanical interlocking, fundamentally solving the technical problems of insufficient connection strength of traditional interfaces and easy failure under tension.

[0051] 2、The present application adopts polymer modified cement mortar, uses the flexible network and micro fiber crack resistance formed by organic polymer in cement matrix, the formed bionic bamboo joint shell has excellent toughness and crack resistance, which can effectively resist the stress caused by soil settlement or temperature change, avoids the brittle cracking of traditional cement materials, and the internal lining welding layer also ensures the absolute sealing of medium transportation, so as to ensure the integrity and protection function of the whole interface structure in the long-term service process.

[0052] 3、The present application adopts tension control and film compaction process to make the film constraint layer, ensures the densification of the constraint layer without defects, so that the hoop tightening effect is maximized. At the same time, the selected modified epoxy resin anchoring glue has high strength, high toughness and anti-flowing performance meeting the requirements of on-site construction. These targeted process and material selection reliably convert the exquisite structure design into entity, which ensures that each interface can meet the expected performance standard. BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1 The figure is the schematic diagram of the structure splicing of the present application;

[0054] Figure 2 The figure is the process flow diagram of the processing technology of the present application;

[0055] Figure 3 The figure is the interface cross section diagram of the present application.

[0056] Among them, 1 is a bamboo winding pipeline; 2 is an inner lining welding layer; 3 is a reinforcing bar reinforcing layer; 4 is a film constraint layer; 5 is a bundle joint fastening layer; 6 is a pouring protection layer. DETAILED DESCRIPTION

[0057] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the specification of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0058] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0059] Please refer to the drawings in the specification of the present application Figure 1 - the drawings Figure 3 :

[0060] Example 1:

[0061] The present application provides a kind of bionic bamboo joint of bamboo winding pressure pipeline, interface is arranged in the connecting position of two axial alignment bamboo winding pipe 1, its structure is sequentially from inside to outside: by the inner lining welding layer 2 formed by the hot melt welding of the high-density polyethylene inner lining of two pipe; the reinforcing layer 3 of embedded tendon consisting of carbon fiber tendon and modified epoxy resin embedded tendon glue after curing in the structure layer of two pipe, wherein carbon fiber tendon forms the cross truss type locking structure between two pipe; the film constraint layer 4 consisting of 12 layers of carbon fiber cloth and impregnated epoxy resin after curing which are wound on the outside of interface;The fastening layer 5 of bundle knot consisting of multiple U-shaped steel fasteners with threads on the surface across two pipe;The pouring protection layer 6 formed by pouring and covering other reinforced structures of polymer modified cement mortar solidification, the weight fraction composition of the mortar is: Portland cement 100 parts, quartz sand 200 parts, polypropylene chopped fiber 1.0 parts, benzene propyl emulsion 20 parts.

[0062] The preparation method of the bionic bamboo joint is:

[0063] S1, pretreatment: two inner lining bamboo winding pipes 1 are aligned, and the pipe wall outside the interface is polished and cleaned with an angle grinder and a louvered grinding wheel.

[0064] S2, inner lining welding: the HDPE inner lining of two pipe is welded from the inside of the pipe using hot melt welding process, to form a continuous inner lining welding layer 2.

[0065] S3, tendon reinforcing: a plurality of inclined holes with mirror image and opposite directions are drilled at the ends of two pipe respectively. Then, the carbon fiber tendon is implanted into the hole by modified epoxy resin tendon adhesive to form a cross truss type locking structure, which constitutes the tendon reinforcing layer 3. The preparation method of the modified epoxy resin tendon adhesive used is as follows: 100 parts of epoxy resin are added to the reaction kettle, heated to 65℃ and stirred at 150 rpm; 15 parts of DBP active diluent and 10 parts of CTBN toughening agent are added dropwise under continuous stirring, and the stirring is continued at 65℃ for 75 minutes; after cooling to 45℃, 3 parts of fumed silica are added in batches, and after each addition, it is sheared and dispersed at a speed of 1000 rpm for 7.5 minutes, and after all the addition, it is continuously stirred for 25 minutes.

[0066] S4, film constraint: after the curing of the tendon reinforcing layer 3, a layer of low viscosity epoxy resin with a thickness of 0.75 mm is first uniformly brushed on the outer surface of the interface as primer. Then, using a tension control device, the carbon fiber cloth is wound along the pipe in 12 layers at a constant tension of 30 N, and low viscosity epoxy resin is brushed on each layer. Finally, two layers of polyethylene stretch wrapping film are tightly wrapped and compacted to form the film constraint layer 4.

[0067] S5, bundle joint fastening: a plurality of U-shaped steel fasteners with threaded surfaces are installed outside the film constraint layer 4 to form a bundle joint fastening layer 5.

[0068] S6, pouring protection: finally, polymer modified cement mortar is poured to completely cover the interface structure. The preparation method of the polymer modified cement mortar is as follows: 100 parts of Portland cement, 200 parts of quartz sand and 1.0 part of polypropylene chopped fiber are placed in a mixer for dry stirring for 2.5 minutes; then, under continuous stirring, a liquid prepared by pre-mixing 20 parts of styrene-acrylic emulsion with an appropriate amount of water is added, and wet stirring is continued for 6.5 minutes. After the slurry is prepared, it is poured and solidified to form a pouring protection layer 6.

[0069] The pouring protection also includes the use of molds and funnels of the required shape, and the molds and funnels are prior art, which will not be described in detail here.

[0070] Example 2:

[0071] The present application provides a kind of bionic bamboo joint of bamboo winding pressure pipeline, interface is arranged in the connecting position of two axial alignment bamboo winding pipe 1, its structure is sequentially from inside to outside: by the inner lining welding layer 2 formed by the 304 stainless steel inner lining of two pipe and the connection of tungsten electrode argon arc welding process;The reinforcing layer 3 of embedded bar is composed of glass fiber bar and modified epoxy resin embedded bar glue after solidification, which are implanted into the structure layer of two pipe, wherein the glass fiber bar forms cross truss type locking structure between two pipe;The film constraint layer 4 is composed of 5 layers of glass fiber cloth and impregnated epoxy resin after solidification, which are wound on the outside of interface;The bundle joint fastening layer 5 is composed of a plurality of special-shaped steel fasteners with grooves across two pipe;The pouring protection layer 6 is formed by pouring and covering other reinforced structures with polymer modified cement mortar, and the weight fraction composition of the mortar is: Portland cement 90 parts, quartz sand 150 parts, polypropylene chopped fiber 0.5 parts, and styrene-acrylic emulsion 15 parts.

[0072] The preparation method of the bionic bamboo joint is as follows:

[0073] S1, pretreatment: two inner lining bamboo winding pipes 1 are aligned, and the pipe wall outside the interface is polished and cleaned.

[0074] S2, inner lining welding: the stainless steel inner lining of two pipe is welded from the inside of the pipe by tungsten electrode argon arc welding process to form an inner lining welding layer 2.

[0075] S3, bar reinforcement: a plurality of mirror image and opposite inclined holes are drilled at the ends of the two sections of the pipeline. Then, glass fiber bars are implanted into the holes by using modified epoxy resin bar adhesive to form a cross-shaped truss locking structure, which constitutes the bar reinforcement layer 3. The preparation method of the modified epoxy resin bar adhesive is as follows: 90 parts of epoxy resin are added to a reaction kettle, heated to 60°C and stirred at a speed of 100 rpm; 10 parts of DBP active diluent and 5 parts of CTBN toughening agent are added dropwise under continuous stirring, and the stirring is continued at 60°C for 60 minutes; after cooling to 40°C, 2 parts of fumed silica are added in batches, and after each addition, it is sheared and dispersed at a speed of 800 rpm for 5 minutes, and after all the addition, it is continuously stirred for 20 minutes to obtain.

[0076] S4, film covering: after the bar reinforcement layer 3 is cured, a layer of low viscosity epoxy resin with a thickness of 0.5 mm is uniformly brushed on the outer surface of the interface as a primer. Then, using a tension control device, a glass fiber cloth is wound along the pipeline in 5 layers at a constant tension of 10N, and low viscosity epoxy resin is brushed on each layer. Finally, two layers of polyethylene stretch wrapping film are tightly wrapped and compacted to form the film covering layer 4.

[0077] S5, bundle fastening: a plurality of special-shaped steel fasteners with grooves on the surface are installed outside the film covering layer 4 to form the bundle fastening layer 5.

[0078] S6, pouring protection: finally, polymer modified cement mortar is poured to completely cover the interface structure. The preparation method of the polymer modified cement mortar is as follows: 90 parts of Portland cement, 150 parts of quartz sand and 0.5 parts of polypropylene chopped fiber are placed in a mixer and dry stirred for 2 minutes; then, under continuous stirring, 15 parts of styrene-acrylic emulsion and an appropriate amount of water are added, and wet stirring is continued for 5 minutes. After the slurry is prepared, it is poured and cured to form the pouring protection layer 6.

[0079] Example 3:

[0080] The present application provides a kind of bionic bamboo joint of bamboo winding pressure pipeline, interface is arranged in the connecting position of two axial alignment bamboo winding pipe 1, its structure is sequentially from inside to outside: by the inner lining welding layer 2 formed by the hot melt welding of the high density polyethylene (HDPE) inner lining of two pipe; the reinforcing layer 3 of embedded tendon consisting of carbon fiber tendon and modified epoxy resin embedded tendon glue after curing implanted in two pipe structure layer, wherein carbon fiber tendon forms the cross truss type locking structure between two pipe; the film constraint layer 4 consisting of 20 layers of carbon fiber cloth and impregnated epoxy resin after curing wrapped in the interface outside; the tight fastening layer 5 of bundle knot consisting of multiple U-shaped steel fasteners with knurled surface across two pipe; the pouring protective layer 6 formed by pouring and covering other reinforced structure of polymer modified cement mortar solidification, the weight fraction composition of the mortar is: Portland cement 110 parts, quartz sand 250 parts, polypropylene chopped fiber 1.5 parts, benzenepropyl emulsion 25 parts.

[0081] The preparation method of the bionic bamboo joint is:

[0082] S1, pretreatment: two inner lining bamboo winding pipes 1 are aligned, and the pipe wall outside the interface is polished and cleaned using an angle grinder and a louvered grinding wheel.

[0083] S2, inner lining welding: the HDPE inner lining of two pipe is welded from the inside of the pipe using hot melt welding process, to form a continuous inner lining welding layer 2.

[0084] S3, tendon reinforcing: a plurality of inclined holes with mirror image and opposite directions are drilled in the ends of two pipe respectively. Then, the carbon fiber tendon is implanted into the hole by modified epoxy resin tendon adhesive to form a cross truss type locking structure, constituting the tendon reinforcing layer 3. The preparation method of the modified epoxy resin tendon adhesive used is as follows: 110 parts of epoxy resin are added to a reaction kettle, heated to 70℃ and stirred at a speed of 200 rpm; 20 parts of DBP active diluent and 15 parts of CTBN toughening agent are added dropwise under continuous stirring, and the stirring is continued at 70℃ for 90 minutes; after cooling to 50℃, 4 parts of fumed silica are added in batches, and after each addition, it is sheared and dispersed at a speed of 1200 rpm for 10 minutes. After all the additions, continue to stir for 30 minutes to obtain the product.

[0085] S4, film constraint: after the curing of the tendon reinforcing layer 3, a layer of low viscosity epoxy resin with a thickness of 1.0 mm is first uniformly brushed on the outer surface of the interface as primer. Then, using a tension control device, the carbon fiber cloth is wound around the pipe at a constant tension of 50 N, and low viscosity epoxy resin is brushed on each layer. Finally, 3 layers of polyethylene stretch wrapping film are tightly wrapped and compacted to form the film constraint layer 4.

[0086] S5, bundle joint fastening: a plurality of U-shaped steel fasteners with knurled surface are installed outside the film constraint layer 4 to form a bundle joint fastening layer 5.

[0087] S6, pouring protection: finally, polymer modified cement mortar is poured to completely cover the interface structure. The preparation method of the polymer modified cement mortar is as follows: 110 parts of Portland cement, 250 parts of quartz sand and 1.5 parts of polypropylene chopped fiber are placed in a mixer for dry stirring for 3 minutes; then, under continuous stirring, a liquid prepared by pre-mixing 25 parts of styrene-acrylic emulsion with an appropriate amount of water is added, and wet stirring is continued for 8 minutes. After the slurry is prepared, it is poured and solidified to form a pouring protection layer 6.

[0088] Comparative Example 1: Compared with Example 1, the difference is that the pouring protection layer material used in step S6 is ordinary cement mortar, which is prepared by stirring 100 parts of Portland cement and 200 parts of quartz sand with water until uniform. The rest are the same.

[0089] Comparative Example 2: Compared with Example 1, the difference is that 1.0 part of polypropylene chopped fiber is not added in the composition of the polymer modified cement mortar used in step S6. The rest are the same.

[0090] Comparative Example 3: Compared with Example 1, the difference is that 20 parts of styrene-acrylic emulsion are not added in the composition of the polymer modified cement mortar used in step S6. The rest are the same.

[0091] Comparative Example 4: Compared with Example 1, the difference is that the anchor adhesive used in step S3 is ordinary epoxy resin adhesive, which is prepared by mixing 100 parts of epoxy resin with 15 parts of DBP active diluent until uniform. The rest are the same.

[0092] Comparative Example 5: Compared with Example 1, the difference is that the process of reinforcing the anchor in step S3 is different. Specifically, a plurality of drill holes perpendicular to the pipe wall are drilled at the ends of the two-section pipe along the radial direction of the pipe, and carbon fiber bars are vertically planted without forming a cross-shaped truss locking structure. The rest are the same.

[0093] Comparative Example 6: Compared with Example 1, the difference is that the process of film constraint in step S4 is different. Specifically, 12 layers of carbon fiber cloth are manually wound, and after winding, the polyethylene stretch wrapping film is not used for wrapping and compacting. The rest are the same.

[0094] Comparative Example 7: Compared with Example 1, the difference is that step S5 bundle joint fastening is omitted. That is, after the formation of the film constraint layer 4, step S6 pouring protection is directly performed. The rest are the same.

[0095] Test Example 1:

[0096] Test samples:

[0097] A total of five groups of samples were prepared, with several (e.g. 3) samples prepared for each group to allow for repeat testing, and all samples were cured for 28 days under standard conditions (temperature 23 ± 2°C, relative humidity 50 ± 5%).

[0098] Main test group: samples of Example 1

[0099] Control group: samples of Comparative Example 1, Comparative Example 4, Comparative Example 5, Comparative Example 7

[0100] Test equipment:

[0101] Microcomputer-controlled electronic universal material testing machine (range no less than 1000 kN) equipped with a special pipe tensile clamp.

[0102] Drop hammer impact testing machine equipped with an impact body of specified mass (e.g. 5 kg) and a hemispherical punch.

[0103] Data acquisition system for recording load-displacement data.

[0104] Test procedure:

[0105] Axial ultimate pull-out test (for Example 1, Comparative Example 4, Comparative Example 5, Comparative Example 7)

[0106] Sample installation: the interface sample to be tested is installed vertically between the upper and lower clamps of the universal material testing machine. The pipes on both sides of the interface are fixed by a special clamp, and are carefully adjusted to ensure that the axis of the applied load is completely coincident with the central axis of the pipe, avoiding eccentric bending.

[0107] Load control: set the testing machine to load in displacement control mode, with a constant loading speed of 2 mm / min. Start the testing machine and begin to apply axial tensile load to the sample.

[0108] Data recording: throughout the loading process, the data acquisition system records and plots the load (kN) versus displacement (mm) curve in real time.

[0109] Test termination and observation: when the load decreases significantly, or the sample exhibits obvious macroscopic damage such as fracture or pull-out, the test is terminated. Record the peak load collected by the system, which is the maximum pull-out force that the sample can withstand.

[0110] Failure mode analysis: remove the damaged sample and carefully observe and record the main failure modes. For example, is the reinforcing material pulled out from the hole as a whole, is the reinforcing material itself fractured, is the adhesive interface between the adhesive and the reinforcing material or the pipe wall failed, or is the structural layer of the pipe body torn.

[0111] Impact resistance test (for example 1, comparative example 1):

[0112] Sample fixation: Place the interface sample to be tested horizontally on the V-shaped rigid base of the falling weight impact testing machine, adjust the position of the sample so that the impact point is aligned with the center top of the cast protective layer 6.

[0113] Set parameters: Raise the falling weight with a mass of 5 kg to a height of 1.0 m.

[0114] Perform impact: Release the falling weight to freely fall and impact the surface of the sample.

[0115] Damage assessment: After the impact is completed, remove the falling weight and carefully visually inspect the impact area. Record and describe the damage characteristics caused by the impact, including but not limited to: whether there are visible cracks, the morphology of the cracks (such as star-shaped, ring-shaped or radial), the depth and diameter of the dents, and whether there are material fragmentation or large area peeling phenomena. The test results are shown in Table 1.

[0116] Table 1: Comprehensive evaluation test results of the overall mechanical properties of the interface

[0117]

[0118]

[0119] From Table 1, we can see that:

[0120] By comparing example 1 with comparative example 5, it can be seen that the interface using the cross-truss locking structure can withstand a much larger maximum pulling force than the interface using traditional vertical dowels. The cross-truss structure of the present application can efficiently decompose the axial tension acting on the interface into compressive stress and shear stress on the two end pipe walls, so that the force is uniformly transmitted to the deep structure of the pipeline, forming a firm "rooted" anchoring. Simple vertical dowels cannot achieve such effective mechanical conversion and can only rely on limited adhesive friction to resist, so the overall pull-out failure occurs at a lower load, proving the superiority of the structural design of the present application.

[0121] The modified epoxy resin anchor adhesive of the present application has excellent toughness after curing due to the introduction of the toughening component, and can absorb and dissipate energy through micro deformation under high stress, avoiding brittle fracture of the bonding interface. In contrast, ordinary epoxy resin adhesive is brittle and will suddenly fail after reaching its strength limit, causing the reinforcing material to be pulled out prematurely. In addition, the impact test results of Example 1 and Comparative Example 1 verify the protective performance of the polymer-modified cement mortar. The composite network formed by the styrene-acrylic emulsion and polypropylene fibers in the mortar effectively absorbs impact energy, exhibiting excellent toughness and crack resistance; while ordinary cement mortar will crack and spall on a large scale under the same impact due to its brittle nature, losing its core function as a protective layer.

[0122] Finally, by comparing Example 1 with Comparative Example 7, it can be seen that the setting of the buckle fastening layer is crucial to ensuring the ultimate safety performance of the interface. In a complete structure, chemical bonding and physical locking work together to make the strength of the interface exceed that of the pipe body, achieving optimal connection effect. However, without the buckle fastening layer, which is a pure mechanical interlocking, the ultimate bearing capacity of the interface decreases significantly. This proves that the buckle fastening layer is not simply additive, but as a redundant design, it provides the final physical protection for the entire connection system under extreme working conditions, ensuring that the interface does not fail suddenly and catastrophically.

[0123] Test Example Two:

[0124] Experimental samples:

[0125] A total of five groups of samples, each prepared with several (e.g. 3) for repeated testing, all samples were cured for 28 days under standard conditions (temperature 23±2℃, relative humidity 50±5%).

[0126] Main experimental group: Example 1 sample:

[0127] Control group: samples of Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 6.

[0128] Experimental equipment:

[0129] Constant temperature and humidity chamber or environmentally stable laboratory.

[0130] Crack width observation instrument or magnifying glass with scale.

[0131] Pipeline hydraulic pressure test system, including manual or electric pressure test pump, high precision pressure gauge, sealing blind plate and connecting pipe fittings.

[0132] Experimental steps:

[0133] Shrinkage and crack resistance test (for Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3).

[0134] Environmental setting: Place the four groups of samples together in an environmentally stable room, keeping them in dry air to simulate the long-term natural shrinkage process.

[0135] Periodic observation: Starting from the 7th day of placement, conduct a careful visual inspection of the entire outer surface of each sample's protective layer 6 every other week.

[0136] Crack recording: As soon as any visible cracks are found, record the time of their appearance. Use a crack width observer to measure the maximum width of the cracks at the time of observation.

[0137] Final evaluation: After 60 days of continuous observation, evaluate and record the final state of each group of samples, including the total number of cracks, morphological characteristics (such as fine, network, through, etc.), and the maximum crack width measured.

[0138] Pressure retention sealing performance test (for Example 1, Comparative Example 6):

[0139] Sample preparation and sealing: Take the samples of Example 1 and Comparative Example 6. Use the matching sealing blind plate to completely seal the pipe openings at both ends of the sample. One end of the blind plate needs to reserve a water injection port and an exhaust port.

[0140] Water injection and exhaust: Place the sample horizontally, slowly fill the inside of the pipe with clean water from the water injection port, and keep the exhaust port open until all air is completely exhausted, then close the exhaust port.

[0141] Pressurization and pressure retention: Connect the hydraulic pressure test system to the water injection port. Start the pressure test pump and slowly and smoothly raise the water pressure inside the pipe to the design working pressure (e.g. 1.0 MPa). After reaching the target pressure, close the valve, stop pressurization, and start timing.

[0142] Leakage observation: During the next 24 hours of pressure retention, conduct continuous and careful visual inspection of all parts of the interface area, especially the junction between the membrane constraint layer and the pipe body. Focus on observing whether there are any signs of leakage such as wet marks, wetting, water seepage, or dripping water.

[0143] Result determination: After 24 hours, record the sealing performance of each group of samples according to the observation results. If there is no leakage, it is determined as "no leakage"; if there is any form of leakage, it is determined as "leakage", and the leakage situation is briefly described. The test results are shown in Table 2.

[0144] Table 2: Comprehensive evaluation test results of interface durability and process reliability

[0145]

[0146]

[0147] From Table 2, it can be seen that:

[0148] By comparing the dry shrinkage and crack resistance of Example 1 with Comparative Examples 1, 2 and 3, it can be seen that the polymer modified cement mortar used in the present application exhibits excellent structural stability. The three-dimensional random "micro-rib" network formed by the polypropylene short fibers in the cement matrix effectively inhibits the propagation of micro-cracks caused by drying shrinkage; at the same time, the flexible polymer film formed between the cement hydration products by the styrene-acrylic emulsion fundamentally improves the toughness of the material and reduces its brittleness. Without either component, as shown in Comparative Examples 2 and 3, the material cannot effectively resist shrinkage stress, leading to different forms of cracking, and Comparative Example 1 using ordinary cement mortar shows serious through cracks, which proves that the composition innovation of the present application in the protective layer material is the fundamental guarantee for realizing its long-term structural integrity.

[0149] On the other hand, by comparing the pressure retaining sealing performance of Example 1 with Comparative Example 6, although both use the same anti-cracking mortar, the interface sealing performance is completely different. The "tension winding-film compaction" coating process used in the present application ensures that the fiber reinforced cloth can tightly and uniformly exert circumferential restraint force through constant tension, and the subsequent film wrapping and compaction step effectively extrudes the residual bubbles and excess resin in the impregnated resin using the shrinkage force of the film itself. This series of process control finally forms a highly dense and defect-free coating restraint layer. In contrast, the ordinary manual winding of Comparative Example 6 cannot guarantee uniform tension and lacks the compaction step, and is prone to leave small bubbles or defects between the layers, which will become leakage channels under the action of internal water pressure, resulting in sealing failure.

[0150] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A biomimetic bamboo joint interface for a bamboo-wound pressure pipe, characterized in that, The interface is a connection point located on two axially aligned bamboo-wound pipes (1), and the connection point includes, from the inside to the outside, the following: The inner lining welded layer (2) is formed by connecting the inner lining layers of the two sections of the bamboo-wound pipe (1) through a welding process; The rebar reinforcement layer (3) is composed of reinforcing material implanted in the structural layer of the two sections of the bamboo-wound pipe (1) and cured rebar adhesive; The film restraint layer (4) is composed of fiber reinforcement cloth wrapped around the outside of the interface and resin impregnated and cured; The fastening layer (5) consists of a plurality of metal fasteners that bridge the two sections of the bamboo-wound pipe (1); The protective layer (6) is formed by curing polymer-modified cement mortar that is poured and covers the rebar reinforcement layer (3), the membrane restraint layer (4), and the joint fastening layer (5). The polymer-modified cement mortar comprises the following components in parts by weight: Silicate cement: 90-110 parts; Quartz sand: 150-250 parts; Polypropylene chopped strands: 0.5-1.5 parts; Styrene-acrylic emulsion: 15-25 parts.

2. The biomimetic bamboo joint interface of a bamboo-wound pressure pipe according to claim 1, characterized in that, The reinforcing material in the rebar reinforcement layer (3) forms a cross-shaped truss locking structure between the structural layers of the two sections of the bamboo-wound pipe (1).

3. The biomimetic bamboo joint interface of a bamboo-wound pressure pipe according to claim 1, characterized in that, The metal fasteners in the fastening layer (5) have a threaded, grooved or knurled irregular surface embedded in the cast protective layer (6).

4. The biomimetic bamboo joint interface of a bamboo-wound pressure pipe according to claim 1, characterized in that, The reinforcing material in the rebar reinforcement layer (3) is carbon fiber rebar or glass fiber rebar; the rebar adhesive is modified epoxy resin rebar adhesive.

5. The biomimetic bamboo joint interface of a bamboo-wound pressure pipe according to claim 1, characterized in that, The fiber-reinforcing fabric in the coating constraint layer (4) is glass fiber cloth or carbon fiber cloth; the resin is epoxy resin.

6. A processing technology for a biomimetic bamboo joint interface of a bamboo-wound pressure pipe, characterized in that, The method for preparing a biomimetic bamboo joint interface for a bamboo-wound pressure pipe according to any one of claims 1-5 includes the following steps: S1. Pre-treatment: Align the two sections of bamboo wrapped around the pipe (1) and polish and clean the pipe wall outside the interface; S2, Inner Lining Welding: The inner lining of the two bamboo-wound pipe (1) is welded from the inside of the pipe to form an inner lining welding layer (2). When the inner lining is high-density polyethylene, hot melt welding process is used; when the inner lining is stainless steel, tungsten inert gas welding process is used. S3, Reinforcing with rebar: Reinforcing material is implanted into the structural layer of the two bamboo-wrapped pipe 1 to form a reinforcing layer (3); S4, Film-coated constraint: Fiber-reinforced cloth is wrapped around the outside of the interface and coated with resin to form a film-coated constraint layer 4; S5, Joint fastening: Multiple metal fasteners are installed on the outside of the film restraint layer (4) to form a joint fastening layer (5). The metal fasteners are used to connect the two bamboo-wound pipes (1) and have irregular surfaces for mechanical engagement with the material of the cast protective layer (6). S6. Casting protection: Cast polymer-modified cement mortar to completely cover the interface structure, and form a casting protection layer (6) after curing.

7. The processing technology of the biomimetic bamboo joint interface of the bamboo-wound pressure pipe according to claim 6, characterized in that, In step S3, the step of implanting the reinforcing material includes: Multiple inclined holes with mirror-image and opposite directions are drilled at the ends of the two bamboo-wound pipes (1), and reinforcing materials are implanted in the inclined holes using modified epoxy resin anchoring adhesive to form a cross-truss locking structure.

8. The processing technology of the biomimetic bamboo joint interface of the bamboo-wound pressure pipe according to claim 7, characterized in that, The preparation method of the modified epoxy resin anchoring adhesive includes the following steps: Preheating and dissolving: Add 90-110 parts of epoxy resin to a reactor equipped with a heating jacket and a mechanical stirrer; stir at a speed of 100-200 rpm and a temperature of 60-70℃. Toughening and dilution: While stirring continuously, slowly add 10-20 parts of DBP reactive diluent and 5-15 parts of CTBN toughening agent, and continue stirring at 60-70℃ for 60-90 minutes to ensure that all components are completely dissolved and a homogeneous transparent mixture is obtained. Thickening and homogenization: Reduce the temperature of the reactor to 40-50℃ and slowly add 2-4 parts of fumed silica in 3-4 batches; after each addition, increase the stirring speed to 800-1200 rpm for high-speed shear dispersion for 5-10 minutes; after all the thixotropic agent has been added, continue high-speed stirring for 20-30 minutes until no particles are formed, thus obtaining the anti-sagging modified epoxy resin rebar adhesive.

9. The processing technology of the biomimetic bamboo joint interface of the bamboo-wound pressure pipe according to claim 8, characterized in that, In step S6, the preparation method of polymer-modified cement mortar includes the following steps: The silicate cement, quartz sand, and chopped polypropylene fibers are placed in a forced mixer and dry-mixed for 2-3 minutes to ensure that the chopped polypropylene fibers are fully dispersed and evenly distributed in the dry powder. While keeping the mixer running, slowly and evenly add the liquid formed by pre-mixing the styrene-acrylic emulsion and water to the dry powder being mixed. After all liquids have been added, continue wet mixing for 5-8 minutes until the slurry has a uniform color and no dry powder lumps, thus obtaining polymer-modified cement mortar.

10. The processing technology of the biomimetic bamboo joint interface of the bamboo-wound pressure pipe according to claim 9, characterized in that, In step S4, the coating constraint step includes: On the outer surface of the reinforced rebar layer (3) after curing, and on the adjacent pipe grinding area, a layer of low-viscosity epoxy resin with a thickness of 0.5-1.0 mm is uniformly applied as a primer. Using a tension control device, the glass fiber cloth or carbon fiber cloth used as fiber reinforcement cloth is tightly wound around the pipe in a circumferential direction with a constant tension of 10-50N. During the winding process, after each layer is wound, a layer of the low-viscosity epoxy impregnating resin is applied with a roller brush or a brush, and 5-20 layers are wound. After all layers of winding are completed, immediately use polyethylene stretch wrap film to tightly wrap 2-3 layers around its outer surface with sufficient tension. The shrinkage force of the film applies pressure to the uncured resin and fibers inside to squeeze out excess resin and air bubbles.

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