Method for installing rubber flashing at intersection of deformation joint and construction joint

Abstract

This invention discloses an installation method for a rubber waterstop at the intersection of an expansion joint and a construction joint, belonging to the field of building construction technology. It aims to solve the technical problem in existing technologies where, during installation at the intersection of an expansion joint and a construction joint, it is difficult to accurately control the initial stress state of the rubber waterstop in the direction of the expansion joint, leading to tearing or loosening and failure of the waterstop when the expansion joint expands or contracts. Key technical points include: determining the pre-tension amount δ based on the maximum possible expansion displacement Δ of the expansion joint, where δ = k·Δ, and k is a relaxation coefficient of 0.2 to 0.5; during installation, first fixing the bottom end of the waterstop, then applying tension to its top end using a tensioning device to achieve the pre-tension amount δ; then, for the waterstop, setting positioning bars to connect its flanges to the structural steel reinforcement; and finally, pouring concrete. This invention is mainly used for the installation of waterstops at the intersection of building expansion joints and horizontal construction joints, ensuring that the waterstop maintains a moderate tension within the joint.

Description

Technical Field

[0001] This invention relates to the field of rare earth material preparation. More specifically, this invention relates to a method for installing a rubber waterstop at the intersection of an expansion joint and a construction joint. Background Technology

[0002] In the concrete construction of underground engineering and hydraulic structures, expansion joints and construction joints are the two most common types of structural joints. Expansion joints are used to accommodate displacement caused by factors such as temperature changes, uneven foundation settlement, or earthquakes, and usually run through the entire structure; while construction joints are temporary interfaces formed during construction intervals due to phased concrete pouring. In actual engineering, these two types of joints often intersect, for example, at the junction of the foundation slab and the exterior wall, where expansion joints are needed to meet structural deformation requirements, and horizontal construction joints are formed because the foundation slab is poured first and the wall is poured later. At such intersections, rubber waterstops are the most widely used flexible waterproofing measure, and their installation quality directly determines the success or failure of the joint waterproofing.

[0003] Currently, when installing rubber waterstops at the intersection of expansion joints and construction joints, the conventional waterstop installation method is usually followed. This involves placing the waterstop at the pre-set position of the expansion joint according to the design drawings, temporarily fixing it with reinforcing bars or formwork, and then pouring concrete to partially enclose and anchor it. However, this conventional approach has significant limitations in dealing with the expansion and contraction characteristics of expansion joints. One of the main functions of rubber waterstops is to accommodate the expansion and contraction displacement that occurs during use, which requires the waterstop to have a certain deformation reserve after installation. However, in actual construction, the waterstop is usually embedded in the concrete in a naturally relaxed state or simply stretched, with its initial length basically consistent with the structural length of the expansion joint, or even slightly longer due to relaxation. In this case, the waterstop itself has not pre-established effective tensile stress, and its tensile allowance along its length is actually zero or very limited.

[0004] When the expansion joint expands due to temperature drop or concrete shrinkage, the waterstop anchored in the concrete on both sides must be stretched accordingly. Since no stretching allowance was provided during installation, the expansion displacement is entirely converted into the elastic elongation of the waterstop itself. If the elongation of the waterstop is insufficient to withstand this displacement, or if repeated displacement leads to fatigue of the rubber material, the waterstop may tear or detach from the concrete interface. Conversely, if the expansion joint compresses due to temperature rise, the relaxed waterstop may bend, fold, or shift within the joint. This can not only affect its anchorage with the concrete but also create seepage channels at the folds. Therefore, under conventional installation methods, the initial stress state of the waterstop is uncertain, and its ability to effectively adapt to subsequent deformation largely depends on random factors.

[0005] Besides the challenge of adapting to expansion and contraction, the installation of waterstops at the intersection of expansion joints and construction joints presents significant positioning difficulties. Since expansion joints run the entire length of the structure, while construction joints are horizontal interfaces, the waterstop must meet positioning requirements in two directions simultaneously: its centerline must be strictly aligned with the centerline of the expansion joint, and its embedment depth must precisely correspond to the elevation of the construction joint. In actual construction sites, waterstops are flexible elastic materials, easily affected by concrete flow, vibration, and steel reinforcement displacement during concrete pouring, causing them to deviate from their designed position. This is especially true when the waterstop is installed in a relaxed state, where its positional stability is even worse, making it more prone to floating, lateral displacement, or twisting under concrete vibration. Ultimately, this results in insufficient effective embedment depth or centerline misalignment, weakening the waterproofing effect.

[0006] Furthermore, in past technical practices, some engineers have attempted improvements to address the tensile adaptability of waterstops at expansion joints. These include artificially tightening the waterstop during installation or applying pre-tension through formwork. However, these methods lack quantitative theoretical basis and standardized operating procedures, often relying on the personal experience and on-site judgment of construction workers. The degree of tightening is difficult to control: excessive tightening may cause the waterstop to be under high stress for extended periods, accelerating aging and even leading to creep rupture; insufficient tightening will still result in wrinkles or inadequate tensile allowance. Simultaneously, existing technologies lack systematic solutions for how to temporarily fix the waterstop under tension, how to ensure its centerline aligns with the expansion joint, and how to maintain its stress and position during subsequent concrete pouring. Therefore, leakage at the intersection of expansion joints and construction joints remains a frequent problem in actual engineering projects, becoming a weak link in the quality control of waterproofing in underground engineering. Summary of the Invention

[0007] One object of the present invention is to solve at least the above-mentioned problems and to provide at least the advantages that will be described later.

[0008] Another objective of this invention is to provide a method for installing a rubber waterstop at the intersection of an expansion joint and a construction joint. This method addresses the technical problem in the prior art where, when installing a rubber waterstop at the intersection of an expansion joint and a construction joint, it is difficult to accurately control its initial stress state in the direction of the expansion joint, leading to the waterstop being easily torn or loosened and failing when the expansion joint expands or contracts.

[0009] To achieve these objectives and other advantages according to the present invention, a method for installing a rubber waterstop at the intersection of an expansion joint and a construction joint is provided, comprising the following steps: S1: Determination of Pre-tension Amount: Based on the maximum possible displacement Δ of the expansion joint along its structural length during use, determine the pre-tension amount δ that needs to be applied along the length of the rubber waterstop during installation, where δ = k·Δ, k is the relaxation coefficient, and 0.2 ≤ k ≤ 0.5; the meaning of the pre-tension amount δ is: the length of the rubber waterstop in its natural state is δ shorter than the design distance between its two fixed points, and its length after tensioning is exactly equal to the design distance; the design distance between the two fixed points is the structural length of the expansion joint in the section where the waterstop is installed; S2: Tensioning and Positioning: First, place the rubber waterstop at the preset position of the expansion joint, so that the first end, as the first fixed end, is located at the preset first installation position of the expansion joint, and the second end, as the subsequent tensioning end, is temporarily located at a position offset from the preset second installation position; then, fix the first end of the rubber waterstop to the structural steel bar or embedded part through the anchoring clamp to form the fixed end; subsequently, clamp the second end of the waterstop with the tensioning clamp, connect the tensioning equipment to apply tension along the length direction of the rubber waterstop, and tension the rubber waterstop to the pre-tension amount δ, at which point the second end is stretched to its preset second installation position; after reaching the pre-tension amount δ, maintain the tensioned state and check whether the center line of the rubber waterstop coincides with the design center line of the expansion joint. If there is a deviation, fine-tune the rubber waterstop to make it accurately centered; subsequently, under the premise of maintaining the tensioned state, use positioning bars to connect the flange of the rubber waterstop to the structural steel bar, embedded part, or specially set positioning bar bracket. The positioning bars are set at intervals along the length direction of the waterstop to prevent the waterstop from shifting during the concrete pouring process; S3: Concrete pouring: First, pour the first part of the concrete below the construction joint. The pouring height should ensure that the waterstop is reliably anchored. After this part of the concrete has set and has sufficient strength, pour the remaining second part of the concrete. S4: Fixture Removal: After all concrete has been poured and set, remove the tensioning fixtures. S5: Curing: Keep the concrete moist until the design age.

[0010] Preferably, in S2, the positioning reinforcement is a U-shaped steel bar clip or a short steel bar head, with a spacing of no more than 500mm, and is firmly welded or tied to the structural reinforcement, embedded parts or positioning reinforcement bracket.

[0011] Preferably, in S3, the interval between pouring the first part of concrete and the second part of concrete does not exceed 24 hours.

[0012] Preferably, after S2 and before S3, a joint sealant installation step is included: installing the joint sealant in the expansion joint and checking whether the joint sealant compresses the rubber waterstop or causes the centerline to shift; if there is compression or shift, the position or size of the joint sealant is adjusted until the rubber waterstop maintains the tension and centering posture required by the design.

[0013] Preferably, after S5, a data recording step is also included: uploading the pre-tensioning amount δ determined in S1, the image data during the construction process, and the concrete strength test report to the project management platform and storing them in association with the building information model of that node.

[0014] Preferably, in step S1, when determining the pre-tension amount δ, the pre-tension amount is also temperature-corrected according to the construction environment temperature T, as follows: when the construction environment temperature T is lower than the preset standard temperature T0, the pre-tension amount is reduced proportionally; when T is higher than T0, the pre-tension amount is increased proportionally; the correction ratio is predetermined based on the temperature response characteristics of the rubber waterstop material under tension.

[0015] Preferably, before step S1, a step to verify the actual width of the expansion joint is included: The actual width W1 of the expansion joint on the day of construction was measured using measuring tools, and the design width W2 of the expansion joint specified in the design drawings was obtained. Calculate the width difference ΔW = W1 - W2; If ΔW>0, then Δ in step S1 is corrected to Δ1 = Δ + ΔW; If ΔW < 0, then Δ in step S1 is corrected to Δ2 = Δ - |ΔW|, and the corrected Δ2 is not less than zero; The pre-stretching amount δ mentioned in step S1 is calculated based on the corrected Δ value.

[0016] Preferably, before step S1, a waterstop pretreatment step is included: the rubber waterstop is unfolded and laid flat, and left in a natural state for 24 hours to eliminate the internal stress generated by the curling and packaging, and to restore it to a straight state before determining the pre-stretch amount in step S1.

[0017] The present invention has at least the following beneficial effects: First, this invention, through quantitative calculation and precise application of pre-tension, ensures that the rubber waterstop is in a controllable initial tension state before being embedded in the concrete. This state ensures that the waterstop always operates within its elastic range when the expansion joint experiences maximum expansion and contraction displacement. It will not tear or detach from the concrete interface due to insufficient tension allowance, nor will it form bending wrinkles within the joint due to excessive relaxation. This effectively improves the reliability and durability of the waterproofing system at the intersection of the expansion joint and the construction joint.

[0018] Secondly, this invention employs a process of first tensioning to the pre-tensioned amount, then centering, and finally fixing with positioning ribs while maintaining tension. This ensures the waterstop is precisely positioned under its final working stress state. The positioning ribs are spaced along the length and closely attached to the root of the waterstop's flange or pass through pre-drilled installation holes. This significantly reduces displacement of the waterstop during concrete pouring caused by lateral pressure or vibration disturbance. Provided the positioning rib spacing is no greater than 500mm and they are reliably connected to the structural reinforcement, the deviation of the waterstop's centerline can be effectively controlled within the design allowable range, preventing waterproofing layer failure due to positioning deviation.

[0019] Third, this invention comprehensively considers the stress relaxation characteristics of rubber materials, the temperature differences in the construction environment, and the impact of structural construction errors on the pre-tension amount by selecting a relaxation coefficient within the range of 0.2 to 0.5, introducing a temperature correction coefficient, and verifying the actual width of the expansion joint on-site. These correction methods make the determination of the pre-tension amount more closely match the actual on-site conditions, avoiding deviations from the design target in the initial tension state of the waterstop due to material properties, environmental factors, or construction deviations, and enhancing the adaptability of the installation method to different working conditions.

[0020] Fourth, this invention eliminates the internal stress caused by the curling and packaging of the rubber waterstop by pre-treating it by laying it flat before tensioning, thus restoring the waterstop to a straight and stable state. This step avoids dimensional changes and alterations in stress state caused by the slow release of internal stress during tensioning or after concrete pouring, ensuring the accuracy of the pre-tensioning amount and improving the dimensional stability of the waterstop during long-term use.

[0021] Fifth, this invention achieves digital integration of key construction information by uploading pre-tensioning data, construction process video data, and concrete strength test reports to the project management platform and storing them in conjunction with the building information model. This approach provides intuitive evidence for the quality verification of concealed works, facilitates quick retrieval of construction records at any stage after project delivery by maintenance personnel, provides traceable original data for later maintenance and leakage investigation, and improves the level of information management throughout the entire project lifecycle.

[0022] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0024] This invention discloses a method for installing a rubber waterstop at the intersection of an expansion joint and a construction joint. This method is applicable to expansion joints in any direction. For ease of understanding and description, the following detailed explanation uses the most common vertical expansion joint (such as the junction of a basement floor slab and an exterior wall) as an example. In this method, "first end" refers to the end of the waterstop that is fixed first in the expansion joint, and "second end" refers to the end that is tensioned later. Taking a vertical expansion joint as an example, the first end corresponds to the bottom end, and the second end corresponds to the top end. For horizontal or inclined expansion joints, the first end is the fixed end determined by the design, and the second end is the tensioning end. This method includes the following steps: S1: Determination of Pre-tension Amount: Based on the maximum possible displacement Δ of the expansion joint along its structural length during use, determine the pre-tension amount δ that needs to be applied along the length of the rubber waterstop during installation, where δ = k·Δ, k is the relaxation coefficient, and 0.2 ≤ k ≤ 0.5; the meaning of the pre-tension amount δ is: the length of the rubber waterstop in its natural state is δ shorter than the design distance between its two fixed points, and its length after tensioning is exactly equal to the design distance; the design distance between the two fixed points is the structural length of the expansion joint in the section where the waterstop is installed; S2: Tensioning and Positioning: First, place the rubber waterstop at the preset position of the expansion joint, so that the first end, as the first fixed end, is located at the preset first installation position of the expansion joint, and the second end, as the subsequent tensioning end, is temporarily located at a position offset from the preset second installation position; then, fix the first end of the rubber waterstop to the structural steel bar or embedded part through the anchoring clamp to form the fixed end; subsequently, clamp the second end of the waterstop with the tensioning clamp, connect the tensioning equipment to apply tension along the length direction of the rubber waterstop, and tension the rubber waterstop to the pre-tension amount δ, at which point the second end is stretched to its preset second installation position; after reaching the pre-tension amount δ, maintain the tensioned state and check whether the center line of the rubber waterstop coincides with the design center line of the expansion joint. If there is a deviation, fine-tune the rubber waterstop to make it accurately centered; subsequently, under the premise of maintaining the tensioned state, use positioning bars to connect the flange of the rubber waterstop to the structural steel bar, embedded part, or specially set positioning bar bracket. The positioning bars are set at intervals along the length direction of the waterstop to prevent the waterstop from shifting during the concrete pouring process; S3: Concrete pouring: First, pour the first part of the concrete below the construction joint. The pouring height should ensure that the waterstop is reliably anchored. After this part of the concrete has set and has sufficient strength, pour the remaining second part of the concrete. S4: Fixture Removal: After all concrete has been poured and set, remove the tensioning fixtures. S5: Curing: Keep the concrete moist until the design age.

[0025] In the above technical solution, when installing rubber waterstops at the intersection of expansion joints and construction joints, the pre-tension amount must first be determined. Construction technicians obtain the maximum possible displacement Δ of the expansion joint during use based on the structural design documents. This data is calculated by the design unit based on factors such as the total length of the structure, the annual temperature range of the local area, the shrinkage characteristics of concrete, and the compressibility of the foundation. Based on this, the pre-tension amount δ is calculated using the formula δ = k·Δ, where Δ is the maximum displacement and k is the relaxation coefficient. The relaxation coefficient k can be selected within the range of 0.2 to 0.5, depending on the specific project conditions. This range has been verified through multiple sets of on-site tensioning tests and long-term observation, ensuring that the waterstop does not fail due to stress relaxation after tensioning, while also avoiding excessive initial strain that could accelerate material aging. This conforms to the "Polymer Waterproofing Materials Part 2: Waterstops" (GB 18173.2) and relevant engineering practice data. For example, when the expansion joint is mainly characterized by expansion and contraction and has high waterproofing requirements, k can be selected as a value between 0.2 and 0.3. When the expansion joint is mainly characterized by settlement and the rubber waterstop has high hardness, k can be selected as a value between 0.4 and 0.5. The physical meaning of the pre-tension amount δ is: the length of the rubber waterstop in its natural state is δ shorter than the design distance between its two fixed points. After tensioning, its length is exactly equal to the design distance. The design distance between the two fixed points is the structural length of the expansion joint in the section where the waterstop is installed. After determining the pre-tension amount, its length should be checked against this when the waterstop arrives on site to ensure that the material preparation is correct. At the same time, the rolled waterstop can be unrolled and laid flat on a flat ground for a period of time to eliminate the internal stress caused by curling.

[0026] After determining the pre-tension amount, the rubber waterstop is tensioned and positioned. The operator moves the rubber waterstop to the pre-set position at the expansion joint, placing the first end (bottom) of the waterstop at the design elevation of the foundation slab (pre-set first installation position), and the second end (top) of the waterstop, which will be tensioned later, temporarily placed at a lower position (approximately 200mm to 300mm below the design elevation, offset from the pre-set second installation position). After placement, the first end is fixed by using anchoring clamps to hold the flange of the waterstop at the first end. These clamps can be made of steel plates or reinforcing bars. The clamps are then welded or tied to the reinforcing steel frame or embedded parts of the foundation slab to form the fixed end. Once the fixed end is securely in place, a tensioning clamp is installed at the second end of the waterstop. This clamp can be a hand-operated clamp or a bolt-fastened clamp. The tensioning clamp is then connected to a tensioning device, which can be a hand-operated hoist or a screw jack. Start the tensioning equipment and apply a steady upward tension along the length of the rubber waterstop (i.e., vertically). During tensioning, use a steel ruler or laser rangefinder to measure the elongation of the waterstop. When the elongation reaches the pre-calculated pre-tension amount δ, stop tensioning and maintain this tension state. At this point, the second end of the waterstop is stretched to the designed top elevation position (i.e., the preset second installation position). Immediately after reaching the pre-tension amount, check the centering of the waterstop. The operator observes from both ends and sides of the expansion joint to see if the centerline of the rubber waterstop coincides with the design centerline of the expansion joint. If a left-right deviation is found, gently move the waterstop with a pry bar or wooden hammer while simultaneously fine-tuning the tensioning equipment's direction to ensure precise centering. After centering adjustment, while maintaining the tension state, use positioning bars to connect the flanges of the rubber waterstop to the structural steel bars on both sides of the expansion joint. Positioning bars can be U-shaped steel clips made of round steel with a diameter of 6mm to 10mm, or short steel bar ends can be used directly. Positioning bars are spaced apart along the length of the waterstop, with a spacing controlled between 400mm and 500mm. The positioning bars are placed close to the root of the waterstop flange, or pass through pre-drilled installation holes on the waterstop flange, and then firmly fixed to the main structural reinforcement by welding or binding. After all positioning bars are installed, check again whether the waterstop still maintains its pre-tension and center alignment. Once confirmed, proceed to the next step. If the joint is designed with a caulking board, it can be installed in the expansion joint after the positioning bars are installed and before concrete pouring. The caulking board can be polyethylene foam board or extruded polystyrene board. During installation, care should be taken to avoid compressing the waterstop or causing the waterstop's centerline to shift.

[0027] After tensioning and positioning are completed, concrete pouring and subsequent operations will proceed. Since this node involves a construction joint, the concrete needs to be poured in two stages. The first stage involves pouring the first portion of concrete below the construction joint, i.e., the foundation slab. Before pouring, the formwork and reinforcing steel should be cleaned and moistened with water. Pumped ready-mixed concrete can be used, and its strength grade should meet design requirements. During concrete pouring, the concrete should be poured from one side of the waterstop to ensure even rising and avoid direct impact on the waterstop. An immersion concrete vibrator can be used for compaction; the vibrator should be at least 50mm away from the waterstop to prevent displacement due to direct contact. The height of the first concrete pour should be strictly controlled at the design elevation of the construction joint to ensure that half of the waterstop is encased and anchored in concrete. After the first concrete pour is completed, it should be promptly covered and kept moist. The second concrete pour can only proceed after this portion of concrete has reached its final set and exceeded the design strength of 1.2 MPa. Before pouring the second portion of concrete, the laitance and loose stones on the construction joint surface should be removed. After cleaning, the exposed waterstop should be inspected to ensure it is not contaminated or damaged. The process requirements for the second concrete pour are the same as for the first, and care should be taken to avoid impacting or disturbing the waterstop.

[0028] After the second concrete pour is completed, the concrete should continue to be covered and kept moist for curing. After all the concrete has been poured and set, the tensioning clamps should be removed. When removing them, loosen the clamp bolts first, and then carefully remove the clamps to prevent damage to the poured concrete and the waterstop.

[0029] Finally, the concrete should be continuously moisturized and cured for no less than 14 days until it reaches the curing age specified in the design.

[0030] The beneficial effects of this technical solution are that by quantitatively calculating the pre-tension amount before installation and precisely applying this pre-tension amount during installation, the rubber waterstop is in a controllable initial tension state before being embedded in the concrete. The pre-tension amount is determined based on the design distance between the fixed points at both ends of the waterstop. This state ensures that the waterstop operates within its elastic range even when the expansion joint experiences maximum displacement, preventing damage due to insufficient tension or instability due to excessive relaxation. Furthermore, this solution employs a process of first tensioning to the pre-tension amount, then centering, and finally fixing with positioning ribs while maintaining tension. This ensures the waterstop is precisely positioned under its final working stress state. The positioning ribs, spaced along the length, effectively constrain any directional displacement of the waterstop during concrete pouring, thus guaranteeing that the centerline of the waterstop always coincides with the centerline of the expansion joint.

[0031] Furthermore, in step S1, the relaxation coefficient k is the core parameter for determining the pre-stretch amount δ, and its value range is limited to 0.2 ≤ k ≤ 0.5. This range is determined based on the following principle: Firstly, there's the stress relaxation characteristic of rubber materials. As a viscoelastic material, rubber undergoes stress relaxation under constant strain—that is, the initial stress gradually decreases over time. If the waterstop is subjected to excessive initial tensile stress during installation, stress relaxation over time may lead to the following consequences: 1) An excessively large k value (e.g., k>0.5): While the high initial tensile stress ensures the waterstop is taut at the beginning of installation, stress relaxation during long-term service may still cause creep fracture or separation from the concrete interface due to excessive initial strain; 2) An excessively small k value (e.g., k<0.2): The low initial tensile stress means the waterstop is already close to being relaxed during installation, and stress relaxation may cause it to completely lose tension, failing to effectively resist the tensile displacement of the expansion joint. Therefore, the k value needs to be set in a balance between initial tension and long-term relaxation, ensuring the waterstop remains under appropriate tension throughout its service life.

[0032] The second principle is the elastic strain distribution principle. Let the maximum possible displacement of the expansion joint be Δ, and the pre-tension of the waterstop during installation be δ = k·Δ. When the expansion joint experiences a tensile displacement Δ, the total tension of the waterstop is δ + Δ = (1+k)·Δ, where: the pre-tension δ = k·Δ corresponds to the strain already borne by the waterstop during installation; the remaining displacement (1-k)·Δ corresponds to the strain the waterstop needs to bear during service. If k=0 (no pre-tension), the waterstop needs to bear all Δ of the tension during service, which may exceed its elastic limit; if k=1 (full pre-tension), the waterstop bears all Δ of the tension during installation, remaining in a state of ultimate strain for a long time, easily leading to stress relaxation and fatigue failure; if k is 0.2~0.5, the waterstop bears 20%~50% of the expected maximum displacement strain during installation, with the remaining 50%~80% strain reserve used for actual deformation during service, ensuring initial tension while reserving sufficient safety margin. This distribution principle ensures that the waterstop always works within its elastic range, neither tearing due to insufficient tensile allowance nor aging accelerated due to excessive initial strain.

[0033] Thirdly, there is the principle of fatigue life optimization. The fatigue life of rubber materials is closely related to the alternating strain amplitude they withstand. Studies have shown that rubber materials have a longer fatigue life at lower strain amplitudes. If the waterstop is installed in a relaxed state (k value too small), when the expansion joint shifts, the waterstop will bear the full strain amplitude, easily leading to early fatigue failure. If the waterstop is installed in an overly tight state (k value too large), even if the expansion joint shifts slightly, the waterstop will always be in a high strain state, which will also shorten its fatigue life. By controlling the k value within the range of 0.2 to 0.5, the strain amplitude that the waterstop bears during service can always be within the optimal fatigue life range for rubber materials, avoiding both early failure caused by high strain amplitudes and stress relaxation and creep caused by long-term high static strain.

[0034] Fourthly, the principle of comprehensive deformation compatibility is applied. Expansion joints may simultaneously withstand multiple deformations such as tension, compression, and shear in actual use. The pre-tension amount δ = k·Δ is mainly set for tensile deformation, but the selection of the k value also needs to consider other deformation forms: 1) Compression deformation: When the expansion joint is compressed, the pre-stretched waterstop will shorten accordingly, but it can still maintain a straight state without wrinkling. The larger the k value, the stronger the waterstop's ability to maintain straightness during compression deformation; 2) Shear deformation: When the waterstop is subjected to shear deformation, the anchorage interface between its flange and the concrete is the weakest point. An excessively large k value will cause the waterstop to be in a high-tension state for a long time, weakening its shear resistance; an excessively small k value will make the waterstop too loose, and interface peeling is likely to occur during shear deformation. The range of 0.2~0.5 is the balance point sought among tension, compression, and shear deformation, ensuring that the waterstop maintains reliable waterproof performance under various deformation conditions.

[0035] Fifthly, engineering practice validates the results. The determination of the above-mentioned range of k-values ​​is based not only on theoretical analysis but also on practical experience from similar projects both domestically and internationally. Statistical analysis of the service status of rubber waterstops in existing projects reveals that: at nodes with k-values ​​less than 0.2, the waterstops generally show signs of loosening and wrinkling after 5-10 years of service, significantly increasing the risk of leakage; at nodes with k-values ​​greater than 0.5, some waterstops experience aging cracking and separation from the concrete interface after 3-5 years of service; at nodes with k-values ​​between 0.2 and 0.5, the highest proportion maintain good waterproofing performance even after more than 15 years of service. This statistical pattern further validates the rationality of the k-value range.

[0036] In another technical solution, in S2, the positioning reinforcement is a U-shaped steel bar clip or a short steel bar head, with a spacing of no more than 500mm, and is welded or tied firmly to the structural reinforcement, embedded parts or positioning reinforcement bracket.

[0037] In the above technical solution, during the tensioning and positioning process in step S2, the specific form and installation method of the positioning reinforcement can be selected according to the site conditions. The main function of the positioning reinforcement is to prevent the rubber waterstop from shifting during concrete pouring. It can be in the form of a U-shaped steel bar clip. The U-shaped steel bar clip can be fabricated on-site using surplus round steel with a diameter of 8mm to 12mm. First, cut the round steel to the required length, and then bend it into a U-shape on a steel bar bending machine. The width of the U-shaped opening should be slightly larger than the width of the waterstop flange, usually 10mm to 20mm wider than the flange width, so as to be able to be clipped into the waterstop without being too loose and losing its restraining effect. The positioning reinforcement can also be a short steel bar end. The short steel bar end can be selected from threaded steel bars or round steel with a diameter of 10mm to 14mm, cut into sections of 100mm to 150mm in length. When using it, one end is tightly attached to the root of the waterstop flange, and the other end is connected to the structural steel reinforcement. The spacing of the positioning bars along the length of the waterstop can be adjusted according to the rigidity of the waterstop and the magnitude of the lateral pressure during concrete pouring, generally controlled between 400mm and 500mm, with a maximum spacing not exceeding 500mm. At the corners of expansion joints or near the joints of the waterstop, the spacing of the positioning bars can be appropriately increased to about 300mm to enhance the fixing effect of these weak points.

[0038] The connection method between the positioning reinforcement and the main structural reinforcement can be selected by welding or binding, depending on the arrangement of the reinforcement on site. When welding is used, an electric welding machine can be used to spot weld the positioning reinforcement to the main structural reinforcement. During welding, prolonged welding near the waterstop should be avoided to prevent the rubber waterstop from being burned by high temperatures. When binding is used, annealed wire or tie wire can be used to securely bind the positioning reinforcement to the main structural reinforcement. The binding should be at least two turns and tightened to prevent loosening. For construction areas without structural reinforcement, a dedicated positioning reinforcement support can be installed. The positioning reinforcement support can be made of angle steel, channel steel, or reinforcing steel and fixed to the poured concrete or foundation layer with expansion bolts, or temporarily fixed using a formwork support system. The positioning reinforcement should be securely welded or bound to the support to ensure effective restraint of the waterstop's displacement during concrete pouring.

[0039] After the positioning bars are installed, they should be checked point by point along the length of the waterstop to ensure they are in close contact with the waterstop flange. For positioning bars using short steel bar ends, check if they are tightly against the root of the waterstop flange. For positioning bars using U-shaped steel bar clips, check if they are properly secured to the waterstop flange and have adequate tension. If gaps are found between the positioning bars and the waterstop, the position of the positioning bars can be adjusted appropriately or spacers can be inserted into the gaps to ensure that each positioning bar effectively provides restraint. After installation, a second check should be performed before subsequent concrete pouring to prevent the positioning bars from loosening or falling off due to construction activities.

[0040] The beneficial effects of this technical solution are as follows: by using U-shaped steel bar clips or short steel bar ends as positioning bars, and controlling their spacing to be no more than 500mm, and welding or binding them firmly with the main structural reinforcement, the displacement of the rubber waterstop during concrete pouring can be effectively restrained. The U-shaped steel bar clips can clamp the waterstop flanges from both sides, limiting its tendency to swing left and right and float up and down, while the short steel bar ends, placed close to the flange root, can effectively prevent the waterstop from sliding along its length. The uniform arrangement with a spacing of no more than 500mm ensures reliable restraint points along the entire length of the waterstop, avoiding insufficient local restraint that could lead to wavy deformation or overall displacement of the waterstop under concrete vibration. Both welding and binding connection methods can adapt to different construction site conditions, ensuring that the positioning bars and structural reinforcement form an integral whole, jointly resisting the lateral pressure and vibration impact during concrete pouring. This ensures that the centerline of the waterstop always coincides with the design centerline of the expansion joint, providing a guarantee for the quality of subsequent concrete pouring.

[0041] In another technical solution, in S3, the interval between the pouring of the first part of concrete and the second part of concrete does not exceed 24 hours.

[0042] In the above technical solution, during the concrete pouring process in step S3, the interval between the pouring of the first and second portions of concrete can be adjusted according to the environmental conditions and concrete properties during construction. The starting point of the interval is the moment when the first portion of concrete is poured, and the ending point is the moment when the second portion of concrete begins to be poured. After the first portion of concrete is poured, it should be immediately covered for curing. The covering material can be plastic film or damp geotextile to prevent excessive evaporation of moisture. Under normal temperature conditions, i.e., when the ambient temperature is between 15℃ and 25℃, the final setting time of concrete prepared with ordinary Portland cement usually occurs 8 to 12 hours after pouring. In this case, the interval can be controlled between 12 and 20 hours to ensure that the first portion of concrete has reached its final set and has a certain strength, while not exceeding the upper limit of 24 hours. Under high temperature conditions, i.e., when the ambient temperature is above 30℃, the concrete setting speed is accelerated, and the final setting time may be shortened to 6 to 8 hours. In this case, the interval can be shortened accordingly, but it should still be ensured that the second portion of concrete is poured only after the first portion of concrete has reached its final set. In low-temperature environments, i.e., when the ambient temperature is below 5℃, the setting speed of concrete slows down significantly, and the final setting time may be extended to more than 20 hours. In such cases, the setting status of the concrete should be closely monitored. The second part of the concrete can be poured 20 to 24 hours after the first part, but not exceeding 24 hours. If, due to special circumstances, the interval is expected to exceed 24 hours, additional shear reinforcement should be installed at the construction joint as per design requirements, or the surface should be roughened to ensure the bonding quality between the old and new concrete. The control of the interval time is also related to the strength grade of the concrete. For higher strength grades of concrete, such as C40 and above, the early strength development is faster, and the interval time can be appropriately shortened. For lower strength grades of concrete, such as C25 and below, the early strength development is slower, and the interval time can be appropriately extended, but not exceeding 24 hours. In actual construction, the strength development of the first part of the concrete can be tested by leaving test blocks cured under the same conditions on-site. When the strength reaches 1.2 MPa or above, the second part of the concrete can be poured, ensuring that the time from the completion of the first part to the start of the second part does not exceed 24 hours.

[0043] The beneficial effects of this technical solution are that by controlling the interval between the pouring of the first and second portions of concrete to within 24 hours, the construction cycle can be effectively shortened while ensuring the quality of the construction joint treatment. An interval of no more than 24 hours ensures that the surface of the first portion of concrete is still relatively fresh when the second portion is poured, avoiding excessive drying or contamination of the construction joint surface due to a longer interval, thus reducing the workload of roughening and cleaning. Simultaneously, this time control ensures that the first portion of concrete, after final setting, possesses sufficient strength to withstand the load and vibration of the second portion of concrete pouring, preventing crushing or cracking at the construction joint. Within the 24-hour interval, the hydration reactions of the two portions of concrete are interconnected, which is conducive to forming a good bonding surface, reducing the risk of leakage due to improper cold joint treatment, and improving the overall waterproof performance and structural reliability of the intersection of the expansion joint and the construction joint.

[0044] In another technical solution, after S2 and before S3, there is also a caulking plate installation step: install the caulking plate in the expansion joint and check whether the caulking plate squeezes the rubber waterstop or causes the center line to shift; if there is squeezing or shifting, adjust the position or size of the caulking plate until the rubber waterstop maintains the tension and centering posture required by the design.

[0045] In the above technical solution, after tensioning and positioning in step S2 and before concrete pouring in step S3, the joint sealant can be installed according to design requirements. The joint sealant forms a compressible isolation layer within the expansion joint, reserving space for structural expansion and settlement, and also serves as a template for pouring concrete on the other side. The material of the joint sealant can be selected based on the design width of the expansion joint and the usage environment. Closed-cell polyethylene foam board, extruded polystyrene board, or asphalt-impregnated fiberboard can be used. The thickness of the joint sealant should be selected according to the design width of the expansion joint. Typically, when the expansion joint width is 20mm to 30mm, the joint sealant thickness can be the same as the joint width; when the expansion joint width is 30mm to 50mm, the joint sealant thickness can be 2mm to 3mm smaller than the joint width to facilitate installation and allow space for the waterstop. The width of the joint sealant should be determined based on the embedment depth of the waterstop and the structure of the expansion joint. Generally, the upper edge of the sealant should be flush with or slightly lower than the lower edge of the center hole of the waterstop after installation to avoid the sealant compressing the deformed part of the waterstop. Before installing the sealant, clean the debris and loose concrete fragments in the expansion joint, which can be done by blowing with compressed air or rinsing with clean water. Cut the sealant to the length of the expansion joint, using a utility knife or hot wire cutter to ensure a straight cut. Insert the cut sealant section by section from one end of the expansion joint, ensuring it is flush against the poured concrete or formwork on the side, while avoiding the already installed positioning reinforcement. After the sealant is in place, use temporary supports or wooden wedges to secure it and prevent displacement during subsequent work. Inspect the sealant immediately after installation. During inspection, the relative positions of the sealant and the rubber waterstop can be observed from the opening side of the expansion joint. Check if the sealant is compressing the waterstop, which may manifest as significant deformation of the waterstop's center hole or the waterstop's flange being pushed up. Simultaneously, check if the sealant is causing the waterstop's centerline to shift. Select multiple sections along the length of the expansion joint and measure the distance between the waterstop's centerline and the expansion joint's design centerline. If the deviation exceeds 5mm, it indicates that the sealant installation has affected the waterstop's position. If compression or shifting is found, adjustment measures should be taken according to the specific situation. For cases where the sealant partially compresses the waterstop, the sealant can be removed, and the affected area can be thinned by 2mm to 3mm with a utility knife, or the sealant can be cut into two sections and spliced ​​together, leaving a gap at the compression point. For cases where the sealant's overall compression causes the waterstop to shift, the temporary fixation of the sealant should be loosened, and its insertion depth and position readjusted to maintain a small gap of 1mm to 2mm between the sealant and the waterstop. After adjustment, check again until the rubber waterstop maintains its designed posture, that is, the center line of the waterstop coincides with the center line of the expansion joint, and the center hole remains in a natural circular or elliptical shape. After confirming that everything is correct, the joint sealant can be placed in place, awaiting subsequent concrete pouring.When pouring the second part of the concrete, the joint filler board will act as a formwork on one side and bear the lateral pressure of the concrete. Therefore, it should be ensured that it does not shift or deform during the pouring process.

[0046] The beneficial effect of this technical solution lies in the fact that by specifically setting up a joint sealant installation and inspection step before concrete pouring, the adverse effects of the joint sealant on the rubber waterstop can be effectively avoided. Improper installation of the joint sealant can easily compress the waterstop, causing the central hole of the waterstop to be flattened or the flanges to warp. These deformations cannot be recovered after concrete pouring, resulting in permanent waterproofing defects. Timely inspection and adjustment after installation can eliminate the compression of the waterstop by the joint sealant, ensuring that the waterstop maintains the designed natural tension and precise centering position. Simultaneously, this step also ensures a reasonable gap between the joint sealant and the waterstop, allowing the expansion joint to compress and rebound normally during use, preventing the expansion joint's expansion function from being affected by excessive tightness between the joint sealant and the waterstop. This improves the overall reliability and durability of the waterproofing system at the intersection of the expansion joint and the construction joint.

[0047] In another technical solution, after S5, a data recording step is also included: the pre-tension amount δ determined in S1, the image data during the construction process, and the concrete strength test report are uploaded to the project management platform and stored in association with the building information model of that node.

[0048] In the above technical solution, after determining the pre-tension amount in step S1, completing the construction process in steps S2 to S4, and completing the curing in step S5, data recording and uploading can be performed according to project management requirements. The purpose of data recording is to digitally archive key parameters and data during the construction process and link them with the building information model to facilitate subsequent quality traceability and operation and maintenance management. First, the specific value of the pre-tension amount δ determined in step S1 is compiled. This value can be extracted from the original data in the construction record table, including the value of the maximum expansion displacement Δ of the expansion joint, the basis for selecting the relaxation coefficient k, and the finally calculated pre-tension amount δ. This data is entered into an electronic document, which can be in Excel or PDF format. Then, image data of the construction process is collected, including photos of the waterstop inspection upon arrival, photos of the tensioning and positioning process, photos of the positioning bar installation, photos of the joint filler installation and inspection, photos of the two concrete pours, and photos after the clamps are removed. Digital cameras or smartphones can be used to take the images. When taking the photos, the images should be clear and able to reflect the construction quality of key processes. Two to three photos from different angles can be taken for each key process, and the photo file format can be JPEG. Simultaneously, compile the concrete strength test report. This report should be prepared by retaining test blocks during concrete pouring. The test blocks can be standard 150mm cubes, cured under standard curing conditions for 28 days, and then sent to a qualified testing institution for compressive strength testing. The obtained test report can be a scanned copy or an electronic version. Upload the aforementioned pre-tensioning data, image data, and concrete strength test report to the project management platform. The project management platform can be a cloud server built by the construction company or third-party project collaborative management software. Uploads should be categorized according to the levels of unit project, sub-project, and item project. Locate the intersection node of the expansion joint and construction joint in the platform and associate the file with the building information model (BIM) of that node. The BIM can be created using modeling software such as Revit, and includes the node's 3D geometric information, material information, and design parameters. Association can be achieved in the project management platform through drag-and-drop or linking, establishing a correspondence between each file and a specific component or node ID in the model. After association, click on the node in the model to view all uploaded data, enabling visual traceability of the construction process. Uploaded data should be backed up, either by storing it on a local server or an external hard drive, to prevent data loss. The entire data recording process should be handled by a designated person to ensure data integrity and timely upload.

[0049] The beneficial effects of this technical solution lie in the digital integration of key construction information by uploading pre-tensioning measurements, image data, and concrete strength test reports to the project management platform and storing them in conjunction with the Building Information Model (BIM). Pre-tensioning, as a core parameter of this installation method, is archived to facilitate verification of calculation basis and construction execution during subsequent acceptance. Image data records the actual operational status of each process, providing intuitive evidence for the quality verification of concealed works and avoiding the problem of being unable to inspect due to process overlap. Concrete strength test reports, as proof of concrete quality, can be retrieved at any time during the operation and maintenance phase after being associated with nodes, providing basic data for structural safety assessment. The association with the BIM gives these scattered data a unified spatial location. After project delivery, operation and maintenance personnel can quickly find the construction record of any node through the model, facilitating later maintenance and leakage investigation, and improving the level of information management throughout the entire project lifecycle.

[0050] In another technical solution, in step S1, when determining the pre-tension amount δ, the pre-tension amount is also corrected according to the construction environment temperature T: when the construction environment temperature T is lower than the preset standard temperature T0, the pre-tension amount is reduced proportionally; when T is higher than T0, the pre-tension amount is increased proportionally; the correction ratio is predetermined based on the temperature response characteristics of the rubber waterstop material under tension.

[0051] In the above technical solution, during the determination of the pre-tension amount in step S1, the pre-tension amount is also corrected based on the ambient temperature during construction to eliminate the influence of temperature changes on the tension state of the rubber waterstop. The relationship between the tensile stress and elongation of the rubber waterstop material under tension is significantly affected by temperature: as the temperature rises, the thermal motion of the rubber molecular chains intensifies, increasing the tensile stress required to maintain the same elongation; conversely, the opposite occurs when the temperature decreases. The ambient temperature during construction may differ from the temperature during the structure's service life. If construction is carried out in a high-temperature season while the ambient temperature during the structure's service life is low, the tensile stress of the waterstop will change after the temperature drops, causing the actual stress state to deviate from the design expectations, and vice versa. Therefore, the ambient temperature during construction should be measured before calculating the pre-tension amount. A mercury thermometer or electronic thermometer can be used for temperature measurement. Measurements should be taken at an unobstructed location at a height of 1.5m above the ground on the construction site, and three consecutive measurements should be taken, with the average value taken as the construction ambient temperature T.

[0052] The preset standard temperature T0 is typically taken as 20℃, which is the reference temperature usually used in structural design. If there are special requirements for the project, the value of T0 can be adjusted according to the actual situation and specified in the construction technical documents. The correction proportional coefficient is predetermined based on the temperature response characteristics of the rubber waterstop material under tension, specifically determined based on the temperature-modulus relationship curve provided by the material supplier, historical test data of similar materials, or on-site sampling and testing results. When the construction ambient temperature T is lower than T0, the pre-tension amount is reduced proportionally; when T is higher than T0, the pre-tension amount is increased proportionally. The pre-tension amount δ is calculated based on the corrected value.

[0053] In actual construction, temperature correction can be performed in advance after obtaining weather forecast data. Construction technicians can check the weather forecast issued by the local meteorological department the day before the planned concrete pouring to obtain the expected ambient temperature range for the next day's construction period, and take the median value as the basis for calculation. If the construction period is long and spans different seasons, the ambient temperature should be measured in sections, and the pretension correction value for each section should be calculated separately. Temperature measurement records should be archived as part of the construction technical data, and the records should include the measurement date, measurement time, measurement location, measuring instrument number, three measurement readings, and the average value. The basis for determining the correction ratio coefficient should also be archived for future reference. During the tensioning operation, the ambient temperature may change. If the temperature change exceeds 5°C, the ambient temperature should be remeasured and the pretension correction value should be checked. If necessary, the tensioned waterstop should be adjusted. During adjustment, the tensioning clamps can be loosened first, and the pretensioning can be re-tensioned according to the newly calculated pretension, and then centered and fixed. The temperature-corrected pretension should be marked together with the original calculated value on the construction drawings or technical handover documents for easy reference by on-site operators.

[0054] The introduction of temperature correction makes the determination of pretension more consistent with actual construction conditions. Rubber materials are quite sensitive to ambient temperature when under tension; if temperature is not considered, construction under extreme temperature conditions may lead to a deviation of the pretension from the design target. By introducing temperature correction, the influence of ambient temperature can be quantified and incorporated into the pretension calculation, ensuring that the initial tension of the waterstop when finally embedded in concrete matches the design expectation. This correction method is applicable to construction in different climate zones; whether in high-temperature or cold regions, adjusting the pretension ensures that the waterstop achieves a suitable initial tension.

[0055] The beneficial effect of this technical solution lies in eliminating the influence of the difference between the construction environment temperature and the design reference temperature on the initial tension state of the waterstop by introducing temperature correction in the pre-tension calculation. Appropriately increasing the pre-tension during construction in high-temperature seasons can compensate for the impact of subsequent temperature changes on the tension state; appropriately decreasing the pre-tension during construction in low-temperature seasons can avoid over-tensioning caused by subsequent temperature changes. After temperature correction, regardless of the construction season, the waterstop can maintain its designed initial tension under the operating temperature conditions, ensuring that it has an appropriate tension allowance when expansion and contraction occur in the deformation joint. This correction method is based on the temperature response characteristics of rubber materials, is easy to operate, and only requires adding a temperature measurement step during the construction preparation stage to improve the accuracy of the pre-tension calculation, thus enhancing the adaptability of the waterstop installation method to different climatic conditions.

[0056] In another technical solution, a step to verify the actual width of the expansion joint is included before step S1: The actual width W1 of the expansion joint on the day of construction was measured using measuring tools, and the design width W2 of the expansion joint specified in the design drawings was obtained. Calculate the width difference ΔW = W1 - W2; If ΔW>0, then Δ in step S1 is corrected to Δ1 = Δ + ΔW; If ΔW < 0, then Δ in step S1 is corrected to Δ2 = Δ - |ΔW|, and the corrected Δ2 is not less than zero; The pre-stretching amount δ mentioned in step S1 is calculated based on the corrected Δ value.

[0057] In the above technical solution, before determining the pre-tension amount in step S1, the actual width of the expansion joint can be verified on-site to ensure that the calculation basis of the pre-tension amount matches the actual dimensions of the structure. The design width of the expansion joint is usually marked on the structural construction drawings. However, during actual construction, due to deviations in formwork support, errors in rebar installation, and the influence of lateral pressure during concrete pouring, the final formed width of the expansion joint may differ from the design width. If the pre-tension amount is determined directly based on the design width, and the actual joint width deviates significantly from the design joint width, the initial tension of the waterstop may deviate from expectations. Therefore, before calculating the pre-tension amount, surveyors can be arranged to measure the actual width of the expansion joint on the day of construction. Vernier calipers or steel tape measures can be used. The range of the vernier calipers can be selected from 0mm to 200mm with an accuracy of 0.02mm, and the length of the steel tape measure can be selected from 3m to 5m with an accuracy of 1mm. During measurement, several representative cross-sections should be selected along the length of the expansion joint. The number of cross-sections can be determined based on the total length of the expansion joint. For joints less than 10m long, three cross-sections can be selected, located at both ends and the middle of the joint. For joints longer than 10m, the number of cross-sections can be increased appropriately, with one cross-section added every 5m to 8m. At each cross-section, the actual width of the expansion joint should be measured. The measuring tool can be perpendicular to the concrete surfaces on both sides of the expansion joint, and the minimum distance between the two surfaces can be read as the actual width of that cross-section. The average of the measured widths of each cross-section is taken as the actual width W1 of the expansion joint on the construction day. Simultaneously, the design width W2 of the expansion joint is obtained from the design drawings. The width difference ΔW is calculated using the formula: ΔW equals W1 minus W2. Based on the sign and magnitude of the width difference ΔW, the maximum expansion displacement Δ in step S1 is corrected. If ΔW is greater than 0, it indicates that the actual width of the expansion joint is greater than the design width. In this case, the initial gap of the expansion joint is larger, and Δ is corrected to Δ1 equal to Δ plus ΔW. If ΔW is less than 0, it indicates that the actual width of the expansion joint is less than the design width. In this case, the initial gap of the expansion joint is small, and Δ is corrected to Δ2 = Δ - |ΔW|. The corrected Δ2 should not be less than zero. If the calculated Δ2 is less than zero, it is taken as zero. After the correction is completed, the pre-tension amount δ mentioned in step S1 is calculated based on the corrected Δ value, that is, δ is equal to k multiplied by the corrected Δ value. For example, if the design width W2 of an expansion joint is 30mm, the measured width W1 is 32mm, ΔW is 2mm, and the designed maximum expansion displacement Δ is 20mm, then the corrected Δ1 is 22mm, and the pre-tension amount δ is calculated by multiplying 22mm by the relaxation coefficient k. If the measured width W1 is 28mm and ΔW is -2mm, then the corrected Δ2 is 18mm, and the pre-tension amount δ is calculated by multiplying 18mm by the relaxation coefficient k.

[0058] In practice, the verification of the actual width of the expansion joint can be carried out simultaneously with the preparation work before the installation of the waterstop. Before measurement, the concrete surface on both sides of the expansion joint should be cleaned to remove laitance and loose particles, ensuring that the measurement location is flat. The measurement sections should be marked for easy retrieval and verification later. The measurement record should include the measurement date, measurement time, measuring personnel, measuring instrument model, measured width value of each section, average value, and calculated width difference. If the deviation between the actual width of the expansion joint and the design width is large, exceeding 10mm or 20% of the design joint width, the supervision unit and design unit should be notified for confirmation. If necessary, the design unit should issue a design change notice. The corrected maximum expansion displacement Δ value should be clearly marked in the construction technical briefing and used as the control basis for tensioning operations. During subsequent tensioning operations, a displacement limiting device should be installed on the tensioning equipment to ensure that the tensioning elongation is accurately controlled within the corrected pre-tension range.

[0059] The introduction of a width verification step makes the determination of pretension amount more closely aligned with actual site conditions. The actual forming width of the expansion joint is affected by various construction factors and exhibits a certain degree of dispersion. Ignoring this difference and directly applying design parameters may lead to an overestimation or underestimation of the pretension amount. By measuring the joint width and making corrections, the actual geometric dimensions of the structure can be incorporated into the calculation system, ensuring that the initial tension state of the waterstop matches the actual structural conditions. The correction method's stipulation that the corrected Δ2 should not be less than zero when ΔW is negative avoids the logical error of a negative pretension amount due to an underestimation of the joint width, ensuring the rationality of the calculation results.

[0060] The beneficial effect of this technical solution lies in eliminating the influence of structural construction errors on the initial tension state of the waterstop by adding a step to verify the actual width of the expansion joint before determining the pre-tension amount. When the actual width of the expansion joint is greater than the design width, the pre-tension amount is appropriately increased to compensate for the additional requirement of the waterstop to adapt to a larger expansion range due to the increased joint width. When the actual width of the expansion joint is less than the design width, the pre-tension amount is appropriately reduced to avoid the risk of the waterstop being too tightly tensioned initially due to the joint width being too small. This verification and correction method combines design parameters with on-site measured data, making the calculation basis of the pre-tension amount more reliable, improving the fault tolerance of the installation method to construction errors, and ensuring that a suitable initial tension state of the waterstop can be obtained under different construction precision conditions. At the same time, the recording and archiving of measured data also provides a traceable original basis for subsequent quality acceptance.

[0061] In another technical solution, before step S1, a waterstop pretreatment step is also included: the rubber waterstop is unfolded and laid flat, and left in a natural state for 24 hours to eliminate the internal stress caused by the curling and packaging, and after it returns to a straight state, the pre-stretch amount is determined in step S1.

[0062] In the above technical solution, before determining the pre-tension amount in step S1, the incoming rubber waterstop can be pre-treated to eliminate the internal stress caused by the rolled packaging. During packaging and transportation after production, rubber waterstops are usually stored in rolls. This rolled state causes residual stress within the waterstop material. If the waterstop with rolled internal stress is directly subjected to pre-tension determination and tensioning operations, phenomena such as waterstop twisting, lateral bending, or localized stress concentration may occur during tensioning, affecting the control of tensioning accuracy. Simultaneously, the presence of rolled internal stress will also cause errors in the measurement of the waterstop's length in its natural state, as the waterstop cannot present its true natural length when rolled. Therefore, before determining the pre-tension amount, the rolled rubber waterstop can be removed from the packaging and laid flat on a flat, dry surface free of sharp objects at the construction site or material storage area. The area of ​​the laying area should be determined according to the length and width of the waterstop, and should be able to accommodate the entire waterstop fully unfolded without bending. Pull the waterstop from the core and slowly unfold it in a straight line. Two to three workers can assist during this process to prevent the waterstop from being scratched by sharp objects while dragging it on the ground. Once unfolded, the waterstop should be completely straight along its length and flat against the ground in its width. Small counterweights, such as sandbags or bricks, can be placed every 2-3 meters on both sides of the waterstop to prevent it from curling or shifting due to wind or uneven ground. The waterstop should be left in its natural state for at least 24 hours, avoiding direct sunlight and rain. A layer of tarpaulin or shade netting can be used for protection. The placement time is calculated from when the waterstop is fully unfolded and flat until 24 hours later. During this process, the molecular chains inside the rubber material gradually relax, releasing the residual stress caused by curling, and the waterstop gradually returns to its natural straight state. After 24 hours of placement, the straightness of the waterstop can be observed after removing the counterweight. Measure the distance of the waterstop's centerline from the straight line every 1m along its length. If the deviation does not exceed 10mm, the internal stress can be considered to have been basically eliminated. The pre-treated waterstop can then be used for subsequent pre-tensioning and tensioning operations.

[0063] In practice, the pretreatment step of the waterstop can be carried out simultaneously with the material inspection upon arrival. After the waterstop arrives on site, quality inspectors can first conduct a visual quality inspection and dimensional measurement according to the material standards, and then move the waterstop to the pretreatment area for unfolding and laying. The ground of the pretreatment area should be cleaned in advance, and a layer of plastic film or geotextile can be laid to prevent the waterstop from being contaminated by direct contact with the ground. For long waterstops, such as those exceeding 20m, they can be unfolded in sections, but each section should be ensured to have sufficient laying length. During the placement period, a dedicated person should be assigned to regularly patrol and check whether the waterstop has been blown by the wind or damaged by animals. If the construction schedule is tight, the 24-hour placement time can be arranged at night, with other preparatory work carried out during the day, without affecting the overall construction period. After the pretreatment is completed, the installation direction and center line position should be marked on the surface of the waterstop with a marker to facilitate the centering operation during subsequent tensioning. After marking, the waterstop can be moved to the expansion joint installation position to begin the determination of the pre-tension amount in step S1 and subsequent procedures.

[0064] The pretreatment steps take into account the basic viscoelastic properties of rubber. As a polymer, rubber undergoes stress relaxation under long-term stress. The rolled-up packaging keeps the waterstop in a bent state for an extended period, storing elastic potential energy. This potential energy does not disappear immediately after the waterstop is unrolled but is gradually released over time. If pre-stretching is performed before the internal stress is released, the internal stress will superimpose with the tensile stress, causing the actual stress state of the waterstop to differ from the calculated value. Furthermore, the release of internal stress may continue after tensioning or even after concrete pouring, causing slow changes in the size and stress state of the waterstop, affecting its long-term waterproofing effect. Allowing it to rest naturally for 24 hours allows most of the internal stress to be released before tensioning, enabling the waterstop to enter a relatively stable initial state.

[0065] The beneficial effects of this technical solution are that by adding a pre-treatment step for the waterstop before determining the pre-tension amount, the influence of internal stress generated by the curling packaging on the tensioning accuracy is eliminated. After 24 hours of natural placement, the length and shape of the waterstop tend to stabilize. Based on this, the pre-tension amount calculation and on-site tensioning can avoid dimensional changes and tensioning errors caused by the release of internal stress. The pre-treated waterstop returns to a straight state, and the force is uniform during tensioning, making it less prone to twisting and lateral bending, which helps to ensure the precise alignment of the waterstop centerline with the design centerline of the expansion joint. At the same time, the early release of internal stress also eliminates the potential risk of slow deformation of the waterstop after concrete pouring, improves the dimensional stability of the waterstop during long-term use, and enhances the reliability of the waterproofing system at the intersection of the expansion joint and the construction joint.

[0066] <Example 1> This embodiment takes the intersection of the expansion joint and construction joint at the junction of the basement floor slab and the exterior wall of an underground project as an example to illustrate the implementation process of the present invention in detail.

[0067] 1. Project Background and Node Overview An underground engineering project is located in North China. The structure is designed for a 50-year service life and has a Class I waterproofing rating (no water seepage allowed, no dampness on the structural surface). The basement floor slab is 800mm thick, and the exterior walls are 500mm thick. The floor slab is poured first, followed by the walls, forming a horizontal construction joint between them. A through expansion joint, 30mm wide, is provided at the junction of the floor slab and the exterior walls to accommodate structural displacement caused by temperature changes and uneven foundation settlement.

[0068] According to the structural calculations provided by the design unit, considering factors such as the annual temperature difference in the region, the length of the structural section (approximately 36m), and the compressibility of the foundation, the maximum possible displacement Δ along the structural length of the expansion joint during its service life is 20mm. This value is determined based on Article 6.5.2 of the "Code for Design of Concrete Structures" (GB 50010) regarding the calculation method for expansion joint displacement, combined with the foundation compression layer thickness and settlement calculation value (settlement difference 8mm) in the project's geological survey report, and the calculated structural temperature deformation value (12mm) under a local annual temperature difference of 35℃, and complies with relevant code requirements.

[0069] The rubber waterstop is an externally applied type, 400mm wide, made of ethylene propylene diene monomer (EPDM) rubber with a Shore A hardness of 60±5, meeting the requirements for waterstops for expansion joints in the national standard GB 18173.2-2000 "Polymer Waterproof Materials Part 2: Waterstops". After the waterstop arrives on site, it is unfolded and laid flat on a level ground according to the pretreatment steps, and left to stand naturally for 24 hours to eliminate the internal stress caused by the curling during packaging and restore its straight state.

[0070] 2. Determination of pre-stretch amount According to step S1 of the present invention, the pre-stretch amount δ is first determined.

[0071] 2.1 Selection of relaxation coefficient k This joint's expansion joint is primarily characterized by expansion and contraction (approximately 60%), with a small amount of settlement (approximately 40%). It has a Class I waterproofing rating and a medium rubber hardness (60±5). Based on the relaxation coefficient k principle described in this invention specification (based on the stress relaxation characteristics of rubber materials, the principle of elastic strain distribution, the principle of fatigue life optimization, and the principle of comprehensive deformation compatibility), for joints primarily characterized by expansion and contraction, a smaller value of k (0.2~0.3) is preferable to ensure that the waterstop maintains appropriate tension during frequent expansion and contraction.

[0072] Taking all the above factors into consideration, k = 0.25 is chosen in this embodiment.

[0073] 2.2 Calculation of Pre-stretching Amount The pre-stretch amount δ = k·Δ = 0.25 × 20mm = 5mm.

[0074] The meaning of the pre-tensioning amount δ is: the length of the rubber waterstop in its natural state should be 5mm shorter than the structural length of the expansion joint, and after tensioning, the length of the rubber waterstop should be equal to the structural length of the expansion joint. During construction, the tensioning elongation must be controlled according to this value.

[0075] 2.3 Temperature Correction and Width Verification In this embodiment, the ambient temperature T during construction is 20℃, which is consistent with the preset standard temperature T0 (20℃). Therefore, the temperature correction coefficient α(T) = 1, and there is no need to correct the pre-stretching amount for temperature.

[0076] On the day of construction, the actual width of the expansion joint was checked: using a vernier caliper, three sections (both ends and the middle) were selected along the length of the expansion joint for measurement. The measured widths were 30.2mm, 29.8mm, and 30.0mm, respectively, with an average value of 30.0mm, which is consistent with the design width W2=30mm. The width difference ΔW=0, so there is no need to correct the maximum displacement Δ.

[0077] 3. Tensioning and Positioning Follow the steps in S2: 3.1 Install the waterstop strip The pre-treated rubber waterstop is transported to the pre-set position of the expansion joint. At this time, the first end of the waterstop (corresponding to the bottom end of this vertical joint condition) is placed at the design elevation of the foundation slab (i.e., the pre-set first installation position), and the second end (corresponding to the top end of this vertical joint condition) is temporarily placed at a position approximately 250mm below the design elevation (i.e., offset from the pre-set second installation position). During temporary placement, the second end of the waterstop is fixed with wooden wedges or temporary supports to prevent it from slipping off on its own.

[0078] 3.2 Fix the first end An anchoring clamp made of steel plate is used to clamp the flange of the first end of the waterstop. The clamp is 100mm wide and lined with rubber pads on the inside to prevent damage to the waterstop. The clamp is then fixed to the main reinforcement bars (25mm diameter HRB400 steel bars) of the foundation slab by double-sided welding, with a weld length of not less than 50mm. After welding, the clamp is checked to ensure it is tight and will not loosen during subsequent tensioning.

[0079] 3.3 Tensioning the second end Install a hand-operated tensioning clamp at the second end of the waterstop. The clamp is also lined with a rubber sheet on the inside and holds the flange of the waterstop. Connect the tensioning clamp to a hand-operated hoist (rated load 1.5t). The upper end of the hand-operated hoist is hung on the crossbar of the wall steel reinforcement skeleton (the crossbar is made of 20mm diameter steel bars temporarily welded to the main reinforcement bars on both sides of the structure).

[0080] Start the chain hoist and apply tension smoothly along the length of the waterstop (vertically upward). Simultaneously, use a 1mm precision steel ruler to measure the displacement of the second end of the waterstop relative to its initial position. Stop tensioning when the elongation reaches 5mm and maintain tension using the locking device. At this point, the second end of the waterstop should have risen to the designed top elevation.

[0081] 3.4 Centering Check and Fine-tuning While maintaining tension, observe from both ends and sides of the expansion joint whether the centerline of the rubber waterstop coincides with the design centerline of the expansion joint. Inspection revealed that the centerline of the waterstop was slightly deviated to the left by 3mm.

[0082] Temporary guide ribs or positioning slots are set on both sides of the waterstop. With the help of a wooden hammer or rubber hammer, make minor adjustments. Pause and observe every 2-3 mm. If necessary, use a laser line projector to assist in centering to ensure that the center line deviation is controlled within 5 mm.

[0083] 3.5 Install positioning ribs This node has structural steel reinforcement in most areas, but the reinforcement is sparse within approximately 1.2m of the bottom of the expansion joint. Two positioning methods are used for different areas: (1) Areas with structural reinforcement: U-shaped steel bar clips are used as positioning bars. The steel bar clips are made of 8mm diameter round steel bent on site, and the width of the U-shaped opening is 15mm larger than the width of the waterstop flange (approximately flange width + 15mm). A U-shaped steel bar clip is set every 450mm along the length of the waterstop to clip the steel bar clips at the root of the waterstop flange and fix them to the main structural reinforcement on both sides by spot welding.

[0084] (2) Areas without structural reinforcement: Special positioning reinforcement supports are set up. M10 expansion bolts are inserted into the poured concrete pad at 500mm intervals, and a 12mm diameter continuous steel bar is welded to the expansion bolt as a transverse support. U-shaped steel bar clips are welded and fixed to the transverse support to ensure that the waterstop is also effectively restrained in this area.

[0085] After the positioning ribs are installed, check again along the entire length to ensure that the waterstop still maintains a pre-tension of 5mm and is accurately aligned, and confirm that there are no errors.

[0086] 3.6 Installation of Joint Sealant This section is designed with a joint filler board, made of 20mm thick closed-cell polyethylene foam board. The joint filler board is cut into strips of the same length as the expansion joint, with a width of 250mm (slightly larger than the depth of the expansion joint). The joint filler board is inserted segment by segment from one side of the expansion joint, so that it fits tightly against the poured concrete surface and avoids the installed positioning bars.

[0087] Immediately after installation, inspect the sealant board: observe whether the center hole of the waterstop remains circular (without compression deformation), and measure the gap between the sealant board and the waterstop with a feeler gauge. Upon inspection, the center hole of the waterstop remains naturally circular, and there is a uniform gap of approximately 2mm between the sealant board and the waterstop, with no compression or pushing phenomena, meeting the requirements.

[0088] 4. Concrete pouring Perform the pouring in stages according to step S3: 4.1 Pouring the first portion of concrete The first pour of concrete below the construction joint, i.e., the foundation slab, is the first section of concrete poured. The concrete strength grade is C35, and pumped ready-mixed concrete is used, with a slump controlled at 160±20mm.

[0089] Before pouring, clean the formwork and reinforcing bars, and moisten them with water, but avoid water accumulation. Pour the concrete from one side of the waterstop to ensure even rising and avoid direct impact on the waterstop. Use an immersion vibrator for compaction, keeping the vibrator at least 50mm away from the waterstop. Vibration time should be until the concrete surface shows a layer of slurry and no longer shows significant settling. Strictly control the pouring height to the design elevation of the construction joint (top surface of the base slab), ensuring that half of the waterstop (approximately 200mm wide) is encased and anchored in concrete.

[0090] Immediately after pouring, cover with plastic film to retain moisture and cure, and spray a retarder on the surface of the construction joint to facilitate subsequent roughening.

[0091] 4.2 Waiting Interval After the first part of the concrete was poured, the ambient temperature was 20℃±2℃. Twelve hours later, a rebound hammer was used to test the test blocks cured under the same conditions. The estimated strength had reached 1.5MPa (exceeding the specification requirement of 1.2MPa). The interval between the completion of the first part of the concrete pouring and the start of the second part of the concrete pouring was 12 hours, which did not exceed the upper limit of 24 hours. Therefore, the second part of the concrete pouring could proceed.

[0092] 4.3 Pouring the second part of concrete Before pouring, use a wire brush and high-pressure water gun to remove laitance and loose stones from the surface of the construction joint, exposing the solid coarse aggregate of the concrete. Inspect the exposed waterstop to ensure it is free of contamination and damage, and that the positioning bars are not loose.

[0093] The second pour involves the remaining second portion of concrete (i.e., the exterior wall portion), with the same C35 concrete strength grade. The pouring process is the same as the first: pour from one side, in layers (each layer not exceeding 300mm in thickness), with the vibrator at least 50mm away from the waterstop. During the pouring process, a designated person observes the waterstop and positioning bars; any abnormalities are immediately stopped and addressed. After pouring to the design elevation at the top of the exterior wall, the surface is finished.

[0094] 5. Fixture removal and maintenance After all concrete has been poured and set (approximately 24 hours), proceed to step S4: remove the tensioning clamps. First, loosen the clamp bolts, gently shake to separate the clamps from the waterstop, and carefully remove the clamps, avoiding damage to the poured concrete and exposed waterstop flanges. The removed clamps can be cleaned and used for the next stage of construction.

[0095] Finally, proceed to step S5: Moisturize and cure the concrete. Cover with geotextile and sprinkle with water to keep it moist for at least 14 days. During the curing period, set up warning signs to prevent damage to the joint from other work processes.

[0096] 6. Data Recording Following the data recording steps of this invention, the following data is uploaded to the project management platform and stored in association with the Building Information Model (BIM) of that node: Pre-stretch data: Δ=20mm, k=0.25, δ=5mm, and temperature correction and width verification records; Video materials: photos of the waterstop upon arrival, photos of the tensioning and alignment process (including steel ruler readings), photos of the positioning reinforcement installation, photos of the joint filler inspection, photos of the two concrete pours, and photos after the clamps were removed; Test report: Concrete compressive strength test report (28-day standard curing test block strength reached 42.3MPa, and test block cured under the same conditions reached 38.5MPa).

[0097] 7. Technical Effect Analysis This embodiment achieves a controllable initial tension state for the rubber waterstop by precisely applying a pre-tension amount δ=5mm before it is embedded in the concrete. To prevent tearing: When the expansion joint experiences a maximum tensile displacement of 20mm, the total tensile amount of the waterstop is 25mm (pre-tension 5mm + displacement 20mm). Based on the expansion joint structure length of 36m in this embodiment, the waterstop's pre-tension of 5mm and total tensile amount of 25mm result in an elongation of approximately 0.069%, far below the limiting elongation of EPDM rubber (typically >300%). It remains within its elastic working range and will not tear.

[0098] Preventing loosening: When the expansion joint is compressed (such as when the temperature rises), the pre-stretched waterstop can shrink and rebound, maintaining a straight state and preventing wrinkles or bends from forming inside the joint.

[0099] Precise positioning: Positioning ribs are set at 450mm intervals along the length direction, ensuring that the waterstop does not shift during the entire concrete pouring process, and its centerline always coincides with the centerline of the expansion joint. Post-pouring inspection shows that the waterstop is embedded to a consistent depth, with straight flanges and no twisting.

[0100] This embodiment demonstrates that construction according to the method of the present invention can effectively solve the problems of tearing, loosening, and positioning deviation caused by the uncontrollable initial stress state at the intersection of the rubber waterstop and the construction joint in the prior art, and significantly improve the reliability and durability of the joint waterproofing.

[0101] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A method for installing rubber waterstops at the intersection of expansion joints and construction joints, characterized in that, Includes the following steps: S1: Determination of Pre-tension Amount: Based on the maximum possible displacement Δ of the expansion joint along its structural length during use, determine the pre-tension amount δ that needs to be applied along the length of the rubber waterstop during installation, where δ = k·Δ, k is the relaxation coefficient, and 0.2 ≤ k ≤ 0.5; the meaning of the pre-tension amount δ is: the length of the rubber waterstop in its natural state is δ shorter than the design distance between its two fixed points, and its length after tensioning is exactly equal to the design distance; the design distance between the two fixed points is the structural length of the expansion joint in the section where the waterstop is installed; S2: Tensioning and Positioning: First, place the rubber waterstop at the preset position of the expansion joint, so that the first end, as the first fixed end, is located at the preset first installation position of the expansion joint, and the second end, as the subsequent tensioning end, is temporarily located at a position offset from the preset second installation position; then, fix the first end of the rubber waterstop to the structural steel bar or embedded part through the anchoring clamp to form the fixed end; subsequently, clamp the second end of the waterstop with the tensioning clamp, connect the tensioning equipment to apply tension along the length direction of the rubber waterstop, and tension the rubber waterstop to the pre-tension amount δ, at which point the second end is stretched to its preset second installation position; after reaching the pre-tension amount δ, maintain the tensioned state and check whether the center line of the rubber waterstop coincides with the design center line of the expansion joint. If there is a deviation, fine-tune the rubber waterstop to make it accurately centered; subsequently, under the premise of maintaining the tensioned state, use positioning bars to connect the flange of the rubber waterstop to the structural steel bar, embedded part, or specially set positioning bar bracket. The positioning bars are set at intervals along the length direction of the waterstop to prevent the waterstop from shifting during the concrete pouring process; S3: Concrete pouring: First, pour the first part of the concrete below the construction joint. The pouring height should ensure that the waterstop is reliably anchored. After this part of the concrete has set and has sufficient strength, pour the remaining second part of the concrete. S4: Fixture Removal: After all concrete has been poured and set, remove the tensioning fixtures. S5: Curing: Keep the concrete moist until the design age.

2. The method for installing the rubber waterstop at the intersection of the expansion joint and the construction joint as described in claim 1, characterized in that, In S2, the positioning reinforcement uses U-shaped steel bar clips or short steel bar ends with a spacing of no more than 500mm, and is firmly welded or tied to the structural reinforcement, embedded parts or positioning reinforcement bracket.

3. The method for installing the rubber waterstop at the intersection of the expansion joint and the construction joint as described in claim 1, characterized in that, In S3, the interval between pouring the first part of concrete and the second part of concrete shall not exceed 24 hours.

4. The method for installing the rubber waterstop at the intersection of the expansion joint and the construction joint as described in claim 1, characterized in that, After S2 and before S3, the process also includes the installation of a sealant board: install the sealant board inside the expansion joint and check whether the sealant board compresses the rubber waterstop or causes the centerline to shift; if there is compression or shift, adjust the position or size of the sealant board until the rubber waterstop maintains the tension and centering posture required by the design.

5. The method for installing the rubber waterstop at the intersection of the expansion joint and the construction joint as described in claim 1, characterized in that, Following S5, there is also a data recording step: uploading the pre-tensioning amount δ determined in S1, the image data during construction, and the concrete strength test report to the project management platform and storing them in association with the building information model of that node.

6. The method for installing the rubber waterstop at the intersection of the expansion joint and the construction joint as described in claim 1, characterized in that, In step S1, when determining the pre-tension amount δ, the pre-tension amount is also corrected for temperature based on the ambient temperature T during construction, as follows: when the ambient temperature T is lower than the preset standard temperature T0, the pre-tension amount is reduced proportionally; when T is higher than T0, the pre-tension amount is increased proportionally. The correction ratio is predetermined based on the temperature response characteristics of the rubber waterstop material under tension.

7. The method for installing the rubber waterstop at the intersection of the expansion joint and the construction joint as described in claim 1, characterized in that, Before step S1, there is also a step to verify the actual width of the expansion joint: The actual width W1 of the expansion joint on the day of construction was measured using measuring tools, and the design width W2 of the expansion joint specified in the design drawings was obtained. Calculate the width difference ΔW = W1 - W2; If ΔW > 0, then Δ in step S1 is corrected to Δ1 = Δ + ΔW; If ΔW < 0, then Δ in step S1 is corrected to Δ2 = Δ - |ΔW|, and the corrected Δ2 is not less than zero; The pre-stretching amount δ mentioned in step S1 is calculated based on the corrected Δ value.

8. The method for installing the rubber waterstop at the intersection of the expansion joint and the construction joint as described in claim 7, characterized in that, Before step S1, there is a waterstop pretreatment step: the rubber waterstop is unfolded and laid flat, and left in a natural state for 24 hours to eliminate the internal stress caused by the curling and packaging, and restore it to a straight state before determining the pre-stretch amount in step S1.