A layered spray construction method of a micro-stress ECC non-joint water conservancy anti-seepage face plate

Abstract

The present application belongs to the technical field of water conservancy and pumped storage engineering, and discloses a layered spraying construction method of a micro-stress ECC joint-free hydraulic anti-seepage face plate. In view of the anti-cracking and anti-seepage challenges of large-scale seamless hydraulic face plates, the micro-stress high-ductility sprayed ECC is sprayed multiple times in the thickness direction of the micro-stress ECC joint-free hydraulic face plate to form a multi-layer composite integral face plate without horizontal and vertical joints. The construction cold joints existing in each spraying layer are covered by the subsequent spraying layers, and the construction cold joints of adjacent spraying layers do not coincide. The integral micro-stress ECC joint-free hydraulic face plate structure is formed by interlacing and superimposing. The staggered joint lap and the crack control design of the ECC layer surface "kink-capture" realize the synergistic improvement of the structure bearing and the anti-cracking and anti-seepage. Compared with the traditional steel-concrete face plate and the asphalt concrete face plate, the present application has the advantages of rigid-flexible combination, fast construction speed, economy and practicality, strong deformation adaptability, anti-disengagement, anti-freezing durability and the like, and solves the problem of giving consideration to the anti-cracking and anti-seepage and safe service of the traditional hydraulic face plate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydraulic engineering and pumped storage engineering, and particularly relates to a layered spraying construction method of a micro-stress ECC joint-free hydraulic anti-seepage panel. BACKGROUND

[0002] The hydraulic panel is a main anti-seepage body of a hydraulic structure, and is widely used in hydraulic engineering such as a panel rock-fill dam and a pumped storage power station. Anti-cracking and anti-seepage of the hydraulic panel are crucial to engineering safety and benefits, and are also one of the main challenges currently faced by the hydraulic panel.

[0003] Traditional hydraulic panels can be mainly divided into reinforced concrete rigid panels and asphalt concrete flexible panels. The tensile capacity of concrete is poor, and in order to alleviate cracking due to temperature, shrinkage and other deformations, the concrete panel must be designed with joints during construction, and the horizontal / vertical joints are connected by a water stop structure for anti-seepage. The commonly used water stop materials for hydraulic engineering include red copper, rubber, asphalt and plastic fillers. Under the action of water load, dam deformation settlement and voiding, panel cracking and water stop failure are the bottleneck problems restricting the safe service of the hydraulic panel.

[0004] The asphalt panel has the advantages of high ductility and strong adaptability to foundation deformation, and can be used to construct a joint-free hydraulic panel by its own anti-cracking capacity. However, the asphalt concrete has the disadvantages of low stiffness / strength, performance sensitivity to service temperature, prominent durability and aging problems, which to some extent restrict its application in hydraulic engineering under harsh service conditions.

[0005] Engineered Cementitious Composite (ECC) is a high-ductility cement-based composite material, which realizes a tensile ductility of more than 30,000 με through multiple micro-cracks after being pulled, and exhibits a tensile hardening capacity. Due to different translation and naming angles, ECC is also commonly referred to as high-ductility concrete HDC, strain-hardening cement-based composite SHCC, bendable concrete, and ultra-high toughness cement-based composite (UHTCC). Compared with traditional concrete and asphalt concrete, ECC material has the advantage of rigid-flexible combination, and is expected to realize the technical breakthrough of rigid-flexible joint-free anti-cracking and anti-seepage hydraulic panel.

[0006] However, the shrinkage deformation of the ECC material can reach 1500-3000 με, which is 3-6 times that of the traditional concrete. The hydraulic panel belongs to an ultra-thin layer structure, and is subjected to strong external constraints, so the shrinkage deformation will induce multiple cracks in the ECC before the impoundment period. Although the ECC material has ultra-high tensile ductility, the existence of cracks will affect the anti-cracking and anti-seepage performance of the hydraulic panel after impoundment.

[0007] To overcome the adverse effects of shrinkage cracking on the face plate, scholars have invented low shrinkage ECC, zero shrinkage ECC, swelling ECC and self-stress ECC. The construction of ECC is difficult to avoid the construction cold joint during the construction of the large area of hydraulic face plate; especially the expansion agent in the swelling ECC and self-stress ECC can accelerate the setting of ECC, greatly increasing the number of construction cold joints. Construction cold joints are still the weak link of anti-cracking and anti-seepage under the action of high water pressure, ground deformation and other loads. Therefore, the current technical level cannot realize the anti-cracking and anti-seepage target of seamless ECC face plate.

[0008] In summary, the design of ECC material, the structure of the face plate, and the construction method need to be considered comprehensively to break through the technical bottleneck of the overall anti-cracking and anti-seepage of the seamless hydraulic ECC face plate. SUMMARY

[0009] The present application is aimed at the challenge of large-scale seamless hydraulic face plate anti-cracking and anti-seepage, and proposes a layered spraying construction method of micro-stress ECC joint-free hydraulic anti-seepage face plate. Through the crack control design of staggered joint and ECC "kink-capture", the structure bearing and anti-cracking and anti-seepage are realized. Compared with traditional steel-concrete face plate and asphalt concrete face plate, it has the advantages of rigid-flexible combination, fast construction speed, economy and practicality, strong deformation adaptability, anti-displacement, anti-frost durability and other advantages, and solves the problem of traditional hydraulic face plate anti-cracking and anti-seepage and safe service. The method can be applied to the fields of rockfill dam face plate, pumped storage face plate, water channel lining, tunnel lining, hydraulic anti-seepage reinforcement and repair, etc.

[0010] The technical scheme of the present application is as follows: a layered spraying construction method of micro-stress ECC joint-free hydraulic anti-seepage face plate, the micro-stress ECC joint-free hydraulic face plate material is micro-stress high ductility spraying ECC; the micro-stress high ductility spraying ECC is sprayed multiple times to form a multi-layer composite integral face plate in the thickness direction of the micro-stress ECC joint-free hydraulic face plate, without horizontal and vertical joints; the construction cold joints existing in each spraying layer are covered by the subsequent spraying layer, and the construction cold joints of adjacent spraying layers do not coincide; the integral micro-stress ECC joint-free hydraulic face plate structure is formed by interlacing and overlapping; the thickness of each spraying layer is 1-5 cm, and the overall thickness of the micro-stress ECC joint-free hydraulic face plate is 20-50 cm.

[0011] The lower limit value of the interlayer bonding strength of adjacent spraying layers is 50% of the straight tensile cracking strength of the micro-stress high ductility spraying ECC material; the upper limit value of the interlayer bonding strength of adjacent spraying layers is 50% of the sum of the straight tensile cracking strength and the final tensile strength of the micro-stress high ductility spraying ECC material.

[0012] The control of the interlayer bonding strength is as follows: when the micro-stress high ductility spraying ECC material of the previous spraying layer is between initial setting and final setting, the adjacent spraying layer is applied.

[0013] The control of the interlayer bonding strength is specifically as follows: the time interval between the application of the adjacent subsequent sprayed layer and the previous sprayed layer is 7 days after final setting; the surface of the previous sprayed layer is not treated after spraying; the previous sprayed layer is sprayed for maintenance every 6-12 hours after 12 hours of application; and the previous sprayed layer is sprayed for maintenance 1-2 hours before the application of the subsequent sprayed layer.

[0014] The control of the interlayer bonding strength is specifically as follows: the time interval between the application of the adjacent sprayed layers is greater than 7 days and less than or equal to 30 days; the surface of the previous sprayed layer is not treated after spraying; the previous sprayed layer is sprayed for maintenance every 6-12 hours after 12 hours of application, for a maximum of 7 days of maintenance; and the previous sprayed layer is subjected to a 1-5 MPa water pressure for hair removal treatment before the application of the subsequent sprayed layer.

[0015] The micro-stress high-ductility sprayed ECC material is composed of 50-100 parts by volume of the volume expansion component, 100-800 parts of cement, 400-1200 parts of supplementary cementitious material, 400-800 parts of aggregate, 200-400 parts of water, 0-30 parts of water reducing agent, 0-5 parts of thickening agent, and 5-40 parts of fiber.

[0016] The micro-stress ECC jointless hydraulic panel can control the real-time and quantitative constraint stress during service; by adjusting the CSA content of the micro-stress high-ductility sprayed ECC material and the early water maintenance time, the micro-stress is quantitatively controlled between tensile 0.5 MPa and compressive 5 MPa from the time of pouring to before water storage service.

[0017] The 90-day free volume deformation of the micro-stress high-ductility sprayed ECC material is between shrinkage 200 με and expansion 3000 με.

[0018] When the micro-stress high-ductility sprayed ECC material is stretched to 0.1%, the permeability coefficient is not higher than 10 -11 m / s order of magnitude; when stretched to 1%, the permeability coefficient is not higher than 10 -10 m / s order of magnitude; and when stretched to 2%, the permeability coefficient is not higher than 10 -9 m / s order of magnitude.

[0019] The micro-stress high-ductility sprayed ECC material has a tensile ductility of 0.5%-10%, a tensile strength of 3-10 MPa, a four-point bending strength of 5-20 MPa, a bending and tensile deformation of not less than 1%-20%, and a cubic compressive strength of 20-100 MPa.

[0020] The micro-stress ECC jointless hydraulic panel is applied to a hydraulic anti-cracking and anti-permeation panel.

[0021] The micro-stress ECC free joint hydraulic faceplate of the present application has the high stiffness and high strength of the traditional steel concrete faceplate and the strong deformation adaptability of the asphalt faceplate, and is a new type of hydraulic faceplate with both rigidity and flexibility. Through the layered structure and the layer "kink-capture" crack control design, the technical breakthrough of the cement-based material hydraulic faceplate free joint is realized. The faceplate has significant advantages in crack resistance, frost resistance, foundation deformation adaptability, durability and the like, and solves the crack resistance and impermeability problems of the traditional hydraulic faceplate. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 are straight pull dog bone specimens of different cross-sectional structural forms; (a) is a schematic diagram of the shape of the straight pull dog bone specimen; (b) is a cross-sectional view of the overall 13cm thick specimen; (c) is a cross-sectional view of the 3-layer 10cm thick specimen; (d) is a cross-sectional view of the overall 30cm thick specimen;

[0023] Figure 2 are ECC straight pull stress-strain curve diagrams of different preparation forms;

[0024] Figure 3 are different layered ECC beam cross-sectional schematic diagrams; (a) is an overall pouring beam; (b) is pouring in two layers, each layer being 50mm thick; (c) is pouring in 4 layers, each layer being 25mm thick; (d) is pouring in 10 layers, each layer being 10mm thick; (e) is a loading schematic diagram;

[0025] Figure 4 are the flexural tensile strength and mid-span deflection of the layered structure ECC beam;

[0026] Figure 5 are layered structure ECC beam crack pattern diagrams under the influence of different layer surface bond strengths; (a) is strong layer surface bond-crack penetration failure; (b) is moderate layer surface bond-crack "capture-kink" multi-crack failure; (c) is weak layer surface bond-layer separation failure;

[0027] Figure 6 are layer strength control limits of the layered structure micro-stress ECC free joint hydraulic faceplate;

[0028] Figure 7 are layered structure-mismatched lapping and crack propagation diagrams; (6 layers S1…S6; construction joints: F1…F6; captured cracks L2…L5);

[0029] Figure 8 are layered structure free joint ECC faceplate and jointed concrete faceplate structural diagrams; (a) is a jointed concrete faceplate; (b) is an overall jointed concrete cross section; (c) is a layered structure free joint ECC faceplate; (d) is a layered ECC faceplate cross section. DETAILED DESCRIPTION

[0030] 1. ECC material mix and performance

[0031] The mix proportions of the examples are listed in Table 1, with Portland cement as the binder, and CSA as the volume expanding component. The volume expanding component CSA is added at 0, 50, 100, 150 kg / m 3 , machine-made sand with average particle size of 200 pm as the ECC aggregate, and Class 1 fly ash as the binder; PE fiber with length of 12 mm as the post-cracking bridging reinforcement.

[0032] Table 1. ECC material mix (unit: kg / m 3 )

[0033]

[0034] This example tests the drying shrinkage deformation of 25 mm * 25 mm * 300 mm ECC specimens according to ASTM C490 / C490M-17. The earliest allowable demolding time is selected as the starting point of the volume deformation test. The volume deformation test specimens are kept wet on the surface by water spraying after demolding, and the high humidity curing is maintained for 2 days, then placed in 50 ± 5% RH air for curing, and the volume deformation of the ECC mix is continuously recorded.

[0035] This example carries out the restrained stress test at 20°C constant temperature according to the restrained stress test method in “He Zhu, Yu Hu, Qingbin Li, R. Ma, Restrained cracking failure behavior of concrete due to temperature and shrinkage, Constr. Build. Mater, 2020, 244 (118318)”. The restrained ECC specimens are kept in high humidity curing for 2 days after casting, then placed in 50 ± 5% RH air for curing, and the stress change of the restrained ECC is continuously monitored.

[0036] Table 2 records the free volume deformation and restrained stress test results of different ECCs after 90 days. Due to the absence of external expansion components, the free volume deformation of C_0 ECC at 90 days is shrinkage of 2000με, the restrained stress result is tension of 3.9MPa, and the ECC has multiple cracks, which will threaten the anti-seepage and safety of the hydraulic panel after impoundment. The free volume deformation of C_50 at 90 days is shrinkage of 200με, and the restrained stress result is tension of 0.5MPa. Although the ECC is under tension, the tension stress level is lower than the cracking strength; therefore, the micro-tension stress of C_50 is still within an acceptable range. The free volume deformations of C_75 and C_100 at 90 days are expansion of 1800με and 3000με, respectively, and the restrained stress results are compression of 2.5MPa and 5.0MPa, respectively. The hydraulic panel ECC has the advantages of self-prestressing under the service state of constraint, and achieves the goal of active crack prevention and overall crack resistance improvement. The free volume deformation of C_150 at 90 days is expansion of 5000με, and the restrained stress result is compression of 9.8MPa.

[0037] During the service of the hydraulic panel ECC material, both the excessive constraint stress causing cracking and the excessive expansion causing panel arching cracking should be avoided. According to the previous material design and engineering calculation experience of the research group, combined with the example results of the present embodiment, the expansion component content of the micro-stress high-ductility jetting ECC material of the present application is controlled to be 50-100 parts; the free volume deformation at 90 days is between shrinkage of 200με and expansion of 3000με; and the micro-stress before impoundment service is quantitatively regulated to be between tension of 0.5MPa and compression of 5MPa.

[0038] Table 2 results of ECC materials with different proportions

[0039]

[0040] 2. Influence of layered structure on mechanical properties of ECC

[0041] The C_75 proportion in Table 1 is selected to test the mechanical properties of the layered hydraulic micro-stress ECC panel. The straight tensile test of the 13mm thick dog bone specimen shows that the cracking strength of C_75 ECC is 3MPa, the final tensile strength is 6MPa, and the tensile ductility is 4.8%.

[0042] In order to illustrate the improvement of the layered structure on the tensile properties of the ECC panel, three different tensile samples are prepared in this example. They are 13mm thick dog bone specimens; layered structure ECC dog bone specimens, each layer of ECC has a thickness of 10mm, and is poured in 3 layers; and whole pouring ECC dog bone specimens, the tensile cross-sectional size is 30mm*30mm. Figure 2 ​​The direct tensile stress-strain curves of three dog bone specimens are shown.

[0043] Figure 2 The direct tensile stress-strain curves of different layering ECC dog bone specimens, monolithic ECC dog bone specimens and concrete are shown respectively. The initial cracking strength of monolithic ECC is about 3 MPa, and then it shows the advantages of multiple cracking and tensile hardening, and the final tensile strength is 4.9 MPa and the tensile ductility is 3%. The initial cracking strength of monolithic ECC is close to that of 13 mm thick ECC, but the final tensile strength is lower. Because the fibers in the cross section of monolithic ECC are randomly distributed in three dimensions, while the fibers in the 13 mm thick ECC specimen are distributed in two dimensions, the tensile properties of thin ECC specimens are better than those of monolithic thick ECC specimens. The tensile strength and deformation capacity of layering ECC are the highest, which are 6.1 MPa and 5.0% respectively, close to the results of 13 mm thick dog bone specimens. Due to the layering design, each 10 mm layer is less than the fiber length, and the fibers in the 10 mm layer are distributed in two dimensions, with more fibers in the direct tensile direction. Compared with the direct tensile strength of about 3 MPa and the direct tensile deformation capacity of only 100 με of traditional hydraulic concrete, the layering ECC proposed in this example has obvious advantages in tensile and crack resistance, and the test proves that the tensile strength and deformation capacity of layering ECC panel are greatly improved compared with traditional monolithic panel.

[0044] Figure 3 Different forming methods of ECC beam specimens are shown. The overall interface size of the ECC beam is 100 mm*100 mm, and the length is 500 mm. (a) is a monolithic casting beam; (b) is cast in two layers; each layer is 50 mm thick; (c) is cast in four layers, each layer is 25 mm thick; (d) is cast in 10 layers, each layer is 10 mm thick.

[0045] Figure 4 The ECC beam flexural stress-strain curves are shown. The flexural strength of the monolithic ECC beam is 6 MPa, and the deflection is about 2 mm; the flexural strength of the ECC beam cast in two layers is 7.5 MPa, an increase of 25%; the flexural strength of the ECC beam cast in four layers is 10.9 MPa, and the deflection is 3.8 mm; the flexural strength of the ECC beam cast in 10 layers is 12.9 MPa, and the deflection is 4.5 mm.

[0046] Compared with the monolithic ECC beam, the flexural strength and mid-span deflection of the ECC beam cast in 10 layers (each layer is 10 mm thick) are increased by more than 200%, showing great advantages in water pressure resistance and anti-displacement settlement of hydraulic panels.

[0047] 3. Influence of different layering methods on the flexural performance of layering ECC beams

[0048] The present example shows the influence of five different processing methods on the interlayer bond strength, which means as follows:

[0049] D1 means that the time interval of adjacent sprayed layers of micro stress high ductility sprayed ECC is 1 hour, which is less than the initial setting time of micro stress high ductility sprayed ECC.

[0050] D2 means that the time interval of adjacent sprayed layers of micro stress high ductility sprayed ECC is 1 day, which exceeds the final setting time of micro stress high ductility sprayed ECC; the surface of the previous sprayed layer is not treated after spraying; water curing is performed every 6-12 hours after the previous sprayed layer is applied for 12 hours; the previous sprayed layer is water cured 1 hour before the subsequent sprayed layer is applied.

[0051] D3 means that the time interval of adjacent sprayed layers of micro stress high ductility sprayed ECC is 7 days; the surface of the previous sprayed layer is not treated after spraying; water curing is performed every 6-12 hours after the previous sprayed layer is applied for 12 hours; the previous sprayed layer is water cured 1 hour before the subsequent sprayed layer is applied.

[0052] D4 means that the time interval of adjacent sprayed layers of micro stress high ductility sprayed ECC is 8 days; the surface of the previous sprayed layer is not treated after spraying; water curing is performed every 6-12 hours after the previous sprayed layer is applied for 12 hours, for a maximum of 7 days; the previous sprayed layer is subjected to hair washing treatment with 1 MPa water pressure 1 hour before the subsequent sprayed layer is applied.

[0053] D5 means that the time interval of adjacent sprayed layers of micro stress high ductility sprayed ECC is 30 days; the previous sprayed layer is water cured 1 hour before the subsequent sprayed layer is applied.

[0054] D6 means that the time interval of adjacent sprayed layers of micro stress high ductility sprayed ECC is 30 days; the surface of the previous sprayed layer is not treated after spraying; water curing is performed every 6-12 hours after the previous sprayed layer is applied for 12 hours, for a maximum of 7 days; the previous sprayed layer is subjected to hair washing treatment with 3 MPa water pressure 1 hour before the subsequent sprayed layer is applied.

[0055] D7 means that the time interval of adjacent sprayed layers of micro stress high ductility sprayed ECC is 30 days; the previous sprayed layer is subjected to hair washing treatment with 5 MPa water pressure 1 hour before the subsequent sprayed layer is applied, and a medium-strength interfacial bonding agent is applied on the layer surface.

[0056] D8 means that the time interval of adjacent sprayed layers of micro stress high ductility sprayed ECC is 30 days; the previous sprayed layer is subjected to hair washing treatment with 6 MPa water pressure 1 hour before the subsequent sprayed layer is applied, and a high-strength interfacial bonding agent is applied on the layer surface.

[0057] After 28 days of curing, the interfacial bond strength of the two sprayed layers was tested by using a universal testing machine. The specimen size was 100 mm cube, and the height of the two sprayed layers was 50 mm. The average value of three parallel specimens was taken as the interfacial bond strength of the two sprayed layers. Table 3 shows the interfacial bond strength of the two sprayed layers under different interfacial treatment methods.

[0058] Table 3 Interfacial bond strength (unit: MPa)

[0059]

[0060] Under D1 condition, the previous sprayed layer has not reached initial setting, and the subsequent sprayed layer can be well fused and set with the previous sprayed layer, with an interfacial bond strength of 4.8 MPa, which exceeds the upper limit of the interfacial strength control . D5 because the interfacial of the previous sprayed layer has been hardened for 30 days, and only water is sprayed on the interfacial, resulting in weak interfacial bond, only 0.9 MPa. D7 due to the double action of interfacial scouring and interface adhesive, the interfacial bond strength is higher, 4.5 MPa, corresponding . The flexural tensile strength of the ECC beam of D7 is 8.5 MPa, which is still higher than that of the overall cast ECC beam. D8 uses higher scouring pressure and strong interface adhesive, and the interfacial bond strength is 4.7 MPa, which exceeds the ECC body , the flexural tensile strength of the layered beam is only 6.6 MPa, which is not significantly improved compared with the traditional overall cast ECC beam.

[0061] According to the different interfacial treatment methods in Table 3, four-layer cast ECC beams (25 mm per layer) were prepared to study the effect of different interfacial treatment methods on the interfacial bond strength. The results in Table 4 show that when the interfacial bond strength of D3, D6 and D7 is between and , the flexural tensile strength and deflection of the layered ECC beam are significantly better than those of the overall cast ECC beam in Figure 4 . D5 has limited improvement in the load-carrying capacity of the layered ECC beam due to the weak interfacial bond. D1 and D8 have high interfacial bond strength, close to the final tensile strength of the ECC body, and the flexural tensile load-carrying capacity of the layered ECC beam is similar to that of the overall cast ECC beam, and there is no obvious improvement due to the layered structure.

[0062] Table 4 Comparison of effects of different interfacial treatment methods (strength unit: MPa, deflection unit: mm)

[0063]

[0064] Figure 5 The crack failure diagram of D5 shows that when the interfacial bond strength of D5 is lower than At that time, the layered ECC beam experienced severe layer separation failure; when the bond strength of layer D1 was higher than In this case, the failure mode of the layered ECC beam under flexural tension is not significantly different from that of the monolithically cast beam; that is, cracks are mainly distributed vertically and rarely extend along the interface. Conversely, for the D3 condition with moderate interlayer bond strength, cracks first appear on the bottom surface, extend upwards to the interface between the two layers, then extend along the interface, are subsequently captured, and continue to intrude upwards; this manifests as a main crack being dispersed into multiple micro-cracks. As the cracks develop upwards, this "torsional-capture" mechanism repeats itself, thereby dissipating more energy and mitigating stress concentration failure. Therefore, this invention proposes... Figure 6 The bonding strength control standard is shown.

[0065] In summary, the specially designed layered ECC beam utilizes a "torsion-capture" mechanism for crack propagation, achieving a revolutionary increase in load-bearing capacity compared to monolithically cast ECC beams. This also highlights the technological advantages of layered hydraulic ECC panels over traditional reinforced concrete panels, asphalt panels, and monolithically cast ECC panels.

[0066] 4. Layered ECC panel design

[0067] Due to limitations such as construction capacity and adverse weather conditions, numerous construction joints are inevitably generated during the construction of hydraulic panels. Although these joints can be reinforced through methods such as roughening, their presence still poses a threat to the crack resistance and impermeability of the hydraulic panels during service. Therefore, it is difficult to construct seamless hydraulic panels using traditional concrete and ECC.

[0068] Figure 7 This patent showcases an innovative solution for seamless ECC hydraulic panels, constructed as a single panel through layer-by-layer spraying. Even though construction cold joints are unavoidable, the special design for bonding the ECC layers, combined with layered construction and staggered overlap design, overcomes the adverse effects of construction joints on crack resistance and seepage prevention. Figure 7 As shown, even if construction joint F1 exists in layer S1, layer S2 completely covers construction joint F1 during the spraying process. When the panel is subjected to bending tensile loads due to water pressure or foundation deformation, construction joint F1 may act as a weak point and develop cracks. However, thanks to the crack "capture-kink" design of the layered ECC structure, the crack will extend along the interface between layers S1 and S2, rather than directly penetrating layer S2. After extending a certain distance, the crack will kink and be captured in layer S2, forming a non-penetrating crack L2. Ultimately, the influence of construction joint F1 is limited to layer S1.

[0069] Similarly, the construction joint F2 in the S2 layer, after the crack initiation, along with the propagation of the cracks in the S2 and S3 layers, is subsequently captured in the S3 layer, forming a non-penetrating crack L3. According to the crack "capture-kink" design described above, the cracks are captured between the layers of the ECC layer by layer, avoiding the formation of penetrating cracks; and then achieving the impermeable goal of crack but not leakage. In addition, the layered structure of the ECC panel has the ability of super high tensile ductility, enhanced bending resistance and deformation, and overall realizes the significant progress of the anti-cracking and anti-permeability of the hydraulic ECC panel.

[0070] Figure 8 The specific implementation form of the seamless ECC panel is introduced in combination with the rockfill dam. (a) is a traditional steel-concrete panel of the rockfill dam, which is subject to the restrictions of dam height and construction capacity, and the panel is constructed in 2-3 stages in the height direction, the panels are divided into several vertical joints with a spacing of about 20 meters in the horizontal river direction, and the vertical joints and the peripheral joints of the panels are connected through water stops. (b) is a thickness cross section of the panel, and the traditional panel is integrally cast into a thick plate structure.

[0071] (c) is the seamless layered structure ECC panel of the application, and (d) shows the cross-sectional view of the layered structure of the ECC panel, and each layer of ECC forms an integral joint-free panel by layer-by-layer spraying. The integral impermeable panel is free of horizontal joints, vertical joints and the like, and overcomes the shortcomings of the water stop structure under the action of high water pressure, uneven foundation deformation and earthquakes.

Claims

1. A layered spraying construction method for a micro-stress ECC jointless hydraulic seepage prevention panel, characterized in that, The material for the micro-stress ECC jointless hydraulic seepage prevention panel is micro-stress high-ductility sprayed ECC material; The micro-stress high-ductility sprayed ECC material is sprayed multiple times along the thickness direction of the micro-stress ECC jointless hydraulic seepage prevention panel to form a multi-layer composite panel without horizontal or vertical seams; the construction cold joints within each sprayed layer are covered by subsequent sprayed layers, and the construction cold joints of adjacent sprayed layers do not overlap; the overall micro-stress ECC jointless hydraulic seepage prevention panel structure is formed by staggered overlapping; the thickness of each sprayed layer is 1cm-5cm, and the overall thickness of the micro-stress ECC jointless hydraulic seepage prevention panel is 20cm-50cm. The lower limit for controlling the layer bond strength of adjacent sprayed layers is 50% of the tensile initiation strength of the micro-stress high-ductility sprayed ECC material; the upper limit for controlling the layer bond strength of adjacent sprayed layers is 50% of the sum of the tensile initiation strength and the final tensile strength of the micro-stress high-ductility sprayed ECC material.

2. The layered spraying construction method for the micro-stress ECC jointless hydraulic seepage prevention panel according to claim 1, characterized in that, The control of the bonding strength of the layer is as follows: the time interval between the application of micro-stress high ductility ECC sprayed material of adjacent sprayed layers is 7 days, and the surface of the preceding sprayed layer is not treated after spraying; 12 hours after the preceding sprayed layer is applied, water curing is carried out every 6-12 hours. One hour before applying the subsequent spray layer, the preceding spray layer is sprayed with water for curing.

3. The layered spraying construction method for the micro-stress ECC jointless hydraulic seepage prevention panel according to claim 1, characterized in that, The control of the bonding strength of the layers is as follows: The time interval between the application of micro-stress high ductility ECC sprayed material of adjacent sprayed layers is 30 days. The surface of the preceding sprayed layer is not treated after spraying. 12 hours after the application of the preceding sprayed layer, water curing is carried out every 6 to 12 hours for a maximum of 7 days. 1 hour before the application of the subsequent sprayed layer, the preceding sprayed layer is roughened with 3MPa water pressure.

4. The layered spraying construction method for the micro-stress ECC jointless hydraulic seepage prevention panel according to claim 1, characterized in that, The micro-stress high-ductility sprayed ECC material is composed of 50-100 parts by mass of volume expansion component, 100-800 parts of cement, 400-1200 parts of supplementary cementitious material, 400-800 parts of aggregate, 200-400 parts of water, 0-30 parts of water-reducing agent, 0-5 parts of thickener, and 5-40 parts of fiber.

5. The layered spraying construction method for the micro-stress ECC jointless hydraulic seepage prevention panel according to claim 4, characterized in that, The 90-day free volume deformation of the micro-stress high-ductility sprayed ECC material is between 200 με for shrinkage and 3000 με for expansion.

6. The layered spraying construction method for the micro-stress ECC jointless hydraulic seepage prevention panel according to claim 4, characterized in that, The micro-stress high-ductility sprayed ECC material, when stretched to a level of 0.1%, has a permeability coefficient not exceeding 10. -11 On the order of m / s; when stretched to the 1% level, its permeability coefficient is no higher than 10. -10 On the order of m / s; when stretched to the 2% level, its permeability coefficient is no higher than 10. -9 On the order of m / s.

7. The layered spraying construction method for the micro-stress ECC jointless hydraulic seepage prevention panel according to claim 4, characterized in that, The micro-stress high-ductility sprayed ECC material has a tensile ductility of 0.5%-10%, a tensile strength of 3MPa-10MPa, a four-point bending strength of 5MPa-20MPa, a bending deformation of not less than 1%-20%, and a cubic compressive strength of 20MPa-100MPa after spraying.

8. The layered spraying construction method for the micro-stress ECC jointless hydraulic seepage prevention panel according to claim 1, characterized in that, The micro-stress ECC jointless hydraulic seepage prevention panel is used in hydraulic crack prevention and seepage prevention panels.

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