Method for rapid construction of rockfill self-compacting concrete gravity dam

Abstract

The present application relates to the technical field of hydraulic engineering, and discloses a method for rapid construction of a rock-fill self-compacting concrete gravity dam, comprising the following steps: S1, treatment of a bedrock surface and preparation of a cleaning site, and pouring of a concrete cushion after the treatment of the bedrock surface is completed; S2, installation of a formwork; S3, screening and storage of rockfills; S4, production and transportation of self-compacting concrete; S5, pouring of the self-compacting concrete; S6, maintenance of the self-compacting rock-fill concrete; and S7, checking of the safety performance of the stepped gravity dam body by means of a numerical simulation method and a rigid body limit equilibrium method. The technical scheme of the present application can reduce the risk of safe operation and construction cost, and improve the construction efficiency and shorten the construction period.

Description

Technical Field

[0001] This invention relates to the field of water conservancy engineering technology, specifically to a method for rapid construction of a rockfill self-compacting concrete gravity dam. Background Technology

[0002] Rockfill concrete is a new type of large-volume concrete construction method developed on the basis of self-compacting concrete technology. It utilizes the high fluidity, good anti-separation performance and self-flowing characteristics of self-compacting concrete to randomly fill the voids in the rockfill with larger-sized boulders to form a complete and dense concrete.

[0003] The surface of the backwater side of existing gravity dams is usually designed as a slope. The backwater side of the slope gravity dam usually uses a back-frame high-strength formwork. When installing the back-frame high-strength formwork, a tower crane is required to hoist the back-frame high-strength formwork, and the previous formwork section needs to be reserved as a supporting mother formwork to provide support for the back-frame high-strength formwork. At the same time, internal reinforcing steel bars are also used to reinforce the back-frame high-strength formwork. The problems encountered during the construction of inclined gravity dams are as follows: 1. When reinforcing the high-strength formwork with a back-frame, workers are in an inclined working position, increasing the risk of safety accidents; 2. The use of internal reinforcing steel bars increases the amount of steel used and occupies space in the rockfill layer, reducing the rockfill ratio and thus increasing the amount of concrete used, thereby increasing construction costs; 3. The installation of the high-strength formwork with a back-frame requires the use of a tower crane for hoisting, and the previous formwork needs to be reserved as a supporting formwork to support the high-strength formwork. Therefore, the investment in the formwork and tower crane increases construction costs, reduces construction efficiency, and prolongs the construction period. Summary of the Invention

[0004] The present invention aims to provide a method for rapid construction of rockfill self-compacting concrete gravity dams, so as to reduce the risks of safe operation and construction costs, while improving construction efficiency and shortening the construction cycle.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for rapid construction of a rockfill self-compacting concrete gravity dam, comprising the following steps:

[0006] S1, bedrock surface treatment and site preparation, after which concrete cushion layer is poured.

[0007] S2, Template installation. The template includes water-facing template and backwater template. The water-facing template is fixed by a mounting bracket. The backwater template adopts a stepped design, and the connecting line of the external corner of the step is consistent with the line of the original slope. That is, the step is recessed into the dam body relative to the original slope. The step size is 1.6m×2.0m. The backwater template is a single-layer template, and the single-layer template is reinforced by reusable back frame with embedded anchor steel bars and bolts.

[0008] S3, screening and storage of rubble;

[0009] The first step is to screen and wash the rubble, with a particle size range of 30–160 cm.

[0010] The second step is to pile up stones and put them into the warehouse. The "backward method" is used to put them into the warehouse, that is, to set up the warehouse from the water-facing side to the back water-facing side, and to pile up the stone layers in the space more than 50 centimeters away from the template on the water-facing side.

[0011] S4, self-compacting concrete production and transportation, the self-compacting concrete is mixed on site, and the water-cement ratio is controlled within the range of -0.02 to 0.01 during mixing;

[0012] S5, pouring of self-compacting concrete;

[0013] The first step is to pour the waterproof panel;

[0014] The second step is the pouring of self-compacting concrete for the riprap layer;

[0015] S6, Curing of self-compacting riprap concrete;

[0016] S7. The safety performance of the stepped gravity dam body was verified by numerical simulation and rigid body limit equilibrium method.

[0017] The beneficial effects of this solution are as follows: Compared with the existing technology, this technical solution has the following advantages:

[0018] 1. Because the backwater surface adopts a stepped design, and the connecting line of the stepped external angle is consistent with the line of the original slope surface, that is, the stepped surface is recessed into the dam body relative to the original slope surface. Therefore, the gravity dam of this technical solution saves construction costs, reduces construction difficulty, improves construction efficiency, and facilitates the control of construction quality.

[0019] 2. Since this technical solution uses reusable back-frames to embed anchor steel bars and bolts to reinforce the backwater formwork, it eliminates the need for internal reinforcing steel bars, reducing the amount of steel bars used and lowering construction costs. At the same time, because this technical solution eliminates the need for internal reinforcing steel bars, it does not occupy the space of the rockfill layer when reinforcing the backwater formwork, increasing the rockfill ratio, reducing the amount of concrete used, and further reducing construction costs.

[0020] 3. Because the backwater surface adopts a stepped design with step dimensions of 1.6m × 2.0m, no mother formwork support is required when installing the backwater surface formwork, saving on the investment in mother formwork. There is also no need to use a tower crane to hoist the formwork. The backwater surface formwork is installed using the cast-in-place stepped surface as a reference, reducing the height of the working surface and thus reducing safety hazards associated with working at heights. Furthermore, since this technical solution eliminates the need for tower crane installation of the formwork, and the stepped slope does not require reverse-angle construction, the working surface is large, the formwork turnover efficiency is high, improving construction efficiency and shortening the construction cycle.

[0021] 4. Regarding the installation and dismantling of the stepped cross-section backwater face formwork, the formwork is easy to reinforce and has good stability. It is also easy to place stones and clean up the gravel on the base surface, and it is easy to control the thickness of the concrete protective layer on the downstream face, so that the self-compacting concrete filling of the stepped surface is more compacted, thus improving the pouring quality.

[0022] 5. The safety performance of the stepped gravity dam was verified by numerical simulation and rigid body limit equilibrium method, and the stepped gravity dam met the safety requirements.

[0023] This technical solution involves piling up a layer of riprap in a space 50 centimeters away from the formwork on the water-facing side. Therefore, when pouring the anti-seepage panel, the unpoured riprap layer serves as the formwork, eliminating the need for the formwork erection process on the inner side of the water-facing formwork. This simplifies the construction process, reduces construction costs, and improves construction progress. Simultaneously, the anti-seepage panel can resist the impact of seepage water pressure, thus achieving the anti-seepage effect. Compared to using other types of concrete for the anti-seepage panel, since it is poured with self-compacting concrete, it can be poured simultaneously with the self-compacting concrete of the riprap layer, eliminating the need for mixing other concrete. Furthermore, self-compacting concrete has advantages such as good fluidity and resistance to segregation, which enhances the anti-seepage effect of the dam.

[0024] By controlling the water-cement ratio within the range of -0.02 to 0.01, the fluidity of the concrete is kept within a suitable range while ensuring the solidification quality, so that the self-compacting concrete can be evenly filled in the riprap layer.

[0025] Furthermore, in S2, the template also includes a groove template, which is L-shaped and includes a connecting part and a forming part connected in sequence. The connecting part is installed on the upper end of the water-facing template, and one side of the forming part contacts the seepage-proof panel. The width of the forming part is 15 cm, and the lower end of the forming part extends into the rockfill layer.

[0026] The beneficial effects of this scheme are as follows: Due to the setting of the groove template, when pouring the self-compacting concrete of the rockfill layer, a 15 cm wide groove will be formed on the side near the seepage barrier panel. Since the rockfill particle size is greater than 30 cm, when the next layer of rockfill is piled up, the rockfill will not fill the groove of the previous layer of dam body. When pouring the next layer of dam body, the groove is filled with pure self-compacting concrete. Under the double protection of the seepage barrier panel and the groove, the seepage prevention effect of the construction joint is improved. Because during the rockfill process, one side of the stone will just fit against the previous layer. On the base surface of the self-compacting concrete in the rockfill layer of the dam, there may be situations where the self-compacting concrete cannot penetrate into the contact surface between the stones and the concrete, thus increasing the risk of dam leakage. However, the groove design allows the self-compacting concrete to flow into the contact surface through the groove when pouring the next layer of the dam, reducing the risk of dam leakage. If water from the water-facing side passes through the seepage-proof surface through the interlayer construction joint and flows to the groove, the water must bend and flow to the bottom of the groove before flowing to the top, thus achieving the seepage-proof effect.

[0027] Furthermore, in the first step of S5, a water-stop plate is provided downstream of the seepage-proof panel. The water-stop plate includes an upper connecting part, a water-stop part, and a lower connecting part connected in sequence. The bottom of the connecting part is provided with a groove. The upper connecting part is locked in the groove. The lower connecting part is integrally cast with the seepage-proof panel of the upper dam body, and the upper connecting part is integrally cast with the seepage-proof panel of the lower dam body, and is perpendicular to the interlayer construction joint.

[0028] The beneficial effects of this solution are as follows: If no slot is provided on the connection, the anti-seepage panel is typically poured first, and before its initial setting, the lower connection of the waterstop is inserted into the anti-seepage panel of the upper dam body to fix it. However, during this insertion process, the waterstop needs to overcome the resistance of the self-compacting concrete, making it prone to damage and more laborious. The slot design, on the other hand, allows the waterstop to be fixed to the pressure groove formwork beforehand. When pouring the anti-seepage panel, the lower connection of the waterstop can be poured into the anti-seepage panel of the upper dam body simultaneously, making the construction process more labor-saving, convenient, and less likely to damage the waterstop. The waterstop design further improves the dam's anti-seepage effect.

[0029] Furthermore, in the first step of S5, the waterstop is U-shaped and located at the interlayer construction joint, with the opening of the waterstop facing the water-facing side.

[0030] The beneficial effects of this solution are as follows: Since the waterstop is U-shaped and the opening of the waterstop is located on the side closer to the water-facing side, if water enters the seepage-proof panel through the interlayer construction joint, the U-shaped waterstop can act as a buffer, thus preventing the dam from leaking.

[0031] Because the waterstop is U-shaped, during the pouring of the next layer of the dam, the self-compacting concrete presses down on the waterstop under gravity, deforming it. This deformation creates creases in the waterstop. When water seeps into the waterstop from the anti-seepage panel, it erodes these creases, damaging the waterstop and shortening its lifespan. However, since the upper connecting part of the waterstop is secured in a groove, when the pressure groove template is disassembled, lifting it upwards causes the waterstop to lift and restore its original shape.

[0032] Furthermore, in the second step of S5, self-compacting concrete is poured using a pumping method. Before pouring the self-compacting concrete, a 1-3m section needs to be poured first. 3 The self-compacting mortar is then poured with self-compacting concrete.

[0033] The beneficial effects of this scheme are: because self-compacting concrete is poured using a pumping method, the first 1-3m of concrete can be poured... 3 The self-compacting mortar acts as a lubricant for the pipes, preventing blockages during the pouring of self-compacting concrete and improving the controllability of the pouring process.

[0034] Furthermore, in the second step of S3, before the rubble is placed into the silo, when the strength of the concrete subbase is greater than 5MPa, the surface of the concrete subbase is roughened, and then the rubble layer is piled up, with stones of different diameters used in combination.

[0035] The beneficial effects of this solution are: by roughening the concrete subbase, the bonding strength between the self-compacting concrete of the riprap layer and the concrete subbase can be improved after the self-compacting concrete of the riprap layer is poured.

[0036] Different diameter stones are used in combination to avoid excessive gaps between the stones, which would result in a low slab ratio and excessive self-compacting concrete usage. During the slab stacking process, it is also important to avoid contact between two relatively flat surfaces of different stones, as this would lead to smaller gaps between the stones and prevent the self-compacting concrete from filling them completely. If contact between two surfaces cannot be avoided, small stones should be used as supports to ensure the compactness of the dam body after the concrete is poured.

[0037] Furthermore, in the second step of S3, the number of stones with a diameter of less than 20 cm contained in the exposed surface of the rockfill layer is less than 10 pieces / m². 2 .

[0038] The beneficial effect of this scheme is that when the number of stones with a diameter of less than 20cm contained in the exposed surface of the rockfill layer is less than 10 pieces / m². 2 The riprap layer can still maintain suitable natural gaps, thus ensuring the filling effect of the self-compacting riprap concrete.

[0039] Furthermore, in step S6, the self-compacting riprap concrete is cured according to the temperature changes.

[0040] The beneficial effects of this scheme are: by curing the self-compacting rockfill concrete, the strength and other properties of the self-compacting rockfill concrete can be fully developed and reach the optimal state, thereby improving the impermeability and strength of the dam.

[0041] Furthermore, in S4, self-compacting concrete is mixed using a twin-shaft forced mixer. When mixing self-compacting concrete, the materials must be added in sequence. First, the weighed aggregates and cementitious materials are put into the mixer for dry mixing, then water and admixtures are added and mixing continues for 60 seconds. After mixing is completed, the fluidity and spread of the concrete are tested.

[0042] The beneficial effects of this scheme are as follows: the twin-shaft forced mixer can produce a mixture with a powdery texture, which effectively improves the fluidity of self-compacting concrete. The purpose of dry mixing of aggregates and cementitious materials is also to improve the crushing and mixing uniformity. Adding water and admixtures afterward can improve fluidity, while the control of gelling materials is mainly to maintain the bonding effect.

[0043] Furthermore, S7 includes the following steps:

[0044] The first step is to use ABAQUS software to establish a numerical simulation finite element model;

[0045] The second step is to use ABAQUS software to automatically create an initial analysis step: determine the conditions of the applied boundary and create a load analysis step, and determine the loads to be applied according to the "Design Code for Concrete Gravity Dams";

[0046] The third step is to analyze the results of the data simulation: under normal water level, design flood level and check flood level conditions, the displacement and stress distribution of the gravity dam under different static load conditions are studied, and the safety of normal operation of the gravity dam is analyzed.

[0047] The fourth step is to calculate the anti-sliding stability safety factor of the stepped gravity dam using the rigid body limit equilibrium method.

[0048] The beneficial effects of this scheme are as follows: Static analysis of the gravity dam was conducted using the finite element analysis software ABAQUS. The stress-strain conditions of the gravity dam under three working conditions—normal water level, design flood level, and check flood level—were analyzed. The analysis revealed that the gravity dam conforms to the general stress distribution law of gravity dams. The maximum tensile and compressive stresses of the dam body did not exceed the allowable tensile and compressive stresses of the concrete, posing no threat to the safety of the gravity dam. Furthermore, the dam deformation was small, with the maximum displacement of the dam body occurring at the dam crest. The calculated anti-sliding stability coefficients of the dam foundation all met the safety values ​​specified in the code, verifying the stability of the dam foundation. Therefore, the stress distribution of this gravity dam is good, and the stability coefficients all meet the safety values ​​specified in the code. The design of this stepped gravity dam meets the requirements. Attached Figure Description

[0049] Figure 1 This is a side sectional view of the present invention;

[0050] Figure 2 This is a side sectional view of the lower dam body and template of the present invention.

[0051] Figure 3 A schematic diagram of the process flow of this invention;

[0052] Figure 4 A distribution diagram of uplift pressure;

[0053] Figure 5 (a) is a lateral displacement contour map of a stepped gravity dam under working condition 1;

[0054] Figure 5 (b) is a contour map of the lateral displacement of the stepped gravity dam under working condition 2;

[0055] Figure 5 (c) is a lateral displacement contour map of the stepped gravity dam under working condition 3;

[0056] Figure 6 (a) is a vertical displacement cloud map of a stepped gravity dam under working condition 1;

[0057] Figure 6 (b) is a vertical displacement cloud map of the stepped gravity dam under working condition 2;

[0058] Figure 6 (c) is the vertical displacement cloud map of the stepped gravity dam under working condition 3;

[0059] Figure 7 (a) is the Mises stress cloud diagram of the stepped gravity dam under working condition 1;

[0060] Figure 7 (b) is the Mises stress contour map of the stepped gravity dam under condition 2;

[0061] Figure 7 (c) is the Mises stress cloud diagram of the stepped gravity dam under working condition 3;

[0062] Figure 8 (a) is a vertical stress cloud diagram of a stepped gravity dam under working condition 1;

[0063] Figure 8 (b) is the vertical stress cloud diagram of the stepped gravity dam under working condition 2;

[0064] Figure 8 (c) is the vertical stress cloud diagram of the stepped gravity dam under working condition 3. Detailed Implementation

[0065] The following detailed description illustrates the specific implementation method:

[0066] The reference numerals in the accompanying drawings include: stepped slope 1, original slope 2, concrete cushion layer 3, interlayer construction joint 4, anti-seepage panel 5, waterstop 6, upper connection part 7, waterstop part 8, lower connection part 9, water-facing formwork 10, water-returning formwork 11, grooved formwork 12, connection part 13, forming part 14, slot 15, rockfill layer 16, groove 17.

[0067] Example

[0068] The construction method of the rockfill self-compacting concrete gravity dam adopts the method of layering rock blocks and filling with self-compacting concrete in layers. In this embodiment, the left side of the dam body is defined as the water-facing side and the right side is defined as the water-repelling side.

[0069] like Figure 1 As shown, the downstream side of the rockfill self-compacting concrete gravity dam adopts a stepped slope 1, and the connecting line of the external corners of the steps is consistent with the line of the original slope 2. That is, the stepped slope 1 is recessed into the dam body relative to the original slope 2. The step size is 1.6m × 2.0m. A concrete cushion layer 3 is poured at the bottom of the rockfill self-compacting concrete gravity dam. There is an interlayer construction joint 4 between each upper and lower step. The upstream side of the rockfill self-compacting concrete gravity dam is covered with a seepage-proof panel 5, which is 50cm thick. Each interlayer construction joint 4 is equipped with a waterstop 6. The waterstop 6 is located inside the anti-seepage panel 5 and is close to the back water side. The waterstop 6 includes an upper connecting part 7, a waterstop part 8 and a lower connecting part 9 connected in sequence. The lower connecting part 9 of the waterstop 6 is integrally cast with the anti-seepage panel 5 of the next layer of dam body. The upper connecting part 7 of the waterstop 6 is integrally cast with the anti-seepage panel 5 of the previous layer of dam body and is perpendicular to the interlayer construction joint 4. The waterstop part 8 is U-shaped and located at the interlayer construction joint 4, and the opening direction of the waterstop part 8 is located on the side closer to the water-facing side.

[0070] like Figure 3As shown, the method for rapid construction of self-compacting rockfill concrete gravity dams includes the following:

[0071] S1, Bedrock surface treatment and site preparation for cleaning;

[0072] The first step is to treat the bedrock surface. First, clean up the loose rocks on the bedrock surface, remove loose stones and debris, clean up the fine debris with an air compressor or high-pressure water gun, and drain the water in the chamber. If there is underground water seepage, develop drainage measures and methods. Finally, pour a concrete cushion layer 3 on the bedrock surface.

[0073] The second step is to prepare the washing site. A washing area is set up in the material yard. The ground of the washing area is hardened with 20cm thick C20 concrete. The washing area is equipped with a water storage tank, a sedimentation tank and a drainage ditch. With the help of a high-pressure water pump, water from the river is pumped into the water storage tank for washing the stones. The washing wastewater flows into the sedimentation tank through the drainage ditch. After sedimentation, it can be recycled for washing the stones. Excess water is discharged into the river after monitoring and meeting the discharge requirements. The mud in the sedimentation tank is cleaned regularly.

[0074] S2, Template installation;

[0075] like Figure 2 As shown, the template includes an upstream template 10, a downstream template 11, and a grooving template 12. The upstream template 10 and the downstream template 11 form the outer outline of the dam body. The upstream template 10 is fixed by a mounting bracket. The fixing of the upstream template 10 is existing technology; as long as the upstream template 10 can be fixed and guaranteed not to deform or overturn, it will not be elaborated here. The downstream side adopts a stepped design with a step size of 1.6m × 2.0m. The downstream template 11 is a single-layer template, and the single-layer template is reinforced by reusable back-frames with embedded anchor steel bars and bolts. The groove template 12 is installed on the upper end of the water-facing template by bolts. Specifically, the groove template 12 includes a connecting part 13 and a forming part 14 connected in sequence. The connecting part 13 and the forming part 14 are integrally formed. The bottom of the connecting part 13 has a slot 15, and the upper connecting part 7 of the water-stop plate 6 is inserted into the slot 15. The width of the forming part 14 is 15 cm, and the lower end of the forming part 14 extends into the rockfill layer 16. In this embodiment, the template is a steel template. The material of the steel template is Q235 and the thickness is 6 mm.

[0076] S3, screening and storage of rubble;

[0077] The first step is the screening and washing of the quarried stones. The stones extracted from the quarry are then washed using a 1m... 3When the excavator loads the stones, it first screens the stones, selecting those with a diameter range of 30-160cm. These stones are then loaded onto the truck and transported to the washing area. Using a high-pressure water gun, the stones are washed with water from a storage tank. The washed stones are then transported to the stockpile. When stacking stones on the silo surface, a 1m... 3 The excavator loads the stones onto trucks, which is the second time the stones are sorted before being transported to the storage area by dump trucks.

[0078] The second step is the placement of the riprap: Before placing the riprap, once the concrete subbase has a strength greater than 5 MPa, the surface of the concrete subbase is roughened. Then, the riprap layer 16 is placed using the "reverse method," that is, the riprap is placed from the water-facing side to the backwater side. Loaders and excavators are used for leveling the riprap. Specifically, within a space more than 50 cm from the inside of the water-facing formwork 10, excavators are used to transport the riprap into the riprap layer and stack it. During the riprap construction, stones of different diameters are used in combination. The number of stones with a particle size of less than 20 cm on the exposed surface of the riprap layer 16 is less than 10 pieces / m². 2 And they must not gather together.

[0079] S4, Production and transportation of self-compacting concrete;

[0080] The first step is to mix the self-compacting concrete on-site. The mix proportion is the basis for mixing the self-compacting concrete. Therefore, it is necessary to conduct comprehensive testing on the incoming raw materials, mainly including the testing of the moisture content and mud content of coarse and fine aggregates. After the test results are available, the theoretical mix proportion of the self-compacting concrete is determined based on the test results of the raw materials on site, and trial mixing is carried out on the construction site for verification. After verification, adjustments are made according to the actual situation of the production system on the construction site, and the self-compacting concrete is mixed according to the optimal construction mix proportion.

[0081] The second step involves mixing the self-compacting concrete using a twin-shaft forced mixer. During mixing, the materials must be added in sequence: first, the weighed aggregates and cementitious materials are added to the mixer for dry mixing; then, water and admixtures are added and mixing continues for 60 seconds. The water-cement ratio is controlled within the range of -0.02 to 0.01. After mixing, the flowability and spreadability of the concrete are tested.

[0082] The third step involves transporting self-compacting concrete using concrete mixer trucks. Before loading, any remaining concrete of other types must be cleaned from the truck, and any accumulated water must be drained. During transport, adding water to the concrete is strictly prohibited. The normal transport time for concrete should be controlled within 30 minutes, and the maximum time should not exceed 60 minutes. Before unloading, the concrete mixer truck should rotate at high speed for at least 1 minute. When adjusting the spread of self-compacting concrete, after adding admixtures, the concrete transport truck should rotate at high speed for 3 minutes to ensure that the self-compacting concrete is uniform and consistent. Unloading is only permitted after the concrete has passed inspection.

[0083] S5, self-compacting concrete, is poured using a pump. Before pouring the self-compacting concrete, a 1-3m section needs to be poured first. 3 Self-compacting mortar is applied, followed by the pouring of self-compacting concrete. The self-compacting concrete pouring points are evenly distributed, with a spacing of less than 3 meters between adjacent pouring points. During the pouring process, the principle of unidirectional point-by-point pouring is followed, starting from one end of the water-facing side and pouring parallel to the dam axis to the other end in an "S" shaped route. Each pouring point can only be moved to the next pouring point after it is filled. Pouring points are not reused. The maximum free fall height during pouring is less than 2 meters. A cylindrical concrete placing machine is used for pouring instead of the original pump pipe for direct pouring. This operation not only reduces the input of personnel for pump pipe disassembly and assembly, but also shortens the distance of concrete self-flow, reduces the risk of concrete segregation, and shortens the pouring time by one-quarter.

[0084] The first step is the pouring of the anti-seepage panel 5. Self-compacting concrete is poured into the space between the water-facing formwork 10 and the rockfill layer 16 to form the anti-seepage panel 5. The water-stop plate 6 is poured between the anti-seepage panel 5 of the upper dam body and the anti-seepage panel 5 of the lower dam body, and is perpendicular to the interlayer construction joint 4.

[0085] The second step is the pouring of self-compacting concrete for the rockfill layer 16. The self-compacting concrete is poured into the space between the seepage barrier panel 5 and the backwater template 11, and the self-compacting concrete surface of the rockfill layer 16 is 5-15 cm lower than the rockfill surface, not exceeding 1 / 3 of the height of the stones. The groove template 12 can form a groove 17 15 cm wide and 10 cm deep on the side near the seepage barrier panel 5. The self-compacting concrete surface in the groove 17, the seepage barrier panel 5, and the self-compacting concrete surface of the rockfill layer 16 are roughened to expose the coarse aggregate. When the strength of the self-compacting concrete reaches more than 2.5 MPa, the next layer of dam body is poured.

[0086] S6, Curing of self-compacting riprap concrete;

[0087] After self-compacting concrete is poured, it should be cured according to the temperature. When the temperature is above 20-35℃, water curing should begin within 6-8 hours after the concrete is poured. When the temperature is above 5-20℃, water curing should begin within 12-24 hours after the concrete is poured. When the temperature is low, heat preservation should be carried out by covering. The curing time should be at least 7 days. For parts with special requirements, the curing time should be appropriately extended.

[0088] S7, the safety performance of the stepped gravity dam body was verified by numerical simulation and rigid body limit equilibrium method;

[0089] The first step is to use ABAQUS software to establish a numerical simulation finite element model;

[0090] The second step is to use ABAQUS software to automatically create an initial analysis step: determine the conditions of the applied boundary and create a load analysis step, and determine the loads to be applied according to the "Design Code for Concrete Gravity Dams";

[0091] The third step is to analyze the results of the data simulation: under normal water level, design flood level and check flood level conditions, the displacement and stress distribution of the gravity dam under different static load conditions are studied, and the safety of normal operation of the gravity dam is analyzed.

[0092] The fourth step is to calculate the anti-sliding stability safety factor of the stepped gravity dam using the rigid body limit equilibrium method.

[0093] Engineering Case Analysis and Verification

[0094] A typical gravity dam located in Guizhou Province was selected. This gravity dam is a C15 rockfill self-compacting concrete gravity dam. The backwater surface of the dam is stepped, and the connecting line of the external angle of the steps coincides with the line of the original slope surface 2. That is, the steps are recessed into the dam body relative to the original slope surface 2. The step dimensions are 1.6m × 2.0m. The dam height is 48.5m, the dam crest width is 5m, the dam base width is 39.8m, the normal reservoir water level is 1475.00m, and the corresponding reservoir capacity is 1.38 million m³. 3 Dead water level: 1454.00m; Dead storage capacity: 146,000 m³. 3 The design flood level is 1476.50m, the check flood level is 1476.90m, and the corresponding total reservoir capacity is 1.58 million m³. 3 Xingli reservoir capacity is 1.234 million m³. 3 .

[0095] The safety performance of the gravity dam was verified using numerical simulation and rigid body limit equilibrium methods, specifically including the following steps:

[0096] The first step is to establish a numerical simulation finite element model using ABAQUS software. A model of the same size is created in the component of ABAQUS software. The material model is an elastic model. The parameters are the specific parameters of C15 concrete. The gravity dam numerical model is meshed, the element type is CPE4, and the element shape is quadrilateral, generating a total of 3024 elements.

[0097] The second step is to automatically create an initial analysis step using ABAQUS software: determine the conditions for applying the boundary, with the upper and left and right sides of the numerical model as free boundaries, and apply fixed constraints to the bottom of the numerical model; create a load analysis step, and determine the loads to be applied according to the "Design Code for Concrete Gravity Dams". The applied loads include self-weight load, upstream and downstream hydrostatic pressure, uplift pressure and silt pressure.

[0098] (1) Determination of self-weight load: Considering only the self-weight of the dam body, it is constructed and applied in one go. The unit weight of C15 concrete used in the dam body is taken as 2400 kg / m³. 3 Massless bedrock was used for finite element analysis calculations;

[0099] (2) Determination of hydrostatic pressure: The hydrostatic pressure acts vertically on the upstream and downstream dam surfaces. The hydrostatic pressure load is calculated based on different water level conditions. The application of the load under hydrostatic pressure begins with the free surface pressure at the corresponding calculated water level in contact with the atmosphere being 0, and the load gradient along the vertical direction of the upstream and downstream dam surfaces is 9800 N / m. 3 ;

[0100] (3) Determination of siltation pressure: The formula for calculating siltation pressure is:

[0101]

[0102] In the formula: p sk —Standard value of siltation pressure (KN / m); γ sb —The buoyancy capacity of sediment is taken as 6 kN / m³; h s —The depth of siltation is taken as 1450.45m; φ s —Internal friction angle of silt, taken as 12°; tg —tangent function.

[0103] (4) Determination of Uplift Pressure: Uplift pressure consists of two parts: seepage pressure and buoyancy force. Since this design considers drainage holes and grouting of the seepage barrier, the uplift pressure of the dam is reduced to a certain extent in the calculation according to the specifications. The distribution diagram of uplift pressure is shown below. Figure 4 As shown;

[0104] The third step is to analyze the results of the data simulation: Under the following three working conditions, the displacement and stress distribution of the gravity dam under different static load conditions are studied to analyze the safety of normal operation of the gravity dam. The specific parameters under the three working conditions are shown in Table 1. Figure 5 This is a contour map of the lateral displacement of a stepped gravity dam under three different working conditions. Figure 6 The image shows the vertical displacement contour maps of a stepped gravity dam under three different working conditions. Figure 7 Stress contour maps of a stepped gravity dam under three different working conditions. Figure 8 Vertical stress cloud diagrams of a stepped gravity dam under three different working conditions;

[0105] Table 1

[0106] Operating conditions Upstream water level (m) Downstream water level (m) Operating Condition 1: Normal Water Level Operating Condition 1475.00 1440.00 Operating Condition 2: Design Flood Level Condition 1476.50 1440.60 Operating Condition 3: Flood Level Verification 1476.90 1440.91

[0107] The fourth step is to calculate the anti-sliding stability safety factor of the stepped gravity dam using the rigid body limit equilibrium method: The formula for calculating the anti-sliding stability safety factor is as follows:

[0108]

[0109] In the formula, K , —Anti-sliding stability safety factor; f—Shear friction coefficient at the contact surface between the dam body and the dam foundation, taken as f = 0.6; ΣW—Normal component of the total load acting on the dam body with respect to the calculated sliding surface, taken as ΣW = 8.453e7N; ΣP—Tangential component of the total load acting on the dam body with respect to the calculated sliding surface, taken as ΣP = 3.702e7N; A—Cross-sectional area (m²) of the contact surface between the dam body and the bedrock. 2 Let A = 39.8m 2 U—Magnitude of lifting pressure, taken as U = 132.6 N; c , —Shear cohesion at the concrete-rock interface (MPa), take c , =0.8MPa.

[0110] Conclusion Analysis:

[0111] from Figure 5 As can be seen from the displacement cloud diagram, the lateral displacement value at the dam crest is the largest. Under condition 1, the maximum lateral displacement is 1.3 mm; under condition 2, the maximum lateral displacement is 1.51 mm; and under condition 3, the maximum lateral displacement is 1.56 mm. Therefore, it can be concluded that as the water level depth increases, the lateral displacement of the dam body gradually increases, indicating that different water levels have a significant impact on the lateral deformation of the dam body. Figure 6 As can be seen, the vertical displacement of the stepped gravity dam under different working conditions is generally less than 0.5 mm. The maximum vertical displacement is 0.42 mm under working condition 1, 0.49 mm under working condition 2, and 0.51 mm under working condition 3. This indicates that the vertical displacement of the stepped gravity dam is not large under different working conditions and will not cause significant deformation to the dam body; the displacement distribution is reasonable. Furthermore, comparing the vertical and horizontal displacement deformations reveals a clear horizontal layered distribution of the dam body's horizontal displacement deformation. The closer to the top of the dam body, the greater the displacement deformation; the closer to the bottom of the dam body, the smaller the deformation.

[0112] from Figure 7 and Figure 8As can be seen from the numerical simulation results, under self-weight load, most of the dam body is under compressive stress, with stress concentration at the upstream dam heel, where compressive stress is generated. The maximum compressive stress on the dam body is 1.43 MPa, while the allowable compressive strength of concrete is 15 MPa and the allowable compressive stress of bedrock is 30 MPa. Therefore, the maximum compressive stress on the dam body is less than the allowable compressive strength of concrete and the allowable compressive stress of bedrock. Under condition 1, with the application of upstream hydrostatic pressure, sediment pressure, and uplift pressure at the dam base, the dam body continues to be dominated by compressive stress, with a small-scale compressive stress concentration at the upstream dam heel, which is consistent with the deformation characteristics of the dam body under condition 1. Under condition 3, with the continued increase of upstream hydrostatic pressure, the stress cloud diagram shows that tensile stress appears at the dam heel, and the vertical stress increases from 0.79 MPa under condition 3 to 0.9 MPa, which is much less than the allowable tensile strength of concrete (1.2 MPa). In summary, the stress of the dam body meets the allowable values ​​of the tensile and compressive strength specifications for concrete.

[0113] The anti-sliding stability safety factor of the stepped gravity dam is calculated using formula (2). The calculated anti-sliding stability safety factor K of the stepped gravity dam is... , The value is 3.52. According to the design specifications, the safety factor K for the anti-sliding stability of the gravity dam meets the safety values ​​specified in the specifications. Therefore, the stepped gravity dam meets the anti-sliding stability safety requirements.

[0114] In summary, a static analysis of the gravity dam was conducted using ABAQUS software, analyzing the stress-strain characteristics of the stepped gravity dam under three working conditions. The stress contour plots show that the overall stress distribution of the dam section is good, conforming to the general stress distribution pattern of gravity dams. The maximum tensile and compressive stresses in the dam body do not exceed the allowable tensile and compressive stresses of the concrete, posing no threat to the safety of the gravity dam. The displacement contour plots under different working conditions show that the dam deformation is small, with the maximum displacement occurring at the dam crest. The calculated anti-sliding stability coefficients of the dam foundation all meet the safety values ​​specified in the code, verifying the stability of the dam foundation.

[0115] Therefore, it can be seen that the stress distribution of this stepped gravity dam (step size: 1.6m × 2.0m) is good, and the stability coefficients all meet the safety values ​​specified in the code. The design of this stepped gravity dam meets the requirements. Furthermore, designing the stepped surface of the gravity dam as a stepped slope 1 has the following advantages: 1. Reduced dam size: Compared with a sloping surface, the stepped slope 1 can reduce the overall size of the dam by increasing the number of steps. 1. It can save construction costs, reduce earthwork excavation, and reduce the self-weight of the dam body; 2. It is convenient for construction: Compared with the sloping slope, the stepped slope 1 facilitates the leveling and construction of the dam surface, and can be leveled more easily, which is convenient for construction and maintenance; 3. It saves costs: When installing the backwater face formwork 11, there is no need for the support of the mother formwork, which saves the investment in the mother formwork, and there is no need to use the tower crane to lift the formwork, nor is there a need to reinforce the backwater face formwork 11 with internal reinforcing steel bars, which reduces the use of steel bars, increases the rockfill ratio, reduces the amount of concrete used, and reduces the cost of repairing the appearance quality of concrete in reverse slope construction, thus saving costs; 4. It shortens the construction period: This technical solution uses the cast-in-place stepped surface as the reference surface for installing the backwater face formwork 11, which reduces the height of the working surface, increases the working surface, eliminates reverse slope construction, eliminates the influence of internal reinforcing steel bars in the formwork, increases rockfill efficiency, improves construction efficiency, and shortens the construction period.

[0116] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for rapid construction of a rockfill self-compacting concrete gravity dam, characterized by: Includes the following steps: S1, bedrock surface treatment and site preparation, after which concrete cushion layer is poured. S2, Template installation. The template includes the water-facing template and the backwater template. The water-facing template is fixed by the installation bracket. The backwater template adopts a stepped design, and the connecting line of the external corner of the step is consistent with the line of the original slope. That is, the step is recessed into the dam body relative to the original slope. The step size is 1.6m×2.0m. The backwater template is a single-layer template, and the single-layer template is reinforced by reusable back frame with embedded anchor steel bars and bolts. S3, screening and storage of rubble; The first step is to screen and wash the rubble, with a particle size range of 30–160 cm. The second step is to pile up stones and put them into the warehouse. The "backward method" is used to put them into the warehouse, that is, to set up the warehouse from the water-facing side to the back water-facing side, and to pile up the stone layers in the space more than 50 centimeters away from the template on the water-facing side. S4, self-compacting concrete production and transportation, the self-compacting concrete is mixed on site, and the water-cement ratio is controlled within the range of -0.02 to 0.01 during mixing; S5, pouring of self-compacting concrete; The first step is to pour the waterproof panel; The second step is the pouring of self-compacting concrete for the riprap layer; S6, Curing of self-compacting riprap concrete; S7. The safety performance of the stepped gravity dam body was verified by numerical simulation and rigid body limit equilibrium method. In S2, the template also includes a groove template, which is L-shaped and includes a connecting part and a forming part connected in sequence. The connecting part is installed on the upper end of the water-facing template, and one side of the forming part contacts the seepage-proof panel. The width of the forming part is 15 cm, and the lower end of the forming part extends into the rockfill layer.

2. The method for rapid construction of a rockfill self-compacting concrete gravity dam according to claim 1, characterized in that: In the first step of S5, a water-stop plate is installed downstream of the seepage-proof panel. The water-stop plate includes an upper connecting part, a water-stop part, and a lower connecting part connected in sequence. The bottom of the connecting part is provided with a groove. The upper connecting part is locked in the groove. The lower connecting part is integrally cast with the seepage-proof panel of the upper dam body. The upper connecting part is integrally cast with the seepage-proof panel of the lower dam body and is perpendicular to the interlayer construction joint.

3. The method for rapid construction of a rockfill self-compacting concrete gravity dam according to claim 2, characterized in that: In the first step of S5, the waterstop is U-shaped and located at the construction joint between layers, with the opening of the waterstop facing the water-facing side.

4. The method for rapid construction of a rockfill self-compacting concrete gravity dam according to claim 3, characterized in that: In the second step of S5, self-compacting concrete is poured using a pumping method. Before pouring the self-compacting concrete, a 1-3m section needs to be poured first. 3 The self-compacting mortar is then poured with self-compacting concrete.

5. The method for rapid construction of a rockfill self-compacting concrete gravity dam according to claim 4, characterized in that: In the second step of S3, before the rubble is placed into the silo, when the strength of the concrete subbase is greater than 5MPa, the surface of the concrete subbase is roughened, and then the rubble layer is piled up, with stones of different diameters used in combination.

6. The method for rapid construction of a rockfill self-compacting concrete gravity dam according to claim 5, characterized in that: In the second step of S3, the number of stones with a diameter of less than 20 cm contained in the exposed surface of the rockfill layer is less than 10 pieces / m. 2 .

7. The method for rapid construction of a rockfill self-compacting concrete gravity dam according to claim 6, characterized in that: In step S6, the self-compacting riprap concrete is cured according to the temperature changes.

8. The method for rapid construction of a rockfill self-compacting concrete gravity dam according to claim 7, characterized in that: In S4, self-compacting concrete is mixed using a twin-shaft forced mixer. When mixing self-compacting concrete, the materials should be added in sequence. First, the weighed aggregates and cementitious materials are put into the mixer for dry mixing. Then, water and admixtures are added and mixing is continued for 60 seconds. After mixing is completed, the fluidity and spread of the concrete are tested.

9. The method for rapid construction of a rockfill self-compacting concrete gravity dam according to claim 8, characterized in that: In S7, Includes the following steps: The first step is to use ABAQUS software to establish a numerical simulation finite element model; The second step is to use ABAQUS software to automatically create an initial analysis step: determine the conditions of the applied boundary and create a load analysis step, and determine the loads to be applied according to the "Design Code for Concrete Gravity Dams"; The third step is to analyze the results of the data simulation: under normal water storage level, design flood level and check flood level conditions, the displacement and stress distribution of the gravity dam under different static load conditions are studied, and the safety of the gravity dam's normal operation is analyzed. The fourth step is to calculate the anti-sliding stability safety factor of the stepped gravity dam using the rigid body limit equilibrium method.

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