Reinforcement structure and construction method of clay core rockfill dam

Abstract

The present invention relates to a reinforcement structure of a clay core rockfill dam and a construction method thereof. The present invention is applicable to water conservancy and hydropower projects. The technical solution of the present invention is a reinforcement structure of a clay core rockfill dam, characterized in that: a row of boreholes are drilled in the clay core of the rockfill dam, upstream and downstream of the middle of the clay core, the boreholes extend downward from the top of the rockfill dam to the concrete base of the foundation, and the boreholes are filled with grouting materials; a concrete anti-seepage wall is provided in the middle of the clay core and between the two rows of boreholes. The two rows of boreholes are respectively located 1m upstream and downstream of the middle of the clay core. The borehole diameter is 0.1-0.2m, and the hole spacing between the boreholes in the same row is 0.5-1.0m. The grouting material includes cement and fine sand, and the mass ratio of cement to fine sand is 3:7-5:5; the proportion of grouting material is determined according to the leakage of the dam body and the damage of the core wall, and the more serious the leakage, the higher the proportion of fine sand.

Description

Technical Field

[0001] The invention relates to a reinforcement structure of a clay core rockfill dam and a construction method thereof, which is suitable for water conservancy and hydropower projects. Background Art

[0002] For the existing clay core rockfill dams, due to poor construction quality, complex basic geological conditions, inadequate dam foundation treatment measures, etc., after a period of operation, some projects were found to have suffered a certain degree of damage to the dam core wall impermeable body and foundation grouting, and the leakage behind the dam increased significantly, far exceeding similar projects. Some even saw water seepage on the downstream dam slope, and the reservoir water level had to be lowered or the reservoir drained for repair. The repair measures are generally to dismantle and rebuild the dam, or to add an impermeable wall at the original core wall to replace the original design impermeable body. The problems with the above practices are mainly the following aspects:

[0003] 1. As the core wall anti-seepage body was severely damaged, demolition and reconstruction is a relatively safe solution. However, this solution not only consumes a large amount of engineering funds, but also causes the project to be unable to play its normal functions of power generation, flood control, and irrigation for a long time, and the huge loss of its economic and social benefits is immeasurable.

[0004] 2. Adding an anti-seepage wall to the original core wall can reset the anti-seepage system. However, due to the large-scale cracks and voids formed in part of the core wall and the transition materials near it under the action of hydraulic pressure, the upper and lower reaches of the concrete anti-seepage wall lack effective protection and support. At the same time, due to its high rigidity and inconsistency with the deformation of the original dam body, it is very easy to cause damage or destruction to the reset anti-seepage wall again after water storage and operation.

[0005] 3. Due to the obvious defects in the core wall anti-seepage body, a large amount of transition materials upstream and downstream are also lost. The existing non-demolition reinforcement plan cannot reset the transition materials around the core wall and prevent the loss of fine particles in the dam body, resulting in a prominent problem of dam body seepage stability.

[0006] 4. The existing reinforcement scheme without demolition is not perfect and cannot withstand the high head of the reservoir. It has poor durability and needs to be reinforced again within a few years, resulting in a large waste of manpower and material resources. Summary of the invention

[0007] The technical problem to be solved by the present invention is: in view of the above-mentioned existing problems, a reinforcement structure of a clay core rockfill dam and a construction method thereof are provided.

[0008] The technical solution adopted by the present invention is: a reinforcement structure of a clay core rockfill dam, characterized in that: a row of boreholes are drilled in the clay core of the rockfill dam, upstream and downstream of the middle of the clay core, the boreholes extend downward from the top of the rockfill dam to the foundation concrete base, and the boreholes are filled with grouting materials; a concrete anti-seepage wall is provided in the middle of the clay core and between the two rows of boreholes.

[0009] The two rows of drill holes are respectively located 1 m upstream and 1 m downstream of the middle of the clay core wall.

[0010] The borehole diameter is 0.1-0.2 m, and the distance between the boreholes in the same row is 0.5-1.0 m.

[0011] The grouting material includes cement and fine sand, and the mass ratio of cement to fine sand is 3:7 to 5:5. The proportion of grouting materials is determined according to the leakage of the dam body and the damage of the core wall. The more serious the leakage, the higher the proportion of fine sand.

[0012] The concrete anti-seepage wall adopts a low elastic modulus and low-grade plastic concrete anti-seepage wall, and the concrete index of the anti-seepage wall is: elastic modulus E = 400-1000MPa; permeability coefficient K < 1×10 -7 cm / s; compressive strength 5-8MPa; water-cement ratio 0.75.

[0013] The concrete anti-seepage wall has a thickness of 0.4 to 0.8 m.

[0014] A reserved grouting pipe for reinforcing grouting the dam foundation curtain below the clay core wall is buried in the concrete anti-seepage wall.

[0015] The filter material, transition material and surface slope protection laid in sequence on the downstream slope of the rockfill dam are used to replace the original slope protection structure below the downstream dam slope verification flood level or below the downstream dam slope leakage outlet point.

[0016] The filter material is 20 to 40 cm thick, and its filling and compaction parameters can be the same as those of the upstream filter material of the rockfill dam; the transition material is 40 to 80 cm thick, and its filling and compaction parameters can be the same as those of the upstream transition material; the surface slope protection is dry stone, mortar stone or precast concrete blocks, with a dry stone and mortar stone thickness of 0.3 to 0.6 m, and a concrete precast block thickness of about 0.10 m.

[0017] A construction method for the reinforcement structure of the clay core rockfill dam, characterized in that:

[0018] S1. Arrange a row of drill holes upstream and downstream of the center line of the clay core wall, and perform filling grouting in the drill holes;

[0019] S2. After the grouting material in the borehole reaches a certain strength, a low elastic modulus, plastic concrete anti-seepage wall is poured in the middle of the clay core wall, and a reserved grouting pipe is buried in the concrete anti-seepage wall;

[0020] S3. When the concrete cut-off wall reaches 75% strength, the dam foundation curtain below the clay core wall is reinforced with grouting through the reserved grouting pipe;

[0021] S4. Remove the slope protection structure and part of the downstream dam shell material below the verification flood level of the downstream dam slope or below the leakage point of the downstream dam slope, and lay filter material, transition material and restore the surface slope protection in sequence along the downstream dam slope;

[0022] S5. Repair the dam top pavement structure.

[0023] The beneficial effects of the present invention are:

[0024] 1. The present invention drills a row of holes upstream and downstream of the middle of the clay core wall and performs filling grouting, thereby blocking the relatively unobstructed seepage channel and providing effective protection and support for the reset concrete anti-seepage wall.

[0025] 2. The concrete anti-seepage wall of the present invention adopts a low elastic modulus and low-grade plastic concrete anti-seepage wall, thereby achieving the purpose of maintaining deformation coordination with the original dam body of the rockfill dam to the greatest extent.

[0026] 3. The grouting materials poured into the borehole of the present invention are cement and fine sand. The fine sand is used to supplement the transition material lost on both sides of the clay core wall of the rockfill dam. If cracks appear in the concrete cut-off wall during operation, the fine sand can fill the cracks in the plastic concrete cut-off wall under the action of hydraulic pressure, achieving a good self-healing effect.

[0027] 4. The present invention removes the slope protection structure and part of the downstream dam shell material below the verification flood level of the downstream dam slope of the original design of the rockfill dam or below the seepage point of the downstream dam slope, and adds anti-filter material, transition material and restores the surface slope protection, thereby preventing fine particles from flowing out of the dam body, and better controlling or slowing down the loss of fine particles in the rockfill dam body, thereby avoiding the serious consequences that may be caused by a small amount of fine particles in the dam body passing through the newly constructed anti-seepage body of the rockfill dam and accumulating for a long time. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of an embodiment.

[0029] 1. Dam crest wave-breaking wall; 2. Dam crest highway; 3. Upstream slope protection; 4. Upstream dam shell material; 5. Upstream transition material; 6. Upstream filter material; 7. Clay core wall; 8. Downstream filter material; 9. Downstream transition material; 10. Downstream dam shell material; 11. Downstream slope protection; 12. Foundation concrete base; 13. Dam foundation curtain; 14. Dam foundation; 15. Upstream drilling hole of core wall; 16. Downstream drilling hole of core wall; 17. Concrete anti-seepage wall; 18. Reserved grouting pipe; 19. Reinforcement grouting; 20. Filter material; 21. Transition material; 22. Surface slope protection. DETAILED DESCRIPTION

[0030] The present embodiment is a reinforcement structure of a clay core rockfill dam. The rockfill dam comprises a clay core and upstream filter material, upstream transition material, upstream dam shell material and upstream slope protection sequentially arranged upstream of the clay core, and downstream filter material, downstream transition material, downstream dam shell material and downstream slope protection sequentially arranged downstream of the clay core. A dam crest wave-breaking wall and a dam crest road are arranged on the top of the rockfill dam, and a foundation concrete base and a dam foundation curtain are arranged below the clay core.

[0031] In this case, the height of the dam crest wave-breaking wall is generally 1.0 to 5.0 m, which is set upstream of the earth-rock dam and closely connected to the clay core wall. The width of the dam crest road is generally 4.0 to 12.0 m. The larger value is taken for high importance, high dam level and high head. The upstream slope protection is generally dry stone, mortar stone or precast concrete blocks. The thickness of dry stone and mortar stone is 0.3 to 0.6 m, and the thickness of concrete precast blocks is about 0.10 m. The upstream dam shell material is the upstream filling material of the clay core wall rockfill dam, which is generally filled with hard stone or gravel. The width of the upstream transition material is 3.0 to 6.0 m, which is determined according to the importance of the project and the operating head. It plays a role in filtering and protecting the upstream anti-filter material. The upstream transition material is generally filled with hard and well-graded stone, with a content of 25% to 40% of particles less than 5 mm and a content of no more than 5% of particles less than 0.075 mm. It is free-draining. The width of the upstream filter material is 2.0 to 4.0 m, which is determined according to the importance of the project and the operating head. It plays a role in filtering and protecting the clay core wall. One or two layers of filter material are set according to the gradation calculation of the dam material. The filter material is generally filled with hard and well-graded stone. The maximum particle size is not more than 10 cm, the content of particles less than 0.075 mm does not exceed 5%, and the permeability coefficient is 1×10 -4 ~1×10 -2 cm / s. The clay core wall is the impermeable body of the dam, and its permeability coefficient is not more than 10 -5cm / s, the top width of the core wall is not less than 3m, and the bottom width is not less than 1 / 4 of the water head. The design of the downstream filter material can be the same as the upstream filter material; the design of the downstream transition material can be the same as the upstream transition material. The downstream dam shell material is the downstream filling material of the clay core wall rockfill dam. It is designed according to the results of the engineering earthwork balance and local conditions. It can be filled with hard stone or gravel, or partially full and strongly weathered stone at high elevations. The downstream slope protection is generally dry stone, mortar stone or concrete precast blocks. The thickness of dry stone and mortar stone is 0.3~0.6m, and the thickness of concrete precast blocks is about 0.10m. The foundation concrete base is a reinforced concrete structure, the concrete grade is not less than C25, and the thickness is not less than 1m. The dam foundation curtain uses cement, ultrafine cement or chemical grouting, and the hole spacing is generally 1.0~2.0m.

[0032] In this embodiment, if the rockfill dam is located on bedrock, a concrete base is set at the core wall foundation and foundation curtain grouting is carried out; if it is located in a thick covering layer, a foundation concrete base is generally set, a concrete anti-seepage wall is set underneath, and foundation curtain grouting is carried out.

[0033] like Figure 1 As shown, in this embodiment, a row of boreholes are arranged at a position 1m upstream and downstream of the center line of the clay core wall, which are respectively the upstream boreholes of the core wall and the downstream boreholes of the core wall. The diameter of the upstream boreholes of the core wall is 0.1m-0.2m, the borehole spacing is 0.5-1.0m, and the boreholes are filled with grouting. The grouting material is cement + fine sand, and the ratio is generally 3:7-5:5. The grouting material ratio is determined according to the leakage of the dam body and the damage of the core wall. The more serious the leakage, the higher the proportion of fine sand, and the grouting pressure does not exceed 0.05MPa or pressureless grouting is used; the diameter of the downstream boreholes of the core wall is 0.1m-0.2m, the borehole spacing is 0.5-1.0m, and the boreholes are filled with grouting. The grouting material and grouting pressure are the same as the upstream filling grouting.

[0034] In this embodiment, a concrete anti-seepage wall is provided in the middle of the clay core wall and in the area between the upstream borehole of the core wall and the downstream borehole of the core wall. The concrete anti-seepage wall is a low elastic modulus, low grade, plastic concrete anti-seepage wall. The concrete indicators of the anti-seepage wall are: elastic modulus E = 400-1000MPa; permeability coefficient K < 1×10 -7 cm / s; compressive strength 5-8MPa; water-cement ratio 0.75, concrete anti-seepage wall thickness 0.4-0.8m, the larger value is used for projects with high importance and large water head. Before the construction of concrete anti-seepage wall, it is advisable to carry out construction tests to obtain relevant information on hole making, wall solidification mud, wall pouring, etc.; the construction of anti-seepage wall should be carried out in strict accordance with the current industry standard "Construction Specifications for Concrete Anti-seepage Walls of Hydropower and Water Conservancy Projects" and the technical requirements for the construction of concrete anti-seepage walls of related projects.

[0035] In this embodiment, a number of reserved grouting pipes are buried along the center line of the concrete anti-seepage wall for reinforcing grouting of the dam foundation curtain below the clay core wall.

[0036] In this case, filter material, transition material and surface slope protection sequentially laid on the downstream slope of the rockfill dam are used to replace the original slope protection structure below the downstream dam slope verification flood level or below the downstream dam slope leakage outlet point. The filter material is 20 to 40 cm thick, and the filling and rolling parameters can be the same as the upstream filter material of the rockfill dam; the transition material is 40 to 80 cm thick, and the filling and rolling parameters can be the same as the upstream transition material; the surface slope protection is dry stone, mortar stone or precast concrete blocks, the thickness of dry stone and mortar stone is 0.3 to 0.6 m, and the thickness of precast concrete blocks is about 0.10 m.

[0037] The construction method of the clay core rockfill dam reinforcement structure in this embodiment includes the following steps:

[0038] S1. On the dam crest road, arrange a row of holes 1m upstream and downstream of the center line of the original clay core wall, with the bottom of the holes reaching the top of the concrete base of the foundation below. The hole diameter is 0.1m to 0.2m, and the hole spacing is 0.5 to 1.0m; fill-type grouting is carried out in the holes, and the grouting material is cement + fine sand, with a general ratio of 3:7 to 5:5. The grouting material ratio is determined according to the leakage of the dam body and the damage of the core wall. The more serious the leakage, the higher the proportion of fine sand, and the grouting pressure does not exceed 0.05MPa or pressureless grouting is used.

[0039] S2. 7 days after the filling grouting is completed (after the grouting material reaches a certain strength), a concrete anti-seepage wall is cast on the dam top road and in the middle of the original clay core wall. The wall bottom is to the top of the foundation concrete base. The wall thickness is 0.4-0.8m. The larger value is used for projects with high importance and large water head. A φ10cm PVC pipe is buried on the center line of the concrete anti-seepage wall as a reserved grouting pipe, with a pipe spacing of 1.0-2.0m.

[0040] Before the construction of concrete anti-seepage wall, it is advisable to carry out construction test in order to obtain relevant information on hole making, wall solidification slurry, wall pouring, etc.; the construction of anti-seepage wall should be carried out strictly in accordance with the current industry standard "Construction Specifications for Concrete Anti-seepage Walls of Hydropower and Water Conservancy Projects" and the technical requirements for the construction of plastic concrete anti-seepage walls of related projects.

[0041] S3. When the concrete cut-off wall reaches 75% strength, the original dam foundation curtain grouting is reinforced through the reserved grouting pipe. The spacing of the grouting holes is the same as that of the PVC grouting pipe, and the hole depth is the same as the original dam design hole depth. Cement, ultrafine cement or chemical grouting can be used, and grouting is divided into 3 sequence holes, with a grouting pressure of 0.4MPa to 2.5MPa.

[0042] S4. Remove the downstream slope protection and part of the downstream dam shell material below the flood level or below the seepage point of the downstream dam slope, and lay filter material, transition material and surface slope protection in sequence along the slope of the downstream dam slope.

[0043] The thickness of the filter material is 20 to 40 cm, and the filling and rolling parameters can be the same as the upstream filter material. The thickness of the transition material is generally 40 to 80 cm, and the filling and rolling parameters can be the same as the upstream transition material. The surface slope protection is generally dry stone, mortar stone or prefabricated concrete blocks. The thickness of dry stone and mortar stone is 0.3 to 0.6 m, and the thickness of concrete prefabricated blocks is about 0.10 m.

[0044] S5. Repair the dam top road surface according to aesthetic needs or owner's requirements.

[0045] According to the description and drawings of the present invention, those skilled in the art can easily manufacture or use the anti-seepage panel layout type and construction method of the present invention for preventing compression damage of vertical seams in a concrete panel rockfill dam, and can produce the positive effects described in the present invention.

[0046] Unless otherwise specified, in the present invention, the orientation or position relationship indicated by terms such as "upper", "lower", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the orientation or position relationship in the present invention are only used for illustrative purposes and cannot be understood as limitations on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood in conjunction with the drawings and according to specific circumstances.

[0047] Unless otherwise clearly specified and limited, in the present invention, the terms "disposed", "clamped" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be internal communication between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0048] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A reinforcement structure for a clay core rockfill dam, characterized in that: A row of boreholes is drilled in the clay core wall of the rockfill dam, upstream and downstream of the middle of the clay core wall, and the boreholes extend downward from the top of the rockfill dam to the concrete base of the foundation, and the boreholes are filled with grouting materials; a concrete anti-seepage wall is provided in the middle of the clay core wall and between the two rows of boreholes; The borehole diameter is 0.1-0.2 m, and the distance between the boreholes in the same row is 0.5-1.0 m; The grouting material includes cement and fine sand, and the mass ratio of cement to fine sand is 3:7-5:

5. The proportion of grouting material is determined according to the leakage of the dam body and the damage of the core wall. The more serious the leakage, the higher the proportion of fine sand. The concrete anti-seepage wall adopts a low elastic modulus and low-grade plastic concrete anti-seepage wall, and the concrete index of the anti-seepage wall is: elastic modulus E=400~1000MPa; permeability coefficient K<1×10 -7 cm / s; compressive strength 5~8MPa; water-cement ratio 0.75; The filter material, transition material and surface slope protection sequentially laid on the downstream slope of the rockfill dam are used to replace the original slope protection structure below the downstream dam slope verification flood level or below the downstream dam slope seepage point; The filter material is 20-40 cm thick, and the filling and compaction parameters can be the same as the upstream filter material of the rockfill dam; the transition material is 40-80 cm thick, and the filling and compaction parameters can be the same as the upstream transition material; the surface slope protection is dry stone, mortar stone or precast concrete blocks, the thickness of dry stone and mortar stone is 0.3-0.6 m, and the thickness of concrete precast blocks is 0.10 m.

2. The reinforcement structure of the clay core rockfill dam according to claim 1, characterized in that: The two rows of drill holes are respectively located 1 m upstream and 1 m downstream of the middle of the clay core wall.

3. The reinforcement structure of the clay core rockfill dam according to claim 1, characterized in that: The concrete anti-seepage wall has a thickness of 0.4-0.8 m.

4. The reinforcement structure of the clay core rockfill dam according to claim 1, characterized in that: A reserved grouting pipe for reinforcing grouting the dam foundation curtain below the clay core wall is buried in the concrete anti-seepage wall.

5. A construction method for the reinforcement structure of a clay core rockfill dam according to any one of claims 1 to 4, characterized in that: S1. Arrange a row of drill holes upstream and downstream of the center line of the clay core wall, and perform filling grouting in the drill holes; S2. After the grouting material in the borehole reaches a certain strength, a low elastic modulus, plastic concrete anti-seepage wall is poured in the middle of the clay core wall, and a reserved grouting pipe is buried in the concrete anti-seepage wall; S3. When the concrete cut-off wall reaches 75% strength, the dam foundation curtain below the clay core wall is reinforced with grouting through the reserved grouting pipe; S4. Remove the slope protection structure and part of the downstream dam shell material below the verification flood level of the downstream dam slope or below the leakage point of the downstream dam slope, and lay the filter material, transition material and surface slope protection in sequence along the downstream dam slope; S5. Repair the dam top pavement structure.

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