Gravity dam foundation treatment structure used under soft rock foundation condition in strong earthquake region
By adopting a combination of concrete dam body, consolidation grouting layer and bored piles in the foundation treatment structure of gravity dam under soft rock foundation conditions in strong earthquake zones, the bearing capacity and anti-sliding stability problems of gravity dam are solved, efficient construction and economic advantages are achieved, and the anti-sliding safety factor is improved.
Patent Information
- Application Number
- CN202511217508.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-28
- Publication Date
- 2025-10-03
AI Technical Summary
Existing technologies have limited effects on improving the bearing capacity and anti-sliding stability of gravity dams under soft rock foundation conditions in strong earthquake zones. In particular, they are unable to effectively solve the problem of deep anti-sliding stability, and there is a risk of sliding instability along weak structural surfaces or rock layers deep in the foundation.
A gravity dam foundation treatment structure is adopted, including a concrete dam body, a consolidation grouting layer and bored piles. The bored piles are set below the concrete dam body and extend below the boundary line of the three types of rock masses. Combined with reinforced concrete rotary bored piles and the consolidation grouting layer, a coordinated bearing system of rigid piles and flexible grouting layer is formed.
The bearing capacity and stability of the dam foundation have been significantly improved, construction efficiency has been increased by 40% to 60%, earth excavation volume has been reduced by more than 30%, material costs have been saved by more than 25%, construction period has been shortened by more than 20%, the overall construction cost has been reduced by 18% to 22%, and the anti-slip safety factor has been increased by 20% to 35%.
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Figure CN120739155A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of water conservancy and hydropower facilities, and in particular to a gravity dam foundation treatment structure used in soft rock foundation conditions in strong earthquake areas. Background Art
[0002] The bearing capacity and anti-sliding stability of gravity dams have always been core issues in their design and construction. With the development of water conservancy and hydropower, dam sites with favorable geological conditions have been gradually developed and utilized. This has forced new gravity dams to be constructed on sites with relatively poor geological conditions, such as those on soft rock foundations in strong earthquake zones. This has greatly increased the importance of studying the bearing capacity and anti-sliding stability of gravity dams.
[0003] Due to its poor integrity, soft rock has poor bearing and deformation capacity in the foundation at the base of the dam. Furthermore, the dam foundation rock mass is characterized by well-developed fissures and weak structural surfaces, leading to stability issues such as anti-slip resistance along the foundation surface, shallow layers, and deep layers. Currently, in the construction of gravity dams with soft rock foundations in strong earthquake zones, the foundation needs to be reinforced to improve the bearing capacity and stability of the dam. One such treatment method is consolidation grouting. The consolidation grouting process involves the high-pressure injection of cement slurry or other specialized grouting materials into the dam foundation rock mass. Subsequently, the concrete dam body is placed on the consolidation grouting layer, thereby systematically improving the dam foundation rock mass. Consolidation grouting can enhance rock integrity, effectively filling various primary and secondary fissures and fracture zones, and improving the physical and mechanical properties of the rock mass, allowing for structural reinforcement of unfavorable geological structures such as fault fracture zones and weak interlayers. However, because consolidation grouting typically operates at a depth of 6-15m, it offers limited improvement to the mechanical properties of the dam foundation and, therefore, has little impact on resolving deep-layer anti-sliding stability issues. Furthermore, the effectiveness of consolidation grouting in reinforcing the dam foundation is closely related to the groutability of the rock mass. When the dam foundation rock mass is weakly permeable, the reinforcement effect is not significant. Therefore, a single consolidation grouting method has limited effectiveness in improving the bearing capacity and stability of gravity dams under soft rock foundation conditions in strong earthquake zones, and cannot effectively resolve deep-layer anti-sliding stability issues. Dams still face the risk of sliding and instability along weak structural surfaces or rock strata deep within the foundation. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a gravity dam foundation treatment structure that solves the problems of gravity dam foundation bearing capacity and anti-sliding stability under soft rock foundation conditions in strong earthquake areas.
[0005] The technical solution adopted by the present invention to solve its technical problems is: a gravity dam foundation treatment structure for soft rock foundation conditions in strong earthquake areas, including a foundation surface of the gravity dam, a consolidation grouting layer, cast-in-place piles and a concrete dam body, the concrete dam body is arranged above the foundation surface, a consolidation grouting layer is arranged below the foundation surface, the cast-in-place piles are arranged below the concrete dam body, the top of the cast-in-place pile is fixedly connected to the bottom of the concrete dam body, and the bottom of at least one cast-in-place pile is arranged below the boundary line of the three types of rock masses.
[0006] Furthermore, the concrete dam body includes a dam heel and a dam toe, cast-in-place piles are provided at the bottom of the dam heel, and cast-in-place piles are provided at the bottom of the dam toe.
[0007] Furthermore, the ratio of the dam heel height to the dam heel length is in the range of 1.5 to 2.
[0008] Furthermore, the ratio of the dam toe height to the dam toe length is in the range of 1.5 to 2.
[0009] Furthermore, cast-in-place piles are provided in the area between the dam heel and the dam toe at the bottom of the concrete dam body.
[0010] Furthermore, cast-in-place piles are provided in the area of the downstream sliding surface of the concrete dam body.
[0011] Furthermore, the cast-in-place piles are reinforced concrete rotary bored cast-in-place piles.
[0012] Furthermore, the deepest potential sliding surface is included, the deepest potential sliding surface is located above the boundary line of the three types of rock masses, and the bottom of the bored pile is set at a depth of at least 2m below the deepest potential sliding surface.
[0013] Furthermore, the horizontal bearing capacity of a single pile at the junction of the cast-in-place pile and the potential deepest sliding surface is included, and the horizontal bearing capacity of the single pile is greater than the shear force at the junction of the cast-in-place pile and the potential deepest sliding surface.
[0014] Furthermore, the dam comprises an earthquake-resistant steel mesh, which is arranged in the concrete dam body along the direction of water flow and perpendicular to the water flow.
[0015] The beneficial effects of the present invention are: 1. Install bored piles and consolidation grouting layers. Bored piles enhance the bearing capacity and stability of the dam foundation. Consolidation grouting strengthens the integrity and uniformity of the dam foundation rock mass, increases the elastic modulus of the dam foundation, reduces its permeability, and improves its bearing capacity. Bored piles and the consolidation grouting layer create a coordinated bearing system of rigid piles and flexible grouting layers, significantly improving the foundation's bearing capacity and addressing anti-slip stability along the foundation surface, shallow layers, and deep layers.
[0016] Second, the bored piles extend downward to below the boundary line of the three types of rock mass, allowing them to cut through the weak structural surface and move the sliding surface down to the hard rock layer. Combined with the slurry vein network formed by the consolidation grouting layer, the anti-sliding safety factor is increased by 20% to 35%.
[0017] Compared to traditional foundation reinforcement technologies, rotary bored piles offer advantages such as faster construction efficiency and the ability to avoid extensive excavation. Construction speed can be increased by 40% to 60%, while excavation volume can be reduced by over 30%.
[0018] 4. Significant Economic Benefits: This solution saves over 25% in material costs, shortens construction time by over 20%, and reduces overall construction costs by 18% to 22%. Furthermore, it aligns with the trend of green construction in water conservancy projects and possesses significant technical and economic advantages.
[0019] The present invention is particularly suitable for gravity dam foundation treatment construction under soft rock foundation conditions in strong earthquake areas. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 It is a schematic diagram of the positional relationship among the concrete dam body, the consolidation grouting layer, the bored piles and the boundary lines of the three types of rock masses according to the present invention.
[0021] Figure 2 It is a schematic diagram of the dam heel and dam toe of the concrete dam body of the present invention.
[0022] Figure 3 It is a schematic diagram showing that the cast-in-place pile of the present invention is divided into an upper pile foundation and a lower pile foundation at the junction of the potential deepest slip surface.
[0023] Figure 4 It is a structural schematic diagram of the combination of the concrete dam body and cast-in-place piles of the present invention.
[0024] Markings in the figure are: concrete dam body 1, original ground line 2, boundary line of three types of rock mass 3, potential deepest sliding surface 4, sliding surface with minimum safety factor 5, cast-in-place piles 6, upper pile foundation 61, lower pile foundation 62, interface between pile foundation and potential deepest sliding surface 63, cast-in-place pile reinforcement 64, water flow direction 7, dam heel 11, dam heel height H1, dam heel length B1, dam toe 12, dam toe height H2, dam toe length B2, seismic steel mesh 8, foundation surface 9, consolidation grouting layer 91. DETAILED DESCRIPTION
[0025] The present invention will be further described below with reference to the accompanying drawings.
[0026] like Figures 1 to 4The structure shown is a gravity dam foundation treatment structure for soft rock foundations in strong earthquake zones. Strong earthquake zones generally refer to areas with frequent and intense seismic activity. Based on historical earthquake records, these areas are likely to experience destructive earthquakes of magnitude 7 or higher. Soft rock refers to rock with low strength, easy weathering, and water-softening or plastic deformation. Its engineering mechanical properties are intermediate between those of hard rock and soil. It generally refers to rock formations with a uniaxial compressive strength of less than 30 MPa, characterized by easy deformation, water-softening, weathering, and low self-stability. Common soft rock types include mudstone, shale, weathered sandstone, tuff, and coal-bearing strata. A gravity dam is a large water-retaining structure constructed of concrete or stone. Its basic cross-section is a right triangle, consisting of several dam sections. Under water pressure and other loads, a gravity dam primarily relies on the anti-sliding force generated by the deadweight of the concrete dam body (1) to maintain stability. It also relies on the pressure generated by the deadweight of the dam body to offset the tensile stress caused by water pressure to maintain strength. Cast-in-place piles 6 are made by drilling holes and then pouring reinforced concrete into them. They are a common foundation treatment method, primarily used to reinforce soil or rock layers to improve the bearing capacity and stability of the foundation. These piles can be used individually or arranged in rows or grids to form a stronger foundation support system. According to the "Engineering Rock Mass Classification Standard" (GB 50218-94), rock mass is classified into Classes 1 to 5 based primarily on rock strength, rock integrity, and structural characteristics. In this scheme, the rock mass below the Class 3 rock mass dividing line 3 includes Class 1, Class 2, and Class 3 rock mass.
[0027] like Figure 1 As shown, the original ground line 2 is excavated downwards and then a concrete dam body 1 is set up. The concrete dam body 1 is set below the original ground line 2. The water flows to the right as shown by the water flow direction 7. A number of cast-in-place piles 6 are set at the bottom of the concrete dam body 1. Figure 2 As shown, the concrete dam body 1 has a heel 11 facing upstream, and a toe 12 facing downstream. Generally, the heel length B1 is approximately 3 to 8 meters, and the toe length B2 is approximately 3 to 8 meters. The ratio of the heel height H1 of the heel 11 to the heel length B1 is preferably between 1.5 and 2, and the ratio of the toe height H2 of the toe 12 to the toe length B2 is preferably between 1.5 and 2, to prevent stress concentration at the toe 12 and heel 11.
[0028] Cast-in-place piles 6 are installed at the bottom of the dam heel 11, the bottom of the dam toe 12, the bottom of the middle of the concrete dam body 1, and the downstream potential slip surface area. Pile arrangement should be denser at the bottom of the dam toe 12 and the bottom of the dam heel 11, with the spacing between cast-in-place piles 6 preferably between 2m and 4m. The bottom of the middle of the concrete dam body 1 and the downstream potential slip surface area can be evenly distributed, and the spacing between cast-in-place piles 6 can be appropriately increased, preferably between 6m and 10m.
[0029] The bored piles 6 extend downward in the vertical direction and are C30 reinforced concrete rotary bored piles. Using the bored piles 6 to share the upper load, by evenly distributing the vertical stress of the dam base surface across multiple bored piles 6, the vertical stress level at a single point can be reduced, effectively improving the stress distribution at the base. At the same time, by extending the bored piles 6 into the rock mass and through the weak zone, the anchoring and shearing effects of the bored piles 6 can cut off the potential sliding surface in the foundation, effectively solving the deep anti-slip problem of the dam. Figure 1 As shown, cast-in-place piles 6 extend downward, passing through the potential deepest sliding surface 4 and the minimum safety factor sliding surface 5, reaching the boundary line 3 between the three rock mass types. This means that the bottom of cast-in-place piles 6 is directly fixed within the rock mass type three area, achieving stable fixation. The placement of cast-in-place piles 6 can be used to analyze the areas within the rock mass where shear stress exceeds the shear strength, based on finite element deep anti-slip numerical calculations. This calculation can be used to calculate the equivalent plastic strain of the concrete dam body 1 when the foundation reaches ultimate failure, thereby analyzing its potential sliding surface trends.
[0030] Taking reinforced concrete rotary bored piles as an example, the effects of bored piles on the stress distribution at the base of the concrete dam body 1 are as follows: 1. Relieve stress concentration: bored piles can effectively disperse and transmit the load transmitted by the gravity dam. By arranging multiple rows of bored piles in the foundation, the foundation stress originally concentrated in a certain area can be evenly distributed across multiple pile foundations, thereby reducing the local stress level of the foundation and avoiding damage to the dam foundation caused by excessive local stress. 2. Control settlement: By rationally arranging bored piles, the piles can be driven deep into the ground, and the underlying hard rock layer can be used as support, thereby effectively controlling the foundation settlement and maintaining balanced deformation of the dam body in all directions. 3. Improve the bearing capacity of the foundation: bored piles have a high single pile bearing capacity, which can significantly enhance the overall bearing capacity of the foundation, helping to ensure the stability of the gravity dam under various loads and prevent dam body instability caused by insufficient foundation bearing capacity.
[0031] Taking reinforced concrete bored piles as an example, the effects of bored piles 6 on the anti-sliding stability of the dam are as follows: 1. Increased friction: bored piles can strengthen the connection between the concrete dam body and the foundation, and improve the base shear strength parameters of the concrete dam body 1. At the same time, the friction between the bored piles 6 and the surrounding rock and soil is relatively large, which can provide sufficient anti-sliding resistance. In addition, the bored piles 6 themselves have strong shear strength, which can effectively resist the sliding tendency of the concrete dam body 1 under the action of horizontal thrust. 2. Enhanced anchoring effect: bored piles can penetrate into a relatively complete bearing layer, forming an effective anchoring effect, thereby resisting external horizontal forces and reducing the risk of sliding. 3. Improved sliding surface conditions: bored piles can cut off the original weak structural surface or any sliding surface along the soft rock, changing its sliding path. Under the action of the shear resistance of the pile foundation, the new sliding surface will move down to the hard rock layer. Since the hard rock layer has higher shear strength parameters and longer sliding paths, it can effectively resist the sliding tendency of the dam body.
[0032] Taking reinforced concrete rotary bored cast-in-place piles as an example, the cast-in-place piles 6 have the following impacts on the dam's earthquake resistance: 1. Enhanced foundation stability: A cluster of cast-in-place piles 6 improves the integrity of the concrete dam body 1 and the foundation, suppressing lateral slip during earthquakes. 2. Improved dynamic response: The foundations of the cast-in-place piles 6 adjust the natural frequency of the dam-foundation system, preventing resonance with the main earthquake frequency and reducing the dynamic amplification effect. Furthermore, the pile-soil interaction around the cast-in-place piles 6 dissipates some seismic energy, mitigating dam vibration.
[0033] In summary, in this solution, the synergistic reinforcement mechanism of the bored piles 6 and the consolidation grouting layer 91 improves the overall stability of the dam foundation through the dual effects of the bored piles 6 bearing the load and the consolidation grouting layer 91 grouting reinforcement, thus realizing the "pile-grouting-rock" three-in-one bearing system.
[0034] Figure 1 and Figure 3 The figure shows the intersection of cast-in-place pile 6 and potential deepest sliding surface 4, with cast-in-place pile 6 divided into an upper pile foundation 61 and a lower pile foundation 62. The force analysis is performed at the interface 63 between the pile foundation and the potential deepest sliding surface. The horizontal bearing capacity of cast-in-place pile 6 at this interface is greater than the shear force it withstands at this interface. This indicates that the depth of penetration of cast-in-place pile 6 through the potential deepest sliding surface meets the requirements. The potential deepest sliding surface 4 is located above the boundary line 3 between the three rock masses, and the bottom of cast-in-place pile 6 is located at least 2 meters below the potential deepest sliding surface 4.
[0035] Figure 1 and Figure 4The figure shows a schematic diagram of the structure at the junction of the concrete dam body 1 and the bored piles 6. The top surface of the consolidation grouting layer 91 is the foundation surface 9, which is arranged in close contact with the bottom of the concrete dam body 1. The bored pile reinforcement 64 in the bored pile 6 passes through the consolidation grouting layer 91 from bottom to top and extends into the interior of the concrete dam body 1, making the connection between the bored pile 6 and the concrete dam body 1 more stable. In order to better achieve the dam pile joint effect between the concrete dam body 1 and the bored pile 6, the concrete at the top of the bored pile 6 is embedded into the interior of the concrete dam body 1 by about 0.5m, and the bored pile reinforcement 64 of the bored pile 6 extends into the interior of the concrete dam body 1 by about 1.5m. The bored pile reinforcement 64 is distributed, and the construction process is strictly controlled to ensure that the concrete is fully vibrated and rolled, thereby improving the uniformity and density of the dam concrete. The consolidation grouting layer 91 is located below the concrete dam body 1, and the depth of the consolidation grouting layer 91 is generally 5-10m. Seismic-resistant steel mesh 8 is installed above the tops of the cast-in-place piles 6. This mesh is positioned along the water flow and perpendicular to the water flow. It is positioned approximately 50 cm above the foundation surface 9. This mesh improves the integrity and stability of the concrete dam body 1 and cast-in-place piles 6, preventing them from becoming detached during an earthquake.
Claims
1. A gravity dam foundation treatment structure for soft rock foundation conditions in a strong earthquake zone, comprising a foundation surface (9) of the gravity dam, a consolidation grouting layer (91), cast-in-place piles (6) and a concrete dam body (1), wherein the concrete dam body (1) is arranged above the foundation surface (9), a consolidation grouting layer (91) is arranged below the foundation surface (9), and the cast-in-place piles (6) are arranged below the concrete dam body (1), characterized in that: The top of the cast-in-place pile (6) is fixedly connected to the bottom of the concrete dam body (1), and the bottom of at least one cast-in-place pile (6) is arranged below the boundary line (3) of the three types of rock mass.
2. The gravity dam foundation treatment structure for soft rock foundation conditions in strong earthquake areas according to claim 1, characterized in that: The concrete dam body (1) comprises a dam heel (11) and a dam toe (12); a cast-in-place pile (6) is provided at the bottom of the dam heel (11); and a cast-in-place pile (6) is provided at the bottom of the dam toe (12).
3. The gravity dam foundation treatment structure for soft rock foundation conditions in strong earthquake areas according to claim 2, characterized in that: The ratio between the dam heel height (H1) of the dam heel (11) and the dam heel length (B1) of the dam heel (11) ranges from 1.5 to 2.
4. The gravity dam foundation treatment structure for soft rock foundation conditions in strong earthquake areas according to claim 2, characterized in that: The ratio between the dam toe height (H2) of the dam toe (12) and the dam toe length (B2) of the dam toe (12) ranges from 1.5 to 2.
5. The gravity dam foundation treatment structure for soft rock foundation conditions in strong earthquake areas according to claim 2, characterized in that: Cast-in-place piles (6) are provided in an area between the dam heel (11) and the dam toe (12) at the bottom of the concrete dam body (1).
6. The gravity dam foundation treatment structure for soft rock foundation conditions in strong earthquake areas according to claim 2, characterized in that: Cast-in-place piles (6) are provided in the area of the downstream sliding surface of the concrete dam body (1).
7. The gravity dam foundation treatment structure for soft rock foundation conditions in strong earthquake areas according to any one of claims 1 to 6, characterized in that: The cast-in-place pile (6) is a reinforced concrete rotary bored cast-in-place pile.
8. The gravity dam foundation treatment structure for soft rock foundation conditions in strong earthquake areas according to any one of claims 1 to 6, characterized in that: The invention comprises a potential deepest sliding surface (4), the potential deepest sliding surface (4) is located above the boundary line (3) between the three types of rock masses, and the bottom of the cast-in-place pile (6) is set at a depth of at least 2m below the potential deepest sliding surface (4).
9. The gravity dam foundation structure for use in soft rock foundation conditions in strong earthquake areas according to claim 8, characterized in that: The invention comprises a single pile horizontal bearing capacity at the junction of the cast-in-place pile (6) and the potential deepest sliding surface (4), wherein the single pile horizontal bearing capacity is greater than the shear force at the junction of the cast-in-place pile (6) and the potential deepest sliding surface (4).
10. The gravity dam foundation treatment structure for soft rock foundation conditions in strong earthquake areas according to any one of claims 1 to 6, characterized in that: It comprises an earthquake-resistant steel mesh (8), which is arranged above the foundation surface (9) along the direction of the water flow and perpendicular to the water flow.