A foundation structure for a gravity dam in an area with interbedded sandstone and mudstone.

Abstract

This utility model discloses a dam foundation structure for a gravity dam in a sandstone-mudstone interbedded area, belonging to the field of hydraulic engineering technology. It solves the problem that existing dam foundation excavation methods in sandstone-mudstone interbedded areas cannot meet design requirements. The dam foundation structure includes: two dam foundation sections on both banks, comprising multiple sandstone slopes formed on sandstone strata and multiple mudstone slopes formed on mudstone strata, with the sandstone and mudstone slopes spaced apart and connected by walkways between adjacent slopes; the slope height of the sandstone slopes is greater than that of the mudstone slopes, and the excavation slope ratio of the sandstone slopes is less than that of the mudstone slopes; and a riverbed dam foundation section, comprising multiple exposed areas after the surface mudstone has been removed and multiple truncated areas formed on interlayered mudstone; the bottom surface of the truncated areas is sandstone strata. This utility model is used for the excavation of dam foundations for gravity dams in sandstone-mudstone interbedded areas.

Description

Technical Field

[0001] This utility model relates to a dam foundation structure for a gravity dam in an area with interbedded sandstone and mudstone, and belongs to the field of water conservancy engineering technology. Background Technology

[0002] Existing dam foundation excavation technologies are typically designed for gravity dams located in areas with homogeneous rock masses or rock masses with relatively uniform physical properties. However, research on dam foundation excavation methods in areas primarily composed of interbedded sandstone and mudstone is scarce. In these areas, sandstone exhibits superior physical and mechanical properties, high bearing capacity, minimal difference in rock mass properties before and after excavation, good durability, and strong resistance to weathering. Mudstone, on the other hand, has poorer physical and mechanical properties, lower bearing capacity, and is prone to dehydration and disintegration in alternating wet and dry environments, resulting in poor durability and weak resistance to weathering.

[0003] For dam foundations in this type of area, it is usually necessary to remove weathered, unloaded, and densely fissured sandstone masses and select sandstone masses with better integrity as the foundation surface. At the same time, mudstone exposure on the foundation surface should be avoided. However, according to the existing gravity dam excavation method that mainly considers the degree of bedrock weathering, it is difficult to avoid the removal of high-quality sandstone or the formation of ramps in mudstone masses. In the end, a dam foundation surface with alternating sandstone and mudstone or a large proportion of mudstone is formed. If the large amount of mudstone exposure is not protected by spraying in time, the exposed mudstone of the dam foundation will continue to deteriorate, causing ramp collapse, and the clearing of weathered layers will result in overhangs. At the same time, due to the poor mechanical properties of mudstone, it will also cause insufficient bearing capacity of gravity dam foundation and anti-sliding stability. Therefore, the existing dam foundation excavation method in areas with alternating sandstone and mudstone layers cannot meet the design requirements. Summary of the Invention

[0004] This invention provides a dam foundation structure for gravity dams in areas with interbedded sandstone and mudstone, which can solve the problem that existing dam foundation excavation methods in such areas cannot meet design requirements.

[0005] This utility model provides a dam foundation structure for a gravity dam in an area with interbedded sandstone and mudstone, the dam foundation structure comprising:

[0006] The dam foundation sections on both sides include multiple sandstone slopes formed on sandstone strata and multiple mudstone slopes formed on mudstone strata. The multiple sandstone slopes and multiple mudstone slopes are distributed alternately, and adjacent sandstone slopes and mudstone slopes are connected by horse trails.

[0007] The slope height of the sandstone slope is greater than that of the mudstone slope, and the excavation slope ratio of the sandstone slope is less than that of the mudstone slope.

[0008] The riverbed dam foundation section includes multiple exposed areas where the surface mudstone has been removed and multiple cut-off areas formed on the interlayered mudstone; the bottom surface of the cut-off areas is a sandstone layer.

[0009] Optionally, when the thickness of the interlayered mudstone is less than the first preset thickness, the sidewall of the cut-off region is a vertical surface;

[0010] When the thickness of the interlayered mudstone is greater than or equal to the first preset thickness, the sidewall of the cut-off area is a slope.

[0011] Optionally, the first preset thickness is 40cm to 60cm.

[0012] Optionally, a protective layer is provided on the mudstone outcrop surface of the riverbed dam foundation section.

[0013] Optionally, the horse trail is located on the sandstone strata.

[0014] Optionally, when the thickness of the mudstone layer is greater than the second preset thickness, the horse trail is set on the mudstone layer.

[0015] Optionally, the width of the horse trail set on the mudstone stratum is greater than the width of the horse trail set on the sandstone stratum.

[0016] Optionally, the second preset thickness is 13m to 17m.

[0017] The beneficial effects that this utility model can produce include:

[0018] The gravity dam foundation structure provided by this utility model for sandstone-mudstone interbedded areas adopts a "high slope, gentle angle" excavation method for sandstone strata and a "low slope, steep angle" excavation method for mudstone strata in the dam foundation sections on both banks. The riverbed dam foundation section adopts a "tooth-shaped excavation" method. The excavation scheme considers both the degree of bedrock weathering and the bedrock type in the design and excavation, preserving the sandstone rock mass as the dam foundation as much as possible and effectively preventing the weathering of the mudstone rock mass. It has important technical guidance for the construction of gravity dams in sandstone-mudstone interbedded areas. Attached Figure Description

[0019] Figure 1 A cross-sectional view of the excavation of the foundation section on both banks of a gravity dam in an area with interbedded sandstone and mudstone, provided for an embodiment of this utility model;

[0020] Figure 2 A cross-sectional view of the riverbed foundation section of a gravity dam in an area with interbedded sandstone and mudstone, provided for an embodiment of this utility model;

[0021] Figure 3 A schematic diagram of the riverbed foundation section of a gravity dam in an area with interbedded sandstone and mudstone, provided for an embodiment of this utility model.

[0022] Figure label:

[0023] 1. Dam foundation excavation line; 2. Weathering degree line; 3. Ground line; 4. Sandstone strata; 5. Mudstone strata; 6. Exposed area; 7. Cut-off area; 8. Excavation boundary of riverbed dam foundation section; 9. Dam foundation zoning. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the embodiments, but the present invention is not limited to these embodiments.

[0025] This utility model embodiment provides a dam foundation structure for a gravity dam in an area with interbedded sandstone and mudstone, such as... Figures 1 to 3 As shown, the dam foundation structure includes:

[0026] The dam foundation sections on both banks include multiple sandstone slopes formed on sandstone layer 4 and multiple mudstone slopes formed on mudstone layer 5. The multiple sandstone slopes and multiple mudstone slopes are distributed alternately, and adjacent sandstone slopes and mudstone slopes are connected by a horse trail. The slope height of the sandstone slope is greater than that of the mudstone slope, and the excavation slope ratio of the sandstone slope is less than that of the mudstone slope.

[0027] The riverbed dam foundation section includes multiple exposed areas 6 after the surface mudstone has been removed and multiple cut-off areas 7 formed on the interlayered mudstone; the bottom surface of the cut-off area 7 is a sandstone layer 4.

[0028] In this utility model, the excavation of the dam foundation section on both banks adopts the "slope + horse path" excavation method, and the excavation of the dam foundation section in the riverbed adopts the "tooth-shaped excavation" method. The excavation scheme takes into account both the weathering degree and the type of bedrock when designing the excavation.

[0029] Normally, the horse trail is set on sandstone layer 4.

[0030] However, when the thickness of the mudstone layer 5 is greater than the second preset thickness, the walkway can also be set on the mudstone layer 5. In this case, the width of the walkway set on the mudstone layer 5 is greater than the width of the walkway set on the sandstone layer 4. In this embodiment of the invention, the second preset thickness is 13m to 17m. For example, the second preset thickness can be 13m, 15m, 17m, etc.

[0031] In practical applications, when the horse trail is set on the sandstone layer 4, the width of the horse trail is generally greater than or equal to 2m; when the thickness of the mudstone layer 5 is greater than 15m, the horse trail can also be set on the mudstone layer 5, in which case the width of the horse trail generally needs to be greater than or equal to 4m.

[0032] refer to Figure 1 As shown, where: 1:m1 is the excavation slope ratio of the sandstone slope, and H1 is the slope height of the sandstone slope; 1:m2 is the excavation slope ratio of the mudstone slope, and H2 is the slope height of the mudstone slope. Figure 1The excavation line 1, weathering degree line 2, and ground line 3 of the dam foundation are also shown.

[0033] For the thick sandstone strata 4 on both banks of the dam foundation, the excavation method of "high slope, gentle angle, and wide ramp" is adopted. That is, the height of a single-level slope is selected according to the general excavation regulations of 15m to 20m, and the upper limit of 20m can be selected as the first-level slope. Similarly, the excavation slope ratio can be selected as the gentler slope ratio corresponding to the weathering range recommended by the survey professionals. The ramp should be set on the sandstone strata 4 as much as possible to facilitate the formation of the ramp and avoid the collapse of the ramp caused by the weathering of mudstone. For the thick mudstone strata 5 on both banks of the dam foundation, the excavation method of "low slope and steep angle" is adopted. That is, the lower limit of the single-level slope height can be selected as the first-level slope, and the excavation slope ratio can be selected as the steeper slope ratio corresponding to the weathering range recommended by the survey professionals.

[0034] When excavating the riverbed dam foundation section, if the thickness of the interlayered mudstone is less than the first preset thickness, the sidewall of the cut-off area 7 is a vertical surface; if the thickness of the interlayered mudstone is greater than or equal to the first preset thickness, the sidewall of the cut-off area 7 is a slope.

[0035] The first preset thickness is 40cm to 60cm. For example, the first preset thickness can be 40cm, 50cm, or 60cm.

[0036] The aforementioned surface mudstone is mudstone above the riverbed dam foundation elevation, while the aforementioned interlayered mudstone is sandstone above the riverbed dam foundation elevation, with the mudstone appearing in interlayers.

[0037] refer to Figure 2 As shown, the excavation of the riverbed dam foundation section adopts the "tooth-shaped excavation" method. When there is a certain height above the designed dam foundation elevation, the excavation begins according to the "surface layer removal and interlayer cutting" scheme based on the exposure of mudstone layer 5. That is, if the surface layer above the riverbed dam foundation elevation is mudstone, it is completely removed during excavation; if the surface layer above the riverbed dam foundation elevation is sandstone, the mudstone appears as interlayers. For thin mudstone layers less than 50cm thick, a vertical cutting method is used; for thicker mudstone layers greater than 50cm thick, a steep slope ratio (1:0.3) is used for cutting, until the lower sandstone layer is reached. Finally, the excavated dam foundation surface has a tooth-shaped shape, and the dam foundation surface can meet the large area of ​​sandstone, thereby improving the anti-sliding stability of the dam.

[0038] Furthermore, a protective layer is installed on the mudstone outcrop surface of the riverbed dam foundation section.

[0039] Because the riverbed dam foundation section typically covers a large area, and mudstone is prone to dehydration and disintegration in alternating wet and dry environments, traditional construction practices often involve applying mudstone spraying and protection measures only after the entire dam foundation excavation is complete. This can easily lead to weathering of the exposed mudstone, requiring repeated cleaning by the construction team and thus increasing the workload. (Reference) Figure 3As shown, this utility model proposes an excavation method of "overall planning, zoned implementation, and protection during excavation." First, based on the excavation boundary 8 of the riverbed dam foundation section, the entire riverbed dam foundation section is divided into multiple dam foundation zones 9 according to references such as bedding layer joints or construction intensity. Then, in each dam foundation zone 9, the excavation method for sandstone and mudstone is considered according to the bedrock exposure conditions, which greatly reduces the intensity of dam foundation excavation. The excavation of a single dam foundation zone 9 can be completed quickly. After completion, the exposed mudstone strata 5 are promptly sprayed to form a protective layer. Simultaneously, areas with significant undulations in the excavated tooth-like morphology can be pre-leveled and backfilled. This effectively implements mudstone protection measures and reduces rework, ensuring the quality of dam foundation excavation.

[0040] This utility model addresses the excavation of the foundation of gravity dams in areas with interbedded sandstone and mudstone. It is divided into two parts: the foundation section on both banks and the foundation section on the riverbed. The excavation scheme is refined by considering the degree of weathering of the bedrock and the type of bedrock. This can solve the design problems caused by the large differences in the mechanical properties of sandstone and mudstone.

[0041] For the sandstone stratum 4 on both banks of the dam foundation, a "high slope, gentle angle, and wide access road" excavation method is adopted, while for the mudstone stratum 5, a "low slope and steep angle" excavation method is adopted. At the same time, access roads are avoided as much as possible in the mudstone stratum 5 to avoid the impact of access road collapse caused by the deterioration of mudstone properties. This also reduces the exposed area of ​​the mudstone slope, thereby reducing the accumulation of rainwater on the slope and slowing down the weathering rate of the mudstone stratum 5 in the alternating wet and dry environment. It also reduces the amount of spraying and protection work for the mudstone stratum 5.

[0042] The mudstone excavation scheme of "removing the surface layer and cutting the interlayer" is adopted in the riverbed dam foundation section to preserve the sandstone rock mass to the greatest extent. For large areas of the riverbed dam foundation section, the excavation method of "overall planning, zoned implementation, and protection as excavation" is adopted.

[0043] The dam foundation structure of the gravity dam in the sandstone-mudstone interbedded area proposed in this utility model is also suitable for interbedded soft and hard rock geological areas. It can effectively avoid the difficulties in dam foundation excavation and construction caused by the poor characteristics of soft rock, such as difficulty in protection, excavation and treatment. The excavation process is simple to control and the objective is clear. It can avoid excavating high-quality hard rock as much as possible, and has good guiding significance for the safety of the project and the control of the construction process.

[0044] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A dam foundation structure of a gravity dam in a sand-shale interbedded area, characterized by, The dam foundation structure includes: The dam foundation sections on both sides include multiple sandstone slopes formed on sandstone strata and multiple mudstone slopes formed on mudstone strata. The multiple sandstone slopes and multiple mudstone slopes are distributed alternately, and adjacent sandstone slopes and mudstone slopes are connected by horse trails. The slope height of the sandstone slope is greater than that of the mudstone slope, and the excavation slope ratio of the sandstone slope is less than that of the mudstone slope. The riverbed dam foundation section includes multiple exposed areas where the surface mudstone has been removed and multiple cut-off areas formed on the interlayered mudstone; the bottom surface of the cut-off areas is a sandstone layer.

2. The dam foundation structure according to claim 1, characterized by When the thickness of the interlayered mudstone is less than the first preset thickness, the sidewall of the cut-off area is a vertical surface; When the thickness of the interlayered mudstone is greater than or equal to the first preset thickness, the sidewall of the cut-off area is a slope.

3. The dam foundation structure according to claim 2, characterized by The first preset thickness is 40cm~60cm.

4. The dam foundation structure of claim 1, wherein A protective layer is provided on the mudstone outcrop surface of the riverbed dam foundation section.

5. The dam foundation structure of claim 1, wherein The horse trail is located on the sandstone strata.

6. The dam foundation structure of claim 1, wherein When the thickness of the mudstone layer is greater than the second preset thickness, the horse trail is set on the mudstone layer.

7. The dam foundation structure of claim 6, wherein The width of the horse trail set on the mudstone stratum is greater than the width of the horse trail set on the sandstone stratum.

8. The dam foundation structure of claim 6, wherein The second preset thickness is 13m to 17m.

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