A method for raising the storage capacity and safety level of an old homogeneous earth dam by heightening the old dam

Abstract

The present invention discloses a method for raising the height of an old dam to increase the reservoir capacity and safety level of an old homogeneous earth dam. Through technical means such as calculation and monitoring, it is determined that the deformation of the old dam caused by the construction of the heightened and thickened dam body is basically stable before the construction of the impervious core wall. An overall impervious system combining the impervious core wall and the grouting curtain is adopted to prevent seepage of the dam body, the dam foundation, and around the dam. A flexible connection is used between the impervious core wall and the grouting gallery to avoid the problem of excessive stress in the impervious core wall. When the construction of the heightened dam body reaches the elevation of the newly built impervious core wall of the old dam, the dam body in the downstream area of the impervious core wall and the soil body of the riverbed overburden are reinforced to reduce the deformation of the old dam body and the riverbed overburden, thereby preventing excessive displacement of the impervious core wall under the action of water pressure.

Description

Technical Field

[0001] The present invention relates to a method for raising the height of an old dam to increase the storage capacity and safety level of an old homogeneous earth dam, belonging to the technical field of hydraulic structure construction. Background Technique

[0002] In recent years, with the rapid development of water conservancy and hydropower construction, the requirements for the utilization rate of water resources of existing hydropower hubs have become higher and higher. Most of the previously built old homogeneous earth dams have problems such as small dam height, generally lower than 30m, poor compaction, generally compacted manually by stacking, uneven material use, large and uneven permeability, etc.

[0003] In order to extend the life of the old dam, improve the safety level, increase the impermeability, and meet the requirements of increasing the storage capacity and power generation, it is necessary to raise and thicken the old dam and add an impervious core wall. Many dams around the world have undergone heightening construction. There are also many examples of dam heightening projects in China, such as the dam of Yingnahe Reservoir, the lower reservoir dam of Baoquan Pumped Storage Power Station, the Yuanyangchi Dam, and so on. On the one hand, dam heightening can further exert various functions of the existing dam, increase the irrigation water volume in the downstream area of the dam, and at the same time provide a new part of emergency and standby water supply sources for the city. On the other hand, due to the poor uniformity and large compressibility of the old dam and the foundation, and the poor impermeability performance, it is particularly important to arrange the impervious system of the dam body.

[0004] However, different from other earth-rock dams, due to the existence of the heightened dam, under the action of asymmetric loads, the old dam will produce uneven deformation. If a special machine is directly used to excavate the slot hole or drill round holes for the construction of the impervious core wall, it will inevitably cause the impervious core wall to crack and deform, thus causing damage to the impervious structure of the dam body, and further affecting the safety of the dam body.

[0005] During the construction and water storage of the old dam and the foundation, due to their poor uniformity and large compressibility, the soil body is continuously compacted and settled, resulting in vertical displacement of the impervious core wall and the grouting gallery. At present, since the impervious core wall and the dam are continuously cast with concrete during dam construction and they are rigidly connected, although the rigid head structure is simple and the construction is convenient, the stress of the impervious core wall is relatively large, and the grouting gallery will also generate relatively large compressive stress, which requires a large amount of steel bars. At the same time, it also reduces the ability of the entire impervious system to resist deformation and cannot ensure the reliability and safety of the impervious body. With the increase of the filling elevation, the concrete core wall may also undergo excessive displacement under the action of water pressure. Summary of the Invention

[0006] Objective: To address the deficiencies in the existing technologies, the present invention provides a method for raising the height of an old dam to increase the storage capacity and safety level of an old homogeneous earth dam. This method adopts an overall anti-seepage system combining an anti-seepage core wall and a grouting curtain to prevent seepage around the dam. A flexible connection is used between the anti-seepage core wall and the grouting gallery for the construction of the grouting curtain to avoid excessive stress on the anti-seepage core wall. When the construction of the heightened dam body reaches the elevation of the anti-seepage core wall inside the old dam, the dam body and the soil of the riverbed covering layer in the downstream area of the anti-seepage core wall are reinforced to prevent excessive displacement of the anti-seepage core wall under the action of water pressure.

[0007] To achieve the above technical objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for raising the height of an old dam to increase the storage capacity and safety level of an old homogeneous earth dam, comprising the following steps:

[0009] Step 1: During the construction of the heightened dam, analyze the process of the deformation of the old dam caused by the dam heightening through monitoring and numerical calculation, and wait for the deformation of the old dam to stabilize;

[0010] Step 2: After the deformation of the old dam stabilizes, set up a grouting gallery at the bottom of the old dam body;

[0011] Step 3: After the completion of the grouting gallery, conduct on-site construction of pouring the anti-seepage core wall, and use asphalt concrete for flexible connection between the anti-seepage core wall and the grouting gallery.

[0012] Step 4: After the completion of the anti-seepage core wall, construct a continuous asphalt concrete wall 9 of the dam foundation in the alluvial layer of the dam foundation and the completely weathered layer of the bedrock. First, pour inverted trapezoidal asphalt concrete, and then pour the continuous asphalt concrete wall of the dam foundation. There is a flexible connection between the continuous asphalt concrete wall of the dam foundation and the grouting gallery. The continuous asphalt concrete wall of the dam foundation extends down to the boundary between the strong and weak weathering of the bedrock for curtain grouting. A flexible material with anti-seepage performance and capable of flowing freely under a certain pressure is filled between the continuous asphalt concrete wall of the dam foundation and the inverted trapezoidal concrete;

[0013] Step 5: Dig a groove at the top of the old dam that extends into the mountain body. Drill a hole from the bottom surface of the groove to the top of the grouting gallery, and place a grouting pipe in the hole to grout to form a first grouting curtain from the groove at the top of the dam to the top surface of the grouting gallery;

[0014] Step 6: Drill a hole and dig a groove from the bottom surface of the grouting gallery in the mountain body to below the impervious boundary with a permeability less than 5 Lu in the bedrock, place a grouting pipe and grout to form a second grouting curtain.

[0015] The permeability coefficient of the asphalt concrete is less than 1×10 -6 cm / s.

[0016] The construction of the impervious core wall in Step 3 is specifically as follows: On the downstream shoulder of the old dam, a grooving machine is used to excavate a groove in the soil to the top of the grouting gallery to form a placement groove for the impervious core wall. First, slurry is used to protect the wall. After cleaning the groove, a steel reinforcement cage is hoisted and placed in the placement groove of the impervious core wall, and then asphalt concrete is poured. After the asphalt concrete self-congeals, an impervious core wall is formed.

[0017] The construction of the asphalt concrete cutoff wall in the alluvial layer and the completely weathered layer of the bedrock foundation in Step 4 is specifically as follows: A grooving machine is used to excavate a groove in the soil until the alluvial layer is reached. First, slurry is used to protect the wall. After cleaning the groove, a steel reinforcement cage is hoisted and placed, and then asphalt concrete is poured. The asphalt concrete self-congeals into a wall.

[0018] On the upstream side of the impervious core wall, at least two copper waterstops are arranged between the groove between the impervious core wall and the top of the grouting gallery; on the downstream side of the impervious core wall, at least one copper waterstop is arranged between the groove between the impervious core wall and the top of the grouting gallery, and the groove is filled with a flexible material with impervious performance.

[0019] On the upstream side of the asphalt concrete cutoff wall of the dam foundation, at least two copper waterstops are arranged between the groove between the asphalt concrete cutoff wall of the dam foundation and the lower part of the grouting gallery; on the downstream side of the asphalt concrete cutoff wall of the dam foundation, at least one copper waterstop is arranged between the groove between the asphalt concrete cutoff wall of the dam foundation and the lower part of the grouting gallery; and the groove is filled with a flexible material with impervious performance.

[0020] When the construction of the heightened dam body reaches the elevation of the impervious core wall in the old dam, the dam body in the downstream area of the impervious core wall in the old dam and the soil body of the riverbed covering layer are reinforced, and the reinforcement measure is taken in a compaction manner.

[0021] The thickness of the impervious core wall is 60 - 80 cm.

[0022] The flexible material with impervious performance is rubber or asphalt.

[0023] Beneficial effects:

[0024] (1) By adopting an overall layout of the impervious system, the dam crest and the grouting gallery are respectively extended into the mountain body, and drilling and grouting are carried out to form a top-down grouting curtain, preventing seepage around the dam and seepage of the dam foundation due to the relatively large permeability coefficient of the strongly (completely) weathered bedrock, making the entire impervious system safer and more effective.

[0025] (2) Compared with the flexible connection method of directly filling the groove with an impervious plastic material, which is complex in construction and difficult in filler selection, the present invention adopts an overall inverted trapezoidal asphalt concrete flexible connection method, which can improve the integrity of the impervious structure and adapt to a certain deformation, and at the same time reduce the stress of the impervious core wall.

[0026] (3) The deformation process of the old dam caused by the dam heightening is obtained through monitoring and numerical analysis. The anti-seepage core wall construction is carried out after the deformation of the old dam is basically stable to prevent the residual deformation of the old dam from causing excessive stress and cracking deformation of the anti-seepage core wall, thereby causing failure of the anti-seepage structure.

[0027] (4) Compared with the anti-seepage geomembrane on the dam surface, the anti-seepage system adopted by the present invention has the advantages of simple construction, low cost, and no influence from the uneven settlement of the dam foundation and the dam body. At the same time, the anti-seepage system is not affected by the slope of the dam, avoiding the problems such as the shear strength between the geomembrane and the protective layer of the composite geomembrane cannot meet the anti-sliding stability due to the steep dam slope.

[0028] (5) The present invention uses compaction grouting and other reinforcement methods to reinforce the soil in the downstream area of ​​the anti-seepage core wall to prevent the anti-seepage core wall from undergoing excessive displacement under the action of water pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is an overall schematic diagram of the anti-seepage system of the heightened and thickened homogeneous earth dam of the present invention;

[0030] Figure 2 A partial enlarged view of the completion of the pouring of the grouting gallery and the asphalt concrete continuous wall of the dam foundation;

[0031] Figure 3 A partial enlarged view of the completion of the pouring of the grouting gallery and the anti-seepage core wall;

[0032] Figure 4 This is a schematic diagram of soil reinforcement in the downstream area of ​​the anti-seepage core wall;

[0033] Figure 5 It is a plan view of the overall layout of the anti-seepage system;

[0034] Figure 6 It is a three-dimensional schematic diagram of the overall layout of the anti-seepage system;

[0035] Explanation of numbers: 1. Anti-seepage core wall; 2. Raised dam body; 3. Water-stop copper sheet; 4. Flexible material; 5. Grouting gallery; 6. Asphalt concrete layer; 7. Inverted trapezoidal concrete; 8. Second grouting curtain; 9. Asphalt concrete continuous wall at dam foundation; 10. Bedrock; 11. Alluvial layer; 12. Old dam body; 13. Grouting pipe; 14. Mountain contour line; 15. Dam top groove; 16. First grouting curtain; 17. Mountain; 18. 5Lu impermeable boundary; 19. Soil reinforcement area. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with the accompanying drawings.

[0037] A method for increasing the storage capacity and safety level of old homogeneous earth dams:

[0038] Step 1: As shown in Figure 1 , during the construction of the heightened dam, the deformation process of the old dam 12 caused by the dam heightening is obtained through monitoring and numerical analysis, and wait for the deformation of the old dam body 12 to stabilize;

[0039] Step 2: After the deformation of the old dam stabilizes, a grouting gallery 5 is set at the bottom of the old dam body; in order to ensure that the mechanical properties of the steel bars in the grouting gallery are not affected by the subsequent construction processes, the steel bars in the grouting gallery are configured at one time. When the heightened dam body 2 is constructed to the elevation of the anti-seepage core wall in the old dam, the dam body and the soil of the riverbed overburden layer in the downstream area of the anti-seepage core wall in the old dam are reinforced, and the reinforcement measure is taken in the compaction method;

[0040] Step 3: As shown in Figure 2 , after the grouting gallery is completed, the anti-seepage core wall 1 is constructed. Use a grooving machine to dig a groove to the top of the grouting gallery, first use slurry to protect the wall, after cleaning the groove, lower the steel reinforcement cage in the groove, and then pour asphalt concrete. The anti-seepage core wall and the grouting gallery are flexibly connected with asphalt concrete, and the permeability coefficient of the asphalt concrete flexible wall is less than 1×10 -6 cm / s; on the upstream side of the anti-seepage core wall 1, two copper water stops are set between the groove between the anti-seepage core wall 1 and the top of the grouting gallery 5;

[0041] On the downstream side of the anti-seepage core wall 1, one copper water stop is set between the groove between the anti-seepage core wall 1 and the top of the grouting gallery 5, and the groove is filled with a flexible material with anti-seepage performance.

[0042] Step 4: As shown in Figure 3 , after the anti-seepage core wall 1 is completed, the dam foundation asphalt concrete cut-off wall 9 in the alluvial layer and the completely weathered layer of the bedrock is constructed. Use a grooving machine to dig a groove, dig to the alluvial layer 11, first use slurry to protect the wall, after cleaning the groove, lower the steel reinforcement cage, and then first pour trapezoidal concrete, and then pour asphalt concrete. The dam foundation asphalt concrete cut-off wall 9 is flexibly connected with the grouting gallery 5, and the permeability coefficient of the dam foundation asphalt concrete cut-off wall 9 is less than 1×10 -6 cm / s. The dam foundation asphalt concrete cut-off wall 9 is curtain grouted down to the boundary between the strong and weak weathering of the bedrock. A plastic material with anti-seepage performance and capable of flowing freely under a certain pressure, such as rubber or asphalt, is filled between the dam foundation asphalt concrete cut-off wall 9 and the trapezoidal concrete.

[0043] On the upstream side of the dam foundation asphalt concrete cut-off wall 9, two copper water stops are set between the groove between the dam foundation asphalt concrete cut-off wall 9 and the lower part of the grouting gallery 5; on the downstream side of the dam foundation asphalt concrete cut-off wall 9, one copper water stop is set between the groove between the dam foundation asphalt concrete cut-off wall 9 and the lower part of the grouting gallery 5; and the groove is filled with a flexible material with anti-seepage performance, such as rubber or asphalt.

[0044] Step 5: As shown in Figure 5, as shown in Figure 6, a groove is dug at the dam crest and extends all the way into the mountain body. Drill holes from the bottom surface of the groove to the top of the grouting gallery. Place grouting pipes in the drill holes to grout and form a first grouting curtain from the dam crest groove to the top surface of the grouting gallery.

[0045] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for raising the storage capacity and safety level of an old homogeneous earth dam by heightening the old dam, characterized in that, It includes the following steps: Step 1: During the construction of the heightened dam, analyze the process of the deformation of the old dam caused by the dam heightening through monitoring and numerical calculation, and wait for the deformation of the old dam to stabilize; Step 2: After the deformation of the old dam stabilizes, a grouting gallery (5) is set at the bottom of the old dam body; Step 3: After the grouting gallery (5) is completed, carry out the on-site construction of the impervious core wall (1). The impervious core wall is flexibly connected to the grouting gallery with asphalt concrete; Step 4: After the impervious core wall (1) is completed, construct the dam foundation asphalt concrete cut-off wall (9) in the alluvial layer of the dam foundation and the completely weathered layer of the bedrock. First, pour trapezoidal inverted asphalt concrete, and then pour the dam foundation asphalt concrete cut-off wall. The dam foundation asphalt concrete cut-off wall is flexibly connected to the grouting gallery. The dam foundation asphalt concrete cut-off wall extends down to the boundary between the strong and weak weathering of the bedrock for curtain grouting. Flexible materials with impervious performance and capable of flowing freely under a certain pressure are filled between the dam foundation asphalt concrete cut-off wall and the trapezoidal inverted concrete; Step 5: Dig a groove at the top of the old dam and extend it into the mountain body. Drill a hole from the bottom surface of the groove to the top of the grouting gallery, and place a grouting pipe in the hole to grout to form a first grouting curtain from the groove at the top of the dam to the top surface of the grouting gallery; Step 6: Drill and dig a groove from the bottom surface of the grouting gallery in the mountain body to below the impervious boundary with a permeability less than 5Lu of the bedrock, place a grouting pipe and grout to form a second grouting curtain.

2. The method for raising the storage capacity and safety level of an old homogeneous earth dam as claimed in claim 1, wherein The permeability coefficient of the asphalt concrete is less than 1×10 -6 cm / s.

3. The method for raising the storage capacity and safety level of an old homogeneous earth dam according to claim 1, characterized in that The construction of the impervious core wall (1) in Step 3 is specifically as follows: Use a grooving machine to dig a groove on the downstream shoulder of the old dam to the top of the grouting gallery to form an impervious core wall placement groove. First, use slurry to protect the wall. After cleaning the groove, lower a steel reinforcement cage in the impervious core wall placement groove, and then pour asphalt concrete. After the asphalt concrete self-cures, it forms the impervious core wall.

4. The method for raising the storage capacity and safety level of an old homogeneous earth dam as claimed in claim 1, characterized in that, The construction of the dam foundation asphalt concrete cut-off wall in the alluvial layer of the dam foundation and the completely weathered layer of the bedrock in Step 4 is specifically as follows: Use a grooving machine to dig a groove. When it reaches the alluvial layer (11), first use slurry to protect the wall. After cleaning the groove, lower a steel reinforcement cage, and then pour asphalt concrete. The asphalt concrete self-cures to form the dam foundation asphalt concrete cut-off wall.

5. The method for raising the storage capacity and safety level of an old homogeneous earth dam according to claim 1, characterized in that, On the upstream side of the impervious core wall, at least two copper water stops are set between the groove between the impervious core wall and the top of the grouting gallery; on the downstream side of the impervious core wall, at least one copper water stop is set between the groove between the impervious core wall and the top of the grouting gallery, and the groove is filled with flexible materials with impervious performance.

6. The method for raising the storage capacity and safety level of an old homogeneous earth dam according to claim 1, characterized in that, On the upstream side of the dam foundation asphalt concrete cut-off wall, at least two copper water stops are set between the groove between the dam foundation asphalt concrete cut-off wall and the lower part of the grouting gallery; On the downstream side of the dam foundation asphalt concrete cut-off wall, at least one copper water stop is set between the groove between the dam foundation asphalt concrete cut-off wall and the lower part of the grouting gallery, and the groove is filled with flexible materials with impervious performance.

7. The method for raising the storage capacity and safety level of an old homogeneous earth dam according to claim 1, characterized in that When the construction of the heightened dam body reaches the elevation of the impervious core wall in the old dam, reinforce the dam body in the downstream area of the impervious core wall in the old dam and the soil body of the riverbed covering layer. The reinforcement measure adopts a compaction method.

8. The method for raising the storage capacity and safety level of an old homogeneous earth dam according to claim 1, characterized in that, The thickness of the impervious core wall is 60 - 80 cm.

9. The method for raising the storage capacity and safety level of an old homogeneous earth dam according to claim 5 or 6, characterized in that The flexible material with impervious performance is rubber or asphalt.

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