A geomembrane cofferdam structure for seepage prevention on steep bedrock slopes

Abstract

This invention provides a geomembrane cofferdam seepage prevention structure for steep bedrock slopes, comprising a dam body, a geomembrane, a connecting structure, and a seepage prevention structure. The seepage prevention structure includes a vertical curtain at the dam shoulder, a seepage prevention wall at the dam foundation, and two longitudinally opposite slope curtains. Each slope curtain includes an inclined hole curtain and two laterally opposite inclined hole gradient curtains. The upper geomembrane and the surrounding grouting curtains are sealed together by a connecting mechanism to ensure the integrity and reliability of the seepage prevention system. While the bank slopes and the bedrock of the dam foundation are grouted with curtain grouting, the slopes are grouted with inclined holes. Gradual transition curtains with inclined holes are installed at the connection areas of the inclined hole curtains and the seepage prevention walls at the ends to achieve a gradual transition and improve the integrity of the connection. Since the inclined holes slope inwards into the mountainside, they can avoid the fractured rock mass areas of the slope's exposed areas and penetrate into relatively intact rock mass areas within the mountainside. This reduces the grouting depth, decreases grout leakage and rock mass grout absorption, and significantly saves on project investment.

Description

Technical Field

[0001] This invention relates to the field of foundation treatment technology for water conservancy and hydropower projects, and in particular to a geomembrane cofferdam seepage prevention structure for steep bedrock slopes. Background Technology

[0002] In the construction of water conservancy and hydropower projects in high mountain valleys with deep overburden, a common approach is to install inclined walls and geomembranes on the upstream slope of an earth-rock cofferdam for seepage prevention. A seepage barrier wall is used for the riverbed overburden. When seepage prevention treatment is required at the junction of the geomembrane and the bedrock of the riverbanks, a combined seepage prevention structure of geomembrane in the cofferdam body and grouting on the bank slope is generally adopted, connected by concrete toe slabs. When the cofferdam has a high design head and a large size, the grouting area on the bank slope is large, and the seepage prevention effect is required to be high. However, due to limitations imposed by the topography and geological conditions of the bank slope, especially on steep slopes, the grouting process suffers from problems such as loose connections and poor seepage prevention. When the grouting holes are close to the bank slope, the grouting cannot seal the permeable strata; when the distance is greater, the grouting and toe slab excavation work is large. Poor connections between the bank slope curtain and the curtains at the ends of the cofferdam crest and the seepage barrier wall at the ends of the cofferdam foundation result in weak grouting areas.

[0003] Vertical holes are often used for curtain grouting at bank slopes, weir tops, and cutoff wall ends. However, vertical holes at bank slopes are close to the free face of the bank slope and are often located in strata with well-developed unloading fractures, relatively broken rock masses, and low rock strength. This poses a high risk of grout leakage and makes it difficult to control the grouting quality.

[0004] Therefore, it is necessary to propose a geomembrane cofferdam structure with inclined walls on steep bedrock slopes to solve or at least alleviate the above-mentioned defects. Summary of the Invention

[0005] The main objective of this invention is to provide a geomembrane cofferdam seepage prevention structure for steep bedrock slopes, in order to solve the problem that the seepage prevention effect is affected by the loose connection between the slope curtain and the cofferdam foundation seepage prevention wall in the prior art.

[0006] To achieve the above objectives, the present invention provides a geomembrane cofferdam seepage prevention structure for steep bedrock slopes, comprising a cofferdam body, a geomembrane, a connecting structure, and a seepage prevention structure connected to the perimeter of the cofferdam body; wherein, The geomembrane is laid on top of the weir, and the top of the seepage prevention structure is sealed to the geomembrane through the connecting structure. The seepage prevention structure includes a vertical curtain at the weir shoulder, a seepage prevention wall at the weir base, and two longitudinally opposite bank slope curtains. The vertical curtain at the weir shoulder and the seepage prevention wall at the weir base are respectively connected to both sides of the weir body in the transverse direction, and the two bank slope curtains are respectively connected to both sides of the weir body in the longitudinal direction. Each of the aforementioned bank slope curtains includes an inclined hole curtain and two inclined hole gradient curtains arranged laterally opposite each other. One inclined hole gradient curtain is respectively arranged between one side of the inclined hole curtain and the vertical curtain of the weir shoulder, and between the other side of the inclined hole curtain and the weir foundation seepage prevention wall.

[0007] Preferably, the inclined hole curtain includes a plurality of first inclined holes arranged in parallel along the transverse direction, the top of each first inclined hole is connected to the geomembrane through the connecting structure, and the bottom of the first inclined hole is inclined longitudinally away from the dam body from the top.

[0008] Preferably, the weir foundation seepage barrier wall includes a plurality of vertical holes arranged in parallel along the longitudinal direction, and the top of each vertical hole is connected to the geomembrane through the connecting structure.

[0009] Preferably, the oblique-hole gradient curtain includes a plurality of second oblique holes, the top of each second oblique hole being connected to the geomembrane through the connecting structure; wherein, the angle between each second oblique hole and the vertical line in the oblique-hole gradient curtain gradually increases along the direction toward the oblique-hole curtain.

[0010] Preferably, the inclination angle of the first oblique hole is 45°, and the included angle in the oblique hole gradient curtain varies from 0° to 45°.

[0011] Preferably, the angle variation between any two adjacent second oblique holes is 1.5°.

[0012] Preferably, the second oblique holes are spaced apart from each other, with a spacing of 1.4m to 1.6m.

[0013] Preferably, the seepage prevention structure further includes reinforcing curtains, and at least one row of reinforcing curtains surrounding the weir body is provided at the junction of both ends of the weir foundation seepage prevention wall and the two inclined hole gradient curtains; wherein, Each row of the reinforcing curtain includes a vertical section and a gradient section. The vertical sections are arranged laterally at intervals on the outer side of the end of the weir foundation anti-seepage wall, and the gradient sections are arranged at intervals on the outer side of the inclined hole gradient curtain near the end of the weir foundation anti-seepage wall.

[0014] Preferably, the length of the vertical segment and the gradient segment is 4.9m to 5.1m.

[0015] Preferably, the connection structure is a concrete connection plate, which is wrapped around and connected to the outside of the geomembrane.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a geomembrane cofferdam seepage prevention structure for steep bedrock slopes, comprising a dam body, a geomembrane, a connecting structure, and a seepage prevention structure connected around the dam body. The geomembrane is laid on the top of the dam body, and the top of the seepage prevention structure is sealed to the geomembrane through the connecting structure. The seepage prevention structure includes a vertical curtain at the dam shoulder, a seepage prevention wall at the dam base, and two longitudinally opposite slope curtains. The vertical curtain at the dam shoulder and the seepage prevention wall at the dam base are respectively connected to the two sides of the dam body in the transverse direction, and the two slope curtains are respectively connected to the two sides of the dam body in the longitudinal direction. Each slope curtain includes an inclined hole curtain and two transversely opposite inclined hole gradient curtains. An inclined hole gradient curtain is respectively provided between one side of the inclined hole curtain and the vertical curtain at the dam shoulder, and between the other side of the inclined hole curtain and the seepage prevention wall at the dam base. The upper geomembrane and the surrounding curtain grout are sealed together by a connecting mechanism to ensure the integrity and reliability of the seepage prevention system. The bank slopes and bedrock of the weir foundation are protected by curtain grouting, while the bank slopes are protected by inclined hole grouting. A gradual inclined hole curtain is set at the connection area between the inclined hole curtain and the end of the weir foundation seepage prevention wall to achieve a gradual connection and improve the integrity of the connection. In this way, the inclined holes are inclined into the mountain, which can avoid the broken rock mass area of ​​the bank slope as much as possible and penetrate into the relatively intact rock mass area inside the mountain. This can reduce the grouting depth, reduce grout leakage and rock mass grout absorption, and significantly save on project investment. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0018] Figure 1 This is a three-dimensional schematic diagram of the overall structure in one embodiment of the present invention; Figure 2 This is a partial planar schematic diagram of the reinforced curtain in one embodiment of the present invention.

[0019] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings.

[0020] Explanation of icon numbers: 10. Geomembrane; 20. Connecting structure; 30. Seepage prevention structure; 310. Vertical curtain wall on weir shoulder; 320. Seepage prevention wall on weir foundation; 330. Slope curtain wall; 331. Inclined hole curtain wall; 332. Gradual curtain wall with inclined hole; 340. Reinforced curtain wall; 341. Vertical section; 342. Gradual section. Detailed Implementation

[0021] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0024] Furthermore, the use of terms such as "first" and "second" in this invention is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this invention.

[0025] Please see the appendix Figure 1-2 This invention provides an embodiment of a geomembrane cofferdam seepage prevention structure for steep bedrock slopes, comprising a cofferdam body, a geomembrane 10, a connecting structure 20, and a seepage prevention structure 30 connected around the cofferdam body. First, it should be noted that in this application, "longitudinal" refers to the direction of water flow from upstream to downstream, and "transverse" refers to the width direction perpendicular to the direction of water flow. Please refer to the accompanying drawings for details; the specific design is as follows: The geomembrane 10 is laid on the top of the dam body, and the top of the seepage prevention structure 30 is sealed to the geomembrane 10 through the connecting structure 20; the seepage prevention structure 30 includes a vertical curtain 310 for the dam shoulder, a seepage prevention wall 320 for the dam base, and two longitudinally opposite bank slope curtains 330. The vertical curtain 310 for the dam shoulder and the seepage prevention wall 320 for the dam base are respectively connected to the two sides of the dam body in the transverse direction, and the two bank slope curtains 330 are respectively connected to the two sides of the dam body in the longitudinal direction; wherein, each bank slope curtain 330 includes an inclined hole curtain 331 and two transversely opposite inclined hole gradient curtains 332. One inclined hole gradient curtain 332 is respectively provided between one side of the inclined hole curtain 331 and the vertical curtain 310 for the dam shoulder, and between the other side of the inclined hole curtain 331 and the seepage prevention wall 320 for the dam base.

[0026] Specifically, the steep bedrock slope inclined wall geomembrane cofferdam seepage prevention structure of this application includes a dam body, a geomembrane 10, a connecting structure 20, and a seepage prevention structure 30 connected around the dam body. The dam body is an earth-rock cofferdam body. The geomembrane 10 serves as the seepage prevention system at the top of the dam body, and is laid on the top of the dam body to effectively prevent water from seeping into the dam body. The seepage prevention structure 30 is used to prevent seepage around the dam body. The top of the seepage prevention structure 30 and the geomembrane 10 are sealed and connected by the connecting structure 20 to improve the seepage prevention at the interface. Preferably, the connecting structure 20 can be a concrete connecting plate, specifically a toe slab concrete, which is arranged around the geomembrane 10 to be connected to the seepage prevention structure 30 respectively. The ends of the geomembrane 10 are fixed by bolt connection, which is convenient to construct, has good sealing performance, and the seepage prevention system is complete and reliable.

[0027] The seepage prevention structure 30 includes a vertical curtain 310 at the weir shoulder, a seepage prevention wall 320 at the weir base, and two longitudinally opposite bank slope curtains 330. The weir shoulder and weir base sections of the weir body both adopt the form of vertical curtains to form the seepage prevention structure 30. The use of vertical curtains at the weir shoulder and weir base is convenient for construction, saves materials, and ensures reliable seepage prevention performance. In detail, multiple vertical holes arranged in parallel along the longitudinal direction can be used to perform vertical grouting to form a vertical curtain seepage prevention system. The bank slope curtains 330 are inclined along the transverse sides. This allows for the setting of appropriate seepage prevention methods according to the conditions of the weir body, the weir base overburden layer, and the bedrock, reflecting the superior adaptability of this application to the construction environment.

[0028] Each of the slope curtains 330 includes an inclined perforated curtain 331 and two laterally opposite inclined perforated gradient curtains 332. The inclined perforations at the slope, pointing inwards into the mountainside, allow for rapid penetration through the fractured rock mass of the exposed area of ​​the slope, reaching the relatively intact rock mass within the mountainside in the shortest distance, thus reducing grouting depth and saving investment. The inclined perforated gradient curtains 332 facilitate a gradual transition from the inclined perforated curtain 331 to the vertical curtain, avoiding issues of loose connections and poor seepage prevention. Therefore, one inclined perforated gradient curtain 332 is installed between one side of the inclined perforated curtain 331 and the vertical curtain 310 of the weir shoulder, and another between the other side of the inclined perforated curtain 331 and the weir foundation seepage prevention wall 320. This forms a combined seepage prevention system of composite geomembrane 10 + vertical curtain grouting + inclined perforated curtain 331 grouting, fully utilizing the terrain conditions to ensure a better seepage prevention effect.

[0029] As a preferred embodiment of the present invention, the inclined hole curtain 331 includes a plurality of first inclined holes arranged side by side in a transverse direction. The top end of each first inclined hole is connected to the geomembrane 10 through the connecting structure 20, and the bottom end of the first inclined hole is inclined in a longitudinal direction away from the dam body from the top end.

[0030] It should be noted that the inclined hole curtain 331 adopts the form of multiple inclined hole grouting to form an inclined curtain grouting seepage prevention system. The top of all the first inclined holes are sealed and connected to the geomembrane 10 to ensure good sealing and seepage prevention performance at the joint. Specifically, the sealing connection is achieved through the connecting structure 20 (concrete connecting plate), while the bottom end is inclined outward (towards the direction away from the dam body) to form an inclined hole. In a preferred embodiment of this application, the inclination angle of the first inclined hole can be set to 45° to ensure good vertical extension into the mountain body. During the grouting construction of the inclined hole curtain 331, reliable results can be achieved through drilling accuracy and grouting quality control.

[0031] In a preferred embodiment of the present invention, the oblique-hole gradient curtain 332 includes a plurality of second oblique holes, the top of each second oblique hole being connected to the geomembrane 10 through the connecting structure 20; wherein, the angle between each second oblique hole and the vertical line in the oblique-hole gradient curtain 332 gradually increases along the direction toward the oblique-hole curtain 331.

[0032] It is worth noting that the inclined hole gradient curtain 332 also adopts the form of inclined hole grouting, that is, multiple second inclined holes. However, the second inclined holes are different from the first inclined holes. All the first inclined holes have the same inclination angle, while the inclination angle between adjacent second inclined holes gradually changes to form a gradient. Specifically, the two ends of the inclined hole gradient curtain 332 are respectively connected to the inclined hole curtain 331 and the vertical curtain (of the weir shoulder or weir foundation). Therefore, the second inclined hole of the inclined hole gradient curtain 332 near the vertical curtain corresponds to the vertical curtain, that is, the inclination angle is 0°. It is worth mentioning that the tilt angle here refers to the angle between the tilt axis of the second oblique hole and the vertical line (0° without tilt forms a vertical curtain hole); while the second oblique hole in the oblique hole gradient curtain 332, which is closer to the oblique hole curtain 331, corresponds to the first oblique hole, that is, the tilt angle is 45°. The change of this angle gradually increases from the vertical curtain towards the oblique hole curtain 331, thus forming an oblique hole gradient form, improving the tightness of the connection to ensure the seepage prevention effect; thus, the angle change range in the oblique hole gradient curtain 332 is 0°~45°.

[0033] Furthermore, the angle variation between any two adjacent second oblique holes is 1.5°.

[0034] It should be noted that, considering the uniformity and stability of the gradient, the angle change range between each pair of adjacent second oblique holes can be set to 1.5°. Thus, taking the next second oblique hole near the end of the vertical curtain in the oblique hole gradient curtain 332 as an example, if the angle between the first second oblique hole and the vertical line is 0°, then the angle between the second second oblique hole and the vertical line is 1.5°, the angle between the third second oblique hole and the vertical line is 3°, and so on, until the angle between the last second oblique hole near the end of the oblique hole curtain 331 and the vertical line is 45°.

[0035] Furthermore, each pair of adjacent second oblique holes is spaced apart, with a spacing of 1.4m to 1.6m.

[0036] It should be understood that the grouting holes in curtain grouting are usually spaced apart to prevent grout from flowing between adjacent holes. Therefore, the interval between any two adjacent second inclined holes can be set to 1.4m to 1.6m. In a preferred embodiment of this application, this interval is set to 1.5m. Those skilled in the art can select according to actual needs.

[0037] Furthermore, the seepage prevention structure 30 also includes a reinforcing curtain 340. At least one row of the reinforcing curtain 340 is provided at the connection between both ends of the weir foundation seepage prevention wall 320 and the two inclined hole gradual curtains 332, which surround the weir body. Each row of the reinforcing curtain 340 includes a vertical section 341 and a gradual section 342. The vertical section 341 is arranged laterally at intervals on the outer side of the end of the weir foundation seepage prevention wall 320, and the gradual section 342 is arranged at intervals on the outer side of the inclined hole gradual curtain 332 near the end of the weir foundation seepage prevention wall 320.

[0038] It should be noted that the rock mass at the end of the cutoff wall is usually a relatively fractured part of the bank slope, and the water head is relatively high. Therefore, in order to avoid seepage damage or large seepage volume after grouting treatment in weak areas, a reinforcing curtain 340 is added for grouting on the upstream and downstream sides of the cutoff wall end (i.e., both ends of the weir foundation cutoff wall 320) and within a certain range on the bank slope side (i.e., at the corner of the cutoff wall and the inclined hole gradual curtain 332). This forms a more reliable seepage prevention effect by setting multiple rows of curtains in weak areas. Considering the economic cost, one row can be set to form a double-row seepage prevention structure 30. Each row of the reinforcing curtain 340 includes a vertical section 341 and a gradual section 342. The vertical section 341 is used to cover the outside of the weir foundation cutoff wall 320, and the gradual section 342 is used to cover the outside of the weir foundation cutoff wall 320. The reinforcing curtains 340 are laid over the inclined perforated gradient curtain 332 to match and reinforce the sections, forming multiple rows. The reinforcement range can be set to 4.9m~5.1m for the lengths of the vertical section 341 and the gradient section 342. In a preferred embodiment, 5m is used, meaning 5m reinforcing curtains 340 are set on both sides from the corner of the seepage barrier wall and the inclined perforated gradient curtain 332. Those skilled in the art can choose according to actual needs. It is worth mentioning that when forming the reinforcing curtain 340, its reinforcing grouting holes can be staggered with the corresponding vertical holes in the vertical section 341 and the second inclined holes in the gradient section 342 to better improve seepage prevention performance and ensure seepage prevention in weak areas. Please refer to the appendix for details. Figure 2 .

[0039] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A geomembrane cofferdam seepage prevention structure for steep bedrock slopes, characterized in that, It includes the weir body, geomembrane, connecting structure, and seepage prevention structure connected around the weir body; wherein, The geomembrane is laid on top of the weir, and the top of the seepage prevention structure is sealed to the geomembrane through the connecting structure. The seepage prevention structure includes a vertical curtain at the weir shoulder, a seepage prevention wall at the weir base, and two longitudinally opposite bank slope curtains. The vertical curtain at the weir shoulder and the seepage prevention wall at the weir base are respectively connected to both sides of the weir body in the transverse direction, and the two bank slope curtains are respectively connected to both sides of the weir body in the longitudinal direction. Each of the aforementioned bank slope curtains includes an inclined hole curtain and two inclined hole gradient curtains arranged laterally opposite each other. One inclined hole gradient curtain is respectively arranged between one side of the inclined hole curtain and the vertical curtain of the weir shoulder, and between the other side of the inclined hole curtain and the weir foundation seepage prevention wall.

2. The seepage prevention structure of the inclined wall geomembrane cofferdam on steep bedrock slopes according to claim 1, characterized in that, The inclined hole curtain includes a plurality of first inclined holes arranged side by side in a transverse direction. The top of each first inclined hole is connected to the geomembrane through the connecting structure. The bottom of the first inclined hole is inclined longitudinally away from the dam body from the top.

3. The seepage prevention structure of the inclined wall geomembrane cofferdam on steep bedrock slopes according to claim 2, characterized in that, The dam foundation seepage prevention wall includes multiple vertical holes arranged in parallel along the longitudinal direction, and the top of each vertical hole is connected to the geomembrane through the connecting structure.

4. The seepage prevention structure of the inclined wall geomembrane cofferdam on steep bedrock slopes according to claim 3, characterized in that, The inclined perforated gradient curtain includes multiple second inclined holes, and the top of each second inclined hole is connected to the geomembrane through the connecting structure; wherein, the angle between each second inclined hole and the vertical line in the inclined perforated gradient curtain gradually increases along the direction toward the inclined perforated curtain.

5. The seepage prevention structure of the inclined wall geomembrane cofferdam on steep bedrock slopes according to claim 4, characterized in that, The first oblique hole has an inclination angle of 45°, and the included angle in the oblique hole gradient curtain varies from 0° to 45°.

6. The seepage prevention structure of the inclined wall geomembrane cofferdam on steep bedrock slopes according to claim 5, characterized in that, The angle variation between any two adjacent second oblique holes is 1.5°.

7. The seepage prevention structure of the inclined wall geomembrane cofferdam on steep bedrock slopes according to claim 6, characterized in that, The second inclined holes are spaced apart from each other, with a spacing of 1.4m to 1.6m.

8. The seepage prevention structure of the inclined wall geomembrane cofferdam on steep bedrock slopes according to claim 4, characterized in that, The seepage prevention structure also includes reinforcing curtains, and at least one row of reinforcing curtains surrounding the weir body is provided at the junction of both ends of the weir foundation seepage prevention wall and the two inclined hole gradient curtains; wherein, Each row of the reinforcing curtain includes a vertical section and a gradient section. The vertical sections are arranged laterally at intervals on the outer side of the end of the weir foundation anti-seepage wall, and the gradient sections are arranged at intervals on the outer side of the inclined hole gradient curtain near the end of the weir foundation anti-seepage wall.

9. The seepage prevention structure of the inclined wall geomembrane cofferdam on steep bedrock slopes according to claim 8, characterized in that, The lengths of the vertical section and the gradient section are 4.9m to 5.1m.

10. The steep bedrock slope inclined wall geomembrane cofferdam seepage prevention structure according to any one of claims 1 to 4, characterized in that, The connection structure is a concrete connection plate, which is wrapped around and connected to the outside of the geomembrane.

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