Cover layer slope support structure in water level fluctuation zone and its construction method

Abstract

The present invention relates to a slope support structure for the water-level fluctuation zone covering layer and its construction method, belonging to the technical field of slope support structures for the covering layer of hydropower stations. The slope support structure for the water-level fluctuation zone covering layer of the present invention includes a water-level fluctuation zone located on the covering layer slope, and multiple rows of steel sheet piles are arranged at intervals along the slope inclination direction of the water-level fluctuation zone. An anti-filter drainage structure is laid on the slope of the water-level fluctuation zone. The anti-filter drainage structure includes a coarse sand layer, a gravel layer, a first fine mesh, a pebble layer, and a second fine mesh arranged in sequence from bottom to top. The mesh diameter of the first fine mesh is smaller than the gravel particle size of the gravel layer; the mesh diameter of the second fine mesh is smaller than the pebble particle size of the pebble layer; an articulated slope protection brick is fixedly arranged on the upper surface of the anti-filter drainage structure, and the articulated slope protection brick is anchored to the slope through grouting anchor bolts. Multiple sand wells are arranged below the anti-filter drainage structure, and the upper ends of the sand wells intersect with the bottom surface of the anti-filter drainage structure.

Description

Technical Field

[0001] The present invention relates to a slope support structure for the covering layer in the water level fluctuation zone and a construction method thereof, belonging to the technical field of slope support structures for the covering layer of hydropower stations. Background Art

[0002] Due to its mature technology, excellent economy, and characteristics such as large-scale energy storage development, pumped-storage power stations have become a hot spot in the development of clean energy in China in recent years. A pumped-storage power station uses water as the energy storage medium. During the low-load period of the power grid, the excess electric energy pumps the water in the lower reservoir to the upper reservoir, converting the electric energy into the potential energy of water. During the peak-load period of the power grid, the water in the upper reservoir flows into the power house for power generation, relieving the pressure of peak power consumption. Most pumped-storage power stations require excavation and filling to be balanced, so the dead storage capacity is generally small. Different from conventional hydropower stations, they are more sensitive to the stability of the bank slopes in the reservoir. When the bank slopes in the reservoir collapse, slump or landslide, the effective storage capacity will be reduced, seriously affecting the power generation efficiency. When the water level rises significantly, it is easy for the water in the reservoir to overflow the dam, which may then cause the dam to burst and lead to engineering accidents.

[0003] The protection of the bank slopes in the pumped-storage power station reservoir is most difficult for the deep covering layer slopes in the water level fluctuation zone, and the difficulty is mainly reflected in two aspects:

[0004] One is the frequent water level fluctuation. Different from the water level fluctuation in natural rivers, the water level fluctuation in natural rivers is generally slow, while the water level fluctuation zone of a pumped-storage power station has the characteristics of short cycle and frequent fluctuation. There may be multiple water level rises and falls in a day, and the pore water pressure in the slope is extremely unstable. When the water level drops, negative pressure is likely to occur. Under the action of the hydraulic gradient, groundwater drags the soil mass towards the free face in the reservoir. When the water level rises and falls cyclically, it is easy to loosen the relatively dense soil mass, reduce the density of the soil mass, and deteriorate the mechanical properties of the soil mass, resulting in slope instability.

[0005] The second is that the deep covering layer slope itself has the characteristic of deteriorating when encountering water. Under the long-term erosion of the water body in the fluctuation zone, fine particles in the conventional slope concrete are easily carried out, easily scoured, collapsed, and then the slope concrete fails.

[0006] The existing slope protection structures for deep covering layers mostly adopt the form of hanging mesh + shotcrete + drainage pipes or slope concrete + drainage pipes for support. Most of them are slope protection structures for the upper water slopes, and rarely consider the water level fluctuation zone and negative pore water pressure.

[0007] The existing bank slope protection structure in the water level fluctuation zone can refer to the patent document with the publication number CN218454380U. It successively sets a natural soil slope, a continuous wall of planted wooden piles, a hydrophilic platform, a vertical retaining wall, a geocell slope protection, and a turf protection slope from the river bottom to the slope top of the river channel bank slope; the hydrophilic platform is located below the normal water level, planting aquatic plants to enhance the ecological landscape effect, and at the same time having the function of bank slope protection; a continuous wall of planted wooden piles is set on the water-facing side of the hydrophilic platform, which can not only prevent the plant roots on the hydrophilic platform from extending outward to the slope surface, but also improve the anti-scouring ability of the bank slope and enhance the stability of the bank slope; the protection structure of using geocells and covering with soil and greening for the green slope platform and the inclined bank slope below the design flood level has better anti-scouring ability compared with the natural soil slope. However, this scheme is mainly aimed at the protection of river channel bank slopes and is not applicable to overburden slopes, nor is it applicable to the bank slopes with frequent water level changes in pumped storage power stations. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a support structure for the overburden slope in the water level fluctuation zone, which is applicable to the overburden slope with frequent water level changes in the pumped storage power station, reduce the disturbance of the water level fluctuation zone to the overburden layer, and improve the stability of the slope in the fluctuation zone.

[0009] The technical solution adopted by the present invention to solve the above technical problem is: a support structure for the overburden slope in the water level fluctuation zone, including a water level fluctuation zone on the overburden slope, arranging multiple rows of steel sheet piles at intervals along the slope inclination direction of the water level fluctuation zone, laying an anti-filter drainage structure on the slope surface of the water level fluctuation zone, the anti-filter drainage structure includes a coarse sand layer, a gravel layer, a first fine mesh screen, a cobblestone layer and a second fine mesh screen arranged in sequence from bottom to top, the mesh diameter of the first fine mesh screen is smaller than the gravel particle size of the gravel layer, and the mesh diameter of the second fine mesh screen is smaller than the cobblestone particle size of the cobblestone layer; an articulated slope protection brick is fixedly arranged on the upper surface of the anti-filter drainage structure, the articulated slope protection brick is anchored to the slope surface through grouting anchor rods, and a plurality of sand wells are arranged below the anti-filter drainage structure, and the upper ends of the sand wells intersect with the bottom surface of the anti-filter drainage structure.

[0010] A further preferred scheme is: at least three rows of steel sheet piles are provided, one row is located at the slope top of the water level fluctuation zone, one row is located at the slope foot of the water level fluctuation zone, and the rest are located in the middle of the water level fluctuation zone.

[0011] A further preferred scheme is: the steel sheet piles are all vertically arranged, and the vertical length of the steel sheet piles at the slope foot of the water level fluctuation zone is not less than 15m.

[0012] A further preferred scheme is: the axes of the sand wells are all vertically arranged.

[0013] A further preferred scheme is: at least two layers of the first fine mesh screen are arranged, and the layers are arranged in a staggered manner.

[0014] A further preferred solution is that the second close-mesh net is arranged in at least two layers, and the layers are arranged staggeredly.

[0015] A further preferred solution is that the axis of the grouting anchor is arranged perpendicular to the slope surface.

[0016] Based on the slope support structure of the overburden layer in the water level fluctuation zone described above, the present invention correspondingly provides a construction method for the slope support structure of the overburden layer in the water level fluctuation zone, including the following steps:

[0017] A. First, use static pile pressing machinery to construct the steel sheet piles, and the construction sequence of the steel sheet piles is from bottom to top;

[0018] B. Use an excavator to excavate the loose soil between the steel sheet piles in the water level fluctuation zone, and excavate at least 2 m in the direction of the slope;

[0019] C. Use a pile driver to construct the sand wells, and perform vibration compaction during the construction process. The construction sequence of the sand wells is from top to bottom;

[0020] D. Construct the coarse sand layer, with a thickness of at least 90 cm, and compact it every 10 cm - 20 cm of laying;

[0021] E. Construct the gravel layer, with a thickness of at least 90 cm, and compact it every 10 cm - 20 cm of laying;

[0022] F. Set the first close-mesh net on the gravel layer;

[0023] G. Construct the pebble layer, with a thickness of at least 90 cm, and compact it every 10 cm - 20 cm of laying;

[0024] H. Set the second close-mesh net on the pebble layer;

[0025] I. Construct the articulated slope protection bricks;

[0026] J. Construct the grouting anchors.

[0027] The beneficial effects of the present invention are as follows: The slope support structure for the covering layer in the water level fluctuation zone of the present invention can form three systems, namely a rapid drainage system, a slope surface protection system, and a slope reinforcement system. Among them, the rapid drainage system includes sand wells and a filter drainage structure with a dense mesh. The vertical sand wells can quickly collect and drain water, and the filter drainage structure can drain the water in the sand wells out of the slope body while preventing fine particles in the slope body from flowing out; the slope surface protection system includes grouted bolts and articulated slope protection bricks. Among them, the articulated slope protection bricks are located above the filter drainage structure to prevent erosion. The grouted bolts are mainly located on the articulated slope protection bricks and are connected to the integrated articulated slope protection brick body to form an "outer attached skeleton" structure to prevent pebbles or gravel from falling off and collapsing; the slope reinforcement system is mainly steel sheet piles, and the steel sheet piles mainly play the role of dividing the covering layer soil mass and retaining soil. The present invention organically combines structures such as steel sheet piles, sand wells, grouted bolts, geogrid, and dense mesh into a whole to reinforce and seal the deep covering layer slope in the fluctuation zone, which can effectively reduce the influence of negative pore pressure in the water level fluctuation zone and improve the stability of the covering layer slope. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic elevation structure diagram when the present invention is implemented.

[0029] Figure 2 is a partial enlarged schematic diagram of the part where the filter drainage structure and the articulated slope protection brick are located in the present invention.

[0030] Markings in the figure: water level fluctuation zone 1, steel sheet pile 2, filter drainage structure 3, coarse sand layer 301, gravel layer 302, first dense mesh 303, pebble layer 304, second dense mesh 305, articulated slope protection brick 4, grouted bolt 5, sand well 6. DETAILED DESCRIPTION OF THE INVENTION

[0031] The present invention will be further described below with reference to the accompanying drawings.

[0032] As Figure 1 and Figure 2 shown, the slope support structure for the covering layer in the water level fluctuation zone of the present invention includes a water level fluctuation zone 1 located on the covering layer slope, multiple rows of steel sheet piles 2 are arranged at intervals along the slope inclination direction of the water level fluctuation zone 1, a filter drainage structure 3 is laid on the slope surface of the water level fluctuation zone 1, and the filter drainage structure 3 includes a coarse sand layer 301, a gravel layer 302, a first dense mesh 303, a pebble layer 304, and a second dense mesh 305 arranged in sequence from bottom to top. The mesh diameter of the first dense mesh 303 is smaller than the gravel particle size of the gravel layer 302, and the mesh diameter of the second dense mesh 305 is smaller than the pebble particle size of the pebble layer 304; an articulated slope protection brick 4 is fixedly arranged on the upper surface of the filter drainage structure 3, the articulated slope protection brick 4 is anchored to the slope surface through a grouted bolt 5, and a plurality of sand wells 6 are arranged below the filter drainage structure 3, and the upper ends of the sand wells 6 intersect with the bottom surface of the filter drainage structure 3.

[0033] Among them, the sand drains 6 and the filter drainage structure 3 with a dense mesh form a rapid drainage system, which replaces and compacts the shallow soil layer of the overburden. Applied to the water level fluctuation zone of a pumped-storage power station, it can connect groundwater and the water in the reservoir, and reduce the impact of negative pore water pressure caused by the change of the reservoir water level on the slope.

[0034] The flexible slope protection system composed of the articulated slope protection bricks 4 and the grouting anchor rods 5 forms an "outer attached skeleton", firmly locking the cobblestone layer 304 to prevent the collapse of the cobblestone layer 304. At the same time, the articulated slope protection bricks 4 can adapt to the irregular slope shape and have good adaptability to the excavated slopes of different forms.

[0035] The quantity and the row and column spacing of the steel sheet piles 2 can be flexibly designed according to the actual working conditions of the water level fluctuation zone 1. To effectively ensure the reliability of the support structure, at least three rows of steel sheet piles 2 are arranged. One row is located at the top of the slope of the water level fluctuation zone 1, one row is located at the bottom of the slope of the water level fluctuation zone 1, and the rest are located in the middle of the water level fluctuation zone 1. The steel sheet piles 2 are all arranged vertically, and the vertical length of the steel sheet piles located at the bottom of the slope of the water level fluctuation zone 1 is not less than 15m.

[0036] To facilitate rapid water collection and drainage, the axes of the sand drains 6 are all arranged vertically.

[0037] To better play the role of fixing the skeleton, the first dense mesh 303 is preferably arranged in at least two layers, and the layers are arranged in a staggered manner. Similarly, the second dense mesh 305 is preferably arranged in at least two layers, and the layers are arranged in a staggered manner.

[0038] To make the structure simple and reliable, the axis of the grouting anchor rod 5 is arranged perpendicular to the slope surface.

[0039] For the above-mentioned slope support structure of the water level fluctuation zone overburden, the specific construction includes the following steps:

[0040] A. First, use static pile pressing machinery to construct the steel sheet piles 2, and the construction sequence of the steel sheet piles 2 is from bottom to top (i.e., from the bottom of the slope to the top of the slope);

[0041] B. Use an excavator to excavate the loose soil between the steel sheet piles 2 in the water level fluctuation zone 1, and excavate at least 2m in the direction of the slope;

[0042] C. Use a pile driver to construct the sand drains 6, and perform vibration compaction during the construction process. The construction sequence of the sand drains 6 is from top to bottom (i.e., from the top of the slope to the bottom of the slope);

[0043] D. Construct the coarse sand layer 301, with a thickness of at least 90cm, and perform rolling every 10cm - 20cm of laying; the compactness should meet the construction requirements;

[0044] E. Construct the gravel layer 302 with a thickness of at least 90 cm, and compact it every 10 cm - 20 cm of laying; the compactness shall meet the construction requirements;

[0045] F. Set the first dense mesh 303 on the gravel layer 302;

[0046] G. Construct the pebble layer 304 with a thickness of at least 90 cm, and compact it every 10 cm - 20 cm of laying; the compactness shall meet the construction requirements;

[0047] H. Set the second dense mesh 305 on the pebble layer 304;

[0048] I. Construct the articulated slope protection brick 4; the articulated slope protection brick 4 is a conventional building material and can be directly purchased. During construction, the joints of the slope protection bricks shall be firm and connected as a whole;

[0049] J. Construct the grouting anchor rod 5; specifically, the anchor rod shall be firmly connected to the articulated slope protection brick 4, and the length shall be not less than 9 m; during anchor rod grouting, low-pressure grouting shall be adopted.

Claims

1. The slope support structure for the covering layer in the water level fluctuation zone, including the water level fluctuation zone (1) located on the covering layer slope, is characterized in that: A plurality of rows of steel sheet piles (2) are arranged at intervals along the slope inclination direction of the water level fluctuation zone (1). A filter drainage structure (3) is laid on the slope surface of the water level fluctuation zone (1). The filter drainage structure (3) includes a coarse sand layer (301), a gravel layer (302), a first fine mesh screen (303), a cobblestone layer (304), and a second fine mesh screen (305) arranged in sequence from bottom to top. The mesh diameter of the first fine mesh screen (303) is smaller than the gravel particle size of the gravel layer (302), and the mesh diameter of the second fine mesh screen (305) is smaller than the cobblestone particle size of the cobblestone layer (304); an articulated slope protection brick (4) is fixedly arranged on the upper surface of the filter drainage structure (3), and the articulated slope protection brick (4) is anchored to the slope surface through a grouting anchor rod (5). A plurality of sand wells (6) are arranged below the filter drainage structure (3), and the upper ends of the sand wells (6) intersect with the bottom surface of the filter drainage structure (3). There are at least three rows of steel sheet piles (2). One row is located at the top of the slope of the water level fluctuation zone (1), one row is located at the bottom of the slope of the water level fluctuation zone (1), and the rest are located in the middle of the water level fluctuation zone (1). The steel sheet piles (2) are all arranged vertically. The vertical length of the steel sheet piles located at the bottom of the slope of the water level fluctuation zone (1) is not less than 15m. The axes of the sand wells (6) are all arranged vertically. The first fine mesh screen (303) is arranged in at least two layers, and the layers are arranged in a staggered manner. The second fine mesh screen (305) is arranged in at least two layers, and the layers are arranged in a staggered manner. The axis of the grouting anchor rod (5) is arranged perpendicular to the slope surface.

2. Construction method of slope support structure for overburden in water level fluctuation zone, characterized in that, Adopt the slope support structure for the covering layer of the water level fluctuation zone as described in claim 1, and it includes the following steps: A. First, use static pile pressing machinery to construct the steel sheet piles (2), and the construction sequence of the steel sheet piles (2) is from bottom to top. B. Use an excavator to excavate the loose soil between the steel sheet piles (2) in the water level fluctuation zone (1), and excavate at least 2m in the direction of the slope inward. C. Use a pile driver to construct the sand wells (6), and perform vibration compaction during the construction process. The construction sequence of the sand wells (6) is from top to bottom. D. Construct the coarse sand layer (301), with a thickness of at least 90cm laid, and compacted every 10cm - 20cm of laying. E. Construct the gravel layer (302), with a thickness of at least 90cm laid, and compacted every 10cm - 20cm of laying. F. Set the first fine mesh screen (303) on the gravel layer (302). G. Construct the cobblestone layer (304), with a thickness of at least 90cm laid, and compacted every 10cm - 20cm of laying. H. Set the second fine mesh screen (305) on the cobblestone layer (304). I. Construct the articulated slope protection brick (4). J. Construct the grouting anchor rod (5).

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