CN117248504A - Full-suspension large-span dam for low-head hydropower station and application - Google Patents

Abstract

The invention relates to a full-suspension large-span dam for a low-head hydropower station and application thereof, and belongs to the technical field of water conservancy equipment. The structure of the invention comprises a steel truss supporting body which is erected on a water channel, wherein two ends of the steel truss supporting body are supported by reinforced concrete bases which are arranged on two sides of the water channel and are close to the sides, a lower chord member structure body of connecting equipment is arranged at the lower part of the steel truss supporting body, a fully-suspended flashboard unit group matched with the width of the water channel is hung at the lower part of the lower chord member structure body, and each flashboard unit consists of a fixed cantilever, a movable cantilever and flashboard which is nested between the movable cantilevers and is driven to move up and down along the movable cantilever through a winch hoist. The structure of the invention can realize barrier-free flood discharge, does not involve migration and migration, and particularly skillfully avoids the problem of depositing a large amount of sediment which is difficult to solve and exists in a dam power station.

Description

Full-suspension large-span dam for low-head hydropower station and application

Technical Field

The invention relates to a full-suspension large-span dam for a low-head hydropower station and application thereof, and belongs to the technical field of water conservancy equipment.

Background

The water and electricity are inexhaustible green and environment-friendly energy sources. The natural geography of China is high and low in east and west, the drop is extremely large, and natural and huge hydropower resources are provided. Most of the domestic existing hydropower stations are high-head (high potential energy) type dam hydropower stations. In addition, in the aspect of the utilization of water resource power generation, the water resource with extremely wide and rich low water head (small potential energy), large kinetic energy and large flow rate is worth utilizing. Such as overflow of a dam power station, tail water; the canyon river and river water which can run around the day and night. The electric energy industrialization development and application of the water resource are basically blank at present. Compared with the photoelectric and wind power, the photovoltaic power station is greatly influenced by the unbalance of the sunlight irradiation intensity and the day-night alternation; wind power is greatly affected by the unbalance of the wind power and the existence of the unbalance. The water energy resources with low water head, large kinetic energy and large flow rate are relatively constant and balanced. If the water energy resources can be reasonably utilized, the water energy resources can be used as a matched supplementing scheme of the hydropower station of the high-head dam, and the utilization value of the water resources can be fully improved. The full-suspension large-span dam for the low-head hydropower station is a precondition for the utilization of the water energy. The existing dam power station is easy to seriously influence natural original ecological environment due to structural design reasons of building a gravity dam, is easy to generate upstream and sediment accumulation at the bottom of the dam, and lacks an effective treatment method and the like.

Disclosure of Invention

The invention aims to provide a full-suspension large-span dam for a low-head hydropower station and application thereof.

The invention adopts a method of combining a low-head dam with a low potential energy, a high kinetic energy and a high flow hydroelectric generating set to realize the utilization of low-head water energy resources. The technical problems are solved by the following technical scheme: firstly, providing a full-suspension large-span dam for a low-head hydropower station, comprising a steel truss supporting body erected on a water channel, wherein two ends of the steel truss supporting body are supported by reinforced concrete bases which are arranged at two sides of the water channel and are close to the sides, a lower chord member structure body of connecting equipment is arranged at the lower part of the steel truss supporting body, a full-suspension flashboard unit group matched with the width of the water channel is suspended at the lower part of the lower chord member structure body, each flashboard unit is formed by a fixed cantilever which is symmetrically arranged left and right, and is suspended and fixed on the lower chord member structure body at the upper end, a movable cantilever which is nested in an inner cavity of the fixed cantilever and is driven to move up and down along the inner cavity of the fixed cantilever by a screw hoist, and a flashboard which is nested between the movable cantilever and is driven to move up and down along the movable cantilever by the hoist; when the movable cantilever stretches into the water, the movable cantilever is matched and nested with a foot anchor arranged at the bottom of the underwater riverbed, and the fixed cantilever, the movable cantilever and the flashboard are all in a hanging state, wherein the fixed cantilever is static and motionless all the time, and the movable cantilever and the flashboard are in a controllable dynamic hanging state. The controllable dynamic suspension state means that the movable cantilever and the flashboard can be controlled to reciprocate up and down along the corresponding guide rail.

The structure synthesizes the whole hanging flashboard group through a plurality of flashboard units capable of realizing independent whole hanging, and realizes the large-span whole hanging of the whole dam.

The invention adopts a dam construction concept completely different from the traditional gravity dam, and the gravity dam is a fixed high-head dam formed by pouring reinforced concrete from bottom to top. The dam of the invention adopts a fully suspended and top-down dam construction mode in terms of technology or structure. Further, the steel truss supporting body is integrally formed by a frame-shaped truss structural body and an arched girder structural body which are made of bearing and stressed steel. The lower part of the steel truss supporting body is provided with a lower chord member structure body of the connecting device, and the lower chord member structure body (seen from a top view) consists of a left lower chord member, a right lower chord member, longitudinal beams, cross beams, lower flat longitudinal links and nodes which are connected with each other. The truss carrier has the greatest advantages that: the span is large, the weight is light, the load bearing capacity is large, and the structure is stable and reliable. The river can span canyon river and river with large span; can be customized in the factory according to the technical size of the structural components; the truss component materials in the decomposed state (and the dam components in the decomposed state) are convenient to transport in mountain areas with bad roads; the dam can be conveniently and quickly spliced and assembled on site, and the construction period is short.

Another important purpose (index) of the large span truss carrier (and dam) is that there can be no building in the waterway, and that the natural original ecology of river and river waterways is maintained to the maximum extent (basic river beds and bank slopes are not changed in principle, but solidification and optimization of river beds and bank slopes are allowed).

Further, the fixed cantilevers are provided with fixed cantilever structures, each pair of fixed cantilevers is connected by an upper beam and a lower beam, the upper ends at the back of the left fixed cantilever and the right fixed cantilever are respectively connected with a rear left beam and a rear right beam which are vertical to the upper ends at the back of the fixed cantilevers, the tail ends of the rear left beam and the rear right beam are connected through the rear beam, inclined support frames are respectively fixed between the rear left beam and the rear right beam and the left fixed cantilever and between the rear right beam and the right fixed cantilever, screw type headstock gear is arranged at the top of the left fixed cantilever and the right fixed cantilever, and a winch type headstock gear is fixedly arranged on the upper beam. The fixed cantilever structure can ensure the stability and strength of the fixed cantilever.

The fixed cantilever (seen from a sectional view) is provided with a rectangular shell, four corners of the inner wall of the rectangular shell are respectively provided with a reinforcing rib, 45-degree included angles are formed between the reinforcing ribs and the adjacent inner wall of the shell, two adjacent reinforcing ribs and a connecting steel plate between the two adjacent reinforcing ribs form a concave track for restraining the movable cantilever to lift, and each reinforcing rib is provided with an antifriction engineering plastic gasket strip which is in contact with the movable cantilever.

The four corners of the movable cantilever are matched with the shape of the reinforcing rib in the fixed cantilever, the middle part of the vertical direction of the opposite surfaces of the pair of movable cantilevers in the flashboard unit is provided with concave track grooves matched with the shapes of two ends of the flashboard, the inner cavity of the movable cantilever is divided into two symmetrical cavities by the concave track grooves, a sealing rubber strip is arranged on the radial upstream surface in the concave track grooves, a lifting screw is fixed at the center of the top of the movable cantilever, the lifting screw is meshed with a lifting nut of the screw type headstock gear, and a rectifying triangle plate is fixed on the upstream surface of the lower part of the movable cantilever to play a role in diversion. When the lifting nut rotates forwards or reversely, the lifting screw rod is lifted or lowered to drive the movable cantilever to lift or lower.

The flashboard in the fully-suspended flashboard unit group can be divided into an intelligent drainage flashboard, a water storage flashboard and a water discharge acting flashboard according to functions, and the water discharge acting flashboard is matched with a corresponding water turbine; each flashboard is a steel flashboard, the steel flashboard is formed by welding an internal steel skeleton and an external steel plate, the left side and the right side of the steel flashboard are provided with convex shape parts matched with the concave track grooves of the movable cantilever in shape, 2 lifting pulleys are fixed at the top of the steel flashboard, and the lifting pulleys are connected with a steel cable of the winch hoist.

The foot anchor is made of steel and is arranged on the position, determined by technical design, of the positive and negative zero reference surface of the underwater foundation, and the foot anchor comprises a steel shell which is positioned on the positive and negative zero reference surface of the underwater foundation and can be correspondingly nested in a cavity of the movable cantilever, and a reinforced concrete anchor ingot positioned below the positive and negative zero reference surface of the underwater foundation.

The screw hoist consists of a motor, a reduction gear box and a screw lifting gear box; the winch hoist is a double-hoisting-point winch hoist and consists of a motor, a reduction gearbox, a brake disc, a steel cable roller and a steel cable.

The invention further provides application of the full-suspension large-span dam for the low-head hydropower station, wherein the dam comprises three working states, namely a water storage state, a water discharge working state and a flood discharge drainage state; when the dam is in a water storage state, the screw type headstock gear drives the movable cantilever to move downwards, the movable cantilever is connected and fixed with a foot anchor of a reference surface of an underwater river bed in a nested manner, the winch type headstock gear drives the flashboard to move downwards to the bottom of the river bed to start water storage, the intelligent drainage flashboard can move upwards to drain water, and a water storage water level line is kept at a rated height; when the dam is in a flood discharge and drainage state, part or all of the shutters move upwards to drain water. And the river bed and the bank slope in the area near the dam are solidified and optimized by reinforced concrete according to the design requirement, the anchor ingot part of the foot anchor for installing the foundation is positioned and manufactured according to the design, and the steel connecting embedded part is manufactured, wherein the embedded part is a reinforced concrete anchor ingot.

The dam of the present invention was designed to have a height (head) of 3.5 meters and a width of about 70 meters. If the upstream regular water source channel length is 1000-2000 m, at least water can be stored as dynamic water energy resources with water head height (potential energy) of 3.5 m, and reservoir capacity of 40-50 ten thousand cubic meters and water supplement all the time.

The invention relates to a totally suspended dam body which is totally different from a gravity dam. The material used is a steel sluice, and the built dam is a totally non-fixed and controllable low-head dynamic dam. The water channel can be in a dam state or a non-dam state. A brand new dam existence mode and dam utilization mode are formed. Thus, a series of revolutionary changes in dam and hydropower development and application are brought. Particularly, the serious natural ecological environment change or damage caused by the construction of the dam by the dam power station is avoided, and the serious influence caused by sediment accumulation on the upstream of the dam and the bottom of the dam which are difficult to eliminate and are generated by the dam power station is completely avoided. Therefore, a brand new way for developing and constructing low-head, large-kinetic-energy and large-flow hydropower stations is developed. Fills the blank in the domestic (international) aspect. Through the full-suspension design, the low-head dam is realized without influencing the river bed and bank slopes, natural ecology of river flow and two banks of a river flow water channel, normal flow of the river flow is not influenced, barrier-free flood discharge is realized, migration is not involved, and the problem of sediment deposition of a large amount of sediment which is difficult to solve and exists in a dam power station is particularly skillfully avoided. The beneficial effects are as follows: the application range is extremely wide, and the construction method is relatively simple. Provides an important precondition for the development and application of low-water-head, high-flow and high-kinetic-energy hydropower stations. Has great market application prospect, possibly leads the development revolution of novel hydropower, drives the novel hydropower industry with huge scale and has great social and economic benefits.

Drawings

Fig. 1 is a schematic structural view of an embodiment of the present invention.

Fig. 2 is a left side view of fig. 1.

Fig. 3 is a schematic structural view of the shutter unit group in fig. 1.

Fig. 4 is a schematic structural diagram of the fixed cantilever structure set in fig. 2.

Fig. 5 is a schematic structural view of the fixed cantilever and the movable cantilever in fig. 1.

Fig. 6 is a schematic view of the movable cantilever of fig. 1.

Fig. 7 is a schematic view of the shutter plate in fig. 1.

Fig. 8 is a schematic view of the foot anchor of fig. 1.

Fig. 9 is a top view of the bottom chord structure of fig. 1.

Detailed Description

Example 1

The structure of this embodiment is shown in fig. 1-9, and a large-span dam for a low-head hydropower station comprises a steel truss carrier erected on a water channel, wherein the steel truss carrier is formed by splicing (including bolting, riveting and welding) prefabricated structural steel, and consists of a frame-shaped truss structure body 2 of bearing stress steel and a steel arched girder structure body 1 of which the shape is a cylinder (or rectangle), and the steel truss carrier is used as a large-span steel truss carrier to bear a fully-suspended steel dam assembly. The lower part of the steel truss supporting body is a lower chord member structure body 3 for connecting and installing the steel full-suspension dam, and the lower chord member structure body 3 (seen from the top view) is formed by interconnecting a left lower chord member 3-1, a right lower chord member 3-2, longitudinal beams 3-3, cross beams 3-4, lower flat longitudinal links 3-5 and nodes 3-6. The two ends of the steel truss supporting body are fixedly supported by bases 9 which are arranged on two sides of the water channel and close to the bank edge, and the bases of the truss supporting body are made of reinforced concrete. The steel truss supporting body is provided with a plurality of groups of full-suspension unit groups matched with the width of the water channel, a certain unit group is fully suspended and is matched with the water turbine assembly 11, each unit is composed of fixed cantilevers 6 which are symmetrically arranged left and right and are fixed on the lower chord member structural body at the upper end, movable cantilevers 7 which are nested in the inner cavity of the fixed cantilevers, are driven by screw type headstock gears 4 to move up and down along the inner cavity of the fixed cantilevers 6, and flashboards 8 which are nested between the movable cantilevers 7, are driven by winch type headstock gears 5 and move up and down along the movable cantilevers 7; when the movable cantilever 7 stretches into the water to be fixed, the movable cantilever is matched and nested with the foot anchor 10 arranged under the water. In the flashboard unit group, each pair of fixed cantilevers 6 are connected by an upper cross beam 6-1 and a lower cross beam 6-2, the back upper ends of the left and right fixed cantilevers are respectively connected with a back left cross beam 6-5 and a back right cross beam 6-6 which are vertical to the upper ends, the tail ends of the back left cross beam 6-5 and the back right cross beam 6-6 are connected through a back cross beam 6-4, and inclined support frames 6-3 are respectively fixed between the back left and back right cross beams and the left and right fixed cantilevers. Screw type headstock gear 4 is arranged at the top of the left and right fixed cantilevers, and winch type headstock gear 5 is fixed on the upper beam.

From a top view cross section, the fixed cantilever 6 is provided with a rectangular shell 6-7, four corners of the inner wall of the rectangular shell 6-7 are respectively provided with a fixed cantilever reinforcing rib 6-8, the reinforcing ribs are welded at right angles of steel plates at two sides, an included angle of 45 degrees is formed between the reinforcing ribs and the adjacent inner wall of the shell, two adjacent reinforcing ribs 6-8-1 and 6-8-2 and a connecting steel plate 6-8-3 between the adjacent reinforcing ribs form a concave track for restraining the movable cantilever to lift, namely, the 45-degree corner cutting part of the adjacent two reinforcing ribs relative to the movable cantilever is a concave guide rail. Each reinforcing rib is provided with an anti-friction engineering plastic gasket strip 6-9 which is contacted with the movable cantilever and is used for solving the stress support and friction requirements of the movable cantilever. The fixed cantilever has the function of bearing the movable cantilever, and particularly, the movable cantilever is installed and nested in the inner cavity of the fixed cantilever, and can move up and down in the inner cavity of the fixed cantilever. In the shutter unit groups, each group has a pair of left and right movable cantilevers 7. From the top view section, four corners of the movable cantilever 7 are matched with the shape of the fixed cantilever reinforcing rib, specifically, two adjacent corners 7-3-1 and 7-3-2 of the movable cantilever and a connecting surface 7-3-3 between the two corners form a convex guide rail 7-3 of a casing of the movable cantilever to be matched with the shape of a concave track formed by the fixed cantilever reinforcing rib and a connecting steel plate, the middle part of the opposite surface of the movable cantilever in the vertical direction is provided with a concave track groove 7-6 matched with the convex shape at the two ends of the flashboard, the concave track groove is in clearance fit with the convex bodies at the left side and the right side of the flashboard, and the convex two ends of the flashboard can be embedded in the concave track groove through the action of the concave track groove, so that the flashboard can move up and down in the track groove. Thus, the flashboard can play two roles of water blocking and water discharging. The concave track groove divides the inner cavity of the movable cantilever into two symmetrical cavities, a sealing rubber strip 13 is arranged on the radial upstream surface in the concave track groove, and the sealing rubber strip has the function of preventing excessive loss of radial inflow water and large leakage of water in the dam (allowing a small amount of leakage). The movable cantilever is nested in the fixed cantilever and can move up and down in the fixed cantilever. The center of the top of the movable cantilever is provided with a lifting screw rod 7-4, the lifting screw rod 7-4 is meshed with a lifting nut of a lifting gear box of the screw hoist, and the lifting nut is a lifting bevel nut 7-5 which is provided with a bevel gear 7-7 and a gear pad 7-8. When the lifting nut is driven by the top speed reducer to rotate forwards or reversely, the lifting screw rod is driven to move up and down, and therefore the movable cantilever is driven to move up and down. When the movable cantilever moves to the bottom, the movable cantilever can be nested and combined with an underwater steel foot anchor at the bottom (the design position of the foundation surface + -0 of the bottom of the riverbed). At this time, the upper part of the movable cantilever and the steel underwater anchor form two stressed support points facing the radial incoming water. Under the common support of a pair of movable cantilevers, the flashboard therein plays a role in water blocking (water storage) when sinking to the bottom. In dam systems, the movable cantilevers are all used in pairs. Depending on the total width of the dam, it may be designed as N sets of (pairs of) movable cantilevers. And a rectifying triangle 7-9 is welded and fixed on the upstream surface of the lower part of the movable cantilever.

The rams in the fully suspended unit group are the basic, important dam components for water retention (impoundment) or drainage. Each flashboard is a steel flashboard 8, the steel flashboard 8 is formed by welding an inner steel skeleton and an outer steel plate, namely, the inner core of the plate is a steel structure frame, and the outer part is welded with the steel plate. The left and right sides of the steel flashboard 8 are provided with convex parts 8-1 which are matched with the concave track grooves of the movable cantilevers, and the flashboard can move up and down in the concave track grooves 7-6 of the pair of movable cantilevers. When the flashboard moves to the bottom, the flashboard plays a role in water blocking (water storage). When the flashboard is lifted, the water draining function is realized. A pair of lifting pulleys 8-2 are fixed on the top of the steel flashboard, and the lifting pulleys 8-2 are used for connecting a lifting steel cable. The steel cable 5-2 of the hoist on the upper beam of the fixed cantilever is pulled down, and the flashboard moves up and down.

In a dam system, N sets of gates may be designed depending on the length of the dam. The N sets of rams function differently. The intelligent drainage valve is divided into a water storage flashboard 8-3, an intelligent drainage flashboard 8-4 and a water discharge acting flashboard 8-5. The intelligent drainage flashboard has the function of timely discharging the incoming water when the upstream incoming water is overlarge, so that the water level of the stored water is guaranteed to be rated. The intelligent is that the winch hoist receives the instruction of the existing dam intelligent control system, and the height of the flashboard is lifted or lowered. The water-discharging acting flashboard has the function that after the flashboard is lifted to a specified height and is opened, the discharged water can impact the rotor of the water turbine to rotate for acting, thereby driving the generator to generate electricity. In flood season, the power generation can be stopped, all the flashboards are lifted, and water can be discharged and downwards passed without obstruction.

The foot anchor 10 is made of steel and is made of steel plates according to technical design requirements and is arranged at a position of a datum line (surface) 12 of the positive and negative zero (+ -0) of the underwater foundation, and the foot anchor 10 comprises a steel shell 10-1 which is positioned on the datum surface of the positive and negative zero of the underwater foundation and can be correspondingly nested in a cavity of the movable cantilever, and a reinforced concrete anchor ingot 10-4 which is positioned below the datum surface of the positive and negative zero of the underwater foundation. The shell 10-1 is provided with a foot anchor mounting base 10-2 which is fixed on the reinforced concrete anchor ingot 10-4 through foot anchor mounting screw holes and foot anchor mounting bolts 10-3. Foot anchors are extremely important points of stress for dam systems. The dam system can bear the radial thrust of water storage under the combined action of the steel truss and the foot anchors. The radial thrust of the water storage is in direct proportion to the water storage height of the dam body. The design of the steel truss and the underwater steel foot anchor has thrust redundancy resistance obviously larger than the radial thrust of the water storage. The river bed and the bank slope in the area near the dam are solidified and optimized by the reinforced concrete 14 according to the design requirement, the installation foundation part of the foot anchor is positioned according to the design, the connecting embedded part 10-5 is manufactured, and the reinforced concrete anchor ingot 10-4 is fixed in the reinforced concrete 14.

The dam may be connected to an existing control system for controlling the opening and closing of the shutters.

The screw hoist 4 is composed of a motor, a reduction gear box and a screw lifting gear box, and when the motor rotates in the forward direction or the reverse direction, the movable nut is driven by the driver 7-1 to rotate in the forward direction or the reverse direction. Thereby, the screw rod can be driven to move upwards or downwards. The movable cantilever can be driven to move upwards or downwards due to the upwards or downwards movement of the screw rod.

The hoist 5 consists of a motor, a reduction gearbox, a brake, four steel cable pulleys 5-1, steel cable rollers and steel cables 5-2, and the shutter 8 can be lifted by forward rotation of the motor. The shutter 8 can be lowered by reverse rotation.

When in operation, the dam has three working states, namely a water storage state, a water discharge working state and a flood discharge drainage state: when the dam is in a water storage state, the movable cantilever is driven to move downwards by the control screw type headstock gear, the movable cantilever is connected and fixed with the underwater foot anchor in a nested manner, the gate plate is driven to move downwards to a designated position (the position of the bottom + -0 of a river bed) by the control screw type headstock gear, water storage is started, and finally the intelligent drainage gate plate is controlled to move upwards, so that the water level line is kept at a rated height; when the dam is in a flood discharge and drainage state, part or all of the shutters are controlled to move upwards to drain water. The working sequence of the movable cantilever and the flashboard is as follows: when water is stored, the movable cantilever firstly falls into position, and the flashboard falls into position; when water is drained, the flashboard firstly rises to the proper position, and the movable cantilever rises to the proper position.

In addition to the implementations described above, other implementations of the invention are possible. All technical schemes formed by equivalent substitution or equivalent transformation fall within the protection scope of the invention.

Claims (10)

1. A low head power station is with full suspension large-span dam, its characterized in that: the steel truss supporting body is arranged on a water channel, two ends of the steel truss supporting body are supported by reinforced concrete bases which are arranged on two sides of the water channel and are close to the sides, a lower chord member structural body of connecting equipment is arranged at the lower part of the steel truss supporting body, a fully-suspended flashboard unit group matched with the width of the water channel is hung at the lower part of the lower chord member structural body, each flashboard unit is formed by a fixed cantilever which is symmetrically arranged from left to right and is suspended and fixed on the lower chord member structural body at the upper end, a movable cantilever which is nested in an inner cavity of the fixed cantilever and is driven to move up and down along the inner cavity of the fixed cantilever by a screw hoist, and flashboard which is nested between the movable cantilever and is driven to move up and down along the movable cantilever by the hoist; when the movable cantilever stretches into the water, the movable cantilever is matched and nested with a foot anchor arranged at the bottom of the underwater riverbed, and the fixed cantilever, the movable cantilever and the flashboard are in a hanging state, wherein the movable cantilever and the flashboard are in a controllable dynamic hanging state.

2. The fully suspended large span dam for a low head hydroelectric power plant of claim 1, wherein: the steel truss supporting body is integrally formed by a frame-shaped truss structural body and an arched girder structural body which are made of bearing and stressed steel.

3. The fully suspended large span dam for a low head hydroelectric power plant of claim 1, wherein: the fixed cantilever is provided with a fixed cantilever structure body, each pair of fixed cantilevers is connected by an upper beam and a lower beam, the upper ends at the back of the left fixed cantilever and the right fixed cantilever are respectively connected with a rear left beam and a rear right beam which are vertical to the upper ends at the back of the fixed cantilevers, the tail ends of the rear left beam and the rear right beam are connected through the rear beam, inclined support frames are respectively fixed between the rear left beam and the rear right beam and the left fixed cantilever and between the rear right beam and the right fixed cantilever, screw type headstock gear is arranged at the top of the left fixed cantilever and the right fixed cantilever, and a winch type headstock gear is fixedly arranged on the upper beam.

4. A fully suspended large span dam for a low head hydroelectric power plant as claimed in claim 3, wherein: the fixed cantilever is provided with a rectangular shell, four corners of the inner wall of the rectangular shell are respectively provided with a reinforcing rib, 45-degree included angles are formed between the reinforcing ribs and the adjacent inner wall of the shell, two adjacent reinforcing ribs and a connecting steel plate between the adjacent reinforcing ribs form a concave track for restraining the movable cantilever to lift, and each reinforcing rib is provided with an anti-friction engineering plastic gasket strip contacted with the movable cantilever.

5. The fully suspended large span dam for low head hydroelectric power plants of claim 4, wherein: the four corners of the movable cantilever are matched with the shape of the reinforcing rib in the fixed cantilever, the middle part of the vertical direction of the opposite surfaces of the pair of movable cantilevers in the flashboard unit is provided with concave track grooves matched with the shapes of two ends of the flashboard, the inner cavity of the movable cantilever is divided into two symmetrical cavities by the concave track grooves, a sealing rubber strip is arranged on the radial upstream surface in the concave track grooves, a lifting screw is fixed at the center of the top of the movable cantilever, the lifting screw is meshed with a lifting nut of the screw type headstock gear, and a rectifying triangle is fixed on the upstream surface of the lower part of the movable cantilever.

6. The fully suspended large span dam for a low head hydroelectric power plant of claim 1, wherein: the flashboard in the fully-suspended flashboard unit group can be divided into an intelligent drainage flashboard, a water storage flashboard and a water discharge acting flashboard according to functions, and the water discharge acting flashboard is matched with a corresponding water turbine; each flashboard is a steel flashboard, the steel flashboard is formed by welding an internal steel skeleton and an external steel plate, the left side and the right side of the steel flashboard are provided with convex shape parts matched with the concave track grooves of the movable cantilever in shape, 2 lifting pulleys are fixed at the top of the steel flashboard, and the lifting pulleys are connected with a steel cable of the winch hoist.

7. The fully suspended large span dam for a low head hydroelectric power plant of claim 1, wherein: the foot anchor is made of steel and is arranged on the positive and negative zero reference surface of the underwater foundation and is determined by technical design, and the foot anchor comprises a steel shell which is positioned on the positive and negative zero reference surface of the underwater foundation and is correspondingly nested in a cavity of the movable cantilever, and a reinforced concrete anchor ingot which is positioned below the positive and negative zero reference surface of the underwater foundation.

8. A fully suspended large span dam for a low head hydroelectric power plant as claimed in claim 3, wherein: the screw hoist consists of a motor, a reduction gear box and a screw lifting gear box; the winch hoist consists of a motor, a reduction gearbox, a brake disc, a steel cable roller and a steel cable.

9. The use of a fully suspended large span dam for a low head hydroelectric power plant according to claim 1, wherein: the dam comprises three working states, namely a water storage state, a water drainage working state and a flood drainage state, when the dam is in the water storage state, the screw type headstock gear drives the movable cantilever to move downwards, the movable cantilever is connected and fixed with a foot anchor nest of a reference surface of an underwater river bed, the winch type headstock gear drives the flashboard to move downwards to the bottom position of the river bed, water storage is started, the intelligent drainage flashboard can move upwards to drain water, and a water storage water level line is kept at a rated height; when the dam is in a flood discharge and drainage state, part or all of the shutters move upwards to drain water.

10. The use of a fully suspended large span dam for a low head hydroelectric power plant according to claim 9, wherein: the river bed and the bank slope in the area near the dam are solidified and optimized by reinforced concrete according to the design requirement, the placement of the foot anchors is positioned according to the design, and the connecting embedded part is manufactured, wherein the embedded part is a reinforced concrete anchor ingot.