Coupling hydroelectric power station with spiral pile body and pile body bearing capacity simulation calculation method

Abstract

The invention discloses a coupled hydroelectric power station with a spiral pile body and a pile body bearing capacity simulation calculation method. The coupling hydroelectric power station comprises a pumped storage power station, the pumped storage power station comprises an upper reservoir and a lower reservoir, the upper reservoir and the lower reservoir are communicated through a water conveying pipe, at least one buoyancy energy storage device is installed at the bottom of the upper reservoir or the lower reservoir, and each buoyancy energy storage device comprises a fixed platform, a buoyancy generator and a floating object. The fixed platform is fixed to the bottom of a reservoir, the buoyancy generator provides floating objects and provides buoyancy, the buoyancy generator is fixed to the fixed platform, the fixed platform is fixed to the bottom of the reservoir through a spiral structure, and the spiral structure comprises a pile body and blades integrally formed with the pile body. The operation stability and the operation efficiency of the hydroelectric power station are improved, and the method has guiding significance for construction and actual use of the hydroelectric power station.

Description

Technical Field

[0001] The invention relates to the technical field of hydropower station buildings, in particular to a coupled hydropower station with spiral piles and a simulation calculation method for pile bearing capacity. Background Art

[0002] Pumped storage power stations are widely used in my country to regulate loads, balance supply and demand, provide grid stability, and achieve efficient integration of renewable energy in power systems.

[0003] Buoyant energy storage power station is a new energy storage technology that uses the buoyancy effect of water to store and release energy. Its cost is about 350-700 yuan / MWh lower than the current chemical battery cost.

[0004] Traditional buoyancy energy storage technology consumes a large amount of electricity to overcome the buoyancy of floating objects in water and pull the floating objects down from the highest point to the lowest point. In addition, traditional buoyancy energy storage devices often lose their function due to the loosening or detachment of the fixed structure of the floating objects.

[0005] To address the above-mentioned issues, the present invention combines conventional hydropower stations with pumped-storage power stations, utilizing the same upper and lower reservoirs as conventional hydropower stations. This coupling of the pumped-storage power station and the floating process of the buoyant energy storage power station allows the buoyant power station to store energy with almost no energy consumption, thereby improving the power generation efficiency of the power station. Furthermore, the structure of the buoyant energy storage device is optimized, and a calculation method for designing the anchoring structure is proposed to ensure the safe operation of the system. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a coupled hydroelectric power station with spiral piles and a simulation calculation method for the pile bearing capacity.

[0007] In order to achieve the above-mentioned purpose, one of the technical solutions adopted by the present invention is: providing a coupled hydropower station with a spiral pile body, including a pumped storage power station, the pumped storage power station includes an upper reservoir and a lower reservoir, the upper reservoir and the lower reservoir are connected by a water pipe, at least one buoyancy energy storage device is installed at the bottom of the upper reservoir or the lower reservoir, the buoyancy energy storage device includes a fixed platform, a buoyancy generator and a floating object, the fixed platform is fixed to the bottom of the reservoir, the buoyancy generator provides buoyancy to the floating object, the buoyancy generator is fixed to the fixed platform, the fixed platform is fixed to the bottom of the reservoir using a spiral structure, and the spiral structure includes a pile body and blades integrally formed with the pile body.

[0008] Furthermore, the output shaft of the buoyancy generator is connected to a reel, and a rope on the reel is connected to a floating object through a pulley.

[0009] Furthermore, the fixed platform is formed by pouring concrete.

[0010] Furthermore, the float is made of high-density polyethylene material.

[0011] Furthermore, when there are multiple buoyancy energy storage devices, the buoyancy generators are connected by cables and connected to the power grid system.

[0012] The second technical solution adopted by the present invention is: to provide a pile bearing capacity simulation calculation method, which is aimed at calculating the bearing capacity Fs of the spiral pile body described in any of the above items, and adopts the discrete element numerical simulation method to simulate the rotary drilling process of the spiral pile body. After the pile body is drilled into place, an upward buoyancy load is applied to the pile body, and the displacement-load curve of the pile body is calculated, and the peak value of the curve is taken as the ultimate tensile pull-out force (qt) of the pile body.

[0013] Furthermore, the method is specifically as follows: first, a cylindrical soil body is generated by stacking discrete units, and the corresponding material parameters of the soil body are assigned, including Young's modulus, Poisson's ratio, tensile strength, compressive strength, internal friction coefficient, and density. A spiral pile body is generated according to the pre-designed parameters, and then the spiral pile body is rotated and drilled into the soil body, and a vertical upward displacement load is applied to the spiral pile body step by step to simulate the buoyancy of floating objects, and the tensile pull-out force applied to the pile body is monitored. Finally, a displacement-tensile pull-out force curve is drawn, and the peak value of the curve is taken as the ultimate tensile pull-out force.

[0014] Furthermore, the bearing capacity Fs of the spiral pile is calculated based on the ratio of the ultimate tensile strength (qt) of the pile to the maximum buoyancy (qb) of the floating object, and the bearing capacity Fs needs to satisfy Fs>2.

[0015] The present invention adopts the above technical solution to improve the operational stability and efficiency of the hydroelectric power station, and has guiding significance for the construction and actual use of the hydroelectric power station. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art and the beneficial effects of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other structures can be obtained based on the structures shown in these drawings without paying any creative work.

[0017] Figure 1 The overall schematic diagram of the embodiment of the present invention is shown.

[0018] Figure 2 A schematic diagram of a buoyancy energy storage device is shown.

[0019] Figure 3A schematic diagram of the helical structure is shown.

[0020] Figure 4 A flow chart of an operating method according to an embodiment of the present invention is shown.

[0021] Figure 5 The flowchart of the numerical simulation method for calculating the ultimate resistance in the embodiment of the present invention is shown. Figure 5 a is a cylindrical soil body generated by stacking discrete units. Figure 5 b is the pre-designed parameters to generate the screw pile structure. Figure 5 c is a schematic diagram of the screw pile rotating into the soil structure. Figure 5 c is a schematic diagram of the structure of the screw pile rotating into the soil. Figure 5 d is the cross-sectional view of the screw pile rotating into the soil.

[0022] Figure 6 The diagram illustrates a process diagram of simulating pile rotary drilling using a numerical simulation method according to an embodiment of the present invention.

[0023] Figure 7 The figure shows the result of calculating the ultimate resistance using the numerical simulation method according to the embodiment of the present invention.

[0024] Figure 8 The embodiment of the present invention illustrates the pile displacement-tensile force curve for calculating the ultimate resistance using the numerical simulation method. DETAILED DESCRIPTION

[0025] Specific embodiments of the present invention:

[0026] like Figure 1 As shown, a coupled hydropower station with a spiral pile body in this embodiment includes a pumped storage power station. After the pumped storage system is built, it is assumed that the upper reservoir 4 is at the lowest water level and the lower reservoir 5 is at the highest water level.

[0027] The upper reservoir bottom surface is leveled and piles 31 are driven in. Parameters such as pile length, pile diameter, and number of blades can be selected based on the geological conditions of the foundation's bearing layer, but must meet the buoyancy required to support floating objects. Refer to Example 2 for pile bearing capacity verification.

[0028] An anchoring platform 32 is cast on top of the pile body, and the connection between the platform and the pile body must be firm.

[0029] The pulley 33, the reel 34 and the buoyancy generator 35 are sequentially installed on the anchoring platform. The connection between the three and the anchoring platform must be firm, especially the pulley must be able to support the buoyancy of the floating object.

[0030] Installing the float: Float 36 can be made of high-density polyethylene, and rope 37 can be made of polyester. One end of the rope is connected to the bottom of the float, passed through a pulley, and wound around a reel. The other end is secured to the reel. The reel should have a self-locking function to secure the float at the highest potential energy point (the reservoir bottom).

[0031] Multiple buoyant energy storage devices can be installed at the bottom of each reservoir, and the generators of each device are connected by cables 8, and finally the cables are connected to the power grid system 2.

[0032] When the buoyancy energy storage system of the upper reservoir is installed, the grid supplies power to the water pump 7 to pump water from the lower reservoir to the upper reservoir, and the above steps are repeated to install the buoyancy energy storage system at the bottom of the lower reservoir.

[0033] The operation process of the embodiment of the present invention includes the following two processes:

[0034] Process 1: Energy storage system generates electricity

[0035] When the power generation of the new energy system 1 does not meet the electricity demand, the energy storage system starts to operate to generate electricity.

[0036] Release the floating objects in the upper reservoir. As the floating objects rise, the rope drives the reel to rotate, and the reel drives the buoyancy generator to generate electricity.

[0037] After all floating objects rise to the highest point, the sluice gate 10 is opened, and the water in the upper reservoir flows to the lower reservoir through the pipeline under the action of gravity potential energy, while driving the hydro-generator 6 to generate electricity.

[0038] When the water level of the lower reservoir rises to the highest point, the floating objects in the lower reservoir are released, and the buoyancy generator in the lower reservoir generates electricity. At the same time, a small amount of electricity is used to drive the reel in the upper reservoir to rotate, thereby tightening the rope connected to the floating objects and fixing the floating objects.

[0039] The electricity generated by the buoyancy energy storage system and pumped storage system of the upper and lower reservoirs will be transmitted to the power grid.

[0040] Process 2: Energy storage system

[0041] When the new energy system generates excess electricity, the energy storage system starts to operate and store energy.

[0042] The grid supplies power to the water pump, which pumps water from the lower reservoir to the upper reservoir.

[0043] When the water level of the lower reservoir reaches the lowest point, the sluice gate 10 is closed, and a small amount of electricity is used to drive the reel of the lower reservoir to rotate to tighten the rope connected to the floating object and fix the floating object.

[0044] The bearing capacity of the pile in the spiral structure of this embodiment is verified.

[0045] Pile body parameters ( Figure 3 ) Generally, the pile diameter D1, pile length L, spiral blade height H1, blade spacing H2, blade thickness T, and blade projected diameter D2 must be determined. Assuming only one pile per buoyant generator set, the values of these parameters must be determined based on the tension exerted on the pile (i.e., the buoyancy of floating objects) to ensure safe and cost-effective operation of the generator set.

[0046] Generally speaking, according to the Technical Specification for Design and Construction of Highway Steel Pipe Piles (DB41 / T 2125-2021) (hereinafter referred to as the "Specifications"), the safety factor of the pile should be no less than 2.0. The safety factor is the ratio of the ultimate tensile strength of the pile (qt) to the maximum buoyancy of the floating object (qb):

[0047] F s =q t / q b (1)

[0048] The "Specifications" stipulate that the failure forms of piles are divided into two types: single-layer blades and multi-layer blades. The corresponding tensile strength calculation is based on the ratio of the burial depth Z (here is the pile length L) and the blade outer diameter projection D2.

[0049] When Z / D2<6, the cylindrical shear mode is used to calculate the ultimate pull-out bearing capacity of a single pile:

[0050] q t =w+f1+f2 (2)

[0051] Where w is the deadweight of the pile; f1 is the frictional resistance between the piles (kN). As the pile drills into the soil, the blades will disturb the surrounding soil, causing it to become loose. This frictional resistance is very small and can often be ignored in the calculation; f2 is the frictional resistance between the soil column between the blades and the surrounding soil (kN), which is calculated according to formula (3):

[0052] f2=D2(m-1)πH2C u (3)

[0053] When Z / D2≥6, the single-blade support mode is used to calculate the ultimate pull-out bearing capacity of a single pile:

[0054]

[0055] fj is the load shared by each layer of leaves, which is related to the soil quality. When the foundation is clay:

[0056]

[0057] In the above formulas, m is the number of spiral blades; Nc is the bearing capacity factor of the foundation, generally 6 to 9; Cu is the consolidated undrained shear strength of the soil, which varies greatly for different soil types and needs to be determined based on triaxial consolidated undrained tests.

[0058] The buoyancy of a floating object in water is:

[0059] q b =ρ w gV (6)

[0060] Where ρw is the density of water, which is 1000 kg / m 3 , g is the acceleration due to gravity, and V is the volume of the floating object.

[0061] Conventional standard calculation methods are limited by the scope of application and assumptions of the formulas, and are often not very adaptable. In particular, they cannot take into account the disturbance of the soil around the pile during the drilling process. Often, during the process of rotating and drilling, the spiral blades will shear and disturb the soil around the pile, causing the strength of the soil around the pile to be lost. Therefore, the ultimate tensile strength calculated by the standard method will be too large, and the design will be relatively unsafe. In this regard, the present invention also provides a numerical simulation method suitable for more complex working conditions. This method is a secondary development based on the matrix discrete element software MatDEM, which takes into account the actual drilling process of the pile. The specific calculation process is: first, discrete units are stacked to generate a cylindrical soil body (such as Figure 5 a), and assign the corresponding material parameters of the soil, including Young's modulus, Poisson's ratio, tensile strength, compressive strength, internal friction coefficient, and density; then generate the screw pile structure according to the pre-designed parameters (such as Figure 5 b); then the screw pile is rotated and drilled into the soil (such as Figure 5 c, cross section Figure 5 d, rotary drilling process see Figure 6 ); further, vertical upward displacement loads were applied to the screw pile step by step to simulate the buoyancy of floating objects and the tensile strength of the pile body was monitored ( Figure 7 ); finally draw the displacement-tensile force curve (such as Figure 8 ), and the peak value of the curve is taken as the ultimate tensile strength.

[0062] Calculation example of ultimate tensile strength: First, assume that the pile diameter D1 = 0.06m, the pile length L = 2m, the spiral blade height H1 = 0.1m, the blade spacing H2 = 0.7m, the blade thickness T = 0.01m, the blade projected diameter D2 = 0.25m, and the floating object volume V = 2m 3, calculate the number of spiral blades m = 1, 2, 3 respectively. The parameters of foundation soil generally need to be determined through experiments. Here, the Young's modulus, Poisson's ratio, tensile strength, compressive strength, internal friction coefficient, and density of the soil are assumed to be 7MPa, 0.18, 50kPa, 50kPa, 0.6, and 2500kg\m respectively. 3 .

[0063] According to the above parameters, the ultimate tensile strength qt of the pile is calculated to be 27, 51, and 54 kN when the number of spiral blades m = 1, 2, and 3, respectively. The buoyancy qb of the floating object in the water is 20 kN, so the safety factors Fs are 1.35, 2.55, and 2.70, respectively, indicating that the two spiral blades can fully meet the safety requirements.

[0064] The core steps of the above-mentioned simulation calculation of the bearing capacity of the screw pile are as follows:

[0065] 1) Generate soil ( Figure 5 a):

[0066] First, define the length, width, and height of the model box. These dimensions must be determined based on the diameter of the screw piles. Ensure that the distance from each boundary to the center of the model box is greater than four times the pile diameter to eliminate boundary effects.

[0067] The soil model is generated by the sand-rain method, and the soil particles are randomly distributed in the simulation area to simulate the heterogeneity of natural soil. The particles are allowed to accumulate freely under the action of gravity to simulate the stratum conditions of gravity deposition.

[0068] 2) Generate spiral pile body according to the designed pile body parameters ( Figure 5 b):

[0069] In the present invention, the pile body is formed by a series of particles arranged and combined in a regular manner.

[0070] First, the dimensions of the pile body need to be defined, including the pile diameter D1, pile length L, spiral blade height H1, blade spacing H2, blade thickness T, blade projection diameter D2, blade number m, and pile particle radius r.

[0071] Then, based on the above parameters, the pile body, spiral blades and bottom cone are generated respectively, and finally these three parts are combined together to form the following Figure 5 b Complete screw pile.

[0072] 3) Set up materials:

[0073] Set the material parameters of soil and pile, including Young's modulus, internal friction angle, tensile strength, compressive strength, Poisson's ratio, and density.

[0074] 4) Drill the screw pile into the soil ( Figure 6 ):

[0075] Define the penetration step parameters of the pile, that is, the distance the pile moves in each time differential step, including the rotation step and the downward movement step.

[0076] Each step rotates a fixed angle (e.g. 1°) while the pile body moves downward, simulating the spiral motion of the drill bit.

[0077] The equilibrium algorithm is called after each displacement to ensure the redistribution of soil stress and avoid numerical divergence.

[0078] The equilibrium iteration algorithm is based on Newton's second law of motion. It calculates the position, velocity and other information of the unit after a differential time step according to the force conditions of the unit at the current time.

[0079] 5) Apply pull-out load and calculate the pull-out force ( Figure 7 and Figure 8 ):

[0080] Define the displacement increment, which is the distance the pile moves upward at each time differential step.

[0081] Gradually load and apply small upward displacements multiple times to simulate the slow effect of buoyancy on the pile (such as Figure 7 shown).

[0082] Extract the stress and calculate the normal force and shear force at the pile-soil contact surface. The sum is the instantaneous tensile strength.

[0083] Draw a curve and determine the peak value through the displacement-tensile pull-out force curve as the ultimate bearing capacity of the pile (such as Figure 8 shown).

[0084] Calculation example of ultimate tensile strength: First, assume that the pile diameter D1 = 0.06m, the pile length L = 2m, the spiral blade height H1 = 0.1m, the blade spacing H2 = 0.7m, the blade thickness T = 0.01m, the blade projected diameter D2 = 0.25m, and the floating object volume V = 2m 3 , calculate the number of spiral blades m = 1, 2, 3 respectively. The parameters of foundation soil generally need to be determined through experiments. Here, the Young's modulus, Poisson's ratio, tensile strength, compressive strength, internal friction coefficient, and density of the soil are assumed to be 7MPa, 0.18, 50kPa, 50kPa, 0.6, and 2500kg\m respectively. 3 .

[0085] According to the above method, the ultimate tensile strength qt of the pile body is calculated to be 27, 51, and 54 kN when the number of spiral blades m = 1, 2, and 3, respectively. The buoyancy qb of the floating object in the water is 20 kN, so the safety factor Fs is 1.35, 2.55, and 2.70, respectively, indicating that the two spiral blades can fully meet the safety requirements.

[0086] The present invention improves the buoyancy energy storage device, ensuring the stability of the float during operation. Combining the characteristics of pumped storage and buoyancy storage, the present invention retracts and releases the buoyancy energy storage float according to the change in the pumped storage water level. When the reservoir water level drops to the lowest point, only a very small amount of electricity is required to pull the float down and secure it to the highest potential energy point (the bottom of the reservoir), thereby improving the efficiency and stable operation of the pumped storage system as a whole. The pile bearing capacity simulation calculation method provided by the present invention takes into account the actual pile drilling process and is applicable to more complex working conditions. The bearing capacity results obtained through simulation calculation are more reliable, ensuring the safe operation of the coupled hydroelectric power station.

[0087] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A coupled hydroelectric power station with a spiral pile, characterized in that: It includes a pumped storage power station, which includes an upper reservoir and a lower reservoir. The upper reservoir and the lower reservoir are connected by a water pipe. At least one buoyancy energy storage device is installed at the bottom of the upper reservoir or the lower reservoir. The buoyancy energy storage device includes a fixed platform, a buoyancy generator and a floating object. The fixed platform is fixed to the bottom of the reservoir. The buoyancy generator provides buoyancy to the floating object. The buoyancy generator is fixed to the fixed platform. The fixed platform is fixed to the bottom of the reservoir using a spiral structure. The spiral structure includes a pile body and blades integrally formed with the pile body.

2. The coupled hydroelectric power station with screw piles according to claim 1, characterized in that: The output shaft of the buoyancy generator is connected to a reel, and a rope on the reel is connected to a floating object through a pulley.

3. The coupled hydroelectric power station with screw piles according to claim 2, characterized in that: The fixed platform is formed by pouring concrete.

4. The coupled hydroelectric power station with screw piles according to claim 3, characterized in that: The float is made of high-density polyethylene material.

5. The coupled hydroelectric power station with screw piles according to claim 4, characterized in that: When there are multiple buoyancy energy storage devices, the buoyancy generators are connected by cables and connected to the power grid system.

6. A method for simulating and calculating pile bearing capacity, characterized in that: This method is aimed at calculating the bearing capacity of the spiral structure described in any one of claims 1 to 5, and adopts the discrete element numerical simulation method to simulate the rotary drilling process of the spiral structure. After the pile body is drilled into place, an upward buoyancy load is applied to the pile body, and the displacement-load curve of the pile body is calculated. The peak value of the curve is taken as the ultimate tensile strength of the pile body.

7. The pile bearing capacity simulation calculation method according to claim 6, characterized in that: The specific method is as follows: first, a cylindrical soil body is generated by stacking discrete units, and the corresponding material parameters of the soil body are assigned, including Young's modulus, Poisson's ratio, tensile strength, compressive strength, internal friction coefficient, and density. A spiral pile structure is generated according to the pre-designed parameters, and then the pile body is rotated and drilled into the soil. Vertical upward displacement loads are applied to the pile body step by step to simulate the buoyancy of floating objects, and the tensile pull-out force applied to the pile body is monitored. Finally, a displacement-tensile pull-out force curve is drawn, and the peak value of the curve is taken as the ultimate tensile pull-out force.

8. The pile bearing capacity simulation calculation method according to claim 7, characterized in that: The bearing capacity of the spiral structure is calculated based on the ratio of the ultimate tensile strength of the pile to the maximum buoyancy of the floating object, and the bearing capacity must meet the condition of being greater than 2.

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