Method for evaluating feasibility of hydropower station construction adit for compressed air energy storage underground cavern

Abstract

The invention mainly relates to the technical field of energy underground storage, and provides a feasibility evaluation method for applying a hydropower station construction adit to a compressed air energy storage underground cavern, and the core of the method is as follows: obtaining adit engineering geological conditions, hydrogeological conditions, shape and size parameters and mechanical property parameters of adit surrounding rock; establishing a three-dimensional numerical model of the compressed air energy storage cavern; according to the method, the boundary and the fixed constraint condition of the three-dimensional numerical model analysis of the gas energy storage cavern are set, the evaluation index is selected, the feasibility of the adit used for the compressed gas energy storage underground cavern under the target operation pressure is evaluated based on the selected evaluation index, and the feasibility of the hydropower station construction adit used as the compressed gas energy storage cavern can be rapidly and conveniently analyzed. And guidance is provided for actual engineering construction.

Description

TECHNICAL FIELD

[0001] The present application mainly relates to the technical field of underground energy storage, in particular to a feasibility evaluation method of a water power station construction adit for a compressed air energy storage underground cavern. BACKGROUND

[0002] The construction of a water power station will excavate many auxiliary facilities such as construction adits, some of which have good surrounding rock conditions, deep burial depth, and are close to the power grid access point, and after being abandoned after construction, there is still a large possibility of being reused. As a clean, environmentally friendly and large-scale energy storage technology, compressed air energy storage can use the water power station construction adit as a storage space for high-pressure air, store high-pressure air, reduce the construction cost of the compressed air energy storage power station, and realize the secondary utilization of the water power station construction adit.

[0003] The high-pressure air stored in the compressed air energy storage cavern is generally 10 MPa or above, and under long-term operating conditions, the inner wall of the cavern needs to withstand the cyclic action of high-pressure gas, so it is a prerequisite for building a compressed air energy storage cavern to maintain the feasibility of the water power station construction adit under the action of high-pressure gas. Reasonably evaluating the geological conditions, hydrological conditions, and mechanical property parameters of the surrounding rock that affect the feasibility of the water power station construction adit to determine whether the water power station construction adit under different geological conditions can withstand the action of high-pressure gas is an important basis for ensuring its safe operation. Therefore, reasonably evaluating the feasibility of the water power station construction adit under the action of high-pressure gas is of great significance to the construction of the compressed air energy storage cavern. SUMMARY

[0004] The technical problem to be solved by the present application is to evaluate the feasibility of using a water power station construction adit as a compressed air energy storage underground cavern.

[0005] The technical solution adopted by the present application to solve the above technical problem is: The present application provides a feasibility evaluation method of a water power station construction adit for a compressed air energy storage underground cavern, which comprises the following steps: obtaining the engineering geological conditions, hydrogeological conditions, shape and size parameters, and mechanical property parameters of the surrounding rock of the adit, and establishing a three-dimensional numerical model of the compressed air energy storage cavern; setting the boundary and fixed constraint conditions for the analysis of the three-dimensional numerical model of the compressed air energy storage cavern, selecting evaluation indexes, and evaluating the feasibility of the adit for the compressed air energy storage underground cavern under the set operating pressure based on the selected evaluation indexes.

[0006] Further, the setting of the boundary and fixed constraint conditions for the analysis of the three-dimensional numerical model of the compressed air energy storage cavern comprises: applying vertical stress on the upper part of the three-dimensional numerical model of the compressed air energy storage cavern according to the adit stress parameters and the set operating pressure of the cavern, applying horizontal stress on the front, rear, left and right four sides, and applying fixed constraint on the bottom.

[0007] Further, the engineering geological conditions include fault type, size, number of surrounding rock, type, number, length of extension of fold area, and the hydrogeological conditions include distribution characteristics of underground water of adit and water inflow condition of adit.

[0008] Further, the geostress parameters include distribution characteristics, size and gradient of geostress.

[0009] Further, the evaluation indexes include whether the stress, displacement, strain and plastic zone of the surrounding rock of the adit are within the set range.

[0010] The beneficial effects of the present application are that the engineering geological conditions, hydrogeological conditions, shape and size parameters and mechanical property parameters of the surrounding rock of the adit are used to establish a three-dimensional numerical model of the compressed gas energy storage cavern, the evaluation indexes are selected, and the three-dimensional numerical model of the compressed gas energy storage cavern is subjected to numerical analysis, so that the feasibility of the construction adit of the hydropower station as the compressed gas energy storage cavern can be quickly and conveniently analyzed, thereby guiding the actual engineering construction. DETAILED DESCRIPTION

[0011] The feasibility evaluation method of the construction adit of the hydropower station for the compressed gas energy storage cavern comprises the following steps: Step S1: obtaining the engineering geological conditions, hydrogeological conditions, shape and size parameters and mechanical property parameters of the surrounding rock of the adit.

[0012] According to the engineering geological survey report of the hydropower station, the engineering geological conditions of the construction adit of the hydropower station are obtained, including fault type, size, number, type, number and length of extension of fold, and the hydrogeological conditions include distribution characteristics of underground water and water inflow condition of the adit. The surrounding rock grade is determined according to the design data of the construction adit of the hydropower station, and the mechanical property parameters of the surrounding rock are determined according to the relevant regulations according to the surrounding rock grade, so as to provide the mechanical property parameters for the establishment of the numerical model of the compressed gas energy storage cavern of the construction adit of the hydropower station. The cross section drawing, profile drawing and plan drawing of the construction adit of the hydropower station are collected, the shape, height, width and length of the adit are obtained, and the space volume is calculated, so as to provide the geometric conditions for the establishment of the numerical model of the compressed gas energy storage cavern of the construction adit of the hydropower station.

[0013] Step S2: according to the small-scale hydraulic fracturing field test carried out by the hydropower station, the size, distribution characteristics and gradient of the surrounding rock geostress are tested and obtained, so as to provide the boundary conditions for the establishment of the numerical model of the compressed gas energy storage cavern of the construction adit of the hydropower station.

[0014] Step S3: Based on the adit engineering geological conditions, hydrogeological conditions, shape and size parameters and mechanical properties of the adit surrounding rock obtained in step 1, a three-dimensional numerical model of the water conservancy construction adit pressure gas storage cavern is established. According to the stress parameters of the adit surrounding rock and the operation pressure of the cavern, the corresponding boundary conditions are applied to the numerical model. The vertical stress is applied to the upper part of the model, the horizontal stress is applied to the front and rear sides and the left and right sides of the model, and the fixed constraint is applied to the bottom of the model. The operating internal pressure is applied to the inner wall of the water conservancy construction adit. The grid size, grid quality and convergence of the calculation results are checked, and the stress, displacement, strain and plastic zone of the water conservancy construction adit surrounding rock under the action of high internal pressure are calculated to determine the suitable range of key evaluation parameters of the water conservancy construction adit for pressure gas storage cavern.

[0015] Specifically, the strength of the surrounding rock is evaluated using the Hoek-Brown or Mohr-Coulomb strength criterion. The maximum principal stress in local areas should not exceed the strength limit of the surrounding rock, otherwise there may be a risk of local damage or overall instability. The displacement of the surrounding rock is the main indicator of deformation response, and "continuous growth of displacement" and "accelerated deformation trend" in the monitoring data should be considered as early warning signals for possible instability of the surrounding rock. In actual engineering, time series analysis of data such as arch settlement and side wall convergence should be combined to dynamically determine the stability of the surrounding rock. Strain is an important parameter for determining shear zones, unloading fractures and potential instability zones, and should be combined with numerical simulation results to focus on the evolution process of strain concentration zones. Regarding the development of plastic zones, if the plastic zone expands to the boundary of the surrounding rock or forms a weak belt structure that is interconnected with adjacent caverns, great attention should be paid to the risk of overall instability.

[0016] According to the above criteria, the feasibility of using the water conservancy construction adit for pressure gas storage cavern is evaluated, so that a suitable water conservancy construction adit can be selected as a pressure gas storage cavern according to the method.

[0017] Embodiment: To verify the feasibility evaluation method of using the water conservancy construction adit for pressure gas storage cavern proposed in the present application, a typical construction adit of a certain under-construction hydropower station in the southwest region is selected as an engineering example. The exposed strata in the construction adit engineering area are mainly Triassic (Xikang group) and Quaternary, with a burial depth of about 580 m, a total length of about 420 m, a circular cross-section structure with a diameter of 10 m, and no permanent lining after construction. The surrounding rock is classified as III1, and the rock mass integrity is good. According to the geological survey results, there are no faults or large-scale fracture zones crossing the adit in this area, the joint structure is less developed, the groundwater type is fissure water, and the rock mass has good density and sealing property, which meets the conditions for compressed air energy storage conversion.

[0018] The in-situ stress test results obtained by hydraulic fracturing method show that the maximum principal stress of surrounding rock is σ1=23.94 Mpa, azimuth angle ɑ=68.6°, inclination angle β=6.1°, the minimum principal stress is σ3=5.73 Mpa, azimuth angle ɑ=32.5°, inclination angle β=-37.3°. The maximum principal stress in the in-situ stress test results is greater than 20 Mpa, and much greater than the minimum principal stress, which indicates that the rock mass may be in a high in-situ stress environment. Combined with the survey and test data, the mechanical parameters of surrounding rock are determined as follows: elastic modulus 6 GPa, Poisson's ratio 0.3, uniaxial compressive strength 95 MPa, cohesion 0.7 MPa, internal friction angle 34°, and the Mohr-Coulomb constitutive model is used for modeling analysis. According to the engineering geological conditions, hydrogeological conditions, shape and size parameters of the adit, and the mechanical property parameters of the adit surrounding rock, a three-dimensional numerical model is established on the FLAC3D platform. The adit is applied with a running pressure of 10 MPa, the external boundary is loaded with the in-situ stress value, the model bottom is fixed, and the rest of the boundary is allowed to diffuse displacement. According to the modeling conditions, the grid quality inspection and convergence analysis of the model are carried out, which meets the requirements of the feasibility of the compressed gas energy storage cavern under the running pressure of 10 MPa.

Claims

1. A method for evaluating the feasibility of using a water power plant construction adit for a compressed air energy storage underground cavern, characterized in that, The method comprises: obtaining the geological conditions, hydrogeological conditions, shape and size parameters and mechanical property parameters of surrounding rock of the flat adit, and establishing a three-dimensional numerical model of the compressed air energy storage cavern; setting the boundary and fixed constraint condition of the three-dimensional numerical model analysis of the compressed air energy storage cavern, selecting an evaluation index, and evaluating the feasibility of the flat adit for the compressed air energy storage underground cavern under the set operating pressure based on the selected evaluation index.

2. The feasibility evaluation method of the water power station construction adit for compressed air energy storage underground caverns according to claim 1, characterized in that, The setting of the boundary and fixed constraint condition of the three-dimensional numerical model analysis of the compressed air energy storage cavern comprises: applying vertical stress on the upper part of the three-dimensional numerical model of the compressed air energy storage cavern according to the in-situ stress parameters and the set operating pressure of the cavern, applying horizontal stress on the front, rear, left and right four sides, and applying fixed constraint on the bottom.

3. The feasibility evaluation method of the water power station construction adit for compressed air energy storage underground caverns according to claim 1, characterized in that, The engineering geological conditions include the type, size and quantity of faults of surrounding rock, the type, quantity and extension length of fold regions, and the hydrogeological conditions include the distribution characteristics of underground water of the flat adit and the water inflow condition of the flat adit.

4. The feasibility evaluation method of the water power station construction adit for the compressed air energy storage underground cavern according to claim 2, characterized in that, The in-situ stress parameters include the distribution characteristics, size and gradient of in-situ stress.

5. The feasibility evaluation method of the water power station construction adit for compressed air energy storage underground caverns according to claim 1, characterized in that, The evaluation index includes whether the stress, displacement, strain and plastic zone of the surrounding rock of the flat adit are within the set range.