Method for determining the axis of a high internal pressure chamber

Abstract

The application discloses a high internal pressure chamber axis determination method, and takes the direction of the minimum horizontal principal stress in the ground stress as a reference standard, and determines the direction of the longitudinal axis of the high internal pressure chamber as a direction which is not more than 25 degrees with the direction of the minimum horizontal principal stress and is maximally close to the strike of the main structure surface of the rock mass, according to the direction of the longitudinal axis of the high internal pressure chamber, the direction of the long axis on the cross section of the high internal pressure chamber should be consistent with the direction of the minimum ground stress. The application provides an effective method for determining the axis of the high internal pressure chamber such as compressed air energy storage, the method can maximize the surrounding rock pressure on the cross section of the chamber, fully utilizes the surrounding rock pressure in the stratum to balance the air pressure in the gas storage chamber, and is more favorable for the stability of the chamber structure; the method can reduce the opening degree of the structure surface in the surrounding rock as much as possible, and is more favorable for the sealing of the high internal pressure gas storage chamber.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of underground energy storage technology for realizing the double targets of "carbon peak and carbon neutral", and in particular relates to a high internal pressure cavern axis determination method, which is suitable for compressed air energy storage caverns and also suitable for CO2, natural gas, hydrogen and other high-pressure gas storage caverns and other application scenarios. BACKGROUND

[0002] The primary measure to achieve the carbon peak target is to reduce the use of fossil energy and increase the use of green renewable energy such as wind power and photovoltaic power. Although these green renewable energies such as wind power and photovoltaic power are more environmentally friendly than traditional fossil energy, they have the characteristics of intermittency and volatility, which leads to relatively insufficient stability and continuity of power generation. To solve the above problems, large-scale energy storage technology needs to be used, and compressed air energy storage is a large-scale energy storage technology with good promotion prospects.

[0003] The large-scale application of compressed air energy storage technology requires a large enough gas storage space. Among them, the hard rock cavern excavated by artificial excavation has the advantages of flexible site selection and strong geological adaptability, and is an important choice for the storage space of compressed air energy storage technology. Cavern excavation involves the problem of cavern axis direction selection. For general caverns without high internal pressure, the main control condition is the condition when the cavern construction is completed. In order to fully exert the self-stability of the surrounding rock and reduce the support, the longitudinal axis of the cavern is generally arranged along the direction with a small angle to the direction of the maximum horizontal principal stress. For example, in the 7.1.3 clause 2 of the "Hydropower Station Design Specification NB / T35011-2013", it is suggested that the longitudinal axis of the cavern should be arranged along the direction with a small angle to the horizontal projection direction of the maximum principal stress (the horizontal projection direction of the maximum principal stress in the project is generally the direction of the maximum horizontal principal stress). The patent with the application number 201611016626.7 and the name "Large Cavern Axis Selection Method under High Geostress Conditions" disclosed on May 10, 2017 also considers that the longitudinal axis of the cavern should be arranged along the direction with a small angle to the direction of the maximum horizontal stress. In addition, in the selection of the cross-sectional axis of the cavern, in order to minimize the stress on the cross section of the cavern and reduce the support, for general caverns without high internal pressure, the direction of the long axis of the cross section of the cavern is usually arranged along the direction of the maximum stress on the cross section.

[0004] However, for the high internal pressure cavern such as compressed air energy storage, the cavern will bear the gas internal pressure as high as 5-10 MPa during the service period, and the main control condition for determining whether it is safe is the high internal pressure operation condition rather than the condition when the cavern construction is completed. Under the high internal pressure operation condition, the larger surrounding rock pressure will not damage the stability of the cavern, but can balance part of the air pressure, thereby being more conducive to the stability of the cavern, so the selection method of the axis of the cavern is different from that of the general cavern, but currently there is no relevant report on how to determine the axis of the high internal pressure cavern. SUMMARY

[0005] To fill in the blank of the determination method of the axis of the high internal pressure cavern, the application provides a method for determining the axis of the high internal pressure cavern such as compressed air energy storage cavern. Different from the general cavern, the main control condition of the high internal pressure cavern is the high internal pressure operation condition. Under the high internal pressure operation condition, in order to fully exert the self-stability of the surrounding rock, under the premise of determining the safety of the construction, completion and maintenance of the cavern, the method takes the direction of the minimum horizontal principal stress in the ground stress as the reference standard, and auxiliary considers the influence of the main structure surface of the rock mass, determines that the direction of the longitudinal axis of the high internal pressure cavern is the direction that the included angle with the direction of the minimum horizontal principal stress is not more than 25° and that is closest to the strike of the main structure surface of the rock mass, and the direction of the long axis of the cross section of the high internal pressure cavern is the direction of the minimum ground stress on the cross section of the cavern.

[0006] The technical scheme adopted by the application to solve the above technical problems is: a determination method of the axis of the high internal pressure cavern, the distribution of the ground stress and the main structure surface of the rock mass in the region where the high internal pressure cavern to be built is obtained through engineering investigation, the direction of the minimum horizontal principal stress in the ground stress is taken as the reference standard, the influence of the main structure surface of the rock mass is auxiliary considered, the direction of the longitudinal axis of the high internal pressure cavern is determined as the direction that the included angle with the direction of the minimum horizontal principal stress is not more than 25° and that is closest to the strike of the main structure surface of the rock mass, and according to the direction of the longitudinal axis of the high internal pressure cavern, the direction of the long axis on the cross section of the high internal pressure cavern is determined to be consistent with the direction of the minimum ground stress.

[0007] The principle of the method for determining the axis of a high-pressure cavern in this invention is as follows: (1) Fully utilize the surrounding rock pressure to balance the internal air pressure: Taking the direction of the minimum horizontal principal stress as the reference standard for the direction of the longitudinal axis of the high-pressure cavern, the direction of the longitudinal axis of the high-pressure cavern is defined as having an angle of no more than 25° with the direction of the minimum horizontal principal stress and being as close as possible to the orientation of the main structural surface of the rock mass. This can maximize the surrounding rock pressure on the cross-section of the cavern, thereby maximizing the use of the surrounding rock pressure to balance the internal air pressure; (2) Minimize the opening of the main structural surface of the rock mass: When the direction of the longitudinal axis of the high-pressure cavern is as close as possible to the orientation of the main structural surface of the rock mass, the main structural surface of the rock mass will be compacted under the action of high internal pressure. After the main structural surface of the rock mass is compacted, the sealing performance of the cavern will be better. In addition, for compressed air energy storage caverns, due to the action of high internal pressure, even when the direction of the longitudinal axis of the cavern is as close as possible to the orientation of the main structural surface of the rock mass, the cavern will not experience the situation of the surrounding rock sliding and failing along the structural surface under high internal pressure conditions.

[0008] As a preferred embodiment, the above-mentioned method for determining the axis of a high-pressure cavern specifically includes the following steps:

[0009] (1) Obtain the distribution of geostress and main structural planes of the rock mass in the area where the proposed high internal pressure cavern is located through engineering survey, namely the magnitude and direction of the three principal stresses and the orientation and dip angle of the main structural planes of the rock mass. Among them, the three principal stresses are the minimum horizontal principal stress S. h Maximum horizontal principal stress S H and vertical principal stress S V ;

[0010] (2) Based on the minimum horizontal principal stress S h The direction of the longitudinal axis of the high-pressure cavern is preliminarily determined to be within the range of the minimum horizontal principal stress S. h The angle between the directions is not greater than Scope;

[0011] (3) Determine the direction of the longitudinal axis of the high internal pressure cavern based on the distribution of the main structural planes of the rock mass. Assume that the orientation of the main structural planes of the rock mass is consistent with the minimum horizontal principal stress S. h The angle between the directions is δ, in In the case of minimum horizontal principal stress S, determine h The direction in which the angle δ is located is the direction of the longitudinal axis of the high-pressure cavern; in In the case of minimum horizontal principal stress S, determine h The angle between the directions is The direction is the direction of the longitudinal axis of the high internal pressure cavern;

[0012] (4) According to the direction of the high internal pressure chamber longitudinal axis, the direction of the long axis of the high internal pressure chamber cross section is determined, and the direction of the long axis of the high internal pressure chamber cross section should be consistent with the direction of the minimum stress: assuming that the cross section perpendicular to the high internal pressure chamber longitudinal axis is plane A, the intersection line of plane A and the horizontal plane is L, the maximum horizontal principal stress S H and the intersection line L is α, the minimum horizontal principal stress S h and the intersection line L is β, then the ground stress σ V of the plane A along the intersection line L is S H cosα-S h cosβ, in the case of σ V >S V , S V is the minimum value of the ground stress of the cross section, therefore, the direction of the long axis of the cross section is arranged along the direction of S V , on the contrary, σ V is the minimum value of the ground stress of the cross section, and the direction of the long axis of the cross section is arranged along the direction of σ V .

[0013] Compared with the prior art, the present application has the following advantages:

[0014] 1. The present application overturns the cognition of the traditional determination method of the axis of the chamber without high internal pressure, and provides an effective method for determining the axis of the high internal pressure chamber such as compressed air energy storage;

[0015] 2. The chamber axis determination method provided by the present application can maximize the surrounding rock pressure on the cross section of the chamber, fully utilize the surrounding rock pressure in the stratum to balance the air pressure in the gas storage chamber, and is more conducive to the stability of the chamber structure;

[0016] 3. The chamber axis determination method provided by the present application can minimize the opening degree of the structural plane in the surrounding rock, and is more conducive to the sealing of the high internal pressure gas storage chamber. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The range of the direction of the high internal pressure chamber longitudinal axis preliminarily determined in the embodiment;

[0018] Figure 2 The direction of the high internal pressure chamber longitudinal axis finally determined in the embodiment;

[0019] Figure 3 The positional relationship in the process of determining the direction of the long axis of the high internal pressure chamber cross section in the embodiment. DETAILED DESCRIPTION

[0020] The present application will be further described in detail below in combination with the embodiment of the drawings.

[0021] Example: A method for determining the axis of a high-pressure cavern. Through engineering surveys, the distribution of geostress and major structural planes of the rock mass in the area where the proposed high-pressure cavern is located is obtained. Using the direction of the minimum horizontal principal stress as a reference standard, and considering the influence of the major structural planes of the rock mass, the direction of the longitudinal axis of the high-pressure cavern is determined to be a direction whose angle with the direction of the minimum horizontal principal stress does not exceed 25° and whose orientation is as close as possible to the strike of the major structural planes of the rock mass. Based on the direction of the longitudinal axis of the high-pressure cavern, the direction of the long axis on the cross-section of the high-pressure cavern is determined to be consistent with the direction of the minimum geostress.

[0022] The above method specifically includes the following steps:

[0023] (1) Obtain the distribution of geostress and main structural planes (faults, fissures, joints, bedding planes) of the area where the proposed high-pressure tunnel is located through engineering survey, namely the magnitude and direction of the three principal stresses and the strike and dip angle of the main structural planes of the rock mass. Among them, the three principal stresses are the minimum horizontal principal stress S. h Maximum horizontal principal stress S H and vertical principal stress S V ;

[0024] (2) Based on the minimum horizontal principal stress S h The direction of the longitudinal axis of the high-pressure cavern is preliminarily determined to be within the range of the minimum horizontal principal stress S. h The angle between the directions is not greater than Scope

[0025] (3) Determine the direction of the longitudinal axis of the high internal pressure cavern based on the distribution of the main structural planes of the rock mass. Assume that the orientation of the main structural planes of the rock mass is consistent with the minimum horizontal principal stress S. h The angle between the directions is δ, in In the case of minimum horizontal principal stress S, determine h The direction in which the angle δ is located is the direction of the longitudinal axis of the high-pressure cavern; in In the case of minimum horizontal principal stress S, determine h The angle between the directions is The direction is the direction of the longitudinal axis of the high internal pressure cavern;

[0026] (4) Based on the direction of the longitudinal axis of the high-pressure cavern, determine the direction of the major axis on the cross-section of the high-pressure cavern. On the cross-section of the high-pressure cavern, the direction of the major axis should be consistent with the direction of the minimum ground stress. Assume that the cross-section perpendicular to the longitudinal axis of the high-pressure cavern is plane A, the intersection of plane A and the horizontal plane is L, and the maximum horizontal principal stress S Hand the angle between the line L and the line L is α, the minimum horizontal principal stress S h and the angle between the line L and the line L is β, the ground stress σ V =S H cosα-S h cosβ, in the case of σ V >S V , S V is the minimum value of the ground stress on the cross section, therefore, the direction of the long axis of the cross section is arranged along the direction of S V , on the contrary, σ V is the minimum value of the ground stress on the cross section, the direction of the long axis of the cross section is arranged along the direction of σ V .

[0027] In the embodiment, the angle between the direction of the main structural plane and the direction of the minimum horizontal principal stress S h is 40° (i.e. the angle of δ is 40°), the value of δ is 25°, thus the range of the direction of the preliminary determined hole axis in step (2) is the range whose angle with the direction of the minimum horizontal principal stress S h is not more than 25°, i.e. Figure 1 the range whose angle with the direction of the minimum horizontal principal stress S h is ±25°. Since thus the direction whose angle with the direction of the minimum horizontal principal stress S h is (i.e. 25°) is the direction of the hole axis, as shown in Figure 2 . Figure 3 The position relationship in the process of determining the direction of the long axis of the cross section of the high internal pressure hole in the embodiment.

[0028] In order to verify the difference between the method for determining the axis of the high internal pressure hole and the method for determining the axis of the general hole, four test schemes are designed for comparison, and the form of the hole is a tunnel with a circular cross section.

[0029] The same ground stress data and physical and mechanical parameters of the surrounding rock are used in the four schemes, as shown in Table 1 and Table 2. The hole sizes of the four schemes are the same, and the constitutive model of the surrounding rock is the Mohr-Coulomb constitutive model. The boundary conditions of scheme one and scheme two are the same, and no air internal pressure is applied after the completion of the hole construction, which is used to simulate the general underground hole without high internal pressure; the boundary conditions of scheme three and scheme four are the same, and 10 MPa of air internal pressure is applied after the completion of the hole construction, which is used to simulate the high internal pressure hole. The direction of the longitudinal axis of the hole in scheme one and scheme three is the direction of the maximum horizontal principal stress S H , and the direction of the longitudinal axis of the hole in scheme two and scheme four is the direction of the minimum horizontal principal stress S hThe direction of the location is the direction of the longitudinal axis of the chamber (NE 160°). The calculation process is carried out in the finite difference software FLAC3D. The calculation results of the four test schemes are shown in Table 3. As can be seen from Table 3, the maximum displacement of the hole and the plastic zone area of scheme one are smaller than those of scheme two, and the maximum displacement of the hole and the plastic zone area of scheme four are smaller than those of scheme three. Therefore, for a general chamber without high internal pressure, the direction of the longitudinal axis of the chamber along the direction of the maximum horizontal principal stress is better than the direction along the minimum horizontal principal stress. However, for a chamber with high internal pressure, the direction of the longitudinal axis of the chamber along the direction of the minimum horizontal principal stress is better than the direction along the maximum horizontal principal stress (i.e. the direction of the location of the longitudinal axis of the chamber and the minimum horizontal principal stress S h The included angle of the direction of the location is zero.

[0030] Table 1 geostress data

[0031] Ground stress category Size / MPa Strike maximum horizontal principal stress S H ]]> 19.50 NE 70° Minimum horizontal principal stress S h ]]> 3.25 NE 160° Vertical principal stress S V ]]> 6.50 Plumb

[0032] Table 2 physical and mechanical parameters of surrounding rock

[0033]

[0034] Table 3 calculation results

[0035]

Claims

1. A method of determining the axis of a high internal pressure chamber, characterized by, The method specifically comprises the following steps: (1) Obtain the distribution of the ground stress and the main structural plane of the rock mass in the area where the high-pressure cavern is to be built, i.e. the magnitude, direction of the three principal stresses and the strike and dip of the main structural plane of the rock mass, wherein the three principal stresses are the minimum horizontal principal stress S h , the maximum horizontal principal stress S H and the vertical principal stress S V ; (2) Based on the minimum horizontal principal stress S h The direction of the longitudinal axis of the high-pressure cavern was initially determined to be within the range of the minimum horizontal principal stress. S h The angle between the directions is not greater than φ Scope; (3) Determine the direction of the longitudinal axis of the high internal pressure cavern by combining the distribution of the main structural planes of the rock mass, assuming that the orientation of the main structural planes of the rock mass is the same as that of the minimum horizontal principal stress. S h The angle between the directions is δ , φ The value is 25°, in δ ≤ φ In the case of minimum horizontal principal stress, determine S h The angle between the directions is δ The direction is the direction of the longitudinal axis of the high-pressure cavern; in δ > φ In the case of minimum horizontal principal stress, determine S h The angle between the directions is φ The direction is the direction of the longitudinal axis of the high internal pressure cavern; (4) Determine the direction of the major axis on the cross-section of the high internal pressure cavern based on the direction of the longitudinal axis of the high internal pressure cavern. The direction of the major axis on the cross-section of the high internal pressure cavern should be consistent with the direction of the minimum ground stress. Assume that the cross-section perpendicular to the longitudinal axis of the high internal pressure cavern is a plane. A ,flat A The line of intersection with the horizontal plane is L Maximum horizontal principal stress S H and intersection line L The included angle is α Minimum horizontal principal stress S h and intersection line L The included angle is β Then in the plane A Upper edge intersection line L Geostress in the direction σ V = S H cos α - S h cos β ,exist σ V > S V In this case, S V It is the minimum value of the geostress on the cross-section; therefore, the direction of the major axis of the cross-section is along... S V Arrange them in the direction they are facing, and vice versa. σ V It is the minimum stress on the cross-section, and the direction of the major axis of the cross-section is along... σ V Arranged in the direction it is located.

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