Multi-structural-surface rock mass underground powerhouse supporting system and grid structure spacing design method

Abstract

The invention discloses a multi-structural-surface rock mass underground powerhouse supporting system and a grid structure spacing design method in the field of underground powerhouse construction, and the system comprises an underground powerhouse, the underground powerhouse is provided with a vault, and the vault is uniformly provided with a plurality of door-arch-shaped grid structures at intervals; the grid structure comprises a plurality of grid units which are sequentially connected, each grid unit comprises a frame body, each frame body comprises six outer surfaces, each outer surface is provided with two crossed diagonal pull rods, and a plurality of diagonal pull rods are arranged in the frame in a crossed mode; the grid structures arranged at intervals and the pull rod structures of the grid units remarkably increase confining pressure, supporting force and bearing capacity, the integrity of surrounding rock is improved, the surrounding rock can better exert the bearing capacity of the surrounding rock, the surrounding rock and a supporting system are cooperatively stressed, a combined bearing arch is effectively formed, and the stability of the top arch surrounding rock under the complex geological condition is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of underground powerhouse construction, and in particular to a support system for underground powerhouses in multi-structure rock masses and a method for designing the spacing of grid structures. Background Technology

[0002] As the geological conditions of underground powerhouses in hydropower stations and pumped-storage power stations become increasingly complex, challenges are posed to existing support technologies. Shotcrete and anchor bolt support alone are sometimes insufficient to ensure the stability of the surrounding rock. The combined intersecting action of rock mass structural planes can easily lead to unstable blocks, and under the strong unloading action of high ground stress excavation, disasters such as shotcrete layer cracking, block instability, and collapse are prone to occur.

[0003] In some existing underground powerhouses, after the arch was supported by the system, cracks occurred in the sprayed layer of the arch during the excavation of the sidewalls. In underground cavern group projects with complex geological conditions, affected by structural surfaces such as faults, weak fault zones, and densely fissured zones, large deformation or collapse and instability of the surrounding rock have occurred in the arch of large-span caverns, threatening construction safety and the stability of the surrounding rock.

[0004] It is evident that existing arch support technologies for large underground powerhouses face severe challenges under complex rock mass conditions, necessitating the development of arch support technologies that can effectively prevent collapse and instability in multi-faceted rock masses. Furthermore, tunnel grid support is difficult to directly apply to underground powerhouses because the tunnel's shape, size, and span differ significantly from those of the powerhouse. Additionally, tunnel grids cannot meet the load-bearing requirements of large-span arches and the long-term stress adjustment and deformation control requirements of powerhouses, thus hindering effective support. Summary of the Invention

[0005] To overcome its shortcomings, the technical problem to be solved by this invention is: to solve the problem that existing underground powerhouse roof arch support technology is unable to cope with block collapse, instability and large deformation under complex rock mass conditions with multiple structural surfaces.

[0006] The technical solution adopted by this invention to solve its technical problem is: A multi-structure rock mass underground powerhouse support system includes an underground powerhouse with an arched roof. The arched roof is provided with multiple arch-shaped grid structures at even intervals. The grid structure includes multiple grid units connected in sequence. Each grid unit includes a frame body. The frame body includes six outer surfaces. The outer surfaces are provided with two intersecting diagonal tie rods. Multiple intersecting apical tie rods are provided inside the frame.

[0007] Furthermore, the spacing between two adjacent grid structures is 2m-6m.

[0008] Furthermore, the width of the aforementioned grid structure is 40cm-60cm.

[0009] This application also proposes a method for designing the spacing of grid structures, used in the above-mentioned grid support system for the roof arch of a large underground powerhouse with multi-structure rock mass, comprising the following steps: S1: Numerical simulation of the factory building was performed to calculate the optimal grid structure spacing under different structural surface orientations and spacing conditions; S2: By fitting the data, a functional relationship is established with the orientation and spacing of the structural surfaces as independent variables and the optimal grid spacing as the dependent variable. S3: Input the known orientation and spacing of the structural planes, and the optimal grid structure spacing can be calculated using the formula.

[0010] Furthermore, in step S1, a three-dimensional numerical model is performed on the underground powerhouse, surrounding rock, and structural surfaces. Then, a numerical simulation is carried out on the excavation and support process of the powerhouse to calculate the deformation of the surrounding rock and the distribution of blocks.

[0011] Furthermore, the numerical simulation employs the 3DEC discrete element method or the FLAC3D finite difference method.

[0012] Furthermore, the plant simulation adopts a layered excavation state simulation; the support measures simulation includes shotcrete, anchor bolts and steel grid. The shotcrete is simulated using Shell elements or Group commands, the anchor bolts are simulated using Cable structural elements, and the grid is simulated using Beam elements.

[0013] Furthermore, in step S2, surface fitting is performed with the structural surface inclination angle and structural surface spacing as x and y coordinates, respectively, and the optimal grid structural spacing as z coordinate, to obtain a functional relationship with the structural surface inclination angle (α) and spacing (s) as independent variables and the optimal grid structural spacing (S) as dependent variable, i.e., S = f(α, s).

[0014] Furthermore, in step S3, after establishing the functional relationship S = f(α, s), for the actual engineering grid structure spacing design requirements, the specific values ​​of the structural surface inclination angle (α) and structural surface spacing (s) measured in the actual engineering can be substituted to calculate the optimal grid structure spacing (S) under this condition.

[0015] Furthermore, if there are multiple sets of advantageous structural surfaces, each set of structural surfaces is calculated separately to obtain the corresponding optimal grid structure spacing, and then the spacing is selected by comprehensive consideration.

[0016] The beneficial effects of this invention are: The spaced grid structure and the tie rod structure of the grid units significantly increase the confining pressure, support force, and bearing capacity, improve the integrity of the surrounding rock, enable the surrounding rock to better exert its bearing capacity, and enable the surrounding rock and the support system to work together to form a joint bearing arch, which significantly improves the stability of the top arch surrounding rock under complex geological conditions.

[0017] The corresponding grid spacing can be calculated by inputting the actual structural surface parameters, which is more targeted and has a more obvious distinction design for different structural surface geometric conditions. It can achieve precise control under different conditions and is convenient for practical application. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the grid unit structure of the present invention; Figure 2 This is a schematic diagram of the underground factory building of the present invention; Figure 3 This is a schematic diagram of the grid structure of the present invention; Figure 4 This is a flowchart of the grid structure spacing design method of the present invention; The diagram is marked as follows: 1-underground factory building, 2-grid structure, 3-grid unit, 4-diagonal tie rod, 5-vertical tie rod. Detailed Implementation

[0019] The invention will be further described below with reference to the accompanying drawings.

[0020] like Figure 1-3 As shown in the embodiment of this application, a grid structure support system for an underground powerhouse in a structural rock mass is proposed, including an underground powerhouse 1. The underground powerhouse 1 is provided with an arched roof, and multiple arch-shaped grid structures 2 are evenly spaced on the arched roof. The grid structure 2 includes multiple grid units 3 connected in sequence. Each grid unit 3 includes a frame body, and the frame body includes six outer surfaces. Two intersecting diagonal tie rods 4 are provided on the outer surfaces, and multiple intersecting top-angle tie rods 5 are provided inside the frame. That is to say, the grid used in traditional tunnels is a planar truss structure. The above-mentioned frame body, diagonal tie rods 4 and top-angle tie rods 5 improve the overall bearing capacity of the structure. For a large underground powerhouse 1, the arch is subjected to high horizontal structural stress and self-weight stress compression. Moreover, the long-term excavation, stress adjustment and deformation response of the powerhouse generate a large load on the support system. Traditional planar truss grid support is difficult to withstand such a large pressure.

[0021] First, it should be stated that the spaced grid structure 2 and the tie rod structure of the grid unit 3 significantly increase the confining pressure, support force, and bearing capacity, improve the integrity of the surrounding rock, enable the surrounding rock to better exert its bearing capacity, and enable the surrounding rock and the support system to work together to form a joint bearing arch, which significantly improves the stability of the top arch surrounding rock under complex geological conditions.

[0022] Traditional plant support systems, consisting of shotcrete layers and anchor bolts, are relatively insufficient for supporting the multi-faceted surrounding rock of the arch. When the structural surfaces intersect to form blocks, these blocks loosen under gravity and excavation unloading disturbances, placing significant pressure on the support system. Insufficient support strength can easily lead to collapse. The proposed solution employs a combined structure of three-dimensional truss-type grid units, which effectively improves the bearing capacity of the surrounding rock and support system, forming a joint bearing arch and ensuring the integrity and stability of the surrounding rock of the arch.

[0023] In addition, the width of the aforementioned grid structure 2 is 40cm-60cm, which means that the width of a single grid unit 3 is 40cm-60cm. At the same time, the spacing between two adjacent grid structures 2 is 2m-6m to ensure optimal support performance.

[0024] Multiple grid structures 2 are arranged along the axis of the plant, and their outlines are basically consistent with the excavation outline of the top arch. The key is to determine the spacing between adjacent grid structures 2, which has a very important impact on the support effect of the grid and is one of the key parameters of grid support.

[0025] In multi-faceted rock mass conditions, the design of the spacing between adjacent grid structures in the grid support system for the roof arch of a large underground powerhouse is crucial. When steel grid support is used for the roof arch of powerhouse 1, the most significant influencing factor in selecting the spacing of the grid structures 2 is the attitude and spacing of the structural faces. This is because different attitudes of the structural faces will intersect with the excavation outline of the roof arch to form different block distributions, thus affecting the stability of the roof arch to varying degrees. Different grid structure 2 spacings will affect the volume of unstable blocks and also influence the stability of the surrounding rock of the roof arch.

[0026] The attitude of the structural surface includes parameters such as dip angle. This is based on the fact that for the top arch of a large-span underground powerhouse, the risk of the top arch collapsing and falling varies under different conditions of steep and gentle dip. Therefore, the dip angle is the main influencing factor and consideration.

[0027] This embodiment also proposes a design for the spacing between adjacent grid structures in a multi-structure rock mass large underground powerhouse roof arch grid support system, including the following steps: S1: Numerical simulation of the factory building was performed to calculate the optimal grid structure spacing under different structural surface orientations and spacing conditions; Three-dimensional numerical models were created for the underground powerhouse 1, surrounding rock, and structural surfaces. Numerical simulations were then performed on the excavation and support process of the powerhouse, calculating the deformation and block distribution of the surrounding rock. The numerical simulation can employ the 3DEC discrete element method or the FLAC3D finite difference method. The powerhouse excavation adopted a layered excavation approach, and the simulation was conducted based on the actual layered scheme of the powerhouse. The support measures simulation included shotcrete, anchor bolts, and grid elements. Shotcrete was simulated using Shell elements or the Group command, anchor bolts were simulated using Cable structural elements, and grid elements were simulated using Beam elements.

[0028] The simulation scheme is used to calculate the surrounding rock deformation and unstable block volume under different structural plane dip angles, spacing, and grid spacing conditions. Typical scheme designs are shown in Table 1. The selection of structural plane dip angles, spacing, and grid spacing in the scheme is not limited to the values ​​in the table, and the number of schemes is not limited to the number in the table. They can be selected according to the actual engineering situation and fitting needs.

[0029] Table 1 Numerical Simulation Scheme Design

[0030] Numerical simulations were conducted on the 27 schemes mentioned above to calculate the maximum deformation of the crown arch and the volume of the unstable blocks of the crown arch after excavation. Under the same structural plane inclination angle and spacing conditions, curve fitting was performed on the maximum deformation of the crown arch and the grid spacing, as well as the volume of the unstable blocks of the crown arch and the grid spacing. Figure 4 As shown in the figure. When the curve does not show a significant increasing trend with spacing, the corresponding spacing is the optimal spacing. Through the above fitting, the optimal grid spacing under different structural surface inclination angles and spacing conditions can be obtained. Figure 2 The optimal grid spacing is 2m.

[0031] Through the above numerical simulation and fitting calculations, the optimal grid spacing can be obtained for structural surface inclination angles of 20°, 50°, and 80°, and structural surface spacing of 2m, 4m, and 6m, respectively.

[0032] S2: By fitting, a functional relationship is established with the orientation and spacing of the structural surface as independent variables and the optimal grid spacing as the dependent variable. Surface fitting is performed with the inclination angle and spacing of the structural surface as x and y coordinates, and the optimal grid spacing as the z coordinate, to obtain a functional relationship with the inclination angle (α) and spacing (s) of the structural surface as independent variables and the optimal grid spacing (S) as the dependent variable, i.e., S = f(α, s).

[0033] S3: Input the known orientation and spacing of the structural surfaces, and the optimal grid spacing can be calculated using the formula. After establishing the functional relationship S = f(α, s), for the grid spacing design requirements in actual engineering projects, the specific values ​​of the actual measured structural surface inclination angle (α) and structural surface spacing (s) can be substituted to calculate the optimal grid spacing (S) under that condition, thus providing a basis for the grid support design of the factory roof arch.

[0034] It should be noted that under complex geological conditions, the roof arch of the plant may develop multiple sets of structural surfaces with different attitudes. In this case, it is advisable to select the attitude and spacing of the dominant structural surface for simulation, fitting, and calculation. If there are also multiple sets of dominant structural surfaces, each set of structural surfaces can be calculated separately in step S3 to obtain the corresponding optimal grid spacing, and then the spacing can be selected by comprehensive consideration.

Claims

1. A multi-faceted rock mass underground powerhouse support system, comprising an underground powerhouse (1), wherein the underground powerhouse (1) is provided with an arched roof, and the arched roof is provided with multiple arch-shaped grid structures (2) at uniform intervals; characterized in that, The grid structure (2) includes multiple grid units (3) connected in sequence. Each grid unit (3) includes a frame body with six outer surfaces. Two intersecting diagonal tie rods (4) are provided on the outer surfaces. Multiple intersecting vertical tie rods (5) are provided inside the frame.

2. The multi-structure rock mass underground powerhouse support system according to claim 1, characterized in that, The spacing between two adjacent grid structures (2) is 2m-6m.

3. The multi-structure rock mass underground powerhouse support system according to claim 1, characterized in that, The width of the grid structure (2) is 40cm-60cm.

4. A grid structure spacing design method, used for designing the spacing between adjacent grid structures (2) in a multi-structure rock mass large underground powerhouse roof arch grid support system according to any one of claims 1-3, characterized in that, Includes the following steps: S1: Numerical simulation of the factory building was performed to calculate the optimal grid structure (2) spacing under different structural surface orientations and spacing conditions; S2: By fitting, a functional relationship is established with the orientation and spacing of the structural surfaces as independent variables and the optimal grid structure (2) spacing as the dependent variable; S3: Input the known orientation and spacing of the structural planes, and the optimal grid structure (2) spacing can be calculated using the formula.

5. The grid structure spacing design method according to claim 4, characterized in that, In step S1, a three-dimensional numerical model is performed on the underground powerhouse (1) and the surrounding rock and structural surfaces. Then, a numerical simulation is carried out on the excavation and support process of the powerhouse to calculate the deformation of the surrounding rock and the distribution of blocks.

6. The grid structure spacing design method according to claim 5, characterized in that, Numerical simulations are performed using the 3DEC discrete element method or the FLAC3D finite difference method.

7. The grid structure spacing design method according to claim 4, characterized in that, The plant simulation uses a layered excavation state simulation; the support measures simulation includes shotcrete, anchor bolts and steel grid. The shotcrete is simulated using Shell elements or the Group command, the anchor bolts are simulated using Cable structural elements, and the grid is simulated using Beam elements.

8. The grid structure spacing design method according to claim 4, characterized in that, In step S2, the inclination angle of the structural surface and the spacing between the structural surfaces are used as x and y coordinates, respectively, and the spacing of the optimal grid structure (2) is used as the z coordinate. The surface fitting is performed to obtain a functional relationship with the inclination angle of the structural surface α and the spacing s as independent variables and the spacing S of the optimal grid structure (2) as the dependent variable, namely S = f(α, s).

9. The grid structure spacing design method according to claim 4, characterized in that, In step S3, after establishing the functional relationship S = f(α, s), for the spacing design requirements of the grid structure (2) in the actual project, the actual measured structural surface inclination angle α and structural surface spacing s values ​​can be substituted to calculate the grid structure (2) spacing S under this condition.

10. The grid structure spacing design method according to claim 7, characterized in that, If there are multiple sets of advantageous structural surfaces, calculate the spacing of the optimal grid structure (2) for each set of structural surfaces separately, and then select the spacing after comprehensive analysis.

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