Four-layer shaft wall structure of pressure pipeline shaft and design method

Abstract

The invention provides a four-layer composite shaft wall structure of a pressure pipeline shaft and a design method. A composite well wall structure is adopted, namely an internal and external pressure-bearing structure of an arch, anchor, net and spray primary support, a reinforced concrete secondary support and an internal steel plate concrete permanent support is adopted, and the special bearing requirement required by the combined action of internal and external pressure of hydroelectric generation of a deep and uneven weak cemented gravel layer is met. An elastic-plastic theory is adopted, under polar coordinates, a geometric equation, an equilibrium equation and a constitutive equation are utilized, a displacement boundary condition, a stress boundary condition, a displacement continuous condition and a stress continuous condition are utilized, a relational expression of the stress and the displacement of each layer of well wall along with the distance between the stress and the displacement and the center of the vertical shaft is obtained, and the distance between the stress and the displacement of each layer of well wall and the center of the vertical shaft is calculated through a lining stress expression and a Mohr-Coulomb criterion. And determining the required minimum thickness of the concrete well wall. According to the method, energy consumption can be reduced, theoretical support is provided for vertical shaft construction in such stratums, and development of shaft sinking design and process in weak cemented gravel layers is promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of pressure pipeline shaft, in particular to a pressure pipeline shaft four-layer composite shaft wall structure and a design method thereof and an application thereof in a weakly cemented gravel layer. Background Art

[0002] The pressure pipe shaft of a hydropower station is one of the most important facilities in the hydropower station, and plays an important role in ensuring the normal operation of the hydropower station and improving the power generation efficiency. At present, the single-layer pressure pipe shaft is mainly suitable for hard rock formations, such as granite, diorite, diabase, basalt, etc. And there are relatively mature theories and analysis methods for the construction of single-layer pressure pipe shafts.

[0003] At present, the widely used pressure pipeline shaft construction methods at home and abroad include: reverse drilling rig drilling method, shaft drilling rig drilling method, artificial forward well method and reverse well method (climbing tank method). The above methods can effectively construct pressure pipeline shafts under most geological conditions, especially in hard rock formations. However, these methods face challenges in soft rock formations, including small drilling diameter, difficulty in controlling well stability, and unsuitability for uneven weakly cemented formations, making it difficult to meet the requirements of project quality and progress. Summary of the invention

[0004] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is how to ensure safe and efficient shaft construction under the condition of a deep, uneven, weakly bonded gravel layer. Based on this, the present invention provides a four-layer composite shaft wall structure for a pressure pipeline shaft and its design method and its application in a weakly bonded gravel layer, and integrates a mechanized short-segment excavation and masonry construction process, and obtains a design method for concrete thickness based on the stress and displacement relationship of each layer of shaft wall.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] The present invention provides a four-layer shaft wall structure for a pressure pipeline shaft, wherein each layer of the shaft wall structure is laid in sequence along the surrounding rock toward the center line of the pressure pipeline shaft;

[0007] The first layer, anchor reinforcement area: including the initial support structure of hollow self-propelled anchors, steel mesh, steel arch frame and mesh shotcrete;

[0008] The second layer, the first lining support area: the first lining structure formed by reinforced concrete lining;

[0009] The third layer, expansive concrete area: the expansive concrete is filled in the primary lining structure and the steel lining structure to form the secondary lining structure;

[0010] Fourth layer, steel lining area: steel lining structure formed by steel plates.

[0011] Preferably, the sprayed concrete in the first layer is C25 concrete; the reinforced concrete in the second layer is C30 concrete; the expansive concrete in the third layer is C25 concrete; and the steel plate in the fourth layer is Q345R steel plate.

[0012] The present invention provides a design method for the four-layer shaft wall structure of the pressure pipeline shaft. According to the elastic-plastic theory, the equilibrium equation, geometric equation, constitutive equation, and Mohr-Coulomb criterion are used to respectively construct the relationship between the stress and displacement of each layer and the distance of each layer from the center line of the pressure pipeline shaft, and calculate the minimum thickness of the reinforced concrete lining in the second layer.

[0013] Preferably, the design method comprises the following steps:

[0014] (1) Establish the relationship between the stress and displacement of the first layer of anchor reinforcement area and the distance between the anchor reinforcement area and the center line of the pressure pipeline shaft;

[0015] (2) Establish the relationship between the stress and displacement of the second layer primary lining support area and the distance between the primary lining support area and the center line of the pressure pipeline shaft;

[0016] (3) Using the Mohr-Coulomb criterion and considering the ultimate bearing capacity of concrete, a relationship between the thickness of the reinforced concrete lining in the second layer and the stress is established to calculate the minimum thickness of the reinforced concrete lining in the second layer; the thickness of the reinforced concrete lining in the second layer is the thickness of the concrete in the second layer;

[0017] (4) Establish the relationship between the stress and displacement of the third layer of expansive concrete area and the distance between the expansive concrete area and the centerline of the penstock shaft;

[0018] (5) Establish the relationship between the stress and displacement of the fourth layer steel lining area and the distance between the steel lining area and the center line of the pressure pipeline shaft.

[0019] Preferably, the specific method of step (1) is:

[0020] The relationship between the stress and displacement of the first layer of anchor reinforcement area and the distance between the anchor reinforcement area and the center line of the pressure pipeline shaft is established, as shown in formula (1);

[0021]

[0022] Where r is the distance between the anchor reinforcement area and the centerline of the pressure pipe shaft, m; u4 is the displacement of the anchor reinforcement area, m; σ r4 represents the radial stress in the anchor reinforcement area, Pa; σ θ4 represents the hoop stress in the anchor reinforcement area, Pa; G4 represents the shear modulus of the anchor reinforcement area, Pa; μ4 represents the Poisson's ratio of the anchor reinforcement area; S represents the row spacing of the anchor, m; D S Indicates the spacing of anchor rods, m; E b represents the elastic modulus of the anchor, Pa; Y represents the cross-sectional area of ​​the anchor, m 2 ; σ M represents the original rock stress, Pa; ε r4 is the radial strain in the anchor reinforcement area, ε θ4 is the hoop strain of the anchor reinforcement area, expressed as formula (2); C7, C8, C 1ini , C 2ini is the coefficient to be determined;

[0023]

[0024] Preferably, the specific method of step (2) is:

[0025] The relationship between the stress and displacement of the second layer first lining support area and the distance between the first lining support area and the center line of the pressure pipeline shaft is established, as shown in formula (4);

[0026]

[0027] Where r represents the distance between the primary lining support area and the centerline of the pressure pipe shaft, m; u3 represents the displacement of the primary lining support area, m; σ r3 represents the radial stress in the primary lining support area, Pa; σ θ3 represents the hoop stress in the primary lining support area, Pa; ε r3 is the radial strain of the first lining support area, ε θ3 is the hoop strain of the first lining support area; G3 represents the shear modulus of the first lining support area, Pa; μ3 represents the Poisson's ratio of the first lining support area; σ M represents the original rock stress, Pa; C5 and C6 are unknown coefficients;

[0028]

[0029] Preferably, the specific method of step (3) is: using the Mohr-Coulomb criterion, establishing a relationship between the thickness of the reinforced concrete lining in the second layer and the stress; the thickness of the reinforced concrete lining in the second layer is the thickness D of the concrete in the second layer, as shown in formula (10);

[0030]

[0031] Where D is the thickness of the concrete in the second layer; r3 is the distance from the inner edge of the anchor reinforcement area to the center line of the pressure pipe shaft, m, where the inner edge of the anchor reinforcement area is the outer edge of the reinforced concrete lining; c is the cohesion, Pa; is the internal friction angle, °; It represents the stress on the inner edge of concrete when only one layer of reinforced concrete lining is used as support, Pa; It represents the stress at the contact surface between concrete and surrounding rock when there is only one layer of reinforced concrete lining, Pa;

[0032] The expression is as follows:

[0033]

[0034] In the formula, Q1-Q6 are unknown coefficients, and the expressions of Q1-Q6 are as follows:

[0035]

[0036] Where r2 represents the distance from the inner edge of the reinforced concrete lining area to the center line of the pressure pipe shaft; r3 represents the distance from the outer edge of the reinforced concrete lining area to the center line of the pressure pipe shaft, m; r ∞ It represents the position infinitely far from the center line of the shaft, m; G5 represents the shear modulus of the surrounding rock; μ5 represents the Poisson's ratio of the surrounding rock.

[0037] Preferably, the specific method of step (4) is: respectively establishing the relationship between the stress and displacement of the third layer of expansive concrete area and the distance between the expansive concrete area and the center line of the pressure pipe shaft, such as formula (11);

[0038]

[0039] Where r is the distance between the expansion concrete area and the centerline of the pressure pipe shaft, m; u2 is the displacement of the expansion concrete area, m; σ r2 , σ θ2 Respectively represent the radial stress and hoop stress in the expansive concrete zone, Pa; ε r2 , ε θ2 are the radial strain and hoop strain of the expansive concrete zone, respectively; G2 represents the shear modulus of the expansive concrete zone, Pa; μ2 represents the Poisson's ratio of the expansive concrete zone; σ M represents the original rock stress, Pa; C3 and C4 are unknown coefficients;

[0040]

[0041] The specific method of step (5) is: respectively establish the relationship between the stress and displacement of the fourth layer steel lining area and the distance between the steel lining area and the center line of the pressure pipeline shaft, such as formula (12);

[0042]

[0043] Where r is the distance between the steel lining area and the centerline of the pressure pipe shaft, m; u1 is the displacement of the steel lining area, m; σr1 , σ θ1 Respectively represent the radial stress and hoop stress of the steel lining area, Pa; ε r1 , ε θ1 are the radial strain and hoop strain of the steel lining area respectively; G1 represents the shear modulus of the steel lining area, Pa; μ1 represents the Poisson's ratio of the steel lining area; σ M represents the original rock stress, Pa; C1 and C2 are unknown coefficients;

[0044]

[0045] Preferably, equations (1), (4), (11), (12) and stress boundary condition equation (13) are combined to calculate: P0, σ A , σ B , σ C , σ D :

[0046]

[0047] The expressions for C1-C8 are as follows:

[0048]

[0049] Where P0 represents the boundary stress at the inner edge of the steel lining area, Pa; σ A represents the radial stress at the junction of the steel lining area and the expansive concrete area, Pa; σ B represents the radial stress at the junction of the expansive concrete area and the reinforced concrete lining area, Pa; σ C represents the radial stress at the junction of the reinforced concrete lining area and the anchor reinforcement area, Pa; σ D represents the radial stress at the junction of the anchor reinforcement area and the surrounding rock area, Pa; σ M Indicates the original rock stress, Pa; N1-N 21 represents the undetermined coefficient;

[0050] N1-N 21 The expression is as follows:

[0051]

[0052] Wherein, r0 represents the distance from the inner edge of the steel lining area to the center line of the pressure pipe shaft, m; r1 represents the distance from the inner edge of the expansive concrete area to the center line of the pressure pipe shaft, m; r2 represents the distance from the inner edge of the reinforced concrete lining area to the center line of the pressure pipe shaft, m; r3 represents the distance from the inner edge of the anchor reinforcement area to the center line of the pressure pipe shaft, m; r4 represents the distance from the outer edge of the anchor reinforcement area to the center line of the pressure pipe shaft, m; G1 represents the shear modulus of the steel lining area, Pa; G2 represents the shear modulus of the expansive concrete area, Pa; G3 represents the shear modulus of the reinforced concrete lining area, Pa; G4 represents the shear modulus of the anchor reinforcement area, Pa; μ1 represents the Poisson's ratio of the steel lining area; μ2 represents the Poisson's ratio of the expansive concrete area; μ3 represents the Poisson's ratio of the primary lining support area; μ4 represents the Poisson's ratio of the anchor reinforcement area; M1-M6 are undetermined coefficients;

[0053] The expressions of M1-M6 are as follows:

[0054]

[0055] Where C 1ini , C 2ini The expression is as follows:

[0056]

[0057] In the formula, σ ini represents the virtual support force, Pa; r5 represents the outer edge of the surrounding rock action area, which is infinite, m.

[0058] The present invention provides an application of the four-layer shaft wall structure of a pressure pipeline vertical shaft in a weakly cemented gravel layer.

[0059] The technical solution of the present invention achieves the following beneficial technical effects:

[0060] The present invention proposes a four-layer shaft wall structure suitable for a weakly bonded gravel layer, which adopts a composite shaft wall structure: an internal and external pressure-bearing structure of "arch, anchor, net, spray" initial support, reinforced concrete secondary support, and internal steel plate concrete permanent support. It meets the special bearing requirements required by the combined action of internal and external pressures of hydropower generation in deep, uneven, weakly bonded gravel layers: (1) Anchor rods + steel mesh + steel arch frame + hanging net spraying are used to form an initial support structure; (2) C30 reinforced concrete lining is designed to form a first lining structure; (3) After the well is completed and the horizontal tunnel is connected, a steel lining with a wall thickness of Q345R is installed from bottom to top, and C25 expansive concrete is cyclically filled between the steel lining and the outer wall to form a "steel-concrete" composite shaft wall structure. A "two excavation and one completion" cycle operation mode is formed, and a construction cycle of "excavation operation → initial support → excavation operation → initial support → first lining support → steel lining construction → filling concrete" is proposed.

[0061] The present invention proposes a four-layer shaft wall structure design method for a pressure pipeline shaft suitable for a weakly bonded gravel layer. The elastic-plastic theory is adopted, and the displacement and stress expressions of the shaft wall structure are obtained by using geometric equations, equilibrium equations, and constitutive equations in polar coordinates. By using displacement boundary conditions, stress boundary conditions, displacement continuity conditions, and stress continuity conditions, the expressions of the relationship between the stress and displacement of each layer of the shaft wall and the distance from the shaft center are obtained, and the required minimum concrete shaft wall thickness (the ultimate thickness of concrete) is determined by the stress expression of the first lining and the Mohr-Coulomb criterion. This method can not only reduce energy consumption, but also provide theoretical support for the construction of shafts in such strata, and promote the development of shaft drilling design and technology in weakly bonded gravel layers. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 A mechanical schematic diagram of a four-layer shaft wall structure of a pressure pipeline shaft according to the present invention;

[0063] Among them, Area A: anchor reinforcement area; Area B: primary lining support area (reinforced concrete lining); Area C: expansive concrete area; Area D: steel lining area; Area E: surrounding rock area;

[0064] Figure 2 A schematic diagram of the initial support structure in the four-layer shaft wall structure of the pressure pipeline vertical shaft of the present invention;

[0065] Figure 3 A schematic diagram of a lining structure in a four-layer shaft wall structure of a pressure pipeline shaft according to the present invention;

[0066] Figure 4 A mechanical schematic diagram of the pressure pipe shaft of the present invention under the condition that only one layer of reinforced concrete is supported;

[0067] Figure 5 A schematic diagram of a steel lining structure in a four-layer shaft wall structure of a pressure pipeline shaft according to the present invention;

[0068] in, Figure 2 , Figure 3 , Figure 5 Middle: 1-Hollow self-propelled anchor rod; 2-Reinforcement mesh, steel arch frame and mesh shotcrete; 3-Reinforced concrete lining; 4-Expansive concrete; 5-Steel lining;

[0069] Figure 6 The relationship curve between the concrete thickness and stress in the embodiment of the present invention;

[0070] Figure 7 A relationship diagram of the influence of the thickness of the C30 reinforced concrete lining on the displacement of the surrounding rock in the embodiment of the present invention;

[0071] Figure 8 A relationship diagram of the influence of the thickness of the C30 reinforced concrete lining on the surrounding rock stress in an embodiment of the present invention;

[0072] Fig. 9 A relationship diagram of the influence of different internal water pressures on the radial displacement of surrounding rocks in an embodiment of the present invention;

[0073] Fig.10 A diagram showing the influence of different water pressures on surrounding rock stress in an embodiment of the present invention. DETAILED DESCRIPTION

[0074] In order to make the purpose, technical scheme and technical effect of the invention of this application clearer, the technical scheme in the embodiment of this application will be clearly and completely described below in conjunction with the drawings in the embodiment of this application. Obviously, the described embodiment is a part of the embodiment of this application, not all the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0075] The following is a detailed description of a four-layer shaft wall structure of a pressure pipeline vertical shaft and its design method and application through specific embodiments of the present invention.

[0076] Taking into account that the strata of the pressure pipeline shaft are mainly weakly cemented gravel, which does not meet the conditions for reverse well construction, and in order to ensure construction safety and construction period, comprehensive mechanized short-segment excavation and masonry operations are selected. When the surrounding rock conditions are poor, the excavation and masonry section height is set to be relatively small; in areas with better surrounding rock, the excavation and masonry section height can be set to be relatively large. A "two excavations and one completion" cycle operation method is implemented, and the initial support and first lining construction cycle is excavation operation → initial support → excavation operation → initial support → first lining support. After the well is completed and connected with the horizontal tunnel, the construction cycle is steel lining installation and welding → filling with concrete → steel lining installation and welding. The mechanical schematic diagram of the four-layer shaft wall structure of the pressure pipeline shaft of the present invention is shown in Figure 1 As shown in Figure 2, the shaft wall structure of the pressure pipeline shaft in each stage is as follows: Figure 2 , 3 , as shown in Figure 5.

[0077] in Figure 1 Among them, Area A: steel lining area; Area B: expansive concrete area; Area C: primary lining support area (reinforced concrete lining); Area D: anchor reinforcement area; Area E: surrounding rock area.

[0078] r0: distance from the inner edge of the steel lining area to the center line of the pressure pipe shaft, m; r1: distance from the inner edge of the expansion concrete area to the center line of the pressure pipe shaft, m; r2: distance from the inner edge of the reinforced concrete lining area to the center line of the pressure pipe shaft, m; r3: distance from the inner edge of the anchor reinforcement area to the center line of the pressure pipe shaft, m; r4: distance from the outer edge of the anchor reinforcement area to the center line of the pressure pipe shaft, m;

[0079] Figure 2 , 3, 5, 1: hollow self-advancing anchor rod; 2: steel mesh, steel arch frame and mesh shotcrete; 3: reinforced concrete lining; 4: expansive concrete; 5: steel lining.

[0080] Step 1: Shaft wall design method in the initial support stage

[0081] like Figure 2 As shown in the figure, the initial support structure adopts hollow self-propelled anchor rods + steel mesh + I-shaped steel arch frame + mesh spraying (mesh spraying C25 concrete) measures to support and form the first layer of anchor reinforcement area.

[0082] In the specific embodiment, manual labor, pneumatic picks, etc. are used in conjunction with small excavators for excavation. As the excavation proceeds, steel mesh is laid in time, hollow anchor self-propelled anchors are installed, and I-beam supports are installed (the anchors are firmly connected to the steel supports and the upper and lower steel bars).

[0083] The present invention is based on the elastic-plastic theory, and uses the equilibrium equation, geometric equation, and constitutive equation in polar coordinates to obtain the displacement and stress expressions of the well wall structure. And using the displacement boundary condition, stress boundary condition, displacement continuity condition, and stress continuity condition, the expression of the relationship between the stress and displacement of each layer of the well wall and the distance from the center of the shaft is obtained.

[0084] Specifically, the influence of anchor parameters and virtual support force needs to be considered during anchor support. The relationship expressions of stress (radial stress or hoop stress)-radius (the distance between the anchor reinforcement area and the centerline of the pressure pipe shaft) and displacement-radius are obtained as follows (1).

[0085]

[0086] Where r is the distance between the anchor reinforcement area and the centerline of the pressure pipe shaft, m; u4 is the displacement of the anchor reinforcement area, m; σ r4 Indicates the radial stress in the anchor reinforcement area, Pa, σ θ4 represents the hoop stress in the anchor reinforcement area, Pa; G4 represents the shear modulus of the anchor reinforcement area, Pa; μ4 represents the Poisson's ratio of the anchor reinforcement area; S represents the row spacing of the anchor, m; D S Indicates the spacing of anchor rods, m; E b represents the elastic modulus of the anchor, Pa; Y represents the cross-sectional area of ​​the anchor, m 2 ; σ M represents the original rock stress, Pa; ε r4 is the radial strain in the anchor reinforcement area, ε θ4 is the hoop strain of the anchor reinforcement area, which is expressed as follows (2); C7, C8, C 1ini , C 2ini is the unknown coefficient, and its expression is shown in equations (14)-(17).

[0087]

[0088] σ M Calculated by Qin's formula: That is: σ M =γ1h1k1+γ2h2k2+…+γ n h n k n

[0089] Where: γ i Indicates the weight of the i-th layer, MN / m 3 ;h i represents the thickness of the i-th layer, m; k i Represents the lateral pressure coefficient; i=1,2,...,n.

[0090]

[0091] In the formula, E i represents the elastic modulus of the i-th layer, Pa; μ i represents the Poisson's ratio of the i-th layer.

[0092] When r is r4, σ r4 Represents the radial stress at the junction of the anchor reinforcement area and the surrounding rock. At this time, σ r4 Use σ D Indicates; when r is r3, σ r4 Represents the radial stress at the junction of the reinforced concrete lining area and the anchor reinforcement area. At this time, σ r4 Use σ C express.

[0093] Step 2: Shaft lining design method for the first lining support stage

[0094] like Figure 3 As shown, the primary lining structure is composed of reinforced concrete lining, forming the primary lining support area of ​​the second layer.

[0095] In the specific embodiment, the first lining is supported by reinforced concrete (C30 concrete), the wall is supported by a multifunctional suspended formwork, the section height can be adjusted according to the actual working conditions, the formwork is suspended by a stable vehicle, and the demoulding is performed by a pneumatic hydraulic pump. The excavation is carried out by manual labor, pneumatic picks, etc. in conjunction with a small excavator.

[0096] For the primary lining support and the subsequent steel lining installation, the relationship between stress (radial stress or hoop stress)-radius (distance from the centerline of the pressure pipe shaft) and displacement-radius can be expressed by formula (3).

[0097]

[0098] In the formula, u i(r) represents the displacement expression of the i-th zone, m; σ ri , σ θi Represents the expression of radial stress and hoop stress in zone i, Pa; ε ri is the radial strain of the first lining support area, ε θi is the hoop strain of the primary lining support area; G i represents the shear modulus of the ith zone, Pa; μ4 represents the Poisson's ratio of the ith zone; C m , C n is the coefficient to be determined.

[0099] Strain general formula:

[0100] Specifically, the relationship between the stress-radius (the distance between the first lining support area and the center line of the pressure pipeline shaft) and the displacement-radius of the first lining support area can be expressed by formula (4).

[0101]

[0102] Where r represents the distance between the primary lining support area and the centerline of the pressure pipe shaft, m; u3 represents the displacement of the primary lining support area, m; σ r3 represents the radial stress in the primary lining support area, σ θ3 represents the hoop stress in the primary lining support area, Pa; ε r3 is the radial strain of the first lining support area, ε θ3 is the hoop strain of the primary lining support area; G3 is the shear modulus of the primary lining support area, Pa; μ3 is the Poisson's ratio of the primary lining support area; C5 and C6 are unknown coefficients, and their expressions are shown in equations (14)-(17).

[0103] When r is r3, σ r3 Represents the radial stress at the junction of the reinforced concrete lining area and the anchor reinforcement area. At this time, σ r3 Use σ C It means (similar to the first step, when r is r3, σ r4 (σ C ) is the same); when r is r2, σ r3 Represents the radial stress at the junction of the expansive concrete area and the reinforced concrete lining area. At this time, σ r3 Use σ B Step 3: Calculation of the concrete thickness of the primary lining support area

[0104] Taking into account the safety and economic benefits of reinforced concrete lining support, the ultimate bearing capacity of concrete must be taken into account when designing the concrete thickness.

[0105] Using the Mohr-Coulomb criterion, it can be known that the shear stress τ and the normal stress σ on the failure surface should satisfy the following relationship:

[0106]

[0107] Among them, τ is shear stress, Pa; σ is normal stress, Pa; tg is tan (tangent); c is cohesion, Pa; is the internal friction angle, °; if the principal stress is used, the above formula (5) can be rewritten as:

[0108]

[0109] Formula (6) is called the Mohr-Coulomb failure condition, where σ1 represents the first principal stress, Pa; σ3 represents the third principal stress, Pa.

[0110] For the concrete structure, σ1=σ θ ,σ3=σ r , substituting formula (4) into formula (6) we get:

[0111]

[0112] Where r2 represents the distance from the inner edge of the reinforced concrete lining to the center line of the pressure pipe shaft, m; r3 represents the distance from the inner edge of the anchor reinforcement area (i.e. the outer edge of the reinforced concrete lining) to the center line of the pressure pipe shaft, m; represents the stress on the inner edge of concrete, Pa; Represents the stress at the contact surface between concrete and surrounding rock, Pa. and Compared with σ in the above B and σ C There is a difference. and represents the stress at the inner and outer edges of C30 reinforced concrete when only one layer of C30 reinforced concrete is supported, σ B and σ C It represents the stress of inner and outer edges of C30 reinforced concrete under four-layer shaft wall condition; It can be determined according to the actual situation, or you can assign the value yourself; According to the calculation, the ground stress σ can also be approximated as M , but the result will be biased towards large;

[0113] in, Through survey, it was found that use and σ M Express it, get The stress expression of

[0114] Only one layer of reinforced concrete support condition (such as Figure 4 The concrete mechanics expression is as follows:

[0115]

[0116] Where r represents the distance between the primary lining support area (i.e. reinforced concrete lining area) and the centerline of the pressure pipe shaft, m; and is the coefficient to be determined; represents the displacement under the condition of only one layer of reinforced concrete support, m; It represents the strain under the condition of only one layer of reinforced concrete support; Represents the stress under the condition of only one layer of reinforced concrete support, Pa.

[0117] The mechanical expression of the surrounding rock area is as follows:

[0118]

[0119] Where r represents the distance between the surrounding rock and the centerline of the pressure pipe shaft under only one lining support, m; is the coefficient to be determined; represents the displacement of surrounding rock under only one lining support, m; It represents the strain of surrounding rock with only one lining support; It represents the stress of surrounding rock under only one lining support, Pa; G5 represents the shear modulus of surrounding rock; μ5 represents the Poisson's ratio of surrounding rock.

[0120] The known stress continuity conditions are:

[0121]

[0122] The undetermined coefficients can be obtained:

[0123]

[0124] According to the displacement continuity condition:

[0125]

[0126] It can be concluded that The expression is as follows:

[0127]

[0128] Among them, Q1-Q6 are unknown coefficients, and their expressions are as follows:

[0129]

[0130] In the formula, r ∞ It indicates the position infinitely far from the center line of the shaft and can be infinite;

[0131] Considering the stress on the inner and outer edges of the concrete well wall, equation (7) can be simplified as:

[0132]

[0133] The concrete thickness D can be expressed using formula (8).

[0134] D=r3-r2 (9)

[0135] Combining equations (8) and (9), we can get the concrete thickness expression as follows:

[0136]

[0137] Step 4: Shaft wall design method during steel lining installation

[0138] like Figure 5 As shown, the first lining structure and the steel lining structure are filled with expansive concrete to form a second lining structure, which is the third-layer expansive concrete area; the steel lining structure formed by the steel plate is the fourth-layer steel lining area.

[0139] In a specific embodiment, after the shaft construction is completed, all the facilities in the shaft, such as the sealing plate, the hanging plate, the template, the compressed air and water supply pipeline, are removed in sequence, the temporary hanging plate during the steel pipe construction is lowered into the shaft, the temporary sealing plate is installed, and then the temporary hanging plate is lowered to the bottom of the shaft. During this period, the steel lining is installed simultaneously, and the facilities such as the ash pipe and power cable required for backfilling the concrete are installed. The steel lining (Q345R steel plate) is lowered by a hoist. The Q345R steel lining is installed from bottom to top, and C25 expansive concrete is cyclically filled between the steel lining and the outer wall.

[0140] Specifically, the relationship between the stress-radius (the distance between the expansive concrete area and the centerline of the pressure pipe shaft) and the displacement-radius of the filling expansive concrete can be expressed by formula (11); the relationship between the stress-radius (the distance between the steel lining area and the centerline of the pressure pipe shaft) and the displacement-radius of the Q345R steel lining can be expressed by formula (12).

[0141]

[0142] Where r is the distance between the expansion concrete area and the centerline of the pressure pipe shaft, m; u2 is the displacement of the expansion concrete area, m; σ r2 , σ θ2 Respectively represent the radial stress and hoop stress in the expansive concrete area, Pa; ε r2 , ε θ2 are the radial strain and circumferential strain of the expansive concrete zone, respectively; G2 represents the shear modulus of the expansive concrete zone, Pa; μ2 represents the Poisson's ratio of the expansive concrete zone; C3 and C4 are unknown coefficients, and their expressions are shown in equations (14)-(17).

[0143] When r is r2, σ r2 Represents the radial stress at the junction of the expansive concrete area and the reinforced concrete lining area. At this time, σ r2 Use σ B It means (similar to the second step, when r is r2, σ r3 (σ B ) is the same); when r is r1, σ r2 Represents the radial stress at the junction of the steel lining area and the expansive concrete area. At this time, σ r2 Use σ A express.

[0144]

[0145] Where r is the distance between the steel lining area and the centerline of the pressure pipe shaft, m; u1 is the displacement of the steel lining area, m; σ r1 , σ θ1 Respectively represent the radial stress and hoop stress of the steel lining area, Pa; ε r1 , ε θ1 are the radial strain and circumferential strain of the steel lining area, respectively; G1 represents the shear modulus of the steel lining area, Pa; μ1 represents the Poisson's ratio of the steel lining area; C1 and C2 are unknown coefficients, and their expressions are shown in equations (14)-(17).

[0146] When r is r1, σ r1 Represents the radial stress at the junction of the steel lining area and the expansive concrete area. At this time, σ r1 Use σ A It means (similar to the above σ when r is r1) r2 (σ A ) is the same); when r is r0, σ r1 Represents the radial stress at the inner edge of the steel lining area, at this time σ r1 Indicated by P0.

[0147] By combining equations (1), (4), (11), (12) and the stress boundary condition equation (13),

[0148]

[0149] Where P0 represents the radial stress at the inner edge of the steel lining area, Pa; σ A represents the radial stress at the junction of the steel lining area and the expansive concrete area, Pa; σ B represents the radial stress at the junction of the expansive concrete area and the reinforced concrete lining area, Pa; σ C represents the radial stress at the junction of the reinforced concrete lining area and the anchor reinforcement area, Pa; σ D represents the radial stress at the junction of the anchor reinforcement area and the surrounding rock area, Pa; σ MRepresents the original rock stress. According to formula (13), the expressions of C1-C8 can be obtained as follows:

[0150]

[0151] Where N1-N 21 Represents the unknown coefficient, where N1-N 21 The expression is as follows:

[0152]

[0153] In the formula, r0 represents the distance from the inner edge of the steel lining area to the center line of the pressure pipe shaft, m; r1 represents the distance from the inner edge of the expansive concrete area to the center line of the pressure pipe shaft, m; r2 represents the distance from the inner edge of the reinforced concrete lining area to the center line of the pressure pipe shaft, m; r3 represents the distance from the inner edge of the anchor reinforcement area to the center line of the pressure pipe shaft, m; r4 represents the distance from the outer edge of the anchor reinforcement area to the center line of the pressure pipe shaft, m; G1 represents the shear modulus of the steel lining area, Pa; G2 represents the shear modulus of the expansive concrete area, Pa; G3 represents the shear modulus of the reinforced concrete lining area, Pa; G4 represents the shear modulus of the anchor reinforcement area, Pa; μ1 represents the Poisson's ratio of the steel lining area; μ2 represents the Poisson's ratio of the expansive concrete area; μ3 represents the Poisson's ratio of the reinforced concrete lining area (i.e., the first lining support area); μ4 represents the Poisson's ratio of the anchor reinforcement area; M1-M6 are unknown coefficients. The expressions of M1-M6 are as follows:

[0154]

[0155] Where C 1ini , C 2ini The expression is as follows:

[0156]

[0157] In the formula, σ ini Represents the virtual support force, Pa, and its size is related to the distance from the excavation surface; r5 represents the outer edge of the surrounding rock action area, which is usually taken as infinite, m.

[0158] Example

[0159] 1 Background:

[0160] The Xinjiang Kuitun River Water Diversion Project Xinlongkou Power Station Penstock Project has a pipe length of 1450.38m, a steel pipe net diameter of 4.1m, and a designed water diversion flow of 48.5m 3 / s, flow velocity in pipe 3.83m / s, design water head 342.304m, maximum water hammer pressure 4.2MPa, power station installed capacity 140MW. 0+710-1+234.20 section is the underground buried pipe section, which consists of a vertical shaft and a lower flat tunnel. The top elevation of the vertical shaft is 1227m, the bottom elevation of the excavation is 999m, the vertical shaft is 228m deep, the excavation diameter is 6.6m, and the excavation section is 34.2m 2 The upper part is Class IV soil, and the middle and lower parts are cemented gravel. The initial support adopts anchor mesh spraying + steel arch frame, in which the anchor rod adopts φ25×5mm, L=4m self-propelled anchor rod (plum blossom arrangement spacing 2.0m, row spacing 2.0m, rock entry 3.45m), the steel mesh adopts φ6mm steel bar, the sprayed concrete thickness is 100mm, the strength grade is C25, and the steel arch frame is processed with 16# I-beam. 8 φ10 soft permeable drainage pipes are evenly arranged in a circle at 3.65m from the center line of the shaft.

[0161] The vertical shaft section is located at the lower part of the slope at the front edge of the IV-level terrace and the rear edge of the III-level terrace on the right bank of the Kuitun River. It adopts the form of a tunnel with a diameter of 6.3m. The surrounding rock of the tunnel is the Lower Pleistocene (Q / 1x) Xiyu conglomerate, which can be divided into two layers: the upper part is blue-gray and khaki, with weak mud cementation and medium permeability. The lower part is grayish white, mud-calcium cementation, with a thickness of more than 100m and medium permeability.

[0162] 2. Material parameters of the weakly cemented gravel layer pressure pipeline shaft model:

[0163] The physical and mechanical parameters of the materials used in the experiment are shown in Table 1-3 below:

[0164]

[0165]

[0166]

[0167] 3. Expressions of displacement, stress and thickness of the four-layer shaft wall structure:

[0168] According to the above formula, combined with Table 1-3, and substituting the relevant parameter values, the following formula is obtained:

[0169] The displacement and stress expressions of the Q345R steel lining area are as follows (18):

[0170]

[0171] The displacement and stress expressions of the C25 expansive concrete zone are as follows (19):

[0172]

[0173] The displacement and stress expressions of C30 reinforced concrete lining area are as follows (20):

[0174]

[0175] The displacement and stress expressions of the anchor reinforcement area are as follows (21):

[0176]

[0177] The calculation formula for the concrete thickness of the primary lining support area is as follows (22):

[0178]

[0179] 4. When only one layer of C30 reinforced concrete lining is used for the shaft wall, the curve of concrete thickness changing with stress is as follows:

[0180] Under the condition of one layer of reinforced concrete lining support (i.e. excluding initial support, filling concrete, and steel lining), if Figure 6 As shown in the figure, according to formula (22), the C30 reinforced concrete lining single-layer shaft wall has no stress in the inner layer. Uniform stress at outer edge The curve of C30 reinforced concrete lining thickness changing with outer edge stress under the condition.

[0181] As the stress increases, the thickness of the concrete gradually increases. In this case, the stress on the outer edge of the well wall is The inner edge stress is According to formula (22), the ultimate thickness of concrete is 18.8 cm, while the concrete thickness used in this case is 45 cm (see Table 3), which meets the actual safety requirements.

[0182] 5. Influence of C30 reinforced concrete lining thickness on displacement and stress under four-layer shaft wall structure:

[0183] Through MATLAB programming, the value range of r is modified, and then the displacement curves under different C30 reinforced concrete lining thicknesses are obtained. Figure 7 The influence of the thickness of C30 reinforced concrete lining on the radial displacement curve of the shaft wall under four-layer shaft wall support is shown. When the thickness is 0.15m, the radial displacement of the innermost shaft wall (i.e. the inner edge of the Q345R steel lining) is 1.15mm; when the thickness is 0.25m, the radial displacement of the innermost shaft wall is 1.02mm; when the thickness is 0.35m, the radial displacement of the innermost shaft wall is 0.91mm; when the thickness is 0.45m, the radial displacement of the innermost shaft wall is 0.82mm. According to the observation of the image law, it can be seen that with the increase of thickness, the radial displacement of the shaft gradually decreases; however, with the increase of shaft wall thickness, the trend of radial displacement reduction begins to weaken.

[0184] Figure 8 The influence of different C30 reinforced concrete lining thicknesses on the characteristic curves of hoop stress and radial stress of the shaft wall is shown. When the support thickness is 0.15m, the radial stress of the surrounding rock at the interface between the C30 reinforced concrete lining and the anchor reinforcement area is 0.40MPa and the hoop stress is 18.56MPa.

[0185] When the support thickness is 0.25m, the radial stress of the surrounding rock at the interface between the C30 reinforced concrete lining and the anchor reinforcement area is 0.39MPa and the hoop stress is 17.62MPa.

[0186] When the support thickness is 0.35m, the radial stress of the surrounding rock at the interface between the C30 reinforced concrete lining and the anchor reinforcement area is 0.38MPa and the hoop stress is 16.81MPa.

[0187] When the support thickness is 0.45m, the radial stress of the surrounding rock at the interface between the C30 reinforced concrete lining and the anchor reinforcement area is 0.38MPa and the hoop stress is 16.11MPa.

[0188] The results show that with the increase of C30 reinforced concrete lining thickness, both radial stress and hoop stress decrease, and the reduction degree of hoop stress is more significant, while the change of radial stress is relatively small.

[0189] 6. Changes of characteristic curves of support structures under different internal water pressures:

[0190] Through the displacement continuity conditions and stress continuity conditions, all the unknown parameters in the four-layer shaft wall structure can be calculated, and then the displacement and stress expressions of the four-layer shaft wall can be obtained. By modifying the P0 value, the displacement at different positions can be obtained as the distance r from the center line of the shaft changes.

[0191] Fig. 9 The influence of internal water pressure on the radial displacement curve of the wellbore under four-layer wellbore support is shown. When the internal water pressure is positive, it indicates water injection; when the internal water pressure is negative, it indicates water pumping.

[0192] When the internal water pressure is 0.0MPa, the radial displacement of the innermost well wall is 0.36mm; when the internal water pressure is -2.0MPa, the radial displacement of the innermost well wall is 0.48mm; when the internal water pressure is -10.0MPa, the radial displacement of the innermost well wall is 0.96mm; when the internal water pressure is 2.0MPa, the radial displacement of the innermost well wall is 0.24mm; when the internal water pressure is 4.0MPa, the radial displacement of the innermost well wall is 0.12mm.

[0193] According to the observation of the image rules, when water is injected, the internal water pressure is opposite to the direction of the ground stress, the internal water pressure plays a supporting role, and the radial displacement of the shaft gradually decreases; however, when we pump water, the direction of the internal water pressure is the same as the direction of the ground stress, and the radial displacement increases.

[0194] Fig.10 The influence of internal water pressure on the stress change curve of the shaft wall under four-layer shaft wall support is shown. When the internal water pressure is 0.0MPa, the radial stress of the surrounding rock at the interface between the C30 reinforced concrete lining and the anchor reinforcement area is 5.19MPa and the hoop stress is 11.78MPa.

[0195] When the internal water pressure is -2.0MPa, the radial stress of the surrounding rock at the interface between the C30 reinforced concrete lining and the anchor reinforcement area is 4.92MPa and the hoop stress is 13.71MPa.

[0196] When the internal water pressure is -10.0MPa, the radial stress of the surrounding rock at the interface between the C30 reinforced concrete lining and the anchor reinforcement area is 3.84MPa and the hoop stress is 21.42MPa.

[0197] When the internal water pressure is 2.0 MPa, the radial stress of the surrounding rock at the interface between the C30 reinforced concrete lining and the anchor reinforcement area is 5.46 MPa and the hoop stress is 9.86 MPa.

[0198] When the internal water pressure is 4.0 MPa, the radial stress of the surrounding rock at the interface between the C30 reinforced concrete lining and the anchor reinforcement area is 5.73 MPa and the hoop stress is 7.93 MPa.

[0199] The results show that as the injection pressure increases, the radial stress increases and the annular stress decreases; as the pumping pressure increases, the radial stress decreases and the annular stress increases.

[0200] Pumping and injecting water from a well have very different effects on a shaft. Pumping water will lower the groundwater level, which may cause the soil around the shaft to settle or collapse, thus affecting the structural stability of the shaft; while injecting water will raise the groundwater level, increase the soil support, help maintain the structural integrity and stability of the shaft, and even prevent the bottom of the shaft from settling. In practical applications, it is necessary to comprehensively consider geological conditions and engineering requirements, and reasonably select a water well management strategy to ensure the safe operation of the shaft.

[0201] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A four-layer shaft wall structure for a pressure pipeline shaft, characterized in that: Lay each layer of shaft wall structure in sequence along the surrounding rock toward the center line of the pressure pipeline shaft; The first layer, anchor reinforcement area: including the initial support structure of hollow self-propelled anchors, steel mesh, steel arch frame and mesh shotcrete; The second layer, the first lining support area: the first lining structure formed by reinforced concrete lining; The third layer, expansive concrete area: the expansive concrete is filled in the primary lining structure and the steel lining structure to form the secondary lining structure; Fourth layer, steel lining area: steel lining structure formed by steel plates.

2. The four-layer shaft wall structure of the pressure pipeline vertical shaft according to claim 1 is characterized in that: The sprayed concrete in the first layer is C25 concrete; the reinforced concrete in the second layer is C30 concrete; the expansive concrete in the third layer is C25 concrete; and the steel plate in the fourth layer is Q345R steel plate.

3. The design method of the four-layer shaft wall structure of the pressure pipeline vertical shaft according to claim 1 or 2 is characterized in that: According to the elastic-plastic theory, using the equilibrium equation, geometric equation, constitutive equation, and Mohr-Coulomb criterion, the relationship between the stress and displacement of each layer and the distance from the center line of the pressure pipeline shaft is constructed respectively, and the minimum thickness of the reinforced concrete lining in the second layer is calculated.

4. The design method according to claim 3, characterized in that: The design method comprises the following steps: (1) Establish the relationship between the stress and displacement of the first layer of anchor reinforcement area and the distance between the anchor reinforcement area and the center line of the pressure pipeline shaft; (2) Establish the relationship between the stress and displacement of the second layer primary lining support area and the distance between the primary lining support area and the center line of the pressure pipeline shaft; (3) Using the Mohr-Coulomb criterion and considering the ultimate bearing capacity of concrete, a relationship between the thickness of the reinforced concrete lining in the second layer and the stress is established to calculate the minimum thickness of the reinforced concrete lining in the second layer; the thickness of the reinforced concrete lining in the second layer is the thickness of the concrete in the second layer; (4) Establish the relationship between the stress and displacement of the third layer of expansive concrete area and the distance between the expansive concrete area and the centerline of the penstock shaft; (5) Establish the relationship between the stress and displacement of the fourth layer steel lining area and the distance between the steel lining area and the center line of the pressure pipeline shaft.

5. The design method according to claim 4, characterized in that: The specific method of step (1) is: The relationship between the stress and displacement of the first layer of anchor reinforcement area and the distance between the anchor reinforcement area and the center line of the pressure pipeline shaft is established, as shown in formula (1); Where r is the distance between the anchor reinforcement area and the centerline of the pressure pipe shaft, m; u4 is the displacement of the anchor reinforcement area, m; σ r4 represents the radial stress in the anchor reinforcement area, Pa; σ θ4 represents the hoop stress in the anchor reinforcement area, Pa; G4 represents the shear modulus of the anchor reinforcement area, Pa; μ4 represents the Poisson's ratio of the anchor reinforcement area; S represents the row spacing of the anchor, m; D S Indicates the spacing of anchor rods, m; E b represents the elastic modulus of the anchor, Pa; Y represents the cross-sectional area of ​​the anchor, m 2 ; σ M represents the original rock stress, Pa; ε r4 is the radial strain in the anchor reinforcement area, ε θ4 is the hoop strain of the anchor reinforcement area, expressed as formula (2); C7, C8, C 1ini , C 2ini is the coefficient to be determined; 6. The design method according to claim 4, characterized in that: The specific method of step (2) is: The relationship between the stress and displacement of the second layer first lining support area and the distance between the first lining support area and the center line of the pressure pipeline shaft is established, as shown in formula (4); Where r represents the distance between the primary lining support area and the centerline of the pressure pipe shaft, m; u3 represents the displacement of the primary lining support area, m; σ r3 represents the radial stress in the primary lining support area, Pa; σ θ3 represents the hoop stress in the primary lining support area, Pa; ε r3 is the radial strain of the first lining support area, ε θ3 is the hoop strain of the first lining support area; G3 represents the shear modulus of the first lining support area, Pa; μ3 represents the Poisson's ratio of the first lining support area; σ M represents the original rock stress, Pa; C5 and C6 are unknown coefficients; 7. The design method according to claim 4, characterized in that: The specific method of step (3) is: Using the Mohr-Coulomb criterion, the relationship between the reinforced concrete lining thickness and stress in the second layer is established; the reinforced concrete lining thickness in the second layer is the thickness D of the concrete in the second layer, as shown in formula (10); Where D is the thickness of the concrete in the second layer; r3 is the distance from the inner edge of the anchor reinforcement area to the center line of the pressure pipe shaft, m, where the inner edge of the anchor reinforcement area is the outer edge of the reinforced concrete lining; c is the cohesion, Pa; is the internal friction angle, °; It represents the stress on the inner edge of concrete when only one layer of reinforced concrete lining is used as support, Pa; It represents the stress at the contact surface between concrete and surrounding rock when there is only one layer of reinforced concrete lining, Pa; The expression is as follows: In the formula, Q1-Q6 are unknown coefficients, and the expressions of Q1-Q6 are as follows: Where r2 represents the distance from the inner edge of the reinforced concrete lining area to the center line of the pressure pipe shaft; r3 represents the distance from the outer edge of the reinforced concrete lining area to the center line of the pressure pipe shaft, m; r ∞ It represents the position infinitely far from the center line of the shaft, m; G5 represents the shear modulus of the surrounding rock; μ5 represents the Poisson's ratio of the surrounding rock.

8. The design method according to claim 4, characterized in that: The specific method of step (4) is: The relationship between the stress and displacement of the third layer of expansive concrete area and the distance between the expansive concrete area and the center line of the pressure pipe shaft is established, as shown in formula (11); Where r is the distance between the expansion concrete area and the centerline of the pressure pipe shaft, m; u2 is the displacement of the expansion concrete area, m; σ r2 , σ θ2 Respectively represent the radial stress and hoop stress in the expansive concrete zone, Pa; ε r2 , ε θ2 are the radial strain and hoop strain of the expansive concrete zone, respectively; G2 represents the shear modulus of the expansive concrete zone, Pa; μ2 represents the Poisson's ratio of the expansive concrete zone; σ M represents the original rock stress, Pa; C3 and C4 are unknown coefficients; The specific method of step (5) is: respectively establish the relationship between the stress and displacement of the fourth layer steel lining area and the distance between the steel lining area and the center line of the pressure pipeline shaft, such as formula (12); Where r is the distance between the steel lining area and the centerline of the pressure pipe shaft, m; u1 is the displacement of the steel lining area, m; σ r1 , σ θ1 Respectively represent the radial stress and hoop stress of the steel lining area, Pa; ε r1 , ε θ1 are the radial strain and hoop strain of the steel lining area respectively; G1 represents the shear modulus of the steel lining area, Pa; μ1 represents the Poisson's ratio of the steel lining area; σ M represents the original rock stress, Pa; C1 and C2 are unknown coefficients; 9. The design method according to claim 4, characterized in that: Combine equations (1), (4), (11), (12) and the stress boundary condition (13) to calculate: P0, σ A , σ B , σ C , σ D : The expressions for C1-C8 are as follows: Where P0 represents the boundary stress at the inner edge of the steel lining area, Pa; σ A represents the radial stress at the junction of the steel lining area and the expansive concrete area, Pa; σ B represents the radial stress at the junction of the expansive concrete area and the reinforced concrete lining area, Pa; σ C represents the radial stress at the junction of the reinforced concrete lining area and the anchor reinforcement area, Pa; σ D represents the radial stress at the junction of the anchor reinforcement area and the surrounding rock area, Pa; σ M Indicates the original rock stress, Pa; N1-N 21 represents the undetermined coefficient; N1-N 21 The expression is as follows: Wherein, r0 represents the distance from the inner edge of the steel lining area to the center line of the pressure pipe shaft, m; r1 represents the distance from the inner edge of the expansive concrete area to the center line of the pressure pipe shaft, m; r2 represents the distance from the inner edge of the reinforced concrete lining area to the center line of the pressure pipe shaft, m; r3 represents the distance from the inner edge of the anchor reinforcement area to the center line of the pressure pipe shaft, m; r4 represents the distance from the outer edge of the anchor reinforcement area to the center line of the pressure pipe shaft, m; G1 represents the shear modulus of the steel lining area, Pa; G2 represents the shear modulus of the expansive concrete area, Pa; G3 represents the shear modulus of the reinforced concrete lining area, Pa; G4 represents the shear modulus of the anchor reinforcement area, Pa; μ1 represents the Poisson's ratio of the steel lining area; μ2 represents the Poisson's ratio of the expansive concrete area; μ3 represents the Poisson's ratio of the primary lining support area; μ4 represents the Poisson's ratio of the anchor reinforcement area; M1-M6 are undetermined coefficients; The expressions of M1-M6 are as follows: Where C 1ini , C 2ini The expression is as follows: In the formula, σ ini represents the virtual support force, Pa; r5 represents the outer edge of the surrounding rock action area, which is infinite, m.

10. Application of the four-layer shaft wall structure of a pressure pipeline vertical shaft as claimed in claim 1 or 2 in a weakly cemented gravel layer.

Images