A method for calculating the safe burial depth of underground high-pressure caverns in non-conformal structural surface slope areas

Abstract

The present invention discloses a method for calculating the safe burial depth of an underground high-pressure cavern in a non-conformal structural surface slope zone, which is based on considering the effect of the internal pressure of the high-pressure cavern on the cavern, the shearing effect of the rock mass, the influence of the weak interlayer or structural surface with a reverse gentle dip angle, the deadweight of the rock mass, and the shearing strength of the rock mass on the side of the slope, and calculates the safe burial depth of the underground high-pressure cavern in the non-conformal structural surface slope zone by establishing a mechanical equilibrium equation. The present invention can more accurately and effectively obtain the safe burial depth of the underground high-pressure cavern under macroscopic geological conditions of deep canyons and areas with large terrain fluctuations, and is more economically feasible under the premise of ensuring safety.

Description

Technical Field

[0001] The invention relates to a method for calculating the safe buried depth of an underground high-pressure cavern in a non-conformal structural surface slope zone, and belongs to the technical fields of geotechnical engineering, underground engineering and energy storage. Background Art

[0002] High-pressure underground caverns are important infrastructure in the energy and chemical industry, such as natural gas caverns and hydrogen storage caverns. High-pressure underground gas storage caverns are also an important part of compressed air energy storage power stations and are the technical key to ensuring their operating performance and reliability. The storage gas pressure of underground gas storage caverns is generally greater than 10MPa, and can be constructed using underground spaces such as abandoned underground caverns, salt rock karst cavities, and artificially excavated underground caverns in hard rocks. Among them, the commonly used forms are salt rock karst cavities and hard rock caverns. Artificially excavated underground caverns in hard rocks are the most widely used form of underground gas storage caverns.

[0003] Jin Weiping et al. believe that the cave site should be located in a place with suitable thickness of overlying and overlying rock mass, hard and complete rock mass, and simple hydrogeological conditions. According to the existing calculation method of underground cavern depth, the most likely high-pressure cavern depth is 750-850m. It can be seen that the current requirements for cave site selection are too high, the burial depth is too large, and it is inconsistent with the macroscopic geological judgment of areas with deep canyons and large terrain fluctuations.

[0004] At present, Xia Caichu and other scholars mainly refer to the Norwegian criterion, hydraulic fracturing criterion and minimum principal stress criterion to determine the depth of underground high-pressure caverns. The principle of the Norwegian criterion is to require that the weight of the overlying rock mass on the pressure tunnel body should not be less than the vertical uplift force acting on the surrounding rock area of ​​the tunnel body. The Norwegian criterion is as follows:

[0005]

[0006] Where: H——minimum covering thickness of high-pressure cavern, m;

[0007] p——pressure of high-pressure gas in the cave, kPa;

[0008] F——empirical coefficient, generally 1.3 to 1.5;

[0009] γ R ——weight of rock and soil, kN / m 3 ;

[0010] α——ground inclination angle, when it is greater than 60°, take 60°.

[0011] The hydraulic fracturing criterion is a method of selecting a reasonable burial depth to avoid hydraulic fracturing. In a high-pressure cavern, the water pressure is converted into the air pressure in the cavern as a design principle. The University of Dronham in Norway proposed that the internal water pressure of an unlined pressure tunnel should be less than the minimum principal stress criterion of the initial stress field of the surrounding rock. This criterion includes the Norwegian criterion, which is expressed as follows after converting the internal water pressure into the air pressure in the cavern:

[0012] pF≤σ min (3.2)

[0013] Where: p——pressure of high-pressure gas in the cave, kPa;

[0014] F——safety factor, generally 1.3~1.5;

[0015] σ min ——Minimum principal stress of the initial stress field of the surrounding rock around the tunnel, kPa.

[0016] Replace σ in formula (3.2) min It is defined as the smaller value of the minimum principal stress of the initial stress field and the normal stress of the fracture, which can include the Norwegian criterion, hydraulic fracturing criterion and minimum principal stress criterion at the same time. Hydraulic tunnels sometimes do not use special sealing measures, mainly relying on confining pressure to prevent leakage, while hard rock compressed gas storage caverns use lining and sealing layers, and the role of surrounding rock sealing is limited. Therefore, using formula (3.2) as the design criterion is too conservative, and the resulting burial depth is too large.

[0017] From the perspective of economic feasibility, in practice the burial depth of the cavern should be as small as possible while ensuring safety. Summary of the invention

[0018] The purpose of the present invention is to provide a method for calculating the safe burial depth of underground high-pressure caverns in non-conformal structural surface slope areas. The method can more accurately and effectively obtain the safe burial depth of underground high-pressure caverns under macroscopic geological conditions in areas with deep canyons and large terrain undulations, and is more economically feasible while ensuring safety.

[0019] The technical solution of the present invention is a method for calculating the safe burial depth of an underground high-pressure cavern in a non-conformal structural surface slope zone, comprising the following steps:

[0020] ① Establish the relationship equation between the vertical burial depth H and the horizontal burial depth L of underground high-pressure caverns in slope areas, and convert the horizontal burial depth into the vertical burial depth;

[0021] ② Considering the shear strength of the rock mass and the influence of the weak interlayer or structural surface with a gentle dip angle, considering the pressure of the high-pressure gas in the cave on the cave wall, gravity and the shear resistance of the structural surface, establish the mechanical equilibrium equation of the horizontal direction of the underground high-pressure cavern, combine the mechanical equilibrium equation of the horizontal direction of the underground high-pressure cavern with the relationship equation in step ①, and solve the vertical burial depth H of the high-pressure cavern1 ;

[0022] ③ Considering the pressure of the high-pressure gas in the cave on the cave top, the deadweight of the rock and soil, and the shear resistance of the rock mass on the slope side, the vertical mechanical equilibrium equation of the underground high-pressure cavern is established, and the vertical burial depth H of the high-pressure cavern is obtained by solving it. 2 If there is a steep-angle weak interlayer or structural surface, the vertical mechanical equilibrium equation of the underground high-pressure cavern is established by considering the balance of the pressure on the cave roof, the deadweight of the rock and soil, and the shear resistance of the interlayer or structural surface. The vertical burial depth H of the underground high-pressure cavern is obtained by solving the equation. 3 ;

[0023] ④ Compare the vertical depth values ​​of step ② and step ③, take the larger value, and obtain the safe burial depth of the underground high-pressure cavern on the slope of the non-conformal structural surface.

[0024] In the aforementioned method for calculating the safe burial depth of underground high-pressure caverns in non-conformal structural surface slope areas, the relationship equation of step ① is H=L·tanα, where H is the vertical burial depth of the high-pressure cavern, L is the horizontal burial depth of the high-pressure cavern, and α is the slope inclination angle.

[0025] In the above-mentioned method for calculating the safe burial depth of underground high-pressure caverns in non-conformal structural surface slope zones, the mechanical equilibrium equation of the underground high-pressure caverns in the horizontal direction in step ② is:

[0026]

[0027] Among them, K h is the safety factor; p is the pressure of high-pressure gas in the cave; h is the height of the high-pressure cavern section; L is the horizontal burial depth of the high-pressure cavern; c is the cohesion of the weak interlayer or structural surface; δ is the inclination angle of the weak interlayer or structural surface with a reverse dip angle; α is the slope inclination; γ is the weight of the rock and soil; It is the internal friction angle of the weak interlayer or structural surface with a reverse and gentle inclination angle.

[0028] In the above-mentioned method for calculating the safe burial depth of underground high-pressure caverns in non-conformal structural surface slope zones, the mechanical equilibrium equation of the underground high-pressure caverns in the horizontal direction in step ③ is:

[0029]

[0030] Among them, K v is the safety factor; p is the pressure of high-pressure gas in the cave; b is the width of the top plate of the high-pressure cavern section; H is the vertical burial depth of the high-pressure cavern; γ is the weight of the rock and soil; θ is the rock mass fracture angle; γ is the weight of the rock and soil; is the internal friction angle of the rock and soil mass; α is the slope inclination angle.

[0031] In the above-mentioned method for calculating the safe burial depth of underground high-pressure caverns in non-conformal structural surface slope zones, the mechanical equilibrium equation 2 of the underground high-pressure caverns in the horizontal direction of step ③ is:

[0032]

[0033] Among them, K v is the safety factor; p is the high-pressure gas pressure in the cave; b is the width of the top plate of the high-pressure cavern section; H is the vertical burial depth of the high-pressure cavern; γ is the weight of the rock and soil; c is the cohesion of the steeply inclined weak interlayer or structural surface; θ is the inclination angle of the steeply inclined weak interlayer or structural surface; is the internal friction angle of the steeply inclined weak interlayer or structural surface; α is the slope inclination angle.

[0034] In the above-mentioned method for calculating the safe buried depth of underground high-pressure caverns in non-conformal structural surface slope areas, as a preferred method, the K h The value is 1.5 to 3.0, and the K v The value ranges from 1.5 to 3.0.

[0035] Compared with the prior art, the present invention is based on the consideration of the shear strength of the rock mass, the influence of the weak interlayer or structural surface with a reverse gentle dip angle, the deadweight of the rock mass, and the shear strength of the rock mass on the side of the slope, and the mechanical equilibrium equation is established to calculate the safe burial depth of the underground high-pressure cavern in the non-conformal structural surface slope zone. The present invention can be applied to the calculation of the safe burial depth of the underground high-pressure cavern under the macroscopic geological conditions of deep canyons and areas with large terrain fluctuations, thus overcoming the problem of "avoiding the selection of cavern sites in deep canyons and areas with large terrain fluctuations" in the prior art. The present invention can be used to predict the burial depth of the cavern in the site selection of underground high-pressure cavern projects on slopes with non-conformal structural surfaces, or to determine whether the burial depth meets the requirements when the cavern location has been preliminarily selected. The safe burial depth obtained according to the present invention is smaller than the burial depth obtained by the current Norwegian criterion, hydraulic fracturing criterion, and minimum principal stress criterion, which greatly reduces the construction cost and has broad application prospects, thus overcoming the problem of "the burial depth obtained by the current Norwegian criterion, hydraulic fracturing criterion, and minimum principal stress criterion is conservative". BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the geological model of the cavern burial depth of the present invention;

[0037] Figure 2 It is a mechanical model and force analysis schematic diagram of the horizontal control of the buried depth of the cavern in the present invention;

[0038] Figure 3 It is a mechanical model of the vertical control situation of the buried depth of the cavern and a schematic diagram of the force analysis.

[0039] Markings in the accompanying drawings: 1 is the rectangular part of the cave section (OAGF), with a height of h-h'; 2 is the semicircular part of the cave section (OFG), with a height of h'; 3 is the slope, with an inclination angle of α; 4 is the top of the slope; 5 is the shear failure surface with a length of s and a rock rupture angle of θ, or a steeply inclined weak interlayer or structural surface (GM) with a length of s and an inclination angle of θ; 6 is a gently inclined weak interlayer or structural surface (AC) with a length of l and an inclination angle of δ. DETAILED DESCRIPTION

[0040] The present invention is further described below in conjunction with the accompanying drawings and embodiments, but they are not intended to limit the present invention.

[0041] Embodiment. In combination with the drawings of the invention and engineering practice experience, in order to simplify the calculation while meeting the engineering accuracy, the mechanical model used for derivation of the present invention makes the following assumptions:

[0042] (1) The buried depth H of the cavern is much greater than the height h of the cavern section, that is, H+h≈H+h'=H;

[0043] (2) Each mechanical model only considers the balance of forces but not the balance of moments.

[0044] The method for calculating and evaluating the buried depth of an underground high-pressure cavern in a non-conformal structural surface slope zone of the present invention comprises the following steps:

[0045] (1) The relationship equation between the vertical burial depth H and the horizontal burial depth L of the underground high-pressure cavern in the slope area is established through mathematical relationships, and the horizontal burial depth is converted into the vertical burial depth;

[0046] (2) Considering the shear strength of the rock mass and the influence of the weak interlayer or structural surface with a reverse dip angle, the pressure of the high-pressure gas in the cave on the cave wall, gravity and the shear resistance of the structural surface, the mechanical equilibrium equation of the underground high-pressure cavern in the horizontal direction is established. The equation is combined with the equation in step (1) to solve the vertical burial depth H of the high-pressure cavern. 1 ;

[0047] (3) Considering the pressure of the high-pressure gas in the cave on the cave roof, the deadweight of the rock and soil, and the shear resistance of the rock mass on the slope side, the vertical mechanical equilibrium equation of the underground high-pressure cavern is established, and the vertical burial depth H of the high-pressure cavern is obtained by solving it. 2 If there is a steep-angle weak interlayer or structural surface, the balance of the high-pressure gas in the cave on the cave top pressure, the deadweight of the rock and soil, and the shear resistance of the interlayer (structural surface) is considered, and the vertical mechanical equilibrium equation of the underground high-pressure cavern is established, and the vertical burial depth H of the high-pressure cavern is obtained by solving it. 3 ;

[0048] (4) Compare the vertical depth values ​​of step (2) and step (3), take the larger value, and obtain the safe burial depth H of the underground high-pressure cavern on the slope of the non-conformal structural surface.

[0049] Furthermore, the relationship equation between the vertical burial depth H and the horizontal burial depth L of the underground high-pressure cavern is established by mathematical relationship in step (1) (see Appendix Figure 1 ):

[0050] H=L·tanα (5.1)

[0051] Where: H——vertical burial depth of high-pressure cavern, m;

[0052] L——horizontal burial depth of high-pressure cavern, m;

[0053] α——slope inclination angle, (°).

[0054] Furthermore, the shear strength of the structural surface considered in step (2) is combined with the Coulomb shear strength formula:

[0055]

[0056] Where: τ f ——shear strength of rock mass structural surface, kPa;

[0057] σ——normal stress on the structural surface, kPa;

[0058] c——cohesion of structural surface, kPa.

[0059] Assuming that there is a weak interlayer or structural surface with a dip angle of δ, combined with Figure 1 , establish the relationship equation between the length l of the anti-dipping gentle-angle weak interlayer or structural surface and the horizontal burial depth L:

[0060] L=l(cosδ+sinδ·cotα) (5.3)

[0061] Where: L——horizontal burial depth of high-pressure cavern, m;

[0062] l——the length of the weak interlayer or structural surface with a reverse dip angle, m;

[0063] δ——the inclination angle of the weak interlayer or structural surface with a reverse dip angle, (°);

[0064] α——slope inclination angle, (°).

[0065] Figure 2 The gravity G of the rock mass in the middle ACD area 1 for:

[0066]

[0067] Where: G 1 —— Figure 2 The gravity of the rock and soil in the ACD area in the mechanical model, kN;

[0068] H——vertical burial depth of high-pressure cavern, m;

[0069] γ——mass density of rock and soil, kN / m 3 ;

[0070] l——the length of the weak interlayer or structural surface with a reverse dip angle, m;

[0071] δ——the inclination angle of the weak interlayer or structural surface with a gentle dip angle, (°).

[0072] The pressure of the high-pressure gas in the cave is p, which generates a horizontal thrust F on the outside of the cave. 气h For (single width):

[0073] F 气h =ph (5.5)

[0074] Where: F 气h ——The high-pressure gas produces a horizontal thrust on the outside of the hole, kN;

[0075] p——pressure of high-pressure gas in the cave, kPa;

[0076] h——height of high-pressure tunnel section, m.

[0077] The gas pressure in the cavern produces a thrust outward along the soft interlayer or structural surface with a reverse and gentle inclination angle. The gravity G 1 The anti-sliding force generated on the soft interlayer or structural surface with a reverse and gentle inclination angle is related to G 1 The sum of the frictional resistance caused by the vertical stress of gravity on the surface is F 1 :

[0078]

[0079] Where: F 1 ——Gravity G 1 The anti-sliding force generated on the weak interlayer or structural surface with a reverse and gentle inclination angle, kN;

[0080] G 1 —— Figure 2 The gravity of the rock and soil in the ACD area in the mechanical model, kN;

[0081] δ——the inclination angle of the weak interlayer or structural surface with a reverse dip angle, (°);

[0082] ——Internal friction angle of weak interlayer or structural surface with reverse dip angle, (°).

[0083] Combined with formula 5.2, resistance F 抗h for:

[0084] F 抗h =(cl+F1 )cosδ (5.7)

[0085] Where: F 抗h ——Resistance of single-width rock and soil mass to horizontal thrust of high-pressure gas, kN;

[0086] l——the length of the weak interlayer or structural surface with a reverse dip angle, m;

[0087] c——cohesion of rock and soil mass in soft interlayer or structural surface with reverse dip angle, kPa;

[0088] F 1 ——Gravity G 1 The anti-sliding force generated on the weak interlayer or structural surface with a reverse and gentle inclination angle, kN;

[0089] δ——the inclination angle of the weak interlayer or structural surface with a gentle dip angle, (°).

[0090] Combining equations 5.1, 5.3 to 5.7, we get the horizontal resistance F 抗h for:

[0091]

[0092] Where: F 抗h ——Resistance of single-width rock and soil mass to horizontal thrust of high-pressure gas, kN;

[0093] L——horizontal burial depth of high-pressure cavern, m;

[0094] c——cohesion of the weak interlayer or structural surface with a reverse and gentle inclination angle, kPa;

[0095] δ——the inclination angle of the weak interlayer or structural surface with a reverse dip angle, (°);

[0096] α——slope inclination, (°);

[0097] γ——mass density of rock and soil, kN / m 3 ;

[0098] ——Internal friction angle of weak interlayer or structural surface with reverse dip angle, (°).

[0099] Establish the mechanical equilibrium equation of the underground high-pressure cavern in the horizontal direction:

[0100] F 抗h =K h F 气h (5.9)

[0101] Where K h is the safety factor, which can be 1.5 to 3.0; F 抗hF is the resistance of single-width rock and soil to the horizontal thrust of high-pressure gas, kN; 气h is the horizontal thrust generated by high-pressure gas on the outside of the hole, kN.

[0102] Combining equations 5.1, 5.5, 5.8, and 5.9, we can get a vertical depth H of the high-pressure cavern: 1 The quadratic equation (see formula 5.10) can be solved to obtain the vertical burial depth H of the high-pressure cavern. 1 (Discard negative solutions to quadratic equations).

[0103]

[0104] Where: K h ——Safety factor, which can be 1.5 to 3.0;

[0105] p——pressure of high-pressure gas in the cave, kPa;

[0106] h——height of high-pressure cavern section, m;

[0107] L——horizontal burial depth of high-pressure cavern, m;

[0108] c——cohesion of weak interlayer or structural surface, kPa;

[0109] δ——the inclination angle of the weak interlayer or structural surface with a reverse dip angle, (°);

[0110] α——slope inclination, (°);

[0111] γ——mass density of rock and soil, kN / m 3 ;

[0112] ——Internal friction angle of weak interlayer or structural surface with reverse dip angle, (°).

[0113] If h=30m,p=10MPa,α=45°,γ=27kN / m 3 , c 1 =0.075MPa, Reference gravity dam foundation anti-sliding stability calculation K h 3.0 can be taken, considering the most unfavorable situation (δ=0). Substituting the data into formula 5.10, the solution is: L=401m, H 1 =401m.

[0114] Furthermore, in step (3), the mechanical equilibrium equation of the vertical direction of the underground high-pressure cavern is established by considering the deadweight of the rock mass and the shear strength of the rock mass on the slope side. The geological model is as follows: Figure 1 As shown in Figure 3 As shown, combined Figure 3The self-weight W of the rock and soil within the model range can be obtained as follows:

[0115] W=W 1 +W 2 (5.11)

[0116] W 1 =Hγb (5.12)

[0117]

[0118] In the formula: W—— Figure 3 Gravity of rock and soil within the scope of the mechanical model, kN;

[0119] W 1 —— Figure 3 The gravity of the rock mass within the DEFG range, kN;

[0120] W 2 —— Figure 3 Gravity of rock mass within the middle DGM range, kN;

[0121] H——vertical burial depth of high-pressure cavern, m;

[0122] γ——mass density of rock and soil, kN / m 3 ;

[0123] b——width of the top plate of the high-pressure cavern section, m;

[0124] s——the length of the sheared rock slope, m;

[0125] θ——rock fracture angle, (°).

[0126] Combination Figure 3 , the relationship between the vertical burial depth H of the high-pressure cavern and the length s of the shear rock slope is obtained:

[0127] H=s(tanα+tanθ)cosθ (5.14)

[0128] Where: H——vertical burial depth of high-pressure cavern, m;

[0129] s——the length of the sheared rock slope, m;

[0130] θ——rock fracture angle, (°);

[0131] α——slope inclination angle, (°).

[0132] Combined with the Engineering Geology Handbook, the rock mass fracture angle θ is:

[0133]

[0134] Where: θ——rock mass fracture angle, (°);

[0135] ——internal friction angle of rock and soil mass, (°);

[0136] α——slope inclination angle, (°).

[0137] The pressure of the high-pressure gas in the cave is p, which produces a vertical lifting force F above the cave. 气v (considering a single-width rock and soil body):

[0138] F 气v =pb (5.16)

[0139] Where: F 气v ——The vertical lifting force exerted by high-pressure gas on the top of the hole, kN;

[0140] p——pressure of high-pressure gas in the cave, kPa;

[0141] b——width of the top plate of the high-pressure cavern section, m.

[0142] If the rock mass is damaged along the fracture angle θ, the rock mass deadweight W 2 The anti-slip force generated on this surface is related to W 2 The sum of the frictional resistances generated by the vertical stress on this surface is F 2 :

[0143]

[0144] Where: F 2 ——Self-weight of rock and soil W 2 The sum of the anti-slip force and friction resistance generated, kN;

[0145] W 2 —— Figure 3 Gravity of rock mass within the middle DGM range, kN;

[0146] θ——rock fracture angle, (°);

[0147] ——Internal friction angle of rock and soil mass, (°).

[0148] Vertical resistance F 抗v for:

[0149] F 抗v =W 1 +F 2 ·sinθ (5.18)

[0150] Where: F 抗v ——Resistance of rock and soil to the vertical lifting force of high-pressure gas, kN;

[0151] W 1—— Figure 3 The gravity of the rock mass within the DEFG range, kN;

[0152] F 2 ——Self-weight of rock and soil W 2 The sum of the anti-slip force and friction resistance generated, kN;

[0153] θ——rock fracture angle, (°).

[0154] Combining equations 5.10 to 5.18, we can get the resistance F 抗v for:

[0155]

[0156] Where: F 抗v ——Resistance of rock and soil to the vertical lifting force of high-pressure gas, kN;

[0157] H——vertical burial depth of high-pressure cavern, m;

[0158] γ——mass density of rock and soil, kN / m 3 ;

[0159] b——width of the top plate of the high-pressure cavern section, m;

[0160] θ——rock fracture angle, (°);

[0161] γ——mass density of rock and soil, kN / m 3 ;

[0162] ——internal friction angle of rock and soil mass, (°);

[0163] α——slope inclination angle, (°).

[0164] If there is a steeply dipping weak interlayer or structural plane with a dip angle of θ, Figure 3 The gravity W of the rock mass within the DGM range 2 The calculation method is the same as that of formula 5.12, but θ should be taken as the inclination angle of the steeply inclined weak interlayer or structural surface:

[0165]

[0166] Where: W 2 —— Figure 3 Gravity of rock mass within the middle DGM range, kN;

[0167] H——vertical burial depth of high-pressure cavern, m;

[0168] γ——mass density of rock and soil, kN / m 3 ;

[0169] s——the length of the sheared rock slope, m;

[0170] θ——The inclination angle of steeply inclined weak interlayer or structural plane, (°).

[0171] Combined with the Coulomb shear strength formula (see formula 5.2) and Figure 3 , the relationship between the vertical burial depth H of the high-pressure cavern and the length s of the failure surface when the steeply inclined weak interlayer or structural surface is destroyed is obtained:

[0172] H=s(tanα+tanθ)cosθ (5.21)

[0173] Where: H——vertical burial depth of high-pressure cavern, m;

[0174] s——the length of the failure surface when the failure is along the steeply inclined weak interlayer or structural surface, m;

[0175] θ——the inclination angle of steeply inclined weak interlayer or structural plane, (°);

[0176] α——slope inclination angle, (°).

[0177] If the rock and soil mass is damaged along the steeply inclined weak interlayer or structural surface, the deadweight W 2 The anti-slip force F 3 :

[0178]

[0179] Where: F 3 ——Self-weight of rock and soil W 2 The sum of the anti-slip force and friction resistance generated, kN;

[0180] W 2 —— Figure 3 Gravity of rock mass within the middle DGM range, kN;

[0181] θ——the inclination angle of steeply inclined weak interlayer or structural plane, (°);

[0182] ——Internal friction angle of steeply inclined weak interlayer or structural surface, (°).

[0183] The vertical resistance F 抗v for:

[0184] F 抗v =W 1 +(cs+F 3 )sinθ (5.23)

[0185] Where: F 抗v ——Resistance of rock and soil to the vertical lifting force of high-pressure gas, kN;

[0186] W 1 —— Figure 3 The gravity of the rock mass within the DEFG range, kN;

[0187] F 3 ——Self-weight of rock and soil W 2 The sum of the anti-slip force and friction resistance generated, kN;

[0188] c——cohesion of steeply inclined weak interlayer or structural surface, kPa;

[0189] s——the length of the failure surface when the failure is along the steeply inclined weak interlayer or structural surface, m;

[0190] θ——The inclination angle of steeply inclined weak interlayer or structural plane, (°).

[0191] Combining equations 5.11, 5.12, 5.20 to 5.23, we can get the vertical resistance F 抗v for:

[0192]

[0193] Where: F 抗v ——Resistance of rock and soil to the vertical lifting force of high-pressure gas, kN;

[0194] H——vertical burial depth of high-pressure cavern, m;

[0195] γ——mass density of rock and soil, kN / m 3 ;

[0196] b——width of the top plate of the high-pressure cavern section, m;

[0197] c——cohesion of steeply inclined weak interlayer or structural surface, kPa;

[0198] θ——the inclination angle of steeply inclined weak interlayer or structural plane, (°);

[0199] ——internal friction angle of steeply inclined weak interlayer or structural surface, (°);

[0200] α——slope inclination angle, (°).

[0201] The mechanical equilibrium equation of the underground high-pressure cavern in the vertical direction is:

[0202] F 抗v =K v F 气v (5.25)

[0203] Where K v is the safety factor, which can be 1.5 to 3.0; F 抗v F is the resistance of rock and soil to the vertical lifting force of high-pressure gas, kN; 气vis the vertical lifting force exerted by the high-pressure gas on the top of the hole, kN.

[0204] When considering the deadweight of the rock mass and the shear strength of the rock mass on the slope side, the combined equations 5.16, 5.19, and 5.25 give a vertical depth H of the high-pressure cavern. 2 The quadratic equation (see Equation 5.26) can be solved to obtain the vertical burial depth H of the high-pressure cavern. 2 (Discard negative solutions to quadratic equations).

[0205]

[0206] Where: K v ——Safety factor, which can be 1.5 to 3.0;

[0207] p——pressure of high-pressure gas in the cave, kPa;

[0208] b——width of the top plate of the high-pressure cavern section, m;

[0209] H——vertical burial depth of high-pressure cavern, m;

[0210] γ——mass density of rock and soil, kN / m 3 ;

[0211] θ——rock fracture angle, (°);

[0212] γ——mass density of rock and soil, kN / m 3 ;

[0213] ——internal friction angle of rock and soil mass, (°);

[0214] α——slope inclination angle, (°).

[0215] When there is a steeply inclined weak interlayer or structural surface, the combined equations 5.16, 5.24, and 5.25 give a vertical depth H of the high-pressure cavern. 3 The quadratic equation (see Equation 5.27) can be solved to obtain the vertical burial depth H of the high-pressure cavern. 3 (Discard negative solutions to quadratic equations).

[0216]

[0217] Where: K v ——Safety factor, which can be 1.5 to 3.0;

[0218] p——pressure of high-pressure gas in the cave, kPa;

[0219] b——width of the top plate of the high-pressure cavern section, m;

[0220] H——vertical burial depth of high-pressure cavern, m;

[0221] γ——mass density of rock and soil, kN / m 3 ;

[0222] c——cohesion of steeply inclined weak interlayer or structural surface, kPa;

[0223] θ——the inclination angle of steeply inclined weak interlayer or structural plane, (°);

[0224] ——internal friction angle of steeply inclined weak interlayer or structural surface, (°);

[0225] α——slope inclination angle, (°).

[0226] When considering the deadweight of the rock mass and the shear strength of the rock mass on the slope side, if p = 10MPa, b = 15m, α = 45°, γ = 27kN / m 3 , rock mass parameters c 2 =1.8MPa, Safety factor K v Take 3.0 and substitute the data into equation 5.19 to obtain the vertical burial depth H of the high-pressure cavern. 2 , that is, H 2 =214m.

[0227] If there is a steeply inclined weak interlayer or structural surface with an inclination angle of θ, p = 10MPa, b = 15m, α = 45°, γ = 27kN / m 3 , steeply inclined weak interlayer or structural surface parameter θ=65°, c 3 =0.075MPa, Substituting the data into equation 5.27, we can solve for the vertical burial depth of the high-pressure cavern H: 3 , that is, H 3 =278m.

[0228] Furthermore, in step (4), the vertical depth values ​​of step (2) and step (3) are compared, and the buried depth H of the underground high-pressure cavern is H 1 Same as H 2 or H 3 The maximum value of H = max{H 1 ,H 2} or H=max{H 1 ,H 3}, that is, H=401m.

[0229] If the following Norwegian criteria are used:

[0230]

[0231] Where: H——minimum covering thickness of high-pressure cavern, m;

[0232] p——pressure of high-pressure gas in the cave, kPa;

[0233] F——empirical coefficient, generally 1.3 to 1.5;

[0234] γ R ——weight of rock and soil, kN / m 3 ;

[0235] α——ground inclination angle, when it is greater than 60°, take 60°.

[0236] Considering a larger safety reserve, when the safety factor is 1.5, the same parameters are used for calculation, H=786m>401m. The burial depth obtained by the Norwegian criterion is too conservative. Similarly, the burial depth obtained by hydraulic fracturing and minimum principal stress criteria is too large. This shows the superiority of the method described in the present invention.

Claims

1. A method for calculating the safe burial depth of underground high-pressure caverns in non-conformal structural surface slope areas, characterized in that: The steps include: ① Establish the relationship equation between the vertical burial depth H and the horizontal burial depth L of underground high-pressure caverns in slope areas, and convert the horizontal burial depth into the vertical burial depth; ② Considering the shear strength of the rock mass and the influence of the weak interlayer or structural surface with a reverse and gentle dip angle, considering the pressure of the high-pressure gas in the cave on the cave wall, gravity and the shear resistance of the structural surface, establish the mechanical equilibrium equation of the horizontal direction of the underground high-pressure cavern, combine the mechanical equilibrium equation of the horizontal direction of the underground high-pressure cavern with the relationship equation in step ①, and solve the vertical burial depth H1 of the high-pressure cavern; ③ Considering the pressure of the cave roof by the high-pressure gas in the cave, the deadweight of the rock and soil, and the shear resistance of the rock mass on the slope side, the vertical mechanical equilibrium equation 1 of the underground high-pressure cavern is established, and the vertical burial depth H2 of the high-pressure cavern is obtained by solving it; if there is a steep-angle weak interlayer or structural surface, considering the balance of the pressure of the cave roof by the high-pressure gas in the cave, the deadweight of the rock and soil, and the shear resistance of the interlayer or structural surface, the vertical mechanical equilibrium equation 2 of the underground high-pressure cavern is established, and the vertical burial depth H3 of the high-pressure cavern is obtained by solving it; ④ Compare the vertical depth values ​​of step ② and step ③, take the larger value, and obtain the safe burial depth of the underground high-pressure cavern on the slope of the non-conformal structural surface.

2. The method for calculating the safe buried depth of underground high-pressure caverns in non-conformal structural surface slope zones according to claim 1 is characterized in that: The relationship equation of step ① is H=L·tanα, where H is the vertical burial depth of the high-pressure cavern, L is the horizontal burial depth of the high-pressure cavern, and α is the slope inclination angle.

3. The method for calculating the safe buried depth of underground high-pressure caverns in non-conformal structural surface slope zones according to claim 1 is characterized in that: The mechanical equilibrium equation of the underground high-pressure cavern in the horizontal direction of step ② is: Among them, K h is the safety factor; p is the pressure of high-pressure gas in the cave; h is the height of the high-pressure cavern section; L is the horizontal burial depth of the high-pressure cavern; c is the cohesion of the weak interlayer or structural surface; δ is the inclination angle of the weak interlayer or structural surface with a reverse dip angle; α is the slope inclination; γ is the weight of the rock and soil; It is the internal friction angle of the weak interlayer or structural surface with a reverse and gentle inclination angle.

4. The method for calculating the safe buried depth of underground high-pressure caverns in non-conformal structural surface slope zones according to claim 1 is characterized in that: The mechanical equilibrium equation of the underground high-pressure cavern in the horizontal direction of step ③ is: Among them, K v is the safety factor; p is the pressure of high-pressure gas in the cave; b is the width of the top plate of the high-pressure cavern section; H is the vertical burial depth of the high-pressure cavern; γ is the weight of the rock and soil; θ is the rock mass fracture angle; γ is the weight of the rock and soil; is the internal friction angle of the rock and soil mass; α is the slope inclination angle.

5. The method for calculating the safe buried depth of underground high-pressure caverns in non-conformal structural surface slope zones according to claim 1 is characterized in that: The mechanical equilibrium equation 2 of the underground high-pressure cavern in the horizontal direction of step ③ is: Among them, K v is the safety factor; p is the high-pressure gas pressure in the cave; b is the width of the top plate of the high-pressure cavern section; H is the vertical burial depth of the high-pressure cavern; γ is the weight of the rock and soil; c is the cohesion of the steeply inclined weak interlayer or structural surface; θ is the inclination angle of the steeply inclined weak interlayer or structural surface; is the internal friction angle of the steeply inclined weak interlayer or structural surface; α is the slope inclination angle.

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