A quantitative determination method for the included angle between the strike of a rock stratum bedding plane and the longitudinal axis of an underground cavern

Abstract

The present invention discloses a method for quantitatively determining the included angle between the strike of a rock stratum plane and the longitudinal axis of an underground chamber, determining the excavation parameters of the chamber; establishing a three-dimensional numerical simulation model with different included angles between the strike of the rock stratum plane and the longitudinal axis of the chamber; plotting the curves of the maximum displacement value, the maximum strain value, and the depth curve of the maximum plastic zone of the chamber surrounding rock under different included angles; obtaining two groups of approximately linearly varying characteristic points at both ends of the three curves; respectively calculating the critical included angles between the strike of the rock stratum corresponding to each curve and the longitudinal axis of the underground chamber, obtaining a total of three included angle values, and taking the smallest one of the included angle values as the critical included angle between the strike of the rock stratum and the longitudinal axis of the underground chamber quantitatively determined by the present invention. θ; When the included angle between the longitudinal axis of the chamber and the rock mass plane θs ≥ θ , the orientation of the longitudinal axis of the chamber is reasonable; the present invention solves the problem of the difference in the requirements for the included angle between the longitudinal axis of the chamber and the rock stratum plane in different specifications, realizes the quantitative determination of the included angle, and provides a scientific basis for the layout design of underground chambers.

Description

Technical Field

[0001] The present invention relates to the field of chamber design in water conservancy and hydropower projects, and particularly relates to a method for quantitatively determining the angle between the strike of a rock stratum plane and the longitudinal axis of an underground chamber. Background Technique

[0002] There is a direct correlation between the stability of the surrounding rock of the side wall of an underground powerhouse chamber and the selection of the orientation of the longitudinal axis of the chamber. According to the "Design Code for Hydraulic Tunnels" (NB / T 10391-2020), the angle between the tunnel line and the strikes of the rock stratum plane, the main structural fracture plane, and the weak zone should preferably be large, and the angle should not be less than 30°; for high-dip thin rock strata with loose interlayer bonding, the angle should not be less than 45°. According to the "Design Code for Underground Powerhouses of Hydropower Stations" (NB / T 35090-2016), the angle between the longitudinal axis of the underground chamber and the strike of the main structural plane of the rock mass should preferably not be less than 50°.

[0003] In the current code system, the requirements for the angle between the rock stratum strike and the tunnel axis are limited to qualitative descriptions, and no quantitative determination method has been clearly given. At the same time, there are differences in the regulations of different codes for the angle of the rock mass, which undoubtedly increases the design difficulty for designers. More critically, when the angle between the longitudinal axis of the chamber and the strike of the rock stratum plane does not meet the code requirements, targeted engineering measures need to be taken to deal with it, sometimes resulting in a significant increase in project investment.

[0004] Therefore, the quantitative determination of the angle between the strike of the rock stratum plane and the longitudinal axis of the underground chamber has important research significance, and there is an urgent need to propose a method for quantitatively determining the angle between the strike of the rock stratum plane and the longitudinal axis of the underground chamber to solve the problem of how to quantitatively determine this angle. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for quantitatively determining the angle between the strike of a rock stratum plane and the longitudinal axis of an underground chamber, to solve the problem of differences in the requirements for the angle between the longitudinal axis of the chamber and the rock stratum plane in different codes, to achieve quantitative determination of the angle, and to provide a scientific basis for the layout design of underground chambers.

[0006] To achieve the above purpose, the technical solution of the present invention is as follows:

[0007] A method for quantitatively determining the angle between the strike of a rock stratum plane and the longitudinal axis of an underground chamber, the method comprising:

[0008] Determine the excavation size of the chamber according to the chamber design data, and determine the physical and mechanical parameters of the rock mass according to the geological data;

[0009] According to the excavation size of the cavern and the physical and mechanical parameters of the rock mass, a three-dimensional numerical simulation model with different angles between the strike of the rock stratum plane and the longitudinal axis of the cavern is established. The three-dimensional numerical simulation model is used to calculate the maximum displacement value of the surrounding rock of the cavern, or the maximum strain value of the surrounding rock of the cavern, or the depth value of the maximum plastic zone of the surrounding rock under the set angle between the strike of the rock stratum plane and the longitudinal axis of the cavern;

[0010] Draw multiple curves, namely, draw the maximum displacement value curve of the surrounding rock of the cavern under different angles, draw the maximum strain value curve of the surrounding rock of the cavern under different angles, and draw the maximum plastic zone depth curve of the surrounding rock of the cavern under different angles;

[0011] Obtain two sets of approximately linearly varying characteristic points at both ends of the multiple curves respectively;

[0012] Draw a straight line through one set of the characteristic points at one end of the maximum displacement value curve of the surrounding rock of the cavern under different angles, draw another straight line through the other set of the characteristic points at the other end of the maximum displacement value curve of the surrounding rock of the cavern under different angles, and calculate the abscissa of the intersection point of the two straight lines ;

[0013] Draw a straight line through one set of the characteristic points at one end of the maximum strain value curve of the surrounding rock of the cavern under different angles, draw another straight line through the other set of the characteristic points at the other end of the maximum strain value curve of the surrounding rock of the cavern under different angles, and calculate the abscissa of the intersection point of the two straight lines ;

[0014] Draw a straight line through one set of the characteristic points at one end of the maximum plastic zone depth curve of the surrounding rock of the cavern under different angles, draw another straight line through the other set of the characteristic points at the other end of the maximum plastic zone depth curve of the surrounding rock of the cavern under different angles, and calculate the abscissa of the intersection point of the two straight lines ;

[0015] Take , , The minimum value of the three values as the critical angle between the strike of the rock stratum plane and the longitudinal axis of the underground cavern ;

[0016] Conduct a quantitative evaluation on the rationality of the orientation of the longitudinal axis of the cavern: When the angle between the longitudinal axis of the cavern and the rock stratum plane θs ≥ θ , it is considered that the current orientation of the longitudinal axis of the cavern is reasonable. When the angle between the longitudinal axis of the cavern and the rock stratum plane θs < θ , it is considered that the current orientation of the longitudinal axis of the cavern is unreasonable, and it is necessary to adjust the orientation of the longitudinal axis or take reinforcement measures.

[0017] Furthermore, the The calculation method is as follows: Obtain two sets of approximately linearly varying characteristic points at both ends of the maximum displacement value curve of the chamber surrounding rock at different included angles. The two sets of approximately linearly varying characteristic points include ( θ a , a ), ( θ b , b ), and ( θ c , c ), ( θ d , d ), where θ a , θ b , θ c , θ d represent the included angles between the strike directions of different rock strata and the longitudinal axis of the chamber; a , b, c and d represent the included angles between the strike directions of different rock strata and the longitudinal axis of the chamber θ a , θ b , θ c , θ d respectively correspond to the maximum displacement values of the surrounding rock. Draw the first straight line θ a , a ), ( θ b , b ), and draw the second straight line y 1, and draw the second straight line θ c , c ), ( θ d , d ), where y 2, where y 1 = ( b - a ) × ( x - θ a ) / ( θ b - θ a ) + a , y 2 = ( d - c ) × ( x - θ c ) / (θ d - θ c )+ c ; When y 1 = y 2, calculate the abscissa of the intersection point of the two straight lines y 1 and y 2 ;

[0018] .

[0019] Furthermore, the calculation method of the is: Obtain two sets of approximately linearly varying characteristic points at both ends of the maximum strain value curve of the chamber surrounding rock at different included angles. The two sets of approximately linearly varying characteristic points include ( θ a , a ), ( θ b , b ), and ( θ c , c ), ( θ d , d ), where θ a , θ b , θ c , θ d represents the included angle between the strike of the different rock stratum planes and the longitudinal axis of the chamber; a 、 b, c and d represent the included angles between the strike of the different rock stratum planes and the longitudinal axis of the chamber θ a , θ b , θ c , θ d respectively correspond to the maximum strain values of the surrounding rock. Draw the first straight line θ a , a )、( θ b , b ), and draw the second straight line y 1, and draw the second straight line θ c , c ), ( θ d , d ), where y 2, where y1 = ( b - a ) × ( x - θ a ) / ( θ b - θ a ) + a , y 2 = ( d - c ) × ( x - θ c ) / ( θ d - θ c ) + c ;When y 1 = y 2, calculate the abscissa y 1 and y 2 of the intersection point of the two straight lines ;

[0020] 。

[0021] Furthermore, the calculation method of the is: Obtain two sets of approximately linearly varying characteristic points at both ends of the maximum plastic zone depth curve of the chamber surrounding rock at different included angles. The two sets of approximately linearly varying characteristic points include ( θ a , a ), ( θ b , b ) and ( θ c , c ), ( θ d , d ), where θ a , θ b , θ c , θ d represent the included angles between the strike directions of different rock strata and the longitudinal axis of the chamber; a , b, c and d represent the included angles between the strike directions of different rock strata and the longitudinal axis of the chamber θ a , θ b , θ c , θ dThe corresponding maximum depth values of the plastic zone of the surrounding rock, passing through ( θ a , a ), ( θ b , b ) to draw the first straight line y 1, and passing through ( θ c , c ), ( θ d , d ) to draw the second straight line y 2, where y 1 = ( b - a ) × ( x - θ a ) / ( θ b - θ a ) + a , y 2 = ( d - c ) × ( x - θ c ) / ( θ d - θ c ) + c ; when y 1 = y 2, calculate the abscissa y 1 and y 2 of the intersection point of the two straight lines ;

[0022] .

[0023] The beneficial effects of the present invention are as follows:

[0024] The present invention provides a method for quantitatively determining the angle between the strike of a rock stratum plane and the longitudinal axis of an underground cavern, which can effectively make up for the defect that the current specifications only qualitatively require the angle between the rock stratum strike and the cavern axis, solve the problem of different requirements for the angle between the longitudinal axis of the cavern and the rock stratum plane in different specifications, realize the quantitative determination of the angle, and provide a scientific basis for the layout design of underground caverns. Description of the Drawings

[0025] Figure 1 is the analysis flow chart of a method for quantitatively determining the angle between the strike of a rock stratum plane and the longitudinal axis of an underground cavern according to the present invention.

[0026] Figure 2Schematic diagram of the curve of the maximum displacement value of the surrounding rock under different included angles between the strike of the rock stratum plane and the longitudinal axis of the underground chamber in the present invention.

[0027] Figure 3 Schematic diagram of the curve of the maximum strain value of the surrounding rock under different included angles between the strike of the rock stratum plane and the longitudinal axis of the underground chamber in the present invention.

[0028] Figure 4 Schematic diagram of the curve of the depth of the maximum plastic zone of the surrounding rock under different included angles between the strike of the rock stratum plane and the longitudinal axis of the underground chamber in the present invention.

[0029] Figure 5 3D numerical calculation model of the maximum displacement value of the surrounding rock under different included angles between the strike of the rock stratum plane and the longitudinal axis of the underground chamber in the specific embodiment of the present invention.

[0030] Figure 6 Calculation results of the maximum displacement value of the surrounding rock of the underground chamber under different included angles between the strike of the rock stratum plane and the longitudinal axis of the chamber in the specific embodiment of the present invention.

[0031] Figure 7 Curve of the maximum deformation value of the surrounding rock of the underground chamber, two groups of characteristic points at both ends and the included angle of the axis under different included angles between the strike of the rock stratum plane and the longitudinal axis of the chamber in the specific embodiment of the present invention. Detailed implementation manners

[0032] In order to make the purpose, technical solutions and advantages of the invention clearer, the present invention will be further described below with reference to the accompanying drawings.

[0033] The present invention provides a method for quantitatively determining the included angle between the strike of the rock stratum plane and the longitudinal axis of the underground chamber, which includes the following steps:

[0034] Step 1: Determine the initial calculation conditions.

[0035] According to the chamber design data, determine the chamber excavation size; according to the geological data, determine the physical and mechanical parameters of the rock mass, such as unit weight, deformation modulus, Poisson's ratio, internal friction angle, cohesion, tensile strength, etc.

[0036] Step 2: Establish numerical models with different included angles between the strike of the rock stratum plane and the longitudinal axis of the chamber and conduct stability analysis of the surrounding rock.

[0037] According to Step 1, establish 3D numerical simulation models with different included angles between the strike of the rock stratum plane and the longitudinal axis of the chamber, and conduct stability analysis of the surrounding rock during chamber excavation. The different included angle models can be β taken at angle intervals, such as 5°, 10°, 15°, etc., 0° ≤ β ≤ 90°, and the corresponding number of 3D numerical simulation models is n ( n = 90 / β + 1).

[0038] The 3D numerical simulation model in Step 2 is used to calculate the maximum displacement value of the surrounding rock during cavern excavation at different included angles and draw the curve of the maximum deformation value of the surrounding rock at different included angles; or used to calculate the maximum strain value of the cavern surrounding rock at different included angles and draw the curve of the maximum strain value of the cavern surrounding rock at different included angles; or used to calculate the maximum depth value of the plastic zone of the cavern surrounding rock at different included angles and draw the curve of the maximum depth of the plastic zone of the cavern surrounding rock at different included angles.

[0039] Regarding the 3D numerical simulation model in the present invention, an existing model can be used. Or obtain the relationship between the included angle between the strike of the rock stratum and the longitudinal axis of the cavern and the maximum displacement value of the cavern surrounding rock by fitting historical data; or obtain the relationship between the included angle between the strike of the rock stratum and the longitudinal axis of the cavern and the maximum strain value of the cavern surrounding rock by fitting historical data; or obtain the relationship between the included angle between the strike of the rock stratum and the longitudinal axis of the cavern and the maximum depth value of the plastic zone of the cavern surrounding rock by fitting historical data. For example, obtain ten groups of historical data, y = f(X1, X2, θ ), where y is the maximum displacement value of the cavern surrounding rock, X1 and X2 each represent a numerical value, and X1 and X2 can be the cavern excavation size or the value of the physical and mechanical parameters of the rock mass, θ is the included angle between the strike of the rock stratum and the longitudinal axis of the cavern. According to the ten groups of historical data, fit the relationship between the included angle between the strike of the rock stratum and the longitudinal axis of the cavern and the maximum displacement value of the cavern surrounding rock. Subsequently, substitute the included angle between the strike of the rock stratum and the longitudinal axis of the cavern into the said relationship to obtain the maximum displacement value corresponding to the said included angle. The relationship between the included angle between the strike of the rock stratum and the longitudinal axis of the cavern and the maximum strain value of the cavern surrounding rock, or the relationship between the included angle between the strike of the rock stratum and the longitudinal axis of the cavern and the maximum depth value of the plastic zone of the cavern surrounding rock can be obtained by the same method as above.

[0040] Step 3: As Figure 2 、 Figure 3 and Figure 4 shown, draw three curves, respectively draw the curve of the maximum displacement value of the cavern surrounding rock at different included angles, or draw the curve of the maximum strain value of the cavern surrounding rock at different included angles, or draw the curve of the maximum depth of the plastic zone of the cavern surrounding rock at different included angles.

[0041] Step 4: Obtain two sets of approximately linearly varying characteristic points at both ends of the curve.

[0042] According to Step 3, obtain two sets of approximately linearly varying characteristic points at both ends of the said curve ( θ a , a ), ( θ b , b ) and ( θ c , c ), (θ d , d ), where θ a , θ b , θ c , θ d represents the angle between the strike of different rock stratum planes and the longitudinal axis of the cavern, with the unit of °; a 、 b, c and d represent the angle between the strike of different rock stratum planes and the longitudinal axis of the cavern θ a , θ b , θ c , θ d correspond to the maximum displacement values of the surrounding rock, with the unit of cm; or a 、 b, c and d represent the angle between the strike of different rock stratum planes and the longitudinal axis of the cavern θ a , θ b , θ c , θ d correspond to the maximum strain values of the surrounding rock, dimensionless; or a 、 b, c and d represent the angle between the strike of different rock stratum planes and the longitudinal axis of the cavern θ a , θ b , θ c , θ d correspond to the maximum depth value of the plastic zone of the surrounding rock, with the unit of cm.

[0043] Regarding the two groups of approximately linearly varying characteristic points at both ends, select the endpoints at both ends of the curve and the turning points where the curve undergoes linear variation.

[0044] Step Five: Draw straight lines through the two groups of characteristic points at both ends respectively, and calculate the abscissa of the intersection point of the two straight lines;

[0045] According to Step Four, draw straight lines through the two groups of approximately linearly varying characteristic points at both ends ( θ a , a ), ( θ b , b ) and ( θc , c ),( θ d , d ),( d , θ d ) draw a straight line y 1 and y 2, where y 1 = ([[]] b - a ) × ( x - θ a ) / ( θ b - θ a ) + a , y 2 = ([[]] d - c ) × ( x - θ c ) / ( θ d - θ c ) + c , specifically including:

[0046] Draw a straight line through a group of the said characteristic points at one end of the curve of the maximum displacement value of the surrounding rock of the cavern under different included angles y 1, and draw another straight line through another group of the said characteristic points at the other end of the curve of the maximum displacement value of the surrounding rock of the cavern under different included angles y 2, and calculate the abscissa of the intersection point of the two straight lines ; Calculate the abscissa of the intersection point of the two straight lines y 1 and y 2 , when y 1 = y 2, ,

[0047] Where: θ a , θ b , θ c , θ d represents the included angle between the strike of different rock strata and the longitudinal axis of the cavern, with the unit of °; a 、 b, c and d represent the included angle between the strike of different rock strata and the longitudinal axis of the cavern θ a , θ b ,θ c , θ d The maximum displacement values of the surrounding rock, corresponding respectively, unit: cm.

[0048] Draw a straight line through a set of the said characteristic points at one end of the curve of the maximum strain value of the surrounding rock of the cavern under different included angles y 1. Draw another straight line through another set of the said characteristic points at the other end of the curve of the maximum strain value of the surrounding rock of the cavern under different included angles y 2. Calculate the abscissa of the intersection point of the two straight lines ; Calculate the two straight lines y 1 and y 2 intersection abscissa , when y 1 = y 2,

[0049] ,

[0050] Wherein: θ a , θ b , θ c , θ d represents the included angle between the strike of different rock strata and the longitudinal axis of the cavern, unit: °; a 、 b, c and d represent the included angle between the strike of different rock strata and the longitudinal axis of the cavern θ a , θ b , θ c , θ d The maximum strain values of the surrounding rock, corresponding respectively.

[0051] Draw a straight line through a set of the said characteristic points at one end of the curve of the maximum depth of the plastic zone of the surrounding rock of the cavern under different included angles y 1. Draw another straight line through another set of the said characteristic points at the other end of the curve of the maximum depth of the plastic zone of the surrounding rock of the cavern under different included angles y 2. Calculate the abscissa of the intersection point of the two straight lines ; Calculate the two straight lines y 1 and y 2 intersection abscissa , when y 1 = y 2,

[0052] ,

[0053] Wherein: θa , θ b , θ c , θ d represents the included angle between the strike of different rock stratum planes and the longitudinal axis of the cavern, with the unit of °; a and b, c and d represent the included angle between the strike of different rock stratum planes and the longitudinal axis of the cavern θ a , θ b , θ c , θ d respectively corresponding to the maximum depth values of the plastic zone of the surrounding rock.

[0054] Take , , The minimum value among the three values is taken as the critical included angle between the strike of the rock stratum plane and the longitudinal axis of the underground cavern ;

[0055] Step Six: Quantitative evaluation of the rationality of the longitudinal axis orientation of the cavern

[0056] According to Step Five, quantitatively evaluate the rationality of the longitudinal axis orientation of the cavern. The evaluation criterion is: when the included angle between the longitudinal axis of the cavern and the rock mass plane θs ≥ critical included angle θ , it is considered that the current longitudinal axis orientation of the cavern is relatively reasonable. When the included angle between the longitudinal axis of the cavern and the rock mass plane θs < critical included angle θ , it is considered that the current longitudinal axis orientation of the cavern is less reasonable and it is necessary to adjust the longitudinal axis orientation or take targeted engineering measures.

[0057] Implementation case:

[0058] The main project of a hydropower station consists of a concrete double-curvature arch dam, flood discharge and energy dissipation buildings, left and right bank diversion power generation systems, and diversion buildings, etc. The total installed capacity is 10,200 MW, and the total reservoir capacity is 7.408 billion m 3 . The underground powerhouse cavern group adopts a layout pattern of parallel arrangement of the main powerhouse, main transformer chamber, and tailwater surge chamber. Among them, the maximum excavation dimensions (length × width × height) of the right bank main powerhouse are 333.00 m × 32.50 m (30.5 m below the rock anchor beam) × 89.80 m.

[0059] Using the method for quantitatively determining the included angle between the strike of a rock stratum plane and the longitudinal axis of an underground cavern of the present invention, quantitatively determine the included angle between the longitudinal axis of the main powerhouse of a hydropower station and the strike of the rock stratum plane, and evaluate the rationality of the longitudinal axis orientation of the cavern. The evaluation process is as Figure 1As shown in the figure, the specific implementation process is as follows:

[0060] Step 1: Determine the initial calculation conditions

[0061] In this example, the maximum excavation dimensions (length × width × height) of the main power house are 333.00m × 32.50m (30.5m below the rock anchor beam) × 89.80m respectively; the rock mass involved in the main power house is mainly medium-thick bedded dolomite Pt 2l 3-2 , and the values of the physical and mechanical parameters of the rock mass are shown in Table 1.

[0062] Table 1: Physical and mechanical parameters of the rock mass

[0063]

[0064] Step 2: Establish a numerical model with different angles between the strike of the rock layer plane and the longitudinal axis of the cavern and conduct a surrounding rock stability analysis

[0065] According to Step 1, establish a three-dimensional numerical simulation model with different angles between the strike of the rock layer plane and the longitudinal axis of the cavern, and conduct a surrounding rock stability analysis for the cavern excavation. For the sake of simplicity in analysis, in this embodiment, a straight line is drawn using two groups of characteristic points at both ends of the curve of the maximum displacement value of the surrounding rock of the cavern under different angles.

[0066] On the basis of meeting the calculation accuracy in this example, it is assumed that the equivalent thickness of the rock layer is 1.5m, that is, the rock mass is approximately simulated by using parallel planes with a spacing of 1.5m to cut the rock mass. In this example, β β is taken as 10°, 0° ≤ β ≤ 90°, and the number of corresponding three-dimensional numerical simulation models is n = 90 / 10 + 1 = 10, as shown in Figure 5 , among which, Figure 5 in (a) is the calculation and analysis model with an angle of 0°, Figure 5 in (b) is the calculation and analysis model with an angle of 10°, Figure 5 in (c) is the calculation and analysis model with an angle of 20°, Figure 5 in (d) is the calculation and analysis model with an angle of 30°, Figure 5 in (e) is the calculation and analysis model with an angle of 40°, Figure 5 in (f) is the calculation and analysis model with an angle of 50°, Figure 5 in (g) is the calculation and analysis model with an angle of 60°, Figure 5 in (h) is the calculation and analysis model with an angle of 70°, Figure 5 in (i) is the calculation and analysis model with an angle of 80°, Figure 5 in (j) is the calculation and analysis model with an angle of 90°.

[0067] Step 3: Draw the curve of the maximum displacement value of the surrounding rock of the cavern under different angles

[0068] According to Step 2, calculate the maximum displacement values of the surrounding rock during the excavation of the cavern at different included angles, as shown in Figure 6 , where Figure 6 in (a), it is the deformation result of the surrounding rock during the excavation of the cavern with an included angle of 0°, and the maximum displacement value of the surrounding rock is 6.5 cm; Figure 6 in (b), it is the deformation result of the surrounding rock during the excavation of the cavern with an included angle of 10°, and the maximum displacement value of the surrounding rock is 5.5 cm; Figure 6 in (c), it is the deformation result of the surrounding rock during the excavation of the cavern with an included angle of 20°, and the maximum displacement of the surrounding rock is 4.75 cm; Figure 6 in (d), it is the deformation result of the surrounding rock during the excavation of the cavern with an included angle of 30°, and the maximum displacement of the surrounding rock is 4.6 cm; Figure 6 in (e), it is the deformation result of the surrounding rock during the excavation of the cavern with an included angle of 40°, and the maximum displacement value of the surrounding rock is 4.4 cm; Figure 6 in (f), it is the deformation result of the surrounding rock during the excavation of the cavern with an included angle of 50°, and the maximum displacement value of the surrounding rock is 4.35 cm; Figure 6 in (g), it is the deformation result of the surrounding rock during the excavation of the cavern with an included angle of 60°, and the maximum displacement value of the surrounding rock is 4.3 cm; Figure 6 in (h), it is the deformation result of the surrounding rock during the excavation of the cavern with an included angle of 70°, and the maximum displacement value of the surrounding rock is 4.27 cm; Figure 6 in (i), it is the deformation result of the surrounding rock during the excavation of the cavern with an included angle of 80°, and the maximum displacement value of the surrounding rock is 4.26 cm; Figure 6 in (j), it is the deformation result of the surrounding rock during the excavation of the cavern with an included angle of 90°, and the maximum displacement value of the surrounding rock is 4.25 cm. According to the maximum deformation values of the surrounding rock during the excavation of the cavern at different included angles, draw the curve of the maximum displacement values of the surrounding rock at different included angles, as shown in Figure 7 .

[0069] Step 4: Obtain two sets of approximately linearly varying characteristic points at both ends of the curve

[0070] According to Step 3, obtain two sets of approximately linearly varying characteristic points (0, 6.5), (10, 5.5) and (50, 4.35), (90, 4.25) at both ends of the curve, as shown in Figure 7 . Among them, (0, 6.5) indicates that the maximum displacement value of the surrounding rock during the excavation of the cavern with an included angle of 0° is 6.5 cm, (10, 5.5) indicates that the maximum displacement value of the surrounding rock during the excavation of the cavern with an included angle of 10° is 5.5 cm, (50, 4.35) indicates that the maximum displacement value of the surrounding rock during the excavation of the cavern with an included angle of 50° is 4.35 cm, and (90, 4.25) indicates that the maximum displacement value of the surrounding rock during the excavation of the cavern with an included angle of 90° is 4.25 cm.

[0071] Step 5: Draw straight lines through the two sets of characteristic points at both ends respectively, and calculate the abscissa of the intersection point of the two straight lines θ

[0072] According to Step 4, draw a straight line through two sets of approximately linearly varying characteristic points at both ends, namely (0, 6.5), (10, 5.5) and (50, 4.35), (90, 4.25). y 1 and y 2, where y 1 = - x / 10 + 6.5, y 2 = (50 - x ) / 400 + 4.35; Calculate the abscissa of the intersection point of the two straight lines y 1 and y 2, which is θ = 20.8°, as shown in Figure 7 . Therefore, the critical included angle in this example θ = is 20.8°. Figure 7 In, the X-axis is the included angle between the strike of the rock stratum and the longitudinal axis of the cavern, and the Y-axis can be the maximum displacement value of the surrounding rock of the cavern corresponding to the included angle, or the maximum strain value of the surrounding rock of the cavern, or the depth value of the maximum plastic zone of the surrounding rock.

[0073] In a specific embodiment of the present invention, a straight line y 1 is drawn through a set of the characteristic points at one end of the curve of the maximum displacement value of the surrounding rock of the cavern under different included angles, and another straight line y 2 is drawn through another set of the characteristic points at the other end of the curve of the maximum displacement value of the surrounding rock of the cavern under different included angles, and the abscissa of the intersection point of the two straight lines is calculated for illustration; The method of calculating by drawing the curve of the maximum strain value of the surrounding rock of the cavern under different included angles and calculating by drawing the curve of the depth of the maximum plastic zone of the surrounding rock of the cavern under different included angles is similar, and will not be elaborated here one by one.

[0074] In a specific embodiment of the present invention, among the three calculated values of , , , is the smallest, and the smallest of the three values is taken as the critical included angle. In this embodiment, θ 1 = 20.8°, so the critical included angle θ is taken as 20.8°.

[0075] Step 6: Quantitative evaluation of the rationality of the longitudinal axis orientation of the cavern

[0076] In this example, the included angle between the longitudinal axis of the cavern and the rock mass bedding θs = 15° < critical included angle θ= 20.8°, the orientation of the longitudinal axis of the cavern is not reasonable. In fact, the layout area of the underground powerhouse cavern group on the right bank of this example project is located in a narrow triangular space surrounded by "riverbed - Baigou fault - extremely thin marbleized dolomite", and this area is located in the core of the fold, with distorted and variable rock strata, well-developed centimeter-level thin-layer steeply inclined rock masses, and a large-scale distribution of fractured rock masses with carbonaceous film attached to the bedding plane. Therefore, the adjustment space of the longitudinal axis of the cavern is very limited. During the actual construction process, targeted engineering measures were taken. The specific measures were to insert tension bolts with a length of 9 m and a prestress of 50 kN with backing plates on the basis of the original system support, and adjust the row spacing of the sidewall T = 2000 kN cables from 4.5 m to 3.0 m to ensure the stability of the surrounding rock of the cavern. This result verifies the accuracy of the present invention.

[0077] Finally, it should be noted that the content not described in detail in this specification belongs to the prior art well-known to those skilled in the art. The above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for quantitatively determining the included angle between the strike of a rock stratum bedding plane and the longitudinal axis of an underground cavern, characterized in that The method includes: Determine the excavation size of the cavern according to the cavern design data, and determine the physical and mechanical parameters of the rock mass according to the geological data; Establish a three-dimensional numerical simulation model with different angles between the strike of the rock stratum and the longitudinal axis of the cavern according to the excavation size of the cavern and the physical and mechanical parameters of the rock mass. The three-dimensional numerical simulation model is used to calculate the maximum displacement value of the cavern surrounding rock, or the maximum strain value of the cavern surrounding rock, or the depth value of the maximum plastic zone of the surrounding rock under the set angle between the strike of the rock stratum and the longitudinal axis of the cavern; Draw multiple curves, namely, draw the curve of the maximum displacement value of the cavern surrounding rock at different angles, draw the curve of the maximum strain value of the cavern surrounding rock at different angles, and draw the curve of the depth of the maximum plastic zone of the cavern surrounding rock at different angles; Obtain two sets of approximately linearly varying characteristic points at both ends of the multiple curves respectively; Draw a straight line through a set of characteristic points at one end of the curve of the maximum displacement value of the chamber surrounding rock at different angles, and draw another straight line through another set of characteristic points at the other end of the curve of the maximum displacement value of the chamber surrounding rock at different angles, and calculate the abscissa of the intersection point of the two straight lines ; Draw a straight line through a set of characteristic points at one end of the curve of the maximum strain value of the chamber surrounding rock at different angles, and draw another straight line through another set of characteristic points at the other end of the curve of the maximum strain value of the chamber surrounding rock at different angles, and calculate the abscissa of the intersection point of the two straight lines ; Draw a straight line through a set of characteristic points at one end of the curve of the maximum depth of the plastic zone of the chamber surrounding rock at different angles, and draw another straight line through another set of characteristic points at the other end of the curve of the maximum depth of the plastic zone of the chamber surrounding rock at different angles, and calculate the abscissa of the intersection point of the two straight lines ; Take , , The minimum value among the three values is taken as the critical angle between the strike of the rock stratum bedding and the longitudinal axis of the underground cavern ; Quantitatively evaluate the rationality of the orientation of the longitudinal axis of the cavern: When the included angle between the longitudinal axis of the cavern and the rock mass bedding plane θs ≥ θ , it is considered that the orientation of the current longitudinal axis of the cavern is reasonable. When the included angle between the longitudinal axis of the cavern and the rock mass bedding plane θs < θ , it is considered that the orientation of the current longitudinal axis of the cavern is unreasonable, and it is necessary to adjust the orientation of the longitudinal axis or take reinforcement measures.

2. The quantitative determination method for the included angle between the strike of a rock stratum bedding plane and the longitudinal axis of an underground chamber according to claim 1, characterized in that The calculation method is as follows: Obtain two sets of approximately linearly varying characteristic points at both ends of the maximum displacement value curve of the cavern surrounding rock at different included angles. The two sets of approximately linearly varying characteristic points include ( θ a , a ), ( θ b , b ), and ( θ c , c ), ( θ d , d ), where θ a , θ b , θ c , θ d represent the included angles between the strike directions of different rock bedding planes and the longitudinal axis of the cavern; a , b, c and d represent the included angles between the strike directions of different rock bedding planes and the longitudinal axis of the cavern θ a , θ b , θ c , θ d respectively correspond to the maximum displacement values of the surrounding rock. Draw the first straight line θ a , a ), ( θ b , b ), and draw the second straight line y 1, and draw the second straight line θ c , c ), ( θ d , d ), where y 2, where y 1 = ( b - a ) × ( x - θ a ) / ( θ b - θ a ) + a , y 2 = ( d - c ) × ( x - θ c ) / ( θ d - θ c )+ c ； When y 1 = y 2, calculate the abscissa of the intersection point of the two straight lines y 1 and y 2 ； 。 3. A method for quantitatively determining the included angle between the strike of a rock stratum bedding plane and the longitudinal axis of an underground cavern, as claimed in claim 1, wherein The calculation method is as follows: Obtain two sets of approximately linearly varying characteristic points at both ends of the maximum strain value curve of the chamber surrounding rock at different included angles. The two sets of approximately linearly varying characteristic points include ( θ a , a ), ( θ b , b ), and ( θ c , c ), ( θ d , d ), where θ a , θ b , θ c , θ d represent the included angles between the strike directions of different rock bedding planes and the longitudinal axis of the chamber; a , b, c and d represent the included angles between the strike directions of different rock bedding planes and the longitudinal axis of the chamber θ a , θ b , θ c , θ d correspond to the maximum strain values of the surrounding rock respectively. Draw the first straight line θ a , a ), ( θ b , b ), and draw the second straight line y 1, and draw the second straight line θ c , c ), ( θ d , d ), where y 1 = ( y ( b - a ) × ( x - θ a ) / ( θ b - θ a ) + a , y 2 = ( d - c ) × ( x - θ c ) / ( θ d - θ c )+ c ； When y 1 = y 2, calculate the abscissa of the intersection point of two straight lines y 1 and y 2 ; 。 4. A method for quantitatively determining the included angle between the strike of a rock stratum bedding plane and the longitudinal axis of an underground chamber according to claim 1, characterized in that The calculation method is as follows: Obtain two sets of approximately linearly varying characteristic points at both ends of the maximum plastic zone depth curve of the chamber surrounding rock at different included angles. The two sets of approximately linearly varying characteristic points include ( θ a , a ), ( θ b , b ), and ( θ c , c ), ( θ d , d ), where θ a , θ b , θ c , θ d represent the included angles between the strike directions of different rock bedding planes and the longitudinal axis of the chamber; a , b, c and d represent the included angles between the strike directions of different rock bedding planes and the longitudinal axis of the chamber θ a , θ b , θ c , θ d are the corresponding maximum plastic zone depth values of the surrounding rock respectively. Draw the first straight line θ a , a ) and ( θ b , b ), and draw the second straight line y 1, and draw the second straight line θ c , c ), ( θ d , d ), where y 2, where y 1 = ( b - a ) × ( x - θ a ) / ( θ b - θ a ) + a , y 2 = ( d - c ) × ( x - θ c ) / ( θ d - θ c )+ c ； When y 1 = y 2, calculate the abscissa of the intersection point of two straight lines y 1 and y 2 ； 。

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