Design method of longitudinal reinforcement of earth-rock dam

Abstract

The invention discloses a design method for a longitudinal reinforcement of an earth-rock dam, wherein the design method for the longitudinal reinforcement of an earth-rock dam comprises the following steps: determining design parameters of the longitudinal reinforcement of the earth-rock dam; calculating the ability of the longitudinal reinforcement of the earth-rock dam to resist deformation; force analysis of the longitudinal reinforcement of the earth-rock dam; hydraulic analysis of the longitudinal reinforcement of the earth-rock dam when the earth-rock dam is overtopping by flood; strength review of the longitudinal reinforcement of the earth-rock dam after being washed away; ensuring that the longitudinal reinforcement of the earth-rock dam has the advantages of anti-seepage, force bearing, resistance to deformation and overtopping without collapse; effectively saving 30-20% of the project investment, with obvious economic benefits; reinforcing conventional earth-rock dams, greatly solving the safety operation risk of dangerous reservoirs, overcoming the inherent defect of earth-rock dams that they are easy to collapse, and ensuring the safe operation of reservoirs.

Description

Technical Field

[0001] The invention belongs to the technical field of water conservancy engineering, and in particular relates to a design method for a longitudinal reinforcement body of an earth-rock dam. Background Art

[0002] Earth-rock dams are the most common type of hydraulic dams built on the planet (not only in China but also abroad), but they still have shortcomings or deficiencies that cannot be overcome by their own development. First of all, the safety operation performance of this "flexible" earth-rock dam is worse than that of a "rigid" gravity dam, and there is a higher risk of safe operation. Most of these collapses occurred in medium and low dams, and the main reason was the collapse caused by floods over the dam top. Recently, a small supporting reservoir of the Xiaolangdi Hydropower Project on the Yellow River overflowed the dam and caused a local dam collapse. From a mechanistic point of view, the collapse of earth-rock dams due to overtopping is a process in which the flood overflows from the dam top and washes the downstream dam slope when encountering excessive floods (there are also cases where the discharge facilities fail and cannot effectively discharge floods), causing the downstream dam body composed of externally strongly compacted granular bodies to be gradually washed away and disintegrated by the water flow, resulting in collapse or even collapse. Secondly, the most critical part of an earth-rock dam is its anti-seepage system. As mentioned above, no matter whether traditional materials such as clay, gravel soil, asphalt concrete, geomembrane, etc. are used to construct the anti-seepage system, they are only anti-seepage bodies rather than structures, so they cannot withstand stress like structures, especially tensile stress that may exist inside the dam body. Thirdly, since the anti-seepage body is not a structure, traditional anti-seepage materials cannot resist deformation inside the dam body, and may suffer from cracking, tensile cracking, and other damage during the operation of the dam. As mentioned above, the anti-seepage system is the key to earth-rock dams, but the defects also lie here, and at least one of the following defects is also included.

[0003] First, the anti-seepage body of the prior art has no structural characteristics and only plays an anti-seepage role;

[0004] Second, the anti-seepage body cannot withstand external forces, especially tensile stress, as a structural body;

[0005] Third, it cannot resist deformation like a structural body, which may cause cracking, tearing and other damage to the anti-seepage body, thus losing its due anti-seepage effect;

[0006] Fourth, when floods overtopping and overflowing occur, flood disasters such as dam overtopping and dam failure are very likely to occur, and there are many lessons in history;

[0007] Fifth, the existing technology cannot effectively reduce the infiltration line in the downstream area of ​​the dam body, thus affecting the stability of the downstream dam slope;

[0008] Sixth, the construction layered rolling technology has a long cycle and many processes, and node control is prone to problems, making it difficult to ensure construction quality;

[0009] Seventh, existing technologies have periodic risks of disease, requiring safety appraisals every 8-10 years, which is time-consuming and costly.

[0010] In view of the above problems existing in the anti-seepage system, the existing solution is to "insert" a rigid structure integrating anti-seepage and force-bearing (i.e., the longitudinal reinforcement of the earth-rock dam) into the interior of the earth-rock dam, and connect its bottom with the fixed end of the dam foundation to form an anti-seepage body, which is a new type of earth-rock dam reinforcement technology. The longitudinal reinforcement of the earth-rock dam has the following functions: ① The function of the anti-seepage body is to effectively reduce the infiltration line and reduce leakage; ② One of the functions of the structure is to withstand stress (or tensile stress) and improve the stability of the reinforcement; ③ The second function of the structure is to resist deformation and improve stress and deformation capacity; ④ The third function of the structure is that the rigid reinforcement can prevent the dam body from breaking when encountering floods, effectively reducing or eliminating the risk of dam breaking; ⑤ In particular, a more thorough solution is proposed for the removal of hazards and reinforcement of dangerous earth-rock dams.

[0011] However, there is no finalized design idea for the longitudinal reinforcement of earth-rock dams at present, so there is no guiding scheme in the actual construction of the longitudinal reinforcement of earth-rock dams, which may lead to unreasonable construction problems. Summary of the invention

[0012] The present invention aims at the fact that there is no formal design idea for the longitudinal reinforcement of the earth-rock dam at present, so there is no guiding scheme in the actual construction of the longitudinal reinforcement of the earth-rock dam, which may lead to the problem of unreasonable construction.

[0013] The purpose of the present invention is to provide a design method for the longitudinal reinforcement of an earth-rock dam. The design method explores corresponding calculation formulas for various parameters of the longitudinal reinforcement of the earth-rock dam, has a guiding role in the actual construction of the longitudinal reinforcement of the earth-rock dam, and reduces the occurrence of unreasonable situations.

[0014] In order to achieve the above object, the present invention adopts the following technical solutions:

[0015] A design method for a longitudinal reinforcement body of an earth-rock dam comprises the following steps:

[0016] S1: Determine the design parameters of the longitudinal reinforcement of the earth-rock dam;

[0017] S2: Calculate the ability of the longitudinal reinforcement of the earth-rock dam to resist deformation;

[0018] S3: Mechanical analysis of longitudinal reinforcement of earth-rock dam;

[0019] S4: Dam failure analysis of the longitudinal reinforcement of an earth-rock dam when it is overtopping by flood;

[0020] Wherein: Step S4 specifically includes the following analysis:

[0021] S4-1: Hydraulic analysis of the longitudinal reinforcement of earth-rock dams when floods overtopping the dam;

[0022] S4-2: Strength review of the longitudinal reinforcement of earth-rock dam after scouring.

[0023] Preferably, the design parameters of the longitudinal reinforcement of the earth-rock dam in step S1 include the downstream side overflow water level height and the thickness of the longitudinal reinforcement of the earth-rock dam , where the calculation method for the high escape water level on the downstream side is: ; Unit: m; Where: —Permeability coefficient of the longitudinal reinforcement of earth-rock dam, m / s; —water head upstream of the dam, m; —Dam body permeability coefficient, m / s; — downstream head, m; --thickness of the longitudinal reinforcement of the earth-rock dam, m;

[0024] The calculation method for the thickness of the longitudinal reinforcement of earth-rock dam is: ; In the formula, is the allowable escape velocity at the interface between the longitudinal reinforcement of the earth-rock dam and the downstream dam shell, m / s; is the allowable hydraulic gradient of the longitudinal reinforcement of the earth-rock dam; is the allowable escape velocity from the downstream dam shell to the downstream interface, Allowable hydraulic gradient of downstream dam shell, m / s; Permeability coefficient of the downstream dam shell;

[0025] Step S2 is specifically as follows:

[0026] S2-1: Rockfill settlement on both sides of the longitudinal reinforcement of the earth-rock dam Calculation

[0027] ; The unit is m; , are the dam settlement caused by its own weight and the overlying rockfill, in m or cm; is the initial compression modulus of the rockfill material, MPa; is the Duncan model parameter; is any dam height, variable, m;

[0028] S2-2: Deflection of the top of the longitudinal reinforcement of the earth-rock dam With corner calculate

[0029] Construction period:

[0030]

[0031] Runtime:

[0032] ;

[0033] Where: is the coupling density of the upstream saturated rockfill dam, T / m 3 ;

[0034] Step S3 is specifically as follows:

[0035] S3-1: Pull-down load Value calculation

[0036] Construction period:

[0037] Runtime:

[0038] Where: ; ; ;

[0039] ; ; ;

[0040] S3-2: Calculation of longitudinal reinforcement of earth-rock dam

[0041] Construction completion period: upstream active earth pressure ; Downstream active earth pressure , where is the unsaturated density upstream of the dam, T / m 3 ; is the unsaturated density downstream of the dam, T / m 3 ; Note that the parameter , , . ;

[0042] Safety factor of upstream and downstream forces ;

[0043] Water storage operation period: horizontal thrust of reservoir water load ; Horizontal thrust of upstream rockfill ; Passive earth pressure of downstream rockfill on longitudinal reinforcement of earth-rock dam , where is the density of water, T / m 3 ; is the buoyant density of the upstream rockfill dam, T / m 3 ; is the acceleration due to gravity, m / s 2; Safety factor of upstream and downstream forces ;

[0044] Reservoir water level drop period: passive earth pressure of upstream saturated rockfill , is the saturated density of the upstream dam, T / m 3 ; Active earth pressure of downstream rockfill on longitudinal reinforcement of earth-rock dam ;

[0045] Safety factor ;

[0046] S3-3: Verification of strength calculation of the bottom fixed end of the longitudinal reinforcement of earth-rock dam

[0047] , , ,

[0048] In the formula, the superscript ( ) indicates construction ( ) working condition or water operation ( ) working conditions, is the longitudinal reinforcement density of the earth-rock dam;

[0049] Step S4 is specifically as follows:

[0050] S4-1: Hydraulic processes of flood overtopping

[0051] The maximum depth of the scour pit on the downstream side is determined by the following formula: ;

[0052] The time to form the largest crater is calculated by the following formula: ;

[0053] Where: is the maximum scour depth, m; The time required to form the maximum scour depth, h;

[0054] --The scour coefficient is related to the physical properties, density, and gradation of the dam material. =3.25-4.25;

[0055] - Difference in water level between upstream and downstream; ——Single-width flow rate when flooding; - Average particle size of downstream rockfill;

[0056] are test coefficients, =0.16-0.30, =0.42-0.56, =0.18-0.24.

[0057] - time coefficient, =3.16-3.88;

[0058] , - Experimental factor, =-(0.40~0.55), =0.12-0.18

[0059] S4-2: Strength review of longitudinal reinforcement of earth-rock dam after scouring

[0060] The shear force and bending moment of the cross section of the longitudinal reinforcement of the earth-rock dam at the lowest point of the scour pit are calculated by the following formula:

[0061] Shear force:

[0062] Bending moment:

[0063] Require:

[0064]

[0065]

[0066] Where: Shear safety factor of earth-rock dam wall structure; is the safety factor of the wall structure under bending moment;

[0067] — Shear strength value of the longitudinal reinforcement of earth-rock dam, MPa;

[0068] —Bending strength value of the longitudinal reinforcement of earth-rock dam;

[0069] ;

[0070] —Compressive strength of longitudinal reinforcement of earth-rock dam, MPa;

[0071] The limit depth when shear failure and bending moment failure are reached is calculated by the following formula:

[0072] ,

[0073] In the formula, is the maximum depth of the wall where the shear force reaches the failure limit, m; is the maximum depth of the wall that reaches the failure limit under the bending moment, m;

[0074] When the actual scouring depth When the longitudinal reinforcement of the earth-rock dam is not damaged, the earth-rock dam will not fail.

[0075] The beneficial effects of the present invention are as follows: through the above-mentioned design method, various parameters of the longitudinal reinforcement of the earth-rock dam are comprehensively calculated and verified, so that the design of various parameters of the longitudinal reinforcement of the earth-rock dam is reasonable and has a substantial guiding role in actual construction, reducing the occurrence of unreasonable situations, so as to be used in the actual application of future water conservancy projects, ensuring that the longitudinal reinforcement of the earth-rock dam has the advantages of anti-seepage, stress bearing, resistance to deformation and overtopping without collapse; saving investment - the present invention can effectively save 30-20% of the project investment, and the economic benefit is obvious; ensuring safety - reinforcing conventional earth-rock dams, greatly solving the safe operation risks of dangerous reservoirs, overcoming the inherent defects of earth-rock dams that are prone to dam collapse, and ensuring the safe operation of reservoirs.

[0076] The present invention also discloses a parameter set of the longitudinal reinforcement of the earth-rock dam, including the height of the escape water level on the downstream side, the thickness of the longitudinal reinforcement of the earth-rock dam, the rockfill settlement on the upper and lower sides of the longitudinal reinforcement of the earth-rock dam, the deflection and rotation angle of the top of the longitudinal reinforcement of the earth-rock dam during the construction period and the operation period, and the downward pull load during the construction period and the operation period.

[0077] Preferably, the method for calculating the high escape water level on the downstream side is: , unit: m; where: —Permeability coefficient of the longitudinal reinforcement of earth-rock dam, m / s; —water head upstream of the dam, m; —Dam body permeability coefficient, m / s; — downstream head, m; --Thickness of longitudinal reinforcement of earth-rock dam, m.

[0078] Preferably, the calculation method for the thickness of the longitudinal reinforcement of the earth-rock dam is: , where is the allowable escape velocity at the interface between the longitudinal reinforcement of the earth-rock dam and the downstream dam shell, m / s; is the allowable hydraulic gradient of the longitudinal reinforcement of the earth-rock dam; is the allowable escape velocity from the downstream dam shell to the downstream interface, Allowable hydraulic gradient of downstream dam shell, m / s; Permeability of the downstream dam shell, m / s.

[0079] Preferably, the calculation method of the rockfill settlement on the upper and lower sides of the longitudinal reinforcement body of the earth-rock dam is: , unit is m; , are the dam settlement caused by its own weight and the overlying rockfill, in m or cm; is the dam height, m; is the initial compression modulus of the rockfill material, MPa; is the Duncan model parameter; is any dam height, variable, m.

[0080] Preferably, the calculation methods of the deflection and the rotation angle at the top of the longitudinal reinforcement body of the earth-rock dam during the construction period are respectively: ; The unit of deflection is m or cm; , is the unsaturated earth pressure coefficient of the upstream and downstream dam bodies; , is the weight of the upstream and downstream dam materials, KN / m 3 ; is the reinforcement volume deformation modulus, MPa; is the moment of inertia of the wall section, m 4 , , where is the thickness of the core wall of the reinforcement body, which is determined by Chapter 3; the reinforcement body takes a unit length along the longitudinal direction (cross river direction), so ; is the deformation constraint coefficient of the reinforcement body. Since the built-in reinforcement core wall in the earth-rock dam is an over-static structure connecting the two sides of the river valley, its stress and deformation conditions are closely related to factors such as the river valley shape, dam height, and dam construction materials. The working properties and the constraint environment make the wall stress and deformation different from those of general free components. Much larger than 1; for the reinforced core wall, (in, is a parameter related to the valley morphology, which can be taken as , It is a coefficient directly related to the wall height (unit: m), and its value range is from the bottom of the dam to the top of the wall: , is the height of the reinforcement, m.). is the height of the dam top filling area, m; the other symbols have the same meanings as before;

[0081] ; The unit of rotation angle is degree.

[0082] Preferably, the calculation methods of the deflection and the rotation angle at the top of the longitudinal reinforcement body of the earth-rock dam during the operation period are respectively: ,

[0083] In the above two formulas, is the density of water, KN / m 3 ; is the earth pressure coefficient of the upstream dam body under saturated state; is the saturated buoyancy weight of the upstream dam, KN / m 3 .

[0084] Preferably, the calculation method of the pull-down load during the construction period is: , where: , , , ; is the static friction coefficient of the interface between rockfill and wall; is the dynamic friction coefficient of the interface between rockfill and wall; is Poisson's ratio.

[0085] Preferably, the calculation method of the pull-down load during the operation period is: , where: , , , . BRIEF DESCRIPTION OF THE DRAWINGS

[0086] Figure 1 This is the seepage profile of the longitudinal reinforcement of the earth-rock dam;

[0087] Figure 2 It is a schematic diagram of the pull-down load of the longitudinal reinforcement of the earth-rock dam;

[0088] Figure 3 This is a diagram of the overtopping and breaching process of the longitudinal reinforcement of the earth-rock dam;

[0089] Figure 4 This is the stress analysis diagram of the largest scour pit formed after the overtopping scour of the longitudinal reinforcement body of the earth-rock dam;

[0090] Figure 5 This is the interface settlement distribution diagram of the longitudinal reinforcement body of the Fangtianba Reservoir earth-rock dam;

[0091] Figure 6 This is the side settlement difference distribution diagram of the longitudinal reinforcement body of the earth-rock dam;

[0092] Figure 7 The downward tensile stress distribution diagram of the longitudinal reinforcement of the earth-rock dam at the completion period;

[0093] Figure 8 This is the stress difference distribution diagram of the longitudinal reinforcement body of the earth-rock dam;

[0094] Fig. 9 The distribution diagram of the downward tension along the depth of the longitudinal reinforcement body of the earth-rock dam;

[0095] Fig.10It is the force difference distribution diagram of the upper and lower sides of the longitudinal reinforcement body of the earth-rock dam;

[0096] Fig.11 This is the plan view of the steel truss structure;

[0097] Fig.12 This is the elevation drawing of the steel truss structure;

[0098] Fig.13 is the calculated value of Fangtianba wetting deformation;

[0099] Fig.14 This is the distribution diagram of tensile stress under water storage and wetting;

[0100] Fig.15 This is the tensile force distribution diagram of the longitudinal reinforcement of the earth-rock dam under wetting. DETAILED DESCRIPTION

[0101] Example 1

[0102] This embodiment discloses the design theory and construction method of the longitudinal reinforcement of the earth-rock dam.

[0103] 1. First, determine the design parameters of the longitudinal reinforcement of the earth-rock dam, which is the basis;

[0104] like Figure 1 As shown,

[0105] 1.1 Determine the high water level on the downstream side

[0106] , unit: m;

[0107] In the formula, —Permeability coefficient of the longitudinal reinforcement of earth-rock dam, m / s; —water head upstream of the dam, m; —Permeability coefficient of downstream dam, m / s; — downstream head, m; --thickness of the longitudinal reinforcement of the earth-rock dam, m;

[0108] 1.2 Determine the thickness of the longitudinal reinforcement of earth-rock dam

[0109] According to the derivation of the seepage principle, the calculation formula is as follows:

[0110]

[0111] In the formula, is the allowable escape velocity at the interface between the longitudinal reinforcement of the earth-rock dam and the downstream dam shell, m / s, is the allowable hydraulic gradient of the longitudinal reinforcement of the earth-rock dam; is the allowable escape velocity from the downstream dam shell to the downstream interface, m / s, The allowable hydraulic gradient of the downstream dam shell, Permeability of the downstream dam shell, m / s.

[0112] 2. Calculate the ability of the longitudinal reinforcement of the earth-rock dam to resist deformation

[0113] 2.1 Rockfill settlement on the upper and lower sides of the longitudinal reinforcement of the earth-rock dam

[0114] , unit is m;

[0115] , are the dam settlement caused by its own weight and the overlying rockfill, in m or cm; is the initial compression modulus of the rockfill material, MPa; is the Duncan model parameter; is any dam height, variable, m;

[0116] Maximum settlement of longitudinal reinforcement of earth-rock dam: The meaning of each parameter is the same as above and will not be repeated here.

[0117] 2.2 Deflection of the top of the longitudinal reinforcement of earth-rock dam With corner calculate

[0118] Construction period:

[0119]

[0120] Runtime:

[0121]

[0122] The unit of deflection is m or cm; , is the unsaturated earth pressure coefficient of the upstream and downstream dam bodies; , is the weight of the upstream and downstream dam materials, KN / m 3 ; is the deformation modulus of the longitudinal reinforcement of the earth-rock dam, MPa; ,

[0123] In the formula, is the moment of inertia of the wall section, m 4， , is the thickness of the longitudinal reinforcement of the earth-rock dam, m; the longitudinal reinforcement of the earth-rock dam takes unit length along the longitudinal direction (cross-river direction), so ; is the deformation constraint coefficient of the longitudinal reinforcement of the earth-rock dam; is the height of the dam top fill area, m; ,in, is a parameter related to the valley morphology, , It is a coefficient directly related to the height of the longitudinal reinforcement of the earth-rock dam. The unit is m. Its value range is from the bottom of the dam to the top of the longitudinal reinforcement of the earth-rock dam: , is the height of the longitudinal reinforcement of the earth-rock dam, m, is the height of the dam top filling area, m; the meanings of other symbols are the same as before and will not be repeated here.

[0124] The unit of the angle is radian; the meanings of other symbols are the same as before and will not be repeated here.

[0125] is the density of water, KN / m 3 ; is the earth pressure coefficient of the upstream dam body under saturated state; is the saturated buoyancy weight of the upstream dam, KN / m 3 .

[0126] 3. Mechanical analysis of longitudinal reinforcement of earth-rock dam

[0127] Due to the inconsistency in deformation between the longitudinal reinforcement of the earth-rock dam and the rockfill on the upstream and downstream sides, differential settlement will occur at the interface between the two, thus forming the so-called pull-down load for the longitudinal reinforcement of the earth-rock dam, such as Figure 2 The basic working conditions of earth-rock dam reinforcement (i.e. completion period, water storage period, and reservoir water drop period) are analyzed;

[0128] 3.1 Pull-down load Value calculation - divided into two working conditions: construction period and water storage operation period

[0129] Construction period:

[0130] Runtime:

[0131] Where: ; ;

[0132] ; ; ;

[0133] is the static friction coefficient of the interface between rockfill and wall; is the dynamic friction coefficient of the interface between rockfill and wall; is Poisson’s ratio, and the other symbols have the same meanings as above and will not be repeated here.

[0134] 3.2 Force calculation of longitudinal reinforcement of earth-rock dam - design review is carried out according to the basic load combination under three working conditions: completed construction, water storage operation, and sudden water level drop.

[0135] Construction completion period: upstream active earth pressure , downstream active earth pressure ;

[0136] In the formula, is the unsaturated density upstream of the dam, T / m 3 ; is the unsaturated density downstream of the dam, T / m 3 ; Note that the parameter , , ;

[0137] Safety factor of upstream and downstream forces

[0138] Water storage operation period: horizontal thrust of reservoir water load , upstream rockfill horizontal thrust (active earth pressure) , passive earth pressure of the downstream rockfill on the longitudinal reinforcement of the earth-rock dam , where is the density of water, T / m 3 ; is the buoyant density of the upstream rockfill dam, T / m 3 ; is the acceleration due to gravity, m / s 2 ;

[0139] Safety factor of upstream and downstream forces

[0140] Reservoir water level drop period: passive earth pressure of upstream saturated rockfill , is the saturated density of the upstream dam, T / m 3

[0141] Active earth pressure of downstream rockfill on longitudinal reinforcement of earth-rock dam , force safety factor :

[0142] 3.3 Calculation and verification of the strength of the bottom fixed end of the longitudinal reinforcement of the earth-rock dam - verify that the compressive stress does not exceed its compressive strength according to the normal section, that is,

[0143] or ,

[0144] In the formula, the superscript ( ) respectively represent construction ( ) and water storage operation ( ) two working conditions, is the longitudinal reinforcement density of earth-rock dam, generally T / m 3 .

[0145] 4. Analysis of dam failure when longitudinal reinforcement of earth-rock dam is overtopping by flood

[0146] 4.1 As Figure 3 As shown, Figure 3 Figure (a) shows the beginning of flood overtopping scouring; Figure (b) shows the situation where the flood scouring causes the dam top to disappear and scouring damage occurs on the downstream side of the longitudinal reinforcement of the earth-rock dam to begin to form a scouring pit; Figure (c) shows that the flood height increases, the scouring pit continues to develop, and the free surface begins to form on the downstream side of the longitudinal reinforcement of the earth-rock dam; Figure (d) shows the situation where the scouring pit reaches its maximum.

[0147] According to the test, the maximum depth of the downstream scour pit is determined by the following formula:

[0148]

[0149] The time to form the largest crater is calculated by the following formula:

[0150]

[0151] Where: is the maximum scour depth, m; The time required to form the maximum scour depth, h;

[0152] --The scour coefficient is related to the physical properties, density, and gradation of the dam material. =3.25-4.25;

[0153] - Difference in water level between upstream and downstream; ——Single-width flow rate when flooding; - Average particle size of downstream rockfill;

[0154] are test coefficients, =0.16-0.30, =0.42-0.56, =0.18-0.24.

[0155] - time coefficient, =3.16-3.88;

[0156] , - Experimental factor, =-(0.40~0.55), =0.12-0.18.

[0157] 4.2 Strength verification of longitudinal reinforcement of earth-rock dam after scouring

[0158] Check whether the longitudinal reinforcement of the earth-rock dam meets the structural strength requirements at the section where the scouring depth is located. If it does, it means that the longitudinal reinforcement of the earth-rock dam has not been damaged, and the entire dam body has not collapsed. Otherwise, if the longitudinal reinforcement of the earth-rock dam is damaged, the dam body will also collapse. For details on the stress conditions when the scouring pit is formed downstream, see Figure 4 As shown,

[0159] The shear force and bending moment of the cross section of the longitudinal reinforcement of the earth-rock dam at the lowest point of the scour pit are calculated by the following formula:

[0160] Shear force:

[0161] Bending moment:

[0162] Require:

[0163]

[0164]

[0165] Where: Shear safety factor of earth-rock dam wall structure; is the safety factor of the wall structure under bending moment; , The values ​​can be checked from the specification;

[0166] ——shear strength value of the longitudinal reinforcement of earth-rock dam, MPa;

[0167] Pick

[0168] ——Bending strength value of the longitudinal reinforcement of earth-rock dam, MPa.

[0169] , MPa.

[0170] It is the compressive strength of the longitudinal reinforcement of the earth-rock dam, MPa, which can be found in the specifications.

[0171] --Structural shear safety factor related to the engineering grade of earth-rock dam.

[0172] --Structural moment safety factor related to the engineering grade of earth-rock dam.

[0173] --Thickness of longitudinal reinforcement of earth-rock dam, m.

[0174] The limit depth when shear failure and bending moment failure is reached ( The value) is calculated by the following formula,

[0175] ,

[0176] In the formula, is the maximum depth of the wall where the shear force reaches the failure limit, m; is the maximum depth at which the wall reaches its failure limit under the action of bending moment, m; other symbols are the same as above.

[0177] Obviously, when the actual scour depth If the longitudinal reinforcement of the earth-rock dam has not been damaged, the dam body will not burst; otherwise, the damage of the longitudinal reinforcement of the earth-rock dam will lead to the collapse of the dam body.

[0178] 5. Construction of longitudinal reinforcement of earth-rock dam

[0179] The construction is carried out according to the specific implementation method of patent number 201610957794.X and invention name: Longitudinal reinforcement construction method for earth-rock dam.

[0180] This embodiment combines the engineering practice and theoretical analysis of a large number of small and medium-sized reservoirs for risk removal and reinforcement, and adopts the idea of ​​"combining rigidity and flexibility" to "improve" the conventional earth-rock dam, that is, "inserting" a rigid structure (i.e., the longitudinal reinforcement of the earth-rock dam) inside the flexible earth-rock dam, thereby realizing innovation in key parts of the earth-rock dam, in order to improve the anti-seepage, force-bearing and deformation resistance capabilities of the earth-rock dam, shorten the construction period, reduce the project cost, effectively reduce the periodic repeated management of the earth-rock dam and the possible dam break disasters, reduce or delay the dam break risk of the earth-rock dam when floods overtopping, and extend the safe operation period of the earth-rock dam; and combined with theoretical design, it is preliminarily shown that this new reinforcement technology has indeed improved the safe operation level and dam break risk resistance of conventional earth-rock dams.

[0181] Engineering Calculation Example 1

[0182] Combined with the actual situation of the completed projects, the deformation, downward tensile stress, downward tensile load and other values ​​of the interface between the rockfill body and the longitudinal reinforcement body of the earth-rock dam at the bottom of the longitudinal reinforcement body of the earth-rock dam are calculated according to the completion period and the water storage period respectively, providing a calculation basis for verifying the mechanical state of the bottom of the longitudinal reinforcement body of the earth-rock dam.

[0183] 1 Calculate various parameters required

[0184] 1.1 Known dam height of Fangtianba Reservoir ;

[0185] 1.2 Taking the longitudinal reinforcement of the earth-rock dam as the boundary, the filling density of the upstream sandstone rockfill is , triaxial shear strength , initial compression modulus , model parameters , floating density after water storage , the upstream dam slope ratio is 1:2.25, the slope angle ; Downstream rockfill filling density , triaxial shear strength , initial compression modulus , model parameters The average slope ratio of the downstream dam is 1:2.25, and the slope angle .

[0186] 1.3 The average density of the rockfill is , porosity ratio , average initial compression modulus ;

[0187] 1.4 The height of the through-fill area is (i.e. the height from the top of the wall to the top of the dam).

[0188] 1.5 Height of longitudinal reinforcement of earth-rock dam ,thickness , elastic modulus ,density .

[0189] 1.6 Vertical static friction coefficient of the contact interface between rockfill and longitudinal reinforcement of earth-rock dam ; Vertical dynamic friction coefficient of the contact interface between rockfill and longitudinal reinforcement of earth-rock dam ; When the upstream rockfill is saturated, take , ; Poisson's ratio of rockfill In fact, the Poisson's ratio of rockfill is relatively complex and can be limited to the elastic range; the static lateral pressure coefficient of rockfill is , the upstream rockfill of this project , downstream rockfill , the average value can be taken as .

[0190] 1.7 Through the large-scale compression test of Fangtianba sandstone rockfill, regression analysis obtained the parameters of the three-parameter model: saturation state, , ; Unsaturated state, , .

[0191] 1.8 In addition, the gravity acceleration must be used in the calculation .

[0192] The above parameters are obtained through design, test, analysis and analogy. The reasonable selection of parameters also directly affects the rationality and safety of the calculation results. Special test studies should be carried out in projects with conditions to obtain reasonable and reliable parameter values.

[0193] 2. Calculation of completion period

[0194] The completion period refers to the period when the rockfill dam body and the longitudinal reinforcement of the earth-rock dam have been completed, and the entire dam body has entered an empty reservoir operation state waiting for water storage. This is a special and necessary working condition. If it is assumed that after the construction of the longitudinal reinforcement of the earth-rock dam is completed, the rockfill bodies on both the upstream and downstream sides are still in the settlement period, the upstream and downstream rockfill bodies will have a downward drag effect on the two interfaces of the longitudinal reinforcement of the earth-rock dam. The calculation formula for this drag effect has been mentioned above, and it is uniformly listed and calculated here as follows:

[0195] 2.1 The calculation formula for settlement of the upstream and downstream rockfill along the longitudinal reinforcement interface of the earth-rock dam is:

[0196]

[0197] As mentioned above, the above formula takes the top of the longitudinal reinforcement of the earth-rock dam as the origin of the coordinates, and the downward direction is positive, so From the top of the wall downward, it is called the wall depth. Obviously, due to the different indicators of the upstream and downstream rockfill materials, the settlements calculated by them are also different, but this difference is also very small and can be ignored. As listed in Table 1, Figure 5 It shows the interface settlement distribution diagram of the longitudinal reinforcement of the Fangtianba Reservoir earth-rock dam. Figure 6 It is the distribution diagram of the side settlement difference of the longitudinal reinforcement body of the earth-rock dam.

[0198] Table 1

[0199]

[0200] 2.2 Downward tensile stress at the interface between rockfill and longitudinal reinforcement of earth-rock dam

[0201] (a) Upstream side:

[0202]

[0203] (b) Downstream side:

[0204]

[0205] (c) Total tensile stress:

[0206]

[0207] Right now

[0208]

[0209] The parameters in the formula are:

[0210] ; ; ;

[0211] The last subscript "1" and "2" represent the upstream and downstream situations respectively.

[0212] When doing specific calculations, first find out the parameters in the formula:

[0213]

[0214]

[0215] The calculation formula of the tensile stress at the upstream interface is:

[0216]

[0217] Its wall depth The changes are listed in Table 2.

[0218] Table 2

[0219] Similarly, the downstream side can be calculated as above.

[0220]

[0221]

[0222] The calculation formula for the tensile stress at the downstream interface is:

[0223] Its wall depth The changes are listed in Table 3

[0224] Table 3 Calculated values ​​of the downward tensile stress distribution along the wall depth on the downstream side of the longitudinal reinforcement of the earth-rock dam

[0225]

[0226] The sum of the downward tensile stress on the upstream and downstream sides of the longitudinal reinforcement of the earth-rock dam and the stress difference on the upstream and downstream sides are calculated, and the results are listed in Table 4;

[0227] Table 4 Calculation results of the sum and difference of the tensile stress of the longitudinal reinforcement of the earth-rock dam at the completion period along the wall depth distribution

[0228]

[0229] It can be seen from Table 4 that the downward tensile stress changes linearly along the wall depth, and the maximum is at the bottom of the longitudinal reinforcement of the earth-rock dam. The calculation also found that due to the different physical and mechanical properties of the upstream and downstream rockfill materials, there must be a difference in the downward tensile stress on the upstream and downstream sides of the longitudinal reinforcement of the earth-rock dam. This difference may be the fundamental reason for the uneven force on the upstream and downstream of the longitudinal reinforcement of the earth-rock dam, resulting in a certain degree of tensile stress, such as Figure 7 and Figure 8 As shown in the figure, the stress difference between the upstream and downstream side walls of the longitudinal reinforcement of the earth-rock dam should not be too large. In other words, the built-in rigid longitudinal reinforcement of the earth-rock dam should try to ensure the uniformity of the physical and mechanical properties of the upstream and downstream rockfill materials, so as to minimize the stress difference on the two sides of the longitudinal reinforcement of the earth-rock dam.

[0230] 2.3 Downward pull load (downward pull force) at the interface between rockfill and longitudinal reinforcement of earth-rock dam

[0231] The pull-down load acting on the interface between the rockfill and the longitudinal reinforcement of the earth-rock dam is a kind of downward dragging effect of the rockfill on the longitudinal reinforcement of the earth-rock dam, which is a kind of force. The formula for calculating the pull-down load is listed as follows:

[0232] 2.3.1 Upstream side

[0233]

[0234] 2.3.2 Downstream side:

[0235]

[0236] 2.3.3 Total pull-down load:

[0237]

[0238] or:

[0239]

[0240] Known parameters,

[0241]

[0242] Substituting other relevant parameters, we can obtain the calculation formula of the pull-down load on the upstream and downstream sides along with the wall depth:

[0243]

[0244]

[0245] The calculation results are listed in Table 5. The variation of pull-down load with wall depth is shown in Fig. 9 As shown in the figure, the downward pulling forces on the upstream and downstream sides are superimposed, and the superimposed resultant force exerts a large pressure on the bottom surface of the longitudinal reinforcement of the earth-rock dam. In addition, the self-weight of the longitudinal reinforcement of the earth-rock dam and the weight of the filling body in the through-fill area can be added. The following steps can be used to verify whether the compressive stress at the bottom of the longitudinal reinforcement of the earth-rock dam meets the requirements of the concrete compressive strength, which can then be used as one of the bases for judging the structural safety of the longitudinal reinforcement of the earth-rock dam.

[0246] Table 5 Calculation results of the downward pull load (downward pull force) on the two sides of the wall

[0247]

[0248] 3.3 Verification of the compressive strength of the longitudinal reinforcement of earth-rock dams at the completion stage

[0249] From the calculation analysis, it can be seen that at the completion stage, the longitudinal reinforcement of the earth-rock dam is subjected to the downward pull of the upstream and downstream rockfill bodies. Function, namely:

[0250]

[0251] In the formula, , It has been calculated above;

[0252] Deadweight of longitudinal reinforcement of earth-rock dam ( - Density of longitudinal reinforcement of earth-rock dam, - Cross-sectional thickness of longitudinal reinforcement of earth-rock dam, - Height of longitudinal reinforcement of earth-rock dam), rockfill weight in filling area ( - Average density of rockfill in the fill area, -fill area height), then calculate and verify the compressive strength of the bottom of the longitudinal reinforcement of the earth-rock dam: ,

[0253] In the formula, - Actual compressive stress at the bottom fixed end of the longitudinal reinforcement of the earth-rock dam at the completion stage;

[0254] - Compressive strength of the longitudinal reinforcement of the earth-rock dam. For the Fangtian Dam project, the longitudinal reinforcement of the earth-rock dam is used in the design and construction. Concrete strength grade, therefore, ;

[0255] - Safety factor of bearing capacity of longitudinal reinforcement structure of earth-rock dam. The Fangtianba Reservoir project is classified as dam and other main buildings as Class 4. ;

[0256] The remaining symbols have the same meanings as before.

[0257] The calculation review process is as follows:

[0258]

[0259] It can be seen that the compressive performance of the longitudinal reinforcement structure of the earth-rock dam at the completion stage is safe.

[0260] 3.5 Verification of bending and tension resistance of longitudinal reinforcement of earth-rock dam at completion stage

[0261] From the above analysis and calculation, it is also found that due to the difference in downward tension on the upstream and downstream sides, as listed in Table 5, the longitudinal reinforcement of the earth-rock dam is subjected to uneven forces on both sides, and the cross-section of the longitudinal reinforcement of the earth-rock dam is subjected to a similar bending moment, thus forming tensile stress or lateral tension.

[0262] The force difference of the downward pull force at the same elevation section upstream and downstream changes along the wall depth as shown in Fig.10 As shown in Figure 2, it can be seen that in the shallower range of the reinforcement (generally within Within ), the force difference is the smallest, and will gradually increase with the increase of wall depth, and its growth law still changes in a quadratic form. Obviously, the force difference reaches its maximum value at the bottom of the wall. According to the above calculation, the maximum force difference per unit length of the bottom of the wall along the dam line is ,Right now

[0263] The most unfavorable combined bending moment at the bottom is According to the provisions of Article 3.2.2 of the Code for Design of Hydraulic Concrete Structures (SL191-2008), the design value of the bending moment is calculated. :

[0264]

[0265] The following is a review of the calculations based on the relevant formulas in Section 2.3.

[0266] First, according to the reinforcement design plan, the wall construction is divided into the first-stage hole and the second-stage hole. The slot holes are formed by the mud wall using the masonry drill. After the slag and hole are cleared, the steel truss is set up. Fig.11 The figure shows the plan view of the steel truss structure. Fig.12 The figure shows the elevation view of the steel truss structure, and the steel bar consumption is listed in Table 6.

[0267] Table 6 Steel truss reinforcement consumption table

[0268]

[0269] Secondly, check whether the amount of steel bars meets the requirements.

[0270] (1) Since the wall thickness is 80 cm and the steel truss thickness is 65 cm, the protective layer thickness is , steel bars are considered as single layer, and the initial diameter is HPB235 hot rolled steel bars, , .

[0271] (2) According to the design, the cross section of the steel bar is known. .

[0272] (3) Calculation height of relative compression zone value:

[0273]

[0274] (4) Since HPB235 hot-rolled steel bars are used, the manual shows ,

[0275]

[0276] The description meets the requirements.

[0277] (5)

[0278] (6)

[0279] (7) Fangtianba Reservoir is a small (I) type reservoir and is considered as a Class 4 hydraulic structure. The bearing capacity safety factor of its concrete structural components is Check the "Design Code for Hydraulic Concrete Structures" (SL191) and select the basic combination. .

[0280] but,

[0281] visible,

[0282] This indicates that the bending bearing capacity of the bottom cross section of the longitudinal reinforcement of the earth-rock dam meets the requirements at the completion stage.

[0283] 2.3 Calculation of water storage period

[0284] After the completion of the reservoir dam, the gates can be lowered to store water after the water storage safety appraisal and water storage acceptance. For newly built dams, no matter how water is stored, the increasing water load has unprecedented impact on the distribution and adjustment of the stress and deformation of the dam body. Therefore, the relevant water storage regulations and specifications have relatively detailed provisions for the initial water storage of earth-rock dams. Earth-rock dams with longitudinal reinforcement bodies are no exception. It should be emphasized here that in the process of gradually storing water upstream to the normal water level, the distribution and adjustment of stress and deformation between the longitudinal reinforcement body of the earth-rock dam and the upstream dam body material are worthy of attention. According to the analysis in this chapter, the design should be re-calculated during the water storage period. Taking the Fangtianba Reservoir in Tongjiang County, Sichuan Province as an example, the relevant calculation process is introduced in detail.

[0285] (1) Wetting deformation of the upstream rockfill during the impoundment period

[0286] As mentioned above, when the reservoir is filled with water, the upstream rockfill will experience wetting and settling deformation due to water immersion, while the downstream rockfill will not experience wetting and deformation. Based on the three-parameter wetting model of rockfill materials and various mechanical parameter indicators of the Fangtianba Reservoir damming, the deformation calculation formula of the upstream rockfill before and after wetting is obtained as follows:

[0287] 1) Before wetting deformation, that is, when the rockfill is in an unsaturated state, considering the one-dimensional compression condition near the reinforcement, its settlement is:

[0288]

[0289] In the formula,

[0290]

[0291]

[0292] 2) After water storage, the rockfill is in a saturated state, and its settlement value is:

[0293]

[0294] In the formula,

[0295]

[0296]

[0297] 3) Calculate the settlement difference of the rockfill dam before and after it is deformed by water:

[0298]

[0299] From this, the wetting deformation value of the upstream rockfill after being soaked in water can be calculated, as shown in Table 7.

[0300] Table 7 Results of wet sedimentation meter for rockfill near the wall

[0301]

[0302] Depend on Fig.13 It can be seen that the wetting deformation increases linearly from top to bottom along the longitudinal reinforcement of the earth-rock dam, and is the largest at the bottom of the wall;

[0303] Tensile stress Calculation

[0304] The downward tensile stress caused by wetting on the upstream side of the longitudinal reinforcement of the earth-rock dam during the impoundment period is calculated.

[0305]

[0306] Substitute the number

[0307] It is calculated that:

[0308] It can be seen that the downward tensile stress is mainly a quadratic function of the wall depth. The deeper the wall, the greater the downward tensile stress.

[0309] The calculation results of the tensile stress along the wall depth are listed in Table 8, and the change trend is as follows Fig.14 As shown;

[0310] Table 8 Calculation table of tensile stress along wall depth

[0311]

[0312] It can be seen from the table that the downward tensile stress is upward within the wall depth of 15m, and the downward tensile effect on the side wall of the longitudinal reinforcement body of the earth-rock dam is gradually formed below 15m.

[0313] (3) Calculation of pulling force under humidification

[0314] Calculate the pull-down force (or pull-down load) caused by wetting deformation ,

[0315]

[0316] From the above formula, we can know that the downward drag force on the upstream side wall of the reinforcement body caused by the wetting and wetting settlement of the upstream rockfill due to the water storage in the reservoir is mainly a cubic function of the wall depth. Since the parameters of other items in the formula are very small, the impact on the shallower part of the wall is not significant during the calculation, but there is a certain impact on the deeper part of the wall. This needs to be analyzed and judged based on the calculation results and cannot be omitted or ignored arbitrarily. Wetting downward pull force The calculation results along the wall depth are listed in the following table. The change trend is as follows: Fig.15 As shown;

[0317] Table 9 Distribution of tensile force along the wall depth under wetting

[0318]

[0319] (4) Verification of compressive strength of longitudinal reinforcement of earth-rock dam during impoundment period

[0320] As a calculation condition, the compressive strength of the longitudinal reinforcement of the earth-rock dam should be reviewed during the impoundment period. When the reservoir is built and the water is first impounded, the wetting deformation of the entire rockfill dam body, especially the upstream rockfill dam body, will cause relative displacement of the side walls of the longitudinal reinforcement of the earth-rock dam, thereby causing downward drag. Therefore, the downward pull load of the earth-rock dam increases the stress burden of the wall in the longitudinal direction. It is believed that water impoundment has no effect on the downward pull load of the downstream rockfill. Similarly, the load on the bottom of the longitudinal reinforcement of the earth-rock dam is the largest. Therefore, it is still necessary to review whether the compressive strength of its bottom during the impoundment period meets the requirements.

[0321]

[0322] Where: - The safety factor of the bearing capacity of the longitudinal reinforcement structure of the earth-rock dam is calculated according to Table 3.2.4 of Section 3.2 of the "Design Code for Hydraulic Concrete Structures (SL-191)", and in combination with the level of the Fangtian Dam project, the longitudinal reinforcement structure of the earth-rock dam is relatively complex, the construction is difficult, the load is difficult to calculate accurately, and there is a lack of mature calculation methods. The value is appropriately increased. ;

[0323] -The combined design value of load effects is determined by Formula (3.2.2-1) in Section 3.2 of the Code for Design of Hydraulic Concrete Structures (SL-191). Here , - Load effects generated by standard values ​​of permanent loads such as earth pressure and silt pressure;

[0324] The above calculation shows that the compressive stress on the bottom concrete of the longitudinal reinforcement of the earth-rock dam during the water storage period is less than its compressive strength, indicating that the compressive stress on the longitudinal wall of the earth-rock dam is safe.

[0325] (4) Verification of the bending and tensile strength of the longitudinal reinforcement of earth-rock dams during the impoundment period

[0326] 1) The bending and tension verification during the water storage period mainly adds the wetting tension force compared with the completion period. The wetting tension force should be superimposed with the force difference between the upstream and downstream wall side walls to form the most unfavorable load combination. The following table shows its combination values.

[0327] Table 10 The most unfavorable combination force difference

[0328]

[0329] From Table 10, we can see that the combined force at the bottom of the longitudinal reinforcement of the earth-rock dam is the largest, with a value of 205.92 kN. Next, we will recheck the calculation of the bottom of the longitudinal reinforcement of the earth-rock dam. In fact, this recheck is the same as the situation at the completion period.

[0330] The design value of the bending moment is calculated by formula (3.2.2-1) in Section 3.2 of the Code for Design of Hydraulic Concrete Structures (SL-191), taking into account the load effects of the standard values ​​of permanent loads such as earth pressure and silt pressure. ;

[0331] 2) The design scheme of the longitudinal wall of the earth-rock dam has been verified by the previous calculations at the completion period. Here, we calculate whether the amount of steel bars can meet the requirements for the amount of steel bars required by the increase in tensile force due to wetting during the water storage period, thereby meeting the tensile and bending stresses.

[0332] It is known that the thickness of the longitudinal wall of the earth-rock dam is 80cm, and the thickness of the steel truss is 65cm. Then the thickness of the protective layer is , steel bars are considered as single layer, and the initial diameter is HPB235 hot rolled steel bars,

[0333] but , .

[0334] According to the design, the steel bar section is known

[0335] 3) Calculation height of relative compression zone value:

[0336]

[0337] 4) Since HPB235 hot-rolled steel bars are used, we can check the manual table to get ,

[0338]

[0339] The description meets the requirements.

[0340] 5)

[0341] 6) 7) Fangtianba Reservoir is a small (I) type reservoir and is considered as a Class 4 hydraulic structure. The bearing capacity safety factor of its concrete structural components is Check Table 3.2.4 of the "Design Code for Hydraulic Concrete Structures (SL191)" and appropriately increase the basic combination. .

[0342] but,

[0343] visible,

[0344] This indicates that the bending bearing capacity of the positive section at the bottom of the reinforcement body meets the requirements during the storage period.

[0345] Engineering Calculation Example 2

[0346] 1.1 Let’s take Fangtianba Reservoir as an example. Fangtianba Reservoir is a newly built earth-rock dam with longitudinal reinforcement in recent years. The engineering grade is IV, the maximum dam height is 41.5m, the upstream water level is 39.5m, the downstream water level is 1.5m, the dam top is 365m long, the dam body is filled with sandstone slag, and the average particle size of the downstream rockfill is 0.45m. The flood characteristics of the reservoir are listed in Table 11.

[0347] Table 11 Flood overtopping scour calculation table

[0348]

[0349] Note: The other operating conditions in the table are mainly used for comparison with the verification and design conditions. Under normal circumstances, other operating conditions do not exist unless the reservoir flood discharge facilities fail.

[0350] 1.2 Calculation Assuming that the upstream reservoir water level is flush with the top elevation of the longitudinal reinforcement of the earth-rock dam after the reservoir water overflows the top, the upstream and downstream water level difference is =39.5-1.5=38m, scour coefficient =3.83, =0.25, =0.50, =0.18; time coefficient 3.52, =-0.45, =0.15. Calculate the depth of flood pits at each frequency and the time required to reach the calculated pit depth It is listed in Table 11. It can be seen from Table 11 that when the reservoir encounters a 300-year verification flood overtopping, the maximum scouring depth can reach 5.26m, and the corresponding time is 4.67 hours; under the design condition of 30-year return, if the flood overtopping, the maximum scouring depth downstream of the dam is 4.17m, and the corresponding time is 5.77 hours.

[0351] 1.3 Check the fracture strength of the longitudinal reinforcement of earth-rock dam. According to 3.2 of the Code for Design of Hydraulic Concrete Structures (SL191-2008), =1.25, =1.20, C25 wall concrete =16.7MPa, then MPa, MPa, for this project, the design thickness of the longitudinal reinforcement of the earth-rock dam , upstream rockfill floating density t / m3, earth pressure coefficient , m, m. Then the safe wall depth of the longitudinal reinforcement wall structure of the earth-rock dam is ,

[0352] 1.3.1 In case of design flood,

[0353]

[0354] Therefore, when designing for floods, there will be no dam breach.

[0355] 1.3.2 When encountering a verification flood, , also when checking flood, there will be no dam breach, the results are shown in Table 12,

[0356] Table 12 Analysis of Fangtianba Reservoir flooding without collapse

[0357]

[0358] Therefore, when the Fangtianba Reservoir encounters a flood that occurs once in 300 years and a flood that occurs once in 30 years, the reinforced earth-rock dam will not produce the extreme situation of so-called collapse like the conventional earth-rock dam. The reinforcement plays a structural support role in resisting the overtopping and collapse of the earth-rock dam, indicating that the safe operation performance of the earth-rock dam with longitudinal reinforcement is better than that of the conventional earth-rock dam.

[0359] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A design method for a longitudinal reinforcement of an earth-rock dam, characterized in that: The following steps are involved: S1: Determine the design parameters of the longitudinal reinforcement of the earth-rock dam. The design parameters of the longitudinal reinforcement of the earth-rock dam include the downstream side overflow water level height and the thickness of the longitudinal reinforcement of earth-rock dam , The calculation method of the downstream side escape water level is: ; Unit: m; Where: —Permeability coefficient of the longitudinal reinforcement of earth-rock dam, m / s; —water head upstream of the dam, m; —Dam body permeability coefficient, m / s; — downstream head, m; --thickness of the longitudinal reinforcement of the earth-rock dam, m; The calculation method for the thickness of the longitudinal reinforcement of earth-rock dam is: ; In the formula, is the allowable escape velocity at the interface between the longitudinal reinforcement of the earth-rock dam and the downstream dam shell, m / s; is the allowable hydraulic gradient of the longitudinal reinforcement of the earth-rock dam; is the allowable escape velocity from the downstream dam shell to the downstream interface, is the allowable hydraulic gradient of the downstream dam shell, m / s; is the permeability coefficient of the downstream dam shell, m / s; S2: Calculate the ability of the longitudinal reinforcement of the earth-rock dam to resist deformation, which includes: S2-1: Rockfill settlement on both sides of the longitudinal reinforcement of the earth-rock dam Calculation: ； In the formula, The unit is m; , are the dam settlement caused by its own weight and the overlying rockfill, in m or cm; is the dam height, m; is the initial compression modulus of the rockfill material, MPa; is the Duncan model parameter; is any dam height, variable, m; is the average density of the rockfill; is the acceleration due to gravity, m / s 2 S2-2: Deflection of the top of the longitudinal reinforcement of the earth-rock dam With corner calculate: Deflection during construction The calculation method is: ; In the formula, The unit is m or cm; , is the unsaturated earth pressure coefficient of the upstream and downstream dam bodies; , is the weight of the upstream and downstream dam materials, KN / m 3 ; is the deformation modulus of the longitudinal reinforcement of the earth-rock dam, MPa; is the moment of inertia of the wall section, m 4 ; is the thickness of the longitudinal reinforcement of the earth-rock dam, m; the longitudinal reinforcement of the earth-rock dam takes unit length along the cross-river direction, so ; is the deformation constraint coefficient of the longitudinal reinforcement of the earth-rock dam; is the height of the dam top fill area, m; ； In the formula, is a parameter related to the valley morphology, , It is a coefficient directly related to the height of the longitudinal reinforcement of the earth-rock dam. The unit is m. Its value range is from the bottom of the dam to the top of the longitudinal reinforcement of the earth-rock dam: , is the water head upstream of the dam, m, is the height of the dam top fill area, m; Corner during construction The calculation method is: ; Deflection during operation The calculation method is: ; In the formula, is the density of water, KN / m 3 ; is the earth pressure coefficient of the upstream dam body under saturated state; is the saturated buoyancy weight of the upstream dam, KN / m 3 ; Turning point in operation The calculation method is: ; S3: Mechanical analysis of longitudinal reinforcement of earth-rock dam; Step S3 is specifically as follows: S3-1: Pull-down load Value calculation: Construction period: ; In the formula, , ,, , , is the static friction coefficient of the interface between rockfill and wall; is the dynamic friction coefficient of the interface between rockfill and wall; is Poisson’s ratio; Runtime: ; Where: , ; S3-2: Calculation of longitudinal reinforcement of earth-rock dam Construction completion period: upstream active earth pressure ; Downstream active earth pressure , where is the unsaturated density upstream of the dam, T / m 3 ; is the unsaturated density downstream of the dam, T / m 3 ; Note that the parameter , , ; Safety factor of upstream and downstream forces ; Water storage operation period: horizontal thrust of reservoir water load ; Horizontal thrust of upstream rockfill ; Passive earth pressure of downstream rockfill on longitudinal reinforcement of earth-rock dam , where is the density of water, T / m 3 ; is the buoyant density of the upstream rockfill dam, T / m 3 ; is the acceleration due to gravity, m / s 2 ; Safety factor of upstream and downstream forces ; Reservoir water level drop period: passive earth pressure of upstream saturated rockfill , is the saturated density of the upstream dam, T / m 3 ; Active earth pressure of downstream rockfill on longitudinal reinforcement of earth-rock dam ; Safety factor ; S3-3: Verification of strength calculation of the bottom fixed end of the longitudinal reinforcement of earth-rock dam ， ， ， In the formula, the superscript ( ) indicates construction ( ) working condition or water operation ( ) working conditions, is the longitudinal reinforcement density of the earth-rock dam; S4: Dam failure analysis of the longitudinal reinforcement of an earth-rock dam when it is overtopping by flood; Wherein: Step S4 specifically includes the following analysis: S4-1: Hydraulic analysis of the longitudinal reinforcement of earth-rock dams when floods overtopping the dam, including: S4-1: Hydraulic processes of flood overtopping The maximum depth of the scour pit on the downstream side is determined by the following formula: ; The time to form the largest crater is calculated by the following formula: ; Where: is the maximum scour depth, m; The time required to form the maximum scour depth, h; --The scour coefficient is related to the physical properties, density and gradation of the dam material. =3.25-4.25; - Difference in water level between upstream and downstream; ——Single-width flow rate when flooding; - Average particle size of downstream rockfill; are test coefficients, =0.16-0.30, =0.42-0.56, =0.18-0.24; - time coefficient, =3.16-3.88; , - Experimental factor, =-(0.40~0.55), =0.12-0.18; S4-2: Strength review of the longitudinal reinforcement of earth-rock dam after scouring, including: The shear force and bending moment of the cross section of the longitudinal reinforcement of the earth-rock dam at the lowest point of the scour pit are calculated by the following formula: Shear force: Bending moment: Require: Where: Shear safety factor of earth-rock dam wall structure; is the safety factor of the wall structure under bending moment; — Shear strength value of the longitudinal reinforcement of earth-rock dam, MPa; —Bending strength value of the longitudinal reinforcement of earth-rock dam; ； —Compressive strength of longitudinal reinforcement of earth-rock dam, MPa; The limit depth when shear failure and bending moment failure are reached is calculated by the following formula: 、 In the formula, is the maximum depth of the wall where the shear force reaches the failure limit, m; is the maximum depth of the wall that reaches the failure limit under the bending moment, m; When the actual scouring depth When the longitudinal reinforcement of the earth-rock dam is not damaged, the earth-rock dam will not fail.

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