A method for controlling the arch closure during the construction of high arch dams considering the arch stress control index

Abstract

The present invention discloses a method for controlling the casting and sealing of a high arch dam taking into account the control index of the arch stress, and relates to the technical field of dam safety control. It includes the following steps: establishing an overall three-dimensional finite element model of the arch dam; dividing the corresponding dam section and casting layer according to the actual casting scheme; simulating the casting and rising process of the dam through the life-death unit technology to truly consider the changes in the dam body gravity load and the center of gravity position during the casting process; deducing the temperature load through the temperature field; calculating the structural stress and transverse joint opening of the dam; proposing the control of the arch stress of the sealed arch dam body; setting stress control standards for the unsealed arch dam section and the sealed arch dam body respectively; dynamically adjusting the casting and sealing process; repeating the above steps, dynamically adjusting the casting and sealing process of each stage until the dam is capped. The present invention dynamically adjusts the sealing process, reduces the risk of secondary opening of the grouted transverse joints and cracking of the dam body during the construction period, and creates conditions for achieving balanced and rapid rising of the dam casting.

Description

Technical Field

[0001] The invention relates to the technical field of dam safety control, and more specifically to a high arch dam pouring and arch sealing control method taking into account arch stress control indicators. Background Art

[0002] An arch dam is a three-dimensional, hyperstatic spatial shell structure. It transmits part of the external forces such as water pressure and sediment pressure to the rock masses on both sides through the action of the arch, and the other part to the bottom foundation through the action of the cantilever beam. The stability and safety of the arch dam are maintained by the support of the rock masses on both sides and the compressive strength of the concrete.

[0003] Arch dams generally do not have permanent structural joints, but according to the concrete construction strength and concrete temperature characteristics, the dam body must be constructed in many dam blocks with transverse joints between each block. When the dam body temperature cools to a stable temperature, the joint grouting technology is used to connect them into a whole and seal the arch dam.

[0004] High arch dams (arch dams with a height of more than 200 meters) require a large amount of concrete pouring, and construction often takes several years. Due to restrictions on temperature control and construction strength, the dam body cannot be sealed at one time, but is carried out in batches according to elevation; before the transverse joints are grouted, the stress state of each dam section is like a cantilever beam. As the pouring height increases, after the unjointed grouting height exceeds a certain value, tensile stress may be generated at the grouted joints of the dam body or the foundation, which is equivalent to the root of the cantilever beam, due to the deadweight load of the inverted suspended dam body. The stress in the sealed arch part of the lower part of the cantilever dam body will also be affected by the deadweight of the upper dam body. During the construction period, the tensile stress of the sealed arch dam body may increase with the pouring process of the upper dam body. During the whole process of arch dam construction, designers pay more attention to whether the principal tensile stress of the unsealed independent dam section and the sealed arch part exceeds the specified value, but not enough attention is paid to the arch stress of the sealed arch part. If the on-site construction organization is poor or the design parameters are unreasonable, it is very likely that some transverse joints will open again after grouting, and the effect of the arch at the corresponding part will be weakened, which may lead to cracks in the dam toe and affect the safety of the dam. At the same time, problems such as uneven progress of dam concrete pouring and prominent high cantilever phenomenon are common. During the construction period, the arch dam may block water in advance in order to meet the needs of safe flood control due to the unfinished dam body. This puts higher requirements on the flexibility of the arch sealing process.

[0005] Therefore, it is necessary to develop a method for regulating the casting and sealing of high arch dams that takes into account the arch stress control index. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the above-mentioned background technology and to provide a high arch dam casting and arch sealing control method taking into account the arch stress control index.

[0007] In order to achieve the above object, the technical solution of the present invention is: a high arch dam casting and arch sealing control method considering the arch stress control index, characterized in that it includes the following steps:

[0008] Establish an overall three-dimensional finite element model of the arch dam, in which the dam body uses solid elements and the transverse joints use interface elements;

[0009] According to the actual pouring plan, the corresponding dam sections and pouring layers are divided, and the dam sections are numbered as j, j = 1, 2...m; the pouring and rising process of the dam is simulated by the life and death unit technology to truly consider the changes in the dam's gravity load and center of gravity during the pouring process;

[0010] Simulate the heat release process of concrete hydration and the cooling process of the dam by water flow, calculate the temperature field of the dam, and deduce the temperature load through the temperature field;

[0011] After obtaining the gravity load and temperature load of the dam, the dam structural stress and transverse joint opening are calculated based on the following control equations:

[0012] σ i =σ i-1 +Δσ i (Formula 1)

[0013]

[0014]

[0015]

[0016] Among them, Δσ i is the stress increment at the i-th time step, Δd i is the increment of the transverse joint opening at the i-th time step, G i is the gravity load at the i-th time step, ΔT i is the temperature increment at the i-th time step, ξ i is the concrete hydration degree at the i-th time step, is the strain increment caused by non-gravity and temperature factors at the i-th time step;

[0017] Based on the stress control standard given in the code, in order to avoid the secondary opening of the transverse joint, the control of the arch stress of the sealed arch dam is proposed;

[0018] Stress control standards are set for the unsealed arch dam section and the sealed arch dam body respectively. The stress control standard for the unsealed arch dam section is:

[0019]

[0020] The stress control standard of the sealed arch dam is:

[0021]

[0022] in, is the principal tensile stress in the unsealed arch area of ​​dam section j at the i-th time step, is the principal compressive stress in the unsealed arch area of ​​the jth dam section at the i-th time step, τ t is the allowable tensile stress of the unsealed arch dam section, is the allowable tensile stress of the sealed arch dam body, is the principal tensile stress of the sealed arch dam body at the i-th time step, is the principal compressive stress of the sealed arch dam body at the i-th time step, is the arch tensile stress of the sealed arch dam body at the i-th time step, f t,i is the concrete tensile strength at the i-th time step, f c,i is the concrete compressive strength at the i-th time step, ψ is the design condition coefficient, γ 0 is the structural importance coefficient, γ d is the structural coefficient, γ m is the material performance partial coefficient;

[0023] The dam body stress at each time step i is counted, and the cantilever height, the height difference of the entire dam section and the height difference of adjacent dam sections are dynamically adjusted according to the stress control standard. In addition, the pouring and arch sealing process is dynamically adjusted in combination with the allowable opening of the transverse joint grouting and the limitations of the dam body arch sealing temperature.

[0024] Repeat the above steps and dynamically adjust the pouring and arch sealing process at each stage until the dam is capped.

[0025] In the above technical solution, the dynamically adjusting pouring and arch sealing process includes:

[0026] 1) If the stress of the unsealed arch dam section and the sealed arch dam body at the i-th time step meets the control standard, the calculation of the next time step is carried out;

[0027] 2) Under the premise of ensuring that the stress of the sealed arch dam body meets the control standard, if the stress of the unsealed arch area of ​​some dam sections in the i-th time step does not meet the control standard, the pouring of these dam sections will be stopped, and the previous pouring step of these dam sections will be cancelled, and these dam sections will be marked as reaching the limit state; for the dam sections whose stress does not exceed the standard, the pouring will continue;

[0028] 3) If the stress of the sealed arch dam body meets the control standard at the i-th time step, but all unsealed arch dam sections have reached the limit state, the pouring of all dam sections is stopped and the sealed arch grouting is started;

[0029] 4) If the stress of the sealed arch dam body at the i-th time step exceeds the allowable value, the pouring of all dam sections is stopped, the previous pouring step is canceled, and the sealed arch grouting is started.

[0030] In the above technical scheme, before the arch sealing grouting begins, the opening of each transverse joint and the temperature of each dam section are counted, and the area where the transverse joint opening reaches the grouting degree and the temperature drops to the arch sealing temperature is divided, so as to determine the start time and target elevation of the arch sealing grouting.

[0031] In the above technical solution, the method for simulating the hydration heat release process of concrete is to use a hydration degree model simulation, and the method for simulating the water cooling process of the dam is to use a simulation based on an equivalent heat conduction equation.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] 1) Starting from the goal of "avoiding the secondary opening of transverse joints and the resulting cracking of the dam toe, ensuring structural safety and improving construction efficiency", the present invention proposes a control index for the arch tensile stress of the sealed arch dam section during the construction period. Combined with the on-site construction organization arrangement, the construction restrictions such as the cantilever height of the unsealed arch dam section, the height difference of the entire dam section and the height difference of adjacent dam sections are dynamically adjusted by region, location and elevation. The arch sealing process is dynamically adjusted to reduce the risk of secondary opening of the grouted transverse joints and cracking of the dam body during the construction period, creating conditions for achieving balanced and rapid rising of the dam casting.

[0034] 2) The present invention provides a complete process for regulating the pouring and sealing process of a high arch dam, which is highly operable and convenient for designers of similar projects to use as a reference.

[0035] 3) The present invention combines the on-site construction organization arrangement to dynamically adjust the cantilever height of the unsealed arch dam section, the height difference of the entire dam section and the height difference of adjacent dam sections by region, location and elevation, which greatly reduces the restrictions on on-site dam concrete pouring construction and helps to improve construction efficiency.

[0036] 4) The present invention proposes a principle for controlling the tensile stress of the arch dam body during the construction period, which breaks through the limitations of the stress control standards of traditional arch dam design, effectively prevents the secondary opening of the grouted transverse joints, and effectively ensures that the diversion tunnel sluice and the middle hole flow goals are achieved as scheduled. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a flow chart of the present invention.

[0038] Figure 2 Schematic diagram of stress control for the unsealed arch dam section and the sealed arch dam body.

[0039] Figure 3 This is the overall three-dimensional finite element model of a certain arch dam.

[0040] Figure 4a This is the cloud diagram of the maximum principal stress distribution of the dam body in Scheme 1 (unit: 0.01MPa).

[0041] Figure 4b This is the cloud diagram of the maximum principal stress distribution of the dam body in Scheme 2 (unit: 0.01MPa). DETAILED DESCRIPTION

[0042] The following detailed description of the implementation of the present invention is made in conjunction with the accompanying drawings, but they do not constitute a limitation of the present invention and are only given as examples. At the same time, the advantages of the present invention will become clearer and easier to understand through the description.

[0043] Referring to the attached drawings, it can be seen that a method for controlling the arch dam casting and sealing the arch considering the arch stress control index is characterized in that it includes the following steps:

[0044] Step 1: Establish an overall three-dimensional finite element model of the arch dam, in which the dam body adopts solid elements and the transverse joints adopt interface elements;

[0045] Step 2: According to the actual pouring plan, the corresponding dam sections and pouring layers are divided, and the dam sections are numbered as j, j = 1, 2...m; the pouring and rising process of the dam is simulated by the life and death unit technology to truly consider the changes in the dam gravity load and the center of gravity position during the pouring process;

[0046] Step 3: Use the hydration degree model to simulate the hydration heat release process of concrete, and simulate the water cooling process of the dam based on the equivalent heat conduction equation, calculate the dam temperature field, and deduce the temperature load through the temperature field;

[0047] Step 4: After obtaining the gravity load and temperature load of the dam, calculate the dam structural stress and transverse joint opening based on the following control equations:

[0048] σ i =σ i-1 +Δσ i (Formula 1)

[0049]

[0050]

[0051]

[0052] Among them, Δσ i is the stress increment at the i-th time step, Δd i is the increment of the transverse joint opening at the i-th time step, G i is the gravity load at the i-th time step, ΔT i is the temperature increment at the i-th time step, ξ i is the concrete hydration degree at the i-th time step, is the strain increment caused by non-gravity and temperature factors at the i-th time step;

[0053] Step 5: Based on the stress control standard given in the specification, in order to avoid secondary opening of the transverse joints, the control of the arch stress of the sealed arch dam body is proposed;

[0054] Stress control standards are set for the unsealed arch dam section and the sealed arch dam body respectively. The stress control standard for the unsealed arch dam section is:

[0055]

[0056] The stress control standard of the sealed arch dam is:

[0057]

[0058] in, is the principal tensile stress in the unsealed arch area of ​​dam section j at the i-th time step, is the principal compressive stress in the unsealed arch area of ​​the jth dam section at the i-th time step, τ t is the allowable tensile stress of the unsealed arch dam section, is the allowable tensile stress of the sealed arch dam body, is the principal tensile stress of the sealed arch dam body at the i-th time step, is the principal compressive stress of the sealed arch dam body at the i-th time step, is the arch tensile stress of the sealed arch dam body at the i-th time step, f t,i is the concrete tensile strength at the i-th time step, f c,i is the concrete compressive strength at the i-th time step, ψ is the design condition coefficient, γ 0 is the structural importance coefficient, γ d is the structural coefficient, γ m is the material performance partial coefficient;

[0059] Step 6: Count the dam body stress at each time step i, and dynamically adjust the cantilever height, the height difference of the entire dam section, and the height difference of adjacent dam sections according to the stress control standard of step 5. Combined with the limit of the allowable opening of the transverse joint grouting and the dam body arch sealing temperature, dynamically adjust the pouring arch sealing process:

[0060] 1) If the stress of the unsealed arch dam section and the sealed arch dam body at the i-th time step meets the control standard, the calculation of the next time step is carried out;

[0061] 2) Under the premise of ensuring that the stress of the sealed arch dam body meets the control standard, if the stress of the unsealed arch area of ​​some dam sections in the i-th time step does not meet the control standard, the pouring of these dam sections will be stopped, and the previous pouring step of these dam sections will be cancelled, and these dam sections will be marked as reaching the limit state; for the dam sections whose stress does not exceed the standard, the pouring will continue;

[0062] 3) If the stress of the sealed arch dam body meets the control standard at the i-th time step, but all unsealed arch dam sections have reached the limit state, the pouring of all dam sections is stopped and the sealed arch grouting is started;

[0063] 4) If the stress of the sealed arch dam body at the i-th time step exceeds the allowable value, the pouring of all dam sections is stopped, the previous pouring step is canceled, and the sealed arch grouting is started.

[0064] Step 7: Repeat the above steps and dynamically adjust the pouring and arch sealing process at each stage until the dam is capped.

[0065] Example

[0066] The total storage capacity of a hydropower station is 7.408 billion m 3 , with an installed capacity of 10,200MW; the hub project consists of a river-blocking dam, a spillway structure and an underground water diversion and power generation system; the dam is a hyperbolic arch dam with a height of 270m, a maximum bottom width of 51.45m, and no longitudinal joints.

[0067] During the feasibility study phase, construction parameters such as cantilever height, maximum height difference between adjacent dam sections, and height difference of the entire dam section were specified according to the specifications:

[0068] 1) When grouting in the irrigation area above 790m, the cantilever height of the unjointed grouting dam section shall generally not exceed 60m.

[0069] 2) The maximum height difference between adjacent dam sections generally does not exceed 12m, and the maximum height difference between the lowest and highest sections of the entire dam does not exceed 30m.

[0070] According to statistics, the transverse joints of many high arch dams opened twice during construction. In order to avoid the secondary opening of the transverse joints of the arch dam, a control method for the tensile stress in the arch direction of the sealed arch dam body was proposed on the basis of the stress control standard given in the specification. In addition, during the implementation of the project, due to the complexity of the construction of the middle hole orifice, it is difficult for the on-site construction to fully meet the requirements of the cantilever height and other parameters in the technical requirements, and the flow demand of the middle hole also puts forward higher requirements for the balance and efficiency of the construction. Based on the above considerations, a high arch dam casting and sealing arch control method considering the arch stress control index is proposed, which specifically includes the following steps:

[0071] Step 1: Create Figure 3 The overall three-dimensional finite element model of the arch dam shown in the figure is divided into 296,238 three-dimensional hexahedral units and 331,200 nodes, and the transverse joints are considered as contacts. In the model, the X-axis is along the river, and the positive direction is from the upstream horizontally to the downstream; the Y-axis is across the river, and the positive direction is from the right bank horizontally to the left bank; the Z-axis is vertical, and the positive direction is vertically upward.

[0072] Step 2: According to the actual pouring plan, the corresponding dam sections and pouring layers are divided. A total of 15 dam sections and 14 transverse joints are set from the left bank to the right bank of the dam body. The pouring and rising process of the dam is simulated by the life and death unit technology to truly consider the changes in the dam's gravity load and center of gravity during the pouring process;

[0073] Step 3: Use the hydration degree model to simulate the hydration heat release process of concrete, and simulate the water cooling process of the dam based on the equivalent heat conduction equation, calculate the dam temperature field, and deduce the temperature load through the temperature field;

[0074] Step 4: After the gravity load and temperature load of the dam are calculated through the above steps, the dam structural stress and transverse joint opening are calculated based on the following control equations:

[0075] σ i =σ i-1 +Δσ i (Formula 1)

[0076]

[0077]

[0078]

[0079] Step 5: Based on the stress control standard given in the specification, in order to avoid secondary opening of the transverse joints, it is proposed to control the arch stress of the sealed arch dam body.

[0080] Stress control standards are set for the unsealed arch dam section and the sealed arch dam body, such as Figure 2 As shown in the figure, the stress control standard of the unsealed arch dam section is:

[0081]

[0082] Considering the tensile stress in the arch direction, the stress control standard of the sealed arch dam body is:

[0083]

[0084] Step 6: Count the dam body stress at each time step i, and dynamically adjust the cantilever height, the height difference of the entire dam section, and the height difference of adjacent dam sections according to the stress control standard of step 5, and dynamically adjust the pouring and arch sealing process in combination with the limit of the allowable opening of the transverse joint grouting and the dam body arch sealing temperature. The calculation scheme for this arch dam is as follows:

[0085] Scheme 1: On the premise of meeting the stress control standards, combined with the on-site construction organization schedule, simulate the pouring and rising process of each cantilever beam to optimize the maximum cantilever height limit of the non-orifice dam section.

[0086] Plan 2: On the basis of Plan 1, combined with the on-site construction organization schedule, speed up the pouring progress of some dam sections (2#, 4#, 6#, 8#, 10#, 12#, 14#), and maintain the original pouring progress of other dam sections to optimize the height difference between adjacent dam sections and the height difference of the entire dam section.

[0087] The calculation results of Scheme 1 are as follows Figure 4a As shown in the figure, the unit is 0.01MPa. When the cantilever height of the non-orifice dam section does not exceed 72m, the vertical stress at the bottom of the cantilever of each dam section is basically compressive stress. Only a small tensile stress appears in the local area of ​​the bottom of the cantilever of the non-orifice dam section, and the maximum does not exceed 0.5MPa. The maximum arch tensile stress of the sealed arch dam body is also less than 0.8MPa, and the dam body is safe.

[0088] The calculation results of Scheme 2 are as follows Figure 4b As shown in the figure, the unit is 0.01MPa. When the height difference between adjacent dam sections is controlled to be ≤18m and the height difference of the entire dam section is ≤32m, the stress of the unsealed arch dam section and the sealed arch dam body both meet the control standards and the dam body is safe.

[0089] Based on the above numerical calculation results, the dam cantilever height and casting height difference can be optimized and adjusted during the actual dam pouring process. The adjusted standards are as follows:

[0090] 1) The cantilever height of the non-orifice section of the dam shall not exceed 72m.

[0091] 2) The maximum height difference between adjacent dam sections shall not exceed 18m, and the maximum height difference of the entire dam section shall not exceed 32m.

[0092] Other parts not described in detail belong to the prior art.

Claims

1. A method for controlling the casting and sealing of a high arch dam taking into account the control index of arch stress, characterized in that: The following steps are involved: Establish an overall three-dimensional finite element model of the arch dam, in which the dam body uses solid elements and the transverse joints use interface elements; According to the actual pouring plan, the corresponding dam sections and pouring layers are divided, and the dam sections are numbered as j, j = 1, 2...m; the pouring and rising process of the dam is simulated by the life and death unit technology to truly consider the changes in the dam's gravity load and center of gravity during the pouring process; Simulate the heat release process of concrete hydration and the cooling process of the dam by water flow, calculate the temperature field of the dam, and deduce the temperature load through the temperature field; After obtaining the gravity load and temperature load of the dam, the dam structural stress and transverse joint opening are calculated based on the following control equations: σ i = σ i-1 + Δσ i (Equation 1) Δσ i = f1(G i , ΔT i , Δε i NGT , ξ i ) (Equation 3) Δd i = f2(G i , ΔT i , Δε i NGT ) (Equation 4) Among them, Δσ i is the stress increment at the i-th time step, Δd i is the increment of the transverse joint opening at the i-th time step, G i is the gravity load at the i-th time step, ΔT i is the temperature increment at the i-th time step, ξ i is the concrete hydration degree at the i-th time step, is the strain increment caused by non-gravity and temperature factors at the i-th time step; Based on the stress control standard given in the code, in order to avoid the secondary opening of the transverse joint, the control of the arch stress of the sealed arch dam is proposed; Stress control standards are set for the unsealed arch dam section and the sealed arch dam body respectively. The stress control standard for the unsealed arch dam section is: The stress control standard of the sealed arch dam is: in, is the principal tensile stress in the unsealed arch area of ​​dam section j at the i-th time step, is the principal compressive stress in the unsealed arch area of ​​the jth dam section at the i-th time step, τ t is the allowable tensile stress of the unsealed arch dam section, is the allowable tensile stress of the sealed arch dam body, is the principal tensile stress of the sealed arch dam body at the i-th time step, is the principal compressive stress of the sealed arch dam body at the i-th time step, is the arch tensile stress of the sealed arch dam body at the i-th time step, f t,i is the concrete tensile strength at the i-th time step, f c,i is the concrete compressive strength at the i-th time step, ψ is the design condition coefficient, γ0 is the structural importance coefficient, and γ d is the structural coefficient, γ m is the material performance partial coefficient; Statistics are made on the dam body stress at each time step i. Based on the stress control standard, the cantilever height, the height difference of the whole dam section and the height difference of the adjacent dam sections are dynamically adjusted. In addition, the pouring and arch sealing process is dynamically adjusted in combination with the allowable opening of the transverse joint grouting and the limit of the dam body arch sealing temperature. Repeat the above steps and dynamically adjust the pouring and arch sealing process at each stage until the dam is capped.

2. According to claim 1, a high arch dam casting and arch sealing control method considering the arch stress control index is characterized in that: The dynamic adjustment pouring and arch sealing process comprises: If the stress of the unsealed arch dam section and the sealed arch dam body at the i-th time step both meet the control standard, the calculation of the next time step is performed; Under the premise of ensuring that the stress of the sealed arch dam body meets the control standard, if the stress of the unsealed arch area of ​​some dam sections in the i-th time step does not meet the control standard, the pouring of these dam sections will be stopped, and the previous pouring step of these dam sections will be cancelled, and these dam sections will be marked as reaching the limit state; for the dam sections whose stress does not exceed the standard, the pouring will continue; If the stress of the sealed arch dam body meets the control standard at the i-th time step, but all unsealed arch dam sections have reached the limit state, the pouring of all dam sections will be stopped and the sealed arch grouting will be started; If the stress of the sealed arch dam body at the i-th time step exceeds the allowable value, the pouring of all dam sections is stopped, the previous pouring step is canceled, and the sealed arch grouting is started.

3. A method for controlling the casting and sealing of a high arch dam taking into account the control index of arch stress according to claim 1 or 2, characterized in that: Before the arch grouting begins, the openings of each transverse joint and the temperature of each dam section are counted, and the areas where the transverse joint openings reach the grouting degree and the temperature drops to the arch grouting temperature are divided, so as to determine the start time and target elevation of the arch grouting.

4. A high arch dam casting and arch sealing control method considering arch stress control index according to claim 1, characterized in that: The method for simulating the hydration heat release process of concrete is to use the hydration degree model simulation, and the method for simulating the water cooling process of the dam is to use the simulation based on the equivalent heat conduction equation.

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