CN111814374A - Seismic response analysis and safety assessment method of arch dam during construction - Google Patents

Abstract

The invention discloses an earthquake response analysis and safety assessment method in an arch dam construction period, which comprises the following steps: acquiring thermal and mechanical parameters of a static analysis material in the construction period of the arch dam; carrying out whole-process simulation calculation in the construction period of the arch dam; earthquake response calculation is carried out during arch dam construction; carrying out overall earthquake-resistant safety evaluation on the arch dam; and (5) providing an anti-seismic measure during the construction period of the arch dam. The invention considers the real boundary conditions and material parameters, simulates the actual construction process of the arch dam, can obtain the real working state of the whole process of the arch dam in the construction period through simulation calculation, superposes the earthquake load effect on the basis, and obtains the earthquake response of the arch dam closer to the reality, thereby being beneficial to accurately evaluating the earthquake safety of the arch dam in the construction period and providing corresponding earthquake-proof measures.

Description

Seismic response analysis and safety assessment method of arch dam during construction

technical field

The invention relates to the technical field of algorithms, in particular to a seismic response analysis and safety assessment method during construction of an arch dam.

Background technique

Since most of the rivers in western my country are located in high mountains and valleys, it is suitable to build high dams and reservoirs. The high arch dams that have been built and are under construction in my country are mainly distributed in the western region, such as the built Xiaowan Arch Grade arch dam (305m), Xiluodu arch dam (285.5m), Dagangshan arch dam (210m), Wudongde arch dam (270m), Baihetan arch dam (289m), Yebatan arch dam (210m) 217m), Mengdigou arch dam (240m), etc. The west is the main earthquake area in my country, and the intensity and frequency of earthquakes are quite high. The conditions that consider the combination of earthquake loads are often the control conditions for the design of these arch dams. At present, most of the research on the seismic response of arch dams is aimed at the long-term operation period of the arch dam. There are few studies on the seismic response of the arch dam when it encounters an earthquake during the construction period, and a reasonable and effective analysis method has not been proposed yet. The arch dam has not been completed during the construction period. During the construction process, a dam section with unsealed arch grouting will be formed. When an earthquake occurs, these dam sections are equivalent to "cantilever beams" that bear the seismic load alone, which may cause a large amount of damage. The stress will adversely affect the structural safety and construction of the arch dam. Therefore, a reasonable and effective method for seismic response analysis and safety assessment during the construction period of the arch dam is proposed, the seismic response characteristics of the arch dam during the construction period are studied, and corresponding anti-seismic measures are put forward to scientifically predict the safety margin of the arch dam in the event of an earthquake and ensure the safety of the arch dam. Construction safety and quality are of great significance.

When carrying out the seismic design and calculation analysis of the arch dam, the static loads such as self-weight, water pressure, temperature, silt pressure, and uplift pressure are firstly considered, and the static calculation of the arch dam is carried out. Response Analysis. Therefore, accurate calculation and analysis of the working behavior of arch dams under static loads is an important premise for seismic response analysis of arch dams. In the seismic design of arch dams in my country, the arch dam is usually completed at one time, and the self-weight load is usually applied at one time. The temperature load is obtained from the quasi-stable temperature of the arch dam during the operation period minus the arch sealing temperature, and the elastic modulus of the dam body is taken from the long-term elastic modulus of concrete. (Considering the influence of concrete creep), the seismic design is mainly based on the seismic analysis results of the arch dam during the operation period, and does not consider the earthquake encountered during the construction period of the arch dam.

In my country's "Standards for Seismic Design of Hydraulic Structures" (GB 51247-2018) and "Code for Seismic Design of Hydraulic Structures in Hydropower Engineering" (NB 35047-2015), the seismic response analysis and safety of arch dams during the construction period are also not analyzed. The assessment is clearly defined, and there are no technical specifications and standards for reference. At present, most of the research on the seismic response of arch dams is aimed at the long-term operation stage of the arch dam, and there are few studies on the working behavior of the arch dam when it encounters an earthquake during the construction period.

In the seismic research of the existing arch dam during the construction period, the technical scheme adopted still has the following defects:

(1) The selection of calculation parameters is unreasonable.

In the calculation, the material parameters (elastic modulus, strength) of the arch dam are taken as design parameters, which are suitable for the calculation and analysis of the arch dam in the long-term operation stage.

(2) The calculation of load application is too simplified.

The self-weight of the dam body is applied at one time in a split-slot manner, and the actual split-silo pouring process of the arch dam is not simulated; the temperature load of the arch dam during the construction period has a great influence on the stress state of the arch dam, and the temperature load during the construction period is related to the design temperature of the arch dam. The load (operation period) is quite different. Therefore, the temperature field during the construction period of the arch dam should be inverted based on the temperature monitoring data.

(3) The technical solution cannot reflect the actual situation.

The deformation and stress state during the construction period of the arch dam are constantly changing with the construction progress, and the occurrence of earthquakes is accidental and sudden. Therefore, the analysis of the earthquake response during the construction period of the arch dam must consider the hardening process and temperature of the dam concrete. The actual deformation and stress state of the arch dam during the entire construction period are obtained by simulation through the control process, the arch sealing and grouting process, and the later temperature recovery process. The technical scheme only considers the difference in the appearance of the arch dam at different time nodes during the construction period, and the static calculation does not simulate the evolution of the dam body's working behavior during the actual construction of the arch dam.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to overcome the existing defects, provide a seismic response analysis and safety assessment method during the construction period of the arch dam, consider the real boundary conditions and material parameters, simulate the actual construction process of the arch dam, and obtain the construction of the arch dam through simulation calculation. On this basis, the seismic response of the arch dam is calculated to be closer to reality, which is conducive to the accurate assessment of the seismic safety of the arch dam during the construction period, and the corresponding anti-seismic measures are proposed. The problems in the background technology are effectively solved.

In order to solve the above-mentioned technical problems, the present invention provides the following technical solutions:

The present invention provides a method for seismic response analysis and safety assessment during construction of an arch dam, comprising the following steps:

S1: Obtain the thermal and mechanical parameters of materials for static analysis during the construction of the arch dam;

S2: Carry out the simulation calculation of the whole process of the arch dam construction period;

S3: Calculate the seismic response during the construction period of the arch dam;

S4: Carry out the overall seismic safety assessment of the arch dam;

S5: Propose anti-seismic measures during the construction period of the arch dam.

As a preferred solution, step S1 includes:

1) Thermal parameters of dam concrete

Based on the regression analysis and numerical simulation of the temperature monitoring data, the temperature field during the construction period of the arch dam is inverted, and the real thermal conductivity, surface heat dissipation coefficient and adiabatic temperature rise of the dam concrete are obtained by inversion;

2) Mechanical parameters of dam concrete

The elastic modulus and tensile and compressive strength of concrete during the construction period of the dam body can be obtained from the laboratory material test. The density and Poisson's ratio of the dam body concrete can be taken as the parameters used in the design of the arch dam.

As a preferred solution, step S2 includes:

1) Concrete pouring process

The pouring process of the arch dam should be divided into joints and blocks, and gradually rise according to the warehouse. The self-weight of the concrete in each warehouse is borne by the lower concrete. The simulation calculation is based on the actual pouring progress of the arch dam project, and the numerical simulation calculation model is arranged. The method of layer addition unit precisely simulates the concrete pouring process of each warehouse of the dam to ensure that the application process of the dam's self-weight load is consistent with the actual situation;

2) Concrete hardening process

The layered and block pouring of the dam directly affects the deformation and stress distribution of the dam. Concrete, as an age-hardening material, starts hydration reaction from the time of mixing, releases heat, and gradually hardens, and the temperature change acts as a load Acting on the entire structure, the concrete parameters change continuously during the hardening process. The hardening process of concrete is simulated by elastic modulus hardening model, creep model, etc.;

3) Temperature control process

The temperature control can be divided into 4 main links: the mixing building link, the transportation link, the pouring link, and the water cooling link. simulation simulation;

4) Meteorological change process

Simulate the impact of actual temperature, rainfall, wind and other climate changes on the engineering boundary conditions during the construction process, and then simulate the resulting changes in boundary temperature, surface heat dissipation coefficient, humidity and other engineering boundary conditions on the arch dam structure;

5) Arch grouting process

In order to release part of the temperature stress caused by the temperature change, the arch dam is poured by joints and blocks. When the temperature of the arch dam reaches the sealing temperature, the transverse joints of the arch dam are grouted.

As a preferred solution, step S3 includes:

1) Calculate the parameters

When calculating the seismic response of the arch dam, the elastic modulus of the concrete of the dam body is the elastic modulus calculated by the static simulation, and the dynamic strength of the concrete is 20% higher than the value calculated by the static simulation;

2) Earthquake load

Three seismic waves of different phases are used as input from the bottom of the dam foundation in three directions. Considering the transient nature of the construction period, the horizontal seismic peak acceleration during the construction period is taken as 1/2 of the design horizontal seismic peak acceleration, and the vertical seismic peak acceleration is taken as the horizontal 2/3;

3) Calculation method

Select the key time node during the construction period, take the deformation and stress obtained by the simulation calculation in step 2 as the initial state, regard the dam body-reservoir water-foundation as the whole open wave system, and consider the inertial effect of the foundation and the surrounding foundation rock mass. Various geological structures, dynamic contact nonlinear effects of transverse joints of arch dams, radiation damping effects of infinite foundations, and inhomogeneity of ground motion input on the dam foundation surface, the time history analysis method is used to calculate the seismic response of arch dams.

As a preferred solution, step S4 includes:

Compare the stress calculated by the seismic response in step S3 with the dynamic tensile and compressive strengths of the arch dam, and analyze and evaluate whether the arch dam is damaged by cracking, crushing, etc. when it encounters an earthquake;

Compare the maximum opening of the transverse joint calculated in step S3 with the maximum opening of the transverse joint water-stop copper sheet, and analyze and evaluate whether the water-stop copper sheet will be damaged.

As a preferred solution, step S5 includes:

According to the evaluation results of the overall seismic safety of the arch dam during the construction period in step S4, targeted seismic measures are proposed.

As a preferred solution, the anti-seismic measures include water filling and slag storage in the upstream of the arch dam in advance, anti-seismic steel bars are arranged at the possibly damaged parts of the dam body, and the cantilever height of the arch dam is controlled.

One or more technical solutions provided in the present invention have at least the following technical effects or advantages:

1. Considering the real boundary conditions and material parameters, the actual construction process of the arch dam is simulated, and the real working behavior of the arch dam during the construction period can be simulated and calculated. Approaching the reality, it is beneficial to accurately evaluate the seismic safety of the arch dam during the construction period, and propose corresponding seismic measures.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the specification, and are used to explain the present invention together with the embodiments of the present invention, and do not constitute a limitation to the present invention.

In the attached image:

1 is a diagram showing the relationship between the measured volume deformation and temperature without a stress gauge and a schematic diagram of a straight line fitting in the method for seismic response analysis and safety assessment during construction of an arch dam according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of the arch dam concrete pouring process simulation diagram of the method for seismic response analysis and safety assessment during the construction period of the arch dam according to the embodiment of the present invention.

FIG. 3 is a schematic diagram of the technical route of the seismic response analysis and safety assessment method during the construction period of the arch dam according to the embodiment of the present invention.

4 is a schematic diagram of the arch dam-foundation integral finite element model of the method for seismic response analysis and safety assessment during the construction period of the arch dam according to the embodiment of the present invention.

5 is a schematic diagram of a finite element model of an arch dam of the method for seismic response analysis and safety assessment during construction of an arch dam according to an embodiment of the present invention.

Figures 6a, 6b, and 6c are schematic diagrams of acceleration time-history curves in three directions generated by the standard response spectrum of the method for seismic response analysis and safety assessment during construction of an arch dam according to an embodiment of the present invention.

7a and 7b are schematic diagrams of the main tensile stress distribution cloud diagrams on the upstream and downstream surfaces of the method for seismic response analysis and safety assessment during construction of an arch dam according to an embodiment of the present invention.

Figures 8a and 8b are schematic diagrams of the cloud diagram of the main tensile stress distribution of the dam body under the static and dynamic superposition of the seismic response analysis and safety assessment method of the arch dam during construction in the embodiment of the present invention.

9a and 9b are schematic diagrams of the main tensile stress distribution cloud diagram of the dam body under the static and dynamic superposition of the seismic response analysis and safety assessment method of the arch dam during construction in the embodiment of the present invention.

Figures 10a and 10b are schematic diagrams of the cloud map of the principal compressive stress distribution of the dam body under the static and dynamic superposition of the seismic response analysis and safety assessment method of the arch dam during construction in the embodiment of the present invention.

11 is a schematic diagram of the distribution and numbering of transverse joints of the arch dam on January 15, 2020 of the seismic response analysis and safety assessment method during the construction period of the arch dam according to the embodiment of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

In order to better understand the above technical solutions, the above technical solutions will be described in detail below with reference to the accompanying drawings and specific embodiments.

Example:

The present embodiment provides an earthquake response analysis and safety assessment method during construction of an arch dam, including the following steps:

Step 1: Obtain thermal and mechanical parameters of materials for static analysis during construction of the arch dam.

(1) Thermal parameters of dam body concrete

Based on regression analysis and numerical simulation of temperature monitoring data, the temperature field during the construction period of the arch dam is inverted, and the real thermal conductivity, surface heat dissipation coefficient and adiabatic temperature rise of the dam concrete are obtained by inversion.

The adiabatic temperature rise model is expressed as

In the formula: T ₁ and T ₂ are the adiabatic temperature rise values; τ is the age; α ₁ , β ₁ , α ₂ , and β ₂ are undetermined coefficients, which can be obtained by inversion.

Based on the monitoring results of the non-stress gauge of the arch dam, the linear expansion coefficient of the concrete of the dam body is obtained by inversion through the correlation analysis of the relationship between the temperature and the micro-strain detected by the non-stress monitoring. Assuming that the coefficient of linear expansion is constant throughout the observation period, all monitoring data satisfy:

In the formula: ui is the volume deformation monitored by the unstressed meter at the _i -th time, including temperature expansion deformation and autogenous volume deformation; Ti is the temperature at the _i -th time, and T _i-1 is the temperature at the i-1th time; ε _0i is the self-generated volume deformation at the i-th moment; α is the linear expansion coefficient. Using the monitoring data expressed by formula (2), the correlation analysis of deformation and temperature can be carried out, as shown in Figure 1, the slope is the linear expansion coefficient α of concrete.

(2) Mechanical parameters of dam body concrete

The elastic modulus, tensile and compressive strength of concrete during the construction period of the dam body can be obtained according to the indoor material test; the density and Poisson's ratio of the dam body concrete can be taken as the parameters used in the design of the arch dam.

Step 2: Carry out the simulation calculation of the whole process of the arch dam construction period.

Considering the real boundary conditions and material parameters, simulate the concrete pouring process, concrete hardening process, temperature control process, meteorological change process, and arch grouting process, carry out the simulation calculation of the whole process of the arch dam construction period, and obtain the stress of the arch dam under static load. and deformation history as the initial conditions for the calculation of the seismic response of the arch dam.

(1) Concrete pouring process

The pouring process of the arch dam should be divided into joints and blocks, and gradually rise according to the warehouse, and the self-weight of the concrete of each warehouse is borne by the lower concrete. The simulation calculation is based on the actual pouring progress of the arch dam project, and the numerical simulation calculation model is arranged. . Figure 2 shows a schematic diagram of the simulation of the concrete pouring process of the arch dam in the simulation calculation.

(2) Concrete hardening process

The layered and block pouring of the dam directly affects the deformation and stress distribution of the dam. As an age-hardening material, concrete starts hydration reaction from the time of mixing, releases heat, and gradually hardens. The hardening process of concrete is simulated by elastic modulus hardening model and creep model.

The elastic modulus hardening model of concrete can adopt an exponential model, namely:

In the formula: E(τ) is the elastic modulus at age τ; E ₀ is the elastic modulus part independent of age, and E ₀ +E _c is the final elastic modulus of concrete.

The concrete creep model is

In the formula: k ₁ , k ₂ , k ₃ , α ₁ , α ₂ are creep rate parameters, dimensionless numbers; A ₁ , A ₂ , B ₁ , B ₂ , D are creep degree parameters, representing the Creep degree; t is time; τ is concrete age.

(3) Temperature control process

Temperature control can be divided into 4 main links: mixing building link, transportation link, pouring link, water cooling link. By simulating the construction process of the arch dam and simulating the function of each link of the cooling water pipe model, the simulation of the whole process of temperature control is realized.

(4) Meteorological change process

Simulate the impact of actual temperature, rainfall, wind and other climate changes on the engineering boundary conditions during the construction process, and then simulate the resulting changes in boundary temperature, surface heat dissipation coefficient, humidity and other engineering boundary conditions on the arch dam structure.

(5) Arch grouting process

In order to release part of the temperature stress caused by the temperature change, the arch dam is poured by joints and blocks. When the temperature of the arch dam reaches the closing temperature, the transverse joints of the arch dam are grouted. The present invention uses a thickness-free contact unit to simulate the transverse joint of the arch dam and the grouting process of closing the arch. Before the grouting of the arch, each dam section is subjected to independent force. During the simulation calculation, the transverse joint has no tensile strength, but only has shear strength. After grouting, the dam sections on both sides of the transverse joint are connected as a whole by the cement slurry poured into the transverse joint, and the tensile strength and shear strength of the contact element of the transverse joint become the strength of cement mortar.

Step 3: Calculate the seismic response during the construction period of the arch dam.

(1) Calculation parameters

In the calculation of the seismic response of the arch dam, the elastic modulus of the concrete of the dam body is the elastic modulus of the static simulation calculation, and the dynamic strength of the concrete is increased by 20% compared with the static simulation calculation value.

(2) Earthquake load

Three seismic waves of different phases are used as input from the bottom of the dam foundation in three directions. Considering the transient nature of the construction period, the horizontal seismic peak acceleration during the construction period is taken as 1/2 of the design horizontal seismic peak acceleration, and the vertical seismic peak acceleration is taken as the horizontal 2/3.

(3) Calculation method

Select the key time node during the construction period, take the deformation and stress obtained by the simulation calculation in step 2 as the initial state, regard the dam body-reservoir water-foundation as the whole open wave system, and consider the inertial effect of the foundation and the surrounding foundation rock mass. Various geological structures, dynamic contact nonlinear effects of transverse joints of arch dams, radiation damping effects of infinite foundations, and inhomogeneity of ground motion input on the dam foundation surface, the time history analysis method is used to calculate the seismic response of arch dams. The dynamic balance equation for the seismic response calculation of the arch dam is:

{u(t)}分别为位移、速度、加速度向量；{F(t)}为作用力矢量。In the formula: [M], [C], [K] are the mass matrix, damping matrix and stiffness matrix of the arch dam, respectively;

{u(t)} are displacement, velocity and acceleration vectors respectively; {F(t)} is the force vector.

Step 4: Carry out the overall seismic safety assessment of the arch dam.

Compare the stress calculated by the seismic response in step 3 with the dynamic tensile and compressive strength of the arch dam, and analyze and evaluate whether the arch dam will be cracked or crushed when it encounters an earthquake; Compare the maximum opening that the transverse seam water-stop copper sheet can withstand, and analyze and evaluate whether the water-stop copper sheet will be damaged.

Step 5: Propose anti-seismic measures during the construction period of the arch dam.

According to the evaluation results of the overall seismic safety of the arch dam during the construction period in step 4, targeted seismic measures are proposed, such as pre-filling the upstream of the arch dam with slag, laying anti-seismic steel bars in the potentially damaged parts of the dam body, and controlling the cantilever height of the arch dam, etc. .

The method and effect of the present invention will be described in detail below with reference to a specific embodiment.

A concrete double-curvature arch dam under construction in China has a dam crest elevation of 988.0m, a minimum elevation of 718.0m for the foundation surface, and a maximum dam height of 270.0m. Using the method of the invention, combined with the actual progress of the dam project, according to the proposed water storage plan during the construction period of the dam project, the dynamic response of the dam under different water storage levels is analyzed, and the seismic safety of the dam is evaluated.

computational model

A finite element seismic response analysis model of the dam is established. The overall finite element model of the arch dam-foundation is shown in Figure 4, and the finite element model of the dam body is shown in Figure 5. The coordinate system is taken as: the x-direction is the horizontal direction, pointing to the left bank; the y-direction is the river-side direction, pointing upstream; the z-direction is the vertical direction.

Calculated parameters

(1) Thermal parameters of dam concrete

①Adiabatic temperature rise

According to the temperature monitoring data and formula (1), the adiabatic temperature rise of the dam concrete can be obtained by inversion, namely:

C35 Concrete:

C30 concrete:

②Linear expansion coefficient

Based on the monitoring results of the stress-free arch dam, the linear expansion coefficient α of the concrete of the dam body can be obtained by inversion by using the formula (2) through the correlation analysis of the relationship between the temperature and the micro-strain detected by the stress-free monitoring.

C35 concrete: α=0.0000078/℃

C30 concrete: α=0.0000078/℃

③ Specific heat

C35 concrete: C=0.992kJ/(kg﹒℃)

C30 concrete: C=0.985kJ/(kg﹒℃)

④ Thermal conductivity

C35 concrete: λ=7.86kJ/(m﹒h﹒℃)

C30 concrete: λ=7.74kJ/(m﹒h﹒℃)

(2) Mechanical parameters of dam body concrete

The elastic modulus, tensile and compressive strength of concrete during the construction period of the dam body can be obtained according to the indoor material test; the density and Poisson's ratio of the dam body concrete can be taken as the parameters used in the design of the arch dam.

①Modulus of elasticity

In the static simulation calculation of the arch dam, the elastic modulus of C35 concrete is E=47.89GPa; the elastic modulus of C30 concrete is E=48.04GPa.

When calculating the seismic response of the arch dam, the elastic modulus of the concrete of the dam body is the elastic modulus of the static simulation calculation.

②Poisson’s ratio

The Poisson's ratio of the dam body C30 and C35 concrete is both taken as 0.17.

③ Density

The density of the dam body C30 and C35 concrete are both taken as 2400kg/m ³ .

④ Tensile and compressive strength

In the static simulation calculation of the arch dam, the tensile strength of C35 concrete is ft = _2.54MPa , and the compressive strength is fc = _25.42MPa ; the tensile strength of C30 concrete is ft = _2.18MPa , and the compressive strength is fc = _21.75MPa .

When calculating the seismic response of the arch dam, the dynamic strength of concrete is 20% higher than the value calculated by static simulation, that is, the dynamic tensile strength of C35 concrete is ft = _3.05MPa , and the dynamic compressive strength is fc = _30.49MPa ; the dynamic tensile strength of C30 concrete is Strength ft = 2.61 MPa, dynamic compressive strength _{f c =} 26.13 MPa.

(2) Earthquake load

The seismic fortification category of the arch dam is Class A, and the peak seismic acceleration at the design level is taken as the peak acceleration of ground motion with a probability of exceeding 2% within 100 years, that is, 0.27g. Considering the transient nature of the construction period, the horizontal seismic peak acceleration during the construction period is 1/2 of the design horizontal seismic peak acceleration, that is, 0.135g, and the vertical seismic peak acceleration is 2/3 of the horizontal direction. Three seismic waves with different phases are used as input from the bottom of the dam foundation as three directions, and the acceleration time-history curves of the three directions generated by the standard response spectrum are shown in Figures 6a, 6b, and 6c.

(3) Seismic response analysis of arch dams

According to the proposed water storage plan during the construction period of the dam project, the seismic response of the arch dam under different water storage levels is calculated as follows:

Condition 1: 890m water level

Working condition 2: 945m water level

① Dam stress

Table 1 shows the maximum principal tensile and principal compressive stresses of the dam body when the stress is large during the earthquake. It can be seen that under the upstream water level of 890m, the tensile stress of the arch dam is the largest at 2.94s of the earthquake, which is 3.65MPa, which appears at the elevation of 928m at the right arch end of the upstream surface; the compressive stress of the arch dam is the largest at the 10.37s of the earthquake, which is -14.97 MPa, appearing at the dam heel. Under the upstream water level of 945m, the tensile stress of the arch dam is the largest at 2.94s of the earthquake, which is 3.55MPa, which appears at the 928m elevation of the right arch end of the upstream face; Dam heel part.

Figures 7a and 7b and Figures 8a and 8b are the cloud diagrams of the main tensile stress distribution on the upstream and downstream surfaces of the dam body when the earthquake is 2.94 s under the water storage level of 890 m and 945 m, respectively. Figures 9a and 9b and Figures 10a and 10b are the cloud diagrams of the principal compressive stress distribution on the upstream and downstream surfaces of the dam body when the earthquake is 2.94s under the water level of 890m and 945m, respectively. It can be seen that the local tensile stress at the upstream arch end of the arch dam is large, which exceeds the dynamic tensile strength of concrete (the dynamic tensile strength of C35 concrete is ft = _3.05MPa , and the dynamic tensile strength of C30 concrete is ft = _2.61MPa ). The tensile stress of other parts is less than the dynamic tensile strength of concrete. The compressive stress of the arch dam is smaller than the dynamic compressive strength of concrete (dynamic compressive strength of C35 concrete f _c =30.49MPa, dynamic compressive strength of C30 concrete f _c =26.13MPa). In general, the stress level of the arch dam under the impoundment level of 890m is higher than that of the arch dam under the impoundment level of 928m.

Table 1 The maximum principal tensile and principal compressive stresses of the dam body when the stress is large during the earthquake

Table 2 is a statistical table of the maximum opening of each transverse joint under earthquake action. It can be seen that as the reservoir water level rises from 890m to 945m elevation, the effect of hydraulic joints in the upstream reservoir is more obvious. Therefore, the opening of transverse joints decreases during the earthquake process of the arch dam, and the maximum opening of transverse joints occurs in the 2# transverse joint. The elevation of the top of the seam, among which, the maximum opening of the top of the 2# horizontal seam is 16.70mm, and the water stop of the horizontal seam will not be pulled apart.

It can be seen that under the upstream water level of 890m, the maximum opening of the transverse joint is 16.70mm, which occurs at the top elevation of the 2# transverse joint. Under the upstream water level of 945m, the maximum opening of the transverse joint is 4.13mm, which occurs at the top elevation of the 1# transverse joint. The calculation results show that the lower the upstream water level is, the smaller the arch compressive stress of the arch dam and the larger the transverse joint opening during the earthquake. Therefore, attention should be paid to the opening of the transverse joints of the arch dam when the water level is low, and engineering measures should be taken to reduce the opening of the transverse joints to prevent the water-stop copper sheets of the transverse joints from being pulled out.

Table 2 Statistics of maximum opening and position of transverse seam

(4) Earthquake safety assessment of arch dams

①The seismic stress calculation results of the arch dam above show that the local tensile stress at the upstream arch end of the arch dam is relatively large, which exceeds the dynamic tensile strength of concrete (dynamic tensile strength of C35 concrete ft=3.05MPa, dynamic tensile strength of C30 concrete ft= 2.61MPa), and the tensile stress of other parts is less than the dynamic tensile strength of concrete. The compressive stress of the arch dam is smaller than the dynamic compressive strength of concrete (the dynamic compressive strength of C35 concrete is fc=30.49MPa, and the dynamic compressive strength of C30 concrete is fc=26.13MPa). Therefore, in the event of an earthquake, the upstream arch end of the arch dam will be partially pulled apart, but the overall safety of the arch dam can be guaranteed.

②The above calculation results of the transverse joint opening of the arch dam show that the maximum transverse joint opening is 16.7mm during the earthquake, and the transverse joint water-stop copper sheet will not be damaged under this opening.

③ The higher the upstream water level during the construction period of the arch dam, the more favorable it is to the structural safety of the arch dam when it encounters an earthquake.

To sum up, the arch dam is safe as a whole under the action of earthquake, and certain seismic measures should be taken to prevent the local cracking of the arch dam.

(5) Anti-seismic measures

According to the results of the safety assessment of the arch dam, it is suggested that the anti-seismic steel bars should be installed in the parts of the arch dam where the local tensile stress is relatively large, and slag can be deposited upstream of the arch dam to store water as early as possible.

Finally, it should be noted that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it is still The technical solutions described in the foregoing embodiments may be modified, or some technical features thereof may be equivalently replaced. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (7)

1. The earthquake response analysis and safety assessment method in the construction period of the arch dam is characterized by comprising the following steps: the method comprises the following steps:

s1: acquiring thermal and mechanical parameters of a static analysis material in the construction period of the arch dam;

s2: carrying out whole-process simulation calculation in the construction period of the arch dam;

s3: earthquake response calculation is carried out during arch dam construction;

s4: carrying out overall earthquake-resistant safety evaluation on the arch dam;

s5: and (5) providing an anti-seismic measure during the construction period of the arch dam.

2. The method for earthquake response analysis and safety assessment during arch dam construction according to claim 1, wherein: step S1 includes:

1) thermal parameters of dam concrete

Based on regression analysis and numerical simulation of temperature monitoring data, inverting the temperature field in the construction period of the arch dam, and inverting to obtain the real heat conductivity coefficient, surface heat dissipation coefficient and adiabatic temperature rise of the concrete of the dam body;

2) mechanical parameters of dam concrete

The elastic modulus, tensile strength and compressive strength of the concrete in the dam construction period can be obtained according to indoor material tests, and the density and Poisson ratio of the concrete in the dam can be parameters adopted in the design of the arch dam.

3. The method for earthquake response analysis and safety assessment during arch dam construction according to claim 2, wherein: step S2 includes:

1) concrete pouring process

The pouring process of the arch dam needs to be divided into seams and blocks, the arch dam gradually rises according to bins, the dead weight of concrete in each bin is borne by the concrete at the lower part of the arch dam, the numerical simulation calculation model is arranged in the bins according to the actual pouring progress of the arch dam project through simulation calculation, the pouring process of the concrete in each bin of the dam is finely simulated in a mode of adding units layer by layer, and the application process of the dead weight load of the dam is ensured to be consistent with the actual application process;

2) concrete hardening process

The deformation and stress distribution of the dam are directly influenced by the layered block pouring of the dam, concrete is used as an age hardening material, a hydration reaction starts from the mixing, heat is released, the concrete is gradually hardened, the temperature change is used as a load to act on the whole structure, and the concrete parameter is continuously changed in the hardening process. Simulating the hardening process of concrete through a spring die hardening model, a creep model and the like;

3) temperature control process

Temperature control can be divided into 4 main links: mixing building links, transportation links, pouring links and water cooling links, and simulating the construction process of the arch dam and the simulation of each link of a cooling water pipe model so as to realize the simulation of the whole temperature control process;

4) weather change process

Simulating the influence of climate changes such as actual temperature, rainfall, wind and the like on the engineering boundary conditions in the construction process, and further simulating the influence of the changes of the engineering boundary conditions such as boundary temperature, surface heat dissipation coefficient, humidity and the like on the arch dam structure;

5) sealing arch grouting process

In order to release partial temperature stress caused by temperature change, the arch dam is cast in a split mode and a block mode, and when the temperature of the arch dam reaches the arch sealing temperature, grouting is conducted on transverse joints of the arch dam.

4. The method for earthquake response analysis and safety assessment during arch dam construction according to claim 3, wherein: step S3 includes:

1) calculating parameters

When the earthquake response of the arch dam is calculated, the elastic modulus of the concrete of the dam body is measured during static simulation calculation, and the dynamic strength of the concrete is improved by 20 percent compared with the static simulation calculation value;

2) seismic load

Three seismic waves with different phases are respectively used as three directions to be input from the bottom of a dam foundation, and in consideration of the instantaneity of a construction period, 1/2 of the horizontal seismic peak acceleration is taken as the horizontal seismic peak acceleration in the construction period, and 2/3 of the horizontal seismic peak acceleration is taken as the vertical seismic peak acceleration;

3) calculation method

And selecting key time nodes in the construction period, taking the deformation and stress obtained by simulation calculation in the step two as initial states, regarding the dam body, reservoir water and foundation as a whole open fluctuation system, considering inertia effect of the foundation, various geological structures in the near-field foundation rock mass, dynamic contact nonlinear effect of arch dam transverse joints, infinite foundation radiation damping effect and non-uniformity of earthquake motion input of the dam foundation surface, and adopting a time-course analysis method to calculate earthquake response of the arch dam.

5. The method for earthquake response analysis and safety assessment during arch dam construction according to claim 4, wherein: step S4 includes:

comparing the stress obtained by the seismic response calculation in the step S3 with the dynamic tensile strength and the compressive strength of the arch dam, and analyzing and evaluating whether the arch dam is damaged by cracking, crushing and the like when encountering the earthquake;

and (4) comparing the maximum opening of the transverse seam calculated in the step (S3) with the maximum opening which can be borne by the transverse seam water-stopping copper sheet, and analyzing and evaluating whether the water-stopping copper sheet is damaged by pulling.

6. The method for earthquake response analysis and safety assessment during arch dam construction according to claim 5, wherein: step S5 includes:

and according to the evaluation result of the step S4 on the overall earthquake-proof safety during the arch dam construction period, providing targeted earthquake-proof measures.

7. The method for earthquake response analysis and safety assessment during arch dam construction according to claim 6, wherein: the anti-seismic measures are that water is filled in the upstream of the arch dam in advance, slag is piled up, anti-seismic reinforcing steel bars are arranged at the position where the dam body is possibly damaged, and the height of an arch dam cantilever is controlled.

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