CN111814374B - Seismic response analysis and safety assessment method of arch dam during construction - Google Patents
Seismic response analysis and safety assessment method of arch dam during construction Download PDFInfo
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Abstract
本发明公开了拱坝施工期地震反应分析及安全评估方法，包括以下步骤：获取拱坝施工期静态分析材料热学、力学参数；进行拱坝施工期全过程仿真计算；进行拱坝施工期地震响应计算；进行拱坝整体抗震安全性评估；提出拱坝施工期抗震措施。本发明考虑真实边界条件及材料参数，模拟了拱坝实际施工过程，能够仿真计算得到拱坝施工期全过程真实工作性态，在此基础上叠加地震荷载作用，计算得到的拱坝地震响应更加接近实际，有利于对拱坝施工期的地震安全性进行准确评估，并提出相应抗震措施。
The invention discloses a seismic response analysis and safety assessment method during the construction period of an arch dam, comprising the following steps: obtaining thermal and mechanical parameters of materials for static analysis during the construction period of the arch dam; performing simulation calculation of the whole process during the construction period of the arch dam; performing seismic response during the construction period of the arch dam Calculate; carry out the overall seismic safety assessment of the arch dam; propose seismic measures during the construction period of the arch dam. The method considers the real boundary conditions and material parameters, simulates the actual construction process of the arch dam, and can simulate and calculate the real working behavior of the arch dam in the whole process of the construction period. 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
Technical Field
The invention relates to the technical field of algorithms, in particular to a seismic response analysis and safety assessment method in an arch dam construction period.
Background
As rivers in western regions of China are located in the gorges of mountains and are suitable for building large banks of high dams, the high arch dams built and built in China are mainly distributed in the western regions, such as built bay arch dams (292m), brocade first-level arch dams (305m), stream luotu arch dams (285.5m), large hillock arch dams (210m), built Udongde arch dams (270m), white crane beach arch dams (289m), leaf bayan arch dams (217m), mengkou arch dams (240m) and the like. The west is a main earthquake area in China, the intensity and frequency of earthquake occurrence are quite high, and the working condition of considering earthquake load combination is often the control working condition of the arch dam design. At present, the research on the earthquake response of the arch dam is mainly aimed at the long-term operation period of the arch dam, the research on the earthquake response of the arch dam when encountering the earthquake in the construction period is less, and a reasonable and effective analysis method is not provided. The arch dam is not built into a complete arch dam in the construction period, dozens of meters of dam sections which are not sealed and grouted can be formed in the construction process, and when an earthquake occurs, the dam sections are equivalent to cantilever beams to bear earthquake load independently, so that large stress can be generated, and the structural safety and the construction of the arch dam can be adversely affected. Therefore, a reasonable and effective method for earthquake response analysis and safety assessment in the construction period of the arch dam is provided, earthquake response characteristics in the construction period of the arch dam are researched, corresponding earthquake-resistant measures are provided, and the method has important significance for scientifically estimating safety margin when an earthquake occurs in the construction process of the arch dam and ensuring the safety and quality of engineering construction.
When the arch dam earthquake-proof design and calculation analysis are carried out, static loads such as self weight, water pressure, temperature, silt pressure, uplift pressure and the like are considered at first, arch dam static calculation is carried out, and the earthquake load effect is superposed on the basis to carry out arch dam earthquake reaction analysis. Therefore, accurate calculation and analysis of the working state of the arch dam under the action of the static load are important preconditions for the earthquake reaction analysis of the arch dam. In the anti-seismic design of the arch dam in China, the arch dam is usually formed once, the dead load is usually applied once, the temperature load is obtained by subtracting the arch sealing temperature from the quasi-stable temperature of the arch dam in the operation period, the elastic modulus of the dam body is the long-term elastic modulus of concrete (considering the creep influence of the concrete), and the anti-seismic design is mainly based on the anti-seismic analysis result of the arch dam in the operation period and does not consider the condition that the arch dam encounters an earthquake in the construction period.
In the 'anti-seismic design standards for hydraulic buildings' (GB 51247-. At present, the earthquake reaction research of the arch dam is also directed at the long-term operation stage of the arch dam, and the working state research of the arch dam encountering earthquake in the construction period is less.
In the existing earthquake-resistant research of arch dam construction period, the adopted technical scheme has the following defects:
(1) the calculation parameters are not selected reasonably.
The design parameters are adopted for calculating the material parameters (elastic modulus and strength) of the arch dam, the method is suitable for calculation and analysis of the long-term operation stage of the arch dam, and inversion is required due to the fact that the difference between the material parameters and the design parameters of the arch dam in the construction period is large.
(2) The computational load application is overly simplified.
The self weight of the dam body is applied once according to a parting mode, and the actual warehouse-dividing pouring process of the arch dam is not simulated; the temperature load borne by the arch dam in the construction period has a large influence on the stress state of the arch dam, and the difference between the temperature load in the construction period and the designed temperature load (operation period) of the arch dam is large, so that the temperature field in the construction period of the arch dam is inverted based on temperature monitoring data.
(3) The technical scheme cannot reflect the reality.
The deformation and stress state of the arch dam in the construction period are continuously changed along with the construction progress, and the earthquake happens occasionally and suddenly, so the earthquake reaction analysis in the arch dam construction period needs to consider the pouring hardening process, the temperature control process, the arch sealing grouting process and the later temperature rising process of the dam body concrete, the real deformation and stress state of the whole process of the arch dam in the construction period is obtained through simulation, the earthquake load effect is superposed on the real deformation and stress state, and the earthquake response of the arch dam with different construction nodes is obtained through calculation. In the technical scheme, the difference of the appearance of the node dam at different time in the construction period of the arch dam is only considered, and the evolution of the working state of the dam body in the actual construction process of the arch dam is not simulated during static calculation.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, provides an arch dam construction period earthquake response analysis and safety assessment method, takes real boundary conditions and material parameters into consideration, simulates the actual construction process of an arch dam, can obtain the real working state of the whole construction period of the arch dam through simulation calculation, superposes earthquake load action on the basis, obtains an arch dam earthquake response closer to the reality through calculation, is beneficial to accurately assessing the earthquake safety of the arch dam during the construction period, provides corresponding earthquake-resistant measures, and can effectively solve the problems in the background technology.
In order to solve the technical problems, the invention provides the following technical scheme:
the invention provides an earthquake response analysis and safety assessment method in an arch dam construction period, which comprises the following steps:
s1: acquiring thermal parameters of dam body concrete and mechanical parameters of the dam body concrete during arch dam construction;
s2: according to the thermal parameters of the dam body concrete and the mechanical parameters of the dam body concrete, controlling the processes of concrete pouring, hardening, temperature control, meteorological change and arch sealing and grouting 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.
Preferably, 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.
Preferably, 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.
Preferably, 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.
Preferably, 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.
Preferably, 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.
As a preferred scheme, 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 a cantilever of the arch dam is controlled.
One or more technical schemes provided by the invention at least have the following technical effects or advantages:
1. the actual construction process of the arch dam is simulated by considering the actual boundary conditions and material parameters, the actual working state of the whole process of the arch dam in the construction period can be obtained through simulation calculation, the earthquake load effect is superposed on the basis, the earthquake response of the arch dam obtained through calculation is closer to the actual earthquake response, the accurate evaluation of the earthquake safety of the arch dam in the construction period is facilitated, and corresponding earthquake-resistant measures are provided.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.
In the drawings:
FIG. 1 is a graph of the relationship between the actual measured volume deformation and the temperature of a stress-free gauge in the method for earthquake response analysis and safety assessment during construction of an arch dam and a straight line fitting schematic diagram in the embodiment of the invention.
Fig. 2 is a schematic diagram of an arch dam concrete pouring process simulation of the arch dam construction period earthquake response analysis and safety evaluation method in the embodiment of the invention.
Fig. 3 is a schematic technical route of the method for earthquake response analysis and safety assessment during arch dam construction according to the embodiment of the invention.
FIG. 4 is a schematic diagram of an arch dam-foundation integrated finite element model of the method for earthquake response analysis and safety evaluation during the construction of the arch dam in the embodiment of the invention.
FIG. 5 is a schematic diagram of a finite element model of an arch dam according to the method for earthquake response analysis and safety evaluation during the construction of the arch dam in the embodiment of the invention.
Fig. 6a, 6b and 6c are schematic diagrams of acceleration time-course curves in three directions generated by a standard reaction spectrum of the method for analyzing earthquake response and evaluating safety during arch dam construction according to the embodiment of the invention.
Fig. 7a and 7b are schematic diagrams of main tensile stress distribution clouds on the upstream and downstream surfaces of the method for earthquake response analysis and safety assessment during arch dam construction in the embodiment of the invention.
Fig. 8a and 8b are schematic diagrams of main tensile stress distribution clouds of a dam body under static and dynamic stack of the earthquake response analysis and safety evaluation method in the construction period of the arch dam in the embodiment of the invention.
Fig. 9a and 9b are schematic diagrams of main tensile stress distribution clouds of a dam body under static and dynamic stack of the earthquake response analysis and safety evaluation method in the construction period of the arch dam in the embodiment of the invention.
Fig. 10a and 10b are schematic diagrams of main compressive stress distribution clouds of a dam body under static and dynamic stack of the earthquake response analysis and safety evaluation method in the construction period of the arch dam in the embodiment of the invention.
Fig. 11 is a schematic diagram of distribution and numbering of transverse joints of an arch dam 1 month and 15 days 2020 in the method for earthquake response analysis and safety assessment in the construction period of the arch dam in the embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
For better understanding of the above technical solutions, the following detailed descriptions will be provided in conjunction with the drawings and the detailed description of the present invention.
Example (b):
the embodiment provides an earthquake response analysis and safety assessment method in an arch dam construction period, which comprises the following steps:
the method comprises the following steps: and acquiring thermal parameters of the dam body concrete and mechanical parameters of the dam body concrete during arch dam construction.
(1) Thermal parameters of dam concrete
And (3) inverting the temperature field in the construction period of the arch dam based on regression analysis and numerical simulation of temperature monitoring data, and inverting to obtain the real heat conductivity coefficient, surface heat dissipation coefficient and adiabatic temperature rise of the concrete of the dam body. Adiabatic temperature rise model is expressed as
In the formula: t is1、T2Is the adiabatic temperature rise value; tau is age; alpha is alpha1、β1、α2、β2The undetermined coefficient can be obtained through inversion.
Based on the monitoring result of the arch dam non-stress meter, the linear expansion coefficient of the dam body concrete is obtained through carrying out correlation analysis on the temperature-micro strain relation monitored by the non-stress meter and carrying out inversion. Assuming that the linear expansion coefficient is constant during the whole observation period, all the monitored data satisfy:
in the formula: u. ofiThe volume deformation monitored by the non-stress meter at the ith moment comprises temperature expansion deformation and autogenous volume deformation; t isiIs the temperature at the i-th moment, Ti-1Is the ith-1The temperature at the moment; epsilon0iIs the autogenous volume deformation at time i; and alpha is a linear expansion coefficient. The monitoring data expressed by the formula (2) can be used for carrying out the correlation analysis of deformation and temperature, as shown in fig. 1, and the slope is the linear expansion coefficient alpha of the concrete.
(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 an indoor material test; the density and Poisson ratio of the dam body concrete can be parameters adopted in the design of the arch dam.
Step two: and according to the thermal parameters of the dam body concrete and the mechanical parameters of the dam body concrete, controlling the processes of concrete pouring, hardening, temperature control, meteorological change and arch sealing and grouting in the construction period of the arch dam.
And (3) simulating a concrete pouring process, a concrete hardening process, a temperature control process, a meteorological change process and an arch sealing grouting process by considering real boundary conditions and material parameters, and performing overall process simulation calculation during the construction period of the arch dam to obtain the stress and deformation process of the arch dam under the static load action, wherein the stress and deformation process is used as an initial condition for earthquake response calculation of the arch dam.
(1) Concrete pouring process
In the pouring process of the arch dam, the arch dam needs to be divided into seams and blocks, the arch dam gradually rises according to the bins, and the dead weight of concrete in each bin is borne by the concrete at the lower part of the bin. And (3) arranging the bins of the numerical simulation calculation model according to the actual pouring progress of the arch dam project through simulation calculation, and finely simulating the pouring process of concrete in each bin of the dam in a mode of adding units layer by layer to ensure that the application process of the dead weight load of the dam is consistent with the actual process. Fig. 2 shows a simulation schematic diagram 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. The concrete is used as an age hardening material, the hydration reaction starts from the mixing, the 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. The hardening process of the concrete is simulated through a spring die hardening model, a creep model and the like.
The concrete elastic mold hardening model can adopt an index model, namely:
in the formula: e (τ) is the modulus of elasticity at age τ; e0Age-independent elastic modulus component, E0+EcAnd finally, forming the concrete elastic mould.
The concrete creep model is
In the formula: k is a radical of1、k2、k3、α1、α2Is a creep rate parameter without dimensional number; a. the1、A2、B1、B2D is a creep degree parameter which represents the creep degree caused by unit load; t is time; tau is the age of the concrete.
(3) Temperature control process
Temperature control can be divided into 4 main links: mixing a building link, a transportation link, a pouring link and a water cooling link. The simulation of the whole process of temperature control is realized by simulating the construction process of the arch dam and simulating the action of each link of the cooling water pipe model.
(4) Weather change process
The influence of climate changes such as actual temperature, rainfall, wind and the like on the engineering boundary conditions in the construction process is simulated, and 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 is further simulated.
(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. The invention adopts the non-thickness contact unit to simulate the arch dam transverse joint and the arch sealing grouting process, before the arch sealing grouting, each dam section is stressed independently, the transverse joint has no tensile strength and only has shear strength during simulation calculation, after the arch sealing grouting, the dam sections at two sides of the transverse joint are connected into a whole by cement grout poured into the transverse joint, and the tensile strength and the shear strength of the transverse joint contact unit are changed into the cement mortar strength.
Step three: and carrying out earthquake response calculation in the construction period of the arch dam.
(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 the dam foundation, and in consideration of the instantaneity of a construction period, 1/2 of the horizontal seismic peak acceleration in the construction period is taken as the horizontal seismic peak acceleration, 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. The dynamic balance equation in the calculation of the earthquake response of the arch dam is as follows:
in the formula: [ M ] A]、[C]、[K]Respectively an arch dam mass matrix, a damping matrix and a rigidity matrix;
{ u (t) } is displacement, velocity, acceleration vector, respectively; { F (t) } is the force vector.
Step four: and carrying out overall earthquake-resistant safety evaluation on the arch dam.
Comparing the stress obtained by the earthquake response calculation in the step three 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 D, comparing the maximum opening of the transverse seam calculated in the step three 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.
Step five: and (5) providing an anti-seismic measure during the construction period of the arch dam.
And according to the evaluation result of the overall anti-seismic safety in the construction period of the arch dam in the fourth step, providing targeted anti-seismic measures, such as advanced water filling and slag piling at the upstream of the arch dam, laying anti-seismic reinforcing steel bars at the possibly damaged part of the dam body, controlling the height of a cantilever of the arch dam and the like.
The method and effects of the present invention will be described in detail with reference to a specific embodiment.
In a certain concrete hyperbolic arch dam under construction in China, the dam crest elevation is 988.0m, the lowest elevation of the foundation surface is 718.0m, and the maximum dam height is 270.0 m. By adopting the method, the dynamic response of the dam under different water storage positions is mainly analyzed according to the planned water storage planning in the construction period of the dam engineering by combining the actual progress of the dam engineering, and the earthquake-resistant safety of the dam is evaluated.
Calculation model
And establishing a dam finite element seismic response analysis model. The 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 a transverse river direction and points to the left bank; the y direction is along the river direction and points to the upstream; the z direction is the vertical direction.
Calculating parameters
(1) Thermal parameters of dam concrete
First, adiabatic temperature rise
The adiabatic temperature rise of the dam concrete can be obtained through inversion according to the temperature monitoring data and the formula (1), namely:
c35 concrete:
c30 concrete:
coefficient of linear expansion-
Based on the monitoring result of the arch dam non-stress meter, the linear expansion coefficient alpha of the dam concrete can be obtained by carrying out correlation analysis on the temperature-micro-strain relation monitored by the non-stress meter and utilizing the formula (2) in an inverting way.
C35 concrete: alpha-0.0000078/° c
C30 concrete: alpha-0.0000078/° c
Specific heat of cold
C35 concrete: c0.992 kJ/(kg. mu.C.)
C30 concrete: c0.985 kJ/(kg. deg.C.)
Heat conductivity coefficient
C35 concrete: λ underlying 7.86 kJ/(m. anatomy. 20 ℃ C.)
C30 concrete: λ 7.74 kJ/(m. anatomy. 20 ℃ C.)
(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 an indoor material test; the density and Poisson ratio of the dam body concrete can be parameters adopted in the design of the arch dam.
(ii) modulus of elasticity
When the static simulation calculation of the arch dam is carried out, the elastic modulus E of the C35 concrete is 47.89 GPa; the elastic modulus E of C30 concrete was 48.04 GPa.
And when the earthquake response of the arch dam is calculated, measuring the elastic modulus of the concrete elastic modulus of the dam body during static simulation calculation.
(ii) Poisson's ratio
The Poisson ratio of the dam C30 and the Poisson ratio of the dam C35 concrete are both 0.17.
(iii) Density
The density of the dam body C30 and C35 concrete is 2400kg/m3。
Tensile and compressive strength
Tensile strength f of C35 concrete during arch dam static simulation calculationt2.54MPa, compressive strength fc25.42 MPa; tensile strength f of C30 concretet2.18MPa, compressive strength fc＝21.75MPa。
When the earthquake response of the arch dam is calculated, the dynamic strength of the concrete is improved by 20 percent compared with the static simulation calculation value, namely the dynamic tensile strength f of the C35 concretet3.05MPa, dynamic compressive strength fc30.49 MPa; dynamic tensile strength f of C30 concretet2.61MPa, dynamic compressive strength fc＝26.13MPa。
(2) Seismic load
The arch dam seismic fortification category is class A, and the designed horizontal seismic peak acceleration is seismic peak acceleration which exceeds 2% of the probability within 100 years, namely 0.27 g. Considering the instantaneity of the construction period, the horizontal seismic peak acceleration in the construction period is 1/2, namely 0.135g, of the designed horizontal seismic peak acceleration, and the vertical seismic peak acceleration is 2/3 of the horizontal direction. Three seismic waves with different phases are respectively used as three directions to be input from the bottom of the dam foundation, and acceleration time-course curves in the three directions generated by the standard response spectrum are shown in figures 6a, 6b and 6 c.
(3) Arch dam seismic response analysis
According to the planned water storage plan of the dam engineering construction period, calculating the seismic response of the arch dam under the following different water storage positions:
working condition 1: 890m water storage level
Working condition 2: 945m water storage level
Stress of dam body
Table 1 shows the maximum principal tensile and principal compressive stresses at the moment when the dam body stress is large in the seismic process. It can be seen that, under the upstream water storage level 890m, the arch dam tensile stress is the largest at 2.94s of earthquake, and is 3.65MPa, and the arch dam tensile stress appears at the right arch end 928m elevation of the upstream surface; the maximum arch dam compressive stress is-14.97 MPa when the earthquake is 10.37s, and the maximum arch dam compressive stress appears at the position of the dam heel. Under the upstream water storage level of 945m, the maximum tensile stress of the arch dam is 3.55MPa when the earthquake occurs for 2.94s, and the maximum tensile stress appears at the right arch end 928m elevation of the upstream face; the maximum arch dam compressive stress is-13.22 MPa when the earthquake is 1.67s, and the maximum arch dam compressive stress appears at the position of the dam heel.
FIGS. 7a and 7b and FIGS. 8a and 8b are respectively principal tensile stress distribution clouds of the upper and lower surfaces of the dam body at 890m and 945m water level and 2.94s earthquake. FIGS. 9a and 9b and FIGS. 10a and 10b are respectively the main compressive stress distribution clouds of the upper and lower surfaces of the dam body at 890m and 945m water level and 2.94s of earthquake. It can be seen that the local tensile stress at the upstream arch end of the arch dam is larger and exceeds the dynamic tensile strength of concrete (dynamic tensile strength f of C35 concrete)tDynamic tensile strength f of C30 concrete under 3.05MPat2.61MPa), and the tensile stress of the rest parts is smaller than the dynamic tensile strength of the concrete. The compressive stress of the arch dam is smaller than the dynamic compressive strength of the concrete (the dynamic compressive strength f of the C35 concrete)cDynamic compressive strength f of C30 concrete under 30.49MPac26.13 MPa). Overall, the arch dam stress level is higher below the impoundment level 890m than below the impoundment level 928 m.
TABLE 1 maximum principal tensile and principal compressive stresses at times of greater dam stress during earthquake
And table 2 is a statistical table of the maximum opening of each transverse joint under the action of the earthquake. It can be seen that as the reservoir water level is raised from 890m to 945m in elevation, the upstream reservoir water pressure seam effect is more obvious, so that the opening degree of the transverse seam is reduced in the earthquake process of the arch dam, the maximum opening degree of the transverse seam occurs at the top elevation of the 2# transverse seam, the maximum opening degree of the top of the 2# transverse seam is 16.70mm, and the transverse seam water stop cannot be pulled open.
As can be seen, the maximum opening of the transverse seam is 16.70mm under the upstream water storage level 890m, and occurs at the top elevation of the No. 2 transverse seam. The maximum opening of the transverse seam is 4.13mm under the upstream water storage level 945m, and the maximum opening occurs at the top elevation of the No. 1 transverse seam. The calculation result shows that the lower the upstream water storage level is, the smaller the arch-direction compressive stress borne by the arch dam is, and the larger the opening degree of the transverse seam is in the earthquake process. Therefore, attention should be paid to the opening degree of the transverse seam of the arch dam at a low water level, engineering measures are taken to reduce the opening degree of the transverse seam, and the transverse seam water-stopping copper sheet is prevented from being damaged by pulling.
TABLE 2 statistical table of maximum opening and position of transverse joint
(4) Arch dam earthquake safety assessment
The calculation result of the earthquake stress of the arch dam indicates that the local tensile stress of the upstream arch end of the arch dam is larger and exceeds the dynamic tensile strength of the concrete (the dynamic tensile strength ft of the C35 concrete is 3.05MPa, and the dynamic tensile strength ft of the C30 concrete is 2.61MPa), and the tensile stress of the rest parts is smaller than the dynamic tensile strength of the concrete. The arch dam compressive stress is smaller than the dynamic compressive strength of the concrete (the dynamic compressive strength fc of the C35 concrete is 30.49MPa, and the dynamic compressive strength fc of the C30 concrete is 26.13 MPa). Therefore, when an earthquake occurs, the upstream arch end of the arch dam is locally pulled apart, but the overall safety of the arch dam can be ensured.
The calculation result of the opening of the transverse seam of the arch dam indicates that the maximum opening of the transverse seam is 16.7mm in the earthquake process, and the transverse seam water-stopping copper sheet cannot be damaged by pulling under the opening.
And the higher the upstream water storage level in the construction period of the arch dam, the more beneficial the structure safety of the arch dam when encountering earthquake.
In conclusion, the arch dam is safe wholly under the action of an earthquake, and certain anti-seismic measures are needed to prevent the local cracking of the arch dam.
(5) Anti-seismic measures
According to the safety evaluation result of the arch dam, the anti-seismic reinforcing steel bars are arranged at the part with larger local tensile stress of the arch dam, and the upstream of the arch dam can be subjected to slag piling to store water as early as possible.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
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| CN117574703B (en) * | 2023-10-30 | 2024-04-12 | 广东省水利水电第三工程局有限公司 | Installation positioning simulation method for water-stop copper sheet |
| CN118427921B (en) * | 2024-04-16 | 2024-11-22 | 中国水利水电科学研究院 | A method for evaluating seismic stability of concrete gravity dams under maximum credible earthquakes |
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