CN110619170A - Method for construction control by utilizing arch dam upstream overhang analysis - Google Patents
Method for construction control by utilizing arch dam upstream overhang analysis Download PDFInfo
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Abstract
The invention provides a method for carrying out construction control by utilizing arch dam upstream overhang analysis, which is characterized in that all dam sections are horizontally layered in the height direction on the basis of arch dam transverse joint parting, and are sharednTaking the center point of the bottom surface of each dam section along the river direction as a 0 point, and respectively calculating the 1 st 1 ~ th position of each dam section according to the same concrete density of the dam bodynThe center of gravity of each layer; at random layering of the obtained dam sectioniOn the basis of the center of gravity, the construction to the first place is calculatediLayer time 1 ~iThe horizontal distance and the vertical distance between the gravity center and the 0 point of the dam section datum plane are respectively delta L1‑iAnd Δ H1‑iDefining a dam sectioniThe layer overhang is alpha = delta L1‑i/ΔH1‑i(ii) a Calculating the pouring of each dam section to the first place by adopting a mechanical method or a numerical methodiVertical stress sigma of dam toe part during individual layering i (ii) a Establishing the overhang degree alpha of each dam section and the vertical stress sigma of the toe part i Wherein the toe stress above the α axis is tensile stress; according to the actual casting heightAnd judging, if the vertical stress of the dam toe is pressure, the dam toe is normal, and if the vertical stress of the dam toe of one dam section in all the dam sections generates tensile stress, upstream slag accumulation and water filling measures are required.
Description
Technical Field
The invention belongs to the technical field of concrete dam design and construction, and particularly relates to a method for construction control by utilizing arch dam overhang analysis.
Background
The arch dam is an arch water retaining building which is convex to the upstream on the plane, and the whole or part of water pressure is transmitted to bedrocks on two sides of a river valley by the action of the arch. In order to fully exert the characteristics of high compressive strength and low tensile strength of the concrete material of the dam body, the arch dam is designed into an arch shape on a horizontal plane, and has the following characteristics on a vertical plane: the middle lower part of the dam body tends to the upstream and then tends to the downstream after reaching a certain elevation. The existing extra-high arch dam has long construction period, for example, the construction period of the extra-high arch dam in the southwest area is generally more than 3 years, the dam body is in a stress state in the construction period for a long time, and the stress safety of the stage is guaranteed to be vital to the later operation safety of the arch dam. In the construction process of the arch dam, as long as the gravity center of a poured dam body is located upstream of the center point of the foundation surface, the dam can continuously deform upstream along with the increase of height and the increase of self weight, the stress state of the toe part of the dam tends to be pulled continuously, and the downstream surface has a large cracking risk such as surface tensile stress caused by the superposition of cold seasons or sudden temperature drop. For example, in the construction process of the Austrian Ke's Braun arch dam, the upstream surface is greatly overhung, and cracks appear on the downstream surface of the arch dam, so that the bearing capacity of the dam is reduced. Therefore, in the dam construction process, the dam upwarping degree needs to be strictly controlled to prevent the downstream surface from tensile cracking, and measures can be taken specifically, including slag piling on the upstream surface and upstream deformation inhibition; the reservoir is charged with water in advance, and upstream deformation is cut off or offset by using the water thrust towards the downstream. However, when the slag piling and the water filling are carried out on the upstream surface, the time judgment is needed, if the slag piling and the water filling are too early, the pressure seam effect on the arch dam can be formed, and the arch sealing grouting is not facilitated; if the slag is piled and the water is filled too late, large tensile stress can be generated on the downstream surface, and the dam is not safe. The opportunity selection generally adopts a full-dam full-process simulation analysis method, but has the characteristics of complex calculation process, high calculation difficulty and difficulty in mastering by general personnel.
The arch dam generally defines the dam face slope ratio or slope in the height direction of the upstream face as the overhang degree, when the upstream face of the dam body inclines to the upstream, the slope is less than 0, the turning point is equal to 0, and the inclination downstream is greater than 0. The overhang analysis method is suitable for dam body design in the operation period, but has a larger problem when being used for construction process control. In the construction process, although the overhang degree of the dam face is equal to 0 or slightly greater than 0, the gravity center of the dam body is still at the upstream of the foundation surface, and the toe tensile stress may be increased continuously, but the conventional overhang degree analysis method cannot reflect the characteristic, and an overhang degree analysis method capable of effectively reflecting the stress change characteristic in the dam construction period needs to be provided.
Disclosure of Invention
The invention aims to provide an overhang degree analysis method for effectively reflecting the stress change characteristics of a dam in the construction period, and provides a basis for safety control in the construction period.
In order to achieve the technical features, the invention is realized as follows:
a method for construction control by utilizing overhang analysis at the upstream of an arch dam comprises the following steps:
step 1, horizontally layering each dam section in the height direction on the basis of transverse seam parting of an arch dam, wherein n layers are formed;
step 2, respectively calculating the gravity centers of the 1 st to nth layers of each dam section by taking the center point of the bottom surface of each dam section along the river direction as a 0 point according to the same concrete density of the dam body;
step 3, calculating the gravity center of the 1-i layer structure when the gravity center is constructed to the i-th layer on the basis of obtaining the gravity center of the dam section in any layering mode, wherein the horizontal distance and the vertical distance between the gravity center and the 0 point of the dam section datum plane are respectively delta L1-iAnd Δ H1-iDefining the i-layer overhang of dam section as alpha ═ delta L1-i/ΔH1-i；
Step 4, calculating the vertical stress sigma of the dam toe part when each dam section is poured to the ith layering by adopting a mechanical method or a numerical methodi；
Step 5, establishing a relational expression or a relational curve of the overhang degree alpha and the dam toe vertical stress sigma i when each dam section is poured to the i layer;
and 6, in the construction process, judging according to the actual pouring height, if the vertical stress of the dam toe is pressure, the dam toe is normal, and if the vertical stress of the dam toe of the dam section exceeds the allowable strength, upstream slag accumulation and water filling measures are required.
In the step 4, the dam toe vertical stress is calculated by adopting a material mechanics formula, and the method specifically comprises the following steps:
in the formula: sigma is the dam toe vertical stress; g is gravity; l is the width of the dam bottom.
In step 6, the allowable strength can be determined by using a concrete strength test or according to the specification requirement.
The invention has the following beneficial effects:
the stress state of the dam toe in the dam construction process is judged by adopting the analysis result of the arch crown beam, and once the tension state of the dam toe exists in the dam section, slag is timely piled or water is pre-filled at the upstream of the dam, so that the tension crack damage of the downstream surface caused by the overhung is prevented.
Drawings
The invention is further illustrated by the following figures and examples.
FIG. 1 is a section of a dam section of the dam body of the present invention.
FIG. 2 is a schematic diagram of the determination of the gravity center of each layer after a dam section of the dam body is layered.
FIG. 3 is a schematic diagram of the calculation process of the i-1 layer overhang of the dam section of the present invention.
FIG. 4 shows the overhang degree alpha of each dam section and the vertical stress sigma of the toe part of the dam of the present inventioniThe relationship of (1).
Detailed Description
Embodiments of the present invention will be further described with reference to the accompanying drawings.
Example 1:
referring to fig. 1-4, a method for construction control using overhang analysis upstream of an arch dam, comprising the steps of:
step 1, horizontally layering each dam section in the height direction on the basis of transverse seam parting of an arch dam, wherein n layers are formed;
step 2, respectively calculating the gravity centers of the 1 st to nth layers of each dam section by taking the center point of the bottom surface of each dam section along the river direction as a 0 point according to the same concrete density of the dam body;
step 3, calculating the gravity center of the 1-i layer structure when the gravity center is constructed to the i-th layer on the basis of obtaining the gravity center of the dam section in any layering mode, wherein the horizontal distance and the vertical distance between the gravity center and the 0 point of the dam section datum plane are respectively delta L1-iAnd Δ H1-iDefining the i-layer overhang of dam section as alpha ═ delta L1-i/ΔH1-i；
Step 4, calculating the vertical stress sigma of the dam toe part when each dam section is poured to the ith layering by adopting a mechanical method or a numerical methodi；
Step 5, establishing the overhang degree alpha and the dam toe position vertical stress sigma when each dam section is poured to the i layeriThe relation or the relation curve of (1);
and 6, in the construction process, judging according to the actual pouring height, if the vertical stress of the dam toe is pressure, the dam toe is normal, and if the vertical stress of the dam toe of the dam section exceeds the allowable strength, upstream slag accumulation and water filling measures are required.
In the step 4, the dam toe vertical stress is calculated by adopting a material mechanics formula, and the method specifically comprises the following steps:
in the formula: sigma is the dam toe vertical stress; g is gravity; l is the width of the dam bottom.
In step 6, the allowable strength can be determined by using a concrete strength test or according to the specification requirement.
The invention has the following beneficial effects:
the stress state of the dam toe in the dam construction process is judged by adopting the overhang analysis result, once the stress of the dam toe in the dam section exceeds the allowable strength, slag is timely piled or water is pre-filled at the upstream of the dam, and the problem that the overhang causes the tension crack damage of the downstream face is prevented.
Example 2:
15 dam sections are formed in a certain arch dam, the height of the dam is 270m, the bottom width is 50m, the width of the top of the dam is 12m, the thickness of main pouring layers is 3m and 4.5m, the thickness of the bottom of each dam section is 6m, 800 multi-storehouses are formed, and the volume weight of concrete of a dam body is 2400t/m3. The section of the dam body arch crown beam dam section is shown in figure 1.
Step 1, horizontally layering 15 dam sections of an arch dam in the height direction, wherein each layer is 3m, the arch crown beam dam section is 270m high and is totally 90 layers, the layering is shown as a figure 1, and the other 14 dam sections are layered by adopting the same method;
step 2, taking the center point of the bottom surface of the arch crown beam dam section along the river direction as a point 0, and solving the gravity centers of the 1 st to the 90 th layers of the arch crown beam dam section according to the same concrete density of the dam body, as shown in the figure 2;
step 3, calculating the gravity center of the 1-i layer structure when the gravity center is constructed to the i-th layer on the basis of obtaining the gravity center of the dam section in any layering mode, wherein the horizontal distance and the vertical distance between the gravity center and the 0 point of the dam section datum plane are respectively delta L1-iAnd Δ H1-iAs shown in fig. 3, the overhang of the dam section i-1 layer is defined as α ═ Δ L1-i/ΔH1-iMechanical methods, geometric methods and numerical analysis methods can be adopted;
step 4, calculating the vertical stress sigma of the dam toe part when each dam section is poured to the ith layering by adopting a mechanical method or a numerical methodiWhen the arch crown beam dam section is poured to 150m and 180m, the toe stress is basically equal to 0, the toe between 150m and 180m is tensile stress, and the toe in other pouring height ranges is compressive stress;
step 5, establishing the overhang degree alpha of each dam section and the vertical stress sigma of the dam toe partiThe relationship or relationship curve of (1), as shown in FIG. 4, wherein the toe stress is tensile stress above the α axis, i.e., at a height of 150-180 m;
and 6, judging the stress state of the dam toe in the dam construction process according to the arch crown beam analysis result and combining the results of other 14 dam sections, and once the tension state of the dam toe exists in the 15 dam sections, timely piling up slag or pre-filling water at the upstream of the dam to prevent the downstream face from being cracked and damaged due to overhung.
Claims (3)
1. A method for carrying out construction control by utilizing the overhang analysis of the upstream of an arch dam is characterized by comprising the following steps:
step 1, horizontally layering each dam section in the height direction on the basis of transverse seam parting of an arch dam, wherein n layers are formed;
step 2, respectively calculating the gravity centers of the 1 st to nth layers of each dam section by taking the center point of the bottom surface of each dam section along the river direction as a 0 point according to the same concrete density of the dam body;
step 3, calculating the gravity center of the 1-i layer structure when the gravity center is constructed to the i-th layer on the basis of obtaining the gravity center of the dam section in any layering mode, wherein the horizontal distance and the vertical distance between the gravity center and the 0 point of the dam section datum plane are respectively delta L1-iAnd Δ H1-iDefining the i-layer overhang of dam section as alpha ═ delta L1-i/ΔH1-i；
Step 4, calculating the vertical stress sigma of the dam toe part when each dam section is poured to the ith layering by adopting a mechanical method or a numerical methodi；
Step 5, establishing the overhang degree alpha and the dam toe position vertical stress sigma when each dam section is poured to the i layeriThe relation or the relation curve of (1);
and 6, in the construction process, judging according to the actual pouring height, if the vertical stress of the dam toe is pressure, the dam toe is normal, and if the vertical stress of the dam toe of the dam section exceeds an allowable strength value, upstream slag accumulation and water filling measures are required.
2. The method for construction control using overhang analysis upstream of an arch dam of claim 1, wherein:
in the step 4, the dam toe vertical stress is calculated by adopting a material mechanics formula, and the method specifically comprises the following steps:
in the formula: sigma is the dam toe vertical stress; g is gravity; l is the width of the dam bottom.
3. The method for construction control using overhang analysis upstream of an arch dam of claim 1, wherein: in the step 6, the allowable strength is determined by adopting a concrete strength test or according to the specification requirement.
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| CN111832107A (en) * | 2020-07-01 | 2020-10-27 | 国家电网有限公司 | Method for solving mutual influence of close-range new and old concrete dams in large-scale hydroelectric junction reconstruction project |
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| CN1335432A (en) * | 2001-08-31 | 2002-02-13 | 清华大学 | Flexible arch for roling concrete on soft foundation |
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