A method for predicting the damage of a dam by a heteromorphic terrace

Abstract

The application provides a prediction method for the damage of a special-shaped terrace to a dam, which comprises the following steps: acquiring a dam valley settlement S 谷 and a dam terrace settlement S 台 , calculating a special-shaped terrace dam terrace damage influence coefficient K, predicting the damage degree of the terrace through the terrace damage influence coefficient K, and the greater the K value, the greater the deformation gradient, the greater the damage to the dam body or the panel, when the K value is greater than or equal to 4, the design and construction need to be processed to avoid settlement or tension cracks, and when the K value is less than 4, the damage is small and no processing is needed. The method can provide guidance for design and subsequent construction, reduce uneven settlement of the dam through corresponding measures, improve the stress state of the dam body and the concrete panel, prevent structural cracks of the dam and the panel due to the terrace topography, and ensure the safety of the dam body anti-seepage.

Description

Technical Field

[0001] This invention belongs to the field of water conservancy and hydropower engineering technology, specifically relating to a method for predicting the hazards of irregular terraces to dams. Background Technology

[0002] Topographical conditions are a crucial factor in dam site selection. Due to site constraints, some dams must be built in narrow river valley bends. Compared to wide valleys, bends in canyons typically have terraced slopes on one side and a relatively steeper slope on the other. The presence of these terraces creates complex topography, resulting in asymmetrical slopes on both sides of the dam site and the formation of irregularly shaped terraced valleys. This leads to significant differences in dam thickness on both sides of the terrace edge, increasing the vertical deformation gradient of the dam within a certain range. This affects the continuity and uniformity of vertical deformation along the dam axis, altering the stress distribution in the dam body and its panels. Consequently, uneven settlement of the rockfill mass occurs, making these areas weak points in the seepage control structure of rockfill dams. In severe cases, this can directly lead to the destruction of the waterstop structure and even the panels. Damage to the waterstop or panels further exacerbates dam deformation, causing cracks and leakage, posing a significant threat to human life and property. Summary of the Invention

[0003] The purpose of this invention is to provide a method for predicting the hazards of irregular terraces to dams, aiming to predict whether the dam body or panels will crack due to terrace hazards before construction, and to provide guidance for design and subsequent construction.

[0004] The objective of this invention is achieved through the following technical means: a method for predicting the hazards of irregularly shaped terraces to dams, comprising the following steps:

[0005] Obtain the settlement S of the valley dam 谷 Settlement S of the terrace dam 台 ;

[0006] Calculate the hazard impact coefficient K of the terraced dam:

[0007] K = S 谷 S 台

[0008] Where: K—the impact coefficient of the terrace hazard;

[0009] The impact coefficient K of the terrace hazard is used to predict the degree of terrace hazard. The larger the K value, the greater the deformation gradient and the greater the hazard to the dam body or face. Terrace hazards need to be reduced during construction and design.

[0010] The estimated settlement S of the valley dam 谷 The estimated settlement S of the terrace dam 台 for:

[0011]

[0012] Where: H 谷 —The valley dam is high;

[0013] H 台 —The dam on the terrace is high;

[0014] E 谷 —Deformation modulus of the valley dam;

[0015] E 台 —Deformation modulus of the terrace dam;

[0016] H1—The height of the existing dam;

[0017] E1—Deformation modulus of the existing dam;

[0018] S1—The amount of settlement on the crest of the existing dam.

[0019] Since the terrace dam and the valley dam are part of the same project, and the deformation modulus of the dam materials is the same, then...

[0020] K = (H 谷 H 台 ) 2

[0021] When the K value is greater than or equal to 4, it indicates that the terrace is highly hazardous and needs to be treated during the design and construction phases to prevent settlement or tension cracks. When the K value is less than 4, it indicates that the hazardous situation is minor and no treatment is necessary.

[0022] The height of the terrace dam is the height from the top of the dam to the terrace, and the height of the valley dam is the height from the top of the dam to the bottom of the valley.

[0023] The beneficial effects of this invention are as follows: It proposes a method for predicting the hazards of irregular terraces to dams. By using the magnitude of the terrace hazard influence coefficient K, the degree of influence of the terrace on the deformation and cracking of the dam or its panels can be predicted in advance. Furthermore, it proposes a criterion for judging the influence coefficient K: when K is greater than or equal to 4, it indicates that the terrace hazard is significant and necessary measures should be taken to reduce the hazard; when K is less than 4, it indicates that the hazard is minor and no action is required. This prediction method is simpler and faster than three-dimensional finite element calculation, and can quickly predict the degree of hazard of irregular terraces to dams and their panels. This provides a reference for subsequent design and construction. By taking corresponding measures, it can reduce uneven settlement of the dam, improve the stress state of the dam body and concrete panels, prevent structural cracking and damage to the dam and its panels due to irregular terraces, and ensure the seepage prevention safety of the dam body. Attached Figure Description

[0024] Figure 1 This is a cross-sectional view of the DSX project dam along its axial direction.

[0025] Figure 2This is a cross-sectional view of the JSX project dam along its axial direction.

[0026] Figure 3 This diagram shows the relationship between the elevation difference, influence coefficient K, and horizontal displacement difference between the valley dam and the plateau dam in the DSX project.

[0027] Figure 4 This diagram shows the relationship between the elevation difference, influence coefficient K, and horizontal displacement difference between the valley dam and the plateau dam of the JSX project.

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0029]

Example 1

[0030] A method for predicting the hazards of irregular terraces to dams includes the following steps:

[0031] Obtain the settlement S of the valley dam 谷 Settlement S of the terrace dam 台 ;

[0032] Calculate the hazard impact coefficient K of the terraced dam:

[0033] K = S 谷 S 台

[0034] Where: K—the impact coefficient of the terrace hazard;

[0035] The impact coefficient K of the terrace hazard is used to predict the degree of terrace hazard. The larger the K value, the greater the deformation gradient and the greater the hazard to the dam body or face. Terrace hazards need to be reduced during construction and design.

[0036] The estimated settlement S of the valley dam 谷 The estimated settlement S of the terrace dam 台 for:

[0037]

[0038] Where: H 谷 —The valley dam is high;

[0039] H 台 —The dam on the terrace is high;

[0040] E 谷 —Deformation modulus of the valley dam;

[0041] E 台 —Deformation modulus of the terrace dam;

[0042] H1—The height of the existing dam;

[0043] E1—Deformation modulus of the existing dam;

[0044] S1—The amount of settlement on the crest of the existing dam.

[0045] Since the terrace dam and the valley dam are part of the same project, and the deformation modulus of the dam materials is the same, then...

[0046] K = (H 谷 H 台 ) 2

[0047] When the K value is greater than or equal to 4, it indicates that the terrace is highly hazardous and needs to be treated during the design and construction phases to prevent settlement or tension cracks. When the K value is less than 4, it indicates that the hazardous situation is minor and no treatment is necessary.

[0048] The height of the terrace dam is the height from the top of the dam to the terrace, and the height of the valley dam is the height from the top of the dam to the bottom of the valley.

[0049] Specifically, the DSX concrete-faced gravel dam has a complex topographical and geological site with poor topographic symmetry on both banks. The left bank slope is steep, while the right bank slope features a large ancient riverbed terrace (approximately 480m long along the river and 260m wide across the river). The terrace elevation is 1594m, the valley elevation is 1460m, the dam crest elevation is 1707m, the valley dam height is 247m, and the terrace dam height is 113m. The calculated hazard factor K for the terrace is 4.78. The terrace structure of the DSX project is as follows: Figure 1 As shown.

[0050] The JSX project's water diversion structures are located on the relatively gentle Class II and III erosion terraces on the left bank, resulting in discontinuous topography on the left bank. The top elevation of the concrete outer casing of the horizontal section of the water diversion steel pipe is 1835.00m. Above this elevation is the dam's fill rockfill, with a valley elevation of 1758m and a dam crest elevation of 1861m. The valley dam height is 103m, and the terrace dam height is 26m. The calculated terrace hazard impact coefficient K is 15.69, which is greater than the DSX terrace hazard impact coefficient K. The JSX project's terrace structure is as follows: Figure 2 As shown.

[0051] Current technologies use horizontal displacement difference as a standard for controlling the coordinated deformation of the dam body, generally considering an allowable horizontal displacement difference of around 1% to be appropriate. When the horizontal displacement difference is controlled to be less than 1%, the dam body deformation is small, and large tension cracks will not occur, thus meeting the operational safety requirements. Three-dimensional finite element analysis shows that the average horizontal displacement difference between the DSX terrace and the critical area of ​​the valley along the dam axis is 1.14%; the average horizontal displacement difference between the JSX terrace and the critical area of ​​the valley along the dam axis is 2.69%, which is greater than that of the DSX project. Both are greater than 1%, requiring corresponding measures to address the issue. The three-dimensional finite element calculation results are consistent with the calculation law of the terrace hazard influence coefficient K.

[0052] Specifically, by constructing a three-dimensional finite element model, the average level displacement difference between the critical area between the terrace and the valley along the dam axis was analyzed and calculated under different elevation terrace conditions for the DSX and JSX projects. This verified the necessity and accuracy of the terrace hazard influence coefficient K. The calculation results are shown in Tables 1 and 2.

[0053] Table 1. Average level displacement difference and terrace hazard impact coefficient K in the critical area between the DSX terrace and the valley along the dam axis.

[0054]

[0055] Table 2. Average level displacement difference and terrace hazard impact coefficient K in the critical area between the JSX terrace and the valley along the dam axis.

[0056]

[0057] As can be seen from Tables 1 and 2, when H 台 ≈1 / 2·H 谷 That is, when K≈4, the average displacement difference between the two engineering terraces and the critical area of ​​the valley along the dam axis is ≈1%, and the terrace hazard influence coefficient K varies with ΔH=H 谷 -H 台 The variation pattern and the average displacement difference of the plateau and valley boundary area along the dam axis direction with respect to ΔH = H 谷 -H 台 The patterns of change are consistent, such as Figure 3 , Figure 4 As shown, it is evident that using the terrace hazard influence coefficient K as a predictive method for the terrace hazard of irregular terrace dams is feasible, and using a terrace hazard influence coefficient K of 4 as a criterion for judging the terrace hazard of irregular terrace dams is accurate. When the K value is greater than or equal to 4, it indicates that the terrace hazard is significant and needs to be addressed during design and construction to prevent settlement or tension cracks. When the K value is less than 4, it indicates that the hazard is minor and no treatment is necessary.

[0058] Compared to three-dimensional finite element analysis, using the terrace hazard influence coefficient K as the prediction standard is simpler and more convenient. It can quickly predict the degree of hazard of irregular terraces to dams and concrete panels, providing guidance for design and subsequent construction. By taking corresponding measures, it can reduce uneven settlement of the dam, improve the stress state of the dam body and concrete panels, prevent structural cracks in the dam and concrete panels due to terrace topography, and ensure the seepage prevention safety of the dam body.

[0059] Furthermore, the Yuanshan Dam in the United States is an earth-rock dam with a valley dam height of 134m and a terrace dam height of 14m. Its terrace hazard impact coefficient K is 91.6, and cracks deeper than 5m appeared on the dam crest. The LSG panel dam in Xinjiang has a valley dam height of 100m. During construction, a 9m wide construction road was excavated on the left bank of the dam foundation. The height difference between the construction road and the dam crest is 30m, meaning the terrace dam is 30m high. Its terrace hazard impact coefficient K is 11.1. After construction, cracks larger than 2cm appeared in the dam body corresponding to the outer edge of the road. This again demonstrates that the terrace hazard impact coefficient K can accurately predict terrace hazards.

[0060] To reduce the damage caused by terraces, the following methods can be adopted:

[0061] (1) Local terrain modification: The slope of the terrace edge can be trimmed within a certain range to reduce the slope, and a low-compression modulus zone of the dam body can be set up on the slope between the terrace and the riverbed. Alternatively, plain concrete can be used to reinforce the slope between the terrace and the riverbed so that the slope is not steeper than 1:0.5, and transition material can be used to fill within a 3m slope range.

[0062] (2) Modify the dam body filling sequence: The dam body can be filled to the platform elevation first, and then the platform can be filled before the dam body is filled; or the platform can be filled into a 1:1.7 slope first, and then the dam body can be filled evenly from the bottom of the riverbed to the top of the dam, etc.

[0063] (3) Conduct pre-settlement or forced pre-settlement. For example, fill the concrete panel with water in advance to simulate the dam's submersion state during operation, thereby accelerating the dam's settlement.

[0064] (4) Set narrow panels and special seams: By setting narrow panels and special seams, the panel’s ability to adapt to deformation is enhanced, and the harm of uneven settlement is reduced.

Claims

1. A method of predicting the damage to a dam by a heteromorphic terrace, characterized by, The method comprises the following steps: Obtaining a valley dam settlement S 谷 and plateau dam settlement S 台 ; Calculate the hazard impact coefficient K of the abnormity terrace dam terrace: In the formula: K — plateau hazard impact coefficient; Through the terrace hazard impact coefficient K, the terrace hazard degree is predicted, the greater the K value, the greater the deformation gradient, the greater the damage to the dam body or the panel, and the need to reduce the terrace hazard in the construction and design process; The expected settlement S of the valley dam 谷 and the expected settlement S of the plateau dam 台 is: In the formula: H 谷 — Height of the valley dam; H 台 — height of the plateau dam; E 谷 - modulus of deformation of the valley dam; E 台 — modulus of deformation of the earth dam; H1—Dam height of the built dam; E1—Deformation modulus of the built dam; S1—Dam crest settlement of the built dam.

2. The method of claim 1, wherein: Since the terrace dam and the valley dam are the same project, the dam material deformation modulus is the same, then 。 3. The method of claim 1, wherein: When the K value is greater than or equal to 4, it indicates that the terrace hazard is large, and it needs to be handled in design and construction to avoid settlement or tension cracks, and when the K value is less than 4, it indicates that the hazard is small and can not be handled.

4. The method of claim 1, wherein: The dam height of the terrace dam is the height from the dam crest to the terrace, and the dam height of the valley dam is the height from the dam crest to the valley bottom.

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