Method for estimating overall crack resistance of U-shaped irrigation canal
By constructing a finite element model of a U-shaped irrigation canal and optimizing the combination of support points using a genetic algorithm, the maximum tensile stress value was calculated. This solved the problem of the difficulty in predicting the crack resistance of the U-shaped irrigation canal, enabling accurate assessment and optimization of concrete grade during the design phase, and improving the quality and economy of the project.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-03
- Publication Date
- 2026-03-10
AI Technical Summary
Existing technologies make it difficult to effectively predict the overall crack resistance of U-shaped irrigation canals during the design phase, leading to the selection of concrete grades that are too high or too low, affecting project quality and economy.
By equating the U-shaped irrigation canal to trapezoidal and circular segments, a finite element model was constructed, support points were randomly generated, equivalent concentrated loads were applied, and a genetic algorithm was used to optimize the combination of support points. The maximum tensile stress value was calculated and compared with the tensile strength of concrete to determine the crack resistance performance.
It enables accurate prediction of the crack resistance of U-shaped irrigation canals during the design phase, optimizes the selection of concrete grade, reduces costs, provides safety thresholds for physical testing, and improves project quality and economy.
Smart Images
Figure CN121637898A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of irrigation canal, in particular to a method for estimating the overall anti-cracking performance of a U-shaped irrigation canal. BACKGROUND
[0002] Irrigation canal is an important project that affects the quality of high-standard farmland construction in China. The cracking problem of irrigation canal concrete is the main disease form of this type of project and an important uncertain factor affecting the quality of the project.
[0003] The U-shaped irrigation canal faces two core problems in the design stage: 1. In actual use, the soil at the bottom of the canal is prone to be not compacted under the long-term action of rainwater and load, and the location of the cavity is random, which leads to random distribution of support points and makes it difficult to simulate the most unfavorable stress state; 2. Existing designs mostly focus on the strength of the concrete itself, without considering actual factors such as thin-walled structure (mostly <100mm in thickness), variable load direction, and random distribution of support points in the design stage. The above problems make it difficult to estimate the actual anti-cracking performance of U-shaped irrigation canals with different size parameters, and it is also difficult to determine whether the pre-selected concrete grade is appropriate (selecting a higher concrete grade will significantly increase the cost, and selecting a lower concrete grade may cause cracking in use).
[0004] Therefore, there is an urgent need for a method that can quantitatively evaluate whether the overall anti-cracking performance of a U-shaped irrigation canal is qualified in the design stage, in order to balance structural safety and economy. SUMMARY
[0005] The present application provides a method for estimating the overall anti-cracking performance of a U-shaped irrigation canal, which solves the problem of difficulty in estimating the actual overall anti-cracking performance of a U-shaped irrigation canal in the design stage of the prior art, and effectively estimates whether the actual overall anti-cracking strength of the U-shaped irrigation canal is qualified.
[0006] The present application provides a method for estimating the overall anti-cracking performance of a U-shaped irrigation canal, which includes the following steps: S1: equivalent the U-shaped irrigation canal to three segments of a trapezoidal segment on the side, a circular arc segment at the bottom, and a trapezoidal segment on the side, and obtain the size parameters of the cross section of the U-shaped irrigation canal; S2: according to the obtained size parameters, construct a finite element model of the U-shaped irrigation canal, and use the material constitutive relationship curve corresponding to the pre-set engineering concrete grade as the material constitutive; S3: randomly generate 1 support point in each of the two trapezoidal segments, and randomly generate 2 support points in the circular arc segment; S4: combine the fixed support points at the top of the two sides of the U-shaped irrigation canal, calculate the distances between all support points, and define the line segment with the maximum curved surface distance as the Lmax segment; S5: Take the midpoint of the Lmax segment as the action point of the equivalent concentrated load, and the action direction is perpendicular to the contact surface; calculate the equivalent concentrated load F 等效 : (1); Wherein, h is the internal height of the U-shaped irrigation water channel, is the maximum horizontal length inside the U-shaped irrigation water channel, is the density of the liquid, water is , is the gravitational acceleration, generally , is the equivalent load reduction coefficient considering different water levels and the action point of the equivalent concentrated load; S6: Apply the equivalent concentrated load F 等效 to the finite element model, carry out finite element calculation, and get the tensile stress value of the position of the equivalent concentrated load on the bottom surface of the U-shaped irrigation water channel; S7: Adopt genetic algorithm to iteratively optimize different combinations of support points, and obtain the maximum tensile stress value; S8: Compare the obtained maximum tensile stress value with the corresponding tensile strength of the preset engineering concrete grade, and determine whether the anti-cracking performance is qualified.
[0007] The beneficial effects of the above embodiments are that: after the finite element model is established, the support point state (that is, the void state) is randomly generated for irrigation water channels with different size parameters, the equivalent concentrated load is applied, and the maximum position and maximum value of the tensile stress are obtained. The prediction method can effectively predict whether the actual overall anti-cracking strength of the U-shaped irrigation water channel is qualified by simulating the stress characteristics of the actual soil body under the condition of non-compaction in the design stage, and provides a basis for water channel structure design optimization, concrete grade selection and subsequent physical detection.
[0008] On the basis of the above embodiments, the present application can be further improved, specifically as follows: In one of the embodiments of the present application, in step S1, the size parameters include channel plate thickness, internal height, maximum horizontal length inside, and trapezoidal segment length, trapezoidal segment slope, circular segment radius, and circular segment radian.
[0009] In one of the embodiments of the present application, in step S3, the support point positioning adopts curved surface length measurement, and the vertex of one side inner wall is taken as zero point. By unifying the coordinate origin and the curved surface length measurement standard, the uniqueness and repeatability of the support point position are ensured, the calculation error of the finite element model caused by the confusion of the positioning method is avoided, and the comparison accuracy between different design schemes is improved.
[0010] In one of the embodiments of the present application, in step S5, The values are as follows: (2); in, This represents the height difference between the midpoint of segment Lmax and the bottom of the U-shaped irrigation canal. By introducing a water level reduction factor α, the equivalent load at different water levels is dynamically corrected. This avoids the problem of excessively amplifying the stress calculation value at high water levels, leading to over-selection of concrete grade, or underestimating the risk at low water levels, resulting in cracking. This makes the load simulation more closely match the actual operating conditions of the irrigation canal.
[0011] In one embodiment of this application, in step S7, within the genetic algorithm: The initial set of individuals includes one set of fixed individuals and three sets of random individuals. The initial fixed individuals are located at the midpoints of the two trapezoidal segments and the two trisection points of the circular arc segment, while the three sets of random individuals are randomly generated in the corresponding segments. The fixed individuals ensure that the algorithm converges to common engineering support patterns, while the random individuals cover extreme empty scenarios. The combination of the two improves the optimization efficiency of the genetic algorithm.
[0012] In one embodiment of this application, in step S7, the fitness function in the genetic algorithm uses the tensile stress value obtained in step S6. Using the tensile stress value as the fitness index directly links the finite element calculation results with the optimization objective, ensuring that the algorithm iteration direction always points to the "most unfavorable stress state," avoiding deviations in the optimal solution caused by indirect indicators (such as displacement and strain), and improving the reliability of the maximum tensile stress prediction.
[0013] In one embodiment of this application, the comparison results in step S8 are also used to assist in adjusting the structural dimensions of the U-shaped irrigation canal or selecting the concrete grade, and the maximum tensile stress value obtained is also used to provide a safety threshold for subsequent physical testing.
[0014] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages: 1. Pre-assessment during the design phase: Simulate cracking risks under actual working conditions in advance to avoid rework later; 2. Economic optimization: Quantitative calculations guide the selection of concrete grade, reducing costs while meeting strength requirements; 3. Reference value for testing: It provides the maximum stress limit, setting a safety threshold for subsequent physical testing (such as load testing). Attached Figure Description
[0015] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.
[0016] Fig. 1 This is a flowchart illustrating the steps of a method for predicting the overall crack resistance of a U-shaped irrigation canal according to an embodiment of this application. Fig. 2 This is a schematic diagram of the equivalent cross-section of the U-shaped irrigation canal in the embodiments of this application. Detailed Implementation
[0017] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims.
[0018] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.
[0019] Example: like Figs. 1-2 As shown, a method for predicting the overall crack resistance of a U-shaped irrigation canal includes the following steps: S1: Equivalently divide the U-shaped irrigation canal into three segments: "trapezoidal segment on the side - circular arc segment at the bottom - trapezoidal segment on the side". Obtain the cross-sectional dimension parameters of the U-shaped irrigation canal, including parameters such as channel plate thickness, internal height, and maximum internal horizontal length, as well as parameters such as trapezoidal segment length, trapezoidal segment slope, circular arc segment radius, and circular arc segment curvature.
[0020] This step is explained as follows: Obtain detailed dimensional parameters to provide detailed data for subsequent analysis and finite element modeling, thereby increasing the accuracy of the estimates.
[0021] S2: Construct a finite element model of the U-shaped irrigation canal, which can be implemented using existing software such as ABAQUS and MIDAS. The dimensional parameters are determined according to the actual structure, mainly including the canal slab thickness, trapezoidal segment length, trapezoidal segment slope, circular arc segment radius, and circular arc segment radius obtained in step S1; the material constitutive model adopts the material constitutive relationship curve corresponding to the pre-set engineering concrete grade.
[0022] S3: Randomly generate 1 support point in each of the two "trapezoidal segments" and 2 support points in the "circular arc segment", for a total of 4 support points. The support points are located by length measurement, with the vertex of the left inner diameter as the zero point, and 4 significant digits are retained.
[0023] The following steps are explained: 1. Considering the actual state of the support points and the balance of forces, support points are generated in segments to avoid situations where support points are generated on one side, which is inconsistent with reality; 2. In actual engineering, the sides are more likely to become detached, and often only one segment provides support. However, the bottom of the canal often forms more support points under the action of gravity, usually with at least two support points to form a balance under the action of gravity, which is more in line with reality.
[0024] S4: Add fixed support points at the top of both sides of the U-shaped irrigation canal. Combined with the support points generated in step S3, sort the spacing between all support points. Considering the surface distance, take out the segment with the largest spacing and mark it as the Lmax segment. This segment is the most unfavorable load-bearing segment under the simulated void condition.
[0025] The following is an explanation of this step: Since concrete pressure beams will be installed on the top of both sides of the U-shaped irrigation canal, the top of the U-shaped canal will form a fixed support point under the gravity load of the pressure beams. Therefore, the support point calculation should take into account that both sides are fixed supports, and the change of support points should simulate possible voiding situations to be in line with reality.
[0026] S5: Take the midpoint of segment Lmax as the point of application of the equivalent concentrated load, with the direction of application perpendicular to the contact surface; then determine the equivalent concentrated load F. 等效 The possible values of: (1); Where h is the internal height of the U-shaped irrigation canal. This is the maximum horizontal length inside the U-shaped irrigation canal. Let be the density of the liquid, and water be . , This is the acceleration due to gravity, typically... , To account for the equivalent load reduction factor at different water levels and equivalent concentrated load application points; (2); in, The value represents the height difference between the midpoint of segment Lmax and the bottom of the U-shaped irrigation canal; 0.3h is an empirical value. The equivalent load will no longer be reduced after 0.3h.
[0027] This step is explained as follows: Consider the U-shaped irrigation canal with multiple vents as a continuous beam with multiple supports. According to the principle of continuous beams, the excess water load in this case actually distributes the bending moment of the longest segment. The reduction in bending moment leads to a decrease in tensile cracks and tensile stress. Therefore, the water level at the midpoint of the longest segment, which forms an equivalent concentrated load, is the most dangerous load in this venting situation. The equivalent concentrated load varies with the venting situation, but it should be noted that when the midpoint of the longest segment is relatively high, the equivalent concentrated load cannot increase indefinitely. That is, the water level cannot increase indefinitely; the maximum water level is h. Therefore, the coefficient formula for α has an upper limit to avoid unreasonable situations.
[0028] The equivalent concentrated load is generated by water pressure, and the direction of the equivalent concentrated load is perpendicular to the contact surface, which is determined by the force characteristics of water pressure.
[0029] S6: Apply an equivalent concentrated load F to the finite element model. 等效 The load application point is the midpoint of segment Lmax. Finite element analysis is performed to obtain the tensile stress value of the bottom surface of the U-shaped irrigation canal at the location of the equivalent concentrated load.
[0030] This step is explained as follows: According to the force principle of continuous beams and slabs, the underside of the slab at the location of concentrated load is the point of maximum tensile stress, which is also the place most prone to cracking. After establishing the finite element model, for irrigation canals with different dimensional parameters, the support point states (i.e., the voided state) are randomly generated. After applying the equivalent concentrated load, the location and maximum value of the maximum tensile stress can be obtained.
[0031] S7: Use a genetic algorithm to iteratively optimize different combinations of support points to obtain the maximum tensile stress value.
[0032] Furthermore, the genetic algorithm is improved upon the conventional approach in the following ways: The initial individual setting includes one set of fixed individuals and three sets of random individuals. The initial fixed individuals are located at the division points of each segment, namely the midpoints of the two trapezoidal segments and the two trisection points of the middle arc segment. The three sets of random individuals are randomly generated in the segment intervals, as shown in step S3 above. The initial individual setting combines fixed individuals with random individuals to avoid getting trapped in local optima. The fitness function uses the tensile stress value obtained from the finite element analysis in step S6 (the tensile stress on the underside of the channel plate corresponding to the location of the concentrated load after applying the equivalent concentrated load). The larger the value, the higher the fitness, in order to find the possible maximum value of the tensile stress. The number of iterations is set according to actual needs, such as 200 times. If the fitness does not improve for N consecutive generations, the iteration will be terminated early.
[0033] S8: Compare the maximum tensile stress value obtained in step S7 with the tensile strength corresponding to the preset grade of engineering concrete to determine whether the crack resistance performance is qualified.
[0034] This step is explained as follows: First, if the maximum tensile stress value is less than the preset concrete tensile strength, it can be estimated that the overall crack resistance of the U-shaped irrigation canal design is qualified and can meet the requirements of actual use scenarios. Second, if the maximum tensile stress value is much less than the preset concrete tensile strength or greater than the preset concrete tensile strength, it can guide the selection of concrete grade (choosing a smaller or larger grade of concrete) or redesign the structure (such as reducing or increasing the wall thickness), thereby minimizing costs while meeting the overall crack resistance requirements. Finally, the obtained maximum tensile stress value provides the maximum stress upper limit, setting a safety threshold for subsequent physical testing (such as load tests).
[0035] The technical solutions described in the embodiments of this application, by simulating the random distribution of support points caused by non-compacted soil in actual engineering, and combining finite element analysis and genetic algorithm optimization, can quantitatively evaluate the crack resistance performance of U-shaped irrigation canals during the design stage, and have at least the following technical effects or advantages: 1. By randomly generating support points in segments and defining the most unfavorable stress segment (Lmax segment), the problem of not being able to consider the randomness of soil voids is solved, the actual working conditions are accurately simulated, and the consistency between the predicted results and the actual engineering is improved. 2. Based on the comparison between the maximum tensile stress and the tensile strength of concrete, the structural parameters (such as channel thickness and radius of the arc segment) or the concrete grade selection can be adjusted in reverse to dynamically optimize the design scheme and balance structural safety and economy. 3. Not only does it provide a pre-assessment of crack resistance performance during the design phase, but its maximum tensile stress value can also serve as a safety threshold for subsequent construction quality inspections (such as load tests), avoiding structural damage caused by excessive test loads.
[0036] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.
Claims
1. A method for predicting the overall cracking resistance of a U-shaped irrigation canal, characterized in that, The method comprises the following steps: S1: equivalent the U-shaped irrigation canal to three sections of trapezoidal section, circular arc section and trapezoidal section, and obtain size parameters of the cross section of the U-shaped irrigation canal; S2: according to the obtained size parameters, a finite element model of the U-shaped irrigation canal is constructed, and the material constitutive is a material constitutive relationship curve corresponding to a preset engineering concrete grade; S3: one support point is randomly generated in each of the two trapezoidal sections, and two support points are randomly generated in the circular arc section; S4: in combination with the fixed support points at the top of the two sides of the U-shaped irrigation canal, the distances between all support points are calculated, and the line segment with the maximum curved surface distance is defined as the Lmax segment; S5: Take the midpoint of Lmax segment as the action point of equivalent concentrated load, and the action direction is perpendicular to the contact surface; calculate the equivalent concentrated load F 等效 The value of: ； wherein h is the internal height of the U-shaped irrigation canal, is the maximum horizontal length inside the U-shaped irrigation canal, is the density of the liquid, is the acceleration of gravity, is the equivalent load reduction factor; S6: applying an equivalent concentrated load F in the finite element model 等效 , carrying out finite element calculation to obtain the tensile stress value at the position of the equivalent concentrated load on the bottom surface of the U-shaped irrigation canal; S7: the genetic algorithm is used to iteratively optimize different combinations of support points, and the maximum tensile stress value is obtained; S8: the obtained maximum tensile stress value is compared with the tensile strength corresponding to the preset engineering concrete grade, and it is determined whether the anti-cracking performance is qualified.
2. The method of claim 1, wherein: In the step S1, the size parameters include the channel plate thickness, the internal height, the internal maximum horizontal length, the trapezoidal section length, the trapezoidal section slope, the circular arc section radius and the circular arc section radian.
3. The method of claim 1, wherein: In the step S3, the support point positioning adopts curved surface length measurement, and the vertex of one side inner wall is taken as the zero point.
4. The method of claim 1, wherein: In the step S5, The values are as follows: ； wherein, Lmax is the length of the U-shaped irrigation channel, and H is the height difference between the midpoint of the Lmax segment and the inner bottom of the U-shaped irrigation channel.
5. The method of claim 1, wherein: In the step S7, in the genetic algorithm: The initial individual setting includes one group of fixed individuals and three groups of random individuals; the initial fixed individuals are positioned at the midpoints of the two trapezoidal sections and the two three-equal points of the circular arc section, and the random individuals are randomly generated in the corresponding sections.
6. The method of claim 1, wherein: In the step S7, in the genetic algorithm: the fitness function adopts the tensile stress value obtained in the step S6.
7. The method of claim 1, wherein: In the step S8, the comparison result is also used for adjusting the structure size of the U-shaped irrigation canal or selecting the concrete grade, and the obtained maximum tensile stress value is also used to provide a safety threshold for subsequent physical detection.