Blockage body outburst mode analysis method

Abstract

The invention provides an analysis method for a blockage body outburst mode, and aims to solve the problem that in the prior art, only a single outburst mode is analyzed, and the situation that multiple outburst modes coexist in practice is difficult to deal with. The method comprises the following steps: defining a dominant channel type on a blockage body, calculating and analyzing a potential dominant channel on the blockage body, and judging a blockage body outburst mode. According to the method, the coupling effect of surface erosion, internal piping and slip surface instability in the outburst process of the blockage body can be comprehensively analyzed, the judgment accuracy of the outburst mode is improved, and reliable theoretical support is provided for stability evaluation of the blockage body and disaster risk prevention and control.

Description

Technical Field

[0001] This invention belongs to the field of water conservancy engineering and geological disaster prevention technology, and relates to geotechnical engineering stability assessment and multi-field coupled numerical simulation, and in particular to an analysis method for blockage body collapse mode. Background Technology

[0002] Blockages in gullies or river channels are mostly composed of collapsed deposits, landslide deposits, residual slope deposits, and glacial till from both banks. They are mixed soil and rock deposits with a loose structure, poor stability, and significant discontinuities and size effects. Under the influence of external forces such as rainfall and upstream water flow, these blockages are prone to instability and collapse, leading to secondary disasters such as floods and mudslides, posing a serious threat to the surrounding ecological environment and human activities.

[0003] The collapse of a dammed body is a complex process involving hydrological, hydraulic, and geological processes. Existing research classifies collapse modes into three categories based on their causes and failure characteristics: overtopping failure, piping failure, and slip surface instability. Analysis is primarily based on these three individual modes. For example, overtopping failure focuses on the scouring effect on the surface layer after water flows over the top of the dammed body; piping failure emphasizes the process of water seeping into the dammed body, forming channels, and gradually expanding; and slip surface instability focuses on the overall instability caused by the formation of a slip surface due to stress imbalance within the dammed body.

[0004] However, in actual engineering, the collapse of clogging bodies is often not the result of a single mode of action, but rather a process involving the coexistence or coupling of multiple modes. On the one hand, the randomness of the clogging body formation process and the heterogeneity of its structure (such as differences in particle size distribution and uneven pore distribution) mean that water flow may simultaneously form erosion grooves on its surface, piping holes inside, and the development of potential sliding surfaces. On the other hand, existing single-mode analysis methods do not consider the interaction between different failure mechanisms, making it difficult to accurately characterize the collapse initiation process under multi-mode coupling. This leads to discrepancies between the assessment results of clogging body stability and the actual situation, thereby affecting the effectiveness of disaster early warning and prevention measures.

[0005] Therefore, given the multi-mode coexistence characteristic in the sluice gate collapse process, there is an urgent need for an analytical method that can comprehensively consider the coupled effects of multiple mechanisms such as surface erosion, internal piping, and slip surface instability, in order to improve the accuracy of sluice gate collapse mode identification and provide more reliable theoretical support for disaster risk assessment. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of this invention is to improve the accuracy of the failure mode judgment, provide reliable theoretical support for the stability assessment of blockage bodies and disaster risk prevention and control, and thus provide an analytical method for the failure mode of blockage bodies.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] This invention provides a method for analyzing the failure modes of blockage bodies, comprising the following steps:

[0009] Step 1, define the dominant channel type on the blockage:

[0010] Based on the causes and damage characteristics of blockage failure, the dominant channels are divided into three categories: erosion gullies, piping tunnels, and sliding surfaces, which correspond to three failure modes: overtopping failure, piping failure, and sliding surface instability failure, respectively.

[0011] Step 2, calculate and analyze the potential dominant channels on the blockage:

[0012] S21. Assuming that erosion trenches, piping holes, and sliding surfaces may all form in the plugging body, establish the seepage field of the plugging body based on the dominant channels;

[0013] S22. Calculate the stress field of the blockage body in the seepage field and determine the safety factor characterizing the stability of each point of the blockage body. The safety factor includes the global minimum safety factor calculated using the slope stability analysis method and the local safety factor calculated using the local safety factor method.

[0014] Step 3, determine the blockage failure mode:

[0015] Based on the on-site investigation data, compare the safety coefficients of potential advantageous channels. If there is an advantageous channel with a safety coefficient of less than 1, then the failure mode corresponds to the formation mode of the advantageous channel.

[0016] If the safety coefficient of all dominant channels is greater than 1, then the failure mode is the mode corresponding to the dominant channel with the lowest safety coefficient.

[0017] Furthermore, in step 1, the erosion trench is located on the surface of the water flow, while the piping hole and sliding surface are located inside the blockage body.

[0018] Furthermore, in step 2, S22, the local safety factor LFS is calculated based on the Mohr-Coulomb criterion. Specifically, by analyzing the change in average effective stress caused by the change in adsorption stress at a certain point in the seepage field, the relationship between the Mohr circle of the stress state at that point and the strength envelope is determined, and then the local safety factor is calculated.

[0019] The calculation formula is:

[0020]

[0021] In the formula, LFS is the local safety factor, τ is the Coulomb stress, and τ * c is the shear strength, and c' is the drainage cohesion. σ is the internal friction angle for drainage. Ι'σ' represents the average effective stress. Ⅱ For deviatoric stresses, σ1 and σ1' are the first principal stress and the first effective principal stress, respectively, and σ3 and σ'3 are the third principal stress and the third effective principal stress, respectively. s This is to absorb stress.

[0022] Furthermore, in step 2, S21, the seepage field is calculated using an unsaturated soil seepage analysis method to simulate the water flow and pore water pressure changes within the blockage.

[0023] Furthermore, in step 2, S22, the slope stability analysis method includes the slice method and the circular arc method, wherein the slice method adopts the Morgenstern-Price slice method.

[0024] Furthermore, in step 2, the calculation of the seepage field and stress field can be achieved using geotechnical engineering numerical simulation software, which includes the SEEP / W module and the SLOPE / W module, wherein:

[0025] The SEEP / W module is used to calculate the seepage field of the blockage body under unsaturated conditions and obtain the pore water pressure distribution.

[0026] The SLOPE / W module is used to calculate the stress field of the plug and the global minimum safety factor based on the seepage field.

[0027] The advantages of this invention compared to the prior art are as follows:

[0028] 1. This invention breaks through the limitations of existing technologies that only analyze a single failure mode (overtopping, piping, or slip surface instability). By establishing a "dominant channel model", it incorporates three types of dominant channels—surface erosion trenches, internal piping holes, and slip surfaces—into a unified analytical framework for the first time. This can accurately identify situations where multiple failure modes coexist in reality, and better reflect the complex failure characteristics of blockage bodies caused by structural heterogeneity and random formation, significantly improving the comprehensiveness and accuracy of failure mode judgment.

[0029] 2. By innovatively combining the concept of dominant flow with the safety factor method in slope stability analysis, the stress field of the blockage body in the seepage field is calculated, and the global minimum safety factor (such as the slice method) and the local safety factor (based on the Mohr-Coulomb criterion) are introduced at the same time. This achieves a refined characterization of the overall and local stability of the blockage body, and can quantitatively analyze the dynamic changes in stability over time. This overcomes the shortcomings of traditional methods in reflecting the non-uniform failure process inside the blockage body, and improves the scientificity and accuracy of the collapse risk assessment.

[0030] 3. The analytical method described in this invention has a clear process and is highly operable. The SEEP / W and SLOPE / W modules of professional software such as Geostudio can efficiently realize the coupled calculation of seepage field and stress field. Combined with field investigation data, the judgment of the failure mode can be completed, which provides reliable technical support for the stability assessment of the blockage body, failure early warning and disaster prevention and control measures, and helps to reduce the risk of secondary disasters caused by the failure of the blockage body.

[0031] 4. A quantitative analysis was conducted on the differences in the impact of different dominant channels (erosion gullies, piping tunnels), clarifying the key role of internal dominant channels in the instability of the blockage body. This provides a theoretical basis for targeted prevention and control (such as prioritizing the monitoring of internal piping development), and improves the targeting and efficiency of disaster prevention and control. Attached Figure Description

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0033] Figure 1 This diagram illustrates the distribution of dominant channels on the blockage.

[0034] Figure 2 For the local safety factor scalar field;

[0035] Figure 3 The geometric dimensions of the example are shown;

[0036] Figure 4 The diagram shows how the safety factor of the blockage changes over time. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments disclosed herein will be described in further detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0038] Example 1

[0039] This embodiment provides a method for analyzing the failure mode of a blockage, including the following steps:

[0040] Step 1, define the dominant channel type on the blockage:

[0041] Based on the concept of dominant flow, the dominant channel on a blockage can be defined as the surface erosion trench through which water flows, or the piping hole or sliding surface inside the blockage, such as... Figure 1 As shown.

[0042] Based on the causes and characteristics of blockage failure, the dominant channels are divided into three categories: erosion gullies, piping tunnels, and sliding surfaces, which correspond to three failure modes: overtopping failure, piping failure, and sliding surface instability failure, respectively.

[0043] Step 2, calculate and analyze the potential dominant channels on the blockage:

[0044] Current theoretical research on dominant channels mainly focuses on soil science and hydrology. The mathematical models include three types: continuous models, discrete models, and fractal models. In addition, some applied research has emerged in the analysis of slope stability, but no relevant research has been found in the stability analysis of blockage bodies.

[0045] Since the development of dominant channels on a blockage is related to its surface density and internal permeability, determining the specific location of dominant channels is quite complex. This application uses the following method to calculate and analyze the potential dominant channels on the blockage:

[0046] S21. Assuming that erosion trenches, piping holes, and sliding surfaces may all form in the blockage body, establish the seepage field of the blockage body based on the dominant channels.

[0047] The calculation of the seepage field adopts the seepage analysis method of unsaturated soil to simulate the water flow and pore water pressure changes in the blockage.

[0048] S22. Calculate the stress field of the blockage body in the seepage field and determine the safety factor characterizing the stability of each point of the blockage body. The safety factor includes the global minimum safety factor calculated using the slope stability analysis method and the local safety factor calculated using the local safety factor method.

[0049] The slope stability analysis methods include the slice method and the circular arc method, wherein the slice method adopts the Morgenstern-Price slice method.

[0050] In the stress field of the blockage, a scalar representing the stability at that point can be defined at each point, such as... Figure 2 As shown, the solid circle (Mohr's circle) represents the stress state at a given point. The local safety factor LFS is calculated based on the Mohr-Coulomb criterion, and is determined when the absorbed stress σ at a point in the seepage field... s Increase, its average effective stress σ Ⅰ The stress field will decrease, thus changing the entire stress field. The Mohr circle will shift to the left until it is tangent to the envelope AB, reaching the instability condition.

[0051] Therefore, the change of stability scalar at each point within the blockage over time can be analyzed according to the stress path movement pattern. When judging the stability of a certain point, the local safety factor LFS is calculated using the following formula:

[0052]

[0053] In the formula, LFS is the local safety factor, τ is the Coulomb stress, and τ * c is the shear strength, and c' is the drainage cohesion. σ is the internal friction angle for drainage. Ι 'σ' represents the average effective stress. Ⅱ For deviatoric stresses, σ1 and σ1' are the first principal stress and the first effective principal stress, respectively, and σ3 and σ'3 are the third principal stress and the third effective principal stress, respectively. s This is to absorb stress.

[0054] Step 3, determine the blockage failure mode:

[0055] Based on the on-site investigation data, compare the safety coefficients of potential advantageous channels. If there are advantageous channels with a safety coefficient of less than 1, then the failure mode corresponds to the formation mode of the advantageous channel (single or multiple coexistence).

[0056] If the safety coefficient of all dominant channels is greater than 1, then the failure mode is the mode corresponding to the dominant channel with the lowest safety coefficient.

[0057] Application examples:

[0058] When analyzing the collapse of a blockage using the dominant channel conceptual model described in this application, the formation location of the dominant channel is first assumed. Then, the seepage field of the blockage is calculated based on the dominant channel, and the stress at each point of the blockage is determined in the seepage field. Finally, the safety factor of the points inside the blockage is calculated using the above formula (1), and the global minimum safety factor of the blockage is calculated using the Morgenstern-Price slice method. The stability variation characteristics over time are then analyzed. Here, the SEEP / W and SLOPE / W modules in Geostudio software are used for example analysis. The SEEP / W module can be used for seepage analysis of unsaturated soil. It can simulate porous materials and obtain the seepage field information inside the soil by analyzing the water flow and pore water pressure changes in soil and rock under non-uniform or unsaturated conditions. The SLOPE / W module can be used for slope stability analysis and can calculate the slope safety factor using various slice methods.

[0059] Since the dominant channel of the slip surface is assumed to be already connected, the calculation of the safety factor is relatively simple. However, the analysis of the dominant channels of erosion trenches and piping holes requires first calculating the stress field and local safety factor at various points of the blockage body, and then obtaining the safety factor of the blockage body, which is relatively more complicated.

[0060] Therefore, the following calculations only take the dominant channels of erosion gullies and piping holes as examples, and the blockage formed by typical sandy gravel accumulation in the gully as the analysis object, whose cross-sectional geometric dimensions are as follows. Figure 3 As shown: The blockage is 10m high, 2m long at the top, and 28m long at the bottom. The upstream slope is 1:1, and the downstream slope is 1:1.6. Assuming the blockage is a homogeneous accumulation, the material parameters are taken from geotechnical engineering specifications and similar engineering values: internal friction angle 28°, cohesion 18kPa, and unit weight 18.5kN / m³.3 The permeability coefficient is 0.05 cm / s, and the saturated water content is 0.37. The boundary condition is set to an upstream water level of 10 m to simulate the collapse process under the action of upstream water.

[0061] The calculation conditions include:

[0062] Operating condition (a): No dominant channel is set;

[0063] Operating condition (b): Surface erosion trenches are installed;

[0064] Operating condition (c): Install an internal piping tunnel;

[0065] Operating condition (d): Simultaneous installation of surface erosion trenches and internal piping holes.

[0066] For various operating conditions, the seepage field of the blockage body over time is first calculated. Then, the stress field and safety factor of the blockage body are analyzed within the seepage field. Curves showing the change of the safety factor of the blockage body over time under four operating conditions are plotted, such as... Figure 4 As shown.

[0067] Operating condition (a): When there is no dominant channel, the initial safety factor is about 2.0, which slowly decreases over time, dropping to 1.4 after 45 hours, without any instability (safety factor ≥ 1);

[0068] Condition (b): When only erosion gullies are present, the initial safety factor is close to that of condition (a). The decrease is small in the first 10 hours, but the rate of decrease accelerates after 10 hours, and drops to 1.2 at 45 hours, indicating that the effect of erosion gullies on stability has a lag.

[0069] Condition (c): When only piping hole is present, the initial value of the safety factor drops to 1.6, and after 45 hours it drops to 1.0 (critical instability state), indicating that the piping hole has a faster and more significant impact on stability;

[0070] Condition (d): When both erosion trenches and piping holes exist, the safety factor decreases in a similar trend to that of condition (c), dropping to 0.9 after 45 hours (instability), and the influence of piping holes is dominant.

[0071] The calculation results show that, considering the seepage field with dominant channels, the stability of the plug body decreases more significantly over time. The influence of erosion channels on the stability of the plug body is not obvious in the initial stage, while the influence of piping channels is significant. This indicates that piping failure has a faster impact on the instability and collapse of the plug body than erosion channels. When both types of dominant channels are considered simultaneously, piping channels have a dominant influence on the stability of the plug body. Therefore, analyzing the internal dominant channels is of great importance when evaluating the stability of a plug body.

[0072] Finally, it should be noted that the above is only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention (such as the application of various formulas, the order of steps, etc.) without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for analyzing the failure modes of a blockage, characterized in that, The analytical method includes the following steps: Step 1, define the dominant channel type on the blockage: Based on the causes and damage characteristics of blockage failure, the dominant channels are divided into three categories: erosion gullies, piping tunnels, and sliding surfaces, which correspond to three failure modes: overtopping failure, piping failure, and sliding surface instability failure, respectively. Step 2, calculate and analyze the potential dominant channels on the blockage: S21. Assuming that erosion trenches, piping holes, and sliding surfaces may all form in the plugging body, establish the seepage field of the plugging body based on the dominant channels; S22. Calculate the stress field of the blockage body in the seepage field and determine the safety factor characterizing the stability of each point of the blockage body. The safety factor includes the global minimum safety factor calculated using the slope stability analysis method and the local safety factor calculated using the local safety factor method. Step 3, determine the blockage failure mode: Based on the on-site investigation data, compare the safety coefficients of potential advantageous channels. If there is an advantageous channel with a safety coefficient of less than 1, then the failure mode corresponds to the formation mode of the advantageous channel. If the safety coefficient of all dominant channels is greater than 1, then the failure mode is the mode corresponding to the dominant channel with the lowest safety coefficient.

2. The analytical method according to claim 1, characterized in that, In step 1, the erosion trench is located on the surface of the water flow, while the piping hole and sliding surface are located inside the blockage body.

3. The analytical method according to claim 1, characterized in that, In step 2, S22, the local safety factor LFS is calculated based on the Mohr-Coulomb criterion. Specifically, by analyzing the change in average effective stress caused by the change in adsorption stress at a certain point in the seepage field, the relationship between the Mohr circle of the stress state at that point and the strength envelope is determined, and then the local safety factor is calculated. The calculation formula is: In the formula, LFS is the local safety factor, τ is the Coulomb stress, and τ * c is the shear strength, and c' is the drainage cohesion. σ is the internal friction angle for drainage. Ι 'σ' represents the average effective stress. Ⅱ For deviatoric stresses, σ1 and σ1' are the first principal stress and the first effective principal stress, respectively, and σ3 and σ'3 are the third principal stress and the third effective principal stress, respectively. s This is to absorb stress.

4. The analytical method according to claim 1, characterized in that, In step 2, S21, the seepage field is calculated using the unsaturated soil seepage analysis method to simulate the water flow and pore water pressure changes in the blockage.

5. The analytical method according to claim 1, characterized in that, In step 2, S22, the slope stability analysis method includes the slice method and the circular arc method, wherein the slice method adopts the Morgenstern-Price slice method.

6. The analytical method according to claim 1, characterized in that, In step 2, the calculation of the seepage field and stress field can be achieved using geotechnical engineering numerical simulation software, which includes the SEEP / W module and the SLOPE / W module, wherein: The SEEP / W module is used to calculate the seepage field of the blockage body under unsaturated conditions and obtain the pore water pressure distribution. The SLOPE / W module is used to calculate the stress field of the plug and the global minimum safety factor based on the seepage field.

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