CN116091281B - A method for dividing the development stages of barrier lake breaches based on the breach mechanism - Google Patents

Abstract

The invention discloses a method for dividing the development stage of a dam burst of a dam crest based on a burst mechanism, which sequentially divides the burst process of the dam crest into a tail undercut stage, a steep sill tracing stage, a full-section undercut stage and a flushing silt balance-restoration stabilization stage according to the development form of the dam burst of the dam crest; the dividing nodes of the tail undercut phase and the abrupt bank tracing phase are as follows: the flood peak water flow forms a nearly vertical abrupt bank on the downstream dam slope of the damming body; the dividing nodes of the abrupt bank tracing stage and the full section undercut stage are as follows: when the large fall abrupt bank retrospectively develops to the drainage groove breach, the undercut of the two sides of the dam slope at the upstream of the dam body is obviously accelerated, the phenomenon of 'dragon opening' appears, and the flow channel is obviously widened; the dividing nodes of the full-section undercut phase and the flushing silt balance-recovery stabilization phase are as follows: the burst flow drops to the inflection point. The invention can effectively identify the flow state of the water burst of the barrier lake and has good scientific value.

Description

A method for dividing the development stages of barrier lake breaches based on the breach mechanism

technical field

The invention relates to the technical field of emergency disposal of high-risk barrier lakes in the field of mountain torrent geological disasters, in particular to a method for dividing the development stages of barrier lake breaches based on the breach mechanism.

Background technique

As a major natural disaster in alpine and canyon areas, barrier lakes are very likely to block natural river channels due to barrier bodies, causing the water level of the channel to continue to rise or even overflow, forming an abnormal burst flood peak, which seriously endangers the lives and property of the people along the downstream coast. Affected by the dynamic scour of the dam body by unsteady burst water flow, the collapse of the dam body presents drastic nonlinear changes, the collapse process is extremely complex, and the burst parameters present diverse and changing characteristics.

Constrained by the complex collapse process of the barrier lake, there is currently no clear indicator to uniformly divide the development process of the barrier lake. According to engineering experience and the collapse changes of the barrier body, scientific researchers generally divide the development process of the collapse into the slow development stage of the collapse and the rapid collapse stage. In the development stage, this division method has no clear measurement indicators, is highly subjective, and it is difficult to reflect the change of the collapse of the barrier body. Therefore, the division and recognition of the division process of the barrier lake collapse process is low, and it is difficult to apply to emergency response to high-risk barrier lakes. processing.

Contents of the invention

Compared with the traditional division method of barrier lake outburst process, the present invention provides a barrier lake outburst development stage division method based on outburst mechanism, which can accurately divide the barrier lake outburst process according to the hydraulic phenomenon of barrier lake outburst development.

In order to solve the problems of the technologies described above, the present invention is realized through the following technical solutions:

A method for dividing the development stages of a barrier lake breach based on the collapse mechanism. According to the development pattern of the barrier lake breach, the process of the barrier lake breach is divided into the tail down-cutting stage, the steep slope tracing stage, the full-section down-cutting stage, and the erosion-silt balance- return to a stable phase;

The division node of the tail downcutting stage and the scarp source tracing stage is: the overflowing water flow forms a nearly vertical scarp on the dam slope downstream of the dam body;

The dividing nodes of the stage of tracing the source of the scarp and the stage of cutting down the full section are as follows: when the steep slope with a large drop develops back to the breach of the drainage trough, the erosion of the toe of the slope on both sides of the upstream dam slope of the dam body is significantly accelerated, and a "dragon opening" appears Phenomenon, the flow channel is significantly widened;

The dividing node between the full-section undercutting stage and the scour-silting balance-restoring stable stage is: the burst flow drops to an inflection point.

Preferably, the hydraulic characteristics of the undercutting stage of the tail are as follows: the overflowing water flow first forms a "braided" erosion ditch on the downstream dam slope of the dam body, and the large-grained sand and gravel materials form a "side moraine" on both sides of the erosion ditch. "Phenomenon, as the downcutting of the tail continues, small-scale collapses gradually form on both sides of the "braided" erosion ditch, and the width of the scouring flow on the downstream dam slope of the dam body gradually increases, and the plane shows a wide tail and gradually shrinks upstream" Inverted Trumpet” form.

Preferably, according to the development pattern of the barrier lake breach, the source tracing stage of the steep slope is divided into two sub-stages: the stage of parallel traceable development of multi-level steep slopes and the stage of traceable development of steep slopes with large drop.

Further, the division node of the multi-level steep slope parallel backtracking development stage and the large drop steep slope development stage is: multi-level parallel steep slopes merge with each other to form a single steep slope with a large drop.

Further, the hydraulic characteristics of the multi-level scarps in the parallel retrospective development stage are: the steep slopes are formed first in the area downstream of the dam slope with relatively weak anti-scour flow velocity, and gradually form the dam slope with the increase of the burst flow velocity. Multi-level parallel backtracking steeps.

Further, the hydraulic characteristics of the development stage of the large-drop scarp are as follows: multi-level parallel scarps merge with each other to form a single scarp with a large drop. runner.

Preferably, the hydraulic characteristics of the undercutting stage of the full section are as follows: when the steep slope with a large drop returns to the breach of the drainage channel, the breach of the drainage channel rapidly expands laterally and cuts down vertically, the flow rate and velocity of the breached water flow increase rapidly, and the ability of scour and erosion is remarkable Intensified, resulting in the rapid collapse of the drainage trough, the rapid discharge of the stored floodwater in the barrier lake, and the rapid drop of the reservoir water level.

Preferably, the hydraulic characteristics of the erosion-silting balance-restoration stabilization stage are: the flow rate to be collapsed drops to the inflection point, the scour and erosion ability of the burst water flow gradually decreases, and the slope of the drainage channel becomes unstable and collapsed sand and gravel gradually accumulate in the drainage channel, The fine-grained sand and gravel are in the form of loose grains and roll along with the burst water, and the coarse-grained sand and gravel gradually accumulate to form a coarse protective layer. When the flow of the barrier lake in and out of the reservoir reaches a balance, the recovery and stabilization phase ends.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

At present, there is no clear quantitative index for the stage division of the barrier lake collapse process. Most of the collapse process is judged subjectively to delineate the barrier lake collapse process, which lacks sufficient judgment basis and is subjective. The mechanism-based method for dividing the development stages of barrier lake breaches has the following advantages:

Systematically reveal the mechanism of barrier lake failure, and divide the process of barrier lake failure based on clear quantitative indicators or hydraulic phenomena such as changes in the water level of the barrier lake reservoir, slump on the dam slope, and backtracking of the sill to the breach, and the balance of the flow in and out of the reservoir. It is convenient for the study of the phase characteristics of the barrier lake burst process, and provides an effective reference for the precise treatment of high-risk barrier lake emergency treatment.

Description of drawings

Figure 1 is a schematic diagram of water flow over the top of a barrier lake (before it bursts).

Figure 2 is a schematic diagram of the tail cutting stage.

Figure 3 shows the stage of steep slope traceability (multi-level steep slope parallel traceback development stage).

Figure 4 is the stage of tracing the origin of the steep slope (the development stage of tracing the origin of the steep drop).

Figure 5 is a schematic diagram of the undercutting stage of the full section ("dragon opening" phenomenon).

Figure 6 is a schematic diagram of the burst flow change curve.

Reference signs: 1, overflow top water flow; 2, dam slope upstream of dam body; 3, top of dam body; 4, dam slope downstream of dam body; 5, dam body; 6, top slope of dam body; 7. Multi-level steep slopes; 8. Large drop steep slopes; Q, burst flow; Q ₀ , inbound flow; T, burst process time; T ₀ , falling inflection point of burst flow change curve; T ₁ , burst process end time.

Detailed ways

In order to enable those skilled in the art to better understand the technical solutions of the present invention, the preferred embodiments of the present invention will be described below in conjunction with specific examples, but it should be understood that the accompanying drawings are for illustrative purposes only, and cannot be interpreted as an explanation of this patent. Restrictions; In order to better illustrate this embodiment, some parts in the drawings will be omitted, enlarged or reduced, and do not represent the size of the actual product; It is understandable that the classification method of barrier lake breach development stages and its description may be omitted. The positional relationship described in the drawings is for illustrative purposes only, and should not be construed as a limitation on this patent.

Referring to Figures 1-6, the present invention provides a method for dividing the development stages of a barrier lake breach based on the breach mechanism. According to the development pattern of the barrier lake breach, the present invention divides the process of the barrier lake breach into the tail down-cutting stage, steep The sill tracing stage, the full-section downcutting stage, and the scour-silt balance-restoration and stability stage, among them, the division nodes of the tail downcutting stage and the scarp source tracing stage are: the overflowing water flow forms a nearly vertical scarp on the dam slope 4 downstream of the dam body; The division nodes of the stage of steep slope source tracing and full-face downcutting stage are as follows: when the large-drop steep slope 8 traces back to the breach of the drainage trough, the erosion of the slope toe on both sides of the upstream dam slope 2 of the dam body is significantly accelerated, and the phenomenon of "dragon opening" appears. The flow channel is significantly widened; the division node of the full-face downcutting stage and the erosion-silting balance-restoration stable stage is: the burst flow drops to the inflection point T ₀ .

The obvious hydraulic characteristics of the breakout flow at each characteristic stage are as follows:

(1) Tail cutting stage, see Figure 1-2:

The water level of the dammed lake reservoir is as high as the top of the dammed body 3, and the flooded water flow 1 is clear, with low flow velocity and weak scouring ability. At the intersection of the top 3 and the downstream folded slope section (i.e., the top slope 6 of the dam body), the slope increases, and the conversion of potential energy causes the flow velocity of the overflowing water to increase rapidly, and the scour and erosion ability is significantly enhanced, and the dam body is rapidly cut and eroded. On the downstream dam slope, a "braided" erosion ditch is formed, and large particles of sand and gravel are even scattered on both sides of the erosion ditch, forming a phenomenon similar to "lateral moraine". As the downcutting at the tail continues, the starting point of downcutting erosion gradually develops upstream. At the same time, the water level of the reservoir continues to rise, and the flow velocity of the overflowing water gradually increases. Small-scale collapses gradually form on both sides of the "braided" erosion ditch, and the downstream of the dam body The scouring flow width of the dam slope 4 gradually increases, and the plane presents an "inverted trumpet" shape with a wide tail and gradually shrinks upstream. The stage of steep slope traceability.

(2) The stage of steep slope tracing, see Figure 3-4:

With the increase of the velocity of the outburst flow, the source tracing stage of the scarp can be divided into two substages:

(2.1) The development stage of multi-level scarps is traced back in parallel. Due to the wide material structure composition of the dam body 5, the corresponding anti-scour flow velocity is significantly different. With the increase of burst flow velocity, multi-level parallel retrograde scarps gradually formed on the dam slope, and the multi-level scarps 7 continued to erode the horizontal and vertical surfaces of the scarps, resulting in the integration and merger of all levels of scarps or the ebb and flow of each other, forming a large drop and steep slope. Hum 8, since then entered the second sub-stage.

(2.2) In the development stage of large-drop scarps traced to the source, the velocity of the water flow to be broken continues to rise, and multi-level parallel scarps merge with each other to form a single scarp with a large drop. The bottom is muddy water), the flow channel is relatively narrow, and the downstream of the steep sill is mainly muddy water, and the flow channel widens significantly. When the steep slope develops back to the breach of the drainage trough, the erosion of the slope toe on both sides of the upstream dam slope 2 of the barrier body is significantly accelerated, the phenomenon of "dragon opening" appears, the flow channel is significantly widened, and the collapse process enters the full-section downcutting stage.

(3) Full-section undercutting stage, as shown in Figure 5:

When the large drop and steep slope trace back to the drainage channel breach, the drainage channel breach rapidly expands horizontally and vertically cuts down, the flow rate and velocity of the breach water flow increase rapidly, and the scour and erosion capacity is significantly enhanced, resulting in the rapid collapse of the drainage channel, and the rapid accumulation of floodwater in the barrier lake. The water level of the reservoir drops rapidly, and the burst process enters the erosion-silting balance-restoration stage when the burst flow drops to the inflection point (T ₀ ).

(4) Erosion-silting balance-recovering stable stage, as shown in Figure 6:

When the burst flow rate drops to the inflection point (T ₀ ), the erosion and erosion capacity of the burst water flow gradually decreases, and the slope of the drainage channel loses stability and the collapsed sand and gravel gradually accumulate in the drainage trench. Coarse-grained sand and gravel materials are gradually accumulated to form a coarser protective layer. When the flow in and out of the barrier lake reaches a balance (that is, when the burst flow drops to the inflow flow Q0), the recovery and stabilization phase ends.

The technical solution of the present invention mainly relates to the emergency treatment of high-risk barrier lakes in the field of mountain torrent geological disasters, especially for landslide-type barrier lakes formed by rainfall or earthquakes in alpine and canyon areas, which can effectively identify the flow pattern of barrier lake bursts and has a good scientific value.

The above descriptions are only preferred embodiments of the present invention, but the present invention is not limited to the specific embodiments described above. Those skilled in the art may also make some modifications, supplements or substitute similar methods without departing from the principle of the present invention, and these shall also be regarded as the protection scope of the present invention.

Claims (1)

1. The method is characterized in that the dam breaking process of the dam is divided into a tail undercut phase, a steep sill tracing phase, a full-section undercut phase and a flushing balance-restoration stabilization phase in sequence according to the dam breaking development form of the dam;

the dividing nodes of the tail undercut phase and the abrupt bank tracing phase are as follows: the flood peak water flow forms a nearly vertical abrupt bank on the downstream dam slope of the damming body;

the dividing nodes of the steep bank tracing stage and the full section undercut stage are as follows: when the large fall gradient ridge retrospectively develops to the drainage groove breach, the erosion of the slope feet at the two sides of the upstream dam slope of the dam body is accelerated, the phenomenon of a dragon opening appears, and the flow channel is widened;

the dividing nodes of the full-section undercut phase and the flushing silt balance-recovery stabilization phase are as follows: the burst flow is reduced to an inflection point;

the hydraulic characteristics of the tail undercut stage are as follows: the method comprises the steps that firstly, a plait erosion ditch is formed on a downstream dam slope of a dam body through water flow on a top, a similar side-wall phenomenon is formed on two sides of the erosion ditch through large-particle sand stone, small-scale collapse is gradually formed on two sides of the plait erosion ditch along with continuous tail cutting, the downstream dam slope erosion flow width of the dam body is gradually increased, and a plane of the dam body is in an inverted horn shape with a wide tail and gradually contracted upstream;

dividing the source tracing stage of the abrupt bank into two sub-stages according to the development form of the breach of the barrier lake: the multistage abrupt bank parallel backtracking development stage and the large fall abrupt bank source backtracking development stage; the multistage abrupt bank parallel backtracking development stage and the dividing node of the large-fall abrupt bank traceability development stage are as follows: the multistage parallel steeprests are mutually intersected and fused to form a single steeprest with large fall; the multistage abrupt bank parallel backtracking development stage has the hydraulic characteristics that: forming a steep bank at the beginning of a region with relatively weak impact flow velocity of a dam slope at the downstream of the dam body, and gradually forming multistage parallel backtracking steep banks on the dam slope along with the increase of the breaking flow velocity; the hydraulic characteristics of the large-fall abrupt bank tracing development stage are as follows: the multistage parallel steeples are mutually intersected and fused to form a single steep bank with a large fall, and the plane of the weir stopper body is an inverted horn-shaped falling bank which continuously goes back to the upstream to develop and erode the runner;

the hydraulic characteristics of the full-section undercut phase are as follows: when the large-fall abrupt bank backtracks to the drainage groove breach, the drainage groove breach is transversely widened and longitudinally cut downwards, the water flow and the flow speed are raised, the scouring and erosion capacity is enhanced, the drainage groove collapses, the flood storage tank is stored under water, and the water level of the storage tank is lowered;

the hydraulic characteristics of the flushing balance-recovery stabilization stage are as follows: and when the flow of the dam-breaking water flows is scoured and the erosion capacity is gradually reduced, the unstably collapse sand and stone materials of the side slope of the drainage groove are gradually accumulated in the drainage groove, the fine sand and stone materials are in a granular form and roll along with the scoured and rolled of the dam-breaking water flows, the coarse sand and stone materials are gradually accumulated to form a coarsened protective layer, and when the flow of the dam-breaking water flows in and out of the dam-breaking lake reaches balance, the stabilization stage is finished.