CN102409640B - Passive-drainage emergency rescue method in case of earth-rock dam break - Google Patents

Abstract

The purpose of the present invention is to provide a way to pre-arrange the discharge channel when the risk of flooding of the earth-rock dam is high, or to arrange the discharge channel in an emergency before the flooding of the earth-rock dam reaches the second stage of the flooding of the dam, so as to reduce the water level of the reservoir. The method for eliminating the risk of dam failure belongs to the field of flood control and emergency rescue of earth-rock dams in water conservancy projects. The method of the present invention mainly includes: (1) determining the position of the discharge groove and the size of the discharge groove door; (2) anchoring the waterproof geotextile at the predetermined position of the body of the discharge groove on the downstream dam slope by using a continuous anchor rod; (3) Protect the dam foot by paving or riprap; (4) use blasting or mechanical excavation to lower the elevation of the dam crest to form the discharge opening of the discharge trough, providing a new passive discharge rescue method for earth-rock dam failure; The shortened construction period avoids the risk of dam collapse when the earth-rock dam is forced to overflow, and guarantees the safety of life and property of the downstream people.

Description

A passive discharge rescue method for earth-rock dam failure

technical field

The invention discloses a method for passively releasing flow from an earth-rock dam and belongs to the field of flood control and emergency rescue of earth-rock dams in water conservancy projects.

Background technique

my country has built more than 86,000 reservoir dams and more than 6.4 million small ponds and dams, of which more than 90% are earth-rock dams. These reservoirs have been constructed for a long time, and many of them were built by local farmers themselves. The hydrological series is short, and the flood control storage capacity and flood discharge capacity of the reservoirs are underestimated. The discharge capacity of the spillway is not up to the standard), once the flood exceeds the standard, it is very likely that the overburden and dam failure will occur, which will bring serious disasters to the downstream. In the past, flood protection of earth-rock dams was mainly based on prevention. The more common method was to build weirs, that is, to build sub-dykes on the top of the dam to prevent flooding from flooding the downstream slope. The commonly used earth weir forms are mainly viscous Earth weir, bagged earth weir, plank earth weir, willow stone earth weir, etc. The traditional technology of rushing to build sub-dikes needs to prepare enough materials in advance, which has disadvantages such as low efficiency and complicated treatment after the flood season. Another commonly used rescue method is to rush to dig a spillway to release the flow. For small reservoirs and ponds and dams with large areas and large volumes in our country, the normal maintenance force is relatively weak. When there is a danger of flooding, the excavation progress of rushing to dig spillways is often slow, and it is often difficult to work. In addition, since earth-rock dams are usually not allowed to overflow the top, there is an important risk of temporarily rushing to dig a spillway, that is, the overflowing water will scour the dam body, and even cause a complete dam failure accident.

In view of this, the present invention proposes a new method, which adopts the combination of "drainage" and "prevention", studies a set of rapid construction technology of emergency drainage tanks, and uses "blasting" technology or mechanical excavation to realize the rapid construction of emergency drainage tanks , using special high-strength synthetic materials to achieve rapid reinforcement of the emergency drainage tank. This technology has many characteristics such as strong practicability, simple implementation, and wide application prospects. It is of great significance to plan, issue flood warning, organize evacuation and escape, and implement emergency rescue.

Contents of the invention

The purpose of the present invention is to provide a way to pre-arrange the discharge channel when the risk of the earth-rock dam overflowing is high, or to arrange the discharge channel in an emergency before the earth-rock dam overflows to the second stage of the overflowing dam to reduce the water level of the reservoir. Ways to eliminate the risk of dam failure.

A passive discharge emergency method for earth-rock dam failure, comprising the following steps:

When the earth-rock dam has a high risk of dam failure but has not yet overflowed, or when the earth-rock dam has begun to overflow but the current situation of the dam collapse has not reached the second stage, use continuous anchor rods to anchor the waterproof type in the design discharge groove in advance. Geotextiles construct passive discharge channels for earth-rock dams. The inventor has carried out many experiments on the collapse of the earth-rock dam overflowing the top, and divided the collapse process of the earth-rock dam overflowing into five stages. The step-shaped sill merges in the third stage, the step-shaped sill cuts down and expands upstream in the fourth stage, and the dam body expands horizontally and finally collapses in the fifth stage. Because the method of anchoring the waterproof geotextile is very fast, this method can be used as a method to avoid expanding losses before the flooded dam reaches the second stage (forming a stepped sill). The specific leakage rescue methods are as follows:

(1) Determine the location of the discharge slot and the size of the discharge slot door;

This step is to know that there will still be a relatively large flood in the upstream through the upstream flood forecast, and the earth-rock dam has reached or approached the check flood level, and the existing flood discharge measures cannot meet the flood discharge requirements. Determine the location of the preparatory discharge trough, and determine the size of the discharge trough door according to the forecast flood flow.

(2) Use the continuous anchor rod to anchor the waterproof geotextile at the predetermined discharge channel body position on the downstream dam slope;

(3) Carry out paving protection or riprap protection for the dam foot.

(4) Use blasting or mechanical excavation to lower the elevation of the dam crest to form the discharge port of the discharge chute.

The above-mentioned utilization blasting is to bury explosives in the discharge channel set at the top of the dam. The elevation distance of the explosive chamber layout is greater than the calculated radius of the blasting compression circle, and has a certain safety value, so as to avoid blasting damage to the fixed structure at the top of the emergency discharge channel;

Since shortening the construction time is the most important part in the rescue process of dam break, the laying method of geotextiles in this method is different from that of traditional geotextiles. Since this method constructs temporary buildings, geotextiles Instead of using conventional anchoring trenches or burying, the construction is carried out as follows.

The above-mentioned construction of passive discharge channels for earth-rock dams by using continuous anchor rods to anchor waterproof geotextiles in the designed discharge channels in advance includes the following contents:

a. The range of anchoring elevation is from the water surface downstream of the dam to the lower edge of the scheduled dam crest discharge groove;

b. The anchoring level range is determined according to the following method:

W _H ≧2～3B,

Where W _H is the horizontal laying width (m),

B is the designed discharge groove width (m).

c. When the dam height is less than or equal to 10m, the waterproof geotextile is arranged by the warp method;

When the dam height is greater than 10m but less than 15m, the waterproof geotextile shall be arranged by crossing latitude and longitude lines;

After many times of practice, the inventors have concluded that such a construction method can quickly lay geotextiles, and the state of the geotextiles can basically meet the stability requirements of the temporary structure during the discharge period.

The above-mentioned meridian arrangement refers to:

The geotextile reel is rolled and laid from top to bottom along the discharge groove. The superimposition method along the axis of the dam is unidirectional and layer by layer. The superimposed intersection width is 2 to 6 times the anchor width. To prevent the impact of water flow from forming an additive effect between the upper and lower layers of geotextiles.

The above-mentioned arrangement of latitude and longitude crossing refers to:

The geotextile reel is first laid on the dam slope directly below the discharge slot door according to the warp method (the place is most susceptible to erosion), and at the position 1/4 of the dam height from the bottom edge of the discharge trough and 1/4 of the dam distance from the downstream water surface. Lay two geotextile reels along the horizontal direction at the high position to protect the downstream dam slope step by step. The laying length is 2-3B. The superimposition method of the two geotextile reels is pressing up and down. Anchor width. The arrangement of the weft is pressed down so that the water flow will not scour the interface of the geotextile.

The above-mentioned continuous anchor rod is a turtle shell type continuous anchor. The turtle shell type continuous anchor includes an anchor head and an anchor rod. There is a hole in the middle of the anchor head, and the anchor rod is fixed through the hole. This design is convenient for transportation.

The above-mentioned waterproof geotextile is a three-dimensional composite filter pad and other impermeable flexible materials with strong erosion resistance.

The beneficial effects of the present invention are:

1. Provide a new rescue method for passive discharge of earth-rock dam failure;

2. This method avoids the risk of dam collapse when the earth-rock dam is forced to overflow, and ensures the safety of people's life and property downstream;

3. The construction time of this method is short, which ensures that the project can be completed before the arrival of the flood.

Description of drawings

Fig. 1 embodiment one design schematic diagram of discharge groove;

Fig. 2 embodiment one schematic diagram of the structure of the discharge groove;

The schematic diagram of gully formation on the downstream slope of the dam in the first stage of the earth-rock dam failure of Fig. 3 embodiment two;

Fig. 4 embodiment two discharge trough structure schematic diagram;

Fig. 5 embodiment three discharge trough structure schematic diagrams;

Fig. 6 embodiment four tortoise shell anchor top view schematic diagrams;

Fig. 7 is a schematic cross-sectional view of a symmetrical axis of a turtle shell anchor in embodiment four;

Fig. 8 Schematic diagram of step-shaped slump formed downstream of the dam in the second stage of earth-rock dam failure;

Fig. 9 Schematic diagram of the merging of stepped sills downstream of the dam in the third stage of the earth-rock dam failure;

Fig. 10 Schematic diagram of the step-shaped drop sill downstream of the earth-rock dam in the fourth stage of the dam failure and expanding upstream;

Fig. 11 Schematic diagram of the lateral expansion and final collapse of the dam downstream of the dam in the fifth stage of earth-rock dam failure.

Detailed ways

Embodiment one

The rescue method for passive discharge of earth-rock dam failure includes the following steps:

According to the dam risk assessment, the earth-rock dam 1-1 in Figure 1 has a high risk of dam failure. The dam crest elevation is 8.0m, and the water level above the dam has reached 7.6m. During the large flow process, the original flood discharge channel of earth-rock dam 1 has been in disrepair for a long time and has been abandoned. It is estimated that the earth-rock dam will overflow in 5 hours, and emergency discharge facilities need to be built within 5 hours.

(1) According to the calculation results, a discharge channel 1-2 with a width of 5m and a top elevation of 7.5m is designed in the middle of the dam crest, see Figure 1. The discharge channel is constructed by differential blasting, and the dam surface under the discharge channel is anchored with a waterproof geotextile three-dimensional composite filter pad.

(2) Use the continuous anchor rod to anchor the waterproof geotextile at the predetermined discharge channel body position on the downstream dam slope;

a. The anchoring elevation range is from the 2.5m elevation of the water surface downstream of the dam to the 7.5m elevation of the lower edge of the scheduled dam crest discharge groove;

b. The anchoring horizontal range is: W _H ≧ 2 ~ 3B, where H _{dam crest} = 8m, B = 5m, H = 2.5m ~ 7.5m, and the horizontal anchoring range is W _H ≧ 10m ~ 15m from top to bottom ;Because the overall dam surface needs to be protected, the horizontal anchoring range is finally selected as 15m, the three-dimensional composite filter pad 1-3 with a width of 5m is selected, and the turtle shell anchor 4 with a width of 30cm is selected;

c. Since the dam height is 8m, the meridian method is used for layout; the layout is four-axis three-dimensional composite filter mat laid in the meridian direction. Stack the two sheets in the middle, then anchor one end of the two three-dimensional composite filter mats at an elevation of 7.5m, then roll the three-dimensional composite filter mat rollers down the downstream dam surface, and then lay two The three-dimensional composite filter pad on the side is then anchored to the seam, and the superposition of the two seams is not less than 2 times the anchor width of 0.6m.

(3) Finally, riprap slope protection 1-4 at the foot of the slope, see Figure 2.

(4) The discharge chute is constructed by differential blasting to form the discharge port of the chute.

The construction was completed within 3 hours. After the blasting, the downstream surface of the earth-rock dam was not scoured, and the flood discharge lasted for 3 days stably without causing inundation loss to the downstream.

Embodiment two

In Figure 3, the crest elevation of earth-rock dam 2-1 is 8m, and the top has begun to overflow. The current situation of the dam failure has reached the first stage and the downstream slope has formed gullies, but has not reached the second stage, forming a stepped sill, as shown in Figure 3.

(1) According to the width of the existing breach, the size of the gate of the chute is determined to be 3.5m;

(2) Use the continuous anchor rod to anchor the waterproof geotextile at the predetermined discharge channel body position on the downstream dam slope;

a. The anchoring elevation range is from the water surface downstream of the dam to the top of the discharge channel, and the laying sequence is from top to bottom;

b. The widest part of the edge of the breach is 3.5m, and the anchoring level range is W _H ≧ 2 ~ 3B, where H _{dam crest} = 8m, B = 3.5m, calculated W _H ≧ 7 ~ 10.5m, in order to increase protection The horizontal anchoring range is 10.5m. A three-dimensional composite filter mat with a width of 5m is selected, and a tortoise shell anchor 4 with a width of 30cm is selected, and the three-dimensional composite filter pad 1-3 is anchored in the discharge channel by using the tortoise shell anchor 4.

c. Since the height of the dam is 8m, the meridian method is adopted to lay out the three-axis three-dimensional composite filter mat by rolling down vertically, and the top is anchored by double rows of tortoise shell anchors.

(3) Finally, riprap slope protection 1-4 at the foot of the slope, see Figure 4.

The construction was completed within 1 hour. The downstream surface of the earth-rockfill dam was not washed away, and the flood discharge lasted for 12 hours, missing the downstream flood peak and causing no inundation loss to the downstream.

Embodiment three

According to the dam risk assessment, it is concluded that the earth-rock dam 3-1 has a high risk of dam failure. The dam crest elevation is 14m, the storage capacity is 80,000m ³ , and the water level on the dam has reached 12.5m. During the large flow process, the original flood discharge channel of the earth-rock dam has been in disrepair for a long time and has been abandoned. It is estimated that the earth-rock dam will overflow in 8 hours, and emergency discharge facilities need to be built within 8 hours.

(1) According to the calculation results, a discharge channel with a width of 10m and a top elevation of 13m is designed in the middle of the dam crest, and a waterproof geotextile three-dimensional composite filter pad is anchored on the dam surface under the discharge channel, as shown in Figure 5.

(2) Use the continuous anchor rod to anchor the waterproof geotextile at the predetermined discharge channel body position on the downstream dam slope;

a. The range of anchoring elevation is from the 4m elevation of the water surface downstream of the dam to the 13m elevation of the lower edge of the scheduled dam crest discharge groove;

b. The design breach width is 10m, and the anchoring horizontal range is W _H ≧ 2 ~ 3B, where H _{dam crest} = 15m, B = 10m, the calculated W _H ≧ 20m ~ 30m, in order to increase the level of protection to choose the anchoring range 30m, select a three-dimensional composite filter pad with a width of 5m, and select a tortoise shell anchor 4 with a width of 30cm;

c. Since the dam height is 14m, the crossing method of latitude and longitude is adopted; the arrangement is five-axis three-dimensional composite filter mat 3-2 along the longitude, and three-dimensional composite filter pad three-three four-axis along the latitude, where the two axes of the latitude are arranged at a distance of four The elevation of three-thirds of the bottom edge of the breach is 9.75m, and the other two axes of the latitude are arranged at a quarter of the bottom of the breach, that is, the elevation of 3.25m. The latitude is superimposed on the warp, as shown in Figure 5. During construction, anchor one end of the triaxial three-dimensional composite filter pad at an elevation of 13m, then roll the roller of the three-dimensional composite filter pad down the downstream dam surface, and then horizontally Lay the first and second parallel three-dimensional composite filter pads, while laying the upper three-dimensional composite filter pads with tortoise shell anchors to continuously anchor, the two joints overlap not less than 6 times the anchor width of 1.8m, and lay the two shafts at the bottom of the dam body After that, lay the upper two shafts of the dam body.

(3) Finally, riprap slope protection 1-4 at the foot of the slope.

(4) Mechanical excavation construction of the discharge chute.

The construction was completed within 5 hours. The downstream surface of the earth-rockfill dam was not scoured, and the flood discharge continued steadily for 3 days without causing submerged losses to the downstream.

Embodiment four

As shown in Figure 6 and Figure 7, the turtle shell anchor 4 includes an anchor rod 41, an anchor body 42, the anchor body is a turtle shell shape to reduce water flow resistance, an anchor hole 43 is provided on the anchor body, and the anchor rod 41 is inserted into the earth-rock dam through the anchor hole 43 .

Claims (6)

1. A method for emergency rescue of earth-rock dam failure by passive discharge, is characterized in that it comprises the following steps: (1) Determine the location of the discharge slot and the size of the discharge slot door; (2) Use the continuous anchor rod to anchor the waterproof geotextile at the predetermined discharge channel body position on the downstream dam slope; (3) Protect the dam foot by paving or riprap; (4) Use blasting or mechanical excavation to lower the elevation of the dam crest to form the discharge gate of the discharge chute; Using continuous anchor rods to pre-anchor waterproof geotextiles in the designed discharge channel to construct passive discharge channels for earth-rock dams includes the following contents: a. The range of anchoring elevation is from the water surface downstream of the dam to the lower edge of the scheduled dam crest discharge groove; b. The anchoring level range is determined according to the following method: W _H ≥ 2 ~ 3B, Where W _H is the horizontal laying width (m), B is the width of the design discharge groove (m), c. When the dam height is less than or equal to 10m, the waterproof geotextile is arranged by the warp method; When the dam height is greater than 10m but less than 15m, the waterproof geotextile shall be arranged by crossing latitude and longitude lines. 2. A method for emergency rescue of earth-rock dam break by passive discharge according to claim 1, characterized in that: the arrangement of the warp method refers to: the geotextile reel rolls down and lays along the discharge groove from top to bottom, along the The lamination method in the direction of the dam axis is one-way lamination layer by layer, and the lamination intersection width is 2 to 6 times the anchor width, and these geotextiles cannot be glued to each other. 3. A method for emergency rescue of an earth-rock dam collapse according to claim 1, characterized in that: the arrangement of the latitude and longitude intersecting means: the geotextile reel is first laid on the discharge slot door according to the warp method Directly below the dam slope, two geotextile reels are laid horizontally at a position 1/4 of the dam height from the bottom edge of the discharge chute and 1/4 of the dam height from the downstream water surface. The laying length is 2-3B. The stacking method of the fabric reels is pressing up and down, and the stacking cross width is 2 to 6 times the anchor width. 4. The rescue method for passive discharge of earth-rock dams according to claim 1, characterized in that: the continuous anchor rod is a turtle-shell type continuous anchor. 5. A rescue method for passive discharge of earth-rock dams according to claim 4, characterized in that: the turtle-shell type continuous anchor comprises an anchor head and an anchor rod. 6. A rescue method for passive discharge of earth-rock dams according to claim 1, characterized in that: the waterproof geotextile is an impermeable flexible material with strong erosion resistance.

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