A structure arrangement and operation method for improving the safety of a weak section of a dike

Abstract

The application discloses a structure arrangement and operation method for improving the safety of a weak section of a dike, comprising the following steps: identifying the weak section of the dike and determining a protection range; setting a strip-shaped water-filled buffer space on the landward side of the weak dike section and setting an outer protection boundary on the outer side; cooperatively determining a target pre-filling water level allowable range, and filling the buffer space with water to the target pre-filling water level; maintaining or adjusting the pre-filling water level during a flood process, forming a backwater side counterpressure on the existing dike, controlling the water head difference between the landward side and the backwater side and the seepage slope, and after local breaching, using the same pre-filling water body to form a water cushion buffer on the backwater side of the breach, and restraining the breaching flood by the outer protection boundary. The application realizes continuous and cooperative protection of the counterpressure before breaching and the water cushion buffer after breaching by the same pre-filling water body, can reduce the seepage damage risk of the dike, slow down the development of the breach, and limit the diffusion of the breaching flood.

Description

Technical Field

[0001] This invention relates to the technical fields of flood control and disaster reduction in water conservancy projects, dike safety and emergency response to dangerous situations, specifically a structural layout and operation method for improving the safety of weak sections of dikes. Background Technology

[0002] Dikes are an important component of river flood control engineering systems. They primarily protect river towns, residential areas, farmland, and infrastructure by confining river floodwaters and preventing them from entering the protected areas behind the dikes. The design and operation of existing dike projects typically focus on preventing seepage damage, slope instability, overtopping, and breaches. Measures such as raising and thickening dikes, slope protection, seepage prevention reinforcement, installation of pressure-reducing facilities, and temporary emergency reinforcement are commonly used to improve dike safety.

[0003] Some existing dikes were constructed relatively early and have undergone multiple heightening and thickening, phased filling, or emergency repairs. Their filling materials, compaction quality, seepage prevention systems, and cross-sectional structures may vary significantly along the dike. Due to factors such as foundation conditions, prolonged high water levels, the impact of structures penetrating the dike, animal burrows, and other biological disturbances, loose areas, seepage channels, localized weak layers, and other hidden defects may exist within the dike body. Under sustained high water levels, these defects may induce concentrated seepage, piping, soil erosion, slope instability, or localized breaches.

[0004] When a flood is imminent and there is a lack of sufficient construction window, traditional emergency measures typically involve temporarily raising and thickening the top of existing dikes or on the water-facing side to reduce the risk of overtopping. While these measures improve overtopping resistance, they do not eliminate existing seepage defects within the existing dike body. After temporary heightening, existing dikes may operate under higher or longer water levels, subjecting the dike body and foundation to greater seepage. The risk of concentrated seepage caused by historical defects, animal burrows, and locally weak foundations remains.

[0005] For dikes already operating at high water levels, direct excavation of the dike body, construction of anti-seepage walls, or overall reconstruction is usually limited by water level, site conditions, construction safety, and flood control conditions, making it difficult to complete before the arrival of floods. If large-scale excavation or filling is carried out on weak sections of the dike without sufficient investigation and safety assessment, it may also disturb the original dike body and foundation, increasing safety risks during construction.

[0006] Once a levee experiences a partial breach, the water level in the main channel is usually significantly higher than the ground level or the receiving water level behind the levee. A large head difference forms between the upstream and downstream sides of the breach, causing floodwaters to rush out at high speed and concentrate through the breach, resulting in severe erosion of the breach base, the levee heads on both sides, and the ground behind the levee. As the breach continues to cut downwards and widen laterally, the breach flow and the area affected by the disaster further increase. If the downstream side of the levee lacks a second protective boundary capable of receiving and restraining the breach floodwaters, the floodwaters can easily spread uncontrollably into residential areas, farmland, and areas containing infrastructure.

[0007] Existing measures for handling dike emergencies mainly include dike reinforcement, raising temporary secondary dikes, constructing filter wells, pressure-seepage platforms, pressure-relief wells, drainage ditches, breach sealing, and personnel evacuation. Among these, filter wells, pressure-seepage platforms, and pressure-relief wells are primarily used to control existing seepage risks; temporary secondary dikes and dike crest raising are mainly used to prevent flooding; and breach sealing is typically implemented after a local breach has formed.

[0008] Research and engineering practice on dam construction in water conservancy and hydropower projects show that raising the water level downstream of the dam opening can reduce the water level difference and hydraulic gradient between the upstream and downstream sides of the opening, increase the submergence degree of the outflow, and reduce the flow velocity and scouring effect at the opening. This principle explains that setting up a receiving water body with a certain depth downstream of the high-velocity outflow outlet can reduce the effective head difference on both sides of the outlet through the water cushion effect, and weaken the scouring effect. However, existing damming and scouring reduction measures mainly serve dam openings with defined locations and short-term construction processes. Their target objects, engineering layout, and operating conditions differ significantly from the protection of weak sections of long-distance dikes.

[0009] Traditional flood storage and detention areas primarily serve to divert floodwaters, reduce flood peaks, and retain flood volume within a river basin or region. Their design typically focuses on the flood inflow and outflow process, storage capacity, regional inundation extent, and population relocation arrangements. They are characterized by their large area and the regional flood inflow and inundation that occur after activation. These projects mainly address regional flood control issues and cannot directly replace counterweight, buffer, and secondary protection facilities installed to address weak sections of existing dikes.

[0010] The existing technology has the following main shortcomings:

[0011] (1) The existing dike emergency response mainly focuses on raising and reinforcing the original dike or plugging it after it collapses, and lacks a second protective boundary that is pre-constructed on the back side of the dike.

[0012] (2) For weak sections of the dike that cannot be thoroughly reinforced in the short term under high water level conditions, there is a lack of backwater counterpressure measures that can quickly reduce the difference in water head between the upstream and downstream sides of the existing dike and the hydraulic gradient of seepage.

[0013] (3) When a local breach occurs in an existing levee, the back side of the breach is usually a low-water ground with a lack of a water cushion with a certain water depth. The difference in water head between the front and back sides of the breach is large, which can easily cause the breach to cut down rapidly and widen laterally.

[0014] (4) Most of the existing energy dissipation and scour prevention facilities are located at the designated outlets or flood diversion outlets, which is difficult to adapt to the uncertain location of potential breaches in the dikes.

[0015] (5) Traditional flood storage and detention areas are mainly for regional flood diversion and flood volume regulation, which is difficult to meet the protection needs of reducing water head difference, buffering outflow from breaches and restricting flood spread in local weak sections of the dike.

[0016] (6) The overall demolition and reconstruction and seepage prevention renovation of existing dikes usually require a construction window during the dry season, which makes it difficult to meet the time requirements for emergency response before the arrival of floods.

[0017] (7) Existing technologies lack a method for coordinating the determination of the outer protection boundary, the pre-filled water level of the buffer space, the allowable head difference, the temporary containment capacity of local breaches, and the controlled discharge capacity.

[0018] Given the shortcomings of existing technologies, there is an urgent need for a structural layout and operation method suitable for weak sections of existing dikes. This method should provide auxiliary protection for these weak sections before floods arrive and limit the impact of the breach flood after a partial breach occurs, thus creating conditions for subsequent emergency response. Therefore, this invention proposes a structural layout and operation method to improve the safety of weak sections of dikes. Summary of the Invention

[0019] This invention provides a structural layout and operation method to improve the safety of weak sections of dikes. It mainly addresses the problem that traditional emergency measures such as temporarily raising and thickening the existing dike are insufficient to eliminate seepage defects in the dike body and foundation when weak sections of existing dikes are vulnerable to flooding, lack sufficient dry season construction windows, or cannot be immediately and thoroughly reinforced. At the same time, it solves the problem that after a local breach of an existing dike, the terrain elevation on the back side of the breach is low and there is a lack of receiving water bodies with sufficient depth, resulting in a large head difference between the upstream and downstream sides of the breach. This causes the breach water flow to easily cause rapid downcutting and lateral widening of the breach, and disorderly diffusion into the protected area behind the dike.

[0020] This invention is achieved using the following technical solution:

[0021] A structural layout and operation method for improving the safety of weak sections of a dike includes the following steps:

[0022] Step 1: Obtain identification information and basic engineering data of weak sections of the dike, and determine the location and protection range of the weak dike sections for setting up protective structures based on the identification information and basic engineering data;

[0023] Step 2: Based on the location and protection range of the weak dike section, determine the layout range and cross-sectional shape of the strip-shaped water-filled buffer space on the backwater side of the existing dike in the weak dike section, and determine the layout location and structural shape of the outer protection boundary outside the strip-shaped water-filled buffer space, forming a composite protection system consisting of the existing dike, the strip-shaped water-filled buffer space and the outer protection boundary arranged sequentially from the water-facing side to the backwater side of the existing dike.

[0024] Step 3: Obtain flood forecast information, main river water level information, existing dike seepage stability conditions, allowable water level at the outer protection boundary, and water level-volume relationship of the strip-shaped water-filled buffer space within the protection area. Determine the allowable range of the target pre-filled water level based on the above information. The lower limit of the target pre-filled water level is determined based on the allowable head difference between the upstream and downstream sides of the existing dike, the allowable hydraulic gradient of seepage, and the minimum water cushion buffer requirement after a local breach. The upper limit of the target pre-filled water level is determined based on the safe allowable water level at the outer protection boundary and the effective volume requirement reserved for the inflow of the designed local breach. Within the allowable range, the target pre-filled water level is determined, and the strip-shaped water-filled buffer space is filled with water to the target pre-filled water level through the filling and drainage facilities.

[0025] Step 4: During the rise of floodwaters in the main river channel and the sustained high water level, the water level of the main river channel, the water level of the strip-shaped water-filled buffer space, and the seepage status information of the existing dike are obtained in real time or periodically. Based on the effective head difference and seepage status of the upstream and downstream sides of the existing dike, the strip-shaped water-filled buffer space is replenished, water filling is stopped, or water is discharged in a controlled manner to keep the water level of the buffer space within the allowable range of the target pre-filled water level. This creates back pressure on the downstream side of the existing dike and controls the effective head difference and seepage hydraulic gradient of the upstream and downstream sides of the existing dike within the allowable range.

[0026] Step 5: After a partial breach occurs in the existing dike of the weak section, the pre-filled water in the strip-shaped water-filled buffer space forms a water cushion on the back side of the breach in the weak section to reduce the flow velocity and scouring intensity of the breaching water. The outer protective boundary receives and constrains the breaching flood, limiting the spread of the breaching flood to the protected objects behind the dike within the protection range.

[0027] Furthermore, in step 1, obtaining the identification information and basic engineering data of the weak sections of the dike, and determining the location and protection range of the weak dike sections for which protective structures are to be installed based on the identification information and basic engineering data, includes:

[0028] Obtain information on the construction date of the dike, historical records of potential dangers, details of previous heightening and reinforcement efforts and emergency repairs, information on filling materials, cross-sectional data of the dike body, data on the anti-seepage system, foundation conditions, contact surface information of structures penetrating the dike, distribution information of animal burrows, monitoring anomaly data, and seepage stability calculation results.

[0029] Based on the above data, sections of the dike with uneven filling materials, large differences in compaction quality along the course, or local failure to meet safety requirements, incomplete anti-seepage system, abnormal contact surfaces of dike-penetrating structures, obvious animal burrows or other biological disturbances, abnormal local seepage, or previous piping and soil erosion incidents are identified as the weak dike sections.

[0030] The protection range is determined based on the length of the weak section of the dike, the potential location of the breach, the possible local breach inflow process, the distribution of protected objects behind the dike, and the available land conditions.

[0031] Furthermore, in step 2, the outer protective boundary is composed of an outer protective dike, which includes the back slope of the outer protective dike, the road at the top of the outer protective dike, and the front slope of the outer protective dike; the outer protective boundary can also be composed of natural high ground, existing roadbed, existing flood control facilities, or a combination of the above structures.

[0032] The strip-shaped water-filled buffer space is arranged along the backwater side of the existing dike, and its longitudinal direction is parallel to or follows the general direction of the main river channel. The strip-shaped water-filled buffer space can be arranged continuously or divided into several segmented buffer units. Adjacent segmented buffer units can be connected in a controlled manner or operate independently.

[0033] Along the water-facing side of the main river channel towards the protected object behind the dike, the sequence is: main river channel, existing dike, strip-shaped water-filled buffer space, and outer protective boundary. The protected object behind the dike is located on the side of the outer protective boundary away from the strip-shaped water-filled buffer space.

[0034] The excavation boundary of the strip-shaped water-filled buffer space shall maintain a safe distance from the toe of the back slope of the existing dike or be equipped with a stable platform. The safe distance shall be determined based on the stability calculation of the back slope and foundation of the existing dike.

[0035] Furthermore, in step 3, determining the target pre-filling water level of the strip-shaped water-filling buffer space based on the flood forecast information and the main river channel water level information specifically involves:

[0036] Obtain the flood level of the main river channel ;

[0037] Based on flood forecasts, the main river water level rise process, the stability of seepage in existing dikes, the minimum water cushion buffer requirement after a local breach, the allowable water level at the outer protection boundary, and the remaining effective volume of the strip-shaped water-filled buffer space reserved for the inflow of the local breach, the lower limit Z of the target pre-filled water level is determined. b, L and the target pre-charge water level upper limit Z b, U And in satisfying Z b, L ≤Z b ≤Z b, U The target pre-filling water level of the strip-shaped water-filling buffer space is determined within the specified range. Target pre-filling water level Within a predetermined allowable range, the lower limit of which is determined by the existing dike seepage stability requirements and the conditions required to form an effective water cushion after a local breach, and the upper limit is determined by the safe allowable water level of the outer protection boundary and the effective volume requirements of the buffer space reserved for the inflow of the local breach.

[0038] The target pre-filled water level The effective head difference between the upstream and downstream sides of the existing dikes is lower than the flood level of the main river channel during the same period. ;

[0039] Based on the existing allowable hydraulic gradient of the dike, the stability conditions of the dike body and foundation, and the safety conditions of the outer protective structure, the effective head difference will be gradually increased. Within the design range, during the rise of floodwaters, when the water level of the main river channel, the seepage status of existing dikes, or the remaining effective volume of the buffer space changes, the target pre-filling water level shall be adjusted in stages according to the monitoring results within the allowable range of the target pre-filling water level, rather than maintaining a single fixed water level throughout the entire flood process.

[0040] Furthermore, in step 4, the pre-filled water in the strip-shaped water-filled buffer space located on the backwater side of the weak embankment section forms a backwater-side counterpressure on the existing embankment, that is, the pre-filled water acts on the backwater side of the existing embankment, with water pressure opposite to the main river flood: based on the main river water level and seepage monitoring results, the strip-shaped water-filled buffer space is continuously filled with water, stopped filling with water, or controlled to drain water, so that the pre-filled water level is kept within the allowable range.

[0041] The strip-shaped water-filled buffer space is filled with water in stages through a water filling and drainage system, and the rate of water level rise is controlled during the filling process.

[0042] Simultaneous monitoring of seepage flow, seepage line, pore water pressure, displacement and deformation of existing dikes;

[0043] If the monitoring results are abnormal, water filling will be suspended, the water level of the strip-shaped water-filled buffer space will be lowered, or measures such as reverse filtration, weighting, drainage, and local reinforcement will be taken.

[0044] Furthermore, in step 5, when the pre-filled water in the strip-shaped water-filled buffer space forms a water cushion buffer on the back side of the breach in the weak dike section:

[0045] The water cushion is formed by the same pre-filled water body determined in step 3 according to the pre-breach counterpressure, post-breach buffer, outer protective boundary safety and remaining effective volume. After the breach water flows into the pre-filled water body, it reduces the effective head difference between the water-facing side and the back side of the breach through water body reception, momentum exchange and turbulent energy dissipation, thereby reducing the direct scouring of the breach bottom, the two sides of the dike head and the ground behind the dike by the high-speed outflow.

[0046] Erosion protection zones are set up in the predicted breach impact area, the filling and drainage outlets and the downstream controlled drainage outlets. The erosion protection zones are constructed using cemented pebbles, masonry blocks, concrete, reinforced concrete, gabions, interlocking blocks or geocell structures.

[0047] Furthermore, in step 5, the act of using the outer protective boundary to receive and constrain the breach flood includes:

[0048] The strip-shaped water-filled buffer space provides an effective volume within the design response time to temporarily accommodate local outburst inflow. The effective volume is the difference between the volume corresponding to the highest allowable operating water level of the strip-shaped water-filled buffer space and the occupied volume corresponding to the target pre-filled water level.

[0049] Within the design response time T, the required effective volume of the buffer space can be checked according to the following formula:

[0050] ;

[0051] in, The available effective volume for the buffer space This is a localized outflow process. The flow rate discharged through downstream controlled outlets, control gates, or other safety channels;

[0052] The strip-shaped water-filled buffer space is equipped with a downstream controlled discharge outlet. Through the downstream controlled discharge outlet, the floodwater entering the strip-shaped water-filled buffer space is transported along the strip-shaped water-filled buffer space towards the downstream controlled discharge outlet, and discharged into the downstream section of the main river channel or a receiving space that has been safety-assessed.

[0053] Furthermore, it also includes step 6, after the flood process has ended:

[0054] Based on the process of water level decline in the main channel, the water level of the strip-shaped water-filled buffer space is reduced in stages to control the rate of water level decline, so that the rate of water level decline is coordinated with the changes in water level in the main channel and the stability conditions of the dike, and to prevent the water level in the buffer space from declining too quickly or remaining higher than the water level in the main channel for a long time.

[0055] Inspect and repair the outer protective boundary, erosion protection area, water filling and drainage facilities, and the strip-shaped water-filled buffer space for erosion, leakage, settlement, and deformation.

[0056] After the outer protective boundary has reliable water-blocking and restraining capabilities, the outer protective boundary is used as an auxiliary protective boundary to carry out segmented testing, seepage prevention reinforcement, dike reconstruction, slope toe treatment, or improvement of monitoring facilities on the existing dike.

[0057] Furthermore, in step 2, when the outer protective boundary adopts a permanent protective structure, the protective structure is divided into multiple construction sections, and a segmented construction interval area is retained between adjacent construction sections.

[0058] Prioritize the construction of foundation treatment, seepage prevention structure, dike filling, reverse filter drainage and slope protection for the outer protective boundary;

[0059] After the outer protective boundary is formed, the strip-shaped water-filled buffer space is formed by excavation or leveling on its inner side; a safe distance or stable platform that meets the stability requirements is always maintained between the excavation boundary of the buffer space and the toe of the back slope of the existing dike.

[0060] After each construction section meets the design requirements, the segmented construction intervals are excavated sequentially under low or controlled water level conditions, so that each section is connected to form a continuous or segmented controlled strip-shaped water-filled buffer space.

[0061] Furthermore, in step 2, when the outer protective boundary adopts an emergency-type protective structure:

[0062] Priority should be given to implementation in the land area on the backwater side of existing dikes, to avoid large-scale excavation of the dike body and slope toe of identified weak sections;

[0063] The strip-shaped water-filled buffer space is formed by prioritizing the use of natural low-lying areas behind the dike, drainage ditches, abandoned trenches, or areas that can be temporarily used.

[0064] An emergency outer protective dike is rapidly constructed along the outer side of the strip-shaped water-filled buffer space. The emergency outer protective dike adopts earth and stone filling, geotextile bags, prefabricated water retaining walls, steel sheet piles, mobile flood control structures, or combinations thereof.

[0065] The two ends of the emergency outer protective dike are connected to natural high ground, existing road high embankments, stable dike sections or other reliable water-retaining structures to form a closed outer protective boundary or a boundary with controlled discharge conditions.

[0066] After the outer protective boundary meets the temporary water blocking requirements, water is gradually pumped into the strip-shaped water-filling buffer space through mobile pump sets, temporary water pipelines, or existing culverts.

[0067] Compared with the prior art, the present invention has the following beneficial effects:

[0068] (1) It can achieve continuous and coordinated protection before and after the breach by using the same pre-filled water body. The present invention does not set up the back water pressure, water cushion buffer and breach flood containment separately, but coordinates the determination of the target pre-filled water level of the strip-shaped water-filled buffer space, so that the same pre-filled water body is used to reduce the head difference and seepage hydraulic gradient on the upstream and downstream sides when the existing dike has not experienced a local breach, and is directly converted into a water cushion on the downstream side of the breach after a local breach occurs, while retaining an effective volume for temporarily containing the inflow of the local breach, thus realizing a continuous conversion between pre-breach protection and post-breach buffer.

[0069] (2) It can form back pressure on the back side of the existing dike before the existing dike is partially breached. By forming a certain water level on the back side of the existing dike, the difference in water head between the front and back sides of the existing dike and the hydraulic gradient of seepage are reduced, which helps to reduce the risk of seepage damage such as concentrated seepage, piping and soil erosion.

[0070] (3) It can form a water cushion buffer after the existing dike partially collapses. The pre-filled water body receives the collapse water flow on the back side of the breach, and reduces the flow velocity and scouring intensity by reducing the effective head difference, momentum exchange and turbulent energy consumption, thereby slowing down the breach incision and lateral widening.

[0071] (4) It can limit the spread of breach floods to the protected area behind the dike. The outer protective dike forms a second protective boundary, allowing local breach floods to preferentially enter the controlled strip-shaped water-filled buffer space and be discharged through controlled drainage facilities, reducing the risk of floods directly entering residential areas, farmland and infrastructure areas.

[0072] (5) It can achieve targeted risk control with a smaller local protection range. The present invention takes the identified weak sections of the existing dikes as the implementation object. The layout range and effective volume of the strip-shaped water-filled buffer space are determined according to the potential local breach inflow, the design response time and the controlled discharge capacity. It does not aim to accommodate large-scale watershed floods. Therefore, it can avoid the large-scale flood diversion and regional inundation methods of traditional flood storage and detention areas, and achieve targeted protection for local weak dike sections.

[0073] (6) Applicable to emergency response when there is a lack of sufficient construction window before the arrival of flood. The outer protection works are mainly located in the land area behind the dike. They can be constructed without large-scale excavation of the existing weak dike sections under high water conditions, and can utilize natural low-lying areas or adopt rapid filling, geotextile bags and prefabricated structures to form a protective boundary.

[0074] (7) The scope of the project can be targeted according to the location of the weak sections of the dike. This invention does not require continuous construction along the entire river channel or the entire dike. It can be deployed only in one or more high-risk weak sections based on historical risks, monitoring anomalies, structural defects and flood risks, thereby avoiding the need to completely renovate the entire dike as the only solution.

[0075] (8) It is conducive to improving the economic efficiency of engineering construction. The strip-shaped water-filled buffer space can be formed by making priority to existing low-lying areas, ditches and available terrain. Excavated material that meets the filling requirements can be used for the filling of the outer protective dike, thereby reducing the need for large-scale waste materials, purchased filling materials and underwater construction.

[0076] (9) It can avoid large-scale disturbance to the existing weak dike body under high water conditions. By forming the outer protective boundary and the strip-shaped water-filled buffer space in advance, it can provide auxiliary protection conditions and construction space for the subsequent inspection, reinforcement or reconstruction of the existing dike.

[0077] (10) It can adapt to the uncertainty of the location of potential breaches. The strip-shaped water-filled buffer space can be set up continuously or in segments along the weak section of the dike. Compared with setting energy dissipation facilities only at fixed outlets or flood diversion outlets, it can cover potential breaches with uncertain locations within a certain length range.

[0078] (11) Flexible structural layout and implementation methods. The outer protective dike can be a permanent earth-rock dike, a temporary earth dike, geotextile bags, prefabricated retaining walls, steel sheet piles or a combination structure; the strip-shaped water-filled buffer space can be formed by utilizing natural terrain or artificial excavation, and can adapt to different terrain and geological conditions, construction period and permanent or emergency protection needs. Attached Figure Description

[0079] Figure 1 This is the original river channel layout plan;

[0080] Figure 2 yes Figure 1 Sectional view along line AA;

[0081] Figure 3 It is a plan layout of the outer protective structure for phased construction;

[0082] Figure 4 This is a cross-sectional layout diagram of the outer protective structure after its completion;

[0083] Figure 5 This is a schematic diagram showing the back pressure of water filling the strip-shaped buffer space before the flood and the water flow at the weak point of the breach;

[0084] Figure 6 This is a schematic diagram of flood diversion in the buffer space;

[0085] Figure 7 This is a schematic diagram of the process for collaboratively determining the target pre-filled water level.

[0086] In the diagram: 1-Protected object, 1.1-Residential dwellings, 1.2-Farmland; 2-Main river channel, 2.1-Existing levee backwater slope, 2.2-Existing levee top road, 2.3-Existing levee water-facing slope, 2.4-Main river channel flood discharge channel; 3-Outer protective levee backwater slope; 4-Outer protective levee top road; 5-Outer protective levee water-facing slope; 6-Ring-shaped water-filled buffer space; 7-Water-filling and drainage control facilities; 8-Water-filling and drainage control gate; 9-Erosion protection and bottom protection zone; 10-Segmented construction interval zone; 11-Pre-filling water flow direction; 12-Controlled transport direction of breach flood; 13-Temporary water-retaining cofferdam during construction; 14-Weak section of levee; 15-Local breach; 16-Main river channel flood level line; 17-Buffer space pre-filling water level line; 18-Downstream controlled discharge outlet. Detailed Implementation

[0087] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0088] This invention provides a structural layout and operation method for improving the safety of weak sections of dikes, comprising the following steps:

[0089] Step S1: Identification of Weak Dike Sections and Determination of Protection Scope - Obtain information on the construction date, historical hazard records, structural status, foundation conditions, seepage monitoring, structures penetrating the dike, biological disturbance, and flood risk of the existing dike. Identify weak dike sections that are difficult to completely reinforce in the short term, and determine the protection scope based on the potential breach impact range and the objects to be protected behind the dike.

[0090] Step S2: Arrangement of protective structure - Determine the layout range of the strip-shaped water-filled buffer space on the back side of the weak section of the dike, and set an outer protective boundary outside the strip-shaped water-filled buffer space, so that the main channel, the existing dike, the strip-shaped water-filled buffer space and the outer protective boundary are formed sequentially from the water-facing side to the back side of the existing dike.

[0091] Step S3: Determining the target pre-filling water level and pre-filling water – Based on flood forecasts, the rise in water level in the main river channel, the stability of seepage in existing dikes, the buffer requirements of local breach water cushions, the allowable water level of the outer protection boundary, the remaining effective volume of the buffer space, and the controlled discharge capacity, determine the target pre-filling water level and allowable range of variation of the strip-shaped water-filling buffer space, and fill the strip-shaped water-filling buffer space with water in stages to the target pre-filling water level before the flood arrives.

[0092] Step S4: Maintaining and dynamically adjusting back pressure during floods – During the rise and sustained high water levels in the main channel, based on the main channel water level, buffer space water level, and existing dike seepage flow, seepage line, pore water pressure, displacement, and deformation monitoring results, maintain or adjust the target pre-filled water level so that the effective head difference and seepage hydraulic gradient on the upstream and downstream sides of the existing dike are within the allowable range.

[0093] Step S5: Water cushion buffer and flood restraint after local breach - When a local breach occurs in the weak section of the dike, the same pre-filled water body formed in step S3 is used to form a water cushion on the back side of the breach to reduce the flow velocity and scouring effect of the breach water; at the same time, the breach flood entering the strip-shaped water-filled buffer space is restrained by the outer protective boundary and discharged to the safe receiving area through the downstream controlled discharge facilities.

[0094] Step S6: Post-flood receding water and restoration of protective status—After the flood process ends, the water level of the strip-shaped water-filled buffer space is reduced in stages according to the main river channel receding process, and the outer protective boundary, water filling and drainage facilities, scour prevention facilities and buffer space are inspected and repaired; when conditions permit, the existing weak sections of the dike are inspected, reinforced or rebuilt.

[0095] The specific implementation methods for each step are described in detail below.

[0096] Step S1: Identification of weak sections of the embankment and determination of the protection scope

[0097] In this step, the identification information and basic engineering data of the weak sections of the dike are first obtained. The identification information and basic engineering data include, but are not limited to: the construction year of the dike, historical records of dangerous situations, the situation of previous heightening and thickening and emergency repairs, information on filling materials, cross-sectional data of the dike body, data on the anti-seepage system, foundation conditions, contact surface information of structures penetrating the dike, information on the distribution of animal burrows, monitoring anomaly data and seepage stability calculation results.

[0098] Based on the above data, sections of the dike with uneven filling materials, large differences in compaction quality along the course, or local failure to meet safety requirements, incomplete anti-seepage system, abnormal contact surfaces of structures penetrating the dike, obvious animal burrows or other biological disturbances, abnormal local seepage, or previous piping and soil erosion incidents were identified as the weak dike section 14.

[0099] The protection range is determined based on the length of the weak levee section 14, the potential breach location, the possible local breach inflow process, the distribution of protected objects behind the levee, and the available land conditions. The protection structure may be arranged only in a single local weak levee section, or it may be arranged separately in multiple independent weak levee sections, and it is not required to be continuously installed along the entire main channel.

[0100] like Figure 1 and Figure 2As shown, the main channel 2 is located between the existing dikes on both sides, and the main channel flood passage 2.4 is located in the flow area between the existing dikes on both sides. Each existing dike includes the upstream slope 2.3 facing the main channel 2, the top road 2.2 of the existing dike located on the top of the dike, and the downstream slope 2.1 facing the area behind the dike. The protected objects 1, such as houses 1.1 and farmland 1.2, are located in the area behind the dike corresponding to the downstream side of the existing dike.

[0101] Step S2: Arrangement of protective structure

[0102] In this step, based on the location and protection range of the weak dike section, the layout range and cross-sectional shape of the strip-shaped water-filled buffer space 6 are determined on the backwater side of the existing dike in the weak dike section. The layout position and structural shape of the outer protection boundary are determined on the outside of the strip-shaped water-filled buffer space 6, forming a composite protection system consisting of the existing dike, the strip-shaped water-filled buffer space 6 and the outer protection boundary arranged sequentially from the water-facing side to the backwater side of the existing dike.

[0103] like Figure 3 and Figure 4 As shown, for the weak section 14 of the dike, a strip-shaped water-filled buffer space 6 is set on the backwater side of the existing dike, and an outer protective boundary is set on the side of the strip-shaped water-filled buffer space 6 away from the existing dike. In the illustrated embodiment, the outer protective boundary is composed of an outer protective dike, which includes the water-facing slope 5 of the outer protective dike, the road 4 at the top of the outer protective dike, and the backwater slope 3 of the outer protective dike; wherein, the water-facing slope 5 of the outer protective dike faces the strip-shaped water-filled buffer space 6, and the backwater slope 3 of the outer protective dike faces the area where the protected object 1 is located. From the main river channel 2 towards the protected object 1 behind the dike, the spatial arrangement of the main river channel 2, the existing dike, the strip-shaped water-filled buffer space 6, and the outer protective boundary is formed in sequence, so that the strip-shaped water-filled buffer space 6 is located between the existing dike and the outer protective boundary. The outer protective boundary can also be composed of natural high ground, existing roadbed, existing flood control facilities, or a combination of the above structures.

[0104] The strip-shaped water-filled buffer space 6 is arranged along the backwater side of the existing dike, and its longitudinal direction is parallel to or follows the general direction of the main river channel 2. The strip-shaped water-filled buffer space 6 can be arranged continuously or divided into several segmented buffer units, and adjacent segmented buffer units can be connected in a controlled manner or operate independently.

[0105] A safe distance or a stable platform shall be maintained between the excavation boundary of the strip-shaped water-filled buffer space 6 and the toe of the existing embankment's back slope. The safe distance shall be determined based on the stability calculations of the existing embankment's back slope and foundation. If necessary, a reverse-filter drainage body, seepage-proof cover, ballast platform, toe protection structure, or other stable protection structure shall be installed between the toe of the existing embankment's back slope and the strip-shaped water-filled buffer space 6.

[0106] The strip-shaped water-filled buffer space 6 can be formed by utilizing existing low-lying areas, ditches or other suitable terrain, or it can be formed by artificial excavation. Its cross-sectional shape is determined according to the terrain conditions, pre-filled water level, local breach inflow process, slope stability and construction conditions.

[0107] The crest elevation of the outer protective dike is determined comprehensively based on the highest possible water level, fluctuation level, settlement allowance, and safety freeboard that the strip-shaped water-filled buffer space 6 may reach under pre-filling and design partial breach inflow conditions. Let the highest instantaneous water level of the strip-shaped water-filled buffer space 6 under the design partial breach inflow condition be... The required safety level is extremely high. The control elevation of the outer protective dike crest is... satisfy:

[0108]

[0109] The cross-sectional dimensions, seepage prevention structure, drainage and filter structure, and slope protection type of the outer protective dike shall be specifically determined based on the aforementioned control elevation, topographic and geological conditions, and stability requirements during the construction and operation periods.

[0110] like Figure 3 As shown, the filling and drainage control facility 7 and the filling and drainage control gate 8 are connected to the strip-shaped filling buffer space 6, and are used to control the filling, water level maintenance, and controlled drainage of the strip-shaped filling buffer space 6. The filling and drainage control facility 7 can be arranged in conjunction with the water supply body, existing water conveyance facilities, or controlled drainage channels; when it needs to cross existing dikes, it should be preferentially arranged in stable dike sections that have undergone safety assessment. The scour protection zone 9 is set at the filling and drainage outlet, the area affected by the predicted local breach 15, the downstream controlled discharge outlet 18, and other locations where large flow velocities or local scour may occur, in order to improve the scour resistance of the corresponding areas.

[0111] To accommodate phased construction, the longitudinal direction of the strip-shaped water-filled buffer space 6 can be divided into multiple construction sections, with a segmented construction interval 10 set between adjacent construction sections. The segmented construction interval 10 is arranged transversely along the strip-shaped water-filled buffer space 6, used to temporarily isolate adjacent construction sections during construction. Once the adjacent sections meet the connectivity requirements, the segmented construction interval 10 is removed, connecting the adjacent strip-shaped water-filled buffer spaces 6. A temporary water-retaining cofferdam 13 is set on the side of the main river channel where the drainage and filling facilities need to be constructed, used to temporarily isolate the corresponding construction area from the main river channel 2 during construction, creating water-retaining conditions for the construction of the drainage and filling control facilities 7 and the drainage and filling control gate 8.

[0112] Specific implementation methods for using a permanent protective structure for the outer protective boundary:

[0113] The protective structure is divided into multiple construction sections, with a segmented construction interval 10 maintained between adjacent sections. Priority is given to the construction of the foundation treatment, seepage prevention structure, dike filling, reverse filtration drainage, and slope protection of the outer protective boundary. After the outer protective boundary is formed, the strip-shaped water-filled buffer space 6 is excavated or leveled on its inner side; a safe distance or stable platform meeting stability requirements is always maintained between the excavation boundary of the buffer space and the toe of the existing dike's back slope. Soil and rock materials meeting filling requirements from the excavation can be used for filling the outer protective dike, and layered spreading, compaction, and quality testing are carried out according to design requirements. When new drainage facilities are required to penetrate the dike, adjacent stable dike sections should be selected first, and a temporary water-retaining cofferdam 13 should be set up on the corresponding main channel side to isolate the construction area from the main channel water. Under the protection of the temporary water-retaining cofferdam 13, the drainage control gate 8, drainage control facilities 7, seepage prevention and water-stopping structure, reverse filtration structure, and scour protection bottom protection zone 9 are constructed. After the filling and drainage control gate 8 is installed and passes the opening, closing, water-stopping and water-blocking tests, the embankment structure at the section penetrating the embankment is restored, and the temporary water-blocking cofferdam 13 during the construction period is dismantled in accordance with the construction organization requirements. After each construction section meets the design requirements, the segmented construction interval zone 10 is excavated in sequence under low water level or controlled water level conditions, so that each section is connected to form a continuous or segmented controlled strip-shaped water-filling buffer space 6.

[0114] Specific implementation methods for using an emergency-type protective structure for the outer protective boundary:

[0115] Priority should be given to implementation on the land area on the backwater side of existing dikes to avoid large-scale excavation of identified weak sections of the dike body and slope toe. The strip-shaped water-filled buffer space 6 should be formed by utilizing natural low-lying areas, drainage ditches, abandoned trenches, or temporarily usable areas behind the dike, minimizing deep excavation and large-scale earthwork. An emergency outer protective dike should be rapidly constructed along the outside of the strip-shaped water-filled buffer space 6. This emergency outer protective dike may employ earth-rock filling, geotextile bags, prefabricated retaining walls, sheet piles, mobile flood control structures, or combinations thereof. The two ends of the emergency outer protective dike should connect with natural high ground, existing road embankments, stable dike sections, or other reliable water-retaining structures to form a closed or controlled drainage boundary. Once the outer protective boundary meets the temporary water-retaining requirements, the strip-shaped water-filled buffer space 6 should be filled with water in stages through mobile pump sets, temporary water pipelines, or existing culverts. Deep excavation near the slope toe of the existing dike should be avoided during emergency construction. If terrain leveling is necessary, the excavation range and depth should be controlled according to the stability conditions of the embankment slope and foundation to prevent construction disturbance from weakening the stability of the existing embankment.

[0116] Step S3: Coordinated determination of target pre-filling water level and pre-filling water

[0117] In this step, flood forecast information, main river water level information, existing dike seepage stability conditions, allowable water level of the outer protection boundary, and water level-volume relationship of the strip-shaped water-filled buffer space 6 are obtained within the protection area. Based on the above information, the allowable range of the target pre-filled water level is determined.

[0118] like Figure 7 As shown, the lower limit Z of the target pre-filled water level b, L The upper limit Z of the target pre-filling water level is determined based on the allowable head difference between the upstream and downstream sides of the existing dike, the allowable hydraulic gradient of seepage, and the minimum water cushion buffer requirement after a local breach. b, U The water level is determined based on the safe allowable water level of the outer protective boundary and the effective volume requirement reserved for the inflow of the designed local breach. Specifically, the flood level of the main channel is obtained. Based on flood forecasts, the main river water level rise process, the stability of seepage in existing dikes, the minimum water cushion buffer requirement after a local breach, the allowable water level at the outer protection boundary, and the remaining effective volume of the strip-shaped water-filled buffer space 6 reserved for the inflow of the local breach, the lower limit of the target pre-filled water level Z is determined. b, L and the target pre-charge water level upper limit Z b, U , and in satisfying Z b, L ≤Z b ≤Z b, U Within the range, determine the target pre-filling water level Z of the strip-shaped water-filling buffer space 6. b .

[0119] Target pre-filled water level Z b The effective head difference between the upstream and downstream sides of the existing dikes is lower than the flood level of the main river channel during the same period. Based on the existing allowable hydraulic gradient of the dike, the stability conditions of the dike body and foundation, and the safety conditions of the outer protective structure, the effective head difference ΔH will be gradually controlled within the design range.

[0120] When determining the target pre-filling water level, the following interdependent relationships need to be comprehensively coordinated: As the pre-filling water level rises, the effective head difference between the upstream and downstream sides of the existing dike decreases, the back pressure on the downstream side and the buffering effect of the water cushion after a local breach increase, but the remaining effective volume of the strip-shaped water-filling buffer space 6 decreases accordingly, and the water pressure on the outer protective boundary increases; as the pre-filling water level decreases, the remaining effective volume increases, but the back pressure on the downstream side of the existing dike and the buffering effect of the water cushion after a local breach weaken accordingly. Therefore, the target pre-filling water level is not uniformly determined by a fixed head difference, nor is a higher or lower pre-filling water level used as a single optimization objective. Instead, based on satisfying the above lower and upper constraints, the target pre-filling water level should be determined by using seepage stability calculations, hydrodynamic calculations, numerical simulations, physical model tests, analogies with similar projects, or a combination of the above methods, taking into account the back pressure before breach, the buffering effect of the water cushion after breach, the safety of the outer protective boundary, and the remaining effective volume of the buffer space.

[0121] Within the design response time T, the required effective volume of the buffer space is checked according to the following formula:

[0122]

[0123] in, The available effective volume of the buffer space is the difference between the volume corresponding to the highest allowable operating water level of the strip-shaped water-filled buffer space 6 and the occupied volume corresponding to the target pre-filled water level. This is a localized outflow process. The flow rate discharged through downstream controlled outlet 18, control gate or other safety passage.

[0124] Once the target pre-filled water level is determined, if Figure 5 As shown, before a flood arrives, when the flood forecast, water level forecast, or dike safety monitoring results meet the preset activation conditions, water is pumped in stages into the strip-shaped water-filling buffer space 6 along the pre-filling water flow direction 11 through the filling and draining control gate 8, fixed pumping stations, mobile pump sets, temporary water conveyance pipelines, existing dike-penetrating structures, or other water sources, so that the pre-filling water level line 17 of the buffer space gradually rises to the target pre-filling water level. During the non-high water level operation phase, the strip-shaped water-filling buffer space can be kept at a low water level or emptied according to operation and management requirements; when the flood forecast, water level forecast, or dike safety monitoring results meet the preset activation conditions, the pre-filling process is initiated.

[0125] Step S4: Maintaining and dynamically adjusting back pressure during the flood process

[0126] In this step, during the rise of floodwaters in the main river channel and the sustained high water level, the water level of the main river channel, the water level of the strip-shaped water-filled buffer space, and the seepage status of the existing dike are acquired in real time or periodically. Based on the effective head difference and seepage status of the upstream and downstream sides of the existing dike, the strip-shaped water-filled buffer space 6 is replenished, water filling is stopped, or water is discharged in a controlled manner to keep the water level of the buffer space within the allowable range of the target pre-filled water level.

[0127] The pre-filled water acts on the back side of the existing dike, forming a relative water pressure with the main river flood, thereby creating a counter pressure on the back side of the existing dike and controlling the effective head difference and seepage hydraulic gradient between the upstream and downstream sides of the existing dike within the allowable range.

[0128] The strip-shaped water-filled buffer space 6 is filled with water in stages through a filling and drainage system, with the rate of water level rise controlled during the filling process. Simultaneously, the seepage flow, phreatic line, pore water pressure, displacement, and deformation of the existing dike are monitored. If any abnormalities are detected, filling is suspended, the water level in the strip-shaped water-filled buffer space 6 is lowered, or measures such as reverse filtration, weighting, drainage, and local reinforcement are implemented to prevent the filling process from adversely affecting the stability of the existing dike, buffer space slope, or foundation.

[0129] During the rise of floodwaters, when the water level of the main river channel, the seepage status of existing dikes, or the remaining effective volume of the buffer space changes, the target pre-filling water level shall be adjusted in stages according to the monitoring results within the allowable range of the target pre-filling water level, rather than maintaining a single fixed water level throughout the entire flood process.

[0130] Step S5: Water cushion buffer and flood restraint after local breach

[0131] In this step, such as Figure 5 and Figure 6 As shown, when a local breach 15 forms in the existing weak section 14 of the dike, the floodwater from the main river channel enters the strip-shaped water-filled buffer space 6 through the local breach 15, and the pre-filled water in the strip-shaped water-filled buffer space 6 forms a water cushion buffer on the back side of the breach in the weak dike section.

[0132] The water cushion is formed by the same pre-filled water body determined in step S3 according to the coordinated consideration of pre-breach back pressure, post-breach buffer, outer protective boundary safety, and remaining effective volume. The pre-filled water level line 17 of the buffer space is located below the main river flood level line 16, and the effective head difference between the upstream and downstream sides is maintained by calculation. The pre-filled water body, which has been determined and maintained in step S4 according to the coordinated consideration of pre-breach back pressure, post-breach water cushion buffer, outer protective boundary safety, and remaining effective volume, directly switches from the downstream back pressure working state to the water cushion buffer working state after the formation of the local breach 15, forming a water cushion with a certain water depth on the downstream side of the local breach 15.

[0133] After the breach water flows into the pre-filled water body, the effective head difference between the upstream and downstream sides of the breach is reduced through water body reception, momentum exchange, and turbulent energy dissipation. This reduces the direct scouring of the breach bottom, the two sides of the dike head, and the ground behind the dike by the high-speed outflow, thereby slowing down the continuous downcutting and lateral widening of the local breach 15. Scour protection zones 9 are set up in the predicted breach impact area, the filling and drainage outlets, and the downstream controlled discharge outlets. These scour protection zones 9 use cemented pebbles, masonry blocks, concrete, reinforced concrete, gabions, interlocking blocks, or geocell structures to reduce the formation of deep scour pits and prevent further threats to existing dikes and outer protective dikes from localized scouring.

[0134] The strip-shaped water-filled buffer space 6 provides an effective volume within the design response time to temporarily accommodate local outflow. The effective volume is the difference between the volume corresponding to the highest allowable operating water level of the strip-shaped water-filled buffer space 6 and the occupied volume corresponding to the target pre-filled water level, as shown in the verification formula in step S3 above.

[0135] The outer protective boundary receives and constrains the breach flood, limiting its spread to the protected objects behind the dike within the protected area. The breach flood entering the strip-shaped water-filled buffer space 6 is constrained by the outer protective dike and transported downstream along the controlled transport direction 12. The strip-shaped water-filled buffer space 6 is equipped with a downstream controlled discharge outlet 18, through which the breach flood entering the strip-shaped water-filled buffer space 6 is transported along the strip-shaped water-filled buffer space 6 towards the downstream controlled discharge outlet 18, and discharged into the downstream section of the main river channel or a receiving space that has undergone safety assessment. The protected object 1 is located on the side of the outer protective boundary away from the strip-shaped water-filled buffer space 6, forming a second spatial protective boundary between the local breach flood entering the strip-shaped water-filled buffer space 6 and the protected object 1.

[0136] Based on the water level in the buffer space, the safety status of the outer protective dike, and the downstream receiving capacity, the downstream controlled discharge outlet 18 is opened to discharge the floodwater in a controlled manner. When the water level in the buffer space approaches the design maximum water level, the downstream controlled discharge capacity should be increased, emergency drainage facilities should be activated, or other emergency dispatching measures should be taken to prevent the outer protective dike from being subjected to water levels exceeding the design conditions.

[0137] After a local breach occurs, personnel and equipment can be organized to seal, carry out emergency repairs and temporary reinforcement of the breach 15 under the constraint and protection of the outer protective dike.

[0138] Step S6: Post-flood receding water and restoration of protective measures

[0139] In this step, after the flood process ends, the water level of the strip-shaped water-filled buffer space 6 is reduced in stages according to the water level drop process of the main river channel. The rate of water level drop is controlled so that the rate of water level drop is coordinated with the water level change of the main river channel and the stability conditions of the dike. This prevents the water level of the buffer space from dropping too quickly or rising too high for a long time relative to the water level of the main river channel, and also avoids the rapid water receding and instability of the existing dike, outer protective dike or buffer space slope caused by the rapid water drop.

[0140] Inspect and repair the outer protective boundary, the anti-erosion bottom protection area 9, the filling and drainage facilities, and the strip-shaped water-filled buffer space 6 for erosion, leakage, settlement, and deformation.

[0141] After the outer protective boundary has proven its reliable water-blocking and restraining capabilities, it serves as an auxiliary protective boundary for segmented testing, seepage prevention reinforcement, dike reconstruction, slope toe treatment, or improvement of monitoring facilities on the existing dike. Only after completing and passing acceptance of one dike renewal section can the work proceed to the next, avoiding large-scale simultaneous demolition or disturbance of the existing dike. This allows for the gradual improvement of the existing dike's material properties, cross-sectional structure, seepage prevention and drainage system, and operational monitoring conditions while controlling flood risks during the construction period. After reinforcement or reconstruction of the existing dike, the outer protective structure can continue to serve as a second line of defense against remaining risks from localized failures; whether it should be retained, adjusted, or demolished subsequently requires a specific assessment based on flood control planning, dike safety, land use, and operation and maintenance requirements.

[0142] This invention addresses the main risks faced by vulnerable sections of dikes during flood season—pre-breach seepage damage and post-breach flood uncontrollability—and achieves the following technical effects through synergistic innovation in structural layout and operation methods:

[0143] I. Pre-collapse protection effect: Reduces the risk of infiltration damage

[0144] This invention creates a backwater-side counterpressure by setting up a strip-shaped water-filled buffer space on the backwater side of a weak section of the dike and filling it with water to the target pre-filled level, thus generating backwater-side counterpressure before the existing dike experiences localized breaches. This counterpressure directly reduces the effective hydraulic head difference between the upstream and downstream sides of the existing dike and the hydraulic gradient of seepage through the dike body and foundation, thereby fundamentally reducing the likelihood of seepage-related hazards such as concentrated seepage, piping, and soil erosion. This effect is particularly significant for existing weak sections of the dike with uneven fill materials, significant differences in compaction quality, or incomplete seepage prevention systems.

[0145] II. Buffering effect during ulceration: slows down the ulceration process.

[0146] When a weak section of an existing dike experiences a localized breach, the same pre-filled water body that already existed within the strip-shaped water-filled buffer space before the breach can be directly converted into a water cushion on the back side of the breach without additional activation time. This water cushion reduces the effective head difference between the upstream and downstream sides of the breach, and decreases the characteristic velocity of the high-speed breach flow and the scouring intensity on the bottom of the breach, the two dike heads, and the ground behind the dike through physical processes such as water body reception, momentum exchange, and turbulent energy dissipation. This slows down the continuous downward cutting and lateral widening of the breach in the time dimension, buying valuable time for subsequent emergency repairs.

[0147] III. Post-collapse restraint effect: Limits the spread of floodwaters.

[0148] The outer protective boundary, serving as a second protective boundary, together with the strip-shaped water-filled buffer space, constitutes a temporary containment and controlled transport channel for outburst floods. Outburst floods entering the buffer space are spatially constrained by the outer protective boundary, and are transported longitudinally along the buffer space in a controlled manner to downstream controlled discharge outlets for safe discharge. This prevents the disorderly spread of floodwaters to residential areas, farmland, and infrastructure areas, thus controlling the impact of the outburst flood within a predictable protective range.

[0149] IV. Synergistic Optimization Effect of Pre-filled Water Level

[0150] This invention unifies four functional requirements—pre-breakdown back pressure, post-breakdown water cushion buffering, outer protective boundary safety, and temporary containment of local breach inflow—in the determination of a single pre-filling water level by setting a lower limit constraint (determined by seepage stability requirements and minimum water cushion buffering requirements) and an upper limit constraint (determined by the safe allowable water level of the outer protective boundary and the remaining effective volume requirements). This collaborative determination mechanism avoids the coordination difficulties caused by setting different water levels or different functional zones separately, enabling the same pre-filled water body to play different but continuously effective protective roles at different stages.

[0151] V. Flexibility of Project Implementation

[0152] The structural layout of this invention can be flexibly selected as either a permanent or emergency implementation method depending on the actual situation. The permanent implementation method, through segmented and phased construction, avoids the impact of large-scale simultaneous excavation on the stability of existing dikes. The emergency implementation method can quickly form a protective boundary using natural low-lying areas, geotextile bags, prefabricated retaining walls, etc., and can still rapidly establish protective capabilities even when there is a lack of sufficient construction windows before a flood. Both implementation methods target identified local weak sections of the dike, do not require continuous construction along the entire line, and keep project investment and land occupation controllable.

[0153] VI. Construction Safety and Renewability

[0154] This invention prioritizes implementing protective structures on the land area on the backwater side of existing dikes, avoiding large-scale excavation of identified weak sections of the dike and its toe under high water conditions, thus reducing the risk of disturbing existing dikes from a construction organization perspective. Simultaneously, once the outer protective boundary is formed, it can serve as an auxiliary protective boundary for subsequent segmented testing, seepage prevention reinforcement, and dike reconstruction of the existing dike, creating safe working conditions for the long-term, gradual renewal of existing dikes and achieving a seamless connection between emergency protection and permanent restoration.

[0155] In summary, this invention utilizes a progressive protection chain of "backwater side counterpressure—breach cushion buffer—outer boundary constraint—controlled discharge" to continuously function in the three stages of pre-breach, during-breach, and post-breach, systematically improving the safety of weak sections of the dike from three aspects: reducing the risk of seepage damage, slowing the development of the breach, and limiting the spread of floodwater.

[0156] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A structural arrangement and operation method for improving the safety of weak sections of a dike, characterized in that, Includes the following steps: Step 1: Obtain identification information and basic engineering data of weak sections of the dike, and determine the location and protection range of the weak dike sections for setting up protective structures based on the identification information and basic engineering data; Step 2: Based on the location and protection range of the weak dike section, determine the layout range and cross-sectional shape of the strip-shaped water-filled buffer space on the backwater side of the existing dike in the weak dike section, and determine the layout location and structural shape of the outer protection boundary outside the strip-shaped water-filled buffer space, forming a composite protection system consisting of the existing dike, the strip-shaped water-filled buffer space and the outer protection boundary arranged sequentially from the water-facing side to the backwater side of the existing dike. Step 3: Obtain flood forecast information, main river water level information, existing dike seepage stability conditions, allowable water level at the outer protection boundary, and water level-volume relationship of the strip-shaped water-filled buffer space within the protection area. Determine the allowable range of the target pre-filled water level based on the above information. The lower limit of the target pre-filled water level is determined based on the allowable head difference between the upstream and downstream sides of the existing dike, the allowable hydraulic gradient of seepage, and the minimum water cushion buffer requirement after a local breach. The upper limit of the target pre-filled water level is determined based on the safe allowable water level at the outer protection boundary and the effective volume requirement reserved for the inflow of the designed local breach. Within the allowable range, the target pre-filled water level is determined, and the strip-shaped water-filled buffer space is filled with water to the target pre-filled water level through the filling and drainage facilities. Step 4: During the rise of floodwaters in the main river channel and the sustained high water level, the water level of the main river channel, the water level of the strip-shaped water-filled buffer space, and the seepage status information of the existing dike are obtained in real time or periodically. Based on the effective head difference and seepage status of the upstream and downstream sides of the existing dike, the strip-shaped water-filled buffer space is replenished, water filling is stopped, or water is discharged in a controlled manner to keep the water level of the buffer space within the allowable range of the target pre-filled water level. This creates back pressure on the downstream side of the existing dike and controls the effective head difference and seepage hydraulic gradient of the upstream and downstream sides of the existing dike within the allowable range. Step 5: After a partial breach occurs in the existing dike of the weak section, the pre-filled water in the strip-shaped water-filled buffer space forms a water cushion on the back side of the breach in the weak section to reduce the flow velocity and scouring intensity of the breach water. The outer protective boundary receives and constrains the breach flood, limiting the spread of the breach flood to the protected objects behind the dike within the protection range.

2. The method according to claim 1, characterized in that, In step 1, obtaining identification information and basic engineering data of weak sections of the dike, and determining the location and protection range of the weak dike sections for which protective structures are to be installed based on the identification information and basic engineering data, includes: Obtain information on the construction date of the dike, historical records of potential dangers, details of previous heightening and reinforcement efforts and emergency repairs, information on filling materials, cross-sectional data of the dike body, data on the anti-seepage system, foundation conditions, contact surface information of structures penetrating the dike, distribution information of animal burrows, monitoring anomaly data, and seepage stability calculation results. Based on the above data, sections of the dike that are identified as weak sections include those with uneven filling materials, significant differences in compaction quality along the dike, local failure to meet safety requirements, incomplete anti-seepage system, abnormal contact surfaces of structures penetrating the dike, obvious animal burrows or other biological disturbances, abnormal local seepage, or those that have experienced piping and soil erosion. The protection range is determined based on the length of the weak section of the dike, the potential location of the breach, the possible local breach inflow process, the distribution of protected objects behind the dike, and the available land conditions.

3. The method according to claim 1, characterized in that, In step 2, the outer protective boundary is composed of an outer protective dike, which includes the back slope of the outer protective dike, the road at the top of the outer protective dike, and the front slope of the outer protective dike; the outer protective boundary can also be composed of natural high ground, existing roadbed, existing flood control facilities, or a combination of the above structures. The strip-shaped water-filled buffer space is arranged along the backwater side of the existing dike, and its longitudinal direction is parallel to or follows the general direction of the main river channel. The strip-shaped water-filled buffer space can be arranged continuously or divided into several segmented buffer units. Adjacent segmented buffer units can be connected in a controlled manner or operate independently. Along the water-facing side of the main river channel towards the protected object behind the dike, the sequence is: main river channel, existing dike, strip-shaped water-filled buffer space, and outer protective boundary. The protected object behind the dike is located on the side of the outer protective boundary away from the strip-shaped water-filled buffer space. The excavation boundary of the strip-shaped water-filled buffer space shall maintain a safe distance from the toe of the back slope of the existing dike or be equipped with a stable platform. The safe distance shall be determined based on the stability calculation of the back slope and foundation of the existing dike.

4. The method according to claim 1, characterized in that, In step 3, determining the target pre-filling water level of the strip-shaped water-filling buffer space based on the flood forecast information and the main river channel water level information specifically involves: Obtain the flood level of the main river channel ; Based on flood forecasts, the main river water level rise process, the stability of seepage in existing dikes, the minimum water cushion buffer requirement after a local breach, the allowable water level at the outer protection boundary, and the remaining effective volume of the strip-shaped water-filled buffer space reserved for the inflow of the local breach, the lower limit Z of the target pre-filled water level is determined. b, L and the upper limit of the target pre-charge water level Z b, U And in satisfying Z b, L ≤Z b ≤Z b, U The target pre-filling water level of the strip-shaped water-filling buffer space is determined within the specified range. Target pre-filling water level Within a predetermined allowable range, the lower limit of which is determined by the existing dike seepage stability requirements and the conditions required to form an effective water cushion after a local breach, and the upper limit is determined by the safe allowable water level of the outer protection boundary and the effective volume requirements of the buffer space reserved for the inflow of the local breach. The target pre-filled water level The effective head difference between the upstream and downstream sides of the existing dikes is lower than the flood level of the main river channel during the same period. ; Based on the existing allowable hydraulic gradient of the dike, the stability conditions of the dike body and foundation, and the safety conditions of the outer protective structure, the effective head difference will be gradually increased. Within the design range, during the rise of floodwaters, when the water level of the main river channel, the seepage status of existing dikes, or the remaining effective volume of the buffer space changes, the target pre-filling water level shall be adjusted in stages according to the monitoring results within the allowable range of the target pre-filling water level, rather than maintaining a single fixed water level throughout the entire flood process.

5. The method according to claim 1, characterized in that, In step 4, the pre-filled water in the strip-shaped water-filled buffer space located on the back side of the weak embankment section forms a back-side counterpressure on the existing embankment. That is, the pre-filled water acts on the back side of the existing embankment, with water pressure opposite to the main river flood. Based on the main river water level and seepage monitoring results, the strip-shaped water-filled buffer space is continuously filled, stopped, or controlled to drain water, so that the pre-filled water level is kept within the allowable range. The strip-shaped water-filled buffer space is filled with water in stages through a water filling and drainage system, and the rate of water level rise is controlled during the filling process. Simultaneous monitoring of seepage flow, seepage line, pore water pressure, displacement and deformation of existing dikes; If the monitoring results are abnormal, water filling will be suspended, the water level of the strip-shaped water-filled buffer space will be lowered, or measures such as reverse filtration, weighting, drainage, and local reinforcement will be taken.

6. The method according to claim 1, characterized in that, In step 5, when the pre-filled water in the strip-shaped water-filled buffer space forms a water cushion on the back side of the breach in the weak dike section: The water cushion is formed by the same pre-filled water body determined in step 3 according to the pre-breach counterpressure, post-breach buffer, outer protective boundary safety and remaining effective volume. After the breach water flows into the pre-filled water body, it reduces the effective head difference between the water-facing side and the back side of the breach through water body reception, momentum exchange and turbulent energy dissipation, thereby reducing the direct scouring of the breach bottom, the two sides of the dike head and the ground behind the dike by the high-speed outflow. Erosion protection zones are set up in the predicted breach impact area, the filling and drainage outlets and the downstream controlled drainage outlets. The erosion protection zones are constructed using cemented pebbles, masonry blocks, concrete, reinforced concrete, gabions, interlocking blocks or geocell structures.

7. The method according to claim 1, characterized in that, In step 5, the act of using the outer protective boundary to receive and constrain the breach flood includes: The strip-shaped water-filled buffer space provides an effective volume within the design response time to temporarily accommodate local outflow. The effective volume is the difference between the volume corresponding to the highest allowable operating water level of the strip-shaped water-filled buffer space and the occupied volume corresponding to the target pre-filled water level. Within the design response time T, the required effective volume of the buffer space can be checked according to the following formula: ； in, The available effective volume for the buffer space This is a localized outflow process. The flow rate discharged through downstream controlled outlets, control gates, or other safety channels; The strip-shaped water-filled buffer space is equipped with a downstream controlled discharge outlet. Through the downstream controlled discharge outlet, the floodwater entering the strip-shaped water-filled buffer space is transported along the strip-shaped water-filled buffer space towards the downstream controlled discharge outlet, and discharged into the downstream section of the main river channel or a receiving space that has been safety verified.

8. The method according to claim 1, characterized in that, It also includes step 6, after the flood process ends: According to the process of water level drop in the main channel, the water level of the strip-shaped water-filled buffer space is reduced in stages to control the rate of water level drop, so that the rate of water level drop is coordinated with the water level change in the main channel and the stability conditions of the dike, and to prevent the water level of the buffer space from dropping too fast or remaining high for a long time relative to the water level in the main channel. Inspect and repair the outer protective boundary, erosion protection area, water filling and drainage facilities, and the strip-shaped water-filled buffer space for erosion, leakage, settlement, and deformation. After the outer protective boundary has reliable water-blocking and restraining capabilities, the outer protective boundary is used as an auxiliary protective boundary to carry out segmented testing, seepage prevention reinforcement, dike reconstruction, slope toe treatment, or improvement of monitoring facilities on the existing dike.

9. The method according to claim 1, characterized in that, In step 2, when the outer protective boundary adopts a permanent protective structure, the protective structure is divided into multiple construction sections, and a segmented construction interval area is reserved between adjacent construction sections. Prioritize the construction of foundation treatment, seepage prevention structure, dike filling, reverse filter drainage and slope protection for the outer protective boundary; After the outer protective boundary is formed, the strip-shaped water-filled buffer space is formed by excavation or leveling on its inner side; a safe distance or stable platform that meets the stability requirements is always maintained between the excavation boundary of the buffer space and the toe of the back slope of the existing dike. After each construction section meets the design requirements, the segmented construction intervals are excavated sequentially under low or controlled water level conditions, so that each section is connected to form a continuous or segmented controlled strip-shaped water-filled buffer space.

10. The method according to claim 1, characterized in that, In step 2, when the outer protective boundary adopts an emergency-type protective structure: Priority should be given to implementation in the land area on the backwater side of existing dikes, to avoid large-scale excavation of the dike body and slope toe of identified weak sections; The strip-shaped water-filled buffer space is formed by prioritizing the use of natural low-lying areas behind the dike, drainage ditches, abandoned trenches, or areas that can be temporarily used. An emergency outer protective dike is rapidly constructed along the outer side of the strip-shaped water-filled buffer space. The emergency outer protective dike adopts earth and stone filling, geotextile bags, prefabricated water retaining walls, steel sheet piles, mobile flood control structures, or combinations thereof. The two ends of the emergency outer protective dike are connected to natural high ground, existing road high embankments, stable dike sections or other reliable water-retaining structures to form a closed outer protective boundary or a boundary with controlled discharge conditions. After the outer protective boundary meets the temporary water blocking requirements, water is gradually pumped into the strip-shaped water-filling buffer space through mobile pump sets, temporary water pipelines, or existing culverts.

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