Some standard content:
Industry Standard of the People's Republic of China
Design Code for Urban Flood Control Projects
CJJ50—92
Editing Unit: Northeast Design Institute of China Municipal Engineering Approving Department: Ministry of Construction of the People's Republic of China Ministry of Water Resources of the People's Republic of China
Effective Date: July 1, 1993
Flood Control Volume·Design
Notice on the Release of Industry Standard
"Design Code for Urban Flood Control Projects" Jianbiao [1993] No. 72
In accordance with the requirements of the former Ministry of Urban and Rural Construction and Environmental Protection Document No. (83) Chengkezi 224 and the Ministry of Water Resources Document No. Shuigui (89) 41, the "Design Code for Urban Flood Control Projects" edited by Northeast Design Institute of China Municipal Engineering has been reviewed and approved as an industry standard, numbered CJJ50-92, and will be implemented on July 1, 1993. This specification is jointly managed by the Ministry of Construction's Urban Construction Standards and Technology Unit, the Ministry of Construction's Urban Construction Research Institute, and the Ministry of Water Resources' Water Resources and Hydropower Planning and Design Institute, and the specific interpretation and other work is the responsibility of the editor-in-chief. It is organized and published by the Ministry of Construction's Standards and Norms Research Institute.
Ministry of Construction of the People's Republic of China
Ministry of Water Resources of the People's Republic of China
February 8, 1993
Design standards
Overall design
Design flood and design tide level
Bank protection and river regulation
Flash flood control
Debris flow control
Flood control gates
Crossing structures
Appendix A Explanation of terms used in this code
Additional explanation:
Explanation of clauses
CJJ50--92
Flood control and military defense volume·Design
1.0.1 This code is formulated to prevent and control flood hazards, protect urban safety, and unify the technical requirements for urban flood control planning, design and construction.
1.0.2 This specification applies to the planning and design of flood control projects such as river (river) floods, sea tides, mountain torrents and mud-rock flow control within the scope of cities in my country. Industrial and mining areas may refer to it for implementation. 1.0.3 The design of urban flood control projects should be based on the overall urban plan and the flood control plan of the river basin where it is located, with comprehensive planning, comprehensive management, overall consideration and emphasis on efficiency. 1.0.4 The use of rivers and coastal land within the city must comply with the flood discharge requirements, and the construction of various projects and their flood control standards shall not be lower than the flood control standards of the city. 1.0.5 The design of flood control projects in important cities should refer to the current "Water Conservancy Economic Calculation Specifications" for economic evaluation during the feasibility study stage, and its content can be appropriately simplified. 1.0.6 For urban flood control projects that have a significant impact on the natural environment and social environment, an environmental impact assessment should be conducted in accordance with the current "Water Conservancy and Hydropower Project Environmental Impact Assessment Specifications" during the feasibility study stage, and the environmental impact report or environmental impact report form should be shortened.
During the feasibility study and preliminary design stage of urban flood control projects, the design documents should include engineering management design content. 1.0.8bzxZ.net
The design of urban flood control projects in earthquake-fortified areas shall comply with the provisions of the current "Code for Seismic Design of Hydraulic Structures". In addition to implementing this code, the design of urban flood control projects shall also comply with the provisions of relevant codes when other disciplines are involved. 2 Design standards
2.1 Urban grades and flood control standards
City grades should be divided into four grades based on the importance and population of the protected cities, as shown in Table 2.1.1. 2.1.1
Table 2.1.1 Urban grades
Urban grades
Grading indicators
Importance
Particularly important cities
Important cities
Urban population (10,000 people)
Note: 1. Urban population refers to the non-agricultural population in urban areas and nearby areas; 2. Cities refer to municipalities, cities, towns and cities established by the state according to administrative systems.
Classification indicators
Importance
Medium cities
Small cities
Urban population (10,000 people)
2.1.2 Urban flood control design standards should be determined based on the city level and flood type, which can be analyzed and determined according to Table 2.1.2. Urban level
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River (river) flood, sea tide
200~100
100~50
Flood control standard
Flood control standard (recurrence period: year)
100~50
Mixed rock flow
100~50
Note: 1. The selection of upper and lower limits of the standard should take into account the impact caused by the disaster, economic losses, difficulty of rescue and investment possibilities. 2. Sea tide refers to the design high position;
3. When the city has flat terrain and it is difficult to discharge flood water, the flood control standard for mountain torrents and debris flow can be appropriately reduced. 2.1.3
For cities with special circumstances, the flood control standard can be appropriately increased or reduced with the approval of the superior competent department. When the city is divided into zones for defense, different flood control standards can be selected according to the importance of each protection zone. For cities along international rivers, flood control standards should be specially studied and determined. The flood control standards for temporary buildings can be appropriately lowered and determined based on the analysis of a recurrence period of 5 to 20 years. 2.2 Flood control building levels
Flood control building levels are divided into four levels based on the city level and its role and importance in the project, which can be determined according to Table 2.2.1.
Table 2.2.1 Level of flood control buildings
City level
Major buildings
Level of permanent buildings
Secondary buildings
Level of temporary buildings
Notes: 1. Major buildings refer to buildings that will cause serious disasters and major economic losses to the city after an accident, such as embankments and flood control rooms; 2. Secondary buildings refer to buildings that will not cause urban disasters or minor economic losses after an accident, such as fills, slope protection, and valley workshops; 3. Temporary buildings refer to buildings used during the construction of flood control projects, such as screening cofferdams, etc. 2.3
Safety superheight of flood control buildings
The safety superheight of flood control buildings shall comply with the provisions of Table 2.3.1. Table 2.3.1
Safety super height
Building name
Building level
Earth embankment, flood wall, flood gate
Revetment, flood drainage channel, ferry
Note: 1. Safety height does not include wave climbing height: 1
2. When the overtopping of waves does not cause any hazard, the safety height can be appropriately reduced
Flood control and drought relief volume·design
The top elevation of the water retaining part of the flood gate and other buildings built on the flood embankment shall not be lower than the top elevation of the embankment (revetment). 2.3.2
2.3.3 The safety super height of temporary flood control buildings can be one level lower than that of buildings of the same type. When the seawall allows overtopping of waves, the super height can be appropriately reduced.
2.4 Stability safety factor of flood control buildings
The safety factor of the anti-sliding stability of the embankment (bank) slope shall comply with the provisions of Table 2.4.1. Safety factor of the anti-clearing stability of the embankment (bank) slope
Load combination
Building level
Basic load combination
Special load combination
The horizontal anti-sliding stability safety factor of the contact surface between the concrete or masonry flood control buildings built on non-rock foundations and the non-rock foundation shall comply with the provisions of Table 2.4.2. Table 2.4.2
Load combination
Building level
Basic load combination
Special load combination
Safety factor of the anti-sliding stability of non-rock foundations
The anti-sliding stability safety factor of the contact surface between the concrete or masonry flood control buildings built on rock foundations and the rock foundation shall comply with the provisions of Table 2.4.3.
Load combination
Building level
Basic load combination
Special load combination
Safety factor of rock foundation anti-sliding stability
Safety factor of anti-overturning stability of flood control buildings shall comply with the provisions of Table 2.4.4 Table 2.4.4
Load combination
Building level
Basic load combination
Special load combination
Safety factor of anti-overturning stability
CJJ5092
3 Overall design
3.1 General provisions
3.1.1 The overall design must be determined on the basis of the overall urban plan and basin flood control plan, according to the characteristics of floods and their impacts, combined with the natural geographical conditions, social and economic conditions and the needs of urban development. In the overall design of important urban flood control projects, countermeasures should be formulated for floods exceeding the design standard to reduce flood losses. 3.1.2 The overall design should implement a combination of engineering flood control measures and non-engineering flood control measures. According to different flood types (river floods, sea tides, mountain torrents and debris flows), various flood control measures should be selected to form a complete flood control system. 3.1.3. The overall design should pay attention to saving land and developing construction land; the selection of buildings should be adapted to local conditions, using local materials to reduce the cost of the project.
3.1.4 The overall design should be closely coordinated with the municipal buildings, and on the premise of ensuring flood control safety, take into account the requirements of the user units and relevant departments to improve the investment efficiency.
3.1.5 The overall design should protect the ecological environment. Natural lakes and ponds in the city should be retained. Necessary drainage measures should be taken for waterlogging caused by the influence of flood control facilities. 3.1.6 The overall design must collect, analyze and evaluate basic data such as hydrology, mud and sand, river channels, coastal erosion and siltation evolution trends, topography, geology, existing flood control facilities, social economy, and flood losses. 3.1.7 In areas of ground subsidence, corresponding prevention and control measures should be taken for the impact of ground subsidence. 3.1.8 In seasonal frozen soil, perennial frozen soil and ice flood areas, corresponding prevention and control measures should be taken for the impact of frost heave. Observation and monitoring equipment should be set up for major flood control buildings. 3.1.9
3.2 Flood control
3.2.1 The overall design should consider whether human activities and river changes affect the consistency of the relationship between flow and water level, and analyze the impact of urban construction and social and economic development on urban flood control. 3.2.2 The overall design should avoid or reduce adverse effects on water flow patterns, sediment movement, river banks, etc., and prevent harmful scouring and siltation in the river.
3.2.3 The overall design should be coordinated with the upstream and downstream, left and right bank basin flood control facilities, and pay attention to the connection treatment of different flood control standards at the junction of urban and rural areas.
3.2.4 The overall design should be coordinated with shipping terminals, sewage interception pipes, riverside roads, riverside parks, swimming pools, etc., to give full play to the multifunctional role of flood control facilities.
3.2.5 Cities located in river network areas should adopt a closed form for flood control projects according to the division of urban areas by river networks.
3.3 Tide Control
3.3.1 The overall design of tide control projects in coastal cities should analyze the characteristics of storm surges, astronomical tides, and tidal bores and possible adverse encounter combinations, and reasonably determine the design tide level.
Flood Control and Drought Relief Volume·Design
3.3.2 The overall design of tide control projects in Haikou cities should analyze the adverse encounter combinations of river floods and design tide levels, take corresponding tide control measures, and carry out comprehensive management. 3.3.3 The overall design should analyze the destructive effects of ocean currents and wind and waves, determine the design wind and wave invasion height, and take effective wave elimination measures and basic protection measures.
3.3.4 The layout of tide control embankments should be coordinated with coastal municipal construction, and the structural selection should be coordinated with the coastal environment. 3.4 Mountain torrent control
3.4.1 Mountain torrent control should be comprehensively managed with small watersheds as units, and the slope catchment area should be mainly based on biological measures, and the ditch leveling management should be mainly based on engineering measures.
3.4.2 The plan layout of the flood discharge channel should be as straight as possible, and it should be discharged directly into the river downstream of the city; when conditions permit, the flood interception ditch can be used to discharge the flood to other water bodies upstream of the city. 3.4.3 When a small reservoir is built upstream of the city to reduce the flood peak, the reservoir design standard should be appropriately improved, and a spillway should be set up to ensure the safety of the reservoir.
3.4.4 When the outlet of the flood discharge channel is supported by floods from other rivers, a flood gate or backwater dam should be set up to prevent flood backflow. 3.5 Debris flow prevention and control
3.5.1 Debris flow prevention and control should adopt the principle of combining prevention and control, with prevention as the main approach, and combining interception and drainage, with drainage as the main approach, and adopt biological, engineering and management measures for comprehensive control. 3.5.2 Appropriate prevention and control measures should be taken according to the harmful forms of debris flow to cities and buildings. 3.5.3 Debris flow ditches should be one ditch and one channel directly discharged into the river, and their feasibility should be demonstrated when merging or changing ditches. The design section of debris flow ditch should consider the influence of sand and gravel deposition, and take corresponding prevention and control measures. 4 Design flood and design tide level
4.1 Design flood
4.1.1 The design flood of various standards based on which the urban flood control project is designed, including peak flow, flood level, flood volume during a period, flood process line, etc., can be calculated in whole or in part according to the requirements of the project design. 4.1.2 The design flood of urban flood control project can adopt the flood of a certain control section of the urban river section. 4.1.3 Basic data must be available for the calculation of design flood. Make full use of the existing measured data, use historical flood and rainstorm data, and focus on reviewing the rainstorm and flood data and basin characteristic data based on which the design flood is calculated. 4.1.4 The flood series should be consistent. When the basin constructs water diversion, water diversion, flood diversion, flood detention and other projects, or when breaches and dam breaches occur, which obviously affect the consistency of floods in each year, the data should be restored to the same basis, and the restored data should be reasonably checked.
4.1.5 According to the data conditions, the design flood can be calculated by the following methods: 4.1.5.1 When the urban flood control section or its upstream and downstream neighboring locations have more than 30 years of measured and interpolated extended flood flow or water level data, and historical flood survey data, the frequency analysis method should be used to calculate the design flood and design flood level.
CJJ50—92
4.1.5.2 When the project area has more than 30 years of measured and interpolated extended rainstorm data, and there is a corresponding relationship between rainstorm and flood, the frequency analysis method can be used to calculate the design rainstorm, estimate the design flood, and then obtain the corresponding design flood level through the flow-water level relationship curve of the control section. 4.1.5.3 When both flood and rainstorm data are scarce in the basin where the project is located, the measured or surveyed rainstorm and flood data of the neighboring areas can be used to conduct a regional comprehensive analysis, calculate the design flood, and then obtain the corresponding design flood level through the flow-water level relationship curve of the control section.
4.1.6 The calculation method used in the design flood calculation and its main links, various parameters and calculation results should be analyzed and checked in many aspects to prove their rationality. 4.1.7 The regional composition of the design flood can be formulated by the following methods: 4.1.7.1 Typical flood composition method: select several representative large floods from the measured data as typical ones, control the design flood volume of the design section, and calculate the corresponding design flow of each sub-district according to the proportion of the flood volume composition of each district of the typical flood. 4.1.7.2 Same frequency composition method: specify a certain sub-district to have a flood volume with the same frequency as the design section, and the corresponding flood volume of the remaining sub-districts is allocated according to the composition ratio of the typical flood. 4.1.8 The design flood process of each sub-district should use the same flood process line as a typical one, so as to control and amplify the flood volume allocated to each sub-district.
4.1.9 The proposed design flood volume regional composition and the design flood process line of each sub-district should be checked for rationality from the aspects of flood area composition law, water volume balance and flood process line shape, and appropriate adjustments can be made if necessary. 4.1.10 When there is a project with a large regulation and storage function upstream of the design section, the regional composition of the design flood volume should be drawn up, the flood process line of each sub-area should be calculated, and the flood after the project flood regulation and the interval flood combination should be used to deduce the design flood affected by the upstream project regulation and storage.
4.2 Design tide level
4.2.1 The design tide level includes the design high tide level and the design low tide level. When analyzing and calculating the high (low) tide level, there should be no less than 20 years of measured tide level data, and investigate the special high (low) tide levels that have occurred in history. 4.2.2 When the measured tide level data is more than 5 years but less than 20 years, the short-term synchronous difference ratio method can be used to perform synchronous correlation analysis with nearby tide gauge stations with more than 20 years of measured data to calculate the design high (low) tide level. The following conditions should be met when using the short-term synchronous difference ratio method:
(1) Similar tidal properties;
(2) Proximity in geographical location;
(3) Similar impacts of river runoff;
(4) Similar meteorological conditions.
4.2.3 The design high (low) tide level can be calculated using the first type extreme value distribution law or the Pearson I type curve. 4.2.4 The selection of the design rain type for the tidal gate should be based on the adverse effects of monsoon rain and typhoon rain on flooding and drainage.
4.2.5 The selection of the design tide type for the tidal gate should be based on the tidal level process that is unfavorable to drainage at the corresponding time in a typical year or the average unfavorable tidal level process at the corresponding time, and the most unfavorable tidal level process should be used for verification. 4.2.6 The determination of the design tide level of the tidal gate should take into account the influence of the reflected wave formed after the gate is built on the natural high tide level wall height and the influence of the low tide level 312
Flood Control and Drought Relief Volume·Design
5 Embankments
5.1 General Provisions
5.1.1 The selection of embankment lines should be determined in combination with existing embankment facilities, taking into account factors such as topography, geology, flood flow direction, flood control and emergency rescue, maintenance and management, and coordinated with municipal facilities along the river. The embankment line should be straight, and gentle curves should be used to connect the turning points. 5.1.2 The distance between embankments should be determined based on technical and economic comparisons based on factors such as the overall urban plan, river topography, water surface line calculation results, engineering quantity, and cost.
5.1.3. Determination of the design water level along the levee. When there is an observed water level close to the design flow along the levee, it can be calculated based on the design water level of the control station and the water surface gradient, and the water shaping effect of buildings such as bridges, docks, river crossings, and river dams should be considered; when there is no observed water level close to the design flow along the levee, it should be determined by calculating the water surface curve based on the design water level of the control station. When calculating the water surface curve, the roughness selection should be as realistic as possible. When there is measured or surveyed flood data, the roughness should be calculated based on the measured or surveyed data. The required water level should be checked by the water level of the upstream and downstream hydrological stations. 5.1.4 The elevation of the levee crest and flood wall item is calculated and determined by the following formula: Z=Zp+he+△=Z,+△H
Where z is the elevation of the levee item or flood wall crest (m); 2, is the design flood (tide) water level (m); h. —Wave climbing height (m):
△-safety super height (m), according to the building level, from Table 2.3.1; AH-super height above the design flood (tide) water level (m). 5.1.5 When a wave-breaking wall is set on the top of the embankment, the elevation of the top of the embankment shall not be lower than the design flood (tide) water level plus 0.5m. 5.2 Flood control embankment
5.2.1 Flood control embankment can be earth embankment, earth-rock mixed embankment or stone embankment. The embankment type should be selected based on the quality, quantity, distribution range, transportation conditions, construction site and other factors of local soil and stone materials, and determined after technical and economic comparison. 5.2.2 When there is enough earth material for embankment construction, homogeneous earth embankment should be used first. When the earth material is insufficient, earth-right mixed embankment can also be used. 5.2.3 The filling of the earth embankment should be compacted to ensure that the filling has sufficient shear strength and small compressibility, does not produce a large amount of uneven deformation, and meets the requirements of seepage control. The compaction degree of cohesive soil should not be less than 0.93~0.96; the relative density of non-cohesive soil after compaction should not be less than 0.70~0.75.
5.2.4 For earth embankments and earth-rock mixed embankments, the width of the embankment top should meet the requirements of embankment stability and flood prevention and rescue, but should not be less than 4m. If the embankment is also used as an urban road, its width should be determined according to the urban highway standard. 5.2.5 When the height of the embankment is greater than 6m, a road (horse path) should be set on the back slope, and its width should not be less than 2m. 5.2.6 The infiltration line of the earth embankment should be calculated based on the water level, embankment soil materials, and whether there is waterlogging at the back slope foot. The escape point of the infiltration line should be below the slope foot.
5.2.7 The arc method can be used to calculate the stability of the earth embankment slope. The impact of sudden drop in water level should be considered for the upstream slope; if the high water level lasts for a long time, the impact of seepage water pressure should be considered for the downstream slope; if there is a soft stratum in the embankment foundation, the overall stability calculation should be carried out.
5.2.8 When the seepage diameter of the embankment foundation cannot meet the anti-seepage requirements, measures such as filling weight, drainage pressure reduction and seepage interception can be taken to prevent seepage deformation.
5.2.9 The upstream slope of the earth embankment should be protected by slope protection. The slope protection forms include dry stone, mortar stone, concrete and reinforced concrete slabs. It should be selected according to the flow pattern and flow velocity. Grass slope protection can be used for the downstream slope. 5.2.10 The upstream slope should be equipped with a foot guard, and its width and depth can be determined by scouring calculation based on the flow velocity and riverbed soil. 5.2.11 When a wave-breaking wall is set on the top of the embankment, the height of the wave-breaking wall should not be greater than 1.2m, and deformation joints should be set. The seam spacing can be: 15~20m for masonry structure; 10~15m for concrete and reinforced concrete structure. 5.2.12 Stone embankments or earth-rock embankments are suitable for embankments with high water flow velocity and strong wind and wave impact on the water surface. Gravity masonry embankments or earth-rock embankments are suitable for seawalls with strong tide and wave impact. Earth-rock embankments can be built with stones or riprap on the water surface, and filled with soil behind them. Between the impermeable body and the embankment shell, a filter layer and a transition layer can be set as needed, or only a filter layer can be set. 5.3 Flood control wall
5.3.1 Flood control walls are suitable for embankment projects in urban central areas. Flood control walls should be reinforced concrete structures. When the height is not large, concrete or masonry flood control walls can be used. 5.3.2 Flood control walls must meet the requirements of strength and impermeability. The length of the base contour line should meet the requirement of no seepage deformation.
5.3.3 Anti-slip, anti-tilting and overall stability calculations must be carried out for flood control. The foundation stress must meet the requirements of the foundation bearing capacity. When the foundation bearing capacity is insufficient, the foundation should be reinforced. 5.3.4 The masonry depth of the flood wall foundation should be determined according to the foundation soil and scour calculation, and it is required to be 0.5~1.0m below the scour line. In seasonally frozen areas, the requirements of freezing depth should also be met. 5.3.5 The flood wall must be equipped with deformation joints, and the joint distance can be: 15~20m for mortar masonry walls; 10~15m for reinforced concrete walls; deformation joints should be added at places where the ground elevation, soil quality, external loads, and structural sections change. 5.4 Foundation treatment
5.4.1 When the seepage control of the embankment foundation and the stability of the foundation do not meet the requirements, foundation treatment should be carried out. 5.4.2 The gravel embankment foundation should be treated for seepage prevention. The treatment measures should be determined through technical and economic comparison based on factors such as the embankment type, gravel burial depth and thickness, local building materials, and construction conditions. 5.4.3 Vertical anti-seepage measures should reliably and effectively cut off the seepage of the embankment foundation. When technically possible and economical, the following measures should be adopted as a priority:
(1) When the gravel layer is shallowly buried and the layer thickness is not large, clay or concrete cutoff walls can be used; (2) When the gravel layer is deep and thick, high-pressure fixed spraying or rotary spraying anti-seepage curtains can be used. 5.4.4 When vertical anti-seepage is not economical or construction is difficult, clay blanketing or backfilling behind the embankment can be used, and anti-filter and drainage bodies can be set up, or measures combined with drainage and pressure relief wells can be set up. 5.4.5 For soil layers that are determined to be likely to liquefy, they should be excavated and replaced with good soil. When excavation is difficult or uneconomical, artificial densification measures should be adopted to achieve a compact state that is compatible with the design earthquake intensity, and drainage and weight-increasing measures should be taken. 5.4.6 Treatment measures for soft soil foundation: soft soil should be excavated. When the thickness is large, the distribution is wide, and it is difficult to excavate, sand wells can be drilled.12 For dike sections with high water flow velocity and strong wind and wave impact on the water surface, stone dikes or earth-rock dikes should be used. For sea dikes with high tide and wave impact, gravity mortar-stone dikes or earth-rock dikes should be used. Earth-rock dikes can be built with stone or riprap on the water surface, and earth can be filled behind them. Between the impermeable body and the dike shell, a filter layer and a transition layer can be set as needed, or only a filter layer can be set. 5.3 Flood control wall
5.3.1 Flood control wall should be used for dike projects in the central area of the city. Flood control wall should be of reinforced concrete structure. When the height is not large, concrete or mortar-stone flood control wall can be used. 5.3.2 Flood control wall must meet the requirements of strength and impermeability. The length of the base contour line should meet the requirement of no seepage deformation.
5.3.3 Flood control must be verified for anti-slip, anti-tilt and overall stability of the foundation. The foundation stress must meet the requirements of foundation bearing capacity. When the bearing capacity of the foundation is insufficient, the foundation should be reinforced. 5.3.4 The depth of the flood wall foundation should be determined according to the foundation soil and scour calculation, and it is required to be 0.5-1.0m below the scour line. In seasonally frozen areas, the freezing depth requirements should also be met. 5.3.5 The flood wall must be equipped with deformation joints, and the joint spacing can be: 15-20m for mortar masonry walls; 10-15m for reinforced concrete walls; deformation joints should be added at places where the ground elevation, soil quality, external loads, and structural sections change. 5.4 Foundation treatment
5.4.1 When the seepage control and foundation stability of the embankment foundation do not meet the requirements, foundation treatment should be carried out. 5.4.2 The gravel embankment foundation should be treated with anti-seepage treatment, and the treatment measures should be determined through technical and economic comparison based on factors such as the embankment type, gravel burial depth, thickness, local building materials, and construction conditions. 5.4.3 Vertical anti-seepage measures should reliably and effectively cut off the seepage of the embankment foundation. When it is technically possible and economical, the following measures should be given priority:
(1) When the gravel layer is shallow and the layer thickness is not large, clay or concrete cutoff walls can be used; (2) When the gravel layer is deep and thick, high-pressure fixed spraying or rotary spraying anti-seepage curtains can be used. 5.4.4 When vertical anti-seepage is not economical or construction is difficult, clay blanketing or backfill behind the embankment can be used, and anti-filter bodies and drainage bodies can be set up, or measures combined with drainage and pressure relief wells can be set up. 5.4.5 For soil layers that are determined to be likely to liquefy, they should be excavated and replaced with good soil. When excavation is difficult or uneconomical, artificial densification measures should be adopted to achieve a compact state that is compatible with the design earthquake intensity, and drainage and weight-increasing measures should be taken. 5.4.6 Treatment measures for soft soil foundations: soft soil should be excavated. When the thickness is large, the distribution is wide, and it is difficult to excavate, sand wells can be drilled.12 For dike sections with high water flow velocity and strong wind and wave impact on the water surface, stone dikes or earth-rock dikes should be used. For sea dikes with high tide and wave impact, gravity mortar-stone dikes or earth-rock dikes should be used. Earth-rock dikes can be built with stone or riprap on the water surface, and earth can be filled behind them. Between the impermeable body and the dike shell, a filter layer and a transition layer can be set as needed, or only a filter layer can be set. 5.3 Flood control wall
5.3.1 Flood control wall should be used for dike projects in the central area of the city. Flood control wall should be of reinforced concrete structure. When the height is not large, concrete or mortar-stone flood control wall can be used. 5.3.2 Flood control wall must meet the requirements of strength and impermeability. The length of the base contour line should meet the requirement of no seepage deformation.
5.3.3 Flood control must be verified for anti-slip, anti-tilt and overall stability of the foundation. The foundation stress must meet the requirements of foundation bearing capacity. When the bearing capacity of the foundation is insufficient, the foundation should be reinforced. 5.3.4 The depth of the flood wall foundation should be determined according to the foundation soil and scour calculation, and it is required to be 0.5-1.0m below the scour line. In seasonally frozen areas, the freezing depth requirements should also be met. 5.3.5 The flood wall must be equipped with deformation joints, and the joint spacing can be: 15-20m for mortar masonry walls; 10-15m for reinforced concrete walls; deformation joints should be added at places where the ground elevation, soil quality, external loads, and structural sections change. 5.4 Foundation treatment
5.4.1 When the seepage control and foundation stability of the embankment foundation do not meet the requirements, foundation treatment should be carried out. 5.4.2 The gravel embankment foundation should be treated with anti-seepage treatment, and the treatment measures should be determined through technical and economic comparison based on factors such as the embankment type, gravel burial depth, thickness, local building materials, and construction conditions. 5.4.3 Vertical anti-seepage measures should reliably and effectively cut off the seepage of the embankment foundation. When it is technically possible and economical, the following measures should be given priority:
(1) When the gravel layer is shallow and the layer thickness is not large, clay or concrete cutoff walls can be used; (2) When the gravel layer is deep and thick, high-pressure fixed spraying or rotary spraying anti-seepage curtains can be used. 5.4.4 When vertical anti-seepage is not economical or construction is difficult, clay blanketing or backfill behind the embankment can be used, and anti-filter bodies and drainage bodies can be set up, or measures combined with drainage and pressure relief wells can be set up. 5.4.5 For soil layers that are determined to be likely to liquefy, they should be excavated and replaced with good soil. When excavation is difficult or uneconomical, artificial densification measures should be adopted to achieve a compact state that is compatible with the design earthquake intensity, and drainage and weight-increasing measures should be taken. 5.4.6 Treatment measures for soft soil foundations: soft soil should be excavated. When the thickness is large, the distribution is wide, and it is difficult to excavate, sand wells can be drilled.
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