Some standard content:
Industry standard of the People's Republic of China
Design code for rolled earth-rock fill damsSL274—2001
Editor: Yellow River Conservancy Commission Survey, Planning and Design InstituteApproving department: Ministry of Water Resources of the People's Republic of ChinaEffective date: March 1, 2002
SL274—2001
Ministry of Water Resources of the People's Republic of China
Notice on the approval and issuance of "Design code for rolled earth-rock fill dams" SL274-2001
Shui Guoke [2002] No. 38
All units directly under the Ministry, water resources (water affairs) departments (bureaus) of provinces, autonomous regions, and municipalities directly under the Central Government, water resources (water affairs) bureaus of cities with independent planning status, and water resources bureau of Xinjiang Production and Construction Corps:
After examination, the "Design Code for Rolled Earth-Rock Fill Dams" is approved as the water conservancy industry standard and is hereby issued. The standard number is SL274-2001, which replaces the original SDJ218--84 and the revised and supplemented provisions of SDJ218-84. This standard is implemented from March 1, 2002. The standard text is published and distributed by China Water Resources and Hydropower Press. January 28, 2002
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The basis for revising SD218-84 "Design Specification for Rolled Earth and Rock Projects" (including the revision and supplementary provisions of the specification by the Ministry of Electric Power Industry and the Ministry of Water Resources in the document No. L19931187 of the Electric Power Office) is the document No. Shuiguishezi (1996) 0013 of the General Institute of Water Resources and Hydropower Planning and Design and SL01-97 "Regulations on the Compilation of Water Resources and Hydropower Technical Standards". Since the promulgation of SDJ218-84, it has played a great role in promoting the construction of earth-rock dams in my country. During this period, high earth-rock dam projects such as Lubuge, Tianshengqiao and Xiaolangdi were built, and research on national scientific and technological projects such as the "Sixth Five-Year Plan", "Seventh Five-Year Plan" and "Eighth Five-Year Plan" was carried out. Foreign earth-rock dams have also made new developments. In order to reflect these new construction experiences, the original specifications have been revised. The contents of this specification include: dam type selection and layout of discharge and diversion structures; dam material selection and filling requirements; dam structure and dam foundation treatment; connection between dam body and dam foundation and other buildings; dam calculation and analysis; phased construction and expansion and heightening; safety monitoring design and other basic regulations and requirements. The revisions to SDJ218-84 mainly include the following aspects: 1. The scope of application of this code has changed; 2. The calculation method of the height of the project has added the situation of calculating the height from the foundation surface at the dam axis to the project top; 3. The main term - chapter has been added;
4. A new compaction standard for cohesive soil has been specified; 5. The calculation of wind and wave has added the calculation of wave climb of dam slopes steeper than 1:1.5; 6. The design method of calculating curtain thickness according to the allowable permeability gradient has been cancelled for bedrock grouting; 7. The design of the filter layer has added a method to protect cohesive soil: 8. It is specified that the shear strength index shall adopt the method of taking the small average value; 9. The nonlinear index of shear strength of coarse aggregate is specified in the stability calculation of concrete panel rockfill dam; 10. The stability calculation stipulates that the method of taking the force between strips and blocks is the main method; 11. The safety factor standard for stability calculation is changed to three application conditions: normal, abnormal and normal plus earthquake. Article 4.1.5, paragraphs 1 to 3, Article 4.1.10, Article 4.1.15, paragraphs 1 to 4, Article 4.2.3, paragraph 1, Article 4.2.5, paragraphs 1 and 2, Article 4.2.6, paragraphs 1 and 2, Article 5.3.6, Article 5.6.2, Article 5.7.2, paragraphs 1 to 2, Article 5.8.1, Article 5.9.1, Article 5.9.2, Article 6.1.1, Article 6.1.2, paragraphs 1 to 9, Article 7.1.2, paragraphs 1 to 4, Article 7.1.3, paragraphs 1 and 2, Article 7.1.4, paragraphs 1 to 4, Article 7.2.1, Article 8.3.10, Article 8.3.11 and Article 8.3.12 of this specification are mandatory provisions and are indicated in bold in the text of the specification. The rest are recommended provisions. Interpretation unit of this code: General Institute of Water Resources and Hydropower Planning and Design, Ministry of Water Resources Editor of this code: Survey, Planning and Design Institute of Yellow River Conservancy Commission Main drafters of this code: Gan Xianzhang Sun Shengli Qian Zhongrou Yan Zhonghua Zong Zhijian Li Zhiming Wang Xinqi Liang Chengxi
Li Xianshe Gao Guangchun Hong Guangwen Pan Shaohua
Han Qiurong
Jiang Suyang
Cao Guoli Dai Qiaozhi
Yang Yongye
Tian Huaxiang Zhao Hongling
Duan Shichao
Main terms
Hub layout and dam type selection
Dam material selection and filling requirements
Dam structure
Dam foundation treatment
SL274—2001
Calculation of the connection dam between the dam body and the dam foundation, bank slope and other buildings And analysis
Construction in stages and expansion and heightening
10 Safety monitoring design
Appendix A
Appendix BwwW.bzxz.Net
Appendix C
Appendix D
Appendix E
Wave and slope protection calculation
Filter layer design
Estimation of pore pressure in dam body…·
Stability analysis
Settlement calculation·
Explanation of terms used in this code
Explanation of clauses
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1.0.1 This code is specially formulated to standardize the design of rolled earth-rock dams in water conservancy and hydropower projects and to meet the requirements of engineering safety, economic rationality and advanced technology.
1.0.2 This specification applies to the design of grade 1, grade 2, grade 3 and grade 3 and below with a height greater than 30m. Special research should be conducted for particularly important grade dams. The grade of grade dams should be determined according to the relevant provisions of GB50201-94 "Flood Control Standard" and SIL252-2000 "Classification and Flood Standards for Water Conservancy and Hydropower Projects". 1.0.3 Earth-rock dams can be divided into low dams, medium dams and high dams according to their height. A low dam is below 30m, a medium dam is between 30 and 70m, and a high dam is above 70m. The height of an earth-rock dam should be calculated from the bottom of the dam body impermeable body (excluding dam foundation impermeable facilities such as concrete impermeable walls, grouting curtains, and intercepting channels) or the foundation surface at the dam axis to the dam top (excluding wave-breaking walls), whichever is greater. 1.0.4 Under the load combination of normal and emergency conditions, earth-rock dams must meet the requirements of stability, seepage, deformation and specified superelevation to ensure that they can be used safely for a long time and give full play to their economic and social benefits. 1.0.5 The design conditions of earth-rock dams should be divided into the following according to the working conditions and the nature of the forces: 1 Normal operating conditions
1) The reservoir water level is in the stable seepage period of various water levels between the normal water storage level and the design flood level and the dead water level; 2) The reservoir water level drops normally and regularly within the above range; 3) The reservoir water level of the pumped storage power station changes and drops regularly. 2 Emergency operating conditions I
1) During the construction period,
2) The situation where the check flood level may form a stable seepage; 3) The emergency drop of the reservoir water level, such as the drop from the check flood level, the drop to below the dead water level, and the rapid discharge of large flow.
3 Emergency operating conditions 1
Normal operating conditions encounter earthquakes.
1.0.6 In addition to complying with this specification, the design of rolled earth-rock dams shall also comply with the provisions of relevant current national standards. 2 Main terms
2.0.1 Homogeneous earth dam A dam whose dam section is not divided into an impervious body and a dam shell, and whose majority is composed of one type of soil material. 2.0.2 Soil impervious zoned earth dam A dam whose dam section is composed of an impervious soil body and several soil-rock partitions with different permeabilities, and can be divided into core wall dams, inclined core wall SL.274—2001
dams, inclined wall dams, and other types of soil impervious zoned earth dams. 2.o.3 Non-soil impervious zoned earth dam495
A dam whose impervious body is composed of concrete, asphalt concrete or geomembrane, and whose remaining parts are composed of soil-rock materials. The anti-seepage body on the upstream side is called a face dam, and the one in the center of the dam is called a core wall dam. 2.0.4 Cohesionless soil Cohesionless soil The clay content (particle size less than 0.005mm) is not more than 3% (mass), the plasticity index is not more than 3, and there is no cohesion between particles.
2.0.5 Gravel ± gravelly soil
Widely graded soil composed of crushed stone, gravel, sand, silt, clay, etc. Various gravelly soils formed by rolling and artificial mixing of glacial, weathered and excavated weathered rocks or soft rocks. 2.0.6 Expansive soil
Highly plastic clay rich in hydrophilic minerals and with obvious water absorption expansion and water loss shrinkage characteristics. 2.0.7 Dispersive clay is easily dispersed when in contact with water, especially pure water, with a high sodium ion content, and most of them are clays with medium and low plasticity. 2.0.8 Soft clay
Clay with a high natural water content, in a soft plastic to fluid plastic state, with low shear strength, high compressibility, low permeability, and high sensitivity. The following standards are generally used for evaluation: Liquidity index IL ≥ 0.75; unconfined compressive strength qu ≤ 50kPa; standard penetration number N63.5 ≤ 4; sensitivity S. ≥ 4. When I ≥ 1.0, the porosity e ≥ 1.5 is silt; when ≥ 1.0, 1.0 ≤ e ≤ 1.5 is silty soil. 2.0.9 Organic soil organicsoil
Clay or silt with a certain amount of organic matter, light grey to dark grey, smelly, and highly compressible. According to the organic matter content Q, it can be subdivided into organic soil (5%≤Q<10%), peat soil (10%≤Q<60%) and peat (Q≥60%). 2.0.10 Collapsible loess It is mainly composed of powder particles, brown or yellowish brown, with large pores or vertical joints. The soil that collapses due to its own weight when it encounters water is called collapsible loess, and the loess that does not collapse due to its own weight is called non-collapsed loess. 2.0.11 Laterite
Reddish brown silt or clay rich in iron and aluminum oxides formed by the weathering of limestone or other lava. 2.0.12 Karst
Various geological phenomena and forms formed by the long-term dissolution of soluble rock layers by water. 2.0.13 Hard rock
Rocks with saturated unconfined compressive strength greater than or equal to 30MPa. 2.0.14 Weak rock
Rocks with saturated unconfined compressive strength less than 30MPa. 2.0.15 Soil flow
The phenomenon of local soil surface uplift, top penetration, or coarse and fine particles floating and losing at the same time under the action of seepage. 2.0.16 Piping
The phenomenon of fine particles in the soil being lost from the skeleton pore channels under the action of seepage. 2.0.17 Erosion on contact surface The phenomenon of fine particles being carried away along the surface when seepage flows along the contact surface of two soil layers with different permeability coefficients. Standard sharing network wWbzfxWcon
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2.0.18 Soil flow on contact surface When the seepage flows perpendicularly to two adjacent soil layers with a large difference in permeability coefficient, the fine particles in the soil layer with a smaller permeability coefficient are carried into the soil layer with a larger permeability coefficient. 2.0.19 Gap-graded soil Soil with steps on the particle size distribution curve due to the lack of a certain range of particle sizes in the soil. 2.0.20 Degree of compaction The dry density of the compacted fill corresponds to the percentage of the maximum density obtained by the laboratory standard compaction test. 3 Hub layout and dam type selection
3.1 Dam axis
3.1.1 The dam axis should be determined based on the topographic and geological conditions of the dam site, the dam type, the dam foundation treatment method, the layout and construction conditions of various buildings in the hub (especially the flood discharge building), etc., and determined through technical and economic comparison of multiple plans. 3.1.2 The dam axis should be selected according to local conditions. A straight line is preferred. When a broken line is used, a curved section should be arranged at the turning point. Broken lines should not be used in areas with a design earthquake intensity of 8 or 9 degrees. 3.1.3 When there are adverse geological conditions such as karst, large faults or soft clay at the dam site, the possibility of avoiding it should be studied. 3.2 Discharge and diversion structures
3.2.1 The discharge structures in the hub should be able to meet the application conditions and requirements specified in the design. The structure should be flexible and reliable in use, and its flood discharge capacity must meet the requirements of discharging design floods and verification floods, and should meet the requirements of sand, sewage and ice discharge. 3.2.2 The layout and form of the discharge structure should be selected after comprehensive comparison of the terrain, geological conditions, flood discharge scale, head size and sand control requirements. Open spillways and tunnels can be used. At dam sites with favorable terrain, open spillways should be laid.
3.2.3 For areas with a design earthquake intensity of 8 or 9 degrees or for earth and rock projects of level 1 or 2, it should be demonstrated whether to set up bottom holes for water discharge. 3.2.4 For rivers with a lot of sediment, sediment discharge buildings should be set up, and anti-siltation and protection measures should be set up at the water inlet. 3.2.5 There should be reliable protection measures for the dam slope and bank slope near the inlet and outlet of the water discharge and water diversion structures. Proper energy dissipation measures should be taken at the outlet, and the water flow after energy dissipation should be kept away from the dam foot at a certain distance. 3.2.6 The water discharge structure should be arranged on the rock foundation on the shore. For high and medium dams, the form of under-dam management arranged on soft foundation should not be adopted. When low dams use buried pipes on soft foundation, technical demonstration must be carried out. Dams in earthquake zones that use buried pipes under the dam should be implemented in accordance with the relevant provisions of SL203--97 "Code for Seismic Design of Hydraulic Structures". 3.3 Dam type selection
The rolled earth-rock project can be selected from the following three basic forms: 3.3.1
1 Homogeneous dam;
2 Earth impermeable body partition dam;
3 Non-earth material impermeable body dam.
3.3.2 The selection of dam type shall be determined after comprehensive consideration of the following factors and after technical and economic comparison: 1. Topographic and geological conditions such as river topography, bedrock at the dam site, characteristics of the covering layer and earthquake intensity; SL274--2001
2. Types, properties, quantity, location and transportation conditions of dam-building materials; 497
3. Construction conditions such as construction diversion, construction progress and staging, filling strength, meteorological conditions, construction site, transportation conditions and initial flood control;
4. Dam height: high dams mostly use earthen impermeable body partition dams, low dams mostly use homogeneous dams, and concrete panel embankment dams are suitable when conditions are appropriate;
5. Hub layout, dam foundation treatment and connection between the dam body and water discharge and diversion structures; 6. Operation conditions: such as the requirements for leakage volume, changes in upstream and downstream water levels, and phased construction; the total engineering volume, total construction period and total cost of the dam and hub. 73
3.3.3 After demonstration, geomembrane anti-seepage body can be used for low-level dams of level 3. 3.3.4 For earth-rock dams with long axis, different dam types can be adopted in sections according to the specific conditions of topography, geology and material field, but gradient sections should be set at the place where the type changes.
4 Selection of dam construction materials and filling requirements
4.1 Selection of dam construction materials
4.1.1 The investigation and geotechnical test of earth and rock materials for dam construction should be carried out in accordance with the relevant provisions of SL251-2000 "Regulations for the Investigation of Natural Building Materials for Water Conservancy and Hydropower Projects" and SL237-1999 "Regulations for Geotechnical Tests", and the properties, reserves and distribution of various natural earth and rock materials near the dam site, as well as the properties and available quantities of excavated materials for key buildings should be found out. 4.1.2 When there are multiple earth and rock materials suitable for dam construction in the local area, they should be selected after technical and economic comparison. The selection of earth and stone materials for dam construction should comply with the following principles:
1 Have or have after processing the engineering properties that are suitable for their purpose of use, and have long-term stability; 2 Take materials locally and nearby to reduce waste materials, occupy less or no farmland, and give priority to the use of excavated materials from hub buildings;
3 Convenient for mining, transportation and compaction.
4.1.3 The use of excavated materials from hub buildings should be the same as the materials mined from natural earth and stone material yards, and should be demonstrated from the perspectives of material properties, quantity, impact of waste materials on the environment, construction schedule and engineering costs. Material yards should be planned in a unified manner. 4.1.4 In principle, excavated materials from material yards or hub buildings can be directly used as dam construction materials, or used in different parts of the dam after being processed, but marsh soil, bentonite and surface soil should not be used. 4.1.5 The anti-seepage soil material shall meet the following requirements: 1 Permeability coefficient: homogeneous dam shall not exceed 1×10-*cm/s, core wall and inclined wall shall not exceed 1×10-5cm/s; 2 Water-soluble salt content (referring to soluble salt and medium soluble salt, by mass) shall not exceed 3%; 3 Organic matter content (by mass): homogeneous dam shall not exceed 5%, core wall and inclined wall shall not exceed 2%, and demonstration shall be conducted if it exceeds this requirement;
4 Good plasticity and permeability stability;
5 Small volume change when immersed in water and dehydrated.
4.1.6 The following types of clay are not suitable for use as anti-seepage filling materials. If they must be used, appropriate measures should be taken according to their characteristics.
1 Alluvial clay with a plasticity index greater than 20 and a liquid limit greater than 40%; Standard Sharing Network wwwbzfxWcon
Expansive soil;
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3 Dry and hard clay that is difficult to excavate and compact;
4 Frozen soil;
5 Dispersed clay.
Red clay can be used to fill the anti-seepage body of the dam. When used in high dams, its compressibility should be demonstrated. 4.1.7
4.1.8 Dispersed clay that has been treated and modified can only be used to fill the anti-seepage body of the 3rd level low dam, and the selected filter material should be verified by test. Dispersed clay shall not be used for filling the parts of the impermeable body that are prone to concentrated seepage, such as the contact between the impermeable body and the dam foundation and the bank slope, and the dam surface that is easily eroded by rainwater. 4.1.9 Collapsible loess or loess-like soil can be used to fill the impermeable body, but it should no longer be collapsible after compaction. The gradation of the anti-filter material used should be verified by experiments.
4.1.10 The content of particles with a particle size greater than 5mm for gravel soil used to fill the impermeable body should not exceed 50%, the maximum particle size should not be greater than 150mm or 2/3 of the soil thickness, and the content of particles below 0.075mm should not be less than 15%. The phenomenon of concentrated overhead coarse materials shall not occur during filling.
4.1.11 The blending ratio of various materials in artificially mixed gravel soil should be verified by experiments. 4.1.12 When gravel soil containing crushable weathered rock or soft rock is used as the impermeable material, its gradation and physical and mechanical indicators should be designed according to the gradation after rolling.
4.1.13 When expansive soil is used as the anti-seepage material of earth-rock dam, the fill moisture content should adopt the wet side of the optimal moisture content, and a cover weight layer should be set on the top. The restraining stress generated by the cover weight layer should be sufficient to restrict its expansion. The cover weight layer should use non-expansive soil. 4.1.14 When geomembrane is used as the anti-seepage material, it should be implemented in accordance with the provisions of GB50290--98 "Technical Specifications for Application of Geosynthetics".
4.1.15 The filter material, transition layer material and drainage material should meet the following requirements: 1. The texture is dense, and the water resistance and weathering resistance meet the requirements of the engineering application conditions; 2. The required gradation;
3. The required water permeability;
4. The content of particles with a particle size of less than 0.075mm in the filter material and drainage material should not exceed 5%. 4.1.16 The filter material can be natural or screened sand and gravel, or rolled block stone or gravel, or a mixture of natural and rolled materials.
4.1.17 After demonstration, geotextiles can be used as filter layers for Class 3 low dams. 4.1.18 Cohesionless soil (including sand, gravel, pebbles, boulders, etc.), stone and weathered materials, and gravel soil from material field mining and building excavation can all be used as dam shell materials, and should be used in different parts of the dam shell according to the properties of the materials. 4.1.19 Uniform medium and fine sand and silt sand can be used in dry areas of medium and low dam shells, but they should not be used in some areas. 4.1.20 When weathered stone and soft rock are used to fill the dam shell, the physical and mechanical indicators of the material should be determined according to the grading after compaction, and the unfavorable conditions such as the reduction of shear strength and the increase of compressibility after immersion in water should be considered. Weathered stone and soft rock with low softening coefficient that cannot be crushed into gravel soil should be filled in dry areas. 4.1.21 The underwater part of the downstream dam shell and the water level fluctuation area of the upstream dam shell should be filled with permeable materials. 4.1.22 The following regulations should be observed when mining the dam shell rockfill: 1 The overburden should be completely removed before mining;
2 Different degrees of weathered materials and fresh stones should be separated; easily weathered soft rocks (such as mudstone and shale) should be mined and filled at the same time; 3
4 Blasting design should be carried out, and blasting tests should be carried out when necessary. SL274—2001
4.1.23 The slope protection stone should be made of hard rock material with dense texture, water resistance and weathering resistance that meet the requirements of engineering application conditions.
4.2 Filling requirements
4.2.1 Filling standards should be determined based on a comprehensive study of the following factors: 1. The level, height, type and different parts of the dam; 2. The compaction characteristics of soil and rock materials and the compaction equipment used; 3. The relationship between the filling density and moisture content of the material and the mechanical properties, as well as the design requirements for the mechanical properties of soil and rock materials;
The natural dry density and natural moisture content of the soil material, as well as the degree of drying or wetting of the soil material; 4.
The impact of local climatic conditions on construction;
The design earthquake intensity and other dynamic loads; 6.
The strength and compressibility of the dam foundation soil;
8. The impact of non-filling standards on the cost and construction difficulty. 4.2.2 The filling standards for gravel-containing and gravel-free clay soils should use compaction and optimal moisture content as design control indicators. The design density should be obtained by multiplying the maximum dry density of the compaction by the compaction. 4.2.3 The compaction degree of clay soil shall meet the following requirements: 1. The compaction degree of 11-level, 2-level dams and high dams shall be 98% to 100%, and the compaction degree of 3-level medium and low-level dams and medium dams below 3 shall be 96% to 98%.
2 In areas where the design earthquake intensity is 8 degrees and 9 degrees, the larger value specified above should be taken. 3 The compaction degree of soil materials with special uses and special properties should be determined separately. 4.2.4 The maximum dry density and optimum moisture content of clay soil shall be obtained according to the compaction test method specified in SL237-1999 "Soil Testing Code". For gravel, the maximum density and optimum moisture content shall be obtained from the full material sample. 4.2.5 The filling standard of gravel and sand should use relative density as the design control index and should meet the following requirements: 1 The relative density of gravel should not be less than 0.75, the relative density of sand should not be less than 0.70, and the relative density of filter material should be 0.70. 2 When the content of coarse particles in gravel is less than 50%, the relative density of fine particles (particles less than 5mm) should also meet the above requirements.
3 The relative density design standard in earthquake zones shall comply with the provisions of SL203-97 "Code for Seismic Design of Hydraulic Structures" 4.2.6 The filling standard of rockfill should use porosity as the design control index and should meet the following requirements: 1 The porosity of rockfill materials for earth impermeable body partition dams and asphalt concrete core wall dams should be 20% to 28%; 2 The porosity of rockfill materials for asphalt concrete face dams should be selected between the porosity of concrete face rockfill dams and earth impermeable body partition dams;
3 When using soft rock and weathered rock to build dams, the porosity should be determined according to the requirements of dam body deformation, stress and shear strength; 4 In areas with design earthquake intensity of 8 and 9 degrees, the smaller value of the above porosity can be taken. 4.2.7 The rolling quality of rockfill can be controlled by construction parameters (including the model of rolling equipment, vibration frequency and weight, travel speed, paving thickness, rolling times, etc.) and dry density at the same time. 4.2.8 Water should be added during rockfill compaction, and the amount of water added should be determined through compaction tests. For hard rock rockfill with a high softening coefficient, whether to add water should be determined through compaction tests. 4.2.9 The design filling standard should be verified through compaction tests at the beginning of construction; when gravel soil, weathered rock, soft rock, expansive soil, collapsible loess and other special soil and rock materials are used, special compaction tests should be carried out for Class 1, Class 2 dams and high dams to demonstrate their filling standards.
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4.2.10 The water content of construction filling of clay soil should be controlled within the deviation range of 1% to 3% of the optimal water content according to the soil material properties, filling location, climatic conditions and construction machinery. The filling water content of clay soil with special uses and special properties should be determined separately.
The moisture content of the filling shall also meet the following requirements: 1 Upper limit value
1) It shall not affect the normal operation of compaction and transportation machinery; 2) The pore pressure generated in the soil during construction shall not affect the stability of the dam slope; 3) No shear failure shall be generated during the compaction process. 2 Lower limit value
1) After the filling is soaked in water, it shall not produce a large amount of additional settlement, so that the dam top elevation does not meet the design requirements, cracks occur in the dam body, and hydraulic fracturing does not occur under the action of water pressure; 2) It shall not produce a loose soil layer that is difficult to compact. 4.2.11 When filling in negative temperatures in winter, the soil material shall not freeze during the filling process, and the filling moisture content of the cohesive soil shall be slightly lower than the plastic limit; the moisture content of the fine material part in the sand and gravel material shall be less than 4%, and the filling density shall be appropriately increased. 5 Dam structure
5.1 Dam division
5.1.1 The dam division design should be determined based on the principle of local material and excavation-fill balance after technical and economic comparison. 5.1.2 The various materials of the dam body should be clearly divided into different zones. There should be specific technical indicators for the properties of the materials in each zone and the construction compaction requirements for assessment, inspection and quality evaluation. 5.1.3 Homogeneous dams should be divided into dam body, drainage body, filter layer and slope protection. 5.1.4 Earthen impermeable body zoning dams should be divided into impermeable body, filter layer, transition layer, dam shell, drainage body and slope protection. When the impermeable body is on the upstream surface, the permeability of the dam body should gradually increase from upstream to downstream; when the impermeable body is in the middle, the permeability of the dam body should gradually increase upward and downstream.
5.1.5 When weathered materials or soft rocks are used to build dams, a protective layer should be set on the dam surface, and the vertical thickness of the protective layer should not be less than 1.50m. 5.1.6 In the zoning design of the dam body, the possibility of combining the cofferdam with the dam body should be studied. 5.2 Dam slope
5.2.1 The dam slope should be determined based on technical and economic comparisons based on factors such as dam type, dam height, dam grade, properties of dam body and dam foundation materials, loads borne by the dam, and construction and operation conditions. 5.2.2 The dam slopes of homogeneous dams, earth impermeable partition dams, asphalt concrete face or core wall dams, and geomembrane core or inclined wall dams can be initially drawn up with reference to the experience of existing dams or approximate methods, and should be ultimately determined by stability calculations. The upstream slope of an asphalt concrete face dam should not be steeper than 1:1.7. 5.2.3 When the shear strength of the dam foundation is low and the dam body does not meet the deep anti-sliding stability requirements, it is advisable to use the method of pressing the dam foot to improve its stability.
5.2.4 In areas with a design earthquake intensity of 9 degrees, the upstream and downstream dam slopes near the dam crest should be gentle at the top and steep at the bottom, or reinforced rockfill,
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