I. Design Phase
Geological Survey
It is of vital importance to have a detailed understanding of the geological conditions of the reservoir. This includes the stratigraphic structure of the reservoir bottom and banks, soil types (such as clay, sand, silt, etc.), and permeability. For example, if there is a sandy soil layer with strong permeability at the reservoir bottom, more effective seepage prevention measures need to be considered to prevent the exchange between groundwater and reservoir water.
Investigate the water level, flow direction, and recharge of groundwater. High - level groundwater may exert an upward buoyant force on the reservoir seepage prevention structure, affecting the seepage prevention effect. Therefore, drainage and decompression facilities should be considered in the design.
Selection of Seepage Prevention Scheme
Select the seepage prevention scheme comprehensively based on factors such as the scale, purpose, geological conditions, and investment budget of the reservoir. For small mountainous reservoirs, clay core wall seepage prevention may be an economical and practical method; while for large plain reservoirs, the scheme of combining geomembrane seepage prevention with concrete slope protection may be more appropriate.
Consider the durability of seepage prevention materials. For example, in an environment with corrosive groundwater, avoid using metal materials that are easily corroded as part of the seepage prevention structure. Instead, choose corrosion - resistant geosynthetics or concrete additives.
II. Material Selection
Quality of Seepage Prevention Materials
For seepage prevention materials such as geomembranes, their quality should be strictly inspected. Indicators such as the thickness, tensile strength, and puncture resistance of the geomembrane must meet the design requirements. When purchasing, choose products from regular manufacturers with quality assurance and request the provision of quality inspection reports.
For natural seepage prevention materials such as clay, test indicators such as its water content and particle composition. Clay with excessive water content is difficult to reach the designed dry density during compaction, affecting the seepage prevention performance; and clay with overly coarse particles will also greatly reduce its seepage prevention effect.
Material Compatibility
When multiple seepage prevention materials are used in combination, ensure their compatibility. For example, when connecting a geomembrane to a concrete structure, consider the bonding method between the two to avoid peeling or leakage caused by differences in material properties.
Pay attention to the chemical compatibility between the seepage prevention materials and the reservoir water body and soil environment. If the water body or soil is strongly acidic or alkaline, some seepage prevention materials may undergo chemical reactions, reducing their seepage prevention performance.
III. Construction Process
Foundation Treatment
Thoroughly clean the foundation of the reservoir bottom and banks, removing debris such as tree roots, weeds, garbage, and loose soil and stones. These debris can damage the integrity of the seepage prevention structure and form leakage channels.
The compaction of the foundation should reach the designed degree of compaction. For example, for soil foundations, the degree of compaction is generally required to be not less than 90% - 95% to reduce the settlement deformation and permeability of the foundation.
Construction of Seepage Prevention Materials
When constructing geomembranes, strictly control the laying flatness and looseness. A geomembrane laid too tightly is likely to tear due to temperature changes or foundation deformation; while uneven laying will lead to local stress concentration, which can also easily damage the geomembrane.
For concrete seepage prevention structures, pay attention to the quality of concrete pouring. This includes the concrete mix ratio, vibration method, and curing conditions. A reasonable mix ratio can ensure the impermeability of concrete, sufficient vibration can make the concrete dense, and good curing can reduce concrete cracks.
The connection parts between seepage prevention materials are weak links in seepage prevention. For example, for the welding or bonding parts of geomembranes, ensure the welding quality or bonding strength. During welding, parameters such as the weld width, welding temperature, and speed should meet the specified requirements, and the use of adhesives should be operated in accordance with the instructions.
Construction Quality Control and Testing
Establish a complete construction quality inspection system. During the construction process, conduct quality inspections on each process, such as the appearance inspection of the laid geomembrane and the non - destructive testing of welds. Rectify problems promptly and prohibit unqualified processes from entering the next construction link.
Adopt a combination of multiple testing methods. For example, for geomembrane welds, both inflation testing and vacuum testing can be used to verify the test results and ensure the quality of the welds.
IV. Operation and Maintenance
Water Level Control
In the initial stage of reservoir operation, store water slowly to avoid excessive water pressure on the seepage prevention structure due to rapid water level rise. Especially for newly - built geomembrane - seepage - prevention reservoirs, rapid water storage may cause the geomembrane to bulge or rupture.
Reasonably control the water level variation range of the reservoir. Frequent and large - amplitude water level changes will subject the seepage prevention structure of the reservoir bank to repeated dry - wet cycles and changes in seepage pressure, accelerating the aging and damage of seepage prevention materials.
Daily Inspection
Regularly inspect the seepage prevention structure of the reservoir, including the reservoir bottom, banks, and connection parts. The inspection mainly includes whether there are phenomena such as damage, cracks, and bulges in the seepage prevention materials, and whether there are situations such as collapse and landslides of the slope protection.
Pay attention to changes in the surrounding environment of the reservoir, such as whether new pollution sources enter the reservoir, and whether geological disasters such as landslides and debris flows threaten the safety of the reservoir seepage prevention structure.
Repair and Reinforcement
For small - area damage to seepage prevention materials found, repair them in a timely manner. The repair materials and methods should be matched with the original seepage prevention materials to ensure the seepage prevention effect after repair.
After the reservoir has been in operation for many years, carry out reinforcement and renovation in a timely manner according to the degree of aging and damage of the seepage prevention structure. For example, replace the aged geomembrane and reinforce the concrete cut - off wall.
