Construction of Geotextile for Seepage Prevention on Reservoir Slopes

Preparation before Construction

1. Material Preparation: Select geotextiles of appropriate specifications and quality. Their physical and mechanical properties (such as tensile strength, bursting strength, coefficient of permeability, etc.) should meet the design requirements for reservoir seepage prevention. At the same time, prepare the materials required for connecting geotextiles, such as sewing threads, adhesives, or welding equipment (if the geotextiles are weldable), as well as anchorages, compression strips, etc. for fixing the geotextiles.

2. Site Investigation and Measurement: Conduct a detailed investigation of the reservoir slope to understand its topography and geological conditions, including the slope gradient, type of rock and soil, and the presence of cracks or unstable areas. Accurately measure the dimensions of the slope to provide a basis for cutting and laying the geotextile.

3. Slope Treatment: Remove sundries such as weeds, tree roots, and stones on the slope. Tamping the loose rock and soil to make the surface of the slope flat and firm. For parts with cracks or holes, they should be sealed and repaired to ensure the stability of the slope and the seepage prevention effect.

Laying of Geotextiles

1. Cutting and Splicing: According to the measured dimensions of the slope, cut the geotextile into appropriate sizes and shapes. For large-area laying, it may be necessary to splice multiple pieces of geotextiles. The splicing method depends on the type of geotextile. Needle-punched non-woven geotextiles are generally sewn, and the sewing thread should have sufficient strength and water resistance. For weldable geotextiles (such as some synthetic geotextiles), hot melt welding or ultrasonic welding is used. During welding, ensure the welding width and quality to avoid problems such as false welding and missed welding.

2. Laying Sequence: Generally, start laying from the top of the reservoir slope downwards. First, fix one end of the geotextile in the anchoring groove or other fixing structures at the top of the slope, and then unfold it along the slope surface. During the laying process, pay attention to keeping the geotextile flat and avoid wrinkles, twists, or hanging situations. If the slope gradient is large, a segmented laying method can be adopted, and the connection between each segment should be firm and reliable.

3. Fixing and Anchoring: During the laying of the geotextile, use U-shaped nails, anchorages, or compression strips to fix the geotextile on the slope at intervals of a certain distance (such as 1-2 meters) to prevent it from sliding or being blown up by the wind. At the top and bottom of the slope, the geotextile should extend into the anchoring groove and be backfilled and compacted with concrete or other materials to achieve reliable anchoring. For the corners and special parts of the slope, strengthen the fixing measures to ensure that the geotextile fits closely with the slope.

Connection with Other Structures

1. Connection with the Dam Body: When the geotextile is laid to the dam body part of the reservoir, it should be properly connected with the dam's seepage prevention structure (such as the clay core wall, concrete face slab, etc.). The geotextile can be embedded in the reserved groove of the dam's seepage prevention structure and sealed with a sealing material to ensure the seepage prevention effect at the connection.

2. Connection with Drainage Facilities: If there are drainage facilities (such as drainage holes, drainage ditches, etc.) set on the reservoir slope, the geotextile should be reasonably connected with the drainage facilities. It is necessary to ensure unobstructed drainage and prevent water from seeping from the connection. Generally, an anti-filtration layer can be set around the drainage facilities, and the geotextile, as a part of the anti-filtration layer, plays the role of filtration and seepage prevention.

Construction of the Protective Layer

1. Material Selection: In order to protect the geotextile from external factors (such as sunlight ultraviolet rays, mechanical damage, water flow scouring, etc.), a protective layer needs to be set on the surface of the geotextile. Commonly used protective layer materials include clay, sand and gravel, concrete, etc. For small reservoirs or parts with relatively low seepage prevention requirements, clay or sand and gravel can be used as the protective layer, with a thickness of generally 30-50 cm. For large reservoirs or important parts, concrete can be used as the protective layer. The strength grade and thickness of the concrete should be determined according to the design requirements, generally with a strength grade not lower than C20 and a thickness of 10-20 cm.

2. Construction Method: If clay or sand and gravel are used as the protective layer, it should be laid in layers and compacted. The thickness of each layer should not be too large to ensure the density and stability of the protective layer. During the laying process, avoid damaging the geotextile. If concrete is used as the protective layer, it should be poured and cured according to the relevant specifications of concrete construction to ensure a tight combination between the concrete and the geotextile and form an effective seepage prevention system.

Quality Inspection and Acceptance

1. Inspection during Construction: During the laying and construction of the geotextile, conduct quality inspection on each construction process. This includes the splicing quality of the geotextile (such as sewing strength, welding quality), fixing and anchoring conditions, and laying flatness. For the problems found, rectify them in a timely manner to ensure that the construction quality meets the requirements.

2. Completion Acceptance: After the seepage prevention construction of the reservoir slope is completed, a comprehensive acceptance inspection should be carried out. The acceptance content includes the laying range of the geotextile, connection quality, and construction quality of the protective layer. Acceptance can be carried out through methods such as appearance inspection, sampling inspection (such as testing the physical and mechanical properties of the geotextile), and water filling test (observing whether there is any seepage on the slope after the reservoir is impounded). Only when all indicators meet the design requirements can the acceptance be passed and the project be put into use.