|The standard trench type prepared for laying GRP pipes is depicted below. The GRP pipes are manufactured in stiffness categories of SN 2500, 5000 ve 10000 N/m2, and offer alternate laying options based on the load (live load, filling load etc.). In general, the bedding material is preferred to be the same as the material used for the initial backfill. h = D/2 (max.300 mm), b= D/4 (min. 150 mm)|
|The initial deformation limit for the GRP pipes laid underground is 3% for pressurized pipes DN≥300 mm and 6% for gravity pipes ≥300 mm.|
Removal of water is always a good application before laying the pipes and backfilling. Well points, deep wells, geotextile, perforated drainages or stone blankets with enough thicknesses are used for removing and controlling the water inside the trench. Underground water shout always be below cutting level thus overflowing through coating or overflowing from the open trench walls are prevented. Water removal methods should be used in order to prevent loss of soil support, to prevent formation of holes inside the in-situ materials and to decrease loss of fine materials. Materials that are layered properly should be used for basic layers in order to divert water flows towards drainage pits or other pits.
|Concrete Coating and Flotation
Concrete should be cast in phases allowing sufficient time gap between layers in order for the concrete to cure and for the surface forces not to exist anymore. Maximum elevation heights are depicted in the table below. The movement of pipe should be restricted during concrete casting or in order to prevent flotation. This is generally realized by fixing the pipe to the trench bottom with a strap or other anchors. The straps are generally 25 mm-wide flat straps, resistant against flotation forces.