The following criteria are taken into consideration in buried GRP pipe systems.
Material placed and compacted in the bottom of the trench to replace over excavated material and/or to stabilize the trench bottom if unsuitable ground conditions are encountered.
Backfill material placed in the bottom of the trench or on the foundation to provide a uniform material on which to lay the pipe.
Backfill material placed at the sides of the pipe and up to 300 mm over the top of the pipe. The backfill materials are classified in different groups based on the soil stiffness when compacted and the groups are shown in the table below. If the backfill material is required to be compacted, a surface plate vibrators, vibratory rollers, or internal vibrators shall be used and
Backfill material placed from the top of the initial backfill to the ground surface in order to preclude damage to the pipe and disturbance to pipe embedment. Depending on the backfill material type, a cover of at least 0,8 m to 1,2 m shall be considered. If there is a risk of pipe flotation, the burial depth should be at least equal to the pipe diameter.
Unbalanced hydrostatic thrust forces occur at changes in direction when a pipeline is subjected to an internal pressure. In order to avoid coupling separation and damages due to pipeline movements, thrust forces must be adequately restrained by using a thrust block.
While connecting GRP pipes to rigid structures, short pipes (rocker pipes) shall be used to minimize the bending and shear stress acting on the pipe due to the excessive settlement difference between pipe systems and rigid structure. The short pipes shall be installed in straight alignment and the surrounding soil shall be compacted properly and with extra care.