One, the bottom of the glass fiber reinforced plastic (GRP) pipeline trench is uneven, containing hard obstacles such as hard soil lumps and stones. Generally, trenches in low-lying areas are excavated mechanically, and due to the low terrain, the trench bottom is often moist or waterlogged, making the presence of hard objects like碎石, brick pieces, and obstructions highly probable, especially when these hard objects are submerged below the water level, making them difficult to detect. After the GRP pipeline is installed on the water surface, it is directly backfilled, causing the pipeline to be pressed directly onto the hard objects. Initially, this may not cause damage due to the loose backfill soil, but as the backfill soil settles and compacts, the internal pressure of the pipeline and the flow of internal liquids lead to minor vibrations over time. These vibrations increase the point load caused by the hard objects on the GRP pipeline, and the points of contact where the hard objects act will inevitably be damaged. Additionally, an uneven trench bottom can lead to uneven stress distribution on the pipeline, causing stress concentration at elevated areas during backfilling, potentially damaging the pipeline or causing unnecessary wear. This wear is exacerbated when pulsating pressure is present in the pipeline system.
Large amounts of accumulated water and cave-ins in the trench. Groundwork construction often coincides with the rainy season, and due to the low-lying terrain of the construction site, the water level in the trench can rise significantly, reaching over 10 meters in depth. Since high-pressure glass steel pipes are lightweight, once installed in the trench, they float on the water surface. Due to the buoyant force of the water, it is difficult to compact the glass steel pipes into the bottom of the trench during backfilling, resulting in a depth that does not meet the design specifications. Additionally, with excessive water in the trench, it is challenging to maintain the levelness of the bottom and to identify any obstacles like pipeline crossings and hard debris such as rocks, making it difficult to ensure the construction quality of the glass steel pipes. Accumulated water in low-lying trench areas can easily lead to cave-ins, with large, solid chunks of soil often falling directly onto the glass steel pipelines, damaging the lines.
Three, the presence of hard objects such as stones in the backfilled trench soil and the impact force from mechanical backfilling. In low-lying areas, the backfilled soil is often more moist, and in some cases, it is mostly in a clayball state. During the backfilling process, if clayballs contain hard objects like stones, they are difficult to detect. These stones, when buried at the bottom of the trench, come into direct contact with the glass fiber reinforced plastic (FRP) pipes, posing significant harm to them. There is also a possibility that during the backfilling process, due to the large size of the stones, the impact of gravity can directly damage the FRP pipeline. During mechanical backfilling, when the bucket is full of soil, it is directly backfilled into the trench from a height, which can also damage the pipeline due to the high impact force.
Other factors, such as improper operation by construction personnel. During construction, due to the poor working conditions in low-lying areas, workers do not follow standard procedures. For instance, when connecting pipes, the mud and water on the threaded parts are not cleaned thoroughly, resulting in insufficient threading depth and water, mud, and debris entering the pipeline. Additionally, workers frequently discard tools haphazardly, which is particularly prone to damaging glass-reinforced plastic (GRP) pipelines. These minor details are potential hazards in the construction of high-pressure GRP pipelines.
