Technological process
The construction process of FRP septic tank is as follows: positioning and setting out Excavation of foundation pit Treatment of base cushion Equipment in place Flushing in the pool Layered backfill Build connection well and inspection well Harden the ground.
Main construction methods
1) Setting out and trenching.
According to the model of FRP septic tank in the drawing, excavate the foundation trench according to the model size, elevation and ash line, and comply with the provisions of relevant construction specifications. Under the condition of high groundwater level, the excavation of pits and grooves requires drainage.
2) Treat the foundation cushion.
The bearing capacity of the foundation at the construction site of FRP septic tank should not be less than 100kn/ O. When there is no groundwater, 200mm thick sand cushion should be used; If there is groundwater or soft base, C10 concrete cushion shall be poured first, and 100mm thick sand cushion shall be paved; In the collapsible loess area, 300mm thick 3:7 lime soil cushion shall be made and compacted in layers, and the compaction coefficient shall not be less than 0.95. Pay attention not to excavate during construction, and the excavation must be backfilled and compacted to ensure compactness. After the treatment of the foundation cushion, a 5cm ~ 10cm sand cushion shall be made on the cushion. The sand cushion shall be made of sand that does not contain grass roots and other organic matters.
3) Equipment in place.
After the FRP septic tank arrives at the site, before the equipment is in place, check whether the surface is free of cracks, scratches and other obvious quality defects, check whether the elevation of each place is correct, and find out the water inlet and outlet direction of the equipment (with arrow marks). After confirmation, hoist the FRP septic tank into the foundation trench treated by the foundation with a crane, and check whether the elevation of the water inlet and outlet pipes of the equipment meets the requirements of the design drawings after it is in place, Whether the horizontal water flow axis is kept on the same axis as the sewer axis.
4) Flush the pool.
After the equipment is in place and meets the requirements, inject water into the equipment. During water injection, water of 1/3 height of the tank body shall be injected first, and soil shall be enclosed under the FRP septic tank to stabilize the FRP septic tank, and then water shall be injected into the tank synchronously according to the backfilling height to eliminate the partial impact force during backfilling as far as possible.
5) Backfill in layers.
After installation and water injection, backfill in time. Fill with yellow sand within 500mm on both sides of the bottom (if the soil is clay, fill all around the tank with yellow sand). When filling sand, sprinkle water into the sand for compaction every 300mm thick, and use a plate vibrator to vibrate when tamping (see Figure). The backfill shall not contain organic matter, frozen soil, large bricks and stones and other hard blocks, and shall not be backfilled with construction waste, but shall be backfilled with fine-grained soil; The backfilling can be carried out according to the virtual paving thickness of each layer of 250mm, which should be tamped manually. It is not allowed to impact violently or backfill mechanically, so as to prevent damage to the pool body.
6) Build connection well and inspection well.
When the backfilling reaches a certain height, the inlet and outlet connecting wells and inspection wells shall be installed. The bottom of the connecting wells and inspection wells must be made of concrete cushion to prevent the uneven settlement of the foundation from damaging the FRP septic tank and pipeline.
7) Harden the ground.
When the FRP septic tank is set under the roadway or parking lot, the covering soil should not be less than 1.5m and should be hardened. When hardening, it should be treated with steel-concrete structure to reduce the load of the FRP septic tank.
