What are the key considerations for the construction quality of geogrids?
On a flat and compacted site, the main force-bearing direction (longitudinal) of the installed and laid geogrids should be perpendicular to the axis of the embankment. The laying should be flat, without wrinkles, and as taut as possible. They should be fixed with pins and weighted down with soil and stones. The main force-bearing direction of the laid geogrids should have no joints throughout their length, and the connection between adjacent sections can be manually bound and overlapped, with an overlap width of no less than 10 cm. The overlapping part should be bound in a “zigzag” pattern using polyethylene ropes. Additionally, U-shaped nails should be used to secure the geogrids in the soil and tighten them, with a spacing of 1.5m*1.5m. If more than two layers of geogrids are installed, the layers should be staggered. After large-scale laying, the overall straightness should be adjusted. After covering with a layer of soil and before compaction, the geogrids should be tightened again manually or with machinery, with even force, to ensure that they are taut and under tension in the soil.
Today, the geogrid manufacturer will guide you through the key factors affecting the construction quality of geogrids. At longitudinal fill-excavation junctions of roadbeds, geogrids should be laid horizontally along the roadbed, extending 30 cm beyond the outer edge of the fill slope, and the exposed part should be trimmed during slope finishing. At transverse fill-excavation junctions of roadbeds, geogrids should be laid longitudinally along the roadbed, extending 30 cm beyond the half-fill and half-excavation roadbed section. The functional parameters of the geogrids should comply with the corresponding requirements of Chinese national standards.
Selection of fill materials: Fill materials should be selected according to design requirements. Practice has shown that, except for frozen soil, swamp soil, domestic waste, chalk soil, and diatomaceous earth, all other materials can be used as fill. However, gravelly and sandy soils have stable mechanical properties and are little affected by moisture content, so they should be preferred. The particle size of the fill should not exceed 15 cm, and attention should be paid to controlling the gradation of the fill to ensure compaction weight. After the geogrids are laid and positioned, they should be promptly covered with soil, and the exposure time should not exceed 48 hours. Alternatively, a continuous operation method of laying and backfilling simultaneously can be adopted. Fill materials should be spread from both ends first to secure the geogrids, and then pushed towards the center. The compaction sequence should be from both sides to the middle. During compaction, the compaction wheel should not directly contact the reinforcement materials. Vehicles are generally not allowed to travel on uncompacted reinforced soil to prevent displacement of the reinforcement materials. The layered compaction thickness should be 20-30 cm, and the compaction degree should meet the design requirements, which is also crucial for the success of reinforced soil projects.
When continuing to fill the roadbed on top of the laid geogrids, when pushing and spreading the well-mixed fill materials, the blade should be raised high first to completely cover the geogrids before spreading according to the loose laying thickness, supplemented by manual inspection and removal of hard block materials to prevent distortion or displacement of the geogrids.
Waterproofing and drainage measures: In reinforced soil projects, proper drainage treatment must be carried out both inside and outside the wall; toe protection must be provided to prevent erosion; filtering and drainage measures should be set up within the soil mass, and if necessary, geotextiles and permeable pipes (or blind ditches) should be installed. Drainage should be guided and not blocked; otherwise, dangers may arise.
