1.Phenomenon The foundation pit (trough) filled with local or a lot of settlement, resulting in the ground on the wall, outdoor water scattered hollow subsidence, building foundation water, and even cause structure sinking, cracks uneven.
2. Analysis of the causes (1) foundation pit (trough) in the water, the soil is not clear on the backfill; or on both sides of the loose soil backfill, based on the Chinese milling machine without separation compaction; or slot edge loose into the pit Treatment is not serious before the backfill by flooding settlement. (2) base width is narrow, the use of manual backfill, does not meet the requirements of the density. (3) backfill material in a large number of dry soil, by flooding settlement; or use a large amount of water content of clay, silt soil, debris soil for soil, backfill substandard quality. (4) backfill Shen bubble method, water content, practical asphalt pits repair equipment cost density can not meet the requirements.
3. Preventive measures (1) before the foundation pit (tank) backfill, the water tank should be drainage net, mud, loose soil, debris clean up, if groundwater or surface water, drainage measures should be taken. (2) backfill to take a strict classification backfill, compaction. Each layer of virtual soil thickness should not be greater than 300mm soil layer, water content should be in line with regulations. Backfill density according to the provisions of sampling inspection to meet the requirements. (3) The soil fill material should not contain more than 50mm diameter soil block, should not have more dry clods, for the urgent need for the next process, road asphalt grouting tool is suitable for use 2: 8 or 3: 7 Lime backfill compaction. (4) is strictly prohibited with the sprinkler method of filling works.
4. Governance (1) foundation pit (trough) caused by the hollow wall of the backfill settlement, such as the concrete surface has not yet destroyed, can be filled with gravel, lateral compression compaction 3, if the surface has cracked, depending on size or damage, All rework. The local treatment may be a hammer, a chisel to the hollow part, a lime or clay-filled mixture, a gravel mixture compacted, and then applied to the surface layer. (2) due to structural settlement caused by backfill settlement, should contact the design department to strengthen measures.