Technical disclosure of sub-project of foundation pit backfilling?

1. 1 This process standard is applicable to artificial backfill soil such as foundation pit, foundation trench, indoor terrace, pipe trench, outdoor fertilizer pond and apron in general industrial and civil buildings.

2. 1 Materials and main machines:

2. 1. 1 soil: soil excavated by foundation trench shall be used first, but it shall not contain organic impurities. Before use, it should be sieved, its particle size is not more than 50mm, and its moisture content should comply with the regulations.

2. 1.2 main machines include frog or diesel rammer, handcart, wooden harrow with sieve (aperture 40 ~ 60 mm), 2m ruler with spade (tip and flat head), rubber hose, string, wooden folding ruler, etc.

2.2 Operating conditions:

2.2. 1 Before construction, the parameters such as water content control range, virtual paving thickness and compaction times of the filler should be reasonably determined according to the engineering characteristics, filler types, compactness requirements and construction conditions. Important backfill earthwork, its parameters should be determined by compaction test.

2.2.2 Before backfilling, the foundation, box foundation wall or underground waterproof layer and protective layer shall be inspected and accepted, and the hidden inspection procedures shall be handled. Its foundation concrete strength should meet the specified requirements before backfilling.

2.2.3 Backfilling of building center and trench shall be carried out after the installation of water and gas pipelines and the reinforcement between trench walls are completed. And clean up the water and organic matter in the trench and the ground.

2.2.4 Before construction, horizontal marks shall be made to control the height or thickness of backfill soil. For example, in the foundation pit (groove) or pipe trench slope, nail a flashing board every 3 meters; Play horizontal lines on indoor and aproll walls or nail elevation control piles on the floor.

3. 1 process flow: cleaning the bottom floor of the foundation pit (trough) → testing soil quality → spreading soil in layers, harrowing → tamping compaction → testing compactness → trimming and leveling. 3.2 Before filling the soil, the garbage and other sundries at the bottom of the foundation pit (trough) or on the floor should be cleaned up; Before the fertilizer box is backfilled, it must be cleaned to the bottom elevation of the foundation, and the scattered loose garbage, mortar, stones and other sundries must be removed.

3.3 Check the quality of backfill soil for sundries, whether the particle size meets the requirements, and whether the water content of backfill soil is controlled; If the water content is high, measures such as scarifying, airing or evenly mixing dry soil can be adopted; When the water content of backfill soil is low, measures such as watering and wetting can be taken in advance.

3.4 Backfill soil shall be laid in layers. The paving thickness of each layer should be determined according to the soil quality, compactness requirements and mechanical properties. Generally, the soil thickness of each layer of frog rammer is 200 ~ 250 mrn, and the artificial compaction shall not exceed 200 mm. After each layer is paved, it should be raked flat.

3.5 Each layer of backfill soil shall be compacted at least three times. Tamping should be done once and a half times. Bad tamping should be connected in rows and crisscrossed. It is also forbidden to use the so-called "water rammer" method to sink the soil by pouring water.

3.6 When two deep foundation pits (grooves) are connected, the compacted deep foundation should be filled first; When it is filled to the same elevation as shallow foundation pit, it will be compacted with shallow foundation. If it is necessary to fill and tamp in sections, the junction should be filled in a stepped shape, and the height-width ratio of the stepped shape is generally 1: 2. The staggered joint distance between the upper and lower floors should not be less than 1.0m 3.7 The backfill of foundation pit (groove) should be carried out at the same time on the opposite side or around. The elevation difference on both sides of the foundation wall should not be too large, so as not to squeeze the wall; For the long trench wall, internal support measures should be taken, and then earthwork should be backfilled on the outside.

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