Process flow: base course cleaning → soil quality inspection → surveying and setting out → soil paving in layers → compaction in layers → compactness inspection → correction, leveling and acceptance.
Foundation backfilling A.
c.
The method and quantity of ring knife method for measuring compactness shall comply with the following provisions: for foundation pit and indoor fill, one group shall be sampled for each layer of 100-500 m2; The site is leveled and filled, and a group of 400-900 M2 samples are taken for each layer; For the backfilling of foundation pit and pipe trench, one group shall be sampled every 50-100 m2, but not less than one group shall be sampled for each layer, and the sampling part shall be in the lower half of each layer after compaction.
5.
The staggered joint distance between the upper and lower layers shall not be less than 1.0m.
During backfilling, the selected construction tools shall be adjusted according to different parts.
Tamping shall be one tamping and half tamping, connected in rows, and crossed vertically and horizontally.
If it is necessary to fill and tamp in sections, the junction shall be filled into a ladder shape with a height of 25cm.
4 garage top backfill the first layer of backfill at the garage top shall be backfilled manually, leveled manually and compacted mechanically.
Construction and safety precautions 1.
General tools: frog type rammer, vertical rammer, trolley, spade, 2m steel tape and rubber tube.
It is very easy to have quality defects such as uncompacted backfill.
b.
3.
In construction projects, however, quality management is often neglected because of rush time and other factors.
Construction preparation 1 construction method rolling compaction method vibration method 2 operation conditions Process Description: the waterproof construction is completed before backfilling, and the backfilling can be carried out after passing the acceptance.
b.
Gravel soil and sandy soil (the use of fine and silty sand shall be approved by the designer) and blasting slag can be used as filler below the surface.
The construction materials and construction waste on the working surface shall be cleaned before filling.
However, the filler shall not contain salt crystals, salt blocks or roots of saline plants, and shall comply with the code for construction and acceptance of earthwork and blasting engineering The specified in Table 1 ~ 8 of Appendix I can be used.
During paving and filling, frozen soil blocks shall be evenly distributed and compacted layer by layer.
This paper is an example of backfill construction on the high-quality project of Beijing company of China Construction Fifth Bureau.
Before backfilling, the foundation pit shall be checked for collapse by a specially assigned person, and the process shall be watched by a specially assigned person..
Saline soil can not be used generally.
After meeting the requirements, the upper layer of soil shall be paved.
When entering the construction site, wear a safety helmet and fasten the hat belt.
The backfill material must be submitted for inspection to test its water content and maximum dry density.
It can be put into use only after passing the inspection and meeting the following requirements.
3.
The fertilizer tank can be backfilled only after the foundation wall reaches a certain strength.
Backfilling parts and requirements 1.
When backfilling by sections, each layer at the joint shall be staggered by more than 1m.
When the deep and shallow foundation pits are connected, the deep foundation pit shall be filled and tamped first.
2 acceptance standard remarks: the paving thickness of each layer of backfill in winter shall be 20% ~ 50% less than that in normal temperature construction; The volume of frozen soil block shall not exceed 15% of the total volume of fill; The particle size shall not be greater than 150 mm.
It comprehensively interprets the key points of the process, which is worthy of reference and study.
Soil: it shall be screened before use, its particle size shall not be greater than 50mm, and shall not contain organic impurities and frozen soil.
The soil shall be paved in layers, and the thickness of each layer shall be determined according to the soil quality, compactness requirements and machine performance.
2.
The maximum particle size shall not exceed 2 / 3 or 3 / 4 of the paving thickness of each layer (when vibratory roller is used), the water content shall meet the requirements.
4.
3.
When it is filled to the elevation of the shallow foundation pit, it shall be filled and tamped together with the shallow foundation pit.
The surrounding of the foundation can be backfilled evenly at the same time, so as to avoid stacking heavy objects on one side or walking heavy machinery and equipment.
The paving thickness of each layer shall be leveled and equal to the elevation on the pit side wall, or checked with ruler and standard rod.
Backfilling and compaction of room core: the number of compaction shall not be less than three times.
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when the backfill soil is deep and the area is large, the original natural soft soil and pits shall be treated to clean up the organic impurities.
The paving thickness of each layer of backfill in winter shall be 20% ~ 25% less than that during normal construction, in which the content of frozen soil shall not exceed 15%, and its particle size shall not be greater than 150 mm, and the particle size of backfill at normal temperature shall not be greater than 50 mm.
Roller compaction machinery: flat roller, sheep foot roller and vibrating roller.
The water content of cohesive soil shall be inspected and can be used only when it meets the requirements of design and construction specifications.
When the length width ratio is large, the backfilling length shall be a section every 15m, the joints of each layer shall be made into a stepped shape, the grinding tracks shall overlap by 0.5 ~ 1.0m, and the staggered joint distance between the upper and lower layers shall not be less than 1m.
Outside 500mm above the pipeline, mechanical compaction shall be used normally.
The backfill at the pipeline is limited by the pipeline, so it is no longer possible to use mechanical compaction, so it shall be compacted manually from below the pipeline; Manually tamp both sides of the pipeline and within 500mm above it to avoid damaging the pipeline.
The filling layer thickness and compaction times shall comply with the provisions of the above table.
Acceptance standards and quality requirements 1.
Backfill soil containing frozen soil shall not be used within 0.5m from the bottom of the backfilled pipe trench to the top of the pipe in winter.
Smoking, slapstick and drunk operation are strictly prohibited.
2.
The site and the second layer of earthwork shall be backfilled and transported to the earthwork backfilling part by loader and bulldozer, and leveled by loader.
Optimum moisture content (weight ratio) should be in conformity with the following requirements: Sand: 8-12%; clay: 19-23%; silty clay: 12-15%; silty soil: 16-22%.
5.
Main machinery and equipment for loading earthwork: shovel truck, dump truck, earth dumper, scraper truck, dumper truck.
After compaction of each layer, ring knife sampling shall be carried out according to the specifications, and the mass density of dry soil shall be measured in the field test.
The backfill work shall be carried out continuously to prevent the foundation soil or filled layer from freezing, and anti freezing measures shall be taken in time.
2.
Material requirements 1 The project is backfilled with plain soil (locally lime soil).
The so-called “water tamping” method of pouring with water to sink the soil is strictly prohibited.
