Backfill refers to the soil that is returned to the ground after the foundation and other works are completed during the construction.Backfill refers to the construction process of borrowing and backfilling within 5m after the completion of foundation, cushion and other concealed works.
(1) The backfill volume of trench and foundation pit is calculated by subtracting the volume of buried objects (including foundation cushion, foundation, etc.) below the designed outdoor terrace from the excavation volume.
Quantities of trench and foundation pit backfill=excavation volume - volume of foundation, cushion, etc. buried below the outdoor floor
（2）Room core backfill, calculated by multiplying the area between main walls by the thickness of backfill.Room core backfill refers to the backfill between the outdoor terrace and the indoor ground cushion, also known as indoor backfill.
Quantity of backfill in the room core=net area between main walls * thickness of backfill
=(Ground floor area - area occupied by main wall) * thickness of backfill
In the formula, the backfill thickness is the distance between the designed outdoor terrace and the indoor ground cushion.
(3) The trench backfill volume of the pipeline is calculated by subtracting the volume of pipe diameter from the excavation volume.If the pipe diameter is less than 500mm, the volume occupied by the pipe will not be deducted;When the pipe diameter exceeds 500mm, the volume of pipe shall be deducted according to the following table.
Pipeline name
Diameter mm
501~600
Diameter mm
601~800
Diameter mm
801~1000
Diameter mm
1101~1200
Diameter mm
1201~1400
Diameter mm
1401~1600
Steel pipe
zero point two one
zero point four four
zero point seven one
Cast iron pipe
zero point two four
zero point four nine
zero point seven seven
Concrete pipe
zero point three three
zero point six zero
zero point nine two
one point one five
one point three five
one point five five
Rules of quantities
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Calculated as per the dimension shown in the design drawing in terms of calculation volume:
1. Site backfill: backfill area times average backfill thickness
2. Indoor backfill: net area between main walls times backfill thickness
3. Foundation backfill: the volume of excavation minus the volume of foundation buried below the designed outdoor terrace (including the foundation cushion and other structures)
Mechanical backfill
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This technical disclosure is applicable to industrial and civil buildings, structures, large-area leveling sites, large foundation pits, pipe trenches and other backfill projects.
1. Material requirements
(1) Gravel soil, sand (the use of fine and silty sand shall be approved by the design unit) and blastingStone ballast, which can be used as filler below the surface.The maximum particle size shall not exceed 2/3 or 3/4 of the paving thickness of each layer (when vibratory rolling is used), and the moisture content shall meet the requirements.
(2) The moisture content of cohesive soil shall be inspected and it can be used only when it meets the requirements of design and construction specifications.
(3) Saline soil cannot be used generally.However, the filling materials shall not contain salt crystals, salt blocks or roots of salt plants, and can be used if they meet the requirements in Table 1-8 of Appendix I of the Code for Construction and Acceptance of Earthwork and Blasting Engineering.
(2) Rolling machines include: hand rolling, sheep foot rolling and vibration rolling.
(3) General tools include frog or diesel rammer, trolley, shovel (two kinds of flat head and pointed head), 2m steel tape, 20 # lead wire, rubber hose, etc.
3. Operating conditions
(1) Before construction, parameters such as the control range of water content of fill soil, virtual paving thickness and compaction times shall be reasonably determined according to project characteristics, fill soil types, compactness requirements, construction conditions, etc;The parameters of important backfill earthwork shall be determined through compaction test.
(2) Before filling, check and intermediate acceptance shall be carried out for the filling base and completed works, and records and acceptance procedures shall be made after they are qualified.
(3) Before construction, horizontal elevation signs shall be arranged properly.For example, horizontal pegs shall be nailed every 10m on the foundation pit or ditch edge or standard elevation points shall be found on the adjacent fixed buildings.Horizontal piles can also be nailed every 10 meters on large areas of the site.
4. Operation process
technological process;
Base cleaning → soil quality inspection → layered soil paving → rolling compaction → leveling acceptance
(1) Before filling, garbage or tree roots and other sundries and caves on the base surface shall be disposed and cleaned.
(2) Inspection of soil quality: inspect whether the moisture content of various soil materials is within the control range.If the moisture content is high, measures such as scarifying and drying can be taken;If the moisture content is low, measures such as pre watering and wetting can be taken.
(3) The fill shall be paved in layers.The thickness of each layer of soil shall be determined according to soil quality, compactness requirements and machine performance.Or select according to Table 2.During rolling, the wheel (tamping) marks shall be overlapped to prevent missing compaction
Laying thickness and compaction times of each layer of fill
Compaction machine
Thickness of each layer (mm)
Compaction times of each layer (times)
Flat roller
Sheep foot roller
Frog rammer
Bulldozer
Tractor
Manual tamping
200~300
200~350
200~250
200~300
200~300
Not more than 200
6~8
8~16
3~4
6~8
6~16
3~4
Note: The particle size of soil block shall not be greater than 5cm during manual tamping.
Earthwork backfilling
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Earthwork backfilling is the filling of construction projects, mainly including foundation filling, foundation pit (trench) or pipe trench backfilling, indoor floor backfilling, outdoor site backfilling and leveling.For the backfill on both sides, around and above the underground facilities (such as underground structures, ditches, pipeline trenches, etc.), various inspections shall be carried out for the underground works first, and the backfill can only be carried out after the acceptance procedures are handled.[1]
Backfilling method
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(1) Manual filling method
(2) Mechanical filling methods generally include bulldozer filling;Earth filling by scraper;There are three types of vehicle fill.
(3) Compaction methods generally include rolling compaction, tamping, vibrating compaction and compaction with earth moving tools.For large-area filling works, rolling and earth moving tools are often used for compaction.Compaction tools should be used for compaction of small area filling works.
