This technology standard is applicable to the backfill of industrial and civil buildings, large sites, large foundation pits and pipe trenches.
2. 1 Materials and main machines:
2. 1. 1 Gravel soil, sandy soil (with the consent of the design unit when using fine sand and silt) and blasting slag can be used as fillers below the surface. The maximum particle size shall not exceed 2/3 or 3/4 of the paving thickness of each layer (when vibratory roller is used), and the water content shall meet the requirements.
2. 1.2 cohesive soil should be tested for water content, and it can only be used after reaching the design control range.
2. 1.3 Saline soil is generally not suitable for use. However, the filler does not contain salt crystals, salt lumps or roots of salt-bearing plants, and the saline soil can be used according to Schedule 1.8 of Code for Construction and Acceptance of Earthwork and Blasting Engineering.
2. 1.4 Main machines and tools:
2. 1.4. 1 Earth-moving machinery for loading includes shovels, dump trucks, bulldozers, scrapers and dumpers.
2. 1.4.2 Rolling machinery includes: flat roller, sheep foot roller and vibrating roller.
2. 1.4.3 general machinery includes frog or diesel rammer, trolley, spade (flat or sharp) 2m steel ruler, No.20 lead wire, rubber hose, 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. The parameters of important backfill earthwork should be determined by compaction test.
2.2.2 Before filling, the filling base and the completed project shall be inspected and accepted in the middle. After passing the inspection, the concealed acceptance formalities shall be handled.
2.2.3 Before construction, horizontal elevation signs shall be set. For example, nail horizontal piles every 1m at the edge of large foundation pits or ditches or copy standard elevation points on adjacent fixed buildings. Nail horizontal piles at regular intervals on a large area or floor.
2.2.4 To determine the walking route of earth-moving machinery and vehicles, it should be checked in advance, and the preparatory work such as reinforcement and widening should be carried out when necessary. At the same time to prepare the construction plan.
Process flow:
Foundation pit bottom cleaning → soil testing → layered soil spreading → layered rolling → density testing →
Finishing, leveling and acceptance
3. 1 Before filling the soil, the roots and garbage on the cave or basement surface on the foundation soil shall be treated and cleaned.
3.2 Check the soil quality. Check the type, particle size, presence of sundries, compliance with regulations and whether the water content is within the control range; If the water content is high, measures such as scarifying, airing or evenly mixing dry soil can be adopted; When the water content of the filler is low, measures such as sprinkling water in advance can be taken.
3.3 Fill shall be carried out in layers. The paving thickness of each layer should be determined according to the soil quality, compactness requirements and machine performance. Or according to table 1-8.
3.5 When rolling, wheel (ram) tracks should overlap each other to prevent pressure leakage or ram leakage. When the length and width are relatively large, it should be filled in sections. The joints of each layer should be made into a slope shape, and the grinding tracks overlap. The lap joint is about 0.5~l.0m, and the staggered joint distance between the upper and lower layers should not be less than1m.
3.6 When the fill exceeds the base surface, the compaction quality of the edge shall be guaranteed. After filling, if the design does not require slope repair, the filling edge should be 0.5m wide; ; If the design requires leveling and compacting the slope, the wide fill can be 0.2m.
3.7 In the filling parts that cannot be crushed by mechanical construction, artificial earth pushing should be used for filling, and frog or diesel rammer should be used for layered compaction.
3.8 After each layer of backfill earthwork is compacted, ring cutter sampling shall be carried out according to the regulations, and the mass density of dry soil shall be measured. After the requirements are met, the next layer of soil shall be spread.
3.9 After the completion of filling, the surface shall be leveled with stay wires, and any place beyond the standard elevation shall be leveled according to the line in time; When the elevation is lower than the standard elevation, it should be filled, leveled and compacted.
3. 10 rainy season and winter construction:
3. 10. 1 The filling works in the rain period shall be completed continuously as soon as possible; The working face should not be too large, and it should be layered and segmented, one by one. Important or special earthwork backfilling should be completed before the rain period as far as possible.
3. 10.2 When it rains, there should be rain-proof measures or schemes to prevent surface water from flowing into the foundation pit and floor, so as to avoid slope collapse or foundation soil damage.
3. 10.3 The filling project is not suitable for construction in winter. If construction must be carried out in winter, the construction method should be determined after technical and economic comparison.
3. 10.4 Before filling in winter, the ice and snow and thermal insulation materials on the basement should be removed; Frozen soil filling shall not be used within the range of 1m from the slope; The upper layer of filled soil should be non-frozen, non-frost heaving or permeable soil, and its thickness should meet the design requirements.
3. 10.5 When the average outdoor temperature in winter construction is above -5℃, the filling height is not limited; When the average temperature is lower than -5℃, the height of filled soil should not exceed the provisions in Table 1-9. However, when filling stones, sandy soil (excluding silt) and ice-free gravel soil, it is not limited by the filling height in the table.
3. 10.6 When backfilling earthwork in winter, the paving thickness of each layer should be reduced by 20% ~ 25% compared with that in normal temperature construction, and the frozen soil volume should not exceed15% of the total filling volume; Its particle size shall not be greater than150 mm. Frozen soil blocks should be evenly distributed and compacted one by one. Backfilling earthwork should be carried out continuously to prevent the foundation from falling off or the filled soil layer from freezing. And take anti-freezing measures in time.
4. 1 guarantee project:
4. 1. 1 basement treatment must meet the design requirements or construction specifications.
4. 1.2 Backfill materials must meet the design requirements or construction specifications.
4. 1.3 Backfill soil must be compacted by layers according to regulations. The mass density of compacted dry soil shall be determined by sampling, and the qualified rate shall not be less than 90%; The difference between the lowest mass density of unqualified dry soil and the design value should not be greater than 0.08g/cm3, and should not be concentrated. The sampling method and quantity of ring knives should comply with the regulations.
12 top surface elevation surface flatness +0, -5020 check with level or stay ruler, check with 2m guide ruler and wedge feeler.
5. 1 During construction, positioning standard piles, axis control rods, standard leveling points and portal frames shall not collide during earthwork filling and transportation, nor shall they be put on the portal frames. And should regularly retest to check whether these standard pile points are correct.
5.2 During construction at night, the construction sequence shall be arranged reasonably and sufficient lighting facilities shall be provided. In order to prevent the paving from being too thick, it is forbidden to pour the soil directly into the foundation pit (groove) by car. However, large floors are not restricted.
5.3 The cast-in-place concrete of foundation or pipe trench shall reach a certain strength to avoid damage due to backfilling, before backfilling earthwork.
6. 1 The dry soil mass density of the soil is not determined as required: the compacted dry soil mass density of each backfill shall be determined, and the upper soil can be paved only after it meets the design requirements. The test report shall indicate the type of soil material, test date, test conclusion and signature of the tester. Do not meet the design requirements, there should be treatment methods and re-inspection results.
6.2 Backfill soil subsidence: Backfill soil subsidence is caused by the fact that the virtual paving soil exceeds the specified thickness or there is a large frozen soil block during winter construction, or the compaction times are not enough, or even the tamping is missed, and the basement organic matter, tree roots, falling soil and other sundries are not thoroughly cleaned up. Therefore, in the construction, we should conscientiously implement the relevant provisions of the code, strictly check and correct the problems in time.
6.3 Backfill soil compaction is not dense: dry earth pressure should be properly watered in real time; Backfill soil is too wet, and it is "rubber soil" if it is not compacted. At this time, we should dig out the "rubber soil", change the soil again, and then compact it.
6.4 Measures should be taken when filling in areas with complex terrain and high density required by engineering geology. (such as drainage culverts, slope protection piles, etc.). ), to prevent the loss of fill particles, resulting in uneven settlement and collapse and other accidents.
6.5 When the filled foundation soil is miscellaneous fill, the foundation should be reinforced according to the design requirements, and the soft and hard points, cavities, old foundations and hidden ponds under the foundation should be properly handled.
6.6 When backfilling the trench, in order to prevent the center line of the pipeline from shifting or damaging the pipeline, fill the soil around the pipeline manually and tamp it at the same time from both sides of the pipeline until the top of the pipeline is more than 0.5m Mechanical backfilling and tamping can only be adopted without damaging the pipeline.
Anti-corrosion insulation layer or adhesive tape wiping interface around cables shall be backfilled with fine-grained soil.
6.7 The settlement of filled soil shall be reserved according to the design requirements. If there is no requirement in the design, it can be determined with the construction unit according to the engineering nature, fill height, filler type, compactness requirements and foundation conditions (the settlement generally does not exceed 3% of the fill height).
This process standard should have the following quality records:
7. 1 foundation treatment record.
7.2 Basic drilling exploration records.
7.3 Hidden acceptance record of foundation.
7.4 Test report of backfill soil.
The detailed information of "Technical Standard for Building Backfill Construction" can be found in the link of Zhong Da Consulting Design, and all the relevant building construction information you want is available.
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