Before tamping, the fill should be initially leveled, and the rammer should tamp in turn, evenly distributed, without gaps.
Unless otherwise specified, the compactness shall be generally compacted to the extent that the wheel settlement does not exceed 25px-50px.
Where the corners and slope edges cannot be compacted, they shall be compacted with manpower or small tamping machines.
2.3 Vibratory compaction method Vibratory compaction method is to place the vibratory compactor on the surface of the soil layer.
If the soil water content is too large, then if the compaction function is increased,/spring phenomenon will occur, and the compaction effect is very poor, resulting in rework waste.
1.1 Manual compaction method 1) Manual compaction method shall be adopted for places where mechanical compaction cannot be achieved and small areas of backfill.
In contrast, strictly controlling the optimum moisture content will yield much more than increasing the compaction function.
Generally, the flat roller and vibrating roller shall not exceed 2km/h, and the number of compaction times shall be controlled.
3.2 Influence of water content Under the same compaction work condition, the water content of fill has a direct impact on the compaction quality.
Before manual tamping, the fill shall be initially leveled.
2) The frog rammer and other small machines and tools are used to tamp the soil in real time.
The loose soil should be compacted with light roller first, and then with heavy roller, with good effect.
1.2 Mechanical compaction method 1) In order to ensure the uniformity and compactness of the filling compaction, avoid the sinking of the roller, and improve the rolling efficiency, it is advisable to use a light bulldozer to flatten the surface before rolling by the rolling machine, and preload it at a low speed for 4-5 times to make the plane flat and compact; The crushed stone soil shall be compacted by vibratory flat roller, and the static pressure shall be first followed by vibratory compaction.
Due to the construction site, construction machinery, special construction technical requirements and other reasons, the backfill construction method generally adopts manual compaction method or mechanical compaction method.
4) When backfilling the pipe trench, the soil around the pipe shall be filled and compacted manually, and the backfilling shall be carried out simultaneously from both sides of the pipe until the pipe top is more than 0.5m.
If the surface of the soil layer is too dry, it shall be watered and then backfilled to ensure a good combination of the upper and lower layers.
Generally, the fill thickness should not be greater than 625px, and the number of compaction times for each layer should be 3-4 times.
When the water content is insufficient and it is difficult to sprinkle water, properly increase the compaction function can achieve results.
The compaction machinery shall keep a certain distance from the foundation pipeline to prevent the foundation and pipeline from being crushed or displaced.
At the beginning of compaction, the dry density of soil increases sharply.
The pressure per unit area of sheep foot roller is relatively large, and the soil compaction effect is good.
3) Manual tamping shall be used in places where the tamping machine cannot work.
When tamping the foundation trench and floor, the tamping route should start from four sides and then tamp to the middle.
In the ramming type, in addition to the manually used stone and wood rammers, the mechanical equipment includes rammers, rammers, pneumatic rammers and frog rammers.
Therefore, in the compaction construction of soil foundation, the control of the optimum water content is the primary key.
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Therefore, in actual construction, do not blindly increase the number of compaction times.
Rolling machines include flat roller and sheep-foot roller.
The tamping shall be carried out in a certain direction.
The thickness of filling soil (plain soil, lime soil and gravel soil) shall not exceed 25-750px.
The distance between the edge of the grinding wheel and the filling edge during operation shall be more than 500mm to prevent slope sliding and chamfering.
1.
The filling compaction methods include rolling compaction, compaction and vibration compaction.
The dry soil is not easy to compact due to the large friction between soil particles.
2.
The dry density of the compacted fill has a certain relationship with the work exerted by the compaction machinery.
When the rolling machinery compacts the fill, the driving speed should not be too fast, and generally the flat rolling should not exceed 2kmPh; The rolling mill shall not exceed 3kmPh.
4) After rolling a layer, the surface shall be roughened by manual or bulldozer.
Sheep foot roller is generally used for rolling cohesive soil, not suitable for sandy soil.
The compaction method is applicable to the deep reinforcement of cohesive soil, collapsible loess and gravel fill foundation.
When it approaches the maximum dry density of soil, although the compaction work increases a lot, the dry density of soil hardly changes.
When the soil has a proper water content, the water plays a role in lubrication, and the friction resistance between soil particles is reduced, so it is easy to compact.
Mechanical backfilling and compaction can be used only when the pipeline is not damaged.
3) The method of “thin filling, slow driving and multiple times” shall be adopted for filling and compaction with the flat roller.
The rolling direction shall be gradually pressed from both sides to the middle.
Flat roller (smooth roller) is a self-propelled roller powered by internal combustion engine, with a weight of 6~15t.
One tamping and half tamping shall be carried out, and the tamping shall be connected, and the rows shall be connected, and the two times shall be crossed vertically and horizontally, and the layered tamping shall be carried out.
Factors that affect the compaction of fill The compaction quality of fill is related to many factors, among which the main factors are: compaction work, soil moisture content and the thickness of each layer of soil.
Under the effect of compaction vibration, the soil particles will have relative displacement and reach a compact state.
When rolling in sandy soil, the soil particles will move in all directions after being subjected to the unit pressure of sheep foot, which will destroy the soil structure.
The number of compaction times of each layer shall be 6-8 times.
2.2 Compaction method Compaction method is to use the free falling impact of the hammer to compact the soil, so that the pores in the soil are compressed and the soil particles are arranged more closely.
On the basis of expatiating the construction methods of backfill, this paper summarizes the concrete methods of backfill compaction, analyzes the factors that affect the compaction of backfill, and finally analyzes the common problems and treatment measures of earthwork backfill.
3.
The width of each overlap of the roller wheel shall be about 375px-625px to avoid missing compaction.
3.1 Impact of compaction work The impact of compaction function (weight of compaction tool, rolling times or hammer height, action time, etc.) on compaction effect.
The virtual paving thickness shall not be greater than 500px.
2.1 Rolling method is to use the pressure of mechanical roller to compact the soil to achieve the required compactness.
2) When the rolling machinery compacts the fill, the driving speed shall be controlled.
A large number of experiments and engineering practice of the filling compaction method have proved that the plastic deformation, permeability coefficient, capillary water effect and thermal insulation performance of the subgrade have been significantly improved after the compaction of the soil foundation.
Under normal conditions, the compaction effect of vibrating type is better for sandy soil.
