It is common to encounter different construction tasks during construction. In general construction, the roller needs to be adjusted according to different materials. Today small make up also prepared full dry goods — & ndash; How to compaction the soil.
Soil is generally composed of solid particles, water and air. The proportion of solid, liquid and gas in the soil reflects the degree of dry and wet and compactness. For the compaction of soil, the construction method of cushion is usually adopted. The cushion method can be divided into mechanical compaction method, heavy hammer compaction method and vibration compaction method.
01
Mechanical rolling method
Mechanical compaction is the use of a roller, Bulldozer, sheep foot, vibration or other compaction machinery to compaction weak foundation soil or layered filling pad. It is often used in projects with large area of foundation pit and large volume of earthwork. Generally, the depth of surface foundation reinforcement by rolling method can reach 2~3m. Generally, the bearing capacity of the foundation can reach 80~100kPa after surface compaction.
Construction key points
1. Dig out the soft soil at a certain depth within the proposed scope to meet the design requirements;
2. Compaction and reinforcement of the bottom soil;
3. Layered filling and layer by layer encryption.
Construction parameters
Such as construction machinery, paving thickness, rolling times and fill water content, etc. by site test to determine. In order to ensure the effective compaction quality, the rolling speed should be controlled to some extent, such as 2.0km/h for flat roll, 3.0km/h for sheep foot roll, and 2.0km/h for vibration roll.
Quality inspection
During construction, the average dry density and water content were tested with the layer. The method of ring tool or penetration is adopted. Set a test point for each foundation pit or 100-500m.
02
Heavy hammer ramming method
Heavy hammer tamping is the mechanical ramming hammer (15~30kN) raised to a certain height (2.5~4.5m), then free fall hammer, repeatedly ramming to strengthen the foundation. Heavy hammer ramming is suitable for a ramming to the ramming construction sequence. In the independent cylindrical foundation pit, ramming should be done in the order of first outside and then inside. If the elevation of the bottom surface of the same foundation pit is different, it should be rammed layer by layer in the order of first deep and then shallow.
Construction key points
1. Test ramming on site;
2. Check the water content of the soil in the pit before ramming;
3. Construction ramming technology;
4. Necessary protective measures shall be taken when there are slopes or adjacent buildings on site.
Quality inspection
Check not only the construction record and the final subsidence of the test compaction, but also the reinforcement quality. Base groove every 30m point, the whole foundation every 100m2 above two points. The bearing capacity of the foundation after ramming with heavy hammer can reach 100~150kPa.
03
Plate vibration method
Vibratory compaction is the use of a variety of vibratory roller, the loose soil vibration and compaction. It is suitable for treating non-viscous soil or loose mixed soil with low clay content and good permeability.
Compaction principle
The vibratory roller is usually driven by the driving device to drive two eccentric blocks to rotate in reverse at the same speed to produce great vertical vibration force, which can effectively compact the rolling material.
Compaction effect
The effect of vibratory compaction is related to filling composition, vibratory time and other factors. Generally, the longer the vibration time is, the better the effect will be. However, when the vibration time exceeds a certain value, the vibration force will affect the basic stability of the subsidence. Therefore, it is necessary to conduct vibration test before construction to get the relationship between stable subsidence and vibration time.
Construction key points
The compaction range should be about 0.6m from the base edge, on both sides of the first vibration base groove and in the middle of the second vibration. The compaction standard is that the vibration of the vibratory roller in situ will not continue to sink, supplemented by light touch test to test its uniformity and affected depth.
Construction parameters
For construction waste mainly composed of slag, broken brick and tile, the vibration time is about 1min or more; The vibration time of the fine filling soil containing furnace ash is about 3~5min, and the effective vibration depth is 1.2~1.5m. The characteristic value of bearing capacity of foundation can reach 100~120kPa.
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