Directory

1. Application field

2. Construction Features

3. Construction technology

The dynamic compaction method is the strong compaction method, also known as the dynamic consolidation method. It is to use a large crawler-type dynamic compactor to freely drop a heavy hammer of 8-30 tons from a height of 6-30 meters, to perform strong compaction on the soil, to rapidly increase the bearing capacity and compressive modulus of the foundation, and to form a relatively uniform and dense foundation. , changes the pore distribution of the foundation soil within a certain depth of the foundation.

Application field

1. After years of practice and the update of dynamic compaction equipment, the dynamic compaction method has been widely used in the construction of highways and railways, airports, nuclear power plants, large industrial areas, port reclamation and other foundation reinforcement projects. There are successful construction cases for fill foundation, high water content foundation, port reclamation foundation, sea water filling foundation, etc.

The dynamic compaction method is suitable for the treatment of gravel soil, sandy soil, low saturation silt and cohesive soil, collapsible loess, plain fill and mixed fill.

2. Before dynamic compaction construction, one or several test areas should be selected on a representative site of the construction site for trial compaction or experimental construction. The number of test areas should be determined according to the complexity of the construction site, construction scale and building type.

Construction Features

Its characteristics are: simple equipment standing on site can be used; construction technology and operation are simple; applicable to a wide range of soil quality, significant reinforcement effect, high bearing capacity can be obtained, general foundation strength can be increased by 2-5 times; compressibility can be reduced by 2- 10 times, the impact depth of reinforcement can reach 6-10m; high work efficiency and fast construction speed (general equipment can reinforce 5000-10000m foundation per month), which can shorten the construction period by half compared with replacing backfill and pile foundation; save reinforcement raw materials; low construction cost , saving investment, saving 50% of the cost compared with soil replacement and backfilling, and saving 50% to 70% of investment compared with prefabricated pile reinforcement.

Construction technology

1. In general, the weight of the rammer can be 10-20t. The bottom form should be round. The area of the bottom of the hammer should be determined according to the properties of the soil. The static pressure of the bottom of the hammer should be 25-40 kPa, and the static pressure of the bottom of the hammer should be a small value for fine-grained soil. The bottom surface of the hammer should be symmetrically set with several exhaust holes that pass through the top surface of the hammer, and the hole diameter can be 250-300mm.

2. Crawler cranes with automatic decoupling devices or other special equipment should be used for dynamic compaction construction. When a crawler crane is used, an auxiliary gantry can be set at the end of the boom, or other safety measures can be taken to prevent the frame from overturning when the weight is dropped.

3. When the groundwater level is high and the water accumulated at the bottom of the rammed pit affects the construction, it is advisable to artificially lower the groundwater level or lay loose materials with a certain thickness. The accumulated water in the ramming pit or site should be removed in time.

4. Before dynamic compaction construction, the location and elevation of underground structures and various underground pipelines within the site should be identified, and necessary measures should be taken to avoid damage caused by dynamic compaction construction.

5. When the vibration generated by the dynamic compaction construction has a harmful effect on the adjacent buildings or equipment, anti-vibration or vibration isolation measures should be taken.

6. The dynamic compaction construction can be carried out according to the following steps:

1) Clean and level the construction site;

2) Mark the position of the first ramming point and measure the site elevation;

3) With the crane in place, align the tamper with the tamping point;

4) Measure the elevation of the hammer top before tamping;

5) Lift the rammer to a predetermined height, and after the rammer is free from the hook, lower the hook and measure the elevation of the top of the rammer. If it is found that the rammer is skewed due to the inclination of the pit bottom, the pit bottom should be leveled in time;

6) Complete the ramming of a ramming point according to the number of ramming strokes and control standards specified in the design;

Repeat steps 3) to 6) to complete the first ramming of all ramming points;

7) Use a bulldozer to fill the rammed pit and measure the site elevation;

8) After the specified time interval, follow the above steps to complete all the ramming times one by one, and finally use low-energy full ramming to compact the loose soil on the surface of the site, and measure the site elevation after ramming.

7. In the process of dynamic compaction, a special person should be responsible for the following monitoring work:

1) The weight and drop distance of the rammer should be checked before tamping to ensure that the single-click ramming energy meets the design requirements;

2) Before each ramming stroke, the ramming point set-out line should be reviewed, and the position of the ramming pit should be checked after the ramming, and the deviation and leakage of ramming should be corrected in time;

3) Check the number of ramming strokes and ramming weight of each ramming point according to the design requirements.

8. During the construction process, various parameters and construction conditions should be recorded in detail.