In the construction project, due to the need to compact the loose soil, dynamic rammer is often used. There are many types of dynamic compaction machines, such as frog type, vibration type, jump type, ramming type and lifting hammer type. According to the needs of the project, different types of dynamic compaction machines are used.
Dynamic compaction machine rental_ Design
1. The applicability and treatment effect of dynamic compaction replacement method must be determined through field test before design. One or several test areas should be selected on the 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 construction site, building scale and building type.
2. The depth of dynamic compaction replacement pier is determined by the soil conditions. In addition to the thick saturated silt, it should penetrate the soft soil layer and reach the hard soil layer. The depth should not exceed 7m.
3. The materials of pier body can be hard coarse-grained materials such as block stone, crushed stone and slag with good grading. The particle size should not be greater than 0.2 times of the diameter of the rammer bottom, the mud content should not be greater than 10%, and the content of particles with particle size greater than 300 mm should not exceed 30% of the total weight.
4. The impact energy of dynamic replacement method should be determined according to the field test. The tamping times of tamping point shall be determined by site trial compaction, and the following conditions shall be met at the same time:
1) The pier bottom penetrates the soft soil layer and reaches the designed pier length;
2) The cumulative settlement is 1.5 ~ 2.0 times of the designed pier length;
3) The average tamping settlement of the last two blows shall not be greater than the following specified values:
When the single click energy is less than 400 kn · m, it is 50 mm; when the single click energy is 4000 ～ 6000 kn · m, it is 100 mm; when the single click energy is more than 6000 kn · m, it is 200 mm;
4) The ground around the tamping pit should not have excessive uplift;
5) It is not difficult to lift the hammer due to the deep tamping pit.
5. Equilateral triangle or square should be used for Pier location layout. The independent foundation or strip foundation can be arranged according to the foundation shape and width.
6. The pier spacing should be selected according to the load and the bearing capacity of the original soil. When the whole hall is arranged, it can be taken as 2-3 times of the rammer diameter. For the independent foundation or strip foundation, 1.5 ~ 2.0 times of the rammer diameter can be taken. The calculated diameter of the pier can be 1.1-1.2 times of the rammer diameter. When the clear distance between piers is large, the rigidity of superstructure and foundation should be increased properly.
7. A layer of compacted cushion with thickness not less than 500mm shall be laid on the top of pier. Cushion materials generally use sand, gravel, stone chips and gravel soil with good water stability. When the material is the same as the pier body, the particle size should not be greater than 100 mm.
8. In the design of dynamic compaction replacement, the ground elevation should be estimated and corrected during the trial compaction.