Extended data
1. The deep dynamic compaction pile method in the hole is different from other technologies. It introduces dynamic compaction into the deep foundation through the tunnel, stratifies the fill in the hole from bottom to top with a special-shaped heavy hammer, and carries out the deep dynamic compaction pile method with high kinetic energy, overpressure and strong compaction, so that the fill in the hole is compacted and consolidated vertically, and the soil around the pile is strengthened laterally by strong compaction. According to different soil conditions, different technologies are adopted to make the pile body beaded, expanded and tray-shaped.
Second, the overall stiffness of the foundation after DDC treatment is uniform, and the bearing capacity can be improved by 2 to 9 times; High deformation modulus, small settlement deformation, not affected by groundwater. The depth of foundation treatment can reach more than 30 meters. ? [ 1]?
Thirdly, its construction is to form a hole first, then fill it, and crush and squeeze it in the deep area of the hole with a specific heavy hammer with high kinetic energy and overpressure, so that the filler is squeezed to the periphery and bottom of the hole under strong push. Dynamic compaction and heavy hammer operation are completed from bottom to top in the hole. The tamping energy can reach 20000 kn. m/m2。 The depth can reach more than 30m.
Fourthly, the foundation treated by DDC technology does not collapse when it meets water, does not liquefy when it meets earthquake, and has small compression deformation, high bearing capacity and uniform stiffness. It can consume a large amount of construction and industrial waste, reinforce the foundation with various inorganic solid wastes, reduce environmental pollution, and turn waste into treasure. This technology has been applied in dozens of foundation treatment projects, eliminating the collapsibility of deep loess foundation, greatly improving the bearing capacity of foundation, reducing the compressibility of foundation, and the foundation treatment effect is remarkable.
Five, column hammer punching pile (DDC) construction work instruction
1. Objective To clarify the technological process, operation points and corresponding technical standards of DDC pile construction, and to guide and standardize the construction of DDC piles.
2. This standard is based on the Interim Standard for Acceptance of Construction Quality of Railway Subgrade Engineering of Passenger Dedicated Line, Technical Guide for Construction of Railway Subgrade Engineering of Passenger Dedicated Line and Design of fuzhou-xiamen railway New Line Station.
3. The scope of application is applicable to the construction of DDC piles in front of Fuxia Railway Station.
4. Material Requirements Mixed materials should meet the design requirements, and the mixture ratio should be strictly controlled.
5, construction process and technical requirements
Six, construction preparation
1, check geological data, and select appropriate construction machinery and construction method in combination with design parameters.
2. Before construction, clear the surface cultivated soil, level the site, remove obstacles, and mark the underground structures and pipelines in the treatment site.
3, measuring unreeling, determine the control axis, piling site sideline and identification.
4. Before construction, test the pile-forming technology to determine the construction technology and parameters. The number of test piles shall meet the design requirements and shall not be less than 2.
7. Building technology
1. Tools in place: the construction tools are in place, so that the column hammer is aligned with the pile position.
2. Hole-forming: Long auger is used for drilling, with a diameter of 400 mm and a depth meeting the design requirements.
3. Hole-filling piling: Fill the mixed filler into the pile hole in layers with a standard hopper or truck, and tamp it with a column hammer to form a pile body. When the hammer weight, hammer length and drop distance are determined, the layered filling quantity and tamping times are determined through process test. Each pile hole shall be rammed to at least 0.5m above the design elevation of the pile top, and the upper pile hole shall be rammed with original trench soil. Technicians should be set up during construction to keep records of each pile, and analyze and handle problems in time when found.
4. Displacement: the construction machinery is displaced, and the above steps are repeated for the next pile construction. The tamping energy of column hammer punching and expanding method is large, which is easy to cause ground uplift, loosen the soil between surface piles and reduce the treatment effect. Therefore, the construction sequence of pore-forming and packing compaction should be carried out at intervals.
References:
Baidu encyclopedia-deep dynamic compaction pile method in hole