Hollow pile backfill material and method for super-long large-diameter dense pile group in water-rich silty-fine sand layer

Abstract

The invention discloses a hollow pile backfill material and method for a super-long large-diameter dense pile group in a water-rich silty-fine sand layer. The hollow pile backfill material comprises the following components in percentage by mass: 76%-78% of sand, 3.7%-4.4% of cement, 0.1%-0.15% of bentonite and 0.15%-0.16% of an additive, with the balance being water. The hollow pile backfill method comprises the steps that underwater concrete pouring is conducted on solid pile parts; after the underwater concrete of the solid pile parts is poured to a preset height, the depth of guide pipes embedded in the concrete is measured; unwanted guide pipes are dismantled before hollow pile pouring, and the bottom ends of the unwanted guide pipes are embedded to a position 0.2-0.3 m below a concrete liquid level; the hollow pile backfill material is poured into hollow piles through the guide pipes, and when the concrete pouring guide pipes are embedded into the hollow pile backfill material by a depth of 2-3.5 m, the unwanted guide pipes are removed to enable the bottom ends of the guide pipes to be embedded to positions 0.2-0.3 m below the liquid level of the hollow pile backfill material; and the above operation is repeated. The method has the advantages that the guide pipes are used for pouring the backfill material, the backfill material arrives at a position below the initially-poured backfill material through the guide pipes, and the initially-poured backfill material and slurry on the initially-poured backfill material are jacked to rise gradually, so continuous and dense pile bodies are formed, and disturbance to the hole walls of the hollow piles is reduced.

Description

technical field [0001] The invention relates to a material and method for backfilling empty piles of ultra-long-diameter dense pile groups in a water-rich fine sand layer, and belongs to the technical field of empty pile backfilling. Background technique [0002] With the development of urban underground space, there are more and more deep foundation pits and ultra-deep foundation pits, and more and more large-diameter and ultra-deep cast-in-place piles are used. In the ultra-deep foundation pit construction of the first phase of the Binjiang Water Environment Improvement and Utilization System Project in Jiangbei New District, Nanjing, the diameters of the anti-floating piles are 1 meter and 1.2 meters, and the empty piles are up to 23.5 meters. The stratum of the empty piles is water-rich fine sand layers, the minimum clear distance between piles is 0.66 meters. [0003] The prior art has the following methods for backfilling empty piles: (1) self-unloading backfill with ...

AI Technical Summary

Problems solved by technology

[0004] If the technology of self-unloading and backfilling stone powder, sand, gravel, clay, cement mixture or multi-material mixture is adopted, since there is mud in the empty pile part, the diameter of the empty pile is large and deep and it is in the fine sand layer. Backfilling is very easy to disturb the hole wall and cause the hole to collapse, causing safety hazards and increasing the construction difficulty of surrounding piles

At the same time, self-unloading backfill is difficult to be uniform and dense, and cannot provide a solid foundation for the pile driver to walk and stand. Under the load and vibration of the surrounding adjacent pile construction pile driver, it is very easy to cause string holes

[0005] If the conduit backfill stone is crushed and then grouted, and the conduit is filled with underwater low-grade concrete, the construction cost is high and the economy is poor, which will increase the construction difficulty of subsequent foundation pit excavation

[0006] If the proportion of mud in the empty pile is increased and the mud in the original hole is replaced by pouring sand after the construction of all the piles is completed, it will not be able to provide a solid foundation for the pile driver to walk and stand, and the amount of mud to be processed at one time is large, which is not conducive Environmental protection, high cost

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