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 ...

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