Underwater construction method of deep foundation pit in water-rich sand layer

Abstract

The invention discloses a water-rich sand layer deep foundation pit underwater construction method. A row of continuous walls is arranged around a pre-excavated foundation pit, a crown beam is arranged at the top of the continuous walls, and concrete supports are erected among the continuous walls. The method includes the following steps that the foundation pit among the continuous walls is excavated to reach the preset depth, and water is poured into the foundation pit to reach the position below the concrete supports; a hole is drilled in the bottom of the foundation pit in the vertical direction, an uplift pile steel framework is put in the hole, a bottom-sealed plate steel framework is put in the preset position of the foundation pit in the horizontal direction, and the bottom-sealed plate steel framework, the uplift pile steel framework and the continuous walls are fixed separately; underwater pouring of uplift pile holes and the bottom-sealed plate steel framework is performed; and grout in the foundation pit is drained, and a plurality of steel supports are erected in the foundation pit along different heights to reach the bottom of the foundation pit. By means of an underwater excavation mode, water pressure of inside and outside of the pit can be mutually cancelled out, the construction danger of excavation of a deep foundation pit support structure is reduced, the built-in depth of the continuous walls can be reduced after a top sealing plate is arranged, and the cost is reduced.

Description

technical field [0001] The invention belongs to the technical field of deep foundation pit engineering, and in particular relates to an underwater construction method of a deep foundation pit in a water-rich sand layer. Background technique [0002] With the continuous development of urban construction, a large number of high-rise buildings and municipal projects such as roads, bridges, subways, etc. have emerged, and underground space has also been continuously developed and utilized, and a large number of deep foundation pit projects have emerged. At present, in the construction of deep foundation pits in water-rich sand layer areas, diaphragm walls are generally used as enclosure structures, and the water level in the pits is lowered below the basement through base reinforcement and dewatering measures at well points inside and outside the pits. Due to the poor geological conditions of the water-rich sand layer, the embedded depth of the diaphragm wall in the traditional ...

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Problems solved by technology

Due to the poor geological conditions of the water-rich sand layer, the embedded depth of the diaphragm wall in the traditional construction method is very deep, the construction is difficult, and the economic cost is high. At the same time, due to the deep foundation pit and sufficient water supply, the precipitation construction is difficult. The excavation process will cause the surrounding ground to subside, which will have a great impact on the surrounding buildings, municipal facilities and underground pipelines; and due to the long construction period, narrow site, rainfall, heavy objects, etc., will also have an adverse effect on the stability of the foundation pit.

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