Method for excavating foundation pit in soft soil stratum

Abstract

The invention discloses a soft soil stratum foundation pit excavation method which is characterized by comprising the following steps: 1) foundation pit support pile construction: measuring the driving position of a support pile according to the size of a foundation pit, firstly driving vertical columnar piles according to the measuring position, driving vertical sheet piles among the columnar piles, and driving the vertical sheet piles into a certain height above the ground, the sinking height of the sheet piles is consistent with the sinking elevation of the columnar piles, and enclosing purlins are arranged on the outer sides of the supporting piles. The trestle bridge in the width direction of the foundation pit is erected on the supporting piles, the trestle bridge can move relative to the foundation pit in the length direction of the foundation pit, the excavator is hoisted to the trestle bridge through a crane, the foundation pit is excavated, advancing and retreating of the excavator are achieved through moving of the trestle bridge, deep sinking of the excavator is avoided due to the fact that the excavator does not make direct contact with the soft soil stratum, and the construction efficiency is improved. A traditional excavation-drying-excavation technology is not needed, the construction period is shortened, the utilization rate of equipment is improved, the operation space of the excavator located on the trestle is increased, and excavation of the foundation pit is better facilitated.

Description

technical field [0001] The invention belongs to the technical field of engineering, in particular to a method for excavating a foundation pit in a soft soil layer. Background technique [0002] Soft clay and silt strata are collectively referred to as soft soil strata. In coastal areas and areas near rivers, soft clay and silt strata are widely distributed. High, high compressibility, low strength, thixotropic and rheological properties, extremely poor self-stabilizing ability. [0003] Excavating foundation pits on soft clay and silt strata requires high technical requirements. Usually, support is done first, and then excavation is carried out. In addition, for soil layers with high moisture content, in order to avoid excavators and transport vehicles and soil After the layer is directly contacted, it is deeply sunk, and the excavation is generally carried out by digging and drying, and then excavating and transporting it after the water is lost to form dry soil. The "dry...

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Problems solved by technology

The "drying" process in the "dig-sun-dig" construction process requires a long waiting time and great uncertainty, which not only cannot meet the construction period requirements of this project, but also has low efficiency of construction machinery and equipment

For soft clay strata, under the condition of good support, due to the rheological characteristics of soft soil, the longer the exposure time of the foundation pit, the greater the displacement and deformation of the foundation pit enclosure structure. As the depth increases, the influence of the lateral pressure generated by the excavator and the transport vehicle will become greater and greater, which will damage and deform the enclosure structure of the foundation pit, and easily cause the foundation pit to become unstable.

For silt formations, because the greater the load, the greater the settlement, it is difficult for the excavator and the transport vehicle to excavate to a suitable position. At the same time, due to the constraints of the small width of the foundation pit, the depth of the excavation depth of the foundation pit, and many horizontal supports, the excavator The working space is limited and it is difficult to excavate

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