Heave deformation resisting construction method for foundation pit excavation above existing tunnel

Abstract

The invention discloses a heave deformation resisting construction method for foundation pit excavation above an existing tunnel. The heave deformation resisting construction method comprises the following steps that grouting pre-reinforcing is conducted on bottom layers around the existing tunnel and overlaying soil layers of the existing tunnel; primary slope putting and soil nailing shotcrete anchor supporting are constructed from the vertical upper part of the existing tunnel; primary slope putting and soil nailing shotcrete anchor supporting are constructed from the periphery of a foundation pit; foundation pit enclosure is constructed, and an internal support are erected; secondary slope putting and soil nailing shotcrete anchor supporting are constructed from reserved core soil; connecting grooves are dug; a grouting pipe curtain is constructed; and the reserved core soil is excavated segment by segment in a groove skipping mode. The heave deformation resisting construction method adopts the mode of combining formation pre-reinforcing with the grouting pipe curtain, the formation stiffness can be effectively increased, the formation is prevented from floating, thus the deformation value of the existing tunnel structure is controlled, long-term stable operation of the tunnel is ensured, and the application range is wide; and a method of reserving original core soil abovethe tunnel is adopted, it can be ensured that the overlaying gravity of the tunnel continuously exists, and interference to the stability of an underground structure is small.

Description

technical field [0001] The invention belongs to the field of excavation construction methods of foundation pits, and in particular relates to a construction method for anti-uplift deformation of foundation pit excavation above existing tunnels. Background technique [0002] With the acceleration of the urbanization process, a large number of subway and foundation pit projects have emerged, and the scale has continued to increase. In view of the construction timing problem, there must be subsequent excavation of foundation pits that need to be constructed above or adjacent to existing underground buildings such as subways and tunnels. Excavating the foundation pit above the existing tunnel will inevitably lead to the release of ground stress and the rebound of the basement, and the deformation of the soil will also lead to changes in the stress field and displacement field of the tunnel. When the deformation of the tunnel exceeds a certain limit, water leakage at the tunnel ...

AI Technical Summary

Problems solved by technology

When the deformation of the tunnel exceeds a certain limit, there will be water leakage at the joints of the tunnel, and it will have a greater impact on the safe operation of the tunnel in severe cases, resulting in the inability to operate safely

[0003] At present, traditional foundation pit construction methods often use large-area soil reinforcement and structural reinforcement technologies, and it is difficult to avoid the base from rebounding again after unloading after loading

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