Construction method of joint freezing bottom sealing for ultra-deep foundation pit

Abstract

The invention discloses a construction method of joint freezing bottom sealing for an ultra-deep foundation pit, and belongs to the field of civil engineering. The construction method comprises the following steps that S1, underground diaphragm walls (1) are constructed, and the verticality of each wall is ensured during construction; S2, a first soil body is excavated from one side of the foundation pit to 2 / 3 of the design depth; S3, drilling and lowering of vertical freezing pipes (3) are carried out; S4, vertical freezing is carried out, and a second soil body of the foundation pit is simultaneously excavated until a complete frozen soil body curtain is formed; S5, a third soil body of the frozen soil curtain is excavated to the design depth, the exposed vertical freezing pipes are cutout, then a horizontal borehole is drilled below a designed excavation surface of the foundation pit, and a horizontal freezing pipe (4) is laid; S6, horizontal freezing is carried out while a fifthsoil body continues to be excavated until a horizontal freezing curtain reaches the design requirements; and S7, a sixth soil body is excavated, and a bottom plate (5) is constructed after all earthwork tasks are completed. According to the construction method, the in-soil depth of building envelopes such as the diaphragm walls can be obviously reduced, and the construction period can be effectively shortened.

Description

technical field [0001] The invention relates to a novel construction method for excavating an ultra-deep foundation pit, in particular to a construction method for combined freezing bottom sealing of an ultra-deep foundation pit. Background technique [0002] With the continuous development of society, the depth of foundation pit excavation is getting deeper and deeper, and the difficulty and risk of construction are also increasing. At present, most excavations of deep and large foundation pits use underground diaphragm walls as the enclosure structure. According to the standard, the range of soil penetration ratio of underground diaphragm walls is generally between 0.7 and 1.0. The depth is not large, and it can be completed with the current technical level; when the excavation depth of the foundation pit increases (over 100m), the depth of the underground diaphragm wall can reach nearly 200m. A series of problems such as deformation and difficulty in decentralization. ...

AI Technical Summary

Problems solved by technology

At present, most excavations of deep and large foundation pits use underground diaphragm walls as the enclosure structure. According to the standard, the range of soil penetration ratio of underground diaphragm walls is generally between 0.7 and 1.0. The depth is not large, and it can be completed with the current technical level; when the excavation depth of the foundation pit increases (over 100m), the depth of the underground diaphragm wall can reach nearly 200m. A series of problems such as deformation and difficulty in decentralization

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