A deep foundation pit is generally defined as a project with a bottom area of less than 27 square meters (not 20), a long side of the bottom less than 3 times of the short side, an excavation depth of more than 5 meters (including 5 meters) or more than three floors of the basement, or a depth of less than 5 meters, but the geological conditions, surrounding environment and underground pipelines are particularly complicated. (On the contrary, shallow foundation pit)

Foundation pit supporting system is a temporary structure with small safety reserve and high risk. Monitoring should be carried out in the process of foundation pit construction and emergency measures should be taken. In case of danger during construction, timely rescue is needed. Pay attention to strengthening drainage and irrigation prevention measures when excavating deep foundation pit, which is risky and should be prepared in advance.

Foundation pit engineering has a strong regional character. Foundations with different engineering geological and hydrogeological conditions, such as soft soil foundation and loess foundation, are very different in foundation pit engineering. There are also differences in different areas of the same city.

The design and construction of supporting system and earthwork excavation of foundation pit engineering should be adapted to local conditions, and foreign experience can be used for reference, but it cannot be simply applied.

Extended data

Excavation depth of more than 5m, or excavation depth of less than 5m, but the site geological conditions and surrounding environment are complex, foundation pit engineering monitoring should be carried out.

In the design stage of building foundation pit engineering, the designer should put forward the technical requirements of foundation pit engineering monitoring according to the specific conditions of engineering site and foundation pit design, including monitoring items, measuring point positions, monitoring frequency, monitoring alarm values and so on.

Before the foundation pit construction, the project owner shall entrust a third party with corresponding qualifications to conduct on-site monitoring of the foundation pit project. The monitoring unit shall prepare a monitoring plan. The monitoring plan should be approved by the construction, design, supervision and other units, and can be implemented only after consultation with municipal roads, underground pipelines, civil air defense and other relevant departments when necessary.

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