Reverse construction method of deep foundation pit in upper soft and lower hard water-rich stratum

Abstract

The invention discloses a reverse construction method of a deep foundation pit in upper soft and lower hard water-rich stratum. The reverse construction method comprises the following steps that step(1) underground continuous wall construction is carried out; step (2) construction of split-type hole drilling cast-in-place piles in row is carried out; step (3) grouting curtain construction at theinterface of soft and hard stratum is carried out; step (4) the small foundation pit of a first floor is excavated, and core soil is pre-reserved; step (5) a water drainage resistance structure layeris arranged, and initial supporting and protecting are carried out; step (6) the reserved core soil in the first layer foundation pit is excavated; step (7) a first support system is arranged; and step (8) the stability of the protecting structure is determined through monitoring measurement results, if the monitoring measurement results are normal, then the next cycle is carried out, the step (4)to the step (7) are repeated until the foundation pit is closed. Through the combined action of the inner and outer protecting structure of the foundation pit and the rational design of the excavation method, and the deep foundation pit engineering in the upper soft and lower hard water-rich stratum can achieve effective water-stopping and deformation control effects on the basis of safe and efficient excavation.

Description

technical field [0001] The invention relates to the technical field of geotechnical engineering design and construction, in particular to a construction method for a deep foundation pit in an upper-soft and lower-hard water-rich stratum. Background technique [0002] With the development and utilization of underground space, foundation pit engineering has become a controlling project for the construction of some large buildings, rail transit, and municipal projects. The geological conditions in quite a few areas in my country are complex, especially the foundation pit deformation and water seepage problems in the upper soft and lower hard and soft water-rich strata conditions are serious, endangering the safety of the foundation pit structure and the surrounding environment, which brings great difficulty to the construction of underground structures . In the existing patents, there is no method of reinforcing water stop and excavating deep foundation pits in upper soft and...

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Problems solved by technology

[0003] When the geological conditions are relatively complex, in practice, pile row type or groove plate type underground diaphragm wall is mostly used to reinforce the foundation pit, but a single support structure is very easy to cause water seepage and leakage due to improper construction methods, lax splicing or poor structural quality problems, and the insufficient support rigidity can easily lead to large deformation of the soft soil foundation pit

In terms of groundwater prevention, the existing technology generally uses conventional high-pressure jet jetting piles or three-axis stirring piles to prevent groundwater. High-pressure rotary grouting piles or three-axis mixing piles are prone to water seepage and leakage between piles or at the junction of pile bottoms due to improper construction methods and lax assembly, endangering structural safety

[0004] In the upper soft and lower hard water-rich formations, the soft-hard boundary of the formation is the weak link, and the problem of water seepage and leakage is more serious. Therefore, it is urgent to find a deep foundation pit construction method in upper soft lower hard water-rich strata to solve the problem The problem of water seepage and leakage at the junction of hard and water-rich strata and the serious deformation of the foundation pit

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