The supporting system formed by retaining pile, wall and inner support system is one of the most widely used forms in foundation pit engineering at present. The structure stress is clear, the calculation method is mature and the construction experience is rich, so it is widely used in foundation pit engineering.
The support structure is commonly used in steel and reinforced concrete structures, which must adopt stable structural systems and reliable connection structures. Retaining piles and walls are discontinuous in the horizontal direction, and the integral structure must be formed by the connection of cap beam and waist beam. The cap beam or waist beam and the inner support constitute the statically indeterminate horizontal frame structure for many times. Even if the partial component fails, the stability of the whole support structure will not be affected.
The common forms of support structure include plane support system and vertical diagonal support system.
1,Plane support system
Generally, the plane support system should be composed of waist beam, horizontal support and column. The horizontal support should have strong integrity and plane stiffness, so that the force transmission of each part of the support is reliable and uniform.
The role of the waist beam is to strengthen the integrity of the retaining pile and transfer the horizontal force to the supporting members. Therefore, the waist beam is required to have large plane stiffness and be connected with retaining pile reliably.
The function of the column is to ensure the longitudinal stability of the horizontal support and bear the dead weight of the horizontal support and other vertical loads. It requires better stiffness and smaller vertical displacement.
According to the specific situation of the project, the horizontal support can be used to brace, bevel brace and figure eight brace form of plane structure system.
2,Vertical diagonal brace system
In general, the plane support system should be preferred, and the vertical diagonal support system can also be used for the foundation pit meeting the following conditions:
(1) foundation pit excavation depth, generally not greater than6mIn soft soil area with high groundwater level is not greater than5m.
(2The engineering geological conditions of the site can satisfy the installation of diagonal support of the reserved soil embankment in the foundation pit and the stability of the reserved slope.
(3The diagonal support foundation has sufficient horizontal and vertical bearing capacity.
(4) Foundation pit plane scale is large, the shape is complex.
The vertical diagonal support system is usually composed of diagonal support, waist beam and diagonal support foundation components. When the diagonal support length is greater than15mWhen, the column should be set up in the middle of the diagonal support.
Inclined support should be made of steel or composite steel section; The vertical diagonal support should be evenly and symmetrically arranged, and the horizontal spacing should not be greater than6m; In general, the Angle between the diagonal support and the foundation pit bottom should not be greater than35°In soft soil area with high groundwater level should not be greater than26°And it is consistent with the stable slope of the soil embankment in the foundation pit. The horizontal distance between the inclined support foundation and the retaining pile should not be less than the insertion depth of the retaining pile below the excavation face1.5Times; The connection between the diagonal support and the waist beam, the diagonal support and the foundation, and the waist beam and the parapet wall should meet the transmission requirements of the horizontal and vertical components of the diagonal support.
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