Top-down construction method for multi-storey basement with full steel structure

A top-down construction method for a multi-storey basement, comprising:

• S1. constructing a diaphragm wall permanent structure (1) along a perimeter of a foundation pit, and setting an intermediate steel pipe column (2) inside the foundation pit, wherein a steel beam connecting plate (101) of basement layers are pre embedded into the diaphragm wall permanent structure (1) during construction;
• S2. conducting an open excavation on an underground first layer earthwork to a first layer open excavation elevation surface (9), and then constructing a first layer structural beam and slab (3), wherein the first layer structural beam and slab (3) is composed of steel beams and steel-bars truss decks, and the first layer structural beam and slab (3) is reserved with an earth intake in a podium area or a basement area, after a completion of the first layer structural beam and slab (3), constructing a tower above-ground structure (20) upwards;
• S3. conducting an underground excavation on an underground second layer earthwork to a second layer underground excavation elevation surface (10), and then constructing an underground first layer structural beam and slab (4) and an underground first layer vertical shear wall (15), wherein the underground first layer structural beam and slab (4) reserves an earth intake in the podium area and the basement area, and synchronously constructing the tower above-ground structure (20) upwards;
• S4. according to step S3, excavating earthworks from an underground third layer to an underground N−1 layer in sequence until a designed excavation elevation surface, and constructing structural beams and slabs from an underground second layer to an underground N−2 layer and vertical shear walls from the underground second layer to the underground N−2 layer, the structural beams and slabs from the underground second layer to the underground N−2 layer are reserved with earth intakes in the podium area and the basement area;
• synchronously constructing the tower above-ground structure (20) upwards, wherein N is a total number of underground layers excavated;
• S5. conducting an underground excavation on an underground N layer earthwork to a Nth layer excavation elevation surface, and constructing an underground N−1 layer inward two-span structural steel beam along an edge of the foundation pit (701);
• S6. conducting an underground excavation on earthworks of bottom plate layer to a bottom elevation surface of the bottom plate (14), constructing remaining structural beams and slabs on the underground N−1 layer (702) and an underground N−1 layer vertical shear wall (18), wherein there are earth intakes provided between the underground N−1 layer inward two-span structural steel beam along an edge of the foundation pit (701) and the remaining structural beams and slabs on the underground N−1 layer (702), and synchronously constructing the tower above-ground structure (20) upwards;
• S7. conducting the underground excavation on earthworks of a bearing platform and a water collection well to the designed elevation, and constructing an underground N layer bottom plate structure (8), then constructing by an underground N layer vertical shear wall (19), wherein the underground excavation on the earthworks of the bearing platform and the water collection well is excavated from a support edge to a direction of the earth intake;
• S8. constructing the earth intakes of the podium and the basement after the construction of the underground N layer vertical shear wall (19) is completed, wherein the earth intakes of the podium and the basement use a combination of the bottom-up construction and the top-down construction.