Construction method of foundation pit external corner three-way steel truss and concrete base combined supporting structure

Abstract

The invention relates to the technical field of foundation pit supporting engineering, and discloses a foundation pit external corner three-way steel truss and concrete base combined supporting structure construction method which comprises the following steps that a foundation pit supporting structure, stand column piles and stand columns are constructed; an integral concrete base is constructed at the external corner position of the foundation pit; the concrete base comprises concrete supporting beams extending in three different directions. Steel truss supports in three directions are installed, and one end of each steel truss support is fixedly connected to the end of the corresponding concrete supporting beam through an embedded connecting piece; the three-way steel truss is integrated through the concrete base, a space force transmission system is formed, and the rigidity of the external corner area of the foundation pit is remarkably improved; a reverse construction method of digging one layer and supporting one layer is adopted, large-range unsupported excavation is avoided, and deformation of the foundation pit is controlled; the three-way beam string structure effectively decomposes concentrated stress at the external corner of the foundation pit, and the risk of support failure caused by stress concentration is reduced; standard components achieve modular installation, and the construction period is shortened.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of foundation pit support engineering, in particular to a foundation pit external corner three-direction steel truss and concrete base combined support structure construction method. BACKGROUND

[0002] At present, the beam string steel truss support structure is widely used in the field of foundation pit support engineering. For the position of the foundation pit external corner, due to the existence of stress concentration, in order to effectively control the stress and deformation of the position of the foundation pit external corner, steel support needs to be set in three directions.

[0003] The single pure steel support has the disadvantages of plane intersection, complex stress, poor stability, and inconvenient construction at the position of the foundation pit external corner. SUMMARY

[0004] The purpose of the present application is to provide a foundation pit external corner three-direction steel truss and concrete base combined support structure construction method, which aims to solve the problem of poor stability of single pure steel support in the prior art.

[0005] The foundation pit external corner three-direction steel truss and concrete base combined support structure construction method is implemented as follows: (1) constructing a foundation pit support structure, a stand column pile and a stand column; (2) constructing an integral concrete base at the position of the foundation pit external corner; the concrete base comprises concrete support beams extending in three different directions; (3) pre-burying a pre-buried connecting piece for connecting a steel structure at the end of each of the three concrete support beams; (4) respectively installing steel truss supports in three directions, one end of each of the steel truss supports being fixedly connected to the end of the corresponding concrete support beam through the pre-buried connecting piece; (5) mutually connecting and fixing the steel truss supports in three directions at a position away from the concrete base to form a space beam string structure system; (6) excavating the foundation pit earthwork in layers, after each layer of earthwork is excavated to a predetermined depth below the design bottom surface elevation of the next layer of support, repeating steps (2) to (5) to construct the next layer of the combined support structure until the foundation pit excavation and support construction are completed.

[0006] Further, in step (4), the three different directionally extending concrete support beams are a direction one concrete support beam, a direction two concrete support beam and a direction three concrete support beam, and the direction one concrete support beam, the direction two concrete support beam and the direction three concrete support beam are respectively arranged on two external corner walls of the foundation pit external corner. The three-direction steel truss supports are direction one steel support, direction two steel support and direction three steel support, the direction one steel support is connected with the direction one concrete support beam through the embedded connecting piece, the direction two steel support is connected with the direction two concrete support beam through the embedded connecting piece, and the direction three steel support is connected with the direction three concrete support beam through the embedded connecting piece.

[0007] Further, the concrete base further comprises a concrete plate connecting the three concrete support beams, and a stiffening structure arranged in or on the concrete base for enhancing the overall rigidity and stability thereof. The stiffening structure comprises one or more of stiffening ribs, shear keys or ribbed plates arranged between the concrete support beams, at the intersection of the beams and the plate or on the plate surface.

[0008] Further, in step (5), the formation of the spatial cable-stayed beam structure system comprises connecting and fixing at the end nodes of the three steel truss supports through the node plate, connecting plate and connecting bolt or pin shaft.

[0009] Further, in step (5), it further comprises tensioning the prestressed cable between or inside the connected and fixed steel truss supports to form a complete cable-stayed beam structure.

[0010] Further, the pit external corner is formed at the pit external corner position, a concrete external base is poured on the pit external corner, and the concrete external base and the concrete base are arranged away from each other.

[0011] Further, the concrete external base comprises back-pulling beams and back-pulling plates, the two corner walls of the pit external corner are connected through a plurality of back-pulling beams, the plurality of back-pulling beams are arranged in sequence and at intervals along the inside-out direction of the pit external corner, the lengths of the plurality of back-pulling beams increase in sequence, the adjacent back-pulling beams are connected through the back-pulling plates, and the plurality of back-pulling beams are connected through the connecting beams.

[0012] Further, the concrete support beam is provided with a steel reinforcement beam cage, the steel reinforcement beam cage is welded and connected with the steel mesh sheet in the concrete base, the steel reinforcement beam cage is welded and connected with the bottom of the embedded connecting piece, the steel reinforcement beam cage and the steel truss support are connected to form a rigid whole through the embedded connecting piece, and the steel truss support and the embedded connecting piece are connected through welding or high-strength bolt connection. The outer end surface of the concrete support beam is embedded with a steel backing plate, and the steel backing plate is connected with the steel truss support through welding or high-strength bolt connection.

[0013] Further, a plurality of counter-pulling structures are arranged in the foundation pit external corner, the counter-pulling structure comprises a counter-pulling column, the counter-pulling column transversely penetrates the foundation pit external corner, and two ends of the counter-pulling column are arranged in the concrete outer base and the concrete base respectively, a plurality of outer support rods are welded on the counter-pulling column, the plurality of outer support rods are arranged along the axial direction of the counter-pulling column and are spaced around the counter-pulling column, part of the outer support rods arranged in the concrete outer base are welded and connected with the steel bars in the back-pulling beam, and part of the outer support rods arranged in the concrete base are welded and connected with the steel mesh or the steel beam cage. Two ends of the counter-pulling column are welded with steel plate structures respectively, the two steel plate structures are arranged in the concrete outer base and the concrete base respectively, and the steel plate structure is formed by crosswise welding of two steel sheets.

[0014] Further, a surrounding frame is arranged on the concrete base, the surrounding frame is arranged around the connecting position between the steel truss support and the concrete support beam in the circumferential direction, an internal cavity penetrating up and down is formed, a shock isolation cushion layer is arranged in the internal cavity and arranged around the inner side wall of the internal cavity in the circumferential direction, a plurality of shock absorption plates are arranged on the bottom of the surrounding frame and arranged perpendicularly to the bottom of the surrounding frame, the plurality of shock absorption plates are arranged around the surrounding frame in the circumferential direction, and the shock absorption plates are connected with the concrete base through connecting bolts. A displacement monitoring system is arranged on the surrounding frame, and the displacement monitoring system comprises an inclination sensor and an optical fiber strain gauge.

[0015] Compared with the prior art, the foundation pit external corner three-way steel truss and concrete base combined support structure construction method provided by the application integrates the three-way steel truss through the concrete base to form a space force transmission system, significantly improves the rigidity of the foundation pit external corner region, adopts the reverse construction method of “digging one layer and supporting one layer” to avoid large-scale non-supported excavation and control the deformation of the foundation pit, effectively decomposes the concentrated stress at the foundation pit external corner through the three-way cable-strut structure to reduce the risk of support failure caused by stress concentration, realizes modular installation through standardized components to shorten the construction period, and solves the problem of poor stability of single pure steel support. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a construction process schematic diagram of the foundation pit external corner three-way steel truss and concrete base combined support structure construction method provided by the application; Figure 2 is a top view structural schematic diagram of the foundation pit; Figure 3 is a top view structural schematic diagram of the connection between the foundation pit external corner and the concrete base and the steel truss support; Figure 4 is a partial cutaway structural schematic diagram of the concrete base; Figure 5It is a side structural schematic diagram of the tension column provided by the present invention.

[0017] In the figure: foundation pit positive angle 10, steel truss support 20, concrete base 30, tensioned beam structure 40, embedded connector 50, tensioned prestressed cable 60, tension structure 70, concrete outer base 11, back tension beam 111, back tension plate 112, connecting beam 113, direction one steel support 21, direction two steel support 22, direction three steel support 23, direction one concrete support beam 31, direction two concrete support beam 32, direction three concrete support beam 33, concrete slab 34, stiffening structure 35, steel beam cage 36, steel mesh 37, enclosing frame 38, seismic isolation pad 381, shock absorbing plate 382, ​​tension column 71, external support rod 72, steel plate structure 73. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0019] The implementation of the present invention is described in detail below with reference to specific embodiments.

[0020] The same or similar numbers in the drawings of this embodiment correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "up", "down", "left", "right", etc. indicate directions or positional relationships, they are based on the directions or positional relationships shown in the drawings. This is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0021] Reference Figures 1-5 The figure shows a preferred embodiment of the present invention.

[0022] The construction method of the combined support structure of the three-way steel truss and the concrete base 30 at the external corner of the foundation pit includes the following steps: (1) Construction of foundation pit support structure, column piles and columns; (2) Construct an integral concrete base 30 at the location of the foundation pit positive corner 10; the concrete base 30 includes concrete support beams extending in three different directions; (3) Embedded connectors 50 for connecting to the steel structure are embedded at the ends of the three concrete support beams; (4) Install three-direction steel truss supports 20 respectively, one end of each steel truss support 20 is fixedly connected to the end of the corresponding concrete support beam through the pre-buried connecting piece 50; (5) The three-direction steel truss supports 20 are fixedly connected to each other at a position away from the concrete base 30, forming a space cable-stayed beam structure 40 system; (6) Excavate the pit earthwork layer by layer, after each layer of earthwork is excavated to a predetermined depth below the design bottom elevation of the next layer of support, repeat steps (2) to (5) to build the combined support structure of the next layer, until the pit excavation and support construction are completed.

[0023] The above-provided construction method of the pit external corner three-direction steel truss and concrete base 30 combined support structure, by integrating three-direction steel trusses through the concrete base 30, forms a space force transmission system, significantly improving the rigidity of the pit external corner 10 area; using the top-down method of "excavating one layer and supporting one layer", avoiding large-scale excavation without support, and controlling pit deformation; the three-direction cable-stayed beam structure 40 effectively decomposes the concentrated stress at the pit external corner 10, reducing the risk of support failure caused by stress concentration; standardized components (concrete base 30 + steel truss) realize modular installation, shorten the construction period; solve the problem of poor stability of single pure steel support.

[0024] In this embodiment, in step (4), the three different directionally extending concrete support beams are a direction one concrete support beam 31, a direction two concrete support beam 32, and a direction three concrete support beam 33, which are respectively arranged on the two external corner walls of the pit external corner 10. The three-direction steel truss supports 20 are a direction one steel support 21, a direction two steel support 22, and a direction three steel support 23, the direction one steel support 21 is connected with the direction one concrete support beam 31 through the pre-buried connecting piece 50, the direction two steel support 22 is connected with the direction two concrete support beam 32 through the pre-buried connecting piece 50, and the direction three steel support 23 is connected with the direction three concrete support beam 33 through the pre-buried connecting piece 50.

[0025] Precise force transmission path: the three-direction support system matches the geometric form of the pit external corner 10, ensuring that the earth pressure is transmitted along the designed path.

[0026] Two-way deformation resistance: the beam arrangement on the two external corner walls enhances the two-way constraint ability of the pit corner deformation.

[0027] In this embodiment, the concrete base 30 further includes a concrete plate 34 connecting the three concrete support beams, and a stiffening structure 35 arranged in or on the surface of the concrete base 30 for enhancing the overall rigidity and stability thereof; The stiffening structure 35 includes one or more of stiffening ribs, shear keys or ribbed slabs provided between the concrete support beams, at the beam-to-slab intersections or on the slab surface.

[0028] Base integrity reinforcement: The concrete slab 34 integrates the three-way beams as rigid joint zones, and the stiffening structure 35 suppresses local buckling.

[0029] Improved torsional performance: The shear keys / ribbed slabs enhance the shear and torsional resistance of the beam-to-slab intersections, reducing the risk of concrete cracking.

[0030] In this embodiment, in step (5), the formation of the spatial cable-strut structure 40 system includes connecting and fixing at the end nodes of the three steel truss supports 20 through node plates, connecting plates and connecting bolts or pins.

[0031] Node reliability: Mechanical connection ensures the stiffness and strength of the truss node, avoiding the influence of welding deformation on precision.

[0032] Fast assembly: Bolt / pin connection facilitates on-site adjustment, improving construction efficiency.

[0033] In this embodiment, in step (5), it also includes prestressed cables 60 between or inside the connected and fixed steel truss supports 20 to form a complete cable-strut structure 40; the steel supports in each direction on the same wall surface in the foundation pit are connected through the cable-strut structure 40.

[0034] Active deformation control: The prestressed cables provide counter-arch stiffness to offset the deflection caused by soil pressure.

[0035] Lightweight design: The steel amount of the cable-strut structure 40 is reduced.

[0036] In this embodiment, a pit outer reentrant corner is formed at the position of the pit sun corner 10, and a concrete outer base 11 is poured on the pit outer reentrant corner. The concrete outer base 11 and the concrete base 30 are arranged away from each other.

[0037] Balancing soil pressure: The inner and outer bases form a counter-pulling system to offset the asymmetric soil pressure in the pit sun corner 10 area.

[0038] Suppress lateral displacement: The horizontal load is transmitted to the stable soil outside the pit through the external counterforce structure.

[0039] In this embodiment, the concrete outer base 11 includes back-pulling beams 111 and back-pulling plates 112. The two reentrant corner walls of the pit outer reentrant corner are connected by a plurality of back-pulling beams 111. The plurality of back-pulling beams 111 are arranged in sequence and at intervals along the inward-to-outward direction of the pit outer reentrant corner, and the lengths of the plurality of back-pulling beams 111 increase in sequence. The adjacent back-pulling beams 111 are connected by back-pulling plates 112, and the plurality of back-pulling beams 111 are connected by connecting beams 113.

[0040] Space truss effect: Multi-channel back pull structure forms a three-dimensional stable frame to disperse external loads.

[0041] Progressive stress transfer: Staircase beam body realizes smooth transition of stress from inside to outside, avoiding stress mutation.

[0042] In this embodiment, a steel beam cage 36 is arranged in the concrete support beam, the steel beam cage 36 is welded with the steel mesh 37 in the concrete base 30, the steel beam cage 36 is welded with the bottom of the embedded connecting piece 50, the steel beam cage 36 and the steel truss support 20 are connected to form a rigid whole through the embedded connecting piece 50, and the steel truss support 20 and the embedded connecting piece 50 are connected through welding or high-strength bolt connection. A steel backing plate is embedded on the outer end surface of the concrete support beam, and the steel backing plate and the steel truss support 20 are connected through welding or high-strength bolt connection.

[0043] The steel backing plate can be a pre-embedded steel plate, a pre-embedded bolt sleeve or a steel end plate with an anchor.

[0044] Rigid-flexible interface optimization: The steel backing plate provides a uniform pressure bearing surface to eliminate stress concentration at the concrete-steel structure interface.

[0045] Integrated construction: The steel beam cage 36 is welded to realize the co-working of concrete and steel structure, and improve the fatigue resistance of the joint.

[0046] In this embodiment, a plurality of counter-pulling structures 70 are arranged in the foundation corner 10, the counter-pulling structure 70 includes a counter-pulling column 71, the counter-pulling column 71 transversely penetrates the foundation corner 10, and the two ends of the counter-pulling column 71 are arranged in the concrete outer base 11 and the concrete base 30 respectively, a plurality of outer struts 72 are welded on the counter-pulling column 71, the plurality of outer struts 72 are arranged in intervals along the axial direction of the counter-pulling column 71, and part of the outer struts 72 arranged in the concrete outer base 11 are welded with the steel bars in the back pull beam 111, and part of the outer struts 72 arranged in the concrete base 30 are welded with the steel mesh 37 or the steel beam cage 36. The two ends of the counter-pulling column 71 are respectively welded with a steel plate structure 73, and the two steel plate structures 73 are respectively arranged in the concrete outer base 11 and the concrete base 30, and the steel plate structure 73 is formed by crosswise welding of two steel sheets.

[0047] Active constraint mechanism: The counter-pulling column 71 provides axial pre-tightening force to control the opening displacement of the foundation corner 10.

[0048] Three-dimensional anchoring system: Radial struts + cross steel plates significantly enhance the anchoring force in the concrete (increase by 300%+).

[0049] In this embodiment, the concrete base 30 is provided with a surrounding frame 38, which is arranged around the connecting position between the steel truss support 20 and the concrete support beam in a circumferential manner, forms an internal cavity penetrating from top to bottom, and is provided with a shock isolation cushion layer 381 arranged around the internal cavity in a circumferential manner along the inner side wall of the internal cavity. The bottom of the surrounding frame 38 extends outwardly and is provided with a plurality of shock absorption plates 382 arranged perpendicularly between the bottom of the surrounding frame 38 and the shock absorption plates 382. The plurality of shock absorption plates 382 are arranged in a circumferential manner along the surrounding frame 38, and the shock absorption plates 382 are connected to the concrete base 30 through connecting bolts. The surrounding frame 38 is provided with a displacement monitoring system, which includes an inclination sensor and a fiber optic strain gauge. Data is uploaded to a cloud platform every 10 minutes.

[0050] Dynamic response control: The shock isolation cushion layer 381 absorbs construction vibration energy and reduces structural dynamic response.

[0051] Intelligent early warning: The inclination sensor and the fiber optic strain gauge monitor node deformation in real time to achieve millimeter-level deformation early warning.

[0052] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. The construction method of the combined support structure of the three-way steel truss and concrete base at the external corner of the foundation pit is characterized by: The following steps are involved: (1) Construction of foundation pit support structure, column piles and columns; (2) constructing an integral concrete base at the positive corner of the foundation pit; the concrete base includes concrete support beams extending in three different directions; (3) Pre-embedded connectors for connecting to the steel structure at the ends of the three concrete support beams; (4) Install steel truss supports in three directions respectively, and one end of each steel truss support is fixedly connected to the end of the corresponding concrete support beam through a pre-buried connector; (5) Connect and fix the steel truss supports in three directions at a position away from the concrete base to form a spatial beam string structure system; (6) Excavate the foundation pit in layers. After each layer of soil is excavated to a predetermined depth below the designed bottom elevation of the next layer of support, repeat steps (2) to (5) to construct the next layer of the combined support structure until the foundation pit excavation and support construction are completed.

2. The construction method of the foundation pit external corner three-way steel truss and concrete base combined support structure according to claim 1, characterized in that: In step (4), the concrete support beams extending in three different directions are direction one concrete support beam, direction two concrete support beam, and direction three concrete support beam, and the direction one concrete support beam, direction two concrete support beam, and direction three concrete support beam are respectively arranged on the two positive corner walls of the positive corner of the foundation pit; The steel truss supports in the three directions are steel support in direction one, steel support in direction two, and steel support in direction three. The steel support in direction one is connected to the concrete support beam in direction one through embedded connectors, the steel support in direction two is connected to the concrete support beam in direction two through embedded connectors, and the steel support in direction three is connected to the concrete support beam in direction three through embedded connectors.

3. The construction method of the foundation pit external corner three-way steel truss and concrete base combined support structure according to claim 2, characterized in that: The concrete base further comprises a concrete slab connecting the three concrete support beams, and a stiffening structure provided in or on the surface of the concrete base for enhancing its overall rigidity and stability; The reinforcing structure includes one or more of stiffening ribs, shear keys or rib plates arranged between concrete support beams, at the junction of beams and slabs or on the slab surface.

4. The construction method of the foundation pit external corner three-way steel truss and concrete base combined support structure according to claim 3, characterized in that: In step (5), the formation of the spatial beam string structure system includes connecting and fixing the end nodes of the three steel trusses through node plates, connecting plates and connecting bolts or pins.

5. The construction method of the foundation pit external corner three-way steel truss and concrete base combined support structure according to claim 4, characterized in that: Step (5) also includes tensioning prestressed cables between or inside the connected and fixed steel truss supports to form a complete tensioned beam structure.

6. The construction method of the foundation pit external corner three-way steel truss and concrete base combined support structure according to any one of claims 1 to 5, characterized in that: An outer pit inner corner located outside the foundation pit is formed at the outer pit inner corner, and a concrete outer base is cast on the outer pit inner corner. The concrete outer base is arranged opposite to the concrete base.

7. The construction method of the foundation pit external corner three-way steel truss and concrete base combined support structure according to claim 6, characterized in that: The concrete outer base includes a back-tension beam and a back-tension plate. The two inner corner walls of the outer inner corner of the pit are connected by multiple back-tension beams. The multiple back-tension beams are arranged in sequence from the inside to the outside of the outer inner corner of the pit, and the lengths of the multiple back-tension beams increase in sequence. Adjacent back-tension beams are connected by back-tension plates, and the multiple back-tension beams are connected by connecting beams.

8. The construction method of the foundation pit external corner three-way steel truss and concrete base combined support structure according to claim 7, characterized in that: A steel cage is provided in the concrete support beam, the steel cage is welded to the steel mesh in the concrete base, the steel cage is welded to the bottom of the embedded connector, the steel cage is connected to the steel truss support via the embedded connector to form a rigid whole, and the steel truss support and the embedded connector are connected by welding or high-strength bolts; A steel plate is embedded in the outer end surface of the concrete support beam, and the steel plate is connected to the steel truss support by welding or high-strength bolts.

9. The construction method of the foundation pit external corner three-way steel truss and concrete base combined support structure according to claim 8, characterized in that: A plurality of tensioning structures are provided in the positive corner of the foundation pit, and the tensioning structures include tensioning columns, the tensioning columns transversely pass through the positive corner of the foundation pit, and the two ends of the tensioning columns are respectively provided in the concrete outer base and the concrete base, a plurality of external support rods are welded to the tensioning columns, and the plurality of external support rods are arranged at intervals along the axial direction of the tensioning columns, some of the external support rods located in the concrete outer base are welded to the steel bars in the back tension beam, and some of the external support rods located in the concrete base are welded to the steel mesh or the steel beam cage; Steel plate structures are welded to both ends of the tension column. The two steel plate structures are located in the concrete outer base and the concrete base respectively. The steel plate structures are formed by cross-welding two steel sheets.

10. The construction method of the foundation pit external corner three-way steel truss and concrete base combined support structure according to claim 1, characterized in that: An enclosure frame is provided on the concrete base, and the enclosure frame is arranged around the circumference of the connection position between the steel truss support and the concrete support beam to form an internal cavity running through from top to bottom. A seismic isolation pad is provided in the internal cavity, and the seismic isolation pad is arranged around the circumference of the inner side wall of the internal cavity. A plurality of shock-absorbing plates extend outward from the bottom of the enclosure frame, and the shock-absorbing plates are arranged vertically to the bottom of the enclosure frame. The plurality of shock-absorbing plates are arranged around the circumference of the enclosure frame, and the shock-absorbing plates are connected to the concrete base by connecting bolts. The enclosing frame is provided with a displacement monitoring system, which includes an inclination sensor and an optical fiber strain gauge.

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