Segmented dismantling construction method for supporting beam in deep and large foundation pit

Abstract

The invention relates to the technical field of support dismantling, in particular to a deep and large foundation pit inner support beam segmented dismantling construction method which comprises the steps that a foundation pit is divided into four parts, namely a first area, a second area, a third area and a fourth area according to an annular support symmetry axis, a construction core tube is arranged, and the bottom of the construction core tube is connected with a bottom plate structure through a bearing plate and shear-resistant studs; a first-layer main body structure is synchronously constructed in a second area and a fourth area which are symmetrical, bottommost-layer supports at the symmetrical positions of the second area and the fourth area are immediately dismantled, the first-layer main body structure is synchronously constructed in the second area and the third area, and bottom-layer supports at the symmetrical positions of the second area and the fourth area are immediately dismantled; according to the segmented dismantling construction method for the supporting beams in the deep and large foundation pit, four-area symmetrical division and synchronous support dismantling are adopted, and unbalanced soil pressure is counteracted through symmetrical subareas of the annular supports.

Description

Technical Field

[0001] This invention relates to the field of support dismantling technology, specifically a method for segmented dismantling of support beams in deep foundation pits. Background Technology

[0002] In the field of deep foundation pit support removal, traditional segmented dismantling methods pose serious safety hazards. Existing technologies, such as patent CN112609701B "A Method for Removing Supports in Deep Foundation Pit," employ segmented dismantling, but suffer from the following drawbacks: Asymmetric dismantling leads to imbalance: This technology does not establish a strictly symmetrical zoning system. During the dismantling process, the soil pressure distribution on the pit wall is uneven, causing the horizontal displacement difference of the support structure to exceed the warning value, increasing the risk of collapse. Insufficient passive stress release: Its unloading structure is only a simple slit, and the residual stress is easily released when it is concentrated, which can easily lead to brittle failure of the structure; Insufficient load transfer capacity: It relies solely on temporary support for conversion, lacks a permanent force transmission structure similar to the core tube and a prestressed active loading system, and axial force compensation lags during dismantling.

[0003] Therefore, we propose a method for the segmented removal of support beams within deep foundation pits. Summary of the Invention

[0004] One of the technical problems that this application aims to solve is that existing technologies suffer from imbalance due to asymmetric dismantling and bracing, insufficient passive stress release, and inadequate load transfer capacity.

[0005] To address the aforementioned technical problems, this application provides a method for the segmented removal of support beams within deep foundation pits, comprising the following steps: S1: Divide the foundation pit into four parts according to the symmetry axis of the ring support: the first region, the second region, the third region, and the fourth region. S2: Construction core tube, whose bottom is connected to the base plate structure through a bearing plate and shear studs, and the top outer wall is provided with a dish-shaped unloading groove; S3: Simultaneously construct the main structure in the symmetrical area and remove the bottom support: Simultaneously construct the first layer of the main structure in the symmetrical second and fourth areas, and immediately remove the bottom support at the symmetrical position in the second and fourth areas. Simultaneously construct the first layer of the main structure in the second and third areas, and immediately remove the bottom support at the symmetrical position in the second and third areas. S4: Repeat S3 until the main structure is completed; S5: Remove the top support of the core tube; The outer wall of the core tube is connected to the bottom plate and the ring support through support beam 2 and support beam 3. Support beam 1 is connected to the ring support through L-shaped steel brackets, bolts and embedded node plates. The two ends of the steel strand are anchored to the prestressed anchor point 1 of support beam 1 and the prestressed anchor point 2 of support beam 2. The ring support is located at the center of the support structure.

[0006] In some embodiments, a bearing plate is provided between the bottom of the core tube and the base plate structure, and the connection is fixed by shear studs.

[0007] In some embodiments, an L-shaped steel bracket is provided on the inner edge of the annular support, and one outer end of the support beam is fixed to the annular support by the L-shaped steel bracket and bolts.

[0008] In some embodiments, the steel strands are tensioned to 70%-90% of the design prestress before dismantling, and their two ends are anchored to prestressed anchor point one of the support beam one and prestressed anchor point two of the support beam two, respectively.

[0009] In some embodiments, a disc-shaped unloading groove is provided on the top outer wall of the core tube. Its cross-section is an inverted trapezoid with a wider top and a narrower bottom. The groove wall makes an angle α of 45°±5° with the vertical direction and is located 110mm inward from the top edge of the core tube.

[0010] In some embodiments, a hydraulic jack reaction frame is installed under the support to be removed before the support is removed, to compensate for the loss of axial force of the support in real time. The compensation value is dynamically adjusted according to the monitoring data and the axial force fluctuation is ≤5%.

[0011] In some embodiments, the steel strand is tensioned between prestressed anchor point one and prestressed anchor point two, and prestressed anchor point two is located at the vertical projection position of prestressed anchor point one.

[0012] In some embodiments, the area of ​​a single demolition of a single construction zone is less than 1 / 8 of the total area of ​​the ring support, and the cut blocks are distributed radially.

[0013] In some embodiments, the time deviation of the demolition operation in symmetrical areas is less than 1 hour, the difference in demolition area is less than 10%, and the difference in the construction progress of the main structure in adjacent construction areas is less than 7 days.

[0014] In some embodiments, a laser scanning positioning system is used during dismantling to control the positioning error of the cutting line to be less than 2mm, and the deformation is monitored by tilt sensors and strain gauges. An early warning is triggered when the horizontal displacement rate is greater than 2mm / d.

[0015] This invention has at least the following beneficial effects: 1. The core tube and prestressed steel strands form an active force-bearing system, which is combined with the hydraulic jack reaction frame to dynamically compensate for the axial force and achieve a smooth transfer of the support load. The disc-shaped unloading groove set at the top of the core tube releases stress through a 45° inclined gradient, which transforms the brittle failure in traditional demolition into controllable stress dissipation and avoids the risk of sudden collapse caused by residual stress concentration.

[0016] 2. The four-zone symmetrical division and forced synchronous dismantling and support are adopted. The unbalanced earth pressure is offset by the symmetrical axis partitioning of the ring support. The strict synchronous control of the construction progress difference between adjacent areas is ≤7 days, which improves the dismantling efficiency by 40%. The laser scanning positioning system combined with tilt sensor + strain gauge real-time monitoring (early warning threshold 2mm / d) realizes millimeter-level deformation control. The block cutting strategy of dismantling support area ≤1 / 8 of the total area at a time significantly reduces the risk of foundation pit instability. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the deep foundation pit support structure of the present invention; Figure 2 This is a schematic diagram of the support structure inside the deep foundation pit from another perspective of the present invention; Figure 3 for Figure 2 Enlarged view of point A in the middle; Figure 4 for Figure 2 Enlarged view at point B in the middle; Figure 5 This is a bottom view of the deep foundation pit support of the present invention; Figure 6 for Figure 5 CC section view; Figure 7 for Figure 6 Enlarged view at point D; Figure 8 for Figure 6 Enlarged view at point E in the middle; Figure 9 for Figure 6 Enlarged view at point F; Figure 10 This is a schematic diagram of the method steps of the present invention.

[0018] In the diagram: 100 - Base plate structure; 101 - Bearing plate; 102 - Shear stud; 200 - Support structure; 201 - Circular support; 202 - First region; 203 - Second region; 204 - Third region; 205 - Fourth region; 206 - L-shaped steel bracket; 207 - Bolt; 300 - Core tube; 301 - Support beam one; 302 - Embedded node plate; 303 - Prestressed anchor point one; 304 - Steel strand; 305 - Support beam two; 306 - Support beam three; 307 - Disc-shaped unloading groove; 308 - Prestressed anchor point two. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1, please refer to Figure 1-10 This invention provides a technical solution: a method for segmented dismantling of support beams in deep foundation pits, comprising the following steps: S1: Divide the foundation pit into four parts according to the axis of symmetry of the ring support 201, namely the first region 202, the second region 203, the third region 204, and the fourth region 205. S2: Construction core tube 300, the bottom of which is connected to the base plate structure 100 through bearing plate 101 and shear studs 102, and the top outer wall is provided with a dish-shaped unloading groove 307; S3: Simultaneously construct the main structure in symmetrical areas and remove the bottom support: Simultaneously construct the first layer of the main structure in the symmetrical first area 202 and fourth area 205, and immediately remove the bottom support at the symmetrical position of the first area 202 and fourth area 205. Simultaneously construct the first layer of the main structure in the second area 203 and third area 204, and immediately remove the bottom support at the symmetrical position of the second area 203 and third area 204. S4: Repeat S3 until the main structure is completed; S5: Remove the top support of the core tube 300; The outer wall of the core tube 300 is connected to the base plate structure 100 and the ring support 201 through support beam 2 305 and support beam 3 306. Support beam 1 301 is connected to the ring support 201 through L-shaped steel bracket 206, bolts 207 and embedded node plate 302. The two ends of the steel strand 304 are anchored to the prestressed anchor point 1 303 of support beam 1 301 and the prestressed anchor point 2 308 of support beam 2 305. The ring support 201 is located at the center of the support structure 200.

[0021] Specifically, the purpose of this design is to ensure that the core tube 300 acts as a vertical load-bearing hub, connecting the base plate structure 100 via the bearing plate 101 and shear studs 102 to form a rigid foundation. For horizontal load distribution, support beams 1-301, 2-305, and 3-306 transfer the load from the ring support 201 to the core tube 300, avoiding stress concentration. For active prestressing control, steel strands 304 connect the prestressing anchor point 303 of support beam 1-301 and the prestressing anchor point 308 of support beam 2-305. The purpose is to pre-tension (70%–90% of the design value) before dismantling, actively transferring the load from support beam 1-301 to the core tube 300 foundation. The dish-shaped unloading groove 307, located on the top outer wall of the core tube 300, has an inverted trapezoidal cross-section (inclination angle 45°±5°) to guide residual stress release along the inclined gradient during dismantling, preventing brittle failure.

[0022] Specifically, in the four-zone symmetrical support removal process, step S3 forces simultaneous support removal in both Zone 1 (202) and Zone 4 (205), and simultaneously in Zone 2 (203) and Zone 3 (204). The benefit is that it offsets the imbalance of lateral earth pressure in the foundation pit, reducing the risk of collapse.

[0023] Specifically, the core tube 300 is removed last, and step S5 is the final step in removing the top support of the core tube 300. This ensures that the residual load of the annular support 201 is completely transferred via the path of support beam 1 301 → steel strand 304 → support beam 2 305. A component coordination mechanism is used, with the L-shaped steel bracket 206 serving as the outer end support of support beam 1 301, and bolts 207 providing a detachable connection. This allows for rapid removal without disturbing the overall stability of the annular support 201.

[0024] Specifically, the dish-shaped unloading groove 307 reduces the stress release rate by 60%, and the hydraulic reaction frame compensates for axial force fluctuations of ≤5%. Dual-path force transmission via support beams 305 and 306 provides redundancy. Symmetrical support dismantling (time difference ≤1 hour) shortens the single-layer construction cycle by 40%. Radial cutting into blocks (≤1 / 8 of the total area) reduces the time required for mechanical relocation.

[0025] Example 2, please refer to Figure 1-9 A pressure plate 101 is provided between the bottom of the core tube 300 and the base plate structure 100, and is fixedly connected by shear studs 102.

[0026] Specifically, the purpose of this arrangement is to ensure that the core function of the bearing plate 101 is stress diffusion, uniformly transferring the concentrated load of the core tube 300 to the base slab structure 100, thus preventing localized concrete crushing (the bearing plate 101 thickness is ≥40mm, and its area is >20% of the core tube cross-section). It also ensures vertical deformation coordination, eliminating the deformation difference between the core tube 300 concrete shrinkage and creep and the base slab structure 100, providing a rigid reaction base for the prestressed steel strands 304. The core function of the shear studs 102 is horizontal load transfer. To resist the horizontal shear force generated during support removal, the stud diameter is Φ19~22mm, the spacing is ≤300mm, and the shear strength of the stud is ensured to be >120% of the shear strength of the concrete. To resolve composite stress and decompose the torque caused by unbalanced earth pressure, such as when the support is removed between the third region 204 and the fourth region 205, to prevent horizontal slippage of the core tube 300.

[0027] Example 3, see Figure 1-9 An L-shaped steel bracket 206 is provided on the inner edge of the ring support 201, and the outer end of the support beam 301 is fixed to the ring support 201 by the L-shaped steel bracket 206 and bolts 207.

[0028] Specifically, this design aims to ensure the core function of the L-shaped steel support 206 is precise force transmission path design. The vertical limb (180mm high) abuts against the inner edge of the annular support 201 concrete, converting the vertical load of the support beam 301 into pressure transmission; the horizontal limb (150mm wide) serves as a rigid support at the outer end of the support beam 301, providing a bending moment resistance plane (bending capacity ≥320kN·m). An error compensation structure is incorporated, with a 12mm adjustment gap to eliminate the impact of core tube 300 construction deviations on the installation of the support beam 301. A 2mm thick rubber pad is placed on the contact surface to buffer the impact of dynamic loads.

[0029] Specifically, the synergistic effect of bolt 207 and the controllable constraint mechanism are achieved by using 10.9 grade high-strength bolt 207 (diameter M24) with a preload of 120kN. Bolt 207 only bears the horizontal force during installation. When removing it, the constraint is released, allowing the load to be transferred smoothly to the steel strand 304. The guide function is removed. The bolt 207 hole is designed as an oblong hole (30×40mm). When removing it, the support beam 301 is allowed to slide radially along the core tube 300 by 3-5mm, avoiding stress oscillation caused by the sudden detachment of the support beam 301.

[0030] With dual structural integrity, the L-shaped steel support 206 serves as a permanent force-transferring component, working together with the core tube 300 until the end of the project. Bolts 207 act as temporary, controllable constraints, released during support removal without disturbing the structure. Prestressed loading works in synergy: when the steel strands 304 are tensioned (before step S3), the vertical limbs of the L-shaped steel support 206 close the gap with the annular support 201, forming a rigid connection; during removal, bolts 207 are released, and the load is transferred through the prestressed steel strands 304, achieving a seamless transition from rigid connection to flexible conversion.

[0031] Example 4, see Figure 1-9 Before dismantling, the steel strand 304 is tensioned to 70% to 90% of the design prestress, and its two ends are anchored to the prestress anchor point 303 of the support beam 301 and the prestress anchor point 308 of the support beam 305, respectively.

[0032] Specifically, this setup aims to establish an axial force relay mechanism, where the tensioned steel strand 304 generates ≥400kN of prestress, actively bearing 70%–90% of the vertical load of the supporting beam 301. The remaining 10%–30% of the load is temporarily borne by the L-shaped steel support 206, creating a dual-path force transmission guarantee. Deformation coordination control ensures that the second prestressed anchor point 308 is precisely located at the vertical projection point of the first prestressed anchor point 303 (error ≤5mm), guaranteeing vertical force transmission through the steel strand 304 and preventing torsion in the supporting beam 301 (torque reduction of 85%).

[0033] The anchoring points function as a closed-loop stress structure. The load path is: Support beam 301 → Prestressed anchor point 303 → Steel strand 304 → Prestressed anchor point 308 → Support beam 305 → Core tube 300. This forms a closed force transmission chain, bypassing the ring support 201 to be dismantled. Double safety measures are provided: Prestressed anchor point 303 is located below the mid-span of support beam 301 (at the point of maximum bending moment), directly offsetting the tensile stress in the structure. Prestressed anchor point 308 is located at the root of support beam 305 (in the area of ​​maximum shear force), utilizing the shear studs 102 of the core tube 300 to dissipate horizontal forces.

[0034] It can proactively prevent three major risks: brittle fracture of the support beam 301: 70% tension makes the remaining load < the critical value of concrete cracking; uncontrolled rebound of the foundation pit: the elastic deformation of the steel strand 304 absorbs more than 40% of the rebound energy; interruption of the force transmission path: the double anchor points form a redundant force transmission system (it can still bear 70% of the load even if a single failure occurs).

[0035] Example 5, see Figure 1-9 The disc-shaped unloading groove 307 is set on the top outer wall of the core tube 300. Its cross-section is an inverted trapezoid with a wider top and a narrower bottom. The groove wall makes an angle α of 45°±5° with the vertical direction and is located 120mm inward from the top edge of the core tube 300.

[0036] Specifically, the purpose of this design is to redistribute stress flow, leveraging the core value of the inverted trapezoidal cross-section (wider at the top and narrower at the bottom). The upper opening width (180mm) is greater than the lower bottom width (60mm), forming a 120mm inclined wall. Stress waves undergo total reflection at the 45° slope, releasing energy horizontally (vertical stress attenuation is 60%). The peak circumferential tensile stress at the top of the core tube 300 decreases from 18MPa to 7MPa. Crack development is controlled by initiating cracking at the bottom of the narrow crack (stress concentration factor 2.1), guiding the crack to develop directionally along the slope and preventing cracks from penetrating the main reinforcement of the core tube 300, maintaining a distance of ≥50mm from the main reinforcement protective layer.

[0037] The precise 120mm inward positioning, coupled with a dual protection mechanism, ensures that the core tube 300's top principal stress zone (peak stress zone within 50mm of the edge) is avoided at 120mm inward from the edge, guaranteeing that the bottom of the trench is ≥70mm from the inner vertical reinforcement of the core tube 300 (reinforcement stress monitoring value <120MPa). In synergy with the steel strand 304, the vertical impact of the prestressed anchorage point 308 (120mm directly below the trench) increases the compressive stress in the dish-shaped unloading trench 307 area to 15MPa during tensioning of the steel strand 304 (step S3), thus preemptively suppressing cracking.

[0038] Meanwhile, the inclined plane requires additional work to overcome gravity to break the concrete. A 120mm recessed space is reserved to provide conditions for the installation of vibration sensors (sampling frequency ≥180Hz) to achieve a 0.5s warning before failure. The concrete in the trench area is under triaxial compression (containment pressure is established by tensioning 304 steel strands), increasing the compressive strength by 22%.

[0039] Example 6: Before the support is removed, a hydraulic jack reaction frame is installed under the support to be removed to compensate for the axial force loss of the support in real time. The compensation value is dynamically adjusted according to the monitoring data and the axial force fluctuation is ≤5%.

[0040] Specifically, the purpose of this design is to construct a closed-loop control system for axial force compensation and structural deformation, and to eliminate the risk of sudden unloading in traditional demolition through intelligent hydraulic intervention.

[0041] The hydraulic jack reaction frame acts as an adjustable temporary support, lifting and compensating for the instant (≤3 seconds) when the structure loses support. After compensation, axial force fluctuations are strictly controlled within ±5%. To prevent sudden collapses, the hydraulic cylinder stroke reserve is ≥50mm (capable of absorbing instantaneous settlement of ≥8mm). The upper limit of the compensation force is set at 120% of the design axial force (to prevent overload accidents). To correct construction deviations, when symmetrical support dismantling is asynchronous (e.g., a lag of >1h in Zone 203), the reaction frame automatically supplements the missing support reaction force, eliminating the horizontal displacement difference of the support structure (controlled <3mm).

[0042] In Example 7, the steel strand 304 is tensioned between prestressed anchor point 1 303 and prestressed anchor point 2 308, and prestressed anchor point 2 308 is located at the vertical projection position of prestressed anchor point 1 303.

[0043] Specifically, the purpose of this design is to leverage the core mechanical value of vertical projection, eliminate eccentric bending moments, and ensure that prestressed anchor point 2 (308) is directly below prestressed anchor point 1 (303) (vertical deviation ≤ 5mm), with steel strand 304 in an absolutely vertical state. When the load of support beam 1 (301) is transmitted through steel strand 304, the bending moment component is reduced by 98%. This forms a consistent force transmission chain in the direction of the gravity field, avoiding the horizontal component force caused by traditional oblique cable arrangement, and saving on structural reinforcement.

[0044] Prestressed anchor point 1 (303) is located at the lower edge of the mid-span of support beam 1 (301), directly offsetting the area of ​​maximum tensile stress. Prestressed anchor point 2 (308) is located at the upper edge of the root of support beam 2 (305), forming a couple with shear stud 102 to dissipate the 250kN shear force.

[0045] The prestressed anchor point 303 features a bidirectional anti-slip structure with an embedded anchor plate (bearing area ≥ 300 cm²). Prestressed anchor point 308 is equipped with a triple-lock system (mechanical, hydraulic, and welded). A deformation coordination mechanism ensures that during tensioning of the steel strand 304, the difference between the settlement of the core tube 300 and the rebound of the support beam 301 is less than 0.2 mm, preventing anchor damage due to displacement differences.

[0046] The dish-shaped unloading groove 307 enhances efficiency, and the second prestressed anchor point 308 is located 120mm directly below the unloading groove. The tension of the steel strand 304 (85% of the design value) brings the bottom compressive stress of the unloading groove to 12MPa, significantly delaying cracking. The hydraulic reaction frame is linked. When the jack compensates for the axial force (fluctuation ≤ 5%), the 304 steel strand automatically adjusts the tension (change rate < 0.3 kN / s) to form a double buffer of "mechanical compensation + prestress adjustment".

[0047] Example 8: The area demolished in a single construction zone is less than 1 / 8 of the total area of ​​the ring support 201, and the cut blocks are distributed radially. The time deviation of demolition operations in symmetrical areas is less than 1 hour, the difference in demolition area is less than 10%, and the difference in the main structure construction progress between adjacent construction zones is less than 7 days. During demolition, a laser scanning positioning system is used to control the positioning error of the cutting line to be less than 2mm, and deformation is monitored by tilt sensors and strain gauges. An early warning is triggered when the horizontal displacement rate is greater than 2mm / d.

[0048] Specifically, the purpose of this design is to ensure that the area removed in a single operation is ≤45° of the central angle (360° / 8=45°), guaranteeing that the remaining support arc segments can form a complete pressure arch. The radial distribution, with the cutting seams extending radially and perpendicular to the direction of the principal bending moment, reduces the stress concentration factor at the cut by 50%. The time difference is <1 hour to prevent torsional instability of the support ring and controls the torque deviation to <120 kN·m. The area difference is <10% to maintain symmetrical mass distribution.

[0049] Specifically, a horizontal displacement rate > 1 mm / d triggers a yellow alert; the load distribution must be checked. A horizontal displacement rate > 2 mm / d triggers a red alert; dismantling must be stopped immediately, and the hydraulic compensation system must be activated.

[0050] The following is combined with Figures 1-10 This section introduces the complete workflow of the segmented dismantling construction method for support beams in deep foundation pits: The overall construction process of the foundation pit internal support and main structure is as follows: The foundation pit is divided into four parts according to the axis of symmetry of the ring support 201: the first region 202, the second region 203, the third region 204, and the fourth region 205. The construction core tube 300 is connected to the bottom plate structure 100 by a bearing plate 101 and shear studs 102 at its bottom, and a dish-shaped unloading groove 307 is provided on the top outer wall. Simultaneously construct the main structure in symmetrical areas and remove the bottom support: Simultaneously construct the first layer of the main structure in the symmetrical first area 202 and fourth area 205, and immediately remove the bottom support at the symmetrical position of the first area 202 and fourth area 205. Simultaneously construct the first layer of the main structure in the second area 203 and third area 204, and immediately remove the bottom support at the symmetrical position of the second area 203 and third area 204. Repeat step S3 until the main structure is complete; Remove the top support of the core tube 300.

[0051] The specific dismantling process is as follows: I. Construction Preparation Stage In the early stages of construction, a three-dimensional model of the foundation pit was established using digital twin technology to simulate the load transfer path, stress distribution, and deformation trend during demolition. The requirement was that the axial force transmission error should not exceed 3%, and the deformation prediction error should be controlled within 0.5 mm. A high-precision monitoring system was simultaneously deployed: fiber optic strain gauges with a sensitivity of 1 micro-strain were installed at the mid-span of the support beams; tilt sensors with an accuracy of 0.001 degrees were arranged on the L-shaped steel support 206; and laser displacement gauges with a resolution of 0.1 mm were deployed on the inner edge of the ring support 201, forming a real-time monitoring network covering the entire structure.

[0052] II. Prestressing Loading Stage First, a hydraulic jack reaction frame is used to pre-lift the support beam by 5% of the design axial force, eliminating mechanical backlash. Then, steel strand 304 is tensioned to 85% of the design prestress, ensuring the load is precisely transferred to the core tube through the vertical anchor points. During this stage, the compressive stress in the dish-shaped unloading groove 307 area is monitored in real time. Tensioning is stopped when it reaches 12 MPa to ensure the unloading groove is under pre-compression to suppress cracking. During tensioning, the vertical projection deviation of the anchor points is strictly controlled to not exceed 5 mm, and the pressure fluctuation of the hydraulic system is limited to within 5%.

[0053] III. Segmented Demolition Phase Radial segmentation cutting Each removal area is limited to 1 / 8 of the total area of ​​the annular support 201 (approximately a sector corresponding to a 45-degree central angle). The cutting seam is arranged radially, coinciding with the bisector of the central angle of the annular support 201. A high-precision point cloud model is generated using laser scanning. The cutting path is automatically corrected by comparing it with BIM design data and compensating for the effects of temperature deformation. The cutting operation is then performed by an intelligent robotic arm, with the positioning error strictly controlled within 2 millimeters.

[0054] Symmetrical synchronous control The time difference between demolition operations in symmetrical areas must not exceed 1 hour, and the area difference must be less than 10%. If the demolition of a certain area results in an axial force loss exceeding 5%, the hydraulic jacks will initiate compensation within 3 seconds. If the progress deviation in symmetrical areas exceeds the limit, the demolition area of ​​subsequent blocks will be automatically adjusted or construction will be suspended. The difference in the progress of the main structure of adjacent construction areas must be controlled within 7 days to ensure the strength matching of the old and new structures and the hydrological balance.

[0055] IV. Stress Dissipation Stage The dish-shaped unloading trough 307 guides stress release through a 45-degree inclined trough wall. After the concrete cracks extend directionally along the inclined surface to a depth of 30 mm, the wedge-shaped fragments fall off in stages, with the entire process taking approximately 120 minutes. During this period, vibration sensors monitor the crack propagation rate (triggering grouting reinforcement when it exceeds 50 micrometers / second) and track the residual stress decay in real time. Subsequent operations can only proceed once the residual stress drops below 0.2 MPa.

[0056] V. Early Warning and Intervention Mechanism A three-tiered response system is established: a yellow alert is triggered when the horizontal displacement rate exceeds 1 mm / day, and the load distribution is checked; a red alert is triggered when it exceeds 2 mm / day, immediately stopping demolition and activating the full-area hydraulic compensation system; when the strain mutation exceeds 50 micro-strains / minute, epoxy resin is automatically injected into the cut seam for reinforcement. The system synchronously links laser scanning data with the BIM model, generating a construction adjustment plan every 20 minutes.

[0057] VI. Completion Verification Stage Geometric acceptance requirements stipulate that the roundness deviation of the ring support 201 should not exceed one-thousandth of its diameter, and the vertical displacement of the L-shaped steel bracket 206 should be less than 2 mm. Mechanical performance testing employs the impact method to assess the concrete breakage volume (which must be less than 5% of the design value), and verifies whether the stress relaxation rate of the steel strand 304 is less than 3%. Finally, by comparing monitoring data before and after demolition, it is verified whether the deformation of the foundation pit is controlled within 0.05% of its depth.

[0058] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0059] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for segmented dismantling of support beams in deep foundation pits, characterized by: Includes the following steps: S1: Divide the foundation pit into four parts according to the symmetry axis of the ring support (201): the first region (202), the second region (203), the third region (204), and the fourth region (205). S2: Construction core tube (300), the bottom of which is connected to the bottom plate structure (100) through a bearing plate (101) and shear studs (102), and the top outer wall is provided with a dish-shaped unloading groove (307). S3: Simultaneously construct the main structure in the symmetrical area and remove the bottom support: Simultaneously construct the first layer of the main structure in the symmetrical second area (202) and fourth area (205), and immediately remove the bottom support at the symmetrical position of the second area (202) and fourth area (205). Simultaneously construct the first layer of the main structure in the second area (203) and third area (204), and immediately remove the bottom support at the symmetrical position of the second area (203) and third area (204). S4: Repeat step S3 until the main structure is completed; S5: Remove the top support of the core tube (300); The outer wall of the core tube (300) is connected to the base plate (100) and the annular support (201) by support beam two (305) and support beam three (306). Support beam one (301) is connected to the annular support (201) by L-shaped steel bracket (206), bolts (207) and embedded node plate (302). The two ends of the steel strand (304) are anchored to the prestressed anchor point one (303) of support beam one (301) and the prestressed anchor point two (308) of support beam two (305). The annular support (201) is located at the center of the support structure (200).

2. The method for segmented demolition of support beams in deep foundation pits according to claim 1, characterized in that: The bearing plate (101) is provided between the bottom of the core tube (300) and the base plate structure (100), and is fixedly connected by the shear studs (102).

3. The method for segmented demolition of support beams in deep foundation pits according to claim 1, characterized in that: The inner edge of the annular support (201) is provided with the L-shaped steel bracket (206), and the outer end of the support beam (301) is fixed to the annular support (201) through the L-shaped steel bracket (206) and the bolt (207).

4. The method for segmented dismantling of support beams in deep foundation pits according to claim 1, characterized in that: Before dismantling, the steel strand (304) is tensioned to 70%~90% of the design prestress, and its two ends are respectively anchored to the prestress anchor point one (303) of the support beam one (301) and the prestress anchor point two (308) of the support beam two (305).

5. The method for segmented demolition of support beams in deep foundation pits according to claim 1, characterized in that: The disc-shaped unloading groove (307) is located on the top outer wall of the core tube (300). Its cross-section is an inverted trapezoid with a wider top and a narrower bottom. The groove wall makes an angle α = 45° ± 5° with the vertical direction and is located 120 mm inward from the top edge of the core tube (300).

6. The method for segmented demolition of support beams in deep foundation pits according to claim 1, characterized in that: Before dismantling the support, a hydraulic jack reaction frame is installed under the support to be dismantled to compensate for the axial force loss of the support in real time. The compensation value is dynamically adjusted according to the monitoring data and the axial force fluctuation is ≤5%.

7. The method for segmented demolition of support beams in deep foundation pits according to claim 4, characterized in that: The steel strand (304) is tensioned between the first prestressed anchor point (303) and the second prestressed anchor point (308), and the second prestressed anchor point (308) is located at the vertical projection position of the first prestressed anchor point (303).

8. The method for segmented demolition of support beams in deep foundation pits according to claim 1, characterized in that: The area of ​​a single demolition in a single construction zone is less than 1 / 8 of the total area of ​​the ring support (201), and the cut blocks are distributed radially.

9. The method for segmented demolition of support beams in deep foundation pits according to claim 1, characterized in that: The time deviation for demolition operations in symmetrical areas is less than 1 hour, the difference in demolition area is less than 10%, and the difference in the main structure construction progress between adjacent construction areas is less than 7 days.

10. The method for segmented demolition of support beams in deep foundation pits according to claim 1, characterized in that: During dismantling, a laser scanning positioning system is used to control the positioning error of the cutting line to be less than 2mm, and the deformation is monitored by tilt sensors and strain gauges. When the horizontal displacement rate is greater than 2mm / d, an early warning is triggered.

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