Construction method of micro-deformation foundation pit enclosure close to super-large diameter rainwater pipeline

Abstract

The application discloses a micro-deformation foundation pit enclosure construction method close to a super-large-diameter rainwater pipeline, and comprises the following steps: temporarily blocking all rainwater branch pipes in the foundation pit excavation range; monitoring the deformation of the rainwater main pipe; constructing MJS method piles on the top of the main pipe and in the lateral soil body to form a reinforced curtain; constructing two rows of triaxial mixing piles on the side of the MJS method piles close to the foundation pit, and constructing a diaphragm wall between the two rows of triaxial mixing piles; laying a dewatering deep well and a pressure-bearing pressure-reducing well, and adjusting the operation state according to the main pipe deformation data; dividing the foundation pit into multiple excavation areas, and excavating in layers according to the sequence from the area far away from the main pipe to the area close to the main pipe; and finally supporting servo steel supports in the last excavation area, and dynamically adjusting the support axial force according to the main pipe deformation data. The application realizes micro-deformation control of the super-large-diameter rainwater main pipe in the whole foundation pit construction process, and ensures the safe operation of the pipeline.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, and in particular to a method for constructing a micro-deformation foundation pit retaining structure adjacent to an ultra-large diameter rainwater pipeline. Background Technology

[0002] With the increasing intensity of urban underground space development, a large number of foundation pit projects are laid adjacent to existing municipal pipelines. Among them, ultra-large diameter rainwater pipelines are the core facilities of urban drainage systems, and their structural safety is directly related to the city's flood control and drainage capabilities. Once deformation exceeds the standard, joint leakage occurs, or pipe wall rupture occurs, it will directly cause regional flooding, resulting in significant social impact and economic losses.

[0003] In soft soil regions, such as Shanghai, the soil is characterized by high water content, high compressibility, low shear strength, and significant rheological effects. This makes the excavation of foundation pits prone to large lateral deformations and surface settlement, placing extremely high demands on the protection of surrounding pipelines. Current technologies for foundation pit support adjacent to pipelines have the following main shortcomings: The rainwater pipeline protection only uses simple shallow mixing pile reinforcement, which cannot prevent deep soil slippage. Under soft soil creep, pipeline deformation is difficult to control. The lack of branch pipe sealing and diversion process means that construction precipitation and soil disturbance cause water flow turbulence in the pipe to impact the pipeline base, exacerbating settlement. Conventional triaxial mixing piles have a limited reinforcement range, and cannot achieve comprehensive deep reinforcement in the narrow gap between the foundation pit and pipelines, resulting in insufficient water stoppage and soil deformation resistance. Traditional concrete or ordinary steel supports only fix the pre-applied axial force. The spatial and temporal effects of foundation pit excavation and the additional earth pressure generated by soft soil rheology cannot be dynamically compensated. The lateral deformation of the retaining wall continues to increase, exceeding the allowable threshold for rainwater pipeline protection. The retaining system is simple, mostly using SMW piles, with weak overall stiffness, no underground continuous wall and multi-level support composite system, and no corresponding deformation control measures during the zoned excavation sequence. The processes of dewatering, excavation, and support removal were not linked to pipeline protection, and there was a lack of integrated technology from pipeline pretreatment, lateral reinforcement, dynamic support to real-time monitoring.

[0004] Therefore, there is an urgent need to develop a micro-deformation foundation pit retaining construction method that minimizes construction disturbance, achieves high deformation control accuracy, and is economical and efficient for construction adjacent to ultra-large diameter rainwater pipelines, in order to solve the problem of deformation control of deep foundation pits adjacent to important pipelines in soft soil areas. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for constructing a micro-deformation foundation pit retaining structure adjacent to an ultra-large diameter rainwater pipeline. Through branch pipe sealing, deformation monitoring, composite retaining structure, dynamic servo and adaptive control, the method achieves micro-deformation control of the ultra-large diameter rainwater pipeline throughout the entire foundation pit construction process, reduces the disturbance and deformation risk to the pipeline during construction, and thus ensures the safe operation of the pipeline.

[0006] To achieve the above objectives, the technical solution adopted in this invention is a method for constructing a micro-deformation foundation pit retaining structure adjacent to an ultra-large diameter rainwater pipeline, comprising the following steps: Step 1: Locate the location of the extra-large diameter main rainwater pipe and all rainwater branch pipes connected to it, and temporarily seal all rainwater branch pipes within the excavation area of ​​the foundation pit; Step 2: Perform deformation monitoring on the main rainwater pipe to obtain deformation data of the main rainwater pipe during the foundation pit construction process; Step 3: Construct MJS method piles in the soil corresponding to the top of the rainwater main pipe and in the soil on the side of the rainwater main pipe that is relatively close to the excavation pit, so that the top MJS method piles and the side MJS method piles are connected to form a reinforcement curtain. Step 4: Construct two rows of triaxial mixing piles in the soil on the side of the MJS method piles that is relatively close to the excavation pit, and construct a diaphragm wall between the two rows of triaxial mixing piles to form a composite retaining structure. Step 5: Install drainage wells and pressure relief wells in the excavation pit, and adjust the operation of the drainage wells and pressure relief wells according to the deformation data of the main rainwater pipe to control the groundwater level and the pressure of the confined water. Step 6: Divide the foundation pit into multiple excavation areas, and excavate in sections and layers in the order that the excavation areas farthest from the main rainwater pipe are excavated before the excavation areas closest to the main rainwater pipe. Step 7: After the last excavation area is completed, a servo steel support is installed inside it, so that the servo steel support abuts against the composite retaining structure, and the supporting axial force of the servo steel support is dynamically adjusted according to the deformation data of the rainwater main pipe.

[0007] A further improvement of the present invention on the micro-deformation foundation pit support construction method adjacent to ultra-large diameter rainwater pipelines is that, when performing step 1 above, sealing airbags are respectively installed upstream and downstream of each of the rainwater branch pipes within the foundation pit excavation range to seal them.

[0008] A further improvement of the micro-deformation foundation pit retaining construction method adjacent to ultra-large diameter rainwater pipelines in this invention is that, in step 2, settlement monitoring points are set up around the main rainwater pipe, settlement change data of the soil around the main rainwater pipe is obtained through settlement monitoring equipment, and the deformation state of the main rainwater pipe is determined based on the settlement change data.

[0009] A further improvement of the present invention is that, before performing step 3 above and after performing step 2 above, a heavy-duty lane is constructed at the top of the excavation pit, relatively close to the main rainwater pipe. During the performance of steps 3 and 4 above, construction equipment is used to carry out construction on the heavy-duty lane. Before performing step 6 above, the heavy-duty lane is removed.

[0010] A further improvement of the micro-deformation foundation pit retaining construction method of the present invention, which is located adjacent to an ultra-large diameter rainwater pipeline, is that, when performing step 4 above, when constructing the triaxial mixing piles, steel sections are inserted into a row of the triaxial mixing piles that are relatively close to the MJS method piles.

[0011] A further improvement of the micro-deformation foundation pit support construction method adjacent to ultra-large diameter rainwater pipelines in this invention is that, when performing step 5 above, the groundwater level in the foundation pit is lowered by using the drainage well, the pressure relief well is lowered by using the pressure relief well, and the pumping speed and pumping volume are adjusted according to the deformation data of the main rainwater pipe.

[0012] A further improvement of the micro-deformation foundation pit retaining construction method adjacent to ultra-large diameter rainwater pipelines in this invention is that, when performing step 5 above, recharge wells are also installed around the main rainwater pipe. When the deformation data of the main rainwater pipe exceeds a preset threshold, the pumping intensity of the drainage well is reduced, and the recharge wells are used to replenish groundwater to the soil around the main rainwater pipe in order to regulate the pore water pressure of the soil.

[0013] A further improvement of the micro-deformation foundation pit retaining construction method adjacent to ultra-large diameter rainwater pipelines in this invention is that, when performing step 6 above, the foundation pit is divided into a first excavation area far away from the main rainwater pipe, a second excavation area in the middle, and a third excavation area close to the main rainwater pipe, and excavation is carried out in the order of the first excavation area, the second excavation area, and the third excavation area.

[0014] A further improvement of the micro-deformation foundation pit retaining construction method adjacent to ultra-large diameter rainwater pipelines in this invention is that, when dividing the foundation pit, a row of support piles is driven between the first excavation area and the second excavation area, and between the second excavation area and the third excavation area. When performing step 7 above, one end of the servo steel support abuts against the composite retaining structure, and the other end abuts against the support pile located between the second excavation area and the third excavation area.

[0015] Compared with the prior art, the advantages of the present invention are: 1. By connecting the top MJS method piles with the side MJS method piles to form an L-shaped reinforcement curtain, compared with conventional single-sided reinforcement, it achieves all-round constraint on the bottom and side soil of the rainwater main pipe, avoids the impact of high-pressure grout and soil disturbance on the pipeline body, and improves the uniformity and reliability of reinforcement. 2. By using a composite retaining structure formed by three-axis mixing piles and diaphragm walls, and inserting steel sections into the three-axis mixing piles, the overall rigidity of the retaining system is greatly improved compared to a single retaining structure, and the deformation of the retaining foundation is significantly reduced. 3. By using deep drainage wells and pressure relief wells and adjusting their operation based on the deformation data of the main rainwater pipe, the impact of soil consolidation and settlement caused by pumping on the pipeline is avoided. At the same time, water is replenished to the soil around the main pipe through the recharge well when the deformation exceeds the standard, so as to achieve a dynamic balance between rainwater and pipeline protection. 4. By adopting the sequence of excavating the area away from the main pipe first and then excavating the area closer to the main pipe, combined with the dynamic adjustment of axial force of servo steel support, the coordinated cooperation between zoned excavation and dynamic support is achieved, reducing the lateral compression of pipelines by the spatiotemporal effects of soft soil. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram showing the connection between the main rainwater pipe and the branch rainwater pipe of the present invention.

[0018] Figure 2 This is a top view of the construction of the MJS method pile of the present invention.

[0019] Figure 3 This is a top view of the construction of the two rows of triaxial mixing piles according to the present invention.

[0020] Figure 4 This is a top view of the construction of the diaphragm wall according to the present invention.

[0021] Figure 5 This is a top view of the construction of the deep well for drainage and the pressure relief well of the present invention.

[0022] Figure 6 This is a top view of the third excavation area of ​​the present invention.

[0023] Figure 7 This is a top view of the servo steel support installation in the third excavation area of ​​the present invention.

[0024] Figure 8This is a cross-sectional view of the MJS method pile of the present invention.

[0025] Figure 9 This is a cross-sectional view of the construction of the two rows of triaxial mixing piles of the present invention.

[0026] Figure 10 This is a cross-sectional view of the trenching of the diaphragm wall of the present invention.

[0027] Figure 11 This is a cross-sectional view of the construction of the diaphragm wall of the present invention.

[0028] Figure 12 This is a cross-sectional view of the reinforced concrete support structure in the third excavation area of ​​the present invention.

[0029] Figure 13 This is a cross-sectional view of the servo steel support installation in the third excavation area of ​​the present invention.

[0030] Figure 14 This is a schematic diagram of the underground structure construction plan within the third excavation area of ​​the present invention.

[0031] Figure 15 This is a schematic diagram of the dismantling of the support structure in the third excavation area of ​​the present invention.

[0032] 1. Main rainwater pipe; 2. Branch rainwater pipe; 3. Heavy-duty lane; 4. MJS method pile; 5. Triaxial mixing pile; 6. Diaphragm wall; 7. Deep drainage well; 8. Pressure relief well; 9. Third excavation area; 10. Servo steel support; 11. Steel section; 12. Triaxial mixing pile machine; 13. Large crane; 14. Reinforced concrete support; 15. Support pile. Detailed Implementation

[0033] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0034] The following description, in conjunction with the accompanying drawings and specific embodiments, provides a more detailed explanation of the micro-deformation foundation pit support construction method adjacent to ultra-large diameter rainwater pipelines of the present invention.

[0035] Please see Figures 1-15 As shown, the construction method for the retaining wall of a micro-deformation foundation pit adjacent to an ultra-large diameter rainwater pipeline includes the following steps: Step 1: Locate the position of the extra-large diameter rainwater main pipe 1 and all rainwater branch pipes 2 connected to it, and temporarily seal all rainwater branch pipes 2 within the excavation area of ​​the foundation pit; Step 2: Conduct deformation monitoring on the main rainwater pipe 1 to obtain deformation data of the main rainwater pipe 1 during the foundation pit construction process; Step 3: Construct MJS method piles 4 in the soil corresponding to the top of the rainwater main pipe 1 and in the soil on the side of the rainwater main pipe 1 that is relatively close to the excavation pit, so that the top MJS method piles 4 and the side MJS method piles 4 are connected to form a reinforcement curtain. Step 4: Construct two rows of triaxial mixing piles 5 in the soil on the side of the MJS method pile 4 that is relatively close to the excavation pit, and construct a diaphragm wall 6 between the two rows of triaxial mixing piles 5 to form a composite retaining structure. Step 5: Install drainage wells 7 and pressure relief wells 8 in the foundation pit to be excavated, and adjust the operation status of drainage wells 7 and pressure relief wells 8 according to the deformation data of the rainwater main pipe 1 in order to control the groundwater level and the pressure of the confined water. Step 6: Divide the foundation pit into multiple excavation areas, and excavate in sections and layers in the order that the excavation areas far away from the main rainwater pipe 1 are excavated before the excavation areas close to the main rainwater pipe 1. Step 7: After the last excavation area is completed, a servo steel support 10 is installed inside it so that the servo steel support 10 abuts against the composite retaining structure, and the supporting axial force of the servo steel support 10 is dynamically adjusted according to the deformation data of the rainwater main pipe 1.

[0036] By constructing two rows of the three-axis mixing piles 5 first, a stable excavation foundation is provided for the subsequent trenching of the diaphragm wall 6, thus avoiding soil disturbance during the trenching of the diaphragm wall 6.

[0037] Specifically, the MJSS method pile adopts an all-round high-pressure jetting process, simultaneously monitors the ground pressure, controls the grout flow rate, avoids the high-pressure grout disturbing the rainwater pipe body, and the pile formation sequence is carried out by skipping from one end to the other along the main rainwater pipe 1 to reduce the single disturbance of the soil. After the MJS method pile 4 is reinforced, the integrity of the pile body and the 28-day unconfined compressive strength are tested by core drilling. Only after the standards are met can subsequent construction be carried out.

[0038] By adopting the MJS method pile 4 and coordinating with ground pressure monitoring and grout discharge control, the high-pressure grout was prevented from disturbing the rainwater pipe body; the skip-driving pile method reduced the impact of single soil disturbance on the pipeline; and core drilling testing ensured that the reinforcement quality met the design requirements.

[0039] Preferably, when performing step 1 above, sealing airbags are installed upstream and downstream of each rainwater branch pipe 2 within the excavation area of ​​the foundation pit to seal it.

[0040] Specifically, after sealing the corresponding rainwater branch pipe 2 with the sealing airbag, a water tightness test is carried out. Only after confirming that there is no leakage can subsequent construction steps be carried out. During the sealing and subsequent construction process, a dedicated person is arranged to inspect the pressure condition of the sealing airbag throughout the process.

[0041] Preferably, when performing step 2, settlement monitoring points are set up around the rainwater main pipe 1, and settlement change data of the soil around the rainwater main pipe 1 are obtained through settlement monitoring equipment, and the deformation state of the rainwater main pipe 1 is determined based on the settlement change data.

[0042] Specifically, when monitoring the settlement of the main rainwater pipe 1, three warning levels are preset: when the monitoring data exceeds the first warning level, the axial force of the servo steel support 10 is adjusted to slow down the rainfall rate; when it exceeds the second warning level, earthwork excavation is suspended and grouting is added to reinforce the outside of the main rainwater pipe 1; when it exceeds the third warning level, work is stopped immediately and emergency pipeline protection measures are activated.

[0043] Through the above-mentioned three-level early warning and graded response mechanism, the deformation status of the rainwater main pipe 1 is controlled in a graded manner during the foundation pit construction process. The first-level early warning focuses on adjusting operating parameters, the second-level early warning focuses on active reinforcement, and the third-level early warning focuses on complete work stoppage and emergency rescue, thus forming a full-chain deformation control system from prevention to disposal.

[0044] Preferably, before performing step 3 above and after performing step 2 above, a heavy-duty lane 3 is constructed at the top of the excavation pit, relatively close to the rainwater main pipe 1. During the performance of steps 3 and 4 above, construction equipment is used to carry out construction on the heavy-duty lane 3. Before performing step 6 above, the heavy-duty lane 3 is dismantled.

[0045] Specifically, the thickness of the heavy-duty lane 3 is 300mm, it is made of C30 concrete, and it is reinforced with double-layer bidirectional steel bars with a diameter of 12@200mm.

[0046] like Figure 9 As shown: The three-axis mixing pile machine 12 completes the construction of the three-axis mixing pile 5 on the heavy-duty lane 3; as Figure 10 As shown: The large crane 13 completes the hoisting of the steel cage of the diaphragm wall 6 in the heavy-duty lane 3; by setting up the heavy-duty lane 3, the construction load is evenly transferred to the deep soil, and the adverse effects of local overload on the underground rainwater main 1 are avoided.

[0047] Preferably, when performing step 4 above, during the construction of the triaxial mixing pile 5, a steel section 11 is inserted into a row of the triaxial mixing piles 5 that is relatively close to the MJS method pile 4.

[0048] Specifically, the steel section 11 is inserted at intervals in a row of triaxial mixing piles 5 that are relatively close to the MJS method pile 4.

[0049] By inserting steel sections 11 into a row of triaxial mixing piles 5 near the MJS method pile 4, the row of triaxial mixing piles 5 can function as both a water-stop curtain and a load-bearing structure, thereby improving the overall bending stiffness of the composite retaining system and reducing the lateral deformation of the retaining structure during the excavation of the foundation pit.

[0050] Preferably, when performing step 5 above, the groundwater level in the foundation pit is lowered by the drainage well 7, the pressure relief well 8 is lowered by the pressure relief well, and the pumping speed and pumping volume are adjusted according to the deformation data of the rainwater main pipe 1.

[0051] By coordinating the dewatering of the deep well 7 and the pressure relief well 8, the dry excavation environment in the foundation pit is ensured, and the risk of sudden surge of pressure water at the bottom of the pit is effectively reduced. At the same time, the pumping speed and pumping volume are adjusted in real time according to the deformation data of the main rainwater pipe 1 to avoid soil consolidation and settlement caused by excessive pumping intensity, thereby reducing the adverse impact of dewatering operations on the adjacent main rainwater pipe 1.

[0052] Specifically, pre-dewatering begins 14 days before the excavation of the foundation pit. The deep drainage well 7 is used to continuously pump water to control the groundwater level in the foundation pit to be more than 1m lower than the excavation surface. The water head of the confined aquifer is monitored in real time, and the pressure relief well 8 is opened as needed to reduce the risk of sudden surge at the bottom of the pit.

[0053] Preferably, when performing step 5 above, a recharge well is also installed around the rainwater main pipe 1. When the deformation data of the rainwater main pipe 1 exceeds a preset threshold, the pumping intensity of the drainage well 7 is reduced, and the recharge well is used to replenish groundwater to the soil around the rainwater main pipe 1 in order to regulate the pore water pressure of the soil.

[0054] By setting up this recharge well, water is replenished in time when the deformation data of the main rainwater pipe 1 exceeds the threshold, thereby adjusting the pore water pressure of the soil around the main pipe and effectively slowing down or stopping the continuous settlement of the main pipe, thus forming a dynamic balance between precipitation and pipeline protection.

[0055] Preferably, when performing step 6 above, the excavation pit is divided into a first excavation area far away from the rainwater main pipe 1, a second excavation area in the middle, and a third excavation area 9 close to the rainwater main pipe 1, and excavation is carried out in the order of the first excavation area, the second excavation area, and the third excavation area 9.

[0056] By delaying the construction of the third excavation area 9, which is close to the main rainwater pipe 1, compared with the first and second excavation areas, the soil near the main pipe side remains relatively stable during the early excavation process. The unexcavated soil is used as passive counter-pressure soil to constrain the lateral sliding of the soil on the main pipe side towards the foundation pit, thereby effectively reducing the lateral compression effect of soft soil rheology on the main pipe and reducing the cumulative horizontal displacement and settlement of the main pipe.

[0057] Specifically, the excavation process strictly follows the principles of layering, segmentation, time limits, and support before excavation. The thickness of a single layer of excavation does not exceed 4m, and the length of a single segment of excavation does not exceed 30m. After each layer of soil is excavated, the servo steel support 10 is erected and pre-loaded within 8 hours. The exposure time of the unsupported soil is strictly controlled. The island excavation method is adopted during excavation. The reinforced cushion layer at the edge of the pit is constructed first. The cushion layer is poured on the same day for the section excavated on the same day to restrain the lateral deformation of the retaining structure as early as possible. For high-low span areas, the lower layer of soil is excavated only after the bottom slab of the lower structure reaches 80% of the design strength, so as to avoid the sudden increase in lateral soil pressure caused by the height difference between the high and low spans from having an adverse effect on the retaining structure and the adjacent rainwater main 1.

[0058] Preferably, when dividing the foundation pit, a row of support piles 15 is driven between the first excavation area and the second excavation area, and between the second excavation area and the third excavation area 9. When performing step 7 above, one end of the servo steel support 10 abuts against the composite retaining structure, and the other end abuts against the support pile 15 located between the second excavation area and the third excavation area 9.

[0059] Specifically, such as Figure 12 As shown: The support pile 15 is also connected to a diagonal brace on the side relatively away from the third excavation area 9, and the diagonal brace abuts against the main structure of the basement in the second excavation area.

[0060] By setting up inclined supports to support the main basement structure in the second excavation area, the lateral earth pressure in the third excavation area 9 is transferred to the completed main structure, thereby reducing the lateral deflection deformation of the support pile 15 and further controlling the squeezing effect of the lateral displacement of the soil on the adjacent rainwater main pipe 1.

[0061] Specifically, when performing step 7 above, three layers of support are set from top to bottom in the third excavation area 9. Each layer contains multiple supports. The first layer is a reinforced concrete support 14 located at the top of the foundation pit. The second and third layers are both servo steel supports 10. Each layer of support abuts against the composite retaining structure.

[0062] The first layer of reinforced concrete support 14 provides rigid constraints, and the second and third layers of servo steel support 10 dynamically adjust the axial force according to monitoring data to form a multi-layer support system that combines rigidity and flexibility. This system enables active control of the lateral deformation of the retaining structure under the excavation of the foundation pit and the rheological action of soft soil. At the same time, multiple supports are set in each layer to ensure that the retaining structure is subjected to uniform stress, thereby effectively controlling the lateral displacement of the composite retaining structure into the pit during the excavation of the third excavation area 9 and reducing the squeezing impact on the adjacent rainwater main pipe 1.

[0063] Specifically, the servo steel support 10 is equipped with a fully automatic hydraulic servo jack, a real-time axial force acquisition module, and a remote control terminal. After the servo steel support 10 is erected, the remote control terminal first controls the hydraulic servo jack to apply the initial design axial force and presets the upper and lower fluctuation thresholds of the axial force. During construction, the real-time axial force acquisition module continuously monitors the measured value of the support axial force. When the measured axial force deviates from the preset threshold due to soft soil rheology or other reasons, the remote control terminal automatically instructs the jack to pressurize or depressurize, so as to achieve basic stability of the axial force. At the same time, when the monitored deformation data of the rainwater main pipe 1 shows abnormal fluctuations, the remote control terminal actively sends an axial force adjustment command to the hydraulic servo jack according to the established deformation-axial force linkage control strategy, so that the support axial force dynamically adapts to the deformation control requirements of the rainwater main pipe 1.

[0064] By combining the self-stabilizing adjustment of the support axial force with the active control based on pipeline monitoring data, a dual-layer linkage mechanism of "local axial force stabilization" and "global deformation control" is formed. This ensures the stress stability of the support system itself and can actively adjust the support stiffness according to the actual state of the rainwater main pipe 1, thereby achieving refined control of pipeline deformation.

[0065] Specifically, after completing step 7 above, during the construction of the main structure of the basement, the force-transferring support belt is constructed simultaneously, so that the support belt and the main structure of the basement form an integral force-bearing system. After the concrete strength of the support belt reaches 80% of the design strength, the servo steel support 10 of the corresponding layer can be removed. The earth pressure borne by the composite retaining structure is transferred to the constructed main structure of the basement using the support belt. During the removal, the servo steel support 10 is removed one by one using a symmetrical segmented unloading method. During the removal process, the axial force of the support is released slowly at the same time to avoid releasing all the axial force at once, which would cause a sudden increase in deformation of the retaining structure.

[0066] The soil pressure borne by the composite retaining structure is transferred to the main structure of the basement by the replacement support belt, so as to achieve a smooth transfer of force during the support removal process; the axial force is released slowly and synchronously by adopting a symmetrical segmented unloading method to avoid the sudden deformation of the retaining structure caused by releasing all the axial force at one time, thereby eliminating the secondary disturbance of the adjacent rainwater main pipe 1 by the support removal action itself.

[0067] Specifically, after the main structure of the basement and the backfilling of the trench are completed, the sealing airbags are removed. First, the upstream and downstream water levels and the air pressure inside the airbags are confirmed to be normal. Then, the double sealing airbags in each branch pipe are depressurized in turn. After the airbags are fully contracted, they are pulled out of the branch pipes. The airbag removal follows the order of downstream first and then upstream to avoid the impact of water flow turbulence on the pipe joint due to sudden water release from one side.

[0068] By removing the sealing airbags in the order of downstream first and then upstream, the turbulent water flow inside the pipe caused by sudden water release from one side can be prevented from impacting the pipe joint interface, thus ensuring the sealing and safety of the branch pipe after it is reconnected.

[0069] It should be noted that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding and reading. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for constructing a retaining wall for a micro-deformation foundation pit adjacent to an ultra-large diameter rainwater pipeline, characterized in that, Including the following steps: Step 1: Locate the location of the extra-large diameter rainwater main pipe and all rainwater branch pipes connected to it, and temporarily seal all rainwater branch pipes within the excavation area of ​​the foundation pit; Step 2: Perform deformation monitoring on the main rainwater pipe to obtain deformation data of the main rainwater pipe during the foundation pit construction process; Step 3: Construct MJS method piles in the soil corresponding to the top of the rainwater main pipe and in the soil on the side of the rainwater main pipe that is relatively close to the excavation pit, so that the top MJS method piles and the side MJS method piles are connected to form a reinforcement curtain. Step 4: Construct two rows of triaxial mixing piles in the soil on the side of the MJS method piles that is relatively close to the excavation pit, and construct a diaphragm wall between the two rows of triaxial mixing piles to form a composite retaining structure. Step 5: Install drainage wells and pressure relief wells in the excavation pit, and adjust the operation of the drainage wells and pressure relief wells according to the deformation data of the main rainwater pipe to control the groundwater level and the pressure of the confined water. Step 6: Divide the foundation pit into multiple excavation areas, and excavate in sections and layers in the order that the excavation areas farthest from the main rainwater pipe are excavated before the excavation areas closest to the main rainwater pipe. Step 7: After the last excavation area is completed, a servo steel support is installed inside it, so that the servo steel support abuts against the composite retaining structure, and the supporting axial force of the servo steel support is dynamically adjusted according to the deformation data of the rainwater main pipe.

2. The method for constructing a micro-deformation foundation pit retaining structure adjacent to an ultra-large diameter rainwater pipeline as described in claim 1, characterized in that, When performing step 1 above, sealing airbags are installed upstream and downstream of each of the rainwater branch pipes within the excavation area of ​​the foundation pit to seal them.

3. The method for constructing a micro-deformation foundation pit retaining wall adjacent to an ultra-large diameter rainwater pipeline as described in claim 1, characterized in that, When performing step 2, settlement monitoring points are set up around the rainwater main pipe, and settlement change data of the soil around the rainwater main pipe is obtained through settlement monitoring equipment. The deformation state of the rainwater main pipe is determined based on the settlement change data.

4. The method for constructing a micro-deformation foundation pit retaining wall adjacent to an ultra-large diameter rainwater pipeline as described in claim 1, characterized in that, Before performing step 3 above and after performing step 2 above, construct a heavy-duty lane at the top of the excavation pit, relatively close to the main rainwater pipe. During the performance of steps 3 and 4 above, use construction equipment to carry out construction on the heavy-duty lane. Before performing step 6 above, dismantle the heavy-duty lane.

5. The method for constructing a micro-deformation foundation pit retaining wall adjacent to an ultra-large diameter rainwater pipeline as described in claim 1, characterized in that, When performing step 4 above, during the construction of the triaxial mixing piles, steel sections are inserted into a row of the triaxial mixing piles that are relatively close to the MJS method piles.

6. The method for constructing a micro-deformation foundation pit retaining wall adjacent to an ultra-large diameter rainwater pipeline as described in claim 1, characterized in that, When performing step 5 above, the groundwater level in the foundation pit is lowered by the drainage well, the pressure of the pressurized water is reduced by the pressure relief well, and the pumping speed and pumping volume are adjusted according to the deformation data of the rainwater main pipe.

7. The method for constructing a micro-deformation foundation pit retaining wall adjacent to an ultra-large diameter rainwater pipeline as described in claim 6, characterized in that, When performing step 5 above, recharge wells are also installed around the main rainwater pipe. When the deformation data of the main rainwater pipe exceeds a preset threshold, the pumping intensity of the deep drainage well is reduced, and the recharge wells are used to replenish groundwater to the soil around the main rainwater pipe in order to regulate the pore water pressure of the soil.

8. The method for constructing a micro-deformation foundation pit retaining wall adjacent to an ultra-large diameter rainwater pipeline as described in claim 1, characterized in that, When performing step 6 above, the foundation pit is divided into a first excavation area far away from the main rainwater pipe, a second excavation area in the middle, and a third excavation area close to the main rainwater pipe, and excavation is carried out in the order of the first excavation area, the second excavation area, and the third excavation area.

9. The method for constructing a micro-deformation foundation pit retaining wall adjacent to an ultra-large diameter rainwater pipeline as described in claim 8, characterized in that, When dividing the foundation pit, a row of support piles is driven between the first excavation area and the second excavation area, and between the second excavation area and the third excavation area. When performing step 7 above, one end of the servo steel support abuts against the composite retaining structure, and the other end abuts against the support pile located between the second excavation area and the third excavation area.

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