A foundation pit safety construction control method

Abstract

The present invention discloses a method for controlling safe construction of a foundation pit, one side of which is adjacent to an existing railway line. The method comprises: monitoring the settlement and displacement of the foundation pit's retaining structure and the existing railway line, and issuing graded early warnings based on the settlement and displacement deformation values and deformation rates at each monitoring point; monitoring the axial force and temperature of each horizontally arranged steel support within the foundation pit, and heating or cooling each steel support based on its axial force or temperature changes. The method can promptly detect deformation trends of the foundation pit, the existing railway, and the surrounding environment during construction, allowing for early detection of potential safety hazards during construction, thereby ensuring the safety of foundation pit construction and the stability of the structure.

Description

Technical Field

[0001] The present invention relates to the field of foundation pit construction, and more particularly to a foundation pit safety construction control method. Background Art

[0002] For foundation pit construction close to existing railway lines, if the bored piles used for foundation pit support are collapsed or shrunken, or if the pressure is too high during the construction of high-pressure rotary jet piles, the stability of the existing railway subgrade will be affected. At the same time, during foundation pit construction, the stability of the foundation pit itself also affects the construction progress and construction safety. Therefore, foundation pit construction generally follows the principle of "vertical layering, support first and then excavation, symmetrical excavation, and no over-excavation". During the foundation pit excavation process, the horizontal and vertical steel support construction in the foundation pit is promptly followed up. However, the steel support is affected by temperature, and the support end is easily moved and detached due to pressure reduction, affecting the support effectiveness. In response to the above problems, the existing technology generally only monitors the deformation of the foundation pit during construction, without considering the impact on the existing railway line. As for the steel supports in the foundation pit, they are usually cooled manually by spraying water or wedging with iron wedges, relying on manual experience, and have low efficiency and reliability. Summary of the Invention

[0003] An object of the present invention is to solve at least the above problems and to provide at least the advantages which will be described hereinafter.

[0004] To achieve these objectives and other advantages according to the present invention, a method for controlling safe construction of a foundation pit is provided, wherein one side of the foundation pit is close to an existing railway line, comprising:

[0005] Conduct settlement and displacement monitoring of the retaining structures of the foundation pit and the existing railway line, and issue graded early warnings based on the settlement and displacement deformation values and deformation rates of each monitoring point;

[0006] The axial force and temperature of each steel support set horizontally in the foundation pit are monitored, and each steel support is heated or cooled according to the axial force or temperature changes of each steel support.

[0007] Preferably, the retaining structure of the foundation pit includes a plurality of protective piles arranged at intervals along the outer periphery of the foundation pit and a double row of high-pressure rotary jet pile water-stop curtains arranged on the outside of the protective piles; the settlement and displacement monitoring points of the retaining structure of the foundation pit include protective piles arranged at the positive corners and a plurality of observation bolts on the top of the protective piles in the middle.

[0008] Preferably, the settlement monitoring and displacement monitoring of the existing railway line includes settlement and displacement monitoring of the track, settlement and displacement monitoring of the roadbed, and settlement and inclination monitoring of the contact network columns.

[0009] Preferably, the settlement and displacement monitoring points of the roadbed include settlement monitoring piles arranged on both sides of the roadbed, a plurality of settlement meters arranged at intervals in the vertical direction within the roadbed body, a plurality of settlement meters arranged at intervals in the vertical direction within the roadbed base, a plurality of observation side piles arranged on the outside of the roadbed slope, and an inclinometer arranged within the roadbed slope.

[0010] Preferably, early warning is carried out in three levels according to the change value and change rate of the settlement and displacement of each monitoring point;

[0011] Level 1 warning: When ΔU i <0.6U i0 or v i When the value is ≤4mm / d, the existing railway line or foundation pit is in normal condition and continuous monitoring is required;

[0012] Level 2 warning: When 0.6U i0 ≤ΔUi≤0.8U i0 or 4mm / d<v i When the value is ≤6mm / d, the existing railway line or foundation pit is in a low-risk state. The monitoring frequency of each monitoring point should be increased, and the foundation pit excavation process should be adjusted for the monitoring points that are in a risky state.

[0013] Level 3 warning: When ΔU i >0.8U i0 or v i When the value is greater than 6mm / d, the existing railway line or foundation pit is in a high-risk state, and the foundation pit construction is suspended. The construction plan, excavation progress, and support parameters are adjusted to ensure that the settlement or displacement deformation value of each monitoring point reaches the first-level warning state before continuing the foundation pit construction.

[0014] Among them, U i0 is the monitoring point U i The control reference value of settlement or displacement, ΔU i is the monitoring point U i The cumulative deformation value of the current frequency of the settlement or displacement on the day, v i is the monitoring point U i The daily rate of change of settlement or displacement.

[0015] Preferably, each steel support is heated or cooled by a steel support auxiliary control system, and each of the steel supports is formed by splicing a plurality of sections of steel pipes;

[0016] The steel support auxiliary control system includes a control element, an integrated water tank, a piping system and a flow regulation system. A temperature control component is provided in the integrated water tank to adjust the water temperature at the water outlet of the integrated water tank; the piping system includes a plurality of temperature control branches, and the plurality of temperature control branches are arranged in a one-to-one correspondence with the steel supports. The temperature control branches include a plurality of temperature control units connected in series, which correspond one-to-one to the steel pipes of each section and are sleeved on the corresponding steel pipes; the two ends of any temperature control branch are respectively connected to the water outlet and the water inlet of the integrated water tank; the flow regulation system includes a plurality of flow regulating valves, which correspond one-to-one to the plurality of temperature control branches, and any flow regulating valve is connected in series to the corresponding temperature control branch near the water outlet of the integrated water tank;

[0017] The temperature control component and each of the flow regulating valves are respectively connected to the control unit.

[0018] Preferably, the two ends of the steel support are respectively fixedly connected to the side walls of the foundation pit, and an axial force meter is provided between the two ends of the steel support and the side walls of the foundation pit. A plurality of temperature sensors are arranged inside the steel support at intervals along its length direction, and each of the axial force meter and each of the temperature sensors is respectively connected to a data acquisition device, and each of the data acquisition devices is respectively connected to the control element.

[0019] Preferably, the temperature control unit includes a flat tube spirally wound on a steel tube, an insulation layer wrapped around the outer periphery of the flat tube, and an outer shell tightly sleeved on the outer side of the insulation layer; the flat tubes of two adjacent temperature control units are connected by a pipeline.

[0020] Preferably, the inner side of the flat tube is coated with a heat conducting layer.

[0021] The present invention has at least the following beneficial effects:

[0022] 1. The foundation pit safety construction control method provided by the present invention monitors the deformation of the foundation pit and the existing railway line. By simultaneously monitoring the settlement and displacement of the retaining structure of the foundation pit and the existing railway line, the deformation development trend of the foundation pit, the existing railway and the surrounding environment during the construction process can be discovered in a timely manner, and safety hazards in the construction can be discovered early, thereby ensuring the safety of the foundation pit construction and the stability of the structure, and achieving the purpose of effectively controlling the impact of the foundation pit construction on the existing railway and the surrounding environment.

[0023] 2. The foundation pit safety construction control method provided by the present invention takes into account the settlement, displacement, deformation value, and deformation rate of the foundation pit retaining structure and the existing railway line, establishes a three-level early warning mechanism, and takes corresponding measures in a timely manner when abnormal deformation is found in the foundation pit retaining structure or the existing railway line.

[0024] 3. The foundation pit safety construction control method provided by the present invention heats or cools each steel support through the steel support auxiliary control system, thereby achieving timely and accurate adjustment and maintenance of each steel support, ensuring that each steel support can be maintained in the axial force state of the set temperature state.

[0025] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic plan view of the arrangement of settlement and displacement monitoring points for the retaining structure of the foundation pit in the present invention;

[0027] Figure 2 A schematic diagram of the layout of settlement and displacement monitoring points for the roadbed of an existing railway line according to the present invention;

[0028] Figure 3 Schematic diagram of the structure of the pipeline system of the present invention;

[0029] Figure 4 Schematic diagram of the cross-sectional structure of the temperature control unit of the present invention; DETAILED DESCRIPTION

[0030] The present invention will be described in further detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0031] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials are commercially available unless otherwise specified; in the description of the present invention, the terms "horizontal", "longitudinal", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0032] like Figures 1 to 4 As shown, the present invention provides a method for controlling safe construction of a foundation pit, wherein one side of the foundation pit is close to an existing railway line, comprising:

[0033] Conduct settlement and displacement monitoring of the retaining structures of the foundation pit and the existing railway line, and issue graded early warnings based on the settlement and displacement deformation values and deformation rates of each monitoring point;

[0034] The axial force and temperature of each steel support 104 arranged horizontally in the foundation pit are monitored, and each steel support 104 is heated or cooled according to the axial force or temperature change of each steel support 104 .

[0035] In this technical solution, the deformation of the foundation pit and the existing railway line are monitored. By simultaneously monitoring the settlement and displacement of the retaining structure of the foundation pit and the existing railway line, the deformation development trend of the foundation pit, the existing railway and the surrounding environment during the construction process can be discovered in time, and the safety hazards in the construction can be discovered early to ensure the safety of the foundation pit construction and the stability of the structure, so as to achieve the purpose of effectively controlling the impact of the foundation pit construction on the existing railway and the surrounding environment.

[0036] The retaining structure of the foundation pit includes a plurality of protective piles 102 arranged at intervals along the periphery of the foundation pit and a double row of high-pressure jet grouting pile water-stop curtains 101 arranged outside the protective piles; Figure 1 As shown, the settlement and displacement monitoring points for the foundation pit's retaining structure include guard piles 102 at the outer corners and multiple observation bolts 105 atop the central guard piles 102. Furthermore, the distance between two adjacent observation bolts 105 is no more than 20 meters. These observation bolts 105 are drilled using an impact drill to a certain depth in the surface of the guard piles 102. Measuring pins are embedded, protruding a certain distance from the surface of the columns, and marked as monitoring points.

[0037] Settlement and displacement monitoring of existing railway lines includes monitoring of track settlement and displacement, roadbed settlement and displacement, and catenary column settlement and inclination. Track and catenary column monitoring is performed manually using relevant instruments during non-traffic periods.

[0038] The settlement and displacement monitoring points for the roadbed of an existing railway line include settlement monitoring piles 202 installed on both sides of the roadbed, multiple settlement meters 203 spaced vertically within the roadbed, multiple settlement meters 205 spaced vertically within the roadbed base, multiple observation side piles 201 installed outside the roadbed slope, and inclinometers 204 installed within the roadbed slope. The settlement meters within the roadbed and the roadbed base can be installed by drilling holes in the roadbed, placing PVC protective pipes, and then placing each settlement meter within the PVC protective pipes.

[0039] The retaining structures of foundation pits and the settlement of existing railway lines are monitored by leveling. The leveling is carried out using a high-precision automatic leveling electronic level in conjunction with a special indium tile ruler. During monitoring, construction control points are selected as leveling base points to establish a benchmark network. There should be no less than three leveling base points in each survey area. After the benchmark network is built, re-measurements should be carried out every 1 to 2 months after the first survey, and re-measurements should be carried out every 3 to 6 months after stabilization. When the absolute value of the daily settlement of each monitoring point is greater than or equal to 1 mm, it is considered that the monitoring point has deformed or has a deformation trend; when the absolute value of the cumulative settlement is greater than or equal to 2 mm, it is considered that the settlement monitoring point has undergone settlement deformation. The observation values and settlement deformation values of each monitoring point are recorded in real time, and the time settlement deformation curve is drawn for deformation analysis.

[0040] The displacement of the retaining structures of the foundation pit and the existing railway line is monitored using the line of sight method, with a Class 2 total station as the instrument. Benchmarks are set in a stable area beyond three times the excavation depth, unaffected by construction. Working base points are also set up at relatively stable locations around the foundation pit. Instruments are then set up directly on these working base points to monitor each monitoring point.

[0041] Then, according to the change value and change rate of settlement and displacement of each monitoring point, early warning is carried out in three levels;

[0042] Level 1 warning: When ΔU i <0.6U i0 or v i When the value is ≤4mm / d, the existing railway line or foundation pit is in normal condition and continuous monitoring is required;

[0043] Level 2 warning: When 0.6U i0 ≤ΔU i ≤0.8U i0 or 4mm / d<v i When the value is ≤6mm / d, the existing railway line or foundation pit is in a low-risk state. The monitoring frequency of each monitoring point should be increased, and the foundation pit excavation process should be adjusted for the monitoring points that are in a risky state.

[0044] Level 3 warning: When ΔU i >0.8U i0 or v i When the value is greater than 6mm / d, the existing railway line or foundation pit is in a high-risk state, and the foundation pit construction is suspended. The construction plan, excavation progress, and support parameters are adjusted to ensure that the settlement or displacement deformation value of each monitoring point reaches the first-level warning state before continuing the foundation pit construction.

[0045] Among them, U i0 is the monitoring point U i The control reference value of settlement or displacement, that is, the maximum allowable deformation value of settlement or displacement, ΔU iis the monitoring point U i The cumulative deformation value of the current frequency of the settlement or displacement on the day, v i is the monitoring point U i The daily rate of change of settlement or displacement.

[0046] When the monitoring point U i ΔU i or v i If any of the items reaches the second-level warning or third-level warning status, corresponding measures must be taken regardless of whether the monitoring point is located in the retaining structure of the foundation pit or the existing railway line.

[0047] During the foundation pit construction process, steel support construction needs to be carried out promptly after each layer of excavation is completed. Considering the adverse effects of ambient temperature stress on the steel support structure, a steel support auxiliary control system is used to heat or cool each steel support to ensure that each steel support can be maintained at the set temperature state, thereby keeping the axial force of the steel support at the set state. Each steel support is composed of multiple sections of steel pipes spliced together according to the required length;

[0048] The steel support auxiliary control system includes a control element, an integrated water tank, a piping system and a flow regulation system. A temperature control component is provided in the integrated water tank to adjust the water temperature of the integrated water tank outlet 301; Figure 3 The piping system includes a plurality of temperature control branches, which are arranged in a one-to-one correspondence with the steel supports. The temperature control branches include a plurality of temperature control units 303 connected in series, which correspond to the steel pipes of each section respectively and are sleeved on the corresponding steel pipes; the two ends of any temperature control branch are respectively connected to the water inlet 304 and the water outlet 303 of the integrated water tank; the flow regulation system includes a plurality of flow regulating valves 302, which correspond to the plurality of temperature control branches respectively, and any flow regulating valve 302 is connected in series to the corresponding temperature control branch near the water outlet 301 of the integrated water tank;

[0049] The temperature control assembly and each of the flow regulating valves 302 are connected to the control unit respectively.

[0050] The two ends of the steel support are fixedly connected to the side walls of the foundation pit, and an axial force meter is arranged between the two ends of the steel support and the side walls of the foundation pit. The interior of the steel support is provided with a plurality of temperature sensors spaced along its length direction. Each of the axial force meters and each of the temperature sensors is connected to a data acquisition device, and each of the data acquisition devices is connected to the control element.

[0051] In the above technical solution, the axial force meter is used to monitor the axial force of the corresponding steel support, and the temperature sensor can be fixed on the inner wall of the steel support to monitor the temperature of the steel support. Each of the data acquisition devices is used to collect the data monitored by each of the axial force meters and each of the temperature sensors, and transmit it to the control element. When it is detected that the axial force of a certain steel support decreases or the temperature value exceeds the set value, the control element adjusts the outlet water temperature of the integrated water tank accordingly by adjusting the temperature control component, and adjusts the corresponding flow regulating valve, so that each temperature control unit 303 on the corresponding temperature control branch heats or cools the steel support. The set value of the temperature value is the temperature change range value when the material used for the steel support is deformed, that is, the corresponding steel support will be deformed when this temperature range is exceeded, thereby affecting its support effectiveness. The control element can adopt a controller conventionally used in this field, such as a PLC controller with corresponding computing power.

[0052] Furthermore, considering that the ambient temperature of the steel supports at different foundation pit depths may not be the same during installation, the water temperature requirements for adjusting their temperatures may also not be the same. The outlet water temperature of the integrated water tank is the average of the required water temperatures for each steel support. Therefore, a flow control valve is installed on each temperature-controlled branch. When the outlet water temperature of the integrated water tank differs significantly from the required water temperature for the corresponding steel support in the temperature-controlled branch, the water flow rate of the temperature-controlled branch is increased to accommodate the temperature control requirements under different operating conditions and achieve precise adjustment of each steel support. The water flow rate corresponding to the difference between the outlet water temperature of the integrated water tank and the required water temperature for the corresponding steel support in the temperature-controlled branch is determined through testing. The required water temperature for each steel support is the temperature change of the steel support after accounting for the attenuation of the water flow. The integrated water tank can use filtered water pumped from the foundation pit. Water flowing out of each temperature-controlled branch is returned to the integrated water tank through the water inlet 304 for reuse.

[0053] Specifically, if Figure 4 As shown, the temperature control unit 303 includes a flat tube 307 spirally wound on a steel tube 305, an insulation layer 308 wrapped around the outer periphery of the flat tube 307, and a shell 309 tightly sleeved on the outer side of the insulation layer 308; the flat tubes 307 of two adjacent temperature control units are connected by a pipeline.

[0054] The inner side of the flat tube 307 is coated with a heat conducting layer 306 .

[0055] Each flat tube 307 is spirally wound around the corresponding steel tube 305. The flat tube 307 is used to increase its contact area with the steel tube 305. The heat-conducting layer 306 can further improve the heat conduction efficiency of the flat tube, transferring the water temperature to the steel tube 305. The heat-conducting layer 306 can be coated with a conventional heat-conducting material on the inner side of the flat tube 307, that is, the side in contact with the steel tube 305. Furthermore, to reduce the exchange of water temperature between the flat tube 307 and the ambient temperature, the outer side of the flat tube 307 is coated with a heat-insulating material, such as glass fiber wool felt, to form the heat-insulating layer 308. The outer shell 309 is then installed on the outer side of the heat-insulating layer 308. The outer shell 309 can be composed of multiple hinged pieces of the same length as the steel tube 305 to accommodate different diameters and facilitate installation and removal.

[0056] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for controlling safe construction of a foundation pit, wherein one side of the foundation pit is close to an existing railway line, characterized in that: include: Conduct settlement and displacement monitoring of the retaining structures of the foundation pit and the existing railway line, and issue graded early warnings based on the settlement and displacement deformation values and deformation rates of each monitoring point; Monitor the axial force and temperature of each steel support installed horizontally in the foundation pit, and heat or cool each steel support according to the axial force or temperature changes of each steel support; The settlement and displacement monitoring of existing railway lines includes the settlement and displacement monitoring of tracks, roadbed, and contact network column settlement and inclination monitoring; according to the change value and change rate of settlement and displacement at each monitoring point, early warning is issued in three levels; Level 1 warning: or v i When the value is ≤4mm / d, the existing railway line or foundation pit is in normal condition and continuous monitoring is required; Level 2 warning: or 4mm / d<v i When the value is ≤6mm / d, the existing railway line or foundation pit is in a low-risk state. The monitoring frequency of each monitoring point should be increased, and the foundation pit excavation process should be adjusted for the monitoring points that are in a risky state. Level 3 warning: or v i When the value is greater than 6mm / d, the existing railway line or foundation pit is in a high-risk state, and the foundation pit construction is suspended. The construction plan, excavation progress, and support parameters are adjusted to ensure that the settlement or displacement deformation value of each monitoring point reaches the first-level warning state before continuing the foundation pit construction. Among them, U i0 is the monitoring point U i The control reference value of settlement or displacement, is the monitoring point U i The cumulative deformation value of the current frequency of the settlement or displacement on the day, v i is the monitoring point U i The daily rate of change of settlement or displacement; Each steel support is heated or cooled by a steel support auxiliary control system, and each of the steel supports is composed of multiple sections of steel pipes; the steel support auxiliary control system includes a control element, an integrated water tank, a piping system and a flow regulation system, and a temperature control component is provided in the integrated water tank to adjust the water temperature at the water outlet of the integrated water tank; the piping system includes multiple temperature control branches, and the multiple temperature control branches are arranged one-to-one with the steel supports, and the temperature control branches include multiple temperature control units connected in series, which correspond one-to-one to the steel pipes of each section and are sleeved on the corresponding steel pipes; the two ends of any temperature control branch are respectively connected to the water outlet and the water inlet of the integrated water tank; the flow regulation system includes multiple flow regulating valves, which correspond one-to-one to the multiple temperature control branches, and any flow regulating valve is connected in series with the corresponding temperature control branch near the water outlet of the integrated water tank; the temperature control component and each flow regulating valve are respectively connected to the control unit.

2. The foundation pit safety construction control method according to claim 1, characterized in that: The retaining structure of the foundation pit includes multiple protective piles arranged at intervals along the outer perimeter of the foundation pit and a double row of high-pressure rotary jet pile water-stop curtains arranged on the outside of the protective piles; the settlement and displacement monitoring points of the retaining structure of the foundation pit include protective piles arranged at the positive corners and multiple observation bolts on the top of the protective piles in the middle.

3. The foundation pit safety construction control method according to claim 1, characterized in that: The settlement and displacement monitoring points of the roadbed include settlement monitoring piles set on both sides of the roadbed, multiple settlement meters set at intervals in the vertical direction within the roadbed body, multiple settlement meters set at intervals in the vertical direction within the roadbed base, multiple observation side piles set on the outside of the roadbed slope, and inclinometers set within the roadbed slope.

4. The foundation pit safety construction control method according to claim 1, characterized in that: The two ends of the steel support are fixedly connected to the side walls of the foundation pit, and an axial force meter is arranged between the two ends of the steel support and the side walls of the foundation pit. The interior of the steel support is provided with a plurality of temperature sensors spaced along its length direction. Each of the axial force meters and each of the temperature sensors is connected to a data acquisition device, and each of the data acquisition devices is connected to the control element.

5. The foundation pit safety construction control method according to claim 1, characterized in that: The temperature control unit includes a flat tube spirally wound on a steel tube, a heat insulation layer wrapped around the outer periphery of the flat tube, and a shell tightly sleeved on the outer side of the heat insulation layer; the flat tubes of two adjacent temperature control units are connected by a pipeline.

6. The foundation pit safety construction control method according to claim 5, characterized in that: The inner side of the flat tube is coated with a heat conducting layer.

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