A receiving construction method for rectangular jacking pipes during the station main enclosure stage

Abstract

The present invention relates to the technical field of pipe jacking construction, and in particular to a method for receiving and constructing rectangular pipe jacking during the station main body enclosure stage. The present invention advances the pipe jacking construction stage to the station main body enclosure stage, and there is no need to wait for the lengthy station main body construction to be completed, thereby significantly shortening the overall construction period of the subway station. By receiving the rectangular pipe jacking machine on a pipe jacking receiving platform reserved when excavating a foundation pit, the investment in human and material resources for additionally building a pipe jacking receiving platform is eliminated, thereby avoiding waste. The uneven stress of the enclosing underground continuous wall during the pipe jacking construction process is balanced by the supporting axial force of the first additional supporting unit, and the temporary ring frame beam has good anti-torsion and mechanical transmission properties, thereby enhancing the stability of the support system.

Description

Technical Field

[0001] The invention relates to the technical field of jacking pipe construction, in particular to a receiving construction method of a rectangular jacking pipe in a station main body enclosure stage. Background Art

[0002] A rectangular pipe jacking machine is a large machine used for excavation in soil. Compared with open-cut tunneling, the advantages of pipe jacking tunneling are that pipe jacking causes less disturbance to the surrounding soil and the construction speed is faster. Therefore, pipe jacking machines are widely used in underground projects. When building subway stations, the structure of the subway station is generally excavated using the open-cut method. Open-cut excavation requires the isolation of the site within the construction area. However, when there is a high level of human activity around the subway station and there are many buildings, there may be situations where the foundation pit of the auxiliary structure cannot be constructed using the open-cut method. In this case, the use of a rectangular pipe jacking machine to excavate the auxiliary structure passage is very appropriate.

[0003] However, in the prior art, there are generally two construction methods for excavating auxiliary structure channels using rectangular pipe jacking machines: the first construction method is to wait until the main station construction is completed before carrying out pipe jacking construction, which will have the following technical problems: first, the main station construction period is long, and waiting for the rectangular pipe jacking machine will seriously slow down the construction progress and extend the construction period; second, an additional pipe jacking receiving platform needs to be built inside the station body to receive the rectangular pipe jacking machine, which wastes manpower and material resources. Another construction method is to carry out pipe jacking construction during the station body enclosure stage, but at this time the force on the underground continuous wall is very complex, and the support system changes very frequently. During the pipe jacking construction process, the uneven ground formation can easily cause the support system to become unstable and twist, leading to safety issues such as water leakage, cracking, and foundation pit instability.

[0004] In view of this, it is necessary to propose a receiving construction method for rectangular jacking pipes during the station main enclosure stage to solve or at least alleviate the above-mentioned defects. Summary of the Invention

[0005] The main purpose of the present invention is to provide a receiving construction method for rectangular jacking pipes during the station main enclosure stage, so as to solve the technical problems in the prior art of long jacking pipe construction period, waste of manpower and material resources, and easy instability of the support system.

[0006] To achieve the above-mentioned object, the present invention provides a receiving construction method for rectangular jacking pipes during the main enclosure stage of a station, comprising the following steps:

[0007] S1. After the construction of the underground continuous wall of the station body is completed, a foundation pit is excavated downward along the inner wall of the underground continuous wall, and a jacking pipe receiving platform is reserved in the foundation pit; wherein, the station body includes a top plate, a middle plate and a bottom plate, and the top of the jacking pipe receiving platform matches the design elevation of the middle plate of the station body.

[0008] S2, constructing a first horizontal support assembly and a second horizontal support assembly in the foundation pit; wherein, the first horizontal support assembly is arranged at the design elevation position of the top plate, and the second horizontal support assembly is arranged between the design elevation position of the top plate and the jacking pipe receiving platform, and the two ends of the first horizontal support assembly are respectively connected to the retaining underground continuous wall, and the two ends of the second horizontal support assembly are respectively connected to the retaining underground continuous wall.

[0009] S3, relying on the jacking pipe receiving platform, a temporary ring frame beam corresponding to the outlet of the jacking machine hole is constructed on the retaining underground continuous wall, and a third support assembly is erected on the inner end face of the temporary ring frame beam; wherein, the bottom beam of the temporary ring frame beam is flush with the height of the jacking pipe receiving platform, and the third support assembly includes a plurality of first additional support units arranged at intervals along the circumferential direction of the temporary ring frame beam, one end of each first additional support unit is connected to the inner end face of the temporary ring frame beam, and the other end is connected to the retaining underground continuous wall, and the support axial force of the first additional support unit can be adjusted.

[0010] S4, adjusting the supporting axial force of each first additional supporting unit to the design value, removing the second horizontal supporting assembly within the range of the temporary ring frame beam, reinforcing the surrounding soil of the outlet of the pipe jacking machine hole, breaking the retaining underground continuous wall on the inner side of the temporary ring frame beam to open an opening corresponding to the outlet of the pipe jacking machine hole on the retaining underground continuous wall.

[0011] S5, jacking the rectangular pipe jacking machine until the hole of the pipe jacking machine is connected to the opening, then relying on the pipe jacking receiving platform to receive the rectangular pipe jacking machine, and then disassembling and lifting the rectangular pipe jacking machine to complete the rectangular pipe jacking receiving construction.

[0012] Furthermore, in step S3, constructing a temporary ring frame beam on the retaining underground continuous wall by relying on the jacking pipe receiving platform specifically includes the following steps:

[0013] S31, roughening the enclosing underground continuous wall and implanting steel bars within the corresponding range of the enclosing underground continuous wall and the temporary ring frame beam;

[0014] S32, tying up the steel bars of the temporary ring frame beam and connecting them with the steel bars in the enclosing underground continuous wall, and then pre-embedding the connecting steel plate for connecting with the third support assembly, and casting to form the temporary ring frame beam.

[0015] Furthermore, the step S5 further includes the following steps:

[0016] S6, continue to erect multiple second additional support units in the bottom beam area of the temporary ring frame beam; wherein one end of each second additional support unit is connected to the inner end surface of the bottom beam, and the other end is connected to the enclosing underground continuous wall, and the support axial force of the second additional support unit is adjustable; wherein the temporary ring frame beam includes a bottom beam, an upper beam and two side beams;

[0017] S7, excavating the jacking pipe receiving platform, continuing to excavate the foundation pit to the design elevation of the fourth horizontal support assembly, installing the fourth horizontal support assembly, and then continuing to excavate the foundation pit to the position of the base plate. The base plate, base plate cushion layer, and underground second floor side wall waterproofing structure are then sequentially installed, and the base plate and side wall concrete are poured; wherein the fourth horizontal support assembly is arranged between the middle plate and the base plate of the station body;

[0018] S8, detect the concrete strength of the bottom plate, and after determining that the concrete strength of the bottom plate reaches the design strength, sequentially construct the underground second-floor side wall, middle plate, underground first-floor side wall and top plate, and simultaneously remove the fourth horizontal support assembly, the second horizontal support assembly, the temporary ring frame beam and the third support assembly. After the concrete strength of the top plate reaches the design strength, backfill the soil and restore the municipal pipelines and roads.

[0019] Further preferably, the step S4 specifically includes the following steps:

[0020] S41, using a simplified model to calculate the support axial force of the first additional support unit and the internal force of the temporary ring frame beam, and based on the calculated values, erecting a plurality of the first additional support units at corresponding positions of the upper beam and the two side beams of the temporary ring frame beam, and adjusting the support axial force on the first additional support units to the design value;

[0021] S42, removing the corresponding second horizontal support assembly within the range of the temporary ring frame beam;

[0022] S43, reinforcing the surrounding soil of the outlet of the pipe jacking machine hole, breaking the retaining underground continuous wall on the inner side of the temporary ring frame beam to open an opening in the retaining underground continuous wall corresponding to the outlet of the pipe jacking machine hole.

[0023] Further preferably, the step S41 specifically includes the following steps:

[0024] S411, selecting the retaining underground continuous wall corresponding to the rectangular jacking pipe as the object, simplifying the surrounding areas of the retaining underground continuous wall into a first hinged support, simplifying the connection between the retaining underground continuous wall and the first horizontal support assembly into a second hinged support, simplifying the first additional support unit, the second horizontal support assembly, the jacking pipe receiving platform, and the soil outside the retaining underground continuous wall into elastic fulcrums, and applying the static water and soil pressure and the rectangular jacking pipe pressure to the retaining underground continuous wall;

[0025] S412: Calculate the support axial force on the first additional support unit and the internal force on the temporary ring frame beam using the finite element method;

[0026] S413: Adjust the number and position of the first additional support units and the size of the temporary ring frame beam according to the calculated support axial force and the internal force on the temporary ring frame beam.

[0027] Further preferably, the step S412 of calculating the support axial force on the first additional support unit specifically includes the following steps:

[0028] Using formula F h =EIδ calculates the support axial force on the first additional support unit, where E is the elastic modulus of the material, I is the section moment of inertia, and δ is the displacement of the first additional support unit simplified to the elastic fulcrum obtained in the software using the finite element method in step S412.

[0029] Further preferably, after step S412, a safety check is performed on the first additional support unit, specifically comprising the following steps:

[0030] S4121, check the diameter-to-thickness ratio; the calculation formula is: D / t≤100(235 / f y ), where D is the outer diameter of the first additional support unit, t is the thickness of the first additional support unit wall, and f y is the yield strength of steel;

[0031] Verify stiffness; the verification formula is: λ x <λ, where λ x is the slenderness ratio of the first additional support unit, λ is the allowable slenderness ratio of the first additional support unit;

[0032] Verify strength; the verification formula is: F h / A+M / rW<f, where F h is the axial force of the first additional support unit, in N, A is the cross-sectional area of the first additional support unit, M is the design value of the bending moment after taking into account the eccentricity, r is the plastic development coefficient of the component, W is the cross-sectional resistance moment of the component, and f is the design value of the compressive strength of the steel;

[0033] Verify stability; the verification formula is: F h / ψ x A+β m M / rW(1-0.8F h / N Ex )≤φ f , where F h is the axial force of the first additional support unit, in N, βm is the equivalent bending moment coefficient, ψ x is the stability coefficient, A is the cross-sectional area of the first additional support unit, M is the design value of the bending moment after taking into account the eccentricity, r is the plastic development coefficient of the component, W is the component section resistance moment, N Ex is the Euler critical force, φ f is the local stability coefficient;

[0034] S4122, determining whether the diameter-to-thickness ratio, stiffness, strength, and stability of the first additional support unit all meet verification conditions;

[0035] S4123: When the diameter-to-thickness ratio, stiffness, strength, and stability of the first additional support unit all meet verification conditions, determine that the first additional support unit meets safety standards;

[0036] S4124: When any one of the diameter-to-thickness ratio, stiffness, strength and stability of the first additional support unit does not meet the verification conditions, it is determined that the first additional support unit does not meet the safety standards, and more first additional support units are preset for verification, and the process returns to step S4121.

[0037] Further preferably, after step S412, a safety check calculation is performed on the temporary ring frame beam, specifically comprising the following steps:

[0038] Use the verification formula Ne≤R w bx(h o -x / 2)+R g A g '(h o -a') Perform safety calculation on the temporary ring frame beam; where N is the axial force on the temporary ring frame beam, e is the distance from the center of gravity of the steel bar to the point of action of the axial force, R w is the ultimate compressive strength of concrete, b is the cross-section width, x is the height of the concrete compression zone, h o is the effective height of the section, R g is the standard value of tensile or compressive strength of steel bars, A g ' is the cross-sectional area of the steel bars in the compression zone, a' is the steel bar A g 'The distance from the center of gravity to the nearest edge of the cross section;

[0039] When the temporary ring frame beam meets the verification formula, it is determined that the current design size meets the structural safety requirements;

[0040] When the temporary ring frame beam does not meet the verification formula, it is determined that the current design size does not meet the structural safety requirements, the design size of the temporary ring frame beam is readjusted and the safety verification is re-performed.

[0041] Further preferably, the step S43 specifically includes the following steps:

[0042] S431, performing grouting reinforcement on the jacking pipe receiving platform, and determining whether the jacking pipe receiving platform meets the grouting standard;

[0043] S432, when the jacking pipe receiving platform reaches the grouting standard, wait until the rectangular pipe jacking machine is pushed to the position of the retaining underground continuous wall, and the cutter head of the rectangular pipe jacking machine is close to the retaining underground continuous wall, break the retaining underground continuous wall on the inner side of the temporary ring frame beam to open an opening in the retaining underground continuous wall corresponding to the outlet of the pipe jacking machine hole.

[0044] Further preferably, the step S8 specifically includes the following steps:

[0045] S81: After the concrete strength of the base plate reaches the designed strength, the fourth horizontal support assembly is removed and the side walls and middle plate structure of the underground second floor are constructed;

[0046] S82, after the concrete strength of the middle plate reaches the design strength, remove the remaining second horizontal support components and cast the side walls of the underground first floor;

[0047] S83, after the underground first-floor side wall reaches the designed strength, the temporary ring frame beam and the third support assembly are removed, and the top slab and the remaining underground first-floor side wall are cast;

[0048] S84, after the concrete of the top plate reaches the designed strength, backfill the soil and restore the road surface and municipal pipelines.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] The present invention advances the pipe jacking construction to the station main enclosure stage, without having to wait for the lengthy station main construction to be completed, and can greatly shorten the overall construction period of the subway station; by receiving the rectangular pipe jacking machine on the pipe jacking receiving platform reserved when excavating the foundation pit, the investment of manpower and material resources for additionally building the pipe jacking receiving platform is eliminated, thus avoiding waste; the uneven stress of the underground continuous wall enclosing the pipe jacking construction process is balanced by the supporting axial force of the first additional supporting unit, and the temporary ring frame beam has good anti-torsion and mechanical transmission properties, thereby enhancing the stability of the support system. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0052] Figure 1 A schematic top view of a support system when a jacking pipe receiving platform is reserved in a foundation pit in one embodiment of the present invention;

[0053] Figure 2 A side view of a jacking pipe receiving platform reserved for a foundation pit in one embodiment of the present invention;

[0054] Figure 3 This is a side view of the support system after the jacking pipe receiving platform is removed in one embodiment of the present invention;

[0055] Figure 4 This is a simplified model diagram for calculating the support system of a rectangular jacking pipe corresponding to an underground continuous wall in one embodiment of the present invention;

[0056] Figure 5 FIG. 1 is a flow chart of an embodiment of the present invention.

[0057] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments.

[0058] Description of Figure Numbers:

[0059] 1. Rectangular jacking pipe; 2. Enclosing underground continuous wall; 3. Temporary ring frame beam; 4. First additional support unit; 5. Second horizontal support assembly; 6. Jacking pipe receiving platform; 7. Top plate; 8. First horizontal support assembly; 9. Second additional support unit; 10. Middle plate; 11. Bottom plate; 12. Fourth horizontal support assembly; 13. Intercepting ditch; 14. First hinge support; 15. Second hinge support; 16. Elastic fulcrum. DETAILED DESCRIPTION

[0060] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0061] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0062] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship and movement status of the various components under a certain specific posture (as described in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0063] In addition, the descriptions of "first", "second", etc. in the present invention are for descriptive purposes only and should not be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in this field. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0064] In the existing subway station construction, due to the high density of human activities around the subway station location and the great safety risks, it is generally required to isolate the construction scope before the subway station construction, and then set up a retaining underground continuous wall 2 underground to isolate the soil around the foundation pit, and then dig the foundation pit, and then construct a support system in the foundation pit to reinforce the retaining underground continuous wall 2. This stage is the station main body enclosure stage, and then the station main body is constructed.

[0065] After the main construction of the station is completed, the stability of the wall structure is improved. For safety reasons, the construction unit usually chooses to carry out pipe jacking construction after the main construction of the station is completed. However, the construction period of the main body of the station is long, and the long wait for pipe jacking construction will seriously slow down the construction progress and extend the construction period. Moreover, the main body of the station generally does not include a platform for receiving the pipe jacking machine, so an additional pipe jacking machine receiving platform needs to be built in the main body of the station to receive the pipe jacking machine.

[0066] If the jacking construction is set in the stage of the main enclosure of the station, the wall stability of the underground continuous wall 2 is not high, and a support system is needed to support it. If the support system is not set up reasonably, the bearing capacity of the underground continuous wall 2 will be insufficient. Moreover, during the construction process, the force of the underground continuous wall 2 will be complex due to the uneven pressure of the stratum and the soil bin of the jacking pipe. If the support axial force cannot be adjusted in time, the change of the underground continuous wall 2 will easily cause the support system to twist, and ultimately lead to safety problems such as water leakage, cracking and foundation pit instability.

[0067] In view of this, the following embodiments all propose methods that can be used for pipe jacking construction during the station body enclosure stage. In the following embodiments, the station body is divided into two layers, including a top plate 7, a middle plate 10 and a bottom plate 11. After construction, the top plate 7, the middle plate 10 and the bottom plate 11 separate the station body into an underground negative first floor and an underground negative second floor. The underground negative first floor is the space range between the top plate 7 and the middle plate 10, and the underground negative second floor is the space range between the bottom plate 11 and the middle plate 10.

[0068] See also Figures 1 to 5This embodiment provides a receiving construction method for rectangular jacking pipes during the station main body enclosure stage, comprising the following steps:

[0069] S1. After the construction of the underground continuous wall 2 of the station body is completed, a foundation pit is excavated downward along the inner wall of the underground continuous wall 2, and a jacking pipe receiving platform 6 is reserved in the foundation pit; wherein, the top of the jacking pipe receiving platform 6 matches the design elevation of the middle plate 10 of the station body, and the inner wall of the underground continuous wall 2 is the side wall facing the station body.

[0070] The width of the jacking pipe receiving platform 6 is preferably three times the width of the rectangular jacking pipe 1, so as to facilitate the disassembly and hoisting of the rectangular jacking machine in the later stage. The jacking pipe receiving platform 6 is hardened with C20 concrete, providing a space for the construction of scaffolding for the temporary ring frame beam 3, and serving as a bottom support during the jacking construction process. The jacking pipe receiving platform 6 can be selected according to the geological conditions to excavate the slope at a stable slope of 1:1.5 or 1:2, and a drainage ditch 13 is set at the bottom of the slope for drainage. The slope surface is supported by spray anchors to prevent rainwater erosion and weathering of the rock and soil, which causes the mechanical parameters of the soil in the foundation pit to soften.

[0071] S2, construct a first horizontal support assembly 8 and a second horizontal support assembly 5 in the foundation pit; wherein, the first horizontal support assembly 8 is arranged at the design elevation position of the top plate 7 of the station body, and the second horizontal support assembly 5 is arranged between the design elevation position of the top plate 7 and the jacking pipe receiving platform 6, the second horizontal support assembly 5 and the first horizontal support assembly 8 are parallel and spaced apart, the two ends of the first horizontal support assembly are respectively connected to the retaining underground continuous wall 2, and the two ends of the second horizontal support assembly are respectively connected to the retaining underground continuous wall 2.

[0072] S3, relying on the jacking pipe receiving platform 6, a temporary ring frame beam 3 is constructed on the retaining underground continuous wall 2, and a third support assembly is erected on the inner end face of the temporary ring frame beam 3; wherein, the temporary ring frame beam 3 corresponds to the outlet of the jacking machine hole, and the bottom beam of the temporary ring frame beam 3 is flush with the height of the jacking pipe receiving platform 6, and the third support assembly includes a plurality of first additional support units 4 arranged at intervals along the circumferential direction of the temporary ring frame beam 3, one end of each first additional support unit 4 is connected to the inner end face of the temporary ring frame beam 3, and the other end is connected to the retaining underground continuous wall 2, and the support axial force of the first additional support unit 4 can be adjusted; the inner end face is the side facing the foundation pit, and the jacking machine hole is the hole left after the rectangular jacking machine enters the foundation pit; in particular, the support axial force of the first additional support unit 4 is carried out through the servo system, thereby adjusting the dynamic adjustment of the support axial force to avoid the distortion of the support system due to uneven force.

[0073] S4: Adjust the axial force of each first additional support unit 4 to the design value, remove the second horizontal support assembly 5 within the range of the temporary ring frame beam 3, reinforce the soil surrounding the exit of the pipe jacking machine hole, and break the retaining underground continuous wall 2 on the inner side of the temporary ring frame beam 3 to create an opening corresponding to the exit of the pipe jacking machine hole on the retaining underground continuous wall 2. Note that the retaining underground continuous wall 2 on the inner side of the temporary ring frame beam 3 must be broken after the cutter head of the rectangular pipe jacking machine is in close contact with the outer side of the retaining underground continuous wall 2.

[0074] S5, the rectangular pipe jacking machine is pushed in until the hole of the pipe jacking machine is connected to the opening, and then the rectangular pipe jacking machine is received by the pipe jacking receiving platform 6, and then the rectangular pipe jacking machine is disassembled and lifted off, completing the receiving construction of the rectangular pipe jacking 1. Specifically, the cutter head posture of the rectangular pipe jacking machine is detected and corrected to ensure that the cutter head of the rectangular pipe jacking machine is in the designed position, and the soil bin pressure in the jacking pipe is adjusted to an underpressure state, that is, the pressure in the rectangular pipe jacking 1 is lower than the static soil pressure.

[0075] S6, continue to erect multiple second additional support units 9 in the bottom beam area of the temporary ring frame beam 3; wherein, one end of each second additional support unit 9 is connected to the inner end face of the bottom beam, and the other end is connected to the enclosing underground continuous wall 2, and the support axial force of the second additional support unit 9 can be adjusted; wherein the temporary ring frame beam 3 includes a bottom beam, an upper beam and two side beams.

[0076] S7, remove the jacking pipe receiving platform 6, continue to excavate the foundation pit to the design elevation of the fourth horizontal support assembly 12, install the fourth horizontal support assembly 12, and apply pre-axial force to the fourth horizontal support assembly 12, and then continue to excavate the foundation pit to the position of the bottom plate 11, and successively install the bottom plate 11, the bottom plate cushion layer and the underground negative second floor side wall waterproof structure, and pour the bottom plate 11 and side wall concrete; wherein, the fourth horizontal support assembly 12 is arranged between the middle plate 10 and the bottom plate 11 of the station body.

[0077] S8, detect the concrete strength of the bottom plate 11, and after determining that the concrete strength of the bottom plate 11 reaches the design strength, sequentially construct the underground negative second floor side wall, the middle plate 10, the underground negative first floor side wall and the top plate 7, and simultaneously remove the fourth horizontal support assembly 12, the second horizontal support assembly 5, the temporary ring frame beam 3 and the third support assembly. After the concrete strength of the top plate 7 reaches the design strength, backfill the soil and restore the municipal pipelines and roads.

[0078] Furthermore, in step S3, constructing the temporary ring frame beam 3 on the retaining underground continuous wall 2 by relying on the jacking pipe receiving platform 6 specifically includes the following steps:

[0079] S31, within the corresponding range of the retaining underground continuous wall 2 and the temporary ring frame beam 3, the retaining underground continuous wall 2 is roughened and steel bars are implanted.

[0080] S32, tie up the steel bars of the temporary ring frame beam 3 and connect them with the steel bars in the retaining underground continuous wall 2, then pre-embed the connecting steel plate for connecting with the third support assembly, and cast to form the temporary ring frame beam 3.

[0081] More specifically, the length of the implanted rebar was 35d (d is the rebar diameter). Scaffolding was erected, formwork was erected, and the reinforcement for the temporary ring frame beam 3 was tied. One end of the L-shaped rebar was welded to the main reinforcement of the retaining diaphragm wall 2, and the other end was welded to the main reinforcement of the temporary ring frame beam 3. The L-shaped rebar was 10d long on both sides, and the connecting steel plate had dimensions of 1m x 1m x 20mm. C35 concrete was then poured, and the formwork was removed after the concrete reached its design strength.

[0082] In another embodiment, a tripod is constructed at the bottom of the temporary ring frame beam 3 to prevent it from falling, and the tripod is connected to the enclosing underground continuous wall 2 by embedding steel bars.

[0083] Furthermore, the step S4 specifically includes the following steps:

[0084] S41, using a simplified model to calculate the support axial force of the first additional support unit 4 and the internal force of the corresponding temporary ring frame beam 3, according to the calculated values, multiple first additional support units 4 are installed at the corresponding positions of the upper beam and the two side beams of the temporary ring frame beam 3, and the support axial force on the first additional support unit 4 is adjusted to the design value.

[0085] S42, dismantling the corresponding second horizontal support assembly 5 within the range of the temporary ring frame beam 3.

[0086] S43, reinforcing the surrounding soil of the outlet of the pipe jacking machine hole, breaking the retaining underground continuous wall 2 on the inner side of the temporary ring frame beam 3 to open an opening in the retaining underground continuous wall 2 corresponding to the outlet of the pipe jacking machine hole.

[0087] In this embodiment, step S41 specifically includes the following steps:

[0088] S411, see Figure 4 , select the retaining underground continuous wall 2 corresponding to the rectangular jacking pipe 1 as the object, simplify the four sides of the retaining underground continuous wall 2 into the first hinge support 14, simplify the connection between the retaining underground continuous wall 2 and the first horizontal support assembly 8 into the second hinge support 15, simplify the first additional support unit 4, the second horizontal support assembly 5, the jacking pipe receiving platform 6 and the outer soil of the retaining underground continuous wall 2 into the elastic support 16, and apply the static water and soil pressure (trapezoidal arrow box) and the pressure of the rectangular jacking pipe 1 (rectangular arrow box) to the retaining underground continuous wall 2.

[0089] S412 , using the finite element method to calculate the supporting axial force on the first additional supporting unit 4 and the internal force on the temporary ring frame beam 3 , where the internal force of the temporary ring frame beam 3 includes the supporting axial force and the bending moment.

[0090] S413 , adjusting the number and position of the first additional support units 4 and the size of the temporary ring frame beam 3 according to the calculated support axial force and the internal force on the temporary ring frame beam 3 .

[0091] More specifically, the static water-soil pressure is divided into water pressure and soil pressure, which increase with depth. Geological survey data provide information on the constant water level at the project site. For conservative calculations, the surface water level can be considered zero. The water pressure per meter of the retaining underground diaphragm wall 2 along the depth direction is P1 = γ1H1 (γ1 is the specific gravity of water, and H1 is the depth of the groundwater level). Along the depth direction, the earth pressure per meter of the retaining underground continuous wall 2 is P2=aγ2H2. When the jacking pipe approaches the retaining underground continuous wall 2 (at this time, the retaining underground continuous wall 2 has not been removed) (a is the average soil lateral earth pressure coefficient, which can be obtained by multiplying the lateral earth pressure coefficient of each layer of soil in the geological survey data by the soil layer thickness, and then dividing the sum by the total soil thickness. γ2 is the average soil bulk density, which can be obtained by multiplying the bulk density of each layer of soil in the geological survey data by the soil layer thickness, and then dividing the sum by the total soil thickness. H2 is the soil depth). The magnitude of the jacking pipe thrust on the retaining underground continuous wall 2 can be determined based on construction experience or actual on-site conditions.

[0092] Furthermore, the calculation of the support axial force on the first additional support unit 4 in step S412 specifically includes the following steps:

[0093] Using formula F h =EIδ calculates the supporting axial force on the first additional supporting unit 4, where E is the elastic modulus of the material, I is the section moment of inertia, and δ is the displacement of the first additional supporting unit 4 simplified to the elastic fulcrum 16 obtained in the software using the finite element method in step S412.

[0094] The calculation formula of the section inertia moment is: I=π / 64(R 2 -r 2 ), R is the outer ring diameter, r is the inner ring diameter.

[0095] Furthermore, after step S412, a safety check calculation is performed on the first additional support unit 4 to ensure that the first additional support unit 4 meets the specification "Steel Structure Design Standard" (GB50017-2017), which specifically includes the following steps:

[0096] S4121, check the diameter-to-thickness ratio; the calculation formula is: D / t≤100(235 / f y ), where D is the outer diameter of the first additional support unit 4, t is the wall thickness of the first additional support unit 4, and f y is the yield strength of steel.

[0097] Verify stiffness; the verification formula is: λ x <λ, where λ x is the slenderness ratio of the first additional supporting unit 4 , and λ is the allowable slenderness ratio of the first additional supporting unit 4 .

[0098] Verify strength; the verification formula is: F h / A+M / rW<f, where F h is the support axial force of the first additional support unit 4, in N, A is the cross-sectional area of the first additional support unit 4, M is the design value of the bending moment after taking into account the eccentricity, r is the plastic development coefficient of the component, W is the component section resistance moment, and f is the design value of the compressive strength of the steel.

[0099] Verify stability; the verification formula is: F h / ψ x A+β m M / rW(1-0.8F h / N Ex )≤φ f , where ψ x is the stability coefficient, N Ex is the Euler critical force, β m is the equivalent bending moment coefficient, φ f is the local stability coefficient.

[0100] In the above formula, the calculation method of each symbol can be found and calculated according to the "Steel Structure Design Standard" (GB50017-2017), and will not be repeated here.

[0101] S4122: Determine whether the diameter-to-thickness ratio, stiffness, strength, and stability of the first additional support unit 4 all meet verification conditions.

[0102] S4123: When the diameter-to-thickness ratio, stiffness, strength, and stability of the first additional support unit 4 all meet verification conditions, it is determined that the first additional support unit 4 meets the safety standard.

[0103] S4124: When any one of the diameter-to-thickness ratio, stiffness, strength and stability of the first additional support unit 4 does not meet the verification conditions, it is determined that the first additional support unit 4 does not meet the safety standards, and more first additional support units 4 are preset for verification, and the process returns to step S4121.

[0104] In this embodiment, after step S412, a safety check calculation is performed on the temporary ring frame beam 3, which specifically includes the following steps:

[0105] Use the verification formula Ne≤R w bx(h o -x / 2)+R g A g '(h o -a') Perform safety calculation on the temporary ring frame beam 3; where N is the axial force on the temporary ring frame beam 3, e is the distance from the center of gravity of the steel bar to the point of action of the axial force, R w is the ultimate compressive strength of concrete, b is the cross-section width, x is the height of the concrete compression zone, h o is the effective height of the section, R g is the standard value of tensile or compressive strength of steel bars, A g ' is the cross-sectional area of the steel bars in the compression zone, a' is the steel bar A g 'The distance from the centroid to the nearest edge of the cross section.

[0106] When the temporary ring frame beam 3 satisfies the verification formula, it is determined that the current design size meets the structural safety requirements.

[0107] When the temporary ring frame beam 3 does not satisfy the verification formula, it is determined that the current design size does not meet the structural safety requirements, the design size of the temporary ring frame beam 3 is readjusted and the safety verification is performed again.

[0108] Similarly, after the retaining diaphragm wall 2 is broken, the load acting on it will contain no thrust. The remaining retaining diaphragm wall 2 is subjected to a safety check using the same method described above for the second additional support units 9 and temporary ring frame beam 3. If the check meets the design requirements, construction can proceed according to the preset number and position of the second additional support units 9 and the dimensions of the temporary ring frame beam 3. If not, adjustments will be made until the design requirements are met.

[0109] Furthermore, the step S43 specifically includes the following steps:

[0110] S431, performing grouting reinforcement on the jacking pipe receiving platform 6, and determining whether the jacking pipe receiving platform 6 meets the grouting standard.

[0111] Specifically, 42 cement slurry is used to reinforce the jacking pipe receiving platform 6 with a grouting pressure of 0.8MPa~1MPa. After the grouting is completed, it is judged whether the grouting effect meets the grouting standard (using drilling core sampling to check whether the 28-day unconfined compressive strength is not less than 1.0MPa and the permeability coefficient is not greater than 1.0MPa). If the grouting standards cannot be met, supplementary grouting is required.

[0112] S432, when the jacking pipe receiving platform 6 reaches the grouting standard, wait until the rectangular jacking machine is pushed to the position of the retaining underground continuous wall 2, and the cutter head of the rectangular jacking machine is close to the retaining underground continuous wall 2, break the retaining underground continuous wall 2 on the inner side of the temporary ring frame beam 3 to open an opening in the retaining underground continuous wall 2 corresponding to the outlet of the jacking machine hole.

[0113] It's worth noting that, given the presence of the pipe jacking holes, the retaining diaphragm wall 2 becomes a cantilever structure. To accurately determine the support axial force and internal forces of the retaining diaphragm wall 2, the simplified model described above can also be used for calculations. The model boundaries are as described above. Earth pressure changes after pipe jacking construction. The upper and lower earth pressures of the rectangular pipe 1 are calculated based on the static earth pressure, while the bottom of the rectangular pipe is calculated based on the lateral earth pressure generated by the upper earth pressure plus the pipe's own weight. Using the finite element method, the support axial force and internal forces at any interface of the retaining diaphragm wall 2 can be determined, allowing verification of the rationality of the support layout and the bearing capacity of the retaining diaphragm wall 2.

[0114] Furthermore, the step S8 specifically includes the following steps:

[0115] S81, after the concrete strength of the bottom plate 11 reaches the design strength, the fourth horizontal support assembly 12 is removed, and the structure of the underground negative second floor side wall and the middle plate 10 is constructed.

[0116] S82, after the concrete strength of the middle plate 10 reaches the design strength, the remaining second horizontal support components 5 are removed, the underground first-floor waterproof structure is constructed, and the underground first-floor side walls are cast.

[0117] S83, after the underground negative first floor side wall reaches the design strength, remove the temporary ring frame beam 3 and the third supporting assembly, construct the top plate 7 waterproof structure, cast the top plate 7 and the remaining underground negative first floor side wall; roughen the side wall around the pipe jacking machine hole, and pre-embed the water stop. In order to fill the gap between the temporary ring frame beam 3 and the pipe jacking machine hole, it is necessary to cast the gap to form a post-cast ring beam. After the concrete strength of the post-cast ring beam reaches the design strength, remove the temporary ring frame beam 3.

[0118] S84, after the concrete of the top plate 7 reaches the designed strength, backfill the soil and restore the road surface and municipal pipelines.

[0119] In the present invention, by analyzing the stress conditions of the support system and the existing retaining underground continuous wall 2 during the construction process, the support system design is made more reasonable and effective, and the bearing capacity of the retaining underground continuous wall 2 can be verified at the same time; the jacking receiving platform 6 reserved in the foundation pit can not only receive the rectangular jacking machine, but also transmit lateral constraints during the jacking construction process to ensure the overall stability of the foundation pit; the servo system in the support system adjusts the support axial force and the integrated cast temporary ring frame beam 3 can dynamically adjust the support axial force during the jacking construction process to adapt to deformation and avoid twisting of the support system; in addition, it can also provide fulcrums for the retaining underground continuous wall 2 above and below, reduce the hole effect of the retaining underground continuous wall 2, and reduce stress concentration; finally, the post-cast ring beam of the present invention is tightly connected to the station body to avoid safety risks such as water leakage.

[0120] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A receiving construction method for rectangular jacking pipes in the station main body enclosure stage, characterized in that: The following steps are involved: S1, after the construction of the underground continuous wall of the station body is completed, a foundation pit is excavated downward along the inner side wall of the underground continuous wall, and a jacking pipe receiving platform is reserved in the foundation pit; wherein the station body includes a top plate, a middle plate and a bottom plate, and the top of the jacking pipe receiving platform matches the design elevation of the middle plate; S2, constructing a first horizontal support assembly and a second horizontal support assembly in the foundation pit; wherein the first horizontal support assembly is arranged at the design elevation of the top plate, and the second horizontal support assembly is arranged between the design elevation of the top plate and the jacking pipe receiving platform, and both ends of the first horizontal support assembly and the second horizontal support assembly are connected to the corresponding retaining underground continuous wall; S3, relying on the jacking pipe receiving platform, construct a temporary ring frame beam corresponding to the outlet of the jacking machine hole on the retaining underground continuous wall, and set up a third support assembly on the inner end surface of the temporary ring frame beam; wherein, the bottom beam of the temporary ring frame beam is flush with the height of the jacking pipe receiving platform, and the third support assembly includes a plurality of first additional support units arranged at intervals along the circumferential direction of the temporary ring frame beam, one end of each first additional support unit is connected to the inner end surface of the temporary ring frame beam, and the other end is connected to the retaining underground continuous wall, and the support axial force of the first additional support unit is adjustable; S4, adjusting the support axial force of each first additional support unit to a design value, removing the second horizontal support assembly within the temporary ring frame beam, reinforcing the soil around the exit of the pipe jacking machine hole, and breaking the retaining underground continuous wall on the inner side of the temporary ring frame beam to create an opening in the retaining underground continuous wall corresponding to the exit of the pipe jacking machine hole; S5, pushing the rectangular pipe jacking machine until the hole of the pipe jacking machine is connected to the opening, then receiving the rectangular pipe jacking machine on the pipe jacking receiving platform, and then disassembling and lifting the rectangular pipe jacking machine away; S6, continue to erect multiple second additional support units in the area of the bottom beam of the temporary ring frame beam; wherein one end of each second additional support unit is connected to the inner end surface of the bottom beam, and the other end is connected to the enclosing underground continuous wall, and the support axial force of the second additional support unit is adjustable; wherein the temporary ring frame beam includes a bottom beam, an upper beam and two side beams; S7, excavating the jacking pipe receiving platform, continuing to excavate the foundation pit to the design elevation of the fourth horizontal support assembly, installing the fourth horizontal support assembly, and continuing to excavate the foundation pit to the position of the base plate, and sequentially installing the base plate, base plate cushion layer, and underground second-basement side wall waterproofing structure, and pouring concrete for the base plate and underground second-basement side wall; wherein the fourth horizontal support assembly is located between the middle plate and the base plate of the station body; S8, detect the concrete strength of the bottom plate, and after determining that the concrete strength of the bottom plate reaches the design strength, sequentially construct the underground second-floor side wall, middle plate, underground first-floor side wall and top plate, and simultaneously remove the fourth horizontal support assembly, the second horizontal support assembly, the temporary ring frame beam and the third support assembly. After the concrete strength of the top plate reaches the design strength, backfill the soil and restore the municipal pipelines and roads.

2. The receiving construction method of the rectangular jacking pipe in the station main body enclosure stage according to claim 1 is characterized in that: In step S3, constructing a temporary ring frame beam on the retaining underground continuous wall by relying on the jacking pipe receiving platform specifically includes the following steps: S31, roughening the enclosing underground continuous wall and implanting steel bars within the corresponding range of the enclosing underground continuous wall and the temporary ring frame beam; S32, tying up the steel bars of the temporary ring frame beam and connecting them with the steel bars in the enclosing underground continuous wall, and then pre-embedding the connecting steel plate for connecting with the third support assembly, and casting to form the temporary ring frame beam.

3. The receiving construction method of the rectangular jacking pipe in the station main body enclosure stage according to claim 1 is characterized in that: The step S4 specifically includes the following steps: S41, using a simplified model to calculate the support axial force of the first additional support unit and the internal force of the temporary ring frame beam, and based on the calculated values, erecting a plurality of the first additional support units at corresponding positions of the upper beam and the two side beams of the temporary ring frame beam, and adjusting the support axial force on the first additional support units to the design value; S42, removing the corresponding second horizontal support assembly within the range of the temporary ring frame beam; S43, reinforcing the surrounding soil of the outlet of the pipe jacking machine hole, breaking the retaining underground continuous wall on the inner side of the temporary ring frame beam to open an opening in the retaining underground continuous wall corresponding to the outlet of the pipe jacking machine hole.

4. The receiving construction method of the rectangular jacking pipe in the station main body enclosure stage according to claim 3 is characterized in that: The step S41 specifically includes the following steps: S411, selecting the retaining underground continuous wall corresponding to the rectangular jacking pipe as the object, simplifying the surrounding areas of the retaining underground continuous wall into a first hinged support, simplifying the connection between the retaining underground continuous wall and the first horizontal support assembly into a second hinged support, simplifying the first additional support unit, the second horizontal support assembly, the jacking pipe receiving platform, and the soil outside the retaining underground continuous wall into elastic fulcrums, and applying the static water and soil pressure and the rectangular jacking pipe pressure to the retaining underground continuous wall; S412: Calculate the support axial force on the first additional support unit and the internal force on the temporary ring frame beam using the finite element method; S413: Adjust the number and position of the first additional support units and the size of the temporary ring frame beam according to the calculated support axial force and the internal force on the temporary ring frame beam.

5. The receiving construction method of rectangular jacking pipe in the station main body enclosure stage according to claim 4 is characterized in that: The calculation of the support axial force on the first additional support unit in step S412 specifically includes the following steps: Using formula F h =EIδ calculates the support axial force on the first additional support unit, where E is the elastic modulus of the material, I is the section moment of inertia, and δ is the displacement of the first additional support unit simplified to the elastic fulcrum obtained in the software using the finite element method in step S412.

6. The receiving construction method of rectangular jacking pipe in the station main body enclosure stage according to claim 4 is characterized in that: After step S412, safety verification is performed on the first additional support unit, specifically including the following steps: S4121, check the diameter-to-thickness ratio; the calculation formula is: D / t≤100(235 / f y ), where D is the outer diameter of the first additional support unit, t is the wall thickness of the first additional support unit, and f y is the yield strength of steel; Verify stiffness; the verification formula is: λ x <λ, where λ x is the slenderness ratio of the first additional support unit, λ is the allowable slenderness ratio of the first additional support unit; Verify strength; the verification formula is: F h / A+M / rW<f, where F h is the axial force of the first additional support unit, A is the cross-sectional area of the first additional support unit, M is the design value of the bending moment after taking into account the eccentricity, r is the plastic development coefficient of the component, W is the cross-sectional resistance moment of the component, and f is the design value of the compressive strength of the steel; Verify stability; the verification formula is: F h / ψ x A+β m M / rW(1-0.8F h / N Ex )≤φ f , where F h is the supporting axial force of the first additional supporting unit, β m is the equivalent bending moment coefficient, ψ x is the stability coefficient, A is the cross-sectional area of the first additional support unit, M is the design value of the bending moment after taking into account the eccentricity, r is the plastic development coefficient of the component, W is the component section resistance moment, N Ex is the Euler critical force, φ f is the local stability coefficient; S4122, determining whether the diameter-to-thickness ratio, stiffness, strength, and stability of the first additional support unit all meet verification conditions; S4123: When the diameter-to-thickness ratio, stiffness, strength, and stability of the first additional support unit all meet verification conditions, determine that the first additional support unit meets safety standards; S4124: When any one of the diameter-to-thickness ratio, stiffness, strength and stability of the first additional support unit does not meet the verification conditions, it is determined that the first additional support unit does not meet the safety standards, and more first additional support units are preset for verification, and the process returns to step S4121.

7. The receiving construction method of rectangular jacking pipe in the station main body enclosure stage according to claim 4 is characterized in that: After step S412, the temporary ring frame beam is subjected to safety verification, which specifically includes the following steps: Use the verification formula Ne≤R w bx(h o -x / 2)+R g A g '(h o -a') Perform safety calculation on the temporary ring frame beam; where N is the axial force on the temporary ring frame beam, e is the distance from the center of gravity of the steel bar to the point of action of the axial force, R w is the ultimate compressive strength of concrete, b is the cross-section width, x is the height of the concrete compression zone, h o is the effective height of the section, R g is the standard value of tensile or compressive strength of steel bars, A g ' is the cross-sectional area of the steel bar in the compression zone, a' is the steel bar A g 'The distance from the center of gravity to the nearest edge of the cross section; When the temporary ring frame beam meets the verification formula, it is determined that the current design size meets the structural safety requirements; When the temporary ring frame beam does not meet the verification formula, it is determined that the current design size does not meet the structural safety requirements, the design size of the temporary ring frame beam is readjusted and the safety verification is re-performed.

8. The receiving construction method of rectangular jacking pipe in the station main body enclosure stage according to claim 3 is characterized in that: The step S43 specifically includes the following steps: S431, performing grouting reinforcement on the jacking pipe receiving platform, and determining whether the jacking pipe receiving platform meets the grouting standard; S432, when the jacking pipe receiving platform reaches the grouting standard, wait until the rectangular pipe jacking machine is pushed to the position of the retaining underground continuous wall, and the cutter head of the rectangular pipe jacking machine is close to the retaining underground continuous wall, break the retaining underground continuous wall on the inner side of the temporary ring frame beam to open an opening in the retaining underground continuous wall corresponding to the outlet of the pipe jacking machine hole.

9. The receiving construction method of rectangular jacking pipe in the station main body enclosure stage according to claim 1 is characterized in that: The step S8 specifically includes the following steps: S81: After the concrete strength of the base plate reaches the designed strength, the fourth horizontal support assembly is removed and the side walls and middle plate structure of the underground second floor are constructed; S82, after the concrete strength of the middle plate reaches the design strength, remove the remaining second horizontal support components and cast the side walls of the underground first floor; S83, after the underground first-floor side wall reaches the designed strength, the temporary ring frame beam and the third support assembly are removed, and the top slab and the remaining underground first-floor side wall are cast; S84, after the concrete of the top plate reaches the designed strength, backfill the soil and restore the road surface and municipal pipelines.

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