A front protection construction method for shield tunneling under underground municipal pipe gallery

Abstract

The application provides a front protection construction method for a shield tunnel to pass through an underground municipal pipe gallery, comprising the following steps: step 1, field lofting: lofting measurement is performed on the shield tunnel and the pipe gallery support pile, and the removal range of the conflict support pile of the shield tunnel and the municipal pipe gallery is accurately determined; step 2, MJS all-directional high-pressure rotary jet grouting pile reinforcement: MJS reinforcement is performed on the positions of the two sides of the pipe gallery deformation joint and the bottom plate of the municipal pipe gallery; step 3, steel flower pipe setting: the steel flower pipe is set in the fat groove between the pipe gallery support pile and the municipal pipe gallery; step 4, conflict support pile obstacle removal construction: the conflict support pile in the removal range determined in the step 1 is removed and backfilled; and step 5, shield secondary grouting: shield tunneling operation is performed on the shield tunnel, and secondary grouting is performed on the soil outside the pipe piece structure. The construction method is simple, feasible, safe and reliable, and can play a good protection role on the existing municipal pipe gallery.

Description

Technical Field

[0001] This invention relates to the field of municipal infrastructure construction technology, and in particular to a pre-construction protection method for shield tunnels passing under underground municipal utility tunnels. Background Technology

[0002] With the booming development of rail transit projects, the subway network is becoming increasingly dense. Subway lines often conflict with the underground structures of existing municipal facilities, among which the common ones are the retaining structures of municipal integrated utility tunnels. Municipal integrated utility tunnels are public underground tunnels used to centrally lay municipal pipelines such as electricity, communications, radio and television, water supply, drainage, heating, and gas. They are made of reinforced concrete and can be single-compartment, double-compartment, or triple-compartment. Retaining piles are set on both sides of the municipal integrated utility tunnel.

[0003] Currently, the main method for subway tunnel construction is shield tunneling. For pile foundations that are numerous, large in diameter, high in strength, and high in steel content, direct grinding by the shield machine can easily cause risks such as cutterhead jamming and machine shutdown. The construction risks are even greater, especially for adverse geological conditions and small-angle oblique crossings. Therefore, before the shield tunnel passes under, it is necessary to clear the retaining piles left over from the underground municipal utility tunnel construction phase. Since the retaining piles are close to the operating municipal utility tunnel, the clearing process will inevitably cause disturbance to the surrounding soil layers, thereby causing deformation of the underground structure and internal facilities. In severe cases, it can lead to cracking and water seepage in the underground structure and damage to the facilities.

[0004] Therefore, a pre-construction protection method is needed for shield tunnels passing under underground municipal utility tunnels, which involves taking protective measures for the underground utility tunnel structure during the removal of retaining piles. Summary of the Invention

[0005] The purpose of this invention is to provide a pre-construction protection method for shield tunnels passing under underground municipal utility tunnels. During the removal of retaining piles, protective measures are taken for the underground municipal utility tunnel structure to effectively reduce settlement and deformation and ensure the safe operation of municipal facilities.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A pre-construction protection method for a shield tunnel passing under an underground municipal utility tunnel, wherein the municipal utility tunnel has expansion joints and retaining piles are installed on both sides of the municipal utility tunnel, comprising the following steps: Step 1, On-site layout: Layout and measurement of the retaining piles of the shield tunnel and the utility tunnel are carried out to accurately delineate the removal range of the retaining piles that conflict between the shield tunnel and the municipal utility tunnel, and at the same time determine the location of the expansion joint of the municipal utility tunnel. Step 2, MJS all-round high-pressure jet grouting pile reinforcement: MJS reinforcement piles are used to reinforce both sides of the expansion joint of the pipe gallery and the position under the bottom plate of the municipal pipe gallery. Step 3, Steel pipe installation: Steel pipes are installed in the trench between the pipe gallery retaining piles and the municipal pipe gallery. Step 4, Clearing the conflict retaining piles: Remove the conflict retaining piles within the removal range determined in Step 1 and backfill; Step 5, Secondary Grouting of the Shield Tunnel: After the shield tunneling machine completes the segment assembly, secondary grouting is performed on the soil outside the segment structure.

[0007] Furthermore, in the aforementioned pre-construction protection method for shield tunnels passing under underground municipal utility tunnels, in step 1, the removal range of the retaining piles of the conflict utility tunnel is determined by extending 0.5m to 1.0m outward from the design edge line of the shield tunnel.

[0008] Furthermore, in the aforementioned pre-construction protection method for shield tunnels passing under underground municipal utility tunnels, in step 2, the MJS reinforcement piles are located in the trench between the utility tunnel retaining piles and the municipal utility tunnel structure. The MJS reinforcement piles are all-around high-pressure jet grouting piles. According to the location of the expansion joint, in the trench between the utility tunnel retaining piles and the municipal utility tunnel, two semi-circular MJS reinforcement piles are arranged on each side of each utility tunnel expansion joint. The diameter of the MJS reinforcement piles is 2m~3m, and the interlocking amount between piles is 0.6m~1m. The center-to-center distance between the two MJS reinforcement piles arranged on the same side of the utility tunnel expansion joint is 1300mm. The MJS reinforcement piles extend from the top plate of the municipal utility tunnel to a position 2m below the bottom of the utility tunnel retaining piles.

[0009] Furthermore, in the above-mentioned pre-construction protection method for shield tunnels passing under underground municipal utility tunnels, in step 2, the grout used for pouring MJS reinforcement piles is 42.5MPa ordinary Portland cement with a water-cement ratio of 1.0 to 1.1 and a cement content of 40%.

[0010] Furthermore, in the above-mentioned pre-construction protection method for shield tunnels passing under underground municipal utility tunnels, in step 2, when pouring MJS reinforcement piles in the area below the bottom slab of the municipal utility tunnel, the grouting pressure is 38MPa ~ 40MPa; when pouring MJS reinforcement piles within the height range of the municipal utility tunnel, the grouting pressure is 25MPa ~ 30MPa.

[0011] Furthermore, in the aforementioned pre-construction protection method for shield tunnels passing under underground municipal utility tunnels, in step 2, after the MJS reinforcement piles are poured and the grout has solidified, core sampling is used to ensure that the 28-day unconfined compressive strength qu>1.5MPa.

[0012] Furthermore, in the aforementioned pre-construction protection method for shield tunnels passing under underground municipal utility tunnels, in step 3, the steel pipes are made of ∅42 hot-rolled seamless steel pipes. Along the longitudinal direction of the municipal utility tunnel, within an area extending 3m outward on both sides of the area where the conflict retaining piles are removed, the steel pipes are driven into the trench at equal intervals of 2m to 4m from the ground. The bottom depth of the steel pipes must accurately reach 5m below the bottom slab of the utility tunnel.

[0013] Furthermore, in the aforementioned pre-construction protection method for shield tunnels passing under underground municipal utility tunnels, step 4 specifically includes the following steps: Step 4.1, determine the pile locations, and identify the pile locations of the retaining piles to be cleared of obstacles and conflicts; Step 4.2: Position the steel sleeve. Align the full-rotation drilling rig with the pile position of the retaining pile to be cleared and press the steel sleeve vertically into the predetermined depth. Step 4.3, core extraction: Use a grab bucket to remove the concrete and slag from the pile body of the retaining pile inside the steel sleeve, and clean the filling material inside the pile body. Step 4.4, segmented twisting: using the torque of the full-rotation drilling rig, the reinforced concrete pile of the conflict retaining pile is twisted into segments, and the pile segments are removed one by one until the designed removal elevation is reached. Step 4.5: Backfill the pile hole. After the pile body of the conflict retaining pile is removed, the pile hole is backfilled. During the backfilling process, the steel sleeve is slowly pulled out until it is completely removed from the ground, thus completing the clearing operation of a single conflict retaining pile. Step 4.6, skip-pile construction: When carrying out the obstacle removal work for the next conflict retaining pile, if the distance between the conflict retaining pile to be removed and the adjacent already removed conflict retaining pile is ≥4 piles, repeat steps 4.1 to 4.5 to carry out the obstacle removal work for the next conflict retaining pile until all conflict retaining piles affecting the shield tunnel excavation are removed.

[0014] Furthermore, in the aforementioned pre-construction protection method for shield tunnels passing under underground municipal utility tunnels, in step 4, during the clearing of conflict retaining piles, when the settlement monitoring data reaches the yellow warning threshold range of 10mm~15mm, compensation grouting is immediately carried out using the steel pipes installed in step 3. The grouting material is P42.5 cement mortar, the cement content of the cement mortar is 1:1, the grouting pressure is 0.3MPa~0.45MPa, and the grout diffusion radius is 0.8m~1.0m.

[0015] Furthermore, in the aforementioned pre-construction protection method for shield tunnels passing under underground municipal utility tunnels, in step 5, shield tunneling is carried out. After the shield machine completes the segment assembly, secondary grouting is performed inside the tunnel through the pre-set grouting holes of the segments.

[0016] Analysis shows that this invention discloses a pre-construction protection method for shield tunnels passing under underground municipal utility tunnels. This method is simple, feasible, safe, and reliable, and can provide good protection for existing municipal utility tunnels. Before removing the conflict retaining piles, MJS reinforcement is carried out on both sides of the expansion joint and under the bottom slab of the utility tunnel. On the one hand, the expansion joint is reinforced and sealed in advance to prevent water leakage caused by differential settlement on both sides of the expansion joint; on the other hand, the foundation under the bottom slab of the utility tunnel is replaced to control the amount of settlement. Steel pipes are arranged longitudinally along the utility tunnel. If there is significant local settlement during pile extraction and soil erosion occurs under the bottom slab, timely grouting can be used to effectively track and compensate for it, thereby reducing the settlement of the utility tunnel. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Wherein: Figure 1 This is a flowchart of a protective construction method according to an embodiment of the present invention.

[0018] Figure 2 This is a schematic diagram of a structure according to an embodiment of the present invention.

[0019] Figure 3 This is a schematic cross-sectional view of the steel perforated pipe arrangement according to an embodiment of the present invention.

[0020] Figure 4 This is a structural schematic diagram of the cross-sectional layout of MJS reinforced piles according to an embodiment of the present invention.

[0021] Explanation of reference numerals in the attached drawings: 1 Municipal utility tunnel; 2 Utility tunnel expansion joint; 3 Utility tunnel retaining pile; 4 Conflict retaining pile; 5 Shield tunnel; 6 MJS reinforcement pile; 7 Steel pipe. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Various examples are provided by way of explanation and not by way of limitation. Indeed, those skilled in the art will recognize that modifications and variations can be made to the invention without departing from its scope or spirit. For example, a feature shown or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desirable that the invention encompass such modifications and variations falling within the scope of the appended claims and their equivalents.

[0023] In the description of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. The terms "connected," "linked," and "set up" used in this invention should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; a direct connection or an indirect connection through intermediate components; a wired connection, a radio connection, or a wireless communication signal connection. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0024] The accompanying drawings illustrate one or more examples of the invention. The detailed description uses numerals and letters to refer to features in the drawings. Similar or analogous reference numerals in the drawings and description have been used to refer to similar or analogous parts of the invention. As used herein, the terms “first,” “second,” and “third,” etc., are used interchangeably to distinguish one component from another and are not intended to indicate the location or importance of individual components.

[0025] like Figures 1 to 4 As shown, according to an embodiment of the present invention, a pre-construction protection method for shield tunnels passing under underground municipal utility tunnels is provided. Figure 2 As shown, the underground municipal utility tunnel 1, serving as a public tunnel for the centralized laying of municipal pipelines such as electricity, communications, broadcasting and television, water supply, drainage, heating, and gas, is typically constructed of reinforced concrete, with common forms including single-compartment, double-compartment, and triple-compartment types. The municipal utility tunnel 1 is equipped with expansion joints 2, specifically designed to accommodate deformations caused by factors such as temperature changes, concrete shrinkage, uneven foundation settlement, and seismic forces, while also ensuring structural adaptability and waterproof sealing. Supporting piles 3, usually made of reinforced concrete, are installed on both sides of the municipal utility tunnel 1. During the open-cut construction phase of the municipal utility tunnel 1, the supporting piles 3 primarily serve to support the sidewalls of the excavation pit, prevent soil collapse, and control the deformation of the surrounding soil.

[0026] like Figure 1 As shown, the construction method includes the following steps: Step 1, On-site layout: Layout and measurement are carried out for the shield tunnel 5 and the retaining piles 3 of the utility tunnel 1 to accurately delineate the removal range of the conflicting retaining piles 4 between the shield tunnel 5 and the municipal utility tunnel 1. At the same time, the location of the expansion joint of the municipal utility tunnel 1 is determined and the precise location of the expansion joint is marked. When delineating the removal range of the conflicting retaining piles 4, the removal range of the conflicting retaining piles 4 is determined by extending 0.5m to 1.0m outward from the design edge line of the shield tunnel 5.

[0027] Using the tunnel excavation outline clearly defined in the design and construction drawings of shield tunnel 5 as the baseline, an outward offset of 0.5m to 1.0m is made from the design boundary of shield tunnel 5, and this extended boundary is used as the final boundary line for the obstacle removal operation. All pipe gallery retaining piles 3 that intrude into this extended boundary are identified as conflict retaining piles 4 that need to be removed and cleared. Considering that the cutterhead outer diameter is larger than that of shield tunnel 5, this 0.5m to 1.0m outward allowance is to match the characteristic that the actual outer diameter of the shield machine cutterhead is larger than the design excavation boundary of the tunnel, and at the same time to offset the small axis offset error during shield tunneling, so as to avoid the risk of pipe gallery retaining piles 3 intruding into the shield tunneling space due to insufficient boundary demarcation, which could lead to cutterhead jamming and machine shutdown.

[0028] Step 2, MJS omnidirectional high-pressure jet grouting reinforcement: MJS reinforcement piles 6 are used to reinforce both sides of the pipe gallery expansion joint 2 and the corresponding location under the bottom slab of the municipal pipe gallery 1. The MJS reinforcement piles 6 are located in the trench between the pipe gallery retaining piles 3 and the municipal pipe gallery 1 structure. The width of this space is usually 0.5~1.2 meters. The MJS reinforcement piles 6 are omnidirectional high-pressure jet grouting piles. MJS reinforcement is an omnidirectional high-pressure jet grouting technology, specifically used to reinforce foundations in complex environments. Its biggest feature is that it can be constructed at any angle of 360° with minimal impact on the surrounding environment. This construction method directly utilizes the trench space reserved in advance during the pipe gallery construction stage to lay out the MJS reinforcement piles 6, without the need for additional large-scale soil excavation, thus completing the reinforcement of the pipe gallery expansion joint.

[0029] Based on the location of the expansion joint, two semi-circular MJS reinforcement piles 6 are arranged vertically on both sides of each expansion joint 2 in the trench between the utility tunnel retaining piles 3 and the municipal utility tunnel 1. The semi-circular structure faces the center line of the utility tunnel. The diameter of the MJS reinforcement piles 6 is 2m~3m and the interlocking amount between piles is 0.6m~1m. The center-to-center distance between the two MJS reinforcement piles 6 arranged on the same side of the expansion joint 2 is 1300mm. The MJS reinforcement piles 6 extend from the top plate of the municipal utility tunnel 1 to a position 2m below the bottom of the retaining piles 3. This arrangement can ensure that the MJS reinforcement piles 6 provide sufficient bearing capacity for the expansion joint 2 of the utility tunnel, restrain uneven settlement at the expansion joint, and avoid the structural misalignment and cracking of the municipal utility tunnel 1 caused by the disturbance of the tunnel boring machine. The grout used for pouring MJS reinforced pile 6 is 42.5MPa ordinary Portland cement with a water-cement ratio of 1.0-1.1 and a cement content of 40%, ensuring that the strength and construction quality of MJS reinforced pile 6 meet the design requirements. MJS reinforced pile 6 contains no reinforcing steel, allowing the tunnel boring machine to directly pass through it during tunnel excavation.

[0030] When pouring the MJS reinforcement piles 6 below the base slab of the municipal utility tunnel 1, the grouting pressure was 38MPa to 40MPa. Ultra-high pressure jet grouting was used to enlarge the effective diameter of the piles and enhance the foundation support reinforcement effect. After this high-pressure grouting reinforcement, the bearing capacity of the soil at the bottom of the tunnel was significantly improved. This effectively prevents the risk of uneven settlement, deformation, and cracking of the tunnel structure during subsequent removal of the conflict retaining piles 4 that intrude into the shield tunnel's range and during shield tunneling construction. It also blocks the seepage channels of groundwater under the base slab of the tunnel, further enhancing the overall structural safety and stability. When pouring the MJS reinforcement piles 6 within the height range of the municipal utility tunnel 1, the grouting pressure was 25MPa to 30MPa. This ensured the quality of the pile forming while avoiding damage to the structure of the municipal utility tunnel 1 from the impact of high-pressure grout.

[0031] After the MJS reinforced pile 6 was poured and the grout solidified, core sampling was conducted to ensure that the 28-day unconfined compressive strength qu > 1.5 MPa, meeting the bearing capacity requirements of the MJS reinforced pile 6. The 28-day unconfined compressive strength is a core mechanical performance indicator in the fields of soil and rock reinforcement and cement-based engineering. Specifically, it refers to the maximum axial pressure limit that a cured specimen, after 28 days of curing, can withstand under test conditions with no lateral confining pressure or lateral restraint.

[0032] Before removing the retaining pile 4, MJS reinforcement was carried out on both sides of the expansion joint 2 of the utility tunnel and under the bottom slab of the municipal utility tunnel 1. On the one hand, the expansion joint was reinforced and sealed in advance to prevent water leakage caused by the settlement difference on both sides of the expansion joint; on the other hand, the foundation under the bottom slab of the utility tunnel was replaced to control the amount of settlement.

[0033] Step 3, Install steel pipe 7: (e.g.) Figure 3 As shown, steel pipes 7 are installed in the trench between the retaining piles 3 and the municipal utility tunnel 1. The steel pipes 7 are made of ∅42 hot-rolled seamless steel pipes. Grouting holes are staggered at 15cm intervals on the pipe wall of the steel pipes 7. The diameter of the grouting holes is 6mm. The lower end of the steel pipes 7 is processed into a cone shape for easy insertion into the soil. Along the longitudinal direction of the municipal utility tunnel 1, in an area extending 3m outward on both sides of the area where the retaining piles 4 were removed, steel pipes 7 are driven into the trench from the ground at equal intervals of 2m to 4m. The steel pipes 7 are installed by pre-drilling and then lowering or by direct vibration pressing. The bottom depth of the steel pipes 7 must accurately reach 5m below the bottom plate of the municipal utility tunnel 1. The steel pipe 7 is installed at an angle, with the bottom of the steel pipe 7 closer to the municipal utility tunnel 1 than the top. The angle of inclination of the steel pipe 7 is determined according to the site conditions. The bottom of the steel pipe 7 is installed as deep as possible below the bottom plate of the municipal utility tunnel 1, while avoiding the side wall of the municipal utility tunnel 1 structure, so as to expand the grouting range.

[0034] During the installation of steel pipe 7, strict control must be exercised according to the bottom elevation (5m below the bottom slab of the utility tunnel). This ensures the bottom of the steel pipe 7 accurately reaches the designed elevation, and it is strictly prohibited for the steel pipe 7 to encroach upon the excavation area of ​​the shield tunnel 5. Precise control of the elevation of the steel pipe 7 ensures that the reinforcement length fully meets design requirements, allowing the grouting reinforcement effect to cover the designated area below the utility tunnel bottom slab. Simultaneously, it prevents the bottom elevation of the steel pipe 7 from encroaching upon the excavation area of ​​the shield tunnel 5, thus avoiding safety hazards to subsequent tunneling operations. The steel pipe 7 is arranged longitudinally along the municipal utility tunnel 1. If excessive local settlement or soil erosion occurs under the bottom slab during pile extraction, timely grouting through the steel pipe 7 can provide timely compensation, thereby reducing the settlement of the utility tunnel and significantly lowering the risk of structural deformation.

[0035] Step 4, Clearing the Conflict Retaining Piles: Using a steel sleeve retaining wall + full-rotation clearing construction process, remove the conflict retaining piles 4 within the removal range determined in Step 1 and backfill. This specifically includes the following steps: Step 4.1, determine the pile location, determine the location of the conflict retaining pile 4 to be cleared; Step 4.2: Position the steel sleeve. Align the full-rotation drilling rig with the pile position of the retaining pile 4 to be cleared of the obstacle and press the steel sleeve vertically into the predetermined depth. Step 4.3, core extraction: Use a grab bucket to remove the concrete and slag from the steel sleeve of the retaining pile 4, and clean the filling material inside the pile body. Step 4.4, segmented twisting: using the torque of the full-rotation drilling rig, the reinforced concrete pile of the conflict retaining pile 4 is twisted into segments, and the pile segments are removed one by one until the designed removal elevation is reached. Step 4.5: Backfill the pile hole. After the pile body of the conflict retaining pile 4 is removed, the pile hole is backfilled. During the backfilling process, the steel sleeve is slowly pulled out until it is completely removed from the ground, thus completing the clearing operation of a single conflict retaining pile 4.

[0036] Step 4.6, skip-pile construction: When carrying out the obstacle removal work for the next conflict retaining pile 4, if the interval between the cleared conflict retaining pile 4 and the adjacent already removed conflict retaining pile 4 is ≥ 4 piles, repeat steps 4.1 to 4.5 to carry out the obstacle removal work for the next conflict retaining pile 4 until all conflict retaining piles 4 affecting the excavation of the shield tunnel 5 are removed. By using the skip-pile construction method, stress concentration in the surrounding soil caused by continuous removal is avoided.

[0037] During the clearing of the conflict retaining piles 4, settlement monitoring of the municipal utility tunnel 1 structure was carried out simultaneously. When the settlement monitoring data reached the yellow warning threshold range of 10mm~15mm, compensation grouting was immediately carried out using the steel pipe 7 installed in step 3. The grouting material was P42.5 cement mortar with a cement ratio of 1:1, the grouting pressure was 0.3MPa~0.45MPa, and the grout diffusion radius was 0.8m~1.0m. Settlement monitoring data was tracked simultaneously during the grouting process. When the settlement monitoring data of the municipal utility tunnel 1 stabilized, the grouting operation was stopped. During construction, the grouting pressure needed to be controlled to ensure that the existing municipal utility tunnel 1 structure was not affected. The grouting parameters could be appropriately optimized and adjusted on-site based on the test data.

[0038] Step 5, Secondary grouting of the shield tunnel: After the shield tunneling machine completes the segment assembly, it performs secondary grouting on the soil within 1m outside the segment structure.

[0039] After all conflicting retaining piles 4 that conflict with shield tunnel 5 have been cleared, the pile holes have been backfilled and compacted, and the tests have been passed, subsequent shield tunneling operations can proceed. After the shield machine completes the assembly of this segment, secondary grouting is carried out inside the tunnel through the pre-set grouting holes of the segment to fully fill the annular gap within 1m outside the segment structure, further reinforcing the soil between the municipal utility tunnel 1 and shield tunnel 5, and preventing uneven settlement during the subsequent operation phase.

[0040] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects: A pre-construction protection method for shield tunnels passing under underground municipal utility tunnels is proposed. This method is simple, feasible, safe, and reliable, and provides good protection for the existing municipal utility tunnel 1. Before the removal of the conflict retaining piles 4, MJS reinforcement is carried out on both sides of the expansion joint 2 and under the bottom slab of the utility tunnel. On the one hand, the expansion joint is reinforced and sealed in advance to prevent water leakage caused by differential settlement on both sides of the expansion joint; on the other hand, the foundation under the bottom slab of the utility tunnel is replaced to control the settlement. Steel pipes 7 are arranged longitudinally along the utility tunnel. If there is significant local settlement during the pile extraction process and soil erosion occurs under the bottom slab, timely grouting can be used to effectively track and compensate for the settlement, thereby reducing the settlement of the utility tunnel.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A pre-construction protection method for a shield tunnel passing under an underground municipal utility tunnel, wherein the municipal utility tunnel has a tunnel expansion joint, and retaining piles are installed on both sides of the municipal utility tunnel, characterized in that... Includes the following steps: Step 1, On-site layout: Layout and measurement of the retaining piles of the shield tunnel and the utility tunnel are carried out to accurately delineate the removal range of the retaining piles that conflict between the shield tunnel and the municipal utility tunnel, and at the same time determine the location of the expansion joint of the municipal utility tunnel. Step 2, MJS all-round high-pressure jet grouting pile reinforcement: MJS reinforcement piles are used to reinforce both sides of the expansion joint of the pipe gallery and the position under the bottom plate of the municipal pipe gallery. Step 3, Steel pipe installation: Steel pipes are installed in the trench between the pipe gallery retaining piles and the municipal pipe gallery. Step 4, Clearing the conflict retaining piles: Remove the conflict retaining piles within the removal range determined in Step 1 and backfill; Step 5, Secondary Grouting of the Shield Tunnel: After the shield tunneling machine completes the segment assembly, secondary grouting is performed on the soil outside the segment structure.

2. The pre-construction protection method for shield tunnels passing under underground municipal utility tunnels according to claim 1, characterized in that, In step 1, the removal range of the retaining piles for the conflict tunnel is determined by extending 0.5m to 1.0m outward from the design edge of the shield tunnel.

3. The pre-construction protection method for shield tunnels passing under underground municipal utility tunnels according to claim 1, characterized in that, In step 2, the MJS reinforcement pile is located in the trench between the pipe gallery retaining pile and the municipal pipe gallery structure. The MJS reinforcement pile is an all-round high-pressure jet grouting pile. Based on the location of the expansion joint, two semi-circular MJS reinforcement piles are arranged on each side of each expansion joint in the trench between the utility tunnel retaining piles and the municipal utility tunnel. The diameter of the MJS reinforcement piles is 2m to 3m, and the interlocking amount between the piles is 0.6m to 1m. The center-to-center distance between the two MJS reinforcement piles arranged on the same side of the expansion joint is 1300mm. The MJS reinforcement piles extend from the top slab of the municipal utility tunnel to a position 2m below the bottom of the utility tunnel retaining piles.

4. The pre-construction protection method for shield tunnels passing under underground municipal utility tunnels according to claim 1, characterized in that, In step 2, the grout used for pouring the MJS reinforced piles is 42.5MPa ordinary Portland cement with a water-cement ratio of 1.0 to 1.1 and a cement content of 40%.

5. The pre-construction protection method for shield tunnels passing under underground municipal utility tunnels according to claim 1, characterized in that, In step 2, when pouring the MJS reinforcement piles in the area below the municipal utility tunnel floor slab, the grouting pressure is 38MPa ~ 40MPa. When pouring MJS reinforcement piles within the height range of the municipal utility tunnel, the grouting pressure is 25MPa ~ 30MPa.

6. The pre-construction protection method for shield tunnels passing under underground municipal utility tunnels according to claim 1, characterized in that, In step 2, after the MJS reinforced pile is poured and the grout has solidified, core sampling is performed to ensure that the 28-day unconfined compressive strength qu>1.5MPa.

7. The pre-construction protection method for shield tunnels passing under underground municipal utility tunnels according to claim 1, characterized in that, In step 3, the steel pipe is made of ∅42 hot-rolled seamless steel pipe. Along the longitudinal direction of the municipal utility tunnel, in an area extending 3m outward on both sides of the area where the conflict retaining piles are removed, the steel pipe is driven into the trench at equal intervals of 2m to 4m. The bottom depth of the steel pipe needs to accurately reach 5m below the bottom plate of the utility tunnel.

8. The pre-construction protection method for shield tunnels passing under underground municipal utility tunnels according to claim 1, characterized in that, Step 4 specifically includes the following steps: Step 4.1, determine the pile locations, and identify the pile locations of the retaining piles to be cleared of obstacles and conflicts; Step 4.2: Position the steel sleeve. Align the full-rotation drilling rig with the pile position of the retaining pile to be cleared and press the steel sleeve vertically into the predetermined depth. Step 4.3, core extraction: Use a grab bucket to remove the concrete and slag from the pile body of the retaining pile inside the steel sleeve, and clean the filling material inside the pile body. Step 4.4, segmented twisting: using the torque of the full-rotation drilling rig, the reinforced concrete pile of the conflict retaining pile is twisted into segments, and the pile segments are removed one by one until the designed removal elevation is reached. Step 4.5: Backfill the pile hole. After the pile body of the conflict retaining pile is removed, the pile hole is backfilled. During the backfilling process, the steel sleeve is slowly pulled out until it is completely removed from the ground, thus completing the clearing operation of a single conflict retaining pile. Step 4.6, skip-pile construction: When carrying out the obstacle removal work for the next conflict retaining pile, if the distance between the conflict retaining pile to be removed and the adjacent already removed conflict retaining pile is ≥4 piles, repeat steps 4.1 to 4.5 to carry out the obstacle removal work for the next conflict retaining pile until all conflict retaining piles affecting the shield tunnel excavation are removed.

9. The pre-construction protection method for shield tunnels passing under underground municipal utility tunnels according to claim 1, characterized in that, In step 4, during the clearing of the conflict retaining piles, when the settlement monitoring data reaches the yellow warning threshold range of 10mm~15mm, compensation grouting is immediately carried out using the steel pipe installed in step 3. The grouting material is P42.5 cement mortar, the cement content of the cement mortar is 1:1, the grouting pressure is 0.3MPa~0.45MPa, and the grout diffusion radius is 0.8m~1.0m.

10. The pre-construction protection method for shield tunnels passing under underground municipal utility tunnels according to claim 1, characterized in that, In step 5, the shield tunnel is excavated. After the shield machine completes the segment assembly, secondary grouting is carried out inside the tunnel through the pre-set grouting holes of the segments.

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