Shield construction method for ultra-short distance under-crossing of newly-built underground structures

Abstract

The present invention discloses a shield construction method for ultra-short distance underpassing of a newly built underground structure. It comprises the following steps: replacing the ordinary steel bars corresponding to the portal area of the underground tunnel in the station support structure with glass fiber bars; carrying out bearing pile construction, underground structure support construction and open cut earthwork construction on the newly built underground structure, successively binding steel bars, embedding grouting pipes, and pouring a reinforced concrete cushion layer at the bottom of the whole foundation pit, and the distance between the bottom of the foundation pit of the newly built underground structure and the top of the tunnel is 0.4 - 0.6 m; installing a steel sleeve in the receiving end of the station; the shield machine tunnels underground in the newly built underground structure and compensates for grouting through the grouting pipes in a timely manner according to the soil deformation condition; the shield machine cuts the glass fiber bars and enters the steel sleeve; the steel sleeve is removed, and the shield machine is hoisted out from the receiving end of the station. The present invention can ensure the safety of the newly built underground structure and the smooth reception of the shield when the reinforcement range of the soil around the shield tunnel is only about 0.5 m under soft soil or sandy layer geological conditions.

Description

Technical Field

[0001] The invention relates to the technical field of shield tunnels, and in particular to a shield construction method for passing through a newly built underground structure at an ultra-close distance. Background Art

[0002] With the rapid development of domestic rail transit, the network of major cities is becoming more and more dense, and the areas where the lines pass through are gradually developed into prosperous areas. In order to make full use of the surrounding land of rail transit, rail transit and the basements of surrounding land can be considered as a whole to maximize the benefits of comprehensive utilization of underground space.

[0003] Rail transit is generally planned as a strip of underground space, and the commonly used construction methods for stations and tunnels are open cut and shield methods, etc.; while the basements of the surrounding plots of rail transit are generally planned as large-scale underground spaces, and the commonly used construction methods are mainly open cut and cover cut methods, etc. In the functional overlapping sections, in order to achieve the comprehensive utilization of underground space, the space layout is generally planned as underground space above and rail transit tunnels below. In order to control investment, the burial depth of rail transit stations is generally increased as much as possible, which will reduce the net distance between the underground space structure of the open cut method and the rail transit tunnel of the shield method.

[0004] Taking into account the mutual influence of open excavation and shield tunneling, the construction process of "open excavation first and shield tunneling later" is generally adopted. The shield excavation influence radius is generally about 0.5 to 1.0D (D is the outer diameter of the tunnel) outside the tunnel, so shield excavation will inevitably affect the newly built underground structure. During the construction of shield tunnels, the shield starting and arrival stages are high-risk sources. Especially in water-rich soft soil and sandy soil, which have the characteristics of high pressure head and strong permeability, whether the shield can smoothly reach the station receiving end from the starting section directly affects the success of the project.

[0005] For shield reception, the soil around the shield tunnel needs to be reinforced to a range of 3m to ensure the safety of shield reception. However, when the distance between the bottom of the new underground structure and the top of the shield tunnel is very close (that is, the reinforcement range of the soil around the shield tunnel is about 0.5m), the risk of the shield tunnel passing under the new underground structure increases sharply, and the risk of shield reception will be greatly increased. The existing construction method of reinforcing the soil around the shield tunnel cannot ensure the safety of the new underground structure and the safety of shield reception when the reinforcement range is only about 0.5m. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention proposes a shield construction method for passing under a newly built underground structure at an ultra-close distance. The method can ensure the safety of the newly built underground structure and the smooth reception of the shield under soft soil or sand geological conditions when the reinforcement range of the soil around the shield tunnel is only about 0.5m, thereby realizing the safe co-construction of open-cut underground structures and shield tunnel projects.

[0007] To achieve the above object, a shield construction method for ultra-short-distance underpassing a newly-built underground structure designed by the present invention is characterized in that it includes the following steps:

[0008] Step 1, during the construction of the station, a vertically arranged station support structure is set between the open-cut receiving end of the station and the newly-built underground structure, and the ordinary steel bars corresponding to the underground tunnel portal area in the station support structure are replaced with glass fiber bars;

[0009] Step 2, after the station is completed, bearing pile construction, underground structure support construction and open-cut earthwork construction are carried out on the newly-built underground structure. After the earthwork is excavated to the foundation pit of the newly-built underground structure, the bottom of the foundation pit of the newly-built underground structure is further excavated. Reinforcing bars are tied, grouting pipes are embedded in sequence at the bottom of the entire foundation pit, and a reinforced concrete cushion is poured. The distance between the bottom of the foundation pit of the newly-built underground structure and the top end of the tunnel to be constructed later is 0.4 - 0.6 m;

[0010] Step 3, after the pouring of the reinforced concrete cushion is completed, the upper part of the newly-built underground structure is backfilled;

[0011] Step 4, install a steel sleeve inside the station receiving end, and the steel sleeve corresponds to the outside of the tunnel portal and is consistent with the axis of the tunnel portal;

[0012] Step 5, the shield machine passes under the newly-built underground structure along the tunnel track, tunnels underground in the newly-built underground structure, synchronously grouts and secondarily grouts the periphery of the tunnel in a timely manner, and compensates for grouting through the grouting pipe in a timely manner according to the soil deformation situation;

[0013] Step 6, the shield machine cuts the glass fiber bars and enters the steel sleeve;

[0014] Step 7, remove the steel sleeve and hoist the shield machine out of the station receiving end.

[0015] Furthermore, in Step 2, the length of the grouting pipe is 0.5 - 3.0 m, and the grouting pipe penetrates 0.2 - 0.4 m into the bottom of the foundation pit of the newly-built underground structure; the plane distance between adjacent grouting pipes is 1.5 - 2.0 m.

[0016] Even further, in Step 2, the reinforced concrete cushion is a C35 reinforced concrete layer with a thickness of 450 - 500 mm.

[0017] Furthermore, in Step 2, when carrying out bearing pile construction, the length, thickness, inclination degree, etc. of the hole section shall meet the following requirements:

[0018] First, the allowable deviation of the hole section length is ±2.0%;

[0019] Second, the allowable deviation of the hole section thickness is ±10 mm;

[0020] Thirdly, the allowable deviation of the perpendicularity of the hole section is ±1 / 300.

[0021] Fourthly, the local protrusion of the wall surface shall not be greater than 100 mm.

[0022] Fifthly, the position deviation of the embedded parts on the wall surface shall not be greater than 100 mm.

[0023] Sixthly, the deviation of the center line at the top of the wall ≤ 30 mm.

[0024] Seventhly, the area of holes, exposed reinforcement, and honeycombing shall not exceed 5% of the exposed area of the unit hole section.

[0025] Eighthly, there shall be no mud inclusion and no water leakage at the joint of the hole section.

[0026] Furthermore, in step 2, when constructing the bearing pile, the control of the final hole depth of the hole section shall meet the following requirements:

[0027] Firstly, the final hole depth of the hole section must ensure the design depth. Within the same hole section, the excavation depth at the bottom of the hole shall be consistent and keep flat.

[0028] Secondly, the bottom of the hole of the extended diaphragm wall within the same hole section shall be at the same excavation depth as the bottom of the hole of the first-stage hole section.

[0029] Furthermore, in step 2, when constructing the bearing pile, after the hole formation is completed, the sediment and debris at the bottom of the hole shall be cleaned up, and then the mud shall be replaced. And 1 hour after the replacement of the mud, the mud specific gravity within a height of 500 mm from the bottom of the hole shall not be greater than 1.15, and the sediment thickness shall not be greater than 100 mm.

[0030] Further, in step 5, the grouting pipe uses cement grouting, the water-binder ratio of the cement slurry is 0.5:1, and the grouting pressure is 0.15 - 0.2 MPa.

[0031] Furthermore, in step 5, when performing grouting compensation through the grouting pipe, the grouting can be terminated as long as one of the following conditions is met:

[0032] Firstly, both the grouting volume and the grouting pressure reach the design requirements.

[0033] Secondly, the grouting volume has reached 75% of the design value, and the grouting pressure exceeds the design value.

[0034] Furthermore, in step 5, when performing grouting compensation through the grouting pipe, after the grouting is completed, the grouting hole is pressure-sealed with a cement slurry with a water-binder ratio of 0.5:1.

[0035] Furthermore, in step 5, when performing grouting compensation through the grouting pipe, the slurry diffusion radius is greater than or equal to 0.25 m.

[0036] The advantages of the present invention are as follows:

[0037] 1. When the geological conditions are soft soil or sand layer, and the reinforcement range of the soil around the shield tunnel is only about 0.5 m, the present invention adopts the process of open excavation first and then shield tunneling. When constructing the new underground structure, the method of thick reinforced concrete cushion + bearing piles + grouting system is adopted to jointly ensure the safety of the new underground structure. When receiving the shield tunnel, the method of glass fiber reinforced bars + steel sleeve receiving is adopted to jointly ensure the safety of the shield tunnel, so as to realize the safe co-construction of the open-excavated underground structure and the shield tunnel project.

[0038] 2. By reducing the net distance between the bottom end of the new underground structure and the top end of the shield tunnel, that is, reducing the reinforcement range of the soil around the shield tunnel from 3 m to about 0.5 m, raising the buried depth of the shield tunnel and the buried depth of the receiving end of the station, not only the construction cost is reduced, but also the excavation risk of the foundation pit at the receiving end of the station is reduced.

[0039] The shield tunneling construction method for the new underground structure with ultra-close underpass of the present invention can ensure the safety of the new underground structure and the smooth reception of the shield when the geological conditions are soft soil or sand layer and the reinforcement range of the soil around the shield tunnel is only about 0.5 m. It not only realizes the safe co-construction of the open-excavated underground structure and the shield tunnel project, but also can be popularized and applied to the co-construction of open-excavated underground structures and shield tunnel projects in various strata. At the same time, it reduces the construction cost and has remarkable economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic cross-sectional structure diagram after pouring the reinforced concrete cushion in the present invention;

[0041] Figure 2 It is a schematic cross-sectional structure diagram after backfilling the upper part of the new underground structure in the present invention;

[0042] Figure 3 It is a schematic cross-sectional structure diagram after installing the steel sleeve in the present invention;

[0043] Figure 4 It is a schematic cross-sectional structure diagram after the shield machine enters the steel sleeve in the present invention;

[0044] Figure 5 It is a schematic plan layout diagram after the shield machine enters the steel sleeve in the present invention;

[0045] Figure 6 It is a schematic cross-sectional structure diagram after hoisting out the shield machine in the present invention;

[0046] In the figure: new underground structure 1, tunnel 2, shield machine 3, steel sleeve 4, receiving end of the station 5;

[0047] The newly built underground structure 1 includes: underground structure support 1-1, bearing piles 1-2, reinforced concrete cushion layer 1-3, and grouting pipe 1-4;

[0048] The station receiving end 5 includes: a station supporting structure 5-1 and glass fiber reinforcement 5-2. DETAILED DESCRIPTION

[0049] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0050] In the description of the present invention, it is necessary to understand that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the invention. The shield construction method of the present invention for ultra-close-range underpass of a newly built underground structure is applied to soft soil or sandy geology in the first phase of Wuhan Metro Line 7.

[0051] like Figures 1 to 6 As shown, the present invention comprises the following steps:

[0052] Step 1: During station construction, a vertically arranged station support structure 5-1 is set between the open-cut station receiving end 5 and the newly built underground structure 1, and the ordinary steel bars in the station support structure 5-1 corresponding to the portal area of ​​the underground tunnel 2 are replaced with glass fiber bars 5-2.

[0053] Step 2, after the station is completed, the new underground structure 1 is constructed with bearing piles 1-2, underground structure support 1-1 and earthwork open excavation. After the earthwork is excavated to the foundation pit of the new underground structure 1, the bottom of the foundation pit of the new underground structure 1 is over-excavated, and the steel bars are tied, the grouting pipes 1-4 are pre-buried, and the reinforced concrete cushion layer 1-3 is poured in sequence at the bottom of the entire foundation pit. The distance between the bottom of the foundation pit of the new underground structure 1 and the top of the tunnel 2 to be constructed later is 0.4 to 0.6m. As shown in Figures 1 to 2, Figure 1 It is a schematic diagram of the cross-sectional structure after pouring the reinforced concrete cushion layer in the present invention, Figure 2 It is a schematic diagram of the cross-sectional structure after backfilling the upper part of the newly built underground structure in the present invention.

[0054] The present invention can adopt the process of open excavation followed by shield construction under soft soil or sand geological conditions when the reinforcement range of the soil around the shield tunnel is only about 0.5m. When constructing a new underground structure, a thick reinforced concrete cushion layer + bearing piles + grouting system is adopted to jointly ensure the safety of the new underground structure.

[0055] The grouting pipes 1-4 in this embodiment are sleeve valve pipes arranged in a plum blossom shape.

[0056] According to the different clear distances between the tunnel and the underground structure, the length of the grouting pipes 1-4 is 0.5-3.0 m, and the grouting pipes 1-4 penetrate 0.2-0.4 m into the bottom of the foundation pit of the newly built underground structure 1, and the plane distance between adjacent grouting pipes 1-4 is 1.5-2.0 m.

[0057] The grouting pipes 1-4 in this embodiment are 1.5 m long, the grouting pipes 1-4 penetrate 0.2 m into the bottom of the foundation pit of the newly built underground structure 1, and the plane distance between adjacent grouting pipes 1-4 is 1.5 m.

[0058] The reinforced concrete cushion layer 1-3 is a C35 reinforced concrete layer with a thickness of 450-500 mm. By pouring the reinforced concrete cushion layer 1-3, the bearing capacity and rigidity of the stratum are improved, and when pouring the bottom plate of the reinforced concrete cushion layer 1-3, its bottom is guaranteed not to deform.

[0059] In the prior art, the cushion layer of newly built underground structures is generally 150-200mm, and its material is C20 plain concrete cushion layer. In order to reduce the impact of the subsequent ultra-close-distance penetration of the shield on the newly built underground structure, the 150-200mm C20 plain concrete cushion layer is adjusted to 500mm C35 reinforced concrete, and the plane layout range is the entire bottom of the foundation pit.

[0060] The present invention solves the problem of how a shield tunnel located in soft soil or sand layer can pass through a newly built underground structure at an ultra-close distance (about 0.5m), that is, the process of first open excavation and then shield construction is adopted. After the foundation pit of the newly built underground structure 1 is excavated to the bottom, a part of the soil is over-excavated and reinforced concrete cushion layers 1-3 are laid. At the same time, in order to reduce the deformation effect of the shield machine 3 excavating the underground of the newly built underground structure 1 in the later stage, the bottom plate of the newly built underground structure 1 is supported by bearing piles, and a grouting system is pre-buried, and grouting compensation is carried out in time according to the deformation of the soil.

[0061] The technical requirements for bearing piles 1-2 are as follows:

[0062] First, during the drilling process of the bearing pile 1-2, the hole should always be filled with mud to keep the hole wall stable;

[0063] Second, the excavation of the hole section should strengthen the observation of stability. If the hole wall has a serious local collapse, it should be backfilled in time and properly handled;

[0064] Third, mud leakage during construction should be replenished in time, the required liquid level should always be maintained, the mud quality should be checked regularly, and the mud indicators should be adjusted in time;

[0065] Fourth, after the excavation of the hole section is completed, the hole position, hole depth, hole width and the perpendicularity of the hole wall shall be inspected, and the hole cleaning and slurry replacement work can be carried out only after passing the inspection.

[0066] In addition, when constructing the bearing pile 1-2, the length, thickness, inclination degree, etc. of the hole section shall meet the following requirements:

[0067] First, the allowable deviation of the hole section length is ±2.0%;

[0068] Second, the allowable deviation of the hole section thickness is ±10 mm;

[0069] Third, the allowable deviation of the hole section perpendicularity is ±1 / 300;

[0070] Fourth, the local protrusion of the wall surface shall not be greater than 100 mm;

[0071] Fifth, the position deviation of the embedded parts on the wall surface shall not be greater than 100 mm;

[0072] Sixth, the deviation of the center line at the top of the wall ≤ 30 mm;

[0073] Seventh, the area of holes, exposed steel bars and honeycombs shall not exceed 5% of the exposed area of the unit hole section;

[0074] Eighth, there is no mud inclusion and no water leakage at the joint of the hole section.

[0075] Meanwhile, when constructing the bearing pile 1-2, the control of the final hole depth of the hole section shall meet the following requirements:

[0076] First, the final hole depth of the hole section must ensure the design depth. Within the same hole section, the excavation depth at the bottom of the hole is consistent and the bottom is kept flat;

[0077] Second, the bottom of the extended diaphragm wall within the same hole section needs to have the same excavation depth as the bottom of the first-stage hole section.

[0078] Preferably, when constructing the bearing pile 1-2, after the hole forming is completed, the sediment and sundries at the bottom of the hole shall be cleaned up, and then the slurry is replaced. And 1 hour after the slurry replacement is completed, the slurry specific gravity within the height of 500 mm from the bottom of the hole is not greater than 1.15, and the sediment thickness is not greater than 100 mm.

[0079] Step 3, after the reinforced concrete cushion 1-3 is poured, the upper part of the newly built underground structure 1 is backfilled. As Figure 2 shown, it is the sectional structure schematic diagram of the upper part of the newly built underground structure after backfilling in the present invention.

[0080] Step 4, install the steel sleeve 4 in the station receiving end 5. The steel sleeve 4 corresponds to the outside of the tunnel 2 portal and is aligned with the axis of the tunnel 2 portal. As Figure 3 shown, it is the sectional structure schematic diagram after installing the steel sleeve in the present invention.

[0081] The dimensions of the steel sleeve 4 need to be determined in combination with construction requirements, the dimensions of the shield machine 3, etc.

[0082] In this embodiment, the outer diameter of the shield machine 3 is 6000 mm and the length of the main machine is 9500 mm. Therefore, the length of the cylindrical part of the steel sleeve 4 is 10500 mm, and the diameter (inner diameter) is 6800 mm. It is divided into four sections, and each section is further divided into upper and lower blocks. The material of the cylinder is Q235A steel plate with a thickness of 16 mm. Longitudinal and circumferential stiffeners are welded to the outer periphery of each section of the cylinder to form a reticular structure to ensure the stiffness of the cylinder. The thickness of the stiffeners is 20 mm, the height is 150 mm, and the spacing is about 550 * 600 mm. The ends of each section of the cylinder and the joint surfaces of the upper and lower two circular arcs are all connected by flanges. The flanges are made of Q235A steel with a thickness of 24 mm. The connections between the upper and lower sections and between the two sections of the cylinder are all connected by 8.8-grade M30 * 90 bolts, and a 3-mm-thick rubber gasket is added in the middle to ensure the sealing effect. The bottom frame of the cylinder is made in four pieces. The bearing plate of the bottom frame is made of Q235A steel plate with a thickness of 20 mm, the stiffeners are made of Q235A steel with a thickness of 20 mm, and the bottom plate is made of Q235A steel plate with a thickness of 20 mm. The bottom frame is welded to the lower cylinder to form an integral body. When welding, the bottom frame plate is first welded to the cylinder, and then the transverse stiffeners are welded, and the bottom plate and the I-beam are welded. After the bottom frame is assembled, the bottom edge of the I-beam is welded to the embedded parts of the station floor, the bracket must be tightened against the side wall of the station with a section steel, and the upper part of the steel sleeve 4 is tightened against the middle plate beam with a channel steel.

[0083] Step 5, the shield machine 3 passes under the newly built underground structure 1 along the track of the tunnel 2, tunnels underground in the newly built underground structure 1, and timely conducts synchronous grouting and secondary grouting around the tunnel 2, and compensates for grouting through the grouting pipe 1-4 in a timely manner according to the soil deformation situation.

[0084] Specifically, the grouting pipe 1-4 uses cement grouting. The water-binder ratio of the cement slurry is 0.5:1, the cement grade is not lower than 42.5, and the grouting pressure is 0.15 - 0.2 MPa.

[0085] When compensating for grouting through the grouting pipe 1-4, the grouting can be terminated as long as one of the following conditions is met:

[0086] First, both the grouting volume and the grouting pressure reach the design requirements;

[0087] Second, the grouting volume has reached 75% of the design value, and the grouting pressure exceeds the design value.

[0088] When compensating for grouting through the grouting pipe 1-4, after the grouting is completed, the grouting holes are pressure-sealed with cement slurry with a water-binder ratio of 0.5:1.

[0089] Preferably, when grouting compensation is carried out through the grouting pipe 1-4, the slurry diffusion radius should be determined according to on-site grouting tests, and in this embodiment, it is greater than or equal to 0.25 m.

[0090] Step 6, the shield machine 3 cuts the glass fiber bars 5-2 and enters the steel sleeve 4. As Figures 4 to 5 shown, Figure 4 This is a schematic cross-sectional structure diagram of the shield machine entering the steel sleeve in the present invention, Figure 5 and this is a schematic plan layout diagram of the shield machine entering the steel sleeve in the present invention.

[0091] In the above step 1, the ordinary steel bars corresponding to the portal area of the underground tunnel 2 in the station support structure 5-1 are replaced with glass fiber bars 5-2. The reason is that: for ordinary steel bars, the shield machine 3 cannot directly cut them, but the shield machine 3 can directly cut the glass fiber bars 5-2.

[0092] To ensure the smooth reception of the shield machine 3 after passing under the newly built underground structure 1, the ordinary steel bars are changed to glass fiber bars 5-2 to avoid manual removal of the portal. A steel sleeve 4 is set in the station receiving end 5, and the shield machine 3 directly cuts the enclosure structure of the station receiving end 5 and then enters the steel sleeve 4, finally realizing the smooth reception of the shield.

[0093] When the shield tunnel is received, the present invention adopts the method of receiving with glass fiber bars + steel sleeve to jointly ensure the safety of the shield tunnel, so as to realize the safe co-construction of the open-cut underground structure and the shield tunnel project.

[0094] In addition, the present invention reduces the net distance between the bottom end of the newly built underground structure and the top end of the shield tunnel, that is, reduces the reinforcement range of the soil around the shield tunnel from 3 m to about 0.5 m, raises the buried depth of the shield tunnel, and raises the buried depth of the station receiving end, which not only reduces the construction cost, but also reduces the excavation risk of the station receiving end foundation pit.

[0095] Step 7, remove the steel sleeve 4 and lift the shield machine 3 out of the station receiving end 5. Figure 6 As shown, this is a schematic cross-sectional structure diagram after the shield machine is lifted out in the present invention;

[0096] The shield construction method for the shield tunnel to pass under the newly built underground structure at a very close distance in the present invention can ensure the safety of the newly built underground structure and the smooth reception of the shield when the reinforcement range of the soil around the shield tunnel is only about 0.5 m under the geological conditions of soft soil or sandy soil. It not only realizes the safe co-construction of the open-cut underground structure and the shield tunnel project, and can be popularized and applied to the co-construction of the open-cut underground structure and the shield tunnel project in various strata; at the same time, it also reduces the construction cost and has remarkable economic benefits.

[0097] The above embodiments are preferred embodiments of the present invention. However, the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A shield construction method for tunneling under a newly built underground structure at a very short distance, characterized in that, The steps include: Step 1: during station construction, a vertically arranged station support structure (5-1) is set between an open-cut station receiving end (5) and a newly constructed underground structure (1), and ordinary steel bars in the station support structure (5-1) corresponding to the portal area of ​​the underground tunnel (2) are replaced with glass fiber bars (5-2); Step 2, after the station is completed, the new underground structure (1) is subjected to the construction of bearing piles (1-2), underground structure support (1-1) and open excavation. After the excavation reaches the foundation pit of the new underground structure (1), the bottom of the foundation pit of the new underground structure (1) is further over-excavated. Rebars are tied and grouting pipes (1-4) are pre-buried at the bottom of the entire foundation pit, and a reinforced concrete cushion layer (1-3) is poured. The distance between the bottom of the foundation pit of the new underground structure (1) and the top of the tunnel (2) to be constructed later is 0.4 to 0.6 m. Step 3, after the reinforced concrete cushion layer (1-3) is poured, the upper part of the newly built underground structure (1) is backfilled; Step 4, installing a steel sleeve (4) in the station receiving end (5), wherein the steel sleeve (4) corresponds to the outside of the tunnel (2) portal and is consistent with the axis of the tunnel (2) portal; Step 5, the shield machine (3) passes under the newly built underground structure (1) along the track of the tunnel (2), excavates underground the newly built underground structure (1), performs synchronous grouting and secondary grouting in a timely manner around the tunnel (2), and performs grouting compensation through the grouting pipes (1-4) in a timely manner according to the deformation of the soil body; Step 6, the shield machine (3) cuts the glass fiber reinforcement (5-2) and enters the steel sleeve (4); Step 7, remove the steel sleeve (4) and lift the shield machine (3) out from the station receiving end (5); In step 2, the length of the grouting pipe (1-4) is 0.5 to 3.0 m, and the grouting pipe (1-4) penetrates 0.2 to 0.4 m into the bottom of the foundation pit of the newly built underground structure (1); the plane distance between adjacent grouting pipes (1-4) is 1.5 to 2.0 m; In step 5, the grouting pipe (1-4) is grouted with cement, the water-binder ratio of the cement slurry is 0.5:1, and the grouting pressure is 0.15-0.2MPa; In step 5, when grouting compensation is performed through the grouting pipe (1-4), the grouting can be terminated when one of the following conditions is met: First, the grouting volume and grouting pressure meet the design requirements; Second, the grouting volume has reached 75% of the design value and the grouting pressure exceeds the design value.

2. The shield construction method for ultra-short distance under-crossing a newly-built underground structure according to claim 1, wherein: In step 2, the reinforced concrete cushion layer (1-3) is a C35 reinforced concrete layer with a thickness of 450 to 500 mm.

3. The shield construction method for ultra-short distance under-crossing a newly-built underground structure according to claim 1, characterized in that: In step 2, when carrying out the construction of the bearing pile (1-2), the length, thickness and inclination of the hole section shall meet the following requirements: First, the hole length is allowed to deviate by ±2.0%; Second, the hole thickness tolerance is ±10mm; Third, the verticality of the hole section is allowed to deviate by ±1 / 300; Fourth, the local protrusion of the wall should not be greater than 100mm; Fifth, the position deviation of embedded parts on the wall should not be greater than 100mm; Sixth, the center line deviation of the wall top is ≤30mm; Seventh, the area of ​​holes, exposed reinforcement and honeycombs shall not exceed 5% of the exposed area of ​​the unit hole section; Eighth, there is no muddy filling or water leakage at the joint of the hole section.

4. The shield construction method for ultra-short distance under-crossing a newly-built underground structure according to claim 3, characterized in that: In Step 2, when constructing the bearing pile (1-2), the control of the final hole depth of the hole section shall meet the following requirements: First, the final hole depth of the hole section must ensure the design depth. Within the same hole section, the bottom excavation depth of the hole bottom is consistent and flat; Second, the bottom of the extended diaphragm wall within the same hole section shall have the same bottom excavation depth as that of the primary hole section.

5. The shield tunneling method for constructing under a newly built underground structure with a super short distance, according to claim 4, wherein: In Step 2, when constructing the bearing pile (1-2), after the hole forming is completed, the sediment and debris at the bottom of the hole shall be cleaned up, and then the mud shall be replaced. After 1 hour of the completion of the mud replacement, the mud specific gravity within a height of 500 mm from the bottom of the hole shall not be greater than 1.15, and the sediment thickness shall not be greater than 100 mm.

6. The shield construction method for ultra-short distance underpassing a newly-built underground structure according to claim 1, characterized in that: In Step 5, when performing grouting compensation through the grouting pipe (1-4), after the grouting is completed, the grouting hole shall be pressure-sealed with a cement slurry with a water-cement ratio of 0.5:

1.

7. The shield construction method for ultra-short-distance undercrossing of a newly-built underground structure according to claim 6, characterized in that: In Step 5, when performing grouting compensation through the grouting pipe (1-4), the grout diffusion radius is greater than or equal to 0.25 m.

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