Active control method for super-small clear distance long distance skew crossing existing underground structure of rail transit

Abstract

The application discloses an active control method for super-small clear distance long-distance oblique crossing of a rail transit existing underground structure, which comprises the following steps: step one, collecting the archived data of the operating rail transit underground structure; step two, detecting the existing rail transit structure and the rail structure to determine the structure continuous deformation control value W; step three, determining the active lifting structure system of the existing operating rail transit underground structure; step four, determining the active lifting structure system, and the lifting structure is divided into vertical lifting structure and horizontal lifting structure; and step five, performing the construction of the new rail transit structure crossing the existing operating rail transit structure; thus, the application realizes the settlement control effect that cannot be achieved by other crossing methods, thereby guaranteeing the operation safety of the existing operating rail transit line during the crossing construction, and the operation is simple, and the cost and construction period are controllable.

Description

Technical Field

[0001] This invention relates to the technical field of underground rail transit construction, and in particular to an active control method for long-distance oblique crossings of existing underground rail transit structures with ultra-small clearance. Background Technology

[0002] With the acceleration of urbanization in my country, rail transit is being planned and constructed on a large scale, characterized by its land-saving, speed, punctuality, and environmental friendliness. However, compared with other urban infrastructure, it has higher requirements for operational safety. Once completed, constructing other buildings or structures around it often involves significant construction risks, long construction periods, and high investment costs.

[0003] However, from the perspective of urban planning and development, many projects need to be built near or through existing urban rail transit projects. In such cases, it is often necessary to assess the feasibility of the project. Many projects have abandoned the idea of ​​crossing urban rail transit due to a lack of construction methods and experience in the construction of underground structures that cross urban rail transit, which has greatly reduced the quality of new construction projects and even led to the suspension or abandonment of some projects. This has affected the level of urban planning and construction and restricted the overall competitiveness of Chinese cities.

[0004] In recent years, underground structure and geotechnical engineers have conducted extensive research, practice, and exploration, achieving significant progress compared to previous years in methods and technologies for traversing underground structures of operational rail transit systems. However, the current overall situation is as follows:

[0005] 1. Current crossing methods mainly focus on vertical crossings (new structures crossing existing rail transit structures at an angle of nearly 90 degrees). Compared with earlier methods, this has yielded relatively more research results and supported the construction of more vertical crossing projects.

[0006] 2. Some research results have been achieved in long-distance oblique crossings with large clearance (usually large clearance refers to the excavation clearance being greater than one times the excavation diameter), and there are a few successful construction cases, but overall it is still in the exploratory stage.

[0007] 3. There are no successful cases of construction on long-distance skew crossings with ultra-small clearance (ultra-small clearance refers to the excavation clearance being less than one times the excavation diameter, including cases where the clearance is zero) and with a new structure crossing an existing rail transit structure at an angle of less than 30 degrees. The core reason for this is that no corresponding construction method has been found.

[0008] The reason why long-distance oblique crossings with extremely small clearances are difficult to achieve in the current engineering field is that the core technical challenge lies in deformation control. Taking Beijing as an example, the allowable deformation control values ​​for underground structures of operating rail transit are 3mm settlement and 2mm uplift. Taking the relatively easier-to-achieve vertical crossing of underground structures of newly built rail transit through underground structures of operating rail transit as another example, the excavation area per meter of single-line track in such crossing projects is typically 35-50㎡, and the excavation volume is 350-500m³. 3 Achieving millimeter-level deformation control under such massive excavation conditions is unimaginably difficult. Failure to meet these deformation control values ​​will lead to structural damage, track deformation, and compromised train safety. Given the high capacity and large number of passengers in rail transit, the consequences of any safety incident would be disastrous.

[0009] In addition to the above characteristics, long-distance oblique crossings with extremely small clearances also feature long crossing times, large excavation volumes, and short distances. It is well known that environmental deformation caused by underground engineering excavation (deformation of the soil within the impact zone of a new construction project, and all underground structures including operating rail transit, during the excavation period is called environmental deformation) is related to excavation time, excavated volume, and clearance. According to experience in underground engineering construction, the longer the excavation time, the larger the excavated volume, and the smaller the vertical clearance, the greater the resulting environmental deformation. In the case of long-distance, small-angle crossings, the excavation time can be 5 to 10 times longer than that of vertical crossings, and the excavated volume can reach 2450 to 3500 m³. 3 (Equivalent to the size of two units in a six-story residential building) and above, and because the net distance is too small and there is no settlement buffer space, its settlement deformation is difficult to meet the operational safety requirements.

[0010] In the third phase of Beijing's subway planning, some projects, due to objective construction constraints, must cross existing operating lines at long, oblique angles with extremely small clearances. The feasibility of these projects is difficult to assess due to current existing line crossing technology, thus hindering the high-quality implementation of Beijing's urban planning. The root cause is the lack of a method for achieving long, oblique crossings with extremely small clearances across existing rail transit lines.

[0011] Therefore, in view of the above-mentioned deficiencies, the inventors of this invention, through dedicated research and determination, and by integrating their long-term experience and achievements in related industries, have developed an active control method for long-distance oblique crossings of existing underground structures of rail transit with ultra-small clearance, in order to overcome the above-mentioned deficiencies. Summary of the Invention

[0012] The purpose of this invention is to provide an active control method for long-distance oblique crossings of existing underground rail transit structures with ultra-small clearance, solving the problem that traditional construction methods for crossing existing underground rail transit structures cannot achieve long-distance oblique crossings of existing operating lines with ultra-small clearance. Furthermore, this method features a clear and controllable active control system, enabling proactive control of deformation of the existing line.

[0013] To achieve the above objectives, this invention discloses an active control method for long-distance oblique crossings of existing underground structures of rail transit with ultra-small clearance, characterized by the following steps:

[0014] Step 1: Collect archived data on the underground structure of the existing rail transit system, and conduct on-site surveys to determine the planar and vertical locations of the underground structure of the existing rail transit system, the geomechanical parameters of the strata, the geometric dimensions of the existing rail transit structure, and relevant information about the track structure.

[0015] Step 2: Conduct a current status inspection of the existing rail transit structure and track structure, evaluate the current mechanical properties of both, and assess their ability to continue deforming based on information such as the degree of crack development, carbonization, and steel corrosion. After the structure continues to deform, determine the control value W for continued structural deformation.

[0016] Step 3: After determining the structural deformation control value W of the existing operating rail transit underground structure, the active support structure system of the existing operating rail transit underground structure is determined. The active support structure system is used to ensure the safe operation of the existing line when the new structural project passes through the operating rail transit underground structure. It bears the soil load, track bed load, track load, vehicle load and all related civil engineering and equipment facilities loads above the existing operating rail transit underground structure. The active support structure system includes the determination of the structural support point location.

[0017] Step 4: After the lifting points are determined, the active lifting structure system is determined. The active lifting structure system consists of the existing underground structure of the operating rail transit and the lifting structure. The lifting structure is divided into a vertical lifting structure and a horizontal lifting structure. The vertical lifting structure is set at the lifting points, and the horizontal lifting structure is set on the upper part of the vertical lifting structure.

[0018] Step 5: After the active support structure system is determined, construction will begin on the new rail transit structure crossing the existing operating rail transit structure.

[0019] Wherein: the structural deformation control value W is taken as the minimum value among the deformation limit W1 corresponding to the bearing capacity, the deformation limit W2 corresponding to the deformation of the structural component, the deformation limit W3 corresponding to the existing structural cracks, and the deformation limit W4 corresponding to the train driving safety.

[0020] Among them: the deformation limit W1 corresponding to the bearing capacity is analyzed by establishing a load structure model through finite element software to simulate the deformation of the structure during the crossing process. When any of the bending moment, shear force and axial force generated in the operating structure and track is about to exceed the limit under the deformation action, the corresponding deformation value is the deformation limit W1 corresponding to the bearing capacity.

[0021] The deformation limit W2 corresponding to the deformation limit value of the structural member is analyzed by establishing a load structure model using finite element software. The analysis simulates the deformation of the structure during the crossing process. The deformation of each beam, slab, and column member under this deformation is statistically recorded. The statistical record results are compared and analyzed with the member deformation limit value in the original drawings. The deformation limit corresponding to the member deformation limit value in the original drawings for any member of each beam, slab, and column is W2.

[0022] The deformation limit W3 corresponding to durability is analyzed by establishing a load structure model using finite element software. The analysis simulates the deformation of the structure during the crossing process and calculates the crack value of each beam, slab, and column component under this deformation. The statistical records are compared with the crack limit in the original drawings. The deformation limit corresponding to any crack in any beam, slab, or column component that reaches the crack limit in the original drawings is W3.

[0023] The deformation limit W4 for train operation safety requirements is determined by analyzing the allowable value of track deformation. Since the track is in close contact with the structure, the allowable value of track deformation is directly equated to W4.

[0024] Among them, the determination of the support point location should take into account the impact of subsequent support structure construction on the safety of existing operating rail transit lines, and avoid construction being too close to the facilities of operating rail transit vehicles, overhead contact lines, and cables, which would affect the operational safety of existing lines. At the same time, the determination of the support point location should reduce the damage to the support structure caused by subsequent construction of new structural projects.

[0025] Among them, the vertical support structure should take into account the impact of construction on the operational safety of existing lines, with a focus on the impact of construction machinery standing and construction on operating trains and equipment, and construction safety isolation measures should be set up.

[0026] Among them: the width of the transverse support structure should be determined after taking all vertical loads P1, P2, P3... in the area served by each support structure, and then performing local pressure verification based on P1, P2, P3... to ensure that the bearing capacity and durability of the existing rail transit structure do not exceed the limits.

[0027] Among them, each horizontal support structure is equipped with no fewer than 2 hydraulic jacks.

[0028] Step 5 includes the following implementation steps;

[0029] Step 5.1: Construct a vertical support structure at the designated support point. The vertical support structure is constructed manually using a small vertical shaft. During the excavation of the vertical support structure, support is provided by a combination of vertical steel grating and shotcrete. A steel casing is installed inside the vertical support structure that needs to be removed later.

[0030] Step 5.2: Set up a transverse support structure inside the vertical support structure. The initial support sidewall and bottom plate of the transverse support structure at the hydraulic jack position adopt a steel grid and shotcrete U-shaped structure. After the initial support of the transverse support structure is closed, put the transverse steel cage of the lower force system inside. Set the pre-embedded hydraulic jack fixing support above it. Set the reserved installation position of the movable steel above and install the movable steel structure. Set the hydraulic jack at the position of the pre-embedded hydraulic jack fixing support.

[0031] Step 5.3: Construct an inter-anchored steel cage within the vertical support structure. The inter-anchored steel cage, together with the steel bars anchored into the transverse steel cage in the transverse support structure and the reinforcing bars inside the all-steel casing, forms an inter-anchored steel structure. After construction, pour concrete to form an integral vertical support structure up to the position of the transverse support hydraulic jack base, thus forming the active support structure system.

[0032] Step 5.4: Construct the advanced support for the new rail transit structure and carry out the initial support construction for the new structure. The construction adopts the equal step method of upper and lower steps.

[0033] Step 5.5: During the excavation of the new rail transit structure, real-time settlement monitoring shall be conducted;

[0034] Step 5.6: Low-pressure grouting is performed on the soil beneath the existing line through the grouting pipe;

[0035] Step 5.7: Continue construction until the new waterproofing and permanent structure are completed;

[0036] Step 5.8: In the area where hydraulic jacks are installed, replace the hydraulic jacks with a structure that supports steel shims with steel support profiles;

[0037] Step 5.9: Pour the concrete of the vertical support structure shaft to form a plain concrete structure to the natural ground, completing all construction.

[0038] In step 5.8, first add the supporting steel support pads. After the support is firm, unload the hydraulic jack and remove it.

[0039] Specifically, the sections were extracted based on monitoring results to ensure the safety of existing line settlement control.

[0040] As can be seen from the above, the active control method for long-distance oblique crossings of existing underground structures of rail transit with ultra-small clearance of the present invention has the following effects:

[0041] 1. The deformation control system consists of two core systems and one auxiliary system. The first core system is the support structure system, and the second core system is the active control system. The auxiliary system involves step-by-step excavation, such as upper and lower steps, and can be omitted if the settlement control effect is good. The support structure system used in this paper is unique to this method, as is the setting method of the active control system. The auxiliary system can also be found in other crossing methods.

[0042] 2. The core system of this method is a pure structural system. Compared with most deformation protection systems formed by deep hole grouting or freezing in the past for underground structures crossing existing operating rail transit, it is calculable (the settlement control effect formed by deep hole grouting and freezing measures cannot be accurately calculated theoretically). Therefore, its deformation control mechanism is simpler and clearer.

[0043] 3. Deformation control is simple and straightforward, operation is easy, and cost and construction period are controllable.

[0044] 4. The main deformation protection measures are vertical and horizontal support structures plus hydraulic jacks. The active protection system formed by this is unique. However, it is based on mature technology, and the operation is not difficult and the amount of engineering work is very small (compared with most of the relatively mature vertical crossing technologies, the amount of cement and steel used is less). At the same time, the hydraulic jacks used can be removed and reused, so it is simple, cost and construction period are controllable.

[0045] The details of this invention will become apparent from the following description and the accompanying drawings. Attached Figure Description

[0046] Figure 1 The steps of the active control method for long-distance oblique crossing of existing underground structures of rail transit with ultra-small clearance shown in this invention are illustrated. Figure 1 .

[0047] Figure 2 The steps of the present invention are shown. Figure 2 .

[0048] Figure 3 The steps of the present invention are shown. Figure 3 .

[0049] Figure 4 The steps of the present invention are shown. Figure 4 .

[0050] Figure 5 The steps of the present invention are shown. Figure 5 .

[0051] Figure 6 The steps of the present invention are shown. Figure 6 .

[0052] Figure 7 The steps of the present invention are shown. Figure 7 .

[0053] Figure 8 Showing Figure 7 A partially enlarged schematic diagram.

[0054] Figure 9 A schematic diagram of the crossing structure of the present invention is shown.

[0055] Figure 10 A schematic diagram of the method of the present invention is shown.

[0056] Figure label:

[0057] 101. Existing rail transit structure; 102. New rail transit structure; 103. Support structure; 10. Vertical support structure; 11. Vertical steel grating with shotcrete structure; 12. Steel casing; 13. Vertical reinforcing cage; 14. Vertical concrete pouring; 15. Reinforcing bars anchored together; 16. Plain concrete structure; 20. Horizontal support structure; 21. Horizontal reinforcing cage; 22. Reserved installation position for movable steel; 23. Pre-embedded hydraulic jack fixing support; 24. Movable steel structure; 25. Hydraulic jack; 26. Steel shims; 27. Supporting steel; 31. Upper step; 32. Lower step; 33. Initial support for new structure; 34. Advanced support; 35. Welded structure; 36. Grouting pipe. Detailed Implementation

[0058] See Figure 1 and Figure 2 This invention demonstrates an active control method for long-distance oblique crossings of existing underground structures of rail transit with ultra-small clearance.

[0059] The method of this invention is suitable for the construction of underground crossing projects for rail transit, such as... Figure 9 As shown, the newly constructed rail transit structure 102 passes through the existing rail transit structure 101. The newly constructed rail transit structure 102 is excavated in the direction of the arrow. Multiple supporting structures 103 are measured and installed in the section of the existing rail transit structure 101 that passes through it. This invention is applicable to the following situations.

[0060] (1) Underground structures of operating rail transit, or other similar underground structures.

[0061] (2) Existing operational rail transit structures are rigid continuous structures, such as cast-in-place reinforced concrete frame structures.

[0062] (3) The base plate of the existing operating rail transit structure is a flat plate or a structure similar to a flat plate.

[0063] (4) The crossing method is a long-distance oblique crossing with ultra-small clearance or other oblique crossings.

[0064] (5) The burial depth of the existing rail transit structure shall not exceed 20m.

[0065] The active control method for long-distance oblique crossings of existing underground structures of rail transit with ultra-small clearance according to the present invention includes the following steps:

[0066] Step 1: Collect archived data on the underground structures of the existing rail transit system, and conduct on-site surveys. Determine the planar and vertical locations of the existing underground structures of the operating rail transit system, the geomechanical parameters of the strata, the geometric dimensions of the existing rail transit structure 101, track structure, and other relevant information.

[0067] Step Two: Conduct a current status inspection of the existing rail transit structure 101 and the track structure, evaluate their current mechanical properties, and assess their ability to continue deforming based on information such as the degree of crack development, carbonization, and steel reinforcement corrosion. The assessment of continued deformation capacity is based on calculations performed according to current national standards. After continued deformation, the existing rail transit structure and track structure must meet requirements for load-bearing capacity, structural component deformation limits, durability, and train safety. The maximum deformation value that simultaneously meets these requirements after continued deformation is the structural continued deformation control value W. In one embodiment, the structural continued deformation control value W is determined according to the following method.

[0068] The deformation limit corresponding to the bearing capacity (W1) is calculated by establishing a load-bearing structural model using finite element software. The analysis simulates the deformation of the structure during the crossing process. When any of the bending moment, shear force, or axial force generated in the operational structure and track is about to exceed the limit under deformation, the corresponding deformation value is the deformation limit W1 corresponding to the bearing capacity.

[0069] The deformation limit corresponding to the structural component deformation limit values ​​(v1, v2, v3, etc.) (referred to as W2) is analyzed using a load-bearing structural model built with finite element software. The analysis simulates the deformation of the structure during the crossing process. The deformation of each beam, slab, column, and other structural component under this deformation is statistically recorded. The statistical records are compared with the component deformation limit values ​​in the original drawings. The deformation limit corresponding to any component in the beam, slab, column, etc., that reaches the component deformation limit value in the original drawings is defined as W2.

[0070] The deformation limit corresponding to durability (W3) is calculated by establishing a load-bearing structural model using finite element software. The analysis simulates the deformation of the structure during the crossing process, calculating the crack value of each beam, slab, column, and other structural member under this deformation. The statistically recorded results are compared with the crack limits in the original drawings. The deformation limit corresponding to any crack in any beam, slab, column, or other structural member reaching the crack limit in the original drawings is defined as W3.

[0071] The deformation limit (W4) for train operation safety requirements is calculated by analyzing the allowable track deformation value. Since the track is in close contact with the structure, the allowable track deformation value is directly equated to W4.

[0072] The minimum value among W1, W2, W3, and W4 is taken as the control value W for continued structural deformation.

[0073] Step 3: After determining the control value W for the continued deformation of the existing operational rail transit underground structure, the determination of the active support structure system for the existing operational rail transit underground structure begins. The active support structure system is used when a new structural project passes through the underground structure of an operational rail transit line to ensure the safe operation of the existing line. It bears the soil load, track bed load, track load, vehicle load, and the loads of all related civil engineering and equipment facilities in the extended track area above the existing operational rail transit underground structure. The determination of this active support structure system may include the following:

[0074] 3.1 Determine the structural support points. The support points should be determined as follows:

[0075] The determination of the support point location should take into account the impact of subsequent support structure construction on the safety of existing operating rail transit lines, and avoid construction being too close to operating rail transit vehicles, overhead contact lines, cables and other facilities, which could affect the operational safety of existing lines. At the same time, the determination of the support point location should minimize the damage to the support structure caused by subsequent construction of new structures.

[0076] 3.2 After locating the support points according to the principles outlined above, calculation and analysis are performed. The analysis uses a load-structure model, which only includes the existing underground structure of the operational rail transit system. Constraints limiting vertical displacement are applied at the support points, while foundation springs are used at other locations. Foundation springs at excavation locations are treated as failure points, and the load is applied according to the actual load. If any of the following situations occur after the calculation and analysis, the support point locations must be determined again, and the layout adjusted, including reducing the distance between support points, until the requirements are met.

[0077] ① The structure does not meet the requirements for determining the load-bearing capacity.

[0078] ②The structure continues to deform beyond 30% of the control value W.

[0079] Step Four: After determining the lifting points, the active lifting structure system is determined. The active lifting structure system consists of the existing underground structure of the operating rail transit and the lifting structure 103, wherein the lifting structure is divided into a vertical lifting structure and a horizontal lifting structure. The vertical lifting structure is located at the lifting points, and the horizontal lifting structure is located on top of the vertical lifting structure.

[0080] The vertical support structure is determined as follows.

[0081] The determination of the construction should take into account the impact on the operational safety of existing lines, with a focus on the impact of construction machinery placement and construction on operating trains and equipment. Construction safety isolation measures should be implemented where necessary.

[0082] Under the premise of ensuring operational safety, large-scale machinery should be given priority in construction. When there are operational safety hazards in the use of large-scale machinery, such as machinery tipping or steel cage hoisting, manual construction should be used.

[0083] The planar dimensions of the vertical support structure should be as small as possible to avoid subsequent structural demolition.

[0084] Since it is inevitable to remove the vertical support structure when crossing the existing underground structure of rail transit over a long distance, it is necessary to make proper arrangements for pre-embedding in the design.

[0085] The vertical support structure should possess sufficient vertical bearing capacity and deformation resistance. The vertical bearing capacity is achieved through the friction between the structure and the soil, as well as the end bearing capacity. The calculation of bearing capacity and deformation resistance is based on the "Code for Determination of Building Foundations" and the "Code for Technical Specification of Building Pile Foundations".

[0086] The lateral support structure is determined as follows.

[0087] First, the width of the components of the lateral support structure should be considered from the following factors;

[0088] The loads are taken as all vertical loads P1, P2, P3... in the area served by each supporting structure. Based on P1, P2, P3..., the local pressure is checked. Under the premise of ensuring that the bearing capacity and durability index of the existing rail transit structure do not exceed the limit, the required widths W1, W2, W3... of the transverse supporting structure are obtained.

[0089] Determine the hydraulic jack layout. To ensure uniform jacking, at least two hydraulic jacks should be installed in each lateral support structure. Based on the specific widths of W1, W2, W3, etc., install as many hydraulic jacks as possible within the space available. This will determine the number of hydraulic jacks at each lateral support position. Divide P1, P2, P3, etc. by the number of hydraulic jacks to determine the model of the hydraulic jacks.

[0090] Step 5: After the active support structure system is determined, the construction of the new rail transit structure passing through the existing operating rail transit structure will be carried out, which may include the following implementation steps;

[0091] Step 5.1, as follows Figure 1 and Figure 2 As shown, a vertical support structure 10 is constructed at the designated support point. To maximize the safety of the existing line, a small, manually constructed shaft is recommended for the vertical support structure 10, with a recommended inner diameter of 1200mm. During the excavation of the vertical support structure, a vertical steel grating plus shotcrete structure 11 is used for support. The vertical steel grating plus shotcrete structure 11 includes a vertical steel reinforcement cage 13 and vertically poured concrete 14. The depth of the shaft excavation is determined by the continued deformation control value W, based on settlement analysis. The settlement analysis must consider the influence of soil skin friction and end resistance.

[0092] A steel casing 12 is installed inside the vertical support structure (which will conflict with the new structure) that needs to be removed later. The inner diameter of the all-steel casing 12 is preferably 1200mm. It is positioned 350mm along the excavation direction of the vertical support structure 10 at the initial support connection point of the new structure. At this location, the vertical steel grating and shotcrete structure 11 is not installed. To increase the stability of the steel casing 12, internal reinforcing bars can be added (the reinforcing bars should avoid conflicting with the main reinforcing bars of the subsequent support structure). Simultaneously, it is connected to the vertical steel grating and shotcrete structure 11 via longitudinal connecting bars (see...). Figure 1 ).

[0093] Step 5.2, as follows Figure 2 and Figure 3 As shown, a horizontal support structure 20 is provided within the vertical support structure 10. The horizontal support structure 20 is formed by excavating inward from the upper end of the vertical support structure 10, and its specific construction is as follows:

[0094] Step four determined the component width of the transverse support structure and the arrangement of the hydraulic jacks. Based on the component widths W1, W2, W3... of the transverse support structure, the width of the clear space inside the excavation was determined by adding 200mm to each. The initial support sidewall and bottom plate of the transverse support structure where the hydraulic jacks are located adopt a U-shaped structure of steel grating and shotcrete.

[0095] After the initial support of the transverse support structure is closed, the transverse steel cage of the lower load-bearing system is placed inside (the transverse steel cage can be anchored into the vertical support structure with anchor bars) and concrete is poured. After the concrete is poured and reaches the required strength, a pre-embedded hydraulic jack fixing support 23 is set on top of it, and a reserved movable steel installation position 22 is set on top of it.

[0096] The transverse support top plate adopts a movable steel structure 24, which is equipped with a constraint mechanism, allowing only vertical displacement, but not horizontal displacement or rotation.

[0097] Hydraulic jacks 25 are installed at the positions of the pre-embedded hydraulic jack fixing supports 23. The number of jacks is determined according to the previous content. The pre-embedded hydraulic jack fixing supports 23 prevent the hydraulic jacks 25 from shifting after being subjected to force.

[0098] Step sequence 5.3 (see) Figure 2 , Figure 3 Anchored steel cages are constructed within the vertical support structure. These cages, along with the steel bars anchored into the transverse support structure and the reinforcing bars within the all-steel casing, form a mutually anchored steel structure. After the anchored steel cages are completed, concrete is poured to form an integral vertical support structure extending to the base of the transverse support hydraulic jacks. The vertical and transverse support structures together form an integrated support structure. This structure is used to support existing rail transit structures after excavation, preventing settlement caused by the excavation. Hydraulic jacks are used for active jacking of the existing line. At this point, the entire active support structure system is complete.

[0099] Step sequence 5.4 (see) Figure 4 ): Construct advanced support 34 for the new rail transit structure. Carry out the initial support 33 for the new structure, using an equal-step method with upper steps 31 and lower steps 32 to minimize impact on the existing line. The initial support uses steel grating and shotcrete.

[0100] When the newly constructed rail transit structure does not conflict with the vertical support structure, it can be excavated independently and formed as a ring independently.

[0101] When the newly constructed rail transit structure begins to conflict with the vertical support structure, the initial support 33 of the new structure is separated, and weldable node plates are installed on the steel grid. The node plates are connected to the pre-reserved steel casing in the vertical support structure by welding structure 35, so as to achieve early closure and control risks and reduce settlement.

[0102] Step sequence 5.5 (see) Figure 4 During the excavation of a new rail transit structure, settlement monitoring should be carried out in real time. If the deformation of the existing rail transit structure exceeds the limit of its continued deformation capacity, hydraulic jacks should be used to lift the existing rail transit structure to ensure that its deformation does not exceed the limit.

[0103] Step sequence 5.6 (see) Figure 5 Low-pressure grouting is performed on the soil beneath the existing line through grouting pipe 36 to replenish the lost soil in a timely manner and ensure that no further settlement occurs after the work is completed. To ensure the settlement control effect, cement-based grout must be used.

[0104] Step 5.7 (see) Figure 6 Continue construction until the new waterproofing and permanent structure are completed.

[0105] Step 5.8 (see) Figure 7 In areas where hydraulic jacks are installed, a structure using supporting steel profiles 27 to support steel shims 26 replaces the hydraulic jacks, thereby removing them and saving on project investment. The following requirements must be met during construction;

[0106] ① First, add the supporting steel 27 and the supporting steel shims 26. After the support is firm, unload the hydraulic jack and remove the hydraulic jack.

[0107] ②The sections should be removed in stages based on the monitoring results to ensure the safety of settlement control of the existing line.

[0108] Step 5.9 (see) Figure 7 ): The vertical support structure is poured with concrete to form a plain concrete structure 16 to the natural ground, completing all construction.

[0109] Therefore, this invention, through its unique deformation control system, can achieve settlement control effects that other crossing methods cannot, thereby ensuring the operational safety of existing rail transit lines during the crossing construction. At the same time, it is simple to operate, and its cost and construction period are controllable.

[0110] Compared with other methods for traversing the underground structures of existing operational rail transit systems, this invention has the following characteristics:

[0111] 1. The deformation control system consists of two core systems and one auxiliary system. The first core system is the support structure system, and the second core system is the active control system. The auxiliary system involves step-by-step excavation, such as upper and lower steps, and can be omitted if the settlement control effect is good. The support structure system used in this paper is unique to this method, as is the setting method of the active control system. The auxiliary system can also be found in other crossing methods.

[0112] 2. The core system of this method is a pure structural system. Compared with most deformation protection systems formed by deep hole grouting or freezing in the past for underground structures crossing existing operating rail transit, it is calculable (the settlement control effect formed by deep hole grouting and freezing measures cannot be accurately calculated theoretically). Therefore, its deformation control mechanism is simpler and clearer.

[0113] 3. Deformation control is simple and straightforward, operation is easy, and cost and construction period are controllable.

[0114] 4. The main deformation protection measures are vertical and horizontal support structures plus hydraulic jacks. The active protection system formed by this is unique. However, it is based on mature technology, and the operation is not difficult and the amount of engineering work is very small (compared with most of the relatively mature vertical crossing technologies, the amount of cement and steel used is less). At the same time, the hydraulic jacks used can be removed and reused, so it is simple, cost and construction period are controllable.

[0115] It is obvious that the above description and account are merely illustrative and not intended to limit the disclosure, application, or use of this invention. Although embodiments have been described and illustrated in the accompanying drawings, the invention is not limited to the specific examples exemplified by the drawings and described in the embodiments as currently considered the best mode for carrying out the teachings of the invention. The scope of the invention will include any embodiments falling within the foregoing description and the appended claims.

Claims

1. An active control method for long-distance oblique crossings of existing underground structures of rail transit with ultra-small clearance, characterized in that... Includes the following steps: Step 1: Collect archived data on the underground structure of the existing rail transit system, and conduct on-site surveys to determine the planar and vertical locations of the underground structure of the existing rail transit system, the geomechanical parameters of the strata, the geometric dimensions of the existing rail transit structure, and relevant information about the track structure. Step 2: Conduct a current status inspection of the existing rail transit structure and track structure, evaluate the current mechanical properties of both, and assess their ability to continue deforming based on information such as the degree of crack development, carbonization, and steel corrosion. After the structure continues to deform, determine the control value W for continued structural deformation. Step 3: After determining the structural deformation control value W of the existing operating rail transit underground structure, the active support structure system of the existing operating rail transit underground structure is determined. The active support structure system is used to ensure the safe operation of the existing line when the new structural project passes through the operating rail transit underground structure. It bears the soil load, track bed load, track load, vehicle load and all related civil engineering and equipment facilities loads above the existing operating rail transit underground structure. The active support structure system includes the determination of the structural support point location. Step 4: After the lifting points are determined, the active lifting structure system is determined. The active lifting structure system consists of the existing underground structure of the operating rail transit and the lifting structure. The lifting structure is divided into a vertical lifting structure and a horizontal lifting structure. The vertical lifting structure is set at the lifting points, and the horizontal lifting structure is set on the upper part of the vertical lifting structure. Step 5: After the active support structure system is determined, construction will begin on the new rail transit structure crossing the existing operating rail transit structure. Its characteristic is that step five includes the following implementation steps; Step 5.1: Construct a vertical support structure at the designated support point. The vertical support structure is constructed manually using a small vertical shaft. During the excavation of the vertical support structure, support is provided by a combination of vertical steel grating and shotcrete. A steel casing is installed inside the vertical support structure that needs to be removed later. Step 5.2: Set up a transverse support structure inside the vertical support structure. The initial support sidewall and bottom plate of the transverse support structure at the hydraulic jack position adopt a steel grid and shotcrete U-shaped structure. After the initial support of the transverse support structure is closed, put the transverse steel cage of the lower force system inside. Set the pre-embedded hydraulic jack fixing support above it. Set the reserved installation position of the movable steel above and install the movable steel structure. Set the hydraulic jack at the position of the pre-embedded hydraulic jack fixing support. Step 5.3: Construct an inter-anchored steel cage within the vertical support structure. The inter-anchored steel cage, together with the steel bars anchored into the transverse steel cage in the transverse support structure and the reinforcing bars inside the all-steel casing, forms an inter-anchored steel structure. After construction, pour concrete to form an integral vertical support structure up to the position of the transverse support hydraulic jack base, thus forming the active support structure system. Step 5.4: Construct the advanced support for the new rail transit structure and carry out the initial support construction for the new structure. The construction adopts the equal step method of upper and lower steps. Step 5.5: During the excavation of the new rail transit structure, real-time settlement monitoring shall be conducted; Step 5.6: Low-pressure grouting is performed on the soil beneath the existing line through the grouting pipe; Step 5.7: Continue construction until the new waterproofing and permanent structure are completed; Step 5.8: In the area where hydraulic jacks are installed, replace the hydraulic jacks with a structure that supports steel shims with steel support profiles; Step 5.9: Pour the concrete of the vertical support structure shaft to form a plain concrete structure to the natural ground, completing all construction.

2. The active control method for long-distance oblique crossing of existing underground structures of rail transit with ultra-small clearance as described in claim 1, characterized in that: The structural deformation control value W is taken as the minimum value among the following: the deformation limit W1 corresponding to the bearing capacity, the deformation limit W2 corresponding to the deformation of the structural components, the deformation limit W3 corresponding to the cracks in the existing structure, and the deformation limit W4 corresponding to the train driving safety.

3. The active control method for long-distance oblique crossing of existing underground structures of rail transit with ultra-small clearance as described in claim 2, characterized in that: The deformation limit W1 corresponding to the bearing capacity is analyzed by establishing a load structure model using finite element software to simulate the deformation of the structure during the crossing process. When any of the bending moment, shear force and axial force generated in the already operational structure and track is about to exceed the limit under the deformation action, the corresponding deformation value is the deformation limit W1 corresponding to the bearing capacity. The deformation limit W2 corresponding to the deformation limit value of the structural member is analyzed by establishing a load structure model using finite element software. The analysis simulates the deformation of the structure during the crossing process. The deformation of each beam, slab, and column member under this deformation is statistically recorded. The statistical record results are compared and analyzed with the member deformation limit value in the original drawings. The deformation limit value corresponding to the member deformation limit value in the original drawings for any member of each beam, slab, and column is W2. The deformation limit W3 corresponding to durability is analyzed by establishing a load structure model using finite element software. The analysis simulates the deformation of the structure during the crossing process and calculates the crack value of each beam, slab, and column component under this deformation. The statistical records are compared with the crack limit in the original drawings. The deformation limit corresponding to any crack in any beam, slab, or column component that reaches the crack limit in the original drawings is W3. The deformation limit W4 for train operation safety requirements is determined by analyzing the allowable value of track deformation. Since the track is in close contact with the structure, the allowable value of track deformation is directly equated to W4.

4. The active control method for long-distance oblique crossing of existing underground structures of rail transit with ultra-small clearance as described in claim 1, characterized in that: The determination of the support point location should take into account the impact of subsequent support structure construction on the safety of existing operating rail transit lines, and avoid construction being too close to facilities such as operating rail transit vehicles, overhead contact lines, and cables, which could affect the operational safety of existing lines. At the same time, the determination of the support point location should minimize the damage to the support structure caused by subsequent construction of new structural works.

5. The active control method for long-distance oblique crossing of existing underground structures of rail transit with ultra-small clearance as described in claim 1, characterized in that: The vertical support structure should take into account the impact of construction on the operational safety of existing lines, with a focus on the impact of construction machinery standing and construction on operating trains and equipment, and construction safety isolation measures should be set up.

6. The active control method for long-distance oblique crossing of existing underground structures of rail transit with ultra-small clearance as described in claim 1, characterized in that: The width of the transverse support structure should be determined after taking all vertical loads P1, P2, P3... in the area served by each support structure, and then performing local pressure verification based on P1, P2, P3... to ensure that the load-bearing capacity and durability of the existing rail transit structure do not exceed the limits.

7. The active control method for long-distance oblique crossing of existing underground structures of rail transit with ultra-small clearance as described in claim 1, characterized in that: Each lateral support structure shall be equipped with no fewer than two hydraulic jacks.

8. The active control method for long-distance oblique crossing of existing underground structures of rail transit with ultra-small clearance as described in claim 1, characterized in that: In step 5.8, first add the supporting steel support shims. After the support is firm, unload the hydraulic jack and remove it.

9. The active control method for long-distance oblique crossing of existing underground structures of rail transit with ultra-small clearance as described in claim 1, characterized in that: The sections were removed based on monitoring results to ensure the safety of existing line settlement control.

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