Design and construction method for newly-built multi-story building over rail transit operation tunnel

Abstract

The invention relates to a design and construction method of a newly-built multi-story building right above a rail transit operation tunnel, and provides a construction method of constructing a vertical supporting system in advance for a small vertical shaft, inversely constructing an underground structure beam plate, sequentially constructing an overground structure beam plate column and excavating a soil body under a first-story plate in a layered manner, which effectively corresponds to a calculation method provided by the invention, and the construction method is simple and mature in process. Compared with other methods close to a new project of rail transit, the method is mainly used for reasonably adjusting construction procedures, so that the method is small in price increasing investment, and good economic benefits are obtained; meanwhile, the method for newly building the multi-story building above the rail transit is comprehensively elaborated in seven aspects of story number design, story height design, main body structure design, foundation design, aseismic design, durability design and vibration reduction design, and the system is complete and comprehensive; and a whole set of solution is provided for newly building a multi-story building right above a rail transit operation tunnel in China, so that the development and utilization of the high-value soil body become possible.

Description

Technical Field

[0001] The present invention relates to the technical field of rail transit construction, and in particular to a design and construction method for a new multi-story building directly above a rail transit operating tunnel. Background Art

[0002] New construction projects around operating rail transit will cause vertical displacement (settlement or uplift) of the track and structure. After the displacement occurs, the height of the track fasteners can generally be adjusted to restore the original track surface elevation. Compared with new construction projects that cause settlement when crossing under the rail transit, construction directly above will cause significant uplift of the rail transit tunnel. The rail fasteners have little ability to cope with uplift deformation. The uplift deformation allowed for operational safety is only 3mm, while the adjustment value of the fasteners to cope with settlement can reach 20mm. Especially for operating tunnels with deformation joints, they are weak points for track, structural connection and water leakage. The differential deformation on both sides of the deformation joints caused by the construction above greatly increases the difficulty of project implementation. If the track uplift disease already exists before the crossing construction, the rail transit operating unit will directly prohibit such construction projects directly above. How to solve the construction problem directly above the operating tunnel, or even the construction problem of new construction projects that are long distances (more than 2 times the width of the operating tunnel) and run in the same direction with the operating tunnel and with small spacing (vertical distance less than 2m), is a technical problem that needs to be solved in my country.

[0003] For partial crossing or vertical crossing projects above, the main solution at this stage is to use a post-made cover structure to achieve a certain inhibitory effect on the vertical uplift of the operating tunnel (such as patent: A method for excavating a foundation pit above an operating rail transit tunnel (authorization announcement number: CN104532849B)), but this type of solution does not solve the problem of reducing the load above from the root, so the operating tunnel will continue to float up during the excavation process, especially in areas with poor soil properties, the above solution cannot be applied. At the same time, the above solution has no active control measures, nor can it achieve dynamic control of the uplift deformation of the operating tunnel during the excavation process. Therefore, the above solution cannot solve the problem of excavation unloading directly above the tunnel. Since the above measures are not ideal for controlling uplift, they are even more unable to deal with the problem of constructing new multi-story buildings directly above the operating tunnel, long distances, and small spacing.

[0004] To this end, in view of the above-mentioned defects, the designers of the present invention have conducted intensive research and design, and integrated the experience and achievements of long-term engagement in related industries to develop a design and construction method for building a new multi-story building directly above a rail transit operating tunnel to overcome the above-mentioned defects. Summary of the invention

[0005] The purpose of the present invention is to provide a design and construction method for a new multi-story building directly above a rail transit operating tunnel, which effectively solves the problem that engineering construction cannot be carried out above an existing operating tunnel. By dynamically controlling the vertical deformation during the excavation process, it is possible to construct new multi-story buildings directly above the operating tunnel, in a long-distance forward direction, and at a small spacing. While ensuring the safety of rail transit operations, the utilization value of available urban core land is released, urban functions are improved, and the quality of urban living is improved.

[0006] To achieve the above-mentioned purpose, the present invention discloses a design and construction method for a new multi-story building directly above a rail transit operating tunnel, which is applicable to shield tunneling, mining, and open-cut tunnel construction, and is characterized in that it comprises the following steps: Step 1: Determine the allowable deformation value of the operating tunnel; Step 2: Develop monitoring plans and arrange monitoring points; Step 3: Based on the deformation control value determined in step 1, carry out the design of the number of floors, floor height, main structure, foundation, vertical clearance with existing tunnels, durability, earthquake resistance and vibration reduction of the building; Step 4: forming a cement soil reinforcement body around the tunnel. The cement soil reinforcement body is constructed by triaxial mixing piles, rotary grouting piles, TRD or CSM to form a portal frame structure having a top surface and a support section extending downward from the top surface to the tunnel periphery; Step 5: Construction of foundation pit support structure, implementation of foundation pit support piles along the outer contour of the building, foundation pit support method using support piles + anchor cables and double-row piles; Step 6: Construction of small vertical shaft at column position; Step 7: Construction of vertical support structure system; Step 8: Tie up the steel bars of the first floor slab, the steel bars of the main and secondary beams in the slab, and effectively connect them with the column head reinforcement before integrated pouring. After the first floor slab structure reaches the designed strength, use the excavation holes to excavate the soil under the slab, calculate the mass of the first floor slab, convert it into the soil layer thickness and excavate to this elevation. After excavating the earth, set up anchor cables, lay out waterproofing, tie up the side wall reinforcement and mechanically connect it with the side wall column reinforcement with steel sleeves, and then pour the concrete side wall. Step 9: Tie the remaining column reinforcement of the first floor to the second floor and throw the reinforcement, tie the second floor slab reinforcement, the main and secondary beam reinforcement in the slab, and effectively connect them with the column head reinforcement for integrated pouring; Step 10: Use the above method until the above-ground structure is capped and all earth excavation is completed. Finally, tie the basement floor reinforcement and mechanically connect it with the reserved reinforcement of the expanded foundation and then cast it as a whole. This completes the construction of a new multi-story building above the rail transit operation tunnel.

[0007] Wherein: Step 1 at least includes the following sub-steps: Step 1.1 Collect archived data on underground structures of existing rail transit, and conduct on-site surveys to clearly detect the plane and vertical positions of existing underground structures of existing rail transit, geomechanical parameters of the strata, geometric dimension information of existing rail transit structures, and information on track structures; Step 1.2: Conduct status inspection on the existing rail transit structure and track structure, evaluate the current mechanical properties of the two, and determine their ability to continue to deform based on information on the extent of crack development, concrete carbonization, steel corrosion, water leakage, track deformation, and fastener integrity. After continued deformation, the existing rail transit structure and track structure must meet the bearing capacity requirements, structural member deformation limit value requirements, durability, and train travel safety requirements. After the structure continues to deform, the minimum allowable deformation value that meets the bearing capacity requirements, structural member deformation limit value requirements, durability, and train travel safety requirements is the allowable deformation value of the operating tunnel.

[0008] Among them: the distance between the cement soil reinforcement body in step 3 and the existing tunnel shall not be less than 2m to avoid adverse disturbance to the soil around the tunnel caused by construction.

[0009] Among them: in step six, according to the designed column position, a locking ring beam is constructed, and the vertical shaft is constructed by the artificial excavation inverted shaft wall method, that is, as the vertical shaft is excavated 0.75m, the first locking foot anchor rod and the first horizontal annular support steel frame are constructed, which are connected to the locking ring beam upwards, and the excavation continues downward for 0.75m. The second locking foot anchor rod and the second horizontal annular steel frame support steel frame are constructed, and connected to the first steel frame through vertical connecting bars. C20 plain concrete is sprayed on the steel frames, and so on and the construction is carried out to the bottom of the pit to finally form a small vertical shaft at the column position.

[0010] Among them: In step seven, structural columns and expanded foundations under the columns are constructed in the vertical shaft. The thickness of the foundation is determined according to the shear bearing capacity of the column bottom. Connectors are reserved around it as the connection conditions between the air sill and the bottom plate. The structural columns and the expanded foundations under the columns are cast-in-place concrete structures. The top of the column is cast to the bottom of the first floor slab and reinforcement is thrown at the column head. After the structural columns and the foundation reach the design strength, fine sand is filled in the vertical shaft to the existing ground.

[0011] Among them: the ground height of the multi-story structure in the floor design shall not exceed 30m, the number of floors shall not exceed 8, the depth of the basement shall not exceed 10m, the number of floors shall not exceed 2, the number of underground floors is represented by i (i=1, 2...), the total number of underground floors is m, and the above-ground floors are represented by j (j=1, 2, 3, 4...), the total number of above-ground floors is n, in order to better establish the corresponding relationship between m and n.

[0012] Among them: In the floor height design, the first floor of the proposed building is divided into positive and negative zero, and the floor heights of each floor of the underground structure are , the height of each floor of the above-ground structure is , with the equal replacement of the load above the interval tunnel as the core, the relationship between the number of floors and the floor height must be as shown in formula (1): (one) In the formula: is the excavation depth of the underground structure foundation pit. , It is the absolute elevation of the first floor of the proposed building. It is the absolute elevation of the existing ground before excavation of the foundation pit. is the thickness of the cushion layer under the structural base plate, is the thickness of the structural base plate, k Excavation depth for basement d The stratigraphic sequence number within the range, is the density of the kth soil layer within the excavation range of the foundation pit, and the floating density is taken below the water level. Excavation depth for foundation pit The thickness of each layer of soil within the range of is the representative value of the equivalent uniformly distributed load on each layer of the underground structure, is the representative value of the equivalent uniformly distributed load on each floor of the above-ground structure, is the equivalent uniformly distributed load on the roof layer, According to the functional requirements of the building, first determine the total number of basement floors and floor heights. , put it into the above formula, and we can get the total number of floors of the above-ground structure n .

[0013] Among them: in the main structure design, the relationship between the height and number of underground structures and the number of above-ground structures is determined through the principle of equal replacement of soil unloading and building loads; the raft foundation is maintained in the foundation design without the need to change to a pile foundation; in the durability design, the thickness of the concrete protective layer is increased, the control requirements for raw materials are improved, and the allowable crack width is reduced, so that the durability design standards of buildings and tunnels are unified; in the seismic design, the seismic fortification standard of the building is not lower than that of the tunnel project below.

[0014] Among them: vibration reduction design includes the following aspects. First, the vertical clearance between the basement and the shield tunnel is reasonably determined based on the buried depth of the basement, and the clearance between the two is increased as much as possible. At the same time, the door frame type cement soil wall reinforcement is used around the interval. Due to the different impedance ratios between the soil and cement soil, the vibration waves will be reflected at the interface between the two, reducing the vibration energy transmitted to the building. Secondly, if the above two measures still cannot achieve the vibration reduction target, the building needs to adopt its own vibration reduction measures, including the installation of vibration reduction pads, vibration reduction springs or vibration reduction room-in-room structures under the bottom plate.

[0015] From the above content, it can be seen that the design and construction method of the new multi-story building directly above the rail transit operation tunnel of the present invention has the following effects: 1. For the first time, a total of seven aspects, including number of floors design, floor height design, main structure design, foundation design, earthquake-resistant design, durability design, and vibration reduction design, were proposed to comprehensively explain the methods of building new multi-story buildings above rail transit. The system is complete and comprehensive, providing a complete set of solutions for the construction of new multi-story buildings directly above my country's rail transit operating tunnels, making the development and utilization of such high-value soil possible.

[0016] 2. The design and calculation method for the number of floors, floor heights, main structures, and foundation proposed in the present invention based on the concept of "dynamic load balance" above rail transit has a mature theoretical basis and clear methods. During the implementation of the new project, the overall stability of the load above the rail transit operating tunnel is achieved and continued to the final state, providing theoretical and calculation support for the construction of new multi-story buildings above the interval tunnel.

[0017] 3. The construction method proposed in the present invention, which includes first constructing a vertical support system in a small shaft, reverse construction of underground structure beams and slabs + sequential construction of above-ground structure beams and slabs, and layered excavation of the soil under the first floor slab, effectively corresponds to the calculation method of the present invention, and the construction method is simple and the process is mature. Compared with other methods for new rail transit projects, the main method is the reasonable adjustment of the construction process, so the investment in the price increase of this method is very small, and good economic benefits have been achieved.

[0018] 4. The present invention proposes to set up a door frame-shaped cement soil structure on both sides and above the tunnel, which realizes the triple functions of isolation protection, vibration control and building foundation reinforcement of the existing rail transit tunnel, achieving multiple goals at one stroke and realizing the control of key issues of the new multi-story structure above the rail transit from three different dimensions.

[0019] 5. Combined with the data feedback provided by the monitoring points on the existing tunnel floor, track and side wall, the deformation of the main structure and track of the existing line can be adjusted in real time through dynamic adjustment of the loading and unloading values, so that the rail transit structure is always in the best operating state. This method has obvious advantages in controlling the deformation of existing lines.

[0020] 6. This method can compensate for the vertical displacement defects before the rail transit overpass project, and incorporate the adjustment value into the displacement adjustment control target of this crossing project. Therefore, this scheme will not only not deteriorate the operating conditions of the existing tunnel, but also adjust the final track state to the optimal state, which is impossible to achieve with the previous design and construction methods of track operations.

[0021] 7. This method has strong applicability and can be applied to all tunnel construction methods including shield method, open-cut method, mining method, etc. It is also applicable to subways, light rails, rail express lines, intercity railways, high-speed railways, etc.

[0022] The details of the present invention can be obtained from the following description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of the structure of a newly built multi-story building directly above the rail transit operation tunnel of the present invention is shown.

[0024] Figure 2 A schematic diagram of an operating tunnel showing a design and construction method for a new multi-story building directly above a rail transit operating tunnel of the present invention.

[0025] Figure 3 A schematic diagram showing step four of the design and construction method of the present invention is shown.

[0026] Figure 4 A schematic diagram showing step five of the design and construction method of the present invention is shown.

[0027] Figure 5 A schematic diagram showing step six of the design and construction method of the present invention is shown.

[0028] Figure 6 A top view of step six of the design and construction method of the present invention is shown.

[0029] Figure 7 A cross-sectional view of the small vertical shaft at the column position in step six of the design and construction method of the present invention is shown.

[0030] Figure 8 The plan view of the small vertical shaft at the column position in step six of the design and construction method of the present invention is shown.

[0031] Fig. 9 A schematic diagram showing step seven of the design and construction method of the present invention is shown.

[0032] Fig.10 A top view of step seven of the design and construction method of the present invention is shown.

[0033] Fig.11 A detailed view showing step seven of the design and construction method of the present invention.

[0034] Fig.12 A schematic diagram showing step eight of the design and construction method of the present invention is shown.

[0035] Fig.13 A schematic diagram showing step ten of the design and construction method of the present invention.

[0036] Fig.14 A schematic diagram showing the specific steps of the design and construction method of the present invention is shown. DETAILED DESCRIPTION

[0037] See also Figures 1 to 14 , showing the design and construction method of a new multi-story building directly above a rail transit operating tunnel of the present invention.

[0038] According to the many years of design and construction experience of the inventor of the present invention, the core technologies for the construction of new multi-story buildings directly above the rail transit operating tunnel should mainly include the anti-upheaval and subsidence problems of the operating tunnel, the seismic performance problems (secondary disaster control) and the vibration control problems. Among these three problems, the first problem is the control core. When taking measures to control the upheaval and subsidence problems, the latter two problems should be taken into account, so as to achieve a variety of control effects, improve project quality, save project investment, and shorten the construction period. In order to better control the upheaval and subsidence problems while taking into account the seismic performance problems and the vibration control problems, the preparatory steps of the design and construction method of the new multi-story building directly above the rail transit operating tunnel of the present invention may include the seven aspects of the building's number of floors design, floor height design, main structure design, foundation design, durability design, seismic design, and vibration reduction design, which are explained one by one below.

[0039] Preparation step 1: number of floors design. In the multi-story structure in this application, the ground height generally does not exceed 30m, the number of floors generally does not exceed 8, the depth of the basement generally does not exceed 10m, and the number of floors generally does not exceed 2. The number of underground floors is represented by i (i=1, 2...), and the total number of underground floors is m. The above-ground floors are represented by j (j=1, 2, 3, 4...), and the total number of above-ground floors is n, so as to better establish the corresponding relationship between m and n.

[0040] Preparation step 2: Floor height design, with the first floor of the proposed building as the boundary, the heights of each floor of the underground structure are , the height of each floor of the above-ground structure is Taking the equal replacement of the load above the interval tunnel as the core, the relationship between the number of floors and the floor height must be as shown in formula (1): (one) In the formula: is the excavation depth of the underground structure foundation pit. , It is the absolute elevation of the first floor of the proposed building. It is the absolute elevation of the existing ground before excavation of the foundation pit. is the thickness of the cushion layer under the structural base plate, is the thickness of the structural base plate.

[0041] k Excavation depth for basement d The stratigraphic sequence number within the range.

[0042] It is the density of the kth layer of soil within the excavation range of the foundation pit, and the floating density is taken below the water level.

[0043] Excavation depth for foundation pit The thickness of each layer of soil within the range of degree.

[0044] It is the representative value of the equivalent uniformly distributed load of each layer of the underground structure. 25kPa can be taken in the scheme design stage. In the construction drawing stage, detailed calculations should be carried out according to the load combinations in the Code for Load Design of Building Structures based on the dead load and live load of each layer.

[0045] It is the representative value of the equivalent uniformly distributed load for each floor of the above-ground structure. In the scheme design stage, 20kPa can be taken for reinforced concrete frame structure, 25kPa for reinforced concrete frame shear wall structure, and 18kPa for steel structure. In the construction drawing stage, detailed calculations should be carried out according to the load combinations in the Code for Load Design of Building Structures based on the dead load and live load of each floor.

[0046] The equivalent uniformly distributed load for the roof layer can be 15kPa for reinforced concrete structures and 10kPa for steel structures in the scheme design stage. In the construction drawing stage, detailed calculations should be performed based on the dead load and live load of each layer according to the load combination in the Code for Load Design of Building Structures.

[0047] In the design stage, the total number of basement floors and floor heights are determined based on the functional requirements of the building. , put it into the above formula, and we can get the total number of floors of the above-ground structure n .

[0048] The following is a calculation example of the design stage to explain the number of above-ground structure layers. n The method to find . Figure 1 As shown, it is planned to build a multi-storey building above the rail transit section tunnel, using a reinforced concrete frame structure. According to the building function and building volume estimation, only one basement is needed (i=1). Considering the pipeline laying within the basement floor height range and the clearance requirements of the underground parking lot, the basement floor height is initially determined to be 4.5m, the structural bottom plate thickness is initially determined to be 1m, the absolute elevation of the first floor of the building is 10m, and the existing surface ground elevation is 9m, with a height difference of 1m.

[0049] Depth of foundation pit

[0050] The groundwater level of the site is buried at a depth of 4m, and there are three layers of soil involved within the foundation pit excavation depth of 4.65m, as shown in Table 1 below.

[0051] Table 1

[0052] According to the formula , the number of above-ground structure layers j is calculated as follows:

[0053] We get j=2.7 floors, and after rounding to the integer j=3 floors, we get that the number of floors of the above-ground structure is 3.

[0054] By ensuring that the unloading of foundation pit excavation is equivalent to the load of building loading, ensuring that the load above the rail transit does not change, combined with reasonable construction process design, a theoretical basis is provided for zero deformation of rail transit.

[0055] Preparation step three: main structure design. In the previous section, the relationship between the height and number of underground structures and the number of above-ground structures was determined by the principle of equal replacement of soil unloading and building loads. However, in actual projects, the number of above-ground structures calculated by the above formula may not meet the scale requirements of above-ground buildings. It is hoped that one or even two floors can be appropriately increased or decreased. This demand can be met for the following two reasons. First, the load calculated by the above formula strictly follows the principle of equal replacement of loads, which is intended to ensure zero deformation of rail transit. However, rail transit allows deformation within a certain range, which generally needs to be controlled within 3mm. According to the stratum conditions, tunnel burial depth, etc., the load difference on both sides of the above equation is generally within 20kPa~40kPa, which is equivalent to the load of 1~2 floors of buildings, which can ensure that the additional deformation of rail transit is within 3mm. Second, the core idea of ​​the above equation is equal replacement of loads, so the number of floors can be adjusted by adjusting the value of the load on each floor. If the number of floors needs to be increased, the weight of each floor of the above-ground structure and underground structure needs to be reduced. The methods include but are not limited to the following: 1. Adjust the structural type of reinforced concrete from frame-shear wall structure to frame structure.

[0056] 2. Adjust the ground structure from reinforced concrete structure to steel structure.

[0057] 3. Reduce the thickness of the floor slab and use hollow slabs or lightweight concrete slabs.

[0058] 4. Adjust the basement foundation from a flat raft foundation to a beam-slab raft foundation to reduce the weight of the bottom plate. When the number of above-ground structure layers needs to be reduced, simply adjust in the opposite direction according to the above method.

[0059] Preparation step 4: foundation design. Multi-story buildings usually have a small upper load. In most areas of my country, the foundation type selected when building multi-story buildings is a raft foundation with good economic efficiency. In order to solve the problem of upper ground load loading, the traditional design scheme adopts the design scheme of pile foundation + cover plate (such as patent CN105862930B). This scheme not only significantly increases the project investment and prolongs the project construction period, but also will still cause later vertical settlement after the completion of the upper building, and the effect of controlling the vertical deformation of the rail transit tunnel is not ideal. This scheme maintains the raft foundation through reasonable design of floor height, number of floors and structural scheme, and cooperates with the construction scheme of partial excavation and partial loading. The foundation scheme maintains the raft foundation without the need to change to a pile foundation. Generally speaking, the cost of pile foundation can account for 1 / 5 to 1 / 4 of the overall investment in civil engineering projects. This method can save millions to tens of millions of investment in a single project, greatly reducing the increase in investment in rail-related projects.

[0060] Preparation step five: Durability design. The design service life of rail transit section tunnels is 100 years, while the design service life of general civil buildings is 50 years. There is a mismatch between the service life of the two. In order to avoid the secondary disasters of rail transit tunnels caused by insufficient durability design of buildings after the upper structure exceeds 50 years, resulting in reduced structural bearing capacity, the durability design standard of buildings above rail transit should be raised to 100 years. According to the relevant requirements of the "Concrete Structure Durability Design Code", the thickness of the concrete protective layer should be increased, the control requirements for raw materials should be improved, and the allowable crack width should be reduced, so that the durability design standards of buildings and tunnels are unified.

[0061] Preparation step six: earthquake-resistant design. Since the building is located above the rail transit tunnel, its earthquake-resistant standard should not be lower than that of the tunnel project below. That is, when encountering an earthquake, the ground building should not be destroyed before the section tunnel to avoid the risk to the rail transit tunnel caused by its prior destruction. The earthquake resistance level of the rail transit tunnel is generally level 2, and the earthquake resistance level of the newly built building above should not be lower than level 2 in principle.

[0062] Preparation step seven: vibration reduction design. The running speed of rail transit section tunnels is generally high, which has a great impact on the vibration of the buildings above. The vibration reduction design should be carried out from the following aspects. First, the vertical clearance with the shield tunnel should be reasonably determined in combination with the buried depth of the basement. The vibration is caused by the unevenness of the train wheels and rails, and eventually spreads to the building through the soil between the section tunnel and the building basement. Therefore, the clearance between the two should be increased as much as possible. At the same time, vibration reduction measures should be adopted around the section tunnel. The door frame type cement soil wall can be used for reinforcement around the section. The impedance ratio of the soil and cement soil is different. The vibration wave will be reflected at the interface between the two, reducing the vibration energy transmitted to the building. This structure also serves as a safety protection measure for the structure and track of the existing tunnel, which can effectively reduce the adverse impact on the tunnel when the upper building is implemented. This structure also serves as the foundation of the building, which effectively improves the bearing capacity of the foundation. Secondly, if the above two measures still cannot achieve the vibration reduction target, the building needs to adopt its own vibration reduction measures, including setting vibration reduction pads, vibration reduction springs, and vibration reduction "room in room" structures under the bottom plate.

[0063] The above vibration reduction targets are determined based on special environmental impact assessment work, and the order of taking measures is also implemented in the order of the above three points until the vibration reduction targets are met.

[0064] Therefore, the technical core of the present invention is to keep the total load above the tunnel basically unchanged, but the traditional construction process of excavating the building foundation pit and loading the upper buildings layer by layer is completely unable to achieve the requirements needed to be achieved by the present invention. For this reason, the inventor of the present invention creatively proposed a "small excavation shaft + reverse construction" construction process for the design and construction method of newly building multi-story buildings directly above the rail transit operating tunnel.

[0065] Moreover, the main parameters of building design, such as the number of building floors and floor heights, main body and foundation design, durability design, earthquake-resistant design, and vibration reduction design, are determined through the above-mentioned multiple preparation steps. After obtaining the above-mentioned parameters, a numerical simulation analysis of the construction of a new multi-story building in the operating tunnel above the rail transit is carried out. Combined with the construction process design, the displacement analysis of the rail transit is obtained, and the rail transit design implementation plan is further deepened based on the calculation structure. Specifically, the design and construction method of the new multi-story building directly above the rail transit operating tunnel of the present invention is applicable to the three common interval tunnel constructions of shield, mining, and open excavation. The following construction process is described by taking the shield method, which is the most difficult to implement, as an example. Fig.14 As shown, it may include the following steps:

[0066] Step 1: Determine the allowable deformation value of the operating tunnel, which includes at least the following sub-steps.

[0067] Step 1.1 Collect archived data on underground structures of existing rail transit and conduct on-site surveys. Detect the plane and vertical position of existing underground structures of existing rail transit, geomechanical parameters of the strata, geometric dimension information of existing rail transit structures, track structures and other related information.

[0068] Step 1.2 Conduct status inspection on the existing rail transit structure and track structure, evaluate the current mechanical properties of the two, and judge their ability to continue to deform based on information such as the degree of crack development, concrete carbonization, steel bar corrosion, water leakage, track deformation, and fastener integrity. The judgment of the ability to continue to deform is based on calculations, which are carried out in accordance with current national standards. The existing rail transit structure and track structure after continued deformation must meet the bearing capacity requirements, structural component deformation limit value requirements, durability, and train driving safety requirements. After the structure continues to deform, the minimum allowable deformation value that meets the bearing capacity requirements, structural component deformation limit value requirements, durability, and train driving safety requirements is the allowable deformation value of the operating tunnel. If the existing tunnel already has vertical deformation problems, the deformation of the existing tunnel should be corrected in conjunction with the implementation of this project. According to the safety control index value of urban rail transit structure in Table B.0.2 of the "Technical Specifications for Safety Protection of Urban Rail Transit Structures GB50909", the allowable deformation value of the track height difference is ±4mm. For example, if the existing tunnel has produced 2mm of uplift deformation, the allowable value this time should be in the range of -6mm~+2mm, and the optimal value for deformation control is -2mm. The above value "+" represents uplift, and "-" represents settlement.

[0069] Step 2: Develop a monitoring plan and arrange monitoring points.

[0070] like Figure 2 As shown in the figure, through real-time monitoring of operating tunnels during construction, the impact of external operations on the urban rail transit structure can be dynamically grasped, and targeted prevention and control measures can be taken in a timely manner to ensure the safety of the urban rail transit structure. The monitoring plan includes four parts: monitoring items, monitoring frequency, monitoring cycle, and monitoring and early warning. The monitoring items of this type of project should include the vertical and horizontal displacement of the tunnel, the vertical and horizontal displacement of the track and the roadbed, structural cracks, convergence and opening and closing, and the static geometry of the track. The monitoring frequency, cycle, and early warning should meet national, industry, and local standards. According to the formulated monitoring plan, the tunnel is monitored and the initial monitoring value is collected during the operation window period.

[0071] Step 3: Based on the deformation control value determined in step 1, the number of floors, floor height, main structure, foundation, vertical clearance with existing tunnels, durability, earthquake resistance and vibration reduction design of the building can be carried out according to the above preparation steps to obtain relevant design parameters.

[0072] Step 4: Form cement soil reinforcement around the tunnel. Specifically, the cement soil reinforcement can be formed by three-axis mixing piles, rotary jet piles, TRD or CSM. Figure 3 The portal frame structure shown in the figure has a top surface and a support section extending downward from the top surface to the tunnel periphery. The distance between the cement soil reinforcement body and the existing tunnel is recommended to be no less than 2m to avoid adverse disturbance of the soil around the tunnel during construction. This cement soil reinforcement body has three functions: 1. It forms a support protection of the "portal frame structure" around the tunnel. During the excavation of the upper foundation pit, it can isolate the adverse effect of the soil uplift above to a certain extent and protect the tunnel structure. 2. The top surface of the cement soil reinforcement body, as the bottom of the shaft, can form the foundation of the later upper structure and effectively support the load transmitted by the structural column. The support section forms a solid bearing layer at the bottom of the shaft, which can distribute and diffuse the column section pressure to the cement soil on both sides, effectively reducing the additional load on the soil directly above the section tunnel. 3. Vibration control. The cement soil reinforcement body formed above and on both sides of the tunnel can block the vibration generated by the subway train from being transmitted upward and to both sides, effectively control the vibration transmitted to the building, and effectively improve the safety performance and vibration isolation effect after construction.

[0073] Step 5: Construction of foundation pit support structure. Figure 4 As shown in the figure, foundation pit support piles are driven along the outer contour of the building. The foundation pit support method adopts the common support piles + anchor cables and double-row piles. This support method has good applicability to foundation pits within 30m. At the same time, the construction technology is mature and the cost is saved.

[0074] Step 6: Construction of small vertical shaft at column position. Figure 5 , Figure 6 , Figure 7 and Figure 8 As shown, according to the designed column position, a locking ring beam is constructed, and the shaft is constructed by the manual excavation inverted shaft wall method, that is, as the shaft is excavated 0.75m, the first locking foot anchor rod and the first horizontal ring-shaped supporting steel frame are constructed, which are connected to the locking ring beam upward. Continue to excavate 0.75m downward, construct the second locking foot anchor rod and the second horizontal ring-shaped steel frame supporting steel frame, and connect it to the first steel frame through vertical connecting bars. C20 plain concrete is sprayed on the steel frame, and so on and so forth, and the construction is carried out to the bottom of the pit, and finally a small shaft at the column position is formed. In principle, the plane size of the shaft should be as small as possible under the condition of meeting the artificial operation space. The recommended value of the internal clearance size is 1.5mX1.5m, and the recommended value of the shaft side wall thickness is 250mm. The shaft is excavated in the order from far to near to the existing tunnel. Since the shaft is small in size and only manually excavated at the column and wall positions, the traditional large foundation pit excavation is transformed into a local small foundation pit, which greatly reduces the safety impact of foundation pit excavation on the operating tunnel.

[0075] Step 7: Construction of vertical support structure system. Fig. 9 , Fig.10 and Fig.11 As shown, the structural columns and the expanded foundation under the columns are constructed in the shaft. The thickness of the foundation is determined according to the shear bearing capacity of the column bottom, and connectors are reserved around it as the connection condition between the air vent and the bottom plate. The structural columns and the expanded foundation under the columns are cast-in-place concrete structures. The top of the column is cast to the bottom of the first floor slab and reinforcement is thrown at the column head. After the structural column and the foundation reach the design strength, the shaft is filled with fine sand to the existing ground. The fine sand should be filled in layers, and the single backfill height should not exceed 50cm, and the compaction degree should not be less than 0.94. During the backfilling process around the column, the verticality error of the column should be controlled to not exceed 0.5%, and the absolute value of the horizontal deviation between the top and the bottom of the column should be less than 10mm.

[0076] Step 8: Tie up the first floor slab reinforcement, the main and secondary beam reinforcement in the slab, and effectively connect them with the column head reinforcement before integral casting. Fig.12 As shown in the figure, an excavation hole is reserved in the floor slab. The size of the excavation hole is recommended to be no less than 6mx6m to meet the operating space of the excavator. After the first floor slab structure reaches the design strength, the soil under the slab is excavated using the excavation hole. The mass of the first floor slab is calculated, converted into the soil layer thickness and excavated to this elevation. In this way, the displacement balance of the load above the tunnel by the first floor slab loading and the unloading of the earthwork below is achieved. After excavating the earthwork, anchor cables are set, external waterproofing is laid, side wall steel bars are tied, and the side wall column reinforcement is mechanically connected with steel sleeves before pouring concrete side walls.

[0077] Step 9: Tie the remaining column steel bars of the first floor to the second floor and throw the bars, tie the second floor slab steel bars, the main and secondary beam steel bars in the slab, and effectively connect them with the column head throw bars for integrated pouring. According to the increased mass of this construction section, convert it into soil layer thickness and excavate to this elevation to achieve load replacement balance. The inverted shaft wall exposed during the excavation process was then removed.

[0078] Step 10: Use the above method until the top of the above-ground structure is capped and all earthwork excavation is completed. Finally, tie the basement floor steel bars and mechanically connect them with the reserved reinforcements for the expanded foundation and then cast them as a whole. This completes the design and construction of a new multi-story building above the rail transit operation tunnel. Fig.13 In the dynamic balance process of cast structure loading and soil excavation unloading, the rail transit track and main structure should be monitored in time, and the loading and unloading values ​​should be adjusted dynamically to always maintain the safety of rail transit operation.

[0079] It is obvious that the above description and record are only examples and are not intended to limit the disclosure, application or use of the present invention. Although the embodiments have been described in the embodiments and described in the drawings, the present invention is not limited to the specific examples of the teachings of the present invention as the best mode currently considered by the drawings and described in the embodiments, and the scope of the present invention will include any embodiment falling within the previous description and the attached claims.

Claims

1. A design and construction method for a new multi-story building directly above a rail transit operating tunnel, suitable for shield, mining, and open-cut tunnel construction, characterized by The following steps are included: Step 1: Determine the allowable deformation value of the operating tunnel; Step 2: Develop monitoring plans and arrange monitoring points; Step 3: Based on the deformation control value determined in step 1, carry out the design of the number of floors, floor height, main structure, foundation, vertical clearance with existing tunnels, durability, earthquake resistance and vibration reduction of the building; Step 4: forming a cement soil reinforcement body around the tunnel. The cement soil reinforcement body is constructed by triaxial mixing piles, rotary grouting piles, TRD or CSM to form a portal frame structure having a top surface and a support section extending downward from the top surface to the tunnel periphery; Step 5: Construction of foundation pit support structure, implementation of foundation pit support piles along the outer contour of the building, foundation pit support method using support piles + anchor cables and double-row piles; Step 6: Construction of small vertical shaft at column position; Step 7: Construction of vertical support structure system; Step 8: Tie up the steel bars of the first floor slab, the steel bars of the main and secondary beams in the slab, and effectively connect them with the column head reinforcement before integrated pouring. After the first floor slab structure reaches the designed strength, use the excavation holes to excavate the soil under the slab, calculate the mass of the first floor slab, convert it into the soil layer thickness and excavate to this elevation. After excavating the earth, set up anchor cables, lay out waterproofing, tie up the side wall reinforcement and mechanically connect it with the side wall column reinforcement with steel sleeves, and then pour the concrete side wall. Step 9: Tie the remaining column reinforcement of the first floor to the second floor and throw the reinforcement, tie the second floor slab reinforcement, the main and secondary beam reinforcement in the slab, and effectively connect them with the column head reinforcement for integrated pouring; Step 10: Use the above method until the above-ground structure is capped and all earth excavation is completed. Finally, tie the basement floor reinforcement and mechanically connect it with the reserved reinforcement for the expanded foundation and then cast it as a whole. This completes the construction of a new multi-story building above the rail transit operation tunnel.

2. The design and construction method for a new multi-story building directly above a rail transit operating tunnel as claimed in claim 1, characterized in that: Step 1 includes at least the following sub-steps: Step 1.1 Collect archived data on underground structures of existing rail transit, and conduct on-site surveys to clearly detect the plane and vertical positions of existing underground structures of existing rail transit, geomechanical parameters of strata, geometric dimension information of existing rail transit structures, and information on track structures; Step 1.2: Conduct status inspection on the existing rail transit structure and track structure, evaluate the current mechanical properties of the two, and determine their ability to continue to deform based on information on the extent of crack development, concrete carbonization, steel corrosion, water leakage, track deformation, and fastener integrity. After continued deformation, the existing rail transit structure and track structure must meet the bearing capacity requirements, structural member deformation limit value requirements, durability, and train travel safety requirements. After the structure continues to deform, the minimum allowable deformation value that meets the bearing capacity requirements, structural member deformation limit value requirements, durability, and train travel safety requirements is the allowable deformation value of the operating tunnel.

3. The design and construction method for a new multi-story building directly above a rail transit operating tunnel as claimed in claim 1, characterized in that: In step 3, the distance between the cement soil reinforcement body and the existing tunnel shall not be less than 2m to avoid adverse disturbance of the soil around the tunnel caused by the construction.

4. The design and construction method for a new multi-story building directly above a rail transit operating tunnel as claimed in claim 1, characterized in that: In step six, according to the designed column position, a locking ring beam is constructed, and the vertical shaft is constructed using the artificial excavation inverted shaft wall method. That is, as the vertical shaft is excavated 0.75m, the first locking anchor rod and the first horizontal annular support steel frame are constructed, which are connected to the locking ring beam upwards. The excavation continues downward for 0.75m, and the second locking anchor rod and the second horizontal annular steel frame support steel frame are constructed, and connected to the first steel frame through vertical connecting bars. C20 plain concrete is sprayed on the steel frames, and so on and the construction is carried out to the bottom of the pit to eventually form a small vertical shaft at the column position.

5. The design and construction method for a new multi-story building directly above a rail transit operation tunnel as claimed in claim 1, characterized in that: In step seven, structural columns and expanded foundations under the columns are constructed in the shaft. The thickness of the foundation is determined according to the shear bearing capacity of the column bottom. Connectors are reserved around it as the connection conditions between the air sill and the bottom plate. The structural columns and the expanded foundations under the columns are both cast-in-place concrete structures. The top of the column is cast to the bottom of the first floor slab and reinforcement is thrown at the column head. After the structural columns and foundation reach the design strength, fine sand is filled in the shaft to the existing ground.

6. The design and construction method for a new multi-story building directly above a rail transit operating tunnel as claimed in claim 1, characterized in that: The ground height of the multi-story structure in the floor design shall not exceed 30m, the number of floors shall not exceed 8, the depth of the basement shall not exceed 10m, the number of floors shall not exceed 2, the number of underground floors shall be represented by i (i=1, 2...), and the total number of underground floors is m, and the above-ground floors shall be represented by j (j=1, 2, 3, 4...), and the total number of above-ground floors is n, so as to better establish the correspondence between m and n.

7. The design and construction method for a new multi-story building directly above a rail transit operating tunnel as claimed in claim 6, characterized in that: In the floor height design, the first floor of the proposed building is taken as the boundary, and the floor heights of the underground structures are , the height of each floor of the above-ground structure is , with the equal replacement of the load above the interval tunnel as the core, the relationship between the number of floors and the floor height must be as shown in formula (1): (one) In the formula: is the excavation depth of the underground structure foundation pit. , It is the absolute elevation of the first floor of the proposed building. It is the absolute elevation of the existing ground before excavation of the foundation pit. is the thickness of the cushion layer under the structural base plate, is the thickness of the structural base plate, k Excavation depth for basement d The stratigraphic sequence number within the range, is the density of the kth soil layer within the excavation range of the foundation pit, and the floating density is taken below the water level. Excavation depth for foundation pit The thickness of each layer of soil within the range of is the representative value of the equivalent uniformly distributed load on each layer of the underground structure, is the representative value of the equivalent uniformly distributed load on each floor of the above-ground structure, is the equivalent uniformly distributed load on the roof layer, According to the functional requirements of the building, first determine the total number of basement floors and floor heights. , put it into the above formula, and we can get the total number of floors of the above-ground structure n .

8. The design and construction method for a new multi-story building directly above a rail transit operating tunnel as claimed in claim 1, characterized in that: In the main structure design, the relationship between the height and number of underground structures and the number of above-ground structures was determined through the principle of equal replacement of soil unloading and building loads. The raft foundation was maintained in the foundation design without the need to change to a pile foundation. In the durability design, the thickness of the concrete protective layer was increased, the control requirements for raw materials were improved, and the allowable crack width was reduced, so that the durability design standards of the building and the tunnel were unified. In the seismic design, the seismic fortification standard of the building was not lower than that of the tunnel project below.

9. The design and construction method for a new multi-story building directly above a rail transit operating tunnel as claimed in claim 1, characterized in that: The vibration reduction design includes the following aspects. First, the vertical clearance between the basement and the shield tunnel should be reasonably determined based on the basement depth, and the clearance between the two should be increased as much as possible. At the same time, the door frame type cement soil wall used around the interval should be used for reinforcement. Due to the different impedance ratios between the soil and cement soil, the vibration waves will be reflected at the interface between the two, reducing the vibration energy transmitted to the building. Secondly, if the above two measures still cannot achieve the vibration reduction target, the building needs to adopt its own vibration reduction measures, including the installation of vibration reduction pads, vibration reduction springs or vibration reduction room-in-room structures under the bottom plate.

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