Design and construction method for a multi-story building newly built directly above an operating rail transit tunnel

Abstract

A design and construction method for newly building multi-story buildings directly above an operating rail transit tunnel. It proposes a construction method of first constructing a small vertical shaft to form a vertical support system, reverse construction of the underground structure beam-slab and forward construction of the above-ground structure beam-slab columns, and layered excavation of the soil under the first-floor slab. This effectively corresponds to the calculation method of the present invention, and the construction method is simple and the technology is mature. Compared with other methods for newly building near rail transit, it is mainly a reasonable adjustment of the construction process. Therefore, the increased investment of this method is very small, achieving good economic benefits. At the same time, it elaborates on the method of newly building multi-story buildings above rail transit from seven aspects, namely floor number design, floor height design, main structure design, foundation design, seismic design, durability design, and vibration reduction design. The system is complete and comprehensive, providing a complete set of solutions for newly building multi-story buildings directly above operating rail transit tunnels in China, making the development and utilization of such high-value soil 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 object of the present invention is to provide a design and construction method for a new multi-story building directly above an operating rail transit tunnel, effectively solving the problem that engineering construction cannot be carried out above an existing operating tunnel. Through the dynamic control of vertical deformation during the excavation process, it becomes possible to construct a new multi-story building directly above the operating tunnel, with long-distance forward movement and small spacing. While ensuring the safety of rail transit operation, the utilization value of available urban core land is released, the urban function is improved, and the urban living quality is enhanced.

[0006] To achieve the above object, the present invention discloses a design and construction method for a new multi-story building directly above an operating rail transit tunnel, which is applicable to the construction of shield, mine, and open-cut tunnel sections. It is characterized by including the following steps:

[0007] Step 1: Determine the allowable deformation value of the operating tunnel;

[0008] Step 2: Develop a monitoring plan and arrange monitoring points;

[0009] 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 net distance from the existing tunnel, durability, seismic resistance, and vibration reduction of the building;

[0010] Step 4: Form a cement-soil solid around the tunnel. The cement-soil solid is constructed with a portal frame structure using a triple-axis mixing pile, jet grouting pile, TRD, or CSM, which has a top surface and a column section extending downward from the top surface to the tunnel perimeter;

[0011] Step 5: Construct the foundation pit support structure. Implement the driving of foundation pit support piles along the outer contour of the building. The foundation pit support method adopts the form of support piles + anchor cables and double-row piles;

[0012] Step 6: Construct small vertical shafts at column positions;

[0013] Step 7: Construct the vertical support structure system;

[0014] Step 8: Bind the steel bars of the first-floor slab, the main and secondary beams in the slab, and effectively connect them with the lapped steel bars at the column head, and then carry out integral pouring. After the first-floor slab structure reaches the design strength, excavate the soil under the slab using the soil outlet hole, calculate the mass of the first-floor slab, convert it into the thickness of the soil layer and excavate to this elevation. After excavating the soil, drive the anchor cables, lay the external waterproofing, bind the steel bars of the side wall and mechanically connect them with the lapped steel bars of the side wall column using a steel sleeve, and then pour the concrete side wall;

[0015] Ninth step: Bind the steel bars of the remaining columns of the first floor to the second floor and lap the bars, bind the steel bars of the second-floor slab, the main and secondary beams in the slab, and effectively connect them with the lapped steel bars at the column head, and then carry out integral pouring;

[0016] Step 10: Adopt the above method until the ground structure is capped and all earthwork excavation is completed. Finally, bind the steel bars of the basement floor slab, mechanically connect them with the reserved extended bars of the enlarged foundation, and then pour them into a whole. Thus, the construction of the new multi-story building above the rail transit operation tunnel is completed.

[0017] Among them: Step 1 at least includes the following sub-steps:

[0018] Step 1.1 Collect the archived materials of the underground structure of the operating rail transit, and at the same time conduct on-site surveys to detect clearly the horizontal and vertical positions of the existing operating rail transit underground structure, the geomechanical parameters of the stratum, the geometric dimension information of the existing rail transit structure, and the information of the track structure.

[0019] Step 1.2 Conduct on-site inspections on the existing rail transit structure and the track structure, evaluate their current mechanical properties, and judge their ability to continue deforming based on the information such as the crack development degree, concrete carbonation degree, steel bar corrosion degree, leakage situation, track deformation situation, and fastener integrity. After the structure continues to deform, the existing rail transit structure and the track structure need to meet the requirements of bearing capacity, structural member deformation limit values, durability, and train running safety. After the structure continues to deform, the minimum allowable deformation value that simultaneously meets the requirements of bearing capacity, structural member deformation limit values, durability, and train running safety is the allowable deformation value of the operation tunnel.

[0020] Among them: In Step 3, the distance between the cement-soil solid and the existing tunnel is not less than 2m to avoid adverse disturbances to the soil around the tunnel during construction.

[0021] Among them: In Step 6, according to the designed column positions, construct the collar beam. The shaft is constructed by the method of manual excavation and inverted shaft wall, that is, as the shaft is excavated by 0.75m, construct the first locking foot bolt and the first horizontal circumferential support steel frame, which is connected upward to the collar beam. Continue to excavate downward by 0.75m, construct the second locking foot bolt and the second horizontal circumferential steel frame support steel frame, and connect them to the first steel frame through vertical connecting bars. Spray C20 plain concrete on all the steel frames, and so on until the bottom of the pit is constructed, and finally form a small shaft at the column position.

[0022] Among them: In Step 7, construct the structural column and the enlarged foundation under the column in the shaft. The foundation thickness is determined according to the punching shear bearing capacity at the bottom of the column. Reserve connecting devices around it as the connection condition between the shaft and the floor slab. Both the structural column and the enlarged foundation under the column adopt cast-in-place concrete structures. The column top is poured to below the first floor slab and bars are extended at the column head. After the structural column and the foundation reach the designed strength, fill the shaft with fine sand to the current ground level.

[0023] Among them: the ground height of the multi-layer structure in the floor number design does not exceed 30m, the number of floors does not exceed 8, the depth of the basement does not exceed 10m, the number of floors does not exceed 2, the number of underground floors is represented by i (i = 1, 2..), the total number of underground floors is m, and each above-ground floor is represented by j (j = 1, 2, 3, 4.....), the total number of above-ground floors is n, so as to better establish the corresponding relationship between m and n.

[0024] Among them: in the floor height design, taking the plus-minus zero of the first floor of the proposed building as the boundary, the floor heights of each underground structure layer are respectively , and the floor heights of each above-ground structure layer are , with the equal replacement of the load above the interval tunnel as the core, so the relationship that the number of floors and the floor height need to satisfy is as shown in formula (1):

[0025] (1)

[0026] In the formula:

[0027] is the excavation depth of the underground structure foundation pit, , is the absolute elevation of the plus-minus zero of the first floor of the proposed building, is the absolute elevation of the current ground before the foundation pit excavation, is the thickness of the cushion under the structural floor slab, is the thickness of the structural floor slab,

[0028] k is the excavation depth of the basement d within the range of the formation serial number,

[0029] is the density of the kth layer of soil within the excavation range of the foundation pit, taking the floating density below the water level,

[0030] is the thickness of the kth layer of soil within the excavation depth of the foundation pit,

[0031] is the representative value of the equivalent uniformly distributed load of each underground structure layer,

[0032] is the representative value of the equivalent uniformly distributed load of each above-ground structure layer,

[0033] is the equivalent uniformly distributed load of the roof layer,

[0034] According to the functional requirements of the building, first determine the total number of basement floors m and the floor height , substitute it into the above formula, and the total number of above-ground structure floors can be obtained n .

[0035] Among them: In the main structure design, based on the principle of equivalent replacement of soil unloading and building load, the relationship between the floor height and number of floors of the underground structure and the number of floors of the above-ground structure was determined. In the foundation design, the raft foundation was maintained without changing to a pile foundation. In the durability design, the concrete cover thickness was increased, the index 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.

[0036] Among them: The vibration reduction design includes the following aspects. First, the vertical clear distance from the shield tunnel is reasonably determined in combination with the buried depth of the basement, and the clear distance between the two is increased as much as possible. At the same time, the portal-type cement soil wall reinforcement adopted around the interval is used. Due to the different impedance ratios of the soil and the cement soil, the vibration wave will be reflected at the interface between the two, reducing the vibration energy transmitted to the building. Second, if the above two measures still cannot achieve the vibration reduction goal, the building needs to adopt its own vibration reduction measures, including setting vibration reduction pads, vibration reduction springs or vibration reduction middle rooms under the floor slab.

[0037] 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:

[0038] 1. For the first time, a method for constructing a new multi-story building above the rail transit is comprehensively expounded from seven aspects, namely, floor number design, floor height design, main structure design, foundation design, seismic design, durability design, and vibration reduction design. The system is complete and comprehensive, providing a complete set of solutions for the construction of new multi-story buildings directly above the rail transit operation tunnels in China, making it possible to develop and utilize such high-value soil bodies.

[0039] 2. The theoretical basis of the design and calculation methods for the number of floors, floor height, main structure, and foundation of the present invention proposed based on the concept of "dynamic load balance" above the rail transit is mature, and the methods are clear. During the implementation of the new project, the overall stability of the load above the rail transit operation tunnel is achieved and continues to the final state, providing theoretical and calculation support for the construction of new multi-story buildings above the interval tunnel.

[0040] 3. The construction method proposed by the present invention, which first constructs the vertical support system in the small shaft, constructs the underground structure beam slab in reverse and the above-ground structure beam slab column in a forward manner, and excavates the soil layer by layer under the first floor slab, effectively corresponds to the calculation method of the present invention, and the construction method is simple and the technology is mature. Compared with other methods for new construction projects near the rail transit, it is mainly a reasonable adjustment of the construction process. Therefore, the investment increased by this method is very small, and good economic benefits are obtained.

[0041] 4. The proposed portal-shaped soil-cement structure installed on both sides and above the tunnel achieves triple functions of isolating and protecting existing rail transit tunnels, controlling vibrations, and strengthening the foundation of buildings, which serves multiple purposes and controls the key issues of newly built multi-layer structures above rail transit from three different dimensions.

[0042] 5. By combining the data feedback provided by the monitoring points on the existing tunnel floor, track, and side walls, and through the dynamic adjustment of the loading and unloading values, the deformation of the main structure and track of the existing line can be adjusted in real time, enabling the rail transit structure to always be in the best operating state. This method has obvious advantages in controlling the deformation of the existing line.

[0043] 6. This method can remedy the vertical displacement diseases before the rail transit overcrossing project and incorporate the adjustment values into the displacement adjustment control objectives of this crossing project. Therefore, this solution will not only not deteriorate the operating conditions of the existing tunnel but also adjust the final track state to the optimal level, which cannot be achieved by the previous design and construction methods for operations near the track.

[0044] 7. This method has strong applicability and can be applied to all tunnel construction methods including the shield method, cut-and-cover method, and mining method. At the same time, it is also applicable to subways, light rails, express rail lines, intercity railways, high-speed railways, etc.

[0045] The detailed content of the present invention can be obtained from the following description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 Shows a schematic structural diagram of a newly built multi-story building directly above the rail transit operation tunnel of the present invention.

[0047] Figure 2 Shows a schematic diagram of the operation tunnel of the design and construction method of a newly built multi-story building directly above the rail transit operation tunnel of the present invention.

[0048] Figure 3 Shows a schematic diagram of Step 4 of the design and construction method of the present invention.

[0049] Figure 4 Shows a schematic diagram of Step 5 of the design and construction method of the present invention.

[0050] Figure 5 Shows a schematic diagram of Step 6 of the design and construction method of the present invention.

[0051] Figure 6 Shows a top view of Step 6 of the design and construction method of the present invention.

[0052] Figure 7 Shows a cross-sectional view of the small shaft for column positions in Step 6 of the design and construction method of the present invention.

[0053] Figure 8 Shows the plan view of the column position small vertical shaft in Step 6 of the design and construction method of the present invention.

[0054] Figure 9 Shows the schematic diagram of Step 7 of the design and construction method of the present invention.

[0055] Figure 10 Shows the top view of Step 7 of the design and construction method of the present invention.

[0056] Figure 11 Shows the detail drawing of Step 7 of the design and construction method of the present invention.

[0057] Figure 12 Shows the schematic diagram of Step 8 of the design and construction method of the present invention.

[0058] Figure 13 Shows the schematic diagram of Step 10 of the design and construction method of the present invention.

[0059] Figure 14 Shows the schematic diagram of the specific steps of the design and construction method of the present invention. Specific implementation mode

[0060] See Figures 1 to 14 , which shows the design and construction method for building a multi-story building above the existing rail transit operation tunnel of the present invention.

[0061] According to the design and construction experience of the inventors of the present invention for many years, the core technologies of the problem of building a multi-story building above the existing rail transit operation tunnel mainly should include the problems of anti-heave and settlement of the operation tunnel, seismic performance (secondary disaster control), and vibration control. And the first problem is the control core among these three problems. When taking measures to control the heave and settlement problem, the latter two problems should be taken into account, so as to achieve multiple control effects, improve the project quality, save project investment, and shorten the construction period. And in order to better control the heave and settlement problem while taking into account the seismic performance problem and vibration control problem, the preparation steps of the design and construction method for building a multi-story building above the existing rail transit operation tunnel of the present invention can include seven aspects: the design of the number of building floors, the floor height design, the main structure design, the foundation design, the durability design, the seismic design, and the vibration reduction design. The following will be elaborated item by item.

[0062] Preparation Step 1: Design of the number of floors. In the multi-story structure in this patent, the ground height generally does not exceed 30m, the number of floors generally does not exceed 8 floors, the depth of the basement generally does not exceed 10m, and the number of basement floors generally does not exceed 2 floors. The underground floors are represented by i (i = 1, 2..), 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.

[0063] Preparation Step 2: Floor height design. Taking the plus-minus zero of the first floor of the proposed building as the boundary, the floor heights of each underground structure layer are respectively , and the floor heights of each above-ground structure layer are . Taking the equal replacement of the load above the interval tunnel as the core, the relationship that the number of floors and the floor height need to satisfy is as shown in Formula (I):

[0064] (I)

[0065] In the formula:

[0066] is the excavation depth of the underground structure foundation pit, , is the absolute elevation of the plus-minus zero of the first floor of the proposed building, is the absolute elevation of the current ground before foundation pit excavation, is the thickness of the cushion under the structural floor slab, is the thickness of the structural floor slab.

[0067] k is the excavation depth of the basement d within the range of the formation serial number.

[0068] is the density of the k-th layer of soil within the foundation pit excavation range, and the buoyant density is taken below the water level.

[0069] is the thickness of the k-th layer of soil within the foundation pit excavation depth.

[0070] is the representative value of the equivalent uniformly distributed load of each underground structure layer. In the preliminary design stage, it can be taken as 25 kPa. In the construction drawing stage, it should be calculated in detail according to the dead load and live load of each layer according to the load combination in the "Code for Design of Building Structures Loads".

[0071] is the representative value of the equivalent uniformly distributed load of each above-ground structure layer. In the preliminary design stage, it can be taken as 20 kPa for the reinforced concrete frame structure, 25 kPa for the reinforced concrete frame-shear wall structure, and 18 kPa for the steel structure. In the construction drawing stage, it should be calculated in detail according to the dead load and live load of each layer according to the load combination in the "Code for Design of Building Structures Loads".

[0072] is the equivalent uniformly distributed load of the roof layer. In the preliminary design stage, it can be taken as 15 kPa for the reinforced concrete structure and 10 kPa for the steel structure. In the construction drawing stage, it should be calculated in detail according to the dead load and live load of each layer according to the load combination in the "Code for Design of Building Structures Loads".

[0073] In the scheme design stage, according to the functional requirements of the building, first determine the total number of basement floors m and the storey height , substitute it into the above formula, and the total number of above-ground structure floors can be obtained n .

[0074] The following specifically illustrates the method of calculating the number of above-ground structure floors through an example in the scheme design stage n . As Figure 1 shown, it is planned to build a multi-storey building above the rail transit interval tunnel, adopting a reinforced concrete frame structure. According to the building function and building volume estimation, one basement floor is required (i = 1). Considering the pipeline laying within the basement storey height and the net clearance requirements of the underground parking lot, the initial basement storey height is set at 4.5m, and the initial thickness of the structural floor slab is set at 1m. The absolute elevation of the plus-minus zero of the first floor of the building is 10m, and the ground elevation of the current surface is 9m, with a height difference of 1m between the two

[0075] Foundation pit depth

[0076] The buried depth of the groundwater level in the site is 4m. A total of three layers of soil are involved within the foundation pit excavation depth of 4.65m. See Table 1 below

[0077] Table 1

[0078]

[0079] According to the formula , the number of above-ground structure floors j is calculated as follows

[0080] It is obtained that j = 2.7 floors, and after rounding up, j = 3 floors. Thus, the number of above-ground structures is 3 floors

[0081] By ensuring that the load of foundation pit excavation unloading is equivalent to the load of building loading, ensuring that the load above the rail transit does not change, and combining with a reasonable construction process design, a theoretical basis is provided for zero deformation of the rail transit

[0082] 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:

[0083] 1. Adjust the structural type of reinforced concrete from frame-shear wall structure to frame structure.

[0084] 2. Adjust the ground structure from reinforced concrete structure to steel structure.

[0085] 3. Reduce the thickness of the floor slab and use hollow slabs or lightweight concrete slabs.

[0086] 4. Adjust the basement foundation from a flat raft foundation to a beam-slab raft foundation to reduce the weight of the bottom plate.

[0087] When the number of above-ground structure layers needs to be reduced, simply adjust in the opposite direction according to the above method.

[0088] 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.

[0089] Preparation Step Five: Durability Design. The designed service life of the rail transit tunnel is 100 years, while that of general civil buildings is 50 years, resulting in a mismatch in service life. To avoid secondary disasters in the rail transit tunnel caused by a reduction in the structural bearing capacity due to insufficient durability design of the building above after 50 years, the durability design standard of the building above the rail transit should be raised to 100 years. According to the relevant requirements of the Code for Durability Design of Concrete Structures, the thickness of the concrete cover should be increased, the index control requirements for raw materials should be improved, and the allowable crack width should be reduced to unify the durability design standards of the building and the tunnel.

[0090] Preparation Step Six: Seismic Design. Since the building is located above the rail transit tunnel, its seismic fortification standard should not be lower than that of the tunnel project below. That is, in the event of an earthquake, the ground building should not be damaged prior to the interval tunnel to avoid the risks brought to the rail transit tunnel caused by its prior damage. The seismic grade of the rail transit tunnel is generally Class II, and the seismic grade of the newly built building above should, in principle, not be lower than Class II.

[0091] Preparation Step Seven: Vibration Reduction Design. The operating speed of the rail transit tunnel is generally high, which has a great impact on the vibration of the building above. Vibration reduction design should be carried out from the following aspects. First, reasonably determine the vertical clear distance from the shield tunnel in combination with the buried depth of the basement. Vibration is generated due to the unevenness of the train wheel-rail, and finally propagates to the building through the soil between the interval tunnel and the basement of the building. Therefore, the clear distance between the two should be increased as much as possible. At the same time, vibration reduction measures should be taken around the interval tunnel. For example, a door-frame type cement-soil wall can be used for reinforcement around the interval. Since the impedance ratios of the soil and the cement-soil are different, vibration waves 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 existing tunnel structure and the track, which can effectively reduce the adverse impact on the tunnel during the implementation of the building above. This structure also serves as the foundation of the building, effectively improving the bearing capacity of the foundation. Second, if the above two measures still cannot achieve the vibration reduction target, the building needs to adopt its own vibration reduction measures, including installing vibration reduction pads, vibration reduction springs, and vibration reduction "room-in-room" structures under the floor slab.

[0092] The above vibration reduction target is determined according to the special environmental impact assessment work, and the order of taking measures is also carried out in the order of the above three points until the vibration reduction target is met.

[0093] Therefore, the technical core of the present invention is to keep the total load above the tunnel basically unchanged. However, the traditional construction process of building foundation pit excavation and layer-by-layer loading of the building above completely fails to meet the requirements of the present invention. For this reason, the inventor of the present invention creatively proposes a construction process of "small excavation shaft + top-down construction" for the design and construction of a multi-story building directly above the operating rail transit tunnel.

[0094] Moreover, the main parameters of building design such as the number of building floors and storey height, main body and foundation design, durability design, seismic design, and vibration reduction design are determined through the above-mentioned multiple preparation steps. After obtaining the above parameters, a numerical simulation analysis of the construction of a new multi-storey building above the operating tunnel of rail transit is carried out. Combining with the construction process design, the displacement analysis of the rail transit is obtained, and the design implementation plan of the rail transit is further deepened based on the calculated structure. Specifically, the design and construction method of the new multi-storey building directly above the operating tunnel of the rail transit of the present invention is applicable to the construction of three common section tunnels, namely shield tunneling, mining method, and open cut method. The following construction process is described by taking the shield tunneling method with the greatest implementation difficulty as an example. As Figure 14 shown, it may include the following steps:

[0095] Step 1: Determine the allowable deformation value of the operating tunnel, which at least includes the following sub-steps.

[0096] Step 1.1 Collect the archived materials of the underground structure of the operating rail transit, and conduct on-site investigation at the same time. Detect clearly the plane and vertical positions of the existing underground structure of the operating rail transit, the geomechanical parameters of the stratum, the geometric dimension information of the existing rail transit structure, the track structure and other relevant information.

[0097] Step 1.2 Conduct on-site inspections on the existing rail transit structure and the track structure, evaluate their current mechanical properties, and judge their ability to continue deforming according to information such as the degree of crack development, the degree of concrete carbonation, the degree of steel bar corrosion, the leakage situation, the track deformation situation, and the integrity of the fasteners. The judgment of the ability to continue deforming is based on calculations, and the calculations are carried out according to the current national codes. After continued deformation, the existing rail transit structure and the track structure need to meet the requirements of bearing capacity, the deformation limit value requirements of structural components, durability, and train running safety. After the structure continues to deform, the minimum allowable deformation value that simultaneously meets the requirements of bearing capacity, the deformation limit value requirements of structural components, durability, and train running safety is the allowable deformation value of the operating tunnel. If there are diseases of vertical deformation in the existing tunnel, the deformation of the existing tunnel should be corrected in combination with the implementation of this project. According to Table B.0.2 of the Technical Code for the Safety Protection of Urban Rail Transit Structures GB50909, the allowable deformation value of the track alignment height difference is ±4mm. For example, if the existing tunnel has a 2mm uplift deformation, the allowable value this time should be in the range of -6mm to +2mm, and the optimal value of deformation control is -2mm. The above numerical value "+" represents uplift, and "-" represents settlement.

[0098] Step 2: Develop a monitoring plan and arrange monitoring points.

[0099] As Figure 2As shown, through the real-time monitoring of the operating tunnel during the construction process, 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 warning. The monitoring items for this type of project should include the vertical and horizontal displacements of the tunnel, the vertical and horizontal displacements of the track and ballast, structural cracks, convergence and opening / closing, and the static geometric profile of the track. The monitoring frequency, cycle, and warning should meet the national, industrial, and local code standards. According to the formulated monitoring plan, the tunnel is monitored and the initial monitoring values are collected during the operation skylight period.

[0100] Step 3: Based on the deformation control values determined in Step 1, and according to the aforementioned preparatory steps, the number of floors, floor height, main structure, foundation, vertical net distance from the existing tunnel, durability, seismic resistance, and vibration reduction design of the building can be carried out to obtain relevant design parameters.

[0101] Step 4: Cement-soil solidified bodies are formed around the tunnel. Specifically, the cement-soil solidified bodies can be constructed by using construction methods such as triaxial mixing piles, jet grouting piles, TRD, or CSM. Figure 3 As shown, the portal frame structure has a top surface and a column section extending downward from the top surface to the periphery of the tunnel. The distance between the cement-soil solidified body and the existing tunnel is recommended to be not less than 2m to avoid adverse disturbance to the soil around the tunnel during construction. This cement-soil solidified body has three functions: 1. Form a "portal frame structure" support and protection around the tunnel. During the excavation of the upper foundation pit, to a certain extent, it can block the adverse effects of the uplift of the upper soil and protect the tunnel structure. 2. The top surface of the cement-soil solidified body serves as the bottom of the shaft, which can form the foundation of the upper structure in the later stage, effectively support the load transmitted by the structural column, and the column section forms a firm 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 of the soil directly above the interval tunnel. 3. Vibration control. The cement-soil solidified bodies formed above and on both sides of the tunnel can play a role in blocking the upward and lateral transmission of the vibration generated by the subway train, effectively controlling the vibration transmitted to the building, and effectively improving the safety performance and vibration isolation effect after construction.

[0102] Step 5: Construction of the foundation pit support structure. As Figure 4 shown, implement the foundation pit support piles along the outer contour of the building. The foundation pit support method adopts the common support pile + cable anchor and double-row pile forms. This support method has good applicability to foundation pits within 30m, and at the same time, the construction technology is mature and the cost is saved.

[0103] Step 6: Construction of small shafts for column positions. As Figure 5 、 Figure 6 、 Figure 7 and Figure 8As shown in the figure, according to the designed column positions, the collar beam is constructed. The shaft is constructed by the method of artificial excavation with inverted shaft wall, that is, as the shaft is excavated by 0.75 m, the first row of foot-locking bolts and the first horizontal circumferential support steel frame are constructed, and the upper part is connected to the collar beam. Continue to excavate downward by 0.75 m, construct the second row of foot-locking bolts and the second horizontal circumferential steel frame support steel frame, and connect them to the first steel frame through vertical connecting bars. C20 plain concrete is sprayed on all the steel frames, and so on until the bottom of the pit is constructed, and finally a small shaft at the column position is formed. The plane size of the shaft should be as small as possible in principle under the condition of meeting the artificial operation space. The recommended value of the internal clear dimension is 1.5 m×1.5 m, and the recommended value of the side wall thickness of the shaft is 250 mm. The shaft is excavated in the order from far to near from the existing tunnel. Since the shaft size is small and only manually excavated at the column and wall positions, the transformation from the traditional large-scale excavation of the foundation pit to the local small foundation pit is realized, greatly reducing the safety impact of the foundation pit excavation on the operating tunnel.

[0104] Step 7: Construction of the vertical support structure system. As Figure 9 , Figure 10 and Figure 11 shown, construct structural columns and enlarged footings under the columns in the shaft. The thickness of the footing is determined according to the punching shear bearing capacity at the column bottom, and connectors are reserved around it as the connection condition between the shaft and the floor slab. Both the structural columns and the enlarged footings under the columns adopt cast-in-place concrete structures. The column tops are poured to below the first-floor slab and reinforcement bars are left at the column heads. After the structural columns and the footings reach the design strength, fill the shaft with fine sand to the existing ground level. The fine sand should be filled in layers and compacted. The single-time backfill height should not be greater than 50 cm, and the compaction degree should not be less than 0.94. During the backfill process around the columns, the verticality error of the columns should be controlled within 0.5%, and the absolute value of the horizontal deviation between the column top and the column bottom should be less than 10 mm.

[0105] Step 8: Bind the steel bars of the first-floor slab, the main and secondary beams in the slab, and effectively connect them with the reinforcement bars left at the column heads, and then carry out integral pouring. As Figure 12 shown, an earth excavation hole is reserved in the slab. The recommended size of the earth excavation hole is not less than 6 m×6 m to meet the operation space of the excavator. After the first-floor slab structure reaches the design strength, use the earth excavation hole to excavate the soil under the slab. Calculate the mass of the first-floor slab, convert it into the thickness of the soil layer and excavate to this elevation. Thus, the replacement balance of the load above the tunnel is realized by loading the first-floor slab and unloading the soil below. After the soil is excavated, install anchor cables, lay the external waterproofing, bind the side wall steel bars and mechanically connect them with the reinforcement bars left at the side wall columns by steel sleeves, and then pour the concrete side wall.

[0106] Ninth step: Bind the steel bars of the remaining columns on the first floor to the second floor and leave reinforcement bars, bind the steel bars of the second-floor slab, the main and secondary beams in the slab, and effectively connect them with the reinforcement bars left at the column heads, and then carry out integral pouring. According to the increased mass of this construction section, convert it into the thickness of the soil layer and excavate to this elevation to realize the load replacement balance. The inverted shaft wall shaft exposed during the excavation process is removed accordingly.

[0107] Step 10: Adopt the above method until the ground structure is capped and all earthwork excavation is completed. Finally, bind the steel bars of the basement floor and mechanically connect them with the reserved extended steel bars of the enlarged foundation, and then pour them into a whole. Thus, the design and construction of the new multi-story building above the rail transit operation tunnel are completed, as Figure 13 shown. During the dynamic balance process of load of pouring structure loading - soil excavation unloading, the rail transit track and the main structure should be monitored in a timely manner, and the loading and unloading values should be adjusted dynamically to always ensure the safe operation of the rail transit.

[0108] It is obvious that the above description and record are only examples and not intended to limit the disclosure, application or use of the present invention. Although the embodiments have been described in the examples and shown in the drawings, the present invention is not limited to the specific examples described in the drawings and examples as the currently considered best mode for implementing the teachings of the present invention. The scope of the present invention will include any embodiments falling within the foregoing specification and the appended 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 a connection condition with the bottom plate. Both 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 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. is the thickness of the kth soil layer within the foundation pit excavation depth, 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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