CN111576921A - Dismantling and rebuilding construction method for existing foundation building in rail transit protection area - Google Patents

Dismantling and rebuilding construction method for existing foundation building in rail transit protection area Download PDF

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Publication number
CN111576921A
CN111576921A CN202010435012.2A CN202010435012A CN111576921A CN 111576921 A CN111576921 A CN 111576921A CN 202010435012 A CN202010435012 A CN 202010435012A CN 111576921 A CN111576921 A CN 111576921A
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construction
foundation
rail transit
dismantling
rebuilding
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胡乐庭
陈德霞
王强
宗旻珏
王东
吴启程
刘光伟
朱歆文
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Suzhou No1 Building Group Co ltd
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Suzhou No1 Building Group Co ltd
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    • EFIXED CONSTRUCTIONS
    • E04BUILDING
    • E04GSCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
    • E04G23/00Working measures on existing buildings
    • E04G23/08Wrecking of buildings
    • EFIXED CONSTRUCTIONS
    • E04BUILDING
    • E04GSCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
    • E04G23/00Working measures on existing buildings
    • E04G23/06Separating, lifting, removing of buildings; Making a new sub-structure

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  • Architecture (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
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  • Civil Engineering (AREA)
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  • Working Measures On Existing Buildindgs (AREA)

Abstract

The invention discloses a construction method for dismantling and rebuilding an existing foundation building in a rail transit protection area, which comprises the steps of adopting layered dynamic dismantling of the existing building; the foundation pit is reinforced or replaced, the soil strength is improved, and the uplift deformation of the soil is reduced; the block and layer excavation is carried out, the unloading area is reduced, and the large-area unloading is avoided; time-limited construction, namely reducing the exposure time of excavation of the foundation pit by utilizing the time-space effect of the foundation pit; and (3) adopting a stacking back pressure measure to ensure that the back pressure is the same as the unloading, reducing the unloading influence and other processes and measures to ensure that the risk of the existing building dismantling and rebuilding process in the rail transit control protection area on the rail transit tunnel structure is almost zero.

Description

Dismantling and rebuilding construction method for existing foundation building in rail transit protection area
Technical Field
The invention belongs to the field of buildings, particularly relates to the dismantling, new construction or reconstruction of an existing shallow foundation building above a rail transit tunnel and above or below the ground surface, and particularly relates to a dismantling and reconstruction construction method of an existing foundation building in a rail transit protection area.
Background
With urban construction and economic development, rail transit has become the main direction for solving urban public transport, marks the quality and development level of a city, and becomes the kernel of the development of a large city. And each city with the rail transit is in the relevant urban rail transit regulations for ensuring the smooth construction and safe operation of the urban rail transit, standardizing the urban rail transit management and maintaining the legal rights and interests of passengers. And chapter three of the regulations sets forth the concept of "protection zones". The protection area is the control protection range of the urban rail transit line and is divided into a control protection area and a construction control area, and the control protection area and the special protection area can be divided according to the actual line condition.
The control protection area range of the subway and light rail under construction and built line is generally defined as follows:
(1) the outer sides of the outer side lines of the underground station and the tunnel structure are within fifty meters, wherein the outer side of the outer side line of the lake-passing tunnel structure is within one hundred meters;
(2) the ground and the elevated station, the ground and the outside of the outer side line of the elevated line structure are within thirty meters;
(3) the outer side of the building structure outer boundary such as an access, a ventilation pavilion, a cooling tower, a vehicle base, a control center, a main substation and the like is less than ten meters.
The special protection area range of the subway and the light rail is generally specified as follows:
(1) the outer sides of the outer side lines of the underground station and the tunnel structure are within five meters, wherein the outer sides of the outer side lines of the lake-passing tunnel structure are within fifty meters;
(2) the ground station and the outer side of the ground line embankment or cutting are within three meters;
(3) the outer sides of the outer side lines of the elevated station and the elevated line structure are within three meters;
(4) the outer side of the building structure such as an entrance, a ventilation pavilion, a cooling tower, a vehicle base, a control center, a main substation and the like is within five meters.
Regulations set up regulations for controlling activities in protected or special care areas:
before relevant departments such as planning, housing urban and rural construction, municipal administration (city management), water conservancy (water affairs), transportation and the like carry out administrative permission according to law on construction or operation activities in a control protection area, the rail transit management unit should ask for opinions in writing, and should give written responses within the time limit specified by the relevant departments. The control contents are listed as "construction projects for carrying out reconstruction and extension of buildings, and obtaining planning and construction permission by law".
At present, with the continuous extension of rail transit in urban underground, the change of the underground and overground surrounding environment and load passing by the rail transit all can influence the safe operation of the rail transit. The removal, new construction or renovation of buildings above, above or below the ground surface of rail transit tunnels is unavoidable. In the past, most researches are carried out on the influence and protection of the rail transit shield construction on the existing ground building, and the influence of the dismantling and unloading of the building above the operated rail transit tunnel and the reconstruction construction loading on the tunnel structure of the rail transit section is reduced.
Due to the fact that large-area unloading and loading above the shield tunnel are caused by the original building dismantling and rebuilding construction, repeated heaving and sinking deformation of the shield tunnel is easily caused, for example, the influence of disturbance that the traffic tunnel floats upwards first and then sinks twice is easily caused, cracking and water seepage of the shield tunnel are further caused, and the operation safety of rail transit is endangered.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a new method for dismantling and rebuilding existing foundation buildings in a rail transit protection area, which can reduce the influence of the dismantling and unloading of buildings above an operated rail transit tunnel and the loading of rebuilding construction on a tunnel structure of a rail transit area to the maximum extent and ensure the safe operation of rail transit.
In order to achieve the purpose, the invention adopts the technical scheme that: a dismantling and rebuilding construction method for an existing foundation building in a rail transit protection area comprises the following steps:
(1) dismantling the original upper structure: in the dismantling process, keeping the load above the rail-crossing shield interval unchanged, and implementing layered dismantling of the existing building;
(2) dismantling the original foundation and excavating foundation earthwork: partitioning and partitioning the original foundation of the existing building, keeping the load unloading and balance weight balance during earth excavation and cushion layer construction during construction of each block, and performing the operation during the daily track traffic outage period;
(3) pouring a foundation and applying an upper load: the step of pouring the foundation comprises: processing reinforcing steel bars, binding the reinforcing steel bars, welding steel plate waterstops, hanging molds and pouring bottom plate concrete, and controlling the replacement of the structural bottom plate and the original earthwork to be finished during the daily outage period of the rail transit, wherein a whole raft foundation capable of dispersing pressure applied to the rail transit tunnel is adopted, and the difference value between the load of the rebuilt load and the load of the excavation unloading of the original foundation in the step (2) is controlled to be less than 20KN/m2(ii) a And the load applied in the upper structure construction and decoration stages is controlled to be uniformly and uniformly increased or decreased;
wherein, in the steps (1) to (3), each step comprises monitoring the deformation of the rail transit structure in the construction process.
According to some preferred aspects of the present invention, in step (1), the original superstructure is removed by using a vibration-free machine or a vibration-free cutting method.
According to some preferred aspects of the invention, in the step (1), during the dismantling operation, the dismantled fragments are uniformly laid on the construction floor, then the method of the chute is utilized, the dismantled fragments uniformly laid on the floor are conveyed to the next floor by the chute, meanwhile, the fragments transferred from the upper layer are uniformly laid on the lower floor, and the like until the fragments are safely dismantled to the ground.
According to some preferred aspects of the invention, in the step (2), the bedding construction is carried out by hoisting the precast concrete plate in place and then paving the hot-melt or self-adhesive waterproof coiled material.
According to some preferred aspects of the present invention, in the step (2), the controlEach block has an area of 50-70m2
According to some preferred aspects of the invention, in the steps (2) and (3), the operation steps of dismantling the original foundation and excavating foundation earthwork and pouring the foundation are carried out in a manner of first far away from the track and then near to the track.
According to some preferred and specific aspects of the present invention, in steps (1) to (3), the absolute settlement amount and the horizontal displacement amount of the rail transit structure caused by construction are controlled to be less than or equal to 10 mm.
According to some preferred and specific aspects of the present invention, in steps (1) - (3), the curvature radius R ≧ 15000m and the relative curvature ≦ 1/2500 of the construction-induced tunnel deformation curve are controlled.
According to some preferred and specific aspects of the invention, in said monitoring, the monitoring period is such that the initial value is determined from the beginning of the month before the construction until 1 month after the construction is completed and the structural deformation is stable, the criterion for said deformation stability being defined as the last 20 balance average speed being not more than 0.01 mm/day.
According to some preferred aspects of the invention, the method further comprises the step of reinforcing the foundation and/or providing a foundation pit enclosure prior to performing step (1).
According to some preferable aspects of the invention, the method further comprises performing numerical simulation analysis on the engineering based on a three-dimensional dynamic model for dismantling and rebuilding the original structure, which is established by the MIDAS/GTSNX geotechnical tunnel structure special finite element analysis software before the step (1) is performed, and ensuring that the deformation amount of the original structure after dismantling and rebuilding is not higher than 10 mm.
Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages:
the invention innovatively adopts the layered dynamic dismantling of the existing building; the foundation pit is reinforced or replaced, the soil strength is improved, and the uplift deformation of the soil is reduced; the block and layer excavation is carried out, the unloading area is reduced, and the large-area unloading is avoided; time-limited construction, namely reducing the exposure time of excavation of the foundation pit by utilizing the time-space effect of the foundation pit; and (3) adopting a stacking back pressure measure to ensure that the back pressure is the same as the unloading, reducing the unloading influence and other processes and measures to ensure that the risk of the existing building dismantling and rebuilding process in the rail transit control protection area on the rail transit tunnel structure is almost zero.
Drawings
FIG. 1 is a view of a location of a modified project of a northern physical examination center building of Suzhou municipal hospital in accordance with an embodiment of the present invention;
fig. 2 is a diagram showing the effect of the reconstruction of the northern physical examination center building of the Suzhou municipal hospital in the embodiment of the invention.
Detailed Description
The above-described scheme is further illustrated below with reference to specific examples; it is to be understood that these embodiments are provided to illustrate the general principles, essential features and advantages of the present invention, and the present invention is not limited in scope by the following embodiments; the implementation conditions used in the examples can be further adjusted according to specific requirements, and the implementation conditions not indicated are generally the conditions in routine experiments.
The following materials and equipment were used:
the main materials are as follows:
the main materials related to the construction method are basically the same as the conventional project construction, and all the materials meet the design requirements and the requirements of related national and industrial standards. The key is that the material of each block needs to be processed and manufactured in advance in the foundation construction stage, and the required quantity is controlled well so as to ensure the time-limited construction requirement of the site.
Construction equipment
The construction equipment related to the construction method is basically the same as the construction of the conventional project, but when the existing building in the rail crossing protection area is dismantled and rebuilt, the use of large equipment with large vibration and concentrated load in the project must be absolutely forbidden. Crushing machines such as long-arm hydraulic shears and rope saw cutters are suitable for the demolition work; the construction of the enclosure structure is preferably carried out by using vibration-free pile forming machinery such as a drilling pile foundation, a deep pile stirring machine, a static pressure pile planting machine and the like; the vertical transportation machinery is reasonably arranged according to the field condition so as to ensure the rail transportation operation safety as the premise.
Construction measuring instrument
The most important work in the implementation of the project of dismantling and rebuilding the existing buildings in the rail transit control protection area is measurement monitoring and inspection. The first-hand key data information of the change of the existing rail transit engineering structure in the project construction process is mastered through monitoring work, so that a constructor can control the construction progress and plan more reasonable construction processes. The influence of construction on the rail-to-tunnel is reduced to the minimum, and guarantee is provided.
The quality of the construction measuring instrument determines the precision of the measured data, so that timely and reliable data and information are provided for a construction party and a rail traffic related party, the influence of construction on the structure of the existing rail traffic engineering is evaluated, the structural safety of the existing rail traffic engineering is judged in time, timely and accurate prediction is provided for possible accidents, and the occurrence of serious accidents is avoided.
Construction detection instrument: 1Leica total station TM 50; 2Leica total station TC 1201; 3 Tianbao level DINI 03; 4, controlling measurement adjustment software Cosawin; 5, a crack microscope; 7, a prism group; 8 interphone GP 88S; a 9-atmosphere thermometer DYM 3; 10 digital camera samsung DSC-W320; 11 miner's lamp.
At present, with the continuous extension of rail transit in urban underground, the change of the underground and overground surrounding environment and load passing by the rail transit all can influence the safe operation of the rail transit. The removal, new construction or renovation of buildings above, above or below the ground surface of rail transit tunnels is unavoidable. In the past, most researches are carried out on the influence and protection of the rail transit shield construction on the existing ground building, and the influence of the dismantling and unloading of the building above the operated rail transit tunnel and the reconstruction construction loading on the tunnel structure of the rail transit section is reduced. Due to the fact that large-area unloading and loading above the shield tunnel are caused by the original building dismantling and rebuilding construction, repeated heaving and sinking deformation of the shield tunnel is easily caused, for example, the influence of disturbance that the traffic tunnel floats upwards first and then sinks twice is easily caused, cracking and water seepage of the shield tunnel are further caused, and the operation safety of rail transit is endangered.
Based on the method, the applicant provides a method for dismantling and rebuilding existing foundation buildings in a rail transit protection area, wherein the methodThe method comprises the following steps: (1) dismantling the original upper structure: in the dismantling process, keeping the load above the rail-crossing shield interval unchanged, and implementing layered dismantling of the existing building; (2) dismantling the original foundation and excavating foundation earthwork: partitioning and partitioning the original foundation of the existing building, keeping the load unloading and balance weight balance during earth excavation and cushion layer construction during construction of each block, and performing the operation during the daily track traffic outage period; (3) pouring a foundation and applying an upper load: the step of pouring the foundation comprises: processing reinforcing steel bars, binding the reinforcing steel bars, welding steel plate waterstops, hanging molds and pouring bottom plate concrete, and controlling the replacement of the structural bottom plate and the original earthwork to be finished during the daily outage period of the rail transit, wherein a whole raft foundation capable of dispersing pressure applied to the rail transit tunnel is adopted, and the difference value between the load of the rebuilt load and the load of the excavation unloading of the original foundation in the step (2) is controlled to be less than 20KN/m2(ii) a And the load applied in the upper structure construction and decoration stages is controlled to be uniformly and uniformly increased or decreased;
wherein, in the steps (1) to (3), each step comprises monitoring the deformation of the rail transit structure in the construction process.
Specifically, in the step (1), the original superstructure is dismantled by adopting a vibration-free machine or a vibration-free cutting method.
Specifically, in the step (1), during dismantling operation, the dismantled fragments are uniformly laid on a construction floor, the dismantled fragments uniformly laid on the floor are conveyed to the next floor by using a chute method, meanwhile, the fragments transferred from the upper layer are uniformly laid on the lower floor, and the rest is done until the fragments are safely dismantled to the ground.
Specifically, in the step (2), the cushion layer construction is carried out by hoisting a precast concrete plate in place and then paving and pasting hot-melt or self-adhesive waterproof rolls.
Specifically, in the step (2), the area of each block is controlled to be 50-70m2
Specifically, in the steps (2) and (3), the operation steps of dismantling the original foundation, excavating foundation earthwork and pouring the foundation are carried out in a mode of moving far from the track and then moving near the track.
Specifically, in the steps (1) to (3), the absolute settlement amount and the horizontal displacement amount of the rail transit structure caused by construction are controlled to be less than or equal to 10 mm.
Specifically, in the steps (1) to (3), the curvature radius R of a tunnel deformation curve caused by construction is controlled to be more than or equal to 15000m, and the relative bending is controlled to be less than or equal to 1/2500.
Specifically, in the monitoring, the monitoring period is that the initial value is measured from the beginning of the first month before the construction until the construction is finished for 1 month, the structural deformation is stable, and the standard of the deformation stability is defined as that the last 20 balance average speed is not more than 0.01 mm/day.
Specifically, the method further comprises the step of reinforcing the foundation and/or arranging a foundation pit enclosure structure before the step (1) is carried out.
Specifically, the method further comprises the step of carrying out numerical simulation analysis on the engineering based on a three-dimensional dynamic model for original structure demolition and reconstruction established by special finite element analysis software for the MIDAS/GTS NX geotechnical tunnel structure before the step (1), and ensuring that the deformation of the original structure after demolition and reconstruction is not higher than 10 mm.
Specifically, before the engineering is implemented, a third party with relevant qualifications should provide a safety influence evaluation report of the reconstruction project on the rail transit; carrying out strict settlement and deformation monitoring on the track of the construction affected area in the whole construction period; on the premise of keeping the load above the rail-to-shield section in operation unchanged as much as possible, implementing layered dynamic dismantling and new construction of the existing house; in the skylight period of rail transit operation, a layered and regional load replacement mode is adopted, and the load change clearance time and the overall construction progress of the project are controlled by combining related monitoring data; by adopting corresponding technical measures, the special requirements of each subsection project on the construction process and the clearance time caused by layering and partition construction are met.
Specifically, the evaluation content of the security impact evaluation report includes: influence of the unloading stage of building demolition on the interval tunnel; influence of original building foundation demolition on the inter-zone tunnel; the influence of the upper structure reconstruction loading stage on the interval tunnel; and (5) analyzing the stress of the tunnel segment. In some embodiments of the present invention, before the construction, the following information is obtained: acquiring starting and ending mileage of a left line and a right line of a shield tunnel part of a track traffic interval related to existing building demolition and reconstruction, line length, and related data of projects including a shield interval tunnel body, a communication channel and a pump room, water prevention and drainage design, shield entering and exiting hole foundation reinforcement and the like; drawing a plan view related to a tunnel interval;
acquiring the longitudinal slope trend of each section of the interval tunnel line, the maximum and minimum longitudinal slope values, the radius parameter of the vertical curve of the line, the buried depth range of the interval line, engineering geology and hydrogeology conditions along the line during rail crossing construction, stratum characteristics, ground environment and other data; drawing a geological profile related to a tunnel interval;
acquiring relevant parameters of shield tunnel segment design: a segment width B; the inner diameter r of the pipe piece; an outer diameter R; the thickness t of the pipe piece; the number of the duct piece blocks s and the assembly form;
acquiring the health condition of duct pieces in a rail transit section by utilizing the rail transit late-time outage period, and acquiring field image data such as whether the duct pieces on the left and right lines have missing edges and falling corners, splicing flatness, wrong platforms, leakage points in a tunnel, repair traces and the like through field investigation;
and determining a tunnel mileage area which is proposed to be built and has influence on the rail transit shield tunnel by the existing building. And acquiring monitoring data of the structural settlement monitoring points for 1-6 months, and drawing a settlement curve graph. And acquiring a tunnel displacement value and an accumulated heave value from the monitoring data. And forming original monitoring data information of the rail transit in the normal operation stage.
Specifically, the method also comprises the following operations before construction: analyzing the general design of the foundation and the structure of the proposed building and the relation between the general design and the rail transit interval, and preliminarily determining the specific construction steps of the reconstruction project: dismantling, foundation reinforcing, foundation construction and superstructure to form a foundation pressure schematic diagram;
and establishing a three-dimensional dynamic model for dismantling and rebuilding the original structure by adopting special finite element analysis software for the MIDAS/GTS NX rock-soil tunnel structure according to the engineering geological conditions of the proposed building, including landform, composition and characteristics of foundation soil, hydrogeological conditions and foundation design parameters.
According to the simulation calculation, when an original building is dismantled, the maximum uplift value of the soil body is obtained, the uplift of the soil body is increased when an original foundation is excavated and dismantled, the uplift value is accumulated, the soil body slightly sinks after the upper building is rebuilt, the final uplift value is obtained after the rebuilding is completed, whether the standard is met or not is judged, and then corresponding improvement and adjustment are carried out.
Specifically, the method also comprises the following operations before construction: and (5) searching reinforcement bars at different embedding depth sections of the duct piece through the section duct piece structural design drawing. And (4) carrying out the reinforcement rechecking calculation of the bending component on the tunnel segment according to the reinforcement arrangement at the outer side and the reinforcement arrangement at the inner side of the segment. And finally, judging the influence degree of the reconstruction on the rail-crossing tunnel by analyzing the internal force of the interval in the process of dismantling and reconstructing.
Specifically, demolition of existing buildings includes:
the principle of existing building demolition is to implement layered dynamic demolition of existing buildings and effectively reduce the vibration effect in the demolition process on the premise of keeping the load above the rail-crossing shield interval in operation unchanged as much as possible;
when an original building is dismantled, the building is generally dismantled by adopting a vibration-free machine or a cutting method, such as a crawler-type long-arm hydraulic shear or a rope saw cutting method, and the machine is parked in an area far away from a light rail tunnel in a construction site during operation, so that adverse effects on the light rail tunnel caused by the self weight of the machine and the vibration generated during construction operation are avoided. When the railway track is dismantled, damping materials are paved on the peripheral ground, so that the adverse effect of impact vibration on the track crossing interval structure is reduced;
during the dismantling operation, the dismantled fragments are uniformly laid on a construction floor. And then, using a method similar to a chute to convey the demolished fragments uniformly laid on the floor to the next floor by using the chute, and meanwhile, paying attention to uniformly lay the fragments transferred from the upper layer on the lower floor, and so on until the fragments are safely demolished to the ground. Therefore, the vibration is reduced, and the adverse effect of the change of the load of the demolition area on the underground light rail tunnel is reduced;
and (3) strictly monitoring the tunnel by adopting an automatic monitoring system, stopping construction for three to four days after each layer is removed, recording and analyzing the corresponding deformation of the tunnel after each layer is removed by a professional organization, and removing the next layer under the condition that the deformation is stable and the corresponding control requirement is met.
Specifically, in order to prevent that the existing foundation from demolising and arousing when newly-built the basis that the soil body warp and then influence the settlement and the uplift in tunnel, in order to avoid adopting the tunnel deformation that dynamic compaction method compaction ground brought simultaneously, the ground treatment commonly used generally has: soil body reinforcing methods such as compaction grouting, triaxial mixing piles, high-pressure jet grouting piles, biaxial mixing piles, replacement and filling and the like. The reinforcing or filling-replacing depth, the soil volume and the like are implemented by design drawings and safety evaluation reports which are approved by rail transit departments.
Specifically, as the reconstruction of the general existing buildings is positioned in the areas with more luxurious cities or higher building density, the construction site is narrower, and the foundation pit enclosure can not only ensure the safety of project construction, but also play a role in guaranteeing the safety of rail transit;
when designing a foundation pit, a retaining form with minimum disturbance to a section shield is generally adopted, for example, an underground diaphragm wall, a bored pile, a deep mixing pile and the like are adopted for a deep foundation, a soil nail wall or a Larsen steel sheet pile and the like can also be adopted for a shallow foundation, a driving-in type or vibration type pile is not suitable to be used, and if the site limitation needs to use a steel sheet pile, a static pressure pile planting method is adopted for construction. The designed enclosing structure is embedded with a certain depth and an embedded area which strictly avoid the shield tunnel for a certain safety distance;
in order to reduce the disturbance to the subway, a well point dewatering mode is not adopted in the foundation pit dewatering principle in the construction area, and the problems of surface water and underground water are solved by adopting a mode of digging a water collecting pit for open drainage while excavating the foundation pit.
Particularly, for shallow foundation reconstruction buildings, the whole raft foundation with good integrity and rigidity is suitable for the foundation, so that the pressure of the tunnel given by the reconstruction building foundation is uniformly dispersed. The difference value of the load loaded after the reconstruction and the load of the soil body unloaded by the excavation of the foundation pit is controlled within 20 KN/square meter. According to the safety influence evaluation report and the rail transit protection special design and construction scheme demonstrated by experts, the size of each block division is regulated, and each block needs to be completely finished in a 'skylight period' of rail transit operation, namely the construction working time of each section is only about 7 hours. According to the 'skylight period' and the load difference control value, the whole plate foundation is divided into a plurality of blocks, and the earthwork excavation, cushion layer pouring, water prevention, bottom plate steel rib plate binding, template supporting and concrete pouring work of each block are completed within 7 hours of the 'skylight period'. Meanwhile, preparation work of all procedures is required to be done. The area of each block can be properly increased by using the foundation pressure diffusion angle theory and through the balance weight heaping and pressurizing at the periphery of the construction block according to the distribution characteristics of soil between the foundation burial depth of the rebuilt building and the tunnel burial depth.
Specifically, the earth excavation is carried out according to the principles of partition, block, symmetry, balance and time limitation. Cleaning, cutting and partitioning the original foundation of the existing building in advance; in order to ensure unloading and balance weight, excavated earthwork or construction waste is determined according to the field condition, and if the weight is required to be balanced, the two sides of the base of the pile can be balanced firstly. In order to accelerate the construction speed, the concrete cushion layer is preferably hoisted in place by adopting a precast concrete plate, and then hot-melt or self-adhesive waterproof coiled materials are paved. If the foundation has no waterproof requirement, the foundation can be directly constructed. The displacement, stress, water pressure, tunnel settlement and the like of the soil body are tracked and monitored in the earth excavation construction.
Specifically, the foundation construction process: processing steel bars → binding steel bars → welding steel plate water stop band → hanging mould → pouring concrete on the bottom plate. And the replacement of the structural bottom plate and the original earthwork is completed within a limited time, so that the rebound deformation of the lower soil body and the tunnel caused by large excavation area is reduced. The construction period of the foundation structure is carried out by utilizing a 'skylight period' of rail transit, so most of the time is in late night and early morning, the supply time and the supply quantity of used steel bar and iron pieces, template supporting materials, installed and pre-buried pipelines and poured concrete are ensured, and the time limit of a construction block is met. Various materials used in the construction of the foundation should be processed in advance. For the situation that the number of the longitudinal blocks is large and the construction joints of the bottom plate are increased, the following technical measures are adopted: the bottom plate reinforcement cage adopts a prefabricated form, is manufactured in the peripheral field in advance, and is hoisted in place. The steel bar joint is connected with a reserved connector; the main reinforcement is divided into blocks to cause more joints, and all the main reinforcement adopts a I-level straight thread connection mode; the end sealing mould can adopt a quick and easy net or a wire netting which is free from being dismantled; when the whole plate foundation with waterproof requirement is constructed, a waterstop is preferably arranged at the construction joint or anti-seepage measures are preferably adopted. The single-component water-swelling sealing glue and the full-section grouting pipe can be combined for water prevention. Related construction operators need to be matched sufficiently, and technicians and acceptance personnel also need to be monitored by a side station to ensure that one-time acceptance passes. If the rail transit protection scheme needs to carry out counterweight stacking pressurization on a new pouring foundation, the bottom plate concrete starts to be stacked after being initially set for 3-5 hours, and the stacking can adopt bagged steel sand. The stacking capacity is adjusted according to the design scheme and the specific stacking capacity is adjusted according to the tunnel monitoring data. In the construction process, the back pressure work can be completed as soon as possible by pouring early strength concrete. The construction of the foundation subareas can adopt a skip method and can also be organized into flowing water construction, and the adjacent blocks can be excavated after the previous block is stacked. However, the construction of the skip method requires care for the connection mode of the steel bars, and not only the construction quality but also the construction time need to be considered.
Specifically, in superstructure construction and decoration: the tunnel interval is raised in the common basement or foundation excavation stage, the tunnel interval sinks with the loading of a newly-built building in the reconstruction process, the maximum deformation value of the tunnel interval reaches the peak value near the foundation or basement bottom plate construction stage, and the tunnel interval is gradually reduced in the subsequent building reconstruction. Therefore, the main work of the upper structure in the construction and decoration stages is to ensure that the whole loading work is balanced at a constant speed and avoid sudden change. And meanwhile, related monitoring data should be mastered in time, and especially the deformation of the tunnel structure at the final loading stage is large.
Specifically, construction monitoring is carried out according to three major stages of construction preparation, construction implementation and completion acceptance. The monitoring aims to master the change of the existing rail traffic engineering structure in the project construction process through monitoring work, provide timely and reliable data and information for a construction party and a rail traffic related party, evaluate the influence of construction on the existing rail traffic engineering structure, judge the structural safety of the existing rail traffic engineering in time, provide timely and accurate forecast for possible accidents and avoid the occurrence of serious accidents.
The monitoring content should include: monitoring the structural deformation of the rail transit, monitoring the environment of the middle part of the rail transit and the construction project,
Monitoring construction projects constructed near the traffic side of the rail and monitoring foundation pit engineering of the construction projects.
The foundation pit engineering monitoring project comprises:
firstly, monitoring the arrangement settlement and horizontal displacement of the fender pile top;
monitoring the settlement displacement of the earth surface outside the pit;
monitoring the settlement of surrounding roads, pipelines and buildings;
fourthly, monitoring the resilience of the soil body;
and fifthly, safely inspecting the foundation pit.
Suzhou track traffic No. 2 line safety monitoring
Monitoring the horizontal displacement of a tunnel structure;
monitoring the vertical displacement of the structure;
monitoring vertical displacement of the ballast bed;
fourthly, monitoring the clearance convergence of the tunnel structure;
differential settlement;
sixthly, structural cracks;
and seventhly, safely patrolling the rail.
The monitoring period is to measure an initial value from one month before construction until the engineering construction is finished for one month and the structure is deformed stably. The deformation stability criterion is that the last 20 balance average speeds are not more than 0.01 mm/day. The track monitoring frequency is 2 times/day in the stage from the existing building demolition to the building capping stage, wherein the track monitoring is performed once in the track traffic operation stage and the shutdown stage respectively.
The tunnel datum points are distributed in a rail traffic track laying base mark or drilling buried point mode, the position of the datum points is outside a deformation area, the number of the elevation datum points is not less than 3, and the number of the plane datum points is not less than 4. And (3) arranging 12 working base points at the two ends of the left and right lines of the tunnel outside the affected area of the foundation pit, wherein the components are L-shaped prisms, holes are drilled in the pipe pieces for installation, and every three prisms are arranged at one section and are positioned on the arch waist of the tunnel.
The arrangement of each monitoring point extends 30 meters from the corresponding area of the project to be reconstructed to two sides respectively in principle, the left line and the right line are uniform, each 5 rings of monitoring sections are provided, and the encryption of the project influence area is provided with 3 rings of sections. Vault settlement monitoring points are distributed at appropriate positions of the tunnel vault, and contact networks are avoided; in the track bed settlement monitoring range, two automatic monitoring points are arranged on the track beds on two sides of the track. One manual monitoring point is arranged in the middle of the ballast bed. The tunnel structure convergence automatic monitoring point and the tunnel structure horizontal displacement and vault settlement automatic monitoring point adopt a common point, the burying principle and the burying method are consistent, data acquisition is completed through a TM50 measuring robot, and then the convergence change value is obtained through coordinate calculation.
In order to ensure the quality of monitoring results and accelerate the information feedback speed, monitoring results must be available for each monitoring, the monitoring results are analyzed in time, and monitoring results and analysis reports are submitted to relevant units in the day.
The above technical solution is further explained by combining specific application examples on the basis of the above technical solution:
the project reconstructed by the northern physical examination center building of Suzhou municipal Hospital is located in northern district of Guanjilu No. 240 municipal Hospital in the Gusu district, and the location of the project is shown in FIG. 1.
The original site of the project is the emergency department and outpatient department of the municipal hospital, the emergency department is 4 layers, the outpatient department is 2 layers, the brick structure, the original building foundation form is raft foundation, the buried depth is about 0.8m (2 independent foundations with the buried depth of 2.9m are arranged at the southwest corner of the original building physical examination center). At present, the construction project needs to be rebuilt in the original site by dismantling the original old building and foundation.
The north physical examination center and the clinic building reconstruction project of the Suzhou municipal hospital are positioned right above the left tunnel between the operated Suzhou rail traffic No. 2 linear pond street station and the operated railway station, are positioned in a special protection area, are respectively 6.45 m and 11.46m away from the right tunnel, and are covered with 9.27m of soil. The project is dismantled and rebuilt within the range of the rail transit control protection area, and the project of the existing rail transit No. 2 line are influenced mutually.
The upper part of the proposed building is 1-4 layers, the physical examination center building (the original emergency call building) is 4 layers above the ground, the outpatient department is 2 layers above the ground, and raft foundations are adopted. Total engineering floor area is about 3083.92m2. The project implementation effect is shown in fig. 2.
Protection standards for track traffic enforcement in suzhou city:
(1) the absolute settlement amount and the horizontal displacement amount of the rail transit structure (facility) caused by project construction are less than or equal to 10mm (the final displacement amount including various loading and unloading).
(2) The curvature radius R of the tunnel deformation curve caused by project construction is more than or equal to 15000m, and the relative bending is less than or equal to 1/2500.
(3) For high-rise and super high-rise buildings, the additional influence on the rail transit caused by post-construction settlement is strictly controlled, and the bearing capacity of a pile foundation needs to be controlled necessarily.
(4) The special protection area ranges of the subway and the light rail are as follows: and the outer sides of the outer side lines of the underground station and the tunnel structure are within five meters, and the outer sides of the outer side lines of the lake-passing tunnel structure are within thirty meters.
Based on a three-dimensional dynamic model of original structure demolition and reconstruction established by special finite element analysis software for the MIDAS/GTS NX rock-soil tunnel structure, the engineering is subjected to numerical simulation analysis, and the following conclusion is preliminarily obtained:
(1) according to the calculation result, when the original building is dismantled, the maximum uplift of the soil body is 3.7mm, the uplift of the soil body is increased when 2m of excavation is carried out to dismantle the original foundation, the accumulated uplift is 6.6mm, the soil body slightly sinks after the upper building is rebuilt, and the final uplift is 2.7mm after the rebuilding is finished.
(2) When the original building is dismantled, the maximum bulge of the left tunnel is 1.7mm, and the maximum bulge of the right tunnel is 0.9 mm; dismantling the raft foundation, and excavating earthwork of 2m, wherein the maximum bulge of the left-line tunnel is 3.4mm, and the maximum bulge of the right-line tunnel is 1.3 mm; after the reconstruction and loading, the left line and the right line both sink, the final bulge of the tunnel of the left line is 1.4mm, and the final bulge of the tunnel of the right line is 0.5mm, and the requirement of a 10mm control value is met.
Earth excavationConstruction is carried out according to the principles of partition, block division, symmetry, balance and time limitation. When the whole raft foundation of the building is rebuilt, the block construction is adopted, the area of each block is controlled to be 50-70m2Within; and the time from excavation of each foundation pit to completion of foundation construction is controlled within 7 hours of the skylight period of the Suzhou rail traffic operation; the scheme of foundation construction should follow the principle of first far and then near the track. In order to ensure unloading and balance weight balance, the excavated earthwork balances the two sides of the piled foundation, and simultaneously accelerates the construction of a cushion layer and a bottom plate of an excavated area, and ensures that the load of the area is balanced and stable.
Existing building demolition construction stage
Dismantling a building:
the existing buildings are all dismantled by manpower, hydraulic pliers and a rope saw. Through multiple times of expert demonstration, the existing building above the ground is directly and dynamically dismantled layer by layer under the condition of strictly monitoring the tunnel. And (3) dismantling the main building from top to bottom, stopping construction for three to four days after each layer is dismantled, evaluating the influence on rail crossing by monitoring data by a monitoring unit, and continuing construction after the permission of a relevant department is obtained. The demolition is implemented in the daytime, and the garbage is cleared at night.
Specifically, in the present example, the principle of existing building demolition is to implement layered dynamic demolition of an existing building on the premise of keeping the load above the rail-crossing shield zone in operation as unchanged as possible, and effectively reduce the vibration effect during demolition;
when an original building is dismantled, the building is generally dismantled by adopting a vibration-free machine or a cutting method, such as a crawler-type long-arm hydraulic shear or a rope saw cutting method, and the machine is parked in an area far away from a light rail tunnel in a construction site during operation, so that adverse effects on the light rail tunnel caused by the self weight of the machine and the vibration generated during construction operation are avoided. When the railway track is dismantled, damping materials are paved on the peripheral ground, so that the adverse effect of impact vibration on the track crossing interval structure is reduced;
during the dismantling operation, the dismantled fragments are uniformly laid on a construction floor. And then, using a method similar to a chute to convey the demolished fragments uniformly laid on the floor to the next floor by using the chute, and meanwhile, paying attention to uniformly lay the fragments transferred from the upper layer on the lower floor, and so on until the fragments are safely demolished to the ground. Therefore, the vibration is reduced, and the adverse effect of the change of the load of the demolition area on the underground light rail tunnel is reduced;
and (3) strictly monitoring the tunnel by adopting an automatic monitoring system, stopping construction for three to four days after each layer is removed, recording and analyzing the corresponding deformation of the tunnel after each layer is removed by a professional organization, and removing the next layer under the condition that the deformation is stable and the corresponding control requirement is met.
Foundation pit bracing:
the excavation depth of the foundation pit is 2.6m, and the original design steel sheet pile cantilever type supporting form is adopted. In order to avoid the influence of vibration generated in the original channel steel driving process on the track operation, through expert demonstration, the original steel plate pile is changed into an SP-IV type Larsen pile, and a static pressure pile planting machine is adopted as a construction machine.
Stage of foundation construction
Earth excavation: the foundation pit earthwork excavation is divided into a south area and a north area, wherein the south area is as follows: S1-S12, wherein the north area is as follows: N1-N14, 26 blocks in total; the excavation area of the upper earthwork block of the interval tunnel is 50m2The excavation area of the rest east earthwork blocks is 70m2And (5) partitioning. During foundation ditch earthwork excavation, if shield interval tunnel structure monitoring data is unusual, surpass alarm value (deflection reaches 7mm), should stop the excavation immediately, wherein, at this in-process, adopted the heap to carry the back pressure, adopt the iron sand package that prepares in advance to carry out the back pressure, the principle is: "the earthwork excavation is layered, blocked, symmetrical, the earth retaining wall is protected, the excavation is finished in limited time".
Bottom plate construction: because the steel bars among the partitioned bottom plates are connected through the connectors, the workload is large, the required time is long, in order to reduce the soil unloading time as much as possible, the upper soil body (1.5m) is firstly excavated during the operation, and after the rail is handed over and is stopped, the excavation of the residual earthwork and the pouring of the bottom plates are completed.
In particular, in this example, for shallow foundation rebuilt buildings, the foundation is preferably a one-piece raft with good integrity and rigidityThe plate foundation enables the pressure of the reconstructed building foundation to the tunnel to be uniformly dispersed. The difference value of the load loaded after reconstruction and the soil load unloaded in the excavation of the foundation pit is controlled to be 20KN/m2Within.
And (3) foundation construction process: processing steel bars → binding steel bars → welding steel plate water stop band → hanging mould → pouring concrete on the bottom plate. And the replacement of the structural bottom plate and the original earthwork is completed within a limited time, so that the rebound deformation of the lower soil body and the tunnel caused by large excavation area is reduced. The construction period of the foundation structure is carried out by utilizing a 'skylight period' of rail transit, so most of the time is in late night and early morning, the supply time and the supply quantity of used steel bar and iron pieces, template supporting materials, installed and pre-buried pipelines and poured concrete are ensured, and the time limit of a construction block is met. Various materials used in the construction of the foundation should be processed in advance. For the situation that the number of the longitudinal blocks is large and the construction joints of the bottom plate are increased, the following technical measures are adopted: the bottom plate reinforcement cage adopts a prefabricated form, is manufactured in the peripheral field in advance, and is hoisted in place. The steel bar joint is connected with a reserved connector; the main reinforcement is divided into blocks to cause more joints, and all the main reinforcement adopts a I-level straight thread connection mode; the end sealing mould can adopt a quick and easy net or a wire netting which is free from being dismantled; when the whole plate foundation with waterproof requirement is constructed, a waterstop is preferably arranged at the construction joint or anti-seepage measures are preferably adopted. The single-component water-swelling sealing glue and the full-section grouting pipe can be combined for water prevention. Related construction operators need to be matched sufficiently, and technicians and acceptance personnel also need to be monitored by a side station to ensure that one-time acceptance passes. If the rail transit protection scheme needs to carry out counterweight stacking and pressurization on a new pouring foundation, the bottom plate concrete starts to be stacked after being initially set for 3-5 hours, and bagged steel sand can be adopted for stacking. The stacking capacity is adjusted according to the design scheme and the specific stacking capacity is adjusted according to the tunnel monitoring data. In the construction process, the back pressure work can be completed as soon as possible by pouring early strength concrete. The construction of the foundation subareas can adopt a skip method and can also be organized into flowing water construction, and the adjacent blocks can be excavated after the previous block is stacked. However, the construction of the skip method requires care for the connection mode of the steel bars, and not only the construction quality but also the construction time need to be considered.
Process scheduling of blocks in tunnel shield interval
Figure RE-GDA0002545980180000131
Main structure construction stage
According to the design scheme requirement during the upper structure construction, the upper structure of the outpatient building is preferentially constructed, the rule of the influence of loading on the tunnel interval is mastered on the basis of the monitoring of the outpatient building, and then the upper structure is used for guiding the reconstruction of the 4-layer emergency building. And (4) according to the monitoring report, when the binding of the reinforcing steel bars of the second floor of each area to the concrete to be cast is completed, the left and right tunnels tend to be stable.
Specifically, the tunnel section is raised in the general basement or foundation excavation stage, the maximum deformation value of the tunnel section is required to reach a peak value near the foundation or basement bottom plate construction stage along with the tunnel section sinking when a newly-built building is loaded in the reconstruction process, and the tunnel section is raised gradually and becomes smaller in the subsequent building reconstruction. Therefore, the main work of the upper structure in the construction and decoration stages is to ensure that the whole loading work is balanced at a constant speed and avoid sudden change. And meanwhile, related monitoring data should be mastered in time, and especially the deformation of the tunnel structure at the final loading stage is large.
Construction survey monitoring
The engineering monitoring period is as follows: and measuring an initial value from one month before construction until the construction of the project is finished for 1 month, and the structure is deformed stably. The deformation stability criterion is that the last 20 balance average speeds are not more than 0.01 mm/day. The track monitoring frequency is 2 times/day in the stage from the existing building demolition to the building capping stage, wherein the track monitoring is performed once in the track traffic operation stage and the shutdown stage respectively.
Final monitoring results and tunnel change rules:
the method comprises the following steps that a foundation pit is dismantled and constructed for foundation pit enclosure construction from 11/4/2017 to 12/18/2017, and when the foundation pit is shared for 38 days, monitoring data show that the vertical deformation and the horizontal deformation of a left wire structure and a right wire structure of a tunnel do not exceed 2mm, and the variation is small; constructing the foundation pit below +/-0.00 from 18 days in 12 months in 2017 to 1 day in 2 months in 2018, wherein monitoring data show that the accumulated vertical displacement deformation of the left and right wire structures of the tunnel reaches 3mm, and the accumulated horizontal displacement and convergence deformation is less than 2mm in 45 days in common; and after the foundation pit construction is finished within +/-0.00 day from 1 month 2 in 2018 to 5 months 3 and 2018, tracking and monitoring data show that the accumulated vertical and horizontal displacement deformation of the left and right line structures of the tunnel is not increased, and the data tend to be stable.
Evaluation of engineering results
The engineering strictly carries out partition and sectional construction according to the design, construction and monitoring scheme demonstrated by experts, related dismantling and rebuilding work is completed safely, on time, quality guarantee and quantity guarantee, the subway tunnel structure between a railway station and a mountain pond street station is not greatly influenced during the construction of reconstruction projects of a physical examination center building in the northern region of Suzhou municipal Hospital, and the data of each monitoring project is within the control index range of a rail company and does not exceed 5 mm. The engineering is scientifically and reasonably constructed according to design, construction and monitoring schemes strictly, the site management is standard, safety measures are in place, the working procedures are linked compactly, no construction idle period exists, monitoring data are fed back timely, the whole construction process can be carried out smoothly, and therefore the foundation pit construction does not have destructive influence on the surrounding environment. Through the application of the engineering, the advancement of the construction method is verified, and good comprehensive benefits are obtained; through the use of the construction method, the existing building above the light rail is proved to be feasible to be dismantled and rebuilt, and valuable experience is provided for the implementation of subsequent related similar construction projects. The method widens the path for finally transforming the existing buildings with high energy consumption and low energy efficiency into the green buildings with energy conservation, low carbon and environmental protection in the rail transit special protection area.
The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims (10)

1. A dismantling and rebuilding construction method for an existing foundation building in a rail transit protection area is characterized by comprising the following steps:
(1) dismantling the original upper structure: in the dismantling process, keeping the load above the rail-crossing shield interval unchanged, and implementing layered dismantling of the existing building;
(2) dismantling the original foundation and excavating foundation earthwork: partitioning and partitioning the original foundation of the existing building, keeping the load unloading and balance weight balance during earth excavation and cushion layer construction during construction of each block, and performing the operation during the daily track traffic outage period;
(3) pouring a foundation and applying an upper load: the step of pouring the foundation comprises: processing reinforcing steel bars, binding the reinforcing steel bars, welding steel plate waterstops, hanging molds and pouring bottom plate concrete, and controlling the replacement of the structural bottom plate and the original earthwork to be finished during the daily outage period of the rail transit, wherein a whole raft foundation capable of dispersing pressure applied to the rail transit tunnel is adopted, and the difference value between the load of the rebuilt load and the load of the excavation unloading of the original foundation in the step (2) is controlled to be less than 20KN/m2(ii) a And the load applied in the upper structure construction and decoration stages is controlled to be uniformly and uniformly increased or decreased;
wherein, in the steps (1) to (3), each step comprises monitoring the deformation of the rail transit structure in the construction process.
2. The method for demolition and rebuilding of existing foundation buildings in rail transit protection areas according to claim 1, wherein in step (1), the original superstructure is demolished by using a vibration-free machine or a vibration-free cutting method.
3. The method for demolishing and rebuilding of existing foundation buildings in rail transit protection areas according to claim 1, wherein in the step (1), the demolished fragments are uniformly laid on the construction floors during demolition work, and then the demolished fragments uniformly laid on the floors are transported to the next floor by using chutes and the fragments transferred from the upper floor are uniformly laid on the lower floor by using chutes, and so on until the fragments are safely demolished to the ground.
4. The method for dismantling and rebuilding an existing foundation building in a rail transit protection area according to claim 1, wherein in the step (2), the cushion layer construction is carried out by hoisting a precast concrete plate in place and then paving a hot-melt type or self-adhesive type waterproof coiled material.
5. The method for demolition and rebuilding of existing foundation buildings in rail transit protection areas according to claim 1, wherein in step (2), the area of each block is controlled to be 50-70m2
6. The method for demolishing and rebuilding of existing foundation buildings in rail transit protection areas according to claim 1, wherein in the steps (2) and (3), the steps of demolishing the existing foundation and excavating foundation earthwork and pouring the foundation are performed in a manner of going from the first to the next to the rail.
7. The method for dismantling and rebuilding an existing foundation building in a rail transit protection area according to claim 1, wherein in steps (1) - (3), the absolute settlement amount and the horizontal displacement amount of the rail transit structure caused by construction are controlled to be less than or equal to 10 mm.
8. The method for dismantling and rebuilding the existing foundation building in the rail transit protection area according to claim 1, wherein in the steps (1) - (3), the curvature radius R of the tunnel deformation curve caused by construction is controlled to be more than or equal to 15000m, and the relative bending is controlled to be less than or equal to 1/2500.
9. The method for demolition and rebuilding construction of existing foundation buildings in rail transit protection areas according to claim 1, wherein in the monitoring, the monitoring period is to measure initial values from the first month before construction until the construction is completed for 1 month and the structure is stable in deformation, and the standard for stable deformation is defined as that the last 20 balance average speed is not more than 0.01 mm/day.
10. The method for demolition and rebuilding of existing foundation buildings in a rail transit protected area according to claim 1, further comprising the step of reinforcing the foundation and/or providing a foundation pit enclosure before performing step (1); and/or the presence of a gas in the gas,
the method also comprises the step of carrying out numerical simulation analysis on the engineering based on a three-dimensional dynamic model for dismantling and rebuilding the original structure established by the special finite element analysis software for the MIDAS/GTS NX geotechnical tunnel structure before the step (1), and ensuring that the deformation of the original structure after dismantling and rebuilding is not higher than 10 mm.
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