CN113309133A

CN113309133A - Pile foundation vibration damping and resistance reducing structure for subway tunnel and design method thereof

Info

Publication number: CN113309133A
Application number: CN202110668350.5A
Authority: CN
Inventors: 林本海; 林宗涛; 唐仁
Original assignee: Guangzhou Zhenglin Engineering Technology Co ltd
Current assignee: Guangzhou Geotechnical Survey and Design Co., Ltd.
Priority date: 2021-06-17
Filing date: 2021-06-17
Publication date: 2021-08-27
Anticipated expiration: 2041-06-17
Also published as: CN113309133B

Abstract

The invention relates to a pile foundation vibration damping and resistance reducing structure for a subway tunnel, which is applied to a super high-rise residential building group right above the subway, wherein the bottom of the super high-rise residential building group is provided with a foundation transfer beam, the lower part of the foundation transfer beam is provided with a plurality of large-diameter pile foundations, the subway tunnel is arranged between the large-diameter pile foundations, and the clear distance between the plurality of large-diameter pile foundations and the side of the tunnel is not less than 3 m; the pile bottom is deeper than the tunnel bottom; the vibration reduction and resistance reduction structure is arranged on the outer surface of the large-diameter pile foundation; through the design of the damping and resistance reducing structure, the safety of the subway can be ensured, the vibration frequency of the upper building caused by subway operation can meet the standard requirement, and the comfort and the quality of the building are improved.

Description

Pile foundation vibration damping and resistance reducing structure for subway tunnel and design method thereof

Technical Field

The invention relates to the field of pile foundation vibration reduction, in particular to a pile foundation vibration reduction and resistance reduction structure for a subway tunnel and a design method thereof.

Background

With the rapid development of city updating and subway construction, the subway upper cover building conditions similar to the project are inevitable and will increase. The subway adopts the public transportation operation, the interval time of each train passing through the building is 2-6 minutes, and the vibration and noise generated by the friction and collision between the wheels of the subway and the steel rail, the friction between the subway carriage and the air and the like can bring adverse effects to the surrounding environment. Subway vibration energy is transmitted to the tunnel structure lining along the track, the railway roadbed, and then is passed to ground and superstructure via intermediate medium such as tunnel lining and surrounding stratum, ground, basis, basement structure, causes secondary vibration and noise, and direct interference upper cover building resident's daily life and rest environment reduce the life comfort level, for avoiding building structure load, the adverse effect that the pile foundation produced the subway tunnel, the clear distance of basement structure bottom plate conversion girder bottom and subway tunnel top must not be less than 1.5D 9.0 m. Therefore, 3 rows of pile foundations are required to be arranged in the middle and the outer sides of two subway tunnels respectively, and meanwhile, the horizontal clear distance between an engineering pile and the tunnels is required to be not less than 3.0m, so that the maximum diameter of the piles in the middle of the two tunnels is 2.0m, the span of a basement floor structure conversion girder is at least 14.0m, and therefore, a structure conversion type of a multi-time conversion beam is adopted for an ultra-large structural load.

In order to solve the adverse effect of vibration and noise generated during subway operation on the surrounding environment or an upper cover building, domestic and foreign scholars develop a lot of researches on vibration reduction and noise reduction on similar subjects. The results mainly based on the vibration reduction research of the subway or the building structure comprise: the method avoids the curve of a small-radius track, the tread of a lubricating wheel or a steel rail, adopts damping wheels or elastic wheels, track shock absorber fasteners, sets an elastic short-rail track, sets an elastic support for a building structure and the like.

However, the vibration and noise transmission process of the underground underpass building is complex, and the underground underpass building is influenced by a subway track structure, a subway tunnel structure and the burial depth, surrounding rocks around the subway tunnel, a building foundation and a building structure according to a transmission path, and relates to multi-disciplinary knowledge of geotechnical engineering, tunnel engineering, foundation engineering, structural engineering, vibration mechanics, structural dynamics and the like; in order to solve the problems, the mutual influence between the subway and the project building needs to be considered, and effective vibration reduction and isolation measures are taken for the upper cover building of the subway tunnel.

Disclosure of Invention

The invention aims to provide a pile foundation vibration damping and resistance reducing structure for a subway tunnel, which is applied to a super high-rise residential building group right above the subway, wherein the bottom of the super high-rise residential building group is provided with a foundation transfer beam, the lower part of the foundation transfer beam is provided with a plurality of large-diameter pile foundations, the subway tunnel is arranged between the large-diameter pile foundations, and the clear distance between the large-diameter pile foundations and the side of the tunnel is not less than 3 m; the pile bottom is deeper than the tunnel bottom; the vibration reduction and resistance reduction structure is arranged on the outer surface of the large-diameter pile foundation;

the manufacturing method of the large-diameter pile foundation comprises the steps that a circle of steel casing is sleeved on the outer edge of a reinforcement cage of the concrete pile to form the steel pipe concrete pile, a rubber layer is adhered to the outside of the steel casing through a binder, and a resistance reducing coating is coated on the outside of the rubber layer; the resistance reducing coating is an industrial lubricating grease layer, a PVC protective film is arranged outside the coating, a concrete protective layer is arranged outside the PVC protective film, and end fixing pieces are arranged at the bottoms of the protective layer and the rubber layer.

The industrial lubricating grease layer is butter.

The thickness of the coating of the industrial lubricating grease layer is 0.5mm, and the thickness of the PVC protective film is 1 mm; the protective layer tightly wraps the rubber layer. The rubber layer length is 18m, and the specification of the rubber coiled material is 6300mm multiplied by 1500mm multiplied by 30 mm.

Through comprehensive comparison of multiple pile foundation vibration damping and isolating materials, such as sand, ceramsite + sand, rubber granule + sand, rubber layer and the like, the sand, the ceramsite + sand and the rubber granule + sand have the effects of vibration damping and resistance reduction, but the construction difficulty is high, the actual engineering is difficult to implement, and the concrete can be damaged or floated due to the light specific gravity of a granular structure in the process of pouring concrete into the engineering pile.

The rubber has the characteristics of hysteresis, damping and reversible large deformation, and has a good vibration reduction effect. The vibration damper made of rubber is widely applied to the industrial and civil fields, and is particularly common in the fields of automobiles, rail traffic, spaceflight, constructional engineering and the like. Research shows that the conductivity of rock-soil mass vibration waves passing through a foundation pile can be obviously reduced by adding a vulcanized rubber layer which has good vibration reduction durability and is not easily influenced by weather on the outer wall of an engineering pile foundation, so that the aim and the effect of vibration reduction of the pile foundation are realized, and the construction difficulty is greatly reduced compared with other three groups of materials.

Therefore, finally determining the damping and resistance reduction of the pile foundation to be carried out by adopting the rubber layer. However, because the engineering pile is made of concrete and is formed after cast-in-place, the concrete pile cannot be well bonded with rubber, and meanwhile, in order to increase the compression resistance, the horizontal shear resistance and the overall stability of the engineering pile, a circle of steel casing is sleeved at the outer edge of a reinforcement cage of the concrete pile to form a steel pipe concrete pile, and a rubber layer is bonded on the outer wall of a steel pipe, the bonding problem of concrete and rubber can be well solved, the strength and the rigidity of the engineering pile are increased, and the problem that the strength and the stability of a pile body are weakened due to resistance reduction at the pile side is solved.

By coating the resistance reducing coating outside the rubber layer, the friction force generated to surrounding rock and soil bodies and the like in the compression and sinking process of the pile foundation under the action of bearing the load of the upper structure can be reduced, so that the adverse effect of the sinking of the pile foundation on the surrounding rock and soil bodies and subway tunnels in the rock and soil bodies is reduced.

The invention has the following beneficial effects: 1. according to the comparison of a plurality of groups of pile foundation vibration reduction isolation materials, such as sand grains, ceramsite, rubber grains, rubber layers and the like, the sand grains, the ceramsite + sand, the rubber grains + sand have the effects of vibration reduction and resistance reduction, but the vibration reduction and resistance reduction applied to the engineering pile has larger construction difficulty, and when the pile foundation is cast with concrete, the granular materials are damaged during construction or float due to light specific gravity. Therefore, finally, analysis and research of various performances and construction convenience are integrated, and a vibration damping scheme of externally wrapping a rubber layer after sleeving a steel casing on the outer edge of the engineering pile reinforcement cage is determined; the steel casing sleeve and the engineering pile reinforcement cage are integrated, so that the requirement on subway protection is met, the strength and rigidity of the engineering pile are improved, and the overall stability of the super high-rise structure and the foundation is ensured.

2. According to the finite element calculation result, when no resistance reducing material is arranged around the pile, the maximum settlement of 8.381mm can be caused to occur adjacent to the tunnel structure under the action of the total load of the upper structure, and the region with the maximum settlement is positioned in the direction of the arch top of the tunnel deviated to the pile foundation. When there is a friction reducing material around the pile, a maximum settlement of 4.054mm will be caused by the total load on the upper structure adjacent the tunnel structure. Therefore, the deformation influence of the resistance-reducing and sinking layer material arranged on the pile side in the tunnel range section of the engineering pile on the subway tunnel is obviously reduced, and the effective protection on the subway tunnel can be realized.

3. When no resistance reducing material is arranged around the pile, the bending moment increment of the adjacent tunnel structure is 33.943 kN.m/m under the action of the total load of the upper structure, the amplification is 56.20 percent, the bending moment increment is very large, the risk of slab staggering or cracking of the pipe piece is very large, and resistance reducing measures are required to be adopted to reduce the risk. When the resistance reducing material is arranged around the pile, the bending moment increment of the adjacent tunnel structure is 11.548 kN.m/m under the action of the total load of the upper structure, the amplification is 19.12 percent, and the tunnel is safe within the safety coefficient range of the tunnel design.

According to the finite element calculation result analysis, after the rotary excavation engineering pile above the tunnel is wrapped and coated with the rubber layer and the resistance reduction lubricating layer is coated on the outer side of the buried depth section of the tunnel, the proportion of the pile side resistance transmitted to the rock and soil mass around the pile is greatly reduced, the tunnel structure does not have large settlement and additional stress, and the safety of the tunnel structure is ensured. However, after the resistance reducing design is adopted, the lateral resistance of the engineering piles at the upper section of the tunnel cannot be exerted, and under the condition that the bearing capacity is not changed, the pile length must be increased to meet the bearing capacity of the foundation pile required by the design.

4. When the disturbance frequency of subway vibration at the pile body is 20Hz, the vibration reduction efficiency is 54 percent, and the vibration reduction efficiency is increased along with the increase of the disturbance frequency. When the disturbance frequency is 100Hz, the damping efficiency is 97%. After the engineering pile is designed by adopting vibration reduction measures, the influence of tunnel vibration on an upper building is greatly reduced, the vibration frequency of the upper building caused by tunnel operation meets the standard requirement, and the comfort and the quality of the building are improved.

Drawings

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is an exterior surface layout view of a large diameter pile of the present invention;

FIG. 3 is an enlarged schematic view of the large diameter pile of FIG. 2 of the present invention at section I;

FIG. 4 is a model diagram of a pile perimeter drag reduction material of the present invention;

fig. 5 is a simplified diagram of the vibration isolator dynamic stiffness calculation.

Detailed Description

The present invention is further described below in conjunction with the appended drawings, but does not represent the only embodiments of the present invention.

As shown in the figure, the first and second,

a pile foundation vibration damping and resistance reducing structure for a subway tunnel is applied to a super high-rise residential building group right above the subway, the bottom of the super high-rise residential building group is provided with a foundation transfer beam 1, the lower part of the foundation transfer beam is provided with a plurality of large-diameter pile foundations 2, a subway tunnel 3 is arranged between the large-diameter pile foundations, and the clear distance between the large-diameter pile foundations and the side of the tunnel is not less than 3 m; the pile bottom is deeper than the tunnel bottom; the vibration reduction and resistance reduction structure is arranged on the outer surface of the large-diameter pile foundation;

the manufacturing method of the large-diameter pile foundation comprises the steps that a circle of steel casing 4 is sleeved on the outer edge of a reinforcement cage of the concrete pile to form the steel pipe concrete pile, a rubber layer 5 is adhered to the outside of the steel casing 10 through a binder, and a resistance reducing coating 6 is coated on the outside of the rubber layer; the resistance-reducing coating is an industrial lubricating grease layer, a PVC protective film 7 is arranged outside the coating, a concrete protective layer 8 is arranged outside the PVC protective film, and an end fixing piece 9 is arranged at the bottom of the PVC protective film and the bottom of the rubber layer.

The industrial lubricating grease layer is butter.

The thickness of the coating of the industrial lubricating grease layer is 0.5mm, and the thickness of the PVC protective film is 1 mm. The rubber layer length is 18m, and the specification of the rubber coiled material is 6300mm multiplied by 1500mm multiplied by 30 mm.

And (3) rubber aging performance. The same as the building rubber shock insulation (vibration) support.

Fatigue properties of the rubber. The fatigue life (vertical loading, frequency of 4 Hz-5 Hz and force amplitude of 8 kN-40 kN) of the rubber is more than 300 ten thousand times, the surface of the rubber has no appearance damage, the change of static rigidity is not more than 15 percent, and the vertical permanent deformation is less than 1 mm.

Damping ratio of rubber. The damping ratio of the rubber is 0.07-0.1.

The rubber layer thickness was designed to be 30mm according to the vibration damping target. According to the influence depth of subway vibration and considering the safety of a pile foundation, the length of the rubber wrapping layer is 18 m. The gauge of the rubber coiled material is 6300mm multiplied by 1500mm multiplied by 30 mm.

The adhesive and the steel plate should have enough adhesion, and the damage type after the adhesion is represented as rubber damage.

TABLE 1 epoxy adhesive Properties

Calculating the vibration reduction efficiency:

(1) the formula for calculating the transmission rate of the passive vibration isolation system is as follows:

（1）

wherein the content of the first and second substances,

the nz vibration isolation system has vertical undamped circular frequency, omega is external disturbance frequency, and xi z is the vertical damping ratio of the vibration isolation system (the value of the project is 0.1).

(2) The vibration isolation system circle frequency calculation formula is as follows:

（2）

wherein the content of the first and second substances,

the dynamic stiffness of the vibration isolation system is improved,

is the mass of the vibration isolation system,

is the weight of the vibration isolation system.

(3) And calculating the dynamic stiffness of the vibration isolation system. When a 1M long steel pipe pile is taken as a research object, the total weight M =3.14 × 12 × 1 × 2500=7850 × 103kg of the steel pipe pile, and the vibration isolation system formed by the outer rubber layer and the steel pipe pile works, the actual pressure-bearing area is calculated according to the projection area, so that the actual pressure-bearing area is rectangular, the side length a is 2M, the side length b is 1M, and the thickness h is 30 mm.

Bearing area

Free area

Area ratio (form factor)

Vertical form factor

Young's modulus was found from FIGS. 1 to 4: when the HS =35, the ratio of the HS =35,

=1.5N/mm2, and the dynamic-static stiffness ratio is 1.4, then

=1.5×1.4=2.1N/mm2

Rubber Hardness (HS) and Young's modulus of elasticity: (

) The relationship of (a) is as shown in the above figures (FIGS. 1-4).

Vertical stiffness (N/mm)

=38.16×106kN/mm

(4) The vertical stiffness is substituted into the formula (2) to obtain the circular frequency of the vibration isolation system,

11（Hz）

(5) the transmission rate of the vibration isolation system can be obtained by substituting the circular frequency of the vibration isolation system into the formula (1),

vibration damping efficiency calculation table

And (4) conclusion: when the disturbance frequency of subway vibration at the pile body is 20Hz, the vibration reduction efficiency is 54 percent, and the vibration reduction efficiency is increased along with the increase of the disturbance frequency. When the disturbance frequency is 100Hz, the damping efficiency is 97%.

Industrial grease is selected as the resistance reducing coating. In order to ensure that the whole construction process can play a role in lubrication. It should also have good temperature adaptability and extreme pressure antiwear property, and have excellent water resistance, mechanical stability, rust resistance, oxidation stability, etc.

Parameter table of industrial lubricating grease

PVC protection film selects PVC plastic cloth, and the thickness is 0.5 mm. The plastic cloth should have sufficient tensile strength and smoothness.

The above description is only for the preferred embodiment of the present invention, and is not intended to limit the present invention in any way. Any simple modification, equivalent change or modification made to the above embodiments according to the technical spirit of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A pile foundation vibration damping and resistance reducing structure for a subway tunnel is applied to a pile foundation of a super high-rise residential building group above the subway, the bottom of the super high-rise residential building group is provided with a foundation transfer beam, the lower part of the foundation transfer beam is provided with a plurality of large-diameter pile foundations, a subway tunnel is arranged between the longitudinally arranged large-diameter pile foundations, and the clear distance between the plurality of large-diameter pile foundations and the side of the tunnel is not less than 3 m; the plane of the pile bottom is arranged below the plane of the tunnel bottom; damping falls and hinders structure setting in the surface of major diameter pile foundation, its characterized in that:

the large-diameter pile foundation comprises a steel pile casing sleeved on the outer edge of a reinforcement cage of the concrete pile to form a steel pipe concrete pile, a rubber layer is adhered to the outside of the steel pile casing through a binder, and a resistance reducing coating is coated on the outside of the rubber layer; the resistance reducing coating is an industrial lubricating grease layer, a PVC protective film is arranged outside the resistance reducing coating, a concrete protective layer is arranged outside the PVC protective film, and end fixing pieces are arranged at the bottoms of the PVC protective film and the rubber layer.

2. The pile foundation vibration damping and resistance reducing structure for the subway tunnel according to claim 1, characterized in that: the industrial lubricating grease layer is butter.

3. The pile foundation vibration damping and resistance reducing structure according to claim 2, wherein the coating thickness of the industrial lubricating grease layer is 0.5mm, and the thickness of the PVC protective film is 1 mm.

4. The vibration-damping and resistance-reducing structure of the pile foundation according to claim 3, wherein the rubber layer is vertically arranged to have a length of 18m, and the rubber coiled material used for the rubber layer has a specification of 6300mm x 1500mm x 30 mm.

5. The pile foundation vibration damping and resistance reducing structure according to claim 1, wherein the method for determining the thickness and hardness of the rubber layer comprises the following steps: according to the actually measured vibration frequency of the surrounding environment caused by subway vibration, the vibration frequency is 20 Hz-100 Kz, and the characteristics of the steel pipe pile, calculating the functional relation between the thickness and the hardness of the rubber layer and the vibration damping effect according to the design method of the rubber vibration damper; taking the length of the steel pipe pile of 1 meter as a calculation object;

wherein, the vertical undamped circular frequency of the ω ny vibration isolation system is the external disturbance frequency, and ξ is the vertical damping ratio of the vibration isolation system (the value of the project is 0.1);

(2) the natural circle frequency calculation formula of the vibration isolation system is as follows:

wherein m is the total weight;

(3) the relation between the static rigidity and the thickness of the shear type rubber vibration isolator with the bushing structure is as follows:

wherein Hctl =15-18m, Gj = shear modulus of rubber (N/m 2), h = r2-r1 is rubber layer thickness; wherein r2=2000+ h, r1= 2000;

after the above formula is simplified, it can be obtained:

(6) formula for calculating compression stiffness of rubber

In the formula, E: young's modulus of elasticity, a: effective pressure area, Tr: the thickness of the rubber layer;

(7) formula for calculating compression deformation of rubber

Wherein P is the lateral surface pressure of the pile body, and K is the rigidity of the rubber

Substituting (6) and (7) into the following steps:

assuming that Tr is 30mm, the pressed area is 1m2, and P is 12X 106E:

。

6. the pile foundation vibration damping and resistance reducing structure according to claim 5, wherein: when E is changed within the range of 1-6, the compression deformation of the rubber is 0.36mm at most and 0.06mm at least.

7. The pile foundation vibration damping and resistance reducing structure according to claim 6, wherein: the rubber hardness was 35 and the rubber thickness was 30 mm.

8. A design method of a pile foundation vibration damping and resistance reducing structure for a subway tunnel according to claim 1 is characterized in that:

1) performing primary treatment on the outer surface of the steel pipe, and performing oil and rust removal on the outer surface of the steel pipe, wherein the roughness meets the requirement;

2) coating the adhesive, namely coating the adhesive for 2 times at intervals of 6 hours, wherein the coating thickness meets the requirement;

3) paving and adhering the rubber coiled material, and firmly adhering the coiled material and the outer surface of the steel pipe to ensure that the thickness of the coiled material meets the requirement;

4) the end head anti-drop treatment is carried out, and an end head fixing piece is arranged at the bottom of the pile body;

5) coating butter on the surface of the rubber layer, wherein the butter is uniformly coated and the thickness of the butter is 0.5 mm;

6) the protective layer construction, PVC protection rete should closely laminate to glue with the gluing agent tightly, two coiled material joints department with adhesive tape firm in connection, end department should be fixed firm, and handle level and smooth, construct the concrete protective layer at last.

9. A design method according to claim 8, wherein:

the pile bottom of the large-diameter pile foundation is required to enter 17-50 m of medium-stroke argillaceous siltstone or 11-30 m of slightly weathered argillaceous siltstone, or 9-27 m of medium-stroke argillaceous sandstone or 9-18 m of slightly weathered gravelly sandstone, and the distance between the pile bottom and the tunnel bottom is not less than 10 m.