CN110847234A

CN110847234A - Pipe gallery protection prestressed beam and construction method

Info

Publication number: CN110847234A
Application number: CN201911242427.1A
Authority: CN
Inventors: 孙庆田; 熊阳阳; 杨壮志; 张�杰; 熊朝东; 古宗华; 王玉卿
Original assignee: China Railway Tunnel Group Co Ltd CRTG
Current assignee: China Railway Tunnel Group Co Ltd CRTG
Priority date: 2019-12-06
Filing date: 2019-12-06
Publication date: 2020-02-28
Anticipated expiration: 2039-12-06
Also published as: CN110847234B

Abstract

The invention provides a pipe gallery protection prestressed beam and a construction method, and belongs to the technical field of constructional engineering. It has been solved current large-scale piping lane perpendicular or the skew of foundation ditch and has adopted to move the pipeline out of the foundation ditch scope, has brought the problem of serious influence to citizen's trip, life. This piping lane protection prestressed beam, including the prestressed beam body that is located the first abutment of main part foundation ditch one side, locates the second abutment of main part foundation ditch opposite side and locates the main part foundation ditch top, the one end of the prestressed beam body is taken on first abutment, and the other end is taken on the second abutment, is equipped with the piping lane hole in the prestressed beam body, and the length direction of the prestressed beam body is followed in the piping lane hole extends. And the construction method for protecting the prestressed beam by using the pipe gallery which occupies a small space on the urban road surface has the advantages of small influence on urban traffic, no water cut, power cut, gas cut and the like.

Description

Pipe gallery protection prestressed beam and construction method

Technical Field

The invention belongs to the technical field of constructional engineering, and relates to a pipe gallery protection prestressed beam and a construction method.

Background

In the construction process of municipal works such as urban subway stations and the like, the condition that a large-scale comprehensive pipe gallery is parallel to or obliquely crossed with an engineering foundation pit is often met. Due to the diversity, complexity, importance and other reasons of the internal pipelines of the large-scale pipe gallery, if the pipe gallery is moved and changed into a scheme for treatment, the conditions of water cut, power failure, gas cut and the like in the urban area can be caused, and the work and life of urban residents are seriously influenced. Especially, under the condition that a large pipe gallery is vertical or an oblique foundation pit is formed, the scheme of moving the pipeline out of the range of the foundation pit needs to occupy a large-range urban road surface, the time is long, and the total construction period, the cost and the resources of the project are obviously increased.

Disclosure of Invention

The invention aims to solve the problems in the prior art and provides a pipe gallery protective prestressed beam capable of effectively controlling deformation and cracks of a pipe gallery. The construction method for protecting the prestressed beam of the pipe gallery with small occupation on the urban road surface during construction is further provided.

The purpose of the invention can be realized by the following technical scheme:

the pipe gallery protection prestressed girder is characterized by comprising a first bridge abutment positioned on one side of a main foundation pit, a second bridge abutment positioned on the other side of the main foundation pit and a prestressed girder body arranged above the main foundation pit, wherein one end of the prestressed girder body is erected on the first bridge abutment, the other end of the prestressed girder body is erected on the second bridge abutment, a pipe gallery hole is formed in the prestressed girder body, and the pipe gallery hole extends along the length direction of the prestressed girder body.

Through this kind of structural design, large-scale piping lane is wrapped up in the prestressing force roof beam body to form a stable, safe, reliable "bridge system", it bears the gravity of self, piping lane and piping lane internal line, effectively restricts the deformation and the crack of piping lane.

In the pre-stressed beam for protecting the pipe gallery, a plurality of pre-stressed pipelines extending along the length direction of the pre-stressed beam body penetrate through the pre-stressed beam body, wherein one part of the pre-stressed pipelines are positioned at one side of the pipe gallery hole, and the rest part of the pre-stressed pipelines are positioned at the other side of the pipe gallery hole.

In the pipe gallery protection prestressed beam, a first bridge abutment pile positioned on one side of the pipe gallery and a second bridge abutment pile positioned on the other side of the pipe gallery are arranged in the first bridge abutment, and the upper ends of the first bridge abutment pile and the second bridge abutment pile are fixedly connected with the prestressed beam body; the second abutment in be equipped with the third abutment stake that is located pipe gallery one side and the fourth abutment stake that is located the pipe gallery opposite side, the upper end and the prestressing force roof beam body of third abutment stake and fourth abutment stake link firmly.

In the pipe gallery protection prestressed beam, a plurality of first abutment piles are uniformly distributed along the length direction of the prestressed beam body; the second bridge abutment piles are distributed uniformly along the length direction of the prestressed beam body; the third bridge abutment piles are distributed uniformly along the length direction of the prestressed beam body; the fourth bridge abutment piles are distributed uniformly along the length direction of the prestressed beam body.

In the pipe gallery protection prestressed beam, the prestressed beam body comprises an upper joist and a lower bracket fixed at the lower part of the upper joist, and the pipe gallery hole is positioned between the upper joist and the lower bracket.

In foretell piping lane protection prestressed beam, the distance of the center of pipe gallery hole to the joist lower surface is less than the radius of pipe gallery hole, the distance of the center of pipe gallery hole to bottom bracket is greater than or equal to the radius of pipe gallery hole. The upper joist is composed of reinforced concrete, and the upper joist has a wrapping part extending to the lower part of the pipe rack through the two sides of the pipe rack and can be used for bearing the gravity of the pipe rack.

The construction method for protecting the prestressed beam of the pipe gallery comprises the following steps:

① drawing the contour lines of the first abutment and the second abutment at the intersection of the pipe gallery and the main foundation pit according to the design drawing, and respectively carrying out stirring pile reinforcement or jet grouting pile reinforcement construction on the areas of the first abutment and the second abutment outside the contour lines of the pipe gallery.

Before construction, the design hole site of the mixing pile should be rechecked according to the conditions of site environment, the position of underground buried objects, namely pipe galleries and the like. The concrete requirements in construction include the following:

1. the cement-soil mixing pile is constructed in a standard continuous mode, and the main foundation pit support structure, namely the cement-soil mixing pile on the inner side of the underground continuous wall, is lapped by 250 mm.

2. Adopting a triaxial mixer for construction, uniformly using P42.5 ordinary Portland cement, wherein the water cement ratio is 0.8, the cement mixing amount is 20%, adding a proper amount of bentonite, the mixing amount is preferably 5-8% of the cement dosage, and the 28-day unconfined compressive strength is required to be not less than 1.0 MPa. The cement mixing amount of the single pile of the reinforcing body in the pit is generally 18%, and the empty stirring part is reinforced and reinforced by adopting 7% of low mixing amount. And the mechanical strength of the reinforced body is not less than the strength of the soil body before reinforcement. The technological pile test is carried out before the construction, and the stirring times or the cement consumption is increased for the relatively soft soil layer.

3. The cement and the undisturbed soil need to be uniformly mixed, in order to ensure that the cement and the soil are uniformly mixed, the sinking and lifting speed of a drilling tool must be well controlled, the drilling and mixing speed of the drilling machine is generally 0.5m/min, the repeated mixing and lifting speed is generally 0.8-1.0 m/min, and the pile bottom part is repeatedly stirred and grouted. The lifting speed is not suitable to be too fast, and the phenomena of vacuum negative pressure, hole wall collapse and the like are avoided. During pile construction, the pile must not be flushed with water and sunk.

4. Underground obstacles in a construction area need to be detected before the construction of the mixing pile, if the obstacles exist, the underground obstacles need to be cleaned and backfilled with plain soil, the plain soil does not contain rock blocks and domestic garbage, and the construction can be carried out after the plain soil is tamped in layers.

5. The construction of the mixing pile should have continuity, and 24-hour construction cold joints cannot occur, except for the reservation of construction organization design. If construction cold joints occur due to special reasons, reinforcement is needed, positions are marked on drawings and sites so that a reinforcement scheme is considered uniformly finally, and high-pressure jet grouting piles are needed to be adopted beside joints for reinforcement when the construction cold joints exceed 48 hours or the cold joints occur.

6. The positioning error of the cement mixing pile must not exceed 15mm, the verticality of the mixing pile must be strictly controlled, and the construction site must be smooth; the maintenance period of the cement-soil mixing pile is not less than 28 days, and the foundation pit can be excavated when the unconfined compressive strength qu is greater than 1.0 MPa.

7. The deviation of the pile position is not more than 50mm, and the deviation of the verticality is not more than 1/200.

8. Before construction, proper construction machinery, especially power equipment, is selected, and meanwhile, the field is leveled to ensure the pile forming quality of the waterproof curtain.

9. The detection requirement is as follows: the mixing pile should detect the size, lap joint width, quality, water interception effect and pile body strength of the cement concretion body.

② drawing an excavation contour line in the area of the first abutment and the second abutment, and constructing the protection row piles along the length direction of the excavation contour line, wherein the area enclosed by the excavation contour line is the excavation area, and the first abutment pile, the second abutment pile, the third abutment pile and the fourth abutment pile are respectively constructed in the excavation area along the length direction of the pipe gallery.

And measuring and controlling a positioning pile point according to a design drawing, determining the plane positions of the row piles and the abutment pile foundation holes, and selecting a drilling machine meeting the requirements of ground construction, narrow space below the pipe gallery and drilling depth. Because the number of the row piles is large, the construction is carried out by adopting a 1, 4 and 7 lattice jumping method, and the pile tops are connected into a whole after the piles are formed. The concrete requirements in construction include the following:

1. and during drilling, a pile casing is adopted, the pile casing is made of a 6-10 mm thick steel plate, and a reinforcing rib and a lifting lug are welded at the top of the pile casing. The inner diameter of the pile casing is 10-15 cm larger than the diameter of the drill bit, 20-30 cm larger than the diameter of the pile, the length is preferably 1.5-2 m, the pile casing is embedded and buried by adopting mechanical excavation, the joint of the bottom of the pile casing and the soil layer is tamped by clay, the outer surface of the pile casing is also tamped by clay, and surface water is prevented from permeating along the joint. The top is 30cm higher than the construction ground, and the vertical gradient of the pile casing is not more than 1%. Whether the pile casing deviates and sinks is often checked in the drilling process, and problems are found and timely treated.

2. The drilling machine base and top end should be stable and not subject to displacement or subsidence. The deviation of the positions of the drill center and the drill hole center is controlled within the range of 2 cm.

3. During construction, the height of a water head is controlled to be 1.5-2.0 m.

4. The connection of the drilling tool is vertical, the initial drilling speed is not too fast, the drilling speed is not more than 2m/h within 4.0m of the hole depth, and the subsequent section is not more than 3 m/h.

5. The method is characterized in that a static mud retaining wall drill bucket is used for taking soil, and the mud is prepared by mixing bentonite, caustic soda and cellulose. During drilling, the footage speed is well mastered, the condition in the hole is observed at any time, the timely compensation is less than 1.1, the viscosity is not more than 20Pa.s, and the sand rate is controlled within 2 percent; the second is the pulp replenishing speed.

6. And after the formed hole reaches the designed elevation, checking the depth, the aperture, the verticality of the hole wall, the deposition thickness and the like. And after the technical requirements are met, hole cleaning is carried out, secondary hole cleaning is carried out before concrete pouring, and the sediment at the bottom of the hole after hole cleaning is less than 10 cm.

7. The installation error of the steel reinforcement framework support seat should meet the design and standard requirements.

8. The length of each section of the catheter is preferably more than 4m, the catheter is spliced before use, a sealing test (1.5 times of hydrostatic pressure at the bottom of a hole) is carried out, and water leakage is preferably avoided within 15 minutes; when the guide pipe is installed, the bottom end of the guide pipe is higher than the bottom of the hole by 30-40 cm, and the depth of the guide pipe embedded into the concrete is 2-5 m.

9. The cast-in-place pile body concrete must be continuously constructed, the casting time of every pile is controlled according to the initial setting time of concrete, and the cast-in-place pile concrete filling coefficient is not less than 1.1 nor more than 1.3. The water cement ratio of the concrete is preferably 0.5-0.55, and the concrete slump is preferably 18-22 cm.

10. When the pouring is started, when the distance between the concrete surface in the drill hole and the bottom opening of the steel reinforcement cage is 1m, the pouring speed is preferably controlled to be 0.2m/min, when the concrete surface rises to be more than 4m of the bottom opening of the steel reinforcement cage, the guide pipe is lifted, so that the bottom opening of the guide pipe is higher than the bottom of the steel reinforcement cage by more than 2m, and the normal pouring speed of 0.5m/min is recovered.

③ dewatering, digging out soil body above the pipe gallery in the excavation area, and constructing prefabricated baffles.

According to design data, precipitation is respectively carried out in large and small foundation pits, and precipitation is carried out according to the sequence of well point paying-off positioning → drilling machine in-place installation → orifice excavation and embedding of mouth protecting pipes → drilling → hole cleaning and slurry changing → well pipe installation → filling pipe wall gap material → water sealing well → well washing → installation of pumping equipment → pumping test → laying of a main drainage pipe and a grit chamber → networking and pumping. The concrete requirements in construction include the following:

1. the foundation pit is provided with a catch basin along the surrounding retaining edge to intercept surface water, and the slope in the surrounding retaining range drains towards the catch basin, so that the surface water is prevented from flowing into the foundation pit and scouring the slope. The ground within the confines of the foundation pit needs to be hardened to prevent surface water from entering. The surface cracks should be sealed, and the collected water in the low concave position of the terrain should be drained timely.

2. Draining and draining the pit before excavation of the foundation pit, pre-dewatering the impervious layer in advance for 30 days, and keeping the water level in the foundation pit 1m below the pit bottom after dewatering.

3. If the substrate is an impermeable or weakly permeable soil layer, the depth of the dewatering well should be 10m into the substrate soil layer to ensure the dewatering effect. If the rock surface is higher, the dewatering well is deep enough to enter 2.0m of weathered medium rock or slightly weathered rock, and water is drained in a pit in the rock stratum.

4. And (4) releasing the well position of the dewatering well according to the well position diagram, the underground pipeline distribution diagram and the coordinate control points provided by the dewatering design scheme, wherein the well position deviation is less than or equal to 50mm under the normal condition.

5. The well pipe must be centered before gravel filling to make the gravel filling thickness uniform, the filter material should be slowly and symmetrically filled from both sides of the well pipe to prevent the filter material from being jammed midway and the well ring from being misplaced, and the filter material is filled with clay when being filled to the well mouth for 1-2 m.

6. After the filter material is filled, the well is washed immediately, and the well washing adopts a circulation method process of injecting clean water outside a well pipe, and the pumping and stopping are alternated until the water is cleaned. And measuring the well depth before the well washing is finished, and cleaning the well bottom to ensure that the sediment of the well bottom is less than 0.3-0.5 m.

7. Before precipitation, a water pumping test is carried out to detect the precipitation capacity of the precipitation well. And after each dewatering well, hole and drainage facility is debugged to be qualified, carrying out dewatering inspection. And after all dewatering wells and drainage facilities are subjected to dewatering inspection, dewatering monitoring and maintenance are required.

8. And (5) the ground water level is measured once before precipitation inspection. After the water pumping is started and before the water reaches the designed water level, the water level and the water yield are observed three times every day; after the designed water level is stable, the observation is carried out once a day.

9. Taking a water sample for testing 30min after the pipe well pumps water and opening the pump, wherein the sand content of the water sample is less than 1/50000; the sand content of long-term operation is less than 1/100000, otherwise, the pumping is stopped and measures are taken to reduce the sand content in the water.

10. Can set up interim escape canal and collector well according to actual conditions in the foundation ditch.

④ dewatering, excavating the soil of the main foundation pit synchronously, symmetrically and hierarchically, excavating the residual soil above the pipe gallery and the soil on the side of the pipe gallery in the excavation area, and constructing a support system of the main foundation pit in time.

⑤ chiseling the parts of the first, second, third and fourth bridge piles extending out of the soil body and exposing the reinforcing steel bars, positioning the reinforcing steel bars for binding the upper supporting beams, and installing the embedded parts and the prestressed pipelines of the lower bracket.

The prestressed pipeline is a corrugated pipe, the appearance of the corrugated pipe is clean, the inner surface and the outer surface of the corrugated pipe are free of oil stains, attachments causing corrosion, holes and irregular wrinkles, and a seaming is free of cracking and tripping. When the corrugated pipe is installed, the joint needs to be sealed well, and the situation that the pipeline is blocked when concrete is poured to influence the penetration is avoided. The pipeline installation needs to meet the following requirements:

1) the pipeline should adopt the firm location of locating steel bar in design position.

2) The pipeline joints are connected by adopting sleeves, and the connecting sleeves adopt the same type of pipelines with one larger diameter.

3) The pipeline is provided with a pulp pressing hole and a pulp overflowing hole, the wave crest position of the pore passage is provided with an exhaust hole, and the lowest part is provided with a water discharging hole.

4) And (4) immediately checking the through hole after the pipeline is installed in place, and dredging in time when blockage is found.

⑥ erecting a template and pouring concrete, wherein the bottom mold is C20 concrete 20cm thick, the template is smooth during construction, the template is a shaped steel mold coated with a release agent before installation, the steel mold requires accurate dimension, rigidity and strength meet requirements, joints are smooth and tight, the concrete does not leak slurry under strong vibration, the surface of the steel mold is required to be polished, the template is processed and manufactured strictly according to drawings and specifications, welding is performed, and the correct position of a reserved hole channel is ensured.

⑦ post-tensioning construction is carried out on the prestressed pipe after the strength of the box girder reaches the designed strength, when the strength of the box girder reaches 90% of the designed strength (the strength of the box girder refers to the strength of a test piece under the same condition maintained along with the girder), the prestressed tensioning can be carried out, the tensioning equipment must be checked before use to determine the curve relation between the tension and the reading of the pressure gauge, the prestressed tensioning needs to pay attention to the following points:

1) the method is carried out according to the design tensioning sequence and requirements, a two-end symmetrical synchronous tensioning process is adopted, the operations of jacking, pressure reduction, elongation measurement and the like of two jacks are consistent during tensioning, and the two ends of the steel strand are tensioned by the same number.

2) And (3) actually measuring the friction loss of the pore channel according to design requirements before tensioning, determining a tensioning control stress value, and determining the theoretical elongation of the pore channel.

3) And according to the designed category of the steel strand, adopting different tensioning programs and simultaneously measuring the actual elongation of the steel strand.

4) In the tensioning process, the friction between the prestressed tendons and the pore channels is reduced as much as possible, so that excessive stress loss is avoided, and cracks and warping of the concrete member are avoided.

The blanking length of the steel strand is accurate, the blanking length is the length of a pore passage through which the steel strand passes plus (the height of a working anchor plus the height of a limiting plate plus the length of a jack plus the height of a tool anchor plus the reserved length convenient for operation), a cutting machine or a grinding wheel saw is adopted, and arc welding or oxy-acetylene flame cutting is not required to be used, so that heat damage is prevented. The steel strands are divided into roots and are bundled, the two ends of each steel strand are numbered, and iron wires are bound at intervals of about 5 m.

Anchorages, clamps, connectors and the like should have reliable anchorage, adequate load-bearing capacity and good suitability and meet the regulations of the relevant specifications.

After tensioning is finished, the concrete is washed by clear water and blown to dry by high-pressure air, duct grouting is carried out as soon as possible, the duct grouting cement is the ordinary silica 42.5 cement which is just delivered from a factory, in order to ensure necessary performance, a proper amount of expanding agent is doped in the cement paste, the water cement ratio is controlled to be 0.4-0.45, the consistency of the cement paste is controlled to be 14-18 s, and the consistency of the cement paste and the strength of a concrete member is ensured to be consistent.

After the pore canal grouting is finished, the cement slurry at two ends is washed clean, dirt of the anchorage device and end face concrete is removed, the end face concrete is roughened, an end reinforcing mesh is bound, anchor sealing concrete is poured, and watering maintenance is carried out.

⑧ excavating the residual soil of main foundation pit layer by layer, excavating the soil on both sides and bottom of pipe gallery, and installing lower brackets.

Through above-mentioned step, the piping lane is wrapped up in the prestressing force roof beam body to form a stable, safe, reliable "bridge system", born the dead weight stress of its self, piping lane and piping lane internal pipeline, effectively restrict the deformation and the crack of piping lane.

Constructing a main foundation pit by ⑨ constructing a main foundation pit supporting system and a temporary main body enclosure structure below a pipe gallery after the construction of the pre-stressed beam protected by the pipe gallery is finished, and constructing a permanent main body enclosure structure drilled pile at the junction after ⑩ excavating the foundation pit below the pipe gallery to a certain depth;

after the pile head of the permanent pile is chiseled, binding reinforcing steel bars and pouring a reinforced concrete wall;

and c, dewatering, excavating the residual foundation pit and erecting a support.

The key for ensuring the construction safety of the prestressed beam is to monitor the change conditions of the foundation pit and surrounding buildings in the whole process, measure the surface settlement change conditions in the excavation process in time, compare the surface settlement change conditions with the analysis calculated values and feed back and guide the design and construction in time.

Compared with the prior art, the invention has the following advantages:

the occupation of the pipe gallery guide and modification construction on urban pavements is reduced, roads are occupied locally only in a short time, the influence on urban traffic is small, and the requirements of high environmental protection and high quality of foreign municipal construction can be met; the pipeline does not need to be changed, so that water cut, power cut, gas cut and the like can not be caused, and the influence on the work and life of surrounding residents is reduced to the maximum extent; the protection piping lane that prestressed beam physical stamina can be fine, at the foundation ditch excavation in-process, the piping lane does not produce deformation and crack basically, has effectively guaranteed the security of piping lane self and inside pipeline.

Drawings

Fig. 1 is a schematic structural view of a pipe gallery protective prestressed beam provided by the invention.

Figure 2 is a cross-sectional view of a pipe lane as provided by the present invention.

FIG. 3 is a schematic diagram of the structure of step ① provided by the present invention.

FIG. 4 is a schematic diagram of the structure of step ② provided by the present invention.

FIG. 5 is a schematic diagram of the structure of step ③ provided by the present invention.

FIG. 6 is a cross-sectional view of step ③ provided by the present invention.

Fig. 7 is a cross-sectional view of the invention after the preformed baffles have been provided in step ③.

FIG. 8 is a schematic diagram of the structure of step ④ provided by the present invention.

FIG. 9 is a cross-sectional view of step ④ provided by the present invention.

FIG. 10 is a schematic diagram of the configuration of the support system provided in step ④ of the present invention.

FIG. 11 is a schematic diagram of

steps

⑤ and ⑥ provided by the present invention.

FIG. 12 is a schematic diagram of the structure of step ⑦ provided by the present invention.

Fig. 13 is a process flow diagram of the mixing pile reinforcement construction in step ①.

Fig. 14 is a flow chart of the construction process for protecting the piles in rows and abutment piles in step ②.

Fig. 15 is a flow chart of the post-tensioning construction process of step ⑦.

In the figure, 1, a main foundation pit; 2. a first abutment; 3. a second abutment; 4. a prestressed beam body; 41. an upper joist; 42. a lower bracket; 4a, concrete; 5. a pipe gallery; 6. a pipe gallery hole; 7. a prestressed pipe; 81. a first abutment pile; 82. a second abutment pile; 83. a third bridge abutment pile; 84. a fourth abutment pile; 9. excavating a contour line; 10. protecting the row piles; 11. excavating an area; 12. prefabricating a baffle; 13. and (4) a support system.

Detailed Description

The following are specific embodiments of the present invention and are further described with reference to the drawings, but the present invention is not limited to these embodiments.

The west subway station of red line of Israel is located below the main road of Telavif, and a large main power supply pipe jacking gallery with the diameter of 3.2 meters is obliquely crossed with the foundation pit. Due to strict requirements of Israel national conditions, culture and local municipal engineering, factors such as construction period and cost are comprehensively considered, the scheme of moving the pipeline out of the range of the foundation pit is basically infeasible, and the scheme of in-situ suspension protection is adopted, so that the technical problem of ensuring the safety of effectively controlling deformation, cracks and suspension of the pipe gallery in the excavation process of the foundation pit is quite important.

Therefore, the prestressed beams are protected by the pipe gallery.

The pipe gallery protection prestressed beam shown in fig. 1 and 3 comprises a first bridge abutment 2 located on one side of a main foundation pit 1, a second bridge abutment 3 located on the other side of the main foundation pit 1 and a prestressed beam body 4 located above the main foundation pit 1, wherein one end of the prestressed beam body 4 is erected on the first bridge abutment 2, the other end of the prestressed beam body is erected on the second bridge abutment 3, a pipe gallery hole 6 used for wrapping a pipe gallery 5 is formed in the prestressed beam body 4, and the pipe gallery hole 6 extends along the length direction of the prestressed beam body 4.

As shown in fig. 2, 16 prestressed pipes 7 extending in the length direction of the prestressed girder 4 penetrate through the prestressed girder 4, wherein 8 prestressed pipes 7 are located at one side of the pipe gallery hole 6, and the remaining 8 prestressed pipes 7 are located at the other side of the pipe gallery hole 6.

As shown in fig. 4, a first abutment pile 81 located on one side of the pipe gallery 5 and a second abutment pile 82 located on the other side of the pipe gallery 5 are arranged in the first abutment 2, and as shown in fig. 1, the upper ends of the first abutment pile 81 and the second abutment pile 82 are fixedly connected with the prestressed beam body 4. A third abutment pile 83 located on one side of the pipe gallery 5 and a fourth abutment pile 84 located on the other side of the pipe gallery 5 are arranged in the second abutment 3, as shown in fig. 1, the upper ends of the third abutment pile 83 and the fourth abutment pile 84 are fixedly connected with the prestressed beam body 4.

As shown in fig. 4, a plurality of first abutment piles 81 are uniformly distributed along the length direction of the prestressed girder body 4; the second abutment piles 82 are distributed uniformly along the length direction of the prestressed beam body 4; the third abutment piles 83 are uniformly distributed along the length direction of the prestressed beam body 4; the number of the fourth abutment piles 84 is several and is uniformly distributed along the length direction of the prestressed girder body 4.

As shown in fig. 2, the prestressed girder body 4 includes an upper joist 41 and a lower bracket 42 fixed to a lower portion of the upper joist 41, and the pipe gallery hole 6 is located between the upper joist 41 and the lower bracket 42.

① drawing the contour lines of the first abutment 2 and the second abutment 3 at the intersection of the pipe gallery 5 and the main foundation pit 1 according to the design drawing, and respectively carrying out the reinforcing construction of the mixing pile for the areas of the first abutment 2 and the second abutment 3 outside the contour line of the pipe gallery 5, wherein the shaded areas at the left and right sides in the drawing 3 are the reinforcing areas of the mixing pile, the step flow refers to fig. 13, before the construction, the design hole sites of the mixing pile should be rechecked according to the conditions of the site environment, the position of the underground buried object, namely the pipe gallery, and the like, and the concrete requirements in the construction include the following points:

② drawing an excavation contour line 9 in the area of the first abutment 2 and the second abutment 3, and constructing the protection row piles 10 along the length direction of the excavation contour line 9, as shown in fig. 4, the area enclosed by the excavation contour line 9 is an excavation area 11, and the first abutment pile 81, the second abutment pile 82, the third abutment pile 83 and the fourth abutment pile 84 are respectively constructed in the excavation area 11 along the length direction of the pipe gallery 5.

And measuring and controlling a positioning pile point according to a design drawing, determining the plane positions of the row piles and the abutment pile foundation holes, and selecting a drilling machine meeting the requirements of ground construction, narrow space below the pipe gallery and drilling depth. Because the number of the row piles is large, the construction is carried out by adopting a 1, 4 and 7 lattice jumping method, and the pile tops are connected into a whole after the piles are formed. The step flow refers to fig. 14. The concrete requirements in construction include the following:

③ as shown in figures 5 and 6, precipitation excavates the soil in the excavated area 11 a distance above the pipe gallery 5, as shown in figure 7, and applies prefabricated barriers 12.

④ As shown in fig. 8, the main foundation pit 1 and the pipe gallery 5 are excavated synchronously, symmetrically and hierarchically by the precipitation, as shown in fig. 9, the remaining soil above the pipe gallery 5 and the soil on the side of the pipe gallery 5 in the excavation region 11 are excavated, as shown in fig. 10, and the support system 13 of the main foundation pit 1 is constructed in time.

⑤ chiseling the parts of the first abutment pile 81, the second abutment pile 82, the third abutment pile 83 and the fourth abutment pile 84 extending out of the soil body and exposing the reinforcing bars, as shown in fig. 11, positioning the reinforcing bars binding the upper joist 41, connecting the reinforcing bars of the upper joist 41 and the reinforcing bars of the first abutment pile 81, the second abutment pile 82, the third abutment pile 83 and the fourth abutment pile 84 into a whole, and installing the embedded parts of the lower bracket 42 and the prestressed pipes 7.

⑥ erecting a template and pouring concrete 4a, covering all the steel bars in step ⑤ in the concrete 4a, using C20 concrete as bottom die 20cm thick, and leveling construction, using shaped steel die, coating release agent before installation, the steel die requires accurate size, rigidity and strength, the joint is smooth and tight, and it ensures concrete leak-proof under strong vibration, and requires steel die surface polishing treatment, processing and manufacturing according to drawing and specification, welding, and making correct position of reserved hole channel, the concrete is layered horizontally, pouring is completed in one time, the concrete is compacted by inserted vibrator, and is vibrated by attached vibrator, the concrete pouring and vibrating need to pay attention to inner die and bellows not shifting at any time, after the concrete pouring is completed, the phi 10 steel bars are used to check whether the bellows has blocking phenomenon, and find problem treatment.

⑦ As shown in FIG. 12, post-tensioning construction is performed on the prestressed pipe 7 after the concrete 4a of the upper joist 41 reaches the designed strength, when the strength of the prestressed concrete box girder reaches 90% of the designed strength (the strength of the box girder refers to the strength of the conditioned test piece along with the maintenance of the girder), the prestressed tensioning can be performed, the tensioning equipment must be checked before use to determine the curve relationship between the tension and the reading of the pressure gauge, the flow of the steps refers to FIG. 15, the prestressed tensioning requires attention to the following points:

⑧ the residual soil of the main foundation pit 1 is excavated layer by layer, and then the lower brackets 42 are installed after the soil on the two sides and the bottom of the pipe gallery 5 is excavated.

Through above-mentioned step, piping lane 5 is wrapped up in prestressing force roof beam body 4 to form a stable, safe, reliable "bridge system", bear its self weight stress,

piping lane

5 and 5 internal pipeline of piping lane, effectively restrict the deformation and the crack of piping lane 5. Meanwhile, the modernized monitoring and measuring means is utilized to monitor the stability of the main foundation pit 1, the pipe gallery 5 and the prestressed beam body 4 all weather and in the whole process, and the construction safety is ensured.

After the construction of the pre-stressed beam is finished under the protection of the pipe gallery 5, the main foundation pit 1 is constructed by the following steps: 9. constructing a main foundation pit 1 supporting system 13 and a temporary main body enclosure structure below the pipe gallery 5; 10. after the foundation pit under the pipe gallery 5 is excavated to a certain depth, constructing a permanent main body enclosure structure drilled pile at the junction; 11. after the pile head of the permanent pile is chiseled off, binding reinforcing steel bars and pouring a reinforced concrete 4a wall; 12. and c, dewatering, excavating the residual foundation pit and erecting a support.

The key for ensuring the construction safety of the prestressed beam is to monitor the change conditions of the foundation pit and surrounding buildings in the whole process, measure the surface settlement change conditions in the excavation process in time, compare the surface settlement change conditions with the analysis calculated values and feed back and guide the design and construction in time. The main monitoring content is referred to the monitoring project summary table.

Monitoring project summary table

The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.

Claims

1. The utility model provides a piping lane protection prestressed beam, its characterized in that, including first abutment (2) that are located main part foundation ditch (1) one side, locate second abutment (3) of main part foundation ditch (1) opposite side and locate the prestressed girder body (4) of main part foundation ditch (1) top, the one end of prestressed girder body (4) is taken on first abutment (2), and the other end is taken on second abutment (3), prestressed girder body (4) in be equipped with pipe gallery hole (6), pipe gallery hole (6) extend along the length direction of prestressed girder body (4).

2. The pipe gallery protective prestressed girder according to claim 1, characterized in that a plurality of prestressed pipes (7) extending in the length direction are arranged in the prestressed girder body (4), wherein a part of the prestressed pipes (7) are located at one side of the pipe gallery hole (6), and the rest of the prestressed pipes (7) are located at the other side of the pipe gallery hole (6).

3. The pipe gallery protective prestressed girder according to claim 2, wherein a first abutment pile (81) located on one side of the pipe gallery (5) and a second abutment pile (82) located on the other side of the pipe gallery (5) are arranged in the first abutment (2), and the upper ends of the first abutment pile (81) and the second abutment pile (82) are fixedly connected with the prestressed girder body (4); and a third bridge abutment pile (83) positioned on one side of the pipe gallery (5) and a fourth bridge abutment pile (84) positioned on the other side of the pipe gallery (5) are arranged in the second bridge abutment (3), and the upper ends of the third bridge abutment pile (83) and the fourth bridge abutment pile (84) are fixedly connected with the prestressed beam body (4).

4. The pipe gallery protective prestressed girder according to claim 3, wherein the number of the first abutment piles (81) is several and is uniformly distributed along the length direction of the prestressed girder body (4); the number of the second abutment piles (82) is a plurality and the second abutment piles are uniformly distributed along the length direction of the prestressed beam body (4); the number of the third abutment piles (83) is a plurality and the third abutment piles are uniformly distributed along the length direction of the prestressed beam body (4); the number of the fourth abutment piles (84) is a plurality and is uniformly distributed along the length direction of the prestressed beam body (4).

5. The pre-stressed girder for protecting a pipe gallery according to claim 1, wherein the pre-stressed girder body (4) comprises an upper joist (41) and a lower bracket (42) fixed to a lower portion of the upper joist (41), and the pipe gallery hole (6) is formed between the upper joist (41) and the lower bracket (42).

6. A construction method for protecting a prestressed girder according to any one of claims 1-5, comprising the steps of:

①, drawing the contour lines of the first abutment (2) and the second abutment (3) at the intersection of the pipe gallery (5) and the main foundation pit (1) according to a design drawing, and respectively reinforcing the areas of the first abutment (2) and the second abutment (3) outside the contour lines of the pipe gallery (5);

②, drawing an excavation contour line (9) in the area of the first abutment (2) and the second abutment (3), and constructing a protection row pile (10) along the length direction of the excavation contour line (9), wherein the area enclosed by the excavation contour line (9) is an excavation area (11), and a first abutment pile (81), a second abutment pile (82), a third abutment pile (83) and a fourth abutment pile (84) are respectively constructed in the excavation area (11) along the length direction of the pipe gallery (5);

③, dewatering, digging soil bodies in the excavation area (11) which are positioned above the pipe gallery (5) for a certain distance, and constructing prefabricated baffles (12);

④, lowering water, excavating the soil of the main foundation pit (1) synchronously, symmetrically and hierarchically, excavating the residual soil above the pipe gallery (5) and the soil on the side of the pipe gallery (5) in the excavation area (11), and constructing a support system (13) of the main foundation pit (1) in time;

⑤ chiseling the parts of the first abutment pile (81), the second abutment pile (82), the third abutment pile (83) and the fourth abutment pile (84) extending out of the soil body and exposing the reinforcing steel bars, positioning the reinforcing steel bars for binding the upper joist (41), and installing the embedded parts of the lower bracket (42) and the prestressed pipelines (7);

⑥ erecting the formwork and casting concrete (4 a);

⑦ post-tensioning construction is carried out on the prestressed pipeline (7) after the concrete (4a) of the upper joist (41) reaches the design strength;

⑧ the residual soil of the main foundation pit (1) is excavated layer by layer, and then the lower brackets (42) are installed after the soil on the two sides and the bottom of the pipe gallery (5) is excavated.

7. The construction method for the pipe gallery protective prestressed beam as claimed in claim 6, wherein step ① is carried out by using a three-axis mixer, using Portland cement with a water cement ratio of 0.8 and a cement content of 20%, and adding bentonite with a bentonite content of 5-8% of the cement content.

8. The construction method of the pipe gallery protective prestressed girder according to claim 6, wherein the construction steps of protecting the row piles and each abutment pile are as follows: a pile casing made of a 6-10 mm thick steel plate is embedded by mechanical excavation, a reinforcing rib and a lifting lug are welded at the top of the pile casing, the joint of the bottom of the pile casing and a soil layer is tamped by clay, and the outer surface of the pile casing is filled and tamped by clay; drilling a drill hole with a set depth through a drilling machine; placing a reinforcement cage in the drilled hole; and (5) pouring concrete.

9. The construction method of the pipe gallery protective prestressed beam, according to claim 8, characterized in that the concrete water cement ratio is 0.5-0.55, and the concrete slump is 18-22 cm.