CN110805053A - Construction method of deep foundation pit open caisson self-sinking supporting system - Google Patents
Construction method of deep foundation pit open caisson self-sinking supporting system Download PDFInfo
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- CN110805053A CN110805053A CN201911072255.8A CN201911072255A CN110805053A CN 110805053 A CN110805053 A CN 110805053A CN 201911072255 A CN201911072255 A CN 201911072255A CN 110805053 A CN110805053 A CN 110805053A
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D23/00—Caissons; Construction or placing of caissons
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D23/00—Caissons; Construction or placing of caissons
- E02D23/08—Lowering or sinking caissons
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D23/00—Caissons; Construction or placing of caissons
- E02D23/08—Lowering or sinking caissons
- E02D23/14—Decreasing the skin friction while lowering
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D23/00—Caissons; Construction or placing of caissons
- E02D23/16—Jointing caissons to the foundation soil, specially to uneven foundation soil
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Abstract
The invention discloses a construction method of a deep foundation pit open caisson self-sinking supporting system, which comprises the following steps: after the measurement and the paying-off, manufacturing a blade foot in a cast-in-place mode, pre-burying a spray head in the blade foot, and manufacturing a first section of ring beam in the cast-in-place mode; installing a first section of prefabricated open caisson body, pre-burying a steel pipe in the open caisson body, connecting the open caisson body with a cutting edge, injecting water to cut soil and discharging slurry, so that the first section of open caisson body sinks to a designed elevation; after the ring beam is cast in place, installing the next section of open caisson well body, performing water injection sinking by adopting the same method as the first section of open caisson well body, and installing all the open caisson well bodies in turn and sinking all the sections of open caisson well bodies to the right position; and sealing bottom and pumping and discharging slurry. According to the construction method of the deep foundation pit open caisson self-sinking supporting system, the open caisson is assembled in a prefabricated mode, soil is converted into slurry to be discharged outside, so that the open caisson sinks automatically, the slurry in the open caisson is used for balancing the soil pressure and the water pressure at the bottom, the excavation difficulty is reduced, and the stability in the sinking and excavating processes is ensured.
Description
Technical Field
The invention relates to the technical field of underground space supporting structures, in particular to a construction method of a deep foundation pit open caisson self-sinking supporting system.
Background
The development of urban underground space is more and more emphasized along with the shortage of construction land resources. The urban underground space gradually develops to ultra-deep and ultra-large type, such as urban underground garages, deep well tunnels, subway stations, underground complexes and the like. The excavation and supporting technology of the deep foundation pit also faces the challenge before the air, the precipitation difficulty is high, and the groundwater can usually induce dangerous situations such as quicksand, piping, inrush and the like, so that the influence on the surrounding building environment is obvious; the excavation influence range is wide, the bearing capacity of the enclosure structure is insufficient due to the extrusion of lateral soil pressure, and the structural deformation is large.
For deep foundation pits, conventional supporting methods include cast-in-situ bored piles, underground continuous walls, open caisson and the like, and a combined structure is usually formed by combining cement stirring and high-pressure jet grouting piles. The combined structure faces a series of problems of poor waterproof effect, high manufacturing cost, poor structural overall stability, insufficient bearing capacity and the like.
Disclosure of Invention
The invention mainly aims to provide a construction method of a deep foundation pit open caisson self-sinking supporting system, aiming at reducing the excavation difficulty and improving the structural stability.
In order to achieve the aim, the invention provides a construction method of a deep foundation pit open caisson self-sinking supporting system, which comprises the following steps:
after measurement and paying-off, manufacturing a cutting edge in a cast-in-place mode, pre-burying a spray head in the cutting edge to be connected with a steel pipe of a prefabricated open caisson well body, and manufacturing a first section of ring beam in a cast-in-place mode;
installing a first section of prefabricated open caisson body, pre-burying a steel pipe in the open caisson body, connecting the open caisson body with a cutting edge, injecting water to cut soil and discharging slurry, so that the first section of open caisson body sinks to a designed elevation;
after the ring beam is cast in place, installing the next section of open caisson well body, injecting water to sink the well body by adopting the same method as the first section of open caisson well body, and installing all the open caisson well bodies according to the method and sinking all the sections of open caisson well bodies to the right position;
and sealing bottom and pumping and discharging slurry.
Preferably, the cast-in-place construction ring beam further comprises:
after the current segment open caisson is sunk to the designed elevation, cement-water glass double-liquid slurry is injected into a steel pipe of the open caisson to reinforce and reinforce the soil body loose on the bottom and the outer side well wall of the open caisson, and then clear water is injected into the steel pipe of the open caisson to wash the pipe.
Preferably, all be provided with the standpipe of many vertical settings and connect the ring pipe of many standpipes in prefabricated open caisson well body and the blade foot, install the block valve in the ring pipe, when the open caisson subsides inhomogeneous all around, according to the pipeline subregion of block valve, control the opening and closing of block valve and sink in order to carry out the water injection with pertinence.
Preferably, when the blade leg is manufactured in a cast-in-place mode, a groove is dug along the center line of the blade leg, concrete is poured along the two sides of the groove to serve as a sunk well guide wall, reinforcing steel bars are bound along the blade leg, a spray head is installed, geotextile is used for wrapping the spray head, a circular ring-shaped pipe is installed to be connected with the spray head, and after a vertical pipe is installed to be connected with the circular ring-shaped pipe, the blade leg concrete is poured.
Preferably, before installing the first prefabricated open caisson well bore, the method further comprises:
and constructing a stirring pile, and arranging a mud pool, a sedimentation tank and a water storage tank.
Preferably, when water is injected to cut the soil body and the mud is discharged, high-pressure water is synchronously injected into a steel pipe of the open caisson body to enable the well body to sink uniformly, a mud pump is arranged along the inside of the open caisson, the mud is discharged to a sedimentation tank through the mud pump in the sinking process of the open caisson, part of the settled mud flows into the mud tank to be stirred to form qualified mud, the qualified mud flows into the open caisson, the other part of the mud flows into a water storage tank through a filter screen, the mud is pumped into the open caisson by the high-pressure pump to cut the soil body, the circulation is carried out, and the sedimentation tank is used for cleaning the mud regularly and transporting the mud.
Preferably, when the water injection cutting soil body and discharge mud, earlier excavate earth through machinery, when the excavation degree of depth reaches conventional equipment and can't excavate, adopt the die-cut soil body of high-pressure squirt, wait the degree of depth simultaneously and set up the slush pump and take out the row, slush pump and high-pressure squirt bottom carry out counter weight and top and set up the buoy, control the clearance position through removing the buoy, set up the horizontal pole between slush pump and the high-pressure squirt in order to ensure that both intervals are not less than and predetermine the interval.
Preferably, the step of constructing the mixing pile and arranging the mud pit, the sedimentation tank and the water storage tank specifically comprises:
and constructing a cement stirring pile outside the open caisson, arranging a mud pit, a sedimentation tank and a water storage tank in a preset area away from the open caisson, and carrying out seepage-isolating treatment by adopting a geomembrane, wherein the elevation of the sedimentation tank is greater than the elevation of the mud pit and is greater than the elevation of the open caisson.
Preferably, when the first section of prefabricated open caisson well body is installed, connecting the steel bars at the reserved part, performing annular welding on the steel pipe by adopting a sleeve, and pouring concrete at the connecting part; when the ring beam is constructed in a cast-in-place mode, the ring beam is arranged along the circumferential direction of the well body, connected with the upper section of reinforcing steel bar and the lower section of reinforcing steel bar in a cast-in-place mode, and poured with concrete.
Preferably, the performing bottom sealing and slurry pumping specifically comprises:
after the soil body in the open caisson is cleaned, performing slurry circulation on the bottom through a slurry pump until the slurry is qualified in detection;
grouting reinforcement is carried out on the bottom of the open caisson by using a steel pipe in the open caisson, and after grouting is finished, washing pipes by using part of the steel pipe for later grouting reinforcement;
carrying out underwater concrete pouring on the bottom of the open caisson by adopting a plurality of guide pipes, wherein the concrete pouring elevation is not lower than the elevation of the bottom of the ring beam so as to carry out bottom sealing;
and pumping and discharging the static slurry in the open caisson after the bottom sealing concrete reaches the strength.
The construction method of the deep foundation pit open caisson self-sinking supporting system provided by the invention has the following beneficial effects:
1. the open caisson is assembled in a prefabricated mode, local cast-in-place reinforcement is achieved, the soil body is converted into slurry to be discharged outwards by utilizing high-pressure water, the open caisson is made to sink automatically, the soil pressure and the bottom water pressure around the open caisson are balanced by utilizing the slurry in the open caisson, the excavation difficulty is reduced, and meanwhile the stability of the open caisson in the process of sinking and excavating is guaranteed.
2. By arranging the spray head on the bevel edge of the blade leg, a circle of gap is formed inside the open caisson after high-pressure water impacts a soil body for storing mud, mud residue at the bottom of the open caisson is discharged by utilizing the mud replacement principle, and the problem of discharging mud at the bottom of the open caisson in the flushing and sinking process is solved;
3. the open caisson can be designed into a round shape, so that the effective transmission of load is kept, and the stress characteristic of the material is fully utilized. The ring beam is arranged along the length direction of the well body to form an effective reinforcing body, and meanwhile, the occupation of the open caisson space due to the arrangement of the horizontal support is reduced;
4. by changing the sinking process, the construction method sinks firstly and then excavates, and forms a firm stress body at the initial stage of excavation, thereby solving the problem that the deep excavation affects the surrounding building environment. In the excavation process, slurry is injected into the open caisson to balance lateral active soil pressure and bottom water pressure, so that a stable stress body is formed;
5. the prefabricated member is used for replacing a cast-in-place structure, and the construction is performed in sections and sections, so that the construction period of concrete is effectively shortened, and the problems of low open caisson speed and long construction period are solved. The soil body at the bottom of the cutting edge and the first section of ring beam is cut by using high-pressure water, the operation time is sustainable, and the sinking rate of the open caisson is improved. The construction process is simple, and the economic benefit is obvious;
6. the open caisson is constructed earlier stage and is consolidated the open caisson outside with cement mixing pile, prevents that the bottom soil body from running off and causing the earth's surface subsidence in the work progress, has solved the open caisson construction and has caused peripheral earth's surface to subside the influence, simultaneously, has restricted the displacement of open caisson at the horizontal direction for the open caisson gradient is controllable.
Drawings
FIG. 1 is a schematic plan view of the present invention in the construction of a caisson;
FIG. 2 is a schematic view of the construction of the open caisson in elevation;
FIG. 3 is a schematic cross-sectional view of the present invention in construction of a caisson;
FIG. 4 is a schematic view of the arrangement structure of the present invention for constructing the open caisson;
fig. 5 is a schematic structural view of the sinking well edge constructed by the invention.
In the figure, 1-a cement mixing pile reinforcing area, 2-a steel pipe, 21-a vertical pipe, 22-a circular ring pipe, 3-a well body, 4-a ring beam, 5-a block valve, 6-a ground, 7-a cutting edge, 8-a buoy, 9-a cross rod, 10-a slurry pump, 11-a high-pressure water gun, 12-a spray head, 13-a pre-buried pipeline, 14-a water storage tank, 15-a sedimentation tank, 16-a slurry tank and 17-a counterweight.
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
It should be noted that in the description of the present invention, the terms "lateral", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
Referring to fig. 1 to 5, in the preferred embodiment, a construction method of a deep foundation pit and open caisson self-sinking supporting system includes the following steps:
step S10, after line laying is measured, a cutting edge is cast in situ, a spray head 12 is pre-buried in the cutting edge to be connected with a steel pipe of a prefabricated open caisson well body, and a first section ring beam is cast in situ;
step S20, installing a first section of prefabricated open caisson body, pre-burying a steel pipe in the open caisson body, connecting the open caisson body with a cutting edge, injecting water to cut a soil body and discharging slurry to enable the first section of open caisson body to sink to a designed elevation;
step S30, after the ring beam is cast in place, the next section of open caisson well is installed, water is injected by the same method as the first section of open caisson well to sink the well, and all the open caisson well are installed and sink in place;
and step S40, performing bottom sealing and slurry pumping.
Further, still include behind the cast-in-place construction collar tie beam:
after the current segment open caisson is sunk to the designed elevation, cement-water glass double-liquid slurry is injected into a steel pipe of the open caisson to reinforce and reinforce the soil body loose on the bottom and the outer side well wall of the open caisson, and then clear water is injected into the steel pipe of the open caisson to wash the pipe.
And reinforcing the loose soil body at the bottom of the open caisson and the outside well wall by adopting cement-water glass double-liquid slurry, so that the side wall frictional resistance and the bottom foundation bearing capacity are increased, and the larger settlement is prevented in the excavation process. The pipe washing is to continue grouting and reinforcing in the later period, so as to keep the pipeline smooth.
Specifically, all be provided with the standpipe 21 of many vertical settings and connect the ring shape pipe 22 of many standpipes 21 in prefabricated open caisson well body and the sword foot, install block valve 5 in the ring shape pipe 22, when the open caisson subsides inhomogeneous all around, according to block valve 5's pipeline subregion, control block valve 5 opens and close and sink in order to carry out the water injection pertinence.
In step S10, when the blade leg is cast in place, a trench is dug along the center line of the blade leg, concrete is poured as a sunk well guide wall along the formwork on both sides of the trench, steel bars are bound along the blade leg and the nozzle 12 is installed, geotextile is used to wrap the nozzle 12, the circular pipe 22 is installed to connect with the nozzle 12, the vertical pipe 21 is installed to connect with the circular pipe 22, and then the blade leg concrete is poured.
Step S20 further includes:
in step S11, a mixing pile is constructed, and a mud pit 16, a sedimentation tank 15, and a water storage tank 14 are provided.
The steps of constructing the mixing pile and arranging the mud pit 16, the sedimentation tank 15 and the water storage tank 14 specifically comprise:
and constructing a cement mixing pile outside the open caisson, arranging a mud pit 16, a sedimentation tank 15 and a water storage tank 14 in a preset area away from the open caisson, and carrying out seepage-proof treatment by adopting a geomembrane, wherein the elevation of the sedimentation tank 15 is greater than the elevation of the mud pit and is greater than the elevation of the open caisson.
In the steps S20 and S30, when water is injected to cut the soil body and discharge mud, high-pressure water is synchronously injected into a steel pipe of the open caisson well body to enable the well body to sink uniformly, meanwhile, a mud pump 10 is arranged along the interior of the open caisson, mud is discharged to a sedimentation tank 15 through the mud pump 10 in the process of sinking of the open caisson, part of the settled mud flows into the mud tank to be stirred to form qualified mud, then the qualified mud flows into the open caisson, the other part of the mud flows into a water storage tank 14 through a filter screen, then the mud is pumped into the open caisson by the high-pressure pump to cut the soil body, and the operation is circulated, and the sedimentation tank 15 is used for cleaning the mud regularly and.
When water injection cutting soil body and discharge mud, earlier excavate earth through machinery (can excavate with the help of machinery such as long arm excavator), when the excavation degree of depth reaches conventional equipment and can't excavate, adopt the die-cut soil body of high-pressure squirt 11, wait the degree of depth simultaneously and set up slush pump 10 and take out the drainage, slush pump 10 and high-pressure squirt 11 bottom carry out counter weight and top and set up buoy 8, control the clearance position through removing buoy 8, set up horizontal pole 9 between slush pump 10 and the high-pressure squirt 11 in order to ensure that both intervals are not less than and predetermine the interval.
When the open caisson well body prefabricated in the first section is installed, connecting the steel bars at the reserved part, performing annular welding on the steel pipe by adopting a sleeve, and pouring concrete at the connecting part; when the ring beam is constructed in a cast-in-place mode, the ring beam is arranged along the circumferential direction of the well body, connected with the upper section of reinforcing steel bar and the lower section of reinforcing steel bar in a cast-in-place mode, and poured with concrete.
Step S40 specifically includes:
after the soil body in the open caisson is cleaned, performing slurry circulation on the bottom through a slurry pump 10 until the slurry is qualified in detection;
grouting reinforcement is carried out on the bottom of the open caisson by using a steel pipe in the open caisson, and after grouting is finished, washing pipes by using part of the steel pipe for later grouting reinforcement;
carrying out underwater concrete pouring on the bottom of the open caisson by adopting a plurality of guide pipes, wherein the concrete pouring elevation is not lower than the elevation of the bottom of the ring beam so as to carry out bottom sealing;
and pumping and discharging the static slurry in the open caisson after the bottom sealing concrete reaches the strength.
The detailed process of the construction method of the self-sinking support system of the deep foundation pit open caisson is described in detail below.
1. And (3) measurement and paying-off: and releasing the edge foot contour line of the open caisson and the reinforcing area of the cement mixing pile by using a full drilling instrument, and arranging a control point outside 3 times of the excavation depth of the open caisson, so that later-period settlement and displacement monitoring are facilitated.
2. Manufacturing a blade leg: digging a groove along the center line of the blade foot, and pouring concrete along the supporting molds at two sides of the groove to form the open caisson guide wall (the thickness of the guide wall is not less than 20cm, the depth of the guide wall is consistent with that of the blade foot, and the depth of the blade foot is not less than 1.5 m). And (3) binding reinforcing steel bars along the edge feet, installing a spray head 12 (extending out of the concrete by 10 cm), wrapping the spray head with geotextile, arranging pipelines in the circumferential direction, and firmly connecting. The vertical steel pipe that sets up, after the pipe connection was accomplished, the water test injection is experimental, and qualified back ligature reinforcing bar concreting.
And manufacturing the well body in sections outside the factory according to design requirements, and reserving steel bars and steel pipe holes at the well body connecting part.
3. Manufacturing a first section of ring beam: and after the edge foot is poured, binding the reinforcing steel bars of the ring beam, installing a pipeline and a spray head 12, and pouring the first ring beam. And a water stop steel plate is arranged at the connecting part of the ring beam and the blade foot.
After the connection of the blade foot and the pipeline in the first section of ring beam is finished, a water test injection test is carried out, and the concrete can be poured only when the water leakage phenomenon is avoided. Manufacturing a well body (each section with the height of 3m and the wall thickness of not less than 50 cm) in sections according to design requirements outside a factory, reserving steel bars and steel pipe holes at the well body connecting part (filling and compacting by adopting high-strength mortar after later installation), and pouring a first section of steel pipe in a blade; and (5) processing the steel pipe in sections (the diameter of the steel pipe is 15.9cm, and the annular distance is 1.5 m).
4. Constructing a stirring pile: and constructing cement mixing piles (the pile diameter is 500@350, the pile length is 1/3 of the depth of the foundation pit, the reinforcing width is 1 time of the depth of the foundation pit) on the outer side of the open caisson according to requirements, arranging a mud pit 16, a sedimentation tank 15 and a water storage tank 14 in a certain area away from the open caisson, and adopting a geomembrane to perform seepage-isolating treatment. Meanwhile, the elevation of the sedimentation tank is more than that of the mud tank and more than that of the open caisson, so that smooth circulation is facilitated.
5. Sinking the first section: and (3) installing the first section of open caisson according to requirements, connecting the steel bars at the reserved part, performing annular welding on the steel pipes by using sleeves (ensuring that water leakage does not occur), and pouring concrete at the connecting part. After the concrete reaches the designed strength of 80%, high-pressure water is synchronously injected into the steel pipes around, and the well body is kept to sink uniformly. When the periphery of the open caisson is not uniformly settled, water is purposefully injected and settled according to the pipeline partition of the isolating valve, and the deviation is corrected.
And mud pumps 10 (annular 3 m/platform) are arranged around the inside of the open caisson, mud residues are discharged to a sedimentation tank through the mud pumps in the process of sinking the open caisson, part of the settled mud flows into a mud tank and is stirred to form qualified mud, the qualified mud flows into the open caisson, the other part of the mud flows into a water storage tank 14 through a filter screen, and the mud is pumped into the open caisson by a high-pressure pump to cut soil bodies, and the circulation is carried out. The sedimentation tank regularly cleans the sludge and transports the sludge outside.
6. Constructing a ring beam: and ring beams are arranged along the circumferential direction of the well body, are connected with the upper section of reinforcing steel bar and the lower section of reinforcing steel bar in a cast-in-place mode, and are poured with concrete.
7. Grouting reinforcement: after the open caisson is sunk to the bottom elevation, the soil body loose on the bottom and the outer side well wall of the open caisson is reinforced and reinforced, namely, proper cement-water glass double-liquid slurry is injected into the steel pipe, and after the reinforcement, a proper amount of clean water is injected into the steel pipe to wash the pipe.
8. Installing other sections of open caisson and carrying out water injection excavation: firstly, after the current open caisson is connected with the open caisson which is installed before, the excavation operation is carried out.
Qualified mud is injected into the open caisson through the mud pit before the excavation, the excavation can be carried out by means of machinery such as a long-arm excavator in the earlier stage, when the excavation depth is deeper and conventional equipment cannot carry out the excavation, the high-pressure water gun 11 is adopted to punch the soil body, and the depth is equal to the depth and the mud pump is arranged to carry out pumping drainage.
The bottom of the mud pump and the high-pressure water gun 11 is weighted to ensure vertical verticality, and the top of the mud pump and the high-pressure water gun is provided with a buoy 8 to facilitate control of cleaning depth. Meanwhile, the cleaning position is controlled by moving the buoy 8, and the cross rod 9 is arranged between the mud pump and the high-pressure water gun 11, so that the distance between the mud pump and the high-pressure water gun is not less than 2m, and mutual winding is prevented.
9. Bottom sealing: and after the soil body in the open caisson is cleaned, performing slurry circulation on the bottom through a slurry pump 10 until the slurry is qualified in detection. And (4) grouting and reinforcing the bottom of the open caisson by using the steel pipes (after grouting is finished, washing the pipes by using every other steel pipe for later grouting reinforcement), and then implementing underwater concrete pouring to the bottom of the open caisson by using a plurality of guide pipes. And concrete must be continuously poured, the depth of the buried pipe is ensured, and the pouring elevation of the concrete is not lower than the bottom elevation of the ring beam.
10. Slurry pumping and discharging: and after the bottom sealing concrete reaches the strength, pumping and discharging the static slurry in the open caisson, and stopping pumping and discharging the slurry and injecting double-liquid slurry for leakage repair into the steel pipe when the open caisson leakage condition is found to be serious. And (4) after plugging, pumping the slurry in the open caisson, and finishing the open caisson construction.
The construction method of the deep foundation pit open caisson self-sinking supporting system provided by the invention has the following beneficial effects:
1. the open caisson is assembled in a prefabricated mode, local cast-in-place reinforcement is achieved, the soil body is converted into slurry to be discharged outwards by utilizing high-pressure water, the open caisson is made to sink automatically, the soil pressure and the bottom water pressure around the open caisson are balanced by utilizing the slurry in the open caisson, the excavation difficulty is reduced, and meanwhile the stability of the open caisson in the process of sinking and excavating is guaranteed.
2. By arranging the spray head 12 on the bevel edge of the blade leg, a circle of gap is formed inside the open caisson after high-pressure water impacts soil to store mud, mud residue at the bottom of the open caisson is discharged by utilizing the mud replacement principle, and the problem of discharging mud at the bottom of the open caisson in the flushing and sinking process is solved;
3. the open caisson can be designed into a round shape, so that the effective transmission of load is kept, and the stress characteristic of the material is fully utilized. The ring beam is arranged along the length direction of the well body to form an effective reinforcing body, and meanwhile, the occupation of the open caisson space due to the arrangement of the horizontal support is reduced;
4. by changing the sinking process, the construction method sinks firstly and then excavates, and forms a firm stress body at the initial stage of excavation, thereby solving the problem that the deep excavation affects the surrounding building environment. In the excavation process, slurry is injected into the open caisson to balance lateral active soil pressure and bottom water pressure, so that a stable stress body is formed;
5. the prefabricated member is used for replacing a cast-in-place structure, and the construction is performed in sections and sections, so that the construction period of concrete is effectively shortened, and the problems of low open caisson speed and long construction period are solved. The soil body at the bottom of the cutting edge and the first section of ring beam is cut by using high-pressure water, the operation time is sustainable, and the sinking rate of the open caisson is improved. The construction process is simple, and the economic benefit is obvious;
6. the open caisson is constructed earlier stage and is consolidated the open caisson outside with cement mixing pile, prevents that the bottom soil body from running off and causing the earth's surface subsidence in the work progress, has solved the open caisson construction and has caused peripheral earth's surface to subside the influence, simultaneously, has restricted the displacement of open caisson at the horizontal direction for the open caisson gradient is controllable.
The above description is only for the preferred embodiment of the present invention and is not intended to limit the scope of the present invention, and all equivalent structural changes made by using the contents of the present specification and the drawings, or any other related technical fields, are intended to be covered by the scope of the present invention.
Claims (10)
1. A construction method of a deep foundation pit open caisson self-sinking supporting system is characterized by comprising the following steps:
after measurement and paying-off, manufacturing a cutting edge in a cast-in-place mode, pre-burying a spray head in the cutting edge to be connected with a steel pipe of a prefabricated open caisson well body, and manufacturing a first section of ring beam in a cast-in-place mode;
installing a first section of prefabricated open caisson body, pre-burying a steel pipe in the open caisson body, connecting the open caisson body with a cutting edge, injecting water to cut soil and discharging slurry, so that the first section of open caisson body sinks to a designed elevation;
after the ring beam is cast in place, installing the next section of open caisson well body, performing water injection sinking by adopting the same method as the first section of open caisson well body, and installing all the open caisson well bodies in turn and sinking all the sections of open caisson well bodies to the right position;
and sealing bottom and pumping and discharging slurry.
2. The construction method of the deep foundation pit open caisson self-sinking supporting system as claimed in claim 1, wherein the step of constructing the ring beam in situ further comprises:
after the current segment open caisson is sunk to the designed elevation, cement-water glass double-liquid slurry is injected into a steel pipe of the open caisson to reinforce and reinforce the soil body loose on the bottom and the outer side well wall of the open caisson, and then clear water is injected into the steel pipe of the open caisson to wash the pipe.
3. The construction method of the self-sinking support system of the deep foundation pit open caisson according to claim 1, wherein a plurality of vertical standpipes and a circular ring pipe connecting the plurality of standpipes are arranged in each of the prefabricated open caisson body and the cutting edge, a block valve is installed in the circular ring pipe, and when the periphery of the open caisson is not uniformly sunk, the block valve is controlled to be opened and closed according to the pipeline partition of the block valve so as to perform water injection and sinking in a targeted manner.
4. The construction method of the self-sinking support system of the deep foundation pit open caisson of claim 3, wherein when the blade leg is cast in place, a groove is dug along the center line of the blade leg, concrete is poured as the open caisson guide wall along the two sides of the groove, reinforcing steel bars are bound along the blade leg, the nozzle is installed, the nozzle is wrapped by geotextile, the circular pipe is installed to be connected with the nozzle, and after the vertical pipe is installed to be connected with the circular pipe, the blade leg concrete is poured.
5. The construction method of the self-sinking support system of the deep foundation pit open caisson of claim 1, wherein before installing the first prefabricated open caisson well body, the method further comprises:
and constructing a stirring pile, and arranging a mud pool, a sedimentation tank and a water storage tank.
6. The construction method of the self-sinking support system of the deep foundation pit and the open caisson according to claim 5, wherein when water is injected to cut the soil body and the mud is discharged, high pressure water is synchronously injected into the steel pipe of the open caisson body to make the well body sink uniformly, simultaneously, the mud pump is arranged along the interior of the open caisson, the mud is discharged to the sedimentation tank through the mud pump during the open caisson sinking process, a part of the settled mud flows into the mud tank to be stirred to form qualified mud, then flows into the open caisson, the other part of the mud flows into the water storage tank through the filter screen, then is pumped into the open caisson by the high pressure pump to cut the soil body, and the circulation is carried out, and the sedimentation tank periodically cleans the mud and transports the mud outwards.
7. The construction method of the self-sinking support system of the deep foundation pit open caisson according to claim 6, wherein when water is injected to cut soil and discharge slurry, soil is excavated by a machine, when the excavation depth reaches the depth that conventional equipment cannot excavate, a high pressure water gun is used for punching the soil, a slurry pump is arranged at equal depth for pumping, the bottom of the slurry pump and the high pressure water gun is used for balancing weight, a buoy is arranged at the top of the slurry pump and the high pressure water gun, the buoy is moved to control the cleaning part, and a cross rod is arranged between the slurry pump and the high pressure water gun to ensure that the distance between the slurry pump and the high.
8. The construction method of the self-sinking support system of the deep foundation pit open caisson according to claim 5, wherein the step of constructing the mixing pile and arranging the mud pit, the sedimentation tank and the water storage tank comprises the following steps:
and constructing a cement stirring pile outside the open caisson, arranging a mud pit, a sedimentation tank and a water storage tank in a preset area away from the open caisson, and carrying out seepage-isolating treatment by adopting a geomembrane, wherein the elevation of the sedimentation tank is greater than the elevation of the mud pit and is greater than the elevation of the open caisson.
9. The construction method of the self-sinking support system of the deep foundation pit open caisson of claim 1, wherein when the first section of the prefabricated open caisson shaft is installed, the reserved part steel bars are connected, the steel pipes are welded by a sleeve ring, and the concrete at the connecting part is poured; when the ring beam is constructed in a cast-in-place mode, the ring beam is arranged along the circumferential direction of the well body, connected with the upper section of reinforcing steel bar and the lower section of reinforcing steel bar in a cast-in-place mode, and poured with concrete.
10. The construction method of the deep foundation pit open caisson self-sinking support system according to any one of claims 1 to 9, wherein the performing bottom sealing and slurry pumping specifically comprises:
after the soil body in the open caisson is cleaned, performing slurry circulation on the bottom through a slurry pump until the slurry is qualified in detection;
grouting reinforcement is carried out on the bottom of the open caisson by using a steel pipe in the open caisson, and after grouting is finished, washing pipes by using part of the steel pipe for later grouting reinforcement;
carrying out underwater concrete pouring on the bottom of the open caisson by adopting a plurality of guide pipes, wherein the concrete pouring elevation is not lower than the elevation of the bottom of the ring beam so as to carry out bottom sealing;
and pumping and discharging the static slurry in the open caisson after the bottom sealing concrete reaches the strength.
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| CN112854273A (en) * | 2020-12-31 | 2021-05-28 | 长广工程建设有限责任公司 | Excavation-free construction process and construction equipment for green urban underground structures |
| CN113216235A (en) * | 2021-05-31 | 2021-08-06 | 上海兴怡基础工程有限公司 | Construction method for large open caisson water storage settlement |
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