CN116446376A - Vacuum preloading construction process - Google Patents
Vacuum preloading construction process Download PDFInfo
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- CN116446376A CN116446376A CN202310562094.0A CN202310562094A CN116446376A CN 116446376 A CN116446376 A CN 116446376A CN 202310562094 A CN202310562094 A CN 202310562094A CN 116446376 A CN116446376 A CN 116446376A
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- soil foundation
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- 238000010276 construction Methods 0.000 title claims abstract description 72
- 238000000034 method Methods 0.000 title claims abstract description 53
- 238000007789 sealing Methods 0.000 claims abstract description 121
- 238000003825 pressing Methods 0.000 claims abstract description 74
- 239000002689 soil Substances 0.000 claims abstract description 68
- 239000004576 sand Substances 0.000 claims abstract description 49
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 40
- 239000004033 plastic Substances 0.000 claims description 28
- 229920003023 plastic Polymers 0.000 claims description 28
- 239000012528 membrane Substances 0.000 claims description 16
- 239000004927 clay Substances 0.000 claims description 12
- 238000005086 pumping Methods 0.000 claims description 12
- 239000002002 slurry Substances 0.000 claims description 12
- 230000000694 effects Effects 0.000 claims description 7
- 229910000831 Steel Inorganic materials 0.000 claims description 6
- 239000010959 steel Substances 0.000 claims description 6
- 238000003756 stirring Methods 0.000 claims description 6
- 230000002708 enhancing effect Effects 0.000 claims description 4
- 238000005520 cutting process Methods 0.000 claims description 3
- 238000003780 insertion Methods 0.000 claims description 3
- 230000037431 insertion Effects 0.000 claims description 3
- 238000002789 length control Methods 0.000 claims description 3
- 238000005507 spraying Methods 0.000 claims description 3
- 239000010410 layer Substances 0.000 description 37
- 239000003292 glue Substances 0.000 description 11
- 238000007596 consolidation process Methods 0.000 description 8
- 239000011148 porous material Substances 0.000 description 8
- 108091006146 Channels Proteins 0.000 description 7
- 230000035882 stress Effects 0.000 description 6
- 238000004140 cleaning Methods 0.000 description 5
- 230000006835 compression Effects 0.000 description 4
- 238000007906 compression Methods 0.000 description 4
- 239000004746 geotextile Substances 0.000 description 4
- 238000005336 cracking Methods 0.000 description 3
- 229920000915 polyvinyl chloride Polymers 0.000 description 3
- 239000004800 polyvinyl chloride Substances 0.000 description 3
- 238000003860 storage Methods 0.000 description 3
- 230000032683 aging Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 239000011229 interlayer Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000004062 sedimentation Methods 0.000 description 2
- 239000002344 surface layer Substances 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000009933 burial Methods 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000003203 everyday effect Effects 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000003673 groundwater Substances 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 238000005192 partition Methods 0.000 description 1
- -1 polyethylene Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 229920011532 unplasticized polyvinyl chloride Polymers 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Classifications
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D3/00—Improving or preserving soil or rock, e.g. preserving permafrost soil
- E02D3/02—Improving by compacting
- E02D3/10—Improving by compacting by watering, draining, de-aerating or blasting, e.g. by installing sand or wick drains
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- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Structural Engineering (AREA)
- Agronomy & Crop Science (AREA)
- Environmental & Geological Engineering (AREA)
- Soil Sciences (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Mining & Mineral Resources (AREA)
- Paleontology (AREA)
- Civil Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Investigation Of Foundation Soil And Reinforcement Of Foundation Soil By Compacting Or Drainage (AREA)
Abstract
The invention provides a vacuum preloading construction process, which comprises the following steps: after the soft soil foundation sand cushion is constructed, a plurality of drain plates are constructed on the soft soil foundation sand cushion, and a plurality of groups of filter tubes are arranged on the drain plates; firstly constructing a sealing wall at the periphery of a soft soil foundation, and then constructing a film pressing ditch above the sealing wall; constructing a soft soil foundation sealing film, manually pressing the sealing film into a film pressing groove, and timely covering water to ensure the sealing performance of the film pressing groove; and (5) vacuumizing the soft soil foundation. The soft soil foundation is sealed by the sealing wall, the sealing film, the film pressing groove and the water covering, and the sealing wall and the film pressing groove are arranged in the range of the separating wall, so that the soft soil foundation can be effectively sealed, and the soft soil foundation is convenient to vacuumize and solidify.
Description
Technical Field
The invention relates to the field of soft soil foundation construction, in particular to a vacuum preloading construction process.
Background
The vacuum pre-pressing construction is to lay a sand cushion layer on the surface of the soft soil foundation to be reinforced, then to embed a vertical drainage pipeline, to isolate the soil from the atmosphere by using an airtight sealing film, to carry out the burial treatment on the end part of the sealing film, to use a vacuum pump or other vacuum means to vacuumize the water suction pipeline embedded in the sand cushion layer, to form a negative pressure under the film, and to increase the effective stress of the foundation.
The existing vacuum preloading method is to insert a vertical drainage channel (such as a sand well, a bagged sand well or a plastic drainage plate) into a soft foundation to be reinforced, then lay a sand cushion layer on the ground, and then cover a layer of airtight film on the sand cushion layer. Vacuum pumping under the membrane forms negative pressure (relative to atmospheric pressure), the negative pressure transmits soil body downwards along the vertical drainage channel and transmits the negative pressure into the soil body in an unequal pressure state of the vertical drainage channel, and pore water gradually infiltrates into the vertical drainage channel under the action of the negative pressure so as to achieve the effects of soil body drainage consolidation and strength increase. The current construction flow of the vacuum preloading method is as follows: measuring and paying off, paving a main filtering drain pipe, paving an upper sand cushion layer, leveling a sand surface, paving a polyvinyl chloride film, constructing a sealing ditch, setting a measuring mark, and installing a vacuum pump to vacuumize and pre-press a consolidated soil layer.
For the large-piece foundation treatment project, the large-piece foundation comprises a soft soil foundation and a non-soft soil foundation, the soft soil foundation and the non-soft soil foundation can be determined according to the exploration situation, and how to solidify the soft soil foundation becomes a problem to be solved urgently.
Disclosure of Invention
The invention aims to provide a vacuum preloading construction process, which adopts a sealing wall, a sealing film, a film pressing groove and water to seal a soft soil foundation together, and the sealing wall and the film pressing groove are arranged in the range of a dam, so that the sealing of the soft soil foundation can be effectively realized, and the vacuum consolidation treatment of the soft soil foundation is facilitated.
The technical scheme for realizing the purpose of the invention is as follows:
a vacuum preloading construction process comprises the following steps:
after the soft soil foundation sand cushion is constructed, a plurality of drain plates are constructed on the soft soil foundation sand cushion, and a plurality of groups of filter tubes are arranged on the drain plates;
firstly constructing a sealing wall at the periphery of a soft soil foundation, and then constructing a film pressing ditch above the sealing wall;
constructing a soft soil foundation sealing film, manually pressing the sealing film into a film pressing groove, and timely covering water to ensure the sealing performance of the film pressing groove;
and (5) vacuumizing the soft soil foundation.
In one possible implementation manner, the construction of the plurality of drainage plates on the soft soil foundation sand cushion layer comprises the following steps:
the drainage plates are arranged in a regular triangle, a sleeve type pumping method is adopted by the crawler type plate inserting machine, the plane position deviation is not more than +/-10 cm, and the construction verticality deviation is not more than +/-1.5%;
the length of the return belt of the drain board is not more than 500mm, and the number of the return belt is less than 5% of the total number of the punched strips;
the exposed length above the sand bedding layer of the drain plate should be greater than 200mm and be reserved for the drain plate to connect with the filter tube.
In one possible implementation, the plurality of drain boards are provided with a plurality of groups of filter tubes, including:
after the drainage plate is arranged, the laying work of the vacuum filter pipe and the vacuum main pipe is started;
the vacuum filter pipe and the vacuum main pipe are required to be grooved and constructed on the sand cushion layer, and the burying depth of the vacuum filter pipe and the vacuum main pipe is 1/2 of the sand cushion layer;
the drain board surrounds the filter tube for more than one circle and ensures firm connection, thereby enhancing the drainage effect.
In one possible implementation, the plurality of drain boards are provided with a plurality of groups of filter tubes, and the method further comprises:
a steel wire rubber hose soft joint is arranged on the vacuum main pipe at intervals of 20-30 m along the length direction, and the deviation of the pipe position of the vacuum main pipe is less than 100mm;
the jet pump for vacuumizing construction is connected with the vacuum main pipe, a flange is processed at the end of the membrane outlet of the vacuum main pipe, and a rubber gasket is arranged in the flange to strengthen the tightness of the membrane outlet.
In one possible implementation manner, after the plurality of groups of filter tubes are installed on the plurality of drain boards, the method further includes:
after the vacuum main pipe and the vacuum filter pipe are buried, the main pipe and the filter pipe are buried by sand manually, and a sand cushion layer of the soft soil foundation is leveled.
In one possible implementation, the sealing wall construction process includes: step 21, setting out the pile position and excavating a guide ditch for guiding and storing slurry so as to intensively clean after finishing; step 22, preparing slurry by clay and water, and making pile position marks with intervals of 500+/-50 mm; step 23, positioning the pile driver, centering and leveling, and checking the diameter of the drill bit and the pile length control mark; step 24, rotating the drill bit, and stirring and sinking in advance; step 25, when the drill bit is sunk to the designed pile bottom elevation, the slurry pumping is started; and 26, lifting the drill and spraying slurry to the surface, finishing piling, and moving the pile machine according to the construction mark to construct the next stirring pile.
In one possible implementation, the drain board construction process includes: step 11, leveling the drainage sand cushion layer and marking the insertion point positions of the plastic drainage plates; step 12, marking the construction depth of the plastic drain board on the rack of the board inserting machine, and moving the machine to be in place; step 13, adjusting the verticality of the plugboard machine and locking the bottom end of the plastic drainage board by using a steel sheet; step 14, starting a hydraulic plugboard system, and starting to plug in a plastic drainage board; step 15, lifting and pulling up the plastic drainage plate until the plastic drainage plate is constructed to the designed bottom elevation, and completing construction record; and step 16, cutting off the plastic drainage plate, and moving the plate inserting machine to start the construction of the next plastic drainage plate.
In one possible implementation, the basement of the sealing wall extends downwards beyond the vacuum pre-compression area of the soft soil foundation and continuously, the wall top of the sealing wall is lower than the vacuum pre-compression area, and the film pressing groove is positioned above the sealing wall;
the sealing film extends to the bottom of the film pressing groove along the groove wall of the film pressing groove, and the clay layer backfilled in the film pressing groove compresses the sealing film.
Compared with the prior art, the invention has the beneficial effects that:
the soft soil foundation is sealed by the sealing wall, the sealing film, the film pressing groove and the water covering, and the sealing wall and the film pressing groove are arranged in the range of the separating wall, so that the soft soil foundation can be effectively sealed, and the soft soil foundation is convenient to vacuumize and solidify.
Drawings
FIG. 1 is a flow chart of a vacuum preloading construction process provided by the invention;
FIG. 2 is a second flow chart of a vacuum preloading construction process provided by the invention;
FIG. 3 is a graphical representation of the solution of alpha, beta values provided by the present invention;
FIG. 4 is a schematic diagram of a vacuum jet pump connection vacuum main pipe provided by the invention;
FIG. 5 is a schematic illustration of the connection of the sealing wall, the film pressing groove and the sealing film provided by the invention;
FIG. 6 is an enlarged view of a portion A of FIG. 5 in accordance with the present invention;
FIG. 7 is a vacuum preloading partition diagram of a soft soil foundation in a foundation provided by the invention;
FIG. 8 is a graph showing the distribution spacing between a vacuum filter tube and a vacuum main tube provided by the invention;
reference numerals: 1-geotechnical cloth layer; 2-a first sealing film; 3-a second sealing film; 4-sealing the wall; 5-film pressing grooves; 6-clay layer; 7-covering the water bank; 8-bank; 9-a drain pipe; 10-a main pipe; 11-flanges; 12-a rubber gasket; 13-a bolt; 100-soft soil foundation; 110-sand cushion.
Detailed Description
The present invention will be described in detail below with reference to the embodiments shown in the drawings, but it should be understood that the embodiments are not limited to the present invention, and functional, method, or structural equivalents and alternatives according to the embodiments are within the scope of protection of the present invention by those skilled in the art.
Referring to fig. 1, the embodiment of the invention provides a vacuum preloading construction process, which comprises the following steps:
step one, after the soft soil foundation sand cushion is constructed, a plurality of drainage plates are constructed on the soft soil foundation sand cushion, and a plurality of groups of filter pipes are arranged on the drainage plates.
In the first step of the vacuum preloading construction process, a plurality of drain boards are constructed on a soft soil foundation sand cushion layer, and the vacuum preloading construction process comprises the following steps: the drainage plates are arranged in a regular triangle, a sleeve type pumping method is adopted by the crawler type plate inserting machine, the plane position deviation is not more than +/-10 cm, and the construction verticality deviation is not more than +/-1.5%; the length of the return belt of the drain board is not more than 500mm, and the number of the return belt is less than 5% of the total number of the punched strips; the exposed length above the sand bedding layer of the drain plate should be greater than 200mm and be reserved for the drain plate to connect with the filter tube.
In the first step of the vacuum preloading construction process, a plurality of groups of filter tubes are arranged on a plurality of drain boards, and the vacuum preloading construction process comprises the following steps: after the drainage plate is arranged, the laying work of the vacuum filter pipe and the vacuum main pipe is started; the vacuum filter pipe and the vacuum main pipe are required to be grooved and constructed on the sand cushion layer, and the burying depth of the vacuum filter pipe and the vacuum main pipe is 1/2 of the sand cushion layer; the drain board surrounds the filter tube for more than one circle and ensures firm connection, thereby enhancing the drainage effect.
In the first step of the vacuum preloading construction process, a plurality of groups of filter tubes are arranged on a plurality of drain boards, and the vacuum preloading construction process further comprises: a steel wire rubber hose soft joint is arranged on the vacuum main pipe at intervals of 20-30 m along the length direction, and the deviation of the pipe position of the vacuum main pipe is less than 100mm; the jet pump for vacuumizing construction is connected with the vacuum main pipe, a flange is processed at the end of the membrane outlet of the vacuum main pipe, and a rubber gasket is arranged in the flange to strengthen the tightness of the membrane outlet.
In the first step of the vacuum preloading construction process, after a plurality of groups of filter tubes are installed on the plurality of drain boards, the vacuum preloading construction process further comprises: after the vacuum main pipe and the vacuum filter pipe are buried, the main pipe and the filter pipe are buried by sand manually, and a sand cushion layer of the soft soil foundation is leveled.
The sand cushion construction and the plastic drainage plate construction shown in fig. 2 correspond to the step one of the embodiment of the present invention. The vacuum preloading construction process comprises a drainage system, a vacuumizing system and a sealing system, wherein pressure difference between the inside and the outside of a membrane is caused by continuous vacuumizing, seepage is generated in pore water in a soil body, and the pore water in the soil body is discharged out of the membrane through a plastic drainage plate, a sand cushion layer and a filter tube under the action of vacuum suction force, so that the purpose of solidifying and compacting the soil body is achieved.
Referring to fig. 2, a boot check-preventing belt is disposed at the lower end of a sleeve of a drain board according to an embodiment of the present invention. The vacuum preloading main pipe of the embodiment of the invention adopts a UPVC pipe with the outer diameter of 76mm and the wall thickness of 3.5-4.0 mm, and can bear 400kPa pressure when the flattening rate is 5%, and the single length is generally 4-6 m. The vacuum filter tube adopts a soft drain pipe with the outer diameter of 50mm, and is connected with the drain plate and the main pipe to consolidate a drainage conveying pipeline.
And secondly, constructing a sealing wall at the periphery of the soft soil foundation, and then constructing a film pressing ditch above the sealing wall.
In the second step of the vacuum preloading construction process, the sealing wall construction process comprises the following steps: step 21, setting out the pile position and excavating a guide ditch for guiding and storing slurry so as to intensively clean after finishing; step 22, preparing slurry by clay and water, and making pile position marks with intervals of 500+/-50 mm; step 23, positioning the pile driver, centering and leveling, and checking the diameter of the drill bit and the pile length control mark; step 24, rotating the drill bit, and stirring and sinking in advance; step 25, when the drill bit is sunk to the designed pile bottom elevation, the slurry pumping is started; and 26, lifting the drill and spraying slurry to the surface, finishing piling, and moving the pile machine according to the construction mark to construct the next stirring pile.
In the second step of the vacuum preloading construction process, the drainage plate construction process comprises the following steps: step 11, leveling the drainage sand cushion layer and marking the insertion point positions of the plastic drainage plates; step 12, marking the construction depth of the plastic drain board on the rack of the board inserting machine, and moving the machine to be in place; step 13, adjusting the verticality of the plugboard machine and locking the bottom end of the plastic drainage board by using a steel sheet; step 14, starting a hydraulic plugboard system, and starting to plug in a plastic drainage board; step 15, lifting and pulling up the plastic drainage plate until the plastic drainage plate is constructed to the designed bottom elevation, and completing construction record; and step 16, cutting off the plastic drainage plate, and moving the plate inserting machine to start the construction of the next plastic drainage plate.
Referring to fig. 5 and 6, a sealing wall and a film pressing groove according to an embodiment of the present invention are shown, wherein the sealing film seals a soft soil foundation 100 treated by a foundation, and includes: the first sealing film 2 and the second sealing film 3 are paved on the soft soil foundation 100, the sealing wall 4 is constructed to surround the soft soil foundation 100, and the film pressing ditch 5 is constructed to surround the soft soil foundation 100; the film pressing groove 5 is positioned above the sealing wall 4, the wall foot of the sealing wall 4 exceeds the vacuum pre-pressing area of the soft soil foundation 100 and continuously extends downwards, and the wall top of the sealing wall 4 is lower than the vacuum pre-pressing area; the first sealing film 2 and the second sealing film 3 extend to the bottom of the film pressing groove 5 along the wall of the film pressing groove 5, and the clay layer 6 backfilled in the film pressing groove 5 compresses the first sealing film 2 and the second sealing film 3. The first sealing film 2 and the second sealing film 3 in the embodiment of the invention need to carefully clean a flat working surface before the sealing films are paved, and clean sharp objects on the surface layer of geotextile. Preferably, the first sealing film 2 and the second sealing film 3 are formed by overlapping a plurality of films, special glue is adopted for on-site paving and bonding, and the overlapping width of the two films is not smaller than 2m. After the whole evaluation of the field area block land survey, a reserved 1.5m deformation allowance is selected to cope with the uneven settlement of the foundation, and the sealing film is properly lifted and laid in a loose mode to prevent the sealing film from cracking. And (3) laying and overlapping the sealing films in layers according to the sequence of areas, after each layer of film is laid, sending special personnel to check whether the film is perfect, finding out a rupture position, cleaning the film with clear water in time, and then pasting the film with glue. The consolidation process of the soil body under the vacuum effect of the embodiment of the invention is a process that the pore water pressure is reduced and the effective stress is increased under the condition of unchanged total stress. Because the plastic sealing film seals the reinforced soil body from the atmosphere, when the vacuum pumping device is used for vacuumizing, the pore water pressure in the sand cushion 110 and the vertical drainage channel is rapidly reduced, a pressure difference is formed between the sand cushion and the pore water pressure in the soil body, and the pore water pressure in the soil body is gradually reduced under the action of the pressure difference. According to the principle of the effective stress of the Taisha, when the total stress is unchanged, the decrease in pore water pressure translates all the way to an effective increase in stress.
With continued reference to fig. 5, the first sealing film 2 and the second sealing film 3 are preferably laminated. With continued reference to fig. 5, it is preferable that the second sealing film 3 is located above the first sealing film 2, and a geotechnical layer 1 is further disposed between the first sealing film 2 and the soft soil foundation 100. Referring to fig. 6, the main pipe 10 is preferably connected by a flange 11 at the perforation of the first sealing film 2 and the second sealing film 3, and after the main pipe 10 and the filter pipe are buried, the main pipe 10 and the filter pipe are buried by using sand manually, and the sand cushion 110 is leveled. With continued reference to fig. 5, the longitudinal section of the film pressing groove is preferably trapezoidal, the bottom of the film pressing groove corresponds to the short side of the trapezoid, and the top of the film pressing groove corresponds to the long side of the trapezoid; the clay layer 6 is lower than the first sealing film 2 and the second sealing film 3 of the soft soil foundation 100. The vacuum is needed to be laid at the film pressing groove the film is tightly attached to the gradient of the film pressing groove and is paved towards the bottom of the film pressing groove. The depth of the sealing film embedded into the film pressing groove is not less than 0.8m, clay is selected to backfill the film pressing groove during construction, and air leakage is prevented. In the film pressing construction of the embodiment of the invention, attention should be paid to the connection between the drain board and the filter pipe near the protection seal ditch, and continuing to refer to fig. 5, preferably, the edge of the film pressing ditch 5 far away from the soft soil foundation 100 is constructed with a water-covered cofferdam 7; water-covered cofferdam 7 winding film pressing ditch 5 are circumferentially arranged. With continued reference to FIG. 5, the water-covered coffer dam 7 is preferably higher than the first sealing film 2 and the second sealing film 3. With continued reference to fig. 5, it is preferable that the top of the film pressing groove 5 is flush with the first sealing film 2 and the second sealing film 3 of the soft soil foundation 100; the water-covered cofferdam 7 extends upwards from the outer edge of the ditch top of the film pressing ditch 5; the membrane pressing ditch 5 is provided with a dam 8 at the side, and the water-covered cofferdam 7 is positioned on the upper surface of the dam 8. With continued reference to fig. 5, a drain pipe 9 is preferably provided below the first sealing film 2 and the second sealing film 3. If the sealing film disclosed by the embodiment of the invention has a damage phenomenon before vacuum preloading, cleaning the film surface by adopting clean water, wiping the film surface by using a towel, and pasting and repairing by adopting special glue. If in the water-covered vacuum preloading process: constructing a temporary small coffer dam by using a small sand bag, draining water at the damaged position, cleaning the damaged position, and adopting special glue to paste and repair; the method is characterized by comprising the following steps of (1) stopping vacuum preloading construction in a large range, removing water on a film, cleaning up damaged parts, and repairing the damaged parts by adopting special glue.
According to the embodiment of the invention, the lateral seal is formed by manually directly stepping the sealing film into the film pressing groove, and the depth of the stepped impervious layer is not smaller than 0.8m. The film pressing groove (width 2m and depth 1 m) is timely covered with water to prevent the occurrence of dry cracking and the formation of an air seepage channel.
The sealing film is broken and air leakage is found, the special PVC glue is adopted to glue and repair (the damaged part is cleaned cleanly, the towel is used for wiping, the glue is coated, a new sealing film is cut and stuck before the glue is dried, and the sealing film is uniformly pressed).
The measures for preventing the sealing film from being damaged in the construction process of the embodiment of the invention are as follows: (1) After the filter tube is laid, the filter tube is buried in sand and cannot be exposed; the pointed objects in the sand layer need to be removed, and geotextile laying can be carried out after the sand layer is inspected to be qualified. (2) The geotextile is closely adhered to the sand cushion layer to be paved, a certain margin is reserved, and the sealing film is properly lengthened and is paved loosely. (3) During construction, personnel and machinery irrelevant to construction must not walk in the construction area. (4) And water is covered in the reinforcing area, so that the sealing film is protected and the pre-compression load is increased. (5) The special person is arranged to watch during the vacuum preloading, and all vacuum pumps are required to work at full load for 24 hours.
In the embodiment of the invention, at the membrane surface where the interlayer water exists, an upper membrane is cut beside a filter tube, a lower membrane is pricked, and after the filter tube absorbs the interlayer water, the membrane surface holes are sealed and repaired. The embodiment of the invention increases the depth of the film pressing groove and tramples the sealing film again, and the sealing film is backfilled and compacted by silt.
And thirdly, constructing a soft soil foundation sealing film, manually pressing the sealing film into the film pressing groove, and timely covering water to ensure the sealing performance of the film pressing groove.
In the second and third steps of the vacuum preloading construction process, the basement of the sealing wall exceeds the vacuum preloading area of the soft soil foundation and extends downwards continuously, the wall top of the sealing wall is lower than the vacuum preloading area, and the film pressing groove is positioned above the sealing wall; the sealing film extends to the bottom of the film pressing groove along the groove wall of the film pressing groove, and the clay layer backfilled in the film pressing groove compresses the sealing film.
The sealing film of the embodiment of the invention is mainly used for sealing and air-closing during vacuumizing, 2 layers of polyethylene or polyvinyl chloride films are paved, and the single-layer thickness is 0.12-0.16 mm.
The sealing film construction of the embodiment of the invention, (1) the smooth working surface is carefully cleaned before the sealing film is paved, and sharp objects on the surface layer of geotextile are removed. (2) The special glue is adopted for field paving and bonding, and the lap joint width of the two films is not less than 2m. After the whole evaluation of the field area block land survey, a reserved 1.5m deformation allowance is selected to cope with the uneven settlement of the foundation, and the sealing film is properly lifted and laid in a loose mode to prevent the sealing film from cracking. (3) And (3) laying and overlapping the sealing films in layers according to the sequence of areas, after each layer of film is laid, sending special personnel to check whether the film is perfect, finding out a rupture position, cleaning the film with clear water in time, and then pasting the film with glue. (4) The vacuum film is tightly attached to the gradient of the film pressing groove and is paved towards the bottom of the film pressing groove. The depth of the sealing film embedded into the film pressing groove is not less than 0.8m, clay is selected to backfill the film pressing groove during construction, and air leakage is prevented. (5) During the film pressing construction, the connection between the drain board and the filter tube near the sealing ditch should be protected. (6) The vacuum main pipe and various buried instruments are connected by flanges at the perforated positions of the vacuum films.
The embodiment of the invention also constructs a water storage cofferdam to protect the sealing film and slow down the aging speed of the sealing film; meanwhile, the sealing film has a bubble phenomenon when air leaks, so that the sealing film is beneficial to on-site inspection of tightness. Therefore, the water-covered cofferdam is constructed by vacuum preloading. (1) After the vacuum degree is improved, after no air leakage hole is confirmed on the film, water is covered on the film for reducing the ageing of the vacuum film and enhancing the sealing performance, and maintenance is carried out during the pre-pressing period. (2) Building clay water-stopping cofferdam with the height of 50cm and the width of 50cm at the outer side line of the film pressing groove, so that the groundwater pumped in the vacuumizing process is discharged to the surface of the reinforced area to form water storage with the thickness of about 30cm, and a water film can be formed and used as a supplementary load. (3) If the water quantity is insufficient, the water pump can be used for pumping an off-site water source to supplement, and the film-covered water of about 30cm is ensured during the pre-pressing period. (4) After the construction of the water storage cofferdam is completed, a channel transmembrane ditch is built, so that monitoring staff can conveniently enter a pre-pressing area to monitor.
And fourthly, vacuumizing the soft soil foundation.
In the fourth step of the embodiment of the invention, the vacuum jet pump shown in fig. 4 is adopted to connect the vacuum main pipe, and when the vacuum pumping construction is performed, the vacuum degree under the film is gradually increased, so as to slow down the smearing effect of the soil layer, and the method specifically comprises the following steps: ensure that the vacuum pumping is free from air leakage (trial pumping), namely 30kPa vacuum, 50kPa vacuum and 80kPa step by step, and the duration of each load grade before full loading is not less than 3 days. More specifically, (1) at the beginning of the vacuumizing stage, along with the discharge of air and water, the sealing state of the sealing film and the sealing groove is comprehensively checked, if air leakage exists, the air leakage part is timely repaired and sealed, and the influence on the vacuum effect is prevented. (2) Whether all jet vacuum pumps in the reinforcement area synchronously run depends on the pre-pressing process, generally, in the initial stage of pre-pressing, the jet vacuum pumps run simultaneously due to large water discharge, and in the middle and later stages of pre-pressing, on the premise of ensuring the vacuum degree under the membrane, part of pumps can be stopped and all pumps can be adopted to run alternately, so that the number of pumps which are started is properly reduced. (3) the vacuum degree under the membrane is stably maintained above 80 kPa. (4) vacuum preloading unloading standard: the measured ground settlement rate is continuously 10d, the average settlement amount is not more than 3mm/d, and after vacuumizing for 90 days, the calculated consolidation degree according to the measured settlement curve is more than 85 percent (wherein the consolidation degree of the A6 area is not less than 90 percent). (5) The pre-compression period adopts effective management measures, and requires that all the vacuum pumps which are started are operated for 24 hours under full load. The effective pump-on rate and the normal working state of the pump machine are ensured, and the pump is not stopped after the approval of owners, designs and supervision. (6) The on-site subcontracting attendant records the vacuum degree according to the required time every day, and the running condition of the equipment is recorded in detail.
In the fourth step, the invention adopts a three-point method or an empirical hyperbolic method to calculate the final settlement of the foundation, the final settlement of the foundation is calculated to have a complete actual measurement settlement p-s-t curve, unreasonable points on the actual measurement s-t curve are removed before the final settlement is calculated, and a smooth curve is fitted. And calculating the consolidation degree by the final settlement amount on the settlement amount ratio at a certain moment.
The calculation method comprises the following steps:
(1) Three-point method:
wherein: u (U) t Consolidation (%) at time t; s is S t -foundation settlement (mm) at time t; s is S ∞ -the final settlement amount (mm) of the foundation calculated from the measured settlement curve; s is S 1 、S 2 、S 3 After full load, the measured sedimentation curve corresponds to t 1 、t 2 、t 3 The amount of sedimentation at time, t 1 、t 2 、t 3 Satisfy t 1 -t 2 ＝t 2 -t 3 ＝t。
(2) Empirical hyperbolic method:
wherein: u (U) t Consolidation (%) at time t; s is S t -foundation settlement (mm) at time t; s is S ∞ -the final settlement amount (mm) of the foundation calculated from the measured settlement curve; s is S 0 -foundation settlement (mm) at full load, i.e. t=0 (assumption); alpha, beta-constants related to foundation and load, according toThe time from full load was determined by the graphical method shown in FIG. 3, t-.
The above list of detailed descriptions is only specific to practical embodiments of the present invention, and they are not intended to limit the scope of the present invention, and all equivalent embodiments or modifications that do not depart from the spirit of the present invention should be included in the scope of the present invention.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present disclosure describes embodiments, not every embodiment is provided with a separate embodiment, and that this description is provided for clarity only, and that the disclosure is not limited to the embodiments described in detail below, and that the embodiments described in the examples may be combined as appropriate to form other embodiments that will be apparent to those skilled in the art.
Claims (8)
1. The vacuum preloading construction process is characterized by comprising the following steps of:
after the soft soil foundation sand cushion is constructed, a plurality of drain plates are constructed on the soft soil foundation sand cushion, and a plurality of groups of filter tubes are arranged on the drain plates;
firstly constructing a sealing wall at the periphery of a soft soil foundation, and then constructing a film pressing ditch above the sealing wall;
constructing a soft soil foundation sealing film, manually pressing the sealing film into a film pressing groove, and timely covering water to ensure the sealing performance of the film pressing groove;
and (5) vacuumizing the soft soil foundation.
2. The vacuum preloading construction process of claim 1, wherein the construction of a plurality of drainage plates on the sand bedding layer of the soft soil foundation includes:
the drainage plates are arranged in a regular triangle, a sleeve type pumping method is adopted by the crawler type plate inserting machine, the plane position deviation is not more than +/-10 cm, and the construction verticality deviation is not more than +/-1.5%;
the length of the return belt of the drain board is not more than 500mm, and the number of the return belt is less than 5% of the total number of the punched strips;
the exposed length above the sand bedding layer of the drain plate should be greater than 200mm and be reserved for the drain plate to connect with the filter tube.
3. The vacuum preloading construction process of claim 1, wherein the plurality of drainage plates are provided with a plurality of groups of filter tubes, including:
after the drainage plate is arranged, the laying work of the vacuum filter pipe and the vacuum main pipe is started;
the vacuum filter pipe and the vacuum main pipe are required to be grooved and constructed on the sand cushion layer, and the burying depth of the vacuum filter pipe and the vacuum main pipe is 1/2 of the sand cushion layer;
the drain board surrounds the filter tube for more than one circle and ensures firm connection, thereby enhancing the drainage effect.
4. A vacuum preloading construction defined in claim 3, wherein a plurality of groups of filter tubes are mounted on the plurality of drain boards, and further comprising:
a steel wire rubber hose soft joint is arranged on the vacuum main pipe at intervals of 20-30 m along the length direction, and the deviation of the pipe position of the vacuum main pipe is less than 100mm;
the jet pump for vacuumizing construction is connected with the vacuum main pipe, a flange is processed at the end of the membrane outlet of the vacuum main pipe, and a rubber gasket is arranged in the flange to strengthen the tightness of the membrane outlet.
5. The vacuum preloading construction of claim 1, wherein after installing the plurality of sets of filter tubes on the plurality of drain boards, further comprising:
after the vacuum main pipe and the vacuum filter pipe are buried, the main pipe and the filter pipe are buried by sand manually, and a sand cushion layer of the soft soil foundation is leveled.
6. The vacuum preloading construction process of claim 1, wherein the sealing wall construction process includes: step 21, setting out the pile position and excavating a guide ditch for guiding and storing slurry so as to intensively clean after finishing; step 22, preparing slurry by clay and water, and making pile position marks with intervals of 500+/-50 mm; step 23, positioning the pile driver, centering and leveling, and checking the diameter of the drill bit and the pile length control mark; step 24, rotating the drill bit, and stirring and sinking in advance; step 25, when the drill bit is sunk to the designed pile bottom elevation, the slurry pumping is started; and 26, lifting the drill and spraying slurry to the surface, finishing piling, and moving the pile machine according to the construction mark to construct the next stirring pile.
7. The vacuum preloading construction process of claim 1, wherein the drainage plate construction process includes: step 11, leveling the drainage sand cushion layer and marking the insertion point positions of the plastic drainage plates; step 12, marking the construction depth of the plastic drain board on the rack of the board inserting machine, and moving the machine to be in place; step 13, adjusting the verticality of the plugboard machine and locking the bottom end of the plastic drainage board by using a steel sheet; step 14, starting a hydraulic plugboard system, and starting to plug in a plastic drainage board; step 15, lifting and pulling up the plastic drainage plate until the plastic drainage plate is constructed to the designed bottom elevation, and completing construction record; and step 16, cutting off the plastic drainage plate, and moving the plate inserting machine to start the construction of the next plastic drainage plate.
8. The vacuum preloading construction process of claim 1, wherein the footing of the sealing wall extends downwardly and continuously beyond the vacuum preloading area of the soft foundation, the wall top of the sealing wall is lower than the vacuum preloading area, and the film pressing groove is located above the sealing wall;
the sealing film extends to the bottom of the film pressing groove along the groove wall of the film pressing groove, and the clay layer backfilled in the film pressing groove compresses the sealing film.
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| CN117387870A (en) * | 2023-12-12 | 2024-01-12 | 华土木(厦门)科技有限公司 | Vacuum preloading underwater sealing film damage visualization accurate positioning method and system |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117387870A (en) * | 2023-12-12 | 2024-01-12 | 华土木(厦门)科技有限公司 | Vacuum preloading underwater sealing film damage visualization accurate positioning method and system |
| CN117387870B (en) * | 2023-12-12 | 2024-03-26 | 华土木(厦门)科技有限公司 | Vacuum preloading underwater sealing film damage visualization accurate positioning method and system |
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