CN114703831A - Construction method of reinforced concrete cast-in-place pile under complex geological condition - Google Patents
Construction method of reinforced concrete cast-in-place pile under complex geological condition Download PDFInfo
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- 239000011150 reinforced concrete Substances 0.000 title claims abstract description 17
- 239000002002 slurry Substances 0.000 claims abstract description 55
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 46
- 239000010959 steel Substances 0.000 claims abstract description 46
- 230000002787 reinforcement Effects 0.000 claims abstract description 36
- 239000004567 concrete Substances 0.000 claims abstract description 34
- 238000000034 method Methods 0.000 claims abstract description 31
- 238000005553 drilling Methods 0.000 claims abstract description 30
- 238000004140 cleaning Methods 0.000 claims abstract description 29
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 18
- 239000011435 rock Substances 0.000 claims abstract description 13
- 230000001681 protective effect Effects 0.000 claims abstract 6
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- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 9
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- 238000003466 welding Methods 0.000 claims description 6
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- 239000011398 Portland cement Substances 0.000 claims description 3
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Classifications
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
- E02D5/22—Piles
- E02D5/34—Concrete or concrete-like piles cast in position ; Apparatus for making same
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D15/00—Handling building or like materials for hydraulic engineering or foundations
- E02D15/02—Handling of bulk concrete specially for foundation or hydraulic engineering purposes
- E02D15/04—Placing concrete in mould-pipes, pile tubes, bore-holes or narrow shafts
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D17/00—Excavations; Bordering of excavations; Making embankments
- E02D17/06—Foundation trenches ditches or narrow shafts
- E02D17/08—Bordering or stiffening the sides of ditches trenches or narrow shafts for foundations
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
- E02D5/22—Piles
- E02D5/34—Concrete or concrete-like piles cast in position ; Apparatus for making same
- E02D5/38—Concrete or concrete-like piles cast in position ; Apparatus for making same making by use of mould-pipes or other moulds
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
- E02D5/22—Piles
- E02D5/34—Concrete or concrete-like piles cast in position ; Apparatus for making same
- E02D5/38—Concrete or concrete-like piles cast in position ; Apparatus for making same making by use of mould-pipes or other moulds
- E02D5/385—Concrete or concrete-like piles cast in position ; Apparatus for making same making by use of mould-pipes or other moulds with removal of the outer mould-pipes
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B7/00—Special methods or apparatus for drilling
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D2250/00—Production methods
- E02D2250/003—Injection of material
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D2300/00—Materials
- E02D2300/0004—Synthetics
- E02D2300/0018—Cement used as binder
- E02D2300/002—Concrete
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D2300/00—Materials
- E02D2300/0004—Synthetics
- E02D2300/0018—Cement used as binder
- E02D2300/0023—Slurry
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D2300/00—Materials
- E02D2300/0026—Metals
- E02D2300/0029—Steel; Iron
Abstract
The invention relates to the technical field of building construction, in particular to a construction method of a reinforced concrete cast-in-place pile under a complex geological condition, which comprises the following steps: s1, leveling the field and setting out the pile position; s2, forming holes, taking soil, and installing a steel protective cylinder to a position X meters away from the natural terrace; s3, performing slurry wall protection construction; s4, entering rock, pulling out pipes and cleaning holes; s5, placing a reinforcement cage; s6, pouring concrete; and S7, post grouting, and checking and accepting. The invention adopts the construction process of the cast-in-place pile with the steel casing and the mud casing and the bored hole, solves the problems of easy hole collapse and buried drilling of the cast-in-place pile under the complicated geological conditions of the ultra-thick fly ash layer, vibration hole collapse during rock entering, water source shortage, serious water leakage, poor wall protection forming and the like, greatly reduces the cost and the working strength, and improves the construction efficiency.
Description
Technical Field
The invention relates to the technical field of building construction, in particular to a construction method of a reinforced concrete cast-in-place pile under a complex geological condition.
Background
Aiming at geological conditions of a deep mountain valley section and a fly ash backfill layer of a power plant, the geological conditions of an original engineering geological landform, different valley bottom elevation, different rock mass strength, non-uniform fly ash layer backfill thickness, thick backfill thickness and the like exist, and meanwhile, the fly ash layer has the defects of non-uniform particle dispersion, loose structure, easy water permeation, easy collapse, large filling coefficient and the like.
By adopting a single construction process to test piles for many times, the requirements of low construction unit cost, tight construction period and high-quality construction cannot be met. The single construction process of the all-steel casing is adopted, the pile foundation quality can be guaranteed, but the required equipment requirement is high, the cost is high, and the method is not economical; the single slurry wall protection is adopted, so that holes are easy to collapse, the water loss is large, the safety of a dam body is influenced, potential safety hazards exist, and the construction requirements cannot be met.
Therefore, there is a need for improvements in the prior art.
Disclosure of Invention
In order to overcome the defects in the prior art, the construction method of the reinforced concrete cast-in-place pile under the complex geological condition is provided.
In order to solve the technical problems, the invention adopts the technical scheme that:
a construction method of a reinforced concrete cast-in-place pile under complex geological conditions comprises the following steps:
s1, leveling the field and setting out the pile position;
s2, forming holes, taking soil, and installing a steel casing to a position X meters away from the natural terrace;
s3, constructing a mud retaining wall to the rock stratum;
s4, entering rock, pulling out pipes and cleaning holes;
s5, placing a reinforcement cage;
s6, pouring concrete;
and S7, post grouting, and checking and accepting.
Further, in the step S2, a pipe rolling machine is used for forming a hole, the position of the pipe rolling machine is adjusted to be in place, a rotary excavating machine is used for taking soil, the first section of steel casing is hung and rolled in, the verticality is corrected, a flushing grab bucket is used for taking soil from the steel casing, the steel casing is pressed down while taking soil, when the steel casing is 12-1.5m higher than the top surface of the guide wall, a second section of steel casing is installed, and soil is continuously pressed down until the position is Xm away from the natural terrace;
and the numerical value of the X is determined according to the elevation of the natural terrace and the excavated soil quality.
Furthermore, in the soil taking process, the depth of the excavation surface exceeding the bottom opening of the steel casing is kept to be more than or equal to 2.5 m.
Further, the S3 includes:
s31, preparing mud, firstly injecting 1Y m3After stirring for half an hour, adding 120YKg composite bentonite while stirring, after the bentonite is dissolved, uniformly adding 0.5YKg carboxymethyl cellulose, and then sequentially adding 1.5YKg caustic soda, 1Ykg water-permeable alum and 2Ykg quicklime, wherein the value of Y is determined according to the actual dosage of the slurry;
and S32, sequentially digging out drilling residues in the holes by using a rotary digging bucket, and putting chemical slurry at the position of X meters till the drilling is finished.
Further, the rock entering comprises: the method comprises the following steps of (1) completing hole forming operation by using an ultra-deep pile, locally backfilling and tamping the periphery of a sleeve, injecting slurry into the sleeve by using a punching and grabbing hammer of a rotary digging machine, sequentially digging out drilling slag in a hole by using a rotary digging drilling bucket, replenishing the slurry at any time in the hole forming process, and ensuring the water head pressure of the slurry in a pile casing;
the clear hole includes: and when the drill hole of the rotary drilling rig reaches the designed depth, cleaning the hole, wherein the thickness of the sediment after hole cleaning is less than or equal to 50mm, cleaning the sediment by using a cylindrical drill with a valve when the drill hole reaches the designed elevation, namely cleaning the hole at one time, and taking out the drill bit after hole cleaning.
Furthermore, the steel reinforcement cage is manufactured strictly according to the design, the equal division distance of the main reinforcement position is controlled by a steel reinforcement positioning bracket, and the allowable deviation of the main reinforcement distance is +/-10 mm; the allowable deviation of the screw pitch of the stirrup or the spiral rib is +/-20 mm; the allowable deviation of the diameter of the reinforcement cage is +/-10 mm; the length of the reinforcement cage is allowed to deviate +/-50 mm; arranging a stiffening hoop every 2m to strengthen the strength of the reinforcement cage, wherein the length of the reinforcement cage is determined by the depth of the excavated hole; the longitudinal steel bar welding adopts single-side lap welding, and the lap length is more than or equal to 10 d; the joints are staggered with each other by not less than 35d, and the number of the joints on the same section is not more than 50%.
Further, concrete pouring adopts the pipe to pour, when laying the pipe, control pipe bottom apart from the hole bottom 40cm, adjustment pipe chuck height, with the pipe card solid, the pipe is laid the back and is accomplished, detects hole bottom mud and hole bottom sediment thickness, if two conditions satisfy the requirement simultaneously, can directly pour the concrete, if one can not satisfy the requirement, need carry out the clear hole of secondary.
Further, the secondary hole cleaning comprises: connecting and sealing a high-pressure pipe of a slurry pump and a pouring guide pipe, starting the slurry pump, circulating slurry, continuously circulating the slurry after the thickness of sediment at the bottom of a hole is less than 5cm so as to replace the slurry and reduce the specific gravity of the slurry, and stopping cleaning the hole when the specific gravity of the slurry is less than 1.15, and immediately pouring;
the time interval between the completion of hole cleaning and concrete pouring does not exceed 45 minutes, so that the occurrence of sediment in the hole re-precipitation and necking of the drilled hole is avoided, and the specific gravity of the slurry within 500mm of the hole bottom is less than 1.20 before the concrete is poured.
In order to ensure that no floating slurry or impurities exist at the top of the pile, the concrete is poured at least 500mm higher than the designed pile top elevation.
Furthermore, in the post-grouting process, the cement paste adopts 32.5MPa slag portland cement, the water cement ratio is 0.6, and the grouting amount is as follows: the pile end is 2000kg, the pile group is grouted firstly from the periphery to the inside, and A, B piles are used for alternate grouting.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention adopts the construction process of the cast-in-place pile with the steel casing and the mud casing and the bored hole, solves the problems of easy hole collapse and buried drilling of the cast-in-place pile under the complicated geological conditions of the ultra-thick fly ash layer, vibration hole collapse during rock entering, water source shortage, serious water leakage, poor wall protection forming and the like, greatly reduces the cost and the working strength, and improves the construction efficiency.
2. The comprehensive effect of the combined construction process of the steel casing and the slurry retaining wall is exerted, the steel casing can be produced in a factory, installed in a forming mode and repeatedly recycled, and the filling coefficient is effectively reduced; the slurry wall protector solves the problem of collapse of the coal ash layer and the junction of the coal ash and the original stratum, has low cost, high efficiency, good pore-forming quality and excellent pile-forming quality, and is beneficial to environmental protection.
3. The invention adopts the independently developed slurry retaining wall proportion to ensure the pore-forming quality.
Drawings
The following will explain embodiments of the present invention in further detail through the accompanying drawings.
FIG. 1 is a process flow diagram of the present invention;
FIG. 2 is a flow chart of the post-grouting construction process of the present invention;
FIG. 3 is a cross-sectional view of a slurry retaining wall hole.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example (b):
a construction method of a reinforced concrete cast-in-place pile under complex geological conditions comprises the following steps:
s1, leveling the field and setting out the pile position;
the method is characterized in that a site is leveled, positioned and laid out by an excavator before construction, 200-thick fly ash is reserved for manual leveling, the site flatness is less than or equal to +/-10 cm, driving and stable in-place of the pile foundation machinery are guaranteed, the perpendicularity of the laid-out and the pile is strictly controlled, the site must be leveled and compacted before the site laying-out, and driving and stable and accurate in-place of the pile foundation machinery are guaranteed. And (3) according to a coordinate control point given by a construction unit, carrying out pile position lofting and elevation measurement by using a total station, and carrying out RTK retesting and error control within 5 mm.
S2, forming holes, taking soil, and installing a steel casing to a position X meters away from the natural terrace;
according to the pile point of measurement lofting, when a crawler crane is roughly in place in cooperation with a pipe rolling machine, retesting again, adjusting the position of the pipe rolling machine until the pipe rolling machine is accurately in place, taking soil by adopting a 280-type rotary excavator, lifting and rolling the soil into a first section of steel casing, checking the verticality, wherein the pressing depth is about 2.5m-3.5m, then taking soil from the steel casing by using a flushing grab bucket, grabbing soil while pressing the steel casing, keeping the depth of an excavation surface exceeding the bottom opening of the steel casing to be more than or equal to 2.5m, when the first section of steel casing is pressed down until the steel casing is 1.5m higher than the top surface of a guide wall, detecting the verticality, performing deviation rectification adjustment if the verticality is not qualified, and installing a second section of steel casing to continue pressing and taking soil if the verticality is qualified. And by parity of reasoning, digging to the Xm position away from the natural terrace.
X's numerical value is confirmed according to natural terrace elevation and the soil property of digging out, through carrying out the analysis discovery to the geological conditions that this embodiment faced: the fly ash layer buried more than 35 m-40 m is filled with slag, the structure is loose, and the water permeability is strongest; the buried depth is less than 40m, the collapse at the junction of the fly ash and the original stratum is serious, but the water permeability is weak, so that X is 40, a 280 drilling machine and a steel grab bucket casing are adopted to follow up hole forming construction from the position below the ground to the buried depth of 40m, and the quality problems that the fly ash is easy to permeate water and collapse, the filling coefficient is large, the fly ash has negative friction resistance, the pile body is not well formed and the like can be solved. Rock drilling with a 400 drill rig combined with self-cementing the wall below 40 m.
S3, performing slurry wall protection construction;
s31, preparation of slurry: first inject 1 x Y m3After stirring for half an hour, adding 120 × YKg composite bentonite while stirring, after the bentonite is dissolved, uniformly adding 0.5 × YKg carboxymethyl cellulose, and then sequentially adding 1.5 × YKg caustic soda, 1 × Ykg water-seepage alum and 2 × Ykg quicklime, wherein the value of Y is determined according to the actual dosage of the slurry.
S32, positioning a drilling machine: firstly, leveling the field, enabling the left and right track shoes of the main machine to be positioned on the same horizontal plane, arranging the power head construction position towards the straight direction of the track, and adjusting the front, back, left and right levels of the machine body. And adjusting the mast of the drilling machine to a horizontal plane perpendicular to the hole opening, so that the center of the drill bit is arranged at the center of the pile in the pile casing.
And S33, sequentially digging out drilling residues in the hole by using a rotary drilling bucket, and putting chemical slurry into the pile hole to the position of 40m until the drilling is finished.
S4, entering rock, pulling out pipes and cleaning holes;
the method comprises the steps of adopting a pile with the pile length L being more than or equal to 50m and the length-diameter ratio L/D being more than or equal to 50, completing hole forming operation by using a special drill rod 44 multiplied by 5 multiplied by 19.5, locally backfilling and tamping the periphery of a sleeve, injecting enough slurry into the sleeve by a 400-turn excavator punching and grabbing hammer, then digging out drilling slag in holes by turning a drilling bucket in turn, replenishing the slurry at any time in the hole forming process, ensuring the water head pressure of the slurry in a pile casing, and arranging a loader to clean the drilling slag dug out by the drilling bucket out of the field. If the diamond drill is replaced when boulders, ladles or large rock masses and hard rock stratums are encountered in the drilling and digging process, the verticality of the mast is checked at any time, and the verticality of the pile hole is controlled until the rock-entering depth is designed.
When the drilling hole of the rotary drilling rig reaches the designed depth, the hole is cleaned in time, and the sediment is not larger than 50mm after the hole is cleaned. When the drill reaches the designed elevation, the barrel-shaped drill with the valve is used for cleaning sediments, namely, the hole is cleaned at one time. And (4) taking out the drill bit after hole cleaning, detecting the aperture, the hole depth and the verticality, moving the drilling machine away after acceptance inspection is qualified, covering a cover plate, and performing next procedure construction.
S5, placing a reinforcement cage;
the steel reinforcement cage is manufactured strictly according to the design, and the position of the main reinforcement is equally divided by the steel reinforcement positioning bracket. The allowable deviation of the main rib spacing is +/-10 mm; the allowable deviation of the screw pitch of the stirrup or the spiral rib is +/-20 mm; the allowable deviation of the diameter of the reinforcement cage is +/-10 mm; the length of the reinforcement cage is allowed to deviate by +/-50 mm. Reinforcing hoops are arranged every 2m to strengthen the strength of the reinforcement cage, and the length of the reinforcement cage is determined by the depth of the excavated hole; the longitudinal steel bar welding adopts single-side lap welding, and the lap length is more than or equal to 10 d. The joints are staggered with each other by not less than 35d, and the number of the joints on the same section is not more than 50%. Deformation of the reinforcement cage is prevented when the reinforcement cage is transported and hoisted; before placing, the condition in the hole needs to be checked to ensure that no collapse and sediment exist in the hole; the placement needs to be aligned with hole positions, and the support is stable, slow and straight, so that collision with hole walls is avoided, and pier cages and torsion cages are strictly forbidden.
S6, pouring concrete;
carry out sediment thickness after the steel reinforcement cage is laid and survey and establish, satisfy sediment thickness and be not more than 5cm back installation concrete pipe, the concrete adopts the pipe to pour into, and the pipe internal diameter is 300mm, and the turnbuckle is connected. The appearance of the conduit is checked, and the inner wall of the conduit is smooth, straight, smooth and clean and has no local concave-convex. And calculating the required length of the guide pipe according to the top elevation of the sleeve and the bottom elevation of the hole, trial splicing the guide pipe and numbering. The guide pipe is installed by matching a crane with manual work, and when the guide pipe is placed, the guide pipe is matched with the manual work to be supported stably so that the guide pipe is positioned at the center of the steel reinforcement cage, and then the guide pipe is stably sunk and prevented from clamping the steel reinforcement cage and colliding with the hole wall. And the bottom of the time control guide pipe is 40cm away from the bottom of the hole during installation. After the height of the guide pipe is determined, the height of the guide pipe clamping disc is adjusted by a crane, and the guide pipe is clamped by the clamping disc.
And after the conduit placing procedure is finished, the thickness of the hole bottom slurry and the hole bottom sediment is detected, and if the two conditions meet the requirements at the same time, the concrete can be directly poured. If one item can not meet the requirement, secondary hole cleaning is needed. When secondary hole cleaning is carried out, a high-pressure pipe of the slurry pump is connected and sealed with the pouring guide pipe, the slurry pump is started to carry out slurry circulation, when the thickness of sediments at the bottom of the hole is smaller than 5cm, slurry circulation is carried out for a period of time to replace slurry and reduce the specific gravity of the slurry, when the specific gravity of the slurry is smaller than 1.15, hole cleaning can be stopped, pouring is carried out immediately, and the interval time between the hole cleaning completion and concrete pouring does not exceed 45 minutes to prevent the sediments in the hole from precipitating again and necking down the hole. Before concrete is poured, the specific gravity of the slurry within 500mm of the bottom of the hole is less than 1.20.
Before concrete is poured, cleaning the hole, wherein the hole wall and the hole bottom must be cleaned, no scum exists at the hole bottom, and the hole wall is not loosened. When the groundwater is present and the water seepage amount is not large, the accumulated water in the holes is pumped out, and then the concrete is poured by a conduit method. The distance between the tail end of the conduit and the bottom of the hole is not more than 1.5 m; the concrete is preferably compacted by an insertion vibrator, and is vibrated once every 1.5m of pouring. The concrete should be continuously poured and vibrated to be compact, and the filling coefficient is more than 1. And pouring concrete at least exceeds the designed pile top elevation by 500mm so as to ensure that no floating slurry or impurities exist at the pile top.
The pile filling process is characterized in that the follow-up pile casing is deeply embedded and cannot be integrally pulled out, pile forming quality is affected, sectional pulling is adopted, when the concrete surface of the filled pile rises into the follow-up pile casing, the follow-up full pile casing is connected with a power head driving sleeve of a rotary drilling rig, the follow-up pile casing is rotated until the follow-up pile casing rotates, pile filling operation can be continued, the concrete surface is 6m per liter, the rotary drilling rig is connected with the full pile casing again, the drilling rig drives the power head driving sleeve to pull out 2 sections of follow-up pile casings, and an assistant worker measures and adjusts the verticality of the follow-up pile casing by using a liquid bubble level gauge. Repeating the steps until all the sleeves are finally filled, and pulling out all the sleeves.
The concrete is C40P 6 commercial concrete, the slump is 160-180 mm, the concrete pouring slump is 180mm +/-20 mm, the initial setting time is not less than 45 minutes and not more than 2 hours, the final setting time is not more than 6 hours, and the concrete pouring time is 10m3And the concrete pouring time is controlled to be 1m/6 min, the height of the submerged pile casing is not more than 3m, the pipe is pulled out after the concrete is poured to the pipe pulling height. And conveying the dregs generated by pore forming to a designated place of an owner by using a dump truck. After the pile is formed, the slurry which is not recycled after pore-forming is transported and abandoned to the place appointed by the owner by adopting a slurry vehicle in a closed way
And S7, post grouting, and checking and accepting.
Stirring cement paste according to the designed water cement ratio → filtering the cement paste to a paste storage tank, preparing for grouting → connecting a slip casting pipe movable joint with a pile body mud jacking pipe → opening an exhaust valve and opening a pump to deflate → closing the exhaust valve to carry out mud jacking, wherein the termination standard is comprehensively controlled by the mud jacking amount, pressure and whether the ground returns the mud or not: when the grouting is stopped, the grout stop valve is closed, the pipe fitting is disassembled after the grouting valve is kept stand for 5 to 10 minutes, and the grouting pipe head is plugged again by a plug.
The grouting pipe adopts phi 25mm x 3mm steel pipe pile bottoms for symmetrical arrangement of 2, the length is matched with the length of a steel reinforcement cage, the grouting pipe is connected with a winding adhesive tape by adopting a thread hoop, the thread processing of the grouting pipe cannot be less than four circles, the grouting pipe is bound on the steel reinforcement cage by using an iron wire, the grouting pipe is arranged in a hole along with the steel reinforcement cage, the grouting pipe is not less than 30cm when exposed out of a construction operation surface after concrete is poured, and the bottom of the grouting pipe extends out of the steel reinforcement cage by 50 cm.
Determining the technical parameters of post grouting at the pile side and the pile end:
cement paste: adopting 32.5MPa slag portland cement, the water cement ratio is 0.6, and the grouting amount is as follows: pile tip 2000 kg.
And (3) pressure control: when the grouting pressure is lower than the normal value for a long time or grout leaks from the ground or surrounding pile holes flee, intermittent grouting is changed, and the intermittent time is preferably 30-60 minutes or the grout-water-cement ratio is adjusted to be low.
Grouting time: after the concrete pouring is finished, the grouting operation is started after 2d, and is not delayed from the pile forming operation for 30d, and the distance between the grouting operation and the hole forming operation point is not smaller than 8-10 m.
Grouting sequence: for the grouting of the pile group, A, B two piles are adopted for alternatively grouting after the periphery and the interior.
Although only the preferred embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the knowledge of those skilled in the art, and all changes are encompassed in the scope of the present invention.
Claims (10)
1. A construction method of a reinforced concrete cast-in-place pile under a complex geological condition is characterized by comprising the following steps:
s1, leveling the field and setting out the pile position;
s2, forming holes, taking soil, and installing a steel casing to a position X meters away from the natural terrace;
s3, performing slurry wall protection construction;
s4, entering rock, pulling out pipes and cleaning holes;
s5, placing a reinforcement cage;
s6, pouring concrete;
and S7, post grouting, and checking and accepting.
2. The method for constructing the reinforced concrete cast-in-place pile under the complicated geological condition according to claim 1, which is characterized by comprising the following steps of: in the step S2, a pipe rolling machine is adopted to form a hole, the position of the pipe rolling machine is adjusted to be in place, a rotary digging machine is used for taking soil, the first section of steel protective cylinder is hung and rolled in, the verticality is corrected, a punching grab bucket is used for taking soil from the steel protective cylinder, the steel protective cylinder is pressed down while taking soil, when the steel protective cylinder is 12-1.5m higher than the top surface of the guide wall, a second section of steel protective cylinder is installed, and soil is continuously pressed down until the position is Xm away from the natural terrace;
and the numerical value of the X is determined according to the elevation of the natural terrace and the excavated soil quality.
3. The method for constructing the reinforced concrete cast-in-place pile under the complicated geological condition as recited in claim 2, characterized in that: and in the soil taking process, the depth of the excavation surface exceeding the bottom opening of the steel casing is kept to be more than or equal to 2.5 m.
4. The method for constructing the reinforced concrete cast-in-place pile under the complicated geological condition according to claim 1, which is characterized by comprising the following steps of: the S3 includes:
s31, preparing slurry, firstly injecting 1 x Y m3After stirring for half an hour, adding 120 × YKg composite bentonite while stirring, after the bentonite is dissolved, uniformly adding 0.5 × YKg carboxymethyl cellulose, and then sequentially adding 1.5 × YKg caustic soda, 1 × Ykg water-seepage alum and 2 × Ykg quicklime, wherein the value of Y is determined according to the actual dosage of the slurry;
and S32, sequentially digging out drilling residues in the hole by using a rotary digging bucket, and putting chemical slurry into the position of X meters until the drilling is finished.
5. The method for constructing the reinforced concrete cast-in-place pile under the complicated geological condition according to claim 1, which is characterized by comprising the following steps of: the rock entering comprises: using the ultra-deep pile to finish hole forming operation, locally backfilling and tamping the periphery of the sleeve, using a punching and grabbing hammer of a rotary excavator to inject slurry into the sleeve, using a rotary drilling bucket to sequentially dig out drilling slag in holes, replenishing the slurry at any time in the hole forming process, and ensuring the water head pressure of the slurry in the pile casing;
the hole cleaning comprises: and when the drill hole of the rotary drilling rig reaches the designed depth, cleaning the hole, cleaning the sediment with the thickness of less than or equal to 50mm after cleaning the hole, cleaning the sediment by using a cylindrical drill with a valve when the drill hole reaches the designed elevation, and taking out the drill bit after cleaning the hole.
6. The method for constructing the reinforced concrete cast-in-place pile under the complicated geological condition according to claim 1, which is characterized by comprising the following steps of: the steel reinforcement cage is manufactured strictly according to the design, the position of the main reinforcement is controlled by a steel reinforcement positioning bracket to be equally spaced, and the allowable deviation of the space between the main reinforcements is +/-10 mm; the allowable deviation of the screw pitch of the stirrup or the spiral rib is +/-20 mm; the allowable deviation of the diameter of the reinforcement cage is +/-10 mm; the length of the reinforcement cage is allowed to deviate +/-50 mm; arranging a stiffening hoop every 2m to strengthen the strength of the reinforcement cage, wherein the length of the reinforcement cage is determined by the depth of the excavated hole; the longitudinal steel bar welding adopts single-side lap welding, and the lap length is more than or equal to 10 d; the joints are staggered with each other by not less than 35d, and the number of the joints on the same section is not more than 50%.
7. The method for constructing the reinforced concrete cast-in-place pile under the complicated geological condition according to claim 1, which is characterized by comprising the following steps of: the concrete pouring adopts the conduit to pour, when the conduit is placed, the bottom of the conduit is controlled to be 40cm away from the bottom of the hole, the height of the conduit clamping disc is adjusted, the conduit is clamped and fixed, after the conduit is placed, the thickness of slurry at the bottom of the hole and the thickness of sediment at the bottom of the hole are detected, if two conditions meet the requirements at the same time, concrete can be directly poured, and if one condition cannot meet the requirements, secondary hole cleaning is needed.
8. The method for constructing the reinforced concrete cast-in-place pile under the complicated geological condition as recited in claim 7, wherein: the secondary hole cleaning comprises: connecting and sealing a high-pressure pipe of a slurry pump and a pouring guide pipe, starting the slurry pump, circulating slurry, continuously circulating the slurry after the thickness of sediment at the bottom of a hole is less than 5cm so as to replace the slurry and reduce the specific gravity of the slurry, and stopping cleaning the hole when the specific gravity of the slurry is less than 1.15, and immediately pouring;
the time interval between the completion of hole cleaning and concrete pouring does not exceed 45 minutes, so that the occurrence of sediment in the hole re-precipitation and necking of the drilled hole is avoided, and the specific gravity of the slurry within 500mm of the hole bottom is less than 1.20 before the concrete is poured.
9. The method for constructing the reinforced concrete cast-in-place pile under the complicated geological condition according to claim 1, which is characterized by comprising the following steps of: and pouring concrete at least 500mm higher than the designed pile top elevation.
10. The method for constructing the reinforced concrete cast-in-place pile under the complicated geological condition according to claim 1, which is characterized by comprising the following steps of: in the post-grouting process, the cement paste adopts 32.5MPa slag portland cement, the water cement ratio is 0.6, and the grouting amount is as follows: the pile end is 2000kg, the pile group is grouted firstly from the periphery to the inside, and A, B piles are used for alternate grouting.
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