CN117026948A

CN117026948A - Underwater rotary digging cast-in-place pile construction method

Info

Publication number: CN117026948A
Application number: CN202311135056.3A
Authority: CN
Inventors: 杨鹏; 彭华; 陈志成; 刁金祥; 吴志雄; 吴烈润; 陈为烈; 肖金明
Original assignee: Shenzhen Shekou Merchants Harbor Engineering Co ltd
Current assignee: Shenzhen Shekou Merchants Harbor Engineering Co ltd
Priority date: 2023-09-05
Filing date: 2023-09-05
Publication date: 2023-11-10

Abstract

The invention discloses an underwater rotary excavation cast-in-place pile construction method, which includes the following steps: Step 1: Carry out site layout, then review drawings, and check fixed-point axis lines at the same time, and then complete pile position setting out; Step 2: Set the drilling rig to the position, make the drill bit of the drilling rig; step three, perform a hole cleaning, and measure the hole depth, hole diameter and inclination after the hole cleaning is completed; step four, make a steel cage, hang weld the completed steel cage and position it for acceptance; step six, After the installation of the conduit is completed, test the mud performance and the sediment at the bottom of the hole, and perform secondary hole cleaning after the test is completed; Step 7: Set the water-proof plug, mix the concrete, make the concrete test block, and measure the elevation of the top surface of the concrete at the same time, and then proceed Concrete is poured into piles underwater, and then the casing is lifted and the drilling rig is moved to complete the pile construction. In the underwater rotary excavation cast-in-place pile construction method of the present invention, through the arrangement of the above steps, the pile position is staked out before the hole is formed, thus ensuring the accuracy of the drilling position.

Description

Construction method of underwater rotary-digging cast-in-place pile

Technical Field

The invention relates to a pile construction method, in particular to an underwater rotary-digging cast-in-place pile construction method.

Background

Pile foundation is a common foundation form in the building field, and cast-in-place piles are formed by casting concrete into pre-drilled holes, and forming pile shafts after the concrete is solidified. Drilling is a key process for forming a cast-in-place pile and a pile foundation, and the conventional drilling is generally finished by using a rotary drilling machine and adopting a forward (reverse) circulation process or using a percussion drilling process and adopting a percussion process, so that the conventional cast-in-place pile forming technology has the following defects: 1. the drilling operation is completed by cutting and grinding the rock (soil) in the stratum and carrying out the orifice through slurry, so that the drilling speed is low and the construction efficiency is low; 2. and a large amount of mud is needed to be used side by side, so that environmental pollution and waste of land resources are caused. According to incomplete statistics, 2.5-3.0 cubic meters of slurry is required to be used and discharged for drilling a cubic meter of volume, more slurry is likely to be discharged when stratum conditions are complex, and a large amount of slurry is required to occupy a large amount of land for storage, so that not only is the environment polluted, but also land resources are wasted; 3. the traditional drilling process is to drill holes by carrying rock (soil) with mud, so that a layer of mud skin is easily formed on the hole wall, and the exertion of the friction resistance of the side wall is reduced. Meanwhile, the unavoidable rock (soil) sediments at the bottom of the hole also affect the exertion of pile end resistance, so the bearing capacity of the traditional bored pile is reduced. Especially when the process is improper, the bearing capacity is severely reduced, and even pile foundation engineering accidents are caused; 4. the bored pile inevitably generates stress relaxation of the hole wall in the pore-forming process, and the pile body concrete inevitably causes non-compact contact with the hole wall in the process of compacting by the pile body concrete, which leads to the reduction of pile bearing capacity. In view of the defects of the pile forming technology of the cast-in-place pile, a plurality of scholars at home and abroad are devoted to researching and exploring the pile forming technology with high construction speed, and a large amount of slurry and high bearing capacity are not needed.

Therefore, the present invention has a patent number of 201710969003.X, and the name of the method is that a construction method for constructing a rotary-excavated bored concrete pile is provided, however, in the construction process of the method, a first step is adopted to directly embed the pile casing, so that deviation of the embedded position of the pile casing is easy to occur, or multiple adjustments are needed to be performed on the pile casing in the process of embedding the pile casing, so that the embedded position of the pile casing is accurate, the construction repeatability is increased, and the construction efficiency is reduced.

Disclosure of Invention

Aiming at the defects existing in the prior art, the invention aims to provide the underwater rotary-digging bored concrete pile construction method which can reduce construction repeatability and increase construction efficiency.

In order to achieve the above purpose, the present invention provides the following technical solutions: the construction method of the underwater rotary-digging cast-in-place pile is characterized by comprising the following steps of: the method comprises the following steps:

firstly, performing site arrangement, then performing drawing consultation, simultaneously checking fixed-point axes, and then finishing pile position lofting;

step two, positioning a drilling machine, manufacturing a drill bit of the drilling machine, measuring the hole depth at the same time, setting a mud system, modulating and detecting mud, and drilling into a pile position through the drilling machine to form a hole;

step three, cleaning the hole once, measuring the hole depth, the hole diameter and the inclination after the hole cleaning is finished, detecting the sediment at the bottom of the hole, and finishing the hole forming acceptance after the hole depth, the hole diameter, the inclination and the sediment at the bottom of the hole are qualified;

step four, manufacturing a reinforcement cage, hanging and welding the manufactured reinforcement cage, positioning and checking, and hanging the reinforcement cage into the hole after positioning and checking;

fifthly, detecting the length of the catheter, simultaneously arranging a hole cleaning device, and then installing the catheter;

step six, detecting the slurry property and hole bottom sediment after the installation of the guide pipe is completed, and carrying out secondary hole cleaning after the detection is completed;

setting a water-proof plug, stirring concrete, manufacturing a concrete test block, measuring elevation of the top surface of the concrete, pouring the concrete underwater to form a pile, lifting a pile casing, and transferring a drilling machine to finish pile construction.

As a further improvement of the invention, the specific steps of the first lofting step are as follows:

step one, according to the provided measuring stations, converging with a supervision unit, setting measuring points in a construction range, calculating azimuth angles and distances, establishing a proper measurement control network in a construction site, and measuring out building plane points;

step two, measuring by adopting control point coordinates, and controlling the angle intersection of the point positions of each building plane;

step three, measuring the level points on a permanent or non-permanent building or structure, wherein the distance between the level points is not more than 100m, and the level points are not less than 2 levels in the field of construction;

and step four, recording the control points and the level points obtained in the step two and the step three, carrying out pile position lofting according to the control points and the level points, and checking and accepting the pile position lofting.

As a further improvement of the invention, the second step is provided with a step of embedding a casing before the drilling machine is in place, and the step of embedding the casing is specifically as follows:

step two, rolling a steel plate with the material of Q235 and delta=2mm to form a steel casing, wherein the inner diameter specification of the steel casing is 1200, and L=12m;

step two, before embedding the protective cylinder, detecting the diameter and roundness of the protective cylinder again, judging whether the diameter error exceeds 5mm, and correcting or reprocessing if the diameter error exceeds 5 mm;

burying a steel pile casing by using a hydraulic vibration hammer corresponding to the well-lofted pile position in the step one, wherein the pile casing is 30cm higher than the ground, and the burying depth of the steel pile casing at the orifice is 11-12 m until the bottom of the pile casing passes through a silt layer and enters a clay layer for more than 1 meter, so that the burying of the steel pile casing is completed;

the whole process measurement is carried out in the process of embedding the steel pile casing, so that the deviation and the inclination of the pile casing are ensured to be within the allowable range, the plane position deviation of the embedded steel pile casing is less than +/-20 mm, and the inclination is less than 0.5%.

As a further improvement of the present invention, the parameters of the slurry system set in the second step are as follows:

when the viscous soil is used for forming holes, clean water is injected, raw soil is used for making slurry and protecting walls, and the proportion of circulating slurry is controlled to be 1.1-1.3;

when holes are formed in sand and a thicker sand inclusion layer, slurry is prepared, and the specific gravity of the slurry is controlled to be 1.2-1.3;

when holes are formed in the sand layer or the soil layer easy to collapse, the specific gravity of slurry is increased to 1.3-1.5;

control indexes of the slurry: viscosity is 18-22S; sand content is not more than 2%; the gel rate is more than 95%;

the surface elevation of the sedimentation tank of the slurry tank is 0.5-1 m lower than the pile casing, the capacity of the slurry tank is the slag discharge amount of each hole, and the capacity of the sedimentation tank is 1.5-2 times of the slag discharge amount of each hole.

As a further improvement of the invention, the drilling machine used in the second step is a rotary drilling machine adopting a barrel type drilling bucket, the concrete steps of drilling holes of the drilling machine are that after the drilling machine is installed in place, the perpendicularity of a drilling rod is adjusted, the prepared slurry is injected, mechanical drilling and soil discharging are started, after the drilling bit descends to a preset depth, the drilling bucket is rotated and pressure is applied to squeeze the soil into the drilling bucket, when an instrument automatically displays that the barrel is full, the bottom of the drilling bucket is closed, the drilling bucket is lifted to discharge the soil at a stacking place, and then the drilling step is completed;

in the drilling process, the size of a drilling bucket is required to be checked, a drill rod is reversely rotated for 1-2 circles when the drill is lifted, so that a drilling bucket door is closed, a main winch is operated to lift the drill rod and a drilling tool out of an orifice while a power head is lifted, a power head is operated to be rotated to a soil unloading position to move downwards to jack the bucket door, dregs are discharged, the upper trolley is operated to be rotated to a pile position, then the rotation angle is cleared through a touch screen, and the next round of drilling operation is continued.

As a further improvement of the invention, the drilling machine is provided with a drill rod unlocking step after hole forming, and the drill rod unlocking step specifically comprises the following steps:

step two, lifting the power head by 200-300 mm by using a pressurizing oil cylinder after the drilling process is completed;

step two, reversely rotating the drilling bucket for 2 to 3 circles;

step two, lifting the drilling bucket at a uniform speed, in particular to slow reverse spiral lifting;

step two, in the process of lifting the drilling bucket, judging whether the drilling rod and the mast move forward and downward after the weight is instantaneously increased when the drilling rod is lifted to the length of one drilling rod, and calling the action as nodding of the drilling machine;

and step two, if the drilling machine does not have a nodding head, immediately stopping lifting the drilling bucket, lowering the drill bit to the bottom of the hole, and repeating the operations from the step two to the step seven until the nodding head appears and the unlocking of the drill rod is completed.

As a further improvement of the invention, the concrete pile-forming concrete pouring under water in the step seven comprises the following concrete steps:

seventhly, detecting the hole depth by using a measuring rope to measure the sediment thickness, and continuing the next step when the sediment thickness of the end bearing pile is not more than 50mm and the sediment thickness of the friction pile is not more than 200 mm;

step seven, after the reinforcement cage is installed, sequentially installing a storage hopper and a concrete conduit and performing secondary hole cleaning, wherein the concrete conduit is made of seamless steel pipes with the outer diameter of phi 273 multiplied by 4mm, and pipe joints are connected by adopting quick threaded joints;

and seventhly, after the concrete conduit is completely discharged, if the thickness of the sediment does not meet the design requirement, carrying out positive circulation by using a slurry pump to clean the holes secondarily, judging whether the performance index of the slurry in the holes after the hole cleaning secondarily is qualified, if so, stopping the hole cleaning operation secondarily, and starting to pour the underwater concrete to finish the underwater concrete pouring operation.

As a further improvement of the invention, the concrete steps of pouring underwater concrete in the seventh three steps are as follows:

(1) The water-proof plug is hung to be close to the mud surface, so that the distance from the bottom end of the concrete conduit to the bottom of the hole is 0.3-0.5 m, and then concrete pouring is started;

(2) Continuously pouring concrete after the first concrete mixture falls, and keeping a water head in the hole in the pouring process;

(3) Synchronously lifting and disassembling the concrete guide pipe along with the rising of the concrete, and keeping the bottom end of the concrete guide pipe to be buried below the concrete surface for 2-6 m;

when the top surface of the poured concrete is 1m away from the bottom of the reinforcement cage, the pouring speed of the concrete is reduced, and when the concrete mixture rises to more than 4m of the bottom opening of the reinforcement cage, the concrete conduit is lifted, so that the bottom opening of the concrete conduit is higher than the bottom of the reinforcement cage by more than 2m, and then the normal pouring speed is recovered until the pouring is completed.

The invention has the beneficial effects that through the arrangement of the first step, the drawing review can be carried out before the pile casing is embedded, the fixed-point axis check is carried out, and then the pile position lofting is completed, so that the pile position can be accurately embedded when the pile casing is embedded later, and the construction efficiency is improved compared with the construction method in the prior art.

Drawings

FIG. 1 is a schematic flow chart of a construction method of the present invention;

FIG. 2 is a schematic illustration of underwater concrete casting.

Detailed Description

The invention will be further described in detail with reference to examples of embodiments shown in the drawings.

Referring to fig. 1 to 2, the construction method of the underwater rotary-digging cast-in-place pile according to the present embodiment is characterized in that: the method comprises the following steps:

step seven, setting up the water proof stopper, stirring the concrete, making the concrete test block, measuring concrete top surface elevation simultaneously, then pouring the concrete under water and piling up, later lifting a pile casing, migration rig accomplishes the stake construction, through the setting of above-mentioned seven steps, alright effectual realization digs the construction of bored concrete pile soon under water, and through the setting of step one, alright carry out the pile position lofting before the construction, so compare in the mode among the prior art, can reduce the repeatability of construction, increase the efficiency of construction.

As an improved specific embodiment, the specific steps of the first lofting step are as follows:

and step four, recording the control points and the level points obtained in the step two and the step three, carrying out pile position lofting according to the control points and the level points, checking and accepting the pile position lofting, and effectively realizing the lofting of the pile position by the arrangement of the steps, and meanwhile, adopting a mode of combining the coordinates of the control points and the level points, and realizing the lofting of the pile position according to the specific conditions of a construction site.

As an improved specific embodiment, the second step further comprises a step of embedding a casing before the drilling machine is in place, wherein the step of embedding the casing is specifically as follows:

the whole process measurement is carried out in the burying process of the steel pile casing, so that the deviation and the inclination of the pile casing are ensured to be within the allowable range, the plane position deviation of the buried steel pile casing is < + -20 mm, the inclination is less than 0.5%, and the manufacturing and the sinking of the steel pile casing can be effectively realized through the steps.

As an improved specific embodiment, the setting parameters of the slurry system in the second step are as follows:

control indexes of the slurry: viscosity is 18-22S; sand content is not more than 2%; the gel rate is more than 95%, and the specific gravity, viscosity, sand content and gel rate of slurry should be measured frequently in construction;

the elevation of the pool surface of the mud pool sedimentation pool is 0.5-1 m lower than that of the pile casing, so that the mud can return smoothly. The positions of the mud pit and the sedimentation pit are reasonably distributed, and the traveling of the crane and the drilling machine cannot be prevented. The capacity of the mud pit is 1.5-2 times of the slag discharge amount of each hole, the mud can be more matched with the external ground by the mode, and meanwhile, in the construction process, special people are required to clean sediment in the mud groove to ensure that the sediment is not silted. The sediment in the sedimentation tank and the mud tank should be removed frequently, and the redundant mud should be transported out of the field in time. The drilling mud is non-dispersive, low-solid-phase and high-viscosity high-quality mud made of fresh water. In order to ensure the slurry performance index of each construction stage, the slurry performance index is periodically detected in the drilling construction process. The method comprises the steps of detecting once every 1 hour during the drilling construction period, detecting once every 4 hours after the slurry performance is stable, and increasing the detection frequency according to the stratum change condition in the drilling process.

The recycled mud is adjusted in time, and materials such as newly stirred mud, tackifier, dispersing agent and the like which cannot meet the requirement on performance indexes are added, so that the performance indexes in use can be achieved.

Drilling slag in the drilling process is loaded into a special slag suspending cylinder and is transported to a designated place for treatment by a slag transporting vehicle. The recycled slurry overflowed in the concrete pouring process is drained to the manufactured steel sediment tank through the communication pipe for storage. The redundant mud with poor quality and no recycling is led to a slag carrier, and then transported to a designated place for treatment and then discharged.

The drilling machine used in the second step is a rotary drilling machine adopting a barrel type drilling bucket, the specific step of drilling holes of the drilling machine is that after the drilling machine is installed in place, the perpendicularity of a drilling rod is adjusted, the prepared slurry is injected, mechanical drilling and soil discharging are started, after a drill bit descends to a preset depth, the drilling bucket is rotated and pressure is applied, soil is extruded into the drilling bucket, when an instrument automatically displays that the barrel is full, the bottom of the drilling bucket is closed, the drilling bucket is lifted to discharge the soil at a stacking place, and then the drilling step is completed;

in the drilling process, the size of a drilling bucket is required to be checked, a drill rod is reversely rotated for 1-2 circles when the drilling is carried out, a drilling bucket door is closed, a main winch is operated to lift the drill rod and a drilling tool out of a hole while a power head is lifted, a power head is operated to be rotated to a soil unloading position to prop down and open the bucket door, dregs are discharged, the power head is operated to be rotated to a pile position, then the rotation angle is cleared through a touch screen, the next round of drilling operation is continued, in the step, the type and the selection of a drill bit are required at first, and the geological report condition provided by a land and design unit and the size of a pile diameter are adopted, and the following corresponding drill bit construction is provided:

(1) The rock-socketed drilling bucket is mainly used for rock breaking and soil taking in backfill soil, full weathering and strong weathering stratum.

(2) The sand-bailing drilling bucket is mainly used for taking out soil from sandy soil and silt clay layers with high water content.

(3) The soil layer drilling bucket is mainly used for taking soil from silt, silt clay and clay layers.

And (3) positioning a drilling machine: when the drilling machine is in place, the drilling machine must be kept stable and no inclination or displacement occurs. And according to the center of the pile hole, aligning the center of the drilling machine with the center of the pile hole, and ensuring that the center of the drill rod and the center of the pile hole are on the same plumb line. In order to accurately control the drilling depth, a scale for controlling is required to be arranged on a frame or a machine pipe so as to observe and record in construction. Drilling machine positioning error: the level difference is not more than 3mm; the center deviation is not more than 15mm.

Before drilling, the drilling can be started after the supervision engineer agrees. In the drilling process, the soil layer change is frequently noticed, slag samples are fished at the soil layer change positions, the soil layer is judged and recorded in a construction record table, and the soil layer is checked with a geological histogram soil layer to determine whether the bearing capacity requirement is met or not, and the important foundation is taken as an important basis in the final hole.

Drilling is then carried out:

after the pile machine is installed in place, the verticality of the drill rod is adjusted, the rotary drilling rig adopts a cylinder type drilling bucket, the prepared slurry is injected into the pile position (with a counterpoint ring), and the mechanical drilling and the soil discharging are started. When the drill bit descends to a preset depth, the drill bucket is rotated and pressure is applied to squeeze soil into the drill bucket, when the instrument automatically displays that the barrel is full, the bottom of the drill bucket is closed, and the size of the drill bucket is frequently checked (the size of the drill bucket can be determined according to the test drilling condition) in the process that the soil is discharged to a stacking place by the lifting drill bucket for drilling. When the drill is lifted, the drill rod is reversed for 1-2 circles, so that the drill bucket door is closed. When the power head is lifted, the main winch is operated to lift the drill rod and the drilling tool out of the hole, the power head is operated to move downwards to jack the hopper door when the upper truck is operated to the soil unloading position, and the dregs are poured out. And (3) operating the upper carriage to rotate to the pile position, resetting the rotation angle through the touch screen, and continuing the next round of drilling operation.

The slurry surface is always not lower than the bottom of the pile casing in the construction process of the drilling machine, the slurry for wall protection and ballast discharging is manufactured according with the requirements of the slurry and the performance requirements of the slurry, and the stability of the hole wall is ensured. The hole wall is supported by rotation, soil cutting, lifting, soil unloading and slurry of the drilling bucket, and drill bits are reasonably selected for drilling according to different geological conditions, and the repeated circulation is carried out until the hole is formed.

(1) Drilling clay

The clay layer has small drilling resistance, strong adsorptivity and difficult falling, the output torque of the power head is not suitable to be too large, the hydraulic handle is controlled to drill at a high speed (about 23rmp is suitable), the pressure is continuously increased during drilling, the primary feeding amount is determined by the diameter of a drilling bucket, and the general diameter is more than 800mm and can be filled with 60-90% of bucket capacity; the slag soil of the drilling bucket below 800mm cannot exceed 60% of the bucket capacity, if the adsorption force of clay is too strong, drilling slag cannot be poured out, the drilling rod can be quickly rotated forwards and backwards to separate the slag soil from the drilling bucket by inertia, longer bucket teeth and the drilling bucket with larger tooth space are selected to avoid sticking, the bottom cutting teeth are frequently checked after the drilling is carried out, the inter-tooth sticky mud is timely cleaned, and the dull bucket teeth are replaced;

(2) Drilling into sand

Particularly, the middle coarse sand layer has no cementing property, the stratum is loose, the sand flow loss in the drilling bucket is larger in the lifting process, the drilling resistance is larger, in order to improve the drilling efficiency, the maximum torque can be provided in the drilling of the power head, meanwhile, the point pressurizing drilling is carried out, when the torque output of the power head reaches the rated value, the power head is lifted to release the pressure for repeated drilling until the drilling bucket is filled with a certain amount of dregs, the drilling is carried out for the second time, the second time drilling is started, the accident of 80% burying drilling of the rotary drilling machine occurs in the sand layer, and experience shows that the three-stage drilling is slow, the lifting drilling is slow, the rotation is slow, and the scale entering is slow;

(3) Drilling of silt layer

Before construction, a steel pile casing is firstly arranged, the depth of the pile casing exceeds 0.5m of a silt layer, a soil layer drill bit is replaced during construction of the silt layer, soil and sand pollution slurry in a drilling bucket is reduced as much as possible during drilling, and the slurry is vertically flushed into a hole as much as possible, so that the pile casing is prevented from sinking due to the fact that the slurry flows down along a pile casing wall to flush and collapse the lower part of the pile casing.

(4) Working condition of pressurization

The 80% drilling working condition of the rotary drilling rig is pressurized in a construction drilling process in a mode of no need of additional load, or the required pressurizing force is very small to meet the drilling requirement, in fact, when the self-weight pressurizing can finish the drilling operation, the output rotating speed of the drilling rig can be automatically reduced, at the moment, the operator of the drilling rig can actively adjust the pressurizing force of the additional load, so that the drilling rig is in an economical and durable state, the external loading mode is only used for pressurizing when various weathered rocks with the hardness of more than or equal to 10MPa are encountered in the drilling process, the pressurizing process is uniform, and the pressurizing force is not too large.

After drilling is completed, locking rod unlocking needs to be carried out, and locking rod unlocking notes are taken:

(1) the drill rod of the locking type lock rod has 3 states: completely unlocked, incompletely unlocked, and completely unlocked. In the latter two states, lifting of the drill rod and subsequent operations are not allowed, and after the drilling process is completed, the machine-locked drill rod must be completely unlocked, and then lifting of the drill rod and subsequent operations can be performed.

In this embodiment, a specific unlocking step is provided, which specifically includes:

a. the drill rod and the drill bucket cannot be lifted by the main winch immediately after the drilling process is completed;

b. lifting the power head by 200-300 mm by using a pressurizing oil cylinder;

c. the drilling bucket is reversely rotated (opposite to the rotation direction of the drilling hole) for 2-3 circles;

d. lifting the drilling bucket at a uniform speed, and lifting the drilling bucket by reversing the spiral at a slow speed;

e. during the process of lifting the drill bucket, the drill rod and the mast need to be carefully careful when lifted to the length of one drill rod, and the drill rod and the mast move forward and downward after the weight is instantaneously increased. This action is called "nodding" of the drill;

f. if the drill is perceived to have no "nodding", the lifting of the drill should be stopped immediately, the drill bit lowered to the bottom of the hole, and the preceding operation repeated until the "nodding" sensation has occurred.

In this embodiment, the full length/segment tool drilling method is used for the drilling operation. The method comprises the following steps:

(1) before drilling the pile foundation, a detailed and careful drilling method is formulated according to the corresponding geological report and the drilling depth of the pile position and the characteristics of a drilling machine, drilling hoppers and bucket teeth which are suitable for the geological report are arranged, different geological layers apply different drilling hoppers, bucket teeth with different lengths and angles are arranged, and specific geological layer selection is combined;

(2) according to different drilling hoppers, bucket teeth and geological conditions, the drilling speed used in the drilling process of a drilling machine, whether drilling is pressurized or not, how much pressurizing force is proper and the like are established, and the standard of specific drilling operation (specific to a specific construction site) is established;

(3) the full-length/sectioning machine drilling method is beneficial to accelerating the hole forming speed and the hole forming quality, improving the utilization efficiency of a drilling machine and reducing the cost of hole forming.

The following points should be noted in the pore-forming process:

(1) When the drill bit is started, the drill bit is required to drill slowly, and after all the drill bit enters the stratum, the drilling can be accelerated.

(2) The pressure-reducing drilling is adopted when the hole is dug, namely the main lifting hook of the rotary drilling machine always bears the gravity of part of the drilling tool, and the drilling pressure borne by the bottom of the hole is not more than 80 percent of the sum of the dead weights of the hole digging machines (deducting buoyancy).

(3) When the holes are dug and deslagged, the drill bit is lifted to remove soil or the drilling is stopped due to reasons, the methods of checking the density of the slurry at any time, replenishing the slurry in time and replacing the pile machine are adopted to keep the specific water level and the required relative density and viscosity of the slurry in the holes.

(4) The slag soil taken by the drilling machine should be processed out of the rotation range of the drilling machine in time so as to facilitate the deslagging of the rotary drilling machine.

(5) Detecting whether the pore-forming quality meets the design requirement according to a mechanical instrument and a mechanical construction record after the drilling machine is activated, and whether the thickness of sediment at the bottom of the pore meets the standard requirement (less than 50 mm); and after the working procedures are finished, the drilling machine is withdrawn from the orifice in time, so that the pile hole is prevented from being collapsed. The orifice is covered by an iron grill to prevent the danger of falling of people and sundries.

(6) And cleaning the earth and stone sides cleaned by drilling at irregular intervals and transporting the earth and stone sides out of the field.

(7) And the rotary drilling rig is used for timely pouring concrete after half an hour of pore forming so as to prevent hole collapse.

(8) And judging the soil layer, and recording the soil layer into a pore-forming record table and checking a geological histogram. The operator must carefully implement the post responsibility system, fill in the drilling construction record at any time, and the operator should take proper amount of rock sample for spare checking in detail for each hole of the work to be checked when the work is shifted, and the rock sample label marks the pile number, the sampling hole depth and the sampling date.

(9) In the drilling process, the slurry surface in the hole is adjusted at any time, and the water head height in the hole is maintained. The mud surface in the hole is 1.5m higher than the sea water surface at any time.

(10) The drilling process is continuously operated, and the drilling process is not stopped for a long time in the middle, so that the pore-forming period is shortened as much as possible. The original record of the drilling hole is filled in detail, truly and accurately, and abnormal conditions found in the drilling are reported and processed in time.

4. Final hole inspection

(1) And the pore-forming inspection method is used for carrying out pore-measuring work of drilling according to the method of underwater concrete pouring construction, and the pile hole which is qualified through quality inspection is timely poured with concrete.

(2) After the pore-forming reaches the design elevation, the pore depth, the pore diameter, the pore wall, the perpendicularity, the sediment thickness and the like are checked, and measures are taken when the pore-forming is unqualified. Measuring the hole depth by using a measuring rope and recording, detecting the aperture by using a hole detector after drilling, checking the inclination by using a drill rod perpendicular line method, checking whether the hole is qualified by using the hole detector with the length conforming to the regulation twice, and cleaning the hole after the hole is qualified.

(3) Pore diameter control: when sand layers or silt layers are encountered during drilling, the drill rod is prevented from shaking to cause the aperture to be enlarged, so that the hole wall is attached to disturbed soil and the hole bottom is increased to fall back soil.

(4) And after the drilling reaches the required depth, checking the hole depth, the hole position, the aperture, the hole shape and the gradient, and filling the checking result into a final hole checking table. After the design requirements are confirmed to be met, and the preparation work of cleaning the bottom of the hole and pouring underwater concrete can be carried out by the approval of a supervision engineer. The aperture, the hole shape and the inclination are detected by hanging a hole detector into a drilled hole.

Quality standard of hole forming of bored pile

Project	Tolerance of
		Center position of hole (mm)	20
Aperture (mm)	10
		Straightness (mm)	Less than 0.5%
Depth of hole	Not less than design rule
		Thickness of precipitate (mm)	50

5. Processing of abnormal conditions:

in the hole digging process, if the conditions of inclined holes, bent holes, shrinkage holes, collapse holes, slurry leakage along the periphery of the pile casing, ground subsidence and the like are found, the hole digging should be stopped immediately, and the construction can be continued after the following effective measures are taken:

(1) When the pile hole is inclined, repeated hole repairing and correcting can be carried out, if the correction is ineffective, clay (clay of the backfilling clip stone during hole digging) is backfilled in the hole to be 0.5m above the offset hole, and then the hole is dug again;

(2) If the hole is collapsed in the drilling process, the hole digging should be stopped immediately, clay is backfilled when the hole is dug, the drilling is performed after the hole wall is stable, the specific gravity of slurry is increased, and the hole is formed after the repeated lifting and falling of the drill to build the wall;

(3) The slurry is sprayed around the pile casing, the straw is mixed with yellow mud to block the hole, and a layer of sand bag is pressed around the pile casing.

6. Hole cleaning

And (3) cleaning the hole by adopting a slurry replacement method after the hole is inspected to be qualified, slightly lifting the drill bit, maintaining the original specific gravity of the slurry to carry out circulating floating slag, then injecting clear water to continue circulating replacement, and cleaning the hole by adopting a slurry pump suction mode for the slag at the bottom of each hole. After hole cleaning, the relative density of slurry should be controlled between 1.03 and 1.10, the sand content should be less than 2%, the viscosity between 17 and 20Pa.s, and the gel content should be more than 98%. And placing a reinforcement cage and a guide pipe after the first hole cleaning, checking the hole again, and performing the second hole cleaning when the thickness of the ballast does not meet the technical specification (the required value is not more than 5 cm). And (3) adopting mud injection in the guide pipe to circularly clean the hole, and immediately injecting concrete after the hole cleaning is completed, so that the drilling operation can be completed.

And then manufacturing and installing the reinforcement cage, which comprises the following steps:

the reinforcement cage is manufactured according to the depth of the final hole, namely the depth of the rock entering. The reinforcing steel bar team needs to deal with technicians in the field management area in advance, and the technicians need to give the reinforcing steel bar team the pile length of the final hole in advance, so that the reinforcing steel bar manufacturing and installation work and the final hole connection work are completed. The reinforcement cage is manufactured and molded in a reinforcement processing field on site. And blanking the reinforcement cage in a processing field and manufacturing the reinforcement cage in the same groove.

1. The manufacture of the reinforcement cage meets the design requirements and relevant regulations of the specification. The stiffening hoop is arranged on the inner surface of the main reinforcement, the main reinforcement is generally not provided with a hook, and the reinforcing steel bar head cannot be bent inwards in a round manner so as not to obstruct the working of the guide pipe; the lap joint and the welding of the main bars are staggered, the welding of the longitudinal bars is preferentially considered, the welding of the D < 22 bars is allowed, the anti-poking piles are mechanically connected, and the number of joints of the longitudinal bars in the same section range is not more than half of the total number of the bars; the longitudinal ribs of the anti-pulling pile are arranged in a full length mode, joints are reduced, and mechanical connection is adopted.

2. Pile reinforcement cages are manufactured in a quasi-sectional mode, and arc welding connection or mechanical connection is adopted when the reinforcement cages are connected.

3. Measures should be taken to prevent torsion and bending during lifting of the reinforcement cage. When the reinforcement cage is installed, the reinforcement cage should be aligned with the hole site, hung straight and steady, slowly sunk, and avoid collision with the hole wall. After the reinforcement cage is sunk to the designed position, the reinforcement cage should be fixed immediately to prevent movement. The upper part of 2-3 phi 48 steel pipes are welded with the pile casing, and the lower part is sleeved on the main reinforcement of the reinforcement cage to support the stiffening stirrup at the uppermost layer so as to prevent the reinforcement cage from floating upwards.

4. In order to ensure the thickness of the protective layer of the reinforcing steel bar, a reinforcing steel bar cushion block is arranged, the space between the reinforcing steel bar cushion block and the reinforcing steel bar cushion block is 2m vertically, and the transverse circumference is not less than 6.

5. The steel reinforcement cage is integrally hoisted by adopting a crawler crane, and 4 hoisting points (less than or equal to 25m steel reinforcement cage) are arranged in total in a hoisting manner, wherein the distance between the hoisting points is 9m. In order to ensure the rigidity and strength during lifting, the lifting point of the steel reinforcement cage is reinforced by phi 20 round steel, and 2 phi 48 steel pipes are longitudinally adopted for reinforcement.

6. After the steel reinforcement cage is lowered, two hanging bars (phi 16 round steel) are adopted for fixing, one end of each hanging bar is welded with one side of a main bar of the steel reinforcement cage, the welding length is 25cm, the other end of each hanging bar is hung on the steel guard bar by a hook, and the length of each hanging bar is strictly processed after calculation according to the elevation of the top of the steel guard bar so as to control the elevation of the top of the steel reinforcement cage.

7. After the reinforcement cage is installed, the reinforcement cage should be subjected to hidden engineering acceptance with a design unit and a supervision engineer, and underwater concrete is poured in time after the acceptance is qualified.

8. The manufacturing tolerance of the reinforcement cage is shown in the following table:

manufacturing tolerance of reinforcement cage

Sequence number	Project	Tolerance (mm)
			1	Distance between main ribs	±10
2	The spacing of stirrups or the pitch of helical ribs	±20
			3	Spacing of reinforcing ribs	According to the specification requirements
4	Diameter of reinforcement cage	±10
			5	Length of reinforcement cage	±50

。

Then pouring underwater concrete;

1. the embodiment is mainly applied to the condition of higher groundwater level, pile body concrete is constructed by adopting an underwater concrete pouring method, the strength grade of the designed concrete is C30, commodity concrete is adopted, the slump of the concrete is controlled to be 180-220 mm during construction, the maximum water-cement ratio required by the mixing ratio is 0.4, the minimum consumption of cementing materials is 340 kg or less and 450 kg/m < 3 >, and other indexes are required to meet the design requirements.

2. The depth of the hole should be detected by a measuring rope again before pouring underwater concrete so as to measure the thickness of the sediment, and the thickness is not more than 50mm, if the thickness exceeds the qualification of the sediment removal again, the concrete can be poured.

3. Lowering catheter and secondary hole cleaning

And after the reinforcement cage is installed, sequentially installing a storage hopper and a guide pipe, and performing secondary hole cleaning. The conduit is made of seamless steel pipes with the outer diameter of phi 273 multiplied by 4mm, and the pipe joints are connected by quick threaded joints.

The conduit is put into use after being qualified by watertight inspection. The length and the installation sequence of each section of the catheter are accurately recorded when the catheter is lowered. The catheter is tightly screwed, so that the occurrence of the accident of falling the catheter is prevented.

4. The following provisions should be made for pouring underwater concrete:

and after the concrete conduit is lowered, if the thickness of the sediment does not meet the design requirement, a slurry pump is used for carrying out positive circulation for secondary hole cleaning. After the secondary hole cleaning, various performance indexes of the slurry taken out from the hole should be as follows: the relative density is 1.1-1.15, and the concentration of the mud which is not allowed under geological conditions is not more than 1.25. Viscosity is 16-22 Pa.s, sand content is less than 4%, gel rate is 96%. And when the thickness of the sediment at the bottom of the measuring hole is not more than 50mm, the hole cleaning operation can be stopped. And after the cleaning of the holes is finished, the mud pump is immediately dismantled after the inspection of the field of a supervision engineer is qualified, and the underwater concrete is poured. The casting of underwater concrete is shown in fig. 2:

(1) When the concrete is poured, the position where the waterproof bolt is hung is close to the mud surface, and the distance from the bottom end of the guide pipe to the bottom of the hole is 0.3-0.5 m.

(2) When the pouring is started, the quantity of the first concrete must meet the requirements of first embedding depth (more than or equal to 1.0 m) of the guide pipe and filling the bottom of the guide pipe.

(3) After the first concrete mixture falls, the concrete should be poured continuously. During the priming process, the head of water in the bore should be maintained. (4) The rising speed of concrete pouring is not less than 2m/h, and the pouring time of each pile is not more than the following rule:

(1) the perfusion amount is within 10m 3: less than or equal to 2 hours;

(2) the filling amount is within 10-20 m 3: less than or equal to 3 hours;

(3) the filling amount is within 20-30 m 3: the time is less than or equal to 4 hours;

(4) the filling amount is within 30-40 m 3: less than or equal to 5 hours;

(5) the perfusion rate of >40m3 should not exceed 6h.

(5) Along with the rising of the concrete, the guide pipe is lifted and disassembled in time, the lower part of the embedded concrete surface at the bottom end of the guide pipe is generally kept 2-6 m, and the bottom end of the guide pipe is strictly forbidden to be lifted out of the concrete surface, so that when the last guide pipe of a broken pile is lifted, the guide pipe is slowly lifted and vibrated back and forth to avoid the phenomenon that a mud core is clamped in the pile or a cavity is formed.

(6) In the pouring process, a special person is arranged to constantly measure the position of the concrete surface in the exploratory hole, timely adjust the burial depth of the guide pipe and fill in an underwater concrete pouring record table.

(7) In order to prevent the reinforcement cage from floating up, the pouring speed of the concrete should be reduced when the top surface of the poured concrete is about 1m away from the bottom of the reinforcement cage. When the concrete mixture rises to more than 4m at the bottom opening of the steel reinforcement cage, the guide pipe is lifted to make the bottom opening of the guide pipe higher than the bottom of the steel reinforcement cage by more than 2m, and the normal pouring speed can be recovered.

(8) The elevation of the poured pile top is higher than the design by a certain height, generally 0.5-0.8 m, so as to ensure the strength of the concrete. (9) And when the pouring is nearly finished, checking the pouring quantity of the concrete to determine whether the pouring height of the concrete is correct, and setting the pile diameter of the pile diameter smaller than 1200 mm and the over-pouring height to be 1 time and not smaller than 0.8m, and setting the pile diameter of the pile foundation over-pouring height larger than 1200 mm and the pile diameter of the pile foundation over-pouring height to be 0.7 time and not smaller than 1.0m.

(10) And 2 groups of concrete test blocks are reserved for piles with the length of less than 20 meters, and 3 groups of concrete test blocks are reserved for piles with the length of more than 30 meters.

(11) And (3) slurry treatment, namely, the slurry in the hole replaced by the concrete flows into other steel casings to be drilled through a communicating pipe for recycling, the waste slurry containing the cement slurry at the part above the pile top poured by the concrete cannot be recycled, the waste slurry is extracted and carried away by a slurry truck, and the waste slurry is discharged into a slurry treatment field for treatment.

In summary, the underwater rotary-digging bored concrete pile construction method of the embodiment adopts a preceding lofting mode, so that the accuracy of the drilling position can be effectively ensured, the construction repeatability is reduced, and the construction efficiency is improved.

The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above examples, and all technical solutions belonging to the concept of the present invention belong to the protection scope of the present invention. It should be noted that modifications and adaptations to the present invention may occur to one skilled in the art without departing from the principles of the present invention and are intended to be within the scope of the present invention.

Claims

1. The construction method of the underwater rotary-digging cast-in-place pile is characterized by comprising the following steps of: the method comprises the following steps:

2. The method for constructing the underwater rotary-excavated bored concrete pile according to claim 1, wherein: the specific steps of the first lofting step are as follows:

3. The method for constructing the underwater rotary-excavated bored concrete pile according to claim 2, wherein: the second step is provided with a step of embedding a pile casing before the drilling machine is in place, and the step of embedding the pile casing is specifically as follows:

4. A method of constructing an underwater rotary-excavated bored concrete pile according to claim 3, wherein: in the second step, parameters of the slurry system are set as follows:

5. The method for constructing the underwater rotary-excavated bored concrete pile according to claim 4, wherein: the drilling machine used in the second step is a rotary drilling machine adopting a barrel type drilling bucket, the specific step of drilling holes of the drilling machine is that after the drilling machine is installed in place, the perpendicularity of a drilling rod is adjusted, the prepared slurry is injected, mechanical drilling and soil discharging are started, after a drill bit descends to a preset depth, the drilling bucket is rotated and pressure is applied to squeeze the soil into the drilling bucket, when an instrument automatically displays that the barrel is full, the bottom of the drilling bucket is closed, the drilling bucket is lifted to discharge the soil at a stacking place, and then the drilling step is completed; in the drilling process, the size of a drilling bucket is required to be checked, a drill rod is reversely rotated for 1-2 circles when the drill is lifted, so that a drilling bucket door is closed, a main winch is operated to lift the drill rod and a drilling tool out of an orifice while a power head is lifted, a power head is operated to be rotated to a soil unloading position to move downwards to jack the bucket door, dregs are discharged, the upper trolley is operated to be rotated to a pile position, then the rotation angle is cleared through a touch screen, and the next round of drilling operation is continued.

6. The method for constructing the underwater rotary-excavated bored concrete pile according to claim 5, wherein: after the drilling machine is used for forming the hole, a drill rod unlocking step is further provided, and the drill rod unlocking step specifically comprises the following steps:

step two, reversely rotating the drilling bucket for 2 to 3 circles;

7. The method for constructing the underwater rotary-excavated bored concrete pile according to claim 6, wherein: the concrete pile-forming concrete pouring under water in the step seven comprises the following specific steps:

8. The method for constructing the underwater rotary-excavated bored concrete pile according to claim 7, wherein: the concrete steps of pouring underwater concrete in the seventh step are as follows:

(4) When the top surface of the poured concrete is 1m away from the bottom of the reinforcement cage, the pouring speed of the concrete is reduced, and when the concrete mixture rises to more than 4m of the bottom opening of the reinforcement cage, the concrete conduit is lifted, so that the bottom opening of the concrete conduit is higher than the bottom of the reinforcement cage by more than 2m, and then the normal pouring speed is recovered until the pouring is completed.