CN116024962A - Construction method of water-rich gravel layer bottom-enlarging bored concrete pile - Google Patents

Abstract

The invention relates to a construction method of a water-rich gravel layer under-reamed bored concrete pile, which adopts the technical scheme that the method comprises the following steps: step S1, leveling the ground and installing a drilling machine; s2, installing a pile casing; s3, drilling holes; s4, cleaning holes; s5, detecting and repairing holes by using a hole detector; s6, installing a circumferential grouting pipe with a grouting valve on the reinforcement cage, and then installing the reinforcement cage into the pile hole; s7, grouting, namely grouting the center of the reinforcement cage by adopting a central grouting pipe; when grouting to the design elevation of the expanded bottom filling pile, pumping high-pressure concrete slurry into the circumferential grouting pipe, and operating the circumferential grouting pipe and the central grouting pipe together; stopping concrete grouting when the grouting height is 1-1.5 meters higher than the design elevation of the expanded bottom filling pile; the bottom-enlarging cast-in-place pile constructed in the water-rich gravel geological environment has better pile side friction force and pile end pulling resistance, and further has better bearing capacity.

Description

Construction method of water-rich gravel layer bottom-enlarging bored concrete pile

Technical Field

The invention relates to the technical field of a construction method of a bottom-expanded bored concrete pile, in particular to a construction method of a water-rich gravel layer bottom-expanded bored concrete pile.

Background

A bored concrete pile is a pile made by boring in place, pouring concrete or reinforced concrete. If the pulling resistance of the cast-in-place pile needs to be enhanced, a bottom of the hole is usually enlarged by a bottom-enlarging drill after the hole forming step is performed, so as to form the bottom-enlarging cast-in-place pile. Under the condition of the same pile diameter, the bearing capacity of the expanded-bottom filling pile is greatly improved, and the expanded-bottom filling pile is widely applied when being constructed during the construction of subway stations.

The construction steps of the cast-in-place pile generally comprise the steps of leveling a field, preparing slurry, installing a drilling machine, positioning, drilling a hole, clearing the hole, checking the quality of the hole, lowering a reinforcement cage, pouring underwater concrete and the like; the concrete existing construction method of the club-footed bored concrete pile can refer to the Chinese patent application publication with publication number CN106939595A, which discloses a construction process of the rotary-excavating club-footed bored concrete pile, which adopts a rotary-excavating drilling machine to rotary-excavate holes, wherein the diameters of screw sheets at the middle part of a drill bit of the rotary-excavating drilling machine are equal, and the diameters of an upper screw sheet and a lower screw sheet are gradually reduced, and the construction method is characterized by comprising the following steps: step one: lofting and positioning; step two: positioning a rotary drilling rig; slowly moving the rotary drilling rig to a drilling platform, adjusting the drilling rig to enable a pile hole to be in the working range of the drilling rig, checking a center hanging line of the cross pile protection before centering the drilling rig, starting a computer automatic resetting device after meeting the standard requirement, adjusting the drilling rig to enable the centers of a drill rod and a drill bit to be aligned with the center point of a pile position, and checking with a vertical line, wherein the lifting slide rim at the top of the drilling rig, the center of a turntable and the center of the pile hole are on the same vertical line, and the deviation is not more than 2cm; step three: primarily drilling; step four: burying a protective cylinder; step five: rotary drilling, namely, drilling holes, adding stabilizing liquid into the holes, starting drilling by a drilling machine according to a preset pile diameter, drilling with the stabilizing liquid while adding the drilling machine, slowly drilling with a low grade, adjusting to a normal speed after drilling to 1m below a pile casing, and selecting drill bits with different forms according to different geological conditions in the drilling process; step six: the method comprises the steps of expanding the bottom of a pile hole and performing primary hole cleaning, lifting a drilling machine from the pile hole, selecting a corresponding bottom expanding drill bit according to the designed diameter of the pile hole, manually adjusting and controlling the opening diameter of the bottom expanding drill bit, fixing the bottom expanding drill bit below the drilling machine, determining the drilling distance of the drill bit, moving the drilling machine into the pile hole, enabling the bottom of the bottom expanding drill bit to be positioned at the bottom of the pile hole, and driving the drilling machine to drill for completing a preset drilling distance; after reaming is finished, maintaining the circulation of the stabilizing solution, continuously idling the reaming bit, and cleaning the large rock slag at the bottom of the hole by 20-30 minutes; step seven: checking holes; step eight: hanging a reinforcement cage, wherein the thickness of a protective layer of the reinforcement cage is ensured by round fine stone concrete cushion blocks with the same label, one layer is vertically arranged every 2m, and 4 quincuncial arrangement is arranged along the circumference of each layer; step nine: installing a concrete conduit and performing secondary hole cleaning; the concrete conduit adopts steel pipes with phi of 300mm, each section is 2-3 m, the length of the bottom section is 4m, and short pipes with 1-2 sections and 1-1.5 m are matched; after the concrete conduit is installed, carrying out secondary hole cleaning, wherein the sediment at the bottom of the hole is required to be not more than 50mm, and the hole cleaning is carried out until the specific gravity of the stabilizing solution reaches the design requirement; step ten: step eleven of pouring concrete: and (5) disassembling the concrete guide pipe and pouring concrete.

The existing construction method of the concrete bottom-expanding bored concrete pile is used for constructing in a stratum with compact soil, and the formed concrete bottom-expanding bored concrete pile has good bearing capacity, but when the bottom-expanding bored concrete pile is constructed in a water-rich gravel layer address area, the surrounding soil is soft after the bottom-expanding bored concrete pile is formed, so that the friction force on the pile side and the pulling resistance of the pile end of the bottom-expanding bored concrete pile are poor, and the bearing capacity of the bottom-expanding bored concrete pile is further affected.

Disclosure of Invention

The invention aims to provide a construction method of a water-rich gravel layer bottom-enlarging filling pile, which ensures that the bottom-enlarging filling pile constructed in a geological environment of the water-rich gravel layer has better pile side friction force and pile end pulling resistance, and further ensures that the bottom-enlarging filling pile has better bearing capacity.

The technical aim of the invention is realized by the following technical scheme: a construction method of a water-rich gravel layer under-reamed bored concrete pile, which comprises the following method steps,

step S1, ground leveling and drilling machine installation: leveling the ground of a pile hole construction area; determining the position of a pile hole, and then centering a drill bit of a drilling machine with the center of the pile hole;

step S2, pile casing installation: burying a pile casing at the position of the pile hole, wherein the inner diameter of the pile casing is larger than the diameter of the pile hole to be dug; the embedded depth of the pile casing is not less than 2.5m and protrudes out of the ground;

step S3, drilling: injecting artificial mud into the pile hole, wherein the pH value of the artificial mud is 7-9, and the liquid level of the injected artificial mud is always kept higher than the bottom surface of the pile casing by more than 2 meters; drilling equal-diameter straight pile drilling until the equal-diameter straight pile drilling is drilled to the designed hole depth; reaming the bottom end of the equal-diameter straight pile hole after the equal-diameter straight pile hole is completed to form a reaming section, wherein the diameter of the reaming section is 1.5-1.6 times that of the equal-diameter straight pile;

step S4, hole cleaning: cleaning the pile hole, measuring the diameter and depth of the pile hole after cleaning the pile hole, and repeating the hole cleaning operation until the depth of the pile hole meets the design size when the depth of the pile hole is smaller than the design size;

step S5, detecting and repairing holes by using a hole detector: the hole probing device is used for descending from the pile hole port to the hole bottom, if the pile hole is blocked, a drilling machine is used for repairing the pile hole again in the middle, and the hole probing device can be smoothly descended; wherein the diameter of the hole detector is 80-100 mm larger than the design diameter of the filling pile;

step S6, installing a reinforcement cage: a plurality of circumferential grouting pipes arranged along the length direction of the reinforcement cage are fixed in the circumferential direction of the reinforcement cage; the circumferential grouting pipe is provided with a plurality of grouting valves which are arranged towards the outer side of the reinforcement cage along the length direction of the circumferential grouting pipe; installing the center of the reinforcement cage pair Ji Zhuangkong into the pile hole;

step S7, grouting the cast-in-place pile: inserting a central grouting pipe into the center of the reinforcement cage, grouting the pile hole through the central grouting pipe, and gradually lifting the central grouting pipe upwards from the bottom of the pile hole during grouting; when grouting to the design elevation of the expanded bottom filling pile, pumping high-pressure concrete slurry into the circumferential grouting pipe, and operating the circumferential grouting pipe and the central grouting pipe together; stopping concrete grouting when the grouting height is 1-1.5 meters higher than the design elevation of the expanded bottom filling pile; and (5) removing the pile casing to finish the construction of the expanded bottom filling pile.

According to the technical scheme, when grouting is performed on the pile hole, grouting is performed inside the pile hole through the central grouting pipe with the larger diameter, so that concrete slurry can rapidly fill the pile hole; when grouting is performed to the designed elevation of the bottom-expanded cast-in-place pile, high-pressure concrete slurry is sprayed to the inner wall of the pile hole through a grouting valve of the circumferential grouting pipe, the geology of a water-rich gravel layer is loose, the concrete slurry can infiltrate into the soil around the peripheral wall of the pile hole under pressure, and the effect of tamping the soil around the pile hole is achieved under the tension of the continuously filled concrete slurry, so that the formed concrete bottom-expanded cast-in-place pile has better pile side friction force and pile end pulling resistance, and the bottom-expanded cast-in-place pile has better bearing capacity; the circumferential grouting pipe is made of steel materials, and is left in a pile hole after grouting is completed and used as a supporting framework of the concrete bottom-expanding filling pile.

Preferably, in step S3, after the reaming section is cut, a plurality of circumferential ring grooves are cut along the radial direction of the equal diameter pile hole, and the diameter of the circumferential ring grooves is 0.5-1 meter greater than the diameter of the equal diameter pile hole.

Through the technical scheme, the circumferential annular groove is formed in the circumferential wall of the equal-diameter straight pile hole, and then after the bottom-expanding bored concrete pile is formed, a plurality of concrete annular bands embedded into surrounding soil are formed along the axial direction of the bottom-expanding bored concrete pile, so that the pulling resistance of the concrete bored pile can be further improved.

In step S1, the ground is hardened after the ground of the pile hole construction area is leveled, and the reserved drilling area is not hardened, wherein the diameter of the reserved drilling area is 1.5-2 times of the diameter of the pile hole.

Through the technical scheme, when leveling the ground, the ground hardening is carried out on the construction areas of the pile holes except the reserved drilling area, the drilling machine and other construction equipment are supported through the ground, and then the drilling machine is not easy to sink when drilling operation is carried out, so that the machining precision of the pile holes can be well guaranteed.

Preferably, in step S6, when the reinforcement cage is inserted into the bottom of the pile hole, the grouting valve is correspondingly installed at the circumferential ring groove.

Through above-mentioned technical scheme, set up the slip casting valve through circumference annular department, and then can be better improve circumference annular soil structure to make circumference annular fashioned concrete ring area fill compacter, have better structural strength.

Preferably, in step S1, 3 positioning piles are installed in the pile hole construction area with the hardened ground surface as a height reference, and the center distances among the 3 positioning piles are equal; the rotatable laser transmitters are arranged on the positioning piles, and the laser intersection points emitted by the 3 laser transmitters are used as pile hole centers.

According to the technical scheme, the hardened ground surface is used as a height reference, positioning piles are installed around pile holes, and then the intersection point of laser emitted by laser emitters on the positioning piles is used as the center of the pile holes, so that the positioning is rapid and accurate.

Preferably, the artificial mud comprises water, bentonite and carboxymethyl cellulose; the mass ratio of the water to the bentonite to the carboxymethyl cellulose is 1000:110-120:1-1.5.

According to the technical scheme, the artificial mud contains bentonite and carboxymethyl cellulose, the carboxymethyl cellulose is white flocculent powder, the performance is stable, the carboxymethyl cellulose is easy to dissolve in water, the mud added with the carboxymethyl cellulose can enable a well wall to form a thin and hard filter cake with low permeability, the water loss is reduced, a drilling machine can obtain low initial cutting force, the mud is easy to release gas wrapped in the mud, and crushed materials are quickly discarded in a mud pit.

Preferably, in step S4, a radial positioner is installed at the upper end of the casing, and an ultrasonic detector is installed at the end of the probe rod matched with the radial positioner; hoisting the probe rod, enabling the probe rod to pass through the radial positioner, and radially restraining the probe rod through the radial positioner; gradually lowering the probe rod to the pile hole, and scanning the shape of the pile hole through the ultrasonic detector.

According to the technical scheme, the ultrasonic detector is arranged on the probe rod of the rigid structure, and the ultrasonic detector is kept to move vertically through the restraint of the radial positioner on the probe rod; the ultrasonic wave detector is used for carrying out ultrasonic wave scanning on the hole wall, so that a shape model of the pile hole can be generated by a computer, and whether the depth and the aperture of the pile hole meet the design requirements or not is detected and judged, and the method is efficient and convenient.

Preferably, in step S5, the hole detector includes a straight cylinder portion and a conical cylinder portion located at two ends of the straight cylinder portion, where the straight cylinder portion and the conical cylinder portion are hollow shells and are detachably connected with each other; the two ends of the inside of the straight cylinder part are respectively fixed with a positioning plate, and the positioning plates are provided with balancing weights which are detachably connected with the positioning plates.

Through the technical scheme, the straight cylinder part and the conical cylinder part of the hollow shell structure of the hole detector can be formed by adopting light metal such as aluminum magnesium alloy in a die casting mode, the surface is smooth, and further, compared with the traditional steel bar welding type hole detector, the hole detector has more accurate detection size; the quality of the hole detector is changed by adjusting the quality of the balancing weight, so that the corresponding hole detecting requirements are met.

Preferably, in step S6, a plurality of groups of guide assemblies are axially installed in the reinforcement cage, each group of guide assemblies comprises four guide wheels uniformly distributed around the axis of the reinforcement cage in the circumferential direction, and the guide wheels are made of precast concrete; a positioning frame is arranged at the position of the pile hole, and a guide rail which is vertically arranged and is used for rolling fit with the positioning guide wheel is fixed on the positioning frame; hoisting the reinforcement cage to the top of the positioning frame, aligning the guide wheels with the guide rails, then landing the reinforcement cage, and installing the reinforcement cage into the pile hole.

Through above-mentioned technical scheme, through setting up the leading wheel on the steel reinforcement cage, when installing the steel reinforcement cage in toward the stake hole, the locating rack that has the guide rail is installed in stake hole position department, when installing the leading wheel on the guide rail, the center of steel reinforcement cage aligns with the center in stake hole, and then when the stake hole is in hoist and mount whereabouts, retrains the steel reinforcement cage through the cooperation of guide rail and leading wheel, and then reduces the beat slope of steel reinforcement cage installation, makes the steel reinforcement cage can more accurate install to the design position, and then makes fashioned club-footed bored concrete pile have better bearing capacity.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of the invention.

Fig. 1 is a flow chart of a method of construction of a water-rich gravel layer under-reamed bored pile.

Fig. 2 is a schematic plan view showing the positional relationship of the center of the pilot pile and the pile hole.

Fig. 3 is a schematic diagram of a structure embodying the mounting of a laser transmitter.

Fig. 4 is a diagram of the operation of the ultrasonic probe in use.

Fig. 5 is a cross-sectional view of the sonde.

Fig. 6 is a schematic structural view showing the cooperation relationship between the reinforcement cage and the positioning frame during installation.

1, positioning piles; 2. rotating the platform; 3. a laser emitter; 4. a protective barrel; 5. a radial positioner; 6. a probe rod; 7. an ultrasonic detector; 8. a hole finder; 81. a straight tube portion; 82. a cone section; 83. a positioning plate; 84. balancing weight; 9. a reinforcement cage; 10. a circumferential grouting pipe; 11. a grouting valve; 12. a guide wheel; 13. a positioning frame; 14. and a guide rail.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings. Wherein like parts are designated by like reference numerals. It should be noted that the words "front", "back", "left", "right", "upper" and "lower" used in the following description refer to directions in the drawings, and the words "bottom" and "top", "inner" and "outer" refer to directions toward or away from, respectively, the geometric center of a particular component.

Examples:

a construction method of a water-rich gravel layer under-reamed cast-in-place pile, referring to fig. 1 to 6, comprising the following method steps:

and S1, leveling the ground and installing a drilling machine. Leveling the ground of a pile hole construction area by engineering machinery such as an excavator, a road roller and the like; and (3) preliminarily determining the position of the designed pile hole, then carrying out concrete hardening on the ground of a pile hole construction area, reserving a drilling area in the pile hole construction area, and not carrying out ground hardening, wherein the diameter of the reserved drilling area is 1.5-2 times of the diameter of the pile hole.

And 3 positioning piles 1 are installed in the pile hole construction area by taking the surface of the hardened ground as a height reference, and the center distances among the 3 positioning piles 1 are equal. In fig. 2, O is shown as the center of the pile hole. The upper end of the spud 1 is provided with a rotary platform 2 driven by a rotary motor, and the rotary platform 2 is provided with a laser emitter 3. The rotation of the rotary platform 2 adjusts the laser emission angle of the laser emitters 3, and the intersection point of the laser emitted by the 3 laser emitters 3 is used as the center of the pile hole. Plumb is arranged below the laser intersection point of the 3 laser transmitters 3 to fix the point on the ground,

the drill is moved to the proper position, the laser transmitter 3 is installed on the drill to strike the ground, and the center of the drill bit of the drill is aligned with the designed center of the pile hole.

And S2, installing a pile casing. After the drilling machine is in place, according to the size of the installed pile casing 4, a corresponding rotary drilling bit is selected, and the diameter size of the rotary drilling bit is slightly larger than that of the pile casing 4. And a pre-buried hole for burying the pile casing 4 is drilled at the pile hole position through a drilling machine, the depth of the pre-buried hole is about 0.5 meter smaller than the length of the pile casing 4, and the pile casing 4 is pressed into the pre-buried hole through pressure equipment. Typically, the casing embedment depth is no less than 2.5m, and the casing diameter is 200mm greater than the effective pile diameter. The upper part of the casing 4 is provided with 1-2 pulp overflow holes.

And S3, drilling. After the step S2 is completed, the drilling machine is provided with a rotary barrel type drill bit, and the rotary barrel type drill bit is used as drilling pressure to excavate the original soil; the artificial mud is injected into the pile casing 4 by a mud pump, the pH value of the artificial mud is 7-9, and the liquid level of the injected artificial mud is always kept higher than the bottom surface of the pile casing 4 by more than 2 meters.

When the drilling bucket of the rotary barrel type drill bit is filled with soil, the drilling bucket is lifted, the drilling machine opens the bucket door of the rotary barrel type drill bit, soil is unloaded onto the dump truck or into the soil unloading area, then the door is closed to move the rotary barrel type drill bit to the drilling position, the upper part of the rotating body of the machine body is locked, the drill bit is lowered, circulation is repeated, mud is filled while drilling, and the drilling is carried out until the drilling of the equal-diameter straight pile reaches the designed hole depth.

And after the equal-diameter straight pile hole is completed, replacing the rotary bottom-enlarging bucket to carry out bottom-enlarging hole-forming operation. During rotation of the rotary bottom expanding bucket, the rotary bottom expanding bucket is divided into two or four parts to cut soil body, horizontal reaming operation is carried out, soil body generated by the reaming operation is accommodated by the bucket, and the bucket is retracted to bring the soil body out of the ground. And cutting the equal-diameter straight pile end by a rotary bottom-enlarging bucket to form a reaming section, wherein the diameter of the reaming section is 1.5-1.6 times of that of the equal-diameter straight pile. After the reaming section is cut, a rotary bottom reaming bucket with smaller size is replaced, a plurality of circumferential annular grooves are cut along the radial direction of the equal-diameter pile hole, and the diameter of each circumferential annular groove is 0.5-1 m larger than that of the equal-diameter pile hole.

When the drilling machine drills a pile hole, artificial mud is injected into the pile hole, and the mud can form a thin and tough mud skin on the hole wall, so that the hole wall can be protected, and clamping and drilling accidents caused by collapse and block dropping can be prevented; and the rock powder sand generated in the drilling passing layer is prevented from sinking into the bottom of the hole quickly, the drilling accident is prevented, the whole slurry is alkaline, the pile hole environment is in weak alkaline, and the concrete slurry can be better molded and maintained in the later period. Because the rotary drilling machine is adopted for hole forming, the wall protection adopts the mode that soil mass around is extruded for hole forming, mud is filled while soil is taken out, and polymer materials in the mud are condensed on the hole wall through the centrifugal force of the drill bit to form a layer of flexible glued film, thereby achieving the wall protection effect and improving the construction efficiency.

Wherein the artificial mud comprises water, bentonite and carboxymethyl cellulose; the mass ratio of the water to the bentonite to the carboxymethyl cellulose is 1000:110-120:1-1.5. The artificial mud contains bentonite and carboxymethyl cellulose, the carboxymethyl cellulose is white flocculent powder, the performance is stable, the carboxymethyl cellulose is easy to dissolve in water, the mud added with the carboxymethyl cellulose can form a thin and firm filter cake with low permeability on the well wall, the water loss is reduced, the drilling machine can obtain low initial cutting force, the mud is easy to release gas wrapped in the mud, and crushed materials are quickly discarded in a mud pit.

And S4, cleaning the holes. And when the step S3 is completed, the drilling machine is replaced with a slag dragging cylinder, and slag dragging is performed on the bottom of the pile hole through the slag dragging cylinder. In fig. 4, a is a foundation, B is a hardened ground, C is a pile hole, and D is a circumferential ring groove. After the first slag scooping is completed, a radial positioner 5 is arranged at the upper end of the casing 4. The radial positioner 5 is of a circular ring structure, and a positioning hole for passing through the probe rod 6 is arranged at the central position, and the axis of the positioning hole is aligned with the center of the pile hole.

The probe rod 6 is made of metal materials. An ultrasonic detector 7 is arranged at the lower end of the probe rod 6. The probe rod 6 is lifted by using the crane, the lower end of the probe rod 6 passes through the positioning hole, and the radial constraint is carried out on the probe rod 6 by the radial positioner 5. Gradually lowering the probe rod 6 to the position of a pile hole through the crane, scanning the shape of the pile hole through the ultrasonic detector 7, and then modeling according to the scanning feedback data of the ultrasonic detector 7 through a computer to obtain a data model of the pile hole, and judging whether the depth and the aperture of the pile hole meet the design standard or not. When the hole depth and the hole diameter of the pile hole do not meet the design standard, repairing the pile hole by a drilling machine, and repeatedly fishing slag and performing ultrasonic detection until the hole depth and the hole diameter of the pile hole meet the design standard.

And S5, installing a reinforcement cage. The hole detector 8 is suspended by using a crane, and after the hole detector 8 is aligned with the center of the pile hole, the hole detector 8 is slowly lowered into the pile hole by using the crane until the hole detector 8 is sunk into the bottom of the pile hole. In the lowering process of the hole detector 8, if the hole detector 8 encounters a clamping in midway and cannot continue sinking, the hole detector 8 is taken out from the heavy pile hole, and the pile hole is repaired by using a drilling machine until the hole detector 8 can smoothly sink to the bottom of the pile hole.

Wherein the diameter of the hole detector 8 is 80-100 mm larger than the design diameter of the filling pile. The hole finder 8 includes a straight cylindrical portion 81 and tapered cylindrical portions 82 located at both ends of the straight cylindrical portion 81. The straight cylinder part 81 and the cone cylinder part 82 are hollow shells of aluminum-magnesium alloy die casting, and have light weight and smooth surface. The straight cylinder part 81 and the cone cylinder part 82 are fixedly connected by bolts. The two ends of the inside of the straight cylinder 81 are respectively fixed with a positioning plate 83, and the positioning plate 83 is provided with a balancing weight 84 connected with the positioning plate 83 through bolts. The hole detector 8 is formed by splicing and assembling the straight cylinder part 81 and the conical cylinder part 82 which are made of aluminum magnesium alloy, so that the hole detector 8 has higher dimensional accuracy and form and position tolerance accuracy compared with a conventional steel bar welded structure, and further the shape of a pile hole can be detected and judged more accurately. In the daily carrying process of the hole detector 8, the balancing weight 84 is not installed, so that the hole detector 8 can be conveniently moved. The pile hole is detected by using the hole detector 8, and the balancing weight 84 with corresponding quality is selected to be installed inside the hole detector 8 according to the size of the pile hole and the specific geological condition of the position, so that the self-weight requirement of the hole detector 8 during use can be better met.

And S6, detecting and repairing holes by using a hole detector. A plurality of circumferential grouting pipes 10 with the length directions along the length directions of the reinforcement cage 9 are circumferentially fixed on the inner wall of the reinforcement cage 9; the circumferential grouting pipe 10 is provided with a plurality of grouting valves 11 along the length direction thereof, which are arranged along the radial direction of the reinforcement cage 9. The circumferential grouting pipe 10 is made of steel materials, and can be used as a part of the framework of the reinforcement cage 9, so that the overall structural strength of the reinforcement cage 9 can be effectively enhanced. The grouting valve 11 is a one-way stop check valve and can withstand a hydrostatic pressure of 1MPa or more. A plurality of groups of guide components are axially arranged on the reinforcement cage 9, each group of guide components comprises four guide wheels 12 which are uniformly distributed around the axis of the reinforcement cage 9 in the circumferential direction, and the guide wheels 12 are made of precast concrete.

When the reinforcement cage 9 is installed, the locating frame 13 is installed at the pile hole position, the locating frame 13 is fixed with the guide rail 14 which is vertically arranged, and the guide rails 14 are in one-to-one correspondence with the locating guide wheels. The position of the positioning frame 13 is adjusted so that the center of the reinforcement cage 9 is aligned with the center of the pile hole when the guide wheel 12 is mounted in the guide rail 14. The reinforcement cage 9 is hoisted to the top of the locating frame 13 through the crane, the guide wheels 12 are aligned with the guide rails 14, then the reinforcement cage 9 is descended, and the reinforcement cage 9 is installed in the pile hole.

And S7, grouting the cast-in-place pile. And hoisting a central grouting pipe by using a crane, and inserting the central grouting pipe into the pile hole from the center of the reinforcement cage 9. Grouting into the pile hole through the central grouting pipe, wherein the central grouting pipe is gradually lifted upwards from the bottom of the pile hole during grouting; when grouting to the design elevation of the expanded bottom filling pile, pumping high-pressure concrete slurry into the circumferential grouting pipe, and operating the circumferential grouting pipe and the central grouting pipe together; stopping concrete grouting when the grouting height is 1-1.5 meters higher than the design elevation of the expanded bottom filling pile; and (5) removing the pile casing to finish the construction of the expanded bottom filling pile.

In the scheme, the used artificial slurry in construction is poured through concrete, the used slurry is pumped back to a slurry storage tank or a slurry storage box by a pump, and then the slurry is purified and sand removed by a comprehensive cyclone vibrating screen for continuous recycling. The conventional forward and reverse circulation bored pile is different, and the proportion of mud to soil discharged by the conventional bored pile is 4:1, the construction process only discharges original soil in the pore-forming process, makes slurry manually, and discharges no slurry, thus solving the problem of large-scale slurry discharge and transportation, ensuring clean construction site and reducing urban environmental pollution.

The diameter of the central grouting pipe arranged in the center of the reinforcement cage 9 is thicker, concrete slurry can be efficiently filled into pile holes, cement slurry is pressed into the pile holes through the pile ends and the embedded pipes at the pile sides, inherent defects of mud skin and pile bottom sediment are eliminated through the modes of seepage and expansion, compaction, splitting and compaction of the slurry, a pile soil interface is improved, soil in a certain range around the pile is reinforced, the soil strength is increased, the friction resistance and the end bearing force at the pile sides are increased, and therefore the ultimate bearing capacity of the pile is greatly improved, and the settlement is reduced. The circumferential annular groove is formed in the peripheral wall of the pile hole, so that the formed concrete filling pile is axially provided with a plurality of concrete annular bands embedded into the surrounding soil structure, and the pulling resistance of the concrete filling pile is further improved. The circumferential grouting pipe 10 is made of steel materials, and is left in a pile hole after grouting is completed to be used as a supporting framework of the concrete bottom-expanding filling pile.

While certain specific embodiments of the invention have been described in detail by way of example, it will be appreciated by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the invention. It will be appreciated by those skilled in the art that modifications may be made to the above embodiments without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.

Claims (9)

1. A construction method of a water-rich gravel layer under-reamed bored pile is characterized by comprising the following method steps,

step S1, ground leveling and drilling machine installation: leveling the ground of a pile hole construction area; determining the position of a pile hole, and then centering a drill bit of a drilling machine with the center of the pile hole;

step S2, pile casing installation: burying a pile casing at the position of the pile hole, wherein the inner diameter of the pile casing is larger than the diameter of the pile hole to be dug; the embedded depth of the pile casing is not less than 2.5m and protrudes out of the ground;

step S3, drilling: injecting artificial mud into the pile hole, wherein the pH value of the artificial mud is 7-9, and the liquid level of the injected artificial mud is always kept higher than the bottom surface of the pile casing by more than 2 meters; drilling equal-diameter straight pile drilling until the equal-diameter straight pile drilling is drilled to the designed hole depth; reaming the bottom end of the equal-diameter straight pile hole after the equal-diameter straight pile hole is completed to form a reaming section, wherein the diameter of the reaming section is 1.5-1.6 times that of the equal-diameter straight pile;

step S4, hole cleaning: cleaning the pile hole, measuring the diameter and depth of the pile hole after cleaning the pile hole, and repeating the hole cleaning operation until the depth of the pile hole meets the design size when the depth of the pile hole is smaller than the design size;

step S5, detecting and repairing holes by using a hole detector: the hole probing device is used for descending from the pile hole port to the hole bottom, if the pile hole is blocked, a drilling machine is used for repairing the pile hole again in the middle, and the hole probing device can be smoothly descended; wherein the diameter of the hole detector is 80-100 mm larger than the design diameter of the filling pile;

step S6, installing a reinforcement cage: a plurality of circumferential grouting pipes arranged along the length direction of the reinforcement cage are fixed in the circumferential direction of the reinforcement cage; the circumferential grouting pipe is provided with a plurality of grouting valves which are arranged towards the outer side of the reinforcement cage along the length direction of the circumferential grouting pipe; installing the center of the reinforcement cage pair Ji Zhuangkong into the pile hole;

step S7, grouting the cast-in-place pile: inserting a central grouting pipe into the center of the reinforcement cage, grouting the pile hole through the central grouting pipe, and gradually lifting the central grouting pipe upwards from the bottom of the pile hole during grouting; when grouting to the design elevation of the expanded bottom filling pile, pumping high-pressure concrete slurry into the circumferential grouting pipe, and operating the circumferential grouting pipe and the central grouting pipe together; stopping concrete grouting when the grouting height is 1-1.5 meters higher than the design elevation of the expanded bottom filling pile; and (5) removing the pile casing to finish the construction of the expanded bottom filling pile.

2. The construction method of the water-rich gravel layer expanded-bottom bored concrete pile according to claim 1, wherein the construction method comprises the following steps: in step S3, after the reaming section is cut, a plurality of circumferential ring grooves are cut along the radial direction of the equal-diameter straight pile hole, and the diameter of each circumferential ring groove is 0.5-1 m larger than that of the equal-diameter straight pile hole.

3. The construction method of the water-rich gravel layer expanded-bottom bored concrete pile according to claim 2, wherein the construction method comprises the following steps: in step S6, when the reinforcement cage is inserted into the bottom of the pile hole, the grouting valve is correspondingly arranged at the circumferential ring groove.

4. The construction method of the water-rich gravel layer expanded-bottom bored concrete pile according to claim 1, wherein the construction method comprises the following steps: in step S1, the ground is hardened after the ground of the pile hole construction area is leveled, and the reserved drilling area is not hardened, wherein the diameter of the reserved drilling area is 1.5-2 times of the diameter of the pile hole.

5. The construction method of the water-rich gravel layer expanded-bottom bored concrete pile according to claim 1, wherein the construction method comprises the following steps: in the step S1, 3 positioning piles are installed in a pile hole construction area by taking the surface of the hardened ground as a height reference, and the center distances among the 3 positioning piles are equal; the rotatable laser transmitters are arranged on the positioning piles, and the laser intersection points emitted by the 3 laser transmitters are used as pile hole centers.

6. The construction method of the water-rich gravel layer expanded-bottom bored concrete pile according to claim 1, wherein the construction method comprises the following steps: the artificial mud comprises water, bentonite and carboxymethyl cellulose; the mass ratio of the water to the bentonite to the carboxymethyl cellulose is 1000:110-120:1-1.5.

7. The construction method of the water-rich gravel layer expanded-bottom bored concrete pile according to claim 1, wherein the construction method comprises the following steps: in the step S4, a radial positioner is arranged at the upper end of the protective cylinder, and an ultrasonic detector is arranged at the end part of the probe rod matched with the radial positioner; hoisting the probe rod, enabling the probe rod to pass through the radial positioner, and radially restraining the probe rod through the radial positioner; gradually lowering the probe rod to the pile hole, and scanning the shape of the pile hole through the ultrasonic detector.

8. The construction method of the water-rich gravel layer expanded-bottom bored concrete pile according to claim 1, wherein the construction method comprises the following steps: in step S5, the hole detector includes a straight cylinder portion and a conical cylinder portion located at two ends of the straight cylinder portion, where the straight cylinder portion and the conical cylinder portion are hollow shells and are detachably connected with each other; the two ends of the inside of the straight cylinder part are respectively fixed with a positioning plate, and the positioning plates are provided with balancing weights which are detachably connected with the positioning plates.

9. The construction method of the water-rich gravel layer expanded-bottom bored concrete pile according to claim 1, wherein the construction method comprises the following steps: in the step S6, a plurality of groups of guide assemblies are axially arranged on the reinforcement cage, each group of guide assemblies comprises four guide wheels which are uniformly distributed around the axis of the reinforcement cage in the circumferential direction, and the guide wheels are made of precast concrete; a positioning frame is arranged at the position of the pile hole, and a guide rail which is vertically arranged and is used for rolling fit with the positioning guide wheel is fixed on the positioning frame; hoisting the reinforcement cage to the top of the positioning frame, aligning the guide wheels with the guide rails, then landing the reinforcement cage, and installing the reinforcement cage into the pile hole.

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