CN113338270B - Full-rotation double-sleeve variable-section retaining wall pile forming method for cast-in-place pile - Google Patents

Abstract

The invention relates to the technical field of cast-in-place pile construction in karst development areas, and discloses a cast-in-place pile full-rotation double-sleeve variable-section retaining wall pile forming method, which comprises the following steps: s1, positioning a full-slewing drilling machine in place, and enabling the full-slewing drilling machine to be coaxially overlapped with a pile core; s2, according to the design requirement of a pile body, a full-slewing drilling machine presses down an outer sleeve to drill to a designed elevation; s3, arranging the inner sleeve and the outer sleeve coaxially, pressing the inner sleeve downwards by the full-slewing drilling machine, and drilling to a holding force layer; s4, the full-slewing drilling machine changes the connection rock drill bit and drives the rock drill bit to drill to the elevation of the pile bottom; s5, hoisting the reinforcement cage into the pile hole, and placing a perfusion conduit; s6, pouring concrete into the pile through a pouring guide pipe to form a pile; s7, pouring concrete and synchronously pulling up the inner sleeve; and S8, pouring concrete and synchronously pulling out the outer sleeve to form the ultra-long pile body with gradually reduced cross-sectional area. The effect of convenient hole forming of the ultra-long cast-in-place pile is achieved by the hole forming method of driving the double sleeves by using the full-rotary drilling machine.

Description

Full-rotation double-sleeve variable-section retaining wall pile forming method for cast-in-place pile

Technical Field

The invention relates to the technical field of cast-in-place pile construction in karst development areas, in particular to a method for forming a full-rotation double-sleeve variable-section retaining wall pile of a cast-in-place pile.

Background

In recent years, the social infrastructure of China is rapidly developed, and meanwhile, various challenges are faced in the process of the infrastructure construction, for example, in the construction of foundation pits, certain regions belong to karst development regions, the stratum distribution is extremely complex, and single-layer and multi-layer (beaded) karst caves exist.

Various construction troubles are easy to occur when the construction of the ultra-long cast-in-place pile is carried out in karst development areas, and the construction difficulty is great; the construction trouble problems include drilling mud leakage, concrete loss and waste, the comprehensive construction cost is greatly increased, and the rotary drilling and drilling are difficult due to the fact that block stone backfilling treatment or clay blocking flushing is adopted; when double-sleeve drilling is carried out, the coaxial positioning precision requirement is difficult to achieve, and meanwhile, the deviation rectifying treatment difficulty of inclined rock surface deviation is high, so that great difficulty is caused for ultra-deep large-diameter drilling hole forming; at present, a grab bucket is adopted for taking soil, so that the drilling time is long when the drilling is ultra-deep, the progress is slow, and meanwhile, the wall protection sleeve with the depth of more than 80m is extremely difficult to pull due to the influence of large frictional resistance of the wall of the ultra-long sleeve.

Disclosure of Invention

The invention aims to provide a full-rotation double-sleeve variable-section retaining wall pile-forming method for a cast-in-place pile, and aims to solve the problem that in the prior art, when an ultra-long cast-in-place pile is constructed in a karst development area, the hole forming of the ultra-long cast-in-place pile is inconvenient.

The invention is realized in this way, the method for forming the cast-in-place pile with the full-revolving double-casing variable cross-section retaining wall comprises the following steps:

s1, measuring a fixed-point pile core in a construction site, and lifting a full-slewing drilling machine to be coaxially superposed with the pile core;

s2, processing a plurality of sections of outer sleeves and inner sleeves with diameters smaller than the diameter of the outer sleeves according to the design requirements of a pile body, hoisting the outer sleeves to be connected with a full-slewing drilling machine, coaxially arranging the outer sleeves and a pile core, and pressing the outer sleeves by the full-slewing drilling machine to drill to a designed elevation;

s3, hoisting the inner sleeve to be connected with a full slewing drilling machine, wherein the inner sleeve and the outer sleeve are coaxially arranged, the full slewing drilling machine presses the inner sleeve downwards, the upper end of the inner sleeve is flush with the upper end of the outer sleeve, and the lower end of the inner sleeve extends to the lower part of the outer sleeve and penetrates through a karst cave area to drill to a holding force layer;

s4, the connection rock drill bit is replaced by the full-slewing drilling machine, the full-slewing drilling machine drives the rock drill bit to drill into the elevation at the bottom of the pile in the inner sleeve pipe to form a pile hole, and the lower end of the pile hole extends to the lower part of the inner sleeve pipe and extends into slightly weathered limestone;

s5, hoisting the manufactured reinforcement cage to the position above the pile hole, lowering the reinforcement cage into the pile hole according to the verticality requirement, then placing a pouring guide pipe in the pile hole, wherein a pouring interval is formed between the bottom of the pouring guide pipe and the bottom of the pile hole, and determining the pouring interval according to the pouring amount of concrete to be poured in the pile hole;

s6, pouring concrete into the pile hole through the pouring guide pipe;

s7, pulling the inner sleeve in the pile hole while pouring concrete; when the inner sleeve is pulled out, the bottom of the inner sleeve is positioned below the liquid level of the concrete in the pile hole, the rising height of the liquid level of the concrete is continuously observed, and when the liquid level of the concrete reaches the pouring design height, the inner sleeve is pulled out of the pile hole;

s8, work as after interior sleeve pipe extracted the stake hole, through full rotary drill plays to pull the outer tube, playing to pull the outer tube when, in step toward the downthehole concrete that pours into of stake, until the top of concrete extends to the top in stake hole, treats after the concrete solidifies, pulls out the outer tube, the concrete forms the pile body in the stake hole, along top-down' S direction, the pile body includes upper segment, middle part section and the lower part section pile body that the diameter reduces according to the preface.

Further, in step S2, the diameter of the outer sleeve is 2.6m, the diameter of the inner sleeve is 2.2m, the outer sleeve is pressed down by the driving of the full-slewing drilling machine, and the drilling depth is 50m below the pile top.

Furthermore, in step S3, according to the requirement of the perpendicularity and the coaxial coincidence of the pile centers, a gap is formed between the outer sleeve and the inner sleeve, and a plurality of positioning structures for adjusting the coaxial arrangement between the outer sleeve and the inner sleeve are embedded in the gap.

Furthermore, in the process of pressing down the outer sleeve or the inner sleeve, a rotary drilling rig is used for synchronously taking soil from the inner sleeve or the outer sleeve, the depth of the bottom opening of the outer sleeve or the inner sleeve, which is ahead of the excavation surface, is kept to be more than or equal to 2.5m, and the drilling is stopped to reach the required elevation.

Further, in step S4, the pile hole has a rock-socketed section extending into the slightly weathered limestone, the rock-socketed section having a diameter of 2m and a depth of 4m.

Furthermore, the diameter of the section of the upper section of the pile body is 2.6m, the diameter of the section of the middle section is 2.2m, and the diameter of the section of the lower section is 2m; the pile depth of the pile body is more than or equal to 80m.

Furthermore, the positioning structures are in a fan-ring shape, the positioning structures are uniformly distributed around the outer wall of the inner sleeve, and the positioning structures are connected with one another through elastic belts; the positioning structure is provided with an outer arc surface and an inner arc surface, the outer arc surface is abutted with the inner wall of the outer sleeve, and the inner arc surface is abutted with the outer wall of the inner sleeve.

Furthermore, the outer arc surface is provided with an elastic layer, a pressure sensor for detecting the extrusion force between the inner wall of the outer sleeve and the outer wall of the inner sleeve is arranged in the elastic layer, and the pressure sensor is connected to a control terminal.

Further, outer arc face has the installation the arc wall of elastic layer, the elastic layer is followed the arc orbit of arc wall is filled and is arranged, the elastic layer court deviates from the arc wall bottom direction extends, and the protrusion extremely the groove limit of arc wall.

Further, the pressure sensors are provided in number in the elastic layer, each of the pressure sensors being arranged in an equidistant manner along an extended locus of the elastic layer.

Compared with the prior art, the full-rotation double-sleeve variable-section retaining wall pile forming method for the cast-in-place pile, provided by the invention, has the advantages that the outer sleeve and the inner sleeve are respectively driven by the full-rotation drilling machine back and forth, the drilling operation of the ultra-long cast-in-place pile is carried out, and the leakage of slurry in the hole is effectively prevented under the action of the retaining wall of the outer sleeve; the inner sleeve and the outer sleeve are coaxially positioned, hoisted and lowered down, so that the hole deviation of the drilled hole is prevented; the outer sleeve is driven to drill, and then the inner sleeve is driven to drill deeply, so that the effects of quickly drilling and reducing the frictional resistance between the wall of the sleeve and the wall of the hole are achieved, and the hole forming of the ultra-long cast-in-place pile can be completed conveniently.

Drawings

FIG. 1 is a schematic illustration of a full slewing drilling rig in place provided by an embodiment of the present invention;

FIG. 2 is a schematic illustration of an embodiment of the present invention providing for drilling of an outer casing to a desired elevation;

FIG. 3 is a schematic illustration of drilling of an inner casing to a holding force level provided by an embodiment of the present invention;

FIG. 4 is a schematic diagram of a full rotary drilling rig according to an embodiment of the present invention, wherein the drill bit is replaced to drill to the elevation of the pile bottom;

fig. 5 is a schematic view of a hoisting reinforcement cage according to an embodiment of the present invention;

FIG. 6 is a schematic view of the inner pulling sleeve provided by an embodiment of the present invention;

FIG. 7 is a schematic illustration of an outer casing, inner casing and bedrock section hole formation arrangement provided by an embodiment of the present invention;

FIG. 8 is a top view of the connection between the positioning structure and the outer and inner sleeves according to the present invention;

FIG. 9 is a schematic cross-sectional view of a positioning structure provided by an embodiment of the present invention;

fig. 10 is a schematic view of a shaped variable cross-section cast-in-place pile provided by an embodiment of the present invention;

fig. 11 is a schematic diagram of a construction process flow provided by an embodiment of the present invention.

In the figure: 100-full rotary drilling machine, 200-outer sleeve, 300-inner sleeve, 400-steel reinforcement cage, 500-perfusion conduit, 600-rock-embedded section, 700-positioning structure, 701-outer arc surface, 7011-arc groove, 702-inner arc surface, 800-elastic layer and 900-pressure sensor.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The following describes the implementation of the present invention in detail with reference to specific embodiments.

The same or similar reference numerals in the drawings of the present embodiment correspond to the same or similar components; in the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", etc. based on the orientation or positional relationship shown in the drawings, it is only for convenience of describing the present invention and simplifying the description, but it is not intended to indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and are not to be construed as limiting the present invention, and the specific meaning of the terms may be understood by those skilled in the art according to specific circumstances.

Referring to fig. 1-11, a preferred embodiment of the present invention is shown.

The method for forming the cast-in-place pile by the full-rotation double-sleeve variable-section retaining wall comprises the following steps of:

s1, measuring a fixed-point pile core on a construction site, and lifting the full-slewing drilling machine 100 to be coaxially overlapped with the pile core. Before the construction equipment enters a construction site, the construction site is leveled, site soil piles are removed, and soft soil is tamped; according to the on-site design requirement and the design requirement of a combined drawing, the specific position of the center point coordinate of the pile needing to be constructed, perforated and piled is calculated, a total station is adopted for positioning, a guide control line is arranged at the position with the pile distance of 2.5m, a base line is sprung, and the deviation of the pile position is guaranteed to be within 0.1 m.

After the center of the pile is measured, a foundation pit with the depth of about 0.3m is dug by a digging machine at the periphery of the center point of the pile, a road substrate is embedded in the foundation pit, the center of the road substrate is aligned with the center of the pile position, and the road substrate plays a role in fixed point guiding and improving the strength of the road substrate. After the road base plate is installed, the full slewing drilling machine 100 is hoisted, the center of the full slewing drilling machine 100 is coaxially coincided with the center point of the pile, and all the lifting hooks are anti-skidding lifting hooks; after the full-rotary drilling rig 100 is in place, the reaction fork is installed, the crawler crane presses the reaction fork to prevent the full-rotary drilling rig 100 from shifting in rotation, the position of the rotary drilling rig is adjusted according to the position of the full-rotary drilling rig 100, and soil is excavated through matching with subsequent drilling, and the rotary drilling rig needs to be stable, well-balanced and level when in place.

S2, according to the design requirements of the pile body, processing a plurality of sections of outer sleeves 200 and inner sleeves 300 with the diameters smaller than the diameters of the outer sleeves, fixedly connecting the hoisting outer sleeves 200 with the full-rotation drilling machine 100, coaxially arranging the outer sleeves and the pile cores, and pressing the outer sleeves 200 to drill to the designed elevation by the full-rotation drilling machine 100. In this embodiment, the pile diameter of the pile body is designed to be 2.2m, and the pile depth is at least 80 m; the processed first section of outer sleeve 200 is about 2.6m, the processed first section of outer sleeve 200 is hoisted and vertically placed into the full-slewing drilling machine 100, the pile center is aligned, the outer sleeve 200 with the special tool bit arranged at the bottom is clamped by a positioning cylinder, the outer sleeve 200 is rotationally pressed downwards, and meanwhile soil is taken out from the outer sleeve 200.

A steel structure construction platform is arranged beside the full-rotary drilling rig 100, the rotary drilling rig utilizes the steel structure construction platform to keep consistent with the full-rotary drilling rig 100 in height so as to facilitate rotary drilling and soil taking, one end of the steel structure construction platform is a slope with an inclination angle of 15 degrees, the other end of the steel structure construction platform is a horizontal section, and the slope section is opened to the horizontal section from the slope section during the construction of the rotary drilling rig and keeps consistent with the full-rotary drilling rig 100 in height; after the first section of outer sleeve 200 is completely pressed into the soil (the upper part is reserved with 50cm to be convenient for taking over), detecting the verticality, if the verticality is not qualified, performing deviation rectification adjustment, if the verticality is qualified, installing a second section of outer sleeve 200, continuously pressing down to take out the soil, and screwing each section of outer sleeve 200 by using a locking sleeve screw after symmetrically locking eight teeth; and when the outer sleeve 200 is pressed down to the bottom of a backfill layer 50m below the pile top, the outer sleeve 200 is drilled, and the rotary drilling rig matched with soil taking is an SWDM-550 long drill rod ultra-high-power rotary drilling rig.

And S3, hoisting the inner sleeve 300 to be connected with the full-slewing drilling machine 100, coaxially arranging the inner sleeve 300 and the outer sleeve 200, namely, hoisting the inner sleeve 300 to be placed into the outer sleeve 200 and keeping a concentric coaxial relationship, starting the full-slewing drilling machine 100 to press the inner sleeve 300 downwards, wherein the upper end of the inner sleeve 300 is flush with the upper end of the outer sleeve 300, and the lower end of the inner sleeve 300 extends to the lower part of the outer sleeve 200 and penetrates through a karst cave area to drill to a holding force level. After the tool bit of the outer sleeve 200 drills to the bottom of the backfill layer, the full slewing drilling machine 100 replaces the clamp of the inner sleeve 300, the full slewing drilling machine 100 is connected with the inner sleeve 300 through the clamp, the full slewing drilling machine 100 is started to press down the inner sleeve 300, and the inner sleeve 300 drills from the lower side of the outer sleeve 200.

The inner sleeve 300 is lowered from the outer sleeve 200 by using a 260T crawler crane in cooperation with the full-slewing drilling machine 100, the perpendicularity of the sleeve is constantly checked in the lowering process, and the center of the sleeve is ensured to coincide with the center of the pile; for the inner sleeves 300, the lower inner sleeve 300 bears smaller friction force when being pulled out, so the length of each section of the inner sleeve 300 at the lowest part is preferably 15m, the length of the rest sections is 5.5m, and the wall thickness of the sleeve is 0.035m; and replacing a drill bit of the rotary drilling rig with the high-power SWDM-550 long drill rod, drilling and taking soil by matching with the inner sleeve 300, and keeping the bottom opening of the sleeve to advance to a certain depth of the excavation surface until the inner sleeve penetrates through the karst cave area to be constructed to a holding force layer.

And S4, replacing the connecting rock drill bit by the full-slewing drilling machine, driving the rock drill bit to drill in the inner sleeve 300 to the elevation of the pile bottom by the full-slewing drilling machine 100 to form a pile hole, wherein the lower end of the pile hole extends to the lower part of the inner sleeve 300 and extends into the slightly weathered limestone. And stopping drilling after the inner sleeve 300 is drilled to the holding level, informing the supervision, geological exploration, design and all building units of an owner to confirm the holding level, replacing a drill bit of the rotary drilling rig after confirmation, and continuously drilling to the elevation of the pile bottom according to the design. When the drilling depth meets the design requirement, the hole position, the hole diameter, the hole depth and the inclination are checked by adopting an ultrasonic method; and after the drilling is confirmed to reach the elevation final hole of the pile bottom, the slag bucket is used for fishing slag in the hole.

S5, hoisting the manufactured reinforcement cage 400 to the position above the pile hole, lowering the reinforcement cage 400 into the pile hole according to the verticality requirement, then placing a pouring guide pipe 500 in the pile hole, enabling the bottom of the pouring guide pipe 500 to have a pouring interval with the bottom of the pile hole, and determining the pouring interval according to the pouring amount of concrete to be poured in the pile hole; preferably, the distance of the perfusion interval is set to 0.5 m. The reinforcement cage 400 is manufactured according to design requirements, the reinforcement cage 400 is preferably set to be 18m in number, each reinforcement cage 400 is connected with each other by a straight thread sleeve, and the reinforcement cage 400 can be hoisted and placed in a pile hole after being manufactured to be qualified; the reinforcement cage 400 is hoisted by a crane, the reinforcement cage 400 needing to be connected with the cage is welded on the full-slewing drilling machine 100, and the welding length needs to meet the design requirement; strictly controlling the verticality in the process of lowering the reinforcement cage 400; and after the placement of the reinforcement cage 400 is finished, placing the cast-in-place conduit 500, and lowering the conduit into the pile hole by adopting the phi 300 conduit until the bottom of the conduit is 0.55m away from the bottom of the pile hole.

And S6, pouring concrete into the pile hole through the pouring guide pipe 500. The pouring amount of the concrete is determined while the concrete is continuously poured, so that the requirement of the initial burying depth of the pouring conduit 500 and the pouring interval between the bottom of the pouring conduit 500 and the bottom of the hole are ensured. Continuously pouring concrete into the inner sleeve 300, wherein the concrete pouring material adopts C40 ultra-retarding self-compacting underwater non-diffusion concrete, and the pouring mode is underwater concrete pouring; the concrete slump is 0.23-0.27m, medium coarse sand is selected, the particle size of aggregate is less than 0.04m and is not more than 1/3 of the minimum spacing between the reinforcing steel bars; the concrete pouring is continuously carried out, and the time of the gap between two adjacent concrete cars is not more than 30 minutes at most.

The dosage requirements for the concrete are shown in the following table:

water (W)	Cement	Fine aggregate	Stone (5-20 mm)	Stone (5-10 mm)	Fly ash	Ore (phosphorous slag)	Additive agent
								183	230	1030	440	300	170	60	9.2

Table 1: the dosage of the ultra-retarding self-compacting underwater non-diffusion concrete material/kg.m < -3 >;

when the concrete is poured, carrying out first batch pouring concrete weight not less than 5m to ensure the initial burying depth (not less than 1 m) of the pouring guide pipe 500 and the requirement of filling the bottom gap of the guide pipe; when the first batch of concrete is poured, the distance from the lower opening of the pouring guide pipe 500 to the bottom of the pile hole is 0.5m; the first concrete pouring is carried out by two concrete pump trucks, and when the initial pouring condition is reached, one concrete pump truck is changed into one concrete pump truck for pouring; the concrete is retained according to the standard requirements, the test piece is subjected to standard maintenance, and a test report table is filled after the strength test; when the strength is not satisfactory, a report is timely provided, and remedial measures are taken.

S7, pulling up the inner sleeve 300 in the pile hole while pouring concrete; when the inner sleeve 300 is pulled out, the height of the concrete level rise is continuously observed below the concrete level in the pile hole at the bottom of the inner sleeve 300, and when the concrete level reaches the pouring design height, the inner sleeve 300 is pulled out of the pile hole. When concrete is poured, pouring of concrete of the inner sleeve is completed firstly, the inner sleeve 300 is pulled up while pouring, the depth of the inner sleeve 300 below the liquid level of the concrete is ensured to be 20m, and the pouring accident in a pile hole caused by leakage of the concrete in a karst cave section is avoided; in a karst cave distribution section, a slow-speed back-jacking pouring method is adopted, the rising height of the concrete surface in the sleeve is observed and measured at regular time, after each concrete tank truck finishes unloading, the rising height of the concrete surface in the pile hole is measured, and the pipe is detached in time according to the pipe burying depth.

Pulling up the inner sleeve 300 by adopting the jacking force of the full-rotary drilling machine 100, pulling out the inner sleeve 300 of 2.2m when the concrete surface enters the ultra-thick backfill layer by more than 10m, and the pulling height of each time is 0.07m; fixing the grouting pipe by using a winch of a crane all the time in the pulling process, loosening the locking screws of the inner sleeve 300 after the section of the inner sleeve 300 is completely pulled out, lifting the section of the inner sleeve 300 to leak out the internal perfusion catheter 500, and timely adopting a fixing measure to fix the perfusion catheter 500; then the auxiliary hoisting machine for fixing the perfusion catheter 500 is loosened, the inner sleeve 300 is hoisted away by a crane, the inner sleeve 300 is timely clamped at the joint of the perfusion catheter 500 by adopting a jacket after being lifted out of the perfusion catheter 500, two groups of steel bars are erected on the steel pile casing, and the jacket is placed on the steel bars to fix the perfusion catheter 500.

S8, after the inner sleeve 300 is pulled out of the pile hole, the outer sleeve 200 is pulled out through the full-slewing drilling machine 100, concrete is synchronously poured into the pile hole while the outer sleeve 200 is pulled out until the top of the concrete extends to the position above the pile hole, and when the height of the poured concrete to the pile cap bottom of the pile hole is 0.5m, the pouring work of the concrete is completed; after the concrete is solidified, the outer sleeve 200 is pulled out, and the concrete forms a pile body in the pile hole, wherein the pile body comprises an upper section, a middle section and a lower section, the diameters of which are sequentially reduced along the direction from top to bottom. After the inner sleeve 300 is completely pulled out, replacing the clamp of the full slewing drilling machine 100, connecting the outer sleeve 200, and pulling out the outer sleeve 200; the requirements for concrete pouring and the pulling-up mode of the outer sleeve 200 in the pulling-up process of the outer sleeve 200 are consistent with the construction process of the inner sleeve 300.

The elevation of the top of the pile poured by the concrete is 0.5m higher than the elevation of the bottom of the designed pile cap until all the floating slurry is extruded out; after the pouring is finished, the pile shape of the ultra-long pile is gradually reduced in three sections, and an ultra-long pile body with the gradually reduced pile section area is formed.

The outer sleeve 200 and the inner sleeve 300 are respectively driven by the full-slewing drilling machine 100 to drill the ultra-long cast-in-place pile, and slurry in the hole is effectively prevented from leaking under the action of the wall protection of the outer sleeve 200; coaxially positioning, hoisting and lowering the inner sleeve 300 and the outer sleeve 200 to prevent the hole deviation of the drill hole; the outer sleeve 200 is driven to drill, and then the inner sleeve 300 is driven to drill deeply, so that the effects of quickly drilling and reducing the frictional resistance between the wall of the sleeve and the wall of the hole are achieved, and the hole forming of the ultra-long cast-in-place pile can be conveniently completed.

In step S2, the diameter of the outer sleeve 200 is 2.6m, the diameter of the inner sleeve 300 is 2.2m, the outer sleeve 200 is pressed down by the driving of the full slewing drilling machine 100, and the drilling depth is 50m below the pile top. Through the diameter design of the outer sleeve 200 and the inner sleeve 300, a reasonable gap is formed between the double sleeves, and the effect of preventing larger friction force during drilling is achieved.

The diameter of the outer sleeve 200 is preferably designed to be 2.6m, and can be selected from 2m to 3m when the use requirement is met, the diameter of the inner sleeve 300 is preferably designed to be 2.2m, and can be selected from 1.5m to 2.5m when the use requirement is met; of course, when the diameter of the double sleeve is selected, the diameter ratio of the double sleeve to the double sleeve needs to be strictly considered; the outer sleeve 200 drilled in the front section does not need to be drilled too deeply, and only needs to be drilled on the surface of the weathered limestone below 50m of the pile top, so that when the inner sleeve 300 is drilled in the rear section, the problem that the upper part is affected by friction can be avoided.

In step S3, according to the requirement of the verticality and the coaxial coincidence of the pile core, a gap is formed between the outer sleeve 200 and the inner sleeve 300, and a plurality of positioning structures 700 which are coaxially arranged between the outer sleeve 200 and the inner sleeve 300 are embedded in the gap. And (4) hoisting and lowering the bottom opening of the inner sleeve 300 to the position below the bottom opening of the outer sleeve 200 through the full-slewing drilling rig 100, and starting drilling from the position below the outer sleeve 200 until the drilling reaches the holding force level.

By lowering the inner sleeve 300 to the bottom of the outer sleeve 200, the inner sleeve 300 can be directly drilled from the lower part of the outer sleeve 200, which is convenient and fast; in addition, a gap with a certain distance is formed between the outer sleeve 200 and the inner sleeve 300, the positioning structure 700 is arranged between the gaps, and the axis coincidence between the two sleeves is adjusted through the positioning structure 700, so that when the inner sleeve 300 is put down, the two sleeves can be ensured to be in a coaxial state, and the deviation of a pile hole is prevented.

After the drilling of the front outer sleeve 200 is completed, the rear inner sleeve 300 is started to be lowered, and the inner sleeve 300 is lowered according to the requirement of perpendicularity and pile center coincidence, specifically, the error value of the perpendicularity when the inner sleeve 300 is lowered is kept below one thousandth of the whole height of the sleeve, or below 30 mm;

in order to ensure the perpendicularity and coaxiality between the double sleeves, a plurality of positioning structures 700 are arranged in the gaps between the double sleeves, the perpendicularity between the double sleeves is controlled through the positioning structures 700, and in practical application, the positioning structures 700 can be freely assembled on the considered positions of the sleeves and can be freely disassembled.

Therefore, the full slewing drilling machine 100 lifts the bottom opening of the inner casing 300 to the position below the bottom opening of the outer casing 200, so as to start continuous drilling and stop drilling to the holding force level.

In the downward-pressing drilling process of the outer sleeve 200 or the inner sleeve 300, a rotary drilling rig is used for synchronously taking soil from the inner sleeve 200 or the inner sleeve 300, the depth of the bottom opening of the outer sleeve 200 or the inner sleeve 300, which is ahead of the excavation surface, is kept to be more than or equal to 2.5m, and the drilling is stopped to reach the required elevation.

The inner and outer sleeves are simultaneously subjected to earth taking operation in the drilling process, so that the drilled earth is prevented from being accumulated to influence the hole forming process; when the double-casing pipe continuously drills, the bottom opening of the casing pipe needs to be kept at a certain depth in advance of the excavation surface, the verticality requirement in the hole forming process is guaranteed, and the casing pipe is prevented from shaking to generate deviation.

The outer sleeve 200 and the inner sleeve 300 are driven by the full-rotary drilling rig 100 to respectively and continuously drill, and in order to prevent the drilled soil from blocking the sleeves, the rotary drilling rig is synchronously used for matching with the drilled soil to take out the drilled soil from the sleeves in the drilling process; when the outer sleeve 200 or the inner sleeve 300 drills 2.5m-3.5m, soil sampling is started, the sleeve is continuously pressed downwards, and the depth of the bottom opening of the sleeve, which is ahead of the excavation surface, is always ensured to be more than or equal to 2.5m, so that the drilling is stopped to reach the required elevation; in the present embodiment, the set drilling height of the outer tube 200 is 50m below the pile top, and the set drilling height of the inner tube 300 is 80m below the pile top.

In step S4, the rock drill continues to drill into the socketed section 600, and the diameter of the hole formed in the socketed section 600 is 2m and the depth is 4m. The diameter of the section of the upper section of the super-long pile body is 2.6m, the diameter of the section of the middle section is 2.2m, and the diameter of the section of the lower section is 2m; the pile depth of the pile body is more than or equal to 80m.

After the inner sleeve 300 is drilled to the bearing stratum, the rock-embedded section 600 is further drilled by replacing a rock drill bit, and the drilled hole of the rock-embedded section 600, the drilled holes of the outer sleeve 200 and the inner sleeve 300 form a cast-in-place pile with a variable cross section together, so that the pile forming quality is improved.

After the rock-forming drill bit is replaced, drilling the rock-embedded section 600 below the bearing stratum, wherein the diameter of a hole formed in the rock-embedded section 600 drilled by the rock-forming drill bit is 2m, and the depth of the hole is 4m; of course, the bore diameter and depth of the litholog section 600 may vary with respect to the diameter of the outer 200 and inner 300 casings.

The diameter of the hole formed by the outer sleeve 200 during drilling is 2.6m, and the diameter of the hole formed by the inner sleeve 300 during drilling is 2.2m, so that the holes formed by drilling through the outer sleeve 200 and the inner sleeve 300 and the holes drilled by combining a rock drill bit form the cast-in-place pile with variable cross section, specifically, the cast-in-place pile is three layers of cross section sections, the cross section area is gradually decreased from top to bottom, and the depth of the whole pile is at least 80m.

The positioning structures 700 are in fan-ring shapes, a plurality of positioning structures 700 are uniformly arranged around the outer wall of the inner sleeve 300, and the positioning structures 700 are connected with each other through elastic belts; the positioning structure 700 has an outer arcuate surface 701 and an inner arcuate surface 702, the outer arcuate surface 701 abutting the inner wall of the outer sleeve 200, and the inner arcuate surface 702 abutting the outer wall of the inner sleeve 300.

The positioning structures 700 surround the inner sleeve 300 and are located between the outer sleeve 200 and the inner sleeve 300, and the two sleeves can be adjusted to be in a coaxial state under the action of the positioning structures 700, so that the deviation of a pile hole is prevented.

The positioning structure 700 is in a fan-ring shape as a whole, the positioning structure 700 is preferably made of a metal material, when the inner sleeve 300 is hoisted into the hole of the outer sleeve 200, a plurality of positioning structures 700 need to be arranged on the outer wall of the inner sleeve 300, and the positioning structures 700 need to be uniformly arranged around the outer wall of the inner sleeve 300; when the plurality of positioning structures 700 are evenly arranged around the inner sleeve 300, each positioning structure 700 is connected to each other by an elastic band, which may be a flexible elastic material such as rubber.

In a preferred embodiment, the positioning structure 700 has an outer arc surface 701 and an inner arc surface 702, and when the positioning structure 700 is inserted into the gap between the outer sleeve 200 and the inner sleeve 300, the outer arc surface 701 needs to be held in contact with the inner wall of the outer sleeve 200, the inner arc surface 702 needs to be in contact with the outer wall of the inner sleeve 300, the contact positions of the outer arc surface 701 and the inner arc surface 702 need to be maintained substantially immovable when they are in contact, and the degree of contact between the contact surfaces in contact with each other needs to be 95% or more.

The outer arc surface 701 is provided with an elastic layer 800, a pressure sensor 900 for detecting the pressing force between the inner wall of the outer sleeve 200 and the outer wall of the inner sleeve 300 is arranged in the elastic layer 800, and the pressure sensor 900 is connected to the control terminal.

Set up elastic layer 800 and pressure sensor 900 on location structure 700's outer arc face 701, pressure sensor 900 detects the extrusion force between two sleeve pipes to monitor by control terminal, rock the action through elastic layer 800 buffering between two sleeve pipes simultaneously, also have the effect of protection to pressure sensor 900, consequently, improved the work efficiency of double cannula pore-forming effectively.

The outer side of the positioning structure 700 is an outer arc surface 701, an elastic layer 800 is arranged on the outer arc surface 701, a pressure sensor 900 is embedded in the elastic layer 800, a pressure value between the outer sleeve 200 and the inner sleeve 300 is detected by the pressure sensor 900, and the verticality of the inner sleeve 300 is adjusted according to the pressure value detected by the pressure sensor 900.

Under the buffer action of the elastic layer 800, the pressure sensor 900 is effectively prevented from being damaged due to excessive pressure, and meanwhile, the buffer effect is achieved on the shaking of the two sleeves; the pressure sensor 900 is connected with the control terminal, and the pressure value between the two sleeves is monitored by the control terminal at any time, so that adjustment can be made in real time.

In this embodiment, the positioning structure 700 may be selectively designed according to practical applications, except for using the positioning structure 700 made of a metal material, a hard rubber material may be used, especially the positioning structure 700 made of a hard rubber material integrally formed by opening a mold, and the positioning structure 700 made of a hard rubber material may be integrally formed with the elastic layer 800, thereby saving the cost of the process.

The outer arc surface 701 has an arc groove 7011 for installing the elastic layer 800, the elastic layer 800 is arranged along the arc track of the arc groove 7011 in a filling manner, and the elastic layer 800 extends towards the direction departing from the bottom of the arc groove 7011 and protrudes out of the groove edge of the arc groove 7011.

By arranging the arc-shaped groove 7011 for assembling the elastic layer 800 on the outer arc-shaped surface 701, the elastic layer 800 can be better integrated with the positioning structure 700, the displacement of the elastic layer 800 is prevented, and the pressure sensor 900 can also more accurately detect the pressure value between the two sleeves.

The radian of the arc-shaped groove 7011 corresponds to the radian of the outer arc-shaped surface 701, and the arc-shaped groove 7011 is arranged along the radian length track of the outer arc-shaped surface 701 and is equal to the length of the outer arc-shaped surface 701; in this way, when the elastic layer 800 is embedded into the arc-shaped groove 7011, so that the elastic layer 800 can be filled and arranged along the arc-shaped track of the outer arc-shaped surface 701, the pressure sensors 900 of the elastic layer 800 are provided in a plurality, and each pressure sensor 900 is arranged along the extending track of the elastic layer 800 in an equidistant manner, so that the detection is more sufficient.

The side sets up the groove limit around the adjacent location structure 700 of arc groove 7011, and when elastic layer 800 embedded into arc groove 7011, elastic layer 800 extended towards deviating from arc groove 7011 bottom direction, and consequently, elastic layer 800 has a part that is higher than arc groove 7011 groove limit, and the part that elastic layer 800 exceeds the groove limit plays the effect of buffering to two sleeve pipes, protects pressure sensor 900's damage simultaneously.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (6)

1. The method for forming the cast-in-place pile by using the full-rotation double-sleeve variable-section retaining wall is characterized by comprising the following steps of:

s1, measuring a fixed-point pile core in a construction site, and lifting a full-slewing drilling machine to coaxially coincide with the pile core;

s2, processing a plurality of sections of outer sleeves and inner sleeves with diameters smaller than the diameter of the outer sleeves according to the design requirements of a pile body, hoisting the outer sleeves to be connected with a full-slewing drilling machine, coaxially arranging the outer sleeves and a pile core, and pressing the outer sleeves by the full-slewing drilling machine to drill to a designed elevation;

s3, hoisting the inner sleeve to be connected with a full slewing drilling machine, wherein the inner sleeve and the outer sleeve are coaxially arranged, the full slewing drilling machine presses the inner sleeve downwards, the upper end of the inner sleeve is flush with the upper end of the outer sleeve, and the lower end of the inner sleeve extends to the lower part of the outer sleeve and penetrates through a karst cave area to drill to a holding force layer;

s4, the connection rock drill bit is replaced by the full-slewing drilling machine, the full-slewing drilling machine drives the rock drill bit to drill into the elevation at the bottom of the pile in the inner sleeve pipe to form a pile hole, and the lower end of the pile hole extends to the lower part of the inner sleeve pipe and extends into slightly weathered limestone;

s5, hoisting the manufactured reinforcement cage to the upper side of the pile hole, lowering the reinforcement cage into the pile hole according to the verticality requirement, then placing a pouring guide pipe in the pile hole, wherein a pouring interval is formed between the bottom of the pouring guide pipe and the bottom of the pile hole, and the pouring interval is determined according to the pouring amount of concrete to be poured in the pile hole;

s6, pouring concrete into the pile hole through the pouring guide pipe;

s7, pulling the inner sleeve in the pile hole while pouring concrete; when the inner sleeve is pulled out, the bottom of the inner sleeve is positioned below the liquid level of the concrete in the pile hole, the rising height of the liquid level of the concrete is continuously observed, and when the liquid level of the concrete reaches the pouring design height, the inner sleeve is pulled out of the pile hole;

s8, after the inner sleeve is pulled out of the pile hole, the outer sleeve is pulled out through the full-slewing drilling machine, concrete is synchronously poured into the pile hole while the outer sleeve is pulled out until the top of the concrete extends to the position above the pile hole, after the concrete is solidified, the outer sleeve is pulled out, the concrete forms a pile body in the pile hole, and the pile body comprises an upper section, a middle section and a lower section, the diameters of which are sequentially reduced, along the direction from top to bottom;

in the step S3, according to the requirements of perpendicularity and coaxial coincidence of pile cores, a gap is formed between the outer sleeve and the inner sleeve, and a plurality of positioning structures which are coaxially arranged between the outer sleeve and the inner sleeve are embedded and adjusted in the gap;

the positioning structures are in a fan ring shape, the positioning structures are uniformly distributed around the outer wall of the inner sleeve, and the positioning structures are connected with one another through elastic belts; the positioning structure is provided with an outer arc surface and an inner arc surface, the outer arc surface is abutted with the inner wall of the outer sleeve, and the inner arc surface is abutted with the outer wall of the inner sleeve; the contact surfaces which are mutually abutted have the attaching degree of more than 95 percent;

the outer arc surface is provided with an elastic layer, a pressure sensor for detecting extrusion force between the inner wall of the outer sleeve and the outer wall of the inner sleeve is arranged in the elastic layer, and the pressure sensor is connected to a control terminal;

the outer arc face has the installation the arc wall of elastic layer, the elastic layer is followed the arc orbit of arc wall is filled and is arranged, the elastic layer court deviates from the arc wall bottom direction extends, and the protrusion extremely the groove limit of arc wall.

2. The method for forming the full-rotation double-sleeve variable-section retaining wall of the cast-in-place pile according to claim 1, wherein in the step S2, the diameter of the outer sleeve is 2.6m, the diameter of the inner sleeve is 2.2m, the outer sleeve is driven by a full-rotation drilling machine to be pressed down, and the drilling depth is 50m below the pile top.

3. The full-rotation double-sleeve variable-section retaining wall pile forming method for the cast-in-place pile as claimed in claim 1, wherein during the pressing-down process of the outer sleeve or the inner sleeve, a rotary drilling rig is used for synchronously taking soil from the inside of the outer sleeve or the inner sleeve, the depth of a sleeve bottom opening of the outer sleeve or the inner sleeve, which is ahead of an excavation surface, is kept to be more than or equal to 2.5m, and the outer sleeve or the inner sleeve is drilled to a required elevation.

4. A full-rotation double-sleeve variable-section retaining wall pile-forming method for a cast-in-place pile as claimed in claim 1, wherein in step S4, the pile hole is provided with a rock-socketed section extending into slightly weathered limestone, and the rock-socketed section has a diameter of 2m and a depth of 4m.

5. The full-rotation double-sleeve variable-section retaining wall pile-forming method for the cast-in-place pile as claimed in claim 4, wherein the diameter of the section of the upper section of the pile body is 2.6m, the diameter of the section of the middle section is 2.2m, and the diameter of the section of the lower section is 2m; the depth of the pile body is more than or equal to 80m.

6. A cast-in-place pile full-revolution double-sleeve variable-section retaining wall forming method as claimed in claim 1, wherein a plurality of pressure sensors are arranged in the elastic layer, and each pressure sensor is arranged along the extending track of the elastic layer in an equidistant manner.

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