CN112281826B - Construction method for forming pile by rotary spraying in ovoid gravel stratum - Google Patents
Construction method for forming pile by rotary spraying in ovoid gravel stratum Download PDFInfo
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
- E02D5/22—Piles
- E02D5/34—Concrete or concrete-like piles cast in position ; Apparatus for making same
- E02D5/46—Concrete or concrete-like piles cast in position ; Apparatus for making same making in situ by forcing bonding agents into gravel fillings or the soil
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- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
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Abstract
The application discloses a construction method for forming a pile by rotary jetting in an ovoid macadam stratum, which comprises the following steps: leading a down-the-hole hammer hole and following a steel casing; drilling by using a down-the-hole hammer drilling process, wherein peripheral pebbles are loosened under the impact action of a hammer head during drilling, and the full length of the steel casing is followed; the steel casing isolates the loose pebble ring body outside the drill hole to prevent the drill hole from collapsing; pulling out the drill bit and lowering the steel branch pipe; lifting the steel casing; the steel branch pipe replaces a steel casing to support the hole wall; lowering a high-pressure rotary spraying drill rod to the bottom of the hole, lifting the steel branch pipe, and directly contacting a nozzle of the rotary spraying drill rod with the hole wall; and (3) spraying high-pressure cement slurry from the rotary spraying drill rod, cutting and disturbing the collapsed pebbles by the high-pressure cement slurry, synchronously lifting the steel branch pipe and the rotary spraying drill rod until the pebbles are lifted to the designed height, and forming a large-diameter pile body after the cement slurry is solidified. The invention can form the large-diameter high-verticality jet grouting pile in the gravel stratum.
Description
Technical Field
The application relates to the field of jet grouting pile construction, in particular to a construction method for forming a jet grouting pile in an ovoid gravel stratum.
Background
The jet grouting method is also called as jet grouting method, is called as jet grouting for short, is called as jet grouting pile for short, is started from the high-pressure jet grouting method in the seventies of the twentieth century, and is comprehensively developed and applied in China in the eight and ninety years. The practice proves that the method has good effects on treating silt, mucky soil, cohesive soil, silt, sandy soil, artificial filling, gravelly soil and the like.
The jet grouting pile is characterized in that a jet grouting pipe and a nozzle drill are arranged at a designed elevation at the bottom of the pile by using a drilling machine, prepared grout in advance is sprayed out from a nozzle at the edge of the grouting pipe at a high speed after obtaining huge energy through a high-pressure generating device to form a stream with highly concentrated energy, a soil body is directly damaged, in the spraying process, a jet grouting drill rod is lifted while rotating, so that the grout and the soil body are fully stirred and mixed, and a columnar solidification body with a certain diameter is formed in the soil, so that a foundation is reinforced.
With the development of the jet grouting pile technology, the jet grouting technology of double pipes and triple pipes is developed on the basis of the original single pipe, and the pile forming diameter is also increased continuously. However, even if the construction is carried out by adopting the triple-tube process with the strongest destructive power to the soil body, the large-diameter pile body cannot be formed in the gravel and pebble stratum.
The patent with the publication number of CN110424385A, namely a construction method of a large-diameter high-verticality jet grouting pile in an ovoid macadam stratum, is applied for the jet grouting pile in the ovoid macadam stratum in 2019, and the technical scheme comprises the following steps: step 1, guiding a hole by a down-the-hole hammer, and following the steel casing in the full length; step 2, pulling out the drill bit, and lowering the temporary support tube; step 3, pulling out the steel casing, and replacing the steel casing with the temporary supporting tube to support the hole wall; step 4, a high-pressure rotary spraying drill rod is placed downwards, high-pressure cement slurry is sprayed out of the rotary spraying drill rod, the high-pressure cement slurry smashes the temporary supporting tube at the corresponding position into fine fragments, pebbles behind the temporary supporting tube collapse and fall into a drilling range, the high-pressure cement slurry cuts and disturbs the collapsed pebbles, the collapse diameter is further enlarged, and the cement slurry fills gaps among the collapsed pebbles; and 5: and lifting the jet grouting drill rod and continuing high-pressure jet grouting, wherein in the lifting process, the temporary supporting pipe is gradually crushed, pebbles behind the temporary supporting pipe gradually collapse until the temporary supporting pipe is lifted to the design height, and cement slurry is solidified to form the large-diameter jet grouting pile.
According to the scheme, a down-the-hole hammer process is utilized for hole leading, and meanwhile, peripheral pebbles are loosened under the impact action of a hammer head to form gaps; the temporary supporting tube is broken when high-pressure injection is carried out, pebbles around the drill hole collapse to form a loose structure with large gaps, and the pebbles have larger movement space under the impact action of high-pressure cement slurry; and finally, after the collapsed pebble gap is filled with cement slurry, a large-diameter pile body is formed.
However, in the gravel and pebble ground, the following conditions can occur in the construction method:
in the high-pressure rotary spraying process, high-pressure cement slurry firstly impacts a temporary supporting tube and can act on peripheral pebbles after the temporary supporting tube is broken; obviously, the temporary supporting tube can interfere the spraying effect of the high-pressure cement slurry, so that the pressure of the high-pressure cement slurry acting on peripheral pebbles is reduced, and finally the pile forming diameter is affected.
The broken stone and pebble stratum can have the hole collapse phenomenon in advance in the high-pressure rotary spraying process, the broken stone and pebble local impact extrusion temporary supporting tube which collapses possibly causes the temporary supporting tube to have a fracture opening, the broken stone and pebble which lose support flow backwards in the temporary supporting tube from the fracture opening, the rotary spraying drill rod is locked underground, the rotary spraying drill rod is directly caused to be scrapped, the previous investment work is completely useless, and the construction period and the construction cost are greatly influenced.
Aiming at the first condition, the pipe wall of the temporary supporting pipe is thinned or a pre-splitting line is arranged on the pipe wall, so that the interference problem of the temporary supporting pipe on the high-pressure cement slurry spraying effect can be improved by easily breaking the pipe wall.
Aiming at the second condition, the pipe wall of the temporary supporting pipe is thickened, so that the pipe wall is firmer, and the risk that the jet grouting drill pipe is locked underground can be reduced.
But the solutions of these two possible scenarios are contradictory. Therefore, the applicant newly develops a construction process capable of realizing stable pile formation in gravel and pebble stratums by adopting rotary spraying.
Disclosure of Invention
Aiming at the defects in the prior art, the application provides a construction method for forming a pile by rotary jetting in an ovoid macadam stratum.
The application provides a construction method for forming a pile by rotary jetting in an ovoid macadam stratum, which adopts the following technical scheme:
step 1, down-the-hole hammer hole leading and steel casing follow-up; drilling by using a down-the-hole hammer drilling process, wherein the diameter of the drilled hole is 273mm-800mm, peripheral pebbles are loosened under the impact action of a hammer head during drilling, and chips in a pebble layer in a certain range around the drilled hole are blown out to form a loose pebble ring body; the steel casing is tracked along the whole length until the hole is drilled to the designed depth; the steel casing isolates the loose pebble ring body outside the drill hole to prevent the drill hole from collapsing;
and step 3: lifting the steel casing; the loose pebble ring body isolated outside the drill hole by the steel casing collapses immediately after losing the support of the steel casing, and the steel branch pipe replaces the steel casing to support the hole wall;
and 4, step 4: high-pressure rotary spraying; lowering a high-pressure rotary spraying drill rod to the bottom of the hole, and lifting a steel branch pipe, wherein the bottom end of the steel branch pipe is higher than a nozzle of the rotary spraying drill rod; the loose pebble ring body collapses for the second time after losing the support of the steel branch pipe, and the spray nozzle of the rotary spraying drill rod directly contacts with the pebbles; high-pressure cement slurry is sprayed out of the rotary spraying drill rod, the collapsed pebbles are cut and disturbed up and down by the high-pressure cement slurry, an existing pebble layer outside the loose pebble ring body is impacted and disturbed by the high-pressure cement slurry and then collapses again, the collapse diameter is further enlarged, and the cement slurry fills gaps among the collapsed pebbles;
the sprayed high-pressure cement slurry returns upwards from a gap between the steel branch pipe and the rotary spraying drill rod, the slurry flowing out of a pipe orifice at the top end of the steel branch pipe is collected and filtered, and returns to the cement slurry stirring pool to be re-prepared and stirred, and then is pressurized by a high-pressure pump and sprayed into the drill hole again from the rotary spraying drill rod, so that the reutilization is realized;
and 5: synchronously lifting the steel branch pipe and the rotary spraying drill rod, and continuing high-pressure rotary spraying: and in the lifting process, the pebbles at the bottom end of the steel branch pipe gradually collapse until the steel branch pipe is lifted to the designed height, and the cement slurry is solidified to form a large-diameter pile body.
By adopting the technical scheme, a drill hole with a larger diameter is led out by utilizing a down-the-hole hammer process, peripheral pebbles are loosened under the impact action of the hammer head, meanwhile, high-pressure air blows off stone chips in a pebble layer around the drill hole out of the drill hole, and the hammer head vibrates to loosen the peripheral pebbles and form a gap; when the steel casing is pulled out, pebbles around the drill hole collapse once; the whole process of the high-pressure rotary spraying is protected by the steel branch pipe, and the steel branch pipe and the rotary spraying drill rod are lifted synchronously, so that hole collapse in the lifting process is effectively avoided, and stable construction is guaranteed; on the other hand, when the steel branch pipe is lifted, pebbles around the drill hole lose the support of the steel branch pipe, secondary collapse occurs, the pebbles are extruded and supported on the rotary spraying drill rod, and the rotary spraying drill rod immediately carries out impact stirring on the collapsed pebbles, so that the pebble layer collapses again, and the collapse diameter is further enlarged; and finally, after the collapsed pebble gap is filled with cement slurry, a large-diameter pile body is formed.
The application is further configured to: and 4, lifting the steel branch pipe, wherein the bottom end of the steel branch pipe is 500-1200mm higher than the nozzle of the rotary spraying drill rod.
By adopting the technical scheme, the pebbles above the rotary spraying drill rod nozzle are in a high loose state, so that the high-pressure cement slurry can disturb the pebbles from the upper direction and the lower direction, the pebble disturbance range is enlarged, and the subsequent impact disturbance degree on the existing pebble layer is further increased. The distance between the bottom end of the steel branch pipe and the nozzle is set to be 500-1200mm, when high-pressure cement slurry is disturbed upwards, pebbles in the range can be rolled better, the gap is more uniform, and finally the pile body is more uniform.
The application is further configured to: the rotary spraying drill rod is provided with a plurality of nozzles which are arranged at intervals up and down along the shaft.
By adopting the technical scheme, the high-pressure cement slurry sprayed out in a rotary mode can simultaneously carry out multilayer disturbance on the pebbles up and down, the mixing degree of the pebbles is improved, and the final pile forming effect is better.
The application is further configured to: and 3, lifting the steel pile casing, and completely lifting the steel pile casing out of the drilled hole or lifting the bottom end of the steel pile casing to the pile top elevation position of the jet grouting pile.
By adopting the technical scheme, the steel casing is completely provided with the drilled holes, so that loose pebbles can be more thoroughly collapsed for the first time; the steel protects a section of thick bamboo part and stays in the stratum, can form out thick liquid passageway between with the steel branch pipe, returns thick liquid reposition of redundant personnel for follow-up, avoids returning thick liquid pressure too big, influences the recovery.
The application is further configured to: and 5, connecting the steel branch pipe to a machine for lifting the rotary spraying drill rod.
Through adopting above-mentioned technical scheme, high pressure spouts soon and is protected by steel branch pipe in the whole journey, and steel branch pipe's rigidity plays the guide effect, when avoiding touchhing soft or hard uneven, the skew problem of easy emergence is showing and is increasing the straightness reliability that hangs down.
The application is further configured to: and filtering the slurry flowing out of the pipe orifice by adopting slurry purification equipment.
By adopting the technical scheme, the mud purification equipment is used for filtering cement paste, so that sand particles above 60 micrometers can be filtered, cement particles smaller than 60 micrometers are recovered into the cement paste stirring pool, and the cement particles are sprayed into the drill hole again after the water-cement ratio is adjusted again.
The application is further configured to: and 4, ejecting the cement slurry sprayed in the high-pressure rotary manner in the horizontal direction or the inclined direction.
By adopting the technical scheme, the large-diameter jet grouting pile is used for forming a waterproof curtain and a waterproof pile at the joint of the underground continuous wall or forming a stressed wall after profile steel is inserted in the waterproof pile between the foundation pit slope protection piles, the row of waterproof piles behind the slope protection piles and the grouting pile which are mutually overlapped.
The application is further configured to: the large-diameter high-verticality jet grouting pile is used for water stop piles among foundation pit slope protection piles, row water stop piles behind the slope protection piles and grouting piles which are mutually overlapped to form a water stop curtain, water stop piles at the joint of an underground continuous wall or a stress wall formed by inserting section steel.
By adopting the technical scheme, the formed pile body comprises pebbles and cement paste to form a concrete-like pile, and the pile is uniform, so that the concrete-like pile has good water stopping and stress bearing performances, and can be suitable for various water stopping structures and stress bearing structures.
The application is further configured to: the gas sprayed out of the bottom end of the rotary spraying drill rod also comprises high-pressure gas, and the high-pressure gas and the high-pressure cement slurry impact the collapsed pebbles together.
Through adopting above-mentioned technical scheme, can increase the effective jet distance of slurry for the diameter that collapses further enlarges, and lets the cobble roll in downthehole better formation, and the clearance is more even, and final pile body is also more even.
The application is further configured to: and 4, replacing high-pressure rotary spraying with high-pressure swing spraying in the step 5 and the step 4 to form a fan-shaped spraying surface, and finally, overlapping the fan-shaped spraying surface with the slope protection piles or automatically overlapping the fan-shaped spraying surface with the slope protection piles to form a waterproof curtain.
By adopting the technical scheme, the pile body with the sector section is formed, and the pile body is better suitable for a water stop pile at the back of a slope protection pile and a water stop pile at the joint of an underground continuous wall and the like; the symmetrical fan-shaped pile bodies are mutually lapped to form a connected waterproof curtain.
In summary, the present application includes at least one of the following beneficial technical effects:
1. forming a large gap in the pebble in the drill hole through the large-diameter guide hole and the three-time hole collapse, spraying and stirring by using high-pressure slurry, uniformly stirring the cement slurry and the pebble up and down, and forming a pile after solidification; the construction method well solves the problems that the existing high-pressure rotary spraying cannot cut or extrude the pebble stratum, and an effective pile body with a large diameter is formed;
2. the steel branch pipe is followed in the whole process of grouting of the rotary spraying drill rod, so that hole collapse in the process of lifting is effectively avoided, and stable construction is guaranteed; on the other hand, the rigidity of the steel branch pipe plays a role in guiding, so that the problem of deflection easily caused by uneven hardness is avoided, and the reliability of perpendicularity is obviously improved;
3. before grouting of the rotary spraying drill rod, the pebble layer in the drill hole has a larger clearance, so that the pile forming diameter is larger under the same rotary spraying pressure compared with the existing construction method; under the same pile forming diameter, the required rotary spraying pressure is smaller, namely the power of equipment can be smaller than that of equipment in the existing construction method, so that the construction method has lower cost;
4. through the reutilization to cement thick liquid, avoid the material waste, and prevent pollution, environmental protection more, make this construction method more economical and applicable.
Drawings
Fig. 1 to 7 are diagrammatic depictions demonstrating the construction process of a jet grouting pile in an ovoid gravel stratum.
Description of reference numerals: 1. a down-the-hole hammer; 2. a steel casing; 3. a pebble layer; 4. loosening the pebble ring body; 5. a steel branch pipe; 51. flower holes; 6. rotating and spraying a drill rod; 7. and (5) a pile body.
Detailed Description
The present application is described in further detail below with reference to figures 1-7.
Example 1: a construction method for forming a pile by rotary jetting in an ovoid gravel stratum comprises the following processes (because ovoid gravel stratum structures are similar, the following embodiments take the ovoid gravel stratum as an example for explanation):
step 1: leading a down-the-hole hammer 1 and following a steel casing 2; as shown in FIG. 1, the down-the-hole hammer 1 is used for drilling holes with a diameter of 273mm-800mm, and this embodiment is described by using 273mm as an example.
Before the hole is led, the verticality of a vertical guide rail of a drilling machine is adjusted, the drill rod of the first section of down-the-hole hammer 1 is slowly advanced in the drilling process, and the verticality of the drill rod and the steel casing 2 is improved. In the drilling process, the peripheral pebble layer 3 is loosened under the impact action of the hammer head, and meanwhile, chips in the pebble layer 3 in a certain range around the drill hole are blown out to form a loose pebble ring body 4; the wall thickness of the steel casing 2 is more than 10mm, and the steel casing follows the whole length until the hole is drilled to the designed depth; the steel casing 2 isolates the loose pebble ring body 4 outside the drill hole to prevent the drill hole from collapsing; when the steel protects a section of thick bamboo 2 and receives the friction and can't be under gravity automatic manhole, can adopt top hydraulic means to press down 2 top surfaces of steel protects a section of thick bamboo, the preferred, and the pipe shoe is installed to drill bit and steel between protecting a section of thick bamboo 2 for the steel protects the frictional force of the better overcoming pore wall of a section of thick bamboo 2, in time struts the pore wall.
When the drilling depth is deeper, for example, the hole depth exceeds 40m, the down-the-hole hammer 1 is matched with a high-wind-pressure and high-wind-volume air compressor, the wind pressure is more than or equal to 3.0MPa, and the wind volume is more than or equal to 30 cubic meters per minute.
Step 2: pulling out the drill bit and lowering the steel branch pipe 5; as shown in fig. 2 and 3, the down-the-hole hammer 1 in the steel casing 2 is pulled out, and the drilling machine of the down-the-hole hammer 1 is removed; the steel branch pipe 5 is lowered by sections by using machinery such as a crane or the like or manually. The wall thickness of the steel branch pipe 5 is larger than 10mm, the diameter is 194mm, and the length is adaptive to the design depth of the drilling hole. The pipe wall of the steel branch pipe 5 is provided with flower holes 51, the diameter of each flower hole 51 is 20mm, and the flower holes 51 are distributed at intervals along the axial direction of the steel branch pipe 5.
And step 3: lifting the steel casing 2; as shown in fig. 4, the steel casing 2 is completely lifted out of the borehole or the bottom end of the steel casing 2 is lifted to the pile top elevation position of the jet grouting pile; the lifting mode can be that a crane and other machines are adopted to pull up the steel casing 2, preferably a hydraulic pipe puller is adopted to pull up the steel casing 2, or after the pipe puller is adopted to pull up the steel casing 2 for a certain height, the crane is changed to pull up the steel casing 2 to a preset position at one time.
After the steel casing 2 is lifted, the pebbles of the loose pebble ring body 4 which are not supported by the wall of the steel casing 2 are initially collapsed, and then are pressed against the steel branch pipe 5, and the steel casing 2 is replaced by the steel branch pipe 5 for supporting.
The bottom end of the steel casing 2 is left in the stratum above the elevation position of the pile top of the jet grouting pile, and the difference from the steel casing 2 in completely lifting out the drilling hole is that a gap exists between the steel casing 2 left in the stratum and the steel branch pipe 5, and the gap can be used as a slurry outlet channel; the thick liquid that returns that follow-up jet grouting produced enters into this out thick liquid passageway through flower hole 51, realizes the reposition of redundant personnel, avoids returning thick liquid and concentrates and gush out from the steel branch pipe 5 mouth of pipe, leads to returning thick liquid pressure too big, influences the recovery.
And 4, step 4: high-pressure rotary spraying; as shown in fig. 5 and 6, the high-pressure rotary spraying drill rod 6 is lowered, and the rotary spraying drill rod 6 is extended into the bottom of the hole at one time by adopting a high drilling rig of a long spiral drilling machine and other machines; the steel branch pipe 5 is moved upwards integrally by machinery, and the bottom end of the steel branch pipe 5 is 500-1200mm higher than a nozzle of the rotary spraying drill rod 6; in this embodiment 700 mm.
The pebbles of the loose pebble ring body 4 which is not supported by the steel branch pipe 5 collapse for the second time, the gap between the pebbles is enlarged again, and the pebbles are finally pressed on the rotary spraying drill rod 6; the nozzle of the rotary spraying drill rod 6 is directly contacted with the secondary collapsed pebbles in the hole.
The part of the steel branch pipe 5, which is positioned outside the drill hole, is connected to a machine for lifting the rotary spraying drill rod 6, so that the steel branch pipe 5 and the rotary spraying drill rod 6 are lifted upwards synchronously; or, a special lifting device is arranged to drive the steel branch pipe 5 to lift upwards at the same lifting speed as the jet grouting drill pipe 6.
The side surface of the rotary spraying drill rod 6 close to the bottom end of the rotary spraying drill rod 6 is provided with a cement paste spraying nozzle and a high-pressure air spraying nozzle, a cement paste grouting pipe and a high-pressure air pipe are arranged in the rotary spraying drill rod 6, and high-pressure cement paste is horizontally or obliquely ejected from the cement paste spraying nozzle.
When the rotary spraying drill rod 6 is in rotary spraying operation, high-pressure cement slurry and high-pressure gas cut and disturb the secondarily collapsed pebbles, the existing pebble layer 3 except the loose pebble ring body 4 is further collapsed after being impacted and disturbed, the collapse diameter is further enlarged, and the cement slurry fills gaps among the collapsed pebbles.
The disturbance degree and the disturbance range of the collapsed pebbles by the rotary spraying operation of the scheme are superior to those of the rotary spraying scheme for crushing the temporary supporting tube; on one hand, the high-pressure cement slurry in the scheme can directly act on pebbles, and no additional factor interferes with the rotary spraying pressure; on the other hand, the pebbles at least 700mm above the nozzle of the rotary spraying drill rod 6 in the scheme are in a high loose state, so that the pebbles can be disturbed by high-pressure cement slurry from the upper direction and the lower direction, the pebble disturbance range is enlarged, and the subsequent impact disturbance degree on the existing pebble layer 3 is further increased.
In the rotary spraying scheme of the temporary supporting tube, pebbles behind the temporary supporting tube collapse downwards only after the temporary supporting tube is broken, namely the pebbles below a nozzle of the rotary spraying drill rod 6 are in a high loose state, so that high-pressure cement slurry can only disturb the pebbles from top to bottom, the disturbing form is single, and the disturbing range is limited; finally, the diameter of the pile body 7 formed by the scheme of the application is larger than that of the pile body 7 formed by the rotary spraying scheme of smashing the temporary supporting pipe.
In this application scheme, can establish the nozzle of spout drilling rod 6 soon into the multiunit, and along axis direction interval distribution from top to bottom, so, the multilayer disturbance about the rotatory spun high pressure cement slurry can carry out the cobble simultaneously, improves the cobble degree of mixing for it is better to finally become the stake effect.
And selecting the angle of the cement paste to be ejected according to different geology and different working conditions. For example, when the proportion of large-particle pebbles in the pebble bed is large, the high-pressure cement slurry ejected horizontally rebounds, and at the moment, the slurry is sprayed obliquely upwards, so that the influence radius of the high-pressure cement slurry is further enlarged due to the upward moving space of the large-particle pebbles.
For another example, when the pile bottom is designed to be lapped with bedrock to form a waterproof curtain, because the position of the nozzle is slightly away from the bottom of the hole, the cement paste can be better lapped with the bedrock by adopting the inclined downward guniting, so that the joint surface of the pebble layer 3 and the bedrock forms a continuous pile body 7, and the situation that the pile bottom is not drilled into the rock is avoided.
The air nozzle of the high-pressure air can be positioned on the pipe wall of the rotary spraying drill rod 6, positioned above or below the high-pressure guniting nozzle, and also concentrically arranged with the guniting nozzle, so that impact of high-pressure air-coated guniting is formed, and the air nozzle can also be positioned at the bottom end of the rotary spraying drill rod 6 and arranged downwards. The high-pressure gas and the high-pressure cement slurry act together, so that the collapse diameter is further enlarged, pebbles are better formed and rolled in the hole, and the gap is more uniform.
The following relevant parameters are preferably selected in the high-pressure rotary spraying process: the diameter of the guniting nozzle is 4-6mm, preferably 5 mm; the grouting pressure of the cement grout is not less than 35MPa, and the flow rate of the sprayed cement grout is not less than 200L/min; the pressure of the high-pressure gas is 1.0-1.8 MPa.
In the spraying process, high-pressure gas carries a large amount of slurry to return upwards from the steel branch pipe 5, so that a slurry outlet channel is formed between the steel branch pipe 5 and the rotary spraying drill rod 6 to discharge the high-pressure gas and the large amount of slurry; on one hand, the arrangement of the flower holes 51 divides the returned slurry, so that the condition that the pressure of the returned slurry is too high and the flow velocity is too rapid to influence the subsequent recovery and cleaning is avoided; on the other hand will circulate in steel branch pipe 5, and be higher than the thick liquid in time discharging that returns on ground, avoid returning thick liquid and continuously walking high in steel branch pipe 5, when overflowing from 5 top mouths of pipe of steel branch pipe at last, too big to the surrounding environment influence.
During the spraying process, the slurry flowing out of the slurry outlet channel comprises cement slurry, pebble chips, soil and the like; the slurry can be filtered, useful cement slurry components are returned to a cement slurry stirring pool for reconstitution and stirring, and then the slurry is pressurized by a high-pressure pump and sprayed into the drill hole again from the rotary spraying drill rod 6, so that the reuse is realized. Slurry purification equipment can be used for filtering the slurry.
And 5: synchronously lifting the rotary spraying drill rod 6 and the steel branch pipe 5; and (5) continuing high-pressure rotary spraying until the rotary spraying drill rod is lifted to the design height, completely pulling out the rotary spraying drill rod 6 and the steel branch pipe 5 from the drilled hole, and forming the large-diameter jet grouting pile after slurry in the drilled hole is solidified, as shown in figure 7. The lifting speed of the jet grouting drill pipe 6 can be 5-15 cm/min.
The principle of the construction process is as follows: firstly, a drilling machine of a down-the-hole hammer 1 is utilized to lead out a drilling hole with a larger diameter, meanwhile, pebbles around the drilling hole are loosened under the vibration action of a hammer head, and in addition, high-pressure air blows off stone chips in a pebble layer 3 around the drilling hole out of the drilling hole, so that the pebbles around the drilling hole form a gap; when the high-pressure rotary spraying is carried out, pebbles around the drill hole collapse twice in sequence to form a loose structure with large gaps. The larger the diameter of the drill hole is, the larger the collapse range is, and the larger the gap between the pebbles is, namely the pebbles have larger movement space under the impact action of high-pressure cement slurry and high-pressure gas. Under the impact of a fan-shaped slurry column with the nozzle diameter of 5mm and under the condition that pebbles have larger moving space, the slurry column with ultrahigh energy can impact the range which is not influenced by the down-the-hole hammer 1, so that the original pebbles in a certain range except the loose pebble ring body 4 collapse, and the pile diameter is further enlarged; in the collapse range, the pebbles and the chippings are continuously rolled and uniformly stirred under the combined action of the high-pressure cement paste and the high-pressure gas, and the cement paste fills gaps to form a complete large-diameter pile body 7.
The whole pile forming process is simple and comprises the following steps: and (3) forming a large gap in the pebbles in the drill holes through the large-diameter guide holes and the three-time hole collapse, spraying and stirring by using high-pressure slurry, uniformly stirring the cement slurry and the pebbles, and forming the pile after solidification. The construction method well solves the problems that the existing high-pressure rotary jet does not cut or extrude the pebble stratum and forms the jet grouting pile with large diameter. The risk that the rotary spraying drill rod is locked underground is effectively avoided through the steel branch pipe 5, and the construction is ensured to be stably carried out; and the self rigidity of the steel branch pipe 5 plays a role in guiding, so that the deflection problem which is easy to occur when the steel branch pipe is uneven in hardness is avoided, and the verticality of the pile body 7 is improved.
The formed large-diameter jet grouting pile can play the roles of supporting, water stopping and the like. The waterproof piles can be used as waterproof piles among foundation pit slope protection piles, rows of waterproof piles and grouting piles behind the slope protection piles, and the waterproof piles are mutually overlapped to form waterproof curtains or waterproof piles at joints of underground continuous walls, and the profile steel can also be inserted to form stress walls.
In the embodiment, the diameter of the guide hole is 273mm, the thickness of the loose pebble ring body 4 can reach 5-15cm, the effective aperture can reach 373mm-523mm after the first hole collapse, the effective aperture can reach 473mm-623mm after the second hole collapse, and the effective pile diameter can reach 700-1150mm after the three hole collapses caused by cutting disturbance of high-pressure cement slurry.
Example 2: the difference from example 1 is that: and 4, replacing high-pressure rotary spraying with high-pressure swing spraying in the step 5 and the step 4 to form a fan-shaped spraying surface, and finally, overlapping the fan-shaped spraying surface with the slope protection piles or automatically overlapping the fan-shaped spraying surface with the slope protection piles to form a waterproof curtain.
Example 3: the difference from example 1 is that: the high-pressure rotary spraying in the step 4 adopts a triple pipe rotary spraying process, pebbles of the loose pebble ring body 4 behind the steel branch pipe 5 collapse into a drilling range, under the joint cutting disturbance of high-pressure water and high air pressure, the existing pebble layer 3 outside the loose pebble ring body 4 is further collapsed after being impacted and disturbed, the collapse diameter is further enlarged, and cement slurry fills gaps among the collapsed pebbles.
The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.
Claims (10)
1. A construction method for forming a pile by rotary jetting in an ovoid gravel stratum is characterized by comprising the following steps: the method comprises the following steps:
step 1, leading a hole of a down-the-hole hammer (1) and following a steel casing (2); drilling by using a down-the-hole hammer (1) drilling process, wherein the diameter of the drilled hole is 273-800 mm, peripheral pebbles are loosened under the impact action of a hammer head during drilling, and chips in a pebble layer (3) in a certain range around the drilled hole are blown out to form a loose pebble ring body (4); the steel casing (2) follows along the whole length until the hole is drilled to the designed depth; the steel casing (2) isolates the loose pebble ring body (4) outside the drill hole to prevent the drill hole from collapsing;
step 2, pulling out the drill bit and lowering the steel branch pipe (5); pulling out a drill bit of the down-the-hole hammer (1) and a drill rod of the down-the-hole hammer (1) in the steel casing (2), and moving away a drilling machine of the down-the-hole hammer (1); putting a steel branch pipe (5) with a flower hole (51) into the drill hole, wherein the outer diameter of the steel branch pipe (5) is smaller than the inner diameter of the steel casing (2);
and step 3: lifting the steel casing (2); the loose pebble ring body (4) isolated outside the drill hole by the steel casing (2) collapses immediately after losing the support of the steel casing (2), and the steel branch pipe (5) replaces the steel casing (2) to support the hole wall;
and 4, step 4: high-pressure rotary spraying; lowering a high-pressure rotary spraying drill rod (6) to the bottom of the hole, and lifting a steel branch pipe (5), wherein the bottom end of the steel branch pipe (5) is higher than a nozzle of the rotary spraying drill rod (6); the loose pebble ring body (4) collapses for the second time after losing the support of the steel branch pipe (5), and the nozzle of the rotary spraying drill rod (6) is directly contacted with the pebble; high-pressure cement slurry is sprayed out of the rotary spraying drill rod (6), the high-pressure cement slurry cuts and disturbs the collapsed pebbles up and down, the existing pebble layer (3) outside the loose pebble ring body (4) collapses again after being disturbed by the impact of the high-pressure cement slurry, the collapse diameter is further enlarged, and the cement slurry fills gaps among the collapsed pebbles;
the sprayed high-pressure cement slurry returns upwards from a gap between the steel branch pipe (5) and the rotary spraying drill rod (6), the slurry flowing out from the pipe orifice at the top end of the steel branch pipe (5) is collected and filtered, returns to a cement slurry stirring pool, is prepared and stirred again, is pressurized by a high-pressure pump and then is sprayed into the drill hole again from the rotary spraying drill rod (6), and the reutilization is realized;
and 5: synchronously lifting the steel branch pipe (5) and the rotary spraying drill rod (6), and continuing high-pressure rotary spraying: in the lifting process, pebbles at the bottom end of the steel branch pipe (5) gradually collapse until the pebbles are lifted to the designed height, and after cement slurry is solidified, a large-diameter pile body (7) is formed.
2. The construction method of the jet grouting pile in the ovoid gravel stratum as claimed in claim 1, which is characterized in that: and 4, lifting the steel branch pipe (5), wherein the bottom end of the steel branch pipe (5) is 500-1200mm higher than a nozzle of the rotary spraying drill rod (6).
3. The construction method of the jet grouting pile in the ovoid gravel stratum as claimed in claim 1, which is characterized in that: the rotary spraying drill rod (6) is provided with a plurality of nozzles which are arranged at intervals up and down along the shaft.
4. The construction method of the jet grouting pile in the ovoid gravel stratum as claimed in claim 1, which is characterized in that: and 3, lifting the steel pile casing (2), and completely lifting the steel pile casing (2) out of the hole to be drilled or lifting the bottom end of the steel pile casing (2) to the pile top elevation position of the jet grouting pile.
5. The construction method of the jet grouting pile in the ovoid gravel stratum as claimed in claim 1, which is characterized in that: in the step 5, the steel branch pipe (5) is connected to a machine for lifting the rotary spraying drill rod (6).
6. The construction method of the jet grouting pile in the ovoid gravel stratum as claimed in claim 1, which is characterized in that: and filtering the slurry flowing out of the pipe orifice by adopting slurry purification equipment.
7. The construction method of the jet grouting pile in the ovoid gravel stratum as claimed in claim 1, which is characterized in that: and 4, ejecting the cement slurry sprayed in the high-pressure rotary manner in the horizontal direction or the inclined direction.
8. The construction method of the jet grouting pile in the ovoid gravel stratum as claimed in claim 1, which is characterized in that: the gas sprayed out from the bottom end of the rotary spraying drill rod (6) also comprises high-pressure gas, and the high-pressure gas and the high-pressure cement slurry impact the collapsed pebbles together.
9. The construction method of the jet grouting pile in the ovoid gravel stratum as claimed in any one of claims 1 to 8, which is characterized in that: the large-diameter high-verticality jet grouting pile is used for water stop piles among foundation pit slope protection piles, row water stop piles behind the slope protection piles and grouting piles which are mutually overlapped to form a water stop curtain, water stop piles at the joint of an underground continuous wall or a stress wall formed by inserting section steel.
10. The construction method of the jet grouting pile in the ovoid gravel stratum as claimed in any one of claims 1 to 8, which is characterized in that: and 4, replacing high-pressure rotary spraying with high-pressure swing spraying in the step 5 and the step 4 to form a fan-shaped spraying surface, and finally, overlapping the fan-shaped spraying surface with the slope protection piles or automatically overlapping the fan-shaped spraying surface with the slope protection piles to form a waterproof curtain.
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| CN113818801B (en) * | 2021-08-20 | 2024-07-12 | 北京建材地质工程有限公司 | Construction method and construction system for eliminating liquefaction of sand layer |
| CN115369862A (en) * | 2022-09-22 | 2022-11-22 | 建基集团地下空间河湖整治研发中心有限公司 | High-pressure rotary spraying construction method and construction device |
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