CN115807418A - Post-grouting composite foundation for prefabricated miniature steel pipe piles and construction method of post-grouting composite foundation - Google Patents

Abstract

The invention belongs to the technical field of composite foundations, discloses a prefabricated miniature steel pipe pile post-grouting composite foundation and a construction method thereof, and aims to solve the problem that the bearing capacity of the miniature steel pipe pile composite foundation is poor due to low strength of a core area of the conventional miniature steel pipe pile composite foundation. The invention comprises a prefabricated miniature steel pipe pile implanted in a pile hole in a stratum or a prefabricated miniature steel pipe pile directly implanted in the stratum, wherein the prefabricated miniature steel pipe pile comprises a seamless steel pipe, a plurality of grout spraying openings are formed in the circumferential wall of the seamless steel pipe, a grouting flower pipe is inserted in the seamless steel pipe, a prefabricated fine stone concrete layer is arranged between the grouting flower pipe and the seamless steel pipe, a jet flow channel for communicating the grouting hole in the grouting flower pipe with the grout spraying openings in the seamless steel pipe is formed in the prefabricated fine stone concrete layer, and concrete layers are poured in the grouting flower pipe and between the grouting flower pipe and a soil body of the stratum through the jet flow channel.

Description

Post-grouting composite foundation for prefabricated miniature steel pipe piles and construction method of post-grouting composite foundation

Technical Field

The invention belongs to the technical field of steel pipe piles, and particularly relates to a prefabricated miniature steel pipe pile post-grouting composite foundation and a construction method thereof.

Background

The deep filling area is very common in the current construction engineering, particularly in hilly areas, the field usually has the problems of digging mountain and filling ditch, the thickness distribution of the filling soil is uneven, the filling material is disordered and is not rolled and tamped, after the engineering construction, the field often has large-area settlement, the terrace is loosened and cracked, the wall is cracked, and the operation work is influenced.

The bearing capacity of the miniature steel pipe pile is similar to that of a conventional pile foundation generally, but in a high backfill region, the buckling failure strength determines the bearing capacity of the miniature pile to a great extent, so that when the miniature steel pipe pile penetrates through thick-layer soil filling, the buckling stability of the miniature steel pipe pile needs to be considered, and the miniature steel pipe pile is more prone to buckling failure than a larger pile.

The post grouting is an auxiliary measure for solving the problem that the peripheral filling gaps are large, and on one hand, filling gaps in the grouting influence range to form a cemented structure layer; on the other hand, the side friction resistance of the filled soil in the range of the cementing layer and the influence radius is improved, and the bearing capacity and the stability of the micro pile are further improved.

Under the action of vertical load, the axial force of the miniature steel pipe pile is mainly borne by core concrete, and is gradually increased along with the increase of the load, and the change curvature of the miniature steel pipe pile tends to rise. Therefore, one of the paths for solving the buckling failure is to improve the strength of the core area of the miniature steel pipe pile, and the construction of the miniature pile has two modes at present: one is to put the seamless steel pipe down after the hole is formed, and then to slip casting and inject cement paste or cement mortar; and the other method is to insert a seamless steel pipe after the cement soil is formed by rotary spraying. Two ways present problems: first, core area intensity is not high, though can consider core area concreting, but miniature steel-pipe pile aperture is less, pours the degree of difficulty greatly, and the long unable vibration of long term of stake. And secondly, the post grouting is orifice pressure grouting, because the full length of the orifice pressure grouting is provided with a grout overflow hole, the position close to a grouting orifice has large pressure and good grouting effect, and the lower part of the orifice pressure grouting is far away from the orifice, so that the grouting effect is extremely poor, and the post grouting is also an important factor influencing the treatment effect. In the current post-grouting process, the grout is injected from the upper part of the grouting pipe, the grout outlet holes on the grouting pipe are distributed over the whole grouting pipe, and the quantity of the grout sprayed out of each grout outlet hole is not uniform in the grouting process due to different positions of each grouting hole, so that the grouting quality is poor; and further causes poor bearing capacity of the micro steel pipe pile composite foundation.

However, if the composite foundation is reinforced by pile foundations (such as concrete mixing piles and cast-in-place piles) to improve the bearing capacity, the construction cost of the pile foundations is high.

Therefore, how to improve the bearing capacity of the micro steel pipe pile composite foundation on the premise of limited construction cost is always the research direction of technicians in the field.

Disclosure of Invention

The invention provides a post-grouting composite foundation of a prefabricated miniature steel pipe pile and a construction method thereof, aiming at solving the problem that the bearing capacity of the miniature steel pipe pile composite foundation is poor due to low strength of the core area of the miniature steel pipe pile in the existing miniature steel pipe pile composite foundation, and the strength of the core area of the steel pipe pile and the buckling stability of the steel pipe pile can be improved, so that the bearing capacity of the miniature steel pipe pile composite foundation is improved.

In order to solve the technical problem, the technical scheme adopted by the invention is as follows:

the post-grouting composite foundation is characterized by comprising a prefabricated miniature steel pipe pile implanted in a pile hole in a stratum or a prefabricated miniature steel pipe pile directly implanted in the stratum, wherein the prefabricated miniature steel pipe pile comprises a seamless steel pipe, a plurality of grouting openings are formed in the circumferential wall of the seamless steel pipe, a grouting flower pipe is inserted into the seamless steel pipe, a prefabricated fine stone concrete layer is arranged between the grouting flower pipe and the seamless steel pipe, a jet flow channel for communicating the grouting hole in the grouting flower pipe with the grouting openings in the seamless steel pipe is formed in the prefabricated fine stone concrete layer, and concrete layers are poured inside the grouting flower pipe and between the grouting flower pipe and a soil body of the stratum through the jet flow channel.

In some embodiments, the spouting passages are provided in an obliquely downward direction.

In some embodiments, the periphery of the seamless steel tube is provided with a spherical or hemispherical protrusion, each grout spraying opening is provided with a protrusion, and the protrusion is arranged at the lower edge of the grout spraying opening.

In some embodiments, the periphery of the grouting perforated pipe is provided with spiral ribs embedded in the prefabricated fine stone concrete layer at two ends close to the seamless steel pipe.

In some embodiments, the pile hole extends to a bearing stratum in the stratum, and the length of the prefabricated miniature steel pipe pile is matched with the depth of the pile hole.

The invention also provides a construction method of the prefabricated miniature steel pipe pile post-grouting composite foundation, which comprises the following steps:

(1) Preparing a prefabricated miniature steel pipe pile in advance;

(2) Opening a pile hole on the stratum according to the designed position and implanting a prefabricated miniature steel pipe pile into the pile hole, or directly pressing the prefabricated miniature steel pipe pile into the stratum according to the designed position;

(3) Placing a post-grouting device into the grouting flower pipe of the prefabricated miniature steel pipe pile, and communicating the post-grouting device with an external grouting pipe for grouting; when grouting is carried out in the grouting floral tube, the rear grouting device firstly fills the space in the grouting floral tube below the rear grouting device with grout, and then grout is injected into each grouting opening in the height range of the grouting floral tube corresponding to the rear grouting device; sequentially and circularly injecting grout along the direction from bottom to top of the grouting perforated pipe until grouting at the top of the grouting perforated pipe is finished so as to finish post-grouting operation; taking the post-grouting device away after the post-grouting operation is finished;

(4) And constructing a mattress layer on the surface of the stratum after the slurry injected by the back grouting device reaches the designed strength.

In some embodiments, the post grouting device comprises an upper floating plug and a lower floating plug, the upper floating plug and the lower floating plug are connected together through a second pipeline and have a space, the upper floating plug and the lower floating plug are both provided with air bags capable of being in sealing contact with the grouting floral tube after being filled with grout, the upper floating plug is connected with a first pipeline for injecting grout, the lower floating plug is connected with a third pipeline, grout can enter the upper floating plug and fill the air bags, the inner part of the lower floating plug and the space between the upper floating plug and the lower floating plug through the first pipeline, the second pipeline and the third pipeline, and grout can also enter the grouting floral tube below the lower floating plug.

In some embodiments, the upper and lower floating plugs each comprise an upper cover plate and a lower cover plate with a gap therebetween; the air bag is connected between the upper cover plate and the lower cover plate, through holes are formed in the upper cover plate and the lower cover plate, the through holes are closer to the outer edges of the upper cover plate and the lower cover plate than the connecting positions of the air bag and the upper cover plate and the lower cover plate, the through holes can be shielded when the air bag is filled with slurry, and the through holes can be exposed when the air bag is not filled with slurry; a sealed cavity is formed among the upper cover plate, the lower cover plate and the air bag, a first pipeline which penetrates through the upper cover plate of the upper floating plug and is mutually communicated with the cavity of the upper floating plug is connected to the upper cover plate of the upper floating plug, and the first pipeline is used for being connected with a grouting pipe; the upper end of second pipeline and the upper cover plate fixed connection who floats the stopper on, the lower extreme of second pipeline passes the lower apron of the stopper that floats in proper order, floats the upper cover plate of stopper then with the lower apron fixed connection who floats the stopper down, be connected with the third pipeline that passes the upper cover plate of stopper and communicate each other with the cavity of lower floating stopper on the upper cover plate of lower floating stopper, seted up a plurality of through-holes on the circumference wall of second pipeline bottom that is located the cavity of upper floating stopper and lower floating stopper.

In some embodiments, a discharge channel is formed in a lower cover plate of the lower floating plug, a spring is mounted at the bottom of the discharge channel, a piston which is in sealing fit with the discharge channel is mounted at the top of the spring, a feed channel is formed at the top of the piston, a through channel which is communicated with the feed channel is formed in the piston, and an ejection port which can be communicated with or disconnected from the through channel is formed in the lower cover plate of the lower floating plug.

In some embodiments, the upper side surfaces of the lower cover plates of the upper floating plug and the lower floating plug are spherical surfaces or hemispherical spherical surfaces, and the second channel is connected to the middle of the arc-shaped groove.

In some embodiments, a weight block is arranged on the periphery of the first pipeline extending out of the upper cover body of the upper floating plug.

In some embodiments, the number of the third pipes is 1, 2, 3 or 4, and when the number of the third pipes is 2, 3 or 4, the third pipes are uniformly distributed on the upper cover body of the lower floating plug.

Compared with the prior art, the invention has the following beneficial effects:

according to the post-grouting composite foundation for the prefabricated miniature steel pipe pile, the structural design of the seamless steel pipe, the grouting floral tube and the prefabricated fine stone concrete layer poured between the seamless steel pipe and the grouting floral tube is adopted, and under the reinforcing effect of the grouting floral tube and the prefabricated fine stone concrete layer, the strength and the bending resistance of the core area of the miniature steel pipe pile can be greatly improved, so that the durability, the buckling stability and the reliability of the miniature steel pipe pile are improved, and the bearing capacity of the composite foundation is further improved. Compared with the mode of reinforcing the stratum (mainly soft stratum) by the pile foundation, the construction cost and the construction period can be greatly reduced (firstly, the miniature steel pipe pile adopts a prefabricated mode, and on the other hand, the pouring amount of slurry can be reduced compared with the pile foundation, so that the construction period is shortened).

In conclusion, the prefabricated miniature steel pipe pile post-grouting composite foundation provided by the invention has the characteristics of low construction cost and high bearing capacity.

Compared with the structure mode that the jet flow channel on the prefabricated miniature steel pipe pile is designed in an inclined and downward mode in the prior art, the structure mode that the jet flow channel on the prefabricated miniature steel pipe pile is designed in an inclined and downward mode can improve impact force on soil in a stratum under the clamping action of the pressure of grout and gravity when the grout is sprayed out of the inclined jet flow channel. Compared with the structure in the prior art, under the same slurry pressure, the composite foundation has larger impact force on the soil body, improves the extrusion capacity on the side wall of the soil body, and forms a concrete layer with larger outer diameter, thereby further improving the bearing capacity of the composite foundation.

According to the invention, the bulge is arranged on the lower edge of the grout spraying opening, when the stratum is silt, the prefabricated miniature steel pipe pile can be directly pressed into the silt, and the bulge can avoid the blockage of the grout spraying opening by a soil body through the structural design, so that the problem that a grouting hole is easy to block when a grouting perforated pipe is directly pressed in the prior art is solved, the smoothness of each grout spraying opening is ensured, and the post-grouting quality is improved.

In the use process of the post grouting device, an upper floating plug and a lower floating plug are arranged at proper positions of a grouting floral tube, so that a grouting hole of the grouting floral tube needing grouting is positioned between the upper floating plug and the lower floating plug, then grout is injected into a first pipeline, the grout enters a cavity of the upper floating plug along the first pipeline, then enters a second pipeline through a through hole in the second pipeline and enters a cavity of the lower floating plug, the grout in the cavity of the lower floating plug is firstly sprayed out through a discharge channel, a feed channel of a piston and a through channel of the piston and then is sprayed out through a spraying hole of the lower floating plug to fill the grouting floral tube below the lower floating plug (at the moment, the through channel of the piston is communicated with a spraying hole of the lower floating plug), so that the grouting floral tube below the lower floating plug is filled, and the grouting floral tube below the lower floating plug is prevented from being hollowed; after the grouting floral tube below the lower floating plug is filled, along with the increasing pressure of slurry, the piston in the lower cover plate of the lower floating plug gradually slides downwards under the action of the pressure of the slurry, so that the through channel and the ejection port are disconnected, the grouting fills the air bag of the lower floating plug, the air bag expands to be in close contact with the inner wall of the grouting floral tube, and the whole device is stabilized in the grouting floral tube under the action of the balancing weight; and along with the increase of the injected grout, the grout flows out of the third pipeline and fills the space between the upper floating plug and the lower floating plug, and then the grout is injected into the stratum through the grouting holes in the grouting floral tubes. After the grouting of the grouting perforated pipe section is completed, grouting is stopped, the whole device (namely an upper floating plug and a lower floating plug) is slowly lifted upwards, along with the reduction of the pressure of slurry in the upper floating plug and the lower floating plug, a piston in a lower cover body of the lower floating plug moves upwards to enable a through channel on the piston to be communicated with a spraying port of the lower cover body again, so that the slurry is filled in a space below the lower floating plug, namely when the upper floating plug and the lower floating plug are lifted upwards, the slurry can automatically fill a space where the upper floating plug and the lower floating plug move to flow out, and the grouting of the whole grouting perforated pipe is completed in a circulating manner. When the slurry filling device is used, the piston in the lower cover body of the lower floating plug can be automatically adjusted according to the pressure change of the slurry, so that the spray port in the lower cover body of the lower floating plug is cut off or communicated with the through channel, and when the upper floating plug and the lower floating plug move upwards together, the slurry can be automatically filled below the lower floating plug; on one hand, the inside of the grouting pipe below the lower floating plug is filled with the grout, so that the grout sprayed out from the grouting hole of the grouting pipe can form a whole with the grout in the grouting pipe in time, the integrity of post grouting is greatly improved, and the grouting quality is improved; on the other hand, the problem that slurry sprayed through the grouting holes flows back under the action of negative pressure to cause grouting cracks is avoided, and the molding quality is further improved.

In addition, in the use process of the invention, the grouting floral tube below the lower floating plug is filled with the grout through the first pipeline, the second pipeline and the third pipeline firstly, then the air bag of the lower floating plug is filled with the grout, and finally the air bag of the upper floating plug is filled with the grout, so that the air between the upper floating plug and the lower floating plug can be discharged through the through hole, the situation of holes caused by the retention of the air in the grout is avoided, and the grouting forming quality is improved. In the prior art as referred to in the background of the present application, the sealing action of the grouting plug causes the internal gas not to be completely discharged, and the solidified slurry has a void. The invention can avoid the condition of cavities caused by air retention (which cannot be exhausted completely), and further improve the quality of post-grouting.

Drawings

FIG. 1 is a schematic structural diagram of a post-grouting composite foundation of a prefabricated miniature steel pipe pile according to the present invention;

FIG. 2 isbase:Sub>A schematic cross-sectional view taken along line A-A of FIG. 1;

FIG. 3 is a schematic structural view of a prefabricated miniature steel pipe pile according to the present invention;

FIG. 4 is a structural diagram of the present invention during post-grouting for a grouting floral tube or steel tube;

FIG. 5 is an enlarged partial view taken at A in FIG. 4, showing the through passage in the piston and the ejection port in the lower cap body disconnected from each other;

FIG. 6 is a schematic view showing a state where a through passage of the piston of the present invention and an ejection port of the lower cap body communicate with each other;

FIG. 7 is a schematic view showing a state where the airbag of the present invention is coupled to the upper cover and the lower cover, in which the airbag is in an unexpanded state to expose the through-hole;

the mark in the figure is: 01. the foundation layer, 101, the weak layer, 102, the holding layer, 02, the grouting perforated pipe, 03, the grouting hole, 04, the grouting pipe, 05, the seamless steel pipe, 06, the prefabricated fine stone concrete layer, 07, the grout spraying port, 08, the jet flow channel, 09, the concrete layer, 010, the mattress layer, 011, the foundation, 012, the spiral rib, 013 and the bulge; 1. the device comprises an upper floating plug, 11, an upper cover body, 111, a through hole, 112, a mounting block, 12, an air bag, 13, a lower cover body, 131, a discharge channel, 132, a piston, 133, a feed channel, 134, a through channel, 135, a spray port, 136, a spring, 2, a lower floating plug, 3, a first pipeline, 4, a second pipeline, 41, a through hole, 5, a third pipeline, 6 and a balancing weight.

Detailed Description

The present invention will be further described with reference to the following examples, which are intended to illustrate only some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, other embodiments used by those skilled in the art without any creative effort belong to the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention; the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance; furthermore, unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, as they may be fixedly connected, detachably connected, or integrally connected, for example; may be a mechanical connection; may be directly connected or indirectly connected through an intermediate. The specific meanings of the above terms in the present invention can be understood by those of ordinary skill in the art in conjunction with specific situations.

With reference to fig. 1 to 3, the prefabricated micro steel pipe pile post-grouting composite foundation of the invention comprises a prefabricated micro steel pipe pile implanted in a pile hole in a ground layer 01 or a prefabricated micro steel pipe pile directly implanted in the ground layer 01, wherein the prefabricated micro steel pipe pile comprises a seamless steel pipe 05, a plurality of grouting ports 07 are formed in the circumferential wall of the seamless steel pipe 05, a grouting flower pipe 02 is inserted into the seamless steel pipe 05, a prefabricated fine stone concrete layer 06 is arranged between the grouting flower pipe 02 and the seamless steel pipe 05, a jet flow channel 08 for communicating the grouting hole 03 on the grouting flower pipe 02 with the grouting ports 07 on the seamless steel pipe 05 is formed in the prefabricated fine stone concrete layer 06, and a concrete layer 09 is poured inside the grouting flower pipe 02 and between the grouting flower pipe 02 and the soil body of the ground layer 01 through the jet flow channel 08.

According to the post-grouting composite foundation of the prefabricated miniature steel pipe pile, firstly, through the structural design of the seamless steel pipe, the grouting perforated pipe and the prefabricated fine stone concrete layer poured between the seamless steel pipe and the grouting perforated pipe, the strength and the bending resistance of the core area of the miniature steel pipe pile can be greatly improved under the reinforcing effect of the grouting perforated pipe and the prefabricated fine stone concrete layer, so that the durability, the buckling stability and the reliability of the miniature steel pipe pile are improved, and the bearing capacity of the composite foundation is further improved. Compared with a mode of reinforcing a stratum (mainly a weak stratum) by a pile foundation, the method has the advantages that the construction cost and the construction period can be greatly reduced (firstly, the miniature steel pipe pile adopts a prefabricated mode, and on the other hand, the pouring amount of slurry can be reduced compared with the pile foundation, so that the construction period is shortened, and in addition, when the method aims at a silt stratum, the miniature steel pipe pile can be directly pressed into the prefabricated miniature steel pipe pile (namely, a pile hole does not need to be formed in the stratum, so that the purpose of shortening the construction period is achieved).

In conclusion, the prefabricated miniature steel pipe pile post-grouting composite foundation provided by the invention has the characteristics of low construction cost and high bearing capacity.

In the implementation process of the invention, no matter the prefabricated miniature steel pipe pile is directly implanted into the stratum 01 or the prefabricated miniature steel pipe pile is directly implanted into the stratum 01 by pressing in the way of constructing the pile hole on the stratum 01, the prefabricated miniature steel pipe pile should penetrate through the weak layer 101 in the stratum 01 and extend into the bearing layer 102 of the stratum 01.

With reference to fig. 1 and 2, preferably, one end of the grouting floral tube 02 extends out of the seamless steel tube 05, so as to facilitate grouting through the grouting floral tube, and after grouting is completed after the grouting floral tube 02 is grouted, the grouting floral tube 02 extending out of the seamless steel tube 05 extends into the mattress layer 010. According to the invention, the grouting floral tube 02 extending out of the seamless steel tube 05 is inserted into the mattress layer 010, so that the bearing capacity of the whole composite foundation can be further improved.

With reference to fig. 2, in order to improve the uniformity of post-grouting, three grouting channels 09 are communicated with the same height position of the grouting floral tube 02, that is, 3 grouting holes 03 are formed in the grouting floral tube 02 at the same height position, each grouting hole 03 corresponds to one grouting channel 09, and correspondingly, 3 grouting holes 07 at the same height position are also provided.

In some embodiments, the jet channel 08 is arranged in an obliquely downward direction. The inclined downward arrangement taught by the present invention means that the jet flow passage 08 is inclined downward when the prefabricated micro steel pipe pile is implanted into the ground 01. Compared with the structure mode that the jet flow channel on the prefabricated miniature steel pipe pile is designed in an inclined and downward mode in the prior art, the structure mode that the jet flow channel on the prefabricated miniature steel pipe pile is designed in an inclined and downward mode can improve impact force on soil in a stratum under the clamping action of the pressure of grout and gravity when the grout is sprayed out of the inclined jet flow channel. Compared with the structure in the prior art, under the same slurry pressure, the composite foundation has larger impact force on the soil body, improves the extrusion capacity on the side wall of the soil body, and forms a concrete layer with larger outer diameter, thereby further improving the bearing capacity of the composite foundation.

In some embodiments, the seamless steel pipe 05 is provided with protrusions 013 in a spherical shape or a hemispherical shape on the periphery, one protrusion 013 is provided for each of the slurry outlets 07, and the protrusions 013 are provided on the lower edges of the slurry outlets 07. The lower edge of the invention is only when the prefabricated miniature steel pipe pile is implanted into the ground 01 (namely, when the prefabricated miniature steel pipe pile is in a vertical state), the bulge 013 is positioned at the lower edge of the grout spraying opening 07. According to the invention, the bulge is arranged on the lower edge of the grout spraying opening, when the stratum is silt, the prefabricated miniature steel pipe pile can be directly pressed into the silt, and the bulge can avoid the blockage of the grout spraying opening by a soil body through the structural design, so that the problem that a grouting hole is easy to block when a grouting perforated pipe is directly pressed in the prior art is solved, the smoothness of each grout spraying opening is ensured, and the post-grouting quality is improved.

In some embodiments, the spiral ribs 012 pre-embedded in the prefabricated fine stone concrete layer 06 are arranged at both ends of the periphery of the grouting perforated pipe 02 close to the seamless steel pipe 05. Through the design that sets up spiral muscle 012, can improve the intensity at prefabricated miniature steel-pipe pile both ends, be convenient for when pressing into miniature steel-pipe pile in the stratum, prevent that the condition of damage from appearing in the prefabricated miniature steel-pipe pile.

The compression and buckling stability of the miniature steel pipe pile (column) is mainly calculated by checking the compression bearing capacity of the miniature steel pipe pile according to the technical Specification of Steel pipe concrete Structure (CECS 28: 2012). Those skilled in the art can calculate and design the concrete filled steel tube structure according to the technical specification (CECS 28: 2012) and will not be described in detail herein.

The invention also provides a construction method of the prefabricated miniature steel pipe pile post-grouting composite foundation, which comprises the following steps:

(1) Preparing a prefabricated miniature steel pipe pile in advance; the method comprises the steps of prefabricating the prefabricated miniature steel pipe pile, namely, firstly, forming a guniting opening 07 on a seamless steel pipe 05, then inserting a grouting floral tube 02 with a grouting hole 03 into the seamless steel pipe, enabling the guniting opening 07 to correspond to the grouting hole 03, then arranging a jet flow channel 08, plugging the grouting hole 03, the jet flow channel 08 and the interior of the grouting floral tube, and finally, injecting fine stone concrete for solidification.

In the specific implementation process, the jet flow channel 08 can be a reserved type (namely, the jet flow channel 08 is formed by a pre-buried die when the fine aggregate concrete is poured); the periphery of the grouting floral tube can be connected with a pipeline which is mutually communicated with the grouting opening 03, and a jet flow channel 08 is formed by the pipeline. The structure according to the invention can be produced by a person skilled in the art and will not be described in more detail here.

(2) Opening a pile hole on the stratum according to the designed position and implanting a prefabricated miniature steel pipe pile into the pile hole, or directly pressing the prefabricated miniature steel pipe pile into the stratum according to the designed position; that is, different implantation methods are adopted for different stratums, for example, when silt is treated, the prefabricated miniature steel pipe pile can be directly pressed into the stratum 01 in a pressing mode; when other strata are used, the hole forming method for the weak strata, which is commonly used in building construction, can be adopted, such as rotary spraying hole forming, down-the-hole hammer hole forming and the like, and can be understood and appreciated by persons skilled in the art, and the description is omitted.

(3) A post-grouting device is arranged in the grouting floral tube 02 of the prefabricated miniature steel pipe pile, and the post-grouting device is communicated with an external grouting pipe 04 for grouting; when grouting is performed in the grouting floral tube 02, the rear grouting device firstly fills the space in the grouting floral tube 02 below the rear grouting device with grout, and then injects grout into each grouting opening in the height range of the grouting floral tube corresponding to the rear grouting device; sequentially and circularly injecting grout along the direction from bottom to top of the grouting perforated pipe until grouting at the top of the grouting perforated pipe is finished so as to finish post-grouting operation; taking the post-grouting device away after the post-grouting operation is finished; that is, since the post-grouting device itself has a certain height (i.e., can occupy a certain depth of the grouting perforated pipe 02), when the grouting perforated pipe 02 is grouted by the post-grouting device, grouting is performed in a manner that grouting is performed sequentially from bottom to top.

(4) And constructing a mattress layer 010 on the surface of the stratum 01 after the slurry injected by the back grouting device reaches the designed strength. After the mattress layer 010 is constructed, a foundation 011 can be constructed above the mattress layer 010.

According to the invention, the prefabricated miniature steel pipe pile is subjected to post grouting through the post grouting device, and compared with the post grouting mode in the prior art, the post grouting uniformity and the grouting quality can be improved.

With reference to fig. 4 to 7, the post-grouting device of the invention comprises an upper floating plug 1 and a lower floating plug 2, wherein the upper floating plug 1 and the lower floating plug 2 are connected together through a second pipeline 4 and have a gap, the upper floating plug 1 and the lower floating plug 2 are both provided with an air bag 12 which can be in sealing contact with a grouting floral tube 02 after being filled with grout, the upper floating plug 1 is connected with a first pipeline 3 for injecting grout, wherein the first pipeline 3 is used for being connected with a grouting tube 04, and grout is injected into the first pipeline 3 through the grouting tube 04; the lower floating plug 2 is connected with a third pipeline 5, slurry can enter the upper floating plug 1 through the first pipeline 3, the second pipeline 4 and the third pipeline 5 and is filled in the air bag 12 and the lower floating plug 3 and is filled in the air bag 12 and a space between the upper floating plug 1 and the lower floating plug 2; and the slurry can enter the grouting flower tube below the lower floating plug. Namely, after entering through the first pipeline 3, the slurry can be filled in the air bag of the upper floating plug 1, the air bag of the lower floating plug 2 and enter the space between the upper floating plug 1 and the lower floating plug 2; the grouting floral tube 02 between the upper floating plug and the lower floating plug is filled, and the grout is injected into the stratum 01 through the grouting hole 03 in the grouting floral tube 02, so that the stratum 01 is impacted, extruded and the like, after the grout is solidified, the stratum 01 and the grouting floral tube 02 form a whole through concrete, and the post-grouting reinforcement operation is completed.

In some embodiments, the upper floating plug 1 and the lower floating plug 2 each comprise an upper cover plate 11 and a lower cover plate 13, and the upper cover plate 11 and the lower cover plate 13 are spaced from each other; an air bag 12 is connected between the upper cover plate 11 and the lower cover plate 13, through holes 111 are formed in both the upper cover plate 11 and the lower cover plate 13, the through holes 111 are closer to the outer edges of the upper cover plate 11 and the lower cover plate 13 than the connecting positions of the air bag 12 and the upper cover plate 11 and the lower cover plate 13, the through holes 111 can be shielded when the air bag 12 is filled with slurry, and the through holes 111 can be exposed when the air bag 12 is not filled with slurry; a sealed cavity is formed among the upper cover plate 11, the lower cover plate 13 and the air bag 12, a first pipeline 3 which penetrates through the upper cover plate 11 of the upper floating plug 1 and is mutually communicated with the cavity of the upper floating plug 1 is connected to the upper cover plate 11 of the upper floating plug 1, and the first pipeline 3 is used for being connected with a grouting pipe 04; the upper end of second pipeline 4 and 11 fixed connection of upper cover plate of upper floating plug 1, the lower extreme of second pipeline 4 passes lower apron 13 of upper floating plug 2 in proper order, the upper cover plate 11 of lower floating plug 2 then with the lower apron 13 fixed connection of lower floating plug 2, be connected with on the upper cover plate 11 of lower floating plug 2 and pass the upper cover plate 11 of lower floating plug 2 and with the third pipeline 5 that the cavity of lower floating plug 2 communicates each other, be located and seted up a plurality of through-holes 41 on the circumference wall of second pipeline 5 bottom in the cavity of upper floating plug 1 and lower floating plug 2.

With reference to fig. 7, the lower end of the upper cover plate 11 and the upper end of the lower cover plate 13 are provided with grooves, the grooves are provided with mounting blocks 112, the upper and lower edges of the airbag 12 are respectively clamped in the grooves and are fixed by the mounting blocks, and the mounting blocks 112 are then fixedly connected with the upper cover plate or the lower cover plate 13 through fastening bolts, so as to respectively mount the upper and lower edges of the airbag 12 on the upper cover plate and the lower cover plate.

Since the bladder needs to be in close contact with the circumferential wall of the grouting pipe 02, it is preferable that the groove is an annular groove and the mounting block 112 is annular. In the use process of the air bag structure, after the pressure of the slurry reaches a certain degree, the slurry fills cavities in the upper floating plug and the lower floating plug, so that the air bag is driven to expand and is tightly contacted and sealed with the inner wall of the grouting floral tube 02, the slurry is sealed in a space between the upper floating plug and the lower floating plug, the grouting hole 03 of the grouting floral tube 02 is grouted, and the stratum 01 is reinforced.

After the grouting floral tube 02 in a section of area (length) is poured, the grouting is stopped from being injected into the grouting tube 04, and along with the reduction of the pressure of the grout, the air bag 12 is gradually separated from the inner wall of the grouting floral tube 02, so that the whole device is lifted to move along the inside of the grouting floral tube.

Preferably, a lifting lug is arranged on the upper cover body 11 of the upper floating plug 1 and used for binding a hauling rope, and the whole device is driven by the hauling rope to move up and down in the grouting floral tube 02.

With reference to fig. 5 and fig. 6, in some embodiments, a discharge channel 131 is formed in the lower cover plate 13 of the lower floating plug 2, a spring 136 is installed at the bottom of the discharge channel 131, a piston 132 that is in sealing fit with the discharge channel 131 is installed at the top of the spring 136, a feed channel 133 is formed at the top of the piston 132, a through channel 134 that is in communication with the feed channel 133 is formed in the piston 132, and an ejection port 135 that can be in communication with or disconnected from the through channel 134 is formed in the lower cover plate 13 of the lower floating plug 2. Wherein, when the slurry pressure is small, the through channel 134 on the piston 132 and the ejection port 135 on the lower cover body are communicated with each other, and when the slurry pressure is large, the through channel 134 on the piston 132 and the ejection port 135 on the lower cover body are disconnected from each other.

In some embodiments, the upper side surfaces of the lower cover plates 13 of the upper floating plug 1 and the lower floating plug 2 are spherical surfaces of a sphere or a hemisphere, and the second channel 4 is connected to the middle of the arc-shaped groove.

In some embodiments, the periphery of the first pipe extending out of the upper cover 11 of the upper floating plug 1 is provided with a balancing weight 6, which is used for maintaining the stability of the whole device, and a filled air bag prevents the whole device from floating upwards under the action of high-pressure slurry.

In some embodiments, the number of the third pipes 5 is 1, 2, 3 or 4, and when the number of the third pipes is 2, 3 or 4, the third pipes 5 are uniformly distributed on the upper cover body of the lower floating plug. Because the grouting holes 03 on the grouting floral tube 02 are uniformly distributed, in order to enable the grouting holes 03 at the same height position of the grouting floral tube 02 to be more uniformly grouted, the number of the third pipelines is the same as that of the grouting holes 03 at the same height position on the grouting floral tube 02, so that the grouting holes 03 at the same height position on the grouting floral tube 02 are more uniformly grouted.

In the use process of the post-grouting device, an upper floating plug and a lower floating plug are firstly arranged at proper positions of a grouting floral tube, so that a grouting hole of the grouting floral tube needing grouting is positioned between the upper floating plug and the lower floating plug, then grout is injected into a first pipeline, the grout enters a cavity of the upper floating plug along the first pipeline, then enters a second pipeline through a through hole in the second pipeline and enters a cavity of the lower floating plug, the grout in the cavity of the lower floating plug firstly passes through a discharge channel, a feeding channel of a piston and a through channel of the piston and then is sprayed out through a spraying port of the lower floating plug to fill the grouting floral tube below the lower floating plug (at the moment, the through channel of the piston is communicated with a spraying port of the lower floating plug), so that the grouting floral tube below the lower floating plug is fully filled, and the grouting floral tube below the lower floating plug is prevented from being hollowed; after the grouting floral tube below the lower floating plug is filled, along with the increasing pressure of slurry, a piston in a lower cover plate of the lower floating plug gradually slides downwards under the action of the pressure of the slurry, so that the through channel and the ejection port are mutually disconnected, the grouting fills an air bag of the lower floating plug, the air bag expands to be in close contact with the inner wall of the grouting floral tube, and the whole device is stabilized in the grouting floral tube under the action of a balancing weight; and with the more and more injected grout, the grout flows out of the third pipeline and fills the space between the upper floating plug and the lower floating plug, and then the grout is injected into the stratum through the grouting holes in the grouting floral tubes. After this slip casting floral tube section slip casting is accomplished, stop the slip casting, slowly upwards promote whole device (be upper floating plug and lower floating plug), along with upper floating plug, the decline of the thick liquid pressure in the lower floating plug, piston rebound in the lower cover body of lower floating plug makes the through channel on the piston communicate again with the blowout port of lower cover body to fill the thick liquid in the space of lower floating plug below, when upwards promoting upper floating plug and lower floating plug, the thick liquid can fill the space that upper floating plug and lower floating plug removed the outflow automatically, so circulate and accomplish the slip casting of whole slip casting floral tube. In the using process of the invention, the piston in the lower cover body of the lower floating plug can be automatically adjusted according to the pressure change of slurry, so that the spray port in the lower cover body of the lower floating plug is cut off or communicated with the through channel, and when the upper floating plug and the lower floating plug move upwards together, the slurry can be automatically filled below the lower floating plug; on one hand, the inside of the grouting pipe below the lower floating plug is filled with the grout, so that the grout sprayed out from the grouting hole of the grouting pipe can form a whole with the grout in the grouting pipe in time, the integrity of post grouting is greatly improved, and the grouting quality is improved; on the other hand, the problem that slurry sprayed through the grouting holes flows back under the action of negative pressure to cause grouting cracks is avoided, and the molding quality is further improved.

In addition, in the use process of the invention, the grouting floral tube below the lower floating plug is filled with the grout through the first pipeline, the second pipeline and the third pipeline firstly, then the air bag of the lower floating plug is filled with the grout, and finally the air bag of the upper floating plug is filled with the grout, so that the air between the upper floating plug and the lower floating plug can be discharged through the through hole, the situation of holes caused by the retention of the air in the grout is avoided, and the grouting forming quality is improved. In the prior art, as mentioned in the background of the present application, the sealing effect of the grouting plug causes the internal gas not to be completely discharged, and the solidified slurry has a cavity problem. The invention can avoid the condition of cavities caused by air retention (can not be exhausted), further improve the quality of post grouting and improve the precision of grouting.

Claims (9)

1. The post-grouting composite foundation is characterized by comprising a prefabricated miniature steel pipe pile implanted in a pile hole in a stratum or a prefabricated miniature steel pipe pile directly implanted in the stratum, wherein the prefabricated miniature steel pipe pile comprises a seamless steel pipe, a plurality of grouting openings are formed in the circumferential wall of the seamless steel pipe, a grouting flower pipe is inserted into the seamless steel pipe, a prefabricated fine stone concrete layer is arranged between the grouting flower pipe and the seamless steel pipe, a jet flow channel for communicating the grouting hole in the grouting flower pipe with the grouting openings in the seamless steel pipe is formed in the prefabricated fine stone concrete layer, and concrete layers are poured inside the grouting flower pipe and between the grouting flower pipe and the soil body of the stratum through the jet flow channel.

2. The prefabricated micro steel pipe pile post-grouting composite foundation according to claim 1, wherein the jet flow channel is gradually inclined downward in a vertical direction of the pile hole.

3. The prefabricated micro steel pipe pile post-grouting composite foundation according to claim 2, wherein spherical or hemispherical bulges are arranged on the periphery of the seamless steel pipe, one bulge is correspondingly arranged at each grout spraying opening, and the bulges are arranged at the lower edge of the grout spraying openings.

4. The prefabricated micro steel pipe pile post-grouting composite foundation according to any one of claims 1 to 3, wherein spiral ribs embedded in a prefabricated fine stone concrete layer are arranged at both ends of the periphery of the grouting perforated pipe close to the seamless steel pipe.

5. A construction method for a post-grouting composite foundation of a prefabricated miniature steel pipe pile is characterized by comprising the following steps:

(1) Preparing a prefabricated miniature steel pipe pile in advance;

(2) Opening a pile hole on the stratum according to the designed position and implanting a prefabricated miniature steel pipe pile into the pile hole, or directly pressing the prefabricated miniature steel pipe pile into the stratum according to the designed position;

(3) Placing a post-grouting device into the grouting flower pipe of the prefabricated miniature steel pipe pile, and communicating the post-grouting device with an external grouting pipe for grouting; when grouting is carried out in the grouting floral tube, the rear grouting device firstly fills the space in the grouting floral tube below the rear grouting device with grout, and then grout is injected into each grouting opening in the height range of the grouting floral tube corresponding to the rear grouting device; sequentially and circularly injecting grout along the direction from bottom to top of the grouting perforated pipe until grouting at the top of the grouting perforated pipe is finished so as to finish post-grouting operation; taking the post-grouting device away after the post-grouting operation is finished;

(4) And constructing a mattress layer on the surface of the stratum after the slurry injected by the back grouting device reaches the designed strength.

6. The construction method of the prefabricated micro steel pipe pile post-grouting composite foundation according to claim 5, wherein the post-grouting device comprises an upper floating plug and a lower floating plug, the upper floating plug and the lower floating plug are connected together through a second pipeline and have a space, the upper floating plug and the lower floating plug are respectively provided with an air bag which can be in sealing contact with the grouting floral tube after being filled with grout, the upper floating plug is connected with a first pipeline for injecting grout, the lower floating plug is connected with a third pipeline, the grout can enter the upper floating plug through the first pipeline, the second pipeline and the third pipeline and fill the air bag and the lower floating plug and fill the air bag and the space between the upper floating plug and the lower floating plug, and the grout can also enter the grouting floral tube below the lower floating plug.

7. The construction method of the prefabricated miniature steel pipe pile post-grouting composite foundation according to claim 6, wherein each of the upper floating plug and the lower floating plug comprises an upper cover plate and a lower cover plate, and a space is formed between the upper cover plate and the lower cover plate; the air bag is connected between the upper cover plate and the lower cover plate, through holes are formed in the upper cover plate and the lower cover plate, the through holes are closer to the outer edges of the upper cover plate and the lower cover plate than the connecting positions of the air bag and the upper cover plate and the lower cover plate, the through holes can be shielded when the air bag is filled with slurry, and the through holes can be exposed when the air bag is not filled with slurry; a sealed cavity is formed among the upper cover plate, the lower cover plate and the air bag, a first pipeline which penetrates through the upper cover plate of the upper floating plug and is mutually communicated with the cavity of the upper floating plug is connected to the upper cover plate of the upper floating plug, and the first pipeline is used for being connected with a grouting pipe; the upper end of second pipeline and the upper cover plate fixed connection who floats the stopper on, the lower extreme of second pipeline passes the lower apron of the stopper that floats in proper order, floats the upper cover plate of stopper then with the lower apron fixed connection who floats the stopper down, be connected with the third pipeline that passes the upper cover plate of stopper and communicate each other with the cavity of lower floating stopper on the upper cover plate of lower floating stopper, seted up a plurality of through-holes on the circumference wall of second pipeline bottom that is located the cavity of upper floating stopper and lower floating stopper.

8. The construction method of the prefabricated micro steel pipe pile post-grouting composite foundation according to claim 6, wherein a discharge channel is formed in a lower cover plate of the lower floating plug, a spring is installed at the bottom of the discharge channel, a piston hermetically matched with the discharge channel is installed at the top of the spring, a feed channel is formed in the top of the piston, a through channel communicated with the feed channel is formed in the piston, and an ejection port capable of being communicated with or disconnected from the through channel is formed in the lower cover plate of the lower floating plug.

9. The construction method of the prefabricated micro steel pipe pile post-grouting composite foundation according to claim 7 or 8, wherein the upper side surfaces of the lower cover plates of the upper floating plug and the lower floating plug are spherical surfaces which are spherical or hemispherical, and the second channel is connected to the middle of the arc-shaped groove.

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