CN112761166A

CN112761166A - Construction method for shallow foundation pit of combined support of piles and pre-grouting steel pipes based on SMW (soil mixing wall) construction method

Info

Publication number: CN112761166A
Application number: CN202110203279.3A
Authority: CN
Inventors: 郑泽棉; 陆国健; 陆锡逢
Original assignee: Guangdong Keneng Project Management Co ltd
Current assignee: Guangdong Keneng Project Management Co ltd
Priority date: 2021-02-23
Filing date: 2021-02-23
Publication date: 2021-05-07

Abstract

The application relates to a construction method of combining a pile in an SMW (soil mixing wall) method with a front grouting steel pipe to support a shallow foundation pit, wherein when the pile in the SMW method is constructed, a grouting steel pipe support penetrates into soil obliquely, so that the construction method is simple and convenient, and meanwhile, the soil around the pile can be compacted to improve the bearing capacity of a soil body; through the arrangement of the grout outlet and the reaming bag, grout can be injected into the steel pipe, discharged from the grout outlet, and spread out the reaming bag, so that the stability of the steel pipe is improved; the steel concrete purlin is poured on the pile in the SMW construction method, the steel pipe is embedded in the purlin, and therefore the pile in the construction method and the steel pipe pile form a combined supporting system.

Description

Construction method for shallow foundation pit of combined support of piles and pre-grouting steel pipes based on SMW (soil mixing wall) construction method

Technical Field

The application relates to the technical field of foundation pit supporting, in particular to a shallow foundation pit construction method combining an SMW construction method pile and a front grouting steel pipe combined supporting.

Background

In foundation pit engineering constructed in modern cities, construction is often performed close to the red line of a building, and the SMW construction method has considerable advantages in this respect, and construction can be performed when the central line of the SMW construction method is 80 cm away from the wall surface of the building.

In the related technology, the SMW method is to use a special multi-shaft mixer to drill and cut the soil body on site, and at the same time, cement grout is injected into the soil body at the end of the drill bit, after fully mixing, H-shaped steel or other sections are inserted into the mixing pile body to form an underground continuous wall body, and the wall body is directly used as a soil retaining and water stopping structure, and in the excavation of a foundation pit, a bracing form, such as a butt brace, a corner brace or a cross brace, is usually adopted.

With respect to the related art among the above, the inventors consider that the following drawbacks exist: due to the fact that an excavation site is limited, a small excavator is often required to repeatedly dig earth in a small range between supports, complex support is carried out in a pit, earth is taken out between lattice columns, construction speed is hindered, and the problem that construction period is long exists, so that improvement space is reserved.

Disclosure of Invention

In order to shorten the construction period, the application provides a construction method for combining a pile with a pre-grouting steel pipe to support a shallow foundation pit by an SMW construction method.

The construction method for the shallow foundation pit combined and supported by the SMW construction method pile and the pre-grouting steel pipe adopts the following technical scheme:

a construction method of a shallow foundation pit of a combined support of a pile and a pre-grouting steel pipe in an SMW construction method comprises the following steps:

s1: measuring and paying off, digging a groove and positioning;

s2: processing a steel pipe: arranging a plurality of grout outlet holes distributed along the length direction of the steel pipe on the pipe side of the steel pipe, and binding a layer of reaming bag on the surface of part of the grout outlet holes;

s3: positioning a drilling machine, preparing slurry and stirring slurry soil: positioning a drilling machine according to the positioning, and preparing and stirring uniform cement slurry;

s4: h-shaped steel processing and inserting: hoisting the H-shaped steel in place, inserting the H-shaped steel into the stirring mud, temporarily fixing the H-shaped steel in the designed elevation after the H-shaped steel reaches the designed elevation until the cement pile soil is hardened, and forming the pile body in the construction method;

s5: and (3) construction of front-supporting type grouting steel pipe support and purlin surrounding: lifting the steel pipe to enable the pile tip of the steel pipe to be vertically aligned with the pile position, slowly putting the steel pipe into the inserting positioning soil, slowly rotating the inclination angle by taking the pile tip as a fulcrum, and pressing the steel pipe into the soil layer when the inclination angle moves to 45 degrees;

s6: grouting in a grading stage: and grouting the upper end of the steel pipe, extruding grout from the grout outlet, expanding the reaming bag, pouring the surrounding purlin at the upper end of the pile body in the construction method, and embedding the inclined upper end of the steel pipe in the surrounding purlin.

By adopting the technical scheme, when the construction of the pile in the SMW construction method is carried out, the groove is extracted and excavated at the inclined strut position outside the reinforced concrete purlin to form a groove, so that the difficulty of digging soil at the inclined strut exposure position after the later-stage grouting of the steel pipe inclined strut is finished is prevented; for soft soil foundation, due to the soft soil texture, the grouting steel pipe supports obliquely penetrate into the soil, so that the method is simple and convenient, and meanwhile, the soil around the pile can be compacted, and the bearing capacity of the soil body is improved; through the arrangement of the grout outlet and the reaming bag, grout can be injected into the steel pipe, the grout is discharged from the grout outlet, the reaming bag is expanded, the reaming bag has restraint on the grout, a grouting enlarged body is favorably formed, the cross section area of the steel pipe in a soil body is improved, the stability of the steel pipe is favorably improved, cement grout is extruded into the soil body through high pressure, a water-drop-shaped hardened soil area is formed at the end part and the periphery of a pile, and the connection stability between the steel pipe and the soil body is improved; the steel concrete purlin is poured on the pile in the SMW construction method, the steel pipe is embedded in the purlin, and therefore the pile in the construction method and the steel pipe pile form a combined supporting system.

Preferably, the method further comprises the following steps:

s7: digging out side pit cushion earthwork: the excavation mode that adopts the layering piecemeal excavates the hole limit soil body, adopts the mode of manual excavation during the layering excavation, to stereoplasm soil, chooses for use small-size excavator cooperation fortune native car to excavate work, and the side excavation adopts symmetrical construction, and the excavation progress part keeps unanimous, to connecting the excavation, adopts the spacer block excavation.

Through adopting above-mentioned technical scheme, because the same side hole limit soil of continuous excavation can cause the unbalance of more symmetrical structure local stress, therefore, the side excavation adopts the symmetry construction, make both sides excavation progress part keep unanimous, and in continuous excavation, along with the scope of excavation increases gradually, local stress can be progressively accumulated, when reaching the resistance limit, can cause local area to warp too big or wholly cave in, consequently, through adopting the spacer excavation, make the excavation regional whole keep the symmetry on more dimensions, be favorable to further improving the problem of the stress concentration aggravation that arouses along with the increase of soil body geometric complexity.

Preferably, the method further comprises the following steps:

s8: constructing prefabricated steel plates, reinforcing bar cushion layers and water stop steel plates: when the excavation of the pit edge reaches the design depth, the construction of the prefabricated steel plate is carried out in time, the construction of a cast-in-place reinforcing bar cushion layer on the steel plate is carried out simultaneously, then the construction of a basement bottom plate and an outer wall is carried out, and a water stop steel plate is additionally arranged at the position, where the grouting steel pipe supports and penetrates through the bottom plate or the surface of the outer wall.

By adopting the technical scheme, the cushion layer is poured in time, the subsequent construction of the basement bottom plate and the outer wall is facilitated, and meanwhile, the grouting steel pipe supports the bottom plate or the outer wall surface to be penetrated, and the water stop steel plate is additionally arranged, so that the problem of water seepage or water leakage in the subsequent construction is favorably solved.

Preferably, the method further comprises the following steps:

s9: excavating earthwork in the pit, and pouring a base plate in time: after the construction of the reinforced concrete cushion layers on the two sides of the pit edge is finished and the strength reaches 80% of the designed strength, the construction of digging in the pit is started, a single bucket excavator outside the pit is adopted for digging remotely, the mechanical digging is carried out to the position 20cm above the base in the construction, the rest 20cm of earthwork is dug by a manual method, after the earthwork in the pit is dug, the construction of the steel concrete cushion plate at the designed standard height of the pit bottom and the foundation or basement is immediately carried out, and the thickness and the method of the cushion plate are consistent with the requirements of the base at the pit edge.

Through adopting above-mentioned technical scheme, because during machinery (especially big machinery) operation, it is more violent to the soil body disturbance, and can not accurately dig the basement, the easy super-excavation phenomenon that appears, and the later stage still need backfill the compaction, influences the construction progress, consequently takes excavator excavation upper strata earlier, combines artifical excavation lower floor again, is favorable to avoiding the super-excavation phenomenon to take place, is favorable to accelerating the construction progress.

Preferably, the method further comprises the following steps:

s10: and (3) cutting off the support of the grouting steel pipe penetrating through the basement or the outer wall at intervals: and pouring a plain concrete force transmission belt between the pile and the pit edge cushion layer, cutting off a steel grouting steel pipe support in the underground chamber, sealing, timely plugging micro-expansion concrete and performing waterproof treatment.

By adopting the technical scheme, the force transmission belt is arranged between the pile in the construction method and the pit edge cushion layer, so that partial stress generated by the pile in the construction method due to the support removal of the steel pipe can be transmitted to the cushion layer through the force transmission belt, thereby achieving new stress balance and being beneficial to improving the stability of the pile in the construction method.

Preferably, in S10, when performing waterproofing treatment on the basement floor underpass grouting steel pipe support node, a waterproof sleeve is sleeved on the periphery of the grouting steel pipe, a cavity is formed between the inner side of the waterproof sleeve and the outer side of the grouting steel pipe, and the cavity is filled three times from bottom to top.

By adopting the technical scheme, before the basement bottom plate is poured, the waterproof sleeve is embedded in advance, the waterproof sleeve is sleeved on the outer side of the grouting steel pipe, the cavity is formed, micro-expansion concrete is filled in the cavity, and the concrete expands to a certain extent under the action of the expanding agent during hydration, so that the contraction of the concrete is compensated, the purposes of preventing and treating concrete cracks and improving the waterproof performance of the concrete are achieved, and the probability of water seepage and leakage is favorably reduced.

Preferably, in S10, when performing waterproofing treatment on the support node of the basement wall-penetrating grouting steel pipe, two limiting pipe sleeves are sleeved on the outer circumferential surface of the grouting steel pipe, the spacing length between the limiting pipe sleeves is the thickness of the basement outer wall, water-stopping steel plates are arranged on the inner sides of the two limiting pipe sleeves and the outer circumferential surface of the wall-penetrating grouting steel pipe, then asbestos cement is filled between the two limiting pipe sleeves, the outer circumferential surface of the wall-penetrating steel pipe is coated with the asbestos cement, the outer side of the asbestos cement is coated with a backing material, and then a coating waterproof layer is arranged between the outer side of the limiting pipe sleeve and the outer circumferential surface.

By adopting the technical scheme, the two limiting pipe sleeves are fixed on the peripheral surface of the grouting steel pipe, a gap between the grouting steel pipe and the inner side of the limiting pipe sleeve is blocked by the water stop steel plate, the gap between the grouting steel pipe and the outer side of the limiting pipe sleeve is sealed by the coating waterproof layer, and the peripheral surface of the grouting steel pipe is sequentially covered by asbestos cement and backing materials layer by layer, so that the gap between the wall-penetrating steel pipe and the outer wall of the basement is further reduced, and the problem of water seepage and leakage is improved.

Preferably, the steel pipe outer peripheral face is provided with a plurality of barbs, and is a plurality of barb and a plurality of grout outlet one-to-one, the barb is located and corresponds go out the outer week side in grout outlet.

Through adopting above-mentioned technical scheme for when inserting the steel pipe in the soil body, the barb plays the effect that expands soil, reduces the probability that silt gets into in the slip casting hole and causes slip casting hole jam.

Preferably, the steel pipe is provided with a plurality of cuffs, and in the connection of each reaming bag and the steel pipe, the two cuffs are bound at the two ends of each reaming bag to realize fixation; the distance between the two hoops of the same reaming bag is equal, and the lengths of the reaming bags gradually increase from the top of the steel pipe pile to the tip of the steel pipe pile.

Through adopting above-mentioned technical scheme, make when impressing the slip casting steel pipe with the thick liquid, each reaming bag is strutted, because the length of each reaming bag increases progressively from steel pipe pile top to steel pipe pile tip, but fix the cuff interval homogeneous phase at reaming bag both ends, make the thick liquid strut the back with the reaming bag, the volume after each reaming bag is strutted increases progressively from steel pipe pile top to steel pipe pile tip, and combine to press the thick liquid outside the soil body, can form the slip casting enlarged footing under the narrow width, be favorable to improving soil body and steel pipe lower extreme contact surface, be favorable to improving the stability of steel pipe.

Drawings

Fig. 1 is a schematic view of a pile and grouting steel pipe combined support in an embodiment of the application.

Fig. 2 is an enlarged schematic view at a in fig. 1.

Fig. 3 is a schematic connection diagram of the basement and the steel pipe in the embodiment of the application.

Fig. 4 is an enlarged schematic view at B in fig. 3.

Fig. 5 is an enlarged schematic view at C in fig. 3.

Description of reference numerals: 1. piling in a working method; 11. h-shaped steel; 12. enclosing purlins; 2. a steel pipe; 21. a ferrule; 22. a slurry outlet; 221. a check valve; 23. a barb; 3. a cushion layer; 4. a force transfer belt; 5. a base plate; 6. reaming the bladder; 7. a soil body; 71. a base plate; 711. a waterproof sleeve; 712. micro-expansion concrete; 72. an outer wall; 721. a limiting pipe sleeve; 722. asbestos cement; 723. a backing material; 724. coating a waterproof layer; 725. and (7) a water stop steel plate.

Detailed Description

The present application is described in further detail below with reference to figures 1-5.

Referring to fig. 1 and 2, the embodiment of the application discloses a construction method for supporting a shallow foundation pit by combining a pile 1 of an SMW construction method and a pre-grouting steel pipe 2, which comprises the following steps:

s1: measuring and paying off, digging a groove and positioning.

Referring to fig. 1 and 2, when the pile 1 of the SMW construction method is constructed, an outer enclosure boundary of a foundation pit is determined, and meanwhile, groove drawing and excavation are performed on the position of an inclined strut at the outer side of a reinforced concrete enclosing purlin 12 by taking the elevation of the bottom surface of the reinforced concrete enclosing purlin 12 as a reference, so that a groove is formed, and the difficulty in digging soil at the exposed position of the inclined strut after the inclined strut of a steel pipe 2 is grouted in the later period is avoided; and then carrying out lofting positioning (including stirring construction lofting positioning) and elevation measurement according to the position of the datum point. And excavating a working groove according to the enclosure center line, paving guiding and positioning section steel on two sides of the working groove, and mutually connecting and fixing by spot welding.

S2: and (5) processing the steel pipe 2.

Referring to fig. 1 and 2, a plurality of grout outlet holes 22 distributed along the length direction of the steel pipe 2 are formed in the pipe side of the steel pipe 2, and a layer of reaming bag 6 is bound on the surface of part of the grout outlet holes 22.

Referring to fig. 1 and 2, the steel pipe 2 is a seamless steel pipe 2 having a diameter of 300mm, and is convenient for penetration. The grout outlet 22 is a circular hole, one end of the steel pipe 2 is conical and serves as the pile tip of the steel pipe 2, the grout outlet 22 at the pile body of the steel pipe 2 is circular, and the grout outlet 22 at the pile tip of the steel pipe 2 is long-strip-shaped. Each outlet hole 22 is provided with a check valve 221 for preventing the mud from flowing backward.

Referring to fig. 1 and 2, one layer of reaming bag 6 covers 4 grout outlet holes 22 at the same height of the steel pipe 2, a plurality of hoops 21 are arranged on the outer circumferential surface of the steel pipe 2, and two ends of each layer of reaming bag 6 are bound and fixed on the outer circumferential surface of the steel pipe 2 through one hoop 21. Two cuff intervals of same reaming bag 6 equal, and a plurality of 6 lengths of reaming bag increase gradually from 2 pile tops of steel pipe to 2 pile tips of steel pipe for when 6 of reaming bag are propped open by the thick liquid, each reaming bag 6 is strutted the volume and is increased gradually from 2 pile tops of steel pipe to 2 pile tips of steel pipe.

Referring to fig. 1 and 2, a plurality of grouting holes at the same height between adjacent reaming bags 6 are exposed, barbs 23 are arranged outside the exposed grouting holes, the barbs 23 can be angle irons or arc steel plates, and the barbs 23 are fully welded and fixed with the steel pipe 2. The setting of angle bar for when inserting steel pipe 2 in the soil body 7, barb 23 plays the effect that expands soil, reduces that silt gets into the downthehole and cause the probability that slip casting hole blockked up of slip casting.

S3: positioning a drilling machine, preparing slurry and stirring the slurry.

Referring to fig. 1 and 2, shotcrete and jet drilling are performed while setting a drilling machine in place according to positioning and mixing a uniform cement slurry.

S4: the H-beam 11 is machined and inserted.

Referring to fig. 1 and 2, steel plates are welded and processed into H-shaped steel 11, after the quality is guaranteed to be qualified, the H-shaped steel 11 is hoisted in place and is slowly inserted into stirring slurry, after the H-shaped steel is up to the designed elevation, the H-shaped steel is temporarily fixed in the designed elevation until cement pile soil is hardened, a pile body 1 of the construction method is formed, and then replaced cement slurry is intensively cleaned and recovered before the next process is constructed or before the cement slurry is hardened.

S5: and (3) supporting and enclosing purlin 12 construction by using a front supporting type grouting steel pipe 2.

Referring to fig. 1 and 2, if the lying soil is soft clay or loose sand, the steel pipe 2 is inserted into the soil body 7 by using a pipe sinking and pile pressing mode, and the specific operation is as follows: after the pile driver is in place, the steel pipe 2 is slowly lifted by utilizing lifting equipment, the pile tip of the steel pipe 2 is vertically aligned to the pile position, the steel pipe is slowly placed into the inserting positioning soil, the inclination angle is slowly rotated by taking the pile tip as a fulcrum, when the inclination angle moves to 45 degrees, the pile cap is fixed at the pile top of the steel pipe 2 by utilizing the return portal frame, and meanwhile, the rigging is removed. The distance between the pile cap and the periphery of the pile is 10mm, a corresponding gasket is arranged between the pile cap and the pile top, and the gasket is made of a hard wood board.

Referring to fig. 1 and 2, when the pile pressing begins, a pile cap is buckled, a gasket is padded, the steel pipe 2 is slowly pressed into the soil layer at an inclination angle of 45 degrees by hydraulic pressure, and the inclination angle and deformation of the steel pipe 2 are corrected every 50cm of pressing stroke. And starting the pile pressing oil cylinder to slowly press the steel pipe 2 pile, and controlling the pressing speed to be less than 2m/min until the main body of the steel pipe 2 is pressed into the soil body 7.

Referring to fig. 1 and 2, if the lower lying soil is soil of dense clay or dense sandy soil, a long spiral lead hole construction scheme is adopted because the length of the lead hole exceeds the depth of the foundation pit. The specific operation is as follows: when the pile driver is in place, stably standing and leveling, aligning a drill bit to the pile position, controlling the deviation to be not more than 50mm and controlling the verticality to be within 1%; when drilling begins, the speed is slow firstly and then the speed is fast, the drilling speed is adjusted according to the soil layer condition, and a record is made; after the drill rod is lifted to a preset depth, soil is cleaned, the drill rod is lifted out of the ground, the drill rig is moved away, the soil around the drill hole is cleaned in time to prevent hole collapse, and after hole forming is completed, the long spiral drill rig slowly moves away from the position of the hole edge. And after the hole guiding is finished, pressing the pile immediately without delay. In the pile sinking process, pile sinking pressure and pile sinking speed control are taken into consideration, pressure control is taken as the main point, but the depth of the pile sinking is as close to the designed elevation as possible, and other subsequent steps are implemented according to the flow of the static pressure pile.

Referring to fig. 1 and 2, when the depth of the foundation pit reaches the deep foundation pit pile driving engineering more than twice the width of the foundation pit, pile extension is needed, and pile extension is carried out according to a common pile extension supporting process of a grouting steel pipe 2.

S6: and grouting in a grading stage.

Referring to fig. 1 and 2, the grouting pipe is a long steel pipe 2 with a diameter about 1/10 of the support diameter of the steel pipe 2, the length of the grouting pipe is equal to that of the steel pipe 2, the end of the grouting pipe is connected with grouting equipment, and the grouting pipe is fixed at a position which is 2/3 times of the radius of the support cylinder section of the steel pipe 2 and is symmetrically arranged. For the area with stronger soil layer structure, the distribution density of the grouting pipes can be properly reduced.

Referring to fig. 1 and 2, during grouting, the confined grouting is performed in a segmented manner from bottom to top, the slurry is extruded from the slurry outlet 22, the reaming bag 6 is expanded, and the hoops 21 at the two ends of the reaming bag 6 play a role in bidirectional sealing to ensure good upper and lower sealing, so that the purpose of positioning grouting is realized. The criteria for the final outer side of the slip casting were: the cement consumption of the single steel pipe 2 is not less than the design value or the final grouting pressure is not less than 2 MPa.

Referring to fig. 1 and 2, the steel pipe 2 is grouted from bottom to top, and P.O.42.5 common cement mortar is used as grouting liquid. Grouting for 3 times, and grouting once every 1.5 hours, wherein the water-cement ratio of grouting is controlled to be 0.5-0.6. The cement consumption of a single pile is not less than 3.0 tons, the grouting flow is controlled to be 20-30L/min, and the final grouting completion standard 1 is that the single cement control amount and the final grouting pressure are controlled to be 1.5-2 Mpa.

Referring to fig. 1 and 2, after grouting, pouring a surrounding purlin 12 at the upper end of a pile body 1 in a construction method, and embedding the inclined upper end of a steel pipe 2 in the surrounding purlin 12.

S7: and digging out the earthwork of the cushion layer 3 of the side pit.

Referring to fig. 1 and 2, adopt the excavation mode of layering piecemeal to excavate hole limit soil body 7, because hole limit soil body 7 scope is less, adopt the mode of artifical excavation during the layering excavation, to stereoplasm soil, when artifical excavation is comparatively difficult, choose for use small-size excavator cooperation fortune soil wagon to excavate work, the side excavation adopts symmetrical construction, and the excavation progress part keeps unanimous, to connecting the excavation, adopts the spacer excavation.

Referring to fig. 1 and 2, S8: constructing a prefabricated steel plate, a reinforcing bar cushion layer 3 and a water stop steel plate 725: and when the excavation of the pit edge reaches the designed depth, the construction of the preassembled steel plate is carried out in time. The size of the steel plate is comprehensively determined by calculating the bearing capacity of the composite cement cushion layer 3 and dividing the area range of the foundation pit. And meanwhile, the construction of the cast-in-situ reinforcing steel bar cushion layer 3 on the steel plate is carried out, and the thickness is not more than 200 mm. And then, constructing the basement bottom plate 71 and the outer wall 72, and adding a water stop steel plate 725 at the position where the grouting steel pipe 2 passes through the bottom plate 71 or the surface of the outer wall 72. The problem of water seepage or water leakage is avoided during subsequent construction or delivery.

S9: excavating earth in the pit, pouring a base plate 5 in time,

referring to fig. 1 and 2, after the construction of the reinforced concrete cushion layers 3 on the two sides of the pit edge is finished and the strength reaches 80% of the designed strength, the construction of digging earth in the pit is started, a single bucket excavator outside the pit is adopted to dig earth remotely, the mechanical digging earth is dug to the position 20cm above the base in the construction, the rest 20cm of earth is dug out by a manual method, after the excavation of the earth in the pit, the construction of the steel concrete cushion plate 5 and the foundation or basement at the designed height of the pit bottom is immediately carried out, the thickness and the method of the cushion plate 5 are consistent with the requirements of the base on the pit edge, and for the problem of water seepage of the pit bottom, waterproof measures are required to be made in time, such as waterproof asphalt is laid in the basement, and a water stop steel plate 725 and.

S10: the support of the grouting steel pipe 2 penetrating through the basement or the outer wall 72 is cut at intervals.

Referring to fig. 2 and 3, a plain concrete force transmission belt 4 is poured between the pile 1 and the pit edge cushion layer 3 in the construction method, a steel grouting steel pipe 2 support in an underground chamber is cut off by a cutting machine, sealing is carried out, micro-expansion concrete 712 is timely filled and blocked, and waterproof treatment is carried out.

Referring to fig. 3 and 4, when the support node of the basement floor 71 passing through the grouting steel pipe 2 is subjected to waterproof treatment, a waterproof sleeve 711 is sleeved on the periphery of the grouting steel pipe 2, a cavity is formed between the inner side of the waterproof sleeve 711 and the outer side of the grouting steel pipe 2, and the cavity is filled with micro-expansion concrete 712 for three times from bottom to top.

Referring to fig. 3 and 5, when the support node of the basement wall-through grouting steel pipe 2 is subjected to waterproofing treatment, two limiting pipe sleeves 721 are sleeved on the outer circumferential surface of the grouting steel pipe 2, the spacing length of the limiting pipe sleeves 721 is the thickness of the basement outer wall 72, a water-stop steel plate 725 is arranged on the inner sides of the two limiting pipe sleeves 721 and the outer circumferential surface of the wall-through grouting steel pipe 2, then asbestos cement 722 is filled between the two limiting pipe sleeves 721, the outer circumferential surface of the wall-through grouting steel pipe 2 is coated with the asbestos cement 722, the outer side of the asbestos cement 722 is coated with a backing material 723, and then a coating waterproof layer 724 is arranged between the outer side of.

The above embodiments are preferred embodiments of the present application, and the protection scope of the present application is not limited by the above embodiments, so: all equivalent changes made according to the structure, shape and principle of the present application shall be covered by the protection scope of the present application.

Claims

1. A construction method of a shallow foundation pit of a combined support of a pile and a pre-grouting steel pipe in an SMW construction method is characterized by comprising the following steps: the method comprises the following steps:

s1: measuring and paying off, digging a groove and positioning;

s2: processing a steel pipe: a plurality of grout outlet holes (22) distributed along the length direction of the steel pipe (2) are formed in the pipe side of the steel pipe (2), and a layer of reaming bag (6) is bound on the surface of each grout outlet hole (22);

s4: h-shaped steel processing and inserting: hoisting the H-shaped steel (11) in place, inserting the H-shaped steel into the stirring mud, temporarily fixing the H-shaped steel in the designed elevation after the H-shaped steel reaches the designed elevation until the cement pile soil is hardened, and forming the pile body (1) in the construction method;

s5: and (3) construction of front-supporting type grouting steel pipe support and purlin surrounding: lifting the steel pipe (2), enabling the pile tip of the steel pipe (2) to be vertically aligned with the pile position, slowly putting the steel pipe into the inserting positioning soil, slowly rotating the steel pipe at an inclination angle by taking the pile tip as a fulcrum, and pressing the steel pipe (2) into the soil layer when the inclination angle moves to 45 degrees;

s6: grouting in a grading stage: grouting the upper end of the steel pipe (2), pressing out grout from a grout outlet (22), expanding the reaming bag (6), pouring the surrounding purlin (12) at the upper end of the body of the pile (1) in the construction method, and embedding the inclined upper end of the steel pipe (2) in the surrounding purlin (12).

2. The SMW construction method of claim 1, wherein the pile is combined with a pre-grouting steel pipe to support shallow foundation pit, and the construction method is characterized in that: further comprising the steps of:

s7: digging out side pit cushion earthwork: the excavation mode that adopts the layering piecemeal excavates hole limit soil body (7), adopts the mode of manual excavation during the layering excavation, to stereoplasm soil, chooses for use small-size excavator cooperation fortune native car to excavate work, and the side excavation adopts the symmetry construction, and the excavation progress part keeps unanimous, to connecting the excavation, adopts the spacer block excavation.

3. The SMW construction method of the shallow foundation pit construction method combining the pile with the pre-grouting steel pipe combination support according to claim 2, characterized in that: further comprising the steps of:

s8: constructing prefabricated steel plates, reinforcing bar cushion layers and water stop steel plates: when the excavation of the pit edge reaches the designed depth, the construction of the preassembled steel plate is carried out in time, meanwhile, the construction of a cast-in-place reinforcing bar cushion layer (3) on the steel plate is carried out, then, the construction of a basement bottom plate (71) and an outer wall (72) is carried out, and a water stop steel plate is additionally arranged on the surface of the bottom plate (71) or the outer wall (72) which is supported and penetrated by the grouting steel pipe (2).

4. The SMW construction method of the shallow foundation pit construction method combining the pile with the pre-grouting steel pipe combination support according to claim 2, characterized in that: further comprising the steps of:

s9: excavating earthwork in the pit, and pouring a base plate in time: when the construction of the reinforced concrete cushion layers (3) on the two sides of the pit edge is finished and the strength reaches 80% of the designed strength, the construction of digging in the pit is started, a single bucket excavator outside the pit is adopted for digging remotely, the mechanical digging is carried out to the position 20cm away from the base in the construction, the rest 20cm of earthwork is dug by a manual method, after the earthwork in the pit is dug, the construction of the steel concrete cushion plate (5) at the designed elevation position of the pit bottom and the foundation or basement is immediately carried out, and the thickness and the method of the cushion plate (5) are consistent with the requirements of the base on the pit edge.

5. The SMW construction method of claim 3, wherein the pile is combined with a pre-grouting steel pipe to support shallow foundation pit, and the construction method is characterized in that: further comprising the steps of:

s10: and (3) cutting off the support of the grouting steel pipe penetrating through the basement or the outer wall at intervals: pouring a plain concrete force transmission belt (4) between the pile (1) and the pit edge cushion layer (3), cutting off a steel grouting steel pipe (2) support in an underground chamber, sealing, filling micro-expansion concrete (712) in time and performing waterproof treatment.

6. The SMW construction method of the shallow foundation pit combined supporting by the pile (1) and the pre-grouting steel pipe (2) according to claim 5 is characterized in that: in the S10, when waterproof treatment is performed on the support node of the basement bottom plate (71) passing through the grouting steel pipe (2), a waterproof sleeve (711) is sleeved on the periphery of the grouting steel pipe (2), a cavity is formed between the inner side of the waterproof sleeve (711) and the outer side of the grouting steel pipe (2), and the cavity is filled three times from bottom to top.

7. The SMW construction method of the shallow foundation pit combined supporting by the pile (1) and the pre-grouting steel pipe (2) according to claim 5 is characterized in that: in the step S10, when the support node of the basement wall-penetrating grouting steel pipe (2) is subjected to waterproofing treatment, two limiting pipe sleeves (721) are sleeved on the outer circumferential surface of the grouting steel pipe (2), the spacing length between the limiting pipe sleeves (721) is equal to the thickness of the basement outer wall (72), a water-stop steel plate (725) is arranged on the inner sides of the two limiting pipe sleeves (721) and the outer circumferential surface of the wall-penetrating grouting steel pipe (2), then asbestos cement (722) is filled between the two limiting pipe sleeves (721), the outer circumferential surface of the wall-penetrating grouting steel pipe (2) is coated with asbestos cement (722), the outer side of the asbestos cement (722) is coated with a backing material (723), and then a coating waterproof layer (724) is arranged between the outer sides of the limiting pipe sleeves (721) and.

8. The SMW construction method of claim 1, wherein the pile is combined with a pre-grouting steel pipe to support shallow foundation pit, and the construction method is characterized in that: steel pipe (2) outer peripheral face is provided with a plurality of barbs (23), and is a plurality of barb (23) and a plurality of grout outlet hole (22) one-to-one, barb (23) are located and correspond go out the outer week side of grout outlet hole (22).

9. The SMW construction method of the shallow foundation pit combined supporting by the pile (1) and the pre-grouting steel pipe (2) according to claim 1 is characterized in that: the steel pipe (2) is provided with a plurality of cuffs (21), and in the connection of each reaming bag (6) and the steel pipe (2), the two cuffs (21) are bound at the two ends of the reaming bag (6) to realize fixation; the distance between the two cuffs of the same reaming bag (6) is equal, and the lengths of the reaming bags (6) gradually increase from the pile top of the steel pipe (2) to the pile tip of the steel pipe (2).