CN114250779A

CN114250779A - Foundation pit construction method

Info

Publication number: CN114250779A
Application number: CN202111384419.8A
Authority: CN
Inventors: 俞剑龙
Original assignee: Keyi College of ZSTU
Current assignee: Keyi College of ZSTU
Priority date: 2021-11-22
Filing date: 2021-11-22
Publication date: 2022-03-29
Anticipated expiration: 2041-11-22
Also published as: CN114250779B

Abstract

The invention relates to a foundation pit construction method, which is characterized in that a foundation pit with a pit bottom and a pit opening both positioned in a planned area is dug, a plurality of soil nails are driven into a side plate of the foundation pit to prevent the side plate of the foundation pit from generating landslide, and the soil nails are pulled out after the construction of a set target is completed in the foundation pit. The invention provides a foundation pit construction method capable of effectively preventing the side wall of a foundation pit from landslide, and solves the problem that the side wall of the foundation pit is easy to landslide due to the fact that the foundation pit is not over planned.

Description

Foundation pit construction method

Technical Field

The invention relates to the technical field of building construction, in particular to a foundation pit construction method.

Background

In the construction process of a building, a foundation pit needs to be dug for construction of an underground part. In many construction requirements, the size of the foundation pit does not exceed the area corresponding to the building area of the building (hereinafter referred to as "foundation pit not exceed the plan") and any objects (including ground and underground objects) generated by the building do not exceed the area corresponding to the building area of the building (hereinafter referred to as "parts not exceed the plan") after the building is completed.

Disclosure of Invention

The invention provides a foundation pit construction method capable of effectively preventing the side wall of a foundation pit from landslide, and solves the problem that the side wall of the foundation pit is easy to landslide due to the fact that the foundation pit is not over planned.

The technical problem is solved by the following technical scheme: a foundation pit construction method is characterized in that a foundation pit with a pit bottom and a pit opening both located in a planned area is dug out, a plurality of soil nails are driven into a side plate of the foundation pit to prevent the side plate of the foundation pit from generating landslide, and the soil nails are pulled out after construction of a set target is completed in the foundation pit. According to the technical scheme, the side wall of the foundation pit is nailed with the soil, so that the landslide phenomenon of the side wall of the foundation pit can be effectively prevented. The soil nails can be driven into the land outside the region to generate component over-planning, and the soil nails are pulled out after the construction is completed by the technical scheme, so that the requirement that the components do not exceed the planning can be met.

Preferably, the soil nail comprises a soil nail shell and a soil nail inner core, the soil nail shell comprises two first side plates, two second side plates, a quadrangular nail head and a tip connected to one end of the nail head, the two first side plates are hinged to two opposite sides of the nail head in a one-to-one correspondence manner through first hinge shafts parallel to the first side plates, the two second side plates are hinged to the two first side plates in a one-to-one correspondence manner through second hinge shafts, the two first side plates and the two second side plates form a square accommodating hole in a surrounding manner, the soil nail inner core is inserted into the accommodating hole in a pluggable manner, one end, far away from the accommodating hole, of the soil nail inner core extends out of the accommodating hole, the first side plates can rotate towards the accommodating hole by taking the second hinge shafts as shafts, and the second side plates can rotate towards the accommodating hole by taking the second hinge shafts as shafts; when soil nail is on the lateral wall of foundation ditch first curb plate and second curb plate all stretch out the lateral wall of foundation ditch, and the process of extracting soil nail does: the soil nail inner core is pulled out, the second side plate and the first side plate are rotated towards the accommodating hole, the first side plate and the second side plate are loosened with the soil body as a result of rotation, and the soil nail shell is pulled out. The surface of the soil nail is rough after the soil nail is nailed in, the soil quality is different, the difference of the extraction force is large, the power of the extraction machine is not easy to control (the extraction cannot be carried out after the soil nail is nailed in, the cost is increased), and the extraction is hard. This technical scheme can control the coefficient of friction between soil nail inner core and the soil nail shell (this face can not produce the finish change at the in-process that the soil nail was nailed in) to upper end soil nail inner core can be extracted laborsavingly, and the soil nail shell can be towards the inside removal of shell and throw off with the soil body after the soil nail inner core was extracted, thereby also laborsaving when the soil nail shell was extracted to the upper end.

Preferably, an arc-shaped hole is formed in the end face of one end, connected with the nail head, of the first side plate, an arc-shaped connecting pin penetrating through the arc-shaped hole is arranged on the nail head, the central line of the circle where the arc-shaped hole is located and the central line of the circle where the arc-shaped connecting pin is located are both the axial line of the first hinge shaft, and the depth of the arc-shaped connecting pin inserted into the arc-shaped hole is increased when the first side plate rotates towards the accommodating hole. Can assist the atress through arc connecting pin under the less condition of first hinge for first hinge can not produce when pulling out soil nail shell and warp the damage. And the connection mode of the structure can not only not interfere the rotation of the side plate, but also realize auxiliary resistance.

Preferably, oil grooves are formed in the surfaces of two opposite sides of the soil nail inner core, the inner end of the oil groove on one side surface of the soil nail inner core is communicated with the inner end of the oil groove on the other side surface of the soil nail inner core through a communication oil passage, and the outer end of the oil groove is exposed outside the soil nail shell; when the soil nail is pulled out, the rust loosening agent is injected into the accommodating hole from the oil groove on one side surface of the soil nail inner core and then flows out from the oil groove on the other side surface of the soil nail inner core. Can further ensure that the labor is saved when the inner core of the soil nail is pulled out.

Preferably, when the soil nail inner core is pulled out, the soil nail inner core is pulled out through an inner core pulling-out machine, the inner core pulling-out machine comprises a supporting seat, two clamping mechanisms connected to the supporting seat and a separating and combining mechanism for driving the two clamping mechanisms to be separated and combined, each clamping mechanism comprises a connecting seat, a clamping round roller rotationally connected to the connecting seat and a driving motor connected to the connecting seat and used for driving the clamping round roller to rotate, a connecting column extending along the two clamping mechanisms in the respective directions is arranged on the connecting seat, the connecting column penetrates through one end of a supporting arm, the other end of the supporting arm is connected with the supporting seat, and the extending direction of the clamping roller is perpendicular to the distribution direction of the two clamping mechanisms; the process of extracting the soil nail inner core through the inner core extractor comprises the following steps: the two clamping structures are supported on two opposite side surfaces of the soil nail inner core in a one-to-one correspondence mode through the clamping rollers, the supporting seat is supported on the side wall of the foundation pit where the soil nail is located, the two clamping structures are driven to be clamped on the soil nail inner core through the split-combination structure, the driving motor drives the clamping circular rollers to rotate, the rotating directions of the clamping circular rollers on the two clamping structures are opposite, and the clamping circular rollers rotate to drive the soil nail inner core and the soil nail shell to be pulled out; after the soil nail inner core is extracted, the first side plate and the second side plate are rotated towards the accommodating hole, so that the first side plate and the second side plate are loosened with the soil, and finally the soil nail shell is extracted. When the soil nail inner core is pulled out, the pulling-out mechanism does not need to extend along with the increase of the pulling-out length of the soil nail inner core, and if the pulling-out mechanism is a mode of pulling out the soil nail inner core by extending the cylinder, the bending problem is easy to occur because the extension is in the horizontal direction.

Preferably, the supporting seat is provided with a hanging through hole, and the soil nail shell is arranged in the hanging through hole in a penetrating mode in the process that the inner core of the soil nail is pulled out by the inner core pulling machine. The inner core puller is convenient to fix on the inclined wall.

Preferably, the dividing and combining structure comprises two cylinders; the connecting seat of one clamping structure is connected with the cylinder body of the air cylinder, and the connecting seat of the other clamping structure is connected with the piston rod of the air cylinder; the soil nail is positioned between the two air cylinders in the process of extracting the soil nail inner core by the inner core extractor. The structure is reduced, and the clamping is stable and reliable.

Preferably, one clamping structure is provided with two clamping circular rollers, the driving motor is a double-end motor, driven gears are arranged at two ends of each clamping circular roller, driving gears are arranged on two power output shafts of the driving motor, the driving gears are meshed with two intermediate gears, the two intermediate gears are meshed with the driven gears on the two clamping circular rollers in a one-to-one correspondence mode, and the driven gears are rotatably connected to intermediate gear connecting plates connected with the connecting seat. The stability of supporting on the soil nail inner core when the clamping structure uses can be improved.

Preferably, oil grooves are formed in the surfaces of two opposite sides of the soil nail inner core, the inner end of the oil groove on one side surface of the soil nail inner core is communicated with the inner end of the oil groove on the other side surface of the soil nail inner core through a communication oil passage, the outer end of the oil groove is exposed outside the soil nail outer shell, and the oil groove is sealed by the soil nail outer shell to form an oil hole; the inner core pulling-out machine also comprises a rust loosening agent storage tank with a recovery opening and an oil pump with an inlet end connected with the rust loosening agent storage tank, wherein the outlet end of the oil pump is connected with one end of an output main pipe, and the other end of the output main pipe is connected with a plurality of nozzles; in the process of extracting the soil nail inner core by the inner core extractor, the spray heads are inserted into the oil holes on one side surface of the soil nail inner core in a one-to-one correspondence mode, the oil pump enables the rust loosening agent in the rust loosening agent storage tank to be sprayed out from the spray heads to enter the oil holes, and the recovery port is in butt joint with the outer end of the oil hole on the other side surface of the soil nail inner core to receive the flowing rust loosening agent. Can save more labor when being pulled out.

The invention also comprises a temperature detection switch for detecting the temperature of the clamping round roller, and the oil pump is started when the temperature detection switch detects that the temperature of the clamping round roller reaches a set value; each clamping circular roller is provided with the temperature detection switch, and all the temperature detection switches are connected together in parallel; the temperature detection switch comprises an annular cavity which is arranged in the clamping round roller and extends along the circumferential direction of the clamping round roller and a lead hole which is arranged at the center of the clamping roller and extends along the axial direction of the clamping roller, a movable conducting ring and two fixed conducting rings are arranged in the annular cavity, the movable conducting ring is electrically connected with the fixed conducting rings through a conducting spring, the annular cavity is filled with paraffin, the movable conducting ring is isolated from the other fixed conducting ring under the isolation action of paraffin, the paraffin is melted when the temperature of the clamping round roller reaches a set value, the movable conducting ring is pressed on the other fixed conducting ring under the action of the conducting spring after the paraffin is melted so as to conduct the two fixed conducting rings, the two fixed conducting rings are correspondingly connected with the two electric brushes one by one through conducting wires, two conductive rods penetrate through the lead hole, and the two electric brushes are in conductive abutting connection with the two conductive rods in a one-to-one correspondence mode. Whether can conveniently learn centre gripping circle roller and produce the phenomenon of skidding, the resistance that the explanation meets after skidding is big, injects the pine rust agent this moment, can reduce the joining force between soil nail inner core and the soil nail shell and reduce the load of inner core pulling-out machine to avoid tasteless injection pine rust agent.

Preferably, the clamping roller is of a metal structure, the fixed conducting ring is fixed in the annular cavity through heat-conducting insulating glue, the electric brush is fixed with the clamping round roller in an insulating mode, and the movable conducting ring is suspended in the annular cavity through the conducting spring. A quick response to the slip can be achieved.

Preferably, the conducting rod is suspended and arranged in the lead hole.

Preferably, one of the current-conducting rods is arranged in the other current-conducting rod in a penetrating mode, and the two current-conducting rods are connected together in an insulating mode. Compact structure, the fixed conducting rod of overall arrangement is convenient.

Preferably, the fixed conductive rings are provided with a plurality of conductive pins, and after paraffin is melted, the movable conductive rings are pressed on the other fixed conductive ring through the contact of the conductive pins and the fixed conductive ring under the action of the conductive springs. The convenience of electrically connecting the movable conductive ring and the other conductive ring can be improved.

The invention has the following advantages: the foundation pit is not over-planned and the components are not over-planned, and the landslide phenomenon of the foundation pit can be effectively prevented; labor is saved when the soil nail is pulled out; whether the soil nail is pulled out in the process of pulling out can be conveniently and accurately known, and lubrication is needed; the part that the centre gripping soil nail was extracted need not move along with the soil nail, also can conveniently extract and lubricate when the soil nail is longer, is equivalent to the mode of prior cylinder hydro-cylinder extension extract, does not have the drippage phenomenon to produce, and the feature of environmental protection is better, the compacter of structure.

Drawings

FIG. 1 is a schematic view illustrating a foundation pit constructed according to the present invention;

FIG. 2 is an axial cross-sectional view of the soil nail;

FIG. 3 is an enlarged view of a portion of FIG. 2 at A;

FIG. 4 is a schematic front view of a soil nail;

FIG. 5 is an enlarged partial schematic view of FIG. 4 at B;

FIG. 6 is a schematic view of a perspective of the inner core puller for pulling out the soil nails;

FIG. 7 is an enlarged partial schematic view of FIG. 6;

FIG. 8 is a schematic view of another perspective of the inner core puller for pulling out the soil nails;

FIG. 9 is a schematic view showing the connection among the nipping roller, the temperature detecting switch and the oil pump;

fig. 10 is a partially enlarged schematic view at C of fig. 9.

In the figure: the pit bottom 1, the pit opening 2, the foundation pit 3, the side wall 4 of the foundation pit, the soil nail 5, the inner core puller 6, the soil nail inner core 7, the first side plate 8, the second side plate 9, the nail head 10, the pointed end 11, the first hinge shaft 12, the second hinge shaft 13, one end 14 of the soil nail inner core far away from the lamp cap, the arc-shaped hole 15, the arc-shaped connecting pin 16, the oil groove 17, the communicating oil duct 18, the oil hole 19, the supporting seat 20, the opening and closing mechanism 21, the connecting seat 22, the clamping round roller 23, the driving motor 24, the connecting column 25, the supporting arm 26, the air cylinder 27, the driven gear 28, the power output shaft 29, the driving gear 30, the intermediate gear 31, the intermediate gear connecting plate 32, the recycling opening 33, the rust loosening agent storage tank 34, the oil pump 35, the output main pipe 36, the spray head 37, the power supply 38, the annular cavity 39, the lead wire hole 40, the movable conductive ring 41, the first conductive ring 42, the second conductive ring 43, the conductive spring 44, the paraffin 45, the conductive needle 46, the soil nail puller, The device comprises a lead 47, a brush 48, a first conductive rod 49, a second conductive rod 50, heat-conducting insulating glue 51, a reset rod 52 and a soil nail shell 53.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1 to 10, in a foundation pit construction method, a foundation pit 3 in which a pit bottom 1 and a pit opening 2 are both located in a planned area is dug, a plurality of soil nails 5 are driven into a side wall 4 of the foundation pit to prevent a side plate of the foundation pit from sliding, and the soil nails are removed after construction of a set target is completed in the foundation pit.

The soil nail comprises a soil nail outer shell 53 and a soil nail inner core 7, wherein the soil nail outer shell comprises a first side plate 8, a second side plate 9, a quadrangular prism-shaped nail head 10 and a sharp head 11 connected to one end of the nail head, and the nail head and the sharp head are integrally formed together. First curb plate has two, and two first curb plates articulate on the both sides that the pin fin is relative through the 12 one-to-one ground of first hinge with first curb plate parallel, and the second curb plate has two, and two second curb plates articulate on two first curb plates through second hinge 13 one-to-one ground first curb plate and two the second curb plate encloses into square accommodation hole, and the soil nail inner core can be pulled out and is worn to establish in the accommodation hole with inserting. One end 14, far away from the lamp holder, of the soil nail inner core extends out of the accommodating hole, the first side plate can rotate towards the accommodating hole by taking the second hinge shaft as an axis, and the second side plate can rotate towards the accommodating hole by taking the second hinge shaft as an axis; be equipped with arc hole 15 on the terminal surface of the one end that first curb plate is connected with the pin fin, be equipped with the arc connecting pin 16 of wearing to establish in the arc hole on the pin fin, the central line of the circle that the arc hole was located and the central line of the circle that the arc connecting pin was located all do the axis of first hinge, when first curb plate orientation accommodation hole internal rotation the arc connecting pin inserts the downthehole degree of depth of arc increases. And when the soil nails are nailed on the side wall of the foundation pit, the first side plate and the second side plate extend out of the side wall of the foundation pit.

The two opposite side surfaces of the soil nail inner core are provided with oil grooves 17, and particularly the oil grooves are positioned on the upper side surface and the lower side surface of the soil nail inner core when in use. The inner end of the oil groove on one side surface of the soil nail inner core is communicated with the inner end of the oil groove on the other side surface of the soil nail inner core through a communication oil passage 18, the outer end of the oil groove is exposed outside the soil nail shell, and the oil groove is sealed by the soil nail shell to form an oil hole 19.

The invention is also provided with an inner core puller 6, wherein the inner core puller comprises a supporting seat 20, two clamping mechanisms connected to the supporting seat and a separating and combining mechanism 21 for driving the two clamping mechanisms to separate and combine. When in use, the two clamping structures are distributed along the up-and-down direction. The clamping mechanism comprises a connecting seat 22, a clamping round roller 23 rotationally connected to the connecting seat and a driving motor 24 connected to the connecting seat and driving the clamping round roller to rotate, a connecting column 25 extending along the two clamping mechanisms in the respective directions is arranged on the connecting seat, the connecting column penetrates through one end of a supporting arm 26, and the other end of the supporting arm is connected with the supporting seat. The extending direction of the clamping roller is perpendicular to the distribution direction of the two clamping mechanisms. The supporting seat is provided with a hanging through hole, and the soil nail shell is arranged in the hanging through hole in a penetrating way in the process of pulling out the soil nail inner core by the inner core pulling machine. The split-combination structure comprises two cylinders 27; the connecting seat of one clamping structure is connected with the cylinder body of the air cylinder, and the connecting seat of the other clamping structure is connected with the piston rod of the air cylinder; the soil nail is positioned between the two air cylinders in the process of extracting the soil nail inner core by the inner core extractor. A clamping structure is equipped with two centre gripping circle rollers, and driving motor is double-end motor, and the both ends of centre gripping circle roller all are equipped with driven gear 28, all is equipped with driving gear 30 on two power output shaft 29 of driving motor, and the driving gear is in the same place with the meshing of two intermediate gear 31, and two intermediate gear one-to-one ground are in the same place with the driven gear meshing on two centre gripping circle rollers, and driven gear rotates to be connected on the intermediate gear connecting plate 32 that links together with the connecting seat. The inner core pulling machine also comprises a rust loosening agent storage tank 34 with a recovery port 33 and an oil pump 35 with an inlet end connected with the rust loosening agent storage tank, wherein the outlet end of the oil pump is connected with one end of an output main pipe 36, and the other end of the output main pipe is connected with a plurality of nozzles 37.

Each clamping round roller is provided with a temperature detection switch for detecting the temperature of the clamping round roller, and the clamping round rollers are of metal structures. All the temperature detection switches are connected together in parallel. The temperature detection switch and the oil pump are connected in series to the power source 38, and the oil pump is started when the temperature detection switch detects that the temperature of the nipping roller reaches a set value. The temperature detection switch comprises an annular cavity 39 arranged in the clamping roller and extending along the circumferential direction of the clamping roller and a lead hole 40 arranged in the center of the clamping roller and extending along the axial direction of the clamping roller. The annular cavity is provided with a movable conducting ring 41 and two fixed conducting rings, namely a first fixed conducting ring 42 and a second fixed conducting ring 43. The movable conducting ring is electrically connected with the first fixed conducting ring through a conducting spring 44, and the annular cavity is filled with paraffin 45, wherein the melting point of the paraffin in the embodiment is 60 ℃. When the paraffin is solid, the movable conductive ring is isolated from the second fixed conductive ring under the paraffin isolation effect. The fixed conductive ring is provided with a plurality of conductive pins 46.

The two fixed conductive rings are connected to the two brushes 48 through the wires 47 in a one-to-one correspondence. Two conductive rods are arranged in the lead holes in a penetrating manner, wherein the two conductive rods are respectively a first conductive rod 49 and a second conductive rod 50. The first conductive rod penetrates through the second conductive rod, and the two conductive rods are connected together in an insulated mode. The two brushes are in one-to-one correspondence and are in conductive abutting connection with the two conductive rods. The fixed conductive ring is fixed in the annular cavity through heat-conducting insulating glue 51, and the electric brush and the clamping round roller are fixed together in an insulating mode. The movable conducting ring is suspended in the annular cavity through a conducting spring. The conductive rod is suspended and penetrated in the lead hole. When the temperature of the clamping roller is raised to melt the paraffin, the conducting ring is moved under the action of the conducting spring and is contacted with the second fixed conducting ring through the conducting needle, and the second fixed conducting ring is pressed on the second fixed conducting ring. The movable conducting ring is also provided with a reset rod 52 which penetrates out of the clamping round roller. When paraffin melts and produces two and decide the conducting ring and switch on the back and need reset and when reseing, be in the fused state at paraffin and move the conducting ring through the release link drive and make conducting pin decide the conducting ring disconnection and the drive spring energy storage with the second, then cooling centre gripping circle roller makes paraffin solidification, unclamp after the solidification to the drive action of release link can.

The process of pulling out the soil nails comprises the following steps: the soil nail inner core is pulled out, the second side plate and the first side plate are rotated towards the accommodating hole, the first side plate and the second side plate are loosened with the soil body as a result of rotation, and the soil nail shell is pulled out. The soil nail is pulled out through the inner core pulling machine, and the process of pulling out the soil nail inner core is as follows: the two clamping structures are supported on two opposite side faces of the soil nail inner core through the clamping rollers in a one-to-one correspondence mode, the supporting seat is supported on the side wall of a foundation pit where the soil nail is located, the two clamping structures are driven to be clamped on the soil nail inner core through the split-combination structure, the driving motor drives the clamping round rollers to rotate, the rotating directions of the clamping round rollers on the two clamping structures are opposite, and the rotating result of the clamping round rollers is that the clamping round rollers are driven to be pulled out of the soil nail inner core and the soil nail shell. In the process of extracting the soil nail inner core by the inner core extractor, the spray heads are inserted into the oil holes on one side surface of the soil nail inner core in a one-to-one correspondence manner, and the recovery ports are butted with the outer ends of the oil holes on the other side surface of the soil nail inner core. If reasons such as corrosion lead to the soil nail inner core to link together with the soil nail shell and the resistance when big, the centre gripping circle roller can skid, and the structure of skidding is that the centre gripping circle roller generates heat and the temperature rises, rises to paraffin melting back oil pump and starts, and the oil pump makes the agent of loosing rust in the agent of loosing rust storage tank come into the oilhole from the shower nozzle blowout and retrieve the mouth and catch the agent of loosing rust storage tank of commemorative day.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A foundation pit construction method is characterized in that a foundation pit with a pit bottom and a pit opening both located in a planned area is dug out, a plurality of soil nails are driven into a side plate of the foundation pit to prevent the side wall of the foundation pit from generating landslide, and the soil nails are pulled out after construction of a set target is completed in the foundation pit.

2. The foundation pit construction method according to claim 1, wherein the soil nails comprise a soil nail outer shell and a soil nail inner core, the soil nail shell comprises a first side plate, a second side plate, a quadrangular prism-shaped nail head and a pointed end connected to one end of the nail head, wherein the number of the first side plate is two, the two first side plates are hinged on two opposite sides of the nail head in a one-to-one correspondence manner through first hinge shafts parallel to the first side plates, the number of the second side plates is two, the two second side plates are hinged on the two first side plates in a one-to-one correspondence manner through second hinge shafts, and the two first side plates and the two second side plates form a square accommodating hole in a surrounding manner, the soil nail inner core is arranged in the accommodating hole in a pluggable and insertable manner, one end, far away from the accommodating hole, of the soil nail inner core extends out of the accommodating hole, the first side plate can rotate towards the accommodating hole by taking the second hinge shaft as an axis, and the second side plate can rotate towards the accommodating hole by taking the second hinge shaft as an axis; when soil nail is on the lateral wall of foundation ditch first curb plate and second curb plate all stretch out the lateral wall of foundation ditch, and the process of extracting soil nail does: the soil nail inner core is pulled out, the second side plate and the first side plate are rotated towards the accommodating hole, the first side plate and the second side plate are loosened with the soil body as a result of rotation, and the soil nail shell is pulled out.

3. The foundation pit construction method according to claim 2, wherein an arc-shaped hole is formed in an end face of one end of the first side plate, which is connected with the nail head, an arc-shaped connecting pin penetrating through the arc-shaped hole is formed in the nail head, a center line of a circle in which the arc-shaped hole is formed and a center line of a circle in which the arc-shaped connecting pin is formed are both axial lines of the first hinge shaft, and the depth of the arc-shaped connecting pin inserted into the arc-shaped hole is increased when the first side plate rotates towards the accommodating hole.

4. The foundation pit construction method according to claim 2 or 3, wherein oil grooves are formed in the surfaces of two opposite sides of the soil nail inner core, the inner ends of the oil grooves on one side surface of the soil nail inner core are communicated with the inner ends of the oil grooves on the other side surface of the soil nail inner core through a communication oil passage, and the outer ends of the oil grooves are exposed outside the soil nail outer shell; when the soil nail is pulled out, the rust loosening agent is injected into the accommodating hole from the oil groove on one side surface of the soil nail inner core and then flows out from the oil groove on the other side surface of the soil nail inner core.

5. The foundation pit construction method according to claim 2 or 3, wherein the soil nail inner core is pulled out by an inner core pulling-out machine when being pulled out, the inner core pulling-out machine comprises a supporting seat, two clamping mechanisms connected to the supporting seat and a separating and combining mechanism for driving the two clamping mechanisms to be separated and combined, the clamping mechanisms comprise a connecting seat, a clamping round roller rotationally connected to the connecting seat and a driving motor connected to the connecting seat and driving the clamping round roller to rotate, the connecting seat is provided with a connecting column extending along the two clamping mechanisms in the respective directions, the connecting column is arranged at one end of a supporting arm in a penetrating manner, the other end of the supporting arm is connected with the supporting seat, and the extending direction of the clamping roller is perpendicular to the distribution direction of the two clamping mechanisms; the process of extracting the soil nail inner core through the inner core extractor comprises the following steps: the two clamping structures are supported on two opposite side surfaces of the soil nail inner core in a one-to-one correspondence mode through the clamping rollers, the supporting seat is supported on the side wall of the foundation pit where the soil nail is located, the two clamping structures are driven to be clamped on the soil nail inner core through the split-combination structure, the driving motor drives the clamping circular rollers to rotate, the rotating directions of the clamping circular rollers on the two clamping structures are opposite, and the clamping circular rollers rotate to drive the soil nail inner core and the soil nail shell to be pulled out; after the soil nail inner core is extracted, the first side plate and the second side plate are rotated towards the accommodating hole, so that the first side plate and the second side plate are loosened with the soil, and finally the soil nail shell is extracted.

6. The foundation pit construction method according to claim 5, wherein the supporting seat is provided with a hanging through hole, and the soil nail outer shell is arranged in the hanging through hole in the process of pulling out the soil nail inner core by the inner core pulling machine.

7. The foundation pit construction method according to claim 5, wherein the split-combination structure comprises two air cylinders; the connecting seat of one clamping structure is connected with the cylinder body of the air cylinder, and the connecting seat of the other clamping structure is connected with the piston rod of the air cylinder; the soil nail is positioned between the two air cylinders in the process of extracting the soil nail inner core by the inner core extractor.

8. The foundation pit construction method according to claim 5, wherein one clamping structure is provided with two clamping circular rollers, the driving motor is a double-head motor, driven gears are arranged at two ends of each clamping circular roller, driving gears are arranged on two power output shafts of the driving motor, the driving gears are meshed with two intermediate gears, the two intermediate gears are meshed with the driven gears on the two clamping circular rollers in a one-to-one correspondence manner, and the driven gears are rotatably connected to an intermediate gear connecting plate connected with a connecting seat.

9. The foundation pit construction method according to claim 5, wherein oil grooves are formed in the surfaces of two opposite sides of the soil nail inner core, the inner ends of the oil grooves on one side surface of the soil nail inner core are communicated with the inner ends of the oil grooves on the other side surface of the soil nail inner core through a communication oil passage, the outer ends of the oil grooves are exposed outside the soil nail outer shell, and the oil grooves are sealed by the soil nail outer shell to form oil holes; the inner core pulling-out machine also comprises a rust loosening agent storage tank with a recovery opening and an oil pump with an inlet end connected with the rust loosening agent storage tank, wherein the outlet end of the oil pump is connected with one end of an output main pipe, and the other end of the output main pipe is connected with a plurality of nozzles; in the process of extracting the soil nail inner core by the inner core extractor, the spray heads are inserted into the oil holes on one side surface of the soil nail inner core in a one-to-one correspondence mode, the oil pump enables the rust loosening agent in the rust loosening agent storage tank to be sprayed out from the spray heads to enter the oil holes, and the recovery port is in butt joint with the outer end of the oil hole on the other side surface of the soil nail inner core to receive the flowing rust loosening agent.

10. The foundation pit construction method according to claim 9, further comprising a temperature detection switch for detecting a temperature of the clamp roller, wherein the oil pump is started when the temperature detection switch detects that the temperature of the clamp roller reaches a set value; each clamping circular roller is provided with the temperature detection switch, and all the temperature detection switches are connected together in parallel; the temperature detection switch comprises an annular cavity which is arranged in the clamping round roller and extends along the circumferential direction of the clamping round roller and a lead hole which is arranged at the center of the clamping roller and extends along the axial direction of the clamping roller, a movable conducting ring and two fixed conducting rings are arranged in the annular cavity, the movable conducting ring is electrically connected with the fixed conducting rings through a conducting spring, the annular cavity is filled with paraffin, the movable conducting ring is isolated from the other fixed conducting ring under the isolation action of paraffin, the paraffin is melted when the temperature of the clamping round roller reaches a set value, the movable conducting ring is pressed on the other fixed conducting ring under the action of the conducting spring after the paraffin is melted so as to conduct the two fixed conducting rings, the two fixed conducting rings are correspondingly connected with the two electric brushes one by one through conducting wires, two conductive rods penetrate through the lead hole, and the two electric brushes are in conductive abutting connection with the two conductive rods in a one-to-one correspondence mode.