CN110984171A

CN110984171A - Steel pipe pile grouting combined waist beam anchor rod supporting method

Info

Publication number: CN110984171A
Application number: CN201911168778.2A
Authority: CN
Inventors: 李树敬
Original assignee: Fourth Engineering Co Ltd of China Railway 14th Bureau Co Ltd
Current assignee: Fourth Engineering Co Ltd of China Railway 14th Bureau Co Ltd
Priority date: 2019-11-25
Filing date: 2019-11-25
Publication date: 2020-04-10

Abstract

The invention relates to the technical field of supporting engineering, in particular to a supporting method of a steel pipe pile grouting combined waist beam anchor rod. The foundation pit support adopts a steel pipe pile, waist beam and self-drilling anchor rod support form; the method comprises the steps of constructing a steel pipe pile and a pile top connecting beam before excavation of a foundation pit, enabling a firm soft soil layer to form a whole, then implementing a self-drilling anchor rod in the excavation process, directly fixing an anchor of the self-drilling anchor rod on a waist beam structure, enabling the anchor rod and the waist beam to jointly bear the load of a reinforcing structure, connecting the anchor rod through the waist beam, transmitting the anchoring force of the anchor rod to a slope body, changing the stress state of the slope body, improving the self-stability capability of the slope body, hanging a phi 8 steel bar net piece on the slope surface and sealing C20 concrete, and arranging drain holes in a 2-3m quincunx shape on the slope surface. The soil retaining structure with large thickness and good rigidity is formed, the traditional soil retaining structure of row piles and continuous walls is replaced, and the process is relatively simple.

Description

Steel pipe pile grouting combined waist beam anchor rod supporting method

Technical Field

The invention relates to the technical field of supporting engineering, in particular to a method for supporting a steel pipe pile by grouting and combining a waist beam anchor rod.

Background

At present, a method for supporting loose and broken soil bodies and deep foundation pit side slopes difficult to form holes under complex geological conditions is to support a cast-in-situ bored pile and a prestressed anchor rod, and the cast-in-situ bored pile and the prestressed anchor rod form a binary soil retaining enclosure structure through a surrounding beam. The supporting system controls the deformation of the foundation pit through the integral rigidity. Retaining soil is carried out through the bored concrete pile on the one hand, and on the other hand, the power transmission that bears supporting construction through the prestressed anchorage pole is for stable ground, and through applying tensile stress to the stock, frictional force between the anchor body and the soil body, stock and the anchor body hold the combined action of strong and stock intensity, make the anchor system remain stable. The support mode has the defects of high construction noise, difficulty in treating slurry, easiness in hole collapse, drill clamping, drill falling, difficulty in hole forming, long construction period and the like in the prestressed anchor rod construction.

Disclosure of Invention

Aiming at the defects of a deep foundation pit supporting method that the anchor rod construction in loose and broken soil is easy to collapse and difficult to form holes in the prior art, the invention provides a supporting method of a steel pipe pile grouting combined waist beam anchor rod, and aims to solve the technical problems.

The technical scheme of the invention is as follows:

a steel pipe pile grouting and waist beam anchor rod combined supporting method is characterized in that a foundation pit support adopts a steel pipe pile, waist beam and self-drilling anchor rod support mode; the method comprises the steps of constructing a steel pipe pile and a pile top connecting beam before excavation of a foundation pit, enabling a firm soft soil layer to form a whole, then implementing a self-drilling anchor rod in the excavation process, directly fixing an anchor of the self-drilling anchor rod on a waist beam structure, enabling the anchor rod and the waist beam to jointly bear the load of a reinforcing structure, connecting the anchor rod through the waist beam, transmitting the anchoring force of the anchor rod to a slope body, changing the stress state of the slope body, improving the self-stability capability of the slope body, hanging a phi 8 steel bar net piece on the slope surface and sealing C20 concrete, and arranging drain holes in a 2-3m quincunx shape on the slope surface.

Further, the method for supporting the steel pipe pile by grouting and combining the waist beam anchor rod specifically comprises the following steps: the method comprises the steps of steel pipe pile slope top reinforcement, self-drilling anchor rod construction, net hanging concrete spraying and water drainage hole construction, waist beam construction, foundation pit monitoring technology and analysis.

Further, the steel pipe pile slope top reinforcing step comprises steel pipe pile construction and pile top connecting beam construction, and specifically comprises the following steps:

(1) steel pipe pile construction process

Leveling the field → measuring and paying off → drilling (drilling with a pipe) and cleaning the hole → manufacturing steel pipe → drilling under the steel pipe → pulling out the pipe → grouting;

(2) pile top connection beam construction process flow;

cleaning a field → measuring and paying-off → erecting a mold → binding reinforcing steel bars → pouring concrete, before the construction of the connecting beam, checking the pile head of the steel pipe pile, and anchoring the steel pipe pile into the connecting beam to a depth meeting the design requirement.

Further, the drilling in the steel pipe pile construction process is specifically operated as follows: drilling: a Hami 90 drilling machine drills holes, and the drilling mode adopts the whole-process pipe following drilling (the outer diameter of the pipe following is 198mm, and the wall thickness is 8 mm); the steel pipe is a seamless steel pipe with the outer diameter phi of 168mm and the wall thickness of 5 mm; the connecting steel pipe is a seamless steel pipe with the outer diameter phi of 140mm and the wall thickness of 5mm, the lap joint length of each end is 50cm, the total length is 1m, the connecting steel pipe is welded with the seamless steel pipe of the pile body, the center of the connecting steel pipe is welded thoroughly, the two ends of the connecting steel pipe are spot-welded by drilling holes at 120 degrees, phi 8 steel bars are used as locators at the periphery of the steel pipe, one locator is welded at each 3-4m position, each locator consists of 3 locators, and the locators are uniformly distributed around the steel pipe; the bottom supporting steel bar is made into an L shape by 2 steel bars with the diameter of 20 mm, the height of the L shape is 20cm, 10cm is welded with the steel pipe, and the lower part of the L shape extends by 8 cm; when the steel pipe is manufactured, welding must be reliable and meet relevant quality technical requirements, and when the steel pipe is manufactured, the welding must be strictly performed according to design and specifications.

Further, the concrete operation of grouting in the steel pipe pile construction process is as follows: grouting is carried out by adopting a hole bottom slurry returning method, and the grouting process of each hole is continuously completed once; placing a grouting pipe (model: phi 25PE grouting pipe) and a steel pipe to the bottom of a hole, grouting at the bottom of the hole by adopting M30 cement mortar, wherein the grouting pressure is 0.6-0.8MPa, and the water-cement ratio of the grout is controlled to ensure that the grouting is full and compact, and the grouting pipe and the steel pipe are stirred uniformly strictly according to the mixing ratio and are used along with the grouting; in order to prevent the phenomena of pile breaking, mud clamping, pipe blocking and the like, the filling process and operation are well controlled, ordered pipe drawing and continuous grouting are the keys for ensuring the pile-forming quality, the grouting speed is proper, and water and mortar in holes are not easy to discharge at too high speed to form broken piles; all indexes of the cement mortar meet the requirements, test pieces are made in time for standard maintenance, and a laboratory is used for carrying out a compressive strength test after the specified maintenance age is reached.

Further, the self-drilling type anchor rod construction steps are as follows:

the self-drilling anchor rod construction process flow is as follows: drilling hole positioning → drilling machine positioning → self drilling → installation of a grout stop plug → grouting → net hanging and concrete spraying + drainage hole construction → waist beam construction → installation of a base plate and a nut.

Further, the self-drilling anchor bolt application tool operates to: the drilling machine adopts a QZJ-100D down-the-hole drilling machine, the air compressor adopts Attapulgite CA160-130, and the self-drilling anchor rod adopts a phi 32 anchor rod; the front end of the anchor rod is provided with an alloy drill bit, and a power joint of the drilling machine is connected with the self-drilling anchor rod through a connector to carry out rotary drilling; the self-drilling anchor rod grouting adopts a pure pressure type grouting process of directly connecting an orifice and an anchor rod, and grouting is performed from a self-drilling anchor rod center hole, wherein the slurry ratio is as follows: water: ash: and (3) sand is 0.6:1:0.3, grout returns to the orifice from the bottom of the hole along the space between the anchor rod and the hole wall after the grout reaches the bottom of the hole through the center hole of the self-drilling anchor rod, and the standard of grouting completion is as follows: when the anchor rod pore canal is fully filled, the grouting can be finished when the concentration of the returned grout is basically consistent with that of the entering grout.

Further, the construction steps of the concrete spraying and water draining holes of the hanging net specifically comprise: the concrete-spraying steel bar net piece of the hanging net adopts phi 8 steel bars, the distance between the transverse direction and the vertical direction is 20cm, the hanging net and the anchor rod are connected by a welding method, the concrete-spraying is C20 concrete, the spraying thickness is 8cm, the distance between the water outlet holes arranged on the slope surface is preferably 2-3m and is preferably arranged according to a quincunx shape, the water outlet holes of the rock slope are preferably arranged at the parts with serious crack development, potential fracture surfaces and water seepage, the parts are phi 48PVC pipes, the length is 600mm, the exposed part is 200mm, the outward-inclined gradient is not less than 5%, and the water inlet side of the water outlet hole is provided with 2 layers.

Further, the steps of the waist rail construction of the invention are as follows: the wale is welded by 20 channel steel and double channel steel, and the uniform gap of the wale is ensured during welding; the waist beam is required to be tightly close to the slope surface, and the whole waist beam is fixedly connected; performing rust prevention treatment on the anchor rod head; the anchor rod head screw is screwed up and then must be welded with the anchor rod, so that the nut is prevented from falling off.

Further, the foundation pit monitoring technology and the analysis steps of the invention specifically comprise:

in order to ensure the safety of engineering construction and the normal use of a near-edge building, the whole process is monitored, the monitoring content comprises the change conditions of the slope top surface of a foundation pit, pipelines, a building (structure) and the axial force of an anchor rod, dynamic deformation values caused by the construction stage of each main process are measured in time and compared with analysis calculated values, and the dynamic deformation values are fed back to guide design and construction in time. See table 1 below for the main monitoring.

Table 1 summary of monitoring items

The slope stability condition can be timely mastered through the monitoring mode. Through deformation observation and analysis, the deformation of the foundation pit does not reach the control value required by the specification, and after the slope support construction is finished, through continuous displacement and settlement observation, the displacement and settlement change are basically avoided, and the slope is stable.

The invention has the beneficial effects that

The invention adopts the technology of combining the steel pipe piles with the waist beam anchor rods, forms the soil retaining structure with larger thickness and better rigidity, replaces the traditional row pile and continuous wall soil retaining structure, and has relatively simple process.

The invention adopts the self-drilling anchor rod technology, solves the problem that the miscellaneous filling anchor rod is difficult to form holes, and simultaneously performs pressure grouting consolidation reinforcement on filling soil to play a good role in anchoring and reinforcement.

The invention avoids the condition that a large amount of water flows out when the conventional pile anchor is formed into a hole, and the original soil is used as a part of a supporting structure after grouting reinforcement, thereby avoiding a large amount of mud pollution and meeting the requirements of energy conservation and environmental protection.

The miscellaneous fill grouting combined with the waist beam and the self-drilling anchor rod as a new construction technology is gradually popularized and applied in the projects of water and electricity, deep foundation pit loose rock and soil slope support and the like in recent years, and some technical problems in loose rock and soil mass anchoring construction are solved. In the deep foundation pit supporting construction, the miscellaneous filling grouting is combined with the waist beam and the self-drilling anchor rod, the problems that the anchor rod construction in a very loose and broken soil body is easy to collapse and difficult to form holes are solved, the comprehensive successful application of various supporting means such as net hanging grouting, water drainage holes and the like is combined, the primary stability of the side slope is realized, and certain experience is accumulated for the further application of the miscellaneous filling grouting combined with the waist beam and the self-drilling anchor rod.

Drawings

In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.

FIG. 1 is a sectional view of a side slope support of a foundation pit;

FIG. 2 is a schematic view of a self-drilling bolt construction;

FIG. 3 is a schematic view of a southern side slope of a foundation pit (before earth backfilling) in example 1;

FIG. 4 is a schematic view of a south side slope (after anchor rod construction) of a foundation pit in embodiment 1;

FIG. 5 is a schematic view of a south side slope (before earth backfilling) of a foundation pit in embodiment 2;

fig. 6 schematic view of east side slope (after anchor rod construction) of foundation pit in embodiment 2.

Detailed Description

In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, and not all 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.

Materials and apparatus

1. Main material table

TABLE 2 Main materials table

2. Implement and labor distribution

TABLE 3 Main implement and Equipment Meter

Serial number

Machine name

Unit of

Number of

Model number

Power (KW)

Remarks for note

1

Concrete proportioning machine

Table (Ref. Table)

2

PLD-800

2×2

2

Air compressor

Table (Ref. Table)

5

W-6/7

5×11

3

Concrete sprayer

Table (Ref. Table)

2

PZ-5B

2×15

4

Anchor rod machine

Table (Ref. Table)

8

ML-11

8×120

5

High-pressure grouting machine

Table (Ref. Table)

2

ZJL-14

2×200

Table 4 labor organization requirements table:

serial number	Procedure (ii)	Unit of	Number of
				1	Installation and grouting of steel pipe	Human being	8
2	Measurement and test	Human being	2
				3	Hanging net spray concrete	Human being	10
4	Maintenance of equipment	Human being	2
				5	Material management	Human being	3
6	Anchor rod drilling	Human being	5
				7	Other persons	Human being	6

Example 1

The foundation of a certain plot project is raft foundation, independent foundation and strip foundation, the structure type is frame-core tube, the total building area is 188000m²Total height 106 m. The length of the foundation pit is about 201m, the width is about 101m, the maximum excavation depth is about 18.5m, and the area of the foundation pit is 21827m²And the average depth of the foundation pit is 17 m.

The engineering foundation pit is large in area, the foundation pit side slope soil quality is loose, the slope is small, the site construction site is narrow and small, and large-slope excavation cannot be performed.

The foundation pit support adopts a steel pipe pile, waist beam and self-drilling anchor rod support form; the method comprises the steps of constructing a steel pipe pile and a pile top connecting beam before excavation of a foundation pit, enabling a firm soft soil layer to form a whole, then implementing a self-drilling anchor rod in the excavation process, directly fixing an anchor of the self-drilling anchor rod on a waist beam structure, enabling the anchor rod and the waist beam to jointly bear the load of a reinforcing structure, connecting the anchor rod through the waist beam, transmitting the anchoring force of the anchor rod to a slope body, changing the stress state of the slope body, improving the self-stability capability of the slope body, hanging a phi 8 steel bar net piece on the slope surface and sealing C20 concrete, and arranging drain holes in a quincunx shape on the slope surface.

The method specifically comprises the following steps: the method comprises the steps of steel pipe pile slope top reinforcement, self-drilling anchor rod construction, net hanging concrete spraying and water drainage hole construction, waist beam construction, foundation pit monitoring technology and analysis.

The steel pipe pile slope top reinforcing step comprises steel pipe pile construction and pile top connecting beam construction, and specifically comprises the following steps:

(1) steel pipe pile construction process

drilling: a Hami 90 drilling machine drills holes, and the drilling mode adopts the whole-process pipe following drilling (the outer diameter of the pipe following is 198mm, and the wall thickness is 8 mm); the steel pipe is a seamless steel pipe with the outer diameter phi of 168mm and the wall thickness of 5 mm; the connecting steel pipe is a seamless steel pipe with the outer diameter phi of 140mm and the wall thickness of 5mm, the lap joint length of each end is 50cm, the total length is 1m, the connecting steel pipe is welded with the seamless steel pipe of the pile body, the center of the connecting steel pipe is welded thoroughly, the two ends of the connecting steel pipe are spot-welded by drilling holes at 120 degrees, phi 8 steel bars are used as locators at the periphery of the steel pipe, one locator is welded at each 3-4m position, each locator consists of 3 locators, and the locators are uniformly distributed around the steel pipe; the bottom supporting steel bar is made into an L shape by 2 steel bars with the diameter of 20 mm, the height of the L shape is 20cm, 10cm is welded with the steel pipe, and the lower part of the L shape extends by 8 cm; when the steel pipe is manufactured, welding must be reliable and meet relevant quality technical requirements, and when the steel pipe is manufactured, the welding must be strictly performed according to design and specifications.

Grouting is carried out by adopting a hole bottom slurry returning method, and the grouting process of each hole is continuously completed once; placing a grouting pipe (model: phi 25PE grouting pipe) and a steel pipe to the bottom of a hole, grouting at the bottom of the hole by adopting M30 cement mortar, wherein the grouting pressure is 0.6MPa, and the water-cement ratio of the grout is controlled so as to ensure that the grouting is full and compact, and the grouting pipe and the steel pipe are stirred uniformly strictly according to the mixing ratio and are used along with the grouting; in order to prevent the phenomena of pile breaking, mud clamping, pipe blocking and the like, the filling process and operation are well controlled, ordered pipe drawing and continuous grouting are the keys for ensuring the pile-forming quality, the grouting speed is proper, and water and mortar in holes are not easy to discharge at too high speed to form broken piles; all indexes of the cement mortar meet the requirements, test pieces are made in time for standard maintenance, and a laboratory is used for carrying out a compressive strength test after the specified maintenance age is reached.

(2) Pile top connection beam construction process flow;

(II) self-drilling anchor rod construction steps, wherein the process flow is as follows: drilling hole positioning → drilling machine positioning → self drilling → installation of a grout stop plug → grouting → net hanging and concrete spraying + drainage hole construction → waist beam construction → installation of a base plate and a nut; the self-drilling anchor bolt application tool is operated as follows: the drilling machine adopts a QZJ-100D down-the-hole drilling machine, the air compressor adopts Attapulgite CA160-130, and the self-drilling anchor rod adopts a phi 32 anchor rod; the front end of the anchor rod is provided with an alloy drill bit, and a power joint of the drilling machine is connected with the self-drilling anchor rod through a connector to carry out rotary drilling; the self-drilling anchor rod grouting adopts a pure pressure type grouting process of directly connecting an orifice and an anchor rod, and grouting is performed from a self-drilling anchor rod center hole, wherein the slurry ratio is as follows: water: ash: and (3) sand is 0.6:1:0.3, grout returns to the orifice from the bottom of the hole along the space between the anchor rod and the hole wall after the grout reaches the bottom of the hole through the center hole of the self-drilling anchor rod, and the standard of grouting completion is as follows: when the anchor rod pore canal is fully filled, the grouting can be finished when the concentration of the returned grout is basically consistent with that of the entering grout.

(III) hanging the construction steps of net concrete spraying and water drainage holes, which specifically comprises the following steps: the concrete-spraying steel bar net piece of the hanging net adopts phi 8 steel bars, the distance between the transverse direction and the vertical direction is 20cm, the hanging net and the anchor rod are connected by a welding method, the concrete-spraying is C20 concrete, the spraying thickness is 8cm, the distance between the water outlet holes arranged on the slope surface is preferably 2-3m and is preferably arranged according to a quincunx shape, the water outlet holes of the rock slope are preferably arranged at the parts with serious crack development, potential fracture surfaces and water seepage, the parts are phi 48PVC pipes, the length is 600mm, the exposed part is 200mm, the outward-inclined gradient is not less than 5%, and the water inlet side of the water outlet hole is provided with 2 layers.

Fourthly, constructing the wale, wherein the wale is welded by 20-channel steel and double-channel steel, and the uniform gap of the wale is ensured during welding; the waist beam is required to be tightly close to the slope surface, and the whole waist beam is fixedly connected; performing rust prevention treatment on the anchor rod head; the anchor rod head screw is screwed up and then must be welded with the anchor rod, so that the nut is prevented from falling off.

The foundation pit monitoring technology and analysis steps are as follows:

in order to ensure the safety of engineering construction and the normal use of a near-edge building, the whole process is monitored, the monitoring content comprises the change conditions of the slope top surface of a foundation pit, pipelines, a building (structure) and the axial force of an anchor rod, dynamic deformation values caused by the construction stage of each main process are measured in time and compared with analysis calculated values, and the dynamic deformation values are fed back to guide design and construction in time. See table 5 below for the main monitoring.

Table 5 summary of monitoring items

Example 2

The foundation of a certain plot project is raft foundation, independent foundation and strip foundation, the structure type is frame-core tube, the total building area is 86000m²Total height 136.2 m. The length of the foundation pit is about 127m, the width of the foundation pit is about 101m, the excavation depth is about 9.7m, and the area of the foundation pit is 12827m²And the average depth of the foundation pit is 10 m.

Backfilling miscellaneous filling soil at the upper part of the east side of the foundation pit, wherein the miscellaneous filling soil is a block stone in the excavation process of the foundation pit, the maximum grain diameter is about 1.2m, the content is about 60%, and cohesive soil is filled; the upper part of the west segment at the north side is all backfilled miscellaneous filling soil (the miscellaneous filling soil is block stone in the excavation process of a foundation pit, the maximum grain diameter is about 1.2m, the content is about 70 percent, and cohesive soil is filled); the upper part of the north side of the foundation pit is filled with backfill miscellaneous filling soil (the miscellaneous filling soil is block stones in the excavation process of the foundation pit, the maximum grain diameter is about 1.0m, the content is about 60 percent, and cohesive soil is filled), the slope rate is about 1:0.2, the lower part of the miscellaneous filling soil is gravel filled with cohesive soil, the maximum grain diameter is 0.5m, the content is about 70 percent, the slope surface is 90 degrees, and a large amount of stones are stacked on the slope top.

The construction method has the advantages that the area of the engineering foundation pit is large, the excavation difficulty of the large gradient is large, the stability of the foundation pit side slope is greatly enhanced by using the method of combining the grouting of the steel pipe pile and the supporting of the waist beam anchor rod, the labor cost and the material cost are effectively saved, and good economic benefit and social benefit are obtained for companies.

The slope surface is 2m and the drainage holes are arranged in a quincunx shape.

In the grouting step, the grouting pressure is 0.8MPa, and the water-cement ratio of the slurry is controlled.

The rest of the technical scheme is the same as that of the embodiment 1.

Although the present invention has been described in detail by referring to the drawings in connection with the preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made on the embodiments of the present invention by those skilled in the art without departing from the spirit and scope of the present invention, and these modifications or substitutions are within the scope of the present invention/any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A steel pipe pile grouting and waist beam anchor rod combined supporting method is characterized in that a foundation pit support adopts a steel pipe pile, waist beam and self-drilling anchor rod support mode; the method comprises the steps of constructing a steel pipe pile and a pile top connecting beam before excavation of a foundation pit, enabling a firm soft soil layer to form a whole, then implementing a self-drilling anchor rod in the excavation process, directly fixing an anchor of the self-drilling anchor rod on a waist beam structure, enabling the anchor rod and the waist beam to jointly bear the load of a reinforcing structure, connecting the anchor rod through the waist beam, transmitting the anchoring force of the anchor rod to a slope body, changing the stress state of the slope body, improving the self-stability capability of the slope body, hanging a phi 8 steel bar net piece on the slope surface and sealing C20 concrete, and arranging drain holes in a 2-3m quincunx shape on the slope surface.

2. The support method according to claim 1, characterized in that it comprises the following steps: the method comprises the steps of steel pipe pile slope top reinforcement, self-drilling anchor rod construction, net hanging concrete spraying and water drainage hole construction, waist beam construction, foundation pit monitoring technology and analysis.

3. The support method according to claim 2, wherein the step of reinforcing the slope top of the steel pipe pile comprises steel pipe pile construction and pile top connection beam construction, and specifically comprises the following steps:

(1) steel pipe pile construction process

(2) pile top connection beam construction process flow;

4. The supporting method according to claim 3, wherein the drilling in the steel pipe pile construction process is specifically performed by: a Hami 90 drilling machine drills holes, and the drilling mode adopts the whole-process pipe following drilling (the outer diameter of the pipe following is 198mm, and the wall thickness is 8 mm); the steel pipe is a seamless steel pipe with the outer diameter phi of 168mm and the wall thickness of 5 mm; the connecting steel pipe is a seamless steel pipe with the outer diameter phi of 140mm and the wall thickness of 5mm, the lap joint length of each end is 50cm, the total length is 1m, the connecting steel pipe is welded with the seamless steel pipe of the pile body, the center of the connecting steel pipe is welded thoroughly, the two ends of the connecting steel pipe are spot-welded by drilling holes at 120 degrees, phi 8 steel bars are used as locators at the periphery of the steel pipe, one locator is welded at each 3-4m position, each locator consists of 3 locators, and the locators are uniformly distributed around the steel pipe; the bottom supporting steel bar is made into an L shape by 2 steel bars with the diameter of 20 mm, the height of the L shape is 20cm, 10cm is welded with the steel pipe, and the lower part of the L shape extends by 8 cm; when the steel pipe is manufactured, welding must be reliable and meet relevant quality technical requirements, and when the steel pipe is manufactured, the welding must be strictly performed according to design and specifications.

5. The supporting method according to claim 3, wherein the grouting operation in the steel pipe pile construction process is as follows: grouting is carried out by adopting a hole bottom slurry returning method, and the grouting process of each hole is continuously completed once; placing a grouting pipe (model: phi 25PE grouting pipe) and a steel pipe to the bottom of a hole, grouting at the bottom of the hole by adopting M30 cement mortar, wherein the grouting pressure is 0.6-0.8MPa, and the water-cement ratio of the grout is controlled to ensure that the grouting is full and compact, and the grouting pipe and the steel pipe are stirred uniformly strictly according to the mixing ratio and are used along with the grouting; all indexes of the cement mortar meet the requirements, test pieces are made in time for standard maintenance, and a laboratory is used for carrying out a compressive strength test after the specified maintenance age is reached.

6. The support method according to claim 2, wherein the self-drilling anchor rod construction steps are as follows:

7. The method of claim 6, wherein the self-drilling bolting tool operates to: the drilling machine adopts a QZJ-100D down-the-hole drilling machine, the air compressor adopts Attapulgite CA160-130, and the self-drilling anchor rod adopts a phi 32 anchor rod; the front end of the anchor rod is provided with an alloy drill bit, and a power joint of the drilling machine is connected with the self-drilling anchor rod through a connector to carry out rotary drilling; the self-drilling anchor rod grouting adopts a pure pressure type grouting process of directly connecting an orifice and an anchor rod, and grouting is performed from a self-drilling anchor rod center hole, wherein the slurry ratio is as follows: water: ash: and (3) sand is 0.6:1:0.3, grout returns to the orifice from the bottom of the hole along the space between the anchor rod and the hole wall after the grout reaches the bottom of the hole through the center hole of the self-drilling anchor rod, and the standard of grouting completion is as follows: when the anchor rod pore canal is fully filled, the grouting can be finished when the concentration of the returned grout is basically consistent with that of the entering grout.

8. The support method according to claim 2, wherein the construction steps of hanging net, spraying concrete and draining holes are as follows: the concrete-spraying steel bar net piece of the hanging net adopts phi 8 steel bars, the distance between the transverse direction and the vertical direction is 20cm, the hanging net and the anchor rod are connected by a welding method, the concrete-spraying is C20 concrete, the spraying thickness is 8cm, the distance between the water outlet holes arranged on the slope surface is preferably 2-3m and is preferably arranged according to a quincunx shape, the water outlet holes of the rock slope are preferably arranged at the parts with serious crack development, potential fracture surfaces and water seepage, the parts are phi 48PVC pipes, the length is 600mm, the exposed part is 200mm, the outward-inclined gradient is not less than 5%, and the water inlet side of the water outlet hole is provided with 2 layers.

9. The support method according to claim 2, wherein the wale construction steps are specifically: the wale is welded by 20 channel steel and double channel steel, and the uniform gap of the wale is ensured during welding; the waist beam is required to be tightly close to the slope surface, and the whole waist beam is fixedly connected; performing rust prevention treatment on the anchor rod head; the anchor rod head screw is screwed up and then must be welded with the anchor rod, so that the nut is prevented from falling off.

10. The support method according to claim 2, wherein the foundation pit monitoring technique and the analysis step specifically comprise:

Table 1 summary of monitoring items