CN116905477A - Construction method of earth surface protection type deep stirring pile - Google Patents

Abstract

The application provides a construction method of a surface protection type deep stirring pile, which comprises the following steps: a decompression hole with a first set depth is formed at a set distance beside a planned position of a stirring pile to be constructed; the first set depth is smaller than or equal to the pile top depth of the stirring pile after construction; and carrying out deep stirring pile forming operation at the planned position of the stirring pile. According to the earth surface protection type deep stirring pile construction method, the pressure release step is added by applying the pressure reducing hole nearby the earth surface protection type deep stirring pile construction method before deep stirring pile forming operation, so that the problems of rising, side shifting, road cracking and the like of soil bodies nearby the construction of the deep stirring pile construction method in the prior art are solved.

Description

Construction method of earth surface protection type deep stirring pile

Technical Field

The application relates to the technical field of building construction, in particular to a construction method of a ground surface protection type deep stirring pile.

Background

Soft soil foundation treatment is a common problem faced by coastal engineering, and is one of projects with large occupied investment and long construction time in engineering construction. The adopted treatment process and construction method are also rich according to different factors such as geological conditions, action load, construction technical capability and the like of the coastal region, such as a dynamic compaction method, a preloading method, a deep stirring method and the like. The deep stirring method is suitable for treating silt, mucky soil, silt and cohesive soil foundations, has high construction speed, no vibration or noise in the construction process, small ground bulge, no pollution discharge, less soil discharge, no environmental pollution and no harmful effect on adjacent buildings, and has good economic and social benefits.

Before deep mixing pile construction, the depth of the pile top needs to be determined in advance. For the reinforcement of the foundation in the subway tunnel section, it is usually not necessary to reinforce to the ground, and the pile top is located at a distance below the ground, for example 10 meters, i.e. the depth of the pile top is 10 meters below the ground. In the construction process of the deep stirring pile, cement slurry is sprayed out from a slurry outlet at the bottom of a drill rod under a larger pressure, the spraying pressure is up to 6Bar or higher, especially, a drill bit blade cuts and drives nearby soil bodies, and then the outer soil bodies are pushed to generate tangential force and radial force, so that the cement slurry permeates into soil layer cracks and gaps simultaneously. The pore water pressure of the undisturbed soil body can suddenly rise, and is accumulated in the under-consolidated soft clay and is not easy to dissipate, so that the nearby soil body radially and tangentially plastically displaces, and the nearby soil body macroscopically appears as bulge and lateral movement of the nearby soil body of the stirring pile, and cracks are generated on the road. In order to solve the problems, the application provides a construction method of a ground surface protection type deep stirring pile.

Disclosure of Invention

The application aims to solve the problems and provides a construction method of a ground surface protection type deep stirring pile.

The application provides a construction method of a surface protection type deep stirring pile, which comprises the following steps:

a decompression hole with a first set depth is formed at a set distance beside a planned position of a stirring pile to be constructed; the first set depth is smaller than or equal to the pile top depth of the stirring pile after construction;

and carrying out deep stirring pile forming operation at the planned position of the stirring pile.

According to some embodiments of the present application, the pressure relief vent is formed according to the following steps:

drilling a drill rod with stirring blades underground at a set distance beside a planned position of a stirring pile to be constructed;

and taking the drill rod out of the ground to form the pressure reducing hole.

According to some embodiments of the present application, the pressure relief vent is formed according to the following steps:

drilling a hollow steel pipe underground at a preset distance beside a planned position of a stirring pile to be constructed;

and (3) emptying the soil in the hollow steel pipe to form the pressure reducing hole.

According to some embodiments of the present application, the first set depth is determined by:

pre-constructing a row of stirring piles, and constructing a pressure reducing hole with a second set depth at a set distance beside a planned position of each stirring pile before constructing each stirring pile; the second set depth is equal to the pile top depth of the stirring pile after construction;

acquiring the pile bottom depth of each stirring pile after construction and the soil rising height in the pressure reducing hole corresponding to each stirring pile, and obtaining a data set about the pile bottom depth and the soil rising height;

fitting to obtain a first linear function of soil elevation with respect to pile bottom depth by taking the data set as a sample value;

predicting the depth of the pile bottom of the non-constructed stirring pile according to the depth of the pile bottom of the constructed stirring pile;

carrying the depth of the pile bottom of the non-constructed stirring pile into a first linear function to obtain the soil rising prediction height;

and setting the first set depth according to the soil rising prediction height.

According to the technical scheme provided by certain embodiments of the application, the deep stirring pile forming operation is performed according to the following steps:

the method comprises the steps of (1) positively and circularly drilling a main drill rod from a planned position of a stirring pile to be constructed to a first depth; the total drill rod comprises a first drill rod and a second drill rod which are connected through a third drill rod connector, and the top end of the first drill rod is connected with a rotary power head of the deep pile stirring machine through the first drill rod connector;

opening a high-pressure grouting pump on the deep pile mixer to spray slurry, and lifting the total drill rod to a second depth in a reverse circulation mode;

drilling the total drill rod in a positive circulation way and spraying cement slurry to the first depth;

turning off the high-pressure grouting pump, and reversely and circularly lifting the total drill rod to the second depth;

removing the third drill pipe joint and drilling the first drill pipe into the ground at the first location;

dismantling the first drill rod joint, and connecting a second drill rod with a rotary power head of the deep stirring pile machine through a second drill rod joint;

starting the high-pressure grouting pump, and positively circularly drilling the second drill rod to a third depth; the third depth is deeper than the second depth, and the depth difference of the third depth and the second depth is 500mm;

lifting the second drill rod in a reverse circulation mode and spraying cement slurry to the designed top elevation;

drilling the second drill rod in a positive circulation mode and spraying slurry to the second depth;

and closing the high-pressure grouting pump, and reversely circularly lifting the second drill rod to the ground surface.

According to the technical scheme provided by certain embodiments of the application, the second drill rod is formed by lengthening a plurality of unit sub drill rods; the unit sub drill rod positioned at the bottommost part is welded with the drill bit for drilling into a whole.

According to the technical scheme provided by certain embodiments of the application, the bottom side wall of the drill bit is provided with only one guniting port; an arc-shaped baffle is arranged on one side of the slurry spraying opening on the outer wall of the drill bit; the arc baffle is positioned in front of the rotation direction of the drill bit when the drill bit drills downwards.

According to the technical solutions provided in some embodiments of the present application, after the high-pressure grouting pump is turned off and the second drill pipe is reversely and circularly lifted to the surface, the method further includes the following steps:

the second drill pipe is lifted up and cement slurry is sprayed in a reverse circulation manner, and light grouting, such as 1-4m depth, is carried out on the ground surface.

According to the technical scheme provided by certain embodiments of the application, two total drill rods are parallelly arranged on a rotary power head of the deep stirring pile machine; the pile forming diameter of the total drill rod is more than 1400mm and less than 1600mm; the axle center distance of the two total drill rods is larger than 1100mm and smaller than 1300mm.

According to the technical scheme provided by some embodiments of the application, all the planning positions of the stirring piles are arranged in rows, each row of planning positions of the stirring piles are sequentially constructed row by row, and the inter-pile spacing between every two adjacent planning positions of the stirring piles is 1300mm to 1400mm.

Compared with the prior art, the application has the beneficial effects that: according to the earth surface protection type deep stirring pile construction method, the pressure release step is added by applying the pressure reducing hole nearby the earth surface protection type deep stirring pile construction method before deep stirring pile forming operation, so that the problems of rising, side shifting, road cracking and the like of soil bodies nearby the construction of the deep stirring pile construction method in the prior art are solved.

According to some embodiments of the application, the depth of the pressure reducing holes corresponding to the non-constructed stirring piles is guided according to the pile bottom depth of the constructed stirring piles and the rising height of soil in the pressure reducing holes corresponding to the constructed stirring piles, so that the reasonable pressure reducing hole depth is determined according to actual requirements, and the construction cost is reduced on the premise of ensuring the earth surface protection.

Drawings

FIG. 1 is a schematic structural diagram of a construction area according to embodiment 1 of the present application;

FIG. 2 is a flow chart of the construction method of the earth surface protection type deep mixing pile in the embodiment 1 of the application;

FIG. 3 is a schematic view showing the structure of the pressure reducing hole in example 1 of the present application;

FIG. 4 is a schematic diagram of the deep stirring construction in example 1 of the present application;

FIG. 5 is a schematic view of the structure of a second drill pipe according to embodiment 1 of the present application;

fig. 6 is a schematic view showing the distribution of stirring piles in example 2 of the present application.

The text labels in the figures are expressed as:

100. a second drill rod; 110. a guniting port; 120. an arc-shaped mud guard; 200. a drill bit; 300. and (3) a blade.

Detailed Description

In order that those skilled in the art may better understand the technical solutions of the present application, the following detailed description of the present application with reference to the accompanying drawings is provided for exemplary and explanatory purposes only and should not be construed as limiting the scope of the present application.

It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.

Example 1

In this embodiment 1, the construction project shown in fig. 1 is exemplified as a subway bed reinforcing project, and the geological structure of the construction area is as follows: a cooling group (Kallang Formation) is used for depositing a lamination layer, a transition layer and sea clay; project tasks comprise foundation improvement construction tasks for a partial area of a tunnel 1# section, equipment rooms and a tunnel 2# section, and the main engineering quantity is as follows: the deep stirring pile is about 27 square, and the deepest depth can reach 52 meters.

Before the deep stirring operation is carried out on the construction area, the following preparation work needs to be carried out:

in this embodiment, the earth structure above the construction base surface of the stirring pile is excavated to reduce the unnecessary stirring length, and the depth of the construction base surface of the stirring pile, namely the depth of the pile top of the stirring pile, is positioned at a position 10 meters below the ground surface.

And (3) flattening the construction site of the stirring pile drilling machine, paving a 300mm thick broken stone cushion layer, and compacting the surface by using a 10t steel wheel road roller to provide a good working platform for the 130t heavy deep stirring pile drilling machine.

The embodiment provides a construction method of a surface protection type deep stirring pile, a flow chart of the method is shown in fig. 2, and the method comprises the following steps:

s1, constructing a pressure reducing hole with a first set depth at a set distance beside a planned position of a stirring pile to be constructed; the first set depth is generally less than or equal to the pile top depth of the mixing pile after construction.

Before deep stirring of the stirring piles is performed, the construction position of each stirring pile needs to be planned in a construction area, and in general, a plurality of rows of stirring pile positions to be constructed are planned in the construction area, wherein each row comprises a plurality of stirring pile positions to be constructed.

When it is intended to perform construction at a certain mixing pile position, it is necessary to construct a relief hole having a first set depth, which may be the position of the next mixing pile to be constructed adjacent to the mixing pile to be constructed, or other positions, for example, 1 to 1.5m, at a set distance below or equal to the pile top depth of the mixing pile, i.e., below or equal to the depth of the mixing pile construction substrate, and in this embodiment below or equal to 10 m.

The first set depth may be designed to be greater than the pile top depth of the mixing pile according to actual needs.

The pressure relief vent is formed according to the steps of:

and S101, drilling a drill rod with stirring blades into the underground at a set distance beside the planned position of the stirring pile to be constructed.

And S102, taking the drill rod out of the ground to form the pressure reducing hole.

Because the pressure reducing holes are arranged near the stirring piles, the pressure born by underground soil during deep stirring is released from the pressure reducing holes, so that the soil near the stirring piles is prevented from rising and moving sideways, and cracks on roads are avoided.

Particularly, when the protective structure is arranged in the construction area or the underground wall structure is arranged at the edge of the construction area, the arrangement of the pressure reducing holes can also avoid damaging the protective structure or the underground wall structure when deep stirring construction is carried out. The protective structure may be, for example, an underground pipeline, in particular, for example, a 6.6kV cable buried 1.5-2 m deep near the ground-handling edge by about 2 m. In the grouting of two rows of opposite sides, a pressure reducing hole is arranged between every two deep stirring piles, as shown in fig. 3, the bottom elevation of the pressure reducing hole is the top elevation of the grouting, and the pressure reducing hole is firstly made and then the grouting is performed.

And S2, carrying out deep stirring pile forming operation at the planned position of the stirring pile.

After the construction of the pressure reducing hole is finished, deep stirring pile forming operation is carried out according to the following steps:

and S201, positively and circularly drilling the total drill rod from the planned position of the stirring pile to be constructed to the first depth.

The total drill rod comprises a first drill rod and a second drill rod which are connected through a third drill rod connector, and the top end of the first drill rod is connected with a rotary power head of the deep stirring pile machine through the first drill rod connector.

In this embodiment, the total drill pipe is configured in a two-section lengthening manner, that is, includes a first drill pipe and a second drill pipe that are detachably connected, the rotary power head of the deep-mixing pile machine may be connected to the first drill pipe through a first drill pipe joint, the rotary power head of the deep-mixing pile machine may also be connected to the second drill pipe through a second drill pipe joint, and the first drill pipe and the second drill pipe may also be connected to each other through a third drill pipe joint; the length of the first drill rod is greater than the length of the second drill rod.

The assembly of the total drill pipe is required to be completed when the total drill pipe is being circularly drilled into the ground to a first depth, and the assembly process of the total drill pipe comprises the following steps:

s201-1, mounting a first drill rod on a rotary power head of the deep stirring pile machine through a first drill rod joint.

In the embodiment, a SWET858 type double-shaft deep-stirring pile machine is adopted, and is originally configured with a 1200mm pile diameter drill bit in a factory, wherein the double-shaft center distance is 1000mm; in this embodiment, in order to improve work efficiency, will adopt 1500mm stake footpath drill bit to adjust the unit head power, specifically improve single unit head power from 110kW to 187.5kW, ensure can provide sufficient moment of torsion cutting soil body, satisfy stake footpath 1500mm power demand.

In this embodiment, the number of the first drill rods is 2 corresponding to the setting of the dual power heads.

s201-2, starting a grouting pump to spray water, and positively and circularly drilling a first drill rod into the ground from a first position beside a planned position of the stirring pile.

In this embodiment, the length of the first drill rod is 30 meters, and the first drill rod is drilled into the ground through a deep-mixing pile machine; in the embodiment, in the process of tripping the drill rod, the clean underwater drill is adopted, so that the blocking of the injection orifice on the drill bit in the drilling process can be prevented, the load torque can be reduced, and smooth drilling is ensured. When the difficult-to-drill area is encountered, the water feeding amount can be increased to smoothly drill. The clear auger speed in this example was 1m/min.

In this embodiment, the first position may be another planned position of the mixing pile beside the current planned position of the mixing pile, and may also be a planned position of the non-mixing pile beside the current planned position of the mixing pile.

s201-3, closing the grouting pump, opening the first drill rod joint, detaching the first drill rod from the rotary power head of the deep stirring pile machine, and installing the second drill rod on the rotary power head of the deep stirring pile machine through the second drill rod joint.

In the step, the drilling of the second drill rod is the start of the deep stirring pile operation, so that the drilling machine is required to be checked and adjusted before the step is started, and basic parameters such as the perpendicularity of the drill rod are ensured; in this embodiment, the length of the second drill rod is 24 meters.

In this step, after the first drill rod is detached from the rotary power head of the deep-mixing pile machine, in order to avoid the first drill rod sinking into the ground due to its own weight, the top end of the first drill rod is ensured to be slightly exposed to the ground when the first drill rod is drilled in step s201-2, and in this step, after the first drill rod is detached from the rotary power head of the deep-mixing pile machine, the top end of the first drill rod is held by a limiting plate with an anchor ear mounted thereon so as to prevent the first drill rod sinking.

In this embodiment, the number of the second drill rods is 2 corresponding to the setting of the double power heads.

And s201-4, starting a grouting pump to spray water, and drilling a second drill rod from the planned position of the stirring pile to a second depth, wherein the second depth is slightly smaller than the length of the second drill rod.

In this embodiment, the second depth is 21 meters. And when the second drill rod drills into the second depth, the top end of the second drill rod is exposed out of the ground.

And S201-5, closing the grouting pump, opening the second drill rod joint, and detaching the second drill rod from the rotary power head of the deep stirring pile machine.

In the step, after the second drill rod is detached from the rotary power head of the deep stirring pile machine, the top end of the second drill rod can be held by a limiting plate provided with an anchor ear so as to prevent the second drill rod from sinking.

s201-6, mounting the first drill rod on a rotary power head of the deep stirring pile machine through a first drill rod joint, and lifting the first drill rod out of the ground.

Specifically, the rotary power head of the deep mixing pile machine is moved to the position above the first drill rod, the first drill rod is installed on the rotary power head of the deep mixing pile machine through the first drill rod connector, and then the first drill rod is lifted from a first position located beside a current mixing pile.

s201-7, connecting a first drill rod and a second drill rod by using a third drill rod joint, wherein the first drill rod and the second drill rod form a total drill rod.

Specifically, the rotary power head of the deep pile stirring machine and the first drill rod are moved to the upper side of the second drill rod, and the top end of the second drill rod is connected with the bottom end of the first drill rod through the third drill rod connector to form a total drill rod.

Through the steps s201-1 to s201-7, the assembly process of the total drill rod is completed, and the assembled total drill rod is circularly drilled into the ground to a first depth; stopping drilling when the drilling depth is judged to reach the first depth, wherein the first depth is confirmed by adopting a depth determining method in the prior art, namely judging that the current value of the rotary power head of the deep mixing pile machine exceeds a set value (the set value is generally more than 200A, for example 220A), judging that the drilling depth reaches a target stratum, and taking the depth of the current drill bit as the target depth of the deep mixing pile, namely the first depth. As shown in steps s201-1 to s201-7, the time period 0-T3 in fig. 4 is the time period of the lower total drill rod, and the lower total drill rod is divided into three stages, wherein the first stage 0-T1 is the time period of the second drill rod being drilled, the second stage T1-T2 is the time period of lengthening the first drill rod and the second drill rod, and the third stage T2-T3 is the time period of continuing to drill after lengthening the drill rod.

Through setting up the drilling rod of deep stirring stake machine into two sections mode of lengthening, under the high of 36m stake machine mast, realized the deep stirring degree of depth requirement of super deep (deepest 52 m), and through setting up first drilling rod length and be greater than the second drilling rod, first drilling rod and second drilling rod all are formed through the drilling rod joint connection of a plurality of standard length, this embodiment will be more than half connect the time spare of drilling rod to the construction operation outside, saved a large amount of time of connecing the drilling rod, promoted work efficiency.

And S202, opening a high-pressure grouting pump on the deep pile mixer to spray slurry, and lifting the total drill rod to a second depth in a reverse circulation mode.

This step is shown in fig. 4 for time periods T3-T4, where the second depth is 21 meters.

In the embodiment, when the total drill rod is sunk to the designed depth, drilling is stopped, rotation is stopped, the high-pressure slurry pump pressure is increased to a construction design value (2-4 MPa), after the grouting is carried out for 30s-60s, the total drill rod is lifted after the grouting is carried out for at least 1min while the grouting is carried out, and a thick foundation is formed at the bottom of the deep stirring pile.

In the embodiment, the cement adopted by the cement paste is not lower than 42.5N, and the proportion of the cement paste is water: cement = 1:1, a step of; wherein the rotating speed of the total drill rod is 18rpm, and the grouting speed is 0.6m/min; the slurry flow rate is 120L/min-160L/min.

s203, drilling the total drill rod in a positive circulation mode and spraying slurry to the first depth.

This step is shown in the time period T4-T5 of fig. 4, and in this embodiment, the target depth of a certain mixing pile is 50 meters, i.e. the first depth is 50 meters.

And S204, closing the high-pressure grouting pump, and lifting the total drill rod to the second depth in a reverse circulation mode.

This step is shown in fig. 4 for time period T5-T6, where the second depth is 21 meters, and after this step is completed, the first drill pipe is completely above the surface, and the top end of the second drill pipe is exposed above the surface.

s205, removing the third drill rod joint and drilling the first drill rod into the ground at the first position.

This step is illustrated in fig. 4 for time periods T6-T7, where the second drill pipe is left in the current mixing pile and the first drill pipe is transferred into the subsurface at the first location beside the mixing pile.

And S206, removing the first drill rod joint, and connecting a second drill rod with the rotary power head of the deep stirring pile machine through a second drill rod joint.

In the step, the first drill rod is detached from the rotary power head of the deep pile mixer, and then the top end of the second drill rod is connected with the rotary power head of the deep pile mixer through the second drill rod connector.

S207, starting the high-pressure grouting pump, and positively circularly drilling the second drill rod to a third depth; the third depth is deeper than the second depth, and the depth difference of the third depth and the second depth is 500mm.

The amount of movement of the second drill rod in this step is relatively small and is therefore not shown in particular in fig. 4. The third depth is deeper than the second depth, and the depth difference is 500mm, in this embodiment, the second depth is 21 meters, and the third depth is 21.5m; by arranging the overlapped deep stirring section between the deep stirring pile formed at the lower part and the deep stirring pile formed at the upper part, the integrity and the continuity of pile forming can be ensured.

And S208, lifting the second drill rod in a reverse circulation mode and spraying slurry to the designed top elevation.

This step is shown in fig. 4 for time periods T7-T8, where the design top elevation is typically a distance below the surface, in this embodiment, 10 meters.

In this step, when the rotary jet pipe is lifted close to the pile top, the rotary jet is lifted slowly from 1.0m below the pile top, the rotary jet is lifted for several seconds, and then lifted slowly upwards until the pile top is lifted to a slurry stopping surface, wherein in this embodiment, the slurry stopping surface is 0.3 m higher than the pile body design elevation. When the slurry spraying opening at the end part of the drill bit of the second drill rod reaches the top of the pile body, lifting is stopped, rotary slurry spraying is kept, pile head grinding is carried out at the pile top part, and the retention time is 1 minute, so that a compact pile head is formed at the top of the pile body.

s209, drilling the second drill rod in a positive circulation mode and spraying slurry to the second depth.

This step is shown as time period T8-T9 in fig. 4.

And S210, closing the high-pressure grouting pump, and reversely circularly lifting the second drill rod to the ground surface.

In the step, the high-pressure grouting pump is turned off at the moment T9, the second drill rod is lifted in a reverse circulation mode, when the distance between the grouting opening and the ground surface is set, for example, 1 meter in the process of lifting the second drill rod, the high-pressure grouting pump is turned on, the second drill rod is lifted in the reverse circulation mode, cement slurry is sprayed, and the ground surface light grouting is implemented according to the set duration. The lifting speed of the second drill rod is 0.8m/min during spraying, and the process of lifting the spraying slurry is shown as a part after the moment T10 in fig. 4. The ground surface is softer, and cement slurry is sprayed on the ground surface to increase the strength of the ground surface by adopting the technical scheme.

As shown in fig. 4, the embodiment adopts the 'reverse V' grouting from bottom to top twice, realizes the 'four-stirring two-spraying' grouting from bottom to top two stages, realizes one-time piling in the environment of lengthening a drill rod, and realizes high-efficiency piling.

In the embodiment, two total drill rods are parallelly arranged on a rotary power head of the deep stirring pile machine, and the pile forming diameter of the total drill rods is larger than 1400mm and smaller than 1600mm; the axle center distance of the two total drill rods is more than 1100mm and less than 1300mm; specifically, in this embodiment, the pile forming diameter of the total drill pipes is set to 1500mm, and the axial center distance between the two total drill pipes is 1200mm. In the embodiment, the pile forming efficiency is greatly improved by adopting the double-shaft large-diameter pile forming design and matching with a high-power head.

In this embodiment, all the planned positions of the stirring piles are arranged in rows, and each row of planned positions of the stirring piles are sequentially constructed row by row, for example, an upper row of stirring piles are firstly constructed, and then a lower row of stirring piles are constructed; the inter-core distance between adjacent stirring piles is 1300mm to 1400mm.

In this embodiment, when it is determined that a protected structure is provided in the construction area or that a diaphragm wall structure is provided at the edge of the construction area, the construction area close to the protected structure and the diaphragm wall structure is set as a priority construction area; and after the other areas are partitioned, construction operation is performed at intervals in each partition. The construction sequence can reduce the squeezing action on the protected structure or the underground diaphragm wall structure so as to protect the protected structure or the underground diaphragm wall structure.

In this embodiment, when it is determined that the edge of the construction area is provided with the diaphragm wall structure, high-pressure jet grouting construction is performed at a position where the construction area is close to the diaphragm wall structure.

In the embodiment, double-pipe high-spraying equipment is used for construction, a soil body is cut by a high-pressure water jet of 20MPa in the drilling stage, meanwhile, an air curtain is formed around jet water by high air pressure of 8Bars, the attenuation speed of the kinetic energy of the jet water is reduced, and the cutting is guaranteed to be full. And in the grouting stage, two medium jet flows of high-pressure cement slurry and air are transversely ejected at the same time to impact and destroy soil. Under the combined action of the high-pressure slurry and the surrounding air flow of the outer ring of the slurry, the energy for destroying the soil body is obviously increased, and finally, a larger consolidated body is formed in the soil.

The high-pressure jet grouting construction is specifically carried out according to the following steps:

(1) And (7) positioning a drilling machine. Moving the jet grouting pile machine to a specified pile position, aligning the drill bit to the center of a hole site, leveling the drill, and placing stably and horizontally, wherein the verticality deviation of the drill rod is not more than 1% -1.5%. After in place, a low pressure (0.5 MPa) water injection test is first performed to check whether the nozzle is clear or not and whether the pressure is normal or not.

(2) And (5) preparing cement paste. When the pile driver is shifted, cement paste is stirred according to the designed and determined mixing ratio.

(3) Drilling (double tubing method). The drill bit drills at a predetermined pile location to a designed elevation (pre-drilled hole diameter is 15 cm). If the treatment depth is greater than the length of the maximum carrying drill rod of the machine body, the drill rod needs to be lengthened in the middle of drilling.

(4) Lifting the guniting pipe and stirring. After the grouting pipe is sunk to the designed depth, drilling is stopped, rotation is stopped, the pressure of the high-pressure slurry pump is increased to a construction design value (20-40 MPa), after the grouting pipe is seated for 30 seconds, the grouting pipe is rotated while the drill rod is lifted according to the design and the lifting speed determined by the test pile. After the design depth is reached, the high-pressure water pipe and the air pressure pipe are connected, the high-pressure clean water pump, the slurry pump, the air compressor and the drilling machine are started to rotate, the pressure, the flow and the air quantity are controlled by the instrument, the lifting is started when the preset values are respectively reached, the rotary spraying and the lifting are continued until the expected reinforcement height is reached, and the rotary spraying and the lifting are stopped.

(5) And (5) pile head part treatment. When the rotary jet pipe is lifted to be close to the pile top, the rotary jet pipe is lifted slowly from 1.0m below the pile top, the rotary jet pipe is lifted for a few seconds, and the rotary jet pipe is lifted upwards slowly by 0.5m until the pile top stops at the slurry surface.

(7) If meeting the gravel stratum, in order to guarantee the stake footpath, can repeat the guniting, stir: repeating the spraying and stirring according to the steps 4-6 until the spraying pipe is lifted to the stopping surface, closing the high-pressure slurry pump (clean water pump and air compressor), stopping the conveying of cement slurry (water and wind), rotating the rotary spraying pipe out of the ground, and closing the drilling machine.

(8) And (5) cleaning. And (3) injecting a proper amount of clean water into the slurry tank, starting the high-pressure pump, and cleaning the residual cement slurry in all the pipelines until the slurry tank is basically clean. And the soil adhered to the guniting pipe head is cleaned.

(9) And (3) shifting. And (5) moving the pile machine to construct the next pile.

In this embodiment, the first drill pipe and the second drill pipe are formed by lengthening a plurality of unit sub drill pipes, and the second drill pipe is taken as an example, as shown in fig. 6, the second drill pipe 100 includes a plurality of unit sub drill pipes, the unit sub drill pipe located at the bottommost is welded with the drill bit 200 for drilling into a whole, in this embodiment, the unit sub drill pipe located at the bottommost adopts a drill bit integrated design structure with a length of 4 meters, so that the problem of slurry leakage between the short drill bit and the drill pipe connected with the short drill pipe is avoided, and the slurry spraying pressure and stability are ensured.

Further, only one guniting port 110 is arranged on the bottom side wall of the drill bit; the outer wall of the drill bit is provided with an arc-shaped mud guard 120 at one side of the guniting port 110; the arcuate mud flaps 120 are positioned forward of the direction of rotation of the drill bit as it drills downward.

Specifically, the slurry spraying ports 110 are arranged on the side surface of the drill bit, and only one slurry spraying port 110 is arranged, so that the pressure of the slurry spraying ports is stable, the problem of unstable pressure when a plurality of slurry spraying ports 110 are solved, the slurry outlet speed is balanced, and the pile forming quality is stable. An arc-shaped mud guard 120 is arranged on the second drill rod 100 corresponding to the guniting port 110; the arc-shaped mud guard 120 has a semicircular structure, and is installed concentrically with the guniting port 110; the arc-shaped mud guard 120 is positioned at the front end of the second drill rod in the rotation direction; during the process of the second drill pipe 100 drilling downwards and rotating, when encountering an underground obstacle, the arc-shaped mud guard 120 can remove sundries at the guniting port 110, thereby ensuring that the guniting port 110 can normally output and avoiding blocking the guniting port 110.

Further, the upper, middle and lower three layers of blades 300 are arranged on the second drill rod, stirring is performed in the construction process, so that slurry and soil are fully stirred to ensure the construction quality, in the embodiment, a layer of steel plate is welded on the blade edge, and alloy teeth with high wear resistance hardness are welded on the outermost side of the blade; the abrasion resistance of the blade is remarkably improved, the problem that the stirring diameter is reduced and the stirring is uneven due to the fact that the length of the blade is changed due to abrasion is avoided, and the construction quality is further guaranteed.

According to the earth surface protection type deep stirring pile construction method, the pressure releasing step is added before deep stirring pile forming operation is carried out, when a construction area is an equipment room or a shield zone, cement slurry is sprayed out from a slurry outlet at the bottom of a drill rod under a larger pressure in the underground of the construction area, the spraying pressure reaches 6Bar, especially a drill bit blade cuts and drives nearby soil bodies, the outer soil bodies are pushed to further push out to generate tangential force and radial force, and cement slurry permeates into soil layer cracks and gaps simultaneously. The pore water pressure of the undisturbed soil body can suddenly rise, and the pore water is accumulated in the under-consolidated soft clay and is not easy to dissipate, so that the radial and tangential plastic displacement of the nearby soil body is realized, the nearby soil body macroscopically appears as bulge and lateral movement, cracks are generated on the road, and the soil squeezing effect brought by deep mixing pile construction can generate non-negligible influence on the surrounding environment. By adopting the technical scheme provided by the embodiment, the technical problems can be solved.

Example 2

The present embodiment provides a construction method of a surface protection type deep stirring pile, and the points of the present embodiment that are the same as those of embodiment 1 are not described in detail, and the difference is that: the pressure reducing holes are formed in different manners. In this embodiment, the pressure relief vent is formed according to the following steps:

and S103, drilling a hollow steel pipe underground at a set distance beside the planned position of the stirring pile to be constructed.

The hollow steel pipe may be gradually inserted into the ground by applying pressure to the top of the hollow steel pipe by high frequency striking from the top. For example, a hydraulic cylinder may be installed above the pressure reducing hole to be constructed, a pressing plate may be installed at a piston rod end of the hydraulic cylinder, the pressing plate may be sized to cover an end surface of the hollow steel pipe, and the pressing plate may be made to continuously apply pressure to the hollow steel pipe from its top by controlling the hydraulic cylinder to continuously extend and retract, so that the hollow steel pipe is gradually inserted into the ground, and the top of the hollow steel pipe is not higher than the ground surface.

And S104, emptying soil in the hollow steel pipe to form the pressure reducing hole.

Specifically, the soil emptying tool or the soil emptying device in the prior art is adopted to realize soil emptying in the hollow steel pipe, for example, the soil emptying device disclosed in the publication No. CN215715302U and the patent name of a simple soil emptying device for the pile core of the prefabricated pipe pile can be adopted, and for example, the soil emptying device disclosed in the publication No. CN113250199A and the patent name of an electric pile core soil emptying device can be adopted.

Further, in the present embodiment, the first set depth (i.e., the depth of the pressure-reducing hole) is determined as follows:

s1-1, pre-constructing a row of stirring piles, and before constructing each stirring pile, constructing a pressure reducing hole with a second set depth at a set distance beside a planned position of each stirring pile; and the second set depth is equal to the pile top depth of the stirring pile after construction.

During construction, the first row of stirring piles are firstly constructed, and guidance is provided for the construction of the next row of stirring piles through data acquired after the construction of the first row of stirring piles. When constructing all stirring piles of a row, the depth of the decompression holes corresponding to each stirring pile is the same, and the second set depth is the pile top depth of the stirring pile after construction, namely the depth of the construction base surface of the stirring pile, and in the embodiment, the second set depth is 10 meters.

s1-2, acquiring the pile bottom depth of each stirring pile after construction and the soil elevation in the pressure reducing hole corresponding to each stirring pile, and obtaining a data set about the pile bottom depth and the soil elevation.

According to the prior art, in the drilling process, the control panel of the deep stirring pile machine can display the current drilling depth in real time, and when any stirring pile is constructed, pile bottom depth data can be obtained. And after the construction of all the stirring piles in the first row is finished, obtaining the pile bottom depth of each stirring pile.

The soil elevation in each relief hole can be measured by: the method comprises the steps of selecting a pipe fitting with the length not smaller than 10 meters as a measuring rod, lifting the measuring rod, installing a circular plate with the inner diameter slightly smaller than that of a hollow steel pipe at the other end of the measuring rod, installing a pressure sensor at the bottom of the circular plate, slowly inserting the measuring rod into the hollow steel pipe, gradually enabling the measuring rod to descend, enabling data detected by the pressure sensor to be transmitted back to a controller in real time, enabling a pressure value detected by the pressure sensor to be zero when the circular plate does not contact soil in the hollow steel pipe in the descending process of the measuring rod, enabling the pressure value detected by the pressure sensor to change when the circular plate contacts soil in the hollow steel pipe, enabling the pressure value to be larger than a set pressure value, for example, enabling the measuring rod to be stopped descending when the pressure value is larger than 5N, enabling the measuring rod to ascend from the hollow steel pipe after the position of the surface of the measuring rod is marked at the moment, enabling the distance between the marked position and the circular plate to be measured to be the first length, and enabling the soil ascending height in a pressure reducing hole to be obtained by subtracting the first length from the second set depth.

Each mixing pile corresponds to a pressure reducing hole, so that pile bottom depth data of each mixing pile corresponds to soil rising height data in the pressure reducing hole, and the pile bottom depth and the soil rising height are paired. In this embodiment, the data set includes 10 pairs of pile bottom depth and soil elevation data.

And s1-3, fitting to obtain a first linear function of soil elevation relative to pile bottom depth by taking the data set as a sample value.

Specifically, sample values in the data set are fitted in a linear fitting mode in the prior art, a first linear function of soil elevation relative to pile bottom depth is obtained, the soil elevation is a function value, and the pile bottom depth is an independent variable.

And s1-4, predicting the depth of the pile bottom of the non-constructed stirring pile according to the depth of the pile bottom of the constructed stirring pile.

Predicting the depth of the pile bottom of the non-constructed stirring pile according to the depth of the pile bottom of the constructed stirring pile adjacent to the non-constructed stirring pile, specifically, sequentially marking all the stirring piles in the order from small to large by Arabic numerals, and if the stirring pile to be constructed currently is the pile with the smallest mark in the row, the constructed stirring pile adjacent to the non-constructed stirring pile is two stirring piles on the same side as the constructed stirring pile in the row in front of the stirring pile, namely, the two stirring piles with the mark being 1 smaller than the mark of the stirring pile to be constructed currently and the stirring pile with the mark being 2 smaller than the mark of the stirring pile to be constructed currently; if the stirring pile to be constructed currently is the pile with the largest mark in the row, the stirring pile to be constructed nearby comprises: stirring piles smaller than the current stirring pile to be constructed by 1 in number, stirring piles adjacent to the current stirring pile to be constructed in the previous row of stirring piles to be constructed, and stirring piles larger than the stirring piles adjacent to the current stirring pile to be constructed in the previous row of stirring piles by 1 in number; if the label of the stirring pile to be constructed currently is larger than the maximum value and smaller than the minimum value of all stirring pile labels in the current row, the constructed stirring pile adjacent to the stirring pile comprises: a mixing pile with a number of 1 smaller than the current mixing pile to be constructed, a mixing pile with a number of 1 larger than the number of mixing piles with a number of 1 larger than the current mixing pile to be constructed in the previous row of mixing piles which are adjacent to the current mixing pile to be constructed in the previous row of mixing piles constructed, and a mixing pile with a number of 1 smaller than the number of mixing piles with a number of 1 smaller than the current mixing pile to be constructed in the previous row of mixing piles.

For ease of understanding, the schematic distribution of the mixing piles shown in fig. 6 is illustrated, and in fig. 6, there are 3 rows of mixing piles in total, each row including 8 mixing piles, which have been subjected to arabic numeral sorting in the order of construction, and the first row of mixing piles (i.e., mixing piles numbered 1-8) are the mixing piles previously constructed in step s1-1, and when the mixing piles of the other rows are constructed, the constructed mixing piles adjacent thereto are determined by the following method:

if the number of the stirring piles to be constructed currently is 9, two stirring piles which are adjacent to the stirring piles to be constructed are provided, and the numbers of the stirring piles to be constructed currently are 7 and 8 respectively; if the number of the stirring piles to be constructed currently is 16, three stirring piles are constructed nearby the stirring piles, and the numbers of the stirring piles to be constructed currently are 1, 2 and 15 respectively; if the current stirring pile to be constructed is marked with 12, four stirring piles are constructed adjacent to the current stirring pile, and the marks are respectively 4, 5, 6 and 11.

After the constructed mixing pile adjacent to the current mixing pile to be constructed is determined, the depth of the pile bottom of the current mixing pile to be constructed can be predicted, and the prediction method comprises the following steps: and taking the average value of the pile bottom depths of all the constructed stirring piles adjacent to the pile bottom.

And s1-5, carrying the depth of the pile bottom of the non-constructed stirring pile into a first linear function to obtain the soil rising prediction height.

And (3) carrying the pile bottom depth of the current non-constructed stirring pile predicted in the step (s 1-5) into a first linear function of the soil rising height obtained in the fitting in the step (s 1-3) relative to the pile bottom depth, and obtaining the soil rising predicted height in the pressure reducing hole corresponding to the current non-constructed stirring pile.

And s1-6, setting the first set depth according to the soil rising prediction height.

The specific prediction method comprises the following steps: the first set depth is greater than the soil elevation prediction height. Preferably, the first set depth is 1 to 3 meters greater than the soil elevation prediction height, for example, the difference between the two may be 2 meters. For example, if the predicted soil elevation height obtained in step s1-5 is 6 meters, the depth of the pressure relief hole corresponding to the stirring pile to be currently constructed is preferably set to 8 meters.

According to the earth surface protection type deep stirring pile construction method, on one hand, the pressure release step is added before deep stirring pile forming operation is carried out, so that the problems of rising, lateral shifting, road cracking and the like of soil bodies nearby construction existing in the deep stirring pile construction method in the prior art are solved, on the other hand, the depth of a decompression hole corresponding to an un-constructed stirring pile is guided according to the pile bottom depth of the constructed stirring pile and the rising height of soil in the decompression hole corresponding to each constructed stirring pile, the reasonable decompression hole depth is determined according to actual requirements, and on the premise of guaranteeing earth surface protection, construction cost is reduced.

The principles and embodiments of the present application have been described herein with reference to specific examples, the description of which is intended only to facilitate an understanding of the method of the present application and its core ideas. The foregoing is merely illustrative of the preferred embodiments of this application, and it is noted that there is objectively no limit to the specific structure disclosed herein, since numerous modifications, adaptations and variations can be made by those skilled in the art without departing from the principles of the application, and the above-described features can be combined in any suitable manner; such modifications, variations and combinations, or the direct application of the inventive concepts and aspects to other applications without modification, are contemplated as falling within the scope of the present application.

Claims (10)

1. The construction method of the earth surface protection type deep stirring pile is characterized by comprising the following steps of:

a decompression hole with a first set depth is formed at a set distance beside a planned position of a stirring pile to be constructed; the first set depth is smaller than or equal to the pile top depth of the stirring pile after construction;

and carrying out deep stirring pile forming operation at the planned position of the stirring pile.

2. The earth surface protection type deep mixing pile construction method according to claim 1, wherein the pressure reducing hole is formed according to the steps of:

drilling a drill rod with stirring blades underground at a set distance beside a planned position of a stirring pile to be constructed;

and taking the drill rod out of the ground to form the pressure reducing hole.

3. The earth surface protection type deep mixing pile construction method according to claim 1, wherein the pressure reducing hole is formed according to the steps of:

drilling a hollow steel pipe underground at a preset distance beside a planned position of a stirring pile to be constructed;

and (3) emptying the soil in the hollow steel pipe to form the pressure reducing hole.

4. A method of constructing a earth surface protected type deep mixing pile according to claim 3, wherein the first set depth is determined by:

pre-constructing a row of stirring piles, and constructing a pressure reducing hole with a second set depth at a set distance beside a planned position of each stirring pile before constructing each stirring pile; the second set depth is equal to the pile top depth of the stirring pile after construction;

acquiring the pile bottom depth of each stirring pile after construction and the soil rising height in the pressure reducing hole corresponding to each stirring pile, and obtaining a data set about the pile bottom depth and the soil rising height;

fitting to obtain a first linear function of soil elevation with respect to pile bottom depth by taking the data set as a sample value;

predicting the depth of the pile bottom of the non-constructed stirring pile according to the depth of the pile bottom of the constructed stirring pile;

carrying the depth of the pile bottom of the non-constructed stirring pile into a first linear function to obtain the soil rising prediction height;

and setting the first set depth according to the soil rising prediction height.

5. The earth surface protection type deep stirring pile construction method according to claim 1, wherein the deep stirring pile forming operation is performed according to the following steps:

the method comprises the steps of (1) positively and circularly drilling a main drill rod from a planned position of a stirring pile to be constructed to a first depth; the total drill rod comprises a first drill rod and a second drill rod which are connected through a third drill rod connector, and the top end of the first drill rod is connected with a rotary power head of the deep pile stirring machine through the first drill rod connector;

opening a high-pressure grouting pump on the deep pile mixer to spray slurry, and lifting the total drill rod to a second depth in a reverse circulation mode;

drilling the total drill rod in a positive circulation way and spraying cement slurry to the first depth;

turning off the high-pressure grouting pump, and reversely and circularly lifting the total drill rod to the second depth;

removing the third drill pipe joint and drilling the first drill pipe into the ground at the first location;

dismantling the first drill rod joint, and connecting a second drill rod with a rotary power head of the deep stirring pile machine through a second drill rod joint;

starting the high-pressure grouting pump, and positively circularly drilling the second drill rod to a third depth; the third depth is deeper than the second depth, and the depth difference of the third depth and the second depth is 500mm;

lifting the second drill rod in a reverse circulation mode and spraying cement slurry to the designed top elevation;

drilling the second drill rod in a positive circulation way and spraying cement slurry to the third depth;

and closing the high-pressure grouting pump, and reversely circularly lifting the second drill rod to the ground surface.

6. The earth surface protection type deep stirring pile construction method according to claim 5, wherein the second drill rod is formed by lengthening a plurality of unit sub drill rods; the unit sub drill rod positioned at the bottommost part is welded with the drill bit for drilling into a whole.

7. The earth surface protection type deep stirring pile construction method according to claim 5, wherein only one guniting port is arranged on the bottom side wall of the drill bit; an arc-shaped baffle is arranged on one side of the slurry spraying opening on the outer wall of the drill bit; the arc baffle is positioned in front of the rotation direction of the drill bit when the drill bit drills downwards.

8. The method for constructing the earth surface protection type deep mixing pile according to claim 5, wherein after the high-pressure grouting pump is turned off and the second drill rod is reversely and circularly lifted to the earth surface, the method further comprises the following steps:

and lifting the second drill rod in a reverse circulation mode, spraying cement slurry, and performing light grouting on the ground surface.

9. The earth surface protection type deep mixing pile construction method according to claim 5, wherein two total drill rods are installed on a rotary power head of the deep mixing pile machine in parallel; the pile forming diameter of the total drill rod is more than 1400mm and less than 1600mm; the axle center distance of the two total drill rods is larger than 1100mm and smaller than 1300mm.

10. The earth surface protection type deep stirring pile construction method according to claim 9, wherein all stirring pile planning positions are arranged in rows, each row of stirring pile planning positions are sequentially constructed row by row, and a pile center spacing between adjacent stirring pile planning positions is 1300mm to 1400mm.