CN111706261A - Construction method for gas lift slag-return pore-forming of roller drill of large-diameter ultralong rock-socketed pile - Google Patents
Construction method for gas lift slag-return pore-forming of roller drill of large-diameter ultralong rock-socketed pile Download PDFInfo
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- CN111706261A CN111706261A CN202010588317.7A CN202010588317A CN111706261A CN 111706261 A CN111706261 A CN 111706261A CN 202010588317 A CN202010588317 A CN 202010588317A CN 111706261 A CN111706261 A CN 111706261A
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- 238000010276 construction Methods 0.000 title claims abstract description 39
- 238000005553 drilling Methods 0.000 claims abstract description 180
- 239000011435 rock Substances 0.000 claims abstract description 41
- 239000002893 slag Substances 0.000 claims abstract description 37
- 238000000034 method Methods 0.000 claims abstract description 28
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 24
- 229910001868 water Inorganic materials 0.000 claims abstract description 24
- 230000008569 process Effects 0.000 claims abstract description 20
- 238000004140 cleaning Methods 0.000 claims abstract description 14
- 238000001914 filtration Methods 0.000 claims abstract description 10
- 239000002002 slurry Substances 0.000 claims description 80
- 229910000831 Steel Inorganic materials 0.000 claims description 59
- 239000010959 steel Substances 0.000 claims description 59
- 239000003570 air Substances 0.000 claims description 35
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B21/00—Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor
- E21B21/01—Arrangements for handling drilling fluids or cuttings outside the borehole, e.g. mud boxes
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B10/00—Drill bits
- E21B10/08—Roller bits
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B21/00—Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor
- E21B21/14—Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor using liquids and gases, e.g. foams
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B21/00—Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor
- E21B21/16—Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor using gaseous fluids
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Abstract
The invention relates to a construction method for forming a hole in a large-diameter ultralong rock-socketed pile by using a roller bit to crush rock after a reverse circulation drilling machine drills to a rock-entering elevation, and the roller bit drills by using a gas-lift reverse circulation method. The drilling process of the reverse circulation drilling machine comprises three stages of drilling. According to the invention, the rock mass is crushed by using the roller bit instead of the percussion bit, so that the drilling efficiency is greatly improved, and the risk of pile foundation hole collapse and concrete over-square is reduced; the invention discharges the rock slag blocks in time while drilling, the hole bottom is clean, the drill cuttings at the hole bottom are broken repeatedly and less, the hole cleaning efficiency is high, and the pile forming quality is better; the mud is recycled between the casing and the mud pit, and special filtering facilities are arranged, so that the pollution of pile foundation construction to the water environment can be effectively prevented, and economic and social benefits are achieved.
Description
Technical Field
The invention relates to the technical field of pile foundation construction, in particular to a construction method for a large-diameter overlong rock-socketed pile roller drill gas lift slag-reversing hole forming.
Background
According to technical specification for highway bridge and culvert construction (JTG/T F50-2011), the definition of large-diameter piles: a cast-in-situ bored pile having a diameter of 2.5m or more; definition of the super-long pile: the length of the cast-in-situ bored pile is greater than or equal to 90 m.
At present, the large-diameter overlong pile hole forming mainly adopts construction technologies such as rotary drilling, impact drilling, rotary drilling and the like. The rotary drilling comprises forward circulation drilling and reverse circulation drilling, wherein the forward circulation drilling and the reverse circulation drilling are used for protecting the hole wall and discharging slag through circulation of slurry, the forward circulation drilling and the reverse circulation drilling are the same in drilling hole forming process, applicable stratums are basically the same, and the difference is the circulation mode of the slurry. The positive circulation drilling machine discharges slag by means of natural circulation of slurry, so that the circulation capacity and the slag discharge capacity are weak, only a part of drilling slag can be discharged during the construction of the large-diameter super-long pile, the drilling slag with large particles cannot be discharged, more drilling slag remains in a hole, the drilling speed is influenced, and the abrasion of a drilling tool is large. The circulation mode of the mud of the reverse circulation drilling machine is just opposite, the mud pump is used for conveying the mud into the hole from the hole opening (outside the drill rod), and then compressed air or the mud pump is used for pumping out the mud from the middle of the drill rod, so that the circulation capacity and the slag discharging capacity are strong, the slag discharging capacity is clean, and the drill slag with larger particles can be discharged, so that the reverse circulation drilling machine is more suitable for drilling holes in a weak stratum of a large-diameter super-long pile.
In recent years, new technology for drilling large-diameter drilling hard rock is explored at home and abroad, although some practical conclusions are summarized, the characteristics of the construction technology and the construction method of the large-diameter overlong rock-socketed pile in water are lack of unified and systematic knowledge.
Aiming at construction of a main pier pile foundation of a super-large bridge with higher navigation requirements and environmental protection requirements, the traditional impact drill is selected for forming holes, the work efficiency is extremely low, the design requirements on the thickness control of sediments are difficult to achieve, the combined conversion of reverse circulation hole forming and the impact drill has higher requirements on various indexes such as mud proportion and the like, and hole collapse and concrete over-square are easily caused. Therefore, when the pile length is long, the aperture is large, and the sediment index is strict, the traditional method can not meet the construction requirement.
Disclosure of Invention
The invention aims to provide a large-diameter overlong rock-socketed pile roller drill gas lift slag-reversing hole forming construction method which can make up for the defects of the traditional hole forming method.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a large-diameter overlong rock-socketed pile roller drilling gas lift reverse slag pore-forming construction method is characterized in that a roller bit is adopted to crush rock after a reverse circulation drilling machine drills to a rock entering elevation, and the roller bit drills by a gas lift reverse circulation method.
Further, the drilling process of the reverse circulation drilling machine is divided into the following three stages:
and (3) drilling in the casing: drilling from the bottom opening of the protective cylinder by adopting reverse circulation pressurized clear water, controlling the footage to be 2-4 m per hour, supplementing clear water into the hole, treating the mixed slurry and then refluxing into the protective cylinder;
the drilling stage of the weak stratum with the casing is as follows: when drilling to a position 1-2 m close to the bottom opening of the steel casing, replacing a mechanical drill bit, reversely circulating and idling the drill bit when the drill is started, starting a slurry circulating system, and replacing slurry in the hole; when the index of the slurry in the hole meets the requirement, the slurry retaining wall is subjected to reverse circulation reduced pressure drilling, the slurry is slowly drilled near the bottom opening of the retaining cylinder to form a stable hole wall, the footage is controlled to be about 0.3-0.8 m per hour, and the drill bit is restored to normal drilling after leaving the distance from one end of the retaining cylinder;
a rock stratum drilling stage: and when the reverse circulation rotary drilling machine drills into a hard rock stratum, stopping drilling and confirming the elevation of the pile foundation entering the rock.
Preferably, in the drilling stage of the weak stratum below the casing, the drill bit resumes normal drilling after 5-6 m out of the casing.
Furthermore, the mud circulation system comprises a steel sedimentation tank and a steel mud tank which are communicated, the steel sedimentation tank and the steel mud tank are supported on water by a support frame, new manufactured mud is prepared in the steel mud tank and is pumped into the drill hole, and the mud with the drill slag discharged from the hole is pumped into the steel sedimentation tank for sedimentation and then enters the steel mud tank for recycling.
Preferably, the drilling stage in the casing adopts a drag bit with the diameter of 2.5m to drill.
Further preferably, in the drilling stage of the weak stratum below the casing, the length of the normal drilling is 1-3.5 m per hour.
Further, slurry is supplemented into the hole in the drilling process of the reverse circulation drilling machine, the height of a water head in the hole is maintained, and the slurry surface in the hole is higher than the water surface by more than 3.0 m.
Further, after confirming the rock entry depth, the reverse circulation rotary drilling machine lifts the drill bit, the roller bit is replaced, and gas-lift slag-returning equipment is installed and comprises an air compressor, an air pipe and a slag filtering device;
in the process that the roller bit drills and rotates on rocks simultaneously, compressed air is conveyed into the air inlet pipe through the air compressor, so that air-lift reverse circulation is formed in a drilling hole, three-phase flow of slurry, air and sediment in the hole moves upwards along the drill rod and is discharged from the hole and enters the residue filtering device, and the filtered slurry enters the hole again for recycling.
Further, cleaning the hole and changing slurry after drilling to the designed elevation, lifting the drilling tool away from the bottom of the hole by 30-50 cm during hole cleaning, slowly rotating the drilling tool, supplementing high-quality slurry, performing reverse circulation hole cleaning, and simultaneously keeping a water head in the hole to prevent hole collapse.
Compared with the prior art, the invention has the following beneficial effects:
1. according to the invention, the rock mass is crushed by using the roller bit instead of the percussion bit, so that the drilling efficiency is greatly improved, and the risk of pile foundation hole collapse and concrete over-square is reduced;
2, the invention discharges the rock slag blocks in time while drilling, the hole bottom is clean, the drill cuttings at the hole bottom are broken repeatedly less, the hole cleaning efficiency is high, and the pile forming quality is better;
3. the mud is recycled between the casing and the mud pit, and special filtering facilities are arranged, so that the pollution of pile foundation construction to the water environment can be effectively prevented, and economic and social benefits are achieved.
Drawings
FIG. 1 is a flow chart of the present invention;
FIG. 2 is a pile foundation drilling sequence diagram;
FIG. 3 is a schematic view of the construction of the mud circulation system of the present invention;
FIG. 4 is a schematic longitudinal section of a steel slurry tank and a settling tank platform;
FIG. 5 is a schematic cross-sectional view of a steel mud pit and settling pond platform;
FIG. 6 is a three-dimensional view of a steel box (reinforcing channels not shown);
FIG. 7 is a schematic view of one side of a steel sheet tank;
FIG. 8 is a schematic diagram of gas lift slag rejection.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings.
As shown in figure 1, the construction method for the gas lift reverse slag pore-forming of the roller cone drill of the large-diameter overlength rock-socketed pile disclosed by the invention adopts a roller cone drill bit to crush rock after a drilling machine drills to a rock-entering elevation, and adopts a gas lift reverse circulation method to drill during drilling of the roller cone drill bit. The hole forming method can discharge rock slag blocks in the hole in time during drilling, the hole bottom is clean, repeated crushing is less, and the drilling efficiency can be greatly improved.
The construction method is described in detail by taking the construction of the pile foundation of the main pier of the Donglihe bridge of the Shantou Shanbeidao Chenghai project as an example.
The navigation grade of the east-li river is a III-grade channel of the inland river, so that the overwater drilling platform is erected and the slurry circulation operation is completed on the platform, so that the high requirements on navigation and environmental protection are met. The pile diameter of the main bridge pier pile foundation is 2.5m, the pile enters rock at the depth of about 120m, weathered rock in the pile bottom embedding is not less than 2.5 times of the pile diameter according to design requirements, the sediment thickness is not more than 5cm, the hole forming work efficiency is extremely low by selecting the traditional impact drill under the rock entering requirement of nearly 6.25m, the design requirement on the sediment thickness is difficult to achieve, the combined conversion of reverse circulation hole forming and the impact drill has higher requirements on various indexes such as mud specific gravity and the like, and hole collapse and concrete over-square are easily caused.
Therefore, the drilling construction of the invention adopts a reverse circulation rotary drilling machine and a construction process of cone drilling gas lift reverse slag drilling, and mainly comprises mud wall protection, drilling hole forming and hole cleaning.
(1) Drilling sequence
As shown in fig. 2, the pile foundation construction requires hole jumping to reduce the influence of the later pile foundation construction on the previous pile foundation concrete before the design strength is not reached.
(2) Drill model selection
The main piers of the Donglihe super bridge totally comprise 36 cast-in-situ bored piles, the depth from the top surface of the pile casing to the bottom of the hole reaches about 130 meters, and the requirements on the torque of a drilling machine and the quality of a drill rod are high. 6 vehicle-mounted Xinfeng 351 type reverse circulation rotary drilling machines with advanced technical performance and stronger lifting capacity are selected for drilling soft strata, and each drilling machine is provided with 1 cone wheel drill bit for drilling strata. The performance index of the Xinfeng 351 reverse circulation rotary drilling machine is shown in the table 1.
TABLE 1 drill performance index Table
Working principle of Xinfeng 351 type reverse circulation rotary drilling machine: the mud is injected between the drill rod and the drill hole, and soil is cut along with the air injection of the drill rod, and the pipe diameter is much smaller than that of the hole, so that the mud, the cut soil slag and the like are quickly discharged out of the ground from the drill rod and can be recycled after entering a mud sedimentation tank for treatment.
(3) Slurry preparation and performance index
The wall protection slurry is very important in drilling, and is especially important for large-diameter deep holes, mud layers and sand layers with poor slurry making performance, and slurry control. The invention selects the PHP slurry with non-dispersion, low solid phase and high viscosity.
In order to ensure the smooth operation of the hole forming construction of the bored pile, before formal drilling, calcium bentonite in different producing areas and water, bentonite, caustic soda, PHP and the like in different proportions are selected for trial preparation and verification again, and the mud proportion with the optimal mud indexes is selected. The preparation of the slurry is carried out in the platform slurry preparation area.
Before drilling construction, firstly, a slurry stirrer is adopted to stir bentonite slurry in a slurry preparation area, then a slurry pump is used to pump the bentonite slurry into the steel casing, and when the performance index of the slurry in the steel casing meets the construction requirement, a hole is drilled for drilling.
The performance index requirements of the slurry in each construction stage are detailed in table 2.
TABLE 2 slurry Performance index List
(4) Slurry circulation system
In order to prevent the pollution of the construction of the pile foundation on the water to the environment, the invention is specially provided with a mud pit and a sedimentation tank with a water sizing and toughening steel structure.
As shown in fig. 3, 4 and 5, the mud circulation system of the present invention comprises a steel mud tank 8, a steel sedimentation tank 9 and a communication pipeline, wherein the steel sedimentation tank 9 is communicated with the steel mud tank 8, and the steel mud tank 8 and the steel sedimentation tank 9 are supported on water by a support frame 10. The plurality of pile foundation steel casing 6 are communicated in series through the communicating pipe 14. The mud pit 8 is communicated with one pile foundation steel casing 6 through a mud outlet pipe 13.
The support frame 10 comprises a plurality of foundation steel pipes 101, a main cross beam 102, a main longitudinal beam 103 and a bridge deck 104, wherein the cross beam 102 is erected on the foundation steel pipes 101, the bottom of the main longitudinal beam 103 is fixedly connected with the cross beam 102, the top of the main longitudinal beam 103 is connected with the bridge deck 104, and a steel mud tank 8 and a steel sedimentation tank 9 are installed on the bridge deck 104.
There are three main beams 102, and each main beam 102 is connected with two foundation steel pipes 101. An inclined strut 105 and a parallel connection 106 are arranged between two foundation steel pipes 101 connected with the same main beam 102.
In this embodiment, the steel-made slurry tank 8 and the steel-made sedimentation tank 9 are both 6m long, 4m wide, and 3m high. The bridge deck 104 is a 12 cm-thick shaping plate, 1021-type Bailey sheets are selected as the main longitudinal beams 103, the main longitudinal beams 103 are connected through connecting beams, and 8-number channel steel is selected as the connecting beams.
The main beam 102 is 45a double-spliced I-shaped steel, the base steel pipe 101 is a circular steel pipe with the diameter of 630mm and the wall thickness of 10mm, and the inclined strut 105 and the cross joint 106 are 20a channel steel.
As shown in fig. 6, a vertical partition 111 is provided in a steel plate tank 11 to divide the steel plate tank into two compartments, one compartment being a steel slurry tank 8 and the other compartment being a steel sedimentation tank 9, and the opening of the steel plate tank 11 is directed upward. As shown in fig. 7, the opening and bottom of the steel-plate case 11 are reinforced with a No. 8 channel 12, and the scissor back ribs are formed around the steel-plate case with the No. 8 channel 12. The top of the vertical partition 111 is provided with an overflow port 112 to realize the communication between the two compartments. The steel plate made box 11 has a plate thickness of 1cm, and the overflow port 112 is a rectangular notch of 50cm x 50 cm.
When in use, new slurry is prepared in the steel slurry pool 8 and is delivered into the pile foundation steel casing 6 through the slurry outlet pipe 13 by a slurry pump. After the drill is started, the drill pumps the slurry carrying the drill slag to the steel sedimentation tank 2 for sedimentation, then overflows into the steel slurry tank 1, then is conveyed to the pile foundation steel casing 6 through the slurry pump through the slurry outlet pipe 5, and flows into each drill hole through the communicating pipe between the pile foundation steel casing 6. A digging machine is specially configured in the drilling process to timely clean the drilling slag in the slurry sleeve box, and the drilling slag is intensively transported to a spoil area by a slag transport vehicle to be abandoned.
(5) Positioning and debugging of reverse circulation rotary drilling machine
Before the drilling machine is in place, all preparation works of drilling are comprehensively checked, and the drilling machine is in place after the completion of the check.
The base and the top end of the drilling machine after installation are stable, and displacement is not generated in the drilling process. The drilling machine should keep a good working state, the electric part has no potential safety hazard, and the motor shell should be grounded.
The drilling machine is positioned and leveled on the machine base, and whether the center of the drill bit and the center of the protective cylinder are on the same plumb line and whether the deviation between the drill bit and the center of the hole site is within the standard allowable range is carefully measured and checked. After the drilling tool is confirmed to be correct, whether the verticality of the drill rod meets the requirement, whether the drill rod, the drill bit and other parts are firmly connected, whether the operation is good, and whether the diameter of the drill bit is the same as the designed pile diameter are checked, the length of the drilling tool is checked, all indexes of the slurry are detected, and the drilling can be started after all the indexes are ready.
And detecting the levelness of the pile foundation base once a day in the drilling process, and stopping the drilling machine to pull out the drilling machine to level the base in time if the height difference of the diagonal line of the drilling machine base is more than 10 mm.
(6) Drilling hole by reverse circulation rotary drilling machine
The drilling process is divided into three stages: the drilling stage in the casing, the drilling stage of the weak stratum below the casing and the drilling stage of the rock stratum.
And (3) drilling in the casing: and (2) performing reverse circulation pressurized clear water drilling by adopting a scraper drill bit with the diameter of 2.5m from the bottom opening of the protective cylinder, controlling the footage to be about 2-4 m per hour, supplementing clear water into the hole, precipitating the mixed slurry in a sedimentation tank, then refluxing the slurry into the protective cylinder, and transferring the drilling slag to a slag disposal site.
The drilling stage of the weak stratum with the casing is as follows: when the drilling reaches about 1-2 m close to the bottom opening of the steel casing, a mechanical drill bit with the diameter phi of 2.5m is exchanged, the drill bit is reversely circulated and idled when the drilling is started, a slurry circulating system is started, slurry in the hole is replaced, after the index of the slurry in the hole meets the requirement, high-quality slurry wall protection is reversely circulated and decompressed for drilling, the drilling is slowly carried out near the bottom opening of the steel casing, a stable hole wall is formed, and the footage is controlled to be about 0.3-0.8 m per hour.
And (3) the drill bit resumes normal drilling after exiting the casing by 5-6 m, and according to the characteristics of different stratums, the indexes of the wall protection slurry and the drilling speed are adjusted in time in the drilling process, the drilling footage is 1-3.5 m per hour, and high-quality slurry is supplemented in the hole.
Corresponding drilling process parameters are adopted according to the geological conditions of the stratum, and the details are shown in a table 3.
TABLE 3 different stratum drilling parameter table
| Formation of earth | Weight drill (KN) | Number of revolutions (r/min) | Drilling speed (m/h) |
| Drilling in casing | ≤4.0 | ||
| Fine sand layer (dense) | 100～150 | 10～15 | 1.5～2.0 |
| Clay layer of silt and powder | 100～120 | 10～15 | 1～2 |
| Middle coarse sand layer (dense) | 150～300 | 5～10 | 2.0～3.0 |
| Bottom opening stratum of pile casing | ＜100 | 5～10 | 0.3～0.8 |
② drilling attention items
a. During the drilling process, the grout is supplemented into the hole at any time, and the water head height in the hole is maintained. The mud surface in the hole is higher than the river surface by more than 3.0m at any time.
b. The lifting drilling tool is stable, and particularly when the drill bit is positioned at the bottom opening of the protective cylinder, the lifting drilling tool must be carefully operated to prevent the drill bit from hooking the protective cylinder and avoiding colliding the steel protective cylinder to disturb the wall of the drilled hole.
c. When a long drill rod is connected, the drilling is stopped, the drilling tool is lifted to 20-30 cm away from the bottom of a hole, the slurry circulation is maintained for more than 10min to remove sediment at the bottom of the hole and carry out and discharge drilling slag in a pipeline, and then the pump is stopped to connect the long drill rod. The drill rod connecting bolt is firmly screwed, and the sealing ring is carefully checked to prevent the drill rod joint from water and gas leakage, so that the reverse circulation cannot work normally.
d. The drilling process should be operated continuously, and should not be stopped for a long time in the middle, so as to shorten the hole-forming period as much as possible.
(7) Confirming the elevation and depth of rock entry
And when the reverse circulation rotary drilling machine drills into a hard rock stratum and cannot drill continuously, confirming the elevation of the pile foundation entering the rock, and giving a specific rock entering depth.
(8) Change roller bit and install gas lift equipment
After confirming the rock-entering depth on site, the reverse circulation rotary drilling machine lifts the drill bit, changes the roller bit and installs the gas lift device. As shown in fig. 8, the gas lift slag returning device comprises an air compressor 1, an air pipe 4 and a slag filtering device 5.
Working platform 2 is installed in the drill way of pile foundation hole 7, and the entry end of pipe 3 stretches into the hole bottom of pile foundation hole 7, and filter residue device 5 is led to the export of pipe 3, and the air outlet of tuber pipe 4 extends to the entry end of pipe 3, and the income wind gap of tuber pipe 4 is connected with air compressor 1.
The outlet of the residue filtering device 5 is connected with the slurry circulating system. Preferably, the air pipe 4 is coaxial with the guide pipe 3, and a slag receiving basket is selected as the slag filtering device 5.
Type selection and installation of gas lift equipment:
as shown in fig. 8, the air duct 4The depth from the bottom to the top surface of the slurry in the hole is h1The height difference from the top surface of the slurry in the hole to the top surface of the slurry in the drill rod is h2The density of three-phase flow in the drill rod is rhonThe density of the liquid outside the drill rod is rhoωThen the pressure difference of the inner liquid column and the outer liquid column acting on the liquid level at the bottom of the air pipe is as follows:
ΔP＝ρω*h1-ρn(h1+h2)＝(ρω-ρn)*h1-ρn*h2(1)
the pressure difference drives the three-phase flow above the bottom opening of the air pipe 4 in the drill rod to rise along the drill rod, and various resistances in the circulation process are overcome to form reverse circulation. In consideration of the pressure loss of the air supply duct, the air pressure in the present invention is calculated by equation (2):
P＝ρn*h1/102+Ps(2)
in the formula (2), PsThe pressure loss of the air pipeline is 0.05-0.1 MPa.
From the equation (1), the slurry density ρ outside the pipeωAnd h1、h2Relatively stable, reducing the density ρ of the three-phase currentnThe pressure difference driving the gas lift reverse cycle will increase (by increasing the compressed air volume), so the air flow and pressure to the holes are important parameters affecting the gas lift slag-removing capacity. h is1The larger, h2The smaller h2 is, the greater the pressure difference is, so that reverse circulation can not be formed when slurry is in the hole, and the slurry surface in the hole is kept to reach a proper height so as to increase h1h1 reducing h2h2；ρωRho w is the density of three-phase flow, when the proportion of slurry solid phase in the hole is larger, reverse circulation can not be formed, and only rho w isωWhen ρ w is relatively small, ρ is increasedωρ w and ρnThe difference value of rho n can improve the slag-removing efficiency.
As can be seen from the equation (2), the choice of the air compressor should be determined by P, mainly by h1h1 and ρnAnd ρ n control. The pressure required is greater when the mud weight is greater when the hole is deeper. Therefore, the model of the air compressor is determined by calculating P according to the actual pile length of the project; reducing P as much as possiblesThe air duct should be checked frequentlyIf the air leaks, the pressure loss is minimized because the joint is tight.
(9) When the roller bit drills in, the gas lift equipment is started to form gas lift reverse circulation in the hole.
The drilling working principle of the roller bit is as follows: the drilling machine applies enough axial pressure and rotary torque to the bit through the drill rod, and when the roller bit rotates, each roller rotates around the self axis, and the rolling direction is opposite to the rotation direction of the bit. The teeth of the gear roll rock in the pressurizing and rolling process; because the teeth of the gear contact the rock alternately with single tooth and double tooth, the axis of the gear is high when the single tooth lands, and the axis is low when the double tooth lands, the process is repeated, so that the rock is impacted periodically; and because of the super-top, shaft withdrawing and moving of the cone and the complex cone shape of the cone, the cone still generates certain sliding when working at the bottom of the hole, thereby generating cutting action on rocks. Thus, roller cone drill bits break up rock in effect by a combination of impact, crushing and cutting.
The method for calculating the relevant parameters of the roller bit during drilling comprises the following steps:
a. axial pressure
The reasonable axial pressure can be calculated according to equation (3):
P＝(0.06～0.07)f D (3)
in formula (3), f is the firmness factor of the rock, and D is the drill diameter.
If the teeth of the roller cone are blunt, the axial pressure is increased; if the rock has cracks or blocks, the axial pressure is reduced appropriately to reduce the vibration of the drilling machine.
b. Torque of drilling tool
The torque M (N · M) of the drill is calculated according to equation (4):
M＝29.6kDP1.5(4)
in the formula (4), k is a rock characteristic coefficient; d, the diameter of the drill bit is mm; p-axial pressure, kN.
c. Drilling speed
The rate of penetration of the roller cone bit is estimated according to equation (5):
in the formula (5), P is axial pressure, kN; n-the rotation speed of the drilling tool, r/min; d, the diameter of the drill bit is mm; f is the hardness coefficient of the ore rock.
The working principle of the gas lift device is as follows: as shown in fig. 3 and 8, the air compressor delivers compressed air into the air duct, which is discharged through the bottom of the duct to form a gas-liquid mixture with the slurry. The sediment at the bottom of the hole is suspended under the impact action of the sprayed gas, and due to the density difference of liquid inside and outside the pipe, three-phase flow of slurry, air and sediment in the hole moves upwards along the drill pipe and is discharged out of the hole opening to enter the sediment receiving basket. And filtering sediments in the slurry, enabling the filtered slurry to flow into a steel sedimentation tank 9 for sedimentation, then overflowing into a steel slurry tank 8, then enabling the filtered slurry to enter the hole again through a slurry outlet pipe 13 by a slurry pump, and repeatedly circulating until the thickness of the sediments at the bottom of the hole meets the standard requirement.
The reverse circulation system takes gas as a power medium and takes liquid fluid as a delay-lift carrying medium to carry solid particles to return upwards to finally complete gas-liquid-solid three-phase mixed motion, thereby achieving the purposes of quickly forming holes and removing sediments and rock debris in the drill hole.
(10) And after the drilling hole reaches the preset drilling depth, measuring the hole depth and the sediment thickness, and confirming the final hole elevation. The sediment thickness is equal to the difference between the drilling depth and the depth of the hole before pouring.
Collecting drilling slag samples of each stratum in the drilling process, and taking the slag samples (2.5-3 m) once when a drill rod is replaced every time when the reverse circulation rotary drilling is carried out; after entering the rock, the slag sample is extracted once every 0.5m of drilling, the slag sample is fished from a slag hole and washed clean by clear water, the extraction amount is 100g each time, and the serial number is stored.
(11) One-time hole cleaning
And after finishing the hole, cleaning the hole in time. And lifting the drilling tool away from the bottom of the hole by about 30-50 cm during hole cleaning, slowly rotating the drilling tool, supplementing high-quality slurry, performing reverse circulation hole cleaning, and simultaneously keeping a water head in the hole to prevent hole collapse. And when the thickness of the sediment at the bottom of the hole meets the design requirement through detection, stopping to lift the drill in time, moving away the drill and detecting the hole after the index of the slurry in the hole after hole cleaning meets the requirement (the circulation time is controlled to be 2-4 hours, and the circulation meets more than 2 cycles). And detecting the pore diameter and the verticality of the formed hole by using a full-automatic ultrasonic pore-forming detector. And (5) performing pile-forming construction as soon as possible after the pore-forming inspection is qualified.
The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is therefore intended that all such changes and modifications as fall within the true spirit and scope of the invention be considered as within the following claims.
Claims (9)
1. A construction method for gas lift slag-reversing pore-forming of a roller drill of a large-diameter ultralong rock-socketed pile is characterized in that: after the reverse circulation drilling machine drills to the rock entering elevation, the rock entering is broken by the roller bit, and the roller bit drills by a gas lift reverse circulation method.
2. The large-diameter overlength rock-socketed pile roller drilling gas lift slag-reversing hole-forming construction method according to claim 1, characterized in that: the drilling process of the reverse circulation drilling machine is divided into the following three stages:
and (3) drilling in the casing: drilling from the bottom opening of the protective cylinder by adopting reverse circulation pressurized clear water, controlling the footage to be 2-4 m per hour, supplementing clear water into the hole, treating the mixed slurry and then refluxing into the protective cylinder;
the drilling stage of the weak stratum with the casing is as follows: when drilling to a position 1-2 m close to the bottom opening of the steel casing, replacing a mechanical drill bit, reversely circulating and idling the drill bit when the drill is started, starting a slurry circulating system, and replacing slurry in the hole; when the index of the slurry in the hole meets the requirement, performing reverse circulation reduced pressure drilling on the slurry retaining wall, slowly drilling near the bottom opening of the retaining cylinder, controlling the footage to be about 0.3-0.8 m per hour, and recovering normal drilling after the drill bit is out of one end of the retaining cylinder;
a rock stratum drilling stage: and when the reverse circulation rotary drilling machine drills into a hard rock stratum, stopping drilling and confirming the elevation of the pile foundation entering the rock.
3. The large-diameter overlength rock-socketed pile roller drilling gas lift slag-reversing hole-forming construction method according to claim 2, characterized in that: and in the drilling stage of the weak stratum below the protective sleeve, when the drill bit is 5-6 m out of the protective sleeve, the normal drilling is recovered.
4. The large-diameter overlength rock-socketed pile roller drilling gas lift slag-reversing hole-forming construction method according to claim 2, characterized in that: the mud circulation system comprises a steel sedimentation tank and a steel mud tank which are communicated, the steel sedimentation tank and the steel mud tank are supported on water by a support frame, new manufactured mud is prepared in the steel mud tank and is pumped into a drilling hole by a mud pump, and the mud with drilling slag discharged from the hole is pumped into the steel sedimentation tank for sedimentation and then enters the steel mud tank for recycling.
5. The large-diameter overlength rock-socketed pile roller drilling gas lift slag-reversing hole-forming construction method according to claim 2, characterized in that: and a drag bit with the diameter of phi 2.5m is adopted for drilling in the drilling stage in the protective cylinder.
6. The large-diameter overlength rock-socketed pile roller drilling gas lift slag-reversing hole-forming construction method according to claim 2, characterized in that: and in the drilling stage of the weak stratum below the casing, the length of the drill rod is 1-3.5 m per hour during normal drilling.
7. The large-diameter overlength rock-socketed pile roller drilling gas lift slag-reversing hole-forming construction method according to claim 2, characterized in that: and replenishing slurry into the hole in the drilling process of the reverse circulation drilling machine, and maintaining the height of a water head in the hole to ensure that the slurry surface in the hole is higher than the water surface by more than 3.0 m.
8. The large-diameter overlength rock-socketed pile roller cone drilling gas lift slag-reversing hole-forming construction method according to claim 1, 2, 3 or 4, characterized in that: after the rock entry depth is confirmed, the reverse circulation rotary drilling machine lifts the drill bit, the roller bit is replaced, and gas-lift slag-returning equipment is installed and comprises an air compressor, an air pipe and a slag filtering device;
in the process that the roller bit drills and rotates on rocks simultaneously, compressed air is conveyed into the air inlet pipe through the air compressor, so that air-lift reverse circulation is formed in a drilling hole, three-phase flow of slurry, air and sediment in the hole moves upwards along the drill rod and is discharged from the hole and enters the residue filtering device, and the filtered slurry enters the hole again for recycling.
9. The large-diameter overlength rock-socketed pile roller drilling gas lift slag-reversing hole-forming construction method according to claim 1, characterized in that: and when the drilling is carried out to the designed elevation, cleaning the hole and changing the slurry, lifting the drilling tool away from the bottom of the hole by 30-50 cm during hole cleaning, rotating the drilling tool, supplementing high-quality slurry, and carrying out reverse circulation hole cleaning.
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