CN101353894B

CN101353894B - Filling pile construction pore-creating method of pervious ultra-deep loose backfill two-piece stone zone

Info

Publication number: CN101353894B
Application number: CN2008101190883A
Authority: CN
Inventors: 金传宏; 杨爱国; 周飞
Original assignee: China Oilfield Services Ltd; China National Offshore Oil Corp CNOOC
Current assignee: China Oilfield Services Ltd; China National Offshore Oil Corp CNOOC
Priority date: 2008-08-28
Filing date: 2008-08-28
Publication date: 2010-06-09
Anticipated expiration: 2028-08-28
Also published as: CN101353894A

Abstract

The invention discloses a drilling method for the construction of a cast-in-place pile of a dank ultra-deep loose refilling rubble area, which comprises the following steps: step 1: a slope area of 4m to 6m is arranged in an area right ahead an arranged pile casing to serve as a slurry return flow line, and a slurry pool is dug outside the slope area; step 2: residue is drawn out once every 1 hour to 3 hours during a punching process; step 3: all the drawn-out slurry flows backwards into a drilling hole by utilizing the slope area; step 4: when punching work is carried out, the proportion of the slurry in the hole is increased, thereby being capable of increasing wall retaining capability and reducing hole collapse risk; and step 5: after drilling is carried out to a stable stratum of certain depth, the proportion of the slurry in the hole is gradually reduced; slurry containing the residue is discharged; and the slurry is discharged once every 2 hours to 3 hours. By adopting the method that the slurry flows backwards naturally, the method of the invention changes the traditional mode of slurry circulation, maintains the balance of the slurry, simplifies the construction process and lowers the construction risk.

Description

Bored concrete pile construction pore-forming method for water-permeable ultra-deep loose backfilling of two-stone area

Technical Field

The invention relates to a construction hole forming method for a filling pile in a permeable ultra-deep loose backfilling two-stone area.

Background

The existing conventional cast-in-place pile hole forming technology is roughly divided into the following steps:

1. forming holes in a non-soil-squeezing mode: for example, drilling (digging) to form a hole by a dry operation method, drilling (digging) to form a hole by a slurry wall protection drill, and drilling (digging) to form a hole by a full casing follow-up wall protection method; wherein,

drilling (digging) a hole and drilling (digging) a hole by a mud retaining wall by a dry operation method are suitable for field construction with good engineering geological conditions, and hole collapse is basically not easy to generate;

the construction cost of drilling (digging) the hole by the full casing follow-up wall protection method is high, and is generally 1/3 higher than that of other methods.

2. Forming holes in a partial soil extrusion mode: long screw spinning pore-forming, punching pore-forming, drilling hole extruding pore-forming, pre-drilling pore-forming and driving (static pressure) precast pile; wherein,

the long-spiral pressure hole forming is suitable for site construction with good engineering geological conditions, basically does not easily generate hole collapse, and is mainly applied to the construction of small-diameter (d is less than or equal to 250mm) and medium-diameter (d is more than 250mm and less than 800mm) piles;

the punching and pore-forming are basically suitable for pore-forming under various geological conditions;

the hole drilling, squeezing and expanding for hole forming is suitable for site construction with good engineering geological conditions, basically does not easily generate hole collapse, and is mainly applied to construction of large-diameter (d is more than or equal to 800mm) piles;

the pre-drilled hole-forming driven (static pressure) precast pile is suitable for site construction with good engineering geological conditions, basically does not easily generate hole collapse, and is mainly applied to construction of small-diameter (d is less than or equal to 250mm) piles and medium-diameter (d is more than 250mm and less than 800mm) piles.

3. Extruding soil to form holes: sinking pipe cast-in-place pile, sinking pipe ramming (squeezing) expanded cast-in-place pile, (driving) static pressure precast pile, closed prestressed concrete pipe pile and closed steel pipe pile; wherein,

the immersed tube cast-in-place pile and the immersed tube ramming (extruding) expanded cast-in-place pile are suitable for forming holes in various soil layers with low penetration degree, and are mainly applied to the construction of small-diameter (d is less than or equal to 250mm) piles and medium-diameter (d is more than 250mm and less than 800mm) piles;

the (driven) static pressure precast pile, the closed prestressed concrete pipe pile and the closed steel pipe pile are suitable for construction of various soil layers with low penetration degree, and are mainly applied to construction of small-diameter (d is less than or equal to 250mm) piles and medium-diameter (d is more than 250mm and less than 800mm) piles;

the cost of the precast pile is higher than that of a cast-in-place concrete filling pile, and the cost of the steel pipe pile is higher than that of the precast pile.

The traditional ready-made hole bored concrete pile construction mud circulation has no two modes: one is a positive circulation mode, wherein slurry is injected into a drill rod (or a slurry pipe and other channels) from a slurry tank through a slurry pump to reach the bottom of a hole, and drilling slag is carried to flow back to a grit chamber along a drill hole and flow back to the slurry tank after being precipitated, and then the slurry is circulated in the mode. This requires that the formation being drilled be relatively stable (not prone to loss of mud, not prone to collapse of the borehole wall). In the other reverse circulation mode, generally adopting a pumping type, the slurry carrying the drilling slag is directly pumped from the bottom of the hole to a grit chamber through a sand pump, and the settled slurry is replenished from the hole opening. This approach is prone to the following problems: 1. when slurry is sucked from the bottom of a hole, the slurry level of the slurry in the hole is changed greatly due to untimely slurry supplement at the hole opening, the wall protection pressure of the hole wall at each position is reduced rapidly, the stress of a soil body is changed, hole collapse is easily caused for unstable stratums (such as quicksand, uncompacted sand, soil layers and the like) of the hole wall, and even accidents of buried drilling and collapse of a drilling machine are caused. 2. Such variations can also have adverse consequences for the formation where the borehole wall is unstable due to large differences in the properties (e.g., viscosity, specific gravity, etc.) of the pumped and replenished mud.

Disclosure of Invention

The invention aims to solve the technical problem of providing a bored concrete pile construction hole forming method for a permeable ultra-deep loose backfilling two-stone area, which can meet the requirement of large-diameter piles, and can avoid hole collapse when bored concrete pile construction hole forming is carried out under the conditions of special engineering geology (permeable areas, tidal range areas, uncompacted huge thick backfill layers and soft sludge interlayers).

In order to solve the problems, the invention provides a method for forming a hole in the construction of a cast-in-place pile in a permeable ultra-deep loose backfilled two-stone area, which comprises the following steps:

step 1, arranging a flooding slope area of 4-6 m as a slurry backflow channel in an area right in front of a well-placed pile casing, and excavating a slurry pool outside the flooding slope area; the flooding slope area is an inclined plane with an inclination angle of 5-8 degrees;

step 2, taking out slag every 1-3 hours in the punching process;

step 3, the drawn mud is completely reflowed back to the drill hole by utilizing the slope-flooding area;

step 4, increasing the specific gravity of the slurry in the hole while performing the punching operation; therefore, the wall protection capability can be improved, and the hole collapse risk is reduced;

and 5, after drilling to a certain depth of a stable stratum (a clay layer in the figure), gradually reducing the specific gravity of the slurry in the hole, and discharging the slurry containing slag once every 2-3 hours so as to shorten the hole cleaning time and ensure that the performance indexes (the specific gravity of the slurry is less than 1.25, the sand content is less than or equal to 8 percent and the viscosity is less than or equal to 28s) of the slurry before underwater concrete is poured are adjusted to be within the standard requirements.

Preferably, the slag is removed by using a slag removing barrel in the step 2.

The invention has the following advantages:

1. by adopting the method of natural backflow of the slurry, the traditional slurry circulation mode is changed, the in-out balance of the slurry is maintained, the construction process is simplified (the sand pump is not required to be used for pumping the slurry at the bottom of the hole), and the construction risk is reduced.

2. By adopting the method of mud natural backflow, the mud performance is easy to keep stable in the process of drilling special strata (permeable, tidal range sections, uncompacted huge thick backfill layers and soft sludge interlayers), the pressure of the hole wall retaining wall is kept relatively stable, and unfavorable results cannot be brought to the construction of the stratum with unstable hole walls.

3. By adopting the method, when the performance of the slurry needs to be adjusted, the method is simple and easy, and is beneficial to shortening the hole cleaning time, thereby reducing the construction time of the whole single hole and increasing the construction efficiency.

Drawings

FIG. 1 is a schematic cross-sectional view of the construction of the embodiment of the present invention.

Detailed Description

As shown in figure 1, the invention carries out bored concrete pile construction pore-forming on a backfilled two-stone layer 1, and a seabed silt layer 2, a powdery clay layer 3, a clay layer 4, a residual soil layer 5 and a strong weathering rock layer 6 are arranged below the backfilled two-stone layer 1 in sequence. The cast-in-place pile construction hole forming method specifically comprises the following steps:

step 1, placing a protective cylinder 9 at a certain depth (not less than 1.5 m) of a backfilled two-stone layer 1, a seabed sludge layer 2 and a silty clay layer 3, wherein the protective cylinder 9 can be placed by adopting a vibration sinking method. And (3) utilizing a drilling machine 7 and a percussion bit 8 to carry out punching construction on the backfilled two stone layers 1. A flooding slope area 10 with the range of 4-6 m is reserved right ahead of the placed casing 9 (namely, the position opposite to the installation position of the drilling machine 7) and is used as a channel for backflow of slurry into a drilling hole 12, and the flooding slope area 10 is an inclined plane with a certain inclination angle, and the inclination angle is preferably 5-8 degrees. In addition, excavating a mud pit 11 outside the general slope area 10;

2, digging slag once by using a slag digging barrel every 1-3 hours in the punching process, pouring the dug slag into a grit chamber (not shown) communicated with a mud tank 11, naturally settling the drilled slag, supplementing and refluxing the mud into the mud tank 11, collecting the mud by using the mud tank 11, and naturally refluxing and supplementing the mud into a drill hole 12 through a sloping region 10;

step 3, the taken out slurry (containing drilling slag) is precipitated in a grit chamber, flows back to a slurry tank 11, then naturally flows back to a drill hole 12 through a sloping region 10, and flows into the drill hole 12 through a top opening of a protective cylinder 9;

step 4, increasing the specific gravity of the slurry in the drill hole 12 through the backflow of the slurry during the punching operation, so that the wall protection capability can be improved, and the hole collapse risk is reduced;

and 5, after drilling to a certain depth of a stable stratum (a clay layer 4 in the figure), reducing the slurry flowing back into the original slurry tank 11 in the drill hole 12, gradually adding water to dilute the slurry to gradually reduce the specific gravity of the slurry in the drill hole 12, and discharging the slurry containing slag once every 2-3 hours to shorten the hole cleaning time and ensure that the performance indexes (the specific gravity of the slurry is less than 1.25, the sand content is less than or equal to 8 percent and the viscosity is less than or equal to 28s) of the slurry before underwater concrete is poured are adjusted within the standard requirements.

By adopting the method of natural backflow of the slurry, the invention changes the traditional slurry circulation mode, maintains the balance of the slurry in and out, simplifies the construction process (the sand pump is not needed for pumping the slurry at the bottom of the hole), and reduces the construction risk; in addition, by adopting the method of natural backflow of the slurry, the slurry performance is easy to keep stable in the process of drilling special strata (permeable, tidal range sections, uncompacted huge thick backfill layers and soft sludge interlayers), the pressure of the wall protection wall of the hole wall is kept relatively stable, and unfavorable results cannot be brought to the construction of the stratum with unstable hole walls.

Therefore, any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A construction hole forming method for a filling pile in a permeable ultra-deep loose backfilling two-stone area is characterized by comprising the following steps:

step 2, taking out slag every 1-3 hours in the punching process;

step 4, increasing the specific gravity of the slurry in the drill hole while performing the punching operation;

and 5, after drilling to a certain depth of a stable stratum, gradually reducing the specific gravity of the slurry in the drilled hole, and discharging the slurry containing the slag once every 2-3 hours.

2. A method according to claim 1, characterized in that the skimming is performed in step 2 by means of a skimming cylinder.