Drill rod capable of automatically eliminating excess pore water pressure in powder spraying pile construction and use method of drill rod

Abstract

The invention discloses a powder spraying pile construction excess pore water pressure autonomous eliminating drill rod and a using method thereof.The drill rod comprises a main drill rod body and a cement powder conveying pipeline, stirring blades are arranged at the lower end of the main drill rod body in the radial direction, an axial vacuum pipe and radial drainage blades are arranged at the upper middle end of the main drill rod body, and a vacuum pump is arranged at the top of the main drill rod body; the upper end of the vacuum pipe is connected with the vacuum pump, the lower end of the vacuum pipe is connected with the drainage blade, and a pipe cavity of the vacuum pipe is communicated with the cavity in the drainage blade. The negative pressure drainage mode is adopted, excess pore water pressure caused by compressed air in powder spraying pile construction is effectively eliminated, and the engineering problems of slope instability, ground cracking and the like induced by the excess pore water pressure are solved.

Description

Technical Field

[0001] The invention relates to the technical field of geotechnical engineering, in particular to a drill rod for autonomously eliminating excess pore water pressure in powder injection pile construction and a use method thereof. Background Art

[0002] Powder injection pile is a method of using compressed air to transport powder solidification materials, and using stirring blades to mix the solidification materials with soft soil to form cement soil piles to reinforce soft soil foundations. Powder injection pile method has the advantages of simple and fast construction and small vibration. It can effectively improve the stability of soft soil foundations and reduce and control settlement. However, the following problems still exist in the existing powder injection pile construction process: ① When there is an open surface, the construction of powder injection piles will cause slope instability; ② Construction near existing structures will cause ground cracks and damage to structures; ③After construction, the powder injection piles will suddenly sink.

[0003] The above problems are related to a short-term lateral pressure generated during the construction of powder injection piles, which leads to an increase in the surrounding pore water pressure. This short-term lateral pressure mainly comes from the lateral pressure exerted on the surrounding soil by the compressed air that sprays cement powder during the construction of powder injection piles and the shear force exerted on the surrounding soil by the mixing blades during mixing. The shear force exerted by the mixing blades on the surrounding soil cannot be avoided, but the increase in soil excess pore water pressure caused by the compressed air during powder injection can currently be eliminated based on the principle of consolidation and drainage. Summary of the invention

[0004] The purpose of the present invention is to provide a drill rod for automatically eliminating excess pore water pressure in powder injection pile construction and a method for using the drill rod, which can eliminate excess pore water pressure in the soil around the pile caused by compressed air during powder injection pile construction.

[0005] The technical solution adopted by the present invention is: A drill rod for automatically eliminating excess pore water pressure in powder injection pile construction comprises a main drill rod and a cement powder conveying pipeline, wherein a stirring blade is radially arranged at the lower end of the main drill rod, an axial vacuum tube and radial drainage blades are arranged at the middle and upper ends of the main drill rod, a vacuum pump is arranged at the top of the main drill rod, a cavity is arranged in the drainage blade, a through hole connected to the cavity is arranged on the surface of the drainage blade, a permeable stone is arranged in the through hole, the upper end of the vacuum tube is connected to the vacuum pump, the lower end is connected to the drainage blade, and the tube cavity of the vacuum tube is connected to the cavity in the drainage blade; the cement powder conveying pipeline is arranged in the cavity of the main drill rod, and the lower end thereof passes through the side wall of the main drill rod and extends from below the stirring blade to form a cement powder spraying outlet.

[0006] Furthermore, a plurality of evenly distributed semicircular grooves are axially provided on the surface of the main drill pipe, the upper end of the semicircular groove passes through the top of the main drill pipe, and the lower end stops above the mixing blade; a vacuum tube and a drainage blade are embedded in each semicircular groove, and the vacuum pump and the vacuum tube are arranged one by one, and each vacuum tube is connected to a vacuum pump and a drainage blade. The vacuum tube is embedded in the semicircular groove, which can protect the vacuum tube from being damaged by soil resistance during construction and reduce the resistance of the drill pipe. The vacuum pump and the vacuum tube are arranged one by one, which can ensure that the vacuum degree in the drainage blade and the vacuum tube meets the requirements of the suction force and does not interfere with each other.

[0007] Furthermore, a plurality of vacuum pumps are installed around the main drill rod, and the installation position is outside the length range of the powder injection pile, so as to ensure that the vacuum pump is always above the ground during the construction of the powder injection pile.

[0008] Furthermore, the drainage blades are arranged in layers, with one drainage blade arranged in each layer, and the interval between two adjacent layers of drainage blades is 30 to 50 cm. Arranging multiple layers of drainage blades evenly distributed in the axial direction can improve the drainage effect of water in the soil and make the water pressure in the soil around the pile evenly distributed.

[0009] Furthermore, the drainage blade is made of a hollow square tube, the width of which is smaller than the diameter of the main drill rod, and the length is the same as the stirring blade, and two circular through holes with a diameter of 3 to 5 cm are arranged on the upper surface of the hollow square tube, and a circular permeable stone is sealed and installed in each circular through hole. The structure is simple and the production cost is low.

[0010] Furthermore, the stirring blades are arranged in layers, each layer includes two stirring blades that are symmetrically distributed on the left and right, the stirring blades of two adjacent layers are spaced 20 to 30 cm apart, and the stirring blades of the bottom layer are located 10 to 30 cm above the cement powder spraying outlet, so as to further improve the stirring effect.

[0011] Furthermore, the stirring blades, the vacuum tube and the drainage blades are all welded to the main drill pipe.

[0012] Any of the above-mentioned methods for using a drill rod to autonomously eliminate excess pore water pressure in powder injection pile construction comprises the following steps: (1) The drill rod is lowered into the hole, cement powder is transported through the cement powder transport pipeline while drilling, and the vacuum pump is turned on at the same time; (2) After drilling to the specified depth, stop delivering cement powder, lift the drill rod upward, and keep the vacuum pump working to maintain the negative pressure inside the vacuum tube and drainage blades stable; (3) When the drill rod is lifted to 0.5 m below the ground, the drill is lowered for the second time and steps (1) and (2) are repeated to complete the construction of the single powder injection pile and the self-elimination of the excess pore water pressure in the soil around the pile.

[0013] The beneficial effects of the present invention are: (1) The present invention adopts a negative pressure drainage method, which effectively reduces the excess pore water pressure in the soil around the piles and the soil around the site caused by the powder injection piles, and reduces the risks of slope instability and ground cracking caused by the powder injection pile construction.

[0014] (2) The method of the present invention eliminates the excess pore water pressure in the soil around the pile and is carried out simultaneously with the construction of the powder injection pile, without increasing the work intensity of the powder injection pile construction, and has high construction efficiency.

[0015] (3) The present invention solves the problem of increased excess pore water pressure in the soil around the piles and the surrounding soil of the reinforcement site caused by compressed air during powder injection of the powder injection piles. It not only improves the construction quality of the powder injection piles, but also improves the safety of the powder injection pile applications. The equipment has a simple structure and is efficient in operation, and has significant social and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention is a schematic diagram of the overall structure of a drill rod for autonomously eliminating excess pore water pressure in powder injection pile construction.

[0017] Figure 2 Schematic diagram of the cross section of the drill pipe below the vacuum pump.

[0018] Among them: 1. vacuum pump; 2. semicircular groove; 3. drainage blade; 4. stirring blade; 5. cement powder spray outlet; 6. permeable stone; 7. upper surface of drainage blade; 8. vacuum tube; 9. main drill rod; 10. cement powder conveying pipeline. DETAILED DESCRIPTION Example 1

[0019] See also Figure 1 and Figure 2 The present invention provides a drill rod for automatically eliminating excess pore water pressure in powder injection pile construction, comprising a main drill rod 9, which is a hollow structure with a conical end. A cement powder delivery pipeline 10 is axially arranged in the cavity of the main drill rod 9, and the lower end of the cement powder delivery pipeline 10 extends to the upper side of the conical end of the main drill rod 9 and radially passes through the circumferential side wall of the main drill rod 9 to form a cement powder spraying outlet 5.

[0020] A plurality of stirring blades 4 are radially arranged at the lower end of the main drill rod 9, and the stirring blades 4 are arranged in layers. For example, three layers are arranged in this embodiment; the stirring blades in each layer are spaced 20 to 30 cm apart, and the net distance between the stirring blades in the bottom layer and the cement powder spraying outlet 5 is 10 to 30 cm, that is, the distance between the bottom surface of the stirring blade and the top surface of the cement powder spraying outlet 5 is 10 to 30 cm; each layer includes two stirring blades symmetrically distributed on the left and right sides of the drill rod, that is, when viewed from top to bottom, the stirring blades on both sides form a straight line.

[0021] In other embodiments, the stirring blades of adjacent layers may also be arranged in a staggered manner, such as three layers of stirring blades are arranged at a circumferential interval of 60°.

[0022] Six semicircular grooves 2 are axially opened on the middle and upper end surface of the main drill rod 9, and the six semicircular grooves 2 are evenly distributed along the circumference of the main drill rod 9. The diameter of the semicircular groove 2 is preferably 1-2 cm, and its upper end passes through the top of the main drill rod, and the lower end stops 50 cm above the stirring blade 4.

[0023] A vacuum tube 8 and a drainage blade 3 are arranged in each groove, that is, in this embodiment, a total of 6 drainage blades 3 and 6 vacuum tubes 8 are arranged.

[0024] The six drainage blades 3 are divided into six layers, radially arranged in six semicircular grooves 2 on the surface of the main drill pipe, with each layer spaced 30 to 50 cm apart. That is, when viewed from top to bottom, the six drainage blades 3 are evenly distributed along the circumference of the main drill pipe at 60° intervals. A cavity is provided inside the drainage blade 3, and a circular hole communicating with the cavity is provided on the upper surface 7 of the drainage blade 3, in which a permeable stone 6 is sealed and installed.

[0025] In this embodiment, the drainage blade is made of a hollow square tube, the width of the hollow square tube is slightly smaller than the diameter of the main drill rod 9, the length is the same as the stirring blade 4, two circular holes are arranged on the upper surface at intervals, the diameter of the circular hole is 3-5 cm, and a circular permeable stone is installed in the circular hole, and the joint between the permeable stone and the circular hole is sealed by a waterproof adhesive. One end of the hollow square tube is set to an arc shape, radially embedded in the semicircular groove 2, and welded to the semicircular groove.

[0026] Six small vacuum pumps 1 are arranged on the top of the main drill pipe 9 . The six small vacuum pumps 1 are installed around the main drill pipe 9 and correspond to the six vacuum tubes 8 one by one.

[0027] Six vacuum tubes 8 of different lengths are axially embedded in six semicircular grooves 2 one by one, and their upper ends extend out of the main drill rod 9 and are connected to a small vacuum pump 1, and their lower ends are connected to the drainage blade 3, and their tube lumens are connected to the cavity of the drainage blade 3.

[0028] Preferably, the lower ends of the vacuum tube 8 , the stirring blade 4 , and the cement powder conveying pipeline 10 are all welded to the main drill pipe 9 .

[0029] The method of use of Example 1 is: (1) The drill rod is lowered into the hole, and cement powder is conveyed through the cement powder conveying pipeline 10 while drilling. The cement powder is ejected from the cement powder ejection port 5 and is evenly mixed with the soil under the action of the stirring blade 4. At the same time, the vacuum pump 1 is turned on; (2) After drilling to the specified depth, the cement powder is stopped, the drill rod is lifted upward, and the vacuum pump 1 continues to work to maintain the negative pressure inside the vacuum tube 8 and the drainage blade 3 stable; the groundwater enters the internal cavity of the horizontal drainage blade 3 through the permeable stone 6 on the upper surface 7 of the drainage blade, and is sucked by the vacuum pump 1 through the vacuum tube 8 and discharged to the surface under the action of negative pressure suction; (3) When the drill rod is lifted to 0.5 m below the ground, the drill is lowered for the second time and steps (1) and (2) are repeated to complete the construction of the single powder injection pile and the self-elimination of the excess pore water pressure in the soil around the pile.

[0030] Application Example 1: A soft soil foundation treatment project for a highway in Lianyungang, Jiangsu Province, has a deep and high-water content soft soil layer with a water content of 67%. It is planned to use powder injection piles for reinforcement. In order to eliminate the excess pore water pressure of the soil around the piles and the soil layer around the site caused by the construction of powder injection piles, the drill rod of the present invention is used to construct powder injection piles, and the steps of Example 1 are carried out during construction. Before construction, pore water pressure gauges are arranged in the depth direction around the soil around the piles and the construction site to monitor the pore water pressure in the soil around the piles and the soil layer around the construction site during the construction of powder injection piles. The monitoring results are shown in Table 1 below.

[0031] It can be seen from Table 1 that when the drill rod of the present invention is used, the pore water pressure in the soil around the pile and the soil layer around the construction site does not increase significantly, indicating that the present invention effectively eliminates the excess pore water pressure caused by compressed air in the powder injection pile construction.

[0032] Although the present invention has been illustrated and described with respect to the preferred embodiments, it will be appreciated by those skilled in the art that various changes and modifications may be made to the present invention without departing from the scope of the present invention as defined by the claims.

Claims

1. A drill rod for automatically eliminating excess pore water pressure in cement injection pile construction, comprising a main drill rod (9) and a cement powder delivery pipeline (10), characterized in that: A stirring blade (4) is radially arranged at the lower end of the main drill rod (9), an axial vacuum tube (8) and radial drainage blades (3) are arranged at the middle and upper end of the main drill rod (9), a vacuum pump (1) is arranged at the top of the main drill rod (9), a cavity is arranged inside the drainage blade (3), a through hole communicating with the cavity is arranged on the surface of the drainage blade, a permeable stone (6) is arranged inside the through hole, the upper end of the vacuum tube (8) is connected to the vacuum pump (1), the lower end is connected to the drainage blade (3), and the tube cavity of the vacuum tube (8) is communicated with the cavity inside the drainage blade (3); The cement powder conveying pipeline (10) is arranged in the cavity of the main drill rod (9), and its lower end passes through the side wall of the main drill rod and extends from below the stirring blade (4) to form a cement powder spraying outlet (5).

2. According to claim 1, a drill rod for automatically eliminating excess pore water pressure in powder injection pile construction is characterized in that: A plurality of evenly distributed semicircular grooves (2) are axially provided on the surface of the main drill rod (9), the upper end of the semicircular groove passes through the top of the main drill rod, and the lower end ends at the top of the stirring blade (4); a vacuum tube (8) and a drainage blade (3) are embedded in each semicircular groove, the vacuum pump (1) and the vacuum tube (8) are arranged in a one-to-one correspondence, and each vacuum tube is connected to a vacuum pump (1) and a drainage blade (3).

3. The drill rod for automatically eliminating excess pore water pressure in powder injection pile construction according to claim 2 is characterized in that: A plurality of vacuum pumps (1) are installed around the main drill rod (9), and the installation position is outside the range of the length of the powder injection pile.

4. The method for autonomously eliminating excess pore water pressure in powder injection pile construction according to claim 2 is characterized in that: The drainage blades (3) are arranged in layers, with one drainage blade (3) being arranged on each layer, and the interval between two adjacent layers of drainage blades is 30 to 50 cm.

5. The drill rod for automatically eliminating excess pore water pressure in powder injection pile construction according to claim 1 is characterized in that: The drainage blade (3) is made of a hollow square tube, the width of which is smaller than the diameter of the main drill rod (9), and the length of which is the same as that of the stirring blade (4). Two circular through holes with a diameter of 3 to 5 cm are arranged at intervals on the upper surface of the hollow square tube, and a circular permeable stone (6) is sealed and installed in each circular through hole.

6. The drill rod for automatically eliminating excess pore water pressure in powder injection pile construction according to claim 1 is characterized in that: The stirring blades (4) are arranged in layers, each layer comprising two stirring blades symmetrically distributed on the left and right, the stirring blades of two adjacent layers are spaced 20 to 30 cm apart, and the stirring blades of the bottom layer are located 10 to 30 cm above the cement powder spraying outlet (5).

7. The drill rod for automatically eliminating excess pore water pressure in powder injection pile construction according to claim 1, characterized in that: The stirring blade (4), the vacuum tube (8) and the drainage blade (3) are all welded to the main drill rod (9).

8. The method for using a drill rod for autonomously eliminating excess pore water pressure in powder injection pile construction according to any one of claims 1 to 7, characterized in that: The following steps are involved: (1) The drill rod is lowered into the hole, cement powder is conveyed through the cement powder conveying pipeline (10) while the drill is lowered, and the vacuum pump (1) is turned on at the same time; (2) After drilling to a specified depth, the cement powder delivery is stopped, the drill rod is lifted upward, and the vacuum pump (1) continues to work to maintain a stable negative pressure inside the vacuum tube (8) and the drainage blade (3); (3) When the drill rod is lifted to 0.5 m below the ground, the drill is lowered for the second time and steps (1) and (2) are repeated to complete the construction of the single powder injection pile and the self-elimination of the excess pore water pressure in the soil around the pile.

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