Microbial pile drilling device suitable for island foundation reinforcement and reinforcement method

Abstract

The invention discloses a microbial pile drilling device suitable for island foundation reinforcement and a reinforcement method, belongs to the technical field of foundation reinforcement, and solves the problem that a traditional high-pressure jet grouting pile construction process is not suitable for island foundation reinforcement. The bottom of the drill rod is provided with a drill bit; an injection pipe is arranged in the drill rod; a one-way valve is arranged between the injection pipe and the drill rod; spiral blades are arranged on the outer side of the drill rod; a liquid outlet is formed in the rod wall of the drill rod, and a grouting hole is formed in the bottom of the drill bit. According to the method, the drill rod is used for drilling the pile hole in the soil body, the excitation slurry is injected into the drill rod, and the excitation slurry flows into the soil body through the liquid outlet to excite mass propagation of strains in the soil body; a cementing solution injected through the injection pipe is sprayed out from the grouting holes to be mixed with a soil body, and propagated microorganisms induce the cementing solution to generate precipitates to reinforce a foundation; according to the method, the drilling technology and the grouting technology are combined, drilling and grouting are conducted at the same time, and the method is suitable for foundation reinforcement in the island sandy soil environment.

Description

Technical Field

[0001] The invention relates to the technical field of foundation reinforcement, and in particular to a microbial pile drilling device and a reinforcement method suitable for island and reef foundation reinforcement. Background Art

[0002] The most important problem faced in the construction of island and reef areas is the high cost of material transportation, which is sometimes even higher than the cost of the materials themselves. Secondly, traditional cement production will produce a large amount of CO2, causing environmental pollution. Large-scale "gray garbage" is also bound to affect the ecological environment of the islands and reefs. Therefore, it is urgent to propose a feasible island and reef construction treatment plan.

[0003] Compared with traditional cement, magnesium oxide can be hydrated in a short time, and the generated magnesium hydroxide can also absorb CO2 in the air. In addition, for island and reef environments, seawater itself is rich in magnesium ions, so the introduction of magnesium oxide reaction will not affect the ecological environment of island and reefs. However, if magnesium oxide is to be used for pile formation, there are the following technical difficulties: First, the pile body is buried in the soil and cannot fully contact CO2, so precipitation cannot occur, which affects carbonization and makes the strength low; secondly, carbonization reaction cannot be carried out inside the pile body. In the traditional pile formation method, air-permeable pipe piles are used to make gas flow on the surface of the pile to promote the carbonization reaction. However, this method is complicated to construct and relies only on CO2 in the air, so the carbonization rate is still low.

[0004] Microbial induced calcium carbonate is a foundation reinforcement technology that uses the principle of microbial mineralization to cement loose soil into a whole with a certain strength. In this foundation reinforcement technology, urease secreted by microorganisms that can decompose urea is used to decompose urea to produce CO3 2- ,CO3 2- With Ca 2+ Mg 2+ The combination of calcium carbonate, magnesium carbonate and other minerals with cementing properties can not only fill the pores of the soil, but also cement the soil particles, and has a good ability to improve the soil; however, it has the disadvantages of long construction period, poor grouting uniformity, and low strength. In the construction process of traditional high-pressure jet grouting piles, it is generally used to drill holes first and use mud wall protection to stabilize the hole wall, but on the sandy foundation of islands and reefs, the hole wall supported by this method is not stable. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a microbial pile drilling device and reinforcement method suitable for island and reef foundation reinforcement, which solves the problem that the construction process of traditional high-pressure rotary jet piles is not suitable for reinforcing island and reef foundations.

[0006] In the first aspect, in order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is:

[0007] A microbial pile drilling device suitable for island and reef foundation reinforcement comprises a drill rod, a drill bit is arranged at the bottom of the drill rod; an injection pipe is arranged inside the drill rod; a one-way valve is arranged between the injection pipe and the drill rod; a spiral blade is arranged outside the drill rod; a liquid outlet is opened on the rod wall of the drill rod, and a grouting hole is opened at the bottom of the drill bit.

[0008] In this scheme, a pile hole is drilled in the soil using a drill rod when pouring the pile body, and an exciting slurry is injected into the drill rod. The exciting slurry can directly flow into the soil through the liquid outlet, thereby stimulating the proliferation of bacteria inside the soil. A cementing solution is then injected into the drill rod through an injection pipe, and the cementing solution is sprayed out from the grouting hole and mixed with the soil. The propagated bacteria induce the cementing solution to precipitate and reinforce the foundation. The drilling device is used to reinforce the foundation, combining the drilling process with the grouting process. Drilling and grouting are carried out simultaneously. There is no need to drill first and then use mud wall protection to build the pile hole. This scheme is suitable for foundation reinforcement in island and reef sandy soil environments.

[0009] Furthermore, the one-way valve includes a plurality of fan-shaped baffles, which are hinged to the inner wall of the drill pipe through hinges; the plurality of fan-shaped baffles form an annular structure, and the middle hole of the annular structure is used for the injection pipe to pass through; a spring is arranged between the side of the fan-shaped baffle away from the drill bit and the inner wall of the drill pipe.

[0010] Furthermore, a conical baffle is provided at the bottom of the injection pipe.

[0011] In this solution, when the injection pipe is passed downward through the fan-shaped baffle, the conical baffle pushes several fan-shaped baffles to open. After the conical baffle passes through the fan-shaped baffle, the fan-shaped baffle rebounds under the tension of the spring. When grouting into the injection pipe, the conical baffle moves up to the fan-shaped baffle under the reverse push of the slurry pressure. However, the fan-shaped baffle cannot rotate upward due to the restriction of the hinge, thereby preventing the conical baffle from moving upward. Therefore, high pressure is formed in the cavity between the fan-shaped baffle and the drill bit, causing the cementing solution to spray out from the grouting hole at the bottom of the drill bit, thereby realizing high-pressure grouting.

[0012] Furthermore, filter screens are provided in the liquid outlet and the grouting hole.

[0013] In this solution, a filter screen is provided to prevent soil particles from entering the drill rod during the drilling process of the drill rod.

[0014] Furthermore, an internal thread is tapped on the inner side of the drill rod, and an external thread is tapped on the outer side of the drill bit. The drill bit is connected to the bottom of the drill rod through the cooperation of the external thread and the internal thread; a positioning pin is also arranged between the drill rod and the drill bit.

[0015] In this solution, the positioning pin can position the drill rod and the drill bit to prevent the thread between the drill rod and the drill bit from loosening when the drill rod is screwed into or out of the soil.

[0016] In a second aspect, the present invention provides a microbial pile reinforcement method suitable for island and reef foundation reinforcement based on a microbial pile drilling device suitable for island and reef foundation reinforcement provided in the first aspect, comprising the following steps:

[0017] S1: Determine the location of the pile hole and drive the drill rod into the soil;

[0018] S2: preparing the stimulating slurry; injecting the stimulating slurry into the drill pipe, and the stimulating slurry flows to the soil around the drill pipe through the liquid outlet and the grouting hole, so as to multiply the urease bacteria existing in the in-situ soil;

[0019] S3: Place the jet pipe into the drill pipe until the conical baffle at the bottom of the jet pipe extends under several fan-shaped baffles;

[0020] S4: Pull out the drill rod upwards; while pulling out the drill rod, inject the prepared cementing solution into the injection pipe, and the cementing solution is sprayed out from the grouting hole at the bottom of the drill bit, mixed with the soil around the drill rod, and the foundation is reinforced;

[0021] S5: After the drill rod is pulled out, grouting is carried out and then left to stand for natural curing.

[0022] In this scheme, the exciting slurry enters the soil through the liquid outlet and grouting holes on the drill pipe, causing the urease bacteria existing in the in-situ soil to multiply in large quantities, providing conditions for the subsequent formation of sediments; the bacteria used are in-situ bacteria in the island and reef environment, which neither introduces new bacteria to cause damage to the ecological environment nor omits tedious steps such as artificially cultivating bacteria; moreover, the in-situ bacteria are more evenly distributed inside the soil, avoiding the uneven distribution of bacteria caused by artificial injection of bacteria.

[0023] Further, in S2, yeast extract, ammonium chloride, nickel chloride and urea are dissolved in water and mixed evenly to obtain an exciting slurry.

[0024] In this scheme, the stimulating slurry can make the urease bacteria in the soil that have the ability to decompose urease obtain sufficient nutrients and multiply in large quantities, thereby reserving a large number of bacteria for the subsequent carbonization of magnesium oxide.

[0025] Furthermore, in S2, after the stimulating slurry is injected into the soil around the drill pipe, it is left to stand for 2-3 days and then the cementing solution is injected for reinforcement.

[0026] In this scheme, after the excitation slurry is injected into the drill pipe, it will slowly seep into the surrounding soil. After the infiltration, it is necessary to induce the reproduction of urease bacteria, so it is necessary to wait for 2-3 days to ensure that the urease bacteria reproduce in large quantities.

[0027] Furthermore, the cementing solution is a mixture of urea, magnesium oxide and water.

[0028] In a third aspect, the present invention provides a method for preparing magnesium oxide based on a microbial pile reinforcement method suitable for island and reef foundation reinforcement provided in the second aspect, comprising the following steps:

[0029] T1: obtaining seawater and concentrating the seawater to obtain an electrolyte solution containing magnesium chloride;

[0030] T2: electrolyzing the electrolyte solution to obtain a precipitate containing Mg(OH)2;

[0031] T3: Filter and dry the Mg(OH)2 precipitate to obtain the precursor Mg(OH)2 powder;

[0032] T4: Calcine the precursor Mg(OH)2 powder to obtain magnesium oxide.

[0033] In this scheme, a large amount of magnesium chloride rich in seawater is used to prepare Mg(OH)2 precipitate through diaphragm electrolysis, and then magnesium oxide is generated through calcination. This method utilizes the seawater resources of the reef island to prepare magnesium oxide on site, saving the cost of raw material transportation.

[0034] The beneficial effects of the present invention are:

[0035] The drilling device for microbial piles suitable for island and reef foundation reinforcement provided by the present invention introduces a jet pipe into a traditional drill rod, and opens a liquid outlet on the side wall of the drill rod to ensure that the stimulated slurry is evenly dispersed into the surrounding soil, and high-pressure grouting can also be performed through the jet pipe; the drill rod and the jet pipe are respectively connected to external drilling equipment and grouting equipment, so that the drilling equipment and jet grouting can work at the same time, and the drilling work can be completed once, which reduces the construction procedures compared to the traditional construction method of drilling first and then grouting.

[0036] The microbial pile reinforcement method for island and reef foundation reinforcement provided by the present invention uses urease bacteria in situ in the island and reef environment, which neither introduces new bacteria to cause damage to the ecological environment, nor avoids tedious steps such as artificial cultivation of bacteria, nor the uneven distribution of bacteria caused by artificial injection of bacteria, thereby solving the problem of affecting the ecological environment of islands and reefs; the urease bacteria used decomposes urea through the urease secreted by it, providing sufficient CO3 for the carbonization of magnesium oxide cement. 2- , which solves the problem of magnesium oxide cement bored piles being blocked from carbonization when buried underground. The magnesium oxide used in the cementing solution can be produced from the seawater in the reef area, which not only ensures that no new substances are introduced to affect the ecological environment of the islands and reefs, but also solves the problem of high transportation costs for raw materials from inland to the islands and reefs. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic structural diagram of a microbial pile drilling device suitable for island and reef foundation reinforcement according to the present invention;

[0038] Figure 2 It is a cross-sectional schematic diagram of a microbial pile drilling device suitable for island and reef foundation reinforcement according to the present invention;

[0039] Figure 3 This is a schematic diagram of the one-way valve structure of the present invention;

[0040] Figure 4 It is a schematic diagram of the horizontal cross-section structure of the one-way valve of the present invention;

[0041] Figure 5 This is a schematic diagram of the internal structure of the drill rod sunk into the soil in Example 2;

[0042] Figure 6 This is a schematic diagram of the structure of injecting the exciting slurry into the drill pipe in Example 2;

[0043] Figure 7 This is a schematic diagram of the internal structure of the injection pipe placed in the drill pipe in Example 2;

[0044] Figure 8 This is a schematic diagram of the structure of pulling out the drill rod upward in Example 2.

[0045] Reference numerals:

[0046] 1. Drill rod; 11. Liquid outlet; 12. Positioning pin; 2. Drill bit; 21. Grouting hole; 3. Injection pipe; 31. Conical baffle; 4. One-way valve; 41. Fan-shaped baffle; 42. Spring; 43. Hinge; 5. Filter screen; 6. Spiral blade; DETAILED DESCRIPTION

[0047] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. The specific implementation of the present invention is described below to facilitate the understanding of the present invention by those skilled in the art, but it should be clear that the present invention is not limited to the scope of the specific implementation. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

[0048] like Figure 1 and Figure 2 As shown, this embodiment provides a microbial pile drilling device suitable for island and reef foundation reinforcement. The drilling device is designed with an injection pipe in a traditional drill rod, and high-pressure grouting can be achieved through the injection pipe; it specifically includes:

[0049] Drill rod 1, drill bit 2, jet pipe 3, one-way valve 4 and spiral blade 6;

[0050] Among them, a drill bit 2 is arranged at the bottom of the drill rod 1; an injection pipe 3 is arranged inside the drill rod 1; a one-way valve 4 is arranged between the injection pipe 3 and the drill rod 1; a spiral blade 6 is arranged on the outside of the drill rod 1; a liquid outlet 11 is opened on the rod wall of the drill rod 1, and a grouting hole 21 is opened at the bottom of the drill bit 2; when pouring the pile body, the drill rod 1 is used to drill a pile hole in the soil, and an exciting slurry is injected into the drill rod 1. The exciting slurry can directly flow into the soil through the liquid outlet 11 to stimulate the proliferation of bacteria in the soil; then a cementing solution is injected into the drill rod 1 through the injection pipe 3, and the cementing solution is sprayed out from the grouting hole 21 to mix with the soil, and the propagated microorganisms induce the cementing solution to produce precipitation to reinforce the foundation.

[0051] like Figure 3 and Figure 4 As shown, the one-way valve 4 includes a plurality of fan-shaped baffles 41, which are hinged to the inner wall of the drill pipe 1 through a hinge 43, and the hinge 43 is a hinge hinge that can only rotate 90 degrees; the plurality of fan-shaped baffles 41 form an annular structure, and the middle hole of the annular structure is used for the injection pipe 3 to pass through; a spring 42 is arranged between the side of the fan-shaped baffle 41 away from the drill bit 2 and the inner wall of the drill pipe 1; a conical baffle 31 is arranged at the bottom of the injection pipe 3. When the injection pipe 3 is passed downward through the fan-shaped baffle 41, the conical baffle 31 pushes several fan-shaped baffles 41 to open. After the conical baffle 31 passes through the fan-shaped baffle 41, the fan-shaped baffle 41 rebounds under the pulling force of the spring 42. When grouting is injected into the injection pipe 3, the conical baffle 31 moves up to the fan-shaped baffle 41 under the reverse push of the slurry pressure. However, the fan-shaped baffle 41 cannot rotate upward due to the restriction of the 90° rotating hinge 43, thereby preventing the conical baffle 31 from moving upward. Therefore, high pressure is formed in the cavity between the fan-shaped baffle 41 and the drill bit 2, so that the cementing solution is sprayed out from the grouting hole 21 at the bottom of the drill bit 2, thereby realizing high-pressure grouting.

[0052] A filter screen 5 is provided in both the liquid outlet 11 and the grouting hole 21 ; the filter screen 5 can prevent soil particles from entering the drill rod 1 during the drilling process of the drill rod 1 .

[0053] An internal thread is tapped on the inner side of the drill rod 1, and an external thread is tapped on the outer side of the drill bit 2. The drill bit 2 is connected to the bottom of the drill rod 1 through the cooperation of the external thread and the internal thread; a positioning pin 12 is also provided between the drill rod 1 and the drill bit 2; the positioning pin 12 positions the drill rod 1 and the drill bit 2 to prevent the thread between the drill rod 1 and the drill bit 2 from loosening when the drill rod 1 is screwed into or out of the soil.

[0054] Example 2

[0055] This embodiment provides a microbial pile reinforcement method suitable for island and reef foundation reinforcement based on a microbial pile drilling device suitable for island and reef foundation reinforcement provided in Embodiment 1, comprising the following steps:

[0056] S1: Level the site, determine the location of the pile hole, and drive the drill rod 1 into the soil; Figure 5 Shown

[0057] S2: dissolving yeast extract, ammonium chloride, nickel chloride and urea in water, and mixing them evenly to obtain an exciting slurry;

[0058] The exciting slurry is injected into the drill pipe 1, and the exciting slurry flows to the soil around the drill pipe 1 through the liquid outlet 11 and the grouting hole 21. Figure 6 As shown;

[0059] The stimulating slurry can make the urease bacteria in the soil that have the ability to decompose urease obtain sufficient nutrients and multiply in large quantities, thus reserving a large number of bacteria for the subsequent carbonization of magnesium oxide;

[0060] Let it stand for 2-3 days, and wait for the stimulated slurry to slowly seep into the surrounding soil. After the infiltration, it will induce the reproduction of urease bacteria and ensure the reproduction of urease bacteria in large quantities.

[0061] S3: Figure 7 As shown, the injection pipe 3 is placed inside the drill pipe 1 until the conical baffle 31 at the bottom of the injection pipe 3 extends under a plurality of fan-shaped baffles 41 .

[0062] S4: Figure 8 As shown, the drill rod 1 is pulled out upward; while the drill rod 1 is pulled out, the prepared cementing solution is injected into the injection pipe 3, and the cementing solution forms a high pressure in the cavity between the drill bit 2 and the fan-shaped baffle 41. The high pressure causes the cementing solution to be sprayed out from the grouting hole 21 at the bottom of the drill bit 2, and mixed with the soil around the drill rod 1 to reinforce the foundation; the cementing solution is a mixture of urea, magnesium oxide and water.

[0063] S5: After the drill rod 1 is pulled out, grouting is performed and then the drill rod is left to stand for natural curing.

[0064] In this embodiment, the exciting slurry enters the soil through the liquid outlet 11 and the grouting hole 21 on the drill pipe 1, so that the urease bacteria existing in the in-situ soil body multiply in large quantities, providing conditions for the subsequent generation of sediments; the bacteria used are in-situ bacteria in the island and reef environment, which neither introduces new bacteria to cause damage to the ecological environment nor omits tedious steps such as artificially cultivating bacteria; and the in-situ bacteria are more evenly distributed inside the soil, avoiding the uneven distribution of bacteria caused by artificial injection of bacteria.

[0065] Example 3

[0066] This embodiment provides a method for preparing magnesium oxide based on a microbial pile reinforcement method suitable for island and reef foundation reinforcement provided in Example 2; the method for preparing magnesium oxide utilizes seawater resources of the reef island to prepare magnesium oxide on site, saving the cost of raw material transportation; and specifically comprises the following steps:

[0067] T1: obtaining seawater and concentrating the seawater by boiling or rotary evaporation to obtain an electrolyte solution with a magnesium chloride concentration of 0.3 mol / L;

[0068] T2: At electrolysis temperature 30°C, current density 300A / m 2 , the electrolyte solution was electrolyzed under the electrolysis condition of an inter-electrode distance of 4 cm to obtain a precipitate containing Mg(OH)2;

[0069] T3: Filter and dry the Mg(OH)2 precipitate to obtain the precursor Mg(OH)2 powder;

[0070] T4: Calcine the precursor Mg(OH)2 powder, raise the calcination temperature to 400°C at a heating rate of 5°C / min, and calcine for 1 hour to obtain magnesium oxide; the maximum specific surface area of ​​the obtained magnesium oxide is 29.3m 2 / g, the minimum CAA is 66s, and the minimum grain size is 27.8nm.

[0071] Those skilled in the art will appreciate that the embodiments herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the invention.

Claims

1. A microbial pile drilling device suitable for island and reef foundation reinforcement, characterized in that: The invention comprises a drill rod (1), wherein a drill bit (2) is arranged at the bottom of the drill rod (1); an injection pipe (3) is arranged inside the drill rod (1); a one-way valve (4) is arranged between the injection pipe (3) and the drill rod (1); a spiral blade (6) is arranged on the outside of the drill rod (1); a liquid outlet (11) is provided on the rod wall of the drill rod (1), and a grouting hole (21) is provided at the bottom of the drill bit (2).

2. The microbial pile drilling device suitable for island and reef foundation reinforcement according to claim 1 is characterized in that: The one-way valve (4) comprises a plurality of fan-shaped baffles (41), wherein the plurality of fan-shaped baffles (41) are hinged to the inner wall of the drill rod (1) via hinges (43); the plurality of fan-shaped baffles (41) form an annular structure, wherein the middle hole of the annular structure is used for the injection pipe (3) to pass through; and a spring (42) is arranged between the side of the fan-shaped baffle (41) away from the drill bit (2) and the inner wall of the drill rod (1).

3. The microbial pile drilling device suitable for island and reef foundation reinforcement according to claim 2 is characterized in that: A conical baffle (31) is provided at the bottom of the injection pipe (3).

4. The microbial pile drilling device suitable for island and reef foundation reinforcement according to claim 3 is characterized in that: The liquid outlet (11) and the grouting hole (21) are both provided with a filter screen (5).

5. The microbial pile drilling device suitable for island and reef foundation reinforcement according to claim 4 is characterized in that: The drill rod (1) is tapped with an internal thread on the inside, and the drill bit (2) is tapped with an external thread on the outside; the drill bit (2) is connected to the bottom of the drill rod (1) through the cooperation of the external thread and the internal thread; a positioning pin (12) is also provided between the drill rod (1) and the drill bit (2).

6. A reinforcement method for a microbial pile drilling device suitable for island and reef foundation reinforcement according to claim 5, characterized in that: The following steps are involved: S1: Determine the pile hole position and drive the drill rod (1) into the soil; S2: preparing an exciting slurry; injecting the exciting slurry into the drill pipe (1), and the exciting slurry flows to the soil around the drill pipe (1) through the liquid outlet (11) and the grouting hole (21), so as to multiply the urease bacteria existing in the in-situ soil; S3: placing the injection pipe (3) into the drill pipe (1) until the conical baffle (31) at the bottom of the injection pipe (3) extends below the plurality of fan-shaped baffles (41); S4: Pull out the drill rod (1) upwards; while pulling out the drill rod (1), inject the prepared cementing solution into the injection pipe (3); the cementing solution is sprayed out from the grouting hole (21) at the bottom of the drill bit (2) and mixed with the soil around the drill rod (1) to reinforce the foundation; S5: After the drill rod (1) is pulled out, grouting is performed, followed by natural curing.

7. The reinforcement method of the microbial pile drilling device suitable for island and reef foundation reinforcement according to claim 6 is characterized in that: In S2, yeast extract, ammonium chloride, nickel chloride and urea are dissolved in water and mixed evenly to obtain an exciting slurry.

8. The reinforcement method of the microbial pile drilling device suitable for island and reef foundation reinforcement according to claim 7 is characterized in that: In the above-mentioned S2, the stimulating slurry is injected into the soil around the drill pipe (1), and then the soil is left to stand for 2-3 days before the cementing solution is injected for reinforcement.

9. The reinforcement method of the microbial pile drilling device suitable for island and reef foundation reinforcement according to claim 6, characterized in that: The cementing solution is a mixture of urea, magnesium oxide and water.

10. A method for preparing magnesium oxide according to claim 9, characterized in that: The following steps are involved: T1: obtaining seawater and concentrating the seawater to obtain an electrolyte solution containing magnesium chloride; T2: electrolyzing the electrolyte solution to obtain a precipitate containing Mg(OH)2; T3: Filter and dry the Mg(OH)2 precipitate to obtain the precursor Mg(OH)2 powder; T4: Calcine the precursor Mg(OH)2 powder to obtain magnesium oxide.

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