Strong-water-permeability sand layer reinforcing method based on environment-friendly slurry

Abstract

The invention relates to the technical field of tunnel construction, and discloses a strong-water-permeability sand layer reinforcing method based on environment-friendly slurry, which comprises the following steps: preparing kaolin slurry and microorganism slurry for later use, determining a drilling position, drilling a preset pile position to a designed elevation, injecting the kaolin slurry into a drilled hole, and injecting the microorganism slurry into the drilled hole; and after the kaolin is completely deposited, injecting the microorganism slurry. According to the idea of first infiltration reduction and then reinforcement, environment-friendly slurry is adopted, high-pressure rotary jet grouting is conducted on the sand layer, kaolin slurry is injected firstly, water in the water-containing sand layer is absorbed, the porosity of the water-containing sand layer is reduced, and therefore the water plugging effect is achieved, the porosity and permeability of the sand layer are reduced, and the adhesion area of bacteria is increased; and then microorganism slurry is injected to reinforce the sand layer in a mode of inducing calcium carbonate crystallization by microorganisms.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel construction, and in particular to a highly permeable sand layer reinforcement method based on environmentally friendly slurry. Background Art

[0002] With the rapid development of underground space development, more and more tunnel projects will encounter highly permeable sand layers. This layer has a certain pressure-bearing capacity, and the amount of sand and water gushing out is large, which may cause accidents such as water inrush, collapse, and falling, thereby affecting the safety of the ground and the surrounding environment, seriously affecting the progress of the project and the quality of construction, and even causing casualties and huge economic losses. Therefore, when encountering a high-velocity water-bearing sand layer, grouting and water blocking are often required before subsequent projects can be carried out.

[0003] At present, the most common method of tunnel surrounding rock grouting reinforcement is high-pressure rotary jet grouting. It is a method of reinforcing the surrounding rock by mixing soil, chemicals or cement slurry together using the high-pressure hydraulic jet mechanism. This method has the advantages of small construction area, small vibration and low noise.

[0004] The grouting materials commonly used in the high-pressure jet grouting method are single-liquid cement slurry and cement-water glass double-liquid slurry. The groundwater seepage velocity in the saturated water-bearing sand layer is relatively high. Due to the scouring and dilution of underground dynamic water, if single-liquid cement slurry is used as the grouting material, the cement particles in the sand layer will be washed away from the pores by the water flow before solidification, so that the jet grouting pile body will be segregated to varying degrees, resulting in a reduction in the diameter of the jet grouting pile and a greatly increased probability of pile breakage, making it difficult to effectively reinforce the high-velocity water-bearing sand layer. At the same time, the loss of cement will cause the pH value of groundwater to increase, causing great damage to the environment. Although the cement-water glass double-liquid slurry has a certain water blocking effect on the saturated water-bearing sand layer, the chemical slurry has a certain toxicity and is very easy to pollute the underground environment.

[0005] The newly emerged MICP technology is an environmentally friendly soil reinforcement technology that induces the formation of calcium carbonate crystals through the metabolism or enzymatic action of microorganisms. The formation rate of calcium carbonate induced by this microorganism and the biochemical reaction process at different stages are controllable. The produced calcium carbonate crystals play a filling and cementing role in the sand layer, bonding the loose sand particles into a new type of green biocomposite geotechnical material with controllable strength and permeability. Its effect is similar to that of cement and is called "biocement". Due to the large pores in the highly permeable sand layer and the high groundwater flow rate, the use of microbial slurry alone does not produce a good water blocking and reinforcement effect on the sand layer. Therefore, a highly permeable sand layer reinforcement method based on environmentally friendly slurry is invented. Summary of the invention

[0006] The purpose of the present invention is to provide a highly permeable sand layer reinforcement method based on an environmentally friendly slurry. The highly permeable sand layer reinforcement method based on an environmentally friendly slurry is based on the idea of ​​first reducing permeability and then reinforcing, and provides a high-velocity water-containing sand layer grouting reinforcement method that first uses kaolin slurry to reduce the porosity and permeability of the sand layer, and then uses MICP technology to consolidate the sand layer. This method can fully utilize the characteristics of kaolin slurry, which has good water blocking properties, a wide diffusion range, and no environmental pollution. At the same time, it utilizes the good adhesion and environmental friendliness of MICP, as well as the advantages of high strength, good impermeability, simple process, and easy operation of the MICP consolidated body. The method has clear ideas and simple steps, and is particularly suitable for grouting and water blocking of high-velocity water-containing sand layers.

[0007] In order to achieve the above object, the present invention provides a highly permeable sand layer reinforcement method based on an environmentally friendly slurry, comprising the following steps:

[0008] Prepare kaolin slurry and microbial slurry for later use;

[0009] Determine the drilling location and drill the predetermined pile position to the designed elevation;

[0010] The kaolin slurry is first injected into the borehole, and after the kaolin is completely deposited, the microbial slurry is then injected.

[0011] Preferably, the mass ratio of the kaolin slurry to the microbial slurry is (1-3):1.

[0012] Preferably, the kaolin slurry comprises the following raw materials in parts by weight: 20-50 parts of kaolin and 80-100 parts of water.

[0013] Preferably, the particle size of the kaolin is 0.0625-16 mm, and the density of the kaolin slurry is 1385 kg / m 3 , viscosity is 0.043Pa·S.

[0014] Preferably, the microbial slurry comprises the following raw materials in parts by weight: 90-100 parts of microbial liquid, 90-100 parts of urea solution, and 90-100 parts of calcium chloride solution.

[0015] Preferably, the microbial liquid is any one of Bacillus subtilis liquid and yeast extract.

[0016] Preferably, the concentration of the microbial liquid is 0.35-0.7 mol / L, the concentration of the urea solution is 0.35-0.7 mol / L, and the concentration of the calcium chloride solution is 0.35-0.7 mol / L.

[0017] Preferably, drilling a predetermined pile position to a designed elevation comprises:

[0018] Move the drilling machine to the designated pile position, align the drill bit with the center of the empty position, ensure that the drilling machine is placed horizontally, and the vertical deviation of the drill rod is less than or equal to 1%;

[0019] The drilling machine is used to drill a hole, and the drill bit is used to drill a hole at a predetermined pile position to a designed elevation.

[0020] Preferably, before using the drilling machine to drill holes, the drilling machine is subjected to a low-pressure water test to check whether the nozzle is unobstructed and whether the pressure is normal.

[0021] Preferably, the drilling machine is a high-pressure rotary jet pile machine.

[0022] The beneficial effects of the present invention are:

[0023] 1. According to the idea of ​​reducing permeability before strengthening, kaolin slurry is first used to fill the pores to increase the fine particle content of the sand layer, reduce the porosity and permeability of the sand layer, and then use MIPC technology to generate calcium carbonate crystals on the surface of the sand particles to generate a new type of green bio-consolidated soil with high strength, good impermeability and good durability. It avoids the bacterial liquid and solidifying liquid in the high-velocity water-containing sand layer from being washed away by water before complete reaction, and gives full play to the anti-scouring property of kaolin slurry and the adhesion of microbial slurry.

[0024] 2. Kaolin particles fill the pores of sand and absorb water in the water-bearing sand layer, thereby reducing the porosity of the water-bearing sand layer and achieving a water blocking effect. The deposition time is slow and the pores of the sand layer are rarely blocked. Driven by the water flow, the slurry has a larger diffusion range, further improving the water blocking effect. At the same time, the addition of kaolin particles increases the attachment area of ​​bacteria, which is conducive to the subsequent microbial mineralization.

[0025] 3. Compared with traditional cement slurry and chemical slurry for grouting and water blocking, the kaolin slurry and microbial slurry used in the present invention are both environmentally friendly slurries, non-toxic and harmless to the environment, and the microbial consolidated soil can maintain a high strength within the designed service life of the tunnel.

[0026] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0028] Figure 1 A diagram showing the reinforcement mechanism of a highly permeable sand layer reinforcement method based on an environmentally friendly slurry according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0030] Example 1

[0031] S1: Slurry preparation: prepare kaolin slurry and microbial slurry and set aside.

[0032] The kaolin slurry includes the following raw materials by weight: 20 parts of kaolin with a particle size of 0.0625 mm, 80 parts of water, and the density of the prepared kaolin slurry is 1385 kg / m 3 , viscosity is 0.043Pa·S.

[0033] The microbial slurry includes the following raw materials in parts by weight: a concentration of 0.35 mol / L, a density of 10 9 cfu / mL, 90 parts of Bacillus pasteuris solution with a viscosity of 2500cp, 90 parts of urea solution with a concentration of 0.35mol / L, and 90 parts of calcium chloride solution with a concentration of 0.35mol / L.

[0034] S2: Engineering survey: Survey the saturated water-bearing sand layer that needs water blocking and reinforcement, and determine the drilling location of the jet grouting pile machine.

[0035] S3: Positioning of the jet grouting machine: Move the high-pressure jet grouting machine to the designated pile position, align the drill bit with the center of the hole, and then place the high-pressure jet grouting machine horizontally, with the verticality deviation of the drill rod less than or equal to 1%; after the high-pressure jet grouting machine is in place, first perform a low-pressure water jetting test to check whether the nozzle is unobstructed and the pressure is normal.

[0036] S4: Drilling: Use a high-pressure rotary jet pile driver to drill holes, and make the drill bit drill holes to the designed elevation at the predetermined pile position.

[0037] S5: Grouting: All boreholes are first injected with kaolin slurry, and the pores of the sand layer are filled with kaolin particles to increase the fine particle content of the sand layer and reduce the permeability of the sand layer. After the injected kaolin slurry is completely deposited, microbial slurry is injected to use microorganisms to induce the formation of calcium carbonate crystals to bond sand particles to form a consolidated body to reinforce the saturated water-containing sand layer. The mass ratio of kaolin slurry to microbial slurry is 1:1.

[0038] Example 2

[0039] In this example, the experimental steps are the same as those in Example 1, except that the composition and ratio of the kaolin slurry and the microbial slurry are different. Specifically, as follows:

[0040] The kaolin slurry includes the following raw materials in parts by weight: 35 parts of kaolin with a particle size of 8 mm, 90 parts of water, and the density of the prepared kaolin slurry is 1385 kg / m 3 , viscosity is 0.043Pa·S.

[0041] The microbial slurry includes the following raw materials in parts by weight: a concentration of 0.5 mol / L, a density of 10 9 cfu / mL, 95 parts of yeast extract with a viscosity of 2500cp, 95 parts of urea solution with a concentration of 0.5mol / L, and 95 parts of calcium chloride solution with a concentration of 0.5mol / L.

[0042] The mass ratio of kaolin slurry to microbial slurry is 2:1.

[0043] Example 3

[0044] In this example, the experimental steps are the same as those in Example 1, except that the composition and ratio of the kaolin slurry and the microbial slurry are different. Specifically, as follows:

[0045] The kaolin slurry includes the following raw materials by weight: 50 parts of kaolin with a particle size of 16 mm, 100 parts of water, and the density of the prepared kaolin slurry is 1385 kg / m 3 , viscosity is 0.043Pa·S.

[0046] The microbial slurry includes the following raw materials in parts by weight: a concentration of 0.7 mol / L, a density of 10 9 cfu / mL, 100 parts of yeast extract with a viscosity of 2500cp, 100 parts of urea solution with a concentration of 0.7mol / L, and 100 parts of calcium chloride solution with a concentration of 0.7mol / L.

[0047] The mass ratio of kaolin slurry to microbial slurry is 3:1.

[0048] The mechanism of action of the present invention is as follows Figure 1 As shown, the present invention adopts an environmentally friendly slurry to perform high-pressure rotary jet grouting on the sand layer based on the idea of ​​reducing permeability first and then reinforcing. Kaolin slurry is first injected. The kaolin slurry not only absorbs water in the water-containing sand layer to reduce the porosity of the water-containing sand layer, thereby achieving a water blocking effect, but also reduces the porosity and permeability of the sand layer, increases the attachment area of ​​bacteria, and then injects microbial slurry to reinforce the sand layer by inducing calcium carbonate crystals through microorganisms. Specifically, the urea solution in the microbial slurry hydrolyzes the sand layer, and induces the formation of calcium carbonate crystals through the metabolism or enzymatic action of the microorganisms themselves. The produced calcium carbonate crystals fill and cement the sand layer, thereby reinforcing the sand layer.

[0049] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, and these simple modifications all belong to the protection scope of the present invention. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0050] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A highly permeable sand layer reinforcement method based on environmentally friendly slurry, characterized in that: The following steps are involved: Prepare kaolin slurry and microbial slurry for later use; Determine the drilling location and drill the predetermined pile position to the designed elevation; The kaolin slurry is first injected into the borehole, and after the kaolin is completely deposited, the microbial slurry is then injected.

2. The highly permeable sand layer reinforcement method based on environmentally friendly slurry according to claim 1 is characterized in that: The mass ratio of the kaolin slurry to the microbial slurry is (1-3):

1.

3. The highly permeable sand layer reinforcement method based on environmentally friendly slurry according to claim 1 is characterized in that: The kaolin slurry comprises the following raw materials in parts by weight: 20-50 parts of kaolin and 80-100 parts of water.

4. The highly permeable sand layer reinforcement method based on environmentally friendly slurry according to claim 3 is characterized in that: The particle size of the kaolin is 0.0625-16 mm, and the density of the kaolin slurry is 1385 kg / m 3 , viscosity is 0.043Pa·S.

5. The highly permeable sand layer reinforcement method based on environmentally friendly slurry according to claim 1 is characterized in that: The microbial slurry comprises the following raw materials in parts by weight: 90-100 parts of microbial liquid, 90-100 parts of urea solution and 90-100 parts of calcium chloride solution.

6. The highly permeable sand layer reinforcement method based on environmentally friendly slurry according to claim 5 is characterized in that: The microbial liquid is any one of Bacillus subtilis liquid and yeast extract.

7. The highly permeable sand layer reinforcement method based on environmentally friendly slurry according to claim 5 is characterized in that: The concentration of the microbial liquid is 0.35-0.7 mol / L, the concentration of the urea solution is 0.35-0.7 mol / L, and the concentration of the calcium chloride solution is 0.35-0.7 mol / L.

8. The highly permeable sand layer reinforcement method based on environmentally friendly slurry according to claim 1 is characterized in that: The drilling of the predetermined pile position to the designed elevation comprises: Move the drilling machine to the designated pile position, align the drill bit with the center of the empty position, ensure that the drilling machine is placed horizontally, and the vertical deviation of the drill rod is less than or equal to 1%; The drilling machine is used to drill a hole, and the drill bit is used to drill a hole at a predetermined pile position to a designed elevation.

9. The highly permeable sand layer reinforcement method based on environmentally friendly slurry according to claim 8 is characterized in that: Before using the drilling machine to drill holes, the drilling machine is subjected to a low-pressure water test to check whether the nozzle is unobstructed and whether the pressure is normal.

10. The highly permeable sand layer reinforcement method based on environmentally friendly slurry according to claim 8, characterized in that: The drilling machine is a high-pressure rotary jet pile machine.

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