A method for sealing cracks in surrounding rock of underground water-sealed cavern

Abstract

The present invention relates to the field of underground engineering technology, and in particular to a method for plugging cracks in the surrounding rock of underground water-sealed caverns, which plugs the cracks in the seepage area of ​​underground water-sealed caverns by microbial mineralization grouting. After microbial slurry is injected into the rock cracks, a large number of bacteria will adhere to the crack surface, and then, under the condition of continuous supply of calcium source, the generated CaCO3 precipitate will fill the cracks developed inside the rock mass, thereby reducing the hydraulic gap width of the cracks. The continuously reduced hydraulic gap width will effectively reduce the permeability of the cracks. The plugging method provided by the present application uses harmless bacteria naturally existing in the soil of nature as reactive bacteria, and has the advantages of no pollution, low grouting pressure, good reinforcement effect, low slurry viscosity, and easy reaction control, etc., which solves the problem of poor effect and repeated leakage after grouting in the conventional cement grouting method.

Description

Technical Field

[0001] The invention relates to the technical field of underground engineering, and in particular to a method for sealing cracks in surrounding rocks of underground water-sealed caverns. Background Art

[0002] Underground water-sealed cavern oil storage has made great progress in recent years due to its advantages of high safety and large reserves, and has become the preferred method for national oil reserves. The selection of underground water-sealed cavern storage sites has high requirements for geological conditions. It is generally built in granite or tuff and other intrusive rock masses with good hardness and integrity. Joints and microcracks are allowed, but no large fractures are allowed. In order to ensure a good water seal effect of the cavern, in addition to increasing the artificial water curtain system to ensure that the groundwater pressure around the cavern is greater than the pressure of the storage medium in the cave to prevent crude oil leakage, it is also necessary to effectively control the seepage of the cavern through surrounding rock grouting during the construction of the cavern. At present, cement slurry is often used as a grouting material in cavern construction. Since cement slurry has a wide source of materials, mature technology, simple preparation, and good application value, it is the most widely used method to control the seepage of fractured surrounding rocks. For the special rock geological characteristics of underground caverns, although the use of cement slurry can effectively reduce the seepage of the cavern, repeated leakage still occurs after the cement grouting is completed, and the design requirements of the seepage of the cavern are not met.

[0003] Therefore, it is necessary to develop a supplementary grouting technology for the widely developed microcracks in the surrounding rock and the micropores formed after conventional cement grouting, and apply it in underground cavern grouting projects to make up for the shortcomings of traditional slurry materials, thereby effectively controlling the water seepage in the cavern. Summary of the invention

[0004] The purpose of the present invention is to provide a method for sealing cracks in the surrounding rock of an underground water-sealed cavern, so as to solve the problems of poor grouting effect and repeated leakage after grouting in the prior art method of sealing cracks by cement grouting.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for sealing cracks in surrounding rocks of underground water-sealed caverns comprises the following steps:

[0007] S1: After the main cavern is excavated, a geological survey of the seepage area is conducted;

[0008] S2: Use microbial mineralization to seal the cracks in the seepage area. Based on the occurrence characteristics of the cracks, determine the layout of the microbial grouting holes and the design depth of the microbial grouting holes, and test the initial permeability coefficient of the microbial grouting holes;

[0009] S3: Before injecting the microbial slurry, a tracer test is performed in the microbial grouting hole to determine the injection amount of the microbial slurry;

[0010] S4: Inject the prepared microbial slurry through the microbial grouting holes; monitor the water seepage in the cavern during the microbial grouting process, and determine the stop time of the microbial grouting according to the design requirements of the water seepage in the cavern.

[0011] Furthermore, the geology of the seepage area is investigated to determine the amount of seepage, and the surrounding rock grade is classified into grades one to five based on the qualitative characteristics of the basic quality of the rock mass and the basic quality indicators of the rock mass;

[0012] When the surrounding rock grade is level one and level two, microbial grouting is used to seal the cracks; when the surrounding rock grade is level three, when the seepage volume is less than the set value, microbial grouting is used to seal the cracks, and when the seepage volume exceeds the set value, a combination of cement grouting and microbial grouting is used to seal the cracks; when the surrounding rock grade is level four and level five, a combination of cement grouting and microbial mineralization grouting is used to seal the cracks.

[0013] Furthermore, cement grouting is carried out in the seepage area of ​​the main cavern, and microbial grouting is carried out in the water curtain cavern above the main cavern layer.

[0014] Furthermore, in step S1, the inclination angle of the fissure relative to the horizontal plane is measured, and the direction of the microbial grouting hole is designed according to the inclination angle of the fissure, so that the direction of the microbial grouting hole intersects with the fissure surface in the seepage area.

[0015] Furthermore, in step S2, the initial permeability coefficient of the microbial grouting hole is tested by a water pressure test.

[0016] Furthermore, in step S3, a tracer is injected into the microbial grouting hole, and the flow path of the microbial slurry after injection is understood through the flow path of the tracer; and the grouting amount of the microbial slurry during the grouting process is selected by monitoring the change of the tracer concentration in the seepage area.

[0017] Furthermore, in step S4, bacterial liquid culture and bacterial liquid fixative and binder are prepared on site, and the prepared microbial slurry is injected into the microbial grouting hole.

[0018] Furthermore, in step S4, the bacterial solution is cultured on site for 24 hours, and the optical density of the bacteria is adjusted to 1.0 before use. The bacterial solution fixative is a 0.05M Ca(CH3COO)2 solution, and the binder is a 0.5M Ca(CH3COO)2+urea solution.

[0019] Furthermore, during the microbial grouting process, the bacterial solution is first injected, then the bacterial solution fixative is injected, and finally the cementing liquid is injected to complete a cycle.

[0020] Furthermore, the injection amount of the bacterial solution is determined according to the tracer test in step S3, the injection amount of the bacterial solution fixative is the same as the injection amount of the bacterial solution, and the injection amount of the cementing liquid is three times the injection amount of the bacterial solution.

[0021] Beneficial effects of the present invention:

[0022] The present invention provides a method for plugging the cracks in the surrounding rock of an underground water-sealed cavern, and the method plugs the cracks in the seepage area of ​​the underground water-sealed cavern by means of microbial mineralization grouting. Microorganisms can induce the generation of minerals such as carbonates and sulfates through mineralization. After microbial slurry is injected into the cracks of the rock mass, a large number of bacteria will adhere to the surface of the cracks, and then under the condition of continuous supply of calcium source, the generated CaCO3 precipitate will fill the cracks developed inside the rock mass, thereby reducing the hydraulic gap width of the cracks. The continuously reduced hydraulic gap width will effectively reduce the permeability of the cracks. The plugging method provided by the present application uses harmless bacteria naturally existing in the soil of nature as reactive bacteria, and has the advantages of no pollution, low grouting pressure, good reinforcement effect, low slurry viscosity, and easy reaction control, etc., which solves the problems of poor effect and repeated leakage after grouting in the conventional cement grouting method. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 A schematic diagram of the on-site design of a method for sealing cracks in surrounding rock of an underground water-sealed cavern provided by an embodiment of the present invention;

[0025] Figure 2 A technical flow chart of a method for sealing cracks in surrounding rocks of an underground water-sealed cavern provided in an embodiment of the present invention.

[0026] In the figure:

[0027] 1-microbial grouting hole; 2-main cavern; 3-water curtain cavern; 4-fracture surface; 5-water seepage area. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] It should be noted that in the description of the present invention, the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0030] It should be noted that in the description of the present invention, the terms "connection" and "installation" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or connected through an intermediate medium; it can be a mechanical connection or an electrical connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] The embodiment of the present invention provides a method for plugging the cracks in the surrounding rock of an underground water-sealed cavern, and the method plugs the cracks in the seepage area of ​​the underground water-sealed cavern by microbial mineralization grouting. Microorganisms can induce the generation of carbonates, sulfates and other minerals through mineralization. After microbial slurry is injected into the rock cracks, a large number of urease bacteria will adhere to the surface of the cracks. Then, under the condition of continuous supply of calcium source, the generated CaCO3 precipitate will fill the cracks developed inside the rock mass, thereby reducing the hydraulic gap width of the cracks. The continuously reduced hydraulic gap width will effectively reduce the permeability of the cracks. The plugging method provided by the present application uses harmless bacteria naturally existing in the soil of nature as reactive bacteria, and has the advantages of no pollution, low grouting pressure, good reinforcement effect, low slurry viscosity, and easy reaction control, etc., which solves the problems of poor effect and repeated leakage after grouting in the conventional cement grouting method.

[0032] Reference Figure 1 , the above method comprises the following steps:

[0033] S1: After the main cavern 2 is excavated, a geological survey of the seepage area 5 is conducted;

[0034] S2: The cracks in the seepage area 5 are sealed by microbial mineralization. Based on the occurrence characteristics of the cracks in the seepage area 5, the layout position of the microbial grouting hole 1 and the design hole depth of the microbial grouting hole 1 are determined, and the initial permeability coefficient of the microbial grouting hole 1 is tested;

[0035] S3: Before injecting the microbial slurry, a tracer test is performed in the microbial grouting hole 1 to determine the injection amount of the microbial slurry;

[0036] S4: Inject the prepared microbial slurry through the microbial grouting hole 1; monitor the water seepage in the cavern during the microbial grouting process, and determine the stop time of the microbial grouting according to the design requirements of the water seepage in the cavern.

[0037] In step S1, the geology of the seepage area is investigated and the amount of seepage is determined. The surrounding rock grade is divided into grades one to five according to the qualitative characteristics of the basic quality of the rock mass and the basic quality index of the rock mass. When the surrounding rock grade is grade one and grade two, the microbial mineralization grouting method is used to seal the cracks. When the surrounding rock grade is grade three, when the seepage amount is less than the set value (the set value of the seepage amount is set to 10L / (m 2 ·d)) In the case of microbial mineralization grouting, the cracks are sealed by means of microbial mineralization grouting. When the water seepage exceeds the set value, the cracks are sealed by means of a combination of cement grouting and microbial mineralization grouting. When the surrounding rock grade is level 4 or 5, the cracks are sealed by means of a combination of cement grouting and microbial mineralization grouting.

[0038] The qualitative characteristics of the basic quality of rock mass and the corresponding relationship between the basic quality index BQ of rock mass and the surrounding rock grade can be found in the classification specifications in the "Engineering Rock Mass Classification Standard" (GB / T 50218) and will not be recorded here.

[0039] Specifically, when there is water seepage in the third-level surrounding rock of the cavern 5 and grouting is required, the priority grouting method needs to be selected according to the amount of water seepage; when the water seepage exceeds 10L / (m 2 ·d), first use conventional cement grouting to seal the cracks and reduce the water seepage to less than 10L / (m 2 ·d), and then use microbial grouting to seal the cracks; when the water seepage after cement grouting is less than 10L / (m 2 ·d), use microbial grouting to seal the cracks. For the caverns with water seepage areas 5 in the fourth and fifth level surrounding rocks, when grouting is required, conventional cement grouting should be used to seal the cracks. When the water seepage after cement grouting is less than 10L / (m 2 ·d) When the cracks are blocked, microbial grouting is used.

[0040] In this embodiment, cement grouting is performed in the water seepage area of ​​the main cavern 2, and microbial grouting is performed in the water curtain cavern 3 above the main cavern layer.

[0041] In step S1, the inclination angle of the fissures in the seepage area 5 of the main cave 2 relative to the horizontal plane is measured, and the direction of the microbial grouting hole 1 is designed according to the inclination angle of the fissures, so that the direction of the microbial grouting hole 1 intersects with the fissure surface 4 of the seepage area 5 of the main cave. There are multiple irregular fissures distributed on the fissure surface 4, and the microbial grouting hole 1 intersects and communicates with one or several of the fissures; the microbial slurry injected into the microbial grouting hole 1 flows into the fissures and fills the fissures through mineralization.

[0042] Optionally, after determining the direction of the microbial grouting hole 1, the depth of the microbial grouting hole 1 is calculated according to the inclination of the fracture surface 4, so that the depth of the microbial grouting hole 1 is about 5m above the main cave 1. In this embodiment, the upper end of the microbial grouting hole 1 is located in the water curtain cave 3, and the lower end is 5m above the main cave 1. The microbial grouting hole 1 intersects and communicates with the fracture on the fracture surface 4; the microbial slurry is injected from the microbial grouting hole 1, and the microbial slurry flows into the fracture along the grouting hole 1 and reaches the water seepage area 5.

[0043] In step S2, the initial permeability coefficient of the grouting hole is tested by a water pressure test.

[0044] In step S3, a tracer is injected into the microbial grouting hole 1, and the flow path of the microbial slurry after injection is understood through the flow path of the tracer; and the grouting amount of the microbial slurry during the field grouting process is selected by monitoring the change of the tracer concentration in the seepage area 5.

[0045] In step S4, bacterial liquid culture and bacterial liquid fixative and binder are prepared on site, and the prepared microbial slurry is used for microbial grouting. In other embodiments, the prepared microbial slurry can also be transported to the site for microbial grouting.

[0046] Specifically, the bacterial solution is cultured on site for 24 hours, and the optical density of the bacteria is modulated to 1.0 before use. The bacterial solution fixative is a 0.05M Ca(CH3COO)2 solution, and the binder is a 0.5M Ca(CH3COO)2+urea solution. During the microbial grouting process, the bacterial solution is first injected, then the bacterial solution fixative, and finally the binder is injected to complete a cycle. Multiple cycles need to be performed every day during the microbial grouting process. In this embodiment, 3 to 4 cycles need to be performed every day during the microbial grouting process.

[0047] In step S4, the injection amount of the bacterial solution is determined according to the tracer test in step S3, the injection amount of the bacterial solution fixative is the same as the injection amount of the bacterial solution, and the injection amount of the cementing liquid is three times the injection amount of the bacterial solution.

[0048] Continue to refer to Figure 1 In step S1, after the direction of the microbial grouting hole 1 is determined, the depth of the microbial grouting hole 1 is calculated according to the inclination of the fracture surface 4, so that the bottom of the microbial grouting hole 1 is about 5m above the water seepage area 5 of the main cave 2. In addition, the position of the bottom of the microbial grouting hole 1 can be determined according to the main cave 2 and the water seepage area 5, and then the direction of the microbial grouting hole 1 is determined, so that the direction of the microbial grouting hole 1 intersects with the fracture surface 4 of the water seepage area 5 of the main cave.

[0049] Reference Figure 2 The detailed steps of the blocking method provided in this application are as follows:

[0050] S1: After the main cavern 1 is excavated, a geological survey is conducted on the seepage area 5; the direction, inclination and inclination of the cracks in the seepage area are determined, the seepage volume of the seepage area 5 is measured, and the surrounding rock grade is classified;

[0051] According to the water seepage volume and surrounding rock grade of the seepage area 5, a combination of conventional cement grouting and microbial mineralization grouting is designed as a post-grouting scheme for the on-site water seepage area; specifically, when the first and second level surrounding rocks of the cavern have water seepage areas 5 that need grouting, microbial grouting is selected to seal the cracks; when the third level surrounding rocks of the cavern have water seepage areas 5 that need grouting, when the water seepage volume exceeds 10L / (m 2 ·d), the cracks should be sealed by conventional cement grouting. When the water seepage after cement grouting is less than 10L / (m 2 ·d), use microbial grouting to seal the cracks. For the caverns with water seepage areas 5 in the fourth and fifth level surrounding rocks, when grouting is required, conventional cement grouting should be used to seal the cracks. When the water seepage after cement grouting is less than 10L / (m 2 ·d) When the cracks are blocked, microbial grouting is used.

[0052] S2: Based on the occurrence characteristics (strike, dip and inclination) of the fissures in the seepage area, determine the layout position of the microbial grouting hole 1 and the design hole depth of the microbial grouting hole 1, so that the direction of the microbial grouting hole 1 intersects with the fissure surface 4 in the seepage area of ​​the main cavern, and the bottom of the microbial grouting hole 1 is about 5m above the main cavern 1;

[0053] The initial permeability coefficient of the microbial grouting hole 1 was tested by a water pressure test.

[0054] S3: Before injecting the microbial slurry, a tracer test is performed in the microbial grouting hole 1, that is, a tracer is injected into the microbial grouting hole 1, and the flow path and concentration change of the tracer are analyzed to determine a reasonable injection amount of the microbial slurry;

[0055] The injection amount of the microbial slurry should be such that the concentration of the microbial slurry at the seepage area 5 is greater than or equal to 0.5M.

[0056] S4: Inject the prepared microbial slurry through the microbial grouting hole 1; monitor the water seepage in the cavern during the microbial grouting process, and determine the stop time of the microbial grouting according to the design requirements of the water seepage in the cavern.

[0057] The present invention has the following beneficial effects:

[0058] 1. This method is used to supplement grouting of widely developed microcracks in the surrounding rock of underground water-sealed caverns and micropores formed after conventional cement grouting, which can solve the problem of repeated infiltration after cement grouting;

[0059] 2. In the process of using microbial grouting to grout the micro cracks in the surrounding rock of the underground cavern to prevent seepage, the grouting pressure used is lower than that of cement slurry, which can avoid damage to the rock mass due to excessive grouting pressure;

[0060] 3. This method can be used to control the injection process of microbial slurry during the grouting of the cave surrounding rock, thereby achieving the effect of artificially controlling the amount of water seepage in the cave.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for sealing cracks in the surrounding rock of an underground water-sealed cavern, characterized in that: The following steps are involved: S1: After the main cavern (2) is excavated, a geological survey of the seepage area (5) is conducted; S2: Use microbial mineralization to seal the cracks in the seepage area, determine the layout position of the microbial grouting hole (1) and the design hole depth of the microbial grouting hole (1) based on the occurrence characteristics of the cracks, and test the initial permeability coefficient of the microbial grouting hole (1); S3: Before injecting the microbial slurry, a tracer test is performed in the microbial injection hole (1) to determine the injection amount of the microbial slurry; S4: injecting the prepared microbial slurry through the microbial grouting hole (1); monitoring the water seepage in the cavern during the microbial grouting process, and determining the stop time of the microbial grouting according to the design requirements of the water seepage in the cavern; Conduct a geological survey of the seepage area (5) to determine the amount of seepage and classify the surrounding rock into grades one to five based on a combination of the qualitative characteristics of the basic quality of the rock mass and the basic quality indicators of the rock mass; When the surrounding rock grade is level one or level two, microbial grouting is used to seal the cracks; when the surrounding rock grade is level three, microbial grouting is used to seal the cracks when the seepage is less than the set value, and a combination of cement grouting and microbial grouting is used to seal the cracks when the seepage exceeds the set value; when the surrounding rock grade is level four or level five, a combination of cement grouting and microbial mineralization grouting is used to seal the cracks; Cement grouting is carried out in the seepage area (5) of the main cavern (2), and microbial grouting is carried out in the water curtain cavern (3) above the main cavern layer; in step S1, the inclination angle of the fissure relative to the horizontal plane is measured, and the direction of the microbial grouting hole (1) is designed according to the inclination angle of the fissure, so that the direction of the microbial grouting hole (1) intersects with the fissure surface (4) of the seepage area (5); after the direction of the microbial grouting hole (1) is determined, the depth of the microbial grouting hole (1) is calculated according to the inclination angle of the fissure surface (4), so that the depth of the microbial grouting hole (1) is about 5m above the main cavern (2).

2. The method for sealing cracks in surrounding rock of underground water-sealed caverns according to claim 1, characterized in that: In step S2, the initial permeability coefficient of the microbial grouting hole (1) is tested by a water pressure test.

3. The method for sealing cracks in surrounding rock of underground water-sealed caverns according to claim 1, characterized in that: In step S3, a tracer is injected into the microbial grouting hole (1), and the flow path of the microbial slurry after injection is understood through the flow path of the tracer; and the injection amount of the microbial slurry during the grouting process is selected by monitoring the change of the tracer concentration in the seepage area (5).

4. The method for sealing cracks in surrounding rock of underground water-sealed caverns according to claim 1, characterized in that: In step S4, bacterial liquid culture and bacterial liquid fixative and binder are prepared on site, and the prepared microbial slurry is injected into the microbial grouting hole (1).

5. The method for sealing cracks in surrounding rock of underground water-sealed caverns according to claim 4, characterized in that: In step S4, the bacterial solution was cultured on site for 24 hours, and the optical density of the bacteria was adjusted to 1.0 before use. The bacterial solution fixative was a 0.05 M Ca(CH COO ) solution, and the binder was a 0.5 M Ca(CH COO ) + urea solution.

6. The method for sealing cracks in surrounding rock of underground water-sealed caverns according to claim 4, characterized in that: During the microbial grouting process, the bacterial solution is injected first, then the bacterial solution fixative is injected, and finally the cementing liquid is injected to complete a cycle.

7. The method for sealing cracks in surrounding rock of underground water-sealed caverns according to claim 4, characterized in that: The amount of bacterial solution injected is determined according to the tracer test in step S3, the amount of bacterial solution fixative injected is the same as the amount of bacterial solution injected, and the amount of cementing liquid injected is three times the amount of bacterial solution injected.

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