Method for judging injectability of surrounding rock

Abstract

The present invention relates to the field of mining technology, and particularly to a method for judging the injectability of surrounding rock, which includes: obtaining the fracture area per unit drilling length according to the fracture area exposed by drilling; obtaining the injectability coefficient of the measured surrounding rock according to the ratio of the fracture area per unit drilling length to the strength stress ratio, wherein the strength stress ratio is a parameter corresponding to the degree of fracture development. By judging the grouting feasibility of the surrounding rock, a quantitative evaluation of the injectability of the surrounding rock is realized, which can intuitively reflect the feasibility of surrounding rock grouting reinforcement, increase the scientificity of grouting engineering decision-making, and provide data support for the estimation of grouting volume, material selection, equipment selection, parameter design, etc., laying a foundation for achieving good engineering effects.

Description

Technical Field

[0001] The present invention relates to the technical field of mining, and particularly to a method for judging the injectability of surrounding rock. Background Art

[0002] Grouting reinforcement is an important means for surrounding rock control. Grouting of surrounding rock is required in engineering practices such as the repair of large deformation and damaged roadways, the reinforcement of unstable roadways, and the advanced pre-reinforcement of soft and broken surrounding rock. However, due to the large differences in surrounding rock under different conditions, grouting reinforcement often has a certain degree of blindness, with an unclear understanding of the object to be reinforced, resulting in incorrect grouting decisions, unreasonable parameter design, small grouting volume, poor reinforcement effect, affecting the engineering effect, delaying the construction period, and wasting costs. Summary of the Invention

[0003] The present invention provides a method for judging the injectability of surrounding rock, which is used to solve one of the defects in the prior art. Through the judgment of the grouting feasibility of the surrounding rock, a quantitative evaluation of the injectability of the surrounding rock is realized, which can intuitively reflect the feasibility of surrounding rock grouting reinforcement and increase the scientific nature of grouting engineering decisions.

[0004] The present invention provides a method for judging the injectability of surrounding rock, including:

[0005] Obtaining the fissure area per unit drilling length according to the fissure area exposed by the drill hole;

[0006] Obtaining the injectability coefficient of the measured surrounding rock according to the ratio of the fissure area per unit drilling length to the strength stress ratio, where the strength stress ratio is a parameter corresponding to the degree of fissure development.

[0007] According to the method for judging the injectability of surrounding rock provided by the present invention, the obtaining of the fissure area per unit drilling length according to the fissure area exposed by the drill hole includes:

[0008] Obtaining the area of a single fissure exposed by the drill hole according to the product of the fissure trace length and the fissure width;

[0009] Obtaining the fissure area exposed by the drill hole according to the sum of the areas of single fissures exposed by the drill hole;

[0010] Obtaining the fissure area per unit drilling length according to the ratio of the fissure area exposed by the drill hole to the drilling length.

[0011] According to the method for judging the injectability of surrounding rock provided by the present invention, the strength stress ratio is obtained according to the ratio of the weighted average strength of the rock stratum within the exposed range of the drill hole to the maximum principal stress in the in-situ rock stress.

[0012] According to the method for judging the injectability of surrounding rock provided by the present invention, the weighted average strength of the rock stratum within the exposed range of the drill hole is obtained according to the in-situ strength of the rock mass of each rock stratum and the thickness of each rock stratum.

[0013] According to a method for judging the injectability of surrounding rock provided by the present invention, the in-situ stress of the original rock is measured by the hydraulic fracturing method or the stress relief method to obtain the maximum principal stress in the in-situ stress.

[0014] According to a method for judging the injectability of surrounding rock provided by the present invention, the structure of the surrounding rock is measured by the borehole peephole method to obtain the number of fissures, the width of the fissures, the trace length of the fissures, and the borehole length.

[0015] According to a method for judging the injectability of surrounding rock provided by the present invention, the in-situ strength of each rock stratum is obtained by the borehole penetration method.

[0016] According to a method for judging the injectability of surrounding rock provided by the present invention, the stratification thickness of each rock stratum is obtained by natural gamma testing and the results of borehole peephole.

[0017] According to a method for judging the injectability of surrounding rock provided by the present invention, the depth of the borehole is greater than twice the width of the roadway.

[0018] According to a method for judging the injectability of surrounding rock provided by the present invention, the grouting feasibility degree of the surrounding rock is judged according to the injectability coefficient and the feasibility reference range.

[0019] The method for judging the injectability of surrounding rock provided by the present invention is a method for judging the grouting feasibility of surrounding rock. Boreholes are drilled in the measured surrounding rock. Based on the exposed fissure area S of the borehole, the fissure area per unit borehole length can be obtained. Based on the ratio of the fissure area per unit borehole length to the strength stress ratio λ, the injectability coefficient k of the measured surrounding rock can be obtained.

[0020] The strength stress ratio λ is a parameter corresponding to the degree of fissure development. The degree of fissure development of the surrounding rock is an important parameter that can characterize the grouting volume and is also the most direct method for judging the injectability of the surrounding rock. Therefore, the degree of fissure development per unit borehole length is used for quantitative evaluation of injectability. In the prior art, the calculation method of the degree of fissure development needs to be based on the void volume formed by the fissures. However, the fissures are irregularly distributed in space, and it is difficult to directly observe and obtain the void volume, that is, the extension length and expansion area of the fissures in the surrounding rock cannot be accurately detected by detection. Therefore, the obtained degree of fissure development is difficult to accurately reflect the actual situation of the fissures.

[0021] However, the degree of development of surrounding rock is closely related to the stress environment in which the surrounding rock is located and the strength of the surrounding rock itself. The greater the stress and the lower the strength, the higher the degree of crack development, that is, the greater the crack extension coefficient. Therefore, the crack extension coefficient can be estimated by the strength-stress ratio λ. The crack extension coefficient is inversely proportional to the strength-stress ratio λ. The present invention calculates and judges by multiplying the crack area S exposed by drilling by the crack extension coefficient. That is, the injectability coefficient k is the ratio of the crack area per unit drilling length to the strength-stress ratio λ, which can not only avoid the method of obtaining the degree of crack development through the void volume formed by cracks, but also more accurately judge the injectability of the measured surrounding rock.

[0022] Moreover, by judging the grouting feasibility of the surrounding rock, the quantitative evaluation of the injectability of the surrounding rock can be realized, which can intuitively reflect the feasibility of surrounding rock grouting reinforcement, increase the scientific nature of grouting engineering decision-making, and provide data support for the estimation of grouting volume, material selection, equipment selection, parameter design, etc., laying a foundation for achieving good engineering effects.

[0023] In addition to the technical problems solved by the present invention, the technical features of the technical solutions constituted, and the advantages brought by these technical features of the technical solutions described above, the other technical features of the present invention and the advantages brought by these technical features will be further described in conjunction with the drawings or understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 It is a schematic flowchart of a method for judging the injectability of surrounding rock provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The following will further describe in detail the embodiments of the present invention in conjunction with the drawings and embodiments. The following embodiments are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0027] In the description of the embodiments of the present invention, it should be noted that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings. These are only for the convenience of describing the embodiments of 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. Therefore, it should not be construed as a limitation on the embodiments of the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0028] In the description of the embodiments of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "connected" and "coupled" 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 a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0029] In the embodiments of the present invention, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature can be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature can be that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is at a higher horizontal level than the second feature. The first feature being "under", "beneath" and "underneath" the second feature can be that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is at a lower horizontal level than the second feature.

[0030] In addition, in the description of the embodiments of the present invention, unless otherwise stated, the meanings of "a plurality of", "multiple roots", "multiple groups" are two or more, and the meanings of "several", "several roots", "several groups" are one or more.

[0031] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the embodiments of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0032] As Figure 1 shown, the method for judging the injectability of surrounding rock provided by the embodiments of the present invention includes:

[0033] Obtain the fissure area per unit drilling length based on the fissure area S exposed by the drilling.

[0034] Obtain the injectability coefficient k of the measured surrounding rock according to the ratio of the fissure area per unit drilling length to the strength stress ratio λ, where the strength stress ratio λ is a parameter corresponding to the degree of fissure development.

[0035] The method for judging the injectability of surrounding rock in the embodiments of the present invention is a method for judging the grouting feasibility of surrounding rock. Drill holes in the measured surrounding rock. Based on the fissure area S exposed by the drilling, the fissure area per unit drilling length can be obtained. Based on the ratio of the fissure area per unit drilling length to the strength stress ratio λ, the injectability coefficient k of the measured surrounding rock can be obtained.

[0036] The strength stress ratio λ is a parameter corresponding to the degree of fissure development. The degree of surrounding rock fissure development is an important parameter that can characterize the grouting volume and is also the most direct method for judging the injectability of surrounding rock. Therefore, the degree of fissure development per unit drilling length is used for quantitative evaluation of injectability. In the prior art, the calculation method of the degree of fissure development needs to be based on the void volume formed by the fissures. However, the fissures are irregularly distributed in space, and it is difficult to obtain the void volume through direct observation, that is, the extension length and expansion area of the fissures in the surrounding rock cannot be accurately obtained through detection. Therefore, the obtained degree of fissure development is difficult to truly and accurately reflect the actual situation of the fissures.

[0037] However, the degree of development of the surrounding rock is closely related to the stress environment of the surrounding rock and the strength of the surrounding rock itself. The greater the stress and the lower the strength, the higher the degree of fracture development, that is, the greater the fracture extension coefficient. Therefore, the fracture extension coefficient can be estimated by the strength-stress ratio λ. The fracture extension coefficient is inversely proportional to the strength-stress ratio λ. The present invention calculates and judges by multiplying the fracture area S exposed by drilling by the fracture extension coefficient. That is, the injectability coefficient k is the ratio of the fracture area per unit drilling length to the strength-stress ratio λ, which can not only avoid the method of obtaining the degree of fracture development through the void volume formed by fractures, but also more accurately judge the injectability of the measured surrounding rock.

[0038] Moreover, by judging the grouting feasibility of the surrounding rock, the quantitative evaluation of the injectability of the surrounding rock can be realized, which can intuitively reflect the feasibility of surrounding rock grouting reinforcement, increase the scientificity of grouting engineering decision-making, and provide data support for the estimation of grouting volume, material selection, equipment selection, parameter design, etc., laying a foundation for achieving good engineering effects.

[0039] According to an embodiment of the present invention, obtaining the fracture area per unit drilling length based on the fracture area S exposed by drilling includes:

[0040] Obtaining the area of a single fracture exposed by drilling according to the product of the fracture trace length l and the fracture width w;

[0041] Obtaining the fracture area S exposed by drilling according to the sum of the areas of single fractures exposed by drilling;

[0042] Obtaining the fracture area per unit drilling length according to the ratio of the fracture area S exposed by drilling to the drilling length L.

[0043] In this embodiment, after drilling on the measured surrounding rock, multiple fractures can be generated within a certain range inside the surrounding rock from the drilling. Each fracture has its fracture trace length l and fracture width w. The area of a single fracture exposed by drilling is the product of the fracture trace length l and the fracture width w of the fracture. The fracture area S exposed by drilling is the total area of all fractures generated by the drilling, that is, the sum of the areas of single fractures exposed by drilling, that is where n is the number of fractures generated by drilling.

[0044] The fracture area per unit drilling length is the ratio of the fracture area S exposed by drilling to the drilling length L. Therefore, the injectability coefficient

[0045] According to an embodiment provided by the present invention, the strength-stress ratio λ is obtained according to the ratio of the weighted average strength R of the rock stratum within the range exposed by drilling to the maximum principal stress σ 1 in the in-situ stress.

[0046] In this embodiment, the intensity-stress ratio λ, a common index in rock mechanics, is used to characterize the degree of fracture development. The intensity-stress ratio λ is the ratio of the weighted average strength R of the rock strata within the range exposed by the borehole to the maximum principal stress σ in the in-situ rock stress, that is 1 So the injectability coefficient So the injectability coefficient

[0047]

[0048] According to an embodiment provided by the present invention, the weighted average strength R of the rock strata within the range exposed by the borehole is obtained based on the in-situ strength R of the rock mass of each rock stratum 0 and the stratification thickness H of each rock stratum

[0049] In this embodiment, through the in-situ strength R of the rock mass of each rock stratum 0 combined with the stratification thickness H of each rock stratum, the weighted average strength of the rock strata within the range exposed by the borehole can be calculated where m is the number of rock strata

[0050] According to an embodiment provided by the present invention, the in-situ rock stress is tested by the hydraulic fracturing or stress relief method to obtain the maximum principal stress σ in the in-situ rock stress 1 . In this embodiment, the in-situ rock stress is tested by the hydraulic fracturing or stress relief method to obtain the maximum principal stress σ in the in-situ rock stress 1 . The maximum principal stress σ in the in-situ rock stress 1 can reflect the actual ground stress level of the surrounding rock to be measured

[0051] According to an embodiment provided by the present invention, the borehole peephole method is used to test the surrounding rock structure to obtain the number of fractures, fracture width, fracture trace length, and borehole length. In this embodiment, the surrounding rock structure is tested by the borehole peephole method, and indexes such as the number n of fractures, fracture aperture w, fracture trace length l, and borehole length L are obtained through processing

[0052] According to an embodiment provided by the present invention, the in-situ strength R of the rock mass of each rock stratum is obtained by the borehole penetration method 0 . In this embodiment, the in-situ strength R of the rock mass of each rock stratum is obtained by the borehole penetration method 0

[0053] According to an embodiment provided by the present invention, the stratification thickness H of each rock stratum is obtained by using natural gamma testing and borehole peephole results. In this embodiment, while the in-situ strength R of the rock mass of each rock stratum is obtained by the borehole penetration method 0 the stratification thickness H of each layer is obtained by combining natural gamma testing and borehole peephole results, and the weighted average strength R of the rock strata within the range exposed by the borehole is calculated in combination

[0054] In the above embodiments, the method for judging the injectability of surrounding rock in the embodiments of the present invention is a method for judging the injectability of surrounding rock based on in-situ rock mass tests. According to the in-situ test data, the injectability of the surrounding rock can be preliminarily evaluated relatively accurately to quickly make decisions, and scientifically and reasonably select grouting materials, processes, and equipment for economic and efficient grouting reinforcement of the surrounding rock. Using on-site in-situ test data to evaluate the injectability of the surrounding rock, firstly, the in-situ test data can better reflect the actual engineering state compared with theoretical estimation or simulation calculation, and the data is more reliable.

[0055] According to an embodiment provided by the present invention, the depth of the borehole is greater than twice the width of the roadway. In this embodiment, boreholes with a certain depth are drilled in the surrounding rock to be grouted, and the depth of the borehole should be greater than twice the width of the roadway.

[0056] According to an embodiment provided by the present invention, the grouting feasibility degree of the surrounding rock is judged according to the injectability coefficient k and the feasibility reference range.

[0057] In this embodiment, based on engineering experience, grouting tests or water pressure tests, etc., the injectability coefficient k of the rock strata at different mining stages or working conditions in a single coal mine or mining area and its statistical relationship with the grouting volume are statistically obtained. This statistical relationship is summarized as the grouting credibility reference range, thereby obtaining the empirical classification standard of the injectability coefficient k, as shown in Table 1 below.

[0058] Table 1

[0059] k。 ≤a a < k ≤ b b < k < c ≥c Injectability. Poor. Medium. Better. Good.

[0060] The injectability coefficient k obtained according to the above method is discriminated according to the classification standard to judge the grouting feasibility degree of the surrounding rock, obtain the injectability evaluation result of the measured surrounding rock, and make grouting feasibility decisions, grouting methods, material and equipment selections according to the evaluation result.

[0061] In a certain coal mine roadway, under the influence of high stress environment and mining, it is severely damaged and has developed internal cracks. Grouting method needs to be used for reinforcement to ensure the normal use of the roadway. Therefore, this method is used to evaluate the injectability of the surrounding rock. The main results and processes are as follows:

[0062] Holes are drilled (drill hole diameter 56 mm, depth 20 m);

[0063] The peephole method is used and digitally processed to obtain 15 cracks exposed by the borehole, as well as the aperture and trace length of each crack. The cross-sectional area of the crack is calculated to be 0.054 m 2 ;

[0064] In the intact rock stratum section at the deep part of the borehole, the hydraulic fracturing method is used for in-situ stress measurement, and the maximum principal stress is obtained as 25.5 MPa;

[0065] The in-situ strength test of rock mass is carried out by the drilling penetration method. Combining with the peep image, the thickness and in-situ strength of each rock stratum are obtained. After weighting, the strength of the drilled rock mass is 21.8 Mpa;

[0066] Through comprehensive calculation, the injectability coefficient of the surrounding rock in the test area is 0.003158.

[0067] By conducting tests and evaluations in different areas of the mine and carrying out grouting tests, according to the statistical results of the single-hole grouting volume, the classification interval of the injectability coefficient of this mine is roughly as shown in Table 2 below:

[0068] Table 2

[0069] k ≤0.001 0.001<k≤0.003 0.003<k<0.005 ≥0.005 Injectability. Poor. Medium. Better. Good.

[0070] 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 foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for determining injectability of surrounding rock, characterized in that: include: Obtain the fracture area per unit drilling length according to the fracture area revealed by drilling; The injectability coefficient of the measured surrounding rock is obtained according to the ratio of the crack area to the strength-stress ratio within the unit borehole length, wherein the strength-stress ratio is a parameter corresponding to the degree of crack development; The method of obtaining the fracture area per unit drilling length according to the fracture area revealed by drilling comprises: The single fracture area exposed by the drilling hole is obtained according to the product of fracture trace length and fracture width; Obtaining the fracture area revealed by the drilling according to the sum of the single fracture areas revealed by the drilling; The fracture area per unit drilling length is obtained according to the ratio of the fracture area exposed by drilling to the length of drilling; The strength-stress ratio is obtained according to the ratio of the weighted average strength of the rock formation within the scope of the drilling exposure to the maximum principal stress in the original rock stress; The sum of the single fracture areas revealed by the drilling, i.e. Among them, n is the number of cracks generated by drilling, l is the length of the crack trace, w is the width of the crack, and S is the crack area exposed by drilling; The fracture area per unit borehole length is the ratio of the fracture area S exposed by the borehole to the length of the borehole L. The strength-stress ratio λ is obtained according to the ratio of the weighted average strength R of the rock formation within the drilling exposure range to the maximum principal stress σ1 in the original rock stress; The strength-stress ratio λ, a common indicator of rock mass mechanics, is used to characterize the degree of fracture development. The strength-stress ratio λ is the ratio of the weighted average strength R of the rock formation within the borehole exposure range to the maximum principal stress σ1 in the original rock stress, that is, So the injectability coefficient is: The weighted average strength of the rock formations in the drilling exposure range is calculated by combining the in-situ strength R0 of each rock formation with the layer thickness H of each rock formation. Where m is the number of layers in the rock formation; The feasibility of grouting in the surrounding rock can be determined based on the injectability coefficient k and the feasibility reference range.

2. The method for determining injectability of surrounding rock according to claim 1, characterized in that: The weighted average strength of the rock formations within the drilling exposure range is obtained based on the in-situ strength of the rock mass of each rock formation and the layered thickness of each rock formation.

3. The method for determining injectability of surrounding rock according to claim 2, characterized in that: The original rock stress is tested by hydraulic fracturing or stress relief method to obtain the maximum principal stress in the original rock stress.

4. The method for determining injectability of surrounding rock according to claim 1, characterized in that: The surrounding rock structure is tested by a borehole peep method to obtain the number of cracks, the crack width, the crack trace length and the borehole length.

5. The method for determining injectability of surrounding rock according to claim 2, characterized in that: The in-situ strength of the rock mass of each rock layer is obtained by using the drilling and penetration method.

6. The method for determining injectability of surrounding rock according to claim 1, characterized in that: The layer thickness of each rock layer is obtained by using natural gamma test and borehole observation results.

7. The method for determining injectability of surrounding rock according to any one of claims 1 to 6, characterized in that: The depth of the borehole is greater than twice the width of the tunnel.

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