A deep-buried long tunnel surrounding rock classification method based on TBM method

Abstract

This application provides a method for classifying the surrounding rock of deep-buried long tunnels based on the TBM method. It includes: a basic framework for detailed classification of surrounding rock based on the "Code for Geological Investigation of Water Conservancy and Hydropower Engineering"; a method for quantitatively assessing the basic quality of the surrounding rock from two aspects: the TBM penetration efficiency coefficient (PEC) based on the fundamental principle of energy conversion conservation and the BQ value of slag characteristics; and a method for comprehensively assessing the basic quality of the surrounding rock based on both. Furthermore, based on industry standards and engineering practice, it establishes a correspondence between corrected values ​​for the surrounding rock categories of deep-buried tunnels under conditions of high ground stress and groundwater activity characterized by water inrush (including high external water pressure). This classification method provides a complete solution for assessing the basic quality of tunnel surrounding rock based on tunneling parameters and slag sample characteristics using the TBM method, and for correcting the surrounding rock category under deep burial conditions. It is highly practical, accurate, and meets the requirements of exploration standards, significantly improving the efficiency and reliability of geological work based on the TBM method.

Claims

1. A method for classifying surrounding rock of deep-buried long tunnels based on the TBM method, characterized in that, include: Based on the basic framework of detailed classification of surrounding rock in the "Code for Geological Investigation of Water Conservancy and Hydropower Projects", this paper proposes a method for quantitatively evaluating the basic quality of surrounding rock from two aspects: the penetration efficiency coefficient PEC of TBM based on the basic principle of energy conversion conservation and the identification of the characteristic BQ value of slag. The basic quality of surrounding rock is comprehensively evaluated through the identification of the penetration efficiency coefficient PEC and the characteristic BQ value of slag. The proposed methods include: quantitatively assessing the basic quality of surrounding rock based on two aspects: the TBM penetration efficiency coefficient (PEC) and the slag characteristic BQ value, both based on the fundamental principle of energy conversion conservation; and comprehensively assessing the basic quality of surrounding rock based on both aspects. Based on the basic framework of detailed classification of surrounding rock, a TBM penetration efficiency coefficient based on the basic principle of energy conversion conservation is proposed. Obtain the tunneling parameters and surrounding rock categories of the TBM in the engineering examples and perform corresponding statistical summarization to create a mapping table of the correspondence between the TBM penetration efficiency coefficient, the basic quality grade of the surrounding rock, and the T1 value of the basic quality of the surrounding rock. Based on the characteristics of TBM slag samples, the basic quality index values ​​of rock mass are identified and quantitatively evaluated to determine the basic quality T2 of surrounding rock. A mapping table is created to show the correspondence between the basic quality index values ​​of rock mass, the basic quality grade of surrounding rock, and the T2 score of surrounding rock. The calculation method for the basic rock mass quality score T' is based on two aspects: the TBM penetration efficiency coefficient and the basic rock mass quality index values ​​identified by the characteristics of the slag sample. A mapping table showing the correspondence between the weighted grading methods and weight values ​​for the basic rock mass quality T1 and T2 is also created. The calculation method for the basic rock mass quality score T', which comprehensively evaluates the TBM penetration efficiency coefficient PEC and the slag material characteristic BQ value, is as follows: T' = T1 × p + T2 × (1 - p) In the formula: p is the weight of the basic quality T1 of the surrounding rock determined by the penetration efficiency coefficient PEC, and 1-p is the weight of the basic quality T2 of the rock mass determined by the basic quality index BQ of the characteristic rock mass of the slag sample. The weighting classification method and the correspondence between the weight values ​​of the basic quality of the surrounding rock (T1) and the basic quality of the rock mass (T2) are as follows: Weighting criteria: |T1-T2| < 10, T1 weight p is 50%, T2 weight 1-p is 50%; Weighting criteria: 10 ≤ |T1-T2| < 20, T1 weight p is 25%, T2 weight 1-p is 75%; Weighting criteria: |T1-T2| ≥ 20, T1 weight p is 0%, T2 weight is 100%. Based on the basic framework of the detailed classification of surrounding rock in the "Code for Geological Investigation of Water Conservancy and Hydropower Projects", a corresponding relationship is established for the correction values ​​of surrounding rock categories of deep-buried tunnels under conditions of high ground stress and groundwater activity as water inrush.

2. The method for classifying surrounding rock of deep-buried long tunnels based on the TBM method according to claim 1, characterized in that, The formula for calculating the penetration efficiency coefficient (PEC) of a TBM, based on the fundamental principle of energy conservation, is as follows: PEC=(π×R 2 ×Pl) / (F×Pl+T×2π); In the formula: PEC is the penetration efficiency coefficient, 10 -6 KN -1 m 2 R is the radius of the cutter head on the TBM, in meters. Pl represents penetration depth in meters (m); F represents the cutterhead thrust on the TBM in kN; and T represents the cutterhead torque on the TBM in kN·m.

3. The method for classifying surrounding rock of deep-buried long tunnels based on the TBM method according to claim 1, characterized in that, The correspondence between the TBM penetration efficiency coefficient PEC, the basic quality grade of the surrounding rock, and the corresponding basic quality T1 score of the surrounding rock is as follows: For penetration efficiency coefficients PEC < 20, the basic quality grade of the surrounding rock is I, and the basic quality of the surrounding rock is T1 > 85; for penetration efficiency coefficients 20 ≤ PEC < 30, the basic quality grade of the surrounding rock is II, and the basic quality of the surrounding rock is 85 ≥ T1 > 65; for penetration efficiency coefficients 30 ≤ PEC < 60, the basic quality grade of the surrounding rock is III, and the basic quality of the surrounding rock is 65 ≥ T1 > 45; for penetration efficiency coefficients 60 ≤ PEC < 110, the basic quality grade of the surrounding rock is IV, and the basic quality of the surrounding rock is 45 ≥ T1 > 25; for penetration efficiency coefficients PEC ≥ 110, the basic quality grade of the surrounding rock is V, and the basic quality of the surrounding rock is T1 ≤ 25.

4. The method for classifying surrounding rock of deep-buried long tunnels based on the TBM method according to claim 1, characterized in that, The method for quantitatively assessing the basic quality T2 of surrounding rock based on the BQ value of TBM slag samples is as follows: BQ = 100 + 3Rc + 250Kv In the formula: BQ is the basic quality index of the rock mass; Rc is the saturated uniaxial compressive strength of the rock, MPa; Kv is the integrity coefficient of the rock mass; The method for determining the saturated uniaxial compressive strength Rc of rock is as follows: based on the lithology or lithological combination of the slag sample, and comprehensively analyzed and determined according to the results of previous exploration tests or on-site measurements during the construction period; The integrity coefficient Kv of the rock mass is determined by a comprehensive analysis of the particle size, uniformity, shape characteristics, relative content, visible structural surface of the rock block, uniformity of slag volume, and tunneling stability of the slag sample. The correspondence between slag sample characteristics and rock mass integrity classification and integrity coefficient Kv value is as follows: If the slag sample is characterized by a particle size of less than 2 cm and uniformity, and is ground or cut into silty gravel and thin flakes by tools, and the TBM excavation is stable with a stable slag volume and intact rock mass, then the integrity coefficient Kv>0.

75. If the characteristics of the slag sample are that the overall particle size is 1-5cm and relatively uniform, the cutter cuts into thin flakes mixed with ground sand and gravel, a small amount of rock blocks with visible joint surfaces, the TBM excavation is smooth, the slag volume is stable, and the rock mass is relatively intact, then the integrity coefficient is 0.75≥Kv>0.

55. If the characteristics of the slag sample are that the particle size varies greatly from 3 to 15 cm, and it is mainly thick, flaky, short, prismatic, or non-cuttable blocks with irregular shape, and some rock blocks show joint surfaces, the TBM excavation is relatively smooth, the slag volume is basically stable, and the integrity of the rock mass is poor, then the integrity coefficient is 0.55 ≥ Kv > 0.

35. If the characteristics of the slag sample are large differences in particle size (3-20cm), rock blocks, long strips, flaky and silty gravel, abrasive materials, many non-cut rock blocks, joint surfaces, unstable TBM excavation, varying slag volume, and relatively broken rock mass, then the integrity coefficient is 0.35 ≥ Kv > 0.

15. If the characteristics of the slag sample are that the particle size varies greatly and is between 5 and 30 cm, the hard rock is mostly non-cut rock blocks, joint surfaces or sandy soil, fully weathered debris, and fragmented stone mixed with mud and loose material are frequently seen, the TBM excavation is often unstable, the amount of slag is unstable, and the rock mass is broken, then the integrity coefficient Kv ≤ 0.

15. The correspondence between the basic rock mass quality index BQ value, basic surrounding rock quality grade, and basic surrounding rock quality T2 score for TBM slag sample feature identification is as follows: The basic quality index BQ of the rock mass identified by the characteristics of slag samples is >550, the basic quality grade of the surrounding rock is I, and the basic quality T2 of the surrounding rock is >85; the basic quality index BQ of the rock mass identified by the characteristics of slag samples is 550-451, the basic quality grade of the surrounding rock is II, and the basic quality T2 of the surrounding rock is 85 ≥ T2 > 65; the basic quality index BQ of the rock mass identified by the characteristics of slag samples is 450-351, the basic quality grade of the surrounding rock is III, and the basic quality T2 of the surrounding rock is 65 ≥ T2 > 45; the basic quality index BQ of the rock mass identified by the characteristics of slag samples is 350-251, the basic quality grade of the surrounding rock is IV, and the basic quality T2 of the surrounding rock is 45 ≥ T2 > 25; the basic quality index BQ of the rock mass identified by the characteristics of slag samples is ≤250, the basic quality grade of the surrounding rock is V, and the basic quality T2 of the surrounding rock is ≤25.

5. The method for classifying surrounding rock of deep-buried long tunnels based on the TBM method according to claim 1, characterized in that, The correspondence between the correction values ​​for the surrounding rock category (i.e., the total surrounding rock score T) of deeply buried tunnels under high ground stress conditions is as follows: T = T' + Ki, where: T is the corrected total score of the surrounding rock; T' is the basic quality score of the rock mass; Ki is the high ground stress correction value; Wherein, K1 is the correction value for the surrounding rock score of the hard rock burst tunnel section under high ground stress conditions. The correspondence between the value of K1 and the basic rock mass quality score T′, the rock burst grade, and the strength-stress ratio is as follows: If the basic rock mass mass T′≥55, and the strength-stress ratio is 7~4 Rc / σmax (where σmax is the maximum principal stress in MPa) during a minor rockburst (Level I), then the correction value K1 is -10; if the basic rock mass mass mass T′≥55, and the strength-stress ratio is 4~2 Rc / σmax (where σmax is the maximum principal stress in MPa) during a moderate rockburst (Level II), then the correction value K1 is -20; if the basic rock mass mass mass mass T′≥55, and the strength-stress ratio is 2~1 Rc / σmax (where σmax is the maximum principal stress in MPa) during a severe rockburst (Level III), then the correction value K1 is -25; if the basic rock mass mass mass mass T′≥55, and the strength-stress ratio is <1 Rc / σmax (where σmax is the maximum principal stress in MPa) during an extremely severe rockburst (Level IV), then the correction value K1 is -30. K2 is the correction value for the surrounding rock score of the soft rock section with large deformation under high ground stress conditions. The correspondence between the value of K2 and the basic rock mass quality score T′, the degree of deformation, and the strength-stress ratio is as follows: If the basic mass mass quality score T′ < 55, the deformation degree is basically stable, the strength-stress ratio is 2–1Rc / σmax, where σmax is the maximum principal stress in MPa, then the correction value K2 is -20; if the basic mass mass quality score T′ < 55, the deformation degree is slight compressive deformation, the strength-stress ratio is 1–0.5Rc / σmax, where σmax is the maximum principal stress in MPa, then the correction value K2 is -22.5; if the basic mass mass quality score T′ < 55, the deformation degree is moderate compressive deformation, and the strength-stress ratio is 0.5–0.25Rc If σmax is the maximum principal stress in MPa, then the correction value K2 is -25; if the basic mass fraction of the rock mass T′ < 55, the deformation degree is severe compression deformation, the strength-stress ratio is 0.25~0.15Rc / σmax, and σmax is the maximum principal stress in MPa, then the correction value K2 is -27.5; if the basic mass fraction of the rock mass T′ < 55, the deformation degree is extremely severe compression deformation, the strength-stress ratio is < 0.15Rc / σmax, and σmax is the maximum principal stress in MPa, then the correction value K2 is -30.

6. The method for classifying surrounding rock of deep-buried long tunnels based on the TBM method according to claim 1, characterized in that, The correspondence between the corrected values ​​of the surrounding rock category (i.e., the total score T) for deep-buried tunnels under groundwater activity conditions and water inrush conditions is as follows: T = T' + D, where: T is the corrected total score of the surrounding rock; T' is the basic quality score of the rock mass; and D is the groundwater correction value. The correspondence between the D value and the groundwater activity state of water inrush and the basic rock mass mass mass fraction T′ is as follows: If the groundwater activity is characterized by a sudden water inrush, with a flow rate q > 250 L / min • 10m tunnel length or a pressure head H > 200, and a basic rock mass mass fraction of 100 ≥ T' > 85, then D is -6 to -10; if the groundwater activity is characterized by a sudden water inrush, with a flow rate q > 250 L / min • 10m tunnel length or a pressure head H > 200, and a basic rock mass mass fraction of 85 ≥ T' > 65, then D is -10 to -14; if the groundwater activity is characterized by a sudden water inrush, with a flow rate q > 250 L / min • 10m tunnel length or a pressure head H > 200, and a basic rock mass mass fraction of 65 ≥ T' > 45, then D is -14 to -18 ... then D is -14 to -18; if the groundwater activity is characterized by a sudden water inrush, with a flow rate q > 250 L / min • 10m tunnel length or a pressure head H > 200, and a basic rock mass mass fraction of 65 ≥ T' > 45, then D is -14 to -18. If the groundwater activity is characterized by sudden water flow (L / min•10m tunnel length or pressure head H>200), and the basic mass fraction of the rock mass is 45≥T'>25, then D is -18 to -20; if the groundwater activity is characterized by sudden water flow (q>250), and the basic mass fraction of the rock mass is T'≤25, then D is -20 to -24.

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