Prediction method of rock mass physical and mechanical parameters based on TSP advanced geological prediction

Abstract

The present invention discloses a method for predicting the physical and mechanical parameters of rock mass based on TSP advanced geological prediction, which belongs to the field of geotechnical engineering and advanced prediction technology, including: advanced prediction technology of rock mass wave velocity in front of the tunnel face based on the TSP method, correcting the apparent wave velocity obtained by the TSP method according to the rock mass wave velocity value actually measured by the rock mass acoustic wave test, thereby obtaining the absolute wave velocity value of the rock mass in the unexcavated section of the tunnel; at the same time, measuring the strength parameters of the rock through the rock point load test, and predicting the strength parameters of the rock mass in front of the tunnel face based on the rock strength parameters and the rock mass wave velocity. Theoretical formulas and empirical formulas are used to fully explore the TSP prediction function, and accurately predict the physical and mechanical parameters of the rock mass in front of the tunnel face within the TSP test range. The method proposed by the present invention has the advantages of simplicity, speed, economy, high accuracy, etc., which gives new functions to the TSP detection method and can provide an effective means for predicting the physical and mechanical parameters of tunnel rock mass.

Description

Technical Field

[0001] The present invention belongs to the technical field of geotechnical engineering and advanced prediction, and in particular relates to a method for predicting the physical and mechanical parameters of rock masses based on TSP advanced geological prediction. Background Art

[0002] The TSP method is a relatively mature and widely used seismic wave reflection method within my country's railway tunnel advanced geological prediction system. It can be used in tunnels excavated by drill-and-blast or TBM methods without having to approach the tunnel face. It offers advantages such as a relatively long prediction range, high accuracy, timely data submission, and cost-effectiveness. The method has an effective prediction range of 100–150 m, with a maximum range of 200 m, making it a widely used long-range prediction method in tunnel engineering. However, TSP advanced geological prediction is currently primarily used for qualitative detection of lithologic changes ahead of the tunnel face, such as irregularities, discontinuities, faults, and fracture zones. It is particularly effective for planar weak zones that intersect the tunnel axis or at large angles, such as faults, fracture zones, weak interlayers, underground caves (including karst caves), and interfaces between strata. However, the wave velocities (and other mechanical parameters) measured using the TSP method are not true (absolute) wave velocities, but rather apparent wave velocities, making it incapable of quantitatively predicting the physical and mechanical parameters of the tunnel rock mass. The physical and mechanical parameters of tunnel rock masses are typically obtained through in-situ testing, which can lead to increased project investment and extended construction periods. Furthermore, it is difficult to predict the physical and mechanical parameters of the rock mass ahead of the tunnel face in advance. Therefore, using TSP data to rapidly predict the physical and mechanical parameters of the rock mass ahead of the tunnel face is of great practical significance for improving construction efficiency and ensuring project safety and stability.

[0003] Therefore, existing technical problems point out that there is currently a lack of a method for predicting the physical and mechanical parameters of rock masses based on TSP advanced geological prediction. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention proposes a method for predicting the physical and mechanical parameters of rock masses based on TSP advanced geological prediction to solve the problems existing in the above prior art.

[0005] To achieve the above objectives, the present invention provides a method for predicting the physical and mechanical parameters of rock masses based on TSP advanced geological prediction, comprising:

[0006] Perform TSP data acquisition based on seismic wave information receiving probes to obtain longitudinal and shear wave velocities;

[0007] Dividing the rock mass in front of the tunnel face based on the longitudinal wave velocity and the shear wave velocity to generate a plurality of sections;

[0008] Performing rock mass acoustic wave testing on the rock mass in front of the tunnel face to obtain measured values ​​of the rock mass transverse and longitudinal wave velocities, and simultaneously conducting point load strength tests on the aforementioned sections to obtain the uniaxial compressive strength value of the rock;

[0009] Obtaining an absolute wave velocity value of the rock mass based on the measured values ​​of the transverse and longitudinal wave velocities of the rock mass obtained by the rock mass acoustic wave test, and obtaining an absolute wave velocity value of the rock mass based on the uniaxial compressive strength value of the rock mass;

[0010] The physical and mechanical parameters of the rock mass are calculated based on the absolute wave velocity value of the rock and the absolute wave velocity value of the rock mass.

[0011] Preferably, the process of performing TSP data acquisition based on the seismic wave information receiving probe includes:

[0012] The seismic wave information receiving probes and explosive packs are buried according to the operating specifications and forecast requirements. If the ambient noise is lower than the noise threshold under the noise monitoring model, TSP data collection is carried out;

[0013] The data obtained by the data acquisition operation are processed to obtain the longitudinal wave velocity and the shear wave velocity of each section of the surrounding rock.

[0014] Preferably, after obtaining the longitudinal wave velocity and the shear wave velocity of each section of surrounding rock, the method further includes:

[0015] Calculating and obtaining dynamic parameters based on the longitudinal wave velocity and the shear wave velocity;

[0016] The expression for obtaining the kinetic parameters is:

[0017]

[0018] Among them, v p is the longitudinal wave velocity, v s is the shear wave velocity, ρ is the density of the surrounding rock, E d is the dynamic elastic modulus, G d is the dynamic shear modulus, μ d is Poisson's ratio.

[0019] Preferably, the process of dividing the rock mass in front of the tunnel face based on the longitudinal wave velocity and the shear wave velocity to generate a plurality of sections includes:

[0020] The rock mass sections with the same longitudinal wave velocity and shear wave velocity are regarded as having the same physical and mechanical properties. According to the fluctuation of wave velocity in the physical and mechanical parameter result diagram of the TSP method, the rock mass in front of the tunnel face can be divided into several sections. The apparent wave velocity values ​​of the several sections are equal, and the starting mileage and mileage range of the several sections are recorded.

[0021] Preferably, the process of performing point load strength tests on the plurality of sections to obtain the uniaxial compressive strength value of the rock includes:

[0022] The point load meter performs a point load strength test on the rock sample at the tunnel face, records the rock failure load, and obtains the rock point load strength index based on the rock failure load;

[0023] The uniaxial compressive strength value of the rock is estimated based on the point load strength index of the rock.

[0024] Preferably, the expression for obtaining the point load strength index of the rock based on the failure load of the rock is:

[0025] p = cF;

[0026]

[0027] Where p is the failure load, in N; D e 2 The square value of the equivalent circle diameter of the failure surface, in mm 2 ; c is the calibration coefficient; F is the failure load, unit is MPa; A f is the area of ​​the damaged surface, in mm 2 ;I s is the point load strength of rock, in MPa.

[0028] Preferably, the expression for estimating the uniaxial compressive strength value of the rock based on the point load strength index of the rock is:

[0029]

[0030] Wherein, P is the uniaxial compressive strength of rock, in MPa; I s(50) It is the rock point load strength index with an equivalent core diameter of 50 mm, in MPa.

[0031] Preferably, the method for obtaining the absolute wave velocity value of the rock mass based on the measured values ​​of the transverse and longitudinal wave velocities of the rock mass obtained by the rock mass acoustic wave test is:

[0032] The rock mass velocity curve on the TSP velocity result image was subjected to a downward v pT -v pS The data corresponding to the transformed curve is the absolute wave velocity value of the rock mass;

[0033] where v pT v is the longitudinal wave velocity value of the rock mass tested by TSP; pT v is the shear wave velocity value of the rock mass tested by TSP; pS v is the rock mass longitudinal wave velocity value obtained from rock mass acoustic wave testing; sSis the rock mass shear wave velocity value obtained from rock mass acoustic wave testing;

[0034] The expression for the absolute wave velocity value of the rock obtained based on the uniaxial compressive strength value of the rock is:

[0035]

[0036] Among them, v pr is the longitudinal wave velocity of the rock.

[0037] Preferably, the rock mass physical and mechanical parameters include rock mass integrity index, rock mass compressive strength value, rock mass weight, rock mass shear strength parameter and rock mass dynamic elastic parameter.

[0038] Preferably, the calculation expression of the rock mass integrity index is:

[0039]

[0040] Among them, K v is the rock mass integrity index, dimensionless; v p is the longitudinal wave velocity of the rock mass, in m / s;

[0041] The calculation expression of the rock mass compressive strength value is:

[0042]

[0043] Where R is the uniaxial compressive strength of rock mass;

[0044] The calculation expression of the rock mass is:

[0045]

[0046] Wherein, γ is the rock mass density;

[0047] The calculation expression of the shear strength parameter of the rock mass is:

[0048]

[0049] Where c is the cohesion of the rock mass; is the friction angle within the rock mass.

[0050] Compared with the prior art, the present invention has the following advantages and technical effects:

[0051] The present invention is based on the TSP method for advanced prediction of the wave velocity of the rock mass in front of the tunnel face. The apparent wave velocity obtained by the TSP method is corrected according to the rock mass wave velocity value actually measured by the rock mass acoustic wave test, thereby obtaining the absolute wave velocity value of the rock mass in the unexcavated section of the tunnel; at the same time, the strength parameters of the rock are measured by the rock point load test, and the strength parameters of the rock mass in front of the tunnel face are predicted based on the rock strength parameters and the rock mass wave velocity. Theoretical formulas and empirical formulas are used to fully explore the TSP prediction function and accurately predict the physical and mechanical parameters of the rock mass in front of the tunnel face within the TSP test range. The method proposed by the present invention has the advantages of simplicity, speed, economy, and high accuracy. It gives new functions to the TSP detection method and can provide an effective means for predicting the physical and mechanical parameters of the tunnel rock mass. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of this application. The exemplary embodiments and descriptions of this application are intended to explain this application and do not constitute an improper limitation on this application. In the accompanying drawings:

[0053] Figure 1 is a flow chart of an embodiment of the present invention;

[0054] Figure 2 Schematic diagram of an experiment of an embodiment of the present invention;

[0055] Figure 3 Schematic diagram of rock mass wave velocity testing using a single-hole method according to an embodiment of the present invention;

[0056] Figure 4 A schematic diagram of a portable point load meter according to an embodiment of the present invention;

[0057] Figure 5 A schematic diagram of TSP wave velocity correction according to an embodiment of the present invention;

[0058] 1. Trigger, 2. Hammer, 3. Wooden pile, 4. Load, 5. Thick plate, 6. Oscilloscope, 7. Three-way detector, 8. Expansion pump, 9. Air bag, 10. Frame, 11. Hand-cranked horizontal oil pump, 12. Jack, 13. Loading cone head, 14. Oil pressure gauge, 15. Vernier caliper, 16. Test specimen. DETAILED DESCRIPTION

[0059] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0060] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0061] Example 1

[0062] like Figure 1 As shown, this embodiment provides a method for predicting rock mass physical and mechanical parameters based on TSP advanced geological prediction, including:

[0063] Perform TSP data acquisition based on seismic wave information receiving probes to obtain longitudinal and shear wave velocities;

[0064] Dividing the rock mass in front of the tunnel face based on the longitudinal wave velocity and the shear wave velocity to generate a plurality of sections;

[0065] Performing rock mass acoustic wave testing on the rock mass in front of the tunnel face to obtain measured values ​​of the rock mass transverse and longitudinal wave velocities, and simultaneously conducting point load strength tests on the aforementioned sections to obtain the uniaxial compressive strength value of the rock;

[0066] Obtaining an absolute wave velocity value of the rock mass based on the uniaxial compressive strength value of the rock;

[0067] The physical and mechanical parameters of the rock mass are calculated based on the uniaxial compressive strength value of the rock and the absolute wave velocity value of the rock mass, specifically:

[0068] Step 1: On-site implementation of TSP measurement

[0069] Seismic wave information receiving probes and explosive packs are buried according to operating specifications and forecast requirements. In the noise monitoring mode, if the noise level in the surrounding environment is low, data collection can be carried out and blasting can begin.

[0070] Step 2: TSP tunnel advanced geological prediction data collection and data processing

[0071] The data collected on site are transmitted to the computer and processed to obtain the TSP test data in front of the tunnel face (unexcavated section), including the longitudinal wave velocity v of each section of the surrounding rock. p and shear wave velocity v s The visual value and the p and v s The dynamic parameters calculated by the visual value, namely the dynamic elastic modulus E d , dynamic shear modulus G d and Poisson's ratio μ d The relative value of .

[0072] Step 3: Segmentation of the tunnel rock mass within the TSP test area

[0073] The rock mass sections with the same apparent wave velocity within the TSP prediction range are considered to have the same physical and mechanical properties. According to the fluctuation of wave velocity in the physical and mechanical parameter results diagram of the TSP method, the rock mass in front of the tunnel face can be divided into several sections. The apparent wave velocity value of each section is equal, and the starting mileage and mileage range of each rock mass section are recorded.

[0074] Step 4: Conduct rock mass acoustic wave testing and point load strength testing

[0075] Rock mass acoustic wave testing uses the single-hole method and requires only a single test. A vertical test hole is located at a suitable point near the tunnel face. A three-component geophone is fixed at a predetermined depth within the hole, close to the hole wall. Ground or in-hole excitation is used as the excitation device. The measured transverse and longitudinal wave velocities of the rock mass are determined based on the wave's propagation time and distance.

[0076] Point load strength testing is performed on every rock mass section within the TSP test area. Rock samples are first collected from the tunnel face for testing. As tunnel excavation progresses, new rock mass sections are exposed and tested. The failure load of each rock sample is recorded, the sample dimensions are measured, and the rock's point load strength index is calculated.

[0077] Step 5: Calculation of absolute wave velocity value of rock mass in TSP test section

[0078] Based on engineering experience, the rock velocity in the section to be excavated as measured by the TSP method is the apparent velocity. This is manifested by the significant discrepancy between the velocity at the tunnel face (initial value) and the measured velocity, while the variation in apparent velocity across different sections is more accurate. Therefore, the rock velocity measured by TSP is relative to the rock velocity at the tunnel face (initial value), which is why a method for calculating absolute rock velocity values ​​is proposed.

[0079] Calculate the difference between the measured wave velocity value obtained by the rock mass acoustic wave test and the apparent wave velocity value of the rock mass tested by the TSP method at the test point (at the tunnel face), and then subtract this difference from the apparent wave velocity value of the rock mass tested by the TSP method in each rock mass section. The apparent wave velocity correction of the TSP test section can be completed, thereby obtaining the absolute wave velocity value of the rock mass.

[0080] Step 6: Calculation of the physical and mechanical parameters of the rock mass in front of the tunnel face

[0081] The uniaxial compressive strength and longitudinal wave velocity of the rock estimated by the point load strength test are substituted into the relevant empirical formula to calculate the physical and mechanical parameters of the rock mass, thereby realizing the prediction of the physical and mechanical parameters of the rock mass in the unexcavated section of the tunnel.

[0082] In the step 2, the longitudinal wave velocity v p and shear wave velocity vs The calculated kinetic parameter formula is as follows:

[0083]

[0084] Where: v p is the longitudinal wave velocity, v s is the shear wave velocity, ρ is the density of the surrounding rock, E d is the dynamic elastic modulus, G d is the dynamic shear modulus, μ d is Poisson's ratio.

[0085] The steps for calculating the point load strength index of rock in step 4 are as follows:

[0086] Use a point load meter to conduct a point load strength test on the rock sample at the tunnel face, record the rock failure load, measure the test sample size, and calculate the point load strength index of the rock according to the following formula.

[0087] p=cF

[0088]

[0089] Where: p is the failure load, unit is N; D e 2 The square value of the equivalent circle diameter of the failure surface, in mm 2 ; c is the calibration coefficient; F is the failure load, unit is MPa; A f is the area of ​​the damaged surface, in mm 2 ;I s is the point load strength of rock, in MPa.

[0090] When the distance between the two loading points is not equal to 50 mm, correction is required according to the following formula.

[0091]

[0092] Where: m is the correction index, and the other letters have the same meanings as above.

[0093] The calculation process of the uniaxial compressive strength value of the rock and the longitudinal wave velocity value of the rock estimated by the point load strength test in step 6 is as follows:

[0094] The uniaxial compressive strength of rock calculated by point load strength test is calculated as follows:

[0095]

[0096] Where: P is the uniaxial compressive strength of rock, in MPa; I s(50) It is the rock point load strength index with an equivalent core diameter of 50 mm, in MPa.

[0097] The longitudinal wave velocity value of the rock calculated by the point load strength test is first calculated by the uniaxial compressive strength of the rock, and then the longitudinal wave velocity of the rock is calculated according to the uniaxial compressive strength of the rock as follows:

[0098]

[0099] Where: v pr is the longitudinal wave velocity of rock, in m / s; P is the uniaxial compressive strength of rock, in MPa.

[0100] In step 6, the rock longitudinal wave velocity value and the absolute wave velocity value of each rock mass section are substituted into the relevant empirical formula to calculate the rock mass physical and mechanical parameters. The process and relevant formula are as follows:

[0101] 1) Rock mass integrity index

[0102] The integrity index of each rock mass section is calculated based on the absolute longitudinal wave velocity of the rock mass obtained after correction in the above steps and the point load strength of the rock in the section. The formula is as follows:

[0103]

[0104] Where: K v is the rock mass integrity index, dimensionless; v pm is the longitudinal wave velocity of the rock mass, in m / s.

[0105] 2) Rock mass compressive strength value

[0106] The compressive strength of the rock mass is calculated by the integrity index of each section of the rock mass and the point load strength value of each section of the rock, as follows:

[0107]

[0108] Where: R is the uniaxial compressive strength of rock mass, in MPa; K v is the rock mass integrity index, dimensionless; I s(50) It is the rock point load strength index with an equivalent core diameter of 50 mm, in MPa.

[0109] 3) Rock mass

[0110] The weight of the rock mass in the unexcavated section of the tunnel is calculated based on the absolute wave velocity value of the rock mass after correction in the following section as follows:

[0111]

[0112] Where: γ is the rock mass; v p is the longitudinal wave velocity of the rock mass, in m / s.

[0113] 4) Shear strength parameters of rock mass

[0114] According to the mathematical relationship between the internal friction angle, cohesion and longitudinal wave velocity of the rock mass, the shear strength parameter of the rock mass in the unexcavated section of the tunnel is obtained as follows:

[0115]

[0116] Where: c is the cohesion of rock mass; is the friction angle in the rock mass; v p is the longitudinal wave velocity of the rock mass.

[0117] In addition, based on the corrected absolute transverse and longitudinal wave velocity values ​​of the rock mass, accurate dynamic elastic parameters of the rock mass can be obtained through calculation using the following formula.

[0118]

[0119] Where: v p is the longitudinal wave velocity, v s is the shear wave velocity, ρ is the density of the surrounding rock, E d is the dynamic elastic modulus, G d is the dynamic shear modulus, μ d is Poisson's ratio.

[0120] Example 2

[0121] This embodiment provides a method for predicting the physical and mechanical parameters of rock masses based on TSP advanced geological prediction, including:

[0122] Step 1: On-site implementation of TSP measurement

[0123] Seismic wave information receiving probes and explosive packs are buried according to operating specifications and forecast requirements. In the noise monitoring mode, if the noise level in the surrounding environment is low, data collection can be carried out and blasting can begin.

[0124] During TSP measurement, the receiver probe is buried in a steel casing, which is tightly coupled to the surrounding rock using a two-component epoxy resin or anchoring agent to facilitate the reception of seismic wave signals generated by the excitation hole.

[0125] Each blast hole is artificially stimulated with a small charge of explosives to generate seismic signals. Detonators must be instantaneous electric detonators, and emulsion explosives must be used. Before blasting, the blast hole is filled with water to maximize the propagation of the blasting energy through the surrounding rock, suppress dust, and extinguish the flame.

[0126] Step 2: TSP tunnel advanced geological prediction data collection and data processing

[0127] Once preparations are complete, data collection can begin. If the ambient noise level is low in noise monitoring mode, data collection can begin and blasting can commence. The electrical signal generated by the initiator triggers the electric detonator to detonate the explosive charge, while also signaling the instrument to open the data transmission channel. The seismic wave signal generated by the explosive charge blasting is quickly picked up and recorded by the receiving probe. This process continues until all 24 blasting holes have been blasted.

[0128] The data collected on site are transferred to a computer and processed using TSPwin software. After waveform processing, the arrival of longitudinal waves and shear waves are picked up from the seismic waveform record, and the longitudinal wave velocity v of each section of the surrounding rock can be calculated based on the distance between the explosion point and the detector. p and shear wave velocity v s .

[0129] P-wave velocity and S-wave velocity v s The value comprehensively reflects the physical and mechanical properties of the surrounding rock. p and shear wave velocity v s The dynamic parameters of the rock mass, namely the dynamic Poisson's ratio, dynamic Young's modulus, and dynamic shear modulus, can be calculated. The density of the rock mass in the excavation section can also be calculated based on the relationship between wave velocity and rock mass density. The calculation formula is as follows (the calculated parameters are relative values):

[0130]

[0131] Where: v p is the longitudinal wave velocity, v s is the shear wave velocity, ρ is the density of the surrounding rock, E d is the dynamic elastic modulus, G d is the dynamic shear modulus, μ d is Poisson's ratio.

[0132] Step 3: Tunnel rock mass segmentation of the TSP test section

[0133] The rock mass sections with the same apparent wave velocity within the TSP prediction range are considered to have the same physical and mechanical properties. According to the fluctuation of wave velocity in the physical and mechanical parameter results of the TSP method, the rock mass in front of the tunnel face can be divided into several sections as shown in the attached figure. Figure 2 As shown, the apparent wave velocity value of each section is equal, and the starting mileage and mileage range of each rock mass section are recorded.

[0134] Step 4: Conduct rock mass acoustic wave testing and point load strength testing

[0135] As attached Figure 3-4 As shown in the figure, the rock mass acoustic wave test adopts the single hole method, and a vertical test hole is arranged at a suitable point near the tunnel face.

[0136] A three-component geophone 7 and an airbag 9 are lowered into the casing. Once the desired depth is reached, the airbag is inflated using an expansion pump 8 to secure the geophone to the borehole wall. At the surface, a hammer 2 equipped with a trigger 1 strikes a thick plate 5 loaded with a weight 4, and an oscilloscope 6 records the waveform.

[0137] For the test of longitudinal wave velocity, a hammered wooden pile 3 is used as the vibration source, and the distance between the wooden pile and the hole mouth should be 1 to 3 meters. Calculate the longitudinal wave velocity of the rock mass at the test point, where t p is the longitudinal wave propagation time, L p is the longitudinal wave propagation distance, v p is the longitudinal wave velocity of the rock mass.

[0138] For the test of shear wave velocity, a wooden board with a heavy object pressed by a hammer is used as the vibration source. The distance between the wooden board and the hole should be 1 to 3 meters; the weight pressed on the board should be greater than 400kg; the wooden board should be in close contact with the ground. Calculate the shear wave velocity of the rock mass at the test point, where t s is the shear wave propagation time, L s is the shear wave propagation distance, and vs is the shear wave velocity of the rock mass.

[0139] Point load strength test should be carried out on each rock mass. First, rock samples are taken from the tunnel face for testing. As the tunnel is excavated, whenever a new section of rock mass is exposed (when the excavation enters the mileage range of the next section), sampling tests are carried out. Figure 2 As shown in the figure, during the test, a small rock sample is first taken from the sampling point and slightly processed with a geological hammer to form a 3-5 cm square rock block specimen 16. The specimen is then installed. Before installation, the upper and lower loading cones 13 of the instrument are checked for alignment. The specimen is then placed in the instrument. After securing the frame 11, the hand-cranked horizontal oil pump 11 is cranked to raise the lower cone under the action of the jack 12. The loading cone is then aligned parallel to and in close contact with the shortest side of the specimen, ensuring that the contact point coincides as closely as possible with the center of the specimen. After the specimen is installed, the oil pressure gauge 14 is adjusted to zero and a uniform load is applied at a rate of 0.05-0.1 MPa per second until the specimen fails. The pressure gauge reading at failure is recorded. The specimen failure characteristics are then characterized. A normal failure surface should pass through both loading points simultaneously; otherwise, the test is invalid and should be discarded. Finally, the failure surface dimensions are measured with a vernier caliper 15 to determine the failure surface area. The results are then processed to determine the point load strength. Record the failure load of the rock samples taken from each rock mass section, measure the sample size, and calculate the point load strength index of the rock.

[0140] Calculate the point load strength index of rock according to the following formula.

[0141] p=cF

[0142]

[0143] Where: p is the failure load, unit is N; D e 2 The square value of the equivalent circle diameter of the failure surface, in mm 2 ; c is the calibration coefficient; F is the failure load, unit is MPa; A f is the area of ​​the damaged surface, in mm 2 I s is the point load strength of the rock, in MPa. When the distance between two loading points is not equal to 50 mm, it needs to be corrected according to the following formula.

[0144]

[0145] Where: m is the correction index, and the other letters have the same meanings as above.

[0146] Step 5: Calculation of absolute wave velocity value of rock mass in TSP test section

[0147] Based on engineering experience, the rock velocity in the section to be excavated obtained by TSP detection is a relative value. This is manifested in significant discrepancies between the initial value of the velocity at the tunnel face and the actual velocity, while the variation in rock velocity across different sections is more accurate. Therefore, the rock velocity obtained by TSP detection is relative to the initial value of the rock velocity at the tunnel face, and a method for calculating the absolute value of the rock velocity is proposed.

[0148] As attached Figure 5 As shown in the figure, the rock mass acoustic wave test value is compared with the TSP predicted value at the test point (at the tunnel face), and the difference between the TSP velocity test value and the in-situ acoustic wave measured value is calculated. Then, this difference is subtracted from the TSP test acoustic wave data as a whole to complete the correction of the TSP velocity data and obtain the absolute velocity value of the rock mass in each section of the tunnel within the TSP test range. The TSP velocity result image shows that the overall data has been subjected to a downward v pT -v pS (or v sT -v sS ) translation transformation, where v pT v is the longitudinal wave velocity value of the rock mass tested by TSP; pT v is the shear wave velocity value of the rock mass tested by TSP; pS v is the rock mass longitudinal wave velocity value obtained from rock mass acoustic wave testing; sS It is the shear wave velocity value of the rock mass obtained by rock mass acoustic wave testing.

[0149] Step 6: Calculation of the physical and mechanical parameters of the rock mass in each section of the tunnel within the TSP test range

[0150] First, the uniaxial compressive strength of the rock is calculated by the load strength test of the rock point in each section, and is calculated as follows:

[0151]

[0152] Where: P is the uniaxial compressive strength of rock, in MPa; I s(50) It is the rock point load strength index with an equivalent core diameter of 50 mm, in MPa.

[0153] The longitudinal wave velocity value of the rock calculated by the point load strength test is first calculated by the uniaxial compressive strength of the rock, and then the longitudinal wave velocity of the rock is calculated according to the uniaxial compressive strength of the rock as follows:

[0154]

[0155] Where: v pr is the longitudinal wave velocity of rock, in m / s; P is the uniaxial compressive strength of rock, in MPa.

[0156] In step 6, the rock longitudinal wave velocity value and the rock mass wave velocity of each rock mass section obtained in the above steps are brought into the relevant empirical formula to calculate the rock mass physical and mechanical parameters. The process and relevant formula are as follows:

[0157] 1) Rock mass integrity index

[0158] The integrity index of each rock mass section is calculated based on the rock mass longitudinal wave velocity obtained after correction in the above steps and the point load strength of the rock in the section. The formula is as follows:

[0159]

[0160] Where: K v is the rock mass integrity index, dimensionless; v pm is the longitudinal wave velocity of the rock mass, in m / s.

[0161] 2) Rock mass compressive strength value

[0162] The compressive strength of the rock mass is calculated by the integrity index of each section of the rock mass and the point load strength value of each section of the rock, as follows:

[0163]

[0164] Where: R is the uniaxial compressive strength of rock mass, in MPa; K v is the rock mass integrity index, dimensionless; I s(50) It is the rock point load strength index with an equivalent core diameter of 50 mm, in MPa.

[0165] 3) Rock mass

[0166] The weight of the rock mass in the unexcavated section of the tunnel is calculated based on the corrected rock mass wave velocity in the following section:

[0167]

[0168] Where: γ is the rock mass; v p is the longitudinal wave velocity of the rock mass, in m / s.

[0169] 4) Shear strength parameters of rock mass

[0170] According to the mathematical relationship between the internal friction angle, cohesion and longitudinal wave velocity of the rock mass, the shear strength parameter of the rock mass in the unexcavated section of the tunnel is obtained as follows:

[0171]

[0172] Where: c is the cohesion of rock mass; is the friction angle in the rock mass; v p is the longitudinal wave velocity of the rock mass.

[0173] In addition, more accurate dynamic elastic parameters of rock mass can be obtained through the following formula by using the corrected rock mass transverse and longitudinal wave velocity values.

[0174]

[0175] Where: v p is the longitudinal wave velocity, v s is the shear wave velocity, ρ is the density of the surrounding rock, E d is the dynamic elastic modulus, G d is the dynamic shear modulus, μ d is Poisson's ratio.

[0176] The above are merely preferred embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A method for predicting rock mass physical and mechanical parameters based on TSP advanced geological prediction, characterized in that: The following steps are involved: Perform TSP data acquisition based on seismic wave information receiving probes to obtain longitudinal and shear wave velocities; Dividing the rock mass in front of the tunnel face based on the longitudinal wave velocity and the shear wave velocity to generate a plurality of sections; Performing rock mass acoustic wave testing on the rock mass in front of the tunnel face to obtain measured values ​​of the rock mass transverse and longitudinal wave velocities, and simultaneously conducting point load strength tests on the aforementioned sections to obtain the uniaxial compressive strength value of the rock; Obtaining an absolute wave velocity value of the rock mass based on the measured values ​​of the transverse and longitudinal wave velocities of the rock mass obtained by the rock mass acoustic wave test, and obtaining an absolute wave velocity value of the rock mass based on the uniaxial compressive strength value of the rock mass; The physical and mechanical parameters of the rock mass are calculated based on the absolute wave velocity value of the rock and the absolute wave velocity value of the rock mass.

2. The method for predicting rock mass physical and mechanical parameters based on TSP advanced geological prediction according to claim 1, characterized in that: The process of performing TSP data acquisition based on the seismic wave information receiving probe includes: The seismic wave information receiving probes and explosive packs are buried according to the operating specifications and forecast requirements. If the ambient noise is lower than the noise threshold under the noise monitoring model, TSP data collection is carried out; The data obtained by the data acquisition operation are processed to obtain the longitudinal wave velocity and the shear wave velocity of each section of the surrounding rock.

3. The method for predicting rock mass physical and mechanical parameters based on TSP advanced geological prediction according to claim 2, characterized in that: After obtaining the longitudinal wave velocity and shear wave velocity of each section of surrounding rock, the following steps are also included: Calculating and obtaining dynamic parameters based on the longitudinal wave velocity and the shear wave velocity; The expression for obtaining the kinetic parameters is: Among them, v p is the longitudinal wave velocity, v s is the shear wave velocity, ρ is the density of the surrounding rock, E d is the dynamic elastic modulus, G d is the dynamic shear modulus, μ d is Poisson's ratio.

4. The method for predicting rock mass physical and mechanical parameters based on TSP advanced geological prediction according to claim 1, characterized in that: The process of dividing the rock mass in front of the tunnel face based on the P-wave velocity and S-wave velocity to generate several sections includes: The rock mass sections with the same longitudinal wave velocity and shear wave velocity are regarded as having the same physical and mechanical properties. According to the fluctuation of wave velocity in the physical and mechanical parameter result diagram of the TSP method, the rock mass in front of the tunnel face can be divided into several sections. The apparent wave velocity values ​​of the several sections are equal, and the starting mileage and mileage range of the several sections are recorded.

5. The method for predicting rock mass physical and mechanical parameters based on TSP advanced geological prediction according to claim 1, characterized in that: The process of performing point load strength tests on the plurality of sections to obtain the uniaxial compressive strength value of the rock includes: The point load meter performs a point load strength test on the rock sample at the tunnel face, records the rock failure load, and obtains the rock point load strength index based on the rock failure load; The uniaxial compressive strength value of the rock is estimated based on the point load strength index of the rock.

6. The method for predicting rock mass physical and mechanical parameters based on TSP advanced geological prediction according to claim 5, characterized in that: The expression for obtaining the point load strength index of the rock based on the rock failure load is: p = cF; Where p is the failure load, in N; D e 2 The square value of the equivalent circle diameter of the failure surface, in mm 2 ; c is the calibration coefficient; F is the failure load, unit is MPa; A f is the area of ​​the damaged surface, in mm 2 ;I s is the point load strength of rock, in MPa.

7. The method for predicting rock mass physical and mechanical parameters based on TSP advanced geological prediction according to claim 5, characterized in that: The expression for estimating the uniaxial compressive strength value of the rock based on the point load strength index of the rock is: Wherein, P is the uniaxial compressive strength of rock, in MPa; I s(50) It is the rock point load strength index with an equivalent core diameter of 50 mm, in MPa.

8. The method for predicting rock mass physical and mechanical parameters based on TSP advanced geological prediction according to claim 1, characterized in that: The method for obtaining the absolute wave velocity value of the rock mass based on the measured values ​​of the transverse and longitudinal wave velocities of the rock mass obtained by the rock mass acoustic wave test is: The rock mass velocity curve on the TSP velocity result image was subjected to a downward v pT -v pS The data corresponding to the transformed curve is the absolute wave velocity value of the rock mass; where v pT v is the longitudinal wave velocity value of the rock mass tested by TSP; pT v is the shear wave velocity value of the rock mass tested by TSP; pS v is the rock mass longitudinal wave velocity value obtained from rock mass acoustic wave testing; sS is the rock mass shear wave velocity value obtained from rock mass acoustic wave testing; The expression for the absolute wave velocity value of the rock obtained based on the uniaxial compressive strength value of the rock is: Among them, v pr is the longitudinal wave velocity of the rock.

9. The method for predicting rock mass physical and mechanical parameters based on TSP advanced geological prediction according to claim 1, characterized in that: The rock mass physical and mechanical parameters include rock mass integrity index, rock mass compressive strength value, rock mass weight, rock mass shear strength parameter and rock mass dynamic elasticity parameter.

10. The method for predicting rock mass physical and mechanical parameters based on TSP advanced geological prediction according to claim 9, characterized in that: The calculation expression of the rock mass integrity index is: Among them, K v is the rock mass integrity index, dimensionless; v p is the longitudinal wave velocity of the rock mass, in m / s; The calculation expression of the rock mass compressive strength value is: Where R is the uniaxial compressive strength of rock mass; The calculation expression of the rock mass is: Wherein, γ is the rock mass density; The calculation expression of the shear strength parameter of the rock mass is: Where c is the cohesion of the rock mass; is the friction angle within the rock mass.

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