Tunnel surrounding rock grade division method and system based on apparent resistivity

Abstract

The invention discloses a tunnel surrounding rock grade division method and system based on apparent resistivity. The method comprises the following steps: detecting and acquiring the apparent resistivity value of each section of surrounding rock of a tunnel cavity based on a geophysical prospecting method; according to the apparent resistivity value of the surrounding rock of each section of the tunnel hole body, calculating and obtaining the rock mass integrity coefficient of each section of the tunnel hole body based on the apparent resistivity; on the basis of the rock mass integrity coefficient of the apparent resistivity of each section of the tunnel body, a surrounding rock basic quality index BQ value of each section of the tunnel body is obtained through calculation; in combination with the influence of underground water, the occurrence of the weak structural plane and the initial crustal stress state, obtaining the correction value of the basic quality index BQ of the surrounding rock of each section of the tunnel body; and according to the correction value of the basic quality index BQ of the surrounding rock of each section of the tunnel cavity, grading the surrounding rock of each section of the tunnel cavity. According to the method, the relation between the resistivity characteristics and the rock mass integrity coefficient is used for grading the tunnel hole body rock mass, the grading range of the tunnel surrounding rock is expanded, and the working efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel surrounding rock grade classification, and in particular to a tunnel surrounding rock grade classification method and system based on apparent resistivity. Background Art

[0002] At present, the commonly used tunnel surrounding rock classification methods mainly include geological survey method, borehole test method, and rock mass longitudinal wave velocity method. Among them, the geological survey method mainly combines the surface rock outcrops and occurrence to infer the surrounding rock conditions of the tunnel body; this method is one-sided, especially for long and deep-buried tunnels, the underground rock mass changes are complex, and the conditions such as hidden structures and groundwater are difficult to ascertain. It is impossible to accurately infer the underground rock mass conditions only from the surface outcrops. In addition, due to the terrain, it is difficult for personnel to conduct investigations in many places, so this method has great defects. The borehole test method can reveal the geological conditions of the rock mass in the tunnel body, which is relatively intuitive, but in actual work, it is very difficult to implement drilling for long and deep-buried tunnels, and the number of boreholes that can be implemented is often very small. Therefore, it is difficult to judge the surrounding rock conditions of the entire tunnel from a small number of boreholes. The rock mass longitudinal wave velocity method is a macroscopic indirect evaluation method. This method is suitable for tunnels with a single stratum lithology. At the same time, due to the control of the explosion source, the application of this method is also limited.

[0003] At present, engineering geophysical exploration runs through every exploration stage of tunnel engineering, especially in all aspects of exploration. Geophysical exploration is an important means to understand adverse geological conditions. Since electromagnetic exploration can provide all resistivity information of tunnels, it is of great significance to classify surrounding rocks by electrical characteristics. At the same time, according to current research results, it is also feasible, because rock resistivity is stable within a certain range, and changes occur because of fragmentation or water. The classification of tunnel surrounding rocks through electromagnetic results has expanded the original classification methods. The classification of tunnel body rock mass using resistivity characteristics is a blank area of ​​research at home and abroad. Summary of the invention

[0004] The present application provides a tunnel surrounding rock grading method and system based on apparent resistivity, so as to solve the problem of grading the tunnel body rock mass by using resistivity characteristics.

[0005] According to the first aspect, an embodiment provides a method for classifying tunnel surrounding rock based on apparent resistivity, the method comprising:

[0006] Step S1, obtaining the apparent resistivity value of the surrounding rock of each section of the tunnel body based on geophysical exploration;

[0007] Step S2, based on the apparent resistivity value of the surrounding rock of each section of the tunnel body, calculate and obtain the rock mass integrity coefficient based on the apparent resistivity of each section of the tunnel body;

[0008] Step S3: Calculate the basic quality index BQ value of the surrounding rock for each section of the tunnel body based on the rock mass integrity coefficient based on apparent resistivity of each section of the tunnel body.

[0009] Step S4: Considering the influence of groundwater, occurrence of weak structural planes, and initial in-situ stress state, obtain the corrected value of the basic quality index BQ of the surrounding rock for each section of the tunnel body.

[0010] Step S5: Divide the surrounding rock grades for each section of the tunnel body according to the corrected value of the basic quality index BQ of the surrounding rock for each section of the tunnel body.

[0011] Furthermore, the specific steps of Step S1 include:

[0012] Step S11: Obtain the apparent resistivity contour map of the entire tunnel longitudinal section based on geophysical prospecting methods.

[0013] Step S12: According to the apparent resistivity contour map of the tunnel longitudinal section and combined with the electrical characteristics of apparent resistivity, divide the surrounding rock sections of the tunnel body.

[0014] Step S13: Based on geophysical prospecting data and the coordinate data of the tunnel body, obtain the distribution range of the apparent resistivity value of each surrounding rock section, and take the average value of the apparent resistivity within the range as the apparent resistivity value ρ of each surrounding rock section. 视

[0015] Furthermore, the specific steps of Step S2 include:

[0016] The rock mass integrity coefficient based on apparent resistivity of a certain surrounding rock section of the tunnel body is represented by λ, and the calculation formula of λ is as follows:

[0017] λ = ρ 视 / ρ 完整

[0018] ρ 视 represents the apparent resistivity value of a certain surrounding rock section of the tunnel body;

[0019] ρ 完整 represents the apparent resistivity value under the relatively intact state of the tunnel rock mass.

[0020] Furthermore, the specific steps of Step S2 include:

[0021] The method for obtaining ρ 完整 is as follows:

[0022] First, through the borehole in-hole engineering logging equipment, obtain the rock mass elastic longitudinal wave velocity V pm and the apparent resistivity ρ 0 of the tunnel body section, and at the same time obtain the rock elastic longitudinal wave velocity V pr through laboratory tests;

[0023] Secondly, calculate the rock mass integrity coefficient Kv at the hole location of the drilling position. The formula is as follows:

[0024] Kv = (V pm / V pr ) 2

[0025] Finally, calculate ρ 0 / Kv. The obtained value is the apparent resistivity value of the rock mass when the Kv value is approximately 1, representing the apparent resistivity value ρ of the tunnel rock mass in a relatively intact state. 完整 .

[0026] Furthermore, the step S2 specifically includes:

[0027] The rock mass integrity coefficient based on apparent resistivity for a certain surrounding rock section of the tunnel body can also be calculated using K r .

[0028] Assume that the rock mass is composed of alternating layers of intact rock and fractured rock. The resistivity of the intact rock is ρ r , and the thickness is Δh 1 . The resistivity of the fractured layer is ρ w , and the thickness is Δh 2 . Then the proportion Kr of the intact rock in the rock mass per unit volume is:

[0029] Kr = Δh 1 / (Δh 1 +Δh 2 )

[0030] Through formula derivation and calculation, we get:

[0031] Kr = ρ r (ρ 视 -ρ w ) 2 / [ρ r (ρ 视 2 -ρ w 2 )+ρ w (ρ r 2 -ρ 视 2 )]

[0032] ρ 视 represents the apparent resistivity value of a certain surrounding rock section of the tunnel body; ρ r is the resistivity of the intact rock, obtained through indoor rock resistivity testing; ρ w represents the apparent resistivity value of the fractured rock layer in the rock mass.

[0033] Further, step S3 specifically includes:

[0034] The calculation formula for the basic quality index BQ value of the surrounding rock of each section of the tunnel body is as follows:

[0035] BQ = 100 + 3Rc + 250*Kv′

[0036] Wherein, Rc is the saturated uniaxial compressive strength of the rock; Kv′ is the rock mass integrity coefficient based on apparent resistivity for a certain surrounding rock section of the tunnel body, and here Kv′ can be λ or Kr.

[0037] Further, step S4 specifically includes:

[0038] The calculation formula for the correction value of the basic quality index BQ of the surrounding rock of each section of the tunnel body is as follows:

[0039] [BQ] = BQ - 100*(K1 + K2 + K3)

[0040] Wherein, K1 is the correction coefficient for the influence of groundwater, K2 is the correction coefficient for the influence of the occurrence of weak structural planes, and K3 is the correction coefficient for the influence of the initial in-situ stress state.

[0041] Further, step S4 specifically includes:

[0042] For the value of K1: During the exploration stage, the groundwater discharge state is obtained by combining pumping tests at the borehole location, and the value of K1 is determined by looking up the table according to the groundwater discharge state. For the remaining sections, the value is calculated using the proportional relationship between the surrounding rock of each section and the adjustment coefficient of the measured target section of the surrounding rock; During the construction stage, when there is actual measured water inflow data at the tunnel face, the value of K1 is determined by looking up the table according to the water discharge Q value;

[0043] For the value of K2: During the exploration and design stage, the assessment of the main weak structural planes is obtained through borehole exploration at the tunnel body location and the value of K2 is determined by combining with looking up the table; During the construction stage, through direct investigation and measurement, the value of K2 is determined according to the actual influence location and degree and by combining with looking up the table;

[0044] For the value of K3: The in-situ stress area is divided according to the in-situ stress measurement results, and the value of K3 is determined by looking up the table in combination with the basic quality index BQ value of the surrounding rock.

[0045] Further, step S5 specifically includes:

[0046] Obtain the surrounding rock grade division results for each section of the tunnel body based on the correction value of the basic quality index BQ of the surrounding rock, and review and correct the surrounding rock grade division results in combination with electrical characteristics, burial depth, and lithological characteristics.

[0047] According to a second aspect, in one embodiment, a system for classifying the levels of tunnel surrounding rock based on apparent resistivity is provided, and the system includes:

[0048] An apparent resistivity acquisition module, configured to detect and acquire the apparent resistivity values of the surrounding rock of each section of the tunnel body based on geophysical prospecting methods;

[0049] A rock mass integrity coefficient acquisition module, configured to calculate and acquire the rock mass integrity coefficients based on apparent resistivity of each section of the tunnel body according to the apparent resistivity values of the surrounding rock of each section of the tunnel body;

[0050] A basic quality index acquisition module of the surrounding rock, configured to calculate and acquire the BQ value of the basic quality index of the surrounding rock of each section of the tunnel body according to the rock mass integrity coefficients based on apparent resistivity of each section of the tunnel body;

[0051] A correction module for the basic quality index of the surrounding rock, configured to obtain the corrected value of the basic quality index BQ of the surrounding rock of each section of the tunnel body by combining the influences of groundwater, the occurrence of soft structural planes, and the initial in-situ stress state;

[0052] A surrounding rock level classification module, configured to classify the levels of the surrounding rock of each section of the tunnel body according to the corrected value of the basic quality index BQ of the surrounding rock of each section of the tunnel body.

[0053] This application provides a method and system for classifying the levels of tunnel surrounding rock based on apparent resistivity, which is particularly applicable to the classification of tunnel surrounding rock in a single stable stratum. Since resistivity can reflect the integrity of the rock mass and the development of fissure water in the underground bedrock, resistivity is sensitive to groundwater, and the degree of groundwater development is highly correlated with the integrity of the rock mass; therefore, the physical property parameter relationship between the apparent resistivity of the rock mass and the rock mass integrity coefficient can be used to further calculate the basic surrounding rock quality index of the segmented rock mass, so as to achieve the purpose of quickly classifying the surrounding rock. Compared with the prior art, the advantages and effects of the present invention are as follows:

[0054] (1) For deep and long tunnels, using the physical property parameter relationship between apparent resistivity and rock mass integrity coefficient, the classification of tunnel surrounding rock can be quickly carried out. Compared with existing exploration methods, the exploration efficiency is improved and the cost is saved.

[0055] (2) It solves the problem that there is no exploration data available for reference in long sections under complex terrain conditions, improves the quality of exploration and design, and ensures the exploration accuracy.

[0056] (3) Through the application of this method, the original means of classifying tunnel surrounding rock levels are expanded, filling the technical gaps in related fields. Description of the Drawings

[0057] Figure 1 It is a flowchart of a method for classifying the levels of tunnel surrounding rock based on apparent resistivity provided by an embodiment of the present invention;

[0058] Figure 2 Specific implementation flowchart of a method for classifying tunnel surrounding rock grades based on apparent resistivity provided by an embodiment of the present invention;

[0059] Figure 3 Longitudinal section contour map of apparent resistivity of magnetotelluric method and surrounding rock grade classification of a certain tunnel in a method for classifying tunnel surrounding rock grades based on apparent resistivity provided by an embodiment of the present invention;

[0060] Figure 4 Table of groundwater influence correction coefficient K1 in a method for classifying tunnel surrounding rock grades based on apparent resistivity provided by an embodiment of the present invention;

[0061] Figure 5 Table of main weak structural plane occurrence influence correction coefficient K2 in a method for classifying tunnel surrounding rock grades based on apparent resistivity provided by an embodiment of the present invention;

[0062] Figure 6 Table of initial in-situ stress state influence correction coefficient K3 in a method for classifying tunnel surrounding rock grades based on apparent resistivity provided by an embodiment of the present invention;

[0063] Figure 7 Schematic diagram of the logical structure of a system for classifying tunnel surrounding rock grades based on apparent resistivity provided by an embodiment of the present invention. Detailed implementation manners

[0064] The present invention will be further described in detail below in conjunction with the accompanying drawings through specific implementation manners. Similar elements in different implementation manners are labeled with related similar element numbers. In the following implementation manners, many detailed descriptions are provided to enable a better understanding of the present application. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other elements, materials, or methods. In some cases, some operations related to the present application are not shown or described in the specification to avoid overwhelming the core part of the present application with excessive descriptions. For those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations based on the description in the specification and the general technical knowledge in the art.

[0065] In addition, the features, operations, or characteristics described in the specification can be combined in any appropriate manner to form various implementation manners. At the same time, the steps or actions in the method description can also be reordered or adjusted in a manner obvious to those skilled in the art. Therefore, the various sequences in the specification and drawings are only for clearly describing a certain embodiment and do not mean a necessary sequence unless it is stated that a certain sequence must be followed.

[0066] A method for classifying the surrounding rock grade of a tunnel based on apparent resistivity provided by the first embodiment of the present invention. At present, engineering geophysical exploration runs through each exploration stage of tunnel engineering and plays an important role in each link of exploration. Geophysical exploration methods are important means to understand adverse geological conditions. Since electromagnetic exploration can provide all resistivity information of the tunnel, it is of great significance to classify the surrounding rock according to electrical characteristics. Classifying the surrounding rock of the tunnel through the results of electromagnetic methods expands the original classification means and improves work efficiency. Using resistivity characteristics to classify the rock mass of the tunnel body is a blank area in current domestic and foreign research. The following combines Figure 1 and Figure 2 for detailed description.

[0067] Classifying the surrounding rock of the tunnel through the results of electromagnetic methods in the present invention expands the original classification means and improves work efficiency. The invention includes the following contents: 1) Obtain the elastic longitudinal wave velocity of the rock mass at the tunnel body and the apparent resistivity of the tunnel section through borehole engineering logging equipment in the borehole, and at the same time obtain the elastic longitudinal wave velocity of the rock through indoor tests; 2) Calculate the rock mass integrity coefficient (Kv) at the tunnel body position of the borehole; 3) Through magnetotelluric exploration, obtain the apparent resistivity values of the surrounding rock of the entire tunnel longitudinal section, and extract the apparent resistivity values of each section of the surrounding rock at the tunnel body position respectively; 4) Propose two calculation methods related to the apparent resistivity value of geophysical exploration and the rock mass integrity coefficient; 5) Calculate the BQ value through the improved calculation formula of the basic quality index BQ of the surrounding rock; 6) Combine the groundwater, occurrence of weak structural planes, and initial in-situ stress state to correct the basic quality index of the surrounding rock, so as to classify the surrounding rock grade. The present invention classifies the rock mass of the tunnel body by using the relationship between resistivity characteristics and the rock mass integrity coefficient, expands the scope of surrounding rock classification of the tunnel, and improves work efficiency. Specifically as follows:

[0068] As Figure 1 shown, in step S1, obtain the apparent resistivity values of each section of the surrounding rock of the tunnel body based on geophysical exploration.

[0069] The above steps specifically include:

[0070] Step S11, obtain the apparent resistivity contour map of the entire tunnel longitudinal section based on geophysical exploration;

[0071] Step S12, according to the apparent resistivity contour map of the tunnel longitudinal section and combined with the electrical characteristics of the apparent resistivity, divide the surrounding rock sections of the tunnel body;

[0072] Step S13, based on geophysical exploration data and the tunnel body coordinate data, obtain the distribution range of the apparent resistivity value of each surrounding rock section, and take the average value of the apparent resistivity within the range as the apparent resistivity value ρ 视 .

[0073] In this embodiment, geophysical exploration lines are arranged along the tunnel axis to obtain the apparent resistivity values of the surrounding rock of the entire tunnel longitudinal section, and the apparent resistivity values of the surrounding rock of each section at the tunnel body position are extracted respectively.

[0074] Common geophysical exploration methods for tunnel engineering include high-density electrical method, magnetotelluric method, high-power direct current method, etc. The high-density electrical method has a better detection effect on tunnels with a burial depth of more than 100m; the magnetotelluric method has a better detection effect on tunnels with a deep burial depth of more than 100m, and its contour map of the apparent resistivity interpretation results is sensitive to water-rich strata and water-rich tectonic zones; the high-power direct current method has strong anti-environmental interference ability, and one of them can be selected according to the engineering geological conditions of the tunnel. The test results of these methods are generally mainly the apparent resistivity contour section diagram, and any method in the geophysical exploration methods can be selected according to the specific situation to obtain the resistivity map of the entire tunnel longitudinal section.

[0075] In this embodiment, the magnetotelluric method can be selected as the geophysical exploration method. The magnetotelluric method survey lines are arranged along the tunnel axis and data are collected. False anomalies caused by high-voltage electricity are excluded, and the terrain effect is considered. At the same time, inversion is carried out with the constraint of the apparent resistivity of borehole logging, and through indoor data processing and interpretation, the apparent resistivity values of the surrounding rock of the entire tunnel longitudinal section are obtained, and the apparent resistivity values of the surrounding rock of each section at the tunnel body position are extracted respectively.

[0076] The apparent resistivity values of the surrounding rock of each section are obtained through the following steps: First, the surrounding rock sections are divided according to the apparent resistivity contour map of the tunnel longitudinal section combined with the resistivity electrical characteristics; secondly, the magnetotelluric method data in the standard surfer format are obtained, and at the same time, the data file of the coordinates of the tunnel body is obtained. The above two data files are read into by MapGen software, and the distribution range of the apparent resistivity values of each surrounding rock section is calculated, and the representative apparent resistivity value of each surrounding rock section is taken as its apparent resistivity value.

[0077] In this embodiment, the division of the surrounding rock sections according to the apparent resistivity contour map of the tunnel longitudinal section combined with the resistivity electrical characteristics specifically means that: the electrical characteristics represent the difference in resistivity values or distribution patterns, and the geological characteristics represent the difference in lithological states. The two are consistent in reflecting the physical properties of the rock mass. Therefore, the surrounding rock sections can be divided in combination with the electrical characteristics: one is that the apparent resistivity contour lines are sparsely distributed and the electrical properties are stable, and the sections can be divided according to the size of the apparent resistivity values; the other is that according to the resistivity gradient change zone extending downward and the shape of the low-resistivity anomaly zone extending downward in the apparent resistivity section diagram, the fault zone can be identified.

[0078] Such as Figure 3As shown in the figure, the longitudinal section contour map of the tunnel apparent resistivity is obtained by the magnetotelluric method. First, the surrounding rock sections are divided according to the longitudinal section contour map of the tunnel apparent resistivity in combination with the resistivity electrical characteristics, and then the apparent resistivity corresponding to each section of the tunnel body is extracted. The representative value of the apparent resistivity corresponding to each section of the surrounding rock is taken, that is, the average value of the apparent resistivity of this section is taken. The division of the surrounding rock sections and the value-taking of the apparent resistivity are as follows: The first section: K0-K100. In the tunnel entrance section, due to the shallow burial depth and poor surrounding rock, and combined with the apparent resistivity value and distribution form, the representative resistivity value is taken as 2000 Ω·m, and the form fluctuation is stable; The second section: K100-K350. The distribution of the apparent resistivity contour lines in this section is dense, and it is initially judged as the position where the Quaternary system meets the bedrock. The representative resistivity value is taken as 2000 Ω·m; The third section: K350-K1500, which is a high-resistance section, and the representative resistivity value is taken as 7000 Ω·m; The fourth section: K1500-K2150, which is a medium-resistance section, and both sides are high-resistance. Therefore, the representative resistivity value of the medium-resistance section sandwiched in the middle is taken as 3800 Ω·m; The fifth section: K2150-K2850, which is a high-resistance section, and the representative resistivity value is taken as 6000 Ω·m; The sixth section: K2850-K3180. According to the resistivity gradient change zone extending downward and the form of the low-resistance anomaly zone extending downward in the apparent resistivity section diagram, the fault zone can be identified and generally directly divided into Class V surrounding rock; The seventh section: The contour line form fluctuates smoothly, which is a medium-resistance section, and the representative resistivity value is taken as 3700 Ω·m.

[0079] As Figure 1 shown, in step S2, based on the apparent resistivity values of the surrounding rocks of each section of the tunnel body, the rock mass integrity coefficient of each section of the tunnel body based on the apparent resistivity is calculated and obtained.

[0080] The rock mass integrity coefficient of a certain surrounding rock section of the tunnel body based on the apparent resistivity is represented by λ or K r denoted.

[0081] The calculation formula of λ is as follows:

[0082] λ = ρ 视 / ρ 完整

[0083] ρ 视 represents the apparent resistivity value of a certain surrounding rock section of the tunnel body;

[0084] ρ 完整 represents the apparent resistivity value of the tunnel rock mass in a relatively intact state.

[0085] Among them, the acquisition method of ρ 完整 is as follows:

[0086] (1) First, through the borehole engineering logging equipment in the borehole, the longitudinal wave velocity V pm of the rock mass at the tunnel location and the apparent resistivity ρ of the tunnel section are obtained0 Meanwhile, obtain the longitudinal elastic wave velocity V of the rock through laboratory tests pr .

[0087] Specifically, it includes:

[0088] a. Select the intelligent engineering logging system commonly used in engineering surveys, including an intelligent engineering logging acquisition recorder, a borehole acoustic logging probe, and a resistivity probe.

[0089] b. The borehole acoustic detection technology is advanced and easy to operate. Through the borehole acoustic logging probe, that is, by lowering the acoustic detection probe into the borehole, obtain the longitudinal elastic wave velocity V of the rock mass at the tunnel cavity at intervals of 0.2 - 1.0 m per point pm ; obtain the apparent resistivity ρ of the tunnel section through the resistivity probe 0 .

[0090] c. Meanwhile, obtain the longitudinal elastic wave velocity of the rock through laboratory tests. Specifically, take standard rock blocks from the tunnel section in the borehole, with dimensions: diameter about 50 mm, height about 100 - 125 mm, and no obvious structural planes, and use a non-metallic acoustic tester to measure the longitudinal wave velocity V of the rock blocks pr .

[0091] (2) Secondly, according to the "Standard for Classification of Engineering Rock Masses" (GB / T 50218 - 2014), calculate the rock mass integrity coefficient Kv at the tunnel cavity of the borehole location. The formula is as follows:

[0092] Kv = (V pm / V pr ) 2

[0093] (3) Finally, using the principle of positive correlation between the geophysical exploration resistivity value and the rock mass integrity, calculate ρ 0 and Kv to obtain ρ 0 / Kv, which is the apparent resistivity value of the rock mass when the Kv value is approximately 1, representing the apparent resistivity value ρ of the tunnel rock mass in a relatively intact state 完整 .

[0094] The principle of positive correlation between the geophysical exploration resistivity value and the rock mass integrity and groundwater development is as follows:

[0095] The resistivity of rock is stable within a certain range. Changes occur due to fracturing or water content. That is, the greater the apparent resistivity of the rock mass, the better the integrity of the rock mass; the smaller the apparent resistivity of the rock mass, the worse the integrity of the rock mass. At the same time, the degree of groundwater development is closely related to the integrity of the rock mass. Only when the rock mass is fractured, groundwater may be relatively developed; when the rock mass is intact, groundwater is not developed. Therefore, conservatively considering, that is, the greater the apparent resistivity of the rock mass, the better the integrity of the rock mass and the less developed the bedrock fissure water; the smaller the apparent resistivity of the rock mass, the worse the integrity of the corresponding rock mass and the more developed the groundwater. Thus, the apparent resistivity can reflect the integrity of the rock mass and the development of groundwater.

[0096] For example, in a certain mountain tunnel research area, the lithology is single hard gneiss, mainly bluish-gray, with a metamorphic texture and a gneissic structure. The main components are quartz, feldspar, mica, etc. The tunnel is about 3.5 km long, with an average buried depth of about 300 m and a maximum buried depth of about 500 m. During the exploration period, 1 deep hole of 550 m was completed at the tunnel body. The tunnel body is located at 500 m. The recommended value of the elastic longitudinal wave velocity of the rock mass measured at the tunnel body is V pm = 3600 m / s, and the apparent resistivity ρ 0 of the tunnel section is 3700 Ω·m. At the same time, the elastic longitudinal wave velocity V pr of the rock is obtained through laboratory tests = 5600. According to the formula, the rock mass integrity coefficient Kv = 0.413 at the tunnel body position of the borehole is calculated. Based on the measured apparent resistivity ρ0 = 3700 Ω·m of the tunnel section and the calculated rock mass integrity coefficient Kv = 0.413 at the tunnel body position of the borehole. From the apparent resistivity value ρ 0 / Kv of the tunnel body at the borehole position, the apparent resistivity value of the rock mass when the Kv value is approximately 1 can be obtained, that is, the apparent resistivity ρ 完整 = 9000 Ω·m representing relatively intact rock mass. In addition, by dividing the apparent resistivity of the surrounding rock of each section of the tunnel body by the apparent resistivity of the relatively intact rock mass, the rock mass integrity coefficient λ based on resistivity for each section of the tunnel body can be obtained.

[0097] It should be noted that in this embodiment, the rock mass integrity coefficient (Kv) at the tunnel body position of the borehole can also be obtained by using methods such as joint statistics to obtain the volume structure plane density, number of groups, structural plane dip angle, aperture, filling, etc. of the rock mass at the tunnel body of the borehole through borehole televiewer images.

[0098] In this embodiment, the rock mass integrity coefficient based on apparent resistivity for a certain surrounding rock section of the tunnel body can also be represented by K r for short.

[0099] According to the correlation analysis between rock mass integrity and resistivity, the relationship between the rock mass integrity coefficient and apparent resistivity can be further deduced. Assume that the rock mass is composed of alternating layers of intact rock and fractured rock, where the resistivity of the intact rock is ρ r , and the thickness is Δh1 , the resistivity of the fractured layer is ρ w , and the thickness is Δh 2 , then the proportion Kr of the intact rock in the rock mass per unit volume is:

[0100] Kr = Δh 1 / (Δh 1 + Δh 2 )

[0101] Through formula derivation and calculation, it is obtained that:

[0102] Kr = ρ r (ρ 视 - ρ w ) 2 / [ρ r (ρ 视 2 - ρ w 2 ) + ρ w (ρ r 2 - ρ 视 2 )]

[0103] ρ 视 represents the apparent resistivity value of a certain surrounding rock section of the tunnel body; ρ r is the resistivity of the intact rock, obtained through indoor resistivity tests of intact rocks; ρ w represents the apparent resistivity value of the fractured rock layer in the rock mass, generally taking 1 / 10 of the value of the resistivity ρ r of the intact rock.

[0104] As Figure 1 shown, in step S3, based on the coefficient of rock mass integrity based on apparent resistivity for each section of the tunnel body, the basic quality index BQ value of the surrounding rock for each section of the tunnel body is calculated and obtained.

[0105] Combining with the specification of "Standard for Classification of Engineering Rock Masses" (GB / T 50218—2014), the calculation formula for the basic quality index BQ value of the surrounding rock for each section of the tunnel body is as follows:

[0106] BQ = 100 + 3Rc + 250 * Kv′

[0107] Among them, Rc is the saturated uniaxial compressive strength of the rock; Kv′ is the coefficient of rock mass integrity based on apparent resistivity for a certain surrounding rock section of the tunnel body, and Kv′ is represented by λ or K obtained from the previous calculation. r It is expressed.

[0108] The saturated uniaxial compressive strength Rc of the rock in the cave can be obtained through laboratory tests on drill core samples or intact unweathered rock blocks taken from the ground surface during the survey and design stage; during the construction stage, it can be quickly obtained on the tunnel face through point load tests. To ensure the accuracy of the measured uniaxial compressive strength of the rock, test result data with an absolute deviation rate greater than 30% will not be statistically analyzed. Deviation rate = (test value - average value) / average value.

[0109] As Figure 1 shown, in step S4, considering the influence of groundwater, the occurrence of weak structural planes, and the initial in-situ stress state, the corrected value of the basic quality index BQ of the surrounding rock for each section of the tunnel is obtained.

[0110] In this embodiment, the calculation formula for the corrected value of the basic quality index BQ of the surrounding rock for each section of the tunnel is as follows:

[0111] [BQ] = BQ - 100 * (K1 + K2 + K3)

[0112] where K1 is the correction coefficient for the influence of groundwater, K2 is the correction coefficient for the influence of the occurrence of weak structural planes, and K3 is the correction coefficient for the influence of the initial in-situ stress state.

[0113] (1) For the value of K1: The correction coefficient K1 for the influence of groundwater is closely related to the apparent resistivity value; during the survey stage, at the drilling location, the groundwater discharge state is obtained by combining pumping tests, and the value of K1 is determined by looking up the table according to the groundwater discharge state. For the remaining sections, the value is calculated using the proportional relationship between the adjustment coefficients of the surrounding rock in each section and the measured target section. During the construction stage, when there is actual measured water inflow data at the tunnel face, the value of K1 is obtained by looking up the table according to the water discharge Q value.

[0114] Specifically, during the survey stage, at the drilling location, first obtain the permeability coefficient of the rock mass in the cave through the drilling pumping test, calculate the water discharge Q (L / min.m) for a 10m tunnel length section using the groundwater dynamics method, and determine the value of K1 by referring to the table in the specification ( Figure 4 ); for the remaining sections, the value is determined using the proportional relationship between the adjustment coefficients of the surrounding rock in each section and the measured target section, and the corrected coefficient K λ1 for the influence of groundwater on the surrounding rock in each section is obtained as follows:

[0115] K λ1 = K1 * (ρ 视 / ρ 0 )

[0116] In the above formula, K1 is the value obtained from the pumping test at the drilling location, ρ 0 is the apparent resistivity value measured in the drill hole at the cave location, and ρ 视 is the apparent resistivity to be calculated for each section of the surrounding rock.

[0117] (2) For the value of K2: During the survey and design stage, the assessment of the main weak structural planes is obtained through borehole detection at the tunnel body location and the value of K2 is determined by referring to the table; during the construction stage, through direct investigation and measurement, the value of K2 is determined according to the actual affected location and degree and by referring to the table.

[0118] Specifically, during the survey and design stage, the assessment of the main weak structural planes can be obtained through means such as borehole imaging at the tunnel body location to determine the correction coefficient K2, as follows: According to methods such as borehole ultrasonic imaging, borehole television, and three-dimensional laser scanning, data such as the dip and dip angle of multiple groups of structural planes at the borehole of the tunnel body can be obtained. Then, by drawing a rose diagram of the joint occurrence of the rock mass, the dip and dip angle of the dominant structural plane at the borehole of the tunnel body (i.e., the main structural plane) can be determined. Then, in combination with the tunnel axis trend, the included angle between the two trends is calculated. Combining the included angle size and the dip angle of the main structural plane, and then referring to the table ( Figure 5 ) to obtain the value of K2.

[0119] During the construction stage, the correction coefficient can be determined through direct investigation and measurement according to the actual affected location and degree. Specifically as follows: According to the specification, the value of K2 is given in combination with the included angle between the main weak structural plane and the tunnel axis and the dip angle of the structural plane. During the construction stage, for the exposed face of the excavated bedrock, first use a compass to measure the strike and dip angle of the main structural plane on site, and secondly measure the tunnel axis trend direction, calculate the included angle between the two trends, combine the included angle size and the dip angle of the main structural plane, and then refer to the table ( Figure 5 ) to obtain the value of K2.

[0120] The main structural plane mentioned above can also be the bedding plane of the rock stratum. When there is only one main structural plane, it has little impact on the stability of the surrounding rock. When there are multiple main structural planes combined with multiple general structural planes, especially when it appears in the arch part, the surrounding rock is extremely likely to become unstable, and at this time, the value of K2 should be larger.

[0121] (3) For the value of K3: Divide the in-situ stress area according to the in-situ stress measurement results, and in combination with the basic quality index BQ value of the surrounding rock, determine the value of K3 by referring to the table ( Figure 6 )

[0122] As Figure 1 shown, in step S5, according to the corrected value of the basic quality index BQ of each section of the tunnel body, the surrounding rock grade of each section of the tunnel body is divided.

[0123] The above steps specifically include: obtaining the surrounding rock grade division results of each section of the tunnel body according to the corrected value of the basic quality index BQ of each section, and rechecking and correcting the surrounding rock grade division results in combination with electrical characteristics, buried depth, and lithological characteristics.

[0124] In this embodiment, the basic quality index BQ of the surrounding rock calculated based on the rock mass integrity coefficient λ of resistivity for each section of the tunnel body and the corrected index [BQ] are shown in the following table. Thus, the surrounding rock grade of each section can be divided by combining the corrected index [BQ] in the "Standard for Classification of Engineering Rock Masses" (GB / T 50218—2014).

[0125]

[0126] In the above calculations:

[0127] (1) The groundwater correction coefficient K1 is taken as described in S4:

[0128] During the exploration stage: For the other sections, using the proportional relationship between the surrounding rock of each section and the adjustment coefficient of the measured target section, the adjusted groundwater influence correction coefficient K for each section of the surrounding rock is obtained λ1 , K λ1 is used to calculate [BQ] instead of K1. During the exploration and design stage, since it is difficult to measure the groundwater pressure and the unit water yield accurately or the measurement accuracy is low, the groundwater influence correction coefficient is often determined by the experience of engineering technicians, which is highly subjective and belongs to qualitative analysis.

[0129] During the construction stage: During the construction stage, the water yield Q can be directly measured at the tunnel face, and K1 can be directly corresponding to the value, so as to refine the classification of the surrounding rock of each section.

[0130] (2) The influence correction coefficient K2 of the occurrence of weak structural planes. Since the influence degree cannot be determined because the tunnel has not been excavated, a unified value of 0.2 is taken.

[0131] (3) The influence correction coefficient K3 of the initial in-situ stress state. According to the borehole in-situ stress test, there is no high to extremely high in-situ stress, so the value is taken as 0.

[0132] After dividing the surrounding rock grade according to the above method, it is also necessary to review the surrounding rock level in combination with electrical characteristics, burial depth, etc. Therefore, for the faults within the same set of strata, they show a downward-extending low-resistance zone in terms of electricity, such as Figure 3 The section A-A1 in is determined as a fault fracture zone by combining electrical characteristics, so it is directly classified as grade V surrounding rock; in addition, the burial depth of the section K0-K100 is relatively shallow, the rock mass is broken, and the resistivity is low. This section is also classified as grade V surrounding rock according to characteristics such as burial depth and lithology.

[0133] In addition, according to the correlation analysis between rock mass integrity and resistivity, the apparent resistivity can also be introduced into the classification of surrounding rock grades according to the relationship between the rock mass integrity coefficient and the apparent resistivity in S2. This is not elaborated in this embodiment.

[0134] The present invention innovatively introduces the physical property parameter relationship between the apparent resistivity of tunnel rock mass and the rock mass integrity coefficient into the field of tunnel surrounding rock classification. Since the resistivity of rock is stable within a certain range and changes occur due to fragmentation or water content, electromagnetic exploration can provide all resistivity information of the tunnel. Therefore, the classification of tunnel surrounding rock can be realized through electrical characteristics, which is of great significance and fills the technical gap in related fields.

[0135] Corresponding to the above-disclosed method for classifying the level of tunnel surrounding rock based on apparent resistivity, the embodiment of the present invention also discloses a system for classifying the level of tunnel surrounding rock based on apparent resistivity, as Figure 7 shown, which specifically includes:

[0136] An apparent resistivity acquisition module, configured to detect and acquire the apparent resistivity values of the surrounding rock of each section of the tunnel body based on geophysical exploration methods;

[0137] A rock mass integrity coefficient acquisition module, configured to calculate and acquire the rock mass integrity coefficient based on apparent resistivity of each section of the tunnel body based on the apparent resistivity values of the surrounding rock of each section of the tunnel body;

[0138] A basic quality index acquisition module of the surrounding rock, configured to calculate and acquire the BQ value of the basic quality index of the surrounding rock of each section of the tunnel body based on the rock mass integrity coefficient based on apparent resistivity of each section of the tunnel body;

[0139] A correction module for the basic quality index of the surrounding rock, configured to obtain the corrected value of the BQ of the basic quality index of the surrounding rock of each section of the tunnel body by combining the influences of groundwater, the occurrence of soft structural planes, and the initial in-situ stress state;

[0140] A surrounding rock level classification module, configured to classify the surrounding rock levels of each section of the tunnel body according to the corrected value of the BQ of the basic quality index of the surrounding rock of each section of the tunnel body.

[0141] It should be noted that the detailed description of the system for classifying the level of tunnel surrounding rock based on apparent resistivity provided in the embodiment of the present invention can refer to the related description of the method for classifying the level of tunnel surrounding rock based on apparent resistivity provided in the embodiment of the present application, which will not be elaborated here.

[0142] Those skilled in the art can understand that all or part of the functions of the various methods in the above embodiments can be implemented in a hardware manner or in a computer program manner. When all or part of the functions in the above embodiments are implemented in a computer program manner, the program can be stored in a computer-readable storage medium, and the storage medium can include: read-only memory, random access memory, magnetic disk, optical disk, hard disk, etc. The above functions can be realized by a computer executing the program. For example, the program is stored in the memory of the device, and when the processor executes the program in the memory, the above all or part of the functions can be realized. In addition, when all or part of the functions in the above embodiments are implemented in a computer program manner, the program can also be stored in a storage medium such as a server, another computer, magnetic disk, optical disk, flash drive or mobile hard disk, and saved to the memory of the local device by downloading or copying, or the system of the local device is updated. When the processor executes the program in the memory, all or part of the functions in the above embodiments can be realized.

[0143] The above uses specific examples to elaborate on the present invention, which is only used to help understand the present invention and is not intended to limit the present invention. For those skilled in the art of the present invention, according to the idea of the present invention, several simple deductions, deformations or substitutions can also be made.

Claims

1. A tunnel surrounding rock classification method based on apparent resistivity, characterized in that: The method comprises: Step S1, obtaining the apparent resistivity value of the surrounding rock of each section of the tunnel body based on geophysical exploration; Step S2, based on the apparent resistivity value of the surrounding rock of each section of the tunnel body, calculate and obtain the rock mass integrity coefficient based on the apparent resistivity of each section of the tunnel body; Step S3, based on the rock integrity coefficient of the apparent resistivity of each section of the tunnel body, calculate and obtain the basic quality index BQ value of the surrounding rock of each section of the tunnel body; Step S4, combining the influence of groundwater, the occurrence of weak structural surface and the initial ground stress state, obtaining the correction value of the basic quality index BQ of the surrounding rock of each section of the tunnel body; Step S5, classifying the surrounding rock grades of each section of the tunnel body according to the revised value of the basic quality index BQ of the surrounding rock of each section of the tunnel body.

2. A tunnel surrounding rock classification method based on apparent resistivity as claimed in claim 1, characterized in that: The step S1 specifically includes: Step S11, obtaining an apparent resistivity contour map of the entire tunnel longitudinal section based on a geophysical prospecting method; Step S12, dividing the tunnel body into surrounding rock sections according to the apparent resistivity contour map of the tunnel longitudinal section and in combination with the electrical characteristics of the apparent resistivity; Step S13: Based on the geophysical data and the tunnel coordinate data, the apparent resistivity value distribution range of each surrounding rock section is obtained, and the average apparent resistivity value within the range is taken as the apparent resistivity value ρ of each surrounding rock section. 视 .

3. The method for classifying tunnel surrounding rock based on apparent resistivity according to claim 1, characterized in that: The step S2 specifically includes: The rock mass integrity factor based on apparent resistivity of a surrounding rock section of the tunnel body is expressed by λ, and the calculation formula of λ is as follows: λ=ρ 视 / r 完整 ρ 视 Represents the apparent resistivity value of a surrounding rock section in the tunnel body; ρ 完整 Represents the apparent resistivity value of the tunnel rock mass in a relatively intact state.

4. A tunnel surrounding rock classification method based on apparent resistivity as claimed in claim 3, characterized in that: The step S2 specifically includes: ρ 完整 The method to obtain is: First, the elastic longitudinal wave velocity V of the rock mass in the tunnel body is obtained by the in-hole engineering logging equipment. pm and the apparent resistivity ρ0 of the tunnel body. At the same time, the rock elastic longitudinal wave velocity V is obtained through indoor tests. pr ; Secondly, calculate the rock mass integrity coefficient Kv at the hole body of the drilling position, the formula is as follows: Kv=(V pm / V pr ) 2 Finally, ρ0 / Kv is calculated, and the value obtained is the apparent resistivity value of the rock mass when the Kv value is approximately 1, which represents the apparent resistivity value ρ of the tunnel rock mass in a relatively intact state. 完整 .

5. The method for classifying tunnel surrounding rock based on apparent resistivity according to claim 1, characterized in that: The step S2 specifically includes: The rock mass integrity factor based on apparent resistivity of a surrounding rock section of the tunnel body can also be expressed as K r calculate; Assume that the rock mass is composed of intact rock and broken rock, where the resistivity of the intact rock is ρ r , thickness is Δh1, and the resistivity of the broken layer is ρ w , the thickness is Δh2, then the proportion of intact rock in the unit volume of rock mass is Kr: Kr=Δh1 / (Δh1+Δh2) Through formula derivation and calculation, we get: Kr=ρ r (r 视 -r w ) 2 / [p r (r 视 2 -r w 2 )+r w (r r 2 -r 视 2 )] ρ 视 Represents the apparent resistivity value of a surrounding rock section in the tunnel body; ρ r is the complete rock resistivity, obtained through indoor rock resistivity testing; ρ w Represents the apparent resistivity value of broken rock layers in the rock mass.

6. The method for classifying tunnel surrounding rock based on apparent resistivity according to claim 1, characterized in that: The step S3 specifically includes: The calculation formula of the basic quality index BQ value of the surrounding rock of each section of the tunnel body is as follows: BQ=100+3Rc+250*Kv′ Where Rc is the saturated compressive strength of rock; Kv′ is the rock integrity coefficient based on apparent resistivity of a surrounding rock section of the tunnel body, where Kv′ can be λ or Kr.

7. The method for classifying tunnel surrounding rock based on apparent resistivity according to claim 1, characterized in that: The step S4 specifically includes: The calculation formula for the correction value of the basic quality index BQ of the surrounding rock of each section of the tunnel body is as follows: [BQ] = BQ - 100 * (K1 + K2 + K3) Among them, K1 is the correction coefficient for groundwater impact, K2 is the correction coefficient for the impact of the weak structural surface attitude, and K3 is the correction coefficient for the impact of the initial geostress state.

8. The method for classifying tunnel surrounding rock based on apparent resistivity according to claim 7, characterized in that: The step S4 specifically includes: Regarding the value of K1: in the survey stage, the groundwater discharge status is obtained at the drilling location in combination with the pumping test, and the K1 value is determined by looking up the table according to the groundwater discharge status. For the remaining sections, the value is calculated by using the proportional relationship between the size of the surrounding rock of each section and the measured target section surrounding rock adjustment coefficient; in the construction stage, when there is measured water inflow data on the face, the K1 value is obtained by looking up the table according to the water output Q value; Regarding the value of K2: During the survey and design stage, the assessment of the main weak structural surface is obtained through drilling detection at the tunnel body position, and the K2 value is determined by looking up the table; during the construction stage, the K2 value is determined by direct investigation and measurement according to the actual impact position and degree and combined with table lookup; Regarding the value of K3: the ground stress zone is divided according to the ground stress measurement results, and the value of K3 is determined by looking up the table in combination with the basic quality index BQ value of the surrounding rock.

9. The method for classifying tunnel surrounding rock based on apparent resistivity according to claim 1, characterized in that: The step S5 specifically includes: The surrounding rock grade classification results of each section of the tunnel body are obtained based on the corrected value of the basic surrounding rock quality index BQ of each section, and the surrounding rock grade classification results are reviewed and corrected in combination with the electrical characteristics, burial depth and lithological characteristics.

10. A tunnel surrounding rock classification system based on apparent resistivity, characterized in that: The system comprises: The apparent resistivity acquisition module is used to obtain the apparent resistivity value of the surrounding rock of each section of the tunnel body based on geophysical detection; The rock mass integrity coefficient acquisition module is used to calculate and obtain the rock mass integrity coefficient of each section of the tunnel body based on the apparent resistivity value of the surrounding rock of each section of the tunnel body; The basic quality index acquisition module of surrounding rock is used to calculate and obtain the basic quality index BQ value of surrounding rock of each section of the tunnel body based on the rock integrity coefficient of each section of the tunnel body based on the apparent resistivity; The basic quality index correction module of surrounding rock is used to obtain the correction value of the basic quality index BQ of surrounding rock of each section of the tunnel body by combining the influence of groundwater, the occurrence of weak structural surface and the initial ground stress state; The surrounding rock grade classification module is used to classify the surrounding rock grades of each section of the tunnel body according to the modified value of the basic quality index BQ of the surrounding rock of each section of the tunnel body.

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