Surrounding rock grading method considering influence of engineering disturbance

Abstract

The invention discloses a surrounding rock grading method considering engineering disturbance influence, which belongs to the technical field of surrounding rock grading and comprises the following steps: constructing a disturbance reduction coefficient expression; sound wave test data in the engineering construction process are collected and analyzed, and key factors influencing the disturbance reduction coefficient are determined; based on the disturbance reduction coefficient expression, determining a disturbance reduction coefficient value table under different key factors; and looking up the table to determine the disturbance reduction coefficient value under the current project, and substituting the disturbance reduction coefficient value into the surrounding rock quality evaluation expression to determine the surrounding rock grade. The surrounding rock grading correction method considering the engineering disturbance influence is feasible, the grading problem that a classic BQ method is not incorporated into the engineering disturbance influence is solved, and effective guidance is provided for tunnel construction.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of surrounding rock classification, and particularly relates to a surrounding rock classification method considering the influence of engineering disturbance. BACKGROUND

[0002] The complex geological evolution history leads to large differences in the geological environment conditions of the railway corridor, and the hydrogeological, engineering geological and environmental geological problems are complex and changeable. Engineering construction activities such as excavation change the stress field of the in-situ rock mass originally in a balanced state, and when the stress borne by the rock mass exceeds its strength, the rock mass will be broken and may cause surrounding rock instability, resulting in engineering disasters such as rock burst and collapse. The rock mass of the major project tunnel is located in a deep and complex geological environment, and the degradation effect of the surrounding rock mass under the influence of excavation disturbance will be more significant. Therefore, in order to ensure the safety and efficiency of engineering construction activities, not only the survey and design work needs to be done well, but also the damage characteristics of the surrounding rock under the influence of engineering excavation disturbance and the degradation of the surrounding rock quality by excavation disturbance need to be considered.

[0003] However, most of the existing and current surrounding rock quality classification methods at home and abroad belong to the surrounding rock stability classification method, which is established by scholars collecting engineering data at that time and summarizing experience. In the process of experience summary, people gradually realized the influence of various factors such as groundwater and ground stress on the stability of surrounding rock, so the evaluation indexes and methods used are gradually enriched. Even so, the commonly used surrounding rock classification methods such as BQ method, HC method, Q system and RMR method still mainly consider the natural factors affecting the quality of rock mass, and less directly consider the engineering disturbance factors affecting the stability of surrounding rock.

[0004] With the increase of engineering construction, the condition of rock mass is complex and changeable, and people gradually deepen the cognition of the influencing factors and mechanism of surrounding rock quality evaluation. Due to the limitation of evaluation index, the original widely used method is not applicable in some engineering construction, so many scholars modify the original surrounding rock classification method based on the engineering practice. The modification is mainly to modify some parameters or add new parameters according to the specific application scene. For example, for RMR method, the ratio of rock compressive strength to maximum horizontal principal stress is taken as the ground stress correction parameter. For Q system, the corresponding relationship between ground stress value and rock burst intensity under high ground stress condition is analyzed based on the rock burst section of deep tunnel engineering of hydropower station, and the ground stress influence reduction value of surrounding rock classification of rock burst section is corrected accordingly. For BQ method, the initial ground stress influence correction coefficient K3 is modified and improved, and BQ-hg surrounding rock classification method under high ground stress condition is put forward. In addition, the influence of ground temperature is not considered in the commonly used surrounding rock classification method, but with more and more engineering construction in extreme environment, some scholars have also begun to explore the surrounding rock classification method considering high ground temperature. Based on the deterioration effect of high ground temperature on the strength of super deep shaft rock, the ground temperature correction coefficient is used to modify the national standard BQ method; based on the measured temperature field and temperature gradient of surrounding rock, the double index is used to divide the classification level of the classification factor, and the HC surrounding rock quality evaluation scheme under high ground temperature condition is corrected according to the different correction values.

[0005] In addition to the influence of complex geological environment, different excavation methods will lead to the difference of stability of surrounding rock after excavation, so some scholars think that the influence of engineering disturbance should be considered in the surrounding rock classification scheme. For example, by comparing the difference of RMR value of surrounding rock under drill and blast method and TBM method, the excavation disturbance influence coefficient of RMR system is put forward; according to the engineering experience, the engineering disturbance correction index value of mining rock mass is put forward to modify the RMR classification method; for the situation after excavation, the evaluation index of Q system after excavation should be used for evaluation, and the Q system score value of rock mass after disturbance is evaluated combined with the acoustic characteristics before and after excavation; for BQ system, some scholars think that the rock strength and rock integrity coefficient after blasting should be measured and evaluated when the rock mass quality is evaluated after blasting disturbance; the rock mass integrity coefficient correction index is established based on the relationship between the disturbance factor of H-B criterion and the acoustic wave attenuation rate to reflect the possible influence of engineering disturbance.

[0006] In the above existing methods, it is found that excavation disturbance often leads to the decrease of rock mass integrity, and the evaluation index of rock mass integrity is included in the classification index of RMR method, Q system, HC method and BQ method, so when the influence of engineering excavation disturbance is considered in the evaluation of surrounding rock grade, the influence of excavation disturbance on rock mass integrity can be considered, so that the evaluation result of surrounding rock grade in construction stage is better, which is in line with the actual situation. SUMMARY

[0007] In view of the above problems in the prior art, the method for surrounding rock classification considering the influence of engineering disturbance provided by the present application solves the problem that the traditional surrounding rock quality evaluation method does not consider the disturbance factor, thereby affecting the accuracy of the surrounding rock grade evaluation result.

[0008] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: a method for surrounding rock classification considering the influence of engineering disturbance, comprising the following steps: S100, constructing a disturbance reduction coefficient expression; S200, collecting and analyzing the acoustic test data in the engineering construction process to determine the key factors affecting the disturbance reduction coefficient; S300, determining the disturbance reduction coefficient value table under different key factors based on the disturbance reduction coefficient expression; S400, determining the disturbance reduction coefficient value under the current engineering by table lookup, and substituting it into the surrounding rock quality evaluation expression to determine the surrounding rock grade.

[0009] Further, in the step S100, the disturbance reduction coefficient expression is: In the formula, denotes the disturbance reduction coefficient, denotes the longitudinal wave velocity of the disturbed rock mass, denotes the integrity coefficient of the undisturbed rock mass, denotes the acoustic velocity of the disturbed rock mass, denotes the acoustic velocity of the undisturbed rock mass, and pr denotes the longitudinal wave velocity of the rock.

[0010] Further, the method for determining the acoustic velocities of the rock mass before and after disturbance is as follows: / The method is as follows: Construct a rock mass acoustic velocity curve with the drilling depth as the horizontal coordinate and the acoustic velocity as the vertical coordinate; In the rock mass acoustic velocity curve, determine the area of the part enclosed by the acoustic velocity curve of the damage deterioration zone and the horizontal coordinate axis; Take the ratio of the area to the depth of the damage deterioration zone as the acoustic velocity of the disturbed rock mass ; Take the average value of the acoustic velocity corresponding to the depth of the smooth section of the acoustic velocity curve as the acoustic velocity of the undisturbed rock mass .

[0011] Further, the step S200 comprises the following sub-steps: S201, collecting the acoustic test data in the engineering detection process; S202, determine the factors affecting the damage degree of rock mass, including excavation disturbance mode, construction method, rock mass basic quality index based on acoustic velocity, span of cavern and height of cavern; S203, based on the acoustic wave test data under different factors, multiple linear regression is carried out; S204, based on the multiple linear regression result, the key factors affecting the disturbance reduction coefficient are determined, including the excavation disturbance mode and the rock mass basic quality index; the excavation disturbance mode includes tunneling excavation, controlled blasting excavation and ordinary blasting excavation.

[0012] Further, for the determined key factors: Under the same excavation disturbance mode, in the process of reducing the rock mass basic quality index, the disturbance reduction coefficient first increases and then decreases; Under the same rock mass basic quality index, the disturbance reduction coefficients corresponding to tunneling excavation and controlled blasting excavation are greater than the disturbance reduction coefficient corresponding to ordinary blasting excavation.

[0013] Further, in the step S400, the surrounding rock quality evaluation expression is: In the formula, surrounding rock quality evaluation value considering the influence of engineering disturbance, m represents the disturbance reduction coefficient, uniaxial saturated compressive strength, undisturbed rock mass integrity coefficient, , and respectively represent the groundwater influence correction coefficient, the soft structure plane occurrence influence correction coefficient and the initial stress state influence correction coefficient.

[0014] The beneficial effects of the present application are: (1) The disturbance reduction coefficient is innovatively introduced in the present application, which supplements the applicability deficiency of the national standard BQ method under the condition of engineering disturbance: The traditional BQ method fails to reflect the influence of disturbance such as blasting and excavation on the integrity of rock mass. Through theoretical derivation and a large amount of field test data (including acoustic wave, geological radar, borehole peeping, etc.), the present application establishes a quantitative relationship between the disturbance reduction coefficient m and factors such as rock mass integrity, excavation mode and surrounding rock quality grade, and can realize scientific correction of the integrity of rock mass after disturbance. The improvement significantly improves the practicability and accuracy of the BQ method in the process of tunnel excavation, and fills the gap that the current classification system does not consider the influence of engineering disturbance.

[0015] (2) The present application proposes a rock mass integrity correction idea based on acoustic wave test, which realizes quantifiable expression of disturbance influence: The application takes acoustic wave longitudinal wave velocity as a core parameter, establishes a mapping relationship between the acoustic velocity difference before and after disturbance and the damage degree of the rock mass, and deduces a disturbance reduction coefficient m; The acoustic wave data has the advantages of non-destructiveness, real-time and continuity, and can dynamically reflect the change of the rock mass structure, and the disturbance reduction coefficient m can effectively quantify the influence of different excavation methods (such as TBM tunneling and controlled blasting) on the rock mass through a large number of actual tunnel cases, thereby providing a scientific basis for tunnel design and support parameter optimization.

[0016] (3) The application constructs a complete evaluation system of "acoustic wave data-disturbance reduction coefficient-modified BQ value", and the evaluation result is more in line with the actual situation: The grading evaluation formula established in the application realizes the unified quantification of the disturbance influence and the original parameters of the rock mass. Through the verification of actual engineering, the results show that: the coincidence rate of the grading results after modification and the actual surrounding rock grading is increased by 10%~30%; the effect is particularly significant for class III and IV surrounding rock, which significantly reduces the overestimation of good quality surrounding rock by the original BQ method. Therefore, the method can more accurately reflect the real stability of the surrounding rock in engineering application, and improve the design safety and economy.

[0017] (4) The application discloses the disturbance effect law under different surrounding rock quality, and provides scientific guidance for tunnel design and construction control: Based on the method of the application, the worse the integrity of the rock mass, the greater the disturbance influence, and the smaller the disturbance reduction coefficient m; but when the surrounding rock is extremely poor (class V), the deterioration degree tends to be stable. This law reveals the grading and zoning characteristics of the sensitivity of the surrounding rock disturbance, which can provide a theoretical reference for the blasting control and support optimization in the construction stage.

[0018] (5) The application realizes a closed-loop application system of "prediction before construction-evaluation during construction-verification after construction": The application is not only suitable for quality modification and evaluation of the surrounding rock of the excavated section, but also can use acoustic wave, radar and drilling data in front of the working face to predict the surrounding rock grade of the unexcavated section. The prediction result can identify high-risk sections in advance, and provide quantitative basis for support design, blasting control and construction organization, thereby realizing integrated dynamic evaluation of surrounding rock grading and construction management. The system effectively improves the safety, economy and controllability of tunnel construction. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 A surrounding rock grading method considering the influence of engineering disturbance is provided.

[0020] Figure 2 A typical curve of rock mass acoustic wave velocity is provided.

[0021] Figure 3The disturbance reduction coefficient based on acoustic wave velocity under different disturbance modes is provided.

[0022] Figure 4 The damage deterioration zone depth under different disturbance modes is provided.

[0023] Figure 5 The disturbance reduction coefficient cases of different excavation modes and different BQ categories based on engineering cases are provided.

[0024] Figure 6 The engineering applicability evaluation result of the surrounding rock classification method considering the influence of engineering disturbance of A tunnel is provided.

[0025] Figure 7 The engineering applicability evaluation result of the surrounding rock classification method considering the influence of engineering disturbance of B tunnel is provided. DETAILED DESCRIPTION

[0026] The specific embodiments of the present application are described below to facilitate the understanding of the present application by those skilled in the art, but it should be clear that the present application is not limited to the scope of the specific embodiments, and for those skilled in the art, as long as various changes are within the spirit and scope of the present application defined and determined by the appended claims, all the application and creation utilizing the concept of the present application are within the scope of protection.

[0027] The embodiment of the present application provides a surrounding rock classification method considering the influence of engineering disturbance, as shown in Figure 1 The steps include: S100, constructing a disturbance reduction coefficient expression; S200, collecting and analyzing acoustic wave test data in the process of engineering construction to determine key factors affecting the disturbance reduction coefficient; S300, determining the disturbance reduction coefficient value table under different key factors based on the disturbance reduction coefficient expression; S400, determining the disturbance reduction coefficient value under the current engineering by table lookup, and substituting it into the surrounding rock quality evaluation expression to determine the surrounding rock grade.

[0028] In step S100 of the embodiment, the disturbance reduction coefficient expression is: In the formula, denotes the disturbance reduction coefficient, denotes the longitudinal wave velocity of the disturbed rock mass, denotes the integrity coefficient of the undisturbed rock mass, denotes the acoustic wave velocity of the disturbed rock mass, denotes the acoustic wave velocity of the undisturbed rock mass, v prThis indicates the longitudinal wave velocity of the rock.

[0029] When the disturbance reduction factor m is 1, it means that the disturbance has a small impact and the longitudinal wave velocity of the rock mass does not change after the disturbance, that is, the rock mass maintains its original integrity. When the disturbance reduction factor m decreases, it means that the disturbance has a larger impact and the longitudinal wave velocity of the rock mass decreases significantly after the disturbance compared to before the disturbance. The rock mass deteriorates and therefore it is difficult to maintain its original integrity.

[0030] As can be seen from the above expression for the disturbance reduction factor m, the disturbance reduction factor m can be calculated using the longitudinal wave velocity of the rock mass before and after the disturbance. A typical acoustic longitudinal wave velocity curve obtained through acoustic testing is shown below. Figure 2 As shown, since shallow acoustic probes often fail to couple with the rock mass during most acoustic tests, resulting in data collection difficulties, the analysis primarily focuses on the damaged and deteriorated sections where data can be collected. The acoustic velocity of the rock mass in the damaged and deteriorated zone ahead of the tunnel face varies with borehole depth, representing the rock mass integrity after disturbance at different depths. However, when calculating the disturbance reduction factor m, a characteristic value of the acoustic velocity v needs to be determined. pm_D This represents the integrity of the entire damaged and deteriorated area.

[0031] Based on this, the acoustic velocity of the rock mass before and after the disturbance is determined. / The specific method is as follows: Construct a rock mass acoustic curve with borehole depth as the abscissa and acoustic velocity as the ordinate; In the acoustic wave curve diagram of the rock mass, determine the area enclosed by the acoustic velocity curve of the damaged and deteriorated zone and the horizontal axis. The ratio of area to depth of the damaged and deteriorated zone is used as the acoustic velocity of the disturbed rock mass. ; The average acoustic velocity corresponding to the stable segment of the acoustic velocity curve is taken as the acoustic velocity of the rock mass before disturbance. .

[0032] In this embodiment, acoustic test data from domestic and international engineering cases are collected, and the disturbance reduction coefficient m is calculated using the above formula. Then, the collected data is analyzed, and a table of values ​​for the disturbance reduction coefficient m is obtained based on different excavation disturbance methods and basic rock mass quality BQ, which can provide a reference for the value of the disturbance reduction coefficient m for the classification of surrounding rock in other engineering projects.

[0033] Specifically, in this embodiment, step S200 includes the following sub-steps: S201. Collect acoustic wave test data during the engineering testing process; S202. Determine the factors affecting the degree of rock mass damage, including excavation disturbance method, construction method, basic rock mass quality indicators based on rock mass acoustic velocity, tunnel span and tunnel height; S203, based on the sound wave test data under different factors, multiple linear regression is carried out; S204, based on the multiple linear regression result, the key factors affecting the disturbance reduction coefficient are determined, including the excavation disturbance mode and the basic quality index of rock mass; the excavation disturbance mode includes tunneling excavation, controlled blasting excavation and ordinary blasting excavation.

[0034] Among them, for the determined key factors: Under the same excavation disturbance mode, in the process of reducing the basic quality index of rock mass, the disturbance reduction coefficient first increases and then decreases; Under the same basic quality index of rock mass, the disturbance reduction coefficients corresponding to tunneling excavation and controlled blasting excavation are greater than the disturbance reduction coefficient corresponding to ordinary blasting excavation.

[0035] The evaluation index used in the surrounding rock classification by using the national standard BQ method in the survey and design stage does not consider the influence of engineering disturbance, but after excavation, the rock mass near the working face is affected by disturbance and damage and deterioration, and the integrity of the rock mass must change, thereby causing the difference between the rock mass quality before and after disturbance. Therefore, the disturbance reduction coefficient m is introduced in the present application to reflect the influence of engineering excavation disturbance on the integrity of the rock mass, and the surrounding rock quality evaluation expression when the disturbance reduction coefficient m is included in step S400 is: In the formula, The surrounding rock quality evaluation value considering the influence of engineering disturbance is represented by m, which represents the disturbance reduction coefficient, The uniaxial saturated compressive strength is represented by The undisturbed rock mass integrity coefficient is represented by 、 And The groundwater influence correction coefficient, the soft structure plane occurrence influence correction coefficient and the initial stress state influence correction coefficient are represented by

[0036] In one embodiment of the present application, a specific example of constructing a disturbance reduction coefficient value table under different key factors is given.

[0037] 570 groups of sound wave data in underground engineering such as highway tunnel and railway tunnel are collected and analyzed. The sound wave velocity curve change trend in different projects is roughly the same (similar to Figure 2), but due to the differences in excavation methods, lithology, rock mass integrity, size of the chamber and cross-section shape, etc., there are certain differences in the characteristic values (damage and deterioration zone acoustic velocity, undisturbed zone acoustic velocity, damage and deterioration zone depth L, etc.) in the extracted acoustic velocity curves. To analyze the influence of the excavation disturbance method, the damage and deterioration zone depth L reflected by the acoustic velocity curve and the disturbance reduction coefficient based on acoustic velocity are extracted, and the different excavation disturbance methods (tunneling machine, controlled blasting, and ordinary blasting) are shown in Figs. Figure 3 and Figure 4 As can be seen from the figures, due to the many factors affecting the final excavation damage degree in different projects and different conditions, the disturbance reduction coefficients m obtained under the three excavation disturbance methods (tunneling machine, controlled blasting, and ordinary blasting) have discreteness, among which the disturbance reduction coefficient based on acoustic velocity of the tunneling machine is relatively large, with a distribution range of 0.43-0.95 in the statistical data, and the disturbance reduction coefficients of controlled blasting and ordinary blasting are relatively small, with distribution ranges of 0.16-0.99 and 0.03-0.93, respectively.

[0038] The collected acoustic data come from a large number of engineering cases, and there are many factors affecting the distribution of acoustic data in engineering practice. In addition, the current data only come from some projects that can be investigated, which leads to some extreme data, but in order to reflect the distribution of all data, Figure 4 After excluding the outliers in the statistical data, the damage and deterioration zone depth of the rock mass under the tunneling machine excavation method is distributed in the range of 1.1-1.8 m, the damage and deterioration zone depth of the rock mass under the controlled blasting excavation method is distributed in the range of 0.3-5.2 m, and the damage and deterioration zone depth of the rock mass under the ordinary blasting excavation method is distributed in the range of 0.3-8.5 m. It can be seen that when the disturbance method is a tunneling machine or controlled blasting, the damage and deterioration zone depth caused by excavation disturbance is relatively small, and ordinary blasting may cause greater damage and deterioration depth.

[0039] The factors affecting the damage degree of rock mass include not only the excavation disturbance mode, but also the basic quality of rock mass itself and the size of the cavern, etc. Therefore, even if the same excavation disturbance mode, the disturbance reduction coefficient m of different projects and different tunnel sections also exists differences. Therefore, based on the collected 103 groups of engineering cases containing excavation mode, construction method, basic quality index BQ of rock mass determined based on lithology category and wave velocity of rock mass without disturbance, span and height information, this paper uses SPSS software to carry out multiple linear regression analysis to study the correlation between the five factors and the disturbance reduction coefficient m. The basic quality index BQ of rock mass should be the case of rock mass without disturbance before excavation, so the wave velocity of rock mass without disturbance and the rock mass category (see Table 1) in the collected engineering data are used to determine the basic quality index BQ value category of rock mass without disturbance according to the specification “Railway Engineering Geological Exploration Specification”. When carrying out multiple linear regression analysis, the excavation mode, construction method and basic quality index BQ of rock mass are analyzed by numerical variables, as shown in Tables 3(a)-(c), and the span and height are the actual cavern size. The multiple linear regression analysis results are shown in Table 4, and the regression equation is significant, F = 46.652, p < 0.001. Among them, the stronger the excavation disturbance (β = -0.396, p < 0.001), the larger the construction method category value (β = -0.515, p < 0.001), and the poorer the basic quality index BQ of rock mass (β = -0.283, p < 0.001), the smaller the disturbance reduction coefficient m. The cavern span (β = 0.011, p = 0.851) and the cavern height (β = -0.146, p = 0.038) cannot predict the disturbance reduction coefficient m. Since the construction method is generally selected after the classification of surrounding rock is determined, the main factors affecting the disturbance reduction coefficient m are the excavation disturbance mode and the basic quality index BQ of rock mass.

[0040] Table 1 Classification of rock types Table 2 Basic quality index BQ of surrounding rock and elastic longitudinal wave velocity of surrounding rock Table 3 Category and category value of related factors When determining the disturbance reduction coefficient value table, refer to “Engineering Rock Mass Classification Standard” (GB / T 50218-2014) to arrange the disturbance reduction coefficient m of different basic quality BQ categories under different excavation modes as follows Figure 5As shown in Table 5, there are relatively few engineering cases involving tunnel boring machines (TBMs) excavation, therefore, the disturbance reduction coefficient m values ​​for rock mass basic quality (BQ) values ​​of 550-351 are lacking. The figure shows that under the same excavation disturbance method, as the BQ value decreases, the disturbance reduction coefficient m generally exhibits a trend of first increasing, then decreasing, and then increasing again. This trend reflects the influence of rock mass basic quality on the degree of damage development after disturbance, and also indicates that the disturbance reduction coefficient m may be affected by the actual disturbance method. When the rock mass basic quality index (BQ) category is consistent, the disturbance reduction coefficient m for TBM and controlled blasting excavation is relatively large, while the disturbance reduction coefficient m for ordinary blasting excavation is relatively small.

[0041] Table 5. Disturbance reduction coefficients for different excavation methods and different BQ categories based on engineering cases. The disturbance reduction coefficients *m* in Table 5 are derived from numerous projects and are influenced by many factors. Therefore, controlling variables was not possible, resulting in a wide distribution range (i.e., some dispersion) of *m* under different excavation methods and different rock mass basic quality index (BQ) categories. Furthermore, although controlled blasting was used in some projects, its effectiveness was not always good, leading to potentially lower calculated *m* values. Therefore, in specific engineering applications, the average value of *m* collected should not be considered alone; it should be selected based on the actual situation. For example, in actual projects where blasting excavation yields relatively good blasting quality and less rock mass deterioration, a larger value for *m* should be chosen.

[0042] The embodiments of the present invention provide engineering application examples of the above-mentioned surrounding rock classification method.

[0043] To verify the engineering applicability of the surrounding rock classification method considering the impact of engineering disturbances, this embodiment calculates the [BQ] value without considering the impact of engineering disturbances and the [BQ] value considering the impact of engineering disturbances, based on typical cross-sections of two excavated tunnel sections of a major project. D The surrounding rock quality was assessed, and the grading results were compared with the actual surrounding rock grade revealed during construction. When determining the disturbance reduction factor *m* for the tunnel in this major project, the actual disturbance reduction factor *m* was not obtained because extensive acoustic testing was not conducted on-site. The rock mass damage degree *s*, based on the complexity of the ground-penetrating radar image, was also assessed. LDAlthough different from the disturbance reduction coefficient m based on the speed of sound wave, it can also roughly reflect the degree of deterioration of the rock mass after excavation disturbance. Therefore, the disturbance reduction coefficient m of the major project tunnel is determined based on the damage characteristics of the complexity of the geological radar image of the surrounding rock of the major project tunnel under the influence of engineering excavation disturbance. However, the basic quality of the rock mass of each tunnel section and the damage characteristics under the influence of excavation disturbance are different, and the surrounding rock quality of A and B tunnels will be evaluated in this embodiment, so the damage characteristics of the surrounding rock under the influence of excavation disturbance of the two tunnels are comprehensively considered to determine the disturbance reduction coefficient m of the major project tunnel as shown in Table 6.

[0044] According to the geological survey data, advanced geological prediction data and other related data of the major project A and B tunnels, the rock strength, groundwater state, main structure surface occurrence information, initial ground stress state and other parameters are obtained, and the values are reasonably selected according to the “Engineering Rock Mass Classification Standard” (GB / T 50218-2014). The TSP longitudinal wave velocity of the major project A and B tunnels can well reflect the integrity of the rock mass, so the relationship between the TSP longitudinal wave velocity and the integrity of the rock mass is summarized in Table 7, and the rock mass integrity coefficient Kv is determined according to the TSP longitudinal wave velocity of the evaluation section and Table 7. After determining the above evaluation indexes, the [BQ]D considering the influence of engineering disturbance is calculated for the typical section surrounding rock of A and B tunnels, so as to obtain the surrounding rock classification results under the influence of engineering disturbance as shown in Tables 8 and 9.

[0045] Table 6 Disturbance reduction coefficient value table of a major project tunnel Table 7 TSP longitudinal wave velocity and rock mass integrity coefficient of a major project tunnel Table 8 Surrounding rock classification of A tunnel auxiliary gallery typical section Note: The values of rock strength, groundwater influence correction coefficient, main structure surface occurrence influence correction coefficient, initial ground stress state influence correction coefficient and the like are determined according to the geological survey report and the results of the working face geological sketch, and the integrity coefficient is determined according to the TSP longitudinal wave velocity, and the same below.

[0046] Table 9 Surrounding rock classification of B tunnel auxiliary gallery typical section are 45-120 MPa, the rock mass integrity coefficient Kv determined based on the longitudinal wave velocity of rock mass before excavation measured by TSP is 0.38-0.74, and the rock mass integrity is relatively broken to relatively complete. The basic quality index BQ calculated according to the rock strength Rc and the integrity coefficient Kv is in the range of 325-577, and the disturbance reduction coefficient m is 0.80-0.84. Overall, the coincidence rate of the [BQ]D surrounding rock classification results considering the influence of engineering excavation disturbance and the actual surrounding rock classification results of the analysis section of the A tunnel main tunnel and auxiliary tunnel is 84%, which is improved by 29% compared with the coincidence rate without considering the influence of engineering excavation disturbance (as shown in Figure 6 ), indicating that the surrounding rock classification correction method considering the influence of engineering excavation disturbance has good engineering applicability for the A tunnel.

[0047] The surrounding rock quality of the B tunnel auxiliary tunnel is poor, and the actual surrounding rock grade during the construction stage is mainly grade IV and grade V. The rock property is mainly carbonaceous slate interbedded with sandstone, the rock strength Rc is mainly 30 MPa, the rock mass integrity coefficient Kv determined based on the longitudinal wave velocity of rock mass before excavation measured by TSP is 0.32-0.52, and the rock mass integrity is broken to relatively broken. The rock basic quality index BQ calculated according to the rock strength Rc and the integrity coefficient Kv is in the range of 269-320, and the disturbance reduction coefficient m is 0.85-0.86. Overall, the coincidence rate of the [BQ]D surrounding rock classification results considering the influence of engineering excavation disturbance and the actual surrounding rock classification results revealed during the construction stage is 87%, which is improved by 10% compared with the coincidence rate without considering the influence of engineering excavation disturbance, as shown in Figure 7 .

[0048] In summary, the surrounding rock quality of most tunnel sections of the A tunnel of a major project is relatively good, mainly grade II, III, and IV. If the influence of engineering excavation disturbance is not considered during the surrounding rock grade evaluation, the surrounding rock stability after excavation may be overestimated. For the tunnel sections with good surrounding rock quality of the A tunnel, it is more reasonable to take the disturbance reduction coefficient m of 0.80-0.86 to consider the influence of engineering excavation disturbance in the surrounding rock grade evaluation, and the coincidence rate with the actual surrounding rock classification results is also relatively high. The surrounding rock quality of most tunnel sections of the B tunnel of the major project is poor, mainly grade V. At this time, the rock mass degradation degree under the influence of engineering excavation disturbance is relatively small, so the disturbance reduction coefficient m of 0.85-0.89 taken for the B tunnel is relatively higher than that for the A tunnel. However, the disturbance reduction coefficient m taken for some tunnel sections may not be completely reasonable, and the surrounding rock grade may be overestimated or underestimated, because the disturbance reduction coefficient m is taken by comprehensively considering the surrounding rock damage characteristics of each tunnel and the disturbance reduction coefficient m based on the acoustic data of other engineering cases, which is more dependent on the accurate judgment of the engineering surrounding rock tunnel damage characteristics and the number of engineering cases. Therefore, the [BQ]D surrounding rock classification results considering the influence of engineering excavation disturbanceD The surrounding rock classification result is more consistent with the actual situation of a major project, and has good engineering applicability.

[0049] The principles and implementation manners of the present application are described by using specific examples in the present application, and the above examples are only used to help understand the method of the present application and its core idea; meanwhile, for the general technical personnel in the art, according to the idea of the present application, the specific implementation manners and application ranges will be changed, and the above description should not be understood as the limitation of the present application.

[0050] The person skilled in the art will understand that the examples described herein are used to help the reader understand the principles of the present application and should be understood as the protection scope of the present application not being limited to such specific statements and examples. The person skilled in the art can make various other specific modifications and combinations without departing from the essence of the present application according to the technical inspirations disclosed in the present application, and these modifications and combinations are still within the protection scope of the present application.

Claims

1. A method for classifying surrounding rock considering the effects of engineering disturbance, characterized in that, Includes the following steps: S100, Construct the expression for the disturbance reduction coefficient; S200. Collect and analyze acoustic test data during the engineering construction process to determine the key factors affecting the disturbance reduction factor; S300. Based on the expression for the disturbance reduction coefficient, determine the value table of the disturbance reduction coefficient under different key factors; S400. Determine the value of the disturbance reduction factor under the current project by referring to the table, and substitute it into the surrounding rock quality assessment expression to determine the surrounding rock grade.

2. The surrounding rock classification method considering the impact of engineering disturbance according to claim 1, characterized in that, In step S100, the expression for the disturbance reduction coefficient is: In the formula, This represents the disturbance reduction factor. This indicates the longitudinal wave velocity of the rock mass after disturbance. This represents the integrity coefficient of the undisturbed rock mass. This indicates the acoustic velocity of the rock mass after disturbance. v represents the acoustic velocity of the rock mass before disturbance. pr This indicates the longitudinal wave velocity of the rock.

3. The surrounding rock classification method considering the impact of engineering disturbance according to claim 2, characterized in that, Determine the acoustic velocity of the rock mass before / after disturbance / The specific method is as follows: Construct a rock mass acoustic curve with borehole depth as the abscissa and acoustic velocity as the ordinate; In the acoustic wave curve diagram of the rock mass, determine the area enclosed by the acoustic velocity curve of the damaged and deteriorated zone and the horizontal axis. The ratio of area to depth of the damaged and deteriorated zone is used as the acoustic velocity of the disturbed rock mass. ; The average acoustic velocity corresponding to the stable segment of the acoustic velocity curve is taken as the acoustic velocity of the rock mass before disturbance. .

4. The surrounding rock classification method considering the impact of engineering disturbance according to claim 1, characterized in that, Step S200 includes the following sub-steps: S201. Collect acoustic wave test data during the engineering testing process; S202. Determine the factors affecting the degree of rock mass damage, including excavation disturbance method, construction method, basic rock mass quality indicators based on rock mass acoustic velocity, tunnel span and tunnel height; S203. Based on acoustic wave test data under different factors, perform multiple linear regression; S204. Based on the results of multiple linear regression, determine the key factors affecting the disturbance reduction coefficient, including the excavation disturbance method and the basic quality indicators of the rock mass; the excavation disturbance method includes tunneling excavation, controlled blasting excavation and ordinary blasting excavation.

5. The surrounding rock classification method considering the impact of engineering disturbance according to claim 4, characterized in that, For the identified key factors: Under the same excavation disturbance method, as the basic quality indicators of the rock mass decrease, the disturbance reduction coefficient first increases and then decreases. Under the same basic quality index of rock mass, the disturbance reduction coefficients corresponding to tunneling excavation and controlled blasting excavation are greater than those corresponding to ordinary blasting excavation.

6. The surrounding rock classification method considering the impact of engineering disturbance according to claim 1, characterized in that, In step S400, the expression for evaluating the surrounding rock quality is: In the formula, This represents the surrounding rock quality assessment value considering the impact of engineering disturbances, where m represents the disturbance reduction factor. Indicates uniaxial saturated compressive strength. This represents the integrity coefficient of the undisturbed rock mass. , and These represent the correction factors for the influence of groundwater, the influence of the attitude of weak structural surfaces, and the influence of the initial stress state, respectively.

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