Improved separated highway tunnel exit construction method

Abstract

The invention provides an improved separated highway tunnel exit construction method, and belongs to the technical field of tunnel engineering construction. The method comprises the steps that firstly, original acceleration data and tunnel face point cloud data in the tunneling process are collected, and instantaneous vibration amplitude parameters, instantaneous vibration phase parameters and structural face density parameters are extracted from the original acceleration data and the tunnel face point cloud data; inputting the parameters into a vibration coupling stability evaluation model, and calculating to obtain a vibration coupling stability index; dividing the tunnel face into a first pilot tunnel area and a second pilot tunnel area according to the vibration coupling stability index and the instantaneous vibration phase parameter, and dynamically determining the excavation sequence and the single excavation length; and finally, regional construction is carried out. According to the method, the mechanical vibration signals are converted into the stability evaluation characteristics, real-time adaptation of the construction parameters and the surrounding rock state is achieved, the problems of sequence rigidity and parameter solidification in traditional out-of-hole construction are effectively solved, and the construction safety and the intelligent level are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of tunnel engineering construction, and particularly relates to an improved separated highway tunnel exit construction method. BACKGROUND

[0002] In the separated highway tunnel engineering, the exit section construction is one of the control difficulties of tunnel safety construction due to the proximity to the ground surface, complex surrounding rock conditions and easy environmental influence. Traditionally, the unilateral wall pilot tunnel method is generally used to reduce the disturbance to the surrounding rock through step-by-step excavation. The construction sequence and the length of the cycle excavation are usually preset according to the geological survey report and remain fixed during the construction process.

[0003] However, this method is essentially an open-loop control based on static geological prediction, lacking real-time response capability to the dynamic changes of the surrounding rock. It is particularly worth noting that in the existing technology, the mechanical vibration signal generated by the excavation equipment is usually regarded as interference noise and filtered out, ignoring the real-time mechanical state information of the surrounding rock contained in the signal. This processing method causes a lag between the geological model on which the construction decision is based and the actual situation, making it difficult to accurately capture the plastic deformation and progressive failure process of the surrounding rock.

[0004] The limitations of the above cognition and technical processing method make it difficult to adaptively adjust to avoid risks even if the surrounding rock conditions have changed adversely in actual construction. Moreover, the mismatch between construction behavior and surrounding rock state may exacerbate the disturbance to the surrounding rock, forming a vicious cycle of vibration intensification and decision-making failure, which seriously restricts the safety and intelligent level of tunnel exit construction. SUMMARY

[0005] The present application overcomes the shortcomings of the prior art and provides an improved separated highway tunnel exit construction method.

[0006] To achieve the above purpose, the technical solution adopted by the present application is as follows: an improved separated highway tunnel exit construction method, comprising the following steps:

[0007] S1, collecting original acceleration data and original tunnel face point cloud data during excavation, extracting instantaneous vibration amplitude parameters, instantaneous vibration phase parameters and structural surface density parameters;

[0008] S2, inputting the instantaneous vibration amplitude parameters, instantaneous vibration phase parameters and structural surface density parameters into a vibration coupling stability evaluation model to calculate a vibration coupling stability index;

[0009] S3, dividing the tunnel tunnel face section into a first pilot tunnel area and a second pilot tunnel area according to the vibration coupling stability index and the instantaneous vibration phase parameters, and determining the excavation sequence and the single excavation length.

[0010] S4, constructing the first pilot tunnel area and the second pilot tunnel area based on the excavation sequence and the single tunneling length.

[0011] Preferably, in step S1, the original acceleration data is collected by piezoelectric acceleration sensors, which are arranged in the surrounding rock area within 3-5 m in front of the tunnel face, with one sensor arranged in each of the upper, middle and lower horizontal layers of the tunnel section, and the sensors in each layer are spaced 2-3 m apart in the horizontal direction, with a total of 3-5 sensors arranged on the full section; the collection frequency is 100-200 Hz, and the vibration response in three orthogonal directions is captured.

[0012] Preferably, in step S1, the original tunnel face point cloud data is collected by a pulse type three-dimensional laser scanner, which is placed in a stable area 5-8 m away from the tunnel face during the period after the end of each tunneling cycle and before the start of the next cycle; the scanning angle range is 120-150° horizontally and 90-120° vertically, and the point cloud density is 500-800 points / m 2 .

[0013] Preferably, in step S1, the extraction of the instantaneous vibration amplitude parameter includes band-pass filtering of the original acceleration data, with a filtering frequency range of 5-50 Hz; a fixed time window of 0.5-1.0 s is set, the filtered acceleration data is segmented according to the time window, and the root mean square value of the three-axis acceleration vector sum in each time window is calculated.

[0014] Preferably, in step S1, the extraction of the instantaneous vibration phase parameter includes frequency domain conversion of the band-pass filtered original acceleration data using fast Fourier transform, with a frequency resolution of 0.1-0.5 Hz, identification of the main vibration frequency, calculation of the vibration period, and obtaining of the phase parameter based on time difference normalization.

[0015] Preferably, in step S1, the extraction of the structural plane density parameter includes denoising of the original tunnel face point cloud data, using a combination of statistical filtering and radius filtering; the RANSAC plane fitting algorithm is used to fit the structural plane, and the number of structural planes per unit area is counted in a statistical area of 1.0 m x 1.0 m to 2.0 m x 2.0 m.

[0016] Preferably, in step S2, the mathematical expression of the vibration coupling stability evaluation model is: wherein is the vibration coupling stability index; is the reference coefficient; is the weight coefficient of the instantaneous vibration amplitude parameter; is the instantaneous vibration amplitude parameter; is the weight coefficient of the instantaneous vibration phase parameter; a phase parameter of transient vibration; a weight coefficient of the structural plane density parameter; a structural plane density parameter.

[0017] Preferably, in step S3, the tunnel face section is divided into the first drift area and the second drift area along the vertical center line in a symmetrical or asymmetrical manner, and the horizontal width ratio of the first drift area and the second drift area ranges from 0.8:1 to 1:0.8.

[0018] Preferably, in step S3, the determination of the excavation sequence includes setting a vibration coupling stability threshold value according to the surrounding rock grade; when the vibration coupling stability index is less than or equal to the threshold value, the excavation sequence of the second drift area before the first drift area is adopted, and the advance excavation amount is calculated; when the vibration coupling stability index is greater than the threshold value, any sequence or synchronous excavation is adopted.

[0019] Preferably, the calculation formula of the advance excavation amount is: wherein is a vibration coupling stability threshold value; is a vibration coupling stability index; is a reference cycle excavation length; is an advance amount amplification coefficient.

[0020] The present application solves the defects in the background art and has the following beneficial effects:

[0021] The present application redefines the mechanical vibration, which is traditionally regarded as an interference signal, as an effective information source reflecting the dynamic mechanical state of the surrounding rock by capturing the micro-vibration response of the tunneling machine to the surrounding rock in real time, and establishes a vibration coupling stability evaluation model of multi-source data fusion in combination with the structural characteristics of the face obtained by three-dimensional laser scanning. The vibration coupling stability evaluation model can quantify the interaction relationship between the tunneling disturbance and the surrounding rock structure, thereby realizing dynamic diagnosis of the stability state of the surrounding rock and effectively overcoming the judgment lag problem caused by relying only on geological prediction or static monitoring in the traditional method. Compared with the method of filtering vibration signals as noise in the prior art, the present application converts vibration parameters into stability evaluation, so that potential instability risks can be identified in time during construction, and the sensitivity and accuracy of the surrounding rock state perception in the tunnel exit stage are significantly improved.

[0022] Based on the dynamic feedback of the vibration coupling stability index and the instantaneous vibration phase parameter, the invention proposes a guide pit area division, which divides the working face into two guide pit areas through vertical segmentation, and adjusts the excavation sequence and single tunneling length according to the stability state, so that the invention can automatically match the optimal excavation mode according to the real-time response of the surrounding rock, form a stress release channel through the advanced excavation of the second guide pit area when the stability is low, and realize synchronous advancement of the two areas when the stability is high, thereby maximizing the tunneling efficiency under the premise of safety. Compared with the fixed excavation sequence and the neglect of disturbance dynamic transmission in the traditional out-hole construction, the method realizes the real-time adaptation of the tunneling process and the mechanical state of the surrounding rock, effectively avoids the disturbance superposition and stress concentration phenomenon caused by the rigidity of the sequence, and fundamentally enhances the anti-risk ability and adaptability of the construction process.

[0023] In the present application, the feature extraction method combining vibration signal analysis and working face structure identification cooperates with the stability evaluation model based on multi-parameter coupling, and both constitute a closed-loop update. The vibration parameters reflect the strength and rhythm of the tunneling disturbance in real time, and the structure surface parameters depict the anti-disturbance ability of the surrounding rock, the fusion of the two enables the model to comprehensively capture the dynamic balance relationship between external excitation and internal structure, and further provides a basis for adjusting the excavation sequence and tunneling length. This data-driven construction parameter can realize local optimization in each cycle, and through continuous parameter updating and iteration, the entire out-hole construction process always maintains the optimal state synchronized with the evolution of the surrounding rock, thereby realizing the unity of safety control and engineering efficiency as a whole. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, a brief introduction will be given below to the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below are only some embodiments described in the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings;

[0025] Figure 1 A flowchart of an improved separate highway tunnel out-hole construction method. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0027] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, it will be apparent to one skilled in the art that the present application can be practiced without the specific details set forth in this description.

[0028] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the scope of protection of the present application. In addition, the terms "first", "second", and the like are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first", "second" and the like can explicitly or implicitly include one or more features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0029] In the description of the present application, it should be noted that unless otherwise specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood through specific circumstances.

[0030] In the following description, unless otherwise specified, all raw materials can be obtained from commercial or prepared by conventional methods in the art.

[0031] As shown in Figure 1 An improved separate highway tunnel exit construction method, comprising the following steps:

[0032] S1, collecting original acceleration data and original tunnel face point cloud data in the tunneling process, extracting instantaneous vibration amplitude parameter, instantaneous vibration phase parameter and structural plane density parameter;

[0033] S2, inputting the instantaneous vibration amplitude parameter, the instantaneous vibration phase parameter and the structural plane density parameter into the vibration coupling stability evaluation model, and calculating the vibration coupling stability index;

[0034] S3, according to the vibration coupling stability index and the instantaneous vibration phase parameter, the tunnel face section is divided into a first pilot tunnel area and a second pilot tunnel area, and the excavation sequence and the single tunneling length are determined;

[0035] S4, according to the excavation sequence and the single tunneling length, the first pilot tunnel area and the second pilot tunnel area are constructed.

[0036] In the following, each step will be described in detail.

[0037] Step S1 is based on the separated highway tunnel exit construction phase, that is, the construction process of the tunnel excavation approaching the transition section of the surrounding rock of the tunnel portal, that is, about to penetrate to the ground. Among them, the separated highway tunnel refers to the type of highway tunnel in which the left and right lines are independently arranged and a certain distance is maintained between the line positions; the face is the working face that advances forward in the tunneling process, and is the area directly affected by the exposure of the surrounding rock and the tunneling operation. In step S1, the original acceleration data and the original face point cloud data are collected respectively according to the interaction between the tunneling operation and the surrounding rock of the face and the structure form of the face, and the original acceleration data and the original face point cloud data are processed respectively, and the instantaneous vibration amplitude parameter, the instantaneous vibration phase parameter and the structure surface density parameter are extracted in turn.

[0038] When collecting the original acceleration data, a piezoelectric acceleration sensor is used as the collection device. This type of sensor has a frequency response range of 10-1000Hz, which can capture the micro-vibration signals of the surrounding rock caused by tunneling vibration, and is suitable for the complex mechanical environment of tunnel construction. The layout of the sensor needs to be combined with the range requirements of the data collection object, and the surrounding rock area within 3-5m in front of the face is selected as the data collection object. This area can directly reflect the disturbance effect of the tunneling operation on the unexcavated surrounding rock, while avoiding the problems of being too close to be directly disturbed by the construction machinery and being too far away to cause the vibration signal to be attenuated and distorted.

[0039] The specific layout operation is as follows: in this surrounding rock area, 1 sensor is arranged along the upper, middle and lower three horizontal layers of the tunnel section, the sensors at each layer are spaced 2-3m apart in the horizontal direction, and a total of 3-5 sensors are arranged on the whole section to form a three-dimensional monitoring network. The sensor is installed by drilling and pre-burying, the drilling diameter is 5-8mm larger than the outer diameter of the sensor, and the drilling depth is 200-300mm. After embedding the sensor probe into the drilling hole, fast-hardening cement mortar is used to fill the drilling gap to ensure that the sensor is in close contact with the surrounding rock and reduce energy loss in the transmission process of the vibration signal. The signal output end of the sensor is connected to the data acquisition instrument through a shielded cable, the laying of the shielded cable needs to be away from the power cable of the construction machinery to avoid electromagnetic interference, and the sampling trigger mode of the data acquisition instrument is set to be synchronized with the start signal of the tunneling machinery to ensure that the collection period is completely consistent with the tunneling period.

[0040] In terms of acquisition parameter setting, the vibration responses in three orthogonal directions are captured at a fixed frequency of 100-200 Hz, wherein the X-axis is along the tunneling direction, the Y-axis is horizontally arranged perpendicular to the tunneling direction, and the Z-axis is vertically arranged. The arrangement in three orthogonal directions can comprehensively cover the spatial distribution characteristics of the surrounding rock vibration, avoiding the omission of vibration energy caused by single direction acquisition. During the acquisition process, the data acquisition instrument synchronously performs analog-digital conversion on the captured analog acceleration signals, and the conversion resolution is set to 16-24 bits, so as to convert the continuous analog signals into discrete original acceleration data. The acquisition frequency of 100-200 Hz can completely cover the main frequency range (5-50 Hz) of the vibration generated by the tunneling operation, and in combination with the high-resolution analog-digital conversion, the original acceleration data can retain all dynamic characteristics in the vibration process.

[0041] When acquiring the original face point cloud data, a pulse type three-dimensional laser scanner is used as the acquisition equipment. Such a scanner has an effective scanning distance of 50-100 m and can quickly obtain the three-dimensional coordinate information of the full cross section of the face under the complex lighting environment of the tunnel. The scanning time is selected in the time period after the end of each tunneling cycle and before the start of the next cycle. At this time, the face is in a relatively stable exposed state without interference from construction machinery, and can truly reflect the natural structure and morphology of the surrounding rock at the current tunneling depth.

[0042] Before scanning, the equipment needs to be calibrated and erected: the three-dimensional laser scanner is placed in a stable area 5-8 m away from the face in the tunnel to ensure that the line of sight of the scanner is not blocked and to avoid the rockfall risk area above the face. A total station is used to calibrate the coordinates of the three-dimensional laser scanner, align the measurement coordinate system of the scanner with the tunnel construction coordinate system, and calibrate the error. In the scanning parameter setting, the scanning angle range is adjusted to be horizontal 120-150° and vertical 90-120° to ensure that the full cross section of the face is covered without omission; the point cloud density of the scanning is controlled to be 500-800 points / m 2 This density range can ensure the detail accuracy required for subsequent structure surface identification, and can also avoid data redundancy and processing efficiency reduction caused by too high density.

[0043] The scanning process adopts a continuous scanning mode, and the scanning time is 30-60 s. The integrity of the point cloud data is monitored in real time during the scanning process. If there is a local area of missing point cloud (the missing area is more than 5%), the position of the scanner is adjusted for re-scanning. After the scanning is completed, the original face point cloud data, including the X, Y, Z three-dimensional coordinate information and the reflection intensity information of each feature point, are transmitted to the data processing terminal through a data line.

[0044] The two data collection needs to keep time synchronization, the original acceleration data collection period completely coincides with the tunneling operation period, the original tunnel face point cloud data collection period is not more than 2 hours apart from the original acceleration data collection period of the last cycle, so as to ensure that the two groups of original data can correspond to the surrounding rock state of the same tunneling stage and time consistency.

[0045] When extracting the instantaneous vibration amplitude parameter, firstly, the original acceleration data is subjected to band-pass filtering processing, the filtering frequency range is set to 5-50 Hz based on the main frequency distribution law of the vibration generated by the tunneling operation, the vibration signal directly related to the tunneling operation is screened out, and irrelevant frequency components such as environmental interference and equipment self-running noise are effectively eliminated. Subsequently, a fixed time window of 0.5-1.0 s is set to completely capture the vibration process of a single tunneling impact, and the filtered acceleration data is segmented according to the time window due to the fact that a too large window causes the characteristics of different vibration events to be superimposed and blurred. For the three-dimensional acceleration data of X, Y and Z axes in each time window, the square values of the acceleration of each axis are calculated and summed to obtain the three-axis acceleration sum, and then the square root of the sum is taken to integrate the vibration energy in three directions and obtain the three-axis acceleration vector sum. Finally, the root mean square value of the three-axis acceleration vector sum in each time window is calculated, which can smooth the instantaneous fluctuations of the vibration signal and accurately represent the average vibration intensity in a single time window. The root mean square value is the instantaneous vibration amplitude parameter.

[0046] When extracting the instantaneous vibration phase parameter, the original acceleration data subjected to band-pass filtering is subjected to frequency domain conversion by using the fast Fourier transform (FFT) algorithm. The fast Fourier transform algorithm has the characteristics of high calculation efficiency and is suitable for real-time data processing requirements. In the processing process, the frequency resolution is set to 0.1-0.5 Hz, the main vibration frequency in the vibration signal is identified through frequency domain analysis, and the main vibration frequency is usually concentrated in the interval of 10-30 Hz. The frequency is determined by the operation parameters of the tunneling machine and the mechanical properties of the surrounding rock, and reflects the essential characteristics of vibration. The vibration period is calculated according to the identified main vibration frequency, and the vibration period and the main vibration frequency satisfy the mathematical relationship (wherein is the vibration period, is the main vibration frequency). Subsequently, the starting time stamp of each time window is selected as the reference point for phase calculation, the time difference between the current time stamp and the reference point is calculated, and the time difference is normalized with the vibration period. The normalization formula is (wherein is the instantaneous vibration phase parameter, is the time difference between the current time stamp and the reference point, The instantaneous vibration phase parameter in the range of 0-2π is finally obtained. The periodicity of the vibration signal determines the different stages of the surrounding rock at different times, and the phase value can accurately locate the specific state of the surrounding rock in the vibration cycle at the current time, reflecting the transmission rhythm of the vibration energy and the response law of the surrounding rock.

[0047] When extracting the structural plane density parameter, first, the original tunnel face point cloud data is denoised. The statistical filtering and radius filtering are combined. The statistical filtering calculates the mean and standard deviation of the coordinates of the points in the local area (the neighborhood range is set to 0.1-0.2 m), and the abnormal points deviating from the mean by more than 3 times the standard deviation are removed. The radius filtering judges the number of neighboring points within a radius of 0.05-0.1 m around a point. If the number of neighboring points is less than 3-5, it is determined that the point is isolated and is removed. The combination of the two algorithms can effectively remove the noise points and interference points generated during the collection process while retaining the structural plane characteristics, ensuring that the point cloud data can truly reflect the structure of the surrounding rock surface. Then, the RANSAC plane fitting algorithm is used to process the denoised original tunnel face point cloud data. The RANSAC plane fitting algorithm selects a set of points that satisfy the plane characteristics from a large amount of point cloud data based on the random sample consensus principle, and then fits the plane representing the discontinuities such as fractures, joints, and bedding of the surrounding rock (i.e., the structural plane, which is a key geometric feature affecting the integrity and mechanical stability of the surrounding rock). Then, a square statistical area of 1.0 m x 1.0 m to 2.0 m x 2.0 m is set. The number of structural planes obtained by fitting is counted in the square statistical area. Then, the structural plane density parameter is obtained by calculating the number of structural planes per unit area (1 m 2 ) in the square statistical area. The value range of this parameter is usually 0-15 / m 2 , and the numerical value directly corresponds to the completeness of the surrounding rock structure.

[0048] Step S2 establishes a vibration coupling stability evaluation model to integrate the coupling effects of the instantaneous vibration amplitude parameter, the instantaneous vibration phase parameter, and the structural plane density parameter. The vibration coupling stability index, which can quantify the real-time stability of the surrounding rock, is obtained by model operation.

[0049] In this step, the vibration coupling stability evaluation model is a multi-element nonlinear weighted mathematical model designed for the surrounding rock characteristics of the separated highway tunnel exit construction. Unlike the general stability evaluation model, the design logic of the vibration coupling stability evaluation model is based on the coupling mechanism of the excavation disturbance and the surrounding rock structure: the stability of the surrounding rock is affected by both the vibration disturbance caused by excavation (characterized by the instantaneous vibration amplitude parameter and the instantaneous vibration phase parameter) and the structural integrity of the surrounding rock (characterized by the structural plane density parameter), and there is a complex nonlinear correlation between the three. A linear model cannot accurately fit this multi-dimensional coupling effect, so a multi-element nonlinear weighted form is used to represent it.

[0050] The mathematical expression of the vibration coupling stability evaluation model is: , wherein is a vibration coupling stability index, dimensionless, and the value range is 0-10; is a reference coefficient, which is determined according to the surrounding rock grade, and the value range is 8-10; is a weight coefficient of the instantaneous vibration amplitude parameter, and the value range is 0.5-2.0; is an instantaneous vibration amplitude parameter, and the unit is m / s 2 , and the value range is 0.1-5.0 m / s 2 ; is a weight coefficient of the instantaneous vibration phase parameter, and the value range is 0.3-1.5; is an instantaneous vibration phase parameter, and the unit is rad, and the value range is 0-2π rad; is a weight coefficient of the structural plane density parameter, and the value range is 0.8-3.0; is a structural plane density parameter, and the unit is piece / m 2 , and the value range is 0-15 piece / m 2 .

[0051] In the above formula, the signs and value ranges of the coefficients are determined based on the influence mechanism of the parameters on the stability of the surrounding rock: the instantaneous vibration amplitude parameter directly reflects the impact disturbance intensity of the tunneling operation on the surrounding rock, the greater the vibration amplitude, the easier the stress balance between the surrounding rock particles is broken, and the worse the stability state, so the negative weighting term ( ) is included in the model; the structural plane density parameter directly reflects the development degree of the internal fissures and joints of the surrounding rock, the higher the structural plane density, the weaker the integrity of the surrounding rock, and the lower the disturbance resistance, and the weakening effect of the structural plane density on the stability is also reflected by the negative weighting term ( ); the instantaneous vibration phase parameter reflects the energy distribution state of the surrounding rock in the vibration cycle, the vibration energy of the surrounding rock is the lowest and the response is the flattest in the trough stage, the vibration energy is the highest and the disturbance is the most intense in the peak stage, the phase value is positively correlated with the vibration energy, so the positive weighting term ( ) is used to adjust the phase parameter to match the real-time state of the vibration response of the surrounding rock.

[0052] The training and calibration process of the vibration coupling stability evaluation model is combined with engineering measured data and indoor test data to ensure that the empirical coefficients are adapted to the actual geological conditions. The specific method is as follows: first, collect 3-5 types of typical surrounding rock grades (including grade III, grade IV, and grade V) of the separated highway tunnel exit construction data, and each type of surrounding rock grade has a sample size of not less than 500 groups. Each group of data includes the corresponding instantaneous vibration amplitude parameter, instantaneous vibration phase parameter, structural surface density parameter, and the accumulated displacement of the surrounding rock obtained by the multi-point displacement meter (as a direct reference index of the stable state); then, the sample data is divided into stable samples (accumulated displacement ≤5 mm) and unstable samples (accumulated displacement >5 mm) by taking the accumulated displacement of the surrounding rock less than 5 mm as the stable state threshold; the least square method is used to perform fitting operation on the sample data, and the matching degree between the vibration coupling stability index calculated by the model and the actual stability state of the surrounding rock is the highest as the target, and four empirical coefficients are iteratively optimized , , and Finally, the exclusive coefficient set corresponding to different surrounding rock grades is determined; after calibration, the corresponding coefficient set is directly called to configure the model according to the surrounding rock grade specified in the geological survey report before construction, without the need for re-calibration to meet the operation accuracy requirements under specific geological conditions.

[0053] The vibration coupling stability index is obtained by real-time parameter input and model operation: the instantaneous vibration amplitude parameter, instantaneous vibration phase parameter, and structural surface density parameter extracted in step S1 are synchronously input into the vibration coupling stability evaluation model which has been calibrated according to the frequency of 100-200 Hz. The vibration coupling stability index is output after the model completes the operation according to the preset formula. The vibration coupling stability index ranges from 0 to 10, where the value range of 0-3 corresponds to the state of the accumulated displacement of the surrounding rock being greater than 5 mm, the value range of 3-7 corresponds to the state of the accumulated displacement of the surrounding rock being between 2-5 mm, and the value range of 7-10 corresponds to the state of the accumulated displacement of the surrounding rock being less than 2 mm. The index value is updated in real time with the change of the input parameter, and a quantitative value is generated independently in each operation period, finally forming a continuous vibration coupling stability index time series, which completely records the dynamic change process of the stability state of the surrounding rock.

[0054] In step S3, the pilot area of the tunnel face section is divided to reduce the risk of disturbance superposition and adapt to the distribution of surrounding rock structure. Before division, the basic properties of the tunnel face section should be determined. The tunnel face section is the exposed surface at the front end of the tunnel excavation direction, and the geometric size is usually 10-18 m wide and 5-8 m high.

[0055] The partition method adopts vertical segmentation. Specifically, the tunnel face section is symmetrically or asymmetrically divided along the vertical center line to form two independent excavation areas, which are defined as the first pilot pit area and the second pilot pit area. The outlines of the first pilot pit area and the second pilot pit area are both polygonal structures. The boundaries need to be calibrated in combination with the structural plane density parameters extracted in step S1, that is, the structural plane density parameters are used to identify the structural plane density in the tunnel face section, and the boundary lines of the pilot pit areas are kept away from the structural plane dense areas (areas with a structural plane density of ≥3 / m 2 , to ensure the continuity of the surrounding rock structure in each pilot pit area. The horizontal width ratio of the first pilot pit area to the second pilot pit area ranges from 0.8:1 to 1:0.8, and the sum of the horizontal projection areas is equal to the horizontal projection area of the tunnel face section, which together constitutes the complete tunnel face section.

[0056] The excavation sequence is determined based on the vibration coupling stability index, which comprehensively reflects the external disturbance intensity caused by the instantaneous vibration amplitude parameter, the internal bearing capacity of the surrounding rock determined by the structural plane density parameter, and the overall stability of the face under the interaction of the two. The value range of the vibration coupling stability index is 0-1. Before determining the excavation sequence, the vibration coupling stability threshold needs to be set. The vibration coupling stability threshold is not a fixed value, but is calibrated in multiple dimensions based on the surrounding rock grade in the tunnel engineering geological survey report, the design anti-disturbance coefficient, and the measured data of similar projects: the vibration coupling stability threshold corresponding to grade III surrounding rock is 0.75-0.8, the vibration coupling stability threshold corresponding to grade IV surrounding rock is 0.7-0.75, and the vibration coupling stability threshold corresponding to grade V surrounding rock is 0.6-0.7.

[0057] When the vibration coupling stability index is less than or equal to the vibration coupling stability threshold, it indicates that the internal structural bearing capacity of the surrounding rock cannot completely offset the external disturbance of the tunneling vibration, and the face is in a low stability state. In this case, the second pilot pit area should be excavated before the first pilot pit area. The principle is to form a local stress release channel in the face by the advance excavation of the second pilot pit area, so that the stress accumulated in the surrounding rock is slowly released along the channel, reducing the stress concentration phenomenon during the subsequent excavation of the first pilot pit area. For this low stability state, the distance by which the second pilot pit area needs to be advanced ahead of the first pilot pit area (advance excavation amount ) needs to be calculated simultaneously. The calculation formula is as follows:

[0058] , wherein is the vibration coupling stability threshold, which is determined according to the surrounding rock grade, and the value range is 0.6-0.8; is the vibration coupling stability index, which is calculated by the vibration coupling stability evaluation model, and the value range is 0-1; The benchmark cycle excavation length is determined according to the excavation efficiency of the excavation machine, the support operation cycle and the designed cycle progress, and the value range is 1.5-3.0 m; The advance quantity amplification coefficient is positively correlated with the structural plane density parameter, and the structural plane density is ≤1 strip / m 2 The value is 1.0-1.2 when the structural plane density is 1-3 strips / m 2 The value is 1.2-1.5 when the structural plane density is ≥3 strips / m 2 The value is 1.5-2.0.

[0059] In the above formula, the gap between the vibration coupling stability threshold and the vibration coupling stability index is used to quantify the gap between the stability state of the surrounding rock and the safety requirement, and the gap is converted into an engineering executable length unit through the benchmark cycle excavation length. Finally, the influence of the structural plane density parameter is introduced through the advance quantity amplification coefficient, so that the advance excavation quantity adapts to the external disturbance intensity and the internal structure characteristics. The calculation result shows that the value range of the advance excavation quantity ΔL is 0.3-3.0 m, which ensures that the advance excavation can effectively release stress and will not cause the second pilot pit area to be unstable due to too large distance.

[0060] When the vibration coupling stability index is greater than the vibration coupling stability threshold, it indicates that the internal structure bearing capacity of the surrounding rock is stronger than the external disturbance of the excavation vibration, and the working face is in a high stability state. At this time, the excavation of the first pilot pit area and the second pilot pit area will not cause instability due to disturbance superposition, so the excavation can be carried out in any order or synchronously, and the advance excavation quantity ΔL is set to 0 m, so that the excavation progress of the two pilot pit areas remains the same, improving the construction efficiency.

[0061] The calculation of the single excavation length takes the instantaneous vibration phase parameter as the core adjustment variable, which is extracted from the original acceleration data after band-pass filtering (filtering frequency range 5-50 Hz) and FFT transformation processing, reflecting the energy distribution law of the excavation machine vibration, and the value range is 0-1. The physical meaning of the instantaneous vibration phase parameter is: when the value tends to 0, the vibration energy is concentrated in the low frequency band, and the disturbance depth to the surrounding rock is large; when the value tends to 1, the vibration energy is dispersed in the high frequency band, and the disturbance depth to the surrounding rock is small. The single excavation length of the first pilot pit area And the single excavation length of the second pilot pit area are both dynamically calculated based on the benchmark cycle excavation length, combined with their respective benchmark coefficients, adjustment coefficients and instantaneous vibration phase parameters, and the calculation formulas are as follows:

[0062] ;

[0063] ;

[0064] Among them, is a reference cycle driving length, and the value range is 1.5-3.0m; is a transient vibration phase parameter, and the value range is 0-1; is a first pilot hole area reference coefficient, and is determined according to a stress level of the surrounding rock of the first pilot hole area, and the stress level is ≤0.3 ( is a surrounding rock uniaxial compressive strength, and the value range is 1.0-1.2 when the stress level is 0.3σ-0.6 , the value range is 0.9-1.0 when the stress level is ≥0.6 , and the value range is 0.8-0.9 when the stress level is ≥0.6 ; is a first pilot hole area adjustment coefficient, and reflects a correction weight of the transient vibration phase parameter on the driving length of the first pilot hole area, and the value range is 0.1-0.3; is a second pilot hole area reference coefficient, and the value range is 0.8-1.2, and the value logic is consistent with the first pilot hole area reference coefficient;

[0065] In the above formula, the driving disturbance of the two pilot hole areas is dynamically balanced through the transient vibration phase parameter: when the transient vibration phase parameter tends to 0 (low-frequency disturbance dominates), tends to 1, the single driving length of the first pilot hole area is increased to 1.1 -1.5 by the positive superposition of the adjustment coefficient , and the single driving length of the second pilot hole area is reduced to 0.7 -1.1 by the reverse deduction of the adjustment coefficient , so that the driving disturbance intensities of the two pilot hole areas are strong and weak, and the disturbance energy is avoided to be superimposed; when the transient vibration phase parameter tends to 1 (high-frequency disturbance dominates), tends to 0, the single driving length of the first pilot hole area and the single driving length of the second pilot hole area both tend to the product of the respective reference coefficient and the reference cycle driving length, and at this time, the disturbance depth is small, and the two pilot hole areas can realize near-synchronous efficient driving. At the same time, the single driving length is set to have a constraint condition: the minimum value of the single driving length of the first pilot hole area is not less than 0.5m, and the maximum value is not more than 1.5 ; and the minimum value of the single driving length of the second pilot hole area is not less than 0.5m, and the maximum value is not more than 1.5 , so as to ensure that the driving operation meets the mechanical performance limit and the supporting operation space requirement.

[0066] Step S4 performs excavation and support operations of the tunnel face section based on the excavation sequence, the first pilot pit area single excavation length, the second pilot pit area single excavation length and the advanced excavation amount determined in step S3. Through construction cycle iteration and parameter dynamic updating, the excavation operation and the real-time mechanical state of the surrounding rock are continuously adapted, and the whole process of the separated highway tunnel exit construction is finally completed.

[0067] In this step, the basic constraint conditions need to be clarified before construction: the termination standard of exit construction is that the tunnel face section completely penetrates the mountain surrounding rock boundary and enters the portal transition section or open excavation section, and the tunnel excavation contour size meets the design requirements (deviation control within ±50mm); all excavation operations need to use mechanical excavation, and the operation parameters (cutting speed, torque) of the excavation machinery need to match the first pilot pit area single excavation length and the second pilot pit area single excavation length, the cutting speed is controlled within 0.5-1.2m / min, and the torque is controlled within 150-300N·m.

[0068] When step S3 determines to use the second pilot pit area before the first pilot pit area excavation sequence, the construction process is based on the advanced stress release and segmented stable surrounding rock. First, the excavation operation of the second pilot pit area is performed, and multi-cycle excavation is used to advance. The control index of each excavation cycle is the second pilot pit area single excavation length. In specific operation, only the second pilot pit area is locally excavated in each cycle, and the excavation length is controlled within 0.5m to the second pilot pit area single excavation length, which cannot exceed this interval, to ensure that the disturbance intensity generated by each excavation matches the current stable state of the surrounding rock. Multiple cycles are executed in sequence until the cumulative excavation length of the second pilot pit area reaches the advanced excavation amount calculated in step S3. At this time, the second pilot pit area forms an independent advanced tunnel section, which provides a stress release space for the excavation of the first pilot pit area.

[0069] After the excavation of the advanced tunnel section in the second pilot pit area is completed, the initial support operation of the tunnel section is carried out. The support operation needs to be carried out within 2-4 hours after the excavation of the advanced tunnel section is completed, so as to avoid the structural instability caused by the long-time exposure of the surrounding rock. The initial support adopts the combined support form of sprayed concrete, anchor rod and steel arch. The strength grade of the sprayed concrete is C25-C30, the spraying thickness is 100-150 mm, the initial setting time of the concrete during the spraying operation is controlled within 5-10 minutes, and the final setting time is controlled within 15-20 minutes. The anchor rod adopts a threaded steel anchor rod with a diameter of 22-25 mm and a length of 2.5-3.5 m. The anchor rod spacing is 0.8-1.2 m, arranged in a plum blossom shape. The pullout resistance of the anchor rod after installation is not less than 150 kN. The steel arch is processed from I16-I20 I-shaped steel, and the arch spacing is 0.6-1.0 m. The steel arch and the anchor rod are fixed by welding to form an integrated support system. The combined support form closes the surface cracks of the surrounding rock through sprayed concrete, anchors the anchor rod into the interior of the surrounding rock, and provides rigid support through the steel arch. The three work together to offset the deformation stress of the surrounding rock, ensuring the stability of the advanced tunnel section in the second pilot pit area and creating a safe environment for subsequent excavation in the first pilot pit area.

[0070] After the initial support operation of the advanced tunnel section in the second pilot pit area is completed, the excavation operation of the first pilot pit area is carried out. The first pilot pit area also adopts the multi-cycle tunneling method, and the excavation length of each excavation cycle is controlled within the range of 0.5 m to the single tunneling length of the first pilot pit area, forming an orderly connection with the excavation cycle of the second pilot pit area. Unlike the second pilot pit area, the initial support operation of the tunnel section formed by each excavation cycle in the first pilot pit area is carried out immediately after the completion of the cycle. The support form is consistent with that of the second pilot pit area, and the support parameters are adjusted slightly according to the stress level of the surrounding rock in the first pilot pit area (when the stress level is high, the thickness of the sprayed concrete is increased by 10-20 mm, and the spacing of the steel arch is reduced by 0.1-0.2 m). This multi-cycle tunneling method of cycle excavation and support can real-time offset the disturbance of the surrounding rock caused by the excavation of the first pilot pit area, avoiding the accumulation of disturbance leading to the instability of the working face.

[0071] When step S3 determines that the first pilot tunnel area and the second pilot tunnel area can be excavated in any order or synchronously, the construction process is based on efficient excavation and balanced disturbance, and parallel work of the two pilot tunnel areas is organized. If synchronous excavation is adopted, the excavation cycles of the two pilot tunnel areas are started and completed synchronously, and the length of a single excavation cycle of each pilot tunnel area is controlled in the range of 0.5 m to the single excavation length of the first pilot tunnel area and 0.5 m to the single excavation length of the second pilot tunnel area, so as to ensure that the disturbance intensity of the two pilot tunnel areas is balanced and the single-side disturbance is avoided to cause the bias of the tunnel face. If any order excavation is adopted, the first pilot tunnel area or the second pilot tunnel area can be excavated flexibly according to the construction machinery configuration and personnel arrangement, and the length of a single excavation cycle of each pilot tunnel area also follows the above constraints, and the interval time between the excavation of the former pilot tunnel area and the excavation of the latter pilot tunnel area is not more than 6 h, so as to prevent the single-side surrounding rock from being stressed unevenly for a long time.

[0072] Regardless of the excavation order, the support work of the two pilot tunnel areas needs to meet the requirement of timely and stable: in the synchronous excavation mode, after the completion of the excavation cycle of the two pilot tunnel areas, the initial support work of each pilot tunnel area is started synchronously; in the any order excavation mode, after the completion of the support work of the former pilot tunnel area, the excavation work of the latter pilot tunnel area is started. The parameters of all support work are matched with the surrounding rock state of the corresponding pilot tunnel area, the parameter range of the sprayed concrete, the system anchor rod and the steel arch is consistent with the initial support of the second pilot tunnel area, so as to ensure that the support effect is adapted to the bearing demand of the surrounding rock.

[0073] During the whole construction process, the closed-loop updating mechanism runs through the whole process, so as to ensure that the construction parameters can be adjusted in real time with the change of the surrounding rock state. The triggering conditions of the closed-loop updating are divided into two kinds: one is that after each excavation cycle is completed, the updating process is automatically started; the other is that when the change amplitude of the vibration coupling stability index exceeds 10%, the updating process is immediately started, the original acceleration data and the original tunnel face point cloud data in the current excavation process are collected, the new instantaneous vibration amplitude parameter, the instantaneous vibration phase parameter and the structural plane density parameter are extracted; based on the newly extracted parameters, step S2 is executed to calculate the new vibration coupling stability index; according to the new vibration coupling stability index and the instantaneous vibration phase parameter, step S3 is executed to re-determine the excavation order, the single excavation length of the first pilot tunnel area, the single excavation length of the second pilot tunnel area and the advanced excavation amount; finally, based on the new parameters, the excavation and support work of step S4 is continued.

[0074] During the tunnel excavation process, the mechanical state of the surrounding rock will continuously change with the excavation disturbance and stress release, and the original parameters corresponding to the construction decision will gradually deviate from the optimal state. Through periodic or triggered parameter updating, the excavation order, the excavation length and other key construction parameters can always be consistent with the real-time state of the surrounding rock.

[0075] The above is based on the ideal embodiment of the application, through the above description, relevant personnel can make various changes and modifications without deviating from the technical idea of the application. The technical scope of the application is not limited to the content of the specification, and the technical scope must be determined according to the scope of claims.

Claims

1. An improved method of separate highway tunnel portal construction, characterized in that, The method comprises the following steps: S1, collecting original acceleration data and original tunnel face point cloud data in the tunneling process, extracting instantaneous vibration amplitude parameters, instantaneous vibration phase parameters and structural surface density parameters; S2, inputting the instantaneous vibration amplitude parameters, the instantaneous vibration phase parameters and the structural surface density parameters into a vibration coupling stability evaluation model to calculate a vibration coupling stability index; S3, dividing a tunnel tunnel face section into a first pilot pit area and a second pilot pit area according to the vibration coupling stability index and the instantaneous vibration phase parameters, and determining a excavation sequence and a single tunneling length; S4, performing construction on the first pilot pit area and the second pilot pit area based on the excavation sequence and the single tunneling length.

2. The improved separate highway tunnel portal construction method according to claim 1, wherein In step S1, the original acceleration data is collected by piezoelectric acceleration sensors arranged in the surrounding rock area within a range of 3-5 m in front of the tunnel face, with one sensor arranged at each of the upper, middle and lower three horizontal layers of the tunnel section, and the sensors at each layer are spaced 2-3 m apart in the horizontal direction, with a total of 3-5 sensors arranged on the full section; the collection frequency is 100-200 Hz, and the vibration response in three orthogonal directions is captured.

3. The improved separate highway tunnel portal construction method according to claim 2, wherein In step S1, the acquisition of the original tunnel face point cloud data uses a pulse three-dimensional laser scanner, which is placed in a stable area 5-8 m away from the tunnel face during the period after each driving cycle ends and before the next cycle starts; the scanning angle range is 120-150° horizontally and 90-120° vertically, and the point cloud density is 500-800 points / m 2 .

4. The improved separate highway tunnel portal construction method according to claim 2, wherein In step S1, the instantaneous vibration amplitude parameters are extracted by performing band-pass filtering on the original acceleration data, with a filtering frequency range of 5-50 Hz; a fixed time window of 0.5-1.0 s is set, the filtered acceleration data is segmented according to the time window, and the root mean square value of the three-axis acceleration vector sum in each time window is calculated.

5. The improved separate highway tunnel portal construction method according to claim 1, wherein In step S1, the instantaneous vibration phase parameters are extracted by performing frequency domain conversion on the band-pass filtered original acceleration data using fast Fourier transform, with a frequency resolution of 0.1-0.5 Hz, identifying the main vibration frequency, calculating the vibration period, and obtaining the phase parameters based on time difference normalization.

6. An improved separate highway tunnel portal construction method according to claim 1, wherein In step S1, the structural surface density parameters are extracted by denoising the original tunnel face point cloud data, using a combination of statistical filtering and radius filtering; the RANSAC plane fitting algorithm is used to fit the structural surface, and the number of structural surfaces per unit area is counted in a statistical area of 1.0 m x 1.0 m to 2.0 m x 2.0 m.

7. The improved separate highway tunnel portal construction method according to claim 1, wherein In step S2, the mathematical expression of the vibration coupling stability evaluation model is: wherein is the vibration coupling stability index; is the reference coefficient; is the weight coefficient of the instantaneous vibration amplitude parameter; is the instantaneous vibration amplitude parameter; is the weight coefficient of the instantaneous vibration phase parameter; is the instantaneous vibration phase parameter; is the weight coefficient of the structural surface density parameter; is the structural surface density parameter.

8. The improved separate highway tunnel portal construction method according to claim 1, wherein In step S3, the tunnel tunnel face section is divided into the first pilot pit area and the second pilot pit area along the vertical center line, and the horizontal width ratio of the first pilot pit area and the second pilot pit area ranges from 0.8:1 to 1:0.

8.

9. The improved separate highway tunnel portal construction method according to claim 1, wherein In step S3, the excavation sequence is determined by setting a vibration coupling stability threshold value according to the surrounding rock grade; when the vibration coupling stability index is less than or equal to the threshold value, the second pilot pit area is excavated before the first pilot pit area, and the amount of advanced tunneling is calculated; when the vibration coupling stability index is greater than the threshold value, any sequence or synchronous excavation is adopted.

10. The improved separate highway tunnel portal construction method according to claim 9, wherein The calculation formula of the advance excavation quantity is: wherein is a vibration coupling stability threshold value; is a vibration coupling stability index; is a reference cycle excavation length; is an advance quantity amplification coefficient.

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