CN114856579A - Construction Methods for Preventing Rock Burst in Tunnels - Google Patents

Abstract

The application relates to the technical field of tunnel construction, and provides a construction method for preventing tunnel rock burst. The construction method for preventing tunnel rock burst comprises the following steps: acquiring characteristic information of surrounding rocks of a target rockburst section; wherein the feature information includes: ground stress and integrity features; according to the ground stress characteristics, secondary stress distribution of surrounding rocks of the target rockburst section in the tunnel excavation process is obtained; judging the rock burst grade according to the secondary stress distribution of the surrounding rock of the target rock burst section; and combining the rock burst grade with the distribution characteristics of the microcracks to determine the construction measures for preventing the rock burst on site. The scheme provided by the application can pertinently provide corresponding construction measures for preventing rock burst on site.

Description

Construction Methods for Preventing Rock Burst in Tunnels

technical field

The present application relates to the technical field of tunnel construction, in particular, the present application relates to a construction method for preventing tunnel rock bursts.

Background technique

For the response to rockburst, the current technical level generally adopts the conventional step method for excavation for safety reasons, gradually releasing the stress, and strengthening the protection strength of the bolt and the steel mesh. Although the possibility of stress concentration outbreaks is greatly reduced and the safety of tunnel construction is improved, most of the rock bursts occur and then the treatment is carried out according to the intensity of the rock bursts.

Therefore, rockburst prediction is particularly important. Due to the complexity of the problem, the current method system for rockburst prediction is still incomplete. The current rockburst prediction methods can be classified into three categories: the first category is based on various rockburst criteria established according to the mechanism of rockburst occurrence; the second category is rockburst prediction methods based on on-site monitoring data; the third category is based on Methods and tools in related disciplines such as mathematics and systems engineering, established rockburst prediction methods considering the comprehensive influence of various factors. However, the currently provided methods are difficult to prevent the occurrence of rockbursts well.

SUMMARY OF THE INVENTION

In view of the technical problem in the prior art that the occurrence of rock bursts cannot be accurately predicted, the present application provides a construction method for preventing rock bursts in tunnels.

The application provides a construction method for preventing tunnel rock burst, comprising the following steps:

Obtain characteristic information of surrounding rock of the target rockburst section; wherein, the characteristic information includes: in-situ stress characteristics and integrity characteristics;

According to the in-situ stress characteristics, the secondary stress distribution of the surrounding rock of the target rockburst section during the tunnel excavation process is obtained;

According to the secondary stress distribution of the surrounding rock in the target rockburst section, the rockburst grade is judged;

Combining the rock burst grade with the distribution characteristics of micro-cracks, the construction measures to prevent rock burst on site are determined.

In an optional embodiment of one aspect, when the characteristic information is an in-situ stress characteristic, the acquiring characteristic information of the surrounding rock of the rockburst section includes:

According to the drilling depth of the surrounding rock of the target rockburst section, obtain the plane maximum principal stress value, the plane minimum principal stress value and the plane maximum principal stress direction, and obtain the maximum level at the maximum buried depth of the surrounding rock of the target rockburst section In-situ stress value, minimum horizontal principal stress value and vertical principal stress value.

In an optional embodiment of one aspect, the obtaining of the secondary stress distribution of the surrounding rock of the target rockburst section during the tunnel excavation process according to the in-situ stress characteristics includes:

A calculation model is established in the finite element program, the tunnel section of the tunnel is placed in the calculation model, and the shape of the tunnel section is preset; wherein, the tunnel section includes the sections located at the top, side walls, bottom, and inside the rock mass. Corresponding observation points are set up on the right side and at the top of the rock mass;

According to the maximum horizontal in-situ stress value, the minimum horizontal principal stress value and the vertical principal stress value at the maximum buried depth of the surrounding rock of the target rockburst section, the secondary stress distribution model for each observation point of each roadway section is obtained.

In an optional embodiment of one aspect, the acquiring a quadratic stress distribution model for each observation point of each of the roadway sections includes:

Determine the initial roadway section on the tunnel, take the initial roadway section as the starting point, obtain the stress values of all observation points of each of the roadway sections on the equidistant excavation length, and obtain the stress value of the observation point Secondary stress distribution information with corresponding excavation depth.

In an optional embodiment of one aspect, the feature information includes rock mass strength;

According to the secondary stress distribution of the surrounding rock of the target rockburst section, judging the rockburst grade, including:

According to the secondary stress distribution information and the rock mass strength of the surrounding rock of the target rock burst section, the corresponding rock burst grade is obtained.

In an optional embodiment of one aspect, when the feature information is an integrity feature, the acquiring feature information of the surrounding rock of the rockburst section includes:

According to the rock type of the surrounding rock of the target rockburst section and the physical state of the sample, the corresponding saturated uniaxial compressive strength and dry compressive strength are obtained, and the overall tunnel excavation position of the surrounding rock of the target rockburst section is obtained. Integrity features.

In an optional embodiment of one aspect, the construction measures for preventing rock bursts on site are determined in combination with the distribution characteristics of micro-cracks, including:

According to the integrity characteristics, the secondary stress is loaded into the corresponding tunnel excavation model including the fracture network, and the micro-crack distribution characteristics of the surrounding rock during excavation and unloading are obtained;

According to the distribution characteristics of the micro-cracks, the damage degree of the surrounding rock caused by the excavation is predicted, and the construction measures for preventing rock bursts on site are determined.

In an optional embodiment on the one hand, the described construction method for preventing tunnel rockburst further comprises:

According to the distribution characteristics of the micro-cracks, the damage degree of the surrounding rock caused by the excavation is predicted, and the quantitative effect of reducing the micro-cracks in the surrounding rock micro-rock excavated by the upper and lower steps is calculated according to the damage degree of the surrounding rock.

In an optional embodiment on the one hand, the described construction method for preventing tunnel rockburst further comprises:

The microseismic signal of the tunnel face is obtained, the corresponding rockburst grade is determined, and the construction measures for preventing rockburst on the site are corrected.

In an optional embodiment on the one hand, the rockburst grades determined by the microseismic signal are compared with the rockburst grades determined by the secondary stress distribution of the surrounding rock in the target rockburst section, and the rockburst grade with the highest grade is used as the The current predicted rockburst grade of the surrounding rock of the target rockburst segment.

The construction method for preventing tunnel rock burst provided by the application has the following beneficial effects:

Based on the construction method for preventing tunnel rockburst provided by this application, the surrounding rock of the target rockburst section is selected as the prediction and evaluation object for rockburst prediction, and characteristic information such as its in-situ stress characteristics and integrity characteristics is obtained, and the According to the stress characteristics, the secondary stress distribution of the surrounding rock of the target rockburst section during the tunnel excavation process can be obtained, so as to judge the corresponding rockburst grade. In addition, according to the distribution characteristics of the micro-cracks in the surrounding rock of the target rockburst section, the damage degree of the surrounding rock caused by the excavation is predicted, so as to determine the construction measures to prevent rockburst on site. Based on the tunnel rockburst prevention construction scheme, the technical problem in the prior art that the occurrence of rockburst cannot be predicted accurately can be overcome, thereby realizing the secondary stress distribution that can be obtained by combining the characteristic information of the surrounding rock of the target rockburst section. Combined with the distribution characteristics of micro-cracks, it is possible to predict the tunnel rockburst more comprehensively, and determine the corresponding preventive construction measures, from accurately preventing the occurrence of rockburst, so as to provide the corresponding on-site prevention of rockburst in a targeted manner. construction measures. Compared with the excavation of the step method, the rock parameters can be accurately predicted to reduce the material consumption of the advance support and the construction time of the advance support, and because the optimized surrounding rock parameters are used, the installation of the rigid support is reduced. The construction time has been improved, and the construction progress has been improved.

Additional aspects and advantages of the present application will be set forth in part in the following description, which will be apparent from the following description, or learned by practice.

Description of drawings

The above and/or additional aspects and advantages will become apparent and readily understood from the following description of embodiments taken in conjunction with the accompanying drawings, wherein:

1 is a schematic flowchart of a construction method for preventing tunnel rock burst provided by an embodiment of the application;

Fig. 2 is a three-dimensional schematic diagram of a calculation model provided by an embodiment of the present application;

3 is a schematic diagram of the in-situ stress at different observation points of the same section of the calculation model provided by an embodiment of the application;

4a is a schematic three-dimensional schematic diagram of stress at the top surrounding rock D of a section of a calculation model provided by an embodiment of the application;

4b is a schematic three-dimensional schematic diagram of stress at the side wall surrounding rock E of a section of a calculation model provided by an embodiment of the application;

4c is a schematic three-dimensional schematic diagram of stress of the top unit A of a section of a calculation model provided by an embodiment of the application;

4d is a schematic three-dimensional schematic diagram of the stress of the side wall unit B of a section of a calculation model provided by an embodiment of the application;

4e is a schematic three-dimensional schematic diagram of the stress of the bottom unit C of a section of a calculation model provided by an embodiment of the application;

5 is a schematic diagram of the stress perspective of the difference between the vertical stress and the horizontal stress of the top unit A, the side wall unit B and the bottom unit C of a section of the calculation model provided by an embodiment of the application.

Detailed ways

The present application will be further described below with reference to the accompanying drawings and exemplary embodiments, wherein like numerals in the drawings refer to like parts throughout. Also, if a detailed description of the known art is not necessary to illustrate the features of the present application, it will be omitted.

Referring to FIG. 1 , FIG. 1 is a schematic flowchart of a construction method for preventing tunnel rock burst provided by an embodiment of the present application.

The present application provides a construction method for preventing rockbursts in tunnels, which can solve the technical problem in the prior art that the occurrence of rockbursts cannot be accurately prevented.

The construction method for preventing tunnel rock burst includes the following steps:

S110. Obtain characteristic information of the surrounding rock of the target rockburst segment; wherein, the characteristic information includes: in-situ stress characteristics and integrity characteristics;

S120, obtaining secondary stress distribution of surrounding rock of the target rockburst section in the process of tunnel excavation according to the in-situ stress characteristics;

S130, according to the secondary stress distribution of the surrounding rock of the target rockburst section, determine the rockburst grade;

S140, combining the distribution characteristics of micro-cracks, determine construction measures to prevent rock bursts on site.

In the process of the above steps S110 to S140, according to the data of the preliminary exploration, the in-situ stress test data for each rockburst section in the tunnel area is obtained. In order to better describe the implementation plan clearly. In the following embodiments, the description is made with respect to a rockburst prediction method for surrounding rock of a target rockburst section.

Before step S110, the surrounding rock of the target rockburst section is explored and drilled, and the measurement is performed to obtain characteristic information of the surrounding rock of the target rockburst section. In this embodiment, the surrounding rock feature information of the target rockburst section includes: in-situ stress feature and integrity feature.

Among them, the in-situ stress characteristic is to measure the internal stress effect of the surrounding rock of the target rockburst section. The in-situ stress feature, during tunnel excavation, may include secondary stress. The secondary stress refers to the normal stress or shear stress required to satisfy the external constraint conditions or the structural self-deformation continuous condition.

The integrity feature is used to measure the development degree of various geological interfaces dominated by fractures in the rock body. Few cracks means good rock mass integrity, while more cracks mean rock mass integrity is poor.

In the process of tunnel excavation, in order to evaluate the surrounding rock of the target rockburst section more comprehensively, in this embodiment, for the surrounding rock of the target rockburst section, especially in the area of the tunnel to be excavated, different areas are set. multiple observation points. In the process of acquiring the characteristic information of the surrounding rock of the target rockburst section, the in-situ stress characteristic of each observation point may be acquired. And according to the in-situ stress characteristics of each observation point, the secondary stress distribution of the surrounding rock in the target rockburst section during the tunnel excavation process is obtained.

According to the secondary stress distribution obtained above, the rockburst level of the surrounding rock of the target rockburst section is evaluated to obtain the corresponding rockburst level. In addition, according to the distribution characteristics of the micro-cracks in the surrounding rock of the target rockburst section, the damage degree of the surrounding rock caused by the excavation is predicted, so as to determine the construction measures to prevent rockburst on site.

Based on the construction method for preventing tunnel rockburst provided by this application, the surrounding rock of the target rockburst section is selected as the prediction and evaluation object for rockburst prediction, and characteristic information such as its in-situ stress characteristics and integrity characteristics is obtained, and the According to the stress characteristics, the secondary stress distribution of the surrounding rock of the target rockburst section during the tunnel excavation process can be obtained, so as to judge the corresponding rockburst grade. In addition, according to the distribution characteristics of the micro-cracks in the surrounding rock of the target rockburst section, the damage degree of the surrounding rock caused by the excavation is predicted, so as to determine the construction measures to prevent rockburst on site. Based on the tunnel rockburst prevention construction scheme, the technical problem in the prior art that the occurrence of rockburst cannot be predicted accurately can be overcome, thereby realizing the secondary stress distribution that can be obtained by combining the characteristic information of the surrounding rock of the target rockburst section. Combined with the distribution characteristics of micro-cracks, it is possible to predict the tunnel rockburst more comprehensively, and determine the corresponding preventive construction measures, from accurately preventing the occurrence of rockburst, so as to provide the corresponding on-site prevention of rockburst in a targeted manner. construction measures. Compared with the excavation of the step method, the rock parameters can be accurately predicted to reduce the material consumption of the advance support and the construction time of the advance support, and because the optimized surrounding rock parameters are used, the installation of the rigid support is reduced. The construction time has been improved, and the construction progress has been improved.

When the feature information provided based on the above-mentioned embodiments is the geostress feature, step S110 includes:

According to the drilling depth of the surrounding rock of the target rockburst section, obtain the plane maximum principal stress value, the plane minimum principal stress value and the plane maximum principal stress direction, and obtain the maximum level at the maximum buried depth of the surrounding rock of the target rockburst section In-situ stress value, minimum horizontal principal stress value and vertical principal stress value.

The surrounding rock of the target rockburst section is explored and drilled, and the measurement is carried out to obtain the characteristic information of the surrounding rock of the target rockburst section. In this embodiment, the surrounding rock feature information of the target rockburst section includes: in-situ stress feature and integrity feature.

Based on the above embodiment, the surrounding rock of the target rockburst section is explored and drilled, the hole depth of the drilled hole in the surrounding rock of the target rockburst section is determined, and the corresponding in-situ stress data is measured by the drilled hole.

In the present embodiment, description is made by taking a borehole data involved in the tunnel excavation project as the characteristic information corresponding to the surrounding rock of the target rockburst section and the data involved in the construction method.

The depth of the drilled hole is in the range of 445.5 to 473.4 m. For the convenience of subsequent data processing, the depth of the drilled hole is fixed at 450 m. For the surrounding rock of the target rockburst section, the obtained measurement data include: the maximum plane principal stress value is between 8.24 and 12.15MPa, the plane minimum principal stress is between 6.41 and 8.95, and the plane maximum principal stress direction is 115 to 1180 MPa. , the maximum principal stress is the self-weight stress (the bulk density is taken as 2660kg/m3). The maximum burial depth of the tunnel where the surrounding rock of the target rockburst section is located reaches 650m.

Since the location of the drilling hole is not at the maximum buried depth, the in-situ stress of the tunnel with the maximum buried depth is determined by extrapolation based on safety considerations. The in-situ stress of the maximum buried depth tunnel includes:

The maximum horizontal ground stress at the maximum buried depth: 11.45*650/450=16.53Mpa

The minimum horizontal principal stress is: 8.85*650/450=12.78Mpa

Vertical principal stress: 650*2.66=17.29Mpa

For the above, according to the in-situ stress characteristics, the secondary stress distribution of the surrounding rock of the target rockburst section during the tunnel excavation process is obtained, which may further include:

A calculation model is established in the finite element program, the tunnel section of the tunnel is placed in the calculation model, and the shape of the tunnel section is preset; wherein, the tunnel section includes the sections located at the top, side walls, bottom, and inside the rock mass. Corresponding observation points are set up on the right side and at the top of the rock mass;

According to the maximum horizontal in-situ stress value, the minimum horizontal principal stress value and the vertical principal stress value at the maximum buried depth of the surrounding rock of the target rockburst section, the secondary stress distribution model for each observation point of each roadway section is obtained.

Referring to FIGS. 2-3 , FIG. 2 is a three-dimensional schematic diagram of a calculation model provided by an embodiment of the application, and FIG. 3 is a schematic diagram of in-situ stress at different observation points of the same section of the calculation model provided by an embodiment of the application.

In this embodiment, the finite element program is a FLAC3D finite element program, and a calculation model with a size of 50m×50m×30m is established in the FLAC3D finite element program. Place the tunnel section of the tunnel at the center of the calculation model, and set the tunnel section as a horseshoe shape. The bottom boundary of the calculation model is a fixed displacement constraint, and a certain surface pressure load is applied to the left and right sides, the front and rear sides and the upper surface. The magnitude of the load depends on the actual ground stress level. Set the maximum horizontal stress perpendicular to the tunnel axis.

Referring to Fig. 3, taking the top unit A, side wall unit B, bottom unit C, right unit E and top unit D of the tunnel section as observation points, the horizontal stress, tunnel axial stress and Variation of vertical stress with advance of excavation face. Refer to Figures 4a-4d for the schematic diagram of the force at each observation point. Wherein, in this embodiment, each excavation length is 3m. In this embodiment, an initial roadway section is determined on the tunnel, and the initial roadway section is used as a starting point to obtain stress values of all observation points of each of the roadway sections along the equidistant excavation length.

Fig. 4a is a three-dimensional schematic diagram of the stress at the top surrounding rock D of a section of the calculation model provided by an embodiment of the application, and Fig. 4b is the side wall surrounding rock of a section of the calculation model provided by an embodiment of the application The three-dimensional schematic diagram of the stress at E, FIG. 4c is the three-dimensional schematic diagram of the stress of the top unit A of a section of the calculation model provided by an embodiment of the application, and FIG. 4d is a section of the calculation model provided by an embodiment of the application. Figure 4e is a three-dimensional schematic diagram of the stress of the bottom unit C of a section of the calculation model provided by an embodiment of the application.

As shown in Fig. 4a-4b, when the excavation surface is far from the observation point, the stress in the three directions of the rock mass at the top of the tunnel or near the side of the tunnel is less affected by the excavation and is basically in the initial state of in-situ stress.

Comparing Fig. 4c-4e, when the excavation face is far away from the observation point, the rock mass near the observation face is in the initial state of in-situ stress. As the excavation face continues to advance, the front of the excavation face is about 3 m, the stress state of each observation point begins to change. The tangential stress of the rock mass at the top and bottom of the tunnel gradually increased, the radial stress gradually decreased to 0, and the axial stress fluctuated to a certain extent under the action of excavation and unloading, and finally remained basically unchanged. The three-direction stress of the rock mass of the roadway wall and sidewall decreased to varying degrees, and the decrease of the radial stress was much greater than that of the tangential stress. When the distance behind the excavation face exceeds the observation face by 3-5 meters, the stress state of the surrounding rock of the roadway tends to be stable again after adjustment.

Referring to FIG. 5 , FIG. 5 is a schematic perspective view of the stress of the difference between the vertical stress and the horizontal stress of the top unit A, the side wall unit B and the bottom unit C of a section of the calculation model provided by an embodiment of the application.

The stress change trend in Fig. 5 is the representation of the respective vertical stress and horizontal stress of the corresponding top unit A, side wall unit B and bottom unit C according to Fig. 4c-4e, and the difference between the vertical stress and the horizontal stress is obtained. Trends that vary with excavation.

In Figure 5, as the excavation face moves forward, the stress difference between the top and bottom elements of the tunnel at the observation face gradually increases significantly, while the stress difference between the tunnel side wall elements gradually decreases. It shows that under this in-situ stress state of the roadway section, the tangential stress of the surrounding rock at the top and bottom of the roadway before and after excavation is loaded to a higher level, the radial stress is unloaded to zero, and the surrounding rock is gradually divided from a relatively uniform three-dimensional stress state. The differential evolution is a two-dimensional stress state; while the surrounding rock of the roadway side wall is in the stress unloading area after excavation, and the stress concentration is weak.

Input the stress value obtained above into the calculation model established in the FLAC3D finite element program to form a secondary stress distribution model of the stress value at the observation point and the corresponding excavation depth. From the secondary stress distribution model, get Tunnel excavation unloads the stress generated in the surrounding rock. This stress includes:

Maximum principal stress: σ _max =37.22MPa

Maximum tangential stress: σ _θ = 27.73MPa

Maximum axial stress: σ _L =11.41MPa

In the above embodiment, the feature information further includes: rock mass strength, on this basis, step S130 may further include:

According to the secondary stress distribution information and the rock mass strength of the surrounding rock of the target rock burst section, the corresponding rock burst grade is obtained.

Wherein, the rock mass strength includes rock uniaxial compressive strength Rc.

According to the stress criterion of rockburst prediction, the rockburst grade corresponding to each stress criterion is obtained, as shown in Table 1.

Table 1 Stress criteria for rockburst prediction

Note: R _c is the uniaxial compressive strength of rock, σ _max is the maximum principal stress, σ _θ is the maximum tangential stress, and σ _L is the axial stress.

For the surrounding rock of the target rockburst section, according to the sample depth of the surrounding rock, the physical state of the sample and the rock type, the uniaxial compressive strength Rc of the rock is obtained.

In this embodiment, the depth of the sample is the drilling depth, that is, the depth of the sample is 450m, the rock type is granite, and the physical state of the sample is saturated, so the corresponding rock uniaxial compressive strength Rc=50Mpa.

According to Table 1, from the numerical calculation results, the section of the surrounding rock of the target rockburst section at the maximum buried depth of the tunnel (650 meters) is only judged to have weak rockburst risk by Tao Zhenyu criterion.

When the feature information is an integrity feature, the obtaining feature information of the surrounding rock of the rockburst section includes:

According to the rock type of the surrounding rock of the target rockburst section and the physical state of the sample, the corresponding saturated uniaxial compressive strength and dry compressive strength are obtained, and the overall tunnel excavation position of the surrounding rock of the target rockburst section is obtained. Integrity features.

According to the sample depth of the surrounding rock and the physical state and rock type of the sample, the dry compressive strength is also obtained as 130Mpa, and the corresponding integrity characteristic is between 0.25-0.6, that is, the integrity is poor.

In this embodiment, the secondary stress distribution information of the surrounding rock of the tunnel obtained in the above-mentioned embodiment is loaded into the tunnel excavation model including the fracture network established by the discrete element software, and the micro-cracks of the surrounding rock during excavation and unloading are obtained. According to the distribution characteristics of micro-cracks, the damage degree of surrounding rock caused by excavation is predicted. According to the damage degree of the surrounding rock, the quantitative effect of reducing the micro-cracks in the surrounding rock micro-rock excavated by the upper and lower steps is calculated, and the construction measures to prevent rock burst on site are determined in combination with the rock burst grade.

Determine the construction measures to prevent rock bursts on site. In this embodiment, the discrete element software is PFC2D.

After step S140, the present application may further include:

Obtain the microseismic signal of the tunnel face to determine the corresponding rockburst level;

According to the rockburst grade and the rockburst grade, corresponding construction measures for preventing rockburst on site are determined.

For installing the sensor of the microseismic monitoring system on the face of the tunnel. The sensor can be installed in a borehole with a hole depth of 2.5m, a hole diameter of 40mm and a height of 1.5m from the ground. One row of sensors is installed about 70m away from the face of the tunnel, and two rows of sensors are installed at an interval of 30m. The last row of sensors is moved forward every 30m with the excavation. In this way, the monitoring equipment moves closely with the face of the tunnel to achieve 24h. Monitor the information of microseisms caused by rock mass rupture near the face during tunnel construction.

In this embodiment, the energy criterion of the microseismic signal is used to discriminate the rockburst. In principle, the number of effective microseismic events within 24 hours should reach 20. When the number of microseismic events in the energy range of each level exceeds 3, it is considered that a rockburst will occur. Rockburst of this level. The energy criteria for judging rockbursts for the microseismic signals are shown in Table 2:

Table 2 Stress criteria for rockburst prediction

In the process of excavation, take the set position of the face on the first day as the initial position, and take the position of the face on the 12th day as the end position. Since the rock mass is in a state of three-dimensional stress balance, very few micro-fractures occur, but with the blasting and excavation destroying the initial stress field, the stress begins to shift and adjust, resulting in a large number of micro-fractures, and a large number of micro-seismic signals. The advancement of the sub-surface shows a changing law of continuous advancement along the tunnel axis. When the stress reaches the secondary equilibrium, the micro-fractures in the rock mass decrease, so the phenomenon that the micro-seismic signal continues to advance with the advancement of the face.

Comparing the judgment conclusion of the energy criterion of microseismic signal for judging rockburst with the actual rockburst situation, if the actual rockburst occurs for a time length less than the judgment conclusion, and the rockburst intensity is also less than or equal to the rockburst intensity of the judgment conclusion, The predicted rockburst level is lower than the rockburst level corresponding to the judgment conclusion; if the actual rockburst occurrence time length and/or rockburst intensity is equal to/or higher than the judgment conclusion, the predicted rockburst level is higher than Determine the rockburst grade corresponding to the conclusion.

The rockburst grades judged by the microseismic signal are compared with the rockburst grades judged by the secondary stress distribution of the surrounding rock of the target rockburst section, and the rockburst grade with a higher grade is used as the current predicted rockburst grade of the surrounding rock of the target rockburst section. Rockburst grades, so as to ensure that the corresponding on-site construction measures to prevent rockbursts can maximize the construction measures to prevent rockbursts.

The corresponding construction measures to prevent rockburst can be divided into three grades according to the characteristics and related properties of rockburst. Weak rockburst, moderate rockburst, strong rockburst. Among the three grades, weak rock bursts have minimal impact on construction, and basically do not pose a threat to personnel and machinery. In actual construction, no special measures are required to deal with them. Based on the idea of strengthening the surrounding rock, the overall support method of steel support and shotcrete-anchor-net (reinforced mesh) is often used to support the medium rock burst section of the tunnel. During the construction process According to the actual situation, passive temporary support measures such as protective nets may also be used; strong rock bursts are extremely dangerous, and various auxiliary measures (such as advanced stress construction release holes, etc.) should be used to weaken the surrounding rock while strengthening the support. , reducing the frequency and energy of rock bursts.

It should be understood that although the various steps in the flowchart of the accompanying drawings are sequentially shown in the order indicated by the arrows, these steps are not necessarily executed in sequence in the order indicated by the arrows. Unless explicitly stated herein, the execution of these steps is not strictly limited to the order and may be performed in other orders. Moreover, at least a part of the steps in the flowcharts of the accompanying drawings may include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but may be executed at different times, and the execution sequence is also It does not have to be performed sequentially, but may be performed alternately or alternately with other steps or at least a portion of sub-steps or stages of other steps.

The above description is only a preferred embodiment of the present application and an illustration of the applied technical principles. Those skilled in the art should understand that the scope of disclosure involved in this application is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, and should also cover, without departing from the above-mentioned disclosed concept, the technical solutions made of the above-mentioned technical features or Other technical solutions formed by any combination of its equivalent features. For example, a technical solution is formed by replacing the above features with the technical features disclosed in this application (but not limited to) with similar functions.

Claims (10)

1. A construction method for preventing tunnel rock burst is characterized by comprising the following steps:

acquiring characteristic information of surrounding rocks of a target rockburst section; wherein the feature information includes: ground stress and integrity features;

according to the ground stress characteristics, secondary stress distribution of surrounding rocks of the target rockburst section in the tunnel excavation process is obtained;

judging the rock burst grade according to the secondary stress distribution of the surrounding rock of the target rock burst section;

and combining the rock burst grade with the distribution characteristics of the microcracks to determine the construction measures for preventing the rock burst on site.

2. The construction method for preventing tunnel rockburst according to claim 1,

when the characteristic information is the ground stress characteristic, the characteristic information of the surrounding rock of the rockburst section is obtained, and the method comprises the following steps:

and acquiring a plane maximum principal stress value, a plane minimum principal stress value and a plane maximum principal stress direction according to the drilling depth of the target rockburst section surrounding rock, and acquiring a maximum horizontal ground stress value, a minimum horizontal principal stress value and a vertical principal stress value at the position of the maximum burial depth of the target rockburst section surrounding rock.

3. The construction method for preventing tunnel rockburst according to claim 2,

according to the ground stress characteristics, the secondary stress distribution of the target rock burst section surrounding rock in the tunnel excavation process is obtained, and the method comprises the following steps:

establishing a calculation model in a finite element program, placing the tunnel section of the tunnel in the calculation model, and presetting the shape of the tunnel section; the roadway section comprises observation points which are arranged at the top, the side wall, the bottom, the right side in the rock body and the top in the rock body and correspond to each other;

and acquiring a secondary stress distribution model of each roadway section to each observation point according to the maximum horizontal ground stress value, the minimum horizontal main stress value and the vertical main stress value at the maximum burial depth of the surrounding rock of the target rockburst section.

4. The construction method for preventing tunnel rockburst according to claim 3,

the acquiring of the secondary stress distribution model of each roadway section to each observation point includes:

determining an initial roadway section on the tunnel, taking the initial roadway section as a starting point, acquiring stress values of all observation points of each roadway section in the equidistant excavation length, and acquiring secondary stress distribution information of the stress values of the observation points and the corresponding excavation depth.

5. The construction method for preventing tunnel rockburst according to claim 4,

the characteristic information comprises rock mass strength;

and judging the rock burst grade according to the secondary stress distribution of the surrounding rock of the target rock burst section, and the judging method comprises the following steps:

and obtaining the corresponding rock burst grade according to the secondary stress distribution information and the rock mass strength of the surrounding rock of the target rock burst section.

6. The construction method for preventing tunnel rockburst according to claim 2,

when the characteristic information is the integrity characteristic, the characteristic information of the surrounding rock of the rockburst section is obtained, and the method comprises the following steps:

and acquiring corresponding saturated uniaxial compressive strength and dry compressive strength according to the rock type of the target rock burst section surrounding rock and the physical state of the sample, and obtaining the integral integrity characteristic of the tunnel excavation position of the target rock burst section surrounding rock.

7. The construction method for preventing tunnel rockburst according to claim 6,

the construction measures for preventing the rock burst on site are determined by combining the distribution characteristics of the microcracks, and the construction measures comprise the following steps:

loading the secondary stress to a corresponding tunnel excavation model containing a fracture network according to the integrity characteristics to obtain micro-fracture distribution characteristics of the surrounding rock during excavation and unloading;

and predicting the damage degree of the surrounding rock caused by excavation according to the micro-crack distribution characteristics, and determining the construction measures for preventing rock burst on site.

8. The construction method for preventing tunnel rock burst according to claim 7, further comprising:

and predicting the damage degree of the surrounding rock caused by excavation according to the micro-crack distribution characteristics, and calculating the quantitative effect of reducing the micro-cracks in the surrounding rock micro-rocks excavated by adopting the upper step and the lower step according to the damage degree of the surrounding rock.

9. The construction method for preventing tunnel rock burst according to claim 1, further comprising:

and acquiring microseismic signals of the tunnel face of the tunnel, judging the corresponding rock burst grade, and correcting the construction measures for preventing the rock burst on site.

10. The construction method for preventing tunnel rockburst according to claim 9,

and comparing the rock burst grade obtained by judging the microseismic signal with the rock burst grade obtained by judging the secondary stress distribution of the surrounding rock of the target rock burst section, and taking the rock burst grade with high grade as the currently predicted rock burst grade of the surrounding rock of the target rock burst section.

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