CN105807321A - Rock mass structure analysis and electromagnetic radiation monitoring combined rock burst prediction method - Google Patents

Abstract

The invention relates to a rockburst prediction method combining rock mass structure analysis and electromagnetic radiation monitoring. Aiming at the shortcomings of the existing rockburst prediction methods, this method proposes a rockburst prediction method in the construction stage that is easy to grasp and widely used by on-site construction technicians, and combines rock mass structure analysis and electromagnetic radiation monitoring; wherein, "rock mass structure "Analysis" mainly conducts a preliminary prediction of whether rockburst may occur in the rock mass in the prediction area; "Electromagnetic radiation monitoring" conducts electromagnetic radiation monitoring on the area where rockburst may occur on the basis of "rock mass structure analysis". The loading degree of rock mass, energy conversion and micro-fracture further predict whether rockburst will occur and the intensity of rockburst. The method of the invention does not need to carry out a large number of ground stress tests and numerical calculations, uses portable monitoring instruments, has low cost and little interference to construction.

Description

Rock Burst Prediction Method Combining Rock Mass Structure Analysis and Electromagnetic Radiation Monitoring

technical field

The invention belongs to the technical field of tunnels and underground engineering, and in particular relates to a comprehensive rockburst prediction method during the construction of tunnels and underground caverns, in particular to a rockburst prediction method combining rock mass structure analysis and electromagnetic radiation monitoring.

Background technique

Rockburst is a phenomenon in which the surrounding rock undergoes brittle failure due to excavation and unloading during the excavation of underground caverns under high stress conditions, and the elastic strain energy stored in the rock mass is suddenly released, resulting in bursting, loosening, spalling, ejection or even throwing. A dynamical instability geological disaster. It directly threatens the safety of construction personnel and machines, affects the progress of construction, and even causes machine crashes and fatal accidents in severe cases. It is of great significance for the construction of tunnels and underground caverns in rockburst areas to avoid or reduce the hazards of rockbursts by using appropriate methods to predict rockbursts, and on this basis to take targeted prevention and control measures for sections and locations where rockbursts may occur.

The rockburst prediction of tunnels and underground caverns is generally divided into two stages: design and construction. Rockburst prediction in the design stage is mostly based on engineering geological survey data, combined with a small number of drilled in-situ stress data and rock test data, using existing criteria (such as the Barton criterion, Hoek criterion, and Russense criterion commonly used at home and abroad). , Turchaninov criterion, etc.) macroscopically predict the possibility of rockburst occurrence and rockburst level in each section of the underground cavern.

For rockburst prediction during the construction stage, there are currently four common methods at home and abroad: 1. With the excavation of underground caverns, necessary in-situ stress tests and rock tests are carried out, and rockbursts are predicted using existing criteria; 2. 1. On the basis of the aforementioned first method, establish the geological model and numerical model of the area where the underground cavern is located, and predict it according to the numerical calculation results and existing rockburst criteria; 3. As the construction progresses, near the tunnel face Carry out acoustic emission and microseismic monitoring, and predict rockburst based on the monitoring results; 4. The above-mentioned first (or second) method is combined with the third method to predict rockburst.

The patents applied in recent years, such as application number 201210210661.8 (name: comprehensive prediction of rockburst in near-horizontal rock formations in high ground stress areas) belong to the second method above; application number 201520202367.1 (name: a rockburst precursor warning system based on acoustic emission ), application number 201310740727.9 (name: a method for identifying key points of microseismic monitoring and early warning of rockburst disasters) belongs to the third method above.

Due to the one-sidedness and limitations of the current rockburst criteria and grading standards, and the complexity of geological conditions and the fact that the measured in-situ stress of a small number of boreholes cannot reflect the specific conditions of each section of the underground cavern, the macroscopic analysis of rockburst in the design stage Forecasting is not a good guide for construction. In the construction stage, it is very important and necessary to further predict the rockburst in front of the construction in combination with the actual site conditions, adjust the design based on this, guide the construction, ensure construction safety, and reasonably arrange the construction progress.

In order to ensure the prediction accuracy, the rockburst prediction methods in the first and second construction phases above require a large number of in-situ stress tests and numerical calculations. In-situ stress testing and numerical calculation is a highly specialized work that requires high-level professional and technical personnel to complete. In addition, the cost of in-situ stress testing is relatively high, and it also takes up a certain amount of construction time. Therefore, it is inconvenient for on-site construction technicians to master and commonly used.

The construction site environment of tunnels and underground caverns is complex, with noisy construction machinery and manual operations, frequent vibrations, rich in sound waves and vibrations of various frequency components, and a lot of test interference, which brings great potential for accurate analysis of acoustic emission and microseismic monitoring results. There were many difficulties. In addition, acoustic emission and microseismic monitoring require the sensor to be well coupled with the surrounding rock, which is also difficult at the construction site; multiple fixed sensors and data acquisition instruments in the acoustic emission and microseismic monitoring system need to be connected through communication cables. Sensors are also vulnerable to damage during blasting construction.

The main purpose of the present invention is to provide a rockburst prediction method in the construction stage that is easy to grasp and widely used by on-site construction technicians for the deficiencies of the existing rockburst prediction methods. This method does not require a large number of in-situ stress tests and numerical calculations, uses portable monitoring instruments, and has low cost and little interference to construction.

Contents of the invention

The object of the present invention is to provide a rockburst prediction method combining rock mass structure analysis and electromagnetic radiation monitoring. Monitoring instrument, low cost and little interference to construction.

In order to achieve the above object, the technical solution of the present invention is: a rockburst prediction method combining rock mass structure analysis and electromagnetic radiation monitoring, comprising the following steps,

Step S1: During the construction process, based on the structural conditions of the rock mass in which the rockburst occurred, and based on the observation of the face of the face and its vicinity, including lithology, grade of surrounding rock, and occurrence of the structural face, preliminarily judge whether the front of the face of the face is possible Rockburst occurrence and the type of rockburst that occurred;

Step S2: Conduct electromagnetic radiation monitoring on the rockburst-probable part of the rockburst preliminarily judged in step S1, and further analyze whether the monitored value of electromagnetic radiation energy, intensity, and pulse are compared with the reference value. a rockburst will occur;

Step S3: Record the location where the rockburst occurs during the construction process, including lithology, surrounding rock level, structural surface occurrence, group number, spacing, location and degree of rockburst occurrence, and statistically analyze to obtain the rock mass where the rockburst occurred Structural conditions and possible locations of rockbursts shall be continuously corrected and improved;

Step S4: On the basis of on-site monitoring of severe rockburst sections, through the comparison and analysis of the monitoring value and the actual occurrence of rockburst, the predicted values of rockburst monitoring at all levels based on electromagnetic radiation monitoring are obtained, and are continuously revised and improved;

Step S5: By repeatedly executing the above steps S1-S4, the purpose of improving the accuracy of rockburst prediction is achieved.

In one embodiment of the present invention, the rock mass structural conditions for rockburst occurrence include lithology and surrounding rock level conditions at the rockburst occurrence site, and the occurrence, group number, and spacing conditions of the structural plane at the rockburst occurrence site.

In an embodiment of the present invention, in the step S2, the electromagnetic radiation monitoring is carried out on the possible rockburst locations through a portable electromagnetic radiation instrument.

Compared with the prior art, the present invention has the following beneficial effects:

1. Compared with the existing method of rockburst prediction through in-situ stress test, rock mechanics test and numerical calculation, this method has low cost and easy on-site construction technology because it does not need to carry out a large number of in-situ stress tests and numerical calculations. Advantages of human mastery and universal application;

2. Compared with acoustic emission and microseismic monitoring, electromagnetic radiation is not affected by construction vibration and noise; in addition to low cost, electromagnetic radiation monitoring can also use portable monitoring instruments to carry out synchronously with blasthole charging after drilling on site. Therefore, There is no need to occupy construction work time; in addition, since there are no other electrical equipment near the blasthole surface except for lighting electricity when charging the blasthole, there is less test interference;

3. Acoustic emission, microseismic, and electromagnetic radiation monitoring all have multiple solutions; the method of combining rock mass structure analysis and electromagnetic radiation monitoring comprehensively considers the main factors and The rock mass microfracture and energy release during the rockburst breeding process improve the prediction accuracy; practice has proved that it is a feasible method for rockburst prediction during construction.

Description of drawings

Fig. 1 is the monitoring point of electromagnetic radiation when rockburst is prone to occur in the arch top to arch waist section of the present invention.

Fig. 2 is a curve diagram of the dynamic change of the electromagnetic radiation intensity of the MK51+357.4 section vault of the present invention.

Fig. 3 is a curve diagram of the dynamic change of electromagnetic radiation energy of the MK51+357.4 section vault of the present invention.

Figure 4 is the rockburst diagram after the first cycle blasting.

Fig. 5 is the rockburst map after the second cycle blasting.

detailed description

The technical solution of the present invention will be specifically described below in conjunction with the accompanying drawings.

A rockburst prediction method combining rock mass structure analysis and electromagnetic radiation monitoring of the present invention comprises the following steps,

Step S1: During the construction process, based on the structural conditions of the rock mass in which the rockburst occurred, and based on the observation of the face of the face and its vicinity, including lithology, grade of surrounding rock, and occurrence of the structural face, preliminarily judge whether the front of the face of the face is possible Rockburst occurrence and the type of rockburst that occurred;

Step S2: Conduct electromagnetic radiation monitoring on the rockburst-probable part of the rockburst preliminarily judged in step S1, and further analyze whether the monitored value of electromagnetic radiation energy, intensity, and pulse are compared with the reference value. a rockburst will occur;

Step S3: Record the location where the rockburst occurs during the construction process, including lithology, surrounding rock level, structural surface occurrence, group number, spacing, location and degree of rockburst occurrence, and statistically analyze to obtain the rock mass where the rockburst occurred Structural conditions and possible locations of rockbursts shall be continuously corrected and improved;

Step S4: On the basis of on-site monitoring of severe rockburst sections, through the comparison and analysis of the monitoring value and the actual occurrence of rockburst, the predicted values of rockburst monitoring at all levels based on electromagnetic radiation monitoring are obtained, and are continuously revised and improved;

Step S5: By repeatedly executing the above steps S1-S4, the purpose of improving the accuracy of rockburst prediction is achieved.

Further, the rock mass structural conditions for rockburst occurrence include lithology and surrounding rock level conditions at the rockburst occurrence site, the occurrence, group number, and spacing conditions of the structural plane at the rockburst occurrence site.

Further, in the step S2, the electromagnetic radiation monitoring is carried out on the possible rockburst locations through the portable electromagnetic radiation instrument.

The specific implementation mechanism of the present invention will be described in detail below.

Researches at home and abroad have shown that the rock mass will release electromagnetic radiation during the process of deformation and rupture under load. Loading degree and deformation and fracture strength, pulse number mainly reflect the frequency of rock mass deformation and micro-fracture, and energy mainly reflects the energy conversion in the process of rock mass deformation and micro-fracture. Electromagnetic radiation signals generated during the deformation and rupture of surrounding rocks can be monitored non-contact with portable instruments.

Rockburst is also a form of deformation and fracture of rock mass, and its incubation process is essentially a process of deformation, rupture, and damage evolution of rock mass in the incubation area. Therefore, electromagnetic radiation can also be used for rockburst monitoring. However, only relying on the monitoring results of electromagnetic radiation cannot directly predict rockburst. This is mainly because: 1. The results of electromagnetic radiation monitoring reflect the loading degree, energy conversion, deformation and rupture of the rock mass; block, large deformation, rockburst, etc., rockburst is just one of them.), and the deformation and destruction of the surrounding rock will be accompanied by deformation and rupture of the rock mass. Therefore, electromagnetic radiation monitoring needs to be combined with other means to predict rockburst.

Research at home and abroad shows that the main factors of rockburst include lithology, rock mass structure, ground stress level and secondary stress concentration caused by cavern excavation. Among the above-mentioned main factors, the lithology and rock mass structure changes at the face of the tunnel and its vicinity can be visually observed with the naked eye; Rupture and energy conversion cannot be observed with the naked eye, but can be monitored with portable electromagnetic radiation instruments.

From the above analysis, it can be seen that rockburst prediction can be carried out by combining rock mass structure analysis and electromagnetic radiation monitoring. Among them, "rock mass structure analysis" mainly predicts whether rock burst may occur in the rock mass in the prediction area; "electromagnetic radiation monitoring" monitors the rock burst area on the basis of "rock mass structure analysis". The rock mass loading degree, energy conversion and micro-fracture reflected by the monitoring results can further predict whether rockburst will occur and the intensity of rockburst.

Therefore the present invention proposes the rockburst prediction method that rock mass structural analysis and electromagnetic radiation monitoring combine, and its technical scheme is made of following main steps:

1. During the construction process, based on the structural conditions of the rock mass where the rock burst occurs, and based on the observation of the lithology, surrounding rock grade, structural surface occurrence, etc. at the face of the face and its surroundings, it is preliminarily judged whether or not rock bursts will occur in front of the face of the face of the face of the face of the face of the face Rockbursts, what types of rockbursts can occur.

Explanation: The "rock mass structural conditions for rockburst occurrence" in this article mainly includes: the lithology and surrounding rock grade conditions at the rockburst occurrence site; the occurrence, group number, and spacing conditions of the structural plane at the rockburst occurrence site.

2. During the construction process, use a portable electromagnetic radiation instrument to monitor the possible rockburst on the working face where rockburst may occur in front of the working face after preliminary judgment. By comparing the electromagnetic radiation energy, intensity, and pulse monitoring value with the reference value, it is analyzed whether a rockburst will occur.

Explanation: The "electromagnetic radiation energy, intensity, pulse reference value" in this article is the reference value of rockburst. When the monitored value is greater than the reference value, a rockburst will occur.

3. Carefully record the lithology, surrounding rock grade, structural surface occurrence, group number, spacing, location and degree of rockburst occurrence during the construction process, and statistically analyze the rock mass structure where the rockburst occurs Conditions and possible locations of rockbursts will be continuously revised and improved as the forecast work progresses.

4. On the basis of on-site monitoring of severe rockburst sections, through the comparison and analysis of the monitoring value and the actual occurrence of rockburst, the predicted values of rockburst monitoring at all levels based on electromagnetic radiation monitoring are obtained, which will be continuously revised as the forecast work is carried out and perfect.

5. With the development of the forecasting work, the above steps are repeated, and the accuracy of rockburst forecasting is continuously improved.

Embodiment one:

In a railway tunnel, the surrounding rocks are mainly quartz porphyry, granite porphyry, granodiorite, andesite and tuff, and the drilling and blasting method is adopted for construction, and rockbursts occur frequently during the construction process. The rockbursts appeared in the vault to the waist of the new excavation section of this blasting. The first time of occurrence was 20-40 minutes after the blasting, and the duration was 3-8 hours, up to 15 hours. Through the statistical analysis of rockburst occurrence in the early stage of construction, it is concluded that the rock mass structural conditions for rockburst occurrence are as follows:

(1) The surrounding rocks are granite porphyry or granodiorite, the grades of the surrounding rocks are II and III, and the groundwater is not developed;

(2) Slight rockburst occurrence section: a group of structural joints is developed, the angle between the joint direction and the tunnel longitudinal direction is >65° or nearly parallel to the tunnel longitudinal direction, and the joint inclination angle is greater than 70°; moderate and strong rockburst sections: 2 groups are developed Joints, of which one group of joints has an included angle greater than 65° with the longitudinal direction of the tunnel, the other group is nearly parallel to the longitudinal direction of the tunnel, and at least one group of joints has an inclination angle greater than 70°.

In view of the fact that the rockburst of this tunnel appeared in the vault ~ arch waist of the new excavation section of this blasting, and began to appear 20 to 40 minutes after the blasting, the electromagnetic radiation monitoring was focused on the vault ~ in front of the tunnel face Arch area. To this end, a measuring point is arranged on the vault and the left and right arches respectively, as shown in Figure 1. Considering that the forecast of any event has the characteristics that the closer the event occurs, the more accurate the forecast will be. At the same time, in order to reduce the interference of monitoring to construction, on-site monitoring is carried out during the charging of blastholes.

During the construction process, a portable electromagnetic radiation monitor is used to monitor the front of the vault to the waist section of the tunnel where it is preliminarily judged that rockbursts may occur in front of the tunnel. Through the comparative analysis of the monitoring value and the actual occurrence of rockburst, it is concluded that when the monitoring time of a single measuring point in this tunnel is 2 minutes, the predicted values of rockburst at all levels are shown in Table 1.

Typical forecast examples:

In the MK51+657.4 section of the tunnel, the exposed rock strata of the tunnel face and its surrounding sections are granodiorite, the groundwater is not developed, the surrounding rock is grade II, and two sets of steep structural joints with a dip angle of 75-90° are developed. One group of joints is nearly parallel to the longitudinal direction of the tunnel (the angle between the two is 5-10°), and the other group of joints is nearly parallel to the transverse direction of the tunnel (the angle between the two is 0-7°). According to the aforementioned rock mass structural conditions where rockbursts occur, it is preliminarily judged that there is a possibility of moderate to strong rockbursts ahead of the excavation.

In order to further predict whether rockburst will occur in front of the excavation of this section, a total of 3 measuring points (as shown in Fig. Monitor. The monitoring results are shown in Table 2. Figure 2 and Figure 3 show the dynamic changes of the electromagnetic radiation intensity and energy of the vault during the monitoring process.

Comparing the monitoring results in Table 2 with Table 1, it can be seen that the electromagnetic radiation energy, intensity and pulse monitoring values in front of the MK51+657.4 section are all greater than the reference value of strong rockburst. Because the rock mass, surrounding rock grade, and discontinuity plane occurrence in front of the section are all in line with the rock mass structural conditions for moderate to strong rockbursts, and the electromagnetic radiation monitoring value is also greater than the benchmark value for strong rockbursts, it is predicted that MK51+657.4 Intense rockbursts will occur at the vault to the waist in front of the section.

The actual situation at the site: During the construction process of the two cycles in front of the MK51+657.4 section (the blasting excavation length of each cycle is 3.5m), strong rockbursts occurred after the blasting and appeared in the vault to the waist of the arch. As shown in Figure 4 and Figure 5. The actual situation of rockbursts is consistent with the predicted results.

The above are the preferred embodiments of the present invention, and all changes made according to the technical solution of the present invention, when the functional effect produced does not exceed the scope of the technical solution of the present invention, all belong to the protection scope of the present invention.

Claims (3)

1. the Rockburst Prediction Method that an Analysis of rock mass structure combines with electromagnetic radiation monitoring, it is characterised in that: comprise the steps,

Step S1: in work progress, the rock mass structure condition occurred with rock burst for foundation, according to face and near include the observation of lithology, Grades of Surrounding Rock, structural plane occurrence, tentatively judge that front of tunnel heading is whether it may happen that the rock burst type of rock burst and generation；

Step S2: step S1 tentatively judge it may happen that on the face of rock burst, rock burst is likely to occur position and carries out electromagnetic radiation monitoring, by electromagnetic radiation energy, intensity, pulse the contrast of monitor value and reference value, analyse whether further rock burst；

Step S3: in work progress rock burst appearance place include lithology, Grades of Surrounding Rock, structural plane occurrence, group number, spacing, rock burst occur that position and degree are recorded, statistical analysis, show that rock mass structure condition that rock burst occurs and rock burst are likely to occur position, and carry out constantly revising and perfect；

Step S4: on the basis of the serious section field monitoring of rock burst, actually occurs the relative analysis of situation by monitor value and rock burst, draws the rock-burst monitoring predictive values at different levels based on electromagnetic radiation monitoring, and carries out constantly revising and perfect；

Step S5: by repeating above-mentioned steps S1-S4, reaches to improve the purpose of the accuracy of Prediction for Rock Burst.

2. the Rockburst Prediction Method that Analysis of rock mass structure according to claim 1 combines with electromagnetic radiation monitoring, it is characterised in that: the rock mass structure condition that described rock burst occurs includes lithology and Grades of Surrounding Rock condition, the occurrence of rock burst point structural plane, group number, the spacing condition of rock burst point.

3. the Rockburst Prediction Method that Analysis of rock mass structure according to claim 1 combines with electromagnetic radiation monitoring, it is characterised in that: in described step S2, by portable electromagnetic radiation instrument, rock burst is likely to occur position and carries out electromagnetic radiation monitoring.