Stability monitoring method in excavation blasting of tunnel underneath passing through high-voltage iron tower

Abstract

The invention provides a stability monitoring method in excavation blasting of a tunnel underneath passing through a high-voltage iron tower, and the method comprises the steps: judging the hardness degree of a rock according to the uniaxial compressive strength of the rock, and determining K and alpha values in a Sadgowski formula according to the hardness degree of the rock; determining a safe allowable vibration speed, an allowable accumulative settlement value and an allowable inclination value of the high-voltage iron tower; dividing a tunnel which is positioned below the iron tower and needs to pass downwards to form a plurality of construction intervals, and determining the nearest distance R from the blasting center point of the middle section of each construction interval to the iron tower foundation; acquiring a crack distribution state at a foundation structure for supporting the high-voltage iron tower; according to the safe allowed vibration speed value, the allowed blasting explosive dosage of each section is determined, and blasting excavation is conducted on the tunnel according to the allowed blasting explosive dosage of each section; during tunnel blasting excavation, vibration, settlement and inclination of the high-voltage iron tower are monitored in real time, monitoring data are sent to a monitoring system, and excavation is stopped when the monitoring data are abnormal.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel excavation under a high-voltage iron tower, and in particular to a stability monitoring method in tunnel excavation blasting under a high-voltage iron tower. Background Art

[0002] When tunnel blasting and excavation passes under a high-voltage tower, in order to ensure the stability of the tower, it is usually required that the vibration, settlement and tilt of the tower do not exceed a certain limit. In order to reduce the impact of tunnel blasting and excavation on the stability of the tower, some methods have been used to deal with this problem. Among them, a common method is to conduct detailed geological exploration and structural evaluation of the underground around the high-voltage tower before blasting to understand the geological conditions around the tower and the bearing capacity of the tower. During the blasting process, a series of measures are taken to reduce the impact of shock waves and vibrations on the tower, such as adjusting blasting parameters, using vibration-reducing materials, and adopting anti-vibration measures. However, most methods are based on the protection of the tower, and external methods are used to reinforce the tower to ensure the stability of the tower. This does not protect the tower from the root, that is, starting from the maximum disturbance that the tower can withstand, to control the disturbance caused by tunnel blasting and excavation, and then solve the problem of tower stability from the root. In addition, the existing tower protection methods are generally poorly applicable, and most of them are only for a specific project.

[0003] In summary, it is urgent to invent a systematic method to ensure the stability of high-voltage towers when tunnels are excavated by blasting. A more systematic and universally applicable method should be adopted to reduce blasting disturbances, thereby ensuring the stability of high-voltage towers when tunnels are excavated by blasting. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a stability monitoring method in tunnel excavation blasting under a high-voltage iron tower.

[0005] In order to solve the above technical problems, the technical solutions provided by the present invention are as follows:

[0006] The stability monitoring method in tunnel excavation blasting under a high-voltage iron tower comprises the following steps:

[0007] The hardness of the rock is determined by its uniaxial compressive strength, and the K and α values ​​in Sadovsky's formula are determined accordingly.

[0008] Determine the safe allowable vibration speed, allowable cumulative settlement and allowable tilt value of the high-voltage tower;

[0009] Divide the tunnel located under the tower and needs to pass through it into several construction sections, and determine the distance R between the blasting center point in the middle section of each construction section and the tower foundation;

[0010] Obtain the crack distribution state at the foundation structure supporting the high-voltage iron tower;

[0011] Determine the allowable blasting explosive dosage for each interval according to the safe allowable vibration velocity value, and carry out blasting excavation of the tunnel according to the allowable blasting explosive dosage for each interval;

[0012] During the blasting excavation of the tunnel, monitor the vibration, settlement and inclination of the high-voltage iron tower in real time, send the monitoring data to the monitoring system, and stop the excavation when the monitoring data is abnormal.

[0013] Furthermore, the uniaxial compressive strength of the rock is obtained through the geological exploration report and the indoor uniaxial compressive strength.

[0014] Furthermore, the hardness is specifically determined according to the coefficient of hardness f of the Protodyakonov theory. When f > 5, it is hard rock; when 3 < f <= 5, it is medium-hard rock, and when f < 3, it is soft rock.

[0015] Furthermore, the length of the construction interval is 3 - 5 footage of the tunnel excavation

[0016] Furthermore, the step of obtaining the crack distribution state at the foundation structure supporting the high-voltage iron tower is specifically to detect the integrity of the foundation structure under the high-voltage iron tower through ultrasonic detection equipment to obtain the condition of the foundation structure.

[0017] Furthermore, the condition of the foundation structure also includes the position, quantity and length of cracks at the foundation structure.

[0018] Furthermore, it also includes the calculation of the blasting explosive dosage for the construction interval, specifically by calculating the blasting explosive quantity through the cross-sectional area of the middle section of the adjacent interval.

[0019] Furthermore, it also includes the monitoring of the vibration velocity generated by the foundation structure due to blasting excavation, specifically that the maximum vibration velocity in any of the X, Y, Z directions recorded by the blasting vibration measuring instrument is less than 0.25 cm / s.

[0020] Furthermore, it also includes the determination of the safe allowable vibration velocity, specifically determined by the K value, α value, distance R value and crack distribution state.

[0021] The present invention has the following beneficial effects:

[0022] Based on the method of theoretical calculation and on-site monitoring, starting from reducing blasting disturbance, the present invention determines a generally applicable systematic method for ensuring the stability of the high-voltage iron tower when the tunnel is blasted and excavated under the high-voltage iron tower. Description of the Drawings

[0023] Figure 1A flow chart of a method for monitoring stability during tunnel excavation blasting under a high-voltage iron tower provided by the present invention;

[0024] Figure 2 A longitudinal cross-sectional view of a tunnel developed by blasting provided by the present invention;

[0025] Figure 3 A transverse cross-sectional view of a tunnel developed by blasting provided by the present invention;

[0026] In the figure: 1. high-voltage iron tower; 2. foundation structure; 3. blasting vibration velocity monitoring point; 4. tunnel; 5. surrounding rock; 6. first interval; 7. second interval; 8. third interval; 9. fourth interval; 10. fifth interval; 11. sixth interval; 12. middle section of the first interval; 13. middle section of the second interval; 14. middle section of the third interval; 15. middle section of the fourth interval; 16. middle section of the fifth interval; 17. middle section of the sixth interval. DETAILED DESCRIPTION

[0027] The present invention is described in detail below in conjunction with the various embodiments shown in the accompanying drawings, but it should be noted that these embodiments are not limitations of the present invention, and any equivalent transformations or substitutions in functions, methods, or structures made by ordinary technicians in the field based on these embodiments are all within the scope of protection of the present invention.

[0028] The stability monitoring method in the tunnel excavation blasting under a high-voltage iron tower in the present invention determines the K value and α value of the Sadovsky formula according to the hardness of the rock around the tunnel, determines the allowable settlement, inclination and vibration values of the high-voltage iron tower according to the specifications, divides the intervals and calculates the distance R from the blasting center of the middle section of each interval to the nearest point of the high-voltage iron tower foundation, conducts ultrasonic detection on the high-voltage iron tower foundation, determines the allowable explosive amount for blasting in each interval, monitors the settlement, inclination and vibration of the high-voltage iron tower foundation, and finally conducts comparative detection and analysis of the ultrasonic waves on the high-voltage iron tower foundation. First, determine the hardness of the rock according to the uniaxial compressive strength of the rock. Based on the hardness of the rock, determine the K value and α value of the Sadovsky formula through the blasting safety regulations, and determine the allowable settlement, inclination and vibration speed values of the high-voltage iron tower according to the specifications. Then, divide the part of the tunnel under the high-voltage iron tower into several intervals, and at the same time determine the distance R from the blasting center point of the middle section of each tunnel interval to the nearest point of the iron tower foundation. After the above basic work is completed, conduct ultrasonic detection on the high-voltage iron tower foundation before the tunnel blasting excavation. After the K value, α value, distance R value and allowable vibration speed in the Sadovsky formula are determined, calculate the allowable blasting explosive amount for each interval, and conduct tunnel blasting excavation according to the allowable blasting explosive amount for each interval. Finally, after the tunnel safely passes through the iron tower, conduct ultrasonic detection on the high-voltage iron tower foundation again, compare and analyze the detection results before the tunnel excavation with the detection results after the tunnel safely passes through the high-voltage iron tower, and combine the settlement, inclination and vibration speed monitoring results to obtain the influence of the tunnel passing under the high-voltage iron tower on the high-voltage iron tower. If the influence is large, reinforcement schemes such as grouting reinforcement and frame beam reinforcement can be used to reinforce the high-voltage iron tower foundation.

[0029] Reference Figures 1 to 3 , to ensure stability, and further in the monitoring method for the stability of the tunnel excavation blasting under the high-voltage iron tower, it mainly includes the following steps:

[0030] Step 1, judge the hardness of the rock based on the uniaxial compressive strength of the rock obtained from the geological exploration report and the indoor uniaxial compressive strength test. The hardness of the rock is determined based on the rock mass rating coefficient f of the Proctor theory, where the rock mass rating coefficient is:

[0031] In the formula, σ c is the uniaxial compressive strength of the rock (MPa), and f is the rock mass rating coefficient.

[0032] When f > 5, it is hard rock; when 3 < f <= 5, it is medium-hard rock; when f < 3, it is soft rock.

[0033] Determine the K and α values in the Sadovsky formula according to the hardness of the rock. The K and α values are determined by Table 3 in Section 13.2.4 of the Blasting Safety Regulations GB6722-2014. The value ranges of the K and α values are selected according to the following table:

[0034] Lithology K α hard 50-150 1.3-1.5 medium hard 150-250 1.5-1.8 Soft rock 200-350 1.8-2.0

[0035] The K value is taken as the middle value of the corresponding interval, and the α value is taken as the smaller value of the corresponding interval. The Sadovsky formula is:

[0036]

[0037] R—Blasting vibration safety allowable distance, in meters (m);

[0038] Q—explosive quantity, total quantity for simultaneous blasting and maximum quantity for delayed blasting, in kilograms (kg);

[0039] V—safety-allowed particle velocity at the location of the protected object, in centimeters per second (cm / s);

[0040] K, α - coefficients and attenuation indexes related to the terrain and geological conditions between the blasting point and the protected object should be determined through field tests; in the absence of test data, they can be selected by referring to the above table.

[0041] The safe allowable vibration speed, allowable cumulative settlement and allowable inclination value of the high-voltage tower 1 are determined according to relevant specifications, wherein the safe allowable vibration speed is determined by the blasting safety regulations, which is a vibration speed not exceeding 3.5 cm / s, the allowable cumulative settlement is given by the tower construction and operation party, and the allowable inclination value is determined by the overhead power transmission line operation regulations, which is an inclination not exceeding 0.5%.

[0042] Step 2: Divide the part of the tunnel 4 that passes under the tower into several sections. The length of each section can be 3-5 feet of the tunnel 4 excavation. The length of the tunnel 4 to be divided into sections is determined by the safe allowable distance calculation in the Sadovsky formula. The most unfavorable situation of each parameter is taken when calculating the safe allowable distance. At the same time, determine the distance R between the blasting center point of the middle section of each tunnel section and the tower foundation.

[0043] Step three, after the above basic work is completed, use ultrasonic detection equipment to detect the integrity of the foundation structure 2, record the current status of the foundation structure 2, and most importantly, detect the current crack distribution of the foundation structure 2, such as the location, number and length of the cracks, so that after the tunnel 4 passes through the high-voltage iron tower 1, analyze the impact of the blasting excavation of the tunnel 4 on the foundation structure 2. At the same time, install inclinometers and settlement monitoring instruments on the tower 1, and place blasting vibration sensors at the blasting vibration velocity monitoring points 3 on the surface of the foundation structure 2.

[0044] Step 4: determine the allowable blasting explosive usage for each section according to the K value, the α value, the distance R value and the safe allowable vibration speed value, and perform blasting excavation on the tunnel 4 according to the allowable blasting explosive usage for each section.

[0045] Step 5. During the blasting and excavation of the tunnel 4, the vibration, settlement and inclination of the high-voltage iron tower 1 are monitored. The monitoring data can be directly plotted into a chart through the wireless monitoring equipment and transmitted to the PC or mobile phone. The relevant personnel can directly view the relevant monitoring data and then determine whether the data exceeds the limit. If the data exceeds the limit, the excavation is stopped immediately, and the ultrasonic detection of the foundation structure 2 is performed again to record the integrity of the concrete of the foundation structure 2. The rock samples after the blasting are sampled and subjected to a uniaxial compressive strength test to determine the rock properties and recalculate the allowable amount of explosives for blasting in each interval.

[0046] Step 6: When the vibration velocity of the high-voltage iron tower 2 caused by the blasting excavation of the tunnel 4, that is, the maximum vibration velocity in any direction of X, Y, and Z recorded by the blasting vibration measuring instrument is much lower than the safe allowable vibration velocity specified in the specification (less than 0.25 cm / s), it indicates that the blasting excavation of the high-voltage iron tower 1 has almost no effect on the stability of the foundation structure 2. At this time, ultrasonic testing is performed on the high-voltage iron tower 1 to record the distribution of cracks in the foundation structure 2, and observe whether the old cracks develop and whether new cracks appear. If the original cracks have a tendency to develop or new cracks appear, it is necessary to adopt grouting repair, frame beam reinforcement and other methods to reinforce the foundation structure 2.

[0047] Example 1

[0048] The uniaxial compressive strength of the rock around a certain tunnel is 125MPa, f=12.5>5, and it is judged to be hard rock. The K value is 100, the α value is 1.3, and the safe allowable vibration speed is 3.5cm / s. The vertical distance and offset distance from the blasting center of the right pilot pit in the middle section of the first interval to the nearest point of the tower foundation are 30.194m and 15.14m respectively, and the calculated distance R is 33.777m.

[0049] Calculate the amount of explosives according to the following formula:

[0050]

[0051] The calculated allowable amount of explosives Q for blasting is 16.828kg. Through on-site blasting vibration monitoring, it was found that when the right pilot pit was blasted with a single-stage explosive amount Q of 16.828kg, the maximum vibration speed of the tower foundation was 2.37cm / s, which was less than the allowable vibration speed of 3.5cm / s specified in the specification. After the tunnel safely passed through the tower foundation, ultrasonic testing was carried out on the tower foundation. The test results showed that no new cracks appeared in the tower foundation and the old cracks had no development trend.

[0052] In this embodiment, at least two foundation structures 2 are arranged under the high-voltage iron tower 1, and then at least one blasting vibration velocity monitoring point 3 is arranged at each foundation structure 2, the foundation structure 2 is located in the surrounding rock 5, and then the tunnel 4 is specifically constructed in the surrounding rock 5. In this embodiment, the first interval 6, the second interval 7, the third interval 8, the fourth interval 9, the fifth interval 10 and the sixth interval 11 are specifically divided. At this time, the middle section 12 of the first interval is located between the first interval 6 and the second interval 7, the middle section 13 of the second interval is located between the second interval 7 and the third interval 8, the middle section 14 of the third interval is located between the third interval 8 and the fourth interval 9, the middle section 15 of the fourth interval is located between the fourth interval 9 and the fifth interval 10, the middle section 12 of the fifth interval is located between the fifth interval 10 and the sixth interval 11, and the middle section 17 of the sixth interval is located at the end of the sixth interval 11.

[0053] Example 2

[0054] A tunnel passes under a high-voltage iron tower. The explosives used are 60kg. The delayed blasting method is adopted, and the maximum single-stage explosives are 25kg. The on-site vibration, tilt and settlement monitoring of the overlying high-voltage iron tower is carried out. The tilt and settlement data are very small, within the allowable range of the specification. The vibration monitoring data shows that the maximum vibration speed of the iron tower in the Y direction reaches 3.85cm / s, which exceeds the allowable vibration speed of 3.5cm / s specified by the iron tower operator. The uniaxial compressive strength of the rock around the tunnel is about 85MPa, f=8.5>5, which is judged to be hard rock. The K value is 100, and the α value is 1.3. The tunnel passing through the iron tower is divided into several sections, and the distance R between the blasting center point in the middle section of each section and the closest point to the iron tower foundation is calculated. According to the on-site measurement, the vertical distance and offset distance between the blasting center of the pilot pit on the middle section of the first section and the closest point to the iron tower foundation are 28.368m and 5.63m respectively, and the calculated distance R is 28.921m.

[0055] Calculate the amount of explosives according to the following formula:

[0056]

[0057] The calculation shows that the allowable explosive quantity Q for a single-stage blasting is 10.563kg. Through on-site blasting vibration monitoring, it is found that when the upper pilot pit is blasted with a single-stage explosive quantity Q of 10.563kg, the maximum vibration velocity of the tower foundation is 0.93cm / s, which is less than the allowable vibration velocity of 3.5cm / s specified in the specification. Since the amount of explosives is small, the tunnel excavation efficiency is low. After coordination with multiple parties, on the basis of ensuring the safety of the tower, the K value is taken as 75 when other Sadovsky formula parameters remain unchanged. The calculation shows that the allowable explosive quantity Q for a single-stage blasting in the first interval is 20.517kg. When the allowable explosive quantity Q for a single-stage blasting in the first interval is 20.517kg, the tunnel is blasted and excavated, and the vibration velocity of the tower foundation is monitored. The maximum vibration velocity is 2.81cm / s in the X direction, which meets the 3.5cm / s required by the specification and the tower operator.

[0058] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0059] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for monitoring stability during tunnel excavation blasting under a high-voltage iron tower, characterized in that: It includes the following steps: Judge the hardness of the rock according to the uniaxial compressive strength of the rock, and determine the values of K and α in the Sadovsky formula accordingly; Determine the safe allowable vibration velocity, allowable cumulative settlement and allowable inclination value of the high-voltage iron tower; Divide the tunnel that needs to be bored under the iron tower to form several construction sections, and determine the closest distance R from the blasting center point of the middle section of each construction section to the iron tower foundation; Obtain the crack distribution state at the foundation structure supporting the high-voltage iron tower; Determine the allowable blasting explosive charge for each section according to the safe allowable vibration velocity value, and carry out blasting excavation of the tunnel according to the allowable blasting explosive charge for each section; During the blasting excavation of the tunnel, monitor the vibration, settlement and inclination of the high-voltage iron tower in real time, send the monitoring data to the monitoring system, and stop the excavation when the monitoring data is abnormal.

2. The stability monitoring method in tunnel excavation blasting under a high-voltage iron tower according to claim 1 is characterized in that: The uniaxial compressive strength of the rock is obtained through the geological exploration report and the indoor uniaxial compressive strength.

3. The stability monitoring method in tunnel excavation blasting under a high-voltage iron tower according to claim 1 is characterized in that: The hardness is specifically determined according to the firmness coefficient f of the Protodyakonov theory. When f>5, it is a hard rock; when 3<f<=5, it is a medium-hard rock; when f<3, it is a soft rock.

4. The stability monitoring method in tunnel excavation blasting under a high-voltage iron tower according to claim 1 is characterized in that: The length of the construction section is 3-5 footage of the tunnel excavation.

5. The stability monitoring method in tunnel excavation blasting under a high-voltage iron tower according to claim 1 is characterized in that: The step of obtaining the crack distribution state at the foundation structure supporting the high-voltage iron tower is specifically to detect the integrity of the foundation structure under the high-voltage iron tower through ultrasonic detection equipment to obtain the condition of the foundation structure.

6. The stability monitoring method in tunnel excavation blasting under a high-voltage iron tower according to claim 5 is characterized in that: The condition of the foundation structure also includes the position, quantity and length of cracks at the foundation structure.

7. The stability monitoring method in tunnel excavation blasting under a high-voltage iron tower according to claim 1 is characterized in that: It also includes the calculation of the blasting explosive charge for the construction section, specifically by calculating the blasting explosive charge through the cross-sectional area of the middle section of the adjacent section.

8. The stability monitoring method in tunnel excavation blasting under a high-voltage iron tower according to claim 1, characterized in that: It also includes the monitoring of the vibration velocity generated by the foundation structure due to blasting excavation, specifically that the maximum vibration velocity in any direction of X, Y, Z recorded by the blasting vibration measuring instrument is less than 0.25 cm / s.

9. The stability monitoring method in tunnel excavation blasting under a high-voltage iron tower according to claim 1, characterized in that: It also includes the determination of the safe allowable vibration velocity, specifically determined by the values of K, α, distance R and crack distribution state.

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