Drilling and Blasting Construction Vibration Testing Scheme in Laolongshan Tunnel

I. Basis and scope of preparation

1. Compilation basis

(1) Construction plan and design instruction for the second phase of the reconstruction project of the Mianyang Ring Road section of the provincial highway 205 line (Youxian section);

(2) analysis of on-site surveys and related consultations;

(3) The basis for design, construction and management of this project and relevant laws and regulations:

1 Blasting Safety Regulations (GB 6722-2014);

2 Technical Specifications for Highway Tunnel Construction (GB 10204);

3 "The People's Republic of China Environmental Protection Law";

(4) Technical specifications and quality acceptance standards related to this project.

(5) Relevant similar engineering data.

2. Scope of preparation

Drilling and blasting of the Laolongshan Tunnel (ZK41+340 to ZK42+545, 1205m in length) of the second phase of the reconstruction project of the line 205 of the provincial highway around Mianyang (Youxian section).

Second, project overview

1. Laolongshan Tunnel Overview

Laolongshan Tunnel is located in Youxian Village, Youxian Town, Youxian District, Mianyang City. It is a four-lane first-class road long-distance tunnel separated by the upper and lower sides. The left tunnel line ZK41+340~ZK42+545 is 1205m long, and the tunnel plane start point to ZK41+709.767 is located at R=1700m left detour curve, ZK41+709.767~ZK42+149.740 is on the straight line segment, ZK42+149.740 to the end point is R=2200m Right-circular curve, tunnel vertical slope - 2.6%. The right line of the tunnel is YK41+350 to YK42+555 and is 1205m long. The plane starting point to K41+755.052 is located at R=1550m left-off-circle curve, K41+755.052 to K42+284.276 is located at the straight-line segment, K42+284.276 to the ending point is located at R=4500m right-circularly-curved curve, the longitudinal slope of the tunnel is -2.6%.

Left and right line tunnel distance, starting point K41+350ï½žK41+510, net distance 11.8mï½ž20m; hole body segment K41+510ï½žK42+420, net distance 20mï½ž32m; K42+420ï½žK42+545, net distance 20m ~9m. The maximum depth of the tunnel is about 80m, and the bamboo tunnel doors are used for the left and right tunnel exits. Two pedestrian crossings and one traffic crossing are set in the tunnel.

This project plans to adopt a two-way excavation drilling and blasting construction. Due to the entrance and exit of the tunnel and public and civil buildings (structures) near the upper part, the vibration induced by the blasting construction will have different degrees of influence on the surrounding buildings (buildings) and environment. Influencing and destroying, therefore, the blasting vibration should be monitored during the blasting operation, and the vibration hazard caused by the blasting activity should be strictly controlled within the permissible range.

2. Positional relationship between Laolongshan Tunnel and adjacent buildings (structures)

After on-site survey on November 21, 2017, the impact of drilling and blasting construction in the Laolongshan tunnel was mainly concentrated on the entrance, exit, and upper areas of the tunnel. The positional relationship between the Laolong Mountain Tunnel and adjacent buildings (structures) is detailed in Attachment 1. Laolongshan Tunnel Site Investigation Map.

2.1. Laolongshan Tunnel Imported House Relations Statistics

Distance to the tunnel (m)

Property Type

267

Two-story brick house

Three-story brick house

154

Two-story brick house

201

Two-story brick house

2.2 Laolongshan Tunnel Upper House Relationship Statistics

No.

Distance to the tunnel (m)

Property Type

112

Two-story brick house

153

Two-story brick house

103

Two-story brick house

Adobe House

(106, 73, 96)

Longteng Villa

Driving school training ground

165

Two-story brick house

208

Three-story brick house

189

Two-story brick house

Mianyang Wisdom City Technology Co., Ltd.

112

Lei Sheng Electrotherapy Mianyang Health Center

twenty one

124

Huang's Villa

2.3 Laolongshan Tunnel Exit Housing Relations Statistics

No.

Distance to the tunnel (m)

Property Type

128

Changchun LPG Station

170

Youxian District Relief Station

160

Resettlement community, residential building

200

Xingfa steel market, private houses

260

Residential area (50 buildings)

1300

Nine Academy military research base (imports of tunnels)

Third, the monitoring program

1. Monitoring purpose

This project excavates tunnel blasting in the mountain, but there are public and civil buildings near the entrance, exit and upper part of the tunnel. The vibration induced by blasting will have different degrees of influence on the surrounding buildings (buildings) and environment. Impact and destruction. In particular, the individual houses in the tunnel are more than 50 meters away from the blasting operation point. Because the blasting environment is more complicated than 50m before the blasting and blasting of the import or export, the blasting safety should be checked and effectively controlled during the blasting operation. To achieve the following purposes:

(1) Accurately and quantitatively detect the vibration intensity of particles and accumulate relevant data to provide scientific basis for guiding correction, restriction and optimization of construction plans.

(2) Defining the scope of influence of the original tunnel drilling and blasting construction scheme through blasting test data, and combining the types of neighboring buildings and safety allowable standards to verify the feasibility of the original scheme.

(3) Perform particle vibration testing on specific buildings to ensure the safety of buildings and operating equipment. Strictly control the vibration hazards caused by blasting and other construction activities within the allowable range and conduct safety assessment on the monitoring objects.

(4) Perform particle vibration testing on specific locations or areas that may cause civil disputes, and provide evidence for project acceptance and possible judicial procedures.

2. Selection of control standards

The blasting test mainly includes two aspects: First, it studies the attenuation law of blasting seismic waves, the influence of geological structure and topographic conditions on it, the relationship between seismic wave parameters and blasting modes; on the other hand, it studies the building (structure), The response characteristics of blasting vibration, and the relationship between this response characteristic and the blasting method and structural characteristics of the structure. As far as the specific content is concerned, the contents of the blasting vibration test include: the surface mass point vibration velocity, vibration displacement, and vibration acceleration tests; and the response spectrum test of structures and buildings. According to the "Blasting Safety Regulations" (GB 6722-2014) stipulates: The criterion of blasting vibration for building (structure) is to use the two indicators of the peak particle vibration velocity and the main vibration frequency in the place where the object is to be protected. The blasting seismic safety of general buildings (structures) shall meet the requirements of safe vibration speed, and the following shall be specified for the safety particle vibration speeds of the main types of buildings:

No.

Protection object category

Safety allowable particle vibration speed V,cm/s

fâ‰¤10Hz

10Hzfâ‰¤50Hz

f>50 Hz

Tujia Cave, Adobe House, Stone House

0.15-0.45

0.45 to 0.9

0.9 to 1.5

General civil buildings

1.5 to 2.0

2.0 to 2.5

2.5 to 3.0

Industrial and commercial buildings

2.5 to 3.5

3.5 to 4.5

4.2 to 5.0

1 Note 1: The particle vibration speed in the table is the maximum of the three components; the vibration frequency is the main vibration frequency.

Note 2: The frequency range is determined according to the measured waveforms at the site or selected as follows: chamber blasting f<20 Hz; open-air deep hole blasting f=10-60 Hz; open shallow blasting f=40-100 Hz; underground deep hole blasting f = 30 ~ 100 Hz; underground shallow hole blasting f = 60 ~ 300 Hz.

Note 3: Blasting vibration monitoring should simultaneously measure the three components of the particle vibration perpendicular to each other.

At the same time, the military research base of Nine Yards is 1,300 meters away from the Laolong Mountain Tunnel. To avoid the impact of construction vibration on the precision instruments of the 9th Academy Research Base, the requirements of the 9th Institute shall be such that the construction vibration during its experimental work is not higher than 1cm/s. Non-experimental construction vibration is not higher than 2cm/s. Therefore, the allowable values â€‹â€‹for vibration safety of this project are as follows:

(1) For brick-concrete buildings adjacent to drilling and blasting construction, refer to the above â€œGeneral Civil Buildingsâ€ for lower values, that is, the allowable vibration safety speed value of this project is 2 cm/s.

(2) For the adobe structure buildings adjacent to the drilling and blasting construction, refer to the above-mentioned â€œTube Caves, Adobe Houses, and Stone Housesâ€ for lower values, that is, the vibration safety allowable speed value of this project is 0.45cm/s.

(3) The allowable vibration value of the 9th Academy military research base during the experiment is 1cm/s, and the allowable vibration value during the non-experimental period is 2cm/s.

3. Detection Plan Overview

Based on the construction plan of the project, on-site survey data, and the purpose of testing, a test plan combining blasting test, analog test, and process test is formulated, as follows:

(1) Blasting test

Through on-site environmental survey, it is planned to conduct two blasting tests at the entrance of Laolongshan Tunnel. The blasting test should be conducted before normal drilling and blasting operations, and the maximum single shot volume selected for the two blasting tests should be the original blasting design scheme. 60% and 80% of the maximum charge capacity is appropriate. Through the test results, we can grasp the relationship among the blasting vibration velocity, the volume of the injection and the distance, and predict and verify the feasibility of the blasting program.

(2) Analogy test

Analog test is a common prediction method for blasting vibration. It is suitable for areas with little lithological changes. It chooses similar vibration propagation media and uses the same construction parameters to predict the scope and extent of future construction vibrations through measured vibration data. Control the vibration hazard caused by blasting activities within the allowable range.

(3) Process Detection

Process monitoring shall be carried out through the entire process of drilling and blasting the tunnel, ie, during the construction process, continuous vibration testing shall be performed on the buildings within the defined safety distance, and the vibration hazards caused by the blasting activities shall be strictly controlled within the permissible range. Monitoring object for safety evaluation.

4. Testing and implementation

4.1 Blasting test

Estimating the vibration velocity based on the empirical formula of MA Sadrafski's maximum ground motion velocity is an important basis for blasting vibration control. Because the K and Î± values â€‹â€‹in the formula are related to site geology and terrain conditions, different geology and terrain conditions are different. Because of the K and Î± values, it is necessary to measure K and Î± values â€‹â€‹in the field.

(1) Measurement point layout

The blasting test should be arranged before the normal construction of the Laolongshan tunnel, and use the explosion heart as the starting point. Pass the extension line of the military base of the Nine-yard Hospital and arrange six three-velocity speed sensors in a close-to-distant manner. (The monitoring points and points should be For the same elevation, if the on-site conditions permit, on the premise of ensuring the safety of the equipment, the distance between each measuring point and the operating point can be set to 10 m, 40 m, 80 m, 160 m, 320m, 400m or adjusted according to the site conditions of the site. . The arrangement of the sensor is shown in Figure 2:

Fig. 2: Vibration parameters test point layout

Blasting test site layout

Measuring point number

Distance to operation point (m)

Note

Test point

160

Test point

320

Test point

400

Test point

Three-story brick-concrete house (Conclusion verification point)

1300

Nine homes designated test points (conclusions verification point)

1300

Nine homes designated test points (conclusions verification point)

(2) Sensor installation

In the first 2 hours, a three-velocity speed sensor is installed according to a predetermined position and requirement, wherein the Z direction is vertical, the X direction is the direction of the blast source and the horizontal radial direction, and the Y direction is the horizontal tangential direction. Number the monitoring points, measure and record the location and height of the source center and sensors.

(3) Instrument connection and debugging

In the first 30 minutes, connect the collector to each sensor, record the number of the sensor and the collector, set the parameters, and select the appropriate opening threshold (preferably 20% of the maximum amplitude and not less than 0.2cm/s, to prevent frequent In case of false triggering, confirm that the instrument is connected and debugged well. Use a protective cover to cover the instrument and sensor and protect it. The personnel were evacuated to the safe area before being on site.

(4) On-site testing

When the vibration generated by the explosion exceeds the opening threshold set by the instrument, the vibration signal begins to be recorded. After the alert was lifted, the staff entered the site to pick up the instruments, sensors and cables. Remove plaster that has stuck on the ground and clean up on-site work waste.

(5) Data Management

The inspectors fill in the "blasting vibration detection original record table", export the stored vibration data through the U disk, analyze and process the waveform using the vibration analysis software, and read the vertical, horizontal radial and horizontal tangential vibration peaks and peaks respectively. Main frequency, main vibration duration and other parameters. When necessary, the vector sum operation is performed on the three-component vibration data to obtain the maximum amplitude of the synthesis.

(6) Calculate the K and Î± values

The vibration attenuation law is related to the site geology, terrain conditions and other factors. According to the variation of the vibration amplitude at each vibration monitoring point located on the straight line, the K and Î± values â€‹â€‹that characterize the vibration attenuation law can be calculated. The calculation method is generally based on the least square method for regression analysis and calculation.

According to Sadovski's formula:

The above equation is a one-dimensional linear regression equation, and k and Î± are regression coefficients of the regression equation.

According to the least-squares method, the particle vibration velocity values â€‹â€‹at each monitoring point, the Q-explosive charge Q, and the blast center distance were respectively substituted into the above equation, and the regression analysis was performed to obtain the K and Î± values â€‹â€‹under the geological and topographic conditions. When necessary, the vertical and horizontal radial and horizontal tangential vibration parameters K and Î± can be calculated separately.

4.2. Analogy Test and Process Control

According to the provisions of the "Blasting Safety Regulations" (GB 6722-2014), the blast vibration monitoring should simultaneously measure the three components of the particle's vibration perpendicular to each other and use the maximum value of the three components to evaluate the safety permit.

(1) Measurement site layout

The test points of the analog tests shall be arranged above the tunnel entrance, and the distances from the blasting operation points shall be 54m, 73m, 80m, 84m, 85m and 86m (select the six points closest to the future operation point of the upper building). Should be placed on bedrock and the slope is not greater than 5Â°. The specific measurement points are as follows:

Measuring point number

Distance to operation point (m)

Note

Tunnel classification ratio measurement point

Some three-story brick houses on the tunnel

1300

Part of the 9 tunnels designated on the tunnel

1300

Part of the 9 tunnels designated on the tunnel

Process monitoring shall be carried out throughout the entire drilling and blasting process. The measuring points shall be laid within the blasting safety distance, close to the building (structure) site in the blast source area, and be able to fully reflect the vibration impact of each monitoring area. The project needs to be In the three areas of the Laolongshan tunnel entrance, exit, and upper area, 2-3 measurement points are arranged. In the actual monitoring, the distance from the field blasting operation site to the construction (structure) distance is adjusted. The installation of the sensor is shown in Figure 3:

Figure 3: Layout of vibration monitoring points

(2) Sensor installation

(3) Instrument connection and debugging

(4) On-site testing

When the vibration generated by the blast exceeds the opening threshold set by the instrument, the vibration signal begins to be recorded. After the alert was lifted, the staff entered the site to pick up the instruments, sensors and cables. Remove plaster that has stuck on the ground and clean up on-site work waste.

(5) Data Management

(6) Vibration impact assessment

According to the monitoring object's nature and age at each monitoring point, the vibration control standard was selected and evaluated with the measured vibration amplitude. If the measured maximum particle vibration velocity in any direction of the monitoring point exceeds the corresponding vibration control standard, the particle vibration velocity exceeds the limit and may or may have caused damage or destruction to the monitored object; if the measured point is in all directions, the measured maximum particle vibration velocity All are less than the corresponding control standards, it means that the monitoring object will not be damaged by vibration and it is safe. If the measured vibration amplitude exceeds the limit, a macro survey shall be conducted on the monitoring object to observe whether the monitoring object has fine cracks, kicking and other damage phenomena. If necessary, sound wave detection and other means may be used to evaluate the degree of vibration impact. If the maximum mass point vibration speed exceeds the limit, attention should also be paid to it and a comprehensive judgment should be made in conjunction with the results of the macroscopic inspection on site.

5. Monitoring frequency and period

The blasting vibration detection work of the Laolongshan tunnel project should be carried out throughout the whole process of controlled blasting and excavation of the entire tunnel. The monitoring frequency is determined according to the blasting operation;

When engineering accidents or other factors cause changes in the monitoring items or the monitoring data is close to the warning value, the construction unit shall be promptly notified and the encrypted observations shall be made according to their requirements. When an accident occurs, continuous monitoring shall be carried out and the relevant units shall be notified immediately.

6. Monitoring data feedback process

Monitoring data feedback process shown in Figure 4

Figure 4; monitoring data feedback process

7. Abnormal situation processing measures

If the particle vibration speed of the object to be monitored exceeds the above-mentioned scope, it shall promptly report to the relevant parties on the site. If there is a dangerous situation, the monitoring unit shall first report it by telephone orally within 2 hours (before the next blasting construction), and then make a written report to sign and confirm it. Corresponding measures should be taken to amend the blasting plan and strengthen other monitoring methods of the monitored objects to ensure their safety. Blasting program amendments include: control of the maximum single-shot volume, use of explosives with low detonation velocity and low power, creation of free surfaces, control of the excavation cycle footage, use of multi-stage differential blasting technology, adjustment of the detonation direction of blasting, and excavation of seismic isolation trenches. Presplit blasting methods are used. These measures can be used simultaneously to ensure safe construction. If the blasting scheme is still close to the limit or even higher than the limit after the amendment of the blasting scheme, the tunnel excavation method shall be reduced from blasting excavation to microvibration controlled blasting construction, and the microvibration controlled blasting construction shall be reduced to non-blasting excavation.

8. Analysis of individual particle vibration velocity and vibration waveform distortion and emergency disposal

In the process of blasting monitoring, there may be cases where the vibration velocity of the individual particles is too high or the vibration waveform is distorted. The main reasons causing the excessive vibration velocity and the emergency response are:

One is that the detonator detonator is not used at intervals, and the superposition of the vibration peak after blasting will increase the vibration speed. The owner and the management parties should be promptly notified.

The second is that the loading of drugs in individual segments exceeds the standard and is not strictly carried out according to the design volume of drill and blast charges. The owners and management parties shall be promptly informed.

Thirdly, bolt loosening at monitoring points, poor contact between monitoring bolts and vibration absorbers, and changes to the system parameters of the vibration tester should be allowed by the railway department to enter the tunnel emergency inspection equipment. If the instrument is damaged, replace the instrument and use a standby instrument.

9. Monitor quality control procedures

(1) House observation: It has rich experience in the detection of gun damage and is subject to relevant training. Before the observation, the objects and contents to be observed during the inspection should be clearly defined, and relevant recording forms and necessary equipment (such as cameras) should be prepared; Observing the implementation of inspections, the construction personnel and supervisors are closely linked, and the frequency of observation within the cave is strengthened in the key construction steps.

(2) Tunnel blasting vibration speed monitoring: through the construction process of the new tunnel, the vibration information of the blasting vibration on the house under the condition of different surrounding rock grades, construction methods, footage, and maximum single explosive volume will be fed back in time to guide optimization. Construction methods, adjustment of excavation steps, correction of support parameters, etc. Minimize the impact of the construction of new tunnels on adjacent buildings, and make the impact control within the allowable scope of relevant regulations.

(3) On-site records: The contents should be complete and clear in writing. No alterations, alterations or transfers are allowed; where the number of changes and the results of over-limitation, the number of pages where the cause and retest results are located should be indicated; The electronic record should pay attention to the power supply of the record storage device and avoid data loss. Pay attention to the manually entered data review and process inspection.

10. Monitoring results and submission forms

(1) After observing the measuring points according to regulations, the data shall be analyzed and arranged in a timely manner in accordance with the scientific, accurate and timeliness requirements of the monitoring work, and the relevant statements shall be submitted within two days after the observation. Including monitoring items, allowable values, alarm values, data analysis, speed-time curves, and monitoring results.

(2) Submit a phased results report within four days after completion of the blasting test and analog test. The phased report includes safety distances, safety doses, and program feasibility opinions.

(3) When the monitoring data approaches or exceeds the alarm value, it shall promptly report to the relevant parties on the construction site. If there is a dangerous situation, the monitoring unit should first report by telephone orally within 2 hours, and then make a written report to sign and confirm.

(4) After the completion of the monitoring work, submit the monitoring report. The contents include: layout plan of monitoring points, monitoring instructions, monitoring results, statistical tables, monitoring curves, monitoring data for each construction phase, vibration analysis, conclusions, etc.

11. To be invested in the project equipment

No.

Device name

Specifications

unit

Quantity

GPS measuring instrument

Pentax/LGN-200

set

Blasting vibrometer

Jiaobo/L20-S

station

Blasting vibrometer

Jiaobo/L20-N

station

2-3

Digital camera

Sony

station

Testing equipment introduction:

Compass burst vibration meter L20-S

It is a portable vibration detector specially designed for engineering blasting. It is used to assess the influence of vibration caused by blasting construction on neighboring buildings, facilities and equipment, and provide basis for project acceptance and possible judicial procedures. The instrument is mature, stable, easy to use, portable, since the market was listed in 2011 has accumulated more than 1,000 sets of sales, completed tens of thousands of vibration detection tasks.

Commerzation Blasting Vibration Meter L20-N

With built-in 4G communication module, in any place where there is a mobile phone network, the blasting vibration data and waveforms acquired by the instrument can be uploaded in real time to a dedicated server. The user can view the data and waveforms at the remote site through the client to monitor the working status of the instrument. Low energy consumption, excellent durability, suitable for bridges, tunnels and other situations that require long-term vibration detection.

Fourth, the monitoring process and related cooperation

1. Workflow chart

Figure 5: Inspection workflow

2. Cooperation with relevant units

Blasting vibration monitoring is characterized by the simultaneous monitoring and blasting construction. The monitoring progress and blasting construction influence each other. Therefore, it is necessary to actively coordinate the relationship with the construction unit, the owner, and the supervision unit, especially the coordination and blasting construction unit. Relationships, in close cooperation with them, optimize monitoring.

Our company plans to set up a special information liaison group to be in charge of communication and coordination with the construction, supervision and construction parties. Its main functions are: continuously collect relevant information on the actual progress of the construction, master the progress and work arrangement of the construction site, and timely adjust our Monitoring work plan. The timely submission of our monitoring results to the construction party, and timely notification to the construction and supervision of the abnormalities found in the monitoring work.

Attachment 1: "Scene Investigation Map of Laolongshan Tunnel"

Attachment 2: Observing Data Records

The on-site monitoring must make monitoring records. The collected blasting parameters, model numbers, sensitivity, numbering, measuring point number, and corresponding position of the vibration pickup and recorder should be tabulated. The format of the recording table is shown in the table below. Original Record Table.

Blasting vibration test original record

Blasting time: Observation number:

project name

Observing operators

Construction unit

Observing unit

construction place

Blasting parameters

Aperture (mm)

Hole depth (m)

Number of holes

Slot hole charge

(kg)

Auxiliary hole charge

(kg)

Peripheral hole charge

(kg)

Detonator segment

The maximum amount of explosives (kg)

Total charge (kg)

Instrument Settings Parameters

Vibration meter model

Sensor model

Trigger method

Trigger level

Sampling length

Sample rate

Sampling delay

Observations

Measuring point position

Explosive area and measuring point distance

(m)

sensor

Vibrometer

Particle peak vibration speed

(cm/s)

Main frequency

(Hz)

Vibration duration

(ms)

Numbering

Sensitivity

(mv/cm/s)

Numbering

Range

(mv)

Description: Blasting parameters and distances are provided or completed by the constructor.

Observation Engineer Review:

Signature: Date:

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