Method for monitoring pressure of filling retaining wall in whole process of drift cemented filling operation
By arranging static, seepage pressure, and dynamic pressure sensors on the filled retaining wall and calculating the safety margin D value using a data acquisition and processing terminal, the problem of monitoring lag in the filled retaining wall was solved, enabling real-time, multi-parameter monitoring of the retaining wall and improving filling safety.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JINCHUAN GROUP NICKEL COBALT CO LTD
- Filing Date
- 2025-12-31
- Publication Date
- 2026-04-28
AI Technical Summary
Existing technologies cannot achieve real-time, multi-parameter, and synchronous monitoring of infilled retaining walls, resulting in monitoring lag and the inability to prevent the risk of retaining wall instability.
Static pressure sensors, seepage pressure sensors, and dynamic pressure sensors are used to monitor the entire process of filling the retaining wall. The safety margin D value is calculated through the data acquisition and processing terminal to determine the stability of the retaining wall.
It enables in-situ, synchronous, and real-time monitoring of the infill retaining wall, providing early risk prevention and control and improving the safety level of infilling.
Smart Images
Figure CN121932233A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of monitoring technology for backfill mining, and particularly relates to a method for monitoring the pressure of the backfill retaining wall throughout the entire process of cemented backfilling operations. Background Technology
[0002] During the filling process, the retaining wall is continuously subjected to complex loads from the filling slurry, including static pressure, dynamic impact pressure, and pore water pressure generated by slurry bleeding. The combined effect of these loads is the root cause of retaining wall deformation and cracking. In order to effectively monitor and prevent the instability risk of the filled retaining wall, many mining companies currently use methods such as manual inspection and displacement scale observation to monitor the macroscopic displacement or deformation of the retaining wall surface. These methods can only capture the results after the load is applied, but cannot fully reveal the source load acting on the retaining wall. The monitoring dimension is single and cannot fully reflect the load state. Moreover, these methods rely on observing visible signs of damage or large displacements before taking action, resulting in significant monitoring lag. They usually do not have continuous, automatic, and real-time monitoring capabilities. Even if pressure and displacement data are collected using these methods, they often lack simultaneous acquisition and correlation analysis of multiple parameters. Summary of the Invention
[0003] To address the shortcomings of existing technologies, this invention provides a method for monitoring the pressure of the retaining wall during the entire process of cemented backfilling operations. This method effectively solves the problem of in-situ, synchronous, real-time, and comprehensive monitoring of the static pressure, dynamic pressure, and pore water pressure of the backfill slurry. It collects multiple parameters and provides reliable technical support for early risk prevention and proactive control of the backfilling process, thereby significantly improving the safety level of backfilling.
[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:
[0005] A method for monitoring the pressure of a retaining wall during the entire process of cemented backfilling operations, comprising a retaining wall, wherein the pressure monitoring method for the retaining wall is as follows:
[0006] 1) The roadway filling operation is divided into filling stages based on the number of filling operations. The first filling is the base filling stage, with a filling height of H1; the second filling is the secondary filling stage, with a filling height of H2; the third filling is the tertiary filling stage, with a filling height of H3; and so on, with the final filling being the top filling stage, with a filling height of H... n ;
[0007] 2) The height of the filling retaining wall is H0. The filling height refers to the filling height within each filling stage. Therefore, the current height of the retaining wall is H0 = H1 + H2 + H3 + ... + H n ;
[0008] 3) The collected data is automatically output to the data acquisition and processing terminal via a data transmission line. The data acquisition and processing terminal is equipped with data acquisition, storage, and processing devices. The stability of the filling retaining wall is judged by calculating and comparing the pressure safety margin D value with the safe value. The formula for the pressure safety margin D of the filling retaining wall is: Among them, P 设计 The design pressure value for the retaining wall; P 静 (t) represents the static pressure value of the retaining wall at time t; k is the influence coefficient, which is generally taken as 1.2 to 1.5 based on experience; ΔP 动 (t) represents the dynamic pressure fluctuation value of the retaining wall (1) at time t, indicating the maximum impact and vibration intensity experienced by the retaining wall (1) at time t, ΔP 动 (t)=max(P 动 (τ))-min(P 动 (τ)),τ∈(t-Δt,t);
[0009] 4) The method for judging the stability of the retaining wall is to compare the safety margin D of the filling retaining wall pressure with the safety value to judge the stability state of the filling retaining wall. When D is less than 80%, the overall structure of the retaining wall is basically stable and the filling retaining wall is in a stable state. When D is greater than 80%, the structure of the filling retaining wall may have begun to be damaged, the strength of the retaining wall gradually decreases, and the filling retaining wall is in an unstable state.
[0010] Preferably, a static pressure sensor is installed inside the retaining wall, a seepage pressure sensor is installed above the starting height of the filling, and a dynamic pressure sensor is installed at the horizontal position of the ending height of the filling. A cable transmission port is reserved on the retaining wall, and the data transmission lines of the static pressure sensor, the seepage pressure sensor, and the dynamic pressure sensor are output to the outside of the filling path through the cable transmission port. The data transmission lines are connected to a data acquisition and processing terminal.
[0011] Preferably, the pressure measuring surfaces of the static pressure sensor and the dynamic pressure sensor face the direction of the slurry pressure, and the pressure measuring surface of the permeation sensor faces the direction of the inlet top plate.
[0012] Preferably, the static pressure sensor is a vibrating wire earth pressure gauge to monitor the static pressure of the slurry on the retaining wall, meeting the requirements of a range of 0–0.2 MPa, a resolution ≤0.2%FS, an operating temperature of -25–+60℃, and waterproof and corrosion-resistant properties; the dynamic pressure sensor is a resistive earth pressure gauge to monitor the dynamic pressure of the slurry on the retaining wall, meeting the requirements of a range of 0–0.3 MPa, a maximum acquisition frequency of not less than 100 Hz, an operating temperature of -25℃–+60℃, and waterproof and corrosion-resistant properties; the pore pressure sensor is a vibrating wire piezometer to monitor the pore water pressure of the slurry, meeting the requirements of a range of 0–0.2 MPa, a resolution ≤0.2%FS, an operating temperature of -25℃–+60℃, and waterproof and corrosion-resistant properties.
[0013] Preferably, the data acquisition and processing terminal is installed outside the filling inlet and is equipped with a metal protective box. The data acquisition and processing terminal is equipped with a sensor data acquisition instrument, which is used to receive data collected by static pressure sensor, dynamic pressure sensor and seepage pressure sensor. It can collect data from multiple sensors at the same time and has data storage and output functions.
[0014] Preferably, before the filling operation begins, the data reporting interval of the static pressure sensor and the seepage pressure sensor is set to 5 to 10 minutes, and the acquisition frequency of the dynamic pressure sensor is set to 50 to 100 Hz.
[0015] The beneficial effects of this invention are as follows:
[0016] This invention provides a method for dividing the filling process into stages based on the number of filling operations. Within each stage, static pressure sensors, seepage pressure sensors, and dynamic pressure sensors are deployed. These sensors are installed on the retaining wall of the slurry side inside the filling inlet. The retaining wall pressure data monitored during the filling operation is transmitted to a data acquisition and processing terminal via a data transmission line. The safety margin D value of the filling retaining wall pressure is monitored according to specific calculation methods and steps, thereby enabling the monitoring of retaining wall pressure changes. This allows for the monitoring of the stability of the filling retaining wall throughout the entire filling operation, effectively monitoring and preventing the risk of instability of the filling retaining wall. Attached Figure Description
[0017] Figure 1 This is a schematic diagram of a method for monitoring the pressure of the retaining wall during the entire process of cemented backfilling operations according to the present invention.
[0018] Figure 2 is a schematic diagram of the filling height of a method for monitoring the pressure of the retaining wall during the entire process of cemented backfilling operations according to the present invention. Figure 3. Schematic diagram of sensor layout for a method of monitoring the pressure of the retaining wall during the entire process of cemented backfilling operation according to the present invention.
[0019] In the diagram: 1. Retaining wall, 2. Static pressure sensor, 3. Dynamic pressure sensor, 4. Seepage pressure sensor, 5. Data transmission line, 6. Cable transmission port, 7. Data acquisition and processing terminal. Detailed Implementation
[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0021] like Figure 1 , Figure 2 , Figure 3 The method shown is for monitoring the pressure of the retaining wall during the entire process of cemented backfilling operation. A static pressure sensor 2 is installed inside the retaining wall 1. A seepage pressure sensor 4 is installed above the starting height of the backfilling on the retaining wall 1. A dynamic pressure sensor 3 is installed at the horizontal position of the ending height of the backfilling on the retaining wall 1. A cable transmission port 6 is reserved on the retaining wall 1. The data transmission lines 5 of the static pressure sensor 2, seepage pressure sensor 4, and dynamic pressure sensor 3 are output to the outside of the backfilling road through the cable transmission port 6. The data transmission lines 5 are connected to the data acquisition and processing terminal 7 (Nanjing Danmo Electronic Technology Co., Ltd.). The pressure measuring surfaces of the static pressure sensor 2 and the dynamic pressure sensor 3 face the direction of the slurry pressure, and the pressure measuring surface of the seepage pressure sensor 4 faces the direction of the top plate of the backfilling road.
[0022] The static pressure sensor 2 is a vibrating wire earth pressure gauge that monitors the static pressure of the slurry on the retaining wall 1. It meets the following requirements: range 0-0.2MPa, resolution ≤0.2%FS, operating temperature -25-+60℃, and waterproof and corrosion-resistant performance. The dynamic pressure sensor 3 is a resistive earth pressure gauge that monitors the dynamic pressure of the slurry on the retaining wall. It meets the following requirements: range 0-0.3MPa, maximum acquisition frequency not less than 100Hz, operating temperature -25℃-+60℃, and waterproof and corrosion-resistant performance. The seepage pressure sensor 4 is a vibrating wire piezometer that monitors the pore water pressure of the slurry. It must meet the following requirements: range 0-0.2MPa, resolution ≤0.2%FS, operating temperature -25℃-+60℃, and waterproof and corrosion-resistant performance.
[0023] The data acquisition and processing terminal 7 (Nanjing Danmo Electronic Technology Co., Ltd.) is installed outside the filling inlet and is equipped with a metal protective box. The data acquisition and processing terminal 7 (Nanjing Danmo Electronic Technology Co., Ltd.) is equipped with a sensor data acquisition instrument, which is used to receive data collected by static pressure sensor 2, dynamic pressure sensor 3 and seepage pressure sensor 4. It can collect data from multiple sensors at the same time and has data storage and output functions.
[0024] Before starting the filling operation, set the data reporting interval of static pressure sensor 2 and seepage pressure sensor 4 to 5-10 minutes, and set the acquisition frequency of dynamic pressure sensor 3 to 50-100Hz. Then start the filling operation and follow these steps:
[0025] 1) The roadway filling operation is divided into filling stages based on the number of filling operations. The first filling is the base filling stage, with a filling height of H1; the second filling is the secondary filling stage, with a filling height of H2; the third filling is the tertiary filling stage, with a filling height of H3; and so on, with the final filling being the top filling stage, with a filling height of H... n ;
[0026] 2) The height of the filling retaining wall 1 is H0. The filling height refers to the filling height within each filling stage. Therefore, the current height of the retaining wall 1 is H0 = H1 + H2 + H3 + ... + H n ;
[0027] 3) The collected data is automatically output to the data acquisition and processing terminal 7 via data transmission line 5. The data acquisition and processing terminal 7 (Nanjing Danmo Electronic Technology Co., Ltd.) is equipped with data acquisition, storage, and processing equipment. It calculates and compares the pressure safety margin D value of the filling retaining wall 1 with the safety margin threshold to determine the stability of the filling retaining wall 1. The formula for the pressure safety margin D of the filling retaining wall 1 is: Among them, P 设计 Design pressure value for retaining wall 1; P 静 (t) represents the static pressure value of retaining wall 1 at time t; k is the influence coefficient, which is generally taken as 1.2-1.5 based on experience; ΔP 动 (t) represents the dynamic pressure fluctuation value of retaining wall 1 at time t, indicating the maximum impact and vibration intensity experienced by retaining wall 1 at time t, ΔP 动 (t)=max(P 动 (τ))-min(P 动 (τ)),τ∈(t-Δt,t);
[0028] The theoretical basis of the above safety margin formula D is the concept of "Factor of Safety", that is: This concept compares the ultimate capacity (such as failure load) of a structure or material with its design service value; the retaining wall monitoring load designed in this invention includes static and dynamic components, wherein the static component adopts the real-time monitored static pressure value P of the retaining wall. 静 (t) represents the continuously applied load; the dynamic component quantifies the intensity of the slurry's "dynamic disturbance pressure" and uses the dynamic pressure fluctuation amplitude ΔP within the monitoring window. 动The amplitude (t) is used instead of the instantaneous maximum value because it better represents the continuous adverse effects of load alternation on structural fatigue and stability, and it is more resistant to measurement noise interference. The amplitude ΔP of the dynamic pressure fluctuation of the retaining wall is... 动 The calculation method for (t) is as follows:
[0029] ΔP 动 (t)=max(P 动 (τ))-min(P 动 (τ)),τ∈(t-Δt,t);
[0030] Based on this, considering the influence of factors such as different retaining wall material properties, retaining wall structure types, and filling process methods on the overall stability of the infilled retaining wall, an influence coefficient k is added to the dynamic component based on experience to amplify the amplitude of dynamic pressure fluctuation of the retaining wall, thereby increasing the adaptability and accuracy of the formula for different working conditions. To evaluate the most unfavorable working condition, a conservative model of linear superposition is adopted: Comprehensive load effect = P 静 (t)+k·|ΔP 动 (t)|, which is the maximum additional effect that may be brought about by superimposing a fluctuation cycle on the basis of the current static load;
[0031] In summary, based on the widely accepted concept of "Factor of Safety" in the field of engineering safety, By comparing the combined load effect of the retaining wall under the pressure of the grout with the design bearing capacity of the retaining wall, a dimensionless ratio is obtained, which is the formula for calculating the safety margin D value:
[0032] 4) The method for judging the stability of the retaining wall is to compare the pressure safety margin D of the filled retaining wall 1 with the safety threshold to judge the stability state of the filled retaining wall 1. When D is less than 80%, the overall structure of the retaining wall is basically stable and the filled retaining wall 1 is in a stable state; when D is greater than 80%, the structure of the filled retaining wall 1 may have begun to be damaged, the strength of the retaining wall 1 gradually decreases, and the filled retaining wall 1 is in an unstable state.
[0033] This invention sets the safety margin D threshold at 80%, primarily based on general principles of engineering safety management, industry experience, and the early warning purpose of this method. In geotechnical and mining engineering, setting a safety factor greater than 1 for structural design is common practice. For example, if the safety factor for a retaining wall design is 1.25, the corresponding allowable load is approximately 80% of the design bearing capacity (i.e., 1 / 1.25 = 0.8). Setting the threshold at 80% means allowing approximately 80% of the design bearing capacity to be utilized, retaining at least a 20% capacity margin to cope with uncertainties such as material performance dispersion, measurement errors, and unforeseen loads, conforming to the traditional conservative design approach in engineering. Through retrospective analysis of monitoring data and subsequent structural conditions of mine backfill retaining walls, the applicant found that when the D value consistently falls below 80%, the retaining wall remains largely intact; however, when the D value repeatedly exceeds or remains above 80% for extended periods, the probability of visible cracks, significant deformation, or localized damage to the retaining wall increases significantly. Therefore, 80% is an effective early warning threshold derived from practical cases.
[0034] Before the filling test begins, the operators install static pressure sensor 2, dynamic pressure sensor 3, and pressure sensor 4 on the slurry side of the retaining wall 1 inside the filling channel. The data transmission lines 5 of each sensor are output through cable transmission ports 6 to the outside of the filling channel and connected to the data acquisition and processing terminal 7 (a product purchased from Nanjing Danmo Electronic Technology Co., Ltd.). After the connection is completed, the cable transmission ports 6 are sealed with cement mortar, the data acquisition device 7 is started, and then the filling operation is started. Filling is carried out sequentially according to the filling height of each stage. After filling is completed, the data collected by the data acquisition device 7 is processed and then used into the calculation formula of the safety margin D value to obtain the proportion of safety margin D. The value of safety margin D each time is compared with the threshold of 80% of safety margin D, thereby judging the stability of retaining wall 1.
[0035] Example 1
[0036] In this embodiment, the filling process is carried out three times. During the initial filling stage, the filling height H1 is 2.5m. During the second filling stage, the filling height H2 is 1m. During the final filling stage, the filling height H3 is 1m. The width L of the filling retaining wall 1 is 5m. The total filling retaining wall height H0 is 4.5m.
[0037] In this embodiment, the design pressure value P of retaining wall 1 is... 设计 The static pressure value P of retaining wall 1 was read at 267.30 kPa after 4 hours and 13 minutes of filling. 静 (t) is 107.71 kPa. The maximum dynamic pressure value of retaining wall 1 is 29.58 kPa and the minimum dynamic pressure value of retaining wall 1 is 4.37 kPa. Then the dynamic pressure fluctuation value ΔP 动The pressure (t) is 25.21 kPa, and the influence coefficient k is 1.3. After substituting the above data into the calculation formula for the safety margin D, the safety margin D is calculated to be 52.56%. Since the safety margin D is less than 80%, it is determined that the overall structure of the retaining wall 1 is basically stable under this filling method.
[0038] Example 2
[0039] In this embodiment, the filling process is carried out twice. Therefore, the filling stage is divided into the bottom filling stage, with a filling height H1 of 3.5m and the top filling stage, with a filling height H2 of 1m. The width L of the filling retaining wall 1 is 5m, and the total filling retaining wall height H0 is 4.5m.
[0040] In this embodiment, the design pressure value P of retaining wall 1 is... 设计 The static pressure value P of retaining wall 1 was read at 255.25 kPa after 3 hours and 45 minutes of filling. 静 (t) is 69.94 kPa. The maximum dynamic pressure value of retaining wall 1 is 18.10 kPa and the minimum dynamic pressure value of retaining wall 1 is 2.76 kPa. Then the dynamic pressure fluctuation value ΔP 动 The pressure (t) is 15.34 kPa, the influence coefficient k is 1.5, the calculated safety margin D is 36.42%, the safety margin D is less than 80%, and it is judged that the overall structure of retaining wall 1 is basically stable.
[0041] Example 3
[0042] The filling operation is divided into filling stages according to the number of filling operations. In this embodiment, the filling operation is carried out twice. Therefore, the filling stages are divided into the bottom filling stage, with a filling height H1 of 3.5m and the top filling stage, with a filling height H2 of 1m. The width L of the filling retaining wall 1 is 5m, and the total filling retaining wall height H0 is 4.5m.
[0043] In this embodiment, the design pressure value P of retaining wall 1 is... 设计 The static pressure value P of retaining wall 1 was read at 255.25 kPa after 6 hours and 23 minutes of filling. 静 (t) is 127.41 kPa, and the maximum dynamic pressure value ΔP of retaining wall 1 is read. 动 With t = 69.05 kPa and the minimum dynamic pressure of retaining wall 1 = 15.33 kPa, the dynamic pressure fluctuation value is 53.72 kPa. The influence coefficient k is taken as 1.5, and the calculated safety margin D is 81.48%. Since the safety margin D is greater than 80%, it is judged that the structure of the filled retaining wall 1 may have begun to be damaged, the strength of retaining wall 1 is gradually decreasing, and the filled retaining wall 1 is in an unstable state.
[0044] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A method for monitoring the pressure of a retaining wall during the entire process of cemented backfilling operations, comprising a retaining wall, characterized in that: The pressure monitoring method during the filling process of the retaining wall (1) is as follows: 1) The roadway filling operation is divided into filling stages based on the number of filling operations. The first filling is the base filling stage, with a filling height of H1; the second filling is the secondary filling stage, with a filling height of H2; the third filling is the tertiary filling stage, with a filling height of H3; and so on, with the final filling being the top filling stage, with a filling height of H... n ; 2) The height of the filling retaining wall (1) is H0. The filling height refers to the filling height within each filling stage. Therefore, the current height of the retaining wall (1) is H0 = H1 + H2 + H3 + ... + H n ; 3) The collected data is automatically output to the data acquisition and processing terminal (7) via the data transmission line (5). The data acquisition and processing terminal (7) is equipped with data acquisition, storage and processing equipment. The stability of the filling retaining wall is judged by calculating and comparing the pressure safety margin D value of the filling retaining wall with the safety value. The pressure safety margin D of the filling retaining wall (1) is calculated as follows: Among them, P 设计 Design pressure value for retaining wall (1); P 静 (t) represents the static pressure value of the retaining wall at time t; k is the influence coefficient, which is generally taken as 1.2 to 1.5 based on experience; ΔP 动 (t) represents the dynamic pressure fluctuation value of the retaining wall (1) at time t, indicating the maximum impact and vibration intensity experienced by the retaining wall (1) at time t, ΔP 动 (t)=max(P 动 (τ))-min(P 动 (τ)),τ∈(t-Δt,t); 4) The method for judging the stability of the retaining wall is to compare the safety margin D of the filling retaining wall pressure with the safety value to judge the stability state of the filling retaining wall. When D is less than 80%, the overall structure of the retaining wall is basically stable and the filling retaining wall is in a stable state. When D is greater than 80%, the structure of the filling retaining wall may have begun to be damaged, the strength of the retaining wall gradually decreases, and the filling retaining wall is in an unstable state.
2. The method for monitoring the pressure of the retaining wall during the entire process of cemented backfilling operation according to claim 1, characterized in that: A static pressure sensor (2) is installed inside the retaining wall (1). A seepage pressure sensor (4) is installed above the starting height of the filling. A dynamic pressure sensor (3) is installed at the horizontal position of the ending height of the filling. A cable transmission port (6) is reserved on the retaining wall (1). The data transmission lines (5) of the static pressure sensor (2), seepage pressure sensor (4), and dynamic pressure sensor (3) are output to the outside of the filling path through the cable transmission port (6). The data transmission lines (5) are connected to the data acquisition and processing terminal (7).
3. The method for monitoring the pressure of the retaining wall during the entire process of cemented backfilling operation according to claim 1, characterized in that: The static pressure sensor (2) and the dynamic pressure sensor (3) have their pressure measuring surfaces facing the direction of the slurry pressure, while the pressure measuring surface of the permeation sensor (4) faces the direction of the inlet top plate.
4. The method for monitoring the pressure of the retaining wall during the entire process of cemented backfilling operation according to claim 1, characterized in that: The static pressure sensor (2) is a vibrating wire earth pressure gauge that monitors the static pressure of the slurry on the retaining wall (1). It meets the requirements of a range of 0 to 0.2 MPa, a resolution of ≤0.2%FS, an operating temperature of -25 to +60℃, and waterproof and corrosion-resistant properties. The dynamic pressure sensor (3) is a resistive earth pressure gauge that monitors the dynamic pressure of the slurry on the retaining wall. It meets the requirements of a range of 0 to 0.3 MPa, a maximum acquisition frequency of not less than 100 Hz, an operating temperature of -25℃ to +60℃, and waterproof and corrosion-resistant properties. The pore pressure sensor (4) is a vibrating wire pore pressure gauge that monitors the pore water pressure of the slurry. It meets the requirements of a range of 0 to 0.2 MPa, a resolution of ≤0.2%FS, an operating temperature of -25℃ to +60℃, and waterproof and corrosion-resistant properties.
5. The method for monitoring the pressure of the retaining wall during the entire process of cemented backfilling operation according to claim 1, characterized in that: The data acquisition and processing terminal (7) is installed outside the filling inlet and is equipped with a metal protective box. The data acquisition and processing terminal (7) is equipped with a sensor data acquisition instrument, which is used to receive data collected by the static pressure sensor (2), the dynamic pressure sensor (3) and the seepage pressure sensor (4). It can collect data from multiple sensors at the same time and has data storage and output functions.
6. The method for monitoring the pressure of the retaining wall during the entire process of cemented backfilling operation according to claim 1, characterized in that: Before the filling operation begins, set a static pressure sensor (2) and a seepage pressure sensor (4) with a data reporting interval of 5 to 10 minutes, and set a dynamic pressure sensor (3) with a sampling frequency of 50 to 100 Hz.