Negative pressure detection method for welding scars of tunnel waterproof board

Abstract

The negative pressure detection method for the waterproof board weld scar provided by the present invention is based on a negative pressure detector. The negative pressure detector includes a diaphragm vacuum pump, a vacuum suction cup, a pressure transmitter, and a control system. Among them, the control system is respectively connected to the diaphragm vacuum pump and the pressure transmitter in a controlled manner; the air extraction port of the diaphragm vacuum pump is connected to the air outlet of the vacuum suction cup; the pressure transmitter is arranged on the connecting pipeline between the diaphragm vacuum pump and the vacuum suction cup; the method includes the following steps: closely attach the vacuum suction cup to the waterproof board weld scar to be detected; control the start of the vacuum pump to load the adsorption pressure to the pressure standard value; then record the air pressure time history curve, and the detection ends after reaching the standard time; judge whether the waterproof board weld scar to be detected is qualified according to the obtained air pressure time history curve; the present invention improves the working efficiency and accuracy of the weld scar density detection.

Description

Technical Field

[0001] The present invention belongs to the field of tunnel engineering construction quality inspection instruments and relates to a method for detecting the negative pressure of the welding scars of tunnel waterproof plates. Background Art

[0002] With the rapid development of transportation infrastructure, there are more and more tunnels in railway, highway, water conservancy, and urban subway projects. During the construction and operation management of tunnels, water seepage and leakage are long-term problems that cannot be effectively solved in tunnel engineering and are also key issues that urgently need to be solved regarding the quality and safety of tunnels.

[0003] Tunnel water seepage and leakage will bring serious adverse consequences to the safety of the tunnel and even the ecological environment in the tunnel area:

[0004] First, it erodes the tunnel lining, accelerates the carbonation reaction of concrete, and causes a decrease in the strength of the lining concrete and structural damage;

[0005] Second, it deteriorates the operating environment in the tunnel, and the water accumulation on the road surface will seriously affect driving safety;

[0006] Third, the humidity in the tunnel increases, which may cause corrosion of equipment such as communication, lighting, and power, short circuits in the lines, and abnormal operation, increasing the maintenance cost;

[0007] Fourth, in winter, it may cause the road surface to freeze or the icicles hanging from the vault to encroach on the boundary, further deteriorating the driving environment;

[0008] Fifth, it forms a groundwater flow channel, which may cause the groundwater level to drop and affect the ecological environment in the tunnel area.

[0009] Strengthening the quality inspection of tunnel water seepage and leakage during the construction process, especially strengthening the inspection of the quality of the welding scars of tunnel waterproof plates, is particularly important for preventing and controlling tunnel water seepage and leakage.

[0010] At present, the waterproof measures for composite lining tunnels mostly adopt laying geotextiles and polymer waterproof coiled materials between the primary support and the secondary lining to achieve the purpose of waterproofing. However, during the laying of the waterproof plate, the phenomenon of waterproof plate damage caused by non-standard construction occurs from time to time. For example, the waterproof plate is punctured by the exposed anchor bolts behind the waterproof plate, the waterproof plate is punctured by the initial support shotcrete of the embedded pipe fittings that is not covered, and the waterproof plate is burned by the welding of steel bars, etc., all of which are likely to cause damage to the waterproof plate and need to be repaired and welded. Inevitably, welding scars are formed. One of the main reasons for water seepage and leakage in the waterproof plate laying is that the quality of the welding scars is unqualified after local damage repair and welding. Therefore, using an effective detection method to ensure the density of the welding scars is crucial for preventing and controlling tunnel water seepage and leakage.

[0011] Although the current tunnel waterproofing and drainage technology has been greatly improved, due to the lack of equipment, methods, and quality acceptance standards for detecting the quality of waterproof board weld scars in tunnels, the detection of the quality of waterproof board weld scars is often overlooked, resulting in the failure to completely solve the problem of tunnel leakage. The annual treatment cost for tunnel leakage reaches hundreds of millions of yuan, causing huge economic losses.

[0012] At present, the detection methods and standards for the quality of waterproof board weld scars in tunnels are not clear and belong to a research blank. Therefore, it is of great significance to determine the detection parameters through experimental research, form a new detection method, design and manufacture a negative pressure detection device for waterproof board weld scars, formulate experimental detection methods and acceptance standards, and promote the application of research results to effectively prevent tunnel leakage. Summary of the Invention

[0013] The purpose of the present invention is to provide a negative pressure detection method for waterproof board weld scars in tunnels, which solves the above-mentioned deficiencies in the prior art.

[0014] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0015] The negative pressure detection method for waterproof board weld scars provided by the present invention is based on a negative pressure detector. The negative pressure detector includes a diaphragm vacuum pump, a vacuum suction cup, a pressure transmitter, and a control system. Among them, the control system is respectively connected to the diaphragm vacuum pump and the pressure transmitter for control; the air extraction port of the diaphragm vacuum pump is connected to the air outlet of the vacuum suction cup; the pressure transmitter is arranged on the connecting pipe between the diaphragm vacuum pump and the vacuum suction cup;

[0016] The method includes the following steps:

[0017] Press the vacuum suction cup tightly against the waterproof board weld scar to be detected;

[0018] Control the start of the vacuum pump to load the adsorption pressure to the pressure standard value;

[0019] Then record the air pressure time history curve, and the detection ends after reaching the standard time;

[0020] Judge whether the waterproof board weld scar to be detected is qualified according to the obtained air pressure time history curve.

[0021] Preferably, judging whether the waterproof board weld scar to be detected is qualified according to the obtained air pressure time history curve, the specific method is:

[0022] If the percentage of negative pressure drop of the waterproof board within the standard time is greater than 4%, the weld scar density detection is unqualified;

[0023] When the percentage of negative pressure drop of the waterproof board within the standard time is less than or equal to 4%, the weld scar density detection is qualified.

[0024] Preferably, the standard pressure value is -40.00 kPa.

[0025] Preferably, the standard time is 15 min.

[0026] Preferably, a check valve is connected to the air suction port of the diaphragm vacuum pump; a ball valve is arranged at the air outlet of the vacuum chuck.

[0027] Preferably, a filter is arranged at the air outlet of the vacuum chuck.

[0028] Preferably, the control system is connected with an industrial control touch display screen.

[0029] Preferably, the control system includes a microprocessor, and the microprocessor is connected to the diaphragm vacuum pump through a solid state relay.

[0030] Preferably, the microprocessor is connected to a pressure transmitter through a converter.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] The tunnel waterproof board weld scar negative pressure detection method provided by the present invention uses a diaphragm vacuum pump and a vacuum chuck to form negative pressure, and uses a control system to accurately reflect the negative pressure change value, realizing timely and accurate determination of whether the weld quality of the weld scar is qualified; by the cooperation of the check valve and the ball valve, a pressure relief pipeline is formed to realize the detachment of the vacuum chuck; the present invention improves the detection work efficiency.

[0033] Furthermore, by setting the standard value, the detection work efficiency and accuracy are improved.

[0034] Furthermore, the microprocessor is connected to the diaphragm vacuum pump through a solid state relay, which can realize variable frequency pumping pressure, further improving the stability of the detection equipment and the accuracy of the detection result. Brief Description of the Drawings

[0035] Figure 1 It is a schematic structural diagram of the detector involved in the present invention;

[0036] Among them, 1. Diaphragm vacuum pump 2. Check valve 3. Vacuum pressure reducing valve 4. Gas storage tank 5. Filter 6. Vacuum chuck 7. Pressure transmitter 8. Ball valve Q1. First air pipe Q2. Second air pipe Q3. Third air pipe Q4. Fourth air pipe Q5. Fifth air pipe Q6. Fifth air pipe T1. Three-way joint T2. Three-way joint. Detailed Embodiments

[0037] The present invention will be further described in detail below with reference to the drawings.

[0038] As Figure 1As shown in the figure, the negative pressure detector for the welding scar of the tunnel waterproof board provided by the present invention includes a diaphragm vacuum pump 1. The diaphragm vacuum pump 1 is sequentially connected with a one-way valve 2, a vacuum pressure reducing valve 3, a gas storage tank 4, a filter 5 and a vacuum suction cup 6 to form a negative pressure tightness detection pipeline.

[0039] Specifically: The air inlet of the diaphragm vacuum pump 1 is connected to the one-way valve 2 through a trachea. One end of the first trachea Q1 is connected to the diaphragm vacuum pump 1, and the other end is connected to the one-way valve 2.

[0040] The one-way valve 2 is connected to the vacuum pressure reducing valve 3 through a second trachea Q2.

[0041] The vacuum pressure reducing valve 3 is connected to the gas storage tank 4 through a third trachea Q3, and the gas storage tank 4 is connected to a tee T1; A pressure transmitter 7 is arranged on a free branch of the tee T1, and the pressure transmitter 7 is connected to the control system through a signal line.

[0042] The other end of the tee T1 is connected to a tee T2 through a fourth trachea Q4. One end of the tee T2 is connected to a fifth trachea Q5, and the other end is connected to a spherical valve 8. The spherical valve 8 is a manual control valve for instrument pressure relief.

[0043] The free end of the fifth trachea Q5 is connected to the filter 5.

[0044] The filter 5 and the vacuum suction cup 6 are connected through a sixth trachea Q6.

[0045] The connection between the vacuum suction cup 6 and the sixth trachea Q6 is detachable.

[0046] The pressure transmitter 7 is connected to a control system. The control system is a 32-bit ARM microprocessor, and its model is TM32F103VBT6 package. The microprocessor is controlled and connected to an industrial control touch display screen with the model of DMT80480T070-15WT, a micro thermal printer with the model of SP-RMDIV40SH, the pressure transmitter 7 and the diaphragm vacuum pump 1. Among them:

[0047] The pressure sensor 7 is sequentially connected to the microprocessor through a resistor and a filter with the model of LM358B.

[0048] The diaphragm vacuum pump 1 is connected to the microprocessor through a solid state relay.

[0049] The negative pressure detection method for the welding scar of the tunnel waterproof board provided by the present invention includes the following steps:

[0050] First, connect the sixth trachea Q6 to the vacuum suction cup 6, turn the spherical valve 8 to the closed state, and then, through the industrial control touch display screen, input the pressure standard value of -40.00 kPa and the lower limit pressure value of -38.40 kPa;

[0051] Then, press the vacuum suction cup 6 tightly against the waterproof board weld scar to be detected, click the start instruction on the industrial control touch display screen, the microprocessor controls the diaphragm vacuum air pump 1 to start by sending a signal to the solid-state relay, the diaphragm vacuum air pump 1 starts to work, and the extracted gas enters the diaphragm vacuum air pump 1 through the filter 5, three-way T2, three-way T1, gas storage tank 4, vacuum pressure reducing valve 3, and check valve 2;

[0052] Among them, when the weld scar area is smaller than the suction cup adsorption area, directly fix the suction cup at the waterproof board repair welding place, load the adsorption pressure to the pressure standard value of -40.00 kPa, the internal system automatically regulates the air pressure to reduce the errors caused by factors such as temperature and humidity, and start to officially record the air pressure time history curve after 1 minute, and automatically end the detection after 15 minutes; when the weld scar area is larger than the suction cup adsorption area, then cut off the weld scar, weld it into a weld form by a crawler welder, and conduct detection according to the weld detection method.

[0053] Finally, if the negative pressure drop percentage of the waterproof board is greater than 4% within 15 minutes, the weld scar tightness detection is unqualified, otherwise when the negative pressure drop percentage of the waterproof board is less than or equal to 4% within 15 minutes, the weld scar tightness detection is qualified.

[0054] The standard value for the detection of the present invention is obtained through the following methods:

[0055] First, conduct an indoor waterproof board weld scar adsorption test to analyze the air pressure loss mechanism under different negative pressure adsorption pressure gradients, and explore the regular relationship between the negative pressure adsorption value of the waterproof board, the adsorption area of the waterproof board, the thickness of the waterproof board, and the adsorption position;

[0056] Then, use ABAQUS finite element software to analyze the stress distribution response characteristics of the plate under different adsorption areas, adsorption pressures, adsorption parts, etc. in the negative pressure vacuum mode;

[0057] Finally, combine the indoor test results and the numerical simulation results to form the quality detection standard value for the tunnel waterproof board weld scar.

[0058] Among them, through the indoor model test study on the adsorption of the tunnel waterproof board weld scar, the regular relationship between the negative pressure adsorption value of the waterproof board, the adsorption area of the waterproof board, the thickness of the waterproof board, and the adsorption position was explored, and the following conclusions were obtained:

[0059] ① During the 30-minute test time, the air pressure loss gradually increases with the increase of the adsorption time, and the air pressure losses under different adsorption pressures roughly form 3 distribution ranges. The air pressure loss growth rate in the uppermost part is the fastest, the air pressure loss growth rate in the middle part is relatively slow, and the air pressure loss growth rate in the lowermost part is the slowest, indicating that the influence degrees of the air pressure losses caused by different adsorption pressures are different. At the same time, in order to eliminate the influence of tests and other factors, the adsorption time of 15 - 30 minutes is taken as the key research section.

[0060] ② The stability of the air pressure loss data under each working condition is judged by sorting the standard deviation of the negative pressure loss. When the adsorption pressure is -35.00 kPa, the standard deviation ranking is the largest, and the reliability during detection is the lowest, so it is not included in the consideration range of the adsorption standard. When the adsorption pressure is -65.00 kPa, the standard deviation ranking is the smallest, and the reliability during detection is the highest. The standard value rankings of the adsorption pressures of -45.00 kPa and -50.00 kPa are the second or the third, and they are less stable compared with other adsorption pressures with smaller standard value rankings. Therefore, the adsorption pressures of -40.00 kPa, -55.00 kPa, and -60.00 kPa ranked fourth to sixth are included in the optional range.

[0061] ③ The sensitivity of the air pressure loss data under each working condition is judged by sorting the average value K1 of the air pressure loss at different adsorption pressures at the same time. The larger the ranking, the stronger the sensitivity. When the adsorption pressure is -35.00 kPa, the K1 ranking is the largest. As the adsorption pressure increases, the K1 ranking gradually decreases. When the adsorption pressure is -65.00 kPa, the K1 ranking is the smallest. Therefore, the adsorption pressures with the top three K1 rankings are selected for consideration, namely -35.00 kPa, -40.00 kPa, and -45.00 kPa. Finally, considering both stability and sensitivity, -40.00 kPa is selected as the standard adsorption pressure value.

[0062] ④ The timeliness is analyzed through the time cost of a single detection and the differential cost of multiple detections. In the time cost of a single detection, a shorter adsorption time should be selected to improve the detection efficiency. In the differential cost of multiple detections, the adsorption time period with the best stability of the air pressure loss data should be selected to improve the decision-making efficiency. Based on the determined standard adsorption pressure of -40.00 kPa, the standard deviations of the air pressure loss data under different adsorption time periods are sorted. When the adsorption time is 15 min, the standard deviation of the air pressure loss data under each working condition is the smallest, indicating that the differential cost of multiple detections is the lowest. Considering comprehensively, when the adsorption time is 15 min, the time cost of a single detection is also the lowest. Therefore, 15 min is selected as the standard adsorption time. The air pressure loss rate data results of all working conditions under the adsorption pressure of -40.00 kPa and the holding pressure of 15 min are statistically analyzed. The maximum air pressure loss rate is 3.80%. After rounding the value to the nearest whole number, 4.0% is selected as the air pressure loss standard. (2) Numerical simulation is carried out through ABAQUS, a numerical simulation model of the negative pressure adsorption of the waterproof board under different adsorption pressures is constructed, and the mechanical response law of the plate during the detection of the welding scar quality of the tunnel waterproof board is analyzed. The conclusions are as follows:

[0063] ①Among the influencing factors of the deformation of the waterproof board, the adsorption area has the greatest influence, followed by the thickness of the waterproof board, and the adsorption position has an insignificant influence. When the suction cup is circular, the greater the thickness of the waterproof board, the less affected it is by the adsorption pressure. When the suction cup is rectangular, it can be seen that the change is very large at -40.00 kPa.

[0064] ②Among each influencing factor, the degree of influence of the deformation of the waterproof board caused by each adsorption pressure is different. Generally speaking, the most severe working conditions of the influence degree under each adsorption pressure are summarized. It is found that -40.00 kPa can meet the detection of most working conditions, verifying the feasibility of -40.00 kPa of adsorption pressure as the standard value of the detection pressure from a mechanical perspective.

[0065] (3) Combining the results of indoor model tests and numerical simulation analysis, the standard value for weld scar detection under the negative pressure detection method is obtained: using -40.00 kPa of adsorption pressure as the standard value for the tightness detection of the waterproof board weld scar, and the cumulative percentage of negative pressure loss within 15 minutes of holding pressure being less than or equal to 4% as the criterion for judging whether the weld scar is qualified.

[0066] During the process of vacuum pumping, the pressure transmitter 7 will generate a standard signal of 4 - 20 mA, send the current signal to the microprocessor through a resistor and a filter. The microprocessor converts the current signal into a digital signal (negative pressure value) through a 6-bit mode converter. When the negative pressure value approaches -40.00 kPa, the microprocessor issues an instruction to make the solid-state relay start and stop intermittently, so that the negative pressure value is accurately stabilized at -40.00 kPa. After stabilizing for a period of time, the solid-state relay stops working. The microprocessor starts to draw the negative pressure - time curve based on the time and the real-time collected negative pressure value, and sends it to the industrial control touch display screen for display. It can also print the processing results through a micro thermal printer, and store them through an SD card at the same time.

[0067] The materials used in the present invention are:

[0068] The air pipe is made of PC pipe, with an outer diameter of 6 mm and an inner diameter of 3 mm.

[0069] The pipe joint check valve 4 is a stainless steel 1 / 4 female thread check valve, and the length of the check valve is 50 mm.

[0070] The gas storage tank 4 is made of 304 stainless steel, with a length of 300 mm and a cross-sectional area of 80 mm * 80 mm.

[0071] The maximum range of the pressure transmitter 7 is -100.00 kPa, and the accuracy class is 0.25.

[0072] The ball valve is a 304 stainless steel 1 / 4 female thread ball valve (working valve).

[0073] The surface of the suction cup is made of silica gel, and the inside is an aluminum plate. The common diameters of circular suction cups are 30 cm and 50 cm, and the common area of rectangular suction cups is 20 cm * 40 cm.

[0074] The microprocessor converts the externally connected 220V power supply into 24V and 9V voltages through a transformer, and then rectifies them into 24V and 9V DC voltages to supply power to the industrial control touch screen and the printer.

Claims

1. A method for detecting the negative pressure of the welding scar of the tunnel waterproof board, characterized in that, This method is based on a negative pressure detector, which includes a diaphragm vacuum pump (1), a vacuum suction cup (6), a pressure transmitter (7) and a control system. Among them, the control system is respectively connected to the diaphragm vacuum pump (1) and the pressure transmitter (7) for control; the air extraction port of the diaphragm vacuum pump (1) is connected to the air outlet of the vacuum suction cup (6); the pressure transmitter (7) is arranged on the connecting pipeline between the diaphragm vacuum pump (1) and the vacuum suction cup (6); This method includes the following steps: Press the vacuum suction cup (6) tightly against the waterproof board weld scar to be detected; Control the vacuum pump (1) to start, so that the adsorption pressure is loaded to the pressure standard value, and the pressure standard value is -40.00 kPa; Then record the air pressure time history curve, and the detection ends after reaching the standard time, and the standard time is 15 min; Judge whether the waterproof board weld scar to be detected is qualified according to the obtained air pressure time history curve. The specific method is: If the percentage of negative pressure drop of the waterproof board within the standard time is greater than 4%, the weld scar tightness detection is unqualified; When the percentage of negative pressure drop of the waterproof board within the standard time is less than or equal to 4%, the weld scar tightness detection is qualified; The weld scar quality detection standard values include the pressure standard value, the standard time and the air pressure loss value. The method for obtaining them includes the following steps: First, conduct an indoor waterproof board weld scar adsorption test to analyze the air pressure loss mechanism under different negative pressure adsorption pressure gradients, and obtain the regular relationship between the negative pressure adsorption value of the waterproof board, the adsorption area of the waterproof board, the thickness of the waterproof board and the adsorption position; Then, use ABAQUS finite element software to analyze the force distribution response characteristics of the plate under the factors of different adsorption areas, adsorption pressures and adsorption parts in the negative pressure vacuum mode; Finally, combine the indoor test results and the numerical simulation results to form the tunnel waterproof board weld scar quality detection standard values.

2. The method for detecting the negative pressure of the welding scar of the tunnel waterproof board according to claim 1, wherein, A one-way valve (2) is connected to the air extraction port of the diaphragm vacuum pump (1); a ball valve (8) is arranged at the air outlet of the vacuum suction cup (6).

3. The negative pressure detection method for the welding scar of the tunnel waterproof board according to claim 1, characterized in that, A filter (5) is arranged at the air outlet of the vacuum suction cup (6).

4. The method for detecting the negative pressure of the welding scar of the tunnel waterproof board according to claim 1, characterized in that, The control system is connected with an industrial control touch display screen.

5. The method for detecting the negative pressure of the welding scar of the tunnel waterproof board according to claim 1, characterized in that, The control system includes a microprocessor, and the microprocessor is connected to the diaphragm vacuum pump (1) through a solid state relay.

6. The method for detecting the negative pressure of the welding scar of the tunnel waterproof board according to claim 5, characterized in that, The microprocessor is connected to the pressure transmitter (7) through a converter.

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