JP5286427B2 - Cavity inspection method for concrete structures - Google Patents

Description

  The present invention relates to a cavity inspection method for a concrete structure. More specifically, the present invention relates to a method for inspecting a cavity of a concrete structure, in which a concrete structure such as a PC structure is perforated and the presence / absence and degree of a cavity existing inside the PC structure is inspected.

  By the way, as a method for inspecting a cavity of a PC structure, there are, for example, 1) a method using radiographic imaging, 2) a method using elastic waves, and 3) a method of drilling holes at a plurality of locations to check communication between them. Was. The thing of patent document 1 is known as what belongs to a 2nd method.

However, the first method cannot be applied when the thickness of the structure exceeds the transmission limit. The second method is effective for the surface layer of the structure, but is difficult to apply at a thickness that does not reach the elastic wave. Furthermore, the third method is complicated because it is necessary to repeatedly perforate a plurality of locations and ventilate between the two locations.
JP 10-54140 A

  In view of such conventional circumstances, an object of the present invention is to provide a method for inspecting a cavity of a concrete structure capable of inspecting the presence / absence and degree of the cavity by perforating the cavity in one place. .

  In order to achieve the above object, the cavity inspection method for a concrete structure according to the present invention is characterized in that a concrete structure is perforated and gas adjusted to a constant pressure and flow rate flows into the cavity communicating with the hole. Alternatively, the time when the pressure fluctuation is measured together with time information after the outflow (hereinafter referred to as “inflow”, etc.) and the measured pressure starts to increase after the start of the inflow and reaches a predetermined reference pressure in a time range before converging to a constant value. Thus, the capacity of the cavity is obtained. It is also possible to estimate the size of the leak hole communicating with the cavity communicating with the hole from the pressure value when the measured pressure is converged to a constant value.

  Another feature of the present invention is that a concrete structure is perforated, a gas adjusted to a constant pressure and flow rate is allowed to flow from the hole into a cavity communicating with the hole, pressure fluctuation is measured together with time information, and a measurement pressure is measured. The measured pressure is divided by a constant pressure value converged to correct the measured pressure ratio, and the measured pressure ratio starts to increase and reaches the predetermined reference pressure ratio in the time range before converging to the fixed value. The purpose is to determine the capacity of the cavity.

The size of the leak hole communicating with the cavity can be estimated from the pressure value when the measured pressure is converged to a constant value.

  In addition, each said characteristic can be implemented about the grout unfilled part in the sheath pipe | tube in the PC structure. Note that air is used as the gas.

  According to the feature of the method for inspecting a cavity of a concrete structure according to the present invention, it is possible to inspect the presence / absence and degree of the cavity by perforating the cavity in one place.

  Other objects, configurations, and effects of the present invention will become apparent from the following embodiments of the present invention.

  Next, the present invention will be described in more detail with reference to the accompanying drawings as appropriate. In the present embodiment, a PC structure 100 used for a PC bridge or the like will be described as an example of a concrete structure.

  As shown in FIG. 1, an inspection apparatus 1 used for the first measurement method (inspection method) includes a compressor 2, a regulator 3, an on-off valve 4, a tank 5, a pressure sensor 6, and a second on-off valve 8 that are sequentially connected. The pressure of the pressure sensor 6 is recorded over time on a recorder 7 such as a digital oscilloscope. Further, the communication pipe 20 continuing to the second opening / closing valve 8 is mounted in a sealed state on the drilled investigation hole 130 via the seal 30.

  A PC (prestressed concrete) structure 100 as a concrete structure is formed by further passing a PC steel material 102 through a sheath tube 101 penetrated by a concrete base material 110 and applying tension to the PC steel material 102. Enlarged portions 103 are attached to both ends, and prestress is applied to the substrate 110. Then, grout 111 is injected into sheath tube 101 to prevent tension dispersion and corrosion of PC steel material 102. Since the unfilled portion of the grout 111 becomes a cavity 120 and becomes a problem, it is an object of the present invention to examine the existence and volume of the cavity 120. Therefore, the previous inspection hole 130 is appropriately drilled, and the communication pipe 20 is attached. The investigation hole 130 is appropriately drilled in the base material 110 and the sheath tube 101. Further, the existence of the leak hole 131 is unknown.

  At the start of the inspection, first, air with a predetermined pressure controlled by the regulator 3 from the compressor 2 is accumulated in the tank 5 as an example of gas with the second on-off valve 8 closed and the on-off valve 4 opened. The tank 5 has a predetermined constant volume and is filled with air to a predetermined constant pressure. By closing the on-off valve 4 in this state, compressed air having a predetermined pressure and a predetermined volume is prepared. When it is desired to change the predetermined capacity, a tank having a different capacity may be selected as appropriate.

  When the second opening / closing valve 8 is opened in such a state, the compressed air in the tank 5 is filled in the cavity 120 through the investigation hole 130 at once. The pressure fluctuation at this time is detected by the pressure sensor 6 and recorded in the recorder 7 together with time information.

  FIG. 2 shows that the volume of the cavity 120 is changed to 0.15 liter, 0.33 liter, 0.49 liter, 1.28 liter, 1.57 liter, and 3.27 liter in the state where the leak hole 131 does not exist. Or a recording result of the recorder 7 in a state where the communication pipe 20 is released to the atmosphere. In the present embodiment, the pressure is measured as a gauge pressure. The measured pressure is displayed as a time variation of the pressure ratio obtained by dividing the compressed air by the predetermined pressure. From this result, the capacity measurement of the cavity 120 is obtained as a correlation value between the pressure ratio and the volume of the cavity in the time zone in which the pressure ratio starts to be relaxed after the pressure ratio is suddenly lowered, as determined by the time variation of the pressure ratio. .

  On the other hand, FIG. 3 shows a case where the leakage hole 131 in FIG. 1 is provided, and shows results of experiments including a state where the cavity 120 having three different capacities denoted as A to C and the open air state where the communication pipe 20 is not connected are included. . By reading the points P1 to P3 determined by the pressure ratio and the time on the curve L1, which is the time zone in which the pressure ratio starts to be relaxed after a sudden pressure ratio drop, it is possible to substantially eliminate errors due to leakage. I can see that there is. The conditions A to C gradually approach a pressure ratio of zero with the passage of time, whereby the presence of the leak hole 131 is confirmed. This first method is advantageous in that the volume of the cavity can be measured in a very short time.

  2 and 3, the volume of the cavity 120 and the presence of the leak hole 131 can be confirmed by comparing the calibration curve obtained in advance with the measurement result. FIG. 4 is a graph showing the correlation between the measured pressure ratio and the actual volume of the cavity. In order to exhibit such a curve, in the case of the sign V1 having a small volume, the estimated volume value does not differ greatly even if the measurement pressure ratio value includes a reading error. However, in the case of the signs V2 and V3, even if a relatively small reading error occurs in the value of the measurement pressure ratio, this may greatly affect the volume measurement error. A second measurement method will be described below as a measurement method that hardly causes such measurement errors. In addition, the same code | symbol is attached | subjected to the member similar to the above below.

  In the second measurement method, gas (air) whose pressure and flow rate are adjusted to be constant is used. In this measuring method, the inspection apparatus 1 shown in FIG. 5 is used. A flow rate adjusting valve 11 is provided between the compressor 2 and the regulator 3 and the opening / closing valve 4. A recorder 7 is connected to the pressure sensor 6.

The test conditions are as shown in Table 1 below. For the leak hole 131, none, 1.1 mm1 diameter, 1.1 mm2 diameter, the cavity volume is 1.52 liters, 2.43 liters, Four cases of 5.46 liters and 9.16 liters were set, and experiments were performed with a total of 8 combinations.

  In the experiment, the communication pipe 20 is connected to the investigation hole 130 of FIG. 1 via the seal 30, the compressor 2 is driven, the pressure is adjusted with the regulator 3, the flow rate is adjusted with the flow rate adjusting valve 11, and a constant pressure / A constant flow of air was sent into the cavity. The graph of FIG. 6 shows the pressure fluctuation with respect to time at that time, and the enlarged view of the Z portion at the beginning of the experiment is the graph of FIG.

  According to the graph of FIG. 7, the cavity volume is grouped according to the time required to reach a predetermined constant pressure (reference pressure Pa, 0.03 MPa in this example) in a low pressure range where the measured pressure starts to increase after the start of inflow. It was done. Therefore, if expressed as such a low pressure range, for example, a pressure range of about 1/3 of the predetermined pressure finally reached after a few seconds, the time of the measured pressure immediately after the pressure starts to increase. It has been found that the capacity of the cavity communicating with the hole can be measured by the fluctuation.

  On the other hand, in the method of the graph of FIG. 6, it has been found that the size (integrated area) of the leak hole can be estimated from the pressure value after 30 seconds after the measured pressure is converged almost uniformly. Note that the “low pressure range” in FIG. 7 means a pressure range in which the influence of pressure fluctuation due to the leakage hole is small, and this concentrated high pressure range is a range of the counter electrode.

  By the way, in the above procedure in the second method, an error occurs in the estimated volume of the cavity due to the presence and the degree of leakage holes. When there is a leak hole, data that does not reach the predetermined pressure is obtained. Therefore, each measurement value is divided by the measurement pressure that is constant in FIG. 6 to obtain a result as shown in FIG. As described above, by correcting the measurement data by the measurement pressure that is constant so as to be a predetermined pressure, it is possible to reduce the error in the estimated volume of the cavity.

Finally, the possibilities of yet another embodiment of the present invention are listed.
In the above embodiment, air is used as the gas. However, a gas other than air may be used.

  In the above embodiment, only the case where gas is introduced from the communication pipe has been described. However, gas may be sucked from the investigation hole by using a decompressor instead of the compressor. In order to confirm this, FIG. 10 shows the result of measuring the relationship between the capacity and pressure of the cavity 121 made of a tank using the inspection apparatus 1 of FIG. In the inspection apparatus 1, a pressure sensor is connected to the communication pipe 20, and a decompression tank 15 that is a decompressor is connected via the opening / closing valve 4. When the volume of the cavity is 300, 250, 222 cc, and the vacuum tank is connected to the cavity 121 by releasing the valve 4 and aspiration is performed rapidly, the pressure corresponding to each volume is -36. It became 7 kPa, -38.4 kPa, and -41.3 kPa. Thereby, it is surmised that the first and second measurement methods function even during decompression (suction).

  INDUSTRIAL APPLICABILITY The present invention can be used for inspection of cavities of other concrete structures, for example, inspection of cavities in concrete structures of dams and rivers, in addition to inspection of cavities of PC structures.

It is the schematic of the block diagram of the test | inspection apparatus used for the cavity test | inspection method of a concrete structure, and the PC concrete structure which is an example of a concrete structure. It is a graph which shows the relationship between time in the case of not having a through-hole in a 1st measuring method (inspection method), and a pressure ratio. It is a graph which shows the relationship between time in the case of having a through-hole in a 1st measuring method, and a pressure ratio. It is a graph which shows the relationship between a measurement pressure ratio and the volume of a cavity part. It is a block diagram of the inspection apparatus used for the 2nd measuring method. It is a graph which shows the relationship between time and pressure in the 2nd measuring method. It is an enlarged view of the test initial part of FIG. It is a graph which shows the relationship between time and pressure ratio in the 2nd measuring method. It is a block diagram of the inspection device used at the time of outflow (vacuum suction). 10 is a graph showing the relationship between volume (capacity) and pressure when the apparatus of FIG. 9 is used.

  1: inspection device, 2: compressor, 3: regulator, 4: open / close valve, 5: tank, 6: pressure sensor, 7: recorder, 8: second open / close valve, 11: flow adjustment valve, 15: decompression tank, 20: Communication pipe, 30: Seal, 100: Concrete structure, 101: Sheath pipe, 102: PC steel, 103: Expanded part, 110: Base material, 111: Grout, 120, 121: Cavity (part), 130: Survey hole 131: Leakage hole

Claims (5)

A concrete structure is perforated, and a gas adjusted to a constant pressure and flow rate is made to flow into or out of a cavity communicating with the hole (hereinafter referred to as “inflow”).
Measure pressure fluctuations with time information,
A method for inspecting a cavity of a concrete structure in which the capacity of the cavity is obtained by a time to reach a predetermined reference pressure in a time range before the measured pressure starts to increase and converges to a constant value after the start of inflow. The method for inspecting a cavity of a concrete structure according to claim 1, wherein the size of a leak hole communicating with the cavity is estimated from a pressure value at the time when the measured pressure is converged to a constant value. Perforate the concrete structure, let the gas adjusted to a constant pressure and flow rate flow from this hole into the cavity communicating with the hole, etc.
Measure pressure fluctuations with time information,
Divide the measurement pressure by a constant pressure value that is the focus of the measurement pressure to correct the measurement pressure ratio,
A method for inspecting a cavity of a concrete structure in which the capacity of the cavity is obtained by a time to reach a predetermined reference pressure ratio in a time range before the measured pressure ratio starts to increase and converges to a constant value. 4. The method for inspecting a cavity of a concrete structure according to claim 3, wherein the size of a leak hole communicating with the cavity is estimated from a pressure value when the measured pressure is converged to a constant value. The method for inspecting a cavity of a concrete structure according to any one of claims 1 to 4, wherein the cavity is a grout unfilled portion in a sheath tube in a PC structure.

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