JP4899164B2 - Measuring method of ground saturation by air injection - Google Patents

Description

  The present invention relates to a measurement method of an air injection state in an air injection means to the ground, which is a measure for preventing liquefaction of the ground, and measures the saturation of the ground that changes due to the air injection to the ground by combining two measurement methods. The present invention relates to a method for measuring the degree of ground saturation by air injection.

  Conventionally, as a technology to prevent liquefaction of the ground, a gas-liquid mixed fluid containing air bubbles (for example, fine air mixed water) is injected into the ground, or only air is directly injected into the ground. Proposals have been made to reduce the saturation of the ground by retaining a large number of air bubbles to prevent liquefaction. The soil saturation referred to here is the volume ratio between the soil particles constituting the ground and the soil particles, and the pore water (ground water) existing in the gaps (between ground water volume / soil particles). This is an index indicating the degree of possibility of liquefaction of the ground.

  However, various techniques such as a method and an apparatus for injecting only air-liquid mixed fluid containing air or air into the ground have been proposed (for example, Patent Document 1). In other words, there has been a problem that an appropriate method for measuring changes in the saturation level of the ground has not been established.

  Specifically, although investigations to investigate the degree of saturation of the ground using a known geophysical exploration method are underway, the investigation target is limited to the shallow depth region of the ground, Or there was a problem that the degree of saturation of the ground could not be measured as a whole for a predetermined ground because it was specified for exploration of a relatively large cavity or gap. Furthermore, even if the technology is based on a combination of multiple measurement methods, the measurement unit of each measurement method (for example, potential difference or frequency) may be different, making the mutual evaluation of measurement values complicated or similar. Even with combinations of different measurement methods depending on the unit of measurement, there is a problem that the unambiguous evaluation is difficult due to a decrease in the accuracy of the measurement value because there is no evaluation method that can absorb the difference in the measurement value obtained there. In addition to the geophysical exploration method, there is a method in which a part of the target ground is frozen and solidified by using, for example, a ground freezing method and then drilled and collected, and a sample of the solidified ground is investigated. Quantitative evaluation becomes difficult because it takes a great deal of time to complete the survey, affects the construction period of the ground liquefaction countermeasures itself, and is expensive, so it cannot be adopted in construction work. There was a problem of being.

  As a result, since the saturation level of the ground during / after air injection is unclear, the method of air injection, determination of the injection location, selection of the injection device and appropriate control of the injection amount cannot be performed, and time This leads to the problem.

Japanese Patent Laid-Open No. 2007-132061

  Therefore, the present invention relates to a method for measuring ground saturation in a ground liquefaction prevention method for insaturating the ground by injecting air into the ground. It is possible to measure two-dimensionally or three-dimensionally, and it is possible to measure with high accuracy so as to complement each other's functional inferiority by a combination of two kinds of measurement methods. In order to enable measurement of air, the method of injecting air, determining the injection location, selecting the injection device and controlling the injection amount appropriately, the air injection means to the ground has been optimized, and the measurement of ground that does not require a long time for measurement It aims at providing the measuring method of saturation.

  In order to achieve the above object and to solve the problems, the present invention is configured as follows.

The method for measuring the degree of saturation of the ground by air injection in the ground liquefaction prevention method for injecting air into the ground according to claim 1 and desaturating the ground,
The soil saturation is measured by measuring the relative permittivity of the ground using a relative permittivity measuring device, and the soil saturation is measured by measuring the specific resistance change rate of the ground using a specific resistance tomography measuring device. The correlation between the degree of saturation of the ground is derived from the measurement result obtained by the specific resistance tomography measurement apparatus and the measurement result obtained by the specific dielectric constant measurement apparatus, and the measurement result obtained by the specific resistance tomography measurement apparatus is derived from the specific dielectric constant measurement apparatus. By calibrating based on the measurement result, saturation of a predetermined ground is measured as a measurement result by the relative permittivity measurement device by a measurement method by the specific resistance tomography measurement device.

In the invention according to claim 1, the ground saturation measurement method by air injection in the ground liquefaction prevention method of injecting air into the ground according to claim 2 of the present application and desaturating the ground,
Highly accurate and wide-range ground saturation by partially arranging the measurement points of the relative permittivity measurement device and arranging the measurement points of the specific resistance tomography measurement device in a wide range and measuring the soil saturation at the same time It is characterized by measuring the degree.

In the invention according to claim 1 or 2, the ground saturation measurement method by air injection in the ground liquefaction prevention method of injecting air into the ground according to claim 3 of the present application and desaturating the ground,
(1) The electrode of the specific resistance tomography measuring device is installed in the ground and the ground surface, and the probe of the relative permittivity measuring device and the air injection pipe are further installed in the ground. (2) The relative permittivity measuring device and the ratio Soil saturation is measured by a resistance tomography measuring device, (3) air is injected from the air injection pipe into the ground, and (4-1) once the measured value of the relative permittivity measuring device changes, the air is injected once. Stop and measure the ground saturation with the resistivity tomography measuring device. (4-2) Or, when the measured value of the resistivity tomography measuring device changes, air injection is temporarily stopped and the relative permittivity measuring device is The ground is newly installed on the ground where the measurement value has changed, and the saturation of the ground is measured. (5) If the predetermined saturation or the distribution of the saturated ground is not satisfied, the steps (3) and (4-1) ) Or (4-2) Wherein the air injected into the ground by a series of the steps (1) to (5) to return.

The ground saturation measurement method in the ground liquefaction prevention method for injecting air into the ground according to claim 4 and desaturating the ground is the invention according to any one of claims 1 to 3. In
The relative dielectric constant measuring device is an FDR measuring device, a TDR measuring device, or an ADR measuring device.

The ground saturation measurement method in the ground liquefaction prevention method for injecting air into the ground according to claim 5 of the present invention to desaturate the ground is the invention according to any one of claims 1 to 4. In
It is characterized in that the saturation of the ground is measured two-dimensionally or three-dimensionally by a specific resistance tomography measuring device.

According to the present invention,
After derivation of the correlation between the measurement results of the relative permittivity measurement device and the specific resistance tomography measurement device, the measurement result by the specific resistance tomography measurement device is calibrated based on the measurement result of the relative permittivity measurement device with high measurement accuracy. And after calibrating, we decided to measure the saturation of the ground with a specific resistance tomography measurement device,
There is no complexity in the evaluation of the two types of measurement values, leading to improvements in measurement accuracy and accuracy.

In addition, in order to arrange a large number of measurement points of a specific resistance tomography measurement device that is easy to install,
Soil saturation can be measured over a wide range without limiting the ground to be surveyed to shallow depths or local areas, or being specified for exploration of cavities and voids. The points can be kept in partial arrangement.

In addition, both types of measurement methods employ a geophysical exploration method in which electrodes and probes for measurement are installed in the ground or on the ground surface.
Compared to the method of directly collecting a part of the ground, it can be measured in a short time, leading to a reduction in the overall construction period of the liquefaction countermeasure work, and at a low cost.

  In addition, the electrode of the specific resistance tomography measuring device is installed in the ground and the ground surface, and the probe of the relative permittivity measuring device and the air injection pipe are installed in the ground, and the relative permittivity measuring device and the specific resistance tomography measurement The saturation of each ground is measured by the device, air is injected from the air injection pipe into the ground, and when the measured value of the relative permittivity measuring device changes, the air injection is temporarily stopped and the specific resistance tomography measuring device ratio When the resistance value is measured or the measured value of the resistivity tomography measuring device changes, air injection is temporarily stopped, and the relative permittivity measuring device is newly installed on the ground where the measured value has changed to measure the saturation of the ground. However, if the saturation level or the distribution condition of the saturated ground is not satisfied, it is a series of steps that repeat the air injection process. It can be more effectively exhibited mutual advantage of the wide area measurement by Fi measuring device.

  In addition, since the relative permittivity measuring device has a degree of freedom to be an FDR measuring device, TDR measuring device or ADR measuring device, a measuring method and measuring device corresponding to the ground condition such as soil and groundwater or other construction conditions are appropriately selected. can do.

  Furthermore, since the saturation distribution of the two-dimensional or three-dimensional ground is clarified by the specific resistance tomography measurement device, it is possible to determine the air injection method, determine the injection location, select the injection device, and control the injection amount appropriately. There is an effect.

  Hereinafter, as a method for measuring the degree of saturation of the ground in the ground liquefaction prevention method for injecting air into the ground of the present invention to desaturate the ground, a case where the relative permittivity measuring device is an FDR measuring device will be exemplified. This will be described with reference to the drawings.

  First, as shown in FIG. 1, the process of installing an air injection device, an FDR measurement device and a specific resistance tomography measurement device on the target ground according to the embodiment of the present invention, and prevention of liquefaction of the ground are shown. An air injection pipe 2b having an air injection hole 2a at the tip is installed (for example, by drilling) on the target ground 1a to take measures for desaturation of the target ground 1 and the surrounding ground 1; An air injecting device 2 for desaturating the target ground 1a is provided by pipe connection to an air production facility comprising an air compressor 2c, an air reservoir 2d, a flow rate control device 2e, and the like installed on the ground. The air injection hole 2a is not limited to the tip portion, and may be at an intermediate position of the air injection pipe 2b or at a plurality of locations. Further, the air injection pipe 2b is spaced in the front-rear direction or the left-right direction. You may install multiple.

  Next, a perforation 5 a is built in the target ground 1 a or the ground 1 in the vicinity thereof, and the probe 3 a is inserted into the target ground 1 a and the ground 1. A measurement connection 3b is connected to the probe 3a, and further, the FDR measurement device 3 is configured by being connected to a controller 3c installed on the ground. Here, as for the installation location of the probe 3a of the FDR measuring device 3, for example, several may be installed at the outer edge main part of the target ground 1a and its intermediate part. The controller 3c is a measurement unit including a tracking generator, a directive coupler, a spectrum analyzer, a computer, and the like.

  Further, a perforation 5b is constructed with a slight separation from the target ground 1a, the electrode 4a is inserted into the ground 1, and the electrode 4a and the far electrode 4a 'are also installed on the ground surface 1b. A measurement connection 4b is connected to the electrode 4a and the far electrode 4a ′, and a specific resistance tomography measurement device 4 is configured by connecting to the controller 4c installed on the ground. Here, it is efficient to arrange the electrodes 4a in a row in the perforations 5b while maintaining, for example, a 1 m interval, and to arrange them on the ground surface 1b in a plane with a similar interval in the front-rear direction and the left-right direction. It is. The number of electrodes 4a or the installation interval may be increased or decreased according to the required measurement accuracy, and a plurality of perforations 5b may be installed so as to surround the target ground 1a. The controller 4c is a measurement unit that includes a transceiver, an electrode switching device, an analysis device, a computer, and the like.

  Here, the perforation 5a and the specific resistance tomography measuring device 4 (hereinafter also simply referred to as “specific resistance tomography”), which are the structural facilities of the FDR measuring device 3 (hereinafter also simply referred to as “FDR”). Each of the perforations 5b may be backfilled with earth and sand generated at the time of perforation after insertion of the probe 3a or the electrode 4a, or the perforated walls may be maintained by filling muddy water made on the ground. Moreover, each measuring device uses the earth and sand which comprises the ground 1 or the target ground 1a, respectively, and calibrates beforehand, respectively, and eliminates the measurement error resulting from soil quality.

  Next, as shown in FIG. 2, the process of calibrating the measurement result of the specific resistance tomography based on the measurement of the FDR, the air is applied to the target ground 1 a and the ground 1 by the FDR measurement device 3 and the specific resistance tomography measurement device 4. The initial relative dielectric constant and the initial specific resistance change rate before injecting 6 are measured, and the initial value of the saturation degree of the ground of the original ground is measured. In the figure, the saturation level of the ground is measured for each of the measurement points 3d of the FDR over several measurement paths 4d where the measurement point 3d is positioned as an intermediate point of the measurement path 4d of the resistivity tomography. It is in form. Of course, it is desirable to measure the saturation of the ground by specific resistance tomography at all the measurement points 3d of the installed FDR probe 3a.

  Accordingly, the measurement point 3d where the FDR probe 3a is installed is usually measured by the FDR measurement device 3 and the specific resistance tomography measurement device 4 and in the case of measurement by the specific resistance tomography measurement device 4, usually a plurality of measurement paths 4d. The saturation of the ground is measured. Here, the measurement accuracy of both measurement devices is that the FDR measurement device 3 measures a local range of several millimeters to several tens of millimeters around the probe 3a by the dielectric constant, whereas the specific resistance tomography measurement device 4 uses the electrode 4a. , 4a is measured based on the rate of change of electrical resistance, and may be processed based on soil-specific parameters (eg, detour coefficient, caking coefficient or saturation coefficient), The measurement result by FDR is excellent. Therefore, the correlation of the ground saturation is obtained from the respective measurement results by the specific resistance tomography measurement device 4 and the FDR measurement device 3, and the measurement result by the specific resistance tomography is calibrated based on the measurement result by the FDR. The measurement results are matched so that the measurement results obtained by resistivity tomography indicate the measurement results obtained by FDR. Further, as shown by the broken line R, it is efficient if the controllers 3c and 4c are connected so that the output signal (FDR measurement result) from the controller 3c can be automatically calibrated in the controller 4c. It is.

  Thus, after installing the air injection device 2, the FDR measurement device 3 and the specific resistance tomography measurement device 4 on the target ground 1a, the ground 1, and measuring the initial value of the saturation of the ground of the original ground as described above, As shown in FIG. 1, air (compressed air) 6 is injected from the air injection device 2 into the ground 1 using the air injection hole 2a as a discharge hole for the air 6, and air bubbles are mixed to desaturate the ground of the target ground 1a. Start. In this embodiment, the desaturation means for directly injecting the air 6 into the ground 1 and the target ground 1a is shown. However, this is the case, for example, when a gas-liquid mixed fluid containing fine air bubbles is injected. However, what is necessary is just by the means to change the saturation degree of the ground.

  Next, after the injection of the air 6 of a certain amount, the injection of the air 6 is temporarily stopped, and the saturation of the ground is measured as shown in FIG. 2 by the FDR probe 3a installed at the predetermined measurement point 3d. . Furthermore, again, by calibrating the measurement result by the resistivity tomography based on the measurement result by the FDR, highly accurate data is collected, and the measurement of the resistivity tomography is similarly performed by the FDR measurement result for the subsequent measurements. While calibrating the results, the operation of injecting the air 6 is continued to promote the desaturation of the ground.

  However, since it is rare that the air 6 to be injected always continues to be stably diffused inside the target ground 1a and the ground 1, measurement with the probe 3a at the initially arranged measurement point 3d is possible at all times. Not necessarily. Therefore, in such a case and when it is necessary to confirm the degree of desaturation of the ground by high-precision measurement of FDR, the measurement procedure described above is reversed and measurement by specific resistance tomography is performed. Based on the result (specify the location where the saturation level of the ground has changed), the perforation 5a and the probe 3a are newly added to the target ground 1a and the ground 1, and connected to the controller 3c by the measurement connection 3b and connected by the FDR. By measuring, it is possible to realize highly accurate saturation measurement in a form in which a change point of saturation is pursued (illustration is omitted). In this case, since the measurement point 3d is directly added to the absolute position where the degree of saturation is changed, quantitative measurement can be performed by the measurement point 3d thereafter.

  Here, if the measurement of ground saturation is repeated a plurality of times, and the work of calibrating the measurement result by resistivity tomography based on the measurement result of FDR is repeated each time, both measurements by FDR and resistivity tomography are performed. From the results, the correlation of the degree of saturation of the ground is clarified, and based on this correlation, it is often possible to obtain an almost stable measurement result only by resistivity tomography.

  Therefore, as shown in FIG. 3, the process of measuring the degree of saturation of the ground by resistivity tomography, when a stable measurement result can be obtained from the resistivity tomography, thereafter, only the resistivity tomography is used. It becomes possible to measure the degree of saturation. In other words, the soil saturation measurement method employs resistivity tomography, and the measurement result can reflect the same numerical value in the FDR measurement result. Problems such as the complexity of value evaluation can be overcome. Note that the FDR measurement device 3 may be always functioned and used for measurement such as checking the instantaneous value of the saturation change.

  Here, as a feature of both measurement methods, in the saturation measurement by FDR, a measurement result can be obtained instantaneously, and in order to enable local measurement, numerical values in the absolute coordinates of the target ground 1a and the ground 1 can be acquired. On the other hand, for a wide range of measurements, the number of installation points of the probe 3a increases and measurement between the probes 3a and 3a is not possible. On the other hand, saturation measurement by resistivity tomography is suitable for wide-area measurement, but it takes a certain amount of time for the measurement itself due to the required amount of the electrode 4a to be installed, and the saturation is further analyzed through analysis of the measured value. As a result, a corresponding time lag occurs from the start of the measurement, and the distance between the electrodes 4a and 4a is increased, so that there is an obstacle in the target ground 1a and the ground 1, so that accurate measurement is possible by cutting the measurement path 4d. Extremely difficult.

  Therefore, in the present invention, by combining the FDR measurement device 3 and the specific resistance tomography measurement device 4 to measure the saturation of the ground, the inferiority of both measurement methods is complemented and eliminated, and accurate and wide-range saturation measurement is performed. Is possible. As a result, it is possible to measure the degree of saturation over the entire ground 1 without limiting the conventional measurement area to a shallow part or a local part, or being specified for exploration of a cavity or a gap. At this time, since the probe 3a of the FDR measuring device 3 mainly functions to calibrate the measurement result of the specific resistance tomography, the probe 3a may be partially arranged, whereas the electrode of the specific resistance tomography measuring device 4 4a is arranged in multiple points over the ground 1 and the ground surface 1b according to the required measurement accuracy.

  Here, as shown in FIG. 4, the relationship between the FDR measurement result and the resistivity tomography measurement result, the ground saturation based on the measurement result by the high-precision measurement method corresponding to the soil condition of the original ground Therefore, the correlation between the measurement result (34b) and the measurement result (34b) by the specific resistance tomography measurement device 4 is obtained with reference to the measurement result of the FDR measurement device 3 using the actual target ground 1a. By obtaining the calibration curve 34a, the specific resistance tomography measurement result can be calibrated based on the FDR measurement result. Therefore, the measurement result by specific resistance tomography can be used as a highly accurate measurement result by FDR. As a result, it is possible to add measurement accuracy equivalent to the measurement by the high-precision measurement method of FDR to the resistivity tomography which is originally good at wide-area measurement. In addition, illustration is an example of the ground which is one test result by the present applicant and has the simplest primary correlation, but when it becomes a quadratic function depending on the properties of soil particles and groundwater constituting the ground, Furthermore, there is a case where the correlation is shown as a higher-order function, and there is a case where the correlation needs to be acquired for each layer when the ground changes greatly.

  Next, as shown in FIG. 5, as an advantage of combining specific resistance tomography with one of the soil saturation measurements, the measurement results can be arbitrarily set as shown in FIG. It is possible to cut out as a horizontal or vertical two-dimensional section, and to visualize progress of desaturation of the target ground 1a and the ground 1 over time. Of course, this measurement result is highly accurate that is calibrated by the FDR measurement result.

  Furthermore, the measurement path 4d by specific resistance tomography, as shown in one cross section in FIG. 3, can be finely set according to the number of the electrodes 4a and the installation interval. It is also possible to display an oblique cross section, and although illustration is omitted, if a plurality of cross sections are three-dimensionally synthesized on a computer, the state of air (air bubbles) 6 injection as a three-dimensional graphic and the change in ground saturation In addition, it becomes possible to grasp the progress of continuous desaturation over time.

  The above also leads to specifying the drilling position of the air injection pipe 2b. For example, from the installation of the air injection pipe 2b at regular intervals found in the prior art, the air 6 can be gathered at places where injection of the air 6 is difficult. It is possible to plan to install the air injection pipe 2b. Furthermore, the various proposed air injection methods also serve as an element for selecting the most appropriate injection method and apparatus, control of the required injection amount of the air 6 is optimized, and the target ground 1a is frozen and solidified, for example. Therefore, the measurement work itself can be completed in a relatively short time, and quantitative evaluation is possible. This leads to cost reduction. The construction period is shortened as a whole.

  Note that the case where the relative permittivity measuring device is a TDR measuring device or an ADR measuring device is basically the same as the case of the FDR measuring device 3 with different measurement units, but the description thereof is omitted. In particular, it is within the scope of the present invention to appropriately change the design of the configuration shown in the embodiment here.

It is a longitudinal cross-sectional view which shows the process of installing an air injection apparatus, a FDR measurement apparatus, and a specific resistance tomography measurement apparatus in the object ground of embodiment of this invention, and the injection | pouring condition of air. It is a longitudinal cross-sectional view which shows the process of calibrating the measurement result of specific resistance tomography based on measurement of FDR of embodiment of this invention. It is a longitudinal cross-sectional view which shows the image of the measurement process of the saturation degree of the ground by the specific resistance tomography of embodiment of this invention. It is a correspondence relationship between the two measurement results for calibrating the measurement result of the specific resistance tomography based on the measurement of the FDR of the embodiment of the present invention, and the degree of saturation of the ground based on the measurement result of the FDR and the measurement result of the specific resistance tomography It is a graph which shows correlation of these. It is the saturation degree and saturation distribution of the ground in the arbitrary cross section of the ground of embodiment of this invention, (A) is the image | video which visualized a part of two-dimensional horizontal cross section of object ground, (B) is 2 of object ground. It is the image which visualized a part of the dimension vertical section.

Explanation of symbols

1 Ground 1a Target ground (ground for desaturation prevention)
1b Ground surface 2 Air injection device 2a Air injection hole 2b Air injection tube 2c Air compressor 2d Air reservoir 2e Flow control device 3 FDR measurement device 3a Probe 3b Measurement connection 3c Controller 3d Measurement point 34a (of FDR and resistivity tomography Calibration curve 34b (corresponding to the measurement result) Measurement result 4 (depending on the target ground) Resistivity tomography measurement device 4a Electrode 4a 'Far electrode 4b Measurement connection 4c Controller 4d Measurement path 5a Perforation 5b (for installation of probe 3a) (Electrode) Perforated 6 air (for 4a installation)
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Claims (5)

About the method of measuring the degree of saturation of the ground by air injection in the ground liquefaction prevention method of injecting air into the ground and desaturating the ground,
By measuring the relative permittivity of the ground with a relative permittivity measuring device, the degree of saturation of the ground is measured,
Furthermore, by measuring the resistivity change rate of the ground with a resistivity tomography measuring device, the saturation of the ground is measured,
A correlation between the saturation degree of the ground is derived from the measurement result by the specific resistance tomography measurement apparatus and the measurement result by the specific dielectric constant measurement apparatus, and the measurement result by the specific resistance tomography measurement apparatus is calculated by the specific dielectric constant measurement apparatus. By calibrating based on the measurement results,
A method for measuring the degree of saturation of a ground by air injection, wherein the degree of saturation of a predetermined ground is measured as a result of measurement by a relative permittivity measuring device using a measuring method by a resistivity tomography measuring device. By partially arranging the measurement points of the relative permittivity measurement device and arranging the measurement points of the specific resistance tomography measurement device in a wide range, and simultaneously measuring the saturation of the ground,
2. The method for measuring the degree of ground saturation by air injection according to claim 1, wherein the degree of ground saturation over a wide range is measured with high accuracy. (1) Install the electrodes of the resistivity tomography measuring device in the ground and the ground surface, and further install the probe of the relative permittivity measuring device and the air injection pipe in the ground,
(2) Measure the saturation level of the ground with a relative permittivity measuring device and a specific resistance tomography measuring device,
(3) Air is injected into the ground from the air injection pipe,
(4-1) When the measured value of the relative permittivity measuring device changes, air injection is temporarily stopped, and the saturation of the ground is measured by the specific resistance tomography measuring device,
(4-2) Or, when the measured value of the resistivity tomography measuring device changes, air injection is temporarily stopped, and a relative permittivity measuring device is newly installed on the ground where the measured value is changed to measure the saturation of the ground. ,
(5) When the saturation level of the predetermined ground or the distribution state of the saturated ground is not satisfied, a series of the steps (1) to (5) in which the steps (3) and (4-1) or (4-2) are repeated. The method for measuring the degree of saturation of the ground by air injection according to claim 1 or 2, wherein air is injected into the ground by the above method. The method for measuring the degree of saturation of the ground by air injection according to any one of claims 1 to 3, wherein the relative permittivity measuring device is an FDR measuring device, a TDR measuring device, or an ADR measuring device. The ground saturation measurement method by air injection according to any one of claims 1 to 4, wherein the soil saturation is measured two-dimensionally or three-dimensionally by a specific resistance tomography measurement device.

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