JPH07224585A - Multi-point thermal logging apparatus - Google Patents

Abstract

PURPOSE:To easily detect information regarding the existance of fluid layer of underground water regardless of the underground water in a bored hole, by providing a sensor checking the thermal chance of hot water injected in the bored hole and connecting it to a computer through a thermal converter. CONSTITUTION:A sensor 2 in which a thermodetector is attached to a cable 12, is provided and connected to a thermal converter 3 and a computer 6. The sensor is inserted in a test borehole 9 to measure the natural thermal distribution. Then hot water 13 is poured and agitated to make the temperature uniform. Immediately after that, the temperature is checked once. After that, it is measured at every specified interval. The returning extent of the temperature due to the inflow of the underground water 16 is measured. The number of fluid layer 17 of underground water, the depth thereof, the thickness thereof, and the extent of the whole water permeable speed are checked. In this way, even in an inconvenient place in an mountainous area, underground water layers can be checked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a logging device for detecting information on a groundwater fluidized bed in a formation.

[0002]

2. Description of the Related Art In recent years, various problems greatly related to groundwater have been raised one after another, such as deep underground development, groundwater pollution by industrial waste, and mountain ground disaster. In order to solve these problems, it has become indispensable to obtain accurate information on the existence of groundwater, which is the cause of occurrence.

For this reason, various measuring methods have been conventionally implemented. As one of the detection methods of this kind, stratified groundwater level observation was carried out to examine the state of the fluidized bed of groundwater in the formation by investigating the water level line of the water level in the borehole accumulated in the borehole with a cylindrical hole There is a way. This method is intended to detect the presence of groundwater from the water level line by directly measuring the water level in the borehole obtained by excavating a cylindrical hole in a landslide site.

Further, as a detection method for more accurate measurement, there is a groundwater logging method. This method is intended to detect the flow condition of groundwater by dissolving salt etc. in the water in the hole and replacing it with an electrolyte solution and measuring the increase in water resistivity due to the groundwater flowing into the hole. .

[0005]

As shown in FIG. 12, the former stratified groundwater logging method uses four boreholes numbered 1 to 4 to determine the water level line in the borehole at any depth. It is represented by the connecting line. The symbol A attached to the figure is the one connecting the water level in the borehole recognized when the drilling depth of each borehole is 10 m, B is the one when the drilling depth is 20 m, and C is the one when the drilling depth is 30 m. It is a thing.

As can be seen from the figure, the groundwater level lines of this landslide site intersect with each other in a complicated manner, and it is impossible to actually determine where the actual groundwater level line is.
In other words, the water level line drawn here is only a water level generated in the borehole at any drilling depth, and these water level lines will change accordingly if the borehole drilling depth changes. I understand that. As shown in Fig. 13, this cause changes depending on the difference in the geology or the difference in the soil properties due to the drilling of the borehole, and as shown in the figure, if there are multiple groundwater layers A and B or groundwater fluidized beds. Is caused by various changes in the water level in the hole depending on the water level and water pressure. Therefore, it can be said that it is extremely dangerous to determine the existence position of the groundwater vein based on the water level line drawn here. According to the results of the experimental study, the probability that the position of the landslide surface may be determined based on the water level in the hole is around 20 to 30%, and if this method is used, the evaluation will be incorrect with a probability of 70%. It is not a reliable measurement method.

On the other hand, the latter method of groundwater logging was made to solve the above-mentioned drawbacks, and there are two methods for performing the measurement.

One of them is called the natural water level method, in which salt or the like is dissolved as uniformly as possible into the water in the borehole to form an electrolyte solution.
The resistivity is measured every cm interval. The subsequent measurement time interval is arbitrarily measured within 10 to 180 minutes.

The other is called a pumping method, and a groundwater fluidized bed which is not detected by the natural water level method can be detected by artificially lowering the water level in the borehole. However, as the excavation depth increases, the water level inside the hole also decreases, so there is the problem that the depth of existence of the groundwater fluidized bed in the formation above the water level inside the hole cannot be detected.

This will be explained based on an example of measurement in a crystal schist landslide. As shown in FIG. 14, the slip surface S in this borehole exists near a depth of 15.5 m. In the groundwater logging method under the natural water level shown in the left half A of the figure, a laminar flow of groundwater flow is detected, although not prominently. The right half B of the figure is the measurement result of the groundwater logging when the water level in the hole is lowered by about 2 m by the pumping method, and the temporal change of the peak value of water resistivity along the slip surface S is sharper. It is also clear that a vertical upward flow is also occurring.

FIG. 15 shows another embodiment in which the weathered shale surface is the slip surface. In this borehole, the slip surface S exists near the depth of 19.4 m. However, in the natural water level method A, no groundwater flow is observed at this depth. Therefore, when the water level in the hole was lowered by about 2 m by the pumping method, a remarkable groundwater fluidized bed was detected near the slip surface as shown in the right half B of the figure.

As described above, in the logging method in the natural state, when the groundwater fluidized bed which seems to have an adverse effect on the slip surface is not detected, the groundwater fluidized bed is artificially lowered to lower the water level in the hole. It turns out that can be detected. However, in fact, the groundwater fluidized bed exists in a complicated manner, and the water level in the hole decreases as the drilling depth increases, so it is easy to cause complicated measurement results due to these factors. No information is available on the depth of existence of the groundwater fluidized bed. In order to eliminate such factors and obtain information about the depth of existence of the groundwater fluidized bed as accurately as possible, various drilling depths should be stepwise changed and groundwater logging should be performed at all depths. (Step-type groundwater logging method)
It is necessary to make a comprehensive judgment from the data obtained by
There was a problem that it required a great deal of labor, experience, time and expense. In addition, this logging method can obtain effective information when the water level in the borehole exists, but there is no groundwater or even if it exists, it flows into the formation during measurement. If it does happen, there is a drawback that the measurement cannot be performed because there is no water itself for forming the electrolyte solution.

The present invention is intended to solve the above-mentioned conventional problems, and there is no water in the borehole from the beginning in the borehole, or it flows into the formation during measurement. Even if it goes down, it does not depend on the presence or absence of water in the hole,
Moreover, it is an object of the present invention to provide a measuring method capable of accurately detecting information on the existence of a groundwater fluidized bed, which could not be detected by conventional measuring methods, by a simple operation.

[0014]

The multi-point temperature logging device of the present invention uses a cable as a temperature measuring element for time-dependent measurement of temperature changes at various depths of hot water poured into boreholes formed in the formation. Provide a sensor part that is installed at every required interval in
This sensor unit is connected to a computer via a temperature converter. Preferably, the measurement accuracy is improved by pouring while giving a stirring effect using an appropriate means so that the temperature of the hot water in the borehole becomes uniform. Further, when the sensor unit inserted into the borehole is lifted and measured at predetermined intervals shorter than the attachment interval, the number of measurement depths increases and a more detailed temperature distribution can be measured. When the pouring temperature of the hot water is about 10 ° C. or higher of the water temperature in the hole, the temperature change is remarkable and the reading becomes easy. In addition to the hot water injected into the borehole,
Other suitable gas having a temperature difference from the air in the hole or water in the hole, or a medium obtained by heating a liquid may be used, but it is inexpensive and
Boiled water is excellent because it can be easily prepared on site and the measurement accuracy is good. Therefore, the hot water referred to in the present invention is used as a general term using other appropriate gas or liquid as a medium.

[0015]

[Operation] To describe the operation, a borehole on a cylinder is opened in the formation to be measured. The sensor section is inserted into this borehole. Hot water is injected into the borehole in a natural state by using an injection means. The temperature inside the hole is forcibly raised while stirring so that the depth is almost uniform. In this state,
If there is a groundwater fluidized bed there, the heated temperature will be changed by the inflowing groundwater and will try to recover the temperature before heating. Also, if there is no groundwater fluidized bed there, the temperature rise will try to return to the temperature before being gradually raised by heat transfer. The temperature changes rapidly when the groundwater is present and slowly when it is not. The temperature change situation at each depth after this temperature rise is measured with a temperature sensor placed in the borehole over time, and the results are displayed on the computer screen via a temperature converter or plotted on a printer. Various information such as the number of groundwater fluidized beds, depth of existence, thickness, and size of infiltration rate is obtained by turning them out.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. As shown in FIGS.
It is a laptop type with a sensor unit 2 to which a temperature measuring element 1 consisting of a thermistor element is attached per cm, a temperature converter 3 (having an interface 4 and an A / D converter 5) and a screen display means. A personal computer (personal computer) is connected to the computer 6 and each of these means is connected to the power source 7.

Reference numeral 8 is an electric heater for boiling the hot water 13 injected into the borehole 9, and 10 is a pump as means for injecting the hot water 13. Each of the above means is connected via a frequency and voltage stabilizer 11 to a power supply 7 (a generator when the measurement is carried out in a mountainous place).

In order to obtain a detailed temperature distribution in the sensor section 2, the temperature measuring element 1 is attached to the cable 12 at intervals of 10 cm so that the borehole 9 can be measured at intervals of 10 cm from the hole opening to the hole bottom. It is better to configure it, but then the sensor part 2 becomes thicker and the normal investigation borehole 9 (inner diameter 5
It becomes difficult to insert it into 0 mm). Therefore, the temperature measuring elements 1 having the same temperature characteristics and accuracy are installed at intervals of 50 cm, the thickness of the cable 12 is suppressed to about 25 mm, and the sensor portion 2 is inserted into the borehole 9 as shown in FIG. , As shown in FIG. 2, every 10 cm, 0 cm, 10 cm,
By measuring the temperature from the mouth of the hole to the hole low at 10 cm intervals at almost the same time (48 seconds is one measurement time) by lifting it up to 20 cm, 30 cm, and 40 cm, it is as if the temperature measuring element 1 was installed at 10 cm intervals. It will be in a state of being.
The sensor unit 2 used has a length of 30 m, and 61 points of the temperature sensing element 1 are set.

Logging is performed as follows. Before pouring hot water, the sensor part 2 is inserted into the borehole 9 in advance and the temperature distribution in the natural state is measured at intervals of 10 cm. Next, the pipe 15 for pouring the hot water 13 in the container 14 is inserted into the borehole 9 in which the sensor unit 2 is installed, and the hot water 13 is poured. In order to make the temperature in the hole uniform, the hot water is poured while the pipe is moved up and down, a large number of holes are made around the pipe 15 to pour it, or the hot water 13 is stirred by a separate stirring means. . Immediately after the temperature is uniformly increased, the measurement is performed once (after 0 minutes). After that, the measurement is continued every 1 minute for 1 to 7 minutes and every 5 minutes for 10 to 60 minutes. As a result, the degree of temperature recovery due to the inflow of groundwater 16 into the hole is measured in detail,
It is possible to examine the number of groundwater fluidized beds 17 and their depths, thicknesses, and overall infiltration rates. It is forcibly measured up to 7 minutes, but at this stage the results measured so far are processed by the personal computer 6 and the results are displayed on the display (or printer).
If the fluidized bed 17 can be clearly grasped here, the measurement is stopped. After that, the measurement is continued at intervals of 10 minutes to 5 minutes, and the result up to that time is displayed at each measurement time. Therefore, the measurement is stopped at an arbitrary time when the fluidized bed 17 can be grasped.

As shown in FIG. 3, the above measurement result shows "temperature-
It is expressed as a "depth curve", and the number of groundwater fluidized beds 17 and their existing depths and their thicknesses are interpreted from the state of return to the natural state of the temperature change curve recorded between the natural state and immediately after the temperature rise. . When the hot water 13 is injected, it may be difficult to determine from the obtained temperature distribution if there are variations in the hole temperature. In such a case, the rate of returning to the temperature in the natural state immediately after the temperature is raised is calculated for each measurement time using the formula shown below, and a "temperature recovery rate-depth curve" (Fig. 4) is created. At the same time, a "temperature recovery rate-time curve" (Fig. 5) is created at an arbitrary depth, and if the groundwater fluidized bed 17 is grasped and the permeation rate is judged to be slow depending on the magnitude of the "temperature recovery rate", there will be variations in the hole temperature. Even if there is, it will be corrected and the judgment will be easier.

The "temperature recovery rate" is obtained by the following equation.

[0022]

[Equation 1] θ ₀ : Immediately after temperature rise (at 0 minutes) θ _t : Temperature at arbitrary elapsed time θ _n : Temperature in natural state When groundwater 16 in a certain fluidized bed 17 flows into borehole 9, it is borehole water 18 If it is assumed that the groundwater fluidized bed 17 is mixed almost uniformly, it is possible to obtain information on the permeation rate of the groundwater fluidized bed 17 by using the “temperature recovery rate-time curve” (FIG. 5). Calculated flow velocity is borehole 9
This is different from that of the groundwater 16 that actually flows around the borehole 9. It has been theoretically and experimentally confirmed that when the actual flow velocity is estimated, the flow velocity estimated in the hole should be one-third.

When the flow velocity is estimated from the "temperature restoration rate-time curve", the flow velocity is determined by using the temperature restoration unit for several minutes after the start of measurement. The reason for this is that in the case of groundwater 16 having a slow flow velocity, the degree of temperature decrease thereafter depends on the degree of temperature decrease of the in-hole water 18 conversely due to the heat of the sensor unit 2 itself warmed by the temperature rise. In most cases, the temperature decrease is not linear and shows an asymptotic temperature recovery.

Further, based on the results measured by the present inventor below, the conventional groundwater logging method (method using an electrolyte solution) cannot measure the water level in the hole far below the slip surface. An example of logging in a landslide area where it exists and an example of logging when it exists near the ground surface are described.

Logging example when the highest water level exists below the slip surface (Example 1: Logging example in A landslide area) As shown in FIG.
The slip surface observed at the borehole 9 where logging was performed has a depth of 1
It exists at 9.0 m. On the other hand, according to the observation result of the water level in the hole, the water level fluctuation occurs between the depths of 31.3 m and 34.1 m. Therefore, it is impossible to know the relationship between the slip surface and the groundwater fluidized bed 17, which has an adverse effect on soil mass fluctuation, from this observation result. However, this landslide is active after rainfall and snowmelt, and it is clear that groundwater is involved in soil mass change. Therefore, for the purpose of obtaining information about the groundwater fluidized bed 17 involved in the slip surface S,
Multi-point temperature logging was performed. As a result, it was clarified that a clear groundwater fluidized bed 17 exists just below the slip surface S. In addition to this, in the borehole 9, cracked water-like groundwater leaching points were detected in the portions indicated by arrows. As described above, such information is difficult to obtain by the conventional groundwater logging method unless the step-type groundwater logging is performed. In this landslide area, as shown in Table 1, most of the boreholes 9 detected the highest water level in the borehole below the slip surface S. Therefore, all boreholes 9 were subjected to multipoint temperature logging. However, it was possible to detect the groundwater fluidized bed 17 estimated to be involved in the slip surface S.

[0026]

[Table 1] (Example 2: Logging example in B landslide area) As shown in FIG.
In this landslide site, there is no hole water level in all boreholes 9. However, at the drilling stage, the water level is recognized in every borehole 9. Slip surface S of this example
Each of the boreholes 9 is also detected at a depth shallower than the excavation depth. The slip surface S shown in FIG. 7 has a depth of 1
It is detected at 3.1m. When multi-point temperature logging was performed in order to detect the groundwater fluidized bed 17 involved in the slip surface S, the "temperature-depth curve" in FIG. 7 or the "temperature recovery rate-depth curve" shown in FIG. ], A clear fluidized bed 17 could be detected from the same depth as the slip surface S to the bottom. In this borehole 9, groundwater leaching points are also recognized between the embankment and the ground at the depths of 2.4 m and 4.5 m.

Logging example when the maximum water level exists near the ground surface (Example 3: Logging example in C landslide area) In this landslide area, the water level in the borehole is generally high, and it remains as it is. When multi-point temperature logging was carried out in, the groundwater fluidized bed 17 estimated to be involved in the slip surface S could not be detected. Therefore, the in-hole water 18 was pumped out, and then the multipoint temperature logging was performed again. At this time, the water level was reduced by about 1 m. The logging results are shown in FIG. 9 in comparison with the observation results of the insertion type strain gauge performed for the purpose of detecting the slip surface S and the conventional groundwater logging results. From this, the slip surface S is detected at a depth of 7.3 m in the observation result of the insertion type strain gauge, but the groundwater fluidized bed 17 is not detected in the conventional groundwater logging result. However, looking at the results of the multipoint temperature logging of the present invention shown on the right side of the figure, the depth of 4.
The groundwater fluidized bed 17 is detected at 0 to 7.2 m, and it can be seen that the flow velocity is the highest in the fluidized bed 17 near the depth of 5.0 m. In addition to this, about two groundwater leaching points like crack water are recognized. Judging from this result, new information was obtained that the fluidized bed 17 detected immediately above the slip surface for the first time by the logging method of the present invention has a high possibility of exerting a large adverse effect on the soil mass fluctuation. Become.

(Example 2: Example of logging in D shallow layer collapse area) In this collapse area, the water level in the hole exists near the mouth of the hole as shown in FIG. As a result of carrying out the multi-point temperature logging in this state, as shown in the figure, although there are only a few, the temperature drop portions due to the outflow of the groundwater 16 like crack water are captured at about four points. This result could not be detected at all by the conventional logging method. By the way, the landslide surface S of this collapsed site is presumed to be between the colluvial soil and the weathered rock, but the groundwater fluidized bed 17 involved in this is not known. Therefore, the water 10 in the hole was pumped out by the pump 10, and the logging was tried again while lowering the water level by about 3 m. The result is shown in FIG. According to this, in addition to the groundwater outflow part that was slightly detected in the natural state, A and B
A new spill was detected at this location. Moreover, it was clarified that the groundwater with a considerably high flow velocity is flowing out from the portion 1 to B compared with the natural state. Among the newly detected groundwater outflow points, A is located near the boundary between the collapsed soil layer and the weathered rock, and it is estimated that it is the groundwater fluidized bed 17 that has the greatest influence on the occurrence of collapse.

[0029]

Since the present invention is constructed as described above, it has the following effects.

Since the measurement can be performed using hot water which can be easily obtained anywhere, the measurement can be easily performed even in an inconvenient place such as a mountainous area.

By mounting a large number of temperature measuring elements at the required intervals in the sensor section and further lifting the temperature measuring elements at predetermined intervals, it is possible to measure an interval shorter than the interval at which the temperature measuring elements are attached. , Detailed groundwater fluidized bed information can be detected over the entire depth of the borehole. As a result, it has become possible to detect groundwater fluidized beds that could not be detected by conventional methods.

Since the measurement result can be displayed on site at the same time when the measurement is started, it is possible to quickly take countermeasures based on the result.

[0033]

[Brief description of drawings]

FIG. 1 is a perspective view of a multi-point temperature logging device of the present invention.

FIG. 2 is a diagram illustrating the use of the sensor unit of FIG.

FIG. 3 is a temperature-depth curve diagram showing the measurement results of the present invention.

FIG. 4 is a temperature recovery rate-depth curve diagram showing the measurement results of the present invention.

FIG. 5 is a temperature recovery rate-time curve diagram showing the measurement results of the present invention.

FIG. 6 is a curve diagram showing the measurement result of the present invention when the water level in the hole is deeper than the slip surface.

FIG. 7 is a temperature-depth curve diagram showing the measurement result of the present invention when the water level in the hole is not recognized.

FIG. 8 is a temperature recovery rate-depth curve diagram showing the measurement results of the present invention.

FIG. 9 is a curve diagram showing the measurement results by the pumping method of the present invention when the water level in the hole is near the ground surface, the measurement results by the conventional groundwater logging method, and the measurement results by the insertion type strain gauge. is there.

FIG. 10 is a temperature-depth curve diagram in the case of a collapsed land in a natural state showing the measurement results of the present invention.

11 is a temperature-depth curve diagram showing the measurement results by the pumping method in the case of FIG.

FIG. 12 is a water level line diagram showing a measurement example of a conventional stratified groundwater logging method.

FIG. 13 is a diagram showing a difference in equilibrium water level in a hole due to a difference in water level / head pressure in a groundwater fluidized bed.

FIG. 14 is an underground logging diagram showing an example of measurement of a groundwater fluidized bed in a crystal schist landslide.

FIG. 15 is an underground logging showing an example of measurement of a groundwater fluidized bed having a weathered shale surface as a slip surface.

[Explanation of symbols]

 1 Thermometer 2 Sensor 6 Computer 9 Borehole 12 Cable 13 Hot water

Claims (1)

[Claims] 1. Hot water 1 injected into a borehole 9 formed in the formation
3 is provided with a sensor unit 2 in which a temperature measuring element 1 for measuring a temperature change at each depth of 3 is attached to a cable 12 at required intervals, and the sensor unit 2 is connected to a computer 6 via a temperature converter 3. A multi-point temperature logging device characterized by being connected to the.