JPH0455790A - Examination of ground - Google Patents

Abstract

PURPOSE:To enable predicting ground density and status with high accuracy and wideness by detecting gamma ray from a gamma ray source in a body penetrated into the ground and simultaneously measuring the parameters of penetration resistance. CONSTITUTION:A penetration hole 1 and an examination hole 4 are bored in a ground A with a certain distance and a penetration body 3 which contains a gamma ray source 2 at the front tip, is penetrated in the penetration hole 1 and a probe 5 is hung down with a cable 9 in the examination hole 4. Following the penetration of the penetration body 3, the probe 5 is moved to keep a gammaray detector 6 at the same depth as the gamma ray source 2. By supplying power from a high voltage source 7 to the detector 6 to detect gamma ray, amplifying the detected signal with a preamplifier 8, and counting it with a counter 10, the density of the ground is measured. Also by measuring the penetration resistance at a certain depth with a penetration resistance sensor, the ground status is predicted based on those data.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a ground investigation method for investigating the condition within the ground or rock (hereinafter referred to as "ground"), and in particular, the gamma ray transmission method is adopted to investigate the condition of the ground. The present invention relates to a ground investigation method capable of estimating ground conditions with high precision over a wide range by measuring density and penetration resistance parameters at the same time.

[Conventional technology]

As a ground investigation method using a radioisotope (RI), a method using a scattering type (reflection type) gamma ray densitometer is conventionally known. This reflection type gamma ray densitometer detects gamma rays that have been scattered once, and the directionality of the injection state can be determined by installing a collimator, but the measurable range is at most a radius of 5 to 10 cm. be. Furthermore, since the measured value is dependent on the density distribution within the measurement range, it cannot be said to represent the average density, and therefore accurate measurement cannot be performed.

In this way, conventional measurement methods using reflective measuring instruments have a narrow measurement range of 5 to 10c+n, so it is necessary to drill a large number of test holes at narrow intervals in order to obtain accurate ground conditions. In addition, the number of measurements increases accordingly, requiring a great deal of effort and time, and furthermore, the accuracy is essentially low.

Furthermore, although the gamma-ray transmission method has the advantage of being able to accurately measure ground density, the measurement range is still narrow, within a radius of several tens of meters, and it takes time to detect gamma-rays, so it is difficult to grasp a wide range of ground conditions. It is difficult to do so.

On the other hand, in order to know the density of the ground or its related strength, various sounding methods are used, such as Kikove type dynamic penetration test, standard penetration test, cone type dynamic penetration test, dynamic cone penetration test, static penetration test, and portal cone test. Penetration tests, Dutch penetration tests, Swedish penetration tests, vane tests, simple vane tests, pull-out tests, Ikismeter tests, etc. are known. Although the above-mentioned sounding can efficiently measure density or its related strength by measuring penetration resistance, it is insufficient to determine the exact density.

Recently, a method has also been adopted in which the strength of the ground is estimated from the drilling resistance generated at the tip pit during drilling using a polling device.

In other words, the relationship between drilling parameters and ground strength was investigated through basic tests using model ground, using water supply pressure, rotational torque, thrust, drilling speed, rotational speed, drilling time, penetration force, etc. during drilling as drilling parameters. This is used to measure the ground condition or the strength of the improved ground. Although this method is excellent in obtaining a ground evaluation in a short time, it is difficult to accurately grasp the ground condition based only on these parameters because the ground density cannot be directly determined. In particular, even if the parameters are made to correspond to the model ground, there is a limit to how many model grounds can be made to correspond.

In addition, accurate ground conditions cannot be grasped unless many parameters are used, making the process extremely complex.

[Problem that the invention seeks to solve]

The present inventor has discovered that if the element of density is further incorporated into the investigation using the above-mentioned sounding or drilling resistance parameters, changes in the ground, the strength of the soil layer, the degree of improvement of the improved ground, etc. can be grasped very accurately. The above-mentioned sounding intruder or borehole pipe is called the intruder, and a T-ray source is attached to this intruder to measure the density of the surrounding soil layer and at the same time measure the penetration resistance value or resistance parameter. By matching the two, it became possible to accurately grasp the ground.

We have also found that it is possible to sufficiently grasp the ground condition by combining a small number of resistance parameters and density without using many resistance parameters. For example, if you measure the drilling speed and density at a certain point, you can predict the density at other times by drilling under the same drilling conditions and measuring the drilling speed. Can understand the conditions.

In this way, if you accurately understand the characteristics of the ground by measuring the density and penetration resistance of a representative ground in a wide range of ground areas, you can easily measure other ground conditions by simply conducting soundings and measuring drilling resistance. The entire target ground can be accurately grasped. Furthermore, by using this method, it is possible not only to investigate the soil condition of natural ground, but also to accurately know the improvement effects before and after injection when performing soil engineering.

Therefore, the purpose of the present invention is to estimate the ground condition with high accuracy and over a wide range by measuring the ground density using the gamma ray transmission method and simultaneously measuring the penetration resistance parameter.
It is an object of the present invention to provide a ground investigation method that improves the drawbacks of the above-mentioned known techniques.

[Means for solving problems]

In order to achieve the above-mentioned object, according to the present invention, a penetrating body containing at least a Ta2 source is penetrated into the ground, and the T
It is characterized by detecting gamma rays from a radiation source with a detector to measure the ground density, and at the same time measuring penetration resistance parameters, thereby understanding the ground condition.

Hereinafter, the present invention will be explained in detail using the accompanying drawings.

FIG. 1 shows a sectional view for explaining the ground investigation method according to the present invention. As shown in FIG. 1, investigation holes 1.4 for inserting a T-ray source and an r@ detector are excavated substantially parallel to each other in the ground A at predetermined distances apart. Furthermore, an insertion tube (sounding penetrating body) 3 containing a gamma ray source 2 at its tip is inserted into the investigation hole 1, and a probe 5 is inserted into the investigation hole 4. The probe 5 houses a gamma ray detector 6, a high-voltage power supply 7 that supplies power to it, and a preamplifier 8 that amplifies the output signal of the detector 6, and is inserted into the investigation hole 4 by a cable 9 with a signal line attached. It is inserted by hanging. 10 is T sent via the signal line
This is a counter that counts line detection signals.

The gamma ray source 2 in the investigation hole 1 and the gamma ray detector 6 in the investigation hole 4 described above are each moved from below to above (or may be moved from above to below) along the investigation hole 1.4.

The same goes for the following. ), the density of the ground is measured by detecting T-rays from the gamma-ray source 2 with the gamma-ray detector 6.

In addition, as shown in the fourth diagram, the present invention is directed to the insertion tube 3 of the investigation hole 1.
A plurality of γ-ray sources 2.2...2 are arranged at predetermined intervals along the axial direction, while one γ-ray source is placed inside the investigation hole 4.
A ray detector 6 is placed, and only this γ-ray detector 6 is inserted into the investigation hole 4.
Each gamma ray source 2.2...2
It is also possible to measure the density at each ground level by detecting T-rays from the ground while moving with one gamma-ray detector 6. Of course, although not shown, in the opposite case, one gamma ray source 2 and a plurality of gamma ray detectors 6 are arranged in the investigation hole 1.4, and only the gamma ray source 2 is placed along the investigation hole 1. The measurement may be performed in the same manner as described above by moving from the bottom to the top.

Furthermore, in the present invention, as shown in the third figure, a plurality of gamma ray detectors 6 are inserted around the investigation hole 1, into which the gamma ray source 2 is inserted, at a predetermined distance from this position (in the circumferential direction). For example, as shown in the figure, six investigation holes 4.4...4 are drilled almost parallel to investigation hole 1, and these investigation holes 1 and 4 are filled with γ-rays, respectively. One source 2 and one gamma ray detector 6 are inserted, and these gamma ray sources 2 and gamma ray detectors 6 are inserted.
The investigation holes 1 are detected by detecting T-rays from the γ-ray source 2 with the γ-ray detectors 6.6 while moving the ray detectors 6 along the investigation holes 1.4 in the same manner as shown in the first diagram. It is also possible to investigate the ground conditions between the gamma ray detectors 6, 6, 6, and 6, respectively. In addition, in FIG. 3, a plurality of either the gamma ray source 2 or the gamma ray detector 6 are inserted into one investigation hole 1 or 4, and one of the other is inserted into the ground in the same manner as in FIG. You can also investigate the situation.

Further, in FIG. 3, the investigation holes 4 are arranged so as to form a regular hexagon on the circumference with the investigation hole 1 as the center, but the shape is not limited to this example, and other regular polygons may be used. .

Further, the distance from the investigation hole 4 to the investigation hole 1 and the intervals between the investigation holes 4 do not necessarily need to be the same. However, investigation hole 4
The advantage of arranging them in a regular polygon makes it easier to analyze planar ground density changes, and by arranging them symmetrically around survey hole 1, it becomes easier to analyze cross-sectional ground density changes. There is.

In the present invention, it is necessary that the investigation holes into which the γ-ray source 2 and the T-ray detector are inserted are installed as parallel as possible. The reason for this is that detection of the T-line is inversely proportional to the square of the distance, so when the distance changes, the effect of the change in distance is greater than that of the change in the soil layer, making accurate analysis difficult.

Furthermore, for the same reason, it is desirable that the γ-ray source and T-ray detector within the investigation hole be moved so that they both maintain approximately the same depth.

This means that measurements can be taken while pulling both up at the same speed (for example, 1 m/min) from the bottom of the investigation hole.
Alternatively, this can be achieved by measuring and pulling up every 0.5 m.

The present invention described above can be used not only for soil investigation of natural ground but also for confirming the effect of improved ground.

For example, in Figure 3, if you measure the ground before injection, inject chemical solution or cement grout through the investigation hole, and then measure the improved ground again through the investigation hole, you can continuously measure the increase in density in each soil layer. can.

Further, it goes without saying that the investigation hole in the present invention does not have to be provided vertically, but may be provided diagonally or horizontally.

Note that the aforementioned insertion tube (sounding penetrating body) 3 may be a borehole tube, and the detector 6 may be installed inside the penetrating body 3. Furthermore, in the present invention, the penetration resistance parameter may be measured by attaching a penetration resistance measurement sensor to the tip of the borehole tube and measuring the pressing force when the borehole tube penetrates.

FIG. 2 shows a sectional view of a borehole tube used in the present invention, which is equipped with a gamma ray source, a T-ray detector, and a penetration resistance measuring sensor. In FIG. 2, a penetration resistance measuring sensor 11 is built into the tip of the borehole tube 3a, a gamma ray source 2 is built into the upper part of the sensor, and a gamma ray detector 6 is built-in. This gamma ray detector 6 is connected to a scaler 14 via a cable 13. 15 is a tip bit.

Of course, the penetration resistance parameters are measured not only by the penetration resistance measurement sensor 11 as shown in FIG. 2, but also by measuring the water supply pressure, rotational torque, drilling speed, rotational speed, drilling time, etc. during drilling. Alternatively, it may be carried out by measuring the pressing force from a suppressing device.

[Effect]

In the present invention described above, in the case of the example shown in the third figure, the γ-ray source 2
If 10 mC4 is used as the source, and the distance between the gamma ray source 2 and the detector 6 is set to 50 marks, the required accuracy can be measured in a measurement time of about 1 minute. First, the counting rate of each detector 6 is recorded at the bottom for a predetermined period of time (1 minute in this example), and then the measurement is repeated while raising the gamma ray source 2 and detector 6 by a predetermined length, or the measurement is continuously performed. It was pulled up at a speed of 1 meter per minute while measuring the distance. In this way, based on this data, it is possible to know the mode of ground density changes, the distribution of ground density, changes in soil layers and their positional relationships, and the three-dimensional relationships between them. Ground conditions can be estimated with high accuracy.

In addition, the measurement of penetration resistance parameters was carried out in investigation hole 1 or 4.
This is done by measuring the rotational torque, drilling speed, rotational speed, drilling time, etc. of a drilling tube (not shown) during drilling. In the present invention, the ground condition is grasped by measuring these ground density and penetration resistance parameters.

In the case of the example shown in the second figure, the penetration resistance parameter when the borehole pipe 3a penetrates into the ground is measured by the penetration resistance measurement sensor 11, and at the same time the γ-ray source 2 The rllA from the ground is detected by a gamma ray detector 6 and measured by a scaler 14 via a cable 13, and the ground condition is determined from these constant values on both sides.

〔Effect of the invention〕

As described above, the present invention is a ground investigation method that uses the gamma ray transmission method to measure ground density and simultaneously measures penetration resistance parameters, thereby estimating the ground condition with high accuracy and over a wide range.

7...High voltage power supply, 8...Preamplifier, 9...
Cable, 10... Counter, 11... Penetration resistance measurement sensor.

Patent applicant: Reinforced Soil Engineering Co., Ltd.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view for explaining the principle of the method of the present invention, FIG. 2 is a cross-sectional view of an example of a drilled tube used in the present invention, and FIGS. 3 and 4 are other specific examples of the present invention, respectively. A cross-sectional view is shown. ■, 4... Investigation hole, 2... γ-ray source, 3...
Insertion tube, 3a...Drilling tube, 5...Probe,
6... T-ray detector, child diagram @ @ Bud diagram Kawa diagram procedural amendment (method) % formula % Incident indication 1990 Patent Application No. 166320 2゜Name of invention Ground investigation method 3゜Amendment Relationship with cases involving persons who commit crimes

Claims (3)

[Claims] (1) Penetrating a penetrating body containing at least a γ-ray source into the ground, detecting γ-rays from this γ-ray source with a detector to measure the ground density, and simultaneously measuring the penetration resistance parameter, A ground investigation method characterized by grasping the ground condition through this method. (2) The ground investigation method according to claim 1, wherein the penetrating body is a borehole pipe or a sounding penetrating body. (3) In the ground investigation method according to claim 1, the detector is mounted inside the penetrating body or in a position substantially parallel to the penetrating body.