JPH05180709A - Ground pressure measuring device - Google Patents

Abstract

PURPOSE:To measure a ground pressure easily and accurately by taking up the image of the surface of a rock ground before stress is released and then comparing the image to find the displacement distance of a specific rock particle. CONSTITUTION:A reference plate 3 as a reference is fixed to a rock ground 1 before releasing stress of the rock ground 1. An insertion leg 3a for fixing of the plate 3 is inserted into a fitting hold of the rock ground 1 and a rock body 3b is made to adhere to the rock ground 1. Then, an area including part of the plate 3 and part of the surface of the rock plate 1 is imaged by a micro- watcher 2. An magnifying lens is provided at the micro watcher 2 and the image is magnified so that the shapes of specific rock particles 1a, 1b, 1c,... can be viewed. When pressure release is completed, the magnified image is taken up by the video camera again. Using the image the distances to specific rock particles 1a, 1b, 1c,... in reference to the plate 3 can be measured and the displacement distances of the specific rock particles 1a, 1b, 1c,... can be judged according to how much the distance changed before and after the stress release.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground pressure measuring method, and more particularly to a ground pressure measuring method suitable for measuring the ground pressure of soft rock.

[0002]

2. Description of the Related Art Conventionally known methods for measuring earth pressure include a method in which a strain gauge is glued to the rock to measure the strain of the rock after the stress is released, and a plurality of measuring pins are planted in the rock. Installed, the method of measuring the change in distance between the measuring pins, the method of measuring the change in bore diameter of the borehole when stress is released, the pressure generated by the pressure generating mechanism in the borehole, and the pressure, deformation and generation at that time. Various methods are known, such as a method of estimating stress from the relationship between the cracks and a method of estimating the stress from the relationship between the crack and the water pressure generated as a result of applying water pressure in the borehole.

However, the above-mentioned conventional method is performed on hard rocks and medium-hard rocks, and it is the actual situation that almost no case of measuring the ground pressure in soft bedrock has been carried out. It is true that various constructions in soft rock usually have a shallow soil cover, and there is a situation in which the ground pressure is not a problem, but it is technically difficult to measure the ground pressure in the soft rock. It is considered that this is a major cause of the small number.

[0004]

That is, soft rock is fragile, and the surface is easily peeled off or deformed. It is porous and often wet. Therefore, the conventional method of gluing the strain gauge requires a step of forced drying before gluing the strain gauge when it is wet, and this forced drying changes the properties of the rock mass and cannot guarantee accurate measurement. Has the problem. Moreover, the method of using this strain gauge also had a problem that complicated steps such as shaping the rock surface, gluing, and solidifying the gluing material were required,
Although other methods can be applied to hard rock, they have a problem that it is difficult to deal with soft rock.

Therefore, the present invention has been made to solve the above problems, and an object of the present invention is to provide a ground pressure measuring method capable of measuring ground pressure easily and accurately.

[0006]

In order to solve the above-mentioned problems, the structure of the present invention, which is based on the above-mentioned claims and has the above-mentioned objects, is provided before and after stress relief on the surface of rock mass by coring or the like. This is a technical measure characterized by taking a video image and comparing the images before and after the stress is released to obtain the displacement distance of a specific rock particle to measure the ground pressure.

[0007]

Therefore, according to the method of the present invention, the displacement distance of a specific rock particle can be detected by comparing the images before and after the stress is released, and the earth pressure can be measured from this displacement distance.

[0008]

EXAMPLES Examples of the present invention will be described below. First, according to the method of the present invention, images are taken before and after stress is released from the surface of rock by coring or the like.

Prior to the above-mentioned photographing, the surface of the bedrock 1 is usually shaped into a flat shape as shown in FIG. 1 in order to maintain the sharpness of the photographing, but in the method of the present invention, the strain gauge is formed on the surface of the bedrock 1. Since there is no need to glue the etc., there is no need for an accurate flat finish such as a mirror surface, and there is no problem even if the surface of this bedrock 1 has some irregularities.

The image capturing is performed both before the stress release shown in FIG. 2 and after the stress release shown in FIG. 4 after the stress release step of FIG.

In the above-mentioned image shooting, various conventionally known cameras such as a camera and a video tape camera can be used as long as an image can be obtained. In the figure, 2 is a microwatcher used for the above-mentioned shooting. The signal received by the microwatcher 2 is composed of a light receiving section of a CCD video camera equipped with a magnifying lens, a light receiving section at the end of an optical fiber, and the like. (Including static hardcopy)
It is adapted to be visualized (the visualization of the rock particles may be visualized or symbolized). When using a normal camera, it goes without saying that the image is recorded on photographic paper or the like.

In the illustrated example, in photographing the rock 1 in the state shown in FIG. 2 before releasing the stress, first, the reference plate 3 indicating the reference is fixed to the rock 1. This reference plate 3
Is formed by projecting a fixing insertion leg 3a at the center of the back surface of the board 3b. The fixing insertion foot 3a is inserted or driven into the mounting hole drilled in the bedrock 1 so that the board 3b becomes the bedrock 1b.
Fix it so that it closely contacts the surface of.

Then, with the microwatcher 2, a part of the reference plate 3 (it is convenient to provide a scale 3C on the plate body 3b of the reference plate 3 as shown in FIG. 5) and a bedrock. The range in which a part of the surface of 1 is taken in together is photographed. This photographing may be carried out at a predetermined one place, but in the present embodiment, the photographing is carried out at a plurality of predetermined places, and the microwatcher 2 is provided with the fixing plug 3
An axis (not shown) concentric with the central axis of a is used as a central axis of rotation to intermittently rotate at a predetermined rotation angle, and image information is obtained every time the rotation is stopped.

Shooting with the above video tape camera,
Since it is usually viewed by CRT, it is necessary to magnify and photograph the rock particles on the surface of the rock that have been photographed. In the illustrated embodiment, the reference plate 3 is used.
Since the distance relationship between the rock particles 1a, 1b, 1c, ... Is determined, a microlens 2 is attached to the microwatcher 2 to visually identify the shape of the specific rock particles 1a, 1b, 1c. It is expanding to some extent. In the near future, the specific rock particles 1a will be automatically
1b, 1c ... are to be identified. In this case, of course, it is required that the specific rock particles 1a, 1b, 1c ... is there.

Then, when the photographing of "FIG. 2" is completed, the stress of the bedrock 1 is released. In the example shown in FIG. 3, the ring-shaped groove 31 is cut in the bedrock 1 to a predetermined depth by a conventional stress relief method called a core ring, and the stress in the region surrounded by the groove 31 is released. The stress relief of the bedrock 1 is not limited to the core ring having the above-mentioned shape, but a circular shape is usually the easiest to grind. In the examples shown in FIGS. 9 to 11, the stress is partially released by cutting the linear groove 32. If the micro-watcher 2 and the reference plate 3 become a hindrance when the stress is released, it is advisable to temporarily remove them.

When the stress relief shown in FIG. 3 is completed, the video camera is used for magnifying the image again. The image obtained by this re-shooting should be shot at the first shooting position, in other words, the contrast image should be shot from the same viewpoint, and a part of the reference plate 3 must be shot in the image. is there. In the case of automatically performing image processing, it is possible to calculate the relative displacement of a plurality of rock particles 1a, 1b, 1c ..., It is not always necessary to set the viewpoint at the time of photographing to a specific location. It is not necessary to incorporate a part of the reference plate 3 into the image.

The image obtained by the above photographing is the actual image of "FIG. 5".
As shown by the line, refer to the reference plate 3
Distance to specific rock particles 1a, 1b, 1c ...
It is possible to measure the separation, and the specific rock from the reference plate 3
Measuring the distance to stone particles 1a, 1b, 1c ...
And how much this distance changed before and after stress relief
And the specific rock particles 1a, 1b, 1c ...
Was found, the strain component was evaluated by this displacement distance, and the ground pressure was
Should be measured, but the distance measurement should be performed twice at this time.
Since it is complicated, the stress release shown by the thin line in the same "Fig. 5" is released.
In the previous shooting, the specific position that fits the edge of the reference plate 3
The rock particle 1b is selected, and this rock particle 1b responds.
Evaluate the strain component from the distance D moved after releasing the force
Just measure it.

In the examples of "FIG. 6" to "FIG. 11", measurement holes 33 are provided for measurement. In this example, first, the measurement holes 33 are drilled ("FIG. 6") and then required. Set the reference plate 4 according to the
(FIGS. 7 and 8), and then the slits 32 are cut (FIGS. 9 and 10) to release the partial stress. ("Fig. 11").

The reference play 4 is composed of a C-shaped ring band that fits the inner circumference of the measurement hole 33. The reference play 4 is provided with a window hole 4a so that the measurement hole 33 can be opened from the center side thereof. The slit 32 portion can be photographed through the hole 4a, and although not shown, it is preferable that the reference play 4 is also graduated.

When a picture is taken on a photographic printing paper or the like with an ordinary camera (not shown), the two photographs before and after the stress release are enlarged (practically 50 to 100 times). The displacement distance of the rock particles 1A, 1B, 1C, ... From the reference point (marked or the edge of the groove 31 is used as the reference point) may be measured. Also in this case, two or more specific rock particles 1a, 1b, 1c ..
・ It is also possible to measure the ground pressure by measuring the change in distance and evaluating the strain component from the relative movement distance.

When using the two photographs before and after the stress is released, the photographs need to be magnified by a magnifying projection device or the like, so the magnified image is written as data in a computer and displayed on a CRT. By moving the images before and after the stress is released onto the desired matching position, or by placing a cursor on the CRT and moving the cursor between the image shifts of the image data of two sheets of the image, the transition distance of a specific rock particle is automatically detected. Calculation display can be easily realized, which is useful for improving the simplicity and reliability of ground pressure measurement.

[0022]

EFFECTS OF THE INVENTION Since the present invention is as described above, it is possible to perform measurement by a simple work without a difficult work such as gluing a strain gauge, and since the comparison of images is highly reliable in measurement accuracy, Further, since the strains in a large number of directions are measured with the same accuracy, it is possible to provide a ground pressure measuring method that enables measurement with less error.

Further, the present invention has the possibility of observing the microscopic changes of rocks caused by the release of stress, and having the possibility of fundamentally evaluating the reliability of measurement.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a rock mass measured by a ground pressure measuring method of the present invention.

FIG. 2 is a vertical cross-sectional view of rock mass at the time of photographing before releasing stress.

FIG. 3 is a vertical cross-sectional view of a measurement hole in a stress release step.

FIG. 4 is a longitudinal sectional view of rock mass at the time of photographing after releasing stress.

FIG. 5 is a plan view of a main part of a captured image.

FIG. 6 is a vertical cross-sectional view of a measurement hole of an example in which the measurement method of the present invention is performed by providing a measurement hole in rock.

FIG. 7 is a vertical cross-sectional view of the measurement hole at the time of photographing before releasing stress.

FIG. 8 is a vertical cross-sectional view in a direction orthogonal to “FIG. 7”.

FIG. 9 is a vertical cross-sectional view of a measurement hole in a stress release step.

FIG. 10 is a vertical cross-sectional view in a direction orthogonal to that of “FIG. 9”.

FIG. 11 is a vertical cross-sectional view of the measurement hole at the time of photographing before releasing stress.

[Explanation of sign]

 1 Bedrock 31 Groove 2 Micro Watcher 1a Rock particles

Claims (1)

[Claims] 1. The surface of rock is photographed before and after stress is released by coring or the like, and the images before and after stress relief are compared to obtain the displacement distance of a specific rock particle to measure the ground pressure. A method for measuring earth pressure, which is characterized by the following.