JP2000171565A - Method for specifying unstable block field in collapsing rock ground - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately specify unstable block field by measuring the horizontal component of fine move constantly at a plurality of depths in a rock ground and specifying an unstable block field part according to a vibration form based on the measurement. SOLUTION: A drilling hole 1 is punched to the inclined surface of a rock ground that may collapse, and a compact slight movement meter is inserted inside and is fixed to a hole wall 1a at a specific depth. Then, the constant slight movement at that depth is measured and a horizontal constituent is amplified, and the dominant frequency of the horizontal vibration and its amplitude (peak value) at a measurement point are calculated and recorded by a frequency analyzer. This sort of measurement and operation/recording are made by successively changing the installation depth of the compact slight movement meter, namely the depth of measurement points A-D, and stability and instability at the measurement points A-D are judged from the difference in relative vibration property in a depthwise direction (relative value of a prominent frequency and its peak value), thus specifying an unstable block field part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for specifying an unstable rock mass on a slope of a rock mass in order to remove an unstable rock mass of a collapsed rock mass facing a road or a railway.

[0002]

2. Description of the Related Art As a result of inspecting rock slopes nationwide from the viewpoint of preventing accidents caused by rock fall, many dangerous places have been pointed out. For this reason, for rock slopes that are likely to collapse, the unstable rock mass portion has been estimated from the appearance discrimination and experience by the operator, and overhanging rock masses and rock masses surrounded by discontinuous surfaces have conventionally been estimated. Removed.

[0003]

SUMMARY OF THE INVENTION Collapseable rock mass
As described above, it is determined how unstable the rock slope is and whether measures need to be taken immediately.However, in the past, the stability of the rock slope was determined based on its appearance and other factors. Therefore, the determination of how much rock mass should be removed greatly depends on the skill of the operator, and it is difficult to reliably remove only the unstable rock mass portion. For this reason, in the related art, there is a possibility that the rock mass removal operation may be performed more than necessary.

The present invention has been made in view of the above-mentioned problems, and has as its object to provide a method for accurately specifying an unstable rock mass in a collapsed rock mass.

[0005]

In order to solve the above-mentioned problems, the present invention measures a horizontal component of a microtremor at a plurality of depths in a rock using a boring hole drilled in a rock slope. Another object of the present invention is to provide a method for specifying an unstable rock mass in a collapsed rock mass, characterized by specifying an unstable rock mass portion from a vibration form based on the plurality of measurements.

Here, the target rock mass is usually a substantially vertical cliff, and the cliff is almost vertically cracked to form an unstable rock mass. Therefore, the horizontal vibration is dominant in the unstable rock mass portion, so that the vibration of the horizontal component among the microtremors may be measured. In addition, the constantly tremor refers to ground vibrations that are constantly occurring such as sea waves, traffic vibrations, factory vibrations, and vibrations generated from tree roots due to wind. This microtremor has almost the same vibration characteristics in the range of several hours, so even when measuring vibration at multiple depths, it is not always necessary to simultaneously measure multiple measurement points. ,
It is also possible to obtain a plurality of measurement values required for specifying an unspecified rock mass by performing sequential measurements within a range of several hours.

[0007] In addition, the above-mentioned microtremor changes its vibration characteristics during the measurement time period, such as different vibration characteristics between daytime and nighttime, and each unstable rock mass has different vibration characteristics. It is difficult to determine the stability / instability of a measurement point from an independent measurement value of only one measurement.

For this reason, according to the present invention, a vibration mode based on a plurality of measured values measured at different depths,
Instability and stability are determined based on the difference in the relative vibration characteristics at multiple measurement points, and the unstable rock mass portion is specified. Here, the frequency that occupies a particularly large ratio among the vibration components, that is, the frequency with the largest amplitude is called the dominant frequency, but the unstable rock mass portion has a lower dominant frequency than the stable rock mass portion, and The amplitude of the vibration is larger than that of the stable rock (the peak value of the dominant frequency is larger).

Therefore, the stability / instability at each measurement point is determined by comparing the vibration property at the measurement point with the vibration property at another measurement point (particularly, a nearby measurement point). Low / high dominant frequency or amplitude of dominant vibration (peak value)
The determination may be made based on large or small values.

As described above, an unstable rock mass can be specified by the present invention.

[0011]

Next, embodiments of the present invention will be described with reference to the drawings. The present invention will be described by taking, as an example, a rock mass removal work performed to remove an unstable rock mass portion from a collapsed rock mass to prevent a collapse accident.

First, a method of specifying an unstable rock mass on the rock slope 10 will be described. In the rock slope 10, as shown in FIG. 1, a boring hole 1 is drilled on a slope that may collapse. Next, a small fine dynamometer 2 is inserted into the boring hole 1 and fixed to the hole wall 1a at a predetermined depth. For example, as shown in FIG. 2, with the rubber packer 3 attached to the side surface of the small micrometer 2, the small micrometer 2 is suspended in the boring hole 1. The small micro-movement meter 2 is pressed against and fixed to the hole wall 1a at the target depth by supplying water to the water and expanding the water. In FIG. 2, reference numeral 4 denotes a water supply pipe.

Here, the installation depth of the small tremor 2 can be specified by the length of the cable 5 inserted into the boring hole 1. Therefore, if a scale or a mark is provided on the cable 5, the small fine dynamometer 2 can be easily arranged at the target depth. In this state, the microtremor 2 constantly measures the microtremor at a fixed depth, amplifies its horizontal component with an amplifier, and subsequently uses a frequency analyzer to measure the dominant frequency of the horizontal vibration at the measurement point and its amplitude. (Peak value) is calculated and recorded.

The above-described measurement, calculation, and recording are sequentially performed by changing the installation depth of the small fine dynamometer 2, that is, the measurement depth. Next, from the measurement results at a plurality of depths in the boring hole 1, as described above, the difference in the relative vibration properties in the depth direction, that is, the relative frequency of the dominant frequency and the peak value (amplitude) thereof. Judgment of stability or instability at each measurement point based on the value, and specifying the unstable rock mass portion.

For example, as shown in FIG. 1 described above, when the vibration properties as shown on the right side are obtained as a result of measuring four places (A to D) in the boring hole 1,
Since the dominant frequency is relatively low and its peak value (amplitude) is also large, it is determined to be an unstable rock mass portion. Further, although the peak value of the portion B is lower than that of the portion A, the dominant frequency is similarly low, so that the portion B is determined to be an unstable rock mass portion. In addition, the portion C and the portion D are determined to be stable rock mass portions because the dominant frequency is relatively high and the peak value is relatively low. further,
The portions C and D have similar horizontal vibration characteristics, and the portions below the portions are determined to be stable rock mass portions. From the above, at the position of the boring hole 1, it can be specified that there is an unstable rock mass portion at least above the C portion. Reference numeral 11 indicates a boundary between the unstable rock mass and the stable rock mass.

The boundary 11 between the unstable rock mass and the stable rock mass
Is between the part B and the part C, so if the vibration measurement is performed with the measurement interval between B and C shortened, the lower limit position of the unstable rock mass can be specified more accurately. Here, the stability
The determination of instability is performed by, for example, determining the change in the dominant frequency along the depth direction and the change in the peak value, and determining the stability or instability of each measurement point from each change state (vibration form). You may make it. At this time, the boundary between the stable rock mass and the uneasy rock mass, that is, the maximum of the unstable rock mass portion, is determined directly from each of the above change states (vibration patterns) without individually determining the stability and instability at each measurement point. The lower part may be specified. This determination may be made visually from a graph of the change state or the like, or automatically determined by the computer from the degree of inclination of the change state to determine whether the state is stable or unstable, or to determine the depth of the lowest part of the unstable rock mass. May be calculated.

Then, as shown in FIG. 3, the unstable rock mass is specified by a plurality of boring holes 1 so that the boundary 1 between the unstable rock mass and the stable rock mass can be two-dimensionally or three-dimensionally.
1 is specified. That is, the lowest part of the unstable rock mass is specified. When the unstable rock mass portion is specified in this way, the rock mass is cut down from the top to the specified portion. This eliminates unnecessary removal of the stable rock mass portion, thereby avoiding unnecessary rock mass removal work.

Here, since the microtremor to be measured has the same vibration characteristic for several hours, for example, even if one measurement takes about 5 minutes, it can be measured by one hour. Measurements at twelve locations can be performed. In the above description, the determination of the stability / unstableness of the measurement position is made based on the difference in relative vibration properties (difference in the magnitude of the dominant frequency, etc.) in the same boring hole 1, that is, in each boring hole 1.
Although the unstable rock mass portion at the position of the boring hole is specified in units, the present invention is not limited to this. Since the microtremor has the same vibration property for several hours, for example, the stability / instability at each measurement position may be determined based on each measurement value measured at another boring hole 1. good.
This means that each boring hole 1 does not need to be drilled vertically, but may be drilled diagonally or horizontally.

Further, in the above description, the entire unstable rock mass portion is specified from the stability and instability in the plurality of boring holes 1 and the cut-down position is determined. After judging the unstable portion, the inside of the borehole 1 is projected on a borehole television and the crack state of the hole wall 1a is observed to identify a crack defining the unstable rock mass. Unstable rock mass may be removed by cutting down the slope side portion. When a crack cannot be specified, the unstable rock mass portion is specified by measuring the plurality of boring holes 1.

Further, in the above description, it has been described that the unstable rock mass portion is specified in advance, and the cut-down portion is estimated thereby to remove the rock mass. Alternatively, the removal of the rock mass may be performed while identifying the unstable rock mass portion by appropriately measuring the horizontal component of the microtremor at each depth. In other words, even when an unstable rock mass is removed from the upper part, it is possible to more accurately determine the depth of the unstable rock mass by measuring the microtremor and repeating the identification of the unstable rock mass. You may.

In this case, a portion where the amplitude decreases and the dominant frequency increases as the upper rock mass is removed is determined to be an unstable rock mass portion. If the amplitude and the predominant frequency do not change as they are removed, it is determined to be a stable rock mass.

In the above embodiment, the vibration measurement at each depth in each boring hole 1 is described as being performed sequentially, but the vibration measurement at a plurality of depths by one boring hole 1 is measured simultaneously. It does not matter.

[0023]

As described above, when the present invention is employed, an unstable rock mass to be removed can be accurately specified in a collapsible rock mass. The deduction length can be estimated in advance, and the unstable rock mass to be removed can be specified even while the rock mass is being removed.

As a result, the removal amount of the stable rock mass portion is reduced, so that it is not necessary to perform an unnecessary rock mass removal operation, and the construction cost is reduced. In addition, since unstable rocks are always identified using microtremors, it is not necessary to simultaneously measure a plurality of measurement points, and it is not necessary to apply vibrations artificially. Measurement work is simple.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a method for specifying an unstable rock mass portion in one boring hole according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a fixing method at each depth of the vibrometer according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating a method for specifying an unstable rock mass portion in a plurality of boring holes according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Boring hole 2 Small tremor 10 Rock slope

Claims (1)

[Claims] 1. A method for measuring microtremors at a plurality of depths in a rock using a boring hole drilled in a rock slope, and specifying an unstable rock mass portion from a vibration form based on the plurality of measurements. A method for identifying unstable rocks in collapsible rock masses characterized by: