JPS5980823A - Monitoring method of slope degradation - Google Patents

Abstract

PURPOSE:To exactly predict a danger of the occurrence of slope degradation by a method in which at least one or more electrodes are set under the ground, and the variations in electric resistance values between the electrodes due to an increase in the water content ratio of the ground between the electrodes are measured. CONSTITUTION:Pipes 2 provided with electrodes 3 are buried at plural places in the ground 1 where slope degradation tends to occur, lead wires 4 sent out from the pipes 2 to the outside are collected for plural pipes 2 as a group, and these wires 4 are connected through resistance measurers 6 to power sources 5. When the amount of rain water permeating into the ground is increased and the water content ratio of the ground 1 is increased, since electric resistance values between the electrodes 3 are varied to smaller ones than those when no rain falls, it follows that when the electric resistance values are lowered beyond set values on the basis of a dangerous water content ratio, a danger of the occurrence of slope degradation is raised.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a monitoring method that can detect the risk of occurrence of slope collapse such as landslides and landslides.

Recently, slope failures occur in various places every time there is a typhoon or torrential rain, resulting in the loss of many lives.

Needless to say, slope failure varies depending on the soil quality and hydraulic conditions of the place where it occurs, but it is also affected by seepage pressure, earthquakes, traffic vibrations, etc.
It occurs due to sagging, etc. Of these, as seen in recent examples, they are often caused by seepage water pressure caused by concentrated heavy rain. In other words, in this case, the water content ratio in the ground increases due to rainfall, running water, etc., and eventually reaches the saturated water content ratio, which lowers the strength of the soil and increases the water pressure in the soil. This will lead to erosion and eventually cause a slope failure.

At present, as a means of predicting the risk of occurrence of such slope failure, the relatively slow collapse velocity (crrL
/year) As a method for measuring the moving speed of slopes such as ground slopes, 1. Moving survey using marker pole, measurement using 2 extensometers,
3. Measurement with an inclinometer, 4. Measurement using a sliding surface measuring tube, 5. Measurement using a histometer measurement tube has been proposed. However, for measuring the movement speed of slopes such as landslides, which have a relatively fast collapse rate (cIIL/sec),
In particular, there is currently no suitable method, such as predicting the danger rate based only on the magnitude of rainfall in each area and issuing a 1M evacuation warning to residents in areas where slope failure is expected to occur. This is done by taking measures to close roads.

However, the method of predicting the occurrence of slope failure based on rainfall is difficult to predict, especially in places where rainwater and groundwater flow from other places in a concentrated manner. Because the data obtained by the method rapidly exceeds the limit, by the time it is determined that the amount of rainfall has reached the danger zone, the danger rate may have already been exceeded.In that sense, it cannot be called an appropriate means of prediction. hard.

The present invention aims to eliminate the uncertainties of the conventional method of monitoring slope failure water based on rainfall, and to provide a reliable and appropriate monitoring method. The method is characterized in that at least one pair of electrodes are placed in the ground in the area where the slope failure is observed, and the risk rate of slope failure is detected based on changes in electrical resistance due to an increase in water content in the ground. .

Before describing the embodiments of the present invention, the following is an example of the results of an experiment conducted by the inventor to measure the electrical resistance between two electrodes in soils with different water content ratios.

1. Moisture content side resistance value of sand 2, Moisture content ratio B9 resistance value of Masago soil 3, Moisture content side resistance value of clay. Specific force: As the specific force increases, the resistance value between the two electrodes changes to a smaller value. Furthermore, when looking at the soil type, it is found that the resistance value of clay is smaller than that of sand and clay.

Next, the present invention based on the above experimental results will be described in detail with reference to an embodiment shown in the drawings. A tube (2) with an electrode (3) attached thereto is embedded at each location.

As shown in Figure 3, these tubes (2) are equipped with electrodes (3) made of a metal that is a good conductor at multiple locations on the outer circumferential surface that comes into contact with the earth and sand, and on the inside of each electrode (3). The connected lead wires (4) pass through the tubes (2) and extend outside the tubes. In addition, each pipe (2) is buried horizontally to the slope as shown in Figure 1a, or vertically as shown in Figure 1, and spaced apart in the vertical and horizontal directions as shown in Figure 2. Ru. Furthermore, the lead wires (4) extending outside the tubes from these buried electrode-equipped tubes (2) are collected into a group of multiple tubes (2) and connected to a power source (5). Resistance measuring device (
6).

As demonstrated by the above experimental example, when there is no rainfall and the moisture content of the ground (1) is low, the electrical resistance between the electrodes (3) in each pipe (2) increases by applying electricity to a large value. shows. On the other hand, when the water content ratio in the ground (1) increases due to an increase in rainwater seeping into the ground, as occurs during torrential rain, the electrical resistance value between each tube electrode (3) becomes the resistance during non-rainfall. Changes to a smaller value compared to the value. Therefore, if the electrical resistance value falls below the value set based on the dangerous water content ratio that would cause a slope failure, the risk of a slope failure occurring in the area immediately increases. It is possible to detect that

As described above, the monitoring method according to the present invention involves burying one or more pairs of electrodes (3) in the ground that is prone to slope failure, and connecting a power source (5) and a resistance measuring device (6) between the two electrodes. ), it is possible to reliably detect changes in the water content ratio in the ground, which were previously undetectable, and therefore the risk of slope failure can be accurately predicted in advance.

Furthermore, the monitoring method according to the present invention uses electrodes (3
) in a hazardous area in advance, monitoring of multiple hazardous areas can be carried out centrally in a safe area away from the hazardous area under sufficient management control. This has the effect of issuing an alarm and taking necessary measures quickly and appropriately.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a slope failure risk area showing an aspect of the slope failure monitoring method according to the present invention, Fig. 2 is a front view of the area, and Fig. 3 is a sectional view showing the configuration of the tube with electrodes. be. In the figure: (1): Ground, (2): Pipe, (3): Electrode, (4): Lead wire, (5) Two power supplies, (6): Resistance measuring device. Kazu Wakasugi, Commissioner of the Patent Office Failure 1. Indication of the case 1981 4 Temple Permit Application No. 190022 2 Name of the invention Slope failure monitoring method 3 Person making the amendment Relationship to the case Patent applicant 4 Agent (Shipping date: Month, Day, 1939) 6. Subject of amendment Specification 7, Contents of amendment As shown in the attached sheet, a part of the specification will be amended as follows. In the "Water content ratio" column, change the value of r90%J to "9.0".
%”. 2. On page 8, line 10 of the specification, it says "...the monitoring method according to the present invention...". "...the monitoring method according to the present invention..."
...” and correct it. that's all

Claims (1)

[Claims] 1. At least one pair or more of electrodes are placed in the ground where there is a risk of slope failure, and the electrical resistance value between the two electrodes changes due to an increase in the water content ratio in the ground between the two electrodes due to rain, running water, etc. A slope failure monitoring method characterized by detecting the risk of occurrence of slope failure.