JP4219100B2 - Prediction device for ground displacement due to slope failure such as landslide and surface layer failure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention belongs landslide that may occur in the slope ground, surface collapse, to the technical field of predictive device ground displacement caused by landslides, such as landslides.
[0002]
[Prior art]
In general, there is a landslide disaster as one of the natural disasters, and as such a landslide disaster, there are disasters caused by landslides, surface collapses, landslides, debris flows, etc. that occur on slopes. Such a sediment disaster on a sloping ground causes the displacement of the ground due to the collapse of the slope ground, that is, the deformation or movement of the ground. Japanese Patent Application Laid-Open No. 5-118851 and Japanese Patent Application Laid-Open No. 10-82667 are known. First, the former uses a high-precision electronic ranging / angle measuring instrument, and changes in distance and angle to an index placed in an area with ground displacement using an arbitrary position deviated from the area with ground displacement as a reference point Is used to measure the ground displacement. On the other hand, the latter one measures the ground displacement by digging a hole for measurement at an arbitrary position with ground displacement, inserting a strained cable here, and measuring the amount of strain caused by the ground displacement. It is what.
[0003]
[Problems to be solved by the invention]
However, the conventional apparatus requires an expensive measuring device and measures the ground displacement during or after the slope failure actually occurs, and predicts the occurrence of the ground displacement. Not what you want. Thus, such a sediment-related disaster caused by ground displacement can be dealt with as long as there is no damage even if it occurs after it has occurred, but there is almost no influence even if it occurs. In many cases, it is a countermeasure after some kind of damage has occurred, and it is generally impossible to prevent landslide disasters.
Thus, in order to prevent the occurrence of landslide disasters, it is required to predict the occurrence of ground displacement due to slope failures such as landslides and surface failure (prediction, sign detection, sign detection). The displacement measuring device has a problem that it is virtually impossible to predict the occurrence of the ground displacement, and there is a problem to be solved by the present invention.
[0004]
[Means for Solving the Problems]
The present invention was created to solve these problems in view of the above circumstances, and is present in the groundwater of an area where ground displacement due to slope failure such as landslide and surface layer failure occurs. Measurement means for measuring the concentration of specific ions to be registered, registration means for registering the measured ion concentration over time, and slope failure such as landslide and surface layer collapse when there is a sudden increase in the registered ion concentration In the prediction device comprising a prediction means for predicting that there is a possibility of occurrence of ground displacement due to and a notification means for notifying the prediction result , the specific ions are sodium ions, and the concentration measuring means includes: A concentration sensor installed at a preselected measurement site and configured to measure sodium ion concentration in groundwater over time. The measurement of the concentration of sodium ions is a measurement at a large number of locations over a wide range, and the measurement is performed over a long period of 1000 days or more, and the measured sodium ion concentration is input to the headquarters terminal via the local terminal, The headquarters terminal is configured to predict the possibility of occurrence of the ground displacement, and to output the ground prediction to the terminal at the part where the prediction result needs to be informed so that the ground displacement prediction is comprehensively managed. a device for predicting ground displacement by landslides of landslides and surface disruption like, characterized in that the.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Slope failures such as landslides and surface layer failures are thought to occur due to increased instability of the slope, and one of the factors is the presence of groundwater. When water molecules exhibiting strong polarity flow as groundwater, it is common to perform ion exchange with ion exchange groups on the surface of soil particles (for example, silanol groups and hydroxyl groups bonded to silicon atoms). The amount (concentration) of ions that are exchanged to form groundwater composition and flow with the groundwater increases as the number of ion-exchange groups that come into contact with groundwater increases. The larger the particle surface area, the greater.
On the other hand, in the process of landslides and surface failures such as surface failure (from microscopic displacement of soil particles inside the ground before the slope failure to ground failure due to the movement of the soil when the slope failure occurs) The change in soil dynamics is related to the increase or decrease in the surface area of the soil particles, and the size of the ion exchange reaction field is also considered to be related. It is inferred to bring about a change in composition.
Based on such inferences, we tried to detect ground displacement due to slope failures such as landslides and surface failure from changes in groundwater composition. That is, in an area where slope failures such as landslides and surface failures were actually observed, changes in groundwater composition and measurements using ground displacement devices due to slope failures were performed simultaneously. As a result, when there is a series of relationships between the two, that is, when ground displacement occurs due to slope failure, the concentration of specific inorganic ions contained in groundwater increases rapidly as a predictive phenomenon. It was recognized that there was a change, and this change phenomenon was found to be an index for predicting the occurrence of ground displacement, and the present invention was completed here.
And, by implementing the present invention, that is, by observing the phenomenon that the concentration of specific ions in groundwater rises rapidly, it is possible to predict the occurrence of ground displacement due to slope failure such as landslide and surface failure. As is clear from the above, the three measurement example areas are landslide occurrence areas in which the main body of the landslide mass is the Tertiary layer, and its sliding form is observed intermittently and repeatedly. And in many districts other than this example, the same phenomenon has been confirmed, and if this is implemented, it can be said that the occurrence of ground displacement due to slope failure can be predicted with high accuracy.
[0006]
In the present invention, in order to predict the occurrence of ground displacement due to slope failure by measuring the concentration of specific inorganic ions in the groundwater of the district where there is a slope failure, the concentration of the specific inorganic ion is periodically, and It is preferable to measure continuously. As a time interval to be measured, an appropriate time unit such as a daily unit such as every other day, a week unit such as every week, every two weeks, or even a monthly unit can be adopted. Needless to say, a shorter time interval is preferable in order to increase prediction accuracy.
The groundwater whose concentration is to be measured is preferably the groundwater where the ground displacement is or is as close as possible to this surface. For example, if the ground displacement surface is already assumed from the results of the geological survey, It is preferable to measure the concentration using groundwater existing as close to the displacement surface as possible by boring or the like.
However, where there is such ground displacement, there are cases where there are many construction restrictions due to factors such as ground instability, and there are areas where slope failures occur in consideration of the surrounding groundwater flow system. Alternatively, groundwater (drainage) obtained from existing facilities such as a drainage well or drainage installed in the ground, or groundwater stored in an existing dip meter hole may be used as a sample for concentration measurement.
[0007]
Thus, as a predictive phenomenon when ground displacement due to slope failure occurs, there is a change in the concentration of specific inorganic ions in groundwater that suddenly increases. It is closely related to the process up to the occurrence of ground displacement due to collapse. The phenomenon that occurs in the groundwater-soil particle system in the ground before this ground displacement occurs can be considered as follows.
In other words, in the pre-stage where there is ground displacement, microscopic displacement (local ground breakage, minute breakage at the soil particle level) occurs at the soil particle level, which causes the groundwater to come into contact with the soil particles. Area (effective area of the reaction field) increases. In this case, the ion exchange reaction that is constantly performed in the groundwater-soil particle system increases the reaction field, that is, the soil particle displacement that increases the surface area of the soil particle occurs, and the groundwater and the soil particle The amount of ion species involved in the ion exchange reaction is increased rapidly, and this is a chemical phenomenon that the specific ion concentration rises before the ground displacement due to slope failure occurs, At this time, it can be considered that the proof strength of the ground is further lowered than the time immediately prior to the metastable state, and then the ground displacement occurs.
As described above, in the present invention, when a change in which the concentration of a specific inorganic ion in the groundwater suddenly increases is observed, it can be predicted as a precursor to the occurrence of ground displacement due to slope failure such as landslide and surface layer collapse. Therefore, it can be an important indicator for the prediction of landslide disasters, and will contribute greatly to disaster prevention.
[0008]
Hereinafter, measurement examples will be described.
<Measurement example 1>
Fig. 1 shows a plan view of a certain area where landslides are actually observed, and Fig. 2 shows a cross-sectional view of the geology, but the surface ground in this area is mudstone that has been heavily weathered, and both the steps and the opening width are small. However, several cracks are observed from the ground surface. In this area, small-scale landslides occur repeatedly every 10 to 20 years. Then, for landslides in this area, we measured changes in precipitation and groundwater level, and examined whether the obtained data had some relation to the occurrence of landslides in the area. However, it can be inferred from this that the occurrence of landslides has a complex behavior that cannot be estimated from changes in precipitation and groundwater level.
[0009]
In this landslide area, as shown in FIG. 1, inclinometer holes were excavated at two positions a and b indicated by ●, and inclinometers were installed in the inclinometer holes a and b, respectively. The inclinometer hole a on the mountain skirt side has a depth of 12.5 m (meter), and the inclinometer hole b on the mountain top side has a depth of 18.5 m. And the existence of a slip surface is confirmed from the measurement by these inclinometers.
[0010]
Therefore, the groundwater stored in one of the clinometer holes a was collected as an analysis sample (collection position A). The collection was conducted by collecting 100 mL (milliliter) of ground water stored here in a polyethylene bottle every two weeks. In the analysis, ion chromatography / electric conductivity detection method was used, and the concentrations of sodium ion (Na ⁺ ), sulfate ion (SO ₄ ²⁻ ) and chloride ion (Cl ⁻ ) in the collected ground water were quantified. FIG. 3 shows the relationship between these quantitative values and the ground displacement appearing on the in-hole inclinometer. As expressed in the displacement of the borehole inclinometer, the displacement of the ground is 102 days after the start of observation (however, the date of discovery of the crack appearing on the slope surface and the error is 17 days at the maximum), from 342 to It is confirmed that they occurred between 377 days, 404 days to 415 days, 593 days to 622 days, 925 days to 952 days, and 1231 days to 1268 days. On the other hand, the peak of sodium ion concentration contained in the groundwater appears after 85 days, 272 days, 300 days, 553 days, 837 days and 1044 days from the start of observation. After 102 days observed, the concentration rapidly increased after 85 days, 300 days, 553 days, and 837 days before 342 days to 377 days, 593 days to 622 days, 925 days to 952 days, and 925 days to 952 days. Each has a tendency to rise. It was confirmed that this rapid increase tendency was clearly more remarkable than the sulfate ion concentration. From this, when a rapid increase in the sodium ion concentration is observed in this way, there is a ground displacement thereafter. Can be predicted.
[0011]
<Measurement example 2>
Next, FIG. 4 shows a plan view of a different area from the measurement example 1, but the landslide situation cannot be read only from this plan view. However, this area is a soft ground, and although no large-scale landslide disaster has occurred in recent years, small collapses can be observed everywhere on the slope where the cedar has been planted to recharge the water source. It is known that it is part of a medium-scale landslide area where disasters occur every time. It is recognized that there is a river terrace below the slope, and a separate survey confirms that there is a terrace reki layer directly below it, and a mudstone layer that serves as the foundation below.
This landslide area is an area where there is not a lot of surface water and abundant groundwater is supplied, but from the results of measurement by a separate landslide meter, the movement of the landslide mainly moves to the bank terrace side. At the same time, it has been confirmed that the ridges are moving toward the valleys on both sides.
[0012]
Moreover, the existence of two cracks (lines indicated by symbols a and b shown in FIG. 4) exceeding 100 mm (millimeter) in width was found on the ground surface of the mountain side slope, but these cracks a and b subsequently grew. It was observed that Therefore, a plate was passed between the cracks a and b at the position indicated by ■ in FIG. 4, and a central portion of the plate was cut in the vertical direction to install a punching plate. The difference in the plate is due to the growth of the cracks a and b, and the difference width corresponds to the displacement of the crack width. By measuring this, the displacement of the ground due to the landslide was observed.
[0013]
On the other hand, in this area, drainage is installed from both sides of the ridge toward the ridge of the ridge to drain the ridge groundwater where landslides occur. Groundwater was collected from the works, and the concentrations of sodium ion, sulfate ion and chloride ion in the groundwater were measured. FIG. 5 shows the relationship between the change in the ion concentration and the amount of displacement of the crack width described above. Looking at the displacement of the ground from the amount of displacement of the crack width, it was confirmed that displacement occurred between 311 days to 370 days, 406 days to 438 days, 560 days to 591 days, and 808 days to 924 days from the start of observation. The
On the other hand, it was confirmed that the sodium ion concentration in the groundwater peaks after 365 days, 740 days, and 1110 days from the start of observation. And comparing this with the time when the displacement of the crack width was significant, also in this case, 406 days to 438 days when the ground displacement was observed, 365 days before 808 days to 924 days, It can be seen that the sodium ion concentration has risen sharply on 740 days. This trend, to predict rather as pronounced as sodium ion for sulfate, from these results, this way, when the rapid increase in the sodium ion concentration was observed, and that subsequently there is a displacement of the ground Can do.
[0014]
< Reference measurement example 3>
In addition, Fig. 6 shows a plan view of another area. In this area, a landslide occurs in which the mass moves intermittently and slowly from the mountain side (upper side of the map) to the foot of the mountain side (lower side of the map). is doing. FIG. 7 shows a vertical geological sectional view obtained by conducting a boring survey in the vicinity of the groundwater sampling position b described later in this area. From FIG. 7, it is confirmed that the area is composed of sandstone / mudstone alternating layers with high groundwater level lines and abundant groundwater supply, and weathered mudstone.
On the other hand, when the surface of the ground is observed, it is estimated that this area is located at the tongue end of a small-scale landslide topography. There are small cedar communities in and around this landslide area, and the water level in the drainage well installed for groundwater drainage in this landslide area was confirmed at position b shown by ● in FIG. However, it is recognized that the price is high, and it is confirmed from these facts that the district is supplied with abundant groundwater.
In this area, a retaining wall made of concrete earth retaining is installed to suppress mass movement due to the sliding of the landslide, but this retaining wall is displaced by the landslide immediately after the construction. Inclinometers were installed at two positions a and b, and the movement of the landslide was measured by measuring the displacement of the retaining wall.
Furthermore, various drainage facilities are installed in this landslide area. Among these, drainage works (positions marked with ● in FIG. 6) provided on the retaining wall near the inclinometer installation position b. Groundwater was collected and the sulfate ion concentration was measured. In addition, since 400 days after the start of observation, no precipitation was recorded over a long period of time, so drainage was depleted and groundwater collection became temporarily impossible.
[0015]
FIG. 8 shows the relationship between the displacement of the retaining wall and the change rate of the sulfate ion concentration. Here, the rate of change of the sulfate ion concentration is defined as the rate at which the concentration changes every 14 days. When this value is 1, the sulfate ion concentration in the groundwater after 14 days is the same and exceeds 1. It shows that it increases and decreases when it is less than 1. In other words, this rate of change is an index indicating the increase and decrease of the sulfate ion concentration and its speed.
Referring to FIG. 8, a small displacement occurs between 201 and 245 days and between 434 and 476 days from the start of observation, and a large displacement between 603 and 650 days and between 971 and 1010 days. Is confirmed to occur. On the other hand, it is confirmed that the change rate of the sulfate ion concentration has changed greatly over 1.5 after 180 days, 250 days, 440 days, 560 days, 890 days and 990 days from the start of observation.
In particular, after 560 days, 890 days, and 990 days, a remarkable increase in the concentration of sulfate ion concentration exceeding 1.75 was confirmed. Correspondingly, between 603 days to 650 days and 971 days to During the 1010 days, a large displacement of the retaining wall was observed, and this was a phenomenon in which the concentration of sulfate ions increased rapidly as a precursor to the occurrence of landslides. When there is a significant rise, this can be predicted as a precursor to the occurrence of a landslide.
[0016]
In this way, when the concentration of specific ions in the groundwater is continuously measured and changes in the measured ion concentration are observed to increase rapidly, the displacement of the ground due to slope failures such as landslides and surface failure is likely to occur. As shown in FIG. 9, an apparatus for predicting ground displacement due to slope failure such as landslide and surface layer failure is implemented.
In FIG. 9A, reference numeral 1 denotes a concentration sensor for measuring the concentration of selected specific ions such as sodium ions, and the concentration sensor 1 is selected in advance such as the dipmeter hole 2 as in the case described above. It is set up to measure the concentration of specific ions in the groundwater over time by being installed at a measurement site at an appropriate place. On the other hand, 3 is a control unit provided with registration (storage) means 4, and the control unit 3 inputs the measurement result from the density sensor 1 and registers it with time. The control unit 3 predicts that a landslide or surface layer collapse may occur when there is a sudden increase in the registered measurement result, and notifies the prediction result. Can be set as appropriate notification means 5 such as display display, sound emission notification by sound or buzzer, lamp lighting, and the like. Of course, a plurality of notifications may be combined.
[0017]
In addition, the determination of whether or not the ion concentration is rapidly rising is based on the rapid increase in specific ion concentration and the rate of change as shown in the above example. It differs based on conditions, etc., and is not considered uniform. Therefore, in order to establish this criterion and increase the accuracy of the prediction, in the district where the slope failure is to be predicted, the ground displacement measurement and the specific ion concentration measurement are actually performed over time, and the measurement results are obtained. It is only necessary to confirm the change state of the ion concentration when the ground displacement is actually observed by making a comparison, and to determine the reference data for predicting the ground displacement due to the slope failure for each site based on this By doing so, it is possible to predict ground displacement due to slope failures such as landslides and surface layer collapse corresponding to each site, and the accuracy of these predictions also increases.
Of course, there are some areas that cannot be measured using such ground displacement equipment. For such areas, the judgment criteria for ground displacement prediction due to slope failure should be set to an average of many data. You can also.
[0018]
On the other hand, if ground displacement due to slope failures such as landslides and surface failures is predicted, it is necessary to take necessary measures, but in the case of railways and roads, measurements at a wide range of locations are required. These are necessary and may be managed individually, but comprehensive management is also required. Therefore, in such a case, as shown in FIG. 9B, the measured ion concentration is input to the headquarters terminal 7 via the local terminal 6, and the slopes such as landslides and surface layer collapse described above at the headquarters terminal 7 are entered. By predicting the ground displacement due to the collapse, and outputting the result to the terminal of the branch (division, district) where it is necessary to know the prediction results, such as the branch terminal 8, etc., landslides and surface collapse It will be possible to perform comprehensive management of ground displacement prediction due to slope failure. In this case, the local terminal 6 and the branch terminal 8 may be the same, and the terminal 9 arbitrarily branched from the branch terminal 8 may be used as the local terminal 6. Furthermore, by setting these terminals 6, 8, and 9 so that the ground displacement due to the slope failure can be predicted, the prediction measures in cooperation with the headquarters terminal 7 can be effectively performed. Become.
[Brief description of the drawings]
FIG. 1 is a plan view of a district of measurement example 1. FIG.
FIG. 2 is a geological sectional view of a measurement example 1 area.
FIG. 3 is a graph showing the relationship between ground displacement and groundwater composition change in the measurement example 1 area.
FIG. 4 is a plan view of a district of measurement example 2.
FIG. 5 is a graph showing the relationship between ground displacement and groundwater composition change in the measurement example 2 area.
FIG. 6 is a plan view of a district of Reference Measurement Example 3.
FIG. 7 is a geological cross-sectional view of the district of Reference Measurement Example 3.
FIG. 8 is a graph showing the relationship between the ground displacement and the change in groundwater composition in the reference measurement example 3 area.
9A is a block circuit diagram of a ground displacement prediction device due to slope failure such as a landslide or surface failure, and FIG. 9B is a state where a ground displacement prediction device due to slope failure such as landslide or surface failure is terminalized. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Concentration sensor 3 Control part 4 Registration means 5 Notification means

Claims (1)

Measuring means for measuring the concentration of specific ions present in the groundwater in the area where the ground displacement due to slope failure such as landslide and surface layer collapse occurs, registration means for registering the measured ion concentration over time, A predicting means for predicting that a ground displacement due to a slope failure such as a landslide or a surface layer collapse may occur when there is a sudden increase in the registered ion concentration; and a notifying means for notifying the predicted result. In the prediction apparatus provided , the specific ion is sodium ion, and the concentration measuring means is installed at a preselected measurement site and is set to measure the concentration of sodium ion in groundwater over time. A concentration sensor, and the measurement of the concentration of sodium ions by the concentration sensor is performed at a large number of locations over a wide range, and the measurement is performed for 1000 days or more. The measured sodium ion concentration is input to the headquarters terminal via a local terminal, and it is predicted that the ground displacement may occur at the headquarters terminal. An apparatus for predicting ground displacement due to slope failure such as landslides and surface layer collapse, which is configured to perform comprehensive management of ground displacement prediction by outputting to the terminal of the part that needs to be informed .

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