JP4404320B1 - Slope topsoil displacement calculation method and disaster prevention information system - Google Patents

Abstract

[PROBLEMS] To enable general residents to predict slope collapse behind their homes via the Internet.
[Solution]
If the slope of the slope is θ,
K = {(cross-sectional shape factor α × tan θ) × (relaxation layer thickness D × relaxation factor δ × X + planar shape factor β × rainfall P × Y) − (tree species coefficient λ × age age coefficient μ + clump friction coefficient τ)}.・ ・ Using the coefficient model that can be expressed by Equation 1, based on the geological structure coefficient X and hydrological coefficient Y, based on the past two rainfall histories, a topsoil displacement calculation model was created, and the slope instability K relative to future rainfall Is provided on the Internet to allow the general inhabitants to estimate the topsoil displacement amount ε of the slope on the back of the house with respect to rainfall information.
[Selection] Figure 1

Description

The present invention relates to a slope topsoil displacement calculation method and a disaster prevention information system for performing software monitoring of a steep slope danger point on a huge number of general slopes.

There are 500,000 steep slope danger points in Japan, and as a countermeasure, expensive prevention work has been carried out in many places. However, the number of dangerous places is enormous, and even though it is a safety measure, the current countermeasure method for endless construction is extremely cost-effective. Is extremely difficult, so we will have to deal with software in the future. Therefore, there is an urgent need to develop disaster prevention technology using software that serves as the receiver.

Looking at the overall technology so far, it is indispensable to examine the stability of the slope in order to evaluate the slope. As the examination method, the static method according to Non-Patent Document 1 expressed by Equation 2 is used. The only method was the split method, which is a fundamental study.
Σ {c × L + (W × cos α−u × L) × tan φ} / ΣW × sin α = F ·· Formula 2
This formula is the safety factor obtained by dividing the total slip resistance obtained by adding the adhesive force c × L and (W × cosα−u) × internal friction angle φ of the slope to be evaluated by the total slip force of W × sinα. It is a dynamic model for calculating F. Although this dynamic model is generally used in studies on landslides where information such as the slip surface position and groundwater level has been revealed by geological surveys, the marking method cannot be applied to general slopes where the conditions are unknown.

As a method for solving the above problem, researches have been made on how to apply the division method to general slopes. However, a method for calculating this uncertain factor has not yet been found. In addition, there is a method of expressing the risk of slopes due to disaster prevention charts by points, but it is not possible to guess which slope will collapse next time, although the risk ranking is generally performed. A hazard map is also provided, but it displays dangerous slopes and does not provide direct evacuation information.

Patent Document 1 discloses a method for solving the problem of uncertain factors by a statistical method. Assuming various soil constants, this method uses a computer to analyze the seepage flow due to rainfall, and gives variation in soil adhesive strength c and internal friction angle φ. The rate is calculated to determine the degree of risk. The basic equation of this method is also the same division method of Equation 2, and the change of groundwater level is obtained by osmotic flow analysis and applied to dynamic analysis. However, the dynamic change has an influence on the component itself of Formula 2, for example, the permeability coefficient itself changes greatly in the process of temporal loosening of the mass and formation of cracks, and the strength of the slip surface itself also changes. Therefore, the effect of such dynamic changes on the prediction accuracy is unknown.

Japanese Patent Application Laid-Open No. 2004-228561 describes a technique for compensating for landslide disasters by compensating for advanced information communication systems instead of slope stability evaluation. This method is designed to create a system that can quickly evacuate by managing related information including resident information in an integrated manner and sharing this information with government agencies and residents in situations where landslides are expected. want to be. However, since the problem of this method is a mixture of important information and unnecessary information in an emergency, it cannot be said to be a reliable disaster prevention system unless a method for determining the importance of information for the parties is established.

Important information for the parties is a precursor to the collapse of the slopes on the back of the house, but there is a way to detect danger and evacuate with a slope monitoring device. However, the extensometer described in Non-Patent Document 1, which is an existing slope monitoring device, is too sensitive and difficult to handle and requires maintenance by an expert, so it cannot be used on ordinary slopes. In order to improve this point, although the simple slope monitoring device shown in Japanese Patent No. 4006732 related to the applicant of the present application has been devised in Patent Document 3, since the actual number of dangerous slopes is as many as 500,000, the number of installation places is one. It is necessary to narrow down to about 50,000 locations of / 10.
JP2002-070029 JP 2003-247238 A Patent No. 4006732 Soil Engineering Society "Soil Engineering Handbook" Soil Engineering Society Publication 1982 Edition

Therefore, the technical problem to be solved by the present invention is to solve various uncertain problems in the current slope evaluation, and to establish an objective slope evaluation method,

The number of dangerous slopes is about 500,000, and the slope displacement amount is more than a certain amount.

The division method according to Non-Patent Document 1 currently used is a soil mechanical stability study, and is used on slopes where sufficient ground surveys have been conducted and groundwater levels and soil constants have been found. Therefore, it cannot be used for stability examination by the division method of general slopes where geological survey is not conducted. Therefore, the present invention
Instability K of the topsoil of the slope,
Cross section shape factor α × topography amount G indicated by tangent function of slope top surface slope angle θ (degrees), slope top soil thickness D (m) × loosening factor δ × geological structure adjustment value X From the unstable total amount consisting of the product of the shape factor β × rainfall P × the center of gravity Q obtained by adding the center-of-gravity movement amount Δh obtained by the adjustment value Y regarding hydrology,
The amount of vegetation S expressed by the tree species coefficient λ × age coefficient μ + the stable total amount obtained by the friction coefficient τ between the soil blocks constituting the top soil is subtracted K = {(α × tan θ) × (D × δ × X + β × P × Y ) − (Λ × μ + τ)}
From the past collapse cases, the degree of instability K ² = the topsoil displacement amount ε (cm) of the slope, the adjustment value X related to the geological structure that cannot be measured and the adjustment value Y related to hydrology are the top soil displacements ε1 and ε2 By estimating, X and Y are obtained by simultaneous equations, and a topsoil displacement calculation model is created, thereby making it possible to predict the topsoil displacement ε of the slope with respect to future rainfall.

When the uncertain numbers X and Y are determined, the degree of instability K and the topsoil displacement amount ε with respect to future rainfall are uniquely determined based on Equation 1, so a program incorporating this equation can be executed on a web server on the Internet. If the general user starts this software via the web and inputs the location information of the slope to be evaluated and each slope data such as topography and vegetation on the existing geographic information database, After that, it automatically calculates the topsoil displacement amount ε of the slope by referring to the nearby rainfall information, and displays the result on the TV screen through a personal computer or digital broadcast in real time.

Create a topsoil displacement calculation model for each individual slope using the method described above, and output each rainfall-topsoil displacement ε (cm) relationship diagram in advance. This figure is based on the rainfall up to the time of the heavy rain day. Further, the topsoil displacement amount ε at that time can be estimated. For this reason, it is possible to get an approximate estimate of the evacuation time in advance by looking at future rainfall forecasts announced by the Japan Meteorological Agency.

With this technology, the topsoil displacement ε corresponding to rainfall can be estimated in centimeters, so it is possible to determine the estimated 50,000 dangerous slopes by assigning the risk ranking of the slope to be evaluated under the same rainfall conditions, and to monitor the dangerous slope slopes The environment for installing the equipment will be prepared.

Based on the above, it is possible to discriminate an estimated 5,000 dangerous slopes by identifying the estimated 50,000 required slopes and attaching the slope monitoring device directly to the displacement amount of the slope. It becomes. The measured data obtained from the slope monitoring device is used for verification of this disaster prevention information system, and the accuracy of the calculation of topsoil displacement as a surface is improved. In this way, by combining the topsoil displacement calculation model and the slope monitoring device according to the present technology, a point-and-surface multiple evacuation warning system is constructed, and the overall safety can be improved. These continuous observation materials will become important basic materials for the subsequent countermeasures.

The topsoil displacement calculation model, which is the present invention, invents a slope topsoil displacement calculation method based on a coefficient model built on the basis of a structural model, which is different from conventional soil mechanics models. A disaster prevention information system is provided to enable the use of coefficient models.

In the structural model, a plurality of blocks (symbol 2) having a width of 1 m and a height of 0.8 m to 1.5 m with a slip stopper on the bottom surface are placed on an inclined base (symbol 1) whose angle can be changed as shown in FIG. If they are tilted little by little by connecting them with thin and easy-to-cut strings (symbol 4), the center of gravity (symbol 3) of the highest building block 2 will deviate beyond 30 °, and some blocks (symbol 2) will be unsatisfactory. Stabilizes and tries to fall down, but at the initial stage, the force to fall is weak, and the front and back blocks (reference 2) can be supported via the string (reference 4). When the inclination is further increased, the force to fall is gradually increased, and the front and rear blocks (reference numerals 2 and 2) gradually become unstable, and a plurality of blocks (reference numerals 2 and) are inclined and unstable parts (reference numeral 5). If you tilt and further tilt, the force to fall will increase, and the string (reference 4) that connects between the blocks (reference 2) will not be able to withstand the force and will cut, and the blocks will fall apart and slide off the table The situation is applied to natural slopes.

Each element of the structural model can be quantified by a coefficient model shown in FIG. That is, the unstable total amount on the balance on the left side of the figure is obtained by the product of the tangent function of the angle of the tilting table (reference numeral 1) and the height (m) of the building block (reference numeral 2), while the stable total quantity is calculated by the building block ( It is determined by the strength of the string (reference 4) connecting the reference 2) and the frictional resistance between the blocks (reference 2 and 2). When this is applied to a general slope, the height of the building (reference 2) The angle of the tilt base (reference numeral 1) is represented by Q and is the amount of topography at the angle θ of the bottom surface of the loose layer. The stable total amount on the balance on the right side of FIG. 2 is the density and strength of the string (reference 4), the vegetation amount S expressed by the product of the tree age coefficient μ and the tree species coefficient λ shown in Table 1, and the building blocks (reference sign). The frictional resistance of 2) is the friction coefficient τ around the mass shown in Table 1.

The relationship between vegetation and slope stability is evaluated as the action of tree roots to keep the soil clumps, and pine and broadleaf trees that spread strong roots have a great deterrent, but shrubs are weak. Since conifers made from plantations have poor root development, they are located between hardwoods and shrubs. In addition, since the root is proportional to the size of the trunk, it can be said that the thicker and taller the trunk, the greater the debris deterrence. The tree species coefficient λ is set to 1 for the largest class of shrubs and 1 for the poor growth of conifers planted with bare trees, and to 3 for the broadleaf trees. These factors were determined with reference to the difference in damage due to differences in past tree species.

The value of the frictional resistance τ is determined by referring to the difference in the degree of damage due to the difference in soil quality from past collapse cases. As shown in Table 1, the topsoil is 2, the weathered soil is 3, and the soft rock is 5 .

The above coefficient model expresses the slope balance. The topsoil collapses when the balance tilts to the left side due to an increase in Δh due to rainfall, the spring breaks, and the balance tilts to the left. The slope failure mechanism with such a coefficient model is easy to understand for ordinary people and can easily collect necessary data, so it is suitable as a slope disaster prevention system with participation by residents.

If each said element is demonstrated in detail, the vegetation amount S as a topsoil collapse inhibitory force by a plant can be represented by the product of a tree species coefficient (lambda) and a tree age coefficient (mu) for this reason.

The stability of the topsoil (symbol 15) is determined by the shape of the slope to be evaluated and the friction coefficient τ based on the soil properties and physical properties of the topsoil (symbol 15). Concerning the influence of topography, the convex topography is isolated and unstable, and the concave top is easy to disperse the force around it, and the topography amount G is the cross-sectional shape factor α shown in Table 1 and the slope angle of the topsoil bottom It can be expressed as the product of the tangent function of θ.

The effect of rainfall P on the slope works as an action to increase the gravity center position of the topsoil, but the water gathering is affected by the topography and hydrological structure, so the plane shape factor β shown in Table 1 and the groundwater supply etc. It is necessary to correct the rainfall P with the adjustment value Y related to hydrology.

The above coefficient is a topographical and geological element that can be said to be the constitution of the slope, and does not change in several decades except for the amount of vegetation S.

On the other hand, topsoil displacement increases due to heavy rain, etc., and the strata may loosen and become easy to collapse. Such looseness of the strata can be said to be a physical condition because it changes depending on the degree of damage caused by heavy rain and the recovery of strength due to the subsequent compaction action. Although the base rock is loosened and topsoil is formed, the difference in the degree of looseness has a great influence on slope stability, so it is important to appropriately set the degree of looseness, that is, the loosening coefficient δ. The values shown in Table 1 can be considered as a guide.

The looseness factor δ is 0.1 for rock, 0.5 for weathered soil, and topsoil corresponding to the slope slope is formed. The looseness coefficient δ is assumed to be 1. And if the root bend with a topsoil displacement of about 5 cm is conspicuous, set it to 1.5, and if the topsoil displacement exceeds 7 cm, set a maximum of 2 if there is a step or the like, or if the tree falls down or dies. To do. The initial setting may be rough to some extent. When topsoil displacement accumulates, it is desirable to make fine adjustments according to the topsoil displacement. Table 1 was decided based on the field survey of the collapsed area. It can be determined by a simple penetration test based on this table.

Such loosening of the strata causes further loosening of the strata, so the topsoil displacement ε is expected to be the square of the degree of instability, but the data obtained from numerical verifications of previous collapse cases are generally correct. Therefore, the degree of instability K ² = the topsoil displacement amount ε may be considered.

In the case of an average constitution, once the damage is received, the topsoil displacement phenomenon in which the earth and sand near the ground surface gradually moves downward, loosens the topsoil, and the physical strength of the slope decreases. If the degree of looseness, or physical strength, takes several years to recover and heavy rain falls again within a few years, the damage accumulates and the topsoil displacement increases in proportion to the acceleration of physical strength. It is formed. The degree of topsoil displacement is proportional to the degree of expansion of cracks on the slope, the degree of formation of new steps, and the degree of growth of trees.

The slope causing the topsoil displacement is estimated to be approximately one-tenth plus slope (symbol 7) of the entire steep slope, and within a group of 50,000 slopes (symbol 8) in the whole country where the topsoil displacement is large. (Symbol 9). And it is thought that about 500 places appear every year from within the dangerous slopes indicated by ++ in about 5,000 places nationwide. In this way, the slopes are classified using the pathological condition and physical strength of the slopes as an index, and the hierarchical distribution model of the places where the steep slope collapse risk is shown in FIG.

The decrease in the physical strength of the slope causes a topsoil displacement, and the topsoil displacement causes a tree growth disorder. On the ++ slope where the topsoil displacement is less than several centimeters every year, the trees can grow little by little while generating root bends. However, if the topsoil displacement exceeds several centimeters every year, the roots are cut and the trees can grow. Only shrub forests and perennials can grow, and there are steps and cracks in the ground.

If years of low rainfall continue and the degree of looseness gradually decreases, then the growth of trees may resume on the + and ++ slopes and the physical condition of the slopes may gradually improve. If there is no heavy rain for several decades, the slope will be stabilized by the reinforcement effect of the trees. However, once it falls into ++, it becomes unstable even with a small amount of rainfall, so it is difficult to recover, and such slopes are likely to collapse several years away.

FIG. 2 shows a model of the slope condition, but the problem is how to determine the adjustment value X related to the invisible geological structure and the adjustment value Y related to hydrology that determines the degree of influence of rainfall. is there. As a solution of this case, the top soil displacement amount ε, which is the right side of Equation 1, is estimated by estimating the ε1, ε2 in the two rainfall conditions of the past heavy rainfall history and year-round rainfall in the growth situation of the above tree, etc. The problem was solved by determining X and Y by simultaneous equations (1).

The topsoil thickness D (m) used for the coefficient model is preferably obtained by a simple penetration test, but it may be searched by a simple method such as a bar, and it is assumed that 1 / tan θ (m) in consideration of the position of the center of gravity. May be. This is because the error on D is adjusted by the value of X, so the influence on the prediction accuracy is not so great. Thus, the right side of Equation 1 of the slope to be evaluated is all known, and the topsoil displacement amount ε with respect to the rainfall P can be calculated.

This coefficient model is effective as an approximate method for handling natural phenomena in which factors are intricately intertwined. Counting the visible factors, first obtaining an evaluation that can be said to be the basic structure of the slope, obtaining the physical condition from the state of vegetation and the ground surface, and then making various black and white black boxes of various natural phenomena that cannot be clarified The actual slope is reproduced with a coefficient model. This method solved the uncertain problem of general slopes, which was impossible until now.

Using this coefficient model, the amount of topsoil displacement on the slope is calculated, the relationship between the amount of topsoil displacement ε and the amount of rainfall P is graphed, and this is a warning for the year. However, the initial estimated value is based on past data, and the displacement amount calculated as a result has a certain amount of error. However, for subsequent rainfall, the topsoil displacement ε can be verified by measuring the length between simple triangulation piles installed on the evaluation slope, so adjustment value X for geological structure, adjustment value Y for hydrology The accuracy of future predictions will be improved by modifying to match the current situation.

As shown in FIG. 4, the above-mentioned work sharing is carried out by the governments such as prefectures, municipalities, etc. from the aerial survey shown on the above-mentioned reference 10 and the basic survey on the desk to the output of the rainfall-displacement map. Under the guidance of government-sponsored researchers and specialists, the basics of the national / prefectural economic support, in principle, are carried out by the residents. At the heart of this is the voluntary disaster prevention organization, which estimates the degree of looseness and topsoil displacement ε based on the field survey, and estimates and evaluates the adjustment value X related to geological structure and the adjustment value Y related to hydrology. The government and residents will collaborate with a consultant or university to create a model for calculating the amount of topsoil displacement on the target slope.

This disaster prevention information system can be used not only for measures against steep slopes but also as a general slope disaster prevention system for debris flow-prone mountain streams, road railways, slopes around dam lakes, and ODA projects. Such various slope information in the country is input to the database in the web server on the Internet together with the existing geographic information database together with the latitude / longitude information (reference numeral 13) and the range information (reference numeral 14) of the evaluation target slope. The topsoil displacement amount ε is calculated in real time by automatically referring to the rainfall information (symbol 12) in the vicinity of the evaluation target slope. These processed slope information is displayed on the screen on the Internet and digital home broadcasting together with the risk map information for each color, so that you can monitor the predicted damage map throughout the country while you are at home. The map information by risk level on the web site is also used to predict the future rainfall situation after an arbitrary number of years. It is possible to construct a comprehensive disaster prevention information system that displays a displacement prediction diagram.

The slope topsoil displacement calculation method and disaster prevention information system will maximize their effects when constructing a resident evacuation warning system for steep slopes. Examples of steep slopes are shown below.

Targeting 500,000 hazardous locations nationwide that have been the subject of uniform construction so far, comparative analysis of vegetation is made based on the difference in the reflectivity of electromagnetic waves such as laser aerial surveys, etc., and the Geographic Information System (GIS) Analyzing the terrain and automatically creating basic data. In an area where GIS is not yet developed, a normal topographic map is used, and the slope as the examination unit is divided into arbitrary shapes based on the difference between the topography and vegetation, and latitude and longitude information (reference numeral 13) of the reference point O shown in FIG. N, NE, E, SE, S, SW, W, NW The range is expressed by the range information (reference numeral 14) of the examination slope of the distance from the eight azimuth lines and the center.

As a normal monitoring system, an estimated 50,000 locations where topsoil displacement is generated by this topsoil displacement calculation model is selected as a + unstable slope (symbol 7), and the warning level is increased by one rank. Install. As countermeasures for these 50,000 locations, it is important to speed up the growth of trees by actively monitoring and managing satoyama and afforestation. Furthermore, based on the observation results of the slope monitoring device, the critical soil level (symbol 8) where the topsoil displacement amount of about 1 in 5,000 exceeds 5 cm is narrowed down, and the warning level is targeted for these 5,000 locations. Further up by one rank, a data logger is installed, and a special danger slope (reference numeral 9) of +++ whose topsoil displacement exceeds 5 cm and increases according to the fluctuation record is specified. Geological surveys and countermeasures will be carried out sequentially on this special danger slope (symbol 9).

The reference rainfall (symbol 12) in the monitoring system shown in FIG. 4 selects either continuous rainfall or effective rainfall, and the rainfall versus topsoil displacement ε graph between rainfalls of several tens to several hundreds of mm. , Door-to-door input data, evacuation location, acquaintance's phone number, evacuation precautions, etc. are output on a single sheet for each door, put in a transparent waterproof vinyl sheet, etc., and stored in an easy-to-understand place in the living room or bedroom Put it with a light to be vigilant.

The rainfall-to-soil displacement ε graph for each door is the same for each spot of the voluntary disaster prevention organization, and the team leader and assistants grasp the situation within the team and the standard displacement determined by the team members in advance. Based on the amount, support the residents as a voluntary disaster prevention team. At that time, the evacuation site and route will be determined in advance by consultation between the residents depending on the personnel composition of each house and the presence or absence of disaster victims, and each house will evacuate voluntarily in an emergency. In addition, the voluntary disaster prevention organization grasps a certain amount of rainfall over the Internet and the situation in other areas, and coordinates with the local government, such as contacting the local government and requesting necessary support.

When one topsoil collapse occurs, it is normal to see the collapse spreading to the surroundings. FIG. 6 shows a procedure for determining the longitudinal influence of the collapse of one topsoil (reference numeral 15) and determining the collapse range. Judgment of the topsoil collapse is determined when the topsoil displacement ε of each unit slope exceeds 10 cm, and the influence on the lower soil mass is expressed as centimeters where the topsoil displacement ε value exceeds 9 cm. In addition to the quantity ε, the collapse area is determined one after the other. FIG. 6 shows a case where the topography of the terrain is a straight standard terrain. In this case, when the top soil of d is collapsed, 10 cm−9 cm = 1 cm is added to 9 cm of ε1 of e as an influence value on e. Since ε2 of e is 10 cm, the topsoil indicated by e in the figure is determined to be collapsed. Further, the influence value on f is similarly 10 cm−9 cm = 1 cm, and if it is added to 8 cm which is ε1 of f, ε2 of f becomes 9 cm and does not collapse. In addition, the influence on the upper part is examined in the same manner by setting the numerical value d (m) of the predicted collapsed layer thickness dm to cm as it is as 1, 2, and 3, and adding it to the upper surface soil displacement.

The spread of the collapse is corrected by the plane shape factor β (symbol 16) shown in FIG. 7, and when calculating the influence value of the topsoil collapse on the surroundings in the previous section, in the case of a straight slope, the plane shape 1/2 of coefficient β (symbol 16), that is, 1 is multiplied by the influence value on the longitudinal section. In the case of a ridge-type slope, 0.5, which is 1/2 of the plane shape factor β (reference numeral 17), is applied to the longitudinal influence value. Similarly, in the case of a valley-shaped slope, 1.5, which is ½ of the plane shape factor β (reference numeral 18), is multiplied by the longitudinal influence value. As an example, if the topsoil layer thickness is assumed to be 2 m, the influence on c is 2 cm, and 5 cm + 2 cm = 7 cm, so that the topsoil c in FIG. 7 does not collapse.

FIG. 8 shows the case of a ridge-type slope. Among the top soils (reference numeral 24) of each ridge-type slope, ε1 of d is 10 cm, and the influence value of the ridge-type slope on the top soil e is {10 cm−9 cm} × planar shape factor β (reference numeral 17) is 0.5 = 0.5 cm, and therefore, ε2 of the top soil e is 9 cm + 0.5 cm = 9.5 cm, and the top soil of e does not collapse because it does not exceed the criterion 10 cm. Similarly to FIG. 7, c in the upper part of topsoil d in FIG. 8 does not collapse.

The case of the valley-shaped slope is examined in the same manner. As shown in FIG. 9, since the plane shape factor β (reference numeral 18) is 3, 3 × 0.5 = 1.5 is set to each of a to i. When the influence value of the topsoil (reference numeral 25) on the valley slope is corrected, as shown in FIG. As in FIG. 7, c in the upper part of topsoil d in FIG. 9 does not collapse.

As for the impact on the side of the collapsed land, add about 2/3 of the upward impact to the lateral topsoil displacement amount ε1, and similarly determine the collapse along the collapse path (symbol 19) and Make a decision and predict the damage to the property to be protected (symbol 20). In addition, (code | symbol 31a) represents a linear slope, (code | symbol 31b, 31c) represents a ridge-type slope and a valley-type slope, respectively.

There are various ways of taking unit slopes, but basically the surface soil thickness is about 7 times the thickness Dm, and the width is about 2/3 of that. A method of ignoring the layer thickness and dividing the terrain and vegetation into unit slopes is also conceivable, but when the length of one unit reaches several tens of meters, the degree of influence is reduced to about 1/3. If the length exceeds 100 m, expansion to the surroundings is not usually considered. Subdividing is close to the actual collapse mode, but the follow-up survey is difficult, so the scale of the unit slope is properly used depending on the situation. When divided roughly, it becomes a probabilistic forecast. In this case, the topsoil displacement amount of the slope is calculated in consideration of the variation in the slope angle θ of the topsoil bottom surface.

The above calculation is automatically performed when the rainfall P is referred to, and a near real-time damage range prediction map corresponding to the rainfall is displayed on the screen of a personal computer on the Internet. At this time, the occurrence of debris flow is automatically determined on the basis of the volume of the collapsed mass of the slope determined to be collapsed and the estimated water content ratio obtained from the rainfall, and the predicted reach is also displayed on the screen.

After confirming safety after heavy rain, a research team led by a voluntary disaster prevention organization observes signs of surface displacement, such as the presence or absence of a ruined site or a fall of a tree, and checks the degree of looseness by pushing a bar or the like into the ground. The situation of the slope is examined by measuring the distance between various triangulation piles. Based on these survey results, the data will be revised to prepare for the next rainfall. This work is important because the slope will collapse even with a little rain if the degree of looseness is large.

After that, if there is no damage due to rain, the system will automatically recover half the looseness in one year and 80% in several years. When topsoil displacement amount ε, etc. is newly generated, the new looseness amount is automatically multiplied by the new displacement amount (ε) /33.3333 (however, 1 or more) to the initial looseness coefficient. The obtained amount of looseness is used for the next calculation of displacement. When ε = 4 cm, 1.2 times; when ε = 5 cm, 1.5 times; when ε = 6 cm, 1.8 times; Although the calculation of the amount of looseness is performed automatically, if it is determined that it does not match the current situation, it must be corrected manually. At this time, it is necessary to review the X and Y settings at the same time.

Further, when the surface soil displacement amount ε of the new surface soil block is several cm or more, the growth rate of the tree is automatically reduced to about half, and when it is 4 to 5 cm or more, the growth is stopped. When the amount of displacement falls within a few centimeters, the tree age coefficient μ is automatically updated using a predetermined tree growth rate. However, since the degree of such looseness varies from one slope to another, it is necessary for the locals to check the loosening recovery status and whether the tree age is appropriate by measuring the distance between simple triangulation piles at least once a year by the local community. There is.

Table 1 shows how to take each coefficient. Data is expressed as 10b 3u30 L1, etc., and numerical processing is performed inside the computer. Vegetation is expressed as c-type or multiple bs. The topography is called the 2i type, and the friction coefficient τ is called the L1 type, and when it is very loose, it is called the L2 type. These coefficients may change slightly depending on future surveys, topographic zones, geological zones, and climate zones.

In this way, it is possible to improve future prediction accuracy by automatically or manually updating the data every time. That is, if a future elapsed year and a predicted rainfall amount P are input on the personal computer screen, the tree age and the like are instantaneously corrected, and a risk prediction diagram after the elapsed years can be obtained. This function can be used as a vegetation evaluation system for disaster prevention planning. As a result, the evaluation of trees is expressed numerically, so it is possible to easily determine the cost-effectiveness when managing satoyama. For this reason, the administrative side can take effective measures for steep slopes involving the participation of residents by providing economic support such as subsidies and subsidies for local residents.

The slope topsoil displacement calculation method and disaster prevention information system are effective not only for residents' participation, but also for wide debris flow monitoring and also for slope monitoring systems on routes. Examples for route monitoring are shown below.

As an embodiment in the road management system, a method of centrally managing the route of the entire jurisdiction area such as a route unit and a civil engineering office can be considered. First, a preliminary survey is created by conducting a desktop survey based on topographic maps and aerial photographs for each route. Based on the preliminary map, the first field survey will be conducted and the data of the slope displacement calculation system will be input. Create a rainfall-soil displacement ε graph for each unit slope, conduct a secondary field survey, and make overall adjustments and partial data corrections. At this time, point out the points of caution, and if necessary, develop a third field survey plan such as a simple penetration test, and propose a plan to install a slope alarm device at the necessary location. Basically, the data is reviewed once a year, the point of caution that has been hit by a large amount of rainfall is checked, and the estimated displacement is verified. After properly arranging the slope monitoring device, it becomes possible to verify the amount of displacement only by patrol around the road surface, leading to a significant reduction in labor costs such as survey costs. When this slope monitoring device is installed, dangerous slopes are grasped, so that part will be subject to rainfall traffic regulation and geological surveys will be used as basic data for countermeasure construction at a later date.

This slope displacement calculation method makes it possible to artificially create an environment in which trees can grow soundly, and the vegetation can prevent the slope from collapsing, which can greatly reduce the cost of hardware measures for the future.

Forest development is excellent not only as a disaster prevention measure but also as an environmental measure, enabling CO2 reduction and effective use of forest resources, which is useful for the promotion of local industries. Now that the critical plains have been submerged due to sea level rise, a safe and comfortable living space is secured in the mountainous area, and a foundation for energy-saving independent industrial locations will be formed in the future.

Now that global warming countermeasures and environmental protection are said globally, this slope displacement calculation method for nurturing forests is considered to be accepted by the world. Especially, as in Japan, heavy rain disasters are serious in Asian monsoon countries and European mountainous areas. It is likely to be used as a warning system in Japan and is expected to be developed as a technology export industry in Japan in the future.

It is a structural model figure which shows the basic concept of topsoil displacement amount calculation. It is the coefficient model figure which digitized the structure model. It is a hierarchy distribution model figure of the steep slope collapse danger part. It is a figure which shows the flow of basic work. It is a figure which shows how to express the position and range of an examination slope. A cross-sectional view of the collapse and expansion of a straight planar shape is shown. A plan view of the expansion of collapse to the surroundings is shown. A cross-sectional study of the collapse and expansion of the ridge slope is shown. A cross-sectional study of the expansion of the valley slope is shown.

DESCRIPTION OF SYMBOLS 1 Inclination stand 2 Building block 3 Center of gravity line 4 String 5 Unstable part 6 Stable slope 7 Unstable slope which produces topsoil displacement of several centimeters in one rainy season 8 Danger slope whose topsoil displacement amount in one rainy season exceeds 5cm 9 One rainy season Specially hazardous slope 10 where the amount of topsoil displacement increases by more than 5 cm 11 The government is responsible 11 The local is responsible 12 Reference rainfall 13 Latitude and longitude information 14 Range information 15 Straight slope topsoil 16 Straight slope shape factor β
17 Plane shape factor β of ridge type slope
18 Planar shape factor β of valley-shaped slope
19 Collapse path 20 Property to be protected 21 a Straight slope 22 b Ridge slope 23 c Valley slope 24 Top soil on ridge slope 25 Top soil on valley slope D Top soil thickness D × δ × X Looseness coefficient and geological structure factor Converted topsoil height G adjusted by X Topography amount Δh Topsoil center of gravity movement due to rainfall K Instability P Rainfall Q Ground mass S Vegetation amount X Adjustment value related to geological structure Y Hydrological adjustment value a Sectional shape factor β Plane shape factor inclination angle λ species coefficient δ slack coefficient ε topsoil displacement θ topsoil bottom surface μ old coefficient τ coefficient of friction

Claims (5)

Instability K of the topsoil of the slope,
Cross section shape factor α × topography amount G indicated by tangent function of slope top surface slope angle θ (degrees), slope top soil thickness D (m) × loosening factor δ × geological structure adjustment value X From the unstable total amount consisting of the product of the shape factor β × rainfall P × the center of gravity Q obtained by adding the center-of-gravity movement amount Δh obtained by the adjustment value Y regarding hydrology,
Determining the degree of instability K by subtracting the total amount of vegetation S expressed by the tree species coefficient λ × the age coefficient μ + the friction coefficient τ between the soil blocks constituting the top soil K = {(α × tan θ) × (D × δ × X + β × P × Y) − (λ × μ + τ)} Equation 1 and the square of the degree of instability K becomes the topsoil displacement amount ε of the slope, and if the topsoil displacement amount ε based on continuous rainfall becomes 5 cm to 10 cm, the situation becomes dangerous. Slope topsoil displacement characterized by substituting coefficients such as vegetation, topography, geology, etc., determined by trials into Equation 1 so that the situation leading to collapse can be explained at the same time as much as possible. Calculation method. The total amount of instability of the topsoil increases as the slope angle θ (degree) of the topsoil bottom of the slope increases, increases as the topsoil thickness increases, and no matter how thick the topsoil is, If the slope of the bottom surface is zero, the total amount of instability is zero. Therefore, the instability of the topsoil on the slope is expressed as (α × tanθ) × (D × δ × X + β × P × Y). The method for calculating the amount of displacement of a topsoil on a slope according to claim 1, characterized in that: The stable total amount of the slope top soil is represented by the sum of the vegetation amount S and the friction coefficient τ between the soil blocks constituting the top soil. Considering the vegetation amount S, as the tree grows, the roots deeply enter and the top soil , And the soil is reinforced, the degree of reinforcement is large in broad-leaved trees, small in herbs, and the vegetation amount S consisting of the product of the tree species coefficient λ and the age coefficient μ The slope topsoil displacement calculation method according to claim 1, characterized by a slope topsoil stability calculation method represented by a sum of friction coefficients τ between soil blocks constituting the topsoil (λ × μ + τ). The total amount of instability of the topsoil on the slope is based on the thickness D of the topsoil on the slope that can be measured, but it must be corrected by other factors including the looseness coefficient δ and the adjustment value X on the geological structure that cannot be measured. On the other hand, the center-of-gravity movement amount Δh based on the rainfall P also needs to be corrected with the adjustment value Y related to the hydrological unmeasurable, but as a method of obtaining these unmeasurable X and Y, the past two rainfall events with different conditions Based on the presence or degree of cracks at the roots of trees in Japan, the past two topsoil displacements ε1 and ε2 are estimated based on coefficients such as vegetation, topography, and geology, and X and Y are obtained by simultaneous equations from the two equations The slope topsoil displacement calculation method according to any one of claims 1 to 2, characterized in that an uncertain value is calculated. General users exclude the rainfall of Formula 1 according to claim 1 and the local data of the evaluation slope regarding the topsoil layer thickness, topography, geology, vegetation coefficients, and adjustment values X and Y in the database in the web server By inputting and updating the data semi-automatically every year, the real-time rainfall is automatically referred to determine the topsoil displacement amount ε relative to the current rainfall by the slope topsoil displacement calculation method according to claim 1 , A disaster prevention information system that uses a geographic information database to display to general users, voluntary disaster prevention organizations, local government computers, and TV screens via the Internet and digital terrestrial broadcasting.

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