JP2009053042A - Landslide evaluating method and auxiliary tool for it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an evaluating method and the like capable of accurately evaluating landslide on a ground formed of stratums of different geologies. <P>SOLUTION: In the evaluating method of the landslide by a three-axis testing method of soil using a three-axis compression device, a specimen 1 is placed in liquid in a three-axis pressure chamber 5P of the three-axis compression device 5, the specimen is placed in a compaction state pressurized from three-axis directions by a cell pressure supply device 8 of the three-axis compression device, and evaluation is performed based on respective main stresses σa and σr and respective effective main stresses σa' and σr' of the axial direction and side direction leading deformation of the specimen when it is compressed from the axial direction by a compression device 20. In a state where the lower surface of the specimen 1 abuts on the upper surface 2A of a columnar mounting stand 2 formed of a rigid body having a groove 2a for drainage axially, the specimen formed so that the whole has a columnar shape extending axially is arranged at a predetermined position in the three-axis pressure chamber, and the three-axis testing method of the soil is performed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for evaluating a landslide using a triaxial compression device (in this specification and claims, the term “landslide” is used in a broad concept including the collapse of a formation) and an auxiliary tool therefor.

  In general, landslides are likely to occur when there is a lot of rainfall such as rainy season or typhoon in a state where stress is applied from above. Therefore, when building or civil engineering facilities (including roads, railways, etc .; referred to as “structures” in this specification and claims), etc., how much stress acts on the ground there will cause a lot of rain, etc. It is extremely important to know in advance whether or not the ground will cause landslides in order to prevent landslides or minimize damage.

  For example, when building and constructing a structure, such as a road or railway, above it, if the possibility of landslide in the created part can be evaluated in advance, that is, how much stress is applied, there is a risk of landslide If it can be predicted whether it will occur, it is possible to take countermeasures (such as ground improvement).

For this reason, conventionally, various researches have been conducted on the evaluation of landslides (see Patent Document 1).
Japanese Patent Laid-Open No. 03-26963.

  However, it is extremely difficult to accurately evaluate a landslide that occurs in nature by reproducing it in a test apparatus or the like. In particular, when there is a boundary surface of different geology on the target ground, specifically, for example, the upper layer is a layer made of earth or sand and the lower layer is a layer of rock or the like In this case, there is not yet provided a “landslide evaluation method” that predicts how much stress is applied to which part of the landslide will occur.

  However, there are many grounds in which layers of different geology are laminated, and it is currently waiting for the provision of a method that can accurately evaluate the possibility of landslides in these grounds.

  The present invention has been made in view of such a situation, and an evaluation method capable of accurately evaluating a landslide in a ground where there is a boundary surface between layers having different geological features and an auxiliary suitable for carrying out the method. The purpose is to provide ingredients.

In the landslide evaluation method according to the first aspect of the present invention, a specimen is placed in a liquid in a triaxial pressure chamber (compression chamber) of a triaxial compressor, and the specimen is placed by a cell pressure supply device of the triaxial compressor. Axial direction and lateral direction (outer diameter direction of the specimen) that lead to deformation of the specimen when compressed from the axial direction (longitudinal direction or up and down direction) with a compression device under the compaction condition pressurized from three axial directions In the evaluation method of landslide by the triaxial test method of soil using a triaxial compression device that evaluates the landslide of the specimen from each principal stress and each effective principal stress of
A state in which the lower surface of the specimen is in contact with the upper surface of a columnar mounting table made of a rigid body in which grooves or holes for drainage are formed in the axial direction, and the entire columnar body extends in the axial direction. The formed material is arranged at a predetermined position in the triaxial pressure chamber, and the soil triaxial test method is performed.

  According to the landslide evaluation method according to the present invention configured as described above, when the specimen is compressed in the axial direction by the compression device, the specimen is placed on a mounting table made of a rigid body. In addition, a situation similar to the boundary between the soil and the rock is formed between them, and since a groove or a hole is formed in the mounting table in the axial direction, a gap is formed from the specimen through the groove or the hole. Since the water forming the water pressure is drained smoothly and the proper pore water pressure accompanying the compression can be obtained, the situation of landslide in the ground having the boundary between the rock and soil in nature can be accurately reproduced. This makes it possible to accurately evaluate landslides.

In the auxiliary device according to the second aspect of the invention, the specimen is placed in the liquid in the triaxial pressure chamber of the triaxial compressor, and the specimen is removed from the triaxial direction by the cell pressure supply device of the triaxial compressor. Evaluation of the landslide of the specimen from axial and lateral principal stresses and effective principal stresses leading to deformation of the specimen when the specimen is compressed from the axial direction by a compression device under pressurized compaction conditions Auxiliary tool used in the evaluation method of landslide by the triaxial test method of soil using a triaxial compression device that performs
This auxiliary tool is a columnar mounting table comprising a rigid body on which the specimen is placed above, having the same cross-sectional area as the specimen and having a groove or a hole for drainage formed in the axial direction. Features.

  And if the auxiliary tool comprised as mentioned above is used, the said 1st invention can be implemented.

  In the evaluation method according to the first aspect of the present invention, the specimen is compressed in the axial direction with the compression device until the specimen breaks, and the values when the breakage occurs are plotted on an effective stress path chart. Thus, by drawing a diagonal line connecting the plotted points and the origin, and determining the ground boundary strength φ ′, the evaluation of the landslide can be performed at a glance and easily. Become.

  In the evaluation method according to the first aspect of the present invention, by changing the pressure in the triaxial direction and the compressive force in the axial direction, making a plurality of the plots in the chart, based on the plotted points, If the tilt line is drawn on the chart to determine the boundary surface strength φ ′ of the ground, the tilt line can be drawn more accurately.

  In the assisting device according to the second invention, when a groove communicating with the groove is formed on the bottom surface of the assisting device, the water forming the pore water pressure is more smoothly drained from the specimen, and the accurate gap It makes it possible to measure the water pressure.

  Further, in the assisting device according to the second invention, when the upper surface of the assisting device is constituted by an inclined surface, in the case where a soil layer is formed on the inclined bedrock, the A state close to the situation can be reproduced in the triaxial compressor.

  According to the landslide evaluation method and the auxiliary tool therefor according to the present invention, it is possible to realize an evaluation method capable of accurately evaluating landslide in the ground where there is a boundary between layers having different geological features.

(Embodiment 1)
Hereinafter, a landslide evaluation method according to one embodiment of the present invention and an auxiliary tool used in the evaluation method will be specifically described with reference to the drawings.

  1A and 1B are views showing a configuration of a mounting table constituting an auxiliary tool according to an embodiment of the present invention. FIG. 1A is an overall perspective view, and FIG. 1B is a bottom view (bottom view). FIG. 2 is a perspective view showing a state in which the specimen is placed on the upper surface of the mounting table (auxiliary tool) shown in FIG. 1, and shows the upper surface of the mounting table in a perspective view. FIG. 3 is a partially sectional side view showing a schematic configuration of a main part of a triaxial compression apparatus for carrying out a soil compaction undrained triaxial test method which is one of the triaxial test methods of soil. It is.

As shown in FIGS. 1 (a) and 1 (b), the mounting table 2 on which the specimen 1 (see FIGS. 2 and 3) is placed upward has a transverse section (cross-sectional area) of the specimen 1 (see FIG. As shown in FIG. 1 (a), a plurality of grooves 2a extending in the axial direction (vertical direction) are formed on the outer peripheral surface. And, as shown in FIG. 1B, a groove 2b is formed radially on the bottom surface 2B of the mounting table 2 so that the center is a confluence, and the outer diameter end of the groove 2b is Water (liquid) that is connected to the groove 2a (see FIG. 1A) and flows downward from the upper end of the groove 2a is configured to be able to flow into the groove 2b. Further, in the case of this embodiment, the groove 2a is formed so as to face straight in the axial direction. However, the groove 2a may be inclined with respect to the axial direction. Alternatively, the groove 2a may be a thin line extending in the axial direction instead of the groove 2a. It may be a hole having a diameter (for example, a diameter of 1 mm to 3 mm). Further, instead of the groove 2a, a small-diameter hole penetrating in the axial direction may be formed in the mounting table 2.
Further, the upper surface 2A of the mounting table 2 is configured with an angle of intersection with respect to the axial direction (vertical direction), that is, an inclined surface.
Further, a cloth file (sand paper) having different roughness is selectively attached to the upper surface 2A so as to be integrated with an adhesive or the like. However, instead of the cloth file, it may be made of another material having a surface roughness, or the surface of the upper surface 2A itself may be processed and roughened with a file or the like.
Moreover, this mounting base 2 is comprised with the rigid body, and is comprised with the thing of the columnar body made from aluminum in this embodiment. However, the mounting table 2 only needs to be a rigid body and is not limited to the above-described aluminum material. For example, the mounting table 2 may be made of stainless steel, steel, or other materials. It may be.

  On the mounting table 2, as shown in FIG. 2, a specimen 1 made of soil to be evaluated for landslide is placed, but the bottom surface (lower surface) 1 </ b> B of the specimen 1 is These are configured with inclined surfaces corresponding to the inclined surfaces of the upper surface 2A of the mounting table 2 described above. The bottom surface 1B of the specimen 1 is in contact with the top surface 2A of the mounting table 2 to which the cloth file is attached. The specimen 1 is made of saturated soil (saturated viscous soil in this embodiment). Instead of the clay soil, other soil may be used.

  And as above-mentioned, the periphery of the test body 1 mounted on the mounting base 2 is packaged by the filter paper 3 as shown in FIG. In the filter paper 3, elongated hole-like slits 3a extending in the vertical direction are formed at appropriate intervals. The slit 3a is for facilitating the discharge of water inside the specimen 1 when the specimen 1 is compressed in the axial direction.

  Then, the specimen 1 in which the outer peripheral surface is wrapped with the filter paper 3 and the mounting table 2 therebelow are further covered with a tube-shaped rubber 4 as shown in FIG. 5 from the outside of the filter paper 3. .

As described above, when the specimen 1 and the mounting table 2 whose outer peripheral surfaces are covered with the filter paper 3 and the rubber 4 are evaluated for landslide, as shown in FIG. The three-axis pressure chamber (compression chamber) 5P is disposed.
That is, as shown in FIG. 3, the triaxial compression device 5 has a glass pressure cylinder 5a made of a cylindrical body as a whole, and the pressure cylinder 5a has an outer peripheral wall of the triaxial pressure chamber 5P. Constitute. The upper end of the pressure cylinder 5a is sealed with a disk-shaped upper board 5A, and the lower end is sealed with a disk-shaped bottom board 5B, thereby forming the triaxial pressure chamber 5P partitioned inside. In addition, a mounting portion 5b is provided in the center of the bottom plate 5B in plan view, and the mounting table 2 is mounted on the mounting portion 5b via the perforated plate 6.
In addition, a circular through hole is formed in the central portion of the upper panel 5A in plan view, and a tip end portion of a round rod-shaped loading piston 7 is inserted into the through hole so as to move up and down. The tip is in contact with the contact hole 8a at the center of the disc-shaped cap 8 having a predetermined thickness.

  Further, the load piston 7 described above is configured such that an axial stress (axial stress) can be applied to the specimen 1 by moving up and down (extending and contracting) by the compression device 20 provided above the piston. Has been. A load measuring device 21 having a load cell is disposed between the compression device 20 and the load piston 7 described above, and axial stress (compression force) acting on the specimen 1 from the compression device 20 can be measured. It is configured as follows.

  Then, a communication passage 5d is formed in the central portion of the mounting portion 5b of the bottom plate 5B in the plan view, the upper end of which opens toward the surface of the mounting portion 5b and communicates with the joining portion of the groove 2b. The downstream side of the communication path 5d is bent at a substantially right angle in the middle, and communicates with the pore water pressure measuring device 8 via the side peripheral surface 5f of the bottom plate 5B.

  Further, at another position of the mounting portion 5b of the bottom plate 5B, a communication path 5e is formed, the upper end of which opens toward the surface of the mounting section 5b and communicates with the triaxial pressure chamber 5P. The downstream side of 5e is bent at a substantially right angle in the middle, and communicates with the cell pressure supply device 9 via the side peripheral surface 5f of the bottom plate 5B. The cell pressure supply device 9 is not particularly limited as long as it can form a cell pressure in the triaxial pressure chamber 5P, and may have any configuration.

And the upper end of the mounting table 2 and the specimen 1 mounted on the mounting section 5 b is held in contact with the cap 8 through the perforated plate 10. In this embodiment, the cap 8 and the perforated plate 10 have the same cross section in plan view.
And the upper end part of the rubber | gum 4 which has sealed the side peripheral surface of the mounting base 2 and the test body 1 described above extends to the side peripheral surface of the cap 8, and at this position, from the outer periphery side by the O-rings 11 and 12. It is clamped and sealed in a tightly clamped state. Similarly, the lower end portion of the rubber 4 extends to the side peripheral surface of the mounting portion 5b, and at this position, the rubber 4 is sandwiched and sealed by the O-rings 13 and 14 from the outer periphery.
In such a state, the mounting table 2 and the specimen 1 are sealed by the rubber 4 and the O-rings 11 to 14 in the triaxial pressure chamber 5P.

The soil compaction undrained triaxial test method for landslide evaluation using the triaxial compression device 5 having the above-described configuration is the Geotechnical Society (Geotechnical Society: 4-38, Sengoku, Bunkyo-ku, Tokyo) In accordance with the standards set out in No. 2), it is carried out as follows. That is, the outline will be explained.
With the triaxial pressure chamber 5P filled with water (liquid: liquid other than water), the cell pressure supply device 9 is operated to increase the pressure in the triaxial pressure chamber 5P. Then, a predetermined pressure (side stress) is applied to the specimen 1 from the triaxial directions to form a desired consolidation state.

  Under such a consolidation condition, the compression device 20 is operated to apply axial stress (axial stress) to the specimen 1. Such an axial stress is applied in a state where the strain rate of the specimen 1 is constant. During this time, change data of the pore water pressure value Ut is obtained by the pore water pressure measuring device 8 disposed at the tip of the communication path 5d. That is, when an axial stress is applied to the specimen 1 by the compression device 20, the water in the specimen 1 passes through the filter paper 4 and is discharged between the rubber 4 and this water passes through the communication path 5d. The change data of the pore water pressure value Ut can be obtained by being transmitted to the pore water pressure measuring device 8 via.

  Further, the load measuring device 21 obtains data of changes in the value σa of the axial stress (principal stress).

  Furthermore, the measurement device provided in the cell pressure supply device 9 obtains data relating to the change in the cell pressure, that is, the principal stress value σr in the triaxial direction (side direction).

  Then, the effective hydraulic stress σa ′ in the axial direction is obtained by subtracting the pore pressure value Ut from the axial principal stress value σa, and the pore hydraulic pressure value is obtained from the triaxial principal stress value σr. The effective principal stress σr ′ in the triaxial direction (side direction) is obtained by subtracting Ut.

  Then, using the axial principal stress value σa, the triaxial principal stress value σr, the axial effective principal stress σa ′, and the triaxial effective principal stress σr ′, -Σr) / 2 is taken, and (σa '+ σr') / 2 is taken on the horizontal axis to express these changes over time.

  Then, when the time-dependent change is expressed by changing the stress in the triaxial direction and the stress in the axial direction, an effective stress path diagram as shown in FIGS. 6 and 7 is obtained. In FIG. 6, the case where the mounting table 2 is not used is indicated by a black circle, the case where the inclination angle of the upper surface 2A is 60 degrees is indicated by a white square, and the case where the angle of the inclined surface 2A is 45 degrees is indicated by a white circle. ing. In addition, FIG. 7 shows a case where the slope of the upper surface 2A is 45 degrees, and the roughness of the slope is different, that is, the case where the cloth file is not used is indicated by a white circle, and the cloth file roughness is No. 320 ( The case of R320) is indicated by white square marks, and the case where the roughness of the cloth file is No. 40 (R40) is indicated by white triangle marks.

Then, from these effective stress path diagrams of FIGS. 6 and 7, the landslide of the target ground can be evaluated. That is,
In any case, when the pore water pressure shows the maximum, for example, when the white square mark is seen in FIG. 6, the horizontal axis is about 300 (kN / m ² ) and the vertical axis is about 140 (kN / m ² ). ² ) It is bent from the left side to the right side. Similarly, when a white square mark is seen in FIG. 6, the horizontal axis is about 100 (kN / m ² ) and the vertical axis is about 50 (kN / m ² ), and is bent to the right.
When the bent points are plotted and an inclination line is drawn so as to connect these points to the origin, an inclination line with an inclination angle φ ′ as shown by a broken line K in FIG. 6 (effective stress path diagram) is obtained. The inclination angle φ ′ (φ ′ = 27.6 degrees in the case of FIG. 6) is the strength against landslide, that is, the boundary strength.

  From FIG. 6, when the mounting table 2 is used, the boundary strength indicated by the broken line K is obtained, but when the mounting table 2 is not used, that is, the specimen is constituted by the soil itself. Is collapsed, the intensity becomes an inclination angle φ ′ (φ ′ = 33.7 degrees) as shown by a solid line G in FIG. From this, in the ground where the soil is deposited on the rock, before the soil collapses, the collapse occurs at the boundary surface with the rock, and the value (φ ′ = 27.6 degrees) is an accurate assessment of landslides.

  Also, from FIG. 7, it was found that the surface roughness of the upper surface 2A hardly affects the value. That is, even when the roughness of the upper surface 2A is different, the boundary surface strength has a value of φ ′ = 27.6 degrees.

  Further, from FIG. 6 and FIG. 7, it is considered that the inclination angle of the upper surface 2A shows the same value in both cases of 60 degrees and 45 degrees, and the value φ ′ is not affected by the inclination angle of the upper surface 2A itself. It is. Therefore, it can be estimated that various tilt angles can be used for the tilt angle of the upper surface 2A.

  As described above, according to the landslide evaluation method according to the present invention, by using the mounting table 2 as an auxiliary tool, even on the ground having different geological boundaries such as soil accumulated on the rock, Can evaluate landslides.

  In the embodiment, the landslide is evaluated using the effective stress path chart. However, the landslide may be evaluated by using the “Mole circle” to obtain and analyze the inclination line. Alternatively, the landslide can be evaluated by obtaining the principal stress in the axial direction and the lateral direction and the calculation using each effective principal stress.

  In the above embodiment, the soil triaxial test method has been described by taking the soil compaction undrained triaxial test method as an example, but the present invention can also be applied to other triaxial test methods. Needless to say.

  It goes without saying that the present invention is not limited to the above-described embodiment, and can be implemented in a mode appropriately modified by those skilled in the art.

  The landslide evaluation method and auxiliary tool (mounting table) according to the present invention can be used for evaluation of landslides on the ground where there are boundaries between layers of different geology.

It is a figure which shows the structure of the mounting base which comprises the auxiliary tool concerning embodiment of this invention, (a) is a whole perspective view, (b) is a bottom view (bottom view). It is the perspective view which represented the upper surface of the mounting base which shows the state which mounted the test body on the upper surface of the mounting base (auxiliary tool) shown in FIG. It is the side view which carried out the partial cross section which shows the outline structure of the principal part of the triaxial compression apparatus for enforcing the soil compaction non-drainage triaxial test method which is one of the triaxial test methods of soil. It is the figure of the state which expanded the filter paper which shows the filter paper which wraps the test body and the outer peripheral surface of a mounting base. It is a perspective view which shows the external appearance of the cylindrical rubber | gum which covers the outer side of the filter paper which wraps the outer peripheral surface of a test body and a mounting base. It is an effective stress path | route figure which performs the evaluation of the landslide concerning embodiment of this invention. FIG. 7 is an effective stress path diagram for evaluating the landslide under the conditions different from those of FIG. 6 for the same specimen.

Explanation of symbols

1 ... Specimen
2 ... Mounting table (auxiliary tool)
2A ... Upper surface of mounting table
2a ... Groove for mounting table
5. Triaxial compressor
5P… Triaxial pressure chamber
8 ... Cell pressure supply device
20 ... Compressor

Claims (6)

Place the specimen in the liquid in the triaxial pressure chamber of the triaxial compression device, and press the specimen from the triaxial direction with the cell pressure supply device of the triaxial compression device. Three axes of soil using a triaxial compression device that evaluates the landslide of the specimen from axial and lateral principal stresses and effective principal stresses that lead to the deformation of the specimen when the specimen is compressed from In the evaluation method of landslide by the test method,
A state in which the lower surface of the specimen is in contact with the upper surface of a columnar mounting table made of a rigid body in which grooves or holes for drainage are formed in the axial direction, and the entire columnar body extends in the axial direction. A method for evaluating landslide, wherein the formed one is arranged at a predetermined position in the triaxial pressure chamber and the triaxial test method for the soil is performed.   By compressing the specimen in the axial direction with the compression device until the specimen breaks, and plotting the values at the time of the break on the effective stress path chart, the plotted point and the origin are determined. The landslide evaluation method according to claim 1, wherein the evaluation of the landslide is performed by drawing a connecting diagonal line and obtaining a ground boundary strength φ '.   A plurality of plots are made on the chart by changing the pressure in the three axial directions and the compressive force in the axial direction, and the inclination line is drawn on the chart based on the plotted points, and the ground The landslide evaluation method according to claim 2, wherein a boundary surface strength φ ′ is obtained. Place the specimen in the liquid in the triaxial pressure chamber of the triaxial compression device, and press the specimen from the triaxial direction with the cell pressure supply device of the triaxial compression device. Three axes of soil using a triaxial compression device that evaluates the landslide of the specimen from axial and lateral principal stresses and effective principal stresses that lead to the deformation of the specimen when the specimen is compressed from Auxiliary tool used for the evaluation method of landslide by the test method,
This auxiliary tool is a columnar mounting table comprising a rigid body on which the specimen is placed above, having the same cross-sectional area as the specimen and having a groove or a hole for drainage formed in the axial direction. Auxiliary tool characterized.   The auxiliary tool according to claim 4, wherein a groove communicating with the groove is formed on a bottom surface of the auxiliary tool.   The assisting device according to claim 4 or 5, wherein an upper surface of the assisting device is constituted by an inclined surface.

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