JP5267811B2 - Field test equipment for landslide prediction - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that conventional testing machines are difficult to be reduced in size and weight and is not brought to an actual site of landslide, making it difficult to measure a pore pressure. <P>SOLUTION: A field test device for landslide prediction has been compacted by connecting the upper end of a central operating shaft 10 with a piston 12 in an upper cylinder 11; arranging a load cell 26 between the lower end of the operating shaft 10 and the upper end of a piston rod 25 in a lower cylinder 28; removing long columns and a beam for mounting a vertical load by connecting lower ends of a plurality of pressure rods 8 and 8 attached to the bottom surface of a support plate 9 of the upper cylinder 11 and a sample pressure plate 7 placed on the top surface of a sample in upper sidewall members 5<SB>1</SB>and 5<SB>2</SB>; minimizing gouging, expansion and contraction, and deflection of these members; attaching water leak preventive rubber edges along lower sidewall members 3<SB>1</SB>and 3<SB>2</SB>to allow measurement of the pore pressure; and liberating a liquid pressure between the cylinder support plate 9 and the piston 12 to mount a load on the sample held in upper and lower shearing boxes 5 and 3. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention uses a sample collected from the site of the landslide and debris flow phenomena in the mountains and areas close to the mountains, and repeatedly performs tests near the site of the occurrence, conditions of landslide and debris flow generation, flow, stop conditions at the site The present invention relates to a lightweight portable landslide prediction field test device that can quantitatively measure.

  A conventional landslide prediction test apparatus includes a loading plate that holds and holds a soil sample in a space formed between an annular stationary container and an annular rotating container opposite to the annular stationary container, and pressurizes the sample in the stationary container; A load-carrying airtight chamber is formed between the upper panel of the device, and the shear load acting on the sediment sample by rotating the rotating container under pressure under saturated or unsaturated conditions with water, vertical load, There is an apparatus that detects a shear rate, vertical displacement, and the like (for example, see Patent Document 1).

  In addition, a lifting shaft that moves up and down with a jack is installed on two struts supported by the base plate and the upper end plate, and a shear shaft that is rotated on the lifting base by a servo motor via a torque meter Pivot. While installing a movable plate that can be placed at any position on the column above the lifting platform, a lower container and an upper container are fixed oppositely between the bottom surface of the water tank supported on the shear axis and the movable plate, The upper end of the pressure rod that penetrates the movable plate and faces the upper container is supported by the pressure plate, and between the pressure plate and the output end of the load platform fixed on the upper surface of the upper plate. There is an apparatus in which a load cell is provided in an intervening manner as appropriate. (For example, refer to Patent Document 2).

  Japanese Examined Patent Publication No. 2-60248 (Rotating water channel type debris flow test method and test apparatus).   JP-A-5-34252 (constant volume, constant pressure combined ring shear test apparatus).

However, in Patent Document 1, as a load mounting means, compressed air is sent into an airtight chamber so that a load can be applied to a sample via a loading plate. Therefore, it is difficult for an equal load to be placed on the entire surface of the loading plate. As a result, the greatest drawback is that the struts are twisted, and it is difficult to place an even stress on the shearing surface.
Moreover, since the sample and pore water in the sample leak from the contact portion of the upper and lower shear boxes, the pore water pressure that greatly affects the frictional resistance during the landslide movement cannot be measured.
A motor is used as a means for applying a shear load to it, and a compressor is used to mount a vertical load, which increases the weight and requires a power source, so it cannot be brought into any place.

  In Patent Document 2 of the conventional example, two struts are set up on the base, an upper end support plate is attached in the form of a beam connecting the two struts, a loading cylinder is attached at the center, and hydraulic pressure is applied to this cylinder. The piston in the cylinder was moved by applying it to obtain a reaction force for applying a normal stress to the sample.

In this conventional method, two long columns are required, and the testing machine cannot be downsized. In addition, since the reaction force of the loading pressure on the specimen is applied to the beam and the long column, it becomes difficult to control the upper and lower container gaps due to expansion and contraction when a sudden stress change occurs during the landslide reproduction test, and it is difficult to control from the shear box It was not possible to stop leakage of pore water and to control the force applied to the sample with high accuracy.
In the conventional method, the side frictional force of the upper shear box acts from the upper piston through the load cell for measuring the vertical stress and the pressure rod until the vertical stress is applied to the sample. The measured value of is more than the force applied to the shearing surface of the sample. On the other hand, when the volume of the sample expands during shearing, it becomes too small. The side friction force is about 1/3 of the vertical stress loaded at the maximum, and an error of about 30% occurs.

  Therefore, it is difficult to reduce the size and weight of the conventional testing machine, and it was not possible to bring it close to the site where landslides occurred. In addition, since pore water leakage cannot be stopped, it was difficult to measure the pore water pressure required for landslide prediction. Furthermore, the measurement accuracy of normal stress was not high because of the influence of side friction.

  By rigidly connecting the load cell 26 for vertical stress measurement, the upper shear box 5, and the piston 12 in the vertical stress loading cylinder to the operating shaft in the center of the apparatus, these four members are combined into one system, and hydraulic pressure is applied to the cylinder. The cylinder was moved by this, and a structure in which normal stress was loaded as an external force on a sample outside the system was constructed. In the case of this structure, the normal stress applied to the shearing surface of the sample is measured by the load cell 26 for measuring the normal stress as an external force of the system. Since the side frictional force applied to the upper shear box 5 is an internal force of the system and is not reflected in the load cell 26, only the normal stress acting on the sample can be accurately measured by the load cell 26 for vertical stress measurement. Stress control with high accuracy became possible.

  Since there are no longer deflected beams and long struts with large expansion and contraction, it is possible to prevent leakage of pore water even if stress changes during the landslide prediction experiment, and measurement of pore water pressure generated during shearing is possible. . Since the long support was not needed, it was possible to make it much smaller and lighter, and it was possible to make it a portable testing machine near the landslide site. In addition, the operability has been improved due to the simplified structure.

  Due to the ease of bringing landslides to the site due to the weight reduction of the equipment, the geological conditions, moisture conditions and weathering conditions, mixing of different soils and sand, pyroclastic flow deposits and many other complicated soil conditions Easy to test. In addition, since the shear load can be manually set by a gear, there is no restriction on the area where it is brought in, and the versatility is high.

  Human resources development, disaster prevention education, and enlightenment for local (domestic and overseas) researchers, engineers, students, high and junior high school students, members of society who are highly interested in disaster prevention, fire brigade, etc. It can be used for a lot.

  Asia, Latin America, Africa and Eastern Europe have high expectations for Japan's high-level landslide prediction technology. For the transfer of landslide disaster prevention technology in these areas, the development of lightweight and portable testing machines is extremely meaningful.

  Since the structure of the testing machine has been simplified and the cost has been reduced, it is easy to purchase or donate in developing countries, and by bringing a single testing machine to the required area when needed. It can be shared in various parts of the country, and the cost performance of the testing machine is extremely high.

In order to predict landslide occurrence and motion, it is indispensable to accurately measure the pore water pressure generated in the shear zone in the sample. In the present invention, the contact pressure between the rubber edge and the bottom surface of the upper shear box is maintained by applying a hydraulic pressure to the lower cylinder 28 to keep the deformation of the rubber edges 18 ₁ and 18 ₂ attached to the upper surface of the lower shear box constant. was kept always higher than the pore pressure generated in the sample to prevent leakage of the pore pressure water, pore water pressure connected to the groove 17 ₁ with filter attached to was close to the shear zone in the sample meter 17 ₂ , the pore water pressure generated in the sample can be accurately measured.

A description will be given below with reference to FIG.
Means A for housing and holding the sample, by opposing arranged on inner and outer concentric circles while maintaining a constant interval donut-shaped lower side wall member 3 _1, 3 ₂ on the bottom plate 2, opposite side walls members 3 _1, 3 ₂ An annular lower shear box 3 for accommodating a sample is formed by the space and the bottom plate 2, and both the lower side wall members 3 ₁ , 3 _{2 and the} bottom plate 2 are rotated together with a rotating base 1 described later.

Further, the lower side wall member 3 _1, 3 to ₂ higher while maintaining a predetermined interval between same inner wall member 5 ₁ and the outer wall member 5 ₂ faces arranged on the inner and outer concentric circles, and the lower side wall members 3 _1, 3 each upper end ₂ and brought into contact with each other freely attached detachably to the lower surface of the fixed top plate 6 to form a higher shear box 5, samples straddling said lower shear box 3 and the upper shear box 5 To keep.

Next, the shearing force applying means B holds the operating shaft 10 upright by a sheath shaft portion of the vertical bearing 21 on a horizontal fixed base plate 23 provided below, and a rotating pedestal via a bearing 20 outside the vertical bearing 21. 1 is pivoted freely. The lower surface of the rotary seat 1 is fixed a ring gear 19 _2, engagement circumscribe the small gear 19 ₁ which rotates by receiving rotation from the shearing wheel 31 which is pivoted to the lower of the fixed base plate 23 Te, and so as to rotate the rotary base 1 by the rolling of the pinion 19 _1.

On the other hand, the load mounting means C for applying a load to the sample passes through the top plate 6 of the upper shear box 5 by a plurality of pressure rods 8, 8. 5 _1, is brought into contact to 5 toroidal sample pressure plate 7 which is fitted into the holding groove _2, the upper end of the pressure圧杆8,8-has been attached to the lower surface of the support plate 9 of the cylinder 11, Further, the upper end of the operating shaft 10 penetrating the support plate 9 is attached to the piston 12 in the cylinder 11, and a loading / unloading control is performed by interposing a spring 13 between the upper end surface of the piston 12 and the inner surface of the cylinder 11. We are trying to improve.

  Further, the lower portion of the operating shaft 10 is interposed between a piston rod 25 of a piston 29 in a cylinder supported by a plurality of support rods 24, 24, which project downward from the horizontal fixed base plate 23, via a load cell 26. Are connected. In addition, a spring 30 is interposed between the lower end surface of the piston 29 and the lower cylinder 28 to enhance control accuracy.

Next, a series of operations will be described. First, the upper part surrounded by the sample seat plate 4 in the lower shear box 3 composed of the lower side wall members 3 ₁ and 3 ₂ and the bottom plate 2 and the upper side wall members 5 ₁ and 5 ₂ . The sample a collected in the field is accommodated in the shear box 5, the sample pressurizing plate 7 is placed on the upper surface of the sample a, and the upper surface of the sample pressurizing plate 7 is pressurized with the pressurizing rods 8, 8. Yes.

After the sample is loaded into the apparatus main body as described above, a screw type pump is connected to the inlet b _1, and the operating shaft 10 is pulled up by feeding a fluid (liquid that does not denature temperature) such as oil. The pressure rod 8 is pushed down in the direction of the arrow using force, and the pressure is loaded on the sample a by the pressure plate 7 attached to the lower end thereof.

By turning the shearing handle 31 manually while applying a constant pressure to the sample, in conjunction pinion 19 ₁ in conjunction with a handle 31, a ring-shaped gear 19 ₂ rotated through the base 1 is horizontally fixed base plate 23 The lower side wall members 3 ₁ , 3 ₂ are rotated about the rod operating shaft 10 holding the sample a together with the bottom plate 2.

In the above operation, the pore water pressure occurring in the vicinity of the shearing surface of the sample a while measured by pore pressure meter 17 ₂ precision, measuring the shearing force at the left and right were attached to the wing two sensors 16 _1, 16 ₂ .

During the loading of the shear load, when the sample a tries to expand or contract, the gap (gap) between the upper and lower shear boxes tends to change due to the side frictional force acting between the upper shear box 5 and the sample. In order to prevent the pressure applied to the rubber edges 18 ₁ , 18 _{2 from} being changed due to the change in the gap and leaking the gap water, the micro displacement meter (gap sensor) 27 passes through the operating shaft 10 and the shear force measuring arm 15 fixed thereto. The pressure between the upper and lower shear boxes is accurately measured, and the pressure applied to the rubber edge is kept constant by putting fluid into and out of the lower cylinder 28 from the inlet b ₂ so as to always keep the deformation of the rubber edge constant. .

  A feature of the present invention is that it is compact and portable, has a system capable of accurately measuring the pore water pressure generated in the vicinity of the shear plane, and moves the piston 12 in a fixed position by preventing the central operating shaft 10 from moving up and down. By holding, the cylinder 11 moves up and down, whereby the vertical load acting on the sample a by the pressure rods 8 and 8... Is measured by one load cell 26.

  Since the present invention is portable, it can be used not only at research institutions such as universities, but also at other equipment development facilities, and the most effective use method is the disaster occurrence site or disaster It can be used in a wide range of fields, such as transporting to the place where it is expected to occur, collecting data on the sediment at each site, and using it for disaster prevention.

  Central longitudinal side view showing an embodiment of the present invention   Enlarged view of main parts   External side view of FIG.   Same as above

a Sample b ₁ , b ₂ Inlet 1 Rotating base 3 Lower shear box 3 ₁ , 3 ₂ Lower side wall member 5 Upper shear box 5 ₁ , 5 ₂ Upper side wall member 6 Fixed top plate 7 Sample pressure plate 8 Pressure rod 9 Support Plate 10 Operating shaft 11 Cylinder (for vertical load)
12 Piston (for vertical load)
13 Spring (for vertical load)
14 Vertical displacement meter 15 Shear force measurement arm 16 ₁ , 16 ₂ Shear force meter 17 ₁ Groove with filter 17 ₂ Gap water pressure gauge 18 ₁ , 18 ₂ Rubber edge 19 ₁ Small gear 19 ₂ Ring gear 20 Bearing 21 Vertical bearing 22 Shear Displacement meter 23 Horizontal fixed base plate 24 Support rod 25 Piston rod 26 Load cell 27 Minute displacement meter (gap sensor)
28 Lower cylinder (for gap adjustment)
29 Piston (for gap adjustment)
30 Spring (for gap adjustment)

Claims (3)

The upper end of the central operating shaft 10 is connected to the piston 12 in the upper cylinder 11, and a load cell 26 is interposed between the lower end of the operating shaft 10 and the upper end of the piston rod 25 in the lower cylinder 28 to support the upper cylinder 11. A lower surface of the plate 9 and a sample pressure plate 7 placed on the upper surface of the sample in the upper shear box 5 are connected by a plurality of pressure rods 8 and 8, and a liquid is provided between the cylinder support plate 9 and the piston 12. By applying pressure, a load is placed on the sample held in the upper shear box 5 and the lower shear box 3 so as to cancel the frictional force acting on the upper inner and outer wall members 5 ₁ , 5 _2. Field test device for landslide prediction, which measures the effective load acting on the shear surface formed in the sample near the boundary surface between the shear boxes 5 and 3 with one load cell 26. The ground test apparatus for landslide prediction according to claim ₁ , wherein rubber edges 18 ₁ , 18 ₂ for non-drainage are installed on a surface of the lower shear box 3 facing the upper shear box 5. Detecting an annular groove for transmitting the pore water pressure which occurs in the upper outer wall member 5 within the sample during the undrained shear test at a portion facing the _second inner surface constituting the upper shear box 5 to a shear box outside provided, the shear box outer surface landslide prediction field testing device of claim 1, wherein the measuring in the attached pore pressure meter 17 ₂

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