JP2001091381A - Method for testing consolidation of ground material and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To evaluate the consolidation characteristics correctly without being affected by circumferential surface friction between a consolidation ring and a specimen and to enable the consolidation testing method to be applied to even heterogeneous ground materials. SOLUTION: This device is provided with a consolidation ring 22 mounted inside a consolidation container 16 to house a specimen 20 inside, a circular external loading plate 30 of a size that can be fitted in the consolidation ring 22, a discoidal internal loading plate 32 concentrically located inside the external loading plate 30, a total load cell 42 to measure the sum of both dead loads of the external loading plate and internal loading plate, an internal load cell 38 to measure the dead load of only the internal loading plate, and a pressurizing device (pneumatic-pressure actuator 14) to apply load onto the external loading plate and internal loading plate. Loads are applied onto both loading plates to provide uniform displacements, and the loading stress and contraction displacements of the internal loading plate are measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a consolidation test for a ground material in which a test sample housed in a consolidation ring is compressed by applying a load, and the applied stress and the compression displacement are measured.
More specifically, the present invention provides a load plate placed on a specimen to which a load is applied and has a concentric double structure of an internal load plate and an external load plate, and a load is applied to both load plates to give an even displacement, and the internal load is applied. The present invention relates to a method and an apparatus for testing a consolidation of a ground material in which the influence of peripheral friction due to a consolidation ring can be avoided by measuring a loading stress of a plate.

[0002]

2. Description of the Related Art Consolidation is a phenomenon in which, when a load is applied to soil (ground material), water and air present in gaps between soil particles are expelled, and the volume of the soil decreases and the density increases. Say. In order to determine the consolidation (compression) characteristics of various ground materials, a consolidation test in which a test specimen is accommodated in a consolidation ring and compressed is performed. The consolidation test of this consolidation ring method
It is defined by the IS standard (JIS A 1217).

[0003] In a conventional consolidation test of a ground material, a specimen is accommodated in a consolidation ring, a loading plate is placed on the specimen, a load is applied to the loading plate by a pressing device, and the specimen is compressed. Measure stress and compressive displacement. Conventionally used loading plates are disks sized to fit exactly into a consolidation ring.

[0004]

In a conventional soil material consolidation test, the load effectively acting on the specimen is usually
It is considered that the load is smaller than the load. The reason is that it is considered that peripheral friction acts between the consolidation ring and the test sample, and the actual consolidation stress is uneven. The effect of surface friction changes depending on the type of ground material to be tested or the stress applied, which may have a significant effect on the accurate determination of consolidation yield stress or the accuracy of consolidation settlement analysis .

In the consolidation test specified by the current JIS standard, a saturated cohesive soil composed of fine soil particles is targeted. Therefore, the dimensions of a specimen having a diameter of 60 mm and a height of 20 mm are standard. I have. Therefore, it cannot be applied to heterogeneous ground materials such as high organic soil containing a large amount of wood chips and plant chips, embankment material mainly composed of sand and gravel, and waste ground that is an aggregate of garbage and the like. .

SUMMARY OF THE INVENTION An object of the present invention is to measure a load near the center of a test specimen, which is less affected by peripheral friction between the consolidation ring and the test specimen, and to perform a consolidation test of a ground material devised so that accurate consolidation characteristics can be evaluated. A method and apparatus are provided. Another object of the present invention is to provide a consolidation test method and an apparatus thereof that can be applied to heterogeneous ground materials such as high organic soil, embankment material, and waste ground.

[0007]

According to the method of the present invention, a specimen is accommodated in a consolidation ring, a loading plate is placed on the specimen, a load is applied to the loading plate, the specimen is compressed, and a load stress is reduced. This is a consolidation test method for ground materials that measures compression displacement. Here, the loading plate has a double structure of an internal loading plate and an external loading plate, and a load is applied to both loading plates to give an even displacement, and the loading stress of the internal loading plate is measured. In this way, the method of the present invention can avoid the influence of the peripheral surface friction due to the consolidation ring by measuring the load at the center of the specimen.

The apparatus of the present invention also includes a base member, a consolidation ring mounted on the base member and accommodating a specimen therein, an annular external loading plate sized to be fit in the consolidation ring, and the external loading member. An internal loading plate located concentrically inside the plate,
A total load detector that measures the total load of both the external load plate and the internal load plate, an internal load detector that measures only the load of the internal load plate, and a load applied to the external load plate and the internal load plate It is a consolidation test device for a ground material, comprising a pressurizing device. A typical example of the base member is a container bottom plate of a consolidation container, which is usually filled with water to form a water tank.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In order to accurately conduct a consolidation test of a heterogeneous ground material such as a high organic soil, an embankment material, or a waste ground, a test apparatus is required to have a large specimen (for example, a diameter of 30 cm and a height of 30 cm). 10 cm).

In the device of the present invention, any pressurizing device can be used, but a pneumatic actuator is preferable from the viewpoint of controllability and operability. Further, a load cell is preferable as the load detector. For example, a central loading frame is erected from the inner loading plate, an internal load cell is installed at the center of the base, a peripheral loading frame is erected from the outer loading plate, and a comprehensive load cell is installed at the center of the base, and the inner load cell and the surroundings are installed. A universal joint is connected to the loading frame base and a universal joint is also connected to the overall load cell and the pneumatic actuator drive shaft. By joining the test pieces with the universal joint in this manner, it is possible to always apply a load only in the vertical direction to the central portion and the peripheral portion of the specimen.

Although any measuring instrument can be used for measuring the displacement of the internal loading plate, for example, a linear gauge type displacement detector is preferable. In that case, a common guide base is provided above the outer loading plate and the inner loading plate, and a slide bearing is disposed on the guide base to slidably support the respective columns of the peripheral loading frame and the central loading frame. It is preferable that the central displacement detector is mounted on the base, and the measuring end of the central displacement detector is brought into contact with the base of the central loading frame.

For the consolidation ring, a metal cylinder is used in a usual measurement. In this case, drainage channels are formed in the inner loading plate, the outer loading plate, and the base member in a dispersed manner, and the contact surfaces between the inner loading plate, the outer loading plate, and the specimen of the base member are covered with a permeable material, and Only directional drainage is allowed.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A consolidation test system comprises a consolidation test device, a pressure supply device, a servomotor-driven regulator, a servo logger, and the like.

FIG. 1 is a block diagram showing one embodiment of a consolidation test apparatus according to the present invention. FIG. 2 is a conceptual diagram of the load measurement. The consolidation test apparatus is assembled on the base 10. A gate-shaped load frame 12 is erected on a base 10, and a pneumatic actuator 14 capable of loading up to 500 kN is mounted thereon.

A consolidation container 16 is set on the base 10. Here, the consolidation container 16 includes a container bottom plate 16a made of stainless steel and a container peripheral wall portion 16b made of transparent acrylic resin. A drain passage 18 is formed inside the container bottom plate 16a, and a reinforcing band 16c is fitted into the container peripheral wall portion 16b from the outside. Then, on the container bottom plate 16a, a consolidation ring 22 that accommodates the specimen 20 is placed. The consolidation ring 22 is fixed by fitting the ring holding ring plate 24 to a step on the outer periphery of the upper end of the consolidation ring 22, and screwing the ring holding ring plate 24 to the container bottom plate 16a with three fixing bolts 26. ing. Here, the consolidation ring 22
Is to be able to accurately measure even heterogeneous ground materials,
A large-diameter cylindrical body with a diameter of 30 cm and a height of 10 cm, made of stainless steel and hard chrome plated on the inner surface to reduce the influence of peripheral friction.

In the upper part of the consolidation ring 22 (above the test piece 20), an annular external loading plate 30 of a size that can be fitted into the consolidation ring 22 and a concentrically positioned inside the external loading plate 30. And an internal loading plate 32 to be provided. Here, a step is formed so as to protrude below the inner peripheral surface of the outer loading plate 30, and a step is formed so as to protrude above the outer peripheral surface of the inner loading plate 32, so that they are engaged with each other. In addition,
A plurality of drainage channels 34 are formed in the outer loading plate 30 and the inner loading plate 32 in the thickness direction. Here, the outer loading plate 30 has a diameter of 30 cm, and the inner loading plate 32 has a diameter of 20 cm.

A central loading frame 36 is erected from the inner loading plate 32, an internal load cell 38 is installed on its base 36a, and a peripheral loading frame 40 is erected from the outer loading plate 30 and placed on its base 40a. An integrated load cell 42 is installed. The center loading frame 36 includes three columns 36 from the apex position of the equilateral triangle.
b, and their upper ends are connected by a horizontal plate-like base 36a. Similarly, the surrounding loading frame 40 has a structure in which three columns 40b are erected from the vertices of an equilateral triangle and their upper ends are connected by a horizontal plate-like base 40a. The columns 36b and the columns 40b are alternately arranged so as to be shifted exactly 60 degrees from the center. Then, the internal load cell 38 and the peripheral load frame base 40a are connected by a universal joint 44, and the integrated load cell 42 and the drive shaft 14a of the pneumatic actuator are also connected by a universal joint 46. By connecting the universal joints 44 and 46 in this manner, a load in the vertical direction can be constantly applied to the central portion and the peripheral portion of the test sample 20. Here, the total load cell 42 measures the total load of both the external load plate 30 and the internal load plate 32, and
Numeral 8 is for measuring the load on the internal load plate 32.

Further, the outer loading plate 30 and the inner loading plate 32
A common guide base 50 is provided above. The guide base 50 is fixed to the container bottom plate 16a by a guide base fixing unit 52. Then, slide bearings 54 and 56 are disposed on the guide base 50 to support the columns 40b and 36b of the peripheral loading frame 40 and the central loading frame 36 slidably. The three supporting columns 40b of the peripheral loading frame 40 are disposed symmetrically with respect to the center.
The three posts 36b are also arranged symmetrically in the opposite direction to the posts 40b. On the other hand, a linear gauge type central displacement detector 60 is mounted on the guide base 50, and the measurement end 60a of the central displacement detector 60 is brought into contact with the central loading frame.

The specimen 20 (diameter 30 cm, height 10 cm) is accommodated inside the consolidation ring 22, and water-permeable materials (porous metal) 62 and 64 are arranged on the lower surface side and the upper surface side, respectively. It goes without saying that the water permeable material 62 on the upper surface side is formed in a concentric shape in accordance with the external loading plate 30 and the internal loading plate 32. Actually, concave portions are formed on the upper surface of the container bottom plate 16a, and the lower surfaces of the external loading plate 30 and the internal loading plate 32, and the water permeable materials 64, 62 are provided in the respective concave portions so that the drainage channels 18, 34 are provided. It is configured to lead to.

In the present consolidation test apparatus, the loading plate has a concentric double structure of the outer loading plate 30 and the inner loading plate 32, and the loading plates 30, 32 are evenly displaced by the pneumatic actuator 14. The total value of the loads applied to the external loading plate 30 and the internal loading plate 32 is measured by the total load cell 42, and the loading stress of the internal loading plate 32 is measured by the internal load cell 38. The load can be controlled by the overall load cell 42 or the internal load cell 38. Although not shown, the pressure control is performed by temporarily storing a set pressure from a high-precision regulator in a pressure tank and supplying the pressure to a pneumatic actuator by opening a solenoid valve. The pressure can be controlled stably within the pressure range described above. With such a configuration, only the loading stress of the internal loading plate 32 can be measured by the internal load cell 38.

As described above, in the conventional consolidation test, it is considered that the actual consolidation stress is uneven due to the influence of the peripheral surface friction acting between the test sample (ground material) and the consolidation ring. On the other hand, the present invention solves the above-mentioned problem by devising the load near the center of the specimen, which is less affected by the peripheral surface friction, as described above, so that accurate consolidation characteristics can be evaluated. are doing.

An example of the result of measurement of a highly organic soil using the present consolidation test apparatus will be described. The physical properties of the high organic soil used in the experiment are as follows. Soil particle density: 1.724 g / cm ³ Wet density: 0.984 g / cm ³ Natural water content: 760.6% Pore ratio: 14.61 Loss on ignition: 52.6% As described above, the natural water content is It is about 760% and the loss on ignition is as large as about 53%. N value is N = 0, uniaxial compressive strength is qu = 10k
N / m ² is small and very soft. The test specimen was collected in a non-disturbed state by large thin wall sampling.

The consolidation test was performed by step loading. The loading stage is as follows. 0 → 4.9 → 9.8 → 19.6 → 39.2 → 78.4 →
156.8 → 313.6 → 627.2 (kN / m ² ) In this test, loading was performed at each loading stage until the end of primary consolidation. The load was controlled by the overall load cell 42, the load having no influence of the peripheral surface friction was measured by the internal load cell 38, and the ring peripheral surface friction force was evaluated. Silicone oil was applied to the peripheral surface of the consolidation ring so that peripheral friction was minimized.

The total loading stress p (measured stress of the total load cell 42) at each loading stage and the stress p 'near the center of the specimen excluding the influence of the ring peripheral friction measured by the internal load cell 38 are represented by p to p. Figure 3 shows the experimental results organized in the relationship
Shown in Note that the values at the end of the primary consolidation were used as the total loading stress p and the stress p ′ at the center in FIG. Also, the loading stress p = 78.4 kN / m ² and p = 627.2 kN / m ²
Time to settlement strain (ε), time to consolidation stress (p
4 and 5 show the relationship between the time and the consolidation stress ratio (p '/ p).

According to the results shown in FIG. 3, the loading stress p =
In the case of 4.9 kN / m ² , p ′ / p = 0.84, but when the stress level becomes higher, p ′ / p = 0.95.
It shows almost constant values before and after. This indicates that the larger the loading stress, the proportionally larger the circumferential friction force.

4 and 5, the temporal change in the consolidation stress ratio p '/ p shows that a considerable part of the peripheral friction is exerted immediately after the loading, and the stress at the center of the specimen decreases. There is a tendency that the circumferential friction gradually increases with the progress of. In other words, with the increase in peripheral friction that continues after loading,
The stress effectively applied to the center of the specimen gradually decreases. Further, as the applied load increases, the time required for completing the primary consolidation increases. Accordingly, the time required for the peripheral friction force to exhibit a constant value also increases.

From these results, even in a consolidation test in which silicon oil was applied to the peripheral surface of the consolidation ring and was carefully performed, about 5% of the applied load acted on the specimen as effective stress due to peripheral surface friction. And proved the effectiveness of the consolidation device according to the present invention.

[0028]

According to the present invention, as described above, the loading plate has a double structure of an external loading plate and an internal loading plate, and a load is applied to both loading plates to give an even displacement, thereby reducing the loading stress of the internal loading plate. Since the consolidation test method and the apparatus are configured to measure, it is possible to avoid the influence of the peripheral surface friction between the consolidation ring and the test sample, and to accurately evaluate the consolidation characteristics. In addition, in the present invention, since the specimen size can be increased, high organic soil,
It is also applicable to heterogeneous ground materials such as embankment materials or waste ground.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a consolidation test apparatus according to the present invention.

FIG. 2 is a conceptual diagram of the load measurement.

FIG. 3 is a graph showing a relationship between a total loading stress p and a loading stress ratio p ′ / p.

FIG. 4 Strain ε, loading stress p, p ′, loading stress ratio p ′
Graph of change over time of / p.

FIG. 5 shows strain ε, applied stress p, p ′, applied stress ratio p ′
Graph of change over time of / p.

[Explanation of symbols]

 14 Pneumatic actuator 16 Consolidation container 20 Specimen 22 Consolidation ring 30 External loading plate 32 Internal loading plate 36 Central loading frame 38 Internal load cell 40 Peripheral loading frame 42 Total load cell 44,46 Universal joint 50 Guide base 54,56 Slide bearing 60 Central Displacement detector

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tomohisa Meken 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi, Osaka Inside Osaka Gas Co., Ltd. (72) Inventor Eiki Nakayama 4-4-2 Kudankita, Chiyoda-ku, Tokyo No. 6 within Applied Geological Co., Ltd. (72) Inventor Fumihiro Mochida 4-6-1 Kudankita, Chiyoda-ku, Tokyo F-term within Applied Geological Co., Ltd. 2F051 AA06 AB09 AC01 AC09 2G061 AA02 CA06 CB02 EA01 EA02 EB05

Claims (2)

[Claims] 1. A consolidation method for a ground material in which a specimen is accommodated in a consolidation ring, a loading plate is placed on the specimen, a specimen is compressed by applying a load to the loading plate, and a loading stress and a compression displacement are measured. In the test method, the loading plate has a dual structure of an internal loading plate and an external loading plate, and a load is applied to both loading plates to give uniform displacement, and the loading stress of the internal loading plate is measured. A method for testing consolidation of ground materials, characterized by avoiding the effect of surface friction. 2. A base member, a consolidation ring mounted thereon and accommodating a specimen therein, an annular external loading plate sized to fit into the consolidation ring, and an inside of the external loading plate. A disc-shaped internal loading plate located concentrically, a total load detector that measures the total loading of both the external loading plate and the internal loading plate, and an internal load detection that measures the loading only of the internal loading plate And a pressurizing device for applying a load to the external loading plate and the internal loading plate.