JPS63235864A - High restraint pressure shearinig soil tank - Google Patents

Abstract

PURPOSE:To enable response analysis with a higher certainty, by a method wherein a shearing soil tank which is soft and elastic like rubber and with a greater mechanical strength is arranged in an air pressure tank with the lower end thereof fixed and vibration is applied thereto obtain a physical value closer to an actual value. CONSTITUTION:A shearing soil tank 2 which is soft and elastic like rubber and with a greater mechanical strength is arranged in an air pressure tank 1 with the lower end thereof fixed. A soil sample taken is put into the shearing soil tank 2 and made ready to dry and compact. A sensor such as accelerometer, strain gauge, soil pressure meter and interval hydraulic gauge is buried into the sample and then, pressure is applied to the pressure tank 1 corresponding to rock pressure at a sampling depth of the sample making a pressure adjust ment with a pressure reducing valve 1j. When a horizontal base 4 or a low acceleration hard to gain with the vibration base 4 is applied, vibration is pro vided from outside the pressure tank 1 with a free vibration jig 3 provided on the shearing oil tank 2.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a confining pressure shearing soil tank for determining the shear elastic constant of a soil sample under confining pressure.

(Prior Art and its Problems) In order to solve land problems and make effective use of land in crowded cities and industrial areas, it has been proposed to install electrical stations such as substations underground, for example, at a depth of about 40 meters. Furthermore, due to the recent increase in the size of buildings and other underground structures resulting in overcrowding, the idea of laying underground power transmission cables approximately 40 meters underground has been proposed.

By the way, in this case, it is especially necessary to prevent accidents such as power outages due to damage to highly public substations and cables due to the effects of earthquakes. Therefore, when designing, it is necessary to accurately grasp the main physical properties such as the shear modulus of elasticity and the damping constant, which are used for response analysis, not only the characteristics under atmospheric pressure (but also the conditions under confining pressure at the depth at which the structure is installed).

However, for example, the triaxial testing machine conventionally used to determine such characteristics has a diameter of 3.5 to 5 am, as shown in A shown in Figure 1, of the soil sample used for the test.
The height is limited to about 7 to 10 cm, and since the load B is applied, inertia cannot be imparted. Note that C is a hydraulic tank. Therefore, it is difficult to obtain excellent dynamic property values at angles close to the actual values.In addition, in order to understand the earthquake resistance of underground structures, it is necessary to create a model of the structure within the collected soil sample. It is necessary to carry out a dynamic test in which the material is buried and subjected to vibration, as well as to understand the above physical property values.However, conventionally, the test method is conducted in an earthen tank with the top open, so it is difficult to obtain the confining pressure. Then, if necessary, an earthen tank with a depth equal to the depth is required, which is extremely difficult to implement at a depth of 40 m or more.Furthermore, with this method, the confining pressure is only the amount due to the overlaying thickness, and it is not practical. It is not possible to perform a test similar to

(Objective of the Invention) The present invention makes it possible to directly apply an inertial force to a sample of sufficient size and determine the shear modulus of elasticity from its resonance frequency, thereby obtaining physical property values that are closer to actual values and increasing accuracy. The present invention aims to provide a confining pressure shearing soil tank that enables high-response analysis, and allows experiments to be conducted using a small device without using a soil tank with a depth equivalent to the confining pressure. This is the purpose.

(Means of the present invention for solving the problems) The present invention is characterized by being flexible and elastic like rubber,
Moreover, a storage soil tank (sheared soil tank) with high mechanical strength is provided with its lower end fixed inside the air pressure tank. When applying horizontal vibration to the pressure tank using a vibration table or applying low acceleration that is difficult to obtain with a vibration table,
Vibrations were applied from outside the pressure tank using a jig installed in the sheared soil tank, allowing closer dynamic physical property values to be obtained. Next, the present invention will be explained by examples.

(Structure of the embodiment) Figure 2 (al (bl) (C1 is a side view, plan view and cross-sectional view showing one embodiment of the present invention, Figure 3 (a) fbl
(C1 is a side view, plan view, and enlarged view of essential parts of the sheared soil tank, and Figure 4 is a sectional view of the free vibration jig. In Figure 2, (11 is a steel pressure tank with a circular cross section. This consists of a tank body (1a), a top cover (1c) attached to the tank body (1a) in a manner that allows it to be detached and sealed, and a mounting plate (1a) fixed to the bottom of the tank body (1a). 1d).Also, the tank body (1a
) has multiple transparent windows (1e) on its side surface for internal observation.
, air pressure inlet (1f), measuring instrument lead wire outlet (
Ig), a free vibration jig outlet (1h) and a hanging fitting (11) to be described later, and the top! (IC) is vacuum pulp (
1j) and a pressure gauge (1k).

(2) is a sheared soil tank with a circular cross section, and is made of a material that is elastic and flexible, such as rubber, and has high mechanical strength. Then, as shown in Fig. 3 (al), it is fixed on the base plate (2a), and further this base plate (2a)
is fixed coaxially with the pressure tank (1) to the bottom of the tank fl) by a screw (2b). In addition, a rubber shear soil tank (2
) is attached with an aluminum shape-retaining ring (2c) with a U-shaped cross section as shown in Fig. 3 (C1), which is attached with a screw (2d), to make it light and strong as shown in Fig. 3. They are fixed at intervals to prevent the circular cross section from collapsing.Adjustment plates (2e) are provided at symmetrical positions of the uppermost shape retaining ring (2c), and these are attached to the base plate (2a). The rubber shearing soil tank (2) is supported by a plurality of support columns (2f) erected to prevent it from shrinking due to downward force during sample preparation, and this is removed during testing. Furthermore, on one side of the adjustment plate (2e), there is a connecting iron (3a) with a universal joint (3a) in the middle, as shown in Figure 4.
3d) and a vibration ring (3c) with a pushing ring (3c).
d) is connected to the free vibration jig (3). In addition, this jig (3) is airtightly fixed to the jig outlet (1h) of the pressure tank (11) so that its push/pull ring (3c) is located outside the pressure tank (1). The bearing case (3e) and slide bearing (3f) pass through the wall of the tank (1) in an airtight manner and are pulled out.(4)
is an excitation vibration table (see Fig. 2 [C)], on which a pressure tank (11) is attached using a mounting plate (1d) during testing.

(Operation of the Example) Remove the screw (lb), remove the top 1 (lc), and place the collected soil sample in the sheared soil tank (2). In this case, conditions such as dry, wet, or saturated conditions are created for the sample depending on the purpose.
Furthermore, depending on the compaction conditions, loose packing or dense packing is performed. Also, when inserting the sample, depending on the purpose of the experiment, an accelerometer,
Sensors such as strain gauges, earth pressure gauges, and water pressure gauges are embedded in the sample, and the lead wires of each measuring instrument are airtightly pulled out to the outside through the outlet (1g) of the pressure tank (1) and connected to the instruments. Further, when the sample preparation is completed, the support column (2r) is removed. Then, after fixing the upper M (lc) airtightly to the tank body (la) with the screw (1b),
Compressed air is sent in from the compressor (not shown). The pressure is adjusted by a pressure reducing valve (1j). If the pressure gauge (1k) is the ground pressure at the sampling depth of the sample, for example, sandy ground at a depth of 10 m, then the confining pressure σ = ρ・Z (ρ: density.

Z: depth) to indicate an air pressure of 1.8 kg/cJ.

And micro-distortion (10-'
degree), a free vibration generating jig (3) pulled out from the pressure tank (1) applies horizontal vibration to the shearing soil tank (2), which is transmitted from directly below the ground. Provides vibrations equivalent to earthquakes caused by shear waves.

In the case of vibration using the vibration table (4), the vibration acceleration is applied from a small force, for example, about 10 gal (10/980G). Further, while keeping the acceleration constant, the vibration frequency is varied from 1 to 20 Hz at intervals of about 0.2511 Hz, and the acceleration response value of the sample at each frequency is measured.

This is summarized as a resonance curve diagram shown in Figure 5 (al), and the resonance frequency ``.'' and response value α are determined from the maximum value point.
From this, the shear modulus of elasticity G = ρ (4HL) 2 (H: height of the soil tank (2)) is determined, and the shear strain γ = 1/H (J:
(displacement at fo) is determined. Then, from these, the G-r curve and damping constant (hl) of FIG.

In addition, a structural model is embedded in the sample in the sheared soil tank (2) to understand the condition of the model due to the earthquake source.

(Effects of the Invention) As described above, the present invention applies inertial force directly to the sample and calculates the shear modulus of elasticity from the resonant frequency. The material properties used for response analysis are closer to the actual state,
Highly accurate response analysis becomes possible. In addition, conventional model experiments are conducted in earthen tanks with the top open, so as mentioned above, a soil tank with a depth corresponding to the depth is required, but in the present invention, the confining pressure for the depth is obtained by air pressure. Therefore, only a small soil tank is required, making the device compact.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the triaxial testing machine, Figure 2 (al (bl
(c) is a side view, a plan view, and a sectional view showing one embodiment of the present invention; FIG. The figure is a cross-sectional view of the free vibration jig, and Figure 5 (al (b) is the resonance frequency diagram and G-r curve. (1)...pressure tank, (1a)...tank body, ( 1b)...Mounting screw, (IC)...Top lid,
(1d)...Mounting plate, (1e)...Observation window, (
if)...Air pressure inlet, (1g)...Lead wire outlet, (1h)...Free vibration jig outlet, (li)
... Hanging tool, (1j) ... Exhaust pulp, (1k)
...Pressure gauge, (2)...Shearing soil tank, (2a)...
・Base plate, (2b)...Mounting screw, (2C)・
...Shape retaining ring, (2d)...Mounting screw, (
2e)...adjustment plate, (2f)...support column, (3)
... Free vibration jig, (3a) ... Universal joint, (3b) ... Rondo, (3c) ... Pushing ring, (3d) ... Vibration Rondo, (3e)
...bearing case, (3f)...slide bearing, (4)...vibration table.

Claims (1)

[Claims] A sheared soil tank having flexibility and elasticity is fixed in a pressure counter having a removable top lid that forms a confining pressure at the sampling depth by injected pressurized air, and one of the upper ends of the sheared soil tank has a A test is carried out by providing a free vibration generation jig that airtightly penetrates the pressure counter wall and having one end pulled out to the outside, and applying horizontal vibration to the pressure tank using the free vibration generation jig or a vibration table. A high confining pressure shear soil tank featuring: