JP2007071853A - Apparatus for measuring water retention curve capable of loading perpendicular stress thereon - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem, wherein water retention features of soil and soil materials (soil test specimen) are evaluated by using water retention curves, however, when measuring the water retention curves, volume changes in the soil test specimen due to perpendicular stress and stress loading on the soil test specimen are not acquired, and there is a need to improve measurement results of the water retention features in actuality, since the load of the structure itself and soil-covered pressure exist in an actual ground. <P>SOLUTION: A mold member, capable of bearing a perpendicular load corresponding to an actual in-ground stress, is used, and the soil test specimen is set in the mold member, and two pressures of a gap air pressure and a gap water pressure are applied on the soil test specimen. A displacement gauge is provided for measuring the displacement of the perpendicular stress of the soil test specimen due to the perpendicular load, the gap air pressure and the gap water pressure. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention makes it possible to apply a compressive force in the vertical direction to the soil and soil material to be tested (hereinafter referred to as a soil specimen) when experimentally examining moisture retention curves of the soil and soil material, etc. It is also possible to give pore air pressure and pore water pressure. Further, the amount of contraction and expansion in the vertical direction of the specimen can be measured in a loaded state of compressive force, air gap and water pressure.

When examining the moisture retention characteristics of a conventional soil specimen, place the soil specimen in a pressure-resistant container and use a ceramic disk with fine pores in combination with the pore air pressure and pore water pressure in the soil specimen. A moisture retention curve is determined by control. It is necessary to measure the vertical displacement of the soil specimen due to the large compressive stress propagating to the soil skeleton and the vertical displacement of the soil specimen accompanying changes in the pore air pressure and pore water pressure in the soil specimen.

None Tomoyoshi Nishimura, Moisture retention curves of soils with different compaction pressures, 32nd Kanto Branch Technical Meeting of the Japan Society of Civil Engineers, Kanto Branch, Japan Society of Civil Engineers, March 2005.

Soil skeleton in the case where a large compressive force is propagated to the soil skeleton formed by the soil particles constituting the soil specimen contacting each other, and at the same time, the pore air pressure in the soil skeleton and the change of pore water pressure are accompanied. It is a problem to be solved by the present invention to measure the overall vertical displacement.

The challenge is to make it possible to apply a large vertical stress to the soil specimen and to measure the vertical displacement of the soil specimen. Ensure sufficient thickness of the mold to store the soil specimen so that it can withstand a large vertical direction. In addition, ensure that the bottom plate supporting the mold has sufficient thickness. A displacement meter shall be attached to the pressure plate with a rod placed on the top of the soil specimen in order to measure the vertical displacement of the soil specimen.

By loading and controlling the stress in the vertical direction along with the control of the pore water pressure and the pore air pressure in the soil specimen, the actual vertical stress in the soil can be reproduced indoors. Moreover, it becomes possible to obtain the volume change of the soil specimen by measuring the vertical displacement of the soil specimen, and it is possible to calculate various amounts of soil composition.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.

FIG. 1 shows a moisture retention curve measuring apparatus capable of loading a vertical stress. The main components of the vertical stress loadable moisture retention curve measuring device are a pressure receiving plate, a pressure-resistant rod, an upper steel plate, a steel ring, a thick steel mold, a bottom plate, a pedestal, and an acrylic cylinder.

In addition to the main configuration of the vertical stress loadable moisture retention curve measuring device, a displacement meter, load meter, and ceramic disk are provided.

The ceramic disc has the role of separating pore air pressure and pore water pressure in the soil specimen. The ceramic disc is fitted in the bottom plate and fixed with epoxy resin.

Put the earth specimen in the thick steel mold and fix the thick steel mold and the bottom plate sufficiently.

An acrylic cylinder is fitted into the groove of the bottom plate, and a porous stone, a perforated pressure plate, a pressure rod, an upper steel plate attachment, and a pressure receiving plate are assembled in this order on the top of the soil specimen. Finally, the whole is assembled by fitting a steel ring.

The deaerated water is supplied into the acrylic cylinder from the deaerated water supply port, and the water supply is continued until the deaerated water flows into the water space from the water immersion hole.

The load cell and the pressure receiving plate are brought into contact with each other, and the tip of the displacement meter is brought into contact with the displacement meter attachment. Read the initial values of load cell and displacement meter.

By moving the pressure loading piston in the direction of the soil test piece, the vertical force is compressed on the soil test piece as a compressive stress through the load meter, the pressure receiving plate and the perforated pressure plate, and a change occurs in the soil test piece.

The displacement caused by the compressive stress can be obtained by measuring the amount of vertical movement of the pressure-resistant rod with a displacement meter.

Simultaneously with the loading of the compressive stress, a gap air pressure of an arbitrary size can be applied to the soil gap of the soil specimen from the gap air pressure supply port.

By applying pore water pressure to the drain outlet simultaneously with the loading of the compressive stress, the pore water pressure works through the ceramic disk and into the soil gap of the soil specimen.

The vertical displacement of the soil specimen produced by applying pore water pressure and pore air pressure to the soil specimen is

It can be measured in the same way.

Sectional drawing of the soil material salt water penetration tool using the dialysis membrane which shows embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Displacement meter 2 Displacement meter attachment 3 Load meter 4 Pressure receiving plate 5 Fixing screw 6 Ball bearing 7 Gap air pressure 8 O-ring 9 Acrylic cylinder 10 Thickness mold 11 Pressure rod 12 Perforated pressure plate 13 Porous stone 14 Earth specimen 15 Ceramic Disc 16 Drain port 17 Deaerated water supply port 18 Epoxy resin 19 Pedestal 20 Bottom plate 21 Steel ring 22 Upper steel plate 23 Water immersion hole 24 Water space 25 Pressure loaded piston

Claims (1)

Compressive stress measurement applied to soil specimens to moisture retention curve measuring instrument mainly composed of pressure plate, pressure rod, upper steel plate, steel ring, thick steel mold, bottom plate, pedestal, acrylic cylinder A device equipped with a load cell and a displacement meter for measuring the displacement in the vertical direction of the soil specimen caused by compressive stress loading and pore air pressure and pore water pressure control.

Images