JP3923954B2 - Consolidation permeability test apparatus and test method - Google Patents

Description

  The present invention relates to a consolidation permeability test apparatus, and more particularly to a consolidation permeability test apparatus capable of simultaneously measuring the permeability and consolidation characteristics of a hardly permeable saturated ground such as bentonite mixed soil or rockfill dam core material.

  The bentonite mixed soil and rockfill dam core material used for the water-impervious layer at the final disposal site have extremely low water permeability, and in order to analyze the water permeability and consolidation characteristics of the specimen, Therefore, it is necessary to grasp and confirm the deformation performance and water permeability performance in a stress state close to the actual ground with high accuracy. For this reason, even in an indoor test performed by collecting a core, it is necessary to perform a test that accurately reproduces the stress state of the target ground, and various tests have been defined or proposed for this purpose.

  For example, in the water permeability test method using a well-known triaxial compression test apparatus, a water permeability test can be performed in a stress state on the site, and a side pressure is applied via a rubber sleeve covering the specimen, preventing water leakage from the side of the specimen. In addition, the degree of saturation of the specimen can be increased by applying back pressure (Non-Patent Document 1). Moreover, there exists patent document 1 as a water-permeable test apparatus which has the same structure and anticipated the same effect.

  By the way, when performing a consolidation test or a water permeability test using the above-described triaxial testing machine, the amount of water discharged from the test body in a separate process is measured for each specimen, and the amount of consolidation or the water permeability is measured. Therefore, there is a problem that even if a volume change occurs in the specimen at the water permeability test stage, the volume change cannot be measured. In addition, it was not assumed that the volume change amount was measured even for soils such as bentonite mixed soil that would expand in volume upon water absorption or unsaturated soils, and that the same specimen was used for the subsequent water permeability test. However, in the consolidation water permeability test of a hardly water permeable material, an isotropic consolidation stress (−0.1 to 1.0 Mpa) is changed stepwise, and a test in which the consolidation process to the water permeability process are repeated over a long period of time is performed. Therefore, in each process, it is important to measure the amount of water drained from the specimen, and to measure the volume change of unsaturated soil during water absorption expansion during the water permeability test. Since this volume change affects the results of the water permeability test, it is necessary to accurately measure the volume change amount of the specimen generated during the water permeability test.

  On the other hand, in the conventional triaxial testing machine, various methods have been proposed for measuring the volume change amount assuming a test of unsaturated soil or the like whose consolidation time is long (Non-Patent Document 2). In this triaxial testing machine, an inner cell is provided in a pressure cylinder (outer cell), the specimen is accommodated with the inside filled with water, and the volume change of the specimen during the test is formed in the inner cell. The volume change of the specimen is obtained by measuring the water level change at the upper mouth portion with a non-contact displacement meter or the like.

JP 2001-183285A. Edited by Geotechnical Society, “Method and Explanation of Soil Testing-First Revised Edition”, published by Geotechnical Society of Japan, March 20, 2000, pp. 417 Edited by Geotechnical Society, “Method and Explanation of Soil Testing-First Revised Edition”, published by Geotechnical Society of Japan, March 20, 2000, pp. 512

  However, in order to measure the volume change by the double cell as described above as a water level change of the inner cell with a non-contact displacement meter or the like, a metal portion is provided on the free water surface of the mouth portion of the inner cell to which pressure is applied. A non-contact type distance measuring sensor such as an eddy current type is used with a float. For this reason, a metal plate must be attached to the float, or the eddy current type sensor has a short length (measurement range) of about 10 to 20 mm, and an internal cell structure is assumed in the above triaxial cell. Since it is difficult to incorporate into an existing triaxial testing machine, there has been a demand for a measuring device having a simple structure that can measure a change in the water level in the inner cell accommodated in the triaxial cell with high accuracy. Accordingly, an object of the present invention is to solve the problems of the above-described conventional technology, and to provide a consolidated permeation test apparatus capable of measuring a volume change of unsaturated soil with high accuracy and simultaneously performing a permeation test, and a test method using the apparatus. It is to provide.

In order to achieve the above object, the present invention pressurizes a triaxial cell installed on a support portion and a free liquid level of a cell liquid filled in the triaxial cell with pressurized air supplied from a pressure source. A first pressure control means capable of controlling the restraining pressure in the triaxial cell; and a cell liquid in the triaxial cell which is housed and fixed in the triaxial cell and is partially fixed on the upper surface of the triaxial cell. The inner cell filled with the cell liquid in a state equal to the confining pressure of the inner cell, and a water passage that can be evenly permeated only in the vertical direction in the test body that has been shaped into a predetermined shape and prevented water from passing from the side. A compact permeation test apparatus comprising a specimen holding means fixedly held in the inner cell, and a water supply means controlled by a second pressure control means and capable of passing water through the water passage section, The inner cell is formed on a part of the upper surface with a sufficiently small diameter with respect to the diameter of the inner cell, and the inner portion of the cell liquid is formed inside the cylinder. And the liquid level position, has an open tubular portion float is accommodated floating inside the tube vertically movably, the disposed above the triaxial cell, formed in a part of the upper cover of the triaxial cell A semiconductor laser displacement meter for measuring the amount of vertical displacement of the float by irradiating and reflecting the measurement laser light on the float through the light transmitting lid and detecting the reflected light by the device, and the triaxial cell A measuring tank which is installed below and permeates the specimen and stores the discharged water discharged outside the triaxial cell; and a discharged water mass measuring means which measures the mass of the stored discharged water in the measuring tank; It is provided with.

  By measuring the volume change accompanying the consolidation of the normal specimen by the above-mentioned consolidation permeability test apparatus, simultaneously performing the water permeability test or measuring the volume change accompanying the water absorption expansion of the unsaturated soil specimen that absorbs and expands, Furthermore, it is possible to conduct a water permeability test while measuring the amount of volume change accompanying consolidation using the specimen.

  According to the present invention, during the water permeability test, it is possible to simultaneously measure the water absorption expansion and the volume change of the unsaturated soil, and the water permeability test is performed with the same specimen under different conditions of consolidation and restraint pressure. It is possible to perform a highly accurate consolidation permeation test efficiently.

  Hereinafter, as the best mode for carrying out the consolidated water permeability test apparatus of the present invention, the following examples will be described with reference to the accompanying drawings.

  FIG. 1 shows a known triaxial compression tester 1 (hereinafter referred to as triaxial tester 1), and a specimen holding means is placed in a triaxial cell 10 installed on a stable support leg 11. The specimen 2 fixedly held via 30 (described later) and accommodated in the specimen 31 is a regulator 2 as a first pressure control means capable of setting an assumed restraint pressure state, and the pore water pressure, back pressure, A regulator 3 as a second pressure control means capable of setting and adjusting the water permeation pressure, various pressure gauges 4, 5 and 6 and tanks 7 and 8 capable of measuring the pressure of each part are provided.

  In the present invention, the triaxial cell 10 includes a bottom plate 12 supported by a support leg 11 having a predetermined space below, and a cylindrical side wall 13 made of a transparent synthetic resin that is installed on the bottom plate 12 while maintaining a watertight state. And an upper lid 14 that closes the cylindrical side wall 13 so as to be watertight.

  Further, the inner cell 20 is housed and fixed inside the triaxial cell 10. The inner cell 20 is composed of a transparent synthetic resin cylindrical side wall 21 detachably installed on the upper surface of the bottom plate 12 of the triaxial cell 10 and an upper lid 22 detachably connected to the upper part of the cylindrical side wall 21. Has been. An open cylinder 23 having a sufficiently narrow diameter compared to the diameter of the inner cell 20 is connected to the center of the upper lid 22 so as to face upward. A specimen 31 held by a predetermined specimen holding means 30 is accommodated and installed in the inner cell 20. In this embodiment, like the known triaxial test specimen, the specimen 31 is shaped into a cylindrical shape having a diameter of 10 cm and a height of 5 cm, and this specimen 31 is placed on the pedestal style 32 as the specimen holding means 30. In addition, the cap 33 is set on the upper surface, the rubber sleeve 34 is brought into close contact with the side surface of the specimen 31, and water is prevented from passing from the side surface, and a predetermined consolidation water permeability test is performed. Hereinafter, the triaxial cell 10 in which the inner cell 20 is accommodated is referred to as the “outer cell 10” with respect to the inner cell 20.

  In the present invention, in order to perform a consolidated water permeability test of the specimen 31, porous stones 35 and 37 having a predetermined thickness are attached to the upper surface of the pedestal 32 and the lower surface of the cap 33 that are in contact with the specimen 31, and A water supply pipe 36 penetrating the pedestal style 32 is connected to the style 32 porous stone 35. Similarly, a drain pipe 38 formed through the cap 33 is connected to the porous stone 37 of the cap 33.

  Hereinafter, a route of water that is supplied to the specimen 31 during the water permeability test and drains through the specimen 31 will be described with reference to FIG. The water supply pipe 36 on the side of the pedestal 32 communicates from a pressure source (not shown) of the triaxial testing machine 1 to a water supply tank 7 whose water pressure can be adjusted via a regulator 3 as a second pressure control means. The water for use is supplied in an adjustable manner by a pressure gauge 6 and an on-off valve 9 on the water supply path. On the other hand, the drainage pipe 37 attached to the cap 33 side extends from the inner cell 20 through the bottom plate 12 to the outside of the outer cell 10, and via a three-way valve 39 on the path, a measuring tank 40 as a drainage amount measuring means. And a receiving tank 8 on the triaxial testing machine 1 side so as to be switchable. The three-way valve 39 is appropriately switched according to the timing of calibration and water permeability test.

Next, the restraint pressure control means that acts on the specimen 31 accommodated and held in the inner cell 20 will be described with reference to FIG.
As shown in FIG. 1, the inner cell 20 is accommodated and fixed in the outer cell 10, but the cell liquid 15 in the outer cell 10 is filled up to the height of the open cylinder 23 at the upper end of the inner cell 20. Yes. Further, the cell solution 24 is filled in the inner cell 20 to about half the height of the open cylinder 23 with the specimen 31 set therein. Therefore, the cell fluid pressure of the outer cell 10 and the cell fluid pressure of the inner cell 20 are in a state where the upper space of the outer cell 10 and the inner cell communicate with each other, and are set to the same fluid pressure (restraint pressure). At this time, a cylindrical float 25 having an outer diameter slightly smaller than the inner diameter of the open cylinder 23 is accommodated in the open cylinder 23. Since the float 25 has a specific gravity smaller than that of the cell liquid 24, the float 25 floats in the open cylinder 23 so as not to contact the inner surface of the open cylinder 23 as shown in an enlarged view in FIG. 2. In the present embodiment, silicone oil as an incompressible liquid is used as the cell liquids 15 and 24 filled in the outer cell 10 and the inner cell 20. Various other liquids can be used as long as sufficient incompressibility and non-volatility are confirmed, and the liquid is easy to handle and safe. Further, deaerated water can also be used if it is possible to prevent evaporation from the stored measuring tank 40 as will be described later.

  In addition, a pressure pipe 18 is connected to the upper cover 14 of the outer cell 10 via a regulator 2 from a pressure source (not shown). The liquid pressure of the cell liquid 15 in the inner cell 20 and the cell liquid 15 in the outer cell 10 transmitted through the open cylinder 23 by bringing the upper space of the outer cell 10 into a predetermined pressure state through the pressure pipe 18. Can be set to a predetermined restraint pressure. At this time, the fluid pressure (specimen restraint pressure) in the outer cell 10 and the inner cell 20 can be confirmed with the pressure gauges 4 and 5.

  On the other hand, the water discharged through the specimen 31 through the specimen holding means 30 during the water permeability test and discharged outside the outer cell 10 is switched in the drainage path by the three-way valve 39 and stored in the measuring tank 40. The measuring tank 40 is installed on an electronic balance 41 so that the mass of water discharged into the measuring tank 40 can be sequentially measured. In addition, a silicone oil film 42 having a predetermined layer thickness is formed on the surface of the water stored in the measuring tank 40, and it is possible to prevent the discharged water from evaporating even during long-term measurement. Further, the entire measuring tank 40 and the electronic balance 41 are accommodated in the windshield case 42, so that data fluctuation during measurement can be minimized.

  Here, the configuration of the means for measuring the volume change amount of the specimen in the present invention will be described with reference to FIG. In the present invention, as shown in FIG. 2, the liquid level of the cell liquid 24 is located at a substantially intermediate height in the open cylinder 23 provided in a part of the upper cover 22 of the inner cell 20, and the draft is contained therein. The float 25 is accommodated in a floating state so as to be at a half of the total height. In this embodiment, the open cylinder 23 is set to a height of 6 cm and an inner diameter of 4 cm, and the float 25 housed therein has a specific gravity of 0. 7 cm and a flat disk shape having an outer diameter of 3.8 cm. It consists of a 90-0.95 polypropylene resin molded product. Needless to say, the shapes of the open cylinder 23 and the float 25 can be appropriately set according to required specifications such as the dimensions of the inner cell 20 and the measurement accuracy of the volume change amount of the specimen.

  On the other hand, as shown in the figure, a circular opening 14a having a predetermined diameter is formed in the central portion of the upper cover of the outer cell 10, and a glass plate cover 16 as a light transmitting cover is fixed to the lower surface side of the circular opening 14a. Yes. The glass plate lid 16 has a plate thickness and rigidity enough to prevent bending deformation even when the outer cell 10 is in a predetermined pressure state. On the other hand, a known laser displacement meter 45 shown in FIG. 1 as a whole is installed above the outer cell 10 via a stand 48 (FIG. 1). As shown in FIGS. 1 and 2, the laser displacement meter 45 is aligned with the upper surface 25a of the float 25 floating in the open cylinder 23 of the inner cell 20, as shown in FIGS. The reflected light is received by a light receiving element (not shown) provided in the light receiving portion 47 of the displacement meter 45, and position (displacement) measurement corresponding to the formed triangular shape is performed. In this embodiment, a laser displacement meter is used in which the measurement distance can be set to about 0.5 m, and the displacement measurement accuracy of the target (float upper surface 25a) is about 50 μm. In this embodiment, the inner diameter of the open cylinder 23 is set to 4 cm, and by continuously measuring the vertical displacement of the float 25, the volume change amount of the specimen 31 accommodated in the inner cell 20 is continuously measured. Can be calculated.

  In the configuration of the means for measuring the volume change amount of the specimen 31, if the measurement distance to the float 25 to be measured and the measurement accuracy meet the specifications, instead of the laser displacement meter 45 using a semiconductor laser, other known methods An optical displacement meter can also be used. Also, the glass plate lid 16 attached to the upper lid 12 of the outer cell 10 is also made of various transparent synthetic resin materials as long as it can secure predetermined rigidity and light transmission and can accurately transmit measurement light. be able to.

In the following, the water permeability and consolidation characteristics of poorly permeable materials, such as water-impervious layers (bentonite mixed soil) and rock fill dam core materials, water absorption and expansion characteristics under various restraint pressures, A series of test methods for measuring the compression characteristics of saturated soil and water permeability after water absorption expansion and after compression of unsaturated soil will be described with reference to FIGS.
This apparatus is large and can perform a consolidation / water permeability test after performing a compression test and a water absorption expansion test on unsaturated soil. That is, after forming a hardly water-permeable unsaturated soil sample into a specimen 31 having a predetermined shape and measuring the initial dimensions, as shown in FIG. 1, the bedded style 32 on the support leg 11 of the triaxial testing machine 1 is formed. The cap 33 and the rubber sleeve 34 are attached, and a predetermined pipe is connected, and is accommodated in the inner cell 20. After the outer cell 10 is assembled, an unsaturated compression test is performed by operating the triaxial testing machine 1 in a state where the outer cell 10 and the inner cell 20 are filled with the cell solutions 15 and 24. At this time, pressure adjustment from a pressure source (not shown) is performed via the regulator 2, and loading / unloading of the restraining pressure in a predetermined cycle is repeated. The volume change of the unsaturated specimen accommodated in the inner cell 20 during that time can be known by measuring the vertical displacement of the float 25 as the liquid level change in the open cylinder 23 above the inner cell 20. After that, it is repeated for the set loading / unloading cycle, and the compression characteristic during this period can be grasped.

  Moreover, the water absorption expansion | swelling characteristic test of the test piece in the meantime can also be performed by letting water pass to an unsaturated test piece and complete saturation. In this case, the water absorption and expansion state can be confirmed by measuring the amount of vertical displacement of the float 25 when the specimen passes through.

  Furthermore, a consolidation water permeability test is performed. In this consolidation water permeability test, a loading / unloading cycle is set for a specified restraint pressure increase (decrease), and the amount of change in the consolidation volume of the specimen in each restraint pressure loading / unloading cycle is consolidated and drained and measured on an electronic scale. It is obtained by measuring the amount of drainage stored in the tank and the amount of vertical displacement of the float 25 in the open cylinder 23 of the inner cell 20. Further, water is passed through the specimen from the supply tank, and the amount of water stored in the measuring tank 40 on the electronic balance 41 and the amount of vertical displacement of the float 25 in the open cylinder 23 of the inner cell 20 are measured. Measure the volume change of the specimen that occurs during the test. By measuring the amount of water drainage (water permeability) with the scale 41 and the displacement of the float 25 with the laser displacement meter 45 at the time of unloading each restraint load, the compact water permeability characteristics of the target poorly permeable material can be accurately obtained. I can grasp it well.

The schematic block diagram which showed one Example of the consolidated water permeability test apparatus of this invention. The model enlarged view which expanded and showed the displacement measuring part of the apparatus shown in FIG. Flow chart showing the procedure of a test method using the test apparatus of the present invention (part 1) The flowchart which showed the procedure of the test method by the testing apparatus of this invention (the 2)

Explanation of symbols

1 Triaxial compression tester 2 First pressure control means (regulator)
3 Second compression control means (regulator)
10 Triaxial cell (outer cell)
15, 24 Cell solution 20 Inner cell 23 Open cylinder 25 Float 30 Specimen holding means 31 Specimens 35, 37 Water flow part (porous stone)
40 Weighing tank 41 Electronic scale 45 Laser displacement meter

Claims (3)

Control the restraint pressure in the triaxial cell by pressurizing the free liquid level of the triaxial cell installed on the support and the cell liquid filled in the triaxial cell with the pressure supplied from the pressure source. A first pressure control means capable of being accommodated and fixed in the triaxial cell, and inside the cell liquid in a state equal to the restraining pressure of the cell liquid in the triaxial cell via a part of the free liquid surface of the upper surface And an inner cell that is shaped into a predetermined shape and that is prevented from passing water from the side surface, is fixedly held in the inner cell through a water passage portion that can be evenly permeable only in the vertical direction. A compact permeation test apparatus comprising: a specimen holding means; and a water supply means controlled by a second pressure control means and capable of passing water through the water passage portion,
The inner cell is formed in a part of the upper surface with a sufficiently small diameter with respect to the diameter of the inner cell, the free liquid level of the cell liquid is located inside the cylinder, and the float floats up and down in the cylinder. Has an open cylinder portion in which is accommodated,
The float is irradiated with and reflected by the measurement laser beam through a light transmitting lid part formed on a part of the upper lid of the triaxial cell , which is installed above the triaxial cell, and the reflected light is reflected by the apparatus. A semiconductor laser displacement meter that detects and measures the vertical displacement of the float ; and
A measuring tank that is installed below the triaxial cell and permeates the specimen and stores the discharged water discharged outside the triaxial cell , and a discharged water mass that measures the mass of the discharged water in the measuring tank. A consolidated water permeability test apparatus comprising a measuring means .   A consolidation / permeability test method characterized in that, by the consolidation / permeability test apparatus according to claim 1, a volume change amount associated with the consolidation of the specimen is measured, and at the same time, a permeability test is performed.   By measuring the volume change accompanying the water absorption expansion of the unsaturated soil specimen that absorbs and expands by using the consolidation water permeability test apparatus according to claim 1, and further measuring the volume change accompanying the consolidation using the specimen, A consolidated water permeability test method characterized by performing a water permeability test.

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