JP2010181232A - Method of preparing test sample for triaxial test - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of preparing a test sample for a triaxial test wherein the test sample can be properly saturated with water without changing the particle size and a difference in a saturation rate of the test sample is not caused by a particle size difference of the test sample. <P>SOLUTION: In the method of preparing a test sample for a triaxial test, a sample X the particle size of which has been adjusted is divided and put into a storage part 7 of each of five deaeration containers 1, and air inside the storage part 7 is sucked with a vacuum pump P while an opening of the deaeration container 1 is covered with a lid 3, so that a negative pressure is applied to the storage part 7. After this, the sample X in the storage part 7 is transferred to the interior of a mold 20 for preparing a test sample wherein the inner wall is covered with a rubber membrane 21, and the sample X is piled up inside the mold from the lower side and compacted by a rammer 28 each time the filling of the sample X of one deaeration container 1 is finished. The step of transferring the sample X from the storage part 7 of the deaeration container 1 to the interior of the mold 20 and the step of compacting the sample X are alternately performed, and thus all the samples X contained in the storage parts 7 of the deaeration containers 1 are compacted. After a test sample Y prepared using the mold 20 is placed in a triaxial testing apparatus 30, deaerated water is supplied while applying a lower negative pressure by the vacuum pump P. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a specimen used for a triaxial test for measuring the strength of soil.

  Depending on the test conditions, the specimen used for the triaxial test may be saturated by supplying water or may not be saturated by water.

  A method for producing a specimen saturated with water will be described below with reference to FIGS. FIG. 13 is a flowchart showing the method for manufacturing the specimen.

  First, as shown in FIG. 14, a cylindrical mold 120 for producing a specimen is fixed to a mold installation portion 124 of a plate-like member 126. This fixing is performed by fitting the mold 120 into a recess 124a formed in the mold setting portion 124. The inner wall of the mold 120 is covered with a rubber membrane 121 after the mold 120 is fixed to the mold installation portion 124.

  Next, as shown in FIG. 14, water is applied to the inside of the mold 120. After that, the sample Q with adjusted particle size (hereinafter referred to as a dotted pattern) is placed inside the mold 120 using the handle 127 and stacked in layers from the lower side (lower side of the drawing) inside the mold 120. (Step S1 and step S2 in FIG. 13). Note that “sample Q with adjusted particle size” means that the composition ratio (particle size distribution) of various large and small particles constituting sample Q is set to a ratio (distribution) suitable for the test conditions of the triaxial test.

  Next, as shown in FIG. 15, a rammer 128 (a tamping machine) is inserted into the mold 120 from the upper side (upper side in the drawing). The sample Q is rammed by moving the rammer 128 many times in the vertical direction indicated by the arrow D and pushing the sample Q many times from the upper side (step S3 in FIG. 13). In addition, in order to make the pressure applied to the sample Q uniform at the time of tamping, the sample moved to the inside of the mold 120 is tamped every time it is moved. That is, every time a certain amount of sample Q is moved into the mold 120, this sample Q is not hardened after all of the sample Q used to manufacture the specimen is moved into the mold 120. Q is tamped. By the above steps, as shown in FIG. 16, an unsaturated specimen R (hereinafter, indicated by a dotted pattern) can be produced. In the specimen R, the boundary line at the stage of tamping is indicated by a dotted line, and the same applies to FIGS. 17 and 18 later.

  The specimen R (unsaturated state) produced through the process shown in FIG. 16 is installed in the triaxial testing apparatus 130 as shown in FIG. 17 (step S4 in FIG. 13). The three-axis test apparatus 130 includes an upper panel 141, a pedestal 142, a pedestal 133, a cap 134, and a support column 132, and main parts thereof are configured. The pedestal 133 is fixed to the pedestal 142, and the cap 134 passes through the center portion of the upper panel 141 and is connected to a loading device (not shown).

A deaerated water supply hole 135 and a carbon dioxide (CO ₂ ) supply hole 136 are formed from the pedestal 142 to the pedestal 133, and two suction holes 137 and 138 are formed in the upper panel 142. Further, a suction hole 139 is formed in the cap 134. The suction hole 139 and the suction hole 138 of the upper board 141 are communicated with each other by a connecting member 140 (tube or the like).

  As described above, the specimen R completed in the process shown in FIG. 16 is installed in the triaxial testing apparatus 130. This installation is performed by removing the mold 120 after moving the specimen R together with the mold 120 to the triaxial testing apparatus 130 and fixing it to the pedestal 133. After the specimen R is fixed to the pedestal 133, the space between the upper board 141 and the pedestal 142 is sealed with a steel cylindrical capsule 131.

  Carbon dioxide is supplied from the carbon dioxide supply hole 136 of the pedestal 142 to the specimen R installed in the triaxial test apparatus 130 as described above, and the air present in the void inside the specimen R is converted into carbon dioxide. Replace (step S5 in FIG. 13). Next, the deaerated water is supplied from the deaerated water supply hole 135 of the pedestal 142, and the specimen R is saturated with water by dissolving carbon dioxide inside the specimen in the deaerated water (see Patent Document 1).

  When the above step is performed under normal pressure, deaerated water is less likely to enter the voids inside the specimen R, and as a result, there is a concern that the time required to saturate the specimen R with the deaerated water may increase. Is done. Therefore, the above steps are performed by using the vacuum pump P from the suction holes 137, 138, and 139 to the inside of the specimen R and the inside of the cell (with the cylindrical cover 131), as in the specimen manufacturing method disclosed in Patent Document 2. The process is performed while sucking air in a sealed space and applying a negative pressure (suction force) to the specimen R (step S5 in FIG. 13). Thereby, the saturation speed (speed at which saturation proceeds) of the specimen R with deaerated water is improved.

In the above process, the negative pressure when the air inside the specimen R is sucked through the suction holes 138 and 139 connected by the connecting member 140 is, for example, −90 kN / m ² . Further, the negative pressure when the air inside the cell is sucked through the suction hole 137 is set to, for example, −70 kN / m ² . A triaxial test is performed using the specimen R produced as described above (step S6 in FIG. 13). The negative pressure is indicated by a negative value as described above, and the larger the absolute value of the negative value, the higher the negative pressure.

JP 2006-8455 A JP 2003-121433 A

  In the above-described conventional method for producing a specimen for a triaxial test, deaerated water is supplied to the specimen R with a vacuum pump P while applying a high negative pressure to saturate the specimen R. Therefore, when the negative pressure described above is applied, fine particles constituting the specimen R may be sucked out of the specimen R, and the particle size of the specimen R may change. This leads to a decrease in strength of the specimen R.

As a means for solving the above-mentioned problem, as shown in FIG. 18, the air inside the cell is not sucked from the suction hole 137, and the inside of the specimen R is drawn at a negative pressure of −20 kN / m ² from the suction holes 138 and 139. A method of sucking air existing in the air gap is conceivable.

  However, this method has a problem in that the time required to saturate the specimen R with deaerated water becomes long because the negative pressure during suction is low.

  Further, in the above-described conventional technique, when the specimen R contains a large number of large particles, the void inside the specimen R becomes large and the air present in the gap is easily sucked. Saturated easily. However, when the specimen R contains a large number of small particles, the void inside the specimen R becomes small and the air present in the gap becomes difficult to be sucked, so that the specimen R is hardly saturated. That is, in the above-described conventional technique, a difference in the saturation rate of the specimen R is likely to occur due to the difference in the particle size of the specimen R.

  The present invention has been made in view of the above circumstances, and can reliably saturate the specimen with water without changing the particle size, and there is a difference in the saturation rate of the specimen due to the difference in the grain size of the specimen. A method for producing a specimen for triaxial testing that does not occur is provided.

  The present invention for solving the above-mentioned problems is a method for producing a specimen used for a triaxial test for measuring the strength of soil, in which a plurality of degassing containers are provided with samples having adjusted particle sizes. The step of placing the sample in water, the step of applying a negative pressure to each of the storage units, and the inside of the mold for preparing a specimen from each of the storage units The method includes a step of sequentially transferring the samples and stacking them inside the mold, and a step of solidifying the samples transferred to the inside of the mold. Here, “acting a negative pressure on the housing part of the degassing container” means that the air present in the housing part of the degassing container is sucked with a vacuum pump (degassing pump) or the like, and the suction force is increased. Refers to acting.

  In this case, since the sample for preparing the specimen is saturated with water using a degassing container, the specimen prepared by tamping is in a state saturated with water. Therefore, after the specimen prepared by tamping is installed in the triaxial test apparatus, a process of adding deaerated water and saturating it while applying a negative pressure as in the prior art becomes unnecessary. Therefore, the particle size of the specimen is not changed by applying this conventional method. In addition, in order to make the sample put separately in the accommodating parts of the plurality of degassing containers to be immersed in water, even when negative pressure is applied to the accommodating part of the degassing container, Insensitive to negative pressure. Therefore, the fine particles constituting the sample are not sucked out of the storage unit together with the air present in the storage unit, and the particle size of the sample does not change.

  It is desirable that the sample obtained by transferring the sample to the inside of the mold is solidified every time it is transferred. This is because if the sample is rammed after all the samples placed in the container of multiple degassing containers are transferred to the frame mold, the pressure applied to the sample at the time of tamping reaches the lower layer side of the stacked samples. This is because it becomes difficult to uniformly squeeze the sample.

Negative pressure to act on the accommodating portion of the degassing vessel, it is desirable to ^{-90kN / m 2 ~-100kN /} m 2. Here, the negative pressure is indicated by a negative value as described above. The larger the absolute value of the negative value, the higher the negative pressure, and the same shall apply hereinafter. If the negative pressure is lower than −90 kN / m ² , the negative pressure is too low, and the time required for saturating the sample with deaerated water may increase. On the other hand, if the negative pressure is higher than −100 kN / m ² , the negative pressure is too high, and the water present in the accommodating portion of the degassing container is sucked out of the accommodating portion together with the air present in the accommodating portion. The sample may become difficult to saturate with water.

  The layer thickness of the sample placed in the container of the deaeration container is preferably 2 to 2.5 times the maximum particle size of the sample. Here, the “maximum particle diameter of the sample” refers to the diameter of the largest particle among the particles constituting the sample. If the layer thickness of the sample placed in the container of the degassing container is smaller than 2.0 times the maximum particle size of the sample, the layer thickness is too thin and it is difficult to make the sample immersed in water. There is a fear. On the other hand, if the layer thickness of the sample placed in the container of the degassing container is larger than 2.5 times the maximum particle size of the sample, the layer thickness is too thick and the time required to saturate the entire sample is long. There is a risk.

  The mold is cylindrical, and the amount of the sample placed in the container of the degassing container is such that the diameter of the specimen prepared from this sample is 4 to 5 times the maximum particle size of the sample. It is desirable to do. If the diameter of the specimen made from the sample is smaller than 4 times the maximum particle size of the specimen, the specimen will be too small, and the specimen will lose its shape when a vertical load is applied to the specimen during the triaxial test. Is concerned. On the other hand, when the diameter of the specimen prepared from the sample is larger than 5 times the maximum particle diameter of the specimen, the specimen becomes too large, and when a vertical load is applied to the specimen during the triaxial test, There is concern that it will be difficult to apply pressure evenly.

  In the inventions described so far, it is desirable that the negative pressure is simultaneously applied to the accommodating portions of the plurality of degassing containers. In this case, since the sample put in the accommodating part of the several deaeration container can be saturated simultaneously, the time required to saturate a sample can be reduced.

  It is desirable to supply deaerated water after the specimen prepared by tamping is installed in a triaxial test apparatus. In this case, since the specimen Y can be reliably saturated, the reliability of the measured value of the triaxial test can be improved.

  In the present invention described above, it is desirable that the deaerated water is supplied after carbon dioxide is supplied to the specimen. In this case, the deaerated water supplied to the specimen after the supply of carbon dioxide is easily replaced with carbon dioxide, so that the specimen installed in the triaxial test apparatus is easily saturated with the deaerated water.

  Furthermore, in the above-described present invention in which deaerated water is supplied to the specimen installed in the triaxial test apparatus, the deaerated water is preferably supplied in a state where a negative pressure is applied to the specimen. Here, “to apply a negative pressure to the specimen” refers to sucking air remaining inside the specimen with a vacuum pump or the like and applying a suction force to the specimen.

  In this case, even if air remains in the gap inside the specimen, this air is sucked out of the specimen. Therefore, the air and water remaining in the voids inside the specimen are easily replaced. As a result, it becomes extremely easy to saturate the specimen installed in the triaxial test apparatus with deaerated water.

  In the above invention, the negative pressure is desirably applied intermittently to the specimen. In this case, the fine particles constituting the specimen are less likely to be sucked out of the specimen together with the air remaining in the voids inside the specimen and the deaerated water supplied to the specimen during the negative pressure action. It is possible to prevent the particle size from changing. Thereby, the intensity | strength of a test body is securable.

Further, in the present invention described above, the negative pressure to be applied to the specimen, it is desirable to ^{-20kN / m 2 ~-30kN /} m 2. If the negative pressure is lower than −20 kN / m ² , the negative pressure is too low and the time required for saturating the specimen with degassed water may be increased. On the other hand, if the negative pressure is higher than −30 kN / m ² , the negative pressure is too high, and fine particles constituting the specimen are left in the voids inside the specimen and deaerated water supplied to the specimen. At the same time, since it is easily sucked to the outside of the specimen, there is a possibility that the particle size of the specimen is changed. This leads to a decrease in the strength of the specimen.

  In the method for producing a specimen for triaxial testing according to the present invention, a sample for producing a specimen is saturated with water using a degassing container. Will be saturated. Therefore, the specimen prepared according to the present invention does not require a process of supplying deaerated water and saturating the specimen while applying a negative pressure to the specimen after being installed in the triaxial testing apparatus. For this reason, by the conventional method described above, the fine particles constituting the specimen are sucked out of the specimen together with the air present in the voids inside the specimen and the deaerated water supplied to the specimen, There is no problem of changing the particle size. As a result, the strength of the specimen can be ensured.

  Thus, in the present invention, since it is not necessary to saturate the specimen installed in the triaxial test apparatus, the conventional problem that a difference in the saturation speed of the specimen occurs due to the difference in the grain size of the specimen. Absent. Further, in the present invention, since the sample is saturated in a state immersed in water, a difference in saturation speed due to a difference in the particle size of the sample is unlikely to occur.

  Furthermore, the sample put separately in the degassing container is immersed in water, so that when negative pressure is applied to the container of the degassing container, fine particles are sucked together with air, The particle size of the sample does not change.

In addition, since the sample put in the storage part of the deaeration container is immersed in water, even when a negative pressure is applied to the storage part, the sample is not easily affected by the negative pressure due to the action of the water pressure. Therefore, the negative pressure applied to the housing portion can be set high (about −100 kN / m ² ). As a result, the time required to saturate the sample can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1, showing an embodiment of the present invention, is a flow diagram illustrating a method for producing a triaxial test specimen. It is a perspective view which shows the container for deaeration used for the preparation method shown in FIG. It is a top view of the main-body part of FIG. It is sectional drawing explaining the process of putting a sample in the accommodating part of the container for deaeration. It is sectional drawing which shows the state which covered the opening part of the main-body part shown in FIG. 4 with the cover body. FIG. 6 is a cross-sectional view for explaining a process of connecting the degassing container shown in FIG. 5 in parallel to a connecting member attached to a vacuum pump and applying a negative pressure to the housing part of the degassing container. It is a perspective view explaining the state which fixed the formwork which produces a specimen. It is a perspective view explaining the fixing method of FIG. It is sectional drawing explaining the process of transferring the sample saturated by the accommodating part of the container for deaeration to the inside of the formwork which produces a test body. It is sectional drawing explaining the process of tamping the sample moved to the inside of the mold which produces a test body. It is sectional drawing which shows the state which produced the test body inside the mold by the process of FIG. It is sectional drawing explaining the process which installs the test body produced in FIG. 11 in a triaxial test apparatus, and is further saturated with deaeration water. It is a flowchart which shows the preparation methods of the conventional specimen for a triaxial test. FIG. 14 is a cross-sectional view illustrating a process of putting a sample in a mold for producing a specimen in the conventional specimen production method shown in FIG. 13. FIG. 15 is a cross-sectional view illustrating a step of tamping the sample after the step illustrated in FIG. 14. It is sectional drawing which shows the state which produced the test body inside the mold by the process of FIG. FIG. 17 is a cross-sectional view for explaining a process in which the specimen prepared in FIG. 16 is installed in a triaxial test apparatus and deaerated water is supplied while high negative pressure is applied to the specimen to saturate the specimen. FIG. 17 is a cross-sectional view for explaining a step of saturating a specimen by installing the specimen prepared in FIG. 16 in a triaxial testing apparatus and supplying deaerated water while applying a low negative pressure to the specimen.

  Embodiments of the present invention will be described below with reference to the accompanying drawings (FIGS. 1 to 12). In addition, the manufacturing method of the specimen for a triaxial test which concerns on this embodiment was shown with the flowchart in FIG.

  First, a sample with adjusted particle size (hereinafter referred to as sample X) and five degassing containers 1 shown in FIG. 2 are prepared (step S1 in FIG. 1).

  As shown in FIG. 2, the deaeration container 1 includes a bottomed cylindrical main body 2 having an opening at the upper end, a bottom plate 5, and a lid 3 as main parts. The main body 2 has a recess 4 therein, and a cylindrical plastic bucket with a bottom having an opening at the upper end is provided from the main body 2 as an accommodating portion 7 for accommodating the sample X. Mates removably. The bottom surface 7a of the housing part 7 and the bottom surface 4a of the recess 4 of the main body part 2 are in contact with each other.

  The main body 2 covers the opening with the lid 3 and fixes the end on the side opposite to the opening to the bottom plate 5. A movement caster 6 for moving the main body 2 is attached to the bottom plate 5. At the center of the lid 3, a convex protrusion 3 a that protrudes on the side opposite to the bottom plate 5 side is provided, and a T-shaped connector 9 is attached to the protrusion 3 a. From the connector 9 to the lid 3 through the protrusion 3a, a suction hole 8 is formed for communicating the connector 9 with the recess 4 of the main body 2. The connector 9 is attached with a connecting member 10 (such as a tube) that connects the connector 9 and another member (such as a vacuum pump or other degassing container). FIG. 3 shows a plan view of the main body 2 viewed from the opening side.

  Next, as shown in FIGS. 4 to 6, water is applied to the accommodating portions 7 of the five degassing containers 1, and then the sample described above using the handle 11 in the accommodating portions 7 of the degassing containers 1. X (hereinafter referred to as a dotted pattern) is put separately, and this sample X is immersed in water (step S2 in FIG. 1). In addition, the sample X put into the accommodating part 7 of the five deaeration containers 1 is made equal in this embodiment. After the above steps, as shown in FIG. 5, the opening of the main body 2 is covered with the lid 3, and the connector 9 attached to the lid 3 and the vacuum pump P (deaeration pump) are connected by the connecting member 10. Link. In the present embodiment, as shown in FIG. 6, five degassing containers 1 are connected in parallel to the connecting member 10 attached to the vacuum pump P via a connector 9.

The vacuum pump P is operated in the above state, and the air present in the accommodating portions 7 of the five degassing containers 1 is sucked at the same time, and as shown in FIG. A negative pressure (suction force) of −100 kN / m ² is applied to (step S2 in FIG. 1). Thereby, since the air which exists in the accommodating part 7 is attracted | sucked, the air which exists in the space | gap inside the sample X is substituted by the water of the accommodating part 7, and the sample X is saturated with water. The type of water stretched in the storage unit 7 is not particularly limited. However, when deaerated water is used, the amount of air present in the storage unit 7 is reduced, so that the time required for the saturation can be reduced. it can.

  Next, as shown in FIG. 7, a cylindrical mold 20 for producing a specimen for triaxial testing is fitted and fixed to the mold installation part 24 formed on the plate-like member 26. Thereafter, the inner wall of the mold 20 is covered with a rubber membrane 21. The mold 20 can be equally divided into two in a direction (left and right sides in the drawing) perpendicular to the vertical direction. As shown in FIG. 8, the above-described fixing of the mold 20 to the mold setting portion 24 is performed by two mold frame constituting members in the recess 24 a formed at the center of the mold setting portion 24 of the plate-like member 26. As shown by arrows A and B, 20a and 20b are fitted and connected in an annular shape.

  A bolt fixing portion 22b is provided at an end portion of the mold constituting member 20b, and a bolt 23 is fixed to the bolt fixing portion 22b. Moreover, the bolt fixing | fixed part 22a in which the bolt penetration hole 25 was formed is provided in the edge part of the mold structural member 20a. After fitting the formwork component members 20a and 20b into the recess 24a of the formwork installation part 24, the end of the bolt 23 of the formwork structure member 20b is inserted into the bolt insertion hole 25 of the formwork structure member 20a. The end is tightened with a nut 12 as shown in FIG. Thereby, it is possible to prevent the formwork constituent member 20a and the formwork constituent member 20b from coming into close contact with each other and to be separated from each other.

  Next, as shown in FIG. 9, an amount of water equivalent to that of the sample X placed in one of the five degassing containers 1 is placed inside a cylindrical mold 20 for degassing. The sample X (saturated with water: see FIG. 6) placed in the container 7 of the container 1 is gently moved into the mold 20 using the handle 27 so that air does not enter. Thus, the sample X is stacked in layers from the lower side (lower side in the drawing) inside the mold 20 (step S3 in FIG. 1). As a method for gently moving the sample X into the mold 20, there is a method in which the sample X is put on water stretched inside the mold 20 using the handle 27, and then the sample X is naturally dropped in water. is there. Further, during the above-described operation, the water is appropriately discharged so that the water does not overflow from the upper part of the mold 20. Further, deaerated water is used as the water stretched inside the mold 20. Thereby, it can prevent that air mixes in the sample X (saturated with water) moved to the inside of the mold 20.

  After the transfer of the sample from one of the five degassing containers 1 to the mold 20, as shown in FIG. 10, the rammer is moved from the upper side (upper side of the drawing) to the inside of the mold 20. 28 is inserted. The sampler X is tamped by moving the rammer 28 many times in the vertical direction indicated by the arrow C and poking the sample X from the upper side many times (step S4 in FIG. 1). Furthermore, it is necessary to transfer all the samples X put in the storage portions 7 of the five degassing containers 1 into the mold 20 and to tamify them all. Therefore, in this embodiment, the process of transferring the sample X of the degassing container 1 to the mold 20 and the tamping process are alternately performed (total 5 times), so that the sample X is placed inside the mold 20. Stack up. By performing tamping in this way, the sample X can be rammed evenly. As shown in FIG. 11, a triaxial test specimen Y (hereinafter, indicated by a dotted pattern) is completed by the tamping. In the specimen Y, the boundary line at the stage of tamping, that is, the boundary line at the stage where the sample X of one deaeration container 1 has been transferred to the mold 20 is indicated by a dotted line, and FIG. The same applies to.

  Next, the completed specimen Y is moved to the triaxial testing apparatus together with the mold 20, and the specimen Y is installed in the triaxial testing apparatus as shown in FIG. 12 (step S5 in FIG. 1).

  The triaxial testing apparatus 30 includes a top board 41, a pedestal 42, a pedestal 33, a cap 34, and a support column 32, and the main part. The pedestal 33 is fixed to a pedestal 42, and the cap 34 penetrates the upper board 41 and is connected to a loading device (not shown).

A deaerated water supply hole 35 and a carbon dioxide (CO ₂ ) supply hole 36 are formed from the base 42 to the pedestal 33, and two suction holes 37 and 38 are formed in the upper panel 42. Further, a suction hole 39 is formed in the cap 34. The suction hole 39 and the suction hole 38 of the upper board 41 are connected by a connecting member 40 (tube or the like).

  The above-described specimen Y is installed on the triaxial testing apparatus 30 after the specimen Y (see FIG. 11) produced by tamping is moved together with the mold 20 to the triaxial testing apparatus 30 and fixed to the pedestal 33. This is done by removing the formwork 20. After fixing the specimen Y to the pedestal 33, the space between the upper board 41 and the base 42 is sealed with a steel cylindrical capsule 31.

Carbon dioxide is supplied from the carbon dioxide supply hole 36 of the base 42 to the specimen Y installed in the triaxial test apparatus as described above, and the air remaining in the void inside the specimen Y is replaced with carbon dioxide. To do. Next, deaerated water is supplied from the deaerated water supply hole 35 of the pedestal 42 to dissolve carbon dioxide present in the voids inside the specimen Y in the deaerated water. The above operation is performed in a state where negative pressure (suction force) is applied to the specimen Y by sucking air inside the specimen Y from the suction holes 38 and 39 connected by the connecting member 40. This negative pressure, and ^{-20kN / m 2 ~-30kN /} m 2.

  A triaxial test is performed using the specimen Y produced through the above steps (step S6 in FIG. 1). In addition, in the flowchart shown in FIG. 1, since the process of supplying deaerated water and carbon dioxide to the test body Y after installing in the triaxial test apparatus 30 is not necessarily required in this embodiment, it is omitted. Yes.

  In the case of this embodiment, since the sample X for producing the specimen Y is saturated with water using a plurality of degassing containers 1 (see FIG. 6), the saturated sample X is made by tamping. After the specimen Y is installed in the triaxial testing apparatus, a process of supplying deaerated water while applying a negative pressure as in the prior art becomes unnecessary. Therefore, by applying a negative pressure to the specimen, the fine particles constituting the specimen Y are mixed with the air existing in the voids inside the specimen Y and the deaerated water supplied to the specimen Y. The particle size of the specimen Y is not changed by being sucked to the outside. As a result, the strength of the specimen Y can be ensured.

  As described above, since the specimen Y installed in the triaxial test apparatus is already saturated with water, it is not always necessary to saturate the specimen Y with deaerated water. Therefore, the conventional problem that a difference occurs in the saturation speed of the specimen Y due to the difference in particle size of the specimen Y does not occur. Moreover, since the sample X for producing the specimen Y is saturated in a state immersed in water, a difference in saturation speed due to a difference in the particle size of the sample X hardly occurs.

  Furthermore, since the sample X placed in the housing part 7 of the degassing container 1 is immersed in water, it is less susceptible to the negative pressure that acts on the housing part 7 due to the action of water pressure. Therefore, the sample X is not sucked to the outside of the container 7 of the degassing container 1 and the particle size of the sample X does not change.

In addition, since the sample X put in the container 7 of the degassing container 1 is immersed in water, even when a negative pressure is applied to the container 7, the influence of the negative pressure is caused by the action of the water pressure. It is hard to receive. Therefore, the negative pressure applied to the housing portion can be set high (about −100 kN / m ² ). As a result, the time required for saturating the sample X can be reduced.

Negative pressure to act on the accommodating portion 7 of the degassing container 1, in this embodiment, in order to ^{-90kN / m 2 ~-100kN /} m 2, the sample X be saturated with water in a reasonable time it can. If the negative pressure is lower than −90 kN / m ² (the absolute value of the negative pressure expressed as a negative value is small), the negative pressure is too low and the time required to saturate the sample X with water becomes longer. There is a fear. On the other hand, if the negative pressure is higher than −100 kN / m ² (the absolute value of the negative pressure represented by a negative value is large), the negative pressure is too high, and the water present in the container 7 of the degassing container 1 is present. However, there is a possibility that it will be difficult to saturate the sample X with water by being sucked out together with the air in the container 7 to the outside of the container 7.

  Moreover, in this embodiment, the layer thickness of the sample X put in the accommodating part 7 of the container 1 for deaeration is 2 times the maximum particle diameter (diameter of the largest particle among the particles which comprise a sample) -2. 5 times. Therefore, the sample X can be efficiently saturated with water. When the layer thickness of the sample X put in the container 7 of the degassing container 1 is smaller than 2.0 times the maximum particle size of the sample X, the layer thickness is too thin, and when the sample X is immersed in water, There is a risk that fine particles constituting X will float in water. This causes a difficulty in soaking sample X with water. On the other hand, if the layer thickness of the sample X placed in the container 7 of the degassing container 1 is larger than 2.5 times the maximum particle size of the sample X, the layer thickness is too thick and the entire sample X is saturated with water. There is a risk that the time required to do this will increase.

  Further, in this embodiment, the mold 20 has a cylindrical shape (see FIG. 7), and the amount of the sample X put into the housing portion 7 of the degassing container 1 is such that the diameter of the specimen Y produced from the sample X is the sample X. 4 times to 5 times the maximum particle size. For this reason, it is possible to produce a specimen Y that is not easily deformed during the triaxial test and that can obtain a highly reliable measurement value in the triaxial test. When the diameter of the specimen Y produced from the sample X is smaller than 4 times the maximum particle diameter of the specimen X, the specimen Y is too small, and when a vertical load is applied to the specimen Y during the triaxial test, the specimen There is a concern that Y may lose its shape. On the other hand, when the diameter of the specimen Y produced by the sample X is larger than 5 times the maximum particle diameter of the specimen X, the specimen Y becomes too large, and a vertical load is applied to the specimen Y during the triaxial test. There is a concern that it is difficult to apply pressure evenly to the entire specimen Y.

As a method of applying a negative pressure to the accommodating portions 7 of the plurality of degassing containers 1, a vacuum pump is connected to only one degassing container 1 to apply a negative pressure, and when the operation is completed, the vacuum pump P Is connected to another deaeration container 1 to apply a negative pressure, and this is repeated by the number of deaeration containers 1 (in this embodiment, 5 times). However, when five degassing containers 1 are connected in parallel to the connecting member 10 attached to the vacuum pump P via the connector 9 as in the present embodiment, all the degassing is performed by the operation of the vacuum pump P. A negative pressure can be applied simultaneously to the container 7 of the container 1. Therefore, the time required for saturating the sample X put in the five degassing containers 1 with water can be reduced. In this case, a uniform negative pressure (in this embodiment, −100 kN / m ² ) can be applied to the accommodating portions 7 of the five degassing containers 1.

  As described above, when the uniform negative pressure is applied to the accommodating portions 7 of the five degassing containers 1, the samples X placed in the accommodating portions 7 of the degassing containers 1 are equalized as in this embodiment. The time required to saturate X can be made equal. Moreover, the saturation state of the sample X put into each deaeration container 1 can be made equal.

  In the case of the present embodiment, the specimen Y installed in the triaxial test apparatus 30 is in a state saturated with water, and thus it is not necessary to supply deaerated water as in the conventional case. However, as in the present embodiment, by supplying deaerated water to the specimen Y after being installed in the triaxial test apparatus 30, it is assumed that air remains in the void inside the specimen Y. Also, the air inside the specimen Y can be replaced with deaerated water. Therefore, the specimen Y can be surely saturated with water. As a result, the reliability of the measured value of the triaxial test can be improved.

  Moreover, in this embodiment, since deaerated water is supplied to the specimen Y after supplying carbon dioxide to the specimen Y installed in the triaxial test apparatus, the time required to saturate the specimen Y is reduced. be able to. This is because when carbon dioxide is supplied to the specimen Y, the air remaining in the voids inside the specimen Y is replaced with carbon dioxide, and by supplying deaerated water in this state, the carbon dioxide is converted into deaerated water. This is because it can dissolve and easily replace carbon dioxide and degassed water.

  Further, the supply of the deaerated water to the specimen Y exists in a state where a negative pressure is applied to the specimen Y, that is, in the space inside the specimen Y from the suction holes 38 and 39 using the vacuum pump P. Perform with air sucked. In this case, even if air remains in the void inside the specimen Y, this air is sucked out of the specimen Y through the suction holes 38 and 39, so the void inside the specimen Y The remaining air and deaerated water are easily replaced. As a result, it becomes extremely easy to saturate the specimen Y with deaerated water.

  When a negative pressure is applied to the specimen Y installed in the triaxial test apparatus 30 by the vacuum pump P, this negative pressure is applied to the specimen Y intermittently. In this case, during the negative pressure action, the fine particles constituting the specimen Y are supplied through the suction holes 38 and 39 together with the air present in the voids inside the specimen Y and the deaerated water supplied to the specimen Y. It is not sucked out of the specimen Y. As a result, the particle size of the specimen Y can be prevented from changing, and the strength of the specimen Y can be improved.

Furthermore, since the negative pressure applied to the specimen Y is -20 kN / m ² to -30 kN / m ² , the specimen is excellent in strength and can obtain highly reliable measurement values in a triaxial test. Y can be produced. If the negative pressure is lower than −20 kN / m ² , the negative pressure is too low, and the time required for saturating the specimen Y with degassed water may be increased. On the other hand, if the negative pressure is higher than −30 kN / m ² , the negative pressure is too high, and the remaining of the specimen Y together with the air remaining in the void inside the specimen Y and the deaerated water supplied to the specimen Y. Fine particles may be sucked out of the specimen Y through the suction holes 38 and 39, and the particle size of the specimen Y may be changed. This leads to a decrease in strength of the specimen Y.

  The embodiment of the present invention has been described above. However, this is merely an example, and modifications can be made as appropriate without departing from the technical idea described in the claims.

  For example, in the present embodiment, as shown in FIG. 2, a plastic bucket is used as the accommodating portion 7 for containing the sample X in the recess 4 formed in the main body portion 2 of the deaeration container 1. In this case, when the sample X saturated with water is transferred to the mold 20, it is possible to remove the storage portion 7 from the recess 4 of the main body portion 2, so that workability when creating the specimen Y (work) Ease of operation and work efficiency). However, the recess 4 can also be used as a housing portion into which the sample X is placed by appropriately selecting the material of the recess 4 of the main body 2.

  The formwork 20 is not limited to an assembly type as in the present embodiment, and is not particularly limited as long as the object of the present invention can be achieved. Furthermore, the means for tamping the sample X is not limited to a method using a ramming machine such as a rammer. Depending on the test conditions, the tip is rammed manually using a disk-shaped thrust bar. You may do it.

  The deaeration container 1 is not limited to a shape as in the present embodiment, and is not particularly limited as long as the actions and effects of the present invention described above can be obtained.

1 Deaeration container 4 Recess 7 Storage part 20 Formwork (for specimen preparation)
30 Triaxial Test Equipment X Sample Y Specimen

Claims (11)

A method for producing a specimen used in a triaxial test for measuring soil strength,
Steps to put the sample with adjusted particle size separately into storage units provided in a plurality of degassing containers, and to make the sample immersed in water, and to apply a negative pressure to each of the storage units, The method includes a step of sequentially transferring the sample from each of the housing parts into a mold for preparing a specimen and stacking the sample in the mold, and a step of tamping the sample transferred to the inside of the mold. A method for producing a characteristic specimen for triaxial testing.   The method for producing a specimen for a triaxial test according to claim 1, wherein the sample transferred to the inside of the mold is solidified each time it is transferred. The negative ^{pressure, -90kN / m 2 ~-100kN} / method for manufacturing a three-for-Axial specimen according to claim 1 or 2 m ² to.   The specimen for a triaxial test according to any one of claims 1 to 3, wherein the layer thickness of the sample placed in the container of the deaeration container is set to be 2 to 2.5 times the maximum particle size of the sample. Manufacturing method.   The mold is cylindrical, and the amount of the sample placed in the container of the degassing container is such that the diameter of the specimen prepared from this sample is 4 to 5 times the maximum particle size of the sample. The manufacturing method of the specimen for a triaxial test as described in any one of Claims 1-4.   The method for producing a specimen for a triaxial test according to any one of claims 1 to 5, wherein the negative pressure is applied simultaneously to the housing portions of the plurality of degassing containers.   The specimen prepared by tamping is a method for producing a specimen for triaxial testing according to any one of claims 1 to 6, wherein deaerated water is supplied after the specimen is installed in a triaxial testing apparatus.   The method for producing a triaxial test specimen according to claim 7, wherein the deaerated water is supplied after carbon dioxide is supplied to the specimen.   The method for producing a specimen for triaxial testing according to claim 7 or 8, wherein the deaerated water is supplied in a state where a negative pressure is applied to the specimen.   The method for producing a triaxial test specimen according to claim 9, wherein the negative pressure is intermittently applied to the specimen. The method for producing a specimen for triaxial testing according to claim 9 or 10, wherein the negative pressure is -20 kN / m ² to -30 kN / m ² .

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