JP2018199957A - Effect confirmation method of foundation structure for countermeasure against expansive ground - Google Patents

Abstract

To provide an effect confirmation method of a foundation structure for countermeasure against an expansive ground for realizing a countermeasure with high reliability, which can experimentally confirm an effect of a foundation structure for countermeasure against an expansive ground.SOLUTION: An effect confirmation method of a foundation structure A for countermeasure against an expansive ground which is constructed by laying granular materials 2a on a surface of an expansive ground 1 comprises: making a test body by laminating a glass bead layer constituted of glass beads simulating granular materials 2a on an expansive soil obtained from the expansive ground 1; immersing the teat body into water in a state where a lateral side of the test body is restricted; gradually applying load pressure onto the test body from above; and obtaining a load pressure at a time when a height of the test body becomes same as an initial height before loading. The obtained load pressure is considered to be an expansive pressure.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method of confirming the effect of a foundation structure for inflatable ground countermeasures in which a structure such as a building is constructed on the inflatable ground.

  For example, in dry and semi-arid areas such as Southeast Asia, Africa, and the Middle East, expanded soil containing expansive clay minerals such as montmorillonite accumulates and expands in the rainy season due to inundation and water absorption, and in the dry season due to drainage and drying. There is a wide range of expanding soil (ground that shows expandability) that shrinks.

  When a structure such as a house or a factory is constructed on such expanded soil, the structure is subject to unsettled uplift or unsettled as the ground deforms due to expansion and contraction of the expanded soil during the rainy and dry seasons. Many damages such as cracks occur in the walls and floor slabs of structures.

  For this reason, conventionally, the following three methods are singly or combined to construct a structure after taking measures against the expanded soil.

  First, after all the ground showing the expansibility below the structure is replaced with high-quality soil, the structure is constructed directly in the form of foundation support. Alternatively, after all the ground exhibiting expansibility is solidified with cement or lime, the structure is directly constructed in a basic support form.

  Secondly, piles are built up to a high-quality ground support layer that does not exhibit expansibility, and this pile resists the lifting force during the expansion of the ground so that no harmful deformation occurs in the structure. (For example, refer to Patent Document 1).

  Third, lay a jig on the ground surface to absorb (accommodate) the soil on the ground surface that floats when the ground expands into the gap, and cushion the expansion force from directly acting on the structure. The structure is built directly on this jig in the basic support form.

  However, in the first countermeasure for the expanded soil, the entire formation is replaced with high quality soil, or cement and lime are stirred and mixed to solidify, so the construction period increases as the thickness of the formation showing the expandability increases. Will be long and costly. For example, when it is necessary to process a stratum having an expansibility of 3 m or more when constructing a large-scale factory or the like on a plane, the construction period becomes very long and enormous costs are required.

  In addition, in the second countermeasure against expanded soil, by supporting the entire structure with a pile, it is possible to effectively prevent the structure from rising and sinking due to expansion and contraction of the expanded soil, Because it is a major measure, the construction period and costs are significantly increased compared to the direct foundation type that does not rely on piles. This makes it practically impossible to apply to structures such as small and medium-sized buildings.

  Furthermore, in the third countermeasure against the expanded soil, the dedicated jig is expensive, and the dedicated jig cannot be easily obtained depending on the site where the structure is constructed, in particular in the developing countries. , Often not applicable. In addition, installation of a dedicated jig over the entire surface requires a lot of labor and labor, and is difficult to apply to a large-scale factory in a plane.

  On the other hand, the applicant of the present application spreads gravel on the expansive ground, forms a groove (recess) in the expansive ground, and fills the gravel with a buffer layer / expansion suppression layer. A patent application has already been filed for the foundation structure for countermeasure against inflatable ground. According to this inflatable ground countermeasure foundation structure, it is possible to take measures against the expanded soil of the structure at a lower cost than in the past.

JP 2008-174936 A

  On the other hand, the above-mentioned foundation structure for inflatable ground countermeasures by the applicant of the present application can take measures against the inflated soil of the structure at a lower cost than the conventional structure, and it can be confirmed that it is a highly reliable inflatable soil countermeasure. However, in order to adopt it at the realization site, it is necessary to establish a method for confirming the effect, in other words, a construction management method.

  In view of the above circumstances, the present invention can verify the effect of the foundation structure for inflatable ground countermeasures on a trial basis, and a method for confirming the effect of the foundation structure for inflatable ground countermeasures to realize a highly reliable countermeasure. The purpose is to provide.

  In order to achieve the above object, the present invention provides the following means.

  The effect confirmation method of the foundation structure for inflatable ground countermeasure of the present invention is a method for confirming the effect of the foundation structure for inflatable ground countermeasure constructed by laying a granular material on the surface of the ground exhibiting the expansibility, A test specimen is manufactured by laminating a glass bead layer made of glass beads simulating the granular material on an expanded soil obtained from a ground exhibiting expansibility, and the test specimen is constrained on the side of the test specimen. Is immersed in water, and a loading pressure is applied to the test body stepwise from above to obtain a loading pressure at which the height of the test body is the same as the initial height before loading, and the loading pressure is defined as an expansion pressure. It is characterized by doing.

  The method for confirming the effect of the foundation structure for inflatable ground countermeasure according to the present invention is a foundation structure for inflatable ground countermeasure constructed by forming a recess in the surface of the ground exhibiting an expandability and filling the recess with a granular material. The test body is manufactured by sandwiching a glass bead layer made of glass beads simulating the granular body with expanded soil obtained from a ground exhibiting expansibility, and the side of the test body. The test body is immersed in water in a constrained state, and a load pressure is applied to the test body stepwise from above to obtain a load pressure at which the height of the test body is the same as the initial height before loading. The loading pressure is an expansion pressure.

  According to the method for confirming the effect of the foundation structure for inflatable ground according to the present invention, the effect of the foundation structure for inflatable ground countermeasure can be confirmed on a trial basis, and a highly reliable inflatable ground countermeasure can be realized. It becomes possible.

It is a figure showing the foundation structure for inflatable ground measures concerning a 1st embodiment of the present invention. It is a figure which shows the method to measure the expansion pressure by the extract | collected expanded soil in the effect confirmation method of the foundation structure for expansible ground measures concerning 1st Embodiment of this invention. It is a figure which shows the effect confirmation method of the foundation structure for expansible ground measures concerning 1st Embodiment of this invention. Using the method for confirming the effect of the foundation structure for inflatable ground countermeasures according to the first embodiment of the present invention, the effect of the granular material of the foundation structure for inflatable ground countermeasures according to the first embodiment and the difference in replacement height is confirmed. It is a figure which shows the result. It is a figure which shows the foundation structure for expansive ground measures concerning 2nd Embodiment of this invention. It is a figure which shows the method of manufacturing the test body used with the effect confirmation method of the foundation structure for expansible ground measures concerning 2nd Embodiment of this invention. It is a figure which shows the effect confirmation method of the foundation structure for expansive ground measures concerning 2nd Embodiment of this invention. Using the method for confirming the effect of the foundation structure for inflatable ground countermeasures according to the second embodiment of the present invention, the effect of the granular material of the foundation structure for inflatable ground countermeasures according to the second embodiment and the difference in groove width was confirmed. It is a figure which shows a result.

  Hereinafter, with reference to FIG. 1 to FIG. 4, a method for confirming the effect of the foundation structure for inflatable ground countermeasure according to the first embodiment of the present invention will be described.

  Here, in the present embodiment, a building is formed on an expandable soil (a ground exhibiting expansibility) containing expansive clay minerals such as montmorillonite, which exists widely in arid and semi-arid areas such as Southeast Asia, Africa, and the Middle East. In particular, the present invention relates to a method for confirming the effect of the foundation structure for inflatable ground countermeasures for constructing such a structure.

  Further, in the present embodiment, as shown in FIG. 1, the surface of the expandable ground 1 is replaced with a crushed stone (granular body) 2a such as limestone, and the buffer layer 2 (and the expansion suppressing layer 3 such as a concrete layer) is replaced. The present invention relates to a method for confirming the effect of the foundation structure A for inflatable ground countermeasures that is formed and reduces the influence of the inflatable ground 1 on the floor slab and the like.

  In the inflatable ground countermeasure base structure A of the present embodiment, the inflatable ground 1 expands and the expansion pressure can be absorbed and reduced by the buffer layer 2 (and the expansion suppression layer 3). The expansion pressure can be prevented from acting on the supported superstructure.

  The effect confirmation method of the foundation structure A for inflatable ground countermeasures of this embodiment for confirming the effect of such inflatable ground countermeasures simulates the actual inflated soil collected from the inflatable ground 1 and crushed stone (granular material). It is a laboratory test method using the glass beads, and is for grasping the influence on the floor and the foundation from the expansion amount and the expansion pressure obtained by the test.

  Specifically, in the method for confirming the effect of the inflatable ground countermeasure foundation structure A of the present embodiment, first, the expansion characteristics (expansion amount and expansion pressure) of the expandable ground 1 are measured according to ASTM D4546-96 (Standard Test Methods for Obtained according to One-Dimensional Swell or Settlement Potential of Cohesive Soils, Method A).

  In the expansion property acquisition process of the expandable ground, a specimen having a predetermined size, for example, a diameter of 5 cm and a height of 2 cm, is cut out from a sample collected from the actual expandable ground 1 (sample collected without disturbance). In addition, the test body used by a post process is cut out similarly.

  As shown in FIG. 2A, the test body 4 is set in a metal-made cylindrical container 5 whose side can be restrained, and the container 5 is installed in a container-like cell 6. Then, a loading means 7 having, for example, a loading plate and a piston is installed on the upper part of the test body 4 in the container 5, and a very small load (for example, about 5 kPa) P 1 is applied to the test body 4 by the loading means 7. Load it.

  As shown in FIG. 2 (b), while maintaining the state where the load P1 does not change, water W is put into the cell 6 and the test body 4 is immersed in the water W together with the container 5, and the test body 4 of the expanded soil 1 is obtained. The expansion is promoted, and at the same time, the displacement at the displacement measuring point of the loading means 7 is read. Thereby, the amount of expansion (Free Swell) (%) at extremely low pressure is acquired.

  As shown in FIG. 2 (c), loads P1, P2, P3,... At this time, the expanded soil specimen 4 contracts due to compaction and the height decreases. The loading pressure is applied in stages until the height of the test body 4 becomes lower than the initial height, and the loading pressure at which the height of the test body 4 becomes the same as the initial height is obtained. ).

  Next, as shown in FIG. 3A, a glass bead simulating a crushed stone (granular material) 2a is set in a cylindrical container 5 made of metal that can be restrained on the side. 8 a is placed in the container 5, and the glass bead layer 8 is laminated on the test body 4. And the loading means 7 is installed in the upper part of the glass bead layer 8 in the container 5, The very small load (for example, about 5 kPa) P1 is loaded to the glass bead layer 8 and the test body 4 by this loading means 7. FIG.

  As shown in FIG. 3 (b), while maintaining the state in which the load P1 does not change, water W is put into the cell 6 and the glass bead layer 8 and the test body 4 are immersed in the water W together with the container 5, and the expanded soil 1 The expansion of the test body 4 is promoted, and at the same time, the displacement of the displacement measuring point of the loading means 7 is read. Thereby, the amount of expansion (Free Swell) (%) at extremely low pressure is acquired.

  As shown in FIG. 3C, the loads P1, P2, P3,... At this time, the expanded soil specimen 4 and the glass bead layer 8 shrink due to compaction, and the height decreases. The loading pressure is applied stepwise until the height of the specimen (test specimen) 9 composed of the specimen 4 and the glass bead layer 8 becomes lower than the initial height, and the height of the specimen 9 becomes the same as the initial height. The loading pressure is obtained, and this loading pressure is defined as an expansion pressure (Swelling Pressure).

  Moreover, in order to confirm the effect of the size of the crushed stone 2a and the effect of the thickness of the buffer layer 2, the above loading test is performed using the diameter of the glass beads 8a and the thickness of the glass bead layer 8 as parameters. In this embodiment, for example, glass beads 8a having a diameter of 1 mm, 2 mm, and 3 mm (3 levels) are used, and the above-mentioned loading is repeated by changing the thickness of the glass bead layer 8 to 10 mm, 20 mm, and 30 mm (3 levels). The test is performed and the loading pressure (expansion pressure) in each test case is obtained.

  And when the diameter of the glass bead 8a is changed, and when the thickness of the glass bead layer 8 is changed, the amount of expansion at an extremely low pressure (Free Swell) and the expansion pressure (Swelling Pressure) obtained by the loading test Seeking a relationship. This relationship makes it possible to quantify and confirm the effect of the inflatable ground countermeasure foundation structure A of the present embodiment. In other words, it is possible to determine the specifications of the inflatable ground countermeasure foundation structure A based on the test results.

  Here, 18 specimens 4 were prepared from the expanded soil sample collected from the expandable ground 1, 9 without countermeasures, and the remaining 9 with countermeasures (for expansible ground countermeasures of this embodiment) The result of acquiring the expansion characteristics in the state of the foundation structure A) and confirming the effect of the countermeasure work will be described.

FIG. 4 shows the test results.
In this figure, the vertical axis represents the amount of expansion obtained by the test, and the horizontal axis represents the expansion pressure. In addition, one plot is a set of results obtained from one specimen 4, and the filled marks indicate the expansion characteristics when there is no countermeasure work, and the white marks indicate the expansion characteristics when there is a countermeasure work.

  First, while the expansion characteristics of the expansive ground 1 used are about 2.5 to 4% in terms of expansion and about 55 to 125 kPa in terms of expansion pressure, an upper replacement type countermeasure work is simulated using glass beads 8 The values obtained by the test method (the method for confirming the effect of the foundation structure for inflatable ground countermeasures of this embodiment) are an expansion amount of 0 to 2.5% and an expansion pressure of 10 to 75 kPa, and the effect by the countermeasure work is sufficiently obtained. It was proved that it can be confirmed.

The influence which it has on the countermeasure effect of the glass bead diameter can be confirmed from FIG.
That is, the larger the glass bead diameter, the smaller the expansion coefficient and the expansion pressure, and it was proved that the larger the diameter of the crushed stone (granular body), the more effective.

FIG. 4B shows the result of comparing the same data with the glass bead thickness.
From this figure, it is confirmed that even if the glass bead thickness is different from 10 mm, 20 mm, and 30 mm, a significant difference cannot be obtained in the expansion characteristics, and it is confirmed that the effect is not increased even if the buffer layer 2 is thickened. It was. That is, it can be said that if the buffer layer 8 has a thickness several times the particle diameter, the effect is exhibited.

  As described above, when the diameter of the glass bead 8a is changed and the thickness of the glass bead layer 8 is changed by using the method for confirming the effect of the foundation structure for inflatable ground according to the present embodiment, the expansion is performed at an extremely low pressure. By determining the relationship between the amount (Free Swell) and the expansion pressure (Swelling Pressure) obtained in the loading test, the effect of the foundation structure A for inflatable ground countermeasures can be quantified and confirmed. Based on this, it was proved that the specifications of the foundation structure A for inflatable ground measures can be determined.

  Therefore, according to the method for confirming the effect of the foundation structure for inflatable ground countermeasures of the present embodiment, the effect of the countermeasure for the inflatable ground of the upper replacement type can be confirmed experimentally, and the highly reliable countermeasure for the inflatable ground Can be realized.

  Next, with reference to FIGS. 5 to 8, a method for confirming the effect of the foundation structure for inflatable ground countermeasures according to the second embodiment of the present invention will be described.

  Here, in this embodiment, as shown in FIG. 5, a groove (recess) 10 is provided in the expansible ground 1, and a crushed stone (granular material) 2 a such as limestone is filled in the groove to provide a buffer layer 2 ( And an expansion suppression layer 3) such as a concrete layer, and a method for confirming the effect of the foundation structure B for the expansible ground countermeasure that reduces the influence of the expansive ground 1 on the floor slab and the like.

  In the inflatable ground countermeasure base structure B of the present embodiment, the inflatable ground 1 expands and the expansion pressure can be absorbed and reduced by the buffer layer 2 (and the expansion suppression layer 3). The expansion pressure can be prevented from acting on the supported superstructure.

  The method for confirming the effect of the inflatable ground countermeasure foundation structure B of this embodiment for confirming the effect of such an inflatable ground countermeasure is the same as in the first embodiment, with the actual inflated soil collected from the inflatable ground 1 and This is a laboratory test method using glass beads simulating crushed stone (granular material), and is used to grasp the influence on the floor and foundation from the expansion amount and expansion pressure obtained by the test. Therefore, in this embodiment, the same code | symbol is attached | subjected with respect to the structure similar to 1st Embodiment, and the detailed description is abbreviate | omitted.

  In the method for confirming the effect of the inflatable ground countermeasure foundation structure B according to the present embodiment, as shown in FIG. 6, the expanded soil is put into a cylindrical molding container 11 and formed into a disk shape, and then the disk-shaped expanded soil. The molded body 12 is taken out from the molding container 11, and the central portion thereof is cut in the diameter direction with a predetermined width dimension.

  The cut portion 13 is removed, a pair of substantially semicircular test pieces 14 and 15 in plan view are formed, and returned to the molded container 11 so that a groove (recess) 16 is formed at the center.

  Then, the groove 16 formed between the pair of test pieces 14 and 15 is filled with the glass beads 8a, so that the glass bead layer 8 is sandwiched between the expanded soils, and the expansive ground of the grooving replacement type of the present embodiment. The test body 17 of the basic structure B for countermeasures is manufactured.

  Next, as shown to Fig.7 (a), the test body 17 is set in the metal-made cylindrical container 5 which can restrain a side. And the loading means 7 is installed in the upper part of the test body 17 in the container 5, and a very small load (for example, about 5 kPa) P1 is loaded on the test body 17 by this loading means 7.

  As shown in FIG. 7 (b), while maintaining the state where the load P1 does not change, the water W is put into the cell 6 and the test body 17 is immersed in the water W together with the container 5, and the expansion of the expanded soil of the test body 17 is expanded. At the same time, the displacement of the displacement measuring point of the loading means 7 is read. Thereby, the amount of expansion (Free Swell) (%) at extremely low pressure is acquired.

  As shown in FIG. 7C, the loads P1, P2, P3,... At this time, the test body 17 contracts due to compaction, and the height decreases. The loading pressure is applied stepwise until the height of the test body 17 becomes lower than the initial height, the loading pressure at which the height of the test body 17 becomes the same as the initial height is obtained, and this loading pressure is determined as the expansion pressure (Swelling Pressure). ).

  Moreover, in order to confirm the effect of the size of the crushed stone 2a and the effect of the thickness of the buffer layer 2, the above loading test is performed using the diameter of the glass beads 8a and the thickness of the glass bead layer 8 as parameters. In the present embodiment, for example, glass beads 8a having diameters of 1 mm, 2 mm, and 3 mm (3 levels) are used, and the groove width (width of the glass bead layer 8) is further changed by 5 mm, 10 mm, and 15 mm (3 levels). The above loading test is performed, and the loading pressure (expansion pressure) in each test case is obtained.

  And when the diameter of the glass bead 8a is changed, and when the groove width of the glass bead layer 8 is changed, the amount of expansion at an extremely low pressure (Free Swell) and the expansion pressure (Swelling Pressure) obtained in the loading test Seeking a relationship. This relationship makes it possible to quantify and confirm the effect of the inflatable ground countermeasure foundation structure B of the present embodiment. In other words, it is possible to determine the specifications of the foundation structure B for inflatable ground countermeasures based on the test results.

  Here, 23 specimens were prepared from the expanded soil sample collected from the expansive ground 1, 14 were in a state without countermeasures, and the remaining nine were countermeasures (the foundation for inflatable ground countermeasures of this embodiment) The result of acquiring the expansion characteristics in the state of the structure B) and confirming the effect of the countermeasure work will be described.

FIG. 8 shows the test results.
In this figure, the vertical axis represents the amount of expansion obtained by the test, and the horizontal axis represents the expansion pressure. Further, one plot is a set of results obtained from one specimen, and a filled mark indicates an expansion characteristic when there is no countermeasure work, and a white mark indicates an expansion characteristic when there is a countermeasure work.

  First, while the expansive property of the expansive ground 1 used is about 3 to 5% in terms of expansion and about 100 to 175 kPa in terms of expansion pressure, a test simulating a groove replacement type countermeasure using glass beads 8 The value obtained by the method (the method for confirming the effect of the foundation structure for inflatable ground countermeasures of this embodiment) is an expansion amount of 2 to 3.5% and an expansion pressure of 20 to 115 kPa, and the effect of the countermeasure work can be sufficiently confirmed. Has been demonstrated.

  From FIG. 8A, the influence of the glass bead diameter on the countermeasure effect could not be confirmed.

FIG. 8B shows the result when the width of the groove is changed.
From this figure, the influence of the groove width on the countermeasure effect is not clearly recognized. That is, if a slight expansion in the horizontal direction can be allowed, it can be said that the influence on the floor in the vertical direction can be reduced.

  Thus, using the method for confirming the effect of the foundation structure for inflatable ground according to the present embodiment, the amount of expansion at extremely low pressure when the diameter of the glass bead 8a is changed and the width of the groove is changed (Free Swell ) And the expansion pressure (Swelling Pressure) obtained by the loading test, it was proved that the effect of the foundation structure B for inflatable ground countermeasures can be confirmed.

  Therefore, according to the method for confirming the effect of the foundation structure for inflatable ground countermeasures of the present embodiment, the effect of the countermeasure for inflatable ground of the grooving replacement type can be confirmed on a trial basis, and the highly reliable countermeasure for the inflatable ground. Can be realized.

  As described above, the first and second embodiments of the method for confirming the effect of the foundation structure for inflatable ground countermeasure according to the present invention have been described. However, the present invention is not limited to the above-described embodiments, and does not depart from the gist thereof. The range can be changed as appropriate.

1 Ground showing expansibility (expanded soil)
2 Buffer layer 2a Crushed stone (granular)
DESCRIPTION OF SYMBOLS 3 Expansion suppression layer 4 Test body 5 Container 6 Cell 7 Loading means 8 Glass bead layer 8a Glass bead 9 Specimen (test body)
10 groove (recess)
DESCRIPTION OF SYMBOLS 11 Molding container 12 Molded body 13 Cutting part 14 Test piece 15 Test piece 16 Groove 17 Test body A Foundation structure B for inflatable ground countermeasures Base structure W for inflatable ground countermeasures Water

Claims (2)

It is a method for confirming the effect of a foundation structure for inflatable ground countermeasures constructed by laying granular materials on the surface of the ground exhibiting expansibility,
A test body is manufactured by laminating a glass bead layer made of glass beads simulating the granular material on the expanded soil obtained from the ground showing expandability,
The test body is immersed in water in a state where the side of the test body is constrained, and loading pressure is applied to the test body stepwise from above, and the height of the test body is the same as the initial height before loading. A method for confirming the effect of the foundation structure for inflatable ground countermeasures, characterized in that a loading pressure is obtained and the loading pressure is used as an expansion pressure. It is a method for confirming the effect of the foundation structure for inflatable ground measures constructed by forming a recess on the surface of the ground showing expandability and filling the recess with a granular material,
A test body is manufactured so as to sandwich a glass bead layer made of glass beads simulating the granular body with expanded soil obtained from a ground exhibiting expansibility,
The test body is immersed in water in a state where the side of the test body is constrained, and loading pressure is applied to the test body stepwise from above, and the height of the test body is the same as the initial height before loading. A method for confirming the effect of the foundation structure for inflatable ground countermeasures, characterized in that a loading pressure is obtained and the loading pressure is used as an expansion pressure.