JP2015055147A - Underground base isolation wall structure and construction method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an underground base isolation wall structure excellent in long-term stability and workability, and a construction method for the same.SOLUTION: A structure of a continuous wall-like underground base isolation wall 16 is provided between peripheral ground 12 and a structure, and made of a clay-based material. The underground base isolation wall 16 is a column row-like underground base isolation wall that comprises a plurality of vertically-long impervious bags 20 installed adjacently in a lateral direction by being inserted into a ditch 18 excavated in ground 12, and the clay-based material 22 with water-absorption expandability, infilled into the bag 20 in the state of having predetermined softness.

Description

  The present invention relates to an underground seismic isolation wall structure constituting a ground displacement absorbing base isolation structure for reducing stress on underground structures such as open tunnels during an earthquake and a method for constructing the same.

  Conventionally, as an underground seismic isolation wall for the purpose of reducing stress during earthquakes to underground structures such as open tunnels, it has been common to install continuously in the extending direction in contact with the underground structure If it is this installation position, it can be constructed simultaneously with the construction of the underground structure. For example, Patent Document 1 proposes a ground displacement absorbing method in which polymer improved soil is cast as an underground seismic isolation wall for the purpose of reducing stress on underground structures during an earthquake.

  On the other hand, Non-Patent Document 1, for example, discloses an underground seismic isolation wall for an underground structure such as an open-cut tunnel that is not continuously installed in the extending direction of the underground structure. In this nonpatent literature 1, the vertical cylinder-shaped polymer improvement soil is intermittently arrange | positioned in the ground along the underground structure.

However, the above conventional underground seismic isolation wall has the following problems.
That is, in the construction method for placing the polymer improved soil as disclosed in Patent Document 1, the polymer seismic isolation material is greatly compressed and deformed due to the influence of normal earth pressure and the like. Therefore, the wall thickness of the predetermined underground seismic isolation wall set at the time of construction cannot maintain the initial wall thickness for a long time, and there is a concern that the seismic isolation wall may be crushed in some cases. Such a change in the thickness of the base isolation wall is caused by a decrease in the displacement absorption performance of the polymer base isolation wall, and the effect of absorbing the ground displacement by the underground base isolation wall is not fully exhibited. There was a problem that the reduction effect was reduced.

  As a countermeasure, Non-Patent Document 1 is considered in which the underground seismic isolation wall is intermittently arranged so as to avoid the continuous arrangement along underground structures such as open tunnels. However, in the seismic isolation walls that are not arranged continuously, the surrounding ground and the structure are connected by soil, so that the seismic isolation effect of sufficiently absorbing the original displacement is significantly reduced. there were.

  Moreover, since the polymer material is dissolved in water in the ground where the groundwater level exists, there is a problem that the construction is not easy. Furthermore, although a predetermined reinforcing agent must be added to the polymer seismic isolation material, there is a problem that an expensive reinforcing agent is required for environmental considerations and costs are increased.

  In this way, when an underground seismic isolation wall is provided along an underground structure such as an open-cut tunnel, it can sufficiently resist the earth pressure acting on the underground isolation wall and ensure long-term stability. On the other hand, in order to exert the seismic isolation effect, it is desirable that the material has low rigidity, and there is a need for an underground seismic isolation wall that provides a good balance between the two. There was room for.

  As a structure for solving such problems, one of the inventors of the present application has already provided the ground displacement absorption seismic isolation structure of Patent Document 2. This structure can ensure the long-term stability of the underground seismic isolation wall and can reduce the stress on underground structures such as open tunnels during an earthquake. (1) to (4) ).

(1) As shown in FIG. 8, a wall-shaped underground seismic isolation wall 3 (underground wall) continuous with a water-absorbing swelling clay-based material is installed between the surrounding ground 1 and the underground structure 2. .
(2) The underground wall is made of a mixture of bentonite and water, or a mixture of bentonite and aggregates (soil materials such as gravel or artificial materials that are difficult to change for a long time such as glass beads) and water.
(3) The area | region filled with the material which consists of a mixture of the bentonite and water in the clay earth material which comprises an underground wall is 300-1200 kg / m < ³ > in a bentonite dry density.
(4) In a material composed of a mixture of bentonite, aggregate, and water in the viscous earth-based material constituting the underground wall, an area filled with bentonite and water (the bentonite filling the area excluding the aggregate area and The water mixture) is 300-1200 kg / m ³ in terms of bentonite dry density.

  On the other hand, one of the inventors of the present application has already provided the underground wall construction method of Patent Document 3 in relation to the above-mentioned Patent Document 2. In this underground wall construction method, not only the material containing 100% bentonite but also “a bentonite material adjusted to have a predetermined bentonite effective dry density, or a material of a mixture of bentonite and aggregate in a bag body. And a step of filling the stuffed material between the hollow spaces.

  On the other hand, a structure and a construction method are known in which a wall structure that absorbs vibration is built in the ground to suppress propagation of ground vibration to the building frame (see, for example, Patent Document 4).

JP 2006-112182 A JP 2012-031662 A JP 2012-031663 A Japanese Patent No. 4915580

Tsuyoshi Murono, Masaru Tateyama, Fumi Kiryu, Shosuke Kobayashi, “Reinforcement of existing excavated tunnels with polymer seismic isolation walls”, Foundation work, 2007.3, P69-71

  In the ground displacement absorption seismic isolation structure described in Patent Document 2 described above, water-absorbing expansive clay (for example, bentonite) that exhibits a swelling pressure (water-absorbing expansion pressure) that can resist soil pressure is used while being a continuous underground wall. Thus, there was a feature in maintaining the structural form of the underground wall. However, there are the following problems (1) to (4) regarding this function.

(1) If the groundwater seepage flow of the surrounding ground is dominant, there is a concern that the soil material (bentonite clay material) constituting the underground wall will be washed away into the gap between the surrounding ground although the amount of particles is small. .
(2) When excavating a ditch or hole to construct an underground wall, the excavated space is often replaced with mud so that the ground wall does not collapse. If a water-swellable clay material is installed in the underground wall construction space filled with muddy water, there is a concern that the material will absorb water during the construction process, causing density changes and deformation, making it difficult to build the intended material specifications. The
(3) When the groundwater level of the surrounding ground is low, the ground near the ground surface is dry, and the underground wall material also undergoes volume reduction, density increase, and rigidity increase due to drying, resulting in deformation during an earthquake. The relaxation effect is impaired.
(4) When the electrolyte concentration of the groundwater in the surrounding ground is large, there is a concern that the groundwater with a high electrolyte concentration will infiltrate into the underground wall material from the ground and the water absorption and expansion performance of the material will deteriorate. It was.

  Here, the concern regarding the drying of the above problem (3) and the concern regarding the water quality of the problem (4) will be described more specifically.

For example, the above Patent Document 2 shows the following example. That is, since the area filled with bentonite and water is in the range of 300 to 1200 kg / m ³ in terms of the bentonite effective dry density, the density range shown in FIG. As shown in 9), the water absorption swelling pressure is 0.03 to 0.3 MPa. Therefore, assuming that the underwater mass of the ground is about 1 g / cm ³ and the lateral earth pressure is 1 times the earth covering pressure, it can withstand earth pressure up to a depth of 30 m. It can be made more effective by constructing by adjusting the density of the material appropriately according to the installation depth of the underground seismic isolation wall.

Here, groundwater exists in the gap between the ground around the underground wall. In Japan, the groundwater level usually exists up to the surface of the ground, and the quality of groundwater is generally freshwater. There is little need to consider the impact on the structural stability of clay.
However, depending on groundwater conditions, the following problems may be a concern.

(Groundwater condition 1)
If the surrounding ground is not completely dry, the water retention ability of bentonite is maintained, so that the thickness and material density of the underground wall can be maintained for a long time. However, if the groundwater level is significantly lower than the ground surface and the clay that makes up the underground wall may dry and shrink, the underground wall will dry and shrink, the thickness will decrease, and the rigidity of the underground wall will be reduced. Increases the displacement absorption capacity, resulting in a decrease in seismic isolation performance.

(Groundwater condition 2)
When the electrolyte concentration of the groundwater quality is high, for example, when the water quality is close to seawater, such as a landfill near the coast, the water absorption expansion pressure decreases as shown in FIG. As a result, the water absorption expansion pressure that can resist the earth pressure acting on the underground wall cannot be exerted, the underground wall is deformed by the earth pressure, the thickness is reduced, and the pore water is drained to remove the underground wall. The density of the constituent clay increases and the rigidity increases. When such a phenomenon occurs, the capacity for absorbing the displacement of the underground wall decreases, and the seismic isolation performance decreases.

  In the above-mentioned Patent Document 2, FIG. 2 shows the relationship between the bentonite effective dry density and the swelling pressure. This relationship is a characteristic when the pore water is pure water. FIG. 9 shows FIG. 2 described in Patent Document 2. On the other hand, FIG. 10 shows the relationship between the effective clay density (dry density) and the water absorption expansion pressure (swelling pressure) of bentonite, which is a water-absorbing clay, when the pore water is pure water and when the NaCl concentration is 1 wt%. It is a comparison. The swelling property of bentonite is due to the osmotic action of the surroundings by the presence of cations that are taken in by electric force between the layered structure of clay mineral called montmorillonite, which is the main component of bentonite. It is exhibited by water absorption and expansion due to the characteristic of absorbing water molecules from the gaps into the clay mineral crystal layer. Therefore, when the electrolyte concentration of the groundwater in the ground around the underground wall is high, the electrolyte concentration of the pore water of the clay constituting the underground wall also gradually increases, and eventually indicated by arrows in FIG. Thus, the expansion pressure in a pure water environment is reduced to the expansion pressure in an environment with a high electrolyte concentration.

  For this reason, development of a structure that can ensure long-term stability and can be easily constructed for the above problems (1) to (4) in the underground seismic isolation wall of the conventional ground displacement absorption isolation structure is required. It was.

  The present invention disclosed below is similar in structure to that described in Patent Document 4, but as a material filling the bag-like film structure, the softness can be maintained for a long period of time as a soil material. The material can be realized by quantitatively aiming at the characteristics of the material, and since it has water absorption and expandability, it can suppress deformation of the underground wall and increase in density due to lateral earth pressure from the surrounding ground. There is uniqueness in a certain material.

  This invention is made | formed in view of the above, Comprising: It aims at providing the underground seismic isolation wall structure excellent in long-term stability and workability, and its construction method.

  In order to solve the above-mentioned problems and achieve the object, the underground seismic isolation wall structure according to the present invention is a continuous wall-like structure provided between the surrounding ground and the structure and made of clay-based material. It is a structure of underground seismic isolation wall, and the underground seismic isolation wall includes a vertically long water-impervious bag installed adjacent to the lateral direction by inserting it into a groove or hole excavated in the ground. And a columnar underground seismic isolation wall comprising a clay-based material having a water-swelling property filled in the bag with a predetermined softness.

  Another underground seismic isolation wall structure according to the present invention is characterized in that, in the above-described invention, the bags are arranged in a staggered manner in the lateral direction.

  Moreover, the other underground seismic isolation wall structure which concerns on this invention is further provided with the connection member which connects between the said adjacent bags in the invention mentioned above.

  Further, another underground seismic isolation wall structure according to the present invention is the above-described invention, the electrolyte concentration is less than 1 wt% with respect to the clay-based material having water absorbability and filled in the bag, and the surrounding ground. It is characterized in that an aqueous solution lower than the groundwater is always supplied from the ground side.

  Further, the construction method of the underground seismic isolation wall structure according to the present invention is a construction of a continuous wall-shaped underground seismic isolation wall structure that is provided between the surrounding ground and the structure and is made of clay-based material. In this method, a vertically long water-impervious bag is inserted into a groove or hole excavated in the ground, and then a clay-based material having water-absorbing expansibility is placed in the bag with a predetermined softness. The bag is filled and inflated so that the outer surface of the bag is in close contact with the wall surface of the groove or hole, and then, in the same manner, it is long in another vertical direction so as to be adjacent to the bag in the lateral direction. A water-impervious bag is inserted and installed in the groove or hole, and the bag is filled with a clay-based material having water-absorbing expansibility with a predetermined softness and inflated, and the groove or hole is filled. By repeatedly bringing the outer surface of the bag into close contact with the wall surface, the underground seismic isolation wall is constructed in a column shape And wherein the Rukoto.

  Moreover, the construction method of another underground seismic isolation wall structure according to the present invention is characterized in that, in the above-described invention, the bags are staggered in the lateral direction.

  Moreover, the construction method of the other underground seismic isolation wall structure according to the present invention is the above-described invention, wherein the clay-based material having water absorbability is filled stepwise in order from the bottom of the bag. Inserting the portion to be filled into the bag into the groove or hole, and filling the portion of the inserted bag with the clay-based material stepwise, and It is characterized by being installed in the hole.

  Further, another underground seismic isolation wall structure construction method according to the present invention includes a plurality of the bags connected in a lateral direction via a membrane-like connecting member in the above-described invention, In a state where the clay-based material is not filled, a sheet-shaped water-impervious sheet is installed in the groove, and the bag is filled with a clay-based material having a water-absorbing expansibility with a predetermined softness. Features.

  Moreover, the construction method of another underground seismic isolation wall structure according to the present invention is the above-described invention, in which the sheet roll formed by rolling the water shielding sheet into a roll shape is inserted into the groove, and then from the sheet roll. A plurality of the bags are installed in the groove by feeding out the water shielding sheet in a lateral direction.

  In addition, in the above-described invention, the method for constructing another underground seismic isolation wall structure according to the present invention is such that the electrolyte concentration is less than 1 wt% with respect to the clay-based material having water absorbability that is filled in the bag. It is characterized by always supplying an aqueous solution lower than the groundwater of the surrounding ground from the ground side.

  According to the underground seismic isolation wall structure according to the present invention is a continuous wall-shaped underground seismic isolation wall structure that is provided between the surrounding ground and the structure and is made of a clay-based material, The underground seismic isolation wall has a vertically long water-impervious bag that is installed in the lateral direction by inserting it into a groove or hole excavated in the ground, and a predetermined softness in the bag. It is a columnar underground seismic isolation wall provided with a clay-based material having a water-absorbing property filled in a closed state. For this reason, by repeating the work of inserting a long water-impervious bag in the vertical direction one by one into the excavated groove or hole and filling the bag with a clay-based material having water-absorbing expansibility, It is possible to easily construct a columnar underground seismic isolation wall in which a plurality of bags that are long in the direction are adjacent to each other in the horizontal direction. In addition, since the bag is water-impervious, the clay-based material filled in the bag is affected by mud water in the excavated trench or hole, and by the seepage flow, water level and water quality of the surrounding groundwater. Absent. Therefore, the underground seismic isolation wall structure excellent in long-term stability and workability can be provided.

  In addition, according to another underground seismic isolation wall structure according to the present invention, since the bags are arranged in a staggered manner in the lateral direction, in addition to the above effects, a columnar underground seismic isolation wall arranged in a staggered manner is obtained. There is an effect that can be.

  In addition, according to another underground seismic isolation wall structure according to the present invention, since it further includes a connecting member that connects between the adjacent bags, in addition to the above effect, the connecting member is connected to the excavated groove. A plurality of bags are inserted and installed in a lump, and each bag is filled with a clay-based material having water-absorbing expansibility, so that a plurality of vertically long bags are adjacent to each other in the horizontal direction. The effect is that the underground seismic isolation wall can be easily constructed.

  Further, according to another underground seismic isolation wall structure according to the present invention, with respect to the clay-based material having water-absorbing expansibility filled in the bag, the electrolyte concentration is less than 1 wt% from the groundwater of the surrounding ground. Since a low aqueous solution is always supplied from the ground side, the water-swellable clay-based material filled in the bag is always saturated with water from the aqueous solution and the water retention capability is maintained. For this reason, the clay-based material can be maintained in a constant state for a long period of time with the diameter of the column of the columns formed by the bags long in the vertical direction and the density of the constituent material thereof without drying and shrinking, and the rigidity can be kept small. As a result, the displacement absorption capacity of the columnar underground seismic isolation wall is maintained, so there is no risk of a decrease in the seismic isolation performance, and it is possible to provide an underground seismic isolation wall structure with excellent long-term stability. There is an effect that can be done.

  Further, according to the construction method of the underground seismic isolation wall structure according to the present invention, the structure of a continuous wall-shaped underground seismic isolation wall provided between the surrounding ground and the structure and made of clay-based material In this construction method, a vertically long water-impervious bag is inserted into a groove or hole excavated in the ground, and then a clay-based material having a water-absorbing expansive property is placed in the bag. Fill and inflate in a soft state to bring the outer surface of the bag into close contact with the wall surface of the groove or hole, and then another longitudinal direction in a similar manner so as to be laterally adjacent to the bag A long water-impervious bag is inserted into the groove or hole, and a clay-based material having a water-absorbing expansibility is filled in the bag with a predetermined softness to inflate the groove or hole. Repeating close contact of the outer surface of the bag with the wall surface of the hole, the underground seismic isolation wall is columnar To build. For this reason, it is possible to easily construct a columnar underground seismic isolation wall in which a plurality of bags long in the vertical direction are adjacent to each other in the horizontal direction. In addition, since the bag is water-impervious, the clay-based material filled in the bag is affected by mud water in the excavated trench or hole, and by the seepage flow, water level and water quality of the surrounding groundwater. Absent. Therefore, the underground seismic isolation wall structure excellent in long-term stability and workability can be provided.

  Moreover, according to the construction method of another underground seismic isolation wall structure according to the present invention, since the bags are arranged in a staggered manner in the lateral direction, in addition to the above effects, the columnar underground seismic isolation in a staggered manner There is an effect that a wall can be obtained.

  Moreover, according to the construction method of another underground seismic isolation wall structure according to the present invention, the clay-based material having water-absorbing expansibility is filled stepwise from the bottom in the bag. The bag is placed in the groove or hole by repeatedly inserting the portion to be filled into the bag into the groove or hole, and filling the inserted portion of the bag with the clay-based material stepwise. Therefore, in addition to the above effects, the clay-based material filled in the bag can be constructed with a density according to the depth.

  Moreover, according to the construction method of the other underground seismic isolation wall structure according to the present invention, it has a plurality of the bags connected laterally via a membrane-like connecting member, and the clay is in the bag. The above-mentioned effect is obtained by installing a water-proof sheet in the form of a sheet in a state where the system material is not filled in the groove and filling the bag with a water-swellable clay-based material having a predetermined softness. In addition, a plurality of bags connected by connecting members to the excavated groove are installed in a lump and installed, and each bag is filled with a clay-based material having water-absorbing expansibility, so that a long bag in the vertical direction can be There is an effect that it is possible to easily construct a columnar underground seismic isolation wall that is adjacent to each other in the direction.

  Moreover, according to the construction method of the other underground seismic isolation wall structure according to the present invention, after inserting the sheet roll formed by winding the water shielding sheet into a roll shape into the groove, the water shielding from the sheet roll. Since the plurality of bags are installed in the groove by feeding out the sheet in the lateral direction, in addition to the above effect, the plurality of bags provided in the water shielding sheet can be easily disposed over the entire length of the groove. There is an effect.

  Further, according to another underground seismic isolation wall structure construction method according to the present invention, with respect to the clay-based material having a water-absorbing property filled in the bag, the electrolyte concentration is less than 1 wt% and the surrounding ground. Since an aqueous solution lower than the groundwater is constantly supplied from the ground side, the water-swellable clay-based material filled in the bag is always saturated with water from the aqueous solution and the water retention capability is maintained. For this reason, the clay-based material can be maintained in a constant state for a long period of time with the diameter of the column of the columns formed by the bags long in the vertical direction and the density of the constituent material thereof without drying and shrinking, and the rigidity can be kept small. As a result, the displacement absorption capacity of the columnar underground seismic isolation wall is maintained, so there is no risk of a decrease in the seismic isolation performance, and it is possible to provide an underground seismic isolation wall structure with excellent long-term stability. There is an effect that can be done.

FIG. 1 is a front sectional view showing the basic configuration of the underground seismic isolation wall structure according to the present invention. FIGS. 2-1 is a cross-sectional perspective view which shows the process 1 of Example 1 of the underground seismic isolation wall structure which concerns on this invention, and its construction method. FIG. 2-2 is a cross-sectional perspective view showing Step 2 of Example 1 of the underground seismic isolation wall structure and the construction method thereof according to the present invention. FIGS. 2-3 is a cross-sectional perspective view which shows the process 3 of Example 1 of the underground seismic isolation wall structure which concerns on this invention, and its construction method. FIG. 2-4 is a cross-sectional perspective view showing Step 4 of Example 1 of the underground seismic isolation wall structure and the construction method thereof according to the present invention. FIG. 3-1 is a cross-sectional perspective view showing Step 1 of Embodiment 2 of the underground seismic isolation wall structure and the construction method thereof according to the present invention. FIG. 3-2 is a cross-sectional perspective view showing Step 2 of Example 2 of the underground seismic isolation wall structure and the construction method thereof according to the present invention. FIG. 3-3 is a cross-sectional perspective view showing Step 3 of Embodiment 2 of the underground seismic isolation wall structure and the construction method thereof according to the present invention. FIG. 3-4 is a cross-sectional perspective view showing Step 4 of Example 2 of the underground seismic isolation wall structure and the construction method thereof according to the present invention. FIG. 4 is a cross-sectional perspective view showing a third example of the underground seismic isolation wall structure and the construction method thereof according to the present invention. FIG. 5-1 is a cross-sectional perspective view showing Step 1 of Example 4 of the underground seismic isolation wall structure and the construction method thereof according to the present invention. FIG. 5-2 is a cross-sectional perspective view showing Step 2 of Example 4 of the underground seismic isolation wall structure and the construction method thereof according to the present invention. FIG. 5-3 is a cross-sectional perspective view showing Step 3 of Example 4 of the underground seismic isolation wall structure and the construction method thereof according to the present invention. FIG. 5-4 is a cross-sectional perspective view showing Step 4 of Example 4 of the underground seismic isolation wall structure and the construction method thereof according to the present invention. FIG. 5-5 is a cross-sectional perspective view showing Step 5 of Example 4 of the underground seismic isolation wall structure and the construction method thereof according to the present invention. FIG. 5-6 is a cross-sectional perspective view showing Step 6 of Example 4 of the underground seismic isolation wall structure and the construction method thereof according to the present invention. FIGS. 6-1 is a figure which shows the process 1 of Example 5 of the underground seismic isolation wall structure which concerns on this invention, and its construction method, (1) is a top view, (2) is a underground longitudinal cross-sectional view. is there. FIGS. 6-2 is a figure which shows the process 2 of Example 5 of the underground seismic isolation wall structure which concerns on this invention, and its construction method, (1) is a top view, (2) is a underground longitudinal cross-sectional view. is there. 6-3 is a figure which shows the process 3 of Example 5 of the underground seismic isolation wall structure which concerns on this invention, and its construction method, (1) is a top view, (2) is a underground longitudinal cross-sectional view. is there. 6-4 is a figure which shows the process 4 of Example 5 of the underground seismic isolation wall structure which concerns on this invention, and its construction method, (1) is a top view, (2) is a underground longitudinal cross-sectional view. is there. 7-1 is front sectional drawing which shows Example 6 of the underground seismic isolation wall structure which concerns on this invention, and its construction method. FIG. 7-2 is a cross-sectional perspective view showing a modification of the sixth embodiment of the underground seismic isolation wall structure and the construction method thereof according to the present invention. FIG. 8 is a schematic perspective view showing a conventional ground displacement absorbing base isolation structure. FIG. 9 is a diagram showing the relationship between the bentonite effective dry density and the swelling pressure described in FIG. FIG. 10 is a diagram comparing the relationship between the bentonite effective dry density and the swelling pressure when the pore water is pure water and when the NaCl concentration is 1 wt%.

  Embodiments of the underground seismic isolation wall structure and its construction method according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

First, the basic structure of the ground displacement absorption seismic isolation structure which is the premise of the present invention will be described.
As shown in FIG. 1, the ground displacement absorbing base isolation structure 10 is for reducing stress during an earthquake that acts on an underground structure 14 such as an open tunnel provided in the surrounding ground 12. The underground structure 14 is a reinforced concrete structure such as a box culvert, and is constructed to extend in a predetermined direction (a direction perpendicular to the paper surface of FIG. 1) while being embedded in the upper ground 12A. The upper layer ground 12A in which the underground structure 14 is embedded is a soft ground having an elastic wave velocity Vs of, for example, 100 to 200 m / s, and exists on the lower layer ground 12B having an elastic wave velocity Vs of, for example, 300 to 500 m / s. ing.

  Between the underground structure 14 and the upper ground 12 </ b> A of the surrounding ground 12, a continuous wall-shaped underground seismic isolation wall 16 (underground wall) made of a clay-based material having water absorption and expansion properties is installed. . The underground seismic isolation wall 16 has a predetermined wall width D (thickness: see FIG. 1), is disposed in contact with the left and right sides of the underground structure 14, and extends in the extending direction of the underground structure 14. It is a continuous wall-like body. The underground seismic isolation wall 16 is disposed in the upper ground 12 </ b> A, and is provided from the ground surface portion to substantially the same depth as the lower end of the underground structure 14. The underground seismic isolation wall 16 is not limited to being provided over the entire length of the underground structure 14 to be extended, and may be provided partially in the extending direction.

  As a clay-based material constituting the underground seismic isolation wall 16, a mixture of bentonite and water (hereinafter referred to as "first mixture") or a mixture of bentonite, aggregate and water (hereinafter referred to as "second mixture"). Is used. Such a clay-based material has a characteristic that when a stress is repeatedly applied during an earthquake, it absorbs the earthquake energy by hysteresis damping and plastically deforms, and returns to its original state after the earthquake ends.

The region filled with the material comprising the first mixture is 300 to 1200 kg / m ³ in terms of bentonite effective dry density. In the material composed of the second mixture, the region filled with bentonite and water is the bentonite effective dry density (in the case of a material in which bentonite and aggregate are mixed, the density of the bentonite portion that fills the aggregate gap). It is 300 to 1200 kg / m ³ in terms of dry density. In addition, as the aggregate of the second mixture, a soil material such as sand or gravel, or an artificial material such as glass beads that hardly deteriorates for a long time can be employed. Further, in the case of the above-mentioned first mixture material that does not contain aggregate, it is bentonite density because it is only bentonite density, but here it is used uniformly as “bentonite effective dry density”.

  Further, the wall width D of the underground seismic isolation wall 16 is preferably 0.2 to 2.5 m, and more preferably 0.25 to 1.0 m. In addition, since use of a general construction apparatus is possible, the wall width D is good also as 0.5-1.0m.

The basic action of the ground displacement absorbing base isolation structure 10 having the above configuration will be described.
As shown in FIG. 1, the ground displacement absorbing base isolation structure 10 is constructed as a continuous wall using a clay-based material as the underground seismic isolation wall 16, thereby reducing the stress reduction effect on the underground structure 16. Can be bigger. The clay-based material has, for example, 0.6 times or less rigidity compared to the surrounding upper-layer ground 12A, so that an effect of reducing the shearing force of the underground structure 14 can be obtained, and the deformation of the ground during an earthquake is alleviated. Can exhibit seismic isolation effect.

  When the clay-based material constituting the underground seismic isolation wall 16 is a first mixture of bentonite and water, or a second mixture of bentonite, aggregate, and water, by adjusting the bentonite effective dry density, Since a predetermined swelling pressure can be exhibited, it is possible to secure a reaction force that resists normal earth pressure received from the surrounding ground.

And in the case of the 1st mixture, since the area | region filled with bentonite and water is the range of 300-1200 kg / m < ³ > by the value of a bentonite effective dry density, if it is this density range, it will be shown in FIG. Thus, the water absorption swelling pressure becomes 0.03 to 0.3 MPa. Therefore, assuming that the underwater mass of the ground (upper ground 12A) is about 1 g / cm ³ , the soil pressure up to a depth of 30 m can be withstood when the lateral earth pressure is 1 times the earth covering pressure. It can be made more effective by appropriately adjusting the material density according to the depth at which the underground seismic isolation wall 16 is installed.

  Similarly, the shear stiffness of bentonite also has different characteristics depending on the bentonite effective dry density. This is because, when the proportion of the aggregate volume in the material is 50% or less, the aggregate particles do not form a particle structure in which the aggregate particles contact each other and transmit stress to each other. This is because a bentonite gel (a mixture of bentonite and water) is interposed between them, so that the shear characteristics of the material are mainly determined by the characteristics of the bentonite gel. Therefore, by adjusting the bentonite effective dry density, the shear stiffness of the contact material can be made smaller than the surrounding ground, absorbing the ground deformation by repeated deformation at the time of earthquake, reducing the adverse effect on the frame, The effect of absorbing external force can be expected.

  Here, it is known that the material of the underground seismic isolation wall 16 is considerably less rigid than the result of Toyoura sand (see, for example, FIG. 3 of Patent Document 2). Moreover, since the nonlinear characteristic of the material of the underground seismic isolation wall 16 draws a hysteresis during an earthquake (during repeated shearing), it is known to be suitable as a hysteresis damping material (damper material) by energy absorption ( For example, see FIG. 4 of Patent Document 2.) This hysteresis damping effect can be increased by mixing sand into bentonite. Therefore, the constraint pressure dependency is not as great as that of the ground material, and the bentonite effective dry density can be appropriately adjusted.

  Moreover, if the wall width D of the underground seismic isolation wall 16 is in the range of 0.2 to 2.5 m, the shear force reduction rate (the shear generated in the underground structure 14 when the underground isolation wall 16 is provided). The value obtained by dividing the force by the shearing force generated in the underground structure when there is no underground seismic isolation wall 16 is smaller than 1, and the shearing force of the underground structure 14 is reduced. This is because the countermeasure area (planar area where the underground seismic isolation wall 16 is arranged) is smaller than the conventional polymer construction method when the vertical cylinder-shaped polymer improved soil is disposed in the ground. A great reduction effect can be obtained, and the cost can be reduced.

  When the underground structure 14 is newly constructed, the underground seismic isolation wall 16 is constructed so as to be in contact therewith. In such a case, a construction space necessary around the underground structure 14 is constructed. Can be reduced. Moreover, although it is assumed that the underground seismic isolation wall 16 is constructed later for the underground in the vicinity of the existing underground structure 14, it is effective even if the wall width D of the underground seismic isolation wall 16 is small. Therefore, it can also be installed as a seismic isolation measure for existing structures in a narrow place where there are adjacent underground structures or inside a narrow site. Further, even in the seismic reinforcement work for the underground structure 14 that does not satisfy the earthquake resistance standard, the ground displacement absorbing seismic isolation structure 10 is used, so that the underground structure 14 that is difficult to be seismically strengthened by the existing structure is used. It can be used effectively for reinforcement.

  Next, the characteristic structure of the underground seismic isolation wall structure and its construction method according to the present invention will be described.

Example 1
First, Example 1 of the present invention will be described. The present Example 1 is an example in the case of excavating a continuous groove in the ground.

  FIGS. 2-1 to 2-4 show schematic construction procedures (steps 1 to 4) according to the construction method of the underground seismic isolation wall structure of the first embodiment in cross-sectional perspective views. Fig. 2-1 is an image of excavating a groove for underground seismic isolation wall in the ground (step 1), and Fig. 2-2 is an image of inserting a long water-impervious bag in the vertical direction (step 2), 2-3 shows an image filled with clay-based material in the bag (step 3), and FIG. 2-4 shows a completed image of the underground seismic isolation wall (step 4).

  First, as shown in FIG. 2-1, a groove 18 is excavated in the ground (the surrounding ground 12). Subsequently, as shown in FIG. 2B, a water-impervious bag 20 that is long in the vertical direction is inserted into the groove 18 and installed. Thereafter, as shown in FIG. 2C, the bag 20 is filled with a clay-based material 22 having a water-absorbing expansibility with a predetermined softness and inflated, and the outer surface of the bag 20 is filled in the wall surface of the groove 18. Adhere. Subsequently, another vertically long water-impervious bag 20 is inserted into the groove 18 so as to be adjacent to the installed bag 20 in the horizontal direction by the same method as described above, and this bag 20 is installed. The inside of the bag 20 is filled with a clay-based material 22 having a water-absorbing expansibility with a predetermined softness and inflated, and the outer surface of the bag 20 is brought into close contact with the wall surface of the groove 18. By doing so, a columnar underground seismic isolation wall 16 as shown in FIG. 2-4 is constructed.

  According to the first embodiment, it is possible to easily construct the columnar underground seismic isolation wall 16 in which a plurality of bags 20 that are long in the vertical direction are adjacent to each other in the horizontal direction. Moreover, since the bag 20 is water-impervious, the clay-based material 22 filled in the bag 20 depends on the influence of mud water in the excavated groove 18 and the infiltration flow, water level, and water quality of the ground water in the surrounding ground 12. Not affected. Therefore, the underground seismic isolation wall structure excellent in long-term stability and workability can be provided.

(Example 2)
Next, a second embodiment of the present invention will be described. The present Example 2 is an example in the case of excavating holes in a columnar shape in the ground.

  FIGS. 3-1 to 3-4 show schematic construction procedures (steps 1 to 4) according to the construction method of the underground seismic isolation wall structure of the second embodiment in cross-sectional perspective views. Fig. 3-1 shows an image of drilling a hole adjacent to an existing hole (step 1), Fig. 3-2 shows an image of inserting a bag into the drill hole (step 2), and Fig. 3-3 shows an excavation. An image of filling a clay-based material in the bag installed in the hole (step 3), and FIG. 3-4 show a completed image of the underground seismic isolation wall (step 4).

  First, as shown in FIG. 3A, it is assumed that one excavation hole 24 has already been constructed, and the bag 20 filled with the clay-based material 22 is inserted into the excavation hole 24. The hole 24 is excavated in the ground (the peripheral ground 12) so as to be adjacent to the existing excavation hole 24 in the lateral direction. Subsequently, as shown in FIG. 3-2, a long water-impervious bag 20 is inserted and installed in the excavation hole 24. After that, as shown in FIG. 3C, the bag 20 is filled with a clay-based material 22 having a water-absorbing expansibility with a predetermined softness and inflated. Adhere the outer surface. Subsequently, another hole 24 is drilled so as to be laterally adjacent to the drilling hole 24 by the same method as described above, and another bag 20 is inserted and installed therein. It is repeatedly filled with a clay-based material 22 having a water-absorbing expansibility with a predetermined softness and inflated, and the outer surface of the bag 20 is brought into close contact with the wall surface of the excavation hole 24. By doing so, a columnar underground seismic isolation wall 16 as shown in FIG. 3-4 is constructed.

  According to the second embodiment, the columnar underground seismic isolation wall 16 in which a plurality of bags 20 that are long in the vertical direction are adjacent to each other in the horizontal direction can be easily constructed. Moreover, since the bag 20 is water-impervious, the clay-based material 22 filled in the bag 20 depends on the influence of the muddy water in the excavated hole 24 and the infiltration flow, water level, and water quality of the ground water in the surrounding ground 12. Not affected. Therefore, the underground seismic isolation wall structure excellent in long-term stability and workability can be provided.

(Example 3)
Next, Embodiment 3 of the present invention will be described. The third embodiment is an example where the bags are arranged in a staggered manner in the horizontal direction.

  As shown in FIG. 4, the holes 24 to be excavated in the ground (the surrounding ground 12) are staggered in the second embodiment. Then, a long water-impervious bag 20 is inserted and installed in each excavation hole 24, and each bag 20 is filled with a clay-based material 22 having a water-absorbing expansibility with a predetermined softness. And the outer surface of the bag 20 is brought into close contact with the wall surface of the excavation hole 24. By doing so, the same effect as in the second embodiment can be obtained, and the columnar underground seismic isolation wall 16 arranged in a staggered manner can be obtained.

Example 4
Next, a fourth embodiment of the present invention will be described. The present Example 4 is an example in the case of filling the clay-based material step by step from the bottom in the bag.

  FIGS. 5-1 to 5-6 show schematic construction procedures (steps 1 to 6) according to the construction method of the underground seismic isolation wall structure of the fourth embodiment in cross-sectional perspective views. 5-1 is an image of excavating a groove for underground seismic isolation wall in the ground (step 1), and FIG. 5-2 is an image of inserting a portion to be filled in a bag (step 2), FIG. -3 is an image in which a portion to be filled is filled with clay-based material (step 3), and FIG. 5-4 is an image in which the portion to be filled in a bag is subsequently inserted into the groove (step 4), FIG. -5 shows an image of a bag that has been filled and installed in the groove (step 5), and FIG. 5-6 shows a completed image of the underground seismic isolation wall (step 6).

  First, as shown in FIG. 5A, a groove 18 is excavated in the ground (the surrounding ground 12). Subsequently, as shown in FIG. 5B, the long water-impervious bag 20 is inserted into the groove 18. At this time, the portion 20 a to be filled in the bag 20 is inserted into the groove 18. Then, as shown to FIGS. 5-3, the clay-type material 22 which has a water absorptivity in the part 20a which is going to be filled in the bag 20 is filled in the state which has predetermined | prescribed softness. Subsequently, as shown in FIG. 5-4, the portion 20b to be filled in the bag 20 is inserted into the groove 18 by the same method as described above. Filling the inserted portion 20b with the clay-based material 22 in a state having a predetermined softness is repeated step by step. By doing so, as shown in FIG. 5-5, the installation of one bag 20 in the groove 18 is completed. The same procedure is applied to another bag 20 provided adjacent to the existing bag 20 to construct a columnar underground seismic isolation wall 16 as shown in FIG. 5-6. Note that this embodiment can be applied not only to the grooves 18 but also to excavation holes provided in a columnar shape in the ground. Moreover, you may implement a present Example, after inserting the bag 20 to the installation depth lower end, as shown to FIGS. 2-2.

  According to the fourth embodiment, the clay-based material 22 having water absorbability is filled stepwise from the bottom in the bag 20, and the portion 20 a (20 b) to be filled in the bag 20. ) Is inserted into the groove 18 and the clay material 22 is filled in the portion 20a (20b) of the inserted bag 20 in a stepwise manner, and the bag 20 is installed in the groove 18. As well as obtaining the same effect as above, it can be constructed by changing the filling density of the clay-based material 22 filled in the bag 20 stepwise or gradually according to the depth. The underground seismic isolation wall 16 of the present invention is softer than the surrounding ground and can absorb the ground displacement at the time of the earthquake, so that it is not deformed by the applied earth pressure from the surrounding ground and the thickness is not reduced. However, for that purpose, it is desirable to increase the density of the material constituting the underground seismic isolation wall 16 as it becomes deeper. Further, a material having a high density and a little softness in a deep part may be used, and a middle part thereof may be an intermediate material.

(Example 5)
Next, a fifth embodiment of the present invention will be described. In Example 5, after inserting a sheet roll formed by winding a water-impervious sheet having a plurality of bags into a groove into the groove, the water-impervious sheet is pulled out from the sheet roll in the lateral direction, whereby a plurality of grooves are formed in the groove. It is an example in the case of installing a bag.

  FIGS. 6-1 to 6-4 show a schematic construction procedure (steps 1 to 4) by the construction method of the underground seismic isolation wall structure of the fifth embodiment in a plan view and an underground vertical sectional view. . Fig. 6-1 is an image during drawing of a water shielding sheet (step 1), Fig. 6-2 is an image of drawing completion (step 2), and Fig. 6-3 is an image during filling of clay-based material (step 3). 6-4 shows a completed image of the underground seismic isolation wall (step 4).

  First, as shown in FIG. 6A, after the sheet roll 26 is inserted and arranged in a part of the groove 18 in the ground (the surrounding ground 12), the water shielding sheet 28 is laterally (horizontal) from the sheet roll 26. Pull out (or pay out). Here, the water-impervious sheet 28 has a plurality of bags 20 connected in the lateral direction via the membrane-like connecting member 30, and in a state where the bag 20 is not filled with the clay-based material 22, the sheet shape. It is comprised as what makes. In this way, as shown in FIG. 6B, a plurality of bags 20 can be collectively inserted into the groove 18 and installed. Then, as shown to FIGS. 6-3, the clay-type material 22 which has a water absorptive expansibility in order in each bag 20 of the water-impervious sheet 28 is filled. By doing so, a columnar underground seismic isolation wall 16 as shown in FIG. 6-4 is constructed.

  According to the fifth embodiment, the plurality of bags 20 provided on the water-impervious sheet 28 can be easily disposed over the entire length of the groove 18, and the columnar seismic isolation wall 16 can be easily constructed. Can do.

(Example 6)
Next, a sixth embodiment of the present invention will be described. Example 6 is an example in which an aqueous solution having an electrolyte concentration of less than 1 wt% and lower than the groundwater in the surrounding ground is constantly supplied from the ground side to the clay-based material having water-absorbing expansibility filled in the bag. It is.

As shown in FIG. 7-1, the underground seismic isolation wall structure of the sixth embodiment has an electrolyte on an upper end portion 16 a on the ground surface GL side of the underground seismic isolation wall 16 made of bags arranged in a columnar shape. Water W having a concentration of less than 1 wt% and a lower electrolyte concentration than the ground water of the surrounding ground 12 (an aqueous solution having an electrolyte concentration of less than 1 wt% and lower than the ground water of the surrounding ground. Is further provided with a water storage section 32 for storing water. The water storage portion 32 has a U-shaped groove shape, and its top end portion is covered with a cover plate 34. The bottom plate 36 of the water storage section 32 has a water-permeable structure, and the water W having a low electrolyte concentration stored in the water storage section 32 permeates the bottom plate 36 and forms the underground seismic isolation wall 16 below. It can penetrate into the upper end 16a.
The water storage structure of the low-electrolyte water W is not limited to FIG. 7A. For example, as shown in FIG. 7B, the low-electrolyte water W is stored at the upper end of the bag 20. May be. At this time, in order to prevent the water-swellable clay-based material 22 at the top of the bag 20 from expanding, a soil material 23 having no water-swelling property such as sand is loaded on the top of the bag 20, The uppermost pore water may be water W having a low electrolyte concentration.

  When water W having a low electrolyte concentration is always supplied from the water storage portion 32 to the upper end portion 16a of each bag, the water-absorbing and expanding clay-based material in each bag is always saturated with water. The water retention capacity is maintained. For this reason, according to the sixth embodiment, the clay-based material does not shrink and dry, and the columnar diameter and the constituent material density of the longitudinally long bag are maintained constant for a long period of time, and its rigidity is reduced. Can be held. As a result, since the displacement absorption capacity of the columnar underground seismic isolation wall 16 is maintained, there is no possibility of causing a decrease in the seismic isolation performance, and an underground seismic isolation wall structure excellent in long-term stability is provided. Can do.

  In addition, when there is always a supply of water W having a low electrolyte concentration by the downward osmotic flow from the water storage portion 32 to the upper end portion 16a of the underground seismic isolation wall 16, the water-absorbing and expanding clay-based material in each bag The pore water is always saturated with water having a low electrolyte concentration. For this reason, according to the sixth embodiment, even if the water shielding property of the bag is impaired due to damage or the like, an increase in the electrolyte concentration of pore water in the clay-based material in the bag due to the infiltration of the ground water in the surrounding ground 12 is suppressed. Is done. Since the swelling pressure of the clay-based material saturated with water having a low electrolyte concentration is kept constant, the change in the diameter of the column due to the bag is suppressed, and the wall width D of the underground seismic isolation wall 16 and the density of its constituent materials are suppressed. Thus, the rigidity of the underground seismic isolation wall 16 can be kept small. As a result, since the displacement absorption capacity of the underground seismic isolation wall 16 is maintained, there is no possibility that the seismic isolation performance is deteriorated. In addition, ground deformation and ground subsidence around the underground seismic isolation wall will not occur. For this reason, even if it is a case where the electrolyte concentration of the groundwater of the surrounding ground 12 is comparatively high like seawater, long-term stable and seismic isolation performance can be exhibited.

  As described above, according to the underground seismic isolation wall structure according to the present invention, the continuous wall-shaped underground seismic isolation wall provided between the surrounding ground and the structure and made of clay-based material. The underground seismic isolation wall has a longitudinally long water-impervious bag installed adjacent to the lateral direction by inserting into a groove or hole excavated in the ground, and the bag It is a columnar underground seismic isolation wall provided with a clay-based material having a water-absorbing property filled in a state having a predetermined softness. For this reason, by repeating the work of inserting a long water-impervious bag in the vertical direction one by one into the excavated groove or hole and filling the bag with a clay-based material having water-absorbing expansibility, It is possible to easily construct a columnar underground seismic isolation wall in which a plurality of bags that are long in the direction are adjacent to each other in the horizontal direction. In addition, since the bag is water-impervious, the clay-based material filled in the bag is affected by mud water in the excavated trench or hole, and by the seepage flow, water level and water quality of the surrounding groundwater. Absent. Therefore, the underground seismic isolation wall structure excellent in long-term stability and workability can be provided.

  In addition, according to another underground seismic isolation wall structure according to the present invention, since the bags are arranged in a staggered manner in the lateral direction, in addition to the above effects, a columnar underground seismic isolation wall arranged in a staggered manner is obtained. be able to.

  In addition, according to another underground seismic isolation wall structure according to the present invention, since it further includes a connecting member that connects between the adjacent bags, in addition to the above effect, the connecting member is connected to the excavated groove. A plurality of bags are inserted and installed in a lump, and each bag is filled with a clay-based material having water-absorbing expansibility, so that a plurality of vertically long bags are adjacent to each other in the horizontal direction. The underground seismic isolation wall can be easily constructed.

  Further, according to another underground seismic isolation wall structure according to the present invention, with respect to the clay-based material having water-absorbing expansibility filled in the bag, the electrolyte concentration is less than 1 wt% from the groundwater of the surrounding ground. Since a low aqueous solution is always supplied from the ground side, the water-swellable clay-based material filled in the bag is always saturated with water from the aqueous solution and the water retention capability is maintained. For this reason, the clay-based material can be maintained in a constant state for a long period of time with the diameter of the column of the columns formed by the bags long in the vertical direction and the density of the constituent material thereof without drying and shrinking, and the rigidity can be kept small. As a result, the displacement absorption capacity of the columnar underground seismic isolation wall is maintained, so there is no risk of a decrease in the seismic isolation performance, and it is possible to provide an underground seismic isolation wall structure with excellent long-term stability. it can.

  Further, according to the construction method of the underground seismic isolation wall structure according to the present invention, the structure of a continuous wall-shaped underground seismic isolation wall provided between the surrounding ground and the structure and made of clay-based material In this construction method, a vertically long water-impervious bag is inserted into a groove or hole excavated in the ground, and then a clay-based material having a water-absorbing expansive property is placed in the bag. Fill and inflate in a soft state to bring the outer surface of the bag into close contact with the wall surface of the groove or hole, and then another longitudinal direction in a similar manner so as to be laterally adjacent to the bag A long water-impervious bag is inserted into the groove or hole, and a clay-based material having a water-absorbing expansibility is filled in the bag with a predetermined softness to inflate the groove or hole. Repeating close contact of the outer surface of the bag with the wall surface of the hole, the underground seismic isolation wall is columnar To build. For this reason, it is possible to easily construct a columnar underground seismic isolation wall in which a plurality of bags long in the vertical direction are adjacent to each other in the horizontal direction. In addition, since the bag is water-impervious, the clay-based material filled in the bag is affected by mud water in the excavated trench or hole, and by the seepage flow, water level and water quality of the surrounding groundwater. Absent. Therefore, the underground seismic isolation wall structure excellent in long-term stability and workability can be provided.

  Moreover, according to the construction method of another underground seismic isolation wall structure according to the present invention, since the bags are arranged in a staggered manner in the lateral direction, in addition to the above effects, the columnar underground seismic isolation in a staggered manner You can get a wall.

  Moreover, according to the construction method of another underground seismic isolation wall structure according to the present invention, the clay-based material having water-absorbing expansibility is filled stepwise from the bottom in the bag. The bag is placed in the groove or hole by repeatedly inserting the portion to be filled into the bag into the groove or hole, and filling the inserted portion of the bag with the clay-based material stepwise. Therefore, in addition to the above effect, the clay-based material filled in the bag can be constructed with a density according to the depth.

  Moreover, according to the construction method of the other underground seismic isolation wall structure according to the present invention, it has a plurality of the bags connected laterally via a membrane-like connecting member, and the clay is in the bag. The above-mentioned effect is obtained by installing a water-proof sheet in the form of a sheet in a state where the system material is not filled in the groove and filling the bag with a water-swellable clay-based material having a predetermined softness. In addition, a plurality of bags connected by connecting members to the excavated groove are installed in a lump and installed, and each bag is filled with a clay-based material having water-absorbing expansibility, so that a long bag in the vertical direction can be It is possible to easily construct a column-shaped underground seismic isolation wall that is adjacent to each other in the direction.

  Moreover, according to the construction method of the other underground seismic isolation wall structure according to the present invention, after inserting the sheet roll formed by winding the water shielding sheet into a roll shape into the groove, the water shielding from the sheet roll. Since the plurality of bags are installed in the groove by feeding the sheet in the lateral direction, in addition to the above effects, the plurality of bags provided in the water shielding sheet can be easily disposed over the entire length of the groove.

  Further, according to another underground seismic isolation wall structure construction method according to the present invention, with respect to the clay-based material having a water-absorbing property filled in the bag, the electrolyte concentration is less than 1 wt% and the surrounding ground. Since an aqueous solution lower than the groundwater is constantly supplied from the ground side, the water-swellable clay-based material filled in the bag is always saturated with water from the aqueous solution and the water retention capability is maintained. For this reason, the clay-based material can be maintained in a constant state for a long period of time with the diameter of the column of the columns formed by the bags long in the vertical direction and the density of the constituent material thereof without drying and shrinking, and the rigidity can be kept small. As a result, the displacement absorption capacity of the columnar underground seismic isolation wall is maintained, so there is no risk of a decrease in the seismic isolation performance, and it is possible to provide an underground seismic isolation wall structure with excellent long-term stability. it can.

  As described above, the underground seismic isolation wall structure and its construction method according to the present invention are useful for reducing stress on underground structures such as open tunnels during an earthquake, and in particular, have long-term stability and It is suitable for obtaining underground seismic isolation walls with excellent workability.

10 Ground displacement absorption isolation structure 12 Surrounding ground 14 Underground structure (structure)
16 Underground seismic isolation wall (underground seismic isolation wall structure)
16a upper end 18 groove 20 bag 20a, 20b portion to be filled 22 clay-based material 24 hole 26 sheet roll 28 water shielding sheet 30 connecting member 32 water storage section 34 lid plate 36 bottom plate W water with low electrolyte concentration (aqueous solution)
GL surface

Claims (10)

It is a structure of a continuous wall-shaped underground seismic isolation wall that is provided between the surrounding ground and the structure and is made of clay-based material,
The underground seismic isolation wall is inserted into a groove or hole excavated in the ground, and a plurality of longitudinal water-impervious bags installed in the lateral direction and a predetermined softness in the bag. An underground seismic isolation wall structure, characterized in that it is a columnar underground seismic isolation wall provided with a clay-based material having a water-absorbing property that is filled in a state of being possessed.   The underground seismic isolation wall structure according to claim 1, wherein the bags are arranged in a staggered manner in the lateral direction.   The underground seismic isolation wall structure according to claim 1, further comprising a connection member that connects adjacent bags.   The clay-based material having a water-swelling property filled in the bag is characterized in that an aqueous solution having an electrolyte concentration of less than 1 wt% and lower than the groundwater in the surrounding ground is constantly supplied from the ground side. The underground seismic isolation wall structure according to any one of claims 1 to 3. A method for constructing a continuous wall-shaped underground seismic isolation wall structure, which is provided between a surrounding ground and a structure and is made of clay-based material
A vertically long water-impervious bag is inserted into a ditch or hole excavated in the ground, and then a clay-based material having water-absorbing expansibility is placed in the bag with a predetermined softness. Fill and inflate to bring the outer surface of the bag into intimate contact with the wall of the groove or hole, and then install another vertically long water-impervious bag in a similar manner so as to be laterally adjacent to the bag. The bag is inserted into the groove or hole, filled with a clay-based material having water absorbability in the bag with a predetermined softness, and inflated, and the wall of the bag is filled in the wall of the groove or hole. A method for constructing an underground seismic isolation wall structure, wherein the underground seismic isolation wall is constructed in a column shape by repeating close contact with outer surfaces.   The construction method for an underground seismic isolation wall structure according to claim 5, wherein the bags are arranged in a staggered manner in the lateral direction.   The clay-based material having water-absorbing expansibility is filled in stages from the bottom in the bag, and the portion to be filled in the bag is inserted into the groove or hole and inserted. 7. The underground seismic isolation wall structure according to claim 5 or 6, wherein the bag is installed in the groove or hole by stepwise filling the bag portion with the clay-based material. Construction method.   A plurality of the bags connected in a lateral direction through a membrane-like connecting member, and a water-impervious sheet that forms a sheet in a state in which the clay-based material is not filled in the bag, is installed in the groove. The construction of the underground seismic isolation wall structure according to any one of claims 5 to 7, wherein the bag is filled with a clay-based material having water-absorbing expansibility in a state having a predetermined softness. Method.   After inserting the sheet roll formed by winding the water shielding sheet into a roll into the groove, the plurality of bags are installed in the groove by feeding the water shielding sheet laterally from the sheet roll. The construction method of the underground seismic isolation wall structure according to claim 8 characterized by the above.   6. An aqueous solution having an electrolyte concentration of less than 1 wt% and lower than the ground water of the surrounding ground is constantly supplied from the ground side to the clay-based material having a water-swelling property filled in the bag. The construction method of the underground seismic isolation wall structure as described in any one of -9.

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