JP5364403B2 - Ground improvement structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a soil improvement structure which can restrain shear deformation from being caused by vertical motion of ground inside an underground wall, and which can suppress the liquefaction of the ground. <P>SOLUTION: This soil improvement structure 10 includes: the underground wall 20 which surrounds the ground 12; a deformation inhibiting plate 22 which is arranged on soft ground 18, which is higher in rigidity than the soft ground 18, and which covers the inside of the underground wall 20; and a joint member 24 for filling the gap between an inner surface of the underground wall 20 and the deformation inhibiting plate 22. In this case, since a vertical load is transferred to the soft ground 18 via the deformation inhibiting plate 22 during earthquakes the effective stress of the upper layer of the soft ground 18 is increased to constrain the vertical motion of the soft ground 18. Additionally, since the rigidity of the surface layer of the soft ground 18 is enhanced than the soft ground 18 by the deformation inhibiting plate 22, a horizontal force is transferred to the underground wall 20 from the deformation inhibiting plate 22 via the joint member 24 during earthquakes. Consequently, the shear strength and liquefaction of the soft ground 18 can be suppressed. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a ground improvement structure.

  Conventionally, as a countermeasure for liquefaction of the ground, there is one in which an oblique wall is provided between underground walls standing in the ground (for example, see Patent Documents 1 and 2).

  The liquefaction countermeasure structure of Patent Document 1 is a structure in which diagonally inclined wall bodies are provided between underground walls provided in the vertical direction. Thereby, in the liquefaction countermeasure structure of patent document 1, the underground wall in the vertical direction is supported by the diagonal wall body to suppress deformation.

  However, in the liquefaction countermeasure structure of Patent Document 1, since there is no means for suppressing the vertical movement of the ground, when the surface layer portion of the ground moves up and down due to an earthquake, the ground becomes insufficiently constrained and liquefaction occurs. Will occur.

  On the other hand, in the liquefaction countermeasure structure of Patent Document 2, a V-shaped wall is provided between the underground walls provided in the vertical direction, and is further horizontally disposed on the surface layer of the ground surrounded by the V-shaped wall. A surface solidified plate spreading in the direction is provided. Thereby, in the liquefaction countermeasure structure of patent document 2, while supporting a vertical underground wall with a V-shaped wall body and suppressing a deformation | transformation, the ground surrounded by the V-shaped wall body by the surface solidified plate The restraint force is increased by suppressing the vertical movement of.

  However, in the liquefaction countermeasure structure of Patent Document 2, since the surface solidified plate is rigidly connected to the underground wall, even if the ground sinks even slightly during an earthquake or when land subsidence occurs at all times, the surface solidified plate ( In addition, the overload due to the structure) does not act on the ground inside the underground wall (is no longer transmitted), the effective stress acting on the ground decreases, and liquefaction easily occurs.

JP-A-5-311638 JP-A-9-32004

  An object of this invention is to obtain the ground improvement structure which can suppress the liquefaction of a ground while suppressing the shear deformation by the vertical motion of the ground inside a underground wall.

A ground improvement structure according to claim 1 of the present invention includes a ground wall surrounding the ground, a rigid plate disposed on the ground and having higher rigidity than the ground, and covering the inside of the ground wall, and water permeability a bag body having, a granular material packed in the bag body, having a joint member for closing the gap between the inner surface and the rigid plate of the underground wall.

  According to the above configuration, by providing the joint member in the gap between the underground wall and the rigid plate, it is possible to prevent damage due to the tensile stress or temperature expansion difference generated between the underground wall and the rigid plate. . In addition, the joint-shaped member, underground wall, and rigid plate form a gate-shaped deformation prevention wall, and even during an earthquake, the vertical load is transmitted to the ground via the rigid plate. It is maintained, and the vertical movement of the ground is restrained by the gate-shaped deformation restraining wall, and shear deformation of the restrained ground is suppressed.

  Furthermore, since the rigidity of the ground surface layer is higher than that of the ground due to the rigid plate, a horizontal force is transmitted from the rigid plate to the underground wall through the joint member during an earthquake, and shear deformation of the ground is suppressed. Thereby, liquefaction of the ground can be suppressed.

Moreover, the said joint member is provided with the bag body which has water permeability, and the granular material packed in the said bag body. According to this configuration, when a shearing force is applied to the joint member, the filling state of the granular material changes and the volume of the bag body expands. Thereby, the operation | movement of the both ends of a rigid board is restrained, and the inclination of a rigid board can be suppressed. Furthermore, since the gap between the underground wall and the rigid plate is blocked by the joint member, it is possible to prevent the ground from flowing out due to sand sand and to dissipate excess pore water pressure.

The ground improvement structure according to claim 2 of the present invention includes a pile that is inserted into a through hole formed in the rigid plate and provided in the ground, and a receiving member that is fixed to the pile above the rigid plate, And an elastic body that is fixed to the rigid plate and the receiving member and causes a reaction force to act on the rigid plate when the rigid plate is raised and lowered. According to this configuration, when the rigid plate rises or sinks during an earthquake, the rigid plate is returned to the original position by the reaction force of the elastic body. Thereby, the displacement of a rigid board can be suppressed.

In the ground improvement structure according to claim 3 of the present invention, the rigid plate is a cement-based surface layer improvement body. According to this configuration, the rigidity of the rigid plate can be increased.

The ground improvement structure according to claim 4 of the present invention is characterized in that the rigid plate has a base embedded part of the building constructed between the underground walls and a foundation beam of the building provided at a lower part of the base internal part. It consists of and. According to this structure, since the base part of a building and a foundation beam become a rigid board, it becomes unnecessary to provide a rigid board separately. Moreover, the effective stress of the ground can be increased by the weight of the building.

The ground improvement structure according to claim 5 of the present invention is a housing of an underground structure in which the rigid plate is constructed between the underground walls. According to this configuration, since the frame of the underground structure is a rigid plate, there is no need to provide a separate rigid plate. Moreover, the effective stress of the ground can be maintained by the dead weight of the underground structure and the soil above it.

  Since this invention was set as the said structure, it can suppress the shear deformation by the vertical motion of the ground inside a underground wall, and can suppress the liquefaction of the ground.

It is a whole lineblock diagram of the ground improvement structure concerning a 1st embodiment of the present invention. It is sectional drawing of the joint material periphery of the ground improvement structure which concerns on 1st Embodiment of this invention. (A), (b) It is explanatory drawing which shows a state when the inertia force by an earthquake acts on the ground of only the underground wall which concerns on 1st Embodiment of this invention. It is explanatory drawing which shows the change of the liquefaction state of a ground when the space | interval of a ground wall is changed in the ground of only a ground wall which concerns on 1st Embodiment of this invention. (A) It is a schematic diagram which shows the liquefaction generation | occurrence | production state of the ground in the structure with a clearance gap between an underground wall and an upper board. (B) It is a schematic diagram which shows the liquefaction generation | occurrence | production state of the ground in the structure where the underground wall and the mounting board were connected. (A), (b) It is sectional drawing which shows the effect | action of the joint material in the ground improvement structure which concerns on 1st Embodiment of this invention. (A) It is a whole block diagram of the ground improvement structure which concerns on 2nd Embodiment of this invention. (B) It is a partial block diagram of the ground improvement structure which concerns on 2nd Embodiment of this invention. (A), (b) It is a fragmentary sectional view which shows the inclination suppression state of the rigid board by the receiving member and elastic body of the ground improvement structure which concern on 2nd Embodiment of this invention. It is sectional drawing which shows the other Example of the ground improvement structure which concerns on 2nd Embodiment of this invention. It is a whole block diagram of the ground improvement structure which concerns on 3rd Embodiment of this invention. It is a whole block diagram of the ground improvement structure which concerns on 4th Embodiment of this invention.

  1st Embodiment of the ground improvement structure of this invention is described based on drawing. FIG. 1 shows a ground improvement structure 10 provided on the ground 12 and a building 14 as a structure constructed on the ground 12. The ground 12 is composed of a hard ground 16 as an impermeable layer and a soft ground 18 that is an upper layer of the hard ground 16 and may be liquefied.

  The ground improvement structure 10 is disposed on the ground wall 20 surrounding the building 14 and standing in the ground 12, and on the soft ground 18 (surface layer) inside the ground wall 20, and is more rigid than the soft ground 18. It has the deformation | transformation suppression board 22 as a highly rigid board, and the joint member 24 which block | closes the clearance gap between the inner surface of the underground wall 20 and the deformation | transformation suppression board 22. FIG.

  The underground wall 20 is composed of a ground improvement body or an RC continuous wall, and the lower end portion of the underground wall 20 reaches the hard ground 16. Thereby, the shear deformation of the ground inside the soft ground 18 surrounded by the underground wall 20 is suppressed. Moreover, the deformation | transformation suppression board 22 is a cement-type surface layer improvement body, and is arrange | positioned horizontally with the underground wall 20 and a clearance gap. In addition, although the thickness of the deformation | transformation suppression board 22 may be selected in the range of 1m-2m, for example, it is not restricted to this and may be thicker than 2m.

  As shown in FIG. 2, the joint member 24 includes a sandbag 26 having water permeability, and a granular body 28 having a plurality of particle sizes made of sand and gravel packed in the sandbag bag 26. A plurality of gaps between the inner surface 20 </ b> A of the middle wall 20 and the side surface 22 </ b> A (end surface) of the deformation suppression plate 22 are filled to close the gap.

  Here, as shown in FIG. 1, the ground improvement structure 10 has a gate shape in which the underground wall 20 and the deformation suppression plate 22 are connected by the joint member 24, and the building 14 has the deformation suppression plate 22. Is supported on the soft ground 18. In addition, the connection of the underground wall 20 and the deformation | transformation suppression board 22 by the joint member 24 in this embodiment does not mean the rigid connection which integrates these with concrete etc., but the underground wall 20 and a deformation | transformation suppression. This means that the gap between the plates 22 is filled to make it difficult for the earth and sand in the soft ground 18 to flow out to the ground, and the deformation suppression plate 22 is held so as to be movable relative to the underground wall 20 in the vertical direction.

  Next, as a comparative example with the ground improvement structure 10 according to the first embodiment of the present invention, the state of the ground 12 when only the underground wall 20 is provided will be described.

  3 (a) and 3 (b) show the displacement state of the ground 12 when the horizontal inertia force (arrows A and B) due to the earthquake is applied to the ground 12 provided with only the underground wall 20, as shown by arrows C1. , C2, C3, D1, D2, and D3. In addition, the magnitude | size and direction of each arrow C1-C3 and D1-D3 are obtained by the ground analysis by an individual element method. Further, the left underground wall 20 is distinguished as 20A, and the right underground wall 20 is distinguished as 20B.

  As shown in FIG. 3A, when an inertial force acts on the ground 12 in the direction of arrow A (the right direction in FIG. 3A) due to the earthquake, the soft ground 18 near the underground wall 20A has the direction of the arrow C1 ( A displacement in the lower right direction in FIG. Further, in the middle soft ground 18 between the underground wall 20A and the underground wall 20B, displacement in the direction of arrow C2 (horizontal right direction in FIG. 3A) occurs. Further, in the soft ground 18 near the underground wall 20B, displacement in the direction of arrow C3 (upper right direction in FIG. 3A) occurs.

  Similarly, as shown in FIG. 3 (b), when an inertial force in the direction of arrow B (leftward in FIG. 3 (b)) acts on the ground 12 due to an earthquake, in the soft ground 18 near the underground wall 20A, Displacement in the direction of arrow D1 (upper left direction in FIG. 3B) occurs. Further, in the middle soft ground 18 between the underground wall 20A and the underground wall 20B, displacement in the direction of arrow D2 (horizontal left direction in FIG. 3B) occurs. Further, in the soft ground 18 near the underground wall 20B, displacement in the direction of arrow D3 (the lower left direction in FIG. 3B) occurs.

  As shown in FIGS. 3A and 3B, in the soft ground 18 surrounded by the underground wall 20A and the underground wall 20B, the amount of displacement caused by the earthquake is larger in the surface layer than in the underground. ing. As a result, the rigidity of the soft ground 18 in the surface layer is reduced in the vicinity of the underground walls 20A and 20B as compared to the underground, and the region S surrounded by the broken line is the reduced rigidity region. Thus, in the structure in which only the underground wall 20A and the underground wall 20B are provided, the rigidity of the soft ground 18 is lowered particularly in the surface layer, but the soft ground 18 between the underground wall 20A and the underground wall 20B is provided. Since there is no means for restraining, it is difficult to prevent liquefaction of the soft ground 18.

  Next, in the structure in which only the underground wall 20 is provided on the ground 12, the difference in the liquefaction occurrence state when the interval between the underground walls 20 is increased will be described.

  FIG. 4 shows the liquefaction analysis result of the soft ground 18 by the individual element method when the distance between the underground walls 20 is changed to W1, W2, and W3 (W1 <W2 <W3). In FIG. 4, the shaded region L indicates that the excess pore water pressure is high and is in a liquefied state.

  As shown in FIG. 4, it can be seen that the liquefaction region L expands on the surface layer of the soft ground 18 as the distance between the underground walls 20 increases to W1, W2, and W3. This is because when the space between the underground walls 20 increases, the displacement at the surface layer of the soft ground 18 increases during an earthquake, and the effect of restraining the soft ground 18 is weakened. As a result, the surface of the soft ground 18 is liquid. This means that a categorized state occurs.

  Next, the liquefaction state of the soft ground 18 when the upper plate is placed on the soft ground 18 will be described.

In FIG. 5 (a), when an earthquake occurs in the state where the underground wall 20 and the clearance d are opened on the soft ground 18 between the underground walls 20 and the upper plate 32 of 10 kN / m ² is placed. An analysis result of the distribution state of the liquefaction region L of the soft ground 18 is shown. The analysis is based on the finite element method, and the region where the excess pore water pressure ratio is high is defined as the liquefaction region L.

  As shown in FIG. 5A, in a state where the underground wall 20 and the upper plate 32 are not connected, the vertical movement of the upper plate 32 due to the earthquake is not restricted, and the earth and sand flows out from the gap d. For this reason, the soft ground 18 cannot be restrained, and liquefaction occurs in a wide range of the surface layer.

On the other hand, FIG. 5 (b) shows an earthquake in a state in which an upper plate 34 of 10 kN / m ² is placed and connected on the soft ground 18 between the underground walls 20 without leaving a gap. The analysis result of the distribution state of the liquefaction area | region L of the soft ground 18 when this occurs is shown.

  As shown in FIG. 5 (b), in the state where the underground wall 20 and the upper plate 34 are connected, the vertical movement of the upper plate 34 due to the earthquake can be restrained, and the outflow of earth and sand can also be prevented. For this reason, the soft ground 18 can be restrained and the liquefaction generation region can be limited to a part near the underground wall 20.

  Here, as described with reference to FIGS. 3 to 5, the liquefaction is suppressed by providing a material corresponding to the upper plate 34 on the soft ground 18 between the underground walls 20 and further connecting to the underground wall 20. It is done. For this reason, in the ground improvement structure 10 (refer FIG. 1) of this embodiment, it is set as the structure which connected the underground wall 20 and the deformation | transformation suppression board 22 via the joint member 24. FIG.

  Next, the operation of the first embodiment of the present invention will be described.

  As shown in FIGS. 6A and 6B, the soft ground 18 in the underground wall 20 moves up and down due to the earthquake, and the deformation suppression plate 22 is moved in the direction of arrow F1 (downward) and in the direction of arrow F2 (upward). When the force (2) is applied, the filling state of the granular material 28 changes due to the shear deformation of the plurality of granular materials 28 (see FIG. 2), and the volume of the sandbag 26 expands. Thereby, the movement of the deformation | transformation suppression board 22 can be restrained.

  Moreover, since the joint member 24 has water permeability, a part of the water (groundwater) in the soft ground 18 passes through the joint member 24 and is drained to the ground. Thereby, the excessive excess pore water pressure of the soft ground 18 is dissipated and liquefaction is suppressed.

  Here, in the general improved ground, since the tensile strength is low at the joint between the underground wall and the surface layer improvement, damage occurs at the joint and the effect of suppressing deformation of the ground is reduced. In the improved structure 10, by using the deformable joint member 24, damage can be prevented even if there is a tensile stress or a temperature expansion difference generated between the underground wall 20 and the deformation suppression plate 22.

  Further, since the end portion of the deformation suppression plate 22 is locked with respect to the underground wall 20, the vertical movement and inclination of both end portions of the deformation suppression plate 22 are suppressed, and a bending moment is transmitted to the underground wall 20. Is possible. Thereby, the underground wall 20 and the deformation | transformation suppression board 22 are integrated via the joint member 24, it becomes a gate-shaped deformation | transformation suppression wall, the whole rigidity of the ground improvement structure 10 increases, and the softness inside the underground wall 20 is increased. The horizontal and vertical shear deformation of the ground 18 can be suppressed.

  Furthermore, in the ground improvement structure 10, since the rigidity of the surface layer of the soft ground 18 is enhanced by the deformation suppression plate 22, the horizontal and vertical shear deformation of the soft ground 18 inside the underground wall 20 is more effectively performed. Can be deterred.

  In the ground improvement structure 10 in this embodiment, since the underground wall 20 and the deformation | transformation suppression board 22 are connected by the joint member 24, the vertical motion of the deformation | transformation prevention board 22 by an earthquake can be restrained, and the outflow of earth and sand can also be prevented. it can. Thereby, in the ground improvement structure 10, the soft ground 18 is restrained and the generation | occurrence | production area | region of liquefaction can be limited to a part of underground wall 20 vicinity. Further, in the ground improvement structure 10, liquefaction can be prevented by the deformation suppressing plate 22 and the joint member 24 even when the arrangement interval of the underground walls 20 is widened.

  As described above, the ground improvement structure 10 does not rigidly connect the highly rigid deformation restraining plate 22 installed on the surface layer of the soft ground 18 and the underground wall 20 via the joint member 24. While transmitting a vertical load to the middle wall 20, it prevents the effective stress of the soft ground 18 inside the ground wall 20 from decreasing.

  Further, the ground improvement structure 10 has a function of suppressing the vertical movement of the end portion of the deformation suppression plate 22 in the vicinity of the underground wall 20, thereby enabling more effective liquefaction countermeasures. In addition, since the horizontal force due to the overload is borne by the underground wall 20, it is not transmitted into the soft ground 18 inside the underground wall 20.

  Next, a second embodiment of the ground improvement structure of the present invention will be described. Note that components that are basically the same as those in the first embodiment described above are given the same reference numerals as those in the first embodiment, and descriptions thereof are omitted.

  A ground improvement structure 40 is shown in FIGS. The ground improvement structure 40 is provided with a deformation suppression plate 41 instead of the deformation suppression plate 22 of the ground improvement structure 10 (see FIG. 1) of the first embodiment, and further includes a pile material 42, a receiving member 44, and a reaction force plate. 46 is provided. A plurality of joint members 24 are packed in the gap between the inner surface of the underground wall 20 and the side surface (end surface) of the deformation suppression plate 41 to block the gap.

  The deformation suppression plate 41 is a cement-based surface improvement body having a higher rigidity than the soft ground 18 and is horizontally disposed with a gap from the underground wall 20. In addition, through holes 41 </ b> A are formed at both ends of the deformation suppression plate 41 from the ground toward the soft ground 18. In addition, although the thickness of the deformation | transformation suppression board 41 may be selected in the range of 1m-2m, for example, it is not restricted to this and may be thicker than 2m.

  The pile material 42 is a columnar member having a diameter smaller than the diameter of the through hole 41A of the deformation suppressing plate 41, and is provided in the ground 12 with the lower end reaching the hard ground 16 through the through hole 41A. ing. Further, a screw groove (not shown) for fixing a fixing bolt 56 to be described later is formed on the upper end side of the pile material 42. A gap between the inner surface of the through hole 41 </ b> A and the outer peripheral surface of the pile material 42 is a friction reducing portion 47.

  The friction reduction part 47 is a part for suppressing the frictional force acting on the deformation restraining plate 41 when the deformation restraining plate 41 is about to move in the axial direction of the pile material 42. It is configured to leave a gap without filling anything. In addition, the friction reduction part 47 should just reduce the friction coefficient of the deformation | transformation suppression board 41 and the pile material 42. FIG. For example, the pipe | tube may have passed the outer side of the pile material 42 like a double pipe.

  The receiving member 44 is formed with a through hole (not shown) having a diameter larger than the diameter of the pile material 42 and is externally attached to the pile material 42. The receiving member 44 is externally attached to the pile material 42 and has one end on the upper surface of the washer 52. Is attached to a screw groove (not shown) on the upper end side of the pile material 42, and a fixing bolt 56 having the other end of the spring 54 attached to the lower surface.

  The reaction force plate 46 is made of an elastic body such as rubber, and is fixed to the upper surface of the deformation suppression plate 41 and the lower surface of the washer 52 so that a reaction force acts on the deformation suppression plate 41 when the deformation suppression plate 41 is raised and lowered. It has become.

  Next, the operation of the second embodiment of the present invention will be described. In addition, since the vertical movement of the deformation | transformation suppression board 41 is the same at both ends, only one edge part is demonstrated here and description of the other edge part is abbreviate | omitted.

  As shown in FIG. 8A, when the deformation restraining plate 41 is displaced downward at a height h1 during an earthquake, the reaction force plate 46 and the washer 52 are displaced downward together with the deformation restraining plate 41. To do. At this time, since the spring 54 expands with the movement of the washer 52, the downward movement of the washer 52 is not obstructed, and the deformation restraining plate 41 and the soft ground 18 are kept in close contact with each other. Thereby, the reduction | decrease of the effective stress which acts on the soft ground 18 can be suppressed.

  Further, when the deformation restraining plate 41 is further displaced downward and the spring 54 is extended, the downward displacement of the washer 52 is restricted. A downward pulling force acts on the reaction force plate 46, but the reaction force plate 46 pulls the deformation suppression plate 41 upward to return to the original state. Thereby, it is suppressed that the excessive displacement to the downward direction of the deformation | transformation suppression board 41 arises.

  On the other hand, as shown in FIG. 8B, when the deformation suppression plate 41 is displaced upward at a height h2 during an earthquake, the reaction force plate 46 and the washer 52 are integrated with the deformation suppression plate 41 in the upward direction. It is displaced to. At this time, the spring 54 contracts as the washer 52 moves, but the spring 54 urges the washer 52 and the reaction force plate 46 downward to return to the original state. Thereby, the deformation | transformation suppression board 41 is pushed down below, and it suppresses that the excessive displacement to the upward direction of the deformation | transformation suppression board 41 arises.

  As described above, by providing the pile material 42, the receiving member 44, and the reaction force plate 46, even if the thickness of the deformation suppression plate 41 cannot be sufficiently increased, it is possible to follow the subsidence, and further, the upward vertical Can resist movement.

  Here, in either case of FIGS. 8A and 8B, the end portion of the deformation suppressing plate 41 is connected to the underground wall 20 due to the volume expansion of the joint member 24. Thereby, the vertical load which acts on the deformation | transformation suppression board 41 is reliably transmitted to the soft ground 18 in the underground wall 20 at the time of a normal time and an earthquake, and the reduction | decrease of the effective stress which acts on the soft ground 18 can be suppressed. And the horizontal force which acts at the time of an earthquake can be sent to the underground wall 20 from the deformation | transformation suppression board 41. FIG.

  Further, since the end portion of the deformation suppression plate 41 is locked with respect to the underground wall 20, the vertical movement and inclination of both ends of the deformation suppression plate 41 are suppressed, and the bending moment is transmitted to the underground wall 20. Is possible. Thereby, the underground wall 20 and the deformation | transformation suppression board 41 are integrated via the joint member 24, it becomes a gate-shaped deformation | transformation suppression wall, the whole rigidity of the ground improvement structure 40 increases, and the softness inside the underground wall 20 is increased. While suppressing horizontal and vertical shear deformation of the ground 18, liquefaction can be suppressed.

  Note that the receiving member 44 may not be constituted by the washer 52, the spring 54, and the fixing bolt 56, but may be a receiving member including only the fixing bolt 58 as shown in FIG. 9. In this configuration, when the deformation suppression plate 41 is displaced downward, the reaction force plate 46 contracts to return to the original state, and the deformation suppression plate 41 is pulled upward. On the other hand, when the deformation suppression plate 41 is displaced upward, the reaction force plate 46 expands to return to the original state, and pulls the deformation suppression plate 41 downward.

  Next, a third embodiment of the ground improvement structure of the present invention will be described. Note that components that are basically the same as those in the first embodiment described above are given the same reference numerals as those in the first embodiment, and descriptions thereof are omitted.

  FIG. 10 shows the ground improvement structure 60. The ground improvement structure 60 is provided with a building 64 having a root insertion portion 64A and a foundation beam 65 of the building 64 provided under the root insertion portion 64A in place of the building 14 and the deformation suppression plate 22 of the first embodiment. Further, a joint member 62 is provided in place of the joint member 24. The root insertion portion 64 </ b> A and the foundation beam 65 are higher in rigidity than the soft ground 18.

  Similar to the joint member 24, the joint member 62 includes a sandbag 26 having a water permeability and a granular body 28 (see FIG. 2), and includes an inner surface of the underground wall 20, a side surface of the root insertion portion 64A, and a foundation beam. By filling a plurality of gaps with 65, the gaps are closed.

  The ground improvement structure 60 has a gate shape in which the underground wall 20, the base portion 64 </ b> A, and the foundation beam 65 are connected by the joint member 62. Note that the connection of the underground wall 20 to the base portion 64A and the foundation beam 65 by the joint member 62 does not mean a rigid connection in which these are integrated with concrete or the like. The gap between the insertion portion 64A and the foundation beam 65 is filled to make it difficult for the earth and sand in the soft ground 18 to flow out to the ground, and the root insertion portion 64A and the foundation beam 65 are held to be movable relative to the underground wall 20. Is meant to do.

  Next, the operation of the third embodiment of the present invention will be described.

  When the soft ground 18 in the underground wall 20 moves up and down due to the earthquake and a vertical force acts on the base 64 A and the foundation beam 65 of the building 64, the volume of the joint member 62 expands. Thereby, the gap | interval of the base insertion part 64A and the foundation beam 65, and the underground wall 20 is block | closed, and the outflow by the sand of soft ground 18 liquefied locally can be prevented.

  Further, since the joint member 62 has water permeability, a part of the water (ground water) in the soft ground 18 passes through the joint member 62 and is drained to the ground. Thereby, the excessive excess pore water pressure of the soft ground 18 is dissipated and liquefaction is suppressed.

  Further, the joint member 62 is brought into a state (locked state) in which the root portion 64A and the ends of the foundation beam 65 are connected to the underground wall 20 by volume expansion. Thereby, the horizontal force which acts at the time of an earthquake can be sent to the underground wall 20 from the rooting part 64A and the foundation beam 65. Further, during normal times and during earthquakes, the vertical load acting on the base portion 64A and the foundation beam 65 is reliably transmitted to the soft ground 18 in the underground wall 20, and the reduction of effective stress acting on the soft ground 18 is suppressed. Can do.

  In addition, since the end portions of the root insertion portion 64A and the foundation beam 65 are locked with respect to the underground wall 20, the vertical movement and inclination of both ends of the root insertion portion 64A and the foundation beam 65 are suppressed, and the ground A bending moment can be transmitted to the middle wall 20. As a result, the underground wall 20, the base portion 64 </ b> A, and the foundation beam 65 are integrated via the joint member 24 to form a gate-shaped deformation suppression wall, and the overall rigidity of the ground improvement structure 60 is increased. 20 can suppress horizontal deformation and vertical shear deformation of the soft ground 18 inside, and can suppress liquefaction.

  Furthermore, since the base 64A and the foundation beam 65 of the building 64 function as a deformation restraining plate, there is no need to provide a separate deformation restraining plate. Moreover, the effective stress of the soft ground 18 can be increased by the weight of the building 64.

  In addition, in the countermeasure against liquefaction of the existing building, it was technically and costly difficult to take measures directly under the building, but in the ground improvement structure 60, the underground wall 20 was installed on the outer periphery of the building 64, Liquefaction of the soft ground 18 directly under the building 64 can be prevented by connecting the base portion 64 </ b> A and the foundation beam 65 and the underground wall 20 using the joint member 62.

  Next, a fourth embodiment of the ground improvement structure of the present invention will be described. Note that components that are basically the same as those in the first embodiment described above are given the same reference numerals as those in the first embodiment, and descriptions thereof are omitted.

  FIG. 11 shows the ground improvement structure 70. The ground improvement structure 70 has a structure in which a structure 72 of an underground structure is provided instead of the building 14 and the deformation suppression plate 22 of the first embodiment, and a joint member 74 is provided instead of the joint member 24. ing.

  The underground structure 72 is a structure of an underground structure such as a common ditch or a digging road (water channel), and has a higher rigidity than the soft ground 18. Moreover, the height of the housing 72 is about 5 m, and is supported by the soft ground 18 </ b> A that is a part of the soft ground 18. Moreover, the soft ground 18B is formed in the upper part of the housing 72 by the earth and sand of backfilling.

  Similar to the joint member 24, the joint member 74 includes the sandbag 26 having a water permeability and the granular body 28 (see FIG. 2), and a plurality of joint members 74 are packed in the gap between the inner surface of the underground wall 20 and the casing 72. This closes the gap.

  The ground improvement structure 70 has a gate shape in which the underground wall 20 and the housing 72 are connected by the joint member 74. The connection between the underground wall 20 and the frame 72 by the joint member 62 does not mean a rigid connection in which these are integrated with concrete or the like, and the gap between the underground wall 20 and the frame 72 is filled. This means that the earth and sand in the soft ground 18 </ b> A are less likely to flow out to the soft ground 18 </ b> B and the ground, and the frame 72 is held so as to be movable relative to the underground wall 20 in the vertical direction.

  Next, the operation of the fourth exemplary embodiment of the present invention will be described.

  When the soft ground 18 (including 18A and 18B) in the underground wall 20 moves up and down due to the earthquake, and a vertical force is applied to the housing 72 of the underground structure, the joint member 74 expands in volume. Thereby, the clearance gap between the housing 72 and the underground wall 20 is block | closed, and the outflow by the sand of soft ground 18 liquefied locally can be prevented.

  Moreover, since the joint member 74 has water permeability, a part of the water (ground water) in the soft ground 18A passes through the joint member 74 and is drained to the soft ground 18B and the ground. Thereby, the excessive excess pore water pressure of the soft ground 18A is dissipated, and liquefaction is suppressed.

  Further, the joint member 74 is brought into a state (locked state) in which the end of the housing 72 is connected to the underground wall 20 by volume expansion. Thereby, the horizontal force which acts at the time of an earthquake can be sent from the housing 72 to the underground wall 20. And the normal load which acts on the housing 72 at the time of a normal time and an earthquake is reliably transmitted to the soft ground 18A in the underground wall 20, and the reduction | decrease of the effective stress which acts on the soft ground 18A can be suppressed.

  Further, since the end portion of the housing 72 is locked with respect to the underground wall 20, the vertical movement and inclination of both end portions of the housing 72 can be suppressed, and a bending moment can be transmitted to the underground wall 20. . As a result, the underground wall 20 and the frame 72 are integrated via the joint member 74 to form a gate-shaped deformation prevention wall, the overall rigidity of the ground improvement structure 70 is increased, and the soft ground 18A inside the underground wall 20 is increased. It is possible to suppress shear deformation in the horizontal and vertical directions, and to suppress liquefaction.

  Furthermore, since the underground structure 72 is functioning as a deformation restraining plate, there is no need to separately provide a deformation restraining plate. Moreover, the effective stress of the soft ground 18A can be increased by the dead weight of the housing 72.

  In addition, this invention is not limited to said embodiment.

  As the joint members 24, 62, and 74, those that can be expanded or contracted, have water permeability, and do not allow earth and sand to flow out can be used. For example, a porous body having sponge-like elasticity may be used.

  The underground wall to be installed in the ground 12 is only required to be able to suppress the horizontal shear deformation of the soft ground 18, and in addition to the grid-like ground improved body, a columnar ground improved body, a sheet pile, and a steel pipe sheet pile are used. Also good.

10 Ground improvement structure 12 Ground 20 Underground wall 22 Deformation suppression plate (rigid plate)
24 Joint members (joint members)
26 Sandbag (bag)
28 Granular body 40 Ground improvement structure 41A Through hole 42 Pile material (pile)
44 Receiving member (receiving member)
46 Reaction force plate (elastic body)
60 Ground improvement structure 64 Building 64A Nesting part 65 Foundation beam 70 Ground improvement structure 72 Frame

Claims (5)

An underground wall that surrounds the ground,
A rigid plate disposed on the ground, having a higher rigidity than the ground, and covering the inside of the underground wall;
A joint member comprising a bag body having water permeability, and a granular body packed in the bag body, and closing a gap between the inner surface of the underground wall and the rigid plate;
Improved ground structure. A pile provided in the ground through the through hole formed in the rigid plate;
A receiving member fixed to the pile above the rigid plate;
An elastic body that is fixed to the rigid plate and the receiving member and causes a reaction force to act on the rigid plate when the rigid plate is raised and lowered;
The ground improvement structure of Claim 1 which has these. The ground improvement structure according to claim 1 or 2, wherein the rigid plate is a cement-based surface layer improvement body . 2. The ground according to claim 1 , wherein the rigid plate is configured by a building base built between the underground walls and a foundation beam of the building provided at a lower portion of the base wall. Improved structure. The ground improvement structure according to claim 1, wherein the rigid plate is a frame of an underground structure constructed between the underground walls .