JP6073617B2 - Ground improvement body for liquefaction countermeasure and formation method thereof - Google Patents

Description

  The present invention relates to a ground improvement body for liquefaction countermeasures and a method for forming the same, and more specifically, by improving the ground grid by a deep mixing treatment method, the liquefaction strength is appropriately and reliably improved. The present invention relates to a ground improvement body and a method for forming the same.

  In sandy ground with a high groundwater level, such as landfills, liquefaction occurs due to earthquake vibration, and manholes and sewer pipes are pushed up and protrude from the ground surface, and damage to the building can occur. ing. In order to prevent such a liquefaction phenomenon, improvement work must be performed on the ground where liquefaction is a concern.

  As a conventional liquefaction countermeasure method, a ground-like improvement of the ground by a deep mixing method is known (for example, see Patent Document 1). The technique described in Patent Document 1 performs a step of jetting a high-pressure fluid jet containing air from an injection port of an injection tube penetrating into the ground and stirring while cutting the ground, and a step of raising the injection tube Thus, the ground improvement body is formed.

  The technique described in Patent Document 1 is an excellent technique capable of forming a ground improvement body having an arbitrary shape (lattice shape, fan shape, etc.). In particular, by using this deep mixing method (high-pressure jet agitation method) to form a grid-like ground improvement body in the underground part of an existing building, the shear deformation of the ground during an earthquake is suppressed, Since the increase in excess pore water pressure can be suppressed, the liquefaction strength can be improved.

JP 2012-62616 A

  If the ground improvement method using the deep mixing method (high pressure jet agitation method) can improve the lattice shape at reasonable and effective intervals in the design, the improvement rate will be optimal, so countermeasures against liquefaction This is a relatively low cost method. Moreover, it can be said that such an optimal lattice improvement is possible in a large-scale construction which is a newly constructed ground having no existing structure and has few construction restrictions. On the other hand, in the case of small-scale construction with many construction restrictions such as countermeasures for liquefaction of existing residential land, which has become a problem in recent years, it is necessary to improve beyond the lattice spacing, which is reasonable in design. Do not meet the required performance, or the cost advantage will be reduced by drilling from the floor of the existing building and adding improvement points, increasing the cost burden on the landowner There is a fear.

  The ground improvement method using the deep mixing method (high pressure jet agitation method) is a method of forming a ground improvement body in the improvement target ground (saturated soil where liquefaction is a concern). While reaching the layer, it is necessary to form ground improvement bodies at predetermined intervals.

  That is, when the interval for forming the ground improvement body is too wide, the effect of suppressing shear deformation by the ground improvement body cannot be exhibited. On the other hand, if the space for forming the ground improvement body is narrowed, the effect of suppressing shear deformation by the ground improvement body can be exhibited, but the cost increases. In particular, in an area where a personal house has already been built, in order to form ground improvement bodies at intervals that are conventionally considered appropriate, a great burden is imposed on the owner of the personal house.

  The present invention has been proposed in view of the above-described circumstances, and is appropriate, reliable, and inexpensive when forming a ground improvement body using a deep mixed processing method in an area where a private house has already been built. An object of the present invention is to provide a ground improvement body for liquefaction countermeasures that can improve liquefaction strength and a method for forming the ground improvement body.

The ground improvement body for liquefaction countermeasure of the present invention and the formation method thereof have the following features in order to achieve the above-described object. That is, the ground improvement body for liquefaction measures according to the present invention penetrates the injection pipe into the improvement target ground including the area where the existing building exists , and the ground from the tip of the injection pipe into the improvement target ground. A ground improvement body formed in the ground to be improved by a high-pressure jet agitation method for injecting the improvement material, the first ground improvement body in a substantially vertical direction and the second ground in a substantially vertical direction or a substantially horizontal direction It consists of an improved body.

The first ground improvement body is formed so that the lower end reaches the basement layer in the area where the existing building does not exist on the improvement target ground, and in the area where the existing building exists, the lower end is Form so as not to reach the base layer. In addition, the second ground improvement body is in a substantially vertical direction that supports a part of the lower part of the existing building or a substantially horizontal direction that covers a part of the lower part of the existing building in the ground immediately below the existing building. Form.

The method of forming a ground improvement body for liquefaction countermeasures according to the present invention includes a jet pipe penetrating into an improvement target ground including an area where an existing building exists, and a ground from the tip of the injection pipe into the improvement target ground. A method for forming a ground improvement body for improving the liquefaction strength of a ground to be improved by a high-pressure jet stirring method for injecting the improvement material, and forming a first ground improvement body in a substantially vertical direction in the ground to be improved And a second step in the substantially vertical direction for supporting a part of the lower part of the existing building or a part of the lower part of the existing building in the vicinity of the immediate lower part of the existing building on the ground to be improved. And a step of forming the ground improvement body.

  The first ground improvement body is formed such that the lower end reaches the basement layer in the area where the existing building does not exist, and the lower end does not reach the basement layer in the area where the existing building exists. To form.

In addition, it is preferable that the second ground improvement body is formed directly and continuously with the first ground improvement body when the first ground improvement body is formed.

  According to the ground improvement body formation method for ground liquefaction countermeasures of the present invention, a ground improvement body in a substantially vertical direction is formed using a deep mixing treatment method (high pressure jet agitation method). Whether the lower end reaches the base layer (the depth of the ground improvement body) is selected in the area where the existing building exists above or the area where the existing building does not exist on the improvement target ground.

  That is, for example, in a place where there is no existing building on the ground to be improved, such as a public land (public road), as in the past, while forming a ground improvement body whose lower end reaches the base layer, for example, In a place where an existing building exists, such as a private residential area, a ground improvement body having a shallower depth than the conventional one is formed. Furthermore, in the ground immediately below the existing building where the ground improvement body having a shallower depth than the conventional one is formed, the vertical direction that substantially supports the lower part of the existing building or the lower part of the existing building is substantially covered. Form a ground improvement body in the horizontal direction.

  Therefore, since a ground improvement body similar to the conventional one is formed in a place where there is no existing building on the improvement target ground, such as a public land (public road), it is possible to perform a reliable liquefaction countermeasure. Moreover, since the ground improvement body of the shallower depth is formed in the place where the existing building exists like a private residential area, cost can be suppressed. Furthermore, by forming a substantially vertical ground improvement body so as to substantially support the lower part of the existing building, or forming a substantially horizontal ground improvement body so as to substantially cover the lower part of the existing building, Even if the ground improvement body has a shallower depth, the ground improvement body in the substantially vertical direction or the substantially horizontal direction suppresses shear deformation of the ground, so that the liquefaction strength can be improved appropriately, reliably and inexpensively. .

The perspective view of the ground improvement object (1) for liquefaction measures concerning the embodiment of the present invention. The perspective view which shows a part of ground improvement body (1) for liquefaction countermeasures concerning embodiment of this invention as a cross section. The top view of the ground improvement object (1) for the liquefaction countermeasures concerning embodiment of this invention. The front view (A arrow line view in Drawing 1) of the ground improvement object (1) for liquefaction measures concerning the embodiment of the present invention. The side view (B arrow view in FIG. 1) of the ground improvement body (1) for a liquefaction countermeasure which concerns on embodiment of this invention. The perspective view of the ground improvement body (2) for the liquefaction countermeasure which concerns on the actual condition form of this invention. The perspective view which shows a part of ground improvement body (2) for a liquefaction countermeasure which concerns on embodiment of this invention as a cross section. The top view of the ground improvement body (2) for the liquefaction countermeasure which concerns on embodiment of this invention. The front view (A arrow line view in FIG. 6) of the ground improvement body (2) for a liquefaction countermeasure which concerns on embodiment of this invention. The side view (B arrow view in Drawing 6) of the ground improvement object (2) for liquefaction measures concerning the embodiment of the present invention. The principle explanatory view of the high-pressure jet stirring method used in the formation method of the ground improvement object for the liquefaction measures concerning the embodiment of the present invention.

  Hereinafter, embodiments of a ground improvement body for liquefaction countermeasures and a method for forming the same according to the present invention will be described with reference to the drawings. FIGS. 1 to 11 illustrate a ground improvement body for liquefaction countermeasures and a method for forming the same according to an embodiment of the present invention. FIGS. 1 and 6 are perspective views of the ground improvement body, FIGS. Is a perspective view showing a part of the ground improvement body as a cross section, FIGS. 3 and 8 are plan views of the ground improvement body, FIGS. 4 and 9 are front views of the ground improvement body, and FIGS. 5 and 10 are views of the ground improvement body. FIG. 11 is a side view, and FIG. 11 is a diagram illustrating the principle of the high-pressure jet stirring method.

<Outline of formation method of ground improvement body>
In Japan, liquefaction of the ground occurs due to the occurrence of a massive plate boundary earthquake, and large scale damage is expected due to this phenomenon. In fact, during the Great East Japan Earthquake, liquefaction occurred in landfills, embankments, banking, and revetments, causing various damage. For this reason, it is desirable to take measures against liquefaction as soon as possible in preparation for a large-scale earthquake that is expected to occur in the near future. The liquefaction countermeasure method according to the embodiment of the present invention is based on the formation of a ground improvement body using a deep mixing treatment method, and the location where the existing building exists on the improvement target ground and the existing building The depth of the ground improvement body differs from that of the nonexistent place, and a substantially vertical ground improvement body is formed so as to substantially support the lower part of the existing building, or a substantially horizontal direction so as to substantially cover the lower part of the existing building. It is characterized by forming a ground improvement body.

  Note that “substantially support” not only means that the lower part of the existing building is fully supported, but also means that there may be a portion that does not support the lower part of the existing building in part. Similarly, substantially covering means not only the case where the lower part of the existing building is entirely covered, but also that there may be a portion that does not cover the lower part of the existing building. Further, “substantially vertical” means that a slight inclination is allowed including the vertical direction, and “substantially horizontal” means that a slight inclination is allowed including the horizontal direction.

<Deep mixing treatment method>
In order to form the ground improvement body according to the embodiment of the present invention, a high-pressure jet agitation method which is a kind of deep mixing treatment method is used. With reference to FIG. 11, the high-pressure jet stirring method will be described. As shown in FIG. 11, the high-pressure jet agitation method penetrates an injection pipe 51 having an injection port 52 at the tip into the ground to be improved, and improves the ground improvement material (curing) from the injection port 52 with a predetermined pressure and a predetermined injection amount. The ground improvement material 10a, 10b, 21, 22 is formed inside the improvement target ground by mixing the ground improvement material (hardening material) while stirring the soil by rotating the injection pipe 51 while spraying the material). It is a construction method.

  Such a high-pressure jet agitation method is characterized in that the soil can be improved in a desired range by adjusting the rotation range of the injection pipe 51 and the injection pressure and injection amount of the ground improvement material (hardening material). Therefore, it can be suitably used especially when forming the ground improvement bodies 10a, 10b, 21, and 22 according to the embodiment of the present invention.

  For example, by adjusting the position of the injection port 52 and the rotation range of the injection pipe 51 and injecting a ground improvement material (hardening material), various shapes such as a columnar shape, a semi-columnar shape, a wall shape, a fan shape, a lattice shape, etc. A ground improvement body can be formed. In addition, the position of the injection port 52 may be one place, and may be two or more places. In addition, when two or more injection ports 52 are provided, by appropriately setting the positions, the ground improvement material (hardening material) can be efficiently injected into the desired range to form the ground improvement body.

  As shown in FIGS. 1 to 10, the ground improvement body according to the embodiment of the present invention is formed by using a high-pressure jet stirring method, and is formed in a substantially vertical direction from the ground toward the ground. 1 ground improvement bodies 10a and 10b and a second improvement body 21 formed in a substantially vertical direction or a second ground improvement body 22 formed in a substantially horizontal direction in the vicinity immediately below the existing building 40. . 1 to 5 show a ground improvement body (1) including a second ground improvement body 21 formed in a substantially vertical method, and FIGS. 6 to 10 show a second horizontal formation in a substantially horizontal direction. The ground improvement body (2) containing the ground improvement body 22 of this is shown.

<First ground improvement body>
The first ground improvement bodies 10a and 10b have a substantially vertical wall shape, and the depths of the place where the existing building 40 exists on the improvement target ground and the place where the existing building 40 does not exist. Is different. For example, as shown in FIGS. 4 and 9, in a place where the existing building 40 does not exist on the ground to be improved, such as a public land (public road 30), the lower end reaches the base layer as in the conventional case. The ground improvement body 10a is formed. On the other hand, for example, as shown in FIGS. 4 and 9, the ground improvement body 10 b having a shallower depth than the conventional one is formed in a place where the existing building 40 exists, such as a private residential area. That is, the ground improvement body 10b formed in the place where the existing building 40 exists does not reach the base layer at the lower end.

  In this way, in the place where the existing building 40 does not exist on the improvement target ground such as the public land (public road 30), the ground improvement body 10a whose lower end reaches the basement layer is formed, so that reliable liquefaction is achieved. Measures can be taken. On the other hand, since the ground improvement body 10b in which the lower end portion does not reach the base layer is formed in a place where the existing building 40 exists, such as a private residential area, the cost can be reduced.

  In addition, when the ground improvement body 10b in which a lower end part does not reach a base layer is formed, there exists a possibility that liquefaction strength cannot fully be improved. Therefore, in the present invention, the second ground improvement body 21 is formed so as to substantially support the lower part of the existing building 40 in the area where the ground improvement body 10b whose lower end does not reach the base layer is formed, or the existing building is formed. The second ground improvement body 22 is formed so as to substantially cover the lower part of 40.

<Second ground improvement body>
As shown in FIGS. 1 to 5, the second ground improvement body 21 is formed so as to substantially support the lower part of the existing building 40 in the ground immediately below the existing building 40. That is, in the ground around the existing building 40, the injection pipe 51 is penetrated to the same depth as that for forming the first ground improvement body 10b, and the wall-shaped second inside the lattice-shaped ground improvement body 10b. The ground improvement body 21 is formed.

  Moreover, as shown in FIGS. 6-9, the 2nd ground improvement body 22 is formed so that the lower part of the said existing building 40 may be covered substantially in the ground near the existing building 40 directly. That is, the injection pipe 51 is penetrated to an appropriate depth in the ground around the existing building 40, and the cross section is substantially circular (cylindrical) or semicircular (half (Cylindrical) ground improvement body is formed. The second ground improvement body 21 or the second ground improvement body 22 substantially supports the lower part of the existing building 40, forms a wall inside the ground to be improved, or substantially covers the lower part of the existing building 40. Thus, a lid can be formed on the upper part of the improvement target ground.

  In addition, when forming the 1st ground improvement body 10a, 10b, the 2nd ground improvement body 21 or the 2nd ground improvement body 22 should form continuously to the 1st ground improvement body 10a, 10b. Is preferred. As described above, since the first ground improvement bodies 10a and 10b and the second ground improvement body 21 or the second ground improvement body 22 are formed substantially simultaneously, the number of construction steps is reduced, so that efficient construction can be performed. It can be performed and the construction cost can be reduced.

  In the experiment by the inventor, even in the area where the first ground improvement body 10b where the lower end portion does not reach the base layer is formed, a wall shape is formed inside the improvement target ground surrounded by the first ground improvement body 10b. The second ground improvement body 21 is formed, or the lid-like second ground improvement body 22 is formed on the improvement target ground surrounded by the first ground improvement body 10b. Deformation was suppressed, and the liquefaction strength could be improved. The second ground improvement body 21 or the second ground improvement body 22 does not need to form a complete lattice wall at the lower part of the existing structure 40, and does not need to completely cover it. If the lower part of 40 is substantially supported or substantially covered, even if a slight gap portion is generated, the shear deformation of the ground can be suppressed.

<Formation of ground improvement body>
In this embodiment, the ground improvement body 10a, 10b, 21, by injecting the injection pipe 51 into the ground to be improved and injecting the ground improvement material (hardening material) from the injection port 52 at a predetermined pressure and a predetermined injection amount. 22 is formed. At this time, in a place where the existing building 40 does not exist on the improvement target ground (for example, the public road 30), the first ground improvement body 10a having a wall shape is formed in a substantially vertical direction so that the lower end reaches the basement layer. To do. On the other hand, in a place where the existing building 40 exists on the improvement target ground (for example, a private residential area), the first ground improvement is shallower than a place where the existing building 40 does not exist on the improvement target ground. Form body 10b.

  Further, the injection pipe 51 is inserted into the ground around the existing building 40 to an appropriate depth, and the injection pipe 51 is inserted while spraying the ground improvement material (hardening material) from the injection port 52 at a predetermined pressure and a predetermined injection amount. By rotating, the lower part of the existing building 40 is substantially supported to form the wall-like second ground improvement body 21, or the lower part of the existing building 40 is substantially covered to form a columnar shape or a half A cylindrical second ground improvement body 22 is formed.

  In this way, whether or not it is a place where the existing building 40 exists on the ground portion, that is, a ground improvement body formed by, for example, a residential land where a personal house is built and a public land such as the public road 30 By varying the depth and shape of 10a, 10b, 21, and 22, the liquefaction strength can be improved appropriately and reliably as a whole without imposing a great burden on the owner of the private residential area. It becomes possible.

10 ground to be improved 10a, 10b first ground improvement body 21 second ground improvement body (substantially vertical direction)
22 Second ground improvement body (substantially horizontal direction)
30 Public road 40 Existing building 51 Injection pipe 52 Injection port

Claims (4)

Existing structures penetrate the injection pipe in improved target ground including existing zone, the high-pressure injection agitation method for injecting soil improvement material from the tip of the injection tube in the improved target ground, the improved target ground in A first ground improvement body in a substantially vertical direction and a second ground improvement body in a substantially vertical direction or a substantially horizontal direction,
The first ground improvement body is formed such that a lower end thereof reaches the base layer in an area where the existing building does not exist on the improvement target ground, and a lower end of the first ground improvement body in the area where the existing building exists. Formed so as not to reach the base layer,
The second ground improvement body is formed so as to support a part of the lower part of the existing building or to cover a part of the lower part of the existing building in the ground immediately below the existing building.
Ground improvement body for liquefaction measures characterized by this. The second ground improvement body is formed directly and continuously with the first ground improvement body,
The ground improvement object for liquefaction measures of Claim 1 characterized by the above-mentioned. The improvement target ground is liquefied by a high-pressure jet agitation method in which the injection pipe penetrates into the improvement target ground including the area where the existing building exists and the ground improvement material is injected into the improvement target ground from the tip of the injection pipe. A method for forming a ground improvement body for improving the strength of the formation,
Forming a substantially vertical first ground improvement body in the improvement target ground;
A second ground improvement in a substantially vertical direction that supports a part of the lower part of the existing building or a part of a lower part of the existing building in the vicinity of the existing building existing on the improvement target ground. Forming a body, and
The first ground improvement body is formed such that the lower end reaches the base layer in the area where the existing building does not exist, and the lower end extends to the base layer in the area where the existing building exists. Not to reach,
The formation method of the ground improvement body for the liquefaction countermeasure characterized by the above-mentioned. In the step of forming the second ground improvement body, the second ground improvement body is formed directly and continuously to the first ground improvement body when forming the first ground improvement body.
The formation method of the ground improvement object for liquefaction measures of Claim 3 characterized by the above-mentioned.

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