JP2005068688A - Sheet pile structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively prevent soft ground change creating filling without placing a sheet pile up to a support layer. <P>SOLUTION: The sheet pile structure creates additional filling 14 to existing filling 12 provided on soft ground 10, and suppresses sideward deformation of the soft ground 10 caused by creation of the additional filling 14. Therefor, prior to the creation of the additional filling 14, a pair of the sheet piles 16 and 18 are placed on a toe-of-slope part of the existing filling 12 and a toe-of-slope part of a creation planned position of the additional filling 14 so as to be mutually opposite. The placing depth of the sheet piles 16 and 18 do not arrive down to support ground 30, and is depth on the way of the soft ground 10. Each pair of the sheet piles 16 and 18 is coupled by a tie rod 20 on the upper end. The sheet piles 16 and 18 are placed in a thoothless shape spacing intervals in the extension direction for instance. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a sheet pile structure for suppressing ground deformation when embankment is created on soft ground.

When embankment is performed on soft ground, ground deformation such as lateral movement of the ground may occur due to the load of the embankment. As a measure for preventing such ground deformation, for example, as disclosed in Patent Document 1, a sheet pile is placed on the slope of the embankment provided on the soft ground. In the construction method disclosed in Patent Document 1, a floating sheet pile inserted halfway through the soft layer is provided between the bottoming struts that have been cast up to the support layer, and their heads are combined and integrated.
JP 2001-317043 A

  Thus, conventionally, it has been usual to drive at least a part of the sheet pile to the depth of the support layer. This is because if the sheet pile is placed only in the middle of the soft layer, the lateral flow cannot be stopped by the sheet pile when a large lateral flow occurs in the ground. For this reason, when the thickness of the soft layer is large, it is necessary to use a large sheet pile having a high rigidity because the depth of the sheet pile is increased and the construction cost is increased, and the cost is further increased.

  This invention is made | formed in view of said point, and it aims at enabling it to suppress effectively the deformation | transformation of the soft ground in which embankment is created, without driving a sheet pile to a support layer.

  In order to achieve the above object, the sheet pile structure according to the first aspect of the present invention includes a pair of sheet piles facing each other up to a midway depth of the soft layer of the ground, and the upper ends of these sheet piles are tie rods. And connected to each other.

  Further, the invention described in claim 2 is a sheet pile structure for suppressing ground deformation of the soft ground when creating an additional bank on the existing bank on the soft ground, the existing bank and the additional bank A pair of sheet piles opposed to each other is driven to a depth in the middle of the soft layer, and the upper ends of these sheet piles are connected to each other by tie rods.

  According to the first and second aspects of the present invention, in the vicinity of the ground surface where the amount of lateral deformation of the ground due to the embankment load is the largest, the placed sheet pile pairs are restrained by the tie rods. For this reason, even if it does not drive a sheet pile to a support layer, the deformation | transformation of the soft ground resulting from embankment can be suppressed effectively.

  The invention described in claim 3 is characterized in that, in the sheet pile structure according to claim 1 or 2, the sheet piles are driven in a tooth-like manner with an interval in the extension direction. In this way, the number of sheet piles can be reduced to shorten the work period and reduce the cost.

  ADVANTAGE OF THE INVENTION According to this invention, the deformation | transformation of the soft ground in which embankment is created can be prevented effectively, without driving a sheet pile to a support layer.

  FIG. 1 is a perspective view showing an embodiment of the present invention. As shown in the figure, in the present embodiment, the additional embankment 14 is created on one side (or both sides) of the existing embankment 12 provided on the soft ground 10, and the softness resulting from the creation of the additional embankment 14 is shown. Side deformation of the ground 10 is suppressed. For this purpose, prior to the formation of the additional embankment 14, a pair of sheet piles 16 and 18 are placed so as to oppose each other on the hull of the existing embankment 12 and the hull of the planned position of the additional embankment 14 to be built. Keep it. The placement depth of the sheet piles 16 and 18 is set to a depth in the middle of the soft ground 10 that does not reach the support ground 30. In the present embodiment, the sheet piles 16 and 18 are driven in a tooth-like shape with an interval in the extending direction. Each pair of sheet piles 16 and 18 are connected to each other by a tie rod 20 at their upper ends. After constructing such a sheet pile structure including the sheet piles 16 and 18 and the tie rod 20 on the soft ground 10, the additional embankment 14 is formed. In this embodiment, steel sheet piles are used as the sheet piles 16 and 18. However, the present invention is not limited to this, and for example, concrete or wooden sheet piles may be used.

  FIG. 2 is a diagram for explaining the principle of preventing lateral deformation of the soft ground by the sheet piles 16 and 18. As shown in the figure, when embankment is created on the soft ground 10, the embankment load is dispersed as the depth of the soft ground 10 increases. For this reason, the amount of lateral deformation of the soft ground 10 caused by the embankment load increases as the depth becomes shallower. Therefore, in the present embodiment, the lateral deformation of the ground is effectively performed by restraining the sheet piles 16 and 18 with the tie rods 20 near the ground surface where the lateral deformation amount is maximum (that is, the upper ends of the sheet piles 16 and 18). It can be suppressed.

  FIG. 3 is a view for explaining design guidelines for the sheet piles 16 and 18 and the tie rod 20 in the present embodiment. In general, when a smashing failure occurs on a slope such as an embankment slope, the sculptured surface has an arc shape as shown in FIG. Therefore, the depth of the sheet piles 16 and 18 is designed so that the sheet piles 16 and 18 pass through the arcuate face. Further, the tie rod 20 is designed to have a rigidity, a thickness, and the like so as to have a strength capable of resisting the resultant earth pressure acting on the sheet piles 16 and 18. By designing the sheet piles 16 and 18 and the tie rod 20 in this way, it is possible to more reliably suppress lateral deformation due to the bending of the soft ground 10. In addition, the arc-shaped grooving surface is obtained by calculating the shear stress generated in the soft ground 10 by the load of the additional embankment 14 and searching for a grooving surface whose value exceeds the shear stress that the soft ground 10 can exhibit. Can do.

  In addition, in this embodiment, since the space between the ground under the additional embankment 14 and the surrounding ground is cut off by the sheet piles 16 and 18, an effect of suppressing the settlement of the ground due to the embankment load can be expected.

  Next, an experiment conducted to produce an experimental model having the embankment structure shown in FIG. 1 and confirm the effect of preventing the lateral movement of the soft ground will be described. In the produced experimental model, a layer of viscous soil (kaolin industrial clay) having a thickness of 26 cm (corresponding to 13 m in actual conversion by application of a centrifugal model experiment) is used as the soft ground 10, and a height of 8 cm is provided thereon. An existing embankment 12 and an additional embankment 14 (corresponding to 4 m in actual conversion) were created. In addition, the sheet piles 16 and 18 were constructed in a tooth-missing shape at intervals of 2 cm using an aluminum plate having a thickness of 5 mm and a width of 3 cm, and the root insertion length was 13 cm. The lateral deformation (horizontal displacement) at each depth of the soft ground 10 (viscous soil layer) when the sheet piles 16 and 18 and the tie rod 20 are constructed and when no measures are taken are image sensors. In addition, the temporal change in the amount of settlement immediately below the shoulder was measured with a displacement sensor.

  FIG. 4 shows the measurement results of the lateral deformation of the ground in the model experiment. In the figure, the vertical axis represents the depth and the horizontal axis represents the horizontal displacement, and the result when the sheet pile and the tie rod are provided is indicated by a solid line, and the result when no countermeasure is taken is indicated by the broken line. As can be seen from the results shown in the figure, it is understood that by providing the sheet piles 16 and 18 and the tie rod 20, the lateral deformation of the ground can be greatly reduced as compared with the case where no countermeasure is taken. In addition, as described with reference to FIG. 3, the lateral deformation in the ground becomes larger as it is shallower, and this is supported by the result of the case of no countermeasure shown by the broken line in FIG.

  FIG. 5 shows the measurement results of the land subsidence amount in the model experiment. In this figure, the vertical axis is the amount of settlement just below the shoulder, the horizontal axis is the elapsed time from the start of embankment, and the results when the sheet pile structure is provided are indicated by solid lines, and the results when no countermeasures are taken are indicated by broken lines. ing. As can be seen from the results shown in the figure, by providing a sheet pile structure including the sheet piles 16 and 18 and the tie rod 20, it is understood that the amount of ground subsidence can be significantly reduced.

  As described above, in the present embodiment, when the additional embankment 14 is created on the existing embankment 12, the sheet piles 16 and 18 are driven at the hail position of the existing embankment 12 and the hail position of the additional embankment 14, By connecting the upper ends with the tie rods 20, the lateral deformation amount and the subsidence amount of the soft ground 10 can be effectively suppressed without driving the sheet piles 16 and 18 to the support ground 30. For this reason, it is possible to reduce the installation cost by reducing the placement depth of the sheet piles 16 and 18, and the rigidity required for the sheet piles 16 and 18 can be reduced to reduce the material cost. Cost reduction can be achieved.

  Moreover, in this embodiment, since the sheet piles 16 and 18 are provided at intervals in the extension direction in the extending direction, the number of sheet piles 16 and 18 can be reduced, and the cost can be reduced in that respect. Figured. However, a configuration in which the sheet piles 16 and 18 are not densely formed but densely placed in the extending direction is also included in the scope of the present invention.

It is a perspective view which shows one Embodiment of this invention. In this embodiment, it is a figure for demonstrating the principle of the side deformation | transformation prevention of the soft ground by a sheet pile. It is a figure for demonstrating the design guideline of the sheet pile and tie rod in this embodiment. It is a figure which shows the measurement result of the side deformation | transformation of the ground in a model experiment. It is a figure which shows the measurement result of the amount of ground subsidence in a model experiment.

Explanation of symbols

10 Soft ground 12 Existing bank 14 Additional bank 16, 18 Sheet pile 20 Tie rod

Claims (3)

  A sheet pile structure characterized in that pairs of sheet piles facing each other are driven to a depth in the middle of the soft layer of the ground, and the upper ends of these sheet piles are connected to each other by tie rods.   When creating an additional embankment on an existing embankment on soft ground, it is a sheet pile structure for suppressing ground deformation of the soft ground, and a pair of sheet piles facing each other at the position of the bottom of the existing embankment and the additional embankment The sheet pile structure is characterized in that the upper end portions of these sheet piles are connected to each other with a tie rod. The sheet pile structure according to claim 1 or 2, wherein the sheet pile is driven in a tooth-missing manner with an interval in an extending direction thereof.

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