JP2751652B2 - Liquefaction prevention structure for lifeline structures - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lifeline structure which is a continuous structure crossing a line on the ground or in the ground, such as a road, a railroad, an underground buried object (a common ditches, a trench road, etc.). It relates to a liquefaction countermeasure structure.

[0002]

2. Description of the Related Art Liquefaction countermeasures for lifeline structures provided through sandy ground that may be liquefied,
Alternatively, the following can be considered as seismic measures.

(1) Countermeasures for soil compaction This measure compacts soft ground containing humus, clay, etc. together with the target ground, so that the ground becomes solid, but its construction area is large and its range is not clear. . In addition, the groundwater environment may be impaired in order to reduce the water permeability of the ground.

(2) Measures against solidification of the ground by injecting or mixing in cement milk and chemicals This measure also strengthens the ground in the same way as soil compaction measures.
Large construction range. In addition, the groundwater environment may be polluted during construction, and after the construction, the water permeability of the ground disappears, and the groundwater environment changes significantly.

(3) Countermeasures against wall structures such as sheet pile walls, concrete continuous walls, etc. This countermeasure can prevent ground deformation during an earthquake because a continuous wall closes off the vicinity of the target structure. The groundwater environment may change.

(4) Countermeasure for drainage by crushed stone drain etc. Crushed stone drain (see JP-A-56-100919 and JP-A-56-116434) or resin drain material is built into the ground in a columnar form, and In order to reduce the rise of excess pore water pressure due to the drainage effect, the soil strength is maintained and the groundwater environment is not greatly changed. However, a large construction area is required and its range is not clear.

[0007]

When the above-mentioned conventional measures are applied to a lifeline structure provided through a sandy ground where there is a possibility of liquefaction, there are the following problems.

In general, when a lifeline structure is provided on a sandy ground that can be liquefied because its length is long, countermeasures reduce the water permeability of the ground, cut off the groundwater flow,
On the downstream side, wells become dry, land subsidence, and industrial water shortage occur.

In addition, there is a possibility that a difference in groundwater level occurs upstream and downstream of the lifeline, which may adversely affect the lifeline structure.

Conventional seismic measures have technical advantages and disadvantages, such as those that change the groundwater environment, those that are not suitable for liquefied ground, and those that have large construction areas and unknown ranges. Absent.

An object of the present invention is to solve the above problems at once.

[0012]

According to the present invention, the liquefaction of the ground near the drainage member can be suppressed by providing the drainage member in the sandy ground (hereinafter referred to as liquefied ground) which may be liquefied. By arranging points, piles with high strength and rigidity discretely, humus without changing the groundwater environment,
A liquefaction countermeasure structure is formed by combining the points that can suppress lateral flow of soft ground containing clay or the like (hereinafter, simply referred to as soft ground).

That is, a pile with a drainage function is formed by forming a drainage channel for dissipating excessive pore water pressure generated in the ground during an earthquake in the longitudinal direction of a pile body having high strength and rigidity (for example, Japanese Patent Laid-Open No. Sho 62-62). No. 211416, JP-A-2-96
No. 018, JP-A-2-132219 and the like, and JP-A-2-30 in which a plurality of drainage members provided with a number of holes and filters on the outer peripheral surface of a pile are attached.
No. 0412, etc.), these are arranged discretely at appropriate intervals, and a type of composite wall composed of piles and the ground between piles surrounds the lifeline structure. Form inside. This prevents soil deformation and protects the lifeline structure, and also allows the groundwater flow to pass through the ground between the piles, thereby preserving the groundwater environment.

[0014]

In general, the lifeline structure is always in an eccentric load condition. For example, in embankment,
Since the own weight of the embankment is an uneven load, and the apparent density of the underground buried structure is lighter than that of the ground, the weight of the surrounding ground is in an uneven load state with respect to the ground directly under the structure.

When the ground liquefies due to an earthquake under such conditions, the earth and sand flows laterally to the periphery of the embankment or the like, or immediately below the buried structure, and the structure is deformed (subsidence, rising). And various states of change are collectively called)
Cause.

[0016] Even when a road or the like is constructed on an almost horizontal ground, if the ground under the liquefied ground is inclined, a slight difference in weight balance occurs when the ground liquefies due to an earthquake. The ground may be deformed and roads may be cut off.

The present invention has been developed in order to prevent these phenomena.
A composite wall structure consisting of piles and ground is formed in the ground.

Next, the operation will be described with reference to FIGS.

FIG. 2 is a schematic horizontal cross-sectional view of the liquefied ground when the piles with drainage function 1 in which four drainage members 3 are attached to the pile main body 2 are arranged in one row.

The single hatched portion is a range where the drainage effect of the drainage member 3 is exerted. During liquefaction, the underground water is drained vertically upward by the individual drainage members 3, and the excess pore water pressure is reduced to this range. The ground strength approaches the normal strength as the excess pore water pressure is lower. Also, at the time of design, a safety factor is generally ensured with a constant ground strength.

In FIG. 2, the double hatched portion is in a state closer to the normal ground strength even during liquefaction because the four effects of the drainage member 3 are superimposed. As a result, the ground between the pile 1 with the drainage function and the pile 1 with the drainage function forms a kind of composite wall, and depends on the balance of the unbalanced load and the acting external force at the time of the earthquake. The flow phenomenon of sand passing between the piles (sand removal from between the piles 1) can be prevented.
This is the basic operation of the present invention.

FIG. 3 shows a two-row arrangement in FIG.
The figures show the case of a staggered arrangement in rows. In each case, the pile pitch can be determined from the design conditions, and the effect on the groundwater environment is extremely small.

In particular, the deformation of the lifeline structure when the ground liquefies greatly depends on the deformation of the ground. Claim 1 of the present invention prevents this,
By surrounding part or all of the lifeline structure with the above-mentioned composite wall, the ground in the liquefied state and the lifeline structure are cut off, and the deformation of the liquefied ground is suppressed by the bending rigidity of the pile. Bring.

A second aspect of the present invention is to increase the number of piles, widen the liquefaction suppression range, and improve the blocking effect against deformation of the ground as a composite wall.

The third object of the present invention is to increase the rigidity of the pile by connecting the head of the pile. That is, when liquefaction occurs in a local part of the ground, if the row of piles is one row, it is dealt with by the horizontal bending rigidity of the member connecting the pile heads, and if it occurs in the entire ground, as in claim 2, Increase the number of pile rows,
By connecting the heads, a rigid frame structure composed of a large number of piles and connecting members can be formed, and the vertical bending rigidity can be greatly increased.

A fourth aspect of the present invention means that in a lifeline structure having a pile foundation, a pile with a drainage function is used for the pile foundation, and the invention is also applied to liquefaction countermeasures.

[0027]

Next, the illustrated embodiment will be described.

FIG. 1 shows an embodiment in which the liquefaction countermeasure structure of the present invention is applied to an abutment 11 of a road 12 on a river embankment 10.

In this embodiment, the piles 1 with the drainage function are constructed at predetermined intervals on both sides of the embankment 13 and the river embankment 10 forming the slope 12b from the flat portion 12a of the road 12 to the abutment 11, and the drainage is performed. The embankment 13 is surrounded in a U-shape by the pile with function 1 to form a composite wall 14 composed of the ground between the pile 1 with drainage function and the pile 1 with drainage function.

If there is no liquefaction measure, the ground 1
When the liquefied ground 15 is liquefied, the weight difference caused by the height difference between the embankment and the embankment surface and the riverbed ground surface causes the liquefied ground 15 to liquefy.
The earth and sand flows out from the center of the embankment 13 on both sides and from the land side toward the river center, and the embankment 13 sinks greatly. Even if the abutment 11 is sound, it cannot be used as the road 12.

In this embodiment, in order to suppress such a situation, as described above, one row is provided on the land side of the abutment 11 and two rows are provided on both sides of the embankment 13 in a staggered manner, and the piles 1 with drainage functions are provided. The portions are joined by reinforced concrete 16 (hereinafter referred to as RC beams) to form a U-shaped composite wall 14 for liquefaction countermeasures. This eliminates the possibility that the earth and sand constituting the liquefied ground 15 flows out during liquefaction. Also, it does not change the groundwater environment.

Drainage from the pile 1 with drainage function is drained to a crushed stone layer (not shown) provided on the lower surface of the RC beam 16. The reason why the head of the pile with drainage function 1 is connected with the RC beam 16 is to increase the rigidity of the wall and to reduce pile displacement during an earthquake. The pitch of the pile with drainage function 1 is determined by the height of the embankment 13, the height difference between the surface of the embankment 13 and the riverbed ground surface, the degree of liquefaction of the ground, and the like.

The liquefaction countermeasure in this embodiment can be implemented before the embankment 13 is constructed. However, when the abutment 11 is newly constructed, the foundation pile 17 of the abutment 11 shown in FIG. One row of liquefaction countermeasures provided on the land side of 11 can be omitted. In the case of an existing road, the abutment 11
The liquefaction countermeasure of the present invention can be applied to the river side of the river. Liquefaction countermeasures on both sides of the embankment 13 can be implemented regardless of whether they are new or existing.

There is a possibility of fluidization during liquefaction from the inclined portion 12b of the road 12 to the flat portion 12a.
In the example of FIG. 1, no liquefaction countermeasures are taken because the embankment gradient is small. Depending on the conditions, the composite walls 1 on both sides of the embankment 13
4 is further extended to the flat portion 12a side, and liquefaction countermeasures are required by using a single-row or double-row staggered pile with a drainage function similar to that provided on the land side of the abutment 11.

Next, an embodiment applied to a common groove which is a buried lifeline structure will be described.

FIG. 4 (a) shows a cross section before the ground where the common groove is installed, FIG. 4 (b) is a horizontal cross section when the common groove is installed in the ground, and FIG. FIG. 3 shows a cross section in a direction perpendicular to the continuous direction of the common groove.

As shown in FIG. 4 (a), the liquefied ground 31, the non-liquefied ground 32, and the confined aquifer 33 form an alternating layer, and the liquefied ground 31 exists locally. (The middle part is largely omitted in the figure). However, the liquefied ground 31 is continuous in a direction perpendicular to the paper surface of FIG. 4 (a), that is, from the mountain side (upper part of FIG. 4 (b)) to the sea side (lower part of FIG. 4 (b)). If there is no countermeasure, the common groove 34 rises and may move locally from the mountain side to the sea side.

As shown in FIGS. 4 (b) and 5, the liquefaction countermeasures are such that a row of piles 1 with drainage functions is arranged on both sides of the common groove 34, and the heads thereof are connected by RC beams 35. Thereby, the portion of the common groove 34 located in the liquefied ground 31 can be surrounded by the composite wall 36 and the non-liquefied ground 32 formed by the drainage function pile 1 and the ground between the drainage function piles 1. .

In this embodiment, the drainage effect of the pile with drainage function 1 eliminates the lifting force to the common groove 34, and the effect of the composite wall 36 prevents earth and sand from flowing to the lower surface of the common groove 34. Large deformation from the mountain side to the sea side of 31 can be suppressed. The composite wall 36 is a confined aquifer 3
3 does not obstruct the groundwater flow.

FIGS. 6 to 8 show examples of the pile 1 with a drainage function used in the present invention.

The pile 1 with a drainage function shown in FIG. 6 is formed on the outer peripheral surface of the steel pipe pile main body 2 along the longitudinal direction of the pile main body.
The drainage member 3 is provided with a number of holes 4 formed therein, and each hole 4 is provided with a filter 5 for preventing intrusion of earth and sand.

The pile 1 with a drainage function shown in FIGS. 7 and 8 is obtained by welding a pipe having a circular or square cross section having a slit 7 as a drainage member 6 to the pile body 2 and crushing stones 8 inside the drainage member 6. (Japanese Unexamined Patent Publication No. Hei 2-9601).
No. 8).

[0043]

EFFECT OF THE INVENTION By arranging piles with drainage function discretely at predetermined intervals in liquefied ground, a composite wall composed of piles with drainage functions and the ground between piles with drainage functions is formed in liquefied ground. It does not lose its strength during an earthquake.

Therefore, it is possible to prevent the target lifeline structure from being damaged by the earthquake.

The liquefaction-suppressing function of the pile with the drainage function and the effect of the composite wall can prevent fluidization of the liquefied ground.

The groundwater can be moved between the piles with the drainage function, and the groundwater environment can be preserved.

[Brief description of the drawings]

FIG. 1 shows an embodiment in which the present invention is applied to the vicinity of an abutment portion of a road on a river embankment, (a) is a plan view,
(b) is a vertical sectional view of the center of the road.

FIG. 2 is a schematic horizontal cross-sectional view of the liquefied ground when the piles with a drainage function are arranged in one row.

FIG. 3 is a schematic horizontal cross-sectional view of the liquefied ground in a case where two rows of piles with drainage functions are arranged in a staggered manner.

FIGS. 4A and 4B show an embodiment in which the present invention is applied to a common ditch. FIG. 4A is a vertical sectional view of a ground where a common ditch is installed, and FIG. It is a horizontal sectional view showing a liquefaction countermeasure structure.

FIG. 5 is a vertical sectional view in a direction perpendicular to a continuous direction of the common groove in the embodiment of FIG. 4;

FIG. 6 is a perspective view of an upper part of a pile showing an example of a pile with a drainage function used in the present invention.

FIG. 7 is a horizontal sectional view showing another example of a pile with a drainage function used in the present invention.

FIG. 8 is a horizontal sectional view showing still another example of a pile with a drainage function used in the present invention.

[Explanation of symbols]

1. Pile with drainage function, 2. Pile body, 3. Drainage member, 4.
Hole, 5: filter, 6: drainage member, 7: slit,
8: crushed stone, 10: river embankment, 11: abutment, 12: road,
13 ... embankment, 14 ... composite wall, 15 ... ground, 16 ... RC
Beam, 17: Foundation pile, 31: Liquefied ground, 32: Non-liquefied ground, 33: Aquifer, 34: Common ditch, 35: RC
Beam, 36 ... composite wall

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yukio Saimura 1-3-1 Otemachi, Chiyoda-ku, Tokyo Sumitomo Metal Industries, Ltd. (56) References JP-A-61-146910 (JP, A) JP-A-4-106220 (JP, A) JP-A-1-271515 (JP, A) JP-A-61-126221 (JP, A) JP-A-62-55640 (JP, U)

Claims (4)

(57) [Claims] 1. A pile with a drainage function, which forms a drainage channel for dissipating excessive pore water pressure generated in the ground during an earthquake in the longitudinal direction of the pile, so as to surround part or all of the lifeline structure. 2. A structure for preventing liquefaction of a lifeline structure, wherein a composite wall comprising the pile with drainage function and the ground between the pile with drainage function is formed at predetermined intervals in a wall shape. 2. The liquefaction countermeasure structure for a lifeline structure according to claim 1, wherein the piles with a drainage function are arranged in a staggered manner. 3. The liquefaction countermeasure structure for a lifeline structure according to claim 1, wherein the heads of the piles with a drainage function are connected to each other. 4. The pile according to claim 1, wherein said pile with drainage function is used as a foundation pile which forms a foundation of said lifeline structure, and is a part of a composite wall surrounding said lifeline structure.
The liquefaction countermeasure structure of the lifeline structure described.