JP4459173B2 - Ground improvement wooden pile and carbon stock method - Google Patents

Description

The present invention relates to a ground improvement wooden pile and a carbon stock method for reducing CO ₂ in the atmosphere.

The reduction of greenhouse gases in the atmosphere is an urgent issue when considering global environmental issues, as the Kyoto Protocol, which came into effect in February 2005, stipulates the obligation to reduce greenhouse gas emissions. Various measures have been taken, and one of the effective measures for CO ₂ reduction is carbon stock technology that absorbs and fixes CO ₂ using forests, seaweeds, and the like.

13, in the case of continuing the repetition of the planting and the trees felled, increase in fixed-storage amount of the carbon of CO ₂ in forests, i.e. showing how the increase in carbon stocks.
In terms of individual trees, the amount of carbon stock gradually increases with growth (section a), but the stock speed becomes dull as it ages (section b).
If logging is done at this point, the carbon stocked in the tree will return to the atmosphere as the decay or combustion progresses (the average amount returned to the atmosphere is expressed as a gradient of line c), but the decay proceeds. It is clear that if it is difficult (if the slope d is reduced), the carbon can be kept in stock for a long period of time, and eventually CO ₂ in the atmosphere can be reduced.

Therefore, for trees whose aging has slowed the stock rate of carbon, not only thinned wood but also main felled wood will be actively cut, and young trees with fast stock speed will be newly planted to rejuvenate the forest. Can maintain the carbon stock speed of the forest.
On the other hand, the total carbon stock amount of the forest and the whole tree after felling can be continuously increased by using the felled tree in a state where it is difficult for the decay to proceed (sections e and f).

Wood has been used as a construction material for a long time, but because it decays due to contact with water and air and its proof strength declines, and once the timber used as a foundation is humated, it is difficult to repair it. Then, cement and iron are often used in the foundation of the structure, and there are many old-age trees in the forest that cannot be used even after the logging season.
This aging of the forest also causes hay fever, so there is a need for measures to promote forest rejuvenation by planting trees while effectively using large amounts of wood.

  In the first place, the decay of wood does not proceed unless the four conditions of water, air, nutrition, and temperature are met, so the progress of decay of wood placed below the groundwater level in the ground or on the underwater ground Will be very slow.

Therefore, if the ground improvement required for construction work on soft ground with high groundwater level is performed by timber placement, the decay of the timber placed there will be very slow and long-term. In addition, it is advantageous in that carbon stock can be produced, and furthermore, since the progress of humus is slow, reliability as a construction material is also ensured. Moreover, the placement of the wood can be easily performed because the ground is soft.
Of course, wood may be placed on such ground simply for the purpose of carbon stock.

  As a technique for placing a wooden pile in the ground, there is a so-called pile net construction method disclosed in Patent Documents 1 and 2, but this only improves the ground by creating a block-like soil mass in the soft ground. The purpose of this is not intended to be carbon stock, but because the minimum number of piles required for ground strengthening are driven, the efficiency of carbon stock is not necessarily good.

JP-A-53-71813 Japanese Patent Publication No. 60-55648

  On the other hand, if a large number of timbers are simply placed densely on the ground in order to increase the efficiency of carbon stock, the volume of the ground between piles decreases and the horizontal stress increases. The effective stress indicated by is not increased, the excess pore water pressure is increased, and as a result, a ground with reduced shear resistance and liquefaction resistance is formed.

Δσh = Δu + Δσh ′
(Where Δσh: horizontal total stress increase, Δu: excess pore water pressure, Δσh ′: horizontal effective stress increase)

  Therefore, it is necessary to devise a method for steadily improving the ground by dissipating the excess pore water pressure at an early stage after placing the wood.

Therefore, an object of the present invention is to provide a ground improvement wooden pile and a carbon stock method that can stock a large amount of carbon in the long term and can also improve the ground reliably.

The present invention according to claim 1, a ground improvement Yoboku piles for improving soft ground, such as sand or silt, the side surfaces of the carbon stock roundwood consists aging the timber in the axial direction flaws This is a wooden pile for ground improvement in which the scratches spread by leaving the product in the air and shrinking by drying are used as drainage grooves, and the drainage grooves are filled with a drain material.

The present invention according to claim 2 is a ground improvement wood pile for improving soft ground such as sand and silt, which is made of felled timber obtained by cutting aged trees, and is a log for carbon stock . This is a ground improvement wooden pile in which a spiral drainage groove is formed on the side of the wood so as to cross the streaks of the wood, and the drainage groove is filled with a drain material.

The third aspect of the present invention is a carbon stock method in which the ground improvement wood pile according to the first or second aspect is placed on a soft ground such as sand or silt .

According to the present invention, by long-term stock ground improvement Yoboku Pile Da設the carbon into the ground, to reduce CO ₂ in the atmosphere can be a global warming, yet, the Soil The improvement of the ground can be done by dissipating excess pore water pressure at an early stage by placing the improvement wood pile .
In addition, since a large amount of wood that has not been used in the past can be used, it is possible to rejuvenate an aged forest by afforestation and solve problems such as hay fever.

Carbon stock method for placing ground improvement wooden piles A, B, C, D or E having drainage means 1... 1 '.

A ground improvement wooden pile with drainage grooves 1 ..., 1 '..., 1 "... formed on the side of the log.

First, Example 1 of the present invention will be described in detail.
For example, A shown in FIG. 8 is formed by engraving and forming eight drainage grooves 1... Which are about 3 cm deep drainage means on the side surface of a log having a diameter of about 20 cm and a length of about 5 m over the entire length in the axial direction. In addition, the drainage ditch 1... Of the present invention ground improvement wooden pile (hereinafter referred to as “ pile”) filled with drain material such as sand, slag, and wood waste filled in a bag-like drain material filling net 2 as required. It is simply called “wood pile”).

The diameter and total length of the wooden pile A can be changed as appropriate. Moreover, it is preferable that the lower end is sharpened. This makes it easy to penetrate the ground. This wooden pile A can be manufactured not only from thinned wood but also from main cut wood.
Since the drain groove 1... Is packed with a drain material filling net 2 filled with a drain material, the drain groove 1... Is prevented from being clogged with soil when the wood pile A is placed in the ground. Is done.

  Note that the drain material may be packed in the drain grooves 1 as it is without filling the drain material filling net 2. Moreover, it is good also as not filling a drain material in the drain ditch 1 ....

  BG shown to FIGS. 9-12 is an example of another this invention wooden pile, respectively.

  The present invention wooden pile B shown in FIG. 9 is different from the present invention wooden pile A only in that the drainage grooves 1 ′... As in the case of the above wooden pile A, if the drainage grooves 1 in the axial direction are sculpted using only the log, the log is easily torn along the line. In this respect, the wooden pile B has the drainage groove 1 ′... Formed in a spiral shape so as to cross the log streaks, so that the logs are difficult to tear when carved.

The wood stake C of the present invention shown in FIG. 10 has a flaw of about several centimeters to 5 cm deep in the axial direction with a sharp blade such as a cutter on the surface of the log, and by leaving the log in the air. The above-mentioned scratches that have been dried and shrunk and spread are defined as drainage grooves 1 ".
The wooden piles A and B require a little effort to carve the drainage grooves 1 and 1 'and generate waste wood. However, the wooden pile C can be manufactured easily and inexpensively, and no waste wood is generated.
It is preferable that the drain material 1 "... of this wooden pile C is filled with the drain material into the drain material filling net 2 or without filling the net 2. However, the drain groove 1" ... It is also possible to stuff nothing.

The wooden stake D of the present invention shown in FIG. 11 is formed by concatenating three logs 3... With sharpened lower ends with tight binding wires 4... And a conical bottom so as to cover the lower ends of the respective logs 3. A cap 5 is attached to facilitate penetration into the ground.
A gap between the three logs 3... Constituting the wooden pile D is a drainage channel 6 as drainage means. Since the bottom cap 5 is attached to the lower end of the wooden pile D as described above, even when the wooden pile D is driven, earth and sand do not enter the drainage channel 6.

The bottom cap is not limited to a conical shape, and may be a pyramid shape as long as it is sharp.
The drainage channel 6 is preferably filled with a drain material in the same manner as the wooden piles A to C. Thereby, the logs 3 are firmly fixed to each other and wobble is prevented.
Note that the number of logs 3... To be bundled can be changed as appropriate, and drainage grooves may be carved and formed on the side surfaces of the respective logs 3.

The wood pile E of the present invention shown in FIG. 12 is formed by bundling seven superposed logs 8... Obtained by polymerizing short logs 7... It is what. The number of polymerized logs 8 to be bundled can be changed as appropriate.

The superposed logs 8... Adjacent to each other are shifted in the longitudinal direction by the positions of the superposed portions of the logs 7... It is preferable that the upper and lower ends of each log 7 are formed with concavities and convexities that fit each other so as not to be displaced.

A gap between each of the superposed logs 8 is a drainage channel 6. It is preferable to pack a drain material in the same manner as the wooden piles A to D. As a result, the polymerized logs 8 are firmly fixed to each other and the wobble of each other is prevented.
It is also preferable to engrave and form drainage grooves on the side surfaces of each log 7.
Reference numeral 9 denotes a conical bottom cap attached so as to cover the lower end of each superposed log 8.

The bottom cap is not limited to a conical shape, and may be a pyramid shape as long as it is sharp.
Further, it is preferable to use a material that does not humus or is difficult to humus as the log 7 on the upper side in the longitudinal direction of the above-mentioned polymerized logs 8.
By making the upper logs 7... Not humus or made of a material that is difficult to humate, it is possible to prevent humus when the portion comes out above the groundwater level surface.

  Since the above wooden piles D and E can be made thick and long even from thin and short thinned lumber, a large amount of thinned lumber that has not been effectively used so far can be used.

  In the carbon stock method of the present invention, the above-described wood piles A, B, C, D, or E of the present invention are placed in the ground to perform carbon stock, and the ground is also improved if necessary. However, in this embodiment, the wooden pile A is placed on soft ground having a high groundwater level, and embankment is created on the ground (FIG. 1).

  The method of the present invention is performed by placing a large number of the above-mentioned wooden piles A ... on the soft ground 11 at a predetermined interval. It is preferable for placing the wooden piles A ... to prevent the humus of the wooden piles A ... so that the entire length or almost the entire length is located below the groundwater level.

Excess pore water pressure generated when placing wooden stakes A ... dissipates over time, but the dissipation time is faster as the drainage distance is shorter. According to the consolidation theory, the dissipation time is proportional to the square of the drainage distance. Since the said wooden pile A ... is equipped with the drainage groove 1, it implement | achieves the early dissipation of excess pore water pressure.
In other words, when one side drainage is assumed when simply placing wood, the one that required a dissipation time of the square of the thickness of the soft ground is the dissipation time of (distance between piles / 2) ² , which is overwhelming. Dissipation time is shortened (in general, soft ground thickness >> (distance between piles / 2) ² ).

The smaller the gap ratio, the smaller the settlement amount, and the greater the shear resistance and liquefaction resistance. However, as the excess pore water pressure is dissipated, the gap ratio of the inter-pile ground decreases earlier. Sinking is suppressed.
Furthermore, as the restraint pressure increases, the shear resistance and liquefaction resistance increase, but at the same time as the gap ratio decreases due to the placement of the wooden piles, the restraint pressure increases due to the increase in the effective stress between the wooden piles A ... However, shear resistance and liquefaction resistance increase.
Therefore, the ground pile is reinforced and improved at an early stage by providing the drainage grooves 1.

  In addition, the ground becomes dense due to the placement of wooden piles A ..., and the frictional stress between the ground and the log increases by increasing the restraint pressure due to the increase in horizontal stress, reducing the amount of consolidation settlement of the ground between the piles. . Furthermore, the strength of the ground between the wooden piles A ... increases due to the effect of increasing the density of the ground and increasing the restraint pressure, and the lateral rigidity of the entire ground is increased, and the resistance in the horizontal direction is also increased.

Further, when the wooden pile A ... is placed on the ground such as sand or silt, the following effects are obtained for the liquefaction of the ground.
That is, the placement of the wooden piles A ... increases the ground density between the wooden piles A, the horizontal stress between the wooden piles A ... increases and the restraint pressure increases, the wooden piles A ... As a result, the shear resistance of the ground is increased by increasing the shear rigidity of the entire ground.
Furthermore, the drainage grooves 1 of the wooden pile A ... reduce the excess pore water pressure at the time of liquefaction at an early stage, and contribute to the reliable strengthening of the ground.

In general, if logs are placed below the groundwater level, the logs will contain water and become saturated over time, but there is concern over the lifting of wooden piles A ... immediately after placement or when the ground is liquefied. May be.
In this case, prior to placing, the wood pile A can be placed in a vacuum chamber and once put under vacuum, and then a saturation treatment for absorbing water can be performed in advance. At this time, if the resin or the like is impregnated instead of water, the saturation progresses and the strength of the wooden pile A.
In addition, this saturation treatment covers the side surface of the wooden pile A ... with a required film in a straw shape with the upper and lower ends opened without using a vacuum chamber, and sucks water or resin from the upper end or the lower end. It can also be made.
This saturation treatment can be similarly applied to the wooden piles B to E.

After placing the wooden pile A ..., the bank 12 is filled on the ground.
The above-mentioned wooden pile A ... is preferably placed so that its entire length or almost the entire length is below the groundwater level in order to prevent the corruption of the wooden pile A .... It is also possible to place the heads in a projecting state from the soft ground, make the heads mesh with a flexible connecting member such as a reinforcing bar, and bend the connecting member downward to connect them.
Then, by embedding the pile head and the connecting member with a sand mat and laying a civil engineering sheet thereon, and performing embankment 12, the embankment load is spread over the deep layer by the group pile effect rather than the surface layer of the soft ground. Can act on.

  The above-mentioned wooden pile A placed on the soft ground reduces the load increment near the surface layer by transmitting the load of the embankment 12 to the deep part of the ground, and reduces the amount of consolidation settlement near the surface layer.

Since the present invention wood pile A can be manufactured from either thinned or main-cutting wood, it is possible to actively use wood that has not been used in the past, and can be used in an overwhelmingly large amount. .
Therefore, while using a large amount of aging trees, reforestation promotes forest rejuvenation and contributes to solving forest problems such as hay fever.

In addition, the wooden piles A ... placed below the groundwater level hardly humus, so carbon can be stocked over a long period of time, thus reducing CO _{2 in} the atmosphere.
Conventionally, civil engineering and construction work for the purpose of roads, water supply, sewerage, railways, architecture, various developments, etc. are considered to be industries with high impact on the global environment that emit large amounts of CO ₂ due to the use of heavy machinery, etc. Although the environmental image was low, the method of the present invention can stock a large amount of carbon through its implementation. Therefore, if construction is actively promoted, as a result, social infrastructure is being improved. At the same time, a lot of carbon can be stocked to improve the global environment.

  In place of the present invention wooden pile A, the present invention wooden piles B to E may be placed.

  In this embodiment, the present invention wood pile is placed on soft ground with a high groundwater level to perform carbon stock, the ground is improved, and a ground, a parking lot, a park, etc. are created on the ground surface (FIG. 2). ).

Grounds, parking lots, parks, etc. require almost no design because there is almost no load on the ground, but when the ground is soft, uneven settlement occurs and the flatness of the ground surface is often lost.
In such a case, the carbon stock can be produced by driving the wooden pile A (or B, C, D, E)... Of the present invention on the soft ground 21 at a predetermined interval. Moreover, since the wooden pile A (or B, C, D, E)... To be placed has a drainage means, the ground can be strengthened at an early stage.
Reference numeral 22 denotes a drainage groove.

  The present embodiment is an example in which the wood pile of the present invention is placed on soft ground to perform carbon stock, the ground is improved, and the wood pile is used as a structure foundation (FIG. 3).

In recent years, due to the fear of humus, timber has been hardly applied to building foundations, but as described above, the present invention wooden pile A (or B, C, D, E) ... is placed below the groundwater level. For example, humus hardly progresses.
Therefore, the carbon pile A (or B, C, D, E) ... of the present invention is placed in the soft ground 31 below the groundwater level by placing the head of the pile or lowering the foundation bottom as necessary. While stocking, this can be the basis for detached houses (Fig. 3 (a)) and factories and low-rise buildings (Fig. 3 (b)).

  The present embodiment is an example in which the wood pile is placed on the ground around the structure to perform carbon stock and the ground is improved (FIG. 4).

Since the structure 41 on the soft ground is generally often supported by a pile foundation 42 such as an HPC pile, the subsidence amount of the structure 41 itself is extremely small.
However, since the surrounding ground of the structure 41 often has no countermeasure, ground subsidence occurs, and a step is often generated between the first floor portion of the structure 41 and the surrounding ground surface.
In such a case, in order to reduce the level difference, the pavement thickness of the surface pavement 43 of the surrounding ground is increased or embanked, but this further sinks, and it becomes a weasel. Even in barrier-free structures, such a step at the entrance is a problem.

Therefore, in order to solve this, the wooden pile A (or B, C, D, E) of the present invention is passed through the soft ground 44 on the structure 41 side of the surrounding ground of the structure 41 and compared. It is placed so as to reach the hard support layer 45 and the length of the wooden pile A is gradually shortened as the distance from the structure 41 increases.
Thus, this invention wooden pile can be used as a support pile or a friction pile.
Thereby, the amount of settlement on the ground surface gradually increases as the distance from the structure increases, so that the problem of the step is solved and carbon stock can be performed.
When using ordinary concrete piles or steel piles, it takes time to produce piles with different lengths, but if the present invention wooden pile A (or B, C, D, E) ... The length can be adjusted easily by cutting on site.

  The present embodiment is an example in which the wood pile is placed on the lower ground of the water channel 51 to perform carbon stock and the ground is improved (FIG. 5).

It is important to secure a gradient in linear structures such as waterways and pipes, but in sewage pipes and the like, damage often occurs due to liquefaction during earthquakes and changes in the soft ground.
In order to prevent this change in gradient, the present invention wooden pile A (or B, C, D, E)...

In the illustrated example, the present invention wood pile A (or B, C, D, E)... Is placed on the ground 52, and a backfill layer 53 is formed on the ground by filling back the poorly mixed soil. Although the water channel 51 is formed, if a drain 54... Communicating with the lower ground 52 is provided at the bottom of the water channel 51 and water is supplied to the lower ground 52, the present invention wood pile A (Or B, C, D, E)... Can be delayed and carbon can be stocked for a long period of time.
In addition, since the ground on which such a linear structure is constructed is linear, the ground layer in the ground is often rich in changes, but the wooden pile A (or B, C, D, E) ... Can be placed by cutting according to the formation and adjusting the length appropriately.

  This example is an example in which the wood pile of the present invention is placed in a landfill to perform carbon stock and the ground is improved (FIG. 6).

In landfills such as oceans and lakes, earth and sand are reclaimed on soft ground, and large settlements often occur thereafter. As countermeasures, there are generally sand lanes, sand compaction, and a deep mixing treatment method in which the ground is solidified by cement or the like. While sand drains and the like need to cut the mountain area to secure sand, according to the construction method of the present embodiment, the present invention wood pile A ...... (or B, C) having drainage grooves 1 for drainage. , D, E), the environmental effects are high while obtaining the same effects as sand drains.
In FIG. 6, 61 is a Pleistocene, 62 is a sand layer, 63 is a clay layer, 64 is a sand layer, 65 is a buried layer, 66 is a solidification improvement layer, and the wood pile A (or B, C, D, E) of the present invention. ) ... is placed to reach the Pleistocene 61 from the buried layer 65.
Since the wooden pile A (or B, C, D, E)... Is completely placed in water, there is no risk of decay, so carbon can be stocked for a long time.

  The present embodiment is an example in which the present invention wood pile is placed on the slope of the seabed soft ground to perform carbon stock and the ground is improved (FIG. 7).

The dredging slope 71 for securing the channel is created only by dredging work, so its slope is gentle, and the seabed 72 is often formed of sand, silt, etc. and is likely to be liquefied. Many.
Since such ground tends to liquefy and become flat after the earthquake, there is a possibility that the water depth of the channel cannot be secured.
Therefore, in this embodiment, in order to stock carbon and stabilize the slope 71, the present invention wooden pile A (or B, C, D, E)...
By placing the wood pile A (or B, C, D, E) of the present invention, the slope surface 71 is stabilized, and the slope slope can be made steep.
Moreover, in the ground which is easy to be liquefied, liquefaction resistance can be increased by placing the wooden piles A (or B, C, D, E)...

  In addition to the examples shown in the above embodiments, the wooden piles of the present invention can be placed on the ground of a revetment or jetty foundation, or can be placed on the ground of a river dike or a super dike.

It is sectional drawing of Example 1 which created the embankment in the ground improved with the carbon stock method of this invention. It is sectional drawing of Example 2 which created the ground, the parking lot, the park, etc. in the ground improved by the carbon stock method of this invention. It is sectional drawing of Example 3 which improved the ground and constructed | assembled the structure foundation by the carbon stock method of this invention. It is sectional drawing of Example 4 which improved the structure surrounding ground by the carbon stock method of this invention. It is sectional drawing of Example 5 which improved the lower ground of linear structures, such as a water channel and a pipe line, by the carbon stock method of this invention. It is sectional drawing of Example 6 which improved the ground of landfill sites, such as the ocean and lakes, by the carbon stock method of this invention. It is sectional drawing of Example 7 which improved the ground of the heel slope by the carbon stock method of this invention. The 1st example of the wooden pile for ground improvement of this invention is shown, (a) is a top view, (b) is a perspective view. The 2nd example of the wooden pile for ground improvement of the present invention is shown, (a) is a top view and (b) is a perspective view. The 3rd example of the wooden pile for ground improvement of this invention is shown, (a) is a top view, (b) is a perspective view. The 4th example of the wooden pile for ground improvement of the present invention is shown, (a) is a top view and (b) is a perspective view. The 5th example of the wooden pile for ground improvement of this invention is shown, (a) is a top view, (b) is a perspective view, (c) is the elements on larger scale of (a). It is the graph which showed the increase in the amount of carbon stock by continuing continuation of tree cutting and afforestation.

Explanation of symbols

A to E Ground improvement wooden piles 1, 1 ', 1 "Drainage groove 2 Drain material filling net 3, 7 Log 4 Tightening wire 5, 9 Bottom cap 6 Drainage channel 8 Superposed log 11, 21, 31, 44 Soft ground 12 Embankment 22 Drainage channel 41 Structure 42 Pile foundation 43 Surface pavement 45 Support layer 51 Water channel 53 Backfill layer 54 Drain 61 Pleistocene 62, 64 Sand layer 63 Clay layer 65 Filled layer 66 Solidification improvement layer 71 Slope 72 Submarine ground

Claims (3)

It is a wooden pile for ground improvement to improve soft ground like sand and silt,
And the scratch drains spread by left drying shrinkage in the gas with a side surface in the axial flaw of carbon stock roundwood consists aging were harvested wood, it filled with drain material to the drainage grooves A wooden pile for ground improvement characterized by It is a wooden pile for ground improvement to improve soft ground like sand and silt,
It is characterized by the fact that a spiral drainage groove is formed on the side of the log for carbon stock , and the drainage groove is filled with drain material. A wooden pile for ground improvement. 3. A carbon stock method, wherein the ground improvement wooden pile according to claim 1 or 2 is placed on a soft ground such as sand or silt .

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