JP5726007B2 - Ground improvement method - Google Patents

Description

  In this invention, in order to improve soft ground and liquefied ground, a large number of holes are drilled vertically by an auger for each position scattered vertically and horizontally in the improved area, and a built pile is formed in each drilled hole This is related to the ground improvement method.

  This conventional ground improvement method will be explained. Generally, a series of operations are performed while operating a self-propelled mechanical vehicle such as a hydraulic excavator with an auger attached as an attachment to the tip of the swivel arm. The excavated holes drilled by the auger at each predetermined point are backfilled with unsolidified material soil obtained by mixing excavated sand or mountain sand with cement-based solidified material. In this case, the auger is also used for promoting or compacting the filling of the unsolidified material soil with forward / reverse rotation or lateral pressing.

  The unsolidified material soil as a mixture of earth and sand filled in the excavation hole and cement gradually absorbs moisture around the cement, and thus retains strength similar to that of a pile through a curing period called curing. Moreover, the surrounding soil water | moisture content decreases and is compacted by the water absorption accompanying hardening, and this also improves the ground.

Japanese Patent No. 3668477

  According to the conventional ground improvement method as described above, it is generally applied to an environmental ground having a high water content. Especially, when construction is performed on a ground having a high groundwater level, water at the bottom of the excavation hole is used. Because it is easily affected, the unsolidified material soil filled in the excavation hole is diluted with water that has risen along the excavation hole at the lower end, and may be weakened partially due to the lack of cement. There is also a possibility that the reliability of compressive strength that can withstand the load as a pile cannot be obtained. In addition, when the underground water rises in the pile-shaped hardened body (excavation hole), the constructed pile sinks by the amount of water missing below it, and even if there is no rise in water, the underground water is separated and retreated. Therefore, it is difficult to obtain the support force at the front end (received at the lower end) as a pile that can withstand the load.

  In the present invention, in view of the above situation, since the waterstop block prevents the groundwater from entering the groundwater, there is no partial weakening due to the dilution of the cement, so that the desired compressive strength of the constructed pile is ensured. In addition, an object of the present invention is to provide a ground improvement method that can secure a large tip support force even in soft ground with a lot of moisture.

  In order to solve the above-mentioned problems, the present invention fills a ground excavation hole drilled by an auger with unsolidified material soil in which cement-based solidification material is mixed with sand such as dug sand or mountain sand. In the ground improvement method in which the excavated hole is backfilled, and the unsolidified material soil backfilled with the excavated hole is hardened while absorbing water contained in the surrounding ground to form a pile that is mainly composed of a solid pile. Before returning, at the lower end of the excavation hole, a stirring step for mixing at least a mixed base material made of sand or the like and a cement-based solidified material is provided, and in the stirring step, water glass is added to the cement-based solidified material to perform rapid hardening. A ground improvement construction method is provided, in which a water stop block bulging in a lump is formed, and the backfill is filled with unsolidified material soil from above the water stop block into an excavation hole.

  Since the ground improvement construction method is configured as described above, a water blocking block is formed at the bottom of the excavation hole, and the unsolidified material soil is filled thereon, so that water entry into the filling portion is prevented. As a result, there is no lack of partial concentration of cement as water enters, and the unsolidified material soil is uniformly cured without impeding the absorption of moisture from the surrounding soil. Moreover, even if there is a lot of underground water, subsidence is prevented by the swelled water blocking block.

  As explained above, according to the ground improvement method of the present invention, the rise of underground water is blocked by the water blocking block, so the influence of groundwater that suddenly enters is eliminated. There is no inconvenience that the concentration is partially reduced, and it is possible to form a reliable pile-shaped hardened body with a uniform cement strength and a high compressive strength, and the bottom end is hardened with water resistance. Since it is a water blocking block, it has an excellent effect of exhibiting a strong tip supporting force even on soft ground without sinking to sandy soil.

  According to Claims 2 and 3, the above-described effect becomes more remarkable.

It is sectional drawing of the ground which shows the state which created the creation pile by the ground improvement construction method of this invention. It is a front view of the field which shows the state where the ground is perforated with an auger as one process of the ground improvement construction method by this invention . It is sectional explanatory drawing which shows the procedure which forms the molding hole of a still water block as an example by the ground improvement construction method. It is sectional explanatory drawing which shows the next procedure which similarly forms the shaping | molding hole of a water stop block.

  In this invention, the creation pile P consists of the pile-shaped hardening body 5 shape | molded by the excavation hole 1, and the water stop block 3 shape | molded by the lower end, and both of them are integrally molded by a series of work. Among these, the molding of the water blocking block 3 requires a stirring step of mixing gravel, sand, cement and the like. The pile-shaped hardened body 5 is back-filled with unsolidified material soil 6 mixed with cement-based solidified material and excavated sand, mountain sand, etc., and stirred or pressed by an auger 9. And since the filled unsolidified material soil 6 is hardened by water absorption from the surrounding ground, the ground G is absorbed and compacted in the same manner as before.

  However, since there is no water rising approach, water absorption from the surrounding ground G is surely performed on the unsolidified material soil 6, and the cement is not diluted and the strength is not lost. In addition, the settlement of the pile due to the swell is also prevented, and the amount of drainage of water and the like of the swelled water blocking block 3 is large.

  As a material for the waterstop block 3, aggregates such as gravel and crushed stone, sand, cement-based solidified material, water glass (sodium silicate), and the like are used. As the cement-based solidifying material, for example, Portland cement is mainly used. In addition, a mixture obtained by mixing quick lime or gypsum with cement (for example, quick lime 8: cement 1: gypsum 1) can be effectively used. In any case, since it hardens immediately by the fusion of the cement-based solidifying material and water glass, a water stop state can be obtained without delay. In addition, as described above, if it is too late, the water that has entered the borehole will dilute the cement.

As an example of the ratio of materials, aggregates such as crushed stone are 50 kg / m ³ , aggregate and cement are about 1/3 of the total in volume, and water glass is 5 to 5 of the total by weight. 6%. In addition, underground sand scraped by stirring when the waterstop block 3 is formed is also effectively used. Further, regarding the unsolidified material soil 6, cement is about 200 kg / m ³ with respect to the excavated sand. However, due to the influence of groundwater, the appropriate material ratio is appropriately determined depending on the site.

  The machine used for the agitation work for mixing aggregate, sand, cement-based solidified material, water glass and the like is not particularly limited, but it is desirable to use the auger 9 for drilling the drilling hole 1 at the same time. Then, the auger 9 can be used for drilling, mixing of unsolidified material soil 6 and pressing and the like, and by providing the stirring blade 18, the molding hole 3a of the water blocking block 3 can be formed. Desirable in terms of efficiency and efficiency.

  However, if a special instrument having a stirring blade attached to the lower end of a special rotating shaft different from the auger 9 is used to form the molding hole 3a, the shape can be set relatively freely by devising. That is, since the water stop block 3 can be formed by inserting a tool in place of the auger 9, the agitation process is various. The following embodiment uses an auger 9 improved in the stirring process, and shows an example different from that using a special machine.

  The drawing shows an embodiment, and the pile P created by the ground improvement method is formed with a drilling hole 1 in the ground G of the improved zone, and a water blocking block 3 is formed at the lower end thereof, and the pile is formed on the pile. It is made by molding the shaped cured body 5.

  As described above, the excavation hole 1 is excavated by rotating the excavator 2 having a plurality of jointed pivot arms 7 on the ground G with the auger 9 attached to the tip of the arm 7 being rotated. At that time, a compacted wall layer 10 in which the sand of the ground G is slightly compacted is formed on the inner peripheral surface of the excavation hole 1 by lateral pressing by the auger 9.

  An inverted conical sharpened body 21 in which a plurality of stirring blades 18 is squeezed is attached to the tip of the auger 9 (FIG. 3), and it opens so that the stirring blades 18, 18,. It has become. Further, water glass is passed through the central shaft 23, and the stirring blades 18, 18,.

  Therefore, when the sharpened body 21 is positioned at the lower end of the excavation hole 1 perforated by the auger 9, it is rotated while the stirring blades 18, 18,. 3a is formed, and then gravel, cement, and water glass are agitated and mixed with the ground sand in the ground to form a frustoconical waterstop block 3.

  Since the water blocking block 3 hardens rapidly, the stirring blades 18, 18,... Are half-closed before being hardened, and the unsolidified material soil 6 is put into the excavation hole 1 from above and the auger 9 is rotated in the reverse direction. Press and harden (Fig. 4). In this way, the unsolidified material soil 6 is densely filled on the water blocking block 3.

The unset material soil 6 by the reverse rotation when pulling up the auger 9 it is compressed is formed as a pressure tight skin layer 20 at the outer periphery. Therefore, a stable filling state of the unsolidified material soil 6 is maintained by the double hardened layer of the compacted wall layer 10 and the compacted skin layer 20 in which the sand of the ground G is solidified.

  Since the molding hole 3a of the water blocking block 3 is formed large by the spread of the stirring blades 18, 18,..., The water blocking block is formed by integrating the consolidated wall layer 10 and the consolidated skin layer 20 (range W). It is in the state where it was just put on 3. Therefore, the integration of the W portion is reliably maintained, and the pile-shaped cured body 5 is cured and maintains strength by absorbing the surrounding moisture without causing collapse, cracking, or the like.

  Moreover, the inconvenience that the water of the ground G rises to the excavation hole 1 is surely prevented, so that the unsolidified material soil 6 absorbs the surrounding water without any inconvenience, and the lower end of the constructed pile P that accompanies the water loss. Settlement is prevented.

G Ground P Ground pile 1 Drilling hole 5 Pile-shaped hardened body 6 Unsolidified material soil 9 Auger 18 Agitation blade 23 Central axis

Claims (3)

  The excavation hole of the ground drilled by the auger was filled with unsolidified material soil in which cement-type solidified material was mixed with sand such as excavated sand and mountain sand, and the excavated hole was backfilled. In the ground improvement method of forming a built-up pile mainly composed of pile-shaped solidified body by absorbing water contained in the surrounding ground into the unsolidified material soil, at least sand etc. at the lower end of the drilling hole before refilling The mixing base material and the cement-based solidified material are mixed, and in this stirring process, water glass is added to the cement-based solidified material to form a water blocking block that swells in a lump with rapid hardening. The ground improvement method is characterized by filling the excavation hole with the backfill of unsolidified material soil from above the water blocking block. In the agitation process performed at the lower end of the excavation hole, the ground sand is scraped off while stirring with a stirring blade to form a mixed base material with the aggregate such as gravel and the water blocking block is formed by scraping the ground sand. the drilling frustoconical, ground improvement method according to claim 1, wherein the shaping into the form of a water shut-off blocks wide receiving a pile-like cured product by its shape. For the agitation step, a water glass spout and a stirring blade are provided at the tip of the central axis of the auger, and the aggregate, sand, cement-based solidified material, and the like are agitated while pouring out the water glass. The ground improvement construction method according to claim 1 or 2.

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