JP5036800B2 - Ground improvement method - Google Patents

Description

  The present invention relates to a ground improvement construction method in which a ground improvement material such as a solidified material slurry is injected into the ground such as soft ground, and the solidified material slurry and soft soil are mixed.

  As a conventional ground improvement device, equipped with a stirring blade extending horizontally in the vicinity of the tip of the single tube rod, and a high-pressure jet stirring monitor having a spiral soil lifting plate in the immediate vicinity of the stirring blade Although there is a high-pressure spray ground improvement device, the high-pressure spray ground improvement method using this device can reduce the displacement as much as possible by controlling the displacement given to the surrounding ground even though it is a single pipe method (see, for example, Patent Document 1). .

  In order to reduce the displacement given to the surrounding ground due to the construction, the ground improvement construction method is based on discharging a ground soil of an amount substantially equal to the solidified material slurry injected into the ground from the improved range. In this earth removal method, first, drilling, agitation, and drawing are repeated with the tip monitor of the ground improvement device to perform edge cutting with the surrounding ground.

  After that, due to the increase in internal pressure due to the injection of the super-high-pressure solidifying material slurry and the effect of the soil lifting plate, the soil equivalent to the amount of the solidifying material slurry is discharged from the improved range.

  The specifications of the standard tip monitor used in the ground improvement method include a stirring blade having a circular trajectory diameter of 60 cm when the rod is rotated, and a spiral soil lifting plate having a planar shape of 50 cm in diameter. Yes. The standard solidifying material slurry injection specifications are an injection flow rate of 80 to 150 l / min and an injection pressure of 20 to 40 MPa.

Japanese Patent Laid-Open No. 2005-120819

  In recent years, it has been demanded that the diameter of a cylindrical improvement body formed in the planned improvement ground be larger than before. Therefore, at present, the ground improvement method is being developed with the aim of further increasing the diameter.

  In the development process, it is necessary to increase the solidified slurry injection amount in order to realize a large diameter, and in order to reduce the ground displacement as much as possible regardless of the increase in the solidified slurry injection amount, the solidified material From the principle of draining almost the same amount of raw soil as the slurry, it is necessary to increase the discharge amount of disturbed soil per hour accordingly.

  As described above, the soil improvement principle of the ground improvement method is that a muddy water film having a diameter of the stirring blade length is obtained by repeatedly drilling, stirring, and drawing with the tip monitor of the ground improvement device, and cutting the edge with the surrounding ground. A cylindrical disturbed soil discharge channel with a hole wall protected is created. And the pressure of the fluid improved soil mixed and stirred with the solidified material slurry injected to the improved portion pushes up the disturbed raw soil above the soil lifting plate and is discharged from the cylindrical disturbed soil discharge channel. By doing so, the volume of the soil discharged is substantially equal to the amount of the injected slurry.

  Here, in order to increase the amount of soil discharged per hour, it is conceivable to increase the cross-sectional area of the cylindrical disturbed soil discharge channel, but in order to do so, the shape of the stirring blade and the soil lifting plate of the tip monitor Need to be larger. However, in this method, it is necessary to increase the drilling ability of the ground improvement device (construction machine), and the construction machine needs to be increased in size.

  Therefore, if the size of the tip monitor is the same as before and the cross-sectional area of the cylindrical disturbed soil discharge channel is the same as the conventional size in order not to impair the economy, the discharged soil passing through the disturbed soil discharge channel It is necessary to increase the flow rate.

  In the present invention, in view of the above circumstances, even when the cross-sectional area of the cylindrical disturbed soil discharge passage is the same size as the conventional one and the amount of the solidified slurry injection is increased, the soil removal rate is 90% to 100% of the injection amount. The purpose is to be able to maintain%.

The present invention, the tip portion of the single pipe type injection rod construction machinery dumping high-pressure injection mixing method, arranged helical soil push-up plate to the upper proximate the stirring blade to the stirring blade the soil push-up plate A ground improvement method using a ground improvement device provided with a pressure adjusting hole in the ground, wherein the single pipe injection rod of the ground improvement device penetrates into the ground of the ground to be improved, and the soil is disturbed by a stirring blade of the injection rod After forming the disturbing part and forming the disturbing soil discharge path, the solidifying material slurry is jetted from the tip nozzle of the stirring blade while pulling up the injection rod, and the solidifying material improving part is disposed on the disturbing part and the outer peripheral part thereof. In the ground improvement method for forming the injection rod, when the injection rod is pulled up, the soil push-up plate pushes up the disturbed soil near the soil push-up plate by the soil push-up plate to form a void below the soil push-up plate, The solidifying material slurry and While absorbing engaged the mixed soil in voids, by releasing the pressure in the improved portion from regulating pressure hole of the soil push-up plate, to push the soil of the disturbance soil discharge channel at the same time to adjust the pressure in the gap It is characterized by.

  A plurality of the pressure adjusting holes of the present invention are provided, and the total opening area of the pressure adjusting holes is 10% to 60% of the total area of the soil lifting plate in a plan view. The soil push-up board according to the present invention is characterized in that a protrusion is provided on a peripheral edge portion, a surface portion thereof, or the both portions.

  In the present invention, since the pressure adjusting hole is provided in the soil lifting plate, even if the injection flow rate of the solidifying material slurry is increased as compared with the conventional case, it is possible to secure the amount of soil discharge without impairing the economy with the conventional construction machine. And the influence on the surrounding ground can be reduced as much as possible.

It is a top view of a 1st embodiment of the present invention. It is a front view. It is a partial cross section front view which shows a use condition.

A first embodiment of the present invention will be described with reference to FIGS.
A cutting blade B is attached to the tip of the single tube rod 1 of the ground improvement device, and this cutting blade B is, for example, a bit such as a metal crown. At the tip of the single tube rod 1, a stirring blade 2 and a soil push-up plate 5 located in the upper part adjacent to the stirring blade 2 are disposed.

  The stirring blade 2 is disposed at a predetermined distance, for example, 15 to 30 cm away from the tip of the rod 2. The stirring blade 2 includes a pair of left and right blades, and the length of each blade is, for example, 30 cm from the center of the rod 2. The stirring blade 2 includes a solidifying material slurry flow path 3b communicating with the rod liquid feeding pipe 3a, and a tip nozzle (solidifying material discharge portion) 4 is attached to the end thereof.

  The soil lifting plate 5 is formed in a spiral shape with a circular projected plane shape, and the radius thereof is the same as the radius of the edge of the circular locus drawn by the rotation of the stirring blade 2, or the radius of the stirring blade 2 10 cm or less, preferably 5 cm or less. The inclination of the spiral stirring blade 2 is 10 to 20 degrees with respect to a line orthogonal to the central axis of the single tube rod 1, and the circular shape of the projection plane shape is approximately one circumference. Is formed.

  The soil lifting plate 5 has a plurality of pressure adjusting holes 6, and the number of the pressure adjusting holes 6 is 2 to 6. The diameter d of the pressure adjusting hole 6 is preferably 8 cm to 16 cm. When the diameter d is less than 8 cm, the pressure on the soil lifting plate 5 due to the upward flow of the soil is not easily dissipated, and when the diameter d exceeds 16 cm, the strength and resistance of the soil lifting plate 5 are adversely affected. There is a risk of affecting.

  The total opening area of each pressure adjusting hole 6 is preferably 10 to 60% of the circular area of the soil push-up plate 5 in a plan view, but a more preferable ratio is 20 to 50%. is there. When the ratio is less than 10%, the pressure on the soil lifting plate 5 due to the rising flow of the soil is not easily dissipated, and when it exceeds 60%, the strength and resistance of the soil lifting plate 5 are adversely affected. There is a fear.

  Protrusions 7 are provided on the peripheral edge portion 5a of the soil lifting plate 5, and a plurality of, for example, ten protrusions 7 are arranged at intervals in the circumferential direction. The protrusion 7 is a rectangular plate-like body, and as shown in FIG. 2, the protrusion 7 is inclined toward the upper surface 5 b side of the push-up plate 5 by an angle θ toward the upper outside. The inclination angle θ is, for example, 120 degrees, and is appropriately selected as necessary.

  In addition, you may provide the said protrusion 7 in the surface part 5b instead of providing in the peripheral part 5a of the soil raising board 5, or both the said parts 5a and 5b.

  The ground improvement method using the ground improvement device of the present invention (single pipe type earth discharging type high-pressure jet stirring method) will be described. As shown in FIG. 2, a traveling carriage 10 equipped with an earth discharging type high-pressure spray ground improvement construction machine 9 is moved to the planned improvement position of the soft ground 14 while traveling on the H steel 12, and the single pipe of the ground improvement device Align the tip of the rod 1 with the pile core (not shown). Thereafter, the single-pipe rod 1 is rotated by driving the earth discharging type high-pressure spray ground improvement construction machine 9 and drilling is started.

  The above-mentioned drilling holes are drilled in a stepped manner by a plurality of times of the entire drilling length up to the planned improvement depth, and are drilled anhydrously or while discharging drilling water from the tip nozzle 4 of the single tube rod 1.

  At that time, it is necessary to disturb the cylindrical portion of the circular trajectory cross section through which the improved ground device passes by the rotation of the stirring blade 2 and to cut off the surrounding soil well. Once the single-tube rod 1 is raised by the first step, then the hole is drilled to the lower end of the second step, and the rod 1 is lifted again to the lower end of the first step, so that it is included in the diameter of the soil lifting plate 5 The soft ground and the area outside the diameter are surely cut off.

  When drilling is performed when the position of the tip nozzle 4 of the stirring blade 2 reaches the depth to be improved, the rotation of the single tube rod 2 is stopped and the drilling is stopped.

  Next, an ultra high pressure pump (not shown) is operated to pressure-feed the solidifying material slurry 23 to the tip nozzle 4 of the stirring blade 2 through the rod liquid feeding pipe 3a and the solidifying material slurry channel 3b. Then, when it is confirmed by a pressure management device (not shown) that the injection pressure has reached the specified pressure, the constant speed step is pulled up at a constant speed. The constant pulling speed of the single tube rod 1 is usually about 3 to 4 minutes / m, but may be changed as necessary.

  In the earth discharge type high-pressure spray ground improvement method, disturbed soil discharge in which the soil soil corresponding to the volume of solidified slurry sprayed at an ultra-high pressure when the rod 1 is pulled up is a cylindrical portion during drilling. The soil is discharged 19 through the road 8. In this soil removal mechanism, the soil 19a in the disturbed portion of the improved ground formed at the time of drilling is pushed upward by the soil lifting plate 5 to form a gap 21 below the soil lifting plate 5 and is injected with high pressure. The mixed soil in which the solidified material slurry 23 a is mixed is absorbed by the gap 21. Therefore, a columnar solidified material improving portion (improved body) 13 is formed in the gap 21 and its peripheral portion (disturbing layer 8 and its outer peripheral portion 8a).

  The absorbing action of the mixed soil into the void 21 is due to the increase in internal pressure by the injected solidifying material slurry 23 and the effect of the soil lifting plate 5. At this time, in the improved range 8a, the ground is cut by the solidified material slurry 23a injected at a high pressure, and the slurry volume increases in the ground. However, since the gap 21 communicates with the upper part of the push-up plate 5 through the pressure adjusting hole 6, the pressure in the gap 21 escapes (escapes) through the pressure adjusting hole 6 to the upper part.

  Therefore, the pressure in the gap 21 is adjusted, and the exhaust pressure passing through the gap 21 pushes up the soil in the disturbed soil discharge path 8, so that the injection flow rate of the solidifying material slurry 23 is increased as compared with the conventional case. However, the conventional construction machine can secure the amount of soil without impairing the economy, and the influence on the surrounding ground can be reduced as much as possible.

DESCRIPTION OF SYMBOLS 1 Single pipe type rod 2 Stirring blade 3a Rod liquid feeding pipe 3b Solidification material slurry flow path 5 Soil push-up board 6 Pressure regulation hole 7 Protrusion 8 Disturbing soil discharge path 13 Improvement body 21 Cavity 23 Solidification material slurry 23a Solidification material slurry injected by high pressure

Claims (3)

At the tip of the single tube injection rod of the construction machine for the earth discharge type high-pressure jet agitation method, a stirring blade and a spiral soil lifting plate in the upper part adjacent to the stirring blade are arranged, and a pressure adjusting hole is formed in the soil lifting plate. A ground improvement method using a ground improvement device provided, wherein the single pipe injection rod of the ground improvement device penetrates into the ground of the ground to be improved, and disturbs the soil with the stirring blade of the injection rod. And forming a solidified material improving portion on the outer peripheral portion of the disturbing portion by spraying a solidifying material slurry from a tip nozzle of the stirring blade while pulling up the injection rod. In the improved construction method,
When pulling up the injection rod, by pushing up the disturbed soil near the soil lifting plate of the stirring blade by the soil lifting plate to form a void below the soil lifting plate,
While absorbing the mixed soil mixed with the solidifying material slurry into the voids,
A ground improvement construction method characterized by adjusting the pressure in the gap and releasing the soil in the disturbed soil discharge path at the same time by releasing the pressure in the improvement portion from the pressure adjusting hole of the soil lifting plate .   2. The ground according to claim 1, wherein a plurality of the pressure adjusting holes are provided, and a total opening area of the pressure adjusting holes is 10% to 60% of a total area of the plan view shape of the soil lifting plate. Improvement method.   The ground improvement construction method according to claim 1 or 2, wherein the soil lifting plate includes protrusions on a peripheral edge portion, a surface portion thereof, or both of the two portions.

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