JP2008101389A - Soil improvement method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soil improvement method which efficiently and surely develops a consolidated pile in a soft ground by using a large diameter casing pipe for soil improvement. <P>SOLUTION: A casing pipe 3 with a large diameter equal to the finished diameter is intruded into a soft ground 1 to forcibly increase the side soil pressure of the peripheral ground by the casing pipe 3. A filler 7 is discharged from the end of the casing pipe 3 into the ground, and the casing pipe is raised while jetting a slurry solidifying material into the filler 7 to develop a consolidated pile 8 in the soft ground 1. The solidifying material is sprayed from a solidifying material jetting hole 5 at the end of the casing pipe 3 diagonally downward. An expansion material is added to the filler 7. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a ground improvement method, in particular, a technique for increasing the strength of the ground around the pile by creating a consolidated pile using a large-diameter casing pipe in soft ground, and further improving and developing the conventional method. Is.

  Conventionally, sand or gravel compaction methods are known as compaction methods for the purpose of ground improvement. The compaction method currently used includes a typical dynamic (vibro type) compaction method and a static (auger type) compaction method.

  All of them are used to increase the bearing capacity, reduce consolidation settlement, increase shear resistance, prevent slip failure, etc. for viscous ground, and prevent liquefaction, increase shear resistance, support capacity of sandy ground. It is a construction method for obtaining each purpose and its effect as measures such as increase, increase in horizontal resistance, prevention of compression settlement, etc. It is a construction method to create vertical compacted sand pile or crushed stone pile in the ground.

  The conventional construction of compacted piles is based on the scaffolding material of construction machinery laid to a thickness of about 0.5 to 1.0 m, and a casing pipe of about φ400 or φ500 from the ground surface of the scaffolding material of this construction machinery is used for soft ground The ground is penetrated to a predetermined depth to be improved, and the casing pipe is repeatedly pulled out and struck back repeatedly while the filling material such as sand or crushed stone thrown into the casing pipe is sequentially discharged from the lower end of the casing pipe. A sand pile or crushed stone pile that has been widened while being compacted inside is created.

  According to those methods, the filling material in the casing pipe is discharged from the lower end of the casing pipe by pulling the casing pipe by its own weight and air pressure, and the discharged filling material is the casing pipe. It is widened to the side while being compacted by hitting back. Therefore, sand that has been expanded and compacted to about φ700 by penetrating a casing pipe of about φ400 or φ500 into soft ground, inserting a filling material into the pipe, and repeatedly pulling and returning the casing pipe. It is a method that can create piles or crushed stone piles.

  Patent Document 1 discloses a ground improvement method in which a quicklime-containing material is placed in a pile shape in the ground, using a double-structure casing composed of an inner tube and an outer tube, and using the inner tube to set a solidifying material. Supplying and supplying the expansion material in the area between the inner pipe and the outer pipe, the solid material is placed on the center side of the pile, and the expansion material is placed on the outer periphery side of the pile to create a pile An improved construction method is disclosed.

  In particular, in Patent Document 2, a hardener discharge port is attached to the lower end of the sand pipe construction casing pipe toward the inside of the casing pipe, and a hardener such as cement is injected from the discharge port at high pressure. Disclosed is a sand pile construction method in which aggregates such as sand and gravel thrown in from a hopper are agitated and mixed in a casing pipe, and the agitated mixed material is discharged into the ground from the lower end of the casing pipe to create a consolidated pile. Has been.

Japanese Patent Laid-Open No. 10-280382 Japanese Patent Laid-Open No. 10-18280 JP 09-125366 A JP 11-323909 A Japanese Patent Laid-Open No. 2002-275484

  In the conventional compaction method described above, the filling material discharged from the lower end portion of the casing pipe is compacted by repeatedly returning and drawing the pipe, and a sand pile or crushed stone pile widened to about φ700 is formed. Due to the construction method, it was necessary to procure a large amount of high-quality sand or crushed stone collected from rivers, seas, and mountains as filling material, including an extra amount by compaction.

  In general, the extra amount of filling material is over 40% including loss, and it is often difficult to procure the required amount because it is used in large quantities. Related to this, price, stable supply, transportation distance, etc. The increase in material costs caused by this problem has been a problem.

  In addition, the drawing of the casing pipe (discharge of the material) and the backlash (consolidation and widening) are repeated several meters at a time, while there are many hard and soft layers in the ground. Depending on the nature, the pile diameter and the shape of the pile, and thus the effect of ground improvement tend to vary. For this reason, there are concerns about quality problems such as insufficient strength of the ground and the uniform finish of the pile diameter.

  Therefore, complicated construction management is required in which the widening time required for drawing and compaction of the retraction cycle is combined with the material discharge amount.

  In addition, since the construction per pile requires repeated compaction work, it takes a considerable amount of construction time, so the construction period is long, and the impact on the surroundings of the construction site and environmental problems, etc. In addition to the heavy burden, the economic cost is very high.

  In addition, when sand is used as the filling material, sand piles are deformed and thinned due to the surrounding earth pressure (immediate and creep) at the time of construction and after the completion of construction. In addition to this, there is a problem that the lateral earth pressure is reduced by long-term stress relaxation and the guarantee that the N value between piles is ensured for a long time is not certain. Moreover, in the rebound type construction, the pile diameter may vary due to the strength of the original ground, which may result in non-uniform quality. Especially in the dynamic compaction method, short-term or long-term ground restraint of sand piles may occur. The reliability for the effect was insufficient.

  Further, in the ground improvement method disclosed in Patent Document 1, the casing pipe has a double structure, the solid material is introduced into the inner pipe, and the expansion material is introduced into the outside. There are concerns about workability problems such as the need for complicated construction management when penetrating into the building.

  Furthermore, in the ground improvement method disclosed in Patent Document 2, the sand and the solidified material are mixed and stirred in the pipe and then discharged. Actually, the sand mixed and stirred by this method is a kind of liquefied state. Therefore, it is easily assumed that the surrounding soil pressure is narrowed at the time of discharge and the effect of restraining the surrounding ground cannot be fully exhibited.

  In addition, when solidified material, groundwater and sand are mixed and stirred in the casing pipe, the mixed material (soil cement) adheres to the pipe as the construction progresses, and the effective inner diameter of the casing pipe decreases, making it difficult to discharge the material. There is a possibility that the work will be impossible.

  The present invention is an improvement and development of the ground improvement method disclosed in Patent Document 2 in order to solve the above-described problems. In particular, “after pile formation, injecting solidified material outside the pipe” and “expanding material” In addition to eliminating the thinning immediately after construction, and further solidifying piles, long-term, permanent and sufficient ground restraint effect can be achieved. The purpose of this project is to provide a ground improvement method that can be used for construction.

  In the ground improvement method according to claim 1, a casing pipe having a large diameter corresponding to the finished diameter is inserted into the ground, and after the side earth pressure of the surrounding ground is forcibly increased by the casing pipe, the casing pipe The improved pile is discharged from the tip of the inside of the ground into the ground, and the casing pipe is pulled up without repeated repulsion while injecting the slurry-like solidified material into the ground and solidified in the ground It is characterized by creating.

  The present invention uses the same construction machine as the conventional compacting pile construction method, and penetrates a casing pipe having a large diameter (about 700 mm or a finished diameter according to the design specifications) into the ground, and starts from the lower end of the casing pipe. A solid consolidated pile with the same diameter as the casing pipe in the ground by discharging the filler, injecting slurry solidified material into the gap of the filling material in a mist, and consolidating the particles of material. A sand pile or crushed stone pile that has been expanded to about φ700 by using a φ400 or φ500 casing pipe and compacting the filling material discharged from the lower end of the pipe by pushing back the pipe. This is completely different from the conventional method of building compacted piles.

  ADVANTAGE OF THE INVENTION According to this invention, a side earth pressure can be forcedly increased with respect to the surrounding ground by dynamically or statically penetrating a large diameter casing pipe into the ground. In addition, it is possible to create a large-diameter pile by pulling out the casing pipe while leaving the filling material put in the casing pipe in the ground. A pile with a uniform diameter from the lower end to the upper end can be created.

  In addition, since the pile to be formed is a consolidated pile made up of the filling material discharged from the lower end portion of the casing pipe and the slurry-like solidified material sprayed in a mist form into the gap of the filling material, It is a construction method in which the improvement effect is permanently maintained for a long time without the thinning of the pile.

  In addition, by using a large-diameter casing pipe, it is possible to create a pile with almost the same diameter without repeated repulsion, so a compacted pile is formed by repeated retraction as in the past. Compared to the construction method, a large additional amount of filling material is not required.

  Also, by using a large-diameter casing pipe, the filling material is discharged more smoothly than the conventional method, and the type of filling material is not limited to sand and crushed stone, but also construction residual soil, recycled crushed stone, and steel slag. It can be widely used with molten slag and the like.

  An appropriate amount of an expanding material is uniformly mixed with these materials in advance, and a forming process is completed by spraying a slurry-like solidifying material into the gap between the materials in the process of being discharged from the lower end of the casing pipe.

  The present invention eliminates the repetitive drawing and retraction process associated with the compaction of the conventional method, and can greatly reduce the time required for pile preparation, and therefore, compared with the conventional compaction pile construction method. However, the ground strength can be obtained by penetrating the casing pipe into the ground without causing any difference in the purpose of the ground improvement design specifications and the effect of the improvement, and the pile creation time can be shortened. It is something to be made.

  In addition, according to the construction method of the present invention, the construction time per pile can be reduced to about half of the dynamic or static compaction method of the conventional construction method.

  Therefore, it is an economical method that can save resources, shorten the construction period, and significantly reduce the construction cost.

  Moreover, it is possible to penetrate a large-diameter casing pipe using the latest large vibrator or a high-power earth auger. Or it can be handled by using water jet together.

  The ground improvement construction method according to claim 2 is the ground improvement construction method according to claim 1, wherein the slurry-like solidification material is jetted obliquely downward from the solidification material injection port located at the tip of the casing pipe. It is a feature.

  The ground improvement construction method according to claim 3 is the ground improvement construction method according to claim 1 or 2, wherein an expansion material is added to the filling material.

  In the present invention, an appropriate amount of an expansion material is supplementarily mixed with the filling material to be used in advance, thereby preventing a reduction in the restraining effect due to the thinned pile formed immediately after the casing pipe is drawn, and further, It is also possible to further improve the improvement effect by adjusting the blending amount of the solidifying material.

  The construction machine is the same as the machine used in the conventional method, and the specifications are the large-diameter casing pipe, the particles of the material used for the filling material, the slurry-like solidified material that fills the voids of the particles, and the injection / spraying device As long as it has.

  In the present invention, while using the same construction machine as a conventional method for forming a compacted pile, a casing pipe having a large diameter (about 700 mm or a finished diameter according to design specifications) is inserted into the ground, and the casing pipe is pulled out. Since only the filling material is discharged and the solidified material is injected, and there is no return by the casing pipe, a solid pile with a uniform caliber that satisfies the design value from the top to the top of the pile can be efficiently and reliably obtained. In particular, the solidified material is injected into the filling material discharged from the tip of the casing pipe into the ground, so as the construction progresses, the filling material becomes clogged. There is no fear that the material will be difficult to discharge and will not be able to be constructed.

  Further, by inserting a large-diameter casing pipe into the ground, the ground strength around the casing pipe can be increased.

  The construction of one pile is completed in three steps: penetration of the casing pipe into the ground, injection of the filling material into the casing pipe, and drawing of the casing pipe while spraying the slurry-like solidified material. In addition to shortening, the purpose and effect of improvement can be obtained with certainty, and the construction diameter of the pile can be established evenly, so there is no design problem and the construction period can be shortened and the construction cost can be reduced. it can.

  In addition, by adding an appropriate amount of expansion material to the filling material in advance, it is possible to prevent the restraining effect from being reduced due to the narrowing of the pile that has been created immediately after the casing pipe is pulled out. By adjusting the blending amount and the addition amount, it is possible to further improve the improvement effect and to make the construction more reliable.

  In addition, there is no need for a large extra amount of materials by the conventional compaction method, saving valuable resources and helping to prevent destruction of the natural environment of rivers, seas and mountains by collecting a large amount of sand or crushed stones. .

  In addition to sand and crushed stone, recycled crushed stone, steel slag, incineration ash of general waste and molten slag obtained from sewage sludge can be used as filling material, and these materials are used instead of sand or crushed stone. This also leads to resource reuse. As described above, it is a construction method that can solve all the problems of the conventional construction method, and brings about an excellent economic effect in reducing the construction cost and shortening the construction period.

Next, the construction procedure of the ground improvement method according to the present invention will be described.
First, a scaffolding material 2 for a construction machine is laid to a predetermined thickness on a soft ground 1 to be constructed to form a construction base. The thickness of the scaffolding material 2 of the construction machine in this case may be about 0.5 to 1.0 m as in the case of creating a conventional compacted pile.

  Next, the casing pipe 3 is vertically built according to the pile core on the scaffolding material 2 of the construction machine. In this case, the casing pipe 3 is set and installed on a construction machine 4 that is generally used in the formation of a conventional compacted pile.

  The casing pipe 3 used here is a casing pipe of about φ700, and a bottom lid (not shown) that can be freely opened and closed and a plurality of solidified material injection ports 5 are attached to the lower end portion. The casing pipe 3 is attached downward from the outside to the inside.

  Further, a plurality of solidified material feed pipes 6 that are continuous from the upper end portion to the lower end portion and are respectively connected to the solidified material injection port 5 are attached to the outside of the casing pipe 3 along the outer wall of the casing pipe 3. Yes.

  Next, the casing pipe 3 is penetrated from above the scaffolding material 2 of the construction machine to a predetermined depth that penetrates the scaffolding material 2 of the construction machine and improves into the soft ground 1. At the same time, the filling material 7 is put into the casing pipe 3 from the upper end of the casing pipe 3.

  In this case, the ground strength can be increased by forcibly penetrating the large-diameter casing pipe 3 into the soft ground 1 and forcibly increasing the lateral earth pressure in the surrounding soft ground.

  As a method of penetrating the casing pipe 3 into the soft ground 1, there are a method of dynamically penetrating using a vibro illustrated in FIGS. 2B and 2C and a method of penetrating statically using an auger. Either method can be used.

  Next, the casing pipe 3 is gradually pulled out by using the construction machine 4 and the filling material 7 in the casing pipe 3 is discharged from the lower end portion of the casing pipe 3 into the ground. At the same time, the slurry-like solidified material is sprayed from the solidified material injection port 5 onto the filling material 7 discharged from the lower end of the casing pipe 3.

  In this case, the filling material 7 in the casing pipe 3 is discharged because the bottom lid is opened by its own weight at the same time as the casing pipe 3 is pulled up. The slurry-like solidified material is supplied from the ground via the solidified material pressure feed pipe 6 attached to the outer wall of the casing pipe 3.

  In this way, the casing pipe 3 is gradually pulled out and the filling material 7 is discharged from the lower end portion of the casing pipe 3, and at the same time, the slurry-like solidifying material is injected from the solidifying material injection port 5 onto the discharged filling material 7. Thus, the consolidated pile 8 having the same diameter as that of the casing pipe 3 is formed in the soft ground 1. Then, by forming a plurality of the consolidated piles in the soft ground 1 with a predetermined interval, the soft ground 1 can be compacted and improved to a ground having a predetermined ground strength.

  3 (a) and 3 (b) show a comparison of the time required for the construction per pile in the ground improvement method of the present invention and the conventional compaction method. In the conventional method, FIG. As shown in the figure, it takes a considerable amount of time for compacting and widening by discharging and filling back the filling material by pulling out the casing pipe.

  In addition, when hard layers are mixed in the ground several times, it takes much time to create a widening by compaction.

  On the other hand, in the case of the present invention, as shown in FIG. 3 (a), there is no retraction by the casing pipe, and only the discharge of the filling material by pulling out the casing pipe, so that it takes a considerably shorter time than the conventional method. One pile can be created.

  The present invention can improve the soft ground by creating a pile solidified using a large-diameter casing pipe in the soft ground and increasing the strength of the surrounding ground.

(A)-(f) is process drawing which shows the construction procedure of this invention. The construction machine is shown, (a) is a side view showing the whole, (b) is a side view of the upper part of the casing pipe showing the dynamic construction method, and (c) is a side view of the upper part of the casing pipe showing the static construction method. . It is the graph which compared the time required for the creation per pile in the ground improvement construction method of the present invention and the conventional compaction construction method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Soft ground 2 Construction material scaffolding material 3 Large diameter casing pipe 4 Construction machine 5 Solidification material injection port 6 Solidification material feeding pipe 7 Filling material 8 Solid pile (Ground improvement pile)

Claims (3)

  After inserting a casing pipe with a large diameter equivalent to the finished diameter into the ground and forcibly increasing the lateral earth pressure of the surrounding ground by the casing pipe, the filling material is inserted into the ground from the tip of the casing pipe. The ground improvement is characterized in that it is discharged and the casing pipe is pulled up without repeated repulsion while injecting the slurry-like solidified material into the filling material, and an improved pile solidified in the ground is created. Construction method.   2. The ground improvement method according to claim 1, wherein the slurry-like solidified material is sprayed in a mist form obliquely downward from a solidified material injection port located at the tip of the casing pipe. 3. The ground improvement method according to claim 1, wherein an expansion material is added to the filling material.

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