JPH0639774B2 - Reinforcement method for residential land - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is preferably used for improving soft ground for individual houses such as wooden structures, lightweight steel frame structures or lightweight concrete structures or for bottom dwelling units. The present invention relates to a method for reinforcing the ground of a residential land.

[Prior Art] Conventionally, as a reinforcement method of this type, for example, a supporting pipe is secured by driving a steel pipe of about Φ100 mm or an RC pile of about Φ200 mm into the ground under the cloth foundation at a required pitch. There are known a method of preventing subsidence and a method of forming a columnar improved body by injecting and mixing a slurry of a cement material into the ground under a cloth foundation.

[Problems to be Solved by the Invention] However, in the former steel pipe driving method, the reinforcing effect may be impaired due to corrosion of the steel pipe, and there is a problem in durability. In addition, since it is essential to drive steel pipes into the ground by impact force during construction, there is a problem that noise and vibrations are unavoidable, and the construction depth changes variously depending on the ground conditions. It is troublesome to cut and weld a steel pipe having a certain length at each site, which is complicated, and a large number of steel pipes are required, which inevitably causes an increase in cost.

On the other hand, the latter pile pile method using the solidifying material slurry requires a pile driver, a slurry plant, a slurry pump, etc. as a construction machine, and since such a pile driver is a relatively large one, it is a small residential land. In many cases, construction is difficult. When the construction machine becomes large and the number of required auxiliary machines increases as described above, the construction cost becomes high. Further, since the solidifying material slurry is used, not only the amount of the solidifying material necessary to secure the required strength of the ground improvement body is increased, but also the slurry overflows to the ground surface of the construction site to deteriorate the workability. There is an inconvenience of causing pollution of the work environment.

The present invention aims to solve the above problems all at once.

[Means for Solving the Problems] In order to achieve the above object, the present invention sets a plurality of reinforcing points at a site where a foundation of a soft residential land is to be constructed, and agitates at each of these reinforcing points. Drill a hole with a drilling machine having a discharging function, and uniformly add and mix the cement-based solidifying material as a powder to the soil discharged while drilling the hole, and add the cement-based solidifying material by mixing. The soil is returned to the inside of the hole, and is reversed by applying the load to the boring machine to compact and form a columnar improved body.
In that case, a track auger device including a screw auger having an enhanced ground compaction function is used as the hole drilling machine. The track auger device of the present invention may be large or small, but a small track base of 2.5t to 4t is particularly suitable.

[Operation] According to such a construction method, only the hole drilling machine such as a truck auger device, which is much simpler than equipment machines such as a pile driving machine and a slurry plant, is introduced into the field, and each point Since a hole is formed in the hole and the cement-based solidifying material is added as powder to the soil discharged from the hole in the drilling hole, the working time for mixing the powder with the soil can be shortened. In particular, since this method is applied to the residential land, which tends to be relatively narrow, it is a great advantage that a slurry plant consisting of a mixer, a pump, a crane, etc. is not required. Moreover, since it does not contain much water like cement milk, the improved product can exhibit high strength. In addition, since the hole drilling machine is reversed under load and the soil mixed with the solidifying material is backfilled in the hole to compact it,
A homogeneous columnar improvement is created. Therefore, it is possible to effectively reinforce the portion where the foundation of the ground should be constructed. The degree of compaction can be appropriately controlled based on the load of the driving device of the screw auger and the like. If the pitch of the reinforcing points is set to an appropriate value in advance, it is possible to prevent harmful subsidence of the ground due to the top load by the columnar improved body made by compacting the solidified material.

[Embodiment] An embodiment in which the present invention is applied to the improvement of a residential land for a wooden house will be described below with reference to the drawings.

FIG. 1 is a plan view of a residential ground which has been improved by the reinforcing method of the present invention, in which A indicates a cloth foundation and B indicates a columnar improved body.

In this reinforcing method, first, a plurality of reinforcing points C are set at locations where the cloth foundation A of the residential ground is to be formed, and columnar improved bodies B are respectively formed at these reinforcing points C. . The method for forming the columnar improved body B is as follows.
In principle, the method shown in FIGS. 2 to 8 is used, but in the case of soil conditions in which the target progress for constructing the improved body B is relatively shallow and the hole wall 2a is maintained without collapsing, FIG. There is also a method of omitting the operation of FIG.

First, as shown in FIG. 2, while pouring a predetermined amount of the ground solidifying material 4 into the surface layer portion of the ground 1 as a powder, the holes 2 are drilled to a depth I at which the hole wall 2a does not collapse. This drilling operation is performed using a drilling machine having a stirring and discharging function, specifically, a track auger device. That is, the screw auger 3 of this track auger device is normally rotated in the arrow X direction and lowered at a predetermined speed in the axial direction to form the hole 2 in the ground 1. At this time, a predetermined amount (for example, 200K) per 1m ³ of discharged soil
The ground solidifying material 4 of g) is sequentially added to the discharged soil so as to be uniform. In this case, in order to promote the mixing of the discharged soil and the solidified material 4, it is effective to sequentially put them into the holes 2 being drilled. By doing so, a predetermined amount of the ground solidifying material 4 can be mixed into the discharged soil.

Next, as shown in FIG. 3, the ground solidifying material 4 is put into the hole 2. The ground solidifying material 4 is a cement-based solidifying material mainly composed of gypsum, blast furnace slag, and ordinary Portland cement, to which halogen compounds or sulfates are added as a hardening accelerator as necessary and well mixed. Yes, Osaka ESC (trade name; made by Osaka Cement Co., Ltd.)
Is marketed as. In other words, the solidifying material 4 has a mixing ratio of gypsum, blast furnace slag and ordinary Portland cement, which are the main materials, of gypsum 15 to 60 (wt%), blast furnace slag 20 to 60 (wt%), ordinary Portland cement. 10 to 50 (% by weight) and pulverize and mix them so that the specific surface area is 4500 cm ² / g or less,
Alternatively, it is prepared by adding 5% by weight or less of a curing accelerator to them and pulverizing and mixing them, and has water absorbency, expandability and hydraulic properties. The amount of the ground solidification material 4 is set as a ratio of the set addition amount (Kg / m ³ ) to the amount of soil in the undischarged portion, that is, the portion from the depth I to the depth II.

In this way, the fourth
As shown in the figure, the screw auger 3 of the hole drilling machine is again inserted, and the screw auger 3 is lowered in the direction of the arrow X while being rotated in the forward direction to advance to the depth II. Then, when the depth reaches the depth II, the descending of the screw auger 3 is stopped, but the normal rotation state of the screw auger 3 is maintained. At this time, the solidified material 4 previously introduced and the excavated soil 5 are further mixed, and
It is sequentially discharged out of the hole 2. Then, when the soil 5 is no longer discharged, the screw auger 3 is pulled out from the hole 2. When the screw auger 3 is advanced and when the screw auger 3 is normally rotated at a fixed position to mix and discharge the soil 5 and the solidified material 4, a part of the solidified material 4 is attached to the hole wall 2a. Will be done. Therefore, the hole wall 2a
Is reinforced so that the hole wall 2a does not collapse even if the screw auger 3 is pulled out of the hole 2.

Then, as shown in FIG. 5, the ground solidifying material 4 similar to the above is charged as powder into the hole 2 dug down to the depth II. The input amount in this case is the set addition amount (Kg / m ³ ) for the soil amount in the part reaching depth II or depth III (for example, 200 Kg / m
^The amount is ³ ).

In this way, the sixth
As shown in the figure, the screw auger 3 of the hole drilling machine is again inserted, and the screw auger 3 is lowered in the direction of the arrow X while rotating in the forward direction to advance to the depth III. Then, when the depth reaches III, the descent of the screw auger 3 is stopped.
The normal rotation state of is maintained as it is. At this time, the ground solidification material 4 and the excavated soil 5 that were input at the stage shown in FIG. 5 are further mixed, and a part of the soil 5 that has been reformed and can be discharged is sequentially discharged to the outside of the hole 2. To be done.

In this way, the screw auger 3 is normally rotated for a predetermined time (about 1 to 3 minutes), and after the soil 5 is not discharged, the screw auger 3 is normally rotated and vertically moved between the depth II and the depth III to mix. Stir. After that, the screw auger 3 is reversed in the direction of the arrow Y as shown in FIG. 7, the mixture of the soil 5 and the ground solidifying material 4 discharged to the outside of the hole 2 is sequentially returned, and the screw auger 3 is rotated normally. The process of excavating and pulling up while reversing is repeated until the uniform mixed state is obtained. Then, after confirming that a predetermined mixed state is obtained, the screw auger 3 is pulled up at a slow speed while reversing in the arrow Y direction. As a result, the soil 5 returned into the hole 2 and the ground solidifying material 4 are further mixed and compacted. The degree of compaction can be controlled by the load of the drive device of the screw auger 3 or the like.

When the target depth of the improved body B is shallower than the depth I of FIG. 2, the solidified material 4 is sequentially added to the discharged soil 5 and then backfilled, and the screw auger 3 is moved forward while being excavated or reversely pulled up. It goes without saying that the improved body can be formed by a relatively simple operation in which the operation is repeated to mix and stir, and finally the material is reversely pulled up while applying a load. In this case, approximately 1 immediately before backfilling the mixed soil in the hole 2.
If 0 kg of the solidifying material 4 is added, the improved body B will be firmly solidified and stable supporting force will be obtained.

As the screw auger 3, the tip shape of the auger head is made symmetrical about the axis so that it can be sufficiently compacted, the screw pitch of the tip is increased by 0 to 20%, the tip screw 3a and the auger head. 3b
The installation angle θ between the shaft and the shaft 3c is 0 as shown in FIG.
It is more effective to use a structure having a structure in which the mounting angle is set downward by 10 ° and the mounting angle is continuously returned to 90 ° within the range of one screw turn. If such a screw auger 3 is used, the soil 5 can be pressed toward the center of the improvement body B when it is reversed and compacted, and the center position of the improvement body B, which tends to be loose, can be sufficiently compacted. .

Further, as the screw auger 3, as shown in FIG. 10, it is desirable to use a screw auger having a shape in which the screw diameter becomes smaller toward the upper part. If this screw auger 3 is used, in the process of excavation, mixing, stirring and compaction, the improvement of the size of the improvement body above the improvement body due to a slight deviation of the screw auger core caused by the vertical movement of the arm of the track auger Can be prevented, and the shape accuracy of the improved body B can be improved.

Then, as shown in FIG. 8, when the screw auger 3 is completely pulled up from the hole 2, the mixture of the soil 5 and the ground solidifying material 4 is completely filled in the hole 2 to form the improved body B. It Thereafter, the upper end of the improved body B is finished to be smooth by using the finishing disc 6 as shown in FIGS. 11 and 12, and the cloth foundation A is constructed thereon.

According to such a construction method, a plurality of improved bodies B are arranged on the cloth foundation ground 1 at a preset required pitch.
Therefore, it is possible to effectively prevent harmful ground subsidence due to the overlaid load, and it is possible to stably support the upper structure constructed on the cloth foundation A.

In order to verify the effectiveness of this method, a compression test and a vertical loading test were conducted on the improved body B. The results are as follows.

Test Example 1 A 3 m improved body was formed by the procedure shown in FIG. 2 and FIGS. 6 to 8, and a compression test was performed on the excavated body. Ground 1 was silty sand with a water content ratio of about 24%. The auger head 3b used had a diameter of 400 mm. The shape of the excavated improved body B was 510 to 540 mm in diameter and 2.99 m in length. The results of the compression test are as shown in Table 1, which was a value sufficiently satisfying the target strength of 12 kgf / cm ² when the effective diameter of the improved body B was 400 mm and the permissible supporting force per one was 3 t. .

Test Example 2 According to the procedure shown in FIG. 2 and FIG. 6 to FIG.
Improved bodies B of m, 10 m and 12 m were created and a vertical loading test was carried out. The N value of the test ground 2 is 0 to -12m and 4 to
It was 50 or more from around 8, -12 m. Auger head 3b
Has a diameter of 500 mm. The results are shown in Table 2 and Fig. 13. The long-term allowable bearing capacity is improved body length 4
m, 10m, 12m 5.0t, 8.5t, 7.5
It was t, and sufficient performance could be confirmed.

In the above examples, addition of the solidifying material to the excavated soil and introduction of the solidified material into the hole → excavation by a screw auger → stirring and discharging by forward rotation of the screw auger → compaction by reverse rotation of the screw auger → The case where the columnar improved body is formed by a series of operations of pulling the screw auger out of the hole has been described, but the present invention is not necessarily limited to this. That is, when the target depth is relatively deep, the series of operations described above may be repeated more times. On the contrary, when the conditions are relatively shallow and the conditions are good, it is of course possible to use a simplified method that is not omitted.

Further, the cement-based solidifying material is not limited to the above, of course, and various kinds such as ordinary Portland cement and blast furnace cement can be used.

Furthermore, the foundation built on the ground is not limited to the cloth foundation,
For example, it may be a solid foundation or a footing foundation.

[Effects of the Invention] Since the present invention has the above-described configuration, the following effects can be obtained.

First, since a stable columnar improvement with a compressive strength of, for example, about 12 to 25 Kgf / cm ² is formed in the ground in the required arrangement, it is possible to effectively prevent harmful ground subsidence due to top load. be able to. That is, according to the construction method of the present invention, the reinforcement points are set according to the shape of the foundation and the degree of softness of the ground, and the columnar improved bodies are formed at the respective reinforcement points. It is possible to effectively and effectively reinforce the soft residential ground so that the constructed building can be stably supported.

Moreover, since the improved body is formed by adding and mixing the cement-based solidifying material to the soil, that is, the soil discharged from the excavated hole, it is economical compared to the case of driving an expensive steel pipe. Also, it has excellent durability because there is no worry of corrosion. Further, in order to create this improved body, it is possible to suppress vibration and noise to a low level because a step of giving an impact force to a rigid body and driving it into the ground is unnecessary. Therefore, noise pollution to the neighborhood of the residential area, which is not a problem at all, will not occur.

In addition, since the solidified material is added as powder to the soil during excavation work from the ground to form an improved body, the solidified material is made into a slurry by adding water, which is disadvantageous in terms of strength development. Compared with the case of using, the consumption amount can be reduced reasonably, and in addition, the soil is filled in the hole because the soil is filled in the hole by reversing the load while loading the hole drilling machine. Can be homogeneously compacted, whereby a columnar improved body can be efficiently formed with high quality. If the solidifying material is used in such a powder state as it is, the solidifying material does not overflow onto the ground surface at the construction site, and it is possible to effectively prevent workability deterioration and work environment pollution. it can. Further, unlike the method of injecting silt mortar or the like into the hole bottom through the auger shaft, according to the present invention, the solidified material and the excavated soil can be kneaded in the hole, so that the solidified material can be applied to the hole wall. It will adhere and reinforce the holes. Therefore, even if the auger screw is pulled out from the hole in the middle of the work, the rear wall can be effectively prevented from collapsing, and quick and efficient construction can be achieved.

Moreover, since the improved body can be constructed by introducing only the truck auger device to the site, it is possible to easily carry out construction even in a small residential area. Further, since a large number of equipment such as a pile driver, a slurry plant, a slurry pump and the like are not required, there is an effect that the construction cost can be reduced.

[Brief description of drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a plan view and FIG.
FIGS. 8 to 8 are process explanatory diagrams, FIG. 9 is an explanatory diagram showing the tip portion of the screw auger, FIG. 10 is an explanatory diagram showing the entire screw auger, and FIGS. 11 and 12 show the upper surface of the improved body. FIG. 13 is an explanatory view showing a disk for forming, and FIG. 13 is a view showing a result of a vertical loading test on the improved body. A ... Foundation (cloth foundation) B ... Improved body C ... Reinforcement point 1 ... Ground 3 ... Screw auger 4 ... Solidifying material 5 ... Soil

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Jun Nonaka 5-313 Naruo-cho, Nishinomiya-shi, Hyogo Prefecture (72) Inventor Toshiyoshi Goto 2-15-8 Kita-Toyonaka-cho, Izumiotsu-shi, Osaka (56) References Japanese Unexamined Patent Publication No. 51-26715 (JP, A) Japanese Unexamined Patent Publication No. 50-143304 (JP, A)

Claims (3)

[Claims] 1. A plurality of reinforcing points are set at a site where a foundation of a soft residential ground is to be constructed, and a hole is drilled at each of these reinforcing points by a drilling machine having a stirring and discharging function, and the hole is drilled. While uniformly adding and mixing the cement-based solidifying material as a powder to the soil discharged at the time, while loading the soil-added soil by mixing the cement-based solidifying material into the hole while applying a load to the hole drilling machine A method of constructing a columnar improved body by compacting by reversing, wherein a truck auger device including a screw auger having an enhanced soil compaction function is used as the hole drilling machine. Ground reinforcement method. 2. The method for reinforcing a residential land according to claim 1, wherein a screw auger having a smaller screw diameter toward the top is used as the boring machine. 3. A track auger device comprising a screw auger having a screw diameter reduced as it goes upward and a ground compaction function is enhanced as the hole drilling machine. Reinforcement method for residential land described in item 1.