JPH0694653B2 - Method for creating rectangular ground improvement body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a soil retaining (Yamadome) construction method for forming a soil retaining (Yamadome) wall in the ground, or a deep soil improvement method for improving a soft deep soil. The present invention relates to a method for forming a rectangular ground improvement body used as

[Prior Art] A method for improving a relatively deep and soft ground. A ground improvement body is prepared by excavating while solidifying material is discharged from the tip by an earth auger or a stirring blade, and is mixed with soil of the excavated or disturbed local ground to be hardened. There is a way to create. Further, recently, a method has also been established in which a solidified material is supplied to soil that has been excavated by an earth auger and then discharged to the ground, and then the soil is backfilled in an excavation hole to form an improved body. Then, the improved body cast by these construction methods is formed into a continuous wall shape, and if necessary, a core material such as steel material is inserted and used as a soil retaining wall or arranged at regular intervals. Foundation structure and embankment
It is also used to stabilize slopes.

Conventionally, when the improved body is formed into a wall shape by these construction methods, in addition to the case where a screw auger or a stirring blade type mixing processor is used as a single shaft, a plurality of pieces which are connected at a predetermined interval by an axial distance holder are used. A high-efficiency construction method is also used in which a screw or a stirring blade is dug into the ground to simultaneously form a plurality of adjoining improved bodies in a single placing operation.

[Problems to be Solved by the Invention] However, even when a screw auger or the like is connected to a plurality of shafts to form an improved body, the sectional shape of each improved body to be formed is a single axis construction. It is basically the same as a circular column or a gourd-shaped wall. However, with such a cross-sectional shape,
Both as a retaining wall and as a foundation ground, there are disadvantages in terms of efficiency.

That is, when using it as a soil retaining (Yamadome) construction method,
As shown in FIG. 6, the improved bodies P ₀ of each circular cross section must be placed by wrapping adjacent ones by wrapping them by a certain dimension α, so that the efficiency is deteriorated by that amount and the effectiveness of the wall W ₀ is reduced. The cross section becomes smaller. In addition, when using the retaining wall W ₀ as an outer formwork for concrete for construction when constructing an underground structure, in order to finish it smoothly and to cut it as a support work, and to install the bellows, a bracket is not required. Since it is often welded to the core material (H-shaped steel) C, even the surface of the core material C requires a troublesome lifting work, which is troublesome.

Furthermore, when it is used as a deep ground improvement method, the improvement rate (area of the improved part / total area × 100%) is low because the improved body P ₀ has a circular cross section. In such a case, the improved body P ₀ is inefficient because it requires complicated lap construction as shown in FIG. 7 (shown by three augers).

The present invention is applied to a high-efficiency construction method for simultaneously forming a plurality of adjoining improved bodies by a ground auger or the like using a plurality of shaft spacing holders in order to solve the problems in the prior art. A method for forming a rectangular ground improvement body is provided.

[Means for Solving Problems] In the method of the present invention, a plurality of screw auger-type mixing processors connected by a shaft spacing holder are used to excavate, and a solidified material is mixed with the soil of the site to be hardened. In the method of forming an improved body, the outer shape of the shaft spacing holder is formed into a square shape, and at least four corners of the upper and lower surfaces of the shaft spacing holder are provided with protruding blade-like protrusions, and the respective protrusions are formed. It is characterized in that an inclined surface that is inclined toward the center of each screw auger is formed inside the portion.

[Operation] That is, if a square-shaped axial spacing holder is used, a drilling hole with a circular cross section is formed in the ground with a plurality of screw augers, etc., and it is lowered into the ground following this. The shaft spacing holder can be expanded so as to cut four corners of each of the drill holes, and finally, an improved body having a rectangular cross section corresponding to the outer shape of the shaft spacing holder can be formed in the ground. In particular,
According to the present invention, at least four corners of the upper and lower surfaces of the shaft gap retainer are provided with protruding blade-like protrusions, and inside thereof, inclined surfaces that are inclined toward the center of each screw auger are formed. , It becomes possible to make the excavation by this shaft spacing retainer sharp and smooth, and it is possible to effectively prevent a large resistance force from acting on the excavation, and the soil generated by the excavation is screw-auger centered. Therefore, the mixing efficiency with the solidifying material can be improved.

[Examples] The present invention will be specifically described below by taking as an example the case where three screw augers are used as a construction machine.

In this case, the axial intervals of the three screw augers 1 are adjusted by using the axial interval holder 2 as shown in FIG. The shaft spacing holder 2 is composed of a frame body in which shaft through holes 3 are opened at equal intervals on the upper and lower surfaces, and three parallel screw augers 1 are loosely fitted in the shaft through holes 3 at their intermediate shaft portions. The screw augers 1 and 1 are inserted in a circular shape and regulate the distance between the adjacent screw augers 1 and 1 at a predetermined interval.
In the illustrated example, the adjacent screw augers 1 and 1 are connected in different steps for lapping.

In the method according to the present invention, the shaft spacing holder 2 having a square outer shape is used. As shown in FIG. 2, the axial distance holder 2 has an outer peripheral surface formed by a pair of orthogonal planes 2a and 2b, and has a long and thin rectangular parallelepiped appearance. Further, the axial gap holder 2 has, on its upper and lower surfaces, four cutting edge-shaped protruding portions 4 protruding from the four corners and the outer peripheral surface 2a at equally divided positions in the longitudinal direction. The protruding portion 4 scrapes off the four corners of each of the drill holes having a circular cross section formed by each screw auger 1 to integrate these three adjacent drill holes, and at the same time, to form the planar shape of the shaft spacing holder 2. It is responsible for expanding to the corresponding rectangular cross section. The ribs 5, 6a, 6b are provided around each shaft through-hole 3, and at the upper and lower surfaces of the shaft spacing holder 2, a conical shape inclined from the outer circumferences 2a, 2b toward the shaft through-hole 3. The inclined surface 7 is formed. Also,
The height of the axial gap holder 2 is adjusted to a length sufficient to form an improved body having a square cross section that correctly corresponds to the ground, as long as friction during excavation does not become excessive.
It is selected in the range of 0.3 to 3 m.

Below, multiple shafts (three) using the above-mentioned shaft spacing holder 2
An example of a construction procedure for forming the improved body into a wall shape with the screw auger 1 will be described with reference to FIG.

(1) Set three screw augers 1 in the vicinity of the tips with shaft spacing holders 2 in the drilling machine 8 so that each screw auger 1 is vertically above the planned construction position.
Are positioned {FIG. 3 (a)}. In addition, when the construction depth is large, a plurality of prismatic axial distance holders 2 may be used at appropriate intervals according to the purpose of improvement.

(2) Next, the powdered solidifying material or the solidifying material slurry is supplied from the injection hose 9 or the like connected to the upper end of the screw auger 1 by a pressure feeding means such as air pressure feeding, mechanical pressure feeding or slurry pump pressure feeding. The screw auger 1 is rotated and excavated while discharging from a discharge port (not shown) provided at the tip. At this time, the excavation force of the screw auger 1 and the downward force due to the weight of the boring machine 8 promote the excavation. However, when the excavation is difficult due to the ground conditions, the excavation force is increased or the auger head or blade is used. The shape of is enlarged to facilitate excavation. Then, at the time of this excavation, the rectangular shaft spacing holder 2 after the screw auger 1 excavates in a cylindrical shape follows and descends, so that the portion drilled in a cylindrical shape by each auger 1 is Furthermore, the four corners are shaved and forcibly expanded into a hole having a square cross section. As described above, on the upper and lower surfaces of the shaft spacing holder 2, the cutting edge-shaped protruding portions 4 are provided at the positions corresponding to the four corners of each drilled hole, and the inside thereof is inclined toward the center of each auger. Since the conical inclined surface 7 is formed, the soil scraped off by the protruding portions 4 at the corners is guided to each inclined surface 7 and pushed to the position of the shaft through hole 3 of the holder 2. , And is mixed with the solidifying material discharged from the tip of each screw auger 1 {Fig. 3 (b)}.

(3) When the predetermined planned depth I is reached in this way, the triple screw augers 1 are moved up and down together with the shaft spacing holder 2 in order to uniformly mix the soil and the powdery solidifying material or the solidifying material slurry. Repeat the exercise {Fig. 3 (c)}.

(4) When finally pulling out the three screw augers 1 together with the shaft spacing holder 2, the augers 1 are reversed and the solidified material is so hard that the slurry-like mixed soil 11 in the excavation hole 10 does not overflow. Withdraw while discharging the slurry. Alternatively, when a powdery solidifying material is used, the screw auger 1 is reversely rotated to be compacted and pulled out.

As described above, by excavating and mixing using a plurality of screw augers 1 that are connected by the outer peripheral angular interval retainers 2, it is possible to form the excavation hole 10 having a square cross section in the ground. Then, the excavation hole 10 is filled with the soil 11 mixed with the solidifying material slurry or the like, or the soil mixed with the powdery solidified material is backfilled with each screw auger 1 and rolled to compress the prismatic improved body P. Can be created.

In addition, in the construction procedure of (2) to (4), the solidified material is discharged from the tip of each screw auger 1 and mixed with the local soil, but instead of this, the excavated soil discharged to the ground is replaced. It is also possible to create an improved body by the procedure of supplying the solidifying material and performing primary mixing, then backfilling into the drilling hole, secondary mixing with a screw auger, and pulling out each screw auger together with the axial spacing holder while compacting. .

In any case, according to this method, a plurality of (three) adjacently-wrapped prismatic improved bodies P are formed in a continuous wall shape in the ground, and a core material C such as H-section steel is inserted or if necessary. By press-fitting, the earth retaining wall (yamadome) wall W as shown in FIG. 4 (a) can be obtained. At this time, as shown in the figure,
By inserting or press-fitting the core material C such as H-shaped steel into the excavation side, the chipping work at the time of constructing the girder after excavation can be significantly reduced. Further, since the surface of the retaining wall W after excavation is finished to be substantially flat, it is possible to significantly reduce the work such as fishing when using it as an outer formwork. If the construction is performed in this way, of course, the efficiency of the improved body P is not reduced when it is lapped and placed, and the thickness of the wall W is almost equal to the plane width of the axial distance holder 2. Therefore, the effective width can be widened and an economical design can be achieved. In addition, if the effective width is large, the water stopping property is also improved. It should be noted that FIG. 4 (b) shows the retaining wall W ₀ by the conventional method for comparison.

Moreover, the improvement etc. of the basic structure ground, in the case particularly as applied entirely improved, improved body P ₀ of the circular cross-section as shown in FIG. 7
In comparison with the conventional construction method that requires complicated wrapping, the construction method of the present invention can realize a highly efficient high improvement ratio only by adjoining the improved bodies P obtained as rectangular cross sections. FIGS. 5 (a) and 5 (b) show the differences in the degree of improvement between the two in the case of the fixed interval arrangement in comparison.

The above is mainly described using a screw auger as an example, but in the present invention, even in the case of using a plurality of mixing processing machines having a stirring blade as a construction machine, the outer shape of the shaft spacing holder is It can be applied in the same manner by forming it into a rectangular shape, and thereby a wall-shaped rectangular ground improvement body can be formed. It should be noted that this agitating blade type mixing processor does not have the function of excavating the soil on the local plate and discharging it out of the hole like a screw auger, and it mixes and hardens the solidifying material while disturbing the local soil. Is.

[Effects of the Invention] As described above, according to the method for forming a rectangular ground improvement body of the present invention, the cutting hole having the circular cross section formed by the screw auger type mixing processor is provided with the cutting edge-shaped point of the axial spacing holder. It is possible to efficiently expand by cutting out the four corners by the projecting portion, and finally it is possible to form an improved body having a rectangular cross section in the ground. Moreover, since the soil generated during the excavation can be concentrated on the screw auger center by the inclined surface provided inside the protruding portion, the movement of vertically moving the screw auger is repeated to mix the soil and the solidified material. When
The mixing efficiency of the soil and the solidifying material can be increased, and the two can be surely and uniformly mixed. Therefore, this construction method can be used both as a soil retaining (yamadome) construction method and a deep ground improvement method, and has the following effects, respectively.

That is, when using it as a soil retaining method, the work of swelling for raising the belly is greatly reduced, a wall body having a large effective cross section can be efficiently constructed, and it is easy to use as an outer frame.

If it is used as a deep ground improvement method, the improvement rate will be 100
There is a possibility that the overall improvement of the foundation ground, which is close to%, can be constructed extremely efficiently.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 to FIG. 3 show an embodiment of the present invention. FIG. 1 is an elevation view of a main part of a screw auger connected by a shaft spacing holder, and FIG. A perspective view of the space holder, FIG. 3 (a),
(B), (c), (d) is each outline explanatory drawing which shows the process of an improved body formation process. FIG. 4 is a perspective view showing a construction example of a retaining wall, (a) relates to an embodiment of the present invention,
(B) shows a conventional method. FIG. 5 is a perspective view showing an example of a complete improvement of deep ground, (a) showing an embodiment of the present invention, and (b) showing a conventional method. FIG. 6 is a plan view showing a conventional retaining wall structure. FIG. 7 is a plan view showing an example of a conventional whole ground improvement. 1 ... Screw auger 2 ... Axial spacing holder, 2a, 2b ... Outer peripheral surface 3 ... Axial through hole, 4 ... Spring portion 5,6 ... Rib, 7 ... Slope 8 ... Drilling Machine, 9 …… Injection hose 10 …… Drilling hole, 11 …… Solid material mixed soil P ₀ , P …… Improved body, W ₀ , W …… Soil retaining wall C …… Core material

Claims (1)

[Claims] 1. A method for forming a ground improvement body by excavating with a plurality of screw auger type mixing processing machines connected by an axial distance maintaining tool, mixing a solidifying material with the soil of the local ground and hardening the soil.
The outer shape of the shaft spacing holder is formed in a rectangular shape, and at least four corners of the upper and lower surfaces of the shaft spacing holder are provided with protruding blade-like protrusions, and the center of each screw auger is located inside each of the protrusions. A method for constructing a rectangular ground improvement body, which comprises forming an inclined surface which is inclined toward the ground.