JP3973637B2 - Ground improvement method - Google Patents

Description

  The present invention relates to a ground improvement method capable of preventing liquefaction and improving the shear strength of soft viscous ground.

Conventionally, this type of ground improvement method includes excavating a hole in the ground with an auger, filling the hole with sand (or improved soil, etc.), re-excavating with an auger, or adding vibration to the filled soil, etc. Then, there was a method of forming a sand pile by compaction. And with the compaction of sand piles, he said that he would expect some ground strengthening by the propagation of pressure to the surrounding ground. In addition, regarding the filling amount of the sand into the hole, the filling of the hole until the hole is finally closed was performed as a control value.
In addition, although such a prior art is widely known among those skilled in the art, since there is no patent document or the like that specifically refers to this construction, prior art documents are not shown.

According to the conventional ground improvement method described above, when the improved soil is used as the filling soil, it is necessary to use an improved material such as cement or water glass, leading to a problem of increasing costs.
Even if these improving materials are not used, there is a problem that noise and vibration are generated with compaction. In addition, the ground improvement range is limited to the range of sand piles filled with soil and the surrounding area, and there is a problem that the efficiency of the ground improvement effect by compaction is low.

  Accordingly, an object of the present invention is to provide a ground improvement method capable of solving the above-mentioned problems, being able to be constructed at low cost, and capable of strengthening the ground over a wide area around the excavation range in a state where noise and vibration are unlikely to occur. It is in.

According to a first characteristic configuration of the present invention, a rotary blade capable of pressing a surrounding ground by being driven to rotate around a rotation axis is disposed on a tip side of the casing so as to be inserted through a casing disposed in the ground. In order to position the soil to be pushed out to the surroundings by the rotary blades, and to drive the rotary blades around the rotation axis to push the soils to the surrounding ground to strengthen the surrounding ground in advance. A target extrusion soil amount necessary for improving the predetermined range of the surrounding ground to a predetermined strength, and a target rotational torque value of the rotor blade for generating a pressing force required to improve the predetermined strength. set advance, during ground improvement construction, the extrusion soil amount to around ground due to the rotation of the rotary blade, and a torque value of said rotating blades is measured, the application of the same depth, the measured extrusion soil amount of the rotation torque value It is, there is to be continue until satisfying each of the target value.

According to the first characteristic configuration of the present invention, it is possible to improve by compacting while pressing the surrounding ground as the rotary blades are driven to rotate. And the soil located in the said casing is pushed out in a surrounding ground by being supplied from the next to the next on the rotation locus | trajectory of a rotary blade, and a ground improvement can be advanced continuously. As a result, it is possible to sequentially expand the improved range to the outer peripheral side of the rotor blade.
As an example of this improvement mechanism, as shown in FIG. 6, in the initial stage of pushing out the soil S to the surrounding ground G with the rotary blade 3, an annular first improved region P <b> 1 is formed on the outer peripheral side of the rotation locus of the rotary blade 3. Is formed. Further, as the soil S is continuously pushed out, the first improved region P1 receives the pressing force of the soil S newly pushed out from the inner peripheral side, and the outer peripheral side ground of the first improved region P1 is changed. Further pressing further increases the second improved region P2. For the sake of convenience, the description has been given here for each area. However, in reality, it is possible to secure a wide improvement range as a whole by repeating these steps over a wide range.
In addition, a target rotational torque of the rotor blade for generating a target extrusion soil amount necessary for improving a predetermined range of the surrounding ground to a predetermined strength and a pressing force necessary for improving the predetermined strength in advance. And the amount of extruded soil to the surrounding ground accompanying the rotational drive of the rotary blades and the rotational torque value of the rotary blades at the time of ground improvement construction are measured. Construction is continued at the same depth until the rotational torque value of the rotor blades satisfies the target rotational torque value while satisfying the amount of soil, so even if there is a variation in ground conditions, the improvement area can be more reliably established. It becomes possible to expand.
That is, for example, when there is a very loose part (or cavity or the like) that could not be predicted in the target ground, even if the amount of extruded soil reaches the initially set target amount of extruded soil, it is realistic. There is a high possibility that a loose part remains in the ground, and even in such a case, the construction is continued until the rotational torque value reaches the target rotational torque value. It can be closed and hardened with extruded soil and improved to a predetermined strength.
Also, as another situation, for example, when there is a stone block such as cobblestone that could not be predicted in the target ground, the reaction force against the pressing force by the rotary blade is large, and the rotational torque value increases. Although it is easy, there is a high possibility that the compaction force does not act on the surrounding ground of the stone block, and even in such a case, by continuing to supply soil until the amount of extruded soil reaches the target amount of extruded soil, The soil compaction force can also be applied to the surrounding ground of the stone block to improve it to a predetermined strength.
Thus, by setting the target extruded soil amount and the target rotational torque value and managing the extruded soil amount and the rotational torque value, the whole is improved to a predetermined strength even if the ground condition varies. It becomes possible to do.

According to a second characteristic configuration of the present invention, an auger that is rotatable around the rotation axis is provided in the casing by a rotation drive system different from the rotary blade, and the tip of the auger is driven by the rotation of the auger . the rotating blade side performs ground improvement in rotational driving of while seeking the rotor blade feed the soil, in the initial stage of its ground improvement construction there is to increase the supply amount of the soil by increasing the rotational speed of the auger .

According to the second characteristic configuration of the present invention, in addition to being able to achieve the above-described operational effects according to the first or second characteristic configuration of the present invention, the soil is fed to the tip side by the rotational drive of the auger. Thus, the soil can be supplied from one to the next in the rotation trajectory of the rotary blade, and the extrusion of the soil to the ground by the rotary blade can be performed efficiently without any interruption. In addition, since the drive systems of the rotor blades and the auger are different, the management of the rotational torque value of the rotor blades as described above can be performed separately from the drive of the auger, so that the construction management accuracy can be maintained. It becomes possible.
Also, in the early stage of ground improvement construction, the amount of soil supply is increased by increasing the rotation speed of the auger. Therefore, a large amount of soil is pushed out to the ground in the early stage of the improvement in which consolidation deformation is likely to occur, and the improvement is advanced at once. It is possible to further improve the efficiency of ground improvement.

  Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of an auger apparatus K for implementing the ground improvement method of the present invention.
Although not shown in the drawing, the auger apparatus K is mounted on a base machine and configured to be set at an arbitrary construction position.
A cylindrical casing 1 that is installed with its axis oriented in the vertical direction, an auger 2 that is installed in the casing 1 and that can be driven to rotate around the axis of the longitudinal axis, and a lower side of the auger 2 Similarly, the rotor blade 3 provided rotatably around the longitudinal axis, and the casing 1, the auger 2, and the rotor blade 3 are each provided with a rotational drive unit 4 that is rotatable around the longitudinal axis. is there.

  The casing 1 may be made of a metal cylindrical material, and a drill bit (not shown) may be attached to the lower end portion. The casing 1 serves as a case for the auger 2 and serves as a guide for discharging excavated soil during excavation. When the ground is improved, the casing 1 is stored and guided in a state where the soil S filled in the inner space of the auger 2 is isolated from the surrounding ground G. Furthermore, the surrounding ground G can be received and made difficult to displace.

The auger 2 is made of metal, and is configured by integrally providing a spiral blade 2b on the outer periphery of a cylindrical auger shaft 2a.
In the present embodiment, the spiral blade 2b guides the soil S positioned between the upper and lower spiral blades 2b in a state where the auger 2 is rotated forward (for example, rotated counterclockwise in a plan view) and reversed (for example, in a plan view). In a state where the soil S positioned between the upper and lower spiral blades 2b is guided downward. The auger shaft 2a is inserted with a drive shaft 3a of the rotary blade 3.

As shown in FIGS. 2 and 3, the rotary blade 3 includes a drive shaft 3a inserted into the auger shaft 2a, a base portion 3b integrally attached to a lower end portion thereof, and an outer periphery of the base portion 3b. And a plurality of wing portions 3c provided radially. In the embodiment, the wing portion 3c scrapes and excavates the target ground in a state where the drive shaft 3a is rotated forward (for example, rotated to the left in plan view), and reversely rotated (for example, rotated to the right in plan view). In such a state, the soil is pushed out to the surrounding ground G to be consolidated.
Specifically, the wing portion 3c is formed in a shape along a left-handed spiral line outwardly from the base portion 3b in plan view. And the cross section of the wing | blade part 3c shows a substantially triangular shape, and the ridgeline part of a lower surface and an inclined surface is comprised as the digging blade H, as shown in FIG.
Further, the blade inner peripheral surface 5 serving as an inclined surface is configured so that the soil S scraped by the excavating blade H can be guided upward as the rotary blade 3 rotates in the forward rotation direction. On the other hand, the wing part outer peripheral surface 6 serving as a vertical surface is configured so that the soil S can be pushed out to the surrounding ground G side with the rotational drive of the rotating blade 3 in the reverse rotation direction.

  The rotational drive unit 4 can be configured by, for example, a drive source using electricity or hydraulic pressure, and is configured to be able to rotationally drive the casing 1, the auger 2, and the rotary blades 3. Although not shown in the figure, the rotation drive unit 4 has a switch mechanism for switching on / off of the rotation drive for the casing 1, the auger 2, and the rotary blade 3, and a rotation direction. A rotation switching mechanism for switching, a speed changing mechanism for changing the rotational speed, a monitor mechanism for displaying a rotational torque value or the like acting in accordance with the rotational drive, and the like are provided.

  In this embodiment, the auger device K is used as a set of three, and as shown in FIG. 5, the auger device K is arranged at the apex portion of an equilateral triangle in plan view.

Next, the procedure of the ground improvement method will be described (see FIG. 7).
[1] Excavate to a predetermined depth. The excavation is performed by rotationally driving the rotary blade 3, the auger 2, and the casing 1 in the forward rotation direction while bringing the auger device K into contact with the ground. The target ground is sent to the inner space of the upper casing 1 by the blade inner peripheral surface 5 while being scraped off by the excavation blade H of the rotary blade 3. In the inner space of the casing 1, the auger 2 further sends the soil upward.
[2] Perform ground improvement work at the relevant step. After the soil S is filled downward from a predetermined position in the inner space of the casing 1, the rotary blade 3 and the auger 2 are rotationally driven in the reverse direction. However, at this time, the rotational driving of the casing 1 is performed in a stopped state. By the rotational drive of the rotary blade 3 and the auger 2, the blade outer peripheral surface 6 pushes the soil S toward the surrounding ground G side, and the spiral blade 2b supplies the soil in the casing 1 toward the rotary blade 3 rotation locus. The Therefore, the consolidation improvement zone continues to expand outward of the rotor blade 3.
And as construction management, in order to generate the target extrusion soil amount D1 necessary for improving the predetermined range of the surrounding ground G to the predetermined strength and the pressing force necessary for improving the predetermined strength in advance. The target rotational torque value T1 of the rotary blade 3 is set, and during the ground improvement construction, the amount S2 of the soil S pushed to the surrounding ground G accompanying the rotational drive of the rotary blade 3 and the rotary blade 3 The rotational torque value T2 is measured, and the extruded soil amount D2 satisfies the target extruded soil amount D1, and the construction at the same depth is performed until the rotational torque value T2 of the rotary blade 3 satisfies the target rotational torque value T1. continue. Note that the extruded soil amount D2 can be determined from, for example, the descending amount of the top surface position of the soil in the space inside the casing 1 or from the amount of soil thrown into the casing 1 during the construction. And the value by the monitor mechanism of a rotational drive part can be employ | adopted for rotational torque value T2.
[3] Raise the auger device K by a predetermined dimension, and perform ground improvement construction in the next step. Thereafter, a columnar improvement is formed by repeating [2] and [3].

The target extruded soil amount D1 and the target rotational torque value T1 are set in consideration of the planned improvement range and the planned improvement strength based on various coefficients set according to the target soil quality. Can do.
The improved strength can be expressed in the form of a standard penetration test value (so-called “N value”), a uniaxial compression test strength, or the like.

  According to the ground improvement method, the ground can be improved to a wider range than the excavation diameter while minimizing noise and vibration associated with the construction. In addition, it is possible to use improvement materials such as cement and water glass, but basically, the improvement area is expanded by the compaction energy of the soil pushed out by the rotor blades. It becomes possible to implement ground improvement more economically. In addition, through the construction management from both sides of the extruded soil volume and rotational torque, the improvement area should be expanded more reliably even when there are variations in physical properties and contamination that cannot be avoided on natural ground. Is possible.

[Another embodiment]
Other embodiments will be described below.

<1> The auger device used in the ground improvement method is not limited to the one described in the previous embodiment. For example, the auger device is replaced with a configuration in which the rotating blades 3 and the auger 2 can be individually driven to rotate. You may comprise so that it may drive by the same rotation with a drive system. By using the same rotation drive system, the apparatus can be simplified and the cost can be reduced.
Moreover, according to the structure provided with the different rotational drive system demonstrated by previous embodiment, it is possible to take the drive system which makes the rotational speed of the rotary blade 3 and the auger 2 differ, for example. As an example, since consolidation deformation of the ground tends to occur at the initial stage of ground improvement construction, a method of increasing the rotation speed of the auger 2 and increasing the amount of soil supplied to the rotary blades 3 at that stage. It is done. This makes it possible to further improve the efficiency of ground improvement. The initial stage in this case means not only the initial stage of construction within one construction step, but also the initial stage may be a sparse state with a small number of constructions in the entire improvement range.
Further, as a configuration of the auger device, in the ground improvement process after the excavation process, the auger 2 is not provided, but only the casing 1 and the rotary blade 3 are provided. You may comprise so that it may fall in a rotation locus | trajectory.
<2> The auger 2 is not limited to the one in which the spiral blade 2b described in the previous embodiment is provided over the entire length, and for example, may be provided in a plurality of locations at intervals in the vertical direction. .
<3> The rotary blade 3 is not limited to the shape described in the previous embodiment, and can be appropriately deformed. For example, as shown in FIG. 8, the wing part 3c is constituted by a spiral wing, and the spiral wing extends obliquely upward from the base end part attached to the base part 3b as shown in the figure. The soil S can be pushed out to the surrounding ground G by the lower surface of the spiral wing.
In addition, in the previous embodiment, the rotary blade 3 itself has been described as having both the excavation function and the soil extrusion function, but the structure is divided for each functional unit. Also good.
<4> The ground improvement method is not limited to being performed using the auger device described in the previous embodiment, and may be performed using an appropriately changed device.
In addition, instead of using three sets of auger devices so that the axis of each auger device is positioned at the apex of an equilateral triangle, construction with one set of auger devices, two sets, or four or more sets Construction using a plurality of sets of auger devices may be used. Even when three sets of auger devices are used, the arrangement is not limited to an equilateral triangle, but may be an arrangement using triangles other than the equilateral triangle, or an arrangement arranged in a line.
Further, the excavation direction by the auger device is not limited to the vertical direction, and can be any direction of 360 degrees, such as diagonally downward, lateral, diagonally upward, and upward. However, it is preferable to separately provide a mechanism for holding the soil in the casing with respect to the construction in the lateral direction or upward.

  In addition, as mentioned above, although the code | symbol was written in order to make contrast with drawing convenient, this invention is not limited to the structure of an accompanying drawing by this entry.

Explanatory drawing showing the concept of the auger device Side view of rotor blade Top view of rotor blade Cross section of the wing Plan view sectional view showing the arrangement of the auger device Plan view diagram showing the improvement mechanism Explanatory drawing showing construction flow Side view sectional drawing which shows the rotary blade of another embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Casing 2 Auger 3 Rotary blade D1 Target extrusion soil amount D2 Extrusion soil amount G Surrounding ground S Soil T1 Target rotational torque value T2 Rotary torque value

Claims (2)

A rotary blade that can press the surrounding ground by being driven to rotate around the axis of rotation is arranged on the tip side so that the casing disposed in the ground is inserted, and is pushed out into the casing by the rotary blade. In order to reinforce the surrounding ground by positioning the soil and pushing the rotary blade around the rotation axis to push the soil to the surrounding ground.
In advance, a target amount of extruded soil necessary to improve the predetermined range of the surrounding ground to a predetermined strength, and a target rotational torque value of the rotor blade for generating a pressing force required to improve the predetermined strength, When the ground improvement work, the amount of extruded soil to the surrounding ground accompanying the rotational drive of the rotor blades and the rotational torque value of the rotor blades are measured. both soil amount and the rotation torque value, soil improvement method to continue until satisfying each of the target value. In the casing, the rotor blades and is previously provided with a rotary drive freely auger to the rotation axis around a different rotational driving system, feeding the soil by the rotation of the auger to the rotation blade side of the distal end while seeking the performed ground improvement in rotational driving of the rotor blade, ground improvement method according to claim 1, Ru increases the supply amount of the soil by increasing the rotational speed of the auger in the initial stages of the ground improvement construction.

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