JP7474998B1 - Screw Auger - Google Patents

Abstract

[Problem] To provide a screw auger that can simultaneously suppress the amount of excavated soil discharged and suppress an increase in excavation resistance. [Solution] The screw auger 1 is a screw auger in which a screw blade 3 is provided on the outer periphery of an auger rod 2, and the auger rod 2 has a tip portion 4 to which a drilling bit 6 can be attached at its lower end and a base portion 5 that extends in the axial direction from the upper end of the tip portion 4, and the diameter of the auger rod 2 at the base portion 5 is longer than the diameter of the auger rod 2 at the tip portion 4. [Selected Figure] Figure 1

Description

The present invention relates to a screw auger for drilling a hole in the ground.

To build piles underground to support buildings, a screw auger is rotated to penetrate to a specified depth and then pulled out to form a hole for building the piles.

One such screw auger is shown in Patent Document 1. The screw auger in Patent Document 1 has screw blades on the outer periphery of the auger rod.

Patent No. 5976723

The screw auger in Patent Document 1 has limitations in suppressing the discharge of excavated soil to the ground during penetration and extraction. If a large amount of excavated soil is discharged, the work yard on the ground will have to be narrowed, making it difficult to ensure safety on site and possibly causing process delays.

In addition, in order to reduce the amount of excavated soil discharged, it is possible to shorten the distance from the outer surface of the auger rod to the outer edge of the screw blade. However, this increases the excavation resistance and increases the excavation time.

The present invention aims to provide a screw auger that can simultaneously reduce the amount of excavated soil discharged and prevent an increase in excavation resistance.

The screw auger of claim 1 of the present invention is a screw auger in which screw blades are provided on the outer periphery of an auger rod, the auger rod having a tip portion at the lower end of which a drilling bit can be attached, and a base portion extending in the axial direction from the upper end of the tip portion, the diameter of the auger rod at the base portion being longer than the diameter of the auger rod at the tip portion, and a circular arc-shaped trowel portion is provided on the outer periphery of the auger rod, the side of which is a curved pressing surface that protrudes outward from the outer periphery of the auger rod, and the width of the trowel portion provided at the base end, parallel to the axial direction of the auger rod, is longer than that of the trowel portion provided at the tip portion .

The screw auger of claim 1 has the above-mentioned configuration, so that the excavated soil rises relatively along the screw blade from the tip to the base, and when it reaches the base end where the diameter of the auger rod is longer, the excavated soil is pressed further toward the hole wall. As a result, a portion of the excavated local soil is packed against the hole wall, suppressing the discharge of excavated soil.

In addition, because the screw auger of claim 1 has the above-mentioned configuration, the distance from the outer peripheral surface of the auger rod to the outer edge of the screw blade is shortened only at the base end, making it possible to suppress an increase in excavation resistance.

Furthermore, the screw auger of claim 1 promotes compaction of the hole walls, preventing the collapse of the hole walls.

In addition, the screw auger of claim 1 can efficiently press the excavated soil against the hole wall with the trowel part, which can suppress the discharge amount of the excavated soil and promote the consolidation of the hole wall, thereby preventing the hole wall from collapsing.

The screw auger of claim 2 of the present invention is the screw auger of claim 1, wherein the trowel portion provided at the base end has a shorter radial distance from the axis of the auger rod to the outermost protruding position of the curved pressing surface from the outer periphery of the auger rod than the trowel portion provided at the tip end.

The screw auger according to claim 3 of the present invention is the screw auger according to claim 1, wherein the ratio of the diameter of the auger rod at the base end to the diameter of the auger rod at the tip end is 1.2 to 1.4.

The screw auger of claim 3 has the same operational effect as that of claim 1, and in addition, can suppress the discharge amount of excavated soil while minimizing the increase in excavation resistance.

The screw auger according to claim 4 of the present invention is the screw auger according to claim 1, wherein the ratio of the blade diameter of the screw blade to the diameter of the auger rod at the base end is 1.5 to 1.2.

The screw auger of claim 4 has the same effect as that of claim 1, and in addition, can improve the dimensional accuracy of the hole formed by excavation.

The screw auger of claim 5 is the screw auger of any of claims 1 to 4 , wherein a plurality of trowel portions are provided on the outer periphery of the auger rod at the base end, and the plurality of trowel portions are arranged in a spiral shape along the outer periphery of the auger rod at the base end.

The screw auger of claim 5 of the present invention has the same effects as those of claims 1 to 4, and in addition, by arranging a plurality of trowel parts at the base end, it is possible to more efficiently press the excavated soil against the hole wall. This makes it possible to further suppress the discharge amount of the excavated soil and further promote the consolidation of the hole wall, thereby preventing the collapse of the hole wall.

According to any one of claims 1 to 5 , the present invention can suppress both the amount of excavated soil discharged during excavation and the increase in excavation resistance. In addition, the consolidation of the hole wall is further promoted, and the collapse of the hole wall can be prevented.

FIG. 2 is a front view of the screw auger according to one embodiment of the present invention. FIG. 2 is a right side view of the screw auger of FIG. 1 . FIG. 2 is a rear view of the screw auger of FIG. 1 . FIG. 2 is a left side view of the screw auger of FIG. 1 . FIG. 1 is a diagram of a miniature screw auger model.

The screw auger 1 according to one embodiment of the present invention will be described with reference to Figures 1 to 4.

The screw auger 1 is attached to an excavator and can be rotated around its axis to excavate a hole.

The screw auger 1 has screw blades 3 on the outer periphery of the auger rod 2.

The auger rod 2 has a tip portion 4 at the lower end of which a drilling bit 6 can be attached, and a base portion 5 that extends axially from the upper end of the tip portion 4.

The diameter of the auger rod 2 at the base end 5 is longer than the diameter of the auger rod 2 at the tip end 4.

The auger rod 2 has a fluid path inside.

As shown in FIG. 4, a discharge port 7 for discharging a fluid is provided near the bottom end of the tip 4. When the screw auger 1 is pulled out, hydraulic solidification material can be injected from the discharge port 7 to build a pile.

Multiple iron pieces 8 are provided on the outer periphery of the auger rod 2.

Each iron part 8 has an arc shape with a curved pressing surface that protrudes outward from the outer periphery of the auger rod 2 as its side.

The multiple iron pieces 8 at the base end 5 are each arranged in a spiral shape along the outer periphery of the auger rod 2.

The upper or lower end surface of each iron tip 8 is flush with the upper or lower surface of the screw blade 3.

Below, we will explain an experiment in which a miniature screw auger model was used to excavate artificial soft soil in order to verify the action and effect of the present invention.

Four types of miniature screw auger models were created, each with a different ratio between the diameter of the auger rod at the base end and the diameter of the auger rod at the tip, and two comparative examples in which the diameter of the auger rod at the base end and the diameter of the auger rod at the tip were constant.

Details of the miniature screw auger models of the four study examples and two comparison examples are shown in Figure 5.

The comparative examples are Comparative Example 1, in which the auger rod has a constant diameter equal to the diameter of the auger rod at the tip of the study example, and Comparative Example 2, in which the auger rod has a constant diameter that is thicker than that of Comparative Example 1.

In each study example, the diameter of the auger rod at the tip is the same. In each study example, the diameter of the auger rod at the base end increases in the order from Study Example 1 to Study Example 4. In other words, the ratio of the diameter of the auger rod at the base end to the diameter of the auger rod at the tip increases in the order from Study Example 1 to Study Example 4.

The blade diameter is the same in each study example. The diameter of the auger rod at the base end increases from Study Example 1 to Study Example 4. In other words, the ratio of the blade diameter of the screw blade to the diameter of the auger rod at the base end decreases from Study Example 1 to Study Example 4.

As shown in Figure 5, the blade diameters of the four study examples and the two comparative examples are all the same. Therefore, the planned excavation volume in the artificial soft soil is also the same for the four study examples and the two comparative examples.

The artificial soft soil was made by mixing bentonite and cement milk.

Four types of screw auger models (examples and two comparative examples) are attached to the tip of an electric drill and used to excavate artificial soft soil.

In the experiment to measure the amount of excavated soil and excavation resistance, the screw auger model is rotated forward and penetrated to a specified depth into the artificial soft soil. The screw auger model is then pulled out while still rotating forward to form a tunnel.

The electric current (resistance) of the electric drill is measured when the screw auger model penetrates. The higher the measured current, the greater the drilling resistance.

The measurement results of the current value for each screw auger model of the four study examples and two comparison examples are shown in Table 1 below.

In Comparative Example 1 and Study Examples 1-4, when the diameter of the auger rod at the tip is the same, it can be seen that the longer the diameter of the auger rod at the base end, the larger the current value and the greater the excavation resistance.

On the other hand, when comparing Study Example 3 with Comparative Example 2, although the base end diameter is the same, it can be seen that Study Example 3 has a smaller current value than Comparative Example 2, and that the excavation resistance is suppressed.

Furthermore, when comparing Study Example 4 with Comparative Example 2, it can be seen that, although the base end diameter is longer in Study Example 4, the current value is smaller in Study Example 4 than in Comparative Example 2, and excavation resistance is suppressed.

Therefore, from the measurement results of the current values of the four types of study examples and Comparative Example 2, it can be seen that the configuration of the study example in which the diameter of the auger rod at the base end is longer than the diameter of the auger rod at the tip end can suppress excavation resistance even if the diameter of the auger rod at the base end is larger.

The amount of excavated soil discharged from the artificial soft soil to the ground surface when the screw auger model is penetrated is defined as the amount of excavated soil during penetration.The amount of excavated soil discharged from the artificial soft soil to the ground surface when the screw auger model is extracted is defined as the amount of excavated soil during extraction.

For each screw auger model, the total volume of soil excavated is the sum of the volume of soil excavated during penetration and the volume of soil excavated during extraction.

The total excavated soil volume for each screw auger model for the four study examples and two comparison examples is shown in Table 2 below.

The distance from the outer surface of the auger rod to the outer edge of the screw blade is the difference between the blade diameter and the base end diameter (tip end diameter).

Comparative example 2 has a smaller difference between the blade diameter and the base end diameter than comparative example 1, so the total amount of excavated soil is significantly less, but as mentioned above, the excavation resistance is also greater.

The total amount of excavated soil in the four study examples was less than that in Comparative Example 1.

Therefore, from the measurement results of the total excavated soil volume for the four types of study examples and Comparative Example 1, it can be seen that the configuration of the study example, in which the diameter of the auger rod at the base end is longer than the diameter of the auger rod at the tip end, is able to reduce the amount of excavated soil discharged.

From the standpoint of reducing the amount of excavated soil discharged during excavation and reducing the increase in excavation resistance, it is desirable for the ratio of the diameter of the auger rod at the base end to the diameter of the auger rod at the tip to be in the range of 1.2 to 1.4.

Below, we explain the cement pillar production experiment in which cement milk was poured into holes formed using each screw auger model in four study examples and two comparison examples.

Cement milk was poured into the four study example and two comparison example pits created in the aforementioned experiment to measure excavation volume and excavation resistance.

After curing for five days, the artificial soft soil was scraped away and four types of test examples and two types of comparative examples of cement pillars were removed.

The circumference of each cement pillar was measured at the top, middle, and bottom to calculate the diameter.

The average diameter of each cement pillar is compared with the blade diameter to evaluate the dimensional accuracy of the pit formed by mining.

The results of the cement pillar production experiments using each screw auger model for the four study examples and two comparison examples are shown in Table 3 below.

When looking at the ratio of the average diameter of the cement pillars to the blade diameter, Study Example 1-4 exceeds 1, unlike Comparative Example 2. As in Comparative Example 2, if the ratio of the average diameter of the cement pillars to the blade diameter falls below 1, this is undesirable as it will result in insufficient finished cement pillars. In addition, Study Example 1-4 has an average diameter of the cement pillars that is closer to the blade diameter than Comparative Example 1. Therefore, Study Example 1-4 has improved dimensional accuracy of the hole formed by excavation.

From the perspective of improving the dimensional accuracy of the hole, it is desirable for the ratio of the screw blade diameter to the auger rod diameter at the base end to be in the range of 1.5 to 1.2.

In the above embodiment, a fluid path is provided inside the auger rod 2, and a discharge port 7 for discharging fluid is provided near the lower end of the tip 4, but this is not limited to the above. A screw auger that does not have a fluid path or a discharge port may also be used.

In the above embodiment, the number of trowel parts 8 is an example and is not limited to this. The number of trowel parts can be freely changed depending on the purpose, such as reducing the amount of excavated soil discharged during excavation, reducing the increase in excavation resistance, and improving the dimensional accuracy of the hole.

1 Screw auger 2 Auger rod 3 Screw blade 4 Tip portion 5 Base end portion 6 Drilling bit 7 Discharge port 8 Trowel portion

Claims (5)

A screw auger having a screw blade provided on the outer periphery of an auger rod,
The auger rod has a tip portion at the lower end of which a drilling bit can be attached, and a base end portion extending in the axial direction from the upper end of the tip portion.
The diameter of the auger rod at the base end is longer than the diameter of the auger rod at the tip end,
An arc-shaped iron part is provided on the outer periphery of the auger rod, the arc-shaped iron part having a curved pressing surface that projects outward from the outer periphery of the auger rod as a side surface,
A screw auger characterized in that the trowel portion provided at the base end has a width parallel to the axial direction of the auger rod that is longer than that of the trowel portion provided at the tip end. The screw auger according to claim 1, characterized in that the trowel portion provided at the base end has a radial distance from the axis of the auger rod to the outermost protruding position of the curved pressing surface from the outer periphery of the auger rod that is shorter than that of the trowel portion provided at the tip end. The screw auger described in claim 1, characterized in that the ratio of the diameter of the auger rod at the base end to the diameter of the auger rod at the tip end is 1.2 to 1.4. The screw auger described in claim 1, characterized in that the ratio of the screw blade blade diameter to the diameter of the auger rod at the base end is 1.5 to 1.2. 5. The screw auger according to claim 1, wherein a plurality of trowel portions are provided on the outer periphery of the auger rod at the base end, and the plurality of trowel portions are arranged in a spiral shape along the outer periphery of the auger rod at the base end.

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