Screw auger

Abstract

To provide a screw auger capable of suppressing both the amount of excavated soil discharged and the increase in excavation resistance.SOLUTION: A screw auger 1 is a screw auger having screw blades 3 provided on an outer periphery of an auger rod 2. The auger rod 2 having a tip portion 4 at a lower end to which a drilling bit 6 can be attached and a base portion 5 extending axially from an upper end of the tip portion 4. A diameter of the auger rod 2 at the base portion 5 being longer than the diameter of the auger rod 2 at the tip portion 4.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a screw auger for drilling holes in the earth. [Background technology]

[0002] In order to construct piles to support a building in the ground, a screw auger is rotated while penetrating to a specified depth and then pulled out to form a hole for constructing the piles.

[0003] Such a screw auger is disclosed in Patent Document 1. The screw auger in Patent Document 1 has screw blades provided on the outer periphery of an auger rod. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5976723 Summary of the Invention [Problem to be solved by the invention]

[0005] The screw auger of Patent Document 1 has limitations in suppressing the discharge of excavated soil to the ground during penetration and extraction. If the amount of excavated soil discharged increases, the work yard on the ground will have to be narrowed, which may make it difficult to ensure safety on site and may cause delays in the process.

[0006] In order to reduce the amount of excavated soil discharged, it is possible to shorten the distance from the outer periphery of the auger rod to the outer edge of the screw blade, but this increases the excavation resistance and increases the excavation time.

[0007] Therefore, an object of the present invention is to provide a screw auger that can simultaneously suppress the amount of excavated soil discharged and the increase in excavation resistance. [Means for solving the problem]

[0008] The screw auger of claim 1 of the present invention is a screw auger in which a screw blade is provided on the outer periphery of an auger rod, the auger rod having a tip portion at the lower end to 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. The auger rod is provided on its outer periphery with an arc-shaped iron part having a curved pressing surface as a side surface that protrudes outward from the outer periphery of the auger rod, and the iron part provided at the base end has a longer width parallel to the axial direction of the auger rod than the iron part provided at the tip end. .

[0009] 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 large, the excavated soil is pressed further toward the hole wall. As a result, a part of the excavated local soil is packed against the hole wall, and the discharge amount of the excavated soil can be suppressed.

[0010] Furthermore, because the screw auger of claim 1 has the above-mentioned configuration, the distance from the outer circumferential surface of the auger rod to the outer edge of the screw blade is short only at the base end, making it possible to suppress an increase in excavation resistance.

[0011] Furthermore, the screw auger of claim 1 can promote consolidation of the hole wall, preventing the collapse of the hole wall.

[0012] 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 collapse of the hole wall.

[0013] 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.

[0014] Claims of the invention 3 In the screw auger of claim 1, 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.

[0015] Claim 3 In addition to the same advantageous effects as those of claim 1, the screw auger of the present invention can suppress the discharge amount of excavated soil while minimizing the increase in excavation resistance.

[0016] Claims of the invention 4 In the screw auger of claim 1, 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.

[0017] Claim 4 In addition to the same effects as those of claim 1, the screw auger of the present invention can improve the dimensional accuracy of the hole formed by excavation.

[0018] Claim 5 The screw auger is Any one of claims 1 to 4 In the screw auger, 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.

[0019] Claims of the invention 5 In addition to the same effects as those of claims 1 to 4, the screw auger can more efficiently press the excavated soil against the hole wall by arranging multiple trowel parts at the base end. This can further reduce the discharge amount of excavated soil and further promote the consolidation of the hole wall, preventing the hole wall from collapsing. Effect of the Invention

[0020] From claim 1 5 According to any one of the above-mentioned inventions, it is possible to 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. [Brief description of the drawings]

[0021] [Figure 1] FIG. 2 is a front view of the screw auger according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a right side view of the screw auger of FIG. 1. [Diagram 3] FIG. 2 is a rear view of the screw auger of FIG. 1. [Figure 4]FIG. 2 is a left side view of the screw auger of FIG. 1. [Diagram 5] FIG. 1 is a diagram of a miniature screw auger model. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] A screw auger 1 according to one embodiment of the present invention will be described with reference to Figs.

[0023] The screw auger 1 is attached to an excavator and can be rotated about its axis to excavate a hole.

[0024] The screw auger 1 has a screw blade 3 provided on the outer periphery of an auger rod 2 .

[0025] The auger rod 2 has a tip portion 4 to the lower end of which a drilling bit 6 can be attached, and a base end portion 5 extending axially from the upper end of the tip portion 4 .

[0026] The diameter of the auger rod 2 at the base end 5 is greater than the diameter of the auger rod 2 at the tip end 4 .

[0027] The auger rod 2 has a fluid passage therein.

[0028] As shown in Fig. 4, a discharge port 7 for discharging a fluid is provided near the lower end of the tip portion 4. When the screw auger 1 is pulled out, a hydraulic solidification material can be injected from the discharge port 7 to build a pile.

[0029] A plurality of iron pieces 8 are provided on the outer periphery of the auger rod 2 .

[0030] Each of the iron portions 8 has an arc shape with a curved pressing surface that projects outward from the outer periphery of the auger rod 2 as a side surface.

[0031] The plurality of iron portions 8 at the base end 5 are each arranged in a spiral shape along the outer periphery of the auger rod 2 .

[0032] The upper end surface or the lower end surface of each iron tip portion 8 is flush with the upper surface or the lower surface of the screw blade 3 .

[0033] In the following, an experiment will be described in which a miniature screw auger model was used to excavate artificial soft soil in order to confirm the action and effect of the present invention.

[0034] Four types of miniature screw auger models were created: four test examples in which the ratio of the diameter of the auger rod at the base end to the diameter of the auger rod at the tip was changed, and two comparison 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.

[0035] Details of the miniature screw auger models of the four study examples and two comparative examples are shown in FIG.

[0036] The comparative examples are Comparative Example 1, in which the diameter of the auger rod at the tip of the examined example is constant, and Comparative Example 2, in which the auger rod has a constant diameter that is thicker than that of Comparative Example 1.

[0037] In each study example, the diameter of the auger rod at the tip end 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 end increases in the order from Study Example 1 to Study Example 4.

[0038] In addition, the blade diameter is the same in each study example. 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 blade diameter of the screw blade to the diameter of the auger rod at the base end decreases in the order from Study Example 1 to Study Example 4.

[0039] 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.

[0040] The artificial soft soil was made by mixing bentonite and cement milk.

[0041] Four types of screw auger models for the study and two types for the comparison are attached to the tip of an electric drill, and artificial soft soil is excavated.

[0042] In the experiment to measure the amount of excavated soil and excavation resistance, the screw auger model was rotated forward to penetrate the artificial soft soil to a predetermined depth. Then, the screw auger model was pulled out while rotating forward to form a hole.

[0043] The electric current (resistance) of the electric drill is measured when the screw auger model penetrates. The larger the measured electric current, the greater the drilling resistance.

[0044] The results of measuring the electric current value for each screw auger model of the four study examples and the two comparative examples are shown in Table 1 below.

[0045] [Table 1]

[0046] 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 tend to be.

[0047] 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 thus excavation resistance can be suppressed.

[0048] 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 the excavation resistance is suppressed.

[0049] 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 becomes larger.

[0050] 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.

[0051] In each screw auger model, the total excavated volume is the sum of the volume of soil excavated during penetration and the volume of soil excavated during extraction.

[0052] The total excavated soil volume for each screw auger model of the four study examples and the two comparative examples is shown in Table 2 below.

[0053] [Table 2]

[0054] The distance from the outer circumferential 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).

[0055] In Comparative Example 2, the difference between the blade diameter and the base end diameter is smaller than in Comparative Example 1, so the total amount of excavated soil is significantly smaller, but as mentioned above, the excavation resistance is also large.

[0056] The four study examples have a smaller total excavated soil volume than the comparative example 1.

[0057] 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.

[0058] From the viewpoints of suppressing the amount of excavated soil discharged during excavation and suppressing an 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.

[0059] Below, we will explain the cement pillar production experiments in which cement milk was poured into holes formed using each of the four study examples and two comparative examples.

[0060] Cement milk was poured into the four types of study pits and two types of comparison pits formed in the aforementioned experiment to measure excavation volume and excavation resistance.

[0061] After curing for 5 days, the artificial soft soil was scraped away and four types of test examples and two types of comparative examples of cement pillars were taken out.

[0062] The circumference of each cement pillar was measured at the top, middle, and bottom, and the diameter was calculated.

[0063] The average diameter of each cement pillar is compared with the vane diameter to evaluate the dimensional accuracy of the pit formed by mining.

[0064] The results of the cement pillar production experiments using each screw auger model of the four study examples and two comparative examples are shown in Table 3 below.

[0065] [Table 3]

[0066] Focusing on the ratio of the average diameter of the cement pillar to the impeller 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 pillar to the impeller diameter falls below 1, it is undesirable because the finished cement pillar will be insufficient. In addition, Study Example 1-4 has an average diameter of the cement pillar closer to the impeller diameter than Comparative Example 1. Therefore, Study Example 1-4 has improved dimensional accuracy of the hole formed by excavation.

[0067] From the viewpoint of improving the dimensional accuracy of the hole, it is desirable that the ratio of the blade diameter of the screw blade to the diameter of the auger rod at the base end be in the range of 1.5 to 1.2.

[0068] In the above embodiment, a description has been given of a case in which a fluid path is provided inside the auger rod 2 and a discharge port 7 for discharging a fluid is provided near the lower end of the tip portion 4, but the present invention is not limited to this. A screw auger that is not provided with a fluid path and a discharge port may also be used.

[0069] 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 suppressing the discharge amount of excavated soil during excavation, suppressing an increase in excavation resistance, and improving the dimensional accuracy of the hole. [Explanation of symbols]

[0070] 1 Screw Auger 2 Ogre Rod 3 Screw blade 4 Tip 5 Proximal end 6 Drilling Bits 7 Outlet 8 Soldering iron part

Claims

1. 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. A screw auger, characterized in that the diameter of the auger rod at the base end is longer than the diameter of the auger rod at the tip end.

2. 2. 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.

3. 2. The screw auger according to claim 1, wherein the ratio of the diameter of the screw blade to the diameter of the auger rod at the base end is 1.5 to 1.

2.

4. 4. The screw auger according to claim 1, wherein the auger rod is provided with a fluid passage therein and a discharge port for discharging the fluid is provided near the lower end of the tip portion.

5. 4. The screw auger according to claim 1, wherein the auger rod is provided on its outer periphery with an arc-shaped iron part having a curved pressing surface as a side surface that protrudes outward from the outer periphery of the auger rod.

6. 6. The screw auger according to claim 5, 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.

Images