JP6549030B2 - Borehole bottom ground plate loading test equipment - Google Patents

Description

  The present invention relates to a borehole bottom ground flat plate loading test apparatus, and more particularly to a testing apparatus capable of reliably and easily removing slime in the bottom of a borehole in order to accurately carry out a flat plate loading test of the ground at the bottom of the borehole. .

  Conventionally, the method of examining the bearing capacity characteristics of deep ground from the ground surface is called deep layer loading test, and has been introduced by the Geotechnical Institute as a method of loading test. When planning a building without underground directly on the foundation, the lower end of the foundation is often about 2 to 3 m lower than the current ground level, and the bearing capacity of the ground should be grasped at an early stage (for example, at the time of building planning) Is very useful because it can raise the accuracy of basic design from an early stage. In general, there are many existing buildings in the planning stage and it can not be surveyed in many cases, and it is not practical to drill widely to the target ground surface and conduct a flat plate loading test.

  Therefore, the inventor pays attention to the load-sink relationship of the ground, which is essential for the performance design of the building foundation, as a loading test method suitable for such a site, and combines the static flat plate loading test and the rapid flat plate loading test. A simple method is applied to the bottom of a borehole, and a method is proposed for early investigation of the load-sink relationship of deep ground (Non-Patent Document 1). Moreover, the invention of the apparatus and test method which set a boring process ground flat plate load test apparatus efficiently, and was to test it is also performed (patent document 1).

Patent No. 5524526 gazette

Kosuke Kinoshita, Tsutomu Nemoto, Hiroshi Sakihama, Kazuyuki Matsuzawa, Yukinori Matsumoto, Evaluation of ground characteristics of consolidated sandy soil by static and rapid plate loading tests (Part 1: Evaluation of bearing capacity by static plate loading test), ( Part 2: Evaluation of variation by rapid plate loading test), 2006 Annual Meeting (Kanto) Abstracts of Academic Lectures, Architectural Institute of Japan, July 31, 2006, vol. 571-P. 574

  By the way, when carrying out the flat plate loading test carried out on the bottom of the borehole mentioned above, if slime (digging) remains at the bottom of the borehole drilled by boring, loose soil will appear between the loading surface and the test ground. Affects the load-sink relationship.

  In the invention disclosed in Patent Document 1, a rotary blade serving as a discharge plate is provided on the side surface of the load plate, and soil around the load plate is discharged upward by rotating the rotary blade together with the load plate. However, there is a problem that the slime which remains in the hole bottom which becomes a load under a loading board can not be removed. Therefore, the object of the present invention is to solve the problems of the above-described conventional techniques, and when drilling a borehole, the loading plate can be maintained in a stable state with respect to the bottom of the borehole, whereby It is an object of the present invention to provide a borehole bottom flat plate loading test apparatus capable of improving accuracy.

In order to achieve the above object, the present invention is accommodated in the test preparation hole in a state where the loading portion is held at the lower end, and the loading surface of the loading portion described above to the test ground surface of the hole bottom ground of the boring hole by the drilling machine. was reached, the test ground surface is pressed by the loading unit, a bowling hole bottom ground flat loading test apparatus for performing a flat plate loading test of the test locations, board, formed on the loading surface by rotating the loading portion performing flat loading test before Symbol test soil surface with been removed slime deposited between the hole bottom ground with slime removing protrusions and loading surface, while being in close contact with said loading surface and the hole bottom ground It is characterized by

  It is preferable that the slime removing protrusion is a curved protrusion having a convex shape in the rotational direction of the loading portion extending from the central position of the loading surface to the outer edge of the loading surface.

  The curved shape of the curved protrusion is preferably a logarithmic spiral.

  As described above, according to the present invention, since the bottom of the borehole, which is a plate surface during testing, can be brought into close contact with the loading plate, the measurement accuracy of various flat plate loading tests by this device can be enhanced. Can.

The elements on larger scale which showed the structure of the loading board which has a loading part holding pipe of a borehole bottom ground flat plate loading test device of the present invention, and a slime removal projection. The bottom view which showed the shape of the slime removal projection formed in the load board bottom, and the explanatory view of the slime removal situation by the model of a slime removal projection. The fragmentary sectional view showing the example of a section of a slime removal projection. The load board bottom view which showed the example of arrangement | positioning of a slime removal protrusion. Explanatory drawing which showed the operation state of the boring-hole bottom ground flat plate load test apparatus of this invention. Explanatory drawing which showed the slime removal condition in the borehole bottom by a slime removal protrusion.

  Hereinafter, the following embodiment is described with reference to an attached drawing as a form for carrying out a borehole bottom ground flat plate loading test device of the present invention.

[Configuration of tip of test device]
In order to solve the above-mentioned problems, the borehole bottom ground flat plate loading test device 10 (hereinafter referred to as the loading test device 10) of the present invention, in particular, the hole bottom 2 as a part of the loading portion of the loading test. The present invention is characterized in the configuration of the means for removing slime and the operation thereof. 1 shows the mounting state of the loading plate 11 and the wing-like projection 13 at the tip of the loading portion holding pipe 12 as means for holding the loading plate 11 at the tip of the loading test device 10, and the loading plate 11 It is the enlarged view which showed the internal mechanism to operate, and the slime removal protrusion 20 formed in the lower surface of the loading board 11. FIG.

  FIG. 1A is a partially cutaway view of the lower end of the loading section holding pipe in order to show a state in which the loading plate 11 is held by the lower end of the loading section holding pipe which is one configuration of the loading test apparatus 10. It is a front view. As shown in the figure, a cylindrical portion 15 having a slit 14 formed on the side surface thereof is integrated with the loading plate 11 on the upper surface of the loading plate 11 to form a loading portion. The distal end of a guide rod 16 welded and attached to the inner surface of the loading portion holding pipe is fitted in the slit 14. Further, two wing-like projections 13 are helically attached at symmetrical positions of 180 ° across the center of the loading portion holding pipe 12 on the lower end outer peripheral surface of the loading portion holding pipe. In the present embodiment, a steel plate processed into a spiral shape is fixed to the side of the pipe by welding. The lower end of the wing-like projection 13 protrudes downward from the lower end of the loading portion holding pipe 12 by the thickness of the loading plate 11, as shown in FIG. 1A. On the lower surface of the loading plate 11, a curd-shaped slime removing projection 20 as shown in FIG. 2 is formed. In the present embodiment, in the slime removing projection 20, the curved strip-like steel material shown in FIG. 2 is fixed to the load plate bottom surface 11b by welding.

  FIG. 1B is a front view in which a part of the lower end of the loading portion holding pipe 12 is cut away to show the configuration and operation of the loading plate 11 when functioning as the flat plate loading test apparatus 10. It is. As shown in the figure, the loading rod 6 is inserted into the loading portion holding pipe 12, and the lower end thereof directly presses the upper surface of the cylindrical portion 15 integrated with the loading plate 11. The figure shows a state in which the loading plate 11 is pressed against the bottom surface (not shown) of the bottom by a predetermined amount together with the slime removing projections 20 by a predetermined loading load. In the present embodiment, a flat cylindrical steel material with a diameter of 100 mm and a thickness of 25 mm is used as the loading plate 11 on which the slime removing projections 20 are formed.

ｒ：θ（０°＝＜θ＜＝α°）に対応した対数螺旋の半径
ただしαはｒが載荷板外縁と横切る位置を範囲とする角度
ａ，ｂ：定数
図２（ａ）に示したように、θ＝０におけるｒが載荷板底面１１ｂの中心点に一致するように、式１の対数螺旋の中心点Ｏがｘ軸上に定められている。定数ａ，ｂは、スライムの除去を確実にするために、式１の曲線と載荷板１１の半径Ｒの円との交点が、中心点Ｏを原点としたθ＞π／２となるような曲線形が得られるように設定することが好ましい。本実施形態では、一例としてａ＝０．５７，ｂ＝０．８３からなる定数の対数螺旋を曲線形状としたスライム除去突起２０が載荷板底面１１ｂに設けられている。なお、この定数ａ，ｂはスライム除去効果が得られる範囲で適宜設定することができる。模型実験等を行い、スライムの状態を考慮して定数を決定することも好ましい。 Here, the curved shape of the slime removing projection 20 and the function thereof will be described with reference to FIG. In this embodiment, a logarithmic spiral is applied as this curve shape. The logarithmic spiral is expressed by the following polar coordinate equation.

r: radius of the logarithmic spiral corresponding to θ (0 ° = <θ <= α °) where α is an angle within the range where r intersects with the outer edge of the load plate a, b: constant shown in FIG. 2 (a) Thus, the central point O of the logarithmic spiral of Equation 1 is set on the x-axis such that r at θ = 0 coincides with the central point of the load board bottom surface 11b. The constants a and b are such that the point of intersection of the curve of equation 1 and the circle of radius R of loading plate 11 becomes θ> π / 2 with center point O as the origin in order to ensure removal of slime It is preferable to set so as to obtain a curved shape. In the present embodiment, a slime removing projection 20 is formed on the bottom surface 11 b of the load plate, with a curvilinear logarithmic spiral of a = 0.57 and b = 0.83 as an example. The constants a and b can be set as appropriate as long as the slime removing effect can be obtained. It is also preferable to conduct model tests and the like to determine the constant in consideration of the slime state.

  The action of the slime removing projection 20 will be described with reference to FIG. 2 (b). FIG. 2 (b) shows the load board bottom surface 11b. Here, it is assumed that the load plate 11 of FIG. 2 is modeled to explain slime removal by the slime removal projection 20, and the load plate bottom surface 11b is in the state of facing upward. The small object 8 (slime is a viscous material (clay material) or granular material (sandy material) which spreads over the entire surface of the slime removing protrusion 20 in a position close to the center position of the loading plate 11 of the slime removing protrusion 20 The object 8 corresponds to the one obtained by modeling a part of the object 8). From this state, as shown in FIG. 2B, when the loading plate 11 is rotated in the direction of arrow A, the small object 8 placed on the front face 20a side of the slime removing projection 20 acts by the rotation of the loading plate 11. It moves gradually along the outer edge of the loading plate 11 along the front face 20a of the slime removing projection 20 having a logarithmic spiral shape by the centrifugal force and the contact force consisting of the outer edge direction vector applied by the front face 20a of the slime removing projection 20 . Then, it is discharged from the outer edge of the load plate 11 to the outside of the load plate 11.

  As a curvilinear shape of the slime removing projection 20, a logarithmic spiral shape is adopted as a shape which can remove the slime continuously by rotating the loading plate 11 as described above, but it is on the front face 20a of the curve like the logarithmic spiral. Various curvilinear shapes may be adopted as long as they can exert an action capable of moving an object such as slime toward the outer edge of the loading plate 11. For example, among the partial curves in which the range of the curve is from the center point (starting point) of the loading plate 11 to the outer edge of the loading plate 11 and the quadrant of polar coordinates is limited, it becomes a convex curve in the traveling direction of the loading plate 11 It is possible to adopt a curve that extends backwards to form a curve. For example, involute curves and parts of various algebraic helices (Archimedean helices, parabolic helices, hyperbolic helices) can be employed.

  FIG. 3 is a partial cross-sectional view showing the cross-sectional shape of the slime removing projection 20. As shown in FIG. With the substantially rectangular cross section shown in FIG. 6A as a standard, a logarithmic spiral shaped steel material corresponding to the projection portion is welded and fixed at a predetermined position on the bottom surface 11b of the load plate to form the slime removing projection 20. Alternatively, as shown in FIG. 6B, the logarithmic spiral groove 11c may be formed in the load plate 11, and the steel material may be bent and fitted along the groove shape to form the slime removing projection 20. . The cross-sectional shape of the slime removing projection 20 may be a triangular shape as shown in FIG. 7C for the purpose of reducing the influence at the time of loading in the flat plate loading test. In that case, it is preferable that the side of the projection front surface 20a that presses the slime be substantially perpendicular to the bottom surface 11b of the loading plate.

  Each drawing of FIG. 4 shows a loading board bottom surface 11b showing a modification of the number of slime removing projections 20 formed on the loading board bottom surface 11b. The slime removing projection 20 can remove the slime on the entire area of the bottom surface 11 b of the loading plate as the loading plate 11 rotates. 2 (a) shows two slime removing projections 20 shown in FIG. 2 (a) with a phase difference of 180 °, and FIG. 2 (b) shows three with a phase difference of 120 ° on the bottom surface 11b of the loading plate. The arrange | positioned modification is shown. By forming a plurality of slime removing projections 20 on the bottom surface 11 b of the load plate as described above, the slime removing operation at the hole bottom 2 of the borehole 4 can be performed more reliably. Further, by supporting the load testing device 10 with a plurality of slime removing projections 20, there is also an effect that the loading plate 11 can be stably grounded on the hole bottom surface 2 (test ground surface).

Hereinafter, the slime removal condition of the hole bottom 2 of the boring hole 4 by this apparatus is demonstrated with reference to FIG. 5, FIG. 6 each figure.
FIG. 5A is an enlarged view of the tip of the loading test device 10 of the present invention. In order to carry out the in-hole flat plate loading test with the device 10 shown in the figure, the loading plate 11 at the tip of the device 10 needs to be in close contact with the hole bottom 2 at the time of the test. In many cases, the bottom surface 2 (test ground surface) of the actual borehole 4 is not clearly exposed due to the disturbance of the ground due to drilling and residual slime. Therefore, at the stage when the loading plate 11 reaches the hole bottom surface 2 of the boring hole 4, the slime remaining in the bottom of the hole is moved to the ground around the loading plate 11 by the slime removing projection 20 formed on the loading plate bottom surface 11b. Discharge to the outside of the loading plate 11. That is, as shown in FIGS. 5A and 5B, when the load holding pipe 12 is rotated and pushed (black arrow), the wing-like projections 13 on the side of the load holding pipe 12 are also rotated. As a result, the periphery of the loading plate 11 is dug down and the slime deposited on the hole bottom 2 by the slime removing projections 20 on the bottom surface of the loading plate 11 is discharged out of the loading plate 11.

  6 (a) is a partial enlarged view of the loading plate 11 showing the state of FIG. 5 (a), and FIG. 6 (b) is a partial enlarged view of the loading plate 11 showing the state of FIG. 5 (b) is there. As shown in FIG. 6 (a), immediately after the loading test device 10 reaches the bottom surface 2 of the boring hole 4, a slime S generated along with drilling between the loading plate 11 and the bottom surface 2 is generated. It has been deposited. From this state, as shown in FIG. 6B, the loading plate 11 is rotated. Along with this, the slime removing projection 20 formed on the bottom surface 11b of the loading plate moves the slime S between the loading plate 11 and the bottom surface 2 along the protrusion of the logarithmic spiral curve toward the outer edge of the loading plate 11. Finally, it discharges from the outer edge of the load plate 11 to the surrounding loose ground portion. Therefore, as shown to FIG. 6C, the load board 11 of a load test apparatus can be closely_contact | adhered to the hole bottom face 2 used as a test ground surface.

  Thereafter, at the time of the loading test, the loading rod 6 (FIG. 1 (b)) is inserted into the loading portion holding pipe 12, and a downward test loading is applied to the cylindrical portion 15 of the loading plate 11 via the lower end. As a result, only the loading plate 11 separates from the loading portion holding pipe 12 and moves downward, penetrates the bottom surface 2 as a test ground surface from which slime has been removed by receiving a predetermined pressing force, and performs a predetermined loading test Will be implemented.

  Thus, the present invention is not limited to the embodiments described above, and various modifications within the scope of each claim are possible. That is, an embodiment obtained by combining technical means appropriately modified within the scope of the claims is also included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 10 loading test apparatus 11 loading plate 12 loading part holding pipe 13 wing-like protrusion 14 slit 15 cylindrical part 20 slime removal protrusion

Claims (3)

With the loading section held at the lower end, the loading surface of the loading section is reached by the drilling machine to the test ground surface of the bottom of the borehole by the drilling machine, and the test ground surface is loaded pressed in parts, a boring hole bottom ground flat loading test apparatus for performing a flat plate loading test of the test locations, board, and the hole bottom ground in the slime removing protrusions formed on the loading surface by rotating the loading portion the slime is deposited between the loading surface is removed, the hole bottom ground and the loading surface and the boring hole bottom ground flat loading which is characterized in that a plate loading test before Symbol test soil surface while being in close contact with Test equipment.   The borehole bottom ground plate loading according to claim 1, wherein the slime removing protrusion is a curved protrusion having a convex shape in the rotational direction of the loading portion, which extends from the center position of the loading surface to the outer edge of the loading surface. Test equipment.   The borehole bottom ground flat plate loading test device according to claim 2, wherein the curved shape of the curvilinear shaped projection is a logarithmic spiral.

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