JP2017218839A - Pressure receiving structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure receiving structure which can facilitate inspection.SOLUTION: A pressure receiving structure 1 according to an embodiment is installed on a slope face 10, and includes a pressure receiving plate 2, an anchor 3, and a pressure bearing plate 4. The pressure receiving plate 2 is arranged on the slope face 10 side. The anchor 3 is arranged to penetrate an inside of the pressure receiving plate 2. The pressure bearing plate 4 is disposed on an upper side of the pressure receiving plate 2 and receives pressure from the anchor 3. The pressure bearing plate 4 is formed of a metallic material having a yield stress of 100 MPa or higher. The pressure bearing plate 4 has an analysis part 41 having surface roughness Ra of 100 or below and enabling X-ray analysis at least on a part thereof.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pressure receiving structure installed on a slope in order to prevent the slope from being collapsed or landslide.

As a structure for preventing the collapse of a slope or the occurrence of landslide, a pressure-receiving structure in which a pressure-receiving plate is installed on the slope and the slope is pressed by the pressure-receiving plate is widely adopted (for example, see Patent Document 1). .)
In detail, a digging hole reaching the rock mass beyond the slip line is formed on the slope, and a through hole is formed in the pressure receiving plate. Anchors are placed in the through holes and mining holes, and the slope is pressed down by the pressure receiving plate using the tensile strength of the anchors to counteract the landslide activity force.

JP 2003-184094 A

However, it cannot be determined from the appearance whether the anchor is functioning normally after the pressure receiving structure is installed. Therefore, although the residual tension, which is an anchor's soundness evaluation index, is generally evaluated by a lift-off test, the cost is high and cannot be easily performed.
An object of this invention is to provide the pressure receiving structure which can test | inspect easily.

  A pressure receiving structure according to a first invention is a pressure receiving structure installed on a slope, and includes a main body portion, an anchor, and a pressure receiving portion. The main body is disposed on the slope side. An anchor is arrange | positioned so that the inside of a main-body part may be penetrated. The pressure receiving part is disposed on the upper side of the main body part and receives pressure from the anchor. The pressure receiving part is made of a metal material having a yield stress of 100 MPa or more. The pressure receiving part has at least a part of an analysis part that has a surface roughness of Ra100 or less and enables X-ray analysis.

Here, by using X-ray diffraction in the elastic deformation region of the pressure receiving portion made of a metal having a predetermined yield point set by the anchor force (several hundred kN), the stress state of the anchor can be specified from the strain state. .
That is, the residual tension force of the anchor can be indirectly evaluated by detecting the strain generated in the pressure receiving portion by the tensile force of the anchor by X-ray diffraction.
For this reason, the stress state of the anchor can be easily specified without using the lift-off test.

The pressure receiving structure according to the second invention is the pressure receiving structure according to the first invention, and the pressure receiving part has an average crystal grain size of 1 to 30 μm.
When the average grain size of the pressure receiving portion is 1 to 30 μm, the residual tension can be more appropriately evaluated and the stress state of the anchor can be specified.

The pressure receiving structure according to the third invention is the pressure receiving structure according to the first invention, and the analysis part is arranged within a radius of 100 mm from the contact outermost position between the anchor and the pressure receiving part.
As described above, by performing analysis at a position within a radius of 100 mm from the outermost contact position, it is possible to appropriately determine the state of distortion in the stress field of the pressure receiving portion by the anchor.
That is, when the analysis is performed at a position far from the contact position between the anchor and the pressure receiving portion, the distortion generated in the pressure receiving portion is reduced, and it becomes difficult to accurately identify the stress state of the anchor, but within a radius of 100 mm from the outermost position of the contact. By performing the analysis at the position, it is possible to specify the distortion generated in the pressure receiving portion more accurately.

A pressure receiving structure according to a fourth aspect of the present invention is the pressure receiving structure according to any one of the first to third aspects of the present invention, and further includes a covering member that covers the surface of the analysis unit.
By providing the covering member in this manner, the analysis unit can be appropriately protected from aging deterioration such as wind and rain, and thus the stress state of the anchor can be specified more accurately.

  According to the present invention, it is possible to provide a pressure receiving structure that can be easily inspected.

The perspective view which shows the pressure receiving structure of embodiment which concerns on this invention. FIG. 3 is a cross-sectional view taken along the line AA ′ in FIG. 1. The disassembled perspective view of the pressure receiving plate 2 of the pressure receiving structure of FIG. (A) The top view of the pressure receiving structure of FIG. 1, (b) The enlarged view of the pressure-bearing plate vicinity of FIG. 4 (a). The schematic diagram which shows the state which is measuring the stress of the bearing plate which used the X-ray in order to judge the state of the anchor in the pressure receiving structure of FIG. The figure which shows the state which is measuring the X-ray stress in the non-loading state in the bearing plate in an Example. (A) The figure which shows an example of the SEM image of the bearing plate formed by S45C, (b) The figure which shows an example of the SEM image of the bearing plate formed by SM490A, (c) The SEM of the bearing plate formed by SM490B It is a figure which shows an example of an image. (A) The figure which shows an example of the Debye ring image of the bearing plate 4 formed by S45C, (b) The figure which shows an example of the Debye ring image of the bearing plate 4 formed by SM490A, (c) It was formed by SM490B The figure which shows an example of the Debye ring image of the bearing plate. The figure which shows the table | surface of the estimated stress of the bearing plate formed with each material of S45C, SM490A, and SM490B, stress estimated standard deviation, and an average particle diameter. The top view which shows the state which covered the analysis part of the pressure receiving structure of embodiment which concerns on this invention with the coating | coated member.

The pressure receiving structure of the present invention will be described with reference to the drawings.
(Outline of pressure receiving structure 1)
FIG. 1 is a perspective view showing a pressure receiving structure 1 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line AA ′ of FIG.
The pressure receiving structure 1 of this Embodiment is mainly provided with the pressure receiving plate 2, the anchor 3, and the bearing plate 4 as shown in FIG.

As shown in FIG. 2, the pressure receiving plate 2 is installed on the slope 10 of the slope. A through hole is formed in the pressure receiving plate 2. The anchor 3 is inserted into the slope 10 through the through hole of the pressure receiving plate 2.
The pressure bearing plate 4 is placed on the upper surface of the pressure receiving plate 2 and is pressed against the pressure receiving plate 2 by the nut member 32 of the anchor 3 from above.

(Pressure plate 2)
The pressure receiving plate 2 includes a first pressure receiving member 21 and a second pressure receiving member 22. FIG. 3 is an exploded view of the pressure receiving plate 2.
As shown in FIG. 2, the first pressure receiving member 21 is disposed in contact with the slope 10. As shown in FIG. 3, the first pressure receiving member 21 includes a bottom plate 211, a frame body 212, a reinforcing member 213, a reinforced concrete member 214, and a top plate 215.

The bottom plate 211 is a rectangular plate-like member and is placed on the slope 10. The bottom plate 211 is formed of a long glass fiber reinforced plastic foam (hereinafter referred to as FFU).
The frame body 212 is a rectangular member in a plan view formed by connecting four bar-shaped members, and is formed of FFU. The frame body 212 has two sets of two sides that are opposed and arranged in parallel. The frame body 212 is disposed above the bottom plate 211. The reinforcing member 213 is formed by two rod-like members 213 b and 213 c perpendicularly intersecting each other, and is disposed inside the frame body 212. The reinforcing member 213 is formed by FFU. The rod-shaped member 213b is disposed in the center of the two sides of one set of the frame body 212 in parallel with the two sides. The rod-shaped member 213c is arranged in the center of the two sides of the other set of the frame body 212 in parallel with the two sides. The space inside the frame body 212 is divided into four rectangular parallelepiped spaces by the reinforcing member 213. A through-hole 213a is formed in the vertical direction at a portion where the rod-shaped member 213b and the rod-shaped member 213c of the reinforcing member 213 intersect. Although not shown in the drawing, the bottom plate 211 also has a through hole 211a (see FIG. 2) at a position corresponding to the through hole 213a.

The reinforced concrete member 214 is arranged in each of four spaces in the shape of a rectangular parallelepiped. The reinforced concrete member 214 is formed by filling mortar or concrete around the reinforced members arranged in a lattice pattern.
The top plate 215 is a rectangular plate-like member, and is formed by FFU. The top plate 215 is disposed on the upper side of the frame body 212. The outer shape of the top plate 215 is formed to match the outer shape of the frame body 212. The top plate 215 has a through hole 215a at a position corresponding to the through hole 213a.

  The second pressure receiving member 22 has a cross shape in a plan view and is formed by FFU. The second pressure receiving member 22 is formed in a stepped shape so that the height increases from the end toward the center in a side view. The second pressure receiving member 22 has a through hole 22a formed in the vertical direction at the center thereof. The second pressure receiving member 22 includes a first stacked portion 221, a second stacked portion 222, and a pressure receiving head 223. In order from the bottom, the first stacked portion 221, the second stacked portion 222, and the pressure receiving head 223 are stacked in this order, and the through hole 22 a penetrates the pressure receiving head 223, the first stacked portion 221, and the second stacked portion 222. Is formed.

The first stacked portion 221 is a plate-like member formed in a cross shape in plan view. The 1st lamination | stacking part 221 is a shape where the plate-shaped member protruded in four directions from the center part in which the through-hole 22a is formed. The first stacked unit 221 is disposed on the top plate 215.
The second stacked portion 222 is a plate-like member formed in a cross shape in plan view. The second stacked unit 222 is disposed on the upper side of the first stacked unit 221 so as to correspond to the cross shape of the first stacked unit 221. The second stacked portion 222 has the same shape as the first stacked portion 221, but is formed so that the plate member protrudes from the central portion where the through hole 22 a is formed shorter than the first stacked portion 221. Has been.

The pressure receiving head 223 is a rectangular plate-like member, and is disposed on the upper side of the central portion of the second stacked portion 222. The pressure receiving head 223 has the same shape as the central portion of the first stacked portion 221 and the central portion of the second stacked portion 222.
As shown in FIG. 2, the through hole 2 a of the pressure receiving plate 2 is formed from the through hole 211 a of the bottom plate 211, the through hole 213 a of the reinforcing member 213, the through hole 215 a of the top plate 215, and the through hole 22 a of the second pressure receiving member 22. Has been.

(Anka 3)
As shown in FIG. 2, the anchor 3 includes an anchor member 31 and a nut member 32.
As shown in FIG. 2, a digging hole 13 is formed in the slope 10 so as to reach the rock 12 beyond the slip line 11. The anchor member 31 is inserted into the mining hole 13 through the through hole 2 a of the pressure receiving plate 2. An underground end of the anchor member 31 is fixed by a grout material 14 such as cement. The end of the anchor member 31 on the pressure receiving plate 2 side is threaded. A nut member 32 is screwed into the threaded portion.

(Supporting plate 4)
The pressure bearing plate 4 is placed on the upper surface of the pressure receiving plate 2 as shown in FIGS. 1 and 2. Specifically, the pressure bearing plate 4 is disposed on the upper surface of the pressure receiving head 223 of the pressure receiving plate 2. As shown in FIG. 2, the support plate 4 has a through hole 4a at a position corresponding to the through hole 22a. A nut member 32 screwed with the anchor member 31 is arranged on the support pressure plate 4. By tightening the nut member 32, the pressure bearing plate 4 is pressed against the pressure receiving plate 2 by the nut member 32 from above, and the pressure receiving plate 2 presses the slope 10.

4A is a plan view of the pressure receiving structure 1, and FIG. 4B is an enlarged view of the vicinity of the pressure bearing plate 4 of FIG. 4A.
As shown in FIGS. 4 (a) and 4 (b), the bearing plate 4 has an analysis unit 41 that enables X-ray analysis. The analysis unit 41 is an area analyzed by X-rays formed on the upper surface 4s of the bearing plate 4 and has a surface roughness of Ra100 or less. The analysis unit 41 is formed within 100 mm from the outermost contact position between the nut member 32 of the anchor 3 and the bearing plate 4. Here, the contact outermost position between the nut member 32 and the bearing plate 4 is the outer peripheral end 32e of the nut member 32 in a plan view of FIG. That is, it is preferable that the analysis unit 41 is formed within 100 mm from the outer peripheral end 32e. In the figure, the analysis unit 41 is hatched for easy understanding.

The bearing plate 4 is made of a metal material having a yield stress of 100 MPa or more. The tightening force of the bearing plate 4 by the nut member 32 is set to such a magnitude that the deformation of the bearing plate 4 is within the elastic deformation region. The average crystal grain size of the bearing plate 4 is preferably 1 μm or more and 30 μm or less.
The bearing plate 4 is more preferably formed of a metal material having a yield stress of 500 MPa or more. Regarding the yield strength, Pb is 5 MPa, Al is 60 to 80 Pa, Brass is 200 to 300 Pa, and Iron is 300 to 400 Pa. Therefore, the support plate 4 is preferably a metal plate mainly composed of brass and iron.

The tension of the bearing plate 4 is about 230 to 1100 kN. When the tension force is 900 kN, a compressive stress of about 450 MPa is generated in the vicinity of the nut member 32 and converges to 100 MPa in the circumferential direction. For this reason, the stress range of the bearing plate 4 has a maximum portion of 100 to 500 MPa and a minimum portion of 20 to 110 MPa. As described above, the analysis unit 41 is shifted to the outer peripheral side with respect to the nut member 32. However, by forming the analysis unit 41 within 100 mm from the outer peripheral end 32e of the nut member 32, a stress capable of estimating X-ray stress described later is provided. Is set within the range where the error occurs.
Ra100 is the lower limit of measurable, and when it is larger than 100, it is assumed that the diffraction image is disturbed and the calculated stress value varies.

(X-ray stress measurement)
FIG. 5 is a schematic side view showing a state in which X-ray stress measurement is performed on the bearing plate 4 of the pressure receiving structure 1 of the present embodiment.

For example, as shown in FIG. 5, the X-ray stress measuring device 5 is disposed above the bearing plate 4, and the analysis unit 41 of the bearing plate 4 is irradiated with X-rays at an incident angle θ. θ is an angle from a straight line L perpendicular to the upper surface 4 s of the bearing plate 4.
Thereby, a Debye ring is formed according to the crystal structure of the analysis unit 41. That is, since the stress is generated by pressing the bearing plate 4 by the nut member 32 of the anchor 3, the crystal structure of the bearing plate 4 is distorted. This distortion of the crystal structure causes distortion in the Debye ring formed by X-ray irradiation.

As described above, the Debye ring in a state where stress is generated in the bearing plate 4 by the anchor 3 and the Debye ring in a state where no stress is generated in the bearing plate 4 (non-loading state) are generated in the bearing plate 4. Stress is estimated.
Based on the stress generated in the bearing plate 4, it can be indirectly determined whether the anchor 3 is functioning normally. That is, when the Debye ring distortion is small and the stress generated in the bearing plate 4 is very small, it can be determined that the anchor member 31 is interrupted by, for example, corrosion, and the tensile force by the anchor 3 is hardly functioning.

Next, the influence of the type and particle size of the metal material forming the bearing plate 4 on the accuracy of stress estimation by X-ray diffraction will be described based on examples.
(Example)
For the bearing plate 4 made of three steel types, S45C, SM490A, and SM490B, a comparative study is performed on the relationship between the average crystal grain size and the stress estimation accuracy.

First, based on JISG0551, the average crystal grain size in each steel material type was calculated as follows.
(1) The surface of the test piece of each steel type is polished and smoothed using a turntable polishing machine.
(2) Each polished specimen is immersed in a corrosive solution for about 10 seconds to be corroded, and immediately rinsed with water to stop the progress of corrosion. Thereby, a structure | tissue can be represented as an unevenness | corrugation by the difference in the progress of corrosion for every structure | tissue. This operation is called etching.
(3) Microscopic observation of each etched specimen using a scanning electron microscope (hereinafter referred to as SEM) provides an SEM image with a clear crystal grain boundary.
(4) A line segment is drawn on the obtained SEM image, and the number of crystal grains on the line segment is counted.
(5) Compare the scale of the SEM image and convert the length of the line segment.
(6) Divide the length of the converted line segment by the number.
(7) The procedures of (4) to (6) are repeated and averaged.

A test piece of 15 × 15 × 9 mm was used for each steel type to be observed. The etchant used was about 1% ethanol nitrate. 4-6 SEM images are prepared for each steel type, and about 20 line segments are drawn per sheet.
As shown in FIG. 6, the X-ray stress is estimated using the X-ray stress measuring device 5 in a non-loading state (supporting plate alone) at a plurality of points on the surface of the three types of bearing plates 4 and the stress estimation accuracy is improved. Evaluation was performed. In short, X-rays were irradiated from the X-ray stress measuring device 5 with the bearing plate 4 placed alone. The evaluation items were the estimated stress value, the average value of the stress estimation standard deviation, and the Debye ring shape.

Twenty points were randomly selected as stress estimation locations. As the X-ray stress estimation apparatus, a portable stress estimation apparatus that employs a two-dimensional stress analysis method based on the cos α method was used. In this embodiment, since the entire bearing plate 4 is etched, the analysis unit 41 is the entire upper surface of the bearing plate 4, and the stress estimation location can be selected from the entire bearing plate 4.
The measurement conditions of the X-ray stress estimation apparatus are an X-ray incident angle θ of 35 °, a sample distance of 39 mm, and an X-ray output of 20 kV and 1 mA. The sample distance indicates the distance from the X-ray irradiation (collimator) position of the X-ray stress measurement apparatus 5 to the measurement target. The angle of the measuring device was measured using an goniometer, and the distance from the material and the measurement positioning were performed visually. The X-ray irradiation point has a diameter of 2 mm and a depth of about 0.01 mm, and the time required for measurement is about 1 to 2 minutes per point.

  Prior to the X-ray stress measurement, the black skin on the surface of the bearing plate 4 was removed with an acid remover to expose the metal structure.

(Observation results of crystal grains)
Fig.7 (a) is a figure which shows an example of the SEM image of the bearing plate formed by S45C. FIG. 7B is a diagram illustrating an example of an SEM image of a bearing plate formed of SM490A. FIG.7 (c) is a figure which shows an example of the SEM image of the bearing plate formed with SM490B.

  The average particle size of S45C used in this example was 34.0 μm and the crystal grains were relatively coarse, whereas the average particle size of SM490A and SM490B was as small as 7.2 μm and 4.6 μm, respectively. confirmed.

(Relationship between crystal grain size and stress estimation accuracy)
Fig.8 (a) is a figure which shows an example of the Debye ring image of the bearing plate 4 formed by S45C. FIG. 8B is a diagram illustrating an example of a Debye ring image of the bearing plate 4 formed of SM490A. FIG. 8C is a diagram illustrating an example of a Debye ring image of the bearing plate 4 formed of SM490B. FIG. 9 is a table showing the estimated stress, the stress estimated standard deviation, and the average particle diameter of the bearing plates formed of the materials S45C, SM490A, and SM490B.

  As shown in FIGS. 8A and 9, in S45C in which the average crystal grains are relatively coarse, the stress estimation standard deviation is large with respect to the estimated stress, and a clear Debye ring was not obtained. On the other hand, as shown in FIGS. 8B, 8C and 9, SM490A and SM490B having a small average particle size have a relatively small value of the stress estimation standard deviation, and a clear Debye ring can be obtained. It can be confirmed.

That is, under the conditions of this example, it was confirmed that a clear Debye ring can be obtained for a steel type having an average particle size of about 7.2 μm.
Thus, by obtaining a clear Debye ring, the stress of the bearing plate 4 when pressed against the pressure receiving plate 2 by the anchor 3 can be measured, and the state of the anchor 3 is indirectly determined. Can do.

(Features etc.)
(1)
The pressure receiving structure 1 according to the present embodiment is a pressure receiving structure that is installed on a slope 10, and includes a pressure receiving plate 2 (an example of a main body), an anchor 3, and a bearing plate 4 (an example of a pressure receiving portion). . The pressure receiving plate 2 is disposed on the slope 10 side. The anchor 3 is disposed so as to penetrate the inside of the pressure receiving plate 2. The pressure bearing plate 4 is disposed on the upper side of the pressure receiving plate 2 and receives pressure from the anchor 3. The bearing plate 4 is made of a metal material having a yield stress of 100 MPa or more. The bearing plate 4 has at least a part of an analysis unit 41 having a surface roughness of Ra100 or less and enabling X-ray analysis.

Here, the stress state of the anchor is identified from the strain state by using X-ray diffraction in the elastic deformation region of the bearing plate 4 made of metal having a predetermined yield point set by the anchor force (several hundred kN). it can.
That is, the residual tension force of the anchor 3 can be indirectly evaluated by detecting the strain generated in the bearing plate 4 by the tensile force of the anchor 3 by X-ray diffraction.
For this reason, the stress condition of the anchor 3 can be easily specified without using the lift-off test.

(2)
In the pressure receiving structure 1 of the present embodiment, the bearing plate 4 has an average crystal grain size of 1 to 30 μm.
When the average crystal grain size of the bearing plate 4 is 1 to 30 μm, the residual tension can be more appropriately evaluated, and the stress state of the anchor can be specified.

(3)
In the pressure receiving structure 1 of the present embodiment, the analysis unit 41 is arranged within a radius of 100 mm from the outermost contact position between the anchor 3 and the bearing plate 4.
Thus, by performing analysis at a position within a radius of 100 mm from the outermost contact position, it is possible to appropriately determine the state of distortion in the stress field of the bearing plate 4 by the anchor 3.
That is, when the analysis is performed at a position far from the contact position between the anchor 3 and the bearing plate 4, the distortion generated in the pressure receiving portion is reduced, and it becomes difficult to accurately identify the stress state of the anchor. By performing analysis at a position within 100 mm, it can be specified more accurately.

[Other embodiments]
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the summary of invention.
(A)
In the above embodiment, the analysis unit 41, which is a region where the surface roughness Ra of the bearing plate 4 is 100 or less, is exposed to the external environment, but is shown in FIG. 10 except when measuring by X-rays. Thus, the surface may be covered with the covering member 42.
By providing the covering member 42 in this manner, the analysis unit can be appropriately protected from aging deterioration such as wind and rain, and therefore, the stress state of the anchor 3 can be specified more accurately.

(B)
In the said embodiment, although the baseplate 211, the frame 212, the reinforcement member 213, and the 2nd pressure receiving member 22 are formed from FFU, it may not be restricted to FFU and may be formed with concrete.
Further, the reinforced concrete member 214 may be formed of only concrete without inserting a reinforcing bar.

(C)
In the above embodiment, the second pressure receiving member 22 is formed in a cross shape in plan view, but the present invention is not limited to this. For example, the first stacked portion 221 and the second stacked portion 222 of the second pressure receiving member 22 are rectangular, and the top plate 215, the first stacked portion 221, the second stacked portion 222, and the pressure receiving head 223 are viewed from above. You may form so that an external shape may become small gradually.

  The pressure receiving structure of the present invention has an effect capable of easily performing an inspection, and can be widely applied to, for example, a ground anchor used for cutting slope stabilization.

1: Pressure receiving structure 2: Pressure receiving plate (an example of main body)
2a: Through hole 3: Anchor 4: Pressure bearing plate (an example of a pressure receiving portion)
4a: Through hole 4s: Upper surface 5: X-ray stress measuring device 10: Slope 11: Slip line 12: Rock 13: Mining hole 14: Grout material 21: First pressure member 22: Second pressure member 22a: Through hole 31 : Anchor member 32: Nut member 32e: Peripheral end 41: Analysis part 42: Cover member 211: Bottom plate 211a: Through hole 212: Frame body 213: Reinforcement member 213a: Through hole 213b: Bar member 213c: Bar member 214: Reinforced concrete member 215: Top plate 215a: Through hole 221: First laminated portion 222: Second laminated portion 223: Pressure receiving head

Claims (4)

A pressure receiving structure installed on a slope,
A main body disposed on the slope side;
An anchor arranged to penetrate through the inside of the main body,
A pressure receiving portion arranged on the upper side of the main body portion and receiving pressure from the anchor,
The pressure receiving portion is formed of a metal material having a yield stress of 100 MPa or more,
The pressure-receiving unit has an analysis unit that has a surface roughness of Ra100 or less and enables X-ray analysis at least in part.
Pressure receiving structure. The pressure receiving portion has an average crystal grain size of 1 to 30 μm.
The pressure receiving structure according to claim 1. The analysis unit is disposed within a radius of 100 mm from the outermost contact position between the anchor and the pressure receiving unit.
The pressure receiving structure according to claim 1 or 2. A coating member that covers the surface of the analysis unit;
The pressure receiving structure according to any one of claims 1 to 3.