JP7442030B2 - Slope surface collapse prevention pile construction method - Google Patents

Description

The present invention relates to a construction method for suppressing collapse of a slope, which is applied to a slope where at least the ground surface layer is composed of a topsoil layer that is softer than the base layer and the ground surface is inclined with respect to a horizontal plane.

Most mountain forest slopes have a hard base layer consisting mainly of rocks, and a relatively soft topsoil consisting of clay, sand, and gravel that is formed by the rock being crushed and weathered to make it finer. It is composed of layers. Mountain forest slope failures include deep failures, in which the topsoil layer and even the base layer collapse, and surface failures, in which the topsoil layer collapses. In some mountain forests, there is a risk that surface layer collapse will occur if the amount of rainfall exceeds a predetermined amount, and it is desired to suppress this. As a construction method for suppressing surface collapse on mountain forest slopes, generally, as disclosed in Patent Document 1, a method is used in which piles are driven from the ground surface so that the tips of the piles reach the foundation layer. It has been adopted. In this construction method, the foundation layer supports the piles and prevents them from falling down, so the piles can prevent the topsoil layer from sliding and flowing.

Japanese Patent Application Publication No. 2012-2012

There are two types of surface collapse on mountain forest slopes: the entire topsoil layer collapses along the interface between the topsoil layer and the bedrock layer, and the surface layer collapses at the surface side of the topsoil layer, which contains a large amount of organic matter. . In the latter type of surface collapse, although the amount of soil that collapses from one collapse site is relatively small, a single heavy rain tends to cause multiple collapses at the same time in areas such as deforestation sites and young forests, and it is difficult to compare in many areas. This could easily occur.

However, conventional construction methods such as those disclosed in Patent Document 1, in which piles are driven up to the foundation layer, require a great deal of work time and cost, so there is a limit to their construction in many areas. Specifically, the foundation layer is a very hard layer, so in order to drive a pile into it, first a hole is drilled in the slope that reaches the foundation layer, then the pile is installed inside the hole. Furthermore, it is necessary to pour cement or the like around the piles to harden them, which takes a lot of time and costs.

The present invention has been made in view of the above-mentioned circumstances, and is a slope surface collapse that can be constructed in a short working time and at low cost, and that can suppress collapse of the topsoil layer, especially the part on the ground surface side. The purpose is to provide a countermeasure pile construction method.

In order to solve the above-mentioned problems, the present invention is applied to a slope where at least the layer on the ground side is composed of a topsoil layer that is softer than the base layer and where the ground surface is inclined with respect to the horizontal plane. A method for suppressing the collapse of a pile body, wherein a pile body extending in a predetermined direction is driven into the slope from the longitudinal end side of the pile body in a posture such that its longitudinal direction intersects the ground surface of the slope. and a pile installation step of arranging a blade member extending in a predetermined direction on the slope in a state connected to a proximal portion in the longitudinal direction of the pile body, the blade member facing the slope. In the pile installation step, the pile body is driven so that the tip of the pile body remains within the topsoil layer, and the blade member is driven along the ground surface of the slope. The blade member is arranged on the slope so as to extend, and a plurality of the pile bodies and the blade members are installed at positions spaced apart from each other on the slope so that the pile bodies and the blade members are independent from each other, When the blade member is arranged on the slope, the facing surface of the blade member is brought into pressure contact with the ground surface .

With this method, when the topsoil layer starts to move, the tensile stress generated inside the pile body can be transmitted to the blade member and the force with which the blade member presses against the ground surface can be increased. The further movement of this part, that is, the collapse of this part can be suppressed. Specifically, when the topsoil layer begins to move down the slope because the pile body has not reached the base layer, the pile body also tilts, and a force acts on the pile body in the direction of pulling it out from the topsoil layer. However, since a frictional force acts between the circumferential surface of the pile body and the soil, the pile body cannot be easily pulled out, and a downward (underground) tensile stress is generated inside the pile body. Here, the pile main body and the blade member are connected as described above. Therefore, the above-mentioned tensile stress is transmitted to the blade member, and a component of this tensile stress in a direction perpendicular to the ground surface is applied from the blade member to the ground surface. This increases the force with which the blade member presses against the ground surface. Furthermore, the movement of the soil down the slope is also suppressed by the component of the downward tensile stress generated in the pile body in the direction along the ground surface.

In this way, the blade member and the pile body can suppress soil collapse near the surface of the topsoil layer without driving the pile body all the way to the base layer. Drive it into the slope so that it stays there. Therefore, compared to the case where the pile is driven up to the base layer, the driving distance of the pile main body can be shortened, the working time related to this driving can be shortened, and the cost can be kept low. In addition, since the length of the pile body is short, the space required for driving the pile is small, making it possible to construct the pile in a variety of locations.

In the above configuration, preferably, the step includes a preparation step performed before the pile installation step to prepare the blade member and the pile body shorter than the thickness dimension of the topsoil layer, and after the preparation step is performed. In addition, before implementing the pile installation step, the pile main body and the blade member are connected.

According to this configuration, in the pile installation process, the driving of the pile body and the arrangement of the blade members can be performed simultaneously, improving work efficiency. Further, the blade member can be arranged along the ground surface while ensuring that the pile main body is driven within the topsoil layer.

In the above configuration, preferably, the blade member is connected to the pile body so as to be rotatable about a rotation center line extending in a direction perpendicular to the longitudinal direction of the pile body, and the blade member is connected to the pile body so as to be rotatable about a rotation center line extending in a direction perpendicular to the longitudinal direction of the pile body. It has a shape extending in intersecting directions.

According to this configuration, by rotating the blade member, the posture of the blade member can be changed to a state in which the blade member extends along the ground surface when the pile body is driven into a slope intersecting the longitudinal direction of the pile body. The position can be easily changed between the position where the pile body is oriented as shown in FIG. If the blade member is set to extend along the ground surface, the area of contact between the blade member and the ground surface is increased, and soil collapse can be suppressed by the blade member over a wider range. By arranging the blade member to extend along the longitudinal direction of the pile main body, the dimensions of the entire pile in the direction orthogonal to the longitudinal direction of the pile main body can be reduced. Therefore, according to this configuration, the posture of the blade member can be easily changed to the above two postures, and the space for accommodating the piles can be reduced while suppressing soil collapse over a wide range.

In the configuration, preferably, the blade member is connected to the pile main body such that the center of gravity of the blade member is located on one side of the rotation center line in the longitudinal direction, and is provided with a regulating member that regulates the rotation of the blade member, and the regulating member is configured to rotate the blade member in the longitudinal direction in a posture in which the blade member extends in a direction intersecting the longitudinal direction of the pile body. The blade member is prevented from rotating in a direction in which the one end portion approaches the tip side of the pile main body.

According to this configuration, the pile body can be driven while maintaining the posture of the blade member in a direction that extends in a direction intersecting the longitudinal direction of the pile body, and furthermore, in a posture that extends along the ground surface, which improves work efficiency. improves.

A different configuration from the above includes a preparation step of preparing the blade member and the pile body shorter than the thickness dimension of the topsoil layer, and in the pile installation step, after driving the pile body into the slope. The blade member may be connected to an upper end portion of the pile main body in a state extending along the ground surface of the slope.

In this configuration, since the pile body is driven into the slope by itself, the pile body can be reliably driven into the slope in an appropriate posture.

In the configuration, preferably, the pile main body and the blade member are made of wood that has been subjected to antiseptic treatment.

According to this configuration, costs can be kept low compared to the case where the pile main body and the blade member are formed of metal such as a steel pipe. In addition, water in the soil can be impregnated into the pile body and the blade member to cause them to expand, thereby increasing the density of the soil around the pile body and the blade member. The preservative treatment can suppress the collapse of the topsoil layer over a long period of time.

As explained above, according to the present invention, it is possible to realize construction in a short working time and at low cost, while suppressing the collapse of the topsoil layer, especially the part on the ground surface side.

1 is a schematic diagram showing a state in which a pile according to an embodiment of the present invention is driven into the ground. It is a side view of a pile. It is a top view of a pile. FIG. 3 is a side view of the pile showing how the blades rotate. It is a flowchart showing the procedure of the fluffy pile construction method. It is a schematic diagram showing a state where a plurality of piles are driven into the ground. FIG. 3 is a schematic top view showing how a plurality of piles are transported. It is a figure for explaining the effect of the fluffy pile construction method. It is a graph showing the experimental results for verifying the effect of the slats, and is a graph showing the relationship between the amount of deformation of the soil clod and the load. FIG. 9 is a diagram showing the experimental apparatus when the experimental results shown in FIG. 9 were obtained, in which (a) is a schematic top view of the experimental apparatus, and (b) is a schematic cross-sectional view of the experimental apparatus. It is a schematic top view which showed the pile based on a modification. It is a schematic top view which showed the pile based on another modification. It is a figure for explaining other steps of the fluffy pile construction method.

EMBODIMENT OF THE INVENTION Hereinafter, with reference to drawings, the slope surface collapse prevention pile construction method based on one Embodiment of this invention is demonstrated. As will be described later, in the slope surface collapse prevention pile construction method of the present invention, on mountain forest slopes, only the relatively soft soil layer 111 (see FIG. 6) located closer to the ground surface than the base layer 104 (see FIG. 6) Since the pile 1 is driven, the slope surface collapse prevention pile method according to the present invention will be referred to as the fluffy pile method in the following description.

(Pile structure)
FIG. 1 is a schematic diagram showing a state after construction of the fluffy pile method, in which a pile 1 used in the fluffy pile method is driven into the ground 100 forming a slope of a mountain forest. 2 and 3 are a side view and a top view of the pile 1, respectively.

The pile 1 includes a pile main body 10 extending in a predetermined direction, and a feather plate (blade member) 20 extending in a predetermined direction. The blade plate 20 has a length comparable to that of the pile body 10. Both the pile body 10 and the slats 20 are made of wood that has been subjected to antiseptic treatment. For example, the pile body 10 and the slats 20 are made of wood that has been subjected to ACQ (Alkaline Copper Quaternary) pressure injection processing. It is said that wood treated with ACQ pressure injection will not rot for about 20 years. Furthermore, in the present embodiment, the slats 20 and the pile main body 10 are made of thinned wood, and the thinned wood is effectively utilized.

The pile main body 10 has a substantially cylindrical shape. For example, the pile main body 10 is made of wood that extends along the core of the wood and has no gaps (the wood fibers are not cut). If the pile body 10 is formed of wood without gaps in this way, the rigidity of the pile body 10 can be increased.

For example, the pile body 10 used has a diameter of about 160 mm and a length of about 1000 mm. Incidentally, it is also possible to prepare a pile body 10 having a sufficient length, drive it into the slope 100, and then cut the part protruding upward from the ground surface at a predetermined height position, but this will be described later. In this embodiment, the length of the pile main body 10 is set according to the depth (thickness dimension) of the soil layer 111 investigated in advance, and the pile main body 10 having the set length is used.

The tip portion 12 of the pile body 10 is subjected to a three-sided cutting process, and this tip portion 12 has a substantially triangular pyramid shape with the tip of the pile body 10 as the apex. As shown in FIG. 1, the pile body 10 is driven into the ground 100 from the tip 12 side. That is, the pile body 10 is driven into the ground 100 with the tip end 12 facing downward. In the following description of the pile 1, the longitudinal direction of the pile main body 10 will be described as the vertical direction, and the top of the pile main body 10 when driven into the ground 100 will be described as the top.

The blade plate 20 has a substantially square column shape and has four side surfaces 21, 22, 23, and 24 extending along the longitudinal direction of the blade plate 20.

The blade plate 20 is connected to the outer circumferential surface of the pile body 10 in such a manner that its two side surfaces are parallel to the central axis X1 of the pile body 10. Hereinafter, among the four side surfaces of the blade plate 20, the surface that extends parallel to the central axis The other side surface extending parallel to the central axis X1 of the main body 10 is referred to as a second side surface 22. In addition, a side surface that extends between one edge in the width direction of the first side surface 21 and the second side surface 22 and constitutes the upper surface of the blade plate 20 in a second attitude A2 (in the state shown in FIG. 1), which will be described later, is a second side surface. The side surface forming the lower surface in the state shown in FIG. 1 is called the fourth side surface 24.

For example, the blade plate 20 has a square shape with a cross section of about 90 mm x 90 mm and a length of about 900 mm.

The blade plate 20 is connected to the upper end of the pile body 10 so as to be rotatable around a rotation center line X2 extending in a direction orthogonal to the central axis X1 of the pile body 10. Hereinafter, this rotation center line X2 will be referred to as a rotation axis X2.

In the present embodiment, as shown by the arrow Y1 in FIG. ) and the center of gravity M of the slat 20 is above the rotation axis X2 (on the proximal side in the longitudinal direction of the pile main body 10) (dotted line in FIG. 4); 20 extends along a direction perpendicular to the central axis X1 of the pile body 10 (the slats 20 extend in a direction intersecting the longitudinal direction of the pile body 10) and a second posture A2 (solid line in FIG. 4). It is rotatable.

Specifically, a through hole 11 is formed in the upper end of the pile body 10, passing through the pile body 10 along a direction perpendicular to the central axis X1. A through hole 25 is formed in the vane plate 20 and is open to the first side surface 21 and the second side surface 22 and passes through the vane plate 20 along a direction orthogonal to the longitudinal direction of the vane plate 20. A common bolt 32a is inserted through each of the through holes 11 and 25 in the pile body 10 and the blade plate 20. The tip of the bolt 32a projects outward from the second side surface 22 of the vane plate 20. A nut 32b is screwed onto the tip of this bolt 32a. Note that the nut 32b is tightened to a position where the first side surface 21 of the blade plate 20 and the outer circumferential surface of the pile body 10 abut, and the outer circumferential surface of the pile body 10 and the first side surface 21 facing this are as follows. are in contact.

In this way, the connecting member 32 consisting of the bolt 32a and the nut 32b allows rotation around the axis X2, which is the central axis X2 of the bolt 32a and extends in a direction perpendicular to the central axis X1 of the pile body 10. The vane plate 20 is connected to the pile body 10.

In the longitudinal direction of the blade plate 20, the position of the rotation axis X2 is offset from the center of gravity M of the blade plate 20. That is, the through hole 25 is formed in the vane plate 20 at a position closer to one side (a position closer to the right side in FIG. 1) than the center of gravity M of the vane plate 20 in the longitudinal direction. It is connected to the pile main body 10 at a position closer to one side in the longitudinal direction than the center of gravity M.

However, the through hole 25 and the rotation axis X2 are located not at one end of the vane plate 20 in the longitudinal direction, but toward the center of the end. For example, in the example of FIG. 1, the ratio of the lengths from the center of gravity M of the blade plate 20 to each end of the blade plate 20 in the longitudinal direction is approximately 1:1, whereas from the rotation axis X2 to the blade plate The ratio of the lengths to each end of 20 is approximately 3:2. From this, as shown in FIG. 4, a part of the vane plate 20 and a part of the pile main body 10 overlap in a state where the vane plate 20 is in the first attitude A1. Further, in the state of being in the second attitude A2, the blade plate 20 extends to the outside of the pile main body 10. In addition, as shown in FIG. 4, in this embodiment, the width dimension of the wing board 20 in the state which exists in 1st attitude|position A1 is smaller than the outer diameter of the pile main body 10.

Hereinafter, in the longitudinal direction of the blade plate 20, a portion of the blade plate 20 on one side of the rotation axis X2 and including the center of gravity M of the blade plate 20 will be referred to as a center-of-gravity side portion 20a, and the opposite side will be referred to as the center-of-gravity side portion 20a. The side is called the opposite-to-center-of-gravity side portion 20b. Further, in the left-right direction of FIG. 4, when the blade plate 20 is in the second posture A2, the side where the center of gravity side portion 20a is located is the left, and the side where the opposite center of gravity side portion 20b is located is the right. I do.

The pile body 10 is provided with a regulating member for regulating the rotation range of the blade plate 20. In this embodiment, the nail 29 nailed to the pile main body 10 functions as this regulating member.

As shown in FIGS. 2 and 4, the nail 29 is nailed to the pile body 10 at a position slightly below the center of gravity side portion 20a of the blade plate 20 with the blade plate 20 in the second posture A2. It is being Further, the nails 29 are inserted from the pile main body 10 in a manner shown in FIG. It is nailed to the pile main body 10 in a state of protruding toward the front side of the page.

As a result, the nail 29 comes into contact with the center-of-gravity side portion 20a of the wing plate 20 in the second attitude A2 from below, and prevents the center-of-gravity side portion 20a from rotating further downward. do.

Further, as shown in FIG. 4, the nail 29 is attached to the pile main body 10 at a position slightly to the left of the portion 20b on the side opposite to the center of gravity of the blade plate 20 when the blade plate 20 is in the first posture A1. It's nailed down.

From this, the nail 29 abuts from the left against the portion 20b on the side opposite to the center of gravity of the blade plate 20 in the first attitude A1, and the portion 20b on the side opposite to the center of gravity faces leftward, that is, the portion 20a on the side opposite to the center of gravity prevents the blade plate 20 from rotating in the rightward direction.

In this way, the blade plate 20 can be rotated only to the left from the first attitude A1, and the rotation angle is limited to 90 degrees until it reaches the second attitude A2.

(Steps for fluffy pile construction method)
Next, the procedure of the fluffy pile construction method using the pile 1 described above will be explained using FIGS. 5, 6, and 7. FIG. 5 is a flowchart showing the procedure of the fluffy pile construction method. FIG. 6 is a schematic diagram showing a state in which a plurality of stakes 1 are driven into the ground.

First, the depth of the soil layer 111 of the target forest slope 100 is measured.

As shown in FIG. 6, the ground 100 constituting the slope of a mountain forest where plants can live mainly consists of a base layer 104 and a topsoil layer 102 formed on the surface side of the base layer 104. The base layer 104 is a layer mainly made of rock, and is a layer made of rock in which cracks and fissures have occurred due to crushing and weathering. The topsoil layer 102 is a layer made of clay, sand, and gravel formed when rocks are crushed and weathered to become fine particles, and is softer and more permeable than the base layer 104. The soil layer 111 is a layer that constitutes the surface side portion of the topsoil layer 102. Trees and herbaceous plants live on the surface side of the topsoil layer 102, and along with this, small animals and soil microorganisms are active. As a result, organic matter such as fallen leaves accumulates on the surface of the topsoil layer 102. The soil layer 111 is a layer formed by the accumulation of organic matter in this way, and is a particularly soft and highly permeable layer of the topsoil layer 102. Note that, on a steep slope in a mountain forest, the entire topsoil layer 102 may be composed of the soil layer 111.

As described above, in the fluffy pile construction method according to this embodiment, the piles 1 are driven only into the soil layer 111. First, the depth D1 of the soil layer 111 on the target slope is measured (step S1).

In this embodiment, the depth of the soil layer 111 is measured using a simple penetration test (simple dynamic cone penetration test) method. The simple penetration test method is a ground investigation method specified in the "Japan Geotechnical Society Standards" (JGS1433), and is generally used in ground investigations. Briefly, the simple penetration test method is to drop a 5kg weight freely onto a rod placed on the ground, and count the number of times it takes for a cone attached to the bottom end of the rod to penetrate 100mm into the ground. It is. The larger the Nd value, which is the number of times, the harder the ground is. Generally, a layer with an Nd value of 30 or more is determined to be a base layer. In this embodiment, when the Nd value is less than 20, it is determined that the layer at the point of cone penetration is a soil layer, and the simple penetration test is repeated until the Nd value exceeds 20, and the cone is inserted in 100 mm increments. It penetrates into the ground. Then, when the cone reaches a layer where the Nd value is 20 or more, the distance from the ground surface of the arrival point is determined as the depth of the soil layer 111.

As shown in FIG. 6, in this embodiment, stakes 1 are driven into multiple locations on the target land. From this, the depth of the soil layer 111 is measured at multiple points in the target area. Specifically, the driving points of the piles 1 are determined in advance, and measurements are taken at each of these points. In addition, when the depth of the soil layer 111 is excessively shallow at a predetermined point, the driving point is changed to a point around the predetermined point where the depth of the soil layer 111 can be ensured.

Next, based on the measurement results in step S1, the lengths of the pile body 10 and the blade plate 20 are determined, and the pile body 10 and the blade plate 20 having the determined lengths are prepared (step S2 : Preparation process).

Specifically, the dimensions of the pile body 10 to be driven into each location are determined to be the same as or shorter than the depth of the measured soil layer 111, respectively. Then, a plurality of pile bodies 10 are prepared corresponding to each location. For example, the pile body 10 is prepared with a number representing the location written on it. Also, a plurality of vanes 20 having a predetermined length are prepared. As described above, in this embodiment, thinned wood is used for the pile main body 10 and the slats 20, and the pile main body 10 and the slats 20 having the determined length dimensions are formed from the thinned wood.

As a result of the inventors' investigations in mountain forests, etc. in various regions, the depth of the soil layer 111 is approximately 1 m to 2 m, and the soil layer 111 is formed at a depth of approximately 1 m to 2 m from the ground surface. has been done. Therefore, as described above, the length L of the pile body 10 is approximately 1 m (1000 mm). Further, the predetermined length (length L2 of the blade plate 20) is approximately 0.9 m (900 mm).

Next, the pile body 10 prepared in step S2 and the blade plate 20 are connected to form the pile 1 (step S3). Specifically, as described above, the pile body 10 and the slat 20 are connected using bolts 32a and nuts 32b, and the nails 29 are driven into the pile body 10. Preparation of the pile body 10 and the slats 20 and their connection work are performed, for example, at a processing factory for thinned wood.

Next, the pile 1 is transported to the driving point (step S4). In this embodiment, the piles 1 are transported by vehicle from the manufacturing site of the piles 1 to a road near the driving target area, and then the piles 1 are transferred to a container, and the container is transported manually or by a vehicle that can drive in the forest. It is towed and transported to the target area. Here, as shown in FIG. 7, the pile 1 is loaded in the first attitude A1 into the storage section 90 of the vehicle, such as a loading platform or a container.

Next, each pile 1 is driven into the ground 100 that constitutes a forest slope, and the pile body 10 of each pile 1 is driven into the ground 100, and the slats 20 are arranged on the ground 100 so as to extend along the ground surface 101. (Step S5: Pile installation process).

In this embodiment, the pile 1 is driven so that the central axis X1 of the pile body 10 and the ground surface 101 are perpendicular to each other. Further, the pile 1 is driven so that the center-of-gravity side portion 20a of the blade plate 20 extends downward from the rotation axis X2 on the slope 100 when the second posture A2 is reached. Here, if the pile 1 is erected on the ground surface 101 in this direction, the center-of-gravity side portion 20a of the blade plate 20 will rotate downward in the vertical direction by its own weight. Then, further downward rotation of the center-of-gravity side portion 20a is restricted by the nail 29, and the posture of the stake 1 becomes the second posture A2. From this, by setting the pile 1 on the ground surface 101, the posture of the pile 1 automatically changes from the first posture A1 to the second posture A2, and the pile 1 in the second posture A2 is placed on the ground 100. You will be driven into it.

The pile 1 is driven to a position where the upper surface of the pile body 10 slightly protrudes upward from the ground surface 101, as shown in FIG. As a result, almost the entire pile body 10 is driven into the soil layer 111. Further, the blade plate 20 is disposed in the soil layer 111 so as to extend along the vicinity of the ground surface 101. In this embodiment, the pile 1 is further driven in a state where the blade plate 20 and the ground surface 101 are in contact with each other, and thereby the blade plate 20 is pressed into contact with the ground surface 101.

Note that the work of setting up the pile 1 on the ground surface 101 and the work of driving the pile 1 into the ground 100 may be performed directly by a worker, or may be performed using a work vehicle.

The driving work of pile 1 is carried out at each driving point. In this embodiment, as shown in FIG. 6, piles 1 are driven at approximately equal intervals along the ground surface 101. Although not shown, a plurality of piles 1 are also driven at approximately equal intervals along the direction perpendicular to the plane of the paper in FIG. For example, a plurality of piles 1 are driven so that the distance between the central axes X1 of the piles 1 is 2 m.

(effect)
As described above, in the fluffy pile construction method according to the present embodiment, the pile body 10 is softer than the base layer 104 and is formed on the soil layer 111 forming the ground surface 101, which is formed closer to the ground surface than the base layer 104. It is only driven in. Therefore, the length of the pile main body 10 can be shortened, and costs can be reduced. Further, since the length of the pile body 10 is short and the layer to be driven is soft, the working time required to drive the pile 1 can be shortened. Further, there is no need to use a large-scale device to drive the pile 1, and this also makes it possible to reduce costs. For example, in the conventional method of driving piles up to the base layer 104, the driving distance of the piles is very long and the base layer 104 is hard. It is necessary to insert the pile into the hole, and then solidify the gap between the hole and the pile with cement. Therefore, with conventional construction methods, the scale of the work is large and the work time is extremely long. On the other hand, in the fluffy pile construction method according to the present embodiment, the pile 1 can be directly driven into the slope without boring. Therefore, the work related to drilling holes and the work of pouring cement around the pile and hardening it can be omitted, the equipment required for this work is no longer required, and the working time can be extremely shortened.

Moreover, in the fluffy pile construction method, the pile body 10 is driven into the slope 100, and the slat 20 connected to the upper end of the pile body 10 is arranged on this in a posture extending along the ground surface 101 of the slope 100. . Therefore, collapse of the soil layer 111 can be effectively suppressed.

This will be explained in detail using FIG. 8. When a large amount of water is supplied to the soil layer 111, the soil layer 111 tends to flow down the slope along the ground surface 101. As a result, a force F1 in a direction parallel to the ground surface 101 is applied to the pile body 10. Among the soil layer 111, the part on the ground surface side is particularly soft. Therefore, in response to the force F1, the upper end of the pile main body 10 moves downward on the slope, and the pile main body 10 falls down downward on the slope as shown by the solid line with respect to the driving position shown by the chain line. Become. Then, the length of the pile main body 10 is extended from the initial state shown by the broken line to the state shown by the solid line, and is pulled upward.

On the other hand, a frictional force F2 generated between the circumferential surface and the soil acts on the circumferential surface of the pile main body 10. This restricts the upward movement of the pile body 10 (movement in the direction of coming out of the ground), and a downward tensile stress F3 equal to the frictional force F2 is generated inside the pile body 10. A component F3_a of this tensile stress F3 in a direction parallel to the ground surface 101 acts upward on the slope and restricts the movement of earth and sand down the slope. Furthermore, a component F3_b of the tensile stress F3 in a direction perpendicular to the ground surface 101 and directed downward (into the ground) is transmitted to the vane plate 20 via the connecting member 32 including the bolt 32a. As a result, the force F4 caused by the above-mentioned tensile stress F3 is added to the force with which the blade 20 presses against the ground surface, and the force with which the blade 20 presses against the ground surface is increased. Therefore, at the initial stage of collapse of the soil layer 111, the frictional force inside the soil below the blade plate 20 increases, and further movement of the soil, that is, progress of collapse, is suppressed.

In this way, according to the fluffy pile construction method according to the present embodiment, it is possible to effectively suppress collapse of the soil layer 111, that is, the surface-side portion of the topsoil layer 102, while reducing cost and work time.

FIG. 9 shows the results of an experiment investigating the effects of the blade plate 20 described above. FIGS. 10A and 10B are a schematic top view and a side view, respectively, of the experimental apparatus used in this experiment. In this experiment, a shear load was applied to a soil clod consisting of a soil layer, in which no pile was driven into the soil clod, when only the pile body was driven into the soil clod, and when a pile with a slat plate and a pile body was driven into the soil clod. The relationship between the load applied to the soil clod and the amount of displacement of the soil clod was investigated in each case.

Specifically, as shown in FIG. 10, soil around a substantially rectangular portion is dug up in a mountain forest to form a clod of soil 301 with length L_a, width W_a, and depth D_a of 1200 mm, 1000 mm, and 1000 mm, respectively. Formed. In the following description, the longitudinal direction of the earth clod 301, which is the left-right direction in FIG. 10, will be simply referred to as the left-right direction. Then, using the hydraulic jack 310, a load was applied diagonally downward to the soil mass 301 from the upper left of the soil mass 301. Specifically, an inclined surface 302 that slopes upward and diagonally to the right is formed at the upper part of the left side surface of the soil clod 301. Here, the range from the top surface of the soil clod 301 to a depth of 400 mm (dimension D_b in FIG. 10(b)) is inclined, and the inclination angle θ of the inclined surface 302 with respect to the horizontal plane is set to 60 degrees. Then, an iron plate 303 with a thickness of 12 mm was applied to this inclined surface 302, and a load was applied to the center of the plate 303 from a hydraulic jack 310. Note that the load from the hydraulic jack 310 is applied to the plate material 303 in a direction perpendicular to this, that is, the load is applied to the soil block 301 from the top on the left side diagonally downward and to the right. Hydraulic jack 310 was supported by support member 320 made of concrete.

Here, as described above, the reason why the force was applied diagonally downward and to the other side of the upper part of one side of the soil clod 301 in the left-right direction is to cause the soil to collapse in the same way as when surface collapse occurs. Specifically, in surface collapse, as described above, force is first applied to the soil in a direction along the ground surface, which distorts the entire soil and causes cracks in the soil. As these cracks develop, the soil collapses. On the other hand, if a force is applied to the earth clod 301 along the ground surface as described above, a moment will be generated in the earth clod 301 with the end opposite to the applied position as a fulcrum, causing the earth clod to It rotates without distortion or cracking, which causes the soil to collapse. Therefore, in this experiment, force was applied to the soil mass 301 as described above so that distortion and cracks were generated in the soil mass without rotation, resulting in a phenomenon closer to surface collapse.

In this experiment, a wooden pile 401 as shown in FIG. 10 was used, which included a pile main body 410 and two slats 421 and 422. In this pile 401, a first slat 421 is connected to the upper part of a pile body 410 with bolts, and a second slat 422 is attached to the pile body in a position perpendicular to the first slat 421 above the first slat 421. 410 with bolts. The diameter of the pile body 410 is 120 mm, and the length is 1000 mm. The first slat 421 and the second slat 422 are made of logs with a diameter of 120 mm that have been subjected to a drum dropping process, and the first slat 421 has a columnar shape of approximately 80 mm x 90 mm x 700 mm. , the second blade plate 422 has a columnar shape of approximately 80 mm x 90 mm x 1200 mm. Each of the vanes 421 and 422 is connected to the vane 422 with a height dimension of 90 mm.

FIG. 9 is a graph in which the horizontal axis represents the amount of displacement of the earth clod 301, and the vertical axis represents the load applied to the earth clod 301. In addition, line L1 in FIG. 10 is the result when no pile is driven into the earth clod 301, line L2 is the result when only the pile body 410 is driven into the earth clod 301, and line L3 is the result when the pile body 410 is driven into the earth clod 301. This is the result when a pile 401 with connected blade plates 421 and 422 is driven. Here, the amount of displacement of the soil mass 301 on the horizontal axis is the amount of displacement of the soil near the slope 302 measured by a displacement meter. Moreover, the load was measured using a load cell.

As shown by line L1 in FIG. 9, if no piles are driven, the load reaches its maximum at point C1 when the displacement of the soil clod 301 is 20 mm, and after that, the load increases as the displacement increases. is decreasing. From this, in this case, it is considered that the collapse of the earth clod 301 occurred when the amount of displacement was about 20 mm, and the maximum resistance force of the earth clod 301 (the minimum value of the load at which the earth clod 301 collapses) is 13 kN, which is the load at point C1. It can be said that it is about a certain extent.

On the other hand, as shown by line L3 in FIG. 9, when the pile 401 in which the vanes 421 and 422 are connected to the pile body 410 is driven, the load becomes maximum at point C3. In other words, it is considered that the earth clod 301 collapsed at point C3 where the displacement of the earth clod 301 was about 85 mm and the load was about 24 kN, and it can be said that the maximum resistance force of the earth clod 301 was about 24 kN.

In this way, if the pile 401 in which the slats 421 and 422 are connected to the pile body 410 is used, the maximum resistance of the soil clod 301 is doubled compared to the case where the pile 401 is not driven. Collapse is suppressed.

Here, as shown by line L2 in FIG. 9, even when only the pile main body 410 is driven into the soil mass 301, the maximum load is approximately 20 kN, and the maximum resistance force of the soil mass 301 is lower than when the pile 401 is not driven. growing. However, compared to the case where the vanes 421 and 422 are provided, the value can be kept small.

In addition, in the fluffy pile construction method according to the present embodiment, first, the depth of the soil layer 111 is measured, and the pile main body 10 that is the same as or shorter than the depth dimension (thickness dimension) of the soil layer 3 is prepared. At the same time, the feather plate 20 is prepared. After connecting the slats 20 to the pile body 10 to form a pile 1 in which the pile body 10 and the slats 20 are integrated, the pile 1 is driven into a slope. Therefore, the driving of the pile main body 10 and the pressure contact of the blade plate 20 to the ground surface can be performed at the same time, improving work efficiency.

Further, in the pile 1 according to the present embodiment, the blade plate 20 has a shape extending in a predetermined direction, and is rotatable around a rotation axis X2 extending in a direction perpendicular to the longitudinal direction of the pile body 10, and It is connected to the pile main body 10 so as to extend in a direction intersecting the rotation axis X2. Therefore, the posture of the pile 1 can be easily changed between a first posture A1 in which the pile body 10 and the slat 20 extend in parallel, and a second posture A2 in which the slat 20 extends in a direction intersecting the pile body 10. can be changed to Therefore, by setting the posture of the pile 1 to the first posture A1 when transporting the pile 1 as described above, the overall dimension of the pile 1 in the direction perpendicular to the central axis X of the pile body 10 can be kept short, The storage space of the container can be used effectively. When driving the pile 1, by setting the pile 1 in the second posture A2, the blade plate 20 can be pressed against the ground surface while extending along the ground surface, and the blade plate 20 and the soil can be pressed against each other. Frictional resistance can be ensured.

In particular, the pile 1 according to the present embodiment is configured such that the center of gravity M of the blade plate 20 and the rotation axis X2 are deviated from each other in the longitudinal direction of the blade plate 20, and the nail 29 moves the blade plate 20 into the second posture. It is configured so that the center-of-gravity side portion 20a of the blade plate 20 does not rotate downward (toward the tip end of the pile body 10) when the position becomes A2. Therefore, the weight of the center-of-gravity side portion 20a of the blade plate 20 changes the attitude of the pile 1 from the first attitude A1, in which the center-of-gravity side portion 20a is located above the rotation axis X2, to the second attitude A2. Can be easily changed. Further, the blade plate 20 can be held in the second posture A2. Therefore, when driving the pile 1, it is possible to prevent the blade plate 20 from tilting from its position along the ground surface, and to appropriately press the blade plate 20 against the ground surface.

Furthermore, in the pile 1 according to the present embodiment, the pile main body 10 and the slats 20 are made of wood that has been subjected to antiseptic treatment. Therefore, costs can be kept lower than when these are made of metal such as steel pipes. In addition, water in the soil can be impregnated into the pile main body 10 and the blade plate 20, making the volume of these larger than when driving. It can increase the frictional force of soil. Furthermore, since the surface of wood is more likely to become rough than that of metal such as steel, by making the pile main body 10 and the slats 20 wooden, it is possible to increase the frictional resistance between them and the soil. Since the pile main body 10 and the blade plate 20 are subjected to the antiseptic treatment, early decay can be suppressed, and collapse of the topsoil layer can be suppressed over a long period of time. Furthermore, in this embodiment, these are made of thinned wood, which is useful for effective use of thinned wood.

(Modified example)
In the embodiment described above, a case has been described in which the pile 1 is driven so that the center axis X1 of the pile body 10 is orthogonal to the ground surface, but the driving angle of the pile body 10 is not limited to this. For example, on a steep slope, it is difficult to drive the pile 1 with the central axis X1 of the pile body 10 aligned with a line perpendicular to the ground surface. In this case, it is possible that the central axis X1 of the pile main body 10 and the above-mentioned line are misaligned. However, even if these central axes Further movement of the soil layer 111 can be suppressed. However, if the pile body 10 is driven so that its central axis X1 and the ground surface are perpendicular to each other, the movement of the soil layer 111 can be effectively suppressed by the pile body 10 and the slats 20. In addition, the pile body 10 is tilted so that the upper end of the pile body 10 is located on the lower side of the slope than the lower end with respect to a line perpendicular to the ground surface. It is known that if the angle formed with the axis X1 is set to about 30 degrees, the resistance to displacement of the soil layer 111 by the pile body 10 can be increased. From this, the pile main body 10 may be driven into the ground surface while being inclined with respect to the direction perpendicular to the ground surface.

Furthermore, in the embodiment described above, the pile 1 is driven into a slope so that the center-of-gravity side portion 20a of the blade plate 20 extends downward from the pile body 10, but the driving posture of the pile 1 is not limited to this. . For example, the pile 1 may be driven so that the center-of-gravity side portion 20a extends above the slope from the pile body 10. Alternatively, the piles 1 may be driven into the slope so that the blades 20 extend horizontally.

Moreover, the material of the pile body 10 and the slats 20 is not limited to wood. For example, these may be formed from steel pipes or the like. However, as mentioned above, if these are made of wood, a cost reduction effect can be obtained. Furthermore, when the pile body 10 and the slats 20 are made of wood, the method of preservative treatment is not limited to the above.

Furthermore, in the above embodiment, the case where the pile 1 is driven into a slope where the soil layer 111 is formed on the surface side of the surface soil has been described, but the pile 1 may be driven to the extent that the pile main body 10 remains in the surface soil. The fluffy construction method according to this embodiment is also applicable to surface soil in which no soil layer is formed. In addition, the pile body 10 may be driven to a position deeper than the soil layer 111 as long as the tip 12 of the pile body 10 remains in the surface soil. For example, in the step of measuring the depth D1 of the soil layer 111, the depth of the surface soil is measured instead of the depth D1 of the soil layer 111, and the pile body 10 is measured in a range shallower than the measured depth of the surface soil. You may also type it in.

Furthermore, in the embodiment described above, a case has been described in which the length of the pile main body 10 driven into each point is individually set according to the measurement result of the depth D1 of the soil layer 111 at each point. According to this method, the pile body 10 can be driven into the soil layer 111 reliably at each location.

However, the procedure for setting the length of the pile body 10 is not limited to this, and the lengths of the pile bodies 10 driven into each location may all be unified to a predetermined value. For example, the length of the pile main body 10 may be made equal to the average value or minimum value of the depth D1 of the soil layer 111 measured at each point. Alternatively, a plurality of pile bodies 10 having different lengths may be prepared, and the pile bodies 10 to be driven into each location may be selected from among the pile bodies 10 prepared according to the measurement results. For example, two types of pile bodies 10 with different lengths are prepared, and a longer pile body 10 is used at a point where the depth D1 of the soil layer 111 is a predetermined value or more, and A shorter pile main body 10 may be used at a point where is less than a predetermined value. Further, as mentioned above, since the depth of the soil layer 111 is approximately 1 m to 2 m, the driving point of the pile 1 can be determined without measuring the depth D1 of the soil layer 111 or by using this measurement result. (e.g., selecting a point where the depth of the soil layer 111 is deeper than the length of the pile body 10 as the driving point), the pile body 10 having a length of about 1 m regardless of the above measurement results. may be prepared. In this way, by making the lengths of the pile bodies 10 uniform to a certain extent, the time required to prepare the pile bodies 10 can be shortened and costs can be kept low.

Furthermore, in the embodiment described above, a case has been described in which the rotation of the wing plate 20 is restricted by the nails 29, but the member for restricting this rotation is not limited to the nails 29. Furthermore, the rotation of the blade plate 20 may not be restricted. However, as described above, if the downward rotation of the center-of-gravity side portion 20a of the vane plate 20 is restricted when the posture of the vane plate 20 is in the second posture A2, the posture of the vane plate 20 can be changed to the second posture A2. Since the posture A2 of No. 2 can be maintained in the posture after driving the pile 1, work efficiency is improved.

Furthermore, in the embodiment described above, the case where only one slat 20 is connected to the pile main body 10 has been described, but a plurality of slats 20 may be connected to the pile main body 10 like the pile 401 used in the above experiment. Good too. Furthermore, even when a plurality of slats 20 are provided, instead of connecting each slat 20 directly to the pile body 10 as in the experiment, the slats 20 may be connected via connecting members as shown in FIGS. 11 and 12. , the slats and the pile body may be indirectly connected.

Specifically, FIG. 11 is a top view of a pile 501 according to another example. In the example of FIG. 11, a connecting plate 502 extending in a direction perpendicular to the central axis X1 of the pile body 510 is fixed to the upper end of the pile body 510, and one blade plate is attached to each longitudinal end of the connecting plate 502. 521 and 522 are connected. In this pile 501 as well, the frictional force generated on the circumferential surface of the pile body 510 is transmitted from the pile body 510 to each of the vanes 521 and 522 via the connecting plate 502, so that soil collapse can be effectively suppressed. I can do it. In particular, in this example, since the frictional force of the soil is increased at positions separated from each other by the pressing force of each of the vanes 521 and 522, it is also possible to suppress the movement of soil in the area between these vanes. This can suppress soil collapse over a wider area.

FIG. 12 is a top view of a pile 601 according to still another example. In the example of FIG. 12, four blade plates 621, 622, 623, 624 are connected to the pile body 10 by two connecting plates 602, 603 extending in directions orthogonal to the central axis X1 of the pile body 610 and mutually orthogonal to each other. It is connected to the pile main body 610 so as to surround the pile and form a well shape. In this pile 601 as well, the frictional force generated on the circumferential surface of the pile body 610 is transmitted from the pile body 610 to each of the vanes 621 to 624 via the connecting plates 602 and 603, thereby effectively suppressing soil collapse. can do. Furthermore, in this example, the frictional force is increased in all directions of the soil around the pile main body 610, so that the movement of the soil can be suppressed more reliably.

Moreover, the specific shape of the pile main body 10 is not limited to the above, and the pile main body 10 may have a prismatic shape, for example. Further, the diameter and length of the pile main body 10 are not limited to those described above. However, as mentioned above, since the soil layer 111 is generally formed within a range of about 1 to 2 m from the ground surface, and from the viewpoint of workability, the length of the pile body 10 is set to 800 mm to 2 m. It is preferable to set it to about 1500 mm. Similarly, the specific dimensions of the blade plate 20 are not limited to the above.

Further, in the embodiment described above, a case has been described in which the pile 1 and the pile body 10 are driven into the slope 100 after the pile 1 is formed by connecting the blade plate 20 to the pile body 10. After driving into the slope 100, the blade plate may be connected to the pile body in a state extending along the ground surface 101. That is, in the pile installation process in which the pile body is driven into the slope 100 and the blade plate is placed on the slope 100 while being connected to the pile body, there are a step of driving the pile body into the slope 100, and a step of driving the pile body into the slope 100. The step of connecting the blades so as to extend along the ground surface 101 may also be performed.

For example, as shown in FIG. 13, first, the pile body 710 is driven into the slope 100 so that its upper end and the ground surface 101 are at approximately the same height position, and then the blade plate 720 is placed on the upper end of the pile body 710. These may be connected by nails 730 or the like.

According to this procedure, the slats 720 do not get in the way when driving the pile main body 710, so the driving work of the pile main body 710 can be easily performed, and the pile main body 710 can be driven in an appropriate posture more reliably. be able to.

In addition, in this method of driving the pile body 710 alone into the slope 100 without connecting the blade plate 720, the pile body 710 can be driven so as to stay in the soil layer 111 (or topsoil layer 102) as follows. I can do it. That is, first, a pile main body 710 (wood that is the source of the pile main body 710) having a sufficient length is driven into the slope 100 so that its tip fits into the soil layer 111 (or topsoil layer 102). For example, when the force applied to driving exceeds a predetermined value, it is determined that the tip of the pile body 710 has reached the interface between the soil layer 111 (or topsoil layer 102) and the layer below, and driving is stopped. Next, the portion of the pile body 701 that protrudes from the ground surface is cut at a predetermined height. After that, the blade plate 720 is connected to the upper end of the pile body. According to this procedure, the step of measuring the depth of the soil layer 111 (or topsoil layer 102) can be omitted or simplified.

1 Pile 10 Pile body 20 Feather plate (blade member)
29 Nail (regulating member)
32 Connecting member 100 Ground 102 Topsoil layer 104 Base layer 111 Soil layer

Claims (6)

A method for suppressing the collapse of a slope, which is applied to a slope where at least the layer on the ground side is composed of a topsoil layer that is softer than the base layer and the ground surface is inclined with respect to a horizontal plane,
A pile body extending in a predetermined direction is driven into the slope from the tip side in the longitudinal direction in a position where the longitudinal direction of the pile body intersects the ground surface of the slope, and a blade member extending in a predetermined direction is driven into the slope. A pile installation step of arranging the pile on the slope while being connected to the proximal end portion in the longitudinal direction of the pile body,
The blade member has a facing surface that is a side surface facing the slope,
In the pile installation step, the pile body is driven so that the tip of the pile body remains within the topsoil layer, and the blade member is placed on the slope so that the blade member extends along the ground surface of the slope. At the same time, a plurality of the pile bodies and the blade members are installed at positions spaced apart from each other on the slope so that the pile bodies and the blade members are independent from each other,
A slope surface collapse prevention pile construction method, characterized in that when the blade member is placed on the slope, the opposing surface of the blade member is brought into pressure contact with the ground surface. In the slope surface collapse prevention pile construction method according to claim 1,
A preparation step that is carried out before the pile installation step and prepares the blade member and the pile body that is shorter than the thickness dimension of the topsoil layer,
A slope surface collapse prevention pile construction method, characterized in that the pile main body and the blade member are connected after the preparation step and before the pile installation step. A method for suppressing the collapse of a slope, which is applied to a slope where at least the layer on the ground side is composed of a topsoil layer that is softer than the base layer and the ground surface is inclined with respect to a horizontal plane,
A pile body extending in a predetermined direction is driven into the slope from the tip side in the longitudinal direction in a position where the longitudinal direction of the pile body intersects the ground surface of the slope, and a blade member extending in a predetermined direction is driven into the slope. a pile installation step of arranging the pile on the slope while being connected to the proximal end portion in the longitudinal direction of the pile body;
A preparatory step carried out before the pile installation step to prepare the blade member and the pile body shorter than the thickness dimension of the topsoil layer,
The blade member is connected to the pile body so as to be rotatable about a rotation center line extending in a direction perpendicular to the longitudinal direction of the pile body, and has a shape extending in a direction intersecting the rotation center line. have,
In the pile installation step, the pile body is driven so that the tip of the pile body remains within the topsoil layer, and the blade member is driven into the slope so that the blade member extends along the ground surface of the slope. place,
A slope surface collapse prevention pile construction method, characterized in that the pile main body and the blade member are connected after the preparation step and before the pile installation step. In the slope surface collapse prevention pile construction method according to claim 3,
The blade member is connected to the pile main body such that the center of gravity of the blade member is located on one side of the rotation center line in the longitudinal direction,
The pile body includes a regulating member that regulates rotation of the blade member,
The regulating member is arranged such that the blade member extends in a direction intersecting the longitudinal direction of the pile body, and the one end in the longitudinal direction of the blade member approaches the tip side of the pile body. A slope surface collapse prevention pile construction method, characterized in that the rotation of the blade member is restricted. In the slope surface collapse prevention pile construction method according to claim 1,
A preparation step of preparing the blade member and the pile body shorter than the thickness dimension of the topsoil layer,
In the pile installation step, after driving the pile body into the slope, the blade member is connected to the pile body in a state extending along the ground surface of the slope. Construction method. In the slope surface collapse prevention pile construction method according to any one of claims 1 to 5,
The pile construction method for preventing slope surface collapse, characterized in that the pile main body and the blade member are made of wood that has been subjected to antiseptic treatment.

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