JP6111530B2 - Collapse suppression structure and collapse suppression construction method - Google Patents

Description

  The present invention relates to a collapse-inhibiting structure and a collapse-inhibiting construction method that suppress a deep layer collapse of a rock mass that occurs between a stable mass and an unstable mass.

  In recent years, the number of occurrences of heavy rain has been increasing, and the risk of deep collapse has increased. This deep collapse is thought to occur due to the concentration of groundwater. For example, if the steep rock is composed of the lower rocks with relatively few cracks and the upper rocks with relatively many cracks, a large amount of rainwater becomes the groundwater due to heavy rain. Infiltrate the rocks. If this groundwater is concentrated at the boundary between the upper and lower rocks, the groundwater pressure rises at the point of concentration and deep collapse occurs.

  As a technique for preventing such a deep layer collapse, there is a suppressor. Suppression work is a method of increasing resistance to the force of unstable soil masses by changing natural conditions such as groundwater conditions, and stopping or mitigating the movement of unstable soil masses. Is mentioned.

  In Patent Document 1, in the ground where the embankment is built on the original ground, a drain pipe (drain hole) is formed along the inclination direction of the original ground at the boundary portion between the embankment and the original ground. A groundwater drainer is described.

JP 2007-231629 A

  The technique described in Patent Document 1 does not consider the groundwater level. For this reason, when this technology is applied to the suppression of deep layer collapse of rock, the following problems may occur depending on the relationship between the height of the drain pipe and the height of the groundwater level.

  For example, if the drain pipe is always provided below the water level, a large amount of groundwater will be discharged, and there will be problems with the drainage of groundwater and the treatment of discharged water on the downstream side. In this case, there are concerns about the impact on the ecosystem. On the other hand, when the drain pipe is always provided above the water level, groundwater concentrates below the drain hole during heavy rain, and there is a possibility that the occurrence of deep collapse cannot be suppressed.

  This invention is made | formed in view of such a situation, The objective is to raise the inhibitory effect of the deep layer collapse at the time of heavy rain.

To achieve the above object, the present invention provides a suppressing collapse suppressing structure deep collapse of rock, in a range of fluctuation is set above and below the constant level obtained in drilling survey based the Constructed along the lower side of the normal water level obtained in the boring survey , the drainage end has a perforated pipe facing outward from the slope of the rock, and the rock has stable and unstable masses. The perforated pipe is provided with a culvert portion constructed along the constant water level, and is integrally provided with the culvert portion, and rises up inside the stable soil mass upstream of the unstable soil mass on the upstream side of the groundwater flow. And a portion.

According to the collapse-suppressing structure of the present invention, since the perforated pipe is constructed along the constant water level in the vicinity of the constant water level, the groundwater in the rock is taken into the perforated pipe and the drainage end. Discharged from. Thereby, it can suppress that a groundwater level becomes always higher than a water level. And since the groundwater near a constant water level becomes a discharge target, the groundwater level is not lowered below the constant water level, and the problem of exhaustion of groundwater on the upstream side and excessive drainage on the downstream side can be prevented. Further, in this configuration in which the perforated pipe is constructed below the normal water level, a small amount of groundwater can be discharged constantly, and the communication state can be easily confirmed.

  In the above-described collapse suppression structure, the rock mass has a stable clot and an unstable clot, and the perforated pipe is provided integrally with the culvert portion constructed along the water level at all times. It is preferable to have a rising portion that rises inside the stable soil mass on the upstream side of the groundwater flow from the unstable soil mass. In this configuration, the rising portion of the perforated pipe can reduce the amount of inflow into the unstable soil mass of groundwater, and can enhance the effect of suppressing deep collapse.

  In the above-described collapse suppression structure, it is preferable to have another perforated pipe communicating between the surface of the rock and the perforated pipe. In this configuration, rainwater penetrating from the rock surface can be poured into the perforated pipe by another perforated pipe, and the effect of suppressing deep collapse can be enhanced.

In the above-described collapse suppression structure, the other perforated pipe is provided with a water level sensor and a drainage pump that operates according to the groundwater level detected by the water level sensor and discharges groundwater to the outside of the rock through a hose. It is preferable. In this configuration, the forced groundwater is discharged by the drainage pump, so that it is possible to more reliably prevent the rock collapse.

In the above-described collapse suppression structure, the perforated pipe constructed along the lower side than the normal water level is radially centered on the drain end facing outward from the slope of the rock in plan view. It is preferable that it is constructed as follows. In this configuration, since a plurality of perforated pipes can be arranged in accordance with the shape of the unstable soil mass, the effect of suppressing the deep collapse can be further enhanced.

  ADVANTAGE OF THE INVENTION According to this invention, the suppression effect of the deep layer collapse at the time of heavy rain can be heightened.

It is a perspective view of the whole structure. It is sectional drawing of the whole structure. It is a top view which shows the layout of a several collapse suppression structure. It is explanatory drawing of a construction procedure, and shows a boring investigation. It is explanatory drawing of a construction procedure, and shows formation of a boring hole. It is explanatory drawing of a construction procedure, and shows installation of a main. It is explanatory drawing of a construction procedure and shows installation of a branch pipe. It is a top view which shows the other layout in a some collapse suppression structure. It is a figure explaining other embodiment which installed the drainage pump. It is a figure which expands and shows the periphery of a drainage pump.

  Embodiments of the present invention will be described below. As shown in FIG. 1, the collapse suppression structure 1 of this embodiment is constructed on a rock G on a steep slope where a stable soil mass G1 and an unstable soil mass G2 are formed. Thereby, the deep collapse of the bedrock G resulting from the groundwater W flowing from the stable soil mass G1 to the unstable soil mass G2 is suppressed. The stable soil mass G1 is a rock with relatively few cracks, and the unstable soil mass G2 is a rock with relatively many cracks.

  In the present embodiment, the groundwater W is filled up to a height at which the lower portion of the unstable soil mass G2 is immersed. When the amount of groundwater W increases due to heavy rain or the like, the groundwater W concentrates on the boundary between the stable soil mass G1 and the unstable soil mass G2, and the groundwater pressure increases. Therefore, the boundary S between the stable clot G1 and the unstable clot G2 becomes a sliding surface on which deep collapse is likely to occur.

  The illustrated collapse suppression structure 1 includes a main pipe 11 and a branch pipe 12. Both the main pipe 11 and the branch pipe 12 are constituted by perforated pipes. The main pipe 11 corresponds to a perforated pipe in the present invention, and the branch pipe 12 corresponds to another perforated pipe in the present invention. The main pipe 11 and the branch pipe 12 have different thicknesses. In the present embodiment, the main pipe 11 is constituted by a thick pipe having a diameter of 800 mm, and the branch pipe 12 is constituted by a thin pipe having a diameter of 50 mm.

  As described above, the reason why the pipes are different in thickness is due to the difference in function between the main pipe 11 and the branch pipe 12. That is, the main pipe 11 has a main function of suppressing an increase in the groundwater level during heavy rain. For this reason, in order to ensure a sufficient amount of drainage, the main pipe 11 is composed of a thick pipe. On the other hand, the branch pipe 12 has a main function of eliminating permeated water from the rock surface. Since the amount of water penetrating from the rock surface is sufficiently smaller than the amount of groundwater W during heavy rain, the branch pipe 12 is constituted by a thin tube.

  As shown also in FIG. 2, the main pipe 11 has a culvert part 13 and a rising part 14. The underdrain portion 13 is a portion mainly responsible for suppressing the rise of the groundwater level during heavy rain. For this reason, the underdrain portion 13 is constructed along the constant water level H in the vicinity of the constant water level H.

  Here, the water level H is not always constant, and some fluctuation occurs. However, with regard to the fluctuation amount of the constant water level H, the knowledge that about 1 to 2 m at the maximum is obtained. Therefore, in this embodiment, a range of ± 2 m is defined as the vicinity with respect to the constant water level H obtained by the boring survey, and the underdrain portion 13 is constructed in the vicinity of the constant water level H. More specifically, the culvert portion 13 is constructed at a height position slightly below the constant water level H obtained by the boring survey.

  The culvert portion 13 is constructed so as to extend from the slope in the rock G to the back. The near end of the underdrain portion 13 is slightly inclined downward toward the slope of the rock G, and the end face faces outward from the slope of the rock G. The end surface 13a of the culvert portion 13 functions as a drainage end. That is, the groundwater W that has flowed into the culvert portion 13 flows through the culvert portion 13 toward the drainage end 13a, and is discharged from the drainage end 13a to the outside.

  The rising portion 14 is provided integrally with the culvert portion 13 on the back side of the culvert portion 13. The interior of the stable soil mass G1 is set up to draw an arc on the back side of the unstable soil mass G2 (upstream side of the groundwater flow flowing from the stable soil mass G1 toward the unstable soil mass G2). That is, the main pipe 11 having the culvert part 13 and the rising part 14 is constituted by a perforated pipe curved upward.

  An upper end portion 14a of the rising portion 14 protrudes upward from the rock surface. That is, the rising portion 14 communicates the surface of the stable soil mass G1 and the culvert portion 13. The rising portion 14 takes in a part of the groundwater flow flowing from the stable soil mass G 1 toward the unstable soil mass G 2 and flows it to the underdrain portion 13. Therefore, the amount of groundwater W flowing into the unstable soil mass G2 can be reduced by the amount taken in at the rising portion 14.

  As shown in FIGS. 1 and 2, the branch pipe 12 is provided in the vertical direction from directly above the culvert portion 13. And the some branch pipe 12 is provided in the state located in a line with the axial direction of the culvert part 13. Each branch pipe 12 has an upper end 12 a protruding upward from the rock surface and a lower end 12 b connected to the underdrain portion 13. A hole is formed in the connecting portion of the culvert portion 13 to the branch pipe 12 and communicates with the branch pipe 12. For this reason, the groundwater W that has flowed into the branch pipe 12 flows down through the internal space and flows into the underdrain portion 13. Each branch pipe 12 takes in groundwater W that has permeated from the rock surface and quickly flows it to the underdrain portion 13. Accordingly, the amount of groundwater W flowing through the unstable soil mass G2 can be reduced by the amount taken in by the branch pipe 12.

  As shown in FIG. 3, in the present embodiment, a plurality of collapse suppression structures 1 are constructed in a fan shape in plan view so as to penetrate the unstable soil mass G2. Specifically, five collapse-suppressing structures 1 are constructed in a radial pattern with the drainage end 13a of the main pipe 11 as the center side. And the back side edge part (rise part 14) of the main pipe 11 which each collapse suppression structure 1 has is arrange | positioned at intervals so that the unstable earth lump G2 may be enclosed. Thus, since the plurality of collapse suppression structures 1 are arranged in accordance with the shape of the unstable soil mass G2, the stable soil mass G1 can be taken in a wide range of groundwater W flowing toward the unstable soil mass G2. The effect of suppressing deep layer collapse can be further enhanced.

  In the collapse suppressing structure 1 configured as described above, the underdrain portion 13 of the main pipe 11 is constructed along the constant water level H in the vicinity of the constant water level H. It is taken into the portion 13 and discharged from the drain end 13a. Thereby, it can suppress that a groundwater level becomes always higher than the water level H constantly. And since the groundwater W in the vicinity of the constant water level is the target for discharge, the groundwater level is not lowered below the constant water level H, and the problem of exhaustion of the groundwater W on the upstream side and excessive drainage on the downstream side can be prevented.

  Moreover, since the underdrain portion 13 is constructed slightly below the water level H at all times, a small amount of groundwater W can be discharged at all times, and the communication state can be easily confirmed.

  In addition, the main pipe 11 has a rising portion 14 that is continuous to the back side of the culvert portion 13, and this rising portion 14 rises inside the stable soil mass G1 upstream of the unstable soil mass G2 upstream of the groundwater flow. Therefore, the inflow amount of the groundwater W to the unstable soil mass G2 can be reduced, and the effect of suppressing the deep collapse can be enhanced.

  Moreover, since the collapse suppression structure 1 has the some branch pipe 12 which connects between the bedrock surface and the culvert part 13, the rainwater which permeate | transmits from the rock surface flows quickly into the culvert part 13 through the branch pipe 12. FIG. And the effect of suppressing deep layer collapse can be enhanced.

  Next, a procedure for constructing the above-described collapse suppression structure 1 will be described.

  First, as shown in FIG. 4, prior to the construction of the collapse suppression structure 1, a boring survey is performed as indicated by an arrow B. By this boring survey, the depth of the unstable soil mass G2, the boundary S between the unstable soil mass G2 and the stable soil mass G1, the constant water level H, etc. are grasped. Therefore, this boring investigation corresponds to a measurement process for measuring the water level H at all times.

  If a boring investigation is performed, as shown in FIG. 5, a boring hole BH1 is formed at a planned construction position of the main pipe 11. In the present embodiment, the boring hole BH1 is formed using a hydraulically driven drill unit (corresponding to a drilling device, not shown). This drill unit is installed on the drainage end 13a side (center side of the fan, see FIG. 3), and the rock G is excavated with a drill head attached to the tip of the drill pipe while feeding muddy water through the drill pipe.

  An electromagnetic wave generator is built in the drill head, and the position of the drill head in the drilling hole is grasped by receiving the electromagnetic wave generated from the electromagnetic wave generator with a receiver. Then, by guiding the drill head to the back side while adding the drill pipe, the culvert portion 13 is always drilled along the water level H so as to extend from the slope of the bedrock G to the back side. Thereafter, the rising portion 14 is drilled by guiding the drill head upward.

  When reaching the upper surface of the bedrock G, the drill head is removed, a back reamer that matches the external shape of the pipe to be buried is attached to the drill pipe, and a perforated pipe is connected to the back reamer. Then, by pulling back the drill pipe while performing muddy water injection and rotation of the back reamer, the natural ground becomes consolidated and the hole diameter is enlarged. Further, since the perforated pipe is connected to the back reamer, the perforated pipe is drawn and embedded in the expanded hole. When the back reamer is pulled back to the drill unit, the installation of the main pipe 11 is finished as shown in FIG. This installation process corresponds to a construction process in which the underdrain portion 13 is always constructed along the water level H.

  When the construction of the main pipe 11 is completed, the branch pipe 12 is installed as shown in FIG. In installing the branch pipe 12, a bore hole BH2 is formed by, for example, a boring rod, and then a perforated pipe constituting the branch pipe 12 is inserted into the bore hole BH2. In this case, the boring hole BH2 is formed vertically downward from the upper surface of the rock. And if it penetrates the bedrock G, the front-end | tip of a boring rod will be contact | abutted on the surface of the main pipe 11 (underdrain part 13), and a hole will also be formed in the surface of the main pipe 11. FIG. Thereafter, the boring rod is pulled out, and the branch pipe 12 is inserted into the boring hole BH2. If the necessary number of branch pipes 12 are inserted into the borehole BH2, the construction of one collapse suppressing structure 1 is completed.

  After that, the construction for the other collapse inhibiting structure 1 is performed in the same procedure. At this time, in this embodiment, since each collapse suppression structure 1 is constructed radially with the drainage end 13a as the center side, a plurality of collapse suppression structures 1 ( The main pipe 11) can be built inside the bedrock G.

  The above description of the embodiment is for facilitating the understanding of the present invention, and does not limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes equivalents thereof. For example, you may comprise as follows.

  In constructing the plurality of collapse suppression structures 1, the radial layout with the discharge end at the center has been described in the above embodiment, but the present invention is not limited to this layout. For example, as shown in FIG. 8, you may build the four collapse suppression structures 1 so that the culvert parts 13 extended in the back | inner side may become mutually parallel.

  Moreover, as shown in FIGS. 9 and 10, a drainage pump P that operates as the groundwater level H rises may be provided in the middle of the branch pipe 12. In this embodiment, a hose HO having a diameter smaller than the inner diameter of the branch pipe 12 is inserted into the branch pipe 12. And one end of the hose HO is always positioned at the height of the water level H. The hose HO is laid along the slope of the rock G through the upper end of the branch pipe 12, and the other end of the hose HO is disposed in the vicinity of the drainage end 13 a of the main pipe 11.

  The drainage pump P pumps up groundwater in the rock mass G and discharges it to the outside of the rock mass G through a hose HO. The drainage pump P is provided with a water level sensor (not shown) and operates when the groundwater level reaches a predetermined height. As this water level sensor, for example, a float type water level sensor capable of moving inside the branch pipe 12 can be used.

  In this embodiment, when the groundwater level becomes higher than the specified height, the drainage pump P forcibly discharges the groundwater. For this reason, the deep collapse of the bedrock G can be prevented more reliably. Furthermore, since the drainage pump P and the hose HO are installed using the branch pipe 12, the installation can be facilitated and the internal space of the branch pipe 12 can be used effectively.

  In this embodiment, since the other end of the hose HO is located in the vicinity of the drainage end 13a lower than the groundwater level, water is continuously discharged by the siphon principle (water head difference). For this reason, the power consumption of the drainage pump P can also be suppressed. Moreover, in this embodiment, although the set of the drain pump P and the hose HO is skipped and installed in the branch pipe 12, what is necessary is just to determine the installation number and installation location according to the field.

  Moreover, although the above-mentioned embodiment demonstrated the case where the five collapse suppression structures 1 were constructed | assembled, the number of structures is not restricted to five. For example, the number of constructions of the collapse suppression structure 1 may be one, three, or six or more.

  Regarding the main pipe 11 (perforated pipe), in the above-described embodiment, the pipe having the culvert part 13 and the rising part 14 is illustrated, but the pipe 11 may be configured by only the culvert part 13. Moreover, the culvert portion 13 is not limited to a linear shape, and may be curved in the horizontal direction.

  Regarding the construction height of the underdrain portion 13, in the above-described embodiment, it is always slightly below the water level H, but may be above the constant water level H as long as it is in the vicinity of the constant water level H. In addition, as mentioned above, if it is constructed slightly below the water level H at all times, the culvert portion 13 is functioning based on the fact that a small amount of groundwater W is continuously discharged (clogging occurs. Can be easily confirmed.

  The branch pipe 12 (other perforated pipe) is constructed in the vertical direction in the above-described embodiment, but is not limited to this configuration. For example, you may construct | assemble in the state inclined to front and rear, right and left.

  Moreover, regarding the main pipe 11 and the branch pipe 12, the diameter and the length are illustrations to the last, and are determined as appropriate according to the construction target site.

DESCRIPTION OF SYMBOLS 1 ... Collapse suppression structure, 11 ... Main pipe, 12 ... Branch pipe, 12a ... Upper end of branch pipe, 12b ... Lower end of branch pipe, 13 ... Underdrain part, 13a ... Drain end (end face of underdrain part), 14 ... Rising part, 14a ... Upper end of rising part, G ... Boulder, G1 ... Stable clot, G2: Unstable clot, S ... Boundary between stable clot and unstable clot, W ... Groundwater, H ... Normal water level, BH1 ... Boring hole, BH2 ... Bowling Hole, P ... drainage pump, HO ... hose

Claims (4)

A collapse-suppressing structure that suppresses the deep collapse of the bedrock,
A range of fluctuation is set above and below the constant level obtained in drilling survey based built along the lower side of the constant water level obtained in the boring survey, the slope of the drainage end the bedrock Having a perforated tube facing outward,
The bedrock has a stable clot and an unstable clot,
The perforated pipe is a culvert part constructed along the normal water level;
A collapse-suppressing structure characterized by having a rising portion that is provided integrally with the culvert portion and rises inside the stable soil mass upstream of the unstable soil mass in the groundwater flow. The collapse inhibiting structure according to claim 1, further comprising another perforated pipe communicating between the surface of the rock mass and the perforated pipe. The other perforated tube, and a water level sensor, according to claim actuated in response to the groundwater level the water level sensor detects, characterized in that interior and drain pump for discharging the groundwater outside the rock through the hose 2 The collapse-suppressing structure as described . The perforated pipe constructed along the lower side of the normal water level is constructed so as to be radial with the drainage end facing the outside from the slope of the rock in plan view. The collapse-suppressing structure according to any one of claims 1 to 3, wherein