JP5806506B2 - Manhole levitation prevention method - Google Patents

Description

In order to dissipate the increase in excess pore water pressure or the increase in groundwater pressure caused by the liquefaction phenomenon that occurred during an earthquake, the present invention provides a manhole that drains groundwater into the manhole through the wall surface. The present invention relates to a manhole levitation prevention method for realizing a levitation prevention structure.

  Many manholes emerged during the earthquake, causing sewer destruction and traffic problems. Many manholes are caused by an increase in buoyancy due to an increase in excess pore water pressure associated with ground liquefaction during an earthquake. However, the rise of manholes is not only caused by an increase in excess pore water pressure accompanying the liquefaction phenomenon of the ground, but may be caused by this increase when groundwater pressure increases.

  Recently, several techniques for preventing manholes from rising have been proposed. Among them, there is a technique for dissipating the excess pore water pressure by forming a through hole in the wall of the manhole and draining groundwater into the manhole when the excess pore water pressure rises due to liquefaction of the ground. is there.

  For example, in the invention described in Patent Document 1, a hole is formed in the wall portion of the manhole body so that the underground side communicates with the inside of the manhole body, and water flow from the underground side into the manhole body is allowed in the hole. In addition, a check valve for blocking the flow of water from the manhole to the underground side is provided. In this technique, even when a liquefaction phenomenon occurs in the ground during an earthquake, the liquefied water flows into the manhole, thereby suppressing the rise of the manhole. In particular, by providing a filter portion in the check valve, it is possible to prevent the inflow of earth and sand into the manhole.

  The invention described in Patent Document 2 includes a through pipe that penetrates the side wall of the manhole, a flexible tubular body that has water permeability connected to the outside of the manhole, and an underground that is connected to the inside of the manhole. And an inner pipe having an opening position higher than the natural water level. With this technology, the groundwater is ejected into the manhole during an earthquake, thereby reducing the increase in water pressure around the manhole and preventing the manhole from rising.

JP 2006-124966 A JP 2009-228392 A

  The techniques described in Patent Documents 1 and 2 prevent the manhole from rising by dissipating excess pore water pressure by taking groundwater into the manhole during an earthquake. In these techniques, it is necessary to smoothly take in the groundwater into the manhole, and if the groundwater cannot be taken in smoothly, the manhole may rise.

  For example, in the technique described in Patent Document 1, the hole formed in the wall portion of the manhole body directly faces the ground, a filter is disposed on the ground side, and a check valve is disposed in the hole. Yes. For this reason, when liquefied water flows in into a manhole, the stone or lump with a large shape can prevent the inflow into a manhole by a filter. However, fine particles of sand or earth may enter the hole and stay in the hole between the check valve. In this case, there is a risk that the smooth inflow of groundwater into the manhole is impaired.

  Further, even in the technique described in Patent Document 2, the inside of the flexible tubular body is hollow, and sand and soil that have passed through the water-permeable functional portion are flexible as groundwater flows into the manhole. There is a risk that it will stay inside the sex tube. In this case, there is a risk that the smooth inflow of groundwater into the manhole is impaired.

An object of the present invention, when an increase in growth and groundwater pressure of excess pore water pressure which causes buoyancy increase for manhole occurs, realizing a floating preventing structure of manholes to smoothly perform the drainage into groundwater manholes It is to provide a floating preventing construction method of the manhole to be.

  The first manhole levitation prevention method according to the present invention is based on the through-hole formed in the wall surface of the existing manhole, and cuts the ground and discharges the earth and sand to the manhole side to make it larger than the diameter of the through-hole. The method includes a step of forming a pilot hole in a water collection region having a large diameter and a step of filling a water collecting material into the pilot hole in the water collection region.

  In addition, the second method for preventing the manhole from rising according to the present invention cuts a natural ground on the basis of a through hole formed in the wall surface of the manhole and discharges earth and sand to the manhole side to form a pilot hole in the water collecting area. A step of forming, a step of filling the pilot hole of the water collection region with a stabilizer that temporarily stabilizes the collapsing region by preventing collapse of the pilot hole of the water collection region, and a lower part of the water collection region filled with the stabilizer A step of filling the hole with a water collecting material, and a step of sucking the stabilizer present in the water collecting region and removing it to the manhole side.

  In the first manhole rising prevention method according to the present invention, the ground is cut with reference to the through hole formed in the wall surface of the manhole and the earth and sand are discharged to the manhole side to form a pilot hole in the water collecting area. By filling the water collecting material into the pilot holes of the water collecting region, a water collecting region in which the ground of the natural ground is replaced with the water collecting material can be configured.

  Further, in the second manhole rising prevention method according to the present invention, the ground is cut with reference to the through hole formed in the wall surface of the manhole and the earth and sand are discharged to the manhole side so that the pilot hole in the water collecting area is formed. After forming and filling the pilot hole with a stabilizer to prevent the collapse of the natural ground and filling the water collection material in a state of being temporarily stabilized, then the stabilizer present in the water collection area is sucked into the manhole By removing to the side, it is possible to configure a water collection area in which the ground of the natural ground is replaced with a water collection material.

In the manhole levitation prevention structure (hereinafter simply referred to as “floating prevention structure”) realized by the manhole levitation prevention technique (hereinafter simply referred to as “method of levitation prevention”) according to the present invention, A water collection area communicating with the formed through hole is formed. In particular, since the catchment area is composed of a catchment material that replaces the ground of the natural ground, when groundwater flows from the natural ground into the manhole, excess pore water pressure or groundwater that causes an increase in buoyancy The increase in pressure (hereinafter simply referred to as “excess pore water pressure”) can be reliably dissipated in a short time.

Thus, it is possible by replacing the ground of rock mass in the catchment material, to form a water collecting area that permits reliable passage of groundwater. For this reason, even when the water collection area is left for a long period of time, if the excess pore water pressure increases due to the fluidization phenomenon that occurred during the earthquake, the groundwater can be surely drained into the manhole.

  Moreover, the surface area of the water collection area | region in a natural mountain can be enlarged because a water collection area | region has a diameter larger than the diameter of a through-hole. For this reason, when the groundwater is discharged into the manhole, it becomes possible to take in the groundwater from a wide area of the natural ground, and the excess pore water pressure can be dissipated in a short time without hindering the flow of the groundwater. In particular, even if the natural permeability of the natural ground is low, it is possible to increase the area for taking in groundwater, and the excess pore water pressure can be dissipated in a short time.

It is a figure explaining the structure of a floating prevention structure. It is a figure which shows the relationship between a water collection area | region and a through-hole. It is a figure explaining the state which wash | cleans a water collection area | region through a through-hole. It is a figure explaining the procedure of the 1st levitation prevention construction method. It is a figure explaining the procedure of the 2nd floating prevention construction method.

Hereinafter, the manhole floating prevention construction method according to the present invention will be described. The levitation prevention structure realized by the levitation prevention method according to the present invention increases the groundwater pressure when an excess pore water pressure that causes buoyancy increases due to the fluidization phenomenon of the ground during an earthquake or for some reason. When the groundwater is drained into the manhole reliably and smoothly, the excess pore water pressure (groundwater pressure) increased can be dissipated in a short time. Therefore, a water collecting area is formed by forming a through hole in the wall of the manhole and replacing the ground of the natural ground with a water collecting material continuously with the through hole, and the formed water collecting area to the manhole of the groundwater It is comprised so that passage of can be permitted.

  The water collection area is formed by forming a pilot hole in the natural ground and replacing the sediment inside the pilot hole with a water collection material. The method for forming the pilot hole in the natural ground is not particularly limited, and it can be formed by cutting the natural ground with a cylindrical cutter (casing) and discharging the earth and sand from the cut portion. . Moreover, it is possible to form a pilot hole by discharging the earth and sand while further widening the hole formed by the casing by other means. And it is possible to comprise a water collection area | region by filling a water collecting material in the prepared hole formed as mentioned above.

  Therefore, the boundary between the natural ground and the catchment area is not necessarily formed as a clear surface. For this reason, the diameter (thickness) and length (depth) of a water collection area | region cannot be expressed as a exact dimension.

  In the present invention, the natural ground includes the surrounding ground of the manhole including a layer made of backfilled earth and sand at the time of construction of the manhole, and a natural earth and sand layer existing around the backfilled earth and sand layer.

  The position and number of the through holes formed in the wall of the manhole and the water collecting areas formed in the natural ground in communication with the through holes are not particularly limited, and the conditions such as the ground level and groundwater level constituting the natural ground are not limited. Accordingly, it is preferable to set appropriately. In particular, it is preferable to form as many through holes and water collection regions as possible in order to dissipate the excess pore water pressure that has risen with the fluidization phenomenon that occurred during an earthquake in a short time. In general, it is preferable to form through holes and water collection regions at 3 to 5 locations in the circumferential direction of the manhole and at 2 to 3 locations in the height direction. However, it is a matter of course that the position and number are not limited.

  It is necessary to allow passage of groundwater to the manhole in the water collection area constructed by replacing the ground of the natural ground with water collection material. The water collecting material may be any material that can allow passage of groundwater, and the material and shape are not limited. As a water collecting material that can be used in constructing such a water collecting area, gravel layers and / or crushed stones (hereinafter simply referred to as “gravel”), a gravel layer formed by compacting, and gravel and fibers as described above are laminated. There are a laminated layer, a fiber layer having an appropriate fiber thickness, a porous layer made of a porous body, and the like, and these can be selectively employed.

  For example, when gravel is adopted as the water collecting material, the gravel needs to have a adjusted particle size. However, the particle size of gravel is not uniquely set, and is preferably larger than the particle size of earth and sand constituting the natural ground. And it is possible to comprise the water collection area | region which can accept | permit passage of groundwater by substituting the earth and sand of the site | part corresponding to the water collection area | region of the natural ground.

  Further, as the water collecting material, for example, natural fibers such as straw, synthetic resin fibers, fibers such as metal fibers, and the like can be employed. In particular, the manhole floating prevention structure needs to maintain a stable function over a long period of time, and the fiber itself is required to have a long life. For this reason, it was formed by rounding long fibers such as a sushi-like product made of a synthetic resin, a three-dimensional network formed using a fiber made of a synthetic resin, and a metal sushi-like product made of stainless steel. It is preferable to adopt a thing as a water collecting material.

  Further, as the water collecting material, a sponge-like porous body made of a synthetic resin foam, a spherical molded body made of a synthetic resin and having a large number of pores on the surface, or made of ceramics. It is also possible to employ a porous body.

  In the water collection area constituted by adopting the water collection material as described above, it is possible to allow groundwater to pass smoothly and to inhibit passage of earth and sand. For this reason, when the excess pore water pressure increases, the groundwater smoothly passes through the water collection region and drains into the manhole according to the increase, and the increased excess pore water pressure can be dissipated in a short time.

  Even if the water collecting area is configured to prevent the passage of sediment, it is difficult to prevent fine sediment from penetrating because it faces the sediment and groundwater for a long period of time. For this reason, it is possible to maintain stable water collection performance by supplying washing water to the water collection area through the through-hole, and returning the accumulated sediment to the natural ground by washing the water collection area. Is possible. The pressure and amount of washing water supplied to the water collection area are not particularly limited, and it is preferable to supply high-pressure water having a pressure higher than the groundwater pressure of the natural ground.

  In particular, it is preferable to provide a connecting member for connecting a supply member for supplying cleaning water to the through hole, so that the supply member for supplying cleaning water can be easily attached and detached. When attaching a connecting member that connects the supply member to the through hole, a base material may be provided in the through hole, and the connecting member may be attached to and detached from the base material as necessary.

  The supply member for supplying cleaning water is not particularly limited as long as it has a function capable of supplying high-pressure water for cleaning safely and reliably. One having such a function is a hose for high-pressure water, which can be preferably used. In addition, the size of the supply member is not limited, and it is preferable that the size is large in order to finish the cleaning of the water collection region in a short time. It is preferable to set appropriately according to conditions such as the diameter of the hole and the dimensions of other members.

  The ratio of the thickness of the water collecting region to the through hole is not particularly limited, but is preferably larger than the through hole. Further, the length of the water collecting area formed in the natural ground is not particularly limited, and is preferably set as appropriate according to conditions such as the hydraulic conductivity of the natural ground and the groundwater pressure in a normal state. In particular, the water collection area preferably has a large surface area in order to drain a sufficient amount of groundwater into the manhole in a short time.

  For example, when the natural permeability of the natural ground is large, the surface area of the water collection region may be small, and even if it is formed with a thickness substantially equal to the through hole, a sufficient amount of groundwater can be allowed to pass. In this case, the thickness of the water collection region may be approximately equal to the diameter of the through hole, and the length may be about 400 mm to about 500 mm. Also, if the natural permeability of the natural ground is small, it is necessary to increase the surface area of the catchment area, about 1.5 times to about 3 times the diameter of the through hole, and about 300 mm to about 400 mm deep. It is preferable to form by.

  When the pilot hole in the water collecting area is formed in the natural ground, it is possible to easily fill the pilot hole with the water collecting material if there is no possibility that the natural mountain will collapse stably. However, when the ground is unstable and the pilot hole is likely to collapse, it is preferable to fill the water collecting material in a state where the pilot hole is filled with a stabilizer to prevent the pilot hole from collapsing. Then, after the filling of the water collecting material into the pilot hole is completed, it is possible to configure a water collecting region that allows passage of groundwater by sucking and removing the stabilizer present in the water collecting region. .

  When forming a through-hole in the wall surface of a manhole, it is preferable to form it in the manufacturing process of the manhole, but it is necessary to construct the manhole currently installed on site. In consideration of introducing a sufficient amount of groundwater into the manhole in a short time, the diameter of the through hole is preferably as large as possible. However, since the strength of the manhole itself decreases as the through hole having a large diameter is formed, there is a limitation naturally. According to the knowledge of the present inventors, the diameter of the through hole is preferably about 100 mm to about 150 mm. However, it is a matter of course that the size is not limited to this.

  When the groundwater level in the ground is lower than the position of the through hole formed in the wall surface of the manhole, the through hole may be a simple hole. In this case, normally, groundwater does not flow into the manhole from the through hole.

  However, when the water level of the groundwater is higher than the position of the through hole, the ground water always flows into the manhole from the through hole, which imposes an excessive burden on the downstream sewage treatment facility. For this reason, it is preferable to provide a valve (pressure setting valve) that opens and introduces groundwater into the manhole when the excess pore water pressure exceeds a preset pressure. By providing such a pressure setting valve, it is possible to prevent the groundwater from flowing into the manhole in a normal state, and to introduce the groundwater into the manhole when the excess pore water pressure increases during an earthquake.

  Even if the water collecting area is configured to prevent the passage of sediment, it is difficult to prevent fine sediment from penetrating because it faces the sediment and groundwater for a long period of time. For this reason, it is preferable to provide a connection member for connecting a hose that supplies cleaning water to the through hole. And by connecting a pump to a connecting member via a hose and supplying high-pressure water periodically, high-pressure water is supplied to the water collection area through the through-hole, and this high-pressure water is fed from the water collection area to the natural ground. It is possible to wash the water collection area by passing it through the water.

  When a pressure setting valve and a connecting member are attached to the through hole, they may be configured so that they can be removed and replaced as necessary. A through hole having a large diameter is formed and pressure is applied to the through hole. You may comprise with both a setting valve and a connection member attached.

Next, a configuration example of the floating prevention structure will be described with reference to FIGS . Levitation prevention structure A, as shown in FIG. 1, when the manhole 1 provided to the conduit B typified conduit for sewer excess pore water pressure during fluidization phenomenon occurring during an earthquake rises It is configured so that it can be prevented from rising due to acting buoyancy.

  The manholes 1 are installed in the pipe B at predetermined distances in the length direction, and each manhole 1 has a dimension corresponding to the depth from the ground surface to the pipe B. For this reason, the manhole 1 is constructed by stacking several straight wall pipes and slant wall pipes provided on the ground surface and firmly connecting them together.

  A plurality of through holes 2 are formed in the wall surface of the manhole 1 so as to penetrate the wall surface. The number of the through-holes 2 is not particularly limited, but in this embodiment, the number of through-holes 2 is formed at a total of eight places, four places on the circumference and two places in the height direction.

In this configuration example , each through hole 2 has a diameter of about 100 mm. As described above, the conditions such as the diameter, the number, and the position of the through holes 2 are not limited, and may be appropriately set according to the conditions of the natural ground C including the geology and the groundwater level constituting the ground. preferable.

  A water collection region 3 is formed in the natural ground C in communication with a through hole 2 formed in the wall surface of the manhole 1. The water collection region 3 is configured to allow passage of ground water in the natural ground C when it is introduced into the manhole 1 through the through hole 2.

The relationship with the diameter of the through-hole 2 in the water collection region 3 and the depth with respect to the natural ground C are not uniquely set, and groundwater can be collected efficiently when the excess pore water pressure rises during an earthquake. Thus, it is possible to set several shapes. For example, in the configuration example of the water collecting region 3 shown in FIG. 2A, the diameter has a dimension equal to that of the through hole 2, and the depth in the natural ground C has a sufficiently deep dimension. .

  Moreover, the water collection area | region 3 shown to the same figure (b) has a larger diameter than the through-hole 2, and the depth with respect to the natural ground C is shallower than the case of (a). Further, the water collecting region 3 shown in FIG. 5C has a diameter sufficiently larger than that of the through hole 2, whereas the depth with respect to the natural ground C is formed to be the shallowest.

The shape of the water collecting region 3 as described above is appropriately selected in accordance with the condition for the water permeability of the natural ground C. For example, the configuration example of the water collecting region 3 having a relatively thin thickness and a long length shown in FIG. 2A is preferably applied when the permeability coefficient of the natural ground is large and the water permeability is good. . Moreover, it is preferable to apply the water collection area | region 3 whose thickness shown in the figure (b) is thicker than the through-hole 2 and whose length is comparatively long when water permeability is a little inferior to the figure (a). . The water collecting region 3 having a sufficiently large thickness and a short length shown in FIG. 5C is preferably applied when the permeability coefficient of the natural ground is small and the water permeability is inferior.

  The structure that allows the passage of groundwater in the catchment area 3 is a gravel layer of gravel with adjusted particle size filled in the catchment area 3, or the water permeability filled in the catchment area. And a layer made of a fibrous body or a porous body that can prevent passage of earth and sand, or a layer in which these are mixed.

In the configuration example shown in FIG. 2 (a), the backfilled ground around the manhole is a mountain sand layer, and the thickness of the water collecting region 3 is approximately equal to the diameter of the through hole 2 formed in the wall surface of the manhole 1. Gravel layer filled with gravel that has a depth of about 400 mm with respect to the natural ground C and is preliminarily packed in the water collecting region 3 so that the particle size is adjusted in the range of about 1 mm to about 5 mm. 4. In addition, as mentioned above, the particle size of gravel is set larger than the particle size of the earth and sand which comprises a natural ground, and is not uniquely set to the said dimension.

  In the water collecting region 3 having the gravel tank 4 as described above, it is possible to allow the passage of groundwater when the groundwater is introduced into the manhole 1 through the through hole 2, and at this time, earth and sand are mixed in. If it is, it is possible to prevent the passage of earth and sand of a certain size or more. In addition, when the groundwater is not introduced into the manhole 1 and no flow is generated, the groundwater penetrates into the gravel layer 4 and, accordingly, earth and sand of a certain size or less also penetrates. However, even when a flow into the inside of the manhole 1 occurs from this state, it is possible to prevent earth and sand of a certain size or more from entering the manhole 1.

In this configuration example , a pressure setting valve 6 is provided in the through hole 2 formed in the wall surface of the manhole 1 as shown in FIG. The pressure setting valve 6 has a function of opening when the excess pore water pressure increases and draining groundwater into the manhole 1, and an operating pressure for opening in advance is set. The structure of the pressure setting valve 6 is not particularly limited. For example, the pressure setting valve 6 is generally used as a relief valve configured to press a valve body against a valve seat provided on a natural ground side by an urging member such as a spring. It is possible to adopt a structure having the same structure.

  The structure in which the pressure setting valve 6 is installed in the through hole 2 is not particularly limited, and is attached to a bracket 7 fixed to the through hole 2. The bracket 7 may be fixed to the through hole 2 using a fixing tool such as a screw or a nail. In this embodiment, the bracket 7 is constituted by a cylindrical member made of synthetic resin, the pressure setting valve 6 is attached using a screw provided on the cylindrical portion 7a, and the spring property is formed continuously with the cylindrical portion 7a. The hook portion 7b having the hook is fixed by being hooked on the surface of the through hole 2 on the ground mountain C side.

  A filter 8 is provided at the boundary between the through hole 2 and the water collection region 3. In the filter 8, when the excess pore water pressure rises and the groundwater is drained into the manhole 1, the gravel constituting the gravel layer 4 in the water collection region 3 is pushed out to the through hole 2 along with the flow of the groundwater. This is to prevent this. Therefore, the structure of the filter 8 is not limited as long as it has the above function.

  In the levitation prevention structure A configured as described above, when the excess pore water pressure increases due to the liquefaction phenomenon that occurred during the earthquake, the increased groundwater pressure acts on the pressure setting valve 6 to open the pressure setting valve 6. Then, groundwater is drained into the manhole 1. The excess pore water pressure increased by the drainage of the groundwater into the manhole 1 is dissipated, and the manhole 1 can be prevented from rising.

  In particular, since the water collection area 3 is formed in the natural ground C, groundwater can be collected smoothly and reliably, and a sufficient amount of groundwater can be drained into the manhole 1 in a short time. It becomes possible. Moreover, since the gravel layer 4 formed in the water collecting region 3 allows passage of groundwater and inhibits passage of earth and sand, in addition to smooth drainage of the groundwater to the manhole 1, it inhibits discharge of earth and sand. It is possible.

  Further, when there is no flow of groundwater to the manhole 1, the groundwater has permeated into the gravel layer 4 in the catchment area 2, and with this infiltration, very fine earth and sand may enter the gravel layer 4 and stay there. There is. However, although the accumulated very fine earth and sand are introduced together when drainage of groundwater into the manhole 1 is started, earth and sand of a certain size or more are not discharged into the manhole 1.

However, when there is no drainage of the groundwater to the manhole 1 for a long period of time, fine particles of earth and sand may enter the gravel layer 4 in the water collection region 2, which may hinder the flow of groundwater. For this reason, in this configuration example , as shown in FIG. 3, a terminal 9 serving as a connection member is attached to the through hole 2, and a cap nut 10a provided on a hose 10 serving as a supply member is connected to the terminal 9 The gravel layer 4 can be washed by supplying high-pressure water from 10.

  The pressure of the high-pressure water supplied to the terminal 9 may be higher than the groundwater pressure. Thus, by supplying high-pressure water from the hose 10 to the gravel layer 4 in the water collecting region 3 through the terminal 9, the supplied high-pressure water flows as indicated by arrows in the figure, and this flow causes the gravel layer to flow. It is possible to remove the earth and sand staying at 4 from the water collection area 3 to the natural ground C side. That is, it is possible to wash the gravel layer 4 in the water collection area 3.

  Next, the 1st construction method and the 2nd construction method at the time of constituting a floating prevention structure are explained. In the construction method according to the present invention, the stage at which the through hole 2 formed on the wall surface of the manhole 1 is processed is not limited. That is, when the manhole 1 is newly installed, it is possible to process the through hole 2 on the straight wall pipe in advance at the factory stage. Further, when the manhole 1 is an existing one, it is necessary to process the through hole 2 at the installation site. In this embodiment, the existing manhole 1 is targeted.

  The first construction method will be described with reference to FIG. This construction method is intended for a natural mountain having a large water permeability coefficient and sufficiently good water permeability, and corresponds to a case where the water collecting region 3 constituting the natural mountain may have the same thickness as the diameter of the through hole 2. .

  First, as shown in FIG. 4A, a setup for forming the through hole 2 in the manhole 1 is performed. In this case, the core boring cutter 15 is installed facing the position where the through hole 2 of the manhole 1 is to be formed. The cutter 15 is formed in a cylindrical shape having an outer diameter corresponding to the diameter of the target through-hole 2, and has a casing 15 a in which a cutting edge for cutting concrete is formed at a tip portion. A casing head 15b that is gripped and rotated by a chuck of a driving device (not shown) is provided on the rear end side of the cutter 15. In particular, the casing head 15 b is configured to be detachable from the casing 15 a of the cutter 15.

  After the setup is completed, the cutter 15 is rotated while being held horizontally, and is advanced in the direction of the manhole 1, whereby the wall surface of the manhole 1 is cut to form the through hole 2. After the through hole 2 is formed on the wall surface of the manhole 1, the cylindrical concrete block cut from the wall surface of the manhole 1 is eliminated by once detaching the cutter 15 from the wall surface of the manhole 1. Thereafter, the cutter 15 is continuously advanced to advance into the natural ground C, so that the portion corresponding to the pilot hole of the water collection region 3 is communicated with the through hole 2 as shown in FIG. .

  After the cutter 15 is advanced to a preset length (depth) to form a portion corresponding to the pilot hole of the water collection area 3 in the natural ground C, the water collection area as shown in FIG. 3 is discharged into the manhole 1 to form a pilot hole. In this operation, first, the state in which the cutter 15 advances to the ground C is held, the casing head 15b is detached from the casing 15a, and then the screw 16 is inserted into the casing 15a and the cover 16a is attached to the casing 15a. Install. Next, by rotating the screw 16 in this state, the screw 16 is caused to function as a discharging conveyor, and the earth and sand inside the casing 15a is discharged.

  After discharging the earth and sand in the casing 15a to form a pilot hole in the natural ground C, gravel as a water collecting material is filled in the pilot hole. As shown in FIG. 4D, the gravel filling of the pilot holes in the water collecting area 3 is performed smoothly by setting the rotation direction of the screw 16 to the direction opposite to that when the screw 16 functions as a discharge conveyor. It is possible. That is, when gravel is supplied to the casing 15a of the cutter 15 with the screw 16 rotated as described above, the supplied gravel is transported to the pilot hole side of the water collection region 3 and packed. Therefore, by appropriately adjusting the casing 15a and the screw 16 from the water collection region 3 and the amount of gravel packed, it is possible to adjust the compaction state of the gravel with respect to the water collection region 3, and to achieve a desired compaction. The state can be realized and filled.

  In addition, it is also preferable that after the gravel is compacted and filled in the prepared hole of the water collection area 3, an operator in the manhole 1 sticks the water collection area 3 with a rod-like object to realize a higher consolidated state. In this way, the gravel layer 4 is formed by filling the prepared holes formed in the natural ground C with gravel, whereby the water collecting region 3 can be configured.

  After forming the water collecting region 3 having the gravel layer 4 on the natural ground C as described above, as shown in FIG. 5E, the bracket 7 is attached to the through hole 2 and the filter 8 is attached. A pressure setting valve 6 is attached to 7.

  By performing the above-described series of operations on the wall surface of the manhole 1 in order or for each process, the anti-floating structure A can be configured.

  Next, the second construction method will be described with reference to FIG. This construction method is intended for a natural mountain where the natural permeability of the natural ground is small and does not have sufficient water permeability, and the water collection region 3 has a thickness larger than the diameter of the through hole 2 in accordance with the hydraulic conductivity of the natural ground. It is configured as follows.

  In this embodiment, an unstable ground is targeted, and a stabilizer is injected into the ground when the pilot hole of the water collection region 3 is formed. However, if the natural ground is sufficiently stable, it is natural that injection of a stabilizer to the natural ground is not necessary.

  Moreover, even if it is a 2nd construction method, the process (FIG. 4 (a), the process of (b)) until it excavates the pilot hole of the water collection area | region 3 in a natural ground is the same as the 1st construction method mentioned above. Therefore, illustration and description are omitted.

  Therefore, the process after the state which formed the through-hole 2 in the manhole 1 and excavated the natural ground with the cutter 15 is demonstrated using FIG.

  As shown in FIG. 5 (a), after excavating the natural ground C with the cutter 15, a pump 17 is connected to the casing 15a to supply a solution-type water glass-based ground stabilizer 18, and this casing 15a is used to By injecting into the natural ground C, the natural ground is temporarily stabilized. At this time, the injection timing of the ground stabilizer 18 and the extraction timing of the casing 15a are not limited. For example, when a hole to the extent that the ground stabilizer 18 can pass is formed in the cylindrical portion of the casing 15a, the ground stabilizer 18 can be injected while maintaining the excavation state with respect to the natural ground C. Further, the ground stabilizer 18 may be injected from the tip of the casing 15a while the casing 15a is pulled out from the natural ground C.

  After the ground stabilizer 18 is injected and stabilized around the water collection region 3 assumed in advance in the natural ground C, the natural ground C is expanded through the through hole 2 as shown in FIG. Thus, a pilot hole for the water collecting region 3 is formed. At this time, the natural ground C is kept in a stable state by the injected ground stabilizer 18, and the surface portion constituting the pilot hole does not collapse.

  A gravel layer 4 is formed by forming a pilot hole in the catchment area 3 having the desired thickness and depth in the natural ground C, and then filling gravel into the pilot hole and filling the gravel while filling the gravel. . When the gravel layer 4 is configured in this way, the ground stabilizer 18 remains in the natural ground C around the gravel layer 4.

  After forming the water collecting region 3 having the gravel layer 4 as described above, a suction pump 19 is connected to the through hole 2 to remove the ground stabilizer 18 from the water collecting region 3 as shown in FIG. Aspirate and discharge. By discharging the ground stabilizer from the water collection region 3 in this way, it becomes possible to allow passage of groundwater in a stable state via the water collection region 4 and the gravel layer 4.

  After the water collecting region 3 is formed in the natural ground C as described above, a bracket 7 is attached to the through hole 2 and a filter 8 is attached to the through hole 2 as shown in FIG. 6 is attached. Furthermore, the floating prevention structure A can be configured by performing the above-described series of operations on the wall surface of the manhole 1 in order or for each process.

  The method for preventing a manhole from rising according to the present invention is advantageous when used for an existing manhole or a new manhole.

A Lifting prevention structure B Pipe line C Ground 1 Manhole 2 Through-hole 3 Water collecting area 4 Gravel layer 6 Pressure setting valve 7 Bracket 7a Cylindrical part 7b Hook part 8 Filter 9 Terminal 10 Hose 10a Cap nut 15 Cutter 15a Casing 15b Casing head 16 Screw 16a Cover 17 Pump 18 Ground stabilizer 19 Suction pump

Claims (2)

A step of cutting a natural ground on the basis of a through hole formed in a wall surface of an existing manhole and discharging earth and sand to the manhole side to form a pilot hole in a water collection region having a diameter larger than the diameter of the through hole When,
Filling a water collecting material into a pilot hole in the water collecting region;
A manhole levitation prevention method characterized by containing Cutting the natural ground on the basis of the through hole formed in the wall surface of the manhole and discharging the earth and sand to the manhole side to form a pilot hole in the water collecting area;
Filling a pilot hole in the water collection area with a stabilizer that prevents the pilot hole in the water collection area from collapsing and temporarily stabilizes;
Filling a water collecting material into a pilot hole in the water collecting region filled with the stabilizer;
Sucking the stabilizer present in the water collection area and removing it to the manhole side;
A manhole levitation prevention method characterized by containing