JP4484068B2 - Open shield method - Google Patents

Description

  The present invention relates to an open shield method for constructing an underground structure such as an underground passage such as a water and sewage system, a common ditch, a telegraph / telephone, etc. in an urban area.

  The open shield method is a rational method that utilizes the advantages of the open cut method (open cut method) and the shield method, and the outline of the open shield machine 1 used in this open shield method is shown in FIG. The front, rear, and top surfaces of the plate 1a and the bottom plate 1b connected to the side wall plates 1a are opened, the front ends of the side wall plate 1a and the bottom plate 1b are formed as blade edges 11, and the center of the side wall plate 1a is formed. Alternatively, the propulsion jacks 2 are arranged close to the rear end in the vertical direction toward the rear. In the figure, 3 indicates a partition wall.

  The open shield method to be constructed using such an open shield machine 1 is not shown in the figure, but this open shield machine 1 is installed in the start pit, and the propulsion jack 2 of the open shield machine 1 is extended so as to be within the start mine. The open shield machine 1 is advanced by taking the reaction force against the reaction force wall, the first concrete box 4 forming the underground structure is suspended from above, and the propulsion is shrunk in the tail portion 1c of the open shield machine 1 Set behind jack 2. A strut is disposed between the propulsion jack 2 and the reaction wall to adjust the distance appropriately.

  In addition, the start pit is made up of a retaining wall, and in order to start the open shield machine 1, a part of this retaining wall is mirror-cut. If necessary, the ground is improved at the front part of the starting pit by chemical injection or the like. Sometimes it is left.

  Excavator 9 such as an excavator excavates and removes soil from the front or top surface of open shield machine 1. At the same time as or after this earth removal step, the propulsion jack 2 is extended to advance the open shield machine 1. In the case of this advancement process, a pushing angle 8 made of a frame made of box steel or mold steel is arranged in front of the concrete box 4, and the open shield machine 1 receives a reaction force from the concrete box 4 set rearward. Take.

  Then, the second concrete box 4 is suspended in the tail part 1 c of the open shield machine 1 in front of the first concrete box 4. Thereafter, the same soil removal process, advance process, and concrete box 4 setting process are repeated as appropriate, and the concrete boxes 4 are sequentially left in the ground as the open shield machine 1 moves forward. Put backfill 5 on the upper surface of the body 4.

  When the concrete box 4 is suspended in the tail part 1c of the open shield machine 1, a height adjusting material 7 such as a concrete block is disposed under the concrete box 4, and the concrete part 4 is placed in the tail part 1c. The grout material 6 is filled in the left and right and lower spaces of the box 4.

  In this way, if the open shield machine 1 reaches the reaching mine, it is removed and the construction is completed.

Concrete a box body 4 is made of reinforced concrete, made of a left side plate 4a, the right plate 4b and the upper floor plate 4c and the lower floor 4d as shown in FIG. 9, is open to the front and rear surfaces as the opening 10.

To describe here the subsequent step of injecting the grout 6 in detail, the injection of grout 6 performs concrete box-body 4 as shown in FIG. 10 after setting, before promoting open shield machine 1 Thus, the grout material 6 is filled as a back-filling injection material as a primary injection between the outside of the concrete box 4 and the tail portion 1c.

Then, if the primary injection is completed, to excavate the working face natural ground 12 in excavating machine such as a backhoe, as shown in FIG. 11. In this case, the stress in the ground that had been maintained before excavation of the face hill 12 by the excavator also changed due to the change in groundwater level of the face hill 12 due to excavation in addition to the release of the stress due to excavation. The natural ground becomes easy to loosen.

  If the groundwater level is high, the ground will be scoured due to changes in the groundwater level due to excavation. In particular, sandy soil with a high groundwater level tends to loosen more easily than viscous soil, even if it has a relatively high fine particle content and can be expected to be self-supporting, and the impact on the surrounding area is also large.

  Therefore, the slide retaining plate 13 provided at the blade edge 11 is extended forward, thereby preventing loosening and collapse of the ground on the side of the face mountain 12.

In this way, if the open shield machine 1 is propelled while preventing the lateral collapse of the face hill 12, tail voids are generated accordingly. Therefore, as shown in FIG. 12 , while propelling the open shield machine 1, the tail void is filled with the back injection material 14 as secondary injection.

  The prior art is generally performed by those skilled in the art, and is not related to a known invention.

  The propulsion of the open shield machine 1 progresses while balancing the jack thrust of the open shield machine 1 and the propulsion resistance acting on the open shield machine 1 sequentially after excavating the face mound 12 or while excavating the face mound 12. However, since there is a difference between the generation rate of tail voids generated by the propulsion of the open shield machine 1 and the filling speed of the secondary injection, back injection is performed on the tail voids generated by the end of the propulsion (shield machine plate thickness) It is difficult to fill (secondary injection) almost completely, and there is a risk that the tail void will collapse due to the looseness of the ground before the completion of the secondary backfill injection, and there is also the effect of land subsidence to the surroundings. It tends to occur.

  The object of the present invention is to reduce the looseness of natural ground during excavation, and at the time until the completion of secondary backfill injection filling into the tail void (shield machine plate thickness) generated by the propulsion of the open shield machine. Can be prevented from collapsing due to the looseness of the natural ground, and the influence on the surroundings can also be prevented, and in this case, if a certain degree of independence can be expected in the natural ground, the looseness of the natural ground can be efficiently taken into consideration It is to provide an open shield method that can prevent the above.

  The present invention eliminates the disadvantages of the conventional example, and the invention according to claim 1 includes a step of excavating and discharging soil in front of the front or upper surface opening of an open shield machine, and a concrete by extending a propulsion jack. The process of advancing the shield machine with the reaction force of the box, and a new concrete box is hung from the top of the propulsion jack shrunk in the tail part of the shield machine and set when propelling the shield machine. In the open shield method of burying concrete boxes in tandem by repeating the process of backfilling the tail void as appropriate, silty sand and silt having a fine particle content (74 μm or less) of about 15 to 20% or more or If the groundwater level is low due to clay-mixed gravel, clay sand, or clay sand gravel, and there is almost no impact on the surroundings due to scouring, N value = 1 In the soft clay soil of about 3 can be expected self-sustainability of natural ground, but at least the side ground is self-supporting, such as when the natural ground deformation during excavation is large and there are concerns about the impact on the surroundings In order to prevent the tail void from collapsing due to the looseness of the side ground before the backfill injection filling is completed, temporary and partial ground improvement is applied to the side ground by chemical injection or high-pressure jet stirring method. The gist is to integrate the soil of the improved body improved with the ground and the soil between the improved bodies and reduce the disturbance of the natural ground by the arch action effect of the unmodified ground.

  According to the first aspect of the present invention, when back injection is carried out into the tail void, even if there is a difference between the generation rate of the tail void generated by the propulsion of the open shield machine and the filling speed of the secondary injection, Since the mountain has undergone ground improvement, it is possible to prevent the looseness of the natural ground, and during this time, the tail void can be prevented from being crushed by the looseness of the natural ground.

  In this case, if there is a certain level of independence in the ground, a certain degree of arch action effect can be expected for the unimproved part, and when the secondary back injection is performed in the tail void, the secondary back injection filling is completed. During this period, it is only necessary to prevent the tail voids from being crushed by the looseness of the ground, so it is sufficient that the looseness of the ground is temporarily reduced. It is not necessary to resist the earth pressure acting from the period ground and suppress loosening. Even with such partial ground improvement, the arch action effect of the unmodified ground and the earth retaining function of the open shield machine itself Therefore, it is possible to achieve the purpose sufficiently without performing the entire improvement, and the economy is excellent.

  In the invention according to claim 2, in the ground improvement, in the place where there is almost no groundwater in the side ground, columnar improvement bodies are arranged in a lattice shape, and each improvement body superposes the corners, The main point is to partially improve the above.

  According to the present invention described in claim 2, since the natural ground is partially improved by arranging the columnar improvement bodies in a lattice shape and partially improving the whole, there is almost no groundwater in the side natural ground. This is especially effective for soils with some degree of independence.

In the invention according to claim 3 , the ground improvement is made by arranging short columnar bodies in the lower part in a place where the groundwater level of the side ground is low, and arranging the columnar bodies having different long and short lengths alternately in parallel. The gist of this is to improve the entire surface by continuously polymerizing the side portions of adjacent columnar bodies in the lateral direction.

According to the third aspect of the present invention, only the lower part is improved entirely, and the upper part is partially improved, so that the soil has a certain degree of independence, and the groundwater level is low. It is effective in places where the collapse of

The gist of the invention according to claim 4 is that the ground improvement is arranged such that the columnar bodies are arranged in a comb tooth shape at intervals.

According to the fourth aspect of the present invention, since the continuous columnar improvements are arranged in the vertical direction, the content of fine particles is about 30% or more, and the soil is free standing. It is effective in places where the impact on the surroundings is expected to be high.

  As described above, the open shield construction method of the present invention aims to reduce loosening of the ground during excavation and to perform secondary backfill injection filling of tail voids (thickness of shield machine plate) generated by propulsion of the open shield machine. By the time it is completed, tail voids can be prevented from collapsing due to loose ground, and the effects on the surroundings can also be prevented.

  And in this case, if there is a certain level of independence in the natural ground, a certain degree of arch action effect can be expected for the unimproved part, and when the secondary back injection is injected into the tail void, Since it is only necessary to prevent the tail void from being crushed by the looseness of the natural ground before completion, the ground improvement may be partial enough to temporarily reduce the looseness of the natural ground.

  Therefore, it is not necessary to resist the earth pressure acting from the ground for a long period of time only by improving the ground surface continuously, and to suppress loosening. The purpose of the mountain can be fully achieved without any improvement by the arch action effect of the mountain and the earth retaining function of the open shield machine itself.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory view showing a first embodiment of the open shield method according to the present invention (FIG. 1 (a) is a view of the ground improvement range seen from the front side, and FIG. 1 (b) is a view seen from the side. ) Since the outline of the open shield method has already been described, detailed description thereof is omitted here.

  In particular, the present invention relates to ground improvement when the side ground has a certain degree of independence. Here, a certain degree of independence means, for example, that the content of fine particles (74 μm or less) is about 15 to 20% or more. If the groundwater level is low due to silty sand and silt or clay mixed gravel, clay sand, clay sand gravel, and there is almost no impact on the surroundings due to scouring, soft soil with N value = 1 to 3 This is a case where natural ground deformation at the time of excavation is large and the influence on the surrounding area is concerned, and a certain degree of arch action effect can be expected for an unimproved portion.

  If the side ground is a soil that satisfies the above conditions and has a certain degree of independence, and there is little or no groundwater, prior to filling the back injection material 14 into the tail void as secondary injection As shown in FIG. 1, short columnar improvement bodies 15 are arranged in a lattice pattern on the side ground, and the ground is partially improved.

  As a ground improvement method, for example, a chemical solution injection method or a high-pressure jet stirring method is used. In the chemical injection method, as shown in FIG. 1, the injection pipe 16 is inserted into the ground where the improved body 15 is formed from the ground, and the chemical (solidification material) is injected into the ground from the injection pipe 16 and consolidated. It creates soil, lowers the water permeability of the ground, and strengthens the ground.

  In addition, the high-pressure jet agitation method uses a boring machine to drill holes to the target depth, and then sprays the improved material (grout) from the lower end of the rod at high pressure to cut the ground and simultaneously mix and agitate the soil particles and grout. This is a method for producing a cylindrical solid body.

  In this way, the side ground of the open shield machine 1 is partially improved by arranging the columnar improvement bodies 15 in a lattice pattern. Such ground improvement has a certain degree of independence in the ground, so a certain degree of arch action effect can be expected for the unimproved part, and when the secondary back injection is injected into the tail void, the secondary back injection filling is completed In the meantime, since it is only necessary to prevent the tail void from being crushed by the looseness of the natural ground, the ground improvement is sufficient to temporarily reduce the looseness of the natural ground.

  And even in the case of partial ground improvement, in addition to the effect of preventing loosening of the natural ground by the partial ground improvement itself, the arch action effect of the natural ground in the unimproved part and the earth retaining function of the open shield machine itself The objectives can be fully achieved without any overall improvement.

  Further, when the ground is cohesive soil and has an adhesive force, a ground pile adheres to the side wall plate 1a of the open shield machine 1 during the propulsion of the open shield machine 1, and the side wall plate 1a of the open shield machine 1 as shown in FIG. Pulling a nearby natural ground, a large amount of propulsive force is required to propel the open shield machine 1.

  As a result, the natural ground in the vicinity of the open shield machine 1 is disturbed and affects neighboring houses and the fence 17 of the house. By improving the ground as described above, the ground as shown in FIG. It is only the soil 18 between the open shield machine 1 and the ground improved that the mountain is pulled. Incidentally, this interval is actually about 0 to 10 cm, and disturbance of natural ground can be reduced.

  Further, as described above, since the ground is pulled only by the soil 18 between the open shield machine 1 and the ground improved, the soil is tightened between the improved bodies 15 as shown in FIG. The soil of the improved body 15 whose effect has been increased and the ground has been improved, and the soil between the improved bodies 15 are integrated, so that the disturbance of the natural ground can be further reduced and the influence on the surroundings can be reduced.

FIG. 2 shows a second embodiment, in which the natural ground has a certain degree of self-supporting soil and the groundwater level is low, but collapse near the bottom of the excavation is assumed when excavating Mt.

  In such a case, the short columnar improvement body 15a is arranged at the lower part, and the short improvement body 15a and the long columnar improvement body 15b are alternately arranged in parallel. The side portions of 15b are continuously polymerized in the lateral direction to continuously improve the entire surface, and in the upper part, only the long improvement bodies 15b are arranged at intervals, and an unimproved ground remains between the improvement bodies 15b. . In this case, the height of the short improvement body 15a is made substantially equal to the groundwater level.

  In this way, it is possible to stop only the necessary minimum ground improvement by improving only the ground at the bottom of the excavated bottom where collapse or the like is assumed and partially improving the upper ground. Since other operations are the same as those in the first embodiment, description thereof is omitted here.

FIG. 3 shows a third embodiment, and the natural ground is a soil having a self-supporting soil content of about 30% or more, but the groundwater level is high and the influence on the surroundings is assumed.

  In such a case, only the long improved bodies 15b having a height substantially equal to the groundwater level are arranged in a comb-like shape at intervals. Thereby, it is possible to partially improve the portion requiring ground improvement, and it is possible to reduce the influence of the groundwater level with the minimum improvement. Since other operations are the same as those in the first embodiment, description thereof is omitted here.

FIG. 4 shows the fourth embodiment. Like the third embodiment, the natural ground is a self-supporting soil with a fine particle content of about 30% or more, but the groundwater level is high and the influence on the surroundings is high. Is assumed.

  In this case as well, only the long improvement body 15b having a height substantially equal to the groundwater level is arranged in a comb-like shape at intervals, but the improvement body 15b is arranged obliquely.

  Even if the improved body 15b is formed obliquely, the intended object is achieved because the improved body 15b is formed up to the level of the groundwater level, and the improved body 15b is formed at an angle close to the angle of the main sliding surface 19 of the collapse. As a result, the influence on the surroundings can be efficiently reduced.

It is explanatory drawing which shows 1st Embodiment of the open shield method of this invention. It is explanatory drawing which shows 2nd Embodiment of the open shield method of this invention. It is explanatory drawing which shows 3rd Embodiment of the open shield method of this invention. It is explanatory drawing which shows 4th Embodiment of the open shield method of this invention. It is explanatory drawing which shows the influence on the side natural ground at the time of an open shield machine promotion. It is explanatory drawing which shows the relationship with the side part natural ground at the time of improving the ground at the time of an open shield machine promotion. It is explanatory drawing which shows the relationship with the side part ground of the unimproved part at the time of partially improving the ground at the time of an open shield machine promotion. It is a vertical side view which shows the outline of an open shield construction method. It is a perspective view of a concrete box. It is a top view at the time of the primary injection before promotion of an open shield machine. It is a top view at the time of excavation of Mt. It is a top view at the time of propulsion and secondary injection of an open shield machine.

DESCRIPTION OF SYMBOLS 1 Open shield machine 1a Side wall plate 1b Bottom plate 1c Tail part 1d Front part 1e Jack part 2 Propulsion jack 3 Bulkhead 4 Concrete box 4a Left side board 4b Right side board 4c Upper floor board 4d Lower floor board 5 Backfill soil 6 Grout material 7 Height adjustment Material 8 Pushing angle 9 Excavator 10 Opening 11 Cutting edge 12 Mount face 13 Slide earth retaining plate 14 Back-filling material 15, 15a, 15b Improved body 16 Injection pipe 17 House rod 18 Soil 19 Main sliding surface

Claims (4)

  The process of excavating and discharging soil in front of the front or top opening of the open shield machine, the process of extending the propulsion jack and advancing the shield machine with the concrete box as a reaction force, and shrinking in the tail part of the shield machine A new concrete box is suspended from the upper side of the propulsion jack and set from the upper side, and the process of back-filling the tail void generated by the propulsion of the shield machine is repeated as appropriate to embed the concrete boxes in series. In the open shield method, the groundwater level is low due to silty sand with a fine particle content (74 μm or less) of 15-20% or more, silt or clay-mixed gravel, clayey sand, clayey gravel, and to the periphery by scouring If there is almost no influence, the N-value is about 1 to 3 soft viscous soil, and the independence of the natural ground can be expected. When at least the side ground has a certain level of independence, such as when there is a concern about the impact on the surrounding area, the tail void will collapse due to the looseness of the side ground until the backfill filling is completed. Soil and improvement body of improved body improved by temporary and partial ground improvement to the side ground by chemical injection or high pressure jet agitation method, and arch action effect of unmodified ground An open shield construction method that integrates the soil between them and reduces the disturbance of natural ground.   In the ground improvement, in the place where there is almost no ground water in the side ground, columnar improvement bodies are arranged in a lattice shape, and each improvement body superposes the corners and partially improves the side ground. The open shield method described in 1.   In the ground improvement, in the place where the groundwater level of the side ground is low, short columnar bodies are arranged in the lower part, and columnar bodies of different lengths are alternately arranged in parallel. The open shield method according to claim 1, wherein the side portions are polymerized in a lateral direction to continuously improve the entire surface.   The said ground improvement is the oven shield method of Claim 1 which arranges a columnar body in the shape of a comb tooth at intervals.

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