JP5210221B2 - Separation structure of core material and method for constructing start shaft of shield excavator using the same - Google Patents

Description

  The present invention relates to a core material separation structure applicable to a core material of a retaining wall such as a continuous underground wall constructed when excavating the ground to provide a vertical shaft, and a start vertical shaft of a shield excavator using the same. Is related to the construction method.

  Conventionally, the ground is drilled using a horizontal multi-axis excavator such as a triaxial auger, and a soil cement pillar is formed in situ by stirring while pouring cement milk into the hole, and H-shaped steel, etc. A continuous underground wall constructed by repeatedly inserting a long core material is known (see Patent Documents 1 and 2, etc.).

  And in these patent documents 1, 2, the method of removing the upper side of the core material embed | buried in this way is disclosed.

  First, in the method disclosed in Patent Document 1, the core material embedded in the ground is suspended from the soil cement at the cutting location, and a chevron cut is made in the core material by a gas cutter. Thereafter, the head of the core material is gripped with a vibro hammer or the like on the ground, and the core material above the cut portion is pulled out while applying vibration.

  On the other hand, in the method disclosed in Patent Document 2, the lower core material and the upper core material separated in advance are connected by a detachable means with a joining plate, and then the connection with the joining plate is performed from the excavation side. A method of releasing and pulling out the upper core material is disclosed.

Japanese Patent Laid-Open No. 8-177049 JP 2002-13144 A

  However, according to the method disclosed in Patent Document 1, it is necessary to perform a hanging work or a cutting work with a special shape on the core material of the retaining wall in a state where the earth pressure is received in a narrow place in the excavation shaft. In addition, it takes time for construction, and there is a concern that the retaining wall will collapse, so it was difficult to apply at locations with high earth pressure or water pressure.

  On the other hand, in the method disclosed in Patent Document 2, the upper core member and the lower core member are surrounded by the joining plate and the displacement is limited. It is not a structure that directly suppresses displacement in the shear direction (direction perpendicular to the axis of the core material), and this separation structure may become a weak part at a large depth and a high earth pressure.

  Therefore, an object of the present invention is to provide a highly rigid core material separation structure that can be applied to places with high earth pressure, and a method for constructing a starting shaft of a shield excavator using the same.

  In order to achieve the above object, the core material separation structure of the present invention is a core material separation structure in which a long core material embedded in the ground and receiving a load from the direction perpendicular to the axis is separable in the vertical direction. The core material includes a lower core material, a joint box that is fixed to the lower core material and has an upper opening, and the lower core material that is inserted through the opening of the joint case. And an upper core member that is detachably fixed to the joint box, and the lower core member and the upper core member are arranged at a position where the shaft of the core member is placed. A shear resistance portion that restricts relative displacement in at least one of the orthogonal directions is provided, and the upper core member is surrounded by an outer shell portion of the joint box.

  Here, the shear resistance portion protrudes from the concave / convex fitting formed at a position where the lower core material and the upper core material are in contact with each other, and protrudes from the lower core material or the upper core material. It can comprise by the shear key used as a pair which clamps an upper core material.

  Further, the shear resistance portion may be two sets of concave and convex fittings that restrict relative displacement of the core material in the direction perpendicular to the two axes.

  Further, the lower core material is surrounded by the outer shell portion, the joint box is fixed to the lower core member with bolts, and the upper core member has the joint box in the direction perpendicular to the axis. It can be set as the structure fixed by the penetration volt | bolt which penetrates to 1 and can be removed from one side.

  Further, an upper end plate orthogonal to the axial direction of the core member is fixed to the upper end of the lower core member, the joint box is fixed to the upper end plate, and the upper core from the upper surface of the upper end plate. A pair of shear keys that sandwich the material is extended, and the upper core material may be fixed by a through bolt that passes through the joint box in the direction perpendicular to the axis and is removable from one side surface. . Furthermore, it is preferable that a friction reducing layer is formed on the side surface of the upper core member.

  Further, a method for constructing a starter shaft of a shield excavator according to the present invention is a method for constructing a starter shaft of a shield excavator constructed by installing a core material on which the core material separation structure is formed, wherein the shield Pushing the lower core material into the ground from above the position where the excavator is started, fixing the joint box to the head of the lower core, and above the joint box The step of inserting the upper core material from the opening and fixing the upper core material to the joint box, and the core material in which the lower core material, the joint box and the upper core material are integrated, The joint box includes a step of pushing until the shield excavator comes into contact with the shield excavator when starting, and a step of excavating the front side of the core material.

  In the core material separation structure of the present invention configured as described above, the upper core material is surrounded by the outer shell portion of the joint case fixed to the lower core material. In addition, a shear resistance portion that restricts relative displacement in at least one direction of the axis orthogonal direction (shear direction) of the core material is provided at a position where the lower core material and the upper core material are in contact with each other. That is, the upper core member has a structure in which displacement in the shearing direction with respect to the lower core member is limited in the inside and the outer periphery.

  For this reason, it becomes the separation structure of a highly rigid core material, and can be applied also to places with high earth pressure and water pressure such as deep underground.

  Further, if the shear resistance portion is formed by a plurality of means including the concave-convex fitting and the shear key, a more rigid core material separation structure can be obtained. Furthermore, the displacement in two directions can be limited by two sets of concave and convex fitting.

  Moreover, if one side of the joint box is exposed by excavation, the upper core is fixed by a through bolt that passes through the joint box and can be removed from one side. The connection with the body can be easily released.

  Furthermore, by fixing the upper end plate to the upper end of the lower core member, the joint box and the lower core member can be fixed with a simple structure.

  And an upper core material can be easily extracted by forming a friction reduction layer in the side surface of the upper core material pulled out.

  In addition, when constructing the start shaft of the shield excavator, the shield excavator was made to face the upper core material if the joint box was placed below the wall surface that the shield excavator contacts when starting. Can be pulled out in the state.

  For this reason, it is not necessary to expose the unstable earth retaining in the start shaft, and the shield excavator can be started safely. Further, if the upper core material is pulled out from the start port of the shield excavator, there is no need to use an expensive material that can be cut by the shield excavator for the start port.

It is a figure explaining the separation structure of the core material of embodiment of this invention, Comprising: (a) is a side view, (b) is the front view seen from the excavation side. It is a perspective view explaining the process of mounting | wearing with the joint box on the head of a lower side core material. It is process drawing explaining the operation | work process which embed | buries the isolation | separation structure of the core material of this invention in the ground, and pulls out an upper core material after that. It is sectional drawing explaining the process of constructing a box culvert on the excavation side of a retaining wall, and pulling out an upper core material. It is a figure explaining the isolation | separation structure of the core material of Example 1, Comprising: (a) is sectional drawing, (b) is the front view seen from the excavation side. It is a figure explaining the isolation | separation structure of the core material of Example 2, Comprising: (a) is a side view, (b) is the front view seen from the excavation side. It is the front view which looked at the core material from the start shaft in order to demonstrate the construction method of the start shaft of the shield excavator of Example 3. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  1 and 2 are a side view, a front view, and a perspective view for explaining the configuration of the separation structure of the core member 10 of the present embodiment.

  The core material 10 is inserted into a soil cement formed by stirring the excavated ground and cement milk, or a mud-solidifying material filled in a excavation groove excavated into a groove shape, and the earth retaining wall and Constitutes part of a continuous underground wall.

  The continuous underground wall is buried in the ground at the time of construction. Thereafter, one side of the core material 10 is excavated to construct a vertical shaft. For this reason, earth pressure (load) from the direction orthogonal to the axis acts on the core material 10.

  The core material 10 includes a lower core material 2, a joint case 3 that is fixed to the lower core material 2 and has an upper opening, and a lower core that is inserted through the opening of the joint case 3. It is mainly comprised by the upper core material 1 contact | abutted to the material 2 and fixed to the coupling box 3 so that attachment or detachment is possible.

  The lower core 2 is formed by flanges 21 and 22 extending in parallel in the vertical direction, and a web 13 that connects the flanges 21 and 22 perpendicularly to the flanges 21 and 22. Shape steel can be used.

  Further, the upper end of the web 23 of the lower core member 2 is cut into a concave shape as shown in FIG. 2, thereby forming a concave portion 24 serving as one of concave and convex fitting as a shear resistance portion.

  Further, on both sides of the concave portion 24, shear keys 25, 25 that are paired with the web 23 interposed therebetween are fixed. The shear key 25 is a prismatic steel material, and the lower part is fixed to the side surface of the web 23 by welding. Further, the upper portion of the shear key 25 protrudes upward from the upper end surfaces of the flanges 21 and 22.

  In addition, a plurality of bolt holes 26,... Are drilled in the flanges 21 and 22 on both sides of the web 23 until the joint box 3 is inserted.

  On the other hand, the joint case 3 attached to the lower core member 2 has an outer shell portion 31 formed of a rectangular tubular steel pipe having an open top and bottom. The inner space of the outer shell portion 31 has two parallel surfaces that are substantially the same width as the flanges 21 and 22 of the lower core member 2, and perpendicular to the two surfaces, and the width of the web 23 is the width of the flanges 21 and 22. A rectangular column-shaped space is formed by two parallel surfaces having the same thickness as the added length.

  Further, a plurality of lower bolt holes 33,... Are formed in the lower half of the joint box 3 in accordance with the positions and sizes of the bolt holes 26,. Perforated.

  A fixing bolt 44 is inserted into the bolt hole 26 and the lower bolt hole 33 as a bolt that serves as a means for fixing the joint case 3 to the lower core member 2. As shown in FIG. 1A, the fixing bolt 44 includes a shaft portion that is slightly longer than the length obtained by adding the thickness of the flange 21 (22) to the thickness of the outer shell portion 31.

  Here, when the shaft portion of the fixing bolt 44 is inserted into the lower bolt hole 33 from the outside of the joint box 3, the tip protrudes toward the web 23 through the bolt hole 26, and thus a nut 45 is attached to the tip. To fix.

  Further, when the joint case 3 is fixed to the lower core member 2 through the lower bolt holes 33 provided in the lower half part of the joint case 3 in this way, the upper half of the joint case 3 The inner space of the part becomes a cavity.

  And since the upper core material 1 will be inserted in the cavity of the upper half part of this joint box 3, the upper half part of the surface which pierced the lower side bolt hole 33, ... in the joint box 3 The upper bolt holes 32 used for fixing the upper core 1 are drilled.

  On the other hand, the upper core material 1 inserted from the opening above the joint box 3 is formed of an H-shaped steel material having the same size as the lower core material 2, and includes flanges 11 and 12 and a web 13.

  Further, a convex portion 14 that protrudes and projects into the concave portion 24 of the lower core member 2 is projected from the lower end of the web 13. That is, the convex portion 14 is fitted into the concave portion 24 when the upper core member 1 is inserted from the opening of the joint case 3, and the upper end surface of the lower core member 2 and the lower end surface of the upper core member 1 are in contact with each other. Become.

  Furthermore, since this convex part 14 will enter between the shear keys 25 and 25 which become the pair fixed on both sides of the web 23 of the lower side core material 2, it is spaced apart in the direction between the flanges 11 and 12. The web 13 is clamped at two points.

  Further, the flange 11 of the upper core material 1 at a position overlapping with the upper bolt holes 32 of the joint box 3 with the lower end surface of the upper core material 1 in contact with the upper end surface of the lower core material 2. , 12 are respectively drilled with bolt holes 16,.

  The bolt hole 16 drilled in the one flange 11 and the bolt hole 16 drilled in the other flange 12 are drilled so as to face the projected positions when viewed in the direction perpendicular to the axis of the core member 10. Therefore, the upper bolt holes 32, 32 of the joint box 3 drilled in accordance with the positions of these bolt holes 16, 16 are also projected onto these bolt holes 16, 16 when viewed in the direction perpendicular to the axis of the core material 10. Will be.

  And the penetration bolt 41 inserted in these upper side bolt holes 32 and 32 and bolt holes 16 and 16 is formed in the length which penetrates joint box 3 in an axis orthogonal direction. That is, when the through bolt 41 is inserted from one side surface of the outer shell portion 31, the tip of the through bolt 41 passes through the upper bolt hole 32, the bolt hole 16 of the flange 11, the bolt hole 16 of the flange 12, and the upper bolt hole 32. It is formed in a length protruding from the other side surface.

  A nut 42 is attached to the tip of the through bolt 41 protruding from the outer shell portion 31. The nut 42 is fixed to the side surface of the outer shell portion 31 by welding so that it cannot rotate.

  Further, since the through bolt 41 is bridged between the flanges 11 and 12, the sheath tube 43 is provided with a shaft portion so as not to be fixed to a solidified material such as soil cement that has entered the inner space of the joint case 3. It is attached to.

  The sheath tube 43 can be formed of a vinyl chloride pipe or the like, and the gap between the inner peripheral surface of the sheath tube 43 and the through bolt 41 is filled with grease or the like.

  Next, referring to FIG. 3, a method for constructing a retaining wall using the separation structure for the core material 10 of the present embodiment and a method for extracting the upper core material 1 will be described.

  First, as shown in FIG. 3 (a), the ground 5 is drilled 51 using a triaxial auger of a horizontal multi-axis excavator, and agitation is performed while injecting cement milk when the triaxial auger is pulled up. A soil cement 52 is formed.

  On the other hand, as shown in FIG. 2, the joint box 3 is inserted into the head of the lower core member 2, and the joint box 3 is lowered using the fixing bolts 44,... And nuts 45,. Fix to the side core 2. Further, as shown in FIG. 3A, one end of the mooring wire 27 is connected near the upper end of the lower core member 2.

  Then, before the soil cement 52 in the drilling hole 51 is hardened, the lower core material 2 is pushed into the soil cement 52 and once pushed at a position where the upper half of the joint box 3 protrudes from the drilling hole 51. To stop.

  Subsequently, as shown in FIG. 3 (b), the upper core material 1 is inserted from the opening of the joint case 3, and the convex portion 14 of the upper core material 1 is fitted into the concave portion 24 of the lower core material 2. Further, the sheath tube 43 and the through bolt 41 in which the upper bolt hole 32 is filled with grease are inserted from one side of the joint box 3, and the nut 42 is attached to the tip of the through bolt 41 protruding from the other side. The upper core material 1 is fixed to the joint box 3.

  Further, a friction reducing layer is formed on the side surface of the upper core material 1 by applying a friction reducing material such as a solvent-based paint or by wrapping a plastic coating material.

  Then, the core material 10 in which the lower core material 2, the joint case 3 and the upper core material 1 are integrated is pushed into the soil cement 52 until a predetermined depth is reached. At this time, since the core material 10 is integrated, it is not separated even when suspended in the fluid-like soil cement 52.

  By repeating the operation of pushing the core material 10 into the soil cement 52 in this way, a continuous underground wall is constructed. Then, one side of the continuous underground wall is excavated to form a shaft, and a box culvert 54 as shown in FIG.

  Further, as shown in FIG. 3C, the upper core member 1 protruding above the box culvert 54 is supported by a cut beam 53. On the other hand, stud gibels 55,... Are projected from the lower core member 2 in contact with the side wall of the box culvert 54, and the box culvert 54 and the lower core member 2 are integrated to use the main body.

  The anchoring wire 27 having one end connected to the lower core member 2 is provided with a fixing portion 27 a at the other end, and is fixed to the inner peripheral surface of the box culvert 54.

  The joint box 3 is located near the upper surface of the box culvert 54. When the head of the through bolt 41 is turned from one side surface of the joint box 3 exposed to the excavation side, the nut 42 becomes the outer shell part. 31, the tip of the through bolt 41 is removed from the nut 42.

  Further, since the shaft portion of the through bolt 41 is accommodated in the sheath tube 43, it is not fixed to the soil cement 52 in the joint case 3, and the through bolt 41 can be pulled out to the excavation side.

  Subsequently, the cut beam 53 is removed as shown in FIG. 3 (d), and the backfilling portion 56 is constructed with soil or fluidized soil to a predetermined position as shown in FIG. Grasp the top of the and pull it up. Then, the upper core 1 is pulled out from the joint box 3 and pulled out to the ground as it is. At the time of this drawing, the lower core material 2 is anchored to the box culvert 54 by the mooring wire 27, so that it does not come out together with the upper core material 1.

  In addition, as shown in FIG. 4, a void is formed in the soil cement 52 from which the upper core material 1 has been pulled out, and a filler is injected into the void to a predetermined depth, and the soil cement 52 near the ground surface is removed. .

  Next, the effect | action of the isolation | separation structure of the core material 10 of this Embodiment is demonstrated.

  In the separation structure of the core material 10 of the present embodiment configured as described above, the joint case 3 that connects the lower core material 2 and the upper core material 1 includes an outer shell portion 31 that surrounds them. Yes. For this reason, generation | occurrence | production of the relative displacement (shift | offset | difference) of the axis orthogonal direction of the lower side core material 2 and the upper side core material 1 can be suppressed, and it can also resist with respect to a twist.

  Moreover, the lower core material 2 in the direction between the flanges 11 and 12, which is one of the axial orthogonal directions (shear directions) of the core material 10, is provided at a position where the lower core material 2 and the upper core material 1 are in contact with each other. As a shearing resistance portion that limits the relative displacement between the upper core material 1 and the upper core material 1, a concave-convex fitting is formed by the concave portion 24 and the convex portion 14.

  Furthermore, a pair of shear keys 25 and 25 project as shear resistance members that limit displacement in a direction orthogonal to the direction between the flanges 11 and 12, which is another shear direction.

  That is, the concave and convex fitting and shearing keys 25 and 25 are provided in the inside where the upper core member 1 and the lower core member 2 are in contact, and the outer shell portion 31 is provided on the outer periphery surrounding the contact portion. It has a structure in which displacement in the shearing direction with respect to the lower core material 2 of the upper core material 1 is limited in the inside and the outer periphery.

  For this reason, the rigidity of the connection location of the lower side core material 2 and the upper side core material 1 can be improved, and the core material 10 can be arrange | positioned also in places with high earth pressure and water pressure, such as a deep underground. .

  Further, the upper core material 1 is fixed to the joint box 3 with a through bolt 41 that passes through the joint box 3 in the direction perpendicular to the axis and can be removed from one side surface. If the side surface, that is, the head of the through bolt 41 is exposed, the head of the through bolt 41 can be turned and removed from the nut 42, and the connection between the upper core 1 and the joint box 3 can be easily released. Can do.

  Moreover, by forming a friction reducing layer on the side surface of the upper core material 1 to be pulled out, the frictional resistance between the upper core material 1 and the soil cement 52 is reduced, and the upper core material 1 can be easily pulled out.

  Hereinafter, Example 1 of a form different from the above-described embodiment will be described. Note that the same or equivalent parts as those described in the above embodiment are given the same reference numerals and detailed description thereof is omitted.

  FIG. 5 is a cross-sectional view and a front view illustrating the configuration of the separation structure of the core material 10A of the first embodiment.

  10A of core materials are the same as the core material 10 demonstrated in the said embodiment, 2 A of lower side core materials, the joint box 3 with the upper opening fixed to the lower side core material 2A, and its joints It is mainly constituted by the upper core 1A that is inserted from the opening of the box 3 and is brought into contact with the lower core 2A and is detachably fixed to the joint box 3.

  The upper end of the web 23 of the lower core member 2A is cut into a V shape as shown in FIG. 5A, thereby forming a recess 24A serving as one of the concave and convex fitting as a shear resistance portion.

  Further, at the lower end of the web 13 of the upper core material 1A, a triangular convex portion 14A that protrudes and projects into the concave portion 24A of the lower core material 2A is projected. That is, the convex portion 14A is fitted into the concave portion 24A when the upper core member 1A is inserted from the opening of the joint case 3, and the upper end surface of the lower core member 2A and the lower end surface of the upper core member 1A are in contact with each other. Become.

  Further, the upper ends of the flanges 21 and 22 of the lower core member 2A are cut into a valley shape as shown in FIG. 5B, so that a flange recess 28A serving as one of concave and convex fitting as a shear resistance portion is formed. It is formed.

  Further, at the lower ends of the flanges 11 and 12 of the upper core material 1A, a mountain-shaped flange convex portion 15A that protrudes and protrudes into the flange concave portion 28A of the lower core material 2A is projected. That is, the flange convex portion 15A is fitted into the flange concave portion 28A when the upper core material 1A is inserted from the opening of the joint case 3, and the upper end surface of the lower core material 2A and the lower end surface of the upper core material 1A are in contact with each other. It will be.

  In the separation structure of the core material 10A of the first embodiment configured in this way, the lower core material 2A and the upper core material 1A are in contact with each other in the axis orthogonal direction (shear direction) of the core material 10A. The first concave-convex fitting is formed by the concave portion 24A and the convex portion 14A as a shear resistance portion that limits the relative displacement between the lower core material 2A and the upper core material 1A in the direction between the flanges 11 and 12. Has been.

  Furthermore, a second concave-convex fitting is formed by the flange concave portion 28A and the flange convex portion 15A as a shear resistance member that limits the relative displacement in the direction orthogonal to the direction between the flanges 11 and 12, which is another shear direction. ing.

  Thus, in the structure in which the displacement in the two directions is limited by the two sets of concave and convex fittings, the relative displacement (displacement) in the shear direction between the upper core material 1A and the lower core material 2A can be reliably prevented.

  Other configurations and functions and effects are substantially the same as those in the above-described embodiment, and thus description thereof is omitted.

  Hereinafter, Example 2 of a form different from the above-described embodiment will be described. Note that the same or equivalent parts as those described in the above embodiment are given the same reference numerals and detailed description thereof is omitted.

  6A and 6B are a side view and a front view illustrating the configuration of the separation structure for the core material 10B according to the second embodiment.

  As with the core material 10 described in the above embodiment, the core material 10B includes a lower core material 2B, a joint box 3B open on the upper side fixed to the lower core material 2B, and a joint thereof. The upper core 1B is mainly constituted by the upper core 1B that is inserted from the opening of the box 3B and is in contact with the lower core 2B and is detachably fixed to the joint box 3B.

  The upper end surface of the lower core member 2B is formed in a plane orthogonal to the axial direction of the core member 10B as shown in FIGS. 6A and 6B, and the upper end plate 28B is welded to the upper end surface by welding or the like. Is fixed. Further, the upper end plate 28B is a steel plate having a rectangular shape in plan view and having substantially the same shape as the outer shape in plan view of the joint case 3B.

  In addition, on the upper surface of the upper end plate 28B, a pair of shear keys 25B, 25B are provided so as to protrude with an interval at which the web 13 of the upper core member 1B can be sandwiched. The shear key 25B is a prismatic steel material, and its lower end is fixed to the upper surface of the upper end plate 28B by welding.

  Further, the upper side of the shear keys 25B, 25B is cut away on the side facing the web 13, and the web 13 can be easily inserted between the shear keys 25B, 25B. The pair of shear keys 25B and 25B are provided at two locations spaced in the direction between the flanges 21 and 22.

  And as for the joint box 3B fixed to the upper end board 28B of this lower side core material 2B by welding etc., the outer shell part 31B is formed of the square cylindrical steel pipe opened up and down.

  The inner space of the outer shell portion 31B has two parallel surfaces having substantially the same width as the flanges 11 and 12 of the upper core 1B, and perpendicular to the two surfaces, and the width of the web 13 is the thickness of the flanges 11 and 12. It is formed in a quadrangular prism-like space by the added length and two parallel surfaces having substantially the same width.

  In addition, since the upper core material 1B is inserted into the cavity of the joint box 3B, upper bolt holes 32,... Used for fixing the upper core material 1B are drilled in the outer shell portion 31B. ing.

  On the other hand, the lower end surface of the upper core member 1B inserted from the upper opening of the joint box 3B is formed in a plane orthogonal to the axial direction of the core member 10B, and is formed on the upper surface of the upper end plate 28B of the lower core member 2B. Abutted.

  By fixing the upper end plate 28B to the upper end of the lower core member 2B in this way, the joint box 3B and the lower core member 2B can be fixed with a simple structure.

  Other configurations and functions and effects are substantially the same as those of the above-described embodiment or other examples, and thus description thereof is omitted.

  Hereinafter, a method for constructing a starting shaft of a shield excavator using the core 10 separation structure described in the above embodiment and a method for starting a shield excavator from the starting shaft will be described with reference to FIG. To do. It should be noted that the same method can be carried out using the separation structure of the core materials 10A and 10B described in the first and second embodiments.

  In Example 3, the cores 10,... Are embedded in the position serving as the start port 7 of the shield excavator (not shown) by the procedure described in the above embodiment. Further, in the place other than the starting port 7, normal fixing cores 6,... That are not pulled out are arranged.

  And after constructing the continuous underground wall with the core material 10, ... and the fixing core material 6, ..., the start shaft (not shown) is excavated by excavating the front side of the continuous underground wall. To construct.

  Further, when excavating, from one side of the upper core material 1,... At the position to be the starting port 7 and from one side of the joint box 3,. 52 is scraped off and exposed.

  The start port 7 serves as a wall surface against which the front surface of the shield excavator is pressed when the shield excavator is started from the start shaft. Further, although not shown, an entrance portion including ring-shaped concrete, a flapper, and a waterproof rubber material is installed on the outer periphery of the starting port 7.

  And core material 10, ... is pushed in until the joint box 3, ... reaches the position below this starting port 7.

  Furthermore, in the start shaft, a shield excavator is assembled and the tip of the shield excavator is inserted into the entrance. Subsequently, the plastic fluidizing material is pressurized and filled in the gap between the front surface of the shield excavator and the start port 7. This plastic fluidizing material is prevented from flowing into the start shaft by a water stop structure (not shown) at the entrance.

  In this state, the heads of the through bolts 41,... Are turned from the inside of the start shaft and the fastening with the nuts 42 is released, and the through bolts 41,. Pull out.

  On the other hand, on the ground, although not shown, the upper core material 1 is gradually pulled out by gripping the head of the upper core material 1 with a vibrator hammer suspended by a crane and rolling up the crane while vibrating the vibrator hammer. . The extraction of the upper core material 1 stops when the lower end of the upper core material 1 is pulled up to a position above the start port 7.

  When the upper cores 1,... Are pulled out from the starting port 7 in this manner, steel or other difficult-to-cut materials are removed from the traveling direction of the shield excavator. You can start towards.

  Thus, when constructing the start shaft of the shield excavator, the joint box 3,... Is arranged below the wall surface of the start port 7 with which the shield excavator is brought into contact when starting. The excavator can be pulled out while facing the upper core members 1.

  For this reason, there is no need to expose the unstable earth retaining with the core material removed to the start shaft, and the shield excavator can be started safely. That is, if the upper core material 1,... Is pulled out from the start opening 7 after the shield excavator is installed at the entrance, the start shaft is always protected by the upper core material 1,. Therefore, even when the earth pressure and the groundwater pressure are high, the inflow of earth and sand and groundwater into the starting shaft does not occur, and the safety is high.

  Further, the separation structure of the core material 10 constituted by the steel material can be manufactured at a low cost, and if the core material 10 is removed from the start port 7 of the shield excavator, it can be cut by the shield excavator. It is economical because it is not necessary to use a new material for the starting port 7.

  Moreover, if it is the core material 10 provided with the separation structure with high rigidity, it can be applied even in a deep underground where a shield excavator is started.

  Other configurations and functions and effects are substantially the same as those of the above-described embodiment or other examples, and thus description thereof is omitted.

  The embodiment of the present invention has been described in detail above with reference to the drawings. However, the specific configuration is not limited to this embodiment, and design changes that do not depart from the gist of the present invention are not limited to this embodiment. Included in the invention.

  For example, in the said embodiment or Example, although the joint case 3 was fixed to the lower core materials 2 and 2A with the fixing bolt 44, ..., it is not limited to this, The welding or the penetration bolt 41 You may fix by fixing means, such as.

  Moreover, in the said embodiment or Example, although core material 10, 10A, 10B was inserted in soil cement, it is not limited to this, It inserts in a muddy water solidification material or a ground. May be.

  Further, in the concave-convex fitting described in the above embodiment or examples, the concave portion and the convex portion may be provided on either side of the upper core material 1, 1A and the lower core material 2, 2A. Further, the shear key 25 may be fixed to either side.

  In the embodiment or example, the core members 10, 10A, and 10B are formed of the H-shaped steel material. However, the present invention is not limited to this, and is a member other than the groove-shaped steel or steel material having a U-shaped cross section. Even a core material can be used.

10, 10A, 10B Core material 1, 1A, 1B Upper core material 14, 14A Convex part (shear resistance part, uneven fitting)
15A Flange convex part (shear resistance part, concave / convex fitting)
2,2A, 2B Lower core member 24, 24A Concave part (shear resistance part, concave / convex fitting)
25, 25B Shear key (shear resistance part)
28A Flange recess (shear resistance, uneven fitting)
28B Upper end plate 3, 3B Joint box 31, 31B Outer shell 41 Through bolt 44 Fixing bolt (bolt)
5 Ground 7 Start

Claims (6)

A core material separation structure that is embedded in the ground and that is formed so that a long core material that receives a load from the direction perpendicular to the axis can be vertically separated,
The core material is a lower core material, a joint box which is fixed to the lower core material and has an upper opening, and is inserted from the opening of the joint box and is brought into contact with the lower core material. And an upper core material that is detachably fixed to the joint box,
Where the lower core material and the upper core material are in contact with each other, a shear resistance portion that restricts relative displacement in at least one direction perpendicular to the axis of the core material is provided, and the upper core material is Surrounded by the outer shell of the joint box ,
The shear resistance portion includes an uneven fitting formed at a position where the lower core material and the upper core material are in contact with each other, and the upper core material protrudes from the lower core material or the upper core material. A core material separation structure comprising a pair of shear keys sandwiching the core. A core material separation structure that is embedded in the ground and that is formed so that a long core material that receives a load from the direction perpendicular to the axis can be vertically separated,
The core material is a lower core material, a joint box which is fixed to the lower core material and has an upper opening, and is inserted from the opening of the joint box and is brought into contact with the lower core material. And an upper core material that is detachably fixed to the joint box,
Where the lower core material and the upper core material are in contact with each other, a shear resistance portion that restricts relative displacement in at least one direction perpendicular to the axis of the core material is provided, and the upper core material is Surrounded by the outer shell of the joint box,
The shear resistance portion, the isolation structure of the core material characterized in that two sets of convex-concave engagement to restrict relative displacement of the two axes orthogonal direction of the core material. The lower core is surrounded by an outer shell portion of the joint box, the joint box is fixed to the lower core by bolts, and the upper core is configured to attach the joint box to the shaft. isolation structure of the core material according to claim 1 or 2, from one side through the orthogonal direction, characterized in that it is secured by a removable through bolts. A core material separation structure that is embedded in the ground and that is formed so that a long core material that receives a load from the direction perpendicular to the axis can be vertically separated,
The core material is a lower core material, a joint box which is fixed to the lower core material and has an upper opening, and is inserted from the opening of the joint box and is brought into contact with the lower core material. And an upper core material that is detachably fixed to the joint box,
Where the lower core material and the upper core material are in contact with each other, a shear resistance portion that restricts relative displacement in at least one direction perpendicular to the axis of the core material is provided, and the upper core material is Surrounded by the outer shell of the joint box,
An upper end plate orthogonal to the axial direction of the core member is fixed to the upper end of the lower core member, the joint box is fixed to the upper end plate, and the upper core member is attached to the upper surface of the upper end plate. shear keys to be paired for clamping is extended, the core material wherein the upper core member you characterized in that it is secured by a removable through bolts from one side through the joint box body in the axial direction perpendicular Separation structure. Isolation structure of the core material according to any one of claims 1 to 4, characterized in that friction reducing layer on a side surface of the upper core member is formed. A method for constructing a start-up shaft of a shield excavator constructed by installing a core material in which the core material separation structure according to any one of claims 1 to 5 is formed,
Pushing the lower core material into the ground from above the position where the shield excavator is started; and
Fixing the joint box to the head of the lower core member;
Inserting the upper core from the opening above the joint box, and fixing the upper core to the joint box;
A step of pushing the core material in which the lower core material, the joint box and the upper core material are integrated until the joint box reaches a position below the wall surface with which the shield excavator is brought into contact when starting. When,
And a step of excavating a wall surface side of the core material that makes the shield excavator contact when starting. A method for constructing a start shaft of the shield excavator.

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