JP2018150731A - Construction method of caisson - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a construction method of a caisson configured to obtain required ground reaction even on a shallow construction depth for a ground anchor without depending on a construction depth of the ground anchor.SOLUTION: A construction method is to press-insert and sink-install a caisson skeleton 1 using a grip jack 7 while ground anchors 10a, 10b receive reaction force at outer side area where the caisson skeleton 1 is press-inserted and sink-installed. Two pairs of ground anchors 10a, 10b different in anchorage depths are previously anchored at shallower positions than a final position of press-inserted and sink-installed depths of the caisson skeleton 1. When a cutting-edge 1a of a caisson skeleton 1 is within the anchorage depth area of one pair of the ground anchor 10a, the caisson skeleton 1 is press-inserted and sink-inserted in the ground while the other pair of the ground anchor 10b receive reaction force.SELECTED DRAWING: Figure 1

Description

  TECHNICAL FIELD The present invention relates to a caisson construction method, and more particularly to a construction method that devises a method of taking a reaction force of a caisson housing that is press-fitted and laid down when a press-fit open caisson is constructed.

  In the press-fitting open caisson method for press-fitting / sinking the caisson housing that will constitute the caisson shaft with a press-fitting device such as a hydraulic jack, as described in Patent Document 1, for example, Steel that extends from the ground anchor while excavating the inside of the caisson skeleton installed on the ground, with ground anchors (also simply referred to as anchors or earth anchors) buried deeply in the ground in advance at multiple locations. By connecting a tension member such as a rod to a hydraulic jack that will function as a press-fitting device, pulling the ground anchor, and applying ground reaction force based on the anchor pulling to the caisson body, the caisson body is brought into the ground. Press-fit and sink.

Japanese Patent No. 5426795

  However, in the conventional technique represented by Patent Document 1, as a position of the ground anchor serving as a fixing portion in the ground, as a depth position where excavation associated with the caisson frame press-fitting / sinking does not reach, Since it is necessary to make the position deeper than the maximum depth of the caisson housing to be constructed (the position deeper than the blade edge), there is a limit to the construction depth of the ground anchor itself in the case of a large depth caisson. There is still room for improvement in terms of workability.

  Here, the position of the ground anchor to be fixed in the ground is generally set to a position deeper than the maximum depth of the caisson enclosure (a position deeper than the blade edge), when the caisson enclosure sinks. This is because the surrounding ground is disturbed, and a predetermined proof stress cannot be secured.

  Therefore, as a result of the measurement of the displacement of the surrounding ground when the caisson was installed by the present inventors, the surrounding ground is displaced laterally when the edge of the caisson housing passes, but thereafter a large displacement is seen. It was confirmed that there was no. In addition, it was confirmed that the displacement of the surrounding ground was very small after the initial press-fitting / sinking stage where the attitude of the caisson housing was not stable.

  The present invention has been made paying attention to the problems and knowledge as described above, and in particular, it does not depend on the ground anchor construction depth, and can obtain the necessary ground reaction force even if the ground anchor construction depth is shallow. The caisson construction method considered to be possible is provided.

  The present invention fixes a ground anchor in the ground outside the area where the caisson housing is press-fitted and laid, and applies a pushing force to the caisson housing by a press-fitting device while applying a reaction force to the ground anchor. It is a caisson construction method that press fits and sinks in the ground. In addition, a plurality of ground anchors having different fixing depths are fixed at a position shallower than the final press-fitting / sinking depth of the caisson housing, and the cutting edge of the caisson housing has a fixing depth of at least one of the ground anchors. When in the area, the caisson enclosure is press-fitted and set in the ground while taking a reaction force on the remaining ground anchors.

  As a more desirable form, a plurality of sets of ground anchors having different fixing depths are fixed at positions shallower than the final press-fitting / sinking depth of the caisson housing, and the blade edge of the caisson housing is one set of ground anchors. The caisson housing is press-fitted and set in the ground while taking a reaction force against at least one other set of ground anchors.

  In another aspect, when three or more sets of ground anchors having different fixing depths are fixed, and the blade edge portion of the caisson housing is in the fixing depth region of any one of the ground anchors, another plurality of sets of ground anchors are used. It is preferable to press-fit / sink the caisson housing into the ground while taking a reaction force on the anchor.

  In addition, it is preferable that the plurality of sets of ground anchors have different fixing depths in stages so that the fixing depths do not overlap each other.

  Furthermore, it is preferable to construct a caisson at a required depth by repeating the press-fitting / sinking of the caisson housing, the addition of the housing segment to the upper portion of the caisson housing, and the excavation / soil removal inside the caisson housing. .

  According to the present invention, it is possible to construct a caisson at a required depth without being influenced by the anchoring depth of the ground anchor, and a small hole drilling depth for the ground anchor can be reduced. It is possible to cope with this, and the construction cost can be reduced and the construction yard can be reduced.

The figure which shows 1st Embodiment of the construction method of the caisson concerning this invention, and is sectional explanatory drawing of the caisson in the middle of construction. Plane explanatory drawing of FIG. It is a figure which shows 2nd Embodiment of the construction method of the caisson based on this invention, and is sectional explanatory drawing of the caisson in the middle of construction.

  1 and 2 show a more specific first embodiment for carrying out the caisson construction method according to the present invention. In particular, FIG. 1 is a cross-sectional explanatory view of the caisson during construction, and FIG. The plane explanatory drawing of each is shown.

  Here, a segment piece Ps made of 1 / n circular steel (steel plate) obtained by dividing a circle into n equal parts in the circumferential direction is assembled into a circular annular segment S on the ground, and the annular segment S is deepened step by step. An example in which the caisson housing 1 is constructed by sequentially press-fitting and sunk while adding in the direction is shown.

  In particular, the right half and the left half of FIG. 1 show different states. In the right half of FIG. 1, after caisson housing 1 in which a circular annular segment S is added in a plurality of stages in the depth direction is press-fitted and set in the ground, the next annular segment S is placed on the uppermost stage of caisson housing 1. It shows a state where they are piled up to be added. On the other hand, the left half of FIG. 1 shows a state immediately after the caisson housing 1 including the annular segment S added in the right half is press-fitted and set in the ground as the next step.

  1 and 2, 1 is a caisson housing in the middle of construction by press-fitting / sinking into the ground, 2 is a press-fitting / sinking device installed on the ground G side, and 3 is suspended on the jib of the crawler crane 30 shown in FIG. This is a clamshell bucket as a bucket excavator supported by being lowered. Further, as will be described later, 10a and 10b are two sets of ground anchors embedded and fixed around a region where the caisson housing 1 is to be constructed prior to press-fitting / sinking the caisson housing 1.

  The press-fitting / sinking device 2 includes, for example, substantially square pillar-shaped post portions 5 erected at four locations so as to surround an area where the caisson housing 1 is to be constructed in plan view, and the four post portions 5 are hung. A press-fitting girder member 6 that also serves as a scaffold that has been passed and formed in a substantially girder shape in plan view, and a grip jack (hydraulic type) as a press-fitting device that is erected at four locations on the press-fitting girder member 6 close to the post portion 5 A press-fitting jack) 7, and an intermediate girder member 8 provided on the lower surface side of the press-fitting girder member 6 and corresponding to the diameter of the caisson housing 1. The press-fitting girder member 6 is guided and supported by the four post portions 5 so as to be able to move up and down, and can be moved up and down in response to the pressing force or pulling-up force of the plurality of grip jacks 7 as will be described later.

  The grip jack 7 includes a center shaft 7a, a casing tube 7b having a composite cylinder structure that forms a hydraulic cylinder mechanism together with the center shaft 7a, a hydraulic grip mechanism built in the casing tube 7b, and the like. It is configured. The grip jack 7 generates a rolling force by extending the casing tube 7b in a state where the center shaft 7a is gripped (clapped) by hydraulic pressure. Further, it is possible to generate a rolling force over a plurality of stages by gripping the center shaft 7a again by the grip mechanism. The grip jack 7 has a known structure.

  Around the area where the caisson housing 1 is constructed, the two sets of ground anchors 10a and 10b described above are buried and fixed deeply in the ground. The two sets of ground anchors 10a and 10b are, for example, a set of four that are respectively fixed and fixed at four locations surrounding the caisson housing 1 in a plan view of a region where the caisson housing 1 is constructed. That is, the two sets of ground anchors 10a and 10b are arranged at positions close to the position of the grip jack 7 shown in FIG.

  These two sets of ground anchors 10a and 10b are of a type referred to as a peripheral friction type, for example, and are more than the final press-fitting / sinking depth of the caisson housing 1 (final construction depth of the caisson housing 1). It is buried in a shallow position and fixed. The two sets of ground anchors 10a and 10b are arranged with different fixing depths so as not to overlap each other in the depth direction.

  A tension member 9 such as an anchor steel bar is connected to each of the two sets of ground anchors 10a and 10b. An upper end portion of each tension member 9 is detachably connected to a center shaft 7a of a corresponding grip jack 7 via an anchor coupler 11. 1 shows a state where the ground anchor 10b having a deep fixing depth is connected to the center shaft 7a of the grip jack 7 via the tension member 9, and in the right half of FIG. 1, the fixing depth is shown. The shallow ground anchor 10 a is connected to the center shaft 7 a of the grip jack 7 via the tension member 9.

  In this embodiment, two tension members 9 connected to two sets of ground anchors 10a and 10b having different fixing depths correspond to each grip jack 7. The two tension members 9 can be selectively or simultaneously connected to the grip jack 7 via the anchor coupler 11. In addition, as will be described later, two sets of ground anchors 10a and 10 having different fixing depths are used properly according to the press-fitting / sinking depth of the caisson housing 1.

  The two sets of ground anchors 10a and 10b are constructed by a known ground anchor method using a grout or the like together with a drilling machine. In addition to the friction type anchors exemplified above, the ground anchor includes a bearing (compression) type anchor represented by a KTB anchor, a composite type anchor, and the like. A thing may be used.

  As described above, the caisson housing 1 is formed by combining a plurality of segment pieces Ps and Ps on the ground using, for example, a 1 / n circular steel (steel plate) segment piece Ps as a unit element. Assemble as segment S). The assembled annular segment S is placed so as to be added to the uppermost stage of the existing caisson housing 1 and then pressed into the ground by the pressing and sinking force of the grip jack 7 so that only the necessary number of annular segments S are provided. The caisson housing 1 is constructed by stacking.

  When the caisson housing 1 is press-fitted and set by the grip jack 7, if the casing tube 7 b is extended downward with respect to the center shaft 7 a of each grip jack 7, the center shaft 7 a of the grip jack 7 is A tensile force acts between the ground anchor 10a or 10b. The reaction force is transmitted as a press-fitting / sinking force to the caisson casing 1 via the press-fitting girder member 6 and the intermediate girder member 8, and as a result, the caisson casing 1 is gradually press-fitted / sunk.

  That is, prior to the construction of the caisson housing 1, the ground anchor 10 a or 10 b is mechanically connected to the center shaft 7 a of each grip jack 7 via the tension member 9 and the anchor coupler 11 as described above. The ground anchors 10a and 10b function as a reaction force receiver when the caisson housing 1 is press-fitted and set.

  The press-fitting / sinking of the caisson housing 1 with such a grip jack 7, the assembly and addition of the annular segment S to be the caisson housing 1, and the excavation / excavation of the inner bottom (bottom) of the caisson housing 1 with the clamshell bucket 3 Repeat with soil removal (so-called floor digging). As a result, as shown in FIG. 1, a caisson housing 1 having a predetermined depth that will eventually function as a shaft is constructed. In addition, the code | symbol Q of FIG. 1 has shown the groundwater level.

  Here, when the caisson as shown in FIG. 1 is constructed, two sets of ground anchors 10a and 10b are selectively used according to the press-fitting / sinking depth of the caisson housing 1. In the initial stage of the press-fitting / sinking of the caisson housing 1, until the blade edge 1 a at the tip, which is the deepest portion of the caisson housing 1, passes through the depth region of the pair of ground anchors 10 a having a shallow fixing depth, as shown in FIG. As shown in the left half, a pair of ground anchors 10b having a deep anchoring depth are connected to the corresponding grip jacks 7, respectively, and ground reaction forces are taken using the ground anchors 10b having a deep anchoring depth. And

  Also, if the caustic housing 1 is pushed and set, the blade edge 1a of the caisson housing 1 reaches the depth region of the pair of ground anchors 10b having a deep fixing depth, and is used as a reaction force receiver at that time. The ground anchor to be switched shall be switched. Specifically, after the blade edge portion 1a of the caisson housing 1 reaches the depth region of the set of ground anchors 10b having a deep fixing depth, the ground anchor 10b having a deep fixing depth is replaced with the set of ground anchors 10b. As shown in the right half of the figure, a pair of ground anchors 10a having a shallow fixing depth are reconnected to the grip jacks 7, and a ground reaction force is taken by using the ground anchors 10a having a shallow fixing depth. And

  As the caisson housing 1 further press-fits and sinks, if the blade edge portion 1a of the caisson housing 1 exceeds the depth region of the ground anchor 10b having a deep fixing depth, the ground anchor 10a or It is assumed that the ground reaction force is taken by using 10b or by using two sets of ground anchors 10a and 10b in combination. As described above, the two tension members 9 attached to the two sets of ground anchors 10a and 10b can be connected to the grip jack 7 via the anchor coupler 11 at the same time.

  In this way, by selectively using the two sets of ground anchors 10a and 10b according to the press-fitting / sinking depth of the caisson housing 1, or by using the two sets of ground anchors 10a and 10b at the same time, the ground anchor 10a , 10b, it is possible to construct a caisson with a required depth without being influenced by the fixing depth. In addition, since the drilling depth for fixing the ground anchors 10a and 10b is small, it is possible to cope with a small drilling machine, and the construction cost can be reduced and the construction yard is also provided. It can be reduced.

  Here, in order to suppress the relative displacement between the respective ground anchors 10a and 10b and the surrounding ground, and to ensure the required proof stress, the peripheral influence prevention work (peripheral frictional resistance reduction work or subsidence promotion work by injection of bentonite etc.) It is desirable to use in combination.

  In the above embodiment, an example is shown in which two sets of ground anchors 10a and 10b, each of which is a set of four, are used. The number of anchors 10a and 10b can be increased or decreased as appropriate. Further, a plurality of sets of ground anchors 10a or 10b having different fixing depths may be included, or the fixing depths of the ground anchors may be individually different. Further, for example, only a plurality of sets of ground anchors 10a or 10b are used, and the ground anchors 10a or 10b may include ones having different fixing depths, or individual ground anchors may be included. The fixing depth may be different.

  Furthermore, in the above embodiment, as described above, an annular segment assembled by combining a plurality of segment pieces Ps and Ps with a 1 / n circular steel (steel plate) segment piece Ps as a unit element. Although an example in the case of using S is shown, the 1 / n circular segment piece Ps may be made of reinforced concrete (RC), or even made of reinforced concrete in which the annular segment S itself is integrated. good.

  FIG. 3 shows a second embodiment for carrying out the caisson construction method according to the present invention, and the same reference numerals are given to the same parts as those in FIG. And

  In the second embodiment shown in FIG. 3, three sets of ground anchors 10 a, having different fixing depths are arranged around the caisson housing 1 to be constructed and at a position shallower than the final construction depth of the caisson housing 1. 10b and 10c are arranged. In addition, it is the same as that of the 1st form shown in FIG. 1 that each ground anchor 10a, 10b, 10c is considered so that it may not mutually overlap in the depth direction.

  Then, in the initial stage of press-fitting / sinking of the caisson housing 1, until the blade edge portion 1a at the tip, which is the deepest portion of the caisson housing 1, passes through the depth region of the pair of ground anchors 10a having the shallowest fixing depth, A pair of ground anchors 10b having a fixed fixing depth and a pair of ground anchors 10c having the deepest fixing depth are respectively connected to the corresponding grip jacks 7, and these two sets of ground anchors 10b and 10c are used. The ground reaction force shall be taken.

  In addition, as the caisson housing 1 is pressed and set, when the blade edge portion 1a of the caisson housing 1 reaches the depth region of the pair of ground anchors 10b having an intermediate depth, a reaction force is generated at that time. The ground anchor used as a receiver shall be switched. Specifically, after the blade edge portion 1a of the caisson housing 1 reaches the depth region of the ground anchor 10b having an intermediate fixing depth, the fixing depth is replaced with the two sets of the ground anchors 10b and 10c. A pair of ground anchors 10a having the shallowest depth and a pair of ground anchors 10c having the deepest anchoring depth are reconnected to the corresponding grip jacks 7, and the ground reaction force is obtained using these two sets of ground anchors 10a and 10c. Shall be taken.

  As the caisson housing 1 further press-fits and sinks, if the blade edge 1a of the caisson housing 1 reaches the depth region of the pair of ground anchors 10c having the deepest fixing depth, it is used as a reaction force receiver at that time. The ground anchor to be switched shall be switched. Specifically, after the blade edge portion 1a of the caisson housing 1 reaches the depth region of the pair of ground anchors 10c having the deepest fixing depth, the fixing is performed in place of the two sets of ground anchors 10a and 10c. A pair of ground anchors 10a having the shallowest depth and a set of ground anchors 10b having an intermediate fixing depth are reconnected to the corresponding grip jacks 7, and the two sets of ground anchors 10a and 10b are used. The ground reaction force shall be taken.

  After that, as the caisson housing 1 further press-fits and sinks, if the blade edge portion 1a of the caisson housing 1 exceeds the depth region of the pair of ground anchors 10c having the deepest anchoring depth, the subsequent operation will remain the same. It is assumed that the ground reaction force is taken by using two sets of ground anchors 10a and 10b in combination or by using two other sets of ground anchors 10a and 10c or 10b and 10c in combination.

  As described above, according to the present embodiment, the three sets of ground anchors 10a, 10b, and 10c having different fixing depths according to the press-fitting / sinking depth of the caisson housing 1 are selectively used, whereby each set of ground anchors 10a and 10b is used. , 10c, the caisson having the required depth can be constructed without being affected by the fixing depth. Therefore, also in the second embodiment, the same effect as in the first embodiment can be obtained.

  In the second embodiment, the case where three sets of ground anchors 10a, 10b, and 10c having different fixing depths are selectively used has been described as an example. However, depending on the construction depth of the caisson housing 1, three or more sets of ground anchors are used. Needless to say, it is also possible to use different types.

DESCRIPTION OF SYMBOLS 1 ... Caisson housing 1a ... Blade part 3 ... Clamshell bucket 7 ... Grip jack (press-fit device)
10a ... ground anchor 10b ... ground anchor 10c ... ground anchor S ... annular segment (body segment)

Claims (5)

The ground anchor is fixed in the ground outside the area where the caisson housing is press-fitted and sunk, and the caisson housing is pushed into the caisson housing by a press-fitting device while the reaction force is applied to the ground anchor. A caisson construction method for press-fitting and sinking,
Fixing a plurality of ground anchors having different fixing depths at a position shallower than the final press-fitting / sinking depth of the caisson housing,
When the blade edge portion of the caisson housing is in at least one of the ground anchor anchoring depth regions, the caisson housing is press-fitted and set in the ground while taking a reaction force on the remaining ground anchor. Caisson construction method. The ground anchor is fixed in the ground outside the area where the caisson housing is press-fitted and sunk, and the caisson housing is pushed into the caisson housing by a press-fitting device while the reaction force is applied to the ground anchor. A caisson construction method for press-fitting and sinking,
A plurality of sets of ground anchors having different fixing depths are fixed at a position shallower than the final press-fitting / sinking depth of the caisson housing,
When the blade edge of the caisson housing is in the anchoring depth region of any one set of ground anchors, the caisson housing is press-fitted and set in the ground while taking reaction force against at least one other set of ground anchors. Characteristic caisson construction method. Fix three or more ground anchors with different fixing depths,
When the blade edge of the caisson housing is in the anchoring depth region of any one set of ground anchors, the caisson housing is press-fitted and set in the ground while taking a reaction force on the other plurality of sets of ground anchors. The caisson construction method according to claim 2.   The caisson construction method according to claim 2 or 3, wherein the plurality of sets of ground anchors have different fixing depths in stages so that the fixing depths do not overlap each other.   A caisson having a required depth is constructed by repeating the press-fitting / sinking of the caisson frame, the addition of the frame segment to the upper part of the caisson frame, and the excavation / soil removal inside the caisson frame. The caisson construction method according to any one of claims 1 to 4.

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