Method for correcting rotation and caisson structure

Abstract

To provide a correction method of rotation of a caisson skeleton and a caisson skeleton in a pneumatic caisson method.SOLUTION: A correction method of rotation of a caisson skeleton 100 accompanied by sinking of the caisson skeleton 100 in a pneumatic caisson method includes: a tensioning step in which a tendon 110 provided at an outer periphery of the caisson skeleton 100 gives tensile force T in a direction correcting rotation; and a correction step of correcting rotation of the caisson skeleton 100 by the tensile force T when the caisson skeleton 100 sinks.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for correcting the rotation of a caisson body in the pneumatic caisson method and to such a caisson body.

Background Art

[0002] In the pneumatic caisson method, the caisson body may rotate horizontally when the caisson body is sunk. Such rotation is not preferable because it reduces the construction accuracy of the caisson body installation and may also affect the accuracy of the structure to be built later.

[0003] Therefore, various methods for suppressing the rotation of the caisson body have been developed. For example, in Japanese Patent Application Laid-Open No. 2015-74941 (Patent Document 1), a rotation correction device is detachably attached to the inner peripheral surface of the blade edge, the caisson body after rotation occurs is sunk into the ground, and the rotation correction device guides the caisson body to rotate in the direction opposite to the direction in which the caisson body has rotated.

[0004] However, the method of Patent Document 1 has a large burden from the viewpoints of controlling the correction amount and removing the rotation correction device. Therefore, a method that can easily correct the rotation of the caisson body has been desired.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] This invention has been made in view of the problems in the prior art described above, and aims to provide a method for correcting the rotation of a caisson structure in a pneumatic caisson construction method, and a caisson structure thereof. [Means for solving the problem]

[0007] In other words, according to the present invention, A method for correcting the rotation of the caisson body during the sinking of the caisson body in a pneumatic caisson construction method, A tensioning step is performed in which a tensioning member provided on the outer circumference of the caisson structure applies tension in the direction that corrects the rotation, A correction step is performed to correct the rotation of the caisson structure by the tension force when the caisson structure sinks. A correction method is provided, which includes [this]. [Effects of the Invention]

[0008] According to the present invention, a method for correcting the rotation of a caisson structure in a pneumatic caisson construction method and a caisson structure thereof can be provided. [Brief explanation of the drawing]

[0009] [Figure 1] A diagram illustrating the general outline of a typical pneumatic caisson construction method. [Figure 2] A diagram illustrating an example of the planar shape of a caisson structure. [Figure 3] A flowchart illustrating a method for correcting the rotation of the caisson structure in this embodiment. [Figure 4] A diagram showing the tensioning process for applying tension to the caisson structure in the method of this embodiment. [Figure 5] A plan view showing the correction of the rotation of the caisson structure by the method of this embodiment. [Figure 6] A cross-sectional view showing the correction of the rotation of the caisson structure by the method of this embodiment. [Figure 7] A diagram showing an example of correcting the rotation of the caisson structure by the method of this embodiment.

Best Mode for Carrying Out the Invention

[0010] Hereinafter, the present invention will be described with embodiments, but the present invention is not limited to the embodiments described later. In each of the figures referred to below, the same reference numerals are used for common elements, and the description thereof will be omitted as appropriate.

[0011] FIG. 1 is a diagram for explaining the outline of a general pneumatic caisson method. The pneumatic caisson method is a construction method adopted when installing underground structures such as the foundations of bridges and buildings, the shafts for shield construction, and the foundations of dams. As shown in FIG. 1(a), in the pneumatic caisson method, at the construction site 1, a caisson body 100 having an excavation space 200 at the lower part is sunk. Compressed air is sent into the excavation space 200, and by increasing the pressure inside the space, it is possible to prevent the inflow of groundwater into the space.

[0012] FIG. 1(b) schematically shows the forces acting on the caisson body 100. W represents the weight of the caisson body 100, U represents the uplift pressure, F represents the circumferential frictional force of the caisson body 100, and R represents the blade edge resistance. W and U are fixed values, and F and R are variables, which are set as F0 and R0 as initial values here. When the sum of U, F, and R is greater than W (the following formula (1)), the caisson body 100 does not sink and remains in the same position.

[0013]

Equation

[0014] On the other hand, when excavation is carried out in the excavation space 200, the values of F and R decrease (F’ << F0, R’ << R0), and when W becomes larger than the sum of U, F, and R (the following formula (2)), the caisson body 100 sinks. Thus, by repeating excavation and sinking, the caisson body 100 can be sunk to a predetermined depth.

[0015]

Equation

[0016] FIG. 2 is a diagram for explaining an example of the planar shape of the caisson body 100. The planar shape of the caisson body 100 can adopt various shapes depending on the use of the structure and the like. In FIG. 2, as examples of the planar shape of the caisson body 100, a rectangle (FIG. 2(a)), a circle (FIG. 2(b)), and a oval shape (FIG. 2(c)) are shown. Also, in the lower diagrams of FIGS. 2(a), (b), and (c), side cross-sectional views of the caisson body 100 are shown. The broken lines on the outer periphery of the caisson body 100 in each figure of FIG. 2 indicate the overexcavation locus due to the friction cut of the blade edge.

[0017] The arrows in the upper diagrams of FIG. 2 correspond to the blade edge reaction forces in the lower diagrams of FIG. 2. Also, the length L from the center of the planar shape of the caisson body 100 to the blade edge reaction force (hereinafter referred to as "arm length L") is long in the order of rectangle, oval shape, and circle as shown in FIG. 2. Here, in the rotation correction of the conventional caisson body 100, it was dealt with by the excavation residue deviation at the lower end of the blade edge and the installation of resistance members on the blade edge, etc., and it was effective for those with a relatively long arm length, but the effect of rotation correction was small for circular and oval shapes with a short arm length. In particular, the oval-shaped caisson body 100 has a relatively large rotatable range within the overexcavation locus area and thus has a tendency to rotate easily, and a correction method for dealing with this has been demanded.

[0018] Therefore, in the embodiment described below, the oval-shaped caisson body 100 is exemplified. However, the embodiments of the invention are not limited thereto, and the present invention can be adopted for caisson bodies 100 with other planar shapes.

[0019] FIG. 3 is a flowchart of a method for correcting the rotation of the caisson body 100 in the present embodiment. When starting the pneumatic caisson method in step S1000, in step S1001, excavation is performed in the excavation space 200 to sink the caisson body 100. Next, in step S1002, the process branches depending on whether the caisson body 100 has reached a predetermined depth.

[0020] If the caisson structure 100 reaches a predetermined depth in step S1002 (YES), the process proceeds to step S1006, and the sinking of the caisson structure 100 using the pneumatic caisson method is completed.

[0021] In step S1002, if the caisson structure 100 has not reached the predetermined depth (NO), the process proceeds to step S1003 to perform further sinking. In step S1003, the process branches depending on whether the amount of rotation of the caisson structure 100 is within the allowable range. The allowable amount of rotation can be arbitrarily set according to the conditions of the construction site 1 and the construction accuracy of the installation of the caisson structure 100. Furthermore, the allowable amount of rotation does not necessarily have to be the limit of the construction accuracy; for example, if the rotation continues without correction and the caisson structure continues to sink to such an extent that it no longer meets the construction accuracy requirements, the rotation may be corrected. In step S1003, if the amount of rotation of the caisson structure 100 is within the allowable range (YES), the process returns to step S1001 and the above processes are repeated. On the other hand, in step S1003, if the amount of rotation of the caisson structure 100 is not within the allowable range (NO), the process proceeds to step S1004 to correct the rotation of the caisson structure 100.

[0022] In step S1004, tensioning members 110 apply tension to correct the rotation of the caisson structure 100. Since the direction and amount of rotation of the caisson structure 100 can vary depending on various conditions such as the excavated ground, tension is applied in a direction and magnitude corresponding to the actual rotation situation.

[0023] Here, the process of applying tension to the caisson structure 100 in step S1004 will be explained with reference to Figure 4. Figure 4 is a diagram showing the tensioning process of applying tension to the caisson structure 100 in the method of this embodiment. Figure 4(a) shows a top plan view of the caisson structure 100 in the tensioning process, and Figure 4(b) shows a side cross-sectional view of the caisson structure 100 in the tensioning process.

[0024] Here, we consider the case where the caisson structure 100 unintentionally rotates counterclockwise (in the direction of arrow A in Figure 4) during the sinking process. In this case, in order to ensure the construction accuracy of the caisson structure 100, it is necessary to correct it by rotating it clockwise. Therefore, in the tensioning process of the method of this embodiment, as shown in Figure 4(a), a clockwise tension force T is applied to the caisson structure 100 by the tensioning member 110. One end of the tensioning member 110 is connected to the caisson structure 100 by the structure embedding jig 120, and the other end is connected to the reaction force receiver 130 provided on the ground at the construction site 1, thereby applying a tension force T to the caisson structure 100 in the direction that corrects the rotation. Since it is important that the tensioning member 110 continues to apply tension during the sinking process, it is effective to use, for example, PC steel wire, but this does not particularly limit the embodiment.

[0025] The structural embedding jigs 120 can be installed on the outer surface of the caisson structure 100, and it is preferable to install two or more. In particular, when installing an even number of structural embedding jigs 120, it is preferable to arrange them symmetrically with respect to the center of the planar shape of the caisson structure 100. The structural embedding jigs 120 can be arranged in positions and numbers depending on the planar shape and rotation of the caisson structure 100.

[0026] Furthermore, as shown in Figure 4(b), it is preferable that the tensioning force T applied by the tensioning member 110 has a component in the downward direction from the horizontal plane where the structural embedding jig 120 is installed. This reduces the tensioning force as the diagonal distance of the tensioning member 110 decreases when the caisson structure 100 settles during the correction process described later, allowing for safe construction with a tensile force lower than the initial tensioning force.

[0027] Let's return to the explanation in Figure 3. Then, in step S1005, while maintaining the tension force applied in step S1004, excavation is carried out in the excavation space 200 to sink the caisson body 100. At this time, since tension force is continuously applied to the caisson body 100 in a direction that corrects rotation, when the circumferential friction force F decreases to the extent that the caisson body 100 sinks, aided by the effect of reducing circumferential friction force by the lubricant, the caisson body 100 rotates in the direction of the tension force as it sinks, thus correcting the unintended rotation that occurred earlier.

[0028] After correcting the rotation of the caisson structure 100 in step S1005, the process returns to step S1002 and the above steps are repeated. This allows the caisson structure 100 to be sunk to a predetermined depth while appropriately correcting its rotation.

[0029] Next, each step of the method of this embodiment will be explained with reference to Figures 5 and 6. Figure 5 is a plan view showing the correction of the rotation of the caisson frame 100 by the method of this embodiment, with Figure 5(a) showing the tensioning process and Figure 5(b) showing the correction process.

[0030] Here, we consider the case where the caisson structure 100 is rotating counterclockwise, as shown by arrow A in Figure 5(a). In this case, first, in the tensioning process, the caisson structure 100 is connected to the excavated ground via tensioning members 110 and reaction force receivers 130, as shown in Figure 5(a). At this time, the tensioning members 110 apply a tensioning force T in the direction that corrects the rotation of the caisson structure 100. In the example in Figure 5, two structure embedding jigs 120 are provided on the caisson structure 100.

[0031] Subsequently, during the correction process, excavation is carried out in the excavation space 200, and as the cutting edge surface plasticizes, the load balance is disrupted (see equation (2)), and the caisson structure 100 sinks in a state close to free fall (hereinafter referred to as "sinking pattern A"). During this time, a tension force T is continuously applied to the caisson structure 100, causing the caisson structure 100 to rotate in the direction that corrects the previous rotation as it falls (Figure 5(b)).

[0032] Here, we consider the rotational moment given during the correction process. Applying the rotation of the caisson structure 100 in the correction direction during the fall as the rotational motion of a rigid body to Newton's equations of motion, assuming that the work done by the rotational motion and the change in rotational energy are equal, the following equation (3) holds.

[0033]

number

[0034] In equation (3) above, the left side represents the work done by rotational motion, and the right side represents the change in rotational energy. In equation (3), M is the rotational moment (kN·m), Δθ is the angle of rotation (rad), and I is the moment of inertia (t·m). 2 ), mi is the mass (t) of a small part of the caisson structure 100, ri is the centroidal radius (m) of a small part of the caisson structure 100, wi is the weight (kN) of a small part of the caisson structure 100, and g is the acceleration due to gravity (m / s²). 2 ω and ω represent angular velocity (rad / s), respectively.

[0035] In reality, the cutting edge resistance and circumferential friction are not zero, and due to factors such as the increase in pressure caused by the decrease in the height of the excavation space 200, it does not fall freely. However, despite these influences, the corrective effect of the tensioning force of the tensioning member 110 is still exerted.

[0036] Furthermore, at depths with a large amount of intervening sand, the bearing capacity at the cutting edge is small and the opening ratio (the ratio of the area of ​​ground remaining at the bottom of the cutting edge to the total area of ​​the caisson body 100) is small. As a result, even if the ground at the cutting edge becomes plastic, the caisson body 100 may not free fall and may settle with a relatively slow movement (hereinafter referred to as "settlement pattern B"). Even in such cases, the rotation of the caisson body 100 can be corrected according to the method of this embodiment.

[0037] Figure 6 is a cross-sectional view showing the correction of the rotation of the caisson structure 100 by the method of this embodiment, where Figure 6(a) shows the tensioning process and Figure 6(b) shows the correction process. Note that Figure 6(a) corresponds to Figure 5(a) and Figure 6(b) corresponds to Figure 5(b).

[0038] As shown in Figure 6(a), during the tensioning process, the caisson structure 100 is connected to the excavated ground via the tensioning member 110 and the reaction force receiver 130. At this time, the tensioning member 110 applies a tensioning force T to two locations on the caisson structure 100 in a direction that corrects the rotation. Furthermore, it is preferable that the tensioning member 110 has a tensioning force that includes a downward component, directed from the structure embedding jig 120 toward the reaction force receiver 130. That is, the structure embedding jig 120 in the tensioning process is positioned higher than the reaction force receiver 130.

[0039] Subsequently, during the correction process, the excavation space 200 is excavated, and as the cutting edge surface plasticizes, the load balance is disrupted (see equation (2)), causing the caisson structure 100 to settle, resulting in the state shown in Figure 6(b). As shown in Figure 6(b), as the caisson structure 100 settles, the tensioning member 110 becomes approximately horizontal. Furthermore, depending on the rotational state of the caisson structure 100, the tensioning and correction processes are repeated to correct the rotation.

[0040] In this way, the rotation of the caisson structure 100 can be appropriately corrected by the method of this embodiment.

[0041] Embodiments of the present invention have been described so far. Hereinafter, embodiments will be described in more detail using specific examples. [Examples]

[0042] The first embodiment described below is an implementation of the method of this embodiment described above under the following conditions. Specifically, the first embodiment involves sinking a caisson structure 100, which has a concrete weight W of 1,370,000 kN and an uplift pressure U of 800,000 kN, with an oval plan shape, a long side of 52 m and a short side of 49 m, to a depth of 80 m. In the construction of the first embodiment, the pneumatic caisson method is applied to the tunnel shaft, and an accuracy of within ±150 mm of the horizontal displacement relative to the tunnel portal is required. In the following description of the embodiment, displacement refers to the horizontal displacement of the opening of the caisson structure 100 relative to the tunnel portal at a predetermined position.

[0043] Under these conditions, the sinking and rotation of the caisson structure 100 were corrected, resulting in the findings shown in Figure 7. Figure 7 shows an example of correcting the rotation of the caisson structure 100 using the method of this embodiment. Note that the horizontal displacement values ​​on the vertical axis in Figure 7 are negative, which indicates that clockwise rotation is represented as positive. The numbers in parentheses in Figure 7 indicate the amount of rotation per 1 m of sinking.

[0044] As shown in Figure 7, when the caisson body 100 was sunk without any countermeasures for a while after the start of sinking, the horizontal displacement exceeded -120 mm when the depth exceeded 20 m. At this time, the caisson body 100 was rotating 6.5 mm counterclockwise horizontally for every 1 m of depth advancement. Therefore, if sinking was continued without any countermeasures, it is predicted that the horizontal displacement would exceed the control value of -150 mm. In Figure 7, the areas shown in lighter colors indicate the geological layers in which the caisson body 100 sunk according to settlement pattern A.

[0045] First, we implemented a conventional rotation correction method, which involves correcting the deviation of the uncut area at the lower end of the cutting edge. As a result, the displacement due to rotation per 1m of depth, which was -6.5mm / m without the countermeasure, was reduced to -0.7mm / m. However, the counterclockwise rotation continued, indicating that further measures were needed.

[0046] Next, as a further measure, the modification method of this embodiment was implemented. First, two PC steel strands were placed in two locations as tensioning members 110, and the modification method of this embodiment was implemented (section A1 in Figure 7). The horizontal component of the tension force of the PC steel strands was 4,000 kN (1,000 kN / (strand / location) × 2 strands × 2 locations = 4,000 kN). At this time, the caisson structure 100 settled in settlement pattern A, and as a result, the caisson structure 100 rotated clockwise at a rate of 0.7 mm / m, correcting the previous rotation.

[0047] On the other hand, since the rotation still required correction, the correction method of this embodiment was continued (section A2 in Figure 7). Here, in order to increase the amount of correction, the number of PC steel strands was increased to 3 per location and the correction was carried out. The horizontal component of the tension force of the PC steel strands was 6,000 kN (1,000 kN / (strand / location) × 2 strands × 3 locations = 6,000 kN). At this time, the caisson structure 100 sank in settlement pattern A, and as a result, the caisson structure 100 rotated clockwise at a rate of 3.7 mm / m, correcting the previous rotation. In other words, without any countermeasures, the structure rotated 6.5 mm counterclockwise per meter of depth, but with the modification according to the embodiment, it rotated 3.7 mm clockwise per meter of depth. As a result, the caisson structure 100 rotated 10.2 mm clockwise {3.7 mm - (-6.5 mm) = 10.2 mm} for every meter of sinking caused by the tensioning force of the tensioning member 110.

[0048] Furthermore, when the modification method of this embodiment was continued under the same conditions as in section A2, the properties of the geological layer changed, and the caisson began to settle in settlement pattern B from a depth of approximately 50m. In Figure 7, the area shown in dark color indicates the geological layer in which the caisson body 100 settles in settlement pattern B. As a result, the caisson body 100 rotated clockwise at a rate of 2.0 mm / m, correcting the previous rotation. In other words, it was confirmed that even when settlement pattern B occurs, the rotation of the caisson body 100 can be appropriately corrected, although the amount of rotation correction is smaller than that of settlement pattern A.

[0049] The first embodiment described above demonstrated that the rotation of the caisson structure 100, which has an oval planar shape, can be appropriately corrected. In particular, in the case of oval shapes, the arm length is short, making it difficult to correct the rotation using conventional methods, but as explained in the first embodiment, the correction method of this embodiment has been shown to be effective.

[0050] According to the embodiments of the present invention described above, a method for correcting the rotation of a caisson structure in a pneumatic caisson construction method and a caisson structure thereof can be provided.

[0051] Although the present invention has been described above with reference to embodiments, the present invention is not limited to the embodiments described above. It is included within the scope of the present invention as long as it achieves the effects and advantages of the present invention within the range of embodiments that a person skilled in the art could deduce. [Explanation of Symbols]

[0052] 1...Construction site, 100... Caisson structure, 110...Tension material, 120... Fixture for embedding in the building structure, 130... receiving the reaction force, 200...Excavation space

Claims

1. A method for correcting the horizontal rotation of a caisson body during the sinking of a caisson body in a pneumatic caisson construction method, A tensioning step is performed in which a tensioning member provided on the outer circumference of the caisson structure applies tension in a direction that corrects the rotation in the horizontal direction, A correction step is performed to correct the horizontal rotation of the caisson structure by the tension force when the caisson structure sinks. Correction methods, including those mentioned above.

2. The tensioning members are provided in multiple locations symmetrically around the center of the planar shape of the caisson structure. The modification method described in claim 1.

3. The tensioning process involves connecting the outer perimeter of the caisson structure and the excavated ground via the tensioning material, and the ground receiving a reaction force thereby applying the tensioning force. The modification method according to claim 1 or 2.

4. In the tensioning process, the tensioning member is joined to the outer circumference of the caisson structure at a position higher than the position where it is joined to the ground. The modification method described in claim 3.

5. The modification method according to any one of claims 1 to 4, characterized in that the planar shape of the caisson structure is oval.

6. A caisson structure used in the pneumatic caisson construction method, A caisson structure characterized by having tensioning members on the outer circumference of the caisson structure that apply tension in a direction that corrects the rotation of the caisson structure in the horizontal direction.

Images