Caisson method

Abstract

To provide a caisson method which reduces an excavation work amount by using an excavation machine such as a clamshell, and achieves shortening of a process and reduction in cost.SOLUTION: In a caisson method, a skeleton is constructed on the ground and is sequentially installed into the ground, and while the skeleton inside is repeatedly excavated, an underground structure of a prescribed depth is constructed. In a previous stage of starting installation of the skeleton 2 into the ground, multiple excavation holes 3, 3,... of a prescribed depth are cylindrically formed in an excavation range inside the skeleton 2, and high-water-absorption polymer stabilizing liquid 4 is filled in the excavation holes 3, 3... to obtain the stability of a porous wall. Then, following the ordinary construction procedure, skeleton construction on the ground, installation into the ground and excavation inside the skeleton are repeated, to thereby construct an underground structure 1 of a prescribed depth.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a caisson construction method that reduces the amount of excavation work required by excavation machines such as clamshells, thereby shortening the process and reducing costs. [Background technology]

[0002] For example, the caisson method has been used for constructing underground structures such as bridge foundations, building foundations, water cut-off walls, underground tanks, and tunnel shafts. This caisson method can be broadly divided into the open caisson method, and an improved version of the open caisson method: the press-in open caisson method, and the pneumatic caisson method. The open caisson method is a method in which the inside of a cylindrical body with open top and bottom surfaces is excavated and carried out from the ground by an excavation machine such as a clamshell, and the body constructed on the ground is gradually lowered (see, for example, Patent Document 1 below). The press-in open caisson is a method in which a gripper rod is connected to a ground anchor driven into the ground, a cylindrical body with a cutting edge at the bottom end is constructed, a loading girder is placed on top of the body via a bearing material, and the loading is applied while the ground inside the body is excavated by an excavation machine such as a clamshell. This is a construction method in which a gripper rod is tensioned by a hydraulic jack attached to the girder, and the ground anchor is used to provide a reaction force while the body is pressed (sunk) into the ground (see, for example, Patent Document 2 below). The pneumatic caisson method involves providing an airtight work chamber below the body, pumping compressed air into the bottom in an amount that matches the pore water pressure in the ground to prevent groundwater from seeping in, and gradually sinking the body constructed on the ground while excavating and transporting the soil and sand by hand or by excavating machinery in a dry state (see, for example, Patent Document 3 below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-50464 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-207152 [Patent Document 3] Patent No. 6653510 construction method Summary of the Invention [Problem to be solved by the invention]

[0004] In particular, in the case of the open caisson method and the press-in open caisson method, excavation is usually carried out using a clamshell bucket suspended by a wire rope from a crane, taking into account that the top of the structure is open and the excavation depth is deep.

[0005] However, due to its structure, clamshell buckets have a lower digging capacity than backhoes, etc., so the excavation work takes up a lot of time and effort in the overall work process, making it difficult to shorten construction time and increasing excavation costs.

[0006] Therefore, the main object of the present invention is to provide a caisson construction method that reduces the amount of excavation work using excavation machines such as clamshells, thereby shortening the process and reducing costs. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the present invention according to claim 1 provides a caisson construction method in which a skeleton is constructed on the ground, and then the skeleton is gradually sunk into the ground, and an underground structure of a predetermined depth is constructed by repeatedly excavating the inside of the skeleton. Before starting to sink the cable underground, the area inside the structure to be excavated is By drilling bucket or hammer grab of earth drill method A plurality of cylindrical boreholes of a predetermined depth are formed, and the borehole walls are stabilized by filling the boreholes with a highly water-absorbent polymer stabilizing liquid. Next, a caisson construction method is provided, which is characterized by constructing an underground structure of a predetermined depth by repeating the steps of constructing a structure on the ground, sinking it into the ground, and excavating the inside of the structure according to normal construction procedures.

[0008] In the invention described in claim 1, before starting to sink the cable into the ground, the area to be excavated inside the body is Drilling bucket or hammer grab for earth drilling method A plurality of cylindrical drilled holes of a predetermined depth are formed, and the holes are filled with a highly water-absorbent polymer stabilizing liquid to stabilize the hole walls. Drilling buckets for earth drilling methods, hammer grabs, etc. This is done using drilling equipment. These drilling rigs Excavation efficiency can be more efficient than excavation using a clamshell bucket inside a caisson, and by forming multiple drilling holes in advance, the amount of soil excavated using a clamshell bucket can be reduced, thereby shortening the process and reducing costs.

[0009] Furthermore, while bentonite stabilizer is typically used to protect the borehole walls, this bentonite stabilizer is a type of clay containing iron ores such as montmorillonite, quartz, and opal, and disposal costs are high because the entire amount must be treated as industrial waste. However, in the case of the superabsorbent polymer stabilizer used in the present invention, adding divalent metal ions such as calcium chloride increases the electrical conductivity of the solvent, thereby utilizing the phenomenon in which water adsorbed on the polymer material separates, making it possible to reduce the amount of waste liquid to be disposed of and therefore disposal costs.

[0010] Claim 2 As the present invention according to the above, a plurality of the drilled holes are formed in a regular lattice arrangement or a staggered lattice arrangement in a plan view inside the body. 1st article The caisson construction method described above is provided.

[0011] The above claims 2 The invention specifies the formation pattern of the boreholes. Specifically, it is desirable to form a plurality of boreholes in a regular lattice or staggered pattern in a plan view. In this case, from the viewpoint of protecting the borehole walls, it is preferable that the area of ​​the boreholes relative to the area of ​​the caisson excavated inside the structure in a plan view be about 15 to 30%.

[0012] Claim 3 As the present invention, the caisson construction method is an open caisson construction method or a press-fit open caisson construction method.、2 Any of the caisson construction methods described above is provided.

[0013] The above claims 3 The invention described here defines the preferred caisson construction method to which the present invention is applicable. In other words, although it can be applied to the pneumatic caisson method, the construction to which the present invention is preferably applied is the open caisson method or the press-fit open caisson method, which employs a clamshell excavation method with relatively low excavation efficiency.

[0014] Claim 4 As the present invention relating to the above, the caisson construction method is a press-fit open caisson construction method, and the borehole is formed in parallel with the construction of the ground anchor and within the period of the ground anchor construction. 、2 Any of the caisson construction methods described above is provided.

[0015] The above claims 4 In the described invention, since it is undesirable for the formation of the borehole to result in an extension of the construction period, when the caisson method is a press-fit open caisson method, it is desirable that the formation of the borehole be carried out in parallel with and within the period of the ground anchor construction.

[0016] Claim 5 As the present invention, the soil and sand generated by excavation inside the framework is disposed of after separation of the superabsorbent polymer stabilizing liquid. 4 Any of the caisson construction methods described above is provided.

[0017] The above claims 5 The described invention aims to reduce the volume of excavated soil by separating the highly water-absorbent polymer and then disposing of it. [Effects of the Invention]

[0018] As explained above in detail, according to the present invention, it is possible to provide a caisson construction method that reduces the amount of excavation work using excavation machines such as clamshells, shortens the process, and reduces costs. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic explanatory diagram of a caisson construction method according to the present invention. [Figure 2] FIG. [Figure 3] This is a construction procedure diagram (part 1) of the caisson construction method according to the present invention. [Figure 4] This is a construction procedure diagram (part 2) of the caisson construction method according to the present invention. [Figure 5] This is a construction procedure diagram (part 3) of the caisson construction method according to the present invention. [Figure 6] This is a construction procedure diagram (part 4) of the caisson construction method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0021] The caisson method involves constructing a framework on the ground, which is then gradually sunk into the ground, while repeatedly excavating the interior of the framework to construct an underground structure 1 of a predetermined depth. Among the various caisson methods, this embodiment will explain the method of the present invention based on the example of the press-in open caisson method.

[0022] In the press-in open caisson method, first, a hole is drilled in the ground for the ground anchor, and then a tendon (tensile material) 13 is inserted into the hole. At the same time, a grout material is injected into the bottom of the hole to create an anchorage 12. Then, the caisson body 2 is installed. n When the tendon 13 is installed, a center hole jack 6 is set on the tendon 13 to introduce tension, and the reaction force causes the body 2 n The construction of the body 2 is carried out on the ground one rod at a time. nOnce this is completed, the excavation is repeated to construct underground structures 1 such as bridge foundations, building foundations, water cut-off walls, underground tanks, and tunnel shafts.

[0023] In the present invention, in the press-in open caisson method, as shown in Figures 1 and 2, in the stage before starting to sink the skeleton 2 into the ground, a plurality of cylindrical excavation holes 3, 3 ... of a predetermined depth are formed in the planned excavation area inside the skeleton 2, and a superabsorbent polymer stabilizing liquid 4 is filled into these excavation holes 3, 3 ... to stabilize the hole walls, Next, following the normal construction procedures, the underground structure 1 is constructed to a predetermined depth by repeating the steps of constructing the skeleton on the ground, sinking it into the ground, and excavating the interior of the skeleton. The skeleton 2 is divided into six vertically separated skeletons 21 to 26, and the separated skeletons 21, 22, 23...26 are constructed on the ground in this order and then sunk into the ground.

[0024] This will be described in more detail below with reference to the drawings. <Ground anchor work and drilling hole formation work> Prior to the installation of the main body, as shown in Figure 3, ground anchor work is carried out and, in parallel with this, a drilling bucket using an earth drill method is used to form multiple cylindrical boreholes 3, 3... of a predetermined depth within the planned excavation area inside the main body 2.

[0025] In the ground anchor work, as shown in the figure, a drilling machine 10 is used to drill a hole 3 of a specified diameter to a specified depth. Next, as shown in the drilling position on the left side of the figure, a tendon 13 (tensile member) is inserted and grout is injected into the tip to form an anchoring part 12, which serves as a fixed part that allows tensile force to be introduced into the tendon 13. As shown in Figure 2, a total of eight ground anchors 5 are installed, two for each loading girder 8 located at the four corners.

[0026] The tendons 13 are made of tension materials such as PC steel rods, PC steel strands, multi-layer PC steel strands, and continuous fiber reinforcement, and are placed underground. Gripper rods 14 are connected to the tendons 13 above ground. The gripper rods 14 are inserted into center hole jacks 6 installed on the top surface of the loading girders 6, and tension is applied by the center hole jacks 6.

[0027] The work of forming the boreholes 3, 3 ... is carried out in parallel with the ground anchor work, preferably within that period. The borehole work is desirably carried out using a drilling bucket 16 used in the earth drill method, as shown in Figure 3. In the illustrated example, a rope method is used with the drilling bucket 16 suspended by a crane 15. The depth of the boreholes 3 may be aligned with the bottom position of the caisson (underground structure 1) to be constructed underground, or may be slightly shorter or longer than this. If it is desired to obtain the effect of forming the boreholes 3 over the entire length of the caisson 1, it is desirably formed to be aligned with the bottom position of the caisson 1.

[0028] The inside of the boreholes 3, 3... is filled with a superabsorbent polymer stabilizer 4 to protect the hole walls. Compared to conventional bentonite-based stabilizers, the superabsorbent polymer stabilizer 4 improves the stability of the excavated ground, improves the quality of cast-in-place concrete structures, reduces the amount of industrial waste generated by the stabilizer excavation method, and streamlines construction work.

[0029] The superabsorbent polymer stabilizer 4 is a swollen superabsorbent polymer stabilizer for ground excavation containing water, superabsorbent polymer particles that have absorbed and swollen water, and at least one of a weighting material, a stabilizer, and an auxiliary agent, and is desirably bentonite-free and has a specific gravity of 1.20 or less. It is also desirably that the superabsorbent polymer particles are sodium polyacrylate, the weighting material is at least one inorganic material selected from fine sand and sulfate minerals with a maximum particle size of 2.0 mm or less, the stabilizer is polyacrylamide, and the auxiliary agent is at least one material selected from sawdust, pulp, rock wool, and fiber lost circulation prevention materials that improve hole wall stability.

[0030] This superabsorbent polymer stabilizing liquid was developed by the present applicant in collaboration with others, and specifically, is the superabsorbent polymer stabilizing liquid described in Japanese Patent No. 6113433.

[0031] By using the superabsorbent polymer stabilizing solution 4 to protect the wall of the borehole 3, it is possible to significantly reduce the amount of excavated soil and sand. Specifically, the superabsorbent polymer stabilizing solution 4 can be separated into soil and water components by utilizing the phenomenon in which the water adsorbed to the polymer material is separated by adding divalent metal ions such as calcium chloride to increase the electrical conductivity of the nutrient solution, thereby making it possible to reduce the amount of industrial waste to be disposed of.

[0032] The boreholes 3 may be formed in a plurality of regular lattice arrangements in plan view, as shown in Fig. 2, or may be formed in a plurality of staggered arrangements. In this case, from the viewpoint of protecting the walls of the boreholes 3, it is preferable that the total area of ​​the boreholes 3, 3... relative to the caisson excavation area inside the skeleton 2 in plan view is about 15 to 30%, and preferably about 17 to 25%.

[0033] <Structure work and submerged structure work> Next, the construction of the main structure and the construction of the main structure begin. The main structure 2 is divided into six vertically separated structures 21 to 26, and the separated structures 21, 22, 23, ... 26 are constructed on the ground in succession on the upper side of the already constructed main structure in this order.

[0034] First, as shown in Figure 4, a first body 21 with a cutting edge at its tip is constructed on the ground. Then, a loading girder 8 is placed across the press-fit force transmission members 7, 7 protruding from the top of the body, and a gripper rod 14 connected to a tendon 13 of the ground anchor 5 is inserted into the loading girder 8 and connected to the center hole jack 6 placed on the top surface of the loading girder 8.

[0035] Next, the center hole jack 6 is hydraulically driven to apply a tensile force to the ground anchor 5, thereby pressing the first body 21 into the ground. Once the pressing is complete, the earth and sand inside the first body 21 is excavated using a clamshell bucket 9, as shown in FIG. The aforementioned The clamshell bucket 9 is an excavator commonly used in the open caisson method or the press-fit open caisson method, and is a type that grabs soil by dropping an open clamshell bucket and then pulling it up to close the bucket. The clamshell bucket 9 can be operated by a crane (rope method), a telescopic arm method, a hydraulic clam method, etc. The excavation capacity is approximately 0.6 m when using the rope method. 3 ~1.0m 3 In the case of the telescopic arm system, it is approximately 0.25m. 3 ~0.6m 3 is.

[0036] Once excavation using the clamshell bucket 9 is complete, the second skeleton 22 is constructed on top of the first skeleton 21, as shown in FIG. 5. The second skeleton 22 can be constructed by the slip-form method using a slip-form device 17, as shown in the same figure. The slip-form method is a construction method in which a concrete form (FORM) is pushed up with a jack and slid up (SLIP) while concrete is continuously poured to build the skeleton. When constructing the second skeleton 22, the press-fit force transmission member 7 is embedded inside the skeleton so as to be continuous with the press-fit force transmission member 7 of the first skeleton 21.

[0037] Once construction of the second body 22 is complete, the loading girder 8 is installed between the press-in force transmission members 7, 7, and the gripper rod 14 is connected to the center hole jack 6 to complete preparations for press-in. A tensile force is introduced into the ground anchor 5 by hydraulically driving the center hole jack 6, and the first body 21 and the second body 22 are pressed into the ground. Once press-in is complete, the earth and sand inside the body 2 is excavated using the clamshell bucket 9.

[0038] By repeating the above-described steps of constructing the separate bodies 21 to 26, pressing the bodies into place, and excavating the interior of the bodies in sequence, all of the separate bodies 21 to 26 are pressed into the ground, the soil inside them is excavated, and then the base slab concrete 18 is poured to complete the underground structure 1, as shown in Figure 6. [Effectiveness calculation by the method of the present invention] When applying the method of the present invention, if the drilling bucket 16 used in an earth drill is used to form the boreholes 3, 3... within the period of driving the ground anchors 5, the process can be shortened by the amount of soil excavated for the clamshell 9, and construction costs can be reduced accordingly.

[0039] (1) Process shortening effect Total excavated volume: 5,765m 3 If the entire volume is excavated using a clamshell, the 3 If the average excavation sinking time per drilling is 2.16 hours, the actual number of operating days will be 38.1 days (7 hours / day).

[0040] In contrast, the method of the present invention was applied, and the total excavated soil volume was 5,765 m 3 If 954.3m3 of the total is excavated using the earth drill bucket method, Clamshell excavation volume: 4,811m3 ⇒ Actual operation days: 31.8 days Earth drill excavation volume: 954.3 m3 ⇒ Since this will be done during ground anchor construction, the actual number of working days will be 0 days.

[0041] Therefore, the method of the present invention can shorten the process by approximately six days.

[0042] (2) Reduction of construction costs Total excavated volume: 5,765m 3 If the entire amount is excavated using a clamshell, the cost will be 5,765 m3 x 5,053 (yen / m3) = 29,132,061 yen.

[0043] In contrast, the method of the present invention was applied, and the total excavated soil volume was 5,765 m 3 If 954.3m3 of the total is excavated using the earth drill bucket method, Clamshell excavation ⇒ 4,811m3 x 5,053 (yen / m3) = 24,309,983 yen Earth drill excavation ⇒ 954.3m3 x 3,846 (yen / m3) = 3,670,237 yen +Equipment removal costs (490,500 yen), totaling 27,980,221 yen.

[0044] Therefore, if the method of the present invention is used, construction costs can be reduced by 1,151,840 yen.

[0045] [Other examples] (1) In the above embodiment, the borehole 3 is formed by the drilling bucket 16 of the earth drill method, but it may be formed by a hammer grab. (2) The caisson construction method according to the present invention is suitably applied to open caisson construction methods and press-in open caisson construction methods, but can also be applied to pneumatic caisson construction methods. [Explanation of symbols]

[0046] 1...underground structure (caisson), 2...main body, 3...borehole, 4...superabsorbent polymer stabilizer, 5...ground anchor, 6...center hole jack, 7...pressure force transmission member, 8...loading girder, 9...clamshell bucket, 10...boring machine, 12...anchoring part, 13...tendon, 14...gripper rod, 15...crane, 16...drilling bucket, 17...slip form device, 18...bottom slab concrete

Claims

1. In the caisson method, a structure is constructed above ground, then gradually lowered into the ground, and excavation is repeated inside the structure to build an underground structure of a specified depth. Prior to starting to sink the pipe into the ground, a number of cylindrical boreholes of a predetermined depth are formed in the area to be excavated inside the structure using a drilling bucket or hammer grab of the earth drill method, and the borehole walls are stabilized by filling the boreholes with a highly water-absorbent polymer stabilizing liquid. Next, in accordance with normal construction procedures, the caisson method is characterized by constructing an underground structure of a specified depth by repeating the steps of constructing a structure on the ground, sinking it into the ground, and excavating the inside of the structure.

2. The caisson construction method according to claim 1, wherein the boreholes are formed in a plurality of locations inside the structure in a regular lattice arrangement or a staggered lattice arrangement when viewed from above.

3. The caisson construction method according to claim 1 or 2, which is directed to an open caisson construction method or a press-in type open caisson construction method.

4. 3. The caisson method according to claim 1, wherein the caisson method is a press-in type open caisson method, and the borehole is formed in parallel with the construction of the ground anchor and within the period of the construction of the ground anchor.

5. A caisson construction method according to any one of claims 1 to 4, wherein the soil and sand generated by excavation inside the structure is subjected to a separation process of a highly absorbent polymer stabilizing liquid and then disposed of.

Images