Pile construction method
The pile construction method uses dry ice in cement-based solidification materials to ensure fluidity and strength of soil cement, addressing the challenges of admixture-dependent soil cement performance and enhancing construction efficiency.
Patent Information
- Application Number
- JP2024130701
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-08-07
- Publication Date
- 2026-02-20
Smart Images
Figure 2026028359000001_ABST
Abstract
Description
[Technical Field]
[0001] The present invention relates to a pile construction method, such as a pre-bored pile construction method. [Background technology]
[0002] Conventionally, a pre-bored pile construction method has been known in the fields of foundation work in architecture and civil engineering, in which foundation piles are buried and fixed in the ground (see, for example, Non-Patent Document 1). This pre-bored pile construction method involves using an excavating and mixing device with a diameter slightly larger than the pile diameter, injecting an appropriate amount of drilling fluid (drilling mud) into the ground while excavating and mixing the ground to a predetermined depth over the same diameter over the entire length, constructing a foot protection section (soil cement) at the bottom of the excavation, then injecting and mixing a fixing fluid around the pile while pulling up the excavating and mixing device to construct a fixing section around the pile (soil cement) in the ground, and then erecting a pre-fabricated pile into the soil cement in the constructed excavated hole to secure it in place.
[0003] When constructing pre-bored piles, it is sometimes necessary to adjust the fluidity and hardening time of the soil cement while maintaining its strength in order to avoid the risk of the pile body remaining high. In particular, when constructing large diameter and long piles, greater care must be taken to ensure the fluidity of the soil cement, as frictional resistance increases when the pile is set down and repeated pile connections take time to complete the installation.
[0004] When delaying the hardening of soil cement and ensuring fluidity for a certain period of time, admixtures used in the concrete industry (superplasticizers and hardening retarders) are often used. [Prior art documents] [Non-patent literature]
[0005] [Non-Patent Document 1] Toyo Base Co., Ltd. website, "Introduction to Construction Method: Pre-boring Foot Protection Method," [online], [Retrieved May 20, 2024], Internet<URL:http: / / toyobase.co.jp / construction_list / phc%E6%9D%AD%E5%B7%A5%E4%BA%8B / > Summary of the Invention [Problem to be solved by the invention]
[0006] The performance of soil cement varies greatly depending on the properties (soil quality) of the soil mixed with the cement-based solidifying agent, so when using admixtures, it is necessary to confirm and understand the chemical reaction between cement and soil in advance and carefully consider the mixture. Furthermore, adjusting the amount of admixture to be added can be difficult. If there is too little admixture, the pile cannot be sunk, and if too much admixture is added out of fear of the pile remaining high, the setting of the cement will be slow, leading to delays in the process.
[0007] On the other hand, the performance of soil cement is evaluated by unconfined compressive strength. The addition of admixtures can lead to a decrease in compressive strength, so it can be difficult to ensure both compressive strength and fluidity.
[0008] Therefore, the inventors of the present invention conducted extensive research into a method for ensuring the fluidity of soil cement without using admixtures. As a result, they noticed that the fluidity of soil cement decreases when dry ice is added, and arrived at the present invention.
[0009] The present invention has been made in consideration of the above, and aims to provide a pile construction method that can ensure the fluidity of soil cement without using admixtures. [Means for solving the problem]
[0010] In order to solve the above-mentioned problems and achieve the object, the pile construction method of the present invention is a construction method in which the ground is excavated to a predetermined depth to form a borehole, an injection liquid containing a cement-based solidification material is injected into the formed borehole, the injected injection liquid is stirred and mixed with the raw soil to create a mixture made of soil cement inside the borehole, and a pile is erected and fixed in the mixture, wherein the mixture contains 5 to 10% dry ice by weight relative to the cement-based solidification material.
[0011] Another pile construction method according to the present invention includes the steps of: drilling a borehole to a predetermined depth while injecting drilling fluid into the ground to form a borehole; injecting a base protection liquid containing a cement-based solidification material into the bottom of the borehole and constructing a base protection section made of soil cement at the bottom of the borehole by stirring and mixing the injected base protection liquid with the original soil; injecting a pile periphery fixation liquid containing a cement-based solidification material above the base protection section of the borehole and constructing a pile periphery fixation section made of soil cement above the base protection section by stirring and mixing the injected pile periphery fixation liquid with the original soil; and erecting and fixing a pile on the constructed base protection section and pile periphery fixation section, wherein the base protection liquid and the pile periphery fixation liquid contain 5 to 10% dry ice by weight relative to the cement-based solidification material, and the drilling fluid contains dry ice in an amount corresponding to the ratio of dry ice contained in the base protection liquid and the pile periphery fixation liquid to the cement-based solidification material. [Effects of the Invention]
[0012] According to the pile construction method of the present invention, the ground is excavated to a predetermined depth to form a borehole, and then an injection liquid containing a cement-based solidification material is injected into the borehole, and the injected injection liquid is stirred and mixed with the raw soil to create a mixture made of soil cement inside the borehole, and the pile is then erected and fixed into the mixture.The mixture contains 5 to 10% dry ice by weight relative to the cement-based solidification material, which has the effect of ensuring the fluidity of the soil cement that makes up the mixture without using any admixtures.
[0013] Another pile construction method according to the present invention includes the steps of: forming a borehole by drilling to a predetermined depth while injecting drilling fluid into the ground; injecting a root hardening fluid containing a cement-based solidification material into the bottom of the formed borehole and stirring and mixing the injected root hardening fluid with the original soil to construct a root hardening section made of soil cement at the bottom of the borehole; and injecting a pile periphery fixing fluid containing a cement-based solidification material above the root hardening section of the borehole and stirring and mixing the injected pile periphery fixing fluid with the original soil to construct a pile periphery fixing fluid made of soil cement above the root hardening section. This construction method includes the steps of constructing a fixing section and driving and fixing a pile into the constructed root fixing section and pile periphery fixing section, wherein the root fixing liquid and the pile periphery fixing liquid contain 5 to 10% dry ice by weight relative to the cement-based solidification material, and the drilling liquid contains dry ice in an amount corresponding to the ratio of dry ice contained in the root fixing liquid and the pile periphery fixing liquid to the cement-based solidification material, thereby achieving the effect of ensuring the fluidity of the soil cement that constitutes the root fixing section and the pile periphery fixing section without using admixtures. [Brief explanation of the drawings]
[0014] [Figure 1] FIG. 1 is a schematic process diagram showing an embodiment of a pile construction method according to the present invention. DETAILED DESCRIPTION OF THE INVENTION
[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A detailed description of an embodiment of a pile installation method according to the present invention will be given below with reference to the accompanying drawings. However, the present invention is not limited to the embodiment.
[0016] (Embodiment) As shown in Figure 1, the pile construction method according to the embodiment of the present invention includes an excavation step S1, a pile periphery fixing part construction step S2, a foot protection part construction step S3, and a pile installation and anchoring step S4. The details of each of steps S1 to S4 will be explained below.
[0017] First, in the excavation step S1, as shown in FIG. 1(1), a drilling and stirring device 10, such as an earth auger, is placed at the pile center position in the ground G. The ground G is excavated to a predetermined depth (bearing layer) using this drilling and stirring device 10 to form a borehole 12. During this process, drilling fluid 14 is injected into the ground G from the bottom of the drilling and stirring device 10. The drilling fluid 14 contains dry ice in a ratio appropriate to the cement-based solidification material contained in the pile periphery fixing fluid and foot protection fluid described below. Then, as shown in FIG. 1(2), the expansion blades of the drilling and stirring device 10 are horizontally extended at the bottom of the borehole 12. Then, as shown in FIG. 1(3), the drilling and stirring device 10 is raised and excavated to expand the diameter of the lower section of the borehole 12. During this process, the drilling may be performed while injecting pile periphery fixing fluid 16, described below, from the drilling and stirring device 10.
[0018] In the next step S2, as shown in Figures 1(4) and 1(5), pile perimeter fixation fluid 16 is injected from the bottom of the excavation and mixing device 10 while the excavation and mixing device 10 is repeatedly raised and lowered to mix and stir the pile perimeter fixation fluid 16 with the excavated soil (raw soil), thereby constructing a pile perimeter fixation fluid 18 (mixture) made of soil cement within the borehole 12. The pile perimeter fixation fluid 16 is an injection fluid filled between the wall of the borehole 12 and the outer perimeter of the pile to ensure the pile's peripheral friction and horizontal resistance. It is composed of a cement-based solidification material and cement milk containing 5 to 10% dry ice by weight relative to the cement-based solidification material. This pile perimeter fixation fluid 16 does not contain so-called admixtures, such as superplasticizers or hardening retarders, to ensure fluidity. This pile perimeter fixation fluid 16 ensures the fluidity of the soil cement in the pile perimeter fixation fluid 18 without the use of admixtures, as described below.
[0019] In the next step, the foot protection section construction step S3, as shown in Figures 1(6) and 1(7), a foot protection liquid 20 is injected into the bottom of the borehole 12 from the excavation and mixing device 10. The injected foot protection liquid 20 and the excavated soil (raw soil) are then mixed and stirred to create a soil-cement foot protection section 22 (mixture) at the bottom of the borehole 12. The foot protection liquid 20 is an injection liquid that integrates the tip of the pile with the bearing layer ground to secure the pile to the bearing layer and ensure tip bearing capacity. It is composed of a cement-based solidification material and cement milk containing 5 to 10% dry ice by weight relative to the cement-based solidification material. This foot protection liquid 20 does not contain so-called admixtures, such as superplasticizers or hardening retarders, to ensure fluidity. This type of foot protection liquid 20 ensures the fluidity of the soil cement in the foot protection section 22 without the use of admixtures, as described below.
[0020] In the next pile installation step S4, as shown in Figures 1(8) and 1(9), the excavating and mixing device 10 is pulled up from the borehole 12, and then the piles 24 are installed and fixed in the foot protection section 22 and the pile circumferential fixing section 18 by self-sinking or rotary press-fitting. The piles 24 are connected vertically with joints as needed. The piles 24 can be, for example, precast concrete piles.
[0021] Therefore, according to the construction method of this embodiment, the fluidity of the soil cement that constitutes the foot protection portion 22 and the pile periphery fixing portion 18 can be ensured without using any admixture.
[0022] In the above embodiment, the order of the pile periphery fixing portion construction step S2 and the foot fixing portion construction step S3 may be reversed. That is, the pile periphery fixing portion construction step S2 may be performed after the foot fixing portion construction step S3. In this case, after the foot fixing portion 22 is constructed, when the excavating and mixing device 10 is pulled up, the pile periphery fixing fluid 16 may be injected into the borehole 12, and the injected pile periphery fixing fluid 16 may be stirred and mixed with the excavated soil (raw soil), thereby constructing the pile periphery fixing portion 18 above the foot fixing portion 22.
[0023] (Amount of dry ice required to ensure soil cement fluidity) As mentioned above, the inventors have already confirmed that adding dry ice to soil cement prevents the soil cement from losing its fluidity (see Reference 1 below). Therefore, during pile construction, if dry ice is mixed into the mixture of injection fluid (pile perimeter fixing fluid and foot protection fluid) and raw soil (excavated soil) in the appropriate amount and at the appropriate timing, soil cement with reduced fluidity can be obtained. This makes it possible to improve the ease of construction during pile installation. [Reference 1] Patent Application No. 2024-010809 (currently unpublished)
[0024] The amount of dry ice to be added can be set based on the results of the blending test described in the above-mentioned Reference 1. The soil cement used in the blending test described in Reference 1 was a mixture of air-dried silica sand No. 7, clay (made from Kibushi clay and kaolin clay in a mass ratio of 1:1), and adjusted muddy water mixed in a mass ratio of 4:1:2.15 with water, and a cement-based solidification material (solidification material addition amount 150 kg / m) converted into an external ratio. 3 The slurry used was a mixture of sand and clay (sample soil: soil material), tap water was used for mixing, and blast furnace cement type B (unit cement amount: 200 kg / m) was used for cement-based solidification.3 The water content of the adjusted mud water and the water-cement ratio (W / C) of the cement milk are both set at 43%, and the target strength of the soil-cement is σ 28 (Compressive strength at 28 days) 1.5N / mm 2 The dry ice used is made by placing dry ice slabs in a plastic bag and crushing them with a wooden mallet to particles of 5mm or less. The amount of dry ice is set to 0, 5, 10, or 15 wt% as a ratio to the amount of cement, and is mixed in proportion to the cement. The soil cement is made by dry mixing the soil, cement, and dry ice, then adding water and mixing it properly.
[0025] Reference 1 shows the slump flow increase rate obtained from slump flow tests of each of the above mix proportions relative to the slump flow rate of a mix without dry ice. The results confirm that the slump flow increase rate is significantly greater when the dry ice content is 5 to 10 wt%. Therefore, the amount of dry ice required to effectively suppress the decrease in fluidity of soil cement used in pile construction, thereby improving the physical and mechanical properties of the soil cement, can be considered to be 5 to 10% of the cement content. In this embodiment, the amount of dry ice can be set within the range of 5 to 10% of the cement content by weight.
[0026] (Example) Next, an embodiment of the present invention will be described. Because pile perimeter fixing fluid does not require the same strength as foot protection fluid, here we calculate the amount of dry ice required to ensure fluidity for the foot protection fluid, which has a relatively high cement content. Based on the verification results of Reference 1 above, the weight ratio (D2 / C2) of the amount of dry ice to be added to the foot protection fluid (D2) to the amount of cement in the foot protection fluid (C2) is set as follows:
[0027]
number
[0028] The water-cement ratio (W2 / C2) of the foot protection liquid is expressed by the following formula:
[0029]
number
[0030] Here, x2 is the water-cement ratio relative to the mix strength of the foot protection liquid, and W2 is the amount of water in the foot protection liquid.
[0031] By solving equations (1) and (2) for C2 and equating them, the amount of dry ice (D2) required to ensure the fluidity of the mixture of root protection liquid and raw soil (soil cement) can be derived.
[0032]
number
[0033] In the construction of the pre-bored pile method, in the first excavation process (corresponding to the above-mentioned excavation step S1), drilling fluid such as drilling mud is injected and circulated inside the borehole to cool the drill bit (drilling and mixing device) and prevent the collapse of the hole wall. By adding dry ice to this drilling mud (drilling fluid) in advance, the fluidity of the mixture of grouting fluid and raw soil used in the subsequent processes (the above-mentioned pile perimeter fixing part construction step S2 and foot protection part construction step S3) can be ensured without complicating the construction process.
[0034] Considering that the drilling mud and injection fluid will eventually be stirred and mixed, the amount of dry ice (D0) to be added to the drilling mud in advance is determined using the following formula so that the ratio of dry ice added to the foot protection fluid (D2 / C2) does not change.
[0035]
number
[0036] Here, W0 is the volume of drilling mud water.
[0037] Dry ice equivalent to 10% of the cement volume is added to the pile perimeter fixation liquid and foot protection liquid before injection. The base protection liquid mix is as shown in formula (1). The amount of dry ice (D1) to be added to the pile perimeter fixation liquid is expressed by the following formula.
[0038]
number
[0039] Here, C1 is the amount of cement in the pile perimeter fixing liquid.
[0040] According to this example, simply replacing the mixing water with foamed water (water with added dry ice) can improve the fluidity of the soil cement and prevent it from remaining high when the piles are driven in. Unlike conventional construction methods that require the addition of admixtures, this method does not require prior mix adjustment, which also contributes to improved productivity.
[0041] In the above embodiment, the application of the soil cement to the base protection section has been described as an example, but the present invention is not limited to this and can also be applied to the soil cement of the pile periphery fixing section. In this case, the same effects as those described above can be achieved.
[0042] As explained above, according to the pile construction method of the present invention, the ground is excavated to a predetermined depth to form a borehole, and then an injection liquid containing a cement-based solidification material is injected into the borehole, and the injected injection liquid is stirred and mixed with the raw soil to create a mixture made of soil cement inside the borehole, and the pile is then erected and fixed into the mixture.The mixture contains 5 to 10% dry ice by weight relative to the cement-based solidification material, so the fluidity of the soil cement that makes up the mixture can be ensured without the use of admixtures.
[0043] Another pile construction method according to the present invention includes the steps of: forming a borehole by drilling to a predetermined depth while injecting drilling fluid into the ground; injecting a foot hardening fluid containing a cement-based solidification material into the bottom of the formed borehole and stirring and mixing the injected foot hardening fluid with the original soil to create a foot hardening section made of soil cement at the bottom of the borehole; and injecting a pile periphery fixing fluid containing a cement-based solidification material above the foot hardening section of the borehole and stirring and mixing the injected pile periphery fixing fluid with the original soil to create a foot hardening section made of soil cement above the foot hardening section. and a step of driving and fixing a pile into the constructed root fixing portion and the pile fixing portion, wherein the root fixing liquid and the pile fixing liquid contain 5 to 10% dry ice by weight relative to the cement-based solidification material, and the excavation liquid contains dry ice in accordance with the ratio of dry ice contained in the root fixing liquid and the pile fixing liquid to the cement-based solidification material, so that the fluidity of the soil cement that constitutes the root fixing portion and the pile fixing portion can be ensured without using admixtures.
[0044] The Sustainable Development Goals (SDGs) are 17 international goals that were adopted at the United Nations Summit in September 2015. The pile construction method according to this embodiment can contribute to achieving one of the 17 SDGs, for example, goal 12, "Responsible Consumption and Production." [Industrial Applicability]
[0045] As described above, the pile construction method according to the present invention is useful for pre-boring pile construction methods applied to foundation work in architecture and civil engineering, and is particularly suitable for ensuring the fluidity of soil cement without using admixtures. [Explanation of symbols]
[0046] 10. Excavation and mixing equipment 12 Boreholes 14 Drilling fluids 16 Pile circumference fixative (injection liquid) 18 Pile circumference fixing part (mixture) 20 Root protection liquid (injection liquid) 22 Foot protection section (mixture) 24 stake G Ground
Claims
1. A construction method in which the ground is excavated to a predetermined depth to form a borehole, an injection liquid containing a cement-based solidification material is injected into the formed borehole, the injected injection liquid and the raw soil are stirred and mixed to form a mixture made of soil cement inside the borehole, and piles are driven into the formed mixture and fixed therein, A pile construction method characterized in that the mixture contains 5 to 10% dry ice by weight relative to the cement-based solidification material.
2. A construction method comprising the steps of: forming a borehole by excavating to a predetermined depth while injecting drilling fluid into the ground; injecting a root fixing liquid containing a cement-based solidification material into the bottom of the formed borehole and constructing a root fixing section made of soil cement at the bottom of the borehole by stirring and mixing the injected root fixing liquid with the original soil; injecting a pile periphery fixing liquid containing a cement-based solidification material above the root fixing section of the borehole and constructing a pile periphery fixing section made of soil cement above the root fixing section by stirring and mixing the injected pile periphery fixing liquid with the original soil; and erecting and fixing a pile into the constructed root fixing section and pile periphery fixing section, The foot hardening liquid and the pile periphery fixing liquid contain 5 to 10% dry ice by weight relative to the cement-based solidification material, A pile construction method characterized in that the drilling fluid contains dry ice in an amount corresponding to the ratio of dry ice contained in the root hardening fluid and the pile circumference fixing fluid to the cement-based solidification material.