JPH0470446B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Industrial Application] The present invention relates to an earth retaining method, and in particular to an earth retaining method that can reduce the pulling force when pulling out a core material installed before soil cement, which is a water-stop hardening material, hardens after construction is completed. . [Conventional technology] In urban areas, earth retaining methods such as the soil cement heaping method and the muddy water solidification heaping method are often implemented. It is practiced to install core materials such as In other words, when constructing columnar earth retaining walls or simple continuous walls, a method is adopted in which the walls are made of soil cement, etc., to ensure water stoppage, and the external forces such as surrounding earth pressure and water pressure are borne by the core material. There is. In such construction methods, the core material is pulled out and reused after construction is completed, from the viewpoint of effective use of materials and energy conservation. When carrying out this core material pulling out, it is strongly desired to reduce the pulling force to facilitate the work and prevent damage to the retaining wall, and several methods have been proposed for this purpose. That is, a method of applying a lubricant such as tar or wax to the core material before erection, a method of attaching bentonite in a semi-solid state to the core material before erection (for example, see Japanese Patent Application Laid-Open No. 57-51329), A method of spraying foam on the core material and cutting the edges in advance, a method of using a cement hardening retarder, or a method of reducing the adhesion force by using a concrete crushing agent during pulling out (for example, Japanese Patent Application Laid-Open No. 57-66230) ) have been proposed. [Problem to be solved by the invention] However, in the case of methods using lubricants, foams, or cement hardening retarders, it is necessary to perform treatment to reduce adhesion before installing the core material, so special treatment is required. The disadvantage is that it requires a detailed implementation process and equipment. In addition, methods using concrete crushing chemicals have the disadvantage that they are complicated and require a long time to implement. It is an object of the present invention to provide an earth retaining method that solves the problems of the prior art and can reduce core material pull-out force through extremely simple steps. [Means for Solving the Problems] A feature of the present invention is that the adhesion force is reduced by energizing the core material after the core material is installed and before the soil cement hardens, thereby achieving the above object. That is, according to the present invention, soil cement consisting of earth and sand, water, cement, etc. is injected into an excavated hole in which the ground is excavated and a retaining wall is constructed, and before the soil cement hardens, a steel core material is injected into the hole. In the earth retaining method, in which an earth retaining wall is built by hardening the soil cement, and then the core material is pulled out from the earth retaining wall, after the core material is erected and before the soil cement hardens, the core material is Provided is an earth retaining method characterized in that the force for pulling out the core material after hardening of the soil cement is reduced by applying a current to the soil cement to reduce the adhesion force with the soil cement. [Operation] According to the above configuration, excavation for the earth retaining wall is performed at the location where the earth retaining wall such as an underground continuous wall is to be constructed, the core material is installed in the soil cement poured into the excavated groove or the excavated hole, and the core material is installed as it is. By simply turning on electricity when the core material is erected and then leaving it as it is, the force required to pull out the core material after the soil cement has hardened can be greatly reduced. [Example] Figures 1 to 6 are diagrams showing one embodiment of the earth retaining method according to the present invention, and Figures 7 to 10 are diagrams showing other embodiments. The present invention will be specifically explained with reference to the following. In the earth retaining method according to the present invention, first, the first
A ground 2 is excavated by an excavator 1 such as a triple earth auger as shown in the figure, and then soil cement 3 is injected into the excavated trench as shown in FIG. 2. The soil cement used is a mixture of earth and sand, water, cement, and a water-stop hardening agent containing bentonite. Next, before the soil cement 3 hardens (usually immediately after pouring the soil cement), a steel core material 4 is built into the soil cement 3 as shown in FIG. The core materials 4 are placed at predetermined intervals as shown in FIGS. 4 and 5. As the core material 4, H-shaped steel, steel pipes, I-shaped steel, or steel sheet piles are used, but various steel materials can also be used as long as they can reinforce the earth retaining wall against external forces such as earth pressure and water pressure. can. When the construction of the core material 4 is completed, as shown in FIGS. 4 and 5, a pair of adjacent core materials 4 form a positive electrode and a negative electrode, and a current is passed between them. This energization can be carried out using either direct current or alternating current, and when energizing with alternating current, a pair of adjacent core members forms a positive electrode and a ground. In addition, if the interval between the core materials 4 is too large, or if the core materials 4 are installed one by one as in the column-row earth retaining method described later in FIGS. 7 to 10, the first
As shown in Figure 0, a temporary electrode 5 of approximately the same length is inserted in the vicinity of the core material 4, and current is applied between them as described above. A steel bar or a steel pipe is usually used as this temporary electrode 5, and this temporary electrode is pulled out after being energized. After the adhesion force is reduced by the above operations and the soil cement hardens, it is used as a retaining wall, and after the construction is completed, the core material 4 is pulled out using a crane 6 or a jack, as shown in FIG. The core material 4 that has been pulled out is reused. According to the earth retaining method explained above, since a current is passed between a pair of adjacent core materials 4 or between a core material and a temporary electrode before the soil cement hardens, the components of the soil cement around the core materials are changed. Therefore, the force required to pull out the core material 4 after the soil cement has hardened can be greatly reduced (for example, from 1/4 to 1/20). The mechanism of this decrease in adhesion is that gas is generated around the core material due to water electrolysis, water collects around the core material when energized, and the bentonite component, which is easily charged, is transferred to the periphery of the core material due to energization. It is judged that this is caused by factors such as being attracted to people. According to the embodiment described in FIGS. 1 to 6, compared to the conventional method for reducing the core material pull-out force as described above, the core material can be removed without requiring any special equipment or construction method, and with an extremely simple implementation procedure. The pulling force can be significantly reduced. Therefore, it is possible to obtain an earth retaining method that is highly reliable, has a low installation cost, and has a very large effect of reducing core material pulling force. FIG. 7 to FIG. 10 are diagrams illustrating the case where the present invention is implemented in the column-row earth retaining method. In this case, an excavator 7 equipped with a series of earth augers as shown in FIG. 7 is used to form cylindrical excavated holes at predetermined pitches. As shown in FIGS. 8 and 9, soil cement 3 is injected into each excavation hole, and then a steel core material 4 is installed. Next, as shown in FIG. 10, a rod-shaped temporary electrode 5 having the same length as the core material 4 is inserted, and a current is passed between them. This energization is carried out before the soil cement hardens, as in the previous embodiment, and after the energization ends, the temporary electrode 5 is pulled out. In addition, for the ground between the excavated holes where the core material 4 was built, additional excavation is performed as shown by the chain lines in Figures 9 and 10, and each additional excavated hole is made consecutively. Soil cement is injected into the area to form a continuous water-tight earth retaining wall. Thus, as in the previous embodiment,
Core material 4 is mainly used for external forces such as earth pressure and water pressure.
A continuous water-tight earth retaining wall will be constructed that will provide strength and strength. After the construction is completed, each core material 4 is pulled out in the same way as in the previous case. For other details, see Figure 1~
The construction method is substantially the same as that shown in Figure 6. Also in this embodiment, substantially the same effects as in the case of FIGS. 1 to 6 can be achieved. Next, test results obtained by actually applying the present invention will be explained. In this test, soil cement, which is a mixture of sand, water, cement, and bentonite in the proportions shown in Table 1, was used as a water-stop hardening material.

[Table] A flat steel with an embedded length of 150 mm x width of 30 mm is used as the core material, and the adhesion area with soil cement is approximately 90 cm ²
It was hot. This core material was erected vertically, and before the soil cement hardened, a current of 12 V DC was passed between the two core materials as a set. Two types of current application time were used: 30 seconds and 5 minutes. The distance between the electrodes of the core material was 7 to 10 cm. Table 2 shows the test results in which the pull-out force after the soil cement had hardened (solidified) after being left for 7 days was compared with the pull-out force without energization.

〔Effect of the invention〕

As is clear from the above explanation, all you need to do is excavate the earth retaining wall at the location where the earth retaining wall such as an underground continuous wall will be constructed, install the core material in the excavated groove, turn on the electricity as it is, and then leave it as it is. The core material pulling force can be greatly reduced. Therefore, the earth retaining method not only has a certain effect, but also eliminates the need to prepare another work area and has an extremely simple work procedure, which can save labor at the construction site and shorten the construction period. is obtained.

[Brief explanation of the drawing]

Figures 1 to 6 are explanatory diagrams showing the construction procedure of one embodiment of the earth retaining method according to the present invention, and Figures 7 to 10 are explanatory diagrams showing the construction procedure of another embodiment of the earth retaining method according to the present invention. It is. 1... Excavator, 2... Earth, 3... Soil cement, 4... Steel core material, 5... Temporary electrode, 6...
crane.

Claims (1)

[Claims] 1. In an excavated hole in which a retaining wall is constructed by excavating the ground,
Soil cement consisting of earth, sand, water, cement, etc. is injected, and before this soil cement hardens, a steel core material is built in. As the soil cement hardens, an earth retaining wall is built, and then the core material is poured from this earth retaining wall. In the earth retaining method of pulling out soil cement, after the core material is erected and before the soil cement hardens, current is applied to the core material to reduce the adhesion force with the soil cement, so that the soil cement hardens after the soil cement hardens. An earth retaining method characterized by reducing the core material pulling force.