JP2008156821A - Structure and cutting construction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To construct a section to be cut of a structure by using mortar or concrete providing excellent cutting property when performing work such as, for example, removal and excavation while the section has sufficient strength for maintaining the structure. <P>SOLUTION: The sections 16, 18 to be cut of the structure 10 are constructed by using the mortar or the concrete containing the calcium aluminate steel slag containing Al<SB>2</SB>O<SB>3</SB>of 20-40 wt.%, CaO of 40-60 wt.%, SiO<SB>2</SB>of 15 wt.% or less, and MgO of 5-15 wt.% as fine aggregate. Since it is conceivable that the calcium aluminate steel slag having the composition has many minute pores in its inside, the mortar or the concrete containing the slag as fine aggregate has more excellent cutting property when compared with the mortar or the concrete using conventional fine aggregate such as fine sand. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a structure and a cutting method, and more particularly to a mortar or concrete structure excellent in machinability and a cutting method thereof.

  Conventionally, mortar or concrete has been widely used as a building material for structures. While this mortar or concrete is required to have sufficient strength to maintain the structure, the mortar or concrete is required to have excellent machinability when the structure is removed or when cutting due to tunnel excavation. . For example, in shield tunneling shafts, the wall provided at the start / reach location of the shield machine has a strength that can stably support the ground before excavation, while the shield machine has a strength sufficient to support the ground during excavation. It is required to be cut by a bit.

  Various improved techniques have been disclosed regarding the structure of the start / reach point in the shield tunnel. For example, Patent Document 1 describes that a composite material in which a plastic foam made of a hard urethane resin is reinforced with inorganic fibers is used as a partition wall body at a start / reach point in a shield tunneling shaft. Patent Document 2 describes that a wall body at a start / reach location in a shield tunneling vertical shaft is constructed using a concrete material reinforced with a fiber reinforcing material (FRP rod or the like).

  In recent years, techniques for using blast furnace slag and steelmaking slag generated at steelworks as mortar or concrete materials have been actively studied. For example, Patent Document 3 describes that a mixture of steelmaking slag containing free lime that is an expansible factor and blast furnace slag is used as an aggregate of mortar or concrete.

JP-A-8-303178 JP 2004-115997 A JP 2002-179451 A

  However, the material used for the wall at the start / reach point of the conventional shield tunneling shaft does not sufficiently satisfy both the requirement for strength for maintaining the structure and the requirement for machinability during excavation. There was a problem. For example, since the wall body described in Patent Document 1 is made of plastic foam, it is excellent in machinability as well as foamed concrete, artificial wood, limestone concrete and the like, but has insufficient strength. On the other hand, since the wall body described in Patent Document 2 uses a concrete material reinforced with a fiber reinforcing material, the strength is high, but further improvement has been demanded in terms of machinability.

  In addition, the technique described in Patent Document 3 is intended to be used as a concrete aggregate by suppressing expansion and collapse of steelmaking slag, and the cutting of concrete produced using slag. No knowledge is disclosed regarding gender.

  Therefore, the present invention has been made in view of the above problems, and the object of the present invention is excellent at the time of work such as removal or excavation while having sufficient strength to maintain the structure. Another object of the present invention is to provide a structure constructed of mortar or concrete capable of exhibiting excellent machinability and its cutting method.

In order to solve the above problems, according to an aspect of the present invention, 20 to 40% by mass of Al ₂ O ₃ , 40 to 60% by mass of CaO, 15% by mass or less of SiO ₂ , and 5 to 15 There is provided a structure characterized by having a portion to be cut that is constructed using mortar or concrete containing calcium aluminate-based steel slag containing MgO in a mass percentage as fine aggregate. In such a configuration, the calcium aluminate-based steel slag having the above composition is considered to have many fine pores therein. Therefore, mortar or concrete containing the slag as a fine aggregate is fine sand. Compared to mortar or concrete using conventional fine aggregates such as

  Moreover, 40-50 mass% may be sufficient as the maximum water absorption of the said calcium aluminate-type steel slag. In this case, since it can be said that the slag has sufficient fine pores, the mortar or concrete containing the slag as a fine aggregate has excellent machinability.

  Moreover, steam curing may be performed with respect to the said cutting object location. Thereby, the mortar or concrete of the cutting object location which performed steam curing can be expanded, and the machinability of the cutting object location can be improved compared with before steam curing. Even if such steam curing is performed, the mortar or concrete at the location to be cut may not expand to the extent that cracking occurs, but even in this case, the machinability at the location to be cut should be improved. Can do.

  Moreover, you may produce a crack in the location for cutting by performing steam curing. As a result, cracks (including microcracks) can be generated in the mortar or concrete at the location to be cut and the strength can be further deteriorated, so that the machinability at the location to be cut can be further improved.

  Moreover, 1: 0.1-30 may be sufficient as the compounding ratio of cement and a calcium aluminate-type steel slag in the said mortar or concrete. With this blending ratio, mortar or concrete can suitably exhibit the machinability improving effect while maintaining the strength required for the structure.

  Further, the location to be cut may be a wall of a start or arrival location excavated by a shield excavator in a shield excavation vertical shaft. In this way, the wall of the start or arrival point, which is the location to be cut by the shield machine, is constructed of mortar or concrete excellent in machinability containing the slag as a fine aggregate, so that the wall of the start or arrival point Prior to excavation, the body has sufficient strength as a wall for a shield digging shaft and can be excavated relatively easily by a shield excavator during excavation.

In order to solve the above problems, according to another aspect of the present invention, there is provided a cutting method for cutting a cutting target portion of the structure, the _Al 2 _{O 3} of 20 to 40 wt%, 40 to 60 The location to be cut is constructed using mortar or concrete containing calcium aluminate-based steel slag containing 5% by mass of CaO, 15% by mass or less of SiO ₂ and 5-15% by mass of MgO as fine aggregate. There is provided a cutting method characterized by cutting a portion to be cut. As described above, mortar or concrete containing the slag as fine aggregate is excellent in machinability. Therefore, by using the mortar or concrete excellent in machinability, it is possible to suitably cut the portion to be cut by constructing the portion to be cut of the structure.

  Moreover, you may make it the maximum water absorption of the said calcium aluminate-type steel slag be 40-50 mass%. In this case, since it can be said that the slag has sufficient fine pores, the mortar or concrete containing the slag as a fine aggregate has excellent machinability.

  In addition, after the above-described cutting target portion is constructed, the cutting target portion may be subjected to steam curing, and then the cutting target portion may be cut. By this steam curing, the calcium aluminate-based steel slag contained in the mortar or concrete at the location to be cut can be expanded to improve the machinability of the location to be cut compared to before the steam curing.

  Moreover, after performing the said steam curing, you may make it cut a cutting object part, after producing a crack in a cutting object part. As a result, cracks (including microcracks) can be generated in the mortar or concrete at the location to be cut and the strength can be further deteriorated, so that the machinability at the location to be cut can be further improved.

  Moreover, 1: 0.1-30 may be sufficient as the compounding ratio of cement and a calcium aluminate-type steel slag in the said mortar or concrete. With this blending ratio, mortar or concrete can suitably exhibit the machinability improving effect while maintaining the strength required for the structure.

  In addition, the cutting target location may be a wall of a start or arrival location excavated by a shield excavator in a shield excavation vertical shaft. As a result, the wall of the starting or reaching point, which is the target for cutting by the shield machine, can have sufficient strength as the wall of the shield tunnel before excavation, and at the time of excavation, the shield machine Can be excavated relatively easily.

  According to the present invention, a part or all of a structure is used by using mortar or concrete that has sufficient strength to maintain the structure, but exhibits excellent machinability at the time of work such as removal or excavation. Can be constructed.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

<Outline of mortar or concrete>
First, the outline of the mortar or concrete for constructing the structure concerning one embodiment of the present invention is explained. The mortar or concrete according to the present embodiment is, for example, various buildings such as buildings, houses, factory facilities, tunnels, roads, dams, viaducts, harbor facilities, river revetments, and temporary structures for civil works. It is a building material used to construct a structure. In general, a mortar is composed of a hydraulic composition (cement, asphalt, etc.), a fine aggregate (fine sand, artificial lightweight aggregate, etc.) having a relatively fine particle size or less, and water at a predetermined mixing ratio. It is a mixture. In addition, the concrete is composed of the hydraulic composition, the fine aggregate, the coarse aggregate having a relatively coarse predetermined particle size range (gravel, crushed stone, artificial lightweight aggregate, etc.) and water at a predetermined blending ratio. It is a mixture. Thus, mortar and concrete are distinguished by whether coarse aggregate is mixed. Since mortar is paste-like and has good workability, it is used as a finishing material for structures, joint materials, adjustment materials for frames, and the like. On the other hand, concrete is suitable as a structural material for structures because it is stronger and cheaper than mortar and is easy to construct.

  In this embodiment, as such a fine aggregate of mortar or concrete, calcium aluminate-based steel slag is used instead of conventional fine sand. Due to the action of this calcium aluminate-based steel slag, the mortar or concrete has sufficient strength to maintain the structure when maintaining the constructed structure, and at the time of removal or excavation of the structure, etc. Can have excellent machinability. Below, this calcium aluminate type steel slag is explained in full detail.

<Composition and characteristics of calcium aluminate-based steel slag>
The calcium aluminate-based steel slag according to the present embodiment is, for example, a steelmaking slag generated in a steelmaking process of stainless steel. For example, in an AOD furnace that is an example of a refining furnace, an alloy such as chromium from molten steel for stainless steel is used. Examples of the steelmaking slag containing various metal oxides generated when the molten steel is forcibly deoxidized using aluminum as a deoxidizing agent during the reduction period in order to recover.

The composition of the main components of this calcium aluminate-based steel slag is 20 to 40% by mass of aluminum oxide (Al ₂ O ₃ ), 40 to 60% by mass of calcium oxide (CaO), 15% by mass or less of silicon dioxide (SiO ₂ ), Magnesium oxide (MgO) is 5 to 15% by mass. The composition ratio of SiO ₂ may be any value as long as it is 15% by mass or less, and the lower limit thereof may be, for example, 0% by mass. The composition of the calcium aluminate-based steel slag varies depending on the steelmaking conditions and the like, but the average composition is, for example, Al ₂ O ₃ 30% by mass, CaO 50% by mass, SiO ₂ 5% by mass, MgO 12 % By mass, balance Fe, Cr ₂ O ₃ , MnO, FeO, TiO ₂ , S, F and the like.

  Calcium aluminate-based steel slag whose main component is in the above range (hereinafter simply referred to as “slag”) has strong hydraulic properties (a property of reacting with water and hardening like cement) When kneaded, the hydration reaction is promoted, and it has the characteristic of hydraulically hardening at a high reaction rate. For this reason, by mixing the slag with cement and water as a fine aggregate to produce mortar or concrete, compared to the case where conventional fine sand is used as a fine aggregate, solidified mortar or concrete Strength can be increased. In addition, since this slag has a hydraulic property comparable to or more than ordinary Portland cement, it can also be used as a substitute for cement in mortar or concrete materials.

  In addition, the slag has a characteristic that it collapses from a lump-like state and is pulverized when it is left in the atmosphere for a long time or is forcibly steam-cured. Furthermore, as a result of diligent efforts by the inventor of the present application, it was found that mortar or concrete using the powdery slag as fine aggregate has higher machinability than conventional mortar or concrete. Furthermore, when the mortar or concrete using the powdery slag as a fine aggregate is cured under a steam atmosphere, the steam-cured part expands and a local micro crack (crack) is generated. It was found that the machinability of the part was further improved. Thus, it has been found that mortar or concrete using the above slag as a fine aggregate is excellent in machinability as it is, and further, the machinability is further improved by applying steam curing. Such a mechanism of collapse to pulverization of slag and a mechanism having excellent machinability of mortar or concrete containing the slag are considered as follows.

Slag of the composition, nCaO · _mAl 2 _{O 3} (calcium aluminate) and consists of mineral phase called nCaO · mSiO ₂ (calcium silicate) (n and m are molar ratios). Among these, some compositions of calcium aluminate (for example, 12CaO · 7Al ₂ O ₃ ) and some compositions of calcium silicate (for example, CaO · SiO ₂ ) are very hydrated, so slag water Hardness becomes high, and as a result, compressive strength, such as mortar using the said slag, increases. In addition, among the above mineral phases, for example, 3CaO · SiO ₂ (tricalcium silicate) undergoes a volume change (structural change) when it is transformed during the cooling process, so that the massive slag naturally collapses, for example, to fine particles of 200 μm or less. Micronize.

  Furthermore, in addition to the strong hydraulic properties described above, this slag in a fine powder state has a characteristic that it can absorb a much larger amount of water compared to natural fine sand of the same particle size. Was found to be extremely high. Specifically, according to experiments conducted by the present inventors, when the particle size is the same, the maximum water absorption amount of ordinary fine sand is 20 to 30% by mass, whereas the maximum water absorption amount of the slag is Was found to be as high as 40 to 50% by mass. Here, among 40-50 mass% of moisture absorbed by the slag, the amount of water (the amount of water of crystallization water) that the above-described mineral phase in the slag can hydrate (chemical reaction) is about 30 mass%. The remaining about 10 to 20% by mass of water is considered to be physically adsorbed water. The reason why the slag has high water absorption is presumably because fine pores (pores) such as zeolite exist in the slag fine particles.

  Since the fine particles of slag contain a lot of fine pores in this way, the mortar or concrete produced using the slag is fine sand even if it is not subjected to treatment such as steam curing. It is considered that the machinability is superior to that of conventional mortar or concrete using, for example. That is, since the measured maximum water absorption amount of the slag is extremely high, it can be said that the porosity of the slag is also high. Therefore, the mortar or concrete produced using this high porosity slag has many fine pores in its interior, and is considered to be excellent in machinability.

  Furthermore, it has been found that the mortar or concrete produced by mixing the slag exhibits a deterioration phenomenon of expansion to generation of microcracks and further improves the machinability when steam curing is performed. This mechanism is considered to be because the MgO component contained in the fine powdered slag expands when hydrated with the water vapor supplied by steam curing. In the first place, it is known that this MgO hydration reaction proceeds very slowly in a natural state, and steam curing is considered to exert an action of forcibly accelerating this MgO hydration reaction. Such a deterioration phenomenon such as mortar due to steam curing is similar to a phenomenon that when an MgO-based refractory is left in the atmosphere, it naturally collapses to become tattered (so-called “dander”).

Generally, the expansion phenomenon of slag (particularly steelmaking slag) is said to be caused by hydratable CaO or MgO contained in the slag, but the powdered slag according to the present embodiment expands during steam curing. The main factor is considered to be that the MgO component in the slag hydrates with the moisture in the steam. This is because the CaO is relatively hydrated, and in the slag according to the present embodiment, most of CaO is nCaO · mAl ₂ O ₃ (calcium aluminate) or nCaO · mSiO ₂ (calcium silicate). This is because it is present in a stable mineral phase and there is little f-CaO (CaO simple substance not bonded to alumina or silica).

  By the above mechanism, it is considered that mortar or concrete using the slag having the above composition according to the present embodiment as a fine aggregate is excellent in both strength and machinability.

<Construction construction and cutting method>
Next, a method for constructing a structure using mortar or concrete using the above-described slag as fine aggregate and cutting the structure will be described.

  When constructing a structure made of mortar or concrete containing the slag, first, cement (hydraulic composition), powdered slag (fine aggregate) according to the present embodiment, and water are mixed in a predetermined ratio. Knead to produce fluid mortar or concrete. In addition, when producing | generating concrete, in addition to the said cement, slag, and water, gravel (coarse aggregate) is also knead | mixed.

  Here, the blending ratio of these materials will be described. The standard blending ratio (mass ratio) is “cement: fine sand: water = 1: 3: 0.5” in general mortar, and “cement: fine sand: gravel: water = 1: 2” in general concrete. : 4: 0.5 ". On the other hand, in this embodiment, slag is mixed instead of fine sand as a fine aggregate, and this slag is rich in water absorption, so the water ratio is increased more than usual. That is, the blending ratio (mass ratio) according to the present embodiment is, for example, “cement: slag: water = 1: 3: 0.8” for mortar and “cement: slag: gravel: water = 1: 2” for concrete. 4: 0.8 ".

  Moreover, it is preferable that the compounding ratio (mass ratio) of cement and slag is "slag: cement = 1: 0.1-30". When the blending ratio of the slag exceeds the upper limit “30”, the strength required for the structure tends to decrease, whereas when it is less than the lower limit “0.1”, the machinability improving effect is obtained. It becomes difficult to express. By setting the blending ratio of the slag in the range of “0.1 to 30”, mortar or concrete that can suitably exhibit the machinability improving effect while maintaining the strength necessary for the structure can be obtained.

  Moreover, as a particle size distribution of the said slag mix | blended, it is preferable that 80 mass% or more of things with an average particle diameter of 2 micrometers or less are contained. This is because the smaller the slag particle size, the denser the structure. Accordingly, the content of slag having an average particle size of 2 μm or less is preferably larger, and the upper limit is 100% by mass.

  In the present embodiment, only slag is used as the fine aggregate, and the conventional fine sand is replaced with slag at a substitution rate of 100%. However, the present invention is not limited to such an example. For example, a mixture of fine sand (natural sand) and slag may be used. This is estimated from the expansion coefficient of the slag in the first place, and when the blending ratio of fine aggregate to cement is large, the above slag is mixed even if the substitution rate from conventional fine sand to slag is about 10%, for example This is because the effect of improving the strength and machinability may be exhibited. Here, when the blending ratio of slag is increased, it is necessary to increase the amount of water added. To reduce the water / cement ratio (W / C) for strength, a water reducing agent (AE agent) ) Can also be added.

  Next, a portion to be cut of the structure is constructed using unsolidified mortar or concrete obtained by mixing the materials as described above. This part to be cut is a part of the structure that is planned to be cut in the future, and may be a part or all of the structure. As this cutting target location, for example, the wall body of the start or arrival location excavated by the shield excavator in the shield excavation shaft (details will be described later), a part or all of the underground continuous wall, Some or all of the temporary structures removed early (for example, temporary foundations of buildings, concrete temporarily laid on roads before asphalt laying, earth retaining walls when pipes are buried in the ground, civil engineering work) Temporary installations), openings that are drilled after construction of the structure (for example, windows on the wall of the building, holes for pipe insertion, etc.), or cutting after temporarily covering the surface of the structure・ Parts to be removed (for example, mortar applied for the purpose of temporary repair of cracks on the inner and outer walls of buildings, slopes beside railroads or roads, and blasts blown for the purpose of temporary repair on the walls of dams or tunnels) Give such as concrete), and the like.

  When constructing such a part to be cut, for example, at the construction site, a mold may be assembled in accordance with the shape of the part to be cut, and the mortar or concrete may be poured into the mold to be cured and solidified. Alternatively, in a factory or the like, the mortar or concrete may be solidified in advance, and one or more parts having a shape corresponding to the part to be cut may be formed, and the parts may be brought into the construction site and assembled. In addition, when the whole structure is a cutting object location (for example, when removing the whole temporary structure after construction), of course, you may construct the whole structure with the said mortar or concrete.

  In the mortar or concrete solidified in this way, each material is firmly bonded due to the high hydraulic properties of the slag, so that its compressive strength is at least comparable to that of conventional mortar or concrete. Therefore, the cutting target portion of the structure constructed as described above can maintain a sufficient strength as a structure when the structure is maintained, and does not collapse.

  Next, the mortar or concrete at the location to be cut of the structure constructed as described above is cut. This cutting work is performed automatically or manually using appropriate cutting means, for example, various cutting machines such as shield machine, concrete cutter, road cutter, rock drill, power shovel, and various cutting tools such as pickaxe. Done in In this cutting step, the mortar or concrete containing the slag is excellent in machinability even without being pretreated, and therefore can be easily cut.

  Furthermore, it is more preferable to perform steam curing with respect to the location of the structure to be cut in advance before the cutting step. This steam curing is to cause water vapor to act on the mortar or concrete at the location to be cut, and can be executed using, for example, a water vapor spraying means for spraying water vapor. By this steam curing, the mortar at the location to be cut or the slag in the concrete can be forcibly expanded to generate microcracks, so that the machinability at the location to be cut can be further improved.

  The temperature of the water vapor that is applied in such steam curing is, for example, 90 ° C. or higher, and the higher the temperature, the better the machinability by promoting the expansion of the slag. From this point of view, it is more preferable that the location to be cut can be placed in a high-pressure atmosphere because high-temperature steam of 100 ° C. or higher can be applied to the location to be cut. In this way, as a technique for placing the cutting target place under a high-pressure atmosphere, for example, after covering so that at least one side of the cutting target position is sealed, a technique of blowing high-temperature high-pressure steam into the inside of the cover, or There is a technique in which one or two or more holes are drilled in a portion to be cut and high-temperature and high-pressure steam is blown into the holes.

<Example of application to shield shafts>
Next, referring to FIG. 1 to FIG. 3, an example in which the concrete using the slag according to the present embodiment as a fine aggregate is applied to the wall bodies 16 and 18 at the starting or reaching position in the shield tunneling shaft 10. explain. FIG. 1 is a longitudinal sectional view showing a schematic configuration of a shield tunneling shaft 10 according to the present embodiment.

  As shown in FIG. 1, the shield excavation shaft 10 excavates the ground 22 at the start position and the arrival position of the shield excavator 20 in order to excavate the shield tunnel 24 in the ground 22 using the shield excavator 20. For example, it is a square shaft. The shield tunneling shaft 10 is composed of, for example, a side wall 12 and a bottom plate 14 made of reinforced concrete. The side wall 12 is disposed on the side of the shaft and supports the ground 22 so as not to collapse, and the bottom plate 14 is provided at the bottom of the shaft and supports equipment such as the shield machine 20. Further, in the shield tunneling shaft 10 at the reaching position, the pressing member 26 and the reaction beam 28 for pressing the inner side of the wall body 18 so that the shield machine 20 can excavate the wall body 18 at the reaching position. Is provided.

  Among the side walls 12 of the shield tunneling shaft 10, the wall 16 at the start of the shield machine 20 and the wall 18 at the destination of the shield machine 20 are excavated by the shield machine 20 at the start and end of the drilling of the shield tunnel 24. It is a part to be cut. For this reason, the wall body 16 at the start location and the wall body 18 at the arrival location are required to be strong enough to support the earth pressure of the ground 22 when the shield tunneling shaft 10 is maintained, and at the time of excavation, the shield machine 20 Therefore, it is required that cutting is possible. Therefore, in the shield tunneling shaft 10 according to the present embodiment, the walls 16 and 18 at the start / reach locations are constructed using concrete containing the above-described slag as a fine aggregate.

  Here, with reference to FIG.2 and FIG.3, the specific example which builds the wall bodies 16 and 18 of the said start / reach location using the said concrete is demonstrated. 2 is a perspective view showing a structural steel member provided with a concrete columnar body including slag according to the present embodiment, and FIG. 3 is a wall body 16 at a start position of the shield tunneling shaft 10 according to the present embodiment. It is the front view which looked at from the shield machine 20 side.

  As shown in FIG. 2, for example, a rectangular columnar concrete columnar body 30 is formed using concrete containing the slag as a fine aggregate. The concrete columnar body 30 is molded into a size corresponding to the shape of the wall bodies 16 and 18 at the start / reach locations. And the structural steel members 50, such as H-shaped steel, are joined to the both ends of the longitudinal direction of this concrete columnar body 30 via the joint member 40. As shown in FIG. The constituent steel member 50 is a reinforcing member that constitutes the side wall 12 of the shield tunneling shaft 10, and the side wall 12 is completed by placing concrete around the constituent steel member 50. The joint member 40 joins the constituent steel member 50 and the concrete columnar body 30, and includes a connection fitting 42 and a fixing jig 44. One end of the connection fitting 42 is joined to the end of the constituent steel member 50 by bolts or welding, and the other end of the connection fitting 42 is connected to the steel end plate 46 of the fixing jig 44. The fixing jig 44 is integrally formed when the concrete columnar body 30 is molded, and is firmly coupled to the concrete columnar body 30. Thus, the concrete columnar body 30 for constructing the wall bodies 16 and 18 of the start / arrival place is attached between the upper and lower constituent steel members 50 using the joint member 40.

  Next, as shown in FIG. 3, the manufactured structural steel members 50 with the concrete columnar bodies 30 are sequentially driven into the ground 22 at the construction position of the shield tunneling shaft 10, and the plurality of structural steel members 50 are spaced at a predetermined interval. Arrange. Furthermore, by placing concrete (not shown) around these plural steel members 50 and solidifying, the side wall 12 on the shield tunnel 24 side of the shield tunneling shaft 10 is constructed. At this time, the structural steel member 50 in which the length of the concrete columnar body 30 is appropriately adjusted so as to conform to the shape of the circular cutting target portion (starting portion wall body 16) by the shield machine 20 is used. Moreover, the structural steel member 50 which does not have the concrete columnar body 30, but was comprised only by H-shaped steel etc. is used for parts other than the wall body 16 of a start location. Note that the concrete placed around the plurality of constituent steel members 50 may be general concrete using fine sand as a fine aggregate, and the slag according to the present embodiment may be used as a fine aggregate. Concrete to be used may be used. In addition, although the construction method of the wall body 16 at the start location has been described here, the same applies to the construction of the wall body 18 at the arrival location.

  Next, the excavation method of the shield tunnel 24 by the shield machine 20 will be described with reference to FIG. 1 again. First, after the shield digging shaft 10 is constructed at each of the start position and the arrival position described above, the shield digging machine 20 is carried into the shield digging shaft 10 at the start position to prepare for excavation. At this time, the wall 16 at the start of the shield tunneling shaft 10 has sufficient strength to withstand the ground pressure.

  Next, steam curing is performed by spraying steam on the wall 16 at the starting point using a steam spraying device (not shown). At this time, the water vapor injection device may be mounted on the shield machine 20 and water vapor may be injected from the head 20a of the shield machine 20 to the wall 16 at the start point, or the main body of the water vapor injection device May be installed inside or outside the shield excavation shaft 10, and in a state where the shield machine 20 is retracted, water vapor may be injected from the injection nozzle of the water vapor injection device to the wall 16 at the start location. At this time, if a plurality of holes are drilled in the wall 16 at the starting point and water vapor is blown into the holes, high-temperature and high-pressure steam is allowed to act on the wall 16 at the starting point, Steam curing can be suitably performed.

Thereafter, the shield machine 20 is started, and the wall body 16 at the start point is excavated by the bit 20b provided on the rotating head 20a. At this time, due to the steam curing, the concrete constituting the wall body 16 at the start location expands and micro cracks are generated, and the machinability of the wall body 16 at the start location is improved. The wall 16 of the location can be easily excavated.
Next, the shield tunnel 24 is constructed by excavating the ground 22 in a substantially horizontal direction by the shield machine 20. Then, when excavation has progressed to the vicinity of the wall 18 at the reaching location, steam curing is performed on the wall 18 at the reaching location in the same manner as described above to improve the machinability of the wall 18 at the reaching location. Thereby, the shield machine 20 can easily excavate the wall body 18 at the reaching point. Thereafter, the shield tunnel 24 is completed by completing the excavation of the wall 18 at the arrival point, and the shield machine 20 is carried out from the shield tunneling shaft 10 at the arrival position.

  As described above, by using the special concrete having the slag according to the present embodiment as a fine aggregate, the wall bodies 16 and 18 of the start / reach locations of the shield excavation vertical shaft 10 are constructed, thereby the shield excavation vertical shaft. When maintaining 10 (ie, when not excavating), the structure can have sufficient strength, while when excavating with the shield excavator 20, the walls 16 and 18 at the start / arrival points are easily cut. become able to. In particular, by performing steam curing before excavation of the wall bodies 16 and 18 at the start / arrival locations, the machinability of the wall bodies 16 and 18 can be greatly improved.

  As mentioned above, although the case where steam curing was performed with respect to the wall bodies 16 and 18 of a start / arrival location has been described, even when steam curing is not performed, machinability is improved as compared with ordinary concrete.

  Next, various test results conducted to verify that the mortar or concrete produced using the slag having the above composition according to the present embodiment is excellent in strength and machinability will be described. In addition, this invention is not limited to a following example.

<1. Results of steam curing test for slag alone>
First, regarding the two types of slag (Examples 1 and 2) in which the composition of the main components of the slag belongs to the composition range of the present invention, and two types of converter slags (Comparative Examples 1 and 2) that do not belong to the composition range, In order to obtain the expansion behavior when the slag single-piece molded body is steam-cured, the results of an autoclave test will be described. In addition, the slag of Examples 1 and 2 is steelmaking slag generated at the time of refining in an AOD furnace in a steelmaking process of stainless steel. Table 1 shows the slag compositions of Examples 1 and 2 and Comparative Examples 1 and 2.

  First, test conditions for this test will be described. After adding 4 g of water to 40 g of slag powder of each composition shown in Table 1 and sufficiently kneading with a spatula, it was placed in a 25 mmφ cylindrical mold and subjected to pressure molding at about 98 MPa to mold each specimen. In addition, after measuring the dimensions of each specimen, curing was performed in moisture to prevent cracking due to drying shrinkage. Next, each of the molded specimens is set in an autoclave, and steam curing is performed under the conditions of 100 ° C. (1 atm: 101325 Pa), 120 ° C. (2 atm: 202650 Pa), and 150 ° C. (5 atm: 506625 Pa). went. Furthermore, after cooling, each specimen was taken out from the autoclave apparatus, and if the shape of the specimen was maintained, the outer diameter and height were measured, and the expansion coefficient was calculated in terms of volume.

The test results are shown in FIG. As shown in FIG. 4, both the slag of Examples 1 and 2 and the slag specimens of Comparative Examples 1 and 2 gradually increased with the increase in the processing temperature of the autoclave device. The slag specimens of Examples 1 and 2 are overwhelmingly larger than the slag specimens of Comparative Examples 1 and 2. For example, at 150 ° C., the expansion coefficient of the slag specimen of Comparative Example 1 is 11.2%, whereas the expansion coefficient of the slag specimen of Examples 1 and 2 is about 82.9% and about 48. It can be seen that it is 8%, which is expanded at least 4 to 7 times or more. According to the steam curing test results of such slag alone, the composition range of the present invention (Al ₂ O ₃ 20 to 40% by mass, CaO 40 to 60% by mass, SiO ₂ 15% by mass or less, MgO 5 to 15% by mass). The slag belonging to) can be said to have extremely high expandability due to steam curing.

<2. Results of steam curing test for mortar containing slag>
Next, a mortar specimen (hereinafter referred to as “mortar specimen of Examples 1 and 2”) using the slag of the composition of Examples 1 and 2 (see Table 1) as a fine aggregate, and a normal one. A mortar specimen (standard sample) using fine sand as a fine aggregate is prepared, and each mortar specimen is heated and cured in a steam atmosphere, and the test results of measuring the volume change will be described.

  First, the test conditions of this test will be described. As a standard sample, 180 g of cement, 540 g of fine sand, and 90 g of water were kneaded (water cement ratio W / C = 0.50) to prepare a JIS A specified mortar having a compressive strength of about 49 MPa. Moreover, 180 g of cement and 540 g of slag of Examples 1 and 2 were mixed, and water was gradually added. At this time, both Examples 1 and 2 could not be mixed without adding more water than the standard sample. For this reason, water was gradually added to the cement and slag to complete the kneading of the mortar when it became a concentrated fluid. The amount of water added at this time was 144 g for the mortar of Example 1 and 252 g for the mortar of Example 2. The standard sample thus obtained and each mortar of Examples 1 and 2 were placed in a 40 × 40 × 150 mm mold, and demolded one day later to obtain a mortar specimen.

  Further, as shown in FIG. 5, these standard samples and the mortar specimens of Examples 1 and 2 were placed in water at 20 ° C. for about one month after placement, and then the first heating steam curing (90 ° C. 32.5 hours). Subsequently, after leaving at room temperature for 135.5 hours and performing normal temperature curing, the second heating steam curing (90 ° C., 10.5 hours) was performed. Thereafter, it was allowed to stand at room temperature for about 1 month and then subjected to room temperature curing. In the middle of this, only the mortar specimen of Example 1 was subjected to the third heating steam curing (90 ° C., 11 hours). During such underwater curing, room temperature curing, and steam curing periods, the volume V is calculated by measuring the length, height, and width of each mortar specimen at appropriate time intervals. The volume ratio (V / V ′) to the volume V ′ of each mortar specimen was determined. In addition, the temperature 90 degreeC at the time of steam curing is a value when it measures with the thermometer with which the test machine was equipped, and the temperature of the water vapor | steam actually acted on the mortar test body is a temperature higher than 90 degreeC.

  The result of the steam curing test for each mortar specimen is shown in FIGS. As shown in FIG. 5, the mortar test of the standard sample showed almost no volume expansion even after the first and second heating steam curing, and the final volume ratio was about 1.005 times. It was. On the other hand, the mortar specimens of Examples 1 and 2 expanded in volume each time the first to third heating steam curing was performed. In particular, the volume expansion of the mortar specimen of Example 2 was intense, and after the second heating steam curing, the volume ratio expanded to about 1.08 times. In addition, even if it was the mortar test body of Example 1, 2, the volume expansion | swelling was hardly seen at the time of normal temperature curing after performing each steam curing.

  Moreover, when the presence or absence of the crack generation | occurrence | production of the test body was examined, even if the mortar test of the standard sample performed the 1st and 2nd heating steam curing, the crack did not generate | occur | produce. In contrast, the mortar specimen of Example 2 cracked in about 26 hours after the start of the first heating steam curing. At the time of the second heating steam curing thereafter, the mortar specimen of Example 2 in which cracks have already occurred has expanded to a volume ratio of about 1.03 to 1.08 times, and no cracks have occurred. Swells significantly more than the mortar specimen of Example 1. This means that once cracking occurs, strength deterioration due to volume expansion due to steam curing is accelerated. Moreover, although the mortar test body of Example 1 had the volume expansion as a result of the first and second heating steam curing (steam curing time: 43 hours in total), there was no occurrence of cracking. When the third heating steam curing was performed (steam curing time: 54 hours in total), cracks occurred.

  The photograph which image | photographed each mortar test body after such a steam curing test is shown in FIG. The mortar specimen of the standard sample has no cracks and is hardly deteriorated in strength (see FIG. 6 (a)). On the other hand, the mortar specimen of Example 1 has minute cracks and is deteriorated in strength (see FIG. 6B). In addition, the mortar specimen of Example 2 collapsed until the original shape did not remain as a result of occurrence and progression of remarkable cracks, and the strength deterioration was remarkable (see FIG. 6C).

  According to the results of the steam curing test of the mortar specimen as described above, the mortar manufactured using the slag belonging to the composition range of the present invention expands significantly more than the normal mortar due to the steam curing, and cracks are generated. It can be seen that the strength is easily deteriorated. For this reason, it can be said that the strength deterioration is promoted and the machinability can be improved by subjecting the slag-containing mortar having high strength at the beginning of casting to steam curing.

<3. Results of machinability evaluation test for mortar containing slag>
Next, a plurality of mortar specimens using the slag having the composition of Example 1 described above (see Table 1) as a fine aggregate were prepared, and after steam curing was selectively performed, the results of the cutting evaluation test were performed. explain.

  First, preparation of the mortar test body concerning this test is demonstrated. First, 6000 g of Portland cement, 9000 g of the slag of Example 1 above, 4000 g of water, and 60 g of a water reducing agent were kneaded (water cement ratio W / C = 0.67) to prepare an unsolidified mortar. The mortar was cast into a 500 × 500 × 100 mm steel frame and solidified by air curing at room temperature for 28 days after demolding to obtain three mortar specimens. Two of these mortar specimens were heated and steamed for 24 hours and 48 hours, respectively, in a steam atmosphere at 90 ° C. As a result, the test specimen that had been subjected to the steam curing for 24 hours generated moderate cracks accompanying expansion, and the compressive strength was about 21 MPa at the age of 30 days or more. On the other hand, the specimen subjected to the steam curing for 48 hours was excluded from the cutting test because excessive cracking due to expansion occurred and the degree of collapse was large.

  As described above, the mortar specimen (hereinafter referred to as “first specimen”) that was not subjected to steam curing after the air curing for 28 days using the slag of Example 1 described above, and 24 hours. A mortar specimen (hereinafter referred to as “second specimen”) subjected to steam curing was prepared. Moreover, the mortar test body (henceforth "the test body of Comparative Examples 1 and 2", respectively) was produced using the slag of the composition of Comparative Examples 1 and 2 (refer to Table 1) as a comparative test body. . The specimens of Comparative Examples 1 and 2 were prepared without performing the steam curing after performing the air curing for 28 days after demolding in the same manner as the first testing body.

  Next, a cutting test method will be described. In this cutting test, a cutting test machine 1 shown in FIG. 7 was used. As shown in FIG. 7, the cutting test machine 1 is a horizontal cutting test machine driven by an electric motor, and a plurality of bits 3 are mounted on the front surface of a face plate 2 that is rotatably provided to rotate the face plate 2. However, it has a structure that can be extruded in the horizontal direction. The cutting test machine 1 can push the rotating bit 3 in the horizontal direction with respect to the test body 4 to cut the test body 4 along a circumferential locus. Furthermore, in order to measure noise and vibration generated during cutting, a noise measuring microphone 5 and a vibrometer 6 were installed at a position 2 m away from the test body 4 attached to the cutting test machine 1. Table 2 shows the specifications of the cutting test machine 1 and the bit 3 and the cutting test conditions.

  Using this cutting test machine 1, the cutting test of the first and second specimens (material age 110 days) of Example 1 described above is performed, and the pressing force (= indentation resistance), cutting torque, and noise level during cutting The vibration level was measured. Of these, the pressing force and cutting torque at the time of cutting are indicators that directly represent the superiority or inferiority of the workability of the workpiece, and the noise level and vibration level at the time of cutting indicate the superiority or inferiority of the workability of the workpiece. It serves as an indirect indicator.

  Table 3 shows the measurement results in the cutting test. Table 3 also shows the vibration level, noise level, and compressive strength measured in the same manner as above for the test specimens of Comparative Examples 1 and 2 and the artificial wood as comparative test specimens.

  First, a 1st test body and a 2nd test body are compared. As shown in Table 3, the vibration level, noise level, pressing force, and cutting torque of the second specimen subjected to steam curing are smaller than those of the first specimen not subjected to steam curing. There is an effect of improving machinability due to expansion. In particular, the noise level at the time of cutting of the second specimen was as very low as 68 db, and the noise accompanying the cutting was hidden by the noise (background noise) accompanying the driving of the cutting test machine 1. In addition, the vibration level, noise level, pressing force, and cutting torque of the first test specimen tended to increase with time as the cutting progressed. The force and cutting torque did not increase as cutting progressed, and were almost constant. This is considered to be because the occurrence of cracks due to expansion is remarkable in the second specimen, and the mortar in the vicinity of the bit 3 is peeled off during cutting, so that friction on the side surface of the bit 3 is reduced.

  Regarding the compressive strength, the compressive strength of the first specimen is as high as 21.0 MPa, whereas the second specimen is deteriorated so that the compressive strength cannot be measured due to expansion or collapse due to steam curing. Was.

  According to such a comparison result between the first test body and the second test body, the second test body that was steam-cured rather than the first test body that was not steam-cured while being a mortar of the same composition. It can be said that is superior in machinability. Therefore, it can be said that the mortar manufactured using the slag belonging to the composition range of the present invention has been proved that, by performing steam curing, crack generation due to expansion proceeds and the machinability is greatly improved.

  Next, the 1st and 2nd test body concerning this embodiment is compared with the test body of the comparative example 1, the test body of the comparative example 2, and artificial wood. The vibration level (49 dB) of the first test body is much smaller than the vibration levels (55, 60 dB) of the test body of Comparative Example 1 and the test body of Comparative Example 2, and is close to artificial wood (45 dB). It has dropped to the level. The difference in vibration level ((55-60) -49 = 6-11 dB) between the first test body and the test body of Comparative Example 1 is the vibration level between the first test body and the second test body due to the expansion. Greater than the difference (49-46 = 3 dB). Therefore, even if it is the 1st test body which is not performing steam curing, it can be said that cutting property is fully improved compared with the test body of the comparative example 1, etc.

  Moreover, the 2nd test body which performed steam curing becomes a level comparable with the artificial wood excellent in both the vibration level and the noise level compared with the test body etc. of the comparative example 1, etc. which were remarkably small. Yes. From the above test results, it can be said that the first and second test specimens have been demonstrated to have significantly improved machinability as compared with the test specimens of Comparative Example 1 and Comparative Example 2.

  As described above, the mortar or concrete including the calcium aluminate-based steel slag according to the present embodiment as the fine aggregate, the structure constructed using the mortar or concrete, and the cutting method thereof have been described in detail. According to the present embodiment, the mortar or concrete containing the slag has higher strength than conventional materials excellent in machinability (plastic foam, foamed concrete, artificial wood, etc.), and conventional fibers It has better machinability than a concrete material reinforced with a reinforcing material. Therefore, the cutting target portion of the structure constructed using the mortar or concrete according to the present embodiment has sufficient strength to maintain the structure, for example, cutting work such as removal or excavation of the structure. Sometimes excellent machinability can be exhibited.

  Furthermore, by performing steam curing on the cutting target portion of the structure, it is possible to generate a minute crack in the cutting target portion, and thus greatly improve the machinability of the cutting target portion. You can also. As described above, the machinability of the structure can be partially improved only by performing a prior simple treatment called steam curing, so that it is very useful in the construction of the structure, and the construction labor and the construction cost can be reduced.

  Further, the above-mentioned industrial by-product called steelmaking slag has little variation in quality and is an environment-friendly recycled material, and therefore can be effectively used as a material for mortar or concrete.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

It is a longitudinal section showing a schematic structure of a shaft for shield excavation concerning one embodiment of the present invention. It is a perspective view which shows the structural steel member provided with the concrete columnar body containing the calcium aluminate type steel slag concerning the embodiment. It is the front view which looked at the wall body of the start location of the shield tunnel vertical shaft concerning the embodiment from the shield tunnel machine side. It is the table | surface and graph which show the steam curing test result of the slag single-piece | unit concerning the Example of this invention. It is a graph which shows the steam curing test result of the mortar containing the slag concerning the Example of this invention. It is a photograph which shows the steam curing test result of the mortar containing the slag concerning the Example of this invention. It is explanatory drawing which shows schematic structure of the cutting test machine used by the machinability evaluation test concerning the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cutting test machine 2 Face plate 3 Bit 4 Specimen 5 Noise measurement microphone 6 Vibrometer 10 Shield digging shaft 12 Side wall 14 Bottom plate 16 Wall body of starting place 18 Wall body of reaching place 20 Shield digging machine 22 Ground 24 Shield tunnel 26 Pressure member 28 Reaction beam 30 Concrete columnar body 40 Joint member 42 Connecting bracket 44 Fixing jig 46 Steel end plate 50 Constituent steel member

Claims (12)

Calcium aluminate-based steel slag containing 20 to 40% by mass of Al ₂ O ₃ , 40 to 60% by mass of CaO, 15% by mass or less of SiO ₂ and 5 to 15% by mass of MgO is fine bone A structure having a portion to be cut constructed using mortar or concrete included as a material.   The structure according to claim 1, wherein a maximum water absorption amount of the calcium aluminate-based steel slag is 40 to 50% by mass.   The structure according to claim 1, wherein steam curing is applied to the portion to be cut.   The structure according to claim 3, wherein a crack is generated in the portion to be cut by performing the steam curing.   5. The blend ratio of cement and the calcium aluminate-based steel slag in the mortar or concrete is 1: 0.1 to 30 by mass ratio, according to claim 1. Structure.   The structure according to any one of claims 1 to 5, wherein the portion to be cut is a wall body of a start or arrival portion excavated by a shield machine in a shield tunneling shaft. A cutting method for cutting a portion to be cut of a structure,
Calcium aluminate-based steel slag containing 20 to 40% by mass of Al ₂ O ₃ , 40 to 60% by mass of CaO, 15% by mass or less of SiO ₂ and 5 to 15% by mass of MgO is fine bone A cutting method characterized by constructing the portion to be cut using mortar or concrete included as a material and cutting the portion to be cut.   The cutting method according to claim 7, wherein a maximum water absorption amount of the calcium aluminate-based steel slag is 40 to 50% by mass.   The cutting method according to claim 7 or 8, wherein the cutting target portion is cut after steam curing is performed on the cutting target portion after the cutting target portion is constructed.   The cutting method according to claim 9, wherein the cutting target portion is cut after the steam curing is performed to cause a crack in the cutting target portion.   The blend ratio of cement and the calcium aluminate-based steel slag in the mortar or concrete is 1: 0.1 to 30 in terms of mass ratio, according to any one of claims 7 to 10. Cutting method.   The cutting method according to any one of claims 7 to 11, wherein the portion to be cut is a wall of a start or reaching portion excavated by a shield machine in a shield tunneling shaft.

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