JP2021188354A - Precast prestressed concrete foundation structure and its construction method - Google Patents

Abstract

To provide a precast prestressed concrete foundation structure that maintains structural stability and its construction method.SOLUTION: A foundation structure comprises a bottom slab 100 made of flat precast concrete 51 placed at a bottom of a subterranean hole formed by ground excavation, a side wall 200 consisting of a wall-shaped precast concrete 23 placed on the bottom slab 100 and along the inner wall of the subterranean hole, a filling material 70 to be filled in the space enclosed by the bottom slab 100 and the side wall 200, a top slab 300 consisting of flat precast concrete 51 that fills the fill material 70, and a fixed foundation 400 to be installed on the top slab 300. A plurality of through holes are formed in each of the bottom slab 100, the side wall 200, the top slab 300, and the fixed foundation 400, and each of the plurality of through holes is continuous from the bottom slab 100 to the fixed foundation 400, and is tensioned and anchored by a tensioning material 1 penetrating the through holes.SELECTED DRAWING: Figure 1

Description

The present invention mainly relates to a basic structure used for a steel tower or a bridge installed at a construction site where the location environment is limited such as a mountainous part or a mountainous part, and a construction method thereof.
More specifically, when the construction site has a limited location environment such as a mountainous area or a mountainous area, specifically, an access lifeline such as a public road or a railroad necessary for transporting construction materials. If this is not the case, various restricted environments for construction will occur. In other words, as a means for transporting construction materials, the use of helicopters, the use of cableway lines and monorails, and the construction of temporary roads for construction are required. Under such a restricted environment in construction, by applying the present invention, a new foundation structure and a construction method thereof that can realize a significant cost reduction and a shortening of the construction period as compared with the conventional foundation structure are related. Is.
The foundation structure of the present invention covers all foundation structures such as the foundation of a transmission line steel tower, the foundation of a bridge pillar, the foundation of an abutment, and the foundation of a building.

It is a well-known fact that reinforcing bars have been used most often as reinforcement materials for foundation structures using concrete materials. The functions required of the foundation structure are the downward pushing axial force from the outside (superstructure), the upward pulling axial force, the horizontal shearing force, the torsional moment, the bending moment, and other cross-sectional forces. The purpose is to maintain the structural stability of the foundation structure by effectively transmitting the structural resistance of the foundation structure itself and the sectional force to the surrounding ground through the foundation structure.
Therefore, the structural type of the foundation structure is influenced by the soil and rock quality of the ground to be installed, and various structural types are selected. As a result, the structural materials used for foundation structures are overwhelmingly concrete and reinforcing bars, and foundation structures to which so-called reinforced concrete is applied are the mainstream.

When constructing a reinforced concrete foundation structure in a mountainous area, it is necessary to transport a large amount of concrete, reinforcing bars, formwork, scaffolding support, earth retaining support, and other construction materials to the construction site. In mountainous areas, there is often no access by public roads, so it is necessary to consider transportation means such as helicopters, cableways, and monorails. Among the construction materials, concrete and reinforcing bars are often more expensive to transport than the material unit price, which has been a major issue for foundation construction in mountainous areas.

The foundation structure will be constructed in the local ground to utilize the reaction force from the ground. Therefore, a large amount of excavated soil is generated, and a large amount of residual soil treatment is required after the foundation construction, and the residual soil treatment method and treatment cost such as discharge and transportation of the residual soil have been problems.

In the case of transmission line tower foundations, the base of the tower legs must be fixed in the reinforced concrete foundation. In many cases, the fixing method adopts the fixing method of the shape of the squid, and the fixing of the squid is carried out by embedding it in the concrete foundation. Therefore, it was difficult to position and fix the base of the tower leg material, which was time-consuming and costly.

The reinforced concrete foundation is a method of placing ready-mixed concrete on site. In the case of concrete casting using a ready-mixed concrete car, it can be constructed by normal construction management. However, in concrete placement in mountainous areas, for example, when a helicopter is applied as a means of transportation, the ready-mixed concrete can be transported to the heliport, the ready-mixed concrete vehicle can be moved to the hopper, the helicopter can be used to transport the hopper, and the hopper can be moved from the hopper to the hopper at the construction site. Concrete placement by, many routes, and transshipment are required. Therefore, there is a great risk of continuously placing the concrete while maintaining the freshness of the concrete. In addition, if the transportation time exceeds the schedule, it will not be possible to secure a construction slump, and cold joints will occur on the concrete joint surface, making it difficult to construct the structure as designed. Become. Especially in the case of helicopter transportation, it is easily affected by the wind, there is a sufficient risk of interrupting construction, and quality control of concrete becomes strict. Therefore, it is considered that the construction operation rate is lowered and the construction cost is increased.

Most of the reinforcing bars applied to reinforced concrete foundations are large-diameter deformed reinforcing bars. Reinforcing bars at the construction site often have to be assembled in an environment where sufficient lifting machines cannot be used in a narrow place as the construction environment, and it is difficult to secure construction workers in such a construction environment. be.

Reinforced concrete foundations often have a massive shape. Therefore, it often becomes mass concrete, and a large amount of hydration reaction heat is generated during concrete curing, and temperature stress is generated. Therefore, it is necessary to take measures against mass concrete. If the mascon control is not sufficiently carried out, through cracks will occur not only near the surface of the foundation but also inside due to thermal stress, increasing the risk of reinforcing bar corrosion inside the concrete.

Since recent reinforced concrete is basically designed to allow the occurrence of cracks on the surface under the limit of use, it is necessary to secure the necessary concrete covering so that the reinforcing bar does not rust. However, there is always a risk of rebar rusting. Therefore, it is inevitable that regular maintenance costs for concrete foundations will be incurred.

Previous patent references related to the present invention are shown below.

Japanese Unexamined Patent Publication No. 2014-169551 Japanese Unexamined Patent Publication No. 10-231527 Japanese Unexamined Patent Publication No. 10-140586 Japanese Unexamined Patent Publication No. 6-316942 Japanese Patent No. 6650995

(1) Japanese Unexamined Patent Publication No. 2014-169551 (Patent Document 1)
Patent Document 1 describes a series of reinforced concrete foundation construction work such as formwork, rebar assembly, concrete placement, and curing at the construction site, as a precast construction block, manufactured in advance at another location, and at the construction site. It is a technology that focuses on assembling. Therefore, although it is recognized that the degree of freedom for on-site construction restrictions will increase, the shape of the completed reinforced concrete foundation is not different from the cast-in-place concrete shape, and the restrictions on transportation (blocks) are based on the shape of the divided construction blocks. It seems that the restrictions on the weight and shape of the concrete cannot be lifted. In addition, although fitting joints are applied to the joining of construction blocks, it is difficult to ensure joining accuracy due to the gaps in the fitting joints, and tensile reinforcing materials such as reinforcing bars are used to join the block foundations to each other. Is not applied, so it is doubtful whether the strength as a foundation structure can be secured.

(2) Japanese Patent Application Laid-Open No. 10-231527 (Patent Document 2)
The subject of Patent Document 2 is the same as a part of the subject of the present invention in that the excavated residual soil and the amount of concrete placed are reduced. As a method of using the residual soil, it is mixed with excavated residual soil, water, and cement to produce a sediment block made of so-called soil cement and applied to a part of the lower concrete layer. The lower concrete is constructed by placing reinforcement in the gap between the earth and sand block and the inner peripheral wall and placing cast-in-place concrete. In the construction of the upper concrete layer, reinforcement is arranged and cast-in-place concrete is constructed by the conventional construction method. Since the earth and sand block shown in Document 2 is blocked, a lifting machine is required to install it at the bottom of the foundation. In the case of cast-in-place concrete, it is possible to construct by bucket casting or pump casting, but it is difficult to construct heavy objects that are blocked. In addition, as the amount of excavated surplus soil, only about 20 to 30% of the total amount of excavated soil can be used, so it cannot be considered that the problem of excavation surplus soil treatment has been solved. In addition, most of the deep foundation foundations in Document 2 are reinforced concrete foundations made of cast-in-place concrete, and it is difficult to think of a large difference from the conventional foundation structure.

(3) Japanese Patent Application Laid-Open No. 10-140586 (Patent Document 3)
Patent Document 3 is a technique for assembling and joining concrete blocks at a construction site in order to solve problems such as concrete transportation cost, deterioration of concrete quality, and labor for assembling reinforcing bars in the deep foundation construction of a transmission line tower. Is provided.

As shown in [0012] of Patent Document 3, "The concrete block is provided with a through hole through which a fluid such as cement mortar can flow in and out in the vertical and horizontal directions, and the foundation is consolidated by injecting the cement mortar. It provides a structure that can be integrated and adhered to the excavated ground of the foundation. " When excavating a deep foundation, earth retaining work is required, and the gap between the concrete block and the ground outside the earth retaining work is about 100 mm to 200 mm. Filling the cement mortar for that purpose from the inside has a high possibility of leaking into the concrete block considering the fluidity of the cement mortar, and the certainty of construction is unreliable. In addition, it is not realistic to fill a large volume of the gap between the foundation body and the excavated ground with cement mortar, which has a high material unit price, considering the high material cost.

As shown in [0014] of Patent Document 3, "By stacking and assembling concrete blocks 1 on an arc into a cylindrical shape, reinforcing bars 3 are pierced through the upper and lower concrete blocks in a skewered state, and both ends are tensioned. , The concrete block group is integrated to form a foundation body 2 having a gap 4. " From the description of the upper and lower concrete blocks and the drawings, it can be seen that the joining of the concrete blocks to each other by the reinforcing bars shown in Document 3 is limited to two concrete blocks. That is, joining a plurality of concrete blocks of three or more is not considered. Also, no method has been shown for further joining another concrete block onto the two joined concrete blocks. However, the length required for the actual deep foundation is at least 15 to 20 m, which is not realistic.

As shown in [0017] of Patent Document 3, "Concrete block 1 is provided with a through hole 6 into which cement mortar can be injected and a groove 7 at an end as shown in FIG. 3, and is mortar when assembled by stacking. It is also possible to strengthen the integration of concrete blocks by injecting. " Even if the mortar is injected into the through hole 6 or the groove 7 at the end, the strength of the mortar as a joining material cannot be expected unlike the steel material. Therefore, the joint strength in the circumferential direction between the concrete blocks cannot be expected, and the resistance force in the lateral direction cannot be expected in terms of design, so that the concrete blocks do not function as a foundation structure.

As shown in [0018] of Patent Document 3, "The tension of the reinforcing bar 3 is maintained in a tense state by a commercially available tension jack and a fixture, and in this state, cement is cemented in the gap between the concrete block 1 and the reinforcing bar 3. After the mortar is poured in and the concrete block and the reinforcing bar are integrated by the mortar solidification, the tension fixture is removed. " Here, as explained by removing the tension fixture, the tension compressive stress generated in the concrete at the end is lost because the fixation of the tension end is released. Therefore, the function as prestressed concrete is limited.

Since the description of Patent Document 3 does not explain the bottom plate, which is indispensable as a deep foundation, its feasibility as a foundation structure is questionable. Further, when the structural resistance material mainly is the reinforcing bar in the vertical direction and the structure is structurally discontinuous in the circumferential direction, which is shown in Document 3, the shape and dimensions of the concrete block are designed. It is necessary to increase the size, and it is unlikely that the weight of concrete blocks transported to the construction site and the capacity of heavy machinery for on-site assembly can be reduced. Instead of the concrete transportation cost, the transportation cost of the concrete block is required without much reduction, and it is difficult to achieve the purpose of reducing the initial transportation cost.

(4) Japanese Patent Application Laid-Open No. 6-316942 (Patent Document 4)
Patent Document 4 is for a steel tower foundation, characterized in that a foundation main body having an adjusting engaging portion that engages with a height adjusting tool and a steel tower receiving portion that receives the lower end of a leg portion of the steel tower is integrally molded with concrete. We provide precast products. The purpose is to reduce cast-in-place concrete, shorten the construction time and reduce costs. In the embodiment according to Document 4, the foundation body having the tower receiving portion can be installed on the discarded concrete as a precast product. However, it is considered that the weight of the basic body will be greatly increased by using a precast product. Therefore, a considerably large-capacity lifting machine is required as compared with the conventional lifting machine required for the installation of the angle material without the precast concrete part + the lower end of the pier. In addition, the foundation work is not completed only with the precast products for steel tower foundations according to Document 4, and the formwork, reinforcement arrangement, and concrete placement of the foundation fixed body are required, and the reduction of cast-in-place concrete and the construction time are required. The contribution to shortening is small.

(5) Japanese Patent No. 6650995 (Patent Document 5)
It is an object of Patent Document 5 to provide a steel tower foundation structure and a construction method capable of simplifying the positioning work of the steel leg portion of the steel tower. The point of Document 5 is that the inner piece made of precast concrete and the tower leg are integrally manufactured and placed on the ground plane treated with pile heads, so that the tower leg can be easily positioned. Is. In addition, the outer piece made of precast concrete is installed on the outside of the pile head, and the horizontal position of the inner piece integrated with the tower leg is adjusted via the jack installed between the inner piece and the outer piece. It is supposed to be. However, in the construction method of Document 5, since the outer piece is not fixed to the pile head, it cannot take charge of the horizontal reaction force of the jack, so that the horizontal position adjustment is difficult. Further, even if the surface treatment of the pile head is performed horizontally, it is necessary to adjust the inclination of the tower pier, and the method is not shown. Further, considering the structure at the time of completion of Document 5, when the pulling force from the steel tower or the cross-sectional force of the bending moment acts, the main reinforcing bar arranged around the pile has the tensile force generated by the pulling force or the bending moment. It is a structure that resists. Therefore, the contact area of the inner piece and the outer piece, which occupy most of the cross-sectional area at the joint, is a structure that is only in contact with the head of the pile, and is a structure that is discontinuous with respect to tensile force and shear force. It has become. That is, it is difficult to transmit the sectional force to the pile body so as to resist the sectional force such as the pulling force and the bending moment generated in the steel tower pier.

(6) Others Although the foundation structures of steel towers and bridges in mountainous areas have severe natural and construction conditions, most of the main structural foundations have traditionally been cast-in-place reinforced concrete structures. Helicopters, cableways, monorails, and other means of transportation have been used to transport heavy materials in mountainous areas. Therefore, the transportation cost may be higher than the material cost. Until now, in the construction of reinforced concrete structures, there have been proposals for foundation structures to be transported and installed at construction sites as precast concrete structures instead of placing ready-mixed concrete. However, the invention of the foundation structure to which the precast prestressed concrete structure is applied by breaking away from the reinforced concrete structure as the structural form of the foundation could not be found as reference information from the past literatures and patent publication materials.

(1) Transportation of a large amount of construction materials required for foundation construction
1) There are various structural types of foundation structures for steel towers and bridges in mountainous areas, but reinforced concrete structures are the overwhelming majority.
2) When constructing a reinforced concrete foundation structure in a mountainous area, it is necessary to transport a large amount of concrete, reinforcing bars, formwork, scaffolding support, earth retaining support, and other construction materials to the construction site. In mountainous areas, there is often no access by public roads, so it is necessary to consider transportation means such as helicopters, cableways, and monorails. Among the construction materials, concrete and reinforcing bars are often more expensive to transport than the material unit price, which has been a major issue for foundation construction in mountainous areas.
3) Especially for concrete materials, the method of placing ready-mixed concrete directly on the foundation structure is often adopted, and if there is no access from the construction site such as ready-mixed concrete cars as described above, the prospect of construction is unclear. There is also.
4) Therefore, the structural form and construction method of the foundation that can reduce the transportation of a large amount of construction materials as described above are required.

(2) A large amount of residual soil is generated in foundation construction
1) The basics of the foundation structure are to maintain the structural stability by the reaction force from the surrounding ground. For that purpose, a large amount of ground at the installation site will be excavated and a reinforced concrete structure foundation will be constructed in it. The excavated soil may be partially used for backfilling, but a volume equal to the volume of the concrete foundation remains as residual soil.
2) It is not permissible to leave the remaining soil as it is from the viewpoint of preserving the natural environment in the mountainous areas. Therefore, it is necessary to transport to a place where the residual soil can be treated, and transportation costs and residual soil disposal costs are incurred.

(3) Fixing method and positioning installation work of transmission tower foundation to reinforced concrete foundation
1) In general, fixing with a squid material is widely used. Steel pipes and angle steel are often used as the material for power transmission towers, and fixing tools with a squid shape are often welded to the fixing part. In order to fix this in reinforced concrete, it is hung, installed, and positioned, but it is necessary to have an accurate direction and accurate positioning at the time of installation, but the work requires time and effort. rice field.
2) There is a fixing method that expects to be integrated with the surrounding reinforced concrete by welding a bearing plate around the power transmission tower. In this case as well, it took a lot of labor and labor to accurately position the position at the time of installation, as in the case of fixing the anchor. In addition, it is necessary to sufficiently increase the concrete diameter of the foundation frame from the fixing mechanism, and it is difficult to obtain an economical foundation shape due to the restrictions of the design conditions of the fixing part when designing as a foundation structure. rice field.
3) As a method of fixing the power transmission tower foundation, there is also a method of welding a bearing plate to the end of the tower and fixing it to the top of the foundation with tension bolts without fixing inside the foundation. Due to the tightening capacity of tension bolts and the limitation of bolt length, it was limited to small-scale tower foundation fixing.

(4) Construction management that is difficult to place on the ready-mixed concrete site
1) A large amount of ready-mixed concrete is required for the foundation structure. At foundation construction sites where access to public roads is not possible in mountainous areas, transportation means such as helicopters and cableways will be applied.
2) In the case of transportation by helicopter, it is transported from the ready-mixed concrete plant to the heliport by a ready-mixed concrete car, transferred to the heliport transportation bucket, helicopter transportation, temporary storage hopper transfer from the helicopter bucket, and placement from the storage hopper to the driving bucket. Material transfer is required.
3) The time from kneading to placing of ready-mixed concrete, depending on the temperature conditions, is 1.0 to 1.5 hours, which is the limit for maintaining fresh properties. Therefore, if the above transportation cycle is out of order, there is a risk such as stopping the placement of ready-mixed concrete.
4) In addition, as a general rule, ready-mixed concrete is placed continuously, and if the placing interval is longer than planned, there is a risk of cold joints occurring. When cold joints occur, the reinforcing bars rust and the continuity of the concrete structure cannot be maintained.

(5) Reinforcing bar assembly labor and construction time
1) As the main reinforcing bar of the foundation structure, a deformed reinforcing bar with a relatively large diameter is often applied. Generally, when the reinforcing bar is adjusted to the basic shape, the long and large diameter reinforcing bar is heavy, and the labor and labor required for assembling the reinforcing bar are large.
2) Generally, the place for assembling the reinforcing bar is often narrow, and it is difficult to handle heavy objects efficiently, so that the construction efficiency is poor and it takes time.

(6) Risk of temperature cracking of mascon
1) Most of the shape dimensions to be cast with ready-mixed concrete have a side length of 1 m or more. In this case, there is a risk that temperature stress will occur due to the mascon, and it is necessary to take measures against temperature cracks.
2) As a countermeasure, mix low-temperature cement for mascon, perform heat insulation curing so that temperature stress is less likely to occur during curing after placing, or perform splicing processing by limiting the amount of ready-mixed concrete. It is necessary to take various measures to prevent the occurrence of cracks caused by the mass control. Therefore, the cost of countermeasures and the construction time will be prolonged.
3) Cracks caused by the mascon become penetrating cracks, which causes problems such as discontinuity of the structure and rusting of the reinforcing bars.

(7) Maintenance of reinforced concrete foundation structure
1) As shown above, the construction management of reinforced concrete foundation structures in mountainous areas has various risks. Therefore, maintenance costs for the conventional foundation structure after completion are incurred.
2) However, the maintenance cost for the foundation structure in the mountainous area is different from the normal location conditions, so it is considered that a large amount of cost will be incurred in the unlikely event that a problem occurs.

(8) Construction period and construction cost due to on-site concrete placement construction
1) As mentioned above, the construction conditions in the mountainous area are very strict, and considering the natural conditions of the location, it is expected that the construction period will be long and the construction cost will be high.
2) In addition, unlike the working conditions of foundation construction in a normal location environment, it is difficult to secure workers because the workers are continuously stationed at the construction site and are forced to work under strict working conditions. ..

The basic role that the foundation structure of a tower or bridge should have is to provide structural stability against various external load loads on the so-called superstructure such as the tower or bridge. The external load is mainly dead load, live load, wind load, snow load, seismic load, construction load and the like. Due to the load from these superstructures, the foundation structure is subject to downward pushing axial force, upward pulling axial force, horizontal shearing force, torsional moment, bending moment, and other cross-sectional forces. The purpose is to maintain the structural stability of the foundation structure by effectively transmitting the above-mentioned sectional force to the surrounding ground through the structural resistance by itself and the foundation structure.

When trying to construct a foundation structure that applies conventional foundation structure types or conventional construction materials in mountainous areas and mountainous areas, there are many restrictions, including high construction costs, long construction periods, and poor construction. He had many issues such as working environment conditions. The present invention has been devised without being bound by the basic structural form and the structural materials required therein.

The precast prestressed concrete foundation structure according to the present invention is a bottom slab composed of one or more flat plate-shaped precast concrete installed at the bottom of an underground hole formed by ground excavation, on the bottom slab and above. Filled inside the space surrounded by one or more wall-shaped (frame-shaped) precast concrete side walls, bottom slabs, and side walls installed along the inner wall surface of the underground hole. A filling material made of earth and sand or soil cement, an upper plate portion made of one or more flat plate-shaped precast concrete installed on the side wall portion and the filling material, and the upper plate portion. It is provided with a fixed foundation to be installed in, and a plurality of through holes are formed in each of the bottom plate portion, the side wall portion, the upper plate portion and the fixed foundation, and each of the plurality of through holes is continuous from the bottom plate portion to the fixed foundation. It is characterized in that it is configured so that the tension material from the lower end portion of the bottom slab portion to the fixed foundation is tension-fixed by the tension material penetrating the through hole. Precast prestressed concrete foundation structures can be used, for example, as foundation structures for steel towers and bridges.

The precast prestressed concrete foundation structure according to the present invention includes concrete members in each of the bottom slab, side wall, and top slab that constitute the foundation structure in consideration of the constraint conditions for transporting special materials to the construction site. It consists of precast concrete members, all of which are set to less than the maximum load weight that can be carried.

For the fixed foundation to be installed on the upper plate portion, it is only necessary to install the base plate joined to the fixed foundation on the upper plate portion adjusted to the horizontal plane. The method equivalent to the conventional fixed foundation is anchoring or pressure plate fixing, and basically, in order to install it inside the concrete foundation structure, a frame for installation is required, and positioning work is also required. It was difficult and took a lot of work time.

In the precast prestressed concrete foundation structure according to the present invention, tension stress is introduced over the entire length of the foundation structure by providing a tension material in the through hole in the section from the bottom slab to the fixed foundation and fixing the tension. As a result, the conventional reinforced concrete foundation structure has a cross-sectional force such as a downward pushing axial force, an upward pulling axial force, a horizontal shear force, a twisting moment, and a bending moment acting on the foundation structure of the present invention. Although the cross section of the member is reduced, the crack resistance, bending moment resistance, and shear resistance increase due to the effect of prestress.

Here, as the tension material, metal strands such as PC steel strands and PC stainless strands, and continuous fibers such as carbon fibers, aramid fibers, and glass fibers are used as epoxy resins, vinyl ester resins, and methacrylic resins. , Polycarbonate resin, continuous fiber reinforcing material focused and impregnated with resin such as vinyl chloride can be used.

Since the precast prestressed concrete foundation structure according to the present invention is reduced in cross section as a member, the weight of the foundation body is required for the pull-out axial force acting on the foundation structure. Therefore, by filling the inside of the voids in the side wall with the earth and sand generated during excavation of the foundation ground, or the filling material made of soil cement mixed with the excavated earth and sand, the weight of the foundation body can be reduced by the conventional foundation body. All of them have almost the same weight as the reinforced concrete foundation, which can contribute to the pulling stability.

In the conventional construction of the foundation structure in the mountainous area and the mountainous area, a large amount of cost and construction time are required to dispose of the residual soil of the excavated soil. In the precast prestressed concrete foundation structure according to the present invention, the amount of earth and sand used for the filling material is smaller than the amount of excavated earth and sand, but it is possible to significantly reduce the amount of residual soil treated compared to the conventional method. Become.

The fixed foundation fixed to the upper plate portion of the precast prestressed concrete foundation structure according to the present invention is fixed to the bottom portion of the foundation structure by a tension material. Generally, as a method of fixing a base plate joined to a foundation structure to a concrete foundation, a method of tightening to the concrete foundation with anchor bolts is adopted. In that case, the applicable tensile strength of the anchor bolt is limited as compared with the tension material used for the bridge superstructure. Furthermore, compared to conventional anchor bolts, the tension material of the present invention is fixed to the bottom of the bottom slab, so the total length of the tension material is on the order of 10 m, tension management is easy, and set loss is 10,000. Even if one occurs, there is no error in the tension between the tension materials. Further, even if a tensile force is generated in the tension material due to a pull-out axial force or a bending moment generated from the fixed foundation by an external force, the tension material is not stretched and deformed by an external force less than the tensile force at the time of tension. That is, there are few design uncertainties in the calculation of the design yield strength against the design external force.

On the other hand, in the case of anchoring or bearing plate anchoring in a conventional reinforced concrete foundation structure, for example, the evaluation of the pulling shear strength of reinforced concrete with respect to the pulling force acting on anchoring is an experiment or three-dimensional. Evaluation by non-linear analysis was required, and there was design effort and design uncertainty.

Since the structure of the precast prestressed concrete foundation structure according to the present invention is a concrete factory product with high quality control, there is little variation in quality and high-strength concrete can be easily adopted, so that tensionable precast -Concrete can be made compact.

The present invention also provides a method of constructing a precast prestressed concrete foundation structure. In the construction method according to the present invention, a bottom slab composed of one or more flat plate-shaped precast concrete is installed at the bottom of the underground hole formed by ground excavation, and the bottom slab is on the bottom slab and the underground hole is formed. One or more wall-shaped (frame-shaped) precast concrete is installed along the inner wall surface, and the space surrounded by the bottom slab and the side wall is filled with a filling material made of earth and sand or soil cement. An upper plate portion composed of one or more flat plate-shaped precast concretes installed on the side wall portion and the filling material is installed, a fixed foundation is installed on the upper plate portion, and a bottom plate portion is installed. , A plurality of through holes formed in each of the side wall portion, the upper plate portion and the fixed foundation, and the tension material is passed through the through holes that continuously penetrate from the bottom plate portion to the fixed foundation, and the tension material is passed near the lower end portion of the bottom plate portion. After fixing the lower end of the concrete in the precast concrete, the tensioning material is tensioned upward on the fixed foundation, and the tensioning material is fixed and fixed on the fixed foundation.

To briefly mention the construction method of the precast prestressed concrete foundation structure, for example, the precast concrete members are piled up while joining from the bottom slab to the side wall, the voids in the side wall are filled with the filling material, and then the top. After stacking the precast concrete members of the plate and setting the foundation structure, the tension material is fixed in the precast concrete near the lower end of the bottom plate, and after tensioning over the entire length, the tension material is fixed to the foundation structure. It is a construction method.

In bridge construction using prestressed concrete (joining + tension method), it was necessary to apply a erection method that temporarily supports precast members against gravity. However, unlike the case of a bridge, the joining method of the present invention facilitates the joining work by, for example, stacking precast members in the vertical direction using a gravitational field.

In the above-mentioned construction method of precast / prestressed concrete foundation structure, it is necessary to introduce tension force over the entire length from the bottom slab to the fixed foundation. Therefore, through holes are provided in all the precast members using, for example, a sheath pipe. Finally, when the precast members are jointly installed, the through holes are also joined at the same time.

In the above-mentioned construction method of precast / prestressed concrete foundation structure, for example, after inserting a tension material to the vicinity of the lower end of the bottom slab, it is fixed to the bottom slab by filling, curing, and developing strength with a time-curing material such as cement grout material. After that, it is a construction method that makes you nervous over the entire length.

In one embodiment, tensioning materials or tensile reinforcements for introducing tension into the flat plate precast concrete constituting the bottom slab and the top slab are provided in one or two horizontal directions. This flat plate precast concrete, as a structural member of the bottom and top slabs, is unidirectional or unidirectional to apply the advantages of prestressed concrete to the cross-sectional forces of out-of-plane bending moments and shear forces. It is a flat plate-shaped prestressed concrete with tension applied in two directions.

In another embodiment, reinforcing bars are horizontally arranged as hoop bars in the wall-shaped precast concrete constituting the side wall portion. It is useful when tensile reinforcement is required against the shearing force acting on the entire foundation structure and the bending moment due to the eccentric pressure of the filling material and the filling material.

In one embodiment of the construction method, a fixing fixing device is provided at the lower end portion of the tension material, and the fixing fixing device at the lower end portion of the tension material is formed on a flat plate-shaped precast concrete constituting the bottom slab portion. It is inserted into the lower end of the through hole, the through hole is filled with a time-curing material, the time-curing material is cured, and after the time-curing material develops strength, the through hole is formed from the bottom slab to the fixed foundation. Tension the upper end of the inserted tensioning material. This construction method requires a fixed fixing device by inserting a tension material having a fixed fixing device such as a twisted type fixing tool or a grip type fixing device at the lower end of the through hole from above the through hole. This is a construction method in which the section from the lowermost end of the bottom slab to the fixed foundation is tensioned after filling, curing, and developing strength with a time-curing material such as cement grout.

In a preferred embodiment of the construction method, the tension fixing device is fixed to the upper end portion of the tension material protruding from the upper surface of the fixing foundation. In this construction method, for example, the upper tip of the tension material fixed at the lowermost end of the bottom slab is fixed by the ram tip of the center hole jack set on the base plate of the fixed foundation, and the tension is upward. After introducing a predetermined tension force, it is a construction method of fixing by a tension fixing device provided on the base plate side of the center hole jack, such as (sleeve with screw + ring nut) or (wedge anchor head).

In one embodiment of the foundation structure, the gap between the inner wall surface of the underground hole and the outer wall surface of the side wall portion is filled with a padding material made of earth and sand or soil cement. The foundation structure is installed in the soil in order to obtain stability as a foundation structure. Therefore, in general, prior to the installation of the foundation structure, the ground excavation is carried out while applying the earth retaining support. For this reason, a gap remains between the foundation structure and the excavated ground, so the excavated earth and sand or soil cement mixed with water and cement is backfilled in the excavated earth and sand to counter the ground from the surrounding ground. Efficiently transfers force to the concrete foundation structure.

In another embodiment of the foundation structure, a bottom leveling material composed of soil cement or waste concrete is placed at the bottom of the underground hole, and the bottom slab is formed on the bottom leveling material. Flat plate precast concrete is installed. In the precast prestressed concrete foundation structure, it is desirable that the supporting ground evenly receives the pressure against the pushing axial force acting on the foundation structure. Therefore, before installing the flat plate-shaped precast concrete of the first bottom slab, a bottom leveling material such as soil cement or waste concrete is placed to apply the pressing pressure from the flat plate-shaped precast concrete of the bottom slab. Evenly transmit to the supporting ground. This makes it possible to avoid local pressing pressure on the supporting ground.

In a preferred embodiment, the side wall portion is configured by stacking a plurality of wall-shaped (frame-shaped) precast concretes in the vertical direction, and the joint portions (joints) of the plurality of wall-shaped precast concretes are dry. It is joined by the joint method, and the above-mentioned joint is manufactured by the matchcast method. The wall-shaped precast concrete joints assembled in the section of the side wall are manufactured so that the joint surfaces of the precast concrete meet with each other by surface touch. In other words, the joint surface of one completed old precast member is used as a formwork, and the joint surface of the other new precast member is manufactured by concrete casting so that the joint surface of the new precast member can be manufactured by surface touch. Mutual precast members are manufactured by the matchcast method. These precast members are joined by a dry joint method. When joining by the dry joint method, an epoxy resin may be applied to one of the joint surfaces in order to bring the joint surfaces into close contact with each other. However, unprocessed methods can also be applied. Further, for the shear transmission on the joint surface, the frictional force due to the tension pressure may be sufficient in design, but if necessary, a shear key may be provided to perform more reliable shear transmission.

In another embodiment, at least one of the bottom plate portion and the top plate portion is configured by stacking a plurality of flat plate-shaped precast concrete in the vertical direction, and the joint portion of the plurality of flat plate-shaped precast concrete. They are joined together by the wet joint method. The joint between the flat plate-shaped precast concrete and the concrete that is assembled in the section between the bottom slab and the top slab has a large area of the joint surface, and the joint between the flat plate-shaped precast member and the wall-shaped precast member. In some cases, the areas of the joint surfaces do not match. Therefore, it may be difficult to apply the match cast method, so the wet joint method will be adopted. In the wet joint method, an appropriate gap is provided between the precast members, a sealing material is installed around the gap, and the gap is filled with a time-curing material such as non-shrink mortar. It is a method of introducing prestress and joining. Since the bottom slab and the top slab are joined in the vertical direction, instead of the non-shrink mortar, a method of laying a hardened cement mortar and installing the precast member in the correct position is also adopted. can. If necessary, a shear key may be provided so that shear transmission between joints can be effectively performed.

In a preferred embodiment, a flat plate-shaped precast concrete having an opening is provided in the middle of the space surrounded by the side wall portion. In this precast prestressed concrete foundation structure, if the diameter of the foundation structure is small and the depth is large, the lateral rigidity may decrease. In such a case, it is possible to improve the lateral rigidity by providing a flat plate-shaped precast concrete member having an opening in the middle of the side wall portion. In that case, it is appropriate to adopt the wet joint method for the wall-shaped precast member to be joined above and below the flat plate-shaped precast member.

Other effects 1
The conventional concrete foundation structure is a reinforced concrete structure, and a large amount of ready-mixed concrete is cast on site for construction. Under the construction location conditions in mountainous areas and mountainous areas, placing a large amount of ready-mixed concrete has various construction management problems. To briefly describe the issue. (I) It is necessary to adopt a special transportation method, and the cost of transporting ready-mixed concrete is enormous. (Ii) There are many delivery cycles for transportation, and accidents that go out of order are likely to occur in the middle, which involves a great risk in terms of quality control and construction costs. (Iii) There is a high risk of cold joints occurring, and foundation structures with cold joints include risks that cannot be covered by maintenance, such as corrosion of reinforcing bars and reduced yield strength in the future. (Iv) In many cases, the shape and dimensions of the foundation structure are shapes that require measures against mascon, and it is necessary to adopt concrete materials compatible with mascon, cure after casting, and take measures to prevent cracks.

As shown above, the precast prestressed concrete foundation structure of the present invention provides solutions to all the problems related to the use of a large amount of concrete material in the conventional concrete foundation structure. do. Specifically, the results of comparing the estimated costs of the transportation costs of the conventional reinforced concrete foundation structure and the precast / prestressed concrete foundation structure according to the present invention are shown. The target foundation structure is a deep foundation with a circular cross section, and in the comparison result when concrete and reinforcement (reinforcing bar / tension material), which are the main construction materials, are transported by helicopter, the main materials of the conventional reinforced concrete foundation structure The result was that the main material weight of the precast prestressed concrete foundation structure of the present invention was 88 tons (23% of the conventional one) while the weight was 377 tons. Since the transportation cost by helicopter accounts for a large proportion of the total construction cost, the precast prestressed concrete foundation structure and its construction method according to the present invention have a total construction cost of about 30 as compared with the conventional construction cost. A reduction of about% can be expected.

The transported object required in the present invention is a precast member, and unlike ready-mixed concrete, there is no risk of transportation delay. Of course, there is no need to take measures against cold joints and mascons. Since the precast members are basically manufactured in the precast factory, the quality of the finished structure is guaranteed because the ones with sufficient quality control are locally joined. As a result, long-term maintenance costs can be expected to be reduced.

Other effects 2
The conventional concrete foundation structure is a reinforced concrete structure, and it is necessary to assemble the reinforcing bars at the construction site. Although it depends on the structural type of the foundation, in many cases, the space for assembling the reinforcing bars is narrow, and the assembly is performed deep from the ground surface. In addition, it may be difficult to secure a sufficient lifting machine, and there are problems in the labor and construction time for assembling the reinforcing bars. On the other hand, in the construction of the present invention, there is no work corresponding to the assembly of the reinforcing bar, and as a similar work, the tension material is built, and the construction labor and the construction time are incomparably easy. On the other hand, there is work of installing and joining precast members. This work is basically to install the precast member in a predetermined place with a lifting machine and to control the installation accuracy, and it is obvious that the construction time is shortened as compared with the conventional cast-in-place construction.

It is a partially enlarged view of the cross-sectional structure and the components of the side view of the deep foundation. It is a perspective view of the flat plate-shaped PCa concrete which constitutes the bottom plate part and the top plate part. It is a perspective view of the wall-shaped PCa concrete which constitutes a side wall part. (A) shows a cross-sectional view of the flat plate-shaped PCa concrete at the lowermost end of the bottom slab, (B) shows a front view of the twisted type fixing tool, and (C) shows a front view of the grip type fixing tool. (A) is a cross-sectional view of the flat plate-shaped PCa concrete at the uppermost end of the upper plate portion and the fixed foundation above it, and (B) is a front view of the tension fixing device when the tension material is a continuous fiber reinforcing material (C). ) Shows a front view of the tension fixing device when the tension material is a PC steel strand. (A) shows the construction method of the wet joint, and (B) shows the structure. (A) shows the construction method of the dry joint, and (B) shows the structure. (A) shows a perspective view of the wall-shaped PCa concrete of the second embodiment, and (B) shows a perspective view of the flat plate-shaped PCa concrete of the second embodiment.

The precast prestressed concrete foundation structure of Example 1 is a standard foundation structure called a deep foundation foundation, and an example in which the cross-sectional shape of the outer shape is circular is taken up. FIG. 1 is a partially enlarged view of a cross-sectional structure and components of a side view of a deep foundation foundation. The structural element member of the precast prestressed concrete foundation structure of the present invention is composed of four elements. It is a bottom plate portion 100, a side wall portion 200, an upper plate portion 300, and a fixed foundation 400. The bottom plate portion 100 and the top plate portion 300 are composed of flat plate-shaped PCa (precast) concrete 51, the side wall portion 200 is composed of wall-shaped (frame-shaped) PCa concrete 23, and the fixed foundation 400 is composed of pedestal 11, base plate 12 and It is composed of a reinforcing material 13 such as a shear plate.

The flat plate-shaped PCa concrete 51 constituting the bottom plate portion 100 and the top plate portion 300 has a shape as shown in FIG. As shown in FIG. 2, a through hole 53 is provided in which a tensioning material 1 for tensioning each PCa concrete member 51 in the vertical direction is inserted. The formation of the through hole 53 is possible by installing a sheath tube (not shown). Since out-of-plane shearing force and cross-sectional force of bending moment act on the flat plate PCa concrete 51, tensioning material or tensile reinforcing bar (not shown) was buried in one or two directions (horizontal) to tension it. Prestressed concrete plate or RC concrete plate. If the cross-sectional force acting on this flat plate is small, it may be manufactured as an RC concrete plate by arranging ordinary reinforcing bars without introducing a tension force. However, in the present invention, weight reduction and high durability in consideration of the special transport efficiency of the PCa concrete member are the points, so that the prestressed concrete plate is considered to be more advantageous. There are no restrictions on the method of introducing prestress for PCa concrete plates, whether it is the preten method or the postten method.

The wall-shaped PCa concrete 23 constituting the side wall portion 200 has a shape as shown in FIG. The planar shape of the wall-shaped PCa concrete 23 shown in FIG. 3 has a circular outer shape, but may be any shape such as a rectangular shape. Further, as shown in FIG. 3, a through hole 25 is arranged and used when the tension material 1 is inserted. Spiral hoop bars (not shown) may be arranged horizontally on the wall-shaped PCa concrete 23 as reinforcing bars.

Of the plurality of vertically stacked flat plate-shaped PCa concrete 51s having three stages in the example shown in FIG. 1, the lowermost flat plate-shaped PCa concrete 51 constituting the bottom plate portion 100 is shown in FIG. 4 (A). As described above, the plate thickness is partially increased in order to provide the fixed fixing device 30, and the lower end portion of the through hole 53 in that portion is closed. The fixed fixing device 30 on the extension line of the lower end of the tension material 1 is inserted to this closed position, and the section where the fixed fixing device 30 is required is filled with a time-curing agent such as cement grout, cured, and develops strength. Let me. As the fixed fixing device 30, as shown in FIG. 4B, when the material of the tension material 1 is the continuous fiber reinforcing material 1A, the untwisted type fixing tool 32 is used. Further, as shown in FIG. 4C, when the material of the tension material 1 is the PC steel strand 1B, the grip type fixing tool 33 is used. All of these fixed fixing devices can be fixed to the surrounding concrete by the mechanism of the bearing pressure resistance of the enlarged diameter portion and the surrounding adhesion resistance with respect to the pulling force.

Of the plurality of vertically stacked flat plate-shaped PCa concrete 51s in the example shown in FIG. 1, which constitute the upper plate portion 300, the pedestal 11 is placed on the uppermost flat plate-shaped PCa concrete 51. The fixed foundation 400 composed of the base plate 12, the shear reinforcing plate 13, and the like is positioned at a predetermined position, and the tensioning material 1 for tensioning over the entire length is inserted from above to below. After fixing the fixed fixing device 30, the tension material 1 is tensioned by the planned tension force, and as shown in FIG. 5A, the tension fixing device 40 is used to fix the tension material 1. As shown in FIG. 5B, when the material of the tension material 1 is the continuous fiber reinforcing material 1A, the tension fixing device 40 including the threaded sleeve 41 and the ring nut 42 is outward through the through hole 12A of the base plate 12. It is fixed to the continuous fiber reinforcing material 1A that comes out. As shown in FIG. 5C, when the tension material 1 is the PC steel strand 1B, the tension fixing device 40 by the wedge anchor head 43 or the like is exposed to the outside through the through hole 12A of the base plate 12 PC steel strand 1B. Fixed to. If there is a concern that a gap will be created between the upper surface of the flat plate-shaped PCa concrete 51 at the uppermost end and the lower surface of the base plate 12, epoxy resin is applied to the upper surface of the flat plate-shaped PCa concrete 51 at the uppermost end. By applying it, it is possible to avoid gaps. In the tension work, the tension work can be performed without bias by controlling the pair of tension devices facing each other at the same time.

The wet joint method is basically good for joining the flat plate-shaped PCa concrete 51 constituting the bottom plate portion 100 and the top plate portion 300 to each other. The structure and construction method of the wet joint 64 are shown in FIGS. 6A and 6B. A ring seal 54A for connecting through holes and a formwork seal 54B for sealing the joint filler (non-shrink mortar) are attached to the upper surface of the lower flat plate-shaped PCa concrete 51 to be joined. As the material of the sealing materials 54A and 54B, closed cell polyurethane foam or the like is suitable. The next flat plate PCa concrete 51 is installed from above, the level is adjusted, and the space surrounded by the seal is filled with the non-shrink mortar 56 from the outside. A groove-shaped shear key 55 can be provided for the purpose of increasing the horizontal shear resistance between the flat plate-shaped PCa concrete 51. In addition, after installing the ring seal 54A, instead of the fluid non-shrink mortar, there is also a construction method in which a hardened cement mortar is spread in advance and the next flat plate PCa concrete 51 is installed on it. .. In order to enable horizontal shear transmission at the joint surface of the flat plate precast concrete 51, as shown in FIG. 6B, a groove-shaped shear key 55 is applied to the joint surface of the flat plate precast concrete 51. Can also be provided.

The dry joint method is basically preferable for joining the wall-shaped precast concrete 23 constituting the side wall portion 200 to each other. The structure and construction method of the dry joint 61 are shown in FIGS. 7A and 7B. Since the joint surface of the wall-shaped precast concrete 23 is basically manufactured by the matchcast method, what is the upper surface of the lower wall-shaped precast concrete 23 and the lower surface of the upper wall-shaped precast concrete 23? , Overlap without gaps. The simplest dry joint method is to join the upper and lower wall-shaped precast concrete 23 into the gaps between them without any treatment. In this method, the joining time can be shortened, and after tensioning, a predetermined tension stress can be introduced into all the members of the wall-shaped precast concrete 23. However, as a point to note in this case, it is important to manage the construction so that there are no foreign substances on the joint surface. On the other hand, there is a method of applying the epoxy resin 26 to the upper surface of the lower wall-shaped precast concrete 23. The purpose of applying the epoxy resin 26 is to evenly adhere the joint surfaces. It is not applied in anticipation of the adhesive strength of the epoxy resin 26. In order to enable horizontal shear transmission at the joint surface of the wall-shaped precast concrete 23, a groove-shaped shear key 27 is applied to the joint surface of the wall-shaped precast concrete 23 during production by the matchcast method. Can also be provided.

The basic construction procedure of the first embodiment will be described with reference to FIG. (I) After surveying the ground contact point of the foundation, the earth retaining support 21 is alternately installed and excavated by a mini excavator, and excavation is performed to a predetermined ground height to form an underground hole. A lightweight steel liner plate or the like can be used as the earth retaining support 21. It is desirable that the diameter of the excavated wall surface be larger than the outer diameter of the foundation structure to secure a work space. (Ii) In order to obtain familiarity between the bottom surface of the foundation structure and the ground, a bottom leveling material 28 is placed, the bottom plate portion 100 is joined, and the side wall portion 200 is joined, and the final wall shape of the side wall portion 200 is formed. Precast concrete 23 is installed. (Iii) Next, prior to the step of charging the filling material 70, a temporary tension force is introduced into the section from the bottom plate portion 100 to the side wall portion 200. This is a countermeasure because it is expected that the joint portion of the temporary joint will shift due to the unbalanced earth pressure generated by the input earth and sand (or soil cement) during the filling work. A fixed fixing device is provided at the tip of the through hole for temporary tension, which is provided between the main tension through holes at the same outer diameter as the through hole for the main tension to be finally introduced, in the same manner as the main tension. Insert the tension material 1 from above. (Iv) Grout mortar is filled and cured in the fixed fixing device 30 of the bottom plate portion 100. After the strength is developed, tension is formed on the upper surface of the wall-shaped precast concrete 23. After tensioning, the grout mortar is filled in the gap between the through hole and the tensioning material 1 in a state where the tensioning is fixed by the tension fixing device 40 and the fixing state is maintained, and the grout mortar is waited for curing and strength development. (V) When the strength development of the grout mortar is completed, the foundation structure is completed in the middle of construction except for the upper plate portion 300. Excavated earth and sand are basically used as the material to put the filling material 70. The purpose of excavated earth and sand contributes to the effective use of residual soil treatment and the stability of the foundation structure as its own weight when the foundation is completed. When water and cement are mixed with excavated earth and sand and used as soil cement, it is also conceivable to use soil cement as a shear rigidity and shear resistance structural material as a foundation structure. (Vi) After filling the filling material 70 up to the upper surface of the side wall portion 200, a wall-shaped precast concrete having a box punch to avoid the tension fixing device after temporary tension is prepared. When the wall-shaped precast concrete having a box punch is not used, a method of cutting the tension fixing device to flatten the surface can also be applied. Alternatively, by attaching a threaded coupler to the inside of the threaded sleeve 41 of the tension fixing device 40 (not shown), the tensioning material 40 for stretching can be connected and re-tensioned as the final tensioning material. (Vii) Joining of the lower surface of the flat plate-shaped precast concrete 51 to the upper surface of the wall-shaped precast concrete is performed by the wet joint method. (Viii) Wet joint the remaining flat plate precast concrete 51 with each other. (Ix) After setting the final flat plate-shaped precast concrete 51, epoxy resin is applied to the upper surface, a fixed foundation is installed, and positioning is performed. (X) Insert the tension material 1 for this tension from the upper part, fill the through hole of the fixed fixing device 30 at the lower end with grout mortar, cure, and develop the strength, and then arrange the tension jack diagonally. Get nervous. After introducing a predetermined tension force into all the tension materials 1, the tension fixing device 40 fixes the tension material 1. (Xi) While removing the earth retaining support 21 around the foundation structure, excavated soil or soil cement mixed with water and cement in the excavated soil is used as a padding material between the excavated ground and the side wall of the foundation structure. Put in as 22. The precast prestressed concrete foundation structure of the present invention is completed by the above construction steps.

In Example 1, a series of explanations were given using a wall-shaped member having a circular outer diameter and a wall-shaped precast concrete of the side wall portion 200 only on the outside as an example. In the second embodiment, the outer shape has a rectangular cross section, and the wall-shaped precast concrete constituting the side wall portion 200 constitutes not only the outer side but also the inner wall-shaped precast concrete. FIG. 8B shows a flat plate-shaped precast concrete 81 having a plurality of through holes 82 constituting the bottom plate portion 100 and the upper plate portion 300 of the second embodiment, and FIG. 8A shows an inner wall constituting the side wall portion 200. FIG. 6 shows a wall-shaped precast concrete 91 having a plurality of through holes 95 also having a plurality of through holes 95.

In the case of FIG. 8A, the wall-shaped precast concrete 91 having a rectangular cross section is composed of four blocks per layer. Lateral joining of individual PCa concrete blocks 91 with tensioning materials, tensile reinforcements, etc. basically does not have to be performed. However, regarding the gap between the blocks 91, the gap is filled with non-shrink mortar 93 in consideration of the influence of the out-of-plane earth pressure and in order to avoid out-of-plane deformation during shear transfer. For construction, the same sealing material 94 used for the wet joint is attached to the outside, and the inside is filled with non-shrink mortar 93. Basically, it is considered that the function as a foundation structure is fully exhibited by joining with a tension material in the vertical direction.

When the inner wall is provided inside, not only the shear rigidity but also the shear strength can be significantly improved as compared with the outer wall alone with respect to the shear force acting on the foundation structure. Moreover, since prestress stress is introduced into the inner shear wall in the vertical direction, further improvement in shear strength can be expected.

Also, with relatively long proportions in the vertical and horizontal directions, when a bending moment is applied to the foundation structure of only the outer wall, the outer wall and the inner wall may be deformed separately out of the plane. .. Therefore, when calculating the resistance bending moment in design, it is considered that the resistance bending moment is lower than the resistance bending moment calculated by using the entire foundation structure as a beam. When the inner wall is provided, a structural function equivalent to that of a web that functions as a girder works, so that a shear force can be transmitted to the inner and outer walls, and plane holding during bending deformation is established. Therefore, when the width of the foundation structure according to the present invention becomes large, it is possible to design an economical cross section by considering the foundation structure provided with the inner wall.

In the cross-sectional view of FIG. 1, only the wall-shaped precast concrete 23 constituting the side wall portion 200 is joined. In the third embodiment, a flat plate-shaped precast concrete is vertically inserted in the middle of the wall-shaped precast concrete 23 by a wet joint method (not shown). The shape of the flat plate-shaped precast concrete sandwiched in the middle should be such that the central part is open. The role of the flat plate precast concrete in the central opening of Example 3 is to improve the lateral rigidity of the precast prestressed concrete foundation structure and to restrain the out-of-plane deformation of the outer wall-shaped precast concrete. Has a role to play. Therefore, it is more effective when the foundation shape is deep.

1 Tension material 1A Continuous fiber reinforcement 1B PC steel strand
11 pedestal
12 Base plate
13 Shear reinforcement plate
22 Stuffing material
23, 91 Wall-shaped PCa concrete
12A, 25, 53 through hole
27, 55 shear key
30 Fixed fixing device
32 Untwisted type fixing tool
33 Grip type fixing tool
40 Tension fixing device
51, 81 Flat plate PCa concrete
70 Filling material
100 bottom plate
200 side wall
300 Top Edition
400 fixed foundation

Claims (12)

A bottom slab composed of one or more flat plates of precast concrete installed at the bottom of an underground hole formed by ground excavation.
A side wall portion made of one or more wall-shaped precast concrete, which is installed on the bottom slab and along the inner wall surface of the underground hole.
Filling material made of earth and sand or soil cement that fills the space surrounded by the bottom slab and the side wall.
A slab made of one or more flat plates of precast concrete installed on the side wall and the filling material, and a fixed foundation installed on the slab.
A plurality of through holes are formed in each of the bottom plate portion, the side wall portion, the top plate portion, and the fixed foundation, and each of the plurality of through holes is continuous from the bottom plate portion to the fixed foundation.
It is characterized in that it is configured so that tension is fixed from the lower end of the bottom slab to the fixed foundation by a tension material that penetrates the through hole.
Precast prestressed concrete foundation structure. It is characterized in that tensioning materials or tensile reinforcing bars for introducing tension force are provided in one or two horizontal directions in the flat plate-shaped precast concrete constituting the bottom slab and the top slab.
The precast prestressed concrete foundation structure according to claim 1. It is characterized in that reinforcing bars are arranged as hoop bars in the horizontal direction on the wall-shaped precast concrete constituting the side wall portion.
The precast prestressed concrete foundation structure according to claim 1. The gap between the inner wall surface of the underground hole and the outer wall surface of the side wall portion is filled with a padding material made of earth and sand or soil cement.
The precast prestressed concrete foundation structure according to any one of claims 1 to 3. A bottom leveling material composed of soil cement or waste concrete is placed at the bottom of the underground hole, and a flat plate-shaped precast concrete constituting the bottom slab is installed on the bottom leveling material. The precast prestressed concrete foundation structure according to any one of claims 1 to 4, wherein the precast concrete foundation structure is characterized by the above. The side wall is composed of multiple wall-shaped precast concrete stacked in the vertical direction.
It is characterized in that a plurality of wall-shaped precast concrete joints are joined by a dry joint method, and the above joints are manufactured by a matchcast method.
The precast prestressed concrete foundation structure according to any one of claims 1 to 5. At least one of the bottom slab and the top slab is composed of a plurality of flat plates of precast concrete stacked in the vertical direction.
It is characterized in that a plurality of flat plate-shaped precast concrete joints are joined by a wet joint method.
The precast prestressed concrete foundation structure according to any one of claims 1 to 6. Shear keys are formed at the joints of the precast concrete.
The precast prestressed concrete foundation structure according to claim 6 or 7. A flat plate-shaped precast concrete having an opening is provided in the middle of the space surrounded by the side wall portion.
The precast prestressed concrete foundation structure according to any one of claims 1 to 8. At the bottom of the underground hole formed by excavation of the ground, a bottom slab composed of one or more flat plate-shaped precast concrete is installed.
Install one or more wall-shaped precast concrete on the bottom slab and along the inner wall surface of the underground hole.
The inside of the space surrounded by the bottom slab and the side wall is filled with a filling material made of earth and sand or soil cement.
An upper plate portion composed of one or more flat plate-shaped precast concrete is installed on the side wall portion and the filling material.
A fixed foundation is installed on the above plate,
A tension material is passed through a plurality of through holes formed in each of the bottom plate portion, the side wall portion, the upper plate portion, and the fixed foundation, which continuously penetrate from the bottom plate portion to the fixed foundation.
After fixing the lower end of the tension material in the precast concrete near the lower end of the bottom slab, the tension material is tensioned upward on the fixing foundation to fix and fix it.
Construction method for precast and prestressed concrete foundation structures. A fixed fixing device is provided at the lower end of the tension material.
The fixed fixing device at the lower end of the tension material is inserted into the lower end of the through hole formed in the flat plate-shaped precast concrete constituting the bottom slab.
The through hole is filled with a time-curing material, and the time-curing material is cured.
It is characterized in that after the time-curing material develops strength, the upper end portion of the tension material inserted into the through hole is tensioned from the bottom slab portion to the fixed foundation.
The method for constructing a precast prestressed concrete foundation structure according to claim 10. It is characterized in that the upper end portion of the tension material protruding from the upper surface of the fixed foundation is fixed by the tension fixing device.
The method for constructing a precast prestressed concrete foundation structure according to claim 11.

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