JP3689217B2 - Heaving force blocking method for foundation frame - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a method for blocking a heaving force on a foundation frame in an underground structure supported by a pile so as to cut off an adverse effect on the foundation frame due to heaving of an excavation bottom.
[0002]
[Prior art]
When the ground is excavated during the construction of an underground structure, a phenomenon that the excavation bottom expands as the effective stress in the ground decreases, so-called heaving (rebound) occurs. Depending on the ground, such as clay layers, this phenomenon may occur gradually, that is, after the construction of the underground structure or the completion of the building.
[0003]
As shown in FIG. 12, in the case of the building B provided with the underground structure A supported by the pile 2, since a large force is applied to the lower surface of the foundation frame 6 by heaving, the foundation frame 6 must be designed to be rigid. As shown in phantom lines in FIG. 12, there is a possibility that the center part of the span of the foundation chassis 6 is pushed upward and is destroyed, and the cross section of the foundation chassis 6 must be enlarged.
[0004]
Therefore, as a heaving force blocking method for reducing the transmission of the force due to the heaving of the excavation bottom to the base frame, the crash board C is laid on the excavation bottom as shown by the solid line in FIG. For example, a method has been developed in which the concrete of the foundation frame 6 is placed and a certain heaving force is applied so that the crash board C is broken and no further force is transmitted. In the figure, a is a thick clay layer, and b is a support layer (for example, a gravel layer) of the pile 2.
[0005]
As the crash board C, for example, as shown in FIG. 13, a laminate of a polypropylene sheet 12a and a polystyrene base 12b having a honeycomb structure is used.
[0006]
However, in the above construction method, the force until the crash board C is broken is transmitted to the base casing 6, so that the base casing 6 needs to be strong enough to withstand it. For example, in the case of a crash board C destroyed at 3 ton / m ² , if the concrete board 6 placed on the upper part of the crash board C is used as a support member and the concrete weight is 2 ton / m ² , the crash board Since a downward force (concrete weight) of 2 tons / m ^{2 has} already been applied to C at the time of construction, only 1 ton / m ² of heaving force is applied after construction. A total of 3 tons / m ² of force is applied, and the crash board C is destroyed, but the foundation housing 6 is applied with a force of 3 tons / m ² .
[0007]
[Problems to be solved by the invention]
The present invention has been made in consideration of the above points. The object of the present invention is to construct a foundation frame by supporting a driving formwork or a precast member with a spacer, and the foundation frame is supported by a pile. After reaching the state, before the excavation bottom heaving occurs, the supporting force of the spacer is lost, and a gap is formed between the base enclosure and the excavation bottom, and the heaving force is transmitted to the foundation enclosure. An object of the present invention is to provide a method for blocking a heaving force to a foundation frame that can effectively block this.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the technical means taken by the present invention are as follows. That is, the heaving force blocking method for the foundation frame according to the first invention is based on the first state that can support the load at the time of foundation foundation construction after excavating the ground in constructing the underground structure supported by the pile. Spacers that can change to the second state where there is no load bearing force due to melting, sublimation, shrinkage, etc., are installed at appropriate intervals on the bottom of the excavation, and the required number of driven formwork is piled over these spacers. Is placed in a state where the head is exposed on the upper surface of the placement formwork, and the concrete of the foundation frame is placed on the placement formwork, and after the strength of the concrete is developed, before the occurrence of the heaving of the excavation bottom, a spacer is placed. By changing to the second state, a gap is formed between the foundation frame and the excavation bottom.
[0009]
In addition to the so-called abandoned molds that are not included in the strength of the foundation frame, as the placement molds, a formwork that is structurally integrated with the cast-in-place concrete, for example, a solid truss-like rebar on the top It may be a half precast plate or a steel formwork projecting.
[0010]
According to the above configuration, a plurality of spacers are installed at appropriate intervals on the bottom of the excavation, and driving molds are installed on the spacers. Therefore, the required number of driving molds set to dimensions that can be carried in the field, The pile can be laid to a predetermined height from the bottom of the excavation, and it is not necessary to stand the pile with a small span in order to support the driving formwork, so the number of piles does not increase. In addition, a plurality of spacers are installed at appropriate intervals on the bottom of the excavation, and driven formwork is erected on this, so there are fewer spacers to be buried than when laying spacers on the entire surface of the excavation bottom. It is economical.
[0011]
Then, after the strength is developed in the concrete placed on the casting formwork, in other words, after the foundation frame is in a pile-supported state, before the excavation bottom heaving occurs, the spacer is dissolved in advance. By changing to the second state by sublimation, contraction, etc., a gap is formed between the foundation chassis and the excavation bottom, so that when the excavation bottom heaves, the bottom surface of the foundation enclosure is pushed up by the raised excavation bottom No heaving force is applied to the foundation frame. Therefore, it is possible to reduce the cross section and the bar arrangement of the foundation frame.
[0012]
In the construction of an underground structure supported by piles, the method of blocking the heaving force on the foundation frame according to the second invention is the method of dissolving from the first state that can support the load at the time of foundation foundation construction after excavating the ground. Spacers that can change to the second state where there is no load bearing force due to sublimation, shrinkage, etc. are installed at appropriate intervals on the bottom of the excavation, and precast members for building the foundation frame are installed over these spacers. After connecting the precast members to each other and connecting the head of the pile to construct the foundation frame, before the excavation bottom heaving, change the spacer to the second state, between the foundation frame and the excavation bottom It is characterized by forming a gap.
[0013]
According to the above configuration, a plurality of spacers are installed at appropriate intervals on the excavation bottom, and the precast members for constructing the foundation frame are erected on this, so the necessary number of precast members set to dimensions that can be carried in the field are provided. In addition, the pile can be laid at a predetermined height from the excavation bottom, and it is not necessary to stand the pile with a small span in order to support the precast member. In addition, a plurality of spacers are installed at appropriate intervals on the bottom of the excavation, and precast members are erected on this, so there are fewer spacers to be buried than when spacers are laid on the entire surface of the excavation bottom. Is economical.
[0014]
And after connecting a precast member mutually and connecting with the head of a pile and constructing a foundation frame, in other words, after a precast foundation frame will be in a state of pile support, heaving of an excavation bottom will occur. Before, the spacer is changed to the second state by dissolution, sublimation, contraction, etc., and a gap is formed between the foundation frame and the excavation bottom, so that the heaving occurs when the excavation bottom heaving occurs The bottom surface of the foundation frame is not pushed up at the bottom of the excavation, and no heaving force acts on the foundation frame. Therefore, it is possible to reduce the cross section and the bar arrangement of the foundation frame.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
First, as shown in FIG. 1 (a), a pile (either a ready-made pile or a cast-in-place pile) whose tip reaches the support layer on the ground surrounded by the mountain retaining wall 1 such as a sheet pile, a column of columns, and an underground continuous wall. 2) and excavating deeper than the lower end of the foundation frame to be constructed. The depth from the lower end of the foundation frame to the excavation bottom 3 is set to a depth corresponding to the predicted amount of heaving.
[0016]
Next, as shown in FIG. 1 (b), on the excavation bottom 3, the first state where the load at the time of building the foundation frame can be supported is changed to the second state where there is no load supporting force. A plurality of possible spacers 4 are installed at appropriate intervals.
[0017]
Thereafter, as shown in FIG. 2 (a), the necessary number of placement molds 5 are placed over the adjacent spacers 4 so that the opening or notch formed in the placement mold 5 faces the head of the pile 2. The pile 2 is placed in a state where the head of the pile 2 is exposed on the upper surface of the driving form 5.
[0018]
In this state, as shown in FIG. 2 (b), after placing the foundation frame 6 (not shown) on the driving form 5, the concrete 7 of the foundation frame 6 is placed on the head of the pile 2. An underground structure A is constructed by placing anchors (not shown) provided on the part or head so as to be buried in the concrete 7.
[0019]
And after predetermined strength expresses to concrete 7, in other words, after foundation foundation 6 will be in a pile support state, before heaving of excavation bottom 3 occurs, as shown in FIG. By changing the spacer to the second state, a gap S is formed between the foundation frame 6 and the excavation bottom 3.
[0020]
According to the above construction method, even if heaving of the excavation bottom 3 occurs in the state shown in FIG. 3, the gap S is formed between the foundation frame 6 and the excavation bottom 3, so that the raised excavation bottom 3 Thus, the bottom surface of the foundation housing 6 is not pushed up, and no heaving force acts on the foundation housing 6. Therefore, it is possible to reduce the cross section and the reinforcing bar arrangement of the foundation frame 6.
[0021]
As the spacer 4, for example, a granular material such as pebbles or sand and a water-soluble adhesive are mixed and pressed into a block shape so that the supporting power is gradually lost due to groundwater, and the supporting power is gradually lost due to corrosion. Those that gradually lose their supporting ability due to sublimation are appropriately selected and used. And in any case, the spacer 4 is at least a period required for the strength development of the concrete 7 (usually 1 to 2 weeks, but when using early-strength cement, it is naturally a shorter period. .) Is set such that the supporting force is maintained and the supporting force is lost by the time when the heaving of the excavation bottom 3 occurs (usually, one to two months after excavation).
[0022]
4 and 5 show another embodiment of the first invention. This embodiment is characterized in that an ice making unit is used as the spacer 4, and the construction procedure is as follows.
[0023]
First, as shown in FIG. 4 (a), a pile (either a ready-made pile or a cast-in-place pile) whose tip reaches the support layer on the ground surrounded by the mountain retaining wall 1 such as a sheet pile, a column of columns, and an underground continuous wall. 2) and excavating deeper than the lower end of the foundation frame to be constructed. The depth from the lower end of the foundation frame to the excavation bottom 3 is set to a depth corresponding to the predicted amount of heaving.
[0024]
Next, as shown in FIG. 4 (b), the spacer 4 that is capable of changing from the first state capable of supporting the load at the time of constructing the foundation chassis to the second state without any load supporting force is waterproof. Using an ice making unit 8 composed of a box-like container 8a formed of paper, a synthetic resin plate or the like and having substantially no supporting force, water 8b accommodated therein, and a freezing pipe 8c, The ice making units 8 in the second state are installed on the excavation bottom 3 at appropriate intervals, and the piping 8c of each ice making unit 8 is installed on the refrigerator main body (not shown) installed on the ground or the excavation bottom via a stand or the like. Connecting.
[0025]
Thereafter, by operating the refrigerator main body and freezing the water 8b, the ice making unit (spacer 4) 8 is changed to the first state, and in this state, as shown in FIG. The necessary number of placing molds 5 over the ice making units 8 are made to face the heads of the piles 2 with the openings or notches formed in the placing molds 5, so that the heads of the piles 2 are the top surfaces of the placing molds 5. Placed in an exposed state.
[0026]
In this state, as shown in FIG. 5 (b), after placing the foundation frame 6 (not shown) on the driving form 5, the concrete 7 of the foundation frame 6 is placed on the head of the pile 2. An underground structure A is constructed by placing anchors (not shown) provided on the part or head so as to be buried in the concrete 7.
[0027]
And after predetermined intensity | strength expresses to the concrete 7, in other words, after the foundation frame 6 will be in a pile support state, before the excavation bottom 3 heaving occurs, the operation of the refrigerator body is stopped. Then, the ice 8b ′ of the ice making unit 8 is thawed, and the ice making unit 8 is returned to the second state as shown in FIG. In this state, since the supporting force by the ice making unit 8 is substantially zero, a gap S in which the spacer 4 does not substantially exist is formed between the foundation frame 6 and the excavation bottom 3. Although the container 8a and the pipe 8c of the ice making unit 8 are buried, the main body of the refrigerator is removed, and the opening of the foundation housing 6 resulting from the removal is closed with concrete as a useless work.
[0028]
According to the above construction method, even if heaving of the excavation bottom 3 occurs in the state shown in FIG. 5 (b), the gap S is formed between the foundation frame 6 and the excavation bottom 3, so that it has risen. The bottom surface of the foundation chassis 6 is not pushed up by the excavation bottom 3, and no heaving force acts on the foundation chassis 6. Therefore, it is possible to reduce the cross section and the reinforcing bar arrangement of the basic frame 6.
[0029]
6 to 8 show other embodiments of the first invention. This embodiment is characterized in that a heat-shrinkable synthetic resin block is used as the spacer 4, and the construction procedure is as follows.
[0030]
First, as shown in FIG. 6 (a), a pile (either a ready-made pile or a cast-in-place pile) whose tip reaches the support layer on the ground surrounded by the mountain retaining wall 1 such as a sheet pile, a column of columns, and an underground continuous wall. 2) and excavating deeper than the lower end of the foundation frame to be constructed. The depth from the lower end of the foundation frame to the excavation bottom 3 is set to a depth corresponding to the predicted amount of heaving. Further, in the predetermined position of the excavation bottom 3 (position where the heat-shrinkable synthetic resin block is installed), the concave portions 3a are excavated and formed at appropriate intervals.
[0031]
Next, as shown in FIG. 6 (b), from the first state that can support the load at the time of constructing the basic chassis, the heat-shrinkable synthetic resin block 10 in which the heater 9 is incorporated is used, and the synthesis is performed. The resin block 10 is installed on the bottom of the excavation 3 so that the lower part of the synthetic resin block 10 is fitted in the recess 3a, and electrical wiring (not shown) to each heater 9 is performed. The synthetic resin block 10 is partially installed in the recessed portion 3a of the excavation bottom 3 in the second state where the synthetic resin block 10 is contracted by heating. Or a gap with a necessary vertical width is secured between the synthetic resin block 10 and the excavation bottom 3.
[0032]
In this state, as shown in FIG. 7 (a), the required number of driving molds 5 are placed over the adjacent synthetic resin blocks 10 so that the opening or notch formed in the driving mold 5 faces the head of the pile 2. As a result, the head of the pile 2 is placed in an exposed state on the upper surface of the driving form 5.
[0033]
In this state, as shown in FIG. 7 (b), after placing the foundation frame 6 (not shown) on the driving form 5, the concrete 7 of the foundation frame 6 is placed on the head of the pile 2. An underground structure A is constructed by placing anchors (not shown) provided on the part or head so as to be buried in the concrete 7.
[0034]
Then, after a predetermined strength is developed in the concrete 7, in other words, after the foundation frame 6 is in a pile-supported state, before the excavation bottom 3 heaving occurs, the power switch (not shown) is turned on. The heaters 9 are energized. As a result, the synthetic resin block 10 is heated and contracts, so that the second state is reached, and a gap S substantially free of the spacer 4 is formed between the foundation housing 6 and the excavation bottom 3 as shown in FIG. Will be.
[0035]
According to the above construction method, when heaving of the excavation bottom 3 occurs in the state shown in FIG. 8, the gap S is formed between the foundation frame 6 and the excavation bottom 3. The lower surface of the foundation housing 6 is not pushed up, and no heaving force acts on the foundation housing 6. Therefore, the cross section and the reinforcement of the basic frame 6 can be reduced as in the previous embodiments.
[0036]
In the embodiment shown in FIGS. 1 to 8, when placing the driving form 5 on the spacer 4 in a state where the head of the pile 2 is exposed on the upper surface of the driving form 5, As shown in FIG. 9, the end of the driving form 5 may be placed in a state where it is supported by the head of the pile 2. In the embodiment shown in FIG. 1 to FIG. 9, as the placement mold 5, a so-called abandoned mold that is not included in the strength of the foundation frame, and the foundation frame are synthesized integrally with the cast-in-place concrete. Any of the molds may be used.
[0037]
10 and 11 show an embodiment of the second invention. This embodiment is the same as the first invention except that the foundation frame is made of precast, and the construction procedure is as follows.
[0038]
That is, first, as shown in FIG. 10 (a), a pile (prepared pile, cast-in-place pile, whose tip reaches the support layer on the ground surrounded by the mountain retaining wall 1 such as a sheet pile, a column of columns, and an underground continuous wall. 2) and digging deeper than the lower end of the foundation frame to be constructed. The depth from the lower end of the foundation frame to the excavation bottom 3 is set to a depth corresponding to the predicted amount of heaving.
[0039]
Next, as shown in FIG. 10 (b), on the excavation bottom 3, the first state in which the load at the time of building the foundation frame can be supported is changed to the second state in which there is no load supporting force. A plurality of possible spacers 4 are installed at appropriate intervals. The spacer 4 includes the spacer 4 shown in each actual embodiment of the first invention (the embodiment shown in FIGS. 1 to 3, the embodiment shown in FIGS. 4 and 5, the embodiment shown in FIGS. 6 to 8). The same thing can be arbitrarily selected and used.
[0040]
Next, as shown in FIG. 11 (A), the necessary number of precast members 11 for constructing the foundation frame are installed across the adjacent spacers 4, and the precast members 11 are connected to each other and connected to the head of the pile 2. A foundation frame 6 that is supported by piles is constructed.
[0041]
In this state, or as shown in FIG. 11B, after the construction of the underground structure A having the first floor and the underground floor is completed, the spacer 4 is inserted into the second space prior to the occurrence of the heaving of the excavation bottom 3. The gap S is formed between the foundation frame 6 and the excavation bottom 3 by changing the state.
[0042]
According to the above construction method, even if heaving of the excavation bottom 3 occurs in the state shown in FIG. 11 (b), the gap S is formed between the foundation frame 6 and the excavation bottom 3, so that it has risen. The bottom surface of the foundation chassis 6 is not pushed up by the excavation bottom 3, and no heaving force acts on the foundation chassis 6. Therefore, it is possible to reduce the cross section and the reinforcing bar arrangement of the basic frame 6. In addition, since a plurality of spacers 4 are installed on the excavation bottom 3 at appropriate intervals, and the precast member 11 is installed on the spacers 4, the spacers are buried as compared with the case where spacers are laid on the entire surface of the excavation bottom 3. The number of spacers 4 is small and economical.
[0043]
【The invention's effect】
As described above, according to the heaving force blocking method for the foundation frame according to the present invention, the foundation frame is constructed by supporting the driving formwork and the precast member with the spacer, and the foundation frame is in a pile-supported state. Later, before heaving of the excavation bottom occurs, the supporting force of the spacer is lost in advance, and a gap is formed between the base enclosure and the excavation bottom, so that the heaving force is transmitted to the foundation enclosure. Can be effectively blocked.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 illustrates an embodiment of the first invention, and is a cross-sectional view showing a state where a ground is excavated and a state where a spacer is installed on an excavation bottom.
FIG. 2 is a cross-sectional view showing a state in which a driving form is placed on a spacer and a state in which concrete of a foundation frame is placed on the driving form.
FIG. 3 is a cross-sectional view showing a state in which a gap is formed between the foundation frame and the excavation bottom by changing the spacer to the second state.
FIG. 4 is a cross-sectional view illustrating another embodiment of the first invention, showing a state where the ground is excavated and a state where a spacer is installed on the excavation bottom;
FIG. 5 is a cross-sectional view showing a state in which a driving form is placed on a spacer and a state in which concrete of a foundation frame is placed on the driving form.
FIG. 6 is a cross-sectional view illustrating another embodiment of the first invention, showing a state where the ground is excavated and a state where a spacer is installed on the excavation bottom;
FIG. 7 is a cross-sectional view showing a state in which a driving form is placed on a spacer and a state in which concrete of a foundation frame is placed on the driving form.
FIG. 8 is a cross-sectional view showing a state in which a gap is formed between the foundation frame and the excavation bottom by changing the spacer to the second state.
FIG. 9 is a cross-sectional view of a main part illustrating another embodiment of the first invention.
FIG. 10 exemplifies the embodiment of the second invention, and is a cross-sectional view showing a state where the ground is excavated and a state where a spacer is installed on the excavation bottom.
FIG. 11 is a cross-sectional view showing a state in which a precast member for building a foundation chassis is placed on the spacer and a state in which a gap is formed between the foundation chassis and the excavation bottom by changing the spacer to the second state.
FIG. 12 is a cross-sectional view illustrating a conventional example.
FIG. 13 is a partially broken perspective view of a crash board.
[Explanation of symbols]
2 ... Pile, 3 ... Drilling bottom, 4 ... Spacer, 6 ... Foundation frame, 7 ... Concrete, 8 ... Ice making unit (spacer), 10 ... Heat-shrinkable synthetic resin block (spacer), S ... Gap.

Claims (2)

When constructing an underground structure supported by piles, after excavating the ground, the second state where there is no load bearing capacity due to dissolution, sublimation, shrinkage, etc., from the first state that can support the load at the time of foundation foundation construction Spacers that can be changed to be placed at appropriate intervals on the bottom of the excavation, and the required number of placement molds are placed across these spacers with the heads of the piles exposed on the top surface of the placement molds. The concrete of the foundation frame is placed on the placement form, the spacer is changed to the second state after the concrete strength is developed and before the excavation bottom heaving occurs, and between the foundation frame and the excavation bottom. A method of blocking the heaving force to the basic structure, characterized by forming a gap. When constructing an underground structure supported by piles, after excavating the ground, the second state where there is no load bearing capacity due to dissolution, sublimation, shrinkage, etc., from the first state that can support the load at the time of foundation foundation construction Spacers that can be changed to be installed are installed at appropriate intervals on the bottom of the excavation, precast members for foundation building construction are installed over these spacers, and the precast members are connected to each other and connected to the head of the pile. After the foundation frame is constructed, before the occurrence of excavation bottom heaving, the spacer is changed to the second state to form a gap between the foundation frame and the excavation bottom. Blocking method.

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