JP7561096B2 - Method for estimating retained concrete and method for constructing concrete structure - Google Patents

Description

The present invention relates to a method for estimating retained concrete and a method for constructing a concrete structure.

In constructing a concrete structure, when pouring concrete from a high position, a tremie pipe may be used to drop the concrete. For example, Patent Document 1 discloses a method for constructing a cast-in-place concrete pile using a tremie pipe. When pouring concrete using a tremie pipe, it is common to insert the tip of the tremie pipe into the already poured concrete.
For example, in the concrete structure construction method of Patent Document 1, when different types of concrete are poured above and below, a tremie pipe is used to pour the lower concrete to a predetermined height (pre-pouring height), and then pouring of the upper concrete is started with the tip of the tremie pipe inserted into the lower concrete, pushing up part of the lower concrete to the switching completion height, and then the upper concrete is subsequently poured above the switching completion height.
When concrete is poured from a high place using a tremie pipe, the concrete inside the tremie pipe is generally treated as having fallen to the pouring location. On the other hand, concrete may be retained inside the tremie pipe when the tip is inserted into the already poured concrete due to the frictional force generated between the inner surface of the tremie pipe and the concrete. Therefore, if concrete is poured up to the designed height, excess concrete will be retained inside the tremie pipe. Therefore, when concrete is poured from a high place to a low place using a tremie pipe, it is desirable to set the concrete pouring completion height (pre-pouring height, etc.) taking into account the amount of concrete retained inside the tremie pipe.

JP 2020-020192 A

The present invention aims to propose a method for estimating the amount of concrete retained in a tremie pipe when pouring concrete using the tremie pipe, and a method for constructing a concrete structure using this method for estimating retained concrete.

The method for estimating retained concrete of the present invention calculates a retained height, which is a height difference between the top surface of the concrete retained in the tremie pipe and the top surface of the already-cast concrete, when concrete is poured by allowing the concrete to freely fall inside the tremie pipe with the tip of the tremie pipe inserted into the already-cast concrete. The retained height is calculated assuming that the tremie pipe external pressure and the tremie pipe internal pressure are equal when concrete is retained in the tremie pipe. The tremie pipe external pressure is a pressure acting from the outside of the tremie pipe based on the insertion depth of the tremie pipe into the already-cast concrete. The tremie pipe internal pressure is a value obtained by subtracting the frictional resistance force between the concrete and the inner surface of the tremie pipe from the force calculated from the self-weight of the concrete retained in the tremie pipe, and dividing the value by the inner hollow cross-sectional area of the tremie pipe 5.
The tremie pipe external pressure is preferably a sum of the insertion depth multiplied by the unit volume weight of the concrete and the depth of the stabilizing liquid retained above the cast concrete multiplied by the unit volume weight of the stabilizing liquid. The tremie pipe internal pressure is preferably a value obtained by multiplying the sum of the retention height and the insertion depth by the unit volume weight of the concrete and the inner cross-sectional area of the tremie pipe, minus the sum of the retention height and the insertion depth multiplied by the friction resistance stress of concrete and the inner circumference of the tremie pipe, divided by the inner cross-sectional area of the tremie pipe. The friction resistance force is a rheological constant when concrete is assumed to be a Bingham fluid, and is preferably a value based on the limit shear stress at which the concrete begins to flow.
According to the method for estimating the amount of concrete retained in the tremie pipe, the amount (height) of concrete retained in the tremie pipe can be estimated, so that concrete can be poured taking into consideration the amount of concrete retained in the tremie pipe, which in turn enables rational construction. For example, when pouring different types of concrete one above the other in succession, the concrete can be appropriately switched at the designed switching depth.

In addition, the method for constructing a concrete structure of the present invention constructs a concrete structure by pouring an upper concrete made of a different type of concrete on top of a lower concrete, and includes a first step of setting a pouring switching depth, which is a position where pouring of the lower concrete is completed, below a switching completion depth, which is a position where switching from the lower concrete to the upper concrete is completed, and pouring the lower concrete up to the pouring switching depth, a second step of starting the supply of upper concrete with the lower end of the tremie pipe positioned below the pouring switching depth and supplying the upper concrete up to the switching completion depth, and a third step of pouring the upper concrete above the switching completion depth.
In the first step, it is desirable to pour the lower concrete to a depth that takes into account the influence of the amount of concrete equivalent to the retained height obtained by the retained concrete estimation method.
In addition, in the second step, it is desirable to perform a first pouring operation of supplying upper concrete into the tremie pipe with an amount of concrete equal to or greater than the amount of concrete corresponding to the retained height determined by the retained concrete estimation method, a tremie pipe adjustment operation of adjusting the insertion depth of the tremie pipe into the lower concrete, and a second pouring operation of resuming the supply of upper concrete into the tremie pipe and pouring the upper concrete up to the switching completion depth.
Furthermore , it is desirable to set the insertion length of the tremie pipe below the pouring switching depth, and to calculate the switching length, which is the difference between the switching completion depth and the pouring switching depth, taking into account the volume of upper concrete supplied from the tremie pipe below the pouring switching depth and the amount of concrete equivalent to the retention height .
According to this method for constructing a concrete structure, the pouring depth of the lower concrete (pouring switching depth) is set taking into account the amount of concrete remaining in the tremie pipe, so that the switching length can be set on the safe side.

The present invention provides a method for estimating retained concrete, which makes it possible to appropriately estimate the amount of concrete retained in a tremie pipe when pouring concrete using the tremie pipe. In addition, a method for constructing a concrete structure using this method for estimating retained concrete enables efficient and economical construction by taking into account the concrete retained in the tremie pipe.

FIG. 2 is a cross-sectional view showing a portion of a cast-in-place concrete pile according to an embodiment of the present invention. 2A to 2C are cross-sectional views showing the construction status of the cast-in-place concrete pile shown in FIG. 1, where (a) is a first step, (b) is a second step, and (c) is a third step. FIG. 1 is a perspective view showing upper concrete supplied below the advance pouring height. FIG. FIG. 1 is a diagram showing an overview of the first evaluation method, in which (a) shows a state in which lower concrete remains in the tremie pipe, and (b) shows a state in which the lower concrete in the tremie pipe has been discharged. 11 is a cross-sectional view showing an overview of the second step in the second evaluation method, where (a) is the first concrete pouring work, (b) is the tremie pipe adjustment work, and (c) is the second concrete pouring work. FIG. 11 is a plan view showing the arrangement of measurement points during on-site construction testing, where (a) is the case where one tremie pipe is used, and (b) is the case where two tremie pipes are used. 1 is a graph showing the results of a field construction test.

In this embodiment, a case will be described in which two types of concrete with different strengths are cast continuously in the depth direction (up and down) in a cast-in-place concrete pile (concrete structure) 1 for the purpose of constructing a rational pile. Fig. 1 shows a part of the cast-in-place concrete pile 1 of this embodiment. The cast-in-place concrete pile 1 of this embodiment is formed by continuously pouring an upper concrete 3, which has a higher design standard strength than the lower concrete 2, on top of a lower concrete 2 in order to increase the concrete strength of the upper part of the pile where stress increases during an earthquake. Fig. 2 shows each construction stage of the method for constructing a concrete structure of this embodiment.
The method for constructing a concrete structure in this embodiment includes a first step (see Figure 2(a)) of pouring a lower concrete 2 up to a predetermined height (hereinafter referred to as the "pouring switching depth H1"), a second step (see Figure 2(b)) of starting to supply an upper concrete 3 from below the concrete pouring surface (top surface of already poured concrete) 2a of the lower concrete 2 and supplying the upper concrete 3 until the top surface of the already poured concrete reaches the switching completion depth H2, and a third step (see Figure 2(c)) of pouring the upper concrete 3 above the switching completion depth H2.

In the first step, as shown in FIG. 2(a), the lower concrete 2 is supplied until the top surface of the already-cast concrete (concrete casting surface) reaches the casting switching depth H1. The lower concrete 2 is supplied from the bottom end of the borehole 6 formed in the ground using a tremie pipe 5 inserted into the borehole 6. A stabilizing liquid sl is stored in the borehole 6 to ensure the stability of the hole wall. The tremie pipe 5 is raised with its tip inserted into the already-cast concrete in accordance with the rise of the concrete casting surface 2a. The casting switching depth H1 is set below the switching completion depth H2, which is the position where the supply of the lower concrete 2 is completed and where the switching from the lower concrete 2 to the upper concrete 3 is completed. The casting switching depth H1 is set to a switching completion depth H2 (range in which concrete strength is increased) based on the estimated value (design value) of the stress acting on the cast-in-place concrete pile 1, and the casting switching depth H1 is set so that the concrete is completely switched from the lower concrete 2 to the upper concrete 3 at this switching completion depth H2.

Here, the pouring switching depth H1 is calculated by Equation 1. The pouring switching depth H1 is calculated by subtracting the switching length h from the switching completion depth H2, which is set based on the acting stress of the cast-in-place concrete pile 1. The switching length h is the section from when the supply of the upper concrete 3 starts after the lower concrete 2 is poured until all of the already poured concrete is switched to the upper concrete 3, and is the height difference between the pouring switching depth H1 and the switching completion depth H2.
H1=H2-h... Formula 1
H1 : Pouring switching depth H2 ：Switching completion depth h : Switching length

In the second step, as shown in FIG. 2(b), the supply of the upper concrete 3 is started with the lower end of the tremie pipe 5 positioned below the casting switching depth H1, and the upper concrete 3 is supplied until the top surface of the already cast concrete reaches the switching completion depth H2. When the upper concrete 3 is supplied below the casting switching depth H1, the upper concrete 3 is injected while pushing aside the lower concrete 2. The upper concrete 3 is supplied in a semi-elliptical or semi-circular shape (tip portion 31) directly below the tremie pipe 5 at the start of supply in the lower concrete 2, and then the upper concrete 3 is supplied in a cylindrical shape (cylindrical portion 32) directly above the tip portion 31 (see FIG. 3). On the other hand, as the upper concrete 3 is supplied, the lower concrete 2, which has a volume equivalent to the upper concrete 3 supplied below the casting switching depth H1, moves from below the casting switching depth H1 to above the casting switching depth H1. At this time, the lower concrete 2 that has moved above the pouring switching depth H1 moves to the outer portion (annular region 21 centered on the tremie pipe 5) above the pouring switching depth H1 (see FIG. 2(c)). The upper end of the lower concrete 2 (annular region 21) that has moved above the pouring switching depth H1 is located below the switching completion depth H2.

Conventional methods for evaluating the switching length h (pouring switching depth H1 and switching completion depth H2) include, for example, the following method (see Patent Document 1).
The annular region 21 is a section where the lower concrete 2 and the upper concrete 3 are mixed, and the height of the annular region ₂₁ (annular region height _hT ) is the reference for the switching length h. As shown in Equation 2, the volume of the annular region 21 is calculated by assuming that the volume V of the upper concrete 3 supplied below the pouring switching depth H1 is the volume of the lower concrete 2 that has moved to the annular region 21. Here, the upper concrete 3 supplied below the pouring switching depth H1 is the sum of the volumes of the tip portion 31 and the cylindrical portion 32, as shown in Fig. 3. Meanwhile, the annular region 21 is a cylindrical body with an inner diameter _φi and an outer diameter _φ0, as shown in Fig. 4.
h = _hT
h _T =V/S...Formula 2
V = V1 + V2
S=π/4×(φ _o ² −φ _i ² )
V1=πφ _r ² /4×T
V2=2/3×πφ _r ² /4×Δh ₀
h _T : Height of annular region V : Volume of upper concrete supplied below the pre-cast height V1 : Volume of the cylindrical part of the upper concrete supplied below the advance pouring height V2 : Volume of the tip of the upper concrete supplied below the advance pour height S : Cross-sectional area of the annular region φ _o : Outer diameter of the cast-in-place concrete pile φ _i : Inner diameter of the annular region φ _r : Diameter of the cylindrical part of the upper concrete supplied below the pre-casting height T _Δh0 : Lower outflow depth, which is the distance from the bottom end of the upper concrete supplied in the second step to the tip of the tremie pipe. In addition, it is also possible to evaluate the switching length h from experimental results, analysis results using flow analysis (CFD), etc.

In the third step, as shown in Figure 2 (c), with its lower end inserted into the already poured concrete (upper concrete 3), the tremie pipe 5 is pulled up and the upper concrete 3 is supplied above the switching completion depth H2.

As a method based on this patent for taking into account the influence of concrete remaining in the tremie pipe 5 on the switching length h (pouring switching depth H1 and switching completion depth H2), for example, the following three methods (first evaluation method to third evaluation method) may be used.
(1) First evaluation method The switching length h is calculated by Equation 3, which takes into consideration the amount of concrete equivalent to the retention height H of the concrete retained in the tremie pipe 5 after the first process. Figure 5 shows an overview of the first evaluation method. The retention height H is the height difference from the top surface of the concrete retained in the tremie pipe 5 to the top surface of the already-cast concrete when concrete is poured by freely dropping into the tremie pipe 5 with the tip of the tremie pipe 5 inserted in the already-cast concrete, as shown in Figure 5(a). When pouring of the upper concrete 3 starts, the lower concrete 2 remaining in the tremie pipe 5 is discharged first, so the timing of switching to the upper concrete 3 is calculated, including the amount of this lower concrete 2 (see Figure 5(b)).
The switching length h is the height obtained by adding the height of the lower concrete (switching length increment Δh) increased by the amount of concrete equivalent to the retention height H to the annular region height _hT .
h=h _T +Δh...Formula 3
Δh=α×ΔT
h: Switching length _hT : Annular region height Δh: Switching length increment ΔT: Embedment length increment corresponding to retained concrete α: Coefficient for embedment increment obtained by fluid analysis (CFD), experiment, etc.

(2) Second Evaluation Method In the second evaluation method, the switching length h is defined as the height obtained by adding an embedment length increment ΔT corresponding to the amount of concrete equivalent to the retention height H to the annular region height _hT , as shown in Equation 4. That is, in the second evaluation method, the switching length increment Δh is defined as the embedment length increment ΔT.
h=h _T +ΔT...Formula 4
h: Switching length _hT : Height of annular region ΔT: Increment of penetration length

When using the second evaluation method, it is desirable to carry out in the second step a first pouring operation in which an amount of upper concrete 3 equivalent to or greater than the amount of concrete corresponding to the retention height H is supplied into the tremie pipe 5 as shown in Figures 6(a) and (b), a tremie pipe adjustment operation in which the insertion depth T of the tremie pipe 5 into the lower concrete 2 is adjusted as shown in Figures 6(b) and (c), and a second pouring operation in which the supply of upper concrete 3 is resumed into the tremie pipe 5 and the upper concrete 3 is poured up to the switching completion depth H2 as shown in Figure 2(b).

(3) Third Evaluation Method In the third evaluation method, as shown in Equation 5, the increment in embedment length ΔT corresponding to the amount of concrete equivalent to the retention height H in Equation 1 is taken into consideration.
H1=H2-h-ΔT... Formula 5
h = V/S
V = V1 + V2
S=π/4×(φ _o ² −φ _i ² )
V1=πφ _r ² /4×(T+ΔT)
V2=2/3×πφ _r ² /4×Δh ₀
H1 : Pouring switching depth H2 ：Switching completion depth h : Switching length _hT : Annular region height V : Volume of upper concrete supplied below the pre-cast height V1 : Volume of the cylindrical part of the upper concrete supplied below the advance pouring height V2 : Volume of the tip of the upper concrete supplied below the advance pouring height S : Cross-sectional area of the annular region φ _o : Outer diameter of the cast-in-place concrete pile φ _i : Inner diameter of the annular region φ _r : Diameter of the cylindrical part of the upper concrete supplied below the pre-casting height T Δh ₀ : Depth of the tremie pipe inserted into the lower concrete in the second step Δh 0 : Lower outflow depth, which is the distance from the bottom end of the upper concrete supplied in the second step to the tip of the tremie pipe

Here, the retention height H is calculated assuming that the tremie pipe external pressure _p0 and the tremie pipe internal pressure _pt are equal when concrete is retained in the tremie pipe 5, as shown in Equation 6.
p ₀ = p _t ... Formula 6
p ₀ : External pressure of tremie tube p _t : Internal pressure of tremie tube

The tremie pipe external pressure _p0 is a pressure acting from outside the tremie pipe 5 based on the insertion depth T of the tremie pipe 5 into the already-cast concrete (see FIG. 2(b)). As shown in Equation 7, the tremie pipe external pressure _p0 is the sum of the insertion depth T multiplied by the unit volume weight _γc of the concrete and the depth _Hsl of the stabilizing liquid sl retained above the already-cast concrete multiplied by the unit volume weight _γsl of the stabilizing liquid sl.
p ₀ = γ _c T + γ _sl H _sl ...Formula 7
γ _c : Unit weight of concrete T : Insertion depth _γsl : Unit weight of stabilizing liquid _Hsl : Depth of stabilizing liquid

As shown in Equation 8, the tremie pipe internal pressure p _t is a value obtained by subtracting the frictional resistance force between the concrete and the inner surface of the tremie pipe 5 from the pressure obtained from the weight of the concrete (lower concrete) retained in the tremie pipe 5. The pressure obtained from the weight of the concrete retained in the tremie pipe 5 is calculated by multiplying the sum of the retention height H and the insertion depth T by the unit volume weight γ _c of the concrete, and then multiplying this value by the inner hollow cross-sectional area A of the tremie pipe 5. In addition, the frictional resistance force between the concrete and the inner surface of the tremie pipe 5 is calculated by multiplying the sum of the retention height H and the insertion depth T by the frictional resistance stress f of the concrete, and then multiplying this value by the inner circumference φ of the tremie pipe.
The internal pressure p _t of the tremie tube is calculated by subtracting the frictional resistance force from the force calculated from the weight, and dividing the result by the internal cross-sectional area of the tremie tube 5.
In this embodiment, the concrete yield value τ is used as the friction resistance stress f of the concrete. The concrete yield value τ (=friction resistance f) is a rheological constant when the concrete is assumed to be a Bingham fluid, and is a value based on the limit shear stress at which the concrete begins to flow.

From equations 6 to 8, the retention height H can be expressed by equation 9. Note that R is the inner diameter of the tremie tube.

As described above, according to the method for constructing a concrete structure of this embodiment, the concrete switching can be completed near the design switching completion height, so that when concretes of different strengths are poured continuously in the height direction, it is possible to rationally set the point at which the strength of the poured concrete changes. As a result, the cast-in-place concrete pile 1 with the required strength can be constructed economically.
Furthermore, according to this embodiment, the amount of concrete remaining in the tremie pipe 5 (retention height H) can be estimated, so that concrete can be poured taking into account the amount of concrete remaining in the tremie pipe 5, thereby enabling rational construction.

Below, the results of a field construction test that confirmed the validity of the method for estimating the amount of concrete retained in the tremie pipe 5 using Equation 9 are shown.
In the construction test, the top level of the concrete inside and outside the tremie pipe 5 was measured for four test specimens after concrete was poured. Figure 7(a) shows test specimens 1 and 2, and Figure 7(b) shows test specimens 3 and 4. In test specimens 1 and 2, the tremie pipe 5 was installed in the center of the borehole 6 as shown in Figure 7(a), and in test specimens 3 and 4, two tremie pipes 5, 5 were installed facing each other across the center of the borehole 6. Measurement points P were measured inside the tremie pipe 5, one point near the center of the borehole 6 outside the tremie pipe 5, and four points set at approximately equal intervals on the outer periphery. That is, as shown in Figure 7(a), a total of six points were measured for test specimens 1 and 2, and a total of seven points were measured for test specimens 3 and 4 as shown in Figure 7(b). The concrete height was calculated from the measured value inside the tremie pipe 5 (average value for test specimens 3 and 4) and the average value of the measured values at each measurement point outside the tremie pipe 5.

The calculation conditions are as follows:
Stable liquid level GL-0m
Stabilizing liquid unit volume weight _γsl = 10kN/ ^m3
Bottom concrete unit weight γ _c = 22.6 kN/m ³
Yield value of the lower concrete τ = 325 Pa
Upper concrete unit volume weight γ _c = 23.5 kN/m ³
Yield value of upper concrete τ＝100Pa

The yield values τ of the upper concrete 3 and the lower concrete 2 were set so that the slump or slump flow would be the target value by separately conducting a flow analysis of a slump test.
Figure 8 shows the relationship between the test results for concrete height and the estimated results.
As shown in Figure 8, the estimated results generally correspond to the experimental results. In addition, since the estimated results (dotted lines in Figure 8) are greater than the experimental results (since they are located above the estimated straight line (dotted line)), it was confirmed that the estimated results are on the safe side.

Next, the pile diameter of the cast-in-place concrete pile and the switching depth for pouring were used as parameters to calculate the retention height H of the concrete remaining in the tremie pipe 5 and the increment in embedded length ΔT. The calculation conditions are shown below. The calculation results are shown in Table 1.
Pile diameter: 1.6m, 2.0m, 2.4m, 3.0m
Pouring switching depth: GL-10m, -20m, -30m, -40m, -50m
Stable liquid level GL-0m
Stabilizing liquid unit volume weight _γsl = 10kN/ ^m3
Tremie pipe: inner diameter 25 cm, root length 2 m
Concrete unit weight γ _c = 22.6 kN/m ³
Concrete yield value τ = 325 Pa

As shown in Table 1, regardless of the pile diameter, the deeper the driving switching depth, the larger the embedded length increment ΔT. Also, the smaller the pile diameter, the larger the embedded length increment ΔT.

Although an embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and each of the above-described components can be appropriately modified without departing from the spirit of the present invention.
For example, in the above embodiment, a cylindrical cast-in-place concrete pile 1 is constructed, but the concrete structure is not limited thereto.
Furthermore, the method for estimating retained concrete is not limited to cases where different types of concrete are poured continuously in the depth direction, but may be used when pouring one type of concrete.
In addition, in the above embodiment, a case has been described in which a single tremie pipe 5 is used for construction on a single cast-in-place concrete pile 1, but the number of tremie pipes 5 is not limited, and for example, multiple tremie pipes 5 may be used.
In the above embodiment, the upper concrete 3 is poured using concrete having a higher design standard strength than the lower concrete 2, but the upper concrete 3 is not limited to this as long as it is a different type of concrete from the lower concrete 2, for example, one having a higher fluidity than the lower concrete 2.
In the above embodiment, in the first step, the lower concrete is poured to a depth that anticipates the amount of concrete equivalent to the retention height, but the method of setting the pouring switching depth is not limited.
In addition, in the above embodiment, the second step includes a first pouring operation of supplying upper concrete into the tremie pipe with an amount of concrete equal to or greater than the retention height, a tremie pipe adjustment operation of adjusting the insertion depth of the tremie pipe into the lower concrete, and a second pouring operation of resuming the supply of upper concrete into the tremie pipe and pouring the upper concrete up to the switching completion depth, but the work procedure of the second step is not limited.

1 Cast-in-place concrete pile 2 Lower concrete 3 Upper concrete 4 Reinforced concrete cage 5 Tremie pipe 6 Borehole

Claims (6)

A method for estimating retained concrete, in which concrete that has been allowed to fall freely into a tremie pipe is poured with the tip of the tremie pipe inserted into already-placed concrete, is provided for calculating a retained height, which is a height difference between an upper surface of the concrete retained in the tremie pipe and an upper surface of the already-placed concrete,
The retention height is calculated assuming that the external pressure of the tremie pipe and the internal pressure of the tremie pipe are equal when concrete is retained in the tremie pipe,
The tremie pipe external pressure is a pressure acting from the outside of the tremie pipe based on the insertion depth of the tremie pipe into the already-cast concrete,
A method for estimating retained concrete, characterized in that the internal pressure of the tremie pipe is a value obtained by subtracting the frictional resistance force between the concrete and the inner surface of the tremie pipe from the force calculated from the weight of the concrete retained in the tremie pipe, and dividing the result by the internal cross-sectional area of the tremie pipe. The tremie pipe external pressure is a value obtained by multiplying the insertion depth by the unit volume weight of the concrete and a value obtained by multiplying the depth of the stabilizing liquid retained above the cast concrete by the unit volume weight of the stabilizing liquid,
The method for estimating retained concrete as described in claim 1, characterized in that the internal pressure of the tremie pipe is a value obtained by multiplying the sum of the retained height and the insertion depth by the unit volume weight of the concrete and the internal cross-sectional area of the tremie pipe, minus the value obtained by multiplying the sum of the retained height and the insertion depth by the frictional resistance stress of concrete and the inner circumference of the tremie pipe, and dividing the result by the internal cross-sectional area of the tremie pipe. The method for estimating retained concrete according to claim 2, characterized in that the frictional resistance stress is a rheological constant when the concrete is assumed to be a Bingham fluid, and is a value based on the limit shear stress at which the concrete begins to flow. A method for constructing a concrete structure by pouring an upper concrete made of a different type of concrete onto a lower concrete, comprising:
A first step of setting a pouring switching depth, which is a position where pouring of the lower concrete is completed, below a switching completion depth, which is a position where switching from the lower concrete to the upper concrete is completed, and pouring the lower concrete up to the pouring switching depth;
A second step of starting to supply upper concrete with the lower end of the tremie pipe positioned below the pouring switching depth and pouring the upper concrete up to the switching completion depth;
and a third step of pouring upper concrete above the switching completion depth,
A method for constructing a concrete structure, characterized in that in the first step, lower concrete is poured to a depth that takes into account the influence of the amount of concrete equivalent to the retained height obtained by the retained concrete estimation method described in any one of claims 1 to 3. A method for constructing a concrete structure by pouring an upper concrete made of a different type of concrete onto a lower concrete, comprising:
A first step of setting a pouring switching depth, which is a position where pouring of the lower concrete is completed, below a switching completion depth, which is a position where switching from the lower concrete to the upper concrete is completed, and pouring the lower concrete up to the pouring switching depth;
A second step of starting to supply upper concrete with the lower end of the tremie pipe positioned below the pouring switching depth and pouring the upper concrete up to the switching completion depth;
and a third step of pouring upper concrete above the switching completion depth,
In the second step, a first pouring operation is performed to supply an upper concrete amount equivalent to the retained concrete height obtained by the retained concrete estimation method according to any one of claims 1 to 3 into the tremie pipe;
a tremie pipe adjustment operation for adjusting the insertion depth of the tremie pipe into the lower concrete;
a second pouring operation of resuming the supply of upper concrete into the tremie pipe and pouring the upper concrete up to the switching completion depth. The method for constructing a concrete structure according to claim 4 or 5, characterized in that the insertion length of the tremie pipe below the pouring switching depth is set, and the switching length, which is the difference between the switching completion depth and the pouring switching depth, is calculated by anticipating the volume of upper concrete supplied from the tremie pipe below the pouring switching depth and the amount of concrete equivalent to the retention height.

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