JPH11271301A - Estimation method for compressive strength of on-the-spot placed concrete and shield driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method in which the compressive strength of covering concrete can be estimated precisely not in a system which collects a core sample but in a system which uses a test piece. SOLUTION: A shield driving method in which the primary covering of a tunnel is performed by on-the-spot placed concrete has a process S1 in which a temperature history in the hardening of covering concrete is measured is provided, a process S2 in which the concrete is cured so as to create the test piece of the concrete while the measured temperature history is being given and in which the compressive strength of the test piece is tested is provided, a process S3 in which the relationship between an integrated temperature and the compressive strength is found on the basis of a test result is provided, a process S4 in which a temperature history after placing the covering concrete is measured in its later execution so as to compute an integrated temperature is provided and a process S5 in which the compressive strength of the covering concrete being cured is estimated on the basis of the relationship between an integrated temperature found in advance by using the test piece and the compressive strength is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for estimating the compressive strength of cast-in-place concrete and a shield method for performing primary lining with cast-in-place concrete.

[0002]

BACKGROUND OF THE INVENTION The primary lining of shield tunnels is constructed using segments or cast-in-place concrete. In order to grasp the quality of the lining, it is important to grasp the compressive strength of the lining. Since the segments are manufactured at the factory, the compressive strength can be easily grasped. Meanwhile, EC
In the L method (construction of cast-in-place concrete in place of segments, and jacking of the shield with hardening after curing), the reinforced concrete is cast using cast-in-place concrete. It is very difficult to grasp directly. Therefore, it is necessary to estimate the compressive strength by some method. In particular, in the ECL method, it is important to grasp the compressive strength of the initial material age of about 1 or 2 days at which the mold is released.

[0003] However, at present, there are few construction results of the ECL method, and no method has been established for estimating the compressive strength of lining concrete constructed by the ECL method. Conventional techniques for estimating the compressive strength of concrete include a method using a standard cured or on-site cured specimen and a method of collecting a core sample from lining concrete.

[0004]

However, applying these methods to lining concrete constructed by the ECL method involves the following various problems.

(1) Problems of the method using a specimen cured by standard curing or on-site curing: The lining concrete constructed by the ECL method has a high temperature history, but as shown in FIG. 5, has a high temperature history. Compressive strength at the initial age differs greatly between lining concrete and specimens obtained by standard curing (20 ° C.) or on-site curing (30 ° C.). Can not be estimated accurately.・ The strength of the standard cured specimen at the initial age is smaller than that of the specimen subjected to the high temperature history.Thus, if the specimen cured with the standard curing is used, the compressive strength of the lining concrete can be evaluated on the safe side. If the composition is designed based on the strength of the standard cured test specimen, the composition is overestimated, and the composition tends to be uneconomical.

(2) Problems in the method of collecting a core sample from lining concrete: Since core boring cannot be performed until the mold is released, the compressive strength before the release can not be grasped.・ Because it is a destructive test, the structure (lining concrete) will be damaged. -Under high water pressure, it is very difficult to recover the holes created after core boring (water leakage prevention, etc.). -One test requires a very long time and labor.

In view of the above circumstances, the present invention provides a method using a specimen instead of a method of collecting a core sample.
It is an object of the present invention to provide an estimating method capable of accurately estimating the compressive strength of lining concrete, and a shield method in which the process proceeds in consideration of the compressive strength estimated by the method.

[0008]

According to the first aspect of the present invention, a concrete specimen is prepared by measuring a temperature history of a cast-in-place concrete at the time of hardening and curing the concrete while giving the measured temperature history. The relationship between the integrated temperature and the compressive strength was obtained by performing a compressive strength test on the specimen, and in the subsequent construction, the integrated temperature was calculated by measuring the temperature history after casting the cast-in-place concrete during curing, The compressive strength of the cast-in-place concrete currently being cured is estimated from the calculated integrated temperature, the relationship between the integrated temperature and the compressive strength previously obtained using the specimen.

According to a second aspect of the present invention, there is provided a shield method in which the primary lining of a tunnel is performed by cast-in-place concrete. The test specimen was prepared, and the relationship between the integrated temperature and the compressive strength was obtained by performing a compressive strength test on the test specimen.In the subsequent construction, the temperature history after placing the lining concrete was measured. The integrated temperature is calculated, and from the calculated integrated temperature and the relationship between the integrated temperature and the compressive strength previously obtained using the specimen, the compressive strength of the lining concrete currently being cured is estimated, and the estimated compressive strength is estimated. The process is performed based on

[0010]

Embodiments of the present invention will be described below with reference to the drawings. Here, a method of estimating the strength of the lining concrete in the ECL method in which the primary lining of the tunnel is constructed with cast-in-place concrete will be described.

FIG. 1 is a block diagram of a system for preparing a specimen for performing a compressive strength test. This system includes a measuring unit 1 for measuring the temperature history of a lining body (cast-in-place concrete), a control unit 2, and a concrete specimen 1
And a curing water tank 3 for creating 0. The temperature of the curing water tank 3 is controlled by the heating unit 4 and the control unit 2
Controls the heating unit 4 to control the temperature of the curing water tank 3 so as to be the temperature history measured by the temperature history measuring unit 1.

FIG. 2 shows a process flow of the intensity estimation method according to the embodiment of the present invention. In this method, first, concrete is poured into a formwork, a thermocouple or the like is embedded in the lining concrete, and a temperature history at the time of hardening of the lining concrete is measured (step S1). FIG. 3 shows the actually measured temperature history at the time of hardening of the lining concrete. Here, two types of temperature histories, high temperature history 1 and high temperature history 2, were measured.

Next, using the system of FIG. 1, a concrete specimen 10 is prepared by curing while giving a measured temperature history, and a compressive strength test is performed on the specimen at a predetermined age ( Step S2). Then, a relationship between the integrated temperature and the compressive strength is obtained (step S3). Integrated temperature M
(° C. · hr) is calculated by the following equation.

M = Σ (A + 10) ΔT where A = concrete temperature during time ΔT (° C.) ΔT = time (hr)

FIG. 4 is a graph showing the relationship between the integrated temperature and the compressive strength. FIG.
(B) shows a case where the integrated temperature is 2160 ° C. · hr or more.
The compressive strength at the early age of the specimens that have undergone a high temperature history is significantly different from the specimens that have undergone standard curing or on-site curing. From FIG. 4A, the relationship between the integrated temperature and the compressive strength can be represented by almost one straight line when the integrated temperature is 2160 ° C. · hr or less. On the other hand, from FIG.
Above r, the case of standard curing and on-site curing and the case of high temperature hysteresis can be represented by different straight lines.

After obtaining the relationship between the integrated temperature and the compressive strength by the strength test of the specimen as described above, from the next construction, the temperature history after placing the lining concrete is measured by a thermocouple or the like to determine the integrated temperature. The compressive strength of the currently cured lining concrete is calculated from the calculated integrated temperature and the relationship between the calculated integrated temperature and the integrated temperature and compressive strength previously obtained using the specimen (the relationship in FIG. 4). .

As described above, by measuring the temperature history of the poured lining concrete, the compressive strength of the lining concrete of an arbitrary age can be estimated only by the integrated temperature without performing the compressive strength test. . Therefore, a rational shield method can be implemented by advancing the subsequent steps using the estimation result.

The present invention is not limited to the shield method, but can be widely applied to a method of constructing with cast-in-place concrete.

[0019]

As described above, the present invention has the following advantages. (1) Since the compressive strength is estimated by using a specimen to which the temperature history at the time of hardening of cast-in-place concrete (lining concrete) is applied, the cast-in-place concrete (covered concrete) actually constructed is compared with the case of standard curing or on-site curing. (Compressed concrete) can be estimated. (2) Since a strength close to the actual compressive strength can be estimated, it is possible to design a more rational and more economical composition with respect to the current strength. That is, it is possible to reduce the amount of cement, change the type of cement, and the like, as compared with a composition designed by standard curing. (3) Since the estimation is performed using the specimen, the compressive strength of the concrete can be easily estimated by a non-destructive method without damaging the cast-in-place concrete (lining concrete). (4) Since the strength development properties of the initial age of concrete can be accurately grasped, it is possible to rationally determine the mold release time.
Therefore, safe work can be performed and the construction period can be reduced. (5) The property of compressive strength development of the concrete immediately after the casting can be grasped. (6) If the relationship between the integrated temperature and the compressive strength is obtained, the compressive strength of any age of the poured concrete can be determined using only the integrated temperature without performing the compressive strength test only by measuring the temperature history. Can be estimated.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a system for creating a specimen in a strength estimation method according to an embodiment of the present invention.

FIG. 2 is a process flow chart of the method.

FIG. 3 is a diagram showing a temperature history of lining concrete measured by the same method.

FIG. 4 is a diagram showing a relationship between an integrated temperature and a compressive strength obtained by the same method, wherein (a) shows that the integrated temperature is 2160 ° C. · hr;
In the following case, (b) is a diagram when the integrated temperature is 2160 ° C. · hr or more.

FIG. 5 is a view showing the results of compressive strength tests having different curing temperature histories.

[Description of Signs] 1 Temperature history measuring unit of lining body 2 Control unit 4 Heating unit 10 Specimen

Claims (2)

[Claims] 1. A concrete test piece is prepared by measuring a temperature history of a cast-in-place concrete at the time of hardening, curing the cast concrete while giving the measured temperature history, and integrating it by performing a compressive strength test on the test piece. Determine the relationship between temperature and compressive strength, and in the subsequent construction, calculate the accumulated temperature by measuring the temperature history after casting the cast-in-place concrete during curing, and calculate the accumulated temperature and the specimen A method for estimating the compressive strength of cast-in-place concrete that is currently being cured from the relationship between the integrated temperature and compressive strength obtained using the method. 2. In a shield method in which the primary lining of a tunnel is made of cast-in-place concrete, the temperature history at the time of hardening of the lining concrete is measured and cured while giving the measured temperature history to prepare a concrete specimen. And
By performing a compressive strength test on the specimen, the relationship between the cumulative temperature and the compressive strength was obtained, and in the subsequent construction, the cumulative temperature was calculated by measuring the temperature history after placing the lining concrete. Estimate the compressive strength of the lining concrete currently curing from the calculated integrated temperature and the relationship between the integrated temperature and the compressive strength previously obtained using the specimen, and proceed with the process based on the estimated compressive strength. Shield construction method characterized by the following.