JP2013072738A - Estimation method of static elasticity modulus of early-age shotcrete - Google Patents
Estimation method of static elasticity modulus of early-age shotcrete Download PDFInfo
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- 230000003068 static effect Effects 0.000 title claims abstract description 43
- 239000011378 shotcrete Substances 0.000 title claims abstract description 35
- 238000000034 method Methods 0.000 title claims abstract description 23
- 238000012360 testing method Methods 0.000 claims abstract description 58
- 238000012669 compression test Methods 0.000 claims abstract description 26
- 230000035515 penetration Effects 0.000 claims abstract description 14
- 238000007586 pull-out test Methods 0.000 claims abstract description 14
- 239000000463 material Substances 0.000 claims abstract description 11
- 230000006835 compression Effects 0.000 abstract 4
- 238000007906 compression Methods 0.000 abstract 4
- 238000005507 spraying Methods 0.000 description 11
- 239000004567 concrete Substances 0.000 description 10
- 238000009412 basement excavation Methods 0.000 description 7
- 238000010276 construction Methods 0.000 description 7
- 239000011435 rock Substances 0.000 description 2
- 238000005070 sampling Methods 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 238000013100 final test Methods 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
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Abstract
Description
本発明は、吹き付けコンクリートの剛性を把握するためにその指標となる弾性係数（ヤング率）を推定するための方法、特に、一軸圧縮試験用のコアを採取不能な若材齢吹き付けコンクリートを対象としてその静弾性係数を精度良く推定するための方法に関する。 The present invention relates to a method for estimating an elastic modulus (Young's modulus) that serves as an index for grasping the rigidity of shotcrete, especially for young age shotcrete that cannot collect a core for a uniaxial compression test. The present invention relates to a method for accurately estimating the static elastic modulus.
大深度で地圧が強大な場合、あるいは地圧は大きくないが地山の持つ強度が小さい場合、すなわち地山強度比（地山の一軸圧縮強度と初期地圧の比）が小さい条件下でトンネルを建設する際には、トンネル構造体全体（すなわち支保構造物とその周囲の地山）の最終的な安定性の確保とともに掘削直後のトンネル近傍の地山や切羽の安定性を確保することが重要である。 When the ground pressure is large at a deep depth, or when the ground pressure is not large but the strength of the natural ground is small, that is, under the condition where the natural ground strength ratio (ratio of natural compressive strength to initial ground pressure) is small. When constructing a tunnel, ensure the stability of the entire tunnel structure (ie supporting structure and surrounding ground) and the stability of the ground and face near the tunnel immediately after excavation. is important.
山岳トンネルの工法では、掘削に伴う安定化のための手段として一次支保工の敷設がなされるが、その一次支保工としては吹き付けコンクリート、鋼製支保工およびロックボルトなどが主要な支保部材として用いられる。これらの支保部材は掘削によって生じる地山の応力変化（応力再配分といわれる）に対応してトンネル周辺地山の不安定化を防ぐための支保機能を十分に発揮する必要がある。
すなわち、トンネルの掘削に伴う周辺地山の安定性を確保するためには、支保と地山の相互作用を考慮した安定設計が必要となる。
In the mountain tunnel construction method, primary support is laid as a means for stabilization during excavation, but as the primary support, spray concrete, steel support, rock bolts, etc. are used as the main support members. It is done. These support members need to fully exhibit a support function for preventing instability of the surrounding rocks in response to the stress change (called stress redistribution) caused by excavation.
In other words, in order to secure the stability of the surrounding ground due to the excavation of the tunnel, a stable design that takes into account the interaction between the support and the ground is necessary.
また、トンネルを効率的に掘削するためには一次支保工としての吹き付けコンクリートが可及的に短時間で高い剛性と高い強度を発現することが望ましく、特許文献１や特許文献２にはそれを可能とするコンクリート材料やトンネル工法についての提案がある。 Moreover, in order to excavate the tunnel efficiently, it is desirable that the sprayed concrete as the primary support works exhibit high rigidity and high strength in as short a time as possible. There are proposals for possible concrete materials and tunnel construction methods.
ところで、掘削直後のトンネルの安定性を評価するには、トンネルの切羽近傍の地山と支保工により構築される構造体の安定性を考慮した部材設計と施工条件を工夫することが必要となる。
その場合、掘削直後に施工される吹き付けコンクリートは、吹き付け後の時間経過とともにその力学特性である強度と剛性が次第に高くなるため、時間の経過に伴うコンクリートの強度と剛性の発現関係を把握して安定設計に反映させることが必要であり、そのことは特許文献１や特許文献２に示されるように早期に強度が発現する特殊な吹き付けコンクリートを用いる場合において特に重要である。
By the way, in order to evaluate the stability of a tunnel immediately after excavation, it is necessary to devise a member design and construction conditions that take into account the stability of the ground constructed near the face of the tunnel and the structure constructed by a supporting work. .
In that case, the sprayed concrete that is constructed immediately after excavation gradually increases in strength and rigidity, which are its mechanical properties, over time after spraying, so understand the relationship between the strength and rigidity of the concrete over time. It is necessary to reflect this in a stable design, which is particularly important when using special sprayed concrete that develops strength at an early stage as shown in
吹き付けコンクリートの強度発現特性を現場にて把握するためには、従来よりプルアウト試験や針貫入試験、一軸圧縮試験が行われることが一般的である。
周知のように、プルアウト試験は試料採取皿に取り付けたピンが隠れるようにコンクリートを吹き付けて試料を作製し、そのピンを反対側から引き抜くことで生じる破壊コーンのせん断面よりせん断強度を求めて換算圧縮強度を求める試験であり、また、針貫入試験は、専用のピンを空気圧によって吹き付けコンクリートに打ち込み、その貫入深さを測って吹き付けコンクリートの強度を推定する試験である。
これらのプルアウト試験や針貫入試験では、吹き付け直後の吹き付けコンクリートの強度を求めることでその発現状況を把握可能ではあるものの、弾性係数を求めることはできないので、それ自体では剛性を把握することはできない。
In order to ascertain the strength development characteristics of shotcrete in the field, a pull-out test, a needle penetration test, and a uniaxial compression test are generally performed.
As is well known, the pull-out test is done by spraying concrete so that the pins attached to the sampling pan are hidden, and then obtaining the shear strength from the shear surface of the fracture cone generated by pulling out the pins from the opposite side. This is a test for determining the compressive strength, and the needle penetration test is a test for estimating the strength of the sprayed concrete by driving a dedicated pin into the sprayed concrete by air pressure and measuring the penetration depth.
In these pull-out tests and needle penetration tests, the strength of sprayed concrete immediately after spraying can be determined to determine its manifestation, but the elastic modulus cannot be determined, so the rigidity cannot be determined by itself. .
一方、一軸圧縮試験は硬化した吹き付けコンクリートから採取したコアに変位計を設置して、載荷時の載荷応力と同時に歪みを計測して応力−歪み関係を求めることによって試料の弾性係数を求めることが可能であるから、強度のみならず剛性も把握することが可能であるが、吹き付け直後のコンクリートは試料のコアの採取が難しいことから一軸圧縮試験を実施できない場合も多い。
コアを採取できず、それ故、一軸圧縮試験を実施できないような吹き付け直後の若材齢吹き付けコンクリートについては、プルアウト試験あるいは針貫入試験により強度は推定し得るもののその弾性係数や剛性については十分に把握することができないため、特に特許文献１や特許文献２に示されるような早期に強度を発現する特殊な吹き付けコンクリートを用いる特殊なトンネル工法を実施する場合において、吹き付け直後の支保工の安定性を精度良く解析して適切に評価することが困難である。
On the other hand, in the uniaxial compression test, a displacement meter is installed in the core taken from hardened shotcrete, and the elastic modulus of the sample is obtained by measuring the strain simultaneously with the loading stress at the time of loading and obtaining the stress-strain relationship. Because it is possible, it is possible to grasp not only the strength but also the rigidity. However, since the concrete immediately after spraying is difficult to collect the sample core, there are many cases where the uniaxial compression test cannot be performed.
For young-aged shotcrete immediately after spraying, where the core cannot be sampled and therefore the uniaxial compression test cannot be performed, the strength and elasticity can be estimated by pull-out test or needle penetration test. In particular, when carrying out a special tunnel method using special sprayed concrete that develops strength at an early stage as shown in
上記事情に鑑み、本発明は一軸圧縮試験のためのコアが採取できないような若材齢の吹き付けコンクリートについても、その剛性を把握するための指標となる静弾性係数を精度良く推定することを可能とする有効適切な推定方法を提供することを目的とする。 In view of the above circumstances, the present invention can accurately estimate the static elastic modulus, which is an index for grasping the rigidity of young-aged shotcrete, for which a core for a uniaxial compression test cannot be collected. It is an object to provide an effective and appropriate estimation method.
本発明は、一軸圧縮試験用のコアを採取不能な若材齢吹き付けコンクリートを対象としてその静弾性係数を以下の（ａ）〜（ｄ）工程によって推定することを特徴とするものである。
（ａ）前記若材齢吹き付けコンクリートからなる試料に対して予備試験としてプルアウト試験または針貫入試験を実施して換算圧縮強度を求めるとともに、該予備試験を所定時間間隔で複数回実施して前記試料における材齢と換算圧縮強度との関係を予め求める予備試験工程、
（ｂ）一軸圧縮試験用のコアを採取可能となった若材齢吹き付けコンクリートから前記コアを採取して本試験としての一軸圧縮試験を実施して、該コアの一軸圧縮強度および静弾性係数を求めるとともに、該本試験を所定時間間隔で複数回実施することにより、前記コアにおける材齢と一軸圧縮強度との関係および材齢と静弾性係数との関係を求める本試験工程、
（ｃ）前記予備試験工程により得られた前記試料における材齢と換算圧縮強度との関係、前記本試験工程により得られた前記コアの材齢と一軸圧縮強度との関係および材齢と静弾性係数との関係から、前記試料の換算圧縮強度と静弾性係数との関係を近似する近似曲線を設定する近似曲線設定工程、
（ｄ）前記近似曲線に基づき、前記予備試験により得られた前記試料の換算圧縮強度から該試料の静弾性係数を推定する静弾性係数推定工程。
The present invention is characterized in that the static elastic modulus is estimated by the following steps (a) to (d) for young age shot concrete for which a core for a uniaxial compression test cannot be collected.
(A) Performing a pull-out test or a needle penetration test as a preliminary test on a sample made of the young age shotcrete to obtain a converted compressive strength, and performing the preliminary test a plurality of times at predetermined time intervals. Preliminary test process for obtaining in advance the relationship between age and converted compressive strength in
(B) The core is sampled from the young-aged sprayed concrete that is capable of collecting a core for a uniaxial compression test, and a uniaxial compression test as a main test is performed. And a main test step for determining the relationship between the age of the core and the uniaxial compressive strength and the relationship between the age of the material and the static elastic modulus by performing the main test a plurality of times at predetermined time intervals.
(C) Relationship between age and converted compressive strength in the sample obtained by the preliminary test step, relationship between age and uniaxial compressive strength of the core obtained by the main test step, and age and static elasticity From the relationship with the coefficient, an approximate curve setting step for setting an approximate curve that approximates the relationship between the converted compressive strength and the static elastic modulus of the sample,
(D) A static elastic modulus estimation step of estimating the static elastic modulus of the sample from the converted compressive strength of the sample obtained by the preliminary test based on the approximate curve.
本発明によれば、吹き付け直後の吹き付けコンクリートに対して予備試験としてのプルアウト試験あるいは針貫入試験を実施した後に、本試験としての一軸圧縮試験を実施することにより、静弾性係数を直接的に求めることができないような若材齢の吹き付けコンクリートについてもその静弾性係数を精度よく推定することが可能であり、したがって吹き付けコンクリートの吹き付け直後における剛性を精度良く把握することが可能となる。 According to the present invention, after performing a pull-out test or a needle penetration test as a preliminary test on sprayed concrete immediately after spraying, a static elastic modulus is directly obtained by performing a uniaxial compression test as a main test. It is possible to accurately estimate the static elastic modulus of young age shotcrete that cannot be obtained. Therefore, it is possible to accurately grasp the stiffness immediately after spraying of shotcrete.
以下、本発明の静弾性係数推定方法の実施形態について説明する。
本実施形態は、静弾性係数を求めるための一軸圧縮試験用のコアを採取することができず、したがって一軸圧縮試験により静弾性係数を直接的には求めることのできないような若材齢吹き付けコンクリートを対象として、予備試験としてプルアウト試験（または針貫入試験）と本試験としての一軸圧縮試験を順次実施することによって、その結果から若材齢吹き付けコンクリートの静弾性係数を推定することを主眼とするものである。
Hereinafter, embodiments of the static elastic modulus estimation method of the present invention will be described.
In this embodiment, a young age shotcrete that cannot obtain a core for a uniaxial compression test for obtaining a static elastic modulus, and therefore cannot obtain a static elastic modulus directly by a uniaxial compression test. Focusing on the estimation of the static elastic modulus of young age shotcrete from the results of the pull-out test (or needle penetration test) as a preliminary test and the uniaxial compression test as the main test. Is.
そのための準備工程として、吹き付けコンクリートの施工時には、後段で本試験として実施する一軸圧縮試験用のコアを採取するための箱吹き作業を実施すると同時に、予備試験として実施するプルアウト試験（あるいは針貫入試験）用の試験体を作製するために試料採取皿にも吹き付けを行っておく。 As a preparatory process for this purpose, during the construction of shotcrete, a pull-out test (or a needle penetration test) is carried out as a preliminary test at the same time as a box blowing operation for collecting a core for a uniaxial compression test carried out as a final test in the subsequent stage In order to prepare a test specimen for), the sample collection dish is also sprayed.
（ａ）予備試験工程
吹き付け直後で一軸圧縮試験用のコアを採取できない段階では、吹き付け直後からコアを採取可能となる時点まで、予備試験としてのプルアウト試験を所定時間間隔で実施して各時点での試料の換算圧縮強度を求め、たとえば図１に示すような材齢と換算圧縮強度との関係を求めておく。
予備試験としてのプルアウト試験の試験間隔は、たとえば１０分後、１時間後、その後は実施工サイクルより施工時の吹き付け直後から次の掘削までの時間間隔から設定することとし、この予備試験を少なくとも一軸圧縮試験用のコアを採取可能となるまで繰り返す。コアが採取可能となる目安としては、吹き付けコンクリートの強度がたとえば10N/mm2程度に達するまで、あるいは材齢が約１日となるまでとすれば良い。
(A) Preliminary test process At the stage where a core for a uniaxial compression test cannot be collected immediately after spraying, a pull-out test as a preliminary test is performed at predetermined time intervals from immediately after spraying until the core can be sampled. For example, the relationship between the age of the sample and the converted compressive strength as shown in FIG. 1 is obtained.
The test interval of the pull-out test as a preliminary test is set, for example, after 10 minutes, 1 hour, and thereafter from the time interval from immediately after spraying during construction to the next excavation from the execution cycle. Repeat until uniaxial compression test core can be collected. As an indication that the core can be collected, it is sufficient that the strength of the sprayed concrete reaches, for example, about 10 N / mm 2 or the age of the material reaches about 1 day.
なお、予備試験としてはプルアウト試験に代えて針貫入試験を実施することも可能であり、その場合も同様の時間間隔で針貫入試験を繰り返し、その結果を図１と同様に材齢と換算圧縮強度との関係として求めておく。 As a preliminary test, it is also possible to carry out a needle penetration test in place of the pull-out test. In this case as well, the needle penetration test is repeated at the same time interval, and the result is converted to age in terms of age as in FIG. Obtained as a relationship with strength.
（ｂ）本試験工程
コアが採取可能となったら、箱吹きしておいた吹き付けコンクリートからコア採取用のボーリング機器を用いてコアを採取し、このコアに対して本試験としての一軸圧縮試験を実施する。この本試験も所定の時間間隔で複数回実施して各時点でのコアの一軸圧縮強度を求め、その結果を図２に示すような材齢と一軸圧縮強度との関係として求めておく。
また、同時に、コアに対する載荷荷重に伴う歪みを計測して応力−歪み関係を求めることにより、各時点でのコアの静弾性係数を求め、その結果を図３に示すように材齢と静弾性係数との関係として求めておく。
(B) Main test process When the core can be sampled, the core is sampled from the sprayed concrete that has been blown into the box using a core-collecting boring device, and this core is subjected to a uniaxial compression test as the main test. carry out. This test is also performed a plurality of times at predetermined time intervals to determine the uniaxial compressive strength of the core at each time point, and the result is determined as the relationship between the age of material and the uniaxial compressive strength as shown in FIG.
At the same time, the stress associated with the loading load on the core is measured to determine the stress-strain relationship, thereby obtaining the static elastic modulus of the core at each time point. The results are shown in FIG. Obtained as a relationship with the coefficient.
（ｃ）近似曲線設定工程
上記の本試験工程により得られたコアに対する材齢と一軸圧縮強度との関係、および材齢と静弾性係数との関係から、図４に示すような一軸圧縮強度と静弾性係数との関係をプロットし、それに基づき、上記の予備試験工程により得られたコア採取以前の試料に対する材齢と換算圧縮強度との関係も考慮した近似曲線を設定する。
その近似曲線は、一軸圧縮試験により求めたコアの一軸圧縮強度と静弾性係数との関係をコア採取以前の試料まで敷衍して、その関係をコア採取以前の試料の換算圧縮強度と静弾性係数との関係として表すものとなる。
(C) Approximate curve setting step From the relationship between the age of the core and the uniaxial compressive strength with respect to the core obtained by the above main test step, and the relationship between the age and the static elastic modulus, the uniaxial compressive strength as shown in FIG. Based on the plot of the relationship with the static elastic modulus, an approximate curve is set in consideration of the relationship between the age of the sample obtained before the core sampling obtained by the preliminary test step and the reduced compressive strength.
The approximate curve shows the relationship between the uniaxial compressive strength of the core obtained by the uniaxial compression test and the static elastic modulus up to the sample before core collection, and the relationship is expressed as the converted compressive strength and static elastic modulus of the sample before core collection It will be expressed as a relationship.
その近似曲線としては、圧縮強度をσｃ、求めるべき静弾性係数をＥとすれば、コンクリートの強度と弾性係数との関係式に準じて Ｅ＝ａ・σc ｂ として、上記各試験によるデータから上式における係数ａ、ｂを決定すれば良い。
上式における係数ｂはコンクリートの分野では一般にｂ＝0.5とされるが、必ずしもそれが適切ではない場合もあり、そのため、最小自乗法により最適な係数を求めることが好ましい。そのためには、上式において両辺で対数をとり、線形式に置き換えて係数ａ，ｂを決定するか、あるいは図５に示すように係数ｂを０から１まで変化させたときの最小自乗を計算して、そのときの相関係数Ｒの２乗が最も１に近くなるように係数ａ，ｂを決定すれば良い。
As an approximate curve, if the compressive strength is σ c and the static elastic modulus to be obtained is E, E = a · σ c b according to the relational expression between the strength and elastic modulus of concrete, Thus, the coefficients a and b in the above equation may be determined.
The coefficient b in the above equation is generally set to b = 0.5 in the concrete field. However, it may not always be appropriate. Therefore, it is preferable to obtain an optimum coefficient by the method of least squares. For this purpose, logarithm is taken on both sides in the above equation and the coefficients a and b are determined by replacing them with the linear form, or the least square when the coefficient b is changed from 0 to 1 as shown in FIG. 5 is calculated. Then, the coefficients a and b may be determined so that the square of the correlation coefficient R at that time is closest to 1.
（ｄ）静弾性係数設定工程
図４に示した近似曲線を用いて、予備試験により求めた試料の換算圧縮強度からその静弾性係数を推定する。
具体的には、たとえば、予備試験により得られている試料の換算圧縮強度が約6N/mm2である場合、図６に示すようにそのデータを横軸に代入することにより、その試料の静弾性係数は約8kN/mm2と推定することができる。
(D) Static elastic coefficient setting step The static elastic coefficient is estimated from the converted compressive strength of the sample obtained by the preliminary test using the approximate curve shown in FIG.
Specifically, for example, when the converted compressive strength of the sample obtained by the preliminary test is about 6 N / mm 2 , the static value of the sample is obtained by substituting the data into the horizontal axis as shown in FIG. The elastic modulus can be estimated to be about 8 kN / mm 2 .
以上のように、本発明によれば、一軸圧縮試験用のコアを採取することができず、したがって静弾性係数を一軸圧縮試験によっては直接的に求めることができないような若材齢の吹き付けコンクリート、たとえば上述したように強度が10N/mm2以下、あるいは材齢が１日以下であるような若材齢の吹き付けコンクリートについても、その静弾性係数を精度よく推定することが可能である。 As described above, according to the present invention, young age shotcrete that cannot obtain a core for a uniaxial compression test and therefore cannot obtain a static elastic modulus directly by a uniaxial compression test. For example, as described above, it is possible to accurately estimate the static elastic modulus of young age sprayed concrete whose strength is 10 N / mm 2 or less or whose age is 1 day or less.
また、本発明は吹き付けコンクリートの施工後に周知のプルアウト試験あるいは針貫入試験と周知の一軸圧縮試験を現場にて繰り返すことのみで容易にかつ簡便に実施することが可能であるから、トンネル掘削に際して吹き付けコンクリートによる支保工の剛性を確実に把握でき、それにより支保工の安定性を適切に評価可能である。
したがって本発明は、特に特許文献１に示されるような早期に強度発現する特殊なコンクリート材料によって支保工を施工しつつトンネルを効率的に掘削する特殊なトンネル工法において支保工の安定性を評価するための手法として有効である。
In addition, the present invention can be easily and simply carried out by repeating a well-known pull-out test or needle penetration test and a well-known uniaxial compression test at the site after construction of sprayed concrete. The rigidity of the support work with concrete can be grasped reliably, and the stability of the support work can be evaluated appropriately.
Therefore, the present invention evaluates the stability of the support in a special tunnel construction method in which the tunnel is efficiently excavated while the support is constructed with a special concrete material that expresses strength at an early stage as disclosed in
Claims (1)
（ａ）前記若材齢吹き付けコンクリートからなる試料に対して予備試験としてプルアウト試験または針貫入試験を実施して換算圧縮強度を求めるとともに、該予備試験を所定時間間隔で複数回実施して前記試料における材齢と換算圧縮強度との関係を予め求める予備試験工程、
（ｂ）一軸圧縮試験用のコアを採取可能となった若材齢吹き付けコンクリートから前記コアを採取して本試験としての一軸圧縮試験を実施して、該コアの一軸圧縮強度および静弾性係数を求めるとともに、該本試験を所定時間間隔で複数回実施することにより、前記コアにおける材齢と一軸圧縮強度との関係および材齢と静弾性係数との関係を求める本試験工程、
（ｃ）前記予備試験工程により得られた前記試料における材齢と換算圧縮強度との関係、前記本試験工程により得られた前記コアの材齢と一軸圧縮強度との関係および材齢と静弾性係数との関係から、前記試料の換算圧縮強度と静弾性係数との関係を近似する近似曲線を設定する近似曲線設定工程、
（ｄ）前記近似曲線に基づき、前記予備試験により得られた前記試料の換算圧縮強度から該試料の静弾性係数を推定する静弾性係数設定工程。 Static elastic modulus of young age shotcrete characterized by estimating its static elastic modulus by the following steps (a) to (d) for young age shotcrete for which a core for uniaxial compression test cannot be collected. Estimation method.
(A) Performing a pull-out test or a needle penetration test as a preliminary test on a sample made of the young age shotcrete to obtain a converted compressive strength, and performing the preliminary test a plurality of times at predetermined time intervals. Preliminary test process for obtaining in advance the relationship between age and converted compressive strength in
(B) The core is sampled from the young-aged sprayed concrete that is capable of collecting a core for a uniaxial compression test, and a uniaxial compression test as a main test is performed. And a main test step for determining the relationship between the age of the core and the uniaxial compressive strength and the relationship between the age of the material and the static elastic modulus by performing the main test a plurality of times at predetermined time intervals.
(C) Relationship between age and converted compressive strength in the sample obtained by the preliminary test step, relationship between age and uniaxial compressive strength of the core obtained by the main test step, and age and static elasticity From the relationship with the coefficient, an approximate curve setting step for setting an approximate curve that approximates the relationship between the converted compressive strength and the static elastic modulus of the sample,
(D) A static elastic modulus setting step of estimating the static elastic modulus of the sample from the converted compressive strength of the sample obtained by the preliminary test based on the approximate curve.
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| JP2023053381A (en) * | 2018-09-07 | 2023-04-12 | 鹿島建設株式会社 | Stress measurement method |
| JP7559303B2 (en) | 2021-07-29 | 2024-10-02 | 大成建設株式会社 | Method for determining equivalent elastic modulus of shotcrete |
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