JP4641456B2 - Test hammer for underwater evaluation and concrete compressive strength evaluation method - Google Patents

Description

  The present invention relates to a test hammer for underwater evaluation useful for quality evaluation of underwater concrete, and a concrete compressive strength evaluation method capable of nondestructively evaluating the quality of underwater concrete.

  In recent years, the collapse of buildings and the like due to earthquakes has continued in Japan, and there is an increasing interest in the durability of these structures, especially their aging (aging) and early deterioration. And from such a background, a technique for rationally maintaining and managing a concrete structure has attracted particular attention.

  In general, the maintenance and management of concrete structures is performed by first assessing the current state of concrete structures, that is, the quality of the concrete that is the material, and determining whether repair or reinforcement is necessary based on the evaluation results. Has been done. That is, in order to realize rational maintenance of a concrete structure, it is indispensable to accurately grasp (evaluate) the quality of the concrete constituting the concrete structure.

  One method for evaluating the quality of concrete is to extract a part of the concrete structure to be evaluated as a test core (test body) and perform various tests such as strength tests and composition analysis on the test core. Are known. However, since this method is a so-called destructive inspection performed by damaging the concrete structure to be evaluated, it is not preferable because it involves a decrease in strength and a deterioration in scenery.

  Thus, conventionally, a method (test hammer method) has been proposed in which the surface of concrete is hit with a test hammer and the compressive strength is estimated from the degree of repulsion (see Patent Literatures 1 to 4). According to this method, it is possible to easily evaluate the quality (specifically, the compressive strength) of the concrete constituting the concrete structure in a non-destructive manner, and at present, this method is mainstream. Hereinafter, the test hammer method and the structure of the test hammer used in this method will be further described with reference to FIGS. FIG. 14 is a cross-sectional view schematically showing the schematic structure of the test hammer as a state before measurement, and FIGS. 15A to 15D show the measurement procedure of the test hammer method using the hammer. It is a schematic diagram shown.

  As shown in FIG. 14, this test hammer is roughly composed of a casing 1 having a protrusion T at the rear end, and a spring (biasing means) 2 having one end fixed to the front end in the casing 1. And a hammer body 3 connected to the other end of the spring 2 and a plunger 4 disposed so as to be accommodated in the protruding direction based on relative movement (sliding movement) with respect to the housing 1. ing. Specifically, a slide member 6 fixed to the rear end of the housing 1 via a spring 5 enables the plunger 4 to slide. Before the measurement, the hammer body 3 is locked to the slide member 6 by the hook of the locking tool 7. Furthermore, a stop button 8 for fixing the sliding movement of the plunger 4 in the housing 1 and a scale 9 indicating the sliding position of the plunger 4 are provided.

  And when actually measuring with such a test hammer, the said plunger 4 is first slid and this is made into the fully extended state. Then, the hammer body 3 is hooked on the hook of the locking tool 7 and fixed to the slide member 6.

  Next, in this state, as shown in FIG. 15A, the concrete structure to be evaluated is brought into contact with the tip of the plunger 4 protruding from the housing 1. Next, as shown in FIG. 15B, the plunger 4 is slid and accommodated in the housing 1 by further pressing the evaluation target side. Thus, when the plunger 4 slides until the locking tool 7 hits the protrusion T provided at the rear end of the casing 1, as shown in FIG. The hammer body 3 biased by the spring 2 collides with the plunger 4. Then, the evaluation object is hit by the plunger 4 that has received this collision, and as shown in FIG. 15D, the plunger 4 is pushed back into the housing 1 (accommodated by the repulsion of the evaluation object). ) Then, by reading (measuring) the position (return amount) of the plunger 4 from the scale 9 as the repulsion degree of the evaluation object, the quality of the concrete structure from the position of the plunger 4 (repulsion degree of the evaluation object). (Compressive strength) is evaluated. At this time, the reading (measurement) of the position (return amount) of the plunger 4 is performed after fixing the sliding movement of the plunger 4 by the stop button 8 after striking to avoid position fluctuation after striking (repulsion). To do.

  Regarding this test hammer method, Japanese Industrial Standard (JIS) “A1153-2003 / Measurement Method of Rebound of Concrete” and Japan Society of Civil Engineers Standard (JSCE) “504-1999 / Hardness Test of Hardened Concrete” The “Method” also defines the test method.

Conventionally, as a method for nondestructive concrete quality evaluation, in addition to the test hammer method, an ultrasonic method is known.
Japanese Patent Laid-Open No. 10-142125 Japanese Patent Laid-Open No. 2004-28624 JP 2004-233372 A JP 2004-239852 A

  Thus, according to the test hammer method described in detail above, it is possible to evaluate the quality of the concrete structure without fail. However, this test hammer method is only supposed to be used on land, and underwater, water penetrates into the casing, and the movement of the hammer body is hindered by the influence of water resistance and the like, so that it does not operate normally. In addition, even when an ultrasonic method is employed, such a method has to rely on an electronic measuring instrument for measurement, and there are many restrictions in water. In addition, the cost of the measuring instrument itself is high, and there are also disadvantages that the measurement becomes large and the measurement cannot be performed easily. For this reason, when it is going to measure the quality of the concrete which comprises a concrete structure non-destructively in water, it exists in the situation which must rely on the destructive inspection etc. which were mentioned above after all.

  However, in order to rationally maintain and manage the concrete structure, the quality evaluation of the underwater part of the concrete structure is as important as the quality evaluation of the land part. In fact, there are many concrete structures such as water and sewage facilities as lifelines, harbor facilities, dams, bridges, etc. that are always underwater in these facilities. From the viewpoint of facility management, it is desirable to quantitatively evaluate the quality of parts. In addition, some of these facilities are buried underground. For example, in storage tanks buried underground, it can be measured only from the inside (underwater). This is one of the reasons for the realization of underwater evaluation of concrete. However, when a completely different method from the already established test hammer method is adopted as an on-shore evaluation technique, there is also a problem that many disadvantages are involved. First, the measurement instrument must be developed from scratch, which requires great effort, time, and cost. Secondly, the measurement data and measurement know-how of the test hammer method accumulated so far are wasted.

  The present invention has been made in view of such circumstances, and based on the test hammer method that has already been established as a simple evaluation technique on land, quality evaluation of concrete that constitutes a concrete structure nondestructively in water. It is an object of the present invention to provide a test hammer for underwater evaluation and a method for evaluating concrete compressive strength, which can be carried out suitably and smoothly.

  In order to achieve such an object, in the invention described in claim 1, the underwater evaluation test hammer used in the above-described test hammer method includes a housing, a plunger, and a hammer body, and protrudes from the housing. A hammer body biased in the casing based on the fact that the plunger is slid and accommodated in the casing by further pressing the evaluation target from the state in which the evaluation target is in contact with the tip of the plunger. A hammer body that measures the degree of repulsion of the evaluation object with respect to a hit applied to the evaluation object via the plunger by colliding with the plunger, an encapsulating part that encapsulates the hammer body, and an encapsulating part The hammer main body is water-tightly sealed with a seal portion that slidably seals between the formed plunger projection and the plunger. A structure comprising a water-resistant closed container.

  As mentioned above, existing land-type test hammers are not waterproof, so if you put the test hammer in the water as it is, water will enter the inside of the test hammer housing, and the resistance of the water will cause the measurement. The movement of the hammer body will be hindered. In this respect, in the test hammer (hammer structure), the hammer body is sealed, so that water does not enter the housing. In other words, if such a structure is adopted, the existing land-type test hammer is used as it is in the water, and it is not submerged in the water based on the test hammer method that has already been established as a simple evaluation technique on land. It becomes possible to perform the quality evaluation of the concrete which comprises a concrete structure by destruction suitably and smoothly.

Also, for the previous SL water sealed container, and the predetermined gap between the hammer body and encapsulation part is formed structure.

By providing such a gap, buoyancy works in the water, and it becomes lighter and easier to handle.
However, if the gap is set too large, there is a concern that another problem (problem) may occur. That is, there is a problem that when the hand is released from the hammer underwater, the hammer will be lifted. When such a test hammer for underwater evaluation is used underwater, it is assumed that the work is carried out underwater with an air cylinder on its back. Therefore, the work was actually carried with the air cylinder on its back. As a result, in a situation where the hammer is lifted by buoyancy when the hand is accidentally released during the work, it is still difficult for the worker (diver) to perform measurement while maintaining a stable posture in water.

Accordingly, the inventors in order to solve these problems (problem) is the weight of those the test hammer is W, the density of water [rho, wherein the volume of the housing of the hammer body VM, the housing of the hammer body water When the volume difference from the sealed container is VS and the volume of the plunger is VP, the relational expression “(VS / VP) ≦ (W / (ρ × VP)) − (VM / VP) −1” holds. A test hammer for underwater evaluation was devised.

  Specifically, when the gravitational acceleration is g, the buoyancy acting on the test hammer can be expressed as “ρ × (VM + VS + VP) × g”. On the other hand, the gravity acting on the test hammer can be expressed as “W × g”. That is, in order to prevent the test hammer from rising, a relational expression “ρ × (VM + VS + VP) × g ≦ W × g” may be satisfied. When this relational expression is modified, the above-mentioned “(VS / VP) ≦ (W / (ρ × VP)) − (VM / VP) −1” is obtained. That is, according to the above structure, the above-described problem (problem) that the hammer is lifted can be accurately solved based on the principle and the principle basis. Assuming use in the sea, there are many obstacles such as seaweeds and fish nets in the water. At this time, if the test hammer is fixed to an operator (diver) with a rope or the like in an attempt to prevent the release of the hammer, there is a high possibility that the work will be disturbed. In order to avoid such inconveniences, the above structure is significant. In consideration of further improving the workability at the time of measurement, the condition “(VS / VP) = (W / (ρ × VP)) − (VM / VP) where neither lift nor sink (becomes neutral buoyancy)” It is more desirable that the structure is such that) -1 "is established.

Further, according to the above Ki構 granulation, also to be suppressed Another disadvantage confirmed by underwater experiments. This is a problem that a slide failure (freeze phenomenon) occurs in the plunger. Specifically, when working in water using one form of the above-described test hammer for underwater evaluation, the plunger is difficult to slide (freezes) and cannot be fully extended when preparing for measurement. Was confirmed. However, as above Ki構 concrete, said by providing a predetermined gap between the hammer body and encapsulation section, the slide failure (freeze phenomenon) was found to not occur.

Furthermore, as a result of the inventor's repeated examination of the freeze phenomenon, the following failure generation mechanism was able to be derived.
That is, the plunger that strikes the evaluation target is in a state of being slidably accommodated in the housing of the hammer body after measurement. In order to perform the next measurement, this must be fully extended. Therefore, before starting the measurement, an operation of returning the plunger to the fully extended state is performed. Although this work can be performed without any problem on land, when this is performed in an environment where there is no air (atmosphere) in the surroundings or in water, pressure fluctuations occur in the housing of the hammer body. Specifically, the interior of the hammer body sealed on land is normally sealed at atmospheric pressure (approximately 1 atmosphere). When the plunger is slid in this sealed state and returned to the fully extended state, the volume (volume) of the hammer body within the housing increases rapidly by the volume of the plunger that has been slid out of the housing. The pressure of the is reduced (the well-known Boyle-Charles law).

As a result of such a phenomenon (decrease in pressure in the housing), the inventor attracted the waterproof seal member provided in the plunger projecting port to the inside of the watertight sealed container (pressed by water pressure), and the waterproof seal member is thus tightening the plunger itself strongly to become (seal member enhances a sealing function as attempt to prevent flooding), so caused is frozen phenomenon described above, i.e., the front Symbol hammer body and said water-sealed container By providing a predetermined gap in between, this pressure decrease can be suppressed low, and as a result, the above-described freeze phenomenon is considered not to occur even when the above-described preparatory work is performed in water.

  And even if this mechanism is further developed and a gap is provided between the hammer body and the watertight sealed container, it is caused by the pressure fluctuation in the housing of the hammer body accompanying the slide movement of the plunger described above. As a result, the pressure balance is lost between the gap (outside the casing) and the space inside the housing of the hammer body (inside the casing), causing gas to move from the outside gap to the inner space. For example, it was considered that the pressure in the outer space outside the casing would eventually decrease, and the above-mentioned waterproof seal member might be attracted.

Based on the analysis of the failure occurrence mechanism, if the volume difference (volume of the void outside the housing) VS between the housing of the hammer body and the watertight sealed container is set larger than the volume VP of the plunger, voids can be suppressed low pressure decreased (housing outer voids), the result, even when performing the preparatory work described above in water, thought not occur freeze phenomenon described above, the housing of the previous SL hammer body wherein When the volume difference from the watertight sealed container is VS and the volume of the plunger is VP, the volume ratio represented by the relational expression “VS / VP” does not cause a slide failure (freeze phenomenon) in the plunger in water. We have devised a test hammer for underwater evaluation that is set to a large extent. In the inventor's experiment, a nitrile oil seal was used as the seal part, and the volume ratio represented by the relational expression “VS / VP” was set to “4”. It has been confirmed that the quality evaluation of concrete constituting a concrete structure can be performed smoothly and non-destructively up to a water depth of 20 m, without causing the above-mentioned freeze phenomenon. Based on the experimental results, when the volume ratio is “4”, it is estimated that the freeze phenomenon will not occur until around 30 m. Further, the volume ratio is not limited to “4”, and if it is “3” or more, the freeze phenomenon can be avoided. However, a more preferable operation can be obtained when the volume ratio is “4” or more.

Moreover, since the volume (volume) in an airtight container becomes large by providing a space | gap, the pressure change accompanying the slide movement of a plunger in water becomes small (the well-known Boyle-Charles law). Therefore, according to the above Ki構 granulation, it is possible to slide the plunger with a small force (projecting and retracting) become more easy such operations to return to the state in which stretched and thus before the start of measurement plunger.

Additionally, water or deeper, with or shallow, when considering the use of in place like depths are significantly different, such as by the invention of claim 2, for underwater evaluated according to the claim 1 In the test hammer, it is effective to have a structure in which the enveloping part is provided with an intake valve and an exhaust valve that adjust the pressure in the watertight sealed container.

In this way, if an intake valve (for pressurization) and an exhaust valve (for decompression) that adjust the pressure inside the container (particularly the pressure of the gap outside the casing) are provided for the watertight sealed container, the intake valve By increasing the pressure in the container through, the freeze phenomenon described above can be prevented as in the first aspect of the invention. Moreover, according to such a structure, when excessive intake is performed through the intake valve, the pressure in the container can be adjusted to an appropriate pressure through the exhaust valve. In actual use, a hose is connected to the intake valve, and pressurization is performed by, for example, a breathing air cylinder carried by the operator himself. And if the pressure in the said water-resistant airtight container is adjusted so that it may become optimal for every work place corresponding to the water pressure which changes with water depth, the freeze phenomenon mentioned above will be prevented more reliably. Specifically, for example, when working from a deep place to a shallow place, the deeper the water, the higher the water pressure, so the air in the container can go out and water can enter the container instead. There is sex. Even in such a case, according to the above structure, water can be prevented from entering the container by reducing the pressure by the exhaust valve. In addition, in order to smoothly adjust the pressure, these intake valves and exhaust valves are valves that automatically open and close to automatically adjust the pressure in the container to a predetermined set value (usually It is more effective to use a reverse valve.

On the other hand, in the invention according to claim 3, as a method based on measurements of the repulsion degree to the test hammer exerted when struck concrete to be evaluated, evaluating the compressive strength of concrete is the evaluation target, wherein The step of hitting the concrete that is the object of evaluation in the water by the test hammer for underwater evaluation according to Item 1 or 2, and measuring the degree of repulsion to the test hammer for underwater evaluation, and the desired relationship by the test hammer for underwater evaluation Based on the relational expression between the degree of repulsion in the water and the compressive strength of the concrete for the relational expression obtained in advance by hitting the concrete for concrete in the water, the degree of repulsion to the test hammer for the underwater evaluation is evaluated as above. And a step of converting into the compressive strength of the target concrete.

By the way, when evaluating the quality of a concrete structure using an underwater evaluation test hammer produced by waterproofing a land evaluation test hammer including the underwater evaluation test hammer according to claim 1 or 2. Since the structure of the test hammer is different from the existing test hammer for onshore evaluation and the measurement environment is also greatly different, the relational expression between the degree of repulsion on the existing land and the compressive strength of concrete cannot be used. In this regard, as in the above method, if the relational expression is obtained by performing the hitting on the concrete for the relational expression in water in advance, the concrete is compressed with higher accuracy based on the more accurate relational expression. The intensity can be measured. Even when the same type of underwater evaluation test hammer is used, accurate evaluation (compressive strength) cannot be obtained due to structural differences of these test hammers due to changes in the use hammer. Is concerned. In this case, by obtaining a relational expression between the degree of repulsion and the compressive strength for each test hammer, it is possible to measure the compressive strength more accurately without depending on the evaluation variation occurring between the test hammers. Such a measuring method is particularly effective when applied to the test hammer having a water-resistant airtight container.

Further, from the viewpoint of the manufacturing method, based on the data of the underwater test, the equation “(volume difference VS between the housing of the hammer body and the watertight sealed container) / (volume of the plunger VP)” is used. It is effective to adopt a method of designing the shape of the watertight sealed container so that the volume ratio expressed is increased to such an extent that no sliding failure (freeze phenomenon) occurs in the plunger. According to such a manufacturing method, for example, according to the above-described claim 1 or 2 , only by designing the shape of the newly added watertight sealed container without adding any hand to the design of the hammer body (existing hammer). Based on the test hammer method that has already been established as an on-shore evaluation technology, the quality evaluation of concrete that constitutes a concrete structure in a non-destructive manner in water can be performed suitably and smoothly. Hammer is realized (manufactured).

  On the other hand, the weight of the test hammer is W, the density of water is ρ, the volume of the housing of the hammer body is VM, the volume difference between the housing of the hammer body and the watertight sealed container is VS, and the volume of the plunger Is a method of designing the shape of the watertight sealed container so that the relational expression “(VS / VP) ≦ (W / (ρ × VP)) − (VM / VP) −1” is satisfied. In the same manner, the above-described hammer body (existing hammer) is not modified at all, and only the shape of the newly added watertight sealed container is used. In particular, a test hammer for underwater evaluation excellent in workability at the time of measurement that does not float up is realized (manufactured). As a method for establishing the relational expression “(VS / VP) ≦ (W / (ρ × VP)) − (VM / VP) −1”, the weight of the test hammer is changed by adding a weight or the like. It is conceivable to increase (increase). However, in this case, the test hammer itself becomes heavier, and eventually the workability is deteriorated. In this sense, the significance of this method is great.

  Hereinafter, an embodiment embodying a test hammer for underwater evaluation and a concrete compressive strength evaluation method according to the present invention will be described with reference to FIGS. As shown in FIG. 1, the test hammer according to this embodiment is also configured based on the existing hammer (land evaluation test hammer) as shown in FIG. 14, that is, a so-called Schmitt test hammer. Has been. However, in this test hammer, a water-resistant airtight container is newly provided, so that the test hammer is sealed in a water-resistant manner so as to be encapsulated. As described above, in this embodiment, the existing land type test hammer is used as it is in the water, and the test hammer method already established as a land evaluation technique is performed non-destructively in the water. The quality evaluation of concrete that can be done is realized.

  First, the schematic structure of the test hammer for underwater evaluation will be described with reference to FIGS. 1 and 2. 1 is a cross-sectional view corresponding to FIG. 14, FIG. 2 (a) is a perspective view showing the external structure of the test hammer, and FIG. 2 (b) is a plan view of the test hammer as seen from the plunger projection opening side. FIG. Also, in these drawings, the same elements as those shown in FIG. 14 are denoted by the same reference numerals, and redundant description of these elements is omitted.

  As shown in FIG. 1, this test hammer basically includes a hammer body HM which is the Schmitt test hammer and a water-resistant airtight container VL made of, for example, acrylic. Among these, since the structure of the hammer body HM itself, which is an existing land type test hammer, has already been described in detail, the description thereof is omitted here (see FIG. 14).

  On the other hand, the watertight sealed container VL includes a portion (encapsulating portion) for encapsulating the hammer body HM and a portion (seal portion) for sealing a portion communicated to the outside in order to maintain a sealed state. Has been. Specifically, for example, a waterproof seal member S1 that slidably seals between the protrusion AP and the plunger 4 of the hammer body HM is provided for the plunger protrusion AP. A waterproof seal member S <b> 2 that prevents the intrusion of water while enabling the switching operation of the stop button 8 is provided at the installation location.

  FIG. 3 shows the details of the cross-sectional structure of the test hammer for underwater evaluation, and the waterproof seal structure will be further described. FIG. 4 shows the cross-sectional structure of the test hammer with only the watertight sealed container VL. 3A is a cross-sectional view showing a cross-sectional structure of the test hammer, and FIG. 3B is an enlarged cross-sectional view showing an area A (near the protruding hole for the plunger) in FIG.

  Here, a nitrile oil seal is used for the waterproof seal member S1, and two O-rings are used for the waterproof seal member S2, thereby realizing a waterproof seal that can withstand water pressure at a water depth of “20 m”. Further, by using a sealing member made of a material having sufficient flexibility (here, nitrile type) as the waterproof sealing member S1 of the plunger projection AP, the sliding operation (protruding operation) of the plunger 4 is inhibited. In addition, a sufficient seal (tightness) is secured to prevent water from entering from the outside.

  This test hammer for underwater evaluation provided with such a water-resistant airtight container VL and a hammer body HM is configured such that the hammer body HM is water-tightly sealed in a form encapsulated in the container VL. If the hammer body HM freely moves in the container VL during measurement, the measurement accuracy is affected and the accurate measurement is prevented. Therefore, the hammer body HM is fixed at a predetermined position in the container VL. Yes. Thereby, even if it is a case where it measures repeatedly in water, the reproducibility comes to be ensured. In particular, it is important to adopt such a structure when increasing the number of measurements to improve accuracy.

  In addition, a gap SC is formed between the water-resistant airtight container VL (specifically, its enveloping part) and the hammer body HM. The volume of the gap SC corresponds to the volume difference between the casing 1 of the hammer body HM and the container VL. When this is VS and the volume of the plunger 4 is VP, it is expressed by the relational expression “VS / VP”. The volume ratio is set to “4”. As a result, the quality evaluation of the concrete constituting the concrete structure can be performed smoothly and non-destructively at least up to a water depth of “20 m” where actual work is assumed, without causing the above-described freeze phenomenon. Become. In addition, by providing such a gap SC, it is possible to slide the plunger 4 with a small force, and it becomes easier to return the plunger 4 to the fully extended state before the measurement.

  Furthermore, when the weight of the test hammer for underwater evaluation is W, the density of water is ρ, and the volume of the housing 1 of the hammer body HM is VM, “(VS / VP) = (W / (ρ × VP)”. Each parameter is set so that the relational expression ")-(VM / VP) -1" is satisfied. As a result, the neutral buoyancy that neither lifts nor sinks in water is obtained, the workability in water is greatly improved, and the rebound degree can be measured extremely smoothly.

Further, in this embodiment, when manufacturing the test hammer for underwater evaluation,
The volume ratio represented by the formula “VS / VP” increases to such an extent that the above-mentioned freeze phenomenon does not occur in the plunger 4 in water (here, “4”).
The relational expression “(VS / VP) = (W / (ρ × VP)) − (VM / VP) −1” is established.
The shape of the watertight sealed container VL is set so as to satisfy the condition. In this way, the test hammer for underwater evaluation is realized (manufactured) only by designing the shape of the newly added water-resistant airtight container VL without making any changes to the design of the hammer body HM (existing hammer). ) Will be. Whether the volume ratio “VS / VP” is large enough not to cause the freeze phenomenon is determined based on the data of the underwater test. The diameter of the plunger to be used in the test hammer method is determined by the Japanese Industrial Standard (JIS) standard.

  Next, a concrete compressive strength evaluation method using the underwater evaluation test hammer will be described. Even when the quality of concrete (specifically, its compressive strength) is evaluated using such a test hammer for underwater evaluation, the procedure is basically the same as that shown in FIGS. 15 (a) to (d). The rebound degree is measured according to the procedure.

  That is, as shown in FIG. 1, with the plunger 4 fully extended, the evaluation object (concrete) is brought into contact with the tip of the plunger 4 and further pressed to the evaluation object side. Then, as shown in FIG. 5, when the locking tool 7 comes into contact with the protrusion T, the hammer body 3 biased in the housing 1 collides with the plunger 4, and the evaluation object is passed through the plunger 4. Since the impact is applied, after the slide movement of the plunger 4 is fixed by the stop button 8, the position (return amount) of the plunger 4 is measured as the degree of repulsion to be evaluated at this time.

  However, since the measurement is performed underwater this time, an optimal measurement method is selected for each measurement location. For example, when working in a deep water place, it is necessary for the worker to work in a breathable state by carrying an air cylinder on his back. In addition, when evaluating concrete quality underwater, the structure of the test hammer is different from that of the existing test hammer for land evaluation, and the measurement environment is also greatly different. Therefore, the degree of repulsion on the existing land and the compressive strength of the concrete Relational expressions cannot be used. For this reason, in this embodiment, the concrete for the relational expression is hit in water in advance, and the relational expression between the degree of repulsion in water and the compressive strength of the concrete for the relational expression is obtained for each test hammer. .

  For details, prepare a specimen (concrete for relational expression), measure the degree of repulsion in water using the test hammer for underwater evaluation, and separately measure the compressive strength of the specimen by an appropriate compression test. Then, a relational expression between the degree of repulsion in water and the compressive strength of the specimen is obtained. In order to secure the generality of such a relational expression, it is desirable to obtain such a relational expression for specimens with a greater variety of concrete blends and for specimens with more ages. Furthermore, it is also effective to perform impact (measurement of the degree of repulsion) on the same specimen under different water pressure environments in order to understand the effect of water pressure on the test hammer, and to correct the water pressure effect as necessary. is there.

  FIG. 6 shows an example of the obtained relational expression (specimen: concrete of age “8 days”). In FIG. 6, the data indicated by the alternate long and short dash line (diamonds) is the measurement result on land by the existing land evaluation test hammer, and the data indicated by the broken line (rectangle) is the underwater evaluation test. The measurement results on land using a hammer and the data indicated by solid lines (triangles) indicate the measurement results in water using the test hammer for underwater evaluation.

  As shown in FIG. 6, measurement data obtained when using an existing land evaluation test hammer, measurement data obtained when using the above-described underwater evaluation test hammer produced by waterproofing, and Then, the measurement results are very different. Moreover, even when the same test hammer for underwater evaluation is used, the measurement result is different between the case of measurement on land and the case of measurement in water, although the degree is small.

  Next, with reference to FIG. 7 to FIG. 13, various experiments and results obtained by the inventor when obtaining such a relational expression will be described in detail. In these experiments, in a water tank adjusted to a desired water pressure by a device (hospital lock) that can artificially adjust the water pressure, according to “JIS A 1155 / Measurement method of rebound degree of concrete”, Stroke (measurement) in the horizontal direction using a test hammer. In addition, a cubic specimen of “300 × 300 × 300 (mm)” was used for the test hammer test, and a cylindrical specimen of “φ100 × 200 (mm)” was used for the compressive strength test.

  FIG. 7 shows the concrete composition and fresh properties of these specimens. As shown in FIG. 7, the water-cement ratio (W / C) was changed by “5%” from “30%” to “75%”, and a total of 10 specimens (for the relationship equation) Concrete) was prepared. Ordinary Portland cement was used as the cement, and a high-performance water reducing agent and AE agent were used as the admixture.

  FIG. 8 is a graph showing a relational expression between the degree of repulsion in water and compressive strength measured using a commercially available test hammer for land evaluation (specimen: ages of “7 days” and “28 days”). concrete). In addition, the curve in a graph is an approximate curve about a measured value.

  On the other hand, FIG. 9 is a graph showing a relational expression between the degree of repulsion and the compressive strength measured using the test hammer for underwater evaluation (see FIGS. 1 to 5) (test specimen: material age “28 days” and “56 days of concrete). In the graph, data indicated by a solid line (rectangle) is a measurement result on land (in the air), and data indicated by a broken line (triangle) is a measurement result in water. Further, the curves (solid lines and broken lines) in the graph are approximate curves for the respective measured values (rectangles and triangles).

  When the two data shown in FIG. 9 are compared, the difference between the two seems to be slight, but when the measured values of the degree of repulsion of the same strength are compared individually, the difference between the two is never It's not small.

  FIG. 10 is a graph showing the relationship between the compressive strength (horizontal axis) of the specimen with the difference in the degree of repulsion of these data as the vertical axis. In general, it is known that the rebound degree of concrete whose surface is wet is smaller than that of concrete whose surface is dry. For this reason, the difference in the rebound degree shown in FIG. 10 is obtained by subtracting the repulsion degree measured in water from the repulsion degree measured on land (in the air). It should be noted that the difference between the obtained degrees of repulsion is negative is not counted.

As shown in FIG. 10, in the range where the compressive strength is “50 (N / mm ² )” or less, the difference in the degree of repulsion is large, and in the range where the compressive strength is “50 (N / mm ² )” or more. Shows a tendency that the difference in the degree of repulsion becomes as small as “0 to 2”. This is considered to be because the concrete structure becomes denser as the strength becomes higher, and the water content in the surface layer portion becomes smaller.

  Fig. 11 shows the relationship between the degree of rebound on the land (in the air) and the compressive strength (specimen: concrete with age 28 days) measured with a land evaluation test hammer (circular, solid line). It is a graph which compares and shows the measurement result when measuring with a test hammer for underwater evaluation (rectangle, broken line). In addition, the curve (a solid line and a broken line) in a graph is an approximate curve about each measured value (circle and a rectangle).

  As shown in FIG. 11, the degree of repulsion at the same strength of both of them tends to be larger in the underwater evaluation test hammer than in the land evaluation test hammer as the compressive strength of the specimen increases. confirmed. This is thought to be due to structural changes that occurred when the test hammer was waterproofed.

FIG. 12 is a graph showing a relational expression between the degree of repulsion and the compressive strength measured using the above-described test hammer for underwater evaluation as in FIG. 9 (Specimen: Age “28 days” and “56 days”). "Concrete). However, about the measurement result in water, the approximated curve calculated | required by the method different from FIG. 9 is shown. Specifically, the study on the graph of the previous Figure 10, the compressive strength "50 (N / mm ^2)" hereinafter range and compressive strength of "50 (N / mm ^2)" separately and more ranges, for these ranges An approximate curve was obtained for each. By doing so, a more accurate relational expression that takes into account the surface condition of the concrete can be obtained.

  Moreover, FIG. 13 is a table | surface which shows the experimental result regarding the influence of water pressure (specimen: concrete of material age "50 days"). Specifically, it is the result of measuring the degree of repulsion by changing the water pressure applied to the concrete in the water and using the test hammer for underwater evaluation.

As shown in FIG. 13, from “0 (N / mm ² )” (water pressure corresponding to a water depth “0 m”) to “0.09 (N / mm ² )” (water pressure corresponding to a water depth “9 m”), Even if it is changed to “0.20 (N / mm ² )” (water pressure corresponding to a water depth of “20 m”), only a maximum of “5%” can be generated. That is, it is possible to evaluate the quality of concrete using the same relational expression as long as the depth is at least in the range of “0 to 20 (m)”.

As described above, according to the test hammer for underwater evaluation and the concrete compressive strength evaluation method according to this embodiment, the following excellent effects can be obtained.
(1) As a test hammer for underwater evaluation that evaluates the quality of concrete underwater based on the test hammer method, a structure including a Schmitt-type hammer body HM and a water-resistant airtight container VL that waterproofly seals the hammer body HM. . And this water-resistant airtight container VL shall be comprised including the encapsulation part which encapsulates the hammer main body HM, and the seal part which seals the plunger 4 slidably by the protrusion opening AP for plungers. . As a result, the existing onshore type test hammer is used in water as it is, and a non-destructive concrete structure is constructed underwater based on the test hammer method already established as a simple evaluation technique on land. It becomes possible to perform the quality evaluation of concrete to be performed suitably and smoothly.

  (2) About the said water-resistant airtight container VL, a predetermined space | gap was formed between the said to-be-encapsulated part and the hammer main body HM. Thereby, buoyancy works underwater, and it becomes light by that much, and it becomes easy to handle a test hammer. Further, by providing the gap, the plunger 4 can be slid and moved (projected and retracted) with a small force, so that the operation of returning the plunger 4 before starting measurement to the fully extended state becomes easier.

  (3) The hammer body HM is fixed at a predetermined position in the water-resistant airtight container VL. Thereby, even if it is a case where it measures repeatedly in water, the reproducibility comes to be ensured.

  (4) When the volume difference between the housing 1 of the hammer body HM and the container VL is VS and the volume of the plunger 4 is VP, the volume ratio represented by the relational expression “VS / VP” is “4”. It was decided to set. As a result, the quality evaluation of the concrete constituting the concrete structure can be performed smoothly and non-destructively at least up to a water depth of “20 m” where actual work is assumed, without causing the above-described freeze phenomenon. Become.

  (5) When the weight of the test hammer for underwater evaluation is W, the density of water is ρ, and the volume of the housing 1 of the hammer body HM is VM, “(VS / VP) = (W / (ρ × VP)” Each parameter was set so that the relational expression “)-(VM / VP) −1” was established. As a result, the neutral buoyancy that neither lifts nor sinks in water is obtained, the workability in water is greatly improved, and the rebound degree can be measured extremely smoothly.

  (6) When the test hammer for underwater evaluation is manufactured, based on the data of underwater test, the volume ratio represented by the formula of “VS / VP” may cause the above-described freeze phenomenon in the plunger 4 in water. The shape of the water-resistant airtight container VL is set so as to be as large as possible (here, “4”). In addition, the shape of the watertight sealed container VL is set so that the relational expression “(VS / VP) = (W / (ρ × VP)) − (VM / VP) −1” is satisfied. . In this way, the test hammer for underwater evaluation is realized (manufactured) only by designing the shape of the newly added water-resistant airtight container VL without making any changes to the design of the hammer body HM (existing hammer). ) Will be.

  (7) The concrete for the relational expression was hit in water, and the relational expression between the degree of repulsion in water and the compressive strength of the concrete for the relational expression was determined in advance for each test hammer. Thereby, the compressive strength of concrete can be measured with higher accuracy based on a more accurate relational expression. In addition, since the relational expression between the degree of repulsion and the compressive strength is obtained for each test hammer, it is possible to measure the compressive strength more accurately without depending on the evaluation variation occurring between the test hammers.

(8) Dividing a range below a predetermined compressive strength (here, “50 (N / mm ² )”) and a range beyond this range, and calculating an approximate curve for each range, the concrete surface condition is also taken into consideration. A more accurate relational expression can be obtained.

The embodiment described above may be modified as follows.
-It can also be set as the structure by which the said enveloping part of the water-resistant airtight container VL was provided with the intake valve and exhaust valve which adjust the pressure in the container VL. According to such a structure, the above-mentioned freeze phenomenon can be prevented even when considering use in a place where the depth is greatly different or the depth becomes deep underwater. In addition, when the air is excessively sucked through the intake valve, the pressure in the container VL can be adjusted to an appropriate pressure through the exhaust valve. In actual use, for example, a hose is connected to the intake valve, and pressure is applied by compressed air from a breathing air cylinder or a compressor carried by the operator himself. Thus, if the pressure in the container VL is adjusted so as to be optimal for each work place corresponding to the water pressure changing with the water depth, the above-mentioned freeze phenomenon can be prevented more reliably. . In order to smoothly adjust the pressure, these intake and exhaust valves are valves that automatically open and close to automatically adjust the pressure in the container VL to a predetermined set value. It is more effective to use.

  If at least the volume ratio represented by the relational expression “VS / VP” is set to a level that does not cause a slide failure (freeze phenomenon) in the plunger 4 in water, the above-described freeze phenomenon is suppressed. Become. It is to be noted that the freeze phenomenon is suppressed by setting the volume ratio “VS / VP” to at least “3” or more, and that a more preferable operation can be obtained by setting the volume ratio to “4” or more. Has already been confirmed.

  If the above parameters are set so that at least the relational expression “(VS / VP) ≦ (W / (ρ × VP)) − (VM / VP) −1” is satisfied, The problem (problem) that raises the test hammer will be solved accurately based on the principle and rationale.

  -At least for the watertight sealed container VL, if the predetermined gap is formed between the encapsulating part and the hammer body HM, the same effect as the effect of (2) or an effect equivalent thereto is It will be obtained.

  In addition, even if there is no gap between the encapsulated portion and the hammer main body HM, the hammer main body HM is hermetically sealed as long as the watertight sealed container VL is provided. Water intrusion is prevented. That is, at least with such a structure, the same effect as the effect (1) or an effect equivalent thereto can be obtained.

  -As said water-resistant airtight container VL, the thing of arbitrary materials and shapes is employable. In short, it is sufficient if the hammer body HM can be sealed in a water-resistant manner.

-Also, as the waterproof seal members S1 and S2, those of any material / shape can be adopted depending on the material / shape, etc. of the water-resistant airtight container VL.
・ Currently, the test hammer for underwater evaluation is mainly used for quality evaluation of concrete structures, but it can also be applied to underwater rock investigation.

Sectional drawing which shows typically schematic structure of this test hammer as a state before a measurement about one embodiment of the test hammer for concrete underwater evaluation and the concrete compressive strength evaluation method concerning this invention. (A) is a perspective view which shows the external appearance structure of the test hammer for underwater evaluation which concerns on the embodiment, (b) is the top view which looked at the test hammer for underwater evaluation from the protrusion opening side for plungers. (A) is sectional drawing which shows the cross-sectional structure of the test hammer for underwater evaluation which concerns on the embodiment, (b) is an expanded sectional view which expands and shows the area | region A (protrusion opening for plungers) in (a). Sectional drawing which shows the test hammer for underwater evaluation which concerns on the embodiment in the state only of a water-resistant airtight container. Sectional drawing which shows typically the test hammer for underwater evaluation which concerns on the embodiment as a state just before hitting. The graph which shows the relational expression of the repulsion degree in water and compressive strength about a specimen (concrete for a relational expression). The chart which shows the concrete condition of the specimen used for experiment, and the property at the time of fresh. The graph which shows the relational expression of the degree of repulsion in water and compressive strength which were measured using the commercially available test hammer for land evaluation. The graph which shows the relational expression of the repulsion degree measured using the test hammer for underwater evaluation which concerns on the said embodiment, and compressive strength. The graph which shows the relationship with the compressive strength (horizontal axis) of a test piece by making the vertical axis | shaft the difference of both repulsion degree about the measurement result in the land (in the air) shown in FIG. 9, and the measurement result in water. Regarding the relational expression between the degree of rebound on the ground (in the air) and the compressive strength (specimen: concrete with the age of 28 days), measure with the test hammer for land evaluation and with the test hammer for underwater evaluation. The graph which shows the measurement result compared with the case where it went. The graph which shows the relational expression of the repulsion degree measured using the test hammer for underwater evaluation which concerns on the said embodiment with the approximate curve calculated | required by the method different from FIG. 9, and compressive strength. The chart which shows the experimental result regarding the influence of water pressure. Sectional drawing which shows typically the schematic structure of the existing land type test hammer as a state before a measurement. (A)-(d) is a schematic diagram which shows the measurement procedure of the test hammer method performed using the existing land type test hammer.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Housing | casing 2, 5 ... Spring, 3 ... Hammer body, 4 ... Plunger, 6 ... Slide member, 7 ... Locking tool, 8 ... Stop button, 9 ... Scale, AP ... Protrusion port for plungers, HM ... Hammer Main body, S1, S2 ... Waterproof seal member, SC ... Gap, T ... Protrusion, VL ... Waterproof sealed container.

Claims (3)

The plunger is configured to include a housing, a plunger, and a hammer body, and the plunger is moved from the state in which the evaluation object is in contact with the tip of the plunger protruding from the housing to the evaluation object side, whereby the plunger is moved to the housing. A hammer that measures the degree of repulsion of the evaluation object with respect to a hit applied to the evaluation object via the plunger when a hammer body that is energized in the housing by being slid into the body collides with the plunger. The body,
An envelope portion for encapsulating the hammer body, and a seal portion that slidably seals between the plunger projecting port formed in the encapsulation portion and the plunger. With a water-resistant airtight container that seals against water ,
In the watertight sealed container, a predetermined gap is formed between the encapsulated portion and the hammer body,
When the weight of the test hammer is W, the density of water is ρ, the volume of the housing is VM, the volume difference between the housing and the watertight sealed container is VS, and the volume of the plunger is VP,
(VS / VP) ≦ (W / (ρ × VP)) − (VM / VP) −1
A test hammer for underwater evaluation characterized in that the following relational expression is established . Wherein the encapsulation unit, underwater evaluating test hammer according to claim 1, characterized in that the intake valve and an exhaust valve for adjusting the pressure of the water closed container is provided. Based on the measurement of the degree of repulsion to the test hammer applied when hitting the concrete to be evaluated, a method for evaluating the compressive strength of the concrete to be evaluated,
Hitting the concrete that is the object of evaluation in water by the test hammer for underwater evaluation according to claim 1 or 2, and measuring the degree of repulsion to the test hammer for underwater evaluation;
Based on the relational expression between the degree of repulsion in the water and the compressive strength of the concrete for the relational expression obtained in advance by hitting the concrete for the relational expression with the test hammer for the underwater evaluation, A method for converting the degree of repulsion to the test hammer into the compressive strength of the concrete to be evaluated, and a method for evaluating the compressive strength of the concrete.

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