Compaction property measuring method

Abstract

To further correctly evaluate quality of a structure.SOLUTION: A compaction property measuring method which measures a compaction property of soil material mixture 20 manufactured by mixing unwashed excavated soil materials, cement and water includes: a storing step of storing mixed soil material mixture 20 in a container 22; a primary compaction step of compacting the soil material mixture 20 stored in the container 22 within one hour after manufacturing of the soil material mixture 20; a secondary compaction step of compacting the soil material mixture 20 stored in the container 22 after elapse of predetermined lapse time which is one hour or longer after manufacturing of the soil material mixture 20; and a property measuring step of measuring a compaction property of the soil material mixture 20 compacted in the container 22. The compaction energy imparted to the soil material mixture 20 in the secondary compaction step is larger than the compaction energy imparted to the soil material mixture 20 in the primary compaction step.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for measuring the compaction characteristics of a soil material mixture. [Background technology]

[0002] Patent Document 1 discloses a CSG construction method in which cement and water are added to and mixed with locally generated materials (excavated soil material), which is then transported to the construction site, leveled with a bulldozer, and compacted with a vibrating roller to build a structure. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-168977 Summary of the Invention [Problem to be solved by the invention]

[0004] In a CSG construction method such as the invention described in Patent Document 1, it can take a relatively long time for the CSG to be compacted after it is produced. If the time until compaction is long, the cement may set, which may result in a decrease in the compaction characteristics of the CSG, such as the degree of compaction. Because the length of time it takes for the CSG to be compacted varies depending on the location where the CSG is laid, it is difficult to accurately evaluate the quality of the entire structure simply by understanding the compaction characteristics of CSG that have been produced for a specific amount of time.

[0005] The present invention aims to more accurately evaluate the quality of a structure. [Means for solving the problem]

[0006] The present invention provides a method for measuring the compaction characteristics of a soil material mixture produced by mixing at least unwashed excavated soil material, cement, and water, the method comprising: a storing step of storing the mixed soil material mixture in a container; a primary compaction step of compacting the soil material mixture stored in the container within one hour after production of the soil material mixture; a secondary compaction step of compacting the soil material mixture stored in the container after a predetermined time of at least one hour has elapsed since production of the soil material mixture; and a characteristic measurement step of measuring the compaction characteristics of the compacted soil material mixture in the container, wherein the compaction energy imparted to the soil material mixture in the secondary compaction step is greater than the compaction energy imparted to the soil material mixture in the primary compaction step.

[0007] The present invention also provides a method for measuring the compaction properties of a soil mixture produced by mixing excavated soil material, the mass fraction of which passing a sieve with a nominal size of 0.15 mm being greater than 3% in accordance with JIS A 1204 "Testing Methods for Soil Grain Size," with cement and water, the method comprising the steps of: a storing step of storing the mixed soil mixture in a container; a primary compaction step of compacting the soil mixture stored in the container within one hour after production of the soil material mixture; a secondary compaction step of compacting the soil mixture stored in the container after a predetermined time of at least one hour has elapsed since production of the soil material mixture; and a characteristic measuring step of measuring the compaction properties of the compacted soil material mixture in the container, wherein the compaction energy imparted to the soil material mixture in the secondary compaction step is greater than the compaction energy imparted to the soil material mixture in the primary compaction step.

[0008] The present invention also provides a method for measuring the compaction characteristics of a soil material mixture produced by mixing at least unwashed excavated soil material, cement, and water, the method comprising: a spreading step of spreading the mixed soil material mixture; a compaction step of compacting the spread-leveled soil material mixture after a predetermined elapsed time of at least one hour has elapsed since the production of the soil material mixture; and a characteristic measurement step of measuring the compaction characteristics of the compacted soil material mixture, wherein the compaction energy imparted to the soil material mixture in the spreading step is smaller than the compaction energy imparted to the soil material mixture in the compaction step.

[0009] The present invention also provides a method for measuring the compaction characteristics of a soil material mixture produced by mixing excavated soil material, the mass fraction of which passing through a sieve with a nominal size of 0.15 mm being greater than 3% in accordance with JIS A 1204 "Testing Methods for Soil Grain Size," with cement and water, the method comprising: a spreading step of spreading the mixed soil material mixture; a compaction step of compacting the spread-leveled soil material mixture after a predetermined elapsed time of at least one hour has elapsed since the production of the soil material mixture; and a characteristic measuring step of measuring the compaction characteristics of the compacted soil material mixture, wherein the compaction energy imparted to the soil material mixture in the spreading step is less than the compaction energy imparted to the soil material mixture in the compaction step. [Effects of the Invention]

[0010] According to the present invention, the quality of a structure can be evaluated more accurately. [Brief explanation of the drawings]

[0011] [Figure 1] A longitudinal cross section of a trapezoidal CSG dam. [Figure 2] This is a front view of the trapezoidal CSG dam seen from the upstream side. [Figure 3] This is a cross-sectional view showing the cross section of the CSG layer that makes up the trapezoidal CSG dam. [Figure 4]1 is a diagram showing, in chronological order, steps for preparing a specimen in a method for measuring compaction characteristics of a soil material mixture according to a first embodiment of the present invention. FIG. [Figure 5] 5 is a diagram showing, in chronological order, the steps of producing a specimen structure in the method for measuring the compaction characteristics of a soil material mixture according to the second embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, a method for measuring the compaction characteristics of a soil material mixture according to an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a structure to be evaluated for quality using the compaction characteristics measurement method is a trapezoidal CSG dam 100 constructed by the CSG (Cemented Sand and Gravel) construction method.

[0013] First, the trapezoidal CSG dam 100 will be described with reference to Figures 1 and 2. Figure 1 is a longitudinal cross-sectional view (upstream / downstream cross-sectional view) of the trapezoidal CSG dam 100, and Figure 2 is a front view of the trapezoidal CSG dam 100 as seen from the upstream side (as seen from the left side in Figure 1).

[0014] As shown in Figure 1, the trapezoidal CSG dam 100 is a trapezoidal dam with a generally trapezoidal cross section in the upstream and downstream directions, and is constructed by covering the surface of the dam body, which is made of a trapezoidal pile of CSG, with protective concrete. As shown in Figure 2, the trapezoidal CSG dam 100 has left and right sides anchored to bedrock 102, 103. For ease of explanation, the left-right direction shown in Figure 1, i.e., the direction in which the river flows, will be referred to as the upstream and downstream directions of the trapezoidal CSG dam 100.

[0015] The CSG, which forms the dam body of the trapezoidal CSG dam 100, is a soil material mixture (cement-based mix) produced by mixing excavated soil material (locally-sourced materials) consisting of sand, gravel, rocks, and other materials readily available near the construction site with water and cement. The aggregate contains coarse aggregates such as crushed stone and coarse gravel with a particle size of approximately 80 mm, which is larger than the maximum particle size (40 mm) of aggregates typically used in ready-mixed concrete. While the excavated soil may be processed to remove oversized particles or be crushed, it is generally not classified, sized, or washed. In other words, CSG, which is primarily made from excavated soil, can be continuously produced using simpler equipment than that used to produce concrete. Therefore, the construction of the trapezoidal CSG dam 100 does not require the aggregate production facilities and other equipment required for the construction of typical concrete dams. Cement can be Portland cement, blended cement, or special cement, but CSG and the CSG method use Portland cement or blended cement (blast furnace cement, fly ash cement, etc.). In particular, moderate-heat Portland cement, blast furnace cement (Type B), Portland cement mixed with fly ash, or moderate-heat Portland cement mixed with fly ash cement can be used.

[0016] The trapezoidal CSG dam 100 is constructed by stacking CSG layers 10, each equivalent to one lift, from bottom to top, which are formed by pouring CSG, a soil material mixture as described above. The height of each CSG layer 10, i.e., the lift height h, is approximately 75 cm to 100 cm.

[0017] 1 and 2 show a trapezoidal CSG dam 100 made up of six CSG layers 10 for simplicity. The CSG layers 10 formed higher are shorter in the upstream and downstream directions. As a result, stepped portions are formed on the upstream and downstream side surfaces of the trapezoidal CSG dam 100.

[0018] The construction of each CSG layer 10 will now be described with reference to Figure 3. Figure 3 shows a cross section of a CSG layer 10 under construction.

[0019] The CSG layer 10 is constructed by spreading CSG thinly and widely, a method known as thin layer spreading. As shown in FIG. 3, the structure is constructed by hardening multiple layers 11, 12, and 13 formed by overlapping CSG layers.

[0020] Specifically, first, the CSG is transported to the construction site by a transport machine such as a dump truck, conveyor, or crane, and then the transported CSG is leveled and compacted by a leveling machine such as a bulldozer, thereby forming the bottom layer 11.

[0021] Next, CSG is transported onto the top surface of the leveled first layer 11 by a transport machine, and the transported CSG is leveled and compacted by a leveling machine to form the second layer 12, which is an intermediate layer.

[0022] Furthermore, CSG is transported onto the top surface of the leveled second layer 12 by a transport machine, and the transported CSG is leveled and compacted by a leveling machine to form the top third layer 13.

[0023] After the third layer 13 is formed, as shown in Fig. 3, the surface of the third layer 13 is compacted by a compaction machine (rolling machine) such as a vibrating roller 16, and the first layer 11, the second layer 12, and the third layer 13 are compacted. In other words, of the three layers 11, 12, and 13 that make up the CSG layer 10, at least the uppermost layer is spread and leveled by a leveling machine, and then compacted and condensed by a compaction machine. Note that the first layer 11 and the second layer 12 may also be spread and leveled by a leveling machine, and then compacted and condensed by a compaction machine, similar to the third layer 13.

[0024] The heights of the layers 11, 12, and 13 thus formed (first height h1, which is the height of the first layer 11, second height h2, which is the height of the second layer 12, and third height h3, which is the height of the third layer 13) are set to about 10 cm to 30 cm. However, the heights of the layers 11, 12, and 13 are not strictly the same, and differences occur depending on the state of spreading and compaction.

[0025] By repeating this process and stacking the CSG layers 10 from bottom to top, the trapezoidal CSG dam 100 is constructed as a structure.

[0026] In the above-mentioned CSG method, it can take a relatively long time (for example, up to six hours) from the time when cement and water are added to and mixed with excavated soil material (on-site generated material) to produce CSG (soil material mixture) until compaction (rolling compaction) begins. If it takes a long time to compact, the cement may have already set to a certain extent before compaction begins, which may result in a deterioration of the compaction characteristics of the CSG, such as the degree of compaction. This deterioration in compaction characteristics affects the density and strength of the structure, leading to a decrease in density and strength and ultimately to a decrease in the quality of the CSG as a structure.

[0027] The length of time it takes for the CSG to be compacted varies depending on the location where the CSG is spread. For example, as described above, if the CSG layer 10 is made up of multiple layers, the lowest first layer 11 will only be compacted together with the second and third layers 12 and 13 by a compaction machine (roller) after the second and third layers 12 and 13 have been spread and leveled. For this reason, the time it takes for the first layer 11 to be compacted after being spread is longer than for the second and third layers 12 and 13. Similarly, the time it takes for the second layer 12 to be compacted after being spread is longer than for the third layer 13.

[0028] Thus, the length of time that the CSG is left after it is spread and before compaction begins varies depending on the location in the structure where the CSG is spread, etc. In other words, the length of time from when the CSG is produced, i.e., when the excavated soil material is mixed with cement and water, to when compaction by a compaction machine (roller) begins varies depending on the location where the CSG is spread, for example, on which of layers 11 to 13 the CSG is spread.

[0029] The time that elapses between the time CSG is manufactured and the start of compaction affects the quality of the CSG structure that is constructed by compacting the CSG, so understanding the compaction characteristics after a specified time has passed is important for maintaining and improving quality.

[0030] Therefore, in the method for measuring the compaction characteristics of a soil material mixture according to an embodiment of the present invention, CSG, which is a soil material mixture used to construct a structure, is compacted under temporal and physical conditions that reflect actual construction, and the compaction characteristics of the compacted soil material mixture are measured, thereby making it possible to grasp the compaction characteristics of the soil material mixture.

[0031] First Embodiment A method for measuring the compaction characteristics of a soil material mixture (CSG) according to a first embodiment of the present invention will be described below with reference to Fig. 4. In the method for measuring the compaction characteristics of a soil material mixture according to the first embodiment, a specimen is prepared using CSG, which is used in the construction of structures, and the compaction characteristics of the prepared specimen are measured. Fig. 4 (A) to (C) are diagrams showing the chronological order of the preparation process of the specimen whose compaction characteristics are to be measured.

[0032] First, with reference to FIG. 4, the process of preparing a specimen for measuring compaction characteristics will be described.

[0033] In preparing the specimen, excavated soil material (on-site generated material) is mixed with water and cement using a mixer such as a pot mixer to produce a soil material mixture 20 (CSG) (production process). Then, the produced soil material mixture 20 is placed in a cylindrical container 22 in the storage process shown in Fig. 4(A).

[0034] The excavated soil material used to produce the soil material mixture 20 is the same material used to construct structures, but is unwashed locally-generated material. The mass fraction of the excavated soil material passing through a 0.15 mm nominal sieve, as specified in JIS A 1204:2009 "Soil Grain Size Testing Method," exceeds 3%, preferably exceeds 5%. The excavated soil material is adjusted to a maximum particle size (80 mm) or less by removing oversized particles as needed. Since the soil material mixture 20 contained in the container 22 includes excavated soil material with a relatively large particle size of approximately 80 mm, the inner diameter of the container 22 is set to at least three times the maximum particle size, preferably approximately 300 mm.

[0035] 4(B), the soil material mixture 20 contained in the container 22 is tamped with a tamping rod (not shown), and then further compacted for a predetermined time, for example, 5 to 10 seconds, with an electric hammer 24. Note that the soil material mixture 20 may be compacted with a vibration tamper instead of the electric hammer 24.

[0036] This primary compaction process is carried out to reproduce the state in which CSG, which is still in a relatively fluid state, is compacted to a certain extent by a leveling machine such as a bulldozer when it is used in actual construction. For this reason, the primary compaction process is carried out in accordance with the timing of leveling in actual construction, for example, within one hour after the soil material mixture 20 is produced.

[0037] In addition, in the primary compaction process, the number of times the soil material mixture 20 is struck with the ram and the time for compacting the soil material mixture 20 with the electric hammer 24 are set in advance so that the density of the soil material mixture 20 after the primary compaction process is completed is equivalent to the density of CSG after it has been leveled by a leveling machine in actual construction.

[0038] In addition, the number of times the thrust rod is used and the time for compaction by the electric hammer 24 may be set so that the impact energy imparted to the soil material mixture 20 is equivalent to the compaction energy imparted to the CSG by the leveling machine in actual construction.

[0039] After the primary compaction step is completed, the secondary compaction step shown in Figure 4(C) and described below is carried out. However, before the secondary compaction step is carried out, the soil material mixture 20 is left to stand for a predetermined time in a leaving step.

[0040] The leaving process is carried out to reproduce the condition that occurs in actual construction, when CSG is left after being leveled by a leveling machine such as a bulldozer and before being compacted by a compaction machine (compaction machine) such as a vibrating roller.

[0041] In actual construction, the time that CSG is left standing is about six hours at most, whereas the time from when the CSG is produced until the leveling is completed is generally less than one hour, which is shorter than the time that it is left standing. Therefore, in actual construction, the time that CSG is left standing before being compacted by the compaction machine can be said to be roughly equal to the time from when the CSG is produced until it is compacted by the compaction machine.

[0042] Furthermore, since the cement setting reaction begins when CSG is produced, i.e., when cement and water are mixed with the excavated soil material, it can be said that the change in the compaction characteristics of CSG over time begins from this time.

[0043] Furthermore, in actual construction, the time for which the CSG is left standing varies depending on the location where the CSG is laid, as described above.

[0044] Taking these factors into consideration, in this embodiment, the time that elapses from the production of the soil material mixture 20 until the start of the secondary compaction process is set to the time that corresponds to the time that the CSG is left after being spread and leveled in actual construction until it is compacted by a compaction machine, and this time is set in advance as the elapsed time for each container 22. Furthermore, since a structure is constructed by finally performing compaction, the time until compaction is completed is closely related to the quality of the CSG as a structure.

[0045] This elapsed time is set to a different length for each container 22, and specifically, is set at 1-2 hour intervals between 1 hour and 8 hours after the production of the soil material mixture 20 so as to ensure that the time during which the CSG is left to stand during actual construction is included. Measurement of the elapsed time begins from the time when the excavated soil material is mixed with cement and water in the production process of the soil material mixture 20.

[0046] The elapsed time that is set is not limited to this, and may be set to a time that exceeds 8 hours after the production of the soil material mixture 20, or may be set to a time that assumes the time when the secondary compaction process begins immediately after the completion of the primary compaction process, i.e., the time that assumes the time the CSG is left standing is 0 hours.

[0047] Furthermore, instead of the elapsed time, the time that elapses from the completion of the primary compaction process until the start of the secondary compaction process may be set as the time that corresponds to the time that the CSG is left standing in actual construction, and this time may be set as the standing time for each container 22. In this case, the start of measurement of the standing time is the time that the primary compaction process is completed.

[0048] After the leaving step is completed, i.e., after the elapse of a predetermined time for each container 22, the soil material mixture 20 contained in the container 22 is compacted by the electric hammer 24 for a predetermined time, for example, 50 to 60 seconds, in the secondary compaction step shown in FIG. 4(C). The maximum time required for compaction in the secondary compaction step is approximately 90 to 120 seconds. Because the compaction time for secondary compaction is significantly longer than that for primary compaction, the compaction energy applied to the soil material mixture 20 by the electric hammer 24 is greater. Therefore, the secondary compaction imposes a greater compaction load than primary compaction, resulting in stronger compaction. In other words, the primary compaction is weaker than the secondary compaction. Furthermore, since the compaction operation takes a maximum of approximately two minutes, the start of compaction generally corresponds to the completion of compaction in the compaction step performed after a predetermined time of one hour or more has elapsed.

[0049] This secondary compaction process is carried out to reproduce the compacted state of the CSG in actual construction, where the CSG is compacted by a compaction machine (roller) such as a vibrating roller. Therefore, the time for compacting the soil material mixture 20 by the electric hammer 24 in the secondary compaction process is set in advance so that the density of the soil material mixture 20 after the secondary compaction process is equivalent to the density of the CSG after being compacted by the compaction machine in actual construction.

[0050] In addition, in the secondary compaction process, the time for compacting the soil material mixture 20 by the electric hammer 24 may be set so that the impact energy imparted to the soil material mixture 20 is equivalent to the compaction energy imparted to the CSG by the compaction machine in actual construction.

[0051] As mentioned above, the secondary compaction process assumes that in actual construction, CSG will be compacted by a compaction machine (roller) such as a vibrating roller, whereas the primary compaction process assumes that when CSG is leveled by a leveling machine such as a bulldozer, it will be compacted as a result. However, in actual construction, the degree of compaction achieved by the leveling machine is much smaller than the degree of compaction achieved by a compaction machine such as a vibrating roller. Therefore, in order to simplify the test specimen preparation process, it is possible to skip the primary compaction process and only perform the secondary compaction process.

[0052] After the secondary compaction process is completed, the soil material mixture 20 in each container 22 is cured for a predetermined period under predetermined curing conditions in a curing process. After a sufficient curing period (for example, 2 to 3 days) has passed, the soil material mixture 20 that has hardened to a certain extent is taken out of the container 22 as a test specimen.

[0053] The cylindrical specimen removed from the container 22 is subjected to a subsequent property measurement process in which its density is measured as the compaction property of the soil material mixture 20 .

[0054] Specifically, the volume and weight of the specimen are measured, and the density is calculated from the measured volume and weight. If there is a risk that the specimen will collapse when measuring the volume, the density of the specimen is measured using an RI density meter, which irradiates the specimen with gamma rays and calculates the density of the specimen from the transmission attenuation rate.

[0055] The density is calculated for each test specimen, i.e., for each soil material mixture 20 that has been placed in a plurality of containers 22 and compacted after being set for different elapsed times. Therefore, it is possible to understand how the compaction characteristics of the soil material mixture 20 change depending on the elapsed time (1 hour to 6 hours).

[0056] As the compaction characteristics of the soil material mixture 20, the water content or compressive strength of the specimen may be measured instead of or in addition to the density of the specimen.

[0057] In this way, by understanding the compaction characteristics of the soil material mixture 20 according to the elapsed time, even if the time left after spreading by a leveling machine and before compaction by a compaction machine varies depending on the location of the CSG being spread, as in the case of a trapezoidal CSG dam 100, by recording the time left for each location where the CSG is spread, it is possible to determine the compaction characteristics corresponding to the time left from the results measured by the above-mentioned compaction characteristic measurement method. Therefore, even for a relatively large structure, by clarifying the compaction characteristics of each part, the quality of the entire structure can be accurately evaluated.

[0058] Instead of the time the CSG is left standing, the time elapsed from the time the CSG is produced until the time the CSG is compacted may be recorded for each location where the CSG is spread. In this case, the recorded elapsed time corresponds to the elapsed time set for each container 22, so the compaction characteristics corresponding to the recorded elapsed time can be determined from the results measured using the above-mentioned compaction characteristic measurement method. Therefore, in this case too, the compaction characteristics of each part of a relatively large structure become clear, allowing for an accurate evaluation of the quality of the entire structure.

[0059] According to the first embodiment described above, the following advantageous effects are achieved.

[0060] In the above-mentioned compaction characteristic measurement method, the compaction characteristics of the soil material mixture 20 are measured through a storage step of storing the mixed soil material mixture 20 in a container 22, a compaction step of compacting the soil material mixture 20 stored in the container 22 after a predetermined time of at least one hour has elapsed since the production of the soil material mixture 20, and a characteristic measurement step of measuring the compaction characteristics of the compacted soil material mixture 20 in the container 22.

[0061] By understanding the compaction characteristics of the soil material mixture 20 according to a predetermined elapsed time in this way, even if the time left before compaction varies depending on the location where the CSG is spread, such as in the trapezoidal CSG dam 100, if the time left for each location where the CSG is spread is recorded, the compaction characteristics corresponding to the time left can be determined from the results measured by the above-mentioned compaction characteristic measurement method. Therefore, even for relatively large structures, the compaction characteristics of each part can be clarified, allowing for an accurate evaluation of the quality of the entire structure.

[0062] Furthermore, in the above-described compaction characteristic measurement method, the conditions for compacting the soil material mixture 20 contained in the container 22 are set assuming spreading and compaction in actual construction. By setting the conditions for compacting the soil material mixture 20 in this way so as to reproduce the compacted state resulting from spreading and compaction in actual construction, it becomes possible to grasp the compaction characteristics under conditions close to those in actual construction, and as a result, the compaction characteristics of the entire structure can be grasped more accurately.

[0063] The following modified examples are also within the scope of the present invention, and it is possible to combine the configuration shown in the modified example with the configuration described in the first embodiment above, or to combine the configurations described in the different modified examples below.

[0064] The soil material mixture 20 of the first embodiment may contain an admixture that delays the setting reaction of cement. The admixture is a so-called set retarder, such as "Floric T (Floric is a registered trademark)" (manufactured by Floric Co., Ltd.), which, for example, increases the difference in cement setting time according to JIS A 1147:2019 "Testing Methods for Setting Time of Concrete" by approximately +95 minutes at the initial setting time and +100 minutes at the final setting time. The admixture may be used as long as the difference in cement setting time according to JIS A 1147:2019 "Testing Methods for Setting Time of Concrete" is +0 minutes or more at the initial setting time and +15 minutes or more at the final setting time.

[0065] Specifically, in the storing step, soil material mixtures 20 containing different amounts of admixture are stored in multiple containers 22 set to the same elapsed time, and in the characteristic measuring step, the compaction characteristics of the compacted soil material mixture 20 are measured. By changing the amount of admixture added to the soil material mixture 20 in this way, the effect of the admixture on the compaction characteristics can be understood.

[0066] Furthermore, by placing soil material mixtures 20 containing the same amount of admixture in multiple containers 22 each set to a different elapsed time, and measuring the compaction characteristics of the compacted soil material mixtures 20, it is possible to understand how the compaction characteristics of the soil material mixtures 20 to which admixtures have been added change with different elapsed times.

[0067] Furthermore, by comprehensively understanding the changes in the compaction characteristics of the soil material mixture 20 due to differences in the elapsed time and the amount of admixture added, even if the amount of admixture added to the CSG differs in each part of the structure, if the amount of admixture added in each part and the time the CSG was left standing or the time elapsed from the production of the CSG to compaction are known, the corresponding compaction characteristics of the CSG can be determined from the results measured using the above-mentioned compaction characteristic measurement method.

[0068] Second Embodiment Next, a method for measuring the compaction characteristics of a soil material mixture (CSG) according to a second embodiment of the present invention will be described with reference to Fig. 5. In the method for measuring the compaction characteristics of a soil material mixture according to the second embodiment, the compaction characteristics of a test structure obtained by spreading and compacting a material equivalent to the CSG used in constructing a structure using equipment equivalent to that used in actual construction are measured. Fig. 5 (A) to (B) are diagrams showing, in chronological order, the process of producing a test structure whose compaction characteristics are to be measured.

[0069] First, with reference to FIG. 5, the process of fabricating a test structure whose compaction characteristics are to be measured will be described.

[0070] In preparing the test structure, excavated soil material (on-site generated material) is mixed with water and cement using a mixer such as a pot mixer to produce a soil material mixture 20 (CSG) (production process). Then, in the leveling process, the produced soil material mixture 20 is spread evenly in a predetermined section divided on the test yard, as shown in Figure 5(A).

[0071] The soil material mixture 20 is spread and compacted to some extent by a leveling machine such as a bulldozer 26, just as in actual construction. The soil material mixture 20 is spread and compacted to some extent by the leveling machine. The leveling process is carried out within one hour of the soil material mixture 20 being produced, in accordance with the timing of leveling in actual construction. Leveling by a leveling machine such as a bulldozer also has a compaction effect, but compared to compaction by a compaction machine (roller) such as a vibrating roller, the compaction energy imparted to the soil material mixture 20 is smaller, so it can be said to be weak compaction.

[0072] After the leveling step is completed, the compaction step described below is carried out. Before the compaction step is carried out, the soil material mixture 20 is left to stand for a predetermined time in a leaving step.

[0073] The leaving process is carried out to reproduce the condition that occurs in actual construction, when CSG is left after being leveled by a leveling machine such as a bulldozer and before being compacted by a compaction machine (compaction machine) such as a vibrating roller.

[0074] In actual construction, the time that CSG is left standing is about six hours at most, whereas the time from when the CSG is produced until the leveling is completed is generally less than one hour, which is shorter than the time that it is left standing. Therefore, in actual construction, the time that CSG is left standing before being compacted by the compaction machine can be said to be roughly equal to the time from when the CSG is produced until it is compacted by the compaction machine.

[0075] Furthermore, since the cement setting reaction begins when the CSG is produced, i.e., when the excavated soil material is mixed with cement and water, it can be said that the change in the compaction characteristics of the CSG over time begins from this point onwards.

[0076] Furthermore, in actual construction, the time for which the CSG is left standing varies depending on the location where the CSG is laid, as described above.

[0077] Taking these factors into consideration, in this embodiment, the time that elapses from when the soil material mixture 20 is produced until the compaction process using the compaction machine is started is set to the time that corresponds to the time that the CSG is left standing in actual construction, and this time is set as the elapsed time in advance for each section where the soil material mixture 20 is spread. Note that the time required for compaction work using a compaction machine (roller) such as a vibrating roller is about 5 minutes, so in the compaction process that is carried out after a predetermined time of one hour or more has elapsed, the time that compaction starts can be said to be the time that compaction is generally completed.

[0078] This elapsed time is set to a different length for each section where the soil material mixture 20 is spread, and specifically, is set to every 1 to 2 hours between 1 hour and 8 hours after the production of the soil material mixture 20 so as to ensure that the time during which the CSG is left to stand during actual construction is included. Measurement of the elapsed time begins from the time when the excavated soil material is mixed with cement and water in the production process of the soil material mixture 20.

[0079] The elapsed time that is set is not limited to this, and may be set to a time that exceeds 8 hours after the production of the soil material mixture 20, or may be set to the time that the compaction process begins immediately after the leveling process is completed, i.e., the time that assumes that the CSG is left standing for 0 hours.

[0080] Alternatively, instead of the elapsed time, the time that elapses from the completion of the spreading process to the start of the compaction process may be set as the standing time for each section, which corresponds to the time that the CSG is left standing in actual construction. In this case, the start of measurement of the standing time is the time that the spreading process is completed.

[0081] When the leaving process is completed, that is, when the predetermined time for each section has elapsed, the soil material mixture 20 is compacted by a compaction machine (roller) such as a vibrating roller 28 in the compaction process, as shown in Figure 5(B), in the same way as in actual construction.

[0082] After the compaction process is completed, the soil material mixture 20 in each section is cured for a predetermined period under predetermined curing conditions in the curing process. After a sufficient curing period (for example, 2 to 3 days) has passed, the soil material mixture 20 hardens to a certain extent and becomes a test structure.

[0083] In a subsequent property measurement step, the density of the test structure is measured as a compaction property of the soil material mixture 20 .

[0084] Specifically, a cylindrical core (specimen) is first extracted from the test structure using a coring machine. The volume and weight of the extracted core are then measured, and the density is calculated from the measured volume and weight. If there is a risk that the core will collapse when measuring the volume, the density of the core is measured using an RI density meter, which irradiates the core with gamma rays and calculates the core density from the transmission attenuation rate.

[0085] The density of the test structure may be measured by placing a scattering-type RI densitometer on the top surface of the test structure, without taking a core.

[0086] A scattering-type RI density meter is installed on the surface of an object to be measured, emits gamma rays toward the interior of the object, and detects the gamma rays scattered from inside the object toward the surface of the object.Since gamma rays are more likely to disappear the higher the density, it is possible to calculate the density of the test structure by measuring the proportion of gamma rays scattered toward the surface of the test structure compared to the amount of gamma rays emitted into the test structure.

[0087] The density is calculated for each test structure, i.e., for each soil material mixture 20 that has been spread and compacted in a plurality of sections set with different elapsed times. Therefore, it is possible to understand how the compaction characteristics of the soil material mixture 20 change depending on the elapsed time (1 hour to 6 hours).

[0088] As the compaction characteristics of the soil material mixture 20, the water content or compressive strength of the test structure may be measured instead of or in addition to the density of the test structure.

[0089] In this way, by understanding the compaction characteristics of the soil material mixture 20 according to the elapsed time, even if the time left after spreading by a leveling machine and before compaction by a compaction machine varies depending on the location of the CSG being spread, as in the case of a trapezoidal CSG dam 100, by recording the time left for each location where the CSG is spread, it is possible to determine the compaction characteristics corresponding to the time left from the results measured by the above-mentioned compaction characteristic measurement method. Therefore, even for a relatively large structure, by clarifying the compaction characteristics of each part, the quality of the entire structure can be accurately evaluated.

[0090] Instead of the time the CSG is left standing, the time elapsed from the time the CSG is produced until the time the CSG is compacted may be recorded for each location where the CSG is spread. In this case, the recorded elapsed time corresponds to the elapsed time set for each section, so the compaction characteristics corresponding to the recorded elapsed time can be determined from the results measured using the above-mentioned compaction characteristic measurement method. Therefore, in this case too, the compaction characteristics of each part of a relatively large structure become clear, allowing for an accurate evaluation of the quality of the entire structure.

[0091] According to the second embodiment described above, the following advantageous effects are achieved.

[0092] In the above-mentioned compaction characteristic measurement method, the compaction characteristics of the soil material mixture 20 are measured through a spreading process in which the mixed soil material mixture 20 is spread evenly, a compaction process in which the spread-even soil material mixture 20 is compacted after a predetermined time of at least one hour has elapsed since the production of the soil material mixture 20, and a characteristic measurement process in which the compaction characteristics of the compacted soil material mixture 20 are measured.

[0093] By understanding the compaction characteristics of the soil material mixture 20 according to a predetermined elapsed time in this way, even if the time left before compaction varies depending on the location where the CSG is spread, such as in the trapezoidal CSG dam 100, if the time left for each location where the CSG is spread is recorded, the compaction characteristics corresponding to the time left can be determined from the results measured by the above-mentioned compaction characteristic measurement method. Therefore, even for relatively large structures, the compaction characteristics of each part can be clarified, allowing for an accurate evaluation of the quality of the entire structure.

[0094] In the above-described compaction characteristic measurement method, the soil material mixture 20 is spread and compacted in the test yard in the same manner as in actual construction. By spreading and compacting the soil material mixture 20 in the same manner as in actual construction, it becomes possible to grasp the compaction characteristics under conditions close to those in actual construction, and as a result, it is possible to grasp the compaction characteristics of the entire structure with greater accuracy.

[0095] The following modified examples are also within the scope of the present invention, and it is possible to combine the configuration shown in the modified example with the configuration described in the second embodiment above, or to combine the configurations described in the different modified examples below.

[0096] The soil material mixture 20 of the second embodiment may contain an admixture that delays the setting reaction of cement. The admixture is a so-called set retarder such as "Floric T (Floric is a registered trademark)" (manufactured by Floric Co., Ltd.), and, for example, the difference in the setting time of cement according to JIS A 1147:2019 "Testing Method for Setting Time of Concrete" is approximately +95 minutes at the initial setting time and approximately +100 minutes at the final setting time. The admixture may be any admixture that causes a difference in the setting time of cement according to JIS A 1147:2019 "Testing Method for Setting Time of Concrete" of +0 minutes or more at the initial setting time and +15 minutes or more at the final setting time.

[0097] Specifically, in the spreading step, soil material mixture 20 with different amounts of admixture added is spread in multiple sections set to the same elapsed time, and in the characteristic measuring step, the compaction characteristics of the compacted soil material mixture 20 are measured. By changing the amount of admixture added to the soil material mixture 20 in this way, it is possible to understand the effect of the admixture on the compaction characteristics.

[0098] Furthermore, by spreading the soil material mixture 20 containing the same amount of admixture in multiple sections set for different elapsed times and measuring the compaction characteristics of the compacted soil material mixture 20, it is possible to understand how the compaction characteristics of the soil material mixture 20 containing the admixture change depending on the elapsed time.

[0099] Furthermore, by comprehensively understanding the changes in the compaction characteristics of the soil material mixture 20 due to differences in the elapsed time and the amount of admixture added, even if the amount of admixture added to the CSG differs in each part of the structure, if the amount of admixture added in each part and the time the CSG was left standing or the time elapsed from the production of the CSG to compaction are known, the corresponding compaction characteristics of the CSG can be determined from the results measured using the above-mentioned compaction characteristic measurement method.

[0100] In the second embodiment, the compaction characteristics of the soil material mixture 20 that has been spread and compacted in a test yard are measured. Alternatively, the compaction characteristics may be measured on a structure constructed from CSG that has been subjected to a spreading process and compacted after a predetermined time has elapsed, such as the trapezoidal CSG dam 100, which is an actually constructed structure.

[0101] Specifically, in this case, cores are taken from at least three parts: the part of the trapezoidal CSG dam 100 where the CSG has been left for the shortest time (for example, the third layer 13, which has been left for the shortest time among the multiple CSG layers 10); the part of the trapezoidal CSG dam 100 where the CSG has been left for the longest time (for example, the first layer 11, which has been left for the longest time among the multiple CSG layers 10); and a part that can be interpolated between these, and the density of the taken cores is measured.

[0102] In this way, by measuring the density of cores taken from multiple parts of the trapezoidal CSG dam 100 where the CSG has been left for different periods of time, it is possible to understand how the compaction characteristics of the CSG in the trapezoidal CSG dam 100 change depending on the elapsed time between the time the CSG was manufactured and the time it was compacted.

[0103] Furthermore, by comprehensively understanding the compaction characteristics of CSG over time, it becomes possible to easily estimate the compaction characteristics of each part of even a relatively large structure such as the trapezoidal CSG dam 100, thereby enabling accurate evaluation of the quality of the entire structure.

[0104] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

[0105] For example, in the above embodiment, the structure to be evaluated for quality using the compaction characteristic measurement method is the trapezoidal CSG dam 100, but the structure to be evaluated is not limited to this and may be, for example, an embankment such as a sabo dam or a seawall. Furthermore, as long as it has a structure constructed using the CSG method, it is not limited to structures that constitute embankments such as dams, and may be any structure. [Explanation of symbols]

[0106] 10...CSG layer 16. Vibration roller (compactor) 20...Soil material mixture 22...container 24 Electric hammer 26 Bulldozer (leveling machine) 28 Vibration roller (compactor) 100 Trapezoidal CSG dam (structure)

Claims

1. A method for measuring compaction characteristics of a soil material mixture produced by mixing at least unwashed excavated soil material, cement, and water, comprising the steps of: A step of containing the mixed soil material mixture in a container; A primary compaction step of compacting the soil material mixture contained in the container within one hour after the production of the soil material mixture; A secondary compaction process in which the soil material mixture contained in the container is compacted after a predetermined time of at least one hour has elapsed since the production of the soil material mixture; and measuring compaction characteristics of the compacted soil material mixture in the container; The compaction energy imparted to the soil material mixture in the secondary compaction step is greater than the compaction energy imparted to the soil material mixture in the primary compaction step. Methods for measuring compaction characteristics.

2. A method for measuring compaction characteristics of a soil material mixture produced by mixing an excavated soil material having a mass fraction of soil passing through a sieve nominal size of 0.15 mm or more in accordance with JIS A 1204 "Soil Grain Size Test Method", cement, and water, comprising: A step of containing the mixed soil material mixture in a container; A primary compaction step of compacting the soil material mixture contained in the container within one hour after the production of the soil material mixture; A secondary compaction process in which the soil material mixture contained in the container is compacted after a predetermined time of at least one hour has elapsed since the production of the soil material mixture; and measuring compaction characteristics of the compacted soil material mixture in the container; The compaction energy imparted to the soil material mixture in the secondary compaction step is greater than the compaction energy imparted to the soil material mixture in the primary compaction step. Methods for measuring compaction characteristics.

3. An admixture having an effect of retarding the setting reaction of the cement is added to the soil material mixture, In the storage step, the soil material mixture having the same elapsed time setting but different amounts of the admixture, or the soil material mixture having the same amount of the admixture added but different elapsed time settings, is stored in a plurality of containers, In the characteristic measuring step, the compaction characteristics of the compacted soil material mixture in each of the multiple containers are measured. The method for measuring compaction characteristics according to claim 1 or 2.

4. A method for measuring compaction characteristics of a soil material mixture produced by mixing at least unwashed excavated soil material, cement, and water, comprising the steps of: A spreading step of spreading the mixed soil material mixture; A compaction process of compacting the spread soil material mixture after a predetermined elapsed time of at least one hour has elapsed since the production of the soil material mixture; and a characteristic measuring step of measuring compaction characteristics of the compacted soil material mixture, The compaction energy imparted to the soil material mixture in the leveling step is less than the compaction energy imparted to the soil material mixture in the compaction step. Methods for measuring compaction characteristics.

5. A method for measuring compaction characteristics of a soil material mixture produced by mixing an excavated soil material having a mass fraction of soil passing through a sieve nominal size of 0.15 mm or more in accordance with JIS A 1204 "Soil Grain Size Test Method", cement, and water, comprising: A spreading step of spreading the mixed soil material mixture; A compaction process of compacting the spread soil material mixture after a predetermined elapsed time of at least one hour has elapsed since the production of the soil material mixture; and a characteristic measuring step of measuring compaction characteristics of the compacted soil material mixture, The compaction energy imparted to the soil material mixture in the leveling step is less than the compaction energy imparted to the soil material mixture in the compaction step. Methods for measuring compaction characteristics.

6. An admixture having an effect of retarding the setting reaction of the cement is added to the soil material mixture, In the spreading step, the soil material mixture having different amounts of the admixture added is spread on each of the sections in which the elapsed time is set to the same length, or the soil material mixture having the same amount of the admixture added is spread on each of the sections in which the elapsed time is set to different lengths, In the characteristic measuring step, compaction characteristics of the compacted soil material mixture in each of the multiple sections are measured. The method for measuring compaction characteristics according to claim 4 or 5.

7. The compaction energy applied to the soil material mixture in the secondary compaction step is set to be equal to the compaction energy applied to the soil material mixture by a compaction machine in actual construction. A method for measuring compaction characteristics according to any one of claims 1 to 3.

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