JP6669543B2 - Construction method of backing structure and mixed material - Google Patents

Description

  The present invention relates to a method of applying a backing structure and a mixed material therefor.

  When constructing seawalls and quays, sand-proofing sheets are laid on the slopes of the backing stones to prevent the buried soil from being sucked out through the backing stones. Drainage and sinking of soil has been reported. Also, since diving work is required for leveling the backing stone slope and connecting the sheets, difficulties are involved in construction at a large depth. In order to solve such a problem, it has been proposed to apply FA mortar or the like to the backing stone slope (Non-Patent Document 1). Further, a method has been proposed in which a large number of bags filled with fluidized clay and further solidified material are laid on the backing stone slope of rubble, and a method of injecting an infiltration solidifying liquid into backfill (Patent Document 1). , 2).

JP 07-82722 A JP 2003-13437 A

2001 Research Papers "Technical Study on the Application of FA Mortar as a Sandproofing Sheet Substitute Material" Takuya Motoki, Koichi Tsuruya, Kenji Yoshihira Published August 2002 Issued by Japan Coastal Development Institute of Technology (http: / /www.cdit.or.jp/ronbun/2002/H13-29.pdf)

  However, the following problems are pointed out in the above-mentioned known methods. That is, in the case of a material using a solidifying material such as cement, cracks and the like may occur, and the function of preventing suction is reduced. During pumping, the fluid material may fall into the voids of the backing stones, causing a loss of material. In order to increase the gradient due to the high fluidity of the material, it is necessary to take measures such as addition of a thickener and soil retention using a sandbag or the like. Also, it takes time and effort to prepare a large number of bags filled with clay or solidifying material, and the method of injecting the infiltration solidification liquid is not suitable before the construction of the backfill.

  In view of the above-mentioned problems of the prior art, the present invention constructs a backing structure capable of maintaining a suction prevention function in a backing structure constructed from a backing stone and a backfill on the back side of an underwater structure. And a mixed material therefor.

The construction method of the backing structure to achieve the above object is a construction method of a backing structure that builds a backing structure composed of backing stones and backfill on the back side of the underwater structure, Cohesive soil whose water content is adjusted to 100 to 300% and steelmaking slag having a particle diameter of 37.5 mm or less are divided into 70 to 90% by volume ratio of the clayey soil and 30 to 10% by volume of steelmaking slag. %, And a mixed material in which a fibrous substance is added in an outer volume ratio of 0.1 to 1.0% is poured into the backing stone underwater.

  According to the construction method of this backing structure, by pouring a mixed material of cohesive soil, steelmaking slag, and fibrous material onto the backing stone, it is possible to form a suction prevention layer of the backfill, By adding a fibrous substance to the mixed material forming such a suction-prevention layer, the generation of cracks is suppressed, and even if cracks are generated by deformation, the strength can be recovered thereafter. In addition, the function of preventing suction by the suction prevention layer can be reliably maintained. In addition, such a mixed material has a lower fluidity than a material using a solidified material, and because of the arching action of the particles of the steelmaking slag, it is difficult for the mixed material to fall into the void of the backing stone, and therefore, is wasted. Material can be reduced.

  In the above method of constructing a backing structure, a layer made of the mixed material may be formed on a slope of the backing stone, and then the backfill may be constructed so as to be in contact with the formed layer. Since the fluidity of the mixed material is relatively small as described above, even if the slope of the backing stone slope becomes large, there is no need to take measures such as addition of a thickener or soil retention using a sandbag or the like, In addition, since there is no restriction on the magnitude of the slope, the degree of freedom in designing the backing structure is increased.

  Further, the first layer is formed by casting the mixed material having low fluidity underwater, and then the second layer is formed by casting the mixed material having high fluidity underwater on the first layer. Thus, a two-layer structure can be obtained.

  Further, the flow rate of the mixed material is adjusted to 82 mm or more and less than 90 mm to form a first layer, and then the flow value is adjusted to 90 mm or more to form a second layer on the first layer. To form a two-layer structure.

  As described above, by making the suction prevention layer a two-layer structure, it is possible to maintain the suction prevention function, reduce the material falling into the voids of the backing stone, and take measures such as adding a thickener and retaining soil. The respective effects of unnecessaryness can be more reliably obtained.

  The fluidity / flow value of the mixed material can be adjusted by changing at least one of the water content of the clayey soil, the mixing amount of the steelmaking slag, and the addition amount of the fibrous substance. In addition, a relatively low-flow mixed material is cast in water as the first layer, and then the mixed material having the same compounding ratio is subjected to impact / vibration during or after casting in water to improve fluidity. The second layer may be formed by increasing the height.

  Further, it is preferable that the first layer is formed by glove injection, and the second layer is formed by pumping.

The mixed material for achieving the above object is a material applied for preventing suction of the backfill on the backfill in a backfill structure composed of backfill and backfill, Cohesive soil whose water content is adjusted to 100 to 300% and steelmaking slag having a particle size of 37.5 mm or less are divided into 70 to 90% by volume, and 30 to 10% by volume of the steelmaking slag. And a fibrous substance in an outer volume ratio of 0.1 to 1.0% .

  According to this mixed material, it is possible to form a layer for preventing suction of the buried soil by being cast on the backing stone, but in such a layer for preventing suction, generation of cracks is suppressed by the fibrous substance, However, even if cracks occur due to deformation, the strength can be recovered thereafter, so that the suction preventing function of the suction preventing layer can be maintained. In addition, such a mixed material has a lower fluidity than a material using a solidified material, and because of the arching action of the particles of the steelmaking slag, it is difficult for the mixed material to fall into the void of the backing stone, and therefore, is wasted. Material can be reduced.

  ADVANTAGE OF THE INVENTION According to the construction method and mixed material of the backing structure of this invention, in the backing structure constructed from a backing stone and a backfill on the back side of an underwater structure, a suction prevention function is reliably maintained on the backing stone. can do.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows the caisson type revetment / quayside structure by this embodiment schematically. It is the schematic which shows a mode that the suction prevention layer 13 of FIG. 1 is constructed by pumping. It is the schematic which shows a mode that the suction prevention layer 13 of FIG. 1 is constructed by grab injection. FIG. 2 is a cross-sectional view of a main part showing a configuration example in which the suction prevention layer 13 of FIG. 1 has a two-layer structure. It is a figure which shows the stress-strain diagram obtained from the uniaxial compression test performed about the mixed material of Table 1 in this Example. It is a figure (a) and (b) which show the relationship between the compression strain and the compression stress ratio obtained from the uniaxial compression test performed about the mixed material of Table 2 for confirmation of strength recovery in this Example. 4 is a graph showing the results of a flow test performed based on JHS A 313 for the mixed materials shown in Table 3 in this example. 4 is a graph showing the results of a mortar flow test performed on the mixed materials in Table 3 based on JIS R5201 in this example. 5 is a graph showing the results of a flow test performed on the mixed materials shown in Table 4 in this example. 9 is a graph showing the results of a flow test performed on the mixed materials shown in Table 5 in this example.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a sectional view schematically showing a caisson-type seawall / quay structure according to the present embodiment.

  As shown in FIG. 1, the revetment / quay structure according to the present embodiment includes a gravity caisson 1 in which the inside 1 a is filled with filling sand, a mound 2 constructed on the bottom of the water by rubble and the caisson 1 is installed, and a revetment. A backing structure 10 constructed on the shore side (right side in FIG. 1) of the quay wall. Necessary superstructures (not shown) will be installed above the revetment and quay structures.

  The backing structure 10 of FIG. 1 includes a backing stone 11 constructed from crushed stone on the back surface 1 b side (shore side) of the caisson 1, a suction prevention layer 13 constructed on a slope 11 a of the backing stone 11, A backfill 12 constructed from earth and sand is provided on the shore side (right side in FIG. 1) so as to be in contact with the suction prevention layer 13.

  The suction-prevention layer 13 is made of a cohesive soil whose water content is adjusted to 100 to 300% (70 to 90% in the inner volume ratio) and a steelmaking slag having a particle size of 37.5 mm or less (10 to 30% in the inner volume ratio). And a mixed material in which a fibrous substance is further added in an outer volume ratio of 0.1 to 1.0%.

  With the suction-prevention layer 13 made of such a mixed material, the earth and sand of the buried soil 12 of the backing structure 10 is sucked to the front side of the caisson 1 through the gap between the crushed stones of the backing stone 11 and the gap between the rubble stones of the mound 2 and the back. It is possible to prevent a suction phenomenon in which the buried soil 12 is reduced.

  As the above-mentioned cohesive soil, in addition to dredged soil, purchased materials such as mountain clay and bentonite can be used. Adjust the water content to 100-300% before use.

  The steelmaking slag described above has a particle size of 37.5 mm or less, and the mixing amount of the steelmaking slag is adjusted within a range of 10 to 30% (volume ratio) with respect to the viscous soil according to the target strength and the like. In addition, it is preferable to use a converter steelmaking slag which is a granular material generated in a step of refining pig iron produced in a blast furnace in a converter as the steelmaking slag.

  Various fibers can be used as the above-mentioned fibrous substance, for example, polyester, polypropylene, polyethylene, vinylon, and the like. The size of the fiber is arbitrary, but since the fiber is caught on the rough surface of the steelmaking slag, it is possible to omit the work of loosening short fibers in advance during kneading. In addition, by using thin fibers, the effect can be exhibited with a small amount of fibers. The amount of addition is adjusted within the range of 0.1 to 1.0% in terms of the outer volume ratio.

  According to the mixed material according to the present embodiment, the strength can be improved by mixing the steelmaking slag with the clayey soil. In addition, the addition of the fibrous substance makes it easier for the fibrous substance to become entangled with the steelmaking slag, which is a granular material, so that it has a high deformation followability and suppresses the decrease in strength even when strain is applied, thereby suppressing the occurrence of cracks. can do. Furthermore, even if cracks occur in the mixed material, it is possible to expect the strength to recover thereafter.

  According to the mixed material according to the present embodiment, the occurrence of cracks in the suction-prevention layer 13 made of such mixed material is suppressed, and even if cracks occur due to deformation, the strength can be expected to recover thereafter. Therefore, the function of preventing the backfill soil from being sucked out by the suction preventing layer 13 can be reliably maintained.

  In addition, the mixed material of the present embodiment has a lower fluidity than a material using a solidifying material such as cement, and has an arching effect due to particles of steelmaking slag. This makes it difficult to fall into the gap, so that the amount of wasted material can be reduced and the material cost does not increase. In addition, even if the slope of the slope 11a of the backing stone 11 becomes large, there is no need to take measures such as adding a thickener or retaining soil using sandbags, etc., and there is no restriction on the magnitude of the slope. Therefore, the degree of freedom in designing the backing structure is increased.

  Further, in the mixed material of the present embodiment, if the water content of the viscous soil is 100% or more, the workability with the steelmaking slag and the fibrous material is good without being reduced, and if the water content is 300% or less, Good without reduction in strength. When the mixing ratio of the steelmaking slag is 30% or less by volume, the fluidity and workability are good without being reduced, and when the mixing ratio is 10% or more, improvement in strength can be expected. When the amount of the fibrous substance is at least 0.1% by volume, the effect of suppressing the decrease in strength, imparting deformation followability and recovering the strength can be obtained, and when the amount of addition is at most 1.0% by volume. In addition, the fluidity and workability can be ensured, and the addition amount does not become too large, so that the cost is not so high.

  Since the mixed material of the present embodiment includes steelmaking slag having a high density, the unit volume weight is larger than the FA mortar (1.65) (about 1.8). In the suction prevention layer 13, it is necessary to resist the transmitted wave pressure transmitted through the mound 2 by its own weight. However, since the mixed material has a large unit volume weight, the thickness of the suction prevention layer 13 must be reduced. It is possible to reduce material and construction costs. Further, since the conventional sandproof sheet is not required, diving work at a large depth for leveling the backing stone slope and connecting the sheet is not required, and therefore, workability is not reduced.

  The backing structure 10 shown in FIG. 1 is configured such that crushed stone is put into the back surface 1b side (shore side) of the caisson 1 to construct the backing stone 11, and then the above-described mixed material is placed on the slope 11a of the backing stone 11. The construction can be performed by constructing the suction-prevention layer 13 by using the above-mentioned method and then putting earth and sand on the shore side in contact with the suction-prevention layer 13 to construct the backfill 12.

  Next, the construction of the above-described suction prevention layer 13 will be further described with reference to FIGS. FIG. 2 is a schematic view showing a state in which the suction prevention layer 13 of FIG. 1 is constructed by pumping. FIG. 3 is a schematic view showing a state in which the suction-preventing layer 13 of FIG.

  As shown in FIG. 2, on the mixed casting outfitting barge 20, the dredged soil is transported from the storage unit 21 by the belt conveyor 23, the steelmaking slag is transported from the storage unit 22 by the belt conveyor 24, and the dredged soil is transported at a predetermined volume ratio. The steelmaking slag is supplied to the mixer 25, the short fibers are supplied to the mixer 25 at a predetermined volume ratio, and the dredged soil, the steelmaking slag, and the short fibers are mixed by the mixer 25, and the mixed material is beaten. Underwater is cast on the slope 11a of the backing stone 11 through the hose 27 and the setting pipe 28 by the setting pump 26, and the suction prevention layer 13 is applied. The casting pipe 28 is suspended and moved by a crane 29 and installed at a predetermined position.

  As shown in FIG. 3, the above-mentioned mixed material M is produced in a land plant, this mixed material M is transported by a tugboat 31 on an earthmoving ship 30, and soil is transferred by a grab bucket 34 suspended by a crane 33 of a crane ship 32. A predetermined amount of the mixed material M of the carrier 30 is formed into a block shape and poured into the slope 11a of the backing stone 11 so that the mixed material M is cast underwater, and the suction prevention layer 13 is constructed.

  As described above, according to the present embodiment, the above-described mixed material is submerged in the slope 11a of the backing stone 11 in FIG. 1 by the pumping in FIG. 2 or the glove in FIG. The anti-suction layer 13 can be constructed.

  Next, another embodiment in which the suction preventing layer 13 of FIG. 1 has a two-layer structure will be described with reference to FIG. FIG. 4 is a cross-sectional view of a main part showing a configuration example in which the suction prevention layer 13 of FIG. 1 has a two-layer structure.

  The first layer 13a formed on the slope 11a of the backing stone 11 by using the above-described mixed material adjusted to have low fluidity, and the above-described layer adjusted to have high fluidity are used as the suction prevention layer 13 in FIG. And a second layer 13b formed on the first layer 13a using a mixed material of

  Specifically, the first layer 13a is formed by adjusting the flow value of the above-described mixed material to a low fluidity of 82 mm or more and less than 90 mm, and then adjusting the flow value to a high fluidity of 90 mm or more, The second layer 13b is formed on the one layer 13a. The fluidity / flow value of the above-mentioned mixed material can be adjusted by changing at least one of the water content of the cohesive soil, the mixing amount of the steelmaking slag, and the addition amount of the fibrous substance. Can be determined by a flow test according to JHS A 313.

  4 is implemented by forming the first layer 13a by glove injection as shown in FIG. 3 and forming the second layer 13b by pumping as shown in FIG. Is preferred.

  Since the mixed material of the present embodiment tends to have lower fluidity than a material using a solidifying material such as cement, it is necessary to prevent the mixed material from falling into the crushed stone gap of the backing stone 11 as described above. On the other hand, a gap is likely to be formed between the poured mixed materials, and if the gap is formed, the portion becomes a water path, and the effect of preventing suction is reduced. In order to solve this problem, according to the two-layer structure of the suction-prevention layer 13 shown in FIG. 4, the first layer 13a is formed from a relatively low-flow mixed material, thereby preventing the mixed material from falling into gaps. Even if a gap is formed between the mixed materials, since the second layer 13b is formed from the mixed material having a relatively high fluidity thereon, the gap can be filled, and the formation of water channels can be prevented. . Thereby, the effect of maintaining the function of preventing the suction of the buried back soil in the suction prevention layer 13 and the effect of preventing the mixed material from falling into the voids can be reliably obtained.

  The fluidity of the mixed material can be adjusted by adjusting the water content of the viscous soil, the mixed amount of the steelmaking slag, and the added amount of the short fiber. The fluidity of the material may be increased. Such impact and vibration can be given to the mixed material using a vibrator, a vibration bucket, or the like.

  In addition, for example, when the two-layer structure shown in FIG. 4 is constructed, the first layer 13a is formed from a normal mixed material, and the mixed material having the same compounding ratio is subjected to impact and vibration to achieve high fluidity. The two layers 13b may be formed.

  The mixed material according to the present invention will be further described with reference to examples, but the present invention is not limited to the examples.

The mixed material of this example is a dredged soil adjusted to a water content of 160% (soil particle density 2.633 g / cm ³ , liquid limit 101.3%) and steelmaking slag (adjusted to a particle size of 9.5 mm or less for laboratory testing) And polyester short fibers (fiber length 20 mm, fiber diameter 14.8 μm) are added at a predetermined volume ratio and mixed. In Examples 1 to 6, the blending ratio of short fibers was changed in six steps from 0.1 to 1.0 vol% in volume ratio, and in Comparative Example 1, short fibers were not blended. The formulations for Examples 1 to 6 and Comparative Example 1 are shown in Table 1 below.

  As shown in Table 1, a mixed material in which the amount of fiber added was used as a parameter was prepared, and a uniaxial compression test was performed 7 days after curing. FIG. 5 shows a stress-strain diagram obtained from the uniaxial compression test. The uniaxial compression test was performed based on JIS A1216.

  From the results in FIG. 5, in Comparative Example 1 in which the short fibers were not mixed, the compressive stress was reduced before reaching 5% compressive strain, whereas the short fibers were 0.2% vol in volume ratio as in Examples 2 to 6. It can be seen that the above addition results in a material whose compressive stress does not decrease even at a large strain level of 5% or more. Further, in Example 1 in which short fibers were added at a volume ratio of 0.1 vol%, it was found that the compressive stress did not decrease when the compressive strain was 5%. In addition, in Examples 2 to 6 in which the amount of added fiber is 0.2 to 1.0 vol% in volume ratio, it can be seen that the effect of retaining the compressive stress is increased at a large strain level of 5% or more according to the amount of added fiber. That is, when the fiber addition amount increases, the deformation following property of the mixed material is improved, and the occurrence of cracks is suppressed.

  As described above, in Examples 1 to 6 in which the fiber addition amount is 0.1 to 1.0 vol%, the compressive stress at a strain of 5% or more does not decrease depending on the fiber addition amount, and the deformation followability is improved. I understand. Also, it is considered that the compressive stress does not decrease even when the fiber addition amount exceeds 1.0 vol%, but no remarkable difference is observed by increasing the addition amount at the strain level of 5%. It is understood that it is appropriate to set the upper limit of the amount of added fiber to 1.0 vol%, since this causes a cost increase.

Next, as shown in Table 2 below, as shown in Table 2 below, a steelmaking slag (grain for laboratory test) was prepared on dredged soil (soil particle density 2.633 g / cm ³ , liquid limit 101.3%) adjusted to a water content of 160%. Polyester short fiber (fiber length: 20 mm, fiber diameter: 14.8 μm) was added at a predetermined volume ratio and mixed at a predetermined volume ratio to obtain a mixed material. The addition amount of the fiber was set to 0.5 vol% because it was close to the median of the addition amount of the fiber (0.1 to 1.0 vol%) in the mixed material according to the present embodiment. Further, in order to compare the recovery of the shear strength depending on the presence or absence of the addition of the fiber, a material in which the amount of the added fiber was 0 vol% was obtained as Comparative Example 2. Assuming that the specific gravity of the fiber is 1.38 g / cm ³ , the fiber weight per unit volume when the fiber addition amount is 0.5 vol% is 6.9 kg / m ³ .

  After the specimen prepared from the above mixed material was cured for 28 days, after uniaxial compression to a strain level of 5%, the loading was temporarily stopped, the specimen was taken out, and after exposing for 85 days, the uniaxial compression test was performed again. . The method of exposure depends on the method of wrapping the specimen in wrap to prevent drying (air exposure). The reason for initially setting the compression strain level to 5% is that, in the specimen of Comparative Example 2 where the fiber addition amount is 0 vol%, when the compression strain exceeding 5% is applied, the specimen is thereafter taken out and prepared for exposure. This is because there is a risk that the specimen will collapse when performing the test.

  FIG. 6A shows the result of each compression test of Comparative Example 2 and FIG. 6B shows the result of each compression test of Example 7. The compressive stress on the vertical axis in FIGS. 6A and 6B is normalized (compressive stress ratio) by the maximum value of the compressive stress at a compressive strain of 5% or less. When the fiber was not added as shown in FIG. 6 (a), when the reloading was performed, the uniaxial compressive strength at the time of the first compression was lower than the initial compression strength. On the other hand, as shown in FIG. %, The addition of steelmaking slag and fiber to the dredged soil exceeds the uniaxial compressive strength at the time of the initial compression, confirming the strength recovery. As described above, according to the mixed material of the present example, even if cracks occur, it is possible to expect subsequent strength recovery.

Next, under the condition that 30 vol% of steelmaking slag having a particle diameter of 37.5 mm or less is added, the water content of the dredged soil (soil particle density 2.668 g / cm ³ , liquid limit 84.3%) is defined as a percentage of liquid limit (wL). The mixed material was prepared by changing the addition amount of the polyester short fiber at a predetermined volume ratio while changing the amount to 125, 150, and 175% in three stages. As shown in Table 3 below, in Examples 8 to 12, the blending ratio of short fibers was changed in five steps from 0.1 to 1.0 vol% in volume ratio, and in Comparative Example 3, no short fibers were blended.

  Flow tests were performed on the mixed materials shown in Table 3 based on the Japan Highway Public Corporation Standard JHS A 313, and the results are shown in FIG. In the flow test based on JHS A 313, the mixed material was filled in a cylindrical tube having a length of 80 mm and a diameter of 80 mm, and the diameter of the mixed material after the tube was pulled up was measured. FIG. 7 shows that the fluidity of the mixed material can be adjusted by the water content of the dredged soil and the amount of added fiber. That is, the composition in the range indicated by the solid line in FIG. 7 can be set to high fluidity with a flow value of 90 mm or more, and the composition in the range indicated by the broken line in FIG. 7 can be set to low fluidity with a flow value of less than 90 mm (82 mm or more). The flow value of 82 mm is a lower limit for obtaining good workability and fluidity.

  Next, a mortar flow test was performed on the mixed materials shown in Table 3 based on JIS R5201, and the results are shown in FIG. In the mortar flow test based on JIS R5201, using a mortar flow tester (compliant with JIS R5201) sold by Nishio Rentall Co., Ltd., the mixed material is filled into a flow cone with an upper inner diameter of 70 mm, a lower inner diameter of 100 mm, and a height of 60 mm. Then, the flow cone was pulled up, and the handle was turned 15 times for 15 seconds to raise and lower the flow table, and then the diameter of the mixed material was measured. From FIG. 8, it is understood that the fluidity of the mixed material can be adjusted by the water content ratio of the dredged soil and the amount of added fiber, as in FIG. 7. In addition, it can be seen that, by giving an impact or vibration to the mixed material, the mortar flow value increases and the fluidity increases. For example, as shown in Fig. 7, the flow value of a dredged soil with a water content of 1.25 wL and a fiber addition of 0.5 vol% is 82.5 mm, and only 2.5 mm widens from the diameter of the filled cylinder. As a result of the given mortar flow test, it was 123.5 mm as shown in FIG.

Next, as shown in Table 4, steelmaking slag was used as dredged soil (having a soil particle density of 2.668 g / cm ³ and a liquidity limit of 84.3%) having a water content of 126.5% (150% of the liquidity limit) as shown in Table 4. (Particle size 37.5mm or less) is mixed at a predetermined volume ratio (20vol%, 30vol%), and polyester short fiber (fiber length 20mm, fiber diameter 14.8μm) is added and mixed at a volume ratio of 0.1 to 1.0vol%. Was subjected to a flow test based on JHS A313. Similar flow tests were also performed on the mixed materials in which the fiber addition amounts were 0 vol% and 1.5 vol% as Comparative Examples 4 to 7.

  These test results are shown in FIG. FIG. 9 shows that, even when the mixing amount of steelmaking slag is 20 vol%, the flow value decreases and the fluidity decreases as the amount of added short fibers increases, as in the case of 30 vol%. Comparing Comparative Examples 5 and 7 in which 1.5 vol% of short fibers were added with Examples 17 and 22 in which 1.0 vol% of fiber was added, in order to secure a flow value of 82 mm or more, the upper limit of the fiber addition amount Is preferably 1.0 vol%.

Next, as shown in Table 5, as Examples 23 to 25, the dredged soil (soil particle density 2.633 g / cm ³ , liquid limit 101.3%) adjusted to a water content of 160% (168% of liquid limit) and steelmaking Slag (adjusted to a particle size of 9.5 mm or less for laboratory testing) is mixed at a predetermined volume ratio, and polyester short fiber (fiber length 20 mm, fiber diameter 14.8 μm) is added and mixed at a volume ratio of 0.5 vol%. In order to improve the fluidity, a mixed material to which 2 kg / m ^{3 of} a dispersant (AMPS type) was added was subjected to a flow test based on JHS A313. Also, as Comparative Example 8, a flow test was performed on the same material except that the volume ratio of the steelmaking slag was 40 vol%.

FIG. 10 shows the test results. FIG. 10 shows that as the mixing amount of the steelmaking slag increases, the flow value decreases, and the fluidity of the mixed material decreases. In Comparative Example 8 in which the mixing amount of the steelmaking slag was 40 vol%, the flow value was less than 82 mm, and it can be seen that the fluidity was considerably low. In contrast, in Examples 23 to 25 in which the mixing amount of the steelmaking slag was 30 vol% or less, the flow value exceeded 82 mm, and it can be seen that the fluidity could be secured. Thereby, it was confirmed that it is appropriate to set the mixing amount of the steelmaking slag to 10 to 30 vol% in the present mixed material. In addition, the uniaxial compressive strength on the 28th day when the mixing amount of the steelmaking slag was 30 vol% was about 300 kN / m ² .

  The embodiments for carrying out the present invention have been described above, but the present invention is not limited to these, and various modifications can be made within the technical idea of the present invention. For example, in the present embodiment, the backing structure according to the present invention is applied to a caisson-type seawall / quay structure, but the present invention is not limited to this, and can be applied to other underwater structures. It may be applied to quay structures.

  When the suction-preventing layer 13 shown in FIG. 1 is formed as a single layer, the fluidity of the mixed material is adjusted so that the mixed material can be prevented from falling into gaps and can be prevented from forming gaps. In this case, the fluidity of the mixed material can be adjusted by the water content of the viscous soil, the mixed amount of the steelmaking slag, and the added amount of the short fiber. This may increase the fluidity of the mixed material.

  Further, in FIG. 2, the dredged soil, the steelmaking slag, and the short fiber are mixed in the plant on the outfitting barge 20 to produce a mixed material. However, the method of producing the mixed material is not limited thereto. In this case, the prepared mixed material is transported by an earth transport ship and pumping is performed. Further, in FIG. 3, the mixed material is produced in a land plant, but similarly to FIG. 2, it may be produced in a plant on an outfitting barge and gloved.

  According to the present invention, in the backing structure constructed from the backing stone and the backfill on the back side of the underwater structure, the function of preventing suction on the backing stone can be reliably maintained, so that the backfill soil is sucked and backed. Depression in buried soil can be prevented.

DESCRIPTION OF SYMBOLS 1 Caisson, underwater structure 1b Back of caisson 2 Mound 10 Backing structure 11 Backing stone 11a Slope 12 Backfill 13 Suction prevention layer 13a First layer 13b Second layer M Mixed material

Claims (6)

A method of constructing a backing structure in which a backing structure composed of backing stone and backfill is constructed on the back side of the underwater structure,
Cohesive soil whose water content is adjusted to 100 to 300% and steelmaking slag having a particle diameter of 37.5 mm or less are divided into 70 to 90% by volume ratio of the clayey soil and 30 to 10% by volume of steelmaking slag. %, And a mixed material in which a fibrous substance is added in an outer volume ratio of 0.1 to 1.0% is cast in the backing stone underwater.   The method of claim 1, wherein a layer made of the mixed material is formed on a slope of the backing stone, and then the backfill is constructed so as to be in contact with the formed layer.   By casting the mixed material having low fluidity underwater to form a first layer, and then casting the mixed material having high fluidity underwater on the first layer to form a second layer. The method according to claim 1 or 2, wherein the backing structure has a two-layer structure.   The first layer is formed by adjusting the flow value of the mixed material to 82 mm or more and less than 90 mm, and then the second layer is formed on the first layer by adjusting the flow value to 90 mm or more. 3. The method according to claim 1, wherein the backing structure has a layered structure.   The method according to claim 3, wherein the first layer is formed by glove injection, and the second layer is formed by pumping. A material applied on the backing stone in the backing structure composed of the backing stone and the backfill to prevent the backfill from being sucked out,
Cohesive soil whose water content is adjusted to 100 to 300% and steelmaking slag having a particle size of 37.5 mm or less are divided into 70 to 90% by volume, and 30 to 10% by volume of the steelmaking slag. And a mixed material further containing a fibrous substance in an outer volume ratio of 0.1 to 1.0% .

Images