JPH0345710A - Fiber material used for reinforcing soil - Google Patents

Abstract

PURPOSE:To obtain filament yarn for fiber-reinforced soil civil engineering work methods, having specific values of tensile characteristics of strength and elongation and capable of reinforcing soil formed from earth and sand, such as gravel, sand or silt. CONSTITUTION:The objective yarn having tensile characteristics of >=1.3g/d, preferably 1.5-18g/d strength at 2% elongation, >=4.5g/d, preferably 5-20g/d strength at 10% elongation and <=20%, preferably 1.5-15% breaking elongation.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a fiber material for reinforcing soil formed from gravel, sand, silt, etc. The present invention relates to fiber materials that are used to create fiber-reinforced soil by continuously and rationally mixing fiber materials and earth and sand when constructing structures or reinforcing soft ground.

(Prior technology) In order to improve the mechanical stability of the soil as a whole, reinforcing particles are mixed into the soil, and the shear deformation inside the soil that occurs due to the soil's own weight and external forces is suppressed, and the apparent strength of the soil is reduced. Many soil reinforcement methods have been developed and implemented to improve soil quality.

As an example of using a continuous thread fiber material in the soil reinforcement method, Japanese Patent Application Laid-open No. 167170/1983 describes a soil reinforcement method that uses a jet nozzle to apply high pressure water or compressed air.
Continuous long fibers, such as polyester filaments, are drawn out and sprayed onto the construction surface, and at the same time earth and sand are removed with compressed air or
Conveyed using a high-speed held conveyor, etc., on the construction surface,
It discloses a soil reinforcement method in which reinforced soil is created by mixing it with polyester filament, compacting it sequentially, and layering it until the required thickness is reached.

In addition, a report by E. Leflep et al. at the 3rd International Geotextile Conference (1986, Vienna, Austria) “
"Reinforcing soil with continuous long fibers" discloses an evaluation method using a triaxial compression test as a method for evaluating the mechanical properties of the reinforced soil produced.

That is, as for the mechanical properties of the reinforced soil produced by the above method, using polyester multifilament of 50 to 330 dTex, the adhesion strength of 134 to 356 KPa/cffl was obtained at a fiber blend ratio of 0.2% by weight to dry sand. It is said that it has some soil and sand (approximately 10
This shows that there is a large difference compared to KPa/c+11). In this construction method, the magnitude of the frictional force (pseudo adhesive force) generated between long fibers and soil particles due to their entanglement is determined by how three-dimensionally and densely entangled the long fibers and soil particles are. This is related to both the aspect that depends on the so-called surface friction force between the earth and sand and the fibers, and the aspect that depends on the mechanical properties of the reinforcing material itself.

(Problem to be Solved by the Invention) However, the above-mentioned Japanese Patent Application Laid-Open No. 167170/1989 describes an example of the reinforcement system in the soil reinforcement method, and the report by E. Leflaive et al. It merely describes the concept of reinforcement theory using fibers, such as showing adhesion dependence on blending ratio using the example of polyester filament for general clothing, and does not provide any information on the mechanical properties of fiber materials that have a large effect on reinforcement performance. Not disclosed. For this reason, the lack of guidelines for selecting suitable fiber materials when implementing this method has become a major problem to be solved in order to spread the method.

(Means for Solving the Problems) The present inventors solved the above-mentioned problems and clarified the appropriate mechanical property range of the fiber material used in the method, thereby solving the problems that have been revealed so far. This made it possible to identify fiber materials suitable for constructing reinforced soil with higher reinforcement performance. That is, the present invention has a 2% tensile strength of 1.3 g/d or more and a 10% tensile strength of 4.58 g/d.
It is a continuous fiber yarn having a tensile property of /d or more and a breaking elongation of 20% or less. In order to satisfy the purpose of the present invention, the 2% tensile strength in a low-speed tensile test (the same deformation rate as the compressive deformation rate in the triaxial compression test of reinforced soil: relative speed 1%/min) must be IJg/d. As mentioned above, it is essential that the continuous fiber yarn has tensile properties such that the 1.0% elongation strength is 4.5 g/d or more and the elongation at break is 20% or less. Preferred tensile property values include a 2% tensile strength of 1
．． 3~18g/d10% elongation strength is 4.5~20g/d
and the elongation at break is in the range of 1.5 to 20%,
More preferably, the 2% and 10% elongation strengths are each 1.
5 to 18 g/d, 5 to 20 g/d, and the elongation at break is 1.
It has a range of 5 to 15%. Table 1, 2
As shown in the table, the 2% and 10% elongation strengths are 1.
If the yarn has a breaking elongation of less than 3.4.5 g/d and a breaking elongation of more than 20%, good reinforced soil performance (overall evaluation) cannot be obtained.

Reinforcement performance can generally be primarily expressed by two factors: the maximum principal stress difference (stress at peak) and strain at peak in a triaxial compression test.The larger the difference in maximum principal stress, the greater the strain at peak. It is said that a reasonably small value is good.

According to the detailed experimental results of the present inventors, as shown in Figure 1, the maximum principal stress difference (σ1-σ3) The maximum stress developed by resisting the shear deformation inside the soil caused by its own weight and external force (where σ3 is the lateral pressure from the pressurized water, and σ1 is the axial stress while applying σ3) is the fibrous material. It has been discovered for the first time that, regardless of the material type, it strongly depends on the 10% elongation strength of the fiber material, and the greater the strength, the greater the maximum principal stress difference. This shows that the 10% tensile strength has a strong correlation with the maximum compressive stress of the reinforced soil, and for the performance to withstand actual use, it must be 4.5 g/d or more.
We found out that it is essential.

Next, as shown in Figures 2 and 3, the peak strain (compressive strain rate at which the maximum compressive stress determined by the triaxial compression test on the reinforcement is shown), that is, the rate of compressive strain that occurs while resisting shear deformation The strain at maximum stress, which is a factor that indicates the deformation resistance of soil, is strongly dependent on the 2% tensile strength of the fiber material and the elongation at break, and the higher the strength, the lower the elongation. It was discovered for the first time that the smaller the size, the better the deformation resistance on reinforcement. It was determined that in order to have performance that can withstand actual use, it is essential that the content be 1.3 g/d or more and less than 20%, respectively.

The continuous fiber thread referred to in the present invention is a general term for threads called "yarn" in boat fishing. In order to increase the size of the yarn, it is preferable that the yarn be in the form of a multifilament.

The types of fibers include, for example, synthetic fibers such as polyamide, polyester, polyolefin, polyacrylic, and aromatic polyamide, and carbon fiber, and are not particularly limited, but from the standpoint of durability in soil, Polyester-based and polyacrylic-based synthetic fibers are particularly desirable. In addition, the soil used in the present invention is gravel (G), gravelly (CF), sand (S), and sandy soil (SF) according to the Japan Unified Soil Classification.
etc. is optimal.

Next, the effects of the present invention will be explained in detail using Examples.

(Examples 1-2) (Comparative Examples 1-3) In order to produce fiber-reinforced soil in which soil and fibers are three-dimensionally intertwined for evaluation of reinforced soil performance, an inner diameter 1
Pre-dried sand (°' S of the Japan Unified Soil Classification
-M” particle size 75 um to 2000 μm),
Continuous fiber yarn shown in Table 1 and water (1% to dry sand)
0% by weight mixture) was added simultaneously and continuously, and sequentially,
While compacting, a 10 cmφ x 20 cmH triaxial compression test specimen was prepared. The fiber mixing ratio at this time was 0.3% by weight. A triaxial compression test was conducted on the specimen under the conditions of a lateral pressure of 1.0 kg-f/d and a relative compression speed of 1%/min, and the stress-strain curve was determined to determine the reinforced soil performance (maximum principal stress difference,
and peak strain rate) were measured. The results are shown in Table 1 in comparison with Comparative Examples 1 to 3, which were measured under the same conditions as Example 1. As the results show, it is clear that the tensile properties of fibers are greatly involved in the performance of reinforced soil. Even with the same material, same denier, and the same mixing ratio, the performance of reinforced soil varies, and how to select the physical properties of the fibers used to mix soil and sand is the key to efficiently implementing this fiber-reinforced soil method. It is clear that this is a key point, and that it is possible to construct excellent reinforced soil by using the fiber material having the physical properties of the present invention.

(Examples 3 to 6) (Comparative Examples 4 to 7) In the same manner as in Example 1, specimens for triaxial compression tests were prepared using the fiber materials shown in Table 2, and the reinforced soil performance was measured. As shown in Table 2, the experimental results using various materials and various deniers clearly show that the performance of reinforced soil strongly depends on the tensile properties of the fibers.

(Effects of the Invention) By using the fiber material of the present invention in a fiber reinforced earth construction method that uses fiber materials to create reinforced soil, it is possible to create fiber reinforced soil with excellent reinforced soil performance as shown in Examples. By using fiber materials with high performance tensile properties, it is possible to reduce the laminated thickness for reinforcement during construction, and it becomes possible to construct civil engineering structures on high-rises and steep slopes. In addition, when obtaining the same reinforcement performance,
It is possible to reduce the fiber blend ratio compared to conventional technology, which leads to an increase in construction capacity and cost rationalization, and will greatly contribute to the spread of fiber-reinforced earthwork methods.

[Brief explanation of drawings]

Figures 1, 2, and 3 are graphs showing the relationships between maximum principal stress difference and 10% elongation strength, peak strain and 2% elongation strength, and peak strain and elongation at break, respectively. .

Claims (1)

[Claims] 2% elongation strength is 1.3 g/d or more, 10% elongation strength is
A continuous fiber yarn for fiber-reinforced earthworks having tensile properties of 4.5 g/d or more and a breaking elongation of 20% or less.