Method for designing a paving structure and an interlocking block paving structure

Abstract

To maintain good road surface conditions on a heavy load area for a long term by applying the multilayer elasticity theory and the fatigue analysis.SOLUTION: A pavement structure design method at least includes: a step (S2) of calculating elastic modulus of a block layer where spread sand laid on the upper subbase and interlocking blocks placed on the spread sand are integrated by using a measurement result obtained by conducting bending measurement to interlocking block pavement in which a road bed, lower subbase, upper subbase, spread sand, and interlocking blocks are laminated; a step (S3) of calculating elastic modulus of the spread sand simple substance and elastic modulus of interlocking block simple substance placed on the spread sand respectively; a step (S6) of calculating bending, stress, or strain of the interlocking block pavement on a heavy load area by applying elastic modulus of the block layer, elastic modulus of the spread sand simple substance, and elastic modulus of the interlocking block simple substance to multilayer elasticity theory; and a step (S7) of confirming the safety of these values.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for designing a paving structure of interlocking block paving in a heavy load area and an interlocking block paving structure.

Background Art

[0002] In the structural design of paving in heavy load areas such as container yards, "multi-layer elastic theory" and "fatigue analysis" are used in combination. When designing using the multi-layer elastic theory, the most important factor is the numerical setting of the elastic coefficients of the ILB (Inter Locking Block) and the sand bedding. If this set value is too low, the stress and strain generated in the paving will increase and the service life will be shortened. On the other hand, if this set value is too high, the stress and strain will decrease and the service life will be prolonged. Among the cases where ILB paving has been constructed in container yards in Japan, there are no cases where "multi-layer elastic theory" and "fatigue analysis" have been applied.

[0003] For example, at the Kawasaki Port Container Terminal constructed about 24 years ago (in 1996), the design method proposed by the British Harbour Association was applied. Also, at Osaka South Port and Kobe Port Island, the construction was carried out by cutting a severely damaged semi-flexible paving or a modified asphalt layer by 12 cm and replacing it with 100 mm of ILB and 20 mm of sand bedding. Since it is planned to adopt 100 mm of ILB in container yards within Tokyo in the future, it has become an urgent task to study the roadbed design.

[0004] Here, regarding the research on the elastic modulus of ILB and spread sand, in 1982, Professor Miura of Nihon University reported that the numerical value obtained by analyzing ILB and spread sand as a single layer using a DC meter was "1648 MPa", and for ILB alone it was about "4335 MPa". Subsequently, in 1989, Professor Kasahara of Hokkaido Institute of Technology (now Hokkaido University of Science) and others reported from the results of measuring the deflection at four points on the ILB pavement at the construction site using a traction type FWD (Falling Weight Deflectometer) device that the elastic modulus of ILB and spread sand was "98 - 392 MPa". In 1998, Professor Murai of Tohoku Institute of Technology and others reported from the test results using an in-vehicle FWD that the elastic modulus of ILB alone was "1960 MPa" and the elastic modulus of spread sand alone was "29 MPa".

[0005] In Patent Document 1, when predicting the pavement life during the pavement design of a pavement structure designed using the two-layer elastic theory, a pavement life prediction method using the multi-layer elastic theory is proposed considering the differences between the two-layer elastic theory and the multi-layer elastic theory. In this technology, the pavement is divided into upper and lower layers, and based on the two-layer elastic theory, the design cross-section of each layer is determined, and by giving the layer thickness of each determined layer and the design elastic modulus corresponding to the materials used in each layer, based on the multi-layer elastic theory, the pavement life caused by the tensile strain occurring on the lower surface of the surface layer and the base layer and the pavement life caused by the compressive strain occurring on the upper surface of the roadbed are calculated from a given failure criterion formula.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Generally, the sound value of the elastic modulus in asphalt pavement is considered to be "6000 MPa", and in winter, it may exceed "10000 MPa". Compared with these values, the values of the previous research results described above are too small. Therefore, when using these values for the structural design of heavy-load areas, it is essential to strengthen the structure of the roadbed and road base, which will lead to high costs.

[0008] Also, compared with asphalt pavement and semi-flexible pavement, a major feature of ILB pavement in heavy-load areas is that since the material is concrete, there is no flow deformation at high temperatures in summer like asphalt pavement, and it is also less likely to crack due to a large number of regular joints like asphalt pavement. However, based on the previous research results, it is not possible to consider that the values reflect the characteristics of ILB pavement. It is considered that the low elastic modulus of the previous research results lies in the pavement diagnosis device and analysis method.

[0009] The present invention has been made in view of such circumstances, and an object thereof is to provide a pavement structure design method and an interlocking block pavement structure that can maintain good road surface properties in heavy-load areas over a long period by applying multi-layer elastic theory and fatigue analysis.

Means for Solving the Problems

[0010] (1) To achieve the above object, the present invention has taken the following means. That is, the paving structure design method of the present invention is a paving structure design method for interlocking block paving in a heavy load area, and for the interlocking block paving in which the roadbed, the lower roadbed, the upper roadbed, the bedding sand, and the interlocking blocks are laminated, using the measurement results obtained by performing deflection measurement, calculating the elastic modulus of the block layer in which the bedding sand laid on the upper roadbed and the interlocking blocks arranged on the bedding sand are integrated; calculating the elastic modulus of the bedding sand alone and the elastic modulus of the interlocking block alone arranged on the bedding sand respectively; and applying the elastic modulus of the block layer, the elastic modulus of the bedding sand alone, and the elastic modulus of the interlocking block alone to the multi-layer elastic theory to calculate the deflection, stress or strain of the interlocking block paving in the heavy load area, characterized by including at least the above steps.

[0011] (2) Further, the paving structure design method of the present invention is characterized in that the deflection, stress or strain of the interlocking block paving in the heavy load area is further calculated using the interlayer slip between the interlocking blocks and the bedding sand, and the interlayer slip between the bedding sand and the upper roadbed.

[0012] (3) Further, the paving structure design method of the present invention is characterized in that the allowable deflection amount of the interlocking block paving is further set.

[0013] (4) Further, the interlocking block paving structure of the present invention is an interlocking block paving structure in a heavy load area, designed using the paving structure design method described in any one of (1) to (3) above, characterized in that the roadbed, the lower roadbed, the upper roadbed, the bedding sand, and the interlocking blocks are laminated.

Advantages of the Invention

[0014] According to the present invention, it is possible to maintain good road surface properties in a heavy load area over a long period of time. In addition, it is possible to realize a pavement structure that is rich in durability, high in reliability and safety. Furthermore, as a result of the improved durability, it is possible to reduce the life cycle cost (LCC).

Brief Description of the Drawings

[0015]

Figure 1

Figure 2A

Figure 2B

Figure 2C

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0016] [Regarding Multilayer Elastic Theory and Fatigue Analysis] The multilayer elastic theory assumes that the materials of each layer constituting the pavement are elastic bodies. As shown in FIGS. 2A to 2C, the displacement (deflection d), stress (σ r ), and strain (ε r、 ε z) is a method for calculating. Figure 2A shows, in a pavement structure composed of a roadbed, a lower base course, an upper base course (asphalt mixture), sand bedding, and an ILB, the deflection (d), strain (ε r、 ε z ) generated in the pavement. Figure 2B shows, in a pavement structure composed of a roadbed, a lower base course, an upper base course (cement-based, concrete-based), sand bedding, and an ILB, the deflection (d), stress (σ r ), and strain (ε r ) generated in the pavement. Figure 2C shows, in a pavement structure composed of a roadbed, a lower base course, an upper base course (cement-based, concrete-based), an upper base course (asphalt mixture), sand bedding, and an ILB, the deflection (d), stress (σ r ), and strain (ε r、 ε z ) generated in the pavement. On the other hand, fatigue analysis is to calculate the allowable number of load repetitions by applying the fatigue curve and fatigue failure criterion formula of the material shown in Figure 3 to the obtained stress and strain. From this calculation result, it is essential to satisfy the following formula. (Allowable number of load repetitions) ≥ (Design traffic volume) [Regarding the elastic modulus] The elastic modulus of a material can be obtained by dividing the stress obtained from indoor tests etc. by the strain. In pavement, the higher this value, the higher the supporting force. When applying the multi-layer elastic theory, the most important factor is the value of the elastic modulus of each layer of the pavement structure. For asphalt pavement and concrete pavement, values of the elastic modulus including the roadbed and subgrade have been proposed based on past research results. In ILB pavement, as described above, it is inappropriate to apply these values because the values from past research results are small.

[0017] The elastic modulus of the new material can be calculated from non-destructive test results such as those of a FWD (Falling Weight Deflectometer) or from indoor repeated loading tests, etc. The FWD is a device that drops a heavy weight on the pavement to apply an impact load and measures the deflection shape of the pavement surface generated at that time. From the deflection shape measured by this device, it is possible to estimate the elastic modulus of the pavement structural layer using a dedicated program (for example, a dynamic inverse analysis program: Wave BALM).

[0018] [Measurement of Elastic Modulus] In order to measure the elastic moduli of the ILB and the sand bedding applied to structural analysis, with the cooperation of major road companies, in September 2018, on the ILB pavement of the Osaka South Port Container Yard, the deflection was measured on the ILB pavement using the latest diagnostic device at that time (vehicle-mounted FWD). As a result of analyzing the amount of deflection obtained from this measurement, when the ILB and the sand bedding were regarded as one layer, the elastic modulus was "3000 - 8000 MPa", and the average value was "5100 MPa". Also, according to the analysis by Professor Kawana of Tokyo University of Agriculture et al., the elastic modulus of the ILB alone was "5000 - 12000 MPa", and the average value was "8200 MPa". Also, the elastic modulus of the sand bedding alone was "10 - 50 MPa", and the average value was "20 MPa".

[0019] In the present invention, for the elastic modulus applied to structural design, the values of the ILB alone and the sand bedding alone, and the value when the ILB and the sand bedding are regarded as one layer (hereinafter referred to as the "block layer") are used. This is because it has been confirmed that there are differences in deflection, stress, and strain between the "ILB alone and the sand bedding alone" and the "block layer" depending on the pavement structure.

[0020] In the ILB pavement, when the bedding sand becomes fine-grained and consolidates, "interlayer slip" occurs at the interface between the block and the consolidated bedding sand, increasing the movement of the block and the disappearance rate of the joint sand, and also increasing the tendency of block damage. Yanaginuma et al. reported this in a paper (co-authored by Yoshida and Yanaginuma: "Durability Evaluation of Cushion Sand in Interlocking Block Pavement by Loaded Vehicle Driving Experiment": "Pavement", April 2001, pp. 26-31). Therefore, the interlayer slip between the ILB and the bedding sand is an important factor in structural analysis. The value of interlayer slip applied to the multi-layer elastic theory is generally set to "0 to 0.99". A case of "0" means that slip is not considered. For the value of interlayer slip applied to the ILB pavement, the maximum value of "0.99" is used. In this embodiment, the interlayer slip is set as follows. For asphalt, the analysis is performed without considering the interlayer slip. For concrete pavement, the slip is considered only for the concrete slab and the roadbed, and the analysis is performed without considering the slip for other layers. In contrast, for the interlayer slip between the ILB and the bedding sand, and between the bedding sand and the roadbed layer, the analysis is performed both with and without considering the slip. This is because considering the slip results in larger values of deflection, stress, strain, etc., leading to a safer design.

[0021] [Setting of Allowable Deflection Amount on ILB Pavement] In the heavy load area, since the wheel load is large, the deflection occurring on the ILB pavement also becomes large. When the deflection becomes large, the blocks compete with each other and corner chipping occurs. To prevent this, the allowable deflection amount is set using the results of past research. According to "Hata, Yananuma: Application of Interlocking Blocks to Road Pavements: Pavement 27-9, 1992", when the damage rate of the block is B, the deflection amount (mm) is W, and the joint width is J, "B = 6.097 + 3.775W - 3.267J" holds, and it is said that claims will occur when the damage rate of the block exceeds 3%. Also, according to the description on page 7 of "Yananuma, Sumika, Kihara, Habimoto: Five-year Investigation Results of Interlocking Block Pavement and Semi-deflection Pavement Test Constructed in the Container Yard: Pavement 55-9, 2020", the damage rate after 5 years is "Semi-deflection Pavement (41.4%) > 100mm ILB Pavement (8.3%) > 80mm ILB Pavement (5.5%)". This damage rate was obtained by classifying the ILB in the measurement section into chipping (mild and severe) and cracking and conducting a complete survey. On the other hand, for the semi-deflection pavement, it was calculated by the mesh method of dividing it into squares of 0.5m vertically and horizontally. Figure 4 is a table showing the correlation between the joint width, damage rate, and deflection amount in the interlocking block pavement calculated from the proposed formula. Based on the above findings and this correlation, it is preferably set that the allowable deflection amount is "1.0mm to 4.0mm" according to the traffic volume.

[0022] In the present invention, the structural design of the ILB pavement in the heavy load area is implemented based on the following concept. That is, in order to apply the multi-layer elastic theory, it is analyzed by two methods: a method of treating the ILB and the bedding sand as one layer (block layer), and a method of separating the ILB alone and the bedding sand alone, so that a safe and reliable structural design can be realized. Regarding the interlayer slip, a safer and more reliable structural design can be achieved by considering the presence or absence of slip. Also, by setting an allowable value for the deflection amount occurring on the ILB pavement, it is possible to prevent excessive corner chipping from occurring in the blocks.

Example

[0023] FIG. 1 is a flowchart showing the procedure of the pavement structure design method according to an embodiment of the present invention. First, the deflection of the interlocking block pavement is measured by an in-vehicle FWD (step S1). Next, in step S1, using the measurement results obtained by performing the deflection measurement, the elastic modulus of the block layer in which the sand layer laid on the upper roadbed and the interlocking blocks arranged on the sand layer are integrated is calculated (step S2). As described above, the elastic modulus calculated here is 3000 to 8000 MPa, and the average value is 5100 MPa. Next, the elastic modulus of the sand layer alone and the elastic modulus of the interlocking blocks arranged on the sand layer are calculated respectively (step S3). The elastic modulus of the interlocking blocks alone is 5000 to 12000 MPa, and the average value is 8200 MPa as described above. Also, the elastic modulus of the sand layer alone is 10 to 50 MPa, and the average value is 20 MPa as described above.

[0024] Next, the interlayer slip between the interlocking blocks and the sand layer, and the interlayer slip between the sand layer and the upper roadbed are set (step S4). Next, the allowable deflection amount of the interlocking block pavement is further set (step S5). Here, as described above, the allowable deflection amount is set to 1.0 mm to 4.0 mm according to the traffic volume. Next, the elastic modulus of the block layer, and the elastic modulus of the sand layer alone and the elastic modulus of the interlocking blocks alone are applied to the multi-layer elastic theory to calculate the deflection, stress or strain of the interlocking block pavement in the heavy load area (step S6). Finally, it is confirmed that all items of deflection, stress, and strain are on the safe side (step S7), and the process ends.

[0025] According to this embodiment, it is possible to maintain good road surface properties in the heavy load area for a long period of time. In addition, it is possible to realize a pavement structure with high durability, reliability and safety. Furthermore, as a result of the improved durability, it is possible to reduce the life cycle cost (LCC).

Claims

1. A method for designing a paving structure of interlocking block paving in a heavy load area, comprising: For an interlocking block paving formed by laminating a roadbed, a lower roadbed, an upper roadbed, bedding sand, and interlocking blocks, using the measurement results obtained by performing deflection measurement, calculating the elastic modulus of the block layer formed by integrating the bedding sand laid on the upper roadbed and the interlocking blocks arranged on the bedding sand; Calculating the elastic modulus of the bedding sand alone and the elastic modulus of the interlocking blocks alone arranged on the bedding sand respectively; Applying the elastic modulus of the block layer, the elastic modulus of the bedding sand alone, and the elastic modulus of the interlocking blocks alone to the multi-layer elastic theory to calculate the deflection, stress or strain of the interlocking block paving in the heavy load area. The paving structure design method is characterized by at least including the above steps.

2. The paving structure design method according to claim 1, further calculating the deflection, stress or strain of the interlocking block paving in the heavy load area by further using the interlayer slip between the interlocking blocks and the bedding sand and the interlayer slip between the bedding sand and the upper roadbed.

3. The paving structure design method according to claim 1 or claim 2, further comprising setting an allowable deflection amount of the interlocking block paving.

4. An interlocking block paving structure in a heavy load area, Designed by using the paving structure design method according to any one of claims 1 to 3, characterized in that a roadbed, a lower roadbed, an upper roadbed, bedding sand, and interlocking blocks are laminated.

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