| 摘要 |
PROBLEM TO BE SOLVED: To provide a surface layer material equipped with proper elasticity and excellent permeability and, at the same time, capable of reducing an amount of soil particles to be scattered and manufacture thereof. SOLUTION: Soil material constituted of soil particles having particle size less than approximately 2 mm is sieved out by a soil material production process, and it is chuted to a chute inlet 41a of a sieve 40 by a conveyor 32. The chuted soil material of soil particles having particle size larger than approximately 0.075 mm is made to flow down a flowing down course W1 by an oscillation member 42, and soil particles having particle size less than approximately 0.075 mm are made to flow down a flowing down course W2. Then, soil particles having particle size less than approximately 0.075 mm flowing down from the flowing down course W2 through an inclined plane of an inclined plate 43a are mixed with soil particles having particle size larger than approximately 0.075 mm moved to a first duct 41b within the range from approximately 12% to approximately 14% to produce a surface layer material H.
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