Studies on the Tension, Compression and Shear of Rice Seedling Mats

Shearing Characteristics

Abstract

The shearing characteristics of rice seedling mats for the Japanese type rice transplanter became clear as fundamental physical properties like the tension and compression characteristics. Conclusions were as follows.
(1) The shearing stress-displacement curves of mats were similar to those of soils with low density. These curves might belong to the strain hardening pattern.
(2) The relationship between normal stresses and shearing strengths of mats was approximated by the Coulomb's equation as same as soils.
(3) In the characteristics indices for shearing strength obtained from tested mats, the values of cohesion (c) ranged from 0.05 to 1.29kgf/cm² (5 to 126kPa) and those of angle of friction (φ) ranged from 25° to 44°.
(4) In consequence of the analysis of effecting factors in the strength and stiffness characteristics, it became clear that a main factor was physical properties of bed soil. The planting density of seed and the weight of roots influenced on the cohesion (c) and the volumetric deformation modules (K). An influence of the weight of roots on the cohesion (c) seemed remarkable in the low compression stress region.
(5) Those shearing characteristics were tried to explain with behaviours of a simple model of mats.