Abstract
Generally speaking, it is not seemed that the shape of granular material with comparatively large grain diameter used in the civil engineering works has been treated as an important factor, though the shape of civil engineering materials has effects on the strength, durability, difficulty in construction works, of the structure. There are several reasons of the aboves, the authors consider. One of these is based on the fact that considerable amount of labour works are needed to measure the shape of granular material by means of the conventional measurement methods. And the other reason is that the results of measurements themselves generally represent only the shape characteristics of individual particle, but not of the aggregate materials which are consisted of many particles with various sizes.
In this paper, using the conventional direct and indirect methods for measuring the shapes, the authors investigate the shape coefficients of the aggregate materials by basing on the results of measurements obtained in the particles of sand and gravel under the following three conditions;
(1) Particles being deposited with parent rocks.
(2) Particles suffered abrasive operations through their transportations.
(3) Crushed stones.
From the above measurements, the following facts were confirmed;
(1) The surface roughness and geometric anisotropy of the particle are two independent parameters, both of which should be used to represent the shape coefficient.
(2) In the aggregate materials, the shape coefficient is affected by the degree of surface roundness of the material.
Depending on the aboves, the authors consider that in relation of the degree of roundnees the aggregate characteristics such as the void ratio and substantiality under a fixed condition are the factors which represent the shape in the aggregate materials and indicate the effect of the surface roughness. As to the geometric quality of materials that is the other parameter, the direct sphericity and flatness are reasonable to be used as the factors indicating the geometric quality. Therefore, the authors analyzed the experimental results and obtained the following capacity coefficient (C), which can be easily measured,
_??_(1)
Where, Vn; volume of the particle, Nm-1; diameter of mesh through which the particle can pass, Nm; diameter of mesh through which the particle can not pass.
Because the capacity coefficient is a factor to indicate the anisotropy in the shape, it is considered that this coefficient can be used as a standard in the selections and classifications of the construction materials, in combination with the void ratio which tightly correlates with the degree of roundness.
