林道路面の良否判定に関する研究

Abstract

本研究は車両の振動現象を利用し, 車両に生ずる衝撃荷重の大きさを尺度として, 林道路面の良否を判定することを目的としたものである｡ 第II章, III章, IV章は本課題に対する研究の母体をなすものであるが, 筆者はこれら各章のなかで, 林道路面の良否判定法についてこれが確立にいたるまでの理論的および実験的考察を中心とし, さらに判定法の実際的適用例を示した｡ 1. まず本研究については, つぎの2つの仮定が問題の出発点となっている｡ すなわち, (1) われわれの経験によれば, 同じ車両でしかも同一の条件で走行する場合でも, 路面が異なれば (例えば林道と舗装道路では) 車両の振動, 衝撃は大いに相違する｡ こうした相違は, 走行路面自体の影響に基づくものであると考えざるをえない｡ (2) 路面の形状, 構造のいかんと車両の振動との間には密接な関係がある｡ 以上の2つの仮定である｡ この見地から, つぎに筆者は車両振動の原因, 車両振動の種類などについて簡単な考察を行い, 本研究が車両振動に関して取扱う範囲を明らかにした｡ また路面のいかんによる車両振動について, 上下振動とそれに基づく上下の衝撃荷重に関し, 車両が凸部乗上げ, 凹部落下を例として理論的考察を行った｡ その結果, 衝撃荷重が凸凹部の大きさに大いに関係があることを見出すとともに, さらにモデル路面をつかった実験によりその事実を確かめた｡ (II. 3, 4) 筆者は, 上に述べた理論と実験の結びつきによって, ここに衝撃荷重の大きさを尺度として林道路面の良否判定を行う方法を確立し, これを提起した｡ 2. つぎにIII章では, 上記判定法のための具体的な問題をとりあげ, 振動加速度の測定方法, 振動計により記録された振動波の解析の仕方, 振動加速度値の計算法等を示し, αH, αV の値による実際上の路面判定につき詳述した｡ 3. IV章では, 代表的な路面, 路線をいくつかとりあげ, 判定法の適用とその数値例を中心に述べた｡ またそれらの実験例は, われわれが一般になす直感判断による結果と一致するものであり, αH, αVによる路面判定がその直感判断に対して科学的な根拠を与えうることをも同時に示した｡

The main purpose of this investigation was to establish a scientific method for estimating the qualities of forest roads by means of the vibro-acceleration occuring in a running motortruck, that is, by means of the impact load produced in the motor-truck. The bases of this paper were described in detail in chapters II ~ IV respectively. 1. On the basis of the following two assumptions I started this investigation: (1) Driving on a forest road by a motor-truck, we often have experiences of uncomfortable riding caused by the great vibration, that is, the impact force occuring in the running motor-truck. On the contrary, driving on an asphalt road (paved road), we have experiences of comfortable riding, that is, smaller vibration. How can we explain this fact? It is one of my assumptions that this fact may be dependent on a difference of the qualities of road surfaces between a forest road and an asphalt road. (2) The other assumption is that the impact load resulting from the motor-truck which runs on rough roads may be dependent on many kinds of shape and type of road surfaces as well as the shake in a vertical direction. These assumptions based on the above fact gave me a start of this study. From this point of view, I first pointed out causes for the vibration of the motor-truck and the kinds of vibration, and then made clear the region of vibration which I dealt with in this study. Secondly, assuming that front and rear wheels ran on humps, or one of them fell in a concave on road surfaces, I carried out a theoretical consideration of the vertical vibration of motor-trucks and their impact load. Thirdly, in order to make sure of the above assumptions I made many experiments for obtaining the relation between the shape or the type of road surfaces studied and the vibro-acceleration. These assumptions were justified here by the fact that the theoretical consideration gave a good agreement with the experimental evidence as discussed in chapters II. 3 and II. 4. On the basis of this fact I could establish a method for the estimation of the qualities of forest roads by vibro-acceleration, in practice, by means of comparison of each coefficient, αH and αV, of the vibro-acceleration for each road. 2. The following practical problems of this investigation were discussed in chapter III: (1) method of measurement; (2) examination in regard to the sensitivity of used vibrograph; (3) condition of measurement; (4) analysis of amplitude by the vibrograph; (5) practical calculation of vibro-acceleration and so on. In addition, the practical examples for the judgments by means of each coefficient αH and αV were given in this chapter. 3. The practical applications of this method were discussed on the basis of the above examples in chapter IV. I showed that the estimation by means of the above-mentioned method was in good agreement with the estimation based on an intuition, and that a scientific ground could be given for the intuitive estimation.