| 概要 |
従来の山地用貫入試験機によって得られる地盤の情報は,n値のみであった.これに対 し,本論文では, ロッド内を伝ぱする縦波を観測し, ロッドと土との境界面での反射係数αを求め, ある場所の任意の深さの土の機械インピーダンスZ_m=ρ･cを精度よく測定する方法を検討した. 土の機械インピーダンスを精度よく測定するためには,できるだけ土のZ_mに近い材質のロッドおよびハンマーを用いる必要がある. このた...め,鉄(従来の貫入試験機で用いられているロッドおよびハンマーの材料, ρ･c=4.02×10^7 N･s/m),アルミニウム合金 (5052, ρ･c=1.37×10^7 N･s/m),マグネシウム合金(AZ 31, ρ･C=9.03×10^6 N･s/m),アクリル樹脂(PMMA, ρ･c=1.93×10^6 N･s/m)の4種類のロッドおよびハンマーを用 いて実験的に検討した.この結果,鉄の機械インピーダンスは,土のZ_m=ρ･cよりも2桁大きく,また, アクリル樹脂は,内部損失が大きいため,土のZ_mを糖度よく求めることが不可能と判明した.したがって,土のZ_mよりも1桁大きなZ_mもつマグネシウム合金(AZ 31)が内部損失も小さく,土のZ_mを精度よく求めるには, アルミニウム合金(5052)よりも有利であると判断した.マグネシウム合金ロッドおよびハンマーを用いることにより,土のZ_m=ρ･cを精度よく測定できることを示し,山地の不攪乱土の物理量ρ･cの測定が可能となった.
In this report we developed the method for obtaining mechanical impedance of soil with high accuracy from the reflection coefficient α at the boundary between the lower end of rod and soil under the test. The results are summarized as follows: 1) Using the simplified penetrating apparatus and strain detecting system, measurements were carried out on the stress waves propagating and reflecting along the rod. 2) The mechanical impedance of soil is obtained from the reflection coefficient α. 3) For the purpose of selecting the best material for rod and hammer, measurements on mechanical impedance of Gum were carried out, which has a similar mechanical impedance with soil, with 4 kinds of rods; iron, aluminum alloy 5052, magnesium alloy AZ31, and PMMA (Plastics). With those material, the mechanical impedance of Gum is measured and the error was 51％ for iron rod, 12.9％ for PMMA rod and O.12％ for magnesium and aluminum alloy rods respectively. In case of using iron and PMMA rod, it is impossible to measure the impedance of soil with high accuracy since the mechanical impedance of iron is so high compared with the soil impedance and for PMMA rod due to it too much internal loss. 4) An alloy of magnesium(AZ31) is the best material for rod and hammer of the simplified penetrating test apparatus, since its internal loss is small and its mechanical impedance was larger than that of soil by one order.続きを見る
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Mendeley出力
