動力夯實引致砂土振動之實驗研究

A Laboratory Study on Vibration of Sand due to Dynamic Compaction

傅聖凱(San-Kai Fu)

指導教授 ： 馮道偉

中原大學/工學院/土木工程研究所/碩士(2004年)

https://doi.org/10.6840/cycu200400302

摘要

摘要

動力夯實係以夯錘夯擊地表，造成表面波及實體波，藉由實體波之傳遞使砂土顆粒重排而提升緊密度，本研究透過室內動力夯實試驗來量測夯擊造成的砂土振動特性，以了解動力夯實改良砂土之機制。
基於上述考量，本研究以麥寮砂、越南砂及標準砂土樣進行室內動力夯實試驗，使用兩個不同錘底形狀(平底、錘底90度錐尖角)之夯錘，量測夯擊形成之壓力波、剪力波及表面波，觀察夯擊前後側向土壓力的變化；並於夯擊後量測試體表面高程變化，及以小型圓錐貫入儀量測試體之圓錐貫入阻抗值，以佐證夯擊成效。
試驗結果顯示，不論何種砂土，使用錐尖角90度夯錘夯擊引起之砂土表面振動均較平底夯錘小，故對砂土改良效益較佳。就所使用夯錘而言，夯擊所產生之實體波加速度最大振幅值以麥寮砂最大、越南砂次之而標準砂最小，顯示砂土顆粒愈大則夯擊引致砂土內部振動較小；此外，實體波加速度最大振幅值，隨著夯擊次數增加而增加，且以麥寮砂增量幅度最大、越南砂次之而標準砂增量幅度最小，此結果顯示，砂土顆粒愈大則實體波振動變化愈不明顯。夯擊引起之側向土壓力增加量以標準砂最大、越南砂次之而麥寮砂最小，此顯示砂土顆粒愈大則夯擊對側向土壓力增加影響愈大。在相同夯擊能量下，以錐尖角90度夯錘夯擊所得到的陷坑體積較平底夯錘大。以貫入阻抗值做比較，標準砂改良效果最差，此顯示砂土顆粒愈大，其動力夯實之改良效果愈不顯著。

關鍵字

動力夯實

並列摘要

Abstract

Pounder impacting earth surfaces cause surface wave and body wave. Transmitting body wave makes sand granular permute again and improves density. This study measures sand vibration in laboratory dynamic compaction test.
Based on this consideration, this study uses Mai-Liao, Vietnam , and Ottawa sands in laboratory dynamic compaction tests. Pounders of different pounder base (flat-bottom and conical-bottom with 90 apex angle) are used. The test is mainly to measure compression waves, shear waves and surface waves, and to observe the variation of lateral pressure during compaction. The test is to measure the height variation of sand surface and to measure cone penetration resistance to evaluate improvement effect.
The results show that for the sands tested the conical-based pounder induces surface vibration of sand less than the flat-based pounder, so it will induce better improvement. Pounders inducing maximum amplitude of acceleration of body waves, Mai-Liao sand is the largest and Ottawa sand is the least. The results show that as the particle of sand is big, the interior vibration of sand is small. In addition, maximum amplitude of acceleration of body waves increase with number of blow. The increment range of amplitude of Mai-Liao sand is the largest, and the increment range of amplitude of Ottawa sand is the least. Conical-based pounder tamp to induce crater volume larger than flat-based pounder in the same impact energy.

並列關鍵字

dynamic compaction

參考文獻

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