標準貫入試驗之打擊能量

Hammer Energy Measurement for Standard Penetration Test

蔡錦松(Jiin-Song Tsai) ； 陳建隆(Chien-Lung Chen) ； 賴建名(Chien-Ming Lai)

《地工技術》 62期 (1997/08) Pp. 53-64

https://doi.org/10.30140/SG.199708.0004

摘要

標準貫入試驗定義簡單明瞭，但在實際操作，往往為求迅速便利，操作及器械上不免與原始定義所期望者，有所出入，使得不同情況下操作所得打擊數（N值）之標準程度受到質疑。因此，本文主要目的在於深入瞭解貫入試驗所採用之落錘落下過程中影響打擊能量傳遞之重要因素。打擊方式採用傳統圈餅式以及自由落下之重錘。為了達到觀察落錘行為，提出新的量測方法－「光學影像法」，將落錘撞擊砧鈑前的運動路徑呈現出來，藉以探討能量損失機制。並配合雷達法及荷重計量測法，輔以應力波動學，解釋撞擊後的力學行為。研究結果顯示光學影像法能夠準確的記錄錘落下行為。在能量傳遞上，自由式落錘在撞擊鉆板前的速度能量比（ERv）為95%，而撞擊後真正傳入鑽桿與取樣器之能量比（ERv）為75%。一般常用兩圈半繫索式標準貫入試驗，打擊砧鈑前之速度能量比均為85%，而撞擊後傳入鑽桿與取樣器之能量比約為62%。結論指出，目前本地常用之繫索式標準貫入試驗，與一般液化分析常用之百分之六十打擊能量之標準貫入試驗相近。

關鍵字

標準貫入試驗 ； 光學影像法 ； 能量比

並列摘要

The procedure of standard penetration test (SPT) has been stated definitively clear in the texts while the test performed in the practices seldom fulfills the ”standard” requirement. Due to most standardless SPT tests, the numbers of blow-counts N values, obtained in different occasions may not have similar correlations with respect to soil properties. The main concern of this paper is to study the amount of energy translation in normal test process. A photographic method with image process technology is proposed to investigate the motion of the SPT hammer. Two types of hammer, a conventional donut hammer and a free-fall hammer, were chosen for this research. A Doppler radar and a load cell were used together in this research to study the entire energy translation. Test results indicated that the energy ratio for the free-fall hammer system before the anvil was about 95% and was about 75% translated to the sampler. The energy ratio for the conventional donut hammer system was about 85% before the anvil and was about 62% translated to the sampler. The conclusion is that the energy ratio of the local practices by using the conventional donut hammer is quite similar to the 60% of most previous researches.

並列關鍵字

standard penetration test ； image process method ； energy ratio