應用簡易動力貫入法判釋地層結構

Applying a Portable Dynamic Cone Penetration Test to Detect Shallow Geological Structures

鄭名宏(Ming-Hung Cheng) ； 梁偉立(Wei-Li Liang)

《中華水土保持學報》 50卷1期 (2019/03) Pp. 22-31

https://doi.org/10.29417/JCSWC.201903_50(1).0003

摘要

土壤厚度及土壤岩層交界面位置為土地利用分級或邊坡穩定分析的重要指標，為獲取土壤厚度等資訊，簡易貫入法為坡地環境中常用的方法，能以重錘打擊次數來描述貫入阻抗N_h的分布。本研究改良「簡易貫入法（PCPT）」為「簡易動力貫入法（PDCPT）」，將重錘改以撞擊馬達，以貫入時間來描述貫入阻抗N_(pd)。利用不同硬度堆疊之試驗槽，發現兩貫入法均可描述阻抗分布特性，其線性對應關係為N_(pd) = 0.0197×N_h。透過野外試驗發現，在地層分明的環境，兩貫入法均能探測阻抗分布及土壤岩層交界位置。但在地層結構複雜之環境，唯有動力貫入能取得風化岩層內結構資訊，並判斷岩層中垂直或水平方向的不連續層面。因此本研究所研發之簡易動力貫入法除了保有可攜帶之特性，並可大幅減少調查時間，甚至取得風化岩層內較深層的地質結構資訊，能更有效率應用於坡地環境中。

關鍵字

不連續層 ； 儀器設備開發 ； 土壤厚度 ； 土壤岩層交界面

並列摘要

Soil depth and soil-bedrock interface location are critical indices for land use classification and slope stability analysis. To evaluate soil depth in hillslope environments, the portable cone penetration test (PCPT) is an extensively applied method for calculating penetration resistance (N_h) based on the number of knocks required for penetration. In this study, we developed a portable dynamic cone penetration test (PDCPT) based on a conventional PCPT design. The PDCPT features a knocking engine instead of the knocking weight of the PCPT. The penetration resistance (N_(pd)) detected by the PDCPT is expressed based on the time of knocks required for penetration. We used an experimental device containing layers with varying levels of hardness to evaluate the PDCPT and PCPT and discovered a strong correlation between the vertical distributions of penetration resistance measured using both tests. The relationship of these two values for penetration resistance can be expressed through the following linear regression: N_(pd) = 0.0197 × N_h. The results of field tests indicated that both the PDCPT and PCPT successfully detected the spatial distribution of penetration resistance and depths of the soil-bedrock interface in a simple environment with an obvious distinction between soil and bedrock layers. By contrast, in a complex environment with heterogeneously geological structures, only the PDCPT was able to analyze deeper structures and detect vertically or horizontally discontinuous layers within weathered bedrock layers. The findings of this study demonstrated that compared with the PCPT, the PDCPT with portability greatly reduced the survey duration and was able to detect deeper geological structures within weathered bedrock layers. Thus, the PDCPT is a more efficient method for use in hillslope environments.

並列關鍵字

Discontinuous layer ； equipment development ； soil depth ； soil-bedrock interface