摘要
在本篇研究中將探討中東地區某工程基地其共193組現地鑽孔資料中之SPT-N值、地下水位深度、細粒料含量及鹽土深度，以半異數函數描述上述四種土壤參數在水平空間變異性。另外，以克利金法作上述四種土壤參數在各自半變異圖條件下之推估，以求得未鑽探點之相關地工參數，接著依克利金法推估之地工參數利用幾種符合此研究中所需之地盤改良方法，依各工法之適用性及限制性結合統計方法得到的預測結果進行大範圍基地的地盤改良評估。為了更進一步了解鑽孔數目對於半變異數函數的影響，本研究亦將原鑽孔數分別減少30孔、50孔、70孔與90孔分別進行分析，以了解鑽孔數目對空間變異性之影響。
主要結果有(1) SPT-N值、細粒料含量、地下水深度及鹽土深度，其各自最佳擬合函數下求得之影響範圍分別為572公尺、673公尺、516公尺、346公尺。(2)在隨著抽離鑽孔的數目變多時，求得各自相對應之參數值、總體半變異數、影響範圍，其變異係數逐漸增大。(3)以SPT-N值大於15者為不需要進行地盤改良之區域占80%，需要地盤改良之區域，分別由滾壓夯實工法佔約1.5%，動力夯實工法佔了約0.07%，需礫石樁工法之區域佔了約14%，快速衝擊夯實工法佔了約4.5%。
關鍵字:半變異數、半變異圖、克利金法、地盤改良、R-Squared法

Abstract
In this research, the horizontal variability of standard penetration test N values (SPT-N), the fines content, the depth of groundwater table, and the depth of Sabkha are discussed in terms of the spatial variability through semivariance and semi-variogram. According to the results of semivariance and semi-variogram, the corresponding unknown values in the study areas are estimated within range and sill by Kriging method. There are total 193 boring logs at the construction site. It is about 8 km in length and 3 km in width. The soil boring depths are in the range of 10 to 30 meters. Since the construction site locates in a deserted area, the subsurface condition is mostly silty and clayey sands. In this research, there are the discussions of applicability and restrictions considering various ground improvement techniques. Various ground improvement techniques are suggested through the estimated geotechnical values by Simple Kriging. In this study, the variability of semivariance and parameters in the semivariogram was also investigated by randomly choosing a given number of soil borings from the database. The selected number of borings are 30, 50, 70 and 90, respectively. The main findings are (1) the range of SPT-N values is 572 m, the range of the fines content is 673 m, the range of the depth of groundwater is 516m, and the range of the depth of Sabkha is 342m. (2) When the number of borings decreases, the coefficients of variation of the estimated values such as the sill, and range in the semivariogram increase. (3)Based on the assumption that areas with SPT-N values of 15 or larger blows do not need ground improvement, the areas that do not need ground improvement is about 80%. With other geotechnical parameters such as the ground water level depth, percent of fine contents and depth of Sabkha, it was estimated that area needing roller compaction is about 1.5%, the areas using dynamic compaction is about 0.07%, the areas using rapid impact compaction is about 4.5%,and the areas using stone column is about 14%. The percentage of ground improvement technique is influenced mostly by the variance of the depth of Sabkha.

Key words: Semivariance、Semi-variogram 、Kriging、ground improvement technique、R-Squared

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