本文主要目的在建立一套三維數值模擬程序以便分析深層拌合樁(Deep Mixing Method, DMM)在曼谷黏土(Bangkok Clay)地盤之改良變形行為及改善效果。為了確認三維數值分析之適當性，首先模擬圓形複合土柱單元(unit cell)之承載變形行為，分析結果顯示，柱頂變形剖面與數學解析解(Alamgir et al., 1996)相當吻合。接著，對兩種不同施工型式(壁式和樁式)之深層拌合改良地盤承受土堤荷重的大型現場試驗進行三維數值分析。分析中採用修正劍橋黏土模式(Modified Cam-clay Model)進行彈塑性壓密沉陷分析，且利用流體流動模式(Fluid Model)模擬在土堤荷重下孔隙水壓之產生及消散機制，監測壁式和樁式之沉陷量、孔隙水壓、以及側向位移等，並與現場量測值做比較，以確認模擬過程的正確性及輸入參數的準確性。最後，依照上述確認之三維現地模擬程序，進行二維平面應變數值模式，並將其模擬結果之土層沉陷與三維分析與現場量測數據來做比較。結果顯示，以二維平面應變分析之沉陷量要較三維分析及現地量測數據要大100%~150%，故可顯示在做現地模擬分析時，三維分析較二維分析更能表示出土層真實的變形狀況及作出更接近現地狀況的模擬分析。

A three-dimensional (3-D) Finite Difference Method (FDM) incorporated with elastic-plastic hardening soil model and fluid model (consolidation model) was proposed to investigate the behavior of Deep Mixing Method (DMM) improved ground. The FDM computer program, FLAC3D, was employed through this study. Initially, the axis-symmetric analysis of DMM unit cell was performed to investigate the deformation behavior of composite ground. The numerical result was compared with the mathematical solutions from Alamgir et al. (1996). Eventually, good agreement was found in the comparison and the capability of computer program was verified.
Subsequently, the full-scale DMM improved ground included two different configurations, namely pile type and wall type under embankment loading at AIT campus was analyzed. It was concluded that the proposed numerical schemes is capable capturing the deformation characteristics effectively.
In addition, based on the 3-D analysis, a 2-D plain strain analysis of full-scale DMM improved ground was also conducted and the numerical results were compared with the field observation and those of 3-D analysis. It was found that the 2-D analysis tends to overestimate the settlement about 100%~150% and the 3-D analysis is capable of revealing more realistic deformation of DMM improved ground and providing better predictions.

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