地下連續壁工法為深開挖工程中廣為採用工法之一,惟因都會區之深開挖工程多為緊臨道路及建築物,因此常造成許多損鄰事件及施工問題產生,又台北盆地屬於軟弱地盤,在槽溝挖掘時遭遇到壁面坍塌及側向位移機會大增。因此對於連續壁施作過程引致之沉陷量及側向位移之機制,值得深入討論。 本研究乃以三維數值模擬軟體PLAXIS 3D Foundation進行模擬槽溝挖掘所引致地盤變位,藉由台北盆地淡二區(T2區)實際案例之監測資料進行材料參數與土壤模式之驗證,並試圖改變連續壁多單元之開挖長度、寬度、深度、地下水位深度進行研析。 由數值分析得知,連續三個單元挖掘所引致之最大地盤側向位移發生位置皆位於在壁面0.5H處,最大地表沉陷量位置皆發生在地表壁面處。再者,控制槽溝尺寸變數下,其挖掘長度與相對應之最大地盤變位則有隨之上升之趨勢,挖掘深度超過30m,最大變位則趨於一定值。另在轉角單元之研析中,目的為探討相異方向之地盤變位,結果顯示,其最大地盤變位則有疊加效應之產生。
Diaphragm wall is one of the commonly used construction methods for deep excavation. However in urban areas, construction sites are mostly right next to roads and buildings. Damage to neighboring buildings and construction problems happen frequently. In addition, Taipei Basin has soft ground, which increases the chance for collapse of wall surface and lateral displacement during the excavation of trenches. Therefore, the mechanism of settlement and lateral displacement due to the construction of diaphragm wall is worth investigating. 3D numeric simulation software, PLAXIS 3D Foundation, is introduced to simulate the stratum displacement due to trench excavation. The excavation monitoring data of a practical case at Tanshui 2 zone (zone T2) of Taipei Basin for verification of material parameters and soil patterns. The analysis is conducted by changing the excavation length, width, depth of diaphragm wall units and groundwater level. From numeric analysis, it is found that the maximum lateral stratum displacement due to the excavation of three consecutive units occurs at 1/2H of wall surface, and the maximum ground settlement occurs at the top of wall surface at ground level. In addition, with the dimensions of trench under control, the excavation length and corresponding maximum stratum displacement show signs of increase. As the excavation depth goes beyond 30m, the maximum displacement approaches a constant value. Also in the analysis of corner units, the purpose is to investigate the stratum displacement at different orientation. The result shows that there is superimposition in the maximum stratum displacement.