基礎開挖施工時,常需施作擋土壁,施工單位多依經驗判斷擋土貫入深度安全,本研究以作用於壁體之被動,與主動側向力之力矩作用為安全係數,並應用Excel撰寫成簡易分析試算表,研究淺層開挖砂土層之影響因素。 研究結果顯示影響因素可分為:土壤條件及外部環境。其中土壤內摩擦角屬於土壤條件,當土壤內摩擦角越大,則安全係數越高。外部環境則包括:水平支撐、地下水及地表荷重。且其中,有水平支撐較無水平支撐者安全,且最下層水平支撐作用越接近開挖地表面則安全係數越高;無地下水位者較有地下水者安全,且地下水位距離地表面越高則擋土壁安全係數越低;反之,地下水位距離地表面越低則擋土壁安全係數越高,無地表荷重者較有地表荷重者安全,當地表荷重越大則擋土壁安全係數越低。
In several kinds of foundation construction, open trenches with vertical soil slopes are excavated. Although most of these are temporary, the sides of the cuts must be protected by proper bracing systems. The bracing consists of sheet piles, wales, and struts. This study use sheet pile-soil interaction relationships to analyze the behavior of excavation. The computer program table developed using Excel. Analytical results show below. The safety factor of sheet piles increase as friction angle and strut progresses. Results from the parametric study show that the most significant factor affecting the safety factor is the strut, ground water, and surcharge. On the other hand, the friction angle of sand has much less influence.