A Study of Displacements of Diaphram Wall with Soil improvement Buttresses for Deep Excavation

[[abstract]]高雄房產因地價高漲，大樓產品數量已超越透天，大樓深開挖工程進行時，經常因檔土壁變形而導致鄰地之沉陷，損及鄰房安全引發民眾及住戶抗爭，其問題多發生於開挖期間連續壁之變形，為改善連續壁變形減少連續壁體之側向變位，目前工程上多採用連續壁內扶壁來減少壁體變形，但因高雄多數區域地質為砂質層與黏土層交錯故內扶壁與連續壁銜接處因黏土包泥較無法達成扶壁之效果，故以CCP改良樁以扶壁方式排列取代連續壁內扶壁，本次研究之目的為探討以改良扶壁樁方式排列分析應用於改善深開挖連續壁變形之狀況。 本研究採RIDO數值進行改良扶壁樁方式排列資料分析，驗證RIDO分析可行性，分別以有、無改良樁扶壁方式排列之案例，進行各項數值分析。扶壁之彈簧係數係採用Reese的樁基礎極限阻抗模式及謝旭昇的扶壁模式，分別計算實際設置改良樁扶壁方式排列之開挖案例進行回饋分析。 本研究結果發現， 引用謝旭昇扶壁模式需將彈簧係數提高至原模式計算值的3倍，方較符合實際監測值，而引用Reese的樁基礎極限阻抗模式時，在最後階開挖時與監測值有相當吻合的結果。本開挖深度僅9m，採用Reese model是否真實反應變形，仍須更多案例來加以證明。[[abstract]]Due to rising price of land in Kaohsiung apartment buildings outnumber townhouses During the deep excavation of new apartment construction projects the settlement of adjacent land often happens due to the displacement of retaining walls which endangers adjacent buildings and results in the protests of residents This problem usually happens when diaphragm walls are displaced (lateral displacement) during excavation In order to ameliorate such problems current engineering projects usually adopt inner buttresses for diaphragm walls to reduce displacement However the geology of most regions in Kaohsiung is composed of alternating sand and clay stratums; therefore at the joining section of the inner buttress and diaphragm wall the effect of the buttress is not good because the clay contains mud inside Therefore CCP improvement piles are used to replace the inner buttress of the diaphragm walls by arraying them as is done for buttresses The purpose of this study was to explore the improvement on the displacement of diaphragm walls during deep excavation using the improved pile buttresses The study adopted RIDO numerical value to carry out data analysis for the arrangement of the improved buttresses and to verify its feasibility Two kinds of cases with or without the buttresses were used for the numeric analysis The buttress model proposed by Hsieh and the model for the ultimate resistance of soil to the pile proposed by Reese are used for the feedback analysis of the diaphragm with the improved buttresses The results showed that the displacement of the diaphragm wall is close to that of the monitoring values if the spring constant of the soil is increased to 3 times that of Hsieh’s model The displacement of the diaphragm wall at the final excavation is well agreed to that of the monitoring values if the Reese model is used The depth of excavation in this case is only 9 m in total the Reese model is require the further study through the number of case studies to proof its feasibilit