圓桶形配置JSG地盤改良應用於 既有建物更新之基礎重建案例研究

Abstract

本論文主題為台北市基隆路上一基礎重建工程之地盤改良案例研究。探討利用舊連續壁內圓桶形配置JSG高壓噴射灌漿改良土，於後續開挖支撐時抑止擋土壁水平變位及地盤沉陷之效益。本基礎重建案例，保留舊擋土連續壁，於舊地下室中，進行JSG地盤改良及加深擋土壁工程，研究中說明其施工流程、遭遇困難、及解決對策。根據監測結果，探討高壓噴射灌漿造成舊連續壁之水平位移及地表沉陷，破除與支撐及開挖造成之舊連續壁水平變位及基地周圍地表沉陷量，並將壁體水平位移監測結果與TORSA程式分析結果比較，獲得以下各項結論。根據空地旁傾度管之監測結果，施作高壓噴射灌漿會對於壁體水平位移造成影響(±3 mm以內)。施作跳孔之JSG高壓噴射灌漿，隨施作點距離壁體遠近，會影響地表面隆起及沉陷(±10 mm)。壁體外有外加荷載，開挖時，壁體頂端位移小於壁體中間深度之水平位移(中12.48 mm>頂3.48 mm)；若壁體外無外加荷載，開挖時，壁體頂端水平位移大於壁體中間深度之水平位移(頂8.02 mm>中4.4 mm)。於舊筏基下之圓桶型JSG改良土中向下開挖，空地旁之壁體最大位移變化量為1.23 mm。根據本研究探討之舊壁體傾度管及地表沉陷點監測資料，在舊連續壁內施作圓桶型配置JSG高壓噴射灌漿及加深擋土壁，對於控制壁體水平位移及地表沉陷量有一定效益。

This thesis introduced a case study which involved the on a renewal of an old foundation by applying cylindrical JSG ground improvement in Taipei. The old diaphragm wall was kept in this reconstruction project. Within the old diaphragm wall, the JSG ground improvement was applied to reduce the horizontal displacement of the old diaphragm wall and the surface settlement of the ground during the cutting and bracing. A deeper H-beam retaining wall was constructed to increase the retaining depth. This paper investigated the effectiveness of the JSG ground improvement and the H-beam retaining wall during the reconstruction. The construction procedure, difficulties encountered, and the solutions for the problem experienced. Based on the monitoring results, this investigation examined the displacement of the diaphragm wall and the settlement of the ground during grouting, cutting and bracing. The monitored field data were compared with those calcultated with software TORSA. The following conclusions were drawn. Based on the data monitored from the inclinometer, the JSG operation caused the adjacent diaphragm wall to move laterally up to ±3 mm. Following the distance between the grouting location and the monitored point, the JSG operation would cause the ground surface to settle or heave. With the reinforcement of a new cylindrical JSG ground improvement within the old diaphragm wall, the maximum lateral wall movement measured during the foundation renewal was 15.96 mm. Based on the monitored data, it was found that the JSG grouting and the extension of H-beam retaining wall had been an effective measure to reduce the horizontal movement of diaphragm wall and the ground settlement due to the cutting and bracing process.