砂礫土層中大面積開挖工法規劃與施工

Assess of the Excavation Plan of a Large-Area Foundation on Gravally Sandy Soil

張瑞仁(Jui-Jen Chang) ； 謝孟達(Men-Da Hsieh) ； 王柏雁(Bao-Yan Wang)

《地工技術》 85期 (2001/06) Pp. 43-50

https://doi.org/10.30140/SG.200106.0002

摘要

砂礫土層因級配組成可使其摩擦角較粉質砂土為高，但因無法確知級配特性的效應，在估算摩擦角時仍多採用較保守的數值。砂礫土層也是滲透性良好的地層，進行地下室開挖與基礎工程時，開挖工法之規劃必需考慮基地內外抽水的影響。在大面積基礎工程，必需詳加考量安全措施工法之可行性。由於基地幅員廣大，結構體多採分區構築，各分區間界面之整合，同時進行結構與開挖施工，是工程管理上一大挑戰。本文就南部砂礫地層上，一廣達近40000平方公尺的基地，工法規劃與施工過程，所面臨的相關問題，作一說明。該基地一側長約350m且與約70棟3層樓建築相鄰，採用連續壁配合扶壁為全區擋土結構，使基地內得以形成無支撐開挖環境。從此一實例得知，砂礫土層之強度依據其級配特性可有更合理之估算；自監測結果觀察，此類型擋土措施在砂礫土層中，能發揮良好的擋土效果，滿足安全維護及工作性的要求。

關鍵字

砂礫土層 ； 地下室開挖 ； 連續壁 ； 扶壁

並列摘要

Gravelly sandy soil has largle friction angel than general silty sand because of the well-graded effect. But due to lack of proper estimation of this effect, friction angle of gravelly sandy soil is usually calculated conservatively. With high permeability, the influence of pumping should be considered in the excavation plan in gravelly sandy soil. For the large-area foundation work, the workability of the excavation and construction method should be assessed very carefully. This paper will discuss some of the problems encountered during excavation process in gravelly sandy soil, in a site with an area of about 40,000m^2 in southern Taiwan. There are 70 buildings along the eastern perimeter of this site about 350m in length. Using a slurry wall with a buttress structure as the retaining system will allow the excavation work to proceed without installation of inner struts. This practical case study shows the shear strength of well-graded gravelly sandy soil will be calculated more properly. Such a kind of retaining structure works well to fill both the workability and safety requirements.

並列關鍵字

Gravelly sandy soil ； basement excavation ； diaphragm wall ； buttress