基礎尺寸對碎石土地基擴底基礎上拔承載力影響的現場試驗研究

崔強　童瑞銘　劉生奎　魯先龍

摘要：

影響基礎上拔承載能力的因素包括地基土物理力學參數及基礎尺寸參數，而確定混凝土方量最小、基礎上拔承載力最大的基礎參數配比是基礎優化設計的關鍵。以戈壁灘碎石土地基中的原狀土擴底基礎為研究對象，采用正交設計方法，以立柱直徑、深寬比、擴展角為影響因素，以基礎上拔承載力為分析指標，設計出9組尺寸的足尺基礎。通過現場試驗，獲得了各試驗基礎的荷載位移曲線和上拔承載力值，提出了采用漸變率的概念表征荷載位移曲線的非線性變化特征，通過分析發現基礎荷載位移曲線漸變率與承載能力呈負相關。結合正交試驗分析結果，得出立柱直徑、深寬比、擴展角3個因素中對碎石土地基原狀土擴底基礎抗拔承載能力的影響程度由大到小依次為深寬比、立柱直徑、擴展角，表明在戈壁灘碎石土地基基礎的工程設計中增加深寬比能提高基礎抗拔承載能力。

關鍵詞：

碎石土；原狀土；輸電線路；擴底基礎；上拔承載力

中圖分類號： TU475

文獻標志碼：A文章編號：16744764（2016）06001707

Abstract：

The uplift bearing capacity of the spread foundation is determined by not only soil physical and mechanical characteristics but also its geometry shapes and scales. The foundation size parameters to determine the minimum quantity of concrete， and the maximum uplift bearing capacity， are key to optimize the foundation design. In order to study their effect on the uplift bearing capacity of the foundation， the undisturbed soil spread foundation in Gobi gravel soil is took as the case. Nine full size test foundations are designed， which use orthogonal test method selected column diameter， the extension angle of the foundation foot and the depthtowidth ratio as influencing factors and the uplift bearing capacity of the foundation as examining goal. The insite static load tests are carried out in the Gobi gravel soil located northwest China. Loaddisplacement curves of nine test foundations are obtained and the uplift bearing capacity corresponding are concluded. An index named gradual change ratio is proposed to expressing plastic deformation characteristic of soil foundation under pull load. Meanwhile， the results of the tests show that the sensitivity sort of these geometry factors on the uplift bearing capacity is the depthtowidth ratio， column diameter， and the extension angle of the foundation foot. The conclusion achieve in this work is that adding the depthtowidth ratio in foundation design is an effective measure for improving the uplift capacity of the spread foundation in Gobi gravel soil.

Keywords：

gravel soil； undisturbed soil； transmission line； spread foundation； uplift bearing capacity

原狀土擴底基礎（輸電線路工程中又稱“掏挖基礎”）是指利用人工或機械的方法在原狀土地基中鉆（挖）成基礎設計外形的基坑，然后將鋼筋骨架和混凝土直接澆注于基坑而成的原狀土基礎，已廣泛應用于輸電線路、高聳建筑物等結構的基礎工程中。此類基礎的上拔承載力主要受基礎結構強度、基礎幾何特征及其周圍土體的物理力學性質影響。……