紅層泥巖樁巖接觸面本構模型試驗及數值模擬

胡啟軍+蔣晶+徐亞輝+石仁丹+張宇浩

摘要：樁巖（土）接觸面力學特性的研究是樁基承載機理研究的基礎。通過紅層泥巖樁巖接觸面大型直剪試驗，研究了紅層泥巖樁巖接觸面的力學特性，結果表明：接觸面剪應力先隨剪切位移增大而增大，在達到峰值后，剪應力隨著剪切位移增大而降低，并最終趨于穩定值，應力應變曲線呈現出應變軟化的特征。根據剪切試驗結果，推導出樁巖接觸面應變軟化本構方程。利用fish語言對FLAC3D中自帶的理想彈塑性接觸單元進行二次開發，并應用開發的模型對樁巖接觸面直剪試驗進行了數值模擬，分析剪應力與剪切位移之間的關系，證明了該本構能夠較好地模擬接觸面間的應變軟化特性。

關鍵詞：紅層泥巖；樁巖接觸面；應變軟化；本構模型；數值模擬

中圖分類號：TU473.1文獻標志碼：A文章編號：16744764（2017）03012207

Abstract：The pilerock（soil） interface mechanical behavior was the basis of pile foundation bearing mechanics. Firstly， the mechanical property of the interface was investigated through the laboratory large direct shear test of red mudstone pilerock interface. The results indicated that the shear stressstrain curve presented strain softening behavior. The shear stress was increasing with the shear strain initially， and when the shear stress came to a peak， the shear stress was decreasing with the shear strain and finally reached a steady. Subsequently， the constitutive equation was deduced based on the interface mechanical property， the ideal elasticplastic contact element in FLAC3D was further developed through fish language. Additionally， the direct shear test of red mudstone was simulated according to the interface constitutive model， and the relationship of shear stress and shear displacement between the pile and soil were analyzed which proved that the constitutive model showed good performance on simulating strain softening features of the interface.

Keywords：red mudstone； pilerock interface； constitutive models； strain softening； numerical simulation

目前，樁基礎在巖土工程中的各個領域得到了廣泛的應用，而樁巖（土）接觸面的力學性質對于樁基承載性能具有重要的影響。紅層泥巖是中國西南地區廣泛分布的一種軟弱巖類，它的強度介于巖與土之間，在建筑物荷載作用下，表現出變形大、承載力低、復雜易變等工程特性[12]。因此，研究紅層泥巖與樁基礎的相互作用機理具有重要的經濟價值和社會意義。

樁巖（土）接觸面上兩種材料的變形不一致常常會引起接觸面上產生較大的剪應力，而接觸面上的力學特性與巖（土）體的性質有著密切的關系[34]。現階段，主要通過樁巖（土）接觸面的剪切試驗來研究樁巖相互作用的力學特性[515]。……