混凝土灌注樁樁周土力學參數(shù)反分析方法研究
發(fā)布時間：2019-06-25 16:00
【摘要】：樁基礎的承載能力主要取決于樁周土的極限承載能力,土的強度主要體現(xiàn)在抗剪強度上。因此,土的抗剪強度指標是決定樁基礎承載力的主要因素。土的強度參數(shù)包括黏聚力c和內(nèi)摩擦角φ,目前,這兩個參數(shù)的取得通常是通過土工試驗完成,包括直接剪切試驗、三軸壓縮試驗等。但由于土工試驗需要將試樣脫離其工作環(huán)境,而且無法精確地模擬真實工作條件下土的破裂面,因此土工試驗得到的強度參數(shù)存在較大誤差。國內(nèi)外專家通過一系列改進的試驗來模擬土的真實工作狀態(tài),但仍未能完全達到預期目標。本文根據(jù)樁周土材料受力特性與三軸壓縮試驗中土樣的力學特性的關聯(lián)性分析,分別研究了樁側(cè)土和樁端土的應力狀態(tài)；應用彈性力學理論,推導了1/4無限平面彈性體在一側(cè)受到均布正應力和均布切應力的條件下的應力解,使用明德林解求解樁端地基單元的應力,進而確定土單元破裂面,求解其第一主應力和第三主應力；結(jié)合巖土材料離散的特性,提出了樁側(cè)土的應力衰減系數(shù),進而應用莫爾-庫倫準則和應力路徑理論提出反分析方法—莫爾應力圓圖解法,求解土的強度參數(shù)。對于樁側(cè)土,采用本文推導的樁側(cè)土單元應力解,求解樁側(cè)土單元應力并應用衰減系數(shù)公式進行修正,通過應力路徑理論,確定樁側(cè)土極限平衡狀態(tài)所在位置。對于樁端土,采用集中力作用于地基內(nèi)部條件下的明德林解計算樁端土有效壓縮層厚度范圍內(nèi)的土單元應力,通過應力路徑理論,確定樁端土極限平衡狀態(tài)所在位置。然后,分別對黏性土材料和無黏性土材料應用對應的莫爾應力圓圖解法,確定樁周土的黏聚力和內(nèi)摩擦角。在建立強度參數(shù)反分析方法后,應用混凝土灌注樁靜載荷試驗的荷載和位移數(shù)據(jù),對混凝土灌注樁樁周土材料強度參數(shù)反分析求解,將反分析得到的強度參數(shù)分別應用于有限元強度折減法、荷載增量法的極限荷載分析,荷載增量法計算的P-s曲線較好的擬合了靜荷載試驗P-s曲線；使用有限元強度折減法研究了樁基礎的極限荷載問題,進一步證明本文提出的莫爾應力圓圖解法可以求解滿足工程設計要求的強度參數(shù)。
[Abstract]:The bearing capacity of pile foundation mainly depends on the ultimate bearing capacity of soil around pile, and the strength of soil is mainly reflected in shear strength. Therefore, the shear strength index of soil is the main factor to determine the bearing capacity of pile foundation. The strength parameters of soil include cohesion force c and internal friction angle 蠁. At present, these two parameters are usually obtained by geotechnical tests, including direct shear test, triaxial compression test and so on. However, because the geotechnical test needs to separate the specimen from its working environment, and can not accurately simulate the fracture surface of the soil under the real working conditions, there is a big error in the strength parameters obtained from the geotechnical test. Experts at home and abroad simulate the real working state of soil through a series of improved experiments, but they still fail to achieve the expected goal. According to the correlation analysis between the stress characteristics of soil around pile and the mechanical properties of soil samples in triaxial compression test, the stress states of soil on pile side and soil at pile end are studied in this paper. Based on the theory of elasticity, the stress solution of 1 鈮，
本文編號：2505810
[Abstract]:The bearing capacity of pile foundation mainly depends on the ultimate bearing capacity of soil around pile, and the strength of soil is mainly reflected in shear strength. Therefore, the shear strength index of soil is the main factor to determine the bearing capacity of pile foundation. The strength parameters of soil include cohesion force c and internal friction angle 蠁. At present, these two parameters are usually obtained by geotechnical tests, including direct shear test, triaxial compression test and so on. However, because the geotechnical test needs to separate the specimen from its working environment, and can not accurately simulate the fracture surface of the soil under the real working conditions, there is a big error in the strength parameters obtained from the geotechnical test. Experts at home and abroad simulate the real working state of soil through a series of improved experiments, but they still fail to achieve the expected goal. According to the correlation analysis between the stress characteristics of soil around pile and the mechanical properties of soil samples in triaxial compression test, the stress states of soil on pile side and soil at pile end are studied in this paper. Based on the theory of elasticity, the stress solution of 1 鈮，
本文編號：2505810
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